Remove the suction scrubber from the compressor train 1

[boonchoo2211]

Hello all,
I am a mechanical engineer who change the working field to the process engineer. This is my first time for posting my question here.I have the suction scrubber installed between the 1st stage separator and compressor for natural gas system.

Is it possible to remove the suction scrubber from the system ?
Do I need to install any additional equipment between them?

Could anyone give me your idea please?

Thank you in advance.
Prutiew

 

[BigInch]

If you have any liquids in the suction stream, its a very bad idea to remove the scrubber.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[25362]

Prutiew, why were you thinking of removing the scrubber ?

 

[boonchoo2211]

I just wonder that why do we need the scrubber though we have the 1st stage separator installed upstream.

I know that the 1st will never work with 100% effeciency but I will install the heater or the coalescer instead.

Is this a good idea in order to save cost?

Prutiew

 

[Montemayor]

Prutiew:

I've posted my comments on your duplicate posting. It's very bad and totally wasteful to double (or triple) post. Which thread are we to respond to? One will probably get deleted - and we don't know which one.

You don't give any pertinent basic data (as seems to be the conventional case) and therefore we're going to amass a variety of responses - most of which don't apply because we're simply guessing.

Is this a natural gas field gathering and compressor application? If so, is the suction gas depleted of any entrained liquids prior to entering either the scrubber or the inlet separator? Have you checked the calculations for both vessels? Are either adequate for protecting the compressor (which I assume is a reciprocating type)? Are you with the operator company or the design company? What is the history or scope around the two vessels?

If you are confident that the compressor is protected by one of the separators (a scrubber doesn't "scrub" - it separates vapor/gas from a liquid), then by all means get rid of the redundent vessel. But you must find out if it is required. We can't do that for you; you haven't given us any basic data or scope of work. We don't even know why you find yourself with two vapor-liquid separators in series. This could be a necessity because one of them (the upstream vessel) acts as a slug catcher or is handling other side streams (or simply was introduced because the installing engineer didn't know any better - a prominant characteristic of field project today). We simply don't know why you have two vessels in series and each is - regardless of the name or title - designed to accomplish the same thing: protect the downstream compressor from liquids. Therefore, the ball is in your side of the court.

 

[25362]

It seems both devices operate on different principles.

Separators, working on inertial and impact forces, may knock out first the large droplets and may also have vanes to remove the smaller ones.

Typical dry "scrubbers" use centrifugal force and gravity in multiple cyclons.

If not adequately designed, both fixtures may suffer from re-entrainment.

 

[tickle]

Does the compressor have a recycle used for loading/unloading the compressor?

If the suction scrubber is removed then you may need to redirect the recycle stream to the inlet of the separator.

Installation of heater does not sound a good idea to me. Compression efficiency is better at lower temperatures. And you may limited by discharge temperature.

A coalescer would offer an increased separation, but at additional cost.

If it is not bust do not mend it. If there is a specific problem then ask it.

 

[madiazr]

I suposse that this compression is in a first stage of compresion, because a separator is upstream of suction scrubber. If that's true, in most cases condensation of water and hydrocarbon liquids happens because liquid carryover from the upstream separator or liquid condensation in the piping connection headers. In some system of gas injection to wells, the compression is in more than one stage and generally at high pressures the gas from a stage of compression is over saturation condition and condensates formation isn't likely.

If liquid are coming to the cylinders of compression, for a reciprocating compressor, the cylinder could be damaged due to extremely high temperatures. That is the reason for a suction scrubber is recommended at process inlet of compressors, regardless type of compressor.

But, you don't have enough information for further assistance.

Regards

 

[JLSeagull]

All natural gas compressors that I have seen have a suction scrubber for each stage.

 

[djack77494]

25362,
I've seen many devices called "Scrubbers" that do not use centrifugal force to effect the vapor-liquid separation. I'm accustomed to seeing Separators as devices that do a "rougher" separation; they are often horizontal vessels. Most Scrubbers I've seen are vertical vessels that have mesh and/or vane demisters. I admit, however, that this is a messy way of classification and would welcome better definitions.
Doug