CA1128894A

CA1128894A - Process for coking coal and coke oven for performing process

Info

Publication number: CA1128894A
Application number: CA323,981A
Authority: CA
Inventors: Dietrich Wagener; Horst Fach; Hayri Ergun
Original assignee: Didier Engineering GmbH
Current assignee: Didier Engineering GmbH
Priority date: 1978-03-22
Filing date: 1979-03-22
Publication date: 1982-08-03
Also published as: AU524426B2; AU4528979A; GB2018813A; GB2018813B

Abstract

ABSTRACT

The invention relates to a process for coking coal or moulded coal using microwave radiation. Milled coal in containers or shaped moulded coal with at least one hole in it is used. Coke-ovens performing the process of the invention can be made to operate on a batch system or continuously. The coke-oven comprises a coking chamber and the coking is carried out by microwave generators, fitted into the walls. Gases produced are removed through vents.
The coke then passes to a cooling zone which is fitted with photocells to take up the radiated energy.

Description

38~'~

The invention relates to a process for coking coal, particularly for production of moulded coke. Such processes are at present performed in conventional chamber ovens of various types in which the heat of combustion of fuel gases is conducted to the walls of the chambers in which the coal for coking is contained. Plants of this type have a high capital cost and they depend on the availability of the required fuel gases. They also contribute significantly to air pollution.
It is an object of the present invention to provide a process of the type mentioned, in which the process of coking can be performed quickly and reliably a-t low cost.
It is well known to use microwave radiation for thawing, heating, cooking and baking food in the catering industry and in domestic households, for hardening of refractory mouldings made of solids with aqueous binding agents, for sintering or melting of ceramic or refractory products or for edge glueing wood. It is also known that the heat generated in a material depends partly on the intensity and the actual frequency of the microwave radiation and partly also on the dielectric constant of the material. It has now been found that microwave radiation is particularly suited for cooking of coal although the di-electric constant of the coal changes during the process of coking.
Thus according to one aspect of the present invention there is pro-vided a process for coking coal comprising introducing coal or moulded coal into a coking chamber, exposing said coal to microwave radiation, thereby form-ing said coal into hot coke, into a cooling zone to form cooled coke, wherein said cooling zone comprises photocells, which convert radiant energy from said hot coke into electricity.
The preferred frequency range is 20 to 3,000 MHz. Due to Post Office regulations only some frequencies are permissible.

To obtain more uniform heating and thus more uniform coking of the coal it is preferred that either the coal is in the form of milled coal and is placed into containers e.g. rectangular containers and exposed to the microwave radiation, or separate mouldings of coal by themselves are exposed to microwave radiation.
In a preferred embodiment the moulded coal for use in the present invention comprises individual mouldings of compact shape each having at least one hole in it. Each moulding preferably has at least one hole passing through it. Each moulding may be rectangular, cylindrical, spherical or rounded e.g.
egg shaped. The hole or bore is preferably centrally placed and serves to avoid the formation of an internal soft region which would allow deformation of the moulding during coking. The hole or bore also allows the escape of distillation gases produced during coking through a larger surface area and thus the gases do not produce excessive internal pressure.
According to another aspect of the present invention there is pro-vided a coke-oven for coking coal in a process as claimed above, said coke-oven comprising a coking chamber which is in the form of duct shaped conductors or resonating cavities, means for generating microwaves for heating said coal, and a cooling zone situated downstream with respect to a direction of flow of the coal and adjacen~ to the coking chamber, wherein the coking chamber and the adjacent cooling zone are in the form of a vertical or sloping duct and the cooling zone is fitted with photocells whereby heat energy in the hot coke can be collected as electrical energy. In the coking oven the coking chambers are duct shaped, e.g. tubular, conductors or resonating cavities. Continuous opera-tion of the coke-oven is possible because of the speed of coking using microwave radiation.
In another embodiment of a coke-oven according to the present inven-_, --tion there is provided at least one filling chamber, preferably a rectangularchamber into which the coal, preferably fine coal, can be put, which can be moved, preferably back and forth, and especially transverse to the plane of the coking chamber, preferably at right angles to the plane of the coking chamber, between one or more filling positions for compressing can be filled with coal, one or more positions for compressing the coal in the chamber and a position for charging coal whereby in the position for charging coal, the coal can be pushed from the chamber into the coking chamber optionally via a preheating zone, and then through the coking chamber and through an adjacent cooling zone by succeeding charges of coal. The movement of the chamber can be repeated in reverse or carried out in the above or reverse order from the opposite side of the vertical axis of the coking chamber. In a preferred arrangement a filling chamber is-moved back and forth between a first filling position and a first compressing position on one side of the coke-oven and a second filling position and a second compressing positioll on the other side of the coke-oven. This embodiment is particularly suitable for coking milled coal in a continuous pro-cess.
Gases produced during coking can be disposed of through vents.
The photocells fitted to the cooling zone improve the dry coke cool-ing, and thereby heat energy in the hot coke can be collected as electricalenergy.
The invcntion also extends to a coking plant comprising a coking oven as described above in combination with a coal treatment plant which com-prises a storage bunker, means defining at least one treatment zone, means for generating microwaves in the treatment zone and a conveyor for transporting the coal from the storage bunker to the said coking oven via the treatment zone.
In a preferred embodiment the coal is transported on a conveyor belt ~ -3-' . .

through the treatment zone. The treatment zone is preferably provided with at least one vent whereby moisture can be removed from the treatment zone. Pre~-erably means are also providcd to enable heated air to be fed into the treatment zone whereby waste heat from the plant for microwave generation may be used for heating the air.
In a preferred embodiment the coking oven has a supply hopper and the plant comprises a coal bunker, optionally a weighing bunker, and a feed chute between the coal bunker and the supply hopper of the coking oven, and -3a-.,~ .

the treatment zone is formed as part of the coal bunker or the weighing bunker or the feed chute or the supply hopper.
The treatment zone may be formed inside the coal bunker or inside the feed chute. When the treatment zone is inside a coal bunker it may be defined by at least two opposed spaced plate electrodes disposed between the inlet and the outlet from the bunker whereby the coal can flow between the plates from the inlet to the outlet of the bunker.
When the treatment zone is inside a feed chute it may be defined by at least two opposed spaced plate electrodes eY~tending from at or near the inlet of the chute to at or near its outlet.
The lower end of each plate electrode may be provided with an air supply duct whereby air can be blown up along the plate.
The invention can be put into practice in various ways and a number of embodiments will be described to illustrate the invention with reference to the accompanying drawings in which:-Figure 1 is a section of a coke-oven for batch operation according to the invention;
Figure 2 is a section of an embodiment of a coke-oven in duct form for continuous operating according to the invention;
Figure 3 is a section showing the embodiment of the zone for cooling;
Figure 4 is an isometric diagram of a coke-oven for continuous coking of fine coal;
Figures 5a35b and 5c are sections of various wall d~signs for the coke-oven or ths zone for cooling according to the invention;
Figures 6a and 6b are diagrammatic perspective views of mouldings which are used for producing moulded coke for use in the present invention;
Figure 7 is a schematic representation of a device for use in the present invention with a zone for microwave treatment of coal and adapted to predry coal for example to provide predried coal for use as the feedstock for the coking plant shown in Figure l;
Figure 8 is a schematic representation of a form of feed chute arranged as a zone for microwave treatment of coal and for use in a coking plant in accordance with the present invention, and Figure 9 is a schematic representation of a form OL coal bunker arranged as a zone for microwave treatment of coal and for use in a coking plant in accordance with the present invention.
The coking chamber 3 of the coke~oven shown in Figure 1 is in the shape of a hood or truncated conical form having a Mansard roof cross-section.
The coal is added in batches through ~he upper opening 9. When a charge of coal has been added the surface of that batch of coal 11 in the coking cham-ber will adjust itself approximately parallel to ~.he sloping walls 10. One or more microwave generators 12 is itted in the sloping walls. The coking chamber is designed as a resonating cavity, and the opening 9 is closed dur-ing the process of coking each batch of coal. Any gases produced, are vented through a vent 6. After completion of the coking process the bottom shutter 5 of the coking ch~mber is opened. The hot coke falls into a cooling zone 4 which is arranged below the coking chamber 3. The inner walls 7 of the cooling zone are fitted with photocells to take up the energy of the thermal radiation from the hot coke. In this way energy can be recovered and fast cooling o~,the coke 13 can be ensured. When the coke 13 has cooled, at least to some extent, the bottom shutter 14 of the cooling zone is opened and the coke falls into a container 15, which is placed under the shutter 14, for transportation.
In Figure 2 the coal for coking is pushed along a horizontal channel 16 of rectangular cross-section. The end of the channel 16 leads into a vertical coking chamber 3, also of rectangular cross-section, with a heating zone 17, and melting zone 18, a zone of solidification 19 and a zone of hardening 20 in which zones the coal is treated with microwave radiation at least in zones 17 and 18. At the junction between the horizontal channel 16 and the vertical coking chamber 3 there isa ramp or projection 36 past which the coal is continuously pushed into the vertical coking chamber 3. The surface of the coal which is exposed in the region of the ramp is dried and preheated by means of a radiator 21 positioned opposite to the ramp or pro-jection. Moisture and gases which are produced can escape through a vent 6. The hardening zone 20 which forms the lower part of the coking chamber 3 consists of grid walls 22 of an appropriate mesh size which are surrounded by a continuous housing wall 23. Any gases which are developed can escape or be withdrawn through the space between the grid wall 22 and the outer housing 23 and out through a gas vent connection 6'. There is a direct transition from the coking chamber downwards into a cooling zone 4 which again may be fitted with photocells ~not shown) on the inside of the walls.
After dry coke cooling in the cooling zone the coke, which has at least ~o some extent cooled down~ is discharged downwards from the cooling zone to a turntable discharge arrangement 24. The feed of coal in the channel 16 and the rate of discharge at the turntable discharge arrangement 24 at the lower end of the cooling zone determine the rate of continuous processing in the coking chamber. In Figure 2 the positioning of the microwave generators is not shown.
Figure 3 shows an alte~lative embodiment for dry coke cooling where the incandescent coke 25, instead of being in a cooling zone as illustrated in Figure 2, is passed continuously on a plate conveyor 26 through a horizon-tal pathway 27 which has an inverted trough shaped cover 28 forming a hood over the conveyor 26. The cover 28 is fitted with photocells 7.

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In the embodiment shown in Figure 4 the coking apparatus is in the form of a narrow tall elongated duct lying in a vertical plane having its longitudinal axis lying at an angle ~ to the horizontal. The duct provides a gas lock and preheating zone 29, a coking chamber 3 provided with a gas vent 6, and a cooling zone 4. A vertically disposed discharge sluice and gas lock 30 is attached to the end of the cooling zone 4. Coal is fed to the gas lock 29 by means of an oscillatable feed mechanism 8. This consists of one open ended chamber 40, of the same cross-section as the duct, arranged to be moveable sideways across the end of ~he gas lock 29. The chamber 40 can occupy five different positions, a filling position 43 ~as shown in Figure 4), a pressing position 44, a charging position 45, another pressing position 46 and another filling position 47. I'hus starting from the position shown in Figure 4, the process starts by the chamber 40 being filled with coking coal in position 43, the chamber 40 is then moved sideways so that it now occupies position 44 and ~he coal therein is compressed e.g. by means of a press die or ram. The mechanism is now moved sideways again so that chamber 40 is in position 45 and the compressed coal therein is extruded into the gas lock 29 by means of a press die or ram. The chamber 40 is now moved across to position 47 and filled with coal, it is then moved back to position 46 and the coal compressed in the chamber. The chamber 40 is then moved back so that it now occupies position 45, the coal is ex~ruded into the gas lock 29 and the e~pty chamber moved back to position 43 and the cycle repeated.
The rears of the positions 43, 44, 46 and 47 are closed by walls 48 and 49. The front of each chamber is similarly provided with a slideable closure.
When the coal has been extruded ou~ of the mechanism and it first enters into the preheating zone and gas lock 29 and from there passes into the coking chamber 3. Here the coal, which has been pushed forward, is exposed to microwave radiation. The gases developed escape through the gas vent 6. After leaving the coking chamber the coke first passes through the cooling zone 4 for dry coke cooling of the type described above. The coke then passes through the discharge sluice and gas lock 30. The sloping arrange-ment of the ~one for preheating and the gas lock 29, the coking chamber 3 and the cooling zone 4 facilitates transport of the coal and coke through the coking apparatus.
Various preferred wall sections which can be used for coke-ovens according to the present invention are illustrated in Figures Sa, 5b, and 5c. Figures 5a and 5b show wall sections of the coking chamber. The coal for coking 31 is enclosed all round by a wall layer 33 of ceramic insulating material. Figure 5a shows a magnetron or a klystron 34 with a resonating cavity 35 located on the outer surface of the wall layer 33. Figure 5b shows an arrangement in which the irradiating microwave energy is conducted to the coal 31 via electrodes 36 positioned on the ou~er surface of the wall layer 31. Figure 5c illustrates the wall section of a cooling zone. The incande-scent coke is again next to a wall 33 of ceramic insulating material with photocells 7 Iocated on the outer surface thereof. Here and in other embodi-men~s~filter glasses can be inserted between the incandescent coke 32 and photocel ls 7 .
Figures 6a and 6b illustrate typical shapes of moulded coal 1 which are preferably used for the coking of coal by means of microwaves. They are cylindrical or spherical with central bores 2 by means of which a central region which is liable to remain soft is avoided and the mouldings are made more suitable for the process of heat and mass transfer.
Figure 7 shows a storage bunker 51 which tapers downwards like a funnel from which milled coal 53 is distributed downwards by a distributing device 57, designed as a bucket wheel lock, onto a conveying device 58. This :~

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is in the form of a vibrating trough, with the aim that the layer of coal should be of uniform thickness over the whole of the trough if possible. A
load distributor 59 is located at the lower end of the conveying device 58 and is arranged to level the layer of coal 53' immediately upstream of the entrance to a microwave treatment zone 52. Just before the inlet opening 60 to the microwave treatment zone 52, the coal 53' is deposited on a conveyor belt 54 the upper rim of which passes through the microwave treatment zone 52. The inlet opening 60 just permits the upper run of the conveyor belt, with a layer of coal, for example 100 mm thick, lying on it to enter the zone 52, but otherwise it is closed, for example by a flap 61 sliding over the layer of coal and, if necessary, by band stops ~not shown) to prevent the escape of microwave radiation. The same applies to the outlet opening 62 at downstream end of the microwave treatment zone 52. Otherwise the microwave treatment zone 52 is enclosed in a housing 63 which contains two opposing electrode plates 64 between which runs the conveyor belt 54 with the layer of coal lying on it. The belt can be run at an adjustable speed for example in the range between 8 and 12 m/minute. The speed at which the conveyor belt 54 is run depends among other factors on the effective length of the microwave treatment zone 52, the water content of the coal to be ; 20 treated, the grain size of the coal, the in~ensity and frequency of the micro-waves and the gap between the electrodes 64 and the layer of coal. The micro-wave field required for heat-treatment i.e. for drying and preheating of coal is generated between the electrodes 64 in a conventional manner, for example by using a voltage of 9,000 V and a frequency of 2,450 MHz. A venting duct 65 is connected to the housing 63. Dry air which has been preheated in a heater 66 is blown from the duct 65 by means of a blower 67 into the micro-wave treatment zone 52 in such a way that it flows over the layer of coal and removes moisture from its surface. Openings 68 are provided in ~he upper f~ , electrode 64 to distribute the heated air evenly over the coal. On one side of the microwave treatment zone 52 the moisture containing air is removed from the microwave treatment zone 52 and after passage through a moisture condenser 69 it is vented from the system as waste air. The condensed water is collect-ed at 70. The heater 66 can be operated by using the waste heat from the plant used to generate the microwave radiation. The dried and possibly pre-heated coal emerges from the outlet opening 62 into a hot coal bunker 71 from whence it can be conveyed through a slide valve 72 to a weighing bunker 73 and thence to the inlet 9 of the coke-oven shown in Figure 1.
Figure 8 shows a feed chute 55 which is equipped with electrodes 74 extending in the direction of flow o the coal in the feed chute 55 to serve as a treatment zone for drying and/or preheating of coal.
The feed chute 55 can be positioned at any chosen place between the bunker for damp coal and the coke-oven e.g. the coke-oven shown in Figure l on the conveying track between the bunker and the oven, or directly above the inlet 9 to the oven in Figure 1. Figure 8 shows the feed chute 55 in a position between a coal bunker 75 which has discharge equipment 76 at its lower end and for example a feed funnel 77 juxtaposed to the inlet 9 of the oven of Figure 1. At the lower end of the feed chute 55 there is also dis-charge equipment 78 to enable dried and possibly preheated coal to be deliver-ed at the desired rate. The rate of delivery from the discharge equipmen* 78 determines the residence time of the coal in the microwave field. In the example shown, that part of the feed chute 55 which forms the treatment zone 52 slopes downwards so that ~he coal is conveyed as on a slide through the treatment zone 52. An air stream from a blower may be blown across the upper part of the feed chute 55 to remove moisture. Such an air stream can be pro-vided to flow along the inner walls of the feed chute 55 for example by arranging a grid of appropriate mesh size in the chute 55. To prevent . ~

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recondensation, air shower heads 86 can be arranged at the inner lower edges of the guide plates to feed hot streams of air over the layers of coal along the slope of the slide plate.
Figure 9 illustrates a coal bunker 56 for use in a coking plant according to the lnvention. Vertical electrode plates 84 are located inside it for producing the required microwave intensity. These constitute the treatment zone 52. The dried and possibly preheated coal 53 is withdrawn from the lower end of the coal bunker 56 at the desired rate by means of discharge equipment 85, for example to feed preheated or predried coal to the inlet 9 of the coking oven shown in Figure 1.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for coking coal comprising introducing coal or moulded coal into a coking chamber, exposing said coal to microwave radiation, thereby forming said coal into hot coke, introducing said hot coke into a cooling zone to form cooled coke, wherein said cooling zone comprises photocells, which con-vert radiant energy from said hot coke into electricity.

2. A process as claimed in Claim 1 in which coal in the form of milled coal in containers or coal in the form of separate moulding is exposed to microwave radiation.

3. A process as claimed in Claim 2 in which the mouldings are cylindri-cal or rectangular or spherical or rounded.

4. A process as claimed in Claim 2 in which each moulding has at least one hole in it.

5. A process as claimed in Claim 4 in which each moulding has at least one hole passing through it.

6. A process as claimed in Claim 1 in which the coal or moulded coal is exposed to microwave radiation to dry or preheat it or dry and preheat it and then to microwave radiation to convert it to coke.

7. A process as claimed in Claim 1 in which the coal is fed continuously through a microwave radiation zone to effect the coking operation.

8. A coke-oven for coking coal in a process as claimed in Claim 1, said coke-oven comprising a coking chamber which is in the form of duct shaped con-ductors or resonating cavities, means for generating microwaves for heating said coal, and a cooling zone situated downstream with respect to a direction of flow of the coal and adjacent to the coking chamber, wherein the coking chamber and the adjacent cooling zone are in the form of a vertical or sloping duct and the cooling zone is fitted with photocells whereby heat energy in the hot coke can be collected as electrical energy.

9. A coke-oven as claimed in Claim 8, in which means are provided for passing coal through the coking chamber in a continuous process.

10. A coke-oven as claimed in Claim 8 in which the cooling zone is separated from the coking chamber by a shutter.

11. A coke-oven as claimed in Claim 8 in which at least one filling chamber, which can be moved between one or more filling positions, one or more positions for compressing the coal in the chamber and a position for charging coal, is provided whereby in the position for charging coal, coal can be pushed from the filling chamber into the coking chamber, and then through the coking chamber and through an adjacent cooling zone by succeeding charges of coal.

12. A coke-oven as claimed in Claim 11 wherein coal can be pushed from the filling chamber into the coking chamber via a preheating zone.

13. A coke-oven as claimed in Claim 11 in which a filling chamber is moved back and forth between a first filling position and a first compressing position on one side of the coke oven and a second filling position and a second compressing position on the other side of the coke-oven.

14. A coke-oven as claimed in Claim 11 or Claim 13 in which the filling chamber is moved transverse to the plane of the coke-oven between said filling position, compressing position and charging position.

15. A coke-oven as claimed in Claim 8 in which the coking chamber has a gas vent.

16. Coking plant comprising a coking oven as claimed in Claim 8 in combination with coal treatment plant comprising a storage bunker, means defin-ing at least one treatment zone, means for generating microwaves in the treat-ment zone, and conveyor means for transporting the coal from the storage bunker to the said coking oven via the treatment zone.

17. Coking plant as claimed in Claim 16 in which the coal passes through the treatment zone on a conveyor belt.

18. Coking plant as claimed in Claim 16 in which the treatment zone is provided with at least one vent.

19. Coking plant as claimed in Claim 16 in which the coking oven has a supply hopper and the treatment plant comprises a coal bunker, and a feed chute connecting the coal bunker to the supply hopper of the coking oven, the treat-ment zone being formed as part of the coal bunker or the weighing bunker or the feed chute or the supply hopper.

20. Coking plant as claimed in Claim 19 wherein the treatment plant further comprises a weighing bunker.

21. Coking plant as claimed in Claim 19 in which the treatment zone is formed inside the coal bunker.

22. Coking plant as claimed in Claim 21 in which the treatment zone is defined by at least two opposed spaced plate electrodes-disposed between the inlet and outlet from the bunker whereby coal can flow between the plates from the inlet valve to the outlet of the bunker.

23. Coking plant as claimed in Claim 21 in which the treatment zone is formed inside the feed chute.

24. Coking plant as claimed in Claim 23 in which the treatment zone is defined by at least two opposed spaced plant electrodes extending from at or near the inlet of the chute to at or near its outlet.

25. Coking plant as claimed in Claim 24 in which the lower end of each plate is provided with an air supply duct whereby air can be blown up along the plate.

26. Coking plant as claimed in Claim 16 in which the treatment zone is constructed as a duct shaped conductor or as a resonating cavity.