JPH072704A - Purification of acetylene gas - Google Patents

Abstract

PURPOSE:To enable acetylene gas of stabilized performance to be purified safely and economically by such a means that, when both hydrogen phosphide and hydrogen sulfide as impurities in a crude acetylene gas are to be absorbed and removed using an aqueous solution of sodium hypochlorite, this aqueous solution is automatically injected and replenished using an effective chlorine concentration meter. CONSTITUTION:The circulating absorbing fluid in a packed column is partly drawn via the delivery piping of a circulating pump and introduced into an effective chlorine concentration meter to determine the effective chlorine content of the fluid automatically. A proper range of the effective chlorine content of the absorbing fluid has been stored in the concentration meter. When the above measurement comes to the lower limit of the above range, a quantitative pump for sodium hypochlorite injection is actuated to effect the upper limit of the effective chlorine content and then shutdown of the pump automatically. To activate the absorbing fluid, a pH meter is set along the identical piping line to ensure the fluid to maintain its optimal pH level automatically in a similar way to the case with the effective chlorine content.

Description

DETAILED DESCRIPTION OF THE INVENTION There are two methods of refining acetylene gas, a dry method and a wet method, and the present invention is a new method of wet refining. Conventional wet refining methods include a method using high-purity sulfuric acid, a method using a metal chloride such as ferric chloride, a method using an aqueous solution of sardine powder, and a method using chlorine water. The chlorine water cleaning method that is widely adopted in Japan has a simple device,
Although it has the advantage that the operating cost is low, it uses special poisonous chlorine gas, so special handling is required as it is regulated by the regulations for prevention of damage such as specific chemical substances and the Air Pollution Control Law. , Has the drawback of corroding almost all metals. For this reason, most of the disinfection and sterilization with chlorine gas has recently been replaced by sodium hypochlorite solution. INDUSTRIAL APPLICABILITY The present invention has a great effect in terms of safety of work environment and prevention of pollution, and by adopting an industrial effective chlorine concentration meter that has made rapid progress, alkaline hypochlorous acid, which has been regarded as dangerous in the past, is adopted. We succeeded in removing hydrogen phosphide and hydrogen sulfide with high efficiency and economically without producing monochloroacetylene which may occur in the reaction of soda and acetylene, and also succeeded in automating the purification equipment. The method will be described below with reference to the drawings. FIG. 1 is a flow chart of the present invention. The crude acetylene gas was used in advance in the absorption tower using a sulfuric acid solution.
Remove alkaline gas such as ammonia. The crude acetylene gas introduced from the lower nozzle of the absorption tower (1) comes into gas-liquid contact with the very thin sodium hypochlorite aqueous solution flowing down from above in the packed portion of the packing (2), and the crude acetylene gas Absorbs and removes hydrogen phosphide and hydrogen sulfide remaining in the. The reaction formula is hydrogen _{phosphide, PH 3 + NaclO → H 3} PO + Nacl H 3 PO + NaclO → H 3 PO 2 + Nacl H 3 PO 2 + NaclO → H 3 PO 3 + Nacl H 3 PO 3 + NaclO → H 3 as PO ₄ + NaCl For hydrogen sulfide, it is expected to be H ₂ S + NaclO → S + Nacl + H ₂ O. In both cases, hydrogen peroxide and hydrogen sulfide are oxidized and absorbed by utilizing the oxidizing power of sodium hypochlorite, so commercially available sodium hypochlorite is added and stabilized with caustic soda before the sulfuric acid washing tower. The point of the present invention is to inject the diluted sulfuric acid to be used in step (3) and bring it close to neutral. On the other hand, as is clear from the reaction formula, hypophosphorous acid generated by oxidizing hydrogen phosphide has the effect of neutralizing the caustic soda component contained in sodium hypochlorite, and the reaction has an oxidizing power. Proceed to the activation method, and only add a very small amount of dilute sulfuric acid to neutralize sodium hypochlorite. The following measures are incorporated to avoid the danger of high-concentration sodium hypochlorite entering the absorption tower and coming into contact with crude acetylene gas, which is a drawback of this method.

An effective chlorine concentration meter (9) is installed on the discharge side of the circulation pump (6) of the absorption tower (1) to predict and control the effective chlorine concentration of the absorption liquid sprayed from the nozzle (3) at the top of the absorption tower. .

The metering pump (11a) for injecting sodium hypochlorite is on-off controlled by the signal of the effective chlorine concentration meter (9).

Sodium hypochlorite (14) was stored as a 6% solution and mixed with fresh water whose required amount was secured by a flow rate indicator (16) using a metering pump (11a) to obtain an effective chlorine concentration of 1,000 p ． p. m. Below, it is injected in front of the circulation pump (6) discharge side line mixer (8). Therefore, even if the circulation pump (6) is stopped, the effective chlorine concentration of the absorbing liquid sprayed from the nozzle (3) is 1,0.
00p. p. m. 2,000 p.m., which has been conventionally used as a guideline for renewing the liquid due to danger. p. m. Is half of.
Also, when the fresh water for dilution stops, the flow rate indicator alarm (1
The alarm is issued from 6), but in this case also the circulation pump (6)
The residual effective chlorine concentration in the absorption liquid circulated by the company is several + p. p. m. The order of the effective chlorine concentration is 300p. p.
m. It becomes the following. The acetylene gas from which the impurities have been oxidized and absorbed and removed in the absorption tower (1) in this way is subjected to pressure removal by the demister (4) to remove the liquid droplets and pressure-feed the gas holder. In order to confirm the performance of the present invention, two small packed towers were manufactured, and one had an effective chlorine concentration of 300 p. p. m. Sodium hypochlorite solution diluted with water, the other is 10 times the concentration of 3,
000p. p. m. When the crude acetylene gas was passed at the same time while pouring the aqueous solution prepared in Example 1 into the solution and circulating the solution with a pump, the results shown in Table 1 were obtained.

That is, the concentration of sodium hypochlorite is reduced to bring the solution closer to neutral, whereby the oxidizing power of available chlorine is activated and the hydrogen phosphide removal performance is improved. In this test, the leakage amount of chlorine gas contained in the purified acetylene gas after washing with neutral sodium hypochlorite water was 5 to 10 p. p. m. It was confirmed that the amount was 1/15 to 1/30 compared to that of the chlorine water washing method, and at the same time, the amount of dichloroethylene generated was also 1/2 to 1/4 of the existing method. Therefore, by constructing the system as described above, it is possible to carry out acetylene gas purification which is safe, economical and has stable performance.

[Brief description of drawings]

FIG. 1 is a flow chart of the present invention. The ammonia removal and absorption tower using the sulfuric acid aqueous solution in the previous stage is omitted because it is a known technique. Explanation of symbols Absorption tower V-2 Circulation pump check valve Filling material V-3 〃
Sample valve nozzle V-4 〃
Discharge valve Demister V-5 Concentration meter Sample valve Water sealing tank V-6 Strainer main valve (2) Circulation pump V-7 Metering pump suction valve (2) Flow meter V-8 〃
Discharge valve (2) Line mixer V-9 〃
Sample valve (2) Effective chlorine concentration meter V-10 〃
Back pressure valve (10) Strainer (2 units) V-11
〃 Injection valve ▲ 11 ▼ Quantitative pump (2 units) V-12 Chemical liquid tank drain valve (2 pcs) ▲ 12 ▼ Detector (2 units) V-13 Dilution water valve (2 pcs) ▲ 13 ▼ Chemical liquid tank (2) Tank) V-14 Fresh water main valve ▲ 14 ▼ 6% sodium hypochlorite liquid V-15 Shimizu check valve ▲ 15 ▼ Stirrer (2 units) V-16 Water injection valve ▲ 16 ▼ Flow rate indicator alarm V-17 Water injection valve ▲ 17 ▼ PH meter V-18 Absorption tower drain valve ▲ 18 ▼ 5% sulfuric acid solution V-19 Constant flow valve V-1 Circulation pump suction valve V-20 Sodium hypochlorite main valve

Claims (1)

[Claims] In order to remove impurities hydrogen phosphide and hydrogen sulfide contained in crude acetylene gas, sodium hypochlorite diluted with water was used as a circulating absorbent for the packed column, and the effective chlorine concentration in the liquid was used as an effective chlorine concentration meter. A method for purifying acetylene gas, characterized by automatically pumping and replenishing sodium hypochlorite in an amount commensurate with the amount of available chlorine consumed, while continuously measuring and controlling.