| 摘要: | 本研究利用旋轉窯氣化系統探討科學園區污水處理廠產出之廢水污泥，與塑膠固體再生燃料(Solid Recovered Fuels, SRF)共同催化氣化產能之可行性，其中氣化操作條件分別為氣化溫度700 ℃及當量比0.1，廢水污泥與塑膠SRF之摻混比例為1:0.2、1:0.6與1:1。為進一步評估催化氣化產能效率，研究設計以添加5 wt.%橄欖石做為評估試驗，分析項目分別包括產物分布特性、產氣組成特性、產能效率以及污染物(重金屬、硫及氯)排放特性等。
根據氣化試驗結果顯示，廢水污泥之氣化產氣熱值僅約為0.04 MJ/Nm3，當SRF摻混比例至1:1(S-100 %SRF組別)時，其氣體熱值可增加至1.54 MJ/Nm3，就冷燃氣效率分析結果，亦由廢水污泥氣化試驗之0.86 %，增加至SRF摻混比1:1時之7.72 %。添加橄欖石催化劑之試驗結果顯示，前述摻混條件之氣體熱值及冷燃氣效率，分別可提升至2.19 MJ/Nm3及10.75 %。綜合前述結果可知，添加塑膠SRF與橄欖石催化劑，將有助於廢水污泥氣化產能效率之提升。
根據氣化產物中硫與氯之分布特性結果顯示，硫主要分布於固相產物中，約占93-97 %；氯則以液相產物之分布比例較高，約占40-69 %。研究結果亦顯示塑膠SRF摻混比例增加，將增加硫及氯化合物在產物之分布比例。添加橄欖石催化劑之試驗結果顯示，產物中硫含量增加，此係橄欖石貢獻部分之硫含量，至於氯之分布特性，則因橄欖石促進焦油之裂解，致使焦油中的氯釋放與金屬氧化物形成固相之氯化合物，因此，液相產物之氯含量減少，並轉換至固相產物。
根據重金屬物種之分布特性與模擬分析結果顯示，在700 ℃氣化溫度及SRF各種摻混比例條件，本研究分析之重金屬Ba、Cd、Cr、Cu、Ga、In、Mo、Mn、Ni、Pb、Zn，主要以固相之金屬化合物形式存在；液相產物中之重金屬物種預測分析，則以Zn、Cu、Pb、In與Ga之物種為主。此外，根據模擬預測之結果顯示，硫傾向與金屬形成固態化合物(如BaSO₄、PbSO₄與ZnSO₄)，氣態化合物方面則以氯化物及ZnS(g)為主，其中預測之形成物種分別為CdCl2、CuCl與ZnCl2。若氣化反應溫度提高，則形成物種可能生成GaCl3、InCl與PbCl2。綜合重金屬物種形成之預測分析，氣化溫度與氯含量為影響重金屬分布特性之重要因素，且塑膠SRF摻混比例增加，亦明顯促進部分氣相重金屬物種之形成。整體而言，本研究結果已初步掌握廢水污泥與塑膠SRF共同氣化之反應特性與產能效率，同時模擬預測重金屬硫及氯化合物之物種形成與污染排放特性，後續將有助於氣化技術應用於相關產業之推動與發展。
;This study investigated the feasibility of catalytic co-gasification of wastewater sludge from a science park water treatment plant with plastic solid recovered fuel (SRF) using a rotary kiln gasification system. Under the operating conditions of a gasification temperature of 700 °C and an equivalence ratio (ER) of 0.1, the effects of various sludge-to-SRF blending ratios (1:0.2, 1:0.6, and 1:1) were examined. Furthermore, the study evaluated the effects of product distribution, syngas composition, energy conversion efficiency, and pollutant emission characteristics (heavy metals, sulfur, and chlorine) by adding 5 wt.% olivine as a catalyst.
Experimental results demonstrate that the gasification of wastewater sludge alone yields a lower heating value (LHV) of approximately 0.04 MJ/Nm³. However, increasing the SRF blending ratio to 1:1 significantly elevates the LHV to 1.54 MJ/Nm³. Correspondingly, the cold gas efficiency (CGE) improves from 0.86% to 7.72%. Notably, the introduction of an olivine catalyst under the same blending conditions further enhances the LHV and CGE to 2.19 MJ/Nm³ and 10.75%, respectively. In summary, integrating plastic SRF with an olivine catalyst effectively optimizes the energy recovery efficiency of wastewater sludge gasification.
Based on the distribution characteristics of sulfur and chlorine in the gasification products, sulfur is primarily distributed in the solid-phase products, accounting for approximately 93-97%; chlorine exhibits a higher distribution proportion in the liquid-phase products, accounting for approximately 40-69%. The results also indicate that increasing the blending ratio of plastic SRF will increase the distribution proportion of sulfur and chlorine compounds in the products. Experiments with olivine catalyst addition showed an increase in sulfur content in the products, attributed to the olivine′s sulfur content. Regarding chlorine distribution characteristics, olivine promotes tar cracking, releasing chlorine from the tar to form solid-phase chlorine compounds with metal oxides. Therefore, chlorine content in liquid-phase products decreases and shifts to solid-phase products.
Based on the distribution characteristics of heavy metal species and simulation analysis results, under the conditions of 700°C gasification temperature and various SRF blending ratios, the heavy metals analyzed in this study—Ba, Cd, Cr, Cu, Ga, In, Mo, Mn, Ni, Pb, and Zn—primarily exist as solid-phase metal compounds. Predictive analysis of heavy metal species in liquid-phase products indicates that Zn, Cu, Pb, In, and Ga are the predominant species. According to simulated predictions, sulfur tends to form solid compounds with metals (e.g., BaSO₄, PbSO₄, ZnSO₄), while gaseous compounds are predominantly chlorides and ZnS(g). Predicted gaseous species include CdCl₂, CuCl, and ZnCl₂. Increased gasification temperatures may generate additional species such as GaCl₃, InCl, and PbCl₂. The comprehensive analysis of heavy metal species formation indicates that gasification temperature and chlorine content are key factors influencing heavy metal distribution characteristics. Notably, increasing the SRF plastic blending ratio significantly promotes the formation of certain gaseous heavy metal species. Overall, this study has preliminarily characterized the reaction properties and energy efficiency of co-gasification between wastewater sludge and plastic SRF. Simultaneously, it simulated and predicted the formation of metal sulfide and chloride compounds along with their pollutant emission characteristics. These findings will facilitate the promotion and development of gasification technology applications in relevant industries. |
