1. Introduction
Shenzhen Weineng Technology Co., Ltd. has always been committed to the technological innovation and development of frequency converters. In the past five years, it has made outstanding contributions to the development and application of high-power and high-performance low-voltage and high-voltage frequency converters. This article introduces the principle of high-capacity high-voltage frequency converters and their application in the steel industry.
2. The current situation of China’s steel industry
Driven by the strong development of the national economy, China’s steel industry has entered a stage of rapid development, which has also driven the rapid development of the blast furnace ironmaking industry. The current situation of China’s ironmaking industry is low concentration, with a large number of blast furnaces (about 900), exceeding 1000 meters ³ There are approximately 110 blast furnaces mentioned above.
High blast temperature is the main technical feature of modern blast furnaces. Improving wind temperature is the main technical measure to increase coal injection rate, reduce coke ratio, and lower production costs. In recent years, the hot air temperature of blast furnaces in domestic steel enterprises has been increasing by 25 ℃ year by year, especially for a batch of newly constructed large blast furnaces (more than 2000m3), with hot air temperatures exceeding 1200 ℃, reaching the international advanced level. For example, after 2002, the hot air temperature of Shougang’s technological transformation or new blast furnaces has achieved the goal of exceeding 1200 ℃. Furthermore, by adjusting parameters such as air volume, air pressure, blast humidity, oxygen enrichment rate, fuel injection, tuyere area and length, the goal of increasing production and blast furnace utilization coefficient can be achieved. This requires better optimization of the air supply system. Therefore, the speed of the motor driving the blast furnace blower must meet the requirements of a wide speed range and fast response, which cannot be achieved through traditional air door regulation. The improvement of the research and design level of domestic high-voltage frequency converters and the maturity of manufacturing technology have made it possible to optimize the air supply system of blast furnace blowers.
2.1 Introduction to Modern Blast Furnace Ironmaking Process
The process of ironmaking is essentially the process of reducing iron from naturally occurring iron containing compounds such as ores. It is usually divided into two stages: sintering and ironmaking. Sintering: It is a method of making iron ore powder into blocks to provide refined materials for blast furnaces. It is a process of using iron ore powder, flux, fuel, and return ore to make block shaped smelting raw materials in a certain proportion; Ironmaking: The main purpose of the ironmaking process is to economically and efficiently obtain liquid pig iron from iron ore that meets the temperature and composition requirements.
2.2 Introduction to the process of blast furnace blower
The blast furnace blower is the most important power equipment in the ironmaking process of the blast furnace. It not only directly provides the oxygen required for blast furnace smelting, but also provides the gas power required to overcome the resistance of the blast furnace material column. The blowers used in modern large and medium-sized blast furnaces mostly use centrifugal or axial flow blowers, and in recent years, there has also been a trend of gradually using large capacity synchronous electric driven blowers. Blast furnace smelting requires the blower to supply a certain amount of stable air to ensure that the blast furnace burns a certain amount of carbon; The required air volume is not only proportional to the furnace capacity, but also related to the degree of blast furnace strengthening. Generally, it is equipped with an air volume of 2.1-2.5m3/min per unit furnace capacity. However, in reality, many blast furnaces, considering the development of production, are equipped with fans with a capacity greater than this proportion. Therefore, inlet air doors and outlet air release valves are generally used for air volume and pressure control to prevent fan surge. The process flowchart is shown in Figure 1.
Figure 1 Process flow diagram of blower
Due to the loss of air dampers, the efficiency of blast furnace blowers is low, and electrical energy consumption is high. Therefore, there is huge energy-saving space for retrofitting with high-voltage frequency converters. However, as the most critical equipment in blast furnace production, the blast furnace blower not only has a large motor power capacity, but also needs to ensure continuous operation. If the blower malfunctions during the production process of the blast furnace, especially during the tapping of molten iron, it will cause slag filling accidents, leading to furnace blockage, shutdown, and an increase in coke ratio, causing huge economic losses. Therefore, there are very few cases of domestic metallurgical industry manufacturers modifying the blast furnace blower with high-voltage frequency conversion. The main reason is that users have doubts about the reliability of the current high-voltage frequency converter operation.
Shenzhen Weineng Technology Co., Ltd. has accumulated more than 20 years of experience in frequency converter design and production. Based on a thorough understanding of motor control theory, proficient mastery of power electronics and microelectronics technology, and integration of microprocessing technology, it has independently developed a super large capacity high-voltage frequency converter with independent intellectual property rights, breaking the design and production record of domestic high-voltage super large capacity high-voltage frequency conversion speed regulation systems. The R&D and technical personnel of Weineng Company, together with the production process and technical personnel of Party A, adhere to the principle of high responsibility, seek truth from facts, and cooperate sincerely. They have conducted multiple on-site investigations on the production line and obtained detailed data on the production process. Guided by the premise of ensuring user safety in production, a thoughtful and comprehensive fault handling backup plan has been developed that is recognized by both parties; The large-scale production and manufacturing, rigorous quality control system, and a large number of stable and reliable performance in the metallurgical industry of Weineng Company have gained the recognition and trust of Party A, further strengthening the determination of users to transform. The user has decided to carry out a high-voltage variable frequency speed regulation transformation on the blower of the 2 # ironmaking blast furnace in the factory, in order to reduce production costs and improve production processes.