slide valve orifice chamber(좋은 자료)

Igniting Minds... Energizing Lives…Haldia Refinery

BY

A.B.PATHAK

DGM-PRODUCTION

HALDIA REFINERY


TOPICS:

1.INTRODUCTION.

2.HISTORY.

3.OPERATIONAL ASPECTS.

4.SALIENT DESIGN FEATURES.


INTRODUCTION:

1.WORK HORSE OF REFINERY.

2.FLEXIBLE IN FEED COMPOSITION.

3.CAN BE OPERATED AT DIFFERENT MODE TO MAXIMISE LPG,C3,C4,MS OR HSD.

4.MOST PROFITABLE UNIT.


Feed stocks:Vacuum gas oil (VGO)Coker gas oil (CGO)De-asphalted oil (DAO)Hydro-cracker bottomHydro-treated VGOReduced crude oil (RCO) / Long residue (LR)Vacuum residue (VR) / Short residue (SR)

Typical products:Dry gas (H2, C1, C2)LPG (C3, C4) Propylene, IsobutyleneLight cracked naphtha (LCN) (C5-150oC) GasolineHeavy cracked naphtha (HCN) (150 - 220oC) Gasoline / Diesel / Cutter

stockLight cycle oil (LCO) (220 - 370oC) Diesel / Cutter stockClarified oil (CLO) or Decant oil (DCO) Fuel oil

INTRODUCTION:


VACDIST

CRU DE

DIST

Gasoline Blending

Gasoline

Kerosene Jet fuel

Visbreaker / Coker

Diesel

STAB

LPG

Gas

Hydrocracker

HDS CCRReformate

HDSHDS

BBU Bitumen

Fuel Oil Coke

Position of FCC in Refinery

FCC


Flue Gas

Air

Products

SteamRegenerator Stripper

Reactor

Feed

Riser

Steam

Schematic of FCC


Feed

HCO

Back flush

To Main fractionator

ReactorReg-2

Reg-1

Air

Riser

To heat recovery section

Steam

Steam

Schematic of RFCC


FLOW SCHEME OF RFCC


Thermal cracking: Heating in big vessels, 1930

Activated alumina accidentally finds way to the thermal Vat

Conversion increased suddenly & significantly

Thus discovered by Eugene Houdry that Alumina was the catalyst for the extra cracking -1930

HISTORY


HISTORY Fixed bed (1936 – 1941)

• Cyclically feed and regeneration air

• Constantly changing catalyst activity

• 140,000 BPD total capacity in 1940

Moving bed (1941 – 1960)

• Continuous cracking process using Thermofor kiln Thermofor Catalytic Cracking (TCC)

• 300,000 BPD capacity by the end of World War-II


Eight companies formed a consortium “Catalytic Research Associates” (CRA) in 1938 to develop catalytic cracking process which would operate outside Houdry’s patents

Standard Oil of New Jersey (currently Exxon)Standard Oil of Indiana M.W. Kellogg Co.Anglo-Iranian Oil Co.Royal Dutch-Shell Co.The Texas Co. (Texaco)Universal Oil Products Co. (UOP) (I.G Farben) (dropped in 1940)

HISTORY

• First up flow circulating system started in May 1942• Fluid bed cracking (FCC) attained 1700 BPD capacity by

July 1942 –continues to grow till today


OPERATIONAL ASPECTS

1.TYPICAL OPERATING CONDITIONS.

2.INTERPLAY OF VARAIBLES IN FCC.

3.PRESSURE BALANCE IN CONVERTOR SECTION.

4.HEAT BALANCE IN CONVERTOR SECTION.

5.ENSURING SMOOTH CATALYST CIRCULATION.

6.ENSURING MINIMUM CATALYST LOSS.


OPERATIONAL ASPECTS TYPICAL OPERATING PARAMETERS

S.NO PARAMETER TYPICAL VALUES1 RISER OUTLET TEMPERATURE 500-520 DegC

2 REACTOR PRESSURE 1.4-2.0 Kg/cm2

3 REGENERATOR 1 PRESSURE 1.8-2.2 Kg/cm2

4 REGENERATOR 2 PRESSURE 1.1-1.4 Kg/cm2

5 RG1 DENSE TEMPERATURE 620-650 DegC

6 RG1 DILUTE TEMPERATURE 620-650 DegC

7 RG2 DENSE TEMPERATURE 720-740 DegC

8 RG2 DILUTE TEMPERATURE 730-750 DegC


OPERATIONAL ASPECTS TYPICAL YIELD PATTERN

Product Yield, wt%Dry gas 6.5

4025104

6.5

4 2LPG 18 10Gasoline (C5-150oC) 41 30TCO (150-370oC) 26 44CLO ( 370oC+ ) 6 10Coke 5 4

MODE LPG MS HSD


OPERATIONAL ASPECTS

Independent Feed rateRecycle ratioFeed preheatRiser Outlet temperatureReactor pressureFresh catalyst activity / Selectivity/make up rate

Major dependentRegenerator temperatureCatalyst circulation rate Regenerator air flowCRC-Coke on Regenerated catalyst Product yields

INTERPLAY OF VARIABLES IN FCC


OPERATIONAL ASPECTS PRESSURE BALANCE

VERY CRITICAL FOR SAFETY OF THE UNIT-HYDROCARBON AND AIR ARE SIDE BY SIDE .

ALSO VERY IMPORTANT FOR SMOOTH AND STEADY CATALYST CIRCULATION.

NEW UNITS ARE PROVIDED WITH VALVES IN BETWEEN REACTOR AND REGENERATOR AND SAFETY INTERLOCK TO CLOSE THE VALVE WHEN THE PRESSURE BALNCE IS UPSET.

CATALYST FLOW IS FROM A VESSEL OF LOWER PRESSURE TO A VESSEL OF HIGHER PRESSURE- CATALYST HEAD.

RCSV


To Main fractionator

FeedHCO

Back flush

Air

Riser

To heat recovery section

Steam

Steam

1.2 Kg/cm2750 degC720 degC

2.0 Kg/cm2670 degC670 degC

1.8Kg/cm2510 degC

SCSV

PRESSURE BALANCE

SCSV-SPENT CATALYST SLIDE VALVE-CONTROLS REACTOR LEVEL

RCSV-REGENERATED CATALYST SLIDE VALVE-CONTROLS REACTOR OUTLET TEMPERATURE.


OPERATIONAL ASPECTS HEAT BALANCE

A catalyst cracker continually adjusts itself to stay in heat balanceThe unit produces and burns enough coke to provide energy to:

1.Increase the temperature of the fresh feed, recycle, and atomizing steam from their preheated states to the reactor temperature.

2.Provide the endothermic heat of cracking.

3.Increase the temperature of the combustion air from the blowerdischarge temperature to the regenerator flue gas temperature.

4.Make up for heat losses from the reactor and regenerator to surroundings.

5.Provide for heat sinks, such as stripping steam and catalyst cooling.


OPERATIONAL ASPECTS HEAT BALANCE

Regenerator Reactor

Spent CatalystFlue gas

Heat losses

Regeneration Air

Feed Pre heater

Recycle

Fresh Feed

Products

Heat LossesHeat of Coke Combustion

Heat of Reaction

Regenerated Catalyst


OPERATIONAL ASPECTS CATALYST CIRCULATION

1.SMOOTH AND STEADY CATALYST CIRCULATION IS VITAL FOR STABLE OPERATION OF THE UNIT AND TO ENSURE STEADY PRESSURE BALNCE.

2.UNSTEADY CATALYST FLOW CAN TRIP THE UNIT ON PRESSURE BALANCE UPSET,LOW REACTOR TEMPERATURE AND LEADS TO UNSTABLE DOWNSTREAM SECTION.

3.UNSTEADY CATALYST FLOW INDUCE VIBRATION IN THE CONVERTOR SECTION AND DAMAGE VARIOUS INTERNALS AND STRUCTURE.

4.STABLE CATALYST CIRCULATION REQUIRES STEADY PRESSURE CONTROL ON REACTOR AND REGENERATOR SIDE AND CORRECT FLUIDISATION IN THE SATNDPIPES.



Standpipe Aeration & FluidizationAeration

Process of replacing volume lost due to compressionAir, steam or HC gas can be used for the purposeAeration taps with Rota meters

Fluidization SystemsFluidization air / steam / HC gas required in standpipes when cat approaches de-aerationAvoids unstable catalyst flow in stand pipes Requires adjustment in line with catalyst circulation rate


OPERATIONAL ASPECTS CATALYST LOSS

1.CATALYST LOSS IS OF GREAT CONCERN DUE TO ITS IMPACT ON ENVIRONMENT,PRODUCT QUALITY AND UNIT OPERATION.

2.HIGHER LOSS MAY BE DUE TO

•CATALYST PROPERTY

•INTERNAL DAMAGE ( CYCLONE,AIR GRID,STEAM RINGS,RISER TERMINATION DEVICE ETC)

•IMPROPER OPERATION ( HIGH FLOW RATE OF FLUIDISATION MEDIUM,CONDENSATE ENTRY ALONG WITH FLUIDSING STEAM ETC)


OPERATIONAL ASPECTS CATALYST LOSS


Total CombustionCoke on regenerated catalyst < 0.05 CO in flue gas < 1000 ppmHigher effective activity & superior selectivity of catalystHigher regenerator temperatureUse of catalyst cooler with residue feed for control of regenerator dense bed temp.

Partial CombustionCoke on regenerated catalyst > 0.05 CO in flue gas > 1000 ppmLower effective activity & superior selectivity of catalystRelatively lower regenerator temperatureRelatively higher afterburning difference between regenerator dense bed temp. and dilute bed temp.Requires CO boiler

OPERATIONAL ASPECTS REGENERATION MODE


SALIENT DESIGN ASPECTS TWO STAGE REGENERATION


SALIENT DESIGN ASPECTS COMPARISON OF REGENERATOR TYPES

Single stage Single stage

Two stage with separate flue gas

Stage no. One One One SecondMode Partial Full Partial FullRegen T (oC) 717 718 707 718CSC wt% 1.78 1.63 1.64 0.66CRC wt% 0.18 0.03 0.66 0.04Delta coke, wt% 1.6 1.6 0.98 0.62Inventory,Tons 150 150 100 50Cat cooler duty, MMBTU/hr 195 250 -- 180Flue gas comp. Vol%O2/CO2/CO

0.0/13.1/4.2 0.9/15.3/0.0

0.0/11.2/6.8

1.1/15.0/0.0

Catalyst make-up, lb/bbl of FF 0.71 0.78 0.77CO-boiler req. Yes No Yes


SALIENT DESIGN ASPECTS



Reactor StripperSurrounds the upper portion of the riserFitted with internals / baffles to enable stripping of the catalyst

using superheated steam.Cat flux 500 – 700 lb/min-ft2Stripping steam rate 2 – 5 lb per 1000 lb of catalystExcess stripping steam may not be beneficial; Loss of

valuable productsCatalyst residence time 1 – 2 minutesPre stripping rings at dip leg bottomsPerformance can be assessed by Hydrogen on coke



Reactor StripperRemoves entrained Hydrocarbons between catalyst particles.

If Hydrogen rich Hydrocarbons enter regeneratorLoss of liquid product.Loss of catalyst activity; Higher regen. temp. combined

with the formation of steam in regen. reduces catalyst activity (Crystalline structure of catalyst is destroyed)


SALIENT DESIGN ASPECTS Reactor Stripper


SALIENT DESIGN ASPECTS CATALYST PRE-STRIPPING


SALIENT DESIGN ASPECTS SLIDE VALVES

Slide ValvesTo regulate flow of catalyst (flue gas for DDSV)Hydraulically operatedRCSV and SCSV isolate reactor from regeneratorCarbon steel body with vibrocast liningSloped bonnet / guides for self draining of catalystSteam / air purge for older design. No purge in normal operation



Differential pressure across slide valves very important. For cat circulation ΔP across RCSV and SCSV be 0.2– 0.4 bar.

ΔP > 0.5 bar valve erosion and to be avoided. Negative ΔP never permitted.

Slide valve must close once ΔP drops to 0.1 bar on interlock activation. Low ΔP override system is on auto mode control.

In ESD slide valve must close fully in < 5 seconds. In normal control mode maximum stroke speed such

that max. 25 seconds for closing valve fully.



Necessary to rapidly & efficiently separate spent catalyst & hydrocarbon vapors at riser exit for desired product qualities & yields.

Inertial separator separates cat & vapors but allows vapors to remain longer in reactor vessel causing some nonselective thermal post riser cracking forming lighter gas and additional coke.

RTD-RISER TERMINATION DEVICE


SALIENT DESIGN ASPECTS RTD-RISER TERMINATION DEVICE



Air GridAIR GRID

For even distribution of air in spent catalystProper air distribution

•Lowers CRC (carbon on regenerated cat)•Minimizes after burn•Reduces local hot spots / catalyst sintering

Mechanically robust to withstand wide range of operations / upsets

Erosion, thermal expansion, mechanical integrity of supports

Pressure drop across air grid



Air GridVarious designs – Flat grid plate, dome, pipe, ring, flat pipe grid

Pipe gridMore uniform coverage (less dependent on air rate)Lower nozzle velocity, lower attrition

RingsCoverage from jet penetrationLess effective at lower than design air rates

AIR GRID


SALIENT DESIGN ASPECTS AIR GRID



Cyclone SeparatorsTo separate catalyst from flue gas / hydrocarbon

vaporsProvided in reactor and regenerator(s)External / InternalSingle stage / Double stageDirect coupled / Close coupledTypical inlet velocities (ft/sec)

•First stage (Rx or Rg) 60 – 70 ft/sec•Second stage 80 – 85 ft/sec•Minimum velocity 25 – 35 ft/sec

CYCLONE SEPERATORS


SALIENT DESIGN ASPECTS CYCLONE SEPERATORS



Dip LegsSubmerged or exposedCatalyst head required in the dip legSplash plate, trickle valve, counter weightRefractory lining depending upon the geometryFluidisation requirement (external cyclones)Common causes of catalyst carry overProblems during start ups



TRICKLE

VALVE

SPLASH

PLATE

COUNTER WEIGHT

FLAPPER


SALIENT DESIGN ASPECTS ORIFICE CHAMBER

Orifice ChamberTo provide back pressure for regenerator

At the D/S of DDSVReduces pressure drop across DDSVNumber of grids with holesDP across each gridCold walled / hot walled



ORIFICE CHAMBER

GRID $ 1

GRID $ 2

GRID $ 3

GRID $ 4

GRID $ 5

GRID $ 6

MANWAY

ABRASION RESISTANT LINING

ORIFICE CHAMBER


SALIENT DESIGN ASPECTS ORIFICE CHAMBER

PHOTO OF SINGLE GRID OF ORIFICE CHAMBER

slide valve orifice chamber(좋은 자료)

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