Improvement of energy recovery potential of wet-refuse-derived fuel through bio-drying process.

This paper proposes novel wet-refuse-derived fuel (Wet-RDF) bio-drying process with the variation of initial organic substrate and moisture content. The bio-drying was carried out using 0.3 m3 lysimeter aerated continuously at different rates. Two conditions of Wet-RDF feedstock tested included: Experiment A ‒ 37% organic substrate and 58% moisture content with an initial heating value of 2,889 kcal/kg; and Experiment B ‒ 28% organic substrate and 35% moisture content with an initial heating value of 4,174 kcal/kg. The bio-drying was performed in both experiments under negative ventilation mode and non-ventilation mode, the ventilation mode was set at the aeration rates of 0.2 m3/kg/day and 0.4 m3/kg/day. The results suggest that the optimum aeration rate was 0.4 m3/kg/day, achieving a 30% moisture reduction and a 60% heating value increase from their initial values. As a result, the improved wet-RDF qualified for the local cement industry's standard in terms of heating value.

Investigation of plastic waste management in Thailand using material flow analysis.

This study uses material flow analysis to investigate the amounts and pathways of municipal plastic waste (MPW) in Thailand. The aim is to understand the country's situation and investigate the effects of Thailand's Roadmap on Plastic Waste Management 2018-2030, which sets a goal for recycling 'target plastic waste' at 100% by 2027. The analysis was conducted using waste statistics between 2008 and 2020 and waste forecasts. Two scenarios of plastic waste management, the business-as-usual, and the national roadmap, were constructed for 2025 and 2030. In 2030, the annual MPW generation is projected to reach 2.19 Mt. Under the business-as-usual (BAU) scenario, the recycling and utilisation rate will be 32.3% of waste generated. About 30.3% of waste generated will not be treated properly and possibly leaked into the open environment. Under the roadmap scenario, the recycling and utilisation rate will increase to 98.4%, while 1.6% of waste generated will not be treated properly. The recycling rate for target plastic waste in 2027 could only reach 67.1% because plastic waste is required as fuel for waste incinerators and industries. With the roadmap fully implemented, certain effects can be foreseen for waste-to-energy and plastic industries. Findings from this study stress on the importance of holistic policy planning, efficient prioritising and allocating of waste as a resource, and cooperation from all sectors for sustainable plastic waste management.

Effects of operating parameters on co-gasification of coconut petioles and refuse-derived fuel.

Coconut agro-industry in the western region of Thailand generates a large amount of residues. This study investigated the energy production potential of discarded coconut petioles, with a focus on co-gasification with refuse-derived fuel (RDF). Gasification tests involving petioles, RDFs and their mixtures (25%, 50%, 75% or 100% by weight) were conducted in a laboratory-scale fixed bed reactor. Fuel samples of 5 g were gasified at 700°C-900°C for 60 minutes, using simulated air (79% N2 to 21% O2, by volume) as a gasifying agent. Gasification of petioles generated producer gas with lower heating values, estimated at 0.43-0.75 MJ Nm-3, while RDF produced 0.92-1.39 MJ Nm-3. Adding greater quantities of RDF to the fuel mixture resulted in an increase in the heating value of the producer gas and cold gas efficiency. The operating temperatures and gasifying-agent flow rates affected the efficiency of process differently, depending on the fuel composition. However, the maximum cold gas efficiency from both fuels was detected in tests conducted at 800°C. In co-gasification and pure refuse-derived-fuel tests, higher temperatures and gasifying-agent flow rates led to outputs with higher energy yields. Our findings suggested that co-gasification of petiole is a viable alternative waste-treatment technology for this region.

Ash deposit characterisation in a large-scale municipal waste-to-energy incineration plant.

The deposition of ash - combustion residues - on superheaters and heat exchanger surfaces reduce their efficiency; this phenomenon was investigated for a large-scale waste-to-energy incineration facility. Over a period of six months, ash samples were collected from the plant, which included the bottom ash and deposits from the superheater, as well as flyash from the convective heat exchanger, the economiser and fabric filters. These were analysed for particle size, unburned carbon, elemental composition and surface morphology. Element partitioning was evident in the different combustion residues, as volatile metals, such as cadmium, antimony and arsenic, were found to be depleted in the bottom ash by the high combustion temperatures (1000+°C) and concentrated/enriched in the fabric filter ash (transferred by evaporation). Non-volatile elements by contrast were distributed equally in all locations (transported by particle entrainment). The heat exchanger deposits and fabric filter ash had elevated levels of alkali metals. 82% of flyash particles from the fabric filter were in the submicron range.