Boiler blowdown evaporation tank

[greg1961]

I would like to build tank for our boiler blow down
and use steam off of boiler to evaporate water.Any
ideas on this project?

 

[pmover]

greg1961,

the question is not clear to me. please clarify.

why use steam to evaporate water (in blowdown tank or ?)?

for low-pressure boiler systems - light industrial use:
typically, boiler blowdown water is very warm, above boiling temp at atmosheric pressure. when boiler is blowndown, the water will evaporate with the blowdown tank. typically, there is also a supply of cooling water to the blowdown tank to cool the water/steam to a point that is acceptable to waste water systems.
i trust this response helps.
please advise.
pmover

 

[greg1961]

Thanks pmover for reply. Let me give you some more info
We have 23 steam boilers 50-150 hp which run at an average
of 30 - 50 psi most used for heating a few for production processes. I need to achieve a 0% sewer discharge from these
boilers. The ph of boiler blowdown is 10-11, our permit allows only 6-9 ph. We had an equalization wastestream to neutralize the ph difference but a change of process has
eliminated the eq water thus creating current situation.
I am now researching different methods for complete evaportion of blowdown. Currently there are no flash tanks or blow down tanks used. I found some water evaporators fired by natural gas but would like to fabricate our own system if possible.Thanks for any ideas you may share.
Thanks
Greg

 

[pmover]

greg,

i've not encountered the described situation before, so i am at a loss as well.

brainstorming thoughts, a lined pond (problem with waterfowl and will likely need leak detection system), use a large above ground tank exposed to atmosphere to evaporate the water (depends upon atmosheric conditions+other environmental considerations), etc.

most likely, the most economical method is to neutralize the blowdown stream as previously accomplished. the other methods listed involved capital costs and environmental concerns (not that the previous method has env. conrns). i trust regulatory agencies shutdown the neutralization system.
good luck,
-pmover

 

[MJCronin]

greg,

The system that you are describing is being manufactured as a packaged unit by several vendors.

"Boiler blowdown" (continuous blowdown, only) is typically used to heat makeup water for the boilers.

try this website:

http://www.pennseparator.com/fsu.htm

Let us know what you decide.....

Good Luck

MJC

 

[KenA]

Greg1961,
Maybe I don't fully understand the system, but I am not sure whether you will ever be able to achieve your aim of 0% discharge. The purpose of thee continuous blowdown is to purge salts from the circulating boiler feed water to prevent scaling. Hence the blowdown will be saline (this is reflected in the pH). There are units available which will do a good job at further concentrating the blowdown by evaporation, but you will always end up with either a highly concentrated salt solution or (if you add a crystaliser) a solid waste.
for more info you could browse

http://www.ionics.com/products/membrane/WasteWater/Crystallization/EvapCrystall.htm

hope this helps!
K

 

[Joesteam]

I have seen zero discharge facilities that have water treatment facitlites that can clean the blowdown and use the cleaned water as make-up for the cooling towers. If you try to evaporate all of the water, you will only get lots of solids.
One way to greatly reduce your blowdown is to change the external treatment of the feedwater. This is probably more economical than using all of the energy needed to evaporate it.

 

[smile1]

greg1961,

I agree with Joesteam. If you are trying to get ZLD, then revising the external treatment is your only reasonable option. Of course you will still get liquid discharge from the pretreatment system, but the volume will be greatly reduced. Depending on the water quality, a WAC/SAC/SBA is most typical, RO is available.

A side benefit is near elimination of internal treatment. A good savings. You still need to limit cycles based on pressure, as I recall something like 100 for your pressure, so there is still some blowdown.

 

[22082002]

May be you can route the part of blowdown to cooling tower, of course you'd need to do salt(Ca/Mg/Phosphates) balance for both the boiler feed water and cooling water.
Generally cooling water can easily accept the purge from Boiler blowdowns. You can check this with some cooling water chemicals supplier like, Betz-Dearborn(name i think is changed recently, it's taken over by GE).
We did successfully recycled blowdown water in cooling water.