US1401212A - Rotary kiln - Google Patents

Description

S. J. VERMAES.

ROTARY KILN.

APPLICATION FILED APR. 26, 1920.

Patented Dec. 27, 1921.

3 SHEETS-SHEET 1- (Imam/tog lannes l/erm if #1 (91mm S. J. VERMAES.

ROTARY KILN.

APPLICATION FILED APR-26,1920.

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STEFANUS JOI-IANNES VERMAES, OF DELFT, 'NETHERLANDS, ASSIGNOR TO SYNDIGAAT ELECTRO-S'IAAL, OF THE HAGUE, NETHERLANDS.

ROTARY KILN.

Specification of Letters Patent.

Patented Dec. 27, 1921.

Application filed April 26, 1920. Serial No. 376.759.

To (all w ham it may concern? Be it known that I, SrnrANUs Jormnnns VERMAES, a subject of the Queen of the Netherlands, residing at Delft, in the Prov-' ince of South Holland, Kingdom of the Netherlands, have invented certain new and useful Improvements in a Rotary Kiln, of which the following is a specification.

The rotary kiln which comes more and more into use in the metallurgical and chemical industries because it has manyadvantages frequently cannot be used when the gases produced by the heating ofthe kiln must be kept out of the interior of the kiln.

The object of the present invention is to enable the rotary kiln to be employed in cases where it is essential to prevent the combustion gases from mixing with the gases which are used in the kiln or produced therein. According to the invention this is obtained by heating the kiln with gaseous fuel which is burnt in channels constructed in the wall of the kiln.

These channels may be constructed in the form of straight lines definitive of a. cylindrical surface or in the form of helical lines having a greater or smaller pitch in order to increase the length of the channels. By varying the cross section ofthe channels and thereby varying the velocity of the fuel gases or by varying the thickness or the material of the wall which separates the channels from the interior of the kiln, it is possible to regulate the heating of difierent parts of the kiln to difi'erent temperatures.

The combustion in the channels may be conducted in parallel current or in'counter current with the movement of the charge in the kiln. In the first case the inlet of the channels is at the charging side of the kiln and most of the heat will be given ofi to the first part of the kiln. In the other case the channels must begin at the discharge end of the kiln, and the largest part of heat will be transmitted at the end of the kiln. The method which is preferable depends on the reactions which take place in the kiln. Of course it is also possible to use combinations of the two principles of heating and also to heat only a part of the length of'the kiln.

When combustible gases are produced in the kiln they may be used as fuel for heatlng the kiln by making a communication between the inlet side of the channels and the interior of the kiln.

. When the gaseous fuel is taken from outslde, this may be done by means of an annular channel extending around the rotary kiln, with which the fuel channels in the wall communicate at their inletends. I Because the heating of the kiln accordmg to the invention is effected indirectly, it is of great importance that no crusts are formed on the walls. Such crusts would de crease the transmission of heat and become superheated themselves. In many cases they would therefore gradually increase in'thickness and hinder more and more the reaction in the kiln. i

To prevent this drawback a scraper may be provided extendingover the whole length of the kiln. Such a scraper should not rotate with the kiln and consequently would scrape oil always a fresh part of the wall. It is advantageous to give a rotating motion to the scraper in opposite direction to the kiln and about an eccentric axis.

The kiln is suitable for several reactions especially when a gas is evolved which should be obtained in non-diluted condition or when the reaction of air or fuel gases or the products of combustion on the charge should be prevented.

The kiln may be used especially for the reduction of finely divided iron-ore by granular carbonaceous material (cokes, coal, charcoal and the like).

The accompanying drawings disclose one form of kiln constructed in accordance with the invention.

In the drawings:

Figure 1 is a vertical longitudinal section of the rotary kiln with the connections to further apparatus for the reduction of grained iron ore by granular carbon.

Fig. 2 is a cross section along the line A A of Fig. 1 perpendicularto the axis of the kiln.

Fig. 3 is a cross section of a part of the wall provided with heating channels.

Fig. 4: is a cross section along the line B B of Fig. '1.

5 is a vertical longitudinal section of the discharge end of another type of the rotary kiln.

Fig. 6 is a front. view of the charging side of the rotary kiln according to Fig. 1.

Fig. 7 is a side view of a part of the wall of the rotary kiln in which the outer covering and the'exterior layers are removed:

showing another form of the channels in the furnace wall.

In the drawings 1 is the rotary fixed back covering; 4t is a preheating kiln for the ore, in this case a directly heated rotary kiln'of known type;'5 is a valve for feeding regularly equal partsofpreheated finely divided ore into the kiln 1, without; making gas communication between; the parts 1 and 1. The valve 6 is of a similar construction and discharges the reducedore into the conduit 7 which may communicate, forv instance, with a melting andrefining kiln. Thekiln 1 is rotated in the way usual for rotary kilns;.the rotating mechanism be-- in indicated generally at 100-in Fig. 1.

Ere-heated ore.is discharged from the kiln 4 by the valve 5 through the conduit 22 into the kiln. A helical conveyer 23 introduceslgranular carbon. The regular int'r'oduction of ore and carbon andthe rotary motion of the kiln assure a goodinixtureof both substances. necessary or desired, a suitable flux maybe introduced with the ore or with the carbon. The conveyer23 is covered in such a way, that the kiln is shut oil gastight from the atmosphere.

The mixture of ore and carbon is now brought to. reactionin the kiln and the ore is reduced to. iron and the carbon burns chiefly to carbon inonoxid. The iron is removed through the valve 6, The'produced gas has a .veryhigh calorific value and is used for heating the rotary kiln. Tothis 'endit is conducted into the channels 11 in the wall of the kiln. Tn the wall are also channels 12 by which air is introduced and the lower part of the covering Qis provided with an approxlmately senal-circularrib 21 which dischargejinto the inlet ends oithe channels 11 and cause combustion thereln. In the construction 1llustrated 1n Fig. 1

the gas channels 152 are exterior of the chan- I nels 11 and pass through the largest part of the kiln wall, so that the air is preheated before it enters the gas channels.

I The combustion is effected in parallel current with the movement ofthe charge. in order to maintain as nearly as possiblethe same temperature inthe whole kiln,.to eliect thegreatest transmission of heat in thebeginning where itisrequired bylthe endothermic reaction of reduction and to pre- 7 vent super-heating of the reduced iron which would lead to melting and undesired carbon icing. V V

To prevent solid material from coming into the channels 11 which would plug them.

of il -section. over which the ore and the carbon fall directly upon the nterior of the rotating wall. V r

nel 111 and the interior of the kiln. the periphery of the channel 111 are small interior kiln'wallis an annular channel 111 in the rotary partof the kiln, in which the channels 11 begin} As the rib'2l only covers N the lower part of the covering 2, there is part of" the kiln; 2 is a fixed front covering; 3 a" ample'gas communication between the chan- Near partitions slanting in the direction of rotation, by which cups 112 (Fig. 6) are formed in such a way, that, when eventually solid material comes into-the channel it. istaken upward and. falls there upon the rib 211over' which it slides into the kiln.

The gas-tight joints; between the kiln 1 andv the coverings 2a11d3, are obtained by water-cooledannular' spaces24 and34, on

the coverings 2 and 3, over which slide surfaces which are connected to the rotary part 1, which surfacesmay be pressed against.

these annular. spaces while lubrication with oil maybe applied. i p

' The wall of the kiln consists of aniron or steel shell,whichfisrotated in the usual way'uponrollers', and in which are three layers 15', .1 1 and 13 of fireproof material.

The inner layer should come up to the highestrequirements. not only regarding its fire-proof quality but especially also inechanlcal resistance against the-friction and the scraping-action of the .ore and the scraper. r q k.

Tn thelayer 13 "the heating channels 11 are formed, In the layer 14 are the airchannels 12 (Fig.

The discharge ends 17* of the heating channels 11 .in thewall discharge into an annular channel 18, which does not rotate and is eccentric with regard to the rotary kiln'and has a discharge at itstop (Figs. landl). H Q

The said ends 17 of thechannels 11 are radial and go through the layers 1e and 15 and the shell. In order notto weaken these too inuch the section of these discharge channels is elongated with the long side parallel to the axis of the kiln,- while the section of the channels 11' is also elongated but with thelongiside in the direction of the periphery of the circle in order to increase the heating surface.

The interior of thejchannel 18 is of lireproot material 181, which encircles and fits against the shell of the cylinder which reinrorced inthis place. In the construction illustrated, frict on s ,prevented by roller-bearings on both sides.

The inlet ends 16 of the: channels are made in a similar wa'y to the discharge ends through which gasmay be introduced or Withdrawn, according to whether more or less gas is formed than is necessary for heating the kiln 1. In thisv manner it is possible to introduce, for instance, water gas or producer gas when the kiln is put into action. action, more gas is produced with most ores than is necessary for the heating of the kiln. The surplus may beused for melting and refining the produced iron, the pre-heating of the ore and other purposes.

A scraper 8 extends through the whole kiln 1. This scraper consists of a steel shaft 83 of hexagonal section having a bore 8% for the passage of cooling water therethrough, said shaft extending through the covers 2 and 3 which are made gas-tight at such points. Upon this shaft aremounted the sockets of a series of T-shaped scrapers 82 of Moncl metal, the sockets and the scrapers proper fitting close against each other and the .whole being kept together by means of end pieces upon the shaft by the covers 2 and 3. The open spaces between the sockets and the scrapers proper are filled up with fire-proof non-conducting material 81 to prevent as far as possible any loss of heat. r

The scraper 8; is rotated in the opposite direction to the kiln, so that the scrapers 82 act against the wall of the furnace and scrape oil all crusts. The scraperv may be moved in any suitable way. (Not shown.)

Fig. 5 represents another construction of the rotary kiln according to which the heat ing is effected in counter current with the movement of the charge; the gas is not taken directly from the interior of the kiln and the air is not .(or only very little) preheated. The annular channel a in Fig. 5 is fixed and is shut off gas tight against angle irons provided upon the shell ofthe rotary kiln. The shutting oifmay also be effected in any other suitable way.

In order to obtain an evenly distributed heating, it is advantageous to construct the heating channels on helical lines around the kiln as indicated in Fig. 7.

In he form of kiln illustrated in Fig. 1 the heating and air channels run along gtraight lines which define a cylindrical surace.

When now the draft in the upper part of the kiln is stronger than below, the upper channels will receive more gas and the heating will be most intense in the upper part. Though the rotation in the, kiln diminishes more or less both drawbacks, yet they are important. If, however, the air and fuel channels are wound in helical lines around the cylinder, both drawbacks are wholly removed, the heating is everywhere equal and the distribution of gas is the same in all channels.

When the furnace is well in' I Fig. 7 shows how. this maybeobtained byforming channels of slanting direction in the inner layer ofbricks of'the wall, the

said channels registering with'the channels in adjacent bricks. The helical form of the channels has also theadvantage of increasing the length the more so when (as represented in Fig. 7) the channels are moreor less curved;

. What I claim is: r

l..A rotary: kiln comprising a gasetight barrel, means for rotating said barrel, com-. bustion. channels in the wall of said barrel, and means for supplying gas and .air for combustion in said channels for heating the kiln without said combustion gasesentering the interior thereof.

2. A rotary kiln comprising a gas-tight barrel,'means for rotating said barrel, combustion channels in the wallof said barrel combustible gas and air channels in the wall of said barrel for supplying. exterior air'to said combustion channels for'the firing of the gas and the heating of the kiln.-

3. A rotary kiln comprising a gas-tight barrel, means for rotating said barrel, a pin rality of combustlon channels formed in the longitudinaliwall of said barrel and extending from one end of said 'wallytoward the other end, and means, for supplying combustible gas and air to said channels.

I e. .A rotary kiln comprisinga gas-tight exhausting said combustion gas external to the kiln, i

5. A rotary kiln comprising a gas-tight barrel, means for'rotating said barrel,' a plurality of longitudinal combustion channels in the wall of said barrel connected with an external source of combustible gas, and. air channels in the wall of said barrel connecting the said combustion channels with the exterior of the barrel to supply air to said combustible gas to maintain combustion in said combustion channels.

6. A rotary kiln comprising a gas-tight barrel, means for rotating said barrel, a plurality of helically arranged combustion passages in the wall of said barrel, an annular channel in said barrel connecting the interior of the latter with said combustion channels, and air passages in the wall of the barrel supplying external air to said combustion tubes.

7. A rotary kiln comprising a gas-tight barrel, means for rotating said barrel, a plurality of helicallyarranged combustion supplying gas and air to said channels in the wall of said barrel connected With an external source of combustible 'gas, and airv channels-1n the Wall of sa1d barrel connecting-said combustion channels with :the exterior ofthe barrehtof'supply airv to. sald gas to mamtam combustion.

18.,A rotary kiln comprising a gas-tight barrel, means for rotating said barrel, a plurality of combustion channels in the Wall of said barrel, said channels being of varying sectional-area'in diiferent parts ofthe barrel to varythe heat distribution, and means for combustion therein.

9. A. rotary kiln comprising a gas-tight barrel, means for rotating said barrel, a plurality of combustion channels in the Walls of said barrel and extending along the length thereof, and means for supplying combustible gases'to said channels .in parallel current with the movement of the charge passing through-the kiln. v 7

110, A rotary kilncomprising a gas-tight barrehmeans for rotating said barrel, a pluralityofchannels in the Walls of said barrel, andextending' along the length of said barrel and means for supplying combustible gases to said chambers in contra-flow to the movement ofthefcharge passing through the 11. A rotary kiln comprising'a gas-tight barreh'means for rotating said-barrel, a phi-.-

rality of combustion channels in the Wall of said barrel, said channels being connected with anexternalsource of combustible gas by means of aifixed annular channel encircling the barrel, and means for supplying air for the combustion of the gas in said channels for heating the kiln.

12. A rotary kilncomprising a rotating gas-tight barrel having combustion channels in the Wallv thereof, means for supplying fuel gas and-air to said channels for heatingsaidbarrel, and a scraper arranged adjacent the interior of thewallfof thebarrel for removmg scale;

-13. A rotarykiln comprising a rotary gastight barrel having combustion channels in channels for r the kiln.

the Wall thereof, a scraper rotatably mount-J ed on: an eccentric axis within: said barrel,

and means for rotating saidscraper oppos 'sitely to the rotationof the barrel.

channels in the wall ofv the drum for combustion' in the said passages Without said 7 combustion gases entering the interior of r 15. A'rotary kiln: comprising a rotatably mounted barrel having combustion channels in 1ts Wall, meansfor'feedlng fuel gas and air. to said channels, fixed end-coverings for the barrel forming gas-tight joints therew th, f eed openings 1n one end-coverllig,

means for feedingmaterials'through said openings into the kiln hile maintaining it air-tight, a rib on said end-covering reachingabove the lnterlorsurface of the rotating drum, and an'annular channel'in the drum connected with the combustion channels and formed with partitions slanl'zingv in the direction of rotation to form cups.

16. A rotarykiln"comprising a rotatable barrel having combustion channels in "its .Wall, means for rotating said barrel, and fixed end-coverings having Water-cooled faces making gas-tightjoints With the rotating barrel.

r 1 '17. A rotary kiln comprising a barrel With an nterior Wall composed of three; layers of slabs of heat-resisting materiahsaid slabs I having grooves in their'faces to form chair nels in said interior Wall, and means for su.p-

plying gas and air to said channels for combustion therein to heat the kiln.

In testimony Whereofl have hereunto set my hand. Y i

STEFANUS JOHANNES VERMA-AES.

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