I. The core process of LECA production
The production process of LECA varies depending on the raw materials, but the core process can be summarized into five steps:
1. Raw material processing
Depending on the type of raw materials (such as clay, fly ash, sludge, shale, etc.), crushing, screening or mixing is required. For example, clay needs to be crushed to 100-200mm and then homogenized; sludge needs to be mixed with fly ash and clay in proportion and naturally dehydrated for 15-20 days in the aging yard to optimize performance.
2. Granulation and molding
The raw materials are squeezed into 5-10mm particles using equipment such as double-roll granulators and ball-forming discs. Fly ash LECA needs to go through the mud balling process, while sludge LECA relies on the strong extrusion of the double-roll granulator.
3. Preheating and roasting
The particles are treated at high temperature in a rotary kiln or sintering machine, usually at a temperature of 1000-1170℃. The expansion method (applicable to clay and shale) forms a porous structure through internal gas expansion; the sintering method improves strength through solid solution bonding. For example, sludge LECA can reach a cylinder pressure strength of 5.8MPa and a water absorption rate of only 7.64% after sintering at 1000℃ for 12 minutes.
4. Cooling and screening
The high-temperature LECA is quickly cooled by a vertical cooler or a grate cooler, and the cooled air is reused as secondary air, with an energy saving efficiency of 70%7. The final product is graded and packaged according to particle size (such as 5mm, 15mm, 25mm).
5. Environmentally friendly dust collection
The flue gas at the end of the kiln is purified by a multi-tube cooler and a bag dust collector, and the dust emission is lower than the national standard, achieving clean production.
2. Technological innovation: both high efficiency and energy saving
The modern LECA production line significantly improves energy efficiency through equipment optimization:
• Sleeve drying technology: using the waste heat of the rotary kiln to pre-dry the raw materials, reducing fuel consumption by 10%.
• Intelligent control: computer automatic batching system is used to accurately control the ratio of water and raw materials to ensure the balance between porosity and strength.
• Waste resource utilization: riverbed mud, urban sludge, etc. are used to replace traditional clay, which not only reduces the consumption of natural resources, but also solves the problem of solid waste pollution. For example, the bulk density of riverbed mud LECA can be as low as 528kg/m³, and the compressive strength can reach 35.38MPa.
III. Environmental protection value: circular economy from raw materials to applications
1. Green raw materials
The utilization of industrial waste such as fly ash, coal gangue, and sludge can reduce the accumulation of millions of tons of solid waste every year. For example, adding 10% steel slag can improve the strength of LECA and reduce water absorption.
2. Low carbonization of process
Biomass fuels (such as rice husks) replace coal and reduce sulfur oxide emissions; rice bran is used as an additive to generate CO₂ and water vapor during burning, which is environmentally friendly and controllable.
3. Application scenario expansion
The weight of LECA concrete is reduced by 12.4%, which is suitable for prefabricated buildings; as a biological filter material, its lead ion adsorption rate exceeds 93%, which helps sewage treatment.
IV. Future Outlook: Intelligence and Standardization Go Hand in Hand
As market demand expands, LECA production is making breakthroughs in two directions:
1. Process standardization: Formulate national standards for LECA filter materials, clarify indicators such as strength and porosity, and promote high-quality development of the industry.
2. Equipment intelligence: Introduce AI algorithms to optimize roasting temperature control, combine the Internet of Things to achieve full-process remote monitoring, and improve production stability
