Absorption and decomposition of ozone in a three-phase split-rectangular airlift reactor under ultrasonic irradiation

2016 ◽  
Vol 73 (8) ◽  
pp. 1796-1801
Author(s):  
Yin Xu ◽  
Xin Zhong ◽  
Hui Zhang
Keyword(s):  
Ultrasonic Irradiation ◽  
Gas Flow ◽  
Airlift Reactor ◽  
Catalyst Loading ◽  
Volumetric Mass Transfer Coefficient ◽  
Absorption Process ◽  
Gas Flow Rate ◽  
Ozone Absorption ◽  
Three Phase ◽  
Absorption Kinetic

Ozone absorption was investigated in a three-phase split-rectangular airlift reactor under ultrasonic irradiation using γ-Al2O3 as catalyst. The reactor consisted of a square column (50 × 50 mm) with the height of 120 mm, divided into a riser and a downcomer by a baffle, 50 mm in width, 4 mm in thickness and 50 mm in total height. An absorption kinetic model was proposed to determine the volumetric mass transfer coefficient of ozone kLaA. The results showed that kLaA increased from 0.409 to 0.712 min−1 as power density rose from 27.2 to 100.3 W L−1, comparing with 0.242 min−1 in the absence of ultrasonic irradiation. The increase in gas flow rate and catalyst loading also favored the increase of kLaA. The degassing effect due to ultrasonic irradiation could be ignored in the ozone absorption process.

Mass Transfer Coefficients during Steel Decarburization in a RH Degasser

2008 ◽  
Vol 273-276 ◽  
pp. 679-684
Author(s):  
Roberto Parreiras Tavares ◽  
André Afonso Nascimento ◽  
Henrique Loures Vale Pujatti
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Gas Flow ◽  
Vacuum Chamber ◽  
Volumetric Mass Transfer Coefficient ◽  
Gas Flow Rate ◽  
Rh Process ◽  
Kinetics Of

The RH process is a secondary refining process that can simultaneously attain significant levels of removal of interstitial elements, such as carbon, nitrogen and hydrogen, from liquid steel. In the RH process, the decarburization rate plays a very important role in determining the productivity of the equipment. The kinetics of this reaction is controlled by mass transfer in the liquid phase. In the present work, a physical model of a RH degasser has been built and used in the study of the kinetics of decarburization. The effects of the gas flow rate and of the configurations of the nozzles used in the injection of the gas have been analyzed. The decarburization reaction of liquid steel was simulated using a reaction involving CO2 and caustic solutions. The concentration of CO2 in the solution was evaluated using pH measurements. Based on the experimental results, it was possible to estimate the reaction rate constant. A volumetric mass transfer coefficient was then calculated based on these rate constants and on the circulation rate of the liquid. The logarithm of the mass transfer coefficient showed a linear relationship with the logarithm of the gas flow rate. The slope of the line was found to vary according to the relevance of the reaction at the free surface in the vacuum chamber. A linear relationship between the volumetric mass transfer coefficient and the nozzle Reynolds number was also observed. The slopes of the lines changed according to the relative importance of the two reaction sites, gas-liquid interface in the upleg snorkel and in the vacuum. At higher Reynolds number, the reaction in the vacuum chamber tends to be more significant.

Predicting bed dynamics in three-phase, fluidized-bed biofilm reactors

1994 ◽  
Vol 29 (10-11) ◽  
pp. 231-241 ◽  
Author(s):  
H. T. Chang ◽  
B. E. Rittmann
Keyword(s):  
Fluidized Bed ◽  
Flow Rate ◽  
Liquid Flow ◽  
Gas Flow ◽  
Liquid Flow Rate ◽  
Gas Flow Rate ◽  
Biofilm Growth ◽  
Biofilm Thickness ◽  
Three Phase ◽  
Proper Design

This paper presents a unified model that inter-relates gas flow rate, liquid flow rate, and hold-ups of each of the liquid, gas, and solid phases in three-phase, fluidized-bed biofilm (TPFBB) process. It describes how carrier properties, biofilm properties, and gas and liquid flow velocities control the system dynamics, which ultimately will affect the density, thickness, and distribution of the biofilm. The paper describes the development of the mathematical model to correlate the effects of gas flow rate, liquid flow rate, solid concentration, and biofilm thickness and density. This knowledge is critically needed in light of the use of TPFBB processes in treating industrial wastewater, which often has high substrate concentration. For example, the proper design of the TPFBB process requires mathematical description of the cause-effect relationship between biofilm growth and fluidization.

Effects of Gas Flow Rate and Catalyst Loading on Polymer Electrolyte Membrane (PEM) Fuel Cell Performance and Degradation

2010 ◽  
Author(s):  
A. Chukwujekwu Okafor ◽  
Hector-Martins Mogbo
Keyword(s):  
Fuel Cell ◽  
Flow Rate ◽  
Gas Flow ◽  
Open Circuit Voltage ◽  
Polymer Electrolyte Membrane ◽  
Open Circuit ◽  
Catalyst Loading ◽  
Gas Flow Rate ◽  
Flow Rates ◽  
Electrolyte Membrane

In this paper, the effects of gas flow rates, and catalyst loading on polymer electrolyte membrane fuel cell (PEMFC) performance was investigated using a 50cm2 active area fuel cell fixture with serpentine flow field channels machined into poco graphite blocks. Membrane Electrode Assemblies (MEAs) with catalyst and gas flow rates at two levels each (0.5mg/cm2, 1mg/cm2; 0.3L/min, 0.5L/min respectively) were tested at 60°C without humidification. The cell performance was analyzed by taking AC Impedance, TAFEL plot, open circuit voltage, and area specific resistance measurements. It was observed that MEAs with lower gas flow rate had lesser cell resistance compared to MEAs with a higher gas flow rate. TAFEL plot shows the highest exchange current density value of −2.05 mAcm2 for MEA with 0.5mg/cm2 catalyst loading operated at reactant gas flow rate of 0.3L/min signifying it had the least activation loss and fastest reaction rate. Open circuit voltage curve shows a higher output voltage and lesser voltage decay rate for MEAs tested at higher gas flow rates.

Investigation of the Effects of Catalyst Loading and Gas Flow Rate on Polymer Electrolyte Membrane (PEM) Fuel Cell Performance and Degradation

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Anthony C. Okafor ◽  
Hector-Martins C. Mogbo
Keyword(s):  
Fuel Cell ◽  
Flow Rate ◽  
Gas Flow ◽  
Open Circuit Voltage ◽  
Polymer Electrolyte Membrane ◽  
Open Circuit ◽  
Catalyst Loading ◽  
Gas Flow Rate ◽  
Flow Rates ◽  
Electrolyte Membrane

In this paper, the effects of gas flow rates and catalyst loading on polymer electrolyte membrane fuel cell (PEMFC) performance was investigated using a 50 cm2active area fuel cell fixture with serpentine flow field channels machined into poco graphite blocks. Membrane electrode assemblies (MEAs) with catalyst and gas flow rates at two levels each (0.5 mg/cm2, 1 mg/cm2; 0.3 l/min, 0.5 l/min, respectively) were tested at 60 °C without humidification. The cell performance was analyzed by taking ac impedance, Tafel plot, open circuit voltage, and area specific resistance measurements. It was observed that MEAs with lower gas flow rate had lesser cell resistance compared to MEAs with a higher gas flow rate. Tafel plot shows the highest exchange current density value of 10−2.05 mA cm2 for MEA with 0.5 mg/cm2 catalyst loading tested at reactant gas flow rate of 0.3 l/min signifying it had the least activation loss and fastest reaction rate. Open circuit voltage-time curve shows a higher output voltage and lesser voltage decay rate for MEAs tested at higher gas flow rates.

scholarly journals Bubble column application on purification of biogas and production of nano-calcium carbonate in continuous process

2020 ◽  
Vol 16 (3) ◽  
pp. 286-291
Author(s):  
Yukh Ihsana ◽  
Putu Adhi Rama ◽  
Sugeng Winardi ◽  
Tantular Nurtono
Keyword(s):  
Calcium Carbonate ◽  
Flow Rate ◽  
Gas Flow ◽  
Bubble Column ◽  
Continuous Process ◽  
Calorific Value ◽  
Co2 Concentration ◽  
Absorption Process ◽  
Gas Flow Rate ◽  
Precipitated Calcium Carbonate

Purification of biogas by removing carbon dioxide content has been developed to increase its calorific value. The CO2  contained in biogas was absorbed by contacting Ca(OH)2 solution and CO2 in the bubble column to produce high purity of biogas and generated precipitated calcium carbonate (PCC) simultaneously. Two sources of CO2 were used in this work, which were CO2 contained in biogas and pure CO2. Pure CO2 was used as a benchmark in this study to show the effect of the presence of methane contained in biogas on the absorption process. The investigation was done in a continuous process. The results showed that the highest absorption of CO2 was obtained in biogas at 79.34 %. PCC with calcite phases was successfully formed in 225–270 nm. Rhombohedral calcite phase was formed by the use of pure CO2 and biogas as a source of CO2. The use of CO2 contained in biogas and pure CO2 in the absorption process did not have an effect on the crystalline phase and morphology of calcite formed. Several factors that significantly affected the absorption of CO2 were gas flow rate, absorbent flow rate, CO2 concentration in the gas inlet, and the initial liquid level in the bubble column. 

Phase inversion phenomena in vertical three-phase flow: Experimental study on the influence of fluids viscosity, duct geometry and gas flow rate

2018 ◽  
Vol 189 ◽  
pp. 245-259 ◽  
Author(s):  
Alex Roger Almeida Colmanetti ◽  
Marcelo Souza de Castro ◽  
Marcel Cavallini Barbosa ◽  
Oscar Mauricio Hernandez Rodriguez
Keyword(s):  
Experimental Study ◽  
Flow Rate ◽  
Phase Inversion ◽  
Gas Flow ◽  
Phase Flow ◽  
Gas Flow Rate ◽  
Three Phase ◽  
Three Phase Flow ◽  
Duct Geometry

SCIENTIFIC AND ENGINEERING PRINCIPLES OF EFFICIENT FUEL USE AND ENVIRONMENTALLY FRIENDLY GAS COMBUSTION IN STOVE PLATES. PART 1. MODERN STATE-OF-THE-ART AND DIRECTIONS FOR IMPROVEMENT THE GAS BURNING IN DOMESTIC GAS COOKERS

2017 ◽  
pp. 3-18 ◽  
Author(s):  
B.S. Soroka ◽  
V.V. Horupa
Keyword(s):  
Natural Gas ◽  
Flow Rate ◽  
Gas Flow ◽  
Renewable Energy Sources ◽  
Combustion Process ◽  
Orifice Diameter ◽  
Firing Process ◽  
Gas Flow Rate ◽  
Gas Combustion ◽  
Gas Stoves

Natural gas NG consumption in industry and energy of Ukraine, in recent years falls down as a result of the crisis in the country’s economy, to a certain extent due to the introduction of renewable energy sources along with alternative technologies, while in the utility sector the consumption of fuel gas flow rate enhancing because of an increase the number of consumers. The natural gas is mostly using by domestic purpose for heating of premises and for cooking. These items of the gas utilization in Ukraine are already exceeding the NG consumption in industry. Cooking is proceeding directly in the living quarters, those usually do not meet the requirements of the Ukrainian norms DBN for the ventilation procedures. NG use in household gas stoves is of great importance from the standpoint of controlling the emissions of harmful components of combustion products along with maintenance the satisfactory energy efficiency characteristics of NG using. The main environment pollutants when burning the natural gas in gas stoves are including the nitrogen oxides NOx (to a greater extent — highly toxic NO2 component), carbon oxide CO, formaldehyde CH2O as well as hydrocarbons (unburned UHC and polyaromatic PAH). An overview of environmental documents to control CO and NOx emissions in comparison with the proper norms by USA, EU, Russian Federation, Australia and China, has been completed. The modern designs of the burners for gas stoves are considered along with defining the main characteristics: heat power, the natural gas flow rate, diameter of gas orifice, diameter and spacing the firing openings and other parameters. The modern physical and chemical principles of gas combustion by means of atmospheric ejection burners of gas cookers have been analyzed from the standpoints of combustion process stabilization and of ensuring the stability of flares. Among the factors of the firing process destabilization within the framework of analysis above mentioned, the following forms of unstable combustion/flame unstabilities have been considered: flashback, blow out or flame lifting, and the appearance of flame yellow tips. Bibl. 37, Fig. 11, Tab. 7.

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