SCR Flue Gas Denitration Catalyst

Selective catalytic reduction (SCR) is a means of converting nitrogen oxides, also referred to as NOx with the aid of a catalyst into diatomic nitrogen (N2), and water (H2O). Please do not hesitate to contact us anytime if you want to know more.

SCR system application overview

Selective Catalytic Reduction (SCR) converts nitrogen oxides in flue gas into nitrogen and water with a catalyst, and the reducing agent is usually ammonia. The ammonia gas is mixed with the flue gas and then passed through the catalyst. The mixing process should ensure uniform distribution of flue gas temperature and reactants. By providing an active area, the catalyst enables the denitration reaction to take place at 280-320°C. Ammonia diffuses into the microporous structure of the catalyst and is absorbed by the active area. NOx will complete the denitration reaction with the absorbed NH3. The main factors affecting the reaction are the active area factor (a function of specific surface area, pore volume and active ingredient concentration), flue gas temperature and reactant concentration.

The SCR catalyst is a porous ceramic structure extruded from various inorganic oxides, and is an integrally extruded catalyst, that is, the integral catalyst unit is composed of uniform catalytic materials. Typically, catalyst units are installed into carbon steel modules, which are then installed into the SCR reactor and reacted with the flue gas.

1. SCR chemical reaction

The main chemical reactions of NH3 and NOx are as follows:

(1) 4NO + O2 + 4NH3 ® 4N2 + 6H2O

(2) NO + NO2 + 2NH3 ® 2N2 + 3H2O

(3) 6NO2 + 4NH3 ® 5N2 + 6H2O

(4) 4NH3 + 5O2 ® 4NO + 6H2O

Among them, reaction (1) is the most dominant reaction, which shows that 1 mole of NH3 is required to remove 1 mole of NO. However, in the actual reaction, in order to achieve the required NO removal rate, it is necessary to inject a small amount of NH3 to compensate for the non-uniformity of mixing. The excess NH3 that passes through the catalyst and does not participate in the reaction is called slip ammonia.

When SCR is operating at design conditions, it has very limited impact on boiler and system operation. And it can reduce NOx emissions in the process of denitrification without producing other pollutants. SCR can also operate stably under different loads and obtain high denitration effect. In general, a well-functioning SCR system has only a very limited impact on the operation of downstream equipment.

3 SCR catalyst

SCR operation depends on the parameters of the catalyst. The catalyst of our company is a product based on vanadium-titanium-tungsten material, which has high reactivity to NOx. Our catalyst is a honeycomb extruded ceramic structure with high specific surface area per unit volume. The high open porosity ensures the lowest pressure drop. The catalysts produced by Hubei Guangjing Environmental Protection Catalyst Co., Ltd. are individually formulated for each specific project, and can selectively reduce NOx while preventing the conversion of NH3 to NO, or the conversion of SO2 to SO3. At the same time, the catalyst can also work normally in the presence of some pollutants in the flue gas (eg ash).