RU2473667C1 - Method of desalinating gas condensates - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of desalinating a gas condensate on a unit for washing the gas condensate with fresh water, involving feeding fresh or low-mineralised water for mixing with the gas condensate, wherein a demulsifying agent is added beforehand in a pipeline. The process is carried out in a turbulent apparatus with a diffuser-confusor design, wherein the prepared gas condensate at 30°C is fed into the input channel of the first section of a tubular turbulent apparatus with a diffuser-confusor design with volume rate of 22-25 m³/h. Further, 1-1.5 wt % washing water is fed into the first section of the mixing apparatus coaxially through a perforated pipe with a closed end.

EFFECT: simple design of the mixing apparatus, low metal consumption, reduced pressure drop and low water consumption.

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Description

The invention relates to the field of gas condensate preparation, in particular to desalination with water, and can be used to reduce scaling during stabilization of the gas condensate in the stabilization column when developing a gas condensate field at a late stage of development with water flooding.

A known method of desalination of gas condensate with water, in which to ensure the extraction of salts with washing water, the mixing is carried out by creating a pressure differential on the mixing valve [Rudenko SV, Khutoryansky FM, Kapustin VM, Molchanova Z.V. On the technological necessity of washing a mixture of gas condensate and oil with water during their preparation at DKS-1 of the Orenburg State Pedagogical University. // Ecological Bulletin of Russia. - 2010. No. 6. - S.10-13]. The process is carried out at large pressure drops across the valve, which is associated with significant energy costs to ensure the required performance.

The known method [Ukhalova NB, Latyuk V.I., Umergalin T.G. The effect of water on the efficiency of fractionation of gas and gas condensate // Materials of the II International Scientific Conference. "Theory and practice of mass transfer processes of chemical technology." - Ufa: Publishing House UGNTU, - 2001. - P.151-152] desalination of gas condensate in a deethanization column at 120 ° C with steam. The disadvantage of the proposed method is the high power consumption, the absence of phase mixing. In addition, water vapor condenses and accumulates on the mass transfer plates for some time, resulting in scaling.

The known method [Rudenko S.V., Khutoriansky F.M., Kapustin V.M. Research on pilot desalination of deep desalination of gas condensates and oils of the Orenburg fields. // Oil refining and petrochemicals. - 2010. No. 11, - S.3-11] an integrated approach for desalination of gas condensates: the use of electric desalination plants ELOU, the selection of effective demulsifiers, the flow rate of wash water. This method does not involve mixing water and gas condensate and is inefficient and metal-consuming, energy-intensive.

The objective of the invention is to simplify the design of the mixing apparatus, reducing metal consumption, reducing the pressure drop and reducing water consumption.

The problem is solved in that in the proposed method for desalting a gas condensate at a gas condensate washing unit with fresh water, including supplying fresh or low saline water to be mixed with a gas condensate to which an oil-soluble demulsifier (for example, disolvan, separol) has been added to prevent the formation of persistent emulsions according to the invention, the process is carried out in a tubular turbulent apparatus of a diffuser-confuser structure, while the prepared gas the condensate at 30 ° C enters the inlet channel of the first section of the tubular turbulent apparatus of the diffuser-confuser structure with a volume flow of 22 ÷ 25 m ³ / h, where dispersion takes place. Then, the washing water 1 ÷ 1.5 wt.% Is coaxially introduced into the first section of the mixer apparatus through a perforated nozzle with a closed end end. The proposed method, in comparison with the known method, can improve efficiency by reducing the volume of washing water, since when mixing creates a high specific contact surface of the phases. Advantages are the absence of mixing devices, the absence of stagnant zones, low pressure drop, low metal consumption.

Figure 1 presents a diagram of a unit for flushing a gas condensate with fresh (low mineralized) water by the proposed method

1 - capacity with a demulsifier;

2 - water tank

3, 4, 5 - pumps;

6 - heat exchangers;

7 - tubular turbulent apparatus;

8 - three-phase separator;

Figure 2 presents a General view of a tubular turbulent apparatus for desalination of gas condensate with water. Figure 3 presents a diagram of the pipe for the introduction of water. Figure 4 presents a graphical dependence of the salinity in the gas condensate after washing in a tubular turbulent apparatus from the volumetric flow rate.

Diameter (internal) of the diffuser d _d = 0.12 m

Diameter (internal) of the confuser d _k = 0.06 m

The length of the diffuser-confuser section L _c = 0.24 m

The length of the inlet section L _p = 0.24 m

The length of the output section L _in = 0.24 m

Total length ~ 2.0 m

Diffuser opening angle γ = 45 ± 5 degrees

Number of diffuser-confuser sections 5

Pressure drop at the ends of the reactor 0.223 atm

The length of the pipe section, coaxial with the direction of flow of the gas condensate: L ₁ = 0.35 m

The diameter (inner) of the pipe for the introduction of water d ₂ = 0.04 m

The distance between adjacent holes L ₂ = 0,055 m

The process of desalination of gas condensate in accordance with the proposed method on the washing unit is as follows. The main stream of stable gas condensate from pipeline I is mixed with oil-soluble demulsifier II (demulsifier is a substance that destroys stable emulsions, which leads to separation of the contacting phases into the corresponding layers; for example, disolvan, separol can be used as a demulsifier). Gas condensate with a demulsifier with a volume flow of 22-25 m ³ / h enters the inlet channel of the first section of the tubular turbulent apparatus 7. Dispersion occurs in five sections of the tubular turbulent apparatus, which is less than 2 meters with a pressure drop at the ends of the apparatus of up to 0.223 atm.

The geometry of this reactor is selected so that the process proceeds with high turbulence. Wash water III pump 5 is sent to the heat exchanger 6, from where it follows the coaxial pipe of the first section of the tubular turbulent apparatus 7 with end nozzles. The pipe is perforated with twenty-one holes with a diameter of d ₁ = 5 mm: twenty holes on the walls of the pipe for radial alkali supply, the closed end end of the pipe is perforated with one hole for injecting a solution of a neutralizing reagent coaxial with the direction of oil movement. Perforations are located symmetrically in cross section (four holes in one AA section). The desalted gas condensate enters the three-phase separator 8. The separator is equipped with valves on the gas line IV, valves on the drainage water line V and valves on the gas condensate line VI.

Since it is possible to increase the quality of mixing gas condensate with water due to fine dispersion and uniform distribution of water droplets throughout the volume of gas condensate, we studied the conditions for creating a homogeneous emulsion on a two-phase model system “liquid-liquid” in a tubular turbulent apparatus (TTA).

In the diffuser-confuser channels, with an increase in the speed of motion of immiscible liquid flows, the size distribution of the droplets of the dispersed phase narrows with the formation of homogeneous finely dispersed systems. An increase in the flow velocity w and the number of diffuser-confuser sections N _c from 1 to 4 leads to a decrease in the volumetric-surface diameter of the droplets of the dispersed phase and, accordingly, to an increase in the specific interface, which intensifies the process as a whole in the case of fast chemical reactions. The inappropriateness of using TTA with the number of diffuser-confuser sections N _c more than 5 ± 1 makes these devices compact - the length does not exceed 8-10 calibers (L / d _d ), as well as simple and cheap to manufacture and operate.

At the same time, there is a certain range of the volumetric velocity of heterophase flows, which corresponds to the diffuser-confuser channel with the optimal ratio d _d / d _k . From below, this interval is limited by the zone of the stratified flow of heterophase flows, from above, by energy costs arising from an increase in the pressure drop at the ends of the apparatus (Δp ~ w ² ). In particular, the ratio d _d / d _k = 3 corresponds to the interval 44 <w <80 ml / s, ad _d / d _k = 1.6 corresponds _{to the} interval 80 <w <180 ml / s, with a further increase in the velocity of the dispersed system ( w> 180 ml / s) determines the need to further reduce the ratio d _d / d _k up to d _d / d _k = 1, i.e. in this case, small-sized TTA of a cylindrical design are quite effective. Thus, in the TTA of the diffuser-confuser structure, in comparison with cylindrical channels, a stream in which the particles of the dispersed phase are uniformly distributed throughout the apparatus volume is formed at lower speeds of the dispersed system, and the lower the required value of w, the greater the higher the ratio d _d / d _to (changes Re in accordance with the ratio Re ~ d _d / d _to ).

Thus, the change in the velocity of liquid flows w in tubular apparatuses and the ratio d _d / d _k are practically the only, but very effective ways of influencing the nature of dispersion and the quality of the resulting emulsions. The obtained regularities make it possible, without technical and technological problems, to create thin homogeneous dispersions in liquid-liquid systems under optimal conditions with a minimum residence time of the reagents in the mixing zone and to use small-sized TTAs of a diffuser-confuser design that are simple in design.

Another important quantity characterizing the quality of the resulting emulsions is the polydispersity coefficient k. Just as in the case of obtaining dispersions with a volume-surface diameter, the ratio L _c / d _d practically does not affect the polydispersity of the resulting emulsions. With an increase in the ratio d _d / d _k , an increase in the dispersion of the particles of the dispersed phase in size is observed, and sufficiently homogeneous emulsions are formed in the diffuser-confuser channel of the tubular apparatus with d _d / d _k = 1.6. In particular, for L _c / d _d = 2-3, the value of k for d _d / d _k = 1.6 is 0.72-0.75, while for a ratio of d _d / d _k equal to 2 and 3, k decreases to 0.63 and 0.41, respectively.

The dependences obtained make it possible to predict the dispersion of water droplets in the gas condensate, which makes it possible to design a mixer for operation in a wide range of flow rates of mixed liquids.

For efficient gas-condensate-water mixing, it is necessary to carry out the process at low pressure drops, which is directly related to the energy consumption to ensure the required plant performance.

Diffuser-confuser type reactor:

Δp≈p _n = 1 · 10 ^-5 w ^2.35

p _k = 2 · 10 ^-10 w ^3.86

,The pressure drop is expressed by the dependence

,

where ζ is the local resistance coefficient.

. Для цилиндрического участка аппарата ζ=1. Коэффициент местного сопротивления для участка аппарата с внезапным сужением (при расчете скоростного напора по скорости в меньшем сечении) ζ=0,38.The value of the coefficient of local resistance for a section of the device with a sudden expansion is calculated (when calculating the pressure head for speed in a smaller section)

. For the cylindrical section of the apparatus, ζ = 1. The coefficient of local resistance for a section of the apparatus with a sudden narrowing (when calculating the pressure head in terms of speed in a smaller section) ζ = 0.38.

The value of the coefficient of friction for a turbulent flow can be calculated by the Blasius formula:

The pressure drop ΔP in the section is equal to the sum of the pressure drops in the smooth pipe, expansion (diffuser) and narrowing (confuser):

ΔP = (P ₁ -P ₂ ) + (P ₂ -P ₃ ) + (P ₃ -P ₄ )

The total pressure drop is calculated as the sum of the pressure drops in each section.

According to the experimental data of pressure measurement at the ends of a tubular turbulent apparatus, consisting of 20 sections with a water flow, a calculation was performed according to the selected formulas. Comparison of the calculated data obtained in relation to the model system correlates with the experimental data for the pressure drop in the apparatus: ΔP _practical = 0.955 atm, ΔP _theory = 1.062 atm

Table 1 Pressure drop in the apparatus of the diffuser-confuser design, calculated for the model system λ _d 0,026 λ _to 0.014 Re _d 244 · 10 ³ Re 22.3 · 10 ³ L 0.032 m d _d 0.016 m d _to 0.008 m ρ 1000 kg / m ³ w 0.7 m / s w _to 2.8 m / s S _to 5 · 10 ^-5 m ² S _d 2 · 10 ^-4 m ² ζ _d 0.25 ζ 0 ζ _to 0.30 ΔP _1-2 1660 kgf / m ² ΔP _2-3 9.56 kgf / m ² ΔP _3-4 1119.6 kgf / m ² ΔP _section 0,053 atm ΔP _{20 sections} 1,062 atm

The diameter of the narrow section (confuser) of the section was calculated using the proposed formulas.

table 2 Calculation of the diameter of the diffuser d _k during the flow of gas condensate in the apparatus of the diffuser-confuser design ΔP _{5 sections} 0.223 atm ΔP _section 0.0446 atm ΔP _3-4 940.12 kgf / m ² ΔP _2-3 4.58 kgf / m ² ΔP _1-2 1390.5 kgf / m ² ζ _to 0.38 ζ 0 ζ _d 0.563 ρ 762 kg / m ³ L 0.24 m λ _to 0.011 λ _d 0.016 d _d 0.12 m Re 6.610 ⁵ Re _d 1.6510 ⁵ w _to 2.48 m / s w 0.62 m / s S _d 0.011 m ² S _to 0.0028 m ² d _to 0.06 m

Thus, the optimal geometric parameters of the tubular turbulent apparatus of the diffuser-confuser design were selected for the stage of desalination of gas condensate, at which the pressure drop is ΔP _{5 sections} ≈0.223 atm and the diameter of the confuser d _k = 0.06 m.

The results of experiments on flushing salts of stable condensate in a tubular turbulent apparatus. The experiments were conducted at the Borankol Kazakhstan field. In the CPGiGK (Gas and Gas Condensate Preparation Workshop), the workshop is a subdivision of the production department of the KazMunaiTeniz branch of JSC “Marine Oil Company” in Aktau.

The salt content of the initial condensate is 97 mg / liter

Condensate flow rate 22 m ³ / h

Condensate temperature t = 47 ° C

Water temperature t = 30 ° C

Experiments were conducted to determine the range of TTA. Condensate temperature t = 47 ° C, water t = 30 ° C.

For the indicated interval of gas condensate flow, a graphical dependence (Fig. 4) of the salinity in the gas condensate after washing in a tubular turbulent apparatus on the volumetric flow rate is constructed. 1 - 0.5 wt.% Water; 2 to 1 wt.% Water; 3 - 1.5 wt.% Water; 4 to 2 wt.% Water.

From the experimental data it can be seen that the ratio of 1 ÷ 2 wt.% Is the optimal volume of water supply, however, in conditions of industrial production, 2 wt.% Of water is expensive.

In our case, the optimal mode for washing the condensate from salts using TTA was determined and amounts to 1.5 wt.%. It seemed appropriate to study the effect of gas condensate flow rate at a constant water ratio of 1.5 wt.%.

Experience No. 1. Condensate flow rate through TTA Q _к = 117 ml / s, water flow rate Q _в = 1,755 ml / s

Result: due to insufficient fluid flow through the TTA, the section was not completely filled with condensate, i.e. sections were not completely filled; slight mixing was observed. Analysis of salinity after washing 83 mg / liter.

Experience No. 2. Condensate flow through TTA Q _k = 210 ml / sec, _a flow rate Q = 3.15 ml / sec

Result: in all 6 sections, intense turbulent mixing of the fluid in the longitudinal and transverse directions was observed. All sections were filled with fluid. Analysis of salinity after washing 17 mg / liter.

Experience No. 3. Condensate flow through TTA Q _k = 234 ml / sec, _a flow rate Q = 3.51 ml / sec

Result: in the first section, visually observed mixing disappeared, the flow became continuous. In the remaining 5 sections, mixing was observed visually in the longitudinal and transverse directions. Analysis of salinity after washing 19 mg / liter.

Experience No. 4. Condensate flow through TTA Q _k = 300 ml / sec, _a flow rate Q = 4.5 ml / sec

Result: in the first 3 sections, the visually observed mixing disappeared, the flow became continuous. In the remaining 3 sections, mixing was observed visually in the longitudinal and transverse directions. Analysis of salinity after washing 45 mg / liter.

Experience No. 5. Condensate flow through TTA Q _k = 400 ml / sec, _a flow rate Q = 6 ml / sec. Result: in all 6 sections the visually observed mixing disappeared, the flow was continuous without mixing due to the high fluid velocity. Analysis of salinity after washing 85 mg / liter.

Conclusions: the use of TTA to intensify the process of mixing liquids is due to certain parameters of the fluid velocity through the cross section of the apparatus and its dimensions. Also, the operation of the apparatus is characterized by a wide area of sustainable operation.

Claims (1)

A method for desalting a gas condensate at a gas condensate washing unit with fresh water, comprising supplying fresh or low-mineralized water for mixing with a gas condensate, to which a demulsifier has been previously added in a pipeline, characterized in that the process is carried out in a tubular turbulent apparatus of a diffuser-confuser structure, while the gas condensate is prepared 30 ° C enters the inlet channel of the first section of the tubular turbulent apparatus of the diffuser-confuser structure with a volume flow of 22 ÷ 25 m ³ / h, where Dispersion occurs, then the washing water 1 ÷ 1.5 wt.% is coaxially introduced into the first section of the mixer apparatus.

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