Method of cooling a hydrocarbon gas in preparation for transport

 

(57) Abstract:

The invention relates to oil and gas industry and can be used in the processes of field and factory processing, hydrocarbon gas, in particular, upon cooling, the crude hydrocarbon gas booster compressors before the subsequent drying and preparation for transport. The technical result of the invention is the provision besidethe cooling raw hydrocarbon gas by reducing its temperature to AVO in the process of air temperature fluctuations in winter conditions. This is achieved by a method of cooling a hydrocarbon gas in preparation for transport after booster compressors in the unit of several parallel connected and working back AVO, including the arrival of a warm wet hydrocarbon gas from the booster station at the junction of the camera unit air coolers, then horizontally oriented heat exchange tube Assembly cells and then by drying, measuring the average gas temperature at the inlet and outlet of the separate unit and the output from the block AVO, off to reserve one unit, if the temperature of the gas at the outlet of the unit AVO apostille from the block AVO has reached room temperature, determined from the formula

< / BR>
where T is the gas temperature at the outlet of the unit air coolers; T1- gas temperature at the entrance to the unit air coolers; T2the temperature at which hydrate formation under temperature and pressure conditions at the outlet of gas from block devices; t - temperature gradient, providing besidethe gas cooling unit air coolers in terms of non-uniformity of heat transfer and the flow of gas by separate devices, partitions, heat exchanger tubes, and so on; n - the number of working devices before turning back. table 1.

The present invention relates to oil and gas industry and can be used in the processes of field and factory processing, hydrocarbon gas, in particular, upon cooling, the crude hydrocarbon gas booster compressors before the subsequent drying and preparation for transport.

It is known that the lower the temperature of the raw gas after the booster compressor, the lower operating costs in the process of drying and gas transport and higher quality of marketable hydrocarbon gas.

There is a method of cooling a crude Ugledar fields of Russia". - M.: JSC "mineral resources", 1999, S. 318 320...), including submission of a warm gas distribution chamber air cooler (air cooler), then the beam horizontally arranged heat exchange tubes, and then into the collecting chamber, followed by drying in preparation for transport. The refrigerating agent in the form of a stream of cold atmospheric air fed by the fan across the bundle of heat exchange tubes. The lower the temperature of the cooled gas, the lower the operational costs of the subsequent drying and preparation for transport in General.

However, in these devices by cooling the gas below the hydrate formation temperature (this temperature is usually above zero degrees) formed crystalline. Introduced in the heat exchanger tube (TT) embryos hydrates are fixed (froze) on the inner walls of TP in the zone of minimum temperatures. The process of hydrate deposits on the inner wall of TP leads to decrease the flow area of the tube and, consequently, to decrease the flow of the refrigerant gas through the tube. Reduced consumption leads to faster cooling of the gas and enhance the process of hydrate formation. Thus, the process is accelerated and leads to the complete overlap of the inner section TT, via the atmospheric temperature. Considering the non-uniformity of heat transfer in an air cooler, the process of the emergence of crystalline hydrates can occur on the background of the average temperature of the exit gas from the air cooling unit above the hydrate formation temperature of the beginning. In connection with the above:

1. Not fully used the technical capabilities of the air cooling unit for cooling the gas.

2. The temperature of the cooled gas after the air cooler must be kept significantly higher than the temperature of hydrate formation.

A known method of regulating the temperature of the cooled raw gas in AVO on the wall temperature TT (see Davletov K. M. and others "Methods of thermal calculation of the air coolers gas with restrictions on the minimum temperature of the inner surface of the pipe. //STC. Ser. Natural gas as a motor fuel. Preparation, processing and use of gas. IDC Gazprom. - 1997. - 9-10, - S. 39-45). However, this method uses averages, and not focused on uneven heat transfer and the flow of gas.

Known methods of cooling the raw hydrocarbon gas in the ABO closest to the claimed method is proposed in the work Davletov K. M. "Speed regulation is Tarnovo fuel. Preparation, processing and use of gas. The energy saving. IDC Gazprom. - 1998. - 5-6, - S. 15-17 (prototype).

This method includes the arrival of a warm wet hydrocarbon gas from the booster station at the junction of the camera unit air coolers, then horizontally oriented heat exchange tube Assembly cells and further drying and gas transport and froze the average gas temperature at the inlet and outlet of the separate unit and the output from the block AVO.

When using this method, the author aims to speed regulation of the gas flow in the ABO and associates it primarily with seasonal changes in ambient temperature. In addition, the author argues that the "step change of the gas flow is not a proper regulation of the cooling process".

The main disadvantage of this method is the focus on a step change of the gas flow, and not on the degree of cooling in conditions conducive to hydrate formation. In addition, a step change of the gas flow is not tied to the beginning of hydrate formation in the gas flow when it is cooled in the process fluctuations tempero of the invention, is providing besidethe cooling raw hydrocarbon gas by reducing its temperature to AVO oscillations in the temperature of the atmospheric air in winter conditions.

This technical result is achieved by a method of cooling a hydrocarbon gas in preparation for transport after booster compressors in the unit of several parallel connected and working back AVO, including the arrival of a warm wet hydrocarbon gas from the booster station at the junction of the camera unit air coolers, then horizontally oriented heat exchange tube Assembly cells and then by drying, measuring the average gas temperature at the inlet and outlet of the separate unit and the output from the block AVO, off to reserve one unit, if the temperature of the gas at the outlet of the unit AVO lowered down to the temperature (T2+t)oC, activation of reserve unit if the temperature T of the gas at the outlet of the unit AVO has reached temperature, determined from the formula:

< / BR>
where T is the gas temperature at the outlet of the unit air coolers;

T1- gas temperature at the entrance to the block devices of air and block devices;

t is the temperature gradient, providing besidethe gas cooling unit air coolers in terms of non-uniformity of heat transfer and the flow of gas by separate devices, partitions, heat exchanger tubes, etc.

n - the number of working devices before turning back.

The technical result of the proposed method is that when the fluctuation of the temperature of the cold air in winter conditions, this method provides optimal speed temperature control chilled raw hydrocarbon gas without the formation of crystalline hydrates in the air cooler.

In addition, the use of the proposed method has a sufficient number of cases to regulate the temperature of the cooled gas. So, one air cooler has three options to regulate the temperature when two fans on the unit: option cooling without a working fan, one and two operating fans. Each additional device in the block AVO gives a further four options for regulation (three plus disable device). Thus, Bq AVO 15 devices has 59 options to regulate the temperature of the cooled gas. In the General case, the number of possible variants is determined by the formula:

V=4n-1,

where n is the number of units in the block AVO.

The essence of the method lies in the fact that at a minimum temperature of the cooled gas below which may appear crystalline, off to reserve one unit, and the gas flow coming through this device, reallocate to other working machines. This increases the mass and velocity of the flow through a single device. Together with the mass increases the amount of heat coming in each remaining in the apparatus, and increases the temperature of the cooled gas at the outlet of the apparatus. With increasing speed quickly carried the germs of hydrates from the danger zone of heat exchange tubes. Thus, the temperature of the cooled gas as if moving away from the border is dangerous from the point of view of hydrate formation mode.

Example. There are 6 devices. If the outlet gas temperature dropped to 11oWith or appeared to signal to the remote operators about the temperature at the outlet of one of the devices 10oWith, carry off into reserve one of the devices. The figures obtained in the research. Remaining in the 5 machines PED helps to remove fluid and embryos hydrates of the tubes. Five devices cannot work optimally in the temperature range (see table) 15,8 11,0...oC.

When the temperature of atmospheric air and gas temperature after AVO disabling devices can be repeated many times. The number of working machines must be at least 3...4, wherein the mass flow rate of gas through the apparatus should be kept no more than 300...450 t/h At higher mass flows significantly increase the pressure loss on the air cooler.

In the case of increasing the atmospheric temperature of the inclusion of another apparatus for further cooling is carried out at a temperature of gas at the outlet AVO 15,8oC and above (5 working devices). The new mode AVO on 6 devices will provide beshitrostny cooling gas without submission to the special gas hydrate inhibitors. For faster warm-up re-enabled device you want the fans were turned off.

The data of examples 1 to 5, the method given in the table.

Method of cooling a hydrocarbon gas in preparation for transport after booster compressors in the unit of several parallel connected and working back apressure station in the distribution chamber unit air coolers, then in horizontally oriented heat exchange tube Assembly cells and then by drying, measuring the average gas temperature at the inlet and outlet of the separate unit and the output of block devices, characterized in that the carry off into reserve one device, if the temperature of the gas at the exit of block devices dropped to temperature (T2+ t)oC, include in the backup apparatus, if the temperature of the gas at the outlet of the unit apparatus has reached the value determined from the formula

< / BR>
where T is the gas temperature at the outlet of the unit air coolers;

T1- gas temperature at the entrance to the unit air coolers;

T2the temperature at which hydrate formation under temperature and pressure conditions at the outlet of gas from block devices;

t is the temperature gradient, providing besidethe gas cooling unit air coolers in terms of non-uniformity of heat transfer and the flow of gas by separate devices, partitions, heat exchanger tubes, etc.;

n - the number of working devices before turning back.

 

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1 cl, 1 dwg

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