JPS61185589A - Coal liquefaction - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION The present invention relates to an improved method for liquefying coal. In particular, the present invention provides for the recovery of high quality heavy fractions while
It relates to a coal liquefaction process in which physical solid separation such as filtration or centrifugation can be replaced by distillation.

During any coal liquefaction process, the liquid product (liquid produced from coal) is a viscous slurry with a highly complex chemical composition containing significant amounts of solids such as ash, char, and refractory organic compounds. . These solids must be separated at some step during the liquefaction process to prevent scaling, clogging and fouling of downstream equipment, and to remove heteroatom contaminants and ash from the final product. Since a significant proportion of the solids contained in liquors obtained from coal are in the micron to submicron range, fine ash, char, and
Separating refractory organic compounds is extremely difficult.

The present invention provides a method for separating solids from liquid produced from coal, which is particularly effective in highly severe coal liquefaction processes.

The present invention also provides a method that does not use solid separation steps such as filtration or centrifugation.

SUMMARY OF THE INVENTION The present invention relates to a method of liquefying coal. The method includes heating a slurry of solvent and fine coal in a melting zone that substantially melts the coal to produce a first effluent;
adding a petroleum residue to at least a portion of the first effluent to produce a second effluent, and distilling the second effluent under reduced pressure conditions to produce an overhead fraction and a bottoms fraction. Consists of processes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method of liquefying coal. Generally, in direct coal liquefaction processes, distillation is used to obtain a circulating oil, which is a middle distillate, with the end point of the distillation being determined by the maximum allowable solids concentration in the residue. For this reason, processes in which higher boiling point materials are produced push down the distillation end point and cause valuable liquids to coexist with unreacted coal and minerals. Furthermore, the effectiveness of the circulating oil is reduced by lowering its endpoint. Because of this problem, it is not necessary to limit the circulating oil to middle distillate oil. If the first solids separation step is used to concentrate the solids in the product,
If distillation is then used to remove these, the problem becomes even worse. In this case, the circulating oil is a total fraction.According to the present invention, in order to alleviate these problems, a residue brought in from outside, preferably a petroleum residue with a low solids content, is used before the vacuum distillation. , most preferably low grade petroleum residues are added. The added residue is sometimes separated by low-boiling seafood for ease of handling, but it ends up mixed with the products from the coal. Using this idea, physical solid separations such as filtration and centrifugation are replaced by much simpler distillation.

This method can be applied to any coal liquefaction method,
This is particularly effective in severe liquefaction.

The most preferred coal liquefaction processes of the present invention are those carried out in at least two separate reaction steps. A solvent (i.e., slurrying medium) and granulated coal are removed from the granulated coal in the presence of hydrogen in the presence of hydrogen to substantially dissolve the coal, i.e., at least about 50% based on the coal, excluding ash and moisture. By heating the slurry, the coal is substantially melted in the high temperature first stage. The effluent slurry from the dissolution stage contains light gases (H2r C4-
It consists of not only undissolved solids (eH20, NH3, H2S, etc.) but also a normally liquid part consisting of hezotan-dissolved oil. Undissolved solids include undissolved coal and ash particles. The normally liquid part is dissolved solvent or coal, and contains non-distillable components. The term "solvent" also includes substances similar to solvents that are converted in the dissolution process.

At least a portion, preferably the entire amount, of what is usually a liquid, including undissolved solids, optionally accompanied by gaseous compounds, is passed to a second reaction zone where, under conditions of hydrogenation, an externally supplied It is reacted with 1 hydrogen in the presence of a hydrogenation catalyst. These hydrogenation condition buttons preferably include a temperature lower than the temperature at which the slurry was heated in the first stage. If desired, the usually liquid effluent from the first stage can be treated in an intermediate stage prior to being sent to the second hydrogenation zone in the present invention. The intermediate stage may be treated in a reactor packed with a catalyst, a reactor without a catalyst, a guard bed reactor, or the like. Such intermediate stages are described in U.S. Patent Application No. 106.580, filed December 26, 1979, entitled "Three Stage Coal Liquefaction Process," April 28, 1981, entitled "Three Stage Coal Liquefaction Process." U.S. Patent No. 4.264, issued on.
No. 430, and US Pat. Reference should be made to the contents of these patent specifications.

According to the invention, with or without treatment in an intermediate stage, at least a portion of the normally liquid product of the first reaction zone, preferably containing undissolved solids,
Hydrogen and catalyst are contacted in the second zone, where it is preferred to operate at lower temperatures. At least some or all of the undissolved solids may be removed in one step, but the solids in such intermediate stages may be of high viscosity and may also reduce the yield. Removal is not recommended. Preferably, the second hydrogenation zone includes a bed of hydrogenation catalyst particles, preferably in the form of a catalytic hydrogenation component supported on an inorganic refractory porous support.

The hydrogenation catalyst can be used as a fixed or packed bed, which may be a continuous or periodically moving bed, or a TP fluidized bed. The feed to the second reaction zone is preferably passed through the catalyst bed in an upward flow.

Feedstock The basic feedstock for the process of the invention is coal, such as bituminous coal, sub-bituminous coal, lignite, lignite, peat, etc. The coal is preferably pulverized to provide adequate surface area for melting. Preferably, the particle size of the coal is less than or equal to 14 inches in diameter, most preferably 100 mesh (Tiller sieve size).
However, larger particle sizes are also available. Coal can be added as a dry solid or as a slurry. If desired, the coal can also be ground in the presence of slurry oil.

Dissolving Solvent The effective solvent or slurrying medium in the process of the present invention preferably comprises at least a portion of the process effluent of the second stage hydrogenation zone. Some of the slurry media may contain other substances, such as crude oil or petroleum-based substances, such as petroleum residues, tar, asphalt-rich petroleum fractions, distilled crude oil, or tar obtained from solvent deasphalting of petroleum. etc. may also be included. It is preferable to include only petroleum-based solvent components having a boiling point of about 20 °C or higher. When crude oil or oil derived from petroleum containing soluble metal impurities such as nickel, vanadium or iron is used as a solvent component, the soluble metals are deposited on unreacted coal or coal ash particles. Furthermore, the presence of coal solids makes coking difficult in the medium used to form a slurry.

The granulated coal preferably has a solvent to coal weight ratio of about 1=2.
to 5:1, more preferably about 1=1 to 2=1. Mixing is done in a slurry tank which transports the slurry to a dissolution tank. In the dissolution zone, the slurry is preferably heated to a temperature of about 400°C to 480°C, more preferably 425°C to 450°C, most preferably 435°C.
to a temperature of 450° C. for a period long enough to substantially melt the coal. At least about 50% by weight, preferably 70% by weight or more, more preferably 90% by weight
The above moisture and ash-free coal is melted in a melting tank, where it forms a solid mixture of solvent, melted coal, and unbathed melted coal. Hydrogen is also introduced into the dissolution zone, either as raw hydrogen or in a mixture with recycle gas. Although carbon monoxide may be present in either reaction zone, it is preferred that the feed gas to both reaction zones is not enriched with carbon monoxide.

The reaction conditions in the dissolution tank are such that at least 5% of the coal solids
Since 0% is dissolved, it can vary within a wide range. Typically, the slurry should be heated to at least about 400° C. to melt at least 50% of the coal in a reasonable amount of time. Furthermore, the coal should not be heated above 480° C. to avoid thermal decomposition, which would significantly reduce the yield of the normally liquid product. Other reaction conditions in the dissolution zone include residence times of 0.1 to 3 hours, preferably 0.1 to 1.0 hours;
The time and pressure are from 70 to 700 atm, preferably 100 atm.
to 350 atmospheres, more preferably 10 to 170 atmospheres, and the hydrogen gas flow rate may be 170 to 350 atmospheres per cubic meter of slurry.
500 m3, preferably 50 per cubic meter of slurry
It might be 0 or 1780 curses 3. The hydrogen pressure in the dissolution zone is preferably maintained at 35 atmospheres or higher. The feed fluid may flow upward or downward in the dissolution zone, but upward flow is preferred. Preferably, the dissolution zone is sufficiently elongated to approach plug flow conditions. A suitable dispersion device for the fluid stream for introducing the feed fluid into the dissolution zone is described in “Spocket Dispersion Device for Upflow Reactors”, filed June 19, 1980.
No. 160,793, to which reference should be made. Although the dissolution zone can be operated without catalyst or contacting particles from an external source, the minerals contained in the coal may have some catalytic effect. However, it has been found that the presence of a suspension dissolving catalyst can increase the yield of light liquid products and, in some cases, can increase the total coal conversion of the process. However, it is preferable that the first-stage dissolution tank does not contain contact particles such as alumina and silica that do not have catalytic ability. "
"Particles without normal catalytic ability" are particles that do not accept transition metals supplied from the outside as hydrogenation components.

The dissolution catalyst may be any well-known material utilized in the prior art and contains active catalyst components in the form of elements or compounds. Examples include tin; lead, or transition elements, especially the Periodic Table of the Elements [Chemical 5try and Phys.
sics) 45th edition (1964)] No. 1 V-B
, V-BVl-finely divided particles of group B or group 1 elements,
salts or other compounds. A dissolving catalyst composition is defined herein as a catalyst composition that is added to a process as a solution or dispersion, regardless of the form of the catalytic elements.

The catalyst for dissolution in a dispersed state in the first stage may be dissolved in the liquid phase, or may be suspended in the liquid phase in the form of fine particles, emulsified droplets, etc. entrained in the liquid effluent. The dispersed catalyst may be added to the coal before contacting the solvent, to the bath agent before contacting the coal, or to the coal-solvent slurry. A particularly good method for adding the catalyst in a dispersed state is to add the water-soluble compounds of the hydrogenation component of the catalyst as an oil/aqueous solution emulsion. For the use of emulsion catalysts of this type for coal liquefaction, reference may be made to U.S. Pat.
, 013 specification. The water-soluble salt of the catalytic metal may be essentially any water-soluble salt of a metal catalyst, such as iron group, tin or zinc. Nitrates or acetates are the most convenient forms of certain metals. When it comes to molybdenum, tungsten or vanadium, complex salts such as alkali metal or ammonium molybdates, tungstates or vanadates are preferred. 2
Mixtures of one or more metal salts can also be used. A particularly preferred salt is ammonium heptamolybdate tetrahydrate [(NH4)6MOfo24.4H2
o], nickel dinitrate/hexahydrate CNi(NO3)2/
6HsO) and sodium tungstate dihydrate (
NaWO4.2H20].

Any convenient method can be used to emulsify the solution of the salt in the hydrocarbon medium. A detailed method of forming an aqueous emulsion is described in U.S. Pat. No. 4.1, cited above.
36.013.

When added as a finely divided solid as a catalyst for dissolution, finely divided metals, their oxides, sulfides, etc., such as Fθ3X,
Waste fines from metal scouring processes, such as iron, molybdenum, and nickel, crushed waste catalysts, such as fluid catalytic cracking waste catalyst fines, hydrotreating waste catalyst fines, recovered coal ash, and solid coal liquefaction residues. good. The finely divided dissolving catalyst added in the first stage is generally intended to be an unsupported catalyst. i.e. silica, alumina,
It does not need to be supported on an inorganic carrier such as magnesia or the like. However, if desired, inexpensive spent catalysts containing catalytic metals may be used.

Further, the dissolving catalyst in a dispersed state may be an oil bath compound containing a catalytic metal, such as phosphomolybdic acid, molybdenum, naphthenates of chromium and vanadium, and the like. Suitable oil-soluble compounds are converted in situ to catalysts for dissolution.

Such catalysts and methods for their use are described in U.S. Pat.
No. 67, the contents of which should be referred to.

The effluent from the dissolution zone includes components that are normally gaseous, components that are normally liquid, and non-bath melted coal, coal ash and dispersions,
Undissolved solid components, including catalyst particles, are removed. The entire effluent from the first stage zone is sent directly to the second stage hydrogenation zone. In some cases, light gases such as C4-
1 Water, NH3, H23, etc. may also be removed from the first stage product before passing the entire effluent and solids, which are usually liquids, to the second stage. The feed to the second stage is at least a majority (50 weight tons) by the usually liquid product of the first stage.
% or more), and further includes undissolved coal solids and a dispersed hydrogenation catalyst. The liquid feed to the second stage is the heaviest liquid part of the liquid product of the first stage, e.g.
It should contain at least one such liquid, which refers to components that are not distilled. In the second stage hydrogenation zone, the liquid-solid feed is contacted with hydrogen. This hydrogen is
It may be contained in the first stage effluent,
It may be added as make-up hydrogen or circulating hydrogen. The second stage reaction zone contains a second hydrogenation catalyst, typically different from the dissolution catalyst used in the first stage. The second stage hydrogenation catalyst is
Preferably, it is one of the commercially available hydrogenation catalysts, such as a commercial hydrotreating or hydrogenation fraction 1γ catalyst. The catalyst suitable for the second stage preferably contains a hydrogenation component and a cracking component. Preferably, the hydrogenation component is supported on a refractory decomposition carrier, most preferably a weakly acidic decomposition carrier such as alumina. Other suitable decomposition carriers include 2! gi or higher refractory oxides such as silica-alumina, silica-magnesia, silica-zirconia, alumina-boria, silica-titania, clays and acid-treated clays such as attapulgite, seviolite, halloysite, chrysolite, palygorskite, kaoli Includes night, light, etc. Suitable hydrogenation components are preferably selected from group Vl-B metals, group I metals or their oxides, sulfides and mixtures thereof. Particularly useful combinations are cobalt-molybdenum, nickel-molybdenum, or nickel-tungsten on an alumina support. A preferred catalyst consists of an alumina matrix containing about 8% nickel, 20% molybdenum, 6% titanium, and 2 to 8 phosphorus. This type of catalyst was introduced on September 10, 1968.
U.S. Patent No. 3.401.125 to Jatuhue entitled "Co-precipitation process for the production of multi-component catalysts" published in Japan - 'tK
A back route can be made using the general co-dellation described and also by using phosphoric acid as the source of phosphorus.

In the process of the present invention, it is important not to raise the temperature of the second stage hydrogenation zone too high because it has been observed that the second stage catalyst becomes rapidly contaminated at high temperatures. This is particularly important for systems using fixed or packed beds where frequent catalyst replacement is required.The temperature in the second hydrogenation zone is typically below about 425°C. Preferably 310°C or higher, and more preferably 340°C
It should be maintained at a temperature between 400°C and 400°C, but there are cases where it is acceptable for the temperature at the end of operation to exceed this temperature. Generally, the temperature in the second hydrogenation zone will be at least about 15°C at all times lower than the temperature in the first hydrogenation zone, preferably from 55°C to 8°C.
Lower the temperature by 5°C. Other hydrogenation conditions in the second hydrogenation zone include a pressure cuff of 0 to 700 atm, preferably 70 to 200 atm, more preferably 100 to 170 atm, hydrogen flow rate of 350 to 35 D Om3/m3 of slurry. , preferably 500 17801n3 per cubic meter of slurry.
And the slurry time space velocity is from 0.1 to 21/hr.

Preferably, 1 to i, Q l/hr are included. If desired, the pressure in the catalytic hydrogenation zone may be essentially the same as the pressure in the bath reactor zone.

The catalytic hydrogenation zone is desirably operated as an upflow packed or fixed bed, although ebullated beds may also be used. The packed bed is moved continuously or periodically, preferably countercurrently to the feed slurry, to allow for periodic incremental catalyst replacement. It may be desirable to remove the light gases produced in the first stage and replenish the feed to the second stage with hydrogen. Doing so will extend the life of the high hydrogen partial pressure species catalyst.

When using a fixed bed or packed bed for the second hydrogenation stage,
It is desirable to limit the severity of the second stage and avoid undesirable asphaltene deposition that results in undue blockage and pressure drop. This method of operation was published June 29, 1981, entitled "Hydroprocessing of Asphaltene-Containing Carbonaceous Feedstocks".
US patent application Ser. The feedstock to the second stage is from the aforementioned U.S. Patent Application No.
Preferably, it is fed through a dispersion device as disclosed in US Pat. No. 60,793.

The effluent from the hydrogenation zone is separated into a gas fraction and a liquid-solid fraction. The gas fraction is a stream of hydrogen, C1
~C3 stream, H20Ar'H3/H2S (7) stream, and C,-c6 naphtha stream. If desired, cleaning solvents can also be added. It is desirable to separate the hydrogen from other gaseous components and recycle it to the second stage hydrogenation step or the first stage dissolution step, as desired.

From the liquid-solid fraction, the gas is generally evaporated and H
Gas containing 2O and naphtha is recovered.

According to the invention, a residue, preferably a petroleum residue, most preferably a low grade residue, is added to the effluent from the liquefaction process. The residue may be added to the effluent from the first stage liquefaction or to the hydrogenation effluent, with or without the pre-separation described above. In either case, a residue, preferably a petroleum residue, typically having a low solids content of about 1% by weight or less, is added to the liquefied effluent after liquefaction. The added residue is sent to a vacuum distillation column where distillation is performed under reduced pressure. In the process of the invention, a vacuum distillation column serves as a means for separating solids from the liquefied effluent. As the vacuum distillation column distills the feed under reduced pressure, an overhead fraction containing light coal products and medium and heavy distillate oils is recovered.

This distillate oil derived from coal may be recycled for use as a coal dissolving solvent.

Any gas removed will be used as fuel or
It is sent to a steam reformer to produce hydrogen that is recycled to necessary processes or used for other purposes.

The bottom fraction extracted from the vacuum distillation column basically consists of a polymeric liquid with a boiling point of 10,000 F1 or more, and contains unreacted coal, minerals, residues derived from coal, and petroleum residues. The amount of petroleum residue added to coal liquefaction effluent is
As long as the residual fraction can be pumped, the solids content can be kept high (
It is decided to do so.

This value is generally about 50 T solids concentration and is believed to be the highest solids concentration that can be handled at the bottom of the vacuum distillation column.

There are many methods available for vacuum distillation column bottoms consisting of unreacted coal, minerals, coal derived residues and petroleum residues. High-severity coal liquefaction processes have high hydrogen consumption, and partial oxidation of the non-distillable fractions produced from coal alone will not meet the demand. In such cases, low grade residue is added to partially oxidize or gasify the mixture of coal residue, petroleum residue and unreacted coal to supply all or a portion of the hydrogen requirement. The bottom fraction is also deasphalted or coked and used as fuel or for other purposes.

Although the invention has been described with respect to particular embodiments,
These embodiments have been described for illustrative purposes only, and those skilled in the art will be able to provide the following without departing from the scope of the invention:
It should be understood that numerical values may be changed or modified. Accordingly, the invention is not to be limited as described above, but only as defined by the claims appended hereto.

Claims (19)

[Claims] (1) (a) substantially melting the coal by heating a slurry consisting of a solvent and fine coal in a melting zone;
(b) adding a residue to at least a portion of the first effluent to produce a second effluent; and (c) producing the second effluent under reduced pressure. A method for liquefying coal, comprising: distilling a column to produce a column top fraction and a column bottom fraction. (2) The method according to claim 1, wherein the residue is a petroleum residue. 3. The method of claim 1, wherein the residue has a solids content of about 1% or less. (4) The method according to claim 1, characterized in that at least a portion of the overhead fraction is recycled to the dissolution zone. (5) The conditions in the melting zone range from approximately 400°C to 4°C.
80° C., a pressure of about 70 to 700 atmospheres, a hydrogen content of about 170 to 3500 cubic meters per cubic meter of slurry, and a residence time of about 0.1 to 3 hours. Method. (6) The method according to claim 1, wherein the dissolution zone contains a dissolution catalyst in a dispersed state. (7) The addition of petroleum residue in step (b) is controlled such that the bottom fraction of step (c) contains about 50% solids. The method described in. (8) The method according to claim 1, wherein the solvent is petroleum or a solvent obtained from petroleum. 9. The method of claim 1, wherein the weight ratio of solvent to coal is about 1:2 to 5:1. (10) (a) heating a slurry of solvent and granulated lime in a dissolution zone to substantially melt the coal and produce a first effluent; (c) producing a second effluent by contacting at least a portion of the effluent with hydrogen in a reaction zone at hydrogenation conditions in the presence of an externally supplied hydrogenation catalyst; (d) distilling the third effluent under reduced pressure to produce an overhead fraction and a bottoms fraction; A method for liquefying coal, characterized by comprising the following steps: (11) The method according to claim 10, wherein the residue is a petroleum residue. 12. The method of claim 10, wherein the residue has a solids content of about 1% or less. (13) Hydrogenation conditions are temperature below 425°C and pressure about 70°C.
11. The method of claim 10, comprising a hydrogen flow rate of 350 to 3500 cubic meters per cubic meter of slurry and a slurry hourly space velocity of about 0.1 to 2 l/hr. (14) The method according to claim 10, characterized in that at least a portion of the overhead fraction is recycled to the dissolution zone. (15) Conditions in the melting zone are a temperature of about 400°C to 480°C, a pressure of about 70 to 700 atm, a hydrogen gas amount of about 170 to 3500 cubic meters per cubic meter of slurry, and a residence time of about 0.1 to 3 hours. 11. The method of claim 10. (16) The method according to claim 10, wherein the dissolution zone contains a dissolution catalyst in a dispersed state. (17) The addition of petroleum residue in step (c) is controlled such that the bottom fraction of step (d) contains about 50% solids. The method described in. (18) The method according to claim 10, wherein the solvent is petroleum or a solvent obtained from petroleum. 19. The method of claim 10, wherein the weight ratio of the solvent to coal is about 1:2 to 5:1.