At Plant 2 of OPTC, the TA slurry used during purification is preheated in multiple stages. The heating sources include flash evaporation and condensate, which are produced in the crystallizer. With improvement measures, the system is capable of capturing residual heat from the condensate at approximately 160^oC. The TA slurry is heated to 125^oC before being sent to the preheater where temperature rises to 136^oC. The system increases preheating temperature by 6^oC, thus reducing the use of high-pressure vapor for heating, as well as natural gas consumption at the boilers. The improvement saves approximately 18,363 metric tons of high-pressure vapor annually, and NT$ 14.6 million in costs.