The Use of Biodrying to Prevent Self-Heating of Alternative Fuel

Abstract

Alternative fuels (refuse-derived fuels—RDF) have been a substitute for fossil fuels in cement production for many years. RDF are produced from various materials characterized by high calorific value. Due to the possibility of self-ignition in the pile of stored alternative fuel, treatments are carried out to help protect entrepreneurs against material losses and employees against loss of health or life. The objective of the research was to assess the impact of alternative fuel biodrying on the ability to self-heat this material. Three variants of materials (alternative fuel produced on the basis of mixed municipal solid waste (MSW) and on the basis of bulky waste (mainly varnished wood and textiles) and residues from selective collection waste (mainly plastics and tires) were adopted for the analysis. The novelty of the proposed solution consists in processing the analyzed materials inside the innovative ecological waste apparatus bioreactor (EWA), which results in increased process efficiency and shortening its duration. The passive thermography technique was used to assess the impact of alternative fuel biodrying on the decrease in the self-heating ability of RDF. As a result of the conducted analyses, it was clear that the biodrying process inhibited the self-heating of alternative fuel. The temperature of the stored fuel reached over 60 °C before the biodrying process. However, after the biodrying process, the maximum temperatures in each of the variants were about 30 °C, which indicates a decrease in the activity of microorganisms and the lack of self-ignition risk. The maximum temperatures obtained (>71 °C), the time to reach them (≈4 h), and the duration of the thermophilic phase (≈65 h) are much shorter than in the studies of other authors, where the duration of the thermophilic phase was over 80 h.

Impact of Calcium Oxide on Hygienization and Self-Heating Prevention of Biologically Contaminated Polymer Materials

“…RDF and UFMSW vary enormously in terms of organic matter content which constitutes a source of nutrients for microorganisms [18]. Also, the structure of the tested materials is irregular, its morphology is heterogeneous, and their porosity is high; these factors undoubtedly facilitate the colonization of the waste surface by microorganisms [41], but the polymer fraction in waste always consists of materials of very similar chemical properties, including those causing flammability and the possibility of ignition [21]. This is due to the mass production of plastics around the world and the fact that they are always thermoplastic polymers with the same or very similar physicochemical characteristics (PE, HDPE, LDPE, LLDPE, PP, PS, PET etc.).…”

“…Gajewska et al [21] suggest that the using of the process of biological drying may prevent the spontaneous heating of waste. Biodrying requires substantial expenditure (specialized infrastructure), and the treatment takes several days.…”

“…Thermography is a method of recording infrared radiation using the thermographic camera [ 21 ]. Thermal radiation (wavelength range from 0.9 to 14 μm) is detected by the optical system of the camera and converted in the detector into an electrical signal [ 33 ].…”

“…Because of the possibility of spontaneous combustion [15] and its negative impact on the health of workers [16], entrepreneurs use various methods of protection and prevention of these harmful effects on the environment [17]. There are sensors, fire extinguishing systems, and infrared cameras installed in halls; materials undergo processes of ozonation [18], use of ultrasound or microwave radiation [19], biological stabilization [20], biological drying [21,22], or pH modifications. A popular method is also agglomeration of those materials [23,24] e.g., by the pellet production process [25,26] or granulation [27].…”

“…UFMSW contains a relatively high percentage of organic substances (40-60%) [20]; therefore, it is directed for biological modification to reduce their volume and weight and subject to sanitation process [32]. RDF produced from the oversize fraction of MSW due to a high polymer content (>60%) [8] is mainly used in cement plants [21] as a coal substitute in the cement production process [31].…”