A combustion facility including: - a combustion chamber, adapted so that solid fuels are introduced thereinto and burn thereinto according to a primary combustion in the presence of primary air, - an intake device, adapted to supply the combustion chamber with primary air, and - a grid, which downwardly delimits the combustion chamber and which is adapted to support a bed which is formed by the solid fuels and which is movable along a direction of advance into the combustion chamber, the intake device opening under this grid so that primary air provided by the intake device enters the combustion chamber by passing through the grid, the intake device including a single box which: - has an air inlet distributed into several subdivisions (132.1-132.3) which are provided so that primary air flows thereinto as distinct primary air streams (V1-V3), each subdivision being provided with a flowrate adjustment member (134.1-134.3) adapted to control flowrate of the primary air stream flowing in this subdivision, and - comprises a casing the inner volume of which forms, under the grid, a single distribution volume of the primary air, into which the subdivisions (132.1-132.3) open, the inner volume of the casing being provided with inner aeraulic arrangements (137.1, 137.2) designed to act on the flow of the air streams (V1-V3), once they have exited the subdivisions, so as to direct these primary air streams towards respective regions (114.1-114.3) of the grid, which succeed along the direction of advance. - a combustion chamber, adapted so that solid fuels are introduced thereinto and burn thereinto according to a primary combustion in the presence of primary air, - an intake device, adapted to supply the combustion chamber with primary air, and - a grid, which downwardly delimits the combustion chamber and which is adapted to support a bed which is formed by the solid fuels and which is movable along a direction of advance into the combustion chamber, the intake device opening under this grid so that primary air provided by the intake device enters the combustion chamber by passing through the grid, the intake device including a single box which: - has an air inlet distributed into several subdivisions (132.1-132.3) which are provided so that primary air flows thereinto as distinct primary air streams (V1-V3), each subdivision being provided with a flowrate adjustment member (134.1-134.3) adapted to control flowrate of the primary air stream flowing in this subdivision, and - comprises a casing the inner volume of which forms, under the grid, a single distribution volume of the primary air, into which the subdivisions (132.1-132.3) open, the inner volume of the casing being provided with inner aeraulic arrangements (137.1, 137.2) designed to act on the flow of the air streams (V1-V3), once they have exited the subdivisions, so as to direct these primary air streams towards respective regions (114.1-114.3) of the grid, which succeed along the direction of advance. - has an air inlet distributed into several subdivisions (132.1-132.3) which are provided so that primary air flows thereinto as distinct primary air streams (V1-V3), each subdivision being provided with a flowrate adjustment member (134.1-134.3) adapted to control flowrate of the primary air stream flowing in this subdivision, and - comprises a casing the inner volume of which forms, under the grid, a single distribution volume of the primary air, into which the subdivisions (132.1-132.3) open, the inner volume of the casing being provided with inner aeraulic arrangements (137.1, 137.2) designed to act on the flow of the air streams (V1-V3), once they have exited the subdivisions, so as to direct these primary air streams towards respective regions (114.1-114.3) of the grid, which succeed along the direction of advance.