5.2　Type Selection of Main Equipment

5.2.1　The type selection of steam turbine shall comply with the following requirements:

1　The unit operating under base load or varying load shall be determined based on the requirements of the power system.

2　In regions where conditions of central heat supply are available,the cogeneration unit shall be selected based on the magnitudes and characteristics of both the near future heat load and the planned far future heat load.

3　In arid areas where drought index is greater than 1.5,air-cooled turbines should be used.

5.2.2　The type selection of boiler shall comply with the following requirements:

1　The type of boiler shall be selected based on the characteristic parameters of design fuel and check fuel.The type of boiler furnace should be selected as per the current industrial code,DL/T 831 Guide on Selection of Furnace Characteristic Parameters for Large Pulverized Coal Fired Power Boilers.

2　The CFB boilers should be adopted when burning fuels that cannot be combusted steadily,such as by-products resulting from coal washing process,coal gangue,oil shale,and petroleum coke；CFB boiler may also be adopted when burning fuels with high sulfur content on an as-received basis,fuels with low ash fusion temperature and low volatile matter content thus susceptible to slagging in boilers,or lignite with low calorific value.

3　When coals with low ash fusion temperature or severe slagging tendency are fired,wet bottom boilers may be used if demonstrated rational through techno-economic comparison.

4　Large-capacity pulverized coal fired boilers may select Π shape or tower shape depending on the specific site conditions.

5.2.3　The combustion mode of boilers shall be determined based on the quality characteristics of the coal as fired in accordance with the following requirements:

1　For coals with the volatile matter on a dry ash-free basis（Vdaf）of 15%or above and the ignition temperature of pulverized coal flow（IT）lower than 700℃,tangential or wall firing mode should be adopted.For lignite with the total moisture Marin excess of 30%,fan-mill direct fired pulverizing system and polygonal tangential firing mode should be adopted；alternatively,ordinary tangential firing mode may be adopted provided that the temperature of hot primary air can satisfy the drying capacity of mills.

2　For coals with IT ranging from 700℃to 800℃,wall or tangential firing mode should be adopted.For coals with IT higher than 750℃and severe slagging tendency,double arch firing mode may be adopted.

3　For coals with the volatile matter on a dry ash-free basis（Vdaf）of 10%or below and the ignition temperature of pulverized coal flow（IT）higher than 800℃,double arch firing mode or CFB firing mode should be adopted.

5.2.4　The type selection of generator shall comply with both the current national standards GB/T 7064,Specific Requirements for Cylindrical Rotor Synchronous Machines and GB 755,Rotating Electrical Machines:Rating and Performance.

5.2.5　The cooling mode of generators shall be proven and reliable as recommended by the manufacturer.