Under CFB boiler combustion conditions, wear of heating surfaces by solid particles has long been a key issue hindering the economic operation and further development of CFB boilers. CFB boilers contain airflows, jets, and bubbles of varying directions, speeds, angles, and concentrations. These variously impact the internal surfaces. Combined with the presence of corrosive gases and other media, this creates a complex wear process. The primary method for boiler maintenance is to install wear-resistant refractory materials in certain areas to protect the heating surfaces. Under reducing conditions, wear-resistant refractory materials are more resistant than steel. Wear-resistant materials provide a cost-effective barrier to prevent wear and ensure safe and reliable boiler operation.
CFB boilers operate at high temperatures, resulting in frequent temperature fluctuations within the furnace, causing cyclic thermal shock. Furthermore, a large number of high-speed, high-temperature solid particles constantly erode the heating surfaces within the furnace, necessitating the installation of wear-resistant refractory materials for protection. This article only discusses wear-resistant refractory materials on the fire-facing (flue gas) side.
(I) Types of Wear-Resistant Refractory Materials
Wear-resistant refractory materials can be divided into shaped materials and unshaped materials based on their delivery state. Based on their function, they can be divided into three categories: wear-resistant refractory materials (including bricks, castables, plastics, and mortar); refractory materials (including bricks, castables, and mortar); and refractory insulation materials (including bricks, castables, and mortar).
1. Shaped Materials
1) Wear-Resistant Refractory Materials (High-Density Refractory Materials): Silica-Alumina Bricks (Clay Bricks, High-Alumina Bricks), Non-Oxide Bricks (Silica-Molybdenum Bricks, Silicon Carbide Bricks).
2) Insulation Materials: Refractory Insulation Bricks, Insulation Bricks, Insulation Blocks, and Ceramic Fiber.
2. Unshaped Materials
Unshaped materials include castables, trowels, plastics, patching materials, spray-on materials, injection-type materials, vibrating materials, and plaster coating materials. Based on their morphology, they can be categorized as powder, mud, and sticky masses.
(II) Performance of Wear-Resistant Refractory Materials
Wear-resistant refractory materials are specialized products that resist damage and deformation at high temperatures. To protect against wear from smoke and fly ash, they are laid inside some susceptible components. Proper selection and installation of these materials is crucial to ensure long-term system performance and minimize wear and tear and the need for repairs.
Wear-resistant refractory materials are primarily chemically composed of aluminum and silicon compounds, with a total content of 80% to 95%.
In CFB boilers, to withstand environmental influences, wear-resistant refractory materials must possess a certain degree of refractoriness, compressive strength, flexural strength, thermal shock resistance, and a sufficiently low linear rate of change.
