7.2　Main Power Building Arrangement

7.2.1　The turbine house，deaerator bay（or combined coal bunker and deaerator bay），coal bunker bay，and boiler house should be arranged in sequence.If there are several optional layouts，the final choice shall be made through techno-economic comparison.

7.2.2　The layout of the main power building shall be in harmony with the layout of the outgoing lines，supply and drainage pipes of circuiting water，heat supply pipeline corridor，main control building（room），buildings abutting steam turbine house，and surrounding ring-shaped roads of the power plant.

7.2.3　The elevation of each floor of the main power building shall be determined according to the following requirements:

1　If both the boiler house and the steam turbine house are of two-storey buildings，the elevation of operating floors of them should be the same.The operating floor of steam turbine house should be of island structure.

2　The elevation of deaerator floor shall ensure that no cavitation would occur at the inlet of the feedwater pump or booster pump under all operating conditions of the steam turbine.

If the climate and arrangement conditions are favorable and the deaerator bay and coal bunker bay are arranged separately，the deaerator and feedwater tank should be installed outdoors.

3　The elevation of coal feeder floor in the coal bunker bay shall be determined in accordance with the following requirements:

1）For circulating fluidized bed（CFB）boilers，the elevation of coal feeder floor shall be determined based on the elevation of coal feeding port（including coal spreading devices），the required number of stages of coal feeder，the coal feeding distance，and the space required for accommodating the outlet valves of coal feeder.

2）For pulverized coal fired boilers，the elevation of coal feeder floor shall be determined based on the space required for accommodating coal mills（except for beater-wheel mills），pulverized coal feeding pipes，and the lifting facilities for repair and maintenance.If the conditions permit，the elevation of coal feeder floor should be the same as that of boiler operating floor.If beater-wheel mills are used，the elevation of coal feeder floor shall meet the requirements for arranging the drying section.

4　The elevation of the coal bunker floor of coal bunker bay shall be determined based on the operating shift system of coal handling system.The effective capacity of the raw coal bunker（including the pulverized coal bunker of bin storage pulverizing system but excluding the raw coal bunker for the standby mill of direct firing pulverizing system）of each boiler shall comply with the following requirements:

1）If the techno-economic comparison of two-shift coal handling system is considered to be reasonable，it may be determined based on 12hours-14hours of coal consumption by the boiler operating under the boiler rated load condition.

2）If three-shift coal handling system is used，it may be determined based on 10hours-12hours of coal consumption by the boiler operating under the boiler rated load condition.

3）If CFB boilers burning coal with low calorific value are used，it may be determined based on 8hours-10hours of coal consumption by the boiler operating under the boiler rated load condition.

4）If pulverized coal fired boilers burning lignite are used，it may be determined based on 6hours-8hours of coal consumption by the boiler operating under the boiler rated load condition.

5）The effective capacity of the pulverized coal bunker may be determined based on 3hours-4hours of coal consumption by the boiler operating under the boiler rated load condition.

7.2.4　If the deaerator and feedwater tank are arranged on top of the unit control room，the top slab of the unit control room must be of a monolithic concrete structure，and appropriate waterproofing measures must be taken for the deaerator floor.

7.2.5　The column spacing and span of the main power building shall be determined based on the capacity and layout of boilers and steam turbines and the planned installed capacity.

7.2.6　When meteorological conditions permit，65 t/h and above boilers should be of outdoor or semioutdoor arrangement and island structure，namely，large platform will not be provided at the operating floor.Outdoor boilers shall be provided with effective measures to protect the boiler from freezing，rain，and corrosion and to withstand wind pressure and reduce heat losses.Precipitators shall be arranged outdoors.The hopper of the dry precipitators shall be provided with anti-condensation measures.Except in severe cold regions，the induced draft（ID）fan of boilers should be arranged outdoors.When boilers are of island structure and arranged outdoors，the associated forced draft（FD）fans and primary air fans should be arranged outdoors as well.The outdoor auxiliary equipment shall be provided with anti-noise measures and motors should be fully enclosed.

7.2.7　The design of raw coal bunkers and pulverized coal bunkers shall comply with the following requirements:

1　The design of the raw coal bunkers of boilers shall be determined taking into consideration the layout of the main power building.

2　For raw coal bunkers of non-cylindrical structures，their inner walls shall be smooth and abrasion resistant，and the included angle between the intersection line of two adjacent walls and the horizontal plane shall not be less than 55° and that between the wall surface and the horizontal plane shall not be less than 60°.If lignite and highly viscous or flammable bitumite is contained，the included angle between the intersection line of two adjacent walls and the horizontal plane shall not be less than 65° and that between the wall surface and the horizontal plane shall not be less than 70°.The inner side of the intersection line of two adjacent walls shall be in circular arc shape.The arc radius should be 200 mm.The angle between the horizontal plane and the surface wall of the outlet section of the raw coal bunker for CFB boilers shall not be less than 70°.

3　The raw coal bunker shall have a large cross-section outlet.For pulverized coal fired boilers，a hyperbolic circular-section or cone-shaped small metal coal hoppers shall be provided at the lowest part of the raw coal bunker outlet.When the used coal is prone to result in clogging，the outlet section of raw coal bunker should be made of stainless steel clad plates，plates lined with stainless steel plates or other smooth，flame-retardant and abrasion resistant materials.The outer walls of metal hoppers should be provided with vibrators or other devices for preventing clogging.

4　In severe cold regions，anti-freeze insulation devices shall be equipped on walls of the raw coal bunker of steel structures and the reinforced concrete raw coal bunker close to the external wall of the main power buildings as well as on walls exposed to the atmosphere.

5　Raw coal bunkers shall be provided with coal level measuring devices.

6　The design of pulverized coal bunkers shall comply with the following requirements:

1）The pulverized coal bunker shall be sealed tightly and the number of openings shall be as few as possible.Any opening must be with reliable sealing structure.Both pulverized coal feeding devices and discharge devices of pulverized coal bunker must have an air lock function.

2）The pulverized coal bunker shall have an internal surface that is even，smooth，abrasion resistant and not prone to dust accumulation and geometric shape and structure that can ensure smooth gravitational flow of pulverized coal.

3）For coal types other than anthracite，the pulverized coal bunker should be provided with automatic open-close type door to prevent explosion.

4）The pulverized coal bunker shall be protected against heat and moisture.In severe cold regions，freezing prevention and thermal insulation measures shall be taken for metal pulverized coal bunkers and the concrete pulverized coal bunker close to the exterior wall of the buildings，as well as on walls exposed to the atmosphere.

5）The included angle between the intersection line of two adjacent side walls of pulverized coal bunker and the horizontal plane shall not be less than 60°，and that between the bunker wall and the horizontal plane shall not be less than 65°.The inner side of the intersection line of two adjacent walls shall be in circular arc shape.The arc radius should be 200mm.

6）The length/diameter ratio of the pulverized coal bunker shall be less than 5∶1.A rectangular pulverized coal bunker shall use the equivalent diameter as reference value.

7）The pulverized coal bunker shall be equipped with facilities for measuring pulverized coal level and temperature，extinguishing fire，absorbing moisture and discharging pulverized coal.

7.2.8　The equipment and piping of the lube oil system of steam turbines shall be arranged far away from high-temperature steam piping.Effective fire protection measures shall be taken for the oil system in accordance with the current national standard GB 50229 Code for Design of Fire Protection for Fossil Fuel Power Plants and Substations.

7.2.9　Temperature and pressure reducing devices and heat supply network heaters should be arranged in the main power building.