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THE RIGS FOR UNDERGROUND GAS STORAGE IN RUSSIA
Shelenkov Alexander Alexandrovich, Astrakhan State Technical University, Astrakhan
E-mail: alex-shele@mail.ru
Nurmuhambetova Svetlana Alexandrovna, the department of "Languages in engineering education" Astrakhan State Technical University, Astrakhan
E-mail: svet.nurmuhambetova2011@yandex.ru
Abstract. The topic of this article is the problem of rational absorbers design in Russia. The main rigs and their structure were reviewed. Absorbers design procedure and details related to the elements of the absorber were considered.
Keywords: gas industry, chemical industry, absorbers design, gas
absorption.
The gas industry is one of the main branches of fuel and energy complex. The orientation to natural gas allows predicting the long-term development of fuel energy. To a certain extent, it depends on the reliable raw-material base. The rapid development of gas industry, the development of new gas and gas condensate fields, construction of gas processing facilities require the improvement of existing underground gas storage facilities and the creation of new ones. At the same time it needs the improvement of storage gas conditions and its methods of dehydration for further transportation to consumers.
Today gas industry is one of the leading sectors of the Russian Federation. A major percentage of produced gas goes for export, therefore, the demand for gas is growing, and this leads to the development of natural gas industry: developing new fields, building new pipelines, construction of refineries and new technologies. Underground gas storage is a complex of engineering structures in reservoirs of geological structures, also in mines-reservoirs created in rock salt deposits, intended for injection, storage and subsequent gas extraction, including gathering system and gas treatment plant, compressor plant. Selection of gas from underground storage facilities is almost the same technological process as extraction from gas fields.
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Passing through the loops, he arrives at the gas collection points, where it is collected in the gas collection manifold. Then gas goes to the separation site for being separated from water and mechanical impurities, then routed to the site cleaning and drying. Cleaned and dried gas is pumped into the gas pipelines.
Natural gas contains mechanical impurities in solid, liquid and gaseous state. Solid impurities include oxides of aluminium, silicon compounds, iron, calcium, magnesium, sulphur, and others; liquid and gaseous impurities include water. The presence of moisture in the gas causes corrosion of pipelines and equipment, and the formation of hydrates. The presence of water vapour in the hydrocarbon gas is connected with a contact gas and water in reservoir conditions. The presence of moisture in gas is undesirable (and sometimes dangerous) to transport, because moisture can appear in a pure form or in the form of hydrates with hydrocarbons, leading to complications in the operation of the transport device. The moisture is unwanted in a gas, if subsequent processing is carried out at low temperatures. Thus, it is advisable to perform gas drying by means of absorption from moisture in storage which is considered to be the most effective method for the further gas transportation to consumers.
о Therefore, it is necessary to take a brief overview of the main absorption gas
dewatering rigs on the territory of the Russian Federation; system analysis of one of the rigs; the design and calculation of geometrical parts of the apparatus and the hydraulic resistance, as well as the choice of the optimal mass transfer of parts of the absorber to the flow of the process.
The largest rigs of absorption gas drying are operated on the fields of the West Tarkosalinskoye, Urengoy and Yamburg. Technological schemes of the dewatering rigs West Tarkosalinskoye and Urengoy gas-condensate fields are close; their difference is related to hardware design. The water vapour is the heat carrier in regeneration blocks at these facilities. Rigs of Urengoy field consist of two units: dehydration and regeneration of saturated glycol solution. Gas dehydration units include absorbers and separators. In some cases absorbers include separation section, resulting in a compact unit. Regeneration blocks include degasser, desorption, reflux tank, the vacuum system, etc. Now the gas pressure is significantly lower than in the initial period of operation of field for all drying units. Another important host rig of gas dehydration is the regeneration unit of a saturated solution, which includes desorption with irrigation system, a regenerative heat exchanger, evaporator, pumps, etc. Besides that, the composition of the gas dewatering rigs includes auxiliary devices separators, sumps, etc. The absorber consists of three sections (inlet separation, mass transfer and trapping of absorbent). Then gas is separated from dropping liquid in the input separation section. Next gas is dehumidified in a mass transfer section interacting with the absorbent. After that gas enters the trapping section of the absorbent and it is discharged from the apparatus. Further, dry gas is sent by pipeline to consumers. In turn, the solution of water with the first absorbent is sent to the
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degasser, and then to desorption, which results in complete regeneration of the absorbent, then the absorbent supplied to the absorber by means of a pump. Water vapour from the desorber is sent to the vacuum pump.
It is best to take the absorber with discs, as it provides better contact of the phases. It is also worth noting, that the disc absorbers have the following advantages: the ability to work under any relationship of weight amounts of liquid and gas, in which packing apparatus is quite impossible to use; keeping the distribution concentration of liquid in the machine while it stops and the subsequent resumption of work, the possibility of removal heat absorption using the refrigerators placed on the plates of the column; smaller size and weight of the devices. In addition, it is necessary to use the perforated plates, because there are simple devices, easy installation, inspection and repair. The hydraulic resistance of these plates is rather small. The perforated plates operate stably in a wide range of gas velocities, and within a certain range of loads on gas and liquid, these plates are highly effective.
The source gas tangentially attached to the fitting of the absorber enters the first separation section. The separation of dropping liquid in this section is performed while passing gas through the mesh baffle and the separating plate, on which there are о centrifugal separating elements. The second section is intended for gas drying and 9 incorporates four plates with contact elements of the centrifugal type. Each centrifugal direct-flow element consists of a cylindrical body and it is equipped in the lower part of the tangential swirler. Tangential swirler can be replaced combined or axial in various modifications of such elements. A short distance from the plates, the centrifugal element is equipped with a pipe used for supplying fluid to the center of the element. There is conical cup above the pipe in the central part of the element, providing the constriction of the gas flow that creates a low pressure area. By reducing the pressure inside the elements, fluid in the tube, having a hole in the bottom, fed into the element. Upon contact with the swirling gas stream, the liquid is distributed over the element wall and rises up. A bump serves for separation liquid membrane from the gas flow. The rich glycol is collected in the internal tank, from where it is diverted for regeneration. The latest gases trap section of the glycol is formed by the separation plate and the plate with the filter-cartridges. Filter-cartridges are made in the form of a perforated cylindrical carcass by winding layers. Layer of the filter material is fastened with two-three layers of tubular mesh inside and outside.
All the physical and chemical processes carried out in chemical apparatus primarily require the carcass. This carcass must be sufficiently strong and airtight. Absorbers usually are made of carbon steel, since this material does not undergo appreciable corrosion cracking, while this material is economically feasible. One of the rational forms of the bottom in the cylindrical apparatus is elliptical shape, since it is a form provides the most uniform stress distribution. It is necessary to check the strength and stability of the device installed in the open air under the wind action. The main role is played here by the bending moment due to the wind load on the serving
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area, located at a height from the base unit.
Also it is necessary to calculate a cylindrical support for the absorber. Cylindrical supports are robust and heavy; loads to support, at considerable torques, as well as conditions of shaking and vibration. Cylindrical supports are characterized by large surface contact and friction torque, low accuracy of direction and alignment. It is important to check the construction for strength and stability. The calculation is made for the cross section at the junction of the carcass and shell. In the design section has various loads: axial compressive force, which is equal to the maximum weight of the column; the bending moment resulting from the wind load; the internal pressure.
It is important to choose the centrifugal pump. First, it is needed to calculate the useful power expended for pumping fluid. Then it is useful to calculate power that must develop the pump motor output shaft during steady state operation. There is an opportunity in future, to modernize the upper part of the device by making modifications to the device, providing a preliminary separation of a drop absorbent (carried away from the absorption section), so it unloads the filter cartridge. This modification provides increasing operating time "failures" as filter cartridges function as the final cleaning of gas from absorbent. It should be noted, that the main reason for о inefficient work of gas dewatering equipment for the criterion of "ash from the dried 9 gas" is unreliable operation of the filter apparatus. Because of the high liquid load and high content of mechanical impurities, already about 3 - 4 months after the revision filter cartridges, mechanical impurities bung it, which leads to an increase of drop pressure at the filter portion, and consequently, an increasing of removal particulate absorbent with dehumidified gas. It is important to carry out a comprehensive assessment of the quality dry gas in general, with the totality of all the selected parameters is carried out by constructing a generalized indicator of quality. This indicator allows combining into one system relative performance in magnitude and in the weighting factor.
In general, it can be noted that the absorption process is currently relevant topic for oil and gas industry, as the combination of absorption with desorption allows reuse of the absorber and the absorbed component to isolate in pure form. In this scheme, (a circular process) absorbent is not consumed, except for some of his losses, and circulates through the system.
Literature:
1. Ветошкин А.Г. Процессы и аппараты газоочистки. Учебное пособие. - Пенза: Изд-во ПГУ, 2006. - с.: ил., библиогр.
2. Дытнерский Ю. И. Процессы и аппараты химической технологии: учебник для вузов. М.: Химия, 1995. - 400с.
3. Технология обработки конденсата и газа. М.: ООО «Недра-Бизнессцентр», 1999. - 596с.
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