Today’s article is a special article on energy saving and consumption reduction in converter steelmaking at the request of our back-end fans. For reference.
The iron and steel industry is a high energy consumption industry, which consumes about 10% of the national energy consumption. In the process of steel production, the converter steelmaking process accounts for a very high proportion of energy loss, and it is also the link that generates the most secondary energy. Therefore, reducing the energy loss of the converter steelmaking process is the fundamental promotion of the steel industry. The foundation of sustainable development.
Many scholars and practitioners have proposed energy-saving and consumption-reducing measures in the converter steelmaking process, including the renewal of energy-saving equipment, the optimization of smelting technology, the improvement of product process structure, energy conversion, recycling, and so on.
Before talking about this, let us first understand the process of converter steelmaking. Converter steelmaking uses molten iron, scrap, and ferroalloy as the main raw materials. It does not rely on external energy sources, but is produced by the physical heat of the molten iron itself and the chemical reaction between the components of the molten iron. The heat is used to complete the steelmaking process in the converter, which is mainly used to produce carbon steel, alloy steel, copper and nickel smelting.
The picture below shows the evolution of the converter steelmaking method.
The energy consumption in the steelmaking production process is mainly divided into direct energy consumption, indirect energy consumption and energy recovery. Direct energy consumption is the energy consumption in the converter steelmaking process, and the consumption of auxiliary equipment in the converter steelmaking process becomes indirect Consumption, operation process, equipment and technology also affect energy consumption. The main purpose of energy consumption calculation analysis and calculation is to strengthen the control and planning of energy, reduce energy consumption, improve production efficiency, and determine that the converter steelmaking process can achieve The consumption level of this product provides a basis for energy management and energy saving, and makes full use of energy while improving processes and reducing raw materials.
The energy media consumed in the converter steelmaking process mainly includes oxygen, coal gas, nitrogen, argon, coke, electricity, water, steam, etc. Electricity, water and gas are the main energy consumption, especially in the cooling process, the energy consumption is very large, and a lot of production Steam carries a lot of energy. Improper control and management are prone to escape, resulting in waste of water and steam resources. The annual energy consumption of China’s iron and steel industry accounts for 10% of the country’s total energy consumption, while electricity consumption accounts for 11% of industrial electricity consumption; new water consumption accounts for 9% of total industrial water consumption.
For the entire energy consumption structure of the steel industry, coal is the first consumable, followed by electricity.
In the converter steelmaking production process, the energy actually consumed by electric energy and various gas forms negative energy steelmaking. Negative energy steelmaking is the largest energy consumption affecting the entire process. Strengthen the research on the recovery of converter gas and analyze the impact of converter productivity. The impact of energy consumption.
The realization of negative energy steelmaking in the converter is an important indicator to measure the production technology level of modern steel mills. Through the calculation of the heat balance of the converter steelmaking, the energy consumption and recycling situation in the converter process are analyzed; there are many energy consumption factors that affect the converter process. The converter process can greatly reduce energy consumption, reduce oxygen and electricity consumption, and improve the steam recovery efficiency of the converter, especially the recovery amount of converter gas.
Oxygen and power consumption account for the largest proportion of energy consumption in the converter steelmaking process. By adopting relevant technical measures to control oxygen and power consumption, the converter steelmaking energy consumption can be effectively reduced. The main methods are: use sub-lance to dynamically control steel tapping, improve the end-point hit rate, and strictly control the tapping temperature; increase the composition and temperature compliance rate of molten steel to the refining furnace, optimize the operating process system, carry out standardized operations, and control the refining power consumption; Advanced steelmaking process equipment to achieve high quality, high yield, low cost and low energy consumption; improve production management level, improve production personnel’s technical operation level; implement full-process insulation measures, control temperature drop, and achieve stable process operation to achieve a low-temperature system throughout the process run.
Main measures to achieve energy saving and emission reduction
(1) The converter gas recovery is completed by the cooperation between the intersections and converter blowing controlled by PLC. The computer improves the gas recovery program, controls the lifting time, determines the best recovery time, and improves the recovery volume and heating value of steelmaking gas. . Positive pressure control is adopted for the furnace mouth, the pressure is controlled at about 5pa during production, and segmented control is adopted to ensure the smooth progress of gas recovery. In addition, it is necessary to control the timing of lifting, distribute the pressure of the system point, and shorten the recovery time.
(2) The oxygen consumption of the converter steelmaking process is about 19% of the total consumption. The oxygen consumption can be reduced by lowering the tapping temperature, controlling the quantity of high-temperature steel, increasing the carbon pulling rate, and prohibiting the use of oxygen blowing hoods. This measure reduces the oxygen consumption of the converter gradually, reducing the energy consumption of the converter steelmaking process. Converter gas is the main energy source in the steelmaking process. Due to the imperfect technical equipment level of converter gas, the recovery volume fluctuates greatly. During converter operation, most operators control according to experience and do not implement falling hood recovery, resulting in a large amount of air in the pipeline. , The reduction of CO content can ensure the reduction of the gas recovery. The recovered gas is provided to the steel-making electric furnace, and part of the gas is released, resulting in a waste of resources.
(3) Improve the recovery of converter steam and reduce power consumption. When recovering coal gas, the coal gas can generate more steam, and the converter steam recovery fluctuates greatly. Using converter steam in the lime rotary kiln can reduce the influence of restrictive factors on the converter residual energy recovery.
(4) The waste heat boiler can recover the steam after the converter flue gas is cooled to realize the repeated use of the high-temperature sensible heat in the converter flue gas. Based on the high and low pressure organic fusion of the evaporator, the steam is recovered.
(5) The frequency conversion transformation of the dust removal system, using frequency conversion dust removal, can reduce the probability of failure, increase the stability of the equipment, and reduce the energy loss caused by the circulation between equipment.
(6) Pay attention to the selection and application of slagging methods. Less slag smelting is to complete the converter smelting work by reducing the amount of slag. Based on the characteristics that the low temperature in the early stage of converter smelting is conducive to the dephosphorization reaction, the dephosphorization slag is poured out, and an appropriate amount of slag is added to carry out the blowing and decarbonization work. The slag is convenient for the dephosphorization of the next furnace, and the slag can be reused, which can reduce the amount and consumption of raw materials such as dolomite and lime. Since the final process has a small amount of slag and no slag dumping, it can improve the yield of molten steel and oxygen. Utilization rate. To carry out this method of smelting with less slag, it is particularly important to prepare dephosphorization slag in the early stage. This is mainly determined by the fluidity of the slag. If the alkalinity is high, the fluidity of the slag will become worse. If the alkalinity is low, the phosphorus will be difficult to remove. Therefore, the fluidity of the slag can be better only when the alkalinity is appropriate. Refer to the ternary phase diagram, the content of the slag is generally controlled within the range of 11%-16%, in order to make the slag become a homogeneous liquid phase. State, the alkalinity is strictly required to be controlled at about 1.6. In this case, the melting performance of the slag can be improved.
(7) Control the splash phenomenon. There are three types of splashes: metal splashes, explosive splashes and foam splashes. No matter which method of spraying, it will bring losses to the metal. The factor leading to the spraying is the unscientific control of the position of the oxygen lance. Reducing metal loss is the primary goal of converter production, which is equivalent to increasing the amount of steel. Output and splashing will not only cause accidents such as burning gun sticking to the gun, but also impact on the furnace lining and hinder the removal of phosphorus. Therefore, it is very important to scientifically control the gun position to reduce splashing. In the initial stage, avoid slag re-drying In the case of circumstance, the slag foaming should be avoided in the middle stage, and the temperature in the furnace should be controlled scientifically.
(8) Reduce the number of tapping downs and waiting time. In the process of converter steelmaking, once the operation is wrong, the position of the oxygen lance will be too high during the blowing process, causing the slag to foam, so that the furnace needs to be poured before the tapping, resulting in no tapping. In the process of dumping the furnace and slag, the temperature of the converter steelmaking will drop accordingly, breaking the original plan. Extend the tapping time, so that the procedures that should be performed after tapping cannot be carried out in time, causing economic losses. Therefore, when the slag foaming is serious, slag pressing materials should be used to treat the slag in time to avoid adverse effects such as temperature reduction. In the process of converter tapping, the waiting time is the primary reason for the temperature drop, and the reasons for the long waiting time include: equal sample composition and equal rhythm. Waiting for the sample composition means that the waiting time for the sample is too long, so the best time to send the sample is delayed, and there will be some deviations in the sample inspection process, resulting in the need to produce special steel grades, unable to achieve timely tapping.
In addition, in terms of resources, catalysts can also be added to the converter to promote combustion, so as to maximize the rate of energy obtained from burning; strengthen the secondary utilization of scrap steel; in terms of operation, pay attention to the loading of each furnace in the converter smelting Too much loading will cause poor mixing of the molten pool, failure to normalize the slag, and eventually residual steel. If the loading is too small, the output will decrease or the furnace bottom will be damaged.