Researches On Dynamics And Control Of An Internal Thermal Coupled Air Separation Column

The amount of greenhouse gas emission from the fossil fuel-based power plant has reached more than one-quarter of the global emission.The fossil fuel that accounted for more than 40%of the world electricity requirement is coal because of its abundant availability,low price,and wide distribution on earth.The traditional power plant based on coal-fired cannot provide adequate mitigation of greenhouse gas emissions.The alternative to this power plant relies on integrated gasification combined cycle(IGCC).At present,the IGCC is internationally recognized as the most promising clean and efficient coal power technology.Some country’s utility supplies depend on a clean coal power supply system.Among them,the air separation unit(ASU)is one of the most significant unit of IGCC,but at present,the energy consumption of the air separation unit is large.The identified single operation unit in the ASU responsible for the energy consumption is the distillation column.To addressed this energy consumption challenge of the ASU in the IGCC process,the cutting-edge energy-saving principle of thermally coupled distillation is examined.The current work takes the energy-saving,consumption reduction,and high-purity control of the IGCC distillation process as the research goal.It carries out the steady-state modeling,simulation,energy consumption analysis,and optimization of internal thermally coupled air separation column(ITCASC)for the IGCC air separation process.Dynamic modeling,simulation,and high purity control strategy are the main work and contributions as follows:1)The steady-state mathematical model of the IGCC thermally coupled air separation column is established.Also,the steady-state simulation and energy consumption analysis are carried out,and the energy-saving optimization is further studied.Based on the principle of mass conservation,energy conservation,equation of state,and thermal coupling principle,the equilibrium stage calculation model of IGCC thermal coupling air separation column is established as the basis of comparative research.Similarly,the conventional air separation column model of IGCC production is also realized.The steady-state simulation results of the IGCC thermal coupled air separation column show that the thermally coupled air separation column has good operating performance in terms of energy consumption and product purity.The energy consumption analysis and optimization result demonstrate the potential of the thermally coupled air separation column in the IGCC in terms of energy efficiency and economic performance.The IGCC thermal coupling air separation column designed in the current work achieves more than 43%energy saving and more than 99.3%product purity compared with the conventional air separation column.2)The dynamic mathematical model of the IGCC thermally coupled air separation column is established.Further carried out the design of high purity advanced control scheme study through dynamic simulation.The results of dynamic simulation show that the thermally coupled air separation tower has complex dynamic behavior and intense interaction,which will increase the difficulty of product purity control.Therefore,four different product purity control schemes of IGCC thermally coupled air separation columns are proposed.These include proportional integral derivative(PID),nonlinear internal model control(NIMC),robust generic model control(RGMC)Adaptive generic model control(AGMC)scheme.The RGMC copes with the challenge of the nonlinear and intense interaction.The AGMC enhanced the adaptation of the controller through the multivariable recursive extended least square method.The comparison results show that the control effect of the four schemes gradually becomes better,and the AGMC control effect is the best,which can better deal with the nonlinearity and strong interaction of the system.3)Two different IGCC thermal coupling air separation model predictive control schemes(MPC-Ⅰ and MPC-Ⅱ)are proposed to realize the high-purity control of ITCASC under distinct disturbance conditions.Among them,MPC-Ⅰ mainly integrates real-time optimization(RTO)and Kalman filter(KF)techniques,and MPC-Ⅱ integrates finitehorizon control(FHC)and successive linearization(SL)methods.The MPCs are compared with the research group adaptive multivariable generalized prediction control(AM-GPC)strategy.The comparison results show that the control performance of MPCⅠ is equivalent to that of AM-GPC,and the control performance of MPC-Ⅱ is better than that of MPC-Ⅰ and AM-GPC.