Objetivo The aim of the project is to evaluate the suitability of heat recovery of magnetite cinders (at 650 deg.C.) from the magnetizing reduction plant obtained in a fluidized bed by the direct injection of fuel oil.Before being used the magnetite cinders must be cooled down to below 200 deg.C.Up to now this cooling procedure has been by dispersion of the heat into the atmosphere.The aim with this project is to recover that heat and to direct it to heating boiler water for high-pressure steam generation and, finally, electrical energy.The total recovery of heat during the operating period amounted to about 87% of the forecast.In particular, the heat recovered in the first section of the plant, i.e. in the surface exchanger, practically coincides with the Project hypothesis.The heat recovered however, from the tail gases in the reduction phase, was considerably less on account of the fact that between the planning stage and construction of the recovery plant, fuel oil consumption in magnetizing reduction was optimized, thereby reducing the energy content of the tail gases.After some three months of regular operating, the plant was shut down to eliminate the reduction phase as a result of a change in the production cycle.The heat recovered as high pressure steam (40 atm, 450 deg. C) is used to produce electric energy by means of turbo-alternators.Total net recovery = 2,066,000 Kcal/h.The process cycle at Scarlino can be summed up briefly as follows.The ungraded pyrite is roasted in fluidized bed furnaces. From the resultant sulphurous gases the sensible heat is recovered in boilers producing steam and hence electric energy.These gases are then treated in further plants to produce acid by a traditional four-stage catalytic conversion system.The pyrite cinders left after roasting are converted from hematite to magnetite by a reduction process (patent by Montecatini-Dorr Oliver) in fluidized bed furnaces with direct injection of fuel into the furnace.After reduction the magnetite cinders are cooled with water and steam and then conveyed to the magnetic separation plants for iron enrichment with a view to obtaining a final concentrate that is chemically suitable for the production of pellets used in iron and steel processes. Once conditioned, the iron concentrate is cold pelletized in a revolving drum and the green pellets obtained are calcined in a furnace with a mobile grid giving pellets for blast furnaces with an iron content of around 65%. The heat recovery plant was installed in one of the five parallel production lines with certain alterations made to the process layout of the cinder cooling phase.The magnetite cinders leaving the reduction furnace at 650 deg.C. were previously cooled to below the critical reoxidation temperature (approximately 200 deg.C.) by direct injection of water into the fluidized bed with low-pressure steam.This avoided the phenomenon of magnetite reoxidization by atmospheric oxygen, but the sensible heat removed from the cinders was completely dispersed into the atmosphere.This system of recovery is based on the replacement of previous cooling apparatus by a special circuit consisting of a surface exchanger in which feedwater for steam generation circulates inside a coil and the cinders pass to the outside, fluidized by spent air in the closed cycle. This achieves the dual objective of recovering heatand inhibiting oxidation of the magnetite by the air.This project also provides for heat recovery of the residual energy content of the gases at the tail of the magnetizing reduction plant, thus promoting complete combustion, with no contact with the cinders, through the injection of air on stream and converging the gas mix in the flow of roasting gases in transit to the main recovery boilers.This amounts to the following energy saving:- saving of low-pressure fluidization steam used in previous coolers.- recovery of sensible heat from cinder cooling;- recovery of energy previously dispersed into the atmosphere in the form of unburnt hydrocarbons. Programa(s) ENG-ENALT 1C - Programme (EEC) of financial support for projects to exploit alternative energy sources, 1979-1984 Tema(s) 1.6 - INDUSTRY Convocatoria de propuestas Data not available Régimen de financiación DEM - Demonstration contracts Coordinador Solmine SpA Aportación de la UE Sin datos Dirección Via S. Teresa 23 00100 Roma Italia Ver en el mapa Coste total Sin datos
