A cooler is modelled in Aspen Plus to cool down the concentrated acid stream from the evaporator. For 61 wt.% acid hydrolysis, the temperature is cooled down to 55 ℃, and for 64 wt.% acid hydrolysis, the temperature is cooled down to 45 ℃. The cooling down can be conducted using a heat exchanger with external water, such as a river flow, thereby leading to negligible utility consumption.