【作者】 余振江；

【导师】 钱宇；

【作者基本信息】 华南理工大学 ， 化学工程， 2011， 博士

【摘要】 煤气化工艺中产生的煤气洗涤污水中含有酚氨等高浓度难降解有机污染物,工业上通常采用化工分离和生化处理两段法来实现酚氨的回收和污水的净化排放。但是,现有的煤气化污水化工处理流程的酚回收效率较低,难以满足后续生化处理段的要求,从而导致最终排放不达标。针对煤气化污水水质的特点,本文采用ElecNRTL和NRTL热力学模型来分别描述现有流程中涉及的NH₃-CO₂-H₂S-NaOH-PhOH-H₂O和水-二异丙醚-苯酚-对苯二酚的多元极性复杂体系的热力学性质,并将这些数据结合ASPEN流程模拟软件对现有流程进行模拟分析。在流程模拟的基础上,结合工业现状,本文分析了现有流程存在的两个主要问题:萃取脱酚效果差和部分管线碳铵结晶问题。针对这两个问题,本文探讨了各种可能的解决方案。通过比较各个方案的优劣,最终提出了采用单塔汽提侧线脱氨技术替代原有的脱酸脱氨单元和采用MT替代原有的二异丙醚作为萃取剂这两个改进方案。前者目的是将污水的pH值从9左右降到6.5,使萃取在偏酸条件下进行,从而提高萃取脱酚效率,并且单塔汽提可以有效地抑制管线碳铵结晶的问题。后者是选择了一种对多元酚的分配系数更高的萃取剂,从而提高现有流程的脱酚效率。由于采用了新的萃取剂,需要重新确定萃取条件和相关参数。本文研究了MT萃取煤气化污水所适宜的温度和pH值,以及所需萃取相比和萃取级数。并对水-MT-苯酚-对苯二酚四元体系进行了液液相平衡研究,用NRTL方程关联得到新流程模拟所需的二元交互作用参数,为新流程的模拟开发提供数据基础。为了保证改造后的新流程能够有效地、稳定地运行,本文对新流程进行了稳态模拟。在此在基础上,设计并优化了新流程诸如塔板数、塔顶温度等各个设备和操作参数。并且在对新流程动态模拟的基础上,提出了合适的控制方案。处理量为130 t/hr的煤气化污水处理新流程目前已在中煤龙化哈尔滨煤化工公司得以成功工业实施。工业实施结果表明,和原有的工艺相比,新流程对CO₂的脱除效率从60%提高到99%以上,对总酚的脱除效率从76 %提升到93 %。新流程的实施提高了有机污染物的脱除率,满足了后续生化处理的要求,并最终实现了污水的达标排放。更多还原

【Abstract】 Coal-gasification process produces a large quantity of gas-washing wastewater, which contains phenols, ammonia, and sour gas. Because of the toxicity of phenols, NH₃, and H₂S, the wastewater has to be treated and purified prior to discharge. Existing coal-gasification wastewater treatment plants usually consist of two sections: a chemical treatment process and a biological treatment process. However, the chemical treatment process can not remove phenols efficiently to meet the discharge standard by the following biological treatment.Based on the analysis of composition and thermodynamics properties of the wastewater, the complex multicomponent systems NH₃-CO₂-H₂S-NaOH-phenol-H₂O and H₂O-Diisopropyl Ether （DIPE）-Phenol-Hydroquinone were analyzed when simulating the wastewater stripping and solvent recovery process, respectively. And ELECNRTL and NRTL activity coefficient models are used to describe the wastewater stripping and solvent recovery process, respectively. Simulation results shows that the bottlenecks of the current wastewater treatment process are low phenols removal efficiency and plugging induced by ammonium bicarbonate crystals. This work proposes two methods to solve the problems. One is that ammonia and sour gas remove simultaneously in a wastewater stripper with side-draw, which reduce the pH value of the wastewater from 9 to below 7, and then remove phenols with solvent extraction in acidic condition. The other is that DIPE is replaced by MT, whose distribution coefficients to phenol and polyhydrics are greater than DIPE.The extraction process conditions of MT were determined, such as temperature, pH value, phase ratio, and extraction stages. The liquid-liquid equilibria of H₂O-MT-Phenol-Hydroquinone were studied. The experimental data were correlated with the NRTL activity coefficient model, and the corresponding binary interaction parameters were regressed. These parameters were used to simulate the new process.Process steady-state simulation was conducted to study the performance of the new process and perform detailed design, such as the number of stages, the top temperature of towers, and the top pressure of towers. And process dynamic simulation was conducted to design the control system of the new process.This new process has been successfully implemented in China Harbin Coal-chemicals Inc. for coal-gasification wastewater treatment with a capacity of 130t/hr. Satisfactory agreement was obtained between the simulation results and the industrial implementation of the new process. Compared with the old process, the new process recovers phenols more efficiently, and yields a satisfactory outflow for the later biological treatment of the wastewater.更多还原