What is the NOx emission standard of boiler?

Industry boiler is an important thermal power device, but the production of boiler NOx is the main component of environmental pollution, which not only causes acid rain but also destroys the ozone layer, and it is the key point of monitoring the products after boiler combustion. Here, ZOZEN Boiler will analyze the source and control method of boiler NOx for everyone.

Principle of NOx generation in boiler

Ultimately, the nitrogen source of boiler NOx is nothing more than fuel or air, so there are two main types of boiler NOx:

Fuel boiler NOx

Fuel NOx is the reaction between the oxygen in the air and the pyrolysis products of nitrogen in the fuel to generate NOx. Not all nitrogen in the fuel is converted into NOx, and there is a conversion rate. Reducing this conversion rate can control the total amount of NOx emissions.

Thermal boiler NOx

Thermal boiler NOx is the boiler NOx generated by N2 and O2 in the air at high temperature during combustion. The main condition is that high combustion temperature makes nitrogen molecules free to increase chemical activity. Then there is a high oxygen concentration.

How to control boiler NOx

Boiler NOx composition control is mainly divided into primary measures and secondary measures.

[One-time measure]

The one-time measure is to control the formation of nitrogen oxides in the combustion process.

The primary measures mainly include low excess air coefficient operation, air staged combustion, flue gas circulation and coal water slurry technology.

[Two-time measure]

The two-time measure is to reduce the generated nitrogen oxides to nitrogen by some means.

Secondary measures now mainly include fuel reburning, selective catalytic reduction (SCR) and non-selective catalytic reduction (SNCR).

Selective catalytic reduction catalyst selective reduction is based on the reaction of ammonia and nitrogen oxides. In this method, ammonia is selected as a reducing agent, and metal-based and carbon-based catalysts are used. Generally, ammonia is injected into the flue gas between economizer and air preheater. And ammonia flue gas mixture passes through catalytic bed, where ammonia reacts with nitrogen oxides to generate nitrogen and water vapor. Non-selective catalytic reduction method Under the condition of proper temperature and no catalyst, reducing agent NH3 converts nitrogen oxides into ammonia molecules and water.

As a leader in the field of low-nitrogen boilers, ZOZEN Boiler firmly grasps the pulse of the times and launches several types of low-nitrogen boilers according to market demand, including WNS series oil-fired gas-fired low-nitrogen boilers and SZS series oil-fired gas-fired low-nitrogen boilers, which can realize that the NOx content of boilers is lower than 30mg/nm; SHX series circulating fluidized bed low-nitrogen steam boiler can realize that the boiler NOx content is lower than 100mg/Nm³.