METHOD FOR SEPARATING SULPHUR OUT OF A GAS THAT CONTAINS SULPHUR

PROCEDE DE SEPARATION DU SOUFRE D'UN GAZ EN COMPORTANT

English 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 (1) is compressed, or
at least
precompressed (V1) before being passed into the absorptive separation process
(A).

Claims

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 (1) is compressed, or at least precompressed (V1) before it is
introduced into the absorptive separation process (A).
2. The method as recited in claim 1, characterized in that the sulphur-
containing gas
(1) is compressed before its introduction into the absorptive separation
process (A)
to at least such a degree that the compression heat generated thereby enables
the
absorber material or materials used in the absorptive separation process (A)
to be
heated to the requisite temperature.
3. The method as recited in claims 1 or 2, characterized in that the sulphur-
containing
gas (3) that is introduced into the absorptive separation process (A) is at a
temperature between 20 and 200°C, preferably between 40 and
100°C.
4. The method as recited in any of the preceding claims 1 to 3, characterized
in that
the gas (4) that is extracted from the absorptive separation process (A)
undergoes
postcompression (V2).
5. The method as recited in any of the preceding claims 1 to 4, characterized
in that
at least a partial stream (5) of the sulphur-containing gas (1) is diverted
around the
absorptive separation process (A), the quantity of this partial stream
preferably
being variable (6).
6. The method as recited in any of the preceding claims 1 to 5, characterized
in that
the sulphur-containing gas (3) that is introduced into the absorptive
separation
process (A) is cooled after it has been (pre)compressed (E).
7. The method as recited in any of the preceding claims 1 to 6, characterized
in that
the absorptive separation process (A) is designed such that besides sulphur at
least one additional component is at least partially separated from the
sulphur-
containing gas.

6
8. The method as recited in any of the preceding claims 1 to 7, characterized
in that
the gas (4, 7, 8) from which sulphur has been removed is delivered to a
vehicle for
use as a power source and/or fuel.

Description

CA 02670356 2009-06-29
P08C063 = IC0075
30.04.2009 - Christoph Zahn/bg
1
Description
Method for separating sulphur out of a gas that contains sulphur
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.
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.

CA 02670356 2009-06-29
P08C063 = IC0075
30.04.2009 - Christoph Zahn/bg
2
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

CA 02670356 2009-06-29
P08C063 = IC0075
30.04.2009 - Christoph Zahn/bg
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- the gas from which sulphur has been removed is delivered to a vehicle for
use
as a power source and/or fuel.
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.
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 I. 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.

CA 02670356 2009-06-29
P08C063 = IC0075
30.04.2009 - Christoph Zahn/bg
4
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 my 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.

Representative Drawing