Electrochemical directed crystallization control: A new approach to prevent blockages in tunnel drainage systems

The sustainable operational capability of a tunnel drainage system is directly related to the overall service safety. This paper presents an electrochemical solution to reduce the ion concentration in water by directionally promoting the transition of ions in the deposition tube toward crystallization. This reduces the ionic concentration, effectively inhibits the precipitation of crystals in the drainage pipes, and prevents clogging. An indoor experimental setup was built to systematically investigate the effects of the electrode materials, pipe inclination, flow rate, voltage, and electrode spacing on the crystallization efficiency of the device. Accordingly, a response surface model of the voltage, flow rate, and electrode spacing was established using Design-Expert 13 software, which revealed the interactions among the key parameters in formulating a multi-objective optimization strategy. The optimized parameter combinations were as follows: voltage U = 8.469 V, flow rate v = 45.949 cm/s, and electrode spacing d = 3.732 cm. The maximization of the drain removal rate (P) was prioritized, whereby the predicted removal rate reached 81.503%. Experimental validation showed that the predicted results were reliable. This study provides theoretical guidance and practical reference for the prevention and control of crystalline blockages in tunnel drainage systems.