Deaerator Sizing - Continued

[Pavan Kumar]

Hi All,

Further to discussion on the below thread, I developed a calculation spreadsheet to perform some sizing calculations for a Pressurized Deaerator.

Deaerator Sizing - Chemical process engineering

Hi All, Can anyone provide me the references or documents that I can use to learn about Pressurized Deaerator sizing. Any help is appreciated. Thanks and Regards, Pavan Kumar

www.eng-tips.com

I am however facing mass balance issues at the Boiler( please see the sketch pasted below, also in the attached spreadsheet). I calculated the following from the provided Boiler Rating and Feed water temperature and the O2 Concentration in the Deaerated water.

1. Steam Generation Rate of the Boiler.
2. Make-Up Water Rate ( Considered Equal to the Boiler Steam Generation Rate as there is no condensate returned).
3. Vent Gas Flow Rate ( Air and Steam Venting Rate).
4. Deaerator Storage Tank Volume and Dimensions.

The issue I am facing is that since I considered the Make-Up water flow rate equal to the Boiler Steam Generation Rate, the input to the Boiler is not matching with the output. The difference is due to the Steam that is condensed in the Deaerator. I want to understand how a Deaerator operates in practice and how this mass balance question can be answered meaningfully. Your inputs in this regard will be very helpful to me.




Thanks and Regards,
Pavan Kumar

 

[pierreick]

HI,
Download MEASUR you will find example of deaerator.
Are you sure about the operating conditions of the deaerator (Pressure and temperature)? what is the quality of the steam at the discharge of the PRV (steam), pressure and temperature?
Your schematic is wrong, steam is supposed to bubble within the deaerator sump meaning steam will condense partially, the trays are there to provide contact between water and steam to help for the realize of O2 through the vent.
Pierre

 

[goutam_freelance]

Mass flows to and from boiler are wrong. Outgoing flow can not be more than incoming.

 

[Pavan Kumar]

Hi Mr. Goutam,

I knew the Mass Balance at the Boiler is wrong and that was my question above.

Hi Mr. Pierre,

Yes I will download MEASUR today and look for the Deaerator example. The sketch is only a schematic, plus the Stripping steam is added on a side nozzle on the dome close to the bottom. There are variations where steam is added into the Deaerator storage Tank as well.

Thanks and Regards,
Pavan Kumar

 

[pierreick]

Pavan,
your mass balance is the following:
Make up water 98.4 t/h
vent : 1.14 t/h
steam to deaerator : 16.47 t/h
feed water to boiler : 113.73 t/h
steam to process : 97.26 t/h
to be tuned.

Pierre

 

[goutam_freelance]

Hi Pavan Kumar,

On which basis you are calculating?
For example , is it not possible to reduce the boiler steam flow or increase the make up water flow?

 

[Pavan Kumar]

Pavan,
your mass balance is the following:
Make up water 98.4 t/h
vent : 1.14 t/h
steam to deaerator : 16.47 t/h
feed water to boiler : 113.73 t/h
steam to process : 97.26 t/h
to be tuned.

Pierre

Hi Mr. Pierre,

I found that my adjusting the Make-Up water flow rate in ratio with Stripping Steam flow rate, I can get the Mass Balance corrected. I was able to do that. My updated spreadsheet is attached.



My final values are as follows:

1. Make-Up water Flow Rate = 98.6 Tonne/hr
2. Stripping Steam = 14.96 Tonne/hr
3. Total Venting Rate = 0.013 Tonne/hr
4. Steam to Process = 98.6 Tonne/hr
5. Deaerated Water to Boiler = 113.54 Tonne/hr

Thanks and Regards,
Pavan Kumar

 

[Pavan Kumar]

Hi Pavan Kumar,

On which basis you are calculating?
For example , is it not possible to reduce the boiler steam flow or increase the make up water flow?

Hi Mr. Goutam,

The Make-Up water control valve operates in the level in the Deaerator storage tank and thus to balance to the output the Make-up water flow rate has to adjust. This is exactly what I did and posted my corrected calculation spreadsheet in my response to Mr. Pierre above.

Thanks and Regards,
Pavan Kumar