Yang Qingfeng, Dussan Karla, Monaghan Rory F D, Zhan Xinmin
Civil Engineering, National University of Ireland Galway, Galway, Ireland; Ryan Institute for Environmental, Marine and Energy Research, National University of Ireland Galway, Galway, Ireland and Centre for Marine and Renewable Energy (MaREI), Galway, Ireland.
Mechanical Engineering, National University of Ireland Galway, Galway, Ireland E-mail:
Water Sci Technol. 2016;74(3):672-80. doi: 10.2166/wst.2016.251.
Sewage sludge is a by-product generated from municipal wastewater treatment (WWT) processes. This study examines the conversion of sludge via energy recovery from gasification/combustion for thermal treatment of dewatered sludge. The present analysis is based on a chemical equilibrium model of thermal conversion of previously dewatered sludge with moisture content of 60-80%. Prior to combustion/gasification, sludge is dried to a moisture content of 25-55% by two processes: (1) heat recovered from syngas/flue gas cooling and (2) heat recovered from syngas combustion. The electricity recovered from the combined heat and power process can be reused in syngas cleaning and in the WWT plant. Gas temperature, total heat and electricity recoverable are evaluated using the model. Results show that generation of electricity from dewatered sludge with low moisture content (≤ 70%) is feasible within a self-sufficient sludge treatment process. Optimal conditions for gasification correspond to an equivalence ratio of 2.3 and dried sludge moisture content of 25%. Net electricity generated from syngas combustion can account for 0.071 kWh/m(3) of wastewater treated, which is up to 25.4-28.4% of the WWT plant's total energy consumption.
污水污泥是城市污水处理（WWT）过程产生的副产品。本研究考察了通过气化/燃烧进行能量回收将污泥转化用于脱水污泥热处理的情况。目前的分析基于先前脱水污泥（含水率60 - 80%）热转化的化学平衡模型。在燃烧/气化之前，污泥通过两种方式干燥至含水率25 - 55%：（1）从合成气/烟气冷却中回收的热量；（2）从合成气燃烧中回收的热量。从热电联产过程中回收的电力可再用于合成气净化和污水处理厂。使用该模型评估了气体温度、可回收的总热量和电力。结果表明，在自给自足的污泥处理过程中，由低含水率（≤70%）的脱水污泥发电是可行的。气化的最佳条件对应于当量比为2.3且干燥污泥含水率为25%。合成气燃烧产生的净电力可为每立方米处理后的废水提供0.071千瓦时，这高达污水处理厂总能耗的25.4 - 28.4%。
