US3013951A

US3013951A - Method for continuous coke production whiled extracting low temperature volatiles

Info

Publication number: US3013951A
Application number: US820213A
Authority: US
Inventors: Mansfield Vaughn
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-06-15
Filing date: 1959-06-15
Publication date: 1961-12-19
Anticipated expiration: 1978-12-19
Also published as: GB953878A

Description

Decflg, 1961 v. MNsr-'IELD METHOD FOR CONTINUOUS COKE PRODUCTION WHILE EXTRACTING LOW TEMPERATURE VOLATILES Filed June 15, 1959 INVENTOR Walibi fdhfz'eid BY H4 ATTORNEY Unitedl States Patent C r""ce 3,013,951 METHOD FOR CONTINUOUS COKE PRODUCTION WHILE EXTRACTING LOW TEMPERATURE VOLATILES Vaughn Mansfield, 301 Olive St., St. Louis, Mo. Filed June 15, 1959, Ser. No. 820,213 7 Claims. (Cl. 20L-15),

This invention relates to the continuous production of coke and usable heat while extracting low-temperature volatiles from coal and, particularly, relates to novel Stroker-furnace construction and the method of operating it so as to produce heat in such manner that part of the heat is utilized in a steam boiler or other heat absorbing device, part drives ofi low-temperature volatiles, and a strong coke end product is produced from the carbonized coal.

In the prior production of coke, such as disclosed in the patent toi Anderson et al., No. 2,209,255, an ignited layer of coal was passed on a chain conveyor grate travelling through a coking oven, and air was fed upwardly through the grate and coal bed in such small amounts that only the volatiles which combust at comparatively low temperatures were burned in the bed, leaving a coked bed at the output end of the oven. The object now is to provide a coking oven with a travelling grate wherein the oven has a relatively low roof over the front portion thereof, under which the coal is partly coked, a higher roof, providing an increase in the oven volume, under which carbonization is nearly completed, an outlet in the rear portion of the oven for feeding heat to a furnace or other heat utilizing device, and an over-lire air feed for producing a. fire ball over the partly coke coal bed as it passes through the rear portion of the oven. Only enough preheated air, plus a small amount of recycle gas, is supplied upwardly through those portions of the bed travelling beneath the front portion of the oven to sweep off the tars and low temperature volatiles while maintaining only enough combustion as to keep the bed ignited and burning at temperatures in the range of 848 `E. to 1OI6O F., and the tire ball in the rear portion of the oven is used to nearly complete the carbonization of the coke at high temperatures and to supply heat to the boiler or other' heat absorbing device. The low volatiles, gases containing much of the tars, and low temperature liquids, are extracted through an outlet in the front of the oven so that they never reach the region toI which over-fire air is supplied, and only those volatiles which are driven off at higher temperatures remain in the operation of the bed which passes beneath the re ball in the rear portion of the oven.

A further object object is the provision of a partition for confining the low-temperature volatile matter, which is driven olf at relatively low temperatures as the coal bed passes beneath the front portion of the oven, from entering the rear portion of the oven where higher temperatures prevail. The partition also serves to prevent the tire ball or high temperature gases in the rear portion of the oven from reaching the low-temperature volaties at the front part of the oven, or from ilowing out through the exhaust outlet provided for the low-temperature volatiles.

Another object is to provides at the rear, or outlet end of the oven, a retort in which residual high-temperature volatiles are driven offrom the hot coke, and in which the coke is then quenched. The retort, described and claimed herein in combination with the cokingoven, is the subject of a copending joint application of Herbert C. McCollum and Vaughn Mansfield, entitled Coke Quenching Retort and Method,"Serial No. 820,172, led June 15, 1959, now abandoned.

3,013,951 Patented Dec. 19, 1961 provide a structural relationship of the coking oven and retort so that part of the latent lheat and virtually all of the residual volatile matter in the coke are fed back into the rear end of the coking oven for utilization, and so that a substantial part of the remaining heat derived in quenching the coke is utilized to pre-heat the primary air for the coking oven.

Still another object is to provide for the feeding back and utilization of part of the low-temperature volatiles, i.e., the fuel gas, derived from the coke for maintaining combustion in the front portion of the coking oven. Another object is to feed back hot stack gases for preheating the coal at the input of the oven, and also the sweeping ott high-temperature volatiles, without burning the iixed carbon, in the coke at the rear of the oven. Another object is to utilize stack gas from the coking oven for sweeping off residual volatiles from the hot coke content of the quenching retort, and for quenching the fully carbonized coke produ-ct.

These and other objects Will be apparent from the following specication and drawing, in which the sole tigure is a diagrammatic longitudinal cross-section through the pertinent portions of the coking oven, quenching retort, and ow diagram for the assembly.

Referring now to the drawing, in which like reference numerals denote similar elements, the ow circuits for the process and apparatus will first be described so that the inter-relationships of the components of the system may be understood and correlated in the description of the details.

Biturninous coal is fed from a supply bin 10 through a suitable chute or conveyor 11 to a preheater, in which the coal is brought up to a temperature of about 350 F. to 450 F. The coal should be preheated up to, but not including, the temperature at which the coal starts to give off appreciable volatile matter, this temperature depending on the particular coal being used. From preheater 12 the coal, which, after preheating, is substantially moisture free, is introduced through the chute or other suitable conveyor 13 to an input hopper 14 having at its outlet end an igniter 116, which may be gas tired or electrically heated, the ignited coal then being evenly distributed by a spreader gate 17 on a travelling grate 18, on which the ignited bed of coal travels through a coking oven 20. In passing beneath the front zone 21 of the oven, wherein the oven roof l2.2 is low, the low-temperature volatiles (those which are driven oil in the temperature range between 848 F. to 1060 F.) are -removed from the coal and, as the bed passes through the rear portion 23` of the oven having ay raised roof 22a, most of the high-temperature volatiles (those which are driven oif at bed temperatures between l060 F. and 1800" F. or 1901)" F.) are removed. As the bed reaches the rear end of travelling grate 18, it passes beneath a hot gas outlet 24 which supplies heat to a boiler or thelike heat utilizing device (not shown) and is then discharged into a quenching retort 26 which lies beneath the rear end 28 or coking oven 20. The residual volatiles, in the range of 4% to 8% of those originally in the coal, which remain in the then nearly completely carbonized product are driven oiin retort 26, by the latent heat in the coke as the coke stack moves through the upper portion 99 of retort 26,

- and the coke is quenched in the lowerportion 1000i The object now is to the retort and then discharged by a feeder 30 onto a conveyor 32, the eolie then having been quenched to elow its ignition temperature.

The low-temperature volatiles removed from the coal as it passes through zone 21 are extracted through an outlet 34 and fed through a suitable conduit 36` to a product recovery unit 38, wherein the lo`wtemperature volatiles are distilled and scrubbed, and taken ofi as light oil, medium oil and pitch through conventional outlets indicated, as a group, at 40. The fuel gas output of product recovery system.38 is discharged through line 42, a portion of the fuel gas output being fed by a line 44 to a suitable utilization device, which may include igniter 16. The remainder of the fuel gas output of product recovery system 38 is fed through a branch 46 and pump 48 to a heat exchanger 50, wherein it is heated and thence passed through a supply line 52 to a fuel gas manifold 54, from which it is recycled by fuel gas lines, one of which is designated FG to the first four zones of an air box S6 which extends beneath the length of travelling grate 18. The feed of fuel gas from manifold 54 to each of zones l to 4, inclusive, is individually controlled by valves, one of which is indicated at 58. Part of the fuel gas output of product recovery system 38 is thus used to sweep off the low-temperature volatiles, and to maintain carbonizing temperature in the coal bed as the latter passes over the first four zones of air box 56, these first four zones lying beneath zone 21 previously designated.

Primary air is supplied through an intake line 60 and thence forced by pump 62 through an air preheater 64. Part of the preheated air is supplied by a line 66 to a preheated air manifold 68, from which the primary air is distributed by individual air lines, one of which is designated AL to all eight zones of the air box 56, the air feed to the separate Zones being individually controlled by valves, one being designated 70. The remainder of the preheated primary air is taken off line 66 through a branch line 67 and thence fed through control valves 70 to over-fire air ports 71 which enter the oven in zone 23 beneath the roof 23a of the high-temperature section of the coking oven.

Part of the stack gas from outlet 24 is taken oil? and circulated through coal preheater 12 via supply and

return lines

72 and 74, respectively, a pump 76 being provided to force the circulation. Some of the other stack gas is taken off via supply line 78 and forced by pump 82 to stack gas manifold 84, and thence distributed by individual supply lines, one of which is designated SG to the last four Zones of air box 56, the supply of stack gas to the separate zones being individually controlled by valves, one being designated 85. A portion of the stack gas is taken off line 80 via branch 88 and thence, through valve 90, into a line 92, in which it is forced by pump 94 to a manifold 96 surrounding the lower part of a quenching retort 26. From manifold 96, cool stack gas, which is substantially inert, passes through ports 98 into the lower portion of the coke stacked in the retort. The stack gas entering ports 98 creates a pressure, sufficiently above atmospheric pressure, to prevent air from entering upwardly through discharge opening 31 at the bottom of retort 26, a small portion of the stack gas leaking outwardly past feeder 30. Most of the stack gasses entering ports 98 pass upwardly through the stack of coke in the lower portion 100 of retort 26, and most of the upwardly flowing stack gases then flow outwardly through ports 102, manifold 104 and through return lines 106 and 106:1 and valve 107 to heat exchanger 50 and air preheater 64, which is also a heat exchanger. Heat in the lower portion of the coke stack in retort 26 transfers to the stack gas and is transmitted thereby to heat exchanger 50 and air preheater 64, wherein a large part of the heat is given up to the fuel gas and primary air which ow through heat exchanger 50 and air preheater 64.

A small portion of the stack gas flowing upwardly through the lower portion of the coke stack in retort 26 does not emit via ports 102 but, rather, passes on upwardly through the hot unquenched coke in the upper portion 99 of the coke stack in retort 26 so as to sweep off the residual volatiles which are driven off the latent heat in the coke in the upper portion 99 of the stack, these volatiles then being consumed in the fire ball 116 described hereinbelow.

Returning now to the entry of the ignited preheated coal into coking oven 20, spreader gate 17 is adjusted to provide a relatively thick but uniformly distributed bed 19 of coal on travelling grate 18. One feature of the invention is that relatively small coal, even 1/4" by 0, may be used to form coke agglomerate. The travelling grate is driven by a suitable source of power, not shown, it being understood that the grate, which may be of chain or perforate sections, moves the bed slowly from left to right, as seen in the drawing. In a typical embodiment, the upper run of the grate is from twenty to thirty feet long and from twenty to thirty feed wide. Spreader gate 17 is adjusted, by control mechanism 108, to provide a comparatively thick bed, in the range of four to twenty inches in depth. The maximum height of roof 22 should be about thirty-six inches above the grate. Preheating of the coal has been found desirable so as to avoid the necessity of extensive ignition, to provide for ready ignition of the entire bed from top to bottom, to eliminate moisture and so that only a small amount of primary air need be fed upwardly from zone l of air box 56 to firmly start and maintain combustion through the bed. Without preheating of the coal, so much primary air must be fed up from zone l to ignite the bed that excessive combustion of the low-temperature volatiles takes place. This results in dilution of the low-temperature volatiles by the CO2 combustion product.

In starting the process, enough primary air is fed upwardly from air box zones 1 to 8 to bring the oven up to its operating temperatures. Thereafter, the air valves 70 for air box zones 2 to 4, inclusive, are closed, or barely cracked, while the air valve 70 for zone l is opened so as to supply enough primary air to completely ignite bed 19 from top to bottom. However, the primary air supply is limited so that the bed temperature does not exceed 1060 F. as it passes above air box zones l to 4.

Fuel gas valves 58 are adjusted so as to feed fuel gas to

zones

2, 3 and 4 of air box 56 so as to sweep off the low-temperature volatiles. It will be understood that bed 19 is initially partly ignited as it enters oven 20 and ignition is completed by forcing air upwardly through it as the bed passes over the first zone, and it remains ignited as it passes over

zones

2, 3 and 4. Assuming that the coal input to the oven had about 40% volatile content, approximately 58% of the original volatiles will have been driven off by the time the bed progresses beyond partition 110. Partition 110 is, of course, adjusted by mechanism 112 so that the top of the bed scrapes along its lower edge. The low-temperature volatiles, including the tars, which are driven off the coal as the bed 19 passes over air box zones 1 to 4, inclusive, are exhausted through outlet 34 as previously outlined.

Air valve 70 leading to air box zone 5 iS adjusted so that substantially more air is fed upwardly through bed 19 over zone 5 than was fed up from zone 1, and the air valves for zones 6, 7 and 8 are closed, or barely cracked. The rate of combustion, when bed 19 passes above zone 5, is sharply increased so that the bed reaches temperatures in the range of 1800" F. to 1900 F. The stack gas feed to zones 6, 7 and 8 is adjusted so as to sweep off the high-temperature volatiles. However, over zones 5, 6, 7 and 8, the bed temperatures are not created solely by combustion within the bed. The unburned high-temperature volatiles, after being swept upwardly through the bed, combine with over-fire air fed in through ports 71 and ignite, thereby creating a fire ball in the region indicated generally at 116. rIlhe radiant heat from fire ball 116 progressively raises the temperature of the bed, from the top downwardly, as the bed progresses over air box zones 5, 6, 7 and 8.

The speed of movement of bed 19 from left to right, as seen in the drawing, is maintained so that by the time the bed passes beyond air box zone 8 and thence off the end of the travelling grate, most of the high-temperature volatiles will have been driven off. However, the bed is moved sufiiciently fast so that the high temperatures de veloped by the radiant heat in passing over the last four air box zones will not have completely worked down to the surface of the grate. By leaving residu-al volatiles in the nearly completely carbonized bed, excessively high temperatures on the grate surface are avoided and thus longer grate life is achieved. In addition, considerably more tonnage can be handled on the grate by moving a thick bed through the coking oven at a rate faster than that which would achieve more complete carbionization, wherein in the bed would rbe retained on the grate for a longer time, and higher :temperatures would be developed on the grate surface. However, the bulk of the bed Will, at the time it passes over the end of the travelling grate, have developed sufficiently high temperatures so that by co-mingling the nearly completely carbonized coke in the upper portion of retor 26, the residual volatiles will be driven off by the latent heat within the bed.

After preheating the oven, lsuliicient coke is run through to till retort 26 nearly to its top, and thereafter feeder 30 is operated to discharge coke on the conveyor 32 at the same rate that the nearly completely carbonized coke is dumped off travelling grate 18 into the top o-f retort 26. For purposes of demonstrating the operation of the system, the stack gas has been considered -as virtually inert. Actually, a small amount of oxygen remains in the gas as it is derived from the stack. If desired, the oxygen content may be removed by conventional apparatus. Sufricient stack gas is fed through line 78, Valve 90 and line 92 so that, upon operation of pump 94, stack gas is circulated into retor 26 through manifold 96, ports 98 and thence upwardly through the lower pontion 100 of the co-ke in retort 26, and thence out ports 102, manifold 104 and lines 106 and 10651 through heat exchanger 50 and preheater 64. When the circuit through heat exchanger 50, air preheater 64 and the lower portion 100 of retort 26 is charged with stack gas, only enough additional stack gad need be introduced through valve 90 to make up the losses resulting from downwardly escaping gas through feeder 30, and the upward flow of stack gas through the upper portion 99 of retort 26, the last mentioned flow being sufficient only to sweep olf the residual volatiles which are driven from the coke as a result of the latent heat remaining as the coke is dumped olf the end of the travelling grate. The high-temperature volatiles swept off the coke in the upper portion 99 comingle with those swept upwardly from the portion of the v bed travelling over air box zones 5, 6, 7 `and 8 and are consumed in re ball 116.

The heat extracted from the coke in the lower portion 100 of retort 26 by the up-flowving stack gases is transferred `in heat exchanger and air preheater 64 to the fuel gas ilowing into manifold 52 and the primary air for manifold 68 and, in turn, the heat fed back to bed 19. It yis contemplated that the coke at the top of the upper portion 99 of retort 26 will be at approximately 1700 F.; the stack gases leaving retort 26 through ports 102 will be at approxi-mately 1500 F.; and the stack gasses entering the retort through ports 98 will be -at ap'- proximately 200 F. f

The relatively high coking temperatures achieved in the bed at the end of travelling grate 18 and at the top of retor 26 result in an extremely strong coke agglomerate, particularly adapted for metallurgical sintering `and as a chemical agent in chemical processes, such as' in the production of carbide and elemental phosphorous. As the coal in the relatively thick bed moves through the furnace, comparatively little relative motion occurs between the adjacent lumps so that, las the coal reaches plasticizing temperature, large lump coking ensues, The products derived from recovery system 38 have widespread use; and the heat output through outlet 24 is usable in an adjacent boiler or the like heat utilizing device.

The invention is not limited to the exact structure and method described and disclosed herein, but it is intended to cover all substitutions, modifications, and equivalents within the scope of the following claims,

I claim:

1. A process of carbonizing Ia plasticisable and carbonizable material containing certain volatiles which may be driven off at relatively low temperatures and certain other volatiles which require higher temperatures -t-o be driven off, which comprises; passing a hot substantially uniformly thick ho-mogeneous bed of said material progressively in a horizontal direction through contiguous first and second discrete portions of a closed chamber, feeding air through -a portion of the bed passing through the rst chamber portion in controlled amounts sucient only to maintain limited combustion of part of the low-temperature volatiles while driving olf substantially all of the remainder of the low-temperature volatiles and to heat the bed to plasticising temperatures, extracting said remainder of the low-temperature volatiles from the iirst chamber portion, and simultaneously feeding air upwardly through a portion of the bed passing through the second chamber portion in controlled amounts suiicient only to maintain limited combustion of only part of the high-temperature volatiles while driving off nearly yall the remainder thereof into the chamber above the bed while simultaneously feeding over-tire air into the chamber above the Ibed in controlledam'ounts sufficient to create a re -ball 4above that portion of the bed passing through the second chamber portion and to heat the bed to carbonizing temperatures.

2. In a process as claimed in claim l, the step of preheating said material as it passes into the rst discrete portion of the closed chamber.

3. In a process as claimed in claim l, the step of passing the products of combustion upwardly from the tire ball for utilization in a heat utilizing device.

v4. In a process as claimed in claim 1, the step of collecting the material, after it passes through the second discrete portion of the closed chamber, in a column in a confined space substantially devoid of oxygen and communicating with the second chamber portion, and maintaining the collected material in said column until the latent heat thereof drives off lsubstantially all the remaining volatiles therefrom whi-le passing said driven-off yremaining volatiles to said re ball.

5. A process of carbonizing a plasticisable and carbonizable material containing certain volatiles which may be driven off at relatively low temperature and certain other volatiles which require higher temperatures to be driven off, which comprises: passing hot substantially uniformly thick homogeneous bed of said material -progressively in a horizontal direction through contiguous iirst and second discrete portions of a closed chamber,

feeding air upwardly through the bed as it enters the first portion in amounts sutlicient only to create limited combustion so as to heat the -bed to plasticising temperature and thereby -release the low-temperature volatiles, n

xed carbon in the bed, feeding over-tireV air into said, second portion above the bed and creating a fire ball overlying the bed so as to radiantly heat the bed and create stack gases, and circulating hot substantially inert gases upwardly through the bed as the latter progresses through the second cham-ber so as to sweep the hightemperature volatiles from the bed into the re ball.

6. A process of carbonizing a plasticisable and carbonizable material containing certain volatiles which may be driven off at relatively low temperature and certain other volatiles which require higher temperatures to be driven off, which comprises: passing a hot substantially uniformly thick homogeneous bed of said material progressively in a horizontal direction through contiguous first and second discrete portions of a closed chamber, feeding air upwardly through the bed as it enters the rst portion in amounts sucient only to create limited combustion so as to heat the bed to plasticising temperature and thereby release the low-temperature volatiles, recovering the low-temperature volatiles thus driven off and separating the same into constituents including fuel gas while preheating and reeirculating at least part of the separated fuel gas upwardly through the bed as the latter progresses through said rst portion so as to sweep 01T the low-temperature volatiles, feeding additional air upwardly through the bed as the latter enters the second zone in amounts sucient to create limited combustion so as to heat the bed to above plasticising temperature and thereby lrelease at least part of the high-temperature volatiles but insuicient to bu-rn substantial amounts of fixed carbon in the bed, feeding over-fire air into said second portion above the bed and creating a re ball overlying the bed so as to radiantly heat the bed and create stack gases, and circulating hot substantially inert gases upwardly through the bed as the latter progresses through the second chamber so as to sweep the hightemperature volatiles from the bed into the fire ball.

7. In a process as claimed in claim 6, the step of splitting ot a portion of the stack gases created in the re ball, the hot inert gases circulated upwardly through the bed `as the latter progresses upwardly through the chamber being the split-off stack gases.

References Cited in the tile of this patent UNITED STATES PATENTS 1,591,023 Ditto et al. July 6, 1926 1,839,741 Davies Jan. 5, 1932 1,918,162 Willson July 11, 1933 2,209,255 Anderson et al. July 23, 1940 2,347,076 Boynton Apr. 18, 1944 2,380,930 Anderson et al. Aug. 7, 1945 2,668,760 Breyer et al. Feb. 9, 1954

Claims

1. A PROCESS OF CARBONIZING A PLASTICISABLE AND CARBONIZABLE MATERIAL CONTAINING CERTAIN VOLATILES WHICH MAY BE DRIVEN OFF AT RELATIVELY LOW TEMPERATURES AND CERTAIN OTHER VOLATILES WHICH REQUIRE HIGHER TEMPERATURES TO BE DRIVEN OFF, WHICH COMPRISES, PASSING A HOT SUBSTANTIALLY UNIFORMLY THICK HOMOGENEOUS BED OF SAID MATERIAL PROGRESSIVELY IN A HORIZONTAL DIRECTION THROUGH CONTIGUOUS FIRST AND SECOND DISCRETE PORTIONS OF A CLOSED CHAMBER, FEEDING AIR THROUGH A PORTION OF THE BED PASSING THROUGH THE FIRST CHAMBER PORTION IN CONTROLLED AMOUNTS SUFFICIENT ONLY TO MAINTAIN LIMITED COMBUSTION OF PART OF THE LOW-TEMPERATURE VOLATILES WHILE DRIVING OFF SUBSTANTIALLY ALL OF THE REMAINDER OF THE LOW-TEMPERATURE VOLATILES AND TO HEAT THE BED TO PLASTICISING TEMPERATURES, EXTRACTING SAID REMAINDER OF THE LOW-TEMPERATURE VOLATILES FROM THE FIRST CHAMBER PORTION, AND SIMULTANEOUSLY FEEDING AIR UPWARDLY THROUGH A PORTION OF THE BED PASSING THROUGH THE SECOND CHAMBER PORTION IN CONTROLLED AMOUNTS SUFFICIENT ONLY TO MAINTAIN LIMITED COMBUSTION OF ONLY PART OF THE HIGH-TEMPERATURE VOLATILES WHILE DRIVING OFF NEARLY ALL THE REMAINDER THEREOF INTO THE CHAMBER ABOVE THE BED WHILE SIMULTANEOUSLY FEEDING OVER-FIRE AIR INTO THE CHAMBER ABOVE THE BED IN CONTROLLED AMOUNTS SUFFICIENT TO CREATE A FIRE BALL ABOVE THAT PORTION OF THE BED PASSING THROUGH THE SECOND CHAMBER PORTION AND TO HEAT THE BED TO CARBONIZING TEMPERATURES.