Method and furnace for incinerating organic matter derived from the treatment of industrial or agricultural waste or wastewater, such as sludge

A method for incinerating organic matter trapped in a mineral and/or liquid matrix issued from the treatment of waste water, industrial or agricultural waste, in a fluidised bed incineration furnace configured to treat a volume of the organic matter equal to a nominal value, the furnace including an enclosure in a lower part thereof, the enclosure including a particle bed constituting a fluidisation zone, the method comprising:

• introducing the organic matter as fuel into the fluidisation zone while injecting air as an oxidant into the particle bed from a wind box through a fluidisation dome on top of the wind box, the air passing through passages provided in the fluidisation dome;
• adjusting a volume of the fluidisation zone and a flow rate of the air coming into the fluidisation zone as a function of a volume of the organic matter to be treated, in which, when the volume of the organic matter to be treated is lower than the nominal value, reducing the volume of the fluidisation zone from an initial volume to a reduced volume, and reducing the flow rate of the air by sealing a portion of the passages so as to leave active only the passages opening into the thus reduced volume fluidisation zone;
• and
• reducing the volume of the enclosure of the furnace above the fluidisation zone by installing an insert extending over an entire height of the furnace.

A furnace for incinerating organic matter from treatment of waste water, industrial or agricultural waste, the furnace being configured to treat a volume of the organic matter equal to a nominal value and comprising an enclosure in a lower part thereof in which there is a fluidised particle bed, the furnace further comprising, at least from bottom to top:

• a wind box having an upper part which supports a fluidisation dome having passages through which air coming from the wind box is distributed into a fluidisation zone corresponding to the fluidised particle bed;
• at least one organic matter feed and at least a supplemental fuel injector configured to feed supplemental fuel to the fluidisation zone;
• an expansion and post-combustion zone above the fluidisation zone;
• an upper vault on top of the expansion and post-combustion zone, the upper vault including a discharge pipe for combustion products;
• and
• when a volume of the organic matter to be treated is lower than the nominal value, an insert in the form of a sleeve having a shape complementary to a portion of the enclosure delimiting the fluidisation zone and extending from the fluidisation dome against the portion of the enclosure delimiting the fluidisation zone such that a volume of the fluidisation zone is reduced from an initial volume to a reduced volume and a portion of the passages in the fluidisation dome are sealed leaving active only the passages opening into the reduced volume fluidisation zone and a flow rate of the air through the passages is reduced.