The disclosure relates to a method and apparatus for producing coke from coal and in particular to an apparatus and method for wet quenching of a flat pushed incandescent slab of metallurgical coke in a single, multipurpose apparatus.
Metallurgical coke is a solid carbon fuel and carbon source used to melt and reduce iron ore in the production of steel. During an iron-making process, iron ore, coke, heated air and limestone or other fluxes are fed into a blast furnace. The heated air causes combustion of the coke which provides heat and a source of carbon for reducing iron oxides to iron. Limestone or other fluxes may be added to react with and remove the acidic impurities, called slag, from the molten iron. The limestone-impurities float to the top of the molten iron and are skimmed off.
In one process, known as the “Thompson Coking Process,” coke used for refining metal ores is produced by batch feeding pulverized coal to an oven which is sealed and heated to very high temperatures for 24 to 48 hours under closely controlled atmospheric conditions. Coking ovens have been used for many years to covert coal into metallurgical coke. During the coking process, finely crushed coal is heated under controlled temperature conditions to devolatilize the coal and form a fused incandescent mass or slab of coke having a predetermined porosity and strength. Because the production of coke is a batch process, multiple coke ovens are operated simultaneously, hereinafter referred to as a “coke oven battery”. For the purposes of this disclosure, the term “incandescent coke” means the normal state of coke when it is discharged from a coke oven. Incandescent coke is typically discharged from a coke oven at a temperature ranging from about 980° to about 1320° C.
In a conventional coke oven process, once the coal is “coked out”, the coke slab is pushed from the coke oven so that it breaks up and drops into a hot car wherein the coke is quenched with water to cool the coke below its ignition temperature. The quenching operation must be carefully controlled so that the coke does not absorb too much moisture. Once it is quenched, the coke is screened and loaded into rail cars or trucks for shipment.
One of the problems associated with the coke making process is dusting problems associated with removing the hot coke from the oven and dropping the coke into a quenching car as the coke is discharged from the coke ovens. As the coke drops into the quenching car, a significant amount of coke dust is created. Likewise, the quenching step produces steam and particulate matter as the coke is quenched. In fact, the largest single source of particulate matter emissions in a coke making process occurs during the coke discharge and quenching operations. Accordingly, elaborate dust collection systems have been devised to capture dust particles generated as the coke is pushed into the quench cars. However, many of these systems rely on pressure drop through a device, such as baffles or multi-cyclones to obtain efficient particulate removal. However, conventional quench systems have very little available pressure drop available for high efficiency removal of particulate matter. In order to reduce the dusting problems associated with coal coking without significantly increasing coke oven cycle times, improved apparatus and methods for quenching coke are needed.
In accordance with the foregoing need, the disclosure provides a method and apparatus for quenching metallurgical coke made in a coking oven. The method includes pushing a unitary slab of incandescent coke onto a substantially planar receiving surface of an enclosed quenching car so that substantially all of the coke from the coking oven is pushed as a unitary slab onto the receiving surface of the quenching car. The slab of incandescent coke is quenched in an enclosed environment within the quenching car with a plurality of water quench nozzles while submerging at least a portion of the slab of incandescent coke by raising a water level in the quenching car. Subsequent to quenching the coke, the planar receiving surface is tilted to an angle sufficient to slide the quenched coke off of the planar receiving surface and onto a product collection conveyer and sufficient to drain water from the quenched coke.
Another embodiment of the disclosure provides a movable apparatus for reducing dusting during a coke quenching step of a metallurgical coke making process. The apparatus includes a substantially fully enclosable quenching car adapted to receive a unitary slab of incandescent coke. The quenching car has an enclosable structure having a tiltable water quenching table disposed between a coke inlet end having an inlet door and a coke discharge end opposite the inlet end, the discharge end having a coke discharge door. Water spray nozzles are disposed between the inlet end and the discharge end above the quenching table. A water quenching sump is provided below the water quenching table for submerging a portion of the slab of incandescent coke in quench water. A dust collection system is attached to the enclosable structure for collecting water droplets and particulates from the coke quenching step.
The method and apparatus described above provide unique advantages for coking operations. In particular, flat pushing of the coke onto a quench car as a unitary slab of incandescent coke may significantly reduce an amount of particulate matter generated during a coke oven discharge operation. Accordingly, dust collection equipment for collecting particulate matter during the coke discharge operation may be substantially smaller and may provide higher dust collection efficiencies. Another advantage of the method and apparatus disclosed herein may be the simplicity of operation and the elimination of structures and equipment necessary to quench the coke and handle the quenched coke product. For example, the dust collection system has no moving parts and may rely only on pressure generated in a substantially enclosed chamber as a motive force for gas flow through the dust collection system.
Further advantages of the invention will become apparent by reference to the detailed description of preferred embodiments when considered in conjunction with the drawings, which are not to scale, wherein like reference characters designate like or similar elements throughout the several drawings as follows:
For purposes of this disclosure, a “unitary slab of coke” is intended to include fused incandescent coke structures as made in a coking oven. The unitary slabs of coke may have sizes ranging from about a meter wide to tens of meters long and up to about 1.5 meters deep and may weigh between about 20 and about 40 metric tons. With reference to
A typical coal coking cycle may range from 24 to 48 hours or more depending on the size of the coal charge to the coke ovens 12. At the end of the coking cycle, the coke is pushed out of the oven 12 with a discharge ram 18 positioned adjacent the inlet end 14 of the ovens 12. The discharge ram 18 may include a device for removing an inlet end 14 oven door prior to pushing the coke out of the ovens 12. The discharge ram 18 may move along rails 20 adjacent the inlet end 14 of the ovens 12.
A coke quenching device 22 may be positioned adjacent the outlet end 16 of the ovens 12 to remove exit doors from the ovens 12 and to quench the incandescent coke pushed from the ovens 12. In an alternative embodiment, a separate exit door removing device may be used to remove the exit doors from the outlet end 16 of the ovens 12 prior to pushing the coke into a quenching car.
The coke quenching device 22 may be adapted to collect a unitary slab 24 of incandescent coke pushed from the ovens by the discharge ram 18. The coke quenching device 22 moves along rails 26 adjacent the coke outlet end 16 of the ovens 12. A detailed description of the quenching device 22, including alternative mechanisms for positioning the quenching device adjacent the outlet end 16 of the ovens 12 is described in more detail below. During a coke pushing operation, the coke is pushed out of the ovens 12 as a substantially unitary slab 24 into an essentially enclosed structure 28 of the quenching device 22.
Once the incandescent coke is loaded onto the quenching device 22, a quenching operation is begun. As shown in
The structure 28 also includes a sump portion 38 containing a volume of quench water 40. The quench water 40 in the sump portion 38 may provide substantially more quench water than the water spray nozzles 36. In one embodiment, the ratio of the volume of water from the water spray nozzles 36 to the quench water 40 in the sump portion 38 may range from about 1:10 to about 1.1 by volume. Make up water to the spray nozzles 36 and sump portion 38 may be provided by a water channel running along the coke oven battery 10 that supplies a pump aboard the quench device 22.
In order to quench the coke using the quench water 40 in the sump portion 38, a plunger 42 (
A typical total amount of quenching fluid suitable for quenching the coke slab 24 may range from about 1.5 to about 2.5 parts by weight water per part by weight coke. The quenching step is typically conducted as rapidly as possible and may range from about 1.5 to about 2.5 minutes total to provide coke having a moisture content of less than about 3.0 percent by weight, typically from about 1.5 to about 3.0 percent by weight.
After quenching of the coke slab 24 is complete, the plunger 42 may be raised to lower the water level below the outlet door 32 level of the structure 28. Once the water level is lowered, the outlet door 32 may be opened and a metering conveyer 48 (
The metering conveyor 48 may discharge the coke onto a belt conveyor 58 for transport to a product receiving area. In the event the belt conveyor 58 is not operating, a by-pass chute may be provided to dump the product coke onto the ground adjacent the metering conveyor 48.
When the quenched coke 24 has been completely discharged from the device 22 and drained, the metering conveyor 48 may be stopped, the door 32 may be closed, and the table 34 may be lowered for receiving another slab of incandescent coke 24. During this process, water may be added to the sump portion 38 from the water channel. Also the device may be moved to reposition the device 22 adjacent another oven 12 for receiving another incandescent slab 24 for quenching.
Due to the fact that the structure 28 is substantially gas tight, steam and water vapor generated during the quenching step may pressurize the structure 28 sufficient to cause gas and vapor flow through attached particulate matter collection devices 54 (
Without desiring to be bound by theoretical considerations, it is believed that the gas tight quench structure 28 describe above may significantly improve the removal efficiency of particulate matter compared to the removal efficiency of conventional induced draft quenching systems. For example, assuming a vapor flow rate ranging from about 416 actual cubic meters per second (m3/sec) to about 250 actual m3/sec in a quenching step, a conventional induced draft quenching system may only provide at most about 0.6 cm of water pressure. Since the available pressure is only about 0.6 cm of water, the pressure drop through any particulate removal device must be less than 0.6 cm of water or about 0.5 cm of water. Accordingly, devices, such as baffles are typically used in an induced draft quench system to create a pressure drop so that particulate matter can be removed from the gas and vapor streams. Accordingly, the pressure generated in a conventional quench system is insufficient for use with high efficiency particulate removal devices such as bag dust collectors and multi-cyclone devices.
By comparison, the same flow rates of gas and vapor in the quenching device 22 described herein may provide a pressure ranging from about 11 cm of water at 416 actual m3/sec to about 4.3 cm of water pressure at 250 actual m3/sec. In view of the higher pressure drop provided by the quenching device 22, a multi-cyclone or other higher pressure drop particulate removal systems may be used. Accordingly, removal efficiency of particulate matter from the gas and vapor streams generated during quenching may be significantly greater than with conventional quenching systems.
Another component of the quenching device 22 may be an integral coke exit door removal device 60. The exit door removing device 60 includes mechanisms to correctly position the device 60 at the outlet end 16 of the oven 12 to be discharged of finished coke, and to remove a coke discharge door 62 (
The exit door removal device 60 may be manually operated and thus may be controlled from a control booth 64 (
Prior to removing the door 62, a laser targeting device may be used by the operator to accurately position the quenching device 22 so that the door removal device 60 is adjacent the coke outlet end 16 of the oven 12. Mechanical interlocks may also be used to assure that the door removal device 60 is in the correct position to unlock and remove the door 62 from the oven 12. A diesel engine may be used to move the quenching device 22 along the rails 26.
With reference now to
After the door removal device 60 has removed the coke exit door 62 from an oven 12, the quenching device 22 may be re-positioned in line with the oven 12 to receive the coke being pushed out of the oven 12 as shown in
With reference now to
With reference again to
A portion of the elevational and translation mechanism 72 is illustrated in more detail in
As set forth above, due to oven height disparities between ovens 12, the alternative elevation and translation mechanism 72 may be used to provide the enclosed chamber 28 at a desired elevation for pushing the substantially unitary slab 24 of coke onto the quenching device 22. Variations in oven height typically range from about 2.5 to about 15 cm. Accordingly, the elevation and translation mechanism 72 should be capable of moving the enclosed chamber 28 up or down from 2.5 to about 15 cm and holding the enclosed chamber 28 at a desired elevation between 2.5 and 15 cm. It will be appreciated that height elevations that may be needed for a particular oven battery may range more than from about 2.5 to about 15 cm.
Once enclosed structure 28 is at an elevation, illustrated in
Referring again to
As shown in
In another alternative embodiment, the quenching system 22 may be positioned on rails 26 closely adjacent to the ovens 10 so that a portion of the quenching system 22 overhangs a coke side bench 96. In such embodiment, the transition section 90 may be used to provide a smooth transfer of the coke slab 24 into the quenching device 22. Hence, the above described the elevation and translation mechanism 72 may not be required for this embodiment.
In order to reduce emissions of gases and particulates during the transfer of the coke slab 24 from the oven 12 to the quenching device 22, the lintel sealing device 110 is provided as shown in more detail in
During the coke pushing step for pushing the coke slab 24 into the enclosed chamber, 28, coke dust may accumulate on the oven sill 94 attached to each oven 12 after removing the oven exit door 62. Accordingly, the oven skirt sweeping mechanism 120, as shown in
Once the coke slab 24 has been pushed into the enclosed structure 28 by the coke discharge ram 18, the operator retracts enclosed structure 28 away from the oven 12 and lowers the structure 28 to the first elevational position illustrated in
As with any coke quenching operation, solids, including coke fines plus ash from the coke slab 24 may accumulate in the quench water 40 in the sump portion 38 of the quenching device 22. It is anticipated that the sump portion 38 may be able to hold the solids from about 50 oven pushes (about 8 hours of quenching operation). After 50 pushes, the quenching device 22 may be trammed to a solids dewatering area 130 illustrated in
Once the quenching device 22 is in the solids dewatering area 130, which may be located at one end of the coke oven battery 10 as shown in
The discharge water with solids is directed to a gently sloping concrete apron 132. The slope of the gently sloping apron 132 may range from about one percent to about five percent slope. As the water and solids flow down the gently sloping apron 132, most of the solids may be left on the apron 132 and the water flows into a holding basin 134. The holding basin may be of a size suitable to hold from about 60,000 to about 100,000 gallons or more. The solids on the apron 132 may be removed periodically using a front end loader 136.
Water from the holding basin 134 may overflow through a weir 138 into a clear well 140. The clear well 140 may be used to provide make up water to the sump portion 38 of the quenching device 22. The clear well may be sized to hold from about 120,000 to about 200,000 gallons of water, or may be sized to hold the same amount of water as the holding basin.
In the foregoing description, the entire apparatus with the exception of conveyor belts, electrical components and the like may be made of cast or forged steel. Accordingly, robust construction of the apparatus is possible and provides a relatively long lasting apparatus which is suitable for the coke oven environment.
The foregoing embodiments are susceptible to considerable variation in its practice. Accordingly, the embodiments are not intended to be limited to the specific exemplifications set forth hereinabove. Rather, the foregoing embodiments are within the spirit and scope of the appended claims, including the equivalents thereof available as a matter of law.
The patentees do not intend to dedicate any disclosed embodiments to the public, and to the extent any disclosed modifications or alterations may not literally fall within the scope of the claims, they are considered to be part hereof under the doctrine of equivalents.
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Number | Date | Country | |
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20100236914 A1 | Sep 2010 | US |