TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The zirconium-based catalyst contains zirconium compound, such as zirconium oxide (ZrO2), which is alloyed with another metal oxide such as aluminum oxide (Al2O3). The zirconium compound is on the surface of an inert carrier or impregnated into the carrier. Preferred Method: The zirconium-based catalyst and metal catalyst are arranged in successive layers or zones in the flow direction of the gas that is to be reformed. They are placed in separate reactors in the flow direction of the gas. Before the catalytic reformation, oxygen, air, or a mixture of oxygen and air is added to the gas flow, which is to be reformed. Oxygen or oxygenous gas, such as air (13) is added to the gas flow after the pre-reformation that takes place on the zirconium-based catalyst before the reformation on the metal catalyst. Preferred Parameter: The reforming temperature is 500-900degreesC. The pre-reformation on zirconium-based catalyst takes place at a lower temperature, such as within 600-800degreesC; and the reformation on the metal catalyst takes place at a higher temperature, such as within 700-900degreesC.    TECHNOLOGY FOCUS - METALLURGY - Preferred Component: The metal catalyst contains metallic nickel or precious metal. EXAMPLE - The product gas of the fixed-bed gasifier (1) was used as feed. The fuel of the gasifier comprised crushed demolition wood (2). The volume flow rate of the gas was 1.5 m3/hour. It was led into a phased reformer comprising first layer including zirconium oxide catalyst and second layer comprising a precious metal catalyst. The catalysts were ceramic honeycombs, to which a coating containing zirconium oxide and a precious metal had been added. The temperature of the gas before the reformer was 600degreesC and air in 5-20% was mixed with it. The composition of the gas in the feed was (vol.%): hydrogen (H2) (6-8), carbon monoxide (CO) (10-12), carbon dioxide (CO2) (9-11), methane (CH4) (1.5-2), C2H4 (1.5-2), water (H2O) (18-28), and nitrogen (N2) (the rest). The tar content of the gas in the feed was 6 g/m3n, and in the output, 0.3-1.3 g/m3n, thus, the tar conversion was 70-90%. The operating temperature of the zirconium zone was 600-700degreesC and that of the precious metal catalyst zone 700-800degreesC. During the test, no increase in the pressure loss indicating an accumulation of carbon in the reformer was observed. The examination of the catalysts after the test also indicated that no carbon had accumulated on the catalysts.