After the urea solution, demineralized water, and compressed air enter the metering and distribution module, the urea solution automatically adjusts the amount of urea solution to be injected through this module based on the feedback information of NOX emission concentration. The demineralized water is also adjusted by a flow meter according to the NOX emission concentration. Compressed air is distributed to each injection unit through a distributor.

The metering and distribution module is equipped with electric regulating valves, mixers, distributors, flow meters, air filters, pressure reducing valves, pressure sensors, solenoid valve sets, gas distributors, and liquid and gas pressure display devices and sensing devices for each circuit. It has the advantages of the simple and compact overall structure, high integration, easy operation and installation, neat and reasonable distribution of liquid & gas pipeline connection, and maintenance-free.