This study aims to determine the fate of P during fluidized bed co-combustion of chicken litter (CL) with K-rich fuels [e.g., wheat straw (WS)] and Ca-rich fuels (bark). The effect of fuel blending on phosphate speciation in ash was investigated. This was performed by chemical characterization of ash fractions to determine which phosphate compounds had formed and identify plausible ash transformation reactions for P. The ash fractions were produced in combustion experiments using CL and fuel blends with 30% CL and WS or bark (B) at 790–810 °C in a 5 kW laboratory-scale bubbling fluidized bed. Potassium feldspar was used as the bed material. Bed ash particles, cyclone ash, and particulate matter (PM) were collected and subjected to chemical analysis with scanning electron microscopy–energy-dispersive X-ray spectrometry (SEM–EDS) and X-ray diffraction. P was detected in coarse ash fractions only, that is, bed ash, cyclone ash, and coarse PM fraction (>1 μm); no P could be detected in the fine PM fraction (<1 μm). SEM–EDS analysis showed that P was mainly present in K–Ca–P-rich areas for pure CL as well as in the ashes from the fuel blends of CL with WS or B. In the WS blend, P was found together with Si in these areas. The crystalline compound containing P was hydroxyapatite in all cases as well as whitlockite in the cases of pure CL and WS blend, of which the latter compound has been previously identified as a promising plant nutrient. The ash fractions from CL and bark blend only contained P in hydroxyapatite. Co-combustion of CL together with WS appears to be promising for P recovery, and ashes with this composition could be further studied in plant growth experiments.

中文翻译：

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磷与小麦秸秆和树皮残渣流化床燃烧中的磷命运

这项研究的目的是确定鸡粪（CL）与富含K的燃料[例如麦秸（WS）]和富含Ca的燃料（树皮）在流化床共燃烧过程中P的命运。研究了燃料混合对灰分中磷酸盐形态的影响。这是通过对灰分的化学表征来确定哪些磷酸盐化合物已形成并确定P的灰分转化反应而进行的。灰分是在燃烧实验中使用CL以及30％CL和WS或树皮（B）的燃料混合物进行燃烧的在5 kW实验室规模的鼓泡流化床中，温度为790–810°C。长石钾用作床层材料。床灰，旋风灰，收集颗粒物（PM）并通过扫描电子显微镜-能量色散X射线光谱仪（SEM-EDS）和X射线衍射进行化学分析。仅在粗灰分中检测到P，即床灰，旋风灰和粗PM分（> 1μm）；在精细的PM组分（<1μm）中未检测到P。SEM-EDS分析表明，对于纯CL来说，P主要存在于富含K-Ca-P的区域以及CL与WS或B的燃料混合物的灰烬中。在WS混合物中，P与Si一起被发现在这些地区。在所有情况下，含P的结晶化合物均为羟基磷灰石，而在纯CL和WS混合物的情况下，含辉石的晶体均为磷灰石，后者先前已被确定为有希望的植物营养素。来自CL和树皮混合物的灰分仅在羟基磷灰石中包含P。CL与WS的共燃烧对于磷的回收似乎是有希望的，并且可以在植物生长实验中进一步研究这种组成的灰烬。