US1291965A - Process for calcining or treating granular material. - Google Patents

Description

. McCGURT. PROCESS FOR CALCINING OR TREATNG GRANULAR MATERIAL.

AFPLICATION FILED 1AN.23, l9l Z. RENEWED MAY 6.1918.

Patented Jan. 21, 1919.

/NVENTOR WTNESSES of which the following is a specification;

` UNITED STATES PATENT OFFICE.

CYRIL DOUGLAS MCCOURT, OF LONDON, ENGLAND, ASSIGNOR, BY MESNE ASSIGNMEN TS,

TO SURFACE COMBUSTION, ING., OF WILMINGTON, DELAWARE, A' CORPORATION OF DELAWABE.

. p a l PROCESS FOB CALCINING OR TREATING GRANULAR MATERIAL.

Specification of Letters Patent.

Patented J an. 21, 1919.

Application filed January 23, 1912, Serial No. 672,808.` Renewed May 6, 1918. Serial No. '232,939.

To all whom it may concem: e

Be it known that I, CYRIL DOUGLAS M c- COURT, a subject of the King of Great Britain, residing at Streatham Common, London England, have made certan new and useful Inventions Relating to Processes for Calcining or Treating Granular Material,

taken in connection with the accompanying drawing, which forms part of the same.

This invention relates especially to processes for calcining or heating or chemcally treating or changing relatvely nfusble granular material bythe surface combuston in connection therewith of an explosve gaseous mixture. The granular or other mate rial under-treatment may be fed forward n a more or less regular stream into which the explosive gascous mixture may be in ected at high speed so. as to cause combuston thereof within the stream of granular material, heating the same to the desired extent and efl'ecting therein or in part thereof the oxidizing, reducing, chlorinating or other Chemical change desired. Such material as limestone orthe like may be calcined in this .way and various ores or ore charges may be smelted or treated to the desired extent, the high temperatures available with accelerated surface combustion making these smelting processes specially effective for high temperature work, although of course by usng explosive gascous mixtures having lower calorific intensity or feeding the material more rapidly past the heating zone the desired regulatio' of the temperature may be effected.

- Many fornis of furnace or other apparatus may be used for carrying out these processes the body portion 4 and if' desired a suitably inclined'hearth 5 may be provided so as to coperate with the arched opposing portion of the casing to form the furnace throat ti, the size of throat and hearth inclination being of course adapted to the particular material to be treated. One or more twyer blocks 7, 8 may be arranged in any way in proper coperation with the throat and as shown may be built into the adjacent portion of the inclined hearth, preferably in such way as to allow their replacement in case of necessity. These twyer blocks may each be formed with one or more twyers or injecting passages 9, 10, 11 through which explosve gaseous mixture and treating gases or mxtures th'ereof may be injected into the stream or charge of material in the furnace.

As indicated these twyers may have the desired amount of explosive or other gascous material supplied thereto' as determined by the in ecting valves 12 regulating their con-- nect1on ,with one or more inJecting pipes 13 which may be connected with any suitable and in the accompanying drawing an illustrative stack or vertical kiln or calcinin furnace is shown somewhat diagrammatica ly in vertical section. The kiln casing 1 may be formed of brickwork or other`suitable material having a lining of the desired refractory character and adjacent the top of the kiln a suitable charging hopper 2 may be provided with which the bell 3 coperates in the usual way. A suitable stack or other draft device such as a suction fan or the like may be connected with the furnace through the exhaust flue 29 in which the draft damper 30 of any desired Construction may be arranged.

The furnace may be 'enlarged somewhat at blower or pressure device14c. As indicated this blower may serve as a mixer by having its suction connection 15 draw the desired amount of air from the air pipel as determined by the air valve 17 while the connected gas pipe 18 admits combustible or fuel gas to the desired extent as governed by the gas valve 19. It will be understood that the valves 17 and 19 should be adjusted to sup ly the combustible gas and air or other com ustion supporter in suitable proportions to form an explosive gaseous mixture and that preferabl i the mixture should be maintained by the lower at suflicient pressure 'in the injecting pipe and twyers to cause it to enter the charge of granulated material in the furnace at a speed greater than the speed of backfiringor the rate of propagation of inflammation through the mixture. Also, if desired suitable gascous or vaporous treating reagents or materials, such as chlorin, hydrochloric acid gas and the like may be supplied through the reagent pipe 20 in amounts regulated by the reagent valve 21. In this way the injected explosive gascous mixture may either contain a suitable excess of air or other oxidizing material or of the combustible gas employed and Chemical gasiform treating reagents of any desired character 'may also be used to the extent desirable with the particular charge under treatment. The heat obtained may also be regulated to a considerable extent by using a combustible gas of the proper calorific intensity, as well as by varying the quantity or rate of supply of the eXplosive mixture. For example, blast furnace gas and some forms of producer gas give low heating values and relatively low furnace temperatures which may be still further reduced when desired by admixture of a suitable proportion of stack gases or other inert gaseous material, while carbureted producer gas, coke oven gas and coal gas have high heating values. WVater gas, carbureted or uncarbureted, petrol air gas and similar hydrocarbon gas and 'other combustible vapors and natural gas and mixtures thereof, all of which are herein referred to as combustible gases may be used for carrying out the process preferably when substantially uniformly mixed with air or other supporter of combustion in approXiuately the *proportions required for perfect or complete combustion. Such a mixture is referred to herein as an explosive gaseous mixture, and this tern is to be understood as neaning agaseous mixture having the property of self propagation of inflammatiom For producing the highest temperature, the supporter of combustion should be oxygen alone and the mixture should contain oxygen and the combustible gas or matter in chemically con'bining proportions at the time of combustion. The miXture may, however, contain an excess of either the combust ble matter or the combustion supporting gas within the limits which determine the property of self propagation, and the miXture may be varied in this respect according to the desired character of the products of combustion; that is, whether it is desired that the products shall be neutral, oxiclizing or reducing; also, the miXture may, of course, contain, as above stated, neutral, or inert, gas so long as the amount of such neutral gas is not suflicient to make the miXture nonexplosive.

The granular material may be fed into the charging hopper of the furnace from time to time in the desired amounts or introduced in a substantially continuous manner in any suitable way, the size of the material being preferably substantially uniforrn and varying from about one-half inch mesh to two or three inch or larger size depending upon the material treated and the size of the furnace which does not of course have to be as large in many cases as the ordinary stack kiln or blast furnace because of the highly accelerated character of the combustion of such eX- plosive mixtures and the facility With which relatively high temperatures can be quickly Secured` thereby. The granular relatively refractory charge is allowed to feed down through the furnace as a substantially continuous traveling stream and in the form of furnace shown this may be accomplished by withdrawing material from time to time from the draw opening or throat and if desired this may be continuously efected by a suitable mechanical drawing device such as the drawing bar 22 which may be provided with a suitable slot 24 coperating with the guide pin 25 while the continuously operated crank shaft 26 having its crank pin 27 engaging a bearing in the bar serves to oscillate its drawing end 23 of any desired shape so as to continuously withdraw material from the draw opening. A continuously traveling stream of granular limestone, for instance may thus be fed through the furnace and calcined by the combustion in contact therewith of explosive mixtures of air and producer gas of the desired character which may be injected through the twyers at suflicient pressure to overcome the resistance of the granular material in the furnace, and to cause the eXplosive mixture to enter the charge at a speed greater than the speed of back-firing. Undesirable discharge of gaseous material from the draw opening may be prevented by the use of a suitable partition such as 31 having a slot through which the drawing bar may pass and having any suitable form of discharge means, such as the pivoted discharge door 32 mounted on this partition so as to allow the granular material to be discharged while preventing undesirable escape of gaseous material or infiow of air. The furnace may be conveniently started by tightly closing the top of the furnace and injecting substantially pure combustible gas through one of the twyers adjacent the throat, such as 9, so that this gas issues from the furnace throattwhere it may be readily ignited. The air valve being then opened, as more air is mixed with the gas the mixture becomes explosve and burns within the granular material adjacent the throat, heating it more and more so as to increase the rate of combustion and establish the accelerated surface combustion of the explosive gases within the same. The draft device of the furnace may then be operated by suitably opening the draft damper 30 and the discharge door 32 may be adjusted to close the throat chamber to the desired extent so that the combustion gases are drawn up through the granular charge and as more explosive miXture is injected through the various twyers the intenser combustion zone is located in its normal position above the twyers or injecting passages, the hot combustion gases passing up through the granular charge above and imparting heat thereto before the stream reaches the active combusw tion zone. Other material, such as ores, may of course be treated in generally similar ways under reducing or oxidizing conditions and with chlorinating or other gaseous reagents to the extent desired and it is of course understood that in some cases additional granular material of a more or less inert character may be mixed with the other portion of the eharge so as to facilitate the surface combustion occurring in connection therewith as'it passes through the furnace. With more readily fusible material, such for instanee as in the smelting of copper ores, the charge may be fed down through the furnace at a more rapid rate and the gases employed may be so chosen and mixed with flue gases or other inert material as to secure the desired smelting temperature by their combustion in connection with the granular eharge which not only acts as the combustion ,aeeelerating material and combustion localizing means, but is also heated and calcined or otherwise treated thereby.

Having described the invention in connection with an illustrative form of apparatus for practising the invention, to the details of which dis'closure the invention is not of course to be limited, what is claimed as new and what is desired to be seeured by Letters Patent is set forth in the appended clains:

1. The process of treating granular material which consists in eedng the same as a eontinuous traveling stream through a furnace chamber, injecting into the charge of granular material at a speed greater than the speed of backfiring an explosive gaseous mixture having combined therewith a gaseous treating reagent capable of combining with said charge, efi'ecting accelerated surface combustion of said explosive mixture within said charge to heat the same and effeet Chemical changes therein, and passing the hot combustion gases through the advancing portions of said traveling stream to gradually heat the material.

2. The process of treating granular material which consists in feeding the same as a continuous traveling stream through a furnace chamber, heating the charge of ranular material in the furnaee chamber y injecting into it at a speed greater than the speed of backfiring an explosive gaseous 'mixture and burning the injeeted explosive mixture within the charge, and supplying with the explosive mixture a treating reagent capable of combining with said eharge and thereby ei'fecting chenieal changes therein.

3. The process of treating solid material which consists in feeding the sane into and through a heating zone, injecting into the eharge of material in said heating zone at a speed reater than the speed of backfiring an exp osive gaseous mixture eonprising a component capable of combining with said charge, eifecting accelerated substantially flameless surface combustion of said explosive mixture within said charge to heat the charge and chemically change a eomponent thereof.

4. The process of treating granular material which consists in feeding the same into and through a heating zone, heating the eharge of granular material in said heating zone by injecting into it at a speed greater than the speed of backfiring an explosive gaseous mixture and burning the injected explosive mixture within the charge, and passing the resulting hot combustion gases through advancing portions of said charge.

5. The process of treating a eharge of granular material which consists in injecting thereinto at a speed greater than the speed of backfiring an eXplosiVe gaseous mixture conprising a component capable of conbining with said charge and effecting aceelerated surface combustion of said explosive mixture within said eharge to heat the same, and passing the resulting hot combustion gases 'through additional portions of said charge.

6. The process of treating solid material which consists in injecting into a porous and permeable bed of said material at a speed grcater than the speed of backfiring an explosive gaseous mixture comprising a component capable of combining with said charge, and burning said explosive mixture within said bed to heat the same and chemically change a component thereof.

7. The process of caleining granular material which consists in substantially continuously feeding a stream of the granular material into and through a heating zone, injecting into said eharge 'within said heating zone an explosive gaseous mixture at a speed greater than the speed of backfiring, and burning said explosve mixture within said eharge and thereby heating and calcining the same.

8. The process of calcinng granular material which consists in injecting into a bed of said ,material an explosive gaseous mixture at a speed greater than the speed of backfiring, and burning the explosive mixture within the bed and thereby heating and calcining the same.

CYRIL DOUGLAS MCCOURT.

Witnesses:

HARRY L. DUNCAN, JEssIE B. KAY.

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