tailieunhanh - Essentials of Process Control phần 3

Tham khảo tài liệu 'essentials of process control phần 3', ngoại ngữ, ngữ pháp tiếng anh phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | IAI riíR V Conventional Control Systems and Hardware 101 Conventional Vapor Dephlegmator FIGURE since they eliminate a separate condenser shell a reflux drum and a reflux pump. Comment on the relative controllability of the two process systems sketched above. . Compare quantitatively by digital simulation the dynamic performance of the three coolers sketched on the next page with countercurrent flow flow and circulating water systems. Assume the tube and shell sides can each be represented by four perfectly mixed lumps. Process design conditions are Flow rate Inlet temperature 250 F Outlet temperature 130 F Heat capacity Cooling-water design conditions are A. Countercurrent Inlet temperature 80 F Outlet temperature 130 F B. Cocurrent Inlet temperature 80 F Outlet temperature 125 F C. Circulating system Inlet temperature to cooler Outlet temperature from cooler Makeup water temperature to system 80 F Neglect the tube and shell metal. Tune PI controllers experimentally for each system. Find the outlet temperature deviations for a 25 percent step increase in process flow rate. 102 PART ONE Time Domain Dynamics and Control Process Water Cocurrent water FIGURE . The overhead vapor from a depropanizer distillation column is totally condensed in a water-cooled condenser at 120 F and 227 psig. The vapor is 95 mol propane and 5 isobutane. Its design flow rate is 25 500 and average latent heat of vaporization is 125 Cooling water inlet and outlet temperatures are 80 F and 105oF respectively. The condenser heat transfer area is 1000 The cooling water pressure drop through the condenser at design rate is 5 psi. A linear-trim control valve is installed in the cooling water line. The pressure drop over the valve is 30 psi at design with the valve half open. The process pressure is measured by an electronic 4-20 mA pressure transmitter whose range is 100-300 psig. An analog electronic proportional controller with a gain of 3 is used to control process pressure .