UA86795C2 - Method of generating power from a pressure control station of a natural gas distribution system - Google Patents

Abstract

A method is described of generating power from a pressure control station of a natural gas distribution system. A first step involves channelling natural gas entering the pressure control station into a turbine (52) which is powered by expansion of the natural gas as the pressure of the natural gas is reduced. A second step involves capturing the output of the turbine (52) for useful purposes.

Description

Referring to figure 2, the configuration in accordance with the presented method is illustrated in relation to the pressure control station of figure 1 of the prior art. It is anticipated that existing infrastructure will remain in place to maintain backup systems for public safety.

In accordance with the description of the presented method, natural gas is removed by passing through the heat exchanger 28 and a number of control valves 34, which reduce the pressure. A key aspect of the present method is the supply of natural gas, which enters the pressure control station, through line 50 to turbine 52, which is driven by its expansion when its pressure decreases. The output power of the turbine 52 is then harvested for useful applications. Preferably, a turbine is used to power generator 54. Turbine 52 may be used with or without preheated natural gas, as will be described below.

The turbine 52 is preferably a turbine known as a "turboexpander". It is a radial inlet turbine with directional adjustable inlet vanes to control the flow used to extract energy from the gas jet. The method uses a turbo expander (turbine 52) to generate power in stations 1b to control pressure in the natural gas distribution system. The expansion through the guide input vanes and the expander wheel creates torque and therefore power on the shaft which can be used to rotate the power generator 54.

Where the characteristics of the natural gas of the working stream allow, the turbine 52 can be used without preheating the natural gas. Natural gas is fed into the turbine 52 in order to artificially create low temperatures. Heat exchanger 56 is provided to maintain low temperatures, designed for use in either refrigeration or air conditioning. The fluid can then be circulated through the heat exchanger 56, which can be used to air condition nearby equipment or cool nearby cold stores. The cooling achieved by gas expansion is usually much greater than that achieved by expansion through a Joule-Thompson (9-T) valve.

Where preheating of natural gas is required, the boiler 26 is replaced by a gas turbine generator 58 of power, which is sometimes called a "microturbine". A portion of the high-pressure natural gas is withdrawn via conduit 60 and passed through a gas conditioning system 62 to condition the natural gas so that it is suitable for the gas turbine power generator 58 . Exhaust gases from the gas turbine power generator flow through the pipeline 64 and are passed through the first heat exchanger 66.

A circuit is provided for circulating hot water, which includes the circulation pipe 68 of the expansion tank, the expansion tank 70, the pump 74 and the valves 76. The expansion tank 70 ensures that the circulation pipe 68 is replenished with water as required. The pump 74 is used to circulate the hot water through the circulation pipe 68. The water is circulated through the pipe 68, which passes through the heat exchanger 66 so that there is a heat exchange with the hot exhaust gases from the gas turbine power generator 58, which heat the water. Then the waste gases are released into the atmosphere. Then, in the second heat exchanger 78, secondary heat exchange takes place between hot water and natural gas. The natural gas, which has been preheated in the second heat exchanger 78, is then supplied via line 50 to the turbine 52. Power is also taken from the output of the gas turbine generator 58 for the useful purpose of generating electricity using the generator part 54. The purpose of the method is the selection and use of energy that is not currently being used. Depending on the circumstances, it may be desirable to place a dryer upstream of the second heat exchanger 78 for drying natural gas.

Suitable desiccants using an adsorptive medium are well known in the art. Usually two are used. One is always running, while the other is regenerating the adsorption medium.

Normally, where the aim is to create low temperatures for air conditioning or cooling, a hot water circuit will not be used.

In this patent document, the word "comprising" is used in a non-limiting sense to indicate that elements are included after the word, but elements not specifically mentioned are not excluded. Reference to an element with the indefinite article "a" does not exclude the possibility that more than one element is present, unless the context clearly requires that one and only one of the elements be present.

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