WO2012121620A1

WO2012121620A1 - Method for dividing gaseous mixtures

Info

Publication number: WO2012121620A1
Application number: PCT/RU2012/000071
Authority: WO
Inventors: Салават Зайнетдинович ИМАЕВ; Леонард Макарович ДМИТРИЕВ
Original assignee: Imaev Salavat Zainetdinovich; Dmitriev Leonard Makarovich
Priority date: 2011-03-10
Filing date: 2012-02-07
Publication date: 2012-09-13
Also published as: RU2458297C1

Abstract

The invention can be used in installations intended for dividing gaseous mixtures, including installations for processing natural and casing-head gases. The invention is of special interest for gas-processing systems in which components crystallizing at low temperatures of a gas are extracted from the gas. The technical result, to the achieving of which the claimed invention is directed, is an expansion in the efficiency range of installations for dividing gaseous mixtures, which installations use gas expansion in cyclone separators, and ensuring the efficiency of said installations in conditions favourable for solidifying individual components included in the composition of the gaseous mixtures. The above-mentioned technical result is achieved by the fact that, in the proposed method for dividing gaseous mixtures comprising a solid phase, the input gas is expanded in a rotating flow in a channel of the cyclone separator, producing a purified flow and a flow enriched with specific fractions at the outlet from the channel of the cyclone separator, wherein, in the expansion process, some of the gas moving near the walls is heated, and the heating is carried out in such a manner that the temperature of the internal surfaces of the channel of the cyclone separator is higher throughout than the temperature for forming the solid phase, wherein the degree of expansion of the flow in the cyclone separator is maintained such that Р_in/Р_pu> 1.01 (where Р_in is the full pressure of the input gas, Р_puis the full pressure of the purified flow at the outlet from the channel of the cyclone separator).

Description

METHOD FOR SEPARATING GAS MIXTURES

Technical field

The present invention can be used in installations intended for the separation of gas mixtures, including installations for the treatment of natural and associated gases. Of particular interest is the invention for gas processing complexes in which the components of gas crystallizing at low temperatures are extracted from gas.

State of the art

A known method for the separation of gas mixtures containing a solid phase is described in GB 898732, published 06/14/1962, in which the inlet gas is expanded in a rotating stream in the channel of the cyclone separator to obtain a purified stream and the stream enriched with target fractions at the outlet of the channel of the cyclone separator.

Also known are methods of low-temperature gas separation, in which the inlet gas is expanded in a rotating stream in a straight-through cyclone separator channel to obtain a purified stream and a stream enriched with target fractions at the outlet of the cyclone separator channel. In this case, when the gas expands in the channel of the cyclone separator, low temperatures are realized at which certain components of the gas solidify, such as carbon dioxide or hydrogen sulfide. An example of such a method is given in application C A 2710915 published on July 9, 2009.

The disadvantage of the described methods is that they are unacceptable for industrial use in the conditions of continuous operation of the installation for many months, because on the walls of the separators there is a gradual formation of deposits of hardening components, which, ultimately, leads to disruption of the flow structure inside the cyclone separator and, accordingly, to a deterioration in the efficiency of the separation process.

Disclosure of invention

The task to which the claimed technical solution is directed is to expand the range of operability of gas separation units mixtures using gas expansion in cyclone separators, and ensuring their operability under conditions favorable for the solidification of the individual components that make up the gas mixtures.

The problem is achieved due to the fact that in the proposed method for the separation of gas mixtures containing a solid phase, the inlet gas is expanded in a rotating stream in the channel of the cyclone separator, with obtaining a purified stream and a stream enriched with target fractions at the outlet of the channel of the cyclone separator, during the expansion process, the part of the gas moving near the walls is heated, the heating is carried out so that the temperature of the inner surfaces of the channel of the cyclone separator is everywhere above the temperature Ia solid phase, the degree of expansion of the flow in the cyclone separator is controlled such that the F _I / F ₀ h> 1.01 (where P _Rin - total pressure of the inlet gas, _Pts F - total pressure raffinate stream at the outlet of the channel of the cyclone separator).

Enriched with target fractions, the stream can be subjected to a repeated separation process with the expansion of the stream in the channel of an additional cyclone separator.

If necessary, the stream enriched with the desired fractions is separated from the liquid and solid phases, and subjected to a second purification process with expansion of the flow in the channel of the additional cyclone separator.

Brief Description of the Drawings

The invention is illustrated by drawings, where:

figure 1 presents a schematic diagram of an installation for implementing the proposed method for the separation of gas mixtures;

figure 2 is a schematic diagram of an installation in which a stream enriched with water is subjected to a repeated separation process with the expansion of the stream in the channel of an additional cyclone separator;

in Fig.3 is a schematic diagram of the installation in which the separation of the liquid and solid phase is carried out using an additional separator

An embodiment of the invention

Installation works as follows. Crude gas 1 enters the inlet of the cyclone separator 2, in which the gas is twisted in a swirler 3, and in the channel 4 of the cyclone separator the gas is expanded in a rotating stream to obtain a purified stream 5 at the outlet of the cyclone separator channel and the stream enriched with target fractions 6 In the process of expansion, part of the gas moving near the walls is heated, heating is carried out so that the temperature of the inner surfaces of the channel 4 of the cyclone separator is everywhere above the temperature of formation of the solid phase. The heat supply is indicated in figure 1 by arrows 7.

The degree of expansion of the flow in the cyclone separator is maintained such that Pvh / Roch> 1.01 (where P _in is the total pressure of the inlet gas, _Pch is the total flow pressure at the outlet of the channel of the cyclone separator in order to ensure sufficiently high flow rates in the channel of the cyclone separator providing sufficient heat transfer from the walls to the part of the gas located near the wall of the channel 4.

In order to assess the temperature of the coolant and its flow rate sufficient to prevent the formation of a solid phase, it is necessary to calculate the heat fluxes to its surfaces on the inner surfaces of the cyclone separator.

The heat flux from the medium to the wall in a wide range of Mach and Reynolds numbers for a turbulent boundary layer can be calculated using the relations of the Spalding-Chi theory. In this case, the gas flow can be both subsonic and supersonic. In this case, the heat flux q can be represented as:

q = StVp (H _w - H _r ), where St is the Stanton number, V is the flow velocity, p is the flux density H _g -

. V ²

the enthalpy of recovery equal to H _g = \ + g ^* -, g ^* is the recovery coefficient, g,

- enthalpy determined by thermodynamic parameters at the outer boundary of the boundary layer.

On the other hand, the heat flux will be:

q »X (T _w2 - T _w ) / S, where δ is the wall thickness, λ is the thermal conductivity coefficient of the wall material, T _wl , T _w2 is the wall temperature on the inner and outer surfaces of the wall. The above ratios make it possible to determine the necessary temperature on the outer wall surface (and thereby choose the coolant parameters) to ensure the necessary gas temperature on the inner wall surface of the cyclone separator.

The temperature of formation of the solid phase can be calculated using software systems, such as, for example, HYSYS, etc.

In cases where a more complex heating system is used to heat the flow, it is necessary to use special calculation systems that allow calculating heat fluxes for complex structures. Examples of such complexes are CFX, FLUENT, etc.

The walls of the channel of the cyclone separator can be heated using the induction heating method, in this case the metal channel must be surrounded by a coaxially located induction coil, the frequency of change and current in which are selected from the condition of sufficient input power.

At low heating capacities, an electric heater located in the cavity surrounding the channel can be used. In this case, the cavity may be filled with heat-conducting material.

In the process of gas expansion in the channel of the cyclone separator, condensation of individual gas components, the formation of droplets of liquid, the formation of a solid phase in the stream and their separation to the walls of the cyclone separator can occur. In these cases, for the correct calculation of heat fluxes, it is necessary to use special software systems, such as, for example, CFX ANSYS, which allow calculating heat fluxes in two-phase flows.

In cases where it is necessary to provide a deeper separation of the gas mixture, the water-enriched stream is subjected to a repeated separation process with the expansion of the stream in the channel of the additional cyclone separator. In this case, as shown in Fig. 2, the water-enriched stream 6 is directed to the cyclone separator 8, in the channel 9 of the cyclone separator, the gas is expanded in a rotating stream, to obtain a purified stream 10 at the outlet of the channel of the cyclone separator, and the stream enriched with target fractions 11. During the expansion process, the part of the gas located near the walls can be heated, if necessary, as, for example, shown in Fig.Z, Heat flow in an additional cyclone separator is indicated by the number 12.

To increase the degree of separation of the gas mixture from the stream 6 enriched with the target fractions, the liquid and solid phases 13 can be separated, as shown in FIG. The separation of the liquid and solid phases can be carried out, for example, using an additional separator 14. The gas phase 15 from the separator 14 is sent to an additional cyclone separator 8.

If necessary, to prevent the deposition of a solid phase on the walls of the separator 14, its walls can also be subjected to heat.

Claims

CLAIM

Item 1. The method of separation of gas mixtures containing a solid phase, in which the inlet gas is expanded in a rotating stream in the channel of the cyclone separator, with obtaining a purified stream and a stream enriched with target fractions at the outlet of the channel of the cyclone separator, characterized in that in the process of expansion the gas moving near the channel walls is heated, the heating is carried out in such a way that the temperature of the inner surfaces of the channel of the cyclone separator is everywhere above the temperature of formation of the solid phase, while the expansion stump of the flow in the cyclone separator is maintained such that Pv _X / Roch ^> 1 -01 (where P _in is the total pressure of the inlet gas, P _Pch is the total pressure of the purified stream at the outlet of the cyclone separator channel).

Clause 2. The method according to claim 1, characterized in that the stream enriched with the desired fractions is subjected to a repeated separation process with the expansion of the stream in the channel of the additional cyclone separator.

Clause 3. The method according to claim 1, characterized in that the stream enriched with the desired fractions is separated from the liquid and solid phases, and subjected to a second purification process with the expansion of the stream in the channel of an additional cyclone separator.