Learn scrap steel preheating system's process flow and advantages

Overview of scrap preheating system

Continuous preheating of scrap steel is an effective method to increase the scrap ratio of the converter. According to the material balance and heat balance calculation of the converter, it can be concluded that the scrap steel is preheated to 800 ℃, and the scrap ratio of the converter can be increased to 30-40%. In order to increase the amount of scrap steel used in converters and increase the output of converter steelmaking, domestic iron and steel enterprises try to use residual temperature preheating, bun baking, scrap steel buckets, rotary kiln + briquetting, tunnel kilns, other kilns (shaft furnaces, etc.), Oxygen burner and other measures.

The tunnel kiln preheating technology is improved on the basis of the scrap preheating of the Constel electric furnace (the main purpose of the preheating of the Constel furnace is to use the hot waste gas of the electric furnace to save energy. Therefore, there is no requirement for the preheating temperature and output). One is to break through the limit of heating scrap temperature, with an average temperature of 800 °C. The second is to break through the limitation of production capacity, and the amount of scrap added reaches about 40%. The amount of scrap steel can be matched according to the production rhythm of the converter. During the conveying process, the converter gas is burned to directly heat the material, thereby improving the utilization rate of thermal energy and heating efficiency. Applied on the converter, and actively control the capacity and temperature.

Process flow and principle of continuous charging system

Process flow:

Scrap crane lifting → chain plate machine → vibrating conveyor → preheating zone → auxiliary burner preheating zone → main burner preheating zone → scrap bucket → battery car → feeding span → converter.

The scrap steel continuous preheating system is equipped with a heating device at the conveyor. The heating source is converter gas, and the burner is directly installed in the high-temperature heating area without a combustion furnace, which simplifies equipment, reduces land occupation and reduces investment.

The heating section is equipped with an arch-shaped insulation cover, and the burner is arranged on the opposite side, and the combustion flame avoids the scrap steel and reduces the oxidation loss. The scrap is heated uniformly along the high temperature airflow.

The heating system is divided into a heating zone and a preheating zone. The heating zone is mainly radiant heating, and the preheating zone preheats the scrap steel through the high temperature flue gas generated by the heating zone.

The setting temperature of the continuous preheating system for scrap steel can be designed with different preheating temperatures and different operating parameters according to the surplus of coke oven gas in the steel plant. The design of this system is more cost-effective: the maximum tapping temperature can reach 800 ℃. In order to reduce the oxidation of scrap steel, our factory controls the preheating temperature of scrap steel at 700-800 ℃. The preheating temperature of the high temperature section is 1100℃, the temperature of the scrap steel is rapidly increased, and the temperature of the scrap steel can be increased by 650℃ within 20min.

Through real-time monitoring of the temperature of the high temperature heating area, the flue gas preheating area, and the flue gas discharge port, the temperature of the outlet material is controlled and the gas output is adjusted. Improve energy consumption utilization to 80%.

The trough part of the heating conveyor is dynamically controlled, and a water cooling system is installed to reduce the stress and deformation of the trough through the cooling effect.

Maximum furnace temperature: 1100°C (burner), 800°C (preheating section).

The whole set of equipment consists of three major parts: heat preservation furnace cover, mobile conveying system and control system. The furnace body consists of a feeding section, a pre-sintering section, a sintering section, a slow cooling section, a water cooling section and a discharging section.

The thermal insulation fume hood of the waste steel preheating system is welded by section steel and steel plate, and the furnace shell is built with heavy castables and aluminum silicate refractory fibers.

Technical advantages of horizontal charging system

1. The scrap steel preheating system is kept warm, and the furnace top heat preservation can be easily matched with a suitable heat preservation thickness to keep the heat dissipation of the furnace wall and the furnace top the same, and the outer surface temperature to be consistent.

2. The thermal insulation fume hood of the scrap steel preheating system adopts full fiber lining, which reduces the heat storage and thermal inertia of the furnace wall, shortens the heating time, improves the control accuracy, reduces the temperature rise of the surface of the furnace shell, reduces heat loss, improves thermal efficiency, and achieves the purpose of high efficiency and energy saving.

3. The heat preservation furnace of the scrap steel preheating system adopts fiber structure, good masonry of refractory fiber, good thermal insulation, and try to reduce the temperature of the top steel structure to reduce deformation.