Fluid Mixing Equipment

SERVICES. Essentially all of the manufacturers of fluid mixing equipment maintain either their own laboratories, or test equipment, for obtaining desi...
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Fluid Mixing Equipment by P. E. GRAYBEAL, Hercules Powder Co., Hattiesburg, Miss., and R. J. BECHTEL, Hercules Powder Co., Parlin, N. J.

A n y application of fluid mixing may have one or more of the following immediate objectives.

^

1.

Blending of miscible

liquids. ^ 2. Blending of solids in liquid suspension. ^ 3. Suspension of solids in liquid. • 4. Dissolving in liquid. ^ 5. ing.

Gas-liquid

of

solids

contact-

^ 6. Liquid-liquid tacting for washing extraction.

conand

• 7. Release of solids from liquids such as flotation, precipitation, and crystallization. • 8. Leaching of solids by liquids. ^ 9. Dispersion of immiscible liquids in other liquids to form emulsions. ^ 10. Promotion of transfer.

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heat

INDUSTRIAL AND ENGINEERING CHEMISTRY

THE manufacturers of fluid mixing equipment are making excellent progress toward keeping pace with the expanding requirements of the process industry. Selection of fluid mixing devices for the wide variety of applications has been treated rather fully by a number of authors (7, 2, 4, 6, 72). This article, therefore, covers only briefly the factors which should be considered in selecting a fluid mixer, but covers in detail the types of equipment which are available today, the services provided by manufacturers, and the new developments in fluid mixing. The ultimate objectives of fluid mixing may be to obtain uniform physical characteristics, or to control a chemical reaction where temperature, ratio of reactants, and contact between reactants are the important features. When two or more of these operations take place in one cycle, one is usually controlling and the mixer design is based on the most difficult or critical operation. An applications engineer who undertakes the design of a fluid mixer for a particular application must consider the physical characteristics of the individual fluids and the mixture, the degree of mixing required, the dimensions of the vessel in which the mixing will occur, and the mixing rate, or time cycle. From these considerations should come a design which relates properly the mixing performance with initial investment, power requirement, and the freedom from mechanical difficulty. Physical characteristics of the components control power consumption and cycle time; hence they are the first items to be considered in a mixing operation. Viscosity, or apparent viscosity, of the individual fluids and the mixture must be known for the mixing conditions. Viscosity is a measure of the resistance of the material to flow and can be characterizedjby: true viscosity, as in a pure liquid or dilute suspension ; plasticity,

where a definite stress must be exceeded to start the material flowing; a n d pseudoplasticity for non-Newtonian fluids, where the a p p a r e n t viscosity decreases with increasing rate of shear. This is a typical characteristic of m a n y liquid-solid suspensions a n d is generally found in those containing fibrous solids. I t is also found in emulsions a n d colloidal suspensions. O t h e r physical properties to be considered a r e : particle size, shape, a n d solubility; t e m p e r a t u r e effects; surface tension; stickiness; ability of solids to be w e t t e d ; a n d changes of the mass d u r i n g mixing—i.e., variation in fluidity or viscosity. Specific gravity of the mixture a n d relative gravities of each c o m p o n e n t m a y govern t h e type of e q u i p m e n t to be used. Cycles a n d relative proportions, as well as order of addition of the separate phases, a r e t h e next factors to be considered. F r o m the physical factors, especially tank size a n d shape, a n d the mixing objective, t h e basic type of mixer can be selected. T h i s will be governed by need for high bulk flow, high shear, or some intermediate condition combining both shear a n d flow to a balanced degree. I t is i m p o r t a n t t h a t the agitator a n d vessel be designed to c o m p l e m e n t each other in order to achieve the best mixing application at lowest over-all cost. S h a p e governs the type of mixer a n d also whether baffles a r e included in t h e design. Vessel size a n d b a t c h volume become of increasing importance with higher viscosities a n d where high shear is required. Generally, the best proportion for mixing is a vertical vessel with ratio of side wall height to d i a m e t e r in t h e r a n g e from 1:1 to 3 : 1 . Vessel size a n d d i e agitator type, size, a n d speed will govern power requirements. T h r e e basic types of fluid mixers a r e employed—namely, the propeller, paddle, a n d turbine. E a c h type has n u m e r o u s modifications for specific uses, described u n d e r the basic types.

MANUFACTURERS' ENGINEERING SERVICES Essentially all of the manufacturers of fluid mixing equipment maintain either their own laboratories, or test equipment, for obtaining design data on new mixing applications. Most manufacturers use standard questionnaires for the customer to supply information on the particular application. In general, a manufac­ turer prefers to recommend the fluid mixer which he has confidence will fill the customer's requirements. There are exceptions to these generalities, however. One manufacturer of a specialty mixer prefers not to use a standard question­ naire, because in many cases there are blank spaces for information which do not apply to the particular mixing job. The customer may be confused and omit some pertinent details which can be obtained best through conference be­ tween the mixing engineer and the customer. This same manufacturer pre­ fers to restrict technical data about his equipment because it may be misleading to persons not familiar with the technical aspects of mixing.

Research and customer service laboratory, Mixing Equipment Co.

On the other hand, another manufac­ turer states that he makes a special point of furnishing technical information to his customers either for their general back­ ground, or to illustrate how this manu­ facturer has si7.ed, powered, and other­ wise selected the mixers recommended for the customer's applications. In many instances, the customers are cither engineering concerns or chemical and petroleum companies which have engineering staffs. One large manufac­ turer of mixers observes a trend for some companies with complete engineering staffs to request quotations on a specific

agitator to perform a particular job. Λ fairly recent entry in the field of manu­ facturing fluid mixing equipment pro­ poses to make it possible for the customer to select a complete machine. Manufacturers recognize that agita­ tion technology has not yet been refined to a science. The applied research in the manufacturer's test laboratory and his past experience should be invaluable in his position as a consultant to the cus­ tomer on fluid mixing. There should be an expanded manufacturer-customer re­ lationship to include mutual accessibility to data, if the most rapid progress in the general field of agitation is to occur.

Engineering Services by Equipment Manufacturers

)

Χ) N a m e of Manufacturer

Use of Standard Questionnaires

A v a i l a b i l i t y of Test Laboratory

V

A b b e Engineering Co. A l s o p Engineering Corp.

V

Chemineer, Inc.

V

V

Cleveland M i x e r Co.

V

Denver Equipment Co.

V

Eclipse A i r Brush Co. G a b b Special Products D i v .

V

International Engineering, Inc.

V

V

M i x i n g Equipment Co.

V

V

M o r e h o u s e - C o w l e s , Inc.

V

N e w England Tank & Tower Co.

V

V

Patterson Foundry & M a c h i n e Co.

V

V

Pfaudler Co.

V

V

Philadelphia Gear Works

V

Premier M i l l Corp.

V

V

Η. Ε. Serner Co.

V

Struthers Wells Corp.

V

V

Turbo-Mixer Division, General A m e r i c a n Transportation Corp.

V

V VOL. 49, NO. 3

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MARCH 1957

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T Y P E S OF M I X E R S

PADDLE MIXER T h e p a d d l e mixer is usually thought of as the simplest form. It is characterized by low power consumption a n d long mixing cycles, and is usually used in moderate volume tanks. By special ar­ rangements, it can be used in extreme viscosity mixes, but then the power consumption is at least equivalent to t h a t of a n y other type for the same work being done. T h e paddle type is also called a slow-speed mixer, or stirrer. Usual speed is in the range from 15 to 60 r.p.m., because above its m a x i m u m speed the time for mixing is not appreciably decreased, while power increases rapidly. Baffles tend to de­ crease time of mixing, but increase power sharply. Variations are numerous, including: 1. 2. 3. 4. 5.

PORTABLE MIXERS

PROPELLER

Portable propeller mixers as illustrated range from fractional to lx/% h p . T h e y are generally m o u n t e d on the shell of open-type tanks. For low viscosity liquids a n d smaller sizes, direct-driven shaft speeds of 1750 a n d 1150 r.p.m. are common. O n the larger units, a n d particularly when the fluid viscosity is in the range of 500 to 3000 centipoises, speed is geared d o w n to about 420 r.p.m. T h e portable propeller mixer is inexpensive, can be moved from one vessel to another, a n d is com­ monly used for blending liquids and incorporating solids into liquids. T h e large n u m b e r of manufac­ turers of this type of equipment speaks for its versa­ tility.

N o r m a l or straight p a d d l e . Anchor type. G a t e type. Horseshoe, simple a n d with vertical arms. Combinations of a n y two or m o r e of the above.

Effective ranges are those in which the p a d d l e covers all, or nearly all, of the tank diameter. Manufacturers of Paddle Type Mixers

Chemineer, Inc. Denver E q u i p m e n t Co. International Engineering, Inc. Mixing E q u i p m e n t Co. N e w E n g l a n d T a n k a n d T o w e r Co. Philadelphia Gear Works Struthers Wells C o r p . T h e majority of fluid mixing applications use either propeller or turbine impellers. Axial flow impellers of the marine propeller type are produced by m a n y manufacturers. R a d i a l flow impellers of the turbine type are available in a n u m b e r of vari­ ations, depending on the manufacturer and the applications.

Portable propeller mixer, Mixing Equipment Co.

Manufacturers of Portable Propeller Mixers

Horsepower Range

Commercial propeller designs Left to right, top. C a g e b e a t e r ; cut-out propeller; studded-cage b e a t e r ; standard three-blade propeller. Bottom. Saw-toothed propeller; folding propeller; p e r f o r a t e d propeller; weedlers propeller; propeller with safety ring g u a r d . Mixing Equipment Co.

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INDUSTRIAL A N D ENGINEERING CHEMISTRY

Alsop Engineering Corp. Chemineer, Inc. Cleveland Mixer Co. Eastern Industries Eclipse Air Brush Co. International Engineering, Inc. Mixing E q u i p m e n t Co. N e w England T a n k & Tower Co. Patterson F o u n d r y & Machine Co.

V20-7V2

V« - 3 Va-3 7*0-5 V2-3

Vi-5 Vs-5 Ά-2 Ά - 3Λ

TYPES OF MIXERS

FIXED SIDE-ENTERING PROPELLER MIXERS

FIXED TOP-ENTERING PROPELLER MIXERS

Fixed side-entering propeller mixers range in size from 1 to 50 hp. Installation of this type of mixer is made on the tank through a side nozzle which usually accommodates passage of the propeller. The side-entering mixer is used for solids suspension and blending of liquids in tanks of all shapes and sizes where a top-entering mixer is impractical because of low head room, or the need for especially long, unsupported shafts. A typical example of the side-entering agitator is the large gasoline blending tank where several agitators may be installed on one vessel (70). The side-entering propeller has also been employed for a high shear application by Chemineer, Inc., and Struthers Wells in their rubber cement dissolvcrs. Manufacturers use a variety of drives including variable speed, belts, and directly coupled reduction gears. Most manufacturers have included techniques for repacking the shaft stuffing box without removal of the agitator from the vessel, or emptying the contents of the vessel.

Fixed top-entering propeller mixers are available in the range of 1 to 25 hp. for open and closed vessels, pressure and vacuum service. With proper baffling or positioning of the propeller this type of agitator can perform satisfactorily in mixing applications where the viscosity of the liquid does not exceed 5000 centipoises. Because of the relatively small diameter of the propeller, it is particularly adaptable where there is a possibility of the impeller becoming locked in solids while the operations may be shut down. Since propeller mixers are available in many standard sizes, their purchase is often economical.

A f i x e d top-entering propeller mixer b y The Mixing Equipment Co.

Side-entering mixer, Mixing Equipment Co. Manufacturers of Fixed Top-¬ Entering Propeller Mixers Manufacturers of Side-Entering Propeller Agitators

Alsop Engineering Corp. Chemineer, Inc. Cleveland Mixer Co. Eastern Industries, Inc. International Engineering, Inc. Mixing Equipment Co. New England Tank & Tower Co. Patterson Foundry & Machine Co. Struthers Wells Corp.

Alsop Engineering Corp. Chemineer, Inc. Cleveland Mixer Co. Denver Equipment Co. Eastern Industries, Inc. Eclipse Air Brush Co. International Engineering, Inc. Mixing Equipment Co. New England Tank and Tower Co. Patterson Foundry and Machine Co. Philadelphia Gear Works Struthers Wells Corp. VOL. 49, NO. 3

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MARCH 1957

45

A

TYPES OF MIXERS

TOP MOUNTED TURBINE MIXERS These are manufactured in sizes from 1 to 500 hp. and are used in essentially all applications of fluid mixing. For most mixing jobs, the desired results can be obtained with many of the several different turbine styles shown below, and the selection of the style will be that generally sold by a particular manufacturer. The factors of shear, turbulence, total liquid pumped, and starting *:.rque should be considered in the selection of the type of turbine (3). Baffles, draft tubes, or shrouds are necessary to minimize swirl and to obtain maximum pumping rate for any given impeller (74).

Commercial turbine designs a. Pitched, 1910 fa. Shrouded with stator, 1913 c. Open tilted, 1932 d. Cone lifter, 1932 e. Center disk, 1934 f. Gas disperser, 1935 g. Three-blade, 1935 h. Brumagin, 1937 ι. Variangle, 1938 /. Vane-disk gas, 1939

Manufacturers of Turbine Agitators Alsop Engineering Corp. Chemineer, Inc. Cleveland Mixer Co. Eastern Industries, Inc. International Engineering, Inc. Mixing Equipment Co. New England Tank and Tower Co. Patterson Foundry and Machine Co. The Pfaudler Co. Philadelphia Gear Works Struthers Wells Corp. Turbo-Mixer Division 46 A

INDUSTRIAL AND ENGINEERING CHEMISTRY

New Developments

As more has been learned of the technology of fluid mixing, special designs have been de­ veloped to provide better me­ chanical design, to utilize high shear, and to make available mixers and vessels for specific services. The manufacturers with whom we have been in contact in this survey of fluid mixing equipment have provided pic­ tures of these newer techniques in fluid mixing. The comments are based for the most part on the claims of the manufacturers rather than experience by the authors.

MECHANICAL

IMPROVEMENTS

V A R I A B L E SPEED DRIVES In many applications where the liquid level or the viscosity of fluid change during the cycle, there is a need for variable agitation. Some continuous flow systems must have a reduction in agitation while the process fluid flow is interrupted. Manufacturers have recognized the need for a variable agitation and are furnishing standard designs using belts and variable pitch pulleys, fluid drives, and variable speed motors. The initial costs, of course, are increased, but often the variable speed pays good dividends in control of the process and plant productivity. Standard variable speed top-entering mixer, by The Cleveland Mixer Company

FLEX PROTECTED DRIVE Long overhung shafts cannot be prevented completely from flexing. This problem becomes acute if the mixer must operate while the tank is being filled or emptied. Shaft flexure can set up severe stresses in the mixer drive. If the shaft is rigidly connected to the drive, vibration and wear on the gears and bearings of the drive may be excessive. The Mixing Equipment Co. has sought to minimize such wear by isolating the gearing from the shaft flexures with the flex-protected drive. The mixer shaft is supported on its own set of bearings and is connected to the quill with a flexible coupling. Cutaway view of a side-entering mixer having flex-shaft construction. Mixer shaft runs on bearings independent of gear reduction unit Mixer shaft runs on bearings independent of gear reduction unit

CHANGE GEARS Although many speed reduction units used with agitators will accommodate different gear ratios, we use the term "change gears" when the gear ratio can be changed without having to disturb the speed reducer-agitator shaft assembly. This is particularly advantageous in a new application where the selection of the agitator may involve some trial and error, or where it is known that the agitator will be used for alternate applications with different mixing requirements. Both Philadelphia Gear Works and Mixing Equipment Co. offer change gear design as standard equipment. Cutaway view of vertical drive showing access to change gears, Mixing Equipment Co.

REPLACEABLE MECHANICAL SEALS Mechanical shaft seals in place of packed stuffing boxes are offered as special equipment by Mixing Equipment Co. and Philadelphia Gear Works. Although the use of mechanical shaft seals on pumps suggests similar use on agitator shafts, the problem of replacing the seal required special design. Quick and easy replacement has been provided by inserting flanged couplings in the shaft just above and below the mechanical seal. By raising the shaft with a special lifting device the mechanical seal can be disconnected and replaced without removing the agitator, or the drive, from the vessel. Cutaway view of vertical drive having a mechanical seal, flanged for quick removal, Mixing Equipment Co.

VOL. 49, NO. 3

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MARCH 1957

47 A

HIGH SHEAR MIXERS

Several of the high shear devices are included for illustration of the types of equipment on the market. We do not mean to suggest that these are the only high shear devices, but rather that greater attention be given to the use of high shear for obtaining short cycles and large capacity from small vessels.

THE DISPERSATOR Dispersator Unit pictured is a 4-inch Duplex type which rotates at 3 6 0 0 r.p.m., Premier Mill Corp.

This is a high speed, high intensity mixer utilizing a slotted cone, or cylinder, as an impeller. Radial baffles rotating with the mixer head displace head contents through peripheral slots at high speed, developing both mechanical and hydraulic shear. Head sizes are available from approximately 1 to 8V2 inches in diameter, and depending on the drive speed and characteristics of material to be mixed, power requirements range up to 25 hp. The model shown is of intermediate size, designed for closed system application at the 3-hp. level. Drive units for closed systems are applicable to top, side, or bottom mounting and arc fitted with mechanical seals to suit process conditions. Parts in contact with process material are available in a variety of materials, including stainless steel and Hastelloys.

Jef mill, installed in plant of a paint company on West Coast, Patterson Foundry & Machine Co.

THE JET MILL The figure shows a modern approach to mixing where dispersion is the requirement for processing low viscosity paints, coatings, and emulsions. The disintegrating force generated in the jet mill comes from the high velocity flow of material through the jet valves as the rotor turns at high speed. The machine is of integral construction with an inbuilt direct connected motor drive to minimize maintenance. The dispersion vessel is of clad stainless steel, jacketed for water cooling. The output shaft from the speed increaser, extends into the vessel where it supports the rotor in its jet housing. The manufacturer recommends this for high rates of production, minimum floor space requirement, freedom from metallic contamination, and case of cleaning the vessel. There are three production size units ranging in working capacity from 7 l /s to 150 gallons.

THE DISPERSALL MIXER The mixer illustrated consists of a bottom-entering shaft, driving a rotor directly under a stator ring which is a part of a baffle cylinder. Mixing action is said to be intense but smooth, owing to the function of the inner cylinder. Both the baffle cylinder, which is supported in three mounting posts, and the rotor are quickly removable for complete cleaning. Top and bottom shaft bearings are antifriction, heavy-duty units protected by a flinger plate. The stuffing box is adjustable and is located just above the flinger plate. The Dispersall mixer is available in the usual metals, in sizes from IV2 t o 880 gallons, and can be adapted to vacuum or pressure service.

Dispersall mixer. Abbe Engineering Co.

SHEAR-FLOW Shear-flow consists of a vertically mounted, totally enclosed drive unit having dual sealed impellers which counter rotate with respect to one another. In contrast to single impeller mixers, it is said, Shear-Flow's counterrotating impellers induce considerable shearing action, together with high pumping pressures. This, plus the material's own disintegrating and abrasive action of particle against particle, results in a more complete reduction of agglomerates within the mixture. ShearrFlow will handle both low and high viscosity materials, dispersing, agitating or homogenizing without any change of impellers or mixing speed. It is available in horsepower ratings of s / 4 , 1, l'/s, 2, and 5 for volumes of 5 to 250 gallons. 48 A

INDUSTRIAL AND ENGINEERING CHEMISTRY

S h e a r-Flow, G a b b Special Products Div.

RADIAL PROPELLER This mixer, according to its developer, incorporates the advantages of the marine-type propeller agitator and the turbine agitator (7). It is mounted on a vertical shaft and creates a flow of the liquids radially outward from the shaft similar to a turbine. It normally runs at propeller speeds giving a shearing and cutting action comparable to the propeller. The high speed of the radial type propeller may provide first cost savings due to low gear ratios in the agitator drive. The radial type agitator works successfully in any combination of liquids with solids, or gases, in which the ordinary propeller, or turbine, can be used. The vertical blade faces are set at an acute angle from the tangent, propelling the liquid radially outward. Angle degree is determined by the required agitation. If severe cutting action is a factor, the degree of the angle is small. If movement of the content is required without extreme cutting action, the pitch of the blade is increased.

Radial propeller shown with removable blades, Struthers Wells Corp.

I N T E R N A T I O N A L INJECTION MIXER The International Injection Mixer consists of a specially designed turbinetype agitator rotor, overhung and underhung by hollow ring-shaped stators. The turbine exerts a pumping action on the contents of the mixing vessel, drawing in through top and bottom impeller inlets and delivering centrifugally over the entire periphery of the turbine. The gas or other treating agent is fed to the hollow stators through the indicated feed pipes and is discharged through perforations on the rotor-faced surfaces of the stators. As the liquid passes between the stators and the rotors it exerts a shearing action on the gas discharged through the bubble holes. The gas-injected liquid is then subjected to a direct mechanical shearing between the radial ribs on the stators and the turbine blades. The combined shearing actions are said to result in complete and instantaneous gas dispersion. The high pumping capacity of the rotor ensures rapid recirculation of the tank contents for continuous reprocessing of the liquid. This is one of the principal factors in promoting gas-liquid reactions—namely, the development of a high area of interphase contact between gas and liquid phases.

VELOFIN IMPELLER The Velofin impeller consists of two or more parallel disks, closely spaced. By varying the number, size, and spacing of the disks, the manufacturer has been able to adapt the Velofin to a variety of operating conditions. It is said the impeller is effective over the entire range of fluid mixing, including semisolids. The Velofin imparts motion to the surrounding fluid through the function of its disk surfaces. In case of nonviscous fluids, the film of fluid in contact with the disk surface travels faster than the next adjoining layer of the fluid, the center layer between two disks having the slowest speed. The action is reversed in case of viscous fluids because the tendency of the liquid to stick to the surfaces causes the adjoining layers to be discharged at progressively higher velocities. In each case the result is said to be similar; since these thin fluid layers travel at different velocities, complete shuffling and mixing of the components is accomplished. The mixer is available in sizes up to 25 hp.

Velofin H. E. Co.

mixer, Semer

COWLES DISSOLVER A Cowles dissolver utilizes a single blade rotating at high speed for effective results in the dispersion, dissolving, and deagglomeration of materials. The effectiveness of the unit is due to the rapid movement of the suspension through itself. The materials discharged from the vanes of the impeller at high speed impinges on the surrounding slower moving portion. This creates intense hydraulic shear which does the work. By proper selection and location of the impeller, the dissolver will impart the desired amount of work without splash or dead spots. The units are designed to handle viscosities in excess of 50,000 centipoises. Illustrated is a 20-hp. Cowles dissolver mounted with a hydraulic lift for raising and lowering into position for mixing in portable tanks. VOL. 49, NO. 3

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MARCH 1957

49 A

CONTROLLED FLOW Controlled flow devices have been developed for use w h e r e the liquid m o v e m e n t should be directed, or restricted. As a result, some of the devices we describe will h a v e only limited use, b u t others a p p e a r to h a v e fairly wide r a n g e of application.

NETTCO FLOMIX The Nettco Flomix is a unique mixer designed for continuous agitation of liquids as they pass through a pipeline. The unit has multiple impellers and baffling in order to impart an extremely intense degree of agitation to the material in the mixing chamber. It utilizes the mixing effect of factional flow by repeated separation, reversing, and combining of the entering flow coupled with a violent mechanical agitation. It is usually desirable to have the several components to be mixed added at a given rate to one another on a continuous basis. This allows the several streams to enter the mixing chamber concurrently and eliminates the necessity for volumetric control in the mixing area. Where this is not possible, the use of a premix tank is desirable, and its size is determined by the rate of stream phasing. As the rotation of the agitator impellers is in the direction of flow, there is little or no frictional loss despite the heavy baffling effect within the Flomix body. In general, the Nettco Flomix will combine liquids, gases and liquids, liquids and solids, that in combination will readily flow through piping. Flomix, New England Tank and Tower Co.

Turbo tube, Chemineer, Inc.

TURBO TUBE AGITATOR The Turbo tube agitator is a top-entering propeller unit with a special unitized draft bend. With this agitator a horizontal flow pattern is obtained from a top-entering installation. It is said to be particularly useful with extremely long tanks, and by developing a flow pattern complementary to the vessel geometry, provides maximum circulation with minimum power requirement. The Turbo tube method of mixing is used in tanks of many different geometries, the variation in design being in the selection of the draft bend style, and the positioning of the unit. The type pictured is designated as T / U and is primarily used in rectangular tanks. When installed, the special draft bend is completely submerged in the mix. A double bend design is widely used for agitation of horizontal cylindrical tanks and tank cars.

Speed-O-Flow, Alsop Engineering Corp.

SPEED-O-PLATE AND SPEED-O-FLOW Speed-O-Plate (not pictured) is a controlled flow mixer developed originally by Alsop Engineering Corp. for accelerating the plating of an extra-heavy silver deposit on the internal surface of aircraft engine bearings. The 6-inch propellers enclosed in the down-flow tube displace upwards of 400 gallons per minute of liquid and send it in upward spiral flow through the interior of a stacked column of bearings. The success of the Speed-OPlate led to the development of Speed-O-Flow, shown at left, which has extended the benefits of controlled, uniform, recirculating action to numerous other applications where the control of the liquid flow is necessary, or more efficient. Examples of its use are heat treating, washing, cleaning, and quenching operations. Volume of flow is controlled by adjusting screws at top of down-flow tube. 50 A

INDUSTRIAL AND ENGINEERING CHEMISTRY

STANDARD M I X I N G SYSTEMS W e have p r e p a r e d from the d a t a of the mixing e q u i p m e n t manufacturers a listing of s t a n d a r d mixing systems which are available today. I n addition to the a d v a n t a g e of reduced costs in using a s t a n d a r d system, there is the distinct a d v a n t a g e of the unit having proved successful in previous applications. Illustrations of three s t a n d a r d systems are shown. M a n y of the s t a n d a r d vessels h a v e been listed in the table.

M U L T I C O M P A R T M E N T CONCURRENT FLOW BAFFLED M I X E R This system was first designed and patented by the Turbo-Mixer Corp. The patent has since expired, but the design continues to be a very important tool in continuous mixing operations. The three-stage treater shown is illustrative of the construction generally used, although there are now manyvariations of the horizontal baffle construction. These would include larger How areas through the baffles for high viscosity material, as well as replacement of the center partition of the horizontal baffle with a disk mounted on the shaft, so that the entire assembly may be removed as a unit. It is said the stator rings around each impeller make for the most perfect circulation pattern and most complete dispersion of the phases present. In less rigorous applications, the stator rings are sometimes replaced with vertical wall baffles. Typical continuous flow applications for the three-stage treater are doctor treating, solutizer treating of gasoline, asphalt cutback blending, lube oil blending, continuous chemical reactions requiring a determined holding time, continuous leaching, etc.

Multicompartment concurrent mixer, Turbo-Mixer Division

flow

HYDROGENATOR The Hydrogenator illustrates the use of turbines for the induction and distribution of gas in a liquid. There are many applications of gas reaction, of which the illustrated unit is a typical example. In this instance, the vegetable oil being hydrogenated would be fed a pure hydrogen gas through the bottom impeller to receive its first scrubbing and absorption. Gas escaping to the vapor space is then reinduced and distributed scrubbed into the oil by the top impeller. The vessel operates as a closed system on pure gas and achieves very rapid hydrogénation time. The impeller, specially designed to give maximum circulation of a gas-liquid mixture, forces the mixture under the hood ring where it is distorted by the stationary deflecting blades and deflected downward into the liquid mass in the vessel. The selfinducing design can be built in sizes with a capacity up to 160 cubic feet per minute of gas induced. The pressure fed type is built in a range of sizes for gas feed capacities up to and exceeding 5000 cubic feet per minute. Hydrogenators are manufactured by Turbo-Mixer Division, Patterson Foundry and Machine Co., and the Cleveland Mixer Co.

Turbo-Hydrogenator, Turbo-Mixer Division

Super Agitator and Conditioner, Denver Equipment Co.

SUPER A G I T A T O R A N D C O N D I T I O N E R The Super Agitator and Conditioner manufactured by the Denver Equipment Co. is used where solids must be suspended in liquid for a variety of treatments such as aeration, leaching, and absorption. The mixing vessel has a central standpipe and wearing plate directly over the propeller. Pulp entering the standpipe over the adjustable weir collar, or through the recirculation ports, is given a circular motion, as it nears the bottom of the standpipe. It is said that mixing of pulp particles and reagent is enhanced greatly by the action of the standpipe. All pulp must pass through the propeller zone for the positive circulation and intimate mixing. The adjustable standpipe controls the flow and helps confine the horsepower consumption to that required for effective treatment of the materials in process. This equipment is available in tank sizes from 200 to 47,000 gallons, requiring drives ranging from l y 2 to 25 hp. V O L . 49, NO. 3

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MARCH 1957

51 A

4 y 2 " DIAl THERMOMETERS

MANUFACTURERS OF STANDARD VESSELS (.A» identified in manufacturer's catalog) Abbe Dispersall mixer Standard mix tanks Rubber cement processor, paste mixer, grease proc­ essor, and standard mix tanks Denver Equipment Co. Super-Agitator and Conditioner Glascote Co. Glass-lined reactors International Engineering, Inc. Type Ο standard mixing tanks Morehouse-Cowles, Inc. Standard dissolver tanks Patterson Foundry and Machine Co. Jet mill, standardized liquid mixers, dissolvers The Pfaudler Co. Glass-lined reactors Struthers Wells Corp. Rubber cement mixer—mixing tanks and auto­ claves Turbo-Mixer Division, General Dissolvers, gas absorbers, and three-stage turboAmerican Transportation Corp. treater.

Made in 3 types to suit any requirements. Rigid stem, wall or flush m o u n t e d , 11 inches of scale read­ ing. Interchangeable with standard indus­ trial separable sock­ e t s . Stem c a n be placed at any angle and case can be ro­ tated to any readable position.

PALMER

SSSS MERCURY ACTUATED

RECORDING THERMOMETERS

Twelve inch die-cast a l u m i n u m case w i t h black or white wrinkle or satin finish. Single or multiple pen con­ struction. Electric or spring wound clock, 24 hour or 7 Day Rev­ olution. Flexible Ar­ mor and bulb of stain­ less steel. Ranges —40 + 950°F or Equivalent in °C.

INDUSTRIAL THERMOMETERS Red-Reading Mercury —Extruded brass case — chrome f i n i s h . Ranges —40 + 950°F or Equivalent in °C.

RED-READING MERCURY LABORATORY THERMOMETERS Thoroughly annealed for permanent accu­ racy. Complete l i n e A.S.T.M. and fractional division types. WRITE FOR CATALOG INFORMATION

PALMER THERMOMETERS, C . n c i n n o h 12 Oh.ο · M E I . o i .

INC. 1500

Abbe Engineering Co. Alsop Engineering Corp. Chemineer, Inc.

Materials of Construction

Selection of the material of con­ struction of an agitator must take into consideration the factors of strength, resistance to chemical cor­ rosion, resistance to wear, and, of course, price. All of these factors combined will indicate the cost of the agitator during its operating life. The manufacturers of agitators have listed as materials of construction essentially all metals and alloys which can be cast and fabricated. These include: Aluminum Bronze Cast iron Hastelloys Monel Nickel Steel

Stainless steels Titanium Steel clad with various metals Lead-covered steel Rubber-covered steel Glass-lined steel Plastic and plastic cov­ ered steel

The agitator shaft must not only have adequate chemical resistance, but it must have strength and rigidity to run without undue distor­ tion under all conditions of load. Whenever it is uneconomical or im­ practical to use a solid shaft, a clad shaft is often the best selection. Lead, rubber, and more recently some of the plastics are used for chemical protection over a steel or stainless steel shaft. Where the shaft is subj'ect to wear at the stuffing box, particularly when the shaft is soft like nickel, a sleeve of Hastelloy or other hardened metal is placed over the shaft at the point of wear. The agitator impeller often is sub­ jected to more abrasive wear than chemical attack, and, therefore, wear life of the impeller is an important consideration. Propellers are stocked by most manufacturers in stainless steels, but are available in all metals and alloys which can be cast. Tur­ bine-type impellers are both cast and fabricated and are available in all

common metals and alloys. Many of the fabricated turbines have re­ movable blades which can be re­ placed inexpensively after deteriora­ tion from chemicals and abrasives. For the most severe conditions of chemical corrosion the glass-lined steel equipment made by the Pfaud­ ler Co. and the Glascote Co. is avail­ able. Because of problems of coating steel with glass, this equipment does not have the variety of impeller shapes which are available in metal. Heat treatment of agitator shafts and impellers should be considered for the best chemical resistance and the maximum freedom from fatigue failure. Acknowledgment

The authors express their appreci­ ation to the manufacturers of fluid mixing equipment, who supplied data and pictures of their equipment for use in this article. References (1) Brumagin, I. S., Chetn. Met. Eng. 53, 110-14 (1956). (2) Lyons, E. J., Chetn. Eng. Progr. 44, No. 5, 341-6 (1948). (3) Lyons, E. J., Parker, N . H., Chcm. Eng. Progr. (December 1954). (4) Perry, J. H., "Chemical Engineers' H a n d b o o k , " 3rd éd., M c G r a w Hill, New York, 1900. (5) Quillen, G. S., Chetn. Eng. 6 1 , 178-224 (1954). (6) Riegel, E. R., "Chemical Process Machinery," 2nd éd., Reinhold, New York, 1953. (7) Rushton, J. H . , Can. Chem. Process Inds. 30, 55-61 (1946). (8) Rushton, J. H., Chem. Eng. Progr. 47, No. 9, 485-8 (1951). (9)

(10) (11) (12) (13) (14)

R u s h t o n , J. H.,

I N D . E N G . C H E M . 44,

2931 (1952). Rushton, J. H., Petroleum Refiner 33, No. 8, 101-7 (1954). Rushton, J. H., Costich, E. W., Everett, H . J., Chem. Eng. Progr. 46, 395-404, 467-76 (1950). Rushton, J. H., Oldshue, J. Y., Chem. Eng. Progr. Symposium Ser. 49, Nos. 4 and 5 (1953). Sacks, J. P., Rushton, J. H . , Chem. Eng. Progr. 50, No. 12, 597-603 (1954). Weber, A. P., Chem. Eng. 60, No. 10, 183-7 (1953).

Circle No. 52 A on Readers' Service Card, page 135 A

52 A

INDUSTRIAL AND ENGINEERING

CHEMISTRY For further information, circle numbers 53 A-1, 53 A-2, 53 A-3 on Readers' Service Card, page 135 A ·