Abstract: A description is given of a method of optimizing the design and operation of a reduction process for iron-containing charge materials (3), preferably in lump form, in a reduction shaft (1) to which reduction gas (9) is fed, for example from a fusion gasifier (6), with a reduced product (13), for example iron sponge, being taken from the reduction shaft (1) for the production of liquid pig iron or liquid primary steel products, in which method the reduction process is described by means of a mathematical-physical-chemical process model, the reduction shaft (1) is modelled multi-dimensionally, in particular three-dimensionally, and the process model is numerically evaluated and the results of the evaluation, obtained as multi-dimensional, in particular spatial, distributions of physical or chemical variables, are taken into account for the reduction process. This allows the reduction process to be quantitatively assessed in the entire reduction shaft and, as a result, the reduction process can be optimized.