WO2015107539A2

WO2015107539A2 - System and method for treatment of flash vapours sent to a crude distillation column

Info

Publication number: WO2015107539A2
Application number: PCT/IN2014/000767
Authority: WO
Inventors: Shenbaga Murthy NAGARATHINAM; Navinchandra TALATI MAYUR; Abhishek Jha; Paras Navinbhai SHAH; Yash GUPTA
Original assignee: Reliance Industries Limited
Priority date: 2013-12-18
Filing date: 2014-12-10
Publication date: 2015-07-23
Also published as: WO2015107539A3; IN2013MU03954A; TW201542803A

Abstract

A system and method for treatment of crude hydrocarbon vapours generated from a pre-flash drum, prior to sending these vapours to a distillation column, is disclosed. The crude hydrocarbon vapours are cooled and condensed in a condenser unit, and the immiscible phases are separated in a separator unit into an aqueous phase, a liquid hydrocarbon phase, and a light hydrocarbon containing vapour phase. The light hydrocarbon containing vapour phase and the immiscible liquid hydrocarbon phase are conveyed to the distillation column, whereas the immiscible phase may be further treated to remove dispersed water droplets. Water and salts are removed from the vapours which reduces the water dew point as well as NH₄C1 de-sublimation temperature at the column overheads. The system and method thereof reduce corrosion problem in the distillation column and simultaneously provide favorable product slate from the given crude blend.

Description

SYSTEM AND METHOD FOR TREATMENT OF FLASH VAPOURS SENT TO A CRUDE DISTILLATION COLUMN

FIELD OF DISCLOSURE

The present disclosure relates to the field of crude oil treatment. In particular, the present disclosure relates to a system and a method for treatment of pre-flash vapours sent to a crude distillation unit.

DEFINITIONS

As used in the present disclosure, the following words and phrases are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used to indicate otherwise.

CDU OH - Crude Distillation Unit, Over Head Unit is a part of the crude distillation unit.

Water dew point - Dew point is the temperature at which water vapour condenses into liquid water at a given pressure. It corresponds to saturation temperature of the pure water at given partial pressure of water in a stream. H₄CI de-sublimation temperature - The temperature at which NH₄CI changes from a gaseous state to a solid state.

Naphtha end point - Naphtha end point is the temperature at which the last drop of Naphtha evaporates at atmospheric pressure.

NH₃ ingress - Entry of NH₃ into the particular section of the crude distillation unit.

Cold Reflux - Cold Reflux is defined as the reflux that is supplied to the crude distillation unit at a temperature which is well below the temperature at the top of the crude distillation unit as it is supplied from the receiver downstream of the air condenser unit or air cooler unit.

BACKGROUND

A Crude Distillation Unit, (CDU), in a petroleum refinery fractionates the crude oil into various fractions/cuts like unstabilized naphtha, jet fuel, diesel, heavy diesel and long residue based on boiling points.

Corrosion is a major problem in the CDU Overhead System (CDU OH system). The CDU overhead system comprises top trays inside the column, dome section, external piping, air cooler and/or air condenser unit and receiver vessel. Crudes which come from different sources into the CDU have different impurities. These impurities include inorganic chlorides, amines, organic acids, surfactants, etc. as well as those species that get picked up during processing namely NH₃, Phenol, HCN, Oxygenates, SO₃, NO₃, etc. Opportunity crudes also bring in undesired species such as chemicals (CS₂, MeOH, etc.) used in upstream crude gathering centre. These salts, dissolved in water, electrochemically react with the equipment material and result in severe corrosion and irreversible weakening of the equipment.

Before entry into the CDU, desaltation of crude is conducted by passing it through a desalter. The major content of the salts (chlorides of sodium, magnesium and calcium) along with water get removed at this step. The desalted crude then passes into the pre- flash tower which improves crude preheat and in turn the off-load charge heater duty.

Traditionally, a pre-flash tower is placed downstream in the crude treatment system. Residual water remaining in the desalted crude along with other basic species / impurities end up in the flash OH vapours and then pass into the crude distillation unit and finally into the CDU OH system. The fractionator top section (vapours leaving that tracks Naphtha end point) is, hence, operated well- above (by a margin of 10 to 20 °C) the water condensing temperature (dew-point) and NH₄C1 de-sublimation temperature to avoid corrosion by de-sublimation of these salts along with water.

Operation of fractionator top section at higher temperature leads to increase in Naphtha cut which eventually results in decreased Jet fuel cut. Maintaining both the margins and still getting desired naphtha end point by the single variable (pressure compensated temperature at column top) is quite challenging and that too when crude mix changes substantially. Any decrease in the required high temperature at the fractionator top section offers more elbow to operation at enhanced reliability, to gain better control on naphtha end-point despite vagaries in crude mix, i.e. crude mix with lower naphtha content. As such, lower production of naphtha is economical as it correspondingly increases high value Jet yield.

US Patent Nos. 2310837, 3779905, 20080319240, and 6159374, and JP Patent No. 3692449 relate to systems and methods for reducing corrosion in crude oil distillation units by removing corrosive impurities by addition of corrosion inhibitors, amine scavenging chemicals, or salt removing agents at the crude distillation unit. Although these patent documents show the use of external wash water with aqueous ammonia solution or use of filming amine for neutralization or partial elimination of basic species/ impurities, they remain silent about the elimination of water during the process steps. Moreover most of these patents suggest corrosion inhibition or prevention in the CDU OH pipelines and downstream equipment but remain silent about any dew point reduction achievement and do not address corrosion prevention in the CDU-OH system, inside the column (i.e. top section trays and dome). Thus, any system which could remove basic species/impurities along with water portion effectively from the feed itself without using costly chemicals and in turn reduce dew point temperature in crude distillation unit top section to obtain increased high value jet yield is desirable. OBJECTS

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:

An object of the present disclosure is to provide a simple, safe and economic system and method to prevent corrosion of the crude distillation overhead system (CDU OH system).

Another object of the present disclosure is to eliminate cold end corrosion potential by enabling 'zero' cold reflux in the main column.

Still another object of the present disclosure is to segregate acidic and basic species to prevent formation of salts in the main column top trays/dome.

Another object of the present disclosure is to provide reduction of water dew point as well as NH₄C1 and amine chlorides de-sublimation temperature at fractionator top section through simultaneous prevention of water ingress and NH₃ and water soluble amines entry into the CDU OH system.

Another object of the present disclosure is to restrict naphtha end point in-line with the downstream user need and for increasing Jet fuel yield.

Another object of the present disclosure is to maintain the main column reliability and provide insulation from impacts of processing of most opportunity crudes.

Another object of the present disclosure is to provide significant reduction in the overhead system pressure drop which helps to lift more distillate from a given crude mix. Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.

SUMMARY

The present disclosure relates to a system for treatment of crude hydrocarbon vapours generated from a pre-flash drum, prior to sending said vapours to a crude distillation column, said system comprising:

• a condenser unit for cooling and condensing said vapours into a stream containing immiscible phases; and

• a separator unit for receiving the said stream and separating said stream into an aqueous phase, an immiscible liquid hydrocarbon phase, and a light hydrocarbon containing vapour phase.

The system of the present disclosure may include a coalescer unit for receiving said immiscible liquid hydrocarbon phase, for separating dispersed water droplets from said immiscible liquid hydrocarbon phase to produce a substantially water free liquid hydrocarbon phase. The coalescer unit of the present disclosure may comprise a coalescing media.

Preferably, in the system of the present disclosure, said condenser unit, said separator unit and said coalescer unit are respectively arranged in series between said pre-flash drum and said distillation column.

The said light hydrocarbon containing vapour phase and said liquid hydrocarbon phase from said separator unit may be conveyed through a one or more conduits to the said distillation column. Preferably, the said substantially water free liquid hydrocarbon phase from said coalescer unit may be conveyed through a second conduit to the said distillation column.

Additionally, the system of the present disclosure may include a heater for receiving said substantially water free liquid hydrocarbon phase from said coalescer unit to produce a heated liquid hydrocarbon phase. The said heated liquid hydrocarbon phase from said heater may be conveyed to the said distillation column. A heating arrangement may also be considered for light hydrocarbon vapour phase before conveying it through a third conduit to the distillation column.

The present disclosure also relates to a method for treating crude hydrocarbon vapours generated from a pre-flash drum, prior to sending said vapours to a crude distillation column, said method comprising:

• cooling and condensing said vapours in a condenser unit to produce a stream containing immiscible phases; and

• receiving said stream in a separator unit and separating said stream containing immiscible phases into an aqueous phase, an immiscible liquid hydrocarbon phase, and a light hydrocarbon containing vapour phase.

The method of the present disclosure may comprise the step of coalescing said immiscible liquid hydrocarbon phase in a coalescer unit for separating dispersed water droplets and producing a substantially water free liquid hydrocarbon phase.

For the method of the present disclosure, the condenser unit, the separator unit and the coalescer unit are operated at a temperature ranging from the pre-flash drum temperature (160 to 190 °C) to an ambient and a pressure ranging from pre-flash drum pressure (4 to 6 bar g) to CDU column pressure slightly above the atmospheric pressure. The method of the present disclosure may comprise the step of conveying said light hydrocarbon containing vapour phase and said liquid hydrocarbon phase to said distillation column.

The method of the present disclosure may comprise the step of heating said liquid hydrocarbon phase in a heater to produce a heated liquid hydrocarbon phase.

The method of the present disclosure may comprise the step of heating said light hydrocarbon containing vapour phase in a heater to produce a heated liquid hydrocarbon phase.

The method of the present disclosure may comprise the step of conveying said heated liquid hydrocarbon phase to said distillation column.

The method of the present disclosure may comprise the step of treating said aqueous phase from said separator unit in a sour water treatment unit.

The method of the present disclosure may comprise the step of treating said separated water from said coalescer unit in a sour water treatment unit.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The system and method for treatment of a fluid stream with different components in a crude distillation unit will now be described with reference to the non-limiting, accompanying drawings, in which:

FIGURE 1 illustrates a treatment of a crude oil in the prior art; and

FIGURE 2 illustrates treatment of crude oil in accordance with the present disclosure. DETAILED DESCRIPTION

A preferred embodiment will now be described in detail with reference to the accompanying drawings. The preferred embodiment does not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.

The embodiment herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiment in the following description. Description of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiment herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiment herein may be practiced and to further enable those of skill in the art to practice the embodiment herein. Accordingly, the example should not be construed as limiting the scope of the embodiment herein.

FIGURE 1 of the accompanying drawings illustrates prior art crude oil treatment method.

Crude oil being conveyed through a conduit 24 is passed through a hot pre-heat train 2 to produce pre-heated crude oil through a conduit 26. The pre-heated crude oil from the conduit 26 is then desalted by passing through a desalter 4 to produce desalted crude oil through a conduit 28. The desalted crude oil through the conduit 28 is heated in a warm pre-heat train 6 to produce heated crude oil which is conveyed through a conduit 30. After passing through the warm pre heat train 6, the heated crude oil from the conduit 30, which is at a temperature between 160°C to 190°C is sent to a pre-flash drum 8, which is maintained at a pressure between 4 to 6 bar.

Flashing occurs in the pre-flash drum 8, where the crude hydrocarbon vapours and the crude hydrocarbon liquid are separated and are conveyed through conduits 74 and 54 respectively. The pre-flash drum 8 includes a pressure control 52 to control the pressure of the pre-flash drum 8. The crude hydrocarbon vapours through the conduit 74 are directly conveyed to the crude distillation column 22, without any treatment. The crude hydrocarbon liquid which is conveyed through the conduit 54, comprises a hydrocarbon range generally greater than C₈, is conveyed through a hot pre-heat train 18 to obtain a pre-heated crude hydrocarbon liquid through conduit 56. The temperature of the preheated crude hydrocarbon liquid which is conveyed through the conduit 56 is between 240°C - 260°C. The pre-heated crude hydrocarbon liquid through the conduit 56 is received at the furnace 20, where the furnace 20 further increases the temperature of the crude hydrocarbon liquid to 370°C - 395°C to provide heated crude hydrocarbon liquid which is conveyed through a conduit 58. The heated crude hydrocarbon liquid conveyed through the conduit 58 is introduced at the crude distillation column 22.

The prior art does not provide any treatment to the pre-flash crude hydrocarbon vapours which are directly fed at the crude distillation column 22 through the conduit 74.

The fractionation of the heated crude hydrocarbon liquid which is conveyed through the conduit 58 and the pre-flash crude hydrocarbon vapours which are conveyed through the conduit 74 in the distillation column 22 provides the fractions - gas and naphtha, light kerosene, heavy kerosene, diesel, heavy atmospheric gas oil through conduits 60, 62, 64, 66 and 68 respectively. Residual crude oil is sent to the Vacuum Distillation Unit (VDU) through a conduit 70.

FIGURE 2 of the accompanying drawings illustrates a system for crude oil treatment in accordance with the present disclosure.

In accordance with the present disclosure, the pre-flash crude hydrocarbon vapours which are conveyed through the conduit 74 generated at the pre-flash drum 8, are treated prior to sending the vapours to the crude distillation column 22. Crude Oil through a conduit 24, having full hydrocarbon range and being at a temperature between 30 - 80 °C, is conveyed through the cold pre-heat train 2 to produce pre-heated crude oil from the conduit 26 having temperature between 140 °C - 160 °C. The pre-heated crude oil from the conduit 26 is desalted in the desalter 4. The desalted crude oil from the conduit 28 is passed through the hot pre heat train 6 to provide a heated crude oil from the conduit 30 having temperature between 160 °C - 190 °C. The heated crude oil from the conduit 30 is received at the pre-flash drum 8. At the pre-flash drum 8, the heated crude oil from the conduit 30 is split into crude hydrocarbon vapours and crude hydrocarbon liquid which are conveyed through the conduits 74 and 54 respectively.

The crude hydrocarbon vapours from the conduit 74 are received at a condenser unit 10. The condenser unit 10 provides indirect media for cooling and condensing the crude hydrocarbon vapours that are conveyed through the conduit 74 to produce immiscible phases containing stream from a conduit 34. The condenser 10 can be either an air cooler or water cooler or any other cooling and condensing device or any combination thereof. The immiscible phases containing stream produced at the condenser unit 10 are received at a separator unit 12 through the conduit 34. In the separator unit 12, said stream from the conduit 34 is split into three phases, viz., an aqueous phase, an immiscible liquid hydrocarbon phase, and a light hydrocarbon containing vapour phase which are conveyed through conduits 40, 38 and 46 respectively. The separator unit 12 is a horizontal or a vertical vessel. The separation in the separator unit 12 occurs based on differential density of the respective phases. The light hydrocarbon containing vapour phase from the conduit 46 is fed at the flash zone of the crude distillation column 22. The aqueous phase from the conduit 40 is an immiscible layer and is discharged from the operative bottom of the separator unit 12. The aqueous phase from the conduit 40 which contains water, salts, and other dissolved ionic species can be sent to a sour water treatment unit (not shown in Figure 2) for further treatment. The immiscible liquid hydrocarbon phase from the conduit 38 is received in a coalescer unit 14. The coalescer unit 14 contains a fine mesh or coalescing media to aid in coalescing of water droplets to increase the diameter of the water droplets, thereby facilitating its separation from the liquid hydrocarbons. In the coalescer unit 14, dispersed water droplets are separated from the liquid hydrocarbon to produce a substantially water free liquid hydrocarbon phase through a conduit 48.

The liquid hydrocarbon phase from the conduit 48 is then heated in a heater 16 to produce a heated liquid hydrocarbon phase through a conduit 50. The heated liquid hydrocarbon phase from the conduit 50 is fed to the crude distillation column 22. The water separated at the coalescer unit 14 contains impurities like salts is conveyed using a conduit 42 and can be sent to the sour water treatment unit along with the aqueous phase.

In accordance with the present disclosure, typically the condenser unit 10, the separator unit 12, and the coalescer unit 14 are respectively arranged in series between the pre-flash drum 8 and the distillation column 22.

The crude hydrocarbon liquid through the conduit 54 from the operative bottom of the pre-flash drum 8 is conveyed through the hot pre-heat train 18 to obtain pre-heated crude hydrocarbon liquid through the conduit 56 having temperature between 240°C - 260°C. The pre-heated crude hydrocarbon liquid through the conduit 56 is received at the furnace 20 to produce a heated crude hydrocarbon liquid through the conduit 58 having temperature between 370°C - 395°C. This heated crude hydrocarbon liquid through the conduit 58 is fed at the flash zone of the crude distillation column 22.

Different fractions are recovered from the crude distillation column 22, including Gas and Naphtha, Light Kerosene, Heavy Kerosene, Diesel, and Heavy Atmospheric Gas Oil through the conduits 60,62,64,66 and 68 respectively. The residual crude oil though the conduit 70 is sent to a Vacuum Distillation Unit (not shown in the Figure 2). The system and method of the present disclosure causes a significant reduction in the overhead system pressure drop, as an outcome of avoiding water from the separator unit and the coalescer going into crude distillation column 22, which in turn helps to lift more distillate from a given crude mix.

Corrosion is prevented in the crude distillation column 22, as a result of the removal of salt forming species and other impurities along with water remains. The crude hydrocarbon vapours through the conduit 74 obtained at the operative top of the pre-flash drum 8 after being passed though the condenser unit 10 andthe separator unit 12, and optionally through the coalescer unit 14, are sent to the crude distillation column 22. This results in removal of more salt forming species e.g. amine, ammonia /impurities than would otherwise be removed. And when this stream is sent to the crude distillation column 22 it results in less corrosion especially in CDU-OH system. The crude hydrocarbon vapours through the conduit 74 are petroleum vapours which include opportunity crude hydrocarbon vapours.

For the method of the present disclosure, the condenser unit, the separator unit and the coalescer unit are operated at a temperature ranging from the pre-flash drum temperature (160 - 190 °C ) to ambient temperature, and a pressure ranging from pre-flash drum pressure (4 - 6 bar) to CDU column pressure slightly above the atmospheric pressure.

In the present disclosure water dew point temperature and NH₄C1 de-sublimation temperature is reduced at the top of the crude distillation column 22 through simultaneous prevention of water ingress and NH₃ entry. This further reduces corrosion of crude distillation column 22. The system of the present disclosure for treatment of crude hydrocarbon vapours that are conveyed through the conduit 74 from the pre-flash drum 8 results in reduction of the NH₃ ingress into the CDU OH by over 90% and facilitates lowering of NH₄C1 de-sublimation temperature by about 12°C. In addition to improving the reliability of the system, these effects help in restricting the Naphtha end point in-line with the downstream unit need. The crude processing thus has a lower naphtha yield which is a desirable business driver.

The present disclosure is further described in light of the following example which is set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure.

Example 1:

A simulation of the Crude Distillation Unit (CDU) was constructed by simulating a model in Aspen software. There are five main columns in Tablel which show the simulation results obtained.

Table 1 illustrates the results obtained after simulation of the improvements made after treatment of the pre-flash vapours, before being sent to the crude distillation column.

Attribute is a particular characteristic of the Crude Distillation Unit (CDU). UOM is the unit of measurement of the attribute. Actual results are those in the actual plant. Simulated Base is the result which is corrected and which should be actually present as per the base-case model prediction. Simulated Proposed are those results which result from the changes made from the treatment of the pre-flash vapours from the pre-flash drum.

Top Temperature and Top Pressure are the temperature and the pressure inside the top section of the crude distillation column. Dew point margin is the difference between the top temperature of the column and the NH₄C1 de-sublimation temperature as assessed based on the number of moles of N¾ and HC1 present in the proposed scheme after implementing the modification, i.e. treatment to crude hydrocarbon vapours. Overall, it is observed that there is a gain of 32 tph of light kerosene due to the improvements made after treatment of the crude hydrocarbon vapours before being sent to the crude distillation column. Table 1

TECHNICAL ADVANCEMENTS AND ECONOMIC SIGNIFICANCE

The system and method for treatment of crude hydrocarbon vapours generated from a pre-flash drum, prior to sending the vapours to a distillation column, in accordance with the present disclosure has several technical advantages including but not limited to the realization of:

• a system and method to prevent corrosion of the crude distillation column overhead system;

• a system and method to eliminate cold end corrosion potential by enabling 'zero' cold reflux in the main column even when crude mix changes significantly specially with respect to yield of Gas, LPG and Naphtha content;

• a system and method to separate most of the acidic and basic species of salts in the form of a solution, with the water from the desalted crude by cooling or condensing pre-flash tower vapours and preventing their direct entry into the CDU top trays, dome and CDU OH system;

• a system and method to restrict naphtha end point in-line with the downstream user need;

• a system and method to maintain main column reliability and provide insulation from impacts of processing of most opportunity crudes;

• a system and method to provide significant reduction in the overhead system pressure drop which helps to lift more distillate from a given crude mix; and

• a system and method to provide reduction of water dew point as well as NH₄C1 and amine chloride de-sublimation temperature at crude distillation unit through simultaneous prevention of water ingress and NH₃ and water soluble amines entry.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the invention as it existed anywhere before the priority date of this application.

Wherever a range of values is specified, a value up to 10% below and above the lowest and highest numerical value respectively, of the specified range, is included in the scope of the disclosure. The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

While considerable emphasis has been placed herein on the particular features of this invention, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiment without departing from the principles of the invention. These and other modifications in the nature of the invention or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

Claims

A system for treatment of crude hydrocarbon vapours generated from a pre-flash drum, prior to sending said vapours to a crude distillation column, said system comprising:

• a condenser unit for condensing said vapours into a stream containing immiscible phases; and

• a separator unit for receiving said stream and separating said stream into an aqueous phase, an immiscible liquid hydrocarbon phase, and a light hydrocarbon containing vapour phase.

The system as claimed in claim 1, wherein said system optionally includes a coalescer unit for receiving said immiscible liquid hydrocarbon phase, for separating dispersed water droplets from said immiscible liquid hydrocarbon phase to produce a substantially water free liquid hydrocarbon phase.

The system as claimed in claim 2, wherein said coalescer unit comprises coalescing media.

The system as claimed in any one of claims 1 and 2, wherein said condenser unit, said separator unit and said coalescer unit are respectively arranged in series between said pre-flash drum and said distillation column.

The system as claimed in claim 1, which includes one or more conduit for conveying said light hydrocarbon containing vapour phase and said liquid hydrocarbon phase to said distillation column.

6. The system as claimed in claim 2, which includes a second conduit for conveying said substantially water free liquid hydrocarbon phase to said distillation column.

7. The system as claimed in claim 2, wherein said system optionally comprises a heater for receiving said substantially water free liquid hydrocarbon phase from said coalescer unit to produce a heated liquid hydrocarbon phase.

8. The system as claimed in claim 7, separate conduit for conveying said heated liquid hydrocarbon phase to said distillation column.

9. A method for treating crude hydrocarbon vapours generated from a pre-flash drum, prior to sending said vapours to a crude distillation column, said method comprising:

• condensing said vapours in a condenser unit to produce a stream containing immiscible phases; and

10. The method as claimed in claim 9, wherein said method further comprises an optional step of coalescing said immiscible liquid hydrocarbon phase in a coalescer unit for separating dispersed water droplets and producing a substantially water free liquid hydrocarbon phase.

11. The method as claimed in any one of claims 9 and 10, wherein the condenser unit, the separator unit and the coalescer unit are operated at a temperature ranging from the pre-flash drum temperature (160 to 190 °C) to ambient temperature and a pressure ranging from pre-flash drum pressure (4 to 6 bar) to CDU column pressure, wherein the CDU column pressure is above the atmospheric pressure.

12. The method as claimed in claim 9, wherein said method further comprises the step of conveying said light hydrocarbon containing vapour phase to said distillation column.

13. The method as claimed in claim 10, wherein said method further comprises the step of conveying said substantially water free liquid hydrocarbon phase to said distillation column.

14. The method as claimed in claim 10, wherein said method optionally comprises the step of heating said substantially water free liquid hydrocarbon phase in a heater to produce a heated liquid hydrocarbon phase.

15. The method as claimed in claim 14, wherein said method further comprises the step of conveying said heated liquid hydrocarbon phase to said distillation column.

16. The method as claimed in claim 9, wherein said method further comprises the step of treating said aqueous phase in a sour water treatment unit.

17. The method as claimed in claim 10, wherein said method further comprises the step of treating said separated water in a sour water treatment unit.