Hydrocyclone Operations 1

[thiru4vino]

Dear Friends
I am working in a Oil Gathering center where hydrocyclone package (Petreco) was installed 5-6 years ago, but not utilised properly. The hydrocyclone and Deoiling vessel (Induced Gas Floatation Unit (Fuelgas)) are designed to handle, say 10000 BPD of oily water from a 3-ph separator whereas the maximum produced water continuously available is 2000 BPD. Design specs: 500 ppmv of oil (inlet) and 50 ppmv (outlet). Package was not brought to regular service since long for reasons stated as "Non-availability of minimum water flow required" and "Scaling inside hydrocyclones". I understand that both demulsifier & anti-scale injections were made available then. Now I am with a team that is asked to revive these units. I am a greenhorn to this area & need experts to opine on what need to be checked out before proceeding to line-up the system & also on how to optimise the system with less water.

 

[zdas04]

Hydrocyclone performance is very much dependent on the Reynolds Number, pressure, and temperature of the incoming stream. They tend to have a very narrow "sweet spot" where they work really well, and performance drops rapidly as you move away from the sweet spot either higher or lower. I saw hundreds of them installed in the early '80's and then removed before 2000. If yours was designed for 10,000 bbl/day and you're giving it 2,000 bbl/day then it is certain that you are way outside its sweet spot. I would expect emulsions, scaling, water in the oil, and oil in the water. You can kind of deal with the first two with chemicals, but the last two are tough.

I've seen several big hydrocyclones specified lately, and none of them had velocity control, temperature control, or pressure control. I don't think any of them are going to be roaring successes.

David

 

[DuncanM]

Depending on the set up of your Hydrocyclone vessels it may be possible to reduce their flow capacity by swapping out some individual hydrocyclones for blanks.

Zdas94 is correct in his statement that they are likely to be below minimum flow - below a certain rate the 'swirl' inside each hydrocyclone breaks down and they will not perform any separation. Max efficiency (removal of oil) is found at max flow rate.

10,000 bpd is a relatively small unit (depending on your available dP); is this a vessel with multiple hydrocyclones inside or a manifolded set of large hydrocyclones?

IG CFU units are tricky to set at the best of times; they can be very 'fussy' with gas rates and chemical regimes.

I'd suggest first step is to review your original doc package and check any flow curves which will help you determine if you are above minimum flow or not.

Second step would be to contact a hydrocyclone vendor. I know that Cyclotech (now part of MI-SWACO) would be able to offer advice & assistance. You could also try other vendors such as Alderly, Cameron, Merpro etc. Google is your friend here.

 

[zdas04]

DuncanM,
Welcome to the forum, if that post is any indication of what you plan to do here you'll be a welcome addition to eng-tips.com.

David

 

[DuncanM]

Thanks Zdas, I've been a lurker for long enough!

 

[thiru4vino]

Dear DuncanM & zdas04!

thanks for the info, let me check the doc as suggested, will come back if more details / understanding is required, further...

The package consists of 2 x 5000 BOPD of hydrocyclones and 1 x 10000 BOPD Fuel Gas induced de-oiler...

thanks again,

Thiru

 

[DuncanM]

2x50% - The Hydrocyclones will almost definitely be below their minimum flow.

The IGFU may work with reduced flow; some tweaks to the set up of it would probably help somewhat. You will find it is being asked to handle more oil than it was designed for as the hydrocyclones will not be doing anything other than acting as a coarse filter!

 

[thiru4vino]

Dear Friends!!
Coming again for details sought after demulsifier, that is used for breaking the oil-in-water emulsion. Will not the regular demulsifier that breaks water-in-oil emulsion help? how they differ and what could be a standard dosage for improving hydrocyclone performance?
Thanks for all your efforts and time,

yours truly
Thiru

 

[DuncanM]

Chillboy,

No, water-in-oil and oil-in-water combinations generally have differing chemical and electro-chemical reasons behind their emulsions, hence your regular demulsifier (water-in-oil) will probably not work on oil-in-water. An on-site bottle test using live fluid sample will help.

Dosages will vary with every application and fluid composition.

I would approach your chemical suppliers with the view to performing a field trial of various chemicals.

Also note that biocides, anti corrosion and oxygen scavenging chemicals can adversely affect separation of oil from water. In my experience turning off all chemical injection can yield better performance from mechanical separators!


Also, from your previous posts I think you are heading down the wrong avenue by looking at chemicals to perform your separation. I believe you will find better results in re-configuring your hydrocyclone vessels for lower capacity. Did you contact any vendors?

DM

 

[thiru4vino]

Dear Duncan

thanks for the info on the difference between the two. I am hearing for the first time and that too from first hand exp, that chemicals affect the performance from mech separators. This is new to me, as I am involved in the revival of a unit which is not operated for a long time with no proper records of previous operations. The available records say that scale inhibitor needs to be injected to avoid scaling and possible choking of suction strainers of product-effluent-water pump. I would like to take some cues from your above stated experience with chemicals and push them into our schemes of bringing the package back in line. thanks again
yours truly
Thiru