DCS control system for SCR SNCR denitrification process of kiln rotary kiln denitrification equipment

1. Overview:

The harm of NOX: The vast majority of nitrogen and oxygen goods generated by various pollution sources are NO, which is not very toxic. However, NO can oxidize to produce NO2 in the atmosphere, which is relatively stable and its toxicity is 4-5 times that of NO. The content of NO2 in the air is 3.5 × 10-8 (volume fraction) lasts for 1 hour and begins to have an impact on the human body; The content is (20-50) × At 10-8 hours, it has a stimulating effect on the human eye; When the content reaches 150 × At 10-8 hours, it has a strong stimulating effect on human organs. In addition, NOX is also involved in the formation of photochemical smog and acid rain.

The DCS distributed control system has many advantages such as high reliability, open system, powerful functions, and simple maintenance. It can provide monitoring for SCR denitrification, improve control stability and coordination, improve denitrification efficiency, and better meet the national requirements for gas emissions.
2. System principle:

The denitrification principle adopts a selective catalytic reduction method, which occurs in a reactor equipped with a catalyst. The flue gas reacts with the injected ammonia under the action of the catalyst to achieve the removal of nitrogen oxides. The nitrogen oxides in flue gas are usually composed of 95% NO and 5% NO2, which are converted into water and nitrogen through the following reactions.

4NO+4NH3+O2->4N2+6 H2O

4NH3+2NO2+O2->3N2+6H2O

NO2+NO+2NH3->2N2+3 H2O
The conversion rate of NOX is expressed by the following formula:



η NOx - Denitration efficiency%

NOxin - NOx concentration at the inlet of the reactor

NOx out - NOx concentration at the outlet of the reactor