Method and device for obtaining gas products

Abstract

The invention relates to a method and to a device for physical gas scrubbing, wherein a feed gas (1) containing hydrogen, carbon monoxide, carbon dioxide and also carbonyl sulphide and/or hydrogen sulphide is conducted through a first scrubbing section (W1) in countercurrent to a scrubbing medium preloaded with carbon dioxide, in order to separate sulphur components substantially selectively off from the feed gas and to generate a desulphurized gas mixture (3). In a second scrubbing section, carbon dioxide is separated off from only a subquantity of the desulphurized gas mixture by scrubbing with an unloaded scrubbing medium (4) and the resultant carbon dioxide-preloaded scrubbing medium is used completely in the first scrubbing section (W1) as scrubbing medium.

Claims

1. A method for physical gas scrubbing comprising: directing a feed gas stream containing hydrogen, carbon monoxide, and carbon dioxide, and also containing at least one of carbon oxide sulfide and hydrogen sulfide, through a first scrubbing section in counterflow to a first scrubbing medium which is preladen with carbon dioxide to selectively separate sulfur components from said feed gas stream and to produce a desulfurized gas mixture stream, and separating carbon dioxide from only a partial quantity of the desulfurized gas mixture stream in a second scrubbing section by scrubbing with an unladen second scrubbing medium and using said second scrubbing medium discharged from said second scrubbing section, preladen with carbon dioxide, in said first scrubbing section as said first scrubbing medium.

2. The method as claimed in claim 1, wherein said first scrubbing medium enters said first scrubbing section in a state saturated with carbon dioxide.

3. The method as claimed in claim 1, further comprising extracting heat of solution from said first scrubbing medium in said first scrubbing section by cooling said first scrubbing medium in at least one cooling step.

4. The method as claimed in claim 3, wherein said first scrubbing medium enters said first scrubbing section at a first temperature, and said cooling of said first scrubbing medium is carried out so that said first scrubbing medium discharges from said first scrubbing section at a temperature which differs by at most 5 C. from said first temperature.

5. The method as claimed in claim 1, further comprising subjecting the part of said desulfurized gas mixture stream which is not fed to said second scrubbing section to work-performing expansion in an expansion turbine.

6. The method as claimed in claim 5, wherein, during said work-performing expansion, said desulfurized gas mixture stream is cooled, and further comprising using the cooled desulfurized gas mixture stream for cooling a sulfur-free scrubbing medium flow which is used during scrubbing-medium regeneration for backwashing of sulfur components.

7. The method as claimed in claim 1, further comprising feeding the part of said desulfurized gas mixture stream which is not fed to said second scrubbing section as fuel to a gas turbine.

8. The method as claimed in claim 1, wherein methanol, dimethyl ether of polyethyleneglycol, or N-methyl-2-pyrrolidone is used as said unladen second scrubbing medium in said second scrubbing section.

9. The method as claimed in claim 1, wherein the part of said desulfurized gas mixture stream which is not fed to said second scrubbing section is fed to a methanol production process.

10. The method as claimed in claim 1, wherein methanol is used as said unladen second scrubbing medium in said second scrubbing section.

11. The method as claimed in claim 1, wherein dimethyl ether of polyethyleneglycol is used as said unladen second scrubbing medium in said second scrubbing section.

12. The method as claimed in claim 1, wherein N-methyl-2-pyrrolidone is used as said unladen second scrubbing medium in said second scrubbing section.

13. The method as claimed in claim 1, wherein said unladen second scrubbing medium is introduced into said second scrubbing section at at least two introduction points arranged at different levels.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the absorption column of a physical gas scrubber, in which a fuel gas for a gas turbine is produced from a raw synthesis gas by separating sulfur components.

(2) Via the line 1, a raw synthesis gas containing hydrogen, carbon monoxide, sulfur components and carbon dioxide is introduced into the lower region of the absorption column A, in which the two scrubbing sections W1 and W2 are arranged one above the other. On its path through the absorption column A, the raw synthesis gas first makes its way into the scrubbing section W1, through which it is directed in counterflow to a physically acting scrubbing medium. The scrubbing medium, being methanol, for example, is already preladen with carbon dioxide so that predominantly sulfur components are separated from the raw synthesis gas, whereas carbon dioxide in the main remains completely in the gas phase. In order to dissipate at least some of the heat of solution being released during the absorption of the sulfur components, the scrubbing medium is stripped via the chimney tray K and via the line 2 is directed through the heat exchanger E where it is cooled against external refrigeration. Some of the gas mixture which is desulfurized in the scrubbing section W1, the carbon dioxide concentration of which is basically that of the raw synthesis gas 1, is stripped via the side-disposed gas stripping line 3 and after a work-performing expansion in an expansion turbine is discharged as a product 8 and, for example, fed as fuel gas to a gas turbine. The remaining part of the desulfurized gas mixture makes its way into the second scrubbing section W2 where it is subjected to scrubbing with unladen scrubbing medium 4. In the second scrubbing section W2, the desulfurized gas mixture is freed of carbon dioxide so that a gas mixture largely consisting of hydrogen and carbon monoxide can be stripped from the head of the absorption column A, via the line 5, as a further product. The scrubbing medium which is laden with carbon dioxide in the scrubbing section W2 is transferred completely into the scrubbing section W1 where it is used as scrubbing medium for separating the sulfur components from the raw synthesis gas. The absorption column A is operated so that the scrubbing medium is largely preladen with carbon dioxide in the scrubbing section W2. In order to be able to achieve this consistently, even under fluctuating operating conditions, the amount of scrubbing medium 4 can be distributed with the aid of the control elements a and b to the two lines 6 and 7 and can be introduced into the scrubbing section W2 at different levels.