tailieunhanh - Lecture Chemical process control - Chapter 7

a | Chapter 7 Development of Empirical Dynamic Models from Step Response Data Black box models step response easiest to use but may upset the plant manager size of input change move to new steady-state other methods impulse - dye injection tracer random - PRBS pseudo random binary sequences sinusoidal - theoretical approach frequency response - modest usage incl. pulse testing on-line under FB control 1 Chapter 7 Some pro cesses too complicated to model using physical principles material energy balances flow dynamics physical properties often unknown thermodynamics Example 1 distillation column 50 plates For a 50 plate column dynamic models have many ODEs that require model simplification and physical properties must be known . HYSYS black box models only good for fixed operating conditions but requires operating plant actual data theoretical models must be used prior to plant construction or for new process chemistry 2 Chapter 7 u t Manipulated inputs d t Disturbances w Process model ________ y t jtt Outputs --------------- Figure Input-output process model. Need to minimize disturbances during a plant test