CA1194307A - Production of solid fuel shapes from coal fines - Google Patents

Abstract

Abstract Dry, random size, mine run coal fines are mixed with a concentrated liquor by-product (e.g. ammonium lignin sulfonate liquor, 40-60% solids by weight) of a sulfite paper making process of an amount sufficient to merely wet the coal fines such that they will hold shape when compressed. The wet coal fines are formed into large shapes (e.g. cylindrical logs or rectangular blocks) and the shapes are compressed. The wet coal fines are hopper fed into mold cavities and within the mold cavities are subjected to pressures within the range of 2,000-3,000 psi.
The dried shapes are coated with a wax substance.

Description

3~7 --1~

Desc_ ption PRODUCTIOM OF SOLID FUEL SHAPES FROM COAL FINES

Technical Field The present invention relates to an inexpen3ive solid 5 fuPl produced from waste coal dust or fines and a concen~rated liquor by-product of the sulfite paper making process, and to a method of manufacturing such solid fuel.
Back~round _ The patent li-t~rature contains a large number of 10patents relating to various methods of casting mixtures oE
coal particles and various binder materials into solid fuel shapeR. With but one exception, a common denominator of these prior patents is the belief that it was not possible to use a sulfite liquor by-product of the sulEite paper 15 making process alone as a binder.
U.S. Patent 1,678,387, granted July 24, 1928, to Robert M. Hale, suggests obtaining a good bond by using coal fine~
which have been oil-coated before being mixed with th~
lignin material. U.S. Patent No. 585,001, granted June 22, 20 1897, to Nicoll MacDonald, discloses adding lirne water to a mixture which include~ coal particles and "pulped paper", coal-tar and crude petroleum. U.S. Patent No. 782,991, granted February 21, 1905, to Sarnuel P. Sadtler, discloses adding sodium carbonate to a mixture of "fine coke-powder"
25 and "concentrated waste liquor of the sulPite wood-pulp process". U.S. Patent No. 969,504, granted September 6, 1910, to Ernst Trainer, discloses the addition of a chromium compound to obtain a good bond. U.S. Patent No.
1,084,479, granted January 13, 1914, to Max Platsch, 30 disclo~e~ the addition oE sulfuric acid. U.S. Patent No.
1,507,676, granted September 9, 1924, to Theodore Nagel, discloses the addi.tion of phosphoric acid. V.S. Patent No.

1,576,248, gran-ted March 9, 1929 to Jacob S. Robeson, discloses adding "crude rnolasses" and "wood tar". U.S.
Patent No. 1,596,239~ gran-ted August 17, 1926, to John P.
Delzeit, discloses adding "sulfur" and "sulfuric acid".
U.S. Patent ~o. 1,615,463, granted January 25, 1927, -to Michael E'. Maginnis, discloses adding "starch", "glue" and "alum". U.S. Patent No. 1,618,24g, granted February 22, 1927, to Samuel F. Walton, discloses adding a "cellulose solution". It is stated in this patent that the cellulose 10 apparently forms a physical union with the sulite liquor.
It is said that the cellulose protects the briquettes from the effects of water or moisture until they are generally carbonized by combustion in use. The patentee states that "unless carbonized or otherwise chemically treated, sul~ite 15 liquor by itself would be unsatisfac~ory as a binder, because it i8 hygroscopic and absorbs moi~ture; so that afte~ mere drawing briquette bonded with ~ulfite liquor alone would absorb moisture from the atmosphere and disintegrate". The patentee further states "cellulose used 20 alone as a binder, on the other hand, would disintegrate in burning".
U.S. Patent No. 1,623t764, granted April 5, 1927, to Srinivas R. Wagel, discloses adding "clay and asphalt".
U.S. Patent No. 1,752,838, granted April 1, 1930, to 25 Francis M. Crossman, discloses adding "raw starch or any farinaceous material containing starch and gluten", and a small percentage of "sodium nitrate". U.S. Patent No.
1,908,862, granted May 16, 1933, to Charles H. Reese, discloses adding "lirne" and "a coagulant such as gellatin 30 or glue". U.S. Patent No. 2,567,136, gran-ted September 4, 1951, to Antoine Vloeberghs, discloses the addition of a "phenolormaldehycle resin". U.S. Patent No. ~329,042, granted August 21, 1906, to Bernhard Wagner, teaches manufacturing briquettes by (1) heating "anthracite" up to about 140 degrees centigrade; (2) heating waste lyes from cellulose-factories up to about 60 degrees centigrade; ~3) mixing the two substances together in a mixing apparatus while maintaining a -temperature of the mi~ture of about 100 5 degrees centigrade; and (4) -feeding the mixture into a press at about 100 degrees centigrade. The patentee states that for the purpose of maintaining the mass at the pro,per degree of temperature in a mixing apparatus, and of enabling anthracite or other material used and the binding 10 medium to be intimately mingled as possible, super heated steam may advantageously be conducted directly into, the mixture.
The single patent which discloses using waste sulfite liquor alone is U.S. Patent No. 1,667,304, granted April 15 24, 1928, to Ernst W. Bowen. Bowen states that he is able to obtain proper bonding by first separating the fine dust or flour from the granular portion of the anthracite or other coal. The granular portion of the coal is mixed with a waste sulphite liquor obtained from wood~pulp mills, and 20 then the dust or flour is added to the mixture "in definite proportions". The patentee suggests separating the flour from the granular parts by a two stage screening process.
The yranular coal is dried and is then mixed with sulphite liquor at about 150 degreeq Fahrenheit in a suitable 25 machinP which ensures a thorough distribution of the liquor throughout the granular material. This mixture consists of 86 percent by weight of granular to 9 percent by weight of sulphite liquor. A~ter these constituants have been thoroughly mixed, approximately 5 percent dust or flour is 30 added and the mixing operation i9 repeated until the mass becomes truly pla~tic. The plastic mass is molded into briquetkes which are baked at a tempera-ture of abou~ 630 degrees Fahrenheit for approximately twenty minutes and are then cooled.

U.S. Patent No. 3,684,465, granted August 15, 1972, to Harry L. Hsu, discloses the use of a~monium lignin sulfonate liquor as a binder material in the manufacture of fuel briquets. SpeciEically, this patent discloses that the amount of binder employed should be be-tween about 3 and about 10 parts by weight per 100 parts of the carbon aggregate employed. It also sta-tes that in all cases the total amount o water employed in any given mixture should be bet~een about 5.0 and about 8.0 parts per weight per 100 10 parts of the carbon aggregate and the parts oE water used is inclusive of the water or moisture contained in the carbon aggregate materials and in the bindex. The mixture is formed into the desired shape in a roll briquetting operation employing a pressure force of at least 1.0 metric 15 ton per centimeter of face con-tact.
The above described patents, and the additional patents listed below, all should be carefully considered for the purpose of putting the present invention into proper perspective: U.S. Patent No. 478,229, granted July 5, 1892, to Jerome W. Frank; U.S. Patent No. 257,985, granted May 16, 1882, to William C. Siffken U.S. Patent No.
829,072, granted August 21, 1906, to Henry Hill; U.S.
Patent No. 1,780,205, grantsd November 4, 1930r to Henry F.
Maurel; U.S. Patent No. 3,297,419, granted January 10, 1967, to Edward E. Eyre, Jr.; U.S. Patent No. 3,635,684, granted January 18, 1972, to Donald E. Seymour; U.S. Patent No. 3,829,297, granted August 13, 1974, to Chester C.
Crawford; U.S. Patent No. 3,883,317, granted May 13, 1975, to Fuhad A. Neme; U.S. Patent No. 4,152,119, granted May 1, 1979, to Helmut W. Schulz; [J.S. Patent No. 4,230,459, granted october 28, 1980, to Jean R. Mareau, Martin P.
Pelletier and Gerard B. Tremblay; and U.S. Patent No.
4,243,393, granted January 6, 1981, to Mi]es W. Christian.
~escription of the Inventlon In accordance with the present invention, waste coal fines are combined with ammonium lignin sulfonate liquor, or an equi~alent by-product oE a paper manufacturing process, -to produce relatively large size fuel shapes, viz.
logs or bricks.
In accordance with an aspect of the invention, substantially dry coal fines are combined with only enough concentrated liquor to wet surface portions oE the fines.
The coal fines, wekted in this manner, are placed into 10 molds and are tightly compressed together to form the fuel shapes. The fuel shapes are then removed from the molds and are dried.
According to an aspect of the invention, the liquor is thinned by heating prior to its being combined with the 15 coal fines. Thinning in this manner facilitates an even distribution of the liquor throughout -the coal fines.
In accordance with another aspect of the invention, coal fines which when obtained have a moisture content of more -than 5~ by weight are dried before combining them with 20 the liquor un-til the ~oisture in them is no more than about 5% by weight. Preferably, the coal fines are dried by fluLdizing them with heated air. The heated air may be air obtained from a dryer used for drying the compressed fuel shapes~
Preferably, the by-product liquor is ammonium lignin sulfate liquor. Preferably also, a liquor is used which includes between 40-60~ solids by weight~
In accoxdance with another aspect of the invention, the by-product liquor is used in a quantity and concentration 30 such that the ratio of wet coal fines to liquor solids i5 between 13:1 and 20:L by weight, and the total moisture i~
between 3~ and 7% by weight.
PreEerably, the by-product liquor is heated to a temperature oE about 180 degrees F. to about 220 degrees F'.

prior to combining it with coal fines.
In accordance with an aspect of the invention, the liquor wetted coal fines are placed into log forming cavities and are compressed by hydraulically moving a piston in through one end of the cavity, against the liquor wetted coal fines, while closing the opposite end of the cavity.
In accordance with yet another aspect of the invention, the shapes are removed from their molds and are dried. Air drying will work. However, the preferred practice is to place the shapes into ovens and heat them in such ovens to no more than about 200 degrees F. until they are sufficiently hardened so that they will hold together during normal handling and during the burning process.
Normally, this requries heat for about 2 to about 6 hours.
In accordance with another aspect of the invention, after drying the soild fuel shapes are coated with a wax substance, e.g. slack wax, parafin etc.
Additional objects, features and advantages of the invention will be appareht form the following description of a preferred embodiment of the invention.
Brief Description o fhte Drawing Figures Referring to the drawing:
Fig. 1 is a flow diagram of an embidoment of the process of the invention;
Fig. 2 is a side elevational view of a first embodiment of a fuel log forming machine;
Fig. 3 is a top paln view of the machine shown by Fig.

2;
Fig. 4 is a pictorial view of a second machine for casting cylindrical fuel shapes or logs;
Fig. 5 is a cross-sectional view taken substantially along line 5-5 of Fig. 4;

Fig. 6 is a longitudianl sectional view taken through the feed station;
Fig. 7 is a longitudinal sectional view taken through the compact station; andact station; and Fig. 8 is a longitudinal sectional view taken through the eject section.
Description of the Preferred Embodiment Referring to Fig. 1, dry coal fines, one quarter minus, and a suitable liquor by-product of a paper making process are combined together in such a manner that the liquor is substantially evenly disbursed or distributed amongst the coal fines.
Preferably, mine run coal fines are used because they are a waste product. At the present time ther is an abundant supply of one quarter minus mine run coal fines.
However, under some circumstances, it might be desirable to crush larger coal particles to produce the coal fines.
The coal fines may come from the mines or storage in a dry enough condition that drying is not necessary before combining them with the by-product liquor. This would be particularly true whne the coal fines are obtained from mining operations conducted during the warm months of the year. However, when the coal fines are obtained with the mositure content greater than about 5% by weight, it is necessary to dry them before use. Preferably, the coal fines are dried by fluidizing them with heated air. Heated air may be obtained from a dryer or oven used to dry the fuel shapes. For example, a fan or pump may be used to remove air from the interior of the dryer to the inlet of a fluidized bed through which the coal particles must pass before being combined with the by-product liquor.
In accordance with the invention, a concentrated liquor is used so that it will add very little moisture which must later be removed. The concentrated liquor is heated, preferably to a temperature of about 180 degrees F. to about 220 degrees F., beEore being combined with -the coal fines. When cold, the concentrated liquor has the consistency of a thick molasses. The heating thins the liquor to a water like consistency, so that it can be substantially uniformly disbursed throughout the coal fines.
By-product liquor is used in only an amount sufficient to wet the coal finesO In other words, it all becomes a thin coating on surface portions of the coal fines and does lO not exist in a liquid form, droplet or otherwise, between the coal fines.
Preferably, the by-product liquor used includes between 40-60~ solids by weight. By way of example, the by-product liquor may be the liquid form of an ammonium lignin 15 sulfonate liquor which is sold by The Scott Paper Company, a Pennsylvania Corporation, under the trademark TREX ~ LTA.
This material is a liquid form of ammonium lignin sulfonate and wood sugars. It is manufactured by the sulfite paper making process as a co-product with wood 20 pulp. Prior to digestion, wood consists of bundles of cellulose ibers cemented together by lignin and hemicellulose. In the sulfite pulping process, ammonium lignin sulfonates and wood pulp are produced simultaneously by a series of chemical reactions when wood chips are cooked under controlled conditions of heat and pressure in an aqueous solution of ammonium bisulfite and sulphur dioxide. This is accomplished in a tall cylindrical pressure vessel known as a "digester". The ammonium bisulfite and sulphur dioxide react with lignin to form 30 water soluable lignin su]phona-te~ The hemicelluloses (carbohydrates) are broken down into water soluable 5-carbon and 6- carbon reducing sugars, such as glucose, glactose, mannose, ylose, and arabinose. Simple filtration separa-tes the wood pulp, which is to be made

3~7 into paper, from the ]ignin sulfonates and other components, which are available as chemical raw materials.
This coffee colored liquid or liquor is collected as a solution of about 10~ solids, and is then concentrated by the removal of water to the 50-55~ solids level in an all stainless evaporator. This concentrate is sold by Scott as TREX ~ LTA and is a mixture of ammonium liynin sulphonates, wood sugars and other chemicals dissolved in water.
Additional information with respect to TREX ~ LTA is 10 contained in a Scott Paper Company brochure, entitled TREX
lignin sulfonates. The contents of this brochure are hereby expressly incorporated by reference into this application. A copy of the brochure is in the patent file.
Fuel shapes constructed in accordance with the present 15 invention typically fall within the size range oE about 40 to about 300 cubic inches. By way of typical and therefore nonlimitive example, cylindrical logs may be manufactured which measure about 3-5 inches in diameter and about 6-15 inches in length. A preferre~ size of log measures about 4 20 inches in diameter by about 12 inches in length.
Rectangular bricks, such as shown in Fig. 1 may measure about 2-3 inches in depth, by about 2-6 inches in width, by about 6-15 inches in length.
Whether the shapes be bricks or logs, in either case 25 the liquor wetted coal fines are introduced into a mold and are subjected while in -the mold to a pressure of at least 2000 psi. In a typical log manufacturing process, the pressure applied is preferably about 3000 psi, for a high quality product.
The liquor wetted coal fines are much like damp beach sand when they are placed in the mold. For example, a common cup could be hand packed with the liquor wetted coal fine~ and then turned upside down and emptied onto a surface and the coal fines would assume a shape corresponding to the inside shape of the cup, in the same manner as if damp beach sand were used.
When the pressurized shapes are removed from the molds, they are relatively firm. The pressure compacting causes the liquor -to bind the coal fines together. Af-ter they havë been dried, the fuel shapes have the ability to hold toyether during shipping and other handling, and during the burning process.
The fuel shapes may be air dried. However, in 10 preferred practice, drying is excellerated by placing the shapes within an oven and heating them to about 180 degrees F. to about 220 degrees F., for about 2 to about 6 hours.
The oven temperature and heating time are so chosen that the fuel shape will solidify withou-t excessive swelling or 15 distortion. A very good product was obtained by heating the shapes in an oven at a temperature of about 200 degrees F. for about 2 hours. The particular shapes were in log forrn and they measured about 4 inches in diameter by about 12 inches in length.
Preferably, the fuel shape is dipped or spray coated with a suitable wax substance, such as "slack wax" or parafin. j "Slack wax" sometimes referred to as "grease wax", is a by-product of the petroleum refining processO
The wax coating has two distinct advantages. It seals the fuel shape, making it relatively clean to handle. That is, it prevents surface coal fines from coming off in the form of dust. Secondly, the wax coating helps the fuel shape become ignited, particularly if parafin is used.
A fuel log manufacturing operation will now be describecl, wi~h reference to Figs. 2-4.
The apparatus shown in Figs. 2 and 3 compxises a main frame 10 which mounts a double acting hydraulic linear motor 12. I,inear motor l2 comprises a cylinder 14, having a fluid line ]6, 18 at each of it's ends. In usual fashion, the lines, 16, 18 convey hydraulic fluid into and outfrom chambers formed on opposite sides of a pis-ton head tnot shown). A piston rod 20 extends outwardly from one end of the cylinder l4 and includes a pressure ram 22 at it's outer end.
A cylindrical mold cavity is formed in line with the piston rod 20. An upper sidewall opening 27 in a firs-t end portion of the cylindrical mold cavity 23 is in coal fine receiving communication with a hopper 26. The liquor wetted coal -Eines are introduced into the hopper 26 and are fed by the hopper 26 into the mold cavity 24. Preferably, a shaft 28 carrying a plurality of paddles 30 is mounted Eor rotation within the hopper 26, and is rotated by a motor 3~, mounted on the frame lO outside of the hopper 26.
The paddles 30 keep the liquor wetted coal fines mass loose, allowing it to drop by gravity into the top opening 27 of the mold cavity 24.
The second end o the mold cavity 24 is opened and closed by means o retraction and extension of a second linear hydraulic motor 34. In the illustrated embodiment, motor 34 is set at an incline. Motor 34 concludes a cylinder 36, shown anchored to a frame member 38, and a piston 40. Piston 40 includes a piston head 42 at it's inner end and a ~losure pad 44 at it's outer end. When the piston 40 is extended, as shown in Fig. 3, the closure pad 44 is moved into a position whereat it closes an end opening provided in the mold cavity 24. Retraction of the piston 40 moves the closure pad 44 both away from the end opening and above the level of the end opening.
In opera-tion, after a sufficient amount of the liquor wetted coal Eines mass has been allowed to enter the mold cavity, the piston rod 20 is extended by operation of c~linder 14 while closure pad 44 is held against the opposite end of the mold cavity 24, by operation of linear motor 24. The pressure pad 22 is hydraulically moved against the liquor wetted coal fines within cavity 24, to in that manner, compress them tightly together. In the illustrated embodiment, the mold cavity 24 measures about 4 inches in diameter. The applied pressure was about 30,000 psi. When this pressure level was reached, the length of the pressurized mass within the cavity 24 was about 12 inches.
Following sufficient pressurization, the pressure is removed, piston 40 is retracted until the closure pad 44 is above the elevation of the end opening, and the piston 20 is again extended, this time for the purpose of moving the compressed fuel shape endwise outfrom the mold cavity 24.
A conveyor (not shown) may be positioned at the outlet of the mold cavity, for conveying the fuel shapes onto the drying station.
A sliding gate (not shown) may be mounted on an upper portion of the mold cavity, to be adjustably movable endwise for the purpose of adjusting the length of the opening 27.
Figs. 4-8 relate to a second embodiment of a mechanized mold for casting cylindrical fuel logs. This embodiment is characterized by a rotating turret 49, mounted for rotation about an axis 50. Turret 48 comprises three chambers 52, 54, 56.
A hopper fed screw feed mechanism 58 is provided for delivered liquor wetted coal fines into the chambers 52, 54, 56, one at a time. An end wall 60 provides a reaction surface at the second end of the particular chamber 52, 54, 56 which is in alignment with the feed mechanism 58. When a given cavity 52, 54, 56 is full, the turret 48 is rotated to palce such cavity in line with the pressure pad 58 of a compaction device. The compaction device is a double acting linear hydraulic motor 60, having a pair of fluid 1ines 62, 64 leading to opposite ends o:E a cylinder chamber from a sw.itching valve 66. When fluid is introduceq into line 62 and removed from line 64, the piston 68 is extended and the pad 56 is moved into pressure applying contact with the liquor wetted coal fines wit'hin the mold cavity. At this s-tation, the second end of the mold cavity is also closed by the wall 60.
Following sufEicient compression, -the switching valve 66 is reversed, directing fluid into line 64 and outfrom line 62, resulting in a retraction of the pressure pad 58 outfrom the mold cavity. ~he turre-t is once again rotated, the mold cavity into alignment with both an outlet opening 70 in the wall 60 and the head 72 of an ejector piston 74.
Switching valve 76 is operated to cause the flow of 'hydraulic fluid into line 78 and the flow of hydraulic fluid outfrom line 80. The extending pis-ton 74 moves against the end of the compressed fuel log L and moves it outfrom the mold cavity, through the opening 70 in wall 60~
Following such removal, the position of valve 76 is reversed. This causes the delivery of hydraulic fluid into line 80 and outfrom line 78, and a retraction of the piston 74. The log L is then moved onto the drying station.
As should be evident, the provi~ion of three mold cavities 52, 54, 56, enables one of the mold cavities to be at each of the three operational station3 at each cycle of the operation. That is, while liquor wetted coal fines are being introduced into one of the cavities, the piston 68 is being extended to compress the liquor wetted coal fines in a second cavity and the pi.qton 74 is being extended to eject a log L outErom the third cavity.
Rectangular shape ~ue'L pieces were successively manufactured in a conventional brick forming machine of the type used Eor casting structural bricks. The bricXs were cast to include through openings 82, provided for the purpo3e of enllancing gasification during the burning proces3.

Claims (18)

Claims

1. A method of manufacturing solid fuel shapes in the nature of a log or brick, from coal particles, comprising:
mixing substantially dry coal particles with ammonium lignium sulphonate, in a quantity and concentration sufficient to produce a mixture in which the ratio of coal particles to lignium solids is between 13:1 and 20:1 by weight;
controlling the moisture in the mixture to an amount sufficient to cause the coal particles to merely be surface wetted;
providing a mold cavity having first and second open ends;
providing a closure over the first open end;
introducing some of said mixture into the second open end;
moving a piston into said second open end to compress the mixture into the shape of the mold cavity;
removing the closure from the first end of the cavity;
moving a piston through the cavity to move the shape outfrom the first end of the cavity;
heating the shape in a kiln to more than about 200° F.
until hardened; and providing the shape with a protective cover to prevent moisture absorption in the shape.

2. The method of claim 1, comprising drying the coal particles before mixing until the moisture in them is no more than about 5% by weight.

3. The method of claim 2, comprising drying the coal particles by fluidizing them with heated air.

4. The method of claim l, comprising using ammonium lignium sulphonate liquor which includes between 40-60%
solids by weight.

5. The method of claim 1, comprising using lignium in a quantity and concentration sufficient to produce a ratio of coal fines to lignium solids of about 16:1.

6. The method of claim 1, comprising and using an ammonium lignium sulphonate liquor which includes between 40-60% solids by weight, heated to a temperature of about 80°F. to about 220°F.

7. The method of claim 1, comprising forming at least one passageway through the fuel shape.

8. The method of claim 7, comprising forming a passageway through the shape while forming the shape.

9. The method of claim 1, comprising providing the shape with a protective cover by coating it with a wax substance.

10. The method of claim 9, comprising coating the shape with slack wax.

11. The product produced by any of claims 1-3.

12. The product produced by any of claims 4-6.

13. The product produced by any of claims 7-9.

14. The product produced by claim 10.

15. A method of manufacturing solid fuel shapes measuring about 40 to about 300 cubic inches, comprising:
mixing substantially dry, one quarter minus coal fines with ammonium lignium sulphonate liquor containing between 40-60% solids by weight, of an amount sufficient to merely wet the coal fines;
forming said liquor wetted coal fines into shapes measuring between 40 to about 300 cubic inches;
subjecting said shapes to a pressure of at least 2,000 10 psi; and drying said shapes to solidify them without excessive swelling or distortion.

16. The process of claim 15, wherein the wet coal fines are formed into shapes by introducing them into an elongated chamber having first and second end openings, and wherein pressure is applied to the wet coal fines by hydraulically moving a piston into the chamber through one of its end openings, against the wet coal fines within said chamber, while the second end opening is closed.

17. The method of claim 16, comprising removing the compressed shape from the chamber by opening one of the end openings and exerting an endwise force on the shape, to move it out from the chamber through said open end opening.

18. The product produced by claims 15-17.