Abstract: The system comprises a boiler (1), main burner groups (2F, 2E, 2D, 2C) located on different levels or zones through which pulverized solid fuel is injected into the boiler (1) and main mills (3F, 3E, 3D, 3C) for solid fuel, where each of them is connected to one of the main burner groups (2F, 2E, 2D, 2C) to which a flow of solid fuel is directed. As a complement, it incorporates a substitution mill (3B) intended to operate only on the main burner group (2F, 2E, 2D, 2C) whose main associated mill (3F, 3E, 3D, 3C) has stopped, as well as a support mill (3A) which operates constantly and directs an additional flow of solid fuel towards the main burner group or groups (2F, 2E, 2D, 2C) selected, supplementing the flow of solid fuel provided by the main mills (3F, 3E, 3D, 3C).

Abstract: Particles are extracted automatically from a duct through which they are transported in a current of gas. The method of applicable for the determination of ash content and volatile content of solid fuels and for unburned materials in ash. The particles are deposited on a crucible (10) that is constantly inside a temperature controlled electric oven (9) The apparatus has a duct (16) that, penetrating the oven (9), terminates in the form of a dome at the height of the upper part of the crucible (10). The sample accesses the oven (9) by gravity through the duct (16) and is deposited in the crucible (10) where it is heated. This crucible (10) is supported on a rod (11) that penetrates the lower part of the oven and rests on an analytical balance (14). After heating, the sample is aspirated by the vertical duct (16) to enable the start of a new cycle.