2 replies to this topic

[chemks2012]

Dear All

 

I am working for one of our clients and there is a need of heating of a small jacketed tank [3m3] using MTHW [medium temp hot water] as the heating medium available at 133.5 deg C from boiler. My query is :

 

As the water boils [converted to steam] at 100degC at atmospheric pressure, it is necessary to maintain the pressure of MTHW continuously at or above 3bara. The MTHW supply pressure is 3.2bara.

As the MTHW flows from a boiler to the process, it will lose the pressure let’s say about 0.5bar and this will bring down MTHW pressure to 2.7bara and it will be converted into steam?. As this is the case, how do I maintain the MTHW pressure to at least 3bara?

 

Any input will be highly appreciated.

 

KS

[prengr]

Dear Chemks2012,

 

Because of your limited information, you might get the unclear answer.

 

If you add a pressure control valve at jacket outlet line and maintain the pressure above 3bara, you can prevent vaporization of MTHW. But, you need to increase the supply pressure of MTHW as much as pressure drop between Pump discharge and the jacketed tank.

 

As i know, In case that Hot water is used by heating medium, this hot water system is a closed system and the pressure of this system is maintained above saturation pressure at the temperature of returned hot wataer to remove the risk of hot water vaporization at least.

In other case that Hot water used by heating medium is boiler feed water, this hot water(boiler feed water) is fed to down grade steam system or is fed to steam condensate drum. For the former, hot water will be steam by desuperheater. For the latter, hot water will be separated by steam and condensate.

 

Thanks.

[shan]

When the hot water is at 2.7 bara, its temperature is not 133.5 C anymore because of heat transfer through the jacket coil. If the water temperature is still higher than boiling point 2.7 bara, you add some chemicals (glycol?) to raise the heating medium boiler point.