PROCESS FOR PRODUCING SYNTHESIS GAS

Abstract

The invention relates to a process for producing synthesis gas (5) in which hydrocarbon (2) is decomposed thermally in, a first reaction zone (11) to hydrogen and carbon, and hydrogen formed is passed from the first reaction zone (Z1) into a second action zone (Z2) in order to be reacted therein with carbon dioxide (4) to give water and carbon monoxide. The characteristic feature here is that energy required for the thermal decomposition of the hydrocarbon is supplied to the first reaction zone (Z1) from the second reaction zone (Z2).

Claims

1. A process for producing synthesis gas, said process comprising: thermally decomposing a hydrocarbon in a first reaction zone to hydrogen and carbon, and passing the hydrogen formed from the first reaction zone into a second reaction zone in order to be reacted therein with carbon dioxide by a reverse water-gas shift to give water and carbon monoxide, wherein energy required for the thermal decomposition of the hydrocarbon is supplied to the first reaction zone from the second reaction zone.

2. The process according to claim 1, wherein thermal energy is generated in the second reaction zone by oxidation of hydrogen and/or by electrical power.

3. The process according to claim 1, wherein hydrocarbon which is undecomposed or incompletely decomposed in the first reaction zone is passed into the second reaction zone and reacted therein with water to give hydrogen and carbon dioxide.

4. The process according to claim 1, wherein the first and the second reaction zones are connected by means of a moving bed which consists of solid granular material and moves from the second reaction zone to the first.

5. The process according to claim 4, wherein solid granular material is circulated.

6. The process according to claim 4, wherein gas leaving the second reaction zone is conducted in countercurrent to the moving bed and is cooled in direct heat exchange therewith.

7. The process according to claim 4, wherein the hydrocarbon is conducted into the first reaction zone in countercurrent to the moving bed and is heated in direct heat exchange therewith.

8. The process according to claim 4, wherein carbon deposited on the solid granular material is removed downstream of the first reaction zone and withdrawn from the moving bed.

9. The process according to claim 1, wherein the solid granular material used is corundum (Al.sub.2O.sub.3) or quartz glass (SiO.sub.2) or mullite (Al.sub.2O.sub.3.SiO.sub.2) or cordierite ((Mg,Fe).sub.2(Al.sub.2Si)[Al.sub.2Si.sub.4O.sub.18]) or steatite. SiO.sub.2.MgO.Al.sub.2O.sub.3) or, coal or coke or carbon produced in the process by then hydrocarbon decomposition.

Description

[0027] The invention shall be more particularly described hereinafter with reference to a working example shown schematically in FIG. 1.

[0028] FIG. 1 shows a preferred configuration of the process according to the invention, which uses a reactor wherein a moving bed composed of a solid granular material is conducted through the reaction space thereof which comprises a first and a second reaction zone.

[0029] Via the feed 1, a solid granular material which is, for example, carbon produced by thermal hydrocarbon decomposition in the process is introduced at ambient temperature from the top into the reaction space R of the reactor K, through which it is subsequently conducted downward in a moving bed W under the action of gravity. A hydrocarbon-containing input gas 2 which is preferably natural gas is simultaneously passed into the reaction space R from the bottom and conducted upward through the moving bed W in countercurrent. The gas 2 which is at ambient temperature on entry into the, reaction space R is heated up on its way upward in direct heat exchange with the moving bed W until it reaches the decomposition temperature of the hydrocarbon in the first reaction zone Z1, and the hydrocarbon decomposes under these conditions in an endothermic reaction to give hydrogen and carbon. The carbon formed here is predominantly deposited on the solid granular material of the moving bed W. Together with unconverted or only incompletely converted hydrocarbon, the hot hydrogen formed flows into the second reaction zone Z2 disposed above the first, in the course of which it is heated up further in direct heat exchange with the moving bed W. In the second reaction zone Z2, a portion of the hydrogen is combusted with oxygen which is fed in via line 3, and thus provides the heat of reaction required for the synthesis gas production. Alternatively or additionally, the heat of reaction can also be introduced into the reaction zone Z2 by means of electrical power. At least a portion of the water formed in the hydrogen combustion is reacted with carbon dioxide supplied via line 4 to give hydrogen and carbon monoxide. Hydrocarbon undecomposed or incompletely decomposed in the first reaction zone Z1 is reformed in the second reaction zone Z2 with water to give hydrogen and carbon monoxide, and so a synthesis'gas flows out of the second reaction zone 22 and is cooled in countercurrent with the moving bed W and is drawn off at the upper end of the reactor K via line 5 with a temperature of between 50 and 500° C.

[0030] At the lower end of the reactor K, solid granular material 6 is removed at a temperature dose to ambient temperature and is fed to a processing unit A in which it is processed, for example, by removing the carbon deposited or by comminuting, sifting and classifying, in order to be recycled back into the reaction space R via line 7.