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Bee Hive Coke Making @ Www.07 Met.Tk


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  • 1. Bee-hive Coke Making
    ))) 07MET.TK (((
    All About Metallurgical & Materials Engineering
    Download This & More Stuff @ WWW.07MET.TK
  • 2. Beehive ovens
  • 3. Oven chambers are kept under slight negative
    pressure or suction.
    Oven shape is much wider than higher
    Maximum achievable temperature higher
    Product coke with improved quality with respect to cold and hot strength properties.
    No wall pressure since coal charge resting on the oven sole is barely in contact with oven walls and has large unrestricted surface area.
    Non-recovery ovens
  • 4. Carbonization process takes place from the top by radiant heat transfer and from the bottom by conduction of heat through the sole floor.
    Partially combusted gases exit the top chamber through "down comer“
    They heat the sole of the oven.
    Since the by-products are not recovered, the process is called Non-Recovery cokemaking.
    The waste gas exits into a waste heat recovery boiler which converts the excess heat into steam for power generation; hence, the process is called Heat Recovery cokemaking.
    Non-Recovery/Heat Recovery Coke Production
  • 5. Coking starts by means of heat retained in the brickwork from the previous coal charge.
    The evolving volatiles are mixed with air drawn (Primary air) into oven and are combusted.
    The oven dome radiates heat to coal mass.
    The heat of the combusted volatiles passes through the downcomers in the side walls into underflues.
    Additional air (Secondary air) is input from the lower sides of the oven to assist in providing heat from the bottom of coal charge.
    Coking proceeds from the top of the charge in the direction of oven floor and also from the bottom of oven to the center of the coal mass.
    Non-Recovery/Heat Recovery Coke Production
  • 6. Complete combustion of the escaping hydrocarbons, if any, is achieved by providing (Tertiary air) in the common flue where the flue gases from individual ovens of each battery of ovens is drawn.
    The hot common stack generates the negative pressure in the common flue.
    Non-Recovery/Heat Recovery Coke Production
  • 7. The negative pressure helps pull air in to the oven & helps keep toxic chemicals from escaping.
    Coal is charged by gravity as is done in the conventional by-product ovens.
    The coal is leveled to a flat profile that ensures optimal coking of all portions of the coal charge
    The ovens are constructed of alumina bricks of different specifications.
    The mosaic of bricks of different specs ensures that high alumina bricks are used in the areas of the oven that call for the higher (and more expensive) specifications.
    Features of Bee-hive oven
    The long thin coking chambers
    Height 6-22 ft.
    Length: 3-52 ft
    Width: 1-2 ft
    NON-RECOVERY oven:
    Length: 10.76m
    Width: 2.75m
    Height: 1.18m
  • 11. After the coking cycle, an ideal charge will have settled downward and became a coke mass having a theoretical coke line below (coal loses up to 20% weight mass) and parallel to the charge level line.
    In the past, an operator at the coke guide visually inspected the coke height.
    Oven must not be pushed unless the visual inspection indicates that there is no smoke in the open space above the coke bed and that there is an unobstructed view of the door on the opposite side of the oven.
    Inspection of coke level
  • 12. Coke guides are provided with five temperature sensors mounted in an expected coke height range, referenced to coke oven floor, to develop coke vertical temperature profile data.
    Each temperature sensor may be a fast-acting optical pyrometer having an analog output signal proportional to coke temperature.
    A pyrometer has the advantage of providing an output signal that is useful not only for coke level analysis, but coke mass and oven wall temperature analysis as well.
    Inspection of coke level
  • 13. Recommended adoption of non-recovery ovens as a pollution control alternative.
    In the energy-recovery coke making process, volatiles evolved during coal carbonization,
    are not recovered as by-products
    They are combusted completely in presence of controlled quantity of air.
    The heat of the volatiles of evolving gases is utilized for coking the coal mass into coke and thus no external heating is required.
    Why non-recovery coke making?
  • 14. The higher level of heat importantly is used to break up the potentially polluting hydrocarbons into the constituent combustible compounds and to burn them thus avoiding the potentially hazardous pollution.
    Why non-recovery coke making
  • 15. There is a 3-5 % burn-off in the energy recovery ovens. With desulphurisation, burning loss can be maintained below 1%.
    The typical specifications of BF grade coke are as under:
    Moisture - 3 – 4% CRI - 16%
    CSR - 74.5%
    V.M. - 1.0 – 1.25%
    Ash - 11.5% max
    FC - 87.3 – 87.9%
    P - 0.03%
    S - 0.5%.
    Coke yield
  • 16. Both processes produce high quality met coke as long as appropriate coal blends are used.
    However since coking temperatures can go up to 12500C, & coking rate is low, hence coking quality is better.
    Circulate air in the foundation below the battery to keep it cool.
    Lower VM in the coal blend is used, resulting in a higher coal to coke yield.
  • 17. ))) 07MET.TK (((
    All About Metallurgical & Materials Engineering
    Download This & More Stuff @ WWW.07MET.TK