Optimum boiler pressure for Waste heat recovery system

[Ali Durrani]

Hello Guys,
I am a mechanical Engineer working on a semester project, to design a waste heat recovery system for a cement plant Air quenching cooler (AQC). For WHR i have to first design a AQC Boiler.
According to the Data provided by the plant incharge, Air at the exit of cooler has a volume flowrate of 125000m^3 / hour at 320 degree centigrade with the available thermal power of 3.75MW. now for designing boiler i have to assume a pressure, i have searched a lot but i couldn't found specific material about it
please guide me thanks.

 

[anorlunda]

Forgive me for asking. Are you qualified to design a boiler? If you were, I don't think you would ask that question.

There are stringent codes and standards for nearly all aspects of boiler design. They leave little freedom to the designer. Have you read them?

They created those codes because so many thousands died from boiler explosions. Often quite talented people designed them, but that doesn't mean that they are expert specifically on boiler design.

 

[Ali Durrani]

Forgive me for asking. Are you qualified to design a boiler? If you were, I don't think you would ask that question.

There are stringent codes and standards for nearly all aspects of boiler design. They leave little freedom to the designer. Have you read them?

They created those codes because so many thousands died from boiler explosions. Often quite talented people designed them, but that doesn't mean that they are expert specifically on boiler design.

Sorry if i have offended you, i just want to setup a rankine cycle, i am not going to fabricate that, i don't think there is any problem with asking this question, i just want to know what is the usual trend for steam pressure in AQC boilers, because my available thermal energy is quite less so i want to extract maximum out of it.

 

[BvU]

So what's against picking a pressure, say 10 Bar, and setting up a design ? You'll run into problems with your heat exchanger design if it's too high and can always lower it, or raise it if there's still room. It's a good exercise.

 

[Ali Durrani]

I started at 30 bars, but the cycle efficiency at 30 bars was way lower, the work output was hardly 1.5 MW but lowering boiler pressure up to 10 bars and the theoretical thermal efficiency of the cycle achieved was 23.94 % which is a nice figure for a starter for a waste heat recovery,
Note: this efficiency is based on single pressure steam cycle, i now have to evaluate it for multi-pressure steam cycle by introducing reheating process