Open Access

ARTICLE

Impacts of Torrefaction on PM₁₀ Emissions from Biomass Combustion

Zihao Wang, Dunxi Yu^*, Jingkun Han, Jianqun Wu

State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan, 430074, China

* Corresponding Author: Dunxi Yu. Email:

(This article belongs to the Special Issue: Advancement of Understanding of PM_2.5 and Hg Emissions and Their Control Technologies for Cleaner Combustion)

Energy Engineering 2021, 118(5), 1267-1276. https://doi.org/10.32604/EE.2021.016107

Received 06 February 2021; Accepted 06 May 2021; Issue published 16 July 2021

Abstract

Typical biomass torrefaction is a mild pyrolysis process under conditions of ordinary pressure, low temperature (200–300°C) and inert atmosphere. Torrefaction is considered to be a competitive technology for biomass pretreatment, but its impacts on the emissions of particulate matter from biomass combustion are worthy of further study. In this paper, three kinds of biomass, i.e., bagasse, wheat straw and sawdust were selected for torrefaction pretreatment and the impacts of torrefaction on the emission characteristics of PM₁₀ from biomass combustion were investigated. The combustion experiments were carried out on a drop tube furnace. The combustion-generated particulate and bulk ash samples were collected and subjected to analyses by various techniques. The results show that torrefaction tends to result in a reduction of PM₁ (particulates with an aerodynamic diameter less than 1 μm) emissions from combustion, but the extent of reduction is dependent on biomass type. The reduction of PM₁ from the combustion of torrefied biomass is mainly because that the torrefaction process removes some Cl and S from the biomass, thereby suppressing the release of alkali metals and the emissions of PM₁ during the combustion process. As for PM_1–10 (particulates with an aerodynamic diameter within 1–10 μm), its emissions from combustion of torrefied biomasses are consistently reduced, compared with their untreated counterparts. This observation is primarily accounted for the enhanced particle coalescence/agglomeration in combustion of torrefied biomasses, which reduces the emissions of PM_1–10.

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