Thermal Power Unit
Steam Power Unit
Boiler burns the fuel, then generates high-temperature and high-pressure steam by heating the feedwater. The steam turbine’s blades are rotated by steam boost and driven the generator to generate electricity.
Nowadays, the developed countries such as America, Japan and from Europe have their advanced technology development of electricity generating be commercialized in succession. With the development of carbon capture and storage technology, coal-fired power generation shall be able to strike a balance between booming economy and environmental protection in the future. Therefore, based on the domestic energy policy, high-efficiency coal-fired ultra-supercritical unit is main option to TPC in the future.
The principle of ultra-supercritical unit is the same as subcritical steam turbine generator. The difference is that the pressure and temperature of working fluid in subcritical unit is below the status of critical point for water (pressure 22.129MPa/temperature 374.13°C) and relatively to the pressure and temperature of working fluid in ultra-supercritical unit is much higher than the status of critical point for water. The efficiency of ultra-supercritical unit is much higher than subcritical unit. On the other hand, the fuel consumption and pollutant emission of ultra-supercritical unit is also relatively reduced. (Refer to the information disclosure / power generation information / operation status and performance of fossil power plant / fossil power generation overview)
Combined Cycle Power Unit
Combined cycle power unit is combined with gas turbine generator (Brayton cycle) and steam turbine generator (Rankine cycle). The gas turbine drives the generator generating electricity, then the residue energy contained in exhausted flue gas is recovered by heat recovery steam generator (HRSG). The steam generated by HRSG rotates the blades in steam turbine and drives the generator to generate electricity.
If the unit is designed to equip with a bypass stack, the flue gas exhausts from gas turbine and passes via bypass stack to atmosphere. In this operation mode, HRSG and steam turbine are stopped running, just the gas turbine operates independently, which is known as “simple cycle power generation”. As combined with steam cycle, which is known as “combined cycle operation”. Except the advantages of high efficiency, fast start-stop and fast load response, the combined cycle power unit is more friendly to environment due to less pollutant emission by usage of natural gas or light diesel as fuel. The cost of power generation for combined cycle power unit is higher than that of coal-fired steam power unit and nuclear power unit. Therefore, in the whole power generation system, it plays as the main role of middle load power supplier.