Development and Integration of Simple and Quantitative Safety, Pollution and Energy Indices into the Design and Retrofit of Process Plants
Ordouei, Mohammad Hossein
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Currently, the main focus in a chemical process design is cost reduction and profitability. This approach results in high expenditure due to the generation of huge amounts of wastes, which in turn requires waste control stations such as wastewater treatment facility, incinerator and so on. In other words, in conventional design the waste reduction is carried out at the late stage of process design, sometimes referred to as the end of pipe treatment, which causes impacts on environment, inventory of hazardous chemicals, energy consumption as well as cost impacts on the process. Due to all the above aspects, the impact of decision making is highest at the conceptual phase of a process design. However, this impact can be minimized by shifting the waste reduction from the late step of the process design to its early stage. There are several barriers for such shifting; the most important of which is the lacking of a methodology to be used as a screening tool at the conceptual design phase in order to select the inherently safer and the environmentally friendlier design. The objective of this thesis is to develop simple and quantitative indices that can be employed in minimizing the adverse effects of material and energy emissions from chemical industries. Several improvements to existing methodologies for pollution minimization are given. These are based on waste reduction concepts and are applicable from the initial step of a process design to revamping of existing processes. A simple risk index for the evaluation of risks to the safety of chemical processes is also developed. The work provides indices for evaluation of potential environmental impacts as well as safety risks of a chemical process in order to reduce the hazardous wastes generation and energy consumptions as well as safety risks reduction while maintaining the process throughput and profitability. This research offers new methodologies, which have significant contributions in sustainability development by providing new and simple indices to be employed at initial step of a chemical process design with minimum available process data for the evaluation of energy impacts of the process on the environment and at the same time for the assessment of the risks to the chemical process. These new indices are combined with the well-known WAR algorithm to offer a composite index to help investors, regulators and also process designers to select the sustainable design from other process design array. The new methodology uses Key Process Index (KPI) for ranking purposes merely from technical point of view. Even when two or more sustainable processes are concerned, the composite index can find the inherently safest, environmentally friendliest process without trade off with process economy and profitability. So, the new indices can be renamed as “Must Know Composite Indices” for chemical process designers. These Must Know Composite Indices are illustrated on several case studies and are proven to be effective tools on several fronts such as: 1. As screening tools for investors/owners who need not be experts in chemical, environmental or safety engineering. They usually receive a bunch of proposals after advertising a tender for a new project or retrofitting an existing chemical process plant. The utilization of the Must Know Composite Indices will allow them to enter the available process and economic and calculate all indices, rank the proposals and recommend the top ranked processes. 2. As screening tools for process designers: A process engineer will get into the insight of design alternatives in terms of environmental protection, inherent safety and energy impacts of the alternative designs. Then, s/he will make necessary changes to make a sustainable design at minimum impacts of decision at conceptual design stage. 3. As a coding system for process design similar to piping codes. For instance, KPI 1234 (234, 500, 500); where 234, 500 and 500 are the contribution of energy impacts, environmental impacts and safety risks to the process design, respectively. 4. As an incentive/penalty tool for the government in order to penalize plants who are harmful to the environment and society or to, otherwise, provide stimulus programs.