Sizing a Steam Blowout quench tank 2

[jalongo]

I need to design a quench tank to accommodate approx. 200,000 lb/hr of steam used during piping blowout. What considerations should I consider? Blowout of line will last for approx. 30 min and I need to assure all steam is rendered safe. Any suggestions for size, capacity, nozzle orientation, vents etc?

 

[poetix99]

You have a good bit of energy to dissipate into a pool. Better have a big pool of water.

Using round numbers:
100000 lb of steam @ 1000 BTU/lb (latent heat of vaporization)
Allowing no more than 100F° temperature rise (I'll say more about this below)
==> 16000 cubic feet of water @ 70°F ( a 25x25x25 ft tank)

ADDITIONAL COMMENTS:
* Use a sparging tube (or a manifold of them) so as to distribute the steam discharge over more area. This is an important safety consideration.

* It is important to provide for a maximum water temperature during steam discharge: as the water temperature approaches saturation (i.e. 212°F or thereabouts), the steam will form larger "bubbles" at the discharge opening(s), which rapidly collapse. These mini thunder claps will have characteristic frequencies and can cause structural damage if they happen to excite mechanical resonant frequencies of your tank/piping system. This is an important consideration in "pressure suppression pools" (transient energy sinks) of nuclear reactors. I have used 170°F max temperature only as an example (to obtain a nice round number for rough calculations). If a sufficient amount of subcooling is maintained, the steam condensation is more rapid and the pressure spikes are not so large as to (likely) be a problem.

* You should discharge the steam nearer to the bottom than the top of the pool; you will get thermal stratification of the water, and less subcooling at the top of the pool.

* Unless you can ensure that the water will be cooled again before you experience a second discharge, you had better figure out how to accommodate another discharge with water that is too hot to condense more steam.

Although the considerations I've cited are real, I don't have some more of the specific numbers that would further assist you. Perhaps someone with practical, experience (in the nuclear industry, for example) will provide a post with the details that I have omitted.

 

[ChasBean1]

jalongo -

I've seen small tanks used on commercial building HP boiler systems (HP in the world I'm in now means these boilers operate at about 90 psig, give or take).

The blowdown tanks use a domestic water quench line - a thermostat on the blowdown separator senses blowdown temperature and quenches the stream by opening a solenoid valve on a domestic water line.

See:

http://www.cleaver-brooks.com/Accessoriesj.html

Might prevent you from having to buy a couple extra acres (and a mule) to perform the function you need. -CB

 

[poetix99]

There was another thing that I'd forgotten to mention in my first post:

You must provide something like a check valve, in the steam discharge pipe, near the discharge end, to prevent the quench water from being induced into the discharge pipe: Once the steam discharge is essentially completed, water can be induced into the pipe as the remaining steam is condensed. Depending upon residual steam flow rates (none or small), you will get a single, very dramatic, potentially damaging water-hammer, or a pulsating, "chugging" phenomenon of a rising and falling water column.

Not a good thing, either way.

A "vacuum breaker" in the steam discharge might be a good idea, as a supplement to the check valve.