JPH1028837A - Method and apparatus for removing sulfur compound contained in natural gas, etc. - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove sulfur compounds efficiently by a method in which impurity gas is separated into concentrated gas consisting chiefly of H2 S and residual gas, and H2 S is recovered from offgas from the Claus reaction of the concentrated gas and the residual gas to be returned to the Claus reaction. SOLUTION: Impurity gas accompanied by natural gas, etc., contains a large amount of CO2 , COS, etc., besides H2 S. The impurity gas is sent to the second absorption tower 8, and most of H2 S and part of CO2 are absorbed by selective absorption liquid. Next, the absorption liquid is sent to the second regeneration tower 11 to be converted into concentrated gas consisting chiefly of H2 S by heating. The concentrated gas is sent to a Claus sulfur recovery apparatus 14, part of H2 S in the concentrated gas is oxidized by oxygen-containing gas into SO2 , and the SO2 and residual H2 S are reacted into sulfur. When the residual gas and offgas, after being heated by a heating furnace 18, are hydrogenated by a hydrogenation reactor 20, the sulfur compounds in SO2 , mercaptan, etc., are reduced into H2 S and after being separated by the third absorption tower 22, returned to the apparatus 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention includes natural gas, petroleum accompanying gas, synthesis gas, process gas, coal gasification gas, heavy oil gasification gas and the like (hereinafter abbreviated as natural gas etc. in the present invention). The present invention relates to a method and an apparatus for removing sulfur compounds such as hydrogen sulfide (H ₂ S), mercaptan, and sulfur oxides.

[0002]

2. Description of the Related Art There are carbon dioxide (CO ₂ ), H ₂ S, COS, mercaptan, and heavy hydrocarbons as impurity gases accompanying natural gas and the like. In recent years, there has been a tendency to gradually increase with the decrease of these, and it is necessary to remove and refine these to obtain product gas.

On the other hand, as a method for removing H ₂ S contained in a gas, there is a method by the Claus reaction. The Claus reaction, and SO ₂ by oxidizing a part of H ₂ S in the gas by separating and recovering elemental sulfur is reacted with H ₂ S of the SO ₂ and the remainder, H ₂ in the gas S is to be removed. A method is also known in which the residual SO ₂ contained in the off-gas after the Claus reaction is hydrogenated in the presence of a catalyst to form H ₂ S, which is returned to the Claus reactor to increase the sulfur removal rate.

[0004] Meanwhile, as described above, various components other than H ₂ S are contained as impurity components accompanying natural gas and the like. If the gas is led to the Claus reactor to remove the sulfur contained therein, the following disadvantages occur. Since the impurity gas contains a large amount of components other than H ₂ S, for example, CO ₂ , the H ₂ S concentration decreases, the reaction rate in the Claus reaction decreases, and the removal rate decreases. Heavy hydrocarbons (benzene, toluene, xylene, etc.) contained in the impurity gas incompletely burn, soot is generated, the recovered sulfur is contaminated with soot, the quality of sulfur is reduced, and the soot forms a Claus catalyst layer. May block.

Conventionally, as a method of causing a Claus reaction of a hydrogen sulfide-containing gas containing a large amount of CO ₂ , for example, there is a method disclosed in Japanese Patent Publication No. 63-17488. In this method, a part of an H ₂ S-containing gas containing 20% by volume or more of CO ₂ is supplied to a Claus plant, and the remainder is brought into contact with an absorbent that bypasses the Claus plant and selectively absorbs H ₂ S. The H ₂ S regenerated and separated by the absorbent is returned to the Claus plant. However, even the prior invention cannot sufficiently solve the above-mentioned disadvantages.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the problem that the impurity gas accompanying natural gas or the like is H ₂ S
In addition, even those containing a large amount of CO ₂ , COS, BTX, mercaptan, etc., can efficiently remove the sulfur compounds in the impurity gas by the Claus reaction, and furthermore, are formed from heavy hydrocarbons such as BTX. An object of the present invention is to prevent blockage of the Claus catalyst layer and deterioration in the quality of recovered sulfur due to soot.

[0007]

SUMMARY OF THE INVENTION The foregoing object, and a residual gas impurity gases separated from the natural gas or the like sent to concentration and separation process consists of concentrated gas and a residual component mainly comprising H ₂ S in the impurity gas The concentrated gas is sent to a Claus reaction step, H ₂ S is recovered and removed, and the off-gas from the Claus reaction step and all or part of the residual gas are sent separately or in combination to a tail gas treatment step, here heating, and hydrogenated sulfur compounds of the gas and H ₂ S, it is solved by returning the Claus reaction step and separating the H ₂ S.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 shows an example of an apparatus for carrying out the removal method of the present invention, which uses crude natural gas mined as natural gas or the like. Crude natural gas is pipe 1
Is sent to the first absorption tower 2 where the impurity gas accompanying the crude natural gas is non-selectively absorbed therein, and the purified product natural gas is led out from the tower by the pipe 3. An aqueous solution such as a sulfolane-amine mixed solution, monoethanolamine, diethanolamine, diglycolamine, methanol, or glycol solution is supplied to the first absorption tower 2 as a non-selective absorption solution. CO
₂ and H ₂ S, small amounts of sulfur compounds such as mercaptans,
Small amounts of hydrocarbons such as BTX are absorbed.

The absorption liquid having absorbed the impurity gas is sent from the bottom of the tower to the first regeneration tower 5 via the pipe 4, where it is heated.
The impurity gas is released. The impurity gas is composed of, for example, about 70 vol% of CO ₂ , about 25 vol% of H ₂ S, a small amount of mercaptan, and a hydrocarbon of BTX. This impurity gas is withdrawn from the top of the first regeneration tower 5 by a pipe 6, and the regenerated absorbent is withdrawn from the bottom of the tower, returned to the first absorption tower 2 via a pipe 7, and reused. .

[0010] The impurity gas from the pipe 6 is introduced into the second absorption tower 8. The second absorption tower 8 is selected from an alkanolamine such as diethanolamine, triethanolamine, diisopropanolamine, and methyldiethanolamine, a mixed solution of sulfolane-amine, an aqueous solution of polyethylene glycol dialkyl ether, and an aqueous solution of N, N-dimethylaminoacetate. A typical absorbing liquid is supplied, where most of the H ₂ S and some of the CO ₂ in the impurity gas are absorbed. Some of these absorbing liquids are used as non-selective absorbing liquids.
It can be a selective absorption liquid which absorbs the ₂ S. The absorption conditions here are 60 ° C. or lower, preferably 5 to 40 ° C.
° C, and the pressure is substantially atmospheric pressure or slightly increased under 2 atm.

From the top of the second absorption tower 8, residual gas comprising residual components not absorbed here is led to a pipe 9. This residual gas is predominantly CO ₂ , to which 0.1 to 5 vol% of mercaptan and BTX, 0
0.3～0.3Vol% of H ₂ S are included. Second
The absorption liquid drained from the bottom of the absorption tower 8 is sent to a second regeneration tower 11 via a pipe 10, where H ₂ S and CO ₂ which have been heated and absorbed are diffused, and H ₂ S Is 50 vol% or more, for example, about 65 vol% of H ₂ S and about 35 vol of CO ₂
1%, and a concentrated gas enriched in H ₂ S is led out from the top of the tower.

From the bottom of the second regeneration tower 11, the regenerated absorbent is returned to the second absorption tower 8 via the pipe 12 and reused. The second absorption tower 8 and the second regeneration tower 11 constitute the concentration and separation apparatus of the present invention, and it is possible to increase the H ₂ S concentration by installing a plurality of these respectively.

The concentrated gas from the second regeneration tower 11 is sent via a pipe 13 to a Claus sulfur recovery unit 14 comprising a Claus reactor and a multi-stage Claus catalyst layer. The Claus sulfur recovery unit 14 has a well-known structure, and has a non-catalytic type and a catalytic type reactor. The catalyst is alumina, bauxite, titania, zirconia, silica, zeolite or a rare earth metal as a heat stabilizer. Alternatively, a material containing an oxide of an alkaline earth metal is used. The reaction temperature is about 1000 to 1500 ° C. for the non-catalytic type, and about 200 to 350 ° C. for the catalytic type. Claus sulfur recovery equipment 1
In 4, a part of H ₂ S in the concentrated gas is oxidized to SO ₂ by an oxygen-containing gas such as oxygen gas and air introduced through the pipe 15, and this SO ₂ and the remaining H ₂ S are converted into SO ₂ . It reacts to sulfur, and most of the H ₂ S is recovered from the pipe 16 as simple sulfur by this reaction.

The exhaust gas (off-gas) from the Claus sulfur recovery unit 14 is trace H ₂ S, SO ₂ , S, COS, C
When S ₂ and a large amount of CO ₂ , H ₂ O, residual oxygen and air are used as an oxygen source, N ₂ is contained. The temperature of this off gas is usually 130 to 170 ° C. The off-gas from the Claus sulfur recovery unit 14 is sent from the pipe 17 to the heating furnace 18, and at the same time, all or part of the residual gas sent from the second absorption tower 8 via the pipe 9 is also supplied to the heating furnace 18.

The heating furnace 18 is equipped with a normal combustion burner, and raises the temperature of the off-gas and the residual gas to a temperature required for the subsequent hydrogenation reaction by combustion with fuel and oxygen in the air. Note that by burning the fuel by partial oxidation, it is possible to produce CO / H ₂ required for the hydrogenation reaction. In the heating furnace 18 or in a pipe 19, if necessary, CO / H ₂ as a reducing agent necessary for the hydrogenation reaction is added. It is also possible to use a heat exchanger instead of the heating furnace 18.

The heated gas is supplied from a pipe 19 to the hydrogenation reactor 2.
0, where sulfur compounds such as SO ₂ , mercaptan and S contained therein are reduced to H ₂ S in the presence of a reduction catalyst. The reduction catalyst used here is Ni-Mo, Co
—Mo, Ni—Co—Mo oxides or sulfides, and these catalysts may be supported on an oxide carrier such as alumina, silica, magnesia, boria, thoria, and zirconia. The reduction reaction is carried out in a temperature range of 180 to 450 ° C., preferably 250 to 350 ° C., under atmospheric pressure or under slight pressure of 2 atm or less. A hydrogen-containing gas for reduction may be added, and if CO / H ₂ has been sufficiently generated in the combustion process in the heating furnace 18, it may not be added again. The mixing volume ratio of CO / H ₂ and the sulfur compound to be reduced is 2: 1 to 15: 1, preferably 3: 1 to 1: 1.
8: 1 is preferred.

The hydrogenated gas from the hydrogenation reactor 20 contains several vol% of H ₂ S, a small amount of hydrocarbons such as BTX, unreacted mercaptan, H ₂ and large amounts of CO ₂ and N ₂ , 2
It is extracted from 1 and, after cooling, is sent to the third absorption tower 22. A part of the regenerated absorbing liquid from the second regenerating tower 11 is supplied to the third absorbing tower 22 via a pipe 23 as the absorbing liquid. In the third absorption tower 22, a part of H ₂ S and CO _{2 in} the hydrogenated gas is absorbed, and the remaining large amount of CO ₂ and N ₂ , a small amount of hydrocarbon such as BTX, mercaptan, H ₂ , A gas containing a trace amount of H ₂ S is introduced from the top of the column into a pipe 24, and the gas is discharged as it is to the atmosphere or burned and discharged to a stack.

From the bottom of the third absorption tower 22, H ₂ S and C
The absorbing liquid having absorbed O ₂ is returned to the second regeneration tower 11 via the pipe 25, where H ₂ S and CO ₂ are diffused and sent to the Claus sulfur recovery unit 14 as a concentrated gas. In this embodiment, the heating furnace 18, the hydrogenation reactor 20, the third absorption tower 22, and the associated pipeline constitute a tail gas treatment apparatus of the present invention.

According to such a sulfur compound removing method, the concentration of H ₂ S in the concentrated gas introduced into the Claus sulfur recovery unit 14 becomes higher than that of the impurity gas, and the concentration of the accompanying CO ₂ decreases. Therefore, the Claus reaction rate increases, and the sulfur recovery rate also increases. In addition, H in the impurity gas
Mercaptans other than ₂ S, other sulfur compounds such as COS also ultimately most is the H ₂ S, because this is also removed by the Claus reaction, the total sulfur content in the exhaust gas discharged into the atmosphere It will be extremely low. Further, since heavy hydrocarbons such as BTX contained in the impurity gas are not introduced into the Claus sulfur recovery unit 14, soot is not generated in the Claus sulfur recovery unit 14, and the quality of the recovered sulfur is reduced. Lowering and clogging of the catalyst layer can be prevented.

In the present invention, the absorbing solution of the third absorbing tower 22 can be used from the aqueous solution used in the second absorbing tower 8 and the second regenerating tower 11. In the case where the absorption liquid is different from the absorption liquid in the second absorption tower 8, it is necessary to separately provide a third regeneration tower to provide a separate system from the concentration separation step.

In the present invention, H ₂ S may be separated from the hydrogenated gas from the hydrogenation reactor 20 by adsorption and returned to the Claus sulfur recovery unit 14. That is, an adsorption tower is provided instead of the third absorption tower 22, and activated carbon,
Alternatively, it may be soaked with an aqueous solution of a compound capable of reacting with hydrogen sulfide, or filled with an adsorbent such as alumina, iron oxide, or zinc oxide, thereby adsorbing and separating H ₂ S.

Further, when the off-gas from the Claus sulfur recovery unit 14 contains CS ₂ and COS, these sulfur compounds are brought into contact with a hydrolysis catalyst such as alumina after or simultaneously with the hydrogenation treatment to convert these sulfur compounds into H 2. ₂ S, which was separated in the third absorption tower 22 and the Claus sulfur recovery unit 14
May be returned.

FIG. 2 shows a second embodiment of the present invention.
The same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In this apparatus, a second heating furnace 26 is provided in addition to the heating furnace 18, and the residual gas from the second absorption tower 8 is sent to the second heating furnace 26 via a pipe 9, where the heating and reducing agent are heated by partial oxidation combustion. The heated gas is sent from a pipe 27 to a second hydrogenation reactor 28,
Here, hydrogenation is performed to convert the sulfur compound into H ₂ S, and this hydrogenated gas is sent from the pipe 29 to the third absorption tower 22.

In this case, the Claus sulfur recovery unit 14
Since the residual gas is heated and hydrogenated separately from the off-gas from, the reaction conditions, catalyst, and hydrogenation conditions can be set according to the composition of the residual gas, further reducing sulfur compound emissions. it can.

FIG. 3 shows a third embodiment of the present invention.
In this reactor, a fourth absorption tower 30 is provided downstream of the second hydrogenation reactor 28, and the heating gas from the second heating furnace 26 is supplied to a pipe 27.
To the second hydrogenation reactor 28, where it is hydrogenated and then sent from the pipe 29 to the fourth absorption tower 30, where it absorbs H ₂ S and discharges the remaining gas as exhaust gas from the pipe 31. Things. The fourth absorption tower 30 has a third pipe
The absorption liquid used in the absorption tower 22 is supplied, and the absorption liquid that has absorbed H ₂ S in the fourth absorption tower 30 is returned to the second regeneration tower 11 via the pipe 33.

In this case, the treatment of the residual gas and the treatment of the off-gas from the Claus sulfur recovery unit 14 are performed completely separately, respectively, so that the heating conditions, reduction conditions, catalysts, It becomes possible to individually set absorption conditions and the like in detail. Therefore, the content of sulfur compounds and hydrocarbons in the exhaust gas is extremely low.

[0027]

As described above, the present invention separates impurity gas accompanying natural gas, petroleum accompanying gas and the like into a concentrated gas mainly composed of H ₂ S and a residual gas composed of residual components, and forms a concentrated gas. Is treated by the Claus reaction, and the sulfur compound in the off-gas and the residual gas of the Claus reaction is hydrogenated to convert the sulfur compound in these gases into H ₂ S. This H ₂ S is separated and returned to the Claus reaction.

For this reason, C other than H ₂ S is contained in the impurity gas.
Even if a large amount of gas such as O ₂ is contained, the concentration of H ₂ S in the concentrated gas used for the Claus reaction can be increased, and the Claus reaction rate increases, thereby improving the sulfur removal rate. In addition, since heavy hydrocarbons such as BTX are not brought into the Claus sulfur recovery device, soot is not generated due to the heavy hydrocarbons, and the quality of recovered sulfur is reduced and the catalyst layer is not blocked. Furthermore, H ₂ S such as mercaptan in impurity gas
Other sulfur compounds are finally converted to H ₂ S and removed by the Claus reaction, so that the total sulfur amount in the exhaust gas exhausted to the atmosphere can be further reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first example of an apparatus of the present invention.

FIG. 2 is a schematic configuration diagram showing a second example of the device of the present invention.

FIG. 3 is a schematic configuration diagram showing a third example of the device of the present invention.

[Explanation of symbols]

 2 1st absorption tower 5 1st regeneration tower 8 2nd absorption tower 11 2nd regeneration tower 14 Claus sulfur recovery apparatus 18 Heating furnace 20 Hydrogenation reactor 22 3rd absorption tower 26 2nd heating furnace 28 2nd hydrogenation reaction furnace

Claims (4)

[Claims] 1. An impurity gas containing a sulfur compound such as hydrogen sulfide separated from natural gas or the like is sent to a concentration separation step, where an impurity gas mainly containing hydrogen sulfide contained in the impurity gas and a residual component are separated from the impurity gas. The concentrated gas is sent to the Claus reaction step, where hydrogen sulfide is recovered as sulfur alone, and the residual gas and the off-gas discharged from the Claus reaction step are sent to the tail gas treatment step. Heating to the required reaction temperature, and then hydrogenating in the presence of a catalyst to convert the sulfur compounds contained in these gases into hydrogen sulfide, separating the hydrogen sulfide and returning to the Claus reaction step. For removing sulfur compounds contained in water. 2. The method of claim 1 wherein said residual gas is sent to a second tail gas treatment step where it is heated to the required reaction temperature and then hydrogenated in the presence of a catalyst to remove sulfur contained in said gas. A method for removing a sulfur compound contained in natural gas or the like, wherein the compound is hydrogen sulfide, and the hydrogen sulfide is returned to the Claus reaction step. 3. An enrichment separation for separating an impurity gas containing a sulfur compound such as hydrogen sulfide separated from natural gas or the like into a concentrated gas mainly composed of hydrogen sulfide contained therein and a residual gas composed of residual components. An apparatus; a Claus reactor for recovering hydrogen sulfide in the concentrated gas from the enrichment / separation apparatus as simple sulfur by a Claus reaction; And then hydrogenating in the presence of a catalyst to convert the sulfur compounds contained in these gases into hydrogen sulfide, and a tail gas treatment device for returning the hydrogen sulfide to the Claus reactor is provided. For removing sulfur compounds contained in water. 4. The removing apparatus according to claim 3, wherein only the residual gas from said concentrating / separating apparatus is heated to a required reaction temperature and then hydrogenated in the presence of a catalyst to sulfide sulfur compounds contained in this gas. A device for removing sulfur compounds contained in natural gas or the like, further comprising a second tail gas treatment device for converting hydrogen to hydrogen and returning the hydrogen sulfide to the Claus reactor.