METHOD FOR SEPARATING SULPHUR OUT OF A GAS THAT CONTAINS SULPHUR

Abstract

A method is described for separating sulphur out of a sulphur-containing gas, particularly hydrogen or natural gas, wherein the gas is compressed and the sulphur is removed in an absorptive separation process. According to the invention, the sulphur-containing gas is compressed, or at least precompressed before being passed into the absorptive separation process.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from German Patent Application Serial No. DE 102008 031 509.5, filed Jul. 3, 2008.

BACKGROUND OF THE INVENTION

The invention relates to a method for separating sulphur out of a gas that contains sulphur, particularly hydrogen or natural gas, wherein the gas is compressed and the sulphur is removed via an absorptive separation process.

Species-related methods for separating sulphur from a gas containing sulphur are used for example at natural gas filling stations. At natural gas filling stations, the natural gas for use as fuel is drawn from the existing natural gas supply network, dried, and compressed to a storage pressure that may reach 300 bar. The sulphur content in the natural gas that is drawn from the supply network is usually too high to be processed effectively with today's engine and exhaust gas cleaning technology. In particular, the catalytic converters needed for subsequent cleaning of the exhaust gas are damaged by the sulphur that is currently included in the natural gas, with the result that they cease to function properly before the end of their specified service lives.

Because of legal provisions regarding odorising natural gas when it is used as fuel—tetrahydrothiophene (THT) and/or mercaptan sulphur are added to the natural gas for this purpose—the sulphur content in natural gas must not fall below a prescribed fraction.

For natural gas processing on a large, industrial scale, selective sulphur absorption processes have been in use for some time. The absorber materials that are suitable for removing sulphur must usually be at an operating temperature from 40 to 80° C. These temperatures are generally assured by explosion-proof electric heaters allocated to the absorbers.

BRIEF SUMMARY OF THE INVENTION

The object of the present invention is to suggest a species-related method for separating sulphur out of a gas that contains sulphur, particularly hydrogen or natural gas, which avoids the problems described above and particularly enables use of an additional heating device for the absorptive separating process to be dispensed with.

To solve this object, a species-related method for separating sulphur out of a gas that contains sulphur is suggested that is characterized in that the sulphur-containing gas is compressed, or at least precompressed, before it is introduced into the absorptive separation process.

In this context, the sulphur-containing gas is preferably compressed before its introduction into the absorptive separation process to at least such a degree that the compression heat generated thereby enables the absorber material or materials used in the absorptive separation process to be heated to the requisite temperature. As a consequence, it is no longer necessary to use additional heating devices for the absorptive separation process.

Further advantageous configurations of the method according to the invention for separating sulphur out of a gas that contains sulphur, which represent the objects of the subordinate claims, are characterized in that

• • the sulphur-containing gas that is introduced into the absorptive separation process is at a temperature between 20 and 200° C., preferably between 40 and 100° C.,
  • the gas that is extracted from the separation process undergoes postcompression,
  • at least a partial stream of the sulphur-containing gas is diverted around the absorptive separation process, the quantity of this partial stream preferably being variable,
  • the sulphur-containing gas that is introduced into the absorptive separation process is cooled after it has been (pre)compressed,
  • the absorptive separation process is designed such that besides sulphur at least one additional component is at least partially separated from the sulphur-containing gas, and
  • the gas from which sulphur has been removed is delivered to a vehicle for use as a power source and/or fuel.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the method according to the invention for separating sulphur out of a gas that contains sulphur as well as other configurations thereof will be explained in greater detail with reference to the embodiment shown in the FIGURE. The embodiment shown in the figure may be used in particular at natural gas filling stations that are provided for the purpose of filling vehicles of any kind with compressed natural gas.

DETAILED DESCRIPTION OF THE INVENTION

The FIGURE illustrates an absorption process A for the selective removal of sulphur. A gas that contains sulphur is introduced into this process via line segments 1, 2 and 3. In the case of a natural gas filling station, this gas is natural gas drawn from the public natural gas supply network. The sulphur-containing gas is compressed by a single- or two-stage compressor or a single- or multistage compressor unit V1 such that the heat of compression generated by the process is sufficient to heat the absorber material or materials used in absorptive separation process A to the temperature required for the process. Additional heating devices for heating the absorber material or materials to the requisite temperature are not required.

In the case of a natural gas filling station, the natural gas containing the sulphur is compressed in the compressor or compressor unit V1 to a pressure between 10 and 30 bar, preferably between 15 and 25 bar.

Heat exchanger E, which may be provided optionally, is used to cool the natural gas that has been compressed, and thus also heated in the compressor or compressor unit V1, to an optimal temperature for the purposes of selectivity of the absorber material or materials used in downstream absorptive separation process A.

In practical terms, absorptive separation process A includes an absorption column preferably having a capacity of 50 l. Besides the absorption material that is used to selectively remove sulphur from the sulphur-containing gas, a drying material is preferably provided in absorption column A as well. In general, this drying material may be located upstream and/or downstream from the absorption material that is used to separate the sulphur.

Bypass line 5, represented by a dashed line, is preferably equipped with a control valve 6 and may be used for diverting a partial flow of the sulphur-containing (natural) gas around absorptive separation process A. In this way, it is possible to vary the quantity of gas that passes through absorptive separation process A. The degree of sulphur reduction in the gas that contains the sulphur may thus be regulated or varied according to requirements

If it is necessary and/or desired, absorptive separation process A may be modified in such manner that other, preferably undesirable components besides sulphur are removed from the sulphur-containing gas as well.

With its sulphur content reduced to the desired lower limit, the cleaned gas then passes through line segments 4 and 7 to a second single- or multistage compressor or a second single- or multistage compressor unit V2, in either of which it may optionally be compressed to desired final pressure. The compressed gas is then forwarded through line 8 for subsequent use, for example intermediate storage.

It should be noted in particular that the method according to the invention for separating sulphur out of a gas that contains sulphur is able to be used for an extremely wide range of gases and gas mixtures in which at least some of the sulphur contained is to be removed by absorption.

Claims

1. A method for separating sulphur out of a gas that contains sulphur, particularly hydrogen or natural gas, wherein the gas is compressed and the sulphur is removed via an absorptive separation process, characterized in that the sulphur-containing gas is compressed, or at least precompressed before it is introduced into the absorptive separation process.

2. The method as recited in claim 1, characterized in that the sulphur-containing gas is compressed before its introduction into the absorptive separation process to at least such a degree that the compression heat generated thereby enables the absorber material or materials used in the absorptive separation process to be heated to the requisite temperature.

3. The method as recited in claim 1t characterized in that the sulphur-containing gas that is introduced into the absorptive separation process is at a temperature between 20 and 200° C.

4. The method as recited in claim 1, characterized in that the sulphur-containing gas that is introduced into the absorptive separation process is at a temperature preferably between 40 and 100° C.

5. The method as recited in claim 1, characterized in that the gas that is extracted from the absorptive separation process undergoes postcompression.

6. The method as recited in claim 1, characterized in that at least a partial stream of the sulphur-containing gas is diverted around the absorptive separation process, the quantity of this partial stream preferably being variable.

7. The method as recited in claim 1, characterized in that the sulphur-containing gas that is introduced into the absorptive separation process is cooled after it has been (pre)compressed.

8. The method as recited in claim 1, characterized in that the absorptive separation process is designed such that besides sulphur at least one additional component is at least partially separated from the sulphur-containing gas.

9. The method as recited in claim 1, characterized in that the gas from which sulphur has been removed is delivered to a vehicle for use as a power source and/or fuel.