Sewage sludge derived fertilizer is a promising solution for phosphorus (P) recovery from biowaste, however, the inherent iron content in the sludge ash (SSA) impedes the P availability of the fused calcium magnesium phosphate fertilizer (FCMP). To achieve the goal of iron removal during the process, carbothermal reduction was adopted for the first time and the performance of carbon addition was systematically evaluated. Results showed that carbon addition at 4.50 % significantly increased the P availability from 9.50 % to 11.00 % and decreased the required amounts of calcium/magnesium. Moreover, ferrophosphate with 20.20 % P can be produced and the melting point of the system can be reduced by manipulating carbon addition. Finally, a process design was provided for the co-production of FCMP and ferrophosphate. This study highlights the addition of carbon to facilitate iron removal in SSA for the production of FCMP with enhanced bioavailability at a reduced energy consumption scenario.

中文翻译：

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优化污水污泥灰中的除铁以提高磷肥的生物利用率


污水污泥衍生肥料是从生物废物中回收磷 (P) 的一种有前途的解决方案，然而，污泥灰分 (SSA) 中固有的铁含量阻碍了电熔钙镁磷肥 (FCMP) 的磷利用率。为了实现工艺过程中除铁的目标，首次采用碳热还原，并对加碳性能进行了系统评价。结果表明，添加 4.50% 的碳显着地将磷的有效性从 9.50% 提高到 11.00%，并降低了钙/镁的需求量。此外，还可以生产含磷量为20.20%的磷酸铁，并且通过控制碳的添加可以降低体系的熔点。最后，提出了FCMP和磷酸铁联产的工艺设计。本研究强调添加碳以促进 SSA 中的铁去除，从而生产 FCMP，并在降低能耗的情况下提高生物利用度。