10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Emission Behaviors of PM10 during Combustion of Pre-Treated Straw and Co-Combustion with Pulverized Coal
WENYU WANG, Chang Wen, Ying Zhou, Changkang Li, Minghou Xu, Huazhong University of Science and Technology, China
Abstract Number: 303 Working Group: Combustion-Generated Aerosols: the Desirable and Undesirable
Abstract At present no study was made to compare the effect of various thermal pretreatment methods of biomass on the emission behaviors of PM10 from biochar combustion, let alone the co-combustion of biochar with coal. The highlight of this article is the effect of thermal pretreatment, i.e., torrefaction (300°C), slow pyrolysis (500°C) and hydrothermal carbonation (240°C), on the emission reduction of PM10 generated from the combustion of biochar and its co-combustion with steam coal. Straw, as a typical and widespread agricultural biomass in China, was collected as raw materials.
The emission reduction of PM10 is explored via the combustion of starw and its biochars and their co-combustion with coal in a drop tube funace (DTF) at 1400°C. Compared with straw, the fuel properties of biochars are enhanced to some extent, varying from different pretreatments. During pretreatments, almost all alkali and alkaline earth metallic (AAEM) remains in T-300 or S-500 while about 10%~65% AAEM (espiclliay for K, only 10%) stay in H-240. Also, the retention of Cl is ~68%, ~58%, ~16% respectively for T-300, S-500 and H-240.
The above difference among three pretreatments may cause large discrepancy on the content of vaporized species and the generation of PM10. Compared with raw straw, the emission reduction at each size range (PM0.3, PM0.3-1, PM1-10) during single combustion (ash-based) are ~55%, ~55%, ~16% respectively under torrefaction, ~67%, ~56%, ~40% respectively under slow pyrolysis, and up to ~94%, ~90%, 70% respectively under hydrothermal carbonization, hydrothermal carbonization exerts the largest reduction on PM10 emission. Furthermore, based on equal energy input, compared with straw (single combustion), torrefaction still shows 12% of emission reduction at PM0.3, and the advantage of H-240 on the emission reduction of PM10 is still encouraging, even up to 92% at PM0.3, while S-500 already exhibits negative effect. As for blended combustion (ash-based), only hydrothermal carbonization still exhibits great advantage on the emission amount of PM10, and the excellence of it gradually decreases as the increase of coal in the blend proportion. But compared with theoretical value calculated from the addition of single combustion of biomass and coal, experimental value from co-combustion exhibits great advantage on the emission reduction at PM1, due to the capture of AAEM by kaolin in coal. However, advantages gradually disappear in the order of straw > T-300 > S-500 > H-240 for each blend ratio. The emission reduction on PM0.3 whether for single combustion or co-combustion for straw and kinds of biochars is linearly related to the Cl content in materials. Generally, it appears that the more AAEM and Cl is released during thermal pretreatment, the less the PM1 is generated during single combustion of biochars, and meanwhile, the less the emission reduction ratio via co-combustion is.