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Energy Saving and Environmental Protection Technology of Cone Column Rotary Cutting Top Combustion Hot Blast Stove





1. Introduction
The energy saving and emission reduction technology innovation of ironmaking process is gradually being valued by the steel industry and all sectors of society. With the development of ironmaking, the indicators of blast furnace continue to improve, the space for reducing fuel consumption of blast furnace system is getting smaller and smaller, and the power medium consumption of blast furnace auxiliary system is becoming more and more prominent in cost control. Therefore, improving the energy efficiency of the hot blast stove system and reducing energy loss are also extremely important for the energy saving and consumption reduction of the ironmaking process. In recent years, the country's low-carbon requirements have been put forward. For the ironmaking industry, it is not only a simple requirement for quality and production capacity, but also must meet the requirements of environmental protection.

2. Analysis and Discussion on Energy Saving and Environmental Protection of Top Burning Hot Blast Stove
With the national energy conservation and emission reduction, as well as the elimination of backward production capacity to increase the pace, hot blast stove all kinds of energy-saving and efficient technology such as the trend of the emergence. Anneke is a domestic high-tech enterprise with refractory material manufacturing, blast furnace hot blast stove technology output and EPC engineering services as its core business. Since its establishment, Anneke has always focused on independent research and innovation of hot blast stove technology, and has accumulated more than ten years of hot blast stove technology research and innovation experience in the field of top-burning hot blast stove. As early as 2013, the company, together with Shougang International and others, drafted the "Technical Specification for Energy Saving of High Efficiency and High Air Temperature Top Combustion Hot Blast Stove for Blast Furnace", which put forward energy saving and emission reduction requirements such as waste heat recovery and utilization of waste gas of hot blast stove and CO emission limit in waste gas. In view of the increasingly prominent environmental protection situation, the above-mentioned norms and standards will be revised in 2021 to increase the emission requirements of pollutants such as nitrogen oxides and sulfur dioxide in the flue gas of hot blast stoves, as well as the energy-saving evaluation requirements of hot blast stoves. After the revision of the standards, it will better lead the popularization and application of energy-saving technologies for top-burning hot blast stoves.

On September 22, 2022, the Ironmaking Branch of the Chinese Society of Metals organized relevant experts to hold a seminar in Beijing on the energy-saving technology of hot blast stoves. The meeting emphasized that in the process of developing energy-saving technology for hot blast stoves, attention should be paid to the low pollution and low emission technology of hot blast stoves. Zhengzhou Annike participated as an invited unit and made a report entitled "Brief Introduction of Energy Saving and Environmental Protection Technology for Top Burning Hot Blast Stove". Through analyzing the energy saving and consumption reduction ways and potential of hot blast stoves, this paper summarized the energy saving influencing factors of gas per ton of iron, and put forward the measures to increase the average temperature of top burning hot blast stoves. And from the production of NOx and harm to the operation mechanism of hot blast stove, the corresponding countermeasures and feasible measures are introduced.

Experts at the meeting agreed that the consumption of gas per ton of iron cannot be simply determined as the key indicator for evaluating the energy consumption of hot blast stoves. The indicators before and after the technological transformation of the hot blast stove system of iron and steel enterprises can better reflect the effect of the technological transformation of hot blast stoves.

3. Structural characteristics of cone column rotary cutting top combustion hot blast stove
The burner is the most critical equipment of the top-fired hot blast stove, and its performance has a great influence on the thermal efficiency, energy consumption, environmental protection and other economic indicators of the hot blast stove. Compared with the conventional top-fired hot blast stove burner, the cone-column rotary cutting top-fired hot blast stove burner has made significant improvements in layout and structure, and is characterized:

The mixing chamber of the burner is a cone-column composite structure, with gas nozzles distributed in the cone section and air nozzles distributed in the cylinder section, which improves the air-gas plane swirling mixed flow field of the traditional top-fired burner into a three-dimensional space swirling flow field, and reduces the height of the burner dome, achieving low investment and high efficiency.

② The gas section of the burner mixing chamber is constructed with steel mold to support the overall pouring. The gas ring and gas nozzle are located in the cone section, and the top space is small, which is conducive to nitrogen purging. It avoids the displacement of the nozzle brick caused by the deflagration of the traditional top-fired hot blast stove, avoids the gas residue of the gas ring nitrogen purging, and eliminates the deflagration phenomenon of the gas nozzle. This design makes the conversion of hot blast stove air supply and burning stove safer and more efficient;

The location of the burner mixing chamber is not the highest temperature, the highest internal temperature will not exceed 1100 ℃, to prevent the mixing chamber shell intergranular stress corrosion, while reducing the heat loss, improve the overall thermal efficiency of the hot blast furnace;

④The combustion mode is three-dimensional mixed combustion. The gas flow and air flow with multiple layers of different radii (less than the radius of the air flow) form a cross three-dimensional mixture of multiple concentric and different diameters, which ensures the full mixing and combustion of air and gas, and improves the theoretical combustion Temperature, thereby increasing the hot air temperature;

⑤ As the area of the hollow column is very small, the negative pressure zone formed after the throat rectification is very small, which ensures the uniform distribution of flue gas entering the lattice brick and effectively improves the utilization rate of the regenerator.

4. Introduction of energy saving and environmental protection technology for cone column rotary cutting top burning hot blast stove
① Low NOx combustion technology of cone-column rotary cutting top-fired hot blast stove, arrangement of multi-layer burners, design the burners into cone-column rotary cutting structure, realize three-dimensional vortex strong mixed combustion, under the condition of realizing the same air temperature, can reduce CO consumption, reduce NOx generation, make hot blast stove NOx emission standard, not only solve CO pollution, but also do not produce new polluting gases, make it an environmentally friendly high temperature air supply equipment.

② Hot blast stove waste heat utilization technology, the use of flue gas, air double preheating, improve the thermal efficiency of hot blast stove to 85%.

③ cold air flow uniform distribution technology, optimize the hot blast furnace grate parts cold air flow uniform distribution, improve the heat exchange efficiency of hot blast furnace.

④ Automatic combustion system, using the full simulation calculation model data, the establishment of hot blast stove mathematical burning furnace model, with three-dimensional mixed burner, can reduce the hot blast stove gas consumption by 3%-8%.

⑤ Optimize the process operation system of hot blast stove, reduce the pressure fluctuation of gas and combustion air, and save energy and improve efficiency.

⑥ Safety purging system, nitrogen purging system is installed in the burner and gas branch pipe to ensure the safe operation of the burner.

⑦ Full burning of 100 blast furnace gas with low calorific value, supporting three cone-column rotary cutting top-burning hot blast stoves, double preheating of gas and combustion-supporting air, under the condition of vault temperature ≤ 1350 ℃, obtaining an air supply temperature ≥ 1250 ℃, ensuring NOx emission ≤ 50 mg/m.

5. Application effect

In March 2022, the 0# hot blast stove of the No.2 blast furnace of an enterprise affiliated to Baowu Group was renovated and put into operation. It also marked that the first top-burning hot blast stove of the steel enterprise was put into production and operation. The No.2 blast furnace has a capacity of 1280m. The hot blast stove was originally equipped with 3 internal combustion hot blast stoves, with lower air temperature and higher energy consumption. Since February this year, after the first Anneke cone column rotary cutting top-burning hot blast stove was put into operation, the air supply temperature of the hot blast stove system has increased by 25 ℃, the daily output has reached 4411 tons, and the gas consumption per ton of iron has been reduced to 443 m/t (HM), which is 6.7 lower than that of the internal combustion hot blast stove before the renovation (see the table below for details). At present, the second cone-column rotary cutting top-fired hot blast furnace is about to be connected to the grid to supply air, and the blast temperature of the blast furnace will be further improved, creating more favorable conditions for improving the fuel efficiency of coal ratio and reducing fuel consumption.

Comparison photo of hot blast stove of No.2 blast furnace before and after technical renovation

6. Application Prospect of Cone Column Rotary Cutting Top Burning Hot Blast Stove
Cone column rotary cutting top-burning hot blast stove has been introduced to the market since 2013. Up to now, more than 180 stoves at home and abroad have adopted this technology. Through PCT patent application, they have obtained patent authorization from Russia, Japan, Ukraine, India and other countries. In particular, in 2021, they signed an EP project with Russia's MMK Steel Group to upgrade the 7# blast furnace-internal combustion hot blast stove into Anike cone column rotary cutting top-burning hot blast stove, as well as India's JSW 5872m ³ blast furnace new top-burning hot blast furnace EP project, marking that the top-burning hot blast furnace technology with China's independent intellectual property rights has reached the international leading level.

The top-burning hot blast stove has initially realized large-scale and high-efficiency in China, and the development of the top-burning hot blast stove in the future will be towards the development direction of high air temperature, long life and low emission. Since the advent of Annike cone column rotary cutting top-burning hot blast stove, remarkable economic and social benefits have been achieved, which is especially suitable for the new construction and transformation of blast furnaces in China, anneke will continue to devote itself to the continuous optimization and improvement of top-burning hot blast stove and the research and development and production of supporting refractory materials. Through the continuous optimization and upgrading of furnace structure and refractory material configuration, Anneke will study and realize low emission or even zero emission of pollutants in exhaust gas, vigorously promote the application of advanced technology of cone column rotary cutting top-burning hot blast stove, and comprehensively promote the development of energy saving and low consumption of hot blast stove.