NATURAL GAS

The ZR Process is a major step in decreasing the size and improving the efficiency of direct reduction plants. Reducing gases are generated in-situ in the reduction shaft by feeding natural gas as make-up to the reducing gas circuit.

Since the reducing gases are generated in the reduction section, optimum reduction efficiency is attained, and thus an external reducing gas reformer is not required. Therefore, the overall energy efficiency of the ZR process is optimized by the in-situ reforming inside the shaft furnace, since the product takes most of the energy supplied to the process, with minimum energy losses to the environment. As compared to other processes for which the overall efficiency is below 80%, for this scheme the efficiency is around 86%.

The impact on plant size of eliminating the external gas reformer is significant. For example, a plant of 1-Mtpy capacity requires only 60% of the area needed by other process plants for the same capacity. For additional capacity, the area required is proportionally smaller in comparison. This also facilitates locating the DR plant adjacent to the meltshop in existing operations. This plant configuration has been operated successfully since 1998 with the HYL DR 4M plant, and also was incorporated in 2001 to the 3M5 plant, both at the Ternium steel minimill in Monterrey, Mexico. The new ZR ENERGIRON plants under construction in Egypt and in the USA will soon be a further reference for this innovative technology.

A remarkable advantage of this process scheme is the wider flexibility for DRI carburization, which allows attaining carbon levels up to 5%. This is due to the improved carburizing potential of the gases inside the shaft, which allow for the production primarily of iron carbide.