US 2511709 A
Description (OCR text may contain errors)
June 13, 1950 c. E. HEMMINGER CARBONIZATION BY DIRECT HEATING IN A ROTARY RETORT Filed Oct. 26. 1946 F A Wm mm a. ma uw 1c 7 b H 4 ow P 2 s PC .I
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Charles E. Hemmirzger Urn/embar- Clbberrzer g efllc'ient carbonization temperatures.
Patented June 13, 1950 CARBO TION BY DIRECT HEATING IN A no'rsnr nr'roa'r Charles E. Hemminger, Westfield, N. 1., amino:
to Standard Oil Development Company, a corporation of Delaware Application October 26, 1946, Serial No. 705,841
The present invention relates to the carbonination of carbonaceous materials and, more perticularly, to an improved method and apparatus for producing volatile carbonization products and highly reactive smokeless coke ag lomerates in the form of lumps or spheroidal briquettes from carbonizable fuels such as all types of coal, lignite, brown coal, asphalt, oil residues and sludges, petroleum, cellulosic materials, including lignin, etc.
Prior to the present invention, spheroidal coke briquettes and volatile carbonization products have been produced by a process utilizing the property of certain strongly coking coals to pass through a lastic state and to develop agglutinating tendencies within a definite range of elevated temperatures. I I
In this process, fines of strongly coking coals having a particle size of minus in. and less, which may be preox idized in any conventional manner, are passed through an inclined rotary kiln heated externally by a countercurrently' flowing heating gas to a final temperature of about 850-900 F., which is slightly above the minimum carbonization temperature of the coal charge. The coal, while undergoing carbonization, passes through the plastic state at about 600.-800 F. The rotating motion of the kiln causes the plastic agglutinating particles to agglomerate to form spheroids or balls of low temperature coke, having diameters of about 1-6 in. 0081 gas, light oil, tar and acidic liquor are the volatile carbonization products which are removed from the kiln by suction.
Coke fines obtained, in addition to the coke balls, are returned to the kiln to establishthe proper ratio of dry and agglutinating materials required for ball formation. On the other hand, liquid carbonizable materials such as various pitches or other heavy residues may be injected into the kiln and carbonized on less volatile coal fines placed therein.
, The indirect heat supply through the kiln walls in combination with the large size of the coal aggregates to be heated to carbonization temperatures leads to excessive temperature requirements in the heat ng jacket and seriously limits the carbonization temperature. This results in undesirably low yields of volatile carbonization.
In actual operation, the temperatures permissible for practical construction materials are i't'isuilicient to beat the kiln charge indirectly to It has, therefore, been necessary to admit an oxidizing gas, such as air. into the discharge end or the kiln so as to generate additional heat by a partial combustion of solid and/or volatile carboniaction products, resulting likewise, in product losses.
Further losses or low temperature ta'r result from excessive tar-cracking taking place during the relatively long residence time of the volatile carbonization products in the high temperature zone of the kiln.
,The present invention overcomes the aforementioned diillculties and affords various additional advantages. These advantages, the nature of the invention and the manner in which it is carried out will be fully understood from the following description thereof, read with referenceto the accompanying drawing.
It is, therefore, the principal object of my invention to provide an improved method of producing' volatile carbonization products and spheroidal coke agglomerates from carbonizable materials.
A more specific object of my invention is to provide an improved apparatus for producing spheroidal coke briquettes and volatile carbonization products from carbonizable materials.
Other objects and advantages of my invention will appear hereinafter.
In accordance with my invention, a direct and highly eillcient heat transfer to the carbonaceous material undergoing carbonization is accomplished by injecting a burning combustion mixture of fuel and oxidizing gas into the rotating carbonization zone, at a point removed from the solid charge, and withdrawing volatile carbonization products from the carbonization zone immediately upon their liberation. In this manner, radiantheat is provided for the coking operation resulting in more eflicient heat utilization and increased liberation of distillation products. The short residence time of the distillation prodnets in the high temperature zone limits cracking to a minimum so that the yield of volatile carbonization products is substantially increased.
I have found that the rapid removal of the distillation products from the carbonization zone and at least qualitative simultaneous separation of these products from gaseous products of the heatgenerating combustion may be accomplished in a highly efllcient manner by utilizing the solids bed of carbonaceous materials undergoing carbonization to establish an appreciable pressm'e diflerentlal between the gaseous combustion products and the volatilized distillation products. For this purpose, the gaseous combustion products are passed through and withdrawn from the rotary carbonization zone above the layer of solids undergoing carbonization and at substantially atmospheric pressure while the distillation products are withdrawn from points beneath the layer of solids undergoing carbonization and at a slightly reduced pressure which may be generated, by suction; on the lines withdrawing the distillation products. 4
In this manner, a negative pressure differential is established across the solids layer from its top to its bottom and distillation products of increasing purity. with respect to their content of combustion products, are withdrawn from points within the solids layer of increasing proximity to the low pressure withdrawal lines.
By properly regulating the pressure din'erential across the solids layer substantially quantitative recovery of volatile distillation products containing considerably less than 30% and nor-. mally less than of gaseous combustion products may be accomplished. Pressure difl'erentials varying from about 0.4 lb. per sq. in. to about 3 lbs. per sq. in., as they may be readily estab- 1 lished across solids layers of about 1 ft. to 4 it, are suitable for this purpose.
In accordance with the preferred embodiment of-my invention, a series of perforated tubes,
1 ing plate 28, supported by tubes 28 adjacent to.
closed at one end and open at the other, is arranged close to the inner wall of the rotary kiln, extending preferably overthe entire length of the-kiln, and evenly distributed over at least a substantial portion of its circumference. At least one stationary suction line, arranged outside the kiln, cooperates with the open ends of the perforated tubes in succession as the kiln ro tates to withdraw volatile products from any tube while the latter is covered with solids undergoing carbonization. A burning combustion mixture is introduced, preferably into an upper section of the free space of the rotary kiln, from a stationary burner means arranged outside the kiln at one end thereof while combustion gases leave through a stationary discharge pipe at the other end of the kiln.
If desired, one or more of the suction lines may cooperate with tubes out of contact with the solids charge of the kiln so as to draw hot combustion gases containing residual oxygen through said tubes. In this manner, tar and coke deposits maybe burnt oil. and clogging of the tubes prevented.
Highly reactive coke balls of the conventional physical and chemical characteristics may be recovered from the lower end of the inclined rotary kiln in any manner known per se.
Having set forth the general nature and ob- Jects. my invention will be best understood from the more detailed description hereinafter in which reference will be made to the accompanying drawing wherein Figure 1 is a, sectional elevation of equipment suitable to carry out a preferred embodiment of my invention, taken along line AA on Figure 2:
Figure 2 is a cross-section taken along line B- B on Figure l; and
Figure 3is a cross-section taken along line C-C on Figure 1.
Referring now in detail to the drawing, the
tively, is provided with stationary end plates I2 and i4. End plate l2 covers the feed end of kiln I O and carries in its upper section suitable means, such as a pipe or burner head It for supplying a burning combustion mixture or hot flue gases to kiln I 0. A feed line II for liquid carbonizable material, which may have the form of a perforated pipe extending over the entire length of kiln I 0, may be supported by the middle sections of plates l2 and M. The top section of plate i 2 carries a feed line 20 for solid subdivided carbonizable material.
Plate [4 supports, in its upper section, a flue gas withdrawal pipe 22. An orifice 24, in the bottom section of plate I, serves the recovery of solid carbonization product.
A series of tubes 2| having suitable perforations 21 and extending preferably over the entire length of kiln II is arranged on or close to the inner surface of kiln II and so supported by the latter that tubes 2. rotate around the axis oi'kiln Ila Tubes 28 are closed at their ends adjacent to plate I4 and open at their ends adjacent to plate l2. However, the open ends of tubes 20 contact plate i2 so as to eifect an, at least, partial seal of their open ends over a major portion of their circular path. An annular sealand contacting plate i2 rotates together with kiln II and tubes 2'.
Plate I2 is provided, in its lower section, with a recess 30 which extends along thecircumference of plate l2 over a distance equal to or greater than the distance between two adjacent tubes 2|. The width of recess 30' may correspond approximately to the diameter of a tube 28. Recess 30 is sealed from the kiln inside by sealing plate 2. except for the openings of such tubes 28 as communicate with recess 30 at any time. i A suction shoe 32 connected to a suction line II, for thewithdrawal of volatile carbonization products from kiln I0 through tubes 26, covers and seals recess 30 on the outside of plate i2. A recess 38 similar to recess 30 may be provided in an upper section of plate l2 to cooperate with a suction shoe 38 similar to suction shoe 32, and a suction line 40, to withdraw combustion gases from tubes 20, if desired.
Tubes 20 are preferably covered by bai'iles 42 over their entire length in order to prevent solid particles from piling up around tubes 20 and plu ing the perforations 21.
In operation, a carbonizable solid such as a carbonization coal having a particle size of preferably less than in., say mostly between 8 and mesh, is supplied-to solids feed pipe 20 by any conventional means such as an aerated standpipe, a pressurized feed hopper, a mechanical conveyor, or the like (not shown) and enters the slightly elevated feed end of kiln l0 behind plate i2. As a result of the rotary motion of the kiln, the coal piles up on the side of the kiln about as shown at 45 in Figure 2. The downward slope of the kiln position causes the coal to move toward the discharge end of kiln l0 and discharge orifice 24.
A burning fuel mixture such as a mixture of fuel gas or finely divided fuel oil with air and/or oxygen is supplied through burner head IS. The radiant heat supplied by the combustion mixture from burner head it should be suflicient to maintain the lower sections of kiln l0 and its charge at a suitable carbonization temperature of about 850-1400 F., sufllcient to liberate the desired amounts and types of volatile carbonization products. Heating gas temperatures of about 1000 I tois'!',arenormally adequstei'orthem in commercial operation. The bulk of the line gas is withdrawn throughpipe I! at normal or slightly reduced pressm'e.
Suction is applied from line It to suction shoe 0! andsuchtubesil asarecoveredbythesolids undergoing carbonisation. As a result. volatile carbonimtion products are drawn through periorations 21 into said tuba I0 and removed from kiln I. at the rate at which they are liberated. Perforations 21 are spaced along tuba 20 so as to uniformly carry away the products as formed. since the vapor evolution is greatest in the middle section of the kiln, about 00% of the perioratiom are arranged in the middle third of the pipe. while only about of the perforations are distributed over that third or the tube length which gun-roe ticles carrying the liquid sprayed thereon agglomerateduringthecarbonisationtreatlnentto formspheroidalcokebriquettes inthemanner describedabove.
WhileI have describedabovespeciiicmeam includingsealingph ellreceallandsuction sheet! for removing volatile distillation products throughtubafldtshouldbeunderstoodthat my invention is not limited to thae specific meambutisintendedtocover'anysuitable means for establishing a pressure diilerential across solidspilelisoastomakepossiblearapidselectiveremovaloi'distillationvaporsiromthe hi h temperature carboniaation zone. For example, tubamaybe provldedadiacent-to their.
open ends with automatic valves 50 which are openwhileatube ltisincontactwiththesoiids is adjacent to the coal feed end and about 30% f II. The pressure in suction line ",is preferably so regulated that small amountasay up to about 10%, of combustion gases from the upper sections of kiln II are drawn together with the volatile carbonization products through solids.
pile 45 into tubes II. In this manner, a substantially quantitative withdrawal of the volatile carbonization products from kiln II is assured. A suction pressure of about 0.5 to 4 in. mercury is generally suitable for this purpose at a greatest solids layer thickness above any pipe of about 1 to 4 ft. Baides l2 prevent solidsparticles from entering or plugging perforation ll of tubes II.
The carbonaceous solids lines. while undergoing carbonization, agglomerate as a result of the tumbling motion on their path through kiln I. to form spheroidal coke briquettes which are withdrawn through orince 24 and collected and. if desired, cooled in a conventional coke receiving device II. The volatile carbonimtion products are passed from line I to a usual product recovery system (not shown) for-the production of coal gas, light oils. tar and chemicals.
The deposition of tar and/or coke in tuba '20 cannot entirely be avoided. In order to prevent plugging of tubes 2' by these deposits, it is desirable to provide means for the removal of such depositsfrom tubes 28, which will not appreciably aiiect the yield of desirable distillation prod ucts. To accomplish this, the combustion mix- 1 ture fed through burner head It may contain av slight excess of oxygen, of say about 10th 40%,
and suction may be applied to suction line ll -of kiln l0, after having been freed of volatile distillation products by suction means I! and II. The oxygen in said oxidizing gas will, at the prevailing high temperatures ofv the upper kiln section, burn off a substantial proportion of the carbonaceous tube deposits and thus prevent an undesirable accumulation of such deposits.
When a liquid carbonizable feed such as crude oil, heavy residues, pitch. molten asphalt or the like is used in place of a solid carbonizable charge, the liquid feed is introduced through pip I. and sprayed on a finely divided, preferably carbonaceous, solid introduced through feed pipe 20. (L'oke, petroleum coke, low volatility coals or carbonizable materials may be used as solids. The carbonizable or non-carbonisable solid parpile ll and/or while communicating with suction linellandwhichareclosed overtheree mainder of the circular path of tubes 20. I
These valves may. take the form of slide valves in the open end of tubes 20, which are spring operated, the spring pressing the slide clued. Whenthetubesareadjacenttoshoafland llcamspressopentheslidevalvestoallowcom munication between the tuba and the respective shoes Other modifications of the means for wiu-ldrawing vapors from tuba Ilmay occur to those skilled in the art without deviating from the spirit or the present invention.
My invention will be further illustrated by the following specific example.
' Type of operation I tier,
nven Wt. Per Cent of Coal Hating Value of Gas B. t. u./cu. it 380 I00 Nitrogen Content of Gas .per cent- 5 sum 0. Pitch in Tar. v. wt. per cent.. 67 40 Amount of Heat Consumed per lb. of
Total Solids l'feed -.B. t. 11-. 550 450 The above data demonstrate the advantages of my invention with respect to tar yield, heating value of product gas and heat economy.
While the foregoing description and exemplary operations have served to illustratespeciflc applications and results of my invention, other modifications obvious to those skilled in the art are within the scope of my invention. Only such limitations should be imposed on the invention as are indicated in the appended claims.
1. The process of producing spheroidal coke briquettes and volatile carbonization products from carbonizable materials at elevated carbonization temperatures which comprises subjecting said carbonizable material in the form of a pile of subdivided solids to a tumbling motion adapted to promote the formation of spheroidal agglomerates of said subdivided solids within a confined 'sp'ace, introducing heating gases having a temperature substantially above said carbonization temperature into said confined space above said pile in amounts sufilcient to heat said pile to said carbonization temperature, establishing a negative pressure differential across said pile from its top to its bottom, withdrawing volatile carbonization products from said space beneath said pile, withdrawing spent heating gas from said space above said pile, and recovering spheroidal coke briquettes from said confined space.
2. The process of claim 1 wherein said pressure diiferential is so controlled that not more than about 10% of spent heating gas, based on withdrawn volatile. carbonization products, is forced across said pile from its top to its bottom.
3. The process of claim 1 wherein said volatile carbonization products are withdrawn by suction through a plurality of passages, individual passag :5 being operated alternatingly for the withdrawal of volatile carbonization products.
4. The process of claim 1 wherein said carbonizable material is a solid.
5. The rocess of claim 1 wherein said carbonizable material is liquid at the carbonization conditions and is sprayed on a subdivided carbonaceous solid,i'orming said pile. I,
6. The process of claim 1 wherein said heating gases are generated by the combustion of a mixture of fuel and oxidizing gas in said space.
7. The process of producing spheroidal coke briquettes and volatile carbonization products from carbonizable materials at elevated carbonization temperatures which comprises subjecting said carbonizable material in the form of a pile of subdivided solids to a tumbling motion adapted to promote the formation of spheroidal agglomerates of said subdivided solids within a confined space, introducing heating gases having a temperature substantially above said carbonization temperature into said confined space above mid pile in amounts suflicient to heat said pile to said carbonization temperature, establishing a negative pressure differential across said pile from its top to its bottom, withdrawing volatile carbonization products by' suction from said space beneath said pile through a plurality of individual length of said kiln, having perforations a...
tributed over at least a substantial portion 11 their length, and having each one open and closed end, stationary suction means outside said rotary kiln, said suction means being connected to said open ends, means for altematingly es tablishing and interrupting communication between said suction means and the open ends of such of said tubes as pass a desired section of the, circular path of said rotary kiln, means e'c centrically arranged for introducing a heating medium into the upper inner space of said rotary kiln, said means being supported by oneof said cover plates above the horizontal center plane of saidkiln, means supported by filo other of said cover plates above the horison'til center plane of said kiln for withdrawing spent heating medium and means supported by first mentioned cover plate for supplying divided solids to said rotary kiln, said named cover plate being provided with an orifice tor the withdrawal of spheroidal coke briquetw.
9. The apparatus of claim 8 which comprises bailie plates supported by and within said rotary kiln, arranged above and close to each of said tubes, the length of said baiiie plates approximate ing the length of said tubes and the width of said baflie plates exceeding the diameter of said tubes passages alternatingly operated in rotation for the withdrawal of volatile carbonization products, passing an oxidizing gas through passages not operated for products withdrawal, at a temperature not below the ignition temperature of car-.
bonaceous deposits within said lines, withdrawing spent heating gas from said space above said pile and recovering spheroidal coke briquettes from as while failing to bridge completely the free space between two adjacent tubes said baiile plate; having a free back edge in the direction of the kiln rotation and a front edge connected to said kiln in front of said tubes, in said direction, infa manner preventing solids from piling up directly on said tubes. 1
10. The apparatus of claim 8 which comprises means for feeding a fluid to a middle section of said rotary kiln.
11. The apparatus of. claim 8 wherein said means for alternatingly establishing and interruptingcommunication between said suction means and the open ends of such of said tubes as Pass a desired section of the circular path of said rotary kiln comprises a suction shoe as a part of said suction means outside said first mentioned plate, said first mentioned plate having a recess. opening into said suction shoe and a sealing means sealing said recess except for the openilig of such of said open ends as communicates with said suction shoe.
12. The apparatus of claim 8 wherein said means for alternatingly establishing and inter rupting communication between said suction means and the open ends of such of said tubes as pass a desired section of the circular path of said rotary kiln comprises spring and cam-operated slide valves arranged in said tubes adjacent to their open ends.
- CHARLES E. HEMMINGER.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PA'I'ENTS Number Namei I Date 1,413,779 Randall Apr. 25, 1932 1,538,490 Randall May 19, 1925 1,602,819 Jakowsky Oct. 12, 1926 1,622,722 Jakowsky Mar. 29, 1927 1,677,784 Kemp July 17, 1928 1,765,702 Roser June 24, 1930 1,814,463 Trent July 14, 1931 2,108,649 Calderwood Feb. 15, 1938