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Reduction of energy consumption has increasingly come into sharp focus in the chemical process industry. This is of great value not only for existing plant but also for the development of new processes. Therefore, the challenge for process design engineers to develop an integrated chemical process that simultaneously satisfies economic and environmental objectives has increased considerably. Particularly, multi-objective optimization in the chemical industry has become increasingly popular during the last decade. The main problem lies, in selecting the alternative best design during decision making with multiple and often conflicting objectives. This thesis work presents a methodology for the multi-objective optimization of process design alternatives under economic and environmental objectives and also to establish the linkage between exergy and the environment. Four distillation units design alternatives with increasing level of heat integration were considered. Each design is analysed from exergy, potential environmental impact (PEI) and economic point of view. A non-dominated solution known as the “Pareto optimal solution” is generated for decision making. The thermodynamic efficiency indicates where exergy losses occur. The demand for industrial process heat by means of solar energy has generated much interest because it offers an innovative way to reduce operating cost and improve clean renewable electric power. Concentrated Solar Thermal Power (CSP) can provide solution to global energy problems within a relatively short time and is capable of contributing to carbon dioxide reduction, which is an important step towards zero emissions in the process industries. This work provides an overview of a simulation model to evaluate the environmental and economic performance of two case studies of solar thermal power plants. A methodology is presented to integrate solar thermal power plant into industrial processes and this is then compared with an existing hydrocarbon recovery (HCR) plant that depends on coal as its energy source. The two process design alternatives where simulated using the process simulator Aspen PlusTM. This thesis work also evaluates two types of power plants based on coal. The plants considered provide utility systems such as steam and electrical energy to the process plants. Exergy analysis was performed for each type of plant. The standard PEI calculation procedure has been modified for consideration of specific energy resources or power plants.
Stringent safety and environmental regulations, and competitions have challenged the chemical process industries to bring products to market at low lifecycle costs without compromising on safety and environmental standards. Frequently, a large number of alternatives with different structure design and process alternatives of distillation unit can be found to satisfy the demanded criteria of improvement target. Therefore, a systematic method for the improvement of distillation unit is of the considerable interest in order to evaluate the improvement objectives of design alternatives that include economic, environmental and safety criteria. Accordingly, this thesis presents integrated improvement of distillation unit based on careful and simultaneous evaluation of economic, environmental and safety criteria of the design alternatives. The approach for integrated plant improvement in this paper bears the consequence that economically attractive plant might not be the ultimate criteria as the decision tools to choose the best design, but put this economic criteria in a degree of preference in comparison to other criteria. Then, the evaluation of safety and environmental objectives in one side and total cost objectives in other side should be taken into account as a critical step in the plant improvement scenario. This research proposes a fundamental work on evaluation of economic, safety and economic criteria in distillation technology in an integrated manner. Economic evaluation will be calculated based on total annualized cost calculation. Environmental evaluation relies on the calculation of potential environmental impact associated with generated heat and mass balances generated by process simulation. Safety evaluation will be based on dynamic simulation of the investigated distillation unit during disturbance or non-standard operation as well as inherent safety index calculation. At the end, this thesis proposed a methodology for the improvement of distillation unit based on a framework of multi criteria decision making analysis. An analytic hierarchy process methodology is used to support decision upon the criteria for selection, rate the relative importance of the criteria and its advantages/ disadvantages as well as to combine the ratings to obtain an overall rating for each choice of design improvement. The concept will be applied in an existing plant as case study. It is supposed that the proposed integrated-scenario is applicable to support a decision making in chemical industries that always deal all the time with improvement tasks.