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Coal is China's dominant energy source, among which bituminous coal is the most extensive and plentiful. Using bituminous coal resources to design a low-emission household fuel is very important for rural poverty areas. In this work, a new type of bituminous coal pellet (BCP) fuel using an automatic prototype pellet stove was designed for the first time. This study mainly shows the emission characteristic results of BCPs and some comparisons with other commercial solid fuels. Fuel property, PM2.5 morphology, and ash characteristics of the novel fuel were also assessed. In terms of fuel properties, BCPs had a cold compressive strength of 637.2 N, a heating value of 22.26 MJ/kg, and many fine pores in the cross-section for air entry. The real-time emissions of BCPs were stable during combustion. The emission factors of PM2.5 and CO of BCPs were 1.36–2.29 g/kg and 11.1–18.0 g/kg, which were significantly lower than those of bituminous chunk and bituminous briquette (p < 0.05). PM2.5 and CO reduced emissions by 83–90% and 61–76%, respectively, compared with raw coal chunk. According to the chemical composition and morphological characteristics, the PM2.5 from BCP combustion can be divided into fine particulates, molten char particles, and char fragmentation. The ash from BCPs had a higher melting temperature (over 1300 °C), with removable ash agglomeration. Overall, the results presented in this study highlight that turning bituminous coal into pellets and burning them in automatic stoves could noticeably reduce PM2.5 and CO emissions, effectively improving rural air quality. [ABSTRACT FROM AUTHOR]

The use of coal in Chinese households for winter heating emits harmful pollutants that severely affect indoor air quality and climate. Therefore, China has made efforts to transition into clean heating using improved heating stoves and biomass pellets. Although the economic and policy implications of such demonstration projects have been extensively investigated, little has been done to understand the real-world performance and adoption trends of such stoves. This study measured in-use emissions from nine different pellet stoves used for heating among 52 rural households in Yangxin, Shandong Province. The temperature of the stove chimney of 21 households was monitored and 56 households were surveyed to explore the stove use trend. The particulate and gaseous emission concentrations for most of the stoves exceeded the limits specified in the Chinese national standard. The measured fuel energy-based emission factors (mean ± standard deviation) for CO 2 , CO, NOx, and PM 2.5 were 103 ± 3, 1.41 ± 1.19, 0.336 ± 0.237, and 0.146 ± 0.108 g/MJ, respectively. Between January to February, the average daily heating duration was 8.71 h, and the sustained use of heating stoves was seen among over 85% of the households. On average, the households used their heating stoves for 3.28 months and the estimated annual pellets consumption for a household was 2.7 tons. Besides inherent variabilities associated with user habits, the stove's design-related shortcomings and low-grade pellets hindered the performance and effectiveness of pellet stoves. This study provides insights into opportunities and challenges for the promotion of cleaner fuels and heating technologies. Furthermore, it will provide information on emissions from rural residential sources to build the emission inventory and inform policymaking for successful stove promotion programs. [Display omitted] • Most households used their stoves regularly during the day and shut them down at night. • In-use emissions from the stoves exceeded the limits of the national standard. • Most of the stoves supplied excess air contributing to higher emissions. • Over half of the pellets used were of inferior quality. • Stove designs based on local habits and better pellets are vital to reduce emission. [ABSTRACT FROM AUTHOR]