US3317289A - Manufacture of smokeless fuel from certain low-grade coal materials - Google Patents

Description

United States Patent Ofi ice 3,317,289 Patented May 2, 1967 3,317,289 MANUFACTURE OF SMOKELESS FUEL FROM CERTAEN LOW-GRADE COAL MATERIALS Frederick W. Braun, Beaverton, Oreg., and Edward Prostel, Laramie, Wy0., assignors to Continental Oil Company, Ponca City, Olden, a corporation of Delaware No Drawing. Filed May 7, 1962, Ser. No. 192,948

5 Claims. (CI. 44-10) This invention relates to the production of substantially smokeless briquettes which may be utilized as a fuel for purposes of outdoor cooking and the like. More particularly, but not by way of limitation, the present invention relates to a process by which low-grade carbonaceous material such as lignite, bituminous and subbituminous coals, may be converted into smokeless briquette materials which have an ignition time and fuel value comparing favorably with smokeless briquettes now marketed, yet which can be prepared more economically than such presently marketed briquettes.

At the present time, smokeless briquettes of carbon-aceous material for use in outdoor cooking and similar activities are produced from either Wood, or from certain types of coal materials, by a rather elaborate process which includes a carbonization or calcining step in converting the wood or coal to a suitable char material for use in the briquettes. The demand for briquettes of this type has been steadily increasing in recent years as a result of the healthy national economy, and the ability of the consumer to afford such items as are utilized in the growing trend towards outdoor living and outdoor cooking. It is thus apparent that a new source of raw material useful in the manufacture of smokeless briquettes, which material and the process of producing briquettes therefrom could be provided at relatively lower cost than previous materials and procedures utilized, would constitute a valuable asset to the national economy.

By the process of the present invention, smokeless fuel briquettes which compare favorably in ignition, burning, odor and smokeless properties with commercial briquettes now marketed may be produced considerably more economically than such previously available briquettes. The raw material which is employed in the production of smokeless briquettes in the present invention is a low grade coal, such as bituminous, subbituminous and lignitic coal. These low grade coals are comparable in their intrinsic value to the wood and coals from which smokeless briquettes have previously been made. However, the process by which the briquettes constituting the end product of the invention are manufactured permits the briquettes to be made at lower cost by (a) deriving additional useful products from the coal which is utilized as the raw material in the manufacture of the briquettes and (b) eliminating, in one embodiment of the process, the need for calcining or carbonizing the rawmaterial in order to attain the desired characteristics in the final briquette product,

At the outset of the process of the invention, the low grade coal constituting the raw material employed is pulverized and is placed in a fixed bed. The coal is then subjected to an extraction process by circulating an inert, high molecular weight, high boiling organic solvent in contact therewith to extract a certain portion of the coal. The extracted material which is removed from the coal bed by the solvent circulated therethrough may then be converted into low ash content coke in accordance with copending application Ser. No; 161,805, now abandoned, filed Dec. 22, 1961. In such extraction process, usually between 25 and percent of the coal is removed as extract, and a substantial portion of this may then be converted to high grade coke.

We have observed that the residue material which remains in the fixed bed following solvent extraction has certain well-defined characteristics which indicate it possesses potential for use in the preparation of smokeless fuel briquettes. For example, the residual coal material is considerably lower in volatile materials than the coal from which it is derived. It has a comparatively high ash content and a rather loose structure. These properties, with the exception of high ash content, indicate that the residue material can be possibly converted to a suitable fuel briquette, and we have devised a process whereby briquettes comparing favorably with those now marketed can be produced from such material.

In practicing the invention, the pulverulent coal material in the fixed bed is initially subjected to contact with an inert organic solvent of relatively high molecular weight and high boiling point. We prefer to employ a solvent selected from the group consisting of gas oils produced by thermal cracking of petroleum oils and gas oils produced by the coking of petroleum oils. Such solvents are capable of extracting up to 75 percent of the coal material depending upon the temperature, pressure and flow rate conditions applied during the extraction. An attractive aspect of the use of such solvents is the facility with which the present process may be utilized in combination with existing petroleum-refining processes. At. the outset in such combined processes, use may be made of readily available gas oil streams derived from thermal cracking operations usually carried on in petroleum refining. After the extractor has been on stream for a while, however, the extract may be converted in part to a high grade coke, and in part to a gas oil which may be recirculated to the extractor.

Following the extraction of the coal with the gas oil solvent, the residue remaining in the fixed bed is subjected to contact with a secondary solvent or a stripping agent in order to remove the occluded primary solvent (gas oil) and extract from the residual coal particles. Although several types of secondary solvents or stripping agents may be employed for this purpose, we prefer to utilize superheated steam since this enables the process to be practiced without the inclusion of a step in which the residue remaining after the extraction is carbonized or calcined by heating to a high temperature in order to remove a large portion of the volatile materials which remain therein.

After the particles of coal residue have been contacted with superheated steam for a suflicient period of time to remove the occluded solvent and extract therefrom, and to reduce the volatile content of the residue particles to a desired level, these particles are then subjected to a briquetting procedure wherein a suitable binder material, such as starch, is mixed with the particles, and the mixture is then subjected to compression to form thefinal briquette products. Although the general principles of briquetteforming are well known in the art, certain inventive concepts of the present process are considered to reside iii the optimum conditions which we have determined to apply in the formation of briquettes from the novel residues which are utilized in the process. Thus, using a standard starch binder material we have found that the employment of residue particles having a general size lying between 20 and 70 mesh may best be utilized in making the briquettes. Also, subjection of these residue particles to a compressive force between 2,000 and 5,000 psi. has been found to give improved results.

The smokeless briquettes which are produced in accordance with the present invention display excellent burning properties, having an ignition time as low or lower than briquettes now being marketed, and producing relatively little smoke and no odor upon burning. Moreover, the low ash content of the briquettes results in a characteristic high heating value which compares favorably with the presently marketed briquettes, and when the preferred briquetting procedure is utilized, the products of the invention have a smooth, bright, shiny appearance with little or no cracking apparent in the compressed carbonaceous material.

From the foregoing discussion, it will be apparent that a major object of the present invention is to provide a novel process for producing a relatively inexpensive, smokeless briquette possessing desirable properties as a fuel material and comparing well with smokeless briquettes now available.

A further object of the present invention is to provide a process which permits the residue remaining after the extraction of low grade coal materials to be converted to a highly useful product for which there is a steadily increasing market.

An additional object of the present invention is to produce a relatively inexpensive, smokeless briquette having good burning properties and high heating value by a process which may be conveniently integrated with a process for producing high grade coke so that low grade coal materials constitute the common raw material source for-both the briquettes and the coke.

Additional objects and advantages of the invention will become apparent to the reader as the following description of the invention proceeds.

The preferred raw materials which are utilized in practicing the process of the present invention are low grade soft coals, such as bituminous and subbituminous coals. However, lignitic types of coal such as lignite and brown coal may also be used. Also, anthracite coal may be used at some sacrifice of economy of production. The preferred feed materials are coals of inferior quality having a fixed carbon content of less than 85%. An example of such coal is Glenrock c-oal of Wyoming which is classified according to the A.S.T.M. classification as subbituminous C coal, having a moist B.t.u. content of about 8,700, a fixed carbon content of about 50%, and an ash content varying from to 24%, depending on the seam.

The ash contents of these coals will vary widely. Ash content, however, is primarily a function of the portion of the seam from which the coal is mined. Generally, the closer to the edge of the seam the coal is mined, the higher its ash content. Ash content can be limited to some extent, therefore, by selective mining. As will subsequently'appear, the lower the ash content of the briquettes which are produced by the process, the higher will be their heating value.

The raw coal is initially pulverized and screened to provide particles which preferably have a size ranging between about mesh (.O33 inch) and /2 inch. We have found, however, that the pulverized coal may include substantial quantities of particles of larger size than /2 inch, and may include as much as 30% by weight of fines which pass a 20 mesh screen. Greater quantities of such fines, however, tend to cause caking during extraction, resulting in excessive pressure drops through the drum in which the pulverized coal is located during extraction. After the coal has been pulverized to provide particles of the described character, the pulverulent coal is disposed in a fixed bed in a suitable container or drum to which a solvent may be charged at one end and discharged at the other end.

The solvent which is employed is an inert, organic liquid which may be maintained in the liquid phase at temperatures in the range of from 600 F. to 1000 F. with little, or preferably no, superatmospheric pressure irnposed. In general, a gas oil material constitutes the most suitable solvent type, and we prefer to employ gas oils selected from the group which includes coker gas oils and gas oils produced in the thermal cracking of petroleum oils, since these materials are readily available products of the petroleum refining process, or are made as byproducts of the production of coke from the material extracted from the coal. The most suitable solvent which we have found is a petroleum-derived special coker gas oil. This material is a highly cracked, relatively high molecular weight, high boiling hydrocarbon mixture of the following general properties:

Gravity, A.P.I 6.0-13.0 Specific gravity at 60 F 09833-10224 Distillation at 760 mm. (corrected):

I.B.P. F 400-500 5% F 448-569 10% PL. 465-580 20% F 505-598 30% F 560-620 40% R. 584-645 50% F 605-659 60% F 618-675 70% F 628-700 P" 640-745 F 659-805 F 670-846 E.P. F 697-905 Carbon, weight percent 88-91 Hydrogen, weight percent 7-11 K factor 10.0-10.6 Viscosity, cs. at 210 F. 1.5-2.6 Mean average boiling point F 600-670 In addition to special coker gas oils of this type, other types of gas oil which may be used include topped special coker gas oils, lignite tar coker gas oils, and, as indicated, coker gas oil produced from the extract derived from the coal extraction step of the present invention. Of these materials, the topped special coker gas oil gives the highest (most efficient) extraction yields, while the lignite tar coker gas oil gives less efficient extraction unless the extraction is carried out at relatively low temperatures. Broadly, the gas oils which may be employed for extraction are characterized by the following general physical and chemical properties:

Gravity, A.P.I 2.0-14.0 Specific Gravity at 60 F. 0.950-1025 Distillation (percent) at 760 mm. (corrected):

IB.P. F 400-525 5 F 430-570 10 P" 460-610 20 F 480-650 30 F 510-680 40 F 540-685 50 F 570-690 60 F 610-710 70 F 620-7-80 80 F 640-840 90 F 650-895 95 F 670-900 E.P F 697-910 Carbon, Weight percent 84-91 Hydrogen, weight percent 7-11 K factor 10.0-10.6 Viscosity, cs. at 210 F. 1.5-2.9 Mean average boiling point 'F 600-700 The drum in which the pulverulent coal is located is preferably positioned vertically and the extraction solvent then preferably circulated upwardly through the coal bed from the bottom to the top thereof. Circulation of the solvent from top to bottom of the drum may also be used, however. Prior to its introduction to the coal bed, the solvent is preheated to about the temperature at which the extraction is to be conducted. Suitable heating elements are provided in association with the drum maintaining the coal therein at the desired extraction temperature.

In practicing the invention, the solvent is passed through the bed of pulverized coal at a temperature of between 500 and 800 F., under pressures sufficient to maintain the extraction solvent in the liquid state. At lower temperatures, the extent of coal extraction is generally less. The yield of extract also generally falls off rather sharply at temperatures exceeding 800 F. In using the preferred gas oil solvents, a temperature of between 680 F. and 775 F. is preferably employed, and a pressure between atmospheric pressure and 500 p.s.i.g. is utilized, depending upon the boiling range of the solvent employed. Generally, in the case of the gas oil types described above, a pressure of 40 p.s.i.g. will be adequate.

The optimum extraction efficiency or percentage of the coal which is removed from the bed by extraction will be determined primarily by the economics of the coke or other product which is produced from the extract and of the smokeless briquettes which are produced by the process of the present invention. The actual degree of extraction is dependent upon the temperature, the time the solvent is in contact with the coal particles, and the amount and type of solvent employed. The particle size of the pulverulent coal in the extraction bed is also a factor affecting the percentage of coal extracted. In any event, the present invention may be practiced over a wide range of extraction efiiciencies ranging from about 20% to 70% extraction with from 30% to 60% being the preferred extent of extraction.

The solvent should be passed through the drum in contact with the coal for aperiod of at least twenty minutes, and preferably should be flowed through the coal bed at a space velocity of between 0.1 and pounds of solvent per hour per pound of coal. The solvent is circulated through the coal at this space velocity until between one and ten parts thereof per part of coal have passed through the bed, keeping in mind the twenty minute contact time which is the preferred minimum.

When the requisite amount of solvent has been passed through the extraction vessel, the flow of solvent through the bed of coal is discontinued, and a substantial portion of the solvent extract mixture remains in adherence to the bed of subdivided coal. To remove the occluded solvent and extract from the bed of the subdivided coal, the bed is washed with a material hereinafter termed the secondary solvent, which is miscible with the solvent at a temperature lower than the extraction temperature, or is stripped from the coal bed using superheated steam as the stripping agent. The latter procedure is preferred for reasons subsequently to be described. When a miscible secondary solvent is utilized for removing the occluded primary solvent used for extraction, it is essential that the miscible secondary solvent material boil at a temperature lower than that of the solvent so that it can be separated therefrom by distillation. Such secondary solvent may be a hydrocarbon fraction produced in a petroleum refining operation, such as a naphtha fraction boiling between 200 F. and 300 F., or it may be some other low boiling material such as methyl ethyl ketone. Before the secondary solvent is used, the temperature of the bed of coal particles can be reduced by the use of low pressure steaming, or by the passage of a purge gas such as flue gas or nitrogen, through the extraction vessel. The temperature of the primary extraction solvent may also be gradually lowered to reduce the temperature of the bed of pulverized coal before the purge gas is introduced thereto. Water can also be used for this purpose, rapid cooling being obtained by the utilization of the latent heat of vaporation absorbed in the conversion of water to steam.

After the bed of coal particles has been reduced to a temperature below that at which the washed material boils at the pressure used, the secondary solvent is passed either upwardly or downwardly through the extraction vessel. However, the washing step is preferably carried out countercurrent to the flow path flowed during solvent extraction, that is, the washing material is introduced to the opposite end of the extraction drum from that into which the exracting solvent was introduced. Carrying out washing in this manner provides an unexpected improvement in the increased removal of residual solvent from the coal bed.

Passage of the secondary solvent wash material through the vessel is continued until all, or the desired amount, of adhering solvent and coal extract is removed therefrom. Ordinarily, about 1 to 6 pounds of wash material per pound of coal will remove substantially all of the solvent and coal extract remaining in the extraction vessel. After the coal residue has been purged with an inert gas, and is removed from the extraction vessel and dried, the coal residue is ready for subsequent processing for conversion to 'briquette form.

As a preferred, alternative procedure to the secondary solvent washing used to remove the residual solvent and extract, coal residue which remains in the extraction drum may be steam stripped at temperatures between 500 F. and 1150 F., and the residue subsequently cooled with water until the temperature is reduced to a level at which the coal residue can be removed from the drum. When utilizing superheated steam as the stripping medium, either co-current or countercurrent flow of the steam can be employed with substantially the same results; that is, the steam can be introduced at the bottom of the extraction drum and flowed upwardly through the coal particles, or in the alternative, can be introduced through the :top of the extraction drum and removed from the bottom thereof.

The utilization of superheated steam for removing or stripping the occluded solvent and extract from the residual coal particles is preferred to accomplishing such removal by the use of a secondary solvent. This is be cause We have found that the employment of a light secondary solvent such as the naphtha fraction described above, or methyl ethyl ketone, leaves residual odor-producing material on the residue particles which results in the evolution of an undesirable odor as the smokeless briquettes are ignited and burned. Moreover, the use of a secondary solvent for removing the primary solvent and extract from the residual coal particles fails to reduce the volatile content of the residual coal particles to a suflicient degree to eliminate the production of smoke from the burning briquettes. As the latter characteristic is extremely undesirable in briquettes which are to be utilized for fuel in outdoor cooking and the like, it is necessary, when using a secondary solvent in the manner described above, to employ an additional step in the process of the present invention which is not required when stripping with superheated steam is utilized. This step consists of carbonizing or calcining the residual coal particles by heating the particles to between 900 F. and 1000 F. in an oxygen-free atmosphere. This additional step, of course, increases the cost of production of the smokeless briquettes and, therefore, is obviously undesirable. It is preferred therefore to accomplish the removal of the solvent and extract which are occluded in the pulverized coal remaining after extraction by the utilization of superheated steam stripping alone, since this step accomplishes not only the removal of such occluded materials, but also effectively removes a substantial portion of the smoke-producing volatile material content of the coal residue, and also does not leave any odorous material absorbed on the surfaces of the coal particles. The steam stripping technique is also preferred from the standpoint of the relative cost of the steam as compared to such solvent types as petroleum naphtha or methyl ethyl ketone.

In utilizing steam stripping to effectively clean the residual coal particles and to remove the smoke and odorproducing materials therefrom, the steam should be substantially dry and should be heated in excess of 600 F. Wet or saturated steam passed through the coal bed at temperatures below 300 F. is entirely ineffective. Excessively high temperatures of the steamsay in excess of 1200 F., however, are to be avoided, since it is believed that the steam bums or reacts with the carbon of the residue at such higher temperatures resulting in some consumption of the residue mass rather than just the stripping of solvent and extract therefrom.

The steam should be passed through the bed of coal residue material at a fairly low space velocity of between 0.25 and 6 pounds of steam per pound of residue material per hour. In general, steam temperatures between 600 F. and 800 F. are preferred since the literature indicates that temperatures exceeding 710 F. are required for steam and coal to react. Acceptable results have been achieved in the present process, however, at temperatures as high as 1120 F. g

If desired, both secondary solvent washing and steam stripping techniques can be combined; that is, removal of the occluded primary solvent and extract by initially washing with a light hydrocarbon washing material followed by stripping with superheated steam' may be effected.

The next step in the process of the present invention is dependent upon whether the light hydrocarbon secondary solvent washing procedure has been utilized to cleanse the coal residue, or whether the steam stripping technique 'has been employed. As indicated above, secondary solvent washing does not remove the volatile materials from the coal to a sufficient extent to prevent excessive smoke when the briquette final products are ignited. In such instances, it is necessary to initially calcine the residue material by heating the material to a temperature of 900 F. to 1,000 P. in the absence of air. This effectively lowers the volatile content of the particles of coal residue to a sufficient level to reduce to a negligible degree the volume of smoke produced in the ignition and combustion of the briquettes. On the other hand, in the residue particles which have been subjected to steam stripping, the calcining step may be omitted, and the particulate residue material is of sufficient quality to permit briquetting without further processing.

In the preparation of smokeless briquettes from the residue material, the particles of the coal residue are initially mixed with a binder material, such as adhesive starch, for example, starch which is sold under the trade name Ceredex or Staley K Briquetting Starch. The amount of binder material which is employed will vary with the particular hinder, the particle size of the coal residue and the briquetting conditions employed. Usually the amount of binder will vary from about 3 to about percent, for example, with starch an amount of about 4 to about 7 percent can be employed.

Although starch is preferred as the binder, other conventional briquette binding materials which are well known to those in the art can also be used. These include, for example, spent sulfite liquor, bituminous materials, such as pitch or asphalt, clays, various kinds of cereal binders, such as high protein cereals, low protein cereals, etc.

The binder-residue mixture is then placed in a suitable die and subjected to compressive forces exceeding 1,000 pounds per square inch. When employing a binder which contains water, it is necessary to dry the resulting briquettes to reduce their moisture content. The drying operation can be carried out at any suitable temperature,

but ordinarily not above about 225 when employing a starch binder. The drying time will, of course, depend on the amount of moisture in the briquette and the temperature employed. At temperatures in the range of 225 F., drying is usually accomplished over a period of several days, for example, from about 2 to about 5 days.

Since the briquettes are hygroscopic and thus can take up moisture from the to condition the briquettes by allowing them to remain at atmospheric temperature for a sufiicient period of time to provide the equilibrium water content, which is usually about 3 percent by weight. Of course, if the briquettes are not to be used immediately, the conditioning process can take place naturally during shipping or warehousing.

The briquetting operation cannot be considered as standardized, inasmuch as a wide variety of procedures are practiced by industry. It is intended that this invention not be limited to any specific briquetting procedure except in the more specific aspects of the invention as hereinafter described and as set forth in the claims.

We have found that the burning qualities of the smokeless briquettes of the present invention may be improved by selectively screening the particles of coal residue to provide a material for mixture with the starch binder having a particle size between 20 mesh and 65 mesh (.033 inch to .0082 inch). The quality of the briquettes is also improved by employing a compressive force between approximately 2,000 p.s.i. and 5,000 p.s.i. In general, briquettes which are made from finer residue particles (on the order of 65 mesh) have a smooth, shiny surface appearance which is quite appealing to the eye. They also ignite in a shorter time than briquettes which have been compounded from the coarser residue particles. On the other hand, the briquettes which are made from the finer aggregate are characterized by a number of fine cracks at the surface thereof and are somewhat crumbly. The surface of briquettes made from the coarser material (on the order of 20 mesh material) have a duller, though more uniform surface appearance, and are firmer and less subject to disintegration. The ignition time of the briquettes made from the coarser aggregate is higher than that of the finer aggregate briquettes. It is believed that the optimum particle size for use in compounding thebriquettes is, therefore,as indicated above, between 20 mesh and 65 mesh. The briquettes which we have made using residue particles of this size and employing pressures between 2,000 and 5,000 pounds per square inch have ignition times and burning properties which compare very favorably with the best smokeless briquettes which are now commercially available.

The following examples are presented in illustration of the various embodiments and aspects of the invention:

Example 1 A number of samples of Glenrock sub-bituminous coal of the type previously described were extracted using various gas oil solvents and various secondary washing solvents or stripping agents. The average analysis of the Glenrock coals was as follows:

Property: Average value Car-bon/ hydrogen mole ratio 1 09 Moist, mm.-free, B.t.u. per pound 8,810 Dry, mm.-free fixed carbon, wt. percent:

All samples 38.3 Fresh samples 50.7 Samples in storage more than 6 weeks 22.3

atmosphere, it is usually desirable different shipments. Table I sets forth the conditions employed in a number of extraction runs and the results obtained.

TABLE 1(a) Primary Secondary Solvent or Coal Solvent Extraction Solvent Rate, Run Solvent Stripping Agent Charge, Charge, Time, Pounds/ Pounds Pounds Hours Hour T.S.G.O.1 M.E.K 8.89 93.2 2.2 42.36 T.S.G.O.1 M.E.K. 9.02 75. 3. 16. 67 L.C.G.O.1 M.E.K. 8.64 76.4 3.5 16.98 T.S.G.O.1 M.E.K 8.86 78.1 3.5 17.36 L.C. G.O.1 M.E.K 8.64 75.2 3. 5 16. 71 L.C.G.O.1 M.E.K-. 8. 92 74. 8 3. 5 16. 62 T.S.G.O.1 Naphtha 8. 72 79.3 3. 5 17. 62 P.C.G.O.1 M.E.K 110.50 396.5 7.0 44.06 T.S.G.O.2 M.E.K 113.50 343.3 7.0 38.14 T.S.G.O.2 M.E.K.- 117.50 460.5 5.0 65.71 T.S.G.O.-3 M.E.K 114.00 544. 5 5. 75 70. 26 E.C.G.O M.E.K-. 8.80 77.9 3.5 17.31 T.S.G.O. M.E.K 116.20 T.S.G.O.- Ste 111 (1,120 F 8. 60 81.5 3. 5 18.11 T.S.G.O. Steam (812 F 116. 50 581. 5 7.0 64. 61 T.S.G.O. Steam (980 F 7. 8 151.0 3. 5 33. 56 T.S.G.O.5 Steam (710 F.) 8. 7 79. 3 3. 5 17. 62 1.S.G.O.1 Steam (725 F.) 106. 7 539. 8 9.0 58. 40 T.S.G.O.2 Steam (700 F.) 109. 5 528. 9 9. 0 57.

TABLE 100) Secondary Wash or Extraction Drum Primary Solvent Stripping Temperature, F. Solvent Residue, Percentage Run Charge, Rate, Temp., Pounds Extraction Pounds Pounds/Hour F.

I Bottom Middle Top N 0TE.Analyses of the gas oil solvents employed in the extraction runs of Table I are set forth in Table II.

TABLE II(a) T.S.G.O.1 1 T.S.G.O.2 T.S.G.0.-3 T.S.G.O.4

Gravity, A.P.I I 8.8 9. 0 10.7 8. 2 Specific Gravity at 60 F 1. 0086 1. 0071 0.9951 1. 0129 Distillation at 760 mm. Hg:

I.B.P

525 523 517 550 540 532 580 566 564 603 585 579 630 600 591 641 615 605 648 630 618 675 640 628 695 651 640 730 674 659 759 690 670 787 722 697 Carbon, Weight Percent 89.62 89. 84 89. 28 Hydrogen, Weight Percent- 8. 52 8. 66 9.06 Oxygen, Weight Percent 0.75 0. 57 0.71 Sulfur, Weight Percent.-- 1. 45 1. 31 Nitrogen, Weight Percent 0.14 0.14 Ash, Weight Percent 0 O K Factor 10. 10.19 10. 25 Molecular Weight 240 228 225 Viscosity, cs. at 210 F 2. 19 1. 72 1. 57 Percent Aromatics 83 60 55. 3 Mean Average Boiling Point, 640 611 601 1 T.S.G.O.=Topped Special Petroleum Coker Gas Oil.

TABLE II(b) Gravity, A.P.I Q Specific Gravity at 60 F Distlilgitipn at 760 mm. Hg:

95. El Carbon, Weight Percent Hydrogen, Weight Percent Oxygen, Weight Percent". Sulfur, Weight PercenL. Nitrogen, Weight Percen Ash, Weight Percent;

ct Molecular Weight Viscosity, cs. at 210 11- Percent Aromatics Mean Average Boiling Point, F

L.C.G.O.=Lignite Tar Coker Gas Oil. 1 P.C.G.O.=Heart Cut Petroleum Coker Gas Oil. E O.G.O.=

. Gas Oil Produced During Conversion of Extract to Coke.

Example 2 extract, yielded the followlng proximate analysis (values given are in percent weight):

Moisture 2.3 Volatile matter 25.7 Fixed carbon 53.5

Ash 20.8

This residue material was briquetted with 5 percent of a precooked starch binder material sold under the trade name of Ceredex. After briquetting, the briquettes were dried and were cured for several days. The briquette made from this residue has a slight, objectionable odor, but showed a compression strength of 120 pounds (International Briquetting Association Standard). The latter value indicates acceptable mechanical strength for a briquette of this type. The briquettes were ignited and showed an ignition time of 42 minutes. The ignition test employed comprises dousing the briquettes with a standard briquette lighter fluid, lighting the fluid, and then measuring the time elapsing between lighting and the time when combustion has spread over 80 percent of the briquette surface. This time is referred to as the ignition time. The ignition time of a good smokeless fuel briquette is generally about minutes.

Example 3 A second coal residue derived from extraction run 13 set forth in Table I above, and having the following proximate analysis was briquetted:

Percent Moisture 0.6 Volatile matter 23.8 Fixed carbon 65.6

Ash 10.0

Prior to mixing with the starch binder material, the residue was ground to pass a No. 12 screen (.066 inch).

The properties of the briquettes so produced are summarized in Table III below.

Example 4 The residue used in Example 3 was ground and screened and the material passing a No. 70 screen (.008 inch) was briquetted using 5 percent Ceredex binder and 1,000 p.s.i. compressive force. Characteristics of the briquettes produced are shown in Table III below.

Example 5 The residue used in Eaxmple 3 was ground and screened, and the material passing a No. 70 screen was briquetted, using a compression of 2,000 p.s.i.

The properties of the briquettes produced are set out in Table III.

All of the briquettes produced in Examples 3-5 were dried at 225 F. and then cured for four days.

Example 6 Three portions of the residue used in Example 3 were calcined or carbonized by heating the residue to 930 F. in the absence of air. The three residue portions were ground to pass a No. 12 screen. Two of these portions were briquetted at 1,000 p.s.i. In one of the two portions so compressed, however, 8 percent sodium nitrate was added to the aggregate as an ignition promoter. The third portion, which was ground to pass a No. 12 screen, was briquetted at a pressure of 2,000 p.s.i. As indicated in Table III below, all of these briquettes, which were calcined before briquetting, displayed shorter ignition times than the briquettes prepared from uncalcined residue ground to pass a No. 12 screen as described in Example 3.

Example 7 Two portions of the residue used in Example 3 were ground to pass a No. 70 screen and then mixed with 5 percent Ceredex starch binder. The first portion was then compressed into briquettes at 1,000 p.s.i., dried at 225 F. and allowed to cure for four days.

The second portion was compressed at 2,000 p.s.i. and given a drying and curing treatment like the briquettes prepared from the first portion. The ignition times of the briquettes prepared from the two portions were 24 minutes and 20 minutes, respectively. This compares well with the best commercially available smokeless briquettes.

13 Example 8 A coal residue resulting from gas oil extraction followed by steam stripping, and produced in Run 18 of Table I above, was ground so that 91 percent by weight of the residue would pass a Nof 70 screen. The entire residue was then mixed with 6.5 percent of a low protein starch binder sold under the trade name of Staley K and pressed into briquettes at 5,000 psi. The briquettes were dried and cured as previously described. Ignition time of the briquettes was 23 minutes, and their smoke and odor characteristics were considered good. (See Table III.)

Example 9 Several portions of the steam stripped residue employed in Example 8 were briquetted, using varying screen sizes of residue particles, varying types and amounts of starch binder, and varying briquetting pressures. The conditions applied, and results obtained, are set forth in Table III.

Example 10 The coal residue produced in Run 19 of Table I above, employing gas oil extraction followed by steam stripping, was ground so that 91 percent by weight of the residue would pass a No. 70 screen. The entire residue was then mixed with 6.8 percent of Staley K starch binder and compressed at 5,000 p.s.i. Additional briquettes were made from the same residue material, but employing varying amounts of Staley K starch, varying residue particle sizes, and varying briquetting pressures. Process conditions and briquette properties are set forth in Table III.

TAB LE III (a) Binder Briouetting Material Particle Run Briquetted Size Kind Percent 1 From Run 13 Pass No. 12. Ceredex.-. 5.

Table I (Example 3 above). 2 From Run 13 Pass No. 70- .do 5. 0

Table I (Example 4 above). 3 From Ruu13 do do 5.0

Table I (Example above). 4 Run 13 Residue Pass N o. 12. Nitrates 5. 0

Calcined at 930 Included F. Oeredex. 5 ..do .do Ceredex... 5. 0 6.... --..do do o 5.0 7.. Calcined Run 13 Pass No. 70. o 5.0

Residue. 8 .--..do do do 5.0 9 Run l8Steam 91%No. Staley K 6. 5

Stripped. 70. 10 ..do 92%-No. 20. .-.do 6. 5 ll. .....d0.. 91%No. 70. 6.0 12- do.. Pass No. 6.5 13..-. ..d0 91%No. 70. 6. 5 14 Run 19-Steam 91%N0. 70- 6.8

92%N0. 20- 6. 7 92%N0. 70- 7. 0 Pass No. 20- 5. 0

TABLE III(b) Briquette Com- Percent Briquetpressure, Briquette Appearance pression ting Run p.s.i. Strength,

Pounds H O Ash 1,000 Fairly smooth, some 70 1 8 9. 4

cracks. 1,000 Coarse, crumbly 50 1. 8 10.2 2, 000 Smooth, crumbly 1. 5 9. 5 1, 000 Coarse, firm 120 1. 9 11.5 1,000 Coarse, crumbly 10 2. 2 9.7 2,000 Medium firm, 40 1. 5 9.8

smooth. 1,000 l0 1.7 10.0 2,000 25 1. 8 10. 3 5, 000 Sh y, some cracks... 60 2. 8 9.8 5,000 .....do 150 2.0 9.8 5, 000 Dull, some cracks 100 2. O 9. 7 2,000 Smooth, some cracks. 130 2. 3 7. 3 000 0 3. 2 10. 1 5,000 0 1.9 13. 3 5,000 Dull, fairly smooth-.. 200 2.0 14. 8 5, 000 Some cracks 2.0 13.1 5,000 Dull, fairly smooth... 90 2. 8 12. 9

TAB LE III(c) Ignition Test Briquetting Specific Run Gravity Time, Smoke 1 Odor 1 Minutes 45 3 2 28 0 4 25 3 3 28 0 4 35 0 2 31 0 4 24 0 3 20 0 2 23 l 1 28 1 2 37 1 5 31 1 l 23 l 1 28 1 1 33 1 1 23 1 2 27 1 1 1 Smoke and Odor graded from 0 to 10 with 0 being least smoke and odor.

From the above examples, and the data given in Table III, several general conclusions can be drawn as to the properties of the residues, and the briquetting conditions which appear to give the most desirable product. Thus, the briquettes may be produced considerably more economically by using superheated steam to strip occluded solvent and extract from the particles of coal residue, than by first washing the residue with a light hydrocarbon, secondary solvent, and then calcining the residue at elevated temperatures. It also appears that briquettes made from residues of relatively low ash content are superior in ignition and combustion properties to those derived from high ash residues.

The particle size of the residue which is briquetted also appears to be an important consideration, both in so far as it affects the ignition time of the briquette, and also due to its apparent relation to the appearance and compression strength of the briquette. Generally, briquettes pressed from rather fine residue material (on the order of 65 mesh-No. 70 screen or finer) show the shortest ignition time. These briquettes also have a smooth, shiny surface appearance which is appealing. However, the compression strength of the fine residue briquettes is not as good as those derived from coarser residue particles. Increasing the briquetting pressure appears to improve the mechanical strength of the briquette.

In general, then, it is believed that the best briquettes may be produced using residue particles between 20 and 65 mesh in size, and pressures of between 2,000 p.s.i and 5,000 p.s.i. present some advantage over the Ceredex starch binder in that it appears to produce less odor upon being consumed in the combustion of the briquettes.

From the foregoing description, it will be apparent that the present invention provides a novel process for producing smokeless fuel briquettes at less cost than, but of comparable properties to, smokeless briquettes now being marketed. The process may easily and usefully be combined with processes for producing other products, such as coke, from low grade coal materials, and the extraction solvent, steam and other materials employed in practicing the process are relatively inexpensive and easily obtained.

Although certain process conditions have been described hereinbefore as being susceptible of employment in the process of this invention, these conditions have been cited as only exemplary of certain preferred embodiments of the invention. Those skilled in the art will thus appreciate that a considerable variation in conditions of temperature, pressure, solvent types, contact times, solvent to coal ratios, and briquetting conditions may be practiced without departure from the basic principles which underlie the invention. Such variations in operating conditions are, therefore, deemed to be contemplated by the disclo- The Staley K briquetting starch may also sure of the present application and to fall within the spirit and scope of the present invention except as they may necessarily be excluded by the language of the following claims.

What is claimed is: 1. A process of producing smokeless, carbonaceous briquettes from low-grade coal which comprises:

contacting particles of coal with a solvent comprising gas oil at a temperature of from 500 F. to 800 F., under a pressure sufficient to maintain a substantial amount of the solvent in the liquid state and for a substantial period of time to remove a substantial amount of hydrocarbonaceous material to provide a residue comprising from about 30 to about 80 percent of said coal; removing occluded solvent, extract and odor and smokeproducing materials simultaneously from said residue by contacting said residue with super-heated steam; and briquetting said particulate coal residue. 2. A process of producing smokeless, carbonaceous briquettes from low-grade coal which comprises:

contacting particles of coal with a solvent comprising gas oil at a temperature of from 500 F. to 800 F., under a pressure sufiicient to maintain a substantial amount of the solvent in the liquid state and for a substantial period of time to remove a substantial amount of hydrocarbonaceous material to provide a residue comprising from about 30 to about 80 percent of said coal; removing occluded solvent and extract from the coal residue remaining after extraction by contacting said coal residue with methyl ehtyl ketone; removing odor and smoke-producing materials from said residue; and briquetting said particulate coal residue. 3. A process of producing smokeless, carbonaceous briquettes from low-grade coal which comprises:

contacting particles of coal with a solvent comprising gas oil at a temperature of from 500 F. to 800 F., under a pressure suflicient to maintain a substantial amount of the solvent in the liquid state and for a substantial period of time to remove a substantial amount of hydrocarbonaceous material to provide a residue comprising from about 30 to about 80- percent of said coal; removing occluded solvent and extract from the coal residue remaining after extraction by contacting said coal residue with a second solvent in which said first-mentioned solvent is soluble;

removing odor and smoke-producing materials from the residue by carbonizing the residue by heating said residue to between about 900 F. and 1000 F.; and

briquetting said particulate coal residue.

4. Theprocess of manufacturing smokeless fuel briquettes from low-grade coals selected from the group consisting of bituminous, sub-bituminous, and lignitic coals which comprises:

preparing a fixed bed of particles of said coal which particles are substantially all of a particle size between 0.001 inch and 0.5 inch;

passing a solvent comprising gas oil through said bed at a temperature of between 500 F. and 800 F. and a pressure sufficient to maintain said gas oil in the liquid state, said solvent being passed through said coal at a space velocity of between 0.5 and 10 pounds of solvent per hour per pound of coal for a substantial period of time to remove a substantial amount of hydrocarbonaceous material to provide a residue comprising from about 30 to about percent of said coal;

cleaning the residual pulverized coal remaining in the bed to remove substantially all of the occluded gas oil solvent and the coal extract dissolved in said solvent therefrom;

removing odor and smoke-producing materials from said residual coal; and

briquetting said residual coal.

5. The process claimed in claim 4 wherein the steps of cleaning the residual pulverized coal and removing odor and smoke-producing materials therefrom are accomplished simultaneously by contacting said residue with super-heated steam at a temperature exceeding 700 F.

References Cited by the Examiner UNITED STATES PATENTS 1,121,325 12/1914 Cann 44-15.3 1,556,036 10/1925 Schoch 44-1004 1,851,689 3/1932 Wolf 44-15.3 2,453,544 111/ 1948 Schabelitz 202-25 2,835,563 5/1958 Dohmen 44--15 FOREIGN PATENTS 320,056 4/ 1920 Germany.

DANIEL E. WYMAN, Primary Examiner.

C. F. DEES, Assistant Examiner.

Claims (1)

1. A PROCESS OF PRODUCING SMOKELESS, CARBONACEOUS BRIQUETTES FROM LOW-GRADE COAL WHICH COMPRISES: CONTACTING PARTICLES OF COAL WITH A SOLVENT COMPRISING GAS OIL AT A TEMPERATURE OF FROM 500*F. TO 800*F., UNDER A PRESSURE SUFFICIENT TO MAINTAIN A SUBSTANTIAL AMOUNT OF THE SOLVENT IN THE LIQUID STATE AND FOR A SUBSTANTIAL PERIOD OF TIME TO REMOVE A SUBSTANTIAL AMOUNT OF HYDROCARBONACEOUS MATERIAL TO PROVIDE A RESIDUE COMPRISING FROM ABOUT 30 TO ABOUT 80 PERCENT OF SAID COAL; REMOVING OCCLUDED SOLVENT, EXTRACT AND ODOR AND SMOKEPRODUCING MATERIALS SIMULTANEOUSLY FROM SAID RESIDUE BY CONTACTING SAID RESIDUE WITH SUPER-HEATED STEAM; AND BRIQUETTING SAID PARTICULATE COAL RESIDUE.