RU2366488C2 - Thermodynamic separator and method of high-c3+-content-gas preparation - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: thermodynamic separator consists of cylindrical housing, inlet nozzle and outlet diffuser. Aforesaid nozzle houses gas flow swirler. Mixing chamber is arranged between aforesaid nozzle and diffuser to make metered orifices to eject low-pressure gas from the said mixing chamber and to withdraw liquid phase into separating chamber, respectively.

EFFECT: maximum extraction of ethane and methane from condensate; subsequent return of condensate into primary gas flow; simplified procedure, lower metal input and production costs.

3 cl, 4 dwg

Description

This proposal relates to one of the technical solutions in the field of the gas industry, namely, the preparation of gas to commercial qualities corresponding to OST 51.40-93.

The development of all types of hydrocarbon deposits has its own difficulties and problems, both economic and technical in nature. If we take the northern regions of Russia, then this is inaccessibility, harsh climate, delivery and installation of technological equipment and the necessary materials related to the development of the field. In the central and southern regions, despite the developed infrastructure, the presence of a processing industry and the possibility of marketing products, the development of small deposits is often also unprofitable due to the high metal consumption of the technological equipment for preparing gas to commercial quality. Therefore, for the development of small and medium-sized fields, it is necessary to create block-modular prefabricated plants with the possibility of supplying commercial gas to local consumers.

To date, there is a standard scheme for the preparation of gas with a high content of C3 + hydrocarbons (see figure 1).

The basis for the preparation of condensate-containing natural gas laid low-temperature separation - Figure 1. Gas 1 is first supplied to the inlet separator 8, as a rule, combined with a cork trap to beat off droplet liquid and capture volley emissions. Then the raw gas is pre-cooled (heat exchanger 10 raw gas - prepared gas) to obtain a lower temperature in the low-temperature gas preparation unit. Depending on the technology and depth of extraction of liquid hydrocarbons, it is also possible to use an additional separation stage, after which the gas is sent to the low-temperature separation unit, which consists of an ejector unit 11 (or expanders) and a low-temperature separator 12 - when the gas is cooled in the ejector unit (or expanders ) C3 + hydrocarbons fall out, which are then beaten off in separator 12. Gas is supplied to consumer 2, and the separated liquid hydrocarbons 4 undergo additional preparation 9. B separation tanks 13 separates condensate, water-methanol solution 3, 5 and partial degassing. Depending on the particular process, several stages of separators can be used. Subsequently, the condensate may undergo partial (deethanization) or complete stabilization. During deethanization, methane and ethane 7 are extracted in a gaseous form due to heating of the condensate. Then, the deethanized condensate is sent for processing.

The negative sides of this technology:

- to prepare large volumes of gas, large-sized apparatuses with large throughput and corresponding effective degree of separation and phase separation are used, which in turn leads to large capital investments;

- To comply with temperature parameters and control the degree of extraction of liquid hydrocarbons, large-sized heat exchanger blocks are used.

Quite a lot is proposed and there are designs of separators for the purification of natural (associated petroleum) gas from dropping liquid and mechanical impurities (A.I.Skoblo, Yu.K. Molokanov, A.I. Vladimirov, V.A. Shchelkunov AND PETROCHEMISTRIES. ”- M .: NEDRA, 2000 [1]). The designs of these devices are, as a rule, a cylindrical body (vertical or horizontal), a gas inlet, a gas outlet, a liquid outlet, internal elements (centrifugal, inertial, filtration, etc.).

Signs of known devices that coincide with the features of this technical solution are the presence of inlet, outlet and drain pipes, the use of centrifugal forces to trap the liquid phase and the deposition of the liquid phase and mechanical impurities due to gravity, followed by removal from the devices.

The main disadvantage of all these devices is the low efficiency of gas purification and dimensions. The larger the volume of gas to be cleaned, the larger the dimensions of the separator. With a sharp increase in the incoming gas flow, pickup and entrainment of the liquid phase is possible, which did not have time to settle in the settling (storage) zone.

A close option is a device for separating gas-liquid mixtures (RF patent for the invention No. 2260467, IPC B01D 19/00, 2004 [2]), consisting of a cylindrical body with inlet and outlet pipes coaxially installed inside the body, a swirler, a disperser of liquid plugs. The mixture inlet pipe passes into the expansion chamber with the confuser, the beginning and end of the pipe are made conoidal, and the beginning of the pipe is placed in the expansion chamber confuser. An intermediate pipe is installed between the inlet and outlet pipes, in the wall of which there are successively arranged tangential, longitudinal and annular slots. Around these slots are stabilizers in the form of coaxial pipes. Fluid outlets are installed in the expansion chamber and behind the expansion chamber.

The reason that prevents the obtaining of a technical result, which is provided by the claimed technical solution, is that it is impossible to isolate sufficiently fine liquid droplets, as well as heavy hydrocarbons (C5 +) from gas, due to imperfect design and entrainment by a gas stream. This device is applicable only in the form of a primary (input) separator.

Similar by analogy is a device containing a nozzle with a prechamber with means for swirling the gas flow located in it, at the nozzle exit a supersonic or subsonic diffuser with means for sampling the liquid phase. In the diffuser there is a means for straightening the swirling gas stream (RF patent for the invention No. 2167374, IPC F25J 3/06, 2005 [3]).

The disadvantage of this device is a constructive solution for the selection of fluid from the diffuser, as well as the location of the diffuser immediately after the nozzle. In the first case, due to the high flow rate, the selection of liquid through the perforated hole will be difficult and there is a high probability of gas leakage. In the second, when the gas stream of the constricting device passes through, a sharp decrease in temperature and an increase in the flow rate will occur, and immediately after expansion, the reverse process will be observed, i.e. the release of C5 + heavy hydrocarbons from the gas in the initial stage, and then the reverse process will immediately be observed.

The objective of the invention is to maximize the quality of separation (gas preparation to OST 51.40-93) and the extraction of C3 + hydrocarbons from gas.

The use of a thermodynamic separator increases the efficiency of gas preparation to the requirements of OST 51.40-93.

This technical result in the implementation of the invention is achieved by the fact that in the thermodynamic separator (figure 2), consisting of a housing 31, input 22 and output 21 pipes, a pipe for draining the liquid 23, a pipe for the inlet of low-pressure gases 24, means for swirling gas (swirl) 25, the nozzle 26, the receiving chamber 20, the calibrated gap between the nozzle and the mixing chamber 27, the mixing chamber 28, the diffuser 30 having the calibrated gap 29 with the mixing chamber for draining the liquid, due to the thermodynamic properties of the gas and design features up to maximum extraction of C3 + components from gas with associated utilization of low-pressure gases is reduced.

The work of the separator are as follows:

At the input of the apparatus 22, a gas mixture is supplied with a pressure of 7.5-13 MPa. The working medium (natural gas) before contact with the ejected stream (gas from the separation tank) is accelerated to a speed exceeding the sonic one, having previously obtained rotation in the swirler 25 in front of the nozzle 26. The swirling flow of active gas enters the receiving chamber 20, where the passive medium is supplied through the nozzle 24. As a result of the presence of viscous friction, a jet turbulent boundary layer is formed at the boundary of the working jet (the result of capture is the ejection of a passive medium). Through this layer there is an exchange of energies between active and passive flows. A jet of the working medium surrounded by a jet turbulent boundary layer growing downstream and accompanying it, the passive medium stream not yet captured by the boundary layer from the receiving chamber 20 enters the mixing chamber 28. In the mixing chamber 28, an intensive exchange of energies between the active and passive flows continues. alignment of the velocity profile with a slight increase in the static pressure of the flow downstream. There is also an intensive decrease in the temperature of the gas stream by increasing its speed to values close to the speed of sound. The required gas velocity and the pressure drop in the active gas nozzle 26 depend on a given drying depth of the commercial gas and are determined by calculation based on known gas dynamics relationships. A decrease in the temperature of a gas moving at a high velocity is accompanied by condensation of the liquid from the gas phase. As you move along the mixing chamber 28, the active stream slows down, and the passive accelerates. The mixed stream from the mixing chamber 28 enters the diffuser 30, where it is braked, accompanied by a further increase in static pressure to a value determined by the resistance of the equipment into which the mixed medium is pumped. By imparting rotational motion to the active stream, the liquid is thrown to the walls of the mixing chamber due to centrifugal forces. Before the conical part of the diffuser 30 starts, the condensed liquid part is discharged through a calibrated gap 29 between the mixing chamber 28 and the diffuser 30 into the storage tank. The decrease in pressure in the tank is provided by ejection of part of the degassing gases to the input of the mixing chamber 9 of the thermodynamic separator. As the gas flow moves along the diffuser 30, both the pressure and the temperature of the gas increase. Moreover, the gas temperature at the outlet 21 from the apparatus exceeds the hydrate formation temperature, which provides significant methanol savings compared to, for example, conventional gas preparation schemes.

The overall dimensions of the apparatus depend on the required flow rate and gas composition. All elements can be manufactured industrially.

We offer two options for a method of preparing gas with a high content of C3 + to commercial quality using a thermodynamic separator (Fig.3, 4).

Option 1. According to the scheme (figure 3), natural gas 40 with a temperature of -10 ° C + 30 ° C and a pressure of 7.5-13 MPa is first supplied to the input of the recuperative heat exchanger 41, where it is partially cooled by the liquid phase 45 released in the result of using the thermodynamic properties of the gas in the separator 49. After the separator 49, the prepared gas is supplied to the consumer 42 before OST 51.40-93. The separated liquid phase 45 enters the heat exchanger 41 and is sent 43 to the separation tank 50, where due to the difference in density, the condensation 47 and in ometanolny solution 48. In the process of separation of liquid phase condensate degassing occurs. The gas evolved 44 due to the ejection process in a thermodynamic apparatus is utilized 46.

Option 2. According to the scheme (figure 4) natural gas 40 with a temperature of -10 ° C + 30 ° C and a pressure of 7.5-13 MPa enters the thermodynamic separator 49. After the separator 49, the prepared gas to the OST 51.40-93 is supplied to the consumer 42 The liberated liquid phase 45 enters the separation vessel 50, where due to the difference in densities, the condensate 47 and the water-methanol solution 486 are separated. During the separation of the liquid phases, the condensate is degassed. The released gas 44 is disposed of through the ejection process in the thermodynamic separator. To exclude the formation of gas hydrates, the separation tank is heated, where heat carrier 51, 52 is used for heating.

Claims (3)

1. Thermodynamic separator, including an ejector for accelerating, cooling reservoir gas with a high content of C ₃₊ hydrocarbons, ejecting the gas released during the degassing of liquid hydrocarbons, consisting of a nozzle in which a device for swirling the gas flow is installed, and a receiving chamber that provides gas ejection degassing from a separation tank, a separation part for separating liquid hydrocarbons, consisting of a mixing chamber and a diffuser, forming a calibrated gap between them for the removal of liquid coal hydrogen in a separation tank. 2. A method of preparing formation gas with a high content of C ₃₊ hydrocarbons, comprising supplying formation gas to a thermodynamic separator according to claim 1, wherein liquid hydrocarbons are separated from the gas, followed by collecting them in a separation vessel for degassing and ejecting the evolved gas and separation of the liquid phase into gas condensate and water-methanol solution, gas preparation is carried out to a predetermined depth of drying of commercial gas by accelerating the flow to a predetermined speed with simultaneous cooling and discharge flow of the condensed components. 3. The method according to claim 2, characterized in that at the outlet of the thermodynamic separator, a gas temperature above the hydrate formation temperature is provided.

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