According to the principle of purification effect, it can be divided into catalytic reduction method, absorption and adsorption.

1. The main effect principle of catalytic reduction method is to reduce the NO in the exhaust gas to pollution-free N2 under the condition of high temperature and the presence of catalyst. Because the reaction temperature is high and catalyst is required at the same time, the equipment investment is large and the operating cost is large.

2. Adsorption method is mainly used to adsorb NO in waste gas with absorbent materials and adsorbent. Because of the small adsorption capacity, this method is only applicable to waste gas treatment with low NO concentration and small gas volume.

3. Absorption method: use water or aqueous solution of acid, alkali and salt to absorb nitrogen oxides in exhaust gas, so that exhaust gas can be purified. This method saves equipment investment and low operating cost.

With the continuous development and improvement of pulse bag filter technology, bag filter has become the equipment for industrial dust removal. However, there is a common problem in the use of bag filter at present, that is, the running resistance of the filter is too high. Therefore, how to reduce the resistance of the precipitator has become a problem to be tackled by environmentalists. The running resistance of the bag filter is the difference between the total pressure at the inlet and outlet, indicating the mechanical energy consumed by the gas flow through the bag filter. General pressure loss can be measured with a pressure gauge at the equipment site of the bag filter. In practical engineering, the running resistance of bag filter is mainly composed of structural resistance and filtering resistance. Therefore, the operation resistance of bag filter is usually confirmed based on the practical experience of treating similar gases and dusts with similar fabrics.

The resistance of pulse bag filter can generally be automatically maintained at the predetermined value when planning through the ash cleaning mechanism. The resistance of bag filter in practice is mostly in the range of 500-2000pa.

Dust removal effect of dust remover:

1. Large power consumption, uneconomical.

2. The resistance exceeds the value taken in the ventilation system planning, and the ventilation cannot meet the needs.

3. When the dust accumulates on the filter bag, the pores become smaller, and the speed of air passing through will increase. When it is increased to a certain degree, "pinholes" will occur in the dust layer, causing a large amount of air to flow through the pinholes with small resistance, forming the so-called "air leakage" phenomenon, affecting the dust removal effect.

4. The filter material is easy to be damaged due to high resistance. Therefore, the bag filter must pass through the dust accumulated on a square dust filter bag during use (even from the perspective of dust collection, the dust collected on the filter bag must be removed before it can be collected). However, generally, there is still quite a lot of dust left in the pores of the fabric after dust removal. From the point of view of residual resistance and time after dust removal and fabric damage, it is uneconomical to do so. In addition, after dust removal, when the next filter cycle begins, the remaining dust can still play a considerable role in dust collection.