7 replies to this topic

[ProcessEng_12]

Dear all,

In the attachment given below, I have done calculation for consumption of steam on the basis of energy balance and mass balance.

My team was supposed to calculate steam taken from the 'Utility plant' as there is no measuring instrument available there. But the calculation done on mass balance contradicts the one done on energy balance.

 

Please review it.

 

Thank you in advance.

Attached Files

•  Book1.xlsx   12.8KB   80 downloads

[ankitg009]

Dear Nishant

 

You are mixing a certain amount of steam @ 18kg/cm2g and certain amount of condensate @ 25 kg/cm2g and getting steam again at 18 Kg/cm2 g. What is the basis of that. How did you came up with this?

[breizh]

hi ,

http://www2.spiraxsa...ting-theory.asp

Consider this link .

Make sure your data are accurate because your steam is far from saturation !

 

http://www2.spiraxsa...Properties.aspx

Good luck

Breizh

Edited by breizh, 22 May 2015 - 07:46 PM.

[ProcessEng_12]

Dear Nishant

 

You are mixing a certain amount of steam @ 18kg/cm2g and certain amount of condensate @ 25 kg/cm2g and getting steam again at 18 Kg/cm2 g. What is the basis of that. How did you came up with this?

Dear Ankit,

I myself had the same doubt. We checked the measuring instruments and calibrated but they showed the same. By the away Ankit the all the pressures are absolute.

Thanks

[Art Montemayor]

Nishant:

 

Pay careful attention to what Breizh is telling you.  You are obviously not thinking out the correct algorithm that you have to employ to do a mass & heat balance.  This is basic chemical engineering and you must correctly think out what is happening in the process.

 

For example, you cannot have "condensate" (which is assumed to be saturated) at 110 oC & 25 kg/cm2A.  I believe you have your thinking all wrong and you have to THROTTLE the 25 kg/cm2 down to 18 kg/cm2 so both can mix.  Is that correct?

 

Another important engineering concept that you are using in a wrong way is the spreadsheet as a tool.  Never use a spreadsheet to post basic calculation data in a text box!  That is totally ignorant of what a spreadsheet tool is for.  Use the cells to contain the data and use the spread sheet to do the calculations.  Post all your thermo data in another spreadsheet within the same workbook and refer to that data in your calculations.  That way you know your calculations are correct and accurate.

 

Refer to the attached revision of your spread sheet.  Do the calculations the correct way and don't use a spread sheet as a bulletin board with data in text boxes.

 Book1 Rev1.xlsx   18.32KB   88 downloads

[ProcessEng_12]

hi ,

http://www2.spiraxsa...ting-theory.asp

Consider this link .

Make sure your data are accurate because your steam is far from saturation !

Good luck

Breizh

Sir the 41kg/cm2a steam by Utility plant is supplied to nearly 14 plants in the site. It is very necessary for them to keep the steam superheated for long distance pipelines.To get the maximum heat from saturated steam that's why more amount of condensate is required.

Thanks for the link. It will be helpful. 

[samayaraj]

Dear Nishanth,

 

Look at the sample excel sheet used to calculate amount of conditioned steam required by using desuperheater. By knowing the amount of conditioned steam at required P & T, you can calculate the amount of superheated steam and condensate required. Already I have attached a excel sheet in this forum for your query regarding temperature of depressurized steam. Kindly look at the link http://www.cheresour...reducing-valve/

 

Use the above excel to analyze your problem by using various function as explained in the spread sheet. Since it has steam data inbulid already which makes you work very simple.

 

Kindly enable macros before using this spreadsheet.

Attached Files

•  7. Sam-Desupeheater Calc.xls   563KB   63 downloads

Edited by samayaraj, 22 May 2015 - 08:30 AM.

[ProcessEng_12]

Nishant:

 

Pay careful attention to what Breizh is telling you.  You are obviously not thinking out the correct algorithm that you have to employ to do a mass & heat balance.  This is basic chemical engineering and you must correctly think out what is happening in the process.

 

For example, you cannot have "condensate" (which is assumed to be saturated) at 110 oC & 25 kg/cm2A.  I believe you have your thinking all wrong and you have to THROTTLE the 25 kg/cm2 down to 18 kg/cm2 so both can mix.  Is that correct?

 

Another important engineering concept that you are using in a wrong way is the spreadsheet as a tool.  Never use a spreadsheet to post basic calculation data in a text box!  That is totally ignorant of what a spreadsheet tool is for.  Use the cells to contain the data and use the spread sheet to do the calculations.  Post all your thermo data in another spreadsheet within the same workbook and refer to that data in your calculations.  That way you know your calculations are correct and accurate.

 

Refer to the attached revision of your spread sheet.  Do the calculations the correct way and don't use a spread sheet as a bulletin board with data in text boxes.

Book1 Rev1.xlsx

Thanks sir I will keep in mind. I will use excel workbook in the way you told.

I looked into the condensate data. It was mistake on my part that I gave the 25kg/cm2a pressure of condensate which is the discharge pressure of condensate pump. It would be throttled due to condensate control valve (desuperheating control valve) which is normally 20% open.