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Process Control Systems Episode 12

Tham khảo tài liệu 'process control systems episode 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | F1G 11.30. The set point of the temperature or composition controller may be adjusted automatically with a summing device and a manual set station. Distillation 1 323 Plotting distillate rate vs. composition for each of these three programs gives an indication of how the optimal program might be implemented. A typical plot is constructed in Fig. 11.29. The optimal program calls for varying the set point of the or composition controller based on the current value of flow. Although the optimal program is not linear it can be approximated to a satisfactory degree by a simple linear equation y kD y 0 11.25 where slope intercept This linear expression may be readily with simple arrangement of analog devices pictured in Fig. 11.30. SUMMARY Unfortunately it is to cover even a sampling of the variety of distillation columns that are in service in industry. They are nearly as individualistic as people. Consequently much is left to the in way of interpreting design rules contained herein in of his problems. In regard a word of warning do not make your particular fit the of the control system. Rather take care to mold the system to the of separation. One very important of is omitted from chapter however. It includes the most difficult boiling mixtures and constant-boiling mixtures azeotropes . The reason for the omission is that distillation alone is insufficient for separation. They will be discussed in as much as seems reasonable after a brief treatment of extraction in the next chapter. REFERENCES 1. MacMullan E. C. and F. G. Shinskey Feedforward Analog Computer Control of a Supcrfractionator Control Eng. March 1064. Applications Lupfer D. E. and M. L. Johnson Automatic Control of Distillation Columns to Achieve Optimum Operation ISA Trans. April 1964. Luyhen W. L. and J. A. Gerster Fcedforward Control of Distillation Columns Ind. Eng. Chem. October 1964. Fenske R. Fractionation of Straight-run Pennsylvania Gasoline Chem. May 1932. The Foxboro Company Fractionating Column