5 replies to this topic

[A mukherjee]

Hii everyone,
I have to design a steam sparger system.I am getting confused about the velocity restriction in the spargers.
In some document I 'm finding it should be lower than 4 cm/sec,Where as in document from MOTT corporation the restriction for non agitated system is 0.68m/sec.
Also from some document I am finding that the restriction of hole size is 3-8mm.
Can any one guide me regarding these confusions?

[katmar]

Is that velocity in the pipe section, or through the holes? Actually, in either case the velocities you have reported are extremely low. I cannot imagine a steam sparger like that. Perhaps the MOTT figure is for liquid/liquid spargers? The 4 cm/sec velocity is much too low for steam.

I cannot recall seeing a limitation on velocities before. In steam spargers I have seen two important criteria. The first is that the pressure down the pipe inside the sparger section should be low enough that all the sparger holes "see" virtually the same pressure and the flow through the holes is uniform. If uniform flow is not important to you then this requirement falls away. The velocity head can be important here as well. Perry has a good section on steam spargers and discusses velocity head restrictions.

The second requirement is that the holes should be small enough to make bubbles of steam that do not collapse too violently. This is the same cavitation you can get in centrifugal pumps. The size of the holes will vary with liquid and steam temperatures, flow rates etc. I have used 5 mm holes sparging 2 bar g steam into water at about 70C and the noise was not bad. The smaller the better, but you might be drilling thousands of holes. If they can be hydro or laser cut on a CNC machine it might be feasible to use these small holes.

[A mukherjee]

Thnx for ur reply.
4 cm/sec restriction is not from MOTT.It is from a separate document,i found in net.
MOTT has given a restriction of 135CFM/ft2.
Perry has got design of pipe distributor ,but it is not specific for steam.
Yes,all the velocity resrtictions are for holes.

[A mukherjee]

Can any one give further info about the design???

[Art Montemayor]

Mukherjee:

Katmar, as usual, has given detailed and valuable information to always keep in mind when applying spargers. I have always followed almost the same criteria in the field.

The method I have employed in the past when designing steam spargers for process operations is that I work with a dependable and recognized supplied of sparger equipment – specifically I try to apply sintered stainless steel elements because I have always obtained excellent results using this type of sparger equipment. This type of design is basically a cylindrical sparger element made of SS sintered metal. It is very porous and yields thousands – if not millions - of tiny bubbles in a very gentle and noiseless manner. This has always yielded an even, slow, and homogenous distribution of tiny steam bubbles that has had good results. I would recommend you contact Mott Corporation (or someone similar in experience) and work with them to apply such a sparger. You can also get the sparger fabricated in Nickel 200, Monel 400, Inconel 600, Hastelloy C-22/C-276/X and Alloy 20. I believe you will be satisfied with the results and the long life of the element.

[Dazzler]

G'Day A Mukherjee
Other contributors here have focused on sparge performance with regard to bubble distribution and resulting contact and mixing effectiveness, however I'm thinking also of some practical considerations to be sure it continues to work at any sort of effectiveness.

The nature of the bulk liquid needs to be considered - if it is a resin and the application is a batch reactor, if any liquid enters the sparge when the steam is off, the liquid need to be able to drain back out of the sparger between batches - ie have a couple of holes in the bottom of the ring for this.

If the steam or sparge gas may react, then what happens if the reaction occurs back in the sparge pipe - will it gum or blockup. Iv'e seen this effect over many batches block a sparge ring and lead to spoilage of batch quality. We had to get in a cut it out. We had to cut it because the sparge ring had not been made with some flanges so it could be easily disassembled and removed and repaired/cleaned.

Finally, as for orifice plates, often holes needed for process applications should not be less that 3mm as they may be prone to blockage. Depends on the application. We would even do this for steam applications. However, when there are ten's or hundred's of sparge holes this need not apply.

Dazzler