Technical Requirements for Self-Baking Coke for Blast Furnace
Abstract
The quality of self-baking coke for blast furnaces is closely related to the yield and quality of iron and the safety of the production process. Therefore, the process, performance and technical requirements of self-baking coke are very important. This paper mainly introduces the process, performance and technical requirements of self-baking coke for blast furnaces, so as to provide a better reference for the production of coke enterprises and the use of blast furnace enterprises.
Keywords: self-baking; blast furnace; technical requirements
1. Introduction
Self-baking coke has characteristics such as low ash and low sulfur, high porosity, high mechanical strength and low resistivity, which is an ideal form of raw material for blast furnace. The use of self-baking coke can reduce the blast furnace top burden, and the sulfur in the coke and molten iron can be reduced by about 80%. The use of self-baking coke can save energy consumption, reduce greenhouse gas emissions and increase the effective volume of blast furnace. On the other hand, self-baking coke is not only the raw material of blast furnace, but also the part of blast furnace charge and the protective material of the periphery of the furnace crown. Therefore, the properties of self-baking coke are crucial for the blast furnace operation. Generally speaking, the quality of self-baking coke for blast furnaces is closely related to the yield and quality of iron, the stability of the blast furnace, and the safety of the production process. Therefore, it is of great significance to clarify the process, performance and technical requirements of self-baking coke.
2. Process and performance requirements
2.1. Process Requirements
Self-baking coke is usually baked at high temperature in the form of calcination or baking. Its production process generally includes cold masses, grinding, mapping, baking, cooling, material removal and other operations.
The cold masses of self-baking coke is made of selected good clean coking coal and some special additives, which are kneaded into a certain shape after grinding and mixing. The shape of the cold masses can be round-shaped, oval-shaped or square-shaped, etc. After the cold masses have been molded, they will be sent into the coke oven for baking. The temperature of the coke oven will be raised at a gradual rate according to the process requirement, but the maximum temperature should not exceed 1700 ℃. During the baking process, the smoke and gas produced should meet the environmental protection requirements. After the furnace is cooled down, the self-baking coke can be taken out.
2.2. Performance Requirements
The performance requirements of self-baking coke for the blast furnace include 9 items: ash (%) > 8; volatile matter (%) < 12; strength (Mpa)> 0.8; porosity (%)> 25; apparent specific gravity (g/cm3)> 1.1; sulfur content (%)≤ 0.3; resistivity (μΩ.m) 60-100; sulfur dioxide emission concentration (mg/MJ) ≤200; free-swelling index (%) ≤ 8.
In addition, self-baking coke should have high mechanical strength, so that it can meet the requirements of compaction and prevent the collapse of the top of the blast furnace. High porosity can speed up the heat transfer and the whole reaction rate of the blast furnace. Control the sulfur element in Self-baking coke, can facilitate the desulfurization of the blast furnace. The resistivity of self-baking coke should be low, otherwise the continuous operation of electric Smelting system will be affected.
3. Technical Requirements
The technical requirements of self-baking coke for blast furnace are mainly divided into physical indicators and chemical indicators.
3.1 Physical Indicators
(1) The size should be adjustable, and the size of the coke and the gap between the coke should be appropriate.(2) The strength of the self-baking coke should be greater than 0.8 Mpa, and the compaction should be no less than 90%.(3) The appearance of the self-baking coke should be flat and smooth, without cracks or broken edges.
3.2 Chemical Indicators
The technical requirements of self-baking coke for blast furnace include 9 items: ash (%) > 8; volatile matter (%) < 12; strength (Mpa)> 0.8; porosity (%)> 25; apparent specific gravity (g/cm3)> 1.1; sulfur content (%)≤ 0.3; resistivity (μΩ.m) 60-100; sulfur dioxide emission concentration (mg/MJ) ≤200; free-swelling index (%) ≤ 8.
In addition to the above indicators, it should also be tested according to clauses such as coking properties, moisture content, thermal stability and chemical composition.
4. Conclusion
In conclusion, the production process, performance and technical requirements of self-baking coke for blast furnace must be strictly implemented according to the process requirements, in order to ensure the normal production and the high quality of blast furnace products. Therefore, enterprises should pay attention to the choosing of raw materials, the technological parameters of each process, the testing of relevant parameters, the monitoring of production process and the acceptance of finished products, so as to ensure the excellent quality of self-baking coke for blast furnace.
