PRESENTED BY:R.L.S.ADITYATMBA/13-06

Man made disasters-coal fire

The term "Coal fire" refers to a burning or smoldering coal seam, coal storage pile or coal waste pile. Two major causes have been identified for coal fires:

Natural causes: coal seam or dust can be exposed by the

erosion or a subsidence event, strike by lightning or ignite by a wildfire.

Human causes: friction, electricity or oxygen can ignite coal

peat or dust during regular extraction, illegal mining, transportation.

Introduction

Coal seam locations -world

Active coal seams and coal fire mines

Anna Waste Dump, Aachen Anthracite Coal Field, Alsdorf,germany

Brennender Berg (Burning Mountain), Saarland,Germany

Smoking Hills in Canada’s Northwest Territories

Benxihu Colliery (1942) - ChinaCourrieres Coal Mine (1906) - FranceMitsubishi Hojyo Coal Mine (1914) - JapanOaks Colliery Explosion (1866) - United

KingdomDhanbad Coal Mine (1965 and1975) - India

Coal field map- India

'spontaneous combustion' means that coal can start to burn without any recognizable outer influence.

Spontaneous combustion depends, amongst others:

on coal typetemperatureavailability of oxygenexposure to surfacethickness of coal seam

Spontaneous combustion

Based on barometric pressure, underground coal fire development

Stage I: Cracks and fissures allow air to enter the ground and reach abandoned mine workings or sealed-off areas. Breathing starts as a result of changing barometric pressure and residual coal is supplied with sufficient

oxygen to ignite. The process of spontaneous combustion has begun.

Cracks and fissures

Stage II: Once sufficient draught has been created by the spreading fire, areas of exclusive in- and out-breathing develop. A continuous air circulation loop forms that enables the fire to progress steadily

DETECTION OF SPONTANEOUS COMBUSTION

Chemical Indication / Fire RatiosThe composites of gas concentration have been

suggested to assist in the interpretation of fire gases.

Some of these are as follows:Graham's ratio [C0]/402Willet's ratio CO2/[excess N2 + CO2 +

combustibles]

As a thumb rule it can be taken that• 0.4% or less indicates normal value• 0.5% ___ necessity for a thorough a checkup• 1% ____existence of heating• 2% ____ serious heating approaches active fire• 3% and above _____ action fire with certainty

CONTROL OF SPONTANEOUS COMBUSTION

three types of gases which have already been used to fight mine fires.

a) Carbon dioxide b) inert gases c)Nitrogen

Inorganic Inhibitorsmagnesium chloride, cadmium chloride &

trisodiumSealant Mica, rubber, bitumenHigh Pressure Foam

Smoking Hills in Canada’s Northwest TerritoriesCause: Auto-ignition of a lignite depositStarting date: Discovered in 1926 but probably

started burning centuries agoAmplitude: Over time the sulfur dioxide from the

smoke has acidified the tundra biome of the whole area -hundreds of hectares

Anna Waste Dump, Aachen Anthracite Coal Field, Alsdorf, germany.

•Cause: Self ignition certainly due to high pressures of a high grade coal waste dump•Starting date: 1850•Amplitude: 42 hectares

CAUSES OF DISASTER IN COAL MINE

1. Explosion

2. Roof fall

3. Fire

•presence of explosive mixture Firedamp alone Coal dust alone •suitable source of ignition

•presence of explosive mixture Firedamp alone Coal dust alone •suitable source of ignition

(I) Accidental fire(II)Spontaneous heating

(||) Spontaneous Heating:

Coal undergoes slow oxidation on exposure to air at ambient temperatures with the evolution of heat, gases and moisture.

The heat generated, if not dissipated, gives rise to an increase the temperature of the coal which in turn increases the rate of oxidation.

• The higher the inherent moisture, the higher the heating tendency.

• The lower the ash content, the higher the heating tendency.

• The higher the oxygen content in the coal, the higher the heating tendency.

Oaks Colliery explosion is the deadliest coal mine disaster in the United Kingdom after the disaster at Senghenyd Colliery. The disaster took place on 12

December 1866 at the Oaks Colliery, South Yorkshire

The Courrieres mine disaster in France, with a total death toll of 1,099, is the deadliest coal mining disaster in history. The coal mining catastrophe occurred on 10 March 1906 due to a massive

explosion sparked by an underground fire in one of the pits of the Courrieres Colliery

The Senghenydd Colliery disaster is the worst ever mining tragedy in the United Kingdom. The

disaster, also known as the Senghenydd Explosion, occurred at the Universal Colliery in Senghenydd,

Wales, on 14 October 1913

Impact on atmospheric environment Release of carbon dioxide, a greenhouse gas, is

one of the major cause to  climate change and global warming, according to the IPCC.

Coal is the largest contributor to the human-made increase of CO2 in the atmosphere.

According to Guan et al., coal fires in northern China discharge into the atmosphere each year:

490,200 t of carbon monoxide (CO), 514,700 t of sulfur dioxide (SO2), 300,000 t of nitrogen dioxide (NO2), 112,000 t of dust, as well as other harmful gases such as carbon

dioxide (CO2) and hydrogen sulfide (H2S).

Impact on soil environment

Soil moisture and air have a great impact on plant growth. Coal fires change the physico-chemical properties of soil. Yellow burned soil is omnipresent in coal fire areas

Soil becomes fragile and prone to crumbling, with very low organic matter content and only small numbers of microorganisms

Impact on human health

Coal tar is a respiratory carcinogen identified by the International Cancer Research Institution of the World Health Organization.

Arsenic contained in coal fire discharge can cause chronic intoxication with after-effects such as pigment deficiency, over-pigmentation, and skin cancer.

Coal fire mitigation

• Trench cutting and filling with incombustible materials;

• Surface sealing with soil (soil with high water-retaining capacity);

• Creation of water pools on the surface, water circulation under pressure, flooding of fire areas;

• Inert gas and/or foam infusion;• Cementing and grouting, flushing with

bentonite and/or fly ash;It was found that a 10 cm layer of bentonite

can reduce air permeation by up to 90 %.

Opencast mining- a blazing fire at the gallery mouth.

The chemicals ultimately used in Shatabdi Opencast Mine were phosphoric acid, boric acid, sodium chloride, sodium silicate, Diammonium phosphate (DAP), and silica gel in varying proportions.

1.A water admix with phosphoric acid (0.05 to 0.10 %) was sprayed onto the flames. They die down within 5 to 7 min.

DAP (0.03 to 0.1 %) was sprayed with a fog fighter. After spraying, temperatures in the debris dropped from 450 to 60 °C and below within 10 to 12 h

overlying rock strata, they fell from 250 to 80°C within fifteen to twenty days

Silica gel, a mixture of sodium silicate and DAP, was applied afterwards to form an impervious coating on the coal surface and thus reduce the risk of re-ignition.

Underground Coal Gasification

A more-controlled version of a natural coal seam fire

produces primarily hydrogen and CO2, with lesser amounts of carbon monoxide, methane, and trace amounts of other gases

syngas and can be combusted directly to produce heat

greatly reduce the impacts associated with coal mining, coal dust, and the emissions of sulfur dioxide and nitrous oxides

Groundwater Contamination- leach out into surrounding groundwater.

ConclusionIndia coal mining industry strive toward zero disaster

proper VigilanceEnvironmental tele-monitoring in fire prone areas.

Thank you