JPS58202021A - Treatment of hydrogen sulfide-containing gas - Google Patents

Abstract

PURPOSE:To carry out the treatment of a hydrogen sulfide-containing gas stably and economically in good efficiency, by a method wherein a gas absorbing liquid having hydrogen sulfide absorbed thereby is treated with potassium hydroxide and the obtained treating liquid is reused in the alkali treatment of the hydrogen sulfide-containing gas. CONSTITUTION:A hydrogen sulfide-containing gas 3 is brought into contact with an aqueous caustic soda solution 5 in a catalytic reaction tower 1 while a gas absorbing liquid 7 is sent to a storage tank 8 to be stored therein. This gas absorbing liquid 7 is heated by a heat exchanger 10 to be supplied to a treating tank 11 while an aqueous potassium hydroxide solution is supplied thereto from the storage tank 12 to treat said absorbing liquid 7. The treated liquid is filtered by a filter apparatus 14 to remove calcium carbonate and a treating liquid 15 comprising sodium sulfide and caustic soda is obtained. This treating liquid 15 is sent to a storage tank 16 to be mixed with the absorbing liquid 7 and the ratio of sodium sulfide and caustic soda is adjusted to 0.6-1.2. Subsequently, this treating liquid is sent to the reaction tower 1 and added to the aqueous caustic soda solution 5 to be reused.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an efficient, stable and economical processing method.

Conventionally, a method of absorbing and removing hydrogen sulfide by contacting a hydrogen sulfide-containing gas with, for example, an aqueous solution of caustic soda has been widely used because the treatment operation is relatively simple.

However, in this method, when hydrogen sulfide and caustic soda are brought into contact, carbon dioxide gas in the air also comes into contact with the caustic soda and reacts, so a large amount of caustic soda is consumed, which essentially becomes an obstacle to the absorption and removal of hydrogen sulfide and is economical. Hydrogen sulfide? Difficult to process.

In particular, when the concentration of hydrogen sulfide in the gas is low, the amount of caustic soda consumed by carbon dioxide gas increases, and if the contact time between hydrogen sulfide-containing gas and caustic soda is increased in an attempt to completely absorb and remove hydrogen sulfide, carbon dioxide The reaction between the gas and caustic soda also progresses, and the amount of caustic soda consumed by carbon dioxide gas increases significantly.

Moreover, when using this method, the alkaline waste liquid produced contains sodium sulfide (Na,S) and sodium hydrogen sulfide (Na
51→ and soda carbonate (N a to 0B ), etc., this alkaline waste liquid cannot be disposed of as it is, and its disposal becomes a problem. In other words, for the treatment of alkaline waste liquid containing such components, the Claus method,
Alternatively, there are methods such as acid decomposition and recovery of highly pure NaSH, but these methods are expensive due to the carbon dioxide gas generated by the decomposition of sodium carbonate in the alkaline waste liquid, and are difficult to maintain in a stable continuous manner. It has drawbacks such as being difficult to drive.

For this reason, the applicant first added a mineral acid to the alkaline waste liquid to remove the sulfur compounds contained therein by turning it into a sulfurized water gas. A combustion method (Japanese Patent Laid-Open No. 152873/1983) was proposed. However, although this method has excellent effects as a treatment method for alkaline waste liquid, it consumes a large amount of mineral acid because the gas absorption liquid contains a large amount of soda carbonate, and the carbon dioxide concentration also increases. The problem remained that stable combustion could not be obtained due to the high

The present invention aims to solve the problems in the conventional method of absorbing and removing hydrogen sulfide-containing gas by alkaline treatment as described above, and has aimed to solve the problems from both the absorption and removal of hydrogen sulfide and the treatment of the gas absorption liquid. The object of the present invention is to treat hydrogen sulfide-containing gas efficiently, stably, and economically in a method for absorbing and removing hydrogen sulfide-containing gas through total alkali treatment, and to process the resulting gas absorption liquid easily and economically.

That is, the present invention provides a method for alkali-treating hydrogen sulfide-containing gas with an aqueous caustic alkali solution and absorbing and removing the hydrogen sulfide-containing gas into sulfide water 1. This is a method for treating hydrogen sulfide-containing gas, which is characterized in that the absorbed gas absorption liquid is treated with all calcium hydroxide and then filtered, and the resulting treated liquid is reused for alkaline treatment of hydrogen sulfide-concentrated gas.

Is this invention the following? More detailed explanation: First, the gas absorption liquid that has absorbed hydrogen sulfide-containing gas in the present invention includes a liquid that is obtained by absorbing and removing ordinary hydrogen sulfide-containing gas by contacting and gelling it with an alkaline aqueous solution such as caustic soda and sodium sulfide. The absorbed and removed liquid also contains sodium sulfide (Na, S), sodium hydrogen sulfide QJaS) 9 and at the same time, sodium carbonate (NatCOa) produced by the reaction of carbon dioxide gas in the air with caustic soda and the like.

Conventionally, this gas absorption liquid was either rendered harmless and disposed of, or re-supplied as is for alkaline treatment, but in the method of the present invention, the eaves are treated with calcium hydroxide and used as a treatment liquid for alkaline treatment. It is intended to be reused. That is, the gas absorption liquid is first treated with calcium hydroxide. In this case, the concentration of calcium hydroxide used is 15-3
A 0% aqueous solution is preferable. In addition, the processing temperature in this case is 90 - 90°C because it takes a long time to process at low temperatures.
Preferably it is carried out at a temperature of 100°C. Although the treatment time depends on the amount of calcium hydroxide added and the treatment temperature, it is 15~
About 60 minutes is sufficient.

The gas absorption liquid treated with calcium hydroxide in this way contains sodium sulfide (CN&tS), caustic soda (Na
Since OH) and calcium carbonate (OaOOA) are generated, filter this to remove calcium carbonate (C!aOOj).
t” is removed and used as a processing solution.

The treatment liquid obtained by smelting is used as it is or after being mixed with a part of the gas absorption liquid, and then caustic soda is added thereto and reused for alkali treatment of hydrogen sulfide-containing gas.

When the conventional hydrogen sulfide gas II-absorbed gas absorption liquid is circulated and used as it is, the gas absorption liquid contains a large amount of soda carbonate, but in the method of the present invention, the gas absorption liquid is Treatment solution treated with calcium hydroxide? Since it is recycled, the equilibrium concentration of sodium carbonate in the gas absorption liquid can be lowered, and therefore there is no trouble caused by crystals of soda carbonate during alkali treatment, and the treatment liquid does not contain caustic soda. Therefore, the amount of newly added caustic soda can be reduced by about 40%.

Especially the amount of processing liquid used? If the ratio of sodium sulfide to sodium hydrogen sulfide (NaSH/Na, s) in the obtained gas absorption liquid is α6~L2, the reaction between caustic soda and carbon dioxide gas is suppressed, and hydrogen sulfide is Since the reaction with the contained gas takes priority, the amount of hydrogen sulfide absorbed and removed from the exhaust gas increases, making it possible to reduce the hydrogen sulfide concentration in the treated exhaust gas to below k 2 ppm, and to reduce the total amount of caustic soda consumed by carbon dioxide gas. can be reduced.

The gas-absorbing liquid obtained by using the treatment liquid in the alkaline treatment in this way can be treated with luciram hydroxide and recycled as a treatment liquid as described above.Also, when the treatment liquid is recycled By adjusting the circulation amount to correspond to the amount consumed by carbon dioxide in the exhaust gas, the equilibrium concentration of soda carbonate can be lowered compared to when the gas absorption liquid is recycled as it is, so it is stable. Alkaline treatment can be carried out.

In addition, since the excess gas absorption liquid obtained when circulating above the treatment liquid does not contain a large amount of sodium carbonate, this n'f treatment can also be carried out by the above-mentioned Claus method or the method of acid decomposition and recovery as Na5H. can do. In addition, when the sulfur compounds contained in the gas absorption liquid are removed as hydrogen sulfide gas using the above-mentioned mineral acid and then burned and treated, the amount of mineral acid consumed is small, and hydrogen sulfide gas is stably generated. However, it has the advantage of being able to burn smoothly as it contains less carbon dioxide.

Incidentally, the calcium carbonate separated from the treatment liquid in the furnace may be used for neutralizing acidic wastewater, or it may be regenerated into calcium hydroxide using a normal method and used for the treatment of gas-absorbing liquid. .

Next, the method of the present invention will be further explained with reference to the accompanying drawings.

The figure is a flow diagram showing an example of the method of the present invention. In the figure, the contact reaction tower (11 is filled with a packing (2) to completely suppress the flow rate of the caustic soda aqueous solution. The sulfide water sac-containing gas ( 3) The gas is brought into contact with the supplied caustic soda aqueous solution in the contact reaction tower (1), and the sulfur compounds and carbon dioxide gas in the gas are absorbed and removed, and the gas is disposed of as treated exhaust gas (6).

On the other hand, an aqueous solution of caustic soda absorbs sulfur compounds and carbon dioxide gas in the gas, producing sodium sulfide and sodium hydrogen sulfide.

Sodium carbonate and the like are formed and sent as a gas absorption liquid (71) to a storage tank (8) by a metering pump (4) and stored therein.

Next, this gas absorption liquid (7) is passed through the metering pump (9), heated by the heat exchanger QG and supplied to the processing tank 0υ, and at the same time, the calcium hydroxide aqueous solution is passed through the metering pump naue from the storage tank (121).・Soda sulfide and caustic soda are obtained as a supernatant liquid, and calcium carbonate is obtained as a precipitate.
141 to remove the calcium carbonate, and process liquid A5.
Set to 1.

The treatment liquid Q51 thus obtained is temporarily stored in the storage tank C1.
61, then continuously fed to the metering pump (17), mixed with the gas absorption liquid (7), and then fed to the metering pump O.
The solution is sent to S, and then the caustic soda aqueous solution (5)? In addition, it will be reused for alkaline treatment of hydrogen sulfide-containing gas.

In this case, what is the supply amount of processing liquid? , the ratio of sodium sulfide to sodium hydrogen sulfide in the obtained gas absorption liquid (Na5H/Na1S
) is 0.6 to L2, the sulfur compounds in the hydrogen sulfide-containing gas (3) can be efficiently absorbed and removed, and the amount of caustic soda consumed by carbon dioxide gas can be reduced. .

On the other hand, calcium carbonate that has been separated by a filtration device (14+) is taken out of the prefecture.

In addition, the excess gas absorption liquid is taken out from the storage tank (8), sent to a waste treatment device (not shown), and sulfuric acid is added thereto.
The sulfur compounds contained are removed as hydrogen sulfide gas and treated by combustion.

As described above, the method of the present invention involves completely absorbing and removing hydrogen sulfide by treating the gas containing hydrogen monosulfide with an alkali aqueous solution using alkali aqueous solution. Since the treatment liquid obtained by treatment with calcium hydroxide is reused for the alkali treatment of gas containing sulfur compounds, the amount of water in the gas absorption liquid is lower than in the conventional case where the entire gas absorption liquid is recycled. The total equilibrium concentration of soda carbonate can be reduced completely, there is no trouble caused by crystals of soda carbonate during alkali treatment, and since the treatment solution contains caustic soda, the amount of new aqueous alkali solution to be added is small. Therefore, alkaline treatment can be carried out stably and economically, and according to the method of the present invention, all of the soda carbonate, which has been considered a drawback in the conventional alkaline treatment of hydrogen sulfide-containing gas, can be fully utilized. Also, the ratio of sodium sulfide to sodium hydrogen sulfide in the gas absorption liquid (Na5
By adjusting N/Na,s) to be 0.6 to 1.2, sulfide water i' (il-) can be efficiently absorbed and removed, and the amount of alkaline aqueous solution consumed by carbon dioxide gas can be reduced. Alkaline treatment can be carried out economically.Furthermore, since the gas absorption liquid does not contain a large amount of soda carbonate, it can be treated easily and economically. Therefore, the method of the present invention has extremely remarkable practical effects in the method of absorbing and removing hydrogen sulfide gas by total alkali treatment.

Hereinafter, the method of the present invention will be specifically explained using examples.

Example 1 A contact reaction tower (1210φ x 647WH) was packed with Virex ÷ 300 (trade name, manufactured by Toyo Tire & Rubber Industries, Ltd.) to a height of 3300vans, and hydrogen sulfide-containing gas generated from the rayon spinning process was collected. (Hydrogen sulfide gas concentration 60
ppm) at an air volume of 1800°-, while the concentration of 2 O
? An aqueous solution of Na5N/Na,s of 1/1 was supplied so that the ratio of Na5N/Na,s was O,'7 to 0.9. At this time, the concentration of hydrogen sulfide gas in the treated exhaust gas was 0.9 ppH1, and the sulfur compounds and carbonate compounds in the gas absorption liquid were as follows.

NatS: a59/l, Na5H: 33%, Na2co,: 151'/l - was taken out, and to this was added 35t' of calcium hydroxide aqueous solution with a concentration of 2L and 3% (
il- was added thereto, and treated at a temperature of 95° C. for 30 minutes to separate p, yielding treated solution 901. The composition of this treatment liquid was as follows.

NaOH: 4t? /1, Na2S: 61r/
z, Na2003: l'7 V/, 1 This treatment liquid is mixed with all the gas absorption liquid, and then added with caustic soda of 2 to 017 concentration, the ratio of sodium sulfide and sodium hydrogen sulfide (Na5H/Ha2S) to be produced is When hydrogen sulfide-containing gas (hydrogen sulfide gas concentration 6 oppm) was supplied in the same manner as above, the total sodium sulfide concentration was 1 OOP/l. The concentration of hydrogen sulfide gas inside was 1 ppm.

When the treatment liquid was circulated and used in this manner, the concentration of the gas absorption liquid reached the equilibrium concentration shown below.

Na, S: 44y/l, Na5H: 34y/l
, NatOOs: 559/1 As described above, in the case of the method of the present invention, since the gas absorption liquid contains only a small amount of soda carbonate, stable continuous operation is possible, and the entire gas absorption liquid is circulated as it is. Compared to the amount of caustic soda newly added in the case of 15-(purity), in the case of the method of the present invention, the amount was reduced by about 40% to 9-(pure).

On the other hand, the excess gas absorption liquid circulated as described above was diluted with twice the total amount of water, and supplied to the gas generator, so that the pressure inside the reactor was 1-0.040 to -0. O15% temperature 45±
The treatment was carried out at 2°C by supplying 60% sulfuric acid while adjusting the pH to 5-6. In this case, the required amount of sulfuric acid is approximately 35% of the amount required when directly treating the gas mother liquid with sulfuric acid.
% reduction, and the sulfuric acid treatment was also extremely easy.

In addition, since the carbon dioxide concentration in the obtained mixed gas is low,
Stable combustion can be carried out, and this exhaust gas can be treated with ordinary flue gas desulfurization equipment.

[Brief explanation of the drawing]

The figure is a flow diagram showing an example of the method of the present invention. (1)...Catalytic reaction tower, (2)... Packing. (3)...Sulfide water sac containing gas. (5)... Caustic soda aqueous solution, (6)... Treated exhaust gas. (7)...Gas absorption liquid. (8)...Gas absorption liquid storage tank. OC...heat exchanger, OC...processing tank. Q21... Calcium hydroxide aqueous solution storage tank. 041...Lacrimal filtration device, a5)...Processing liquid. 06)...Processing liquid storage tank. Patent applicant Unitika Co., Ltd.

Claims (1)

[Scope of Claims] l In a method of absorbing and removing hydrogen sulfide by treating hydrogen sulfide-containing gas with an alkaline aqueous solution, the gas absorption liquid that has absorbed hydrogen sulfide is treated with calcium hydroxide, and then subjected to p-filtration. A method for treating a hydrogen sulfide-containing gas, characterized in that the entire treated solution is reused for alkaline treatment of the hydrogen sulfide-containing gas. The ratio of sodium sulfide and sodium hydrogen sulfide in the gas absorption liquid is 0.
．． 6. The method for treating hydrogen sulfide-containing gas according to claim 1, wherein the amount is reused for the alkali treatment on the treatment liquid in an amount of 6 to 2 L2.