Production process and device for preparing high-purity sodium cyanide or potassium cyanide with high yield

Abstract

The invention discloses a production process and device for preparing high-purity sodium cyanide or potassium cyanide with high yield. The process comprises the following steps: 1) removing ammonia, and cooling to obtain ammonia gas removing HCN; 2) shunting the ammonia gas removing HCN; 3) carrying out an absorption reaction to obtain a crude cyanide solution; (4) carrying out decarburization reaction to obtain a decarburized solution; 5) adjusting the content of free alkali, and carrying out an absorption reaction on the decarburized solution obtained in the step 4) and the ammonia gas removing HCN entering an absorber II in the step 2) in the absorber II to obtain high-purity liquid sodium cyanide or potassium cyanide; and 6) carrying out tail gas treatment. The invention discloses a production device for preparing high-purity sodium cyanide or potassium cyanide with high yield. According to the invention, one part of HCN synthesis gas is utilized to generate a decarburized solution, the other part of HCN synthesis gas and the decarburized solution are subjected to continuous absorption reaction, and the content of free alkali in the decarburized solution is adjusted, so that the high-purity liquid sodium cyanide or potassium cyanide can be obtained, the cost is low, the yield is high, and the side reaction that the cyanide is decomposed at high temperature to generate formate is effectively inhibited.

Description

technical field [0001] The invention belongs to the technical field of cyanide production, and in particular relates to a method and a device for producing high-purity sodium cyanide or potassium cyanide from hydrocyanic acid synthesis gas produced by the Angle method or methanol ammoxidation method without purification. Background technique [0002] As an important chemical product, sodium cyanide and potassium cyanide have multiple uses, and can be widely used in electroplating, metal surface treatment, extraction and recovery of precious metals, pesticide manufacturing, organic synthesis, heat treatment processes, etc. The products include: Both liquid and solid types. [0003] At present, the process routes for producing sodium cyanide or potassium cyanide at home and abroad are roughly the same. They all adopt hydrocyanic acid (HCN) to react with an aqueous solution of sodium hydroxide or potassium hydroxide to generate liquid sodium cyanide or potassium cyanide, and th...

AI Technical Summary

Problems solved by technology

This method has a long process flow and complex operation, the residence time of impure HCN gas in the reactor is short, the absorption tail gas also contains a large amount of HCN, and the utilization rate of HCN is not high

[0010] Chinese patent CN88106890 has introduced the method that directly absorbs impure HCN synthesis gas containing carbon dioxide in sodium hydroxide solution to produce solid sodium cyanide, that is, the sodium carbonate produced by the reaction of sodium hydroxide and carbon dioxide can be precipitated, and the formed containing The liquid sodium cyanide precipitated by sodium carbonate directly enters the crystallizer without removing sodium carbonate. The crystallizer is preferably a graded crystallizer. The fine crystals containing sodium carbonate are discharged from the upper part of the crystallizer along with the mother liquor, and the mother liquor goes to the absorber. Circular absorption, the larger sodium cyanide crystal slurry is discharged from the bottom of the crystallizer; this method requires that the carbon dioxide in the impure HCN gas is best controlled at 0.5-1.5%, and the reaction liquid is at a higher temperature for a long time, which is easy to form Formate, there is still a relatively large amount of sodium carbonate produced during the absorption process, and high-purity liquid sodium cyanide with low sodium carbonate content cannot be directly obtained

Sodium carbonate is graded in the crystallizer and discharged with the mother liquor, and then returned to the absorber for cyclic absorption. The production process is complicated

[0011] Chinese patent CN102502708 proposes a high-yield, high-purity preparation method of alkali metal or alkaline earth metal cyanide, which mainly contains HCN, water, ammonia, carbon dioxide, carbon monoxide, hydrogen and nitrogen, etc. The HCN synthesis gas with a temperature of 150-300°C is absorbed in two stages. The first stage adopts alkali circulation absorption to prepare cyanide solution, and the second stage adopts formaldehyde absorption to prepare hydroxyacetonitrile solution; the reaction time of the first stage absorption is 0.1-2.0 seconds, the absorption temperature is 40-95°C, preferably 60-75°C; the reaction temperature of the second-stage absorption is 0-40°C, preferably 10-25°C; although this process does not need to separate carbonate Liquid cyanide with relatively high purity can be produced, but due to the restriction of its reaction conditions, the content of carbonate and formate in liquid cyanide cannot be further reduced, which is comparable to that of liquid cyanide produced from pure hydrocyanic acid. The difference in specific quality is still large, and the liquid cyanide produced by it contains a small amount of ammonia; direct absorption causes most of the water in the synthesis gas to enter the liquid cyanide, reducing the concentration of cyanide. In order to produce high-concentration cyanide, A higher concentration of alkali is required as a raw material; the synthesis temperature of the HCN entering the first stage of absorption is too high. In order to ensure that the absorption is carried out at a lower temperature, a large amount of absorption circulating fluid is required to cool down, which increases the energy consumption of the circulating pump. Even so , it is still difficult to effectively control the side reaction of cyanide in the absorption liquid being heated to formate; due to the short absorption time of the first stage, the absorption of hydrocyanic acid in the synthesis gas is not complete, so formaldehyde absorption has to be used as the second stage It is forced to co-produce a small amount of hydroxyacetonitrile, which is not conducive to product planning, and the absorption reaction of hydroxyacetonitrile needs to be carried out at a lower temperature, which requires a supporting refrigeration system, which increases investment; due to the inconsistent products absorbed by the two stages, in order to avoid the cyanide Chemicals and alkalis are brought into the later process, and strict gas-liquid separation is required after the first stage of absorption

Images