Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations IDS on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

cheap chemical to separate oil from water efficiently 4

Status
Not open for further replies.

tcchandran

Mechanical
Mar 26, 2004
3
Dear Friends

I am looking for a cheap chemical which can demulsify oil from water.The oil is petroleum based.

Any suggestion from you will be very helpful.

Thanks.

TC
 
Replies continue below

Recommended for you

Guess you need an antifoam. You could try Ondeo/Nalco to see what they can offer.
 
O/W macroemulsions can be destabilized by electrolytes. Try them first in the lab.
 
epoisses and 25362,
could you please elaborate on your replies and specify something in particular based on your experience. I am also intrested in a cheap demulsifier.
Thanks in advance.
 
To khan101. Emulsions differ, so do the surfactants used to break them. I've no direct experience on the subject. I was trying to raise an idea for you to check. You better describe the kind of emulsion you are trying to break, or destabilize, to get good advice. Heating has many times helped to break emulsions as well as foams. At the end, epoisses' suggestion may be the best approach.
 
tcchandran
We have used salt NaCl to break emulsions. You can use caustic to break water/ oil emulsions. You can also use a pressure shock. Like passing the emulsion through an orfice plate with a high pressure drop and then into a settling tank. As mentioned earlier sometimes temperature will break the emulsion.

Good Luck

StoneCold
 
Maybe it's possible to freeze the oil out of the water and have it essentially precipitate out?

TTFN
 
Khan, as 25362 wrote, it all depends on the emulsion you are trying to break. I have some experience with silicon-based antifoam from Nalco but I have no idea whether that works for you.
If you're looking for the CHEAPEST chemical, though, that would be carbon steel (at least per kg!), in the form of a large settling drum, which would do at least part of the job for you. :)
Antifoam costs somewhere in the order of 5-10$/kg if I remember correctly, and you obviously need an injection skid.
But once again, it all depends on what emulsion you have. If it is caused by very small particles, a fine filter (say 1 micron) may help a great deal too.
 

The importance of knowing what type of emulsion tcchandran and khan101 are referring to, can be exemplified by a typical W/O emulsion as it occurs during normal operation of IC engines.

In addition to the primary functions of lubrication, oils must also contend with various combustion products, mainly acidic gases, moisture, metallic catalysts, oxygen, partly oxidized chemicals and carbon particles. For this reason dispersant and detergent additives are formulated with the lube. Unfortunately, these and other additives, such as VI improvers, act as surfactants having a stabilising effect on foams and emulsions that may form under the high shear regime.

Typical demulsifiers for these W/O type of emulsions comprise more than one component, that must be attracted to the interface and have limited solubility in the bulk phase. Their greater affinity to the water-oil interface ensures that the stabilising molecules are displaced.

Another important feature they exhibit is a reduced inter-droplet repulsion, allowing the droplets to aggregate. The final demulsifying stage is typified by a decrease in interfacial tension and surface area. Apart from good filtration to remove the resulting concentrated solid and debris, stubborn emulsions require the application of a chemical at the final film-rupture stage.

It has been said that the skill of formulating a demulsifier is a "black art". In effect, the selection of an effective demulsifier relies on a "trial and error" approach, suplemented by some knowledge of what has worked before.

The rate of water coalescence is taken as a measure of the effectivenes of the product. Almost every class of surfactant has been found to exhibit demulsification properties.

The most commonly used products in motor oil formulations contain anionic surfactants (e.g. alkyl naphthalene sulphonates) and nonionic surfactants such as alkoxylated alkyl phenol resins and block copolymers of ethylene oxide and propylene oxide.

[smile]
 
Stonecold

Which is a better demulsifier Sod.Chloride or Caustic Soda?

Normally what doses would you recommend? In my case I am trying to separate oil from the water and not water from the oil.

Your suggestion will be most helpful.

Thank you

TC
 
Removal of small amounts of oil from boiler feedwater has been a major objective of steam plants during the age of reciprocating steam machinery with condensers.

Strong emulsions are formed with compounded oils and detergent oils. Separation is next to impossible by gravity separation or filtering. Chemical methods are complicated and expensive.

In practice, reasonable separation could be obtained by using only pure mineral oils, with no animal oil or detergent additives. Then the oil would float on the water surface and could be collected. Sponges, excelsior, or toweling filters would catch the oil. This system was installed on every Liberty Ship of WWII.

The reciprocating steamships of the last century developed methods to do away with oil lubrication of the steam cylinders altogether, just to avoid the problems of oil in feedwater.

Note that purchasing "non-detergent" oil does not usually mean there is no detergent in the oil, it only means that the oil did not meet the specification requirements for a better grade of detergent oil, and is therefore marketed as "non-detergent". I use straight Veterinary Grade mineral oil for applications where I need to collect traces of oil from the water.
 
We have an oil sand operation. In a nut shell, oil sand (7-10% HC) is mixed with hot water and steam in a tumbler and caustic is added to help in seperation. HC & water in the form of froth is taken out of tumbler and then fed to a settling vessel. Then froth comes out of top and water is removed from the bottom. Froth is mixed with naphtha to get the required consistency and fed to centrifuges to remove solids. The product is called Bitumen. Now this bitumen is fed to another centrifuge and a glycol based demulsifier is added for further water removal.... and the process goes on and on to make synthetic crude. So now you know that we use two types of demulsifiers (caustic and glycol based). Both of these cost us good amount of money and we are always looking for a cheaper version.
 
tcchandran
What you really need to do is get in the lab and do some experiments based on the information you have gained here.
As other have explained the "best" or cheapest separating agent will depend a lot on the actual process conditions and the oil to be separated. Try some of our ideas and then come back with more questions and more information if you do not like the results.

Goodluck
StoneCold
 
Have you considered using a coalescer? This might help by breaking up the emulsion in a mechanical way, and are commonly used for oil water separation systems.
 
Tcchandran:

Save yourself some grief and contact Nalco or GE Betz, to name two of many, and let them do the screening work for you to find the most effective, least expensive demulsifier for your system. As this technology is very mature, it should be a simple matter to satisfy your requirements.

Orenda
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor