Temperature Variation during the Preparation Process of a Large-Diameter Cryogel and its Properties
Kejian Yao · Journal of Chemical Engineering of Chinese Universities · 2010
Temperature is one of the most important factors in the preparation of large-diameter cryogels.An online temperature measuring system was established to monitor the temperature variation during the formation of a large-diameter cryogel with 7%(w/w) acrylamide solution in the stainless steel mold equipped with 9 thermocouples in its different positions.The diameter and height of the mold are 140 and 20 mm,respectively.The solution at these monitoring positions began to crystallize when the temperature decreased for about 20 to 40 minutes.The crystallization temperature of the solution was about-4.5 to-6.4℃,and its freezing point was about-2.4℃.The crystal growth duration at different positions were approximately from 2 to 18 minutes.The heat transfer characteristics in the cryogel mold based on the temperature curves obtained at various axial and radial positions were discussed.The basic properties of the large-diameter cryogel,i.e.,pressure drop,residence time distribution(RTD),and height equivalent to a theoretical plate(HETP),were also measured.The results show that the temperature varies irregularly during the formation of large-diameter cryogels.The HETP and permeability of the obtained cryogels ranges from 0.21～0.41 cm and(3.54～4.17)×10-11 m2,respectively.