The co-combustion performance and reaction kinetics of refuse derived fuels with South African high ash coal

Abstract

This research focuses on the co-firing of low-quality coal with refuse derived fuel (RDF) as a means to reduce the volume of waste dumped in landfill sites. The co-combustion behaviour and kinetics of various RDF/coal blends at different weight ratios, along with their physicochemical characteristics were investigated. The physicochemical analysis revealed that the run-of-mine and discard coal have relatively low calorific values of 21.7 MJ/kg and 16.7 MJ/kg, respectively. The RDF samples, plastic blend (31.2 MJ/kg) and paper blend (22.4 MJ/kg), were found to have higher energy contents. The thermogravimetric analysis was performed in an atmosphere of air, over a temperature range of 25-850 C, and the results showed that the RDF samples had lower ignition, devolatilisation, and burnout temperatures compared to the coals. The ignition temperatures for the blended fuel occurs in the lower temperature region when RDF is added to the blend, likewise the peak temperatures and burnout temperature shifted to a lower temperature zone. The activation energies (E a ) were determined using the Coats-Redfern method. The E a for the run-of-mine (ROM) coal of 104.4 kJ/mol, was found to reduce to 31.4 kJ/mol for the 75% PB þ 25% ROM coal blend and 35 kJ/mol for the 75% PL þ 25% ROM coal blend, respectively. The discard coal which had an E a of 109.9 kJ/mol was reduced to 30.9 kJ/mol for the 75% PB þ 25% discard blend, and 33.5 kJ/mol for the 75% PL þ 25% discard coal blend. It was determined that the most favourable blend for co-combustion was 70% discard coal þ 30% PL RDF due to the similarity of the combustion profile to that of 100% coal and the simultaneous reduction in apparent activation energy.

Review on the Current Status of the Co-combustion Technology of Organic Solid Waste (OSW) and Coal in China

“…When coal was pyrolyzed together with OSW, the volatiles released from OSW may react with coal or coal volatiles. The co-combustion of sawdust and coal indicated that the interactions may promote the formation of volatiles from the fuel mixture and further inhibit the char yield. − A possible explanation is that the devolatilization of OSW may produce relatively large amounts of H 2 , which can prevent the recombination and cross-linking reactions of free radicals, thereby suppressing the char formation …”

Bibliometric Analysis; Characteristics and Trends of Refuse Derived Fuel Research

“…There is increasing diversity in research methodologies and focus. On the contrary, there are recent studies emerging from Africa and other developing countries [29,30,[59][60][61][62] with new and holistic methods of approach. Thus, a holistic approach towards sustainable waste management.…”

“…Aluri et al [28] performed pyrolysis and gasification experiments on RDF samples. Co-combustion experiments [29,30] conducted on RDF samples resulted in a net gas cost saving of 65 USD/h for cement production. Decision support tools have become inevitable in assessing waste-to-energy systems.…”

Novel ceramic composites produced from coal discards with potential application in the building and construction sectors

“…The combustion of SA coal discard in a circulating fluidized bed (CFB) boiler was demonstrated and reported by Belaid et al (2013). Due to the similar combustion profile of the co-combustion of 70% coal discard and 30% refusederived fuel compared to 100% coal, Isaac and Bada (2020) proposed that the blend could be considered an alternative fuel for use in existing pulverized boilers. The use of different South African coal discards to produce activated carbon as porous adsorbents for natural gas storage was reported by Abdulsalam et al (2019;.…”