Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
1998-11-19
2001-01-16
Drodge, Joseph W. (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C095S016000, C095S187000, C095S228000, C096S242000, C096S244000, C096S281000, C210S101000, C210S511000, C418S005000, C418SDIG001
Reexamination Certificate
active
06174440
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device and to a method for processing a fluid comprising at least one fraction A to be separated by means of a two-phase compression device and a solvent phase which is selective towards the fraction to be separated.
2. Description of the Prior Art
It is well-known to process gases by contacting them with a solvent phase in absorption columns.
French Patents 2,605,241 and 2,616,087 describe processes for treating gases comprising acid gases and hydrocarbons by using physical solvents. These processes dehydrate these gases which separates the heavy hydrocarbons from the light ones and removes the acid gases from the hydrocarbons.
However, the methods described in the prior art have drawbacks, some of which are given hereafter:
during processing, part of the hydrocarbons can be co-absorbed in the solvent,
solvents are generally expensive products which are used in large amounts,
the processing units require many peripheral equipments which reduce the reliability of the system,
the contact columns are large in size,
they do not raise the pressure level of the fluids processed, for example in order to facilitate the transportation thereof or to increase the absorption power of the solvent.
SUMMARY OF THE INVENTION
The present invention consists in using a compression device allowing to mix and to dissolve the type A fraction(s) in a solvent phase while increasing the pressure level of the compressed fluids.
The invention is notably applied in cases where the fluid is a natural gas comprising acid gases to be removed, such as hydrogen sulfide H
2
S and/or carbon dioxide CO
2
, the acid gases representing fraction A.
In the description hereafter, the term “solvent” or the expression “solvent phase” both designate the same product capable of collecting constituents to be separated from a fluid, and which can be a physical or a chemical solvent.
Similarly, the term “fluid” refers to liquids, gases or to a mixture of liquid and gas.
The present invention relates to a device for processing a fluid F comprising at least one fraction A to be separated, the fraction to be separated being at least soluble in a solvent phase. The device comprises
at least one line for delivering the fluid F to be processed,
at least one line for delivering the solvent phase,
at least one two-phase compression device permitting the different phases of the fluid F and the solvent phase to homogenize so as to dissolve most of the fraction A in the solvent phase and to produce a mixture made up of a solution F
1
consisting of the solvent phase and of the fraction A dissolved in the solvent phase, and of a fluid F
2
depleted in at least most of fraction A,
at least one line for discharging the mixture,
a separation device provided with lines for discharging respectively solution F
1
consisting of the solvent phase and of fraction A, and fluid F
2
.
The delivery line(s) can comprise compression and/or pumping devices and the discharge line can be fitted with a cooling device.
The device can comprise a means located upstream from the two-phase compression device, which “mixes” the fluid to be processed and the solvent phase prior to feeding it into a line.
The compression device comprises for example at least two sections, a first section providing a mixture Mi with a pressure level Pi and a second section providing, from mixture Mi, a mixture Ms with a pressure level Ps, a line for discharging mixture Mi and a line for feeding a fluid Mi into the second part, the two sections being separated by a seal and the hydraulics of the two sections being mounted “back to back” for minimizing axial thrust stresses.
The device according to the invention can comprise a fluid processing and/or mixing unit, the processing and/or mixing unit being connected to the compression device by fluid delivery and discharge lines.
A heat-exchanger is for example included in the processing unit.
When a heat-exchanger is provided, the latter comprises for example a circuit for heat-exchanging, separation and recycling at least part of the two-phase mixture withdrawn from the two-phase compression device.
The device can comprise means for determining parameters linked with the fluid and/or the operation of the compression device and data computing and processing means capable of changing the rotating speed of the two-phase compression device and/or acting on the efficiency of a refrigeration device and/or on the flow rate of the fluid recycled to the cooling circuit.
The present invention also relates to a method for separating at least one fraction or constituent A from a fluid F by using a solvent phase selective towards the fractions to be separated. The fluid F and solvent phase S are sent to a two-phase compression device under conditions which dissolve the fractions A to be separated in the solvent phase and provide a mixture of fluids made up of a solution F
1
consisting of the fractions to be separated dissolved in the solvent and a fluid F
2
freed from at least most of fraction A.
According to an embodiment of the method, solution F
1
consisting of the solvent phase and of the dissolved fraction A can be separated from the rest of fluid F
2
free from at least most of fraction A, and fluid F
2
can be recycled at least partly upstream from the two-phase compression device.
The method can comprise at least one stage of withdrawal of at least part of the mixture of fluids after compression through a number of stages m of the twos phase compression device, a stage of processing the withdrawn part and a stage of feeding the processed withdrawn part back, after processing, to a stage of the compression device of a higher order than the order of the withdrawal stage m.
The fluid and/or a fluid such as part of the two-phase mixture withdrawn and/or part of the liquid phase extracted from the two-phase mixture withdrawn or at least part of the liquid coming from the two-phase compression device for example is treated and the treated fluid is recycled to the fluid extracted from the two-phase compression device.
The treatment maybe exchanging heat, refrigeration or heating.
The flow rate of the amount of solvent phase can be controlled as a function of the fraction A to be separated.
The solvent phase can be regenerated and recycled to the inlet of the two-phase compression device.
An aqueous phase is for example used as a liquid solvent phase.
According to another embodiment, the rotating speed of the compression device is for example controlled.
The device and the method can be advantageously used for processing a fluid comprising a physical solvent phase, acid gases and a minor fraction of hydrocarbons in order to recover the minor fraction of hydrocarbons.
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Charron Yves
Rojey Alexandre
Antonelli Terry Stout & Kraus LLP
Drodge Joseph W.
Institut Francais du Pe'trole
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