US3794483A

US3794483A - Process for delivering fuel and air to a rotary reduction kiln

Info

Publication number: US3794483A
Application number: US00302606A
Authority: US
Inventors: E Rossi
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1972-10-31
Filing date: 1972-10-31
Publication date: 1974-02-26
Anticipated expiration: 1991-02-26
Also published as: DE2354604A1; JPS4976707A; ZA738405B; NL7314873A; OA04566A; DE2354604B2; NO134768B; ES420116A1; AU465274B2; BR7308532D0; FR2205182A5; AU6187173A; CA989611A; NO134768C; IN140689B; JPS5232723B2; IT996352B; GB1448263A; SE402128B

Abstract

A PROCESS AND APPARATUS ARE DISCLOSED FOR DELIVERING FUEL AND AIR TO A ROTARY REDUCTION KILN WHEREIN BOTH THE FUEL AND AIR ALTERNATELY FLOW THROUGH THE SAME NOZZLE.

Description

Feb. 26, 1974 R0551 3,794,483

PROCESS FOR DELIVERING FUEL AND AIR TO A ROTARY REDUCTION KILN Filed Oct. 51, 1972 2 Sheets-Sheet l Feb. 26, 1974 v RO$$| 3,794,483

PROCESS FOR DELIVERING FUEL AND AIR TO A ROTARY REDUCTION KILN Filed Oct. 51, 1972 2 Sheets-Sheet 2 United States Patent Office 3,794,483 Patented Feb. 26, 1974 3,794,483 PROCESS FOR DELIVERING FUEL AND AIR TO A ROTARY REDUCTION KILN Eugene F. Rossi, Wauwatosa, Wis., assignorfo Allis Chalmers Corporation, Milwaukee, Wis. Filed Oct. 31, 1972, Ser. No. 302,606

Int. Cl. C22]! 5/12 U.S. CI. 75-91 2 Claims ABSTRACT OF THE DISCLOSURE A process and apparatus are disclosed for delivering fuel and air to a rotary reduction kiln wherein both the fuel and air alternately flow through the same nozzle.

This invention relates to rotary kilns used for such purposes as reducing iron ore to a lower state of oxidation having nozzles mounted on the outer surface of the kiln projecting radially through the kiln shell for injecting air and fuel into the kiln at axially and circumferentially spaced locations along the kiln length. In particular the invention relates to such a rotary kiln wherein the same nozzle can be utilized to alternately provide both the fuel and the air to the kiln charge.

In the prior art rotary kilns are known wherein a plurality of nozzles are provided through the shell of the kiln to admit air and fuel into the interior or ore reduction chamber of the kiln. A charge of ore is provided in the reduction chamber and it is reduced to a higher state of iron.

Examples of such prior art kilns are disclosed in U.S. patents 1,216,667 issued Feb. 20, 1917, U.S. 2,091,850 issued Aug. 31, 1937 and U.S. 3,182,980 issued May 11, 1965.

In the prior art kilns fuel and air are delivered through the nozzles by piping supported on the exterior of the kiln or on the interior of the kiln. This piping is connected to the nozzles for injecting the fuel and air into the reduction chamber. In the prior art a mixture of both fuel and air has been admitted through the nozzles at the same time or fuel is admitted through one nozzle and air admitted through a different nozzle.

In certain instances it is desirable to admit only one fluid through a nozzle when it is beneath the charge and only the other fluid when the nozzle is above the charge. As an example it is desirable in certain instances to admit fuel to the reduction chamber through nozzles as they pass directly beneath the bed of the charge whereby the fuel flows directly into the charge. When this nozzle has moved beyond the bed of the charge the fuel is shut off and no fluid is passing through the nozzle. At the same time air is admitted to the reduction chamber above the charge through additional nozzles. Before these air nozzles pass beneath the bed the air is turned off so that no fluid passes through these nozzles as they pass beneath the bed. From the above it can be seen that quite a large number of nozzles are required. It is not unusual to have as many as 300 nozzles in a rotary kiln of a 150 foot size. Further more these nozzles are exposed toextremely high temperatures in the range of 2000 degrees Fahrenheit. While the fluid is flowing through a nozzle the fluid itself has a tendency to cool the nozzle. However when no fluid is passing through the nozzle it approaches the temperature within the reduction chamber thereby reducing the effective life of the nozzle.

It is therefore the intention and general object of this invention to provide a process for reducing ore and apparatus for practicing the process wherein the number of nozzles required is reduced by one-half and the temperature of the nozzles is reduced by admitting fluid through the nozzles during a substantial part of the kiln rotation.

An additional object of this invention is to provide a process wherein both fuel and air are admitted through the same nozzles at different points of rotation of the kiln.

A more specific object of the subject invention is to provide a process for reducing ore of the hereinbefore described type wherein the fuel and air are admitted through the nozzle at a speed which is greater than the speed of flame propagation of a combustible mixture of the fluid flowing throuhg the nozzle.

Another object of the invention is to provide a process for a rotary ore reducing kiln of the hereinbefore described type wherein the reducing fuel is admitted through a nozzle while the nozzle is beneath the ore charge and alternately air is admitted through the same nozzle while the nozzle is above the ore charge.

An additional object of the subject invention is to provide a rotary kiln with fluid distribution means which alternately delivers fuel or air to each nozzle at preselected points of rotation of the nozzle relative to the kiln charge.

A more specific object of the subject invention is to provide a rotary ore reducing kiln of the hereinbefore described type wherein valve means connect both the fuel and air to a single nozzle for selective alternate flow of both fluids through the same nozzle.

An additional object of the subject invention is to provide a kiln of the hereinbefore described type wherein a single valve is utilized to alternately direct either fuel or air through the same nozzle at selected points of rotation of the kiln.

These and other objects of the subject invention will become more fully apparent as the following description is read in light of the attached drawings wherein:

FIG. 1 is a side elevation of a portion of a kiln constructed in accordance with the invention;

FIG. 2 is a section taken along the lines II--II of FIG. 1 and additionally showing means for operating the fluid distribution means;

FIG. 3 is a cross-section of a particular type of valve showing one inlet port connected to the outlet port;

FIG. 4 shows the same valve as FIG. 3 with both inlet ports shut off; and

FIG. 5 shows the same valve with the other inlet port connected to the outlet port.

Referring to the attached drawing the kiln shown herein for purposes of illustration is provided with an elongated cylindrical body portion 6 which defines a cylindrical reduction or combustion chamber 7. The shell or inner wall 8 of the kiln may be constructed of any suitable refractory material such as firebricks. Any well-known means may be provided for supporting and rotating the kiln. Since such means form no part of this invention and are well known in the art they are not shown herein. A charge of ore generally designated 9 is shown in FIG. 2. A main burner 11 is provided at the right-hand end of the kiln to preheat the kiln.

A plurality of circumferentially spaced and axially spaced nozzles 12 are provided about the surface of the kiln opening into the chamber 7. These nozzles may be constructed of any conventional manner and are preferably constructed in accordance with my co-pending application entitled Nozzle for Rotary Kiln. The nozzles may be supported by the outer kiln plate 13 in any conventional manner such as by welding. A plurality of circumferentially spaced fuel and

air conduits

14 and 16 respectively are also supported about the surface of the kiln. Any conventional means in the form of a manifold (not shown) may be provided to deliver fuel and air to the

conduits

14 and 16.

A fluid distribution means generally designated 17 connects the respective fuel and air conduits to the associated nozzles. This fluid distribution means may comprise a plurality of valves or as shown herein for purposes of illustration may comprise a single three-way 'valve generally designated 18 and fluid transfer conduit means 19 connecting the outlet of the valve 18 to the associated nozzles 12. The particular valve 18 shown herein for purposes of illustration is more clearly defined in FIGS. 3 through 5. The valve consists of a valve body 20 having two opposed

inlet ports

21 and 22 and a single outlet port 23. A rotary plug 24 having a passageway 26 in the configuration shown is rotatably supported in the valve body and has a valve stem 27 attached thereto and extending to the exterior of the valve body.

In many instances of reducing iron ore the fuel from conduit 14 is delivered through the nozzles 12 while they are beneath the charge 9. Such fuel is only admitted while the nozzles are beneath the charge and air from conduit 16 is admitted through the same nozzles while they are above the charge 9. To this end means are provided to operate the valve 18 to effect this alternate delivery of fuel and air through each of the nozzles.

A preferred relatively inexpensive mechanical operating mechanism for controlling the flow of fuel and air into the chamber 7 is shown most clearly in FIG. 2. It should be understood that while this control mechanism is perfectly acceptable other means for operating the fluid distribution means 17 could be employed such as a solenoid valve operating hydraulic or air actuators. Referring to FIG. 2 a frame generally designated 28 is provided about the kiln 6. This frame 28 is provided with four strategically located trip means 29, 31, 32 and 33.

Each valve shaft 27 is connected to a cam plate 34 which is supported for rotation on brackets 36 connected to the exterior of the kiln for rotation therewith. Each cam plate 34 has four

cams

37, 38, 39 and 41 supported about the periphery thereof. The cams are spaced substantially 90 degrees from one another and are located to engage a particular trip means when they are in the radially outermost position relative to the axis of the kiln.

The operation of the apparatus will now be described. In order to assist in understanding the operation the trip means are identified on the drawings starting with the trip 33 and progressing in the direction of rotation of the kiln as air-oiffuel-onfuel-ofl and air-on. As a starting point assume that the cam 38 is about to contact the fuelon trip 29. This causes the valve 18 to move to the position shown in :FIG. connecting the fuel conduits 14 to the associated nozzles through the transfer conduits 19. As the kiln continues to rotate the cam 39 will contact the trip 31 and the valve 18 will be in the OE position shown in FIG. 4. As the kiln continues to rotate the cam 41 will contact the trip 32 and the valve will be in the position shown in FIG. 3 permitting air to pass from the conduits 16 through the connected nozzles 12. Further rotation of the kiln causes cam 37 to contact trip 33 moving the valve 18 to the opposite position as that shown in FIG. 4 interrupting the flow of air to the nozzles. This process of alternate admission of air and fuel through the nozzles will repeat as the kiln rotates.

From the above it can be seen that both fuel and air are alternately admitted through each of the nozzles 12. This results in a reduction in the number of nozzles required by one-half over those kilns which have a separate nozzle for fuel and a separate nozzle for air. Furthermore because fuel or air is flowing through each nozzle during a substantial part of the revolution of the kiln the nozzle temperature is reduced due to the relatively cooler fuel or air passing through the pipes on the exterior of the kiln. It should be understood that the control mechanism could be so arranged that the air flowing through the nozzle is only turned off as the fuel is turned on thereby having no period of time that a fluid is not flowing through the nozzles.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for reducing a charge of ore in a rotating kiln having nozzles open to the interior of the kiln comprising the steps of:

(a) delivering a reducing fluid through those nozzles that are beneath said charge at a speed greater than the speed of flame propagation of a combustible mixture of said reducing fluid and an oxidizing fluid;

(b) interrupting the flow of said first fluid through said nozzles when they are no longer beneath said charge;

(0) delivering an oxidizing fluid through said nozzles when they are above said charge;

((1) interrupting the flow of said oxidizing fluid through said nozzles when they are again beneath said charge; and

repeating steps (a) through (d) while the reduction process continues whereby the temperature of said nozzles is lowered because of the passage therethrough of said reducing fluid and said oxidizing fluid during a substantial part of the kiln rotation.

2. The process according to claim 1 wherein said reducing fluid is a reducing gas and said oxidizing fluid is air.

References Cited UNITED STATES PATENTS 2,091,850 8/1937 GOhIe 432-109 X ALLEN B. CURTIS, Primary Examiner J. F. NIEBLING Assistant Examiner U.S. Cl. X.R.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,794,483 Dated February 26, 1974 lnventoflg Encrene F. -Rossi It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 29, "first" should read reducing Signed and sealed this 2nd day of July 1974' '(SEAL) Attest: v H

EDWARD M. FLETCHER,JR. C.'MARSHALL DANN I Attesting Officer Commissioner of Patents