下水污泥添加H3BO3以低溫共燒技術燒製輕質骨材之特性研究

下水污泥的處理為城市發展的重要課題，在眾多污泥處理技術中，熔融燒結法可將污泥燒結成輕質骨材，作為建築材料再利用，但該處理法具有高耗能的缺點。本研究嘗試以下水污泥為原料，經過調整SiO2/Al2O3比例為4後，加入H3BO3，在900℃以下進行燒結形成輕質骨材，並測試骨材之吸水率、視孔隙率、體密度、抗壓強度、健性及鹼反應性等性質。H3BO3可促進污泥在低溫形成黏滯玻璃相而包覆內部產生的氣體，形成輕質骨材，但因黏滯玻璃相阻隔氧氣擴散進入試體內部，故使骨材產生黑心現象。依據實驗結果顯示，添加CaO使CaO／污泥＝0.03，有助於維持試體中氧氣擴散通道而消除黑心現象。當污泥加入3％CaO、13％H3BO3在400℃持溫30min，850℃燒結60min可得到抗壓強度最高之骨材，其吸水率、視孔隙率、體密度、抗壓強度分別為3.88％、3.93％、1.05g/cm^3、29.7MPa，而在同樣的配比下，以400℃持溫30min，900℃燒結15min可得密度最小之輕質骨材，其吸水率等四項性質分別為1.49％、1.47％、0.76g/cm^3、11.4MPa。兩種燒結方式所得之骨材符合CNS對粒料健性與鹼反應性的要求，顯示污泥可藉低溫共燒技術，在900℃以下燒製成高抗壓與低吸水、低密度之輕質骨材。

關鍵字

下水污泥；輕質骨材；低溫共燒； H3BO3

並列摘要

Sewage sludge disposal is an important issue for modern city development. Current researches were focused on sludge recycling as lightweight aggregates by sintering above 1000℃. In our study, SiO2 was added to the sludge to a SiO2/Al2O3 ratio at 4, then. H3BO3 and CaO were added as a flux and black core eliminating agent. The mixture was preheated at 400℃ for 30min and sintered under 900℃. The characteristics of synthetic aggregates such as water adsorption, apparent porosity, bulk density, compressive strength, soundness, and silicon-alkalinity reactivity were determined with CNS methods. The aggregate of higher compressive strength was synthesized at 850℃. The water adsorption rate was 3.88%, apparent porosity was 3.93%,, bulk density was 1.05g/cm^3, and compressive strength was 29.7 MPa. The lower bulk density was obtained at 900℃. The water adsorption rate was 1.49%, apparent porosity was 1.47%,, bulk density was 0.76g /cm^3, and compressive strength was 11.4MPa. All aggregates met the requirement of soundness and silicon-alkalinity reactivity of CNS. Sewage sludge can be recycled and sintered at lower temperature, and the synthetic aggregate satisfies the requirement of construction material.

並列關鍵字

sewage sludge ； lightweight aggregates ； co-melting technology ； H3BO3

國際替代計量

下水污泥添加H3BO3以低溫共燒技術燒製輕質骨材之特性研究

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