A brief introduction
Aluminium hydroxide roasting is the last working procedure of alumina production process, the roasting process is to dry the crystalline water in the aluminium hydroxide cake，and the partial gamma -Al2O3 is converted into alpha -Al2O3 to meet the requirements of metallurgical grade finished products.
Main furnace type: 300t/d~3800t/d
Main material: aluminium hydroxide
Major fuels: gas, natural gas, gas, heavy oil, light oil, etc.
Main products: alumina
Purpose of the GSAC is to transform Hydrated alumina to calcined alumina. The quality of alumina produced in the calciner should be metallurgical grade (sandy alumina).
Hydrated alumina is introduced at the inlet gas duct to the first preheater cyclone. It is subsequently preheated by hot, countercurrent gas flow as it is continuously collected and passed down to the other cyclone stages in the preheater before entering the main calcination vessel. The GSAC is a vertical design in which fuel combustion is in intimate contact with alumina. Preheated combustion air is introduced into the bottom of the furnace (main calcination vessel) where it is mixed with fuel and preheated feed material. The turbulent swirling mixture of combustion gases, fuel and material produces a highly uniform temperature profile throughout the furnace. A cyclone at the outlet of the furnace separates the gas and alumina. The calcining temperature can be closely controlled for even burning, uniform product quality and emission control. Flue gasses will be treated in a bag-filter in order to ensure low dust concentration before released to environment. Calcined alumina will be extracted from GSAC after cooling down in fluidized bed coolers.
· Calciner feed system,
· Drying and precalcination,
· Calcination furnace,
· Main and preheating burners system,
· Multistage primary coolers,
· Fluidized bed secondary coolers,
· Bag-filter for dust removal and recovery system,
Wet filter cake of aluminum hydroxide will be fed to the hydrate bin of the GSAC by a belt conveyor from filtration building.
Cold water will be used for the final cooling of alumina in two fluidized bed coolers. Cold water in a closed circuit system will be circulated inside the tube bundles of the coolers. Closed circuit water shall in turn be cooled via a heat exchanger by cooling water recirculating in a cooling tower.
The flue gases shall be treated in bag filter equipped with suitable dust collecting and recycling system.
The GSAC may be designed to burn natural gas 、 heavy fuel oil、coal gas etc .
Control of the calcination plant shall be foreseen by PLC with adequate supervisory equipment. All measurement and control equipment which are mandatory for the operation and troubleshooting of the GSAC will be included in the engineering and supply.