Modeling, simulation and optimization of a heat exchanger network for Mmximum energy eficiency and minimum cost

Heat Exchangers are one of the major items of equipment applied in combination with almost all the unit operations in the process industry. Therefore, optimizing heat exchangers would be an ideal solution for the problem of increasing energy costs in the industry. Pinch analysis can be used to identify minimum energy cost and energy efficient heat exchanger networks through the recognition of pinch point as referred to the temperature profile of the process at which the minimum level of allowable temperature difference is achieved. The pinch analysis first predicts the minimum requirement of external energy, heat exchanger network area and the number of units for the typical process at the pinch point. Then, the heat exchanger network design that satisfies the minimum energy target is synthesized. Finally, it is optimized by comparing the energy cost and the capital cost. Pinch analysis to reduce external utility loads can be performed in special computer software packages for even rigorous heat exchanger networks. The prime objective of this research is to utilize a computer aided modelling and simulation approach to provide a generalized methodology for the optimization of a heat exchanger network through pinch analysis for a typical distillation column

Architecture for Digital Spare-Parts Library: Use of Additive Layer Manufacturing in the Petroleum Industry

Part 9: Operations Management in Engineer-to-Order ManufacturingInternational audienceSpare parts management (SPM) is a typical challenge in the offshore and onshore petroleum industry. SPM consumes a significant amount of operational expenses that are attributed to maintaining the integrity of production and process facilities (P&PFs) at the anticipated level. Productive SPM approaches are essential for maintaining integrity; in particular, ageing P&PFs and legacy assets exacerbate the challenge of maintaining integrity at the anticipated level. This manuscript firstly provides an overview of how additive layer manufacturing/three-dimensional (3D) printing has been effectively utilized by different manufacturers to produce equipment, which resembles the equipment used in the petroleum industry. Then, it discusses the potential use of a digital spare parts library and the optimal strategy to mitigate current challenges pertaining to SPM. Finally, it proposes an architecture for a digital spare-parts library

Maintenance Strategy Selection for Critical Shipboard Machinery Systems using a Hybrid AHP-PROMETHEE and Cost Benefit Analysis: A Case Study

The engine rooms of ships accommodate different machinery systems that are critical to ship operations. For these critical machinery systems to continue delivering the high level of service, operators are required to select and apply the best maintenance interventions. Currently, the selection of appropriate maintenance strategies for different engine room’s machinery systems is handled in a traditional way, regardless of in what condition such systems are. The aim of this paper is to propose a semi-qualitative model integrating AHP and PROMETHEE to select appropriate maintenance strategies for different critical machinery found in the engine rooms of ships. The proposed model consists of three maintenance alternatives among which decision-makers must select the best strategy according to four comparison criteria. The model is applied to select the best maintenance strategies for 17 different shipboard machinery systems in the engine room of a barge operating within West African waters. Finally, the results are compared with those obtained from a cost-benefit analysis approach (quantitative) as well as a survey of the experienced marine engineers who operate these machinery in the engine rooms of ships (qualitative). The results of the case study indicate that the proposed semi-qualitative method is a more robust approach for selecting maintenance strategies of shipboard machinery systems

Effect of the COVID-19 pandemic on surgery for indeterminate thyroid nodules (THYCOVID): a retrospective, international, multicentre, cross-sectional study

Background: Since its outbreak in early 2020, the COVID-19 pandemic has diverted resources from non-urgent and elective procedures, leading to diagnosis and treatment delays, with an increased number of neoplasms at advanced stages worldwide. The aims of this study were to quantify the reduction in surgical activity for indeterminate thyroid nodules during the COVID-19 pandemic; and to evaluate whether delays in surgery led to an increased occurrence of aggressive tumours. Methods: In this retrospective, international, cross-sectional study, centres were invited to participate in June 22, 2022; each centre joining the study was asked to provide data from medical records on all surgical thyroidectomies consecutively performed from Jan 1, 2019, to Dec 31, 2021. Patients with indeterminate thyroid nodules were divided into three groups according to when they underwent surgery: from Jan 1, 2019, to Feb 29, 2020 (global prepandemic phase), from March 1, 2020, to May 31, 2021 (pandemic escalation phase), and from June 1 to Dec 31, 2021 (pandemic decrease phase). The main outcomes were, for each phase, the number of surgeries for indeterminate thyroid nodules, and in patients with a postoperative diagnosis of thyroid cancers, the occurrence of tumours larger than 10 mm, extrathyroidal extension, lymph node metastases, vascular invasion, distant metastases, and tumours at high risk of structural disease recurrence. Univariate analysis was used to compare the probability of aggressive thyroid features between the first and third study phases. The study was registered on ClinicalTrials.gov, NCT05178186. Findings: Data from 157 centres (n=49 countries) on 87 467 patients who underwent surgery for benign and malignant thyroid disease were collected, of whom 22 974 patients (18 052 [78·6%] female patients and 4922 [21·4%] male patients) received surgery for indeterminate thyroid nodules. We observed a significant reduction in surgery for indeterminate thyroid nodules during the pandemic escalation phase (median monthly surgeries per centre, 1·4 [IQR 0·6-3·4]) compared with the prepandemic phase (2·0 [0·9-3·7]; p<0·0001) and pandemic decrease phase (2·3 [1·0-5·0]; p<0·0001). Compared with the prepandemic phase, in the pandemic decrease phase we observed an increased occurrence of thyroid tumours larger than 10 mm (2554 [69·0%] of 3704 vs 1515 [71·5%] of 2119; OR 1·1 [95% CI 1·0-1·3]; p=0·042), lymph node metastases (343 [9·3%] vs 264 [12·5%]; OR 1·4 [1·2-1·7]; p=0·0001), and tumours at high risk of structural disease recurrence (203 [5·7%] of 3584 vs 155 [7·7%] of 2006; OR 1·4 [1·1-1·7]; p=0·0039). Interpretation: Our study suggests that the reduction in surgical activity for indeterminate thyroid nodules during the COVID-19 pandemic period could have led to an increased occurrence of aggressive thyroid tumours. However, other compelling hypotheses, including increased selection of patients with aggressive malignancies during this period, should be considered. We suggest that surgery for indeterminate thyroid nodules should no longer be postponed even in future instances of pandemic escalation. Funding: None