Abstract: Fine-grained fuels are gasified in a fluidized state with a mixture of gasifying agents which comprise oxygen, water vapor and/or carbon dioxide. NH.sub.3 is substantially entirely removed from the product gas from the gasifier. All or part of the NH.sub.3 is combusted and any remaining NH.sub.3 is added to the exhaust gas from the combustor. In a preferred embodiment the content of nitrogen oxides and/or NH.sub.3 in the exhaust gas from the combustor and NH.sub.3 is supplied to the combustor at such a controlled rate that the contents of nitrogen oxides and NH.sub.3 in the exhaust gas to which NH.sub.3 has been admixed are minimized.

Abstract: Fuels are gasified in a fluidized state by a treatment with oxygen-containing gas and water vapor in a gasifying reactor. A solids mixture which contains ash and fine-grained fuels is combusted in a heating-up phase, which precedes the gasification and in which the temperature in the reactor is increased approximately to the temperature desired for the gasification. In a succeeding inertizing phase the supply rate of oxygen-containing gas is decreased and an inert gas is fed to the reactor until the product gas no longer contains free oxygen whereas the temperature is maintained virtually constant. In the succeeding gasification the fuel supply rate is increased and, after an adjusting time, the temperature is maintained virtually constant at the value desired for the gasification in the range from 600.degree. to 1500.degree. C. The gasification temperature is controlled by a change of the fuel supply rate.

Abstract: The lock container is connected to a reactor, which serves to gasify or to combust solid fuels. The lock container serves to remove ash from the reactor. A pressure of at least 2 bars prevails in the reactor. The lock container is pressurized and pressure-relieved in alternation. The pressure relief line communicates with a filter element, which is permeable to gas and substantially impermeable to solids and is disposed within the lock container. When the lock container is filled to the usual level during a pressure relief, at least one half of the filter element is surrounded by ash. The filter element may be tubular.