Cement, Energy and Environment

37 A SNCR system normally consists of the following main parts: Storage tank The tank can be a single wall or double wall type and it should be manufactured in stainless steel. The single wall tank will require a retention bund in concrete around the tank to capture any possible leaks. The tank is designed for pump filling from a tank lorry and with a return line for displaced gas back to the tank lorry. The tank has to have certain instruments like overfill protection, pressure/ vacuum valve with flame arrestor, leakage indicator, level transmitter for indication of the tank volume and a tank pressure transmitter. Fig. 3 Double wall storage tank and emergency shower Pump module for filling of the storage tank The pump module is for the filling of the reduction agent, from a tank lorry without own pump, into the storage tank. Pump module for reduction agent The pump module is for transporting and pressurizing reduction agent from storage tank to the process units. The pump module is normally located outdoors close to the storage tank. Fig. 5 Pump module for reduction agent with all the instruments and electrical components required preinstalled Pump module for softened water It is also advisable to have a pump module for transporting and pressurizing softened water. For some applications with low reagent consumption, it is needed for dilution of the reduction agent solution in order to achieve sufficient spraying. For cement applications, the consumption of reagent is normally quite high and thus no dilution water is needed. However it will still be needed for flushing of the system when the system is stopped for maintenance, etc. Process unit The process unit should be located as close as practically possible to the injection area. The unit includes one blending module and injection modules, one for each injector. The blending module produces the required quantities of reduction agent for the current operating condition demands and each injector module manages one injector. The injector module is designed to open and close reduction agent flow, and purges with water when stopped. The big difference between SNCR systems for cement kilns and for CPP boilers is the typically more complex load range (temperature profile) and wider cross-sectional area of a boiler. Therefore the amount of process units and injectors required to be able to flexibly react on the shifting of the temperature profile is increasing. Additionally Fig. 4 Pump module for filling of the storage tank