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Contenido archivado el 2022-12-27

USE OF INDUSTRIAL SLUDGES AS ALTERNATIVE FUEL INSTEAD OF COAL IN A CEMENT FACTORY

Objetivo

The aim of the project is to recover matters and energy and to reducte the CO2 emissions from the new treatment of mixed sludge obtained from the wastewater treatment situated in the Petrochemical Plant in Ravenna. The project consists of the drying up of sludges and their use as non conventional fuels in a clinker furnace. Such a treatment substitute the present sludge disposal system is a old multiple hearth furnace requiring auxiliary fuel and without Energy recovery.
About 2200 ton/h of belt filtered sludge, with an average dry matter content of 25% are supplied to the drier, obtaining about 550 kg/h of dried sludge with a dry matter content higher than 90% and a mean lower heating value of about 4900 kcal/kg.
The dried sludge is then transported to the cement factory and mixed with coal in the grinding mills (about 5% in weight of the coal) to obtain powder to be fed as a fuel to the rotary kilns; the quality of the clinker does not worsen when is used as a fuel coal added with dried sludge.
Extrapolating on a yearly basis (8000 hours) the data gathered so far there is a total energy regeneration of 4500 TEP/year. This regeneration is due to the saving of natural gas and electricity deriving from the replacement of the multiple hearth furnace with the drier (about 2300 TEP/Year) and to the energy content of the died sludge (2200 TEP/Year).
A new law concerning the re-use of non-conventional fuels limited the possibility to use the dried sludge at the cement factory even if the test made revealed that the re-use is technically feasible; the emanation of new laws is scheduled for the end of 1998.
The unique characteristics of the sludge to be dried (with high solvent and thermoplastic resin content) meant that special technical and measures engineering had to be adopted, aimed at guaranteeing the safety of the plant and easier management of the process.
The new solution calls for the water-treatment sludge to be dried first and then fed into the rotary kiln of the cement factory, blended with the coal dust used as fuel. The preliminary drying permits the elimination of volatile products. Feeding into the hot zone will result in the complete combustion of the fines of rubber present in the sludge.
The dried sludge has a high heat value (5500 Kcal/Kg) and is thus considered an alternative fuel, not waste requiring disposal. The filtered sludge is fed into the top of a horizontal cylindrical dryer and kept in centrifugation by a turbo-agitator. The dryer is heated by steam in a coaxial steam jacket, while the damp material is suspended in a flow of hot air with a high degree of turbolence. Vapour is thus released around the material being dried and is forcibly removed by suction.
The solid particles are separated from the gases in cyclone, downstream from which a scrubber is installed to retain the solids not arrested by the cyclone and a dehumidifer column to remove the vapour. A fan sends justified air to a heater and then to the drying unit.

Convocatoria de propuestas

Data not available

Régimen de financiación

DEM - Demonstration contracts

Coordinador

Ambiente SpA
Aportación de la UE
Sin datos
Dirección
Via fabiani 3
20097 San donato milanese
Italia

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Coste total
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