减压膜蒸馏热量回收过程研究

减压膜蒸馏作为一种新型的脱盐技术在海水淡化和高盐废水处理等方面具有广泛的应用价值。针对解决减压膜蒸馏过程中热量消耗大的问题展开了探索性研究,研制出了1套三级热量回收式减压膜蒸馏组件, 考察了不同操作条件对热量回收利用率的影响。研究结果表明,所设计的热量回收式组件能够有效回收利用减压膜蒸馏过程中的蒸汽潜热,而进料液温度、进料液流速和蒸汽透过侧真空度等操作条件都对其热量回收利用率具有一定程度的影响。为进一步提升减压膜蒸馏热量回收效率的研究和降低运行成本工艺技术的开发奠定了基础。     

Which separation scenarios are advantageous for membranes or distillations?

We systematically analyze power requirements of membrane and distillation processes for binary mixtures where the desired product component is more permeable and also more volatile. We first derive a shortcut method to compare the efficiency of heat pump and steam-driven distillations. Then, power requirements of heat pump distillation and membrane separation are discussed. Distillation generally requires lower power when either high component recoveries are needed (at all tested product purities), or high purity product streams with modest recoveries are needed. For high purity products at modest recoveries, membranes have a potential to provide energy benefits for highly enriched feeds, especially those composed of close boiling components. Additionally, when feed concentration is moderate to high and product recovery and purity are modest, membranes are likely to show efficiency gain. For the advantageous distillation scenarios studied, the power was generally lower than the membranes by a factor of two to seven.     

新型中空纤维空气隙式膜蒸馏用于海水淡化

利用自制的添加隔热管状隔网并呈螺旋缠绕结构编排的中空纤维膜组件进行了空气隙式膜蒸馏(AGMD)海水淡化过程性能研究, 实验以模拟标准海水(质量分数3.5%, 总溶解性固体含量35000 mg·L^-1)为热料液进水, 考察了热料液进水温度、热料液流量、冷凝液进水温度和冷凝液流量对膜通量、造水比和热效率的影响。结果表明, 随着热料液进水温度增加, 膜通量、造水比和热效率均增加;冷凝液进水温度增加, 膜通量下降而造水比和热效率增加;热料液流量增加, 膜通量上升而造水比和热效率明显下降;冷凝液进水流量对膜蒸馏过程性能影响较小。实验过程中产水TDS始终保持在3.0 mg·L^-1以下, 相应的离子去除率高于99.99%, 膜通量、造水比和热效率最高可分别达5.87 L·m^-2·h^-1、5.37和0.943。研究表明, 引入清洁能源取代传统电加热驱动热源将进一步突出膜蒸馏技术的实际应用潜力。     

Mass transfer, fluid flow and membrane properties in flat and corrugated plate hyperfiltration modules

Concentration polarisation, decreasing the efficiency in membrane separation processes, can be reduced by increasing mass transfer between membrane surface and bulk of the feed stream. Analogous to techniques used in plate heat exchangers efforts have been made to enhance mass transfer in a plate hyperfiltration module by using a corrugated membrane in stead of a flat one. The corrugations are pressed into an originally flat membrane. These corrugations do not only have an influence on the mass transfer, but also on such membrane properties as salt and water permeability. Corrugations enhance mass transfer in a more effective way than increase of flow rate does.

The effect of the corrugations on membrane properties shows a large spread. For corrugated membranes prepared by our group, flux increases of 100% at almost the same or even slightly higher retentions have been obtained.     

电渗析用于烟气脱硫吸收剂再生的研究

烟气脱硫工艺的脱硫吸收剂在反复的吸收-解吸过程中不可避免地要生成一些热稳定盐(HSS)。HSS在吸收剂中过度增加，将严重影响吸收剂的脱硫效率。因此应当采取措施控制HSS在吸收剂中的含量。本文介绍了用电渗析设备脱除HSS的研究结果。     

膜蓄能器放能过程的传热传质特性分析

膜构架蓄能器是以中空纤维膜为基本结构，不仅能够实现蓄能，同时能够解决溴化锂溶液浓度差蓄能器中结晶后的放能困难的问题。搭建了膜蓄能器放能过程传热传质实验测试系统，建立了应用于太阳能吸收式制冷系统中的膜架构蓄能器传热传质的三维数学模型，并利用 CFD 软件进行了求解。将计算结果与实验结果相比较，验证了该三维非稳态数学模型的可靠性。实验和仿真结果表明，质量分数为70% 的溴化锂溶液的水蒸气分子平均传质速率比质量分数为60%的溶液高44.03%；当蒸发温度从4.5℃提高到12.3℃时，水蒸气分子的平均传质速率将提高108.34%；当膜通道的有效长度从80 mm减少到30 mm时，水蒸气分子的传质速率会提高40.77%。     

Rh/γ-Al2O3 Catalytic Layer Integrated with Sol–Gel Synthesized Microporous Silica Membrane for Compact Membrane Reactor Applications

An efficient and compact catalytic membrane reactor for reforming of CH₄ was developed by integrating a hydrogen perm-selective silica membrane with an Rh/-Al₂O₃ catalyst layer. The catalytic layer was sandwiched between the outer surface of the -Al₂O₃ support tube and the silica membrane with an aim of improving the heat and mass transfer rates through the system and to simplify the reactor geometry. The system showed improved efficiency for reforming of CH₄ at comparatively lower operating temperatures and steam to C molar ratios than the conventional fixed-bed steam reforming systems. Under optimized conditions, a nearly 25-30% improvement from the equilibrium conversion level was achieved as a result of abstraction of hydrogen from the product stream by the silica membrane integrated with the catalyst layer. The performance of the system was evaluated as a function of various process parameters. Because of the compactness and efficiency, the present system emerges as a promising alternative to the conventional membrane reactors, which possess separate catalytic and membrane units.     

Heat transfer in the rectangular cross-flow flat-sheet membrane module for vacuum membrane distillation

This paper presents a study of heat transfer coefficients of boundary layers in a laboratory-scale rectangular cross-flow flat-sheet membrane module by using distilled water vacuum membrane distillation (VMD) experiments. Results show that the traditional heat transfer correlations, which are mostly employed in the membrane distillation literature, are not suitably used to predict the heat transfer process in the VMD system for the Reynolds numbers ranging from 300 to 1090. This study formulates a new semi-empirical heat transfer correlation by suggesting Knudsen-viscous mechanism governs the water vapour across the membrane. Compared to the feed flow rate, the feed temperature is the limit to the heat transfer. The heat transfer coefficients are strongly dependent on the physical properties of the feed solution, but less relied on the design of the membrane module.     

基于质子交换膜燃料电池的微型天然气热电联产研发进展

基于质子交换膜燃料电池(PEMFC)的微型天然气热电联产系统有着广阔的市场发展前景。这种系统将千瓦级天然气制氢、燃料电池发电及余热利用有机的结合在一起,可以将天然气的一部分高品质的化学能通过氢气这个中间介质转化为电能,其余的低品位的能量用于采暖及生活热水供应,可有效提高系统的可用能利用程度,实现天然气这种清洁能源的"温度对口、梯级利用"。介绍了微型燃料电池热电联产系统的技术路线,并对国内外微型制氢技术的研发及热电联产系统的产业化状况进行了介绍和分析。     

10千瓦级分布式天然气-质子交换膜燃料电池示范电站(英文)

A 10 kW-scale natural gas fueled proton exchange membrane fuel cell (PEMFC) distributed power plant is presented in this paper, which is designed for cogeneration of power and heat. With homemade catalysts for CO removal in a two-stage methanation process and integrated reactor in the fuel processing system, the reformed fuel with CO molar fraction less than 105 is obtained for the fuel cell stack. Based on Matlab/Simulink/Stateflow and xPC Target platform, a rapid control prototype (RCP) is developed for real-time condition management, signal tracking and parameter tuning, data storing, and man-machine interaction. In a typical running with 4.3 kW stack power, the hydrogen production efficiency, gross power generation efficiency and heat recovery efficiency approach to 76%, 41% and 50%, respectively. The peak stack power reaches 7.3 kW. Though there is still considerable distance to long-term operation at 10 kW-scale net power generation, it is a milestone for the PEMFC-based stationary application in China.