US 3642608 A
Coal is solubilized in highly aromatic petroleum byproduct streams such as catalytic cracker recycle oil and slurry oil to produce a coal solution having a low viscosity which is readily deashed by settling and/or filtering. The coal solution has a low sulfur and mineral ash content and it may be used in the preparation of fuels or as a feedstock to a furnace process for producing carbon black. All or part of the solvent content of the coal solution may be recovered and recycled in the process as a solvent, and the deashed and desulfurized coal thus produced may be used as a solid or molten fuel, or it may be blended with petroleum refinery streams to produce liquid fuels having desired specifications and a feedstock for producing furnace carbon black.
Description (OCR text may contain errors)
United States, Patent Roach et a1.
721 Inventors: Jack w. Roach; Leo cor-win, both of Oklahoma City, Okla.
Kerr-McGee Corporation, Oklahoma City, Okla.
 Filed: Jan. 9, 1970  Appl.No.: 1,688
 US. Cl ..208/8, 23/209.1, 44/51  Int. Cl ..Cl0g 1/00 208/8  Field ofSearch  References Cited- UNITED STATES PATENTS 1 Feb. 15, 1972 3,341,447 9/1967 Ball etal ..2os/s 3,375,188 3/1968 Bloomer ..20s/s Primary Examiner-DelbertE. Gantz Assistant Examiner-Veronica OKeefe An0rney-Shanley and ONeil ABSTRACT Coal is solubilized in highly aromatic petroleum byproduct streams such as catalytic cracker recycle oil and slurry oil to produce a coal solution having a low viscosity which is readily deashed by settling and/or filtering. The coal solution has a low sulfur and mineral ash content and it may be used in the preparation of fuels or as a feedstock to a furnace process for producing carbon black. All or part of the solvent content of the coal solution may be recovered and recycled in the process as a solvent, and the deashed and desulfurized coal thus produced may be used as a solid or molten fuel, or it may be blended with petroleum refinery streams to produce liquid fuels having desired specifications and a feedstock for producing furnace carbon black.
17 Claims, 2 Drawing Figures PAIENTEDFEB 15 I972 SHEET 1 or 2 S R o m mm v W N m. K mm ATTORNEYS PATENTEUFEB 15 1912 saw 2 or z m: QE
INVENTORS JACK W. ROACH LEO GARWIN ATTORNEYS SOLVATION OF COAL IN BYPRODUCT STREAMS BACKGROUND OF THE INVENTION The potentially soluble substances in fossilized carbonaceous materials such as coal are composed largely of high molecular weight three-dimensional cyclic structures which contain predominantly six-membered rings. For example, coal contains bitumen and humin which have large flat aromatic lamellar structures that differ in molecular weight, degree of aromaticity, oxygen content, nitrogen content, and the degree of cross-linking. Coal also contains volatile matter, fusain, mineral matter, moisture, and sulfur which is present as pyritic sulfur, inorganic sulfates and/or organic sulfur compounds.
. The mineral matter remains behind as ash when the coal is burned, and fusain is a mineral charcoal which is consumed during burning at high temperatures in the presence of sufficient oxygen for complete combustion. The presence of sulfur in substantial quantities results in contamination of the atmosphere with sulfur oxides upon combustion which, upon reaction with atmospheric moisture, produce highly corrosive sulfurous acid and/or sulfuric acid. As a result, air pollution regulations in metropolitan areas often require that the sulfur content of fuels be reduced so as to control atmospheric pollution. The mineral content of the coal, which may be -15 percent by' weight or higher in many instances, reduces the B.t.u. value of the raw coal per unit weight and this results in increased transportation costs. There is an additional cost when the ash containing coal is burned as the ash residue must be .removed from the combustion zone and disposed of in some manner.
The presence of fusain, mineral matter and sulfur in substantial quantities also reduces the value of the coal in certain specialized uses. If these substances are removed, the coal may be used for preparing high purity coke for use in anodes for the production of aluminum. High-purity coke for anodes has a much higher value than impure coke produced from the original coal.
In view of the foregoing and for still other reasons, it is desirable to reduce the fusain, mineral matter and sulfur content of coal. One process for removing these substances involves solvation of the solvent-soluble coal constituents including the bitumen and humin contents in an organic solvent. Thereafter, the insoluble fusain, mineral matter and inorganic sulfur are separated from the coal solution.
A wide variety of organic solvents have been proposed heretofore for solubilizing coal. However, the solvents used heretofore have left much to be desired from the standpoint of low-cost, solvent capacity for the desired coal constituents, and easeof separation of the insoluble substances from the coal solution. In some instances, the solvent did not have sufficiently high solvent capacity for the coal constituents, in other instances the coal solution was viscous for rapidly separating the micron-size particles of insoluble substances in the coal solution by settling and/or filtration, and in still other instances the cost of the solvent was prohibitive for use in commercial operations.
, Raw or untreated coal is not a satisfactory feedstock for producing carbon black for a furnace process. The carbon black product is contaminated with the mineral ash and sulfur content of thecoal, and the sulfur oxides produced upon partial combustion of the coal present corrosion problems. Additionally, the furnace process involves a partial combustion of the feedstock and critical amounts of air and fuel must be fed to the partial combustion zone under carefully controlled conditions. The conditions are relatively easy to control when liquid hydrocarbon feedstocks are used, but are very difficult to control when solid fuels such as powdered coal are used as feedstocks.
The production of carbon black by the furnace process also requires a special hydrocarbon feedstock if a high yield is to be obtained. As a general rule, the highly aromatic hydrocarbon feedstocks are more satisfactory and the lower the hydrogen-to-carbon ratio, the better thefeedstock for carbon black production. A Bureau of Mines correlation index of approximately 1 l0l30 or higher is necessary in order to achieve a satisfactory yield of carbon black. The correlation index requirement of suitable carbon black feedstock greatly reduces the quantity of petroleum byproduct streams which are available, and the byproduct streams which are suitable for this purpose command a relatively high price.
There are a number of petroleum byproduct streams with low correlation indices which render them unsuitable for carbon black production. These streams are available at a'relatively low cost and would be suitable for carbon black production provided the correlation index could be raised sufficiently. However, prior to the present invention there was no satisfactory process for upgrading the correlation indices of petroleum byproduct streams.
The average sulfur content of heavy fuel oil products produced by petroleum refineries is often too high to meet air pollution regulations in metropolitan areas and the cost of desulfurizing is a substantial percentage of the selling price. Thus, it would be highly desirable to provide a process wherein a low sulfur fuel material is added to heavy fuel oil stocks so as to reduce the average sulfur content and meet the requirements of air pollution regulations without appreciably lowering the heating value.
SUMMARY OF THE INVENTION The present invention provides an economical and commercially attractive process for solubilizing coal in petroleum byproduct streams, and thereafter deashing the coal solution to produce a deashed and desulfurized coal product.
The'invention further provides a novel process for preparing carbon black by the furnace process in which the feed stock includes the deashed and desulfurized coal product of the invention. The invention further provides a novel process for raising the correlation index of highly aromatic petroleum refinery byproduct streams, thereby upgrading such streams and increasing their value as feedstocks to a furnace process for producing carbon black.
The invention further provides a novel process for upgrading petroleum refinery streams used in the preparation of fuel oils. In one variant, heavy fuel oil such as Number 6 fuel oil is prepared from petroleum refinery streams including residual oils and the deashed and desulfurized coal product of the invention.
The invention further provides novel compositions of matter including the carbon black feedstocks and the fuels produced by the processes of the invention.
The invention further provides a novel continuous process for producing deashed and desulfurized coal wherein highly aromatic petroleum byproduct streams are used as a solvent, the coal solution has a low viscosity and is deashed by settling or filtration, and the solvent is recovered and recycled to reduce solvent costs.
BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A andlB of the drawings illustrate one presently preferred arrangement of apparatus for use in practicing the process of the invention. FIG. 1B is a continuation of FIG. 1A.
DETAILED DESCRIPTION OF THE INVENTION INCLUDING PREFERRED VARIANTS THEREOF Referring now to the drawings, a highly aromatic hydrocarbon solvent which is preferably a petroleum refinery byproduct stream to be defined more fully hereinafter, is passed from storage vessel 10 to mixer 11 via conduit 12 at a rate controlled by valve 14. Finely divided coal in storage vessel 15 is also passed to mixer 11 via conduit 16 at a rate determined by meter l7. The relative feed rates of solvent and coal are controlled so that the weight ratio of solvent to coal in mixer 11 is between about 1:1 and 20:1, and preferably between 2:1 and 5:1. The best results are usually obtained when the weight ratio of solvent to coal is approximately 3: l.
The coal and solvent in mixer 11 are agitated with a motordriven agitator 18 and the slurry thus prepared is passed via conduit 13 to pump 19, which increases the pressure and controls the flow rate, and then via conduit 20 to gas-fired heater 21. The slurry flowing in coil 22 is heated to an elevated temperature which preferably closely approximates the desired initial temperature of solvation, and the heated slurry is withdrawn via conduit 23 and is passed to solutizer 24.
While it is not essential, it is usually preferred to carry out the solvation in the presence of added gaseous hydrogen. When gaseous hydrogen is added, it may be passed into the slurry flowing in conduit 20 upon opening valve 25 in conduit 26.
The solutizer 24 preferably operates under a superatmospheric pressure which is determined by the overpressure of gaseous hydrogen when present, the vapor pressure of the solvent at the operating temperature, and/or the hydraulic pressure applied by pump 19. The solvation temperature is determined by the initial temperature of the slurry flowing in conduit 23 and by the temperature control fluid which is supplied to coil 27 via conduit 29 at a rate controlled by valve 28 and withdrawn via conduit 30. The solvent is contacted with the coal under the temperature and pressure conditions existing in solutizer 24 for a sufficient period of time to solubilize a substantial amount of the extractable carbonaceous material and to produce a solution which contains suspended finely divided fusain, mineral ash and other insoluble constituents.
The coal solution containing the insoluble constituents is withdrawn from solutizer 24 via conduit 31 and is passed to header 33 which is provided with a plurality of spaced outlets 34. The header 33 is positioned in ash separator 35 a substantial distance beneath the interface 36 between the relatively heavy slurry layer 37 and the lighter clarified coal solution 38. The slurry layer 37 contains suspended mineral ash, fusain and other insoluble material, and it is withdrawn via conduit 39 at a rate controlled by valve 40. The slurry layer 37 is withdrawn at a rate to maintain the interface 36 substantially above the outlets 34 on header 33. Inasmuch as the coal solution flowing in conduit 31 is at an elevated temperature and has a low viscosity, the heavier insoluble material suspended therein tends to settle out rapidly when it is passed into ash separator 35, Injecting the solution into the heavy slurry layer 37 tends to agglomerate the micron-size solid particles of insoluble material and larger particles are formed which settle even more rapidly. While the mechanism is not fully understood at this time, it is believed that the presence of the coal solution aids in this respect as it seems to coat the individual particles of micron-size solids and promotes agglomeration to thereby produce heavier larger particles. As a result, the lighter clarified phase 38 is substantially free of insoluble material and often it does not require filtering.
The clarified coal solution 38 is withdrawn from the top of ash separator 35 via conduit and, upon opening valve 46 and closing valves 47 and 49, it is passed via conduit 44 t0 coil 51 in heat exchanger 52. A coolant such as water is supplied to heat exchanger 52 via conduit 53 at a rate controlled by valve 54, and it is withdrawn therefrom via conduit 55. In instances where it is desired to filter the clarified coal solution for the purpose of removing additional insoluble material, valve 46 is closed and valves 47 and 49 are opened, and the clarified coal solution 38 is passed via conduits 45 and 48 to filter 56. The clarified and filtered coal solution is withdrawn via conduit 50 and is passed to conduit 44, and then to coil 51 in heat exchanger 52.
The coal solution may be cooled in heat exchanger 52 to any suitable desired temperature such as 75-200 F. or higher, or to a temperature which is suitable for feeding to vacuum distillation column 57. The solution is withdrawn via conduit 58 at a rate controlled by reducing valve 59 and is passed into gas separator 60.
The gas separator 60 is partially filled with a liquid coal solution phase 61 which has a vapor space 62 thereabove. The coal solution flowing in conduit 58 contains any excess hydrogen which was added initially via conduit 26, hydrocarbon gases produced during the solvation step, and other gases which are released into the vapor space 62 upon reducing the pressure on the solution as it passes through reducing valve 59. The pressure existing within vapor space 62 may be, for example, from substantially atmospheric pressure to l or 2 atmospheres. The gases in vapor space 62 are withdrawn via conduit 63 at a rate controlled by valve 64. In instances where the entire degassed, deashed and desulfurized coal solution is to be used for a desired purpose, it may be withdrawn from gas separator 60 via conduit 68 upon closing valve 65 and opening valve 67. The coal solution as withdrawn via conduit 68 is useful as a fuel, or it may be mixed with other petroleum refinery streams and the mixture may be used as a fuel. Inasmuch as it is liquid at room or slightly elevated temperatures, it may be readily pumped and transported by pipeline.
It will be recognized by those skilled in this art that it is not necessary to operate ash separator 35, filter 56 and heat exchanger 52 at approximately the same pressure as solutizer 24. For example, pressure-reducing valve 59 may be relocated in conduit 31 and gas separator 60 may be relocated immediately downstream therefrom, and in such instances, separator 35, filter 56 and heat exchanger 52 may be operated at approximately the same pressure as gas separator 60.
In instances where it is desired to recover a portion or all of the solvent for recycle in the process, this may be accomplished by closing valves 67 and 70, opening valves 65 and 72, and passing the coal solution via conduits 66 and 71 to vacuum distillation column 57. The vacuum distillation column 57 may be of a prior art type used in petroleum refinery operations for separating a hydrocarbon stream having an atmospheric boiling range of, for example, 600-l ,()00 F. An overhead stream, which contains all or part of the solvent and hydrocarbons produced during the solvation step, is withdrawn via conduit 74 and is passed to vacuum fractionator 75 where it is fractionated into a light fraction which is withdrawn via conduit 76, an intermediate solvent fraction which is withdrawn via conduit 77, and a heavy residue or bottoms fraction which is withdrawn via conduit 78.
The deashed and desulfurized coal, which contains some solvent, is withdrawn from vacuum distillation column 57 via conduit 79, and it may be used for a number of purposes to be discussed more fully hereinafter. Makeup solvent is fed to conduit 77 via conduit 80 at a rate controlled by valve 81, and the mixture of recovered solvent and makeup solvent is passed to solvent storage 10. When substantially all of the solvent is removed from the deashed coal, the makeup solvent that is required is usually a small percentage of that flowing through the system such as l-lO percent, and most often is about 5-6 percent.
The deashed and desulfurized coal solution is very useful as a feedstock to prior an oil furnace processes for the production of carbon black, ln instances where it is desired to produce carbon black from the solution in its entirety, then valves 67 and 72 are closed, valves 65 and 70 are opened, and the coal solution is passed to carbon black furnace 82 via conduits 66, 69 an 73. Carbon black furnace 82 is of prior art construction and is operated in accordance with conventional practice for the partial combustion of a hydrocarbon fuel feedstock to produce carbon black therefrom. The same general partial combustion conditions may be used when feeding the coal solution of the present invention to carbon black furnace 82 as would be used when the slurry oil solvent is fed thereto as a feedstock in prior art processes. However, the amount of carbon black produced from the coal solution is greater than that which would be produced from the slurry oil alone. Carbon black product is withdrawn from furnace 82 via conduit 83 and is passed to storage 84.
The vacuum distillation column 57 may be operated to remove substantially all of the solvent and normally liquid hydrocarbon content of the solution fed thereto via conduit 71 so as to produce a solid friable deashed and desulfurized coal. If desired, only about 40-90 percent of the light ends of the solvent are recovered and a substantial amount of the heavy ends of the solvent and/or liquid hydrocarbons may be allowed to remain in the deashed coal product so as to lower its softening point appreciably. For instance, the deashed coal having a boiling range of about 425l ,00O F., e.g., a catalytic cracker recycle stock such as light catalytic cracker recycle oil, heavy catalytic cracker recycle oil and clarified catalytic cracker slurry oil, thermally cracked petroleum stocks, and
d t th i ithd i d it 79 may contain 6() 5 lubricating oil aromatic extracts such as bright stock phenol percent and preferably 40-55 percent by weight of solvent extract The boiling range of the byproduct Team is and/or liquid hydrocarbons so as to lower the softening point Preferably between about and L and Should be to about 200 400 P f bl about 50 percent by weight about 700-900 F. for best results in most instances. Refrac or more of solvent and/or liquid hydrocarbons are present to y highly ammimc Streams wherein the Tommie lowelh ft i point to 200 or 1 whereby the Q stituents contain two or more fused benzene rings per deashed coal product is liquefiable with steam and may be molecule and make P at lens 50 P weigh transported by pumping f d m furnaces as a i i The hydrocarbon solvent are preferred, and for better results the deashed coal product also may be admixed with suitable aromatic constituents should be present in an amount of at matic streams from petroleum refineries such as those nor- 5 leash 9- Pement by Clarified catalyiiccl'flckel' slurmally used in the production of Number 6 fuel oil to lower the usually Pl' most msumces as has a high viscosity and produce a Pumpabhe mixture which meets the capacity for the soluble constituents of the coal and produces viscosity requirements. lfdesired,the deashed coal may be ada C03] solulion hafacterized by an unusually low Viswsilya mixed with a highly aromatic petroleum stream which is hop Typical characteristics of preferred solvent species appear in mally used in carbon black manufacture, and the mixture is Table passed to carbon black furnace 82 for the purpose of prepar- The presence of added. elemental hydrogen is not always ing carbon black therefrom. In some instances, it is possible to necessary, but it is usually beneficial and aids in more rapid prepare a mixture of a petroleum byproduct stream which is and complete solubilization and/or hydrogenation. In a connot suitable normally as a carbon black feedstock and the tinuous process, the feed may include 0.1-2 percent and deashed coal, and then feed the mixture to carbon black furpr ferably 0.25-l percent by weight of hydrogen based upon mice 2- the weight of coal. The excess hydrogen which does not enter The carbonaceous material to be solubilized may be coal, into the solubilization and/or hydrogenation reaction may be which preferably is coal of a rank lower than anthracite, such recovered from the coal solution and recycled if desired, and as subanthracite, bituminous, subbituminous, and lignite or thus higher percentages than 2 percent by weight may be used brown coal. Peat may also be used when desired, and is emsuch as up to 5 percent by weight. The hydrogen content of braced within the term coal as used herein. The particle size the vapor phase in contact with the liquid solvent phase may of the coal may vary over wide ranges, but preferably the parbe 5-50 percent and is preferably about l0-35 percent by ticles should be sufficiently small to be slurried in the solvent volume, but it may be higher or lower. However, the higher and pumped. For instance, the coal may have an average parthe partial pressure of hydrogen, the faster the solubilization ticle size of up to one-fourth inch in diameter or greater in and/or hydrogenation reaction as more hydrogen is available some instances, and as small as minus 200 mesh (Tyler in the solvent.
TABLE I I Density Mid Bureau of Viscosity cs. at 775 F. Critical Gravity, boiling UPO'K Mines correla- (saturated tempera- Typo of oil API point, F, factor tion index 130 F. 210 F. liquid g./cc.) turo" F.
f ntnlytic'crnckcr lhzhi: rncyclc oll 21.0 525 10. 6 76 2. 1 1.0 0. 53 880 (lntnlyllc orttckcr heavy recycle nil 17.0 632 10. 8 74 6. 7 2. 3 0.62 990 Catalytic crnckcr slurry 0il 2. 2 800 2 114 70 11.0 0. 74 l, 200 'lhcrmally crttckctl slurry oil 2. 3 741 9. 7 136 1 43 6. 5 0.8 1, 200 Lubricating oil aromatic extract- 16. 2 970 11.8 58 950 71 0.73 1, 230
Screen) or smaller. The most practical particle size in most in- The temperature should be sufficiently high to result in a stances is between minus 30 mesh and minus 100 mesh as less fast solvation and/or hydrogenation rate. The upper limit is energy is required to produce this particle size range and yet the temperature at which the coal and/or carbonaceous the particles are sufficiently small to achieve an optimum rate material derived therefrom is coked and/or the organic solof solvation. However, it is understood that the particle size is vent is decomposed. The temperature may be about 550-l, not of great importance provided extremely large particles are, 000 F., and preferably is at least 650 F. to 700 F. In most innot present as the solvent penetrates the coal particles ra idly stances, the temperature should be about 650-900 F., and and causes marked swelling initially, and finally solvation of for best results, about 700-850 F. The solvation temperature the potentially soluble carbonaceous constituents. 60 should not be sufficiently high to result in substantial coking The hydrocarbon solvent that is used in practicing the inwithin the period of treatment. The coking temperature varies vention is a highly aromatic petroleum byproduct stream from coal to coal, and usually coals having a higher rank also which preferably has one or more of the following additional have a higher decomposition or coking temperature. properties: Oklahoma bituminous coal usually cokes at about 800-840 Pmpmy vuluc ,5 F. and more highly volatile coals such as the Wyoming coals usually coke at lower temperatures. In instances where a tubu- AH filmy Minus 5 m P 2' lar reactor is employed and a slurry of coal in the solvent is K MW b2 w H, passed through the tubes on a continuous basis, somewhat Bum. r Min, 55 150 higher temperatures may be employed due to the dynamic na- Ctltrcltllion index ture of the system. Also, the rate of flow through the tubes is FY sufficiently fast to reduce coking on the tube surfaces. Density m 775'- F- The solvent is contacted with the coal and/or carbonaceous (rltit'ttlTemperature ti ltt"-l,1tl0"|'-. material derived therefrom for a sufficient period of time to m m, solubllize a substantial amount of the extractable material in The solvent may be a petroleum refinery byproduct stream the coal. For example. the solvent may be contacted with the coal over about 0.1-2 hours. The contact period should not be more than about 0.2-1 hour for economic reasons, and is preferably 0.25-0.5 hour.
The weight ratio of solvent to coal may vary over wide ranges. The minimum weight ratio of solvent to coal is usually about 1:1 or 2:1, and the upper limit is practical in nature and may be as high as 20:1. There is little improvement in the degree of extraction beyond solvent to coal weight ratios of :1 or :1, and as the cost of handling the solvent increases with the amount used per unit weight of coal, the lowest ratio necessary to give a desired degree of extraction is preferred. Usually, this is a solvent to coal weight ratio between about 2:1 and 5:1.
The pressure in solutizer 24 is at least sufficient to maintain liquid phase conditions and it may be as high as 10,000 pounds per square inch absolute (p.s.i.a.), and is preferably about l,0005,000 p.s.i.a. for most solvents. The pressure should be sufficient to provide a solvent density of at least 0.5 g./cc. and preferably at least 0.6 g./cc. There is no upper limit on the solvent density within the foregoing pressure range as the highest solvent density that can be achieved under practical operating conditions is usually more satisfactory. The solvents defined herein have a solvent density of about 0.5-0.9 g./cc., and preferably about 0.6-0.7 g./cc. under the practical temperature and pressure conditions.
The pressure on the system is not important in the absence of a hydrogen overpressure provided the solvent has the necessary minimum density. If the solvent density is too low, then it is necessary to resort to pressure to increase the density. Usually pressurized hydrogen is preferred as a pressurizing medium, but other gases or gaseous mixtures may be employed. Also, the pressure may be imposed by suitable hydrostatic means such as a high-pressure pump. With light catalytic cracker recycle oil and other light solvents it may be desired to increase the pressure substantially above atmospheric in order to provide a solvent density of at least 0.6 g./cc. When using light catalytic cracker recycle oil, usually the pressure should be approximately 2,000 p.s.i.g. or higher for best results. With heavier catalytic cracker recycle oil, the pressure may be 1,000 p.s.i.g. or higher. Slurry oil is substantially heavier and a pressure above atmospheric is not necessary but may be used when desired.
The coal solution produced in accordance with the invention has an exceptionally low viscosity and may be easily separated from the undissolved mineral ash, fusain and other insoluble constituents following prior art practices. For instance, it is possible to allow the coal solution to settle for a suitable period of time such as l/4-1 hour in separator 35 under the conditions of solubilization, and then withdraw the heavy phase 37 containing the undissolved material in the form of a slurry or liquid-appearing phase. It is also possible to filter the nonviscous solution very rapidly and remove the ash constituents, or the ash constituents may be separated by centrifuging.
The coal solution or solid deashed coal may be admixed with one or more petroleum refinery streams normally used in preparing fuel oil in an amount to provide about l-50 percent by weight of deashed coal therein. In most instances, it is preferred that the deashed coal be present in the resultant blend of fuel oil in an amount of 5-25 percent by weight. It is possible to prepare heavy fuel oil, such as Number 6 fuel oil from petroleum refinery streams having a substantially lower initial viscosity than required by specifications by admixing the deashed coal of the invention therewith in an amount to increase the viscosity sufficiently to meet specifications. It is also possible to admix the deashed coal with a residual fuel oil, and then adjust the viscosity of the blend by addition of heavier or lighter petroleum refinery streams which are normally used in the manufacture of fuel oil in quantities designed to meet viscosity specifications.
The deashed coal may be admixed with a highly aromatic hydrocarbon oil in an amount of at least 5 percent by weight, and the blend may be used as a feedstock to a prior art oil furnace process for producing carbon black. It is usually preferred that the blend contain about 5-50 percent by weight and for best results about 15-30 percent by weight of the deashed coal. It is not necessary to change other variants in the operating procedure as the prior art process may be followed with the exception of changing the feedstock to the above described blend. For example, the blend may be fed to prior art oil furnace processes for producing carbon black such as are disclosed in Kirk-Othmer, Encyclopedia of Chemical Technology, Second Edition, Vol. 4, pages 254-265, and in U.S. Pat. Nos. 2,292,355, 2,553,199, 2,652,313, 2,799,665, 2,825,632, 2,981,604 and 3,039,853.
The invention is further illustrated by the following specific examples.
EXAMPLE 1 This example illustrates the solvation of coal when employing the apparatus shown in FIGS. 1A and 1B of the drawings.
Dry Oklahoma bituminous coal (Stigler Seam, Evans Coal Company) having a particle size of minus 65 mesh and clarified catalytic cracker slurry oil having a boiling range of 650-950 F. are fed to mixer 11 at feed rates to provide three parts by weight of the slurry oil for each part by weight of the coal. The suspension of coal in the solvent is passed to pump 19, which develops a pressure of 1,500 p.s.i.g., via conduit 13, and then via conduit 20 to heating coil 22 in heater 21 where the temperature is raised to 750 F. Elemental hydrogen in an amount of 1.0 part by weight based upon the weight of the coal is added via conduit 26 to the suspension flowing in conduit 20.
The heated hydrogen-containing slurry is withdrawn via conduit 23, and is passed to solutizer 24 which is a tube still at a feed rate to provide a residence time of 30 minutes. A heating fluid is supplied to coil 27 to maintain a temperature of 750 F. in solutizer 24 over the 30 minutes residence time. Coal solution containing suspended micron-size particles of mineral ash, fusain and other insoluble constituents is withdrawn via conduit 31 and is passed to header 33 in ash separator 35. The header 33 is positioned below the surface 36 of sludge layer 37 whereby the micron-size particles of insoluble constituents are agglomerated as the coal solution ejected via outlets 34 passes through the sludge layer 37. The average residence time for the solution in ash separator 35 is 30 minutes, and this is sufficient time to allow substantially all of the insoluble constituents to be agglomerated and retained in the heavy sludge layer 37. The sludge layer 37 is withdrawn as a fluid phase via conduit 39 at a rate sufficient to maintain the interface 36 at the level illustrated in the drawings.
The lighter clarified phase 38 of coal solution in the upper section of ash separator 35 contains very small amounts of micron-size insoluble material, and this is removed by passing the coal solution through filter 56 via conduits 45 and 48. The clarified and filtered coal solution is withdrawn via conduit 50 and is passed via conduit 44 to heat exchanger 52 where the temperature is reduced to below the boiling point of gasoline, and the cooled solution is passed to gas separator 60 via conduit 58. The pressure in gas separator 60 is about 1 to 2 atmospheres. Excess hydrogen and gases produced during the solvation are withdrawn via conduit 63 upon opening valve 64.
During the initial portion of the run, valves 67 and 70 are closed, valves 65 and 72 are open, and the coal solution is passed to vacuum distillation tower 57 via conduits 66 and 71. Substantially all of the solvent and liquid hydrocarbons produced during the solvation step, such as anthracene oil, are removed from the coal solution in vacuum distillation tower 57, and are withdrawn via conduit 74 and introduced into fractionator 75. The desulfurized and deashed coal containing some solvent is withdrawn as a fluid phase via conduit 79 and is allowed to cool and harden into a friable solid. The light ends of the solvent fraction having a boiling point less than 650 F. are withdrawn from fractionator 75 via conduit 76,
and a purified 650-950 F. solvent fraction which is substantially free of anthracene oil and a heavy ends fraction are withdrawn via conduits 77 and 78, respectively. Make up solvent is added via conduit 80 to the recovered purified solvent flowing in conduit 77. The combined fresh solvent and purified recovered solvent is introduced into solvent storage vessel 10, where it is stored awaiting recycle in theprocess.
The coal is solubilized to an extent of approximately 85-90 percent of the potentially soluble carbonaceous matter initially present in the coal. The deashed coal withdrawn via conduit 79 contains less than 1'0 weight percent each of ash and sulfur, and it may be used as a low sulfur fuel for combustion in metropolitan centers, or it may be blended with petroleum .refinery streams to produce low-sulfur fuels. The deashed coal burns readily, and the combustion gases are very low in sulfur content.
By admixing the desulfurized deashed coal with residual fuel oil'in quantities to provide approximately percent by weight of deashed coal in the blend, and then cutting the blend with a cutter oil to arrive at the viscosity specification for Number 6 fuel oil, a heavy fuel oil blend is produced which has a substantially lower sulfur content. Thus, the deashed coal is useful in producing relatively low sulfur heavy fuel oils from petroleum refinery streams which normally are not suitable for this purpose without further treatment.
In a second portion of the run, the vacuum distillation column 57 is operated to leave sufficient heavy ends of solvent in the'deashed coal so that the product withdrawn via conduit 79 is liquid at 300 F. Approximately one-third of the recirculated solvent is retained in the coal, and approximately two- ,thirds is recovered for recycle. The blend is readily liquefiable with stream under moderate pressure and is pumpable.
in a third portion of the run, the valve 65 is closed, valve 67 is opcn, and the coal solution is withdrawn via conduit 68. The coal solution has a low sulfur content and it meets the specification for sulfur content required for fuels burned in metropolitan areas. The solution could be blended with residuum in the preparation of Number 6 fuel oil, or with distillate oils to produce lighter fuel oil.
EXAMPLE II This example illustrates the preparation of carbon black from a blend of deashed coal and a highly aromatic petroleum byproduct stream.
The general procedure of Example I is followed with the exception of closing valves 67 and 72, opening valves 65 and 70, and passing the coal solution in the slurry oil to carbon black furnace 82. Air is also introduced into carbon black furnace 82 in an amount to assure partial combustion of the coal solution. The blend of deashed coal and slurry oil is partially combusted in the restricted air supply to thereby produce carbon black in a yield which is significantly higher than is obtainable from a similar weight of the slurry oil alone. Thus, the presence of the deashed coal increases the Bureau of Mines correlation index of the slurry oil very substantially, and also increases the efficiency of the oil furnace process for producing carbon black as the output is much greater. Comparable results are obtained with a feedstock containing 20 percent by weight of the deashed coal withdrawn via conduit 79 in Example l in slurry oil.
1. A process for deashing coal comprisingintimately contacting the coal in particulate form with a highly aromatic hydrocarbon petroleum refinery byproduct stream as a solvent selected from the group consisting of catalytic cracker recycle stocks, thermally cracked stocks and lubricating oil aromatic extracts to produce a solution containing solubilized coal and suspended insoluble material including ash, the said hydrocarbon solvent being contacted with the coal at a temperature of about 550-l,000 F. and a solvent density of at least 0.5 gram per cc. whereby the coal is solubilized herein, the hydrocarbon solvent consisting essentially of polycyclic hydrocarbons having normal boiling points of about 425-l, 000 F. and at least two condensed benzene rings, and separating the insoluble material from the solution of solubilized coal.
2. The process of claim 1 wherein said hydrocarbon solvent is contacted with the coal in the presence of elemental hydrogen.
3. The process of claim 1 wherein each part by weight of the coal is contacted with about 22O parts by weight of the said hydrocarbon solvent.
4. The process of claim I wherein the coal is contacted with the said hydrocarbon solvent at a temperature of at least 650 F.
5. The process of claim 1 wherein said hydrocarbon solvent is catalytic cracker slurry oil.
6. The process of claim 1 wherein each part by weight of the coal is contacted with said hydrocarbon solvent in the presence of elemental hydrogen at a temperature of at least 650 F. with about 2-20 parts by weight of said hydrocarbon solvent for about 0.1-2 hours.
7. The process of claim 6 wherein said hydrocarbon solvent is catalytic cracker slurry oil.
8. The process of claim 7 wherein each part by weight of the coal is contacted with about 2-5 parts by weight of the catalytic cracker slurry oil in the presence of elemental hydrogen at a temperature of about 700-850 F. and the solvent density is at least 0.6 gram per cc.
9. The process of claim 1 wherein fuel oil is produced by admixing at least a portion of the solution of solubilized coal having insoluble material separated therefrom with at least one petroleum refinery stream.
10. The process of claim 1 wherein a solvent fraction is recovered from the solution of solubilized coal having insoluble material separated therefrom by distillation under vacuum. and the recovered solvent is recycled in the process.
11. The process of claim 10 wherein the recovered solvent contains hydrocarbons produced during the coal solubilization, and the recovered solvent is further fractionated to produce a purified solvent fraction which is recycled in the process.
12. The process of claim 10 wherein about 50-90 percent of the light ends of the solvent are recovered.
13. The process of claim 12 wherein sufficient heavy ends of the solvent are allowed to remain in the solubilized coal having insoluble material separated therefrom whereby the mixture ofsolvent and solubilized coal is fluid at about 300 F.
14. The process of claim 1 wherein the insoluble material is separated from the solution of solubilized coal by settling to produce a deashed coal solution.
15. The process of claim 14 wherein the solution of solubilized coal containing insoluble material is introduced into a body of a relatively heavy slurry comprising settled insoluble material.
16. The process of claim 14 wherein the coal and solvent are continuously introduced into a contacting zone and contacted therein to produce the solution of solubilized coal containing insoluble material, a stream of the coal solution is continuously withdrawn from the contacting zone and introduced into a settling zone where the insoluble material is settled therefrom as a heavy slurry phase, the slurry containing insoluble material is withdrawn as a heavy phase from the settling zone at a rate to maintain a body of the slurry in the bottom thereof, the solution of solubilized coal having insoluble material separated therefrom is continuously withdrawn as a light phase from the settling zone and is introduced into a vacuum distillation zone, solvent is continuously recovered from the solution of solubilized coal by vacuum distillation in the vacuum distillation zone and is withdrawn therefrom and recycled to said contacting zone where it is contacted with ad- Y ditional coal, and deashed solubilized coal containing solvent in an amount to flux the same is withdrawn from the vacuum distillation zone.
17. The process of claim 16 wherein about 50-90 percent of the light ends of the solvent are recovered from the solution of