New Tunnel Kiln
Heyuan Xinlong Industrial Group Co., Ltd. collaborated with the School of Ecological Engineering at University of Science and Technology Beijing and the Steel Metallurgy Research Institute at Northeastern University at the end of 2008 to conduct research and development on stainless steel oxide scale. This project involved component analysis, chemical testing, and a systematic exploration of the processes for extracting metals such as Cr, Ni, Mn, and Cu. Following small-scale industrial trials and continuous refinement of the process, the project successfully implemented a technological approach combining tunnel kilns with a two-step reduction process using slag washing furnaces.
Main Process Flow:
Stainless steel oxide scale is piled in the raw material yard, where it undergoes screening, mixing, and briquetting before being loaded into a roasting tank.
Inside the tunnel kiln, the roasting tank is subjected to preheating, roasting, and thermal insulation cooling to achieve an initial reduction and produce semi-finished products. During this process, Fe, Cr, and some Mn and Ni in the stainless steel oxide scale are partially reduced to metal form, but the semi-finished products still contain significant impurities.
The semi-finished products are then crushed and magnetically separated before entering the slag washing furnace. The slag in the slag washing furnace is meticulously designed to minimize the oxidation of the metals in the semi-finished products (patent application is in preparation).
As the semi-finished products are subjected to high-temperature molten slag in the slag washing furnace, the impurities are adsorbed by the slag, allowing for further purification of the metals. This results in the separation of slag and iron, enabling the full recovery of metal elements such as Cr, Fe, Ni, and Mn from the stainless steel oxide scale.
Finally, the high-quality ferrochrome alloy is obtained through induction furnace heating and refining in an AOD furnace, achieving the recycling of stainless steel oxide scale.
Advantages over Electric Furnace and Blast Furnace Processes:
Effective recovery of iron and valuable metals such as chromium and nickel from stainless steel oxide scale.
Higher quality ferrochrome alloy can be achieved through subsequent processing in induction furnaces and AOD furnaces.
Strong adaptability to raw materials, large processing capacity, ease of controlling composition, simple and reliable operation, and low costs.
Minimal generation of waste gas and wastewater during production, providing excellent environmental benefits.
Innovative Design of Environmentally Friendly Tunnel Kiln:The newly developed practical and safe tunnel kiln features:
A kiln body consisting of preheating, reduction, and cooling sections.
The reduction section of the kiln is connected to the preheating section via a preheating pipe, with the preheating section linked to an absorption pool containing alkaline liquid through a smoke exhaust pipe.
The preheating pipe extends into the alkaline liquid, and the absorption pool is equipped with an exhaust pipe.
Both the preheating and smoke exhaust pipes are fitted with filters, one-way valves, and fans, all connected to a central control system.
This innovative construction of the tunnel kiln enhances environmental protection, ensures employee safety, and maintains normal production.
