JPS6121721A - Treatment of h2s in gas - Google Patents

Abstract

PURPOSE:To simply treat H2S in gas in low cost, by adding seed sulfur to a post-absorbing solution, which contains colloidal sulfur generated upon the absorption of H2S by a ferric sulfate solution oxidized by iron oxidizing bacteria, to perform the precipitative separation of simple sulfur. CONSTITUTION:An FeSO4 solution, of which pH is adjusted by sulfuric acid, is flowed into an oxidizing tank 1 receiving iron oxidizing bacteria and ammonium sulfate is added to said Fe2SO4 solution as a nutritive agent and air is blown therein. The oxidized Fe2(SO4)2 solution is overflowed to be guided to the aspirator 4 of an absorbing process through a separation tank 2 and supply tank 3 and H2S-containing gas (a) is fed in the aspirator 4 to be absorbed by said Fe2SO4 solution. After absorption, the Fe2SO4 solution is guided to a sedimentation tank 7 to be subjected to sedimentation againg and, after solid-liquid separation, the overflow solution is introduced into a ferrous supply tank 1 through a cushion tank 9 while a seed sulfur slurry is recovered from the underflow in a sulfur recovery tank 8 and a part thereof is returned to a flocculation tank and the remainder is recovered as simple sulfur.

Description

[Detailed Description of the Invention] (a) Technical Field The present invention relates to a method for treating H2S in gas, and more specifically, a method for producing a ferric sulfate solution from a ferrous sulfate solution using iron-oxidizing bacteria. The ferrous sulfate solution absorbs and reduces H2S with the ferric sulfate solution, and the ferrous sulfate solution is oxidized again by iron-oxidizing bacteria and is used repeatedly to absorb H2S as ferric sulfate. This provides an extremely inexpensive H2S treatment method in which fine 30 minute particles in the absorption liquid produced by the reaction are fixed and recovered as elemental sulfur by contacting with seed sulfur added separately.

(B) Background Art As methods for removing H and S from gases, absorption methods using caustic soda and absorption methods using ferric sulfate are known, but methods using ferric sulfate are extremely expensive. It is rarely used for this purpose, and a method using caustic soda is generally used. However, this caustic soda method also requires considerable cost and cannot be called an ideal treatment method.

(C) Disclosure of the Invention The present invention provides a method that can treat H and S at a lower cost than the caustic soda method, and moreover can recover 3 minutes as nutrient sulfur.

In JP-A No. 59-46117, the present applicant previously oxidized ferrous sulfate to ferric sulfate using iron-oxidizing bacteria, and used the ferric sulfate solution as an absorbent to absorb H2 in gas.
Although we have proposed a method of separating elemental sulfur by collecting S and flotating the absorbed liquid, we have conducted extensive research on methods to process it more easily and at lower cost, and have discovered the processing method of the present invention. be. The details will be explained below.

In the method of the present invention, the first step is to introduce a sulfuric acid solution containing ferrous sulfate into an oxidation tank, add a small amount of inoculum of iron oxidizing bacteria (hereinafter simply referred to as bacteria), and blow air to kill the bacteria. At the same time, I and ferrous acid are diluted to ferric sulfate.

In this case, nonferrous metal mine drainage, smelting drainage, factory drainage, etc. can be used as the ferrous sulfate-containing liquid, and Fe2+
If the concentration is in the range of 1 to 50 g/view, it will be sufficiently oxidized by bacteria.

The pH is adjusted to 3.0 or lower by adding sulfuric acid if necessary, while not causing precipitation in the oxidation tank and maintaining oxidation efficiency.

In addition, when the liquid does not contain the above-mentioned bacteria or their nutrient sources, such as smelting wastewater, nutrients (N, P, K salts, etc.) may be added because it is necessary to propagate the bacteria.

Furthermore, in order to trap the grown bacteria without letting them escape, it is preferable to add acid-resistant porous material particles as a carrier agent to increase the bacterial cell concentration in the oxidation tank. and,
This acid-resistant porous material particle has molecules 11. After separation in a tank, it is used repeatedly in an oxidation tank.

Here, acid-resistant porous material particles refer to porous materials with a large surface area on which iron oxide/pulled chilia can settle and inhabit as many bacteria as possible, and which can be easily fluidized by stirring in a liquid. Moreover, it has the property of easily settling when left standing. The present inventors have confirmed that although there are zeolite, activated carbon, Fuller's earth, etc. as particles having such characteristics, diatomaceous earth is particularly excellent.

In addition, in place of the acid-resistant porous material described in 2.
It is also possible to raise H to hydrolyze the ferric sulfate in the absorption liquid and use the produced iron precipitate as a carrier agent.

Next, H2S is absorbed using a ferric sulfate solution oxidized by bacteria in an oxidation tank as an absorption liquid. (For the second stage absorption method, H
2S may be diffused or the liquid may be sprayed from above. Note that although an aspirator was used in the embodiment of the present application for a small-scale test, the present invention is not limited to this.

In the absorption process, the following reactions occur.

Fe2 (504)3 +H2S-+'2FeSO/
L+1 (2so, +S.

As a result, H2S is oxidized to S. The ferrous sulfate solution is regenerated.

This post-reaction liquid contains fine colloidal sulfur, resulting in yellowish-white sulfur pores, and if this is directly returned to the bacteria oxidation tank, the sulfur value will accumulate in the oxidation tank. This creates a sulfur atmosphere, and some of the hectoria oxidizes the l& value, which causes a decrease in iron oxidation ability.

Therefore, in the method of the present invention, as the third step, a seed sulfur slurry is added to this post-reaction solution to coagulate the colloidal sulfur produced, and separate and recover it as simple sulfur with good sedimentation separation properties. is repeated in the oxidation tank of the first step.

The tailing liquid from which sulfur has been removed in this way is a ferrous sulfate solution, which is repeatedly fed into the oxidizing tank (in the first step), where it is oxidized by bacteria that have been sufficiently cultured and have become active. Ferric sulfate is oxidized and used to absorb H2S.

The bacteria used in the present invention is known rThi.

Bacillus Ferrooxidanca J
The iron-oxidizing bacteria in the treated mud are cultured in a liquid containing a high degree of ferrous ions, etc., using wastewater mud as a seed strain.

・"The oxidizing ability of the iron-oxidizing bacteria cultured by this method is 2 to 5 times higher than the normal oxidizing ability (Deposit number: Microtech Research Institute No. 7443, Microtechnology Research Institute No. 7444) No.).

An embodiment of the method of the present invention will be described below with reference to the accompanying drawings.

(d) In the example, sulfuric acid was added to an oxidation tank 1 with a capacity of 500 fL containing 20 volumes of iron oxidation/Ecutilia cultured at a mine wastewater treatment plant and diatoms with a pulp concentration of 15%, and the pH was adjusted to 2.0.
SOa (F e2" 1 m degree 5-20 g/m) solution was continuously flowed in at a rate of 2!; L/min, and ammonium phosphate was added as a nutrient in tank 1 at 50 tags.
/ min, and air blowing was performed at 80 m/min.

The overflow liquid from the oxidation tank 1 was introduced into a separation tank 2 with a capacity of 300 liters, and then introduced into a ferric supply tank 3 with a capacity of 400 liters. The overflow liquid contains almost completely oxidized Fe.
7(504)3 solution.

Next, the ferric sulfate solution is introduced into the aspirator of the absorption process at a flow rate of 2 g/min, and H2S with a concentration of about 75% is introduced.
Gas was introduced and absorbed at a rate of 4 min. When the absorbed gas was tested using the north-side detection tube, it was not detected for 3 minutes.

Next, the absorbed liquid was introduced into a flocculation tank 6 with a capacity of L 70 x, and the seed sulfur slurry was approximately 120 g/n at a liquid ratio of 2.
It was added at a ratio of 0% and stirred with a stirrer.

Next, the treated liquid is introduced into a sedimentation tank 7 with a capacity of 1709 to undergo sedimentation Wj aging, solid-liquid separation is carried out, and the overflow liquid is introduced into a cushion tank 9 with a capacity of 300.
Introduced into the 1st iron supply tank of 0 sentences.

The ferrous solution was recycled into the oxidation bath.

- On the other hand, the seed sulfur slurry is recovered from the underflow in the sulfur recovery tank 8, and a part of it is recycled to the flocculation tank.
The remaining 1 part was recovered as elemental sulfur.

(E) Effects of the Invention As described above, the method of the present invention uses sulfuric acid, which is inexpensive for treating H2S.
This method uses iron repeatedly, and can be processed at less than one-third the cost of the caustic soda method. It also uses flotation agents, etc., compared to the flotation-based elemental sulfur separation method proposed earlier by the applicant. This has the advantage of significantly reducing costs.

[Brief explanation of drawings]

The figure is a flow sheet showing an example of the method of the present invention. Symbol explanation 1 - Oxidation tank 2 - Separation tank 3 - Ferric supply tank 4 - Aspirator - 5 - Absorption tank 6 - Coagulation tank 7 - Sedimentation tank 8 - Sulfur recovery tank

Claims (4)

[Claims] (1) The first step of oxidizing the ferrous sulfate solution to ferric sulfate using iron-oxidizing bacteria, and contacting the ferric sulfate solution obtained in the first step with H_2S in the gas as an absorption liquid. A second step in which seed sulfur is added to the absorbed liquid containing the colloidal S_0 generated in the second step, and the colloidal S_0 is separated and recovered as elemental sulfur with good sedimentation separability. A method for treating H_2S in a gas, the method comprising: a third step in which the separated liquid is repeated in the first step. (2) Part of the elemental sulfur with good sedimentation separation properties obtained in the third step is used as the seed sulfur.
A method for treating H_2S in a gas as described in Section 1. (3) A method for treating H_2S in a gas according to claim 1 or 2, wherein acid-resistant porous material particles are used as a carrier agent for the iron-oxidizing bacteria. (4) The method for treating H_2S in a gas according to claim 3, wherein the acid-resistant porous material particles are diatomaceous earth.