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Alternative TitleStudy on carbonating ammoniacal solution recycle in a novel method for lactic acid recovery from fermentation broth
Thesis Advisor丛威
Degree Grantor中国科学院研究生院
Degree Discipline生物工程
Keyword乳酸   电渗析   碳化氨水   沉淀置换   氨水浓缩
Abstract传统的乳酸钙盐法提取工艺用硫酸酸解后析出CaSO4·2H2O(石膏渣), 由于石膏渣中混有发酵过程中的菌体、有机物,且其pH值较低,使其成为难利用的废弃物,带来严重的环境问题。为避免使用浓硫酸酸解工艺产生石膏渣的问题,本实验室提出了一种钙盐法与电渗析耦合清洁生产乳酸的工艺。本文针对其中的沉淀置换步骤,根据工艺的要求,解决了碳化氨水中氨碳浓度测定、最适碳化氨水的制备工艺参数以及制备工艺三个问题。 针对碳化氨水中含碳离子成分复杂,且各含碳离子的形态随着碳化氨水pH值变化而相互转化的问题,采用过量CaCl2将碳化氨水中含碳离子和含氮离子分别转变为CaCO3和NH4+(或NH3和NH4+),通过甲醛法测定上清液中氮量计算得到碳化氨水中总氨浓度,用EDTA滴定过量Ca2+得到碳化氨水中总碳浓度和有效碳浓度。结果表明,总碳浓度、有效碳浓度和总氨浓度的测定结果与理论值间的相对误差分别在1.0%、1.5%和1.5%以内;该测定方法能快速准确测定碳化氨水中总碳浓度、有效碳浓度及总氨浓度。 采用碳酸铵、氨基甲酸铵及碳酸氢铵与氨水的混合溶液作为沉淀剂,研究它们对置换上清液中钙残留的影响,优化了碳酸氢铵和氨水混合溶液作为沉淀剂的最佳的混合比,采用文献报道的关于碳化氨水制备过程中不同pH值条件下各种含碳离子的摩尔分数推导出最适碳化氨水满足的条件,并根据碳化氨水制备过程中其NH3/effective CO2与pH值的关系,及吸收剂浓度变化对制备得到碳化氨水NH3/effective CO2的影响的研究,得到了最适碳化氨水的制备工艺参数。结果表明,碳酸铵、氨基甲酸铵及碳酸氢铵与氨水的混合溶液(NH3/effective CO2=2.15)都适合用作与乳酸钙反应的沉淀剂;置换用最适碳化氨水满足的条件为:NH3/effective CO2不小于2.06;最适碳化氨水的制备工艺参数为:常压26℃,pH=9.80,且最适碳化氨水的制备工艺参数数值不随吸收剂中氨浓度变化而发生很大变化。 针对铵盐双极膜电渗析碱室再生得到的氨水浓度较低不适用于直接通过吸收二氧化碳来制备高浓度碳化氨水的问题,采用低温吹脱-同步吸收和低温吹脱-分步吸收的方法以稀氨水为原料制备得到了高浓度的碳化氨水,比较了不同操作条件,不同的吸氨装置对原料氨和二氧化碳的利用率的影响。结果表明,采用低温吹脱-分步吸收的方法可以由稀氨水为原料制备得到高浓度的碳化氨水,该方法操作简便,原料利用率较高,氨和CO2的利用率分别为90%、85%左右;且使用搅拌釜式反应器作为氨吸收装置在二氧化碳利用率方面优于鼓泡塔,在碳化氨水的pH= 9.50-9.60的操作条件下,使用搅拌釜式反应器作为氨吸收装置时CO2利用率比使用鼓泡塔时高10%左右。
Other AbstractThe conventional process for recovery of lactic acid will inevitably results in calcium sulfate, which together with retained organic impurities poses an environmental problem, is uneconomical to be disposed of, and causes the high consumption of sulfuric acid and calcium carbonate in acidification and neutralization steps. In order to deal with the severe problem, a new recovery process has been proposed for recovery of lactic acid from calcium lactate solution, which mainly consists four parts including lactic acid fermentation, conversion of calcium lactate to ammonium lactate, eletrodialysis and recycling of carbonating ammoniacal solution. As a part of detailed studies of this method, the possibility of converting calcium lactate into ammonium lactate and the conditions for preparing carbonating ammoniacal solution will be presented in this study. In the thesis, on the basis of the complex composition of the solution of carbonating ammoniacal solution and variation of relative ammounts of different species in carbonating ammoniacal solution with changes of its pH value, a method for determining the concentration of total CO2, effective CO2 and total NH3 is proposed. EDTA titration method is adapted to determine the concentration of total CO2 and effective CO2, and formol-titration method is used to measure the concentration of total NH3. The results showed that EDTA titration and formol-titration method could be used to determine the concentration of total CO2, effective CO2 and total NH3 in a simulating carbonating ammoniacal solution. And relative error of the method for determining concentration of total CO2, effective CO2 and total NH3 was less than 1.0%, 1.5%, 1.5%. Therefore, this method can be adapted to determine the concentration of total CO2, effective CO2 and total NH3 in carbonating ammoniacal solution. The effects of (NH4)2CO3, NH2COONH4 and a mixture of NH4HCO3 and NH3H2O on calcium residues in supernatant were investigated. The results showed that compared with ammonium carbonate and ammonium carbamate, the concentration of Ca2+ in the supernatant obtained from the reaction between lactate acid and the mixture of ammonium bicarbonate and aqueous ammonia was much higher. In order to decrease the calcium resides in supernatant after lactate acid reacted with the mixture of ammonium bicarbonate and aqueous ammonia, calcium residues for various ratios of NH3 to effective CO2 were investigated, after lactic acid fermentation reacted with theoretical amount of mixture of ammonium bicarbonate and aqueous ammonia with different ratios of NH3 to effective CO2, and It turned out that the proper mole ratio of NH3 to effective CO2 in the mixture of ammonium bicarbonate and aqueous ammonia was 2.15. And according to some data reported, combined with the obtained concentration of NH3 and total CO2, NH3/effective CO2 for the proper carbonating ammoniacal solution could be finally determined, which was about 2.06. Subsequently, taken the variation of initial concentration of aqueous ammonia into consideration, the proper carbonating ammoniacal solution for conversion process could be produced at the following condition: the final pH value should be around 9.80 at 26 ℃ under atmospheric pressure. On the basis of the fact that the concentration of aqueous ammonia produced in the lactic acid recovery process is quite low, it could not be directly used into preparing high concentration of carbonating ammoniacal solution. Actually, the techniques of steam stripping or distillation can be adapted firstly to get a higher concentration of aqueous ammonia, which should meet the lowest standard of requirement. However, using such techniques will inevitable increase of the energy consumption, the cost of final products as well as the equipment investment. To tackle the problem, stripping under a low temperature and absorption of NH3 and CO2 separately was proposed to preparing a higher concentration of carbonating ammoniacal solution, which is environmentally-friendly and less energy-consuming. Compared with CO2 and NH3 absorption in the same apparatus, CO2 and NH3 absorption separately took a lot of advantages in improving the utilization rate of CO2 and NH3. The results showed that CO2 and NH3 absorption separately had a higher utilization rate of CO2 and NH3, which was higher than 90% and 85% respectively. And compared with a buble column used for absorbing CO2, the utilization rate of CO2 was more than 10% higher when a stirred column was adopted for absorbing CO2.
Document Type学位论文
Recommended Citation
GB/T 7714
刘明. 发酵法乳酸提取新工艺中碳化氨水循环再生的研究[D]. 中国科学院研究生院,2013.
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