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Centrifugal pump selection for dissolved gases on stream

Centrifugal pump selection for dissolved gases on stream

Centrifugal pump selection for dissolved gases on stream

(OP)
I would like to know about centrifugal pumps models and its suppliers address who are able to handle flows with up 70% vol gases, without cavitation.
Thanks.

RE: Centrifugal pump selection for dissolved gases on stream

The basis of all centrifugal pumps is the same and all centrifugal pumps fall under the same "rules of engagement."  While some seem to be able to bend the rules a little bit because of various factors (such as using an inducer), I do not think that your above scenario is even close to being suitable to any centrifugal pump.

Unless you run the pump at very, very low speeds (in which case you will get hardly nothing out of the pump), you will caviatate just about any centrifugal pump because of the offgassing that will occur at the impeller eye.  In addition, you will vapor bind the pump even if you are lucky enough to run without cavitation.

My advice is to reduce the concentration of dissolved gasses to less than about 5% and then you can start looking at centrifugals.

Regards,  
Tim S.

RE: Centrifugal pump selection for dissolved gases on stream

(OP)
Thanks Tim for your fast reply. Of course, I know the basic about pump's laws, but, in this case, I am looking for a special equipment that can be suitable to work well, without damage or failing in service. Some times, manufacturers (a few!) make special equipment(and expensive ones) to work under special conditions. I am looking for this special suppliers.

Thanks

Orama/Brasil (aombr@yahoo.com)

RE: Centrifugal pump selection for dissolved gases on stream

I believe you need a type of positive displacement pumps to handle the fluid you want. Depending on the flow rate several are available.

For low flows consider a diaphram pump.

For higher flows you might consider a pressure pump.

Several options more information about the system and I think you are right the problem has known solutions.

Regards,

Dan Price

RE: Centrifugal pump selection for dissolved gases on stream

There are specialized centrifugal pumps for handling paper stock which can handle some gas, but not the amount you are looking for.  Goulds, Ahlstrom and Kamyr make these "MC" pumps (for medium consistency stock).  They incorporate a connection near the impeller eye and a vacuum system to pull the gas off to avoid vapor locking, so they don't really pump the gas downstream.  

You might consider looking to the oil production industry for a suitable pump.  There are several types of positive displacement pumps that are capable of reliably handling multi-phase fluids which include oil, gas and solids.  One of these manufacturers is Moyno Pumps.  Their website, www.moyno.com, includes information on their product. Click on the "Products" button on the right and then look for the "Tri-Phaze" pump icon to get to the information.  Progressing cavity pumps will pump large volumes of gas with liquids.  In fact, the originator of the concept was trying to develop  a compressor.

Good Luck!

RE: Centrifugal pump selection for dissolved gases on stream

What would be if the charge pressure is high enough - would cavitation be still a problem?
TM

RE: Centrifugal pump selection for dissolved gases on stream

Cavitation, by itself, is not the only critical issue for a centrifugal pump here, although it would be a substantial problem.

As I understood the original question, it involved a multi-phase fluid which contained a very high volume (70%) of gas. How would you pressurize the suction of the pump sufficiently to dissolve all of the gas into the liquid?   It is this gas that creates the problem for any centrifugal pump because of their basic operating principal.  That is, the fluid enters the eye (center) of the impeller and is accelerated outward via centrifugal force along the impeller vanes.  Since the liquid phase is generally more dense than the gas phase, the centrifuge effect separates the two and "concentrates" the gas at the center of the impeller.  Eventually the volume of gas at the center is large enough to vapor lock the pump and fluid no longer enters the suction.  You can fiddle with this by removing the gas or improving the pump's ability to pass it (pardon the pun), but these efforts can only go so far.

Positive displacement pumps, on the other hand, are capable of and are routinely used to handle multi-phase fluids without damage or loss of performance.  

RE: Centrifugal pump selection for dissolved gases on stream

Depending on suction and discharge conditions you may want to consider a Liquid Ring Vacuum Pump.

These are centrifugal, relatively low head, machines suitable for 'pumping' wet gases.

There are plenty of manufactures who offer this type of machine. Search on google.com for 'liquid ring vaccum pumps'

RE: Centrifugal pump selection for dissolved gases on stream

There is one more option - use a knock-out pot or separation vessel to separate liquid from gas and a centrifugal pump UNDER the knock-out pot or vessel  ontrolled by a level switch in the pot/vessel.  The switch will turn the pump on at high level and off at low level.  

If the vented gas can be put back in the process and pressure balance the operation great, other wise try use it elsewhere in the process.  If it has to be discherged to atmosphere clean it up to best environmental requirements first.

The things I give away for free!!!!!!!!!!

Regards,

Mike S

RE: Centrifugal pump selection for dissolved gases on stream

Try to contact Sulzer, I know they have manufactured some MPP (multiphase pumps) for the Dunbar field operated by Total in the North Sea. They send the Oil,Gas and Water produced to another platform for pretreatment.
I think they only have a slug catcher and a suction scrubber where the Gas Liquid Ratio is tunned.

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