JPS6336815A - Method for purifying gas - Google Patents

Abstract

PURPOSE:To improve the efficiency in removing H2S by bringing a gas contg. CO2 and H2S into contact with an aq. soln. of an alkali carbonate, then bringing the gas into contact with an aq. soln. of an alkali carbonate contg. V<5+>, separating the S generated by the contact of the aq. soln. with an oxidizing agent, and circulating the soln. CONSTITUTION:The gas contg. CO2 and H2S is introduced into a first absorption tower 1, and brought into contact with an aq. soln. of an alkali carbonate such as an aq. K2CO3 soln. The liq. absorbent is heated in a regeneration tower 2 to liberate the absorbed CO2 and H2S, and then circulated as the regenerated liq. absorbent from a duct 9. Meanwhile, the gas is introduced into a second absorption tower 3, and brought into contact with an aq. K2CO3 soln. contg. V<5+>. The H2S and CO2 in the gas are absorbed, and an oxidizing agent is added to the liq. absorbent from a tank 6 for an aq. soln. of an oxidizing agent. The absorbent is recovered in a tank 4 for a hot aq. K2CO3 soln. and passed through a strainer 5 to separate deposited solid S. The absorbent is then circulated to the second absorption tower 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for purifying gas, and more specifically, a method for purifying gas containing CO2 and H2S as impurities by bringing it into contact with an aqueous alkali carbonate solution. It is about improvement.

[Conventional technology]

For example, when CO is produced by gasifying coke by passing O2-containing gas through a coke layer kept at high humidity, the generated CO gas contains a considerable amount of Co and H2S. For those who use this gas as a raw material for various chemical reactions, it can be purified to produce Co and H2.
It is necessary to remove S. As a method for purifying such a gas, a method of contacting the gas with an aqueous alkali carbonate solution is generally known. This method usually involves continuously contacting the gas with a hot aqueous solution of potassium carbonate in an absorption tower, and
O, and H2S are absorbed, and then the treated absorption liquid is heated in a regeneration tower to purge the CO, H, and S'i generated to regenerate the absorption liquid, which is then recycled to the absorption tower again. It is implemented by The chemical formula for this is as follows.

x2cos + Co2+a, o = , 2KHOO3
2co, + H3S = KHCO3 + K
H8 [Problem to be Solved by the Invention] However, with this method, although CO can be removed relatively easily, it is difficult to remove Its to the trace level. The ultimate effect of HIB can be improved by increasing the regeneration rate of the absorption liquid in the regeneration tower, but
In order to increase the regeneration rate of this absorption liquid, a large amount of thermal energy is required, which is an industrially disadvantageous method.Also, even if the regeneration rate is increased, the purification effect may be limited depending on the target gas. That's it.

In view of the above circumstances, the present invention was developed by CO! The object of the present invention is to provide a method that can efficiently remove H and Sf when purifying a gas containing HIB and HIB using an aqueous alkali carbonate solution as an absorption liquid.

[Means for solving problems]

The present inventors discovered that H2S absorption is effectively carried out when j-valent vanadium is present in an aqueous alkali carbonate solution.Based on this knowledge, the present inventors conducted further studies and found that CO□ and H2S can be absorbed with industrial advantage. , we have completed a process that can remove S.

That is, the gist of the present invention is to provide a gas purification method in which a gas containing Cog and HIS is brought into contact with an aqueous alkali carbonate solution, and the treated aqueous alkali carbonate solution is regenerated and then used for circulation. After contacting the pretreated gas with an aqueous alkali carbonate solution containing j-valent vanadium, and contacting the aqueous alkali carbonate solution containing vanadium after the treatment with an oxidizing agent to separate the precipitated solid sulfur, A gas purification method characterized by cyclic use.

The present invention will be explained in detail below.

In the present invention, the gas containing CO and H2El'i as impurities is N-type, but the content of these impurity components is usually 70 to ≠ Ovow in the case of Co2, and in the case of F12S. /Qθ~/θ, 0θOpp
It is m. The target main gas is not particularly limited as long as it is inert to alkali carbonates, but usually CO
Gas is a typical example. A specific example of such a gas is, for example, in a tf14 layer filled with coke that is maintained at a temperature of 7100°C or higher, preferably 7100°C or higher. and C.O.

Examples include crude cobalt gas, which is generated by diluting this mixed gas with nitrogen or cobalt and aerating nitrogen gas. In this case, the composition of the gas to be vented is, for example, 0! and C
When there are two components of o2, 0! : CO2=Lis %
s o: y ~ s o, 02, CO, and N
When there are three components of t or CO, 02: Cog
: Nt or CO=/θ~Hiroo:10~San〇:2
θ~? It is θ.

In the present invention, the gas containing CO, H, and S as impurities obtained in this manner is brought into contact with an aqueous alkali carbonate solution to absorb and remove CO2 and H2S in the gas, but the alkali carbonate used here is Usually, it is potassium carbonate or sodium carbonate, and its concentration is 70 to 90%
t%.

Further, the aqueous alkali carbonate solution may contain a small amount of known additives such as jetanolamine, boric acid, potassium metavanadate, and the like. In industrial implementation, contact with the aqueous alkali solution is preferably carried out in an absorption tower, and regeneration of the aqueous alkali solution is preferably carried out in a regeneration tower.

The contact treatment in the absorption tower is usually carried out in accordance with a conventional method by supplying gas from the lower part of the absorption tower, while injecting an aqueous alkali carbonate solution from the upper part. The conditions at this time are usually 0 to 700°C under pressure or normal pressure, preferably t0
-0°C.

By this contact treatment, 002 and H! in the gas! Most of the S is absorbed and the original plate is then processed in a regeneration tower, usually for 7
Heating to 10℃ or higher, CO2711 gas and H,
By releasing the S gas, the regenerated absorption liquid is recovered from the bottom of the column. This regenerated absorption liquid is then circulated to the absorption tower and reused. In the present invention, it is necessary to regenerate the absorption liquid in the regeneration tower to a level that is not inconvenient for absorbing Co21, but it is technically disadvantageous to regenerate more than the mantle wall, and the regeneration rate is usually limited. (alkali hydrogen carbonate mol t/total alkali metal compound mol bond x 100) /!
~-! It is desirable that the

On the other hand, a trace amount of H! after the above-mentioned contact treatment! The gas containing S is further contacted with an aqueous alkali carbonate solution containing pentavalent vanadium in the second absorption tower. The aqueous alkali carbonate solution used here may be the same as that explained in the first absorption treatment above, and the treatment operations and treatment conditions may also be the same.

As pentavalent vanadium present in alkali carbonate,
Usually, pentavalent vanadium compounds that are dissolved in aqueous aqueous carbonate solutions such as vanadium pentoxide, alkali vanadate, and alkali metavanadate are preferred;
It is also possible to generate pentavalent vanadium in the system using a vanadium compound having a valence or μ valence. The amount of pentavalent vanadium present is usually 150 to 10,00099 m1, preferably /θθθ
~jθθOppm.

If the content of this pentavalent vanadium is too low atp, the trace amount of HIEJ contained in the gas cannot be effectively removed in the second absorption tower, and even if it is too large, the effect will not change. Therefore, it is not economical.

The t-absorbent liquid used in the second absorption tower is recycled, but in this case, the sulfur component is absorbed into the alkaline carbonate aqueous solution by contact treatment with gas, and the vanadium component is reduced to valent or trivalent. Therefore, it is necessary to contact the absorbent with an oxidizing agent prior to circulation. In short, by contacting the absorption liquid with the total oxidizing agent, the sulfur component becomes solid and precipitates, and the vanadium component, which has become valent, valent, or trivalent, returns to its pentavalent state. If the absorbent is used for circulation without this treatment.

The H and S purification effect in the second absorption tower is the same as that of the first absorption tower.

It becomes no different from the Km effect of .

As the oxidizing agent used in the oxidation treatment, hydrogen peroxide or alkali nitrite is usually most desirable. If the amount of this oxidizing agent used is too small, the precipitation of sulfur components and the oxidation of vanadium components cannot be performed well.On the other hand, even if the amount of oxidizing agent is too large, there is no change in the effect. It is 7 to 3 times the mole of S. In addition, this oxidation treatment is usually carried out in a pipe or stirring tank during the transfer of the absorption liquid.
This is done by mixing an aqueous solution of the oxidizing agent at a temperature of 100°C. After the treatment, the absorbed liquid is circulated to the second absorption tower after separating the precipitated solid sulfur using, for example, a strainer.

〔Example〕

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example/~≠ In the j-echo process shown in the flow sheet of Fig. 1,
A processing of lees CO gas was carried out continuously.

First, crude CO gas (C02 content y%) 30 wa 1%, H2
S containing 1jθθppm) was introduced at 700 go/hr,
On the other hand, from the top, 25wt% potassium carbonate aqueous solution (containing jetanolamine/,!wt% and boric acid o, swt%)
An absorption liquid consisting of 1-20d/hr is sprayed and contact treatment is carried out at a temperature of 60°C under normal pressure.Then, the absorption liquid is extracted from the bottom of the tower and introduced into the upper part of the regeneration tower through a conduit. It is heated to a temperature of 730°C, and the absorbed CO and H2Sf are purged from the top of the column and regenerated (regeneration rate: 0.9%).

The regenerated liquid is continuously circulated from the lower part of the absorber 2 to the upper part of the first absorption tower via a conduit.

Further, the gas discharged from the top of the first absorption tower / is subsequently introduced into the lower part of the second absorption tower 3 through the conduit /θ, and a 60°C 2 j wt potassium thicarbonate aqueous solution /j is sprayed from the upper part. contact treatment with Go/hr.

Guide? ! // After all, the oxidizing agent aqueous solution from the oxidizing agent aqueous solution tank B was added to the absorption liquid extracted from the bottom of the No. 1 absorption tower at a temperature of 0℃, and then it was once collected into the hot potassium carbonate aqueous solution tank ≠ The precipitated stationary sulfur was separated by passing through a post-strainer j and circulated to the second absorption tower again.

This continuous gas purification method is carried out in the second absorption tower!
＋ component and oxidizing agent were changed, and after the system became stable, the v5 concentration in the absorption liquid and the CO, H, and S concentrations in the purified gas were measured. I got the result shown
0 Comparative Example/Example was carried out in the same manner as in Example, except that an aqueous potassium carbonate solution containing no vanadium component was used as the absorption liquid in the second absorption tower.

The results are also recorded in Table 1.

Comparative Examples 2 to 3 Examples/Mat are the same as Examples/or Examples ≠ except that the absorption liquid extracted from the second absorption tower is recycled to the second absorption tower without being treated with an oxidizing agent. Perform the same procedure and record the t0 results in Table 1.

*/) Amount of vanadium component used As V for potassium carbonate aqueous solution The weight percentage of total vanadium is shown.

*, 2) Use of oxidizing agent Oxidizing agent for sulfur components in absorption liquid indicates the molar ratio of

*3) ■5+ concentration in absorption liquid of trivalent vanadium present in the absorption liquid. Weight percentages are shown.

This value was obtained by developing a sample with a 7-elon aqueous solution of V5+ under acidic sulfuric acid, and extracting this with n-butanol. O
The absorbance was determined by the standard addition method at a wavelength of 1 nm.

〔Effect of the invention〕

In the present invention, an aqueous alkali carbonate solution containing S-valent vanadium is constantly circulated to the first absorption tower.
H! which could not be sufficiently absorbed by the absorption tower! S can be efficiently absorbed.

Therefore, in the method of the present invention, even if the regeneration rate in the regeneration tower is kept low, the remaining H2S can be easily removed in the λth absorption tower, and purified gas free of CO and H213 can be obtained industrially advantageously. be able to.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing a crude CO gas purification process carried out in an example of the present invention. /: 1st absorption tower =: Regeneration tower 3: 2nd absorption tower Potassium carbonate aqueous solution / S strainer - Dioxidant aqueous solution tank / 2: Reboiler Applicant: Mitsubishi Kasei Kosai Co., Ltd. Representative: Patent attorney For Hase - others/names

Claims (1)

[Claims] (1) A gas purification method in which a gas containing CO_2 and H_2S as impurities is brought into contact with an aqueous alkali carbonate solution, and the treated aqueous alkali carbonate solution is regenerated and then recycled for use, The gas after being brought into contact with the aqueous alkali carbonate solution is further brought into contact with an aqueous alkali carbonate solution containing pentavalent vanadium, while the aqueous alkali carbonate solution containing vanadium after the treatment is brought into contact with an oxidizing agent to separate the precipitated solid sulfur. A gas purification method characterized by recycling and reusing the gas. (2) The purification method according to claim 1, wherein the pentavalent vanadium is vanadium pentoxide or alkali metavanadate. (3) The purification method according to claim 1, characterized in that the content of pentavalent vanadium (V) is 150 to 5000 ppm based on the aqueous alkali carbonate solution. (4) The purification method according to claim 1, wherein the oxidizing agent is hydrogen peroxide or an alkali nitrite. (6) The purification method according to claim 1, wherein the gas containing CO_2 and H_2S is a gas mainly composed of CO. (6) The purification method according to claim 1, characterized in that the contact with an aqueous alkali carbonate solution containing pentavalent vanadium is carried out at a temperature of 40 to 100°C.