The boiler shall be circulation fluidized bed combustion, balanced draft, drum and natural circulation type. The CFBC boiler shall be capable of firing coal fuel producing continuous hot water flow to heat consumer.
The boiler shall be designed to suitable furnace construction and high combustion efficiency with coal fuel burning. The solid separation systems such as cyclone to separate solids from the flue gas stream shall be lined with refractory. The solids which have been separated from the flue gas stream are reinjected to the furnace through solids recycle loop.
The boiler shall be included furnace, solid separation system and solids re-injection system, drum, economizer, EHE(external heat exchanger, if required), attemperators, soot blowing system and all others concerned.
Fuel combustion in a fluidized bed combustion boiler takes place in a vertical chamber referred to as the furnace, in which the fluidization of the fuel and the fuel combustion take place.
Properly sized coal fuel is fed into the furnace and is burned at a relatively low temperature. Fine grained limestone is also introduced into the furnace to capture the sulfur dioxide released when burning the coal fuel.
The bed material in the furnace consists of combustibles, ash, limestone and limestone reaction products. The bed material is fluidized by primary air introduced through a air distribution nozzle at the bottom of the furnace and by the flue gas which flows upwards with a relatively high fluidizing velocity.
The entire furnace contains suspended solids of a high concentration which creases continuously towards the top. The solids are separated from the gas in solid separation systems provided downstream of the furnace and are continuously returned to the bed by solids re-injection system.
The very high internal and external circulating rates of solids result in consistently uniform temperatures throughout the furnace and the solids re-injection system.
Combustion air is introduced into the furnace. Part of the combustion air is passed as primary fluidizing air through the air distribution nozzle at the bed of the furnace and the balance is admitted as secondary air through multiple ports in the enclosure walls.
All air distributor shall be wind box type to prevent back-shifting and nozzle plugging, and control respectively flow rate.
The main specification of boiler is as follows.
a)Quantity of boiler : 3 sets
b)Type : Circulating Fluidized Bed
c)Installation : Indoor
d)Boiler heat output : 3 x 5 Gcal/h
e)Boiler inlet water temperature(DH return water) : 70 ℃
f)Boiler outlet water temperature(DH supply water) : 120 ℃
g)Boiler design pressure : 16 bar.g
h)Boiler efficiency(Based on HHV) : ≥ 86%
i)Minimum stable load(MSL) : 40% BMCR
j)Boiler supporting method : by Contractor
k)Main fuel : Brown Coal
l)Start-up fuel : Diesel oil
m)Draft system : Balanced draft
For the DH water return temperature that is lower than 65℃ from the heat consumer, boiler shall be provided the recirculation water system to protect the corrosion from condensates due to the low temperature in flue gas.
The boiler shall be a complete system, including :
a)Boiler proper and auxiliaries
(1)Coal surge bin with feeder
(2)Diesel oil start-up burner
(3)Boiler management system (BMS)
(4)Forced circulation furnace
(5)Drum and headers
(7)On-line boiler cleaning
(9)Bed material storage silos and injection/reclamation system
(10)Limestone injection system
(11)Primary air fans and silencers
(12)Secondary air fans and silencers
(13)Induced draft (ID) fans and silencers
(14)Flues, ducts and dampers
(15)Acoustic leak detection
(17)Boiler house lifts
(18)Flue gas cleaning
(19)Casing, framing and supporting steelwork
(20)Inner flue cylinder for stack
b)Coal and limestone handling system
(1)The equipment as required at the unloading area including coal receiving hopper, magnetic separators, belt scale, dust suppression system and dust collection system.
(2)Conveying and handling facilities for transportation of coal fuel from the receiving point to the coal fuel surge.
(3)Coal fuel processing including screening, metal detector, and removal of ferrous tramp material, etc. to ensure that the coal fuel is adequately prepared for handling, storage and any other plant requirement.
(4)As fired coal fuel sampling system
(5)Limestone silo storage silo with accessary and surge bin
(6)Limestone unloading station
(7)Limestone blower for limestone pneumatic conveying
(8)The weighing systems
c)Ash handling system
(1)Bottom ash storage silo with accessary including unloader
(2)Fly ash storage silo with accessary including unloader
(3)Bottom ash cooling screw conveyor
(4)Bottom ash crusher
(5)Air compressor for ash including unloader
(6)Bottom ash cooling system including water tank, water circulation pump and heat exchanger, etc.
(7)The weighing systems
d)Fly ash precipitation
Bag filter system and auxiliaries
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