US3152063A - Hydrogenation of coal - Google Patents

Description

Oct. 6, 1964 Filed April COAL CATALYST SOLUTION DRYER GRINDER GCKEE/V HEATER (UMP/8555012 W. C. SCHROEDER ETAL HYDROGENATION 0F 7 COAL CML-HYDPOG'EN FEEDER 2 Sheets-Sheet 1 CA TALYZE'D c041. & HYDROGEN $522 %&

HOT (50555 D Z 52 x 54 i 56 T i mom If a 55 ASH REACTOR CONOENSEE 5 m STORAGE 0E FELGE ugu/o PRODUCT INVENTORS M ATTOENEYS w. c. SCHROEDER ETAL 3, 52,063

Oct. 6, 1964 HYDROGENATION F COAL 2 Sheets-Sheet 2 Filed April 21, 1961 ram K uaulo 6445 RESIDENCE TIME 6550.) can 0 0 w m m 0 0 w m m .Rxm QEQEQ 32$ RQBQQES 55% k m 23% W MWNK EPEE/ V M T W oam mm Y 0C m w 5 a. M Z w W M M m w W6 m w v w wm w I0 20 a0 40 ans RESIDENCE TIME (sea) CONVERSION v5. 77ME 2000 -600C 6A5 RESIDENCE TIME (sec) COM/E HTTOE/VEYS United States Patent 3,152,063 HYDRGGENATION 0F CGAL Wilhurn C. Schroeder, College Park, Md, Lawrence G.

Stevemon, Merriam, Kuhn, and Thomas G. Stephenson, El Paso, Tern, assignors to Fossil Fuels, Inc, a corporation of Delaware Filed Apr. 21, 1961, Ser. No. 104,742 11 Claims. .(Cl. 208-) This invention provides for the production of liquid and gaseous hydrocarbons by the rapid and direct hydrogenation of dry pulverized coal, lignite or char, in the absence of pasting oil, at relatively low pressures, at temperatures below 600 C. and with very short contact times between the pulverized coal and hydrogen. The reaction conditions are much less severe than previously required for coal hydrogenation processes and the process can be performed with fewer process steps and in simplified equipment.

The production of synthetic fuels by the hydrogenation of coal has been extensively investigated and a great many processing schemes and variations of processing conditions have been proposed. Many of these processes require more than one hydrogenation stage to produce use ful liquid fractions. Substantially all require the use of a recycled pasting oil for initial admixture with the coal particles to provide a pumpable mass. In this procedure the useful liquid fraction is actually produced from the pasting oil, the coal being converted to heavy oil for use in recycling. Thus, the operation although it may use only one hydrogenation reactor, is essentially a two-stage hydrogenation.

For example, in the Bergius process, which has been operated commercially, the coal to be hydrogenated was crushed, mired with heavy oil produced in the process to form a slurry or paste, a catalyst such as a compound of tin, molybdenum or iron was added and the resulting mixture was then pumped to a pressure in the range of 3,000 to 10,000 p.s.i.g., and put through a preheater along with the hydrogen gas at this same pressure, where the tempera ture was raised into the range of 460480 C. From the preheater the mixture of coal, heavy oil, catalyst and hydrogen flowed into a large vessel called a hydrogenation converter, where the mixture was allowed to soak at temperatures around 480 C. for period ranging from 15 minutes to over an hour to complete the hydrogenation reactions. Additional high pressure hydrogen was introduced into the mixture in the converter to provide the hydrogen needed, to agitate the reacting mass and to control the temperature.

This process and others of a similar nature incorporates many difiicult and unavoidable steps which have prevented coal hydrogenation from becoming an economic process, either in Europe or in the United States, since World War 11. One of the most difiicult of these steps involves the mixing, pumping, and handling of the pulverized coal and pasting oil. This requires agitating the coal and oil together to secure intimate dispersion. Usually this has to be done hot or the oil is too viscous to secure the intimate mixing necessary.

A second problem concerns pumping the paste into the high pressure system. After the coal is dispersed in the oil, the mixture is of the consistency of a heavy tar, containing particles of solid coal and ash. To make it possible to pump the mixture at all it must be hot. Even so wear on pistons, valves and packing glands is severe and the pumps must be slow acting. This means a large number of pumps is necessary to handle any quantity of liquid. Maintenance problems are continuous and severe.

From the pumps the paste must go to the preheater and then to the reactor. It is difiicult to get the hydrogen gas to disperse through the oil-coal mixture in the reac- 3,15Zfih3 Patented Get. 6, 1904 tor. The gas tends to form large bubbles which rise quickly through the oil without efiectively contacting the coal particles. Mechanically agitated reactors or tubular reactors have been suggested to overcome this difficulty. However, the use of such reactors does not permit a decrease in pressure and the reactors are costly to build for the high pressure system involved.

It is also evident that the oil which is carrying the coal is using up valuable reaction space which might much better be used for the hydrogenation of coal. Since the oil is more than 50 percent by weight of the material being charged to the reactor, this is an important item. Under normal conditions the feed to the reactor is 40% coal and 60% heavy recycle oil, so that less than half of the reactor space is being effectively used to hydrogenate coal.

Hydrogenation of dry coal by fluidization procedure at lower pressures has been proposed, but requires a substantial residence time of the coal in a fluidized reactor and produces a substantial amount of char from the coal. It is not a complete answer to the hydrogenation problems.

It is the general object of this invention to provide a process for the hydrogenation of coal which will eliminate or substantially reduce many of the problems encountered in the earlier processes.

Another object of the invention is to provide a coal hydrogenation process which may be accomplished with fewer steps and with much simpler equipment than previously required, thereby providing a much more economical operation.

A further object of the invention is to provide a process for substantially complete conversion of dry powdered coal to hydrocarbon liquids and gases in a short period of time, at low pressure, and on a continuous basis.

Another object of the invention is to provide a process for the rapid and continuous hydrogenation of coal wherein temperature and contact times may be selected to provide a. high yield of liquid hydrocarbons with respect to gaseous carbons.

A further object of the invention is to provide a process for the hydrogenation of coal without the use of pasting oil and at relatively low pressures and wherein the temperature may be selected to provide either a high proportion of liquid to gaseous hydrocarbon products or to provide substantially all gas.

A still further object of the invention is to provide a hydrogenation process utilizing dry powdered coal wherein tars produced in the initial hydrogenation are substantially immediately converted into lighter oils or gaseous products without removal from the hydrogenation reactor.

These and other objects and advantages of the invention, and the means by which they are accomplished, will be further understood from the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a flow sheet illustrating diagrammatically the process of the invention;

FIG. 2 is a diagrammatic illustration of a modified form of reactor that can be used in the system shown in FIG. 1;

FIG. 3 is a graph showing the effect of gas residence time upon the conversion of the coal to liquids, gas and tar at a pressure of 2000 p.s.i.g. and a temperature of 500 C.;

FIG. 4 is a graph similar to that of FIG. 3 showing conversion versus time at a pressure of 6000 p.s.i.g. and a temperature of 500 C.; and

FIG. 5 is a graph similar to those of FIGS. 3 and 4, showing conversion versus time at a pressure of 2000 p.s.i.g. and at a temperature of 600 C.

The process of the invention, in general, comprises dispersing pulverized and catalyzed coal, in the absence of a pasting oil, in hydrogen under a pressure of about 500 to 4000 p.s.i.g., reacting the mixture of coal and hydrogen at a temperature in the range of about 450 to 600 C. for a gas residence time of less than about 200 seconds (preferably less than one minute), cooling the reaction products and recovering liquid and gas hydrocarbon products therefrom.

Referring now to FIG. 1 of the drawings, operation of the process is described as follows:

Coal from any suitable source, preferably ground to approximately 70% through 200 mesh, is catalyzed by slurrying or spraying with an ammonium molybdate solution or with a solution of any other suitable catalyst followed by drying in a dryer 10. The dried catalyzed coal is reground in grinder 12 and is then screened on screen 14 to elimiate lumps. The dry, pulverized and catalyzed coal is then charged to a coal hopper 16 which is capable of being closed and pressurized. This hopper may be provided with a low-speed agitator (diagrammatically shown at 18) to prevent bridging of the coal. After the hopper has been filled it is closed. by suitable means (not shown), and the unit is brought up to full operating pressure by the introduction of hydrogen through line 20 from the compressor 22. The hydrogen may be supplied from any suitable source e.g., it may be produced in the plant or shipped in by tank truck or other means. If desired, it may be preheated to a temperature below that at which it will react with the coal by. passing all or a portion thereof through a suitable heater 24. The hydrogen line 20 is connected to the coal hopper 16 and also to the end of a feed screw 26, which as shown is an integral part of the bottom of the coal hopper 16. The feed screw feeds coal in a horizontal direction from the bottom of the hopper 16. to the top of a tubular reactor 28. The feed screw is driven by a variable speed transmission (not shown) through a stuffing box at the end of the screw opposite the discharge end.

Hydrogen pressure in the coal hopper is equalized with that in the feeder and in the reactor. The hydrogen introduced at the end of the screw feeder 26 sweeps the coal particles from the screw feeder into the top of the reactor 28. A plurality of hoppers and feeders may be connected to the top of the reactor to provide continuous operation, one being on cycle while another is being filled. It will be understood that the coal-feeding arrangement illustrated is merely one of any number of suitable devices that could be used. An improved device which eliminates the use of mechanical agitators, feed screws and stuffing boxes is disclosed in copending application Ser. No. 769,380, filed May 11, 1959, entitled Methods and Apparatus for Feeding Finely Divided Solids.

The reactor 28, as illustrated, is in the form of an elongated, vertical tube. Tubular reactors 8 feet long of stainless steel and having inside diameters of 0.625 and 1.116 have been satisfactorily used in extensive test runs. It will be understood, however, that commercial apparatus may employ other types of reactors including those containing a multiplicity of tubes surrounded by a heating medium, and that the flow through the reactor may be either downward or upward, depending upon the design of the particular reactor and the velocity of flow of the. suspension of coal and hydrogen therethrough. However, downward flow of coal and hydrogen as shown in FIG. 1 has been found most satisfactory.

The reactor 28, as shown in FIG. 1', may be selectively heated at different zones thereof to any desired temperature up to 800 C. by means of a series of separately controlled electric heaters 30, which receive their power from associated transformers.

From the reactor 28 the reaction products enter a catch pot 32 where heavy tars, ash and/or unreacted solids are deposited. The catch pot may be suitably cooled by introduction of cooling fluids such as air or water, into the jacket, as shown. The tar and ash from the catch pot may be sent to a further hydrogenator, if desired, whereby the tar is converted to light liquid and gaseous products, and catalyst is recovered from the ash. The gaseous products and the lighter, uncondensed liquid products pass through the catch pot and into a condenser 34. Light oils condensed at this point are collected in a trap 36 and form one of the products of the hydrogenation reaction. The trap 36 may be cooled by any suitable means. The noncondensable gases pass through a let-down valve 38 into suitable collecting tanks or are passed into other portions of the plant for reuse.

It will be understood that the coal hopper, coal feeder, reactor, catch pot, condenser and all connecting equipment are designed to withstand the pressures of the system.

The reactor tube as depicted in FIGURE 1 may, if desired, be used largely for the preheater and the actual hydrogenation reactions may all take place or be completed in a chamber at the bottom of the tube, the temperature in such chamber being in the range of 450 C. to 600 C. It has been found further that the mixture of coal and hydrogen may be taken out of the tube at temperatures in the range between 300 and 450 C. and introduced into the further chamber and that the exothermic heat of the coal hydrogenation reactions will then raise the temperature in the chamber to the range between 480 and 600 C. By properly controlling the tempcrature of the incoming stream of coal and hydrogen containing gases, it has been found possible to maintain the desired temperature in the reaction chamber Without introducing other cooling means.

At temperatures in the range from 480 to 600 C. the products are tar, oils and gases. If an attempt is made to further hydrogenate the tars and heavy oils to lighter oils, either by extending the time of hydrogenation in the reaction vessel or by removing all these products to a separate vessel, it was found that the existing light oils were hydrogenated to less valuable gases, While the heavier oils and tars were being hydrogenated to lighter oils. In other words, it is imperative that once the light oils are formed, they must be prevented from undergoing further hydrogenation if they are to be preserved as light oils. A preferred way to do this is to quickly remove them to a lower temperature region. The tars on the other hand need further hydrogenation to be converted to lighter oils.

At pressures in the range from 500 to 4,000 p.s.i.g. and temperatures from 480 to 600 C. the tars and heavy oils from the hydrogenation of coal exists as liquids and they will collect as liquids in the chamber 32 at the bottom of the heating tube (FIGURE 1). Lighter oils exist as vapors under these conditions and are carried off with the outlet gases, where they may be cooled and the hydrogenation reactions stopped.

The tars and heavy oils in the tar collection chamber contains most of the ash and unreacted coal from the process. Most of the catalyst also accumulates in this mixture. By passing fresh hydrogen into the mixture at pressures from 500 to 3,000 p.s.i.g. and from 480 to 600 C. experiments have demonstrated that the tar can be further hydrogenated to volatile oils and gases. which pass out, leaving the solid material behind. This is a. simple method of separating the tar from solids and at the same time converts the tar to more valuable products. It eliminates the need for centrifuging, steam distillation and coking to separate heavy oils and tar from ash and unreacted coal.

A modified type of reactor whereby the tars can be hydrogenated without hydrogenating the light liquids already formed is shown in FIGURE 2. The reaction vessel is a cylinder 40 constructed as shown. Coal and hydrogen containing gases are brought into the top of this cylinder through inlet 42 and pass through a conical shaped section 44 with holes 46 in it, the holes 46 being arranged in such a manner as to distribute the coal and gases into preheating tubes 48 as uniformly as possible. The preheating tubes 48 are designed to withstand the operating pressure of the system. Hot gases introduced through inlet 50 are circulated around these tubes to supply the heat to the coal and gases passing through them. The hot gas may be provided from any suitable furnace burning coal, oil, gas or other fuel.

The mixture of coal and hydrogen containing gases is preheated sufficiently to emerge from the preheat tubes 48 at preferred temperatrues up to about 480 C. This mixture then enters reaction zone 52 Where the temperatures are between 480 and 600 C., staying in this zone for periods not to exceed 30 seconds. Vaporized oil and gas products as well as unused hydrogen are drawn oil through outlet 54 and quickly cooled. The oil and gases can then be separated by well known means. The oils are refined to gasoline and aromatic chemicals.

Heavier oil and tar products collect below the reaction zone to a level, for example, as shown at 5d. Pres hydrogen (preheated or cold as needed to control the temperature) is introduced through inlet 53 and distributor 60 to further hydrogenate the heavier oil and tars. The vaporized oils and gaseous products from this hydrogenation join the other products leaving the reaction zone by outlet 54. Remaining solids containing ash, unreacted coal and catalyst are Withdrawn from the bottom of the reaction zone through discharge outlet 62.

The hydrogenation catalyst may be selected from any of those known to the art. Thus, materials having a hydrogenating reaction such as tungsten or molybdenum oxides or sulphides, tin or iron group metals such as iron, nickel, cobalt and/ or their compounds may be utilized. The coal is preferably impregnated with catalyst in the form of a solution of a soluble salt or complex. A water solution of ammonium molybdate has been found quite suitable. From 0.5 to 1.0% catalyst is usually employed, the presence of catalyst having been found to have a marked effect upon conversion of the coal, particularly at temperatures below 600 C. Thus, at 2,000 p.s.i.g., 500 C. and 35 seconds gas residence time only 6% of the coal is converted to tar plus liquid and the total conversion is only 22%; with /2 molybdenum catalyst the conversion to tar plus liquid is 31% with 76% total conversion, and with 1% molybdenum catalyst the conversion to tar plus liquid is 50% with 100% total conversion.

Coals from different sources show some variations in conversion percentages but, in general, the maximum conversions are obtained under substantially the same conditions for all coals. Increased coal particle size decreases the conversion of the coal to liquids and tars and increases gas make but seems to have very little effect on total conversion.

As aforestated, the temperature utilized in carrying out the hydrogenation reaction may be selected from the range of 450 to 600 C. The exact temperature selected depends upon the nature of the products desired and to some extent upon the other conditions utilized in the reaction. With all other conditions remaining constant, variations in temperature have a significant effect upon the product distribution to solids, tars, liquids, and gases, and upon the reaction rates. An increased temperature increases the reaction rate and the conversion to gas. Substantially complete conversion of the coal is reached with shorter residence times as the temperature is increased. At temperatures below 600 C. and with suitable residence times over 50% of the coal may be converted to liquids and tars with the balance being converted to gas. At temperatures above about 600 C. with excess hydrogen as employed in the present process, over 90% of the coal may be converted to a gaseous product. While temperatures in the 450-600 C. range may be used, the temperature range most favorable for the production of a high proportion of liquids and tars is between approximately 475 C. and 525 C. On the other hand, the reaction temperature most favorable to production of gaseous products is between approximately 650 C. and 700 C. Lower temperatures, in general, require longer gas residence times for complete conversion of the coal. At a temperature of approximately 500 C. and a pressure of 2,000 p.s.i.g., a gas residence time of about 22 seconds provides a maximum yield of liquid products at complete conversion. At a temperature of 450 C., residence time would have to be increased to approximately 200 seconds, in order to obtain complete conversion. Above about 490 C. residence times of less than one minute can be used.

The exact pressure selected from the range specified depends to some extent upon the other conditions of the reaction. However, it is preferred to keep the pressure as low as possible. At lower pressures and temperatures it may be desirable to use slightly longer gas residence times in order to secure 100% conversion of the coal. However, it has been found that pressures as low as 500 p.s.i.g. provide almost as good conversion to light liquid products as do pressures at 6,000 p.s.i.g. The maximum conversion to light liquids is believed to be eiiected at about 1,500 to 3,000 p.s.i.g. However, the advantages to be realized in the use of low pressure makes the use of pressure down to 500 p.s.i.g. quite satisfactory.

While a nange for gas residence time of up to 200 seconds has been specified, it should be realized that in most instances much shorter residence times would be employed. Thus, for each condition of temperature and pressure, it has been found that a rather limited range for gas residence time provides a maximum conversion of the coal into liquid products. This is illustrated in FIG. 3. Thus, at a pressure of 2,000 p.s.i.g. and a temperature of 500 C., it will be observed that approximately total conversion of the coal took place in about 20 seconds, and that good conversion to liquids and tars occurred between about 20 to 30 seconds, the maximum conversion of these products being at aoout 22 seconds wherein about 30% liquid, 40% tar and 30% gas was produced. At the gas residence time at reaction temperatures increased, gas was produced at the expense of liquids and tars.

It will be seen from FIGURE 4 that increase in pressure to 6,000 pounds per square inch has slightly lowered the gas residence time necessary to produce maximum quantities of liquids and tars. Thus, better than 90% total conversion of the coal occurs within about 15 seconds at this pressure and maximum production of liquid is also obtained at approximately such residence time. However, the proportion or" liquid to gaseous products at the maximum value is less with the higher pressure. Therefore, it is indicated that lower pressures are desirable for maximum production of liquid products, as well as being considerably more desirable from the standpoint of equipment and economy.

in FlGURE 5, it will be observed that the same peaks at short residence time occur for maximum production of liquids and tars with respect to gas at higher temperature. Thus, at 600 C. maximum conversion to liquid appears at about 18 seconds. However, the proportion of liquid to gas decreases rapidly as the temperature is raised.

The ratio of hydrogen to coal in the process described in the present application is maintained in excess of that which would be required to completely convert all of the coal to the products desired. This excess of hydrogen insures that each particle of coal is surrounded with a substantial partial pressure of hydrogen throughout the entire course of the reaction even though other gases and reaction products are being formed. The process described in copending application Ser. No. 720,684, filed March 11, 1958, by one of the co-inventors involves hydrogenation at temperatures of 600 C. or higher, utilizing a limited amount of hydrogen in order to enhance the production of liquid products. The present invention pro- Vides a process wherein liquid products may be obtained by means of use of lower temperatures and with excess hydrogen.

The residence times given herein have been calculated on the basis of gas flow through the reactor starting with an unheated mixture of coal and hydrogen. Since no reaction takes place at temperatures below 425450 C. the upper part of the reactor is simply a zone in which preheating of the coal-hydrogen mixture takes place. The actual time in which the coal particles are in the temperature range at which the reaction is taking place is therefore less than the residence time specified. At the 475 -525 C. range, for example, the actual time at temperature is estimated to be approximately one-half the total gas residence time specified.

It is clearly apparent from the foregoing that the residence times are or" a completely difierent order of magnitude than those disclosed in previous processes. Complete conversion of the coal is accomplished in a matter of seconds in contrast to 15 to 60 minutes previously required.

The invention will be further illustrated by the following examples of practice, all based on the use of apparatus of the type shown in FIGURE 1:

Example 1 The coal hydrogenation unit feed hopper was charged with 6810 g. of bituminous coal, which has been ground to allow 70% to pass through a 200-mesh screen and to which 1% by weight of molybdenum had been added as an aqueous ammonium molybdate solution, and which had been dried and rescreened. The reaction zone of the 1.16" I.D. reactor was heated to 500 C. The system was purged and pressurized with hydrogen to 2,000 p.s.i.g.; and the hydrogen flow rate was adjusted to 3.9 s.c.f.m., resulting in a calculated residence time of 29 seconds. The dry, catalyzed coal was fed to the reaction zone at the rate of 418 g./hr. or 18.5 lbs./hr./ft. of reactor volume for a period of ten hours. The reactor temperatures during the operating period were 262 C. at the reactor inlet, 502 C. one-fourth of the way through the reactor, 501 C. one-half way through the reactor, 502 C. three-fourths of the way through the reactor, and 501 C. at the reactor exit.

A total of 4,267 g. of coal were fed during the ten hour period. Conversions were calculated on the basis of carbon content of the feed stock and products. On that basis, unhydrogenated material constituted 7.6% of the charge; tars and heavy liquids constituted 26%; light liquid 29%; and gas 37.3

Gas analysis was as follows (hydrogen free basis):

Percent Methane 50 Ethane 33 Propane l3 n-Butane 3 Example 2 To the feed hopper of the coal hydrogenation unit were charged 6810 g. of bituminous coal which had been ground to allow 70% to pass through a 200-mesh screen, which 1% by weight of molybdenum had been added to as an aqueous ammonium molybdate solution, and which had been dried and rescreened. The 0.62" 1D. reactor was heated to 450 C. in the reaction zone. The systern was purged and pressurized with hydrogen to 6,000 p.s.i.g., and the hydrogen flow rate was adjusted to 1.2 s.c.f.m., resulting in a residence time of 193 seconds. The dry, catalyzed coal was fed to the reaction zone at the rate of 144 g./hr. or 19 1bs.-/hr./ft. of reactor volume for a period of 4 /2 hrs. The reactor temperatures during the operating period were 234 C. at the reactor inlet, 452 C. one-fourth of the way through the reactor, 456 C. one-half way through the reactor, 453 C. three-fourths of the way through, and 450 C. at the reactor exit.

A total of 644 g. of coal were fed during the 4 /2 hr. period. No coal passed through the reactor unconverted. Conversions were calculated on the carbon content of the feedstock and the products formed. On that basis, 22 Wt. percent of the feedstock was converted to tars and heavy liquids; 38.3% was converted to light liquids; and 39.6% was converted to hydrocarbon gases. A sample of gas taken near the end of the experiment analyzed, on a hydrogen free basis: 20% CH 50% C2H6 and CgHg.

Example 3 To the feed hopper of the coal hydrogenation unit were charged 6810 grams of bituminous coal which had been ground to allow to pass through a 200 mesh screen, which 1% by weight of molybdenum had been added to as an aqueous ammonium molybdate solution, and which had been dried and rescreened. The 0.62 inch I.D. reactor was heated to 475 C. in the reaction zone. The system was purged and pressurized with hydrogen to 6,000 p.s.i.g.; and the hydrogen flow rate was adjusted to 2.1 s.c.f.m., resulting in a residence time of seconds. The dry, catalyzed coal was fed to the reaction Zone at the rate of 125 g./hr. or 16.5 lb./hr./ft. of reactor volume for a period of 6% hours. The reactor temperatures during the operating period were 265 C. at the reactor inlet, 485 C. A of the way through the reactor, 475 C. /2 way through the reactor, 475 C. way through, and 475 C. at the reactor exit.

A total of 769 grams of coal were fed during the 6% hour period. No coal passed through the reactor unconverted. Conversions were calculated on the carbon content of the feed stock and the products formed. On that basis, 27 weight percent of the feed stock was converted to tars and heavy liquids; 29.8 percent was converted to light liquids; and 43.1 percent was converted to hydrocarbon gases. A sample of gas taken near the end of the experiment analyzed, on a hydrogen-free basis: 43 mole percent CH and 57 percent C H Example 4 To the feed hopper of the coal hydrogenation unit were charged 6810 grams of bituminous coal which had been ground to allow 70% to pass through a 200 mesh screen, which 1% by weight of molybdenum had been added to as an aqueous ammonium molybdate solution, and which had been dried and rescreened. The 0.62 inch I.D. reactor was heated to 500 C. in the reaction zone. The system was purged and pressurized with hydrogen to 500 p.s.i.g.; and the hydrogen fiow rate was adjusted to 0.215 s.c.f.m., resulting in a residence time of 64 seconds. The dry, catalyzed coal was fed into the reaction zone at the rate of g./hr. or 14.5 lb./hr./ft. of reactor volume for a period of 3 hours. The reactor temperatures during the operating period were 360 C. at the reactor inlet, 500 C. A of the way through the reactor, 500 C. /2 way through the reactor, 505 C. of the way through, and 500 C. at the reactor exit.

A total of 323 grams of coal were fed during the three hour period. No coal passed through the reactor unconverted. Conversions were calculated on the carbon contents of the feed stock and the products formed. On that basis 15.5 weight percent of the feed stock was converted to tars and heavy liquids; 30.7 percent was con- 9 verted to light liquids; and 53.6 percent was converted to hydrocarbon gases. A sample of gas taken near the end of the experiment analyzed, on a hydrogen-free basis: 73 mole percent CH and 23 percent C H Example To the feed hopper of the coal hydrogenation unit were charged 6810 grams of bituminous coal which had been ground to allow 70% to pass through a 200 mesh screen, which 1% by weight of molybdenum had been added to as an aqueous ammonium molybdate solution, and which had been dried and rescreened. The 0.62 inch 1.1). reactor was heated to 500 C. in the reaction zone. The system was purged and pressurized with hydrogen to 4,000 p.s.i.g.; and the hydrogen flow rate was adjusted to 3.1 s.c.f.m., resulting in a residence time of 35.7 seconds. The dry, catalyzed coal was fed to the reaction zone at the rate of 134 g./hr. or 17.7 lb./hr./ft. of reactor volume for a period of 7 /4 hours. The reactor temperatures during the operating period were 300 C. at the reactor inlet, 515 C. A; of the way through the reactor, 505 C. /4 of the way through, and 510 C. at the reactor exit.

A total of 972 grams of coal were fed during the 7% hour period. No coal passed through the reactor unconverted. Conversions were calculated on the carbon contents of the feed stock and the products formed. On that basis, 29.4 weight percent of the feed stock was converted to tars and heavy liquids; 23.9 percent was converted to light liquids; and 46.7 percent was converted to hydrocarbon gases. A sample of gas taken near the end of the experiment analyzed, on a hydrogen-free basis: 60 mole percent methane, 25 percent ethane, and 15 percent propane.

Example 6 To the feed hopper of the coal hydrogenation unit were charged 6810 grams of bituminous coal which had been ground to allow 70% to pass through a 200 mesh screen, which 1% by weight of molybdenum had been added to as an aqueous ammonium molybdate solution, and which had been dried and rescreened. The 0.62 inch 1.1). reactor was heated to 500 C. in the reaction zone. To shorten the residue time without changing the flow rate through the reactor, for this experiment, the reaction zone was decreased to 4 ft. in length from 8 ft. in length. The system was purged and pressurized with hydrogen to 6,000 p.s.i.g.; and the hydrogen flow rate was adjusted to 3.3 s.c.f.m., resulting in a residence time of 24.4 seconds. The dry, catalyzed coal was fed to the reaction zone at the rate of 136 g./hr. or 36 lb./hr./ft. of reactor volume for a period of 3 /3 hours. The reactor temperatures during the operating period were 245 C. at the reactor inlet, 510 C. /2 way through the reactor, and 505 C. at the reactor exit.

A total of 500 grams of coal were fed to the reaction zone during the 3 /3 hour period. Only 1.3% of the coal passed through the reactor unconverted. Conversions were calculated on the carbon contents of the feed stock and the products formed. On that basis, 30.9 weight percent of the feed stock was converted to tars and heavy liquids; 18.8% was converted to light liquids; and 49% was converted to hydrocarbon gases. A sample of gas taken near the end of the experiment was determined to be methane.

Example 7 To the feed hopper of the coal hydrogenation unit were charged 6810 grams of bituminous coal which had been ground to allow 70% to pass through a 200 mesh screen, which 1% by weight of molybdenum had been added to as an aqueous ammonium molybdate solution, and which had been dried and rescreened. The 0.62 inch I.D. reactor was heated to 550 C. in the reaction zone. The system was purged and pressurized with hydrogen to 2,000 p.s.i.g.; and the hydrogen flow rate was adjusted to 2.51 s.c.f.m., resulting in a residence time of 20.4 seconds. The dry, catalyzed coal was fed to the reaction zone at the rate of g./hr. or 15 lb./hr./ft. of reactor volume for a period of 9% hours. The reactor tem peratures during the operation period were 280 C. at the reactor inlet, 555 C. A of the way through the reactor, 550 C. /2 way through the reactor, 550 C. A of the way through, and 550 C. at the reactor exit.

A total of 1176 grams of coal were fed during the 8% period. No coal passed through the reactor unconverted. Conversions were calculated on the carbon contents of the feed stock and the products formed. On that basis, 24 weight percent of the feed stock was converted to tars and heavy liquids; 20 percent was converted to light liquids; and 56 percent was converted to hydrocarbon gases. An analysis of a gas sample taken near the end of the experiment indicated that methane was the only hydrocarbon gas present.

Example 8 To the feed hopper of the coal hydrogenation unit were charged 6810 grams of bituminous coal which had been ground to allow 70% to pass through a 200 mesh screen, which 1% by weight of molybdenum had been added to as an aqueous ammonium molybdate solution, and which had been dried and rescreened. The 0.62 inch I.D. reactor was heated to 600 C. in the reaction zone. In order to shorten the reaction time without decreasing the flow rate through the reaction system, the reaction zone was decreased to 6 ft. from 8 ft. for this experiment. The system was purged and pressurized with hydrogen to 2,000 p.s.i.g.; and the hydrogen flow rate was adjusted to 2.8 s.c.f.m., resulting in a residence time of 12.9 seconds. The dry, catalyzed coal was fed to the reaction zone at the rate of 139 g./hr. or 24.5 lb./hr./ft. of reactor volume for a period of 4 /2 hours. The reactor temperatures during the operating period were 140 C. at the reactor inlet, 605 C. /3 of the way through the reactor, 605 C. of the way through the reactor, and 600 C. at the reactor exit.

A total of 615 grams of coal were fed during the 4 /2 hour period. Only 3% of the coal passed through the reactor unconverted. Conversions were calculated on the carbon contents of the feed stock and the products formed. On that basis, 11 weight percent of the feed stock was converted to tars and heavy liquids; 11 percent was converted to light liquids; and 75 percent was converted to hydrocarbon gases. A sample of gas taken near the end of the experiment analyzed, on a hydrogen-free basis: 45 mole percent methane, 33 percent ethane, and 22 percent propane.

In the foregoing description and in the claims the term tar refers to the carbonaceous portion of the hydrogenation product which is soluble in benzene and boils above 250 C. at 20 mm. of Hg. The term liquid refers to the carbonaceous portion of the hydrogenation product that is not volatile at atmospheric temperature and pressure and which boils up to 250 C. at 20 mm. of Hg. The term gas refers to the carbonaceous portion of the hydrogenation product that is normally in the form of a vapor at atmospheric temperature and pressure.

As a result of the present invention it is now possible to greatly simplify the entire coal hydrogenation operation. This leads directly to greatly lowered capital and operating costs for the plant as Well as much lower costs for the product. Specific items included in the invention are: reaction times which are in the range of a few seconds in the high temperature zone, relatively low pressures in the range of 500 to 3,000 p.s.i.g., separation of gas and vaporized liquid products from heavier oils and tars during and immediately after the hydrogenation step so that they later can be further hydrogenated and separated from the ash and unreacted coal, and passage of only coal and hydrogen (with catalyst, if desired) through the reactor, without using reaction space for oil, tar or other vehicle to carry the coal.

It is evident that the various features of the invention can be applied in several ways to hydrogenation processes for coal to greatly simplify the equipment, as well as its operation.

We claim:

1. A process for the hydrogenation of coal, comprising: dispersing pulverized coal containing a hydrogenation catalyst, in the absence of a pasting oil, in hydrogen under a hydrogen pressure of about 500 to 6000 p.s.i.g., reacting the mixture of coal and hydrogen at a temperature above about 450 C. but below 600 C. for a gas residence time of less than about 200 seconds, and with no increase in temperature substantially immediately cooling the reaction products, and recovering liquid and. gaseous hydrocarbon products therefrom.

2. The process of claim 1 wherein the hydrogen pressure is in the range of 500 to 4000 p.s.i.g., and the temperature is in the range of from 475 C. to 525 C.

3. The process of claim 1 wherein the temperature is in the range of from about 490 C. to 525 C., the hydrogen pressure is in the range of about 1500 to 3000 p.s.i.g., and the gas residence time is less than about one minute.

4. The process of claim 1 wherein the coal is catalyzed by impregnation with about /2 to 1% Mo catalyst in the form of ammonium molybdate.

5. A process for the hydrogenation of coal, comprising: dispersing pulverized coal impregnated with a hydrogenation catalyst, in the absence of a pasting oil, in hydrogen under-a pressure of about 1500 to 3000 p.s.i.g., the hy drogen being present in excess of that amount required for complete conversion of the coal to the desired product's, reacting the mixture of coal and hydrogen at a temperature of approximately 500 C. for a gas residence time in the range of about 20 to 30 seconds to eifect substantially complete conversion of the coal into liquid, tarry and gaseous hydrocarbons, the liquid fraction comprising at least about 20% of the reaction products, and with no increase in temperature substantially immediately cooling and recovering said reaction products.

6. The process of claim 5 wherein said coal is catalyzed with about 1% of molybdenum, and the hydrogen pressure is approximately 2000 p.s.i.g.

7. A process for the hydrogenation of coal, comprising: entraining pulverized coal containing a hydrogenation catalyst, in the absence of pastin oil, in a flowing stream of hydrogen at a pressure of about 500 to 4000 p.s.i.g., passing the resulting com-hydrogen stream through a zone having a temperature in the range of 475 C. to 600 C. and thereby heating said stream to a temperature above about 450 C. but below 600 C., the retention time in said zone being not more than 200 seconds, and with no increase in temperature substantially immediately cooling the efiiuent mixture flowing from said zone, and recovering liquid, tarry and gaseous hydrocarbon products from said mixture.

8. The process of claim 7 wherein said zone is defined by a substantially vertically disposed tube and the coalhydrogen mixture is passed downwardly through said tube.

9. A process for the hydrogenation of coal, comprising: dispersing pulverized coal containing a hydrogenation catalyst, in the absence of a pasting oil, in hydrogen under a hydrogen pressure of about 500 to 4000 p.s.i.g., passing the coal-hydrogen mixture through a preheating zone and then into a reaction zone, the temperature in the preheating zone and rate of flow of the mixture through such zone being such that the temperature in the reaction zone is maintained by exothermic heat of reaction above about 450 C. but below 600 C., the gas residence time of the mixture in said reaction zone being no longer than about 200 seconds but suficient to permit substantially complete conversion of the coal into liquid, tarry and gaseous hydrocarbons, and with no increase in temperature substantially immediately cooling and recovering the reaction products.

10. A process for the hydrogenation of coal, comprising: dispersing pulverized coal containing a hydrogenation catalyst, in the absence of a pasting oil, in hydrogen under a hydrogen pressure of about 500 to 4000 p.s.i.g., reacting the mixture of coal and hydrogen at a temperature above about 450 C. but below 600 C. for a gas residence time of less than about 200 seconds to produce tars, liquids and gases, collecting the tarry fraction of the reaction products at the temperature and pressure of the system, while simultaneously passing the volatile liquid and gaseous reaction products to a cooling zone, and passing additional hydrogen into the collected tarry fraction at said temperature and pressure for further hydrogenation into volatile liquids and gases, the maximum temperature of the entire hydrogenation operation being below 600 C.

11. The process of claim 10 wherein the mixture of coal and hydrogen at approximately reaction temperature is passed into a reaction zone, the tarry fraction collects at the bottom of said zone, said additional hydrogen is passed into the collected tarry fraction at the bottom of said zone, and liquid and gases resulting from the coal hydrogenation and from the hydrogenation of the tarry fraction are passed together to the cooling zone.

References Cited in the file of this patent UNITED STATES PATENTS 1,872,839 Snyder Aug. 23, 1932 2,221,952 Pier et al Nov. 19, 1940 2,654,695 Gilbert et al. Oct. 6, 1953 2,885,337 Keith et al. May 5, 1959 2,989,461 Eastman et al. June 20, 1961 3,030,297 Schroeder Apr. 17, 1962

Claims (1)

1. A PROCESS FOR THE HYDROGENATION OF COAL, COMPRISING: DISPERSING PULVERIZED COAL CONTAINING A HYDROGENATION CATALYST, IN THE ABSENCE OF A PASTINGOIL, IN HYDROGEN UNDER

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