JFE Steel and Shinagawa Refractories improve the rate of recycled raw materials to 20%

2023-10-25

Oct. 24, 2023 - JFE Steel and major refractory manufacturer Shinagawa Refractories have been working together to expand the recycling of refractories used for steelmaking. The used refractories collected from JFE Steel’s steel plants are sent to Shinagawa Refractories, and after the used refractories undergo processing, they are reused as raw materials for refractories. The ratio of recycled raw materials utilized for manufacturing refractories used to be around 10%, but currently the companies have succeeded in raising the ratio to about 20%. Expanding recycling will lead to such benefits as curbing the amount of carbon dioxide (CO2) emitted when manufacturing refractories, and so this endeavor will likely gather interest since it can simultaneously contribute to resource circulation and function as a measure against climate change.

Facilities for upstream processes, including converters, ladles and secondary refining furnaces, undergo repairs after they are used for a certain number of times. During repairs, the refractories applied to the inner walls of furnaces are removed by heavy machinery and other devices. In order to reuse these refractories, the iron and slag impregnated in the refractories need to be removed. This is because if the used refractories impregnated with iron and others are re-utilized as is, there is a risk that it will lead to reducing the performance of the refractories.

In the past the sorting of used refractories was conducted by hand, but recently it has become common practice to utilize an automatic sorting device.

During automatic sorting, the device sorts the used refractories based on such differences as (1) Color. (2) Density. (3) Magnetic properties. JFE and Shinagawa adopted to utilize a sorting technology based on color that sorts refractories according to the changes in color tones of refractories caused by the impregnation of iron and others. The companies have acquired the know-how for ensuring that they can sort the refractories into those that can be reused and those that are difficult to do so. This technology has enabled the companies to raise the utilization ratio of used refractories.

When pursuing maximizing the utilization of used refractories, quality control becomes important as well. Shinagawa has been pursuing measures to ensure that the increase in the utilization ratio of recycled raw materials does not affect the performance of refractories by strongly pursuing conducting pre-treatment of the refractories at their plants to minimize the expansion of refractories, since this is one of the factors that lead to deteriorating refractories.

As of now it is difficult to recycle all used refractories removed from various facilities including converters. This is because there are no technologies that can completely remove the metal and slag impregnated in refractories. However, it may be possible to raise the utilization ratio of recycled refractories depending on how the used refractories are sorted. Going forward JFE and Shinagawa will pursue making the sorting technologies more sophisticated, including through the use of AI (artificial intelligence) technologies.