US 1925005 A
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Patented Aug. 29, 1933 1,925,005 COAL TREATMENT PROCESS Harold J.
This invention relates to treatment of coal and to obtaining products therefrom, and to eliminating undesirable constituents from coal; more particularly, the present invention relates to the substantially complete solution of coal at elevated temperatures and substantially normal pressures, or substantially just a pressure raised to keep the solvent in liquid state at the solution temperatures; and the objects of the invention include the production of a homogeneous product lower in ash and sulphur content than the original coal. The invention further relates to the recovery of the said coal in a purified state from the said solution. The process and products of this invention possess other important advantages, as will be exemplified below.
The invention further consists in such other new and useful improvements, and has for further objects such other operative advantages or results, as may be found to obtain in the processes and products hereinafter described or claimed.
Extraction of only certain of the constituents of coal at normal and elevated temperatures and pressures, with various solvents, such as pyridine, 25 is well known in the laboratory, but the results obtained have been of little or no commercial utility by reason of the facts that the solvents used have been costly and available only in limited quantities, and that the percentages of coal 39 constituents extracted have been low. 0n the other hand, others have treated coal with oils or tars in the presence of hydrogen at high pressures and temperatures, in attempts to increase the yield of oils obtainable from coal. However, no one before the present inventors has discovered the producing of a direct solution, in oil, of substantially all the coal, without substantially modifyingthe chemical nature of the coal, and no one before the present inventors has recovered 40 the coal as such from the said treatments.
The present inventors have discovered that certain cheap and readily obtainable oils, such as water gas tar and coal tar, and certain distillates therefrom, when brought together with certain coals and heated at normal or only moderately elevated pressures and moderately elevated temperatures of from about 200 C. to about 400 C., dissolve substantially all of the said coals, form- 50 ing homogeneous solutions which remain stable at temperatures below the point of rapid volatilization or even below the dissolving temperatures. The coals soluble in such solvents are in general the coking coals. Substantially all of such coals are soluble, the insoluble portions consisting of the mineral matter or ash, and the mineral char- Rose, Penn County, and William H.
aasignors to The Koppers Company,
a corporation of Pennsylvania Township, Allegheny Hill, Pittsburgh, Pa...
Application March 25, 1926 Serial No. 97,467
coal or fusain which may be present in limited amount. On the other hand, the non-coking constituents of poorly coking or non-coking coals are, generally speaking, only partly soluble, when such coals are treated under the conditions of the 0 present invention.
The products of this invention have the characteristics and virtues of true solutions, and may be considered as such. If they are not in fact technically true solutions they are at least so 5 similar as to have the characteristics and utility thereof. They do not tend to separate into the original constituents under ordinary conditions of handling and storage, and can be filtered. At the blending temperatures or even lower, they remain stable, freely flowing liquids, suitable for use as liquid fuels and many other purposes. They are easily handled at these temperatures, and by reason of their fluid nature, the non-uniform charring and carbonizing effects that are incident to the treatment or handling of ordinary solid coal at these temperatures are avoided.
When coals are treated according to the present invention, mineral charcoal or fusain, and constituents which may be generally designated by the term ash and include slate, shale, bone, pyrite, marcasite, phosphates and other minerals, are precipitated and by reason of the fluidity of the product at the solution temperature and the difference in specific gravities of the solution and 8 of such undesirable constituents, the latter are readily separated from the former. In many cases, simple decantation is sufiicient to remove most of this undesirable material from the solutions but, instead or supplementally, filtering or centifuging may be employed, if either proves desirable. Thus substantially all of even the most finely divided mineral charcoal and ash can be removed. For example, phosphorous present in the form of finely divided phosphate, and ordinarily regarded as inseparable from coal, can be separated by centrifuging the solution while in a very fluid state.
The fluid nature of the solution is a tremendous advantage apart from the considerations of handling and ash removal. Processes such as long practiced in treating petroleum and other fluid carbonaceous materials, but of limited application in the treatment of solids such as ordinary coal, may readily be practiced with the product of the invention, in the fluid state, as a raw material economically produced at substantially normal or relatively limited pressures and only moderately elevated temperatures. Furthermore, the use of catalysts to assist in the accomplishment of such or other processes is made practical, whereas in processes dealing with ordinary solid coal, catalysis has in general, proved impracticable or impossible. Thus the invention provides a superior process of preparing a material for subsequent treatment with reagents.
Referring again to the problem of purification, by reason of the fluid nature of the solution, impurities such as organic sulphur which it has heretofore been impossible to remove from ordinary coal, can be removed to a large extent. It has long been possible in the petroleum industry to remove organic sulphur from oils by the addition to the said oils of suitable metals, oxides, salts, absorbents, etc. The solid nature of ordinary coal has rendered such treatment futile. The fluid and homogeneous nature of the product of this invention renders the constituents of ordinary coal susceptible for the first time to such treatment.
An advantage of the present invention resides in the superior adaptability of the product of the invention to extraction with organic solvents, liquid sulphur dioxide, etc., which are known to exert a selective action on the various constituents of coal. In the fluid state, this action is particularly facile, and is enhanced by the fact that the coal is diluted by an oil and that the coal structure is thus in a comparatively open and available state. Sulphur dioxide, for example, is useful in the separation of paraffin and aromatic hydrocarbons from each other and can be produced for such use by burning the sulphur-bearing residues removed from the coal.
A further advantage of the present invention resides in the above-mentioned fact that the constituents of a poorly coking or non-coking coal differ in solubility; coking coals are practically completely soluble, while such materials as splint, cannel, anthracite, and lignite are much less so. The present invention thus provides a means of separating desirable and undesirable constituents from such coal. To illustrate, certain coals are not regarded as suitable for coking. Although there may be contained in such coals a large proportion of coking constituents, the presence of other and non-coking constituents may render the whole unsuitable for use. By treating such coal in accordance with the present invention the coking constituents of the coal are dissolved, leaving a residue which, although non-coking, may be suitable for fuel or other purposes. Similarly the separation of different types of coals which occur adjacent to each other, as in narrow strips or bands, but which are of widely differing utilities, can be effected.
The adaptability of this invention to remove ash and mineral charcoal that has been impractical or exceedingly difficult to remove by existing processes is of great importance, and possesses a number of special utilities and applications. For example, the process is usable as an adjunct to known ash reduction processes. Such processes, while producing valuable results in the removal of adventitious ash from coal, do not successfully rea move pyrite, and the mixture of coal and. oil
which is the product of such processes is of limited utility. If, however, oil and coal used in some of such processes are selected with a view to the requirements of this invention, the existing ash reduction processes may be a means of supply for our process, in that the resultant pasty and nonhomogeneous mixture or amalgam constitutes a raw material in which both the coal and solvent are present. Furthermore, the process of this invention will remove pyrite, finely disseminated ash and mineral charcoal which the existing-ash reduction processes do not succeed in removing.
The specific nature of the product of this invention will depend upon the specific natures of the coal and oil,..tar, or other solvent used, and the ratio of the amounts thereof, and also upon the temperature and the time factor. The invention is not limited to any specific ratio, for useful results are obtained with any proportion of suitable materials, nor is the invention to be limited to any specific coal or oil so long as these may be shown to blend under the conditions of this invention. The preferred ratios are from two parts by weight of coal and one part of oil, to one part of coal and two parts of oil, as such ratios represent a combination of the good effects of using considerable quantities of each of the constituents, and we have successfully dissolved coal in oil in widely differing ratios, as for instance one to ten. It is preferable to use coking bituminous coals, but coals of both coking and non-coking character have been successfully treated as above recited by this invention. Pulverization of the coal is not ordinarily necessary, except for a rough grinding in the interests of good handling. However, when dealing with coals containing large amounts of unblendable material it is desirable to pulverize the coal merely to promote the rateof solution.
The oils which are preferred are in general the cyclic hydrocarbons or their derivatives, or oils, resins, etc. containing these. For example, water gas and coal tars, especially the higher boiling distillates thereof, and anthracene, phenanthrene, naphthylamine and rosin have proved suitable. Some of these of course are solid at normal atmospheric temperature but become liquid oils at higher temperatures, and the term oils is employed herein with that fact in view. The first fractions obtained in the distillation of coal tar, including such substances as benzols, are not suitable for use at ordinary pressures, epecially on account of their low boiling points. As will be mentioned below, addition of these materials and other light boiling materials such as ligroin or petroleum ether can be made with a view to throwing the dissolved coal out of solution in the oil. The reason for this is the low solubility of coal in these materials at relatively low temperatures. In general, when petroleum oils are to be used as solvents for coal, it is preferable to subject them to a prior cracking process. For example, water gas tar, which has been found to give excellent results, is composed largely of products of petroleum oil cracked in the process of carburetion. Ordinarily it is preferable to use an oil or oils which do not volatilize appreciably at the solution temperature, but this is not essential, as the volatile material may be condensed and removed, or returned to the blend by suitable refluxing apparatus. When tars are used it is desirable to allow comparatively lowboiling constituents to be driven off as they have shown a tendency to retard the solvent action.
The temperature at which the solution is accomplished will vary widely according to the nature of the coal and oil used, and is preferably about 350 C. but can be as low as about 200 C. or as high as about 400 C., and the coal and its solvent, or either, can be preheated before they are brought together, or heated to substantially the solution temperature either before or afterwards. Preheating is advantageous in certain respects, such as the elimination of moisture and facilitating the maintenance of the solutiontemperature in continuous operation That temperature suitable for use with a particular coal or oil may be unsuitable, or unnecessary, with another. The solution can be prepared below the temperature at which volatilization and decomposition occur to any substantial extent. If, as above recited, certain low boiling constituents believed to be harmful are present in the oil, the temperature may be maintained high enough to permit volatilization and removal of such materials. In case low boiling oils are to be used somewhat elevated pressures can be employed simply for the purpose of raising the boiling point of said oil to the solution temperature. Such pressures are adequately produced by merely confining the solution mixture during its heating and permitting the initial oil vapors to develop their own pressure requisite to raise the boiling point of the main body of the oil. Certain coals happen to dissolve most easily at temperatures corresponding to the point of maximum plasticity, but this is not always true, and coals which do not become noticeably plastic have been dissolved successfully.
Variations in the physical nature of the product from liquids or semi-liquids to'solids, hard and brittle, at ordinary temperatures, are easily obtained by varying the ratio of coal and oil, or the natures of these raw materials. Such variations make possible a wide range of utility. The solutions are useful as fuel and may be burned while still in the fluid state or they can be allowed to cool for storage or transportation and subsequently be re-melted, or if they are solid at ordinary temperatures, they can be used as a fuel or working material in that condition. Like most solutions, these may upon cooling separate somewhat into their original constituents. But the solutions of this invention become more viscous or even solid as they approach normal temperatures, and any separation is so retarded as to be harmless in effect. As soon as the products are re-heated, the state of liquid solution is regained. In the liquid state the solutions are easily cast into molds or converted into granular or pellet form. They are useful as substitutes for pitch, asphalt and similar materials, as briquetting or coating materials, as varnishes, or paints, or ingredients thereof. In fact, the utilities of our product are of wide scope and great number, and only some of the more immediate ones are herein noted.
This invention provides, for the first time, a liquid coal which is stable and easily handled, fluid at substantially normal or only moderately high temperatures, which are well below those at which rapid distillation or decomposition takes place, substantially free from ash and sulphur and mineral charcoal and obtainable over a wide range of physical characteristics with a minimum of effort and preparation and which is composed of substances commercially available and useful.
The foregoing has considered solutions of coal in oil, of various characteristics, but all of which are easily liquefied at only moderately high tem-- peratures, and possess numerous important attributes and advantages as herein set forth. The invention further provides for the recovery of the coal in purified form from the said solutions. In general, two methods of recovering the said coal which we shall hereinafter designate as recovered coal or recovered solute coal are available either supplementing each other or separately. The first of these is distillation,
whereby the oil is volatilized. In general, it is preferable to conduct such distillation in the presence of a current of steam or other carrier gas whereby the removal of the oil is effected at temperatures below its nomal boiling point and/or at reduced pressures. Thus, the coal'is freed from oil without being subjected to high temperatures and resultant decomposition. By reason of the fluidity of the solution, it can be sprayed into a current of hot gas, for the purpose of removing oil and recovering the coal substance in solid form. When distillation is resorted to, it is preferable to condense the volatilized oil, which can thus be used over and over again. The other or supplemental method of recovering coal from the solution is precipitation thereof, which may be done by the use of suitable oils miscible with the oils used as solvents, but in which the coal is substantially insoluble. The oils which are preferred for this purpose are low boiling hydrocarbon or derivatives thereof such as benzol (CsH-s), carbon tetrachloride, and gasolines. It has been determined that when such substances are added to solutions of coal in oil, which can be done for instance in an ordinary extraction apparatus, the solvent oil can be extracted and the coal recovered in solid form.
The recovered coal is substantially free from ash and mineral charcoal or at least ash-free to a degree never heretofore practicably obtained, and is substantially or wholly unimpaired in relation to coking quality as compared to the original coal. It is an important advantage of this recovered coal that, at least when the solutions have been prepared without any of the more extensive variations such as treatment with reagents and the like, the coal has undergone no substantial process of decomposition or reaction and thus is substantially the original coal purified or homogenized. As has been mentioned above, previous processes have sometimes produced certain useful results at high temperatures,
and pressures and in the presence of reagents and the like but these results have been accompanied by a breaking down of the original coal so that no recovery of the coal as such was possible. With the present invention we can, if desirable, accomplish such reactions or decompositions or other modifications of coal, and our liquid material as above-stated, represents a superior material for such usages, but in the present instance we ordinarily wish to recover the original coal in a state as close to the original state of the same as possible, except for more homogeneous character and the removal of mineral charcoal, ash, sulphur, etc., and this the invention enables us to do. Thus the recovered product is useful as original coal is useful and possesses important advantages over the original coal, residing in the freedom from ash and otherwise as herein recited.
One of the most important aspects of such a recovered material is the fact that it may be carbonized to produce a coke unimpaired in strength and physical nature, and free from ash and sulphur to a degree never heretofore attainable commercially. To where one of the essential requirements is the production of a metal of low sulphur content, the advantages of such a coke can hardly be exaggerated. It has been demonstrated by repeated tests and observation that the operators of foundries, blast furnaces, and other metallurgical smelters can Well afford a'substantial addi-- tional cost for coke only slightly lower in sulphur the metallurgical industries,
content over that which they are ordinarily forced to use. The values of freedom from ash other than sulphur is hardly less important. Furthermore, the sources and available amounts of desirable coal are becoming more and more restricted, whereas great quantities of high-ash and sulphur-bearing coal are available, but find a limited market even to local consumers by reason of their impurity. Thus the present invention renders available to the metallurgical industry enormous quantities of coal, frequently very near to the consumer, heretofore unfit for use even at lowered prices, with a minimum of expense and manipulation. By allowing a portion of the oil to remain in the final product, a superior material for the manufacture of enriched gas can be obtained, free from the disadvantages inherent in the use of relatively nonhomogeneous coal-and-oil mixtures for such purposes.
As above mentioned, the recovered coal can be a preferred portion of a material originally containing more than one constituent. On the other hand, it is well known that mixtures of various coals often possess advantages over these coals alone. Mixtures of high and low volatile coals are frequently used for coking purposes, and thus render available for coking many coals which would not otherwise be suitable. a mixture of such coals in oil or mixing previously prepared solutions of coals and subsequently recovering the coal substance according to this invention, a mixture of these coals more intimate than is possible to obtain in any other known way can be secured, and such a product, aside from the advantages of ash removal, is of superior coking quality.
It is often desirable to mix various finely divided foreign materials such as coke breeze, an-, thracite culm or iron oxide with coal or coke. According to our invention we can dissolve coal in oil, suspend such a foreign material in the resultant solution, and subsequently recover the coal in solid form. In the solid form the recovered coal will contain the foreign material suspended therein in a finely dispersed manner never before attainable.
By thus suspending in coal materials which exert favorable effects, catalytic or otherwise, upon combustion, coking, and partial or complete gasification of coal, the invention produces a superior material for such purposes. Furthermore, by the addition of suitable well known substances, the physical qualities, such as structural strength, of the recovered coal, or coke made therefrom, may be modified in a way not before possible.
Mixtures of coal and/or coke and pitch are well known and have been used for many purposes, such as in coking and the manufacture of carbon electrodes. With the present invention, we can dissolve coal in tar, and subsequently distill the solution (which may be done in the presence of carrier gas and/or under reduced pressure), and thereby obtain, in addition to the distillates which include valuable solvent oils, a blend of coal and pitch lower in ash content than even the recovered coal alone might be. (This is on account of the extremely low ash content of the pitch). Coke made from this product is particularly suitable for the manufacture of carbon electrodes, in foundry work, and in any other industry in which a coke of extremely low ash content is desired. Moreover, this process provides a suitable method By dissolving of coking pitch in by-product coke ovens which has not hitherto been commercially feasible.
The utility of the present invention as well as its importance to the coal and metallurgical industries may more readily be understood by consideration of the following example of the commercial application of the present invention to a steel plant which includes by-product coke oven, blast furnace and steel making departments. At present a large number of such plants havin such equipment exist and have proved the use of such equipment to be an excellent combination in that the quality of the coke is readily controlled in accordance with the operation of the blast furnaces and the gas and coal tar produced in the coking process offer excellent fuel for heating open hearth and other furnaces for the manufacture of steel from iron. Comparatively few of these plants are able to obtain locally mined coal that is suitable for coke manufacture without elaborate washing or flotation processes for the removal of ash or which may be coked without admixture of other coal. Frequently additional coal must be brought from distant sources. By applying the process of the present invention for the removal of ash from coal hitherto unsuitable coal is rendered suitable for use in coking. Inasmuch as the oil used as a solvent is subsequently recovered in order to recover the coal in solid form, it may be used over again and thus only losses of the oil incident to handling need be taken into account. The coal tar which is produced in the carbonization of coal, or certain distillates thereof, offers an excellent and immediately available solvent for the coal.
As regards the coke produced from the recovered coal, this would be of excellent quality and by reason of the fact that substances which would exert a favorable influence on the coking process can be added in such a way as to produce the greatest possible effect, it can be modified considerably with regard to physical nature. The cost of preparing the coal for carbonization would be extremely low as the solvent used is produced in the consumers plant from the coal itself, in the regular carbonization process.
A further important application which immediately suggests itself is the solution of coal in the tar produced in the plant, and subsequently burning the solution as fuel. By dissolving coal in an equal amount of tar a product is made which is suitable as a fuel for open hearth or other furnace heating and which is thus available in much larger quantities than coal tar alone. Furthermore, by reason of the fact that coal is relatively much cheaper than tar, this solution may be a cheaperliquid fuel than tar alone.
If the same coalis used for carbonization and. for production of a liquid fuel in this manner only one dissolving plant is necessary and the recovery of the coal and oil from the product may be restricted to that portion of the material which it is desired to carbonize. The cost of preparing the recovered coal for carbonization would be offset by the great advantages inherent in the use of a coke of low ash and sulphur content, for blast furnace purposes. Thus the application of the invention to a combination of 'coking and steel making processes is particularly advantageous. In certain cases where it is desired to remove more sulphur than would be removed by decanting the solution, the additional procedure provided for in the present invention can be applied with good results. Other substances, such as phosphates, which might be present in the coal, are practically removed when so desired.
Substances which the blast furnace operator might desire to incorporate in the coke structure, such as lime or iron oxide, can readily be distributed throughout the same in a manner never heretofore possible, as above mentioned: and coke breeze, which is often of limited utility, can be similarly incorporated in the product with advantageous results.
In addition to their application to the iron and steel industries, the products of our invention are equally applicable to other metallurgical processes and industries and all this is apart from the advantages which would be apparent in their application to the coal industry considered alone.
Examples A and B below show the results of actual solutions, obtained by this invention, of a Pittsburgh seam coal which is ordinarily known as a high volatile bituminous coal.
Example A.In this specific example one part by weight of the above coal and three parts of crude coke oven tar were heated in an open vessel suspended in a molten lead bath having an average temperature of 410 C. Water and light boiling constituents were allowed to escape until the solution was of satisfactory consistency,
which occurred at the end of 15 minutes. The
temperature of the solution at this time was found to be 362 C. and the product was of a rather thin syrupy consistency at this temperature. It was poured out into molds and it was noted that the ash remained in the open vessel. After the product had been cooled to atmospheric temperature it was found to be hard and brittle with a smooth, glossy black surface. A portion was tested according to one of the standard meth-.
ods for determining the softening point of coal tar pitch and by this method was found to have a softening point of 155 C.
Example B.-In this test one part by weight of similar coal and two parts by weight of a high boiling distillate of water gas tar were heated in a vessel suspended in a molten lead bath with an average temperature of 390 C. Practically no volatilization occurred. The coal began to dissolve at once and the solution was soon found to be of very light and free-running consistency. At the end of ten minutes the temperature of the solution was found to be 352 C. and the product was poured out of the vessel, leaving behind the ash and other insoluble material. At ordinary temperatures the product was somewhat plastic and could be formed into various shapes by pressure of the fingers. The color was apparently black but when the product was drawn along a white surface it left a brown mark. When tested according to the softening point method mentioned above, it was found to have a softening point of 156C.
ErampZe C.The following shows the result of a test made with a View to determining the ability of the present process to remove ash and pyrite from coal. The coal used was a 25% volatile matter coal with good coking properties. This deal on analysis showed-9.72% ash exclusive of mineral characoal and 2.78% total sulphur. The coal was dissolved with heavy distillate of watergas tar, in a vessel suspended in an apparatus maintained at approximately 330 C. by a constant temperature jacket. The temperature inside the vessel varied during the test from 270 C. to 320 C. The vessel was removed and extracted with benzene and the insoluble residue remaining in the vessel was dried and weighed. It amounted ,be termed to 22% of the original coal, indicating a solution of 78% of the original sample. This insoluble residue, on analysis showed 39.3% ash and 8.66% sulphur which when calculated back to the weight of the original coal is the equivalent of 8.64% ash and 1.91% sulphur in the original coal. The remainder of this residue is composed largely of mineral charcoal which it is very desirable to remove from the coal. In other words, approximately 8 of the ash and 68% of the sulphur, as well as substantially all of the mineral charcoal, present in the original coal remained in the vessel after the extraction. This insoluble material when examined under the microscope was seen to consist of mineral characoal, slate, shale, pyrite, etc. The solution of coal in the water gas tar oil was mixed with ligroin and extracted in a suitable extraction apparatus until substantially all of the oil was removed. The recovered coal was found to be a hard, black solid possessing good coking qualities. When analyzed it was found to possess 0.46% ash and 1.39% sulphur, that is, only 3.7% of the original ash and 40% of the original total sulphur present in the coal remained in the final product. The discrepencies between the amounts of ash found by analysis in a portion of the original coal and the amounts found in the recovered coal and in the insoluble residue were actually small and due to mechanical losses. The apparent gain in total sulphur, extracted and remaining, is due to -a small amount of the same contributed to the product by the oil and could be avoided by using a sulphur-free oil. Such sulphur as remained in the recovered coal was substantially all organic sulphur, the removal of which requires special treatment, as above mentioned, namely: The coal solution, before recovery of the coal, and while maintained in the freely liquid state, is mixed or agitated with metallic copper turnings or with fine black copper oxide,
which is then separated by decantation or precipitation before recovery of the coal; and the recovered-coal then shows a removal of over a third of its organic sulphur, over and above the before stated removal of inorganic sulphur.
The term original coal or original raw coal" is conveniently employed in the same sense in which original coal is used in the last preceding paragraph and elsewhere in this specification, that is to say, to mean raw coal as it ordinarily comes from the mine to the dealers or users, substantially without other treatment than the usual sizing or cleaning or drying, and which is a raw material having aggregated or agglomerated in it or with it such impurities as ash, mineral charcoal, sulphur and the like, as before mentioned, all of which are of course insoluble as before said, and the remainder being true coal or what may the pure coal substance already referred to in this specification as the coal substance and the thing acted upon by the solvent oil.
Our invention is hereinbefore set forth as embodied in certain exemplifying instances, but it may be variously otherwise embodied within the scope of the claims hereinafter made for the purpose of defining it.
1. A process of producing in effect a substanuid at the temperatures employed in the process and comprises one of the group consisting of cyclic hydrocarbons and their derivatives and oils and resins containing them, and subjecting them to a temperature above about 200 C. and below that at which there is any substantial chemical heat-decomposition of the pure coal substance that constitutes substantially the entire bulk of the given raw original coal other than its content of ash, mineral charcoal, sulphur and like insoluble impurities, and continuing the treatment, without exceeding the aforesaid upper limit or temperature, until there has been in effect a substantially complete dissolving, without substantial chemical decomposition or extraction of constituents, of the said pure coal substance retaming substantially unchanged the chemical characteristics of the pure coal substance of the original raw coal, irrespectively of any disinte gration or separation of the aforesaid ash, mineral charcoal, sulphur and like impurities of said original raw coal.
2. A process as claimed in claim 1 and comprising the further step of removing substantially all of the solvent and leaving the pure coal substance substantially unchanged in chemical characteristics from that of the raw original coal.
3. A process as claimed in claim 1 and comprising the further steps of recovering, substantially unchanged in chemical characteristics, the solute coal substance from the solvent, after separation HAROLD J. ROSE. WILLIAM H. HILL.