沼渣生物炭在甲苯吸附與固體再生燃料的應用

Abstract

沼渣是厭氧消化的副產物，沼渣中剩餘未消化完全的豐富有機物含量使其具有資源再利用的價值。生物炭是一種具有豐富孔隙結構且富含碳的材料，利用生物質在隔絕氧氣的狀態下熱解製備而成，被視為經濟且環保的廢物處理和碳封存方案，可作為沼渣的去化管道。本研究分別利用豬糞尿沼渣以及豬糞尿與農業廢棄物共消化的沼渣作為作為生產生物炭的原料，經過高溫熱解後製備而成的生物炭，先進行甲苯吸附，再將吸附飽和的生物炭作為燃料使用。 在熱解之前對固體沼渣採用碳酸鉀浸漬的方法進行前處理，用以提升生物炭的表面性質，該方法旨在改善生物炭的孔隙特性和甲苯的吸附能力。生物炭通過慢熱解法在500至800°C的溫度下製備而成。結果表明，透過碳酸鉀浸漬後的沼渣做為原料製備而成的生物炭具有非常高的比表面積，最高達到1673 m2/g，並表現出優異的甲苯吸附能力，最高達到876 mg/g。 在熱解溫度800°C下製備的改質生物炭的淨熱值為8030 kcal/kg，在經過甲苯吸附後，吸附飽和的生物炭的淨熱值提高到9070 kcal/kg，提升了1040 kcal/kg。這一發現表明，生物炭孔隙內所吸附的甲苯可以在作為燃料利用時產生能量，進而增加生物炭整體的淨熱值。沼渣製備生物炭是一種有效的去化方式，不僅可以控制甲苯排放，還能進一步作為固體再生燃料，實現廢棄物再利用和延長生命週期，達成循環經濟的願景。

Digestate is a by-product of anaerobic digestion. The abundance of organic matter content in digestate has generated significant potential for its resource valorization. Biochar is a highly porous and carbon-rich material, which has been seen as an economical and environmentally friendly solution to waste disposal, carbon sequestration, and the treatment of digestate. This study utilized two different types of solid digestate: one derived from pig manure and the other derived from a mixture of pig manure with agricultural waste as the raw materials for producing biochar. Biochar prepared through high-temperature pyrolysis was first employed for the adsorption of toluene, and then the adsorbed saturated biochar was used as fuel. The modification method of potassium carbonate impregnation was employed on solid digestate prior to pyrolysis as a means to enhance the properties of the biochar. This approach aimed to improve the characteristics of biochar and the performance of adsorption toluene. The biochar was produced through slow pyrolysis at temperatures ranging from 500 to 800°C. The results showed that the biochar produced from digestate exhibited a remarkably high specific surface area, reaching up to 1673 m2/g, and demonstrated excellent toluene adsorption capacity, reaching 876 mg/g. The low heating value (LHV) of modified biochar produced at 800°C was 8030 kcal/kg. After the adsorption of toluene, the LHV of the biochar increased to 9070 kcal/kg, representing a 1040 kcal/kg enhancement. This finding demonstrates that the adsorption of toluene within the pores of biochar can increase LHV. The preparation of biochar from digestate is an effective management of waste treatment that is not only appropriate for the control of toluene emissions but also enables its utilization as a solid renewable fuel, thus facilitating waste reuse and extending its life cycle, thereby achieving the circular economy.