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Research on the complexity mechanism and prediction of blast furnace smelting process

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Abstract: Steel plays a major role in social development. It is a basic project to promote social development and a pillar industry for the development of the national economy. In the steel industry, blast furnace ironmaking has become an upstream main process, playing an irreplaceable role and significance in the development and energy-saving optimization of the entire steel industry. This article is based on the boiler operation data of a steelmaking plant and analyzes the practical problems existing in ironmaking production. Based on the complexity of boiler temperature changes and prediction requirements, the operating mechanism and prediction methods are explored and studied, and the relevant theoretical value and research significance are put forward.

Keywords: iron and steel industry; boiler; smelting; complexity mechanism; prediction

Since the industrial revolution, steel has always played a leading role in social development and is one of the indispensable structural materials for the production of all walks of life. It can be said that in the current social development, every step of progress in human civilization is closely linked to the steel industry. In a certain sense, the production capacity and consumption level of steel are directly related to the comprehensive capabilities of a country and the level of its people. In recent years, with the development of science and technology, various advanced steelmaking technologies have continued to emerge, which has promoted the rapid development of the steel industry and also brought about serious energy supply problems. Facing the increasingly severe global energy crisis, the steel industry, as a major energy-consuming field, has gradually attracted people’s attention and attention, especially the energy consumption requirements of blast furnace ironmaking in the past. In social development, it is an urgent problem that needs to be solved in order to reduce the comparison of blast furnace ironmaking and improve the utilization of coefficients by combining it with the laws of scientific development.

Overview of blast furnace smelting work

Blast furnace iron smelting is based on the study of mathematical models for furnace temperature prediction, which is not only an automation problem for iron making but also the primary and core problem in actual production work. In the current work, the analysis of furnace temperature fluctuations is of great significance and role in the accurate control and prediction of furnace temperature, and will help improve the level of smelting technology to maximize energy requirements.

In the current development of the ironmaking industry, the main equipment is blast furnace. As a type of shaft furnace, blast furnace must have high fire resistance requirements. Generally, in construction and composition, an upright cylindrical shape with good fire resistance is used, and relevant steel plates are installed on the outside for reinforcement and sealing, and certain embedded cold equipment must be installed inside the structure for related protection. For general work, in addition to strengthening the body, the ironmaking process of the boiler also needs to be comprehensively processed and analyzed. Ensure that its various processes and equipment can operate well and systematically during work, as the main steelmaking mode.

Under normal circumstances, steelmaking projects are dominated by internal physical and chemical reactions. Generally, the reaction process can be briefly summarized as the placement of charge. The charge is basic energy such as ore, solvent and coke, which are placed in the blast furnace loading system in a certain proportion, and then enter the furnace from the top of the furnace. When the blast furnace hot air system is used for heating and improving combustion intensity, air is generally blown from the lower tuyere for wind transportation, thereby increasing the coke and high-temperature reduction reaction to form a reducing gas. During the descent process, the charge is heated by the rising gas flow, and undergoes a series of physical and chemical reactions such as reduction, melting, and slagging. Finally, liquid slag and iron are generated and accumulated in the furnace hearth, and are periodically discharged from the blast furnace slag iron outlet; During the rising process of the gas flow, the temperature continues to decrease and the composition gradually changes, and finally the blast furnace gas is formed and discharged from the top of the furnace. Blast furnace ironmaking is a continuous process. Solid charge is periodically loaded from the top of the furnace, and liquid products are continuously or regularly discharged from the furnace. Hot air containing certain hydrocarbons is continuously injected through the tuyere, and blast furnace gas and furnace dust are discharged from the furnace top.

Regarding personnel control requirements at work, it is generally necessary to set up different professional technical personnel in different positions to carry out strict control. These control work are not independent modes, but a management and control mode that communicates and coordinates with each other through the furnace and the main control room. Generally, during work, it is necessary to cooperate and coordinate to achieve process control and blast furnace control management, and to deal with failures in any link in a timely manner, and to comprehensively deal with problems that affect the furnace smelting process.

Compared with non-blast furnace ironmaking such as direct reduction and smelting reduction, the advantages of blast furnace ironmaking are: sufficient heat exchange can be achieved through the convection function of descending solid charge and ascending reducing gas, and the thermal efficiency is high. It can process a large amount of raw materials, has high production efficiency, and is easy to form large-scale production; the raw material composition used in smelting has a wide range; at the same time, the main equipment of smelting, the blast furnace, has a relatively long life (15 to 20 years), and the iron output is relatively stable. Its main disadvantage is: due to the closed nature of the blast furnace body, many parameters cannot meet the requirements of visibility and controllability, and the composition of the molten iron is difficult to accurately control. In view of the complexity of the blast furnace smelting process, there is still a long way to go to realize the overall closed-loop automatic control of the smelting process, especially the accurate predictive control of furnace temperature.

Furnace temperature concept and blast furnace smelting process requirements for furnace temperature prediction

Since the second half of the 20th century, the rapid development of electronic computer technology, information technology, advanced control technology, etc. has provided advanced technical means for the steel industry. Many sub-processes of blast furnace smelting, such as batching, distribution, air supply, etc., have gradually been automated. However, people have developed mathematical models for blast furnace temperature control and tried to realize automatic control of the blast furnace smelting process, but so far they have not been successful. Therefore, in the realization of closed-loop automatic control of blast furnace ironmaking, furnace temperature control is the most difficult. Blast furnace temperature refers to the temperature of molten iron and slag in the furnace.

The steady development of blast furnace temperature is a key link in realizing automatic control of blast furnace smelting. As we all know, the lower part of the blast furnace is a dead coke layer in the furnace core. When high-temperature gas fully flows through the dead coke layer, the dead coke layer is in an active state, which increases the temperature of the furnace hearth. On the contrary, when the operating conditions change and the air permeability of the dead coke layer becomes poor, and the high-temperature gas cannot fully pass through, the dead coke layer is in a sluggish state, thus causing the furnace temperature to drop. By controlling the furnace temperature within the normal range, the blast furnace will run smoothly. If the furnace temperature fluctuates greatly, the furnace hearth will be overheated or overcooled, which will not only increase unnecessary heat loss, but may even easily induce blast furnace failure. When the blast furnace operating conditions change, the blast furnace temperature must also be adjusted accordingly. How to grasp the change and development trend of blast furnace temperature to stabilize furnace conditions is the core technology of blast furnace operation and a major indicator to measure the level of “blast furnace ironmaking automation mathematical model”.

International and domestic research status and progress

During the blast furnace smelting process, the silicon content [Si] of the molten iron is not only an important indicator for evaluating the quality of the molten iron, but also characterizes the internal thermal state of the blast furnace. In order to effectively control the blast furnace smelting process and grasp its furnace temperature development trends, the study of molten iron [Si] prediction methods has always been an important topic in ironmaking production. But due to the complexity of the blast furnace process, the difficulties with this type of model are:(1) The blast furnace smelting process is carried out in a closed state. Many parameters cannot be directly observed, and the input and output variables of the process can only be measured indirectly. The values of the input parameters of the model rely on the integration of the knowledge and experience of many operators and are mixed with the influence of noise ; (2) The blast furnace smelting process is not a stable process. Changes in furnace conditions are often the combined influence of multiple parameters. When the operation is stable, the model effect is good. When the furnace conditions fluctuate, the model is difficult to reflect such effects, and the effect declines rapidly.

Conclusion

The steel industry in our country is a pillar industry for the development of the national economy. Therefore, it is very important to conduct research on the complex mechanisms and predictions of the steel smelting process to improve the development of the steel industry. It is also of great significance to realize the modernization of the steel industry.

LMM YOTAI established in 2007. Our production technology comes from Japanese Yotai. As an experienced and international player in the refractories industry. We have succeeded in expanding both the breadth of its product range and the depth of its services. From raw material selection, refractory portofio & optimization, installation & services & recycle of used refractories on site to further reduce client’s Opex & Capex in refractory consumption per ton steel output, meanwhile improve product quality of client.

Our Product have been supplied to world’s top steel manufacturer Arcelormittal, TATA Steel, EZZ steel etc. We do OEM for Concast and Danieli for a long time

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