Undesired emulsification

[Alexander R.]

Hi all,
I am on the look after the indutries and processes where undesired emulsification can take place. Our Company is developing low shear Equipment, primarly for the oil indsutry, where water and oil form emulsions which require later separation. We want to hear where else Our equipment can be helpfull. The main work principle of low shear Equipment is to reduce Level of turbulence during the fluid flow and thus redue droplet break up of the dispersed phase. This in turn would increase the efficiency of the separation Equipment as larger droplets flow faster to the phase Interface.
I would appreciate to hear what other industrial processes encounter separation issues of the Liquid-Liquid mixtures.
Thanks in advance.

 

[shvet2008]

Hi, Alexander R.

I've met an undesired emulsification in refinery and petrochemical.

1. Drains
The problem is related to closed drain system and drain vessel that is used to collect drains and separate it in 3 phases: light liquid (usually chemical or hydrocarbons), heavy liquid (usually water) and gas. Drain vessels usually has a baffle to separate liquids and very often it was a big problem. During draining through drain valves high pressure drop occurs. Operators usually has 4 phases in drain vessels: gas, light liquid, emulsion (stable) and heavy liquid. So designers usually has to apply guided level meters (an example) to measure 2 liquid-liquid interfaces.

Because of emulsion is stable it is accumulated in drain vessel and operator needs pump it from time to time to sewer system. Moreover when large quantities of drains come to drain system operator has no chance to separate liquids and needs pump this emulsion (unstable) straight to sewer system without settling. This situation is very undesirable and in my plant ecology service has made a lot of efforts to solve it without any result.

Because of drains usually contain solids and polymers only limited quantity of technologies can be used.

2. Crude oil desalting
In crude oil units before crude oil to be dryed in electro dehydrators it should (usually) be desalted (washed) with fresh water. Static mixers is used for this purpose. But the more effective this mixer is the worse dehydrator works. So sometime coalescer is used downstream of mixer to enlarge droplets.

Because of crude oil is crude and so contains solids, salts and asphaltenes only limited quantity of technologies can be used.

As I know crude oil washing is used also in gas and oil middle stream sector so this problem can be related not only refinery.

 

[Alexander R.]

Hi, shvet2008,

Thank you for the response.

As you mentioned high pressure drop across the valve is a common source for emulsification. Our original application of low shear valves are choke valves and control valve upstream gravity separators in the oil industry. When strong emulsification take place, efficiency of the separators is reduced and it becomes a bottleneck for the overall system.
Does the drain liquids in your plant have any additional treatment stages apart the drain vessel?

 

[shvet2008]

Hi, Alexander R.

Does the drain liquids in your plant have any additional treatment stages apart the drain vessel?

Usual refinery/petrochemical wastwater treatment system.

 

[moltenmetal]

Emulsification in crude oil desalting isn't as a result of accidental emulsion formation, it's as a result of a deliberate attempt to contact oil and water with one another.

You're looking to replace valves which are a cause of accidental emulsification because they're venting both oil and water. Sorry, but I don't have any examples of that for you.

 

[Alexander R.]

Hi moltenmetal,

Yes, I understand now the process of desalting. Nevertheless, effluent water shall carry over some of the oil with it, possibly in form of emulsion. This effluent water requires treatment. As I understood the waste water treatment facilities utilize pumps and valves in order to have control of the process. These pumps and valves would usually promote further emulsification if they transfer contaminated water. Am I correct?

 

[shvet2008]

Yes, you are correct. But it is not so big problem. For this purpose primary oil/water separators are used. For example google API separator, parallel plate separator (cross flow or downflow), daburt separator, hydrocyclone etc.

 

[Alexander R.]

It is exactly the current area of Application of our low shear Equipment. The efficiency of the separators depends upon the average droplet size of dispersed phase and the level of emulsification. On offshore platforms produced water is usually processed by hydrocyclones or flotation units. If gravity separators do not efficiently handle primary separation, significant percentage of oil is carried over to produced water treatment facility. Since the operators are bound to meet certain level of water quality prior the discharge, hydrocyclones can become the bootleneck for the whole plant if produced water from the API separators conatin too much oil.