Requirements for Lime in Metallurgical Industry
As an important pillar of the national economy, the metallurgical industry has extremely high requirements for the selection and use of raw materials in its production process. Lime, as an indispensable flux and slag material in the metallurgical industry, its quality directly affects the effectiveness and product quality of metallurgical production.
1、 Appearance requirements
The appearance of metallurgical lime is the first impression of its quality and an important basis for preliminarily judging its quality. Qualified metallurgical lime should be white or slightly yellow, with uniform color and no obvious impurities or mechanical impurities. The appearance should be delicate, uniform, and free of lumps and crystallization. This appearance feature indicates that lime has undergone sufficient calcination and screening during the production process, ensuring its purity and uniformity.
2、 Chemical composition
1. Calcium oxide content
The main component of metallurgical lime is calcium oxide (CaO), and its content is an important indicator for evaluating the quality of lime. The calcium oxide content in high-quality metallurgical lime should not be less than 90%. A high content of calcium oxide means that lime has stronger melting ability and higher reactivity, which can better meet the needs of metallurgical processes.
2. Magnesium oxide content
Magnesium oxide (MgO) is one of the impurities in lime, and its high content can affect the melting rate and reaction performance of lime. Therefore, the content of magnesium oxide in metallurgical lime should be controlled at a low level, generally not exceeding 1.5%.
3. Effective alkalinity and active calcium content
Effective alkalinity is an important indicator for evaluating the ability of lime to produce alkaline substances after melting, and has a significant impact on reactions such as desulfurization and dephosphorization in metallurgical processes. The effective alkalinity of high-quality metallurgical lime should not be less than 85%. Meanwhile, the active calcium content is also an important parameter for measuring the reactivity of lime reaction, which should not be less than 75%.
4. Sulfur and iron oxide content
Sulfur and iron oxide are harmful impurities in lime, and their presence increases the sulfur content in the alloy, affecting product quality. Therefore, the sulfur content in metallurgical lime should not exceed 0.1%, and the iron oxide content should not exceed 0.5%.
3、 Physical performance
1. Limestone content
Limestone is the main raw material for lime production, but its content should be minimized as much as possible in the finished lime. Excessive limestone content can reduce the melting rate and reaction activity of lime, affecting metallurgical efficiency. Therefore, the limestone content in metallurgical lime should not exceed 5%.
2. Ash content
Ash is an impurity in lime that has not been completely decomposed, and its high content can affect the purity and reactivity of lime. The ash content in metallurgical lime should be controlled at a low level, generally not exceeding 3%.
3. Particle size distribution
Particle size distribution is an important factor affecting the reaction performance of lime. The particle size of metallurgical lime should be uniform and meet certain screening requirements. The material passing through a 60 mesh sieve should not be less than 95%, and the material passing through a 200 mesh sieve should not be more than 10%. This particle size distribution can ensure better reactivity and higher utilization of lime in metallurgical processes.
4、 Lime quality control
1. Production standards
The production of metallurgical lime should be strictly carried out in accordance with national standards. Metallurgical lime produced using limestone as raw material shall comply with the requirements of the national standard GB/T 3280; Metallurgical lime produced using limestone and lime as raw materials shall comply with the requirements of the national standard GB/T 3281. These standards provide detailed regulations on the chemical composition, physical properties, particle size distribution, and other aspects of lime, ensuring the stable and reliable quality of lime.
2. Quality Management System
Metallurgical lime production enterprises should establish a sound quality management system and develop strict quality control standards and processes. Monitor the entire process of raw materials, production, and finished products to ensure stable and reliable product quality. At the same time, enterprises should regularly inspect the quality of lime, including appearance, chemical composition, physical properties, etc., to ensure that the products meet national standard requirements.
5、 Packaging and Storage
1. Packaging requirements
Metallurgical lime should be packaged with moisture-proof, rainproof, and sun proof packaging materials, and the packaging should be intact and clearly labeled. Good packaging can prevent lime from getting damp and contaminated during transportation and storage, and maintain its stable quality.
2. Storage conditions
Metallurgical lime should be stored in a dry and ventilated warehouse, away from acidic and alkaline substances, and protected from moisture and rain. Such storage conditions can reduce the absorption of moisture and carbon dioxide in the air by lime, maintain its dryness and purity, and avoid affecting the metallurgical effect.
6、 Application scope
Metallurgical lime is mainly used in production processes such as ironmaking and steelmaking in the metallurgical industry. During the ironmaking process, lime can be used to melt ores and remove impurities such as sulfur; During the steelmaking process, lime serves as an important flux and slagging material, which can remove harmful elements such as phosphorus and sulfur from the molten steel and improve its quality. In addition, metallurgical lime can also be used in fields such as sewage treatment and soil improvement.
The metallurgical industry has very strict requirements for lime, with detailed regulations on appearance, chemical composition, physical properties, quality control, packaging, and storage. These requirements aim to ensure that lime can fully utilize its melting, slagging, desulfurization, phosphorus removal and other functions in metallurgical processes, improving the efficiency and product quality of metallurgical production.
