基于污泥调理-脱水-热解工艺的铁修饰污泥生物炭循环响应特性及机理研究

Sludge conditioning, dewatering and pyrolysis are important in sludge treatment and disposal, respectively. Currently, most of the skeleton builders for sludge dewatering and materials for sludge co-pyrolysis are foreign substances, increasing the difficulty of collecting raw materials. Meanwhile, the systematic technology of sludge conditioning-dewatering-pyrolysis which could improve sludge pyrolysis have not yet formed. In other words, the sludge pre-treatment is disconnected with sludge disposal. And the mechanism of sludge conditioners in all system of sludge treatment and disposal is not clear. In this study, the Fe-embedded sludge biochar which is the product of sludge pyrolysis used in sludge conditioning-dewatering-pyrolysis is investigated. The mechanisms of Fe-embedded sludge biochar for improving sludge dewaterability and efficiency of pyrolysis were analyzed. The cycled evolution properties of Fe-embedded sludge biochar was studied by characterization analysis of solid particle in this system. The function of Fe-embedded sludge biochar on each link of sludge conditioning-dewatering-pyrolysis was analyzed to illustrate the responding mechanism of Fe-embedded sludge biochar as conditioner and product. The expected results will promote the sludge treatment and disposal.

污泥调理、脱水、热解分别在污泥处理与处置中具有重要地位。目前，促进污泥脱水的骨架调理剂和促进污泥热解的共热解物质大多采用外源物质颗粒，增加了调理剂原材料的收集难度；同时，以污泥热解为目标的污泥调理-脱水-热解系统工艺尚未形成，即污泥前处理与后续资源化处置方式脱节，污泥调理剂在整个系统工艺中的作用机制尚不清晰。本项目以污泥热解产物——铁修饰污泥生物炭循环制备和应用于污泥调理-脱水-热解工艺作为切入点，探讨铁修饰污泥生物炭的调理-催化作用，分析其在各环节的促进作用机制；通过对循环系统中每一环节产生的固体颗粒的表征分析，阐明铁修饰污泥生物炭的循环演变特性；同时，通过分析铁修饰污泥生物炭对系统各环节之间的关联作用机制，阐明铁修饰污泥生物炭作为过程“参与物”与系统“产物”之间的响应机制。预期成果将对污泥处理与资源化处置具有重要的推动作用。

目前，以污泥热解为目标的污泥调理-脱水-热解系统工艺尚未形成，污泥调理剂在整个系统工艺中的作用机制尚不清晰。本研究以污泥热解产物——铁修饰污泥生物炭循环制备和应用于污泥调理-脱水-热解工艺作为切入点，明确了铁修饰污泥生物炭在污泥调理脱水和热解环节的作用，并明确了其在各环节的促进作用机制；通过分析铁修饰污泥生物炭对系统各环节之间的关联作用机制。研究结果得出，三氯化铁单独调理城市剩余污泥-脱水-热解时，三氯化铁投加量128.21 g/kg DS、热解温度900 ℃、热解时间20 min、泥饼含水率31.53%，污泥热解产气效果最佳；三氯化铁与铁修饰污泥生物炭联合调理城市剩余污泥-脱水-热解时，三氯化铁投加量64.10 g/kg DS、铁修饰污泥生物炭投加量90% DS、泥饼含水率79%（联合调理泥饼原含水率），污泥热解产气效果最佳。铁修饰污泥生物炭对污泥脱水有明显的促进效果，能有效降低污泥Zeta电位的绝对值，使污泥更容易发生絮凝；铁修饰污泥生物炭的投加能有效提高污泥泥饼的渗透性，减轻了污泥滤液后续处理的难度；且铁修饰污泥生物炭调理污泥成本低廉，经济可行。铁修饰污泥生物炭参与调理过程后，污泥热解产气率与气体的低位热值明显提高，且与单加FeCl3相比，联合调理所需的FeCl3含量明显降低，这说明铁修饰污泥生物炭的加入降低了以热解为目标的污泥调理-脱水-热解系统中调理剂FeCl3的使用量，并且铁修饰污泥炭抑制了含N污染物的释放，降低了污泥热解所需的活化能，对污泥热解起到一定的催化作用。此研究对污泥处理与资源化处置应用打下理论基础。