Steam Injection Detail 3

[sshep]

I have a project to install a waste water steam stripper. The feed rate will be up to 400gpm to the top tray of the new stripper. I would like to use 0 to 2000pph direct steam injection into the feed as supplemental heat (i.e. after feed bottom interchange) to insure that the feed enters the tower near the boiling point.

At the bottom of the tower I want to inject 8000pph to 12000pph of steam into the tower sump below the liquid level. I think into the base is best, but feel free to comment on this decision if you think differently.

How to design the feed steam injection is not much concern to me (it will be a spool anyway) but the tower stripping steam injection seems like it would benifit greatly from a purposefully designed steam sparger (including avoiding hammers at start-up). I am asking for recommendations on steam injection equipment or design considerations for these applications.

Thanks, sshep

 

[cawse001]

I have recently selected, but not yet installed, the Komax Scepter for direct steam injection into an agitated slurry tank.

One thing to bear in mind is that the sparger has a diffuser head on the end, which is larger than the pipe size and hence your nozzle arrangement needs to accomodate this.

Given that your duty is water, you could also contact Spirax Sarco.

One of the advantages (at least for our duty) of the Komax unit is that air is not required to cushion the collapsing steam, which is a feature of many of these devices. I presume you also wouldn't want non-condensible gases in a steam stripper either.

Cheers,

Nigel

 

[katmar]

I have seen quite a few towers operate very successfully with simple ring spargers installed below the liquid level in the sump. The trick is to keep the holes in the sparger small to avoid noise and vibration as the bubbles collapse. We always used 3 mm (1/8 inch) holes, but it can turn out that you need lots of holes.

We put the holes on the bottom of the sparger to get best contact with the liquid and to allow the sparger to drain at shutdown. Hammer can still be a problem starting with a cold sump, and you have to start slowly. Once the unit is hot it is very quiet. I have not costed a sparger against a proprietary device, but I suspect the sparger would be cheaper.

We heated the feed in much the same way, with a straight sparger inserted coaxially into a widened section of the feed pipe. The piping design should ensure that the sparger is always flooded with feed on the outside.

 

[unclesyd]

We have used and have very good results using heaters and mixers from Komax. The Scepter mentioned by
Cawse001 is a very good tank heater by design but may work in your case. We replaced several sparger style steam injectors in solution tanks with the Scepter tank heater with outstanding results. Look at their steam injector spools.

http://www.komax.com/specs.html

 

[sshep]

Gentlemen,

Thanks for all your responses. It took a while to get back to this detail of the job, but now my situation is that we have ordered one 4" steam injector spool, and a set of Scepter heaters.

With respect to pricing (approx $6k), the injector spool seemed more costly than a homemade job and a bit more than I expected. On the otherhand it was pretty compact as I would have spooled out a longer heavy walled sacrificial piece with some sort of steam sparger or quill. In the end the cost was small in the context of the whole project so I went with it, and am quite happy that this is one less detail to worry about.

The Scepters for steam injection below the waterline of my tower were individually cheap, but rather than one large Scepter a set of four were recommended. One important reason given for this recommendation was noise. These Scepters could have been mounted either on a manifold inside the tower, or as individual inserts. It was decided that four seperate inserts connected by an external steam ring was preferred, so that was our final decision. The total cost for all four (including the double sided flanges for bayonet installation) was under $10k. Again in the big scheme this cost was less important than avoiding the hassel and potential problems of a homemade job such as katmar described- good description of design detail and rational by the way.

Anyway thanks for the assistance and recommendations. It is inquiries like this that make these forums very useful to me.

best wishes always,
sshep