Mixing horsepower

Note carefully however that space velocity is intimately associated with emulsification, contacting, and mixing horsepower. It can be very misleading to compare reactors or plants of different designs using space velocity as a primary criterion ... 

Horsepower required based on material of 50-60-lb/fF bulk density, medium free-flowing, using 10 hp/ton for average mix cycle of. 3-10 min (depending on material, range can be. 3-18 hp/ton). 

Impeller Type Horsepower (Op. cost mix. heat added) N rpm Torque Initial cost... 

Figure 5-5T. Standard six-blade vertical curved blade turbine impeller. Gives good efficiency per unit of horsepower for suspensions, mixing fibrous materials. Gives high pumping capacity. Courtesy of Philadelphia Gear Corp.

Figure 5-18. Laminar flow mixing. For known impeller type, diameter, speed, and viscosity, this nomograph will give power consumption. Connect RPM and diameter, also viscosity and impeller scale. The intersection of these two separate lines with alpha and beta respectively is then connected to give horsepower on the HP scale. By permission, Quillen, C. S., Chem. Engr., June 1954, p. 177 [15].

Power input to impeller, ft-lb/sec (see Equation 5-19) or if in a ratio can be as horsepower Power, horsepower used b impeller mixing system... 

Variation in the actual brake horsepower required to operate a mixer is the primary indicator of its performance envelope. Mixer design, whether propeller- or screw-type, is based on the viscosity of both the incoming and finished product. These variables determine the brake horsepower required to drive the mixer, which will follow variations in the viscosity of the products being mixed. As the viscosity increases so will the brake horsepower demand. Conversely, as the viscosity decreases, so will the horsepower required driving the mixer. 

Figure 5-5S. Four-blade, vertical Figure 5-5T. Standard six-blade fiat blade turbine Impeller. Very vertical curved blade turbine versatile, one of the most used impeller. Gives good efficiency in wide application range. Cour- per unit of horsepower for sus-tesy of Philadelphia Gear Corp. pensions, mixing fibrous materials. Gives high pumping capacity. Courtesy of Philadelphia Gear Corp.

Mixing concepts, fundamentals, 297 Actual motor horsepower, 307 Axial flow, 291 Baffle diagrams, 318 Baffles, 311 Calculations, 297 Characteristic curves, 306 Draft lubes, 309, 312, 313 Entrainment, 309 Flow number, 298 Flow patterns, 309-313 Flow, 298... 

Double suction, 166, 167 Efficiency, 200 High speed, 169 Illustrations, 161, 164 Impellers, 164, 170 In parallel, 177, 178 In series, 176, 178 Liquid horsepower, 200 Materials of construction, 211 Mixed flow, 169 Multistage, 167 Operating curves, 180 Packing, shaft, 170... 

In the pesticide industry, neutralization is provided prior to GAC and resin adsorption, pesticide hydrolysis, and biological treatment. The neutralization basin is sized on the basis of an average retention time of 6 minutes and 70 horsepower per million gallons for mixing requirements [7]. 

Besides savings that may result from pressure and horsepower reduction, it is generally known that the more violent mixing of oil and water also creates an emulsion that would require more emulsion breaker chemical... 

The combination of HP and rpm that corresponds to a particular superficial velocity depends on the size of the tank, the size of the impeller, and certain characteristics of the system. Tables 10.3, 10.4, and 10.5 are abbreviated combinations of horsepower and rpm that are suitable at particular pumping rates for the three main categories of mixing. More complete data may be found in the literature cited with the tables. 

The lower horsepower is an important factor in the efficient design of axial flow or fluidfoil impellers. Such lower horsepower must be considered in the efficient design involving fluid velocity and overall macroscale mixing phenomena. On the other hand, if the process involves a certain amount of microscale mixing, or certain amounts of shear rate, then the fluidfoil impeller may not be the best choice. 

These low-intensity units are less energy-intensive, requiring lower horsepower, but they do not achieve mixing of the same quality in comparable cycle times. They are limited in use to such jobs as blending additives and fillers into low- to medium-viscosity... 

The term apparent viscosity refers to a viscosity that has been back-calculated from impeller torque or horsepower. A true-viscosity reading should be measured at a fixed and known shear rate. The effective shear rate developed by a mixing impeller is really a distribution of different shear rates. This distribution is probably most closely related to the shear between the helix blade and the tank... 

In addition to the particular design of the alkylation reactor and the amount of horsepower going into the mixing, the mixing and alkylation results are usually improved by having 50% or more by volume of acid catalyst in the emulsion so that the acid is in the continuous phase. Recycle of emulsion containing... 

Example 6.1 A turbine with six blades is installed centrally in a baffled vessel. The vessel is 2.0 m in diameter. The turbine, 61 cm in diameter, is positioned 60 cm from the bottom of the vessel. The tank is filled to a depth of 2.0 m and is mixing alum with raw water in a water treatment plant. The water is at a temperature of 25°C and the turbine is running at 100 rpm. What horsepower will be required to operate the mixer ... 

Using a paddle with sufficient manual mixing will suffice for the initial preparation of a dilute solution, although it will not be sufficient to prevent stratification. Therefore, a mechanical mixer is preferred. Mixers are available in various sizes, with shafts and propellers made of various materials to meet chemical-resistant requirements for different fluoride chemicals. Depending on the size of the mixing tank, a fractional horsepower mixer with a stainless-steel shaft and propeller will be satisfactory for sodium fluoride solution, and a similar mixer with a corrosion-resistant alloy or plastic-coated shaft and propeller will handle fluosilicic acid (15). 

Internal mixers must be ran in a full or nearly full condition, so a batch recipe is calculated to provide an appropriate volume. If not filled, the ingredients will not be properly sheared and heat transfer will be compromised. Typical commercial mixers have a batch size of at least 100 pounds of compound. A mixer of this size will have a drive motor of no less than 75 horsepower. Proper dispersive mixing is a balance between proper shear, sequence of addition of ingredients, and thermal stability. Mixers have extensive monitoring instrumentation that provides continuous feedback about thermal conditions, rotor torque, and rotor speed. Once a mixing process has been developed, a standard protocol is followed for preparation of the compound. 

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