Treatment system and method of nitric oxide in nitrotoluene nitric acid oxidation tail gas

Abstract

The invention discloses a treatment system and method of nitric oxide in nitrotoluene nitric acid oxidation tail gas, belonging to the field of chemical engineering. The system comprises a plurality of acid absorption towers, gas mixers, alkali absorption towers and urea absorption towers, wherein mother liquid used in the reaction process is used as an acid solution for absorption, is subjected to step-by-step absorption treatment by virtue of the acid absorption towers in an adverse current mode, and is then subjected to the treatment of the alkali absorption towers and the urea absorption towers again, so that residual nitric oxide is completely broken into nitrogen to be discharged to the upper air; the acid absorption liquid required in the whole process is the auto-reacted mother liquid; after full absorption, the obtained acid liquid can completely meet the production requirement, thus greatly reducing the unit consumption of the raw material nitric acid. According to the treatment system and method, the treatment rate of the nitric oxide in the tail gas is more than 99%, the maximum recovery rate can reach more than 90% along with the increase of the numbers of the acid towers, and the absorption efficiency and comprehensive utilization level of the nitric oxide tail gas are improved.

Description

technical field [0001] The invention relates to a system and method for treating nitrogen oxides in nitrotoluene nitric acid oxidation tail gas, belonging to the field of chemical industry. Background technique [0002] Nitrotoluene nitric acid oxidation reaction, nitrogen oxides (NO x ) is one of the main pollutants in the atmosphere. At present, there are generally the following methods for the treatment of nitrogen oxide tail gas: one is to absorb and discharge through lye or limestone; the other is to use ammonia water to absorb and use it as nitrogen fertilizer; The method adopted in the "Treatment method of nitrogen oxides in the chlorination tail gas of aromatic nitro compounds" of 200910131859.5: use sulfuric acid as the absorption liquid to make mixed acid for nitration reaction, and the remaining tail gas is absorbed and treated with lye. [0003] Among the above three methods, the first two methods are commonly used methods: the first method will generate a large...

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Problems solved by technology

[0003] Among the above three methods, the first two methods are commonly used methods: the first method will produce a large amount of high-concentration saline wastewater, which cannot be discharged directly, but only changes the gas into liquid, which also pollutes the environment

The second method can solve the problem of tail gas outlet, but its reaction products are ammonium chloride, ammonium nitrate, and ammonium nitrite aqueous solution, and ammonium nitrite is very easy to decompose at high temperature, it is difficult to obtain solid ammonia salt, so there are additional products. Low value, high storage risk, etc.

The third method has improved the deficiencies of the above two methods, relatively improved the comprehensive utilization of acid tail gases such as nitrogen oxides and nitroxyl chloride produced in the reaction process, but this method has the following deficiencies: nitrogen oxides in the tail gas React with water to generate nitric acid and generate nitrous acid at the same time, and the solubility of nitrous acid in water is very low. The high temperature generated by the absorption makes the nitric oxide decomposed from nitrous acid cannot be absorbed by water or alkali

If oxygen cannot be supplemented in time to oxidize nitric oxide into nitrogen dioxide, the overall absorption efficiency will not be high, and there will be a large amount of nitrous acid in the nitric acid generated by water absorption, and a large amount of nitric oxide will be discharged to the atmosphere, unable to achieve its intended purpose

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