Abstract: Iron ore pellets on a grid in a treatment chamber are hardened by contact with a heat treated, low calorific gas. The gas is generated in the gasification chamber of a slag bath generator. The generator receives a gasification agent and solid fuel that preferably further includes sulfur-binding materials, such as dolomite for generating a stream of low calorific gas. Inclined water-cooled pipes at the upper end of the slag bath generator extract liquid slag from the gas stream. The slag drips from the pipes into the slag bath generator. A mixing chamber receives the gas at a temperature of about 1450.degree. C passed beyond the inclined water-cooled pipes together with an air supply for heat treating the gas to a temperature of about 1100.degree. C. The heat treated gas is then passed into the treatment chamber for hardening the iron ore pellets contained therein.

Abstract: Fine-grain fuel is carbonized at a low temperature by feeding the fuel from a hopper downwardly into the gap formed between two vertically-arranged, plate-type conveyors. The plates of each conveyor move downwardly while their back face surfaces bear against the wall of a heating chamber. The position of the heating chambers is controlled to maintain a narrow gap, e.g., 10-30 millimeters between the plates of the conveyors. The conveyors and heating chambers are located within a container wherein a pressure of up to 100 bars is maintained and a clear gas is passed countercurrently to the downward advancement of the fuel in the gap between the conveyors. Breaker rollers below the conveyors subdivide the carbonized fuel issuing from the gap for passage into a gasification chamber. Part of the gas yield is used as fuel for the heating chambers.