Application Of Fuzzy Predictive Control In Steam-injection Boiler

Steam-injection boiler is the key equipment of thermal drive, and it is also the equipment whose energy consumption is the largest in the thermal drive process. With the enlargement of heavy oil recovery's scale, the problem how to enhance the dryness quality and decrease the energy consumption of steam-injection boiler is getting more and more important. Since steam-injection boiler was introduced from America at 1980s, the manufacture of it has realized industrialization interiorly. But the control system of steam-injection boiler still stays at the quondam technologic level. It's control efficiency is not high, too. Along with the constant development of advanced control theory and computer technology, that applying the advanced control technologies such as fuzzy control, predictive control to the control of steam-injection boiler and enhancing the control efficiency of control system has became an inevitable trend. Based on the systematic expatiation on technologic process of steam-injection boiler, this paper analyzes the control effects that the control system of steam-injection boiler must achieve and puts forth the difficulties that control system may encounter. Dryness fraction and steam pressure are the important parameters of steam-injection boiler. They are the bottlenecks that hamper the safe and economical operation of steam-injection boiler, too. So according to the characteristics of boiler system, this paper proposed the control scheme based on fuzzy predictive control to adjust the run parameters of boiler. In this scheme, a two dimension fuzzy controller is employed to steady steam pressure, and error and error change of steam pressure are used as the input variables of this fuzzy controller. A fuzzy predictive controller based on T-S fuzzy model is employed to obtain the control variable of fuel-dryness closed loop. And this control variable is multiplied by the feedforward control variable to form the feedforward-feedback control of dryness fraction. Finally, this paper achieved the hardware and software design of control system. The control system of steam-injection boiler proposed in this paper has been applied in a steam-injection boiler of kelamayi oil field successfully. This control system has enhanced the steam quality to large extent and has reduced the consumption of energy. It has an excellent control performance.