预测板式换热器污垢热阻的新方法

通过动态监测板式换热器冷却水污垢热阻及影响污垢热阻的松花江水水质参数（如pH值、溶解氧、铁离子、氯离子、细菌总数、浊度、电导率、化学需氧量、碱度和硬度等）变化。采用BP神经网络主成分分析、主成分回归、全要素BP神经网络三种预测方法建立板式换热器污垢热阻预测模型,选取1-15号样本为训练或回归拟合样本,16-20号样本为测试样本,并将三种方法的预测结果进行了对比。结果表明,三种方法均可对板式换热器污垢特性进行有效预测,而基于主成分分析的BP神经网络方法的预测结果误差小,优于另外两种方法。     

MBR法处理污水的研究

本文介绍了目前MBR的主要类型、膜污染情况、膜清洗方式以及MBR在不同领域的应用情况和工程实例,并对MBR技术未来的发展趋势进行了预测。     

注汽锅炉高含盐回用水引发爆管分析

辽河油田锦州采油厂注汽锅炉采用回注水生产蒸汽,由于回注水水质超标使二氧化硅和盐在过热段结垢和结晶,造成炉管局部过热,导致炉管材料的许用应力急剧下降,发生爆管。由于注汽锅炉使用油作燃料,火焰最大直径为3m,二氧化硅和盐在此同时结垢和结晶,这两种最恶劣工况同时在此发生,导致爆管。降低蒸汽干度或干度交替变化,使这两种最恶劣工况在此不同时发生是解决问题的主要方法。     

Effects of silica sol on ion exchange membranes: Electrochemical characterization of anion exchange membranes in electrodialysis of silica sol containing-solutions

The fouling potential of the negatively charged silica sol in electrodialysis (ED) by adsorption on the surface of an anion exchange membrane was investigated. Since the fouling potential is related to the physical and electrochemical properties of the silica sol and anion exchange membranes, it is important to characterize the properties of silica sol and membranes. The surface charge of silica sol was investigated by the electrophoretic mobility and its isoelectric point was determined as pH 3. The commercial anion exchange membranes were characterized in terms of exchange capacity, water content, the zeta potential and the electrochemical properties of the membranes using impedance spectroscopy to predict the effects on the electrodialysis performances. Among the characterized properties, exchange capacity and some electrochemical properties of the anion exchange membranes were rather improved after ED experiments. In the electrodialysis of solution containing silica sol, deposition of the silica sol did not decrease the desalting performance of the anion exchange membranes because of loosely packed cake layer on the membrane surface.     

PROTEIN ADSORPTION AND FOULING OF CERAMIC MEMBRANES AS MEASURED BY SCANNING ELECTRON MICROSCOPY WITH DIGITAL X-RAY MAPPING

A technique for studying fouling in ceramic membranes using the energy dispersive x-ray spectroscopy capability of an electron microscope is described. The location and amount of foulant within the membrane are presented on a digital x-ray map showing elements constituent to or stained on the foulant.

Fouling of alumina membranes during filtration of the protein hemoglobin has been studied as a function of filtration time, pH, and membrane pore size. After each filtration run, the protein within a piece of the membrane was stained with phosphotungstic acid and located on a digital map of either phosphorus or tungsten.

For a 0.2 μm pore size membrane, time dependent fouling was observed consistent with an observed flux decline within the first few minutes of filtration. A pH dependence was also observed indicating much greater fouling at pH 6.9 near the protein isoelectric point than at pH 8.5. This observation is consistent with pH dependent adsorption, flux, and rejection studies. No internal fouling was observed for a 40 Å pore size membrane, which is consistent with the size of hemoglobin in solution being larger than the 40 Å pores and with the fact that the 40 Å membrane can be more easily cleaned after use than can the 0.2 μm membrane.     

Critical flux in cross-flow ultrafiltration of protein solutions

The effect of solute size relative to membrane pore size on the critical flux during the ultrafiltration of protein solutions was investigated using the constant pressure method. Hydrophilic regenerated cellulose membranes with a cut-off of 10, 30 and 100 kg mol⁻¹, model proteins and skimmed milk solutions were used. The critical flux mainly increased with the pore size of the ultrafiltration membrane. The lowest critical fluxes, 40-50 L m⁻²h⁻¹, were obtained with the retentive 10 kg mol⁻¹ cut-off membrane. This membrane had a very low permeability and, thus, the critical fluxes were achieved at high transmembrane pressures (TMP): 1.7-2.3 bar. With the 100 kg mol⁻¹ cut-off membrane critical fluxes were obtained at 0.2 bar TMP, which were around 100 L m⁻² h⁻¹, slightly declining with increasing protein molar mass. In skimmed milk experiments the permeate flux decreased when the protein molecules were enzymatically split to peptides. A critical flux for skimmed milk solution could not be found unless the protein concentration was diluted to 0.3-w% or lower. The results with model proteins were then compared to those obtained with skimmed milk resulting in β-lactoglobulin being the worst foulant.     

Influence of hemicellulose aggregate and gel layer formation on flux and retention during nanofiltration of alkaline solutions

Nanofiltration of process liquors from viscose-type textile fibre production was investigated using a laboratoryscale crossflow test apparatus. Feed solutions contained about 200 g/l sodium hydroxide and a high concentration of hemicellulose as a contaminant originating from the raw material wood. The effects of various pretreatments and the addition of reagents on flux, retention and irreversible fouling were studied. Reagent addition affected the solution state of hemicellulose thus purposely provoking aggregate formation. Dynamic light scattering and turbidity measurements were used to track the evolution of hemicellulose aggregates. Aggregation generally coincided with distinct flux decline during nanofiltration thus indicating that this phenomenon may result in the build-up of gel layers at the membrane surface. Partial neutralisation with sulfuric acid caused extremely severe fouling, whereas methanol addition had a minor effect. The impact of heat treatment and oxidative degradation of hemicellulose on nanofiltration performance was attributed to changes in molar mass distribution.     

Color and COD retention by nanofiltration membranes

In the present study the application of the nanofiltration process was investigated mainly in the retention ofcolor and chemical oxygen demand (COD) present in textile industry wastewater. Nanofiltration experiments were carried out in a pilot unit, operating in crossflow. Three different types of spiral wound membranes, DK 1073, NF 45 and MPS 31 were used simultaneously in the same unit. The results of the tests showed that for color retention, the values were around 99% for the DK 1073 and NF 45 membranes and the 87% for COD retention for the DK 1073. The permeate flux for the different wastewaters varied from 30.5 to 70 L/h.m². Fouling was observed in all membranes due to the accumulation of molecular species close to the filtering surface. The process was efficient and promising for the reuse of wastewater from this type of industry.     

Modification of polysulfone ultrafiltration membranes by CO2 plasma treatment

Carbon dioxide plasmas were used to modify hydrophobic polysulfone ultrafiltration membranes to create hydrophilic surfaces throughout the membrane structure. The water contact angle of the upstream side of the membrane (facing the plasma) decreased to zero after treatment and did not change even after several months of aging. The water contact angle of the downstream side decreased with increasing CO₂ plasma treatment time and became zero for treatment times ≥ 1 min (P = 10 W). Functional groups introduced by CO₂ plasma treatment were examined using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). For the treated membranes, the atomic concentration of oxygen increased dramatically and small amounts of nitrogen incorporation were also observed. Membrane performance was tested with water flux measurements as well as protein fouling studies. For treated membranes, the water flux recovery measured after protein fouling was significantly higher than that for control membranes, with nearly 100% recovery after gentle cleaning in water. Moreover, the amount of protein adsorption decreased by over 75% for the treated membranes compared to control membranes. This suggests the protein fouling layer is essentially completely reversible on the CO₂ plasma treated membranes.     

UiO-66/PES混合基质超滤膜的制备及性能

以聚醚砜(PES)为主要膜材料、溶剂热法合成UiO-66并掺入铸膜液中,通过非溶剂相转化法(NIPS)制备了混合基质超滤膜.利用X射线衍射仪(XRD)、傅里叶红外光谱(FTIR)、扫描电镜(SEM)、接触角测量仪及原子力显微镜(AFM)对制备的UiO-66和混合基质膜进行表征.重点考察了UiO-66添加量对膜表面形貌、...