GB2037809A

GB2037809A - Conversion of Carbonaceous Materials into Fluid Products

Info

Publication number: GB2037809A
Application number: GB7941837A
Authority: GB
Original assignee: American Minechem Corp
Current assignee: American Minechem Corp
Priority date: 1978-12-04
Filing date: 1979-12-04
Publication date: 1980-07-16
Also published as: FR2443285A1; FR2443285B1; CA1141315A; BE880432A; NL7908769A; GB2037809B

Abstract

Solid carbonaceous materials and particularly coal are converted to gas hydrocarbon fluids, e.g., gas, by forming an aqueous slurry in which an amalagam of carbonaceous and non- carbonaceous particles are suspended in a suspension liquid such as water. The slurry is mixed together with an agglomerating liquid lyophobic to resuspension liquid and non- carbonaceous particles and lyophilic to carbonaceous particles to form a mixture, and the mixture is agitated to preferentially agglomerate carbonaceous fine particles to form discrete agglomerates having chemical and physical properties which are known and which are substantially uniform and constant. The non-carbonaceous fine particles remain substantially unagglomerated in the slurry and are separated from the discrete agglomerates. The discrete agglomerates or reconstituted particles are then heated to greater than 1500 DEG F and preferably greater than 2000 DEG F in a controlled atmosphere to convert them into a gaseous product. Alternatively, the reconstituted particles or discrete agglomerates are to a temperature of about 750 DEG F to 1000 DEG F under controlled conditions to form a liquid product.

Description

SPECIFICATION Improvements in or Relating to the Conversion of Solid Carbonaceous Materials to Fluid Products This invention relates to the conversion of carbonaceous materials, more particularly but not exclusively coal, into gaseous or liquid products.

With the steady increase in the demand for hydrocarbon products of petroleum and natural gas and a growing reliance upon imported petroleum and natural gas to satisfy this demand, there has been increased emphasis on development of alternative sources of energy. In view of the relatively large domestic supply of available coal, the advance of mining technology, and the faster rising cost of other forms of energy, more complete exploitation of our coal resources has become increasingly more attractive.

Processes for the conversion of coal into liquid and gas fuels are described in the literature. For example, the Lurgi, Koppers-Totzek, Hygas, CO2 Acceptor, BiGas, and Synthane and other related processes convert different grades of solid coal into various gaseous products. Similarly, the PAMCO and Synthoil processes convert solid coal into liquid products.

Coal is generally classified into grades of anthracites, semi-anthracites, bituminous, and subbituminous coals, and lignites. Most conversion processes have tended to use bituminous, semibituminous and lignitic non-caking coals which are generally the feed to steam and electric generating plants. Anthracites and semi-anthracites are generally not suited for conversion because they are low in volatiles, tend to be unreactive, are in relatively short supply, and generally have a ready market in domestic and commercial central heating systems.

Low grade lignites have generally been considered unsatisfactory for known conversion processes because of their low calorific value and their high water and ash contents. Since conversion processes of the prior art have generally been in competition for bituminous, sub-bituminous, and noncoking coal with steam and electric power generation, coal conversion has been economically feasible only where substantial reserves of bitummous, sub-bitummous, and non-coking coal are located distant from substantially industrialized or populated areas. Thus, even though coal is a relatively plentiful resource, few of the known coal reserves are suited for economical conversion to a fluid product in accordance with prior conversion processes.

The known conversion systems are in general slow and energy intensive in that they involve heating of the coal to typically between 7500F and 20000 F, and separation of heated waste solids from the liquified or gasified carbonaceous material. In liquification processes, the separation has been performed by filtration and centrifuging processes which are relatively slow, incomplete and limit the speed of the process. In gasification processes, the separation has been performed by scrubbers which are expensive to build and expensively require large amounts of energy to operate. Additionally, in all such processes, the solid wastes must be cooled, with an accompanying loss of additional energy, and removal to a disposal area.

Certain impurities in the coal have been identified as undesirable pollutants that form stable oxides, most notably sulphur oxides, in the conversion process and report as exhaust emission. Another such impurity is nitrogen. Some of the volatile metallic impurities can also be included in the gas or liquid product of the conversion. These include arsenic beryllium, cadmium, lead, mercury, and selenium. Accordingly, prior conversion systems have also been limited by environmental controls which are required by state and federal regulations.

Coal conversion processes to date have usually attempted to control emissions of pollutants through the installation of pollution control equipment on the system. This has, however, necessitated equipment of increased size and complexity, and has substantially increased capital costs and operating costs, as well as consumption of energy to operate the pollution control equipment.

The present invention substantially reduces, eliminates, and avoids these disadvantages of the previous coal conversion systems. It sharply reduces the energy requirements for conversion and the environmental hazards and control requirements for conversion. At the same time, the invention increases the processing speed by avoiding quenching difficulties with solids present in the separation of large quantities of solid particulate from the gas or liquid product. The invention provides a purified product free of large quantities of impurities and eliminates solid disposal difficulties present in previous systems. It also provides a product of improved quality that can be produced from coal deposits previously considered unacceptable for conversion to fluid products.

Summary of the Invention The present invention provides a simple method of rapidly converting carbonaceous material into a fluid product of a liquid or gaseous hydrocarbon. The present method also provides a fluid hydrocarbon product of unique purity and quality.

An amalgam of carbonaceous and non-carbonaceous fine particles, preferably of ash and coal, are first dispersed in a suspension liquid such as water to form a slurry. The fine particles are preferably formed by comminuting coal from a mine head in a ball mill, agitated-media mill or the like.

Alternatively, the fine particles may be the waste from a coal washing plant or refuse from a settling pond of a coal washing plant.

Added to the slurry is an agglomerating liquid lyophobic to both the suspension liquid and the non-carbonaceous fine particles and lyophilic to the carbonaceous fine particles. The agglomerating liquid is preferably a hydrocarbon that can be volatilized and/or carbonized along with the carbonaceous fine particles as hereinafter described, having an initial boiling point greater than about 1490F (65 OC) and preferably greater than 3020F (1 500C).

The mixture is then agitated to preferentially agglomerate the carbonaceous fine particles into discrete agglomerates while leaving the non-carbonaceous fine particles substantially unagglomerated in the mixture. Thereafter, the agglomerated carbonaceous fine particles are separated from the mixture. The chemical and physical properties of the discrete agglomerates are substantially uniform throughout and are substantially constant for a considerable period of time. The size and packing (density) of the agglomerates have substantial uniformity, and the size can be controlled by the composition and percentage of the liquid and the degree and duration of the agitation. The ash content is uniform and low, generally less than 4 to 6.5 percent. The moisture content of the discrete agglomerates is uniformly distributed throughout and typically is in the range of about 7 to 20 percent.

The agglomerating liquid coats the coal particles of the discrete agglomerates to make the agglomerates substantially inert to atmospheric oxidation such that the chemical and physical properties of the agglomerates remain constant for substantial periods of time. After separation, the discrete agglomerates are heated to greater than 7500F in a controlled atmosphere to form a fluid hydrocarbon product.

The hydrocarbon product thus formed may be liquid or gas depending on the heating temperature and rate and the chemical composition of the controlled atmosphere. In any case, the hydrocarbon product has unique properties caused by the unique purity and uniform and constant chemical and physical properties of the discrete agglomerates. Specifically, a higher yield of the hydrocarbon product is produced owing to the uniform size, packing, moisture content and oxidation of the discrete agglomerates. Also, the hydrocarbon product has notably reduced solid contamination and substantially lessened impurities such as sulphur, lead, beryllium, cadmium, and the like due to the separation of the non-carbonaceous material. As well as a higher calorific value than products of conversion process known to the prior art due to the benefication of the coal by the hydrocarbon agglomerating liquid.

Other details, objects and advantages of the present invention will become apparent as the following description of the presently preferred methods of practicing and making the same proceeds.

Brief Description of the Drawings In the accompanying drawings, the presently preferred embodiments of the invention and the presently preferred methods of practicing the invention are shown in which: Figure 1 is a schematic illustrating a method for converting coal to a gas in accordance with the present invention; Figure 2 is a schematic illustrating another method for converting coal to a gas in accordance with the present invention; Figure 3 is a schematic illustrating a method for converting coal to a liquid in accordance with the present invention; and Figure 4 is a schematic illustrating another method for converting coal to a liquid in accordance with the present invention.

Description of the Preferred Embodiments The reactions that are fundamental to the conversion of carbonaceous material can be described as hydrogenation or, alternatively, decarbonization. As used herein, hydrogenation is defined to be the addition of hydrogen to a more complex hydrocarbon molecule and decarbonization is defined to be the removal a source of the carbon from a more complex hydrocarbon molecule.

Conversion of coal into a fluid product basically involves the conversion of a heavy hydrocarbon having a carbon to hydrogen atomic ratio of about 1:1 into methane, which has a carbon to hydrogen ratio of 1:4. Hydrogenation generally occurs either through hydrogenolysis, in which gaseous hydrogen is reacted with the heavy hydrocarbon according to the general formula: 4n-m CnHm+ H2-nCH4 (1) 2 or hydrolysis, in which steam is reacted with the heavy hydrocarbon according to the general formula: CnHm+xH2OyCH4+zCO2+wH2 (2) In decarbonization processes, a carbon product such as carbon dioxide, coke or char is formed and then removed from the system.Carbon dioxide is formed by oxygenolysis in which the hydrocarbon is heated with oxygen according to the formula:

The carbon dioxide is generally removed by scrubbing the gas with amine or hot potassium carbonate solution. Char is normally formed by pyrolysis, or heating the hydrocarbon to cracking temperatures.

Pyrolysis proceeds according to the formula:

In the course of any of the basic conversions, a large number of intermediate compositions are formed. Specifically, the chemical equilibrium that determines the product yields of the conversion process are believed to be as follows: Table 1 Equilibrium in Conversion Reactions Heat of reaction Volume Equilibrium H(kcal/mole change constant Reaction at 2980K (250C)) (AV) rKp No.

(CO2) C+O2-CO2 -94.056 1 to 1 (5) (02) (CO) C+CO2-2CO +41.203 1 to 2 (6) (CO2) (H2)(CO) C+H20-H2+CO +31.356 1 to2 (7) (H20) (H2)(C02) CO+H2O-H2+CO2 -9.847 2to2 --------- (8) (CO)(H20) (CH4)(H20) CO+3H2-CH4+H2O -49.243 4 to 2 ------ (9) (Co)(H2)3 (CH4) C+2H2-CH4 -17.889 2to1 (10) (H2)2 (CH4)(H2O)2 CO2+4H2-CH4+2H2O -39.410 5 to 3 -------- (11) (CO2)(H2)4 (H2)2(C02) C+2H20-2H2+CO2 +21.510 2 to 3 (12) (H2O)2 (CO)2(H2)2 CH4+CO2-2CO+2H2 +59.093 2 to 4 (13) (CH4)(C02) (C2H2) 2C+H2-C2H2 +54.163 1 to 1 (14) (H2) (C2H2)(H2)3 2CH4-C2H2+3H2 +89.918 2 to 4 (15) (CH4)2 Table 1 (contd.) Equilibrium in Conversion Reactions Heat of reaction Volume Equilibrium H(kcal/mole change constant Reaction at 298 OK (250C)) (AV) (Kp) No.

(C2H4)(H2)2 2CH4-C2H4+2H2 +48.246 2 to 3 (16) (CH4)2 (C2H4)(H2) C2H6-C2H4+H2 +32.710 1 to 2 (C2H4)(H2) (17) (C2H6) (CO)(H2)3 CH4+H2O-CO+3H2 +49.242 2 to 4 --------- (18) (CH4)(H20) Development of coal conversion processes has been complicated by the fact that not only do most of the reactions of Table 1 occur at some point in the conversion of the coal to a fluid product, but also at some stage of the conversion, most of the above equilibria are believed to coexist. The most important considerafion in designing a coal conversion process in view of the foregoing equation is the enthalpy change (bH) of the different reactions.The enthalpy, or heat of reaction, is a measure of the endothermicity (+AH) or exothermicity (-AH) of the reaction and therefore indicates whether supplying heat or withdrawing heat will drive the reactions 5-1 8 toward the right or left. In order to produce a lower molecular weight fluid product from the higher molecular weight materials found in coal in the most efficient and economic fashion, it is important to balance the enthalpy change of the various steps, thereby minimizing the net thermal energy transfer to or from the process.

In accordance with the foregoing table, the volume, change (åV) indicates whether the effect of a pressure increase would be to drive the equilibrium to the right or to the left depending upon the volume charge.

The equilibrium constant (Kp) indicates the composition of the final gas mixture at a given temperature after chemical equilibrium is established. Table 2 is a list of values of the respective equilibrium constants of each reaction in Table 1 for three different temperatures.

Table 2 Value of Equilibrium Constant Kp in Conversion Reactions Equilibrium Value of up constant 980 OF 1340 OF 1 700 OF (Kd at (527 C) (727 C) (927 C) (CO2) 6.709x 1025 4.751x1020 1.738x1017 (5)' (O2) (CO) 1.098x102 1.900 57.09 (6)' (CO2) (H2)(CO) 4.399x102 2.609 39.77 (7)' (H20) (H2)(C02) 4.038 1.374 0.6966 (8)' (Co)(H2o) (CH4)(H20) - - - 8.821 x 102 4.383 59.585 (9)' (CO)(H2)3 (CH4) 1.411 9.829x102 1.608x102 (10)' (H2)2 Table 2 (contd.) Value of Equilibrium Constant Kp in Conversion Reactions Equilibrium Value of Kp constant 9800F 13400F 17000F lKd at (52 7 C) (7270C) (9270C) (CH4)(H2O)2 2.185x102 3.190 85.537 (11)' (CO2)(H2)4 (H2)2(CO2) 0.1777 3.608 28.01 112)' (H2O)2 (CO)2(H2)2 7.722 x 10~3 7.722x 10- 19.32 3.548x10 (13)' (CH4)(C02) (C2H2) 1.602x10-'2 1.337x10-9 1.156x10-7 (14)' (H2) (C2H2)(H2)3 8.017x10-'3 1.384x10-7 4.474x10-4 (15)' (CH4)2 (C2H4)(H2)2 1.021x10-7 6.939x10-5 5.540x10-3 (16)' (CH4)2 (C2H4)(H2) 4.557x10-3 4.557 x 10- 0.3443 6.224 (17)' (C2He) (Co)(H2)3 3.120 x 10- 26.56 2.473 x 10 (18)' (CH4)(H2O) Where Kp tends to increase with increased temperature, an increase in the process temperature will drive the reaction equilibrium of the respective equation in Table 1 to the right. Where Kp tends to decrease with increased temperature, a decrease in the process temperature will drive the reaction equilibrium to the right.

The time in which equilibrium conditions will be established in reactions (5)-(1 8) is determined by the velocity constants of both forward and reverse reactions. The velocity constants are a function of the reactivity of the different species and, for many conversion reactions, the presence of a catalyst, either homogeneous or heterogeneous, is required in order to reach equilibrium conditions within an acceptable time.

Heterogeneous catalysts are materials that provide a surface on which reactions between gas molecules take place due to surface forces exerted by certain active materials or centres. However these catalysts tend to attract molecules other than those with which they are intended to react.

Specifically, polar impurities of the coal such as a sulphur, nitrogen, oxygen, and metal compounds deposit on the catalyst, block the active centres, and eventually poison the catalyst. Accordingly, it is essential for processes based on the catalytic conversion of coal that the reacting gases prepared from the coal be purified before they contact the catalyst.

The presently disclosed process has been developed with careful attention given to the considerations discussed above. The conversion steps carefully assess enthalpy considerations of the various reactions that occur and then carry out the conversion through an advantageous combination of stages. In the various stages, pressure, temperature, volume, process rate, and other variables are controlled to achieve desirable product ratios.

In the prior art, conversion processes have assumed a carbonaceous feed material, typically coal, having physical and chemical properties which are known and which are constant throughout.

However, both the physical and chemical properties of coal vary greatiy from deposit to deposit and, furthermore, within the same deposit.

The carbonaceous molecules that are hydrogenated or decarbonized cover a broad range of molecular weights and structural complexity. Moreover, the carbonaceous feedstock is non-uniformly contaminated with non-carbonaceous material. Accordingly, prior coal conversion methods had to be individually adapted to the widely different grades and types of coal. Furthermore, surface effects such as oxidation and moisture cause variations in the properties of a single lump or a single particle of coal.

The deviation in physical and chemical properties of various grades of coal and nonuniformity of these properties within a single coal deposit have previously meant that a process designed for conversion of one grade of coal may have to be extensively modified or may even be unsuited for conversion of other grades of coal. In accordance with the present invention, carbonaceous materials of various grades and purities are converted to carbonaceous agglomerates having properties that are known and substantially constant despite variation in the properties of the carbonaceous feed material.

Referring to Figure 1, the carbonaceous material is converted to a fluid hydrocarbon product by first dispersing carbonaceous and noncarbonaceous fine particles of the carbonaceous material in a suspension liquid to form a slurry 10. As used herein, "fine particles" is specifically defined to mean small particles which are preferably less than 0.590 millimeters in diameter (28 mesh Tyler) and typically less than 0.210 millimeters in diameter (65 mesh Tyler). As also used herein, "carbonaceous material" is hereby defined to include any raw material containing carbon which, when divided into fine particles, contains fine particles of both non-carbonaceous and carbonaceous materials. Most desirably, the carbonaceous material is an anthracite or lower rank coal such that the carbonaceous fine particles are coal and the non-carbonaceous fine particles are ash.As used herein, "ash" fine particles are defined to include small particles of materials such as clay and slate that generally appear as ash rather than volatiles on complete burning of coal.

Slurry 10 may be formed in various alternative ways from such coal. For example, particulate coal 11 may be conveyed directly from a mine to a comminuting means 12. Comminuting means 12 may be any suitable, commercially available comminuting means such as a ball mill. Comminuting the coal into small particles is effective in freeing sulfur compounds and other non-carbonaceous particles. High sulphur content, as for example from pyrites, is particularly undesirable in that, among other effects, it can interfere with subsequent reactions in the conversion process. This is especially true where catalytic reactions are included in the process. Other contaminants released by comminuting the coal include oxygen and nitrogen containing compounds. Oxygen is undesirable in the conversion process particularly where hydrogenation is used because, it increases hydrogen consumption.The presence of nitrogen in the coal will result in the presence of ammonia or nitrogen oxides in the fluid product, thus diluting the calorific value thereof.

Alternatively, slurry 10 may be underflow 14 from a conventional coal washer, which typically has a relatively low solids content of about 5 to 1 5 percent solids in water. Underflow 14 may be mixed with refuse slurry 1 5 of coal and ash fine particles of relatively high solids content, i.e. at least about 50 percent solids, formed by a water dispersion of the sediment of an existing settling pond adjacent the coal washing plant. The mixing of underflow 14 and refuse slurry 1 5 should provide a slurry 10 of about 5 to 40 percent and most typically 20 to 25 percent solids of coal and ash fine particles. In this case, the carbonaceous and non-carbonaceous particles are already sufficiently small so that sulfur compounds and other non-carbonaceous particles are free in the slurry.

Slurry 10 is processed in agitator apparatus 1 6 to preferentially agglomerate the carbonaceous (e.g. coal) fine particles, while the non-carbonaceous (e.g. ash) fine particles remain substantially unagglomerated and dispersed in the slurry. Added to slurry 10 at the inlet to agitator apparatus 1 6 is agglomerating liquid 17, which is lyophobic to both the suspension liquid (e.g. water) and to noncarbonaceous fine particles and lyophilic to the carbonaceous fine particles to form a mixture.

"Lyophiiic" as herein used means that, in a disperse system, there is a marked affinity (wettability) between a disperse component and the dispersion medium and/or another disperse component. Some examples are glue and water, or rubber and benzene. "Lyophobic" as used herein means that, in a disperse system, there is substantially no affinity (wettability) between the disperse component and the dispersion medium and/or another disperse component. Examples are oil and water, or colloidal "solutions" of metals.

Agglomerating liquid 1 7 is preferably a hydrocarbon liquid that can be converted along with the carbonaceous fine particles as hereinafter described. Materials particularly suitable for agglomerating liquid 17 are hydrocarbons having an initial boiling point greater than about 1 47 OF (650C). and preferably greater than 302 OF (1 5O0C). Specifically suitable are light oil, light fuel oil, heavy fuel oil, and kerosene. Also suitable are creosote, filtered anthracene oil, hydrogenated filtered anthracene oil, lubricating oil such as SAE 20, and chlorinated biphenyls. Heavy hydrocarbon materials such as a heavy crude petroleum, crude shale oil or coal tar are not preferred. Heavy hydrocarbon liquids typically contain molecular groups lyophilic to non-carbonaceous fine particles as well as carbonaceous fine particles and, therefore, do not provide the degree of separation of carbonaceous fine particles from non-carbonaceous fine particles preferred in the present method. In addition, such heavy hydrocarbon liquids often need to be heated to provide sufficient fluidity for the operation of the present invention.

Agglomerating liquid 1 7 is selected and added in measured amounts to control the agglomeration of carbonaceous fine particles as hereinafter described. Preferably, liquid 1 7 is added in amounts of about 2 to 10 percent by weight and most desirably between 3 and 7 percent by weight of the total solids in slurry 13 for high recovery, (e.g. 88-89 percent by weight). Greater amounts of liquid 1 7 up to and exceeding 30 percent by weight may in some instances be utilized. However, such lesser and greater amounts are not preferred because, on the on hand, sufficient agglomeration and binding of coal fine particles is not provided while, on the other hand, a waste of highly refined petroleum or coal tar derivative results.

The mixture of slurry 10 and agglomerating liquid 1 7 are mixed and agitated in agitator apparatus 1 6. Agitator apparatus 16 may be any suitable agitating apparatus such as a modified turbine, a disc or cone impeller mixer, or a tank with recirculation. Preferably, however, agitator apparatus 1 6 is a tank equipped with a motor driven high shear impeller 1 8 extending to the bottom portion of the tank.

During agitation in agitator apparatus 16, the carbonaceous fine particles are preferentially wetted by agglomerating liquid 17, which is preferably immiscible in water, and the carbonaceous fine particles are agglomerated into coarser particulate. The size of the agglomerates is primarily determined by the composition and the percentage of liquid 1 7 added to slurry 10, and is controlled to provide the desired size and density for efficient conversion to the gaseous and liquid product. For the preferred percentage of 2 to 10 percent by weight of liquid 1 7, the agglomerates typically have sizes of from about 1 to 2 millimeters. The time required to effect agglomeration is generally dependent upon the degree of turbulence or agitation, with the shorter agglomeration time being associated with the higher agitation speed.The degree and duration of the agitation in apparatus 1 6 is also controlled to provide the desired size and packing (density) of the agglomerates.

The carbonaceous agglomerates, being impregnated and having absorbed on the surfaces thereof liquid 1 7, which is generally less dense than the suspension liquid, will tend to float to the top of the mixture. Agglomerated first mixture 1 9 is thus removed from the top of agitator apparatus 1 6 to a separator 20, where the carbonaceous agglomerates 22 are separated from the suspension liquid and unagglomerated non-carbonaceous fine particles by size and/or density. Preferably, separator 20 is a sieve bend of an appropriate mesh size, e.g. 100 or 200 mesh Tyler, such as that manufactured by authority from DSN NV Vedernaldse Staatsmijnen. Alternatively, other types of separators such as an elutriator, cyclone or spiral separator, which are commercially available, may be utilized.Alternatively, the carbonaceous agglomerates 22 may be also separated in a float-sink tank where the carbonaceous agglomerates 22, which tend to float, are skimmed off by a rotating paddle through an over flow, while the water and unagglomerated non-carbonaceous fine particles, which tend to sink, are removed from the bottom of the tank as slurry 21 containing the non-carbonaceous fine particles and substantially free of carbonaceous fine particles and agglomerating liquid.

Carbonaceous agglomerates 22 have low ash and impurities content, uniform size and packing (density), and even distribution of moisture throughout the agglomerates. Typically, the moisture content of the discrete agglomerates is in the range of about 7-10 percent. The low content of noncarbonaceous materials, typically less than about 4-6.5 percent, and uniform size and packing as well as the uniform distribution of moisture throughout the discrete agglomerates permits the subsequent steps of the conversion process to proceed in predictably and efficiently in accordance with the design of the various stages of the process.

The calorific value of the fluid product is generally dependent on the calorific value of the carbonaceous agglomerates 22. The inclusion of agglomerating liquid 17, which is a hydrocarbon, in agglomerates 22 beneficiates the calorific value of the agglomerates and therefor, improves the quality of the fluid product by beneficiating its calorific value.

The quality of the fluid produced in accordance with the presently disclosed method is further improved in that agglomerates 22 are protected from partial oxidation of the coal particles by exposure to air. Agglomerating liquid 1 7 coats the individual coal particles and thereby protects them from oxidation prior to the conversion process.Partial oxidation of agglomerates 22 is undesirable for this reason that it destroys the uniformity of the chemical and physical properties thereby effecting the efficiency of the conversion process and the quality of the fluid product by altering the conversion process in accordance with equations 5-1 9. Accordingly, agglomerates 22 are resistant to changes in their chemical and physical composition caused by oxidation and can be stored for substantial periods, for example 4-6 months, without applicable oxidation. Moreover, agglomerates 22 require no special storage facilities and can be stored in open stockpiles if desired.

At this stage, separated carbonaceous agglomerates 22 may be processed (not shown) by pelletizing into larger particulates. The agglomerates may be pelletized to generally uniform particle sizes of 0.10 to 1.0 inch in diameter by feeding the agglomerates to a pelletizing disc or tumbler along with a binder liquid to form a second mixture and then agitating said mixture. Alternatively, the agglomerates may be agitated, extruded or otherwise molded into pellets upon addition of a binder liquid to form said second mixture. Binder liquids particularly suitable for this purpose are heavy hydrocarbons such as coke-oven coal tar, crude shale oil, petroleum crude or heavy fuel oil such as Bunker C, which is preferably heated to, for example, 1 000C., to bond the binder to and within the agglomerates. Heating in this manner will also further serve to dewaterize the agglomerates uniformly, typically to the range of about 5 to 12 percent moisture. An accelerator is also preferably included in the binder liquid to hasten bonding of the binder in shorter times and/or at lower temperatures. The heavy hydrocarbon binder liquid serves to further beneficiate the discrete agglomerates without disturbing the uniform chemical and physical properties of the discrete agglomerates 22. Accordingly, the quality of a fluid conversion product of the pellets is further improved by increasing the calorific value of the fluid product.Also, the addition of the heavy hydrocarbon builder liquid enhances the inertness of the carbonaceous material to atmospheric oxidation so that the chemical and physical properties of the pellets remain uniformly constant for even longer periods than the discrete agglomerates 22.

A variety of steps for the final conversion of carbonaceous agglomerates 22 to a fluid product may be alternatively used in accordance with the presently disclosed invention. These various final conversion steps are comprised of various process stages that are designed to selected ash and moisture contents for the optimum conversion of the carbonaceous agglomerates 22 to a fluid product based on the physical and chemical properties of carbonaceous feed material. Advantageously, the above described steps for removal of the non-carbonaceous or ash fine particles from the carbonaceous particles results in carbonaceous agglomerates 22 having a low, uniform and generally constant ash and moisture content regardless of the source or quality of the carbonaceous material added to the slurry 10.Specifically, agglomerates 22 have an ash content of generally less than 6.5% for most coals and generally less than 4% for higher grade coals, and have a moisture content of generally about 5 to 12 percent. Accordingly, regardless of which particular conversion step is used and despite the preferred ash and moisture content for achieving optimum conversion of the carbonaceous material to a fluid product in accordance with the design of the particular conversion step employed, optimum conversion for any selected process may be attained by introducing where necessary, an appropriate quantity of ash and/or water to the carbonaceous agglomerates 22. Since the ash and moisture content of carbonaceous agglomerates 22 is known, the quantity of ash and/or moisture which is to be introduced in accordance with the optimum conversion for the particular method is also known.Moreover, since the ash and moisture content of the carbonaceous agglomerates 22 is substantially uniform, the additional ash and/or moisture can be introduced at a constant rate. Accordingly, existing conversion processes can be modified and new processes designed without regard to the peculiar physical and chemical properties of a particular source of carbonaceous feed material such as a particular deposit of coal.

According to the conversion method illustrated in Figure 1, the final conversion step converts the agglomerates 22 to synthesis gas, a mixture of carbon monoxide and hydrogen that can be converted to methane or heavier hydrocarbons in the presence of a catalyst. The final conversion step is based on the partial oxidation of agglomerates 22 in the presence of oxygen and steam. When necessary, the carbonaceous agglomerates 22 are given a moisture content of 2 to 8 percent by adding water 24 and are then reduced to about 70% through 200 mesh fineness in a size reducer 26. Nitrogen 28 or other non-oxidizing gas is added to the size reducer 26 and the smaller sized agglomerates are carried in a nitrogen stream to a service bunker 30. The pulverized coal agglomerates are then discharged into a stream of oxygen 31 and steam 32 to a gasifier 34 in which they are partially oxidized.Gasifier 34 is a refractory-lined, horizontal, cylindrical vessel with conicalends. Gasifier 34 is provided with a steam jacket 36 which cools the refractory and burners of gasifier 34 and generates the steam 32 used in the partial oxidation of the pulverized agglomerates in gasifier 34. Under atmospheric or slightly positive pressure and a flame temperature of about 3,30O0F-3,5OO0F., the agglomerated dust, oxygen and steam react at the burner heads of gasifier 34 to form crude synthesis gas 38 which contains carbon monoxide and hydrogen.

Approximately one-half the ash content remaining in the pulverized agglomerates precipitates in gasifier 34 as molten slag which is cooled in a slag quench tank 40. The unprecipitated ash reports with the synthesis gas 38 which, as it leaves gasifier 34, is water quenched in a primary washer 41 to scrub out the entrained ash. The gas stream is then passed through a secondary washer 42 to reduce further the quantity of entrained solids and through a gas cooler 44 to lower the gas temperature to about 950F. The cooled gas is then cleaned of remaining entrained particles in a disintegrator 55.

A waste heat boiler 46 recovers heat from the slag quench tank 40 and generates high pressure steam 48 which may be applied to turbine drives of compressors or pumps. Water from primary washer 41, secondary washer 42, and gas cooler 44 is pumped to a clarifier 50 which removes the slag particulates as sludge 51. The clarified water is pumped from the clarifier 50 to a cooling tower 52 and is then recirculated through the gas cleaning apparatus. A stream of water 54 is added to make up for evaporation and windage losses at the cooling tower 52 as well as moisture losses in the clarifier sludge 51.

Synthesis gas 38 is composed principally of carbon monoxide, carbon dioxide and hydrogen. The major impurities are nitrogen and hydrogen sulfide which are generally removed either by a chemical reaction process or by a physical absorption process (not shown). Synthesis gas 38 can be processed to yield various chemicals, such as hydrocarbons, ammonia, or methanol. Alternatively, synthesis gas 38 can also be converted to pipeline quality gas by further cleansing the gas in precipitators followed by desulfurization, water gas shift conversion, removal of excess carbon dioxide, and methanation. (see equation (9)).

Figures 2, 3 and 4 illustrate alternative embodiments of the present invention in which carbonaceous agglomerates 22 are produced in the same manner as described with respect to Figure 1. Accordingly, the same reference characters have been applied to like parts of Figures 2, 3 and 4, and the practice of the method is described in the same manner as with respect to Figure 1. However, in Figures 2, 3 and 4, carbonaceous agglomerates 22 are converted to different products by alternative final conversion steps.

In Figure 2, carbonaceous agglomerates 22 are reduced to -20 mesh carbonaceous particles in a size reducer 58 and placed in a fluidised bed pretreater 60 together with steam and oxygen. The mixture of carbonaceous particles steam, and oxygen is maintained at of about 1000 psig pressure and a temperature of about 800"F to perform surface oxidation of the carbonaceous particles and retard their agglomeration property. The partially oxidized, carbonaceous particles are then provided to the top of a gasifier 66 while additional steam and oxygen are provided to the bottom of the gasifier 66 such that a fluidized bed of carbonaceous particles is maintained in gasifier 66.Gasifier 66 is operated at a typical pressure of about 1,000 psi and a typical temperature of about 1 ,80O0F to produce a product gas 67 and char 68 from the carbonaceous particles.

Product gas 67 is taken off the top of gasifier 66 while char 68 is removed from the bottom.

Preferably, the char is used to fire a boiler (not shown) that produces the steam required for the process. Product gas 67 contains tar, particulates, sulfur compounds, and light oil. The tar and particulates are removed from product gas 67 by a spray tower 68. The cleaned gas is passed through a shift converter 70 to produce carbon monoxide and hydrogen with the desired ration of hydrogen to carbon monoxide. The carbon monoxide and hydrogen from shift converter 70 are cleaned in a hot carbonate scrubber 72 and sulfur cleaning apparatus 74. The cleaned gas having the correct ratio of hydrogen to carbon monoxide is converted in a catalytic methanator 76 to produce pipeline gas.

Preferably, methanator 76 is of a type employing nickel catalysts.

In the process of Figure 3, carbonaceous agglomerates 22 are converted into primarily liquid products. The carbonaceous agglomerates are reduced to carbonaceous particles 81 of about 70% -200 mesh in size reducer 80. Carbonaceous particles 81 are provided to a feed tank 82 in which they are mixed with a portion of the product oil 84 to form a slurry 86. Hydrogen rich gas is added to slurry 86 and this mixture is introduced under turbulent flow conditions to a fixed-bed reactor 88 containing an immobilized Co-Mo/SiO-Al2O3 catalyst. The temperature within reactor 88 is typically about 8500F and the pressure is in the range of about 2,000--4,000 psi. The output product of reactor 88 is provided to a vapor/liquid separator 90 in which the gases are separated from the liquids and unreacted solids.The liquid and solid mixture is passed to a centrifuge 92 to remove the unreacted solid particles. The liquid from centrifuge 92 is product oil 84, a portion of which is recycled to feed tank 82 to form slurry 86. The solids from centrifuge 92 are provided to a pyrolyzer 93 to yield an additional quantity of product oil together with gases and a carbonaceous residue generally consisting of mineral matter.

Gas from vapor/liquid separator 90 is provided to a gas separator 94 which removes NH3, H2S and gaseous hydrocarbons from the hydrogen in the gas. The NH3 and H2S are useful by-products. The hydrogen. is recycled to reactor 88. The residue and gases from the pyrodizer 93 and the gaseous hydrocarbons from the gas separator 94 are provided together with water and oxygen to a gasifier 96 and a shift converter 98 to provide make-up hydrogen. The make-up hydrogen together with the hydrogen provided by the gas separator 94 are added to the slurry 86 that is fed to reactor 88. If necessary, some of the ground carbonaceous particles 81 can be added to the gasifier 96 and shift converter 98 to prepare a volume of hydrogen sufficient for the process requirement.

In Figure 4, carbonaceous agglomerates 22 are converted to synthetic crude oil, as well as to gas and a combustible char by yet another conversion process. Carbonaceous agglomerates 22 are reduced to granules of less than 1/8 inch diameter in a size reducer 100 and pyrolyzed at successively higher temperatures in a series of four fluidized bed reactors 102-105 in this example. A fraction of the volatile matter of the carbonaceous granules is released in each fluidized bed. The temperature of each bed is selected to be slightly lower than the temperature at which the granules will agglomerate and defluidize the reactor bed. A typical temperature of each reactor 102-105 is about 6000F., 8500F., 1,0000F. and 1,5000F. respectively.

In reactor 105, a mixture of oxygen and steam is introduced at the bottom to provide process heat and hot crude synthesis gas and flows against the movement of the carbonaceous granules such that the mixture passes upward through reactors 103-105 to fluidize the beds. The volatile matter removed from reactors 103-105 is carried to a scrubber 105' that condenses an oil-water mixture produced from the coal-tar vapors of the volatile matter by contacting the product gas stream with water. The condensed oil-water mixture is then sent to a separator 106 which separates gases 108 from the condensed oil-water mixture and removes the water from the mixture by phase separation and dehydration to provide condensed oil 110. The gas 108 from separator 106, together with gas 112 from reactor 102 is delivered to a scrubber 114 such that synthesis gas 11 6 is provided at the output of the scrubber 114. Synthesis gas 11 6 is introduced at the bottom of reactor 102 and flows against the movement of the carbonaceous granules such that gas 11 6 passes upward through reactor 102 to fluidize the bed. Condensed oil 110 is provided to a filter 11 7 which removes solids carried from reactors 102-105. Oil from filter 11 7 is provided to a fixed bed hydro-treatment 11 7r where it is treated with hydrogen that is separated from the synthesis gas of scrubber 114 by a separator 11 5.

The treatment of the oil with hydrogen in fixed bed hydro-treatment 11 7' removes sulfur, nitrogen and oxygen from the filtered oil and provide a high quality synthetic crude oil 11 8. It is preferred that hydrotreating be done at a temperature in the range of 700--8000F. in the presence of a nickelmolybdenum catalyst. Residual char is removed from reactor 1 05. It can be gasified to produce fuel gas, burned as a boiler fuel to assist in heating reactors 102-104, or used to produce hydrogen for treating the oil in fixed bed hydro-treatment 11 7'. Other process methods are adaptable to a coal feed of constant composition.

Advantageously, the present invention is totally compatible with the efficient transportation of the purified carbonaceous material. Thus, when the final conversion of the carbonaceous material is performed at a location remote from the source of the carbonaceous material, carbonaceous agglomerates 22 are readily transportable to the conversion site. Preferably, carbonaceous agglomerates 22 are transported in a liquid slurry. Alternatively, carbonaceous agglomerates 22 can be shipped in conventional transportation, such as covered railroad hopper cars, or briquettes can be formed from agglomerates 22, which are then reduced to the proper size distribution prior to conversion.

In accordance with the foregoing description, a method for the conversion of a carbonaceous material to a fluid product has been described in which non-carbonaceous particles are removed from the carbonaceous material prior to the gasification or liquidation step. The efficiency and economy of the final conversion step are thereby improved since significantly less non-carbonaceous material remains to be separated from the fluid product by relatively difficult and expensive purification or clarification procedures. Furthermore, the disclosed method for conversion of carbonaceous material improves the rate of conversion of the carbonaceous material into fluid product because the carbonaceous agglomerates developed in the process have a higher carbon content, they are substantially uniform and constant physical and chemical properties, and because less noncarbonaceous material is processed through the final conversion step where removal of noncarbonaceous material is relatively slow, difficult, and expensive. Also, the disclosed method is completely compatible with situations in which the conversion step is performed at a location which is remote from the source of the carbonaceous material since the carbonaceous agglomerates are readily transportable, preferably as a liquid slurry that is pumped through pipelines.

Claims

1. A method of converting a solid carbonaceous material into a fluid comprising the steps of: A. dispersing an amalgam of carbonaceous and non-carbonaceous fine particles in a suspension liquid to form a slurry; B. adding to the slurry a liquid lyophobic to the suspension liquid and the non-carbonaceous fine particles and lyophilic to the carbonaceous fine particles to form a mixture; C. agitating the mixture to preferentially agglomerate carbonaceous fine particles into discrete agglomerates having chemical and physical properties that are substantially uniform throughout and substantially constant for a considerable period of time while non-carbonaceous fine particles remain substantially unagglomerated in the mixture; D. separating the discrete agglomerates from the mixture; and E. heating the separated discrete agglomerates to at least 75O0F to convert the agglomerates to a fluid product.

2. A method of converting a solid carbonaceous material into a fluid according to Claim 1, wherein: Step C includes agitating the mixture to preferentially agglomerate carbonaceous fine particles into discrete agglomerates that are substantially inert to atmospheric oxidation; and Step E includes heating the separated discrete agglomerates to form a liquid product.

3. A method of converting a solid carbonaceous material to a fluid according to Claim 1 wherein: Step C includes agitating the mixture to preferentially agglomerate carbonaceous fine particles into discrete agglomerates that are substantially inert to atmospheric oxidation; and Step E includes heating the separated discrete agglomerates to form a gaseous product.

4. A method of converting coal into a fluid comprising the steps of: A. dispersing an amalgam of coal fine particles in a suspension liquid to form a slurry; B. adding to the slurry a liquid lyophobic to the suspension liquid and non-carbonaceous fine particles in the coal and lyophilic to carbonaceous fine particles in the coal to form a mixture; C. agitating the mixture to preferentially agglomerate carbonaceous fine particles into discrete agglomerates having chemical and physical properties that are substantially uniform throughout and substantially constant for a considerable period of time while non-carbonaceous fine particles remain substantially unagglomerated in the mixture; D. separating the discrete agglomerates from the mixture; and E. heating the separating discrete agglomerates to at least 7500F to convert the agglomerates to a fluid product.

5. A method of converting coal into a fluid according to Claim 4 wherein: Step C includes agitating the mixture to preferentially agglomerate carbonaceous fine particles into discrete agglomerates that are substantially inert to atmospheric oxidation, and Step E includes heating the separated discrete agglomerates to form a liquid product.

6. A method of converting coal to a fluid according to Claim 4 wherein: Step C includes agitating the mixture to preferentially agglomerate carbonaceous fine particles into discrete agglomerates that are substantially inert to atmospheric oxidation, and Step E includes heating the separated discrete agglomerates to form a gaseous product.

7. A method of converting a solid carbonaceous material into a fluid substantially as hereinbefore described with reference to the accompanying drawings.

8. A fluid whenever made by a method according to any one of Claims 1 to 7.