Experts

Mixing

Mixing by Dave Dickey, senior consultant, MixTech Inc.

Dave Dickey is senior consultant for MixTech Inc., Dayton, Ohio, which focuses on mixing processes and equipment. He has 25 years of experience in the field, both as a consultant and with equipment suppliers. He gives a number of short courses related to mixing and has written numerous articles and contributed to several handbooks.

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What is the torque required for speed reducer and what horsepower is required to run it smoothly?
What torque of speed reducer is required to mix 300 kgs of sand? Mixing type where drum is stationary and blades rotates in horizontal position. Features a 3 hp motor, gearbox ratio 30:1.

Additionally, the drum size is 30 inches in diameter and 42 inches in length in horizontal position. Blades are paddle type.
Category: Mixing

What is the general formula of agitator flow capacity?
I'd like to know the general formula of agitator flow capacity. I found as follows:

Flow capacity: Q = C1 x n x D2 x S

Power required: P = C2 x r x n3 x D5

Q = Agitator flow (m³/min)
P = Power (kW)
n = Revolution speed (rps)
D = Propeller diameter
S = Propeller pitch
r = Density (Kg/m³)
C1 = Factor specific for the propeller
C2 = Factor depending on turbulence

Can this be applied to a side-entry agitator?
Category: Mixing

How do you determine the power number for a mixing system?
I am looking for an estimated power number for a low-shear impeller (commonly called an elephant ear impeller) for a system operating in the turbulent regime with the following characteristics:

Baffled Tank (4 baffles)
Dagit/Dtank ~ 0.4 - 0.5
Density/Visc ~ water
The impeller is down-pumping

How would you recommend experimentally determining the power number for a larger system if torque measurement isn't an available option?
Category: Mixing

Is my mixer size too large?
Would a four-blade, 45-deg pitched, 14-inch diameter impeller be too large or about right to mix a square IBC - 340 gallons of sp gr = 1 and viscosity of up to 100 centipose liquid, turning at up to 350 rpm, 2 HP motor.
Category: Mixing

For mixing, how do I convert from hydraulic power to an electric motor?
Presently we are using hydraulic drive for the mixing of our paint ingredients in 150 lit mixer pot (maximum viscosity 35000 cP at RT).This pot is having heavy duty stirrer centrally located and one cowler at the off center (pot wall side located). The directions of these stirrers are opposite to each other. The shaft diameter of center stirrer is 52mm and of cowler is 40.5mm. Can I convert this to electrical drive? Also we are going to have 300 lit capacity new pot mixer so can I go for electrical drive instead of hydraulic drive to get cost benefit?
Category: Mixing

What is the best indicator of performance and efficiency of a mixer?
We will be constructing a plant that will require many agitators. We have bids out to suppliers and have received responses. In addition to the cost, what would be the best indicator of performance and efficiency that could be used given the normal feedback from vendors such as installed power, weight, gearboxes, shafts, shaft speed, impellers, and materials of construction? Is there a best factor or ratio of these parameters that one could use to decide upon the best vendor? Simple relationships would be preferred that do not need such things as mixing constants and fluid densities.
Category: Mixing

Can you recommend an agitator that will fully suspend and dissolve salt?
I am looking to dissolve fine salt in water in a continuous process. The aim is to produce near-saturated brine without any suspended solids.

Fine Salt
• Mass flow rate = 1000 kg/hr
• Bulk density = 1200kg/m³
• Temperature = 60-70 degrees C

Water
• Mass flow rate = 4000 kg/hr
• Temperature = 20-50 degrees C (water is generally at 50 degrees But sometimes at lower temp of 20 degrees)
• Dynamic Viscosity = 1.003 – 0.55 cP
• Pressure = 4 Bar
• Total flow rate into the tank = 5 m³/hr
• Residence time of 5 minutes
• Total flow rate out of tank= 5 m³/hr

Vessel is under atmospheric pressure. I am having difficulty in selecting a stirrer that can both fully suspend the salt while also dissolving it. Can you recommend an agitator and a desired operating speed?
Category: Mixing

What are the problems with running a mixer in air?
Agitator mechanical test in air is one of the requirements of our client. But most vendors claim they can't test in air. They say, "We cannot satisfy the deflection requirement when agitator would be tested in air, but if you want the 4 hour air test the shaft and agitator should be overdesigned." But they don't clarify the reason why the deflection will be increased in case of air operation. Could you clarify technically why deflection is increased?

Our liquid contents are 45% mixing xylene and solid contents is px-xylene.
Motor power is 7.5kW
Shaft diameter is 63.5mm
Length 5500mm
RPM 56RPM
Category: Mixing

How do I determine torque?
I need to determine the torque required to mix H₂O and some chemicals in a 4,000 gallon vertical tank. The viscosity is SAE90 after mixing. The tank inside diameter is 119 inches with four blades that are 45 inches across, 8 inches wide with a 45 degree angle. The blade is 31 inches from the bottom and is mounted on a 2-inch vertical shaft. They need to run this from 60 rpm to 120 rpm -- can you help?
Category: Mixing

Is chemical "Injection" used anywhere other than the carwash industry?
Is chemical "Injection" used anywhere other than the carwash industry? It seems to me that there would be quite a few applications in the paper-making industry where this might make sense.
Category: Mixing

How do I determine the mixer design size of the impeller, the baffle plates and motor?
I have a formalin flat-bottom tank made of stainless steel and the size of 8m (height) and 4.570 diameter wide. The formalin viscosity is very low -- close to water. How do I determine the size of the impeller, the baffle plates and motor?
Category: Mixing

How can I update the efficiency of very old mixers?
I am new to the job and have been assigned to look at the efficiency of our very old mixers (salvaged from other plants). We use our mixers to dissolve rubber in solvents to make adhesives. (Final products viscosity ranges from average 5000cP, max around 10,000 cP)

Some data I have collected:

Tank: vertical cylinder diam = 1.25m, height = 5m, no baffles
Stirrer: 2 number of Rushton turbine, 8 blades
Motor: belt type 40hp, 330rpm

Deep vortexes are noticed during operation. From what I have read this indicates fluid swirling, which is the worst kind of mixing because very little axial mixing is taking place.

Using the general guidelines for solid dissolution, I am considering installing baffles and changing the stirrer to a pitched blade turbine in the hope to bring down mixing time and hopefully the hp of the motor as well. Where do I start and how do I estimate the "improvement" quantitatively?
Category: Mixing

Can you provide the power number for anchor-type impeller and Cowles disc impeller?
Can you provide the power number for anchor-type impeller and Cowles disc impeller?

I am calculating power for agitator by using P = (Np * Sp. Gr * N3 * D5)/ (1.524*1013)
Category: Mixing

Why does the motor trip on the anchor impeller with wall baffles?
I am have a 12 KL reactor with 4 Nos of baffle. I have fixed anchor agitator with 48 RPM. But during trial, the motor is tripping at volume of 6.5 KL. The media is water.

Reactor diameter: 2250 mm ID
Shell length: 2700 mm WL to WL
Agitator details

Capacity: 12KL
Shaft Diameter: 115mm, SS 316
RPM: 48
Agitator: Anchor, SS 316
Sweep Diameter: 1850 mm
Height: 1300 mm
Blades: 125W x 12Thk
Stiffeners: 50W x 8Thk
Bushes: ID115 x OD170 x 135Ht
Shaft Sealing: Single Dry Mechanical Seal
Gearbox: Ratio 30:1, In-line Helical
Motor: FLP Vertical Flange Mounted,1440RPM
Category: Mixing

How do I calculate the kLa of a mixed gas system using 75% air and 25% O₂?
How do I calculate the kLa of a mixed gas system using 75% air and 25% O₂ from mass transfer data collected using the gassing out method with 100% air?
Category: Mixing

How do you calculate the power number of an impeller?
How do you go about calculating the power number (Np) of an impeller?
Category: Mixing

When is it appropriate to use a recirculation loop?
How does the mixing from recirculation loop from the bottom of the vessel compare to that provided by the agitator? I am guessing this will depend on various parameters like agitator rpm, agitator impeller types, recirculation flow rate, recirculation discharge height, where is recirculation discharged from, volume to be mixed.
Category: Mixing

Mixing: What's causing the blades to bend?
Many blades on our melter agitator line have become bent. Can you give advice based on the below specification?

Specification of melter agitator line 1:
• tank size diameter 2200 mm x 2500 mm height
• using gear box with ratio: 20:1
• motor KW: 7.5 KW, 750 rpm
• rpm shaft agitator: 48 rpm
• shaft agitator dia 80 mm pipe schedule 80
• 2 – blades position (bottom and center of tank height) with size diameter 1590 mm x 100 mm wide
• Handle slurry liquid with spec: sodium sulphate slurry (Na₂SO₄), temperature 110 deg C, concentration 20%, density 1.4, level 100%
Category: Mixing

Are power requirements for multiple impellers additive?
With multiple impellers on a single shaft, are the effects on total power additive? For example, if two impellers are of the same type, would the power be determined as P = Np*rho*N^3*(D1^5+D2^5)? Also, what is a "rule of thumb" for empirically calculated power requirements vs. actual power input that a VFD might show?
Category: Mixing

What are the power requirements for turbulent mixing?
We have an agitator with the following designation:

Speed: 31/46 rpm
Absorbed power:1.5/5.4 kW
Impeller type: paddle (and blades angle is reversed in tip area)
Shaft dia: 85 mm
Shaft length: 3300 mm
Impeller dia: 1600 mm
Impeller num.: 2
Space in: 650 mm
Motor rating: 12/3.7 kW
Motor speed: 1470/980 rpm

Materials specification: density (kg/m³)/viscosity (cp)
1- liquid 1166/1
2- powder 600/-
3- liquid 794/0.32
4- liquid 971/0.36
5- liquid 1408/9.1

This agitator is installed on a drum with 2400 mm diameter and 3754 mm height and the agitator is top entry.

We want to change the process media with a liquid that its density is 1200 kg/m³ and the viscosity is 200 cp.

Is the change in density and viscosity (as above mentioned) allowed or is this agitator (with no change in motor rating, gear box, shaft diameter and blade length) capable to mix the new media without any failure?
Could you please to send us the required formula to obtain the shaft power, power number and etc.?
Category: Mixing

Which agitator seal will work best for outlet piping?
I have a question about outlet piping of condensers. I have made a pilot reactor (top entry agitator) and now I want to use an agitator seal (except mechanical seal). Which type of agitator seals can I use so it works in higher pressure, stuffing box or the others?

Reactor properties:

Cap diameter: 500mm
Max viscosity: 50000 cp
Max temperature: 110 C
Max pressure: 6 bar
pH range:3-9
Shaft diameter: 48 mm
Max rotation speed: 160 rpm
Reactor content: water, emulsifiers, monomers such as: acrylic esters, styrene, vinyl acetate, oxidizer initiators and etc.
Category: Mixing

How much horsepower is required to mix this specific material?
I am designing a jacketed mixer that will mix coconut oil + 60% water. The operating speed is 10 rpm, and the operating temperature is 70 degrees C. The mixer has these specifications:

• material SS304
• inner vessel 1,250 mm X 1,295 mm
• gross capacity 1,650 liter
• blades: anchor & marine
• shaft rod 63 mm diameter
• housing shaft 70 mm diameter

Please tell me the correct hp required to mix the material. Per my thinking, 15 hp will be more than sufficient.
Category: Mixing

Are there limitations to the Zwietering correlation for suspending solids in liquids?
I'm curious as to the limitations of the Zwietering correlation for suspending solids in liquids.

I'm particularly interested in how well it applies to very large tanks, say 500,000 gallons, and how to determine a representative mean particle diameter in a substance where particle diameter can vary dramatically.

Furthermore, how can I be sure of uniform suspension? If the Zwietering correlation is not a good fit for this application, can you recommend another method for determining the impeller speed and estimating the power requirement?
Category: Mixing

Can I simplify mixing calculations for a bottom-mounted impeller?
Can I simplify mixing calculations for a bottom-mounted impeller on a Breddo Likwifier by using the equations for a six-blade turbine with disk?
If so, what would I substitute for the gap between the bottom of the impeller and tank?
Category: Mixing

Calculating the Agitator Torque For Adhesive Production
We are trying to calculate the agitator torque for adhesive production. What size electrical motor and gearbox is required to drive this agitator? How about with a hydraulic drive?

Here are the specs:

ID of reactor is 1,250 mm
Height of reactor is 2,360 mm
Rod diameter is 80 mm
Agitator has two 45-degree pitched blades
Length of blade is 530 mm
Diameter of agitator with blade is 1,140 mm
Material viscosity is 100,000 cp
Require speed is variable from 30 to 100 rpm
Density of material is 1250 kg/m³

Category: Mixing

How do we calculate unbalanced horizontal load, amplitude and mass movement?
We have a mixing vessel (diameter 2,000 mm , height 2,200 mm, weight 4,000 kg). It is an anchor type mixer -- length 1,900 mm (tip blade 2no.,180D, diameter 11 in., 2nd step 800 mm - blade 2no.,180D, perpendicular to associate steps, diameter 9 in., 3rd step 1,600 mm - blade 2no.,180D, diameter 6 in.);140 rpm; 3no. baffle 120D spacing.

We mix sulphuric acid (sp. gr. 1.80) = 5,000 kg, LAB (sp. gr.0.85) = 2,500 kg, water =1,000 kg.

How do we calculate unbalanced horizontal load, amplitude of the vessel, and mass movement of inertia for proposed 4 lug support?
Category: Mixing

What is a suitable mixer design for liquid detergents?
I have a mixer tank with these dimensions: width 1.55m, height 2.5m. I want to use this mixer for liquid detergent industries where viscosity is between 1000-3000 cps at ambient temperature. What is the most suitable design for motor power, shaft, and impeller?
Category: Mixing

Planning the Perfect Mixing Tank
We are planning a mixing tank for making a uniform solution.
It is heat transfer activity. The density is 1,200 kg/m³ and viscosity of 35,000 cps. It is a thick solution with no solid particles. The jacketed tank has an internal diameter of 1,800 mm and tank shell length is 2,000 mm. The bottom and top of the tank have torispherical dished ends. What is the right type of mixture, its geometry and motor?
Category: Mixing

What is the formula for laminar mixing?
I wanted to know the formula for power for laminar mixing.

I have read the “Handbook of Industrial Mixing” as you previously advised. But it doesn’t have a clear formula for laminer flow stirrer (power, shaft design, gearbox design, etc.)

tank inner diameter = 36 inches
impeller diameter = 15 inches
impeller type = pitched blade (45 degree)
Reynolds no. = 3
specific gravity = 1.2
cp;(viscosity coefficient)= 10000, nearly. (tomato suspension in boiling water)
tank height = 84 inches
RPM = 15
Category: Mixing

Why are identical product units drawing different electric current?
We have two identical production units in our facility. In each production unit there is one agitator and two stage impellers - one impeller with parabolic blades and one impeller with flat blades. The vessel on which the agitator is mounted is a flash crystallizer. The agitator is used to maintain the solid in a suspended state. The flash vapor is removed from the top of the vessel. The dimensions of vessel in both units are identical.

The problem is, since commissioning the motor in one of the units it is drawing more electric current than the motor in other unit. Why?

Another question, what will be the effect of rotating an impeller with parabolic blades in the reverse direction?
Category: Mixing

What type of impeller ensures good dispersion?
I have a 1-ton mixing tank with dimension of 1 m (dia) x 1.5m (H). The tank is used to mix two different kinds of liquids: Butter oil, viscosity of 50-80 Pa.s @ 45 degrees C; and emulsifier, viscosity of 800 mPa.s @ 20 degrees C. What type of impeller is good for mixing to have good dispersion, homogeneous and have some shearing force? How many hp for the motor is sufficient?
Category: Mixing

What is a suitable mixer for square tanks?
We would like to install a mixer for a square effluent tank that is 15 meters x 15 meters x 5 meters water depth containing 3% settling solids. What is a suitable mixer that will keep the solids from settling at the bottom?
Category: Mixing

Finding the Hydraulic Load
How do I find the hydraulic load to calculate the shaft deflection of a vessel agitator? A mixing agitator incorporates a six-blade turbine impeller (90 degree - flat) that spins at 650 rpm to mix 200L of a water-like fluid in a 260L fermenter. The tank has a 31" ID. What is the calculation used to determine the hydraulic load at this high rate of mixing? The impeller pulls a vortex to the bottom of the vessel, so it is not fully submerged in the fluid at all times. The next step would be to then calculate the shaft deflection that is experienced with this hydraulic load.
Category: Mixing

Can you predict the vortex depth?
I am looking for an equation that will predict the vortex depth in an unbaffled tank with a centrally mounted mixer. Process is a solid liquid dispersion where powder must be drawn from top of the tank and incorporated into the mix.
Category: Mixing

Specifications for Agitating Hot Water
I had to design a tank for agitating hot water with CB (stone-like material of size 5/8 inches and specific gravity of 1.51) of 10 MT. What are suitable gearbox, agitator dimension, motor capacity and tank specifications?
Category: Mixing

Understanding The Baffle Effect
I have a reactor with:

• Tank Diameter = 2.736 m
• Volume = 24 cubic meters
• 2 Baffles = D-Baffles for glass lined tanks;
• The distance from reactor wall is 0.723 m
• 1 rushton 6 flat bladed turbine with W/D = 0.2 and impeller D = 1.012 m
• Fluid density = 835 Kg/cubic meter @220°C
• Fluid viscosity = 18.1 cP @220°C
• N = 120.7 rpm

• With the equation P = Np * density *N^3*D^5
• Np = 5.2 for standard rushton with turbulent conditions
• P = 37.52 KW, considering our driver and gear reducer efficiency = 41.14 KW.

We monitored the power consumption directly on the driver, and we obtained power consumption much lower than calculations (about 26 - 27 KW). I probably have to use a power correction factor because of D-Baffles, then the power should be lower. Can you suggest the correction factor for this kind of baffles?
Category: Mixing

Determining the Agitator Shaft Loading and Power
I am working on the design for a fluid bed reactor. The design includes an agitator that will move the aggregate in the bed. Do you know of equations that I can use to determine the agitator shaft loading and the power required for the agitation?
Category: Mixing

Calculating The Bending Moment on a Mixer Shaft
We have one agitator with the following configuration: A single shaft with two mounted impellers -- one flat-blade impeller (inclined at 45 degrees to shaft) and 06 blades are present in an impeller assembly, and one gas-foil impeller (Parabolic contour), 06 blades are present in an impeller assembly. The power consumption is split in 70:30 with 70% for gas-foil blade. The agitator works in a gassed condition -- air bubbles are dispersed in liquid/solid stream, and for decontamination, the same agitator is run in 5% caustic solution. The question -- How do I calculate the force, which can cause a bending moment in the shaft, at gas-foil impeller and flat-blade impeller? And how can the resulting bending moment be calculated?
Category: Mixing

Merging Two Gas Streams
If a cold gas stream merges in a hot gas stream, how do you calculate the distance where their temperature becomes uniform?
Category: Mixing

Calculating the Power Requirement for Mixing
I'm trying to calculate the power requirement for mixing. The company makes tanks of all sizes and has to be able to mix many different liquids. They gave me equations for the Reynolds Number, Froude Number and the Power Number and one more equation that relates them. However, I'm not sure how this translates to a power requirement. Is there an equation I can use to find the power requirement for mixing?
Category: Mixing

Mixing Time and Residence Time
I'm going to calculate residence time in a static mixer, but I don't know what the exact difference is between mixing time and residence time. Are the baffles shape and their numbers and the Re number of the mixed fluid the only parameters that affect the residence time? What about the entrance distance of the mixer? Is that up to me, or it has a specified amount? If the mixed flow regime is laminar at the beginning, it must be Turbulent after passing the inserts? Should I consider this change of Re number through mixer for my calculation? About the mixer specification, I am going to use a helical static mixer for just mixing two different fluids (there is no suspension or bubble in the mixed flow.)
Category: Mixing

Finding The Right Agitator Design for PVC Production
We have a 20 m3 reactor for PVC production and H/D ratio of 6.0m/2.26m. The agitator consists of a 40kw motor, stirrer of 3 layer, 2 blades impeller of 1200mm x 200mm, and a paddle type at 120 rpm plus a single-blade baffle. The issue we are facing is a quality problem with the resins produced. Despite many trials in recipe changes, as it is lower in porosity and bulk density and consists of many odd shaped particles instead of round particles, some looked like tadpoles. Do you think we have the right agitator design and what can be done to improve it?
Category: Mixing

Mixing thixotropic fluid
I need to mix a 4000 cp thixotropic fluid on a 10-in. diameter by 15-in. 5-gallon container. I am planning to use two 6.5-in. plastic propellers placed on a 14.5-in. shaft. The mixing will be at 180 rpm. I need to know the torque required for this.
Category: Mixing

What are the power numbers for standard agitator impellers?
I wish to know different power numbers for standard agitator impellers (Pitched blade. Straight blade. Anchor. Disperser etc.)
Category: Mixing

Calculating the Effect of Baffles on Power Calculations
Agitator power calculation formula does not include Baffle's size or width, but it definately affects. How to calculate the effect of Baffles on Power Calculations?
Category: Mixing

Achieve good top to bottom slurry suspension
A general question regarding suspension of fine ore slurries, of the following properties: solids spg=2.9, mean dp=60 microns; liquid is 50wt% sulfuric acid at 100oC. slurry is 45wt% solids. Vessel is 90% full The vessel is brick lined, approx 16ft diam x 17ft T-T. Bottom head is ASME F&D, OD=204 inches,1/2" thick. There are 3 baffles made into "V" shape using bricks fastened to the vessel walls (ie, no spacing between baffle and vessel wall) The agitator is 40 HP, and there are 2 hydrofoil type impellers, approx 68 inch diam. I believe that they are A310'S. The impellers are spaced approx 68" apart. I do not know the distance from the bottom to the lower impeller, but I suspect it is about 35 -40". In your expert opinion, is this system adequate to achieve good top to bottom slurry suspension? The desired objective is to achieve as close as possible a uniform suspension within the vessel. Please give me your assessment and recommendations on how to improve this system?
Category: Mixing

Shaft and gearbox size
What should be the required power for agitating a syrup with a density of 1500kg/m3, volume is 15m3, minimum rpm is 350, impeller diameter is 600mm. What should be the size of the shaft and gearbox?
Category: Mixing

Making an agitator for a composting unit
I am interested in making an agitator for a composting unit. The diameter of the compost tub is about 2000 millimeters, while the diameter of the agitator will be about 1500 millimeters. The vertical shaft will be approximately 500 millimeters long, and I want the unit to run at 15 RPM. I need to find out the motor capacity, the shaft diameter and the expected torque for this operation.
Category: Mixing

Redesigning the impeller blade for a batch polyurethane tank
I need to redesign the impeller blade of my batch polyurethane tank. I'm currently using a marine-type impeller, which incorporates a lot of air into the polymer polyol while mixing, causing a lot of bubbles. I need an impeller that mixes well but does not cause turbulence or a lot of bubbles. Please suggest the best option. Polyol has a viscosity of around 420-520 cSt. I'm mixing approximately 50 to 130 kilograms per batch.
Category: Mixing

Reducing dissolving time
We are using a mixing system including v=40000lit,d=1m rpm=56 visc=120-800cst mixer type=pitched turbine kw=2.4. We want to reduce dissolving time by upgrading mixer diameter or rpm. Which one is the best selection for this viscous liquid? What about the other required changes followed selected upgrading? What about the amount of increasing diameter or rpm?
Category: Mixing

Power estimation for turbulent and laminar mixing
Is there a simple rule of thumb for power estimation in either turbulent or laminar mixing?
Category: Mixing

Proposing a suitable tank volume for a specific viscosity
We have experienced when the mixture viscosity increase the proper mixing tank volume would be reduced why is that for theoretically? And how we can propose the suitable tank volume for a specific viscosity by the way how we can specify the required rpm for a specified impeller diameter against viscosity of mixture?
Category: Mixing

HP Motor Size Requirements
If I currently have a mixer that has a one hp motor inputting 3300 rpm to a gear reducer to obtain 800 RPM output, then if I was to remove the motor and reducer to put a VFD driven 1750 motor direct drive to my mixer what size HP motor would be required. If you know please can you also provide the formula.
Category: Mixing

Designing a Support Bracket for a Baffle
I have a vertical 3100mm dia nad 7000 overall length agitator. The baffle supports were failing due to improper loading. I do not have any book so that I can use the formulae for redesign the support. Please provide me a sample calculation for designing support bracket for the baffle.
Category: Mixing

Pilot plant digester mixing
I would like to continually mix 4% DS anearobic sludge in a 1cu.m pilot plant digester(h/d aspect ratio 1.3/1), using an external pump system with 2 nozzle injections. Sludge throughput is 3l/hour. @ 37degC. Max. solids size = 10mm. What would be minimum injection velocity and flow rate required? Any other requirements i.e nozzle angles, nozzle, injection height, baffles, etc.?
Category: Mixing

Vessel | Fixing a Vessel Agitator | Chemical Processing
I want to fix an agitator to a vessel for mixing viscous chemicals. The viscosity of the fluid range from 600 cPs-800cPs. vessel. The capacity is 3000 gallons. I want to keep the agitator rpm at 60. What should the HP of the motor and gear box be?
Category: Mixing

Input power of electromotor, power of gearbox and the safety factor
We are going to produce water base resins. These resins have an average viscosity of 60000 cp in a 6-ton industrial reactor, and an anchor mixer has been used for mixing the content of reactor (with the speed of 20-60 rpm). Therefore, we have made the impeller with proper dimensions (shown below). Now we must fix an electromotor and gearbox to the shaft and impeller system. What is your recommend about input power of electromotor, power of gearbox and the safety factor (the agitation system works continuously about 7 hours /day). My calculations show, M2(out put torque) is about 3000N.m and P(motor)= 20 KW and P(gearbox)=20*1.5=30KW, f=1.5 Characteristics of our anchor Impeller with two horizontal arm: D=1.75m, w (blade wide) =0.2 m, H=2m, t (thickness of blades)=0.02m blades are in 45 degree.
Category: Mixing

Efficient Impeller Blade or Mixer
We make a solution of water & benzoyl peroxide (in various percentages - 1%, 4%, 8%, etc...) in a mix tank & transfer it into several poly lined 55 gallon drums to store the solution until we are ready to fill from each drum - one at a time - until empty - into finished product containers. We have to stir each drum for approx. 2 hrs prior to beginning filling to get a homogenous solution in the drum - to get the BP back in suspension. Do you have any suggestions as to a more efficient, specific type of impeller blade or mixer to keep the BP in suspension - so we can keep the drum of solution as homogenous as possible in each drum? We currently have air mixers with a stirrer type 3 blades at the bottom of the shaft. Drum dimensions: int.hgt.= 37 1/16", int.diam. = 21.8 with 2 " Bung/opening with removable lid. Must be kept covered.
Category: Mixing

Designing a Mixing Tank
I want to design a mixing tank to prepare a slurry of very fine catalysts in water. This tank will have an agitator to keep solids suspended. In this case how would you consider the vortex height generated during mixing?
Category: Mixing

Jet Mixers vs. Mechanical Mixers
I would like to know the differences between jet mixers and mechanical mixers. Are there any situation that I have to use jet mixers instead mechanical ones?
Category: Mixing

KW Rating | KW Rating and Bearing Size | Chemical Processing
We need to offer a drive ( GearMotor) for a Mixer with Blade sweep Dia. of 6.56 Ft., Height of Stirrer shaft is 8.202 Ft., rpm - 60, Viscosity - 30 poise, but there is no bearing at the bottom. The question is what would be the KW rating of the Motor and what size of Bearing should be there at the Gearbox output shaft ?
Category: Mixing

Mixing Time and Multipropeller
I would like to know if there is a correlation to estimate mixing time in a vessel with a multipropeller?
Category: Mixing

Horsepower calculations for a specific viscosity
I need to calculate the horsepower required to agitate a solution with viscosity of 0.3 cps and density of 839 kg/m3 at 60 rpm. The tank has an inner diameter of 1,500 mm and tangent-to-tangent length of 4,500 mm. The agitator has three impellers (pitched turbine, I do not know the number of blades) with 900-mm diameter. The tank has four mixing baffles. Using equations from a handbook, I found that the power required is about 1 hp. However, I am not sure if this equation considers the use of multiple impellers.
Category: Mixing

Baffle fabrication
I am presently setting up a micro manufacturing plant for mixing Polymers and other cleaning products. I have two tanks, one that is eight feet,a stainless steel tank and one four-foot poly tank. My question is regarding baffles. Can I fabricate something locally that would work for both steel and poly tanks and is there any tricks to installing these baffles?
Category: Mixing

Calculate "downward force" on an impeller
I am trying to calculate the "downward force" of an impeller. Is this the same a hydraulic force? (e.g. (19,000 x horsepower x service factor)/(rpm x impeller diameter).
Category: Mixing

Blended viscosity and stirred tank content relation
I feel there would be a relation between the blended viscosity of any stirred tank content and the tank volume physically, is that correct? If so, why and what is the rule of thumb criteria for selecting a vessel’s volume with respect to blended viscosity?
Category: Mixing

Agitator design procedures
I want to know the selection criteria and standard design procedure for all types of agitators, mainly anchor and turbine). Please also suggest some books.
Category: Mixing

Sizing mixers
How do you select the type of impeller for different applications? How do you determine the measurement of the impeller size and dimension?
Category: Mixing

Suitable reactor capacity
We have installed a cylindrical dish-end type of SS reactor with a capacity of 1,500 L, diameter of 1,200 mm; height of 1,350 mm; depth of 50 mm; total height of 1,650 mm; and the required rpm at the agitator end is 500-600 rpm. Process details are: paste type liquid (free flowing); specific gravity around 1.0; viscosity of liquid is 350-600 cSt.; agitator is vertical with four, 45-degree vertical turbine-type impellers. Suggest the suitable capacity of torque with its rpm selection to have the desired rpm at the end of the impeller withstanding the torque generated by the liquid during the mixing. Can we operate the same system with gear motor?
Category: Mixing

Agitator capable of dispersing air through the shaft/blades
I am looking for an agitator that can disperse compressed air through the agitator shaft/blades. Is there a manufacturer out there that makes an agitator like that?
Category: Mixing

Motor requirements for varying fluid viscosity
I have an agitator with a 40-hp motor. The service fluid viscosity is 1,000 cp. I want to use the same shaft and motor for a 10,000-cp fluid. Can I use same shaft, and if so, what parameters need to be changed?
Category: Mixing

Power requirement for a constant stirring vessel
What is the power requirement (motor specification, gearbox size and the shaft size) for a constant stirring vessel that is an open type with a 60-degree inclined pitched blade agitator running at 14-15 rpm? The contents of the vessel can be UF (Urea Formaldehyde resin), Melamin formaldehyde resin, MUF, phenol formaldehyde resin, etc. The diameter of the tank is 3,500 mm and the height is 5,500 mm. The stirring is required to not let the liquid gel-up.
Category: Mixing

Power requirement for a gearbox
I have a 1,000-mm diameter and 1,800-mm high tank. Material to be mixed with an agitator is 76% solid and 24% water (calcium carbonate slurries), with a viscosity of 350-450 cps. I want to use a gearbox for mixing with output speed between 18-36 rpm. How much power (kW) do I need for the gearbox? How many blades must be made in order to make slurries?
Category: Mixing

Agitator type for batch reactor
I would like to know what kind of agitator in a batch reactor I should use. Reactor dimensions are 1160 mm in height and 800 mm in diameter. Reactor contents are 250 Kg of 853 Kg/cubic meter dense liquid and the gas is purged to the liquid through dip tube at 75Kg/hr. What kind of agitator should we introduce to this batch reactor?
Category: Mixing

Power consumption equation
I would like to know the formula for calculating power consumption for an agitator and grinding mill. I have all the process data information for this equipment, but I don’t know how to calculate approximate power from the data.
Category: Mixing

Follow-up to previously answered impeller diameter question
A few days ago, I posed this question: Q: I have a vessel with a top entering agitator without baffles. The vessel height is 2 m and vessel inside diameter is 1.5 m. The impeller type is three 60-degree pitched blades. Each blade has an inclination of 60-degress in respect to the agitator shaft too. The impeller diameter is 880 mm. The pitched blades are fixed to a cylinder that is 122 mm in height and with a 125 mm diameter. The width of the blade at the cylinder is 112 mm and at the end is 80 mm. The shaft diameter is 100 mm. The agitator has a velocity redactor of 1 to 10. The agitator has no driver and has no characteristics label. I want to use this vessel in the production of 50% calcium nitrate solution with a density of 1,450 Kg/cubic meters and a dynamic viscosity of 1.35-1.8 cp. What will be the calculated power at 180 rpm and 360 rpm?

I received this answer: A: The answer is don’t do it. There is no way an impeller that large should ever be rotated at 180 rpm in a vessel that size. Without baffles, the liquid contents would swirl over the top to the tank an splash everywhere around the tank. At 180 rpm, without baffles, the impeller power draw would be about 7.8 kW, that's kilowatts, not watts. At 360 rpm, the power jumps to 61 kW. The mixer described is suitable for a much larger tank, not for one 2 m tall and 1.5 m in diameter, regardless of the contents. Baffles only make the design >worse, because the power levels are about three times the levels without baffles. Do not attempt to operate the mixer in the manner described!

Of course, I am satisfied with the answer, but now I have a new idea. Can I do the blades of my impeller shorter, keeping up the original design, except the diameter? If I can do it, what would be the optimum impeller diameter to avoid having the liquid contents swirl over the top of the tank and splash? What would be the consumed power in this case? I attempted to calculate it, using the Perry’s Manual, but there wasn’t any similar impeller in the figure.
Category: Mixing

Agitator speeds for different fluids
Can I get the same maximum agitator speed for a given motor for different types of fluid?
Category: Mixing

Calculating rpm power
I have a vessel with a top entering agitator without baffles. The vessel height is 2 m and vessel inside diameter is 1.5 m. The impeller type is three 60-degree pitched blades. Each blade has an inclination of 60-degress in respect to the agitator shaft too. The impeller diameter is 880 mm. The pitched blades are fixed to a cylinder that is 122 mm in height and with a 125 mm diameter. The width of the blade at the cylinder is 112 mm and at the end is 80 mm. The shaft diameter is 100 mm. The agitator has a velocity redactor of 1 to 10. The agitator has not driver and has not characteristics label. I want to use this vessel in the production of 50% calcium nitrate solution with a density of 1450 Kg/cubic meter and a dynamic viscosity of 1.35-1.8 cp. What will be the calculated power at 180 rpm and 360 rpm?
Category: Mixing

Agitator design
How do you design the shaft diameter, impeller rpm and power required to drive an agitator?
Category: Mixing

Agitator efficiency equation
I am looking for a formula to calculate the efficiency of an agitator. I am currently designing a mixing impeller for the dissolution of ammonium persulphat in denim water. Now I want to compare between the efficiencies of the propeller and the turbine impeller designs with respect to their efficiencies. Can you help with the formula? The shaft is a top, off-center entering at an angle in a closed hemispherical tank.
Category: Mixing

Pitched-blade impeller direction
I would like to know the direction of 60-degree angle pitch-blade impeller and whether it should be facing upward or downward while the agitation is in clock-wise direction. I also am seeking information on how much distance is required from the bottom dish of the reactor to the bottom impeller. As far as I know, if the pitch-blade impeller's angle is facing upward during its clock-wise rotation, the material lifts from bottom to top and gets radial and axial agitation to lift the reaction mixture. If the pitch-blade impeller's angle is facing downward during its clock-wise rotation, the material pushes down and may be not getting proper mixing effect. In either case what should it be?
Category: Mixing

Agitator design
I have a tank of 4.5m diameter and 2m height containing water. I want to install an agitator consist of two blades of sweep diameter 2 m. The agitator's speed should be 20 rpm. Gear ratio is 60:1. Motor is of 3.7 kW. Please tell me how I should design this agitator? Also tell me the specification of the gear box and motor.
Category: Mixing

Suspension agitation
In several parts of our process we are making suspensions of solids in mixing tanks with agitators. Some solids tend to float on the surface. Some suspensions also tend to create a lot of foam on top of the water surface causing problems (flooding). A higher rotation speed creates a better mixing but creates also more foam. We use antifoam chemicals to reduce the foam. Is there a way to prevent or reduce foam? By using another agitator or agitator position or another trick?
Category: Mixing

Design for an off-centered agitator shaft
I am trying to design an off-centered agitator shaft. The shaft would be offset 20% of the tank’s inner diameter. What service factor would I need to use for the off-center?
Category: Mixing

Hydraulic load factor for water, oil mix
What is the hydraulic load factor for a fluid made up of oils and water being stirred by a three-blade propeller with the blade fully submerged under the mixer? Can you also help with the diameter of the shaft? Details are: power equals 2.2 kw; length of shaft equals 2.228s; speed equals 460 rpm; and impeller diameter is 390 mm.
Category: Mixing

Liquid mixing equation
I know there is an equation that can be used to determine the adequate mixing time of two liquids (viscosity of water). Can you give me the name of the equation? I saw it once a long time ago and, if I remember correctly, it was a person's name.
Category: Mixing

Agitator force
I have an agitator which is used to mix the dough. The agitator is running at 150 hp motor at 84 rpm. Taking 1005 efficiency, how do I calculate how much force will the dough exert on a fixed cold bar? The idea is that the dough gets squeezed between the agitator and the fixed cold bar.
Category: Mixing

Hydraulic load calculations
An agitator has a steady bearing (a PTFE bush bearing), a radial bearing (rolling element bearing) and a locating bearing (rolling element bearing - in the gear box). How do you calculate the reaction loads at each of these bearings due to hydraulic load and other loads. Do you have any examples for this type of problem?
Category: Mixing

Mix throttled liquid/flash gas and hot gas
What is a good way to mix throttled liquid/flash gas and hot gas in the low side of a refrigeration system to achieve a uniform superheated vapor? Both the feed streams are currently injected at a common point and then allowed to run through about 20 ft of tubing with four 180-degree return bends. There is a liquid stream rolling along the bottom of the pipe where incomplete evaporation is evident. There is insufficient room to add much additional piping. Would static mixers, which I believe are typically used for liquid blending, be of any benefit?
Category: Mixing

Calculating torque exerted by liquid
We have a vessel of 6,500-L capacity. It needs to be driven by a top agitator with 2 Nos. of turbine impeller with four 300-diameter blades. I want to know the torque exerted by the liquid. The viscocity of the liquid is 250 cp.
Category: Mixing

Service factor for an unbalanced hydraulic load
The following is the data for an application:

Fluid composition: Hydrocarbon/Acid/Water/0.5% suspended solid

Solid concentration %w/w: 0.5

Motor: 24.79 hp

Speed: 68 rpm

Single impeller downflow turbine type, with a steady bearing about 800 mm above the impeller.

Can you please give the service factor that needs to be used while computing the hydraulic unbalanced load?

Category: Mixing

Calculating unbalanced hydraulic force
When calculating the unbalanced hydraulic force on an agitator impeller, one of the articles says that the calculation of force can be done by the formula: Force = (2000*Output hp*12*Position factor)/(rpm*DIa. of turbine in inches). What does that position factor stand for, and what are the values for a top entry type agitator, with a 11kW motor? In another text it was written that the force can be computed by the formula F = Torque/(0.75*Radius of blade in mm). Which of the two gives an accurate result?
Category: Mixing

Suspending salt mixtures in a PVC solution
I am interested in keeping a mixture of 30% salt suspended in a liquid PVC material. The goal is to produce products that are heavy and weigh the same without any salt collecting on the bottom.
Category: Mixing

Installing an agitator in a reactor | Chemical Processing
We represent a company that sells second - hand equipment, our customer needs a practical way to mix a viscous product and the agitator is a 36 hp - 120 RPM, but the structure to handle this agitator in a 1200 gal SS reactor is very complicated according to our main engineer in USA. We do not have more in the inventory, what could be the mechanical structure suitable to install the agitator in the reactor?
Category: Mixing

Recommendation for small pilot plant batch mixer
I'm looking for a recommendation for small pilot plant batch mixer (idal capacity target 1 to 4 liters) that handles powder and can be heated to about 80 C. Mixing should be possible at low speed.
Category: Mixing

Formula for position of impeller
We have a pilot mixing plant here on site. Ever since it was stripped down and rebuilt due to its PM schedule, it hasn't worked properly. We use the tank to mix a powder and a liquid. Now when it runs, no vortex is created (or be it a very poor one) and the powder does not go into solution, it just sits on the top of the liquid. We have tried moving the impeller up and down the shaft but to no avail. Unfortunately, the original dimension drawing are missing and so we do not know the original position of the impeller and its dimensions etc. Are there formula that might help us to determine the optimum position for the impeller etc. if we measure the various aspects of the tank, baffles etc.?
Category: Mixing

Solid particle size distribution
Can give me the various general solid particle size distribution used in chemical industries in various applications or a link or reference where i can get this data?
Category: Mixing

Blade RPM speed
I have a tank (7-meter diameter 8.5-meter told), with and old agitator for milk of lime suspension and a double blade 84 inches wide each. At what RPM do I have to turn the blades in order to keep the lime in suspension at 8 or 10% of solid?
Category: Mixing

Mixing powders of similar micron sizes
I would like to know what are the factors to consider when mixing two types of powder with similar micron sizes. What would be the most cost effective way to mix big volume quantity in the rangeof 500 000 to 1 million lbs a year? This mix will have to be filled in individual products, and I would like to know if there is a group out there that can guide us in the design and implementation of a production system.
Category: Mixing