Abstract
Long-distance gas transfer requires high pressure, which has to be reduced before the gas is conveyed to the customers. This pressure reduction takes place at natural gas pressure reduction stations, where gas pressure is decreased by using gas flow energy for overcoming local resistance, represented by a throttling valve. This pressure energy can be reused, but it is difficult to implement it at small pressure reduction stations, as the values of unsteadiness significantly increase when the gas approaches consumers, whereas gas flow rate and pressure decrease. This work suggests replacing throttling valves at small pressure reduction stations for expander-generator units, based on volumetric expanders. Two implementations are proposed. A mathematical model of gas-dynamic processes, which take place in expander-generator units, was developed using math equations. With its help, a comparison was made of the stability of the operation of two possible control schemes in non-stationary conditions, and the feasibility of using an expander-generator regulator as a primary one for a small natural gas pressure reduction station was confirmed.
Highlights
Natural gas transportation and distribution networks are extensive; there are branched systems, with many natural gas pressure reduction stations (GPRSs), units for protection of gas pipelines from corrosion, and electrochemical protection (ECP) units
The gas distribution network in Russia includes over 90,000 ECP units and over 300,000 GPRSs
The main purpose of a GPRS is to lower the high pressure at which gas is transported over long distances [2] in order to compress gas and increase mass flow to a level required by consumers, and to maintain it at this level
Summary
Natural gas transportation and distribution networks are extensive; there are branched systems, with many natural gas pressure reduction stations (GPRSs), units for protection of gas pipelines from corrosion, and electrochemical protection (ECP) units. When the gas approaches consumers, gas flow rate and pressure decrease, and the unsteadiness of gas consumption increases It leads to instability in the work of turbines, power surges in the electricity network of the expander-generator [16,17], as well as energy utilization inefficiency and a lack of economic feasibility of using an expander [18,19]. The least studied is the issue of energy recovery in small reduction points, which have the worst conditions for the operation of energy recovery facilities They are characterized by high unsteadiness of flow because of uneven gas extraction by consumers (hourly, daily, and seasonal), low flow rates and pressure drops, limited dimensions, and high distribution over the territory. A comparison of the effectiveness of the two proposed schemes is given below
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