Figure 1.0 Conventional grinding circuit a) Identify three main control objectives for this grinding circuit. [3 marks] b) Identify the measurements required to achieve each of the stated control objectives and name the associated measuring instruments. [ 6 marks] c) From the variables labelled in figure 1.0 , identify the manipulated variables that can be adjusted freely to control the grinding circuit. [ 2 mark] d) Suppose that online measurement of the mill product size is avallable, develop a cascade control scheme for ore size control. [5 marks] e) The performance of the cyclone is affected by feed rate, feed density and pressure. The feed density is also aflected by water addition to the sump. Propose (sketch) an inferential control configuration for mill product size control. [ 5 marks] f) Identify three sources of disturbances for the operation of the grinding circuit shown in figure 1.0 and explain the circumstances under which each of the identified disturbances may arise [6 marks] Question 2 a) Explain the principle of operation of a PID controller and discuss the purpose of controller tuning. [3 marks] b) The dynamic behaviour in terms of temperature changes for the stirred-tank heater (STH) system is described by the unsteady-state energy balance expressed in deviation variable form as VCndtd(TTi)=FCn[(TiTi,)(TTi)]+(QQi) The process is controlled by a P-only feedback controller which varies the heat input to the STH as Q=Q,+Ke(T,T) The following data relates to the operation of the stirred-tank heater: Figure 1.0 Conventional grinding circuit a) Identify three main control objectives for this grinding circuit. [3 marks] b) Identify the measurements required to achieve each of the stated control objectives and name the associated measuring instruments. [ 6 marks] c) From the variables labelled in figure 1.0 , identify the manipulated variables that can be adjusted freely to control the grinding circuit. [ 2 mark] d) Suppose that online measurement of the mill product size is avallable, develop a cascade control scheme for ore size control. [5 marks] e) The performance of the cyclone is affected by feed rate, feed density and pressure. The feed density is also aflected by water addition to the sump. Propose (sketch) an inferential control configuration for mill product size control. [ 5 marks] f) Identify three sources of disturbances for the operation of the grinding circuit shown in figure 1.0 and explain the circumstances under which each of the identified disturbances may arise [6 marks] Question 2 a) Explain the principle of operation of a PID controller and discuss the purpose of controller tuning. [3 marks] b) The dynamic behaviour in terms of temperature changes for the stirred-tank heater (STH) system is described by the unsteady-state energy balance expressed in deviation variable form as VCndtd(TTi)=FCn[(TiTi,)(TTi)]+(QQi) The process is controlled by a P-only feedback controller which varies the heat input to the STH as Q=Q,+Ke(T,T) The following data relates to the operation of the stirred-tank heater
