Process synthesis and optimization of an integrated chilled and cooling water system for resources conservation

Globalization, economic development and population growth have led to a sustained upward trend in world energy demand. The increasing level of energy consumption, especially in the industrial sector, has also contributed to adverse environmental impact via carbon emissions. Water chillers, which are used in many industrial processes for heating, ventilating and air conditioning (HVAC) and process cooling, are among the major energy consumers in many industrial facilities. Energy sources depletion and the increasing greenhouse gas pollutions have driven the worldwide effort to reach the highest possible level of energy efficiency. One of the strategies to improve energy efficiency is by having multiple plants located in a close proximity known as eco-industrial park (EIP); cooperate in a joint effort to achieve a greater overall energy savings. Forming an EIP which is operated by independent entities requires the consensus from all parties, thus there exists a need for a strategic decision-making tool. Moreover, periodical circumstances such as seasonal and market demand changes by each participating plant would result in different mode of process operation in an EIP. Thus, there is a need to study explicitly the effect of such periodical operations due to the high level of connectivity within an inter-plant network. In this research, we have developed four different approaches for EIP by integrating both chilled and cooling water systems (CCWS). First contribution in this work is the introduction of free cooling in an integrated superstructure for CCWS. It is found that the interaction between both systems could enhance the overall resource conservation beyond those achievable by individual system alone. Second contribution is the adoption of fuzzy analytic hierarchy process (FAHP) approach in the development of decision-making framework for the synthesis of inter-plant chilled and cooling water network (IPCCWN). This approach considers all the participating plants‘ interest for the establishment of an EIP so as to reach the consensus of cooperation. Third contribution is the development of a systematic stepwise approach for obtaining a flexible multi-period IPCCWN that could accommodate for the variation of cooling utility flow rate and temperature. Lastly, we proposed an integrated analytic hierarchy process (IAHP) approach to the development of multi-objective optimization of IPCCWN that embeds multiple design criteria simultaneously. In future work, we suggest extending the aforementioned approaches to CCWS with waste heat recovery scheme through absorption chilling process