RU2631186C1 - Method for processing low-pressure hydrocarbon gases of flare systems - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method includes processing of low-pressure hydrocarbon gases of flare systems by ejecting them from flare manifolds by a stream of compressed hydrocarbon gas to be drawn into a hydrocarbon gas stream before receiving a compressor, for subsequent compression, amine treatment in an absorber tower and further use as fuel for process furnaces.

EFFECT: use of hydrocarbon gases with low excess pressure, previously burned in flare plants, as fuel for process furnaces.

1 dwg

Description

The invention relates to the oil and gas industry, in particular to methods and devices for utilization of low-pressure hydrocarbon gases of flare systems in order to obtain fuel gas for process furnaces from oil and gas processing products.

A known method of utilization of low-potential hydrocarbon gases (patent No. 2560188, RF, IPC C10L 3/10, B01D 53/52), which includes an absorption column for the purification of hydrocarbon gases, with a supply line to it for supplying an aqueous solution of monoethanolamine (MEA) equipped with a pump and a heat exchanger for cooling the MEA aqueous solution, a separator for drying the purified hydrocarbon gases, two parallel gas-jet ejectors with supply lines for the purified and dried hydrocarbon gases and VSG, a separator for drying and eploobmennik heating the resultant fuel gas.

The disadvantage of this method is that when ejecting flare gases, the possibility of a vacuum in the flare collector, due to the lack of automatic control, is not ruled out.

A known method of utilization of low-grade gases (patent No. 1805727, RF, IPC F04F 5/54), in which the low-pressure gas is supplied to the primary separator, from where it is ejected by the liquid coming from the pump with the mixture in the secondary separator, and the liquid from the primary separator to primary recirculation is carried out with its simultaneous cooling.

The disadvantages of this method are:

- increased energy costs for raising the pressure in the pump from the liquid pressure equal to the low-pressure gas to the pressure at the pump outlet necessary for ejecting the gas;

- the impossibility of ejecting two or more streams with different parameters or different in composition;

- carrying out the process in two devices, a separator and a three-phase separator, which leads to increased capital costs.

A known method of utilizing low-grade hydrocarbon gases (RF patent No. 2179660, IPC F04F 5/54, priority 25.05.2000), including ejection compression of two low-grade gases of different composition by high-pressure liquid (of the same composition, pressure and temperature) and subsequent separation of the mixtures in separate separators on compressed gas and liquid, gas supply to the consumer. In this method, the disadvantage of the impossibility of ejecting two or more streams is eliminated.

The disadvantage of increased energy costs at the pumps was partially eliminated, as pump pressure is raised not from the pressure of low-grade gases, but from a pressure equal to the pressure at the outlet of the ejectors, i.e. from the pressure of compressed gases. However, at different pressures of low-pressure gases, the pressure of the active liquid must be kept maximum based on the compression of a gas of lower pressure, which leads to increased energy costs.

The disadvantage of carrying out the process in two separators of different designs remains. In addition, the active liquid recirculated by the pump is saturated with various gases, which is not always acceptable from the point of view of fire safety or saturation of the liquid with corrosive components.

A known method of disposal of low-grade gases (patent No. 2435990, RF, IPC F04F 5/54). The installation includes ejectors for compressing low-grade gases with high-pressure fluid flows from recirculation pumps, a three-phase separator for separating a gas-liquid mixture into gas, hydrocarbon and aqueous liquids, separation-coalescing nozzles for separating gas from a liquid, and separation-coalescing nozzles for final separation of a hydrocarbon liquid into hydrocarbon and water phases.

The disadvantage of this method is the complexity of the process equipment, high energy costs and the impossibility of simultaneous and complete processing of low-grade gases.

The objective of the invention is to develop a facility that allows the disposal of low-pressure hydrocarbon gases of flare systems in order to obtain fuel gas for process furnaces. The problem is solved by utilizing low-pressure hydrocarbon gases of flare systems with an overpressure of 0.0001 to 0.3 MPa, using a compression and purification unit for fuel gases, including a compressor, separators, water and air coolers, an ejector jet pump, and an amine absorber. The fuel gas compression and purification unit operates as follows: a portion of the compressed, cooled, and separated gas from the compressor discharge is mixed with the gases taken from the flare systems using an ejector jet pump and returned to the hydrocarbon gas stream coming from technological plants to the compressor receiving separator for subsequent compression , cooling and amine purification in order to obtain purified fuel gas for process furnaces, while the optimal selection of carbohydrates burly gas flare systems in which stable combustion flame is provided is provided an automatic control system.

The use of the process of utilization of low-pressure hydrocarbon gases in flare systems by ejection with a compressed gas stream allows maximum extraction of hydrocarbon gases from flare collectors with an overpressure of 0.0001 to 0.3 MPa, with a view to their subsequent use as fuel gas, that is, to minimize the flow of low-pressure hydrocarbon gas flared.

Applicants and authors have not found similar signs that could ensure the utilization of low-pressure hydrocarbon gases of flare systems from flare collectors using a stream of compressed gas.

In FIG. The scheme of utilization of low-pressure hydrocarbon gases of flare systems is presented, which shows the positions of the following devices:

1 - ejector;

2 - shut-off and control valve

3 - compressor receiving separator;

4 - compressor;

5 - air cooling apparatus;

6 - water refrigerator;

7 - compressed gas separator;

8 - absorber column for cleaning a gas stream with methyldiethanolamine solution (hereinafter referred to as MDEA);

9 - check valve.

In FIG. The following streams are marked:

I is the flow of low-pressure hydrocarbon gas of the flare system, taken from the flare collectors;

II - flow of ejected hydrocarbon gas;

III - hydrocarbon gas flow from process units;

IV - combined flow of hydrocarbon gas;

V — compressed and cooled hydrocarbon gas;

VI - hydrocarbon gas, purified by a solution of MDEA;

VII - a regenerated aqueous solution of MDEA;

VIII - an aqueous solution of MDEA saturated with hydrogen sulfide.

In FIG. a diagram illustrating the proposed method of disposal of low-pressure hydrocarbon gases of flare systems with an excess pressure of from 0.0001 to 0.3 MPa is shown.

The low-pressure hydrocarbon gas of the flare system is selected from the existing flare collectors (I) by the ejector 1. For this, part of the compressed and cooled gas (V) after the compressed gas separator 7, whose pressure is higher than the pressure of the ejected low-pressure hydrocarbon gases of the flare systems, is supplied to the ejector 1.

The principle of regulating the flow of hydrocarbon gas in the flare system: if the flow or pressure on the flare barrel starts to increase in the flare manifold, the control unit sends a signal to close the shut-off and control valve 2. This leads to a decrease in pressure in the pipeline of low-pressure hydrocarbon gas of the flare system in front of the ejector. Consequently, the suction of hydrocarbon gas from the flare manifold also increases. In the case of a decrease in the flow rate and pressure of hydrocarbon gas in the flare collector, everything happens in the reverse order. To prevent gas from flowing through the shut-off and control valve 2 into the flare manifold, a check valve 9 is installed. The flow of hydrocarbon gas through the ejector nozzle is assumed to be constant depending on the performance of the ejector. The ejected gas stream (II) is then mixed with the hydrocarbon gas stream coming from the process units (III).

Next, the combined stream of hydrocarbon gases (IV) enters the compressor receiving separator 3, located at the compressor 4 receiving. After compression by the compressor 4 and subsequent cooling by means of an air cooling apparatus 5, a water cooler 6 and separation of gas condensate in the compressed gas separator 7, the main part compressed hydrocarbon gas stream (V) enters the absorber column 8 for cleaning from hydrogen sulfide with a solution of MDEA. A cooled MDEA (VII) aqueous solution is supplied to the top of the column. Countercurrent contact of an aqueous solution of MDEA with a hydrocarbon gas leads to the absorption of hydrogen sulfide by an aqueous solution of MDEA.

An aqueous solution of MDEA (VIII) saturated with hydrogen sulfide is discharged from the bottom of the absorption column 8 and is sent for regeneration.

Purified hydrocarbon gas (VI) as fuel gas is supplied to consumers for technological needs.

Claims (1)

A method of utilizing low-pressure hydrocarbon gases of flare systems with an overpressure of 0.0001 to 0.3 MPa, using a compression and purification unit for fuel gases, including a compressor, separators, water and air coolers, an amine absorber, characterized in that part of the compressed, cooled and the separated gas from the compressor discharge is mixed with the gases taken from the flare systems using an ejector jet pump and returned to the flow of hydrocarbon gas from the process units in the compressor receiving separator for subsequent compression, cooling and amine purification in order to obtain purified fuel gas for technological needs, while the optimal selection of hydrocarbon gases from flare systems is supported by an automatic control system.

Images