US1932296A

US1932296A - Process for carbonizing solid carbonizable fuel

Info

Publication number: US1932296A
Application number: US262472A
Authority: US
Inventors: Walter E Trent
Original assignee: Trent Process Corp
Current assignee: Trent Process Corp
Priority date: 1928-03-17
Filing date: 1928-03-17
Publication date: 1933-10-24
Anticipated expiration: 1950-10-24

Description

Oct. 24, 1933. 1,932,296

PROCESS FOR CARBONIZING SOLID CARBONIZABLE FUEL W. E. TRENT Filed March 17, 1928 3 Sheets-Sheet 1 I Waller-z. 5611/ BY Y ATTORNEY w. E. TRENT 1,932,296

PROCESS FOR CARBONIZING SOLID CARBONIZABLE FUEL Oct. 24, 1933.

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Oct. 24, 1933. w. E. TRENT 1,932,296

PROCESS FOR CARBONIZING SOLID CARBONIZABLE FUEL Filed March 17, 1928 3 Sheets-Sheet 3 INVENTOR.

WY had/7 ATTORNEYS.

an incandescent state in the hotter portions of Patented Oct. 24, 1933 UNITED STATES PROCESS FOR CABBONIZIN G SOLID CARBONIZABLE FUEL Walter E. Trent, New

York, N. 122, allimor to The Trent Process Corporation, a corporation of Delaware Application March 17,

8 Claims.

The invention relates to a continuous process of treating finely divided coal to effect carbonization of the same without producing substantial agglomeration of the particles thereof, and also to wholly or partially gasify the carbon particles as an integral part of the continuous process, thereby effecting separation of the ash constituents of the coal from the fuel constituents thereof.

It is an object of the invention to feed coal in finely divided form by gravity through a heating zone in which the coal is brought progressively under the influence of hotter and hotter temperatures, the heating being so conducted that heat is applied substantially uniformly and gradually over a suflicient period of time to permit of the carbonization and removal of the distillable fractions of the coal in the cooler portions of the heating zone without agglomerating the residual carbon particles.

It is a further object of the invention to discharge the ash constituents of the coal, if compiete gasification of the coal is being brought about in the heating zone, or the residual carbon particles and ash constituents, if only partial gasification of the coal is being sought, through a water seal at the discharge end of the retort, and to utilize the steam evolved by reason of the contact of the hot carbon and/or ash with the water to transfer heat from the heating surfaces in the hotter portions of the retort to the coal in the cooler portions thereof.

Another object of the invention is to produce water gas from at least a portion of the carbonized particles by bringing the steam into contact with such carbonized particles brought to the retort.

The invention further comprises, as a modification of the process, the complete gasification oi the carbon particles remaining after removal of the distillable fractions of the coal, the gasification produced by the action of the steam being supplemented by the admission of controlled amounts of air or oxygen so that a mixture of water gas and producer gas, either with or without the products of distillation removed in the earlier stages of the treatment or the gases remaining after the condensable fractions thereof have been removed, is obtained.

A further object of the invention is to prevent the entrance of air into the heating zone-both at the entrance end and at the exit end-except under controlled conditions when producer gas is being produced from the carbonized residue.

1928. Serial No. 262,472

A still further object of the invention is to provide gravity feeding of the finely divided coal to the retort so as to insure that the charge will be substantially uniformly distributed over the entire cross-sectional area of the retort.

Another object of the invention is to accomplish the uninterrupted and continuous discharge of solid residual material from the entire bottom area of the retort through the water seal.

Further objects and advantages of the invention will appear from the appended detailed description taken into conjunction with the accompanying drawings, in which:

Figure 1 is a part vertical section and side elevation of an apparatus for use in carrying out my new process;

Figure 2 is a part vertical section and side elevation taken on the line 22 of Figure 1;

Figure 3 is a horizontal section taken on the line 33 of Figure 1; I

Figure 4 is a detailed sectional view taken on the line H of Figure 1; and

Figure 5 is a sectional view taken on the line 5-5 of Figure 4.

In the drawings 10 indicates generally a carbonizing apparatus adapted to carry out the present invention. The apparatus comprises a vertical retort 12 formed by the side walls 14 and the end walls 16. Extending across the retort 12 are a plurality of tubes 18 which open at their ends into spaces defined between the side walls 14 and outer walls 22 for the reception of the products of combustion from gas burners 24 disposed near the lower end of the retort.

The spaces at each side of the retort are divided by vertical partition walls 26 and horizontal partition walls 28 into a plurality of separate compartments 20a--20h so as to insure that the heating gases shall be circulated back and forth through the tubes 18 in countercurrent relation to the coal descending into the retort 12. As shown in Figure 3, a. single combustion chamber 30 is provided at each side of the retort 12 common to all of the burners on the respective sides. As shown more clearly in Figures 2 and 3, gases from the respective combustion chambers 30 pass into the tubes in the alternate vertical sections of the retort in order to permit the circulation of the gases from the respective combustion chambers upward through the retort, and to prevent short circuiting and intermingling of the gases from the combustion chamber with those from the other, baflles 32 are provided in the respective combustion chambers. The gases from those burners directly opposite the portions of the vertical sections of tubes communicating with the combustion chamber containing such burners are led directly into thelower sets of tubes in that particular section. The gases from the adjacent burners which are opposite the adjacent bafiies 32 pass around such baflies, mingle with the gases .from the burners first mentioned, and are led with them into the lower tubes of the adjacent vertical sections. It will be apparent that the provision of the bailies 32 permits of the doubling of the number of burners that may conveniently be located on each side of theretort, thereby insuring the utilization of substantially the entire available space for combustion on each side of the retort. Some heat will also be transbailles to the hot gases passing through the ad- 7 jacent chambers a from the opposite combusits tion chamber. A coal storage hopper or chamber 34 is provided at the upper end of the retort. The discharge opening from' this hopper to the retort is preferably made of the same cross-sectional area as the retort and is adapted to be closed by a sliding gate or gates 36, two being shown in the drawings. These gates are shown as being operated through a rack and pinion mechanism 38 by a conventional operating chain 40. Other suitable actuating means may of course be employed. Normally, in the operation of the process, the gates 36 are maintained in fully opened position to permit the feeding and distributing of the coal over the entire cross-sectional area of the retort to take place evenly and entirely by gravity.

A plurality of sets of eduction tubes 42 are positioned in the upper portions of the retort. The upper set of tubes is shown as connected to a suitable suction fan 44 and has for its purpose to withdraw air which may be introduced with the coal being fed from the coal' storage hopper 34 and thereby prevent its intermingling with the distillation products. The remaining sets of tubes 42 are shown as connected through suitable headem 46 and a conduit 48 to a condenser'50 in which the condensable fractions of the distillable portions of the coal may be separated from the fixed gases. If desired, the upper set of eduction tubes '42 may be connected to the condenser 50 as well as to the air suction fan 44,-and suitable valve means maybe provided for optionally diverting the gases withdrawn through such set of tubes either to the condenser 01' through the suction fan 44. This arrangement is recommended when treating high volatile coals.

At the discharge end of the retort a water seal 52 is provided. Disposed beneath the normal water level of the seal is a conveyor or discharging bottom 53 consisting of a plurality of conveyor shafts 54 having a series of conveyor blades 56 mounted thereon at such a pitch as to tend to move the carbonized particles and ash residue from the lower end of the descending column end- Wise of the retort to a common discharging conveyor 58. The conveyor shafts 54 and the blades 56 can'ied thereby are shown as mounted in longitudinally-disposed troughs 60. As shown in the drawings, the discharging conveyor 58 comprises two conveyor shafts 54 and their appurtenant blades 56 mounted in troughs 60, the whole being disposed at right angles to the discharging bottom beneath the same and positioned at a point intermediate the ends thereof. If desired, the discharging conveyor may be placed at one end of the discharging bottom, or separate discharging conveyors may be placed at each end reeaaee or in any other suitable relation thereto. It will be understood that in the arrangement as shownthe blades 56 on the respective shafts 54 of the conveyor comprising the discharging bottom are oppositely pitched on one side of the centrally disposed discharging conveyor to those on the other side so that the residual carbonized particles and/or ash being discharged is led from both ends of the retort toward the center.

The discharging conveyor 58 leads the material being discharged laterally of the retort to a point outside the side walls thereof and discharges it into a sump from which it is picked up by a drag line or other suitable conveyor 62 and carried to a point above the water level where it is discharged to any suitable disposal means. In Figure 1, the conveyor 62 is shown as discharging into a pug mill 64 which in turn discharges into an amalgamator 66 in which separation of the ash constituents from the residual carbonized particles may be efi'ected and the amalgamation of such particles with oil to form amalgam brought about as disclosed in my earlier patents, for example, see Patents Nos. 1,420,164 and 1,420,165.

The water level is maintained at the desired point by discharge from the overflow of the condenser through the pipe 68.

In order better to control the rate of heating of the solid carbonaceous fuel in the retort, means is provided for returning a portion of the rela tively cool gases issuing from the chambers 20h at the upper end of the apparatus to the combustion chambers 30 and in mixing such gases with fresh products of combustion developed at the burners 24 disposed therein. This means comprises a return conduit 70 leading from the oiftake flue 72 to a header 74 near the lower end of the apparatus, from which header the return gases are led to the combustion chamber 30 through a plurality of branch pipes 75. Control of the amount and rate of circulation of the gases is had by means of a slide valve 76 and a suction fan 78 driven by a variable speed motor or other source of power not shown.

In order to afford still further flexibility of operation as regards the application of heat to the retort, by-pass dampers 80 are disposed in the walls 22, so that heating gases may be bypassed from the

chambers

20c, 20d, 20c and 20f as desired to the by-pass flues 82 defined between the walls 22 and the walls 84. Y The by-passed gases are led upwards through the flues 82 and discharged, either into the adjacent chambers 20h through the openings 85 as shown, from which chambers they are withdrawn, with the gases flowing into such chambers from the sets of tubes communicating therewith, to the ofitake flue '72 by way of the outlets 86, or such gases may be led directly from the by-pass flues to the offtake flues 72. It will be understood that the flues 72 lead to a stack, not shown.

Clean-out doors 80 are disposed at the lower ends of the respective by-pass flues 82 to permit of removal of ash and dust particles which may become deposited therein.

In Figures 1 and 2, a series of air inlet pipes are shown as discharging into the lower end of the retort through the side walls 14. These pipes are connected tocommon headers 92 which are connected to a blower, not shown.

A by-pass conduit 94 is shown in Figure 2 as connected to the conduit 48 intermediate the point of discharge thereinto of the lowermost eduction header 46 and the condenser 50. By

'tion tubes 42.

suitably manipulating the

valves

96 and 98 the evolved gases and vapors may be diverted to any suitable fuel consuming apparatus, not shown. Further flexibility of operation is aflorded, particularly when it is desired to collect the distillable vapors and gases and water gas and/or producer gas separately, by providing a valve 100 in the connection between the conduit 48 and the lowermost header 46, and withdrawing gases led to such header through a pipe 102 to a suitable gas purifier not shown or to a fuel consuming device.

In my application Serial No. 135,471, filed September 14, 1926, now Patent No. 1,838,883, I have disclosed that by applying heat sufficiently slowly and uniformly to finely divided coal while feeding it through a heating zone the contained volatiles may be distilled oil? and the coking properties, where a coking coal is being treated, destroyed, thereby preventing substantial agglomeration of the finely divided coal particles and recovering the same in such form. The present invention involves an improvement on the process above mentioned in that the feeding of the finely divided coal to and through a heating zone is carried out continuously by gravity, thereby eliminating pumps and the power required for operating the same. The present process and apparatus are also adapted for treating coarser non-coking coal.

According to the present invention the hopper 34 is kept filled to such an extent as to maintain a hydrostatic pressure upon the material in the retort sufficient to cause such material to tend to move downwardly as rapidly as the residual material is withdrawn from the lower end of the retort. The gates 36 are withdrawn to full open position during normal operation of the apparatus so that the feed of the coal into the retort is sumciently uniform over the entire crosssectional area thereof.

As the finely divided coal descends into the retort its temperature is progressively and gradually raised to a point where the distillable fractions are evolved. These fractions are withdrawn substantially as fast as formed through the educ- The rate of feed of the material and the rate of transference of heat thereto are preferably so adjusted that substantially all of the distillable fractions are removed in the zone between the second row of eduction tubes 42, reading from the top, and the bottom row of such tubes. Such fractions are withdrawn through the two intermediate sets of tubes and normally discharged to the condenser 50 where the condensable vapors are recovered. The fixed gases passing through the condenser may be applied to the burners 2%, as through pipe 104, and thereby utilized in heating the retort.

The uppermost set of eduction tubes d2 is used normally to withdraw air which would otherwise be carried into the heating zone with the descending coal particles.

In order to retard and substantially prevent the formation of carbonaceous deposits upon the tubes 18 and. eduction tubes 42 disposed in the path of the descending coal, these tubes may be coated or covered with a silicious or earthy material such as described in my pending application Serial No. 200,445, filed June 21, 1927.

The maintenance of the water seal at the lower end of the retort is an important feature of the present invention for several reasons. One is, that in this manner the retort is positively sealed against ingress of uncontrolled amounts of air during the discharge of the carbonized material. The water seal cooperates with the air eduction tubes 42 in positively sealing the retort against undesired ingress of air while at the same time permitting the process to be carriedv on continuously. Another important function of the water seal is to abstract the sensible heat of the hot carbonized material and/or ash and return the greater portion thereof to the material in the retort in the steam which is formed upon contact of such heated carbonized residual material with the water. In addition to carrying heat back into the retort that would otherwise be lost.

the steam also assists very materially in carbonizing the coal by removing heat from the tubes 18 around which it travels upwardly in the retort and carrying the steam into contact with the coal particles. The water seal accomplishes another purpose, that of permitting the removal of the wet coal sludge from the bottom 0! the retort by means of the conveyor blades 56, and thence by a drag line conveyor 62 from below the water level to above the water level.

The steam when brought into contact with the hot carbonized material in the zone of highest temperature tends to react with the carbon according to the reactions:

The water gas produced is withdrawn through the lowermost set of eduction tubes 42 and led to a gas holder, not shown, or directly to a fuel consuming means. In case complete removal of the distillable fractions of the coal has not resulted before the lowermost set of tubes 42 has been reached by the descending coal, it may be desirable to lead the mixed water gas and distillation products that are withdrawn from such set of tubes through the condenser.

According to the method of operation above outlined only partial gasiflcation of the carbonized particles remaining after completion of distillation takes place, and the residual carbon intermixed with ash is withdrawn as a sludge through the water seal to the amalgamating apparatus where separation of the ash from the carbon particles may be effected by the process described in my Patent No. 1,420,164.

For some purposes it is desirable to effect complete gasification of the coal and then transfer the gases thus produced unmixed with ash to a fuel consuming means. Such a process is disclosed and claimed by me in my copending application Serial No. 144,162, filed October 25, 1926, now Patent No. 1,758,630. The present invention comprises as one modification a highly satisfactory method of gasifying the coal and converting the same into gases possessing high fuel values while at the same time effecting the removal of the ash as a continuous process. In order to effect complete gasification of the carbonized residual particles, I propose to supplement the water gas reaction by introducing controlled amounts of air or oxygen-containing gases into the descending material near the discharge end of the retort. The air passes upward into the hottest zone where it reacts upon the solid carbon according to the reaction:

2C+O2=2CO The producer gas thus formed, together with the water gas, may be withdrawn through the lowermost set of eduction tubes 42 to a boiler heating unit or other fuel consuming means, or to materials, such for example as lignites.

the storage as above described for water gas. In this way a gas relatively rich in fuel values is produced. In case a gaseous fuel still higher in thermal values is desired, the distillable fractions withdrawn through the sets of eduction tubes may, instead of being led to the condenser, be mixed with the producer gas and water gas and burned. Or, optionally, the fixed gases passing from the condenser may be mixed with the combined producer gas-water gas mixture to improve its fuel value.

The temperatures to which the descending body of coal or other carbonaceous material is to be subjected will varysomewhat dependingupon whether distillation and carbonization only are to be accomplished or the production of producer gas and/or water gas is also contemplated. In carrying out the process so as to bring about distillation and carbonization only,the application of heat should be so controlled that the temperature of the gases leaving the upper tubes 18 will be such as to transmit a heat of about 300 F. to the coal, and the gases entering the tubes at the bottom will give the coal a maximum heat treatment of about 1500 F. When the process is being conducted so as to produce the water gas reaction in the lower part of the retort, the heat applied must be such as to create a zone where the carbonized particles of coal are brought to a temperature of about 1500 F. When air is admitted for the formation of producer gas, the application of heat will be so controlled as to produce a temperature in the body of the carbonized material in the gas producing zone that will reach as high as-1800 F.

The present process is adapted for the treatment of anthracite, semi-anthracite, or bituminous coal as well as various other carbonaceous The coal is preferably crushed to a finely divided condition, say from 10 to 200 meshes per linear inch although it is to be understood that the invention is applicable to the treatment of coarser materials,

, especially when the end sought to be attained is merely to gasify the coal and effect separation of the ash. For such purposes the process is particularly adaptable in treating various finely divided coal residues hereto considered as waste materials, such as anthracite coal in the form of 7 culm or buckwheats.

While I have described a preferred form of the process, it is to be understood that various modifications in the details of the procedure may be made without departing from the invention, which is not to be deemed as limited other than as indicated in the appended claims.

What I claim is:

1. A process for carbonizing solid carbonaceous fuel, which comprises continuously feeding the material in subdivided form downwardly by gravity through a heating zone, controlling the rate of the gravity feed of the advancing material and the application of heat thereto to allow time for substantially all constituents thereof that are voiatilizable below the normal fusion temperature of the material to be removed therefrom before it reaches its normal fusion temperature, thereafter raising the temperature of the material above its normal fusion temperature to complete clevolatilization and carbonization without substantially coking the same by slowly increasing the temperature thereof and regulating the heat imparted thereto, and continuously discharging the carbonized fuel from the heating zone at a rate moaned substantially equal to the rate of feed to the heating zone.

2. A process for carbonizing coal, which comprises continuously feeding the coal in subdivided form downwardly by gravity through a heating zone wherein the coal is subjected to progressively increasing temperatures during its passage therethrough, controlling the rate of the gravity feed of the advancing coal and the application of heat thereto to allow time for substantially all constituents thereof that are volatilizable below the normal fusion temperature of the coal to be removed therefrom before it reaches its normal fusion temperature, thereafter raising the temperature of the coal above its normal fusion temperature to complete devolatilization and carbonizatlon without substantially coking the same by slowly increasing the temperature thereof and regulating the heat imparted thereto, and continuously discharging the carbonized coal from c the heating zone at a rate substantially equal to the rate of feed to the heating zone.

3. A process for carbonizing and gasifying coal, which comprises continuously feeding the coal in subdivided form downwardly by gravity through a heating zone wherein the coal is subjected to progressively increasing temperatures during its passage therethrough, controlling the rate of the gravity feed of the advancing coal and the application of heat thereto to allow time for substantially all constituents thereof that are volatilizable below the normal fusion temperature of the coal to be removed therefrom before it reaches its normal fusion temperature, thereafter raising the temperature of the coal above its normal fusion temperature to complete devolatillzation and carbonization without substantially coking the same by slowly increasing the temperature thereof and regulating the heat imparted thereto, converting at least a portion of the carbonized coal into gas in a hotter portion of the heating zone, and continuously discharging the remaining carbonized coal from the heating zone at a rate substantially equal to the rate of feed to the heating zone.

4. A process for carbonizing and gasifying coal, which comprises continuously feeding the coal in subdivided form downwardly by gravity through a heating zone wherein the coal is sub: Jected to progressively increasing temperatures during its passage therethrough, controlling the rate of the gravity feed of the advancing coal and the application of heat thereto to allow time for substantially all constituents thereto that are volatilizable below the normal fusion temperature of the coal to be removed therefrom before it reaches its normal fusion temperature, thereafter raising the temperature of the coal above its normal fusion temperature to complete devolatilization and carbonization without substantially coking the same by slowly increasing the temperature thereof and regulating the heat imparted thereto, introducing steam into a hotter portion of the heating zone to form water gas from at least a portion of the carbonized coal, and continuously discharging the remaining carzonized coal from the heating zone at a rate substantially equal to the rate of feed to the heating'zone.

5. A process for carbonizing and gasifing solid 145 carbonaceous fuel, which comprises continuously feeding the material in subdivided form downwardly by gravity through a heating zone, controlling the rate of the gravity feed of the advancing material and the application of heat #39 thereto to allow time for substantially all constituents thereof that are volatilizable below the normal fusion temperature of the material to be removed therefrom before it reaches its normal. fusion temperature, thereafter raising the temperature of the material above its normal fusion temperature to complete devolatilization and carbonization without substantially coking the same by slowly increasing the temperature thereof and regulating the heat imparted thereto, continuously discharging the hot residual material from the heating zone at a rate substantially equal to the rate of feed of the material to the heating zone, contacting the hot residual material with water thereby forming steam, and passing the steam thus formed into the heating zone to produce water gas.

6. The process as defined in claim 2 further characterized in that the residual coal is discharged into a body of water maintained in sealing relationship to the lower portion of the heating zone and the resultant steam passed countercurrent to the descending coal in the heating zone to form water gas.

7. A process for carbonizing and gasifying coal, which comprises advancing the coal in finely divided form through a heating zone, controlling the rate of travel of the advancing coal and the application of heat thereto to allow time for substantially all constituents thereof that are volatilizable below the normal fusion temperature of the coal to be removed therefrom before it reaches its normal fusion temperature, thereafter raising the temperature of the coal above its normal fusion temperature to complete devolatilization and carbonization without substantially coking the same by slowly increasing the temperature thereof and regulating the heat imparted thereto, introducing an oxygen-containing gas into a hotter portion of the heating zone to convert at least a portion of the carbonized coal into gas, and continuously discharging the remaining carbonized coal from the heating zone at a rate substantially equal to the, rate of feed to the heating zone.

8. A process for carbonizing and gasifying coal, which comprises advancing the coal in finely divided form through a heating zone, controlling the rate of travel of the advancing coal and the,

application of heat thereto to allow time for substantially all constituents thereof that are volatilizable below the normal fusion temperature of w the coal to be removed therefrom before it reaches its normal fusion temperature, thereafter raising the temperature of the coal above its normal fusion temperature to complete devolatilization and carbonization without substantially coking the same-by slowly increasing the temperature thereof and regulating the heat imparted'thereto, continuously discharging the remaining carbonized coal'from the heating zone at a rate substantially equal to the rate. of feed to the heating zone and contacting the same with water thereby forming steam, and introducing the steam thus formed into the heating zone to convert at least a portion of the carbonized coal therein to water gas.

WALTER E. TRENT.