Abstract: A device for the combustion of fluid materials, especially particulate (i powdered or granular) solid fuels, suspended in a fluid medium, for example coal suspended in water, with a nozzle and a combustion chamber. The nozzle is located in a precombustion chamber opening into the combustion chamber, and the device directs a minor part of the combustion air to the region of the orifice of the nozzle in the precombustion chamber, and a major part of the combustion air to the region of the mouth of the precombustion chamber where it opens into the combustion chamber.