New Characteristics of Ferrosilicon Smelting

New Characteristics of Ferrosilicon Smelting

This paper describes the new characteristics of ferrosilicon smelting of ferrosilicon submerged arc furnace, including the main trends of large-scale, stepped utilization, etc. Aiming at the problems existing in the silicon iron smelting industry in China, the corresponding solutions are proposed, such as the use of large submerged arc furnace smelting silicon iron, waste heat recovery technology, new environmental protection technology, etc., to achieve the goals of energy conservation and emission reduction, comprehensive utilization and environmental protection. Meanwhile, the application of refining technology, local low-pressure compensation technology and cascade utilization of flue gas waste heat are introduced. Finally, by comparing the indexes of domestic enterprises in the same industry, the production level of smelting silicon iron with large furnace is proved to be the advanced level in China.

1 Overview

With the energy shortage and increasing environmental pressure in our country, as a high energy consuming industry, ferrosilicon smelting enterprises must change their original extensive and high pollution mode.At present, the capacity of ferrosilicon smelting in China is mainly below 36000KVA, with high energy consumption, and most of it has not been recycled, resulting in a large amount of pollution. In response to this situation, major ferrosilicon production enterprises in China are gradually implementing large furnace smelting ferrosilicon, waste heat recovery technology, and new environmental protection technology to reduce energy consumption and achieve the goal of "green mountains and clear waters are as valuable as mountains of gold and silver".

2 Main Trends

2.1 Large Scale Furnace Type

When ferrosilicon is smelted in Submerged Arc Furnace with different capacities, there are differences in the electrothermal conversion law in Submerged Arc Furnace, the smelting process operation system of different furnace types is different, and the raw material conditions in different regions are also slightly different, which will cause great changes in the smelting characteristics of Submerged Arc Furnace, and some smelting characteristic parameters are difficult to accurately measure.In order to further understand the change law of smelting characteristics of Submerged Arc Furnace, it is necessary to combine the actual production situation of the factory, summarize its internal law through a large number of actual production data statistics, and simulate it into approximate values.

The 12500kVA, 25000kVA, 36000kVA and 81000kVA silicon iron ore furnaces that have been built by an enterprise in Inner Mongolia are used for production. Through long-term data analysis in the past 20 years, with the increase of furnace type, its thermal efficiency also increases by varying degrees. When the 81000kVA Submerged Arc Furnace is selected, the maximum increase of thermal efficiency is 10%.

In addition, a mineral thermal furnace with a capacity of 81000kVA is used, which has stable furnace temperature, stable operation, uniform product quality, and reduced smelting power consumption.At the same time, the increase in furnace capacity has created conditions for the mechanization and automation control of raw material transportation and operation, improved labor productivity, and reduced operating costs.

2.2 Application of Refining Technology

The raw materials for ferrosilicon smelting use high-quality combined carbonaceous reducing agents.Mainly using metallurgical coke, combined with gas coal coke, anthracite or bituminous coal as reducing agents, can save 200-300 kWh/t of energy in ferrosilicon products.Calculated at 0.4 yuan per 1kWh of electricity, the annual electricity cost savings are 158004 × 200 × 0.4=1.264 million yuan;

Improve the preparation technology of ore entering the furnace.Ensure that the furnace material has appropriate block size to ensure good breathability and achieve better smelting indicators.

2.3 Adopting a Fully Automatic Fabric System

The traditional fabric method uses artificial fabric, which results in high labor intensity and poor working environment for workers.Based on this situation, some enterprises adopt fully automatic fabric distribution methods, which do not require manual fabric distribution and improve the workshop environment.

Full automatic distribution devices are arranged on the top cover of Submerged Arc Furnace at 120 ° to each other, which can realize circular distribution, sector distribution and fixed point distribution within the 120 ° sector.The β angle of the chute (the circumferential angle of the fabric chute) is rotated by the motor, which drives the small gear and large gear ring to rotate. The motor rotates in both directions, achieving a 120 ° fabric range for the chute. The α angle of the chute (the inclination angle of the fabric chute) tilts by the motor, which drives the screw elevator and then drives the connecting rod to change the angle of the chute, allowing the material to be distributed on different ring surfaces and achieving uniform fabric distribution;By coordinating the throttle valve under the hopper, flow control of the fabric at different positions can be achieved.

The device realizes automatic feeding at any point in the Submerged Arc Furnace, making the material distribution more uniform, facilitating the realization of large-scale Submerged Arc Furnace and reducing the power consumption of Submerged Arc Furnace.

2.4 Application of On sS

2.5 Cascade Utilization of Flue Gas Waste Heat

During the production of semi closed submerged arc furnace, the gas burns into smoke when encountering air. The amount of smoke is 10~15 times that of the closed type, and the amount of smoke is large and dusty, which is difficult to purify, and is not conducive to energy recovery. It will pollute the environment and cause energy loss for a long time. Therefore, the high-temperature Submerged Arc Furnace smoke is designed for dry bag dedusting after being used for waste heat.

The utilization and power generation of semi enclosed waste heat boilers have become the main way of utilizing flue gas waste heat in this furnace type. After recovering the heat from the high-temperature flue gas of the ore blast furnace, power generation is carried out to achieve the goals of energy conservation, emission reduction, comprehensive utilization, and environmental protection.The process flow is as follows: the high-temperature mineral heat furnace flue gas (with a temperature of around 650 ℃) is sent to the waste heat boiler (horizontal or vertical boiler) through the mineral heat furnace flue (2 or 3). After heat exchange in the waste heat boiler, the high-temperature and high-pressure steam generated is sent to the steam turbine generator unit through a steam pipeline (with a length controlled within 1 kilometer) to drive the unit to generate electricity.

The temperature of high-temperature Submerged Arc Furnace flue gas is reduced to about 250 ℃ after heat exchange by waste heat boiler, and its energy can also be used.At present, the main practical utilization method is to generate supplementary steam for waste heat boilers.

In addition, the outlet flue gas temperature of the waste heat boiler has already met the requirements of the bag filter, and there is no need to add additional cooling devices (such as air coolers) to reduce project investment.

3. Comparison of 3 Main Economic and Technical Indicators

The following table is a comparison of indicators for domestic enterprises in the same industry.According to the analysis of the progressiveness of process equipment, resource and energy consumption and other indicators, as well as the comparison with domestic and foreign enterprises in the same industry, the production level of ferrosilicon smelting with large furnace is advanced at home.

4 Conclusion

Through the above analysis, I believe that the use of large-scale Submerged Arc Furnace smelting, mainly metallurgical coke, with gas coal coke, semicarbon or bituminous coal as reducing agent, and the use of fully automatic distribution technology, after the high temperature flue gas of Submerged Arc Furnace is cooled by waste heat boiler, the realization of waste heat ladder recovery and utilization of flue gas has become a new feature of ferrosilicon smelting industry in the future.

Reference:

[1] Guo XinSmoke and dust characteristics and waste heat recovery and utilization of ferrosilicon smelting furnace [J]. Applied Energy Technology, 2014 (5)

[2] Zhu HeLow voltage reactive power compensation for ore blast furnaces [J]. Industrial Heating, 2008 (3)

[3] Wu Rongyang, Wu GuohuaComprehensive utilization of Submerged Arc Furnace flue gas resources [J]. Comprehensive utilization, 2011 (8)