An expander-generator is a turbo-expander unit in which the mechanical energy of rotor rotation is used to rotate the shaft of an electric generator and, accordingly, to generate electrical power.
The expander-generator units can be applied:
1. To generate electrical power at natural gas reduction units at gas distribution stations, at gas letdown stations of large gas consumers – thermal power plants, metallurgical, chemical plants and other large gas consumers of gas transmission systems.
2. To generate electricity during reduction of various process gases having excess pressure: in the chemical, petrochemical, metallurgical and other industries.
3. To generate power during regasification of liquefied natural gas.
4. To generate power by recovering low-grade (low-pressure) heat (ORC cycle / Rankine cycle).
The power of the expander-generator units is determined by two main factors: differential pressure of the gas at the inlet / outlet of the unit and gas flow through it.
Gas passing through the expander-generator is being cooled. To compensate for the excessive decrease in temperature, the gas at the expander inlet is heated. Therefore, technical and economic parameters of the expander-generator plants are largely determined by the cost of gas heating. For this purpose, various sources of heat can be used, for example, heaters in which fuel or secondary energy resources of high and low potential are burned.
This makes it possible to organize operation of expander-generator units either without burning fuel at all, using the heat of secondary energy resources, or still burning fuel, providing its 2.5-3 times lower specific consumption for power generation compared to traditional steam turbine or gas-turbine units.
Depending on the features of the implementation facilities, Turbogaz develops and manufactures expander-generators in several structural designs:
– In case of a low pressure drop across the turbine and high gas flow rates multi-stage (up to 6 steps) multi-stage axial turbines are developed that operate without reduction gears;
– When high pressure drops are triggered on the turbine, the expander generators are made with a gearbox.
Main advantages of power plants based on expander generators are that the unit cost of potential power generated by the expander-generator is about 3 times lower than while generating similar capacities with traditional gas or steam turbines.
Expander-generators of low capacity can be used as an additional / standby source of power supply for own needs and auxiliaries at gas distribution stations and units.
Expander-generators of medium capacity can be used to meet the own needs and auxiliaries of compressor stations and gas distribution stations.
Expander-generators of high power can be installed at gas distribution stations to provide for their own needs and auxiliaries and to sell power to third-party electricity consumers.
At present our company is developing and manufacturing expander-generator units of its own design having various capacities: 8 kW, 300 kW, 500 kW, 1 MW, 2.5 MW; 4 MW; 5 MW; 6 MW; 8 MW; 12MW for gas inlet pressure up to 7.5 MPa and with a gas flow rate of 0.05-6 million nm³/day.
| Standard Size | Power, кW e | Gas flow, St.m³/hour | Gas Pressure, bar | Expander Type | Reduction Gear (Yes/No) | Generator Type | Bearing Type |
| Small | Up to 25 | Up to 10,000 | Up to 63 | Radial | Not used | High-speed | Oil |
| Medium | From 100 to 500 | Up to 50,000 | Up to 63 | Radial | Not used | High-speed | Magnetic bearing |
| Large | From 1000 to 6000 | Up to 250,000 | Up to 160 | Radial or axial | Yes | Synchronous or induction (1500 or 3000 rpm) | Oil |
| Very large | From 8000 to 16000 | Up to 800,000 | Up to 160 | Radial or axial | Yes | Synchronous or induction (1500 or 3000 rpm) | Oil |
We use the international standards ANSI, API, ASME, DIN, ISO, GOST, DSTU.
