Boilers are mainly classified by combustion mode, pressure grade and application purpose. The core differences of refractory materials suitable for different types of boilers lie in high‑temperature strength and thermal insulation performance.
I. Main Classification of Boilers (By Core Dimensions)
1,By combustion mode (most commonly used)
Grate‑fired boiler: Fuel burns in layers on the grate. Examples include hand‑fired boilers and chain‑grate boilers, suitable for solid fuels.
Pulverized‑fuel (suspension‑fired) boiler: Fuel burns in suspension inside the furnace. Examples include pulverized coal boilers and gas‑fired boilers, featuring high combustion efficiency.
Fluidized‑bed boiler: Fuel burns in a fluidized state under the action of airflow, suitable for low‑grade coal.
2,By pressure grade
Low‑pressure boiler: Pressure ≤ 2.5 MPa, mostly used for heating and domestic hot‑water supply.
Medium‑pressure boiler: 2.5 MPa ＜ Pressure ≤ 6 MPa, commonly applied in medium‑and‑small‑sized power stations.
High‑pressure / Super‑high‑pressure boiler: Pressure ＞ 6 MPa, mainly used for large‑scale thermal power plants.
3,By application
Industrial boiler: Used for factory production and heating, with relatively low pressure and small capacity.
Utility boiler: Applied for power generation. It features high pressure, large capacity and stringent requirements.
II. Refractory Materials Suitable for Different Boilers
The core functions of refractory materials are high‑temperature resistance, thermal insulation and furnace body protection. They shall be selected according to material composition and service conditions:
1,General‑purpose Basic Refractory Materials (Suitable for Medium‑low Pressure and Industrial Boilers)
Fire‑clay brick: Temperature resistance 1300‑1400 ℃, low cost. Suitable for furnace walls and flues of grate‑fired boilers and industrial boilers.
High‑alumina brick: Temperature resistance 1500‑1700 ℃, higher strength than fire‑clay brick. Applied in high‑temperature zones such as boiler combustion chambers and furnace crowns.
2,Special Refractory Materials for High‑temperature and High‑pressure Boilers (Suitable for Utility and Super‑high‑pressure Boilers)
Corundum brick: Temperature resistance 1700‑1800 ℃, featuring good wear resistance and corrosion resistance. Suitable for combustion zones of pulverized‑coal boilers and fluidized‑bed boilers.
Silicon carbide brick: Temperature resistance above 1600 ℃, with excellent thermal conductivity. Applied to high‑temperature flues and cyclone separators of boilers.
3,Insulating Auxiliary Materials (General for All Boilers)
Diatomaceous earth brick / board: Excellent thermal insulation performance, temperature resistance of approx. 900 ℃. Used for furnace body insulation layers and outer layers of flues.
Ceramic fiber blanket: Light‑weight with superior heat‑insulating effect, temperature resistance 1200‑1400 ℃. Suitable for boiler sealing and thermal insulation of local high‑temperature zones.
III. Core Matching Principles
The higher the temperature: Prioritize materials with excellent high‑temperature performance such as high‑alumina bricks and corundum bricks.
The higher the pressure: Both material strength and sealing performance shall be considered to avoid deformation under high‑temperature and high‑pressure conditions.
For highly corrosive fuels (e.g. low‑grade coal, heavy oil): Give priority to corrosion‑resistant materials such as silicon carbide bricks.
