【作者】 李海燕；

【导师】 马伟；

【作者基本信息】 大连理工大学 ， 无机化学， 2006， 硕士

【摘要】 发展海水淡化技术是解决水资源短缺的重要途径。反渗透海水淡化技术由于设备投资省、能量消耗低、建设周期短等诸多优点,近10年来发展速度很快,今后将成为海水淡化的主导技术。目前,膜垢污染是反渗透海水淡化中遇到的一个主要问题。在反渗透海水淡化过程中,由于膜的浓缩作用,浓水中的钙、镁等离子浓度大大增加,从而使难溶盐的离子积大于其溶度积,在反渗透膜表面形成膜垢,影响整个反渗透装置的正常运行,缩短了反渗透膜的使用寿命。 首先本文针对大连地区打井取水膜法海水淡化中海水水质和膜垢的特点,在实验室制备了一种环境友好的,易生物降解的阻垢剂PAP-1。采用静态阻垢的实验方法评价了PAP-1对Ca²⁺和Mg²⁺结垢的抑制能力,在实验水质条件下,当pH在3.00和9.00之间时适合的PAP-1加药量为3-5mg/L;pH为3.00时,3mg/L PAP-1阻垢剂可使阻垢率达到100%;pH为9.00时,9mg/L PAP-1阻垢剂对钙垢的阻垢率为97.24%,对镁垢的阻垢率达到98.63%。藻类毒性实验结果表明藻类的生长不受PAP-1的限制;生物降解性评价得出PAP-1是易生物降解的,第8d其生物降解率达到38.25%,第20d时达到58.3%。 在静态阻垢实验的基础上,本文通过现场实验进一步研究了阻垢剂PAP-1的性能,以成垢离子在膜元件上的结垢速率作为阻垢性能的评价指标,与目前市场上使用较多的进口阻垢剂PermaTreat 191进行对比。结果表明PAP-1的阻垢性能优良,在一些条件下优于进口阻垢剂,PAP-1具有更好的抑制钙和镁离子结垢的能力,连续六个月随机取样分析结果得出使用PAP-1的2# RO系统钙的平均结垢速率为2.822g/h,低于1# RO系统3.585g/h;2# RO系统中镁的平均结垢速率为5.562g/h,略低于1# RO系统5.849g/h。两套系统中产水电导率在整个实验期间几乎不变,膜的脱盐率始终在99.5%以上,进水压力保持51bar不变,产水流量始终处于22～23m³/h之间,说明PAP-1具有较好的稳定性;并且在价格上PAP-1具有更大的优势,有很强的市场竞争力和广泛的应用前景。 同时本文采用电子扫描电镜、X射线衍射等手段对加入阻垢剂PAP-1前后CaCO₃晶体的变化情况进行了研究,结果表明PAP-1在阻垢过程中不仅存在着宏观的晶貌改变和微观的晶格畸变,还存在着晶型转变问题。 最后本文在VB平台基础上,根据阻垢剂的性能、反渗透系统的运行参数以及现场水质分析数据开发了加药计算软件和结垢速率计算软件,为阻垢剂投加、阻垢剂的性能评价以及膜的清洗工作提供指导。通过对上述内容的系统研究,本文在膜法海水淡化阻垢剂研究方面建立了一个完善的体系。更多还原

【Abstract】 Developing seawater desalination technology is an important approach to solve the problem of water shortage. Reverse osmosis (RO) seawater desalination technology has an instant development in recent 10 years and will become the primary desalination technology in the future because it has many advantages, such as less equipment investment, lower energy consumption and shorter construction period than other desalination method. However, at present membrane scaling is a serious problem which affects the operator of seawater RO plants and shortens the life of membrane, so it must be solved in the RO desalination process. Membrane scaling is caused by the deposition of unsoluble salts as feedwater is converted to brine. In this process the ion concentration of calcium, magnesium and so on increases greatly which will lead to that the ion product of sparingly soluble salts exceeds its solubility product, and the unsoluble salts deposite on the surface of RO membrane to form membrane scaling.In our research the component of membrane scaling and feedwater in Dalian RO desalination plant is analysed first. Based on the characteristic of Dalian seawater, a new environmental friendly and biodegradable antiscalant named PAP-1 is prepared in the laboratory. The performance of PAP-1 to inhibit calcium and magnesium-containing scale is studied in the laboratory with static method. It is found that PAP-1 is effective in inhibiting scale formation. The experimental results in the lab indicate that the proper dose is 3-5mg/L when the concentration of calcium is l000mg/L and magnesium is 2800mg/L. When pH is 3.00, the efficiency to inhibit scale formation reaches 100% with 3mg/L PAP-1. While pH is 9.00, calcium scale inhibition percentage of PAP-1 is 97.24% and magnesium scale inhibition percentage is 98.63% with 9mg/L PAP-1. At the same time, the algae growth inhibition test shows that the addition of PAP-1 doesn’t affect the normal growth of algae, which is an indication that PAP-1 has no toxicity. The experiment of biodegradability shows that percentage biodegradability of PAP-1 reaches 38.25% at day 8 and 58.3% at day 20. PAP-1 is eazily biodegraded at the test conditions.Based on the results of static experiment, the pilot plant test is performed in Dalian RO desalination plant. A direct comparison between PAP-1 and PermaTreat 191 in inhibiting calcium and magnesium scale has been carried out. The random samples of feed, reject and product are analysed, simultaneously scale formation rates of calcium and magnesium are calculated at a fixed recovery. The test confirms the scale inhibition ability to calcium andmagnesium scale of PAP-1 compared with scale inhibitor PermaTreat 191. The average scale formation rates in each membrane unit of calcium and magnesium are 2.822g/h and 5.562g/h separately with the addition of PAP-1, while they are 3.585g/h and 5.849g/h for PermaTreat 191. PAP-1 is more effective compared to PermaTreat 191. And PAP-1 is cheaper, so it will be of advantage in market.Moreover the CaCC>3 crystal structure and morphology are determined with X-ray diffraction and scanning electronic microscopy. It has been found that the crystal type of precipitated CaCO3 has been changed from stable calcite to less stable vaterite and morphology is altered due to the presence of antiscalant PAP-1.In the last part of this paper, the softwares to calculate the dose of antiscalant and scale-formation rate are developed based on the VB flat according to the performance of antiscalant, RO system parameters and water analysis data. The dose-calculation software can supply useful help for the application of antiscalant PAP-1. Because it can calculate the dose required in the RO desalination accurately, the dose-calculation software is favorable for reducing the waste of antiscalant and promotes the rational utilization of it. The software to calculate the scale-formation rate is a useful tool for evaluating the performance of antiscalant and selecting the time and frequency of membrane cleaning. Through the systemic research on the above content, a whole system about the antiscalant in RO membrane desalination is developed.更多还原