US1867344A - Carbonization of bituminous fuel - Google Patents

Description

Jul 12, 1932. c J WRlGHT 11,867,344

CARBONIZATION OF BITUMINOUS FUEL Filed July 17. 1925 2 Sheets-Sheet 1 1925 2 Sheets-Sheet 2 r I 1 9 1, 1 3 1/ il/ 1 1 9 1 0/010 0 y 12, 1932- c. J; WRIGHT CARBONIZATION OF BITUMINOUS FUEL Filed July 17 Patented July 12, 1932 UNITED STATES PATENT, OFFICE CARL a. WRIGHT, OF WEST NEW BRIGHTON, NEW YORK, AssIGNoR To COMBUSTION UTILITIES CORPORATION, on NEW YORK, N. Y., AOORIORATION F MAINE GARIBONIZATION OF Application filed J'ulyl? This invention relates to the heat treatment of solid volatile-containing carbonaceous fuel, and more particularly to an improved method of and apparatus for making combustible gas and industrial coke of high quality from coking bituminous coal.

Most of the coke at present'produced for industrial and metallurgical uses is made by distilling bituminous coal out of contact with 3 air in closed retorts or coke Ovens of the beehive or by-product type. In these retorts the heating and distillation of the coal is accomplished by the indirect application of heat, i. e. heat for supporting the carbonization 5 is generally supplied by the combustion of gas in fiues around the outside wall of the retort, the heat of the burning gas passing by convection to the retort wall, then by conduction through the wall, then by radiation 0 and conduction through the coal charge. The charge of coal in the retort is held in a stationary position during the whole period of its carbonization and accordingly there is little breeze produced and the coke is in 5 large solid pieces having a high market value. Owing to the resistance to heat transfer of the system and particularly to the low heat conductivity of the coal it is necessary to maintain high temperature gradients between 0 the retort walls and the center of the charge.

In fact the walls are heated to a temperature such that most of the volatile products liberated from the coal on distillation are almost immediately cracked down into gaseous hydrocarbons on coming in contact therewith. Another disadvantageof the coke oven method of carbonizing coal which results from the low heat conductivity of the coal and from the low rate of heat transfer through the system is that it is only possible to treat charges of relatively narrow cross section, and therefore in order to.- produce gas and coke in commercial quant' a large capital outlay is necessary for in ing' and operating the large number offn rrow retorts, each having a relatively low individual fuel treating capacity, {which are required. Accordingly while the coke oven or indirect heating method'ofrcarboniiing'c'oal is in general characterized by the production of-relatively large BITUMINOUS FUEL 1925. Serial NO. 44,181. g

1 yields of high quality coke and rich coal gas together with a relatively small amount of high temperature tar,-the cost of manufacture of the eoke' and coal gas is so high as to make theiruse for most types of industrial heating operations prohibitive.

The primary object of the present invention is to provide a method and apparatus of .the direct heating type by means of which good yields of heating gas and industrial coke of high quality. can be economically produced from coking bituminous coal.

Another object of the invention is to reduce the number of individual apparatus units normally employed and the loss of heat normally resulting from radiation to the atmosphere when bituminous fuel is carbonized by direct heat transfer with a gas of lovl: heat value to produce mixed gas and co e.

Another object of the invention is to provide a method and apparatus by means of p which low B. t. u. gas can be generated and its sensible heat can be efficiently utilized for carbonizing bituminous coal to produce maximum yields of marketable coke, high quality mixed gas and primary tar oil.

In accordance with these objects one feature of the invention contemplates providing an improved method and apparatus in which I the advantageous features of both the standard direct and indirect heating methods of carbonizing coal are applied and by which the steps of fuel carbonization by direOt application of heat and of generation and superheating of a lean gas carbonizing medium can be conducted simultaneously and substantially independently within the confines of a single shaft generator.

Another object of the invention is to provide an improved method of'and apparatus I for making combustible gas of high calorific value by enriching a heated low B. t. u. gas with the volatile products of carbonization of solid volatile-containing carbonaceous fuels.

A further object of the invention is to pro- .vide a method and apparatus by means of which coking bituminous coal can be carbonized by direct heat transfer with heated low B. t. u. gases to produce high quality coke in excess of that required to generate the low B. t. u. gas carbonizing medium.

With these .and otherobjects and features in view the invention consists essentially in the improved method of and apparatus for making combustible gas and industrial coke hereinafter described and particularly defined in the claims.

The various features of the invention are illustrated in the accompanying drawings, in which 1 Fig. 1 is a view in vertical section of a gas generator of the shaft type having a plurality of metal carbonizing retorts disposed in itsupper portion in accordance with the apparatus arrangement embodying the preferred form of the invention;

Fig. 2 is a view in enlarged horizontal section of the gas generator taken on the line 22 of Fig. 1;

Fig. 3 is a vertical section of a metal carbonizing retort illustrating one type of mechanism by which it can be emptied;

Fig. 4 is a vertical section of a carbonizing retort, showing the arrangement for discharging coke into the gasification zone of the generator;

Fig. 5 is a sectional elevation of a car.- bonizing retort showing the arrangement whereby carbonized fuel can be discharged to the outside of the generator; and

Fig. 6 .is a sectional elevation of the lower portiomof a carbonizing retort fitted up with trap doors whereby carbonized fuel can be discharged both to the outside of the shaft and into the gasification chamber.

The apparatus embodying the preferred form of the invention, as illustrated in the drawings, consists essentially of a shaft generator 10 of the general type and arrangement illustrated in the U. S. Patent 1,426,159 to Henry L. Doherty into which bituminous coal or other solid volatile-containing carbonaceous fuel which is to be carbonized is periodically admitted from a hopper 12 by opening one or more of a number of charging gates 14. The interior walls and roof of the shaft 10 are lined with refractory heat insulating, material 15, and for purposes of description the interior of the shaft may be considered as comprising an upper heating chamber 16 openly communicating with a lower and larger gas generating chamber 18 (see Fig. 1). The lining of the shaft adjacent the upper part of chamber 18 is constructed to form two vertically spaced circumferential arches or rackbacks 19 and 20, and combined blast inlets-and exhaust gas olftakes 21 and 22 open into the interior of the shaft immediately beneath these arches. A

charge supporting and waste discharging mechanism 24 is movably mounted in the lower portion of the shaft directly'above and vertically spaced from a gas sealing ash door 26 at the base of the shaft. A number of indithese retort closures are shown as stationary plates 29 or as hinged trapdoors 30 arranged to open downwardly and outwardly of the retort to permit carbonized fuel to empty into the gas generating chamber 18 (see Figs. 3 and 4). Preferably some of the retorts are equipped with vertically mounted trap doors 31, Fig. 5, in the wall of the shaft arranged to open outwardly for the discharge of coke or other carbonized fuel from the retort directly to the outside of the shaft. In Fig. 1 of the drawings some of the retorts are shown as equipped with downwardly swinging trapdoors 30 while others of the retorts are shown as equipped with stationary bases 29 and outwardly swinging trapdoors 31, but as indicated in Fig. 6, it may often be found of advantage to equip one or more or all of the retorts with both types of trapdoors. Both doors can then be opened simultaneously to permit a certain proportion of the carbonized fuel produced to pass directly tothe outside of the shell as a by-product of the operation while at the same time permitting the remainder of the carbonized fuel to empty into gas generating chamber 18 for use in generating gas and heat suflicient to carry on the fuel carbonization. A central unobstructed passage 32 extends vertically through the center of heating chamber 16 from the top of the gas generating chamber to an open space in the roof of the generator immediately overlying the open tops of retorts 28. Likewise between the side walls of adj acentretorts there are additional passage ways 34, and these with the passage 32 serve for conducting producer gas, water gas or whatever type of lean combustible gas is in process of gen eration in generating chamber '18 upwardly past the outer walls of the retorts into the top of the shaft. A number of, fuel loading chutes 36, in each of which one of the charging gates 14 is mounted, extend from the base of hopper 12 to the open tops of the carbonizing retorts, and eachchute discharges into Ill alt

The method of making industrial coke and I fuel gas comprising the preferred form of the invention is carried on in the apparatus illus- .source through one or both of the inlets 21 or 22 into the upper portion of abed of car bonized fuel in the gasification chamber 18 to maintain high temperatures therein, and gas generated in the gasification chambi (producer gas, water gas, etc.), after passin through the upper high temperature blast zone of the fuel bedto take on superheat is conducted directly upward through passage 32 and passages '34: to the top'of the shaft above the open tops of carbonizing retorts 28. From the top of the shaft this preheated lean gas is drawn downwardly through beds of uncarbonized or partially carbonized bituminous fuel in each of the retorts. After giving up most of its preheat by direct heat transfer with the fuel and picking up volatile components distilled from the fuel the cooled and enriched gas mixture is withdrawn from the retorts through gas ofitakes 38 and valves 40, preferably by the operation of exhausters in the purification circuit (not shown).

According to the preferred method of operation the retorts 28 are operated on successive cycles, i. e. the fuel charges of the retorts are maintained at any given instant in progressively advanced stages of carbon ization and the retorts are charged and discharged on successive cycles. To charge the retorts the'charging gate 14 at the head of the loading chute 36 leading to the top of the particular retort'to be charged is opened, and sufficient fuel is admitted from hopper 12 to substantially fill-the retort to the top. Valve 40 in the. gas offtake 38 leading from the retort being charged is closed during the process of charging and likewise discharge gates 30 and 31 remain closed ex'ceptfor the short period during which the retort is emptied. As soon as the charging operation is completed charging gate 14- is closed, valve 40 is opened wide and hot low B. t. u. gas

produced in the gasification chamber of the generator immediately enters the fuel at the top of the retort and passes downwardly through the charge to the ofltake 38. By absorption of sensible heat from the hot gas the temperature of the fuel quickly rises above the temperature at which its volatile components begin to liberate themselves and as the temperature of the fuel continues to rise more and more of the volatile components of higher and higher boiling point are set free and carried off by the current of heating gas. As the temperature of the heating gas is lowered by direct heat transfer with the fuel during its passage downwardly through the retort some of the higher boil- .ing volatile constituents liberated from the fuel condenseout of the gas on the cooler portions of fuel lower down in the retort. By the present method of operation the baffiing effectto gas flow which normally results from the condensation of such volatile components on the fuel in the more common uprun methods of direct heat carbonization is not encountered since thecondensed liquefied components, i. e. tar oils, are driven downwardly ahead of the gas toward the base of the retort, where the suction created i 42 of oiftake 38 serves to entrain the corn densed oils collected at the foot of the retort with with the outgoing gas. and to carry them out of the retort into the condensing and scrubbing apparatus of the purification train.

'lVhen carbonizing retorts 28 of large fuel treating capacity are employed in the. top of the generator it may take several hours to complete the carbonization of each charge. Accordingly it is of distinct advantage to charge and discharge the retorts on alternate cycles and to provide each retort with a separate gas ofitake 38 and valve 40 by means of which to control the rate atwhich heating gas is passed through each retort and to maintain the temperature of the gas leaving the shaft at a uniformly low point. Thus as the degree of carboniz'ation'of the fuel in any retort reaches an advanced stage at which a considerable portion of the volatile components have been liberated, by partly thrown open to permit the charge of coke or carbonized fuel to empty from the retort into the gasification chamber 18 of the generator and to the outside of the shell. Immediately after the retort is emptied the traps 30 and 31 are again closed, a fresh 3 charge of green fuel is admitted to the retort by opening charging gate 14, valve 40 in the gas ofi'take 38 is opened wide to permit a large volume of the heating gas to pass downwardly through the charge and the carbonizing operation in this retort begins a new cycle. m

While the type of mechanism to be employed for opening and closing the trap door closures 30 and 31 o f-the carbonizing retorts '28 is-no't claimed as an essential part of the invention and is left to the option of the operator, for purposes of illustration several types and arrangements of mechanism of this class have been suggested in the drawings. Essentially the mechanisms illustrated in the drawings consist-of rods 44 extending vertically or diagonally of the horizontal axis of the retort and having one end either movably mounted in abearing connected to the base of the retort (see Fig. 5) or attached by pins to the movable trap door closures 30 and 31, and connected at the other end to bellcranks 46, which are in turn connected to and actuated by the piston rods of hydraulic or pneumatic cylinders 48. The driving cylinders 48 are preferably supported on the outside of the shell, as by brackets .50, in order that'they may be easily accessible for adjustment and repairs. Cross bars 52 are mounted on the rods 44 for the purpose of breaking up and disturbing the coke in the retorts simultaneously with the movement of the rods in order that the charge will readily empty from the retort when doors 30 and'3l are thrown open.

In case waterwgas is produced in thegasification chamber 18 of the generator as the medium for carrying heat to support the carbonization of the fuel in retorts 28, the blast air for intermittently raising the temperature of the bed of fuel in the gasification chamber to incandenscence between periods of gas making is preferably admitted through only one of the nostrils 21 or 22 and at the same time,the blast gases produced are exhausted through the opposite nostril. These exhaust blast gases are preferably burned inv refractory lined preheaters 54 in order that their potential heat may be regenerated and utilized in preheating the blast air and in generating and superheating the make steam. Between periods of air blasting the make steam may be introduced through one or both of nostrils 21 and 22, and additional steam is admitted into the shaft through a pipe 56 and distributing coil 58, mounted in the lower portion of. the generator immediately below the discharge mechanism 24.

If producer gas is generated in thegasification zone of the generator and used 'asthe heating medium for carbonizing the coal or other bituminousfuel in retorts 28, the blast mixture of air and steam may be introduced simultaneously from the preheater 54 through one or both of nostrils 21 and 22 andpart or all of the blast gases produced may be passed to the top of the shaft and downwardly through. the fuel in the carbonizing retorts, the rate at which gas is passed through any individual retort being regulated by the degree to whichvalve 40 in the gas ofitake 38 is thiottled. I

In general theamount of coke orcarbo n ized fuel charged into the generator. at intervals from the carbonizing retorts 28 1s pref.-

I erabl'y regulated so that the coke willbecomby the discharge mechanism from the foot of the column of fuel in the generator, and

the heat thus regenerated from the fuelin the generator is then carried upwardly by the steam to the high temperature gasification zone in the form of latentheat of vaporization and superheat in the steam. By operating the carbonizing retorts 28 on successive cycles, with periodic charging and discharging of each retort, the amount of coke or other carbonized fuel that is periodically added to the bed of fuel in the gasification chamber 18 by emptying one of the retorts constitutes a relatively small proportion of the total volume of the charge in the gasificati'on zone. Accordingly with this method of operation it is possible to maintain a Substantially uniform output of lean gasfrom the generator and a substantially uniform output of rich gas of a substantially uniform heating value from the carbonizing retorts.

In carbonizing some classes of coking coals it is desirable and sometimes absolutely necessary to charge a certain percentage of coke or other refractory distributing material with the coal into each retort in order to maintain the charge in a sufliciently porous condition for the passage of heating gases therethrough, particularly during the period in which the coal is passing through the plastic stage of carbonization.

The present method of carbonizing fuel resembles the more common indirect heating or coke oven method in that the coal is held in a stationary position while it is undergoing carbonization and the coke produced accordingly carries a minimum percentage of breeze and is in large solid piecesfcomparing favorably in quality with the best grades of cokeoven or beehive coke. The greatly reduced cost of manufacturing coke and gas products, the greatly increased fuel treating capacity of the apparatus, the great reduction in number of apparatus units and in installation and clearly distinguish the present method from' the more common coke-oven or beehive methods.

One advantage of the present method of carbonizing coal is that it can be applied in conjunction with either a water gas or a pro-' ducer gas operation 'to yield an enriched .mixed gas having asufliciently high calorific value to make it. suitable for most industrial heating operations and for househeating, and

to yield valuable by-products in the form of excess coke and primary tar oils from the carbonizing step. The yield of tar oils is large since the fuel is carbonized at moderate temperatures by passing heating gas downwardly through the charge in such a way as to drive any tar that is condensed out of the gas ahead of it toward the base of the retort, rather than permitting the condensed tar to run back into a high temperature gas generating zone where it would be cracked down into fixed gases and lost. An other advantage of the present invention is that it provides for regulating the rate at which heating gas is passed through a charge of the fuel undergoing carbonization in accordance with the stage to which the carbonization has advanced. Thus by putting a large amount of heating gas through a retort which has just been charged, and by' simultaneously putting a small amount of 'gas through a retort which is almost ready to dump, as by opening wide or throttling control valves 40 in the individual retort offtakes, it is possible to control the carbonization of the fuel in such a way as to give maximum yields of tar and an excellent grade of coke and also to effectively utilize the" sensible-heat carried by the heating gas in completing the fuel carbonization.

Among the chief features of the invention are the various provisions for securing an efficient utilization of the heat developed in the generating zone of theshaft and for reducing to a minimum the losses of heat which normally occur by .radiation to the atmosphere and by removal from the apparatus in the form of sensible heat in the .blast and make gases and in the waste fuel. By utilizing a shaft generator having its walls lined with refractory and heat insulating material and by utilizing the lower portion of the shaft as a gas generator and disposing the retorts in which to carry out the fuel carbonization in the upper portion of the same shaft, it is possible with the present method and apparatus to carry out the carbonizing step with a minimum "radiation loss and to efiect car- 50 bonization of a maximum volume of raw fuel v by means of the heat liberated in the gas generating zone of the shaft. By using carboniz ing retorts of high heat resistant metal construction it is possible to increase the fuel carbonizing capacity of the upper portion of a shaft having a gas generating chamber of given gas making capacity in its lower portion so as to make the combined fuel carbonizing capacity of the retorts exceed the fuel treating capacity of the generating chamber, and ther'eby with this arrangement a relatively large yield of excess coke for industrial sale can be produced in addition to thesupply' of'coke required as fuel in thegas generating chamberto supply heat for carrying on the carbonizing operation. Retorts of metal construction are preferred because in general they are much less bulky than retorts of like capacity constructed of refractory material such as firebrick,-and furthermore the metal retorts are much stronger, much less subject to developing cracks and gas leaks under pressure and strain, and they can be much more readily installed, replaced or repaired in an apparatus of this type. Moreover the greater heat conductivity of the metal is a decided advantage in an apparatus of this type.

The generating chamber is arranged with the vertically spaced blast air inlets below but near the top of the generator fuel, bed

in order that the high temperature gas making zone of the fuel bed can be kept near the top of the fuel bed, for the double purpose, first, of insuring that themake gases carry a high degree of preheat at the time they leave the top 'of the fuel bed and also at the time they enter the bed of green fuel in the carbonizing shell, and second, in order that a maximum amount" of the excess heat radiated from the blast zone may be transtor fuel bed is that the carbonized fuel charge,

as emptied from the retorts onto the top of the bed of fuel in the generating chamber,

generally carries'a relatively high degree of preheat. Heat carried out of the gas'making zone of the generator as sensible heat in the lean make gases is substantially all utilized in effecting carbonization of the fuel in retorts 28 and enrichment of the make gases with volatile components liberated from the fuel, while most of the excess heat left in the retorts in the from ofcarbonized fuel or coke is again returned to the gas making zone of the generator with the hot coke Which is charged from the retort directly onto the bed of fuel in the generator.

It is not intended by the above description to limit the invention to the use of a shaft generator of any particular type having any particular number or arrangement of carbonizing retortsm'ounted in its top. It is believed that the particular type of shaft generator, the number of carbonizing retorts mounted therein, and the manner of arranging'carbonizing retorts in the top of the shaft are best left within the option of the operator.

While the invention has been described with particular reference to the carbonization of coking bituminous coals to produce high B. t. u. mixed gas, marketable coke and primary tar oils, it is apparent that the invention is not restricted to the treating-of coals but may be readily applied, possibly with "a few minor changes, to the distillation of other fuels such as lignite coals and oil shales.

The invention having been thus described, what is claimed as new is:

1. The method of heat treating solid volatile-containing carbonizable fuel which comprises, gasifying a previously carbonized charge of said fuel so as to produce a supply of hot combustible gas, passing said hot gas.

previously carbonized charge of said fuel to incandescence so as to produce said hot gas carbonizing a separate uncarbonized body of said fuel closely spaced above said charge by passing a stream of said hot gas in direct heat transferring relationship therethrough, and utilizing a substantial portion of the heat liberated as radiation from the incandescent gasification zone of said charge in promoting the carbonization of said overlying fuel body.

3. The method of heat treating solid volatile-containing carbonizable fuel comprising,

generating a continuous supply of hot combustible gas by gasifying a previously carbonized charge of fuel in a gas generator, utilizing the sensible heat of said hot 'gas so as to effect carbonization of an uncarbonized body of said volatile-containing fuel located above and in close proximity to said-generator charge by passing said hot gas directly from said charge upwardly around and downwardly through said body, removing the thus'cooled gas enriched with volatile products ofsaid carbonization from the lower ortion of said body, periodically replenishing said generator charge with hot carbonized fuel removed directly by gravity from said body, and replacing said-body after its carbonization is completed with a fresh un carbonized body of the volatile-containing fuel and carbonizing the same.

4. The method of heat treating solid volatile-containing carbonizable fuel which comprises, generating a supply of hot combustible gas by asifying a previously carbonized charge 0 'said' fuel, utilizing the senrlble heat of said hot gas so as to effect carbonization of a plurality of stationary bodies of said volatile containing fuel located above and in close proximity to said charge bypassing streams of said hot gas directly from said charge upwardly around and then downwardly through each of said fuel bodies, periodically and successively replacing each of said fuel bodies as its carbonization is completed with p a fresh body of the uncarbonized fuel and carbonizing the same, replenishing said charge of fuel undergoing asification at intervals with hot carbonizetf fuel transferred directly thereto by gravity from one of said bodies undergoing carbonization, and withdrawing carbonized fuel at intervals from one of said bodies undergoing carbonization without subjecting it togasification.

5. The method of heat treating solid volatile-containing carbonizable fuel which comprises holding a plurality of separate bodies of said fuel in a stationary position while effecting their carbonization by direct heat transfer with streams of hot low B. t. u. combustible gas passed downwardly therethrough, removing the gas and volatile prod- ,ucts of said fuel carbonization from the lower portion of each of said bodies, periodically discharging hot carbonized fued from each body and replacing such carbonized fuel with a. fresh supply of the uncarbonized fuel and carbonizing the same, asifyin a portion but not all of the hot car onized fuel thus discharged to generate said hot low B. t. u. gas carbonizing'medium, and separately controllin the volume of hot gas passed through each 0 said fuel bodies so as to pass relative ly large volumes of heating gas through such of said fuel bodies as are in a substantially uncarbonized condition while throttling the flow of heating gas through such of the bodies as have reached an advanced stage of carbon-' ization.

6. The method of heat treating solid 'volatile-containing carbonizable material which comprises gasifyi ng a previously carbonized charge of solid fuel so as to produce a supply of. hot combustible gas, cokinga body of solid carbonizable material located in close prox- 1m 1ty to and above the charge of'fuel undergoing gasification by passing said hot gas through said body, periodically removing the thus coked material and replacing it with a fresh body of the uncarbonized material and coking the same, and transferrin additional heat liberated during said gasification step by radiation from said charge and conduction to the body of material undergoing carbonization, each of the said bodies of carbonizable material being maintained substantially quiescent throughout substantially the whole ofthe coking step.

7. The method of heat treating solid volatile-containing carbonizable material which comprises successively gasifying each of a plurality of previously carbonized charges of said materialso'as to produce a supply of hot combustible gas, coking a body of solid carbonizable material by passing said hot gas in direct heat transferring relationship mousse throughthe said body while maintaining the material therein substantially quiescent throughout substantially the whole of the coking step, the said body of material being located in close proximity to the zone of the gasification of the carbonized material, transferring additional heat liberated during the said gasification step by radiation and conduction to the body of the fuel undergoing carbonization, and gradually reducing the rate of flow of heating gas being passed through the body of fuel undergoing 'carbonization as the carbonization proceeds while simultaneously passing other portions of the heating gas at a higher flow rate through a separate quiescent body of the fuel undergoing carbonization in an earlier stage.

8. The method of heat treating solid volatile-containing carbonizable material which comprises blasting with air and steam a hot previously carbonized charge of said material so as to form an upper incandescent zone therein so as to generate a supply of hot combustible and non-combustion supporting gas, continuously passing said hot gas in heat exchange relation with but out of contact with a non-combustion supporting gas, continuously passing said hot gas in heat exchange relation" with but out of contact with a non-carbonized body of carbonizable material and then in direct contact with said body,so as to carbonize the fuel of said body and enrich said gas with its volatile compo nents, the said body of carbonizable material being located in close proximity to the incandescent zone of said charge and being maintained quiescent throughout substantially the entire carbonizing step, replenishing the charge of fuel undergoing gasification at intervals with hot carbonized fuel from the body undergoing carbonization, replacing the thus removed body of carbonized fuel with a fresh body of the uncarbonized material, and'carbonizing the same.

9. The method of heat treating solid volatile-containing carbonizable material which comprises developing a continuous supply of a hot, low heat value combustible gas, passing a stream of said gas in heat exchange relation but out of contact with a body of carbonizable material and then in contact with said body while maintaining the latter substantially quiescent during the time the said. stream of gas is passed in said heat exchange relation, thereby efleeting its coking by successive indirect and direct heat transfer therewith, removing the thus cooled gasfrom the fuel body in admixture with volatile products distilled from said material, controlling the volume of hot gas passed through said body of carbonizable material independently of the volume of the gasflowing in the said stream thereof, replacing the body of material after coking is completed with a fresh body of the uncarbonized material, and coking the same.

10, The method of heat treating solid volatile-containing carbonizable fuel comprising, developing a continuous supply of hot lOW B. t. u. combustible gas, coking a plurality of spaced, quiescent bodies of solid carbonizable fuel by passing streams of said hot gas in such'of the fuel bodies as have reached an advanced stage of carbonization.

11. The method of heat treating solid vola-- tile-containing carbonizable fuel comprising holding each of a plurality of spaced bodies of the fuel in a quiescent condition substantially throughout the coking thereof accomplished by passing streams of hot com bustible gas in heat exchange with but out of direct contact with each of the said bodies and then in direct contact therewith, generating said hotcombustible gas by gasifying a previously coked charge of the said fuel located in a gas making zone in proximity to but substantially below each of the said firstnamed fuel bodies, conducting said hot gas streams from the point at which they are generated to the upper surfaces of the bodies of fuel being coked, and thence downwardly therethrough, transferring additional heat from the gas making zone to each of said fuel bodies by radiation and conduction, periodically and'successively completing the coking of one of the said fuel bodies and replacing each of the coked fuel bodies with another body of the uncarbonized fuel, and separately controlling the rate of flow of said heated gas passed through each of the said fuel bodies so'as to pass the heating gas at a high-rate through such of said fuel bodies as are in the initial stages oficarbonization while throttling the fiow of heating gas through such of the fuel bodies as have reached an advanced stage-of carbonization.

12. The method of heat treating solid volature of,the mixture of said gas and the volatile products of distillation removed from each of the said bodies, periodically and successively completing the coking of each of said fuel bodies and successively replacing each of such coked fuel bodies with another body of the uncarbonized fuel, and passing the heating gas at high rates through such of said fuel bodies as are in a substantially uncarbonized condition while throttling the flow of heating gas through such of the fuel bodies as have reached an advanced stage of carbonization. p

13. The method of heat treating solid volatile-containing carbonizable fuel comprising generating a continuous supply of hot low calorific value combustible gas, coking an uncarbonized body of said fuel by holding it in a quiescent condition during a coking thereof effected by passing a stream of said hot gas in heat exchange but out of direct contact therewith and subsequently in contact with the said body, driving liquid tar oils distilled from said fuel and condensed out of said heating gas stream downwardly toward the foot of said body ahead of said gas and removing said oil by entrainment in the enriched gas stream leaving the said body, and periodically suspending the flow of said gas, replacing said body with a fresh body of uncarbonized fuel and re-starting the flow of the gas and conducting it through the said fresh body.

In testimony whereof a affix my signature.

CARL-J. WRIGHT.

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