板式换热器中豆浆的沉积行为

Fouling behavior of soy milk in plate heat exchanger

采用热交换器加热豆浆时,在换热表面会形成沉积物,从而影响换热效率。该研究组装了一套小型的板式换热设备系统,探讨在不同pH和不同进料温度下,蛋白质质量分数3.50%的豆浆加热到105~125℃时的沉积行为及沉积物组分的变化。结果表明,当豆浆pH≥6.5时,总传热系数(U)及沉积因子(Rf)随着加热时间增加而表现为渐进变化过程;而在pH 6.3时,U和R f在90 min左右出现突变。随着豆浆进料温度的升高,Rf增大。沉积物的成分分析表明,随着豆浆pH与进料温度的降低,沉积物中的蛋白质和脂肪含量逐渐升高,而灰分含量逐渐降低。豆浆pH在中性附近且豆浆直接进入加热段而不进行预热,是缓解沉积问题的关键。

When soy milk is heated by a heat exchanger,deposits are formed on the heat exchange surface,thereby affects its heat exchange efficiency.In this study,a small plate heat exchanger system was first assembled.The fouling behavior and compositions of deposit by soy milk with a protein concentration of 3.50%at 105-125℃were studied at different pH and different feed temperatures.The results showed that when the pH of soy milk was≥6.5,the overall heat transfer coefficient(U)and fouling factor(Rf)showed a gradual change with heating time.At pH 6.3,U and Rf showed a mutation process at about 90 min.The fouling factor of the soy milk increased with the increase of the feed temperature.According to the composition analysis of the deposits,as the pH and feed temperatures of the soy milk decreased,the protein and fat content in the sediment gradually increased,while the ash content gradually decreased.From the perspective of alleviating fouling problems,the first is to ensure that the pH of the soy milk is near neutral,and the second is that the soy milk directly enters the heating section without preheating.