SCR system

We have SCR technology introduced from Mitsubishi Heavy Industries, Japan. To get better denitration performance, we developed straightening grid for SCR system. Innovative straightening grid could guarantee ammonia is mixed evenly with flue gas. Speed deviation of mixed gas before the first catalyst layer is smaller than 15%, ammonia concentration deviation is smaller than 10%.

We are the first company to serve in DeNOx market in China. Our SCR system could cover 7-1350MW boiler unit. Capacity of boiler installed with our SCR system adds up to 100GW. There are two ways to control NOx emission. One is to reduce NOx generation inside furnace, one is to convert NOx in flue gas into something else. Our DeNOx technology: low NOx combustion, selective non-catalytic reduction (SNCR), selective catalytic reduction, and solution in combination of these technology.

Staged combustion is a good method to achieve low NOx combustion. Traditionally, all the air and pulverized coal is sent into furnace. Temperature inside furnace is very high, lots of NOx is generated. Staged air supply could achieve low oxygen combustion at early stage to lower furnace temperature, and keep heat loss caused by incomplete combustion at the lowest level.

SCR: Under temperature 320-420℃, NH3 would react with NOx in the presence of catalyst V2O5/TiO2. Final product is N2 and H2O.

4NO + O2 + 4NH3 → 4N2 + 6H2O

6NO + 4NH3 → 5N2 + 6H2O

2NO2 + O2 + 4NH3 → 3N2 + 6H2O

6NO2 + 8NH3 → 7N2 + 12H2O

When reaction temperature is lower than 280℃, SO3 in flux gas would react with NH3 and form NH4HSO4, which is sticky and corrosive. It would attach on the surface of catalyst and influence catalyst activity. Also, it would attach on heating surface of air preheater to cause corrosion or blockage. When reaction temperature is higher than 420℃, catalyst structure would be unstable. So, it is important to control temperature for SCR process. Efficiency is normally 70-90%.

SNCR: NH3 or urea is sprayed into furnace and react with NOx under temperature 850-1100℃. Efficiency is normally 25-50%.

4NH3 + 4NO + O2 → 4N2 + 6H2O

NO + CO(NH2)2 + 1/2O2 → 2N2 + CO2 + H2O