Resumo:
The development of an efficient and low-cost treatment for sanitary sludge meets the 6th UN
objective that aims to and provide sanitation for the world population by the year 2030. In
view of the above, this study evaluated, by means of a thermodynamic model, the drying of
sanitary sludge at low temperature by the method of the granular bed, previously centrifuged,
which was integrated into a heliothermic system with thermal storage. Scenario 1 was
modeled with the dryer operating for 9h.d-1 and scenario 2 for 24 h.d-1 (continuous operation),
and the same amount of sludge per day was processed in each scenario. Experimental assays
were also conducted on the mixture of wet and thermally treated sludge to study the influence
of the mixture on the drying process. The results showed that, in the conditions studied, the
contents of 50 and 90% of total solids are the most suitable for sludge, respectively, in the
inlet and outlet of the sludge dryer. While the drying temperature was defined at 80°C, as the
tests did not indicate the advantage over any temperature within the range evaluated (60 to
104°C). The drying method of the granular bed, produced a less coarse profile sludge and
with drying rates of up to 3.10 times higher than the convective method. The modeling
achieved thermodynamic viability for the integration of the heliothermic system when
scenarios 1 and 2 presented, respectively, a mirrored area of 3,848 and 3,345m², thermal
demand (with global losses of the model) of 3.23 and 2.81GJ.tv
-1 and thermal storage of 1,594
and 4,550kWht, demonstrating that the size of the modeled system is employed commercially
in several countries and that scenario 2 is the most interesting for indicating a smaller plant.
The model still showed that it is possible to produce condensed water naturally to maintain a
cycle of cleaning the solar concentrators with periodicity less than 2 days. In view of the
above, it is concluded that the integration of the drying with the heliothermic energy is
feasible from a technical and energetic standpoint and still presents the benefit of producing
water for cleaning or other non-potable purposes, mitigating one of the main impacts
environment of this technology and becoming attractive in regions of water stress. It was also
demonstrated that the sludge mixing technique can to modify the morphological and
rheological characteristics of the material, improving the permeability and drying rate, in
addition to reducing the plasticity of the original sludge. Finally, it is proved that the drying
method of the granular bed is able to produce an attractive granular, dry, possibly sanitized
biosolid, suitable for use in various production processes.