1 A process for producing a synthesis gas,which contains carbon monoxide and hydrogen, wherein a solid fuel is gasified under a pressure of from 5 to 150 bars by treatment with free oxygen-containing gas and steam in a first reactor to produce a steam-containing crude gas at an exit temperature of 35 () to 700 C, and wherein the steam-containing crude 5 gas is fed without cooling to a following second reactor containing a bed of granular material having a particle size of 3 to 8 () mm where it is reacted under a pressure of 5 to 150 bars with free oxygen-containing gases to produce an intermediate product gas, which leaves the second reactor at a temperature of from 800 X) to 1400 C, this intermediate product gas being thereafter cooled and freed from sulphur compounds 10 2 A process as claimed in claim 1, wherein a fuel in dust form and/or a liquid hydrocarbon is/are added to the steam-containing crude gas.
3 A process as claimed in claim 1, wherein a fuel in dust form and/or a liquid hydrocarbon is/are first contacted with oxygen in a reaction chamber and the reaction products are further reacted together with the steam-containing crude gas in said second reactor 15 4 A process as claimed in claim 2 or 3, wherein the fuel in dust form has a particle size below 2 mm.
A process as claimed in claim 2, 3 or 4 wherein the fuel in dust form has a particle size of from O 03 to 0) 3 mm.
6 A process as claimed in claim 2 or 3, wherein Ilhe liquid hydrocarbon is vaporized or 20 formed into a fine spray before it is reacted.
7 A process ais claimed in any one of clainls 2 to 6, wherein exhaust gases are used as an atomizing agent for dispersing the liquid hydrocarbon or fuel in dust form.
8 A process as claimed in any preceding claim, wherein exhaust gases having combustible constituents are fed to the second reactor for producing the intermediate product gas 25 9 A process as claimed in any preceding claim, wherein the reaction in the second reactor is carried out under turbulent conditions of flow.
A process as claimed in any preceding claim, wherein the second reactor contains a granular bed having a particle size of 5 to 30 mm.
11 A process ais claimed in claim 10, wherein the bed consists at least in part of a 30 catalyst.
12 A process as claimed in claim 1, wherein the catalyst is nickel, cobalt, chromium or an oxide or sulphide thereof.
13 A process as claimed in any one of claims 10 to 12, wherein the bed or a support for the catalyst consists of alumina, magnesia or a mixture thereof or of a spinel or silicate of 35 aluminium and/or magnesium.
14 A process as claimed in any one of claims 10 to 13, wherein the bed is moved by a vibrator, a movable grate or other mechanical means.
A process as claimed in any one of claims 10 to 13, wherein the bed is maintained in a fluidized state 40 16 A process as claimed in any one of claims 10 to 15 wherein the bed of granular material is freed from combustible residues outside the reactor and is returned at elevated temperature into the reactor.
17 A process as claimed in any preceding claim, wherein at least part of the heat of reaction required in the second reactor for producing the intermediate product gas is sup 45 plied by high-frequency electric fields or electric resistance heating.
18 A process as claimed in any preceding claim, wherein oxygen, steam and carbon dioxide are used as gasifying agents for gasifying the solid fuel.
19 A process as claimed in any preceding claim, wherein the reaction in the second reactor is carried out in the presence of a free oxygen-containing gas and of carbon dioxide 50 A process for producing a synthesis gas substantially as hereinbefore described with reference to the accompanying drawing and/or in either of the foregoing Examples.
21 A synthesis gas produced by the method claimed in any preceding claim.
TREGEAR THIEMANN & BLEACH.
Chartered Patent Agents 55 Enterprise House.
Isambard Brunel Road.
Portsmouth P 01 2 AN and 49/51, Bedford Row, London, WC 1 V 6 RL 60 Printed for Her Majesty's Stationery Office by Croydon Printing Company Limited, Croydon, Surrey, 1979.
Published by The Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.
1,554,638
Description
PATENT SPECIFICATION ( 11) 1 554 638
qo ( 21) Application No 27923/76 ( 22) Filed 5 Jul 1976 ( 19) ^ ( 31) Convention Application No 2532197 ( 32) Filed 18 Jul 1975 in i ( 33) Fed Rep of Germany (DE) t' ( 44) Complete Specification Published 24 Oct 1979 tn ( 51) INT CL 2 C Oi B 2/14 2/26 C 1 OJ 3/00 If C 011 B 2/20 2/22 C 1 OK 3/00 ( 52) Index at Acceptance C 5 E AG ( 72) Inventors: GERHARD BARON HERBERT BIERBACH CARL HAFKE GUNTER POCKRANDT FRANZ BIEGER CLAUS LOHMANN ( 54) A PROCESS FOR PRODUCING SYNTHESIS GASES ( 71) We, METALLGESELLSCHAFT AKTIENGESELLSCHAFT, of Reuterweg 14, 6 Frankfurt am Main, German Federal Republic, a body corporate organized under the laws of the German Federal Republic, and RUHRGAS AKTIENGESELLSCHAFT, a body corporate organized under the laws of the Fed Rep of Germany, of 60 Huttropstrasse 4300, Essen 1, German Federal Republic, do hereby declare the invention, for which we 5 pray that a patent may be granted to us, and the method by which it is to be performed, to
be particularly described in and by the following statement:-
This invention relates to a process for producing synthesis gases, which consist of carbon monoxide and hydrogen The synthesis gases may consitute, e g, starting products for the synthesis of methanol or ammonia, or for oxo or Fischer-Tropsch synthesis 10 A crude gas which can be economically converted to a synthesis gas can be produced by the pressure gasification of coal including brown coal, by a treatment with oxygen and/or air and, as further gasifying agents, steam and possibly carbon dioxide The pressure gasification of coal may be effected under a pressure of 5 to 150 bars, preferably 10 to 80 bars, and results in a steam-containing crude gas at a temperature of 350 to 700 'C Various processes 15 for the pressure gasification of coal have been proposed.
Coal is normally gasified under pressure in a countercurrent operation in which the fuel to be gasified and the gasifying agents are fed into a reaction chamber of a reactor or gas producer from opposite directions and move in said chamber in opposite directions Operation in this manner is desirable because the sensible heat of the product gas is advantageous 20 ly utilized to heat the fuel to the reaction temperature In the reactor or gas producer, the fuel travels through several zones, the fuel being first dried and then degasified in a dry distillation zone before it enters the gasification zone, in which a major portion of the endothermic reactions are carried out In a combustion zone, the remaining fuel is finally reacted to a large extent with the free oxygen and an incombustible residual ash consisting 25 of mineral constituents is left, the gasifying agent which flows into the reactor receiving sensible heat from that ash and this being an advantage from the aspect of heat economy.
Experience has shown that the gasifying agents are suitably supplied at a metered rate which is selected so that the maximum combustion temperature in the reactor is below the melting point of the ash 30 In addition to steam, the crude gas produced by the pressure gasification of coal contains mainly hydrogen and oxides of carbon as well as methane Numerous further substances.
such as condensible hydrocarbons, particularly tars having various boiling ranges, are present in smaller quantities Whereas these are often considered as valuable constituents of coal, they are not always desirable in gas Unless they can be directly used for the produc 35 tion of energy, they must be fed to a further beneficiation stage, e g, for hydrogenation.
The processing of such substances is often problematic because they become available as a result of a gasification in quantities which are not sufficient to enable them to be utilized economically They are also undesirable because they become available together with an aqueous condensate formed from the gaseous constituents during the further processing of 40 I 1,554,638 2 the crude gas A considerable expenditure is required to purify this condensate, whicfl contains not only hydrocarbons but, inter alis, also phenols, fatty acids, and ammonia.
According to the present invention there is provided a process for producing a synthesis gas, which contains carbon monoxide and hydrogen, wherein a solid fuel is gasified under a pressure of from 5 to 150 bars by treatment with free oxygen-containing gas and steam in a 5 first reactor to produce a steam-containing crude gas at a temperature of 350 to 700 C, and wherein the steam-containing crude gas is fed without cooling to a following second reactor containing a bed of granular material having a particle size of 3 to 80 mm where it is reacted under a pressure of 5 to 150 bars with free oxygen-containing gases to produce an intermediate product gas, which leaves the second reactor at a temperature of from 800 to 14000 C, 10 this intermediate product gas being thereafter cooled and freed from sulphur compounds.
As the crude gas is converted to the intermediate product gas, the hydrocarbons contained in the crude gas as well as the phenols, fatty acids, and ammonia are converted mainly to hydrogen and oxides of carbon by gasification and cracking and for this reason need not be separated from the gas The reaction to produce the intermediate product gas is 15 suitably effected under the pressure which is also maintained in the reactor for the pressure gasification of coal.
Fuels in dust form, particularly coal dust, or liquid hydrocarbons, particularly tar and/or tar oil, may be gasified by a treatment with oxygen before or in the second reactor for producing the intermediate product gas, and the gasification products may be fed to the 20 reaction for producing the intermediate product gas Exhaust gases and undesired byproducts of other processes can also be processed by such -thermal gasification treatment with oxygen Carbon dioxide may be used as one of the gasifying agents in the production of the intermediate product gas.
The thermal gasification of the fuel in dust form, liquid hydrocarbons, exhaust gases or 25 by-products by treatment with oxygen results in reaction temperatures of 900 to 1400 C and in the production mainly of hydrogen and carbon monoxide, which subsequently deliver heat to the endothermic reactions carried out in the reactor for producing the intermediate 3 product gas The thermal gasification may be effected in a separate reactor or in the reactor 30 for producing the intermediate product gas.
The fuels in dust form to be subjected to the thermal gasification preferably have a particle size of below 2 mm, more preferably from 0 03 mm to 0 3 mm, while liquid hydrocarbons to be subjected to the thermal gasification are first vaporized or formed into a fine spray Exhaust gases which contain combustible constituents may be used as atomizing agents for dispersing the liquid hydrocarbons or fuels in dust form.
The second reactor for producing the intermediate product gas may be designed in various ways In the reactor, if the starting materials include dust, the dust and gas are suitably subjected to centrifugal forces or turbulent conditions of flow This may be achieved as the reactor contains a bed of granular material having a particle size of 3 to 80 mm preferably 5 to 30 mm The granular material may consist of heat-resisting inert material, which serves primarily to agitate the gas and dust particles.
The reactor for producing the intermediate product gas preferably contains a catalyst such as nickel, cobalt, chromium, or an oxide or sulphide thereof For this purpose known 4 catalysts are selected which accelerate the cracking of the gases and vapours to hydrogen and oxides of carbon in the reactor for producing the intermediate product gas whereas the formation of carbon black is avoided The catalysts may be supported on alumina magnesia or mixtures of these two substances as well as silicates of aluminium and/or magnesium The catalyst support may also consist of an aluminium spinel or magnesium spinel In order to improve the rate of reaction in the reactor for producing the intermediate product gas, the granular bed may be carried by a movable grate Alternatively, the bed may consist of a 50 fluidized bed.
Because the cracking reactions in the intermediate product gas reactor are endothermic reactions, care must be taken that sufficient energy is available for the reaction To this end.
the bulk material contained in the reactor may be periodically removed from the reactor and freed from combustible residues whereafter the bulk material is returned at an elevated 5 temperature to the reactor At least part of the energy required for the reaction may be supplied by high-frequency fields or electric resistance heating In most cases however it will be possible to supply the required energy by partial oxidation with the oxygen which is fed.
In order to enable the invention to be more readily understood, reference will now be 6 made to the accompanying drawing, which illustrates diagrammatically and by way of example a plant diagram of plant for producing synthesis gas.
Referring now to the drawing coal e g, hard coal or brown coal, is fed through a conduit 2 to a gas-producing reactor 1 and is gasified therein using gasifying agents which consist of steam and oxygen and which are injected through conduits 3 and 4 into the 65 3 1,554,638 3 reactor 1 at the lower end thereof As a further gasifying agent, carbon dioxide may be-fed to the reactor 1 through the conduit 3 or 4 When it is desired to produce ammonia synthesis gas, the gasifying agents may consist at least in part of air The ash which is produced by the gasification treatment is withdrawn through a conduit 5 The gasification carried out in the reactor 1 is known per se and is effected under a super-atmospheric pressure of 5 to 150 5 bars, preferably 10 to 80 bars.
The steam-containing crude gas produced by the gasification is at temperatures in the range from 350 to 700 'C when it leaves the reactor 1 through a conduit 7 This crude gas may be passed through a cyclone for the coarse separation of dust, if this is required, this optional feature not being shown on the drawing A second reactor 8 for the after 10 gasification of the crude gas receives the latter from the conduit 7, the pressure of the gas remaining substantially unchanged from that in the reactor 1 and, in the present example, the pressures in the reactors 1 and 8 are the same.
The reactor 8 is fed at its top 8 a with coal dust through a conduit 9 and with oxygen through a conduit 10 and the coal dust and oxygen interreact in the reactor with production is of high temperatures of 900 to 1400 'C The reaction products, together with the crude gas from the conduit 7 then flow through a bed 11 of inert granular material, such as alumina, which has a particle size of 3 to 80 mm, preferably 5 to 30 mm, and is carried by a grate 12.
The coal fed to the reactor has a particle size of below 2 mm, preferably 0 03 to 0 3 mm.
The bed 11 serves mainly intensely to agitate the fluid flowing into the bed so that the 20 probability of reactions between the components of that flowing fluid is increased The bed may alternatively consist of catalytically active material for intensifying the gasification reactions taking place in the reactor 8 The gasification reactions comprise reactions of solid fuels and hydrocarbons and, inter alia, phenols, fatty acids, and ammonia, with oxygen and steam to produce mainly hydrogen and hydrocarbons These gasification or cracking reac 25 tions are endothermic reactions.
The reaction in the reactor 8 is so controlled that the resulting intermediate product gas is at a temperature of 800 to 1400 'C as it leaves the reactor The intermediate product gas flows through a conduit 13 to a scrubber-cooler 14 and is subsequently fed to a desulphurizing scrubber 15 When a shift conversion is required, some of the desulphurized gas is 30 branched off through a conduit 17 a represented by a dotted line, and fed to a shift converter 16, in which carbon monoxide and steam are catalytically converted to form carbon dioxide and hydrogen in known manner, in order to increase the hydrogen content of the gas The shift-converted gas is then returned to the main stream of gas flowing in the conduit 17.
The desulphurization in the scrubber 15 may also be carried out in known manner, e g by the "Rectisol" process, in which the gas is scrubbed with scrubbing agents such as methanol at a temperature below O C to remove impurities, mainly sulphur compounds and carbon dioxide The gas which has been desulphurized and some of which, if desired, has been shift-converted is then freed from carbon dioxide in a scrubber 18 if and to the extent to 40 which this is required in view of the synthesis to which the gas is fed through conduit 19.
The invention will now be further illustrated by the following Examples:Example 1
A gas producer having an average diameter of 2 6 m and operated under a pressure of 20 bars is fed with 15 metric tons (t) of coal per hour The coal has the following composition 4 based on water and ash-free matter:
Proximate Analysis Moisture 251 9 kg /t.
Ash 298 5 kg /t 50 Tar 143 0 kg /t.
Water removable by dry distillation 80 3 kg /t.
Phenols 8 0 kg /t.
Fatty acids 1 8 kg /t.
Net calorific value 7,044 5 kcal /kg.
Elemental Analysis of Pure Coal kg./t.
C 762 6 H 55 8 O 157 4 60 N 13 2 S 10 7 Cl 0 3 257 standard m 3 oxygen per metric ton of coal and 5 5 kg steam per standard m 3 of oxygen are fed as gasifying agents into the gas producer Crude gas is produced at a rate of 65 1,554,638 1913 standard m 3/h on a dry basis and has the following composition in percent by volume:
CO 2 28 2 I 1 S 0 4 C 2 H 4 0 4 CO 20 1 5 H 2 38 9 CH 4 11 1 C Gf 0 6 N 2 + Ar 0 3 The crude gas also contains 0 5 standard m 3 steam per standard m 3 dry gas and has an exit 10 temperature of 600 'C.
Cooling of the crude gas to 250 C would make the following by-products available per metric ton of water and ash-free coal:
Tar 59 kg.
Oil 32 kg 15 Gasoline 16 kg.
Ammonia 13 6 kg.
Phenols 8 kg.
Fatty acids 1 8 kg.
The crude gas is fed, without cooling, to the after-gasification reactor 8 and is reacted 20 therein with 0 15 standard m 3 oxygen and 0 4 kg steam per standard m 3 of crude gas About one-half of the reactor is filled with alumina balls having an average diameter of 30 mm.
The reaction chamber is 2 m in diameter and the alumina balls form a bed 4 m high.
As a result of the reaction in the reactor 8, a temperature of about 1300 'C is attained near the oxygen inlet The gas leaving the reactor is at a temperature of 900 'C and has the 25 following composition in percent by volume:
CO: 25 7 H 2 S 0 2 CO 23 8 H 2 49 3 30 CH 4 0 4 N 2 + Ar 0 6 This intermediate product gas is free from condensible hydrocarbons and no longer contains free oxygen The gas is cooled to 40 'C in a scrubber-cooler and is then desulphurized by being scrubbed with liquid methanol at about -250 C, whereby about onehalf of the 35 content of carbon dioxide is removed When the gas has been reheated to 350 'C, it is shift-converted in contact with a catalyst consisting of iron oxides The gas is scrubbed with hot potassium carbonate solution (or with monoethanolamine or methanol) to remove the carbon dioxide and is then scrubbed with liquid nitrogen to remove residual carbon monoxide and methane, whereafter the required amount of nitrogen is added to make the gas suitable for ammonia synthesis The resulting synthesis gas has the following composition in percent by volume:
H 2 75 5 N 2 + Ar 24 5 Example 2 45
0.25 standard m 3 oxygen and 0 4 kg steam are added to the crude gas produced in accordance with Example 1 per standard m 3 of said gas, as well as coal dust having a particle size of 0.03 to 0 3 mm at a rate of 300 kg per metric ton of the fuel fed to the gas-producing reactor 1, the coal dust having the same analysis as the coal used in Example 1.
Crude gas, oxygen, steam and coal dust are reacted in the reactor 8 used in Example 1.
The resulting intermediate product gas is at a temperature of 950 C as it leaves the reactor 8 and has the following composition in percent by volume:
CO 2 22 9 H 2 S 03 CO 29 0 55 H 2 47 0 CH 4 0 3 N 2 + Ar 0 5 In order to produce an ammonia synthesis gas, the intermediate product gas is processed further in the manner described in Example 1 60 In the Specification of our co-pending Patent Application No 27922/76 Serial No.
1554637, of even date herewith, we have described and claimed a process for producing gases which have a high calorific value and contain more than 50 % of methane by volume, the process being similar to that of the present Application save that the intermediate product gas in subjected to a methanation step 65 A A 1,554,638 S
