Academic literature on the topic 'Molecular operational taxonomic unit'
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Journal articles on the topic "Molecular operational taxonomic unit"
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Galimberti, Andrea, Martina Spada, Danilo Russo, et al. "Integrated Operational Taxonomic Units (IOTUs) in Echolocating Bats: A Bridge between Molecular and Traditional Taxonomy." PLoS ONE 7, no. 6 (2012): e40122. https://doi.org/10.5281/zenodo.13484858.
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(Uploaded by Plazi for the Bat Literature Project) Background: Nowadays, molecular techniques are widespread tools for the identification of biological entities. However, until very few years ago, their application to taxonomy provoked intense debates between traditional and molecular taxonomists. To prevent every kind of disagreement, it is essential to standardize taxonomic definitions. Along these lines, we introduced the concept of Integrated Operational Taxonomic Unit (IOTU). IOTUs come from the concept of Operational Taxonomic Unit (OTU) and paralleled the Molecular Operational Taxonomic Unit (MOTU). The latter is largely used as a standard in many molecular-based works (even if not always explicitly formalized). However, while MOTUs are assigned solely on molecular variation criteria, IOTUs are identified from patterns of molecular variation that are supported by at least one more taxonomic characteristic. Methodology/Principal Findings: We tested the use of IOTUs on the widest DNA barcoding dataset of Italian echolocating bats species ever assembled (i.e. 31 species, 209 samples). We identified 31 molecular entities, 26 of which corresponded to the morphologically assigned species, two MOTUs and three IOTUs. Interestingly, we found three IOTUs in Myotis nattereri, one of which is a newly described lineage found only in central and southern Italy. In addition, we found a level of molecular variability within four vespertilionid species deserving further analyses. According to our scheme two of them (i.e. M. bechsteinii and Plecotus auritus) should be ranked as unconfirmed candidate species (UCS). Conclusions/Significance: From a systematic point of view, IOTUs are more informative than the general concept of OTUs and the more recent MOTUs. According to information content, IOTUs are closer to species, although it is important to underline that IOTUs are not species. Overall, the use of a more precise panel of taxonomic entities increases the clarity in the systematic field and has the potential to fill the gaps between modern and traditional taxonomy.
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Galimberti, Andrea, Martina Spada, Danilo Russo, et al. "Integrated Operational Taxonomic Units (IOTUs) in Echolocating Bats: A Bridge between Molecular and Traditional Taxonomy." PLoS ONE 7, no. 6 (2012): e40122. https://doi.org/10.5281/zenodo.13484858.
Full textAbstract:
(Uploaded by Plazi for the Bat Literature Project) Background: Nowadays, molecular techniques are widespread tools for the identification of biological entities. However, until very few years ago, their application to taxonomy provoked intense debates between traditional and molecular taxonomists. To prevent every kind of disagreement, it is essential to standardize taxonomic definitions. Along these lines, we introduced the concept of Integrated Operational Taxonomic Unit (IOTU). IOTUs come from the concept of Operational Taxonomic Unit (OTU) and paralleled the Molecular Operational Taxonomic Unit (MOTU). The latter is largely used as a standard in many molecular-based works (even if not always explicitly formalized). However, while MOTUs are assigned solely on molecular variation criteria, IOTUs are identified from patterns of molecular variation that are supported by at least one more taxonomic characteristic. Methodology/Principal Findings: We tested the use of IOTUs on the widest DNA barcoding dataset of Italian echolocating bats species ever assembled (i.e. 31 species, 209 samples). We identified 31 molecular entities, 26 of which corresponded to the morphologically assigned species, two MOTUs and three IOTUs. Interestingly, we found three IOTUs in Myotis nattereri, one of which is a newly described lineage found only in central and southern Italy. In addition, we found a level of molecular variability within four vespertilionid species deserving further analyses. According to our scheme two of them (i.e. M. bechsteinii and Plecotus auritus) should be ranked as unconfirmed candidate species (UCS). Conclusions/Significance: From a systematic point of view, IOTUs are more informative than the general concept of OTUs and the more recent MOTUs. According to information content, IOTUs are closer to species, although it is important to underline that IOTUs are not species. Overall, the use of a more precise panel of taxonomic entities increases the clarity in the systematic field and has the potential to fill the gaps between modern and traditional taxonomy.
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Beck, D., M. Settles, and J. A. Foster. "OTUbase: an R infrastructure package for operational taxonomic unit data." Bioinformatics 27, no. 12 (2011): 1700–1701. http://dx.doi.org/10.1093/bioinformatics/btr196.
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Kharat, Milindkumar M., Santosh G. Atram, Vikas M. Kothare, and Pranav T. Bhoyar. "COI gene variability in Wallago attu and its close related species Ompok bimaculatus." International Journal of Advance and Applied Research 5, no. 23 (2024): 405–12. https://doi.org/10.5281/zenodo.13637687.
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<strong>Abstract:</strong> Taxonomy based of Cytochrome Oxidase 1 Gene is a novel technique in the field of animal identification. DNA sequences to be aligned for the taxonomic process are aligned in software MEGA. Alignment of different sequences world over for the fish <em>Wallago attu </em>have been worked out in the present study with its taxonomically close individual <em>Ompok bimaculatus</em>. Different nucleotide sequences in the alignment are pointed out which vary within the species as well as between the species. Interspecific variations are designated as Molecular Operational Taxonomic Units. Thus comparison of both morphological characters and Molecular Operational Taxonomic Units in the present study helps to identify the effectiveness of both the methods together giving a better insight in coevolution of sequences with altering morphology
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Hu, Gui-Lin, Kai Gao, Ji-Shen Wang, Paul D. N. Hebert, and Bao-Zhen Hua. "Molecular phylogeny and species delimitation of the genus Dicerapanorpa (Mecoptera: Panorpidae)." Zoological Journal of the Linnean Society 187, no. 4 (2019): 1173–95. http://dx.doi.org/10.1093/zoolinnean/zlz059.
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Abstract Given that species is the fundamental unit in systematic biology, rigorous species delimitation is crucial for taxonomic studies, yet routine species delimitation remains an ongoing challenge in the taxonomic practice of insects. The two-horned scorpionfly Dicerapanorpa is a small genus in Panorpidae (Mecoptera) endemic to the Qinling-Bashan and Hengduan mountains, a biodiversity hotspot. However, species of Dicerapanorpa are difficult to delineate owing to marked intraspecific variation and interspecific similarity. Here, we investigate the diversity and species boundaries of Dicerapanorpa using an integrative approach based on DNA barcoding, morphological, geometric morphometric and molecular phylogenetic analyses. This integrative analyses confirmed the 13 described species of Dicerapanorpa and revealed three new species: Dicerapanorpa lativalva sp. nov., Dicerapanorpa hualongshana sp. nov. and Dicerapanorpa minshana sp. nov. Most molecular operational taxonomic units are in congruence with morphological clusters. Possible reasons for several discordances in Dicerapanorpa are tentatively discussed.
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Fortunato, Caroline S., David B. Carlini, Evan Ewers, and Karen L. Bushaw-Newton. "Nitrifier and denitrifier molecular operational taxonomic unit compositions from sites of a freshwater estuary of Chesapeake Bay." Canadian Journal of Microbiology 55, no. 3 (2009): 333–46. http://dx.doi.org/10.1139/w08-124.
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Temporal and spatial changes in the molecular operational taxonomic unit (OTU) compositions of bacteria harboring genes for nitrification and denitrification were assessed using denaturing gradient gel electrophoresis (DGGE), clone-based DNA sequencing of selected PCR products, and analyses of ammonium and organic matter concentrations. Sediment, overlying water, and pore-water samples were taken from different vegetated sites of Jug Bay National Estuarine Research Reserve, Maryland, during spring, summer, and fall 2006. OTU richness and the diversities of nitrifiers and denitrifiers were assessed by the presence of bands on DGGE gels, both ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were seasonally dependent. AOB OTU richness was highest in the summer when NOB richness was decreased, whereas NOB richness was highest in the spring when AOB richness was decreased. The OTU diversities of nitrifiers did not correlate with ammonium concentrations, organic matter concentrations, or the presence of vegetation. The OTU diversities of denitrifiers possessing either the nirK or nosZ genes were not seasonally dependent but were positively correlated with organic matter content (p = 0.0015, r2 = 0.27; p < 0.0001, r2 = 0.39, respectively). Additionally, the presence of vegetation significantly enhanced nosZ species richness (Wilcoxon/Kruskal–Wallis test, p < 0.008), but this trend was not seen for nirK OTU richness. Banding patterns for nirK OTUs were more similar within sites for each season compared with any of the other genes. Over all seasons, nirK OTU richness was highest and AOB and nosZ OTU richness were lowest (Wilcoxon/Kruskal–Wallis test, p < 0.0001). High levels of sequence divergence among cloned nirK PCR products indicate a broad diversity of nirK homologs in this freshwater estuary.
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Jin, Boyang Tom, Feng Xu, Raymond T. Ng, and James C. Hogg. "Mian: interactive web-based microbiome data table visualization and machine learning platform." Bioinformatics 38, no. 4 (2021): 1176–78. http://dx.doi.org/10.1093/bioinformatics/btab754.
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Abstract Summary Mian is a web application to interactively visualize, run statistical tools and train machine learning models on operational taxonomic unit (OTU) or amplicon sequence variant (ASV) datasets to identify key taxonomic groups, diversity trends or taxonomic composition shifts in the context of provided categorical or numerical sample metadata. Tools, including Fisher’s exact test, Boruta feature selection, alpha and beta diversity, and random forest and deep neural network classifiers, facilitate open-ended data exploration and hypothesis generation on microbial datasets. Availability Mian is freely available at: miandata.org. Mian is an open-source platform licensed under the MIT license with source code available at github.com/tbj128/mian. Supplementary information Supplementary data are available at Bioinformatics online.
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Clare, Elizabeth L., Frédéric J. J. Chain, Joanne E. Littlefair, and Melania E. Cristescu. "The effects of parameter choice on defining molecular operational taxonomic units and resulting ecological analyses of metabarcoding data." Genome 59, no. 11 (2016): 981–90. http://dx.doi.org/10.1139/gen-2015-0184.
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The combination of DNA barcoding and high-throughput (next-generation) sequencing (metabarcoding) provides many promises but also serious challenges. Generating a reliable comparable estimate of biodiversity remains a central challenge to the application of the technology. Many approaches have been used to turn millions of sequences into distinct taxonomic units. However, the extent to which these methods impact the outcome of simple ecological analyses is not well understood. Here we performed a simple analysis of dietary overlap by skinks and shrews on Ile Aux Aigrettes, Mauritius. We used a combination of filtering thresholds and clustering algorithms on a COI metabarcoding dataset and demonstrate that all bioinformatics parameters will have interacting effects on molecular operational taxonomic unit (MOTU) recovery rates. These effects generated estimates covering two orders of magnitude. However, the effect on a simple ecological analysis was not large and, despite the wide variation in estimates of niche overlap, the same ecological conclusion was drawn in most cases. We advise that a conservative clustering programme coupled with larger sequence divergences to define a cluster, the removal of singletons, rigorous length filtering, and stringent match criteria for Molecular Identifier tags are preferable to avoid MOTU inflation and that the same parameters be used in all comparative analyses.
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SEMENCHENKO, ALEXANDER A., and EUGENYI A. MAKARCHENKO. "On the taxonomy and distribution of Diamesa gregsoni Edwards, (Diptera: Chironomidae: Diamesinae), with morphological redescription and DNA barcoding of species from the Far East." Zootaxa 5636, no. 3 (2025): 499–510. https://doi.org/10.11646/zootaxa.5636.3.5.
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By analyzing the DNA barcoding data of the Diamesa gregsoni Edwards syntype, we carried out a genetic study of this species from the Far East and made a comparison with DNA barcodes of North American populations. A morphological redescription of the adult male and a description of the pupa and larva are given, and the taxonomy and distribution of the species are clarified in this study. The Bayesian tree revealed two well-supported clades of D. gregsoni from Nearctic and Palaearctic. The average K2P genetic divergence between these clades was 1.67%, which corresponds to intraspecific differences. Overall intraspecific p-distances within 23 DNA barcodes of D. gregsoni were 1.19%. The Automatic Barcode Gap Discovery (ABGD), Assemble Species by Automatic Partitioning (ASAP), and Multi-rate Poisson tree processes (mPTP) approaches for the species delimitation confirmed that Nearctic and Palaearctic DNA barcodes belong to a single molecular taxonomic unit, while general mixed Yule-coalescent (GMYC) delimit the dataset into three different molecular operational taxonomic units (mOTU).
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ABEYSEKARA, SHASHIKA, HELANI SAMARASINGHE, KELUM MANAMENDRA-ARACHCHI, et al. "Taxonomic status of Pseudophilautus conniffae (Anura: Rhacophoridae) an endemic shrub frog restricted to South–Western wet zone of Sri Lanka." Zootaxa 5258, no. 1 (2023): 130–40. http://dx.doi.org/10.11646/zootaxa.5258.1.6.
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Pseudophilautus conniffae from Lowland wet zone of Sri Lanka, was described as a new species in 2019. The validity of the new species was questionable and was often challenged as it shares strong morphological resemblance with P. limbus. Moreover, the phylogenetic placement of P. conniffae was unknown as no molecular data was available until now. Here, we generated 16S DNA sequences and re-examined the external morphological characters to assess its taxonomic distinctiveness. Pseudophilautus conniffae was recovered as being close to P. limbus with strong posterior probability and bootstrap support. The uncorrected pairwise genetic distance between P. conniffae and P. limbus was negligible, being less than 0.3% for the 16S gene fragment. Further two molecular species delimitation methods, ABGD and mPTP suggested that P. conniffae and P. limbus are a single operational taxonomic unit. The Principal Component Analysis of the morphometric characters also resulted in overlapping clusters. These results suggest that the newly described P. conniffae is not a valid species and we conclude that P. conniffae as a junior synonym of P. limbus.
Dissertations / Theses on the topic "Molecular operational taxonomic unit"
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Mann, Jenna D. "DNA barcodes and meiofaunal identification." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4732.
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In recent years there has been a desire to definitively catalogue the life on our planet. In light of the increasing extinction rates that are driven by human activities, it is unlikely that this will be achieved using traditional methods. Whilst most organisms which have a body size of more than 1cm have been described, the vast majority of animal life is smaller than this, collectively known as meiofauna, and is yet to be catalogued. Meiofaunal organisms present a range of problems for traditional taxonomy. Firstly they are microscopic, meaning that morphological features are often difficult to resolve. Secondly these creatures often exhibit cryptic diversity meaning that different species often look the same. Thirdly, it is often the case that the organisms are poorly described in the literature making it very difficult to confirm identification, assuming that someone has already described it. It is possible, however, to obtain DNA sequences from these organisms. DNA barcoding, the use of short sequences of DNA to identify individuals, is now commonly used in a wide range of applications. It has been proposed that a single target gene should be sufficient to describe all organisms this way. Barcodes can be acquired from individuals or from bulk extractions from environmental samples. In the latter case, many of the sequences obtained are novel and unlikely to ever have a type specimen associated with them. When this is the case, assessing the diversity of a sample becomes a computational exercise. However, as yet, there is no agreed standard method adopted for analyzing the barcodes produced. Indeed most methods currently employed lack objectivity. This thesis investigates the efficiency of a range of gene targets and analysis methods for DNA barcoding, with an emphasis on meiofaunal organisms (nematodes, tardigrades and thrips). DNA barcodes were generated for up to three genes for each specimen. Sequences for each gene were analysed using two programs, MOTU_define.pl and DOTUR. These programs use different methods to assign sequences to operational taxonomic units (OTU), which were then compared. An objective method for analysing sequences such as MOTU_define.pl, which relies on only the information contained in the sequences, was found to be most suitable for designating taxa. It does not attempt to apply evolutionary models to the data, and then infer taxa from the derived data. In addition to barcoding, some samples were pre-processed using video capture and editing (VCE). This creates a virtual slide of a specimen so that a sequence can be linked to a morphological identification. VCE proved to be an efficient method to preserve morphological data from specimens.
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Cressman, Michael David. "A molecular approach to understanding the interrelation between the microbiomes in the litter and intestines of commercial broiler chickens." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1243872965.
Full textBooks on the topic "Molecular operational taxonomic unit"
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Taberlet, Pierre, Aurélie Bonin, Lucie Zinger, and Eric Coissac. DNA metabarcoding data analysis. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198767220.003.0008.
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DNA metabarcoding generates huge amounts of data containing noise introduced by molecular methods. Chapter 8 “DNA metabarcoding data analysis” discusses the analytic steps and available software to curate and evaluate DNA metabarcoding data prior to final ecological analyses. It provides command lines to perform primary analyses of Illumina sequencing data with the OBITools, ranging from read assignment to samples to the formation of molecular operational taxonomic units (MOTUs) and their assignment to a taxon through comparison against reference databases. Chapter 8 also develops several methods to further curate sequencing data from contaminants or dysfunctional PCRs by using DNA extraction, PCR, and sequencing blank controls as well as PCR/biological replicates. It also presents several classical analyses to ensure that the diversity of the sample or the study site is appropriately covered. Finally, this chapter considers what conclusions on biodiversity and ecological processes can be really drawn from metabarcoding data.
Book chapters on the topic "Molecular operational taxonomic unit"
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Rowe, Graham, Michael Sweet, and Trevor J. C. Beebee. "Species, populations, and individuals." In An Introduction to Molecular Ecology. Oxford University Press, 2017. http://dx.doi.org/10.1093/hesc/9780198716990.003.0005.
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This chapter discusses the importance of species. It looks into the possibility of solving the species problem using the concepts of biological species, morphological species, phylogenetic species, and the operational taxonomic unit. Speciation is the process resulting in the formation of new species and accounts for biological diversity which is then divided between anagenesis and cladogenesis. The chapter also explores the concept of hybrids, hybrid zones, environmental DNA, and ancient DNA techniques. It includes molecular markers which it states are delivering new insights into the nature of species and boundaries. Spatial differences are emphasized for studying speciation mechanisms alongside investigating the balance of local adaptation and gene flow.
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Rowe, Graham, Michael Sweet, and Trevor J. C. Beebee. "Microbial ecology and metagenomics." In An Introduction to Molecular Ecology. Oxford University Press, 2017. http://dx.doi.org/10.1093/hesc/9780198716990.003.0011.
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This chapter explores microbial ecology and metagenomics. It notes the role of microbial communities in nature in line with outstanding issues in microbial ecology such as species identification, population dynamics, and community structure. Moreover, the chapter explains immunological and genomic approaches to microbial ecology. An example of which would be antibody identification. The chapter also discusses metagenomics in relation to ribosomal sequences and microbial ecology. The chapter looks at the genetic variability of bacteria species. It also discusses the phylogeography of viruses, bacteria, and fungi. DNA hybridization methods based on DNA microarray technology offer great promise on microbial identification and community analysis, especially where it is necessary to resolve closely related operational taxonomic units (OTU).
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Crandall, Keith A., and Alan R. Templeton. "Applications of intraspecific phylogenetics." In New Uses for New Phylogenies. Oxford University PressOxford, 1996. http://dx.doi.org/10.1093/oso/9780198549857.003.0006.
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Abstract Recent advances in population genetics theory, especially coalescent theory (Tavaré 1984; Watterson 1984; Ewens 1990; Hudson 1990), coupled with an explosion of molecular techniques have allowed detailed phylogenetic information at the population level. Such genealogical relationships are termed gene trees, allele trees, or haplotype trees (we use haplotype throughout this chapter) in which different haplotypes are the operational taxonomic units. Avise and colleagues were the first to utilize this powerful molecular phylogenetic approach for studies of population genetics, especially relating to biogeographic patterns (Avise et al. 1987; Avise 1989, 1994). Their approach explores qualitatively the relationship between lineage divergence and the extent of geographical partitioning among haplotypes.
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"Operational Taxonomic Unit." In Encyclopedia of Astrobiology. Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-44185-5_100825.
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"Operational Taxonomic Unit." In Encyclopedia of Astrobiology. Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-11274-4_2864.
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"Operational Taxonomic Unit." In Encyclopedia of Astrobiology. Springer Berlin Heidelberg, 2023. http://dx.doi.org/10.1007/978-3-662-65093-6_300951.
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"Operational Taxonomic Unit (OTU)." In Encyclopedia of Genetics, Genomics, Proteomics and Informatics. Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-6754-9_11891.
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"OTU (operational taxonomic unit)." In Encyclopedia of Genetics, Genomics, Proteomics and Informatics. Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-6754-9_12016.
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Whittaker, Robert J., José María Fernández-Palacios, and Thomas J. Matthews. "Colonization, evolutionary change, and speciation." In Island Biogeography, 3rd ed. Oxford University PressOxford, 2023. http://dx.doi.org/10.1093/oso/9780198868569.003.0008.
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Abstract ‘Colonization, evolutionary change, and speciation’ considers how founder populations may develop into island endemic forms. It briefly reviews the nature of the species unit, where species and subspecies fit into the taxonomic hierarchy, and the use of molecular methods, stem age, and crown age, in the depiction and dating of evolutionary relationships. It notes the distinctions between allopatry, sympatry, and parapatry in island evolution, and between novelty arising within islands and endemism through relictualism. It describes and evaluates, using case-study evidence, the phenomena of founder effects, genetic bottlenecks and genetic drift, natural selection and sexual selection, alongside processes of ecological release, density compensation, and character displacement. It describes general speciation models under the frameworks of allopatric/geographical speciation, competitive speciation, and hybridization, noting the imperfectly understood links between hybridization, polyploidy, and apomixis. It concludes with a brief evaluation of anagenesis and cladogenesis as frameworks for insular analysis.
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Govindaraj, R. "Application of Powder X-Ray Diffraction Studies for Single Crystals." In CHARACTERIZATION OF SINGLE CRYSTALS. Royal Book Publishing, 2025. https://doi.org/10.26524/225.2.
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Powder X-Ray Diffraction (PXRD) is an analytical technique that employs X-Rays to investigate the molecular and crystallographic structures of substances. This technique identifies phases, determines unit cells, and examines microstructure. When the incident X-Ray beam strikes the sample, it generates intense reflected Xrays via constructive interference, as long as the conditions satisfy Bragg’s Law. This law explains the correlation between the wavelength of the incoming X-rays, the angle at which the beam strikes, and the spacing of the atomic lattice planes. PXRD provides many benefits, such as non-destructive testing, high sensitivity and reliability, easy sample preparation, user-friendly systems, convenient operational processes, quick processing times, excellent resolution, low maintenance expenses, suitable automation features, and simple data interpretation, making it applicable for both qualitative and quantitative analyses in various fields. PXRD is a very useful technique in accessing the preferred orientation of the grown single crystals.
Conference papers on the topic "Molecular operational taxonomic unit"
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Bakr, M. Khaleel. "Enhancing Sustainability and Efficiency in Gas Dehydration: Smart Optimization of Molecular Sieve Unit Regeneration." In Mediterranean Offshore Conference. SPE, 2024. http://dx.doi.org/10.2118/223140-ms.
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Abstract The objective of this study is to optimize the regeneration criteria of Molecular Sieve Units (MSUs) to enhance sustainability and operational efficiency in gas dehydration processes. The methodology involves revising the regeneration cycle of MSUs to align with current operational demands. By analyzing the underutilization of desiccant beds within the existing 12-hour adsorption cycle, a tailored regeneration cycle was implemented. This strategy focuses on reducing fuel gas consumption and electricity usage, while extending the operational lifetime of the desiccants. The process includes a detailed assessment of current operations and the development of an optimized regeneration schedule. Implementing the revised regeneration cycle led to substantial improvements: an 85% reduction in fuel gas consumption and an 83% decrease in electricity usage. The desiccant's operational lifetime was extended from 5 years to 25 years, significantly reducing downtime and maintenance requirements. Additionally, the optimization resulted in notable reductions in spare parts usage and operational expenses (OPEX). The environmental benefits, including reductions in greenhouse gas (GHG) emissions, are currently being quantified. This approach demonstrates the potential for significant environmental and economic gains, highlighting the importance of tailored regeneration cycles in enhancing the efficiency and sustainability of gas dehydration processes. This paper introduces a novel optimization strategy for MSU regeneration cycles, demonstrating significant improvements in resource utilization and operational efficiency. It provides valuable insights into extending the operational life of desiccants and reducing energy consumption, contributing to the sustainable management of industrial operations.
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Vieira, Anderson Jalles de Meneses, Cassiano Gomes Aimoli, and Dárley Carrijo de Melo. "Comparison Between Molecular Sieves and Activated Alumina for Gas Dehydration in an Ultra-Deepwater Production Unit." In Offshore Technology Conference. OTC, 2023. http://dx.doi.org/10.4043/32580-ms.
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Abstract Activated alumina and molecular sieve performances are compared regarding key parameters such as adsorbed water load, outlet moisture content, pressure drop and adsorption capacity using different regeneration conditions. The comparison was done by operating one out of three vessels of a Brazilian pre-salt FPSO gas dehydration unit loaded with activated alumina, whereas the other two vessels were loaded with molecular sieves with a silica gel top layer. During the early operation of the alumina, tests were performed by increasing adsorption time until the moisture breakthrough, conducted in two operational setups as follows: 1) a parallel-flow arrangement in which each vessel is loaded with one of the adsorbent materials, named dual bed phase; 2) a single stream flow to the vessel containing activated alumina, named single bed phase. Different regeneration temperatures were tested to verify the impact on the alumina capacity caused by low temperature regeneration. The results were compared to historical data collected using both type 4A and chabazite zeolites. During preliminary capacity tests performed in laboratory and in pilot scale, the activated alumina delivered gas with moisture content generally between 1 and 10 ppm. However, during the industrial scale test reported here, the activated alumina was able to consistently deliver gas with moisture under 1 ppm after its first regeneration, operating both in single bed and dual bed arrangement. This result indicates that activated alumina was able to achieve gas specification once considered possible only by the use of molecular sieve. The initial dynamic capacity calculated for the alumina was comparable to the maximum dynamic capacities observed for the molecular sieves. In this test, the larger particle size of the activated alumina compared to the zeolites resulted in lower pressure drop through the alumina bed, culminating into an uneven flow distribution between both beds when in parallel-flow arrangement. Recommended regeneration temperatures are lower for alumina in comparison with the zeolites, resulting in lower energy consumption and associated CO2 emissions when using electrical heaters. The novelty of this work lies in the use of activated alumina as the main adsorbent material in an ultra-deepwater gas dehydration unit with gas processing capacity over 6 MMSCMD achieving dry gas moisture as low as obtained by using molecular sieves. The use of activated alumina shows potential to improve efficiency and cost reduction that has yet to be confirmed by a longer test phase to check its stability and long-term performance.
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Diwakar, Philip, and Jonathan Berkoe. "Operation Improvement, Reliability and Performance Optimization With Analysis and Simulation." In ASME 2009 Power Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/power2009-81223.
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Rapid development in computers has led to significant advancement in simulation technology. The analysis tools such as CFD and FEA are now household tools used for improving plant operations, building reliable equipment with enhanced safety features with an eye on improving and optimizing performance. In this paper a few case studies are selectively presented to demonstrate the value of these tools to the customer — improved efficiency, reduced schedule times and cost. These examples are chosen to show how these technologies are used to identify and mitigate any safety and operational risks associated with plant design and improve the design over the projects life cycle. The first example considers a design and operation improvement in a Heat recovery Steam generator (HRSG). To reduce material and equipment costs, it is very easy to design the HRSG with sharp corners and steep angles from one module to another and keep them closer to each other. This essentially reduces the overall efficiency of the plant due to gas turbine exhaust flow non-uniformity and re-circulation zones. The existing flow correction device consisting of 32 large tubes running across the sides produces a very large pressure drop. Using CFD, a flow distribution grid is designed, providing at least a 20% improvement in velocity distribution. The second example considers a coal burning boiler performance optimization. In this boiler upgrade project, CFD is used to confirm the feasibility of increasing the capacity and reducing the particulate emissions of the coal fired furnace and steam boiler units. Some of these factors were difficult to evaluate reliably using physical scale modeling techniques that were performed mainly only for cold flow pressure drop analysis. However the experimental results were used for benchmarking the CFD results. A third example shows how fluid dynamic analysis combined with thermal and structural analysis may be used to obtain the thermal fatigue life of various components of a molecular sieve dehydrator unit, where the design life is governed by the thermal loads generated during the regeneration cycle. Based on the fatigue analysis a more effective support is designed to withstand a higher flow capacity thus increasing production.