Dispersion and co-combustion studies for disposal of agro-industrial effluents in bubbling fluidized bed
- CNR/Ist. di Ricerche sulla Combustione, Napoli (Italy)
- Univ. di Parma (Italy). Dipt. di Ingegneria Industriale
The present work was developed in the frame of a collaboration between CNR/Istituto Ricerche Combustione, University of Parma and ENEA. It was aimed at exploiting and recovering the thermal energy from liquid effluents and solid wastes derived from typical Italian manufacturing of agro-industrial companies. This paper focuses on an organic sludge that is obtained as a residue during steam concentration of waste water from alcohol production in distilleries. This sludge has a very low calorific value and cannot be directly used in a combustion process. The first objective was to turn the sludge into a coal/waste/water mixture, easy to prepare and to burn on site in a bubbling fluidized combustor. To do so, some preliminary runs were carried out on a significant experimental scale by employing the 2100 kW{sub t} FBC-370 pre-pilot facility and by feeding underbed a South African coal/dry residue/water mixture with a maximum particle size of 1 mm. Very satisfactory values of co-combustion efficiency (i.e., larger than 98%), were attained as a function of the dispersing air velocity. It was proven that the mechanism of combustion passes through the formation of carbon-sand aggregates and tiny carbon deposits on bed sand particles. Another outcome was that pumping the mixture directly into the bed without any atomization is feasible and favorable from the point of view of co-combustion efficiency. Therefore, a second objective was to investigate aggregate formation as a result of mixture injection into the hot bed. This has been pursued through a review of the fundamental aspects underlying the behavior of a liquid issuing from an orifice. Two simple approaches, one based on Scheele and Meister`s (1968) results and the other one based on a balance of force moments, were followed. These two approaches provided two different equations to predict the diameter of a drop that detaches from the injection nozzle. Furthermore, aggregate formation was investigated through the set-up of batch experiments with mixtures injection into the FBR-40 bench-scale bubbling-bed facility. The characteristic size of the aggregates formed follows a similar trend as the predicted drop diameter, i.e., it increases with the nozzle size at a constant injection velocity and decreases with injection velocity for a constant orifice diameter.
- OSTI ID:
- 357907
- Report Number(s):
- CONF-9705116-; ISBN 0-7918-1557-9; TRN: IM9932%%252
- Resource Relation:
- Conference: 14. international conference on fluidized bed combustion, Vancouver (Canada), 11-16 May 1997; Other Information: PBD: 1997; Related Information: Is Part Of Proceedings of the 14. international conference on fluidized bed combustion: Volume 2; Preto, F.D.S. [ed.] [Canada Centre for Mineral and Energy Technology, Ottawa, Ontario (Canada). Energy Technology Centre]; PB: 647 p.
- Country of Publication:
- United States
- Language:
- English
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