【作者】 姜立；

【导师】 毛忠贵；

【作者基本信息】 江南大学 ， 生物化工， 2012， 硕士

【摘要】 本文主要研究“酒精沼气双发酵耦联”工艺中影响酒精发酵的因素,探索厌氧沼液回用的可行方法。通过研究发现,硫酸盐还原产物中的SO32-与S2-均会对酒精发酵产生影响。当发酵液中SO32-的浓度为30mM时,发酵结束时残总糖高达2.25%,淀粉利用率下降到79.66%;随着S2-浓度的增大,发酵醪的残总糖由1.62%增大到2.60%,淀粉利用率也由88.20%下降到79.30%。这两种物质对酒精发酵的不利影响主要是由发酵过程中低pH条件下生成的SO₂和H₂S气体造成的。前者会导致甘油产量增多,最终酒精产量下降,淀粉利用率降低;后者会导致酵母的生命活力下降,严重时会造成酵母细胞破裂死亡,致使发酵过程延迟或停滞,甘油产量上升,淀粉利用率下降。所以厌氧沼液回用过程中对于这些还原态物质必须去除,避免对后期酒精发酵造成影响。厌氧沼液直接回用作为酒精发酵的配料水时,酒精产量比空白低4.49%,对于原料的高效利用不利,因而必须对厌氧沼液进行处理,否则会影响酒精发酵的效果。在现有的几种资源化处理方式中,温和氧化,脱氨处理以及活性炭吸附都能够很好的改善厌氧沼液的发酵效果,最终的酒精产量比空白高1%,是比较有效的资源化方式。考虑到经济性和可操作性,选择温和氧化的方式作为厌氧沼液的处理手段,该方法能耗小。该法处理的厌氧沼液,发酵最终酒精产量（14.50%）与对照（14.47%）相当,满足回用的要求。通过实验优化后发现,适用于工业应用的温和氧化工艺为:55℃,通气,相对真空度为-0.04—-0.05MPa,处理时间160min。假若通气量再增大一些,该处理方式的时间可以适当缩短。用该方法处理过的厌氧沼液,在料水比为1:3时,最终的发酵乙醇产量略优于去离子水配料。发酵过程无异常,甘油产量没有增多,残糖含量<1%。厌氧沼液温和氧化过程pH的上升是由于HCO₃^-分解和CO₃^2-水解造成的,温和氧化的温度越高,pH上升越高;同时厌氧沼液中碱度和铵态氮的比例越大,pH上升越高。温和氧化过程中碱度下降与铵态氮去除同时进行,且二者去除的当量（HCO₃^-和NH₄⁺）相等。pH越高铵态氮去除越干净,铵态氮去除量越大,碱度下降幅度越大,温和氧化处理的终点应为铵态氮浓度小于100mg/L。厌氧沼液中碱度稳定存在依附于体系中的阳离子,这些阳离子主要是NH₄⁺和一些金属阳离子,其中NH₄⁺和Na⁺含量较高分别为32.14mM和30.43mM。通过氢型阳离子树脂交换吸附,能够将碱度完全去除,可以考虑作为一种工业废水处理除碱度的方法。更多还原

【Abstract】 The effect of inhibit factors in Dual Coupling of Ethanol and Methane Fermentation Technology on ethanol fermentation was studied in this article. We explored available alternatives to reuse the anaerobic efflux and laid foundation for the process goes smoothly.Under the research, we found that both sulfite ion and sulfidion inhibited the ethanol fermentation. The remnants of total sugar reached up to 2.25%, and the starch utilization rate dropped to 79.66% at the end of the fermentation when there were 30mM SO₃^2- in the fermentation mash. With the increase of sulfidion’s concentration, the remnants of total sugar reached up to 2.60% from1.62%, and the starch utilization rate dropped to 79.30% from 88.20%. The negative impact of these two substances on ethanol fermentation was caused by sulphur dioxide and hydrogen sulfide which were generated in low pH during the fermentation. The former one lead to more glycerol was produced, and then the ethanol yield decreased, as well as the starch utilization rate. The latter brought about the viability of the yeast decreased; severe cases could lead to the yeast fracture and die. And then, the fermentation process would be delayed or stagnated, the output of glycerol increased, and the starch utilization rate declined. Thus, we have to wipe of those reducing substances during the process of reusing anaerobic efflux to avoid the harmful effect they may cause to the ethanol fermentation.The ethanol yield was fell 4.49% compared to the blank when the anaerobic efflux was used as water for ethanol fermentation directly. It is not good for the utilization of raw material. So the anaerobic efflux must be treated before reused, if not, the ethanol fermentation will be influenced. Among the present resources recovery methods, mild oxidation, process of taking off the ammonia and activated carbon adsorption had great improved the character of anaerobic efflux for ethanol fermentation, the final ethanol yield was improved 1% compared to the constant. All of these were effective resources recovery methods. In consideration of economy and operability, we took the mild oxidation as the treatment of anaerobic efflux. It’s low energy consumption. The anaerobic efflux treated by this method met demands for ethanol fermentation. The final ethanol yield （14.50%） was equal to the blank’s （14.47%）.After optimized the treatment of mild oxidation, we found that the best condition for industry was: temperature 55℃,ventilate, relative vacuum between -0.04 to -0.05MPa, and last for 160min. If the ventilatory capacity was bigger, the handling time would be shorter.We used the anaerobic efflux treated as the condition for ethanol fermentation. The final ethanol yield was a bit better than the deionized water’s when the solid-to-liquid ratio was 1:3. The whole fermentation process was normal, the glycerol yield wasn’t increased, and the final remnant of total sugar was less than 1%.The increase of pH during mild oxidation process was caused by decomposing of HCO₃^- and hydrolyzing of CO32-. The temperature was higher, the pH was higher. The ratio of alkalinity to ammonium-N went up also made the pH increased. In this process, alkalinity and ammonium-N decreased at the same time and the same equivalent （HCO₃^-and NH₄⁺）. The pH was higher, the rate of getting rid of ammonium-N and alkalinity was higher. The finishing point of the process should be the concentration of ammonium-N less than 100mg/L.The steady of alkalinity in the anaerobic efflux was hooked on to positive ions. Main of those positive ions are NH₄⁺ and metallic cations. The concentration of NH₄⁺ and sodion are higher, they are 32.14% and 30.43% respectively. After treated by hydrogen type of cation exchange resin, the alkalinity of anaerobic efflux was removed completely. The hydrogen type of cation exchange resin adsorption could be considered as a treatment for removing alkalinity in industrial sewage.更多还原