JPS63256117A - Method for removing water soluble impurity incorporated in gas containing high-concentration sulfur compound - Google Patents

Abstract

PURPOSE:To efficiently remove impurities by firstly bringing gas contg. high- concn. sulfur compd. incorporating water soluble impurities into contact with large amounts of water in a cooling part to cool it and simultaneously to absorb impurities and then bringing it into contact with a small amount of water in an absorption part to absorb the residual impurities. CONSTITUTION:Gas contg. water soluble impurities such as HCN and high-concn. sulfur compd. such as H2S is introduced into an absorption tower 1 and directly brought into contact with circulating water circulated with a circulating pump 4 in the gas cooling part of the lower step of the tower and with supply water after absorbing HCN in the absorption part thereof in the upper step and thereby cooled and simultaneously the greater part (50-80%) of HCN is absorbed and removed. At this time, the temp. of circulating water is adjusted at 20-30 deg.C with a heat exchanger 5. Then the gas is brought into contact with water of minimum flow rate in the absorption part of the upper step to absorb and remove the residual part of HCN and discharged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides a method for absorbing a gas containing a highly concentrated sulfur compound containing gaseous water-soluble impurities (hereinafter referred to as the impurities), such as hydrogen cyanide (HCN), using water as an absorbent. The present invention relates to a method of removing impurities by treatment with an absorption tower, and particularly relates to a method of removing these impurities from a high concentration H, S-containing gas obtained from a coke oven gas purification facility. For convenience, the case where the impurity to be deposited is HCN will be exemplified below.

[Conventional technology]

As a method for recovering hydrogen sulfide (Has) from coke oven gas, coke oven gas is introduced into an absorption tower using Na1CO1 aqueous solution as an absorption liquid, and the
Highly concentrated H! is absorbed into a CO3 aqueous solution and the absorbed liquid is regenerated under reduced pressure in a regeneration tower. There is a method of recovering S-containing gas. In the chemical absorption method using this alkaline absorption liquid, in addition to H and S, HCN and Cot in coke oven gas are
Acid gases such as Naphthalene, etc. are also absorbed and removed, and HCN, Cot, Naphthalene, etc. are also recovered along with H and S by reduced pressure regeneration. The recovered high-concentration 8-containing gas is used as a raw material for sulfuric acid, sodium hydrogenide, sodium sulfide, and the like. There are no particular problems when using the gas recovered in this way as a raw material for sulfuric acid production, but
When producing hydrogen sulfide (I)9um or sodium sulfide, contamination with I(CN, naphthalene, etc.) must be removed in advance because it causes quality deterioration.

In addition, some of the high-concentration SO and gases used to produce various sulfur compounds, such as high-concentration SOW-containing gas recovered by regenerating the adsorbent in the dry flue gas desulfurization process, also contain HCN, depending on the purpose of use. It is necessary to perform purification to remove HCN.

One way to easily absorb and remove HCN in gas is to use alkali to absorb it, but H2S.

When removing HCN from a gas containing sulfur compounds such as So, this method cannot be used because not only HCN but also the sulfur compounds are absorbed and removed.

Conventionally, in the process of producing sodium hydrogen sulfide and sodium sulfide from high-concentration H, S-containing gas recovered from gas furnace gas, the method of removing HCl1 was specifically an absorption method as shown in Figure 2. tower is used.

The high concentration % S-containing gas is introduced into the absorption tower 1 from the supply fin 2, and after HCN is absorbed and removed by the water supplied from the top of the tower, it is sent to the next step as a deHCN gas, and the Nl!
It is absorbed and reacted with LOH aqueous solution and converted into sodium hydrogen sulfide and sodium sulfide.

[Problems to be solved by the invention]

However, since industrial water is usually used as the water for absorption and removal of I(CN), fluctuations in water temperature have a large effect on the removal of HC'H. A gas containing H,8 concentration is normally supplied at a temperature of 70 to 90°C.On the other hand, for the absorption and removal of HCN, it is more advantageous to process at a low temperature, and this gas is supplied at a temperature of 70 to 90°C. When treating using an absorption tower to absorb and remove HCN, it is necessary to suppress the temperature rise of the liquid by using a large amount of feed water.

The present invention solves the above problems and provides an improved method for efficiently washing away water-soluble impurities in a sulfur compound-containing gas while minimizing the amount of water supplied.

[Means to solve the problem]

The present invention provides a method for removing gaseous impurities by treating a gas containing highly concentrated sulfur compounds containing gaseous water-soluble impurities in an absorption tower using water as an absorbent. Using a stage-type absorption tower, the treated gas is introduced from the bottom of the tower, cooled by contacting with a large amount of circulating water in the cooling section and absorbing some of the impurities, and then contacted with a small amount of water in the absorption section. This is a method for removing impurities contained in a gas containing a high concentration of sulfur compounds, by absorbing and removing the remaining impurities.

Hereinafter, the method of the present invention will be explained based on the drawings.

FIG. 1 is a flow diagram of an exemplary rush flow embodiment of the method according to the present invention. 1 is an absorption tower, with 2 parts: an upper absorption section and a lower cooling section.
It is made up of two parts. Gases containing sulfur compounds are
It is introduced into the absorption tower 1 by the feed gas twin 2, and after cooling and absorption and removal of E (CM), it is sent to the next step through the exhaust gas fin 3.

The sulfur compound-containing gas introduced into the absorption tower is mixed with the circulating water circulated by the circulation pump 4 in the gas cooling section at the lower stage of the absorption tower, the feed water after HCN has been absorbed in the HCN absorption section at the upper stage, and the inside of the absorption tower 1. Most of the HCN (50-80%) is absorbed and removed at the same time as it is cooled by direct contact. At this time, the temperature of the circulating water in the cooling section is controlled by the heat exchanger 5 to 20 to 30°C, preferably 20 to 25°C, and then supplied to the absorption tower 1. If the temperature is too high, HC
If the absorption of H is too low, the cooling equipment becomes too large and the required energy becomes large, which is not preferable.

In this cooling section, in order to prevent the liquid level in the tower from rising due to the condensation of moisture in the sulfur compound-containing gas and the supply water in the upper stage, and to prevent the concentration of HCN in the circulating water, blowing is performed on the discharge side of the circulation pump 4. A portion of the circulating water is drained from the water fins 8.

At this time, the liquid-gas ratio (L/()') in the lower cooling section is:
15-25 (17m”), preferably 18-22
(t/ is).

The sulfur compound-containing gas cooled to a temperature of 20 to 30°C, preferably 20 to 25°C in the lower stage is highly absorbed and removed by water at the minimum flow rate necessary for removing HC'H in the upper stage T (CN absorption section). The liquid-gas ratio (L/G) at this upper stage is
4 to 7 (t/ms). In the conventional method shown in FIG. 2, it is necessary to set L/a to 10 or more, and water can be saved to about half the amount of water used in the conventional method. In addition, a heat exchanger 6 is also installed in the upper supply water line 9, and the temperature of the supply water is kept at 30°C.
Hereinafter, it is preferable to supply the mixture to the absorption tower at a temperature of 20 to 25°C.

According to the method of the present invention, gaseous water-soluble impurities, especially HCN, can be completely removed by only replenishing about half the amount of absorption water compared to the conventional method, and a large amount of HCN can be removed in the cooling section. Because the gas is directly cooled by contact with the circulating water, there is no risk of problems such as pipe blockage even if the gas contains sublimable substances such as naphthalene.

The method of the present invention will be specifically explained below using Examples.

〔Example〕

Using the apparatus shown in FIG. 1, a gas containing high concentrations of H and S having the composition shown in Table 1 was washed with water according to the conditions shown in Table 2. The composition of the purified gas was as shown in Table 1, and the cyanogen removal rate was 99%.

Table 1 Table 2 [Comparative Example] The same gas as in the example was treated according to the conventional method shown in FIG. That is, as a result of processing at a supply gas amount of 800 to 900 m3 N, a supply gas temperature of 70 to 80 °C, a supply water volume of 1 s (t/one supply gas), a liquid gas ratio of 13 (t/mJ, and a liquid f!L of 20 °C), the present invention was obtained. Compared to the method of Example, the cyanogen removal rate was 95% even though y2 times the amount of water was required.
Met.

〔Effect of the invention〕

As is clear from the above description, the present invention has the following excellent effects.

■ Since the amount of water supplied can be reduced, the amount of water discharged can be reduced.
Furthermore, since the concentration of recovered water-soluble impurities, such as cyanide compounds, is high, wastewater treatment equipment can be made smaller and more efficient, and the cost F of the treatment equipment can be reduced.

■ There is no fluctuation in the temperature of the make-up water, so HC is always stable.
N altitude removal is possible.

■ Since the gas is directly cooled with a large amount of circulating water in the cooling section, even if the gas contains sublimable substances such as naphthalene, there will be no blockages etc.)'? The pull is suppressed as much as possible.

■ The amount of water supplied can be reduced, making it an even more effective method in areas with limited water resources.

[Brief explanation of drawings]

Figure 1 shows H in gas containing high concentration sulfur compounds according to the present invention.
FIG. 3 is a process diagram of an absorption tower circumference for removing CN. FIG. 2 is a process diagram of a conventional process around an absorption tower for removing HCN from a gas containing a high concentration of sulfur compounds. In the figure, 1 is an absorption tower, 2 is a supply gas line, 5 is an exhaust gas twin, 4 is a circulation pump, 5.6 is a heat exchanger, 7 is a circulation water fin, 8 is a blow water line, and 9 is a supply fin. .

Claims (5)

[Claims] (1) In a method in which a gas containing high concentration sulfur compounds containing gaseous water-soluble impurities is treated in an absorption tower using water as an absorbent to remove the impurities, the upper stage is the absorption section and the lower stage is the cooling section.2 Using a stage-type absorption tower, the treated gas is introduced from the bottom of the tower, cooled by contacting with a large amount of circulating water in the cooling section and absorbing some of the impurities, and then contacted with a small amount of water in the absorption section. A method for removing impurities in a gas containing a high concentration of sulfur compounds, the method comprising absorbing and removing the remaining impurities by absorbing and removing the impurities. (2) The method according to claim 1, wherein the gaseous water-soluble impurity is HCN. (3) The method according to claim 2, wherein the liquid that has absorbed HCN in the absorption section is used as circulating water in the cooling section, and a part of the circulating water is extracted to prevent cyanide from concentrating. . (4) Liquid/gas ratio in the cooling section is 15 to 25 l/m^
3, and the liquid/gas ratio in the absorption section is 4 to 7 l/m^3.
A method according to any one of claims 1 to 3. (5) The method according to any one of claims 1 to 4, wherein the temperature of the circulating water in the cooling unit and the water supplied to the absorption unit is maintained at 20 to 30°C.