基于沉淀置换的发酵法生产有机酸的清洁工艺过程

发布时间：2018-06-05 21:20

本文选题：有机酸 + 清洁生产　；参考：《中国科学院研究生院(过程工程研究所)》2015年博士论文

【摘要】：有机酸的传统钙盐法生产伴生大量酸性硫酸钙固体废弃物,给环境带来较大压力,但钙碱对有机酸发酵菌体友好,是某些有机酸浓度积累不可缺少的物质,钙盐沉淀步骤有利于提升有机酸产品的纯度。本论文针对传统钙盐发酵生产有机酸过程中产生大量固体废弃物的共性问题,研究采用有机酸钙盐与可溶性碳酸盐进行沉淀置换反应,拟解决有机酸生产过程产生硫酸钙固体废弃物、实现清洁生产。以乳酸和柠檬酸为研究对象,重点研究沉淀置换、离子交换、酸碱再生等步骤的问题和解决方法,在此基础上构建具有一定普适性的有机酸清洁生产新工艺。首先研究乳酸钙和柠檬酸钙与碳酸铵进行沉淀置换反应的可行性,考察了反应条件对沉淀置换反应及碳酸钙颗粒粒度的影响。结果表明,碳酸铵的加入量是乳酸钙发酵液中钙的物质的量的1.06倍为佳,钙离子去除率可达99%以上,乳酸钙与碳酸铵之间的沉淀置换反应可在15 min内完成。碳酸铵与柠檬酸钙中钙的比值为1：1时,柠檬酸回收率达95%以上,柠檬酸钙与碳酸铵之间的沉淀置换反应所需的时间较长,本实验条件下所需的反应时间在2.5 h以上。沉淀置换反应得到的悬浊液可采用自然沉降、再用板框过滤的方式进行固液分离。考察了离子交换法提取乳酸钙沉淀置换上清液中的乳酸的工艺条件。乳酸钙沉淀置换上清液的pH较高,使D319树脂对乳酸的吸附量变小,残留的碳酸根可被吸附到树脂上,随后用盐酸洗脱时产生二氧化碳气体,造成离子交换过程无法稳定运行。提出的解决方法为：用乳酸调节沉淀置换上清液的pH值至7.0以下,然后采用加热减压法和离子交换法可有效去除残留碳酸根。根据柠檬酸钙沉淀置换上清液的特性,选择“盐-碱”两室双极膜膜堆结构进行酸碱再生,考察了残留钙离子对酸碱再生的影响、钙的存在形态及其去除方法。柠檬酸钙沉淀置换上清液中的残留钙浓度有8.0 g/L以上,酸碱再生过程中可在盐室产生柠檬酸钙盐固体。选择草酸沉淀去除残留钙离子,钙去除率约为60%。草酸沉淀法除钙后的沉淀置换上清液的酸碱再生过程中,盐室液仍会产生草酸钙,沉积于隔网和离子交换膜表面。发现盐室液开始出现浑浊与草酸钙固体在膜堆内沉积之间有一定的时间差,由此建立了间歇式堆外沉淀法去除残留钙离子的方法,可有效避免草酸钙盐在膜堆内沉积,铵离子跨膜迁移的平均电流效率、膜通量和能耗分别达到95%、12.5 mol/(m2·h)和60 kWh/kmol,与柠檬酸铵水溶液的酸碱再生参数相当。考察了沉淀置换剂制备与沉淀置换反应两步骤的耦合,表明耦合可降低体系中的产物(碳酸铵)浓度,从而增大碳酸铵的表观生成速率。考察了乳酸生产工艺中的酸碱再生步骤与离子交换的洗脱步骤的耦合,表明耦合可有效降低酸室液中游离H+和C1-浓度,缓解了酸室中H+渗漏的程度,使Cl-的跨膜迁移通量提高了3.5%,平均电流效率提高了56.25%,能耗降低了29.61%。考察了碳酸钙(沉淀置换步骤得到的碳酸钙)循环利用的效果,表明使用循环碳酸钙进行乳酸发酵可大幅提高乳酸发酵水平,乳酸浓度增加了32.41%,产酸速率提高了33.17%,菌体浓度提高了19.34%；循环碳酸钙的比表面积大,具有较好的pH维持能力,颗粒内含有少量氮元素,且乳酸杆菌可在颗粒上形成洞状结构,为其自身提供较好的微环境,有效提高了乳酸发酵水平。在实验室规模下,对乳酸和柠檬酸的清洁生产工艺进行串联,结果表明,乳酸总收率可达90%以上：乳酸清洁生产新工艺的估算成本约为6782.5元,与传统钙盐法生产乳酸的成本相当；乳酸清洁生产工艺得到的精制乳酸符合某聚乳酸生产企业的原料采购要求。草酸脱钙后的柠檬酸沉淀置换上清液经酸碱再生得到的盐室终点液,经阳离子交换树脂除杂、常规减压浓缩、结晶得到柠檬酸固体,其中未检出草酸、铵离子和钙离子。
[Abstract]:The traditional calcium salt method of organic acid produces a large amount of acid calcium sulfate solid waste, which brings great pressure to the environment, but calcium alkali is friendly to organic acid fermentation bacteria. It is an indispensable substance for the accumulation of some organic acid concentration. The calcium salt precipitation step is beneficial to the promotion of the purity of organic acid products. This paper is aimed at the production of organic acid by traditional calcium salt. In the process of acid, a large number of common problems of solid waste are produced. The study uses organic acid calcium salt and soluble carbonate for precipitation replacement reaction. It is intended to solve the production process of organic acid to produce calcium sulphate solid waste and realize clean production. On this basis, a new process of clean production of organic acids with certain universality was constructed. The feasibility of precipitation replacement reaction of calcium lactate and calcium citrate with ammonium carbonate was first studied, and the effects of reaction conditions on the precipitation replacement reaction and the particle size of calcium carbonate were investigated. The results showed that the addition of ammonium carbonate was added. The amount is 1.06 times the amount of calcium in the calcium lactate fermentation liquid, the removal rate of calcium ion is above 99%, the precipitation replacement reaction between calcium lactate and ammonium carbonate can be completed within 15 min. The recovery rate of citric acid is over 95% and the precipitation replacement reaction between calcium citrate and ammonium carbonate is more than 95% when the ratio of calcium carbonate to calcium citrate is 1:1 The time required for this experiment is more than 2.5 h. Natural sedimentation can be used in the precipitation replacement reaction. The process conditions for the extraction of lactate in the supernatant from calcium lactate precipitation and replacement of supernatant by ion exchange method are investigated. The pH is higher, which makes the adsorption and quantitative change of lactic acid by D319 resin small, the residual carbonate can be adsorbed on the resin, and then the carbon dioxide gas is produced by hydrochloric acid elution, which causes the ion exchange process to not run steadily. The solution is to adjust the pH value to less than 7 with lactic acid in the precipitation replacement, and then use the heating and decompression method. And ion exchange method can effectively remove residual carbonate. According to the characteristics of calcium citrate precipitation replacement supernatant, "salt alkali" two chamber bipolar membrane reactor structure is selected for acid base regeneration, and the effect of residual calcium ion on acid base regeneration, the existence form of calcium and the removal method of calcium in the supernatant of calcium citrate precipitation replacement supernatant are investigated. Calcium citrate solid can be produced in the salt chamber during the process of acid base regeneration. The concentration of calcium citrate can be removed by oxalic acid precipitation. Calcium removal rate is about 60%. oxalic acid precipitation process. Calcium oxalate can be produced in the process of precipitation replacement supernatant. Salt chamber liquid will still produce calcium oxalate, deposited on the surface of septum and ion exchange membrane. There is a certain time difference between the turbidity and the deposition of calcium oxalate in the membrane reactor. Thus the method of removing residual calcium ions by intermittent heap precipitation method is established, which can effectively avoid the deposition of calcium oxalate in the membrane reactor, the average current efficiency of the transmembrane migration of ammonium ions, the flux and energy consumption of the membrane are 95%, 12.5 mol/ (M2 h), respectively. And 60 kWh/kmol, which is equivalent to the acid base regeneration parameters of ammonium citrate solution. The coupling of the preparation of precipitate replacement agent and the two step of the precipitation replacement reaction is investigated. It shows that the coupling can reduce the concentration of the product (ammonium carbonate) in the system, thus increasing the apparent formation rate of ammonium carbonate. The acid base regeneration steps and ions in the lactic acid production process are investigated. The coupling of the elution steps of the exchange shows that the coupling can effectively reduce the concentration of free H+ and C1- in the acid chamber, alleviate the degree of H+ leakage in the acid chamber, increase the transmembrane migration flux of Cl- by 3.5%, increase the average current efficiency by 56.25%, and reduce the energy consumption by 29.61%. to investigate the efficiency of calcium carbonate (calcium carbonate from the precipitate replacement step). The results showed that the lactic acid fermentation could greatly improve the lactic acid fermentation level, the lactic acid concentration increased by 32.41%, the acid producing rate increased by 33.17%, the body concentration increased by 19.34%, the specific surface area of the circulating calcium carbonate was large, the pH maintenance ability was better, the particles contained a small amount of nitrogen elements, and the Lactobacillus could form on the particles. In the laboratory scale, the total yield of lactic acid and citric acid can be over 90%: the estimated cost of the new lactic acid cleaner production process is about 6782.5 yuan, and the lactic acid is produced with the traditional calcium salt method. The refined lactic acid obtained from the lactic acid cleaner production process meets the purchasing requirements of the raw material of a polylactic acid production enterprise. The citric acid precipitation replacement supernatant after the calcium oxalic acid decalcification is obtained by acid base regenerated salt chamber end solution, and the citric acid solid is obtained by the cation exchange resin removal, the conventional decompression condensation, and the crystallization of the citric acid. Acids, ammonium ions and calcium ions.
【学位授予单位】：中国科学院研究生院(过程工程研究所)
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ921

【参考文献】