HEAT RECOVERY STEAM GENRATOR

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INTRODUCTION

Heat recovery boilers, also known as waste heat recovery boilers or heat recovery steam generators (HRSGs).

Waste heat boilers are used to cool waste gas streams from a given inlet temperature to a desired exit temperature for further processing purposes. A common application for an HRSG is in a combined cycle power station .

The output of the HRSG is solely dependent on the performance and load of the gas turbine.


Water Tube Boiler
Water tube boilers are more difficult to design compared to fire tube boilers, due to the complex arrangement or disposition of heating surfaces such as super heaters , evaporators andeconomizers. Due to the higher heat transfer coefficients associated with gas flow over the tubes , water tube boilers requires less surface area and hence the gas pressure drop can be lower than in a fire tube boiler.

Natural

Natural circulation units have vertical tubes
and horizontal gas flow orientation . In natural circulation units, the difference in density between water and steam drives the steam–water mixture through the evaporator tubes and risers and back to the steam drum.