RU2300062C2 - Method and device for drying gas pipelines - Google Patents

Abstract

FIELD: power mechanical engineering.

SUBSTANCE: method comprises preliminary evacuating and subsequent blowing of the space under vacuum by outer atmospheric air. The atmospheric air is throttled immediately upstream of the inlet to the space and is dried directly inside the space under vacuum by its expanding. The section of pipeline to be dried is separated from the remainder part by means of valves or plugs. The device comprises vacuum system, pipeline connected with the system and the space to be dried and provided with valve, means for control of pressure and residual humidity and cock that defines the passage for blowing with controlled throttle. The control throttle connects the space to be dried with the ambient air.

EFFECT: enhanced reliability.

5 cl, 2 dwg

Description

The invention relates to a technology for drying a cavity of gas pipelines and various equipment and can be used in power engineering, chemical, oil, gas, oil and gas processing and other industries.

A known method of drying the internal highways, including multiple sequential operations of evacuating and pressurizing the mains with dry gas and a device for its implementation, including vacuum pumps, piping, valves, gas meter [1].

The disadvantages of the known method and device are:

- high energy costs associated with multiple operations of evacuation and pressurization of highways;

- limited scope, due to the fact that this method is mainly intended for drying the working lines of the external cooling circuit of the temperature control system in the rocket and space field.

The closest technical solution is the method of drying gas pipelines, based on the initial evacuation and subsequent purging of the cavity under vacuum with external atmospheric air, which is introduced directly from the surrounding space, throttled when entering the cavity and dried directly in the cavity under vacuum, by extensions.

The device for drying the equipment cavity according to the prototype includes a vacuum system, a pipe connected to it for attaching to the drainable cavity, in which a valve, pressure and residual humidity control means are installed, and another valve forming a purge channel with an adjustable choke, which communicates the drainable cavity directly with the surrounding space [2].

The disadvantage of this method and device are:

- fire hazard when supplying main gas to a gas pipeline filled with atmospheric air;

- the formation of hydrocarbon hydrates when filling the drained cavity of the gas pipeline with main gas;

- lack of reliability associated with the lack of repair of the vacuum system when the device is running.

The task of the invention is to remedy these disadvantages, which will provide:

- fire safety when supplying main gas to a gas pipeline filled with an inert gas mixture based on nitrogen;

- the exception of the formation of hydrocarbon hydrates when filling the drained cavity of the gas pipeline with main gas;

- maintainability associated with the possibility of repair or replacement of the vacuum system when the device is running.

The problem is solved in that, in contrast to the known method of drying gas pipelines, based on the initial evacuation and subsequent purging of the cavity under vacuum, the outside atmospheric air, which is introduced directly from the surrounding space, is throttled when entering the cavity and dried directly in the cavity located under vacuum, by expanding it, according to the invention, the pipeline section to be dried is cut off by taps from the rest of the pipeline, taps in in the open position they are sealed or caps are sealed to the end parts of the gas pipeline; to a candle line located at one of the ends of the pipeline, connect the vacuum unit and pump air from the cavity of the pipeline to a pressure of from 0.2 to 0.005 kgf / cm ² ; maintaining the achieved vacuum, pump out water vapor from the cavity of the pipeline until the water film is completely boiled away; they purify atmospheric air from mechanical impurities, extract an explosion-proof inert gas mixture based on nitrogen with an oxygen content of up to 0.1% from atmospheric air in the gas separation unit, feed an inert gas mixture based on nitrogen into the cavity under vacuum, dry the inert gas the nitrogen-based gas mixture directly in the cavity under vacuum, by expanding it, while the inert nitrogen-based gas mixture is introduced in an amount that provides a stationary mode in -vacuum purge and for a time until a predetermined value of residual humidity in the cavity drained, the vacuum system is disconnected and the gas separation unit from. drained section of the gas pipeline and connect the drained section of the gas pipeline to the existing gas pipeline; fill the drained cavity of the gas pipeline with main or neutral gas, connect the drained section of the gas pipeline to the rest of the gas pipeline.

The option provides the duration of evacuation to absolute pressure from 0.01 to 0.001 kg / cm ² from 2 to 10 days and the duration of pumping water vapor from the cavity of the pipeline from 3 to 20 days; introducing hydrate formation inhibitors into the main gas from the following: methanol, ethyl alcohol, isopropyl alcohol, ammonia, ethylene, propylene, glycol, diethylene glycol ammonia, ethylene, propylene, glycol, diethylene glycol; filling the drained cavity of the gas pipeline with this gas through the bypass pipeline and the crane of the existing main gas pipeline or through shut-off valves of the remaining part of the gas pipeline under repair.

In contrast to the known device for drying a gas pipeline cavity, including a vacuum system, a pipe connected to it for attaching to a drainable cavity, in which a valve, pressure and residual humidity control means are installed, and another valve forming a purge channel with an adjustable choke, communicating the drainable cavity directly with the surrounding space, the proposed device has from one or more transportable by road and rail transport vacuum units connected by Allelic via flexible hoses ruggedized filter separator installed at the outlet overall exhaust line, gauge thermoelectric power locking, air filter, gas separation unit, valves, connecting lines; each vacuum unit is mounted on a common frame, has a vacuum spool pump, an oil tank, a drive motor, for example, an electric motor connected to a vacuum pump, a filter separator, oil line valves, electromagnetic oil supply valves, gas ballast electromagnetic valves, protective device, ball valves , a cooling system for a vacuum pump, vacuum gauges, temperature sensors, connecting pipelines and a rack with a control and control panel, suction and exhaust pipelines.

The option involves the use of a weighing container and a dispenser for inhibitors, a short-cycle adsorption or membrane gas separation unit containing adsorption or gas diffusion gas separation vessels, neutral gas tanks, an internal combustion engine using liquid or gaseous fuel, with a gearbox, clutch and a radiator of an internal combustion engine, gas filter and piping.

The vacuum drying method is based on the fact that with a decrease in pressure the boiling point of water decreases and, with a sufficiently deep vacuum, it becomes lower than the ambient temperature. The film of water remaining on the walls of the tank boils off due to the heat of the wall and the environment. The resulting steam is pumped out of the tank by a vacuum unit.

The required amount of nitrogen-based inert gas mixture introduced is determined by many factors: pressure, humidity and ambient temperature, volume of the drained cavity, residual pressure in it, and the performance of the vacuum system — and is provided by the cross-sectional area of the gas distribution unit through which the outside atmospheric air is sucked when communicating drained cavity with the surrounding space by opening the purge channel. The optimal energy consumption and drying speed is the residual pressure in the cavity, at which the regime of vacuum purge, equal to from 0.01 to 0.001 kg / cm ² . Moreover, the higher the temperature and humidity of the inert gas mixture based on nitrogen, the lower should be the level of residual pressure in the drained cavity provided by the vacuum system. At this level of residual pressure in the cavity, an inert gas mixture based on nitrogen, passing through the throttling channel formed by the gas distribution unit, rapidly expands tens of times, as a result of which the absolute and relative humidity of the inert gas mixture based on nitrogen decreases proportionally to the increasing volume of the inert gas mixture by nitrogen base, reaching a dew point temperature of (-20 ...- 40) ° C, and the inert gas mixture based on nitrogen is dried.

The nitrogen-based inert gas mixture thus dried absorbs residual moisture in the cavity: at the beginning of the purge - near the air inlet, and then progressively as the saturation front moves to the vacuum system - in the entire drained cavity. The degree of drying is controlled by the humidity of the inert nitrogen-based gas mixture leaving the cavity by known means. When reaching a residual moisture content equal to a predetermined value at the outlet of the drained cavity, the supply of an inert gas mixture based on nitrogen into the drained cavity is stopped. In the proposed method, an inert nitrogen-based gas mixture for purging is drained by rapid expansion, and the gas cavity is dried by absorbing residual moisture and aspirating by the vacuum system a saturated inert gas mixture based on nitrogen.

The technical result of the invention is to increase the maintainability of the vacuum system, the degree of drying of the cavity of the gas pipelines and the efficiency of the vacuum system.

The design of the proposed device is sufficient to solve the problem due to the more efficient use of technological equipment, which is expressed in the fact that for each productivity there is a certain set of transportable vacuum and road transport units by road and rail connected in parallel using flexible hoses of increased strength, which eliminates the effect of inaccuracy installation of vacuum units during installation and the impact of vibration during operation.

The reliability and maintainability of the evacuation unit is determined by the parallel connection of the evacuation units with the help of flexible hoses of increased strength, which allows the gas cavity to be dried during the repair of one of the evacuation units.

The function of the desiccant of the inert gas mixture based on nitrogen is performed by a set of gas distribution vessels of the gas separation unit, the passage area of which is selected from the condition for ensuring the residual pressure in the drainable cavity, which is necessary for the stationary regime of vacuum purging from 0.01 to 0.001 kg / cm ² .

An analysis of the information showed that the claimed technical solution is unknown from the achieved level of technology, and therefore it meets the criterion of "novelty."

Such a technical solution does not explicitly follow from the prior art and, therefore, meets the criterion of "inventive step".

The foregoing indicates that the invention meets the criterion of "industrial applicability".

The invention is illustrated in Fig.1, 2, which depicts a schematic diagram and a vacuum unit of the proposed device for drying a gas pipeline, which is fundamentally no different from other drying devices.

The device consists of two evacuation units 27 connected in parallel using hoses of increased strength 28. A filter separator 32 is installed at the output of the common exhaust line. For drying the gas pipeline cavity and filling it with neutral gas, for example, an inert gas mixture based on nitrogen, the device has successively arranged atmospheric air inlet, air filter 31, gas separation unit 35, valve 38. To fill the drained cavity of the gas pipeline with main gas, a valve 42 or valve 36. In order to prevent the formation of hydrocarbons idratov drained while filling the cavity 40 trunk pipeline gas device has a weighting container 34 and dispenser 37 hydrate inhibitor.

Each evacuation unit 27 has: a support frame 47, a vacuum spool pump 21, a drive motor 15, a filter separator 11, a protective casing 46, a protective device 9, a ball valve 3, a cooling system for a vacuum pump, consisting of: a radiator 6, four electric fans 5, water pump 12, expansion tank 8, connecting pipelines and four manual taps 7, 10, 13, 14; oil tank 25, gas-ballast solenoid valves 16, 17, 18, 19, 20, two vacuum gauges 2 and 4, a temperature sensor 24, connecting piping 28 and a rack 45 with a control and monitoring panel 44. On one of the racks, except for the control and monitoring panel, a thermoelectric blocking vacuum gauge is installed common to all blocks (not shown).

The drying of the cavity of the pipeline is as follows.

End caps 41 are sealed to the end parts of the drained section of the gas pipeline 40; to a candle line located at one end of the gas pipeline, a vacuum unit consisting of two evacuation units 27 is connected through a valve 33.

Before starting the installation, the valves 3 are closed, the shaft of the vacuum pump 21 is manually rotated 3 ... 4 turns to remove excess oil from the rotor chambers.

Then, alternately, when starting the vacuum pump 21 of each of the evacuation units 27, open the cooling water supply valves 13, 14 to the body of the vacuum pump 21 and the oil tank 25, open the manual oil line valve 23 and the electromagnetic oil supply valve 22, and start the vacuum pump 21. Startup is carried out with the ball valve 3 closed by three short-term shocks, lasting 2 ... 3 seconds, monitoring the suction pressure, they work for several seconds until the absolute value of the suction pressure of 0.2 kgf / cm ^{2 is} reached.

After the installation is started, the gas pipeline cavity is dried in two stages.

At the first stage, air is pumped out to a suction pressure of 0.2 kgf / cm ² , at which water located on the inner surface of the pipe in the form of a film begins to boil. To do this, slightly open the ball valves 3 of the suction lines of each block 27, avoiding the increase in pressure at the inlet to the vacuum pump 21 above 0.2 kgf / cm ² . Gradually, opening the taps 3 and supporting the pressure of 0.2 kgf / cm ² at the inlet of the vacuum pumps 21, pump out the air until the pressure in the evacuated cavity of the pipeline from 40 to 0.01 kgf / cm ^{2 is} reached. The estimated time of evacuation to an absolute pressure of 0.01 kg / cm ² - 2 days.

At the second stage, maintaining the achieved vacuum, water vapor is pumped out until the water film is completely boiled away.

To pump water vapor from the cavity of the pipeline close the ball valve 3 of the suction line, turn off the fans 5, open the gas-ballast solenoid valves 16, 17, 18, 19, 20 and work until the oil temperature rises to 70 ° ... 75 ° C. If necessary, taps 13 and 14 are covered.

Next, close one or more gas-ballast solenoid valves 16, 17, 18, 19, 20. Depending on the pressure in the tank, they are left open:

- one valve at a pressure of less than 0.013 atm;

- two valves at a pressure of 0.013 ... 0.022 atmospheres;

- three valves at a pressure of 0.022 ... 0.031 atm;

- four valves at a pressure of 0.031 ... 0.04 atm;

and, maintaining the oil temperature 70 ° ... 75 ° C, the vapors are pumped out until the water is completely boiled away. During boiling, the pressure in the vessel remains almost constant. The end of the process of pumping water vapor from the cavity of the pipeline is determined by the beginning of a further decrease in pressure. The oil temperature is maintained by turning the fans 5 on and off and, if necessary, by closing-opening the taps 13, 14.

When pumping out vapors, the presence of water in the oil is monitored, for which a small amount (0.5 ... 1 cm ³ ) of oil is periodically drained through the valve 26 in the lower part of the oil tank 25, checking for the absence of water. At the same time, it is necessary to monitor the appearance of the oil (through the glass of the oil indicator). The oil should remain clear.

The gas separation unit 35 and the air filter 31 are connected to the drained section of the gas pipeline 40 through the valve 38, the atmospheric air is cleaned from the mechanical impurities in the filter 31, an explosion-proof inert gas mixture based on nitrogen with an oxygen content of 5% is extracted from the atmospheric air in the gas separation unit 35, and fed to the cavity of the gas pipeline 40, under vacuum, an inert gas mixture based on nitrogen, drain the inert gas mixture based on nitrogen directly in the cavity of the gas pipeline 40, under vacuum, by asshireniya, wherein the inert gas mixture based on nitrogen is introduced in an amount providing a stationary vacuum purge mode and for the time until a residual humidity in the cavity drained predetermined value. An inert nitrogen-based gas mixture under the influence of a pressure drop is introduced through the throttling section of the gas separation unit 35 into the cavity of the gas pipeline 40, where it is drained by rapid expansion, since the expansion of the inert gas mixture based on nitrogen decreases its absolute and relative humidity in proportion to the degree of expansion, and The set dew point temperature is reached. The dried portions of the nitrogen-based inert gas mixture absorb the residual moisture first near the inlet of the nitrogen-based inert gas mixture and then, as the saturation front moves inside the cavity of the gas pipeline 40, up to the end of the drainable section of the gas pipeline 40 due to the operation of the vacuum system and continuous absorption from the atmosphere inert gas mixture based on nitrogen drained by throttling.

At this stage, there is a vacuum purge of the cavity 40 dried with an inert gas mixture based on nitrogen. The amount of nitrogen-based inert gas mixture introduced is required, on the one hand, to realize the required expansion ratio for drying it, and on the other hand, to provide a stationary regime of vacuum purging, provide the necessary set of gas separation vessels in the gas separation unit 35. This stage is continued for the time required to achieve a given value of residual moisture in the drained cavity of the gas pipeline 40. After that, the vacuum purge is stopped by blocking the purge channel m 33. The vacuum system continues to operate, and thus the final vacuum step is carried out until a residual pressure in the cavity 11 values of 0.005 kg / cm ^2. After this, the drying process is considered complete.

The drying process is controlled using vacuum gauges 2 and 4, a temperature sensor 24. Thanks to the vacuum in the drained cavity, you can easily verify the quality of drying by disconnecting the drained cavity of the gas pipeline 40 from the vacuum system by closing the valve 33. In this case, the residual moisture turns into a vaporous state. Any measurable rise in pressure and dew point is a direct indication of the presence of residual moisture in the cavity of the gas pipeline 33.

Next, the vacuum unit and the gas separation unit 35 are disconnected from the drained section of the pipeline 40 and connected through the valve 41 to the drained section of the pipeline 40 to the existing pipeline 43 or through the valve 36 to the remaining repaired section of the pipeline 39. In order to exclude hydrocarbon hydrates, a hydrate inhibitor is introduced into the drained cavity of the pipeline. from the number: methanol, ethyl alcohol, isopropyl alcohol, ammonia, ethylene; propylene, glycol, ethylene glycol. Fill the drained cavity of the gas pipeline 40 with this gas or fill it with an inert gas mixture based on nitrogen or another neutral gas; connect the drained section of the pipeline 40 to the rest of the pipeline 39.

The claimed method and device were tested during the drying of the gas pipeline "Bukhara-Ural" 1919-1945 km. There were no traces of moisture on the inner walls of the gas pipeline. Vacuum units are planned for production at Uraltransgaz LLC using available materials, components and technologies.

Information sources

1. Patent RU No. 2170608 of July 20, 2001.

2. Patent RU No. 2198361 dated January 4, 2001.

Claims (5)

1. The method of drying gas pipelines, based on the initial evacuation and subsequent purging of the cavity under vacuum, the outside atmospheric air, which is introduced directly from the surrounding space, throttled when entering the cavity and dried directly in the cavity under vacuum, by its expansion, characterized by the fact that the section of the gas pipeline to be dried is cut off by taps from the rest of the gas pipeline, the taps in the closed position are sealed or welded to the end parts of the gas pipeline ayut sealingly plugs; to a candle line located at one of the ends of the pipeline, connect the vacuum unit and pump air from the cavity of the pipeline to a pressure of from 0.2 to 0.005 kgf / cm ² ; maintaining the achieved vacuum, pump out water vapor from the cavity of the pipeline until the water film is completely boiled away; they purify atmospheric air from mechanical impurities, extract an explosion-proof inert gas mixture based on nitrogen with an oxygen content of up to 0.1% from atmospheric air in the gas separation unit, feed an inert gas mixture based on nitrogen into the cavity under vacuum, dry the inert gas the nitrogen-based gas mixture directly in the cavity under vacuum, by expanding it, while the inert nitrogen-based gas mixture is introduced in an amount that provides a stationary mode in -vacuum purge and during the time until a residual humidity in the cavity drained predetermined value, the vacuum system is disconnected and the gas separating unit from the dried portion of the pipeline and the pipeline is connected dried portion to the existing pipeline; fill the drained cavity of the pipeline with main gas, connect the drained section of the pipeline to the rest of the pipeline. 2. The method according to claim 1, characterized in that the duration of evacuation to absolute pressure from 0.01 to 0.001 kg / cm ² from 1 to 10 days and the duration of pumping water vapor from the cavity of the pipeline from 1 to 30 days, fill the main gas drained the gas pipeline cavity through the bypass pipeline and the crane of the existing main gas pipeline or through shut-off valves of the remaining part of the gas pipeline under repair. 3. The method according to claim 1, characterized in that a hydrate formation inhibitor of methanol, ethanol, isopropyl alcohol, ammonia, ethylene, propylene, glycol, diethylene glycol is introduced into the main gas supplied to the drained cavity of the gas pipeline. 4. A device for drying a gas pipeline, including a vacuum system, a pipe connected to it for attaching to a drainable cavity, in which a valve, pressure and residual moisture control means and another valve forming a purge channel with an adjustable choke are installed, which communicates the drainable cavity directly with the surrounding space , characterized in that it has from one or more transportable by road and rail transport vacuum units connected in parallel with flexible hoses Accelerating strength filter separator installed at the outlet overall exhaust line, gas separation unit, air filter, valves, connecting lines and gauge locking thermoelectric power; each evacuation unit is mounted on a common frame, has a vacuum spool pump, an oil tank, a drive motor, for example an electric motor connected to a vacuum pump, a filter separator, oil line valves, electromagnetic oil supply valves, gas ballast electromagnetic valves, protective device, ball valves, vacuum pump cooling system, vacuum gauges, temperature sensors, connecting pipelines and a rack with a control and control panel, suction and exhaust pipelines. 5. The device according to claim 4, characterized in that it has a short-cycle adsorption or membrane gas separation unit containing adsorption or gas diffusion gas separation vessels, a neutral gas tank, a weight container and a hydrate inhibitor dispenser, an internal combustion engine using a liquid or gaseous fuel with a gearbox, clutch and radiator of an internal combustion engine, a filter and a gas pipeline.

Images