Analysis and Improvement of Harmful Components in Commonly Used Binders for Cement Kilns Refractory Brick

Refractory bricks are an indispensable material in cement kilns and various high-temperature industrial equipment. Refractory bricks are inorganic non-metallic materials with a refractoriness of not less than 1580℃, possessing excellent high-temperature stability and resistance to chemical erosion. Refractory bricks are not only used in cement kilns but also widely used in industries such as steel, non-ferrous metals, glass, ceramics, petrochemicals, and power generation, serving as a key basic material for ensuring equipment safety and production efficiency in high-temperature industrial operations.

I. Main Performance Indicators of Refractory Bricks

The performance of refractory bricks mainly includes five aspects: structural performance, thermal performance, mechanical performance, service performance, and operational performance.

(1) Structural Performance: According to GB/T2997—2015 standard, the main indicators include porosity, bulk density, and water absorption. With increasing firing time, the porosity and bulk density of refractory bricks change accordingly, significantly affecting their heat resistance and mechanical strength. 

(2) Thermal Properties: Based on GB/T7320—2008 standard, these include thermal conductivity, coefficient of thermal expansion, specific heat, and thermal emissivity, and are key parameters for evaluating the stability of refractory bricks under high-temperature conditions.

(3) Mechanical Properties: Based on GB/T5072—1985 and GB/T3001—2000 standards, these include compressive strength, flexural strength, and impact resistance.

(4) Service Performance: These include refractoriness, load softening temperature, thermal shock resistance, slag resistance, and oxidation resistance, and are important criteria for determining whether refractory bricks are suitable for critical parts of cement kilns.

(5) Workability: These include fluidity, plasticity, cohesion, and hardening properties, which directly affect the performance of refractory bricks during molding and construction.

II. The Role and Problems of Binders in Refractory Brick Production

In the refractory brick production process, binders play a crucial role in firmly bonding various refractory raw materials and are important additives for ensuring the stability and molding quality of the brick blanks. Common refractory brick binders fall into two main categories: organic and inorganic.

Organic binders include phenolic resin, pulp waste liquor, dextrin, syrup, and asphalt.

Inorganic binders include clay, water glass, cement, and phosphates.

Refractory bricks require binders before firing to ensure a dense body. However, during high-temperature firing and use, the organic matter in the binder decomposes and volatilizes, releasing various harmful components. These components not only affect the quality of the refractory bricks but may also adversely impact the performance of cement clinker and the environment.

III. Sources and Impacts of Harmful Components in Refractory Bricks

Currently, phenolic resin, organic powders, and pulp waste liquor binders commonly used in cement kilns easily decompose during sintering or use, generating VOCs (volatile organic compounds). These mainly include benzene compounds, organochlorides, ketones, alcohols, and ethers. These chemicals, when decomposed at high temperatures, may cause the following problems:

Environmental pollution: VOCs, during emission, form ozone and photochemical smog, impacting air quality;

Affecting product quality: Gases formed after the decomposition of organic binders can cause micropores or cracks inside refractory bricks, reducing their density and corrosion resistance;

Harm to operator health: Some volatile organic compounds are toxic, imposing higher environmental protection requirements on the production environment.

IV. Directions for Improving Refractory Brick Binders

To reduce harmful emissions during the use of refractory bricks, the industry is gradually promoting environmentally friendly binders and inorganic bonding systems. Key areas for improvement include:

Replacing organic binders with inorganic binders: such as phosphates, water glass, and aluminate cement. These binders offer higher stability at high temperatures and do not produce harmful VOCs.

Optimizing binder ratios and formulations: By controlling the amount and reactivity of binders, the molding strength of refractory bricks can be ensured while reducing the content of organic impurities.

Improving the firing process: By precisely controlling sintering temperature and time, the complete decomposition or transformation of the binder can be promoted, reducing residual organic matter.

Developing low-carbon and environmentally friendly binders: Utilizing new raw materials such as natural inorganic minerals and composite cementitious materials to enhance the green performance of refractory bricks.

As a key material in the high-temperature system of cement kilns, the performance and environmental performance of refractory bricks are closely related. By improving the binder system, optimizing the production process, and promoting inorganic environmentally friendly binders, harmful emissions during the production and use of refractory bricks can be effectively reduced, achieving green and low-carbon manufacturing and contributing to the sustainable development of the cement industry.