Comparison of safety indexes for chemical processes under uncertainty

PresentationThe fatal consequences of industrial incidents have made evident the need for suitable tools to develop inherently safer process designs. Traditionally, in a process design project, the evaluation of safety aspects is left for analysis after the detailed design has been completed. This approach leads to the use of control loops, barriers and protection layers as the only ways to prevent incidents and to reduce the possible outcomes. An alternative to this approach is the application of the concept of inherent safety, which was introduced to set up several principles that aim to enhance process safety by eliminating, avoiding or minimizing sources of risk. In this work, we present a comparison of different safety metrics in their role to evaluate the risk associated with a given process design. The indices selected for consideration are better applied at the conceptual stage of the process design, and they were the Dow’s fire and explosion index (F&EI), the fire and explosion damage index (FEDI), the process route index (PRI) and the process stream index (PSI). All these indices use different input information and their outcomes have different rankings. The metrics were applied to an ethylene production process to identify risk levels, and the location of streams and pieces of equipment that pose the highest risk within the process. An evaluation of the indices in their capability to track design changes in operating conditions aiming to improve the safety level of the process was developed. To perform the assessment of the safety metrics in a more extensive manner, an uncertainty analysis based on a Monte Carlo simulation framework was implemented and compared to the traditional use of single-value design variables. Within this context, an insightful assessment of uncertainty’s effect on process safety characteristics was achieved because of the identification of ranges of safety- relevant performance outcomes (zones of risks and opportunities) that can be probabilistically characterized. The approach was applied to a case study related to the production of ethylene from shale gas. The results showed how some indexes are better suited to capture the risk characteristics associated with the process when changes in the operating conditions of the section with highest risk were implemented. The methodology can be extended to other processes of interest, and may serve as a basis for the safety and process design community to propose adjustments in the structure of the safety indices based on a better understanding of their performance and reliability as part of the efforts towards the continued improvement of those safety metrics

The Options Value of Blue Hydrogen in a Low Carbon Energy System

A developer considering the construction of a Steam Methane Reforming facility for the production of hydrogen from natural gas faces the decision as to whether to incorporate and operate a Carbon Capture and Storage (CCS) unit, as part of the facility, in an environment where the costs of inputs and the price of hydrogen are uncertain. Conventional valuation methodologies such as Discounted Cash Flow (DCF) cannot systematically integrate uncertainty from changing market and regulatory conditions. Such methods are also unable to account for the ability of management to make use of flexibility to respond as the uncertainties are progressively resolved proactively. Consequently, an Engineering Flexibility / Real Options approach has been developed to allow the calculation of the additional value that the developer might obtain if a CCS unit is not fitted at the time of construction of the SMR plant. Instead, the plant is constructed so that the CCS unit can be retrofitted during the plant’s lifetime if the economic conditions are such that it appears that this will increase the value of the SMR plant. Application of this approach has shown that, for this example, the Net Present Values are increased in a range of energy price and cost of CO2 release scenarios, i.e. the Real Option has a positive value. These findings hold for a range of discount rates. Similarly, the approach improves the Value at Risk and the Value at Gain. Whilst in this work, the approach has been applied to the example of the decision of whether to fit a CSS unit to an SMR plant for the production of blue hydrogen, it is believed that a similar approach can be applied to other situations

Selective Process Steps for the Recovery of Scandium from Jamaican Bauxite Residue (Red Mud)

We report the development of a process allowing the selective, sustainable recovery of scandium (Sc) with 75% efficiency from Jamaican bauxite residue (red mud), a waste product from aluminum production. The process design is inspired by green chemistry principles and focuses on establishing highly selective process steps (sulfation, leaching, and precipitation) in order to minimize costs and waste produced. In addition to scandium oxide, the chosen approach produces mixed rare earth oxides as a side product, thus isolating an average of 88% of all rare earth elements contained in red mud. Furthermore, in light of predicted supply shortages of the critical material Sc and the need to establish cost-effective bauxite residue remediation techniques, a systematic Monte Carlo-based economic performance assessment framework is developed in order to evaluate the economic prospects of the proposed process system in the presence of irreducible uncertainty

Model reduction and coarse-graining approaches for multiscale phenomena

Model reduction and coarse-graining are important in many areas of science and engineering. How does a system with many degrees of freedom become one with fewer? How can a reversible micro-description be adapted to the dissipative macroscopic model? These crucial questions, as well as many other related problems, are discussed in this book. Specific areas of study include dynamical systems, non-equilibrium statistical mechanics, kinetic theory, hydrodynamics and mechanics of continuous media, (bio)chemical kinetics, nonlinear dynamics, nonlinear control, nonlinear estimation, and particulate systems from various branches of engineering. The generic nature and the power of the pertinent conceptual, analytical and computational frameworks helps eliminate some of the traditional language barriers, which often unnecessarily impede scientific progress and the interaction of researchers between disciplines such as physics, chemistry, biology, applied mathematics and engineering. All contributions are authored by experts, whose specialities span a wide range of fields within science and engineering

Cost Analysis as a Tool for the Development of Sc Recovery Processes from Bauxite Residue (Red Mud)

Process development for the recovery of rare earth elements (REEs) from production wastes is generally seen as one strategy to address potential supply shortages for these critical materials. However, very few reported process systems are both technologically feasible and economically viable. Herein, we propose a strategy which considers comprehensive cost analysis in the presence of irreducible uncertainty as a core strategy introduced early on at the process design stage for the recovery of scandium (Sc) from bauxite residue (red mud). The latter represents an important process example of REE recovery from what is typically considered a waste material. In particular, using both a classical and a probabilistic framework for cost model development and assessment, cost is considered as a key design parameter in addition to selectivity and yield to design processes primed for industrial applications. We further show that such an approach affords significantly enhanced prospects of economic viability to the proposed process system when comparatively evaluated against reported ones, thus promising to drive environmental remediation of red mud through recovery of a valuable material (Sc₂O₃) under enhanced environmental and economic performance profiles

Data for "Thermodynamic feasibility of shipboard conversion of marine plastics to blue diesel for self-powered ocean cleanup"

The data provided here accompanies the soon to be published article titled "Thermodynamic feasibility of shipboard conversion of marine plastics to blue diesel for self-powered ocean cleanup". Contained within the file is the raw data generated from the integrated Monte Carlo simulation and sensitivity analysis. Data is provided for Figure 2 as well as SI Figures SI.2 and SI.3. The data shows the probability of meeting ship exergy requirements in percentage for varying surface plastic volume percent for all the plastics studied for HTL, pyrolysis and varying flowrates. Data is also provided for Figure 4 generated from the framework showing the varying time to clear the Great Pacific Garbage Patch and the associated number of booms for varying boom-boom distances