Waste treatments

The physical matrices we work with are gaseous, liquid, and solid. We have experience in developing processes for the treatment of waste materials, aiming either at their valorization or inertization, as well as in obtaining energy from non-conventional biomass.

Beyond experimental activities, we also perform modeling activities, processing data collected in the lab to develop advanced simulation models. This provides clients with effective tools to optimize their processes and/or products, laying a solid foundation for potential plant scale-up.

Case Studies

Papers

• Onset and propagation of smouldering in pine bark controlled by addition of inert solids.
  Renewable Energy

  Onset and propagation of smouldering in pine bark controlled by addition of inert solids.

  Renewable Energy

  Abstract

  We investigated the smouldering onset and propagation in a biomass (pine bark) bed to mitigate or control the process.

  By the addition of sand, the bed porosity has been modified. Sand of different average particle size, in different arrangements and proportions (from 30 to 70%) has been used, modifying the bed porosity (between 0.44 and 0.67). Experiments have been carried out in a flow reactor, with controlled O2 content in the feed. The packed bed was large enough to allow the development of a reaction front, as expected in large scale applications. Pressure drop measurements revealed as a useful indication to monitor the smouldering onset and the front evolution. The process appears always controlled by the flux of O2, as expected for smouldering. Properly tuning the bed porosity with inert solids, allows to control the self-heating propagation, in view of its exploitation for low temperature heat production with simultaneous controlled conversion. The addition of sand supports a well-defined reaction front. The inert solid preserves the bed texture when the biomass is progressively consumed and allows to evenly distribute O2 to the biomass, thus regulating the heat dissipation and keeping the smouldering front confined.

  Full article
• On the understanding and control of the spontaneous heating of dried tannery wastewater sludge.
  Waste Management

  On the understanding and control of the spontaneous heating of dried tannery wastewater sludge.

  Waste Management

  Abstract

  We studied the spontaneous heating of dried sludge produced by treating wastewater mainly originating from tanneries.

  Heating up to burning has been observed in the presence of air and moisture, starting at ambient temperature. To understand and prevent the process we combined chemical and morphological analyses (ESEM) with thermal activity monitoring in insulated vessels. Selective additions of chemicals, either to amplify or depress the reactivity, have been used to investigate and identify both the chemical mechanism causing the sludge self-heating, and a prevention or a mitigation strategy. FeS additions accelerate the onset of reactivity, while S sustains it over time. On the contrary, Ca(OH)2, Na2CO3, NaHCO3, FeCl2, EDTA, NaClO can limit, up to completely preventing, the exothermic activity. All the experimental evidences show that the reactions supporting the dried sludge self-heating involve the Fe/S/O system. The total suppression of the reactivity requires amounts of additives that are industrially incompatible with waste reduction and economics. The best prevention requires reduction or removal of S and Fe from the dried solid matrix.

  Full article