What are the Factors that Cause Damage to High-Chrome Bricks during the Use of Gasifiers?

The refractory brick layer on the fire-facing side of the gasifier, as a consumable layer requiring high temperature resistance, corrosion resistance, and erosion resistance, is generally made of high-purity chromium oxide material, also known as chromium aluminum zirconium brick or high-chrome brick. This refractory material is required to possess excellent high-temperature resistance, high creep strength, thermal shock stability, and good high-temperature chemical stability. 

Rongsheng High-Chromium Bricks

During use, the main factors contributing to the damage of high-chromium bricks used in gasifiers include:

Chemical Erosion

High-chrome bricks are primarily eroded by molten slag during use, followed by erosion from strongly reducing gases within the furnace. Slag erosion involves the dissolution of ZrO2 and Al2O3 from the bricks into the slag. Additionally, SiO2 and CaO from the slag strongly penetrate the bricks and react with refractory components to form a thick altered layer. The erosion by strong reducing gases like CO and H2 is mainly due to the interaction of these gases with impurities in the brick. For example, SiO2 and iron oxides react to generate gases that escape, or iron oxides react with CO to form carbon that deposits in the brick, causing the high-chromium bricks to bulge and crack.

Mechanical Wear

Mechanical wear mainly comes from the scouring effect of high-speed gases and the molten slag they carry on the high-chrome bricks used in gasifiers. This scouring accelerates the chemical reaction between the molten slag and the high-chromium bricks. It also carries away low-melting-point reaction products from the brick surface. Furthermore, it accelerates the peeling process of the altered layer and cracked areas of the brick.

Operating Conditions

The operating process of the gasifier is also a key factor causing damage to high-chrome bricks.

• a) Operating Temperature. Practice has shown that for every 100°C increase in the gasifier's operating temperature, the erosion rate of refractory bricks can increase by nearly 3-4 times.
• b) Coal Type: The ash melting point of the coal determines the operating temperature of the gasifier. If the ash melting point of the raw coal is too low, the viscosity of the ash under production conditions will be very low, which will exacerbate the erosion and penetration of the molten slag onto the hot-face bricks. For coals with excessively high ash melting points, a certain amount of additives, such as CaO and Fe2O3, are often introduced when preparing the coal-water slurry to lower its melting flow temperature to an optimal value. With the increase in the amount of CaO and Fe2O3 added, the erosion of high-chromium bricks also intensifies.
• c) Production Load and Number of Start-ups and Shutdowns: Statistics show that for every 30% increase in production load, the service life of the hot-face bricks decreases by approximately 33%. Typically, each start-up and shutdown results in 5-20mm of erosion on the hot-face bricks, especially when the CaO content in the slag is high. d) Burner: Experimental studies and actual field operations show that the normal burner spray angle should be around 35°. If the angle is too large, it will cause severe erosion and peeling at the top. If the spray angle is too small, complete gasification will occur, leading to reduced gasification efficiency. Misalignment of the burner installation will exacerbate localized corrosion of the furnace lining.