Water supply for steam line. 2

[acr2003]

Hello,
We are designing a steam line and some debate has been risen regarding the amount of water that will supply our steam demand. We know how much steam we need to run our application (liters/hour), according to a specific flow that we need inside the equipment tha uses it, but the question now is how to calculate the amount of water to feed our boiler in order to get the amount of steam we need?
Could anybody give a detailed explanation, please?
Thank you in advance.
acr

 

[TBP]

One pound (or kilogram) of water into a boiler, will be one pound (or kilogram) of steam, when fully evaporated, except for blowdown. If you assume worst case blow down to be 10%, then for a 100,000 lb/hr boiler, you need to deliver 110,000 lbs per hour, plus bottom blow down - say 115,000 or 120,000 to be safe.

 

[abcmex]

I agree with TBP, and I would like to expand his explanation: as he said 1 kg water gives always 1 kg steam. The problem is the losses that your system will always have (theory vs. reality).
Let start with the easiest: Steam losses on the system (valve stems, leaky flanges, condensate traps).

The second group of water losses are induced by the purification system to feed your boiler with adequate water quality. This will depend on the quality of the water and the operation conditions of the boiler. For example a reverse osmosis system losses up to 25% of the incomming water.

The third group of water losses is created by the blowdown of the boiler. The water will evaporate and all salts will stay inside of the boiler. To aviod precipitation and other problems a part of the boiler water has to be disposed. Depending on the feed water quality you clould have around 10% but I have already seen more than this in Boilers operating only with softeners and no condensate return.

Kind regards

 

[acr2003]

Thanks abcmex and TBP for your fast an accurate response.
The detailed explanation about the points where I could loose steam has enable me to calculate in a more accurate way the amount of water I would need for our system. I am checking all the "leaking spots" , how much the purification would consume (we will use distilled water) and how is the boiler blow down. Based on that, I am also adding a security factor of 15%, just in case.
Thanks a lot once again

 

[yogibear1]

Among the useful tools is an enthalpy diagram for your system. This would show you all the ins and outs. I thought I would add another potential loss in steam generated but not recovered - steam soot blowers - they use a specific amount based on the number of sootblowers and frequency used; this steam which is lost to atmosphere - up the stack. Not everyone uses steam, some use high pressure air.

 

[GenB]

1GL/3.78 litters

1GL approx. 8.3 Lbs

1 lb of water = 1 lb of steam

so I would multiply the result x 2 to account for losses/leaks and blowdown.
ER