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Nutrition, disease, and general wellbeing can be affected by the microbial communities associated with the digestive tracts of aquaculture species. Different sections of aquaculture species’ digestive tracts have distinctive surfaces and structures, which can change microbial communities. The present study examined the composition and distribution of bacterial species in the intestine of hybrid grouper (Epinephelus fuscoguttatus E. polyphekadion) and its aquaculture environment. Using high-throughput pyrosequencing, a 16S rRNA sequence analysis was performed on hybrid grouper foregut, midgut, and hindgut, as well as cultured water and feed. There were 610,452 sequences obtained from five components (foregut, midgut, hindgut, water, and feed). Among operational taxa (OTUs), 506 of them were detected in the foregut, 605 in the midgut, 510 in the hindgut, and 573 in aquaculture water and feed samples. A total of 113 were detected in 5 samples. A species annotation revealed that hybrid grouper intestinal tracts were dominated by Proteobacteria (67.3%–73.7%), Firmicutes (8.4%–14.0%), and Actinobacteria (6.9%–10.5%). In aquaculture culture water, Proteobacteria were predominant (36.3%), Actinobacteria (30.0%), and Planctomycetes (14.0%). Acinetobacter (1.4%–17.9%) and Photobacterium (32.0%–57.5%) dominated the intestine. Photobacterium (3.6%) and Mycobacterium (7.1%) dominated the water bacteria. The water and intestine contained five potentially pathogenic bacteria: Pseudomonas, Flavobacterium, Escherichia coli, Aeromonas bacteria, and Vibrio. The highest proportion of Vibrio was found in the water (1.7%), while Pseudomonas dominated the midgut (2.6%). Six potential probiotics were detected in the aquaculture water and intestine (Lactococcus, Streptococcus, Bdellovibrio, Lactobacillus, Bacillus, and Bacteroides). Aquaculture water and intestines contained Bacillus, Bacteroides, and Lactobacillus. According to the findings, the intestinal flora of hybrid grouper is closely correlated with its pond culture environment. Results from the study provide an experimental basis for the controlled breeding of hybrid groupers and the regulation of their microecological processes in the breeding environment deepen our understanding of the intestinal bacterial population of healthy hybrid groupers.

While expanded polystyrene (EPS) microplastics have been widely recognized as one of the most important components of plastic litter in the intertidal zones of the global ocean, our understanding of their environmental fate on island beaches is insufficient. In this study, we intended to reveal that the latest EPS microplastic pollution status on 5 island beaches in the Pearl River Estuary, China, by comprehensively assessing the abundance, distribution, size, surface texture and carrying capacity of heavy metals (Cd, As, Cr, Ni, Cu, Pb, Mn, Fe, Al). High level of EPS microplastic abundance ranged from 328 to 82,276 particles m−2 was found, with the highest abundance at Guishan Island and the lowest at Dong’ao Island. Spatial distribution of EPS microplastic abundance was significantly different among different islands. EPS microplastics in the size range of 1–2 mm were the most abundant. The content of heavy metals in EPS microplastics collected on the beaches was greater than that in the new EPS products. The average concentrations of heavy metals in EPS microplastics from 5 islands are Cd (0.27 ± 0.19 μg g−1), As (5.50 ± 3.84 μg g−1), Cr (14.9 ± 8.25 μg g−1), Cu (15.0 ± 7.66 μg g−1), Ni (17.2 ± 17.6 μg g−1), Pb (24.8 ± 7.39 μg g−1), Mn (730 ± 797 μg g−1), Fe (8340 ± 4760 μg g−1), and Al (9624 ± 6187 μg g−1), respectively. The correlation between heavy metals in EPS microplastics and sediments was better than that between heavy metals in EPS microplastics and seawater. The study results indicated that EPS microplastics could act as a carrier for the transport of heavy metals, which might pose a threat to biological and human health.

The heme oxygenase gene plays a role in many biological processes and is an important protective factor in hypoxic stress. Research on the HO gene of fishes has attracted increasing attention, but there is yet little information about the cobia (Rachycentron canadum) heme oxygenase gene. In this study, the full-length cDNA of the cobia heme oxygenase gene (heme oxygenase, HO) was cloned using rapid amplification of cDNA ends technology. The full-length cDNA was 1639 bp and the open reading frame (ORF) was 840 bp encoding 279 amino acids, with 5′-UTR 518 bp and 3′-UTR 281 bp. The results of real-time quantitative PCR showed that cobia HO was expressed in all the tissues tested, with the highest expression in gills. The mRNA expression of gill HO increased after hypoxia stress. There was no significant change in the expression of HO mRNA in the liver after hypoxia stress. The amino acid sequences of HO in diverse fish and mammals have varying levels of homology. Our results indicate that the biological functions of HO may be similar in fish and mammals, suggesting an important protective factor in response to hypoxic stress.

The incidence of infections by pathogenic microorganisms, coupled with the experimental manifestation of infections, refers to a regular phenomenon in aquaculture species. A number of environmental changes generally give rise to traumatic scenarios, and activating the transient provocative reactions in the gut normally constitutes a factor to the anatomical and efficient intestinal diseases. These infections have frequently given birth to the momentous economic chaos in aquaculture sector. Putting efforts into resolving this issue, the inclusion of antibiotics in the diets of aquaculture species has been introduced either as growth promoters or the stimulation of the immune system against diseases. Nevertheless, both the fears and discussions of consumers and scientists over the antibiotic-resistant microbes and drug remains in meat have resulted into contentious views concerning the uses of antibiotics. This has resulted into forbidding the use of human antibiotics as growth promotants in the diet of animal since the year 2006 by the European Union; also, subsequent to that, in the year 2013, the United States also initiated a plan for the removal of human antibiotics in the diet as growth promotants. Making use of the prebiotics, synbiotics and probiotics as an alternative has proven as improving not just the growth but also the immunity and maintenance of intestine health of cultured species. They are administered in the feeds of culture species for the purpose of stimulating the good health, safeguarding the intestine against pathogenic microorganisms and reducing the inflammation. In the current investigation, we throw discussion on the present uses, together with the limitations and future directions, the immunomodulatory exploit of probiotics, synbiotics and prebiotics, which triggering directly or enhancing the non-specific immune structure of aquaculture species.

Many factors contribute to the underdevelopment of oceanic aquaculture. The most significant factor of the development of hybrid grouper culture is the supply of satisfactory quantities of fast growing juveniles to stock grow-out systems at a minimized cost. In order to evaluate the growth hormone status of hybrid grouper (Epinephelus fuscoguttatus â™€× Epinephelus polyphekadion ♂), cDNA encoding growth hormone from the liver of juvenile fish was cloned and characterized. qPCR method was used to determine the expression of the growth hormone in the tissues. Relative expression of growth hormone in the brain was found to be highest (290.91 folds) and lowest in the stomach (1.35 folds). Bioinformatics tools were used to analyze the growth hormone proteins and prediction of its physicochemical properties, and amino acid compositions, as well as Gene Ontology, GO term predictions. The cloned hybrid grouper growth hormone gene sequence was found to be clustered monophyletically with solid bootstrap backing. It was found to be close to the Cromileptes altivelis growth hormone gene sequence and is positioned in the identical clade and consequential from the identical family. The expression pattern is comparable to that comprehended in other fishes and provides extra data for molecular biological studies on hybrid grouper fish. Key words: Growth hormone, bioinformatics analysis, tissue expression, gene ontology, hybrid grouper

Recognized for its traditional roles, estrogen is ever-present in all vertebrates, regulates reproduction by binding and activating estrogen receptors (ERs), and also controls several functions of vertebrates, including reproductive immune, and central nervous systems. In order to access any other possible functions of the estrogen receptors in the development of the juvenile Hybrid grouper (Epinephelus fuscoguttatus â™€× Epinephelu polyphekadion ♂), full-length of ERs cDNA sequences were isolated and analyses were found to be 2391 bp for hgERα, 2626 bp for gERb1 and 2339 bp for hgERb2, respectively. The results of amino acid and phylogenetic analysis revealed that each hgER was grouped in consistent taxonomic groups of perciformes and demonstrated great evolutional conservation in functional domains. Real-time PCR examination discovered that the receptors expressed in all tissues examined, though, at a different level, the ERα mRNA level expressed higher than ERβ1, and ERβ2 in tissues examined. The ERα mRNA level of expression was found to be highest in the tissue of the heart, followed by muscle, and liver. The ERβ1 mRNA level was greatest in heart tissue, trailed by liver and muscle and ERβ2 was highest in the heart trailed by stomach and liver. The minimal expression was recorded in the kidney, the gill, and the brain for ERα, ERβ1, and ERβ2 respectively. These results put forward that steroid hormone estrogen receptors might be playing a significant part in the controlling of social behavior complexity, plasticity behavior, and the assessment of a gratifying inducement in Hybrid grouper. Key words: Estrogen receptors, Real-time POR, tissue expression, hybrid grouper.

Climate change has gradually become a great challenge for heritage conservation. This study demonstrated that a hierarchal strategy corresponding to the scale of climate or weather date can be an alternative approach to making heritage conservation more efficient and sustainable. Therefore, the passive environmental control strategies at neighborhood and block scales are developed to effectively connect climate actions, normally at global or city scales, and the traditional preservation methods at building scale. The research results reflect the same conclusion as previous studies in that wind is the key factor affecting degradation mechanisms on heritage assets. Moreover, the adoption of weather data is a critical factor that influences the accuracy of computational fluid dynamics (CFD) simulation results of the detailed regional wind performance, which is supportive for strategy development. According to the simulation results, the study site, Huatzai village, with neighborhood-scale strategy can gain an improvement in overall wind impact. The velocity reduction is more than 70% in the windward areas. The block-scale strategy with the reuse of existing structures can bring 90% velocity reduction for the wake areas and the high-risk zones with strong turbulence.

Cobia (Rachycentron canadum) is an important cultured marine fish species in southern China. It is characterized by fast growth. Due to the effects of climate change on water oxygen levels and seawater temperatures, the understanding of the influence of environmental changes on cobia culture has become important. In this study, to explore the stress and adaptability of cobia under hypoxia-reoxygenation conditions, the fish were exposed to an oxygen-deficient environment with dissolved oxygen (DO) level of 2.64 ± 0.25 mg/L. Serum liver function target, lipid metabolism-related enzymes and the serum antioxidant capability were detected in cobia under acute hypoxic stress after which fish returned to normal DO level (6.34 ± 0.15 mg/L) at 8, 24 and 48 h. Conventional paraffin sectioning and hematoxylin and eosin (H-E) staining were used to observe gill and liver tissues of cobia by electron microscopy. After hypoxic stress, the activities of alkaline phosphatase (ALP), total protein (TP), albumin (ALB), triglyceride (TG), total cholesterol (TC) and superoxide dismutase (SOD) in cobia decreased. Under acute hypoxic stress, the gill patches of the fish were contracted and slightly curved. Liver disorder and vacuoles appeared between liver tissues. After reoxygenation, SOD and catalase (CAT) were recovered to the level of the control group with time, and all peaks appeared. The gill and liver of fish were also recovered with time. The results showed that hypoxic stress could cause oxidative damage to cobia.

Environmental hypoxia affects the survival and development of organisms. It is also an important environmental factor that leads to oxidative damage. Hypoxia is a condition in which tissues are deprived of oxygen; reoxygenation is the phenomenon in which hypoxic tissues are exposed to oxygen. Hypoxia-reoxygenation is vital in pathogenesis, where the production of reactive oxygen species and antioxidant disparity significantly contribute to disease progression, and it is one of the most common physiological stressors in the aquaculture industry. In this study, the full length of complementary DNA (cDNA) of the manganese superoxide dismutase (Mn-SOD) gene of healthy cobia Rachycentron canadum was analysed using rapid amplification of cDNA ends. The real-time quantitative Polymerase Chain Reaction was used to measure the expression levels of Mn-SOD mRNAs in various tissues (heart, muscle, brain, liver, kidney, gill, intestine, and spleen). The 2–ΔΔCT method was used to performed the expression analysis. The experimental data were analysed using SPSS ver. 19.0 ( https://spss.software.informer.com/19.0/ ). P

At present, due to the influence of global warming, seasonal change, diurnal variation, and eutrophication of the water body, hypoxia has become one of the major factors limiting the stable development of cobia (Rachycentron canadum) culture. In this study, the miRNAs involved in hypoxia stress were screened, and the target genes of miRNAs were annotated and analyzed. The results showed that a total of 184 conservative microRNA (miRNA) and 121 newly predicted miRNA were obtained by sequencing the liver of control (C) and hypoxic (dissolved oxygen, DO (2.64 ± 0.25) mg/L; 3 h) (S) groups. The pathways involved in energy metabolism included starch and sucrose metabolism (ko00500), glycosaminoglycan degradation (ko00531), and galactose metabolism (ko00052). The results indicate that the body maintains physiological activities by regulating some important pathways at the transcriptional level under hypoxia stress, such as the conversion of aerobic metabolism and anaerobic metabolism, the reduction of energy consumption, and the promotion of red blood cell proliferation to maintain the homeostasis of the body.

Background COVID-19 continuously threated public health heavily. Present study aimed to investigate the lymphocyte subset alterations with disease severity, imaging manifestation, and delayed hospitalization in COVID-19 patients. Methods Lymphocyte subsets was classified using flow cytometry with peripheral blood collected from 106 patients. Results Multivariate logistic regression showed that chest tightness, lymphocyte count, and γ-glutamyl transpeptidase were the independent predictors for severe COVID-19. The T cell, CD4+ T cell and B cell counts in severe patients were significantly lower than that in mild patients (p = 0.004, 0.003 and 0.046, respectively). Only the T cell count was gradually decreased with the increase of infiltrated quadrants of lesions in computed tomography (CT) (p = 0.043). The T cell, CD4+ T cell, and CD8+ T cell counts were gradually decreased with the increase of infiltrated area of the maximum lesion in CT (p = 0.002, 0.003, 0.028; respectively). For severe patients, the counts of T cell, CD4+ T cell, CD8+ T cell gradually decreased with the increased delayed hospitalization (p = 0.001, 0.03, and + T cell gradually decreased with the increased delayed hospitalization (both p p = 0.007, and 0.002, respectively). For mild patients, only the NK cell count was gradually decreased with the increased delayed hospitalization (p = 0.012). Conclusion T lymphocyte and its subset negatively correlated with disease severity, CT manifestation and delayed hospitalization. The counts of lymphocyte subset were changed more profound than their proportions.

Salinity is an important abiotic stress that affects metabolic and physiological activities, breed, development, and growth of marine fish. Studies have shown that cobia (Rachycentron canadum), a euryhaline marine teleost fish, possesses the ability of rapid and effective hyper/hypo iono- and osmoregulation. However, genomic studies on this species are lacking and it has not been studied at the transcriptome level to identify the genes responsible for salinity regulation, which affects the understanding of the fundamental mechanism underlying adaptation to fluctuations in salinity. To describe the molecular response of cobia to different salinity levels, we used RNA-seq analysis to identify genes and biological processes involved in response to salinity changes. In the present study, 395,080,114 clean reads were generated and then assembled into 65,318 unigenes with an N50 size of 2758 bp. There were 20,671 significantly differentially expressed genes (DEGs) including 8805 genes adapted to hypo-salinity and 11,866 genes adapted to hyper-salinity. These DEGs were highly represented in steroid biosynthesis, unsaturated fatty acid metabolism, glutathione metabolism, energy metabolism, osmoregulation, and immune response. The candidate genes identified in cobia provide valuable information for studying the molecular mechanism of salinity adaptation in marine fish. Furthermore, the transcriptomic sequencing data acts not only as an important resource for the identification of novel genes but also for further investigations regarding cobia biology.

The feeding habits and growth of larvae and juveniles under artificial culture conditions were examined using the ecological method of simple random sampling to better understand the feeding characteristic of cobia (Rachycentron canadum) during the early development stage. The results showed that cobia larvae had a good foraging capability. After three days of the hatch (DAH), the larvae began feeding, and the feeding incidence was 70%. Feeding incidence was 100% in the case of juveniles. Feed intake of larvae and juveniles increases with increased body mass and could be expressed using the binomial equation (R2 = 0.9188). The digestive tract fullness coefficient of 3–24-day-old larvae and juveniles fluctuated from 0.1% to 1.0%. The larvae and juveniles of cobia were satiated within 1 h. The digestion time of larvae to rotifers and copepods was between 0.5 and 1.5 h and 0.5–2 h, respectively, while that of juveniles was 1–3 h. The daily feeding rates of larvae and juveniles were 61.38% (5-day-old), 54.18% (10-day-old), and 24.85% (24-day-old), and could be used as a reference for the daily feeding (%) of both larval and juvenile stages of cobia. The feeding patterns of larvae and juveniles showed a circadian rhythm, suggesting that they were fed during the day. The average daily growth rate of full-length larvae and juveniles aged 3 to 24 days was 35.90%, with an average daily weight gain rate of 56.97%. The relationship among total length, body mass, and age were expressed using a quadratic equation of one variable (R2 > 0.90) and a power function (R2 > 0.90) for the regression equation of body mass and full length. This study provides useful insights on the early development stage, and a reference for large-scale production of cobia larvae and juveniles.

Hypoxia is one of the most frequently arising stressors in aquaculture. Hypoxia causes huge financial losses and degradation of resources. However, the response of cobia (Rachycentron canadum) to hypoxia stress is not completely understood. In this study, the effects of hypoxia on the intestinal microflora of juvenile cobia were investigated. The diversity and structure of microflora after 4 weeks of hypoxia stress were analyzed using high-throughput sequencing technology. A total of 210 fish were divided into two treatment groups, namely, hypoxic stress and normoxic control groups, with 3 replicates per group and 35 fish per replicate. The results showed that the richness and diversity of intestinal microflora increased significantly first and subsequently decreased significantly after invitation of the hypoxia stress (P

With improvements in endoscopy and laser technology, flexible ureteroscopy (FURS) has been a viable treatment option for large renal stones. Here, we share our experience of the FURS treatment for renal stones 2 cm or greater.We evaluated 251 consecutive patients who underwent FURS and holmium laser lithotripsy for renal stones 2 cm or greater between January 2015 and April 2019. Stone size was defined as the longest axis on non-contrast computed tomography. Data were retrospectively collected from electronic medical records. Patient demographics, stone clearance rates and perioperative complications were evaluated.There were 165 male patients and 86 female patients with an average age of 46.9 years (range 22-80 years). Mean stone size was 2.7 cm and the average number of procedures was 1.4 (range 1-5). The stone-free rate at the end of the first, second and third procedure was 61.9%, 82.9%, and 89.5%, respectively. The final stone-free rate decreased as stone size grows, and it was only 58.3% for kidney stones larger than 4 cm after an average of 2.3 procedures. The lowest clearance rates were observed in lower calyx calculi (87.2%) and multiple calyx calculi (83.5%). The overall complication rate was 15.1%, and the most common complication was postoperative fever (9.6%). One patient required blood transfusion, owing to postoperative coagulation disorders induced by urosepsis.Single or staged FURS is a practical treatment option for the renal stones sized 2 to 4 cm with acceptable efficacy and safety. Stone clearance rate of FURS treatment is mainly affected by stone size and location.

Radiant cooling ceiling systems have already been proven to potentially provide an improved thermal comfort environment. This work conducted a full-scale experiment in an office, and a computational fluid dynamics (CFD) simulation study for a radiant cooling ceiling system integrated with air dehumidification equipment installed in this test space. The obtained results from the experiment were compared with the values from the CFD simulation to validate the accuracy of the model. Predicted mean vote (PMV) index was used to assess the original indoor thermal condition and improved conditions according to the simulation results. Experimental variables included supply air temperature from the diffuser, surface temperature, and the area of the cooling panels. In addition, diffuser position in the mechanical ventilation system was analyzed that provided suggestions on improving the design of radiant cooling ceiling panels. This study proposed solutions alongside limitations on improving indoor thermal comfort and energy efficiency using a radiant cooling ceiling system in the subtropical regions of Taiwan.

This study applies the oxygen/recycled flue gas (O(2)/RFG) combustion technology for waste incineration and investigates the effects of different RFG rates on the concentrations of gas pollutants as well as the partitioning characteristics and particle size distributions of five heavy metals (Cr, Cu, Pb, Zn, and Cd). Experimental results show that the combustion efficiency can be improved and the concentration of CO(2) is increased by appropriately controlling the RFG rate in the O(2)/RFG incineration system. The partitioning characteristics and size distributions of heavy metals in O(2)/RFG combustion system are different from those in general air combustion system. Under O(2)/RFG combustion system, the partitioning percentages of heavy metals in sand bed, bottom ash, and collected ash are increased. The particle size distributions of heavy metals display the triple-peak curves. As the RFG rate rises, the concentrations of volatile heavy metals are increased in small-size (1 microm) fly ash, decreased in medium-size (1-10 microm) fly ash and increased in large-size (10 microm) fly ash. These phenomena will benefit to increase the overall control efficiency of heavy metals in the incineration system.

This study applies the oxygen/recycled flue gas (O2/RFG) combustion technology for waste incineration in a laboratory-scale fluidized bed incinerator to investigate the effects of different RFG percentages and O2 concentrations on the emission characteristics of organic pollutants (PAHs, phenol and benzene hydrocarbons). Experimental results show that most PAHs with high-ring structures were present in solid-phase and most low-ring PAHs were present in gas-phase. The major compounds of benzene and phenol hydrocarbons were benzene, toluene, trichlorobenzene and 2,4-dinitrophenol, phenol, dichlorophenol, respectively. As the O2 concentration in feed gas was increased from 21% to 40%, the emissions of solid- and gas-phase PAHs and phenol compounds were decreased but not for benzene compounds. Increasing RFG percentages would decrease the emissions of gas-phase PAHs, benzene and phenol compounds, but increased those of solid-phase pollutants. The best operating conditions of such O2/RFG combustion system to reduce the emissions of PAHs and phenol compounds were 40% O2, 35% RFG, and that for benzene compounds was 21% O2, 75% RFG. Comparing with conventional air combustion system, the best diminution efficiencies of PAHs, benzene and phenol compounds at such O2/RFG conditions were 59.54%, 70.97% and 52.60%, respectively. With proper feed gas compositions and RFG percentages, the combustion efficiency and destruction efficiency of organic pollutants can be improved by this O2/RFG combustion technology.

This study applies the modified O2/recycled flue gas (RFG) combustion technology to waste incineration and investigates the emission characteristics of CO2, CO, NOx, SO2, and HCl at different operation conditions. The operation parameters under investigation include the O2 concentration in the feed gas, the rate of RFG, the total flow rate of feed gas, the type of incinerator, and the chemical compositions of feedstock. Experimental results show that the concentrations of CO2, SO2, and HCl in the exhausts can be enhanced by properly adjusting the O2 concentration in the feed gas and the RFG rate. This facilitates the removal of these pollutants by conventional control equipment. With 21% O2 feed gas and 75% RFG rate, the highest CO2 concentration can achieve 54%. A fluidized bed incinerator had better combustion efficiency than a fixed bed incinerator. The combustion efficiency levels were 96.68−99.99% and can be improved by increasing the RFG rate and O2 concentration. Moreover, the total flow rate of fe...

For mitigating the emission of greenhouse gas CO 2 from general air combustion systems, a clean combustion technology O 2 /RFG is in development. The O 2 /RFG combustion technology can significantly enhance the CO 2 concentration in the flue gas; however, using almost pure oxygen or pure CO 2 as feed gas is uneconomic and impractical. As a result, this study proposes a modified O 2 /RFG combustion technology in which the minimum pure oxygen is mixed with the recycled flue gas and air to serve as the feed gas. The effects of different feed gas compositions and ratios of recycled flue gas on the emission characteristics of CO 2 , CO and NO x during the plastics incineration are investigated by theoretical and experimental approaches. Theoretical calculations were carried out by a thermodynamic equilibrium program and the results indicated that the emissions of CO 2 were increased with the O 2 concentrations in the feed gas and the ratios of recycled flue gas increased. Experimental results did not have the same trends with theoretical calculations. The best feed gas composition of the modified O 2 /RFG combustion was 40% O 2 + 60% N 2 and the best ratio of recycled flue gas was 15%. As the O 2 concentration in feed gas and the ratio of recycled flue gas increased, the total flow rates and pressures of feed gas reduced. The mixing of solid waste and feed gas was incomplete and the formation of CO 2 decreased. Moreover, the emission of CO was decreased as the O 2 concentration in feed gas and the ratio of recycled flue gas increased. The emission of NO x gradually increased with rising the ratio of recycled flue gas at lower O 2 concentration ( 2 concentration (>60%).

This study investigates the emission characteristics of CO(2), SO(2) and NOx in the flue gas of coal combustion by varying the compositions and concentrations of feed gas (O(2)/CO(2)/N(2)) and the ratios of recycled flue gas. The differences between O(2)/recycled flue gas (O(2)/RFG) combustion and general air combustion are also discussed. Experimental results indicate that the maximum concentration of CO(2) in O(2)/CO(2) combustion system is 95% as the feed gas is 30% O(2)/70% CO(2). The average concentration of CO(2) in the flue gas of O(2)/CO(2) coal combustion system is higher than 90% and much higher than that of O(2)/N(2) coal combustion system. This high concentration of CO(2) is beneficial for the separation of CO(2) from the flue gas by adsorption or absorption technologies. The maximum concentration of CO(2) in O(2)/N(2) combustion system is only 34% at the feed gas 50% O(2)/50% N(2), the concentration of CO(2) is increased with the concentration of O(2) in feed gas. By O(2)/CO(2) combustion technology, higher concentration of SO(2) is produced as the feed gas is 30% O(2)/70% CO(2) or 40% O(2)/60% CO(2), while higher concentration of NOx is produced as the feed gas is 20% O(2)/80% CO(2) or 50% O(2)/50% CO(2). The mass flow rates of CO(2), SO(2) and NOx in the flue gas are all increased with the ratio of recycled flue gas except for the feed gas 20% O(2)/80% CO(2). The enhanced mass flow rates of air pollutants in such O(2)/RFG combustion system are also beneficial for improving the control efficiencies of air pollution control devices. By O(2)/N(2) combustion technology, higher concentrations of SO(2) and NOx are produced as the feed gas is 21% O(2)/79% N(2). The results also indicate that the formation of NOx in general air combustion system is higher than that in O(2)/RFG or O(2)/CO(2) combustion system.

This study investigated the combustion efficiencies and emission characteristics of oxygen/recycled flue gas (O2/RFG) coal combustion processes. The effects of different operating conditions such a...