FIELD
The present disclosure relates to an apparatus and a process for low pressure
hydrogen sulfide absorption from a feed gas.
5 BACKGROUND
Environmental deterioration has become serious issue in today’s scenario therefore
air pollution reduction has become very important globally. The feed gas released
from various industries contain significant amount of sulfur compounds which
create serious environmental damage. Therefore, treatment of these gases has
10 become important. These feed gas i.e. flue gases, landfill gases, Biogas, hot well
off gases etc. are generally low pressure gases and desulfurization of low pressure
gases is difficult. Low pressure feed gases are very useful due to their high calorific
values but presence of impurities such as H2S creates problem while utilizing these
gases as fuel.
15
The hot well off gases from a Vacuum Distillation Unit (VDU) contain very high
concentration of sulphur compounds, especially hydrogen sulphide (H2S). The
concentration of H2S can be as high as 1-30% by weight which creates corrosion
problems and reduces heat recovery. The light feed gas, which is a mixture of
20 hydrocarbons, is released from hot wells of VDU and can be either used as a fuel
or flared in the flare stacks. The released feed gas from the VDU hot wells are
referred to as hot well off-gas (HWOG). Typical components of HWOG include
H2S, H2, N2, CO, C1-C6 hydrocarbons, etc. These HWOG have a high calorific
value and hence used as a fuel. Direct burning of these gases results in an increase
25 in SOx emission and causes corrosion to the burners and associated equipment such
as vacuum heater. It also deteriorates the quality of the environment. Therefore, it
is necessary to remove or minimize the content of H2S in these gases.
The Indian patent application no. 1264/CHE/2009 discloses an in-house treatment
30 of vacuum unit hot well feed gas for preventing corrosion of vacuum unit heater
3
and air pre-heater. A re-generable amine solution such as Di-Ethanol Amine (DEA)
is used as an absorption medium for absorbing H2S.
A low pressure absorption column having structured packing, for removal of H2S
using N-methyl-diethanolamine (MDEA) solution from 5 HWOG is known. The
column has two low pressure packed beds with special low pressure liquid
distributors. The spent amine is regenerated in a regeneration unit and lean MDEA
is supplied back to the column. The column operates at 40-45°C and at atmospheric
pressure. The maximum allowable pressure drop in the column is 25mmWC.
10 Though, this process is capable of removing H2S at low pressure with a lesser
pressure drop, there still exists a substantial amount of H2S in the product stream
which further needs to be removed in an efficient manner.
Many apparatus and processes exist for amine absorption of H2S but these
15 processes operate at very high pressures since at low pressure they are not able to
remove H2S to a very low concentration in the product.
Absorption based processes available for desulfurization of gases are either amine
based absorption processes or caustic based processes. Amine based absorption
20 processes are high pressure processes. In caustic based processes, caustic
consumption is very high as regeneration of spent caustic is difficult and disposal
of spent caustic is not environment friendly.
Hence, there is a need to overcome one or more drawbacks of prior known
25 apparatus and/ or processes and provide an environment friendly H2S absorption
method.
SUMMARY
The present disclosure provides an apparatus for desulphurization of low pressure
30 feed gas. The apparatus 10 of the present disclosure provides for removal of
hydrogen sulfide from low pressure feed gas using amines at very low pressures
4
such as atmospheric pressure. The apparatus for desulfurization of low pressure
feed gas has two sections. The first section of the apparatus is an amine absorption
section while in the second section is caustic absorption section. The apparatus has
low pressure drop internals in each section. A blower/compressor is used to raise
the operating pressure from0.1-0.4 kg/cm2g to 0.15-0.3kg/5 cm2g in order to
enhance H2S absorption and reduce the caustic consumption.
Further, the present disclosure provides a process for low pressure absorption of
H2S. The process includes treating the feed gas in the apparatus in accordance with
10 this disclosure. The feed gas is introduced in the first section of the apparatus,
where it is contacted counter currently with the lean amine. In order to increase the
mass transfer between the two phases, low pressure drop high performance
internals are used. The feed gas from the first section is then introduced in the
second chamber where the feed gas is treated with a caustic solution. As re15
generation of spent caustic is difficult, the present apparatus or process utilizes a
substantially less amount of the caustic solution to reduce the H2S content to very
low concentration levels.
A blower/compressor may be used in the process scheme to raise the pressure to
20 0.15-3 kg/cm2g. This enhances the product specification and reduce the caustic
consumption further as per process requirement.
The process is useful for removal of hydrogen sulphide from low pressure feed gas
using amines (DEA,MDEA, DGA etc. or combination of amines). The process
25 consists of two section packed/trayed absorber for continuous removal of hydrogen
sulfide. A blower/compressor is used to increase pressure of the feed hot well offgas
to 0.15-3 Kg/cm2g. An aqueous solution of amine is contacted with low
pressure feed gas in first section. And H2S rich amine is routed to amine
regeneration section. A very low quantity of caustic solution is added in second
30 section to improve H2S removal from low pressure feed gas. Low pressure drop
packing and column internals are used in the process.
5
BRIEF DESCRIPTION OF FIGURES
Fig. 1 schematically shows an apparatus for low pressure absorption of H2S in
accordance with an embodiment.
DETAILED 5 DESCRIPTION
An apparatus 10 for low pressure absorption of H2S is disclosed. Referring to FIG.
1, the apparatus 10 may have an absorber column 12 and a regenerator 14. The
absorber column 12 has a first absorption section 16 and a second absorption
section 18. The absorber column 12 may be made of any material known in the art
10 suitable for treating feed gas. In an embodiment, the absorber column 12is divided
into first absorption section 16 and the second absorption section 18 using a
separator. The first absorption section 16 and the second absorption section 18 may
be configured for preventing an unintended leakage of any fluid from the first
absorption section 16 and the second absorption section 18.
15
A first conduit 20 is connected to the first absorption section 16 and configured for
introducing a feed gas into the first absorption section 16. The first conduit 20 may
be coupled with any known source of low pressure feed gas known in the art. For
example, a source of low pressure feed gas may be hot-well feed gas. The first
20 conduit 20 may be connected to a bottom portion 22 of the first absorption section
16. The first conduit 20 may be made of any suitable material known in the art.
In an embodiment, the first conduit 20 may be coupled to a compressor 24. The
compressor 24 may be positioned along the first conduit 20 between the first
25 absorption section 16 and the source of feed gas. The compressor 24 may be
configured for facilitating introduction of feed gases in the first absorption section
16. In addition, the compressor 24 may further be configured for increasing
pressure of the feed gas that is introduced in the first absorption section 16. In an
embodiment, using the compressor 24, the pressure of the feed gas may be
30 maintained in a range of 0.1-0.4kg/cm2g to 0.15-3.0kg/cm2g. The compressor 24
may be any pump, blower, etc. known in the art. Since the feed gas is a low pressure
6
gas, the compressor 24 may help in an increased absorption of the H2S by providing
favorable conditions for amine and caustic absorption.
In an embodiment, the feed gas may be fed via a first gas sparger 26 placed inside
the first absorption section 16. The first gas sparger 26 may be 5 positioned towards
the bottom portion 22 of the first absorption section 16. In an embodiment, the first
gas sparger 26 may be placed above the lean amine solution collected at the bottom
portion 22 of the first absorption section 16 for absorption of H2S from the feed
gas, when the feed gas is introduced in the first absorption section 16.
10
Further, the first absorption section 16 may be connected to a second conduit 28.
The second conduit 28 may be configured for feeding a regenerated lean amine
solution in the first absorption section 16. Monoethanolamine (MEA),
diethanolamine (DEA), N-methyl-diethanolamine (MDEA), diglycolamine
15 (DGA), mixed amines, activated amines and their mixtures in concentration
ranging between 10-60% by weight can be utilized for absorption of H2S. As
illustrated in FIG. 1, the second conduit 28 may be positioned towards a top portion
30 of the first absorption section 16 in order to provide for maximum contact
between the lean amine solution and the feed gas. In an embodiment, the second
20 conduit 28 may be connected to a liquid distributor 32, e.g. a sprayer, placed in the
top portion 30 of the first absorption section 16 for distribution of the lean amine
solution in the first absorption section 16.
The first absorption section 16 may further have low pressure drop internals 34 for
25 distribution and contacting of feed gas and the regenerated lean amine solution in
the first absorption section 16 for absorption of H2S. The low pressure drop
internals 34 may be used as known in the art. For example, low pressure drop
internals may be absorber trays, structured packing, random packing or any other
gas and liquid distributor 32. The low pressure drop internals 34 provide for
30 increase in the mass transfer between the two phases by facilitating increased
contact surface area between the feed gas and the absorber element, i.e. lean amine
solution for enhancing absorption of the H2S from the feed gas. The first absorption
7
section 16 may be configured for receiving the feed gas and converting it into a
lean feed gas by absorbing a portion of H2S content using the lean amine solution.
The low pressure internals 34 may be designed so as to minimize a pressure drop
resulting from the contact of the two phases (liquid absorbent and feed gas).
5
The first absorption section 16 may further have a first sump 36 defined at the
bottom portion 22 of the first absorption section 16. The first sump 36 may be
designed so as to collect spent amine solution at the bottom portion 22 of the first
absorption section 16.
10
As illustrated in FIG. 1, in an embodiment, the second absorption section 18 may
be positioned over the first absorption section 16. Further, the second absorption
section 18 may be connected with a third conduit 38 for feeding a lean feed gas
from the first absorption section 16. A first end 40 of the third conduit 38 may be
15 connected with the first absorption section 16 and a second end 42 of the third
conduit 38 may be connected to the second absorption section 18. Preferably, the
first end 40 may be connected towards the top portion 30 of the first absorption
section 16 and the second end 42 may be connected to a lower portion 44 of the
second absorption section 18. This way, the lean feed gas, i.e. the feed gas after it
20 is treated with lean amine solution, may be collected from the top portion 30 of the
first absorption section 16 and then introduced in the lower portion 44 of the second
absorption section 18 for further treatment. In an embodiment, the lean feed gas
may be fed via a second gas sparger 46 placed inside the second absorption section
18. The second gas sparger 46 may be positioned towards the bottom portion 22 of
25 the first absorption section 16. In an embodiment, the second gas sparger 46 may
be placed above to the caustic solution collected at the lower portion 44 of the
second absorption section 18 for absorption of H2S when the lean feed gas is
introduced in the second absorption section 18.
30 The second absorption section 18 may further be connected with a fourth conduit
48 for feeding a fresh caustic solution in the second absorption section 18. The
fourth conduit 48 may be coupled to a source of fresh caustic solution. The caustic
8
solution may have a concentration ranging between 0.1-20% by weight. The
caustic solution is introduced in the second absorption section 18 for treatment of
lean feed gas received in the second absorption section 18 from the first absorption
section 16. Preferably, the fourth conduit 48 may be connected towards an upper
portion 50 of the second absorption section 18. In an embodiment, 5 the fourth
conduit 48 may be connected to a liquid distributor 32, e.g. a sprayer, placed in the
upper portion 50 of the second absorption section 18 for distribution of the caustic
solution in the second absorption section 18.
10 Similar to the first absorption section 16, the second absorption section 18 may
have low pressure drop internals 34 for distribution and contacting of lean feed gas
and the caustic solution in the second absorption section 18 for absorption of H2S.
The low pressure drop internals 34 may be used as known in the art, for example
absorber trays, structured packing, random packing or gas and liquid distributor
15 32. The low pressure drop internals 34 facilitate contact between the feed gas and
the absorber element, i.e. caustic solution for further enhancing absorption of the
H2S from the lean feed gas.
The second absorption section 18 may further have a second sump 52 defined at
20 the lower portion 44 of the second absorption section 18. The second sump 52 may
be designed so as to collect spent caustic solution at the lower portion 44 of the
second absorption section 18.
The second absorption section 18 may further be connected to a fifth conduit 54
25 towards the lower portion 44 of the second absorption section 18 for extracting
spent caustic solution from the second absorption section 18. Further, a sixth
conduit 56 may be provided on the upper portion 50 of the second absorption
section 18 for removal of the treated feed gas from the second absorption section
18. The feed gas treated using the present apparatus 10 may have H2S content of
30 less than 100 ppmw.
9
Further, the apparatus 10 may have a generator 14 for providing regenerated lean
amine solution to the first absorption section 16. Any known regenerator 14 may
be used, for example, in an embodiment, the regenerator 14 may be a distillation
column. The regenerator 14 may be connected to the first sump 36 of the first
absorption section 16 for receiving spent lean amine solution 5 rich in H2S and
converting the rich amine solution again in a lean amine solution for reuse in the
first absorption section 16. The regenerator 14 may be connected to the second
conduit 28 for supply of regenerated amine solution in the first absorption section
16. This way, the regenerator 14 may recycle the amine solution and thereby
10 reducing overall costs of operation of the apparatus 10.
In an embodiment, a pump 58 may be used for facilitating supply of amine solution
from the first absorption section 16 to the regenerator 14. It may be understood that
that the regenerator 14 or the pump 58 may be connected towards the bottom
15 portion 22 of the first absorption section 16 as the spent lean amine solution trickles
and gets collected towards the bottom portion 22in the first sump 36 of the first
absorption section 16.
In an embodiment, a mist eliminator (not shown) may also be provided in the
20 apparatus 10 to remove the absorber fluid, i.e. lean amine or caustic solution,
carried by the feed gas.
The operation of the apparatus 10 may be described as following. The feed gas is
introduced in the apparatus 10 into the bottom portion 22 of the first absorption
25 section 16. The feed gas moves in the first absorption section 16 in a direction
towards the top portion 30 of the first absorption section 16. Simultaneously, a lean
amine solution is distributed in the first absorption section 16 from the top portion
30 of the first absorption section 16. During this travel of the feed gas from the
bottom portion 22 towards the top portion 30, the feed gas comes into contact with
30 the lean amine solution which absorbs a portion of H2S present in the feed gas. As
the feed gas reaches stop portion 30 of the first absorption section 16, the feed gas
leaves the first absorption section 16 and moves towards the second absorption
10
section 18 via the third conduit 38. Then the feed gas gets introduced in the lower
portion 44 of the second absorption section 18 and the feed gas subsequently moves
in a direction toward the upper portion 50 of the second absorption section 18. The
fourth conduit 48 continuously distributes caustic solution for treating the feed gas
passing through the second absorption section 18. As the feed 5 gas moves towards
the upper portion 50, the feed gas gets in contact with the caustic solution and a
second phase of H2S absorption takes place. The feed gas after treatment in the
second absorption section 18 gets discharged from the apparatus 10 via the sixth
conduit 56 of the apparatus 10 positioned towards the upper portion 50 of the
10 apparatus 10. The present apparatus 10 utilizes a substantially less amount of the
caustic solution to reduce the H2S content to very low concentration levels. The
feed gas leaving the apparatus 10 may contain H2S at concentrations of 100-550
ppmw.
15 In the above operation, the feed gas is provided at a pressure in the range of 0.1 to
0.4kg/cm2g and temperature between 25 to 50˚C to the bottom portion 22 of the
first absorption section 16 of the absorber column 12. The regenerated lean amine
solution at the top portion 30 of the first absorption section 16 of the absorber
column 12 comes in contact counter currently with the regenerated lean amine
20 solution by means of liquid distributor 32 over the low pressure internals such as
structured packing, thereby providing the lean feed gas at the top portion 30 of the
first absorption section 16 and the rich amine solution at the bottom portion of the
first absorption section 16. The rich amine solution is pumped into the regenerator
14 to recycle the regenerated lean amine solution. The lean feed gas is obtained at
25 the lower portion 44 of the second absorption section 18 of the absorber column
12 wherein the fresh caustic solution by means of liquid distributor 32 at the upper
portion 50 of the second absorption section 18 is fed. The spent caustic solution is
obtained at the lower portion 44 of the second absorption section 18 and treated
gas at the upper portion 50 of the second absorption section 18. The treated gas has
30 H2S content of less than 100 ppmw.
11
In an embodiment of the present disclosure, the feed gas is a low pressure hot well
off gas having H2, N2, CO, C1-C6 hydrocarbons and H2S.
In an embodiment of the present disclosure, the H2S is present in the range between
5 1% to 30% by weight.
In an embodiment of the present disclosure, the regenerated lean amine solution is
an aqueous amine solution selected from a monoethanolamine, diethanolamine, Nmethyl-
diethanolamine, diglycolamine, mixed amines, activated amines and a
10 combination thereof.
In an embodiment of the present disclosure, the regenerated lean amine solution
has a concentration of amine ranging between 10 to 60% by weight.
15 In an embodiment of the present disclosure, the fresh caustic solution is an aqueous
solution of sodium hydroxide ranging between 0.1 to 20% by weight.
In an embodiment of the present disclosure, the feed gas in step (a) is optionally
compressed in the compressor 24 to increase the pressure of the feed gas ranging
20 from 0.1-0.4kg/cm2g to 0.15-3.0kg/cm2g.
The apparatus 10 in accordance with the present disclosure operates at a low
pressure. Further, the apparatus 10 also uses low pressure drop internals 34. The
apparatus 10 may provide for reduction of H2S content in the treated feed gas to
25 nil or a very low concentration. Moreover, the apparatus 10 and the process in
accordance the present disclosure requires lesser amount of lean amine and caustic
solution for absorption or treatment of feed gas.
EXAMPLE
30 A low pressure feed gas stream having H2S 14-15 wt.% is treated with 40 wt.%
MDEA solution in amine absorber column 12. Absorber column 12 used for
experiment comprises of two section absorber. At a liquid gas ratio 8-10, in first
12
section H2S comes down to 500-600 ppmw in sweet gas and further reduces to
<100 ppmwto nil occurs in second section.
Typical composition of low pressure off gas before and after performing the
treatment as per subject invention is mentioned in 5 the table below:
Parameters Feed Product
Hot well off-gas Flow
Rate (Kg/hr)
3000-4000
H2S 10-20 wt% <100 ppmw to nil
Temperature (0C) 40-50 45-50
Pressure (Kg/cm2g) 0.1-0.4
This example belongs to low pressure hot well off gases.
10 Generally, hot well off gases are either sent to flare or routed to CDU (crude
distillation unit) furnace without any treatment. Therefore, a comparison is made
between present apparatus 10 and process with a single stage treatment process and
wherein there is no treatment of hot well off gases.
15 The hot well off gases with H2S content without H2S treatment, if goes to furnace
it produces SO2.
Generally, in a typical refinery using a single stage treatment process, quantity of
hot well off gases produced in refinery could replace 60% CDU furnace duty and
20 40% duty is met by fuel oil which contains 1% sulfur. The flue gas produced from
firing of this combination contains ~ 1 wt% SO2 in flue gases, which lead to SOX
dew point of 159 oC.
However, when hot well off gases are treated using present apparatus 10 or process,
25 after first bed, H2S in treated gas is achieved to 800 ppmw. The SO2 in flue gas
produced from firing of treated hot well off gases and fuel oil is reduced to 400
ppmw, which leads to SOX dew point of 127 oC.
13
Moreover, treatment of hot well off gases with present apparatus 10 or process
further reduces H2S to 100 ppmw which results in reduction of SO2 emission and
SOx dew point.
Advantages of treatment of hot well off gases using present apparatus 5 10 or process
are as follows;
 The reduction in SO2 in flue gas which will reduce SOX dew point by 30oC
 Heat recovery from flue gases increases the efficiency of heater by 1%
 SOX emission to environment also decreases.
10  Direct savings on fuel are achieved by utilizing low pressure feed gas as
fuel.
 After using desulfurized low pressure off-gas as fuel in furnace/heaters,
SOx dew point in flue gas reduces by 25-30 oC and waste heat recovery
increases by same degrees. Indirect savings can be achieved by additional
15 heat recovered.
14
List of Elements
Apparatus 10
Absorber column 12
Regenerator 14
First absorption 5 section 16
Second absorption section 18
First conduit 20
Bottom portion 22
Compressor 24
10 First gas sparger 26
Second conduit 28
Top portion 30
Liquid distributor 32
Low pressure drop internals 34
15 First sump 36
Third conduit 38
First end 40
Second end 42
Lower portion 44
20 Second gas sparger 46
Fourth conduit 48
Upper portion 50
Second sump 52
Fifth conduit 54
25 Sixth conduit 56
Pump 58

We Claim:
1. An apparatus (10) for low pressure absorption of H2S from a feed gas, the
apparatus comprising:
an absorber column (12) comprising:
a first absorption section 5 (16), comprising:
a first conduit (20) at a bottom portion (22) of the first absorption
section (16) for introducing a feed gas in the first absorption
section (16);
a second conduit (28) on a top portion (30) of the first absorption
10 section (16) for feeding a regenerated lean amine solution in the
first absorption section (16); and
low pressure drop internals (34) for distribution of the feed gas
and the regenerated lean amine solution and absorption of H2S in
the first absorption section (16); and
15 a second absorption section (18), comprising
a third conduit (38) at a lower portion (44) of the second
absorption section (18) for receiving a lean feed gas from the first
absorption section (16);
a fourth conduit (48) on an upper portion (50) of the second
20 absorption section (18) for feeding fresh caustic solution in the
second absorption section (18);
low pressure drop internals (34) for distribution of lean feed gas
and fresh caustic solution and absorption of H2S; and
a regenerator (14) coupled to the bottom portion (22) of the first
25 absorption section (16) for providing the regenerated lean amine solution
to the first absorption section (16).
2. The apparatus as claimed in claim 1, wherein the feed gas is a low pressure
hot well off gas.
16
3. The apparatus as claimed in claim 1, wherein the low pressure drop
internals (34) are selected from a group comprising of structured packing,
random packing, gas and liquid distributor.
4. The apparatus as claimed in claim 1, wherein the regenerator (14) is a
5 distillation column.
5. The apparatus as claimed in claim 4, wherein the distillation column
receives a rich amine solution from the bottom portion (22) of the first
absorption section (16) by means of a pump (58) and the distillation column
recycles the regenerated lean amine solution to the top portion (30) of the
10 first absorption section (16) of the absorber column (12).
6. The apparatus as claimed in claim 1, wherein the second absorption section
(18) of the absorber column (12) is provided with a fifth conduit (54) at the
lower portion of the second absorption section (18) to remove a spent
caustic solution.
15 7. The apparatus as claimed in claim 1, wherein a sixth conduit (56) is
provided on the upper portion (50) of the second absorption section (18) of
the absorber column (12) to remove a treated gas; said treated gas having
H2S content of less than 100ppmw.
8. The apparatus as claimed in claim 1, wherein the absorber column (12) is
20 coupled to a compressor (24).
9. The apparatus as claimed in claim 8, wherein the compressor (24) is
configured to increase pressure of the feed gas ranging from 0.1-
0.4kg/cm2g to 0.15-3.0kg/cm2g.
10. A process for low pressure absorption of H2S from a feed gas, said process
25 comprising the steps of:
a. providing the feed gas at a pressure in the range of 0.1 to 0.4kg/cm2g
and temperature between 25 to 50˚C;
b. feeding the feed gas of step (a) to a bottom portion (22) of a first
absorption section (16) of an absorber column (12);
30 c. feeding are generated lean amine solution at a top portion (30) of the
first absorption section (16) of the absorber column (12);
17
d. contacting the feed gas in step (b) counter currently with the
regenerated lean amine solution of step (c) by means of a liquid
distributor (32) over a structured packing, thereby providing a lean
feed gas at the top portion (30) of the first absorption section (16) and
a rich amine solution at the bottom portion (22) of the 5 first absorption
section (16);
e. pumping the rich amine solution obtained in step (d) to a regenerator
(14) to recycle the regenerated lean amine solution to step (c);
f. receiving the lean feed gas obtained in step (d) at a lower portion (44)
10 of a second absorption section (18) of the absorber column (12);
g. feeding afresh caustic solution by means of a liquid distributor (32)
at an upper portion (50) of the second absorption section (18);
h. contacting the lean feed gas of step (f) counter currently with the fresh
caustic solution of step (g) over a structured packing and obtaining a
15 spent caustic solution at the lower portion (44) of the second
absorption section (18) and treated gas at the upper portion (50) of the
second absorption section (18),
wherein the treated gas has H2S content of less than 100ppmw.
11. The process as claimed in claim 10, wherein the feed gas is a low pressure
20 hot well off gas comprisingH2, N2, CO, C1-C6 hydrocarbons and H2S.
12. The process as claimed in claim 11, wherein H2S is present in the range
between 1% to 30% by weight.
13. The process as claimed in claim 10, wherein the regenerated lean amine
solution is an aqueous amine solution selected from a group comprising of
25 monoethanolamine, diethanolamine, N-methyl-diethanolamine,
diglycolamine, mixed amines, activated amines and a combination thereof.
14. The process as claimed in claim 13, wherein the regenerated lean amine
solution has a concentration of amine ranging between 10% to 60% by
weight.
18
15. The process as claimed in claim 10, wherein the fresh caustic solution is an
aqueous solution of sodium hydroxide ranging between 0.1% to 20% by
weight.
16. The process as claimed in claim 10, wherein the feed gas in step (a) is
optionally compressed in a compressor (24) to increase 5 the pressure of the
feed gas ranging from 0.1-0.4kg/cm2g to 0.15-3.0kg/cm2g