•Carbonized Refuse Derived Fuel may be qualified as 1st class quality fuel.•Torrefaction allows on RDF/SRF improvement, and recycling as a CRDF.•Torrefaction temperature has an effect on Carbonized ...Refuse Derived Fuel properties.
The influence of Refuse Derived Fuel (RDF)/Solid Recovery Fuel (SRF) torrefaction temperature on product characteristic was investigated. RDF/SRF thermal treatment experiment was conducted with 1-h residence time, under given temperatures: 200, 220, 240, 260, 280 and 300°C. Sawdust was used as reference material. The following parameters of torrefaction char from sawdust and Carbonized Refuse Derived Fuel (CRDF) from RDF/SRF were measured: moisture, calorific value, ash content, volatile compounds and sulfur content. Sawdust biochar was confirmed as a good quality solid fuel, due to significant fuel property increase. The study also indicated that RDF torrefaction reduced moisture significantly from 22.9% to 1.4% and therefore increased lower heating value (LHV) from 19.6 to 25.3MJ/kg. Results suggest that RDF torrefaction may be a good method for increasing attractiveness of RDF as an energy source, and it could help unify RDF properties on the market.
Increasing production of waste has compelled the development of modern technologies for waste management. Certain fractions of municipal solid wastes are not suitable for recycling and must be ...utilised in other ways. Materials such as refuse-derived fuel (RDF) fractions are used as fuel in cement or CHP (combined heat and power) plants. The low bulk density leads to many problems pertaining to transportation and storage. In the case of biomass, these problems cause reduction in pelletisation. This paper therefore presents a comprehensive study on RDF pellet production, which is divided into three major areas. The first describes laboratory-scale tests and provides information on key factors that affect pellet quality (e.g., density and durability). Based on this, the second part presents a design of modified RDF dies to form RDF pellets, which are then tested via a semi-professional line test. The results show that RDF fraction can be compacted to form pellets using conventional devices. Given that temperature plays a key role, a special die must be used, and this ensures that the produced pellets exhibit high durability and bulk density, similar to biomass pellets.
Red mud is a promising candidate for promoting the incineration of Refuse Derived Fuel (RDF) and stabilizing the resulting incineration ash. The combustion conditions, notably temperature, ...significantly steers the migration and transformation of harmful metal components during combustion, and ultimately affect their retention and speciation in the ash residue. The study attempted to investigate the effect of co-combustion temperature on the enrichment and stability of Cr, Ni, Cu, Zn, Cd and Pb within bottom ashes, and to reveal the underlined promotion mechanism of red mud addition. As temperature increased, red mud's active components formed a robust matrix, helping the formation, melting, and vitrification of silicates and aluminosilicates in the bottom ashes. The process significantly contributed to the encapsulation and stabilization of heavy metals such as Ni, Cu, Zn, Cd, and Pb, with their residual fractions ascending to 71.37%, 55.75%, 74.78%, 84.24%, and 93.54%, respectively. Conversely, high temperatures led to an increase in the proportion of Cr in the extremely unstable acid-soluble fraction of the bottom ashes, reaching 31.52%, posing a heightened risk of environmental migration. Considering the stability of heavy metals in the bottom ashes and the combustion characteristics, 800 °C is identified as the optimal temperature for the co-combustion of RDF and red mud, balancing efficiency and environmental safety. The findings will provide valuable insights for the co-utilization strategy of RDF and red mud, contributing to more informed decision-making in waste-to-energy processes.
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•RM promotes the formation of aluminosilicate matrix to fix heavy metals in ash residues.•The increase of temperature can promote the stability of Ni, Cu, Zn, Cd and Pb.•The immobilization mechanism of heavy metals in RDF/RM ash was revealed.•The findings offer us new references on the co-utilization of RDF and RM.
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•CFD-simulations of rotary cement kilns considering coating layers are conducted.•Numerical models for RDF, coating and clinker bed are presented and combined.•The impact of coating ...regions on RDF combustion and clinker properties is investigated.•Light and evenly distributed coating profiles are found to be beneficial for the process.•Heavy and locally concentrated coating can result in a high free lime content of 2 wt%.
The formation of regions of solid coating, where agglomerated clinker material adheres to the refractory lining of the kiln wall, is very common during cement clinker production. While a thin coating layer protects the refractory lining, strong deposit formation can impair the material flow through the kiln. In this study, the impact of these coating layers on the clinker production process within a rotary kiln is investigated with CFD simulations. The fuel injected at the main burner is a mixture of pulverized coal and refuse derived fuel (RDF). Advanced models were developed to accurately describe the trajectories and thermal conversion of non-spherical RDF particles in the gas phase. These models are based on a detailed fuel analysis of major RDF fractions. A blocked-off region approach is used to consider different coating profiles within the simulation domain. The thermochemical processes in the clinker bed of the kiln are approximated with a one-dimensional model that calculates heat and mass exchange with the gas phase, the incorporation of fuel ashes into the bed and the chemical-mineralogical reactions of the clinker. The blocked-off region approach is also employed to account for the clinker bed geometry in the kiln, which greatly depends on the considered coating profile. Two cases, one with a thin and evenly distributed coating profile and one with a thick and locally concentrated coating, are simulated. The resulting impact on RDF conversion, gas phase properties and clinker phase formation are assessed and compared to a reference case without any coating. Results show that the insulation effect of a thin coating profile increases the gas phase temperature in the kiln and helps to reduce the free lime content of the final clinker product. In the case of heavy coating, a temperature shift towards the solid material inlet of the kiln occurs, which outweighs the beneficial insulation effect of the coating in the sintering zone and leads to lower local gas phase temperatures. In combination with reduced clinker residence times, this results in a slight increase of the free lime content in the clinker.
•COVID-19 pandemic brought huge amount of medical wastes, which is mainly made of plastic polymer.•Thermochemical treatments (incineration, torrefaction, pyrolysis, and gasification) are ...reviewed.•The review focuses on the applicability of those technologies to convert the medical wastes.•Incineration has the highest material flexibility, followed by gasification and pyrolysis.•Gasification and pyrolysis are considered as the most promising conversion technologies.
COVID-19 pandemic has brought tremendous environmental burden due to huge amount of medical wastes (about 54,000 t/d as of November 22, 2020), including face mask, gloves, clothes, goggles, and sanitizer/disinfectant containers. A proper waste management is urgently required to mitigate the spread of the disease, minimize the environmental impacts, and take their potential advantages for further utilization. This work provides a prospective review on the possible thermochemical treatments for those COVID-19 related medical wastes (CMW), as well as their possible conversion to fuels. The characteristics of each waste are initially analyzed and described, especially their potential as energy source. It is clear that most of CMWs are dominated by plastic polymers. Thermochemical processes, including incineration, torrefaction, pyrolysis, and gasification, are reviewed in terms of applicability for CMW. In addition, the mechanical treatment of CMW into sanitized refuse-derived fuel (SRDF) is also discussed as the preliminary stage before thermochemical conversion. In terms of material flexibility, incineration is practically applicable for all types of CMW, although it has the highest potential to emit the largest amount of CO2 and other harmful gasses. Furthermore, gasification and pyrolysis are considered promising in terms of energy conversion efficiency and environmental impacts. On the other hand, carbonization faces several technical problems following thermal degradation due to insufficient operating temperature.
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•Addition of rice husks to coal and RDF suppressed PM yields during co-firing.•Creation of liquid substances was experimentally and numerically studied.•AAEMs were preferentially ...condensed on the Si-rich and Al-Si species.•Viscous particles of Na/K/Ca-Al-Si captured the inorganic vapor and grains.
A self-designed drop tube furnace (DTF) was constructed to investigate the particulate matter (PM) emissions generated from blending 0–30 wt% refuse derived fuel (RDF) and 0–20 wt% rice husks (RH) with bituminous coal during co-firing. The physiochemical characteristics of PM were determined using XRD, XRF, and SEM-EDS, and the creation of the liquid components at varying temperatures was investigated using theoretical thermodynamic calculations based on fuel composition and combustion atmospheres. The results demonstrated that blending 0–30 wt% RDF with coal did not result in significant PM emissions. PM0.5 and PM2.5 yields declined by 31.5% and 39.5%, respectively, with the addition of 20 wt% RH. By solely adding RDF, more Ca-Al-Si and K/Ca-Si formed viscous surfaces or particle bodies that could capture Ca/K vapor released from the volatiles of RDF in the gas bulk. Si-rich and Al-Si species from coal were consumed and transformed into Na/K-Ca-Al-Si to enhance the production of the liquid phase by the abundant Si in the volatiles of RH. Two possible paths of mineral transformations during co-firing were discussed to prove that alkali metals and alkaline earth metals preferentially condensed on Si-rich and Al-Si species to form liquid substances and capture the vapor and grains in the gas bulk, rather than combining with nonmetallic elements to generate precursors for PM generation via the evaporation–condensation mechanism. This study contributes to the search for an efficient pathway to realize simultaneous waste utilization and greenhouse gas reduction.
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•Pyrolysis technology can be successfully applied into RDF conversion.•Heating value of pyrolytic gas was estimated at the level about 24 MJ/m3.•Residence time significantly ...influences the pyrolytic gas composition.•Computer simulations predicted the chemical composition of pyrolytic gas.
The current COVID-19 pandemic situation and the associated restrictions have increased the amount of generated waste. It results from the necessity to wear personal protective equipment. Thus, the disposal of masks and gloves is a topical issue and requires immediate investigation. The main aims of this work are management and environmental studies of municipal solid wastes (MSW), which have been generated during the COVID-19 pandemic time. Effective waste management in relation to a circular economy is presented. A sample of refuse derived fuel (RDF) with a high content of plastics was used for the experimental and calculation studies. Pyrolysis was selected as the best thermal decomposition process for this kind of wastes. Proximate and ultimate analyses were performed for RDF and its products. Pyrolysis was carried out using a pilot-scale reactor with acontinuous flow of 250 kg/h at 900 °C. Thermogravimetric analysis was applied during the pyrolysis investigation and showed that the main decomposition of RDF took place in the temperature range of 250–500 °C. The pyrolysis gas contained combustible compounds like CO (19.8%), H2 (13.2%), CH4 (18.9%) and C2H4 (7.1%), giving a high calorific value – 24.4 MJ/m3. The experimental results were implemented for numerical calculations.
Chemkin-Pro software was applied to predict the chemical composition of the pyrolysis gas. The performed computer simulations demonstrated very good agreement with the results obtained during the experiments. They also indicated that there is a strong relationship between the chemical composition of the pyrolysis gas, the process temperature and residence time in the reactor.
This paper presents CFD simulations of an industrial scale rotary kiln for cement clinker production. The fuel for the kiln flame is a mixture of pulverized coal and a Refuse Derived Fuel (RDF). ...Advanced models were developed to appropriately describe the thermal conversion characteristics and aerodynamics of non-spherical RDF particles. The models are based on detailed fuel analyses (e.g. flight and combustion characteristics, physical and chemical fuel properties) of major RDF fractions, like plastic foils, 3D plastic particles, paper & cardboard and textiles. The processes in the clinker within the kiln are approximated using a simplified one-dimensional model that calculates heat and mass exchange with the gas phase and the resulting chemical-mineralogical reactions in the solid bed. Calculation results of the one-dimensional model are compared to measurements obtained from a semi-industrial laboratory rotary kiln. Two cases, one with 100% lignite and one where 50% of the fuel heat input is substituted with RDF, are simulated. Based on the simulation results, the shift of flame shape and fuel conversion as well as the resulting effects on the clinker phase transition are analyzed and discussed. Results show that co-combustion of RDF can lead to lower gas and clinker temperatures in the sintering zone, which can affect the clinker properties.
•Drag and lift coefficients are important to describe the flight behaviour of particles.•Refuse derived fuel (RDF) has a non-trivial flight behaviour due to its complex shapes.•A computer vision ...based method to derive the shape and flight characteristics of RDF particles is presented.•A frequency distribution of the drag and lift coefficients of RDF is provided.
This research investigates the flight behavior of refuse-derived fuel (RDF) in a drop shaft using Computer Vision to obtain statistical data on the aerodynamic properties of the particles.
Methods to determine 3D geometry models of complex-shaped particles by photogrammetry and to obtain time resolved particle positions and velocities are described. Furthermore, an approach to obtain the frequency distribution of drag and lift coefficients from photogrammetric analysis and drop shaft experiments is presented. The image evaluation is based on algorithms of the open-source libraries OpenCV, COLMAP as well as MeshLab and Open3D. The precision of the system is validated employing model particles with known geometry. The 3D particle models overestimate the particle surface area by 4.58 %, the position detection works with a mean deviation of 2.73 %. The average sink rate is calculated with an accuracy of 4.87 % and the drag coefficient with an accuracy of 2.08 %. Finally, the frequency distribution of four RDF fractions, namely, textiles, cardboard, 3D plastic particles and 2D plastic foils are presented.
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