scholarly journals Mixing time study in agitated multiple-lamp UV photoreactor using electrical resistance tomography

2021 ◽  
Author(s):  
Zhen Fang Zhao
Keyword(s):  
Electrical Resistance ◽  
Uv Light ◽  
Mixing Time ◽  
Water Disinfection ◽  
Electrical Resistance Tomography ◽  
Rushton Turbine ◽  
Disinfection Process ◽  
Impeller Type ◽  
Uv Lamps ◽  
The Impact

The present study is devoted to the mixing time investigation in a single stirrer UV photoreactor aiming at the drinking water disinfection process. Electrical resistance tomography (ERT) was employed to measure the mixing quality due to the significant advantages. The reactor was a flat-bottomed cylindrical tank with a diameter of 38.1 cm and a height of 60.1 cm fitted with four symmetrically located vertical baffles. The performaces of a 6-blade Rushton turbine and a 4-blade 45° pitched-blade turbine were explored in this study. In the absence of the UV light, four PVC rods were used to replace four UV lamps and evaluate the impact of the locations of the UV tubes on the mixing time. The experimental results demonstrated the feasibility of the ERT system to monitor the mixing process in the UV photoreactor. The ERT results also indicated that the locations of the UV tubes had a signigicant impact on the mixing performance in such a batch stirred tank reactor. Other parameters encompassing the impeller rotational speed the impeller type, and off-bottom clearance were presented with respect to the extensive effects on the mixing time and power consumption.

scholarly journals Mixing time study in agitated multiple-lamp UV photoreactor using electrical resistance tomography

2021 ◽  
Author(s):  
Zhen Fang Zhao
Keyword(s):  
Electrical Resistance ◽  
Uv Light ◽  
Mixing Time ◽  
Water Disinfection ◽  
Electrical Resistance Tomography ◽  
Rushton Turbine ◽  
Disinfection Process ◽  
Impeller Type ◽  
Uv Lamps ◽  
The Impact

The present study is devoted to the mixing time investigation in a single stirrer UV photoreactor aiming at the drinking water disinfection process. Electrical resistance tomography (ERT) was employed to measure the mixing quality due to the significant advantages. The reactor was a flat-bottomed cylindrical tank with a diameter of 38.1 cm and a height of 60.1 cm fitted with four symmetrically located vertical baffles. The performaces of a 6-blade Rushton turbine and a 4-blade 45° pitched-blade turbine were explored in this study. In the absence of the UV light, four PVC rods were used to replace four UV lamps and evaluate the impact of the locations of the UV tubes on the mixing time. The experimental results demonstrated the feasibility of the ERT system to monitor the mixing process in the UV photoreactor. The ERT results also indicated that the locations of the UV tubes had a signigicant impact on the mixing performance in such a batch stirred tank reactor. Other parameters encompassing the impeller rotational speed the impeller type, and off-bottom clearance were presented with respect to the extensive effects on the mixing time and power consumption.

scholarly journals Using electrical resistance tomography to measure the yield stress of pretreated wheat straw and wheat straw slurries

2021 ◽  
Author(s):  
Yasaman Naghavi-Anaraki
Keyword(s):  
Wheat Straw ◽  
Yield Stress ◽  
Electrical Resistance ◽  
Low Cost ◽  
Electrical Resistance Tomography ◽  
Fiber Concentration ◽  
Active Motion ◽  
Fiber Size ◽  
Pretreated Wheat Straw ◽  
Impeller Type

Wheat straw is a low-cost feedstock for production of biofuels as a viable alternative to fossil -based fuels. Pretreatment process is an important stage in producing biofuels. Pretreated wheat straw slurries (PWS) are non-Newtonian fluids with yield stress. In mixing operations, the presence of yield stress creates a region of active motion (cavern) around the impeller and stagnant zones elsewhere which causes difficulties in the production of biofuels. In this study, for the first time electrical resistance tomography (ERT) was utilized to measure the cavern dimensions as a function of the impeller type (A200, A100, and A315), impeller speed (20 to 110 rpm), fiber size (≤ 2 and ≤ 6 mm), and PWS concentration (6, 8, and 10 wt%). The cavern sizes were used to measure the yield stress of PWS slurries as a function of fiber size and fiber concentration. The average yield stresses of 6, 8, and 10 wt% PWS slurries with the fiber sizes of ≤ 2 mm were 2.00, 5.43, and 8.51 Pa, respectively, and 4.26, 9.30, and 13.84 Pa for the fiber sizes of ≤ 6 mm.

scholarly journals Using electrical resistance tomography (ERT) and computational fluid dynamics (CFD) to study the mixing of pseudoplastic fluids with a SCABA 6SRGT impeller

2021 ◽  
Author(s):  
Leila Pakzad
Keyword(s):  
Flow Field ◽  
Flow Pattern ◽  
Electrical Resistance ◽  
Mixing Time ◽  
Three Dimensions ◽  
Cfd Modeling ◽  
Cube Root ◽  
Mixing Times ◽  
Electrical Resistance Tomography ◽  
Good Agreement

The objective of this work is to use electrical resistance tomography (ERT) and computational fluid dynamic (CFD) modeling to investigate the flow field generated by a Scaba 6SRGT impeller in the agitation of the xanthan solution, as a pseudoplastic fluid with yield stress. ERT provides a non-destructive technique to measure, in three dimensions, the concentration fields inside the mixing tanks. Using ERT, the impeller flow pattern, the dimensions of the cavern formed and the mixing time in the agitation of xanthan solutions were evaluated. The sizes of cavern measured using ERT were in good agreement with that calculated using Elson's model (cylindrical model). ERT provides both overall mixing time using 1264 probes (316 probes for each plan) and local mixing time using 4 selected probes or pixels. The dimensionless mixing times obtained from ERT were correlated well with the Moo-Young correlation, confirming that increased impeller speeds decreases the mixing times. The 3D flow field generated by a Scaba 6SRGT impeller and tracer homogenization in the agitation of xanthan gum were also simulated using the commercial CFD package (FLUENT). The experimental torque measurements were used to validate the numerical simulations. The validated CFD model provided useful information regarding the impeller pumping capacity and flow pattern, the velocity profiles, the formation of cavern around the impeller, and the mixing time. CFD results show good qualitative as well as quantitative agreement with the experimental results and theory. The sizes of cavern measure using CFD were in good agreement with that calculated using Elson's model. The local mixing times predicted from CFD simulations agreed well with literature in a way that mixing times varied inversely with the cube root of the power consumed per unit volume of the solution. CFD under predicted the local mixing times measured using ERT by 11-47%.

scholarly journals Demonstration and evaluation of germicidal UV-LEDs for point-of-use water disinfection

2010 ◽  
Vol 8 (3) ◽  
pp. 479-486 ◽  
Author(s):  
Christie Chatterley ◽  
Karl Linden
Keyword(s):  
Uv Irradiation ◽  
Uv Light ◽  
Low Pressure ◽  
Water Disinfection ◽  
Light Emitting ◽  
E Coli ◽  
Point Of Use ◽  
One Year ◽  
Uv Lamps ◽  
Uv Leds

Ultraviolet (UV) irradiation is a common disinfection option for water treatment in the developed world. There are a few systems installed in developing countries for point-of-use treatment, but the low-pressure mercury lamps currently used as the UV irradiation source have a number of sustainability issues including a fragile envelope, a lifetime of approximately one year, and they contain mercury. UV light emitting diodes (LEDs) may offer solutions to many of the sustainability issues presented by current UV systems. LEDs are small, efficient, have long lifetimes, and do not contain mercury. Germicidal UV LEDs emitting at 265 nm were evaluated for inactivation of E. coli in water and compared to conventional low-pressure UV lamps. Both systems provided an equivalent level of treatment. A UV-LED prototype was developed and evaluated as a proof-of-concept of this technology for a point-of-use disinfection option, and the economics of UV-LEDs were evaluated.

scholarly journals Using electrical resistance tomography (ERT) and computational fluid dynamics (CFD) to study the mixing of pseudoplastic fluids with a SCABA 6SRGT impeller

2021 ◽  
Author(s):  
Leila Pakzad
Keyword(s):  
Flow Field ◽  
Flow Pattern ◽  
Electrical Resistance ◽  
Mixing Time ◽  
Three Dimensions ◽  
Cfd Modeling ◽  
Cube Root ◽  
Mixing Times ◽  
Electrical Resistance Tomography ◽  
Good Agreement

The objective of this work is to use electrical resistance tomography (ERT) and computational fluid dynamic (CFD) modeling to investigate the flow field generated by a Scaba 6SRGT impeller in the agitation of the xanthan solution, as a pseudoplastic fluid with yield stress. ERT provides a non-destructive technique to measure, in three dimensions, the concentration fields inside the mixing tanks. Using ERT, the impeller flow pattern, the dimensions of the cavern formed and the mixing time in the agitation of xanthan solutions were evaluated. The sizes of cavern measured using ERT were in good agreement with that calculated using Elson's model (cylindrical model). ERT provides both overall mixing time using 1264 probes (316 probes for each plan) and local mixing time using 4 selected probes or pixels. The dimensionless mixing times obtained from ERT were correlated well with the Moo-Young correlation, confirming that increased impeller speeds decreases the mixing times. The 3D flow field generated by a Scaba 6SRGT impeller and tracer homogenization in the agitation of xanthan gum were also simulated using the commercial CFD package (FLUENT). The experimental torque measurements were used to validate the numerical simulations. The validated CFD model provided useful information regarding the impeller pumping capacity and flow pattern, the velocity profiles, the formation of cavern around the impeller, and the mixing time. CFD results show good qualitative as well as quantitative agreement with the experimental results and theory. The sizes of cavern measure using CFD were in good agreement with that calculated using Elson's model. The local mixing times predicted from CFD simulations agreed well with literature in a way that mixing times varied inversely with the cube root of the power consumed per unit volume of the solution. CFD under predicted the local mixing times measured using ERT by 11-47%.

Particles dissolution and liquid mixing dynamics by Electrical Resistance Tomography

2019 ◽  
Vol 42 (4) ◽  
pp. 647-654
Author(s):  
Alessandro Paglianti ◽  
Francesco Maluta ◽  
Giuseppina Montante
Keyword(s):  
Particle Size ◽  
Electrical Resistance ◽  
Stirred Tanks ◽  
Electrical Resistance Tomography ◽  
Novel Approach ◽  
Mixing Dynamics ◽  
Speed Up ◽  
Time Required ◽  
Simultaneous Identification ◽  
The Impact

Salt particles dissolution in slurry stirred tanks provides an ambitious challenge for the application of Electrical Resistance Tomography in the process industry, because the presence of high loadings of inert particles requires a purposely developed post-processing method of the experimental data. For the optimization of the working conditions of the dissolution process, two characteristic times are required: the time for the liquid homogenization in the tank and the time required for the complete dissolution of the salt particles. The former time has been experimentally determined in previous investigations both in stirred tanks working with single-phase and with multiphase mixtures. The latter characteristic time has not been analyzed so far, due to the lack of experimental procedures for distinguishing it from the former. In this work, a novel approach for the simultaneous identification of the two characteristic times is presented. The impact of the new procedure is significant for the production processes, since it offers a tool for identifying when the soluble particle size has an impact on the dissolution dynamics, and when the stirred tank dynamics is influenced by the liquid homogenization only, and therefore a reduction of the particle size does not speed up the process accomplishment.

scholarly journals Using electrical resistance tomography to measure the yield stress of pretreated wheat straw and wheat straw slurries

2021 ◽  
Author(s):  
Yasaman Naghavi-Anaraki
Keyword(s):  
Wheat Straw ◽  
Yield Stress ◽  
Electrical Resistance ◽  
Low Cost ◽  
Electrical Resistance Tomography ◽  
Fiber Concentration ◽  
Active Motion ◽  
Fiber Size ◽  
Pretreated Wheat Straw ◽  
Impeller Type

Wheat straw is a low-cost feedstock for production of biofuels as a viable alternative to fossil -based fuels. Pretreatment process is an important stage in producing biofuels. Pretreated wheat straw slurries (PWS) are non-Newtonian fluids with yield stress. In mixing operations, the presence of yield stress creates a region of active motion (cavern) around the impeller and stagnant zones elsewhere which causes difficulties in the production of biofuels. In this study, for the first time electrical resistance tomography (ERT) was utilized to measure the cavern dimensions as a function of the impeller type (A200, A100, and A315), impeller speed (20 to 110 rpm), fiber size (≤ 2 and ≤ 6 mm), and PWS concentration (6, 8, and 10 wt%). The cavern sizes were used to measure the yield stress of PWS slurries as a function of fiber size and fiber concentration. The average yield stresses of 6, 8, and 10 wt% PWS slurries with the fiber sizes of ≤ 2 mm were 2.00, 5.43, and 8.51 Pa, respectively, and 4.26, 9.30, and 13.84 Pa for the fiber sizes of ≤ 6 mm.

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