焚化灰渣作為水泥生料對卜特蘭水泥影響之研究

Abstract

焚化處理儼然已成台灣未來都市廢棄物處理之主流，目前台灣對於焚化灰渣仍以掩埋處理為主，相對於其他先進國家積極開發灰渣資源化，台灣在這方面稍嫌落後。近年來水泥產業在廢棄物處理上扮演重要角色，考量飛灰與底渣在主要化學成份CaO、SiO2、Al2O3及Fe2O3與水泥主要成份相似，飛灰與底渣可作為水泥之原料；利用水泥窯高溫燒結方式燒成水泥熟料且將重金屬固封於水泥礦物中，使灰渣達無害化。

研究顯示焚化灰渣含大量氯鹽、硫化物、P2O5與重金屬，會造成旋窯堵塞與影響水泥品質。本研究以水洗（L/S=10、15 min）搭配醋酸酸洗（L/S=20、醋酸濃度0.1 M、30 min）方式進行，可有效減少焚化灰渣氯鹽及少部分SO3。處理後之飛灰與底渣氯含量為5749 ppm及2876 ppm，針對本研究所採集之灰渣樣品，若將生料中總氯含量控制在100 ppm，則飛灰與底渣最大添加量為1.75%及3.5%。生料經混合、造粒、燒結後，即為水泥熟料，其中熟料礦物分析與未添加灰渣之水泥熟料相比並無太大差異。水泥品質檢驗顯示添加飛灰與底渣會稍微降低水泥易磨性與抗壓強度，且有延緩凝結時間之現象發生。整體來說，除凝結時間受燒成過當之影響，造成初凝與終凝有緩凝超過標準之現象外，其餘均符合CNS 61Ⅱ型水泥規範。

In Taiwan, landfill disposal and solidification are two major strategies for MSWI ash disposal. However, MSWI ash is rich in heavy metals and salts, which may cause serious environmental problem if without proper treatment. Recently, cement industry has played an important role in the disposal of solid wastes because it can utilize various kinds of wastes as fuels or raw materials. In addition, the heavy metals can be safely captured in the cement clinker. In this study, the feasibility of incorporating MSWI fly ash and bottom ash into cement clinker was evaluated. Sintering process was attempted to simulate the cement making. The goal of this study is to find a practical way to dispose the MSWI ash.

The chemical property of the incineration ash was analyzed. The MSWI ash was washed with water and acid to remove the chlorides in order to prevent the clogging and the rusting of the cement kiln. The greatest chloride removal was achieved by a 15 min water washing at L/S=10 followed by a 30 min wash with 0.1 M acetic acid at L/S=20. After the pre-treatment, various amount of the ash was added to replace the clay component of the cement raw material. The effect of its addition on sintering condition and the quality of the Portland cement were evaluated.

The maximum percentage of fly ash and bottom ash could be added were 1.75﹪and 3.50﹪, respectively. The results showed that the compressive strength of the clinker with fly ash and bottom ash addition was similar to that of the blank sample. However, the setting time of the masonry was much longer. All cement products conformed to the Chinese National Standard of second degree Portland cement, with one exception that the setting time of the clinker was much longer.