Air Products (United Kingdom)

We consider the problem of aggregating the judgements of a group of experts to form a single prior distribution representing the judgements of the group. We develop a Bayesian hierarchical model to reconcile the judgements of the group of experts based on elicited quantiles for continuous quantities and probabilities for one-off events. Previous Bayesian reconciliation methods have not been used widely, if at all, in contrast to pooling methods and consensus-based approaches. To address this we embed Bayesian reconciliation within the probabilistic Delphi method. The result is to furnish the outcome of the probabilistic Delphi method with a direct probabilistic interpretation, with the resulting prior representing the judgements of the decision maker. We can use the rationales from the Delphi process to group the experts for the hierarchical modelling. We illustrate the approach with applications to studies evaluating erosion in embankment dams and pump failures in a water pumping station, and assess the properties of the approach using the TU Delft database of expert judgement studies. We see that, even using an off-the-shelf implementation of the approach, it out-performs individual experts, equal weighting of experts and the classical method based on the log score.

To maximise economies of scale of future CO2 transport infrastructure, new CO2 pipelines within the carbon capture utilisation and storage (CCUS) value chain, should ideally have excess capacity to satisfy future transportation demand. However, in scenarios where booster compressors cannot be employed along the pipeline, the rise in pipeline mass flow rate over time culminates in higher energy consumption of upstream compression/liquefaction. This work explores the optimisation of various CO2 pressurisation pathways and assesses their flexibility in handling a variability in pipeline mass flow rates whilst delivering a captured CO2 stream at a fixed final pressure of 100 barg. The study is based on the Dunkirk 3D Project, which has a planned nameplate capture capacity of 1 MtCO2/y, with other CO2 point sources taking up additional pipeline utilisation capacity. Two categories of CO2 pressurisation pathways are considered, gas compression and subcritical liquefaction and pumping. These pathways are optimised to enable a fair comparison, considering the number of compression stages, compression ratio, and cooling/liquefaction system. Modelling results indicate that the temperature of the cooling utility has the greatest influence in reducing the overall work duty and sensitivity to a variability in pipeline mass flow rate. Furthermore, the utilisation of 5 °C seawater as a cooling and liquefaction utility reduces the work duty of the conditioning process by 25.4% and requires fewer compression stages relative to conventional gas compression utilising cooling water at 30 °C.

In recent years, piece-wise convex relaxations of power flow equations have attracted substantial academic interest. These approaches build such relaxations by partitioning the variables’ domain. However, the ensued formulations grow very rapidly in size with the number of partitions, thus becoming computationally intractable to achieve strong dual bounds for realistic-size instances. In this work, we propose piece-wise polyhedral relaxations of power flow equations utilizing the latest advancements in mixed-integer programming (MIP) modeling techniques. A computational campaign conducted on 24 PGLib benchmark instances of the OPF problem shows that the choice of MIP formulation on piece-wise polyhedral relaxation of power flow equations significantly impacts the computational time.

Abstract With the recently approved IEC 61511 and ANSI/ISA‐84.00.01 standards, process industry companies are being challenged to determine the level of performance required from their safety instrumented functions (SIF) and to verify that the design, installation, operation, and maintenance employed is sufficient to ensure that the required performance is sustained until the SIF is decommissioned. As a practical matter, user companies must self‐certify or user approve their SIF equipment, since they are responsible for the correct operation of the SIF in the operating environment, not just individual components as manufactured. To accomplish this, user companies need lifecycle assistance from equipment manufacturers, irrespective of hardware or software certification status related to IEC 61508. One of the best means to communicate the necessary information is via a safety manual for those involved in instrument system design installation and operation. IEC 61508 requires that equipment manufacturers provide a safety manual with any product claimed to comply with IEC 61508. Although required for product certification, it is the authors' current experience that quality and consistency in safety manuals is lacking. Part of this is due to IEC 61508 not providing a clear concise template with minimum requirements. The safety manual requirements are scattered throughout the rather complex standard. This article seeks to provide a user's perspective of what essential information is needed from equipment manufacturers to not only comply with IEC 61508, but also to provide enough information to the user of the product to allow the essential balance of reliability and safety in both SIF and instrumented protective function applications. © 2007 American Institute of Chemical Engineers Process Saf Prog 2007

A novel fibre optic sensor system has been developed to enable the linear location of acoustic emission. The demonstration of linear location of acoustic emission was conducted using a pair of serial multiplexed fibre coupler-based acoustic emission (AE) sensors in conjunction with a single light source. The simulated AE source, via a pencil lead-break test, was located to within ± 5mm.