Inlet water for gas fired steam boiler

[SWMechanical]

Hi,

What are the requirements for the inlet water of a gas fired steam boiler?

Since impurities in water cannot be 100% removed, how to solve the scaling problem in the boiler?

Thanks,

 

[vpl]

What are the requirements for the inlet water of a gas fired steam boiler?

It depends... on your application and the water supply and how much tolerance you have. Some boilers are oversized enough that the employees don't need to worry about the mineral content of the water. Some plants are located in areas where the mineral content of the water is low enough that they don't have to worry about scale build-up. Some plants have the luxory of taking a unit off-line every so often for cleaning.

Since impurities in water cannot be 100% removed, how to solve the scaling problem in the boiler?

Maybe you can't remove 100% of the impurities ... but you can get it pretty darn close, depending on how much money you're willing to put into it. Also, just because you don't remove 100% of the impurities doesn't mean you will get scale buildup.

So are you wanting to know what steps to take to alter your boiler water input system to improve the water quality? Or are you wanting to know how to remove scale that's already there?

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[MJCronin]

SW...

This question has been around for 150 years

Read up..

http://www.watertreatmentbooks.com/water-treatment-boiler.asp

http://www.thermidaire.on.ca/boiler-feed.html

 

[toothless]

Generally the boiler feedwater purity specifications are a function of the boiler operating pressure. The higher the pressure (the higher the temperature) and thus the stricter the water requirements.

A google search should find the table that gives the BFW specs based on boiler pressure.

 

[SWMechanical]

Thank you all for you help.

I know that boiler water needs to be treated before going to the boiler.

The reason I am asking this question is that I asked for a quote from a water treatment unit vendor. And I was told that since the boiler pressure is low (at atmosphere pressure) and there is no blowdown to remove the impurities left in the water after water treatment as it does in high pressure steam generator/drum, there will be scaling build up in the boiler tube. The boiler we will purchase is a gas fired steam boiler.

The water to be boiled off is produced water separated from process gas. It has high content of Na and Ca, Mg, K, Cl, HCO3. I meant to ask to what content the water won't cause much scaling in the boiler so we don't have to spent too much money of water softening or clean the tube too often.

 

[rmw]

That is an ugly brew for boiler water.

rmw

 

[vpl]

I agree with rmw. You're in a "pay now or pay later" situation -- either you pay up front to clean up your water or you pay later to clean your boiler tubes (and possibly replace the boiler).

I know that a lot of nuclear reactors in the US have opted to impose stringent water control options up front -- after having faced replacing their steam generators (a steam boiler by another name). They basically try to get as close to demineralized water as they can get.

I think you need to do some economic analyses to figure out which is going to be cheaper. But I wouldn't be surprised if you could justify a lot of water treatment as compared to downtime and cost for cleaning or replacing the boiler.

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[SWMechanical]

Thanks everybody.

I talked to the water treatment vendor. He suggested we can use evaporator for our case. I wasn't very familiar with wastewater evaporator to avoild scaling. Is water treatment required for evaporator?

 

[rmw]

Oh yes, same problem, just shifted somewhat due to temperature differences, but scaling of evaporators due to impurities in the evaporated liquid is worth mega money to water treatment companies. The difference is that you are dealing with lower driving temperatures across the tube wall which may change the characteristic of the scale.

rmw

 

[screenzzzz]

Has anyone tried a household drinking water micro-filtration systems or slow sand filters or this, I also just found

http://www.virginpacificwater.com/esf.html

 

[chicopee]

Use a descaling agent. Contact your boiler chemical treatment "provider" for testing and treatment.

 

[vpl]

Has anyone tried a household drinking water micro-filtration systems or slow sand filters or this, I also just found

http://www.virginpacificwater.com/esf.html

For a commercial boiler? Nope

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[GenB]

feedwater and not inlet water.
economics! no one mentioned the size of the boiler.
if a small coffe pot or cappuchinomaker, a filter will do, and up the ladder cost adds up
for small boilers a cheap watetr softener will do.

 

[djack77494]

SW,
I agree with some of the earlier comments about this being quite ugly. What are you trying to do, generate steam or dispose of a waste water stream? I've never heard of combining the two and don't think you can do so successfully. And why don't you have blowdown? You ALWAYS have blowdown in a steam generator. That's how you limit the buildup of non volatile materials such as solids and salts. There's a lot in your postings that just ain't right.

 

[rmw]

I had a client quite a few years back that put a new mill manager in place and due to problems with nearby steam pollution due to overflow from the pond that the blowdown went to, he issued an edict to the boiler house that they were to cease blowing down the boiler. And, they did; after all, he was the boss wasn't he? (How nice it must be not to be burdened by facts.)

I made quite a bit of money off of that one when it all caught up with them. I've never seen anything so ugly. I think I could have paved the roads in his plant with that scale it was so tough (and plentiful).

rmw