US1172682A - Process for carbonizing coal. - Google Patents

Description

H. L. DOHERTY. PROCESS FOR CARBONIZ ING COAL.

APPLICATION FILED DEC.27, 1909 1,172,682. Patented Feb. 22,1916.

3 SHEETS-SHEET I- twee-Eco: Henry LDOherty, 5mm [for H. L. DOHERTY.

PROCESS FOR CARBONIZING COAL. APPLICATION FILED DEC.27,1909.

1, 1 72,682. Patented Feb. 22,1916,

3 SHEETS-SHEET 2- Ln gkx 23% 2' LI- Ll xl W H n ry L. Doherty, Sin-newton 7t $513712 (lac 0mm M H.-L. DOHERTY.

PROCESS FOR CARBONIZING COAL.

-APPLICATION FILE'D 0:021, 1909.

Patented Feb. 22,1916.

3 SHEETS-SHEET 3.

m w (j U 3513 ado mug M vwe wtoz HENRY L. DOHERTY, OF NEW YORK, N. Y.

PROCESS FOR CARBONIZING COAL.

Specification of Letters Patent.

Application filed December 27, 1909. Serial No. 535,036.

To all whom it may concern Be it known that I, HENRY L. DOHERTY, a citizen of the United States, and resident of New York city, in the county of New York and State of New York, have invented certain new and useful Improvements in Processes for Carb'onizing Goal, of which the following is a specification. 4

This invention relates to processes for carbonizing coal and particularly to that kind of such processes in which the heat for the carbo-nizatio-n of the coal is supplied to the same by conduction from a bath of molten material.

The object of my invention is the furnishing of a method for carbonizing coal in which the carbonization can be carried on at a uniformly low temperature and yet with a speed much greater than by carbonization in fireclay retorts according to the process at present in use. I

Briefly my process consists in circulating a suitable molten material in a closed circuit first through a reheating chamber and then through a carbonizing chamber, feeding crushed coal onto the molten material in the carbonizing chamber, allowing said coal to remain in contact with the molten material in the carbonizing chamber for a suflicient length of time to carbonize the said coal and removing from the carbonizing chamber the gas and coke resulting from the 'carbonization of the coal.

In the accompanying drawings, Figure 1, is a vertical longitudinal section through the carbonizing chamber on a plane through the line A B of Fig. 2 and A B of Fig. 7. Fig. 2 is a horizontal cross-section through the carbonizing and reheating chambers on a plane through the line C D of Fig. 1. Fig; 3, is a vertical longitudinal section through the recuperator on a plane through the line G H of Fig. 7. Fig. 4 is a vertical cross-section of the recuperator on a plane through the line E F of Fig. 7. Fig. 5 is a partial vertical section through the wall separating the reheater and carbonizing chambers, across the connecting passage, showing the device for operating the circulating apparatus. Fig. 6 is a horizontal partial section through the passage connecting the reheater and carbonizer showing a top View of the circulating means. Fig. 7 is a diagrammatic plan of the apparatus.

The apparatus figured, of course, is only one of the many means of carrying out my process that may be used, and I do not-limit myself to this particular design of apparatus.

In the form of apparatus shown, 1, is the carbonizing chamber, 2, the reheater for reheating the material of the molten-bath, 3, is the recuperator. The coal to be distilled is fed into the charging hopper, 4, the coal being preferably first crushed to such a size as will pass through a screen of 3,; inch mesh. Reduction to this size is not an imperative requirement of my process but I find that this size is well adapted to give the best results. The larger the size of ,the coal fragments the longer is the time, "that the coal' must be allowed to remain in contact with them'olten bath. Therefore, I find it preferable in order to increase the speed of op eration, to crush the coal, as mentioned, although I do not restrict myself to the use of crushed coal in my process.- From 4 the coal is dropped into the feed-box 5 by raising the lever arm 6 which causes the lowering of the charging cone 6. The bottom of 5 slopes to a narrow slot.7 which is in communication with a cylindrical casing 8 in which works the feed-roll 9.

10 is a slot in the bottom of easing 8 which communicates with the vertical chute 10; the latter discharging into the interior chamber 11 of c'arbonizer 1. The feed roll 9 has a shaft, 9', operated by a suitable mechanism 9", and has longitudinal grooves 9 on its surface. On causing the shaft 9 to rotate the coal in 5 enters the grooves 9 as they pass under the slot 7 andfalls out of the grooves again as they .pass over the discharge slot 10, falling through the chute 10' on to the surface of the bath of molten material 12, in chamber 11. The slot 10 and chute 10 extend across thefull width of the carbonizing chamber. The feed roll working fairly tight in the casing S shuts offrall communication between 11 and 5 thus preventing any loss of gas through 5 and 4 when the latter is opened for the introduction of coal. The coal floats on the surface of the flowing bath or stream of molten material 12 and moves with it to the'discharge end of the carbonizing chamber. While a resting on the surface of the bath the coal is,

Patented Feb. 22, 1916.

of course, subjected to the action of the heat I of the molten material, and is therefore,

quickly carbonized, its volatile matter dis tilling off. Since I prefer to use some material having a high co-efficientof conduc- 40 the retort walls and from evolved. from the coking coal. ,Radiation with also 45 part.

55 carbonizing tivity for the bath and there is always in chamber 11 a weight of the material constituting the bath many times the weight of the coal present at any given time, the distillation takes place withgreat rapidity, the

heat capacity of the bath being very great relative to. that of the coal'present. I prefer to Work with a layer of coal of comparative thinness, "advantageously, not exceeding, say 1}" in thickness, although, of course,

this depth of coal may be considerably increased if desired. With the layer of coal restricted to the given thickness the distillation takes place very quickly, not requiring '15 more than about 2 minutes to reach completion.

ith an increase of thickness of the layer of coal charged, the rate of flow of the bath or stream of molten material must, of course, be materially diminished, since, in

this case, the coal of the upper portion of the layer is not in direct contact with the molten material and must receive its heat by conduction through the lower stratum of the layer in immediate contact with the molten bath. Therefore, I deem it preferable to work-with the practical maximum rate of flow of the bath and the practical minimum thickness of fuel.

It is true that it has been experimentally determined that in the ordinary carbonizing retort the carbonization proceeds toward the center of the charge at the rate of about 1 inch per hour. .Here, however, the conditions are entirely different from those which obtain in my process; The fragments of the charge in the ordinary method of carbonization are of considerable size and the f charge is quiescent, the transfer of heat tak- I In my process of carbonization, which is the subject of this application, the transfer of heat takes place almost entirely by conduction from a molten substance having a Q very'high co-efficient of conductivity. In-

stead of the charge being quiescent there is an active mixing or agitation-of the charge due to the rapid circulation of the molten 'bath. As" shown, the material enters the chamber ati'a high velocity and 1n a direction transverse to the general direction of flow through the chamber.

As a consequence there is a whirling or eddying v movement given; to the material of the bath as well as the movement of progression longitudinally of the chamber. This insures a thorough mixing and stirring up of the floating particles of coal that brings all parts of the floating blanket into direct contact with the metal of the bath.

The velocity of flow given to the bath is such as will give the coal just the proper time to become thoroughly carbonized in passing from the inlet end of the chamber 11 to the discharge end. Since the rate offlow of the bath depends, solely, upon the speed of rotation of the propeller or other circulating means, it is plain that I have a thorough and complete control over the time during which the coal is exposed to a carbonizing heati The temperature of distillation may, 0bviously, be adjusted to any point desired. It is simply a question of the temperature to which reheater. By choosing an appropriate ma terial for the carbonizing bath the distillation may be carried out at any desired temperature. It has been found that coal distils completely at a temperature approximating 800 Fah. When distilled at this temperature both the calorific and illuminating power of the gas obtained per unit weight of coal is much greater than that of the gas obtained' from the same weight of coal distilled under the conditions that obtain in the present commercial processes of distillation.

When the carbonized coal reaches the discharge end of the carbonizing chambersit is skimmed oil" from the surface of the bath by the projecting ribs or paddles on the revolving drum 13 which has a shaft 14 extending through thewall of the carboniz ing chamber through a suitable stufling box 15, and having a suitable spur wheel 16, on its outer end. A suitable driving gear 17 operates the spurwheel 16, and causes the revolution of the drum 13. The coke is skimmed from the surface oft bath and raised over the dam 1 8 falling irough the chute 19 into the water seal 20, where it is immediately quenched. The coke is withdrawn from 20 by the elevator 21. Asewithdrawn from the Watersealthe coke is often in the form of irregular aggregates of a size much'larger than that of the coal particles introduced into the carbonizer. The condition of the carbonized fuel depends, however, to a great extent upon the character of the raw fuel used. With good caking coals the carbonized product is, as stated, in

the molten material is raised in the lumps of appreciable size., With non-caking coals the discharged carbonized coal will be. for the most part, of nearly the size charged, while with coals that decr'epitate upon heating and immersion in water the discharged material may be in a thoroughly disintegrated condition. If desired, it may be used directly as a fuel for boiler firing, for instance, briquets before marketing it.

The gas and vapors evolved from the coal during carbonization are withdrawn from the carbonizing chamber through the pipe but I prefer to make it up into 22 and discharged into the hydraulic main 23 through the sealed dip-pipe 24.

The reheater 2 consists simply of a suitable furnace chamber 25, having a hearth or crucible 26 for holding the molten ma- I terial and a burner 27 for heating the bath.

-' As shown, the circulating device is located in the passage 28. The device shown consists of a propeller 31 having a shaft 32 working in bearings 33 and 33 and having a sprocket wheel 34. A driving chain 35 is operated from a driving sprocket 36 on the shaft 37. It is obvious that any proper circulating means mav be substituted for the one described. The molten material heated in 2 is forced through the passage 28 by the circulating device, a reverse current being automatically established through passage 29 from the carbonizer to the reheater. The flame from burner 27 plays along the surface of the molten bath in the hearth 26 heating the metal therein and escapes from chamber 25 through the pipe 38. In the arrangement shown the products of combustion from chamber 25 are led through a recuperator for the. purpose of imparting their sensible heat to the current of air which is supplied to burner 27. Burner 27 need not differ materially from the devices now used in firing cement kilns. It consists of a nozzle 39, discharging through the burner tube 40, and having an opening 41 through which powdered fuel is fed to the air blast by the conveyer 42. The pipe 43 conducts the hot air from the recuperator 3 to the burner 27.

The recuperator shown consists simply of two sets of return bend fiues, one set 44, for the combustion gases from reheater 2, and another set, 45, enveloping 44, conducting the air through the recuperator. Cross-fines 46 and 47 connect the several flues 44 and cross-fines 48 and 49 the separate air flues 45. The air is supplied under pressure to the lines 45 through the pipe 50 by blower 51. As shown, the combustion gases are drawn through the recuperator by an exhauster 52 connected with the crossflue 47 by the pipe 53.

In most of the present used methods of making coal gas the coal is charged into chambers or retorts with comparatively thick walls of fireclay, set in suitable furnaces. The heat for the carbonization of the coal. is generated in the furnaces and must betransmitted through the comparatively thick walls of the chambers or re conductor.

torts to the charge of coal inside. This charge is usually of a thickness of several inches, about six inches in ordinary retort charging. In order to carbonize the coal in the interior of the charge the heat must pass through the outer layers of the charge itself. Now coal, and more particularly, carbonized coal or coke, is an excellent non- The transfer of heat from the walls of the retort or coking chamber to the interior of the charge is therefore, a very slow process. necessity of allowing the charge to remain in the retorts for an undue length of time it is, therefore, necessary to maintain a high temperature differential between the interior of the walls of the retort and the interior of the charge of coal therein, since the quantity of heat transmitted through a conducting medium in a given period increases with the increase in the difference of temperature between the surface where the heat enters the conducting medium and the surface at which it makes its exit therefrom. Considerations of economy make it necessary that the time of carbonization' should be kept as short as possible. In order to properly carbonize the coal in the interior of a charge within the period of time available therefor it is necessary to heat the outer layers of the charge to a temperature greatly in excess of the most advantageous temperature from a chemical point of view. The gas evolved from the interior. layers of the charge must therefore pass in contact with the highly heated outer layers before it can escape from the carbonizing chamber. This results in the destruction of the bulk of the chemical combinations which were initially formed in the distillation of the coal, and which are of more value than the condensable products of the secondary reactions. It is generally recognized by gas engineers that the successful distillation of coal at a comparatively low temperature, will yield products whose aggregate value is greatly in excess of the value of the products of distillationunder conditions which obtain in the present processes of coal-gas manufacture. The difficulty heretofore, has been that of the many proposed methods none would permit of the carrying on of the distillation of the coal at a uniformly low temperature. It is for the satisfactory solution of this problem that my invention is intended. Again, in the present method of making coal-gas in externally heated retorts, it is necessary to maintain in the furnace a temperature much in excess of that of the interior of the walls of the retort itself, in order to drive the heat from the furnace through the retort walls with suflicient rapidity. Thus in order to maintain the walls of the retort at a temperature of In order to avoid the tors or regenerators. In order to be suflicient such recuperators or regenerators must have a large heating surface and,

therefore, not only occupy considerable space but add greatly to the cost of the apparatus required. Besides, owing to the fact that the heat carrying capacity of the air is much less than the heat capacity of the combustion products and that a considerable difference of temperature must exist between the combustion products and the air, in order to secure a suficiently' rapid transmission of heat through the Walls of the recuperator flues, it is never possible to heat the air to the temperature of the combustion products. In retort methods of gas making, therefore, the heat actually utilized in the distillation of' the coal constitutes a comparatively small portion of the total heat developed in the furnace. s

In my invention the heat for distillation is transmitted directly to the coal by conduction from the bath of molten substance upon which it rests. Since the coal is crushed previous to its introduction into the carbonizing chamber and rests upon the molten bath in a thin sheet the distance to which the heat must be transmitted to reach the most remote particle of coal is only a fraction of an inch, whereas in the,

present retort methods of distillation it must pass through at least three inches of fireclay and, say, six inches of the charge 7 itself. As is well known, the retardation to I can be withdrawn therefrom, This results heat transmission in passing from one transmitting medlum to another 1s greater than the retardation in passing through a.

considerable thickness of even such a poor conductor as fireclay. Therefore, by my method of heating the coal by contacting it with a bath of molten material heated to the proper temperature, I secure the -most favorable conditions possible for the transfer of heat to the coal undergoing carbonization.

Another great advantage of my method is that the evolved gas is not exposed to a" temperature above that selected as the proper one for the carbonization. In the ordinary -method of carbonization the evolved gas is subjected to contact with the highly heated walls of the retort before it in secondary dissociating reactions which cause a splitting up of the carbon com-' pounds originally formed and the formation, in general, of simpler combinations.

molten bath in the hearth of the chamber,

They are, therefore, at a much lower temperature than the bath itself.

The material which I consider best suited for the molten bath is lead. I do not,however, limit myself to the use of lead as it is manifest that I can secure the same results with any'suitable material which is molten at the temperature of carbonizationf I am aware that types of apparatus have been proposed before to carbonize coal by feeding the same onto a bath of molten. slag from smelting furnaces, or onto a bath of molten glass or similar material. Apparatus so operated, however, would necessarily produce a gas of low illuminating value and yielding but little condensable hydrocarbon, owing to the relatively high temperature necessary to maintain such slag in a molten condition. As is well known, slags produced in smelting operations seldom or never attain to a condition of true fluidity below 2500 F. Ordinary iron blast furnace slag requires a temperature about bers in the manner in which I use mycar bonizing bath.

Having described my invention, what I claim is V 1. The process of carrying out the distilla tion of coal at a temperature below the temperature of active dissociation of illuminating constituents of the distillation products of said coal to produce gas and coke which comprises continuously circulating a stream of molten metal in a closed circuit through a heating chamber and a carbonizing chamher, the said stream .being heated to a temperature not above 1200 during its passage through saidheating chamber whereby the temperature of distillation of sald coal is maintained below that at which a substantial proportion of the distillation products will be broken up, feeding crushed coal.

=3200 to reduce it to a thoroughly fluid coniso 2. The process of manufacturing gas and carbonized materials which comprises establishing and maintaining a flowing bath or stream of molten material at a temperature not exceeding 1200 F., feeding a solid carbonaceous material containing hydrogen on and to said flowing bath, maintaining such carbonaceous material onand in contact withvsaid bath till a desired amount of volatile material is expelled from said carbonaceous material by heat taken up from said molten material, withdrawing residual carbonaceous materials after the desired length of contact has been effected, reheating the molten material to a temperature not in excess of 120Q F. and returning the reheated molten material into contact with a fresh portion of carbonaceous material.

3. The process of manufacturing gas and carbonized fuel which comprises subjecting solid carbonaceous matter containing volatile compounds to heating by contact with a flowing bath of molten lead, said bath being maintained at a temperature such that the volatile constituents of the said carbonaceous matter are caused to, be distilled therefrom but below 1200 F., and withdrawing the gases and vapors distilled from said carbonaceous material from contact with the molten lead without exposing them to a temperature that will cause the dissociation of the initial products of the distillation, substantially as described.

4. The process of manufacturing gas and producing carbonized fuel which comprises continuously circulating a bath of molten lead, or alloys of the same, first, through a heating chamber and, second, through a carbonizing chamber, feeding crushed coal onto said bath-in said carbonizing chamber, contacting the said coal with the said bath during the progress of said bath through the said carbonizing chamber, whereby the volatile matter of said coal is distilled therefrom, and the carbonized residue of the coal left on the surface of said bath, removing the gaseous products of the distillation and the residual coke from said carbonizing chamber, substantially as described.

5. The process .of manufacturing gas which comprises heating a bath of molten lead, in afurnace chamber, by direct contact with a heating flame, circulating the so-heated bath through a carbonizing chamber, feeding crushed coal to the heated bath in said carbonizing chamber, whereby a portion of the heat of the bath of molten material is communicated to the said crushed coal subjecting the same to destructive distillation, withdrawing the gaseous products of the distillation and the coke from said carbonizing chamber, subjecting the said gaseous products to condensation, whereby the condensable portion of said gaseous products is separated from the noncondensable portion, withdrawing the partially cooled bath of molten lead from said carbonizing chamber and returningit to said furnace chamber, reheating said bath of molten lead in'said furnace chamber and returning the so reheated bath of molten lead to the said carbonizing chamber for heating another portion of coal, substantially as described.

6. The process of manufacturing gas which comprises continuously circulating a stream of molten lead in a closed circuit I through a heating chamber and a carbonizing chamber, feeding crushed coal onto the stream of molten lead at its place of en-' trance into said carbonizing chamber, contacting said coal with saidstream of molten lead during the progress of the latter through the carbonizing chamber, whereby the volatile matter of said coal is distilled therefrom, removing the fixed. residue of .such distillation from the stream of molten lead at the place of exit of said stream from lation of coal at a temperature below the temperature of dissociation of the illuminating constituents of the distillation products of said coal, which comprises continuously circulating a stream of molten lead in a closed circuit through a heating chamber and a carbonizing chamber, the said stream being heated to a temperature not exceeding 1200 during its passage through said heating chamber, feeding crushed coal onto the stream of molten lead at its place of entrance into said carbonizing chamber, contacting said coal with said stream of molten lead during the progress of the latter through the carbonizing chamber, whereby the volatile matter of said coal is distilled therefrom, removing the fixed residue of such distillation from the'stream of molten lead at the place of exit of said stream from said carbonizing chamber, removing the gaseous products of said distillation from said carbonizing chamber and subjecting them to condensation, whereby the condensable constituents of said gaseous products stituents, substantially as described.

8. The process of manufacturing gas and producing carbonized material which com- .-are separated from the non-condensable-c'nn prises contacting carbonaceous matter containing hydrogenous compounds with an advancing stream of moltenmaterial containing lead, until the said carbonaceous matter has been carbonized to the desired degree,

withdrawing the resulting gas and carbonized material from contact with said stream of molten material, re-heatin'g said molten 7 material to a temperature that is substan tially below'the dissociation temperature of the illuminating constituents of the distillation productsof said coal and reusing the same, substantially as described.

9. The process of subjecting coal to distillation to produce volatile products and coke which comprises feeding the said coal in comparatively small fragments onto the surface of an advancing stream of molten material maintained at a temperature below that at which water will react withcarbon to form water'gas, contacting the said tillation has progressed to the coal with the said molten material until carbonization has been efl'ected and then removing the residual coke from contact with said molten material,'substantially as described.

10. The processof subjecting coal to distillatibnto produce volatile products and coke which comprises feeding the said coal onto the surface of an advancing stream of molten material to form a comparatively thin layer on the surface of said stream,

whereby the said coal is heated by direct conduction froniieithe said molten material and the volatile matter of said coal distilled therefrom, and removing the fixed residue from such distillation from thesurface of.

the said molten material, when the said disv point desired, substantially as described.

11. The process of distilling coalato produce volatile products and coke which comprises continuously feeding coal onto an advancing stream" of molten material con tained in an inclosed chamber, the said coal being fed onto the said stream at substantially its place of entrance to said chamber in a comparatively thin layer whereby the said coal is heated chiefly by direct conduction of heat from said molten material and its volatile matter distilled, causing the said coal to be borne through said chamber by said stream of molten material, and removing the fixed residue of such distillation from said molten material at substantially its place of exit from said chamber, substantially as described.

12. The process of distilling coal to produce volatile distillation products and coke which comprises continuously feeding coal onto a stream of molten material flowing through an inclosed chamber, the said coal being fed onto the said stream at substanr tially its place of entrance to said chamber,

' causing said coalrto be borne through said chamber on the surface of said stream of molten material and removing the products of the distillation of said coal from said chamber in proximity to the place of exit of said molten material from said chamber,

whereby the said distillation products are withdrawn from said-chamber without exposing'them to'a temperature higher than that at which said coal was distilled, substantially as described.

13 The process of distilling carbonaceous material containing volatilizable constitucuts to produce distillation gases and coke, which "comprises continuously feeding the said carbonaceous material in a relatively thin layer onto the surface of a stream of molten material flowing through an inclosed chamber, whereby the said carbonaceous material is quickly heated to a carbonizing temperature by direct conduction ofheat from said molten material, causing said coal to be transported through said chamber on the surface of said stream of molten material and continuously removing the coked residue from the distillation of said carbonaceous material at a place approximately the point of exit of said molten material from said inclosed chamber, substantially as described. e

14. The process of distilliiig coal which comprises heating a stream of molten material by directly contacting the same with hot combustion gases, forcibly injecting the so-heated molten material into an inclosed carbonizing chamber, the said molten material being injected into the said inclosed chamber at such'an angle. to the axis of said 1 chamber that a vortex is created in the said stream of molten material, continuously feeding int said" vortex crushed or otherwise formed fine coal, whereby the particles of said coal are immediately brought into intimate contact with the said molten mateposite to. that at which it was introduced,

substantially as described.

15.,Th'e process of distilling coal which comprises heating a stream of molten material to a temperature below 1200 Fah. by directly contacting the same with hot combustion gases, forcibly injecting the soheated molten material into an inclosed carbonizing chamber, the said molten material being injected into the said inclosed chamber at such an angle to the axis of said chamber that a vortex is created in the said stream of molten material, continuously feeding into said vortex crushed, or otherwise produced, fine coal, whereby the particles of said coal are immediately brought into intimate contact with the said molten material and quickly heated to a distilling temperature, continuously withdrawing said molten material from the extremity of said carbonizing chamber opposite to that at which it was introduced thereinto, whereby the said molten material is caused to flow from end to end of said chamber, thereby transporting the said coal through said carbonizing chamber while the said coal is undergoing carbonization and continuously removing the carbonized residue of said coal of said crushed coal are from the extremity of said carbonizing chamber opposite to that at which it was introduced thereinto, substantially as described.

16. The method of subjecting coal to quick distillation at a relatively low temperature'which comprises heating a bath of molten material to a temperature of between 800 and l200 Falr, creating a vortex in said bath and continuously feeding crushed coal into said vortex whereby the particles immediately brought into contact with the material of said bath and are quickly heated to the temperature of distillation by direct conduction of heat from said molten material, substantially as described.

Signed at New York city in the county of New York and State of New York this 23rd day of Dec. A. D. 1909.

HENRY L. DOHERTY.

W. G. BERRYMAN.

Images