CA1194443A

CA1194443A - Coal hydrogenation process using thermal countercurrent flow reaction zone

Info

Publication number: CA1194443A
Application number: CA000417085A
Authority: CA
Inventors: Paul D. Schuler; Edwin S. Johanson
Original assignee: HRI Inc
Current assignee: HRI Inc
Priority date: 1981-12-07
Filing date: 1982-12-06
Publication date: 1985-10-01
Also published as: AU9107282A; DE3244251A1; GB2110712A; ZA828858B; JPS58104987A

Abstract

ABSTRACT

Thermal hydrogenation of coal to produce hydrocarbon liquid and gas products is performed in a thermal reaction zone, in which a coal/oil slurry flows generally downwardly countercurrent to upflowing hydrogen. An effluent stream containing light hydrocarbon liquid and gas is withdrawn from the thermal reaction zone upper end, and a heavy liquid stream containing unconverted coal and ash is withdrawn from the reaction zone bottom end. Both streams are passed to phase separation and distillation steps for recovery of hydrocarbon gas and liquid products. A portion 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. If desired, the heavy liquid bottoms stream from the thermal reaction zone and containing unconverted coal and ash 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.

Description

COAL HYDROGENATION PROCESS USING
THERMAL COUNTERCURRENT FLOW REACTION ZONE
.

This invention pertains to thermal hydrogenation and conversion of coal utilizing countercurrent flow of the coal feed and hydrogen to produce hydrocarbon gas and liquid products. It pertains particularly to such process wherein a thermal countercurrent flow hydrogenation zone is used upstream of a catalytic hydrogenation reaction zone.

BACKGROUND OF THE INVENTION
In thermal hydrogenation conversion operations on coal to produce lower boiling product liquids and gases, the coal eed and hydrogen have generally both been introduced into the bottom of the reactor and both passed upwardly there-through. However, reactor plugging often occurs due to heavy particulate mineral matter that forms in the reactor, settles and accumulates in the bottom of the reactorO Such accumulated deposits in the reactor interfere with sustained process operations and are thus quite undesirable.
U.S. Pat nt 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 rhar material. For example, U.S.
3,876,392 to Kalina, et al, discloses a coal gasification process in which coal is introduced into the upper portion of a fluidized bed hydrogasification zone maintained at 1500-1800F temperature, and char solids are wLthdrawn from .~

the bottom for separate heating and recycle. U. S. Patent 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 4,111,788 to Cher~enak et al discloses a two-stage coal hydrogenation process using a thermal fixst stage reaction zone and catalytic second stage reaction zone; however, counterflow of coal feed and hydrogen is not used. Thus, a coal thermal hydrogenation and liquefaction proces~ utilizing countercurrent ~low of coal-oil slurry and hydrogen is needed to avoid undesirable solids accumulations in the reaction zone.

SUMMARY OF I~ENTTON
_. _ _ _ The present invention discloses a coal hydrogenation process having a thermal reaction zone which utilizes a counter-current flow arrangement for the coal ~eed and hy-drogen. 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. Tha downward flow of coal-oil slurry and upward ~low of hydrogen provides ~u~ficient 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 ~one lower end, The coal residence time in the t.hermal reaction zone can be preferably increased and controlled by providing some recycle of reactor light liquid ef~luent from the upper portion back to the lower portion o~ the reactor. Such liquid ~ecycle provldes an upflowing liquid veloclty which 4~3 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 agi tation and desirably strips hydroconverted ]ight ends from the reactor liquid, Reaction conditions used in the thermal reaction zone are withln the rangesof 775-900F temperature and 1000-5000 psig hydrogen partial pressure. A temperature gradient usually exists within the reaction zone and helps provide internal reflux. The downflow of liquid serves to carry the ash particulates out o 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 reco~
very 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 advan-tageously passed on to a catalytlc reaction zone, in which such material is further hydrogenated and converted to pro-duce increased yields of hydrocarbon gaseous and lower boiling liquid products.

DESCRIPTION OF DRAWINGS

Figure 1 is a schematic drawing showing a coal hydro-genation process utilizinq a thermal reaction zone arranged for countercurren-t flow of coal slurry feed and hydroaen to produce hydrocarbon gas and liquid products.

Figure 2 is a schematic f]owsheet showing a thermal countercurrent flow reaction zone used upstream of an ebullated catalyst bed reaction zone to produce increased yields of hydrccarbon liquid products.

DESCRIPTION OF PREFERRED EMBODIMENT
_ _ _ . _ _ _ _ _ As shown in Figure 1, coal such as bituminous) sub-bituminous or brown coal at 10 is introduced into a prepara-tion unit 12, wherein the coal is dried to remove substan-tially 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 par~icles are passed to slurry mix tank 14 where the coal is blended with suEficient slurrying oil at 16 to provi~e a pumpable mixture. This slurrying oil ls produced in the process as described below, and the welght ratio of oil to coal should be at least about l.O but nee~ not exceed about 6.

The coaL-oil slurry is pressurized by pump ]7 and passed through slurry heater 18, in whlch the slurry i~ heated to a temperature usually near the-reaction zone temperature. The heated slurry at 19 is then introduced into the upper por-tion of ther~al reac-tor 20. Heated hydrogen is lntroduced at 15 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 counter-current relation at controlled residence tlme, and the coal hydrogenation reaction is achieved therein without use of an added catalyst.

Reaction conditions in the thermal reactor are main-tained within the broad range~ of 775-900F temperature and 1000-5000 p~ig hydrogen partial pressure, and preferably at 800-900F and 1500-4500 p5ig hydrogen partial pressure.
Space velocity for the coal can be within the range of 15~50 pounds coal/hr/ft3 reactor volume, and preferably is 20-40 pounds/hr/f~3.

An effluent stream of gas and li~ht liquidfsuch ~s nor-mally boiling in the range up to ~ ut 550F, is wi~hdrawn at 21 from the reactor upper end and is passed to hot phase separator 22. Stream 21 preferably comprises a major part of the reactor total effluent, From separator 22, the resulting vapor portion 23 is usually passed to further ~hase separation at 24 and then to hydrogen purification step 25. Recovered hydrogen stream at 25a is reheated and recycled at 15 to the reactor 20, with make~up hydrogen being provided a~ 15a as needed. From separator 24, the liquid portion 24b is passed to atmospheric distillation step.

From ~eparator 22,liquid stream 26 is pressure-reduced at 29 and passed to phase separator 30. Also, a par~ 27 of liquid stream 26 is preferably racycled to the bot~om of reactor 20 for providing an upward liquid flow velocity therein to hinder the downward flow and se~tling of heavy liquids and coal solids and to provide for controlled increased re~idence tlme for the larger uncoffverted coal particles and for achievina urther thermal hy~lrogenation reaction therein, The recycle weight ratio of recycle ~tream 27 to coal in feed 5tream 1~ should usually be within the range of from about 0.5 to 1Ø

, A bo~tom stream 28, usually all boiling above about 500F and containing resi.duum, unconverted coal sollds and ash, is withdrawn from the lower end of thermal reactor 20 nd is usually also pressure reducecl at 29a and passed to portion 31 phase separator 30. From separa~or 30, the vapor~is passed to atmospheric distillation step 38, from which hydrocarbon liquid product streams are withdrawn as desired. ~he resulting bottoms stream 32 from separator 30 is passed to a liquid-solids separation step 34, rom which at least a por~
tion of overflow stream 35 containing reduced solids con centration is used as slurrying oil 16. The remaining bot-toms stream 36 contalning increased solids concentration is passed to vacuum distillation step 407 from which overhead s~ream 41 comprises a portion of the liquid product stream ~2. A heavy vacuum bottoms stream 44 normally boiling above abou~ 975F and containing unconverted coal and ash is withdrawn for gasification or disposal . If needed~ a por-tion 42a of liquid stream ~12 can be recycled to supplement slurrying oil 16.
An a'ternatlve embodiment o the present invention ls shown in Figure 2, which is similar to the Figure ] em~odi-ment 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 hydrogena-tion reaction and conversion to produce increased yieldsllower boiling liquid products. As shown in Figure 2, light effluent s~ream 21 is pa~sed ~o phase separator 22, from which vapor stream 23 is passed to further phase separa-tion at 24 and then to hydrogen pur fication step 25, The remaining liquid stream 24b is passed to the bottom of reac-tor 50.

From separator 22, a portion 27a of liquid stream 26a is recycled to thermal reactor 20, and the remainder is passed, together with additional hydrogen at 46, as stream 49 to ebullated bed reactor 50. Also bottom liquid stream 28a withdrawn from the lower end of thermal reactor 20 i5 passed into the lower end of reactor 50, which contains an ebullated bed of commercial catalyst 52, such as cobalt-molybdenum on alumina extrudates having diameter of 0.030-0.065 inch.
In this embodiment, the coal-oil feedstream l9a 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.
Reaction conditions in catalytic reactor 50 are maintained within the broad range of 750-875F temperature and 1000-4000 psig hydrogen partial pressure, and preferably at 770~870F
and 1500-3500 psig hydrogen partial pressure. Space velocity for the coal can be within the rangP of 15-50 pounds coal/hr/
ft3 reactor volume, and preferably is 20-40 pounds/hr/ft3.
The liquid and gas mixture is passed uniformly upwardly through the catalyst bed 52 a-t a velocity suf~icient 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.
An effluent stream of liquid and gas mixture is withdrawn from the reactor upper end at 53 and is passed -to hot phase separator 54. The resulting vapor portion is usually cooled at 55 and passed to further phase sep~ration at 56, from which vapor stream 57 is passed to hydrogen purification step 25. Recovered hydrogen stream 25a is recycled at 45 to the reactor 20, and at 46 to reactor 50.

From phase separator 54, bottoms liqui~ tream 58 is pressure-red-lced at 59 and passed to phase separator 60, along with liquid stream S8a from separator 56. A vapor portion 61 is removed and passed to atmospheric distillation step 6S, from which overhead liquid product can be withdrawn at 67 and bottoms liquid wi~hdrawn at 69. Also rom separator 60, the resulting bo~toms liquid stream 62 is passed to a liquid-solids separation s~ep 64, which i5 pr2-ferably multiple hydroclone units connected in parallel. An overflow stream 65 containing reduced solids concentration is used as slurrylng oil at 16. The remaining bo~toms stream 66 containing an increased concentration of uncon-ver~ed coal and ash solids is passed to vacuum distillation step 70. An overhead stream 71 is combined with stream 6 anh comprises the liquid product stream 72. A heavy vacuum bottoms ~tream 74 boiling above about 975F and containin~
some unconverted coal and ash solids i5 wlth~rawn for gasi-fication or disposal. If needed, a portion 72a of product stream 72 can be recycled to suppl~ment slurrying oil stream 16.
Although this invention has been disclosed in terms of the accompanying drawings and preferred embodiments, it will be appreciated by those skilled in the art.that adaptations and modifications of the proces may be made within ~he spiri~ and scope of the invention, which is. ~eflned solely by the following claims.

' .

Claims

We Claim:

l. 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 at conditions within the ranges of 775-900°F tem-perature and 1000-5000 psig 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 con-taining unconverted coal and ash from the bottom por-tion of the reaction zone, and passing said stream to further processing steps to recover hydrocarbon liquid products.
2, The process of claim l, wherein the coal feed is mixed with a slurrying oil in an oil/coal weight ratio of between about 1.0 and 6.
3. The process of claim 1, wherein the reaction zone conditions are within the ranges of 800-900 °F temperature, 1500-4500 psig hydrogen partial pressure, and the coal space velocity is 15-50 pounds coal/hour/ft3 reactor.
4. The process of claim 1, 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 reac-tion time.
5. The process of claim 1, 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. The process of claim 1, wherein the effluent material withdrawn from the upper portion of the reaction zone comprises a major part of the reaction zone total effluent.
7. The process of claim 1, wherein the botom liquid stream withdrawn from the thermal reaction zone bottom por-tion is passed with additional hydrogen into an ebullated bed catalytic reacton zone for further hydroconversion of residuum and unconverted coal to produce 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 between about 1.0 and 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 at conditions within the ranges of 775-900°F tempera-ture, 1000-5000 psig hydrogen partial pressure and coal space velocity of 15-50 pounds coal/hour/ft3 reactor, (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 resi-dence and reaction time; and (e) withdrawing a heavy hydrocarbon liquid stream con taining unconverted coal and ash from the bottom por-tion 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 por-tion 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 temperature and 1000-5000 psig 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 con-taining unconverted coal and ash from the bottom por-tion of the reaction zone and passing said liquid together with additional 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. The process of claim 9, wherein the ebullated bed reaction zone conditions are maintained within the ranges of 750-875°F temperature, 1000-4000 psig hydrogen partial pressure, and coal liquid space velocity of 20-40 pounds coal/hour/ft3 reactor volume.
11. A process for the thermal hydrogenation and conver-sion 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 introduced together with hydrogen into the reaction zone maintained at conditions within the range of 700-950°F temperature and 1000-5000 psig hydrogen partial pressure, wherein the impro-vement comprises:

(a) introducing the coal-oil slurry into the upper por-tion of the thermal reaction zone for downward flow therein;

(b) introducing hydrogen into the lower portion of the thermal reaction zone for upward flow therein coun-tercurrent to the coal liquid, and (c) withdrawing a light hydrocarbon effluent material from the upper portion of the reaction zone and withdrawing a heavier hydrocarbon stream containing unconverted coal and ash from the bottom portion of the reaction zone.
12. The process of claim 11, wherein the light hydrocar-bon 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.