Calcination unit for decarbonating raw materials
A calcination unit able to decarbonate raw materials intended for clinker production, the unit including: a main duct in which the raw materials circulate according to a first movement direction, the raw materials being calcined in the main duct; a solid fuel supply duct opening onto the main duct via a fuel outlet, the solid fuel moving according to a second movement direction; a retaining device located in the main duct and arranged opposite the solid fuel outlet so that the solid fuel arriving in the main duct via the fuel outlet passes through the retaining device.
1 . A calcination unit able to decarbonate raw materials intended for clinker production, the unit comprising:
a main duct in which the raw materials circulate according to a first movement direction, the raw materials being calcined in the main duct, the main duct including a recess,
a solid fuel supply duct opening onto the main duct via a fuel outlet, the fuel outlet opening into the recess, the solid fuel moving according to a second movement direction,
a retaining device located in the recess of the main duct and arranged opposite the solid fuel outlet so that said solid fuel arriving in the main duct via the fuel outlet is sent towards said retaining device,
wherein the retaining device includes retaining elements and passages separating two adjacent retaining elements.
2 . The unit according to claim 1 , wherein the main duct includes a lateral wall, said lateral wall defining an inlet portion having an inlet section, and an enlarged portion having an enlarged section larger than the inlet section and an outlet portion having an outlet section smaller than the enlarged section, the recess being located in the enlarged portion between two points extending according to the first movement direction of the raw materials.
3 . The unit according to claim 2 , further comprising a hot air supply duct opening into the recess via a hot air outlet, said hot air outlet being arranged opposite the retaining device so that the hot air passes through the retaining device.
4 . The unit according to claim 2 , further comprising a lower wall located in the recess and arranged opposite and upstream of the retaining device according to the movement direction of the raw materials, the calcination unit including at least one cleaning channel opening onto the lower wall via at least one air injection outlet, said air injection outlet allowing evacuating solid fuels stuck on said lower wall.
5 . The unit according to claim 2 , wherein the main duct includes a narrowed portion having a narrowed section smaller than the inlet section, the narrowed portion being located upstream of the enlarged portion and downstream of the inlet portion, according to the first movement direction of the raw materials.
6 . The unit according to claim 1 , wherein the fuel retaining device is able to retain solid fuel one of the dimensions of which is at least equal to a determined value.
7 . The unit according to claim 1 , wherein two adjacent retaining elements are spaced apart by a distance comprised between 30 and 70 millimetres.
8 . The unit according to claim 7 , wherein the retaining elements are arranged so as to define an angle of inclination comprised between 5° and 30°, said angle of inclination being measured between a transverse axis substantially perpendicular to the movement direction of the raw materials, and an axis of extension passing through all of the retaining elements.
9 . The unit according to claim 8 , wherein the angle of inclination is measured clockwise so that the retaining elements are oriented so that the solid fuels are projected towards the recess.
10 . The unit according to claim 1 , wherein the retaining device is able to block solid fuels at least one of the dimensions of which is larger than 50 millimetres.
11 . A clinker production plant comprising:
a preheating unit, in which raw material is preheated,
a calcination unit according to claim 1 , in which the preheated raw material is at least partially decarbonated,
a furnace in which the preheated and at least partially decarbonated raw material is fired,
a cooler in which the fired material from the furnace is cooled by cooling air.
12 . A method for producing clinker by means of a plant according to claim 11 , wherein the latter includes the following operations:
injecting an alternative solid fuel into the calcination unit via the solid fuel supply conduit, said alternative fuel comprising particles with a dimension larger than 50 millimetres, hereinafter referred to as large-size particles,
retaining large-size particles by means of the retaining device,
consuming the large-size particles on the retaining device until their dimensions become smaller than 50 millimetres, said particles then passing through the passages between the retaining elements.
13 . The method for producing clinker according to claim 12 , further comprising injecting hot air into the recess via the hot air supply duct.
14 . The clinker production method according to claim 13 , wherein the hot air is derived from cooling of the clinker in the cooler.
15 . The method for producing clinker according to claim 12 , further comprising injecting compressed air via the cleaning channels to evacuate the solid fuel stuck on the lower wall of the recess.