Cleaning and liquid contact with solids – Processes – Including regeneration – purification – recovery or separation...
Reexamination Certificate
1999-09-22
2001-11-13
El-Arini, Zeinab (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including regeneration, purification, recovery or separation...
C134S025100, C134S109000, C210S195100, C210S512100, C210S787000, C210S805000, C210S808000
Reexamination Certificate
active
06315837
ABSTRACT:
This is a national stage application of PCT/GB99/00334 filed Feb. 2, 1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to oil-sand separation.
2. Discussion of Prior Art
When crude oil is produced from an oil well, the production stream contains a mixture of oil, gas, water and solids (usually referred to as sand) in varying proportions. The oil, water and gas are separated from one another in one or more pressure vessels commonly known as production separators. If sand is present in significant concentrations, it settles to the bottom of the production separators, where it accumulates, reducing the efficiency of separation of the fluids. The sand is commonly removed by jetting of the production separator, whereby water is introduced into the base of the vessel at high pressure through multiple nozzles. The sand is fluidised to form a slurry and flows out of the production separator through sand outlets provided for the purpose. This sand is often contaminated with oil and needs to be cleaned before it can be disposed of. In addition, the jetted sand slurry, may also contain large quantities of dissolved gas which must be released. It is the aim of this invention to provide an efficient method and compact apparatus for removing this oil and gas.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a method of cleaning oil-coated sand wherein, in a first stage, a slurry of contaminated sand and water is delivered to a solid/liquid hydrocyclone which substantially separates the sand and water, the sand being directed to one, accumulator part of a pressure vessel in the form of a concentrated slurry and the water being directed to another, degassing part of the pressure vessel, the parts being divided by a barrier that ensures equal pressure in both parts but which prevents migration of the sand from said one to said other part, and wherein, in a second stage, accumulated sand in said one part is flushed therefrom and circulated back through the hydrocyclone and said one part in a cyclic manner, each passage through the hydrocyclone progressively releasing oil from the sand while the flush water circulated with it is directed to said other part of the vessel.
The first stage is carried out under high pressure with the recirculation channel used in the second stage isolated. The second stage is carried out under low pressure with further delivery of contaminated sand cut off.
The water directed to the second part of the pressure vessel is degassed, and having settled to allow any oil to form a surface layer, it may then be pumped back for re-use in the same production separator from which it came or in a production separator from which the next batch of slurry to be cleaned is delivered. The flow of released gas can be regulated to control the pressure in the pressure vessel, thereby controlling the flowrate of contaminated slurry fed to the pressure vessel.
In the second stage it will be preferred to use clean, water to fluidise the sand, which may be treated water originating from the production separators.
Generally, there will be a bank of hydrocyclones in parallel.
According to another aspect of the present invention there is provided apparatus for cleaning oil-coated sand by such a method, the apparatus comprising a pressure vessel divided into two parts by a barrier that allows communication between the parts near the top of the vessel, a solid/liquid hydrocyclone surmounting the vessel with its solid output by gravity into one accumulator part and its separated liquid output to another, degassing part, means for delivering a slurry of contaminated sand to the hydrocyclone, and recycling means for fluidising and circulating the contents of said one part back through the hydrocyclone, these delivery and recycling means being operable mutually exclusively.
Preferably, there will also be means for recycling liquid from said other part back to a production separator for use in forming further slurry of contaminated sand.
REFERENCES:
patent: 4159036 (1979-06-01), Wilson
patent: 4435196 (1984-03-01), Pielkenrood-Vinitex
patent: WO 92 19351 (1992-11-01), None
patent: WO 96 09895 (1996-04-01), None
Axsia Serck Baker Limited
El-Arini Zeinab
Nixon & Vanderhye P.C.
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