RU2273510C1 - Method of dehydration of gas - Google Patents

Abstract

FIELD: preparation of natural and oil gases for transportation and processing.

SUBSTANCE: proposed method includes cleaning of gas flow from mechanical impurities and dropping liquid, condensation of water and/or hydrocarbon components, separation and removal of them from gas. Components are subjected to capillary condensation from gas flow in anisotropic porous capillary structure made from wettable solid material condensed by components. Sizes of pores and capillaries of structure decrease to one side. Condensed components are removed through pores and capillaries towards decrease of their sizes. Gas flow in structure is directed towards increase of sizes of pores and capillaries. Gas flow is fed at normal to direction of motion of component being removed. Agents increasing wettability of solid material are fed to condensed components at removal. Part of removable condensed components is recirculated to side at increased sizes of pores and capillaries. Capillary condensation and removal of condensed components are performed repeatedly - at several stages. At repeated condensation, removal of condensed components is performed from previous stage to side at increased sizes of pores and capillaries of previous gas dehydration stage.

EFFECT: enhanced efficiency of dehydration; reduced losses of gas pressure.

7 cl, 13 dwg, 1 ex

Description

The invention relates to field processing of multicomponent hydrocarbon gases, mainly their drying, and can be used to prepare natural and petroleum gases for transport and processing.

A known method of field preparation of multicomponent hydrocarbon gas (Gritsenko A.I., Istomin V.A., Kulkov A.N., Suleymanov R.S. Collection and field preparation of gas in the northern fields of Russia - M .: Nedra - 1999 - C. 372-373), including the purification of gas from mechanical impurities and a droplet liquid, the condensation of aqueous and (or) hydrocarbon components by cooling the gas during its isoenthalpic expansion (in the throttle), and the separation of condensed components from gas.

However, with this method of gas preparation, an irretrievable loss of gas pressure occurs. Moreover, the stronger the cooling of the gas and, as a consequence, the deeper it is dried from the liquid (lowering the dew point of the condensed components), the greater the pressure loss. The pressure loss of natural gas is 1 · 10 ⁵ PA with a decrease in its temperature by 0.466 ° C.

More effective is the method of preparation of multicomponent hydrocarbon gas (Bekirov T.M., Lanchakov G.A. Technology of gas and condensate treatment - M .: Nedra - 1999 - S.314-315), including gas purification from mechanical impurities and dropping liquid, condensation of water and (or) hydrocarbon components by cooling the gas with isentropic expansion (in a turboexpander), and separation of the condensed components from the gas.

In this method, the pressure loss of the gas is 1 · 10 ⁵ Pa with a decrease in its temperature by 0.611 ° C.

However, in the first and in the second analogues, quite a lot of gas energy in the form of its pressure is lost during condensation.

The purpose of the invention is the reduction of gas pressure losses during its drying and increasing the efficiency of the latter.

Common for analogues and the proposed method for the preparation of multicomponent hydrocarbon gas are: cleaning the gas stream from mechanical impurities and dropping liquid, condensation of water and (or) hydrocarbon components, separating and removing them from the gas.

The difference of the proposed method from analogues is that the components are subjected to capillary condensation from a gas stream in an anisotropic porous-capillary structure made of a solid material wetted by the condensed components, the pore and capillary sizes of which decrease in one direction, the condensed components are removed in the pores and capillaries in the direction decrease in their size.

The difference is that the gas flow in the structure is given a direction in the direction of increasing the size of its pores and capillaries.

The difference, in addition, is that the gas flow is fed along the normal to the direction of movement of the removed component.

The difference is also that when removed, substances that increase the wettability of the solid material are supplied to the condensed components.

The difference is also that part of the removed condensed components are recycled to the side with increased pore and capillary sizes.

The difference is also that capillary condensation and the removal of condensed components are carried out repeatedly - in several stages.

The difference is also that with repeated condensation, the removal of condensed components is carried out from the subsequent stage to the side with increased pore and capillary sizes of the previous stage of gas dehydration.

Capillary condensation ( ¹ Physics. Big Encyclopedic Dictionary / Ed. By A.M. Prokhorov - M .: Big Russian Encyclopedia - 1999 - S.242-243) of water and (or) hydrocarbon components from a gas stream in an anisotropic porous-capillary the structure of the solid material wetted by the condensed components, the pore and capillary sizes of which decrease in one direction (Fig. 1), differs significantly from traditional condensation in free space or on a flat surface. During condensation on the anisotropic porous-capillary structure of a wettable solid material, the main role is played by capillary phenomena.

In the pores and capillaries 1 (Fig. 2), the precipitating liquid forms concave menisci 2. The curved surface of the meniscus initiates capillary condensation of the component vapors from the gas stream at a pressure P _GM lower than the saturated vapor pressure P _{0 of the} component in the gas at the same temperature T of gas. The pressure value P _{GM is} the smaller, the more curved the meniscus surface, i.e. the smaller the radius r of its curvature. So, at a temperature of T = 313 K (40 ° C), a meniscus radius of r = 1 · 10 ^-5 m, the capillary condensation pressure of water is P _GM = 2170 Pa, and in free space, the water condensation pressure is P ₀ = 7370 Pa. Due to the fact that the capillary condensation pressure P _{GM is} less than the saturated vapor pressure P ₀ (3.4 times in the case under consideration), then capillary condensation occurs more intensively earlier, which leads, as a result, to deeper gas dehydration. Experimental studies have recorded a decrease in the dew point of the water component by 1.5-2 ° C during capillary condensation compared to conventional condensation in open space and (or) on a flat surface. A decrease in the dew point by 2 ° C during capillary condensation occurs without the expenditure of energy for cooling the gas. This technique allows you to save the energy spent on cooling the gas, in particular, saves the gas pressure by 3.27 · 10 ⁵ PA. In this case, water and (or) hydrocarbon components are additionally condensed from the gas, which increases the efficiency of gas drying.

The removal of the condensed components through the pores and capillaries in the direction of decreasing their size is based on the fact that in narrowing capillaries, the liquid moves from a larger area 3 of the cross section of pores and capillaries to less than 4 (Fig. 3) under the influence of the difference in intracapillary pressures. The larger the meniscus radius, the greater the pressure under its surface, and the smaller the meniscus radius, the lower the pressure under its surface. It is experimentally confirmed that the pressure difference created in the narrowing capillaries reaches (1.5-2) · 10 ⁵ Pa. This difference in capillary pressures under menisci with radii r ₁ > r ₂ > r ₃ > r ₄ > r ₅ provides fluid movement through the pores and capillaries from large menisci to smaller ones (Figs. 3, 4). Thus, the movement along the narrowing capillaries and the removal of liquid from them occurs due to the action of capillary forces and, therefore, the energy (pressure) of the prepared gas is not expended to remove the liquid, which ultimately reduces its pressure loss and ultimately increases the drying efficiency .

Giving the gas flow 5 (Fig. 4) in the directional structure towards an increase in the size of its pores and capillaries allows not to mix the dried gas with the separated condensed components 6 and thereby increase the drying efficiency.

The flow of gas 5 along the normal to the direction of movement of the removed component 7 (Fig. 5) allows you to not counteract the flow of the removed fluid 8, reduce the hydraulic resistance and, ultimately, increase the efficiency of gas drying.

The supply of substances 9 (Fig.6) to the condensed components 6 during their removal increases the wettability of the solid material 10 and thereby reduces the meniscus radii in the capillaries and pores, which intensifies capillary condensation and the driving force that moves the liquid through the pores and capillaries and removes it from them . As a result, this leads to an increase in the efficiency of gas dehydration.

Recirculation (for example, by the ejector 11 (Fig. 7)) of the part of the removed condensed components 12 to the side with increased pore and capillary sizes allows the surface of the structure to be wetted with a small content of condensing components, to ensure the formation of menisci in the pores and capillaries and thereby intensify the process capillary condensation and capillary removal and increase the efficiency of gas drying.

The production of multiple capillary condensation (Fig. 8) and the removal of condensed components allows more deeply drain the gas from the components.

Removing the condensed components 8 (Fig. 8) from the subsequent stage 13 to the side with increased pore and capillary sizes of the previous gas drying stage 14 during repeated condensation allows the surfaces of the previous structures to be wetted and menisci formed in the pores and capillaries, thereby intensifying the process of capillary condensation and capillary removal at each stage of drying and, as a result, increase the efficiency of gas drying.

The applicant and the authors are not known from the existing level of technology to reduce the pressure loss of gas during its drying and increase the efficiency of the latter in a similar way.

The method is carried out in devices, schematically presented in Fig.9-13.

The applicant and the authors are not known from the existing level of technology in which the reduction of gas pressure losses during its drying and increasing the efficiency of the latter would be achieved in the manner described above.

Gas dehydration is performed in the apparatus (Fig. 9) as follows.

Natural multicomponent gas containing solid impurities, dropping liquid and water vapor enters through the nozzle 15 into the lower part of the housing 16. Here, due to gravitational force, coarse solid particles and droplet liquid are separated from the gas. The pre-purified gas enters the separation device 17, where it is cleaned from fine particulate matter and droplet liquid.

Then a gas containing water vapor and liquid particles, the size of which is comparable with the mean free path of the molecules, is fed to the filter cartridges 18. Each of the filter cartridges 18 (Fig. 10) is made of wettable condensable components [water and (or) liquid hydrocarbons] solid material. This material includes nickel, titanium, stainless steel and alumina. The filter cartridge 18 has an anisotropic porous-capillary structure, such as that shown in figure 1. The sizes of pores and capillaries of this structure decrease towards the periphery (Fig. 10). On the periphery is a layer 19 (figure 10) having small sizes of pores and capillaries. The inner layer 20 contains large pores and capillaries.

The flow of drained gas 21 passes in the direction of the side of the increase in the size of pores and capillaries.

In the anisotropic porous-capillary structure of the filter cartridge, capillary condensation of the aqueous and hydrocarbon components and their separation from the gas occur. Dried from water vapor and hydrocarbon components gas 22 (figure 10) is removed from the filter cartridge 18 and then from the apparatus through the pipe 23 (figure 9).

Due to the action of capillary forces, the condensed components move to the periphery of the filter cartridge. They accumulate on its outer surface and, under the action of gravity, flow down 24 (Fig. 10).

The flowing liquid condensate washes away the settled solid impurities from the separating surfaces of the device 17 (Fig. 9). The latter are deposited and accumulate in the hemispherical removable bottom 25 (figure 10) of the apparatus. Periodically, the bottom 25 is cleaned of solid sediment.

In order to intensify the removal, the condensed components are fed through the nozzle 26 (Fig. 9) to the plate 27 and then to the periphery of the filter cartridges 18 substances that increase the wettability of the solid material. For example, to intensify the removal of water serves methanol, glycols. To remove hydrocarbon condensates - kerosene.

With a low content of condensable components in the gas in order to intensify capillary condensation, part of the removed condensed components are recycled by the pump 26 through the nozzle 27 and the distribution device 28 to the filter cartridges 18. Moreover, the condensed components enter the inner side 20 (Figs. 9 and 10) with increased dimensions then and capillaries.

In order to increase the efficiency of gas drying in the apparatus shown in Fig. 11, the gas flow 5 is fed along the normal to the direction of movement of the removed component 7. The dried gas does not come into contact with the removed condensed liquid and does not carry it away with itself. This allows, ultimately, to increase the efficiency of gas drying.

To achieve in-depth gas dehydration in the column apparatuses of Figs. 12 and 13, capillary condensation and the removal of condensed components are performed repeatedly - in several stages.

In the column apparatuses (FIGS. 12 and 13), flat-plate filter elements 28 and 29 are made. They are made of a material similar to that of which the filter cartridges 18 are made (FIGS. 9, 10). Filter elements are located in the apparatus one above the other. Moreover, the side 30 with large pores and capillaries of each filter element 28 and 29 is located above, and below the side 31 with small pores and capillaries. The filter elements 28 are different from the filter elements 29. Each filter element 28 is equipped with a pan 32 for collecting condensed liquid and a pipe 33 for its drain.

In the apparatus of FIG. 12, condensed liquid is discharged through drain pipes 34 to the surface of a separation device 17 similar to that of FIG. 9 and to the lower part 35 of the housing. The separation device 17 is equipped with the apparatus of FIG. 13.

In the column apparatus (Fig. 12), the source gas is supplied through a pipe 36 to the lower part 35 of the housing. The source gas is preliminarily cleaned of droplet liquid and solid impurities in the lower part 35 of the housing and the separation device 17. Then it is dried, successively passing from the bottom up the filter elements 28. The direction of gas movement in the filter elements 28 is normal to the direction of movement of the discharged liquid ( similarly, as shown in Fig.7 and 11). The drained liquid is collected in trays 32 and is removed through the nozzles 33 and drain pipes 34. The dried gas 37 is removed from the apparatus through the nozzle

In order to intensify the processes of capillary condensation in the filter elements 29 and capillary removal of liquid from them with a low content of condensable components in the gas in the apparatus of Fig. 13, the condensed components are removed from the subsequent stage 39 to side 30 with increased pore and capillary sizes of the previous stage 40 gas dehydration. This technique during multiple condensation allows wetting the surfaces of previous structures, thereby ensuring the formation of menisci in pores and capillaries at each stage of drying and, as a result, to increase the efficiency of gas drying.

EXAMPLE

Natural wet gas having:

- temperature 40 ° C;

- pressure 5.0 MPa;

drained by the proposed method and the dew point is reduced:

in the apparatus (Fig.9) at 2 ° C;

in the apparatus of figure 11 at 2.3 ° C;

in the apparatus of FIGS. 12 and 13 by 3-5 ° C.

In this case, the pressure drop at a flow rate of 0.12 m / s of gas on the anisotropic porous-capillary surface is:

in the apparatus of Fig.9 - 2 · 10 ⁴ PA;

in the apparatus of FIG. 11, 1.7 · 10 ⁴ Pa;

in a 7-speed apparatus (Fig 11) - 1.2 · 10 Pa;

in a 7-speed apparatus (Fig.13) - 1.4 · 10 ⁵ PA.

Claims (7)

1. The method of drying the gas, including cleaning the gas stream from mechanical impurities and a dropping liquid, condensation of water and (or) hydrocarbon components, separating and removing them from the gas, characterized in that the components are subjected to capillary condensation from the gas stream in an anisotropic porous-capillary structure made of a solid material wetted by the condensed components, the pore and capillary sizes of which decrease in one direction, the condensed components are removed along the pores and capillaries in the direction of their decrease sizes. 2. The method of drying gas according to claim 1, characterized in that the gas stream in the structure is given a direction in the direction of increasing the size of its pores and capillaries. 3. The method of drying gas according to claim 1, characterized in that the gas stream is fed along the normal to the direction of movement of the removed component. 4. The method of drying gas according to claim 1, characterized in that when removed into the condensed components, substances are added that increase the wettability of the solid material. 5. The method of drying gas according to claim 1, characterized in that part of the removed condensed components are recycled to the side with increased pore and capillary sizes. 6. The method of drying gas according to claim 1, characterized in that the capillary condensation and removal of the condensed components is carried out repeatedly in several stages. 7. The method of drying gas according to any one of claims 1 and 6, characterized in that during repeated condensation, the removal of the condensed components is carried out from the subsequent step to the side with increased pore and capillary sizes of the previous gas drying step.

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