Processing method of chlorine-containing tail gas produced by mercuric chloride production

Abstract

The invention discloses a processing method of chlorine-containing tail gas produced by mercuric chloride production. The processing method comprises the following steps: producing a sodium hypochlorite solution from tail gas which contains chlorine and mercuric chloride vapor, and then adding nickel chloride (or nickel oxide or nickel hydroxide) for nickel oxide hydroxide generating reaction; mixing sodium hypochlorite with nickel oxide hydroxide in a decomposition reaction kettle for two to three hours; performing coexistence of a solution from the decomposition reaction kettle with nickel oxide hydroxide in a continuous decomposition tank for three to five days, wherein when the pH value approaches to seven to eight, decomposition is completed; then putting a sodium chloride solution into a soluble alkali trough, adding alkali until the concentration of sodium hydroxide reaches 5% to 10%, and then returning to an absorption reaction kettle to be used again; sucking chlorine dioxide, chlorine and hydrochloric acid gas which are decomposed everywhere into a reduction treatment tower by negative pressure generated by a fan to enable the gases to contact with alkali liquor, wherein sodium chloride returns to an alkali liquor precipitation tank, and gases are exhausted by an induced draft fan. With the processing method, stable by-products can be obtained, highly toxic mercury chloride can be recycled, and the up-to-standard release of tail gas can be realized.

Description

technical field [0001] The invention relates to the technical field of chemical industry, in particular to a method for treating chlorine-containing tail gas in the production of mercuric chloride. [0002] Background technique [0003] At present, the fire-method mercuric chloride synthesis process is to pass chlorine gas into a quartz glass retort filled with high-temperature mercury liquid, and the chlorine gas and mercury vapor undergo a combustion reaction to generate mercuric chloride vapor, and the generated mercuric chloride vapor is sucked into ceramics under negative pressure. In the cooling tower, rise and cool along the tower; when the temperature drops below the boiling point of mercuric chloride, which is 302°C, the mercuric chloride vapor begins to crystallize and fall to the bottom of the tower; the mercuric chloride at the bottom of the tower is regularly taken out and packaged That is the finished product mercury chloride crystal. Chlorine-containing tail...

AI Technical Summary

Problems solved by technology

The chlorine-containing tail gas enters the absorption reactor. Usually, in order to prevent the formation of mercurous chloride (Hg2Cl2), the amount of chlorine gas introduced is more than the theoretical requirement 70-80%; the excess chlorine cannot be discharged directly, and is absorbed by sodium hydroxide solution to generate sodium hypochlorite solution; the main problems of sodium hypochlorite solution are as follows: (1) Poor stability and easy decomposition: sodium hypochlorite solution is exposed to light and heated Both are easy to decompose: the temperature is higher than 30 ℃, and the decomposition speed is obviously accelerated. If it is exposed to sunlight for about 20 hours, 90% of the available chlorine will be decomposed; even sodium hypochlorite at room temperature is unstable and has strong oxidation and volatility. It brings many difficulties to transportation, storage, use, etc.; (2) Low content of available chlorine: As the sodium hypochlorite solution produced by using residual chlorine in the tail gas and dilute sodium hydroxide solution, the content of available chlorine can only reach 2-3% , not reaching 5-13% of the national standard requirements, which is difficult for users to accept; (3) Contains highly toxic mercury chloride: when the lye is absorbed, the mercury chloride (vapor partial pressure) in the tail gas dissolves in the solution, making the solution Containing more than 0.012% mercury chloride, it is easy to cause mercury pollution to spread when used

The above-mentioned reasons make this sodium hypochlorite solution unable to be used in conventional sodium hypochlorite fields such as bleaching, sterilization, and disinfection, resulting in a backlog of sodium hypochlorite solution, which seriously restricts the production of mercuric chloride.

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