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Unformatted text preview: University of California, Davis Department of Chemical Engineering and Materials Science ECH 157 Process Dynamics and Control Ahmet Palazoglu EXAM 1 / SOLUTION Fall 2010 ( Open book and no notes ) 1. (5 pts) A fired heater (furnace) is used to heat a process stream containing an intermediate product that will be sent to a downstream reactor. It is not only important to maintain a constant outlet temperature but also to keep the furnace temperature below a certain critical value for safety reasons (metallurgical limits of the furnace tubes). A simple schematic representation is shown in the figure below. Process Stream Fuel Flue Gas Heated Process Stream • What is the control objective for this process? • Identify all external disturbances that could affect the operation of the furnace. • Identify all manipulated variables for the control of this unit in the presence of disturbances. • Construct a feedback control configuration and a feedforward control configuration that would satisfy the control objectives in the presence of disturbances. Solution: The control objective is to maintain constant temperature of the heated process stream at the desired operating point in the presence of disturbances and safety limits. External disturbances: Fuel flow rate and its heating value (function of composition), inlet process stream flow rate and temperature (and composition). Manipulated variables: fuel flow rate, inlet stream flow rate. A feedback configuration would measure the outlet process stream temperature and adjust the fuel flow rate. 1 A feedforward configuration would measure the inlet process stream flow rate and again, adjust the fuel flow rate. 2. (6 pts) A single equilibrium stage in a distillation column is shown in the figure below....
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- Spring '08
- lim, Trigraph, University of California, process stream, Davis Department of Chemical Engineering and Materials Science