Large Air Separation Plants Of Advanced Control And Optimization Strategy

Air separation is important productive process in industry to produce high-purity oxygen, nitrogen, argon and other industrial gases.Air separation unit is key equipment of iron&steel and chemical enterprises. Along with megatrends of air separating equipment, air separation customers increasingly concern on reduction of reactive power production, lower oxygen blow-off rate, balancing supply&demand, controling total energy consumption of equipment at underload to keep low cost operation. At present, most of air separateion equipments use DCS control system. So, currently it's feasible method for air separation customers that increasing upper management computer based on initial DCS control system and configuring optimized control software which accord with production operating principle and actual working to achieve auto-varying load productive process, and it's pressing request that further improving automatization level of air separation equipment to realize saving energy & reducing consumption.How to keep oxygen blow-off rate less than 5% is the target of control and key study points for all of iron&steel enterprises as air separation equipments are high power-consupmtion. It's ideal scheme of reducing oxygen blow-off rate to achieve adjusting load of air separation equipment on line by upgrading & reforming the equipment's control system and make it as match as possible with production.The thesis has its industrial background of the air separation equipment 2x28000Nm3/h of Tianjin Iron & Steel Group Co. to do advanced control optimization, achieve initial air separateion equipment optimization on the basis of multiple control of the equipment HENGHE CS-3000DCS to carry out auto-varying load advanced control technology. Mainly reserch the following control problems: By reserching adsorption characteristic of molecular sieve, change traditonal"time to switchover"regenerated control to automatically alter switchover time"Adaptive Control"mode,this makes switchover time can be adjusted automatically according to load size and actual adsorption status, give full play to adsorption function to cut down energy consumption. Achieve bare machine control of imported air compressor, supercharger, Nitrogen Compressor, developed full set of control software on DCS to replace the equipment manufacturer's own PLC control systems i.e. so-called"Black Box", this will realize functions of the quick step-up&small starting current energy-efficient auto-loading & auto-unloading as well as two-parameter anti-surge control. On the basis of above advanced controlling optimization, series connecting the whole air separation process to achieve auto-varying load controlling of the air separation equipments in order to enhance equipment's ability to resist disturbance, raise stability of key technological parameter, improve consistence of products quality. Under precondition of making qualified products to improving yield co-efficiency of the object products to realize the goal of energy saving and consumption reducing, in the meantime optimize operating conditon of the processing equipment and decrease intensity of labor to maximize processing ability of the equipments.