Influence of run time and aging on fouling and cleaning of whey protein deposits on heat exchanger surface.
Influence of run time and aging on fouling and cleaning of whey protein deposits on heat exchanger surface.
复制标题
运行时间和老化对热交换器表面乳清蛋白沉积物的结垢和清洁的影响。
DOI：
10.5539/jfr.v1n1p212
复制
发表时间：
2012
影响因子：
8.3
通讯作者：
X. Chen
中科院分区：
文献类型：
--
作者：
A. Fickak;E. Hatfield;X. Chen
在乳品加工厂的换热表面清洁操作中，加热/运行时间（HT）和老化对换热器结垢/清洁的影响尚不清楚。相同沉积物的较长加热时间预计会导致形成更坚固且可能更耐清洁的沉积物。本研究利用实验室生产的热诱导乳清蛋白凝胶（HIWPG）研究了加热和老化现象对乳品污垢形成和清除的影响。还利用中试工厂试验中形成的乳清蛋白沉积物对这些过程进行了研究。 HIWPG 在管状胶囊中生产，加热（或运行）时间不同（分别为 60、120、240、1440 和 2880 分钟），然后溶解在氢氧化钠水溶液（0.5 wt%）中。这里的加热过程是“纯粹”老化的。根据先前建立的紫外分光光度计分析计算溶解速率。使用扫描电子显微镜（SEM）和质地分析仪分析凝胶的结构和质地。在中试规模的工厂研究中，乳清蛋白污垢层是通过在不同的加热时间（分别为 30、60 和 90 分钟）内循环乳清蛋白溶液（6 wt%）而产生的。然后通过再循环氢氧化钠水溶液（0.5重量％）去除沉积层，并以传热系数恢复的形式监测清洁效率，同时记录流体电导率和浊度作为清洁完成的指示。结果发现，增加 HIWPG 加热时间会显着增加凝胶硬度和溶解时间，这意味着清洗的难度。与凝胶上的这些结果类似，增加中试规模工厂加热/运行时间会增加结垢程度。靠近金属表面形成的污垢层经历了最长的老化时间，并且在最终清洁阶段看到的传热系数增加的斜率与这种老化效应有关。金属表面上最初形成的沉积物的清洁率较低，表明表面附近沉积物的“纯粹”老化效应。
In the cleaning operations of heat exchange surfaces in dairy processing plants, the effect of heating/run time (HT) and aging on the fouling/cleaning of heat exchangers is not well understood. Longer heating time of the same deposit is expected to result in the formation of stronger and perhaps more cleaning resistant deposit. In this study, the phenomenon of heating and aging on the formation and cleaning of dairy fouling is investigated using the heat induced whey protein gels (HIWPG) produced in laboratory. The processes were also investigated with the whey protein deposits formed in pilot-scale plant trails. The HIWPGs were produced in tubular capsules for various heating (or run) times (60, 120, 240, 1440 and 2880 min respectively) and then dissolved in aqueous sodium hydroxide (0.5 wt %). The heating process here would have been of ‘pure’ aging. The dissolution rate was calculated based on the previously established UV Spectrophotometer analysis. The structure and texture of the gels were analysed using Scanning Electron Microscope (SEM) and texture analyser. In the pilot-scale plant study, whey protein fouling layers were generated by recirculating whey protein solution (6 wt %) for various heating periods (30, 60, and 90 min respectively). The deposit layers were then removed by recirculating aqueous sodium hydroxide (0.5 wt %) and the cleaning efficiency was monitored in the form of the recovery of heat transfer coefficient while both fluid electric conductivity and turbidity were recorded as indications of cleaning completion. It was found that increasing the HIWPG heating time significantly increased the gel hardness and dissolution time, implicating the difficulty in cleaning. Similarly to these results on gels, increasing the pilot-scale plant heating/run time increased the extent of fouling. The fouling layer formed next to the metal surface experienced the longest period of aging and the slope of the heat transfer coefficient increase seen at the final cleaning stage is related to this aging effect. The rate of cleaning for deposits formed initially on the metal surface is lower indicating a ‘pure’ aging effect of the deposit near surface.