The necessity of recycling anthropogenically used phosphorus to prevent aquatic eutrophication and decrease the economic dependency on mined phosphate ores encouraged recent research to identify potential alternative resource pools. One of these resource pools is the ash derived from the thermochemical conversion of sewage sludge. This ash is rich in phosphorus, although most of it is chemically associated in a way where it is not plant available. The aim of this work was to identify the P recovery potential of ashes from sewage sludge co-conversion processes with two types of agricultural residues, namely wheat straw (rich in K and Si) and sunflower husks (rich in K), employing thermodynamic equilibrium calculations. The results indicate that both the melting behavior and the formation of plant available phosphates can be enhanced by using these fuel blends in comparison with pure sewage sludge. This enhanced bioavailability of phosphates was mostly due to the predicted formation of K-bearing phosphates in the mixtures instead of Ca/Fe/Al phosphates in the pure sewage sludge ash. According to the calculations, gasification conditions could increase the degree of slag formation and enhance the volatilization of K in comparison with combustion conditions. Furthermore, the possibility of precipitating phosphates from ash melts could be shown. It is emphasized that the results of this theoretical study represent an idealized system since in practice, non-equilibrium influences such as kinetic limitations and formation of amorphous structures may be significant. However, applicability of thermodynamic calculations in the prediction of molten and solid phases may still guide experimental research to investigate the actual phosphate formation in the future.

回收人为使用的磷以防止水体富营养化并减少对开采的磷矿的经济依赖的必要性鼓励了最近的研究，以确定潜在的替代资源池。这些资源库之一是来自污水污泥热化学转化的灰分。这种灰分富含磷，尽管大多数以化学方式缔合，而这种灰分是植物无法获得的。这项工作的目的是利用热力学平衡来确定污水污泥与两种农业残余物（麦秸（富含钾和硅）和向日葵壳（富含钾））的共转化过程中灰分的磷回收潜力。计算。结果表明，与纯净污泥相比，使用这些燃料混合物可以提高熔融态和植物有效磷酸盐的形成。磷酸盐提高的生物利用度主要是由于预计在混合物中形成了含钾的磷酸盐，而不是在纯净的污水污泥中形成了Ca / Fe / Al磷酸盐。根据计算，与燃烧条件相比，气化条件可以增加炉渣的形成程度，并增加钾的挥发。此外，可以显示出从灰熔体中沉淀出磷酸盐的可能性。要强调的是，该理论研究的结果代表了一个理想化的系统，因为在实践中，非平衡影响（例如动力学限制和非晶结构的形成）可能很重要。