Optimization Control Of The Circulating Fluidized Bed (CFB) Boiler

For a long time, we have put emphasis on control of CFB Boiler , especially combustion control and the steam temperature but have obtained no good results for diverse reasons. The combination of single loop control with cascade control couldn't offer satisfactory stability, run ratio and combustion efficiency due to the big lag and the time changing. Fuzzy control was reported to be used abroad, but no ready scheme is provided and the equipment price was high .After a brief introduction of structure , strongpoints and operation theory of CFBBoiler, the author demonstrated the principle of fuzzy control and analyzed the routine control programs in great detail. This paper delivers bran-new control methods based on broad research of methods used both at home and abroad and the current boiler structure in our country.1) Set steam flux--------fuel supply relation curve and air flux—fuel supplyrelation curve online study unit, change the inflexion coordinates to adapt to the influence brought by the change of fuel supply.2) The obtain of fuel supply set point with steam flux --------fuel supplyrelation curve as the primary, and steam pressure, steam flux fuzzy controller, bed temperature fuzzy controller as the secondary greatly enhances the run ratio of the control system and the efficiency of the boiler.3) Mount bed temperature fuzzy controller to stablize the temperature during combustion control. Here the author brings a detailed explanation of the design and the operation.4) Multilevel Steam temperature fuzzy controller used on steam temperature control and got good results.The above-mentioned control system is based on SUPMAX800 DCS from SHANGHAI AUTOMATION INSTRUMENTATION CO.,LTD. The system has been tested in the real plant and it shows a run ratio high to more than 80% and and a 2-3% higher efficiency. The cost is cut down a great deal with home-made (either hardware or software) SUPMAX800 DCS system. This promotes not only fame of the home-made DCS system but also the prevalence of SUPMAX800 DCS from SHANGHAI AUTOMATION INSTRUMENTATION CO.,LTD.