pH调控预水解对蔬菜废物机械破碎能耗的影响

Effect of pH regulated Pre hydrolysis on the Energy Consumption of Mechanical Size Reduction of Vegetable Wastes

摘要:

采用控制初始pH值分别为5，6，7，8和9的泔水滤液预水解蔬菜废物，研究原样和预水解后废物的机械破碎能耗.结果表明：在pH 值为7，8和9的工况下，蔬菜废物的机械破碎能耗由原样的0.304 J·g-1（湿基）下降至0.032，0.025和0.027 J·g-1（湿基），下降幅度近90%；而pH值为5和6的工况下的机械破碎能耗仅下降至0.200和0.219 J·g-1（湿基）.在8 h预水解过程中，pH值为6，7，8和9工况的液相pH值、总有机碳、挥发性脂肪酸和氨氮的质量浓度以及固相木质纤维素的质量分数没有显著变化，说明蔬菜废物未发生显著的生物水解；溶胀吸水和纤维素在碱性环境下结构变化而造成的强度降低可能是蔬菜废物机械破碎能耗下降的主要原因.

Abstract:

Pre hydrolysis of vegetable wastes was conducted with swill at different initial pH equal to 5, 6, 7, 8, and 9, and then the energy consumption of mechanical size reduction of raw and pre hydrolysed vegetable wastes was studied. Experimental results showed that at initial pH equal to 7, 8 and 9, the energy consumptions of vegetable wastes after pre hydrolysis were decreased from the original 0.304 J·g-1(wet basis) to 0.032, 0.025 and 0.027 J·g-1(wet basis), respectively, which declined by up to 90%; while those at initial pH equal to 5 and 6 slightly dropped to 0.200 and 0.219 J·g-1(wet basis). During the 8 h pre hydrolysis at initial pH equal to 6, 7, 8 and 9, the pH and mass concentration of total organic carbon, volatile fatty acids and ammonia nitrogen in the liquid phase as well as the mass fraction of lignocellulose in the solid phase had little variations, indicating that the effect of biotic hydrolysis was not obvious. The swelling and moisture absorbing and the structural change of celluloses under alkaline conditions, which can reduce the strength of lignocellulosic material, might be the main reasons for the decrease of energy consumption for mechanical size reduction.