National Laboratory of Energy and Geology, Estrada Paço Lumiar, 22, Ed. J, 1649-038 Lisbon, Portugal; Department of Environment and Planning, Centre for Environmental and Marine Studies, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
National Laboratory of Energy and Geology, Estrada Paço Lumiar, 22, Ed. J, 1649-038 Lisbon, Portugal.
Waste Manag. 2015 Dec;46:304-15. doi: 10.1016/j.wasman.2015.08.036. Epub 2015 Sep 3.
Bottom and fly ashes streams collected along a year in several biomass thermal plants were studied. The bulk composition of ashes and other chemical characteristics that may impact soil application showed a high variability depending on the ash stream, combustion technology and ash management practice at the power plants. The acid neutralization capacity (ANC) and metal's availability for leaching at fixed pH 7 and 4 was performed according with EA NEN 7371, as a quick evaluation method to provide information on the long-term behavior of ashes, regarding heavy metals and also plant nutrients release. Also the pH dependence leachability study was performed according to CEN/TS 14429 for predicting the leaching behavior under different scenarios. Leachability profiles were established between pH 3 and 12, allowing to distinguish different solubility control phenomena of toxic heavy metals (Cu, Cr, Mn, Ni, Zn, Pb) as well as other salts (Ca, K, Mg, Na, Cl). The ANC of fly ashes at pH 4 (3.6-9.6 molH(+)/kg) were higher than that observed for the bottom ashes (1.2-2.1 molH(+)/kg). Ashes were also characterized for persistent organic pollutants (POP), such as polycyclic aromatic hydrocarbons (PAH) and paradibenzodioxines and furanes (PCDD/F). Contents were found to be much higher in fly ash than in bottom ash streams. None of the PAH levels did reach the current national limit value of sewage sludge application in soils or the guide value for ash in north European countries. However, PCDD/F contents, which are not regulated, varied from non-detectable levels to high amounts, regardless the level of loss on ignition (LOI) or unburned carbon content in fly ashes. Given the current ash management practices and possible use of blends of bottom and fly ash streams as soil conditioners resembles clear the urgent need to regulate ash utilization in soils, incorporating limit values both for heavy metals, PAH and PCDD/F.
在数座生物质热能发电厂，我们对一整年采集的底灰和飞灰进行了研究。灰分的总体成分和其他可能影响土壤应用的化学特性，显示出高度的变异性，这取决于灰分流、燃烧技术和发电厂的灰分管理实践。酸中和能力（ANC）和固定 pH 值 7 和 4 下金属浸出的可用性，根据 EA NEN 7371 进行，作为一种快速评估方法，提供关于灰分的长期行为的信息，涉及重金属以及植物养分的释放。此外，还根据 CEN/TS 14429 进行了 pH 依赖性浸出研究，以预测不同情况下的浸出行为。在 pH 3 和 12 之间建立了浸出率曲线，允许区分毒性重金属（Cu、Cr、Mn、Ni、Zn、Pb）以及其他盐（Ca、K、Mg、Na、Cl）的不同溶解控制现象。飞灰在 pH 4 时的 ANC（3.6-9.6 molH(+)/kg）高于底灰（1.2-2.1 molH(+)/kg）。还对持久性有机污染物（POP）进行了灰分特性研究，如多环芳烃（PAH）和对二苯并二恶英和呋喃（PCDD/F）。发现飞灰中的含量远高于底灰流。在 PAH 水平方面，没有任何一种达到当前国家规定的污水污泥在土壤中的应用限值或北欧国家对灰分的指导值。然而，未被监管的 PCDD/F 含量，无论飞灰的灼烧损失（LOI）或未燃烧碳含量水平如何，都从无法检测到的水平到大量水平不等。鉴于当前的灰分管理实践和可能将底灰和飞灰混合用作土壤调节剂，很明显，迫切需要对灰分在土壤中的利用进行监管，为重金属、PAH 和 PCDD/F 都制定限值。
