The main purpose of using wear-resistant refractory material as lining in CFB boiler is to protect the steel shell of furnace body from erosion and wear by the burning material.
The low-quality coal burned by CFB boiler has high ash content and large size of fly ash particles. The separator separates and circulates the ash, resulting in a high concentration of fly ash in the flue gas. In this way, the collision heat transfer of fly ash particles on the heating surface and lining of the furnace and serious erosion wear problems occur.
The circulating combustion path of the materials burned in the circulating fluidized bed boiler: pulverized coal (generally with particle size 0~10mm) and limestone powder are sent into the fluidized bed combustor (dense phase area) by the feeder, and the fuel is boiled and burned in this area. The flue gas rises and enters the cyclone separator through the thin phase area to the separator entrance, and the coarse particles sink through the return valve to the combustion chamber for re-combustion. The flue gas with fly ash rises through the convection flue and enters the external heat exchanger. The refractory material is mainly lined in the combustion chamber, ceiling, separator inlet, high temperature cyclone separator and return valve.
1. Taking 220t circulating fluidized bed boiler as an example, the working conditions of refractories in each part are as follows: 1) dense phase area
The depth of the zone is 220~1530mm, the length is 2100mm, the sand-like medium (pulverized coal and limestone powder) boils here, the pressure in this zone is 13818~20580pa, the flue gas flow rate is about 1.2~ 1.8m /s, the normal working temperature is 820~900℃.
2) Dilute phase area
The area above the secondary tuyere is the concentration of fine particles of fuel combustion, where the solid material concentration is about 12~ 16kg/m3, the flue gas flow rate is 1.2~3m/s, and the normal working temperature is 930-980℃
The normal working temperature of the furnace top zone is 850~ 1100℃, and the flue gas flow rate at the inlet of the separator is increased
by 18m/s.
4) Cyclone separator
The normal working temperature of this part is 850~930°C, and the flue gas flow rate at the cyclone outlet can reach 29m/s.
5) Cyclone separator air main
The dust content of smoke here is 70~530g/m3, the normal working temperature is 850~930°C, and the flue gas flow rate is 18m/s.