Evaluation of an alternative chlorine production process for energy saving toward sustainability

Exergetic-based solutions are proposed in this work to reduce the energy footprint of an alternative chlorine production process. By presenting exergy analysis results in the form of visualized exergetic process flowsheets using a solution panel, this study does not only find the low-exergy-efficient unit operations, but also proposes ways to improve the exergy efficiency based on the major sources of irreversibility of individual unit operations. Based on the amount of exergy losses, the alternative chlorine production process is divided into three main functional blocks. The total internal and external exergy losses for the entire process are calculated as 14,523.5 and 286.1 kJ/kg, respectively. The electrolysis block shows the highest potential for improvements with the largest exergy loss (responsible for more than 96.0% of total losses; with 14,093.2 kJ/kg of internal losses and 146.5 kJ/kg of external losses). Isothermal mixing, lower reaction temperature, and reduced pressure drop are suggested as avenues for improvement. Exergy losses in the gas treatment block with total exergy losses of 411.7 kJ/kg (equivalent to 2.8% of total losses) are mainly due to the cooling column (241.9 kJ/kg), where modifications in column might be helpful as concentration and temperature gradients along the tower are sources of exergy loss. The highest exergy loss in the feed pretreatment block with the total exergy losses of 158.2 kJ/kg (i.e., 1.1% of total losses) belongs to the mixers (106 kJ/kg) where isothermal and also isobaric mixing is required. (c) 2016 American Institute of Chemical Engineers Environ Prog, 35: 1512-1520, 2016