Gas distribution station with power plant

A gas distribution station with a power plant using the energy of the gas in a gas main (6) by removing gas from the gas main (6) and supplying the gas to a first heat exchanger (5) to be pre-heated by a back gas flow from a turbo-expander (1). From the heat exchanger (5), the gas flows to a second heat exchanger (4) to be heated by combusted gases of a gas turbine engine (3), and the heated gas then proceeds to the turbo-expander (1). The gas is expanded in the turbo-expander (1) which drives an electric generator (2) also drivingly connected to the gas turbine engine (3). The expanded and partially cooled gas from the turbo-expander flows to the heat exchanger (5) for pre-heating the gas withdrawn from the gas main and then into the gas main (6) downstream of a pressure reducer (7) at a temperature insignificantly above the temperature of the gas in the gas main (6) upstream of the pressure reducer (7).

TECHNICAL FIELD 
The invention relates to gas main equipment, more specifically to a gas 
distribution station with a power plant using the gas energy of the gas 
main. 
PRIOR ART 
Known in the art is a gas distribution station comprising a turbo-expander 
for actuating an electric generator connected at the input to a gas main 
before a reducer and at the output-behind the latter (Journal "Gazovaya 
promyshlennost" N II,1988, Moscow, cover page 4). 
The conventional installation cannot be used in practice, with a pressure 
differential&gt;1,5-2 on the reducer (turbo-expander) because of a 
considerable drop of temperature thereat of natural gas behind the reducer 
(turbo-expander), and under the strength conditions of gas lines, gas 
cannot be fed thereinto after reducing at a temperature below 10.degree. 
C. 
And the pre-heating of gas to an initial temperature in a heat-exchanger 
utilizing the heat of burnt gas reduces utilization to zero, which is why 
such installations find no application in the given field. 
Also known is a gas distribution station comprising a turbo expander for 
actuating an electric generator, a gas-turbine engine with the electric 
generator, the heat of whose burnt gases is used for pre-heating the 
natural gas removed from a gas main before a reducer and fed to the 
turbo-expander. 
Owing to the pre-heating of gas at the input to a turbo-expander of the 
conventional station, there is increased power generated by the latter as 
is the gas temperature behind a reducer, which permits expanding the range 
of its use, including the above-identified pressure 
differential&gt;1,2-2(EP,A2 No. 0004398). 
The conventional station is not efficient enough due to the incomplete 
utilization of burnt gases because the insulation used on gas pipe lines 
does not enable one to considerably increase the temperature of said burnt 
gases behind an expansion valve (over 70.degree. C.) according to strength 
conditions thereof and also brings about a limitation of the transmissive 
capacity of the gas pipe line and an increased resistance in the latter 
due to an increase in the gas volume with its invariable mass flow rate. 
SUMMARY OF THE INVENTION 
It is the principal object of the present invention to eliminate 
restrictions of the temperature conditions of a gas pipe line, to enhance 
efficiency of the power plant of a station and to improve the latter's 
reliability. 
Said object is accomplished owing to the fact that in a gas distribution 
station with a power plant comprising a gas main with a reducer, a 
gas--turbine engine with a heat exchanger-utilizer at the output for 
heating the gas removed from the gas main before the reducer, and a 
turbo-expander with an electric generator, and along with this, the input 
of the turbo-expander is connected to the output of the heat 
exchanger-utilizer, the provision is made of a heat exchanger-regenerator 
for pre-heating said gas taken away. Moreover, the 
heat-exchanger-regenerator is mounted before the heat-exchanger-utilizer 
and connected, as to a heating medium, with its input and output to 
respectively the output of the turbo-expander and the gas pipe line after 
the reducer, and as to a heated medium, respectively with the input--to 
the gas main before the reducer and with the output--to the input of the 
heat exchanger-utilizer. 
In the gas distribution station, a gas turbine engine can be connected 
kinematically with the electric generator of the turbo-expander.

DETAILED DESCRIPTION OF A EMBODIMENT OF THE INVENTION 
A gas distribution station is shown in the drawing and comprises a gas main 
6 with a reducer 7, and a pipe line 8 for the gas to be withdrawn into a 
power plant, comprising a turbo-expander 1, an electric generator 2, a gas 
turbine engine 3, a heat exchanger-utilizer 4, and a heat 
exchanger-regenerator 5. 
Natural gas is taken away from the gas main 6 before the reducer 7 to be 
admitted via the pipe line 8 to the heat exchanger-regenerator 5, where it 
is warmed by a back gas flow from turbo-expander 1. From the heat 
exchanger-regenerator 5, the gas is first admitted to the heat exchanger 4 
to be pre-heated by the burnt gases of the gas turbine engine 3 and then 
to the turbo expander 1, wherein said gas is expanded with the performance 
of work transmitted to the electric generator 2, to which the gas turbine 
engine 3 is connected kinematically to transmit its generated power to the 
electric generator 2. 
The expanded and partially cooled gas is admitted after the turbo-expander 
1 to the heat-exchanger-regenerator 5 for pre-heating the gas withdrawn 
from the gas main to be subsequently reintroduced into the gas main after 
the reducer 7, having been cooled to a temperature insignificantly (by 
10.degree.-50.degree. C.) exceeding the gas temperature in the gas main 6. 
The pre-heating of the gas from the gas main in a heat 
exchanger-regenerator with the heat of the burnt gas in a turbo-expander 
makes it possible to enhance efficiency and reliability of a gas 
distribution station by way of increasing the efficiency of a power plant 
incorporated therein, subsequent to regeneration of the heat of gases 
escaping from the turbo-expander and optimization of the temperature of 
the gas coming out of the turbo-expander into the gas main in consequence 
of a reduction of hydroloss in said gas main and an increase in the 
latter's strength reliability. 
Thus, mounting at the output from a turbo-expander of a heat 
exchanger-regenerator reducing the temperature of gas to be fed to a gas 
pipe line enables one to also overcome a restriction as to a temperature 
rise in pre-heating the gas before the turbo-expander. 
The kinematic coupling of a gas turbine engine with the electric generator 
of a turbo-expander protects the plant also in the event of emergency 
electric load shedding, because the compressor of the gas turbine engine 
is a superload in speed-up. 
A system for controlling the plant is simplified, inasmuch as the necessity 
falls away in maintaining a frequency of rotation by a separate system 
because this function is performed by the system of control of a gas 
turbine engine by way of effecting the power of a turbo-expander through a 
change of the temperature of burnt gases. 
Industrial applicability 
The invention will find application in transportation of natural gas over 
mains, in supplying the natural gas to users (industrial plants, say, 
chemical combines, thermal electric stations and also municipal networks).