the lime industry, a potential business area for kanthal - diva

UPTEC Q10 001

Examensarbete 30 hpMars 2010

The lime industry, a potential business area for Kanthal

Jesper Ejenstam

Teknisk- naturvetenskaplig fakultet UTH-enheten Besöksadress: Ångströmlaboratoriet Lägerhyddsvägen 1 Hus 4, Plan 0 Postadress: Box 536 751 21 Uppsala Telefon: 018 – 471 30 03 Telefax: 018 – 471 30 00 Hemsida: http://www.teknat.uu.se/student

Abstract

The lime industry, a potential business area forKanthal

Jesper Ejenstam

The subject of this M.Sc. thesis is to find out whether the lime industry is a possiblebusiness area for Kanthal AB. The lime industry is one of the biggest chemicalindustries in the world and it is very energy demanding. In the process of makingquicklime, calcium oxide, a lot of energy is needed as the dissociation of limestone,which consists mainly of calcium carbonate, takes place in the temperature spanbetween 900°C and 1300°C. The total production of quicklime was in 2009 about280 million tonnes, and the selling price was about $100 per ton. Today, all limekilnsare driven by fossil fuels, i.e. oil, coal and gas. The increasing demand on lowering theemissions of carbon dioxide strongly affects the industry, as it is responsible for about2 % of the total emissions of carbon dioxide. The industry itself claims that theemissions may only be reduced about 10 %, although at very high costs. Kanthal ABproduces electric heating solutions that may be suitable for lime production.However, the lime industry is conservative and the use of electricity for limeproduction is not economically feasible today. Most of the electricity comes from coalpower plants and therefore the use of electricity would not be more environmentallyfriendly in most countries. New limekilns, which are more environmentally friendly,are on the way. These kilns do not necessarily have to use fossil fuels, provides apurer end product and the emission of carbon dioxide is minimized. The size of theproduction is also much lower, but the end products might be used in moredemanding areas, e.g. the pharmaceutical industry, and be sold at a higher price. It isthis area Kanthal has to focus on if going to enter the lime industry at this point.

Sponsor: Kanthal ABISSN: 1401-5773, UPTEC Q10 001Examinator: Åsa Kassman RudolphiÄmnesgranskare: Håkan EngqvistHandledare: Gustaf Lorenzson

Kalkindustrin, en möjlig marknad för Kanthal

Jesper Ejenstam

Bakgrund och syfte Kalkindustrin är en av världens största kemikalieindustrier, näst störst efter svavelsyraindustrin. Tekniken som används är ungefär densamma som för 100 år sedan, dock har den optimerats en hel del. Industrin hävdar att metoderna är så pass utvecklade de kan bli, vilket är ett problem eftersom effektiviteten ligger mellan 30 och 80 %. 2009 producerades ca 280 miljoner ton bränd kalk, varav Kina stod för ca 180 miljoner ton, och det ungefärliga priset ligger på 100 dollar per ton. Kanthal AB vill med det här examensarbetet få svar på frågan om kalkindustrin kan vara ett möjligt affärsområde. Därför syftar examensarbetet till att vara kunskapsbyggande och ska kunna ligga som underlag vid ett eventuellt ”business case” om Kanthal bestämmer sig för att satsa på kalkindustrin. Bränd kalk Kalksten har används av människan i tusentals år. Ett exempel på det är pyramiderna i Egypten som består av kalksten. Kalksten består i huvudsak av kalciumkarbonat och det finns mycket god tillgång till mineralen över hela världen. När kalciumkarbonat upphettas till ca 900°C sönderdelas det till ungefär lika stora delar kalciumoxid och koldioxid . Kalciumoxid, även kallat bränd kalk, är en viktig ingrediens i många andra processer, till exempel stålframställning där det används som slaggbildare. Idag används framförallt två typer av ugnar för framställning av bränd kalk, roterugnar och schaktugnar. En roterugn består av en enorm lätt sluttande cylinder med en längd på ca 100 m och en diameter på ca 3-4 m. I ena änden finns en brännare som drivs med fossila bränslen såsom olja eller kol. I andra änden matas kalksten in i cylindern och när cylindern sätts i rotation transporteras kalkstenen mot brännaren där bränd kalk bildas. En schaktugn består av ett högt torn på ca 30 m, med en diameter på 4-5 m. Kalksten matas in i toppen av schaktet, i mitten bränns den och i botten plockas den brända kalken ut. I och med att brännarens låga är i direkt kontakt med kalkstenen i bägge dessa kalkugnar är en viss förorening av slutprodukten oundviklig. Detta medför att kvalitén på den brända kalken blir något sämre, vilket påverkar priset. Energi och miljöaspekter Eftersom det går åt mycket energi att framställa bränd kalk, och att fossila bränslen används som energikälla, är stora utsläpp av koldioxid oundvikligt. Kalkindustrin står för ca 2 % av världens totala koldioxidutsläpp, där upp till 40 % kan kopplas till förbränningen av fossila bränslen. Miljöskatter, såsom koldioxidskatt, påverkar industrins resultat kraftigt. Enligt representanter från kalkindustrin skulle utsläppen kunna minskas med 7 till 10 %, fast till mycket höga kostnader. Detta är långt ifrån tillräckligt och nya produktionsmetoder måste till. I dagsläget skulle en kalkugn inte kunna drivas av elektricitet eftersom elpriset är så högt i förhållande till fossila bränslen. Dessutom produceras stora delar av världens elektricitet idag genom förbränning av fossila bränslen, framförallt kol. Detta medför att elanvändning inte

skulle vara mer miljövänlig i dagsläget, utan endast flytta problemet till den energiproducerande sektorn. Dock tar koldioxidneutrala energikällor, såsom kärnkraft, vindkraft, vattenkraft och solenergi, hela tiden nya marknadsandelar. Detta faktum, kombinerat med ett ökat pris på fossila bränslen, gör att många vetenskapsmän tror att el som energikälla kan vara konkurrenskraftig runt 2050. Ny teknik På senare år har nya förslag på kalkugnar presenterats av forskarlag och kalkföretag. Gemensamt för alla dessa prototyper är att slutprodukten ska bli mycket renare och därför kunna användas inom nischade produktområden, till exempel inom läkemedelsindustrin. Detta beror framför allt på att den brända kalken aldrig förorenas av en öppen låga, vilket är ett av problemen idag. Stort fokus ligger även på energifrågan, och ett forskarlag har tagit fram en idé där koncentrerade solstrålar är värmekälla. Gemensamt för de nya teknikerna är att slutprodukten blir dyrare än den är i dagsläget, storleken på produktionen blir mindre men slutprodukten blir mycket renare. Slutsats

I dagsläget är det inte ekonomisk lönsamt att storskaligt producera bränd kalk med elektricitet som energikälla. Det skulle heller inte bidra till minskade utsläpp av växthusgaser. Däremot kan produktion av bränd kalk i mindre skala kunna vara ett intressant område för Kanthal. Flera forskargrupper har presenterat goda resultat och ett intresse från bland annat läkemedelsindustrin finns. Detta är det område som Kanthal idag bör satsa på, vilket även ger större inblick i industrin. Förslagsvis ska Kanthal delta på internationella kalkkonferenser där kontakter med kalkföretag och ugnsbyggare kan skapas. Dessutom diskuteras energiproblem och ny teknik vilket är områden där Kanthal kommer in i bilden.

Examensarbete 30 hp på civilingenjörsprogrammet Teknisk fysik med materialvetenskap

Uppsala universitet, mars 2010


Contents

1 Introduction 1

1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Basic definitions and notifications . . . . . . . . . . . . . . . . . . . . 31.3 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Methodology 4

3 Limestone 5

3.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53.2 Formation of limestone . . . . . . . . . . . . . . . . . . . . . . . . . . 63.3 Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63.4 Quarrying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.5 Limestone preparation . . . . . . . . . . . . . . . . . . . . . . . . . . 73.6 Environmental aspects of limestone quarrying . . . . . . . . . . . . . 7

4 Quicklime 9

4.1 Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.2 Theory of calcination . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.2.1 Calcitic quicklime . . . . . . . . . . . . . . . . . . . . . . . . . 94.2.2 Dolomitic quicklime . . . . . . . . . . . . . . . . . . . . . . . . 104.2.3 Stages of calcination . . . . . . . . . . . . . . . . . . . . . . . 114.2.4 Dissociation of calcite . . . . . . . . . . . . . . . . . . . . . . . 114.2.5 Sintering of high calcium quicklime . . . . . . . . . . . . . . . 14

4.3 Production of quicklime . . . . . . . . . . . . . . . . . . . . . . . . . 154.3.1 Shaft kiln . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154.3.2 Rotary kiln . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174.3.3 Distribution of kiln types . . . . . . . . . . . . . . . . . . . . . 184.3.4 Environmental aspects of lime burning . . . . . . . . . . . . . 18

4.4 Slaked lime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194.5 Largest quicklime producing countries . . . . . . . . . . . . . . . . . . 204.6 Uses of quicklime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4.6.1 Agriculture . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214.6.2 Glass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224.6.3 Metal refining . . . . . . . . . . . . . . . . . . . . . . . . . . . 224.6.4 Pulp and Paper . . . . . . . . . . . . . . . . . . . . . . . . . . 234.6.5 Caustic soda . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234.6.6 Soil stabilization . . . . . . . . . . . . . . . . . . . . . . . . . 234.6.7 Steelmaking . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234.6.8 Sugar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244.6.9 Water treatment . . . . . . . . . . . . . . . . . . . . . . . . . 244.6.10 Flue gas desulphuration . . . . . . . . . . . . . . . . . . . . . 25


5 Research and Development 26

5.1 Solar reactors for quicklime production . . . . . . . . . . . . . . . . . 265.2 Indirect fired limekiln . . . . . . . . . . . . . . . . . . . . . . . . . . . 295.3 Energy source outlook . . . . . . . . . . . . . . . . . . . . . . . . . . 30

5.3.1 Fossil fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305.3.2 Renewable energy sources and Nuclear energy . . . . . . . . . 31

6 Idea for an alternative heating solutions for lime-burning 326.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326.2 Kanthal APMT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326.3 Radiant tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

6.3.1 Tubothal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336.3.2 Ecothal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

6.4 Prototype proposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

7 Investigation of the impact of the calcination process on Kanthal

APMT 377.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377.2 Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

7.3.1 Visual observations . . . . . . . . . . . . . . . . . . . . . . . . 387.3.2 Light Optic Microscopy . . . . . . . . . . . . . . . . . . . . . 387.3.3 Scanning Electron Microscopy . . . . . . . . . . . . . . . . . . 397.3.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

8 Discussion 43

8.1 Quicklime production . . . . . . . . . . . . . . . . . . . . . . . . . . . 438.2 The market potential . . . . . . . . . . . . . . . . . . . . . . . . . . . 438.3 Energy sources and environmental aspects . . . . . . . . . . . . . . . 438.4 Effects of limestone calcination on Kanthal APMT . . . . . . . . . . 448.5 The alternative limekiln prototype . . . . . . . . . . . . . . . . . . . . 448.6 Other proposed prototypes . . . . . . . . . . . . . . . . . . . . . . . . 45

9 Conclusions 46

10 Future work 47

10.1 Porcupine heating cassettes as pre-heaters in cement production . . . 4710.2 Alloys as construction material in lime and cement facilities . . . . . 4710.3 Lance tubes for quicklime shaft kilns . . . . . . . . . . . . . . . . . . 47

11 Acknowledgments 49

References 50

The lime industry, a potential business area for Kanthal 1

1 Introduction

1.1 Background

The lime industry is one of the largest chemical industries in the world. Every year,about 280 million tons of quicklime (calcium oxide) is produced. The lime productsare very versatile, whereas many areas of usage have been defined. Quicklime is pro-duced in large kilns, which often have poor efficiency. The kilns also use fossil fueland are one of the largest contributors of green house gases, such as carbon dioxide.The burner in conventional limekilns does also affect the product. The flame of theburner is in direct contact with limestone and therefore the end product will bepolluted. This reduces the selling price of the product, which is already low fromthe beginning. It also decreases the areas of use of quicklime. Because quicklimeis a fairly cheap chemical, about $ 100 per ton, many producers are struggling tosurvive. Thus, long range exporting of the products is just not economically fea-sible. Therefore a lime plant often only supplies the local industries near by. Thehigh fuel prices, emission-taxes and low efficiency of the kilns force the producersto find new ways of lime production. A lot of work has been done in small exper-imental setups, but as the lime industry is very conservative the development ofnew solutions is progressing slowly. The whole lime production cycle is very largeand therefore the main focus in this report will be at the calcining processes, figure 1.

Quicklime is produced by dissociation of calcium carbonate (CaCO3) to calciumoxide (CaO) and carbon dioxide (CO2). The process takes place at high tempera-tures, about 900◦C to 1300◦C depending on which properties are requested. Someof the processes that are common today have large energy and heat losses and thisproblem may be solved by modifications or using other heating techniques.

Kanthal AB is producing and selling heating solutions and is constantly lookingfor new market areas where their products may fit in. The lime industry is newground for Kanthal AB that are hoping their products can make a difference in thisarea.


Figure 1: Schematic figure of the lime production process. This report focuses onthe calcining process, which is illustrated in the square [1].


1.2 Basic definitions and notifications

The phrase lime is often used rashly by representatives and people connected tothe lime industry. This may lead to misunderstandings, as the word lime implicatesboth quicklime and slaked lime. However, this does not mean that these productshave the same properties. Unfortunately this misleading phrase is commonly usedand the reader has to know the differences. Beneath, the common words are listedtogether with a short explanation [2].

• Limestone is a mineral that occurs naturally in the nature, and consists mostlyof calcium carbonate (CaCO3). It occurs all over the world and is one of themost important minerals known to mankind.

• Quicklime consists almost entirely of calcium oxide (CaO), and is producedby thermal dissociation of limestone.

• Slaked lime is produced by adding water to quicklime. This is an endothermalreaction where calcium hydroxide (Ca(OH)2) is the end product.

1.3 Purpose

Kanthal AB wants to know whether quicklime processing can strengthen its busi-ness, and if the company can contribute to the industry. There is a need to knowmore about lime and lime production, what furnace types are used, energy usageand research done in the area, and also to get an estimate of how big the marketpotential is.

Kanthal also wants to find new systems for quicklime processing, by renewableenergy or with higher efficiency. If it turns out to be possible for Kanthal to enterthis industry, ideas of a prototype limekiln, using Kanthal products are wanted.

This M.Sc. thesis is supposed to be the base for an upcoming business case.


2 Methodology

This M.Sc. thesis is mainly a literature study of the lime industry and informationhas been gathered from scientific reports, books and web pages. To further un-derstand the processes, technology and important factors of lime production, limefacilities were visited. Experts in interesting areas, who had great importance to theconclusions in this report, have been interviewed and cited. The literature study ispresented in Chapters 3-5.

A prototype proposal, using Kanthal heating system, is presented in Chapter 6.A small experimental work was carried out to examine whether a Kanthal alloy

was affected by the calcination when getting in direct contact with quicklime. Thiswork is presented in Chapter 7.


3 Limestone

3.1 History

Limestone has been used for thousands of years. One proof is the pyramids in Giza,figure 2 [3], which are about 5000 years old. Also the ancient Greeks and Romansused limestone as construction material long time before the birth of Christ (BC) [2].Moreover, in Yugoslavia, excavations have found limestone constructions that havebeen dated to 5-6000 years BC. In addition to limestone, excavations have shownthat quicklime was also used in mortar to strengthen buildings. During the 19thand 20th century several cities in USA and Canada were built in pure limestone.An example is Kingston in Canada, where several buildings consist of limestone.Hence, the city is known as the ”Limestone City”. These are just a few examplesof how important limestone has been to mankind throughout the years, and eventoday limestone is an essential part of construction materials [2, 4].

Figure 2: Cheops pyramid in Giza, an early example that limestone has been usedas a construction material a long time.


3.2 Formation of limestone

Limestone is formed mainly in warm, shallow and still waters. It is in these envi-ronments where organisms, which form shells and skeletons, flourish. The limestoneis in fact formed when these organisms die and accumulate onto the seabed. Whatkind of organisms that flourishes in a certain area highly affects the composition ofthe limestone. Apart from the organism, the environment itself at a certain areaaffects the formation of limestone as well. This is why there are different types oflimestone at different places throughout the world. The formation is a very slowprocess, which takes several million years to complete [2, 4].

Limestone is also formed when water evaporates. Water often consists of someamount calcium, which is transferred to the ground when water either absorbs tothe ground or evaporates.

3.3 Properties

Limestone is a sedimentary rock that consists primarily of CaCO3, but MgCO3 andseveral other minerals are also to be found within the rock. It can be both crystallineand amorphous, but the structure mainly depends on the age of the rock. Very oldlimestone, typically more than 600 million years old, tends to be crystalline whereasyounger limestone often is amorphous. This property, among others, is the reasonthat a classification system for different limestone types has been invented. Thelimestone classification depends on microstructure, texture, impurities, age, grainsize and CaCO3-content. This system has been constructed because of the wideuse of limestone and different uses have different demands. For example, whenburning limestone the temperature of the process depends of the composition of thelimestone. Further on, the temperature affects the resulting product. The amountof a certain impurity can be crucial to one process, but is devastating to another.The properties of limestone therefore depend very much on where, when and how itwas formed [2].

The color varies from white to grey, but can be slightly red or yellow dependingof what kind of impurities are present at a certain quarry. The crystal structurecan be orthorhombic (aragonite), hexagonal (vaterite) or rhombohedral (calcite).Aragonite is semi stable, which means that it slowly converts to calcite in presenceof water or at temperatures above 400◦C. The same implies for vaterite, althoughit is even less stable than the aragonite and converts into calcite at temperaturesabove 60◦C [2, 4].

CaCO3 has a molar mass of 100.09g/mole. The density varies from about1.5g/cm3 to 2, 9g/cm3, depending of the composition of the limestone. Limestonehas a hardness of about 2-4 Mohs, a scale from 1 to 10 where diamond has thehighest value. Specific heat capacity is about 0.22cal/g, and the pH is about 9 [2].


3.4 Quarrying

Limestone is one of the most common minerals in the crust of the earth, and canbe found all over the world as it covers about 10 % of the surface of the earth.It is a relatively young mineral and therefore it can be found near the surface.Limestone quarries are often open quarries, i.e. it is deposited from the surface anddown. Limestone mines are not feasible from an economic point of view, as walls oflimestone would have to be left behind.

The quarrying can be divided into five steps; overburden removal, drilling, blast-ing and transportation. First of all, the limestone has to be exposed. It can be foundless than 1 m to tens of meters down in the ground. This is done by conventionalexcavators and is considered to be the most demanding part of the quarrying. Whenthis is done, blasting holes are drilled. They are drilled with a twenty-degree angle,which has been shown to be most effective. Further on, the limestone is loaded ontolorries using excavators or rolling hoops. All steps in the quarrying have over theyears been accurately developed to ensure as high profit as possible [2].

In Sweden, limestone is quarried at several places but the largest quarry is foundnear Slite, Gotland. The largest limestone quarry in the world is found near Roger’scity in USA, and is owned by Michigan Limestone and Chemical company [2].

3.5 Limestone preparation

Before the limestone can be transported to the lime facilities for processing, it hasto be crushed and screened in different fractions. In some cases washing is necessaryas well. When crushing limestone, two different methods are used, impact crushersand compression crushers. Impact crushers have the advantage of producing cubicalfractions, although a lot of powder is obtained as well. The compression crushingobtains a more even fraction distribution, but the limestone tends to be slightlyrounded. Washing of limestone is often not necessary, as most limestone quarrieshave very clean limestone that is not contaminated by clay and dirt. However,for some areas, which demand extra clean limestone, washing is needed to achieverequired purity. Washing in rotating barrels is also used to reduce fractions size,when fractions smaller than 10 mm are necessary [2].

3.6 Environmental aspects of limestone quarrying

The environmental effects of lime production start with the limestone quarrying.The limestone quarries are large areas, which looks like giant craters. This resultsin a disturbance in the wildlife of the area. The quarrying companies have a bigresponsibility to ensure that the wildlife is not disturbed too much in the area, and aplan has to be made how to restore the area when the quarry has served its purpose.

Another environmental effect of quarrying is the dust, which the process creates.The dust mainly originates from crushing of the quarried limestone. There is always


a risk that the dust is spread by the wind and causes over-fertilization of lakes,forests and agricultural land. The dust is unhealthy when inhaled as well.

Huge industrial machinery is used in the process and these generate noise, vi-brations and exhaust gases. Although noise is mainly from the explosives that areused when large pieces of limestone are being quarried. This is the main source ofvibrations as well, which may cause damage to near-by buildings [2, 4].


4 Quicklime

4.1 Properties

Quicklime is a porous rock, which often appears white or slightly discolored due toimpurities. Impurities may be found naturally within the limestone or may comefrom the burning of fossil fuels while burning the limestone [4].

To the naked eye, CaO appears like an amorphous material, although this isnot the case. It consists of many small crystals in NaCl structure with the latticeconstant of 4.81A. The melting point is about 2850◦C.

Quicklime is a very reactive substance that reacts strongly with water, thus gen-erating a large amount of heat, about 1140kJ/kg, and calcium hydroxide (Ca(OH)2)[2, 4, 5].

4.2 Theory of calcination

To produce quicklime, limestone is heated to a temperature over the dissociationtemperature. The dissociation temperature depends on the type of limestone thatis used, and cannot be generally defined. This is because the limestone differs fromquarry to quarry, and experiments have to be carried out to find the optimal calciningtemperature for each limestone. Limestone can be divided in two subgroups, calciteand dolomite.

4.2.1 Calcitic quicklime

Calcite consists mostly of CaCO3 and is the type of limestone that is most widelyused in the lime industry. This is because of the fact that most customers want ahigh level of pure CaO as possible in their processes. The decomposition of highcalcium limestone is expressed in reaction 1 [2, 4, 5].

CaCO3100g

+ heat ! CaO56g

+ CO244g

(1)

At atmospheric pressure, it has been shown that CaCO3 decomposes to CaOaround 900◦C. The amount of heat that is needed for the reaction has been closelyinvestigated through the years and values from 695 kcal/kg of CaO to 834 kcal/kgof CaO have been reported. These values have been calculated relative an ambienttemperature of 25◦C. This is not entirely correct due to the fact that heat, whichis needed to raise the temperature from 25◦C to 900◦C, has to be taken into con-sideration. Furthermore, when CaO and CO2 are cooled from 900◦C to 25◦C, someenergy is gained by exothermic reactions. The net sum of the total required heatis therefore a little lower than for the heat required for the decomposition. Withrespect to this, values from 698 kcal/kg of CaO to 723 kcal/kg of CaO have beenreported [2, 4, 5].


4.2.2 Dolomitic quicklime

Dolomite is a magnesian limestone, which consists of both CaCO3 and MgCO3.When dolomite decomposes, it can be done in a two-stage decomposition, a directdecomposition or by a mix of these reactions [2, 4, 5].

MgCO3 · CaCO3

184g

+ heat ! CaCO3 · MgO140g

+ CO244g

(2)

CaCO3 · MgO140g

+ heat ! CaO · MgO96g

+ CO244g

(3)

MgCO3 · CaCO3

184g

+ heat ! CaO · MgO96g

+ 2CO288g

(4)

The different reaction stages depend on the starting temperature of the calcina-tion. At low temperatures, the two-stage reaction, 2 + 3, has been reported whereasreaction 4 has been reported for temperatures around 900◦C. The heat of dissoci-ation of dolomite has been reported to be about 700 kcal/kg of (CaO · MgO), i.e.about the same as for calcitic limestone [2, 4, 5].


4.2.3 Stages of calcination

Throughout the years, the calcination process has been closely studied. The processcan be divided in five steps [2].

1. Limestone is preheated to about 800◦C by using exhaust gases from the mainprocess.

2. When the limestone reaches 800◦C, the pressure from the dissociated CO2

equals the pressure of the hot gases in the limekiln. The surface of the lime-stone starts to dissociate even faster and when the temperature reaches about900◦C, the layer of quicklime is about 0.5 mm thick for a limestone lump ofabout 25 mm radius.

3. When the temperature rises above 900◦C, which is about the optimal dissoci-ation temperature, the partial pressure within the lump surpasses the atmo-spheric pressure and the dissociation proceeds beneath the surface layer.

4. The dissociated limestone begins to sinter after some time, which correspondsto the temperature in the furnace. A higher temperature implies a fastersintering. The sintering process results in less reactive quicklime due to asmaller surface area.

5. The quicklime leaves the calcination zone and is cooled by air.

4.2.4 Dissociation of calcite

The disassociation of high calcium limestone, calcite, always starts from the surfaceof the limestone and proceeds gradually into the core. As earlier mentioned, thedissociation process starts at the surface of the limestone at temperatures slightlybelow the calcining temperature, whereas a quicklime shell encapsulates it. Attemperatures higher than the calcining temperature, the CO2-pressure is higherinside the limestone than outside that forces CO2 to escape. This implies thatgreater radius of the limestone will require a higher temperature to fully calcine it.For some types of limestone the dissociation temperature can vary 150◦C to 350◦Cfrom the surface to the center of the limestone. In addition to higher temperatures,there is often a longer calcining time for larger fractions of limestone. The variationof the calcining time with respect to the temperature and radius is shown in figure3 [5].


Figure 3: The variation in calcining time with temperature and lump diameter. a.)150 mm, b.) 125 mm, c.) 100 mm, d.) 75 mm and e.) 50 mm.

The dissociation of calcitic limestone, illustrated in figure 4 [5], can be summa-rized as:

(a) Heat is transferred from the hot ambient to the surface of the limestone

(b) Heat is conducted through the decomposed layer into material, which is yet tobe dissociated.

(c) CaCO3 dissociates into CaO and CO2.

(d) CO2 migrates from the inside of the limestone through the decomposed layer.

(e) CO2 migrates from the surface limestone.


Figure 4: A schematic of the calcination process of high calcium limestone.

The processes (a), (b) and (c) are well known as they are relatively straight for-ward. However, (d) and (e) are more complex as the properties of the decomposedlayers will change due to sintering of CaO, slagging of the surface and absorptionof sulfur dioxide [2, 5].

The following list roughly rates the most important factors of limestone calcina-tion [2, 5].

1. Characteristics of the limestone.

2. Particle size distribution.

3. Shape of particles.

4. Temperature profile of the calcining zone.

5. Rate of heat exchange between the gases and the particles.

Because different limestone types have slightly different properties, each typemust be properly investigated. The optimum temperature cycle may vary betweentypes, whereas it is important to characterize the limestone type properties individ-ually, with respect to the optimal calcining temperature cycle. The heating cyclehave great impact on lime quality, shrinkage and reactivity. Experiments have shownthat a gradual increase of temperature, rather than shock heating, gives the bestquicklime quality. However, little is investigated in this area and perhaps even bet-ter quicklime could be produced with better understanding of the impact of thetemperature cycle [5].


4.2.5 Sintering of high calcium quicklime

One process that may disturb the calcining process is sintering. When high cal-cium limestone is heated, the volume increases due to thermal expansion. At, andabove, the calcining temperature small crystals of CaO are formed. This processproceeds until the whole limestone has been converted into CaO, which consists ofseveral small crystals at this point. This leads to an extremely large surface area,and therefore highly reactive quicklime, due to the large amount of small crystals.When the furnace temperature is higher than the calcining temperature, these smallcrystals starts to unitize and larger crystals are formed. This leads to shrinkage ofthe material due to the settle up of the CaO-crystals. Another effect of to highcalcining temperature is when the surface of the material has been severed sinteredit may disrupt the continuous dissociation of limestone core, and stops it. Whenthis happens, so called dead burned quicklime is formed. On the other hand, thesintering process that occurs after completion of the calcination is very common anduseful. Soft, medium and hard burnt quicklime are common products, and refers tothe level of sintering of the material. Soft burnt quicklime is very reactive but maycontain small amounts of CaCO3, as the calcination process was stopped to ensuresmall crystal sizes in the material. Therefore a full calcination of the core has to besacrificed. Hard burnt lime has a high CaO-content but is not as reactive as softburnt quicklime due smaller total surface area because of fewer grains. What typeof quicklime is requested depends on the buyer’s processes. Some processes requirehighly reactive lime, while others require not so reactive lime [2].


4.3 Production of quicklime

4.3.1 Shaft kiln

The shaft kiln, figure 5 [6], is a vertical furnace, in which the limestone is insertedfrom the top, and passes down through the kiln during the process. The top of thekiln works as a preheating stage where the limestone is heated and partly calcined.This is due to the hot exhaust gases created by the calcining burners. In the middleof the kiln, the calcining zone is found. The limestone is heated with a flame, whichis led into the limestone through pipes. The bottom of the kiln is the cooling area.Cooled air is blown into the kiln, which help cooling the limestone. The air is thenheated in the calcining zone and travels upwards in the kiln and helps preheatingthe incoming limestone.

Figure 5: Schematic of shaft kiln.

A typical shaft kiln is about 30 meters high and has a diameter of 2 to 7 me-ters. Firebricks build up the walls, which have a thickness of about 400 mm. Themost common shaft kiln has two shafts connected to each other, called parallel flowregenerative (PFR), to acquire as high efficiency as possible. The idea is to let hot


exhaust gases travel through as much limestone as possible before leaving the fur-nace, figure 6. As there are two shafts in a PFR, the hot exhaust gases from theactive shaft are used to heat the limestone in the passive shaft. In the next cycle, theactive and passive shaft shifts. This solution makes the shaft kiln the most efficientlimekiln today. The down side is that a maximum temperature in the furnace isabout 1000◦C, due to the thick limestone mass. The ”low” temperature implies toa high sulphur content in the quicklime as the temperature is to low for formationof SO2. This fact reduces the number of possible users, e.g. stainless steel produc-ers. On the other hand, the low temperature leads to a low level of sintering andtherefore highly reactive quicklime is obtained. The production capacity of modernPFR shaft kilns is about 100 to 600 tones per day. Today the shaft kiln is the mostcommon lime-burning furnace, mainly because of the high efficiency. The efficiencyof a PFR shaft kiln is about 80 % [7], and the consumed heat is about 4 MJ per kgquicklime [2, 6].

Figure 6: The heat flow in a PFR shaft kiln.


4.3.2 Rotary kiln

The rotary kiln, figure 7, is the other major type of lime-burning furnaces. It wasinvented in the beginning of the 20th century, and at that time the rotary kilnwas superior all other kilns. The reason to the success was because wider range oflimestone fractions could be calcined, from very fine fractions and upwards. Anotheradvantage of the rotary kiln was the possibility to remove sulphur from the quicklime.Quicklime is used in the metallurgical process as a slag remover. If high levels ofsulphur contaminate the stainless steel, the corrosion resistance is affected as thesulphur makes passivation of the steel surface difficult [8]. The reason that sulphurcan be removed is because of the high operating temperatures, which is possible toachieve in the kiln. At these temperatures, sulphur complexes dissociate and leavethe limestone as sulphur dioxide is transported out of the kiln with the exhaustgases. A typical rotary kiln produces about 1000 tones of quicklime per day.

The theoretical heat requirement for dissociation of CaCO3 is about 3,15 MJper kg of lime. The rotary kiln consumes about 8 MJ per kg of lime, which givesan approximate efficiency of 40 % [7]. The burners is often of flexible fuel type, i.e.gas, coal, oil or waste can be burnt individually or simultaneously. The power of theburner is decided by the heat exchange of the fuel that is burnt, but has an averagepower of 50 to 100 MW [7].

In contrast to shaft kilns, the rotary kiln has a much higher operating costs.This is mainly due to the higher fuel cost due to poor heat exchange. Some modernrotary kilns have a pre-heating system that uses the heat from the exhaust gases toheat the limestone before it enters the kiln. The loss of heat in the rotary kiln systemis another problem. The shell is built up of firebricks and a thin steel mantle, whichhave the combined thickness of about 250 mm. There are rotary kilns of all sizes,longer with smaller diameter as well as shorter with greater diameter. A modernkiln is about 100 m long with a diameter and about 4-5 meters. The weight variesbetween models, but is often greater than 1000 tonnes. The rotary kiln also has asmall gradient, which is needed for transportation of limestone through the kiln.

Rotary kilns have a few support points, called riding rings, which also are thepoints where the rotating motion is created. The rotating motion is needed to movethe limestone through the kiln during the process. The length of the kiln decidesthe number of support points that are needed. Riding rings are machined to obtainas smooth surface as possible. This is to ensure that the friction is low betweenthe riding rings and the kiln. The rotation speed of the kiln is typically 4 to 5 rpmand a drive gear creates the motion. To start the rotating motion a strong electricengine, of about 800 kW, is used. The engine has a variable speed drive, which isneeded, as the rotation speed of the kiln is proportional to the flow of lime troughthe furnace.

These days the rotary kiln is the standard furnace type in many applications,not only for lime burning. Other products made by rotary kilns are; cement, ironore pellets, alumina silicate, titan dioxide, vermiculite. Rotary kilns are also usedfor roasting sulfide ores [2, 9].


Figure 7: Schematic figure of a typical rotary kiln. The limestone is transportedthrough the kiln due to the rotating motion and the small gradient of the kiln.

4.3.3 Distribution of kiln types

Because of the higher efficiency of PFR-kilns, they have become the most commonkiln type, figure 8 [10]. In China, which is the largest lime producing country, thereare lots of unknown types of limekilns. This is due to many locally constructedkilns and a rapid expansion of the lime industry within China. In Japan, severalsmaller alternative limekilns have been developed during the past years, mainly forexperimental work [7, 10].

Figure 8: Chart showing the distribution of limekilns used in the world.

4.3.4 Environmental aspects of lime burning

During the calcining process, a lot of greenhouse gases are emitted, especially nitrousgases and carbon dioxide. The chemical process itself gives rise to carbon dioxide,which constitute about half the mass of CaCO3. This part of the CO2-emissionshould not be calculated as a true emission of carbon dioxide as CaO want toconvert into CaCO3 again, and for this process CO2 is needed.


During the process of making quicklime, a large amount of CO2 is created. Theindustry is responsible for almost 2% of the global CO2 emissions. Up to 40% ofthese emissions is derived from the fuel, burnt in the process. The total sum ofthe emitted CO2 by mankind is about 29 billion tons per year. Up to about 220million tons are directly derived from the usage of fossil fuels [5], figure 9. The globalwarming rate is estimated to about 0.2◦C every 10 year, and during the 20th centurythe mean temperature in Europe have risen about 0.95◦C. Reports are showing thatin about 100 years the mean temperature will rise about 2.0 - 6.3◦C, due to globalwarming [11]. However, this is lively debated and some scientists claims that theglobal mean temperature actually are decreasing.

Figure 9: Distribution of CO2-emissions within the lime industry (in million tonnes).

4.4 Slaked lime

Slaked lime consists of calcium hydroxide (Ca(OH)2) and is obtained when CaOreacts with water in an exothermal reaction; see reaction 5. Slaked lime is oftenused for several lime products consisting Ca(OH)2 such as hydrated lime, milk oflime and lime putty. In this section, only hydrated lime will be considered. Theother products are basically variations of the hydrated lime.

At temperatures lower than 350◦C, CaO reacts with water, and heat is released.About 276 kcal/kg of CaO have been reported for this process [2]. However, if thetemperature exceeds 350◦C, the counter-reaction occurs.

CaO56.1g

+ H2O18g

! Ca(OH)2

74.1g

+ Heat (5)


For dolomitic lime, with high magnesium content, the process is done slightlydifferent. The reaction is similar to the reaction of CaO and water; see reaction 6,although under steam pressure at temperatures above 100◦C. The released heat hasbeen reported to 211 kcal/kg of CaO [2].

MgO · CaO96.4g

+ 2(H2O)36g

! Ca(OH)2 · Mg(OH)2

132.4g

+ Heat (6)

An interesting thing to notice is the low solubility of Ca(OH)2 in water, whichis 1.28 g/l at 50◦C and 0.71 g/l at 100◦C. Magnesium hydroxide hardly solute inwater, only 0.01 g/l has been reported [2].

4.5 Largest quicklime producing countries

In 2009, the world production of lime was estimated to about 280 million tonnes.This was a decrease in production from 2008 with about 5 %, due to the world widefinancial crisis. However, the price of quicklime continued to increase, which it hasdone every year. In 2009, the quicklime price increased with about $11 per ton to $101 per ton. The increasing price is mainly because of increasing production costs.Earlier years the increasing fuel costs, and taxes, strongly influenced the price ofquicklime. In 2009, the fuel prices decreased dramatically but the lime companiesstill struggled with increasing production costs. China is today, by far, the largestlime-producing country in the world with more than 50 % of the total production,see figure 10 [12].


Figure 10: Countries with 90 % of the total world lime production (in milliontonnes).

4.6 Uses of quicklime

Quicklime is one of the most versatile chemicals known to man and the areas of useare almost countless. It is also one of the largest chemical industries in the world[4].

The areas that consume the most tonnage of lime will be presented in this section,but remember that there are other areas of use as well. Many areas of use may noteven have seen the light of the day at this point.

4.6.1 Agriculture

Agricultural lime, mostly slaked lime, is mainly used to neutralize the pH-value ofsoil to improve vegetation. It also improves the stability of the soil by decreasingcrusting of the surface and therefore reducing soil erosion. Another effect is thatthe water penetration, of the soil, is improved. Other important minerals, such asmagnesium, phosphorous, nitrogen and potassium, can be added to the agriculturallime to improve the fertility of the soil. If the soil has high levels of iron andaluminum, the lime helps to neutralize those elements. Agricultural lime can alsobe used to prevent spreading of diseases among plants and animals. By increasingthe pH-value of the treated soil, spreading of bacteria is prevented [2, 13].


4.6.2 Glass

Soda-Lime glass is one of the most common types of glass. It is mostly used forglass containers, such as coca cola bottles, and windowpanes. The glass is madeby melting and mixing of quicklime, limestone, sodium carbonate, silicon dioxide,aluminum dioxide, and fining agents at a temperature of about 1700◦C. For glasscontainers, limestone is mainly used, but for windowpanes high calcium quicklimeis used. This is because high calcium quicklime improves the transparency of theglass within the wavelengths of visual light [2, 13].

4.6.3 Metal refining

Quicklime is a very important ingredient when refining non-ferrous metal ores. Thequicklime controls the pH value of the solution and acts depressant that is neces-sary to extract pure metals, such as gold, silver and nickel from cyanide extraction.Quicklime also enables copper pyrites (Cu2S) to be separated from arsenopyrite(As2S5).

When producing magnesium, dolomitic quicklime is used to reduce magnesium ox-ide with ferrosilicon (FeSi). The process takes place at temperatures above 1200◦Cand at low pressures, about 13 to 670 KPa. When the magnesium oxide has beenreduced, gaseous magnesium is obtained that condensates at about 450◦C.

2CaO + 2MgO + Si → 2Mg + Ca2SiO4 (7)

Pure calcium is another metal that is produced by thermal reduction. Highcalcium quicklime is mixed with aluminum, and heated to about 1200◦ at about 0,1Pa.

3CaO + 2Al → Al2O3 + Ca (8)

Mercury is produced by a similar process and the mineral that is used is cinnabarite(HgS). Cinnabarite is reduced in presence of oxygen, but can be reduced in absenceof oxygen as well, see reaction 9 and reaction 10. There are two ways of reducingcinnabarite, with or without presence of oxygen. Both processes take place at about300◦C [2, 13].

4HgS + 4CaO → 3CaS + CaSO4 + 4Hg (9)

HgS + CaO + 1, 5O2 → CaSO4 + Hg (10)


4.6.4 Pulp and Paper

In the paper industry, slaked lime is used in the sulfate process or the Kraft-processas it is called. In this process, wood is converted into wood pulp that consistsmostly of cellulose fibers. Kraft is called ”black liquor” and is dehydrated and burntto produce a mix of sodium carbonate and sodium sulfide. This smelt is then mixedwith slaked lime, which has a caustic effect, and calcium carbonate and sodiumhydroxide liquor is obtained. The calcium carbonate is filtered from the solutionand is later re-calcined in a kiln and can therefore be recycled. The same impliesfor the sodium hydroxide. About 250 kg of slaked lime is used in this process.

A lot of slaked lime was earlier used in the sulfite pulp process as well, but hasnow been exchanged for other alkalis that are easier to handle than lime products[2].

4.6.5 Caustic soda

Slaked lime and soda ash converts into caustic soda and calcium carbonate, whenmixed. Caustic soda is an essential ingredient in many products such as soap anddetergents, bleach, aluminum, petroleum products and in several chemical processes[13].

4.6.6 Soil stabilization

Quicklime and slaked lime are commonly used at building sites to dry wet soil andincrease the stability of the ground. This is necessary when heavy machinery is usedat these sites. By stabilizing the soil, building time is reduced and money is saved.

The soil is stabilized because quicklime modifies clay, due to the exchange ofcations from the calcium and the minerals the clay consists of. The result is swelling,hardening and drying of the clay.

Because both quicklime and slaked lime are relatively cheap chemicals, this areaof use has been very popular as it is very cost effective [2, 13].

4.6.7 Steelmaking

There are two different methods commonly used in steel production today, themethod of Basic Oxygen Steelmaking (BOS) or re-melting steel scrap. When pro-ducing steel with BOS, oxygen are blown through the melted pig iron to reducethe high level of coal in the melt. At the same time, quicklime is mixed into themelt. This is done to remove impurities, such as phosphor, sulphur and silica, byforming slag. Typically 30 to 50 kg CaO is used per ton produced steel. About30 to 50 % of the lime is dolomitic lime, high magnesium content, which is addedfor two reasons. First of all, magnesium oxide help produce certain slag productsthat calcium oxide is unable to elaborate. Secondly, magnesium oxide slag productsprotect the furnace, increasing refractory lining lifetime. Steel can also be producedby scrap melting. This is very common today, whereas lots of steel is recycled. The


steel-scrap is often melted in blast furnaces, and lime is once again used for impurityremoval through slag forming. The used quicklime is often in form of lumps, butsome modern steel plants uses quicklime powder as it has shown to be more effectivein modern refractories.

When producing ultra pure steel, a secondary refining is often necessary. In thisproduction step, quicklime is used for further impurity removal, but also to adjustthe temperature and the chemistry of the steel-melt [14, 15].

4.6.8 Sugar

Sugar can be produced from either sugarcanes or sugar beets. When using sugar-canes, slaked lime is used in both the production and refining of the sugar. Whenthe canes are harvested they are treated with water, which lowers the pH to about4 to 5. Slaked lime is added to raise the pH, which is needed to destroy enzymes,e.g. invertase. Further on, slaked lime is also used to remove inorganic and organiccompounds by forming insoluble calcium salts. These salts are then filtered fromthe solution.

When producing sugar from sugar beets, quicklime is used instead of slaked lime.The sugar beet is washed in hot water to extract the sugar, which also contains col-loidal, suspended and dissolved compounds. At this point the extract is treatedwith quicklime to raise pH and to create deposits of calcium salts and ”carbonationsludge” that are filtered from the solution.

When producing sugar from canes, about 3 kg of slaked lime is used to produce1 ton of sugar. Sugar from sugar beets requires about 200 kg of quicklime per tonproduced sugar. The latter industry often has its own quicklime production closeto the sugar refinery [2, 13].

4.6.9 Water treatment

Lime is essential in water treatment. In municipal wastewater treatment, lime isused to remove nitrogen and phosphor. This is because of the high pH caused bylime. The result is that nitrogen and phosphor are precipitated and can be removedfrom the wastewater. Due to this, algae growth can be prevented. Lime also acts asa filter, in which sludge is removed. In industrial water treatment, lime is used toneutralize acids and to remove heavy metals by precipitation. For drinking watertreatment, lime is used for softening, pH adjustment, removal of impurities (e.g.arsenic) and to kill bacteria and viruses. The latter is done by raising the pH of thewater to about 11 for about 1 to 3 days [2, 13].


4.6.10 Flue gas desulphuration

When fossil fuels and waste are burnt, sulphur dioxide (SO2) is formed. SO2 isresponsible for the formation of acid rain, which affects the environment negativelydue to acidifying of lakes and grounds. Use of lime prevents large emissions of SO2.Exhaust gases, which consist partly of SO2 is filtered through lime and calciumsulfite (CaSO3). This can be achieved through wet or dry filtering. Wet filtering ofSO2 is done by using slaked lime, reaction 11, and dry filtering, reaction 12, by usingquicklime. The resulting product, CaSO3, is commonly used as a preservative. It isalso used to produce gypsum, which is done by adding water and oxygen to CaSO3,see reaction 13. Then the solution is dried and gypsum plates are formed, which areused in constructions etc [2].

SO2 + Ca(OH)2 → CaSO3 + H2O (11)

SO2 + CaO → CaSO3 (12)

2CaSO3 + 4H2O + O2 → 2(CaSO4 · H2O) (13)


5 Research and Development

5.1 Solar reactors for quicklime production

Anton Meier, doctor at the Solar Technology Laboratory at the Paul Scherrer In-stitute, has during the last years been working, together with his team, on a solarreactor for quicklime production. The idea is to use mirrors to concentrate solarbeams to calcine limestone. This would generate highly pure quicklime for specialsectors, such as the chemical and pharmaceutical industry because no exhaust gasesare polluting the end product. However, this is true for any indirect heated limekiln.Another advantage is the huge reduction of emitted CO2. This solution is entirelyCO2-free, in contrast to conventional limekilns that emit about 2 % of the totalglobal emissions. A solar lime reactor plant would therefore be able to reduce emis-sions up to 20 %. The fraction of limestone that the group focused on is in the rangeof 1 to 5 mm, and results showed that over 98% of the limestone were calcined. Thiswas done in a laboratory kiln of about 10 kW, which managed to produce about15 tones per day. Concentrated solar beams were not used in the experiment, butsilicon carbide (SiC) elements from Kanthal AB, figure 11. The heat source itselfdoes not influence the resulting quicklime, and therefore electric heating was usedto produce reference samples of quicklime [1, 16].

Figure 11: SiC element from Kanthal AB was used to produce reference quicklime.

For industrial use A. Meier et. al., proposed three different solutions for solarbeam lime burning [1, 16]. All of these solutions use mirrors to concentrate thesolar beams, but some minor differences were introduced as all of them had theiradvantaged. The ”Top Tower” (TT), figure 12a, uses heliostat mirrors to focus thesolar beam into the reactor, which is located in the top of a tower. The ”Beam down”(BD), figure 12b, is very similar but instead of having the reactor in the top of thetower, it is located in the bottom. In the top of the tower, a parabolic concentratoris mounted that collects the solar beams from the heliostat mirrors and focus thebeam into the reactor. The reason for having two solutions is because of how muchareal available at a certain location. The TT-solution may be the best solution if theareal is limited, although as the reactor is located in the top of the tower handling


of the quicklime is an issue. The BT-solution makes quicklime handling easier, buttends to be more expensive due to the extra parabolic concentrator [1, 16].

Figure 12: a.) Illustration of a tower top system (TT), b.) Illustration of a beamdown system (BD).

The third solution, figure 13, is supposed to be applied at areas that are moun-tainous or where land area is limited. Heliostat mirrors are mounted on a southfacing hill, natural of artificial, and the solar beams are concentrated into a verticallime reactor [1, 16].


Figure 13: Illustration of a mountainside mounted solar lime plant.

A disadvantage of this lime burning solution is the geographic areas, figure 14,where it can be applied, as the minimum solar insolation is 2000 kWh/m2. Solarbeam produced lime have higher production costs than conventional lime, due tomore expensive production equipment. The capacity of the plants is calculated toabout 50 tones per day, which is notably less than a conventional kiln such as theshaft kiln. This leads to a cost of about $ 128 per ton to $ 157 per ton, for solarbeam produced lime. The selling price for conventional lime is about $ 100 per ton,about 1 to 1.5 times less than solar produced lime. However, solar produced limehas far greater purity and therefore may be interesting in special sectors such as thepharmaceutical industry [1, 16].

Figure 14: Regions with annual solar irradiation of at least 2000 kWh/m2.


5.2 Indirect fired limekiln

At the international lime association congress in 2002, H.E. Willis of MerichemCompany, USA presented an idea of an indirect fired limekiln [17]. He had beensketching on a horizontal limekiln, consisting of a ceramic tube, in which a ceramicscrew was inserted. The screw was supposed to rotate slowly, and therefore movethe limestone through the kiln while being calcined, see figure 15 [17]. The kiln issupposed to have three main advantages over conventional limekilns:

1. Possibility to calcine very fine limestone lumps and powder.

2. CO2 decomposed from the calcination can be separated from exhaust gasses,and be recovered.

3. Any heat source can be used.

Figure 15: Schematic view of the indirect fired limekiln.

H.E Willis, Yoshizawa lime industry, JP Steel Plantech and Haldenwanger startedcollaboration and a prototype kiln was constructed. The prototype was of semi-industrialized size and was finished in 2003. The total length of the kiln was 5.4m, in which the ceramic tube, consisting of six sections, with length of 0.9 m anddiameter of 0.3 m, was mounted. Inside the ceramic tube, the ceramic screw wasinserted. In figure 16, a cross section sketch of the prototype can be observed. Earlyin the project they were able to produce quicklime with quality equal to conven-tional quicklime. However, some problems occurred. The limestone had ambienttemperature when entered the kiln. This caused thermal stress to the first ceramictubes, which broke. There was not enough room for a limestone pre-heater so thesolution was to change the first two ceramic tubes to metallic tubes. Further testingshowed that the prototype were able to calcine very fine limestone powder with goodresults. This cannot be done in conventional limekilns today. However, fine limepowder tended to aggregate and adhered to the ceramic screw. This caused therotation torque to increase and less limestone could be calcined due to less space inthe kiln. The result was that the calcination capacity of the kiln decreased from 150kg per hour, to about 100 to 120 kg per hour [17].


Figure 16: Cross sectional view of the indirect fired limekiln.

The conclusion was that the indirect limekiln prototype is very successful. Fur-ther work is to be carried out with a goal to commercialize the prototype kiln. Theceramic tube is very sensitive to thermal stress whereas other materials were con-sidered, such as aluminum oxide, which can withstand higher temperatures. Thiswould also open for other high temperature applications, such as high temperaturetreatment of inorganic materials etc [17].

5.3 Energy source outlook

5.3.1 Fossil fuels

Fossil fuels have been the major energy source the last centuries, but now new energysources must be invented. There are two major reasons for this, the environmentalimpact and the fact that oil fields and natural gas resources are starting to peter.Coal findings, however, do not show signs of declination [18]. Fossil fuels havelately become the topic of conversation all over the world, due to the environmentalaspects. The majority of emitted CO2 originates from burning of fossil fuels, andscientists claims that this is one of the reasons why the temperature of the earthis rising. One attempt to reduce the use of fossil fuels has been to introduce theCO2-tax, where companies, which emit large amounts of CO2, have to pay a certainfee. However, companies have been allocated a certain amount of CO2 that theycan emit without being charged with any taxes. Companies, which have reducedtheir emissions, can sell emission rights to other companies that have exceededtheir amount of allocated CO2. Due to this, these companies gets lower CO2-tax.However, every year the allocated amount of ”free” CO2 is reduced and the CO2-tax increases [19]. The reason for this system is to force the companies that usefossil fuels, as their main energy source, to find other more environmentally friendlysolutions. However, the associates of the lime industry claims that the processes


used today are as optimal as they can be. The emissions can only be reduced about10 %, but this would cost a lot [20].

5.3.2 Renewable energy sources and Nuclear energy

Renewable energy sources, such as wind, solar, wave, and hydroelectric power havebeen increasing their market shares the last decades. Today, electricity from re-newable energy sources have about 15 % of the total energy market but is rapidlyincreasing 17 [21]. Nuclear energy has always been controversial due to the securityissues because of the accidents in Harrisburg 1979 and in Chernobyl 1986. Thethreat of nuclear weapons and the issue of handling of nuclear waste products havealso infected the debate around nuclear energy. The need of CO2-free energy, andthe highly effective nuclear energy have overcome many obstacles and today the de-velopment of nuclear power is very intense. New reactors are invented, which aimsat reducing the half-life of the nuclear waste from some hundred thousand years toabout 500 years [22]. Today, about 30 % of the produced electricity in the worldcomes from nuclear energy and this figure is increasing every year [21].

Figure 17: Distribution of energy sources for electricity production, within the Kyotomember countries.


6 Idea for an alternative heating solutions for lime-

burning

6.1 Background

One part of this M.Sc. thesis was to propose a prototype lime-burning kiln, using aKanthal heating system. The design, which is presented in this section, was chosenafter a company visit where a similar furnace was studied. The company, HASopor,produces foam glass for ground stabilization in a furnace where their product isapplied on a rolling hoop and is heated as the hoop slowly moves through thefurnace. Electric radiant tubes are used, beneath and over the hoop, to heat theproduct to about 900◦C.

The glass foam that HASopor produces has no resemblance with quicklime what-soever but the heating solution may be used successfully in both processes.

6.2 Kanthal APMT

Kanthal APMT (Advanced Powder Metallurgical Tube) is an alloy consisting mostlyof iron, chromium and aluminum. It offers high strength and corrosion resistance,together with a long working life. In contrast to nickel-chromium alloys, KanthalAPMT withstands higher temperatures. Kanthal APMT also offers high creep re-sistance, a property that can be derived to the high corrosion resistance. Corrosionreduces strength, due to local or general undermining of the material. Another as-pect of the creep resistance of Kanthal APMT is the linear deformation behaviorover time and temperature. The high corrosion resistance of Kanthal APMT is dueto the protective aluminum oxide (Al2O3), which is formed on the surface when thealloy is heated. This oxide is thermodynamically stable, has good adhesion to thebulk material and has a slow growth rate. The slow growth rate is important toensure a long-term protection of the material. Due to the protective oxide, KanthalAPMT can be used in troublesome environments such as high carbon atmospheresand sulphur atmospheres. Kanthal APMT is recommended in temperatures from600◦C up to 1250◦C to ensure even and good performance, however it can withstandeven higher temperatures [23].

6.3 Radiant tubes

Radiant tubes, figure 18 are extruded from a powder metallurgical (PM) base mate-rial, which gives benefits over traditional tubes, e.g. higher mechanical strength dueto dispersion strengthening. Kanthal offers two PM materials, Kanthal APM andKanthal APMT. Kanthal APMT is a further development of Kanthal APM, withhigher strength [23].


Figure 18: Kanthal radiant tubes.

6.3.1 Tubothal

Tubothal, figure 19, is an electric heating solution from Kanthal, which offers highpower, low weight and long lifetime. The heating elements that are made from aKanthal alloy are inserted into a radiant tube. The system has an operating tem-perature interval of 600◦C to 1250◦C, and the temperature can be easily controlled.Ability to fine tune the temperature in the furnace gives Tubothal a big advantagein processes where temperature cycling is of great importance. Another advantageis that the elements can easily be replaced, without having to remove the radianttubes and therefore the process does not have to be interrupted [23].


Figure 19: Kanthal Tubothal.

6.3.2 Ecothal

The Ecothal Single-Ended Recuperative burner (SER), figure 20, was designed forhigh efficiency, reliability and low emissions. It has an efficiency of about 80 % andhas been shown to be about 10 % more effective than other commercial burners.The design of the Ecothal makes it the cleanest burner on the market, due to thewell-defined combustion. This leads to lower emissions of green house gases andlower operating costs. The high efficiency and low emissions are obtained when theexhaust gases heat the gas at the inlet, and therefore a more effective burning ofthe gases is achieved. The Ecothal is mounted into a Kanthal APMT radiant tube,and therefore the burner offers indirect heating through the radiant tube [23].


Figure 20: Kanthal Ecothal.

6.4 Prototype proposal

The prototype, figure 211, proposal that was discussed during this M.Sc. thesishas some advantages. The magnitude of the lime production can easily be decided,and the amount of power needed depends on how many radiant tubes are fittedinside the furnace. Tubothal or Ecothal heaters could be used, which gives the userthe ability to use either electricity or gas as energy source. Other Kanthal heatingsolutions may be of interest as well, but these two options seem to be the mostappropriate at the time. The throughput of lime also depends on the width of theconveyor belt, and for large quantities this may be a problem as the hoops often arearound 1 m in width. However, in such case several parallel systems may be usedto increase quicklime output. The system can also be divided into different heatingzones, as each radiant tube is individually controlled. This gives the producer theopportunity to fine-tune the optimal heating cycle for their process. The prototypeis designed for temperatures of about 900◦C to 1000◦C, as this temperature is usedin about 60 % of the conventional limekilns today. For higher temperatures, otherheating elements may be of use. However, problems with the rolling hoop may alsooccur at higher temperature as the common materials does not withstand those

1Figure by Per Kruse, Kanthal AB


temperatures.

Figure 21: Prototype sketch, using Kanthal radiant tubes.


7 Investigation of the impact of the calcination

process on Kanthal APMT

7.1 Background

If used in the lime industry, the Kanthal alloy may be exposed to highly reactivequicklime. In theory this would not happen, as the heating system would neverbe in contact with lime or limestone. However, if direct contact would occur, theheating system must not be severely damaged.

7.2 Experimental

Test samples of Kanthal APMT (Advanced Powder Metallurgical Tube), an alloyconsisting of mostly iron, chromium and aluminum, were exposed to a powder con-sisting of crushed calcitic limestone, which has high calcium content greater than 95%. The limestone powder was applied on the test samples, which then were placedinside an electric furnace for about one hour. During this hour, the limestone pow-der calcined, and quicklime was obtained. After one hour, the test samples weretaken out of the furnace, the quicklime was removed and new limestone powder wasapplied. This was repeated eight times for every test sample.

Four experiments were conducted, table 1. Two test pieces were pre-oxidizedin 1050◦C for 8 hours, to ensure that they were protected with a covering layer ofaluminum oxide when exposed to the lime. The other two test pieces were not pre-oxidized. Two different temperatures were chosen, 950◦C and 1250◦C. These twotemperatures were chosen, as they are about the same temperatures that are usedin conventional kilns. The working temperature in a shaft kiln is around 900◦C to1000◦C, and around 1200◦C to 1300◦C in a rotary kiln.

A final furnace cycling test was preformed to find out whether the alloy wouldheal if affected to lime, and form a protective aluminum oxide. The test was pre-formed in a special furnace where the samples were kept in the furnace chamber for1 hour at 1200◦C and where then kept in room temperature for 1 hour. This cyclewas all automatic, and was repeated 24 times. The total cycle time was therefore48 hours.

Table 1: Overview of the test samples and their conditions

APMT sample Temperature Pre-oxidized1 950◦C Yes2 950◦C No3 1250◦C Yes4 1250◦C No


7.3 Results

7.3.1 Visual observations

The non-oxidized samples 2 and 4 were severely affected by the calcination process,figure 22. Visual inspection of the pre-oxidized samples 1 and 3 did not show anysigns of being affected.

Figure 22: Visual observation of sample 4 after eight calcination cycles.

7.3.2 Light Optic Microscopy

Using a Leica stereomicroscope, it could be seen that the non-oxidized samples 2and 4 were affected by the calcination, figure 23. Sample 2 was less affected thansample 4, probably due to lower temperature during the calcination.

(a) Sample 2 (b) Sample 4

Figure 23: Close-up on the damaged areas of sample 2 and sample 4.


7.3.3 Scanning Electron Microscopy

The pre-oxidized samples, 1 and 3, did not show any signs of being affected even atvery high resolutions, when examined with the Zeiss Scanning Electron Microscope(SEM). The protective aluminum oxide was all there, and no aluminum nitrides hadbeen formed. The lighter areas, figure 24, were identified as aluminum oxide, usingEnergy-Dispersive x-ray Spectroscopy (EDS).

Figure 24: SEM-picture showing lighter and darker areas of aluminum oxide onsample 1.

The non-oxidized sample 4 was also examined. EDS-analysis identified the com-position of the damages areas as aluminum oxide, iron oxide, chromium oxide andbulk alloy, figure 25.


Figure 25: The surface of sample 4. 1.) Iron oxide, 2.) Bulk alloy, 3.) Chromiumoxide, 4.) Aluminium oxide.

Cross-sectional analysis of the pre-oxidized samples 1 and 3 did not show anysigns of influence of the calcination, while in the non-oxidized samples 2 and 4,aluminum nitrides were found, figure 26. The number of aluminum nitrides insample 4 was far greater than in sample 2.


Figure 26: Cross-sectional view, showing aluminum nitrides under the surface ofsample 4.

7.3.4 Summary

The results of the experimental work are summarized in table 2. The importance ofpre-oxidation of the alloy is clearly noticed.

Table 2: Overview of the results of the experimental work

Sample Temperature Pre-oxidized Iron oxides Aluminum nitrides1 950◦C Yes No No2 950◦C No Yes Yes3 1250◦C Yes No No4 1250◦C No Yes Yes


The final furnace cycling test did give a positive result. The healing effect ofKanthal APMT had rebuilt the aluminum oxide, and the samples were at this pointcovered with an aluminum oxide. No further growth of aluminum nitrides wasnoticed.


8 Discussion

8.1 Quicklime production

Future limekilns do not have to look like the kilns used today. To produce quicklime,heat is needed and only heat. However, to produce quicklime of really good qualityone has to be able to control the heat very carefully. The most suitable temperaturecycle should be investigated very carefully as the calcination of limestone is sensitiveto correct heat treatment. There are some different quicklime qualities, which havedifferent properties depending on at what temperature they have been processed.This is desirable as some customers are looking for qualities that are formed athigher temperatures, and others are looking for qualities that are formed at lowertemperatures. It is also important to minimize the energy losses in the process.Quicklime is a relatively cheap product, about $ 100 per ton, and therefore energylosses are directly affecting the profit.

8.2 The market potential

The market potential for lime products is huge. There are endless of areas wherelime is used or may be used in the future. The production has increased over theyears, and China is the main lime producing country today. The market is overheated as it is, and it is very tough to introduce a new type of limekilns, as it wouldbe too costly. The economy of the producers is not good enough to let them trynew solutions. In 2009, a lot of producers had to shut down their businesses dueto high production costs that undermined most of the profits. The use of lime inpharmaceutical areas or as a part of a biomaterial could be a future market wherenew types of kiln may flourish. In these areas the need for extremely pure lime isincreasing. The tonnages are and will be very small, but the price of the extremelypure lime is a lot higher than of conventional lime. Another view of the marketpotential is to look at the amount of consumed energy, which is about 2.4 TWh peryear based on an annual production of 280 million tonnes of lime. This gives anindication of the potential market for future electrical limekilns.

8.3 Energy sources and environmental aspects

The debate on future energy sources and environmental effects of using fossil fuelshas greatly influenced the lime industry, as it is one of the largest users of fossilfuel and therefore one of the largest emitters of CO2. The CO2-tax was introducedin Europe as a result of the Kyoto protocol, which aims to lower the emissions ofgreen house gases such as CO2. This was also the beginning of the emission tradingexperiment. The cost of exceeding the amount of emitted CO2 was about 40 Europer ton CO2

2. If one plays with the thought that all no allocations were given

2According to the Swedish environmental protection agency, 2006


to the lime companies, their total amount of about 560 million tonnes of emittedCO2 would be charged for. In such a case, with the above-mentioned CO2-tax fee,about 22,5 billion Euros would be the final fine. This is more than the total profitfor all produced quicklime in the world. The industry would not survive such ascenario. However, this is not going to be realized but is an indicator of how brittlethe industry is. The natural step to take is to move towards ”green” energy in thisindustry as well. The world is seeing a big expansion of renewable energy sourcesand even in the nuclear power sector, which will provide CO2-free energy in thefuture. However, producing electricity from fossil fuels is still the major source inproduction of electricity and will probably be in the near future. If renewable energyand nuclear power will be the main energy sources in 50 to 100 years nobody knows,but it is a time of change so it is not impossible as reports are showing decreasingoil and gas production and increasing development of ”green” energy.

8.4 Effects of limestone calcination on Kanthal APMT

The radiant tubes in the prototype will not be in direct contact with limestoneduring the calcining process, although the experimental work showed the outcome ifthis would occur. The pre-oxidized APMT samples showed good resistance againstthe quicklime, which is very good as the radiant tubes are always delivered in thisstate. However, the oxide may spall off and in such case the bulk material wouldnot be protected. A non pre-oxidized APMT sample that had been in direct contactwith limestone, during eight calcination cycles, was severely affected. Brown-orangepoints could be seen where the quicklime had been lying. These dots were identifiedas iron oxide (Fe2O3). This oxide is porous and has not the protective properties,which aluminum oxide has, and therefore this was not very good from a materialperspective. SEM-analysis discovered aluminum nitrides beneath the iron oxide,which partly explains why no aluminum oxide had been formed. It is also interestingto notice that even though the non pre-oxidized samples were severe affected by lime,they were able to heal when not exposed to lime. These results are interesting, but tofurther investigate the effects of limestone calcination on APMT more experimentsare needed. For example, the APMT samples must be exposed to lime during thecalcination process for a longer time.

8.5 The alternative limekiln prototype

The limekiln prototype, which is proposed in this report, has some advantages anddisadvantages. First of all, the prototype will be able to be used whatever the sizeof the lime production. It is just a matter of how many radiant tubes that are fittedinside the kiln. This makes the kiln very versatile, and a growing lime companycould easily expand their furnace. However, this is only in theory. Today it is tooexpensive to produce conventional lime, e.g. for the steel industry, in this way. Thefurnace may be suitable for lime companies that focus on special areas such as the


pharmaceutical market. The fact that the kiln could be driven with both Tubothaland Ecothal makes it even more versatile. In areas where natural gas is cheap, theEcothal solution may be more preferable. However, this is not the most environ-mentally friendly solution, which would be the Tubothal fed with ”green” energy,but the most environmentally friendly when it comes to gas solutions. The width ofthe rolling hoop is a disadvantage as it is often not more than about 1 m. To walkaround this problem several prototypes could be installed side by side.

8.6 Other proposed prototypes

There are several other prototypes, which have been developed at research institutesand at lime companies. Their purposes are to find alternative ways to produce lime,and to be able to produce purer lime. In this report two prototypes, which arevery interesting, have been presented. The solar reactor has been shown to bevery successful, in theory. However, this solution could be usable for larger limeproductions, as very large land area would be used. For applications, which requiresmaller amounts of lime than e.g. the steel industry, this method may be successfullyused. Another drawback is that the solar reactors only can be used at some areas inthe world, where the sunlight contains enough energy. The other kiln, which usesa silicon carbide pipe with an internal silicon carbide screw, is also very interesting.Their purpose is the same as for the prototype proposed in this report. They do notsay anything about a specific heat source, and Kanthal elements may be suitable.The kiln had a drawback with limestone sticking to the screw and with thermalinduced stresses in the tube, but a part from that it is a very good solution. Both ofthese prototypes are interesting models, and will hopefully be noticed by associatesof the lime industry.


9 Conclusions

The purpose of this M.Sc. thesis was to find out whether the lime industry isa potential business area for Kanthal or not. Twenty weeks have passed since theinvestigation started, and a lot of information has been gathered. However, a straightanswer cannot be given because it depends on where in the lime industry the focuslies. If Kanthal wants to focus on the large producers and short-term profits, itis probably not a potential business area today. It is simply too expensive for theproducers to change their furnaces and to use electricity as energy source. If Kanthaldecides to focus on smaller areas, such as the special chemical industry that providethe pharmaceutical industry with lime, it could very much be a potential businessarea for Kanthal in the future. However, this would probably not generate profit forsome time, as the focus would be at experimental setups in the beginning. Due tothe complexity of the lime industry, a suggestion is that Kanthal should:

• Focus on small scaled lime production for special areas of lime, such as thepharmaceutical area (5 - 10 years)

• Extend the presence in the lime industry by starting to look at more conven-tional lime products (10 - 20 years)

• Develop a full-scaled lime kiln that has the potential of becoming the newconventional lime kiln (20 - 40 years)

To start with, Kanthal has to make business contacts within the lime industry,preferably at lime conferences held by lime associations such as European LimeAssociation (ELA), International Lime Association (ILA) or Svenska Kalkinstitutet.This is probably the best way to integrate with the lime industry and to find outwhat is going on in the industry.


10 Future work

During this investigation, some additional business areas have been found. If theseareas could be improved with help from Kanthal, they would most certainly generateprofit in shorter terms than an introduction of Kanthal in the lime industry woulddo.

10.1 Porcupine heating cassettes as pre-heaters in cement

production

Producing cement has little resemblance with lime production, aside from rotarykilns as clinker burners. Clinker is a product, which is obtained when limestone andclay are heated to temperatures around 1450◦C. Then the clinker is crushed andgypsum is added to form cement. In this process, exhaust gases from the furnaceprocess is used to heat ingoing material in a pre-heating tower. This tower consistsof some stages, so called cyclones, in which the limestone clay is heated in differentsteps. When the clinker burners are using fuel with low energy value, for examplesome biogases, a separate burner is needed to add heat to the pre-heating process.Instead adding a separate burner, a Kanthal porcupine heating cassette may beuseful. The porcupine works like a large hair dryer, which heats air to about 900◦C.It is a very versatile product, which can be built after the customer’s demands.

10.2 Alloys as construction material in lime and cement fa-

cilities

Rotary kilns for cement production uses a cooling system to cool the clinker andthe gases in the end of the production lime. The gases are led from the kiln througha cooling system before it is used in the pre-heating system. These gases are hotand contain a lot of corrosive elements such as sulphur. Kanthal alloys have goodresistance to sulphur attacks due to the protective aluminum oxide, and may beuseful as construction material in a cement facility.

10.3 Lance tubes for quicklime shaft kilns

In shaft kilns the heat source is several flames, which comes from so-called lace tubes,figure 27 [10]. In these lances, fuel (often oil) is transported into the kiln and ignitesin the nozzle of the lances. As the lances are in direct contact of limestone, someproblems occur. First of all, the lance tubes are exposed to a lot of wear as they arein direct contact to limestone that continuously flows through the kiln. However, inmodern shaft kilns the lances are often protected to minimize wear. Secondly, theenvironment inside is crude. Quicklime is very reactive and attacks the material ofthe lance tubes. In this harsh environment, Kanthal alloys may be useful.


Figure 27: Lance tubes in a shaft kiln


11 Acknowledgments

First of all I would like to thank Kanthal AB for giving me the opportunity towork with this project. I would like to thank my supervisor, Gustaf Lorenzson, whoassisted me in my work from day one. Your positive attitude to the progress ofmy work has been very encouraging. I would also like to thank Fernando Rave forshowing great interest in my work and providing assistance whenever I needed it.During my work, I have met many friendly people as well that assisted me. I wouldlike to thank you all for making my time at Kanthal memorable and pleasant.

Beside Kanthal AB, I would like to thank Nordkalk and SMA Mineral for helpingme understand the lime industry and the processes involved by patient answer myquestions and showing me the conventional production methods used today.


References

[1] A. Meier, N. Gremaud, and A. Steinfeld, “Economic evaluation of the industrialsolar production of lime,” Energy Conversion and Management, vol. 46, no. 6,pp. 905 – 926, 2005.

[2] J. A. H. Oates, Lime and Limestone: Chemistry and Technology, Productionand Uses. John Wiley and Sons Inc, 1998.

[3] http://en.wikipedia.org/wiki/File:Kheops-Pyramid.jpg, 25th of february 2010at 11.02.

[4] R. S. Boynton, Chemistry and Technology of Lime and Limestone. John Wileyand Sons Inc, 1980.

[5] Y.-T. H. Lawrence K. Wang and N. K. Shammas, eds., Handbook of Environ-mental Engineering, vol. 5, ch. 14, pp. 611–633. Humana Press, 2007.

[6] http://en.wikipedia.org/wiki/Lime kiln, 25th of february 2010 at 16.53.

[7] Personal contact with Mikael Wendell at Nordkalk.

[8] Personal contact with Matti Gronvall at Nordkalk.

[9] http://en.wikipedia.org/wiki/Rotary kiln, 25th of february 2010 at 15.17.

[10] I. Quintar and M. Okuma, “High temperature project.” Sandvik report, 2009.

[11] J. Petrel, “Policies to reduce climate change impacts,” in 11th ILA-Congress,Prague, May 16-19, International Lime Association, 2006.

[12] U. G. Survey, “Mineral commodity summaries 2010.”

[13] http://www.graymont.com/applications.shtml, 25th of february 2010 at 17.57.

[14] http://www.britishlime.org/tech iron01.php, 25th of february 2010 at 18.10.

[15] http://www.lime.org/ENV02/Metal802.htm#IS, 25th of february 2010 at18.09.

[16] A. Meier, E. Bonaldi, G. M. Cella, W. Lipinski, and D. Wuillemin, “Solarchemical reactor technology for industrial production of lime,” Solar Energy,vol. 80, no. 10, pp. 1355 – 1362, 2006.

[17] K. Tsurunaga, “Progress in development of a new indirect fired lime kiln,” in11th ILA-Congress, Prague, May 16-19, 2006.

[18] K. Aleklett, “Fossil motor fules around 2050,” in Energy 2050, Stockholm, oc-tober 19-20, 2009.


[19] http://www.naturvardsverket.se/sv/Lagar-och-andra-styrmedel/Ekonomiska-styrmedel/Handel-med-utslappsratter/, 25th of february 2010 at 19.33.

[20] G. Flament and T. Schlegel, “Potential reduction of co2 emissions & associatedabatement costs in the european lime industry,” in 11th ILA-Congress, Prague,May 16-19, 2006.

[21] I. E. Agency, “Co2 emissions from fuel combustion,” 2009.

[22] M. S. Kazimi, “The future of nuclear energy,” in Energy 2050, Stockholm, 19-20october, 2009.

[23] Kanthal, “Radiant tubes and heating systems.” Product description booklet.

the lime industry, a potential business area for kanthal - diva

Documents