Mechanical Engineering Department, Colorado School of Mines, Golden, CO 80401, United States.
Civil and Environmental Engineering Department, Colorado School of Mines, Golden, CO 80401, United States.
Bioresour Technol. 2014 Jun;161:385-94. doi: 10.1016/j.biortech.2014.03.040. Epub 2014 Mar 24.
The successful management of wastewater sludge for small-scale, urban wastewater treatment plants, (WWTPs), faces several financial and environmental challenges. Common management strategies stabilize sludge for land disposal by microbial processes or heat. Such approaches require large footprint processing facilities or high energy costs. A new approach considers converting sludge to fuel which can be used to produce electricity on-site. This work evaluated several thermochemical conversion (TCC) technologies from the perspective of small urban WWTPs. Among TCC technologies, air-blown gasification was found to be the most suitable approach. A gasification-based generating system was designed and simulated in ASPEN Plus® to determine net electrical and thermal outputs. A technical analysis determined that such a system can be built using currently available technologies. Air-blown gasification was found to convert sludge to electricity with an efficiency greater than 17%, about triple the efficiency of electricity generation using anaerobic digester gas. This level of electricity production can offset up to 1/3 of the electrical demands of a typical WWTP. Finally, an economic analysis concluded that a gasification-based power system can be economically feasible for WWTPs with raw sewage flows above 0.093m(3)/s (2.1 million gallons per day), providing a profit of up to $3.5 million over an alternative, thermal drying and landfill disposal.
小型城市污水处理厂（WWTP）的废水污泥的成功管理面临着一些财务和环境方面的挑战。常见的管理策略是通过微生物过程或热量来稳定污泥，以便进行土地处置。这些方法需要大型的处理设施或高能源成本。一种新的方法是将污泥转化为燃料，可用于现场发电。本工作从小型城市 WWTP 的角度评估了几种热化学转化（TCC）技术。在 TCC 技术中，发现鼓风气化是最合适的方法。在 ASPEN Plus®中设计并模拟了基于气化的发电系统，以确定净电和热输出。技术分析确定，使用当前可用的技术可以构建这样的系统。鼓风气化可将污泥转化为效率大于 17%的电力，这是使用厌氧消化器气体发电效率的三倍左右。这种发电水平可以抵消典型 WWTP 的三分之一的电力需求。最后，经济分析得出结论，对于 raw sewage 流量超过 0.093m³/s（210 万加仑/天）的 WWTP，基于气化的电力系统在经济上是可行的，可为替代的热干燥和垃圾填埋处置提供高达 350 万美元的利润。
