การออกแบบระบบการนำน้ำกรดทิ้งกลับมาใช้ใหม่ในอุตสาหกรรมรีดเหล็ก / ประไพรัตน์ เอนกนันท์ = System design of acid recycle in the metal wire industry / Prapairat Anakenant
The waste acid recycling system has been design using the continuous process by installing the Ion exchanger unit (retardation unit) was performed to investigate its performance on free acid recovery in spent pickling acid solution. The pickling acid solution circulates continuously between the pickling bath and the regeneration plant. The financial profitability can be analyzed by calculating the amortization of the capital investment. To design this system, the unit operation, consist of 1 the pickling bath, 1 unit of waste storage tank to hold waste acid drainage from reactor tank, and 1 unit of ion exchanger unit. Part of the pickling solution is pumped from storage tank into the retardation unit which recoveries free acid and removes the metal salt. The free acid is pumped through into preparation tank to mixing with 35% HCL then can be reuse in pickling process. The system has been designed using 15% hydrochloric acid to remove the oxides and rust. The iron salt concentration increases, while the concentration of free acid decreases. This means, that the pickling effect will be reduced continuously until the concentration of dissolved metals reaches a ‘critical value’ at which the pickling solution has to be renewed. The pickling solution fed into retardation unit to recovery acid, the retardation unit can recover acid at 88.83% and can remove Fe+2 from 41.89% while flow rate and concentration of pickling solution has no effect to capability of recycling acid and eliminate of rust. Economic evaluation value of this process found that the owner can save a lot of cost up to 1,536,450 Bath/year and the payback period for this technology is 3 years. The design to recycling waste acid using continuous process above has been proved that appropriate to use in the each metal finishing industry using retardation unit to recovery of free acid. This system can save cost for the loss of free acid and equivalent demand of sodium hydroxide for neutralization, decreasing salt effluent into watercourse and also reduce impact the environment which lead to an economic value for society.
