A reactor is cooled by circulating liquid through a heat exchanger that produces low pressure

$(10$ psig$)$ steam. This steam is then split between a compressor and a turbine. The portion that

goes through the turbine drives the compressor. The portion that goes through the compressor

is used by $50-$psig steam users. The turbine can also use $100-$psig steam to provide power

required beyond that available in the $10-$psig steam. $($See figure below$).$

Sketch a control concept diagram that includes all valve actions and the following control

strategies:

i$.$ Reactor temperature is controlled by changing the set point of the turbine speed

controller.

ii$.$ Turbine speed is controlled by two split$-$range valves, one on the $10-$psig inlet to the

turbine and the other on the $100-$psig inlet. Your instrumentation system should be

designed so that the valve on the $10-$psig steam is wide open before any $100-$psig

steam is used.

iii. Liquid circulation from the reactor to the heat exchanger is flow controlled.

iv$.$ Condensate level in the condensate drum is controlled by manipulating BFW $($boiler

feed water$).$

v$.$ Condensate makeup to the steam drum is ratioed to the $10-$psig steam flow rate

from the steam drum. This ratio is then reset by the steam drum level controller.

vi$.$ Pressure in the $50-$psig steam header is controlled by adding $100-$psig steam.

vii. A high$-$pressure controller opens the vent valve on the $10-$psig header when the

pressure to the $10-$psig header is too high.

viii. Compressor surge is prevented by using a low$-$flow controller that opens the valve in

the spillback line from compressor discharge to compressor suction.