CA1293468C

CA1293468C - Treatment of slop oils

Info

Publication number: CA1293468C
Application number: CA000581392A
Authority: CA
Inventors: Michael A. Kessick
Original assignee: ALBERTA ALKALI PETROLEUMS LIMITED
Current assignee: ALBERTA ALKALI PETROLEUMS Ltd
Priority date: 1988-10-26
Filing date: 1988-10-26
Publication date: 1991-12-24
Anticipated expiration: 2008-12-24

Abstract

ABSTRACT OF THE DISCLOSURE

Slop oils, both refinery and field, are treated to recover oil therefrom. The water-in-oil emulsion of the slop oil first is inverted to an oil-in-water emulsion by contact with a non-ionic surfactant and oil is removed from the oil-in-water emulsion.

Description

3~6~1 TREATME~T OF SLOP OIL
~he present invention relates to the treatment of slop oil for the recovery of oil therefrom.
Refinery slop oil, particularly from heavy oil refineries, typically comprises desalter cuff and residue from solvent extraction, in the form of a water-in-oil emulsion, which may range from 10 to 9~% in BS&W
content. Field slop oil i5 similar but tends to have less calcium soaps. The aqueous component often is in the form of brine.
Owing to its high viscosity, high BS&W slop oil cannot be cleaned by centrifugation, even after addition of as much as 30~ diluent. The stability of the emulsion is believed to be caused by a significant content of calcium and possibly iron soap type surfactants that are probably calcium and iron salts of asphaltic acids.
In accordance with the present invention, it has been found possible to invert the water-in-oil emulsion of slop oils to an oil-in-water emulsion by contacting the slop oil with at least one non-ionic surfactant.
~ Once inversion of the emulsion has taken place, oil may ; be recovered from the oil-in-water emulsion, for example, by centrifugation.
It usually also is desirable to raise the pH of the emulsion following contact with the non-ionic surfactant, usually to at least about 12, using any convenient alkalinating agent, such as aqueous sodium hydroxide. In this way, solid or semi-solid particles that stabilize the water droplets in the water-in-oil emulsion become highly negatively charged and disperse into the continuous water phase of the inverted emulsion.
Depending on the source of the slop oil, some pretreatment may be desirable to promote inversion of the water-in-oil emulsion. For field slop oils, simple dilution with brine or water is sufficient and may not be required for dilute slop oils. For refinery slop ~k .

3~

oils, treatment with aqueous sodium carbonate solution prior to contact with the surfactant, usually at elevated temperature, promotes the inversion.
It is believed that the sodium carbonate reacts with calcium soaps in the water-in-oil emulsion to form calcium carbonate and sodium soaps, driven by the low solubility of calcium carbonate. The sodium soaps so-formed tend to stabilize oil-in-water emulsions, so that the system inverts to a water-thin oil-in-water system.
The washing of the slop oil by the sodium carbonate solution may be effected in any convenient manner, for example, by simple mixing of the sodium carbonate solution and then heating the mixture to an ele~ated temperature. The temperature generally is above about 60C, typically about 80C.
A preferred procedure involves an initial reaction of sodium carbonate with the slop oil followed by triggering inversion to the oil-in-water emulsion by subsequent addition of water containing a small amount of surfactant.
The lower viscosity which results when the water-in-oil emulsion inverts to form the oil-in-water emulsion enables the emulsion to be centrifuged which, combined with the lesser effectiveness of the sodium soaps as emulsifiers, results in the emulsion breaking.
The soap-type materials and any clays and minerals are removed as a solid phase, which may be further processed by centrifugation, with or without chemical addition, as required.
The oil phase can be recovered from the agueous phase such as by skimming, and subjected to further cleaning, if necessary or desired, or may be returned to the refinery stream. The aqueous phase may be disposed of or reused.
As noted earlier, another procedure which can be used to separate the oil from the oil-in-water emulsion is to adjust the pH of the emulsion to a highly alkaline value, typically about 12, and then permit the emulsion to stand for an extended period for the oil to separate ~ ~93~6~3 out into a discrete layer. Separation of the discrete oil layer may be speeded up by centrifugation.
The amount of water added to the slop oil, in the form of aqueous non-ionic surfactant solution and sodium carbonate solution depends on the water content of the slop oil itself and may range from about 10 to about 60 wt.% of the 510p oil.
The amount of surfactant required to form the oil-in-water emulsion in accordance with the invention varies depending on the sur~actant used and the quantity of oil present in the slop oil. Typically, about 0.025 wt.% of non-ionic surfactant is sufficient.
Higher molecular weight members of the alkyl phenyl polyethoxyethanol series of non-ionic surfactants having a cloud point above 100C are more effective than lower molecular weight members. Typical examples of useful non-ionic surfactants are those sold under the trademarks Triton X-405 and Igepal C0-897.
The invention is illustrated by the following Examples:
Example l 200 ml of a refinery slop containing about 70% BS&W
was added to 200 ml of water containing 0.4 g of sodium carbonate and 0.1 g of Triton X-165. On stirring the mixture at 80C, an oil-in-water emulsion formed in about 1 minute. The emulsion was stirred for l hour at 80C and then centrifuged at 1900 g for 30 seconds.
A typical 40 ml quantity produced 2.0 ml of solid phase, 12 ml of an oil phase and 26 ml of an aqueous phase. The oil phase was formed to have a BS&W content of less than 25%. Further centrifugation of the oil at about 60C at 1900 g for 30 seconds after addition of 20% diluent, decreased the BS&W content to less than 1.0%.
Example 2 400 g of refinery slop oil containing about 70%
BS&W was reacted with 40 ml of a 6~ solution of sodium carbonate for ~ hour at 80~C with stirring. 160 ml of water containing 0.1 g of Triton X-405 then was added.

~ ~ Z~346~3 Upon stirring, the emulsion inverted to an oil-in-water one. After a further ~-hour stirring, the oil-in-water emulsion was centrifuged for 30 seconds at 1900 G, causing separation of a solids phase. The liquid layer was decanted from the solids and placed in a containment ; vessel where it further separated into an oil layer and a water layer. After standing for two hours, the oil layer was found to have a BS&W content of less than 10%.
Example 3 10The procedure of Example 2 was repeated using Igepal 897 as the non-ionic surfactant. Following addition of the Igepal 897, the mixture was stirred for 10 minutes and the pH of the oil-in-water emulsion was adjusted to about 12 with the addition of sodium hydroxide and stirred for another 10 minutes.
On quiescent standing at 80 to 90C for twelve hours, the mixture separated to provide greater than 90%
recovery of a clean oil layer ~less than 0.5% BS&W), a water layer and a solids layer.
Example 4 200 ml of field slop from a heavy oil recovery project was inverted to an oil-in-water emulsion by agitation at 80c with an equal volume of 4% brine containing O.lg of Igepal CO 8~0 surfactant. The pH of the system was raised to 12 by addition of sodium hydroxide and agitation was continued for a further two minutes. Centrifugation of a sample at l900g for 30 seconds then caused separation of a solid phase and two clearly defined liquid phases. The upper oil phase was found to contain less than 0.5% BS&W.
In summary of this disclosure, the present invention provides a novel method of treatment of slop oils by treatment with non-ionic surfactants to cause emulsion inversion, followed by oil r~covery from the resulting less stable oil-in-water emulsion.
Modifications are possible within the scope of the invention.

Claims

1. A method of treatment of slop oil to recover oil therefrom, which comprises:
contacting said slop oil with at least one non-ionic surfactant to form an oil-in-water emulsion, and removing oil from said oil-in-water emulsion.

2. The method of claim 1 wherein said oil removal step includes raising the pH of said oil-in-water emulsion to about pH 12 to form a coalesced oil phase, and removing said coalesced oil phase.

3. The method of claim 2 wherein said slop oil comprises a water-in-oil emulsion having a BS&W content of about 10 to about 90%.

4. The method of claim 1, 2 or 3 wherein said slop oil comprises refinery slop oil and said refinery slop oil is contacted with sodium carbonate prior to contact with said non-ionic surfactant.

5. The method of claim 1, 2 or 3 wherein said slop oil is field slop oil and said field slop oil is diluted with brine or fresh water prior to contact with said non-ionic surfactant.

6. The method of claim 1, 2 or 3 wherein said slop oil is refinery slop oil and said refinery slop oil is contacted with an aqueous sodium carbonate solution at a temperature above about 80°C.

7. The method of claim 1 wherein said oil is removed from the oil-in-water emulsion by centrifuging said oil-in-water emulsion to break the emulsion and form a coalesced oil phase, and separating the coalesced oil phase.

8. The method of claim 1, 2 or 3 wherein said slop oil is diluted with an aqueous medium in an amount of about 10 to about 60 wt % of the slop oil during or prior to said contact with said non-ionic surfactant.

9. The method of claim 1, 2 or 3 wherein said non-ionic surfactant is contacted with said slop oil in the form of an aqueous solution thereof.

10. The method of claim 1, 2 or 3 wherein said non-ionic surfactant is contacted with said slop oil in the form of an aqueous solution thereof and said non-ionic surfactant is an alkyl phenyl polyethoxyethanol surfactant having a cloud point above about 100°C.