US1930377A - Process and apparatus for manufacture of solid fuel - Google Patents

Description

H. ARCHBALD 1,930,377

PROCESS AND APPARATUS FOR MANUFACTURE OF SOLID FUEL Get. 10, 1933.

Filed June 26, 1929 5 Sheets-Sheet l INVENTOR. W C

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Oct. 10, 1933.

H. ARCHBALD PROCESS AND APPARATUS FOR MANUFACTURE OF SOLID FUEL Filed June 26, 1929 3 Sheets-Sheet 2 0/ b I 40 414 Q 1 I aaaaliiafi. I 0 Z? ,000,0zz4 r .17 1 1 1 v wyzwwhwmww H. ARCHBALD 1,930,377

E OF SOLID FUEL Oct. 10, 1933.

PROCESS, AND APPARATUS FOR MANUFACTUR Fil'ed June 26, 1929 5 Sheets-Sheet 3 m A M m M H a r wfi r flflaadaaldd J a wxm m 4 A 4 4 3 0 0 03 4 4 4 .zwvwwwwwwmwwwmw mmm m r r v @RN wQN $\N m m m m Patented Oct. 10, 1933 UNITED STATES PATENT OFFICE PROCESS AND APPARATUS FOR MANUFAC- TUBE OF SOLID FUEL 1'7 Claims.

My present invention relates to the preparation of coals and cokable mixtures for coking and to their performance in the process and apparatus which I have invented for coking and for producing coke of a definite structure, and is the result of continued experiment in the art or" coking as set forth in my co-pending applications, Ser. No. 30,343, filed May 14., 1925; Ser. No. 86,048, filed Feb. 4, 1926; and Ser. No. 261,- 356, filed March 13, 1928. The preparation of the coals and the operation of the process and the design of the apparatus are so interwoven and interdependent that a full explanation of l the one cannot be given without a description of the others. Each phase and its interaction with other phases is set forth in the following specifications.

In order that what I am about to set forth may be understood in detail, I will first in a broad way state that I originally conceived the idea that it might be possible to mix anthracite silt with bituminous coal and then to coke this mixture at lower temperatures than are common for coking, after having moistened it with the tar which would be produced in the coking. The idea of moistening with a tar was included for the reason that it was also conceived that it might be possible to extrude a continuous core of cokable coals into a metallic tube heated sufficiently to accomplish the coking and to do the coking, at least in good part, while the coals were being forced through the tube, thereby producing a. continuous stick of coke which-would break into usable pieces. The moistening with tar was necessary for the moulding operation which would occur in the extruder and after extrusion to hold the coals together until they-were coked. I also find that the character of the moistening agent has a vital effect on the quality of the coke produced and that the variations which are feasible in it makes it possible to coke an unlimited range of mixtures. Consequently it is an essential third element in the preparation of coals for coking.

At the present day anthracite silt is a waste. fine coal produced in the mining and preparation of that coal for market. With one colliery it may be of a size which will pass through a screen having openings of ands of an inch; at another it may be aths of an inch. It is only in relatively recent years that screens of such a small size have been used. In past yearssizes of coal such as buckwheat, rice and barley were not salable and were classed with silt. Fifty years ago even ,pea coal was unmarketable and discarded onto culm banks. I mention this fact as fine coal means a diflerent thing at different periods and I find that the size of the coal makes a difference in the operation of coking and in the quality of the coke produced.

When anthracite is referred to, the immediate thought ordinarily is of Pennsylvania anthracite. But for. the making of lump fuel I find that it is not necessary that only this coal be used to dilute the bituminous coal. If a pure fuel is desired, it can be made from any anthracitic material, such as Virginia anthracite, or coke, or semi-coke from the low temperature coking of bituminous coal, all of which have been tried.

The accompanying drawings show, more or less diagrammatically, apparatus, within the scope of the invention, for practicing the process. In said drawings Fig. 1 shows a vertical section of the feeding, moulding and coking apparatus, Fig. 2 shows a vertical section of the lower end of the coking apparatus and a housing in which the process completes itself. Fig.

3 shows 'a modified extruding and molding device using a reciprocating plunger instead of a screw, and adapted for use in particular with very fine coals.

The apparatus which I find can be used to accomplish coking of properly prepared coals, consists of a means of extrusion of a continuous mass of coal coupled to a metallic tube set in an oven where it can be heated in a proper manner. In order that the propriety of the details may be understood, a vertical section of the apparatus is given in diagram in Figure 1 accompanying these specifications. In this figure the parts numbered from 1 to 7 comprise a means of extrusion in which part 1 is shown as a hopper as a means of feeding the coals to the advancing and compressing member which is shown as a rotating screw (2) so located in the bottom of the hopper as to pick up the material and to advance it into the die 3 wherein the extension of the die beyond the end of the screw the coals are compressed against other coals which have been already introduced. The screw 2 may be made with a hole lengthwise through the center so that it may rotate around a fixed rod 4, which rod extends beyond the end of the screw and through the die and may project for a short distance into the coking tube.' An optional manner of construction in place of the fixed rod 4 is to have the extension of the rod beyond the end of the screw 2 an integral part of the screw and rotating with it. The part numbered 5 is a means of rotating the screw 2 from any suitable source of power. Part 0 6 is a base on which the means of extrusion is so mounted that the material issuing from the die 3 moves immediately intothe coking tube 9, either concentrically or eccentrically, the tube 9 being 5 of a larger internal diameter than the mouth of the die 3. Part 7 is a means of tight coupling of the die 3 and the tube 9 so that air may be excluded and the vapors formed during coking may be controlled and recovered by themselves. It

10 may be a faced flange fastened to die 3.

Except for part 7 and the extension of the rod 4 beyond the end of the die 3, the means of extrusion by itself is not new and not claimed as part of this invention. It is rather the necessities of the manner of its use and its combination with the coking element and the variation in the character of the product according to variations in construction of the means of extrusion and the character of the materials fed, which is new and will be set forth. As far as extrusion by itself is concerned, it is possible to purchase on the market a core making machine for iron foundry work in which a single screw rotates in the bottom of a hopper. Such machines are used for making sand cores and are ordinarily provided with plain tubular dies and rods which do not project beyond the end of the die. They are for free'extrusion. In my invention I find that it is advisable to have multiplemeans of advancing my materials and multiple dies set integral with a single hopper. For I find that though the unit of construction is one tube, it is economic to have a number of tubes set in one oven, and therefore need multiple means of extrusion and these,'I

find, may be set connected with one source of feed.

The coking of the coals is accomplished by heating them while in motion through a tube (or tubes) to which heat is applied. In Figure 1 the part numbered 9 is such a tube of any practical length. It is preferably made of some heat resisting material such as stainless steel and may be die drawn tubing. It encloses the coals being of somewhat larger internal diameter than the external diameter of the core issuing from the die 3. Around the tube 9 is a space for the application of heat to the tube. Part 10 is the insulat-- ing or brickwork part of the oven. Part 12 is an exhaust for spent gases when the heating is by means of the combustion of gases or tar or other fuel. Parts 13 and 14 are the end plates of the oven. Parts 16, 16, 16, etc. are indicated as sources of heat and may be ports for the combustion of gases which may be those given ofi by the coals during coking. Heat, and not the material used for heating, is the essential.

The part 8 is a means for fastening the end of tube 9 so that it is fixed in position relative to the means of extrusion. Under the action of heat tube 9 will expand and I find it advisable to have this expansion take place opposite to the means for extrusion. Therefore tube 9 is shown as free to move through the end plate 14. The part 8 may be a flange fastened to the tube 9, and if desired may also be fastened to the end plate 13 by a bolt or otherwise. Held between the part 7 and. the part 13, part 8, as shown, holds the end of tube 9 in closed connection with the means of extrusion. I find it also advisable to create a lip 21 at the discharge end of tube 9, as will be explained later.

The part 15 is a base for the whole apparatus, supporting both the heating element and the means for extrusion and allowing them to be placed in line. I find it advisable to set this base at an angle to the horizontal and the specific angles will be set forth in discussion of the operations performed.

Figure 3 is a partial longitudinal section of the feed end and part of the furnace and coking chamber of an alternate modification of the invention, In this view (Fig. 3), the part numbered 20a is a hopper into which the material to be coked is fed. 21a is a plunger, reciprocating at the bottom of the hopper, the object of the plunger being to push masses of the coking material forward, compressing them meanwhile within the die 22a against material previously forced into the die. 23a is a source of power by means of which a reciprocating motion is given to the plunger 21a. 24a is a rod suitably fastened at 2511 so as to remain fixed in longitudinal position. It passes through a hole in the plunger 2141, which compresses the cokable material around it. The die 22a is suitably connected to a tube 26a located within an oven 27a. 28a indicates gas ports as a source of heat for the oven 27a. 29a is an exhaust port through which the burnt gases from the oven may pass.

In the modification shown in Figure 3, the means of extrusion and the coking mufile and its heating arrangement may also be set at an angle to the horizontal, and the inside of the die 22a may be tapered as shown in the drawings.

In making the connection between the die 22a and the tube 26a flanges may be employed between which may be inserted a non-heat conducting gasket 36a, such that little heat will be conducted back into the die 22a. 35a is such a fiange fastened to the die 22a, and 37a is a flange fastened to the tube 26a, while between them is positioned the gasket 36a, which may be of asbestos or other similar material. The flanges 35a and 37a may be employed not alone to connect the die 22a to the tube 26a, but also to connect both of them to the end plate 38a of the oven. As shown in the drawings, and as described in connection with the modification shown in Figures 1 and-2, the tube 26a is larger in cross section on the inside than the outlet of the die 22a. The gasket 36a in Figure 3 serves the function of impeding or interrupting the passage of heat from the heating chamber to the die 22a.

The material to be passed through this apparatus is fine sized, moistened cokable coals. The product which is made is a coke having an analysis and burning characteristics similar to anthracite coal and also a particular structure. The temperatures used in its making are below those commonly employed for the making of metallurgical coke, though the operation performed is a coking operation and can be performed at any temperatures which the material of the apparatus will withstand. With lower temperatures than are ordinarily employed in coke ovens, the coke produced in this apparatus has ahigher volatile content than that of metallurgical coke (6 to 12 percent as against 0.5 to 2.5 percent). I find that coke which drops much below 6 percent in volatile, acquires more the burning character of metallurgical coke and loses the anthracitic character desirable for domestic i'uel.

I find that to produce rapidly at relatively low temperatures a coke which has good physical qualities, it is necessary to do what might be characterized as creating an ideal coal for coking, that is to compound a cokable mixture.

I Virginia anthracite in its natural state, to mention one coal, is nearly suitable for straight 0012- ing after moistening, but such naturalcoals are rare. nous coal, while rich in recoverable by-product and suitable for high temperature coking, is at the same time too rich to produce a good coke at lower temperatures, and therefore it needs dilution, its needs to be made lean. For I find, lean coals work where rich coals will not. And in that respect, for instance, crop coal is better than deep mined coal for coking in the manner to be described and without much dilution. For the weathering which crop coal has undergone naturally, has reduced its richness.

As anthracite silt is easily obtainable and ac-. complishes the purpose of dilution, much of the work in developing the product and process which I am describing, has been done with Pennsylvania anthracite. In order to give an explanation of the interwoven action of compounding the coals and the operation of the apparatus, I will first give an approximate sieve analysis of three anthracite coals which were used for dilution.

Sieve analysis The proof that proper mixtures have been compounded for coking is that the coked core holds its, moulded shape and-that having been moulded into what is practically a cylinder with a hole through thecenter, that this central opening remains after the green core has been subjected to a coking heat and as the core issues from the coking tube, and at the same time that the body of coals have been turned into a strong coke. In other words though a 2%ths inch diameter core is likely to shrink 5th, of an inch in diameter, the coals when properly balanced in the mixing, coke without practical deformation. If

' the compounded coals are too rich, the coals will swell (puff) during coking just as ordinary bituminous coals do, and the central opening will be closed. If on the other hand the coals are too lean, I find that though the central opening remains, the resultant coke lacks good strength.

The difierence between too rich and too lean is not a sharply drawn line, but a shading difference.

The size of the anthracite used in compounding mixtures, has a vital effect on its power of acting as a diluent. Atthe same time bituminous coals vary in their richness and consequently in their need of dilution. A rich low vola- Ordinarily fresh and deep mined bitumiv ucts are inert, acting merely as moistening agents.

The effect of the size of the anthracite is shown by a comparison of the diluting power of the three coals given; that it increases with the fineness of the coal. Its dilution was not alone of the bituminous coal, but of the combined effect of the bituminous coal and the moistening agent. No. 1 produced aproper coke when mixed in the proportions of 80 percent of anthracite to 20 percent by volume of bituminous coal plus 6 percent of Glover-West vertical retort tar. No. 2 with the same amount of tar could offset 30 percent of bituminous coal and No. 3, percent. As the tar remained the same, on the basis of bituminous coal alone these are practical ratios of 4 to 1, '7 to 3, and 2 to 1. In each of these comparative products the bituminous coal used was the same, namely Clearfield County low volatile ground in preparation so as mainly to pass through a 40 mesh screen on 80) The effect of swelling during coking is not always such as to ruin the marketability or practicability of the product. For instance when the No. l, the coarsest coal given, was used with 25 percent of bituminous coal (and the same tar), the main body of the coals were made into a strong coke. The diameter of the core was 2%th inches while the central hole had a diameter of %ths of an inch. It was only the interior fith to th of an inch of the annular ring which 105 swelled closing the central vent. When the coked core was split lengthwise this interior puffed coke was crumbly under the thumb. Such an effect is quite visible, but it only represents a small fraction of the body of the coalsand as a product 110 its misadvantage is that it would make fines during shipment. Had a larger percentage of the same bituminous coal and tar been used, the swelling would have deformed the moulded shape and affected the operation of the apparatus.

The results from No. 2 and No. 3 with increased percentages of bituminous coal, were similar, the tar remaining the same in quality and quantity. No. 3, for instance, in a mixture of percent anthracite and 40 percent bituminous and 6 percent of tar, was too rich. However when the same amounts of coalswere used but the tar changed, the balance of the mixture was thereby changed and consequently the results. When motor benzol (recovered from the coking of bituminous coal) was used in place of the stated Glover-West tar, all coking action was practically destroyed. The coals passed through the apparatus only because a ring of coke, a sixteenth of an inch or so, was formed on the outside, while the central mass came through as a dry, brown powder. When in a third mixture the moisten- Y ing-agent was again changed by making a mixture of 50 percent motor benzol and 50 percent of the Glover-West tar, a proper coke was obtained as a proper balance between the three elements entering into the compounding had been established.

A mixture of merely the Clearfield County bituminous coal and motor benzol, I find, limits the swelling ordinarily occurring with this coal at low temperatures, but-at the same time makes a weak coke. The presence of much naphthalene in a tar also seems to weaken the coke.

No. 2 of the given coals was obtained from a retail dealer and wasthe fine coal caused by railroad shipment of domestic size anthracite. As received from the dealer it contained all sizes from buckwheat down. Before use in the process it was crushed. When prepared so that approxi- 150 coals, makes a good coke.

mately 90 percent passed through a ten mesh sieve, only 25 percent of bituminous coal could be added to the mixture. When crushed to the size given, 30 percent could be used, an increase of twenty percent in the amount of bituminous coal.

As an example of controlling the compound by changing the bituminous coal, I find that a anthracite-25% bituminous coal mixture (Glover-West tar) where the largest particle of anthracite was through 8 mesh and there was approximately fifteen percent of fines through mesh, that when using a 35 percent volatile coal, the product was weak, but by changing to a Cambria County low volatile a good coke can be made.

As an example of the use-of other anthracitic material, I find that a mixture of '75 percent of semi-coke made from bituminous coal and containing approximately 14 percent of volatile matter, when added to 25 percent of the Clearfield bituminous coal and then moistened with Glover- West tar equal in volume to 6 percent of the But in this case for mechanical reasons, as will be explained later under a further discussion of the mechanical effect of moisture, as the semi-coke was very absorbent, to give a mixture sufliciently moist for extrusion and in order not to increase the amount of tar, several percent of motor benzol was added to the mixture. As benzol is here used only to give moistness, water could have been used as the additional moistening agent.

In contrast to the control over the percentages of coals entering into the mixtures through the fineness of the anthracitic material, I find that in the mechanical operation of the process of coking, the size and quantity of the largest particles in the mixtures is important. The mechanical features comprise, amongothers, feeding, moulding, movement of a coking mass, and discharge from the coking tube.

In feeding I find that material which is moist but not wet is advantageous. The dimensions of the apparatus of my invention ar not large: proportionately small in contrast to the ordinary by-product coke oven. They are purposely,. small in order to make a certain product. The chestnut size of coal is preferable for domesticuse; lump for water gas manufacture.

To obtain a product of the size of chestnut coal, I find that a core having a diameter of 2%ths inches and a central hole %ths of an inch in diameter, can be used. This exact diameter is not necessary as a core 2% inches in diameter with a 3 inch central hole would produce practically thev same results. For other size products other diameters can be used. It is the principles and not the exact dimensions which are important. Obtaining a definite sized product is dependent upon co-ordinating the preparation of the coals and the operation of the process and the dimensions of the apparatus for coking, as.

will appear in the further portions of the specification.

For mechanical reasons the amount of moistening agent which I find the best, is approximately 6 /2 percent by volume of the coals, when the main body of the coals is anthracite silt orits equivalent in freshly crushed coal. Above approximately 7 percent the material becomes too wet when freshly mixed, and below 5 percent it does not mould well. When wet the tendency is for the coals to archover and not feed down into the webs of the screw where they can be moved into the die for moulding and thereafter through the oven. Wet material needs exwhether the mixtures are made wet or not aslong as the moistening agent possesses the proper character in relation to the coals employed. The condition of moisture, although it cannot be given in a figure universally applicable, is, however, a real practical condition and easily determined by inspection and handling.

In this connection I find that if the mixtures are allowed to stand for a period oftime before an attempt is made to coke them, that they become apparently dry though retaining plasticity so as to mould easily, particularly when tars containing primary tars are used as the moistening agent. The preferable tars for increasing cokability are those which contain primary tars, that is tars from the low temperature treatment of bituminous coal. These .tars have an apparent softening action on the coal, as if they were absorbed by the bituminous coal particularly. A simple evidence of this fact is that when the mixture is freshly made, it is noticeable that the tars will come off upon the hands (coat them) if a ball is made between the palms. But after standing over night or for a day, though the ball can still be easily made, the palms of the hands remain practically clean and without a coating of tar. The action is as if free tar were gone. Such standing over a period of time is, I find, advantageous in feeding, for the material is equivalent to dry, granular material though still plastic.

This action is also, I find, sometimes advantageous in coking. For mixtures which are somewhat too rich for immediate coking, may coke without distortion after standing 24 to '72 hours.

In mixing the coals I find it advantageous to mix the tars with the anthracitic material and then to mix in the bituminous coal. For the tars spread more easily over the anthracitic material"particularly anthracite coalthan over the bituminous coal. When the coals are first mixed and then the tars added, I find there is a tendency for the formation of wet balls coated with dry coal.

The moulding action which occurs in the die of the extruder, I find is best performed in a constricting die, particularly if the means employed for propulsion of the material is a screw. For with a screw the material travels at right angles to the face of the screw and unless means is employed within the die to counteract against this twist, the material twists after issuing and only a relatively short length (nine to twelve feet for a 2%ths inch core) can be extruded without the core breaking. In proportion as this twist is controlled, the length of core extruded can be extended. Control may be by means of fins within a tubular die or by the fiatt sides of a'hexagonal die.-

In any extrusion the packing of the material in the die increases with the fineness of the material and the amount of moisture (until excessively wet) and with the length of the die. With too long a die the resistance may be enough to make the material pack solidly and stop the extrusion; with too short there may not be enough resistance to mould the material. With a plain tubular die the variations of the length of the die as materials are changed is excessive. having about ten to fifteen percent reduction in area and where dependence is put upon compression rather than merely upon frictional resistance, the length of die becomes practically constant for all materials. For such aconstricting die the total length of die and enclosed screw is, I find, ordinarily less than ten inches long for a 2 th inch core of coals.

The maximum amount of pressure which I find is necessary is that exerted by a thirty pound Weirht acting at twenty five inches -of leverage on a 2' gth inch diameter face. Such a pressure is very small in contrast to the pressures of seven and ten thousand pounds per square inch used in briquetting and eventhe twenty odd thousand pounds per square inch developed in briquetting German brown coal by forcing it through a long constricting die. I find that it is not the pressure used which makes good coke, but the balance of the materials. And only enough pressure is needed in my invention to mould the coals and advance them through the coking tube.

Coarse materials have a body resistance and do not mould well. I find that a coal of such a size as the No. 1 given, does not mould particularly well; that No. 2 is of a practical size; and that No. 3 moulds the best of these three. Again I find that a bituminous coal ground so that practically all passes through a 40 mesh screen (50% on is too fine to use with a simple screw as it does not have body enough to resist the alternating pressure first on one side and then on the other which occurs as the screw rotates. Such fine material needs a plunger instead of a screw as an advancing means. A sketch of this alternate means of extrusion is given in cross section in the accompanying diagram Figure 3.

When it comes to the coking of coals, it needs to be realized that there are four zones existing in the mass duririg heating: (1) an outside, more or less impervious ring of coke, the result of fusion; (2) an interior zone where gases are being evolved as the fused coals dry out into coke; (3) a further zone where tars are being re-.

leased and under the gas pressure behind them,

- are being forced into the (4) unaffected zone of coking the graded particles separately. Moreover uniformly sized particles are more equally afiected by heat and coking progresses in a better manner.

As the tars move toward the center in the coking of a core such as I am describing, I find that the central part is being enriched during coking and that the central opening in the core provides a final means of escape for the tars and vapors,

With a die to such a heat.

It may. be created by grading the coals coals vass through a fusion stage where they are sticky. This stickiness has been the outstanding trouble encounteredbwall workers with coking coal. It commences when the coals reach temperatures around 400 C. I find that coking coals will not stick to metals if the temperature is high enough and that the temperature where stickingvanishes again is around 600 0. S0 in my apparatus it is necessary, to carry on the process, that at least this temperature be maintained in the coking tube at, or so close to, the connection to the extruder that the coals when they come in contact with the tube are subjected I find that if this proper heat is maintained, I can quickly create a dry surface of coke on which the core can freely slide through .die, may be extendedlbeyond the end of the die and so support the core free and clear of the coking tube. Such an extension can be an inch and a half or two inches long (or somewhat longer) and does assist, I find, in landing the fresh coal clear into the tube where a greater body of heat is more easily maintained.

By economizing inches and half inches and by taking care that there is a quick application of heat to the coals, I find that it is possible to'jump the range of sticking temperatures.

I find that a coking heat (and even an emollescent heat) must not be permitted-to pass back into the die of the extruder, though the end of the die may get warm from its proximity to the coking tube. For if a coking .heat is allowed to pass back to the die; the surface of the coals will turn to coke within the die and ofier a new frictional resistance. In this [case too the coals will also come in contact with'metal which is at the sticking temperatures, for as the metal of the die is continuous, heat will be conducted back. In consequence of offering new and greater resistance the extrusion will jam. Therefore I find that the extrusion needs to be from the cold into the hot. This is also necessary as the coals contain distillable tars and preheating is therefore not advisable.

The passage of the coals through the die may be at the rate of a foot or more per minute. As the die'for -a 2%th inch core is only a few inches long, the continuous passage of fresh cold coals tends to keep the die cool and the heat away from the die. Set in-the open the die also has e chance to radiate heat away. The asbestos gasket 360. (Fig. 3) also operates to impede or interrupt passage of heat to the die and prevents undesired heating of the die.

There is also another reason for extruding from the cold directly into the hot. For the effect of preheating, I find, is to alterthe coking v power. In coking a 50-50 mixture made up from equal parts of anthracite crushed to pass through 9 mesh and Cambria county low volatile bituminous coal and eight percent by volume of Glover-West tar figured on thevolume of the coal, I find that deformation takes place with immediate coking and that a' worthless coke is produced. Heating moulded shapes of this same mixture for ten minutes between the tempera,- tures of 350 and 400 C., at which temperatures coals do not stick to iron and are merely distilled and not coked, allowed the shapes to be later coked at temperatures somewhat above 600 C. and produce a good coke. Increasing the pre heating period to fifteen minutes, also increases the counter action and to a sufficient extent as to considerably weaken the coke produced on later coking. As a consequence I find that were preheating below coking temperatures indulged in, the coals would have to be adapted to preheating and also that the extent of preheating is important in producing good coke. element in preheating will not permit the variable'speeds of extrusion which I findpossible with extrusion from the cold into the hot. Moreover I find it is simpler to change the original mixtures so as to avoid any need of preheating than to alter the character of the coals by preheating.

After the surface of coke is made in the passage of the core through the coking tube, I find that such questions as the uniformity of heating of the tube is relatively unimportant. The only thing is that the heat should not be allowed to drop below the coking temperatures or a weak ring will be formed in the core. Otherwise the temperatures maintained at different points through theoven may vary widely, though, of course, as a practical operating matter, relative uniformity is desirable.

The size of the largest particles present in quantity in the mixed coals is important, I find, among other things, in relation to the formation of the surface of coke. With larger particles the thickness of the primary skin must be deeper than would be necessary when only small particles need to be incorporated into it. Small par- .ticles mould more smoothly and make a, more even and uniform surface. Large particles, of anthracite particularly, snap and cracklewhen subjected to sudden heat, deflagrate, and breaking into two, fly out of the core, and then with other particles accumulate into masses and gather under the core to confound its free move-v ment through the coking tube. With coarse material particles also fall out of the core as the coals issue from the die to do the same thing. Moreover it is easier to rub large particles out of a core than small particles. In the movement of the core through the coking tube it is the largest particles which are freed and collect at the bottom of the tube.

It is hard to keep a coking tube absolutely smooth. Irregularities in the original metal and other irregularities such as pitting, will scratch at the surface of the coked core. Large particles are angular and do not roll. Fine particles roll and even act as a lubricant between the tube and the stiff core. It is for all these reasons that it is easier to movethrough the coking tube a core madefrom finely ground coal rather than from coarsely ground. And it so happens, I find, that the sizes of coal which are advantageous as diluents of bituminous coal, are also advantageous for passage through a coking tube.

I find that anthracite of the size such as the No. 1 given, is more diflicultgto coke mechanically than the other two sizes. In a mixture where only twenty percent of bituminous coal was added to the No. 1, and six and a half percent of tar was used, some three and a half per.- cent of the coals were likely to be produced as fines not incorporated into the core. The loos.-

This time ened particles were all of the largest size of the largest particles in the original coals. On the other hand No. 3 as given, where only five percent of the particles is larger than twenty mesh and to whicha larger proportion of bituminous coal could be added, moves, I find, with ease through the coking tube, while No. 2 is about the largest size for easy mechanical operation, as well as being at about the upper limits for economic operation and the production of enough by-products to make the process completely selfsustaining.

With excessive resistance to the movement of the coking core, such as occurs when a large body of loose particles gather under it and even pinch it against the top of the tube, the green core crushes as it issues from the die, that is at the point where it is weakest. The sooner and the faster the outside of the core is turned into coke, the better it is from an operating standpoint. For though a cold uncoked core can be extruded through a'level tube for lengths above'twenty feet, a green core has relatively little strength. Therefore high oven heats near the extruder are often advisable, though not at the same time maintained throughout the oven. For a ring of coke on the 'outside of the core adds greatly to its columnar strength and the closer this ring of coke is to the extruder, the stronger the column to push material ahead of it.

The maximum angle to the horizontal at which the coking tube and therefore the whole apparatusshould be set, is, I find, in part dependent upon the size of the material passing through the tube. The angle decreases as the fineness of the material increases. If the angle is too great so that the core is practically hanging, or under tension in the tube, the core may part at some point and the free section slide, emptying the tube before the coals have a chance to properly coke. The maximum angle which I find advisable is approximately fifteen percent. With a coal of a s ze such as the No. 1 given, such an angle is desirable with a rough tube. With the No. 3 even with this angle and a rough tube there is a tendency for the core to slide, and therefore a slightly less angle can well be used.

I find that the discharge end of the coking tube is best made with a lip 21 (see Fig. 2). If it is square, then a piece of coked core may break so that part is within the tube and part overhanging the end. As the free piece is moved forward by the oncoming, unbroken core, it will hang at agreater and greater angle in the open end of the tube and as the angle increases the obstruction which it presents increases and may become suflicient to cause the weak part of the core near the extruder to fail. With a lip whose top side is free, the angle at which the free piece The product is in its nature a mixed affair.

Anthracite coal has been considered by many as unalterable by heat. An examination of a product, made in the manner being described and in which anthracite coal had been used in the making of the mixture, disclosed that under the of the tube, I find, also 7 microscope at approximately fifty magnifications none of the fine dust in the original coal was visible and that such large particles as, could be recognized as to have been anthracite, had no sharp separation from parts which on account of their shape were evidently coke. Moreover the surface of the anthracitic parts were, under scratching, more graphitic in character than the dry brittle scratches of the same natural anthracite. The surface of the parts of the original anthracite showed no coating of dust, no granu lation, as was evident in a baked briquet made with a petroleum binder and which was examined in comparison. The showing of the microscope is, I find, that the finest particles of the anthracitic coal have disappeared and the larger particles have been modified on their surface.

Ihe loss of weight in coking is' an evidence of a mixed action. For a mixture of three quarters anthracite and one quarter low volatile bituminous coal showed a loss attributable to the coals of eight percent, a loss. which was greater than could be attributed to the bituminous coal alone, which was reported as having only sixteen to seventeen percent volatile.

Another indication that the surface of the larger particles has its effect, as well as the body of the finer, is that the No. 3 coal previously given, although containing approximately the same amount of fines as the No. 2, still on account of' the greater surface in the mass of the coals was able to care for some sixteen percent more bituminous coal than the No. 2.

The approximate analysis of the product varies according to the time under heat and the temperatures employed in the coking. Two samples of coke strong enough for practical shipment from plant to consumer and which had been heated for 13 minutes, gave on analysis:

Moisture 3. 86

Volatile matter 7.73 8.99 Fixed carbon 77.01 77.97 Ash 11.40 13.04 B.T.U 12,960

Another coke which had been made under a heating period of sixteen to seventeen minutes gave a volatile matter percent.

I find that the product does not need to be completely coked within the tube alone. With a 2%ths inch-core and a %ths central hole, the

heat travels through to the central opening in ten minutes and the core is given shape. In operation the temperature of the oven, I find, can be held between 1350 and 1400 F. within an inch of the end of the die of the extruder and drop to temperatures of 1150 to 1250 F. at the discharge end and with such temperatures and a rate of extrusion of 9 inches per minute, produce a good coke in a tube ten feet long. Such an oven temperature at the beginning, I find gives a heat head sufficient to overcome sticking and to form an immediate surface of coke. With a thirteen and a half minute heating period within the tube, the product issues with enough residual heat (or it may be exothermic action, or both)- to complete its coking into a strong coke if allowed to stand without quenching even though standing in the open air. F the product issues from the tube with approximately half to. five eighths of. its .depth converted into hard coke, while the centeris soft and partly in a state of fusion. Under a coking periodof twenty one to twenty two minutes, the product will issue of between six and seven As a matter of fact 1 find that it is better not to have the coking completed within the tube. For in the latter case the coke issues with such a strength that it hangs out of the tube in inadvisable lengths three and four feet long, (for the 2%th inch diameter core) or occasionally longer. With the shorter heating period of 13% minutes the lengths will be from eighteen to thirty inches. Other diameters for the cores would give other heating periods. 7

There is another reason for not completing the coking within the tube alone but rather in some receptacle where the hot core would be protected and given slow cooling, or additional heat after being broken into lengths.

Mixtures which are a shade on the side of richness, .I find, will discharge from. the tube at the 13% minute heating period, with the central hole still open and discharging vapors. Later with continued coking under natural cooling, thatcentral opening may close on account of the swelling of the center of the mass, as has been explained. It is possible, I find, that when too rich mixtures are used and heating in the tube is continued until the central opening is closed, to occasionally accumulate such a gas pressure within the coking core as to disrupt it at some point and to discharge the free section in the manner of "a missile, although ordinarily the disruption will be merely a vent through to the exterior of the coke.

Coarse materials, I find, tend to coke into somewhat longer lengths than fine material; Long lengths are not ordinarily wanted. The fine coals are formed into shape under 13 minutes heating period and no advantage is gained by holding them longer within the tube, when any further coking that might be desired, can be done -in a less confined space.

Discharging into a closed receptacle also permits the recovery of the by-products released during the heating of the core. This recovery is moreimportant from thecconomic standpoint than from the standpoint of merely making coke. For the recovery of by-products allows them to be used in making the original mixtures or in heating the oven. But for the mere production of 'coke only the coking tube is essential. I find that it is preferable to use slightly lean mixtures 'in coking. Material'of the size of the No. 2 of the previously given coals, though it can be used with thirty percent of bituminous coal (the same percentage and character of tar being used in each case) gives a more advantageous product with only twenty five percent of the same bituminous coal.

For I find that when the means of expulsion of themixtures through the die is a screw, that in reality a closely pressed spiral-has been fed at the planes where pressure has been applied. With rich mixtures this tendency to break is not as evident but rather to coke into long pieces.

I find that even separately 'moulded, highly pressed briquets, when made out of rich mixtures, will coke firmly together at the faces is fed forward at each revolution of the screw.

The breakage in the coked core is not at each half sections of a spiral and relatively uniformly sized and possess the real strength of the coke. The breaking produces verylittle fines. With a 1 inch lead on a screw and a 2%th-inch diameter core, the resulting pieces I find with a slightly lean mixture, are of the size of chestnut coal with some pea coal and practically none of the size which in the coal trade is known as undersize.

The result with a screw and the proper condition of leanness of the mixture, is that the equivalent of the long sought,,irregularly shaped briquet is produced. This shape is advantageous on the fire in the way that the irregular shape of natural coal is advantageous. Moreover slightly lean mixtures break at shorter intervals on discharge from the tube and fine material breaks at better intervals than coarse material.

In consequence material of the'size of the No. 3

in the given comparison, is more advantageous, I find, than the other two, though the other two can be successfully manipulated.

With a plunger reciprocating on a fixed rod in place of the screw in the extruder, the columnar pieces of coke will break into cylindrical sections.

The product has the advantage that it hardens when put upon the fire and is completely consumed without disintegration. Also it can be put upon a hot fire and will not deflagrate in the manner that anthracite often does.

The smokelessness of the product is dependent upon the completeness of the coking. In a report upon some two tons of this coke which was made for testing in a laboratory equipped for testing anthracite and briquets in, household heaters, the report was: The fire picked up rapidly after fresh charges of fuel and did not require any more attention than anthracite coal. After firing, however, it had a tendency to smoke as would be expected from the volatile content [9%l, but this smoking was easily eliminated by proper adjustment of the secondary air, that is, the air admitted over the fire. The coke which was submitted for this test had had a coking period of thirteen and a half minutesand the original mixture was composed of seventy percent of anthracite of the size of the No. 2 given and thirty percent of low volatile bituminous coal and six and a half percent of Northern Liberties vertical retort tar. Similar mixtures which have been subjected to a coking period, of sixteen to seventeen minutes give off a slight haze for a period on fresh firing.

Although the products are practically completely formed within the coking tube, the discharge of the products, I find, can be done into some receptacle. Byso doing and not having a free discharge to the atmosphere, the gases and tar vapors formed during the application of heat, can be collected for useful purposes. This receptacle may have the purpose of merely a collecting agency or may be for the purpose of cite coal formerly served. The connection of the discharge ends of the coking tubes directly to 'a gas retort can also serve, I find, as a continuous charger for'gas sets.

A simple form of receptacle is shown in Figure 2. In this figure part 21 is the lipped discharge end of the coking tube 9, free to move in the end plate 14 of the oven and in the side plate 22 of the receptacle. 23 is a packing gland to enclose the coking tube 9 and prevent the admission of air and the escape of gases and vapors. 24 is an exhaust for the gases and vapors and may lead to the ordinary condensers and gas purifiers known in the art of handling gases and vapors. 25 is a port set opposite to the coking tube 9 so that access may be had to the tube for repairs or in case of trouble in operation. 26 is ameans of discharge through which the coke may be withdrawn and by means of which free access of air to the interior of the receptacle is practically prevented. 2'? is a means of controlled admission of air or steam or both to the interior of the receptacle in case it is desired to subject the coke to further heating through burning of the coke, or to the 0001- mg action of steam. I find that a number of coking tubes 9 may discharge into one receptacle. r e

If the coked product issues from the coking tube at approximately 1200 to 1250 F.- (at least 15- for its surface temperature), I find that it is at what might be characterized as the flash point in that it will commence to burn of its own accord in the open air, particularly if pieces of the coke are piled together and contribute to the burning action by their mutual reaction. The burning is a fiameless burning and separated pieces cool as separated pieces of coal would. I find that advantage can be taken of this action in the receptacle by the admission of some air, obviating the need of exterior heating of the receptacle and at the same time .when properly controlled, increasing the amount of gas created in the whole operation.

As the product is artificial, the quantity and quality of the ash can be controlled in the product. There is a growing argument among engineers as to the part which the ash plays in the transfer of heat from the'coal to the material being heated, that it may act as a radiant material and thereby assist 'in the heat transfer. Moreover in the manufacture of water gas it is advantageous to have a fuel whose ash will clinker in a granular way and clinkering is in good part dependent upon the chemical analysis of theincombustible. The presence of a certain percentage of iron in a fuel may enhance its reactivity. I have notfound that the amount of ash made any appreciable difference in the product. The coke made from the No. 1 and No. 3 of the given anthracite coals, was equally good as to strength, though the No.1 anthracite had only approximately ten percent ash, while the No. 3 had thirteen percent or more. I lmow from experience that in nature, underground in the coal seams, it is the high ash coal, the honey coal, which is ordinarily stronger than the pure coal, as if naturally dilution of the coal material produced a stronger product.

I again call attention to the fact that in the heating operation, there is no stage where the coal softens to the sticky stage, while in contact withthe walls of the tube. Hence I desire to emphasize thefact that the mould is kept always below this sticking range of temperature, while the next section of the tube with which the shaped material comes into contact is well above the 'range of stickiness. Between these two points of contact the stick of coal is being heated by heat radiated from the hot tube wall, which is slightly spaced away from the stick of coal. The coking of the outer skin of the stick may thus be initiated while out of contact with the tube wall.

The range of temperature in which the stickiness occurs varies more or less with different coals. While 400 C. has been stated above, as the beginning of this range, this figure may vary between 375 and 425 (3., depending on the different coals and mixtures stated above. Likewise the top-range may vary between about 600 and 650 C.

The sticking range isalso a semi-fusion range suchthat briquets compressed originally under very high pressure will loose all the strength due to these pressures and if slid across metal heated at the sticking range, will loose the softened portion of their mass. If the length of slide is'at all extensive, the briquet will be practically destroyed.

I claim:-- V

1. The process which consists in making a mouldable cdkable mixture whose constituents are so balanced with respect to each other as to coke without substantial deformation and to substantially retain as planes of facile fracture the faces where pressure has been applied and extruding such mixture in the form of a thick walled tube having a small bore, without substantial preheating, into a coking zone so heated that-the surface of said extruded material is immediately subjected to-a temperature above the range of sticking temperatures of coking coals and thereafter coking such extruded material while still in the form of a tube, and while passing through said coking zone.

2. The process which consists in making a mouldable, cokable mixture whose constituents are so balanced with respect to each other as to coke without substantial deformation and extruding such mixture without any sumcient preheating as to produce stickiness, into a tubular zone heated to such a temperature that the mixture immediately becomes subjected to a temperature above the range of sticking temperatures of coking coals and thereafter at least partially coking them as they pass through the tubular heated zone, such coking operation involving forming a skin of coked material on the surface of said extruded body..

3. In the manufacture of fuel, the steps of forming a readily cokable mixture including anthracitic material, bituminous coal and a tarry material, and extruding such mixture in columnar formation into 'a coking zone, and coking the mixture while in-such columnar formation in said coking zone, and while its surface is free from contact with hot metal surfaces within the ran e of sticking temperatures until-its surface has been coked.

4. The process of forming anthracitic small masses into larger masses which comprises extruding a substantially unheated cokable mixture containing said small masses into a tube of somewhat larger cross-sectional area than said extruded material and heating said tube to such an extent as to coke the extruded material 'exteriorly before sticking occurs.

5..The process of forming anthracitic small masses into larger masses which comprises forming a cokable mixture containing said small masses into-a column-like body without rendering said mixture sticky by the application of heat, thereafter passing said column-like body through an elongated heated coking zone of only slightly larger cross section than the columnlike body, to coke the same, and impeding passage of heat from the coking operation to the material during'its formation into said columnlike body. i A

6. The process of forming small masses of coal into larger masses which'comprises forming a cokable mixture containing said small masses into a column-like cokable body by cold pressing and thereafter passing said body endwise into and through an elongated coking zone of only slightly larger cross section than said columnlike body, heated at such a temperature near its inlet asto substantially immediately sear the outside of said column-like body to a hard dry non-sticky condition.

'IIIn an apparatus for coking carbonaceous material, an extruding means, a heating chamber adapted to receive the extruded material from said. extruding means, the saidheating chamber being so disposed with relation to said extruding means as to impede the passage of heat from the former to the latter, said chamber being slightly larger in cross section than the outlet of said extruding means.

8. In an apparatus for coking carbonaceous material, an extruding means, an elongated heating chamber adapted to receive the extruded material from said extruding means, and means between said heating chamber and said extruding means for impeding thev conduction of heat from said heating chamber to said extruding means, said chamber being slightly larger in cross section than the outlet of said extruding means,

- andmeans carried by said extruding means for supporting the material during a portion of its passage through said heating chamber.

9. In an apparatus for coking carbonaceous material, an extruding means, a heating tube adapted to receive materialextruded from said extruding means, means capable of interrupting the passage of heat from said heating tube to saidextruding means, said tube having a slightly larger cross-sectional area than the exit of said extruding means.

10. The method of uniting fine size carbonaceous material containing cokable material which comprises collecting said fine size material into a larger body at a temperature below which the cokable material becomes sticky by the action of heat, thereafter heatingthe exterior of said body high and long enought'o coke the exterior surface thereof to a dry non-sticky condition and thereafter sliding said body through a zone heated to a temperature sufficient to complete the coking, all of said stepsbeing carried out while out.of contact with sufiicient air to of said larger body formed.

11. In. an apparatus of the character described the combination of means for forcing a mass of cokable material through a die, tube-like coking means adapted to directly receive said material after passage through said die and having a somewhat larger cross-sectional area than the outlet of said die, and means for internally supporting said material as it passes from the die into said tube-like coking means.

12. The process of forming anthracitic small masses into larger masses which comprises forming a mixture containing anthracitic small' masses and coking material into a tubular continuous columnar mass, substantially without use of heat, thereafter rapidly heating the exterior of said mass until its exterior becomes coked and presents a non-sticky condition and thereafter without destruction of the shape of the mass, further heating the mass sufliciently to produce further coking within its interior, while preventing combustion thereof, all of said steps being performed on different portions of the same len th of a columnarmass of said material.

13. In the process of forming anthracitic small masses into larger masses, the steps which comprise extruding substantially in the cold, a continuous columnar tubular cokable mixture containing saidsmall masses, into a zoneheated to such an extent as to coke the extruded material exteriorly to a non-sticky condition shortly after its entry into said zone and before said material hot metal surfaces, all without destruction of the shape of the mass, and thereafter without destruction of the shape of the mass, further heating such massfrom the exterior sufficiently to initiate the formation of coke from the said cokable material throughout the cross section of the interior of said mass, while preventing combus tion thereof.

15. A process of forming anthracitic small masses into larger masses which comprises form-.

ing such anthracitic smalf masses mixed with a cokable material and a moistening agent of tarry character, into a continuous tubular self-sustaining columnar mass, substantially without the use of heat, thereafter rapidly heating the exterior ofsuch columnar-mass until the exterior presents a non-sticky condition which will not adhere to hot metal surfaces, all without destruction of the shape of the mass, and thereafter without destruction of the shape of the mass, further heating such mass from the exterior, all of said steps being performed upon different portions of the length of thesame columnar mass of said material.

16. A process which comprises forming a continuous compacted tube of a solid cokable mixture containing coking coal and an oily moistening agent, which mixture is substantially non-deformable by cok ng the same, and delivering said continuous tube, without previously heating same tfally continuous compacted tubular mass of materials including anthracitic fines, solid bitumin'ous fine coal and a tar oil constituent as a temporary binder previously so prepared that when the mass is subjected to coking heats it will coke without substantial defamation of the shape into which it has been formed," thereafter without destruction of the shape of the tubular mass and while the exterior surface of the mass is out of contact with other surfaces, exposing the exterior surface of the tubular mass to suflicient heat to initiate coking on the surface of the mass and thereafter without destruction of the shape of the mass and while preventing its combustion, further heating the mass so as to continue the coking within its interior, all of said steps being successively performed upon the tubular mass, and'all of said heat-treating steps being performed in the substantial absence of air, to prevent combustion of the material.

I-IUCjH ARCHBALD.

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