by T. W. Roder
are free of condensation, and a better control over moisture is obtained; over-all power consumption is less; to give data on specialized applica- cooler grinding improves stock classitions of pneumatic conveying in the fication; infestation is reduced to a minimum; and yield, color, and aging chemicals industry. Heated air has been employed to dry are improved. An official of another in transit such materials as ammonium flour company, in discussing the sulfate. Limited cooling has also been power requirements of a pneumatic achieved by the use of refrigerated air. transport system, has drawn an inEfficient blending has been achieved in teresting analogy. He points out that the conveying line. I n this case, dif- it costs no more to run a 200-hp. motor ferent materials, or different batches than to pay a man a t the rate of $1.50 of the same material, are fed into the an hour. Such power represents a conveying line separately. Inert gases large conveying capacity in a pneuhave been employed to avoid the pos- matic system, with considerable savsibility of oxidation in transit or ex- ings in labor costs. I n comparing conveyors using air plosion hazard. The entraining gas is frequently recycled after separation for transport with mechanical confrom the solids. veyors, the most obvious advantage of the pneumatic systems is the freedom Pneumatic conveying offers in conveyor and plant arrangement special advantages for longwhich is provided. By eliminating distance handling the necessity for straight-line conveyAlso of interest to the chemical in- ing, new plant design can be simplified, dustry should be the fact that in- with emphasis on convenience in creased application of pneumatic mill- storing and handling, and advantage ing is developing among American can be taken of ground conditions and flour millers, who have for some time existing rail and highway facilities. been large users of pneumatic trans- In old plants, modernization and adport systems for the bulk handling of ditions of new equipment can be acraw materials and finished products. complished substantially without refI n the milling operation itself, many erence to conveying problems, since unique problems arise due to the materials can be transported anywhere multiplicity of small streams which a pipeline can be placed. Materials must be kept flowing simultaneously can be delivered almost instantly to with varying solids loading. Several remote parts of the plant; they can be installations in this country and in conveyed far beyond the distances Canada have confirmed the previously which are practical with mechanical tried European flow sheets, and pneu- conveyors. Several materials can be matic milling is commercially success- successively conveyed in the same ful in spite of the small streams han- equipment without contamination. dled. Various chemical plant transport Dust nuisances and hazards and meproblems should be re-examined to chanical hazards of many types are determine whether similar specialized eliminated. The number of points to forms of transport equipment might which a single system can deliver matenot be profitably employed. rial is almost limitless. Systems can I n referring to the operation of pneu- be operated by automatic and remote matic conveying in a new plant, a control from a single panel operated milling company executive has re- by one man. Lower maintenance cently stated that installation time, costs are a decided advantage, prospace, and cost are less; stock flow is vided the material is appropriate for accelerated with fewer chokes; spouts pneumatic handling.
DIscussIoN of the use of air as a A conveying medium, started in this column last month, is continued
November 1953
For short conveying distances or elevations, higher equipment and installation costs favor mechanical conveyors. As the conveying distance or elevation is increased, when several changes in direction are required, or when multiple delivery points must be served, this advantage decreases or disappears, and pneumatic conveyors offer progressively greater savings. In a pneumatic conveyor system, the principal items of equipment are common to all systems, and long or complex installations require only additional piping and valves and a relatively small increase in power and air supply * I t is difficult to make a general statement as to the relative power consumption of pneumatic and mechanical conveyors. As with the cost of installation, power requirements for conveying short distances are usually less with mechanical devices. However, the pneumatic systems show progressive increases in power savings with longdistance conveying. The importance of power consumption has decreased within the past years; a t the same time, increasing labor costs have greatly influenced the trend toward the use of pneumatic conveyors. Air-activated gravity conveyor transports flne dry materials
The air-activated gravity conveyor was developed by the Huron Portland Cement Co. and has been marketed by the Fuller Go. under exclusive license for less than 3 years. I t is used for transporting fine dry materials and is made in two forms, the open type, for use under head in a storage vessel, and the closed type, which is a point-topoint conveyor. An inclined porous medium supports a stream of material sufficiently fluidized, by air passing through the medium, that gravity causes tha material to flow. The principal feature of the device which distinguishes it from a previously proposed trough conveyor of German origin is the low permeability
INDUSTRIAL AND ENGINEERING CHEMISTRY
121 A
Materials Handling
i
announces new line of
natural iron oxide
/
MAIL COUPON TODAY
-I---
I
II C. K. Williams & Co. Easton, Pa. East St. louis, 111. Emeryville, CaI.
E. K. WlLLlAMS 8 CO., Easton, Pa., Dept. 2
-
I I
Please send me VVF TECH REPORT giving physical and chemical specifications and list of suggested applications.
I
Name
I
"OUR 75th YEAR"
----
,ij I
I I
Title
Company
Address
1
1
I I 122 A
I N D U S T R I A L A N D E N G I N E E R I N G CHE
of the porous medium. This medium, usually canvas, must have a peimeability such that it ensures uniform distribution of air throughout the length of the air chamber beloir the medium. The niininium slope for a self-cleaning conveyor is usually between 4" and 8 " , and the air pressuie in the plenum chamber from 6 to 15 inches of water. I n a n open-type Airslide under head the pressure used ivill be about 1 to 2.5 pounds per square inch. The range of particle size is a ciitical property of the conveyed material, since fluidization must be effected by low velocity air. d wide variety of materials have been successfully handled by this conveyor, including many pulverized oies and rock products, clays, catalysts, resins, soap products, alumina, dicalcium phosphate, several sodium phosphates, soda ash, sodium sulfate, hydrated lime, and fly ash. The following description will illustrate the versatility of the F-H Airslide conveyor, with its various accessories. when used for conveying and feeding fine dry materials fiom bins and delivering to an automatic weighing scale, and finally to process bins in predetermined quantities. Air from the inlet end of the Airslide enters the cylindrical bin with a cone bottom and promotes the flow of material t o the Airslide, mhich, in t u n , conveys the material to a R-eigh hoppei associated irith the scale. The flow gate is normally set t o control the rate of f l o ~from the storage bin t o the n-eigh hopper. It can also serve as a manually operated cutoff gate. The automatic quick cutoff gate, a t the dischaige end of the Airslide, which is actuated by an air motor, cuts off the flow of material t o the weigh hopper r h e n the scale beam is in balance. The operation of the air motor is controlled by a solenoid opeiated air ralve actuated by the scale beam. The Airslide, m t h accessory equipment, serves the dual purpose of conveying t o and feeding the scale, at a controlled rate, without the use of complicated equipment. The fluidization of material a t the discharge of the bin prevents arching a i d subsequent breakdowns in the bin vvhich ~ ~ o u lnormally cl result in starving the scale, follon-ed by flooding. Distribution of material over the length of a storage bin can be accomplished by means of an Airslide ISTRY
Vol. 45, No. 11
with side discharge valves, which divert the entire stream, or any part of the stream, into the bin. Discharge of material from such a bin is normally difficult to accomplish with conventional types of equipment. By applying an open-type Airslide to the bottom of the V-bin, the entire contents of the bin can be discharged without the use of compartments, hoppers, gates, or power-driven conveying equipment. The open-type Airslide discharges directly into a closed-type conveyor which delivers the material t o a desired point. Below the hopper underneath the scale, a conveyor Airslide delivers weighed quantities to remote destinations for further processing. The Airslide may be used t o maintain a constant head of material over one or more volumetric feeders, particularly screw feeders. Such arrangements have proved of great value in reducing the fluctuations in feeder screw discharge caused by irregularities in delivery to the screw. Airslide conveyors have a numbei of operating features which contrast with mechanical conveyors. Thc streams may be divided a t wil and can be passed around corners They may be started and stoppec under full load conditions. After tht feed is stopped, they are substantial13 self-cleaning, leaving only l/S to l / inch of residue on the porous medium The capacity is very high, and thr power requirement very low. Po, example, a 12-inch-wide Airslide con veys 250 tons of pulverized limestonc per hour a distance of 125 feet. Thi air for this is supplied by a 5-hp. fan which represents about one eighth o the power required for a screw con veyor. The principal disadvantage of thl Airslide conveyor is the rsquiremen for an inclination. A 4' slope mean about 7 feet of headroom per 100 fee of conveyor. The particle size rang of the transported material is critica and the conveying channel must b vented in long installations. Acknowledgment
The author is grateful t o Alfred M Sadler, director of research for th Fuller Co., for his discussions of t h subject contained in the foregoing. Correspondence concerning this column will 1: forwarded promptly if addressed to the autho Editor, INDUSTRIALAND ENQINEERIN OHEMISTRY, 1155--16th St., N . W . , Washingtc 6 , D. C.
November 1953
INDUSTRIAL AND ENGINEERING CHEMISTRY
123 A
?
T h e r e s no middle ground with
TANTALUM .
*
e
its use is either
pointless or imperative known properties of Tantalum, as well as countless “case histories” of its application, clearly define where this unusual acid-proof metal should be used. There’s n o guesswork in d e c i d i n g on T a n t a l u m . . . n o c o m p r o m i s e of its natural advantages. If you are processing hot or strong acid solutions, if you are making a pure product in which equipment contamination or side reactions cannot be tolerated, Tantalum might be wisely employed. Taking a closer look, if the multiple costs of product spoilage, equipment maintenance and repair, shutdowns, and labor dislocations outweigh the single cost of Tantalum, Tantalum is indeed imperative. Call in a Fansteel engineer to help you decide on your possible need for Tantalum. @he
Use Tantalum with economy for most acid solutions and corrosive gases or vapors except H F , alkalis, or substances containing free SOa.
Ask f o r a c o j y of our free booklet “Acid-Proof Tantalum Equipment for Chemical Operations ’’
and ALUMINUM PRODUCTS..
.
a r e fabricated by Littleford t o meet t h e d e m a n d for specialized equipment i n t h e Chemic a l Industry. To produce this exacting equipment t a k e s experience a n d skilled c r a f t s m e n ; t h i s i s w h e r e Littleford definitely fits into t h e picture. Since 1882 Littleford has developed c r a f t s m e n to lay out, shear, f o r m a n d weld products of all descriptions, T a n k s , (plain or code), Bins, Hoppers, Troughs, Vats, Covers, Tables, Special P a r t s and Sub-Assemblies. Do not overlook t h e f a c t t h a t Littleford t a k e s a definite
FOR INDUSiRY
FANS TE EL ME TA LLURGI C A L C 0RPO RAT1 O N N O R T H C H I C A G O , I L L I N O I S , U.S.A.
&ALITTLEFO
32404C
124 A
INDUSTRIAL AND ENGINEERING CH
MISTRY
Vol. 45, No. 11
C H E C K THESE 3 WAYS Y O U C A N S A V E WITH THIS MULTbPURPOSE I N S T R U M E N T Here is the most sensible idea you've ever seen in a recorder or controller-an instrument you can change as your instrument needs change, that you can add to, subtract from, or whose functions you can increase or decrease at little or no expense. Save money when you add new functions by adding only those new assemblies needed.
Save time-delays by making changes on the job site without returning to factory.
Save money on inventory. Parts are interchangeable, fit all Gotham Convertible recorders. You can service a whole group with a minimum stock of basic elements.
What you can do with the Gotham Convertible Depending on the chart size of the recorder (6", 9" or 12") you can have a 1-2-3 or 4 pen recorder with 14 pressure, temperature and time operation combinations or a recorder-controllerwith 38 possible pressure, temperature, and time combinations. L
.
I
I
SELF-CONTAINED PORTABLE RECORDER
RECORDING PSYCHROMETER
RECORDING HYGROMETER
A portable recorder whkh has o carrying handle, legs ond retaining holder for capillary and bulb. Built from Gotham standard elements, Interchangeablewith other Gotham instruments. 6': 9" and 12' chart sizes. Mercury, Vapor or Pressure Activated. Spring or electrk chart drive. See Catolog 400.
Incorporates the same highly occurote and responsive thermal systems a n d contolns 011 o t h e r Gotham standard convertible features. Wet ond dry bulb type. Motor-driven s u c t i i fan. 12" chart sire. Catalog 400.
A 2-pen recorder of the wet and dry bulb type. Mercury or Vapor Actuated. 9" and 12" chart s1zes.Avoiloblewithvariety of wet and dry bulb assemblies depending on application. Catolog 400.
GOTHAM INSTRUMENTS
Keep everything under control with Gotham
Division of Amerkon Machine and Metals, In Dept.2, 233 Broadway New York 12, New York Please send me o copy of your 0 Catolog 100Industrial Thermometers 0 Catolog 200Diol Type Thermometers '0Catalog 500-Controllers 0 Catalog 400--Recorders, 0 Have your representative call. Psychrometers, Hygrometers No obligation.
I
I
Name-
1
Company
I
city
Title
Address
November 1953
INDUSTRIAL AND ENGINEERING CHEMISTRY
Zone-State
125 A
WOW
HIGH PRESSURE-HIGH TEMPERATURE HOT WATER PIPING SYSTEM
to plan a
For etRcient space and water heating
-
and for numerous processing needs as well a high pressure-high temperature sys. tem offers several distinct advantages over a steam system.
-
Often operated a t pressures up to 215 psi, with a corresponding temperature of
388"F,a HP-HT system of this type eliminates the need for pitch, drainage, or traps and provides a greater amount of heat transmission for a given pipe size. Moreover, it requires no feed-water treatment and, when used for processing services, eliminates large pressure drops due to sudden load conditions. The hot water is generated i n a shell and tube heat exchanger by means of high pressure steam from either turbine extrac. tion or exhaust. Unit heaters on the HPHT lines provide for space heating requirements and a shell and tube heat exchanger supplies warm water for lava-
tories, kitchens, and processing which requires moderate temperatures. When used with accumulators, this system eliminates the need for taking additional steam directly from the steam generating source and, thus, provides a better plant heat balance.
Prevent Backtlow
M N
3 2
IR I
2
Fig. 204 IBBM Gate Fig. 280.U Bronze Gate Fig. 962 Bronze Swing Check Fig. 280 Bronze Gate Fig. 1010 Cost Steel Gat"
I Fig'
__I_
Return Main Shutoff Makeup Pump Shutoff Prevent Backflow Makeup Meter Shutoff Thermostatic Valve Chlltn#
I Condensate Line Shutoff 1
Consultation with accredited piping engineers and contractors is recommended when planning any major piping instal. lation.
To save time, to simplify planning, to get all the advantages of Jenkins special. ized valve engineering experience, select all the valves you need from the complete Jenkins line. It's your best assurance of lowest cost in the long run. Jenkins Bros., 100 Park Ave., New York 17. Complete description and enlarged diagram of this layout free on request. Includes additional detailed information. Simply ask for Piping Layout No. 68.
2&@? 126 A
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 45, No. 11
