China generates approximately 200 million tons of iron and steel waste annually, encompassing various forms such as trimming scrap, scrapped machinery, and household waste. The LF (Ladle Furnace) ladle refining furnace serves as a post - primary furnace (converter or electric furnace) molten steel refining device. Its operating principle involves using electrode arc heating to warm up the molten steel, taking over the reduction - period operations from the primary furnace. This process includes heating, deoxidizing, desulfurizing, degassing, alloying, and argon blowing and stirring, all aimed at enhancing the quality of the molten steel.
Given the substantial annual production of scrap steel resources in China, the LF furnace can be equipped with a scrap preheating system. This system utilizes gas produced by blast furnaces or converters to preheat scrap steel to a temperature range of 450 - 600℃. The preheated scrap is then continuously fed into the LF furnace, where it is added to the 1500℃ molten steel. Combined with the LF's inherent electric arc heating function, the scrap melts rapidly and undergoes refining treatment within the LF furnace, resulting in qualified molten steel that meets process requirements.
During each refining cycle, each LF refining furnace can incorporate 10% - 20% of scrap steel. This addition enables a daily increase in molten steel output by 10% - 20%. The key characteristic of this process lies in the recycling and reuse of iron and steel elements present in the waste. From the perspective of sustainable development, this scrap steel smelting process represents a recycling economic model that relies on waste recycling.
By leveraging the LF furnace's own molten steel temperature and arc heating function, along with using blast furnace or converter gas as the baking heat source, significant resource waste reduction can be achieved. This approach substantially lowers the production cost per ton of steel, thereby saving production costs for enterprises and enhancing their economic efficiency.
The scrap steel preheating and feeding system is a mechatronic, multi - station special equipment designed for baking and heating crushed steel scrap materials. The size of the scrap steel materials is controlled within the range of 50 - 100mm. These materials are baked and heated to the required process temperature inside the furnace, typically maintained between 450℃ and 600℃ to meet steelmaking production requirements.
The system features a steel - structured furnace body lined with refractory materials. Each system can be configured with 1 to 4 stations, and the furnace body is mounted on a steel structure frame. A single preheating furnace body has the capacity to preheat 5 to 10 tons of scrap steel per hour.
In the raw material storage yard, the scrap steel is loaded into a bottom - opening tank. A crane in the workshop is then used to lift the tank and add the cold material into the scrap preheating furnace. The upper part of the preheating furnace body serves as the feeding bin, equipped with a pneumatic gate valve at the feed port. The middle and lower sections constitute the scrap steel baking chamber. At the bottom, a vibrating continuous feeding device is employed to continuously transport the baked high - temperature scrap to a chute below the vibrating feeder, which then adds it to the LF furnace.
A weighing device is installed on the preheating furnace body, enabling precise control over the feeding amount. The vibrating feeder adopts frequency conversion control, allowing for adjustable feeding speeds to suit different production needs. This well - designed scrap steel preheating and feeding system ensures efficient and controlled integration of scrap steel into the LF refining process, contributing to the overall optimization of steel production.
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