GB2110712A

GB2110712A - Coal hydrogenation

Info

Publication number: GB2110712A
Application number: GB08234510A
Authority: GB
Inventors: Paul D Schuler; Edwin S Johanson
Original assignee: HRI Inc; Hydrocarbon Research Inc
Current assignee: HRI Inc; Hydrocarbon Research Inc
Priority date: 1981-12-07
Filing date: 1982-12-03
Publication date: 1983-06-22
Also published as: AU9107282A; CA1194443A; ZA828858B; JPS58104987A; DE3244251A1

Abstract

Hydrogenation of coal to produce hydrocarbon liquid and gas products is performed in a thermal reaction zone 20, in which a coal/ oil slurry 19 flows generally downwardly countercurrent to upflowing hydrogen 15; an effluent stream 21 containing light hydrocarbon liquid and gas is withdrawn from the thermal reaction zone upper end, and a heavy liquid stream 28 containing unconverted coal and ash is withdrawn from the reaction zone bottom end. A portion 26 of the light liquid effluent is preferably recycled to the reaction zone lower end for upflow therein to help increase coal residence time and for further hydrogenation reaction. As shown in Fig. 2 the heavy liquid bottoms stream from the thermal reaction zone and containing unconverted coal and ash and a liquid portion of the upper effluent can be passed with additional hydrogen to a second catalytic reaction step for further hydrogenation reaction to increase the yield of lower-boiling hydrocarbon liquid products. <IMAGE>

Description

SPECIFICATION Coal hydrogenation process using thermal countercurrent flow reaction zone This invention relates to thermal hydrogenation and conversion of coal utilising counter current flow of the coal feed and hydrogen to produce hydrocarbon gas and liquid products.

It relates particularly to such a process wherein a thermal countercurrent flow hydrogenation zone is used upstream of a catalytic hydrogenation reaction zone.

In thermal hydrogenation conversion operations on coal to produce lower boiling product liquids and gases, the coal feed and hydrogen have generally both been introduced into the bottom of the reaction and both passed upwardly therethrough. However, reactor plugg ing often occurs owing to heavy particulate mineral matter than forms in the reactor, settles and accumulates in the bottom of the reactor. Such accumulated deposits in the reactor interfere with sustained process operations and are thus quite undesirable.

U.S. Patent No. 3,660,267 to Rieve, et al, discloses a non-catalytic coal hydrogenation process using an upflow reactor with contact solids being purged from the bottom end as needed. Also, some coal gasification processes have used bottom withdrawal of char material. For example, U.S. Patent No.

3,876,392 to Kalina, et al, discloses a coal gasification process in which coal is introduced into the upper portion of a fluidised bed hydrogasification zone maintained at 1500-1800 F (816-982 "C) temperature, and char solids are withdrawn from the bottom for separate heating and recycle. U.S.

Patent No. 3,700,584 to Johnson, et al, discloses a process for two-stage catalytic processing of coal, wherein the gaseous effluent from the first stage bypasses the second stage. Also, U.S. Patent No. 4,111,788 to Chervenak et al discloses a two-stage coal hydrogenation process using a thermal first stage reaction zone and a catalytic second stage reaction zone; however, counterflow of coal feed and hydrogen is not used. Thus, a coal thermal hydrogenation and liquefaction process utilising countercurrent flow of coal-oil slurry and hydrogen is needed to avoid undesirable solids accumulations in the reaction zone.

The present invention provides a process for thermal hydrogenation and conversion of coal to produce hydrocarbon gaseous and liquid products, which comprises: (a) mixing coal in particulate form with sufficient slurrying oil to form a pumpable mixture; (b) introducing the coal-oil slurry feed into the upper portion of a thermal reaction zone, and introducing hydrogen into the bottom portion of said zone for upward flow countercurrent with said slurry feed; (c) hydrogenating the slurry feed in said reaction zone under conditions within the ranges of 775-900"F (413-482"C) temperature and 1000-5000 psig (69-345 bar gauge) hydrogen partial pressure;; (d) withdrawing a light hydrocarbon liquid effluent material from the upper portion of the reaction zone, and passing said effluent to phase separation and distillation steps to recover gas and liquid product; and (e) withdrawing a heavier hydrocarbon liquid stream containing unconverted coal and ash from the bottom portion of the reaction zone, and passing said stream to further processing steps to recover hydrocarbon liquid products.

The invention thus discloses a coal hydrogenation process having a thermal reaction zone which utilises a countercurrent flow arrangement for the coal feed and hydrogen.

The coal feed is introduced as a coal-oil slurry into the upper portion of the thermal reaction zone, and hydrogen is introduced into the bottom portion and flows upwardly through the coal slurry in the reaction zone. The downward flow of coal-oil slurry and upward flow of hydrogen provides sufficient residence time for the hydrogenation reaction and conversion of the coal to produce hydrocarbon gases and liquids, and precludes undesirable accumulation of agglomerated solids in the reaction zone lower end.

The coal residence time in the thermal reaction zone can be preferably increased and controlled by providing some recycle of reactor light liquid effluent from the upper portion back to the lower portion of the reactor. Such liquid recycle provides an upflowing liquid velocity which retards the settling rate of the coal solids in the reaction zone and thereby increases their residence and reaction times.

Also, the upflow of hydrogen gas provides some agitation and desirably strips hydroconverted light ends from the reactor liquid.

The reaction conditions used in the thermal reaction zone are within the ranges of 775-900"F (413-482"C) temperature and 1000-5000 psig (69-345 bar gauge) hydrogen partial pressure. A temperature gradient usually exists within the reaction zone and helps to provide internal reflux. The downflow of liquid serves to carry the ash particulates out of the reaction zone before they increase in size or accumulate therein in appreciable quantity. Effluent streams are withdrawn from both the upper and lower portions of the reaction zone, and are passed to phase separation and distillation steps for recovery of hydrocarbon gas and liquid products.

Alternatively, the heavy liquid fraction or stream withdrawn from the lower portion of the countercurrent flow thermal reaction zone of this invention can be advantageously passed on to a catalytic reaction zone, in which such material is further hydrogenated and converted to produce increased yields of hydrocarbon gaseous and lower-boiling liquid products.

Reference is now made to the accompanying drawings showing preferred embodiments of the invention, in which: Figure 1 is a schematic drawing showing a coal hydrogenation process utilising a thermal reaction zone arranged for countercurrent flow of coal slurry feed and hydrogen to produce hydrogen gas and liquid products; and Figure 2 is a schematic flowsheet showing a thermal countercurrent flow reaction zone used upstream of an ebullated catalyst bed reaction zone to produce increased yields of hydrocarbon liquid products.

As shown in Fig. 1, coal such as bituminous, sub-bituminous or brown coal at 10 is introduced into a preparation unit 12, wherein the coal is dried to remove substantially all surface moisture, ground to a desired particle size and screened. For this process, the coal feed should have a particle size of 20-350 mesh (U.S. Sieve Series). The coal particles are passed to a slurry mix tank 14 where the coal is blended with sufficient slurrying oil at 1 6 to provide a pumpable mixture. This slurrying oil is produced in the process as described below, and the weight ratio of oil to coal should be at least about 1.0 but need not exceed about 6.

The coal-oil slurry is pressurised by a pump 1 7 and passed through a slurry heater 18, in which the slurry is heated to a temperature usually near the reaction zone temperature.

The heated slurry at 1 9 is then introduced into the upper portion of a thermal reactor 20.

Heated hydrogen is introduced at 1 5 into the bottom portion of the reactor 20, and passes upwardly in countercurrent flow relation with the coal slurry feed. The coal slurry and hydrogen flow in countercurrent relation with a controlled residence time, and the coal hydrogenation reaction is achieved therein without the use of an added catalyst.

The reaction conditions in the thermal reactor are maintained within the broad ranges of 775-900"F (413-482"C) temperature and 1000-5000 psig (69-345 bar gauge) hydrogen partial pressure, and preferably at 800-900"F (427-482"C) and 1500-4500 psig (103-310 bar gauge) hydrogen partial pressure. The space velocity for the coal can be within the range of 15-50 pounds coal/hr/ft3 reactor volume (240.801 kgh-'m 3), and preferably is 20-40 pounds/hr/ft3 (320-641 kgh - 1 m - 3).

An effluent stream of gas and light liquid, such as normally boiling in a range up to about 550"F (288"C), is withdrawn at 21 from the reactor upper end and is passed to a hot phase separator 22. The stream 21 preferably comprises a major part of the reactor total effluent. From the separator 22, the resulting vapour portion 23 is usually passed to a further phase separation step at 24 and then via line 24a to a hydrogen purification step 25 provided with a vent 25b. Recovered hydrogen in a stream 25a is reheated and recycled via line 1 5 to the reactor 20. with make-up hydrogen being provided at 1 5a as needed. From the separator 24, the liquid portion 24b is passed to an atmospheric distillation step 38.

From the separator 22. a liquid stream 26 is pressure-reduced at 29 and passed to a phase separator 30. Also. a part 27 of the liquid stream 26 is preferably recycled to the bottom of the reactor 20 for providing an upward liquid flow velocity therein to hinder the downward flow and settling of heavy liquids and coal solids and to provide for a controlled increased residence time for the larger unconverted coal particles and for achieving further thermal hydrogenation reaction therein. The recycle weight ratio of the recycle stream 27 to the coal in the feed stream 1 9 should usually be within the range of from about 0.5 to 1.0.

A bottom stream 28, usually all boiling above about 500"F (260to) and containing residuum, unconverted coal solids and ash, is withdrawn from the lower end of the thermal reactor 20 and is usually also pressure-reduced at 29a and passed to the phase separator 30. From the separator 30, the vapour portion 31 is passed, together with the product stream 24b, to the atmospheric distillation step 38, from which hydrocarbon liquid product streams, such as an overhead light liquid product 37, are withdrawn as desired.

The resulting bottoms stream 32 from the separator 30 is passed to a liquid-solids separation step 34, from which at least a portion of an overflow stream 35 containing reduced solids concentration is used as the slurrying oil 16. The remaining bottoms stream 36 containing increased solids concentration is passed to a vacuum distillation step 40, from which an overhead stream 41 is combined with a bottom stream 39 from step 38 to form a liquid product stream 42. A heavy vacuum bottoms stream 44 normally boiling above about 975 F (524"C) and containing unconverted coal and ash is withdrawn for gasification or disposal. If needed, a portion 42a of the liquid stream 42 can be recycled to supplement the slurrying oil 1 6.

An alternative embodiment of the present invention is shown in Fig. 2, which is similar to the Fig. 1 embodiment except that upper effluent and bottoms streams withdrawn from the countercurrent flow thermal reactor 20 are passed on to a second reactor 50 containing an ebullated catalyst bed for further catalytic hydrogenation reaction and conversion to produce increased yields of lower-boiling liquid products. Reference numerals in Fig. 2 have the same meanings as the corresponding ref erence numerals in Fig. 1, unless specified otherwise below. As shown in Fig. 2, the light effluent stream 21 is passed to the phase separator 22, from which a vapour stream 23 is passed to a further phase separation step 24 and then to a hydrogen purification step 25. The remaining liquid stream 24b is passed to the bottom of the reactor 50.

From the separator 22, a portion 27a of the liquid stream 26a is recycled to the thermal reactor 20, and the remainder is passed via line 48, together with additional hydrogen at 46, as stream 49 to the ebullated bed reactor 50. Also, a bottom liquid stream 28a withdrawn from the lower end of the thermal reactor 20 is passed into the lower end of the reactor 50, which contains an ebullated bed of commercial catalyst 52, such as cobaltmolybdenum on alumina extrudates having a diameter of 0.030-0.065 inch (0.76-1.65mm). In this embodiment, the coal-oil feedstream 1 9a is introduced into the thermal reactor 20, from which most of the reactor effluent material is usually removed from the top of the reactor as stream 21, and the remaining portion is removed from the lower end as stream 28a.

The reaction conditions in the catalytic reactor 50 are maintained within the broad range of 750-875"F (399-468"C) temperature and 1000-4000 psig (69-276 bar gauge) hydrogen partial pressure, and preferably at 770-870"F (410-466"C) and 1500-3500 psig (103-241 bar gauge) hydrogen partial pressure. The space velocity for the coal can be within the range of 15-50 pounds coal/hr/ft3 reactor volume (240-801 kgh-'m-3), and preferably is 20-40 pounds/hr/ft3 (320-641 kgh-1m-3). The liquid and gas mixture is passed uniformly upwardly through the catalyst bed 52 at a velocity sufficient to expand the bed by 10-100% over its settled height and to achieve intimate contact of the liquid slurry with the catalyst. using commercially known procedures.A downcomer 51 is provided for internal recycle.

An effluent stream of liquid and gas mixture is withdrawn from the reactor upper end at 53 and is passed to a hot phase separator 54.

The resulting vapour portion is usually cooled at 55 and passed to a further phase separation step at 56, from which a vapour stream 57 is passed to the hydrogen purification step 25. The recovered hydrogen stream 25a is recycled at 45 via heater 45a to the reactor 20, and at 46 to the reactor 50.

From the phase separator 54, a bottoms liquid stream 58 is pressure-reduced at 59 and passed to a phase separator 60, along with a liquid stream 58a from the separator 56, which is pressure-reduced at 59a. A vapour portion 61 is removed and passed to an atmospheric distillation step 68, from which an overhead liquid product can be withdrawn at 67 and a bottoms liquid withdrawn at 69, as well as an intermediate product at 67a.

Also from the separator 60, the resulting bottoms liquid stream 62 is passed to a liquid-solids separation step 64, which is preferably multiple hydroclone units connected in parallel.An overflow stream 65 containing reduced solids concentration is recovered in line 65 and used as slurrying oil at 1 6. The remaining bottoms stream 66 containing an increased concentration of unconverted coal and ash solids is passed to a vacuum distillation step 70. An overhead stream 71 is combined with stream 69 and comprises the liquid product stream 72. A heavy vacuum bottoms stream 74 boiling above about 975"F (524"C) and containing some unconverted coal and ash solids is withdrawn for gasification or disposal. If needed, a portion 72a of the product stream 72 can be recycled to supplement the slurrying oil stream 1 6.

Claims

1. A process for thermal hydrogenation and conversion of coal to produce hydrocarbon gaseous and liquid products, which comprises: (a) mixing coal in particulate form with sufficient slurrying oil to form a pumpable mixture; (b) introducing the coal-oil slurry feed into the upper portion of a thermal reaction zone, and introducing hydrogen into the bottom portion of said zone for upward flow countercurrent with said slurry feed; (c) hydrogenating the slurry feed in said reaction zone under conditions within the ranges of 775-900"F (413-482"C) temperature and 1000-5000 psig (69-345 bar gauge) hydrogen partial pressure; (d) withdrawing a light hydrocarbon liquid effluent material from the upper portion of the reaction zone, and passing said effluent to phase separation and distillation steps to recover gas and liquid product; and (e) withdrawing a heavier hydrocarbon liquid stream containing unconverted coal and ash from the bottom portion of the reaction zone, and passing said stream to further processing steps to recover hydrocarbon liquid products.

2. A process as claimed in claim 1, wherein the coal feed is mixed with a slurrying oil in an oil/coal weight ratio in the range of from 1.0 to 6.

3. A process as claimed in claim 1 or 2, wherein the reaction zone conditions are within the ranges of 800-900"F (427-482"C) temperature, 1500-4500 psig (103-310 bar gauge) hydrogen partial pressure, and the coal space velocity is 15-50 pounds coal/hour/ft3 reactor (240-801 kgh-'m-3).

4. A process as claimed in any of claims 1 to 3, wherein a part of the light liquid effluent from the thermal reaction zone upper portion is recycled to the lower portion of said reaction zone and flows upwardly therein to hinder the downward flow of coal particles and thereby increase the coal residence and reaction time.

5. A process as claimed in any of claims 1 to 4. wherein the heavy hydrocarbon liquid stream withdrawn from the bottom of said thermal reaction zone is phase separated and distilled for further recovery of hydrocarbon liquid products.

6. A process as claimed in any of claims 1 to 5, wherein the effluent material withdrawn from the upper portion of the reaction zone comprises a major part of the reaction zone total effluent.

7. A process as claimed in any of claims 1 to 6, wherein the bottom liquid stream withdrawn from the thermal reaction zone bottom portion is passed with additional hydrogen into an ebullated bed catalytic reaction zone for further hydroconversion of resdiuum and unconverted coal to produce an increased yield of lower boiling hydrocarbon liquids.

8. A process for thermal hydrogenation and conversion of coal to produce hydrocarbon gaseous and liquid products which comprises: (a) mixing coal in particulate form with sufficient process-derived slurrying oil to form an oil/coal weight ratio in the range of from 1.0 to 6; (b) introducing the coal-oil slurry feed into the upper portion of a thermal reaction zone, and introducing hydrogen into the bottom portion of said zone for upward flow therein countercurrent with said slurry feed; (c) hydrogenating the slurry feed in the reaction zone under conditions within the ranges of 775-900"F (413-482"C) temperature, 1000-5000 psig (69-345 bar gauge) hydrogen partial pressure and coal space velocity of 15-50 pounds coal/hour/ft3 reactor (240-801 kgh-1m-3);; (d) withdrawing a light hydrocarbon liquid effluent material from the upper portion of the reaction zone, passing the effluent to phase separation and distillation steps, and recycling a part of the light liquid effluent to the lower portion of the thermal reaction zone to hinder the downward flow of coal particles therein to increase the coal residence and reaction time; and (e) withdrawing a heavy hydrocarbon liquid stream containing unconverted coal and ash from the bottom portion of the reaction zone, and passing said stream to further processing steps to recover hydrocarbon liquid products.

9. A process for thermal hydrogenation and conversion of coal to produce hydrocarbon gaseous and liquid products, which comprises: (a) mixing coal in particulate form with sufficient slurrying oil to form a pumpable mixture; (b) introducing the coal-oil slurry into the upper portion of a thermal reaction zone and introducing hydrogen into the bottom portion of said zone for upward flow countercurrent with said slurry feed; (c) maintaining the reaction zone conditions within the ranges of 750-900-F (399-482"C) temperature and 1000-5000 psig (69-345 bar gauge) hydrogen partial pressure; (d) withdrawing a light hydrocarbon liquid effluent material from the upper portion of the reaction zone, and passing said effluent to phase separation and distillation steps to recover gaseous and liquid products: and (e) withdrawing a heavy hydrocarbon liquid stream containing unconverted coal and ash from the bottom portion of the reaction zone and passing said liquid together with additionai hydrogen to an ebullated bed catalytic reaction zone for further hydroconversion of residuum and unconverted coal to produce increased yields of hydrocarbon gases and lower boiling liquids.

10. A process as claimed in claim 7, wherein the ebullated bed reaction zone conditions are maintained within the ranges of 750-875"F (399-468"C) temperature, 1000-4000 psig (69-276 bar gauge) hydrogen partial pressure, and a coal liquid space velocity of 20-40 pounds coal/hour/ft3 reactor volume (320-641 kgh-'m 3).

11. A process for the thermal hydrogenation and conversion of coal without catalyst to produce hydrocarbon gaseous and liquid products wherein the coal is mixed with a process-derived slurrying oil and the mixture is introduced together with hydrogen into the reaction zone maintained at conditions within the range of 700-950"F (371-510'C) temperature and 1000-5000 psig (69-345 bar gauge) hydrogen partial pressure, characterised in that: (a) the coal-oil slurry is introduced into the upper portion of the thermal reaction zone for downward flow therein; (b) the hydrogen is introduced into the lower portion of the thermal reaction zone for upward flow therein countercurrent to the coal liquid; and (c) a light hydrocarbon effluent material is withdrawn from the upper portion of the reaction zone and a heavier hydrocarbon stream containing unconverted coal and ash is withdrawn from the bottom portion of the reaction zone.

1 2. A process as claimed in claim 11, wherein the light hydrocarbon liquid effluent withdrawn from the upper portion of the reaction zone is passed to a phase separation step, from which a minor part of the liquid is recycled to the lower portion of the reaction zone, and the heavy hydrocarbon liquid fraction containing unconverted coal and ash withdrawn from the lower portion of the reaction zone is passed to further processing steps to recover hydrocarbon gaseous and liquid products.

1 3. A process for thermal hydrogenation and conversion of coal, substantially as hereinbefore described with reference to the accompanying drawings.

14. Hydrocarbon gaseous or liquid products when produced by a process as claimed in any of claims 1 to 13.