Effect of Tie-in Recirculation Line to Water Skimmer

[123engr]

Good day All,

I am involved in a project whereby I need to transport a produced water from a flotation cell on a platform to another platform through a pipeline. The pumping system is designed to operate with a recirculation line for minimum flow protection of the pump. The operating pressure of the flotation cell is atmospheric pressure while the discharge pressure from the pump is 110 psig. The pump is designed for rated capacity of 25,000 BWPD and the minimum flow recirculation line is designed for 7,500 BWPD.

The challenge is that we cannot recirculate back into the inlet of the flotation cell because of the pressure challenge. My understanding is that if I reduce the downstream pressure from the recirculation valve to atmospheric pressure, I would choke the minimum flow required by the pump.

It was proposed that the recirculation line should be tie-in to the upstream equipment of the flotation cell which is the water skimmer. The primary function of the water skimmer is for oil recovery from the produced water from the FWKO/Coalescers. To achieve this, it was proposed that the line should be tie-in at the fluid inlet line to the watre skimmer. The water skimmer operates at 10 psig.

My challenge are as follows:
[ul]
[li]What is the impact of recirculating treated water to commingle with incoming fluid to the skimmer?[/li]
[li]What is the effect of the recirculation on the water skimmer operation?[/li]
[li]Is there any other location I need to consider to suit the recirculation line connection?[/li]
[/ul]

Please, I need your insights to solve this challenge.

(I learn daily)

I am what I am by His grace

 

[LittleInch]

This is probably posted in the wrong forum hence the lack of replies, but it also is quite difficult to follow. Can you sketch out the flow path and insert figures (pressure, flow) where appropriate.

However I am struggling to understand your comment "My understanding is that if I reduce the downstream pressure from the recirculation valve to atmospheric pressure, I would choke the minimum flow required by the pump."

On the face of it this is not correct. All it affects is the sizing of your control valve in that the downstream side has a pressure of nearly 0 psig (you need a small amount to flow from the valve back to the tank and the upstream side 110 psig. So there is either something missing in your explanaition or your control valve is undersized. I must admit I have assumed you are using a control valve, but you don't say what sort of device you are using to control the flow to 7,500 BWPD.

Clearly if you add more water to the incoming fluid you could affect the operation of the skimmer, but without a bit more info it is difficult to say.


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