Sato Eri, Ochi Yusuke, Horiguchi Hiroo, Takenaka Katsuhide, Wu Jie, Parthasarathy Rajarathinam, Komoda Yoshiyuki, Ohmura Naoto
Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe-shi 657-8501, Hyogo, Japan.
Sumitomo Heavy Industries Process Equipment Co., Ltd, 1501 Imazaike, Saijo 799-1362, Ehime, Japan.
ACS Omega. 2021 Sep 6;6(37):24070-24074. doi: 10.1021/acsomega.1c03503. eCollection 2021 Sep 21.
The material deposition in a mixing tank agitated by the MAXBLEND impeller in a turbulent state was quantified and compared between cases with and without baffle clearance. Magnesium hydroxide formed from the chemical reaction between calcium hydroxide and magnesium chloride was used as a model of scale formation. Flow velocity in the tank was investigated by employing computational fluid dynamics simulation and experimentally validated by an ultrasonic velocity profiler method. Results showed that the amount of scale decreased with the increase in the rotational speed of the impeller due to the erosion effect on the tank wall. In the case without baffle clearance, the smaller weight of the scale was deposited on the front of the baffle plate due to the flow impingement, which enhanced the removal of the scale deposition. However, the lower-velocity magnitude behind the baffles resulted in an enhancement in the formation of scale. Installation of baffle clearance caused a contraction flow in between the tank wall and baffles, and consequently, the higher flow velocity reduced the amount and thickness of the scale. Measurement of the torque showed that the baffle clearance did not affect the power consumption, so the installation of baffle clearance can be a promising approach to reduce scale deposition in terms of saving operational costs and increasing process efficiency and safety.
对由MAXBLEND叶轮在湍流状态下搅拌的混合罐中的物料沉积进行了量化，并比较了有无挡板间隙情况下的沉积情况。由氢氧化钙与氯化镁之间的化学反应形成的氢氧化镁被用作结垢模型。通过计算流体动力学模拟研究了罐内流速，并通过超声速度剖面仪方法进行了实验验证。结果表明，由于对罐壁的冲刷作用，结垢量随叶轮转速的增加而减少。在无挡板间隙的情况下，由于水流冲击，较轻的水垢沉积在挡板前部，这增强了水垢沉积的去除。然而，挡板后面较低的流速导致结垢增加。安装挡板间隙会在罐壁和挡板之间产生收缩流，因此，较高的流速减少了水垢的量和厚度。扭矩测量表明，挡板间隙不影响功耗，因此，从节省运营成本、提高工艺效率和安全性的角度来看，安装挡板间隙可能是减少水垢沉积的一种有效方法。
