SNCR Demonstrating of NOx Control for a Cyclone Fired Boiler Burning High Sulfur Coal

Page 10

10 A16SE738.T A 21,000 gallon insulated tank was located in front of the administration building. Penn anent stainless steel, insulated and heat-traced piping was run from the tank to the system control trailer located adjacent to the Unit 1 boiler. Two penn anent stainless steel chemical risers were installed from the trailer into the building and up to the 8th floor injection level. The pumping and metering trailer included a tank recirculation pump, electric heater and chemical pumping and metering skids. The trailer was also equipped with a control panel to properly meter the chemical flow rate to the unit in the proper proportion with the dilution water. The injection trailer was equipped with a water pump and a static mixer to mix and deliver the diluted reagent to the injectors. The injection skid was capable of providing independent flow and concentration control to each level of injectors. The Levell injectors were controlled by two injector distribution panels, one with six injector modules and one with five injector modules. Distribution Module No.1 controlled the six injector modules on the south wall (front) and was located in the southeast corner of the building. Distribution Module No.2 controlled the three rear wall injectors and the two side wall injectors at Levelland was located inside the building at the south wall of the boiler. Atomizing air was piped into each injector distribution module from the plant atomizing air riser located in the southeast corner of the building. The injectors located outside the building on Level 1 were heat traced and insulated. The injectors were installed in air-aspirated observation ports. Each injector had a removable nozzle tip to control the spray orientation. Distribution Module No. 3 controlled the Level 2 injectors on the south wall of the boiler and was located in the southeast corner of the building on the 8th floor elevation. Atomizing air was taken from the plant riser located adjacent to the distribution module. Pennanent stainless steel tubing was run from each injector distribution module to the injector flexible hoses. Each injector had flexible hoses for the atomizing air and chemical. Control of the system was done by use of a steam flow signal and NOx concentration feedback signal. The steam flow was characterized in segmented ranges to the proper level of injection and NOx setpoint with attendant maximum and minimum reagent pumping rates. A corrected NOx concentration from the plant CEMS was tied into the control as feedback for reagent pump rates trim within the limits established by the loa4. The pump rates and the injection levels used at the different steam flows were detennined as testing proceeded, in order to attain NOx setpoint while minimizing ammonia slip. LONG-TERM TEST CONDITIONS The objective for the longer-tenn test was to demonstrate what reduced NOx emission rate could be maintained under economic unit dispatch. Some of the specific concerns that could not be addressed in the conceptual test that needed to be addressed in the longer-tenn test were load following and area regulation requirements and the impact of various levels of resulting ammonia slip on air heater fouling.