Coke Oven Consultants

Technologies

PROCESS DESCRIPTION FOR PROPOSED COKE OVEN PLANT:
Coal Preparing

Carbonization of Coal into low ash Metallurgical Coke is the main process in the Coke oven plants. Coal from the mines/ports is transported to the plant by means of trucks and stored at coal yard as a reserve. Coal stockyard is paved and lifted 0.5 m above ground level as a preventive measure from flooding. The entire coal stockyard is covered in a shed. During unloading of coal, spraying arrangements are provided for suppressing the coal dust during unloading operation. Pay loader is engaged for transferring of coal from stockyard to receiving pit of coal at handling plant. Here also, water spraying arrangements are provided for controlling the dust pollution. Ground hoppers fiddling 2-4 blended coal after is conveyed to over had coal bunker, Coal handling plant is with a receiving pit, an elevated covered conveyor of raw coal, a crusher, an elevated covered conveyor of crushed coal upto top of bunker, magnetic separator, overhead bunker and chutes for discharging coal into charging car which will further transport coal from the bunker end up to the oven ready for charging.
Coal from the receiving pit will be carried by means of a raw coal elevating conveyor and feeding the same to a crusher of hammer mill type. One magnetic separator is proposed at the receiving mouth of the crusher to eliminate iron impurities before crushing. The crusher will crush the coal. This crushing unit has been equipped with dust suppressing system with water so that there will not be any chance of generating dust during crushing operation.
This crushed coal will be carried out by another elevating covered conveyor at the top of the bunker and stamped charging car ,and then stamped into a coal cake of size -----------(L)mm x ------------(w)mm x ---------(H)mm and density of 0.9-1.05 t/m3 and weight ( with 8 to10 % m.)of ------- metric tons.
Coal cake stamped along with the charging plate is transferred to the coal charging car with pusher machine The coal cake along with the charging plate is pushed into coke ovens chamber.Pusher machine draws the charging plate out and immediately closes the charging –side door.
The temperature for carbonization is usually controlled at 1250-1300 c0. Coke pushing car pusher the ready coke, out of carbonization chamber and immediately closes the coke – side floor. The pushed burning coke is sent to quenching tower for quenching after quenching the coke is an loaded on to wharf, then conveyers belt/by loader to the coke cutter/coke screening plant. The screened size is decided as per customer’s requirements finally, the coke is sent to product stock coke yard.
The coke receiving & quenching car will move to and under the quenching tower by automatic positioning, and automatically switch on the motor-driven controlling valve for the two high level water tank to start quenching. The quenching process will last for about 4 - 5 minutes. The quenching tower will be 36 meter high with two 200 m3 high level water tanks. Inside the tower, a baffle-plate dust collector is arranged. The water spraying to clean the baffle-plate dust collector will start 1 minute before quenching and 1 or 2 minutes after completion of quenching, so as to ensure the efficiency of the dust collecting system. The water tanks of the quenching tower are equipped with level meters, in which the lower and higher limits are preset. The water after quenching, flow from the tower to the coke breeze clarifier along a trench with 5% slope. The water after clarifying will be pumped back to quenching tower for reusing and no discharge of effluents will take place. The coke breeze in the clarifier will be taken out with a bucket and dried in air and sold to mini cement plants, briquetting plants etc. After quenching, the coke receiving & coking car will keep staying for 2 or 3 minutes allowing extra water to flow out, then tilt the coke down to the coke wharf. If some coke has not been fully quenched, workers can quench it further manually with a water hose. Then the car will move to the next oven for the next round of operation.
The pushed burning coke is sent to quenching tower for quenching after quenching the coke is an loaded on to wharf, then conveyers belt/by loader to the coke cutter/coke screening plant. The screened size is decided as per customer’s requirements finally, the coke is sent to product stock coke yard.

Diagram for Stamp Charging System
    
The composition of coal that will be used in the coke making process is as follows


SPECIFICATION OF COKE
1. PROXIMATE ANALYSIS (A) Ash
(B) Volatile matter
(C) Fixed carbon :- 85 -87 max.
:- 12% + 1.00 %
:- 1.25% maximum

:- 85 -87 max.

2.IMPURITY (I) Sulphur
(ii) Phosphors
:- 00.65% max.
:- 00.05% max
3. STRENGTH (A) Shatter Index
(B) Micum Index
:- 95% mini
(i) M-40=85% min.
(ii) M-10=7.0% max.
4.REACTIVITY

(I) CRI (coke reactivity index)

(ii) CSR (coke strength after rection)

:- 22.00% max.  
4.REACTIVITY + 6900 Kcal/kg :-  65.00% min.

SPECIFICATION OF COAL
• Ash :- 8.00-9.00 % max.
• V.m :-21-23 % max.
• F.c. :- 68% min.
• Sulphur :-0.36% max
• Phosphors :- 0.021 % max.
• DDPM (FLUIDITY) :-1200/ Approx
• MMR :1.12
• Vitrinite :-52-58
• Size :-0 to 50 mm
• Csn :- 7 to 8
SELECTION OF COKEMAKING TECHNOLOGY
  • Coke Quality
  • Cost of Coke
  • Environmental Regulations
  • Operational Expenses
  • Flexibility Coal Quality Usage
  • Flexibility of Operation
  • Service Life of Coke Oven Battery
  • Installation Time
  • Design Simple
  • Shape Ovens wider then taller
  • Brick work Few brick shapes
  • Operating Pressure Slightly Negative
  • Wall Pressure Not Susceptible
  • Heat Transfer Direction Vertical
  • Heat Transfer mode Direct: (Dome) Radiation and Convection Indirect (Under- Flue)
  • Coke Quality
    • Higher Coking temperature
    • Longer soaking tike
    • Ability to Use high rank coals
  • Relevance Compacted charging
    • No dangerous oven wall pressure
    • CSR improvement -5 points
    • Significantly better coke M-10 leading to lower
    • coke fines generation
    • Improved hot Strength properties of coke
    • Higher oven productivity due to high bulk density
SALIENST FEATURES
  • Stabilied Quality                - Fuel Efficiency $ Reduce Pollution.
  • Low Sulphur Content        - Low sulshur pickup
  • Low Volatiles                       - Reduce blow holes due to H2, N2
  • Low phosphorus                  - Low micro shrinkage
  • High shatter index            -Reduce handing loss.
  • Low Reactivity                   -medium carbon pickup control, carbon monoxide
CONDITION OF COKING COAL/COKE
Temperature condition of the coal/coke
100 0 c _ Water (Surface and Hydration)
3300—4400c _ Coking coals begin to soften.
4260c _ Rapid Decomposition Begins with Evolution of tars, oils, and Gas
4260 _ 4400c _Degree of Fluidity and Rate of Decomposition in crease Rapidly.
4400 _ 4800c _ Fluidity Decreases, usually Rapidly
4480 _5100c _ Material Solidifies to semi-coke.
4960 _Evolution of condensable products ceases But production of fixed Gases continues. Further Decomposition and scrimmage of the Semi-coke
8910 _ 9820c _Evolution of carbon monoxide Hydrogen and some Hydrocarbons. Such as methane and Ethylene.
9260 _10370c _ coke is Ready to be pushed.
The following table lists some of those coal properties which a coke maker considers important.
PARAMETER LIMITS COMMENTS
Total Moisture Max. 10% (AR) Too high moisture creates difficulties in handling. Also lowers amount of carbon available.
Ash Max. 10% (ad)High ash reduces efficiency in blast furnace.
Volatile Matter 16-36% (ad) Best quality coking coals 20-35%. High volatile matter results in lower coke yield.
Sulphur Max. 0.8% (ad) Some of the sulphur in coal reports to hot metal and has delaterious effects on steel quality.
Phosphorus Max. 0.1% (ad) Makes basic carbon steel brittle.
Crucible Min. 6 Prime coking coals.
Swelling Number Min. 3 Semi soft coking coals.
Max. dilatation Min. 50% Depends to some extent on other blend components.
Max. Fluidity Min. 100 ddpm Depends on other blend components. Better quality coals exceed 1000 ddpm.
Sodium potassium oxides Max. 3% in ash High alkalis in ash cause high coke reactivity.
Mean max. Reflectance 0.7 – 1.5% Mean max. Reflectance of Japanese blends about 1.1-1.2%.
Main technical perameters.
a.Coke ovens Carbonization chamber height -------------
b. Coke ovens Carbonization chamber length -------------
c.Coke ovens Carbonization chamber center distance -------------
d.Coke ovens Carbonization chamber with (avg.) ------------
e.Density of coal cake charged (dry basis) 0.95-1.05 T/m3
f.Weight of coal cake charged (dry basis) ---------------
g.Operation cycle -------------