Design Calculations For Agitators 4m3c4x
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12/30/2015
Design Calculations for Slurry Agitators
RAJENDRA KUNWAR Associate Vice President Projects at JSW Steel Limited
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Design Calculations for Slurry Agitators Aug 15, 2015
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Hi Friends, Today I am presenting the gist of my technical paper on "Motor rating calculations for slurry mixing agitators in Alumina refinery" which has been published recently in aluminium issue of the magazine "Minerals & Metals Review" (page 30 and 31 in MMR, August 2011 issue). In various technical forums, process experts as well as equipment manufacturers have opined that the design of agitators for mixing bauxite, residue and hydrate in Alumina refinery is complicated and tricky issue. In this paper, we will discuss the subject with brief description of involved terminology, associated design parameters and methodology with sample motor rating calculations for the slurry mixing agitator of a Predesilication tank of Alumina refinery.
Method to arrive at motor rating: Impeller power for slurry mixing agitator is calculated using following https://www.linkedin.com/pulse/designcalculationsslurryagitatorsrajendrakunwar
1/41
12/30/2015
Design Calculations for Slurry Agitators
mathematical relations Impeller Power, P = N * ρ *N3 * D5/(16*104) h.p. Where D = Diameter of impeller in meters, N = Revolution per minute for impeller, N = Power number for impeller and ρ = Specific gravity of slurry.
Sample calculations: Simplified calculations to arrive at the motor rating for the agitator of Pre desilication tank of around 3000 m3gross capacity with realistic assumptions have been presented below Fluid Height in Tank , H = 16 m and Diameter of tank, D = 14 m Slurry volume in tank = π *D2*H/4 = π * (14)2*16 /4 = 2463 m3 Solid consistency in Slurry = 50 % (w/w), Specific gravity of slurry, ρ = 1.602, Viscosity of slurry, μ = 550 Agitator Impeller Diameter, D= 33 % of tank diameter = 14 * 33% m = 4.62 m
https://www.linkedin.com/pulse/designcalculationsslurryagitatorsrajendrakunwar
2/41
12/30/2015
Design Calculations for Slurry Agitators
Tip speed of Impeller = 290 m/minute, Drive motor RPM = 1500 rpm. Gear Box Reduction Ratio = 75 ∴ Agitator RPM, N = Drive Motor RPM/Gear Box Reduction Ratio = 1500/75 = 20 rpm Flow Number N = 0.56 and Power Number, N = 0.51 (assumed figures) ∴ Pumping Capacity = N * N * D3 m3/minute = 0.56 * 20 * (4.62)3 = 1104.44 m3/min. = 18.41 m3/sec. Area of Tank = π * D2 = π *(14)2 / 4 = 153.94 m2 Bulk fluid Velocity = pumping capacity/area of tank = 1104.44 / 153.94= 7.18 m/min.= 23.55 ft./min. Degree of Agitation = bulk fluid velocity / 6 (For 6 ft/min., degree of agitation =1 and Degree of agitation varies from 0 to 10) = 23.55 / 6 = 3.93 ~ 4 Annular Area = π * (D2 D2 ) /4 Where D = Diameter of tank and D= Diameter of impeller in meters. https://www.linkedin.com/pulse/designcalculationsslurryagitatorsrajendrakunwar
3/41
12/30/2015
Design Calculations for Slurry Agitators
= 3.14 * (142 – (4.622) / 4 = 137.18 m2 Rising velocity of particles = pumping capacity / annular area = 1104.44 / 137.18 = 8.051 m/min. = 0.1342 m/sec. Tank Turnover rate = Pumping capacity / tank capacity = 1104.44 / 2463 = 0.45 times / min. Power Number N = 0.51 Shaft Power, P = N* ρ *(D)5 * N3 /(16 *104) Where N = Impeller power no., D = Diameter of impeller in meters, Shaft RPM, N = revolutions per minute ∴ Shaft Power, P = 0.51 * 1.602 * (4.402)5 * 203 / (16 *104) = 85.98 h.p. Taking Gear Box Efficiency = 80% and Drive Motor Efficiency = 95%, Design margin = 1.15 ∴ Drive Motor Rating = 1.15 * 85.98/(0.80 * 0.95) =130 h.p. = 97.0 kW. Thus the drive motor of about 100 kW shall be adequate for successful operation of agitator of 3000 m3 capacity Predesilication What is LinkedIn? https://www.linkedin.com/pulse/designcalculationsslurryagitatorsrajendrakunwar
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12/30/2015
Design Calculations for Slurry Agitators
tank in Alumina refinery.
Pulse Rajendra Kunwar Design Calculations for Slurry Agitators
RAJENDRA KUNWAR
2015 was a tipping point for six technologies that will change the world Written by Vivek Wadhwa
RAJENDRA KUNWAR
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In 2016, Nations May Govern Like Comment But Cities Rule Bruce Katz
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Wait a Second. Can Crude Oil Really Fall Below $20/bbl? Ankur Gera Floris Laly
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Engineer at BKT Tyres Thanx for sharing sir .
Would You Let One Person Like Reply 4 months ago Decide the Fate of Your Career? Don't Let a Judge… Randy Kessler Decide Your Family's Fate Show More How to Transform Frustration into Innovation? Gijs van Wulfen
The Facebook Pushback in India: AntiCorporate, Anti American, AntiPoor David Kirkpatrick
https://www.linkedin.com/pulse/designcalculationsslurryagitatorsrajendrakunwar
5/41
Design Calculations for Slurry Agitators
RAJENDRA KUNWAR Associate Vice President Projects at JSW Steel Limited
Follow
Design Calculations for Slurry Agitators Aug 15, 2015
172 views
14 Likes
2 Comments
Hi Friends, Today I am presenting the gist of my technical paper on "Motor rating calculations for slurry mixing agitators in Alumina refinery" which has been published recently in aluminium issue of the magazine "Minerals & Metals Review" (page 30 and 31 in MMR, August 2011 issue). In various technical forums, process experts as well as equipment manufacturers have opined that the design of agitators for mixing bauxite, residue and hydrate in Alumina refinery is complicated and tricky issue. In this paper, we will discuss the subject with brief description of involved terminology, associated design parameters and methodology with sample motor rating calculations for the slurry mixing agitator of a Predesilication tank of Alumina refinery.
Method to arrive at motor rating: Impeller power for slurry mixing agitator is calculated using following https://www.linkedin.com/pulse/designcalculationsslurryagitatorsrajendrakunwar
1/41
12/30/2015
Design Calculations for Slurry Agitators
mathematical relations Impeller Power, P = N * ρ *N3 * D5/(16*104) h.p. Where D = Diameter of impeller in meters, N = Revolution per minute for impeller, N = Power number for impeller and ρ = Specific gravity of slurry.
Sample calculations: Simplified calculations to arrive at the motor rating for the agitator of Pre desilication tank of around 3000 m3gross capacity with realistic assumptions have been presented below Fluid Height in Tank , H = 16 m and Diameter of tank, D = 14 m Slurry volume in tank = π *D2*H/4 = π * (14)2*16 /4 = 2463 m3 Solid consistency in Slurry = 50 % (w/w), Specific gravity of slurry, ρ = 1.602, Viscosity of slurry, μ = 550 Agitator Impeller Diameter, D= 33 % of tank diameter = 14 * 33% m = 4.62 m
https://www.linkedin.com/pulse/designcalculationsslurryagitatorsrajendrakunwar
2/41
12/30/2015
Design Calculations for Slurry Agitators
Tip speed of Impeller = 290 m/minute, Drive motor RPM = 1500 rpm. Gear Box Reduction Ratio = 75 ∴ Agitator RPM, N = Drive Motor RPM/Gear Box Reduction Ratio = 1500/75 = 20 rpm Flow Number N = 0.56 and Power Number, N = 0.51 (assumed figures) ∴ Pumping Capacity = N * N * D3 m3/minute = 0.56 * 20 * (4.62)3 = 1104.44 m3/min. = 18.41 m3/sec. Area of Tank = π * D2 = π *(14)2 / 4 = 153.94 m2 Bulk fluid Velocity = pumping capacity/area of tank = 1104.44 / 153.94= 7.18 m/min.= 23.55 ft./min. Degree of Agitation = bulk fluid velocity / 6 (For 6 ft/min., degree of agitation =1 and Degree of agitation varies from 0 to 10) = 23.55 / 6 = 3.93 ~ 4 Annular Area = π * (D2 D2 ) /4 Where D = Diameter of tank and D= Diameter of impeller in meters. https://www.linkedin.com/pulse/designcalculationsslurryagitatorsrajendrakunwar
3/41
12/30/2015
Design Calculations for Slurry Agitators
= 3.14 * (142 – (4.622) / 4 = 137.18 m2 Rising velocity of particles = pumping capacity / annular area = 1104.44 / 137.18 = 8.051 m/min. = 0.1342 m/sec. Tank Turnover rate = Pumping capacity / tank capacity = 1104.44 / 2463 = 0.45 times / min. Power Number N = 0.51 Shaft Power, P = N* ρ *(D)5 * N3 /(16 *104) Where N = Impeller power no., D = Diameter of impeller in meters, Shaft RPM, N = revolutions per minute ∴ Shaft Power, P = 0.51 * 1.602 * (4.402)5 * 203 / (16 *104) = 85.98 h.p. Taking Gear Box Efficiency = 80% and Drive Motor Efficiency = 95%, Design margin = 1.15 ∴ Drive Motor Rating = 1.15 * 85.98/(0.80 * 0.95) =130 h.p. = 97.0 kW. Thus the drive motor of about 100 kW shall be adequate for successful operation of agitator of 3000 m3 capacity Predesilication What is LinkedIn? https://www.linkedin.com/pulse/designcalculationsslurryagitatorsrajendrakunwar
Today
Sign In 4/41
12/30/2015
Design Calculations for Slurry Agitators
tank in Alumina refinery.
Pulse Rajendra Kunwar Design Calculations for Slurry Agitators
RAJENDRA KUNWAR
2015 was a tipping point for six technologies that will change the world Written by Vivek Wadhwa
RAJENDRA KUNWAR
Follow
In 2016, Nations May Govern Like Comment But Cities Rule Bruce Katz
14 likes 2 comments
Add your comment
Wait a Second. Can Crude Oil Really Fall Below $20/bbl? Ankur Gera Floris Laly
Newest
Engineer at BKT Tyres Thanx for sharing sir .
Would You Let One Person Like Reply 4 months ago Decide the Fate of Your Career? Don't Let a Judge… Randy Kessler Decide Your Family's Fate Show More How to Transform Frustration into Innovation? Gijs van Wulfen
The Facebook Pushback in India: AntiCorporate, Anti American, AntiPoor David Kirkpatrick
https://www.linkedin.com/pulse/designcalculationsslurryagitatorsrajendrakunwar
5/41
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