Influence of Molding Technology on Thermal Efficiencies and Pollutant Emissions from Household Solid Fuel Combustion during Cooking Activities in Chinese Rural Areas

Abstract

Resident combustion of solid fuel has been widely acknowledged as a high potential for pollutant reduction. However, there is a marked asymmetry between more pollutant emission and less burned volatiles of biomass and coal in the combustion process. To study the solid fuel optimum combustion form in a household stove, both the pollution reduction and energy efficient utilization of crop straws and coals were investigated. Taking the molding pressure and clay addition ratio as variable process conditions, the research of bio-coal briquette (made from the mixture of anthracite and biomass) was implemented in the range of 15~35 MP and 5~15%, respectively. Biomass and coal work complementarily for each other’s combustion property development. In particular, the pyrolysis gas produced by biomass low-temperature devolatilization is featured with low ignition point and is distributed in the bio-coal briquette. Its own combustion provides energy for anthracite particle combustion. Consequently, a positive effect was identified when bio-coal briquettes were used as residential fuel, and further improvement manifested in reducing more than 90% of particle matter (PM) and achieving about twice the thermal efficiencies (TEs) compared with the mass-weighted average values of coal briquettes and biomass briquettes. 88.8 ± 11.8%, 136.7 ± 13.7% and 81.4 ± 17.7% more TEs were provided by wheat straw–coal briquettes, rice straw–coal briquettes and maize straw–coal briquettes. 93.3 ± 3.1% (wheat straw–coal), 97.6 ± 0.2% (rice straw–coal) and 90.4 ± 2.2% (maize straw–coal) in terms of PM2.5 emission factors (EFs) was reduced. For bio-coal briquette, a 25 MPa and 10% addition were determined as the optimum molding pressure and clay addition ratio. Bio-coal briquettes with higher TEs and lower PM EFs will bring about substantial benefits for air quality promotion, human health and energy saving.

Effects of Bio-Coal Briquette for Residential Combustion on Brown Carbon Emission Reduction

“…In order to reduce environmental pollution, Chinese government has encouraged application of biomass briquette and coal briquette in residential combustion since 2014. Bio-coal briquettes, a mixture of biomass and coal, have been recommended as suitable alternative solid fuel because of their low pollutant emissions and high thermal efficiency [35,36]. During bio-coal briquette combustion, the drawbacks of biomass and coal complement each other; therefore, better combustible qualities can be achieved [37].…”

“…In addition, biomass that scatters in bio-coal briquette is burnt before coal and numerous pores are formed. Such a structure facilitates the transfer of mass and heat, reduces the formation of oxygen-depleted zones, and hence declines emissions of pollutants [35,36]. Therefore, there is tremendous significance for exploration of bio-coal briquette on BrC emissions based on the hazards and impacts mentioned above.…”

Improving Combustion Technology for Cooking Activities for Pollutant Emission Reduction and Carbon Neutrality

“…The measurement method for TEs adopted in our research has been reported in previous publications [23,26]. CO, NO x , SO 2 (Thermo Scientific; 43i, and 42i for CO, NO X , and SO 2 , respectively; Thermo Fisher Scientific Inc, Waltham, MA, USA), and CO 2 (GC-0012; Gas Sensing Solutions Ltd., Cumbernauld, Scotland) were tested using online gas analyzers.…”

“…A kettle with 2.0 kg of room temperature water was employed to test the TEs each time. A second kettle with the same amount of room temperature water replaced the previous one when the water temperature reached 90 • C in case water vapor ran into the flue piper [23,26]. The kettles were exactly the same, and the initial water temperature was kept constant every time.…”

“…Refined fuel and stoves will most likely serve as practical solutions to the above issues [3,23,24]. First, compressing raw biomass into pellets or briquettes is an effective way to reduce pollutant emissions because they generate far lower EFs than the corresponding raw (or unprocessed) materials [25][26][27][28].…”