基于燃烧优化的CFB锅炉最优静态调节特性研究

摘要

At present,the automatic generation control (AGC) system for circulating fluidized bed (CFB) unit is always in the process of turbulent regulation,making the control mechanisms act frequently.The reason is that the change rules of control variables with load (namely the static characteristics) are not clear for the CFB combustion system.Therefore,taking account of the capacity and structure of the CFB boiler,the cyclone performance and the desulphurization efficiency,through regulating the particle size distribution of the feedstock,the bed pressure drop and the mass ratio of the primary air to secondary air,the optimized combustion of CFB boiler can be achieved which is featured by the optimal particle size distribution of bed material,land the carbon content in fly ash and bottom ash also can be reduced.Then,by setting up the equations of energy balance,material balance and carbon balance in the furnace,and solving the nonlinear equation groups by Newton method,the static behaviors of the CFB boiler under conditions with different loads,different coal types and different particle size distributions of feedstock were obtained.The optimal regulation amounts for control variables such as the feed coal flow,primary air flow,secondary air flow,limestone flow and bottom ash flow were ascertained and used as the set values.Thus,the decoupling control of combustion system can be realized for CFB boilers.%目前,循环流化床(CFB)机组自动发电控制(AGC)一直处于动荡调节过程之中,致使各调节机构动作频繁,这主要是由于对CFB锅炉燃烧系统各调节量随负荷的变化规律(即静态特性)不明所致.因此,根据CFB锅炉的容量、结构、分离器性能、脱硫效率等,通过调节给煤粒度分布、床压降和一二次风比,获得最优物料质量浓度分布,并降低底渣含碳量和飞灰含碳量,然后建立炉内热量平衡、物料平衡和碳量平衡方程,采用牛顿法求解非线性方程组,获得CFB锅炉在不同负荷下燃用不同煤质及其在不同给煤粒度分布下的静态调节特性,确定CFB锅炉优化运行时的燃料量、一次风量、二次风量、石灰石量和排渣量等最佳调节量,将其作为CFB锅炉燃烧调节设定值,可实现CFB锅炉燃烧解耦控制.