1 Introduction to the boiler structure
The CFB boiler should be designed by coal-fired circulating fluidized bed boiler, can be up and running under constant pressure with steam turbine. Use circulating fluidized bed combustion technology for boiler, high temperature and insulating cyclone separator for separator of recyclable materials, balanced ventilation for boiler.
Technical performance of the boiler and the range of conditions of the safe and stable operation should be seen from the product specifications of circulating fluidized bed boiler.
The boiler is mainly composed of drum, all suspended membrane wall furnace, insulating cyclone, feed back loop and the convecting and heating surface. Furnace using suspended structure; high temperature superheater should suspend above shaft flue. Drum, cyclone should be shelved or hung on the steel beam; low temperature superheater, economizer should be supported on load-bearing beam by the tube clip, load-bearing beams hold the rear retaining shelf; the tube style air preheater supported on steel beams. The boiler furnace overall expandes downward, There is non-metallic expansion joint of flexible material between the exit flue of furnace water wall boiler and cyclone inlet ,as well as among feed back legs
Between the shaft furnace and convection, furnished with insulation cyclone separator, the upper part is cylinder, lower part is cone.There is supporting device in the jiont of the cylinder and cone, hold on the steel beams.
It set feed back device separately under cyclone, revert is self-balanced U-feeding device, put refeed air plant at the bottom of refeed plant , make meterial flow and return chamber, refeed air supplied by the blower.
In the tail shafts arranged high and low temperature superheater, high and low temperature economizer as well as air preheater according to the flow of flue gas.
In superheater system, place primary spray desuperheater between high temperature superheater and low temperature superheater.
Employing balanced ventilation for boiler, the chamber’s pressure zero sets in the furnace exit.
It has set two or more coal points for boilers , evenly arranged in the blast furnace.
Adding limestone FGD design for boiler according to furnace, the limestone enters to the furnace through coal feeder to coal tube or directly to the furnace.
At the bottom of the furnace with an air chamber.
It is equipped with igniting burner when firing under the bed; if on the bed , igniting burner can be omitted.
2.The main Introduction for boiler
2.1, water system for the boiler
Loop water system, includes tail economizer, drum, evaporating heating surface (furnace water wall), convection shaft superheater.
Water supply for the single mother tube . The main feedwater pipe is divided into two pipes , one is to the spray desuperheater, the other to the economizer inlet boxes, in addition layout the auxiliary pipes with two pipes adjusting load (one is used for regulation under 70% load, the other for the use of low-load adjustment).
After treatment, feed water reaching the required standard , first imported from connecting pipe of inlet header of economizer at one side convecting shaft, then go against the current upward through two low temperature economizer tubes which layout horizontally. Enters into the middle header after heating, extracting and going upward against the current upward through one high temperature economizer tubes which layout horizontally. Then entered into the middle header outlet and induced into the boiler by connecting tube of main feedwater on the outlet header of economizer .It redistributes no more thanφ57 × 3.5 pipe for every main feed water connecting tube into the drum, setting recycling pipes between cylinder and inlet of low temperature economizer.When starting up ,open the valve to form natural recirculating loop between the economizer and drum, in order to prevent the water in economizer vaporizing, as well as ensure the safety of start-up for economizer . When the boiler is to establish a certain amount of water, you can close the valve.
The circulation system of the Steam boiler , includes drum, down tube, water wall tubes and soft drinks leads. Down tubes from the bottom of the drum , respectively, connecting with down header of front, rear, left and right water wall, composed of four separate circulation loop. mixture collecting into the upper header when the water flow through furnace absorbing heat ,then it is induced into drum by steam leading-out tubes. Soda mixture in the drum,can be separated successfully through the cyclone separator and steel mesh, vent panels. the water separated re-entering the drum in the water cycle, dry saturated steam is induced from the steam tube at the top drum leading to superheater system.
Saturated steam is induced from the connecting pipe at the top of drum into the header inlet of low-temperature superheater, the steam flowing through the low-temperature superheater heating surface, leading to outlet header of low-temperature superheater,entering spraying desuperheater by leading pipe. Importing leading pipes to the other side of the high-temperature superheater, the steam flowing through the high temperature superheater heating surface, entering separately into two hanging header, make the superheat steam get into high-temperature superheater header by hanging tubes. so that superheated steam can achieve the rated steam parameters for users.
2.2, the boiler smoke ventilation system
2.3, ash recycling system
2.4, slag and ash system
2.5, security, accessories and control systems