Xu Chunbao, Lancaster Jody
Department of Chemical Engineering, Lakehead University, Thunder Bay, Ont., Canada P7B 5E1.
Water Res. 2008 Mar;42(6-7):1571-82. doi: 10.1016/j.watres.2007.11.007. Epub 2007 Nov 17.
The present work demonstrated that secondary pulp/paper sludge powder, with a higher heating value of 18.3MJ/kg on a dry basis, could be effectively converted into liquid oil products by direct liquefaction in hot-compressed water with and without catalyst. Treatments of secondary pulp/paper sludge in water at 250-380 degrees C for 15-120min in the presence of N(2) atmosphere resulted in yields of water-soluble oils at 20-45wt% and yields of heavy oils at 15-25wt%, with higher heating values of 10-15 and >35MJ/kg, respectively. The higher caloric values for the heavy oil products were accounted for by their compositions of long-chain carboxylic acids, heterocyclic nitrogen compounds and phenolic compounds and derivatives as evidenced by the gas chromatograph (GC)/MS measurements. The liquefaction product yields were significantly influenced by the liquefaction temperature, the residence time, the initial biomass concentration, catalysts and the liquefaction atmosphere (inert or reducing). Within the temperature range (250-380 degrees C) tested, the lowest temperature produced the highest yield of total oils (at 60wt%), while the greatest yield of heavy oil (at about 24wt%) was obtained at 350 degrees C. If the temperature was fixed at 280 degrees C, a greater yield of heavy oil (reaching as high as 25wt% for 120min) was obtained as the length of reaction time increased. Similarly, a higher initial biomass concentration produced a greater yield of heavy oil but a reduced yield of water-soluble oil. The presence of 0.1M K(2)CO(3) dramatically enhanced organic conversion, but suppressed the formation of both heavy oil and water-soluble oil. The use of the two alkaline earth metal catalysts, i.e., Ca(OH)(2) and Ba(OH)(2), did not alter organic conversion, but it catalyzed the formation of water-soluble oil and produced higher yields of total oil products. It was also demonstrated that the reducing atmosphere (i.e., H(2)) in the liquefaction process promoted the heavy oil formation while suppressing the water-soluble oil formation. With the presence of 0.1M Ca(OH)(2) and 2MPa H(2), liquefaction of the sludge powder in water at 280 degrees C for 60min produced a higher yield of heavy oil (26wt%), almost two times as high as that in N(2) (13.6wt%), resulting in a greater net energy efficiency. It was thus suggested that direct liquefaction of secondary pulp/paper sludge in hot-compressed water with Ca(OH)(2) catalyst and in the presence of H(2) could be an effective approach to recovering energy from the waste for production of liquid oil products.
目前的研究表明，二次纸浆/造纸污泥粉末在干燥基上具有18.3MJ/kg的较高热值，在有或没有催化剂的情况下，通过在热压缩水中直接液化可有效地转化为液体油产品。在N₂气氛下，将二次纸浆/造纸污泥在250 - 380℃的水中处理15 - 120分钟，水溶性油的产率为20 - 45wt%，重油产率为15 - 25wt%，其较高热值分别为10 - 15MJ/kg和>35MJ/kg。气相色谱（GC）/质谱测量表明，重油产品的较高热值是由其长链羧酸、杂环氮化合物以及酚类化合物和衍生物的组成所致。液化产物产率受液化温度、停留时间、初始生物质浓度、催化剂和液化气氛（惰性或还原性）的显著影响。在所测试的温度范围（250 - 380℃）内，最低温度产生的总油产率最高（60wt%），而在350℃时获得的重油产率最高（约24wt%）。如果温度固定在280℃，随着反应时间延长，重油产率更高（120分钟时高达25wt%）。同样，较高的初始生物质浓度产生较高的重油产率，但水溶性油产率降低。0.1M K₂CO₃的存在显著提高了有机转化率，但抑制了重油和水溶性油的形成。使用两种碱土金属催化剂，即Ca(OH)₂和Ba(OH)₂，并没有改变有机转化率，但催化了水溶性油的形成并产生了更高的总油产品产率。还表明，液化过程中的还原性气氛（即H₂）促进了重油的形成，同时抑制了水溶性油的形成。在0.1M Ca(OH)₂和2MPa H₂存在的情况下，污泥粉末在280℃的水中液化60分钟产生了更高的重油产率（26wt%），几乎是在N₂中（13.6wt%）的两倍，从而产生了更高的净能量效率。因此，建议在Ca(OH)₂催化剂和H₂存在的情况下，将二次纸浆/造纸污泥在热压缩水中直接液化可能是从废物中回收能量以生产液体油产品的有效方法。
