Treatment method and device for waste gas containing nitrogen oxides

Abstract

The invention discloses a treatment method and a device for a waste gas containing nitrogen oxides. By utilizing the properties that Fe<2+> easily reacts with NO to form relatively stable Pi-acid site complex, and the Fe<2+> is easily oxidized by NO2, the method adopts Fe<2+> solution as an absorbent, and conducts purification treatment to the nitrogen oxides by a two-step cycle method of absorption-oxygen oxidation. The nitrogen oxides in the waste gas reach emission standard after the treatment, and a coagulant ferrite or polymeric ferric salt product is obtained in the treatment process. The method can be used for the coagulation and purification treatment of water, and thus truly realizes the purpose of 'using waste for treating waste, and changing wastes into valuables'. The device comprises an absorption tower, a first circulating pump, an oxidation reaction tower and a second circulating pump which are sequentially connected in the process through pipelines to form circulation. The Fe<2+> solution in the device conducts secondary absorption treatment to the nitrogen oxides, and the Fe<2+> solution is oxidized for two times, thus ensuring good absorption effect.

Description

technical field [0001] The invention relates to the field of atmospheric environmental pollution control, in particular to a control and device for nitrogen oxide pollution in waste gas. Background technique [0002] Nitrogen oxides (NO x ) Pollutants mainly refer to NO and NO 2 It has a wide range of sources: the combustion of fossil dyes such as coal, heavy oil and diesel oil is the largest source of nitrogen oxide pollutants in the atmosphere, and the exhaust gas emitted from industries such as nitric acid, nitrogen fertilizer, and gunpowder is also an important source of nitrogen oxide pollutants in the atmosphere. In addition, during the nitrification of metal surfaces and the nitrification of organic matter, exhaust gases containing nitrogen oxides with varying concentrations are also emitted. due to NO x Special chemical characteristics, if treated by general absorption method, it often cannot be completely absorbed, the effect is not good, and there is always a ce...

AI Technical Summary

Problems solved by technology

[0005] There are three kinds of chemical absorption methods: alkali absorption method, oxidation absorption method and reduction absorption method. Among them, the alkali absorption method has the problem of incomplete absorption, and the concentration of nitrogen oxides in the exhaust tail gas is still relatively high, generally maintained at 800~1500mg / m 3 , or even higher; oxidation absorption method is to use concentrated sulfuric acid, H 2 o 2 , Potassium dichromate, Potassium permanganate and other strong oxidizing solutions will NO x NO is oxidized to NO 2 or HNO 3 and is further absorbed, but due to H 2 o 2 , potassium permanganate, etc. are expensive and need to add recovery equipment, etc., the operating cost is high, and it is difficult to be widely used in industry; the reduction absorption method mainly uses urea to absorb NO in the nitric acid tail gas x , generating N 2 direct discharge

Prolonged Absorption Utilization of NO 2 with H 2 The principle of O reaction to generate nitric acid is to add an absorption tower behind the original absorption tower to increase the oxidation space of tail gas, prolong the oxidation time of NO and NO 2 Absorption time, so as to eliminate NO in exhaust gas x The purpose of this method, but the absorption effect of this method is not obvious, and the emission requirements cannot be met

[0006] Adsorption of NO in nitric acid tail gas by conventional adsorption method using porous adsorbent x , in order to achieve the purpose of purification, it has the characteristics of high purification efficiency, resource recycling, simple equipment, and convenient operation. Investment costs and operating costs

The pressure swing adsorption method has the advantages of simple process, convenient operation, and automatic control of the operation of the entire device, but the wide applicability of the pressure swing adsorption process is poor, and it is greatly affected by the nitric acid production process. Different nitric acid production tail gases need to be used Different pressure swing adsorption processes

[0007] Selective catalytic reduction can make NO in exhaust gas x content down to 600mg / m 3 Below, but there are also problems such as strict operating conditions, the need to consume a large amount of ammonia, and the need to strictly control the content of ammonia in the tail gas.

The non-selective catalytic reduction method has a wide selection range of reducing agents, a high reaction temperature (generally 550~850°C), and waste heat can be recovered, but it is sensitive to the composition of exhaust gas and eliminates NO x The effect is not good, and a large amount of catalyst is required, and it is easy to generate secondary pollutants such as cyanide

Images