RU2236891C2 - Method of cleaning hydrocarbon gas - Google Patents

Abstract

FIELD: preparation of hydrocarbon gases for transportation and/or processing.

SUBSTANCE: proposed method includes scrubbing of gas by circulating water; at least part of circulating water flow directed for scrubbing the gas is heated to boiling point and then steam phase is separated from liquid phase and cooled for obtaining water condensate, after which it is fed to recirculating line. After scrubbing, gas is compressed and water is heated to boiling point by heat of compressed gas. Concentration of salts in water fed for scrubbing shall not exceed 12 g/l. Flow rate of water fed for heating shall not be below 2.0 m/s.

EFFECT: increased degree of cleaning gas from toxic admixtures to 98-99.9%; reduction of residual content of salts in gas to 0.17 mg/cu m.

4 cl, 2 ex

Description

The invention relates to a technology for the preparation of hydrocarbon gases for transport and / or processing, and can be used in the oil and gas and oil and gas processing industries.

A known method of wet cleaning of gases, which consists in the fact that the gases are irrigated in the pipeline with washing liquid, and then the resulting mixture of gas with liquid is passed through a cyclone separator from which the purified gas is discharged (patent of the Russian Federation No. 2121866, publ. 11/20/98, IPC6 B 01 D 47/06).

Common features of the known and proposed methods are: gas purification with washing liquid and separation of the purified gas from the liquid.

The disadvantage of this method is the high operating costs and low cleaning efficiency associated with the low intensity of mixing gas and liquid and, as a result, the increased flow rate of the liquid for washing.

The closest in technical essence to the proposed one is the method implemented on the installation of gas compression (RF patent No. 2073182, publ. 02/10/97, class F 25 J 3/08). The method consists in washing the hydrocarbon gas with washing water.

A common feature of the known and proposed methods is flushing hydrocarbon gas with circulating water.

In the known method, an insufficiently high degree of gas purification from harmful impurities is achieved - 75-80%. The residual salt content in the gas after washing is about 4 mg / st.m ³ , i.e. significantly exceeds the requirements of further technology (for example, the process of drying and purifying gas from sulfur compounds).

The disadvantage of this method is also the high capital and operating costs associated with a large flow of water for flushing. In addition, this technology involves the use of a special unit for preparing water for washing. Since the concentration of salts in the circulating water after washing is very high, such water cannot be used for repeated washing.

The technical problem is to increase to 98-99.9% the degree of gas purification from harmful impurities (heavy organic substances, surfactants, corrosion inhibitors, mechanical impurities), to reduce the residual salt content (alkali and alkaline earth metal chlorides) in the gas after washing to a value not exceeding 0.17 mg / stm ³ , and reducing capital and operating costs due to flushing gas with circulating water with a low content of harmful impurities.

The problem is achieved in that in the method of purification of hydrocarbon gas, including washing it with circulating water, at least part of the flow of circulating water directed to the washing is diverted and heated to boiling point. Then the vapor phase is separated from the liquid, cooled to obtain aqueous condensate and returned to the recirculation of water.

In a variant of the purification method, the gas after washing is compressed and the water is heated to the boiling point of water with the heat of compressed gas.

In addition, in the water supplied for washing, the salt concentration should not exceed 12 g / l.

In addition, to reduce the intensity of scaling in heat exchange equipment, the flow rate of the water when it is supplied to the heating stage should be at least 2.0 m / s.

The claimed combination of features allows to achieve a high degree of purification of gas from harmful impurities - 98-99.9% at a fairly low capital cost. The residual salt content in the gas after washing meets the requirements of further technology (for example, the process of drying and purifying gas from sulfur compounds), i.e. does not exceed 0.17 mg / st.m ³ . The concentration of salts in the circulating water corresponds to the required quality. This is achieved by regenerating part of the circulating water flow (the optimum amount of circulating water is 5-50% of the total flow directed to the flushing), replenishing the regenerated flow with fresh water and directing the water flow to the gas flushing stage, while water saturated with harmful substances is discharged into drainage. The regeneration of a part of the circulating water flow is carried out by heating it to a boiling point, separating the liquid phase in which the harmful impurities are concentrated from the vapor phase, condensing water vapor and directing the formed condensate-free water condensate to the gas washing stage. As a result of such operations, there is no need for a special water treatment unit.

In a variant of the gas purification method, the latter is washed with water, separated from the liquid and compressed, and part of the water flow (the optimum amount of circulating water is 5-50% of the total flow directed to the washing) is diverted and heated to the boiling point by heat exchange with heated by compression gas.

Example 1

The method of purification of hydrocarbon gas is as follows. Hydrocarbon gas in an amount of 260,000 st.m ³ / h at a pressure of 0.4 MPa and a temperature of 23 ° C, containing impurities, for example, surfactants - 0.8 mg / st.m ³ , alkali and alkaline earth metal chlorides - 20 mg / st. m ³ , served for washing in a scrubber. Water is also fed into the scrubber in an amount of 7.5-10 t / h (surfactant - 0.17-0.42 g / l, alkali and alkaline earth metal chlorides - 4.46-12 g / l) coming from the recirculation tank. Hydrocarbon gas after washing in a scrubber contains: surfactant - 0.0026-0.0064 mg / st.m ³ , which corresponds to a degree of gas purification of approximately 99.7%. The residual content of salts (chlorides of alkali and alkaline earth metals) is 0.07-0.17 mg / st.m ³ in gas, which meets the requirements of further technology. Part of the flow of circulating water in an amount of 5-50% of the total flow directed to the washing is diverted and heated to boiling point at a pressure of 0.12-0.14 MPa, after which the vapor phase is separated from the liquid. To prevent the deposition of salts on the walls of the tubes of the heat exchanger, the flow rate of the water when it is supplied to the heating stage should be at least 2.0 m / s. Water vapor is cooled in an air cooler to a condensation temperature, the resulting water condensate is sent to a water recirculation tank and then to the gas washing stage in a scrubber, and the liquid phase saturated with harmful impurities (surfactant is 0.85 g / l, alkali and alkaline earth chlorides metals - 22.24-22.39 g / l) are drained. As a make-up, technical water is supplied to the water recirculation tank in the amount necessary to maintain the required amount of circulating water and the concentration of salts in the wash water.

Example 2

In a variant of the method for gas purification, hydrocarbon gas in an amount of 260,000 st.m ³ / h at a pressure of 0.4 MPa and a temperature of 23 ° C, containing impurities, for example surfactant - 0.8 mg / st.m ³ , alkali and alkaline earth metal chlorides - 20 mg / st.m ³ , served for washing in a scrubber. The scrubber also serves water in an amount of 7.5-10 t / h from the recirculation tank. Hydrocarbon gas after washing in a scrubber contains: surfactant - 0.0026-0.0064 mg / st.m ³ , which corresponds to a degree of gas purification of approximately 99.7%. The residual content of salts (chlorides of alkali and alkaline earth metals) is 0.07-0.17 mg / st.m ³ in gas, which meets the requirements of further technology. Hydrocarbon gas after separation in the separator from the liquid phase is supplied for compression, for example to 5.6 MPa, while it is heated by compression to a temperature of 159 ° C. The circulation water supplied for regeneration in an amount of 0.5-1.2 t / h and at a speed of at least 2.0 m / s is heated by a hot stream of compressed gas to a temperature of 104-109 ° C at a pressure of 0.12-0, 14 MPa and sent to the separation. The vapor phase withdrawn from the separator is condensed in an air cooler in an amount of 0.24-0.97 t / h and the condensate obtained is sent to a water recirculation tank, and from there to a wash. The liquid phase from the separator containing harmful impurities is diverted to the drain. As a recharge, the process water is supplied to the water recirculation tank in the amount necessary to maintain the required amount of circulating water and the concentration of salts in the wash water (surfactant -0.17-0.42 g / l, alkali and alkaline earth metal chlorides - 4.46- 12 g / l). The compressed gas is cooled to a temperature of 155-158 ° C by heat exchange with water coming from a recirculation tank, it is cooled to a temperature of 40-50 ° C, separated and sent for further processing or transportation.

Claims (4)

1. The method of purification of hydrocarbon gas, including rinsing it with circulating water, characterized in that at least a portion of the circulating water flow directed to the gas rinsing is diverted and heated to the boiling point of water, then the vapor phase is separated from the liquid, cooled to obtain water condensate and serves for recirculation of water. 2. The method according to claim 1, characterized in that the gas after washing is compressed, and the water is heated to the boiling point of water with the heat of compressed gas. 3. The method according to claim 1 or 2, characterized in that in the water supplied to the washing, the salt concentration should not exceed 12 g / L. 4. The method according to claim 1, or 2, or 3, characterized in that the flow rate of the water when it is supplied to the heating stage should be at least 2.0 m / s.