RU2413901C2 - Procedure for reducing pressure of natural gas - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention refers to process of reducing pressure of natural gas of gas reducing objects: gas distributing stations (GDS), gas mains (GM) and gas distributing posts (GDP) of gas distributing system. The disclosed here isothermal procedure of reducing is based on utilisation of energy potential of compressed gas. At expansion of gas of high pressure in a vortex energy dividing device there are generated hot and low temperature flows of gas of low pressure used for alternate heating and cooling drinking water in a jacket-tube heat exchanging installation.

EFFECT: simultaneously with reducing there is produced biologically activated water as independent commodity product, selling of which covers operational expenses and capital expenditures for construction of system.

1 dwg

Description

The invention relates to a technology for reducing natural gas at gas-reducing facilities: gas distribution stations (GDS) of gas pipelines (MG) and gas distribution points (GRP) of a gas distribution system.

To eliminate the possibility of supplying a gas with a low pressure gas with a temperature of less than 0 ° C, a reduction method is proposed and used, based on heating the high pressure gas before it enters the pressure regulators of the gas-reducing object. High-pressure gas is heated by the regenerative utilization of the heat of the gaseous products of combustion of part of the natural gas that is throttled. Ionin A.A. Gas supply. Textbook for high schools. Moscow, Stroyizdat, 1981.

The disadvantage of this method is the high level of operating costs due to irreversible losses of natural gas associated with its combustion.

A known energy-saving method of isothermal reduction, in which the consumption of natural gas for combustion is not carried out. RF patent №2309322, 10.27.2007 - prototype.

The essence of the method consists in reducing part of the stream of compressed natural gas entering the gas-reducing object during energy separation in a vortex tube and subsequent heating of the cold stream in the tube space of a shell-and-tube heat exchanger due to the selection of crystallization heat of partially frozen water in the annular space of the heat exchanger. In this case, ice frozen on the tube bundle of the heat exchanger after its melting due to heat removal from the hot gas stream of the vortex tube is considered as an independent competitively capable commodity product that covers capital and operating costs for the practical implementation of the method.

The disadvantage of the prototype method is the high specific energy costs for the production of marketable products associated with the need to implement phase transitions during freezing and thawing of ice and its relatively small fraction (30-50%) in the total mass subjected to processing of the aqueous medium.

The objective of the invention is to reduce the level of energy costs for the production of marketable products while maintaining the advantages inherent in a similar approach to solving the problem of reduction.

The problem is solved and the technical result is achieved by the fact that the method of reducing the pressure of natural gas at the gas distribution facility includes preliminary energy separation of a portion of the reduced gas stream in the vortex tube into hot and cold flows, and their alternate introduction into the shell-and-tube heat exchanger, the annular space of which is filled with drinking water , periodically drained for consumption, while new is that initially in the pipe space of the heat exchanger under A hot gas stream from the vortex tube is added to heat the entire mass of liquid in the apparatus, and then a cold stream to cool it.

In the proposed method, it is supposed to use not “thawed”, but “thermally activated” water with close bioactive properties as a marketable product.

In this case, in contrast to the prototype method, initially, a warm low-pressure gas stream is supplied from the vortex tube to the tube space of the shell-and-tube heat exchanger. Warm gas provides intensive heating of drinking water filling the annular space of the heat exchanger. After warming up, the water is rapidly cooled by heat exchange with a cold stream of low-pressure gas supplied to the tube bundle of a shell-and-tube heat exchanger. The thermally activated water obtained in this way is drained from the heat exchanger and is considered as an independent commercial product. The attribution of the energy costs incurred to the entire mass of liquid products provides the claimed advantages of the considered method over the prototype method.

To ensure the continuity of the process of obtaining thermally activated water, it is carried out in two shell-and-tube heat exchangers, which are alternately put into operation. The warm and cold gas streams worked out in the described cycle are output to the consumer low-pressure network, providing the energy-saving nature of the claimed technology.

An example of calculating the reduction of the specific energy costs during the implementation of the method.

The cost of energy in the proposed method:

Q = c _p · ΔT ₁ + c _p · ΔT ₂ = 398.1 kJ / kg,

where the first term of the equation is the energy cost of heating the treated water (initial liquid temperature 15 ° C; final - 65 ° C);

the second - energy costs for cooling the processed fluid (initial temperature 65 ° C; final - 20 ° C);

c _p - heat capacity of water, 4.19 kJ / kg, K;

ΔT ₁ is the temperature difference when heating the liquid.

ΔТ ₂ is the temperature difference during cooling of the liquid.

With the accepted notation in relation to the prototype method, energy costs are:

Q = [0.3 (c _p · ΔT + λ) + 0.7c _p · ΔT] + [0.3 (c _p -ΔT + λ)] / 0.3 = 1031.1 kJ / kg,

the first term of the equation is the energy cost of cooling and partial freezing of water (initial temperature of the liquid is 20 ° C; the proportion of frozen water is 30%);

the second is the energy cost of melting and heating the processed fluid (final fluid temperature - 20 ° C);

λ is the heat of crystallization and melting of ice, 334 kJ / kg.

A comparison of the estimated energy costs for the production of a unit mass of marketable products indicates that in the proposed method they are 2.6 times lower than in the prototype method.

Schematic diagram of the organization of the process of natural gas reduction at the gas reduction station (point) by the proposed method is shown in the drawing.

When implementing the proposed method, the high-pressure gas in front of the gas-reducing object is divided into two independent streams. The first of them (the smaller part) goes to the pressure regulators of the gas-reducing object, and the second (most) goes to the vortex tube 1. The hot stream of low pressure gas generated by the vortex tube 1 is directed into the tube space of the shell-and-tube heat exchanger 2 filled with drinking water. At the same time, to ensure the continuity of the production cycle, the cold stream from the vortex tube 1 enters the tube space of the shell-and-tube heat exchanger 3, where it cools the previously heated water. After cooling the water to ambient temperature, the finished product is drained from the annular space of the shell-and-tube heat exchanger 3, a new portion of tap drinking water is poured into it and gas flows from the vortex tube 1 are redirected: warm enters the tube space of the shell-and-tube heat exchanger 3, and cold enters the tube space shell-and-tube heat exchanger space 2.

Claims (1)

A method of reducing natural gas pressure at a gas distribution facility, comprising preliminary energy separation of a portion of a reduced gas stream in a vortex tube into hot and cold flows and their alternate introduction into a shell and tube heat exchanger, the annular space of which is filled with drinking water, periodically drained for consumption, characterized in that it is initially a hot gas stream from the vortex tube is fed into the tube space of the heat exchanger to warm the entire mass of liquid in the device ate, and then cold - to cool it.