Effects of Combined Torrefaction and Pelletization on Particulate Matter Emission from Biomass Pellet Combustion

Abstract

Combined torrefaction and pelletization can effectively improve the quality of the biomass fuel. In this work, particulate matter (PM) emissions from combustion of corn stalk pellets derived from the torrefaction and pelletization process were investigated using a fixed-bed reactor combined with a Dekati low-pressure impactor (DLPI). The obtained ash samples were subjected to various analytical techniques. Results indicated that, after torrefaction, the lower heating value (LHV) of the torrefied sample increased by 8−28% with an increase of the ash content by 9−30% and a decrease of the O content by 14− 48%. Although 10−41% Cl and 27−60% S were released in the torrefaction, the absolute content of Cl increased from 7.6 mg/g for raw corn stalk to 9.2 mg/g for torrefied biomass at 300 °C. In comparison to the raw pellet, the total PM emission from torrefied pellets increased by 25−68% with the torrefaction temperature increasing, largely resulting from the increase of PM 0.1−1 . Chemical composition analysis of the PM showed that torrefaction changed PM 1 composition from being dominated by KCl to mainly K 2 SO 4 . The variation of PM emission characteristics between the raw pellet and torrefied biomass pellet could be attributed to the changes of the contents and occurrence forms of ash-forming species in the torrefaction process. Although combined torrefaction and pelletization clearly enhanced the fuel properties of the corn stalk, it also increased PM emissions, especially PM 1 , to various degrees. Therefore, effective countermeasures are needed to mitigate the PM emission issues in industrial application.

Effect of Torrefaction on Aerosol Emissions at Combustion Temperatures Relevant for Domestic Burning and Power Generation

“…18,43,65 This could be due to differences in the torrefaction process but is also likely due to differences in the type of biomass, specifically the ash content. For example, the ash content of the raw and torrefied biomass (corn stalk) in Shao et al 18 was 8.69 and 11.29%, respectively. In Cheng et al, 43 the ash content of the raw biomass (cotton stalk) was 5.17% and increased to 6.24− 29.55%, depending on the employed torrefaction process.…”

“…Under such conditions, the aerosol emissions are often dominated by inorganic species, 28,41 and their formation potential is correlated with the ash content of the fuel. 18 Torrefied biomass fuels usually have higher ash content than their raw counterparts. 42 This has been hypothesized to lead to higher aerosol mass emissions from the combustion of torrefied biomass compared to raw biomass observed in several studies at conditions representative of power generation combustion.…”

Using of Adhesives and Binders for Agglomeration of Particle Waste Resources

“…As a result, biomass as a binder has only lately come to the attention of domestic and international industries [46,47]. According to Shao et al [48], a binder was combined with several types of biomass, including agricultural waste, aquatic plant, forestry biomass, and aquatic plant. The technology not only skillfully blends renewable and nonrenewable energy (coal), but also provides options for biomass energy consumption.…”

Torrefaction of Wood in a Quiescent Layer of Talc

“…24 At the same time, it can lead to an increase in particulate matter emission. 25,26 In addition to the direct use of torrefied biomass as a fuel, it can be used in the process of pyrolysis 27,28 and gasification. 29 Despite significant development in torrefaction technologies, their wide industrial application is limited and sometimes is not economically feasible.…”

“…Torrefaction of biomass improves the grindability of raw biomass by the transformation from a fibrous structure to a more brittle, coal-like material. , Moreover, biomass torrefaction favors the increase in the energy density and the hydrophobization of the biofuel surface . At the same time, it can lead to an increase in particulate matter emission. , In addition to the direct use of torrefied biomass as a fuel, it can be used in the process of pyrolysis , and gasification . Despite significant development in torrefaction technologies, their wide industrial application is limited and sometimes is not economically feasible.…”