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Michel Gradeck - One of the best experts on this subject based on the ideXlab platform.
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Experimental study of dispersed Flow film boiling at sub-channel scale in LOCA conditions: Influence of the Steam Flow Rate and residual power
Applied Thermal Engineering, 2020Co-Authors: Arthur Vieira Da Silva Oliveira, Alexandre Labergue, Tony Glantz, J.d. Peña Carrillo, Michel GradeckAbstract:Abstract Reflooding experiments with rod bundles at Loss Of Coolant Accident (LOCA) conditions usually use intrusive methods with limited access and, consequently, their data are not always adequate and comprehensive to validate simulation codes. For this reason, sub-channel scale experiments are useful to obtain detailed data in a more controlled environment for an accuRate thermal–hydraulics investigation. In this study, we present experiments of the cooling phase with an internal Steam-droplets Flow in a vertical pipe simulating an undamaged sub-channel in a nuclear reactor. Simultaneous measurements were performed of the wall temperature and droplets characteristics (velocity, diameter and temperature) using only optical techniques. An analysis is made on how the Steam Flow Rate and maintained heating power during the cooling phase affect the wall heat dissipation, wall rewetting and droplets dynamics. Results show that wall rewetting normally occurs from bottom to top, and the temperature at minimum heat flux is highly affected by the droplets dynamics. Furthermore, droplets are acceleRated when passing through the heated tube, especially at higher wall temperatures, and their temperature is nearly the same up- and downstream of the test section. Results with heating during the cooling phase show that wall rewetting takes place at higher wall temperatures and advances slower with the increase in the maintained heating power. Moreover, for the time period and Flow conditions used in this work, wall rewetting does not occur for maintained powers higher than 1.5 kW/m.
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Experimental thermal-hydraulic study of a Steam-droplets Flow inside a vertical pipe during the cooling phase in LOCA conditions -effect of the Steam Flow Rate
2019Co-Authors: J David Peña, Arthur Oliveira, Alexandre Labergue, Tony Glantz, Michel GradeckAbstract:This study concerns the cooling capacity of a high-temperature vertical pipe by a two-phase Flow of superheated Steam and droplets under Loss of Coolant Accident (LOCA) conditions. In order to characterize the cooling capacity, an experimental setup was developed. The heat flux removed from the wall during the cooling phase is investigated with the use of infrared thermography (IRT) while, simultaneously, the droplet diameter and velocity are characterized by a Phase Doppler system. In parallel, measurements of Laser Induced Fluorescence (LIF) are performed to obtain the mean droplet temperature. The present paper regards the influence of the inlet Steam Flow Rate for a representative non-deformed nuclear core geometry at sub-channel scale. In general, rewetting occurs from bottom to top in the tube, starting early with the increase in the Steam Flow Rate. As expected, during the Leidenfrost regime, the heat transfer is enhanced when increasing the Steam Flow Rate. Finally, smaller droplets have higher velocities and the droplets temperature does not increase significantly from up-to downstream.
S T Chaudhari - One of the best experts on this subject based on the ideXlab platform.
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production of hydrogen and or syngas h2 co via Steam gasification of biomass derived chars
Energy & Fuels, 2003Co-Authors: S T Chaudhari, A K Dalai, N N BakhshiAbstract:Steam gasification of two biomass-derived chars was studied at 700, 750, and 800 °C in a fixed bed microreactor at different Steam Flow Rates in the range of 1.25 to 10 g/h/g of char. The chars used in the present study were (i) bagasse charobtained from Natural Resources Canada, CANMET Energy Technology, Ontario (produced by Dynamotive Technologies Corp., Vancouver, BC), and (ii) commercial charobtained from ENSYN Technologies Inc., Ontario (produced during the fast pyrolysis of biomass using their RTI process). Both chars were highly reactive, particularly at 800 °C with Steam Flow Rate of 5 and 10 g/h/g of char. In the case of bagasse char, maximum conversion of 81% was achieved at 800 °C with a Steam Flow Rate of 10 g/h/g of char, whereas maximum conversion of 69% for commercial char was obtained at 800 °C with Steam Flow Rates of 5 and 10 g/h/g of char. The product gas obtained was mainly a mixture of H2, CO, CO2, and CH4 with a high H2/CO molar ratio (about 4:7 for bagasse char and 9:15 for commerci...
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Production of hydrogen and/or syngas (H2 + CO) via Steam gasification of biomass-derived chars
Energy & Fuels, 2003Co-Authors: S T Chaudhari, A K Dalai, Narendra N. BakhshiAbstract:Steam gasification of two biomass-derived chars was studied at 700, 750, and 800 °C in a fixed bed microreactor at different Steam Flow Rates in the range of 1.25 to 10 g/h/g of char. The chars used in the present study were (i) bagasse charobtained from Natural Resources Canada, CANMET Energy Technology, Ontario (produced by Dynamotive Technologies Corp., Vancouver, BC), and (ii) commercial charobtained from ENSYN Technologies Inc., Ontario (produced during the fast pyrolysis of biomass using their RTI process). Both chars were highly reactive, particularly at 800 °C with Steam Flow Rate of 5 and 10 g/h/g of char. In the case of bagasse char, maximum conversion of 81% was achieved at 800 °C with a Steam Flow Rate of 10 g/h/g of char, whereas maximum conversion of 69% for commercial char was obtained at 800 °C with Steam Flow Rates of 5 and 10 g/h/g of char. The product gas obtained was mainly a mixture of H2, CO, CO2, and CH4 with a high H2/CO molar ratio (about 4:7 for bagasse char and 9:15 for commerci...
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Steam gasification of biomass derived char for the production of carbon monoxide rich synthesis gas
Energy & Fuels, 2001Co-Authors: S T Chaudhari, N N Bakhshi, Ajay K DalaiAbstract:There is growing interest in the conversion of biomass and related materials into gaseous and liquid fuels. During fast pyrolysis of biomass in a fluidized-bed reactor, 15% of biomass is converted to char whereas 70% is converted to liquid and the rest to gas. In the present work, a systematic study has been conducted to explore the possibilities of using biomass-derived char for the production of various types of gaseous fuels and synthesis gas through pyrolysis and Steam gasification in a tubular reactor. The pyrolysis experiments were carried out in the presence of nitrogen ( Flow Rate of 20 mL/min) in the temperature range of 700−800 °C. Steam gasification experiments were carried out in the temperature range of 650−800 °C, Steam Flow Rate of 2.5−15 g/h/g of char. The reaction time was varied from 0.5 to 2.0 h. It has been found that a combination of lower Steam Flow Rate (about 2.5 g/h/g of char), lower temperature (about 700 °C), along with lower reaction time (about 0.5 h) produces synthesis gas ha...
Paul T. Williams - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen production from high temperature Steam catalytic gasification of bio-char
Journal of the Energy Institute, 2016Co-Authors: Qari M.k. Waheed, Paul T. WilliamsAbstract:Hydrogen production from the catalytic Steam gasification of bio-char derived from the pyrolysis of sugar cane bagasse has been investigated in relation to gasification temperature up to 1050 °C, Steam Flow Rate from 6 to 25 ml h−1 and type of Nickel catalyst. The catalysts used were Ni-dolomite, Ni–MgO and Ni–Al2O3, all with 10% nickel loading. The hydrogen yield in the absence of a catalyst at a gasification temperature of 950 °C was 100.97 mmol g−1 of bagasse char. However, the presence of the Ni–MgO and Ni–Al2O3 catalysts produced significantly improved hydrogen yields of 178.75 and 187.25 mmol g−1 of bagasse char respectively at 950 °C. The hydrogen yield from the char with the Ni-dolomite only showed a modest increase in hydrogen yield. The influence of gasification temperature showed that the optimum temperature to obtain the highest hydrogen yield was 950 °C. Increase in gasification temperature from 750 to 950 °C significantly increased hydrogen yield from 45.30 to 187.25 mmol g−1 of bagasse char at 950 °C, but was followed by a decrease in yield at 1050 °C. The influence of Steam Flow Rate showed that with the increase in Steam Flow Rate from 6 to 15 ml h−1 hydrogen yield was increased from 187.25 to 208.41 mmol g−1 of bagasse char. Further increase in Steam Flow Rate resulted in a decrease in hydrogen yield.
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Pyrolysis/reforming of rice husks with a Ni–dolomite catalyst: Influence of process conditions on syngas and hydrogen yield
Journal of the Energy Institute, 2016Co-Authors: Qari M.k. Waheed, Paul T. WilliamsAbstract:The influence of process conditions on the production of syngas and H2 from biomass in the form of rice husks was investigated using a two-stage pyrolysis/catalytic reforming reactor. The parameters investigated were, reforming temperature, Steam Flow Rate and biomass particle size and the catalyst used was a 10 wt.% Ni–dolomite catalyst. Biomass was pyrolysed in the first stage, and the product volatiles were reformed in the second stage in the presence of Steam and the Ni–dolomite catalyst. Increase in catalyst temperature from 850 °C to 1050 °C marginally improved total syngas yield. However, H2 yield was increased from 20.03 mmol g−1 at 850 °C to 30.62 mmol g−1 at 1050 °C and H2 concentration in the product gas increased from 53.95 vol.% to 65.18 vol.%. Raising the Steam Flow Rate increased the H2 yield and H2 gas concentration. A significant increase in H2:CO ratio along with a decrease in CO:CO2 ratio suggested a change in the equilibrium of the water gas shift reaction towards H2 formation with increased Steam Flow Rate. The influence of particle size on H2 yield was small showing an increase in H2 production when the particle size was reduced from 2.8–3.3 to 0.2–0.5 mm.
A Bitenc - One of the best experts on this subject based on the ideXlab platform.
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Low-cost Steam consumption control system for batch pulp cooking
Control engineering practice, 2017Co-Authors: Stanko Strmčnik, Janko Petrovčič, Nadja Hvala, A BitencAbstract:In batch pulp cooking the heating Steam is used only in some phases of the technological procedure. This causes large variations in Steam Flow-Rate and imposes high dynamic load at the Steam generation plant. In the paper, a system for smooth Steam consumption control is presented. It is based on three multiloop microprocessor-based controllers. The designed control structure is simple enough to be implemented as a stand-alone small-sized control system. Also, it provides a low-cost solution by eliminating the need to measure the Steam Flow-Rate on each digester. After the installation a reduction of 70% in Steam Flow-Rate variance was measured. © 1995.
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Steam Consumption Control System for Batch Pulp Cooking
IFAC Proceedings Volumes, 1992Co-Authors: Janko Petrovčič, A Bitenc, Stanko StrmčnikAbstract:Abstract In batch pulp cooking the heating Steam is used only in some phases of the technological procedure. This causes very irregular total Steam consumption. High Steam Flow-Rate variations impose a high dynamic load at the Steam generation plant which reduces the efficiency of the Steam generation. In this contribution a system for Steam consumption control is presented, which is based on the three multiloop microprocessorbased controllers. The implemented control structure consists of a set of temperature controllers, a set of “smooth”temperature set-point generators, a set of state-machine algorithms for sequential control, a Steam distribution algorithm, a simple Steam Flow-Rateestimation and a Steam Flow-Rate controller. The control structure is simple enough to allow the implementation as a stand-alone small-size control system. The lowcost solution is provided also by elimination of the need for asepaRate Steam Flow-Rate measuring system for each digesterʼs heat exchanger. After the installation a reduction of 70% in Steam Flow-Rate variance was measured. The reduction may be adjusted by the operator as a compromise between the acceptable dynamic loading of the Steam boilerand the requested pulp production Rate.
Rishabh Verma - One of the best experts on this subject based on the ideXlab platform.
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Low temperature Steam gasification to produce hydrogen rich gas from kitchen food waste: Influence of Steam Flow Rate and temperature
International Journal of Hydrogen Energy, 2020Co-Authors: Dharminder Singh, Sanjeev Yadav, Nitish Bharadwaj, Rishabh VermaAbstract:Abstract Large amount of food waste is geneRated from Indian kitchens and disposing off such a large amount possesses a great challenge in terms of environmental degradation and viable food waste processing technology. In this work, Steam gasification was tested as an alternative viable technology to process the kitchen food waste. Preliminary study was carried out at low temperature on Steam gasification in a fixed bed reactor to study the influence of Steam Flow Rate (SFR) and temperature on the syngas yield, syngas composition, hydrogen yield. Performance parameters such as carbon conversion efficiency (CCE), and apparent thermal efficiency (ATE) are also calculated. Steam Flow Rates are varied from 0.125 mL/min to 0.75 mL/min and the temperatures are varied from 700 °C to 800 °C. The highest hydrogen yield is obtained at 0.5 mL/min SFR and 800 °C temperature and its highest value is 1.2 m3/kg. The highest value of performance parameters, CCE and ATE are found to be 63% and 1.8.
