US1390335A - Parallel-current calcining-kiln - Google Patents

Description

H. E. BROOKBY. PARALLE'L CURRENT cALclNlNG KILN. `APPLICATION FILED MAR. 10, 1919.

Patenteasept. 13, 1921.

' tion, viz.,

process mentloned the temperature at which trate,

ed to me HARRY E. BROKBY, 0F EVANSTON, ILLINOIS.

PARALLEL-CURRENT CALCINmG-KILN.

specification of'tetterrsratent. Patented Sept. 13, 1921.

I Application led March 10, 1919. Serial No. 281,772.

To all whom it concern.: Be it known that I, HARRY citizen of the United States, residin E'. BRookBY, a at -Evanston, in the county of Cook and tate of Illinois, have invented a certain new and useful Improvement in Parallel-Current Calcining-Kilns, of which the following 1s a specification.

My invention relates. to common' direction or parallel current calcining kilns, and the object of the invention vis to provide a kiln so constructed that high initial temperatures may be employed, so as to reduce the time of heat treatment to a minimum and yet make it possible to so accurately control and dis' tribute the heat as to avoid volatilization or fusion of substances inthe charges that are easily volatilized or easily fused. To illusin Patent vNumber 1,297,078, grant- Marchv 11, 1919`,I have described a process for obtaining a water soluble potassium compound from hydrous, potassium bearing silicates, and it is important in that process to avoid the volatilization of any appreciable amount of the potassium comound. For commercial reasons it isdesirable to fire the kiln with powdered coal instead of employing liquid or gaseous fuel.

vBut powdered coal requires quite a high maintain combustemperature to properly C. whereas in the about 1500o the reaction should take place (and to which it must be limited during the reactive period if the process is to be efficiently carried out) is much lower than this. My purpose is to make it possible to deal with high initial temperatures, and specifically to use powdered coal as fuel, and at the same time make it possible to efliciently practice p rocesses having heat limitations such as typified in the process described in my said patent.

Other objects of the invention are to provide means for completing the heat treatment effectively and inl a minimum perio of Atime and with a minimum amount of fuel; to render the process continuous; to

make'it possible for the apparatus to remain long. in service without requlring repairs ;l

Figure 1 is a longitudinal '.vertical section` tudinal axis.

d be drawnV back from the hed of the 'complete apparatus omitting the lower or far end of the kiln proper.

vF 1g. 2 is a. transverse sectional elevation on the line 2-2, Fig. 1.

.Like numerals denote like parts in both vlews. E Y

` In the form selected to illustrate the invention, the kiln proper consists of a shell comprlsing a lining 2 of fire brick er other refractory material. The shell is supported so as to be able 15o-'rotate about its longitudinal axis, 1t being suiicient for the present purpose to show but one of the supports, which consists of an annular track 3 encircling the shell and running upon a flanged roller 4 journaled in a bearing 5 y'mounted upon a pedestal 6. The axisof the shell is tilted downward from the head or receiving end, and suitable means (not shown) are provided for rotating the shell about its longi- In this artit is common to employ the term countercurrent kilns for those in which the gases move inone direction and thecharge moves in the opposite direction.

Where the gases and the charge movev through the kiln in the same direction, the apparatus is referred to as a parallel current kiln. My apparatus is a parallel current kiln.

The head end of the' shell is closed by a non-rotary hood 8 which has an annular Bange 9 inclosing and making a running fit with the shell. The hood consists of refractory -material and is mounted upon a truck framelO having four flanged wheels 11, 11 adapted .to travel'upon rails 12, 12 arranged .longitudinally of the kiln. The rails aire mounted upon a suitable foundation or pedestal 13 and :the construction and arrangement are such that when repairs are necessary the entire hood with the parts car- Tied-thereby (presently to be described) may g end of the shell a distancesufficient to Aafford access thereto.

By preference holes 14 are placed in the hood to afford means for introducing secondary air, also to facilitate inspection.

The hood has a comparatively large opening near the bottom into which .fits a combustion chamber 15. By vpreference this consists of a cylindrical -metallic casing 16 having a lining 17 of refractory material.

and the combustion chamber 15 move with `While the dimensions may of course be varied, in a kiln whose shell is about 6 feet in diameter the combustion chamber may appropriately be approximately 3 feet in diameter and 6 feet long and extend about 2 feet more orless into the shell. Although the combustion chamber makes a comparatively tightfit in the hood 8, it is desirable to afford it sufficient play to enable it to be rotated by hand about its longitudinal axis occasionallyfor example, once every day or so to equalize the wear.

Fuel, preferably in 'the form of powdered coal, is introduced into the combustion chamber through the head v19 thereof, by means of a pipe 20. Peep holes 22 are formed in the head of the combustion chamber, these being normally closed by suitable plugs 23.

'llhe material which is to be heat treated is introduced into the kiln by a continuous feed apparatus consisting preferably of a worm or screw 26 working in a cylindrical casing 27 and mounted upon a shaft 28 driven by a pulley 29. The material is fed into the casing 27 by a hopper 31 which in the best form is mounted upon and removable in unison with the casing 27. Said casing is supported by the hood 8 of the kiln with the result that when the hood is withdrawn from the end of the kiln both the feed mechanism it. A storage bin 35 is supported in fixed position by stationary beams 36, 36 or other suitable supports. The flow lof material from the bin to the hopper is controlled by a shut-.off valve 37 of any suitable design.

rllhe casing 27 extends a short distance into.the shell of the kiln, preferably for a distance of 6 to 12 inches. Secured vto shaft v28 and spaced a few inches from the inner end of casing 27 is a deflector 40. This deiector has rotating vanes`or paddles which brush aside, from ol'l'l the top of the vcombustion chamber, the material which would otherwise tend to collect there.

In operation, the shell 1, 2 of the kiln is started rotating and the supply of fuel turned on. When powdered coal is used, as'

particularly contemplated in my apparatus, combustion is started in chamber 15 by withdrawing one of the plugs 23 and inserting conveyer.

plug replaced. As soon as the valve 37 is slid to open position, the material to' be heat treated will enter the 'hopper'31 and be directed by it into the casing 27 of the screw x The screw is rotated continuously and hence the process is continuous.

As above stated, to insure maintenance of combustion of powdered coal, a temperature in the neighborhood of 1500o C. must be maintained, which temperaturewould tend to volatilize and fuse many substances and thus interfere with the proper carrying on of such processes as I have above referred to. But with my apparatus the combustion chamber is long enough to enable the gaseous contents to acquire a more or less uniform temperature throughout their volume before they 'leave the combustion chamber. Furthermore, the cold material falling upon the outside of the combustion chamber tends to cool it slightly, thus reducing the temperature of the emerging gases somewhat below the highest temperature in the chamber. rllhe result is that by this arrangement the cold material is introduced at the side of the entering `blast and the temperature of the blast tends to be reduced somewhat and the temperature of the cold material raised somewhat before the. gases and the charge come into contact with each other. Another advantage in thus introducing the material at the side of the blast is thatit eliminates dust losses. Due to handling, some of the .material becomes powdered by the time it leaves the feed mechanism. By keeping this away from the blast it prevents the blast from" blowing the powder orl dust out through the kiln. lin my apparatus also, the preheating period-that is, the period during which the material is being raised to the temperature at which the reaction will occur, occurs in that portion of the kiln which is hottest; and the critical portion of the process occurs in those parts of the kiln which are relatively cooler and where the temperatures may be more accurately controlled.

l bring the inner end of the combustion chamber a considerable distance in through the hood and bathe the surface of the combustion chamber, so to speak, with the incoming material which is to be treated. Such operation causes the temperature of the gases of combustion .to be reduced somewhat before coming into contact with the charge. By the same token, the temperature of the charge is elevated somewhat, with the result that it does not have to be raised so high when it does meet the gases before the reaction commences to take place. In other words, there is a tempering or equalizing of the temperatures to a certain extent before the two things mingle, thus not only saving time but precluding the danger of volatilizing some of the valuable constituents of l the charge.

My apparatus is therefore particularly adapted for processes such as the one herein above mentioned, and in addltion the process 1s continuous and efficient and when repairs become necessary access to the` parts may easily be obtained by simply rolling back the hood 8 on the tracks 12. As all the opconveyer being within said shell.

eratingvparts except the rotating kiln itself are mounted upon the hood, repairs become a comparatively simple matter, for when the hood is drawn back access is afforded to the inner end of the parts on the hood as lwell as to the interior of the body vof the kiln. By rotating the combustion chamber about its axis once every day or two, any Swear which ma occur from the constant dropping of t e material ontothe top of the combustion chamber maybe distributed over the entire inner end of the combustion chamber and hence the wear becomes practically a negligible consideration. The heat and Veloclty of the burning fuel passing through the combustion chamber tends to wear and channel it. By rotating the .combustion chamber occasionally, the wear becomes equally distributed.

Having thus described my invention what I claim as new and desire to secure by Letters Patent, is

1. A common direction, calcining kiln having a rotary shell, a combustion chamber projecting into the shell, and means for introducing the charge into the shell and passing lit over a portion o surface of the combustion chamber for raising the temperature of the charge and lowering the temperat re of the gases of combustion before the two mingle in the shell.

2. A common direction, parallel lcurrent calcining kiln having a rotary shell, a combustion chamber projecting into the shell, means for introducing into said combustion chamber fuelbelow the temperature of ignition, means for introducing the charge into said shell and passing it over a portion of the surface of said combustion chamber parallel current,

.3. A common direction parallel current calcining kiln having a rotary shell, a combustion chamber projecting into the shell,

and means for dropping the charge onto the projecting portion o-f the combustionA chamber. .j

4. A parallel current kiln having a rotary shell provided with a hood, a cylindrical combustion chamber arranged substantially lengthwise of the shell for directing the hot gases of combustion into it, and a screw conve er mounted in the'hood and arranged paral el and adjacent to the combustion chamber for delivering a'continuous chargev into the shell, the delivery end of the screw above the combustion chamber and terminating short ofthe delivery end thereof, so as to drop the material to be treated on to the top of the combustion chamber.

5. A parallel current kiln having a rotary chamber at a f the bustion chamber 6. A parallel current kiln having a rotary l shell, a hood movable longitudinally toward and from the head ond of the shell, and adapted to form a closure therefor, a c0111- bustion chamber for introducing hot gases into the shell, and continuously operating means for feeding the charge into the shell, said combustion chamber and the feeding means being mounted upon the hood.

7. A common directionl parallelcurrent kiln having a cylindrical rotary shell, a

hood closing the head thereof, a combustion chamber mounted in the hood and extending a considerable distance into the shell from the inner face of the hood, and means for delivering the charge onto the combustion oint between the inner' face of the hood and) the inner end of the combustion chamberA the charge is raised land thetemperature j of the products of combustion are reduced before the two mingle in the shell.

8; A parallel current calcining kiln having a cylindrical rotary shell,'a hood closing the. headv end thereof, a combustion chamber extending an ap reciable distance into 'the shell from the inner face of the hood, and a screw conveyer mounted inthe whereby the. temperature ofl hood and'having its inner end located above the combustion chamber and projecting yabout half-as far into the kiln as the combustion chamber does, said combustion chamber being cylindrical, and the screw conveyer being located centrally above the combustion 5chlamber for discharging the material onto the top of it.

9. A parallel current calcining kiln having a rotary shell, a hood forming a closure for the head end of the shell, and a cylindrical combustion-chamber mounted in the hood and rotatableabout its longitudinal.

axis.

10. A parallel current calcining kiln having a rotary shell, a hood forming a closure for the head end of the shell, a cylindrical combustion chamber projectin a considerable distance into the head en of the and a conveyer adapted tol dro the material to be treated onto the top o? the inner end of the combustion chamber, said combeing rotatable about its longitudinal axis to 'distribute the wear caused by the dropping material.

11. A common direction parallel current kiln having a cylindrical rotary -`shell, a hood closing the head thereof, a combustion shell,

chamber mounted in the hood and extending a considerable distance into the shell from the inner face of -the hood, means for intro-' ducng into said combustion chamber fuel below the temperature of ignition, and means for delivering the charge in an approximately continuous stream f onto the combustion chamber at a poinl between the inner face of the hood and the inner end of the combustion chamber and causing the 10 charge to pass down around the surface of said combustion chamber.

ln witness whereof l have hereunto subscribed my name.

HARRY E. BROOKBC

Images