RHF direct iron smelting can be divided into INMETCO method, DRYIRON method, FASTMET method and process due to the different raw material processing conditions and product quality requirements.In the last article we have introduced the FASTMET method, this article will introduce the ITKM3 method.

The FASTMET rotary hearth furnace process, developed by MIDREX and Kobe Steel, is mainly used for blast furnace dust and rolling sludge treatment. It is reported that dezinization rates can be greater than 95% and DRI with metallization rates of 70-90% can be obtained. The world's first FASTMET process, which uses iron containing waste as raw material, was put into production in The second quarter of 2000 at Nippon Steel Hiroda Plant in Japan, with an annual processing capacity of 190,000 tons.

RHF direct iron smelting can be divided into INMETCO method, DRYIRON method, FASTMET method and ITKM3 process due to the different raw material processing conditions and product quality requirements.In the last article we have introduced the INMETCO method, this article will introduce the DRYIRON method.

In the last article, we compared the advantages and disadvantages of several coal-based reduction processes, and concluded that the rotary hearth furnace process is more suitable. This article will introduce the development of rotary hearth furnace process and the INMETCO method in rotary hearth furnace process.

At present, there are mainly the following technical routes for direct reduced iron. Coal-based direct reduced iron and gas-based direct reduced iron,Among them, gas-based reduction technologies include: COREX, Midrex, FINEX, HIsmelt, etc.Among them, coal-based reduction technologies include: tunnel kiln, RHF, rotary kiln, etc. Gas-based reduction technology can achieve large-volume industrial production. The comprehensive economic indicators are good, but the investment is relatively large. Coal-based reduction technology generally has low output and relatively low investment.

Non-blast furnace iron making technology has grown significantly in recent years, driven by increasing environmental requirements, the need for high-quality steel materials, and especially the Chinese government's commitment to "carbon neutrality" to the world. Non-blast furnace iron-making technology is dominated by the gas-based shaft furnace process, because the gas-based shaft furnace can use hydrogen reduction technology, which greatly reduces carbon emissions, In addition to the gas - based shaft furnace process, rotary kiln, tunnel kiln, RHF and other technologies are also used.

To further enhance DRI for steelmaking, it can be converted to pig iron or hot metal via melting. There are existing processes in the industry that use electric energy in furnaces such as submerged arc furnaces to convert DRI into hot metal. Air Products’ novel DRI melting process uses oxy-fuel combustion in place of electric power to accomplish this melting. Figure 4 provides a process diagram (patent pending) .

Advantages of charging DRI hot coming out of the shaft reactor have been well documented, namely productivity increase and decrease in power use. Few DRI plants in the world have the ideal setup with an EAF downstream of the DRI plant, where the DRI coming out of the shaft furnace can be charged hot into the EAF.

Direct Reduced Iron (DRI) is the second most viable source of virgin iron used in steelmaking after pig iron or hot metal produced in blast furnaces. DRI is produced by direct reduction of iron ore using carbon monoxide and hydrogen. Natural gas-based shaft reactors are commonly used in North and South America for DRI production while coal-based DRI is common in Asian markets. Inexpensive supply of natural gas in the United States makes DRI an attractive source of iron for steelmakers.

Rotary hearth furnace technology (RHF) was developed and built in the United States in 1978 by the International Metal Company affiliated to INCO Group of Canada in order to treat and utilize metallurgical wastes. It can not only be used to treat dust produced by metallurgical plants and other wastes containing iron, chromium， and zinc, but also be used to reduce iron ore.