Abstract
We have been advancing the concept of carbonized refuse-derived fuel (CRDF) by refuse-derived fuel (RDF) torrefaction as improved recycling to synergistically address the world’s energy demand. The RDF is a combustible fraction of municipal solid waste (MSW). Many municipalities recover RDF for co-firing with conventional fuels. Torrefaction can further enhance fuel properties and valorize RDF. Energy demand for torrefaction is one of the key unknowns needed for scaling up CRDF production. To address this need, a pioneering model for optimizing site-specific energy demand for torrefaction of mixed RDF materials was developed. First, thermogravimetric and differential scanning calorimetry analyses were used to establish thermal properties for eight common RDF materials. Then, the model using the %RDF mix, empirical thermal properties, and torrefaction temperature was developed. The model results for individual RDF components fitted well (R2 ≥ 0.98) with experimental torrefaction data. Finally, the model was used to find an optimized RDF site-specific mixture with the lowest energy demand. The developed model could be a basis for estimating a net energy potential from the torrefaction of mixed RDF. Improved models could be useful to make plant-specific decisions to optimize RDF production based on the energy demand that depends on highly variable types of MSW and RDF streams.
Highlights
Refuse-derived fuel (RDF) refers to the combustible fraction of municipal solid waste (MSW) characterized by high calorific value, which includes common waste groups: plastics, packaging waste, textiles, wood, and rubber [1,2]
This is needed for decision-making that considers the evaluation of cost, life cycle analysis (LCA), and for optimizing the carbonized refuse-derived fuel (CRDF) torrefaction that has inherently variable inputs in the available MSW streams
We propose to use relatively simple input data that can be obtained by standard methods, i.e., the thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) [11] for individual materials in RDF mix and their relative percentage weight
Summary
Refuse-derived fuel (RDF) refers to the combustible fraction of municipal solid waste (MSW) characterized by high calorific value, which includes common waste groups: plastics, packaging waste, textiles, wood, and rubber [1,2]. The overall working hypothesis is that the purposeful separation and physical/chemical treatment of RDF can be exploited to maximize the energy recovery in CRDF This is needed for decision-making that considers the evaluation of cost, life cycle analysis (LCA), and for optimizing the CRDF torrefaction that has inherently variable inputs in the available MSW streams. Since RDF is a mixture of different organic materials, such as plastics, paper, cardboard, leather, hygienic waste, and biodegradables [13], it is reasonable to hypothesize that different MSW composition can influence the overall energy demand for torrefaction. The model considers initial heating (from 20 to 300 ◦C), and thermal processing for eight typical types of organic and plastic waste materials in RDF separated during mechanical and biological pre-treatment. Results were used to develop an experimental database for model inputs of the specific heat (ESH, i, T, J·g−1)
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