Influence Of Residence Time Research Articles

Formation of Modern Ski Complex

The paper relevance is determined by the growing popularity of active extreme tourism, where ski holidays offer increasing accessibility to ski infrastructure and are supported by the government.Purpose: Identification of design principles and trends in a modern ski complex.Methodology: The analysis of Russian and foreign experience; functional typology of ski complexes; principles of creating modern architecture integrated into the environment; ski resorts in Russia, European countries, Japan and the USA in the 20-21st centuries.Research findings: The historical aspect of the emergence of skiing as a popular tourism is considered herein. Based on the comparative analysis, the principles of designing ski complexes are formulated. The connection between these principles and sustainable architecture is shown. The classification is given to ski complexes. The influence of residence time on functional content is highlighted. The functional planning aspects of design and the influence of architectural and stylistic solutions on them are formulated. The functional planning structure is presented. The dependence of spatial arrangement with the functional planning structure is demonstrated.Practical implications: The results can be used in the design of ski complexes.Originality: The paper studies Russian and foreign experience in design of ski complexes; factors influencing the design in the complex terrain; determines the functional and planning structure and nomenclature of the premises of ski complexes.

Effect of Residence Time and Carrier Gas on the Dehydrogenation of n-Hexane over Alumina-supported Chromium Catalyst

CrOx/γ-Al2O3 catalyst was prepared by incipient wetness impregnation method, and the influence of residence time and carrier gas on the dehydrogenation of n-hexane were studied. It is found that n-hexane dehydrogenation over CrOx/γ-Al2O3 catalyst with H2 as carrier gas exhibits totally different catalytic behaviors with that of diluting n-hexane with N2. When diluting feed with N2, the selectivity to dehydrogenation product is promoted while the cracking reaction is exhibited with reducing residence time. However, the selectivity to dehydrogenation product is significantly decreased while the isomerization of n-hexane is promoted when using H2 as carrier gas. It is proposed that H2 undergoes dissociation on the dehydrogenation active site, and further facilitates the olefinic dehydrogenation products to form carbocation, which performing isomerization reaction on the acid site on the γ-Al2O3 surface. Therefore, the isomerization of n-hexane is promoted in cost of the selectivity to dehydrogenation product when using H2 as carrier gas.

Stability and WBE biomarkers possibility of 17 antiviral drugs in sewage and gravity sewers

Wastewater-based epidemiology (WBE) is a promising technique for monitoring the rapidly increasing use of antiviral drugs during the COVID-19 pandemic. It is essential to evaluate the in-sewer stability of antiviral drugs in order to determine appropriate biomarkers. This study developed an analytical method for quantification of 17 typical antiviral drugs, and investigated the stability of target compounds in sewer through 4 laboratory-scale gravity sewer reactors. Nine antiviral drugs (lamivudine, acyclovir, amantadine, favipiravir, nevirapine, oseltamivir, ganciclovir, emtricitabine and telbivudine) were observed to be stable and recommended as appropriate biomarkers for WBE. As for the other 8 unstable drugs (abacavir, arbidol, ribavirin, zidovudine, ritonavir, lopinavir, remdesivir and efavirenz), their attenuation was driven by adsorption, biodegradation and diffusion. Moreover, reaction kinetics revealed that the effects of sediments and biofilms were regarded to be independent in gravity sewers, and the rate constants of removal by biofilms was directly proportional to the ratio of surface area against wastewater volume. The study highlighted the potential importance of flow velocity for compound stability, since an increased flow velocity significantly accelerated the removal of unstable biomarkers. In addition, a framework for graded evaluation of biomarker stability was proposed to provide reference for researchers to select suitable WBE biomarkers. Compared with current classification method, this framework considered the influences of residence time and different removal mechanisms, which additionally screened four antiviral drugs as viable WBE biomarkers. This is the first study to report the stability of antiviral drugs in gravity sewers.

Shifting the natural deep eutectic solvent based liquid lipase extraction from batch to continuous for more efficient process performance

Natural deep eutectic solvents (NADES) have been recognised as a promising alternative to conventional aqueous media in biodiesel production because of their dual function, as lipase extractants and transesterification enhancers. To use lipase in NADES, lyophilized lipase must be dissolved in NADES or lipase must be extracted from liquid lipase formulations in NADES. The extraction processes, although efficient, is time consuming because it is highly limited by mass transfer. To enhance the extraction process and shift it from batch to continuous, the aqueous two-phase extraction (ATPS) based on NADES was tested as a possible tool for continuous extraction of lipase from raw liquid formulation to NADES in a microextractor. The fast screening of NADES was performed in a batch extractor and betaine-urea NADES-based was selected for further research. The process was then transferred to a microextractor where the influence of residence time, ultrasound, temperature and channel diameter were studied. Room temperature (T = 25 °C) and 1000 μm channel diameter were optimal for continuous microextraction. The extraction process was significantly intensified in a microextractor. The lipase extraction efficiency obtained in a batch reactor was 94.70% for 30 min, while an extraction efficiency of 98.50% was achieved for a residence time of 30 s in a microextractor. Finally, the extracted lipase was used for biodiesel synthesis in a batch reactor, obtaining a biodiesel yield of 96.11%. The reusability of the extracted lipase was also investigated, and the enzyme was successfully reused in three cycles, after which the biodiesel yield decreased.

A Study of Temperature and Residence Time Influence on Waste Tire Pyrolysis Products Yield

A Study of Temperature and Residence Time Influence on Waste Tire Pyrolysis Products Yield

Experimental investigation on the degradation of polymer-containing oily sludge in sub-/supercritical water

ABSTRACT Polymer-containing oily sludge (PCOS) has caused tremendous hazards with the broad application of polymer flooding technology. Traditional methods cannot meet the treatment demand due to the high-water content of PCOS. In this work, the degradation of PCOS in sub-/supercritical water is studied to explore an appropriate treatment method. The influence of residence time (15–90 min), temperature (340–700°C), catalysts (sulfates, carbonates, and alkalis), and co-solvents (methanol-water and ethanol-water) on the distribution of end products is studied in details. Results show that PCOS is hardly gasified under the subcritical conditions and the increase in residence time and temperature has positive effects on the phase conversion. The conversion rate reaches 81.77% at 60 min, 340°C, compared to 67.09% at 15 min. Supercritical water shows a great solubility for PCOS, and no solid residues are detected at supercritical conditions (400–700°C, 23 MPa). Organic matter in liquid phase is classified into nine types, and the increase in temperature greatly changes its composition. The relative proportion of ketones reaches more than 50% of the organic matter in liquid at 400°C. Ketones are proven to be the main source of CO2 and disappear at above 500°C. Moreover, the migration of elements (carbon and nitrogen) is comprehensively studied.

Intensification of endo-1,4-Xylanase Extraction by Coupling Microextractors and Aqueous Two-Phase System

The extraction of xylanase was performed using an aqueous two-phase system (ATPS) based on polyethylene glycol (PEG1540) and various salts. Preliminary studies in a batch extractor showed that the highest extraction efficiency, E = 79.63 ± 5.21%, and purification factor, PF = 1.26 ± 0.25, were obtained with sodium citrate dihydrate-H2O-PEG1540-based ATPS for an extraction time of 10 min. The process was optimized using the experimental Box-Behnken design at three levels with three factors: extraction time (t), xylanase concentration (γ), and mass fraction of PEG in the ATPS (wPEG). Under optimal process conditions (γ = 0.3 mg/mL, wPEG = 0.21 w/w, and t = 15 min), E = 99.13 ± 1.20% and PF = 6.49 ± 0.05 were achieved. In order to intensify the process, the extraction was performed continuously in microextractors at optimal process conditions. The influence of residence time, different feeding strategies, and channel diameter on extraction efficiency and purification factor was further examined. Similar results were obtained in the microextractor for a residence time of τ = 1.03 min (E = 99.59 ± 1.22% and PF = 6.61 ± 0.07) as in the experiment carried out under optimal conditions in the batch extractor. In addition, a batch extractor and a continuous microextractor were used for the extraction of raw xylanase produced by Thermomyces lanuginosus on solid supports.

Investigation into Effect of Residence Time on Cooling Characteristics of RP-3

Efficient utilization of chemical heat sinks and enhancement of heat transfer are key issues for the thermal protection of advanced hypersonic flight vehicles. However, the influences of residence time on the pyrolysis and convection heat transfer of hydrocarbon fuel are different, which is important for the design and optimization of cooling systems. Therefore, a multidimensional numerical simulation model based on a molecular reaction model of aviation kerosene, RP-3, is established. This model reveals that the residence time has a great influence on the heat sink and heat transfer characteristics under the supercritical condition. With the increase of the residence time, the chemical heat sink and physical heat sink increase, whereas the convective heat transfer coefficient decreases. The heat transfer is not only affected by flow structures but also by the ratio of the chemical heat sink to the physical heat sink. With the increase of the residence time, this ratio first increases and then decreases. It has a maximum value, and the residence time corresponding to this maximum value is exactly the residence time when the total chemical heat sink rate reaches the maximum. A correlation predicting the maximum heat sink ratio is proposed based on these data.

Textile wastewater treatment in anaerobic reactor: Influence of domestic wastewater as co-substrate in color and COD removal

Treatment of textile wastewater with domestic wastewater as co-substrate was investigated in this study. Combined textile and domestic wastewater at different mixing ratios (100:0, 80:20, 60:40) was treated under anaerobic reactor. The influence of residence time, textile wastewater fraction and initial pH were determined in view of COD and color removal. Response Surface methodology (RSM) with Box–Behnken design (BBD) was employed to determine conditions for higher simultaneous removal of COD and color. The highest simultaneous removal of COD and color were satisfied at initial pH of 8.6, residence time of 9 days while textile and domestic wastewater ratio was 77:23. The highest removal efficiencies realized were 70% and 72% for color and COD respectively. In general, longer residence time and higher initial pH favored higher simultaneous removal of COD and color. Furthermore, textile wastewater fraction in range of 0.65 – 0.8 favored simultaneously high COD and color removal. Therefore, co-digestion of textile and domestic wastewater at specific ratio is a novel finding that can be further developed for treating textile wastewaters. Moreover, this technology is a promising approach to enhance biological treatment of textile wastewater.

Coupling donann dialysis and electro-reduction process for nitrate removal from simulated groundwater

In this study, Donnan dialysis (DD) was applied to denitrify synthetic groundwater and electro-reduction was utilized as a post-treatment to remove the nitrate from the secondary waste generated during the DD process. Combined experiments were performed under continuous operating mode using a synthetic solution mimicking nitrate-contaminated groundwater found in agriculturally intensive regions of Italy. The influence of residence time on thie removal efficiency of nitrate in each reactor was studied. The effects of nitrate concentration, accompanying ions, and by-product formation were tested in the electrolyzer. In DD, nitrate, along with the accompanying ions bicarbonate and sulfate, was transported through an anion exchange membrane into a 100 mM NaCl receiving stream. Higher removal efficiencies were obtained with prolonged residence time, up to 65% at RT of 120 min. A maximum of 60% electro-reduction of nitrate, using a Cu-DSA electrode pair, was achieved at a residence time of ≥90 min. The specific energy consumption did not change significantly with the electrolysis RT ranging from 40 to 120 min. An increase in the nitrate concentration resulted in higher removal efficiency and reduced energy consumption. During the electrolysis of the DD waste, no ammonia was formed and 100% N2-selectivity was obtained.

Influence of process temperature and residence time on the manufacturing of amorphous solid dispersions in hot melt extrusion

The manufacturing of amorphous solid dispersions via hot melt extrusion is a topic of high interest in pharmaceutical development. By this technique, the drug is dissolved in the molten polymer above solubility temperature within the process time. In this study, an experimental framework is proposed determining the minimum required process temperature and the residence time using particularly low quantities of material. Drug/polymer mixtures in different ratios were processed in a micro-scale extruder while the process temperature and residence time were varied systematically. The phase situation was assessed by the turbidity of the final extrudate. Four different drug/polymer mixtures were investigated in three drug/polymer ratios. The minimum required process temperature was close to solubility temperature for each specific formulation. Moreover, an influence of residence time on the phase situation was found. About three minutes were required in order to dissolve the drug in the polymer at these process conditions.

Hydrogen-Rich Gas Production from Two-Stage Catalytic Pyrolysis of Pine Sawdust with Nano-NiO/Al2O3 Catalyst

Hydrogen production from biomass pyrolysis is economically and technologically attractive from the perspectives of energy and the environment. The two-stage catalytic pyrolysis of pine sawdust for hydrogen-rich gas production is investigated using nano-NiO/Al2O3 as the catalyst at high temperatures. The influences of residence time (0–30 s) and catalytic temperature (500–800 °C) on pyrolysis performance are examined in the distribution of pyrolysis products, gas composition, and gas properties. The results show that increasing the residence time decreased the solid and liquid products but increased gas products. Longer residence times could promote tar cracking and gas-phase conversion reactions and improve the syngas yield, H2/CO ratio, and carbon conversion. The nano-NiO/A12O3 exhibits excellent catalytic activity for tar removal, with a tar conversion rate of 93% at 800 °C. The high catalytic temperature could significantly improve H2 and CO yields by enhancing the decomposition of tar and gas-phase reactions between CO2 and CH4. The increasing catalytic temperature increases the dry gas yield and carbon conversion but decreases the H2/CO ratio and low heating value.

Study on the influence of residence time on the componential evolution of biomass pyrolysis vapors during indirect heat exchange process through a combining method of bio-oil composition inversion and function fitting

A novel and effective experimental method for describing the evolution curves and hot maps of biomass pyrolysis vapors with the adjustment of sweeping gas flow rate was developed during condensation. The composition proportion of pyrolysis vapors was inverted from the composition quantification of segmental bio-oil recovered by the specific condenser with two flumes. The mathematical relationship between location and vapor composition was fitted by Slogistic function. The condensable proportion of water decreased from 85% to 60% as N2 flow rate increased from 100 mL/min to 500 mL/min under 340 K water bath. But 500 mL/min N2 flow rate accelerated the disturbance of condensing field and improved the recoveries of components with stronger condensing abilities than water. The condensable proportion of guaiacol and its derivatives decreased from 60% to 40% under 300 mL/min but increased to 55% under 500 mL/min. Furthermore, the evolution difference between high-proportion and low-proportion components in pyrolysis vapors in the condensing field was also discussed as well as the unique evolution of components with azeotrope phenomenon or special solubility. For the first time, the adjustment mechanism of constant non-condensable components on the evolution of condensable components was clarified during water bath condensation, which would remarkably improve the comprehension for the complex phase transition process during the selective condensation of biomass pyrolysis vapors.

Hydrothermal carbonization of the waste straw: A study of the biomass transient heating behavior and solid products combustion kinetics

In this study, HTC impact on the waste straw fuel properties and waste straw hydrochars combustion kinetics have been presented. HTC experiments were carried out at Parr 4650 250 ml batch reactor, at temperatures of 225, 250, and 275 °C. Each temperature was investigated at 4 residence times: 10, 20, 30, and 40 min. Denoted hydrochars yields were more influenced by temperature than residence time, with different decomposition patterns observed at 275 °C compared to 225 and 250 °C, with final solid yields of 42.0%, 66.9%, and 65.3% at 40 min residence times respectively. The study of the transient HTC period resulted in the determination of the exothermal WS activity with the heat release of the 254.9 ± 48.8 kJ/kg of biomass. LHV values of the obtained hydrochars were 18.7–20.2 MJ/kg, 19.9–22.2 MJ/kg, and 23.1–26.2 MJ/kg for HTC temperatures of 225, 250, and 275 °C respectively. TGA analysis of the hydrochar combustion highlighted significant changes in the kinetic interpretation of the combustion profiles throughout investigated temperature ranges. The influence of residence time was only significant in the case of the 275 °C HTC samples, where a major shift of the combustion reactivity towards higher-temperature char oxidation was denoted. Hydrochars combustion kinetics were modeled with the implementation of Fraser-Suzuki deconvolution, and model-fitting of nth-order Arrhenius equation, with R2 values within 0.98–0.99.

Fate of trace elements in Oxygen Carrier Aided Combustion (OCAC) of municipal solid waste

Oxygen Carrier Aided Combustion is a novel fluidized bed concept for burning waste. This study analyzed solid samples from an industrial OCAC application using municipal solid waste and the oxygen carrier ilmenite. The presence of oxygen carriers impacts the ash chemistry, which can influence corrosion and ash characteristics. By investigating samples obtained from industrial applications, unique and highly relevant information on the solid-state chemistry and the fate of important elements can be obtained. In total, 20 bottom ashes and 17 fly ashes were sampled over a period of 38 days. In a preceding study, the surface interaction between ilmenite and Zn, Cu and Pb was investigated. In this paper, the distribution of these elements throughout the particle cross-section and the influence of residence time has been studied using XRD, SEM-EDX and XPS. The results show that Zn is incorporated in the Fe-rich ash layer over time in the form of Zn ferrites, while Cu accumulates inside the ilmenite particles with time, and Cr is enriched in the magnetically separated bottom ash. Low concentrations of Pb were detected in the bottom ashes, suggesting that a significant part is released in the gas phase. The influence of temperature, bed material and reduction potential were evaluated using multicomponent, multiphase equilibrium calculations. It is shown that an ilmenite bed is less prone to form melts in comparison to a bed of silica sand and that the addition of sulfur could decrease the volatilization of Pb.

Sustainable fuel production from steam reforming of waste motor oil over olivine-supported Fe catalyst

Waste Motor Oil (WMO) has great potential to be utilized as a green fuel feedstock via thermochemical process as its high carbon content is suitable as alternative source during steam reforming reactions (SR). This process not only has potential for high syngas (CO and H2) production but also elimination of undesirable components, polyaromatic hydrocarbons (PAHs) and heavy metals in WMO. Here, evaluation of optimal conditions for WMO catalytic steam reforming in fixed-bed laboratory reactor to produce quality syngas was carried out. Influences of residence time (7–20 s), reaction temperature (700–900 °C), steam to carbon (S/C) ratio (1:2, 1:1, and 2:1), and Fe loadings (5% and 10%) on olivine support on carbon and hydrogen conversions were investigated. Results showed that the highest carbon and hydrogen conversions could be obtained after 10 s due to reactions achieving equilibrium. As for temperature, carbon and hydrogen conversions increased with temperature from mainly endothermic reactions which cause more hydrocarbon cracking. S/C volume ratio of 1:1 was preferable to obtain better carbon and hydrogen conversions due to superior heat distribution. Thus, the optimal conditions of WMO reforming were 10 s and S/C ratio of 1:1 at 800 °C which resulted in 94.68% and 79.34% carbon and hydrogen conversions, respectively, while gas product LHV was 4.44 MJ/m3. As for Fe loading on olivine, the best performance was acquired at 800 °C, residence time of 15 s, and S/C ratio of 1:1 with 10% Fe/olivine. Carbon and hydrogen conversions increased by 7.60% to 69.91% and by 13.70% to 69.31%, respectively, when compared to non-catalytic cases. This is because of higher cracking of heavy hydrocarbons from greater Fe active sites. Application of this work may lead to decrease in environmental impact from WMO disposal and make available the green fuel for sustainable power generations or as chemical intermediates in many industries.

Influence of Residence Time on Syngas Composition in CaO Enhanced Air–Steam Gasification of Biomass

Influence of Residence Time on Syngas Composition in CaO Enhanced Air–Steam Gasification of Biomass

Pyrolysis waste char supported metallic catalyst for syngas production during catalytic reforming of benzene

Waste rice husk char supported Fe and Ni were synthesized to prepare the monometallic and bimetallic catalysts for removing the tar model compound benzene in a laboratory dual-stage reactor. The prepared catalysts were examined by microstructure and textural characterization to analyse catalytic performance and stability. The molar proportions of CO, H2, CO2 and CH4 in the generated gas and the influence of residence time (τ) and the steam-to-carbon ratio (S/C) on the catalytic reaction were investigated. The results show that the rice husk char-based catalysts showed excellent catalytic activity for syngas production and benzene conversion. Under optimized conditions, the benzene conversion can reach 95.2%, and the mol% of syngas in the generated gas is greater than 93.0%, of which 91.0% is H2. The experimental results show that the influence of residence time on catalytic performance is greater than that of the steam-to-carbon ratio, and that excessive τ or S/C values will have no more positive effect on the performance of the catalyst. The stable active sites on the catalyst surface can guarantee the catalytic activity in the reaction. Ultimately, rice husk char-based catalysts can be used to remove tar and produce syngas.

An extensive parameter study of hydrotropic extraction of steam-pretreated birch

Efficient fractionation of lignocellulosic biomass is an important step toward the replacement of fossil-based products. However, the utilisation of all of the components in biomass requires various fractionation techniques. One promising process configuration is to apply steam explosion for the recovery of hemicelluloses and a subsequent hydrotropic extraction step for the delignification of the remaining solids. In this work, the influence of residence time, temperature and biomass loading on lignin recovery from birch using sodium xylene sulphonate as a hydrotrope was investigated. Our results show that residence time, temperature and biomass loading correlate positively with lignin extraction, but the effects of these parameters were limited. Furthermore, when steam explosion was implemented as the initial step, hydrotropic extraction could be performed even at room temperature, yielding a lignin extraction of 50%. Also, hydrothermal degradation of the material was necessary for efficient delignification with sodium xylene sulphonate, regardless of whether it occurs during steam explosion pretreatment or is achieved at high temperatures during the hydrotropic extraction.

Continuous Protein Crystallization in Mixed-Suspension Mixed-Product-Removal Crystallizers

The metastable needlelike form of lysozyme can be obtained from continuous crystallization in mixed-suspension mixed-product-removal (MSMPR) crystallizers for conditions at which the stable tetragonal form is obtained from batch crystallization. A 3D-printed airlift crystallizer and stirred tank crystallizer are used, which both approximate an MSMPR crystallizer well. The influence of residence time, precipitant concentration, and agitation mechanism on the attainable solid-state form is presented. The needlelike crystals appear after nucleation of the tetragonal form. An earlier transition from the tetragonal form to the needlelike form is observed in an airlift crystallizer compared to a conventional stirred crystallizer, which is possibly caused by reduced attrition and the presence of a gas–liquid interface in the airlift crystallizer. Furthermore, a long residence time and high precipitant concentration favor the formation of the needlelike crystals. This work demonstrates how the mode of operation of well-mixed crystallizers affects the attainable solid-state form of a model protein. The results generally show the importance of obtaining a quantitative understanding of the dynamic interplay between stochastic primary nucleation processes and deterministic growth and secondary nucleation processes so that future continuous MSMPR crystallizers can be designed and operated robustly to produce protein crystals of a desired solid-state form.