单选题The PRIMARY function of a waste heat boiler is to （）.A reduce engine exhaust noiseB reduce engine back pressureC recover heat which otherwise would be lostD increase turbocharger efficiency

not；but

neither；nor

either；or

not only；but also

Control of evaporation

A separate means to prevent feed-water contamination

Power circulating pump

Super-heater

operating the boiler at less than normal water level

installing fins on the firesides of water-tubes

increasing the amount of excess air to the burners

treating the boiler water with chemical oxygen scavengers

bypass exhaust gas at high loads to prevent excessive back pressure

bypass a portion of the exhaust gas at peak loads for better efficiency

recycle exhaust gas to the turbocharger

minimize moisture condensation in the boiler gas passages at low loads

To prevent internal damage form local overheating

To ensure the fuel nozzles are flushed clean

To clear the smoke stack

To let the waste heat boiler reduce its rate of steam generation

Receives saturated steam from the generating tubes

Serves as a reservoir of boiler feed water

Holds internal fittings for separation of moisture from steam

Collects steam exhausted from the turbines

prevent engine back pressure at heavy loads

increase total engine efficiency at low loads

prevent boiler corrosion at low engine loads

improve engine fuel consumption at any load

increased heat transfer

fireside erosion

high steam demand

overheated tubes