Study on Pretreated MSWI Bottom Ash Utilized as Cement Raw Material

• Main Authors: Tz-Hau Guo, 郭子豪
• Other Authors: Chang, Juu-En
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/36864381491678991947

碩士 === 國立成功大學 === 環境工程學系 === 89 === In Taiwan, a large amount of municipal solid waste incinerator (MSWI) bottom ash (BA) is produced each year. MSWIBA is primarily composed of silicon, calcium, aluminum and iron oxides that are similar to cement raw materials. Utilization of MSWIBA as replacement of cement raw materials should be one possible strategy on waste reuses. However, bottom ash contains trace amount of interferences such as heavy metal, sulfate, and chloride. When cement raw material is replaced by MSWIBA, some of the interference might produce adverse effects on cement burning or hydration. In this research, three kinds of pretreatments (water-wash, EDTA-extraction, and heavy fluid separation) were taken on magnet-distracted (MD) MSWIBA to remove interferences indicated previously. Removal efficiency and best operating condition on burning were also investigated. Then, variant replacement percentage samples were burned with best operating condition separately. Finally, hydration characteristics of each burned sample were tested. Therefore, effectiveness of pretreatments and replacements with pretreated MSWIBA could be evaluated as suggestions for future engineering applications. The results are as follows, with 1% (by weight) BA addition to cement raw material, all samples with pretreated MDBA show higher compressive strength than samples with MDBA. It reveals that pretreatments have positive influence on burned material. Even though the BA addition percentage increased to 5%, samples could still meet CNS standard. But when the addition percentage rises up to 15%, the compressive strength of all samples drops dramatically. By crystal phase generation latency and LSF equations, it appears that when the BA addition percentage rises to more than 15%, the latency of C3S generation in clinker drops, and it is the major cause of decrease on the compressive strength of cement. To verify this inference, samples with 15% pretreated BA addition were tuned by substituting calcium oxide. All the tuned clinkers not only have strong strength on x-ray diffraction (XRD) spectrum but also have met CNS compressive strength criteria at 3 and 7 aging days. Therefore, pretreated MSWIBA with appropriate tuning is applicable to cement raw material replacement.