Acrylonitrile device tail-gas treatment technique

Abstract

The invention discloses a technique for treating the tail gas of an acrylonitrile device, which is suitable for treating acrylonitrile tail gas discharged by the acrylonitrile device. The technique is characterized in that: after free water is separated out by a gas-liquid separator, the acrylonitrile tail gas is mixed with air, a noble metal monolithic catalyst is taken as a catalyst and catalytic oxidation reaction is carried out to turn harmful volatile organic compounds into carbon dioxide and water; then a selective reduction monolithic catalyst is taken as a catalyst and selective catalytic reduction reaction with added ammonia is carried out to reduce nitrogen oxide in the tail gas into nitrogen and water. The technique has the advantages of simple technique, turning the harmful volatile organic compounds and nitrogen oxide in the tail gas into carbon dioxide, nitrogen and water, without secondary pollution, the test results totally meeting the environmental protection control requirements of the State Standard of China, adopting a tail gas heat exchanger to recycle reaction heat to heat input tail gas, needing no additional fuel during the normal operation process, small system resistance and low operation cost.

Description

technical field [0001] The invention relates to a process for treating tail gas in the industrial production of acrylonitrile, in particular to a process for treating tail gas of an acrylonitrile plant using catalytic oxidation and catalytic reduction processes. Background technique [0002] The production of the acrylonitrile plant adopts the propylene ammoxidation process, with propylene, ammonia and air as the main raw materials, under the action of the catalyst, the reaction produces acrylonitrile and other by-products, and then undergoes rapid cooling, recovery, refining and other processes to obtain acrylonitrile products . In the recovery process, an acrylonitrile absorption tower is arranged, and a stream of gas is discharged from the top of the tower, which is called the absorption tower tail gas (AOG). The main components of acrylonitrile tail gas are nitrogen, water vapor and carbon dioxide, and also contain a certain amount of carbon monoxide, acrylonitrile, pro...

AI Technical Summary

Problems solved by technology

Due to the low concentration of organic matter and high toxicity in the tail gas of the absorption tower of the acrylonitrile plant, the general tail gas treatment process cannot meet the environmental protection requirements

[0003] At present, the tail gas of the absorption tower of the acrylonitrile plant is generally discharged directly from the high point of the chimney, which causes serious pollution to the environment.

[0004] In addition, some acrylonitrile plants use thermal oxidation methods such as thermal incineration process and regenerative thermal oxidation process to treat tail gas, but the disadvantages of thermal incineration process and regenerative thermal oxidation process are that they need to consume a lot of fuel and have high operating costs. And the incineration exhaust volume is large, some nitrogen will be oxidized into nitrogen oxides during the thermal oxidation process

[0005] Patent CN1903415 adopts a catalytic oxidation treatment process to convert non-methane total hydrocarbons in the tail gas of the absorption tower of the acrylonitrile plant into carbon dioxide and water, but does not take into account the treatment of nitrogen oxides, another environmentally harmful component in the tail gas of acrylonitrile, and Without effective measures to separate gas and liquid, the presence of a small amount of liquid in the tail gas will reduce the service life of the catalyst and the safety of the boiler

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