(206b) Root Cause Analysis in Design for Sustainability

In process design, a base design usually has lots of room for improvement. After knowing the sustainability performance of a particular design, questions will arise naturally: why its sustainability performance is not good enough? Which aspects contribute most to the overall sustainability performance? Can we adjust any design elements to improve the overall system's performance? Solving these problems is practically impossible without taking into account many factors and their cause-and-effect relationships between them. Root Cause Analysis (RCA) techniques, such as Fishbone Diagram, Pareto Chart, check sheet, have been widely used in quality control, management, failure analysis and process safety. However, so far, there is no particular technique available for sustainability analysis. In this paper, a novel Sustainability Root Cause Analysis methodology will be presented. It will facilitate designers to define and display the fundamental causes, related causes and root causes that impact the sustainability of a process, understand the potential interrelationships of various causes which ultimately lead to the sustainability issue. Moreover, it will prioritize the importance of different causes so that the designers can focus on the highest value efforts to conceive possible solutions to improve sustainability. The applicability of this methodology will be illustrated by case studies on syngas production. One method of producing syngas is by using coal and natural gas together as feed. Coal is cheap and readily available, whereas natural gas is a clean burning fuel and is useful in adjusting the H2/CO ratio, which is a key factor in the manufacture of chemicals from syngas. In this research, a complete flowsheet of a process has been developed and root cause analysis has been applied in order to identify the true root causes, discover ways to improve the overall sustainability of the process concerning economic, environmental, efficiency and safety issues.