(164c) Application of Inherently Safer Design Tool (i-SDT) for Health Risk Assessment during Fugitive Emission

Monzure-Khoda Kazi^a, Fadwa Eljack^a,*, Mimi H. Hassim^b

^aQatar University, Department of Chemical Engineering, College of Engineering, Doha, Qatar, P.O. Box-2713

^b Universiti Teknologi Malaysia, Faculty of Chemical and Energy Engineering/Centre of Hydrogen Energy, 81310, Johor, Malaysia

Industrial processes are losing significant portion of hydrocarbon or valuable materials from their equipment due to fugitive emission, which is also contributing to the global issues of air pollution and anthropogenic climate change (Kletz & Amyotte, 2019). Fugitive emissions are not only of economic and environmental concern, but also a major source of health risk exposure to workers that may lead to various diseases including cancer. More people die every year from occupational diseases as compared to the number killed in industrial accidents. Therefore, fugitive emissions are becoming less and less tolerated by regulating agencies.

From the context of occupational health, long-term exposure as a result of fugitive emissions is the most important sources of hazards for worker exposure in chemical plants. Despite being very small and mostly invisible, fugitive emissions are the main sources of the continuous background exposure to workers. Fugitive emissions are often neglected as their amount of emissions is always claimed as insignificant in comparison to point source emissions i.e. stack. Human health risk assessment can be one of the ways to estimate the nature and probability of adverse health effects in humans who may be exposed to chemicals in contaminated environmental media through fugitive emissions.

A health risk assessment requires the evaluation of toxicity, or hazard of an agent and the exposure to the agent. This assessment should be conducted at the early stage of chemical process design when the cost of making changes is the lowest. Early evaluation of process hazards is beneficial because process can be made inherently benign at lower cost. This is however impeded by the limited knowledge on the leak sources, since the process is still under design. Thus, it would be advantageous if the amount of fugitive emissions can be measured properly during the design phase. As many of the costs associated with fugitive emissions are invisible, the true costs are not appreciated. These are mostly related to health risk exposure. Therefore, a proper methodology of health risk assessment should be established to measure the effects of fugitive emissions on human health.

In this work, the scope of Inherently Safer Design Tool (i-SDT) has been extended to identify the leakers for fugitive emission based on equipment failure data considering type of equipment and operational conditions. It also tracks the risk associated with fugitive emission and assesses the associated health risk exposure index to characterize the impacts of leaked gases on human health. The metric is built on a property platform and employs characteristic equations to evaluate the safety parameters (i.e., flammability, explosiveness, toxicity, etc.) under various operating conditions (Eljack et al., 2019). Hence, it is capable of continuously evaluating the safety performance of a process. This will allow the designer to estimate the health risk exposure using the toxicity parameter in i-SDT. The final output of this i-SDT tool is the cluster safety parameter score that evaluates the inherent safety of a process. It provides the designer means of applying the four major principles of inherent safety at the early stages of process synthesis and design. The designer can identify components that pose higher risk and then decide on whether to minimize the amount of chemical constituents, use moderate operating conditions to impact chemical properties or substitute alternative constituents for inherently safer operation when possible. The resulting process that is inherently safer will require less complex control and safety measures, hence achieving the fourth inherent principle of simplification. The emissions’ assessment from a case study of LNG supply chain and the storage systems is presented to demonstrate the proposed approach.

References

Eljack, F., Kazi, M.-K., & Kazantzi, V. (2019). Inherently safer design tool (i-SDT): A property-based risk quantification metric for inherently safer design during the early stage of process synthesis. Journal of Loss Prevention in the Process Industries, 57, 280-290.

Kletz, T., & Amyotte, P. (2019). Chapter 18 - Leaks. In T. Kletz & P. Amyotte (Eds.), What Went Wrong? (Sixth Edition) (pp. 345-372): Butterworth-Heinemann.