Laaongnaun Sunthorn, Patumsawad Suthum
Department of Mechanical & Aero-space Engineering, Faculty of Engineering, King Mongkut University of Technology North Bangkok, Bangkok 10800, Thailand.
Heliyon. 2022 Aug 22;8(8):e10392. doi: 10.1016/j.heliyon.2022.e10392. eCollection 2022 Aug.
This research study examines the levels of particulate matter (PM) which result when two different unprocessed agricultural waste products were burned in a fixed bed combustor under varied air supply conditions. The properties of the PM emissions obtained are: 1) the overall number/mass concentration along with the emission factors (EFs), 2) the distribution of the number and mass size, and 3) the establishment of the morphology of the particles and the trace elements they contain. The findings indicated a total concentration of 3.1 ± 1.9×10 and 9.6 ± 4.5×10 particles/cm (or number EFs = 3.52×10-2.26×10 and 1.88-5.65×10 particles/kg), whereas the total particle mass was found to be in the range of 5.51-10.4 and 1.45-6.08 mg/m (or mass EFs = 1.58-3.26 g/kg and 0.53-3.37 g/kg) in the case of rice husk and bagasse combustion, respectively. The distribution of the particle sizes was shown to be bimodal for rice husk combustion, but had only a single mode for bagasse combustion. For both fuel types, the predominant particle size emerging during combustion was 0.07μm. From the gravimetric perspective, the dominant sizes were 3.07, 5.13, and 8.09 μm. PM emissions are also affected by the properties of the fuel involved in the combustion process, with ash content, homogeneity of the fuel, and the mineral content all known to be influential factors. It is also understood that the air staging can affect PM emissions during the combustion of rice husks, so a rise in the ratio of secondary air to total air might reduce nanoparticle formation (PM) through a shift to the accumulation mode (PM). The results of assessment of the particle shapes and the evaluation of trace elements showed that the particles formed by the combustion of rice husks were predominantly spherical, which can be explained by the dominance of carbon. In contrast, irregular shapes of particle were obtained in coarse-sized particles and the most dominant element is calcium (Ca) and silicon (Si).
本研究考察了两种不同的未加工农业废弃物在固定床燃烧器中于不同空气供应条件下燃烧时产生的颗粒物（PM）水平。所获得的PM排放特性包括：1）总体数量/质量浓度以及排放因子（EFs）；2）数量和质量粒径分布；3）颗粒形态及其所含微量元素的确定。研究结果表明，稻壳和甘蔗渣燃烧时，颗粒物总浓度分别为3.1±1.9×10和9.6±4.5×10颗粒/cm³（或数量排放因子=3.52×10⁻².26×10和1.88⁻5.65×10颗粒/kg），而颗粒总质量分别在5.51⁻10.4和1.45⁻6.08mg/m³范围内（或质量排放因子=1.58⁻3.26g/kg和0.53⁻3.37g/kg）。稻壳燃烧时粒径分布呈双峰型，而甘蔗渣燃烧时只有一个峰型。对于两种燃料类型，燃烧过程中出现的主要粒径均为0.07μm。从重量分析角度看，主要粒径为3.07、5.13和8.09μm。PM排放还受燃烧过程中所涉及燃料的特性影响，灰分含量、燃料均匀性和矿物质含量均为已知影响因素。还了解到空气分级会影响稻壳燃烧过程中的PM排放，因此二次空气与总空气之比的增加可能会通过向积聚模式（PM）的转变减少纳米颗粒的形成（PM）。颗粒形状评估和微量元素评估结果表明，稻壳燃烧形成的颗粒主要为球形，这可以用碳的主导作用来解释。相比之下，粗颗粒中获得的颗粒形状不规则，最主要的元素是钙（Ca）和硅（Si）。
