Title: Sewage Sludge Incineration Ash Treatment for Energy and Material Recycle
Date and Time: Friday, January 24. 1:00 p.m.
Location: CHBE Room 202
Speaker: Masahiro ITO, Ph. D, Professional Engineer, General Manager/R&D centre, Sanki Engineering Co., LTD
Abstract
Global warming, resource depletion, food crises, pandemics, and in Japan, population decline and deterioration of infrastructure have become major social issues. We are working on various initiatives to address these challenges, primarily in the fields of sewage treatment and waste management. Some of the sludge generated during sewage treatment is incinerated in facilities with fluidized bed incinerators, resulting in remaining sewage sludge incineration ash. In sewage sludge incineration facilities, problems due to ash adhesion frequently occur, such as defluidization, blockage of exhaust gas ducts, and reduced heat transfer efficiency. To solve these problems, we investigated the adhesion mechanism and control methods of ash at high temperatures using unique experimental equipment. We confirmed that phosphorus promotes the adhesiveness of sewage sludge ash, while iron suppresses the adhesiveness derived from phosphorus. Furthermore, not only chemical effects but also physical effects are important for controlling ash adhesion. By the way, since sewage sludge ash contains an abundance of phosphorus, it is a promising raw material for fertilizer. However, sewage sludge ash also contains trace amounts of heavy metals, which must be below standard regulation levels. Although there are several methods for reducing heavy metals, existing methods are complicated and costly, hindering their market implementation. We explored a simple method to reduce heavy metals in ash, and the Elbow jet air classifier using the Coanda effect is promising due to its purely physical method and particle range adjustability. With the air classifier, we found that finer particles contain more arsenic, cadmium, and lead. The results conclude that ash particles larger than approximately 10 μm are suitable for utilizing sewage sludge ash as fertilizer.
Biography
After obtaining a Master’s degree in Engineering from Tohoku University in 2000, I had over 10 years of experience in the field of air diffuser for wastewater treatment. For the past decade, I have been involved in the development of sewage sludge treatment technologies and utilization technologies of sewage sludge as resources, and obtained my Ph.D. from Tokyo University of Agricultural and Engineering in 2022. Currently, I am involved in two national projects related to converting sewage sludge and sewage sludge incineration ash into fertilizer or animal feed.