US1948472A - Carbonization process - Google Patents

Description

H. O. LOEBELL El AL Feb. 20, 1934. I

CARBONI ZATION PROCE S S Filed Feb. 14, 1950 2 Sheets-Sheet 2 fJ-wvwntozs HENRY O. LOEBELL ALBERT L. KLEES III Patented Feb. "20, 1934 1,948,472 CARBONIZATION rnocass Henry 0. Loebell, Malba, and Albert Ludwig Klees, Long Beach, N. Y., assignors to Henry L. Doherty, New York, N. Y.

Application February 14, 1930. Serial No. 428,297 15 Claims. (01402-26) The invention relates to processes for carbonizing solid carbonaceous materials in thin layers,

and more particularly it concerns the carbonization of fuel mixtures containing bituminous 5 materials in which the fuel mixtures are subjected to pressure and/ or to a briquetting operation prior to, during or subsequent to the carbonizatlon step.

Various methods are already known for th carbonization of solid fuel mixtures in thin layers.

An example of such a process which makes possible the successful production of high grade smokeless fuel briquets, is disclosed in the copending application of Henry 0. Loebell for United States, Patent Ser. No. 347,802 filed March 18, 1929.' The invention therein described provides for the carbonization of fuel mixtures in thin layers while holding the. same under determinate pressures.

The necessary carbonization a rotatable idler member.

.The fuel mixture is fed in an even layer upon the endless belt and the latter is then moved to bring the fuel into engagement with the rotor by means of traction between the belt and rotor. .The degree of the pressure developed upon the fuel layer being carbonized is varied by modifying the tension in the endless, fuel-carrying belt,

While the process and apparatus as described in the aforementioned copending application yields satisfactory results when utilizing certain types of fuel mixtures, it has been found that when other mixtures,-and especially those containing a large percentage of volatile constituents,-were processed, there was sometimes a tendency for a porous cell structure to develop in the briquets and for the briquets in some instances to stick slightly in the molds and to fail to discharge uniformly from the belt. more, dueto the considerable period of time dur- Furtherened crusts to form on the upper surface thereof; and this crust would fracture when it came into pressing engagement with the rotor, thus giving the finished briquet a roughened appearance.

Sometimes these cracks would appear in the briquets after carbonization and during the cooling thereof.

It has now been discovered that it is possible to overcome these various difficulties in connection with carbonization operations involving a process of the type mentioned. Any tendency of the briquetted fuel mixture to stick in the mold after carbonization may be neutralized by compacting the thin layer of fuel through application of a relatively low degree of prepressure to it immediately after its distribution upon the carbonizing belt and before any substantial part of it has been brought to a carbonization temperature. Furthermore this sticking may be prevented by preheating the mold or belt to a carbonization range, prior to charging the layer of fuel onto the hot belt. This permits the rapid formation of a surface film of carbonized fuel upon the belt, which film is weak and brittle, and permits the carbonized briquet later to be readily discharged from the belt. 1

The undesirable formation of an upper crust on the fuel layer prior to contact thereof with the rotor is preferably prevented by the employment of a radiation screen of suitably-reenforced refractory material, so disposed as to prevent direct radiation of heat from the hot rotor to the fuel until the latter is closely adjacent the rotor.

While the preforming and compacting of the fuel layer upon the conveyor belt may be accomplished by either a roller or a flat plate or equivalent device, it is desirable in any event that the device be adapted to give the free surface of the fuel layer the same general contour as the cylindrical surface of the rotor. It will thus serve both to give satisfactory density to the raw fuel-and a corresponding increase in density to the carbonized briquet,--as well as to so shape the upper surface of the fuel layer as to substantially minimize any tendency to cracking thereof upon contact thereof with the grooved surface of the hot rotor. Where the material therefore is compressed by the preforming device and shaped so that its top surface conforms with the cylindrical surface of the rotor, the latter is not forced to break through this upper surface of the fuel which may have been caked already to some degree, especially in the absence of a suitable radiation screen.

In the accompanying drawings showing certain preferred forms of apparatus adapted to carry out the invention,

Fig. 1 is a vertical section through one form of the earbonizing apparatus taken on the line 1-1. Of Fig. .2; n

Fig. 2 is a vertical section through the carbonizing apparatus taken along the line 2--2 of Fig. 1;

Fig. 3 is a verticalsection through another modification of the invention;

Fig. 4 is a view in perspective of the prepressure device and interassociated parts; and

Fig. 5 is a somewhat diagrammatic view in perspective of the retort, showing the charging and discharging apparatus and associated parts.

Referring to Figs. 1 and 2 of the drawings, 10 designates a closed, refractory-lined retort housing provided with inspection and explosion doors 12, 12. A hollow rotor 14 of heat-resistant metal or alloy such as Hybnickel is disposed within the retort and has sloping side portions 16 extending through openings in opposite side walls of the retort. The rotor is rotatably mounted at its respective ends on suitably journalled rollers 17, 17, and journals 20, 20 carried by supports 22, 22. A ring gear 24, secured to one end of the rotor, is driven from a suitable source of power through an intermeshing worm gear 26.

For sealing the interior of the retort so as to prevent gas leakage therefrom past the sloping sides of the rotor, each side wall has secured thereto, adjacent the openings through which the ends of the rotor extends, a hollow annulus 28, having fluid inlet and outlet connections and adapted to have a cooling fluid circulated therethrough. Extensions at each end of the side members 16, are shaped to form flat plates 30,

each provided with a plurality of annular grooves 32, 32 therein. Secured to each plate is a collar 34 faced with high temperature packing. An annular sealing member 36 has bearing surfaces respectively adapted to contact with a surface of the annulus 28 and with the grooved plate 30, and is normally urged into pressing engagement with both by a spring-operated bellcrank 38, as shown. The annular members 28 and 36, with the plate 30 at each side of the rotor forms an annular lubricant-containing receptacle. Suitable packing rings 39 are set within the members 28.

A fluid fuel inlet pipe 40, closed at its mid portion, extends axially of the rotor and has both ends connected with a source or sources of fuel gas. Concentric therewith is a second pipe 42 adapted to accommodate a flowing stream of cooling fluid such as water. A layer of refractory material 44 enclosed in a heat resistant metal casing surrounds the pipes 40, 42, as shown. A plurality of fuel nozzles 46 directed in a general downward direction are provided within the rotor. The interior of the rotor is in communication with a pair of flues 43, 48 through the annular passageways 50, 50 surrounding the respective ends of the rotor.

A flexible endless conveyor belt of heat-resistant metal or alloy 60, such as those described in the aforementioned copending application of Henry 0. Loebell, Ser. No. 347,802, is adapted to surround the rotor 14 and also to pass around an idler roller 62, disposed within the retort 10 with its axis parallel to that of the rotor. ,The exterior surface of the rotor and the rotor-contacting surface of the belt 60 may be smooth as shown in Figs. 1 and 2, or they may be suitably designed in the manner disclosed in my aforementioned copending application for cooperating to produce carbonized fuel in briquet form as shown here more particularly in Fig. 4. The interior of the idler 62 may if desired be heated. This may be accomplished in the same manner as the rotor is heated, or it may be .done in other gases being withdrawn through the flue 72. A

transverse pipe 73 disposed below the rotor is provided with a plurality of fan-shaped outlet nozzles 75, and has its ends in communication with a source of hot flue gases such as those produced in the rotor or in the heating chamber 64. Thus a steady flow of these gases over the radiant window 66 is accomplished which serves to keep the latter free from carbon and the like which might interfere with radiant heat transfer, and which serves also to remove from this zone the carbonization vapors as rapidly as they issue through the belt and before they can be cracked or otherwise injured by contact with the highly-heated radiant window. Nitrogen or other neutral gases or other slightly oxidizing gases may be substituted for the flue gases.

For providing the desired degree of tension in the belt 60 during operation, and to secure a suitable change in direction thereof as it leaves the rotor, a plurality of weighted rolls 76, 76 are mounted in swingable frame members 78 supported on a cross member 79, which is adapted for vertical sliding movement in slotted end members 80, 80, on the inside of the retort walls.

For conveying fuel to be carbonized to the belt 60. and for removing the carbonized fuel from the retort, a transverse endless scraping conveyor 90, driven from a suitable power source, is provided, the same having upper and lower runs and comprising a plurality of cross members or scrapers 92 secured in spaced-apart relation by link members 94 moving along track Ways inthe refractory side walls 96, 96 at the respective sides of the conveyor. The upper reach of the conveyor travels in a grooved trough 98.

Solid fuel passes from the hopper 100 through 125 the sealing and measuring valve 102 onto the lower reach of the conveyor 90. Any surplus fuel not deposited on the belt 60 during the movement of the conveyor 90 across the same, is discharged by the feed conveyor through a gastight seal valve 104 and may be returned to the hopper 100 or conveyed elsewhere. The carbonized fuel deposited upon the upper reach of the conveyor upon the separation of the carbonizing belt and rotor, is discharged from the retort through the seal valve 106 to a closed conveyor leading to a suitable quenching vessel or to an annealing oven (not shown).

A radiation screen 110 of refractory material, preferably having a portion thereof of heat resistant metal, which may if desired be cooled by the flow of a suitable fluid therethrough,is disposed between the charging conveyor and the rotor 14, for the purpose of preventing transmission of radiant heat to the upper surface of the fuel layer until the latter is substantially in contact with the hot rotor.

For applying a controlled degree of prepressure to the thin layer of fuel prior to contact thereof with the hot rotor, for shaping the top surface 15 of the fuel layer to conform with that normally imparted to it later by the rotor, and for compacting the fuel charge before it has been subjected to substantial surface heating,-a press-, ing member 116 is provided. This may be a roller or a flat plate or equivalent device, but in the form shown this member consists of one or more rollers mounted on a'rotatable shaft 118 for limited sliding movement thereon and for rotation therewith. Each rollers may have its curved surface fluted. grooved or otherwise shaped to correspond to the surface shape of the rotor. a suitable driving connection with the rotor or with an independent source of power, in such manner that the outer surface of the rollers 116 and the carbonizing belt 60 move at substantially the same speed.

The respective ends of the shaft 118 are resiliently urged downward by suitable means such as the tension springs 120 in a manner to yieldingly press the rollers 116 with a predetermined pressure against the carbonizing belt and the fuel carried thereby. Any well-known means may be employed for adjusting the degree of the downward pressure exerted upon the shaft and rollers by the springs l20,-to vary the amount of pressure applied to the fuel on the belt.

For adjusting the thickness of the layer of fuel to be deposited upon the carbonizing belt by the conveyor 90, a vertically-adjustable, supporting member 130 is disposed within the retort below the belt 60 and rollers 116. and in contact with the former. A series of rollers are mounted as shown in the upper surface of the member 130 to reduce friction between the belt 60 and member 130.

A vapor and coal gas outlet 132 leads from the upper part of the retort to the'usual scrubbers and condensers.

According to the modification shown in Fig. 3, tlie fuel mixture to be carbonized is deposited by the lower reach of the conveyor 90 into an elongated hopper 140 from which it is fed continuously through the sealing and measuring valve 142 and then quickly falls by gravity upon the carbonizing belt 60 at approximately the point of juncture of the latter with the hot rotor, as

shown. A roll or the like 144, driven at about the same speed as the belt 60, maintains a uniform point of contact of the rotor and the belt, and serves to compact the fuel as it contacts with the rotor. A troughlike member 91 cooperates with the belt 60 to convey the carbonized fuel or briquets from the rotor to the upper reach of conveyor 90. In this modification, the elapsed time between the feeding of the fuel to the belt and the passing thereof into pressing contact with the .hot rotor is so short that the radiation screen and. the prepressure member, such as shown in Fig. 1, are not necessary. A heating chamber 64, provided with a radiant window or heat-trans ferring surface 66, is also provided. Conduit 146 conveys the carbonization vapors from the retort; and conduit 148 conducts away flue gases from the chamber 64. The rotor is heated and otherwise served in the same manner as described in connection with the modification shown in Figs. 1 and 2. The, refractory side wall 96 of thehousing forthe fuel feeding device adjacent the carbonizing belt is out back sufficiently to permit ready escape past this point of the carbonization vapors and gases first formed at the point of contact of the fuel with thehighly heated vtion heat in-the process.

The shaft is adapted to be rotated by rotor and before they have been substantially cracked or otherwise injured by heat flowing from the'rotor.

' The vapors and coal gas formed in the retort during the carbonization of relatively high volatile coals and fuel mixtures are subjected to the usual scrubbing and condensing operations and may then be takento storage, or they maybe burned for supplying the necessary carboniza- In certain instances the carbonization' vapors within the retort may be diluted with hot flue gases such as those produced by the combustion within the rotor for reducing the plastic properties of the fuel, and assisting in the carbonization. Air or other oxygen-containing gas may be introduced into the carbonizing chamber with or without flue gases for supplying additional heat directly to the fuel mixture being processed.

In a type of operation where the mixture carbonized consists of anywhere from 25 to 50% of through the machine and the final mixture of flue gases, and carbonization vapors leaving the carbonizing furnace will be sufficiently combustible so that this hot mixture can be used to provide the heat for the carbonization process. In such a case, low grade coals can be carbonized to form a high grade product; and no condensing, scrubbing or auxiliary equipment is necessary, because the carbonization gases made are directly returned to the machine to provide the heat necessary for carbonization. The flue gases have a slight oxidizing effect tending to destroy the plastic nature of the fuel mixture, thus assisting to retard any tendency of the mixture to stick in the cells of the carbonizing belt. This sticking tendency may also be retarded by preheating the carbonizing belt prior to introducing the fuel mixture upon it, as for example by heat applied thereto as it passes around the heated idler roll. (See Fig. 1.) Other means for applying heat to the belt previous to the placing of the fuel charge thereon may be substituted for the indirect heating thereof through the idler roll, as will be apparent to those skilled in the art.

Very satisfactory smokeless fuel briquets have been prepared by processing in accordance with the present invention a fuel mixture containing 80% anthracite culm and 20% Skelly pitch, (a petroleum pitch having a melting point around 275 F.,) all ground to less than 20 mesh. This fuel mixture was preheated in a fluxing vessel to 625 F., and was charged hot in a thin layer the neighborhood of 1385 F. and was carbonized over a period of 10 minutes by this heat applied to both the top and bottom surfaces of the layer, following which the briquets were discharged and quenched.

Similar results were obtained by processing a fuel mixture containing 50% of a petroleum coke (produced bythe pressure distillation of petroleum oil), which had been given a preheating treatment to 1400 F. 30% of the same petroleum coke untreated, and 20% of Skelly pitch, all ground to less than 10 mesh. After preheating the mixture to 640 F., it was charged in a thin layer 1% inches in thickness on the briquetting belt. This fuel layer was then passed under the prepressure and preforming roller where it was reduced to 1%; inches in thickness under a pressure of 10 pounds per sq. in. The preformed fuel layer was then passed into contact with two highly heated surfaces maintained at average temperatures of 1425 F. for 10 minutes while under a low pressure of lb. per square in.- The pre-, pressed fuel layer was subjected to 1 minute preheat radiated thereto from the rotor prior to contacting therewith. Prepressures of between 1 pound to 100 pounds per sq. in. on the raw fuel mixture may be employed with good results. For

degree of compression pressure free from substantial unregulated variations due to volume changes occurring in the fuel during such carbonization.

3. The process of carbonizing solid fuel which comprises, compacting'and shapingunder pressure a thin layer of finely divided solid carbonizable fuel while preventing substantial carbonization of the fuel, thereafter moving the compacted and shaped fuel layer along a curved path in a carbonization zone while carbonizing it by heat applied to at least one side of the layer during such movement, continuously exerting a low regulated pressure upon the fuel layer being carbonized in a direction transversely of the free surface of the latter irrespective of volume changes occurring in the fuel during such carbonization,

instance, prepressures of 25 pounds per sq. inch preventing substantial change in the surface are suitable when briquetting and carbonizing Dubbs pressure still residues, whereas to 100 pounds per sq. inch may be used in high volatile coals under like conditions.

The modification of the invention shown in Fig. 3 is especially adapted for processing flowing preheated fuel mixtures which are near the carbonization temperature as they enter the retort. The use of preheated fuel is preferable though not essential, and cold fuel mixtures have been satisfactorily carbonized according to the invention. carbonization temperatures of from 900 F. to 1800 F. have been used; and good smokeless fuel briquets have been produced in as short a time as three minutes exposure to heat from the rotor.

A wide variety of carbonaceous fuels and fuel mixtures may be processed satisfactorily in accordance with the invention. For example, ores for metallurgical purposes may be briquetted with carbonaceous materials. The use of prepressure is particularly advantageous where fuel mixtures of relatively-high volatile content and of comparatively low density are being processed. The

' resultant briquets possess dense structure, and

the external surfaces thereof are relatively free from cracks such as are sometimes caused by shrinkage of an uncompacted mass during carbonization or by the action of the rotor in breaking through a partially-carbonized upper surface of fuel which covers underlying layers of loose, uncompacted fuel.

The invention is susceptible of modification within the scope of the appended claims.

We claim:

1. The process of carbonizing solid fuel which comprises, compacting and reshaping the opposite surfaces of a uniform thin layer of finely divided solid carbonizable fuel while the same is below its carbonization temperature, thereafter carbonizing the compacted and reshaped fuel while preventing substantial disturbance of the individual fuel particles and while continuously maintaining a regulated low pressure upon the said fuel, applied thereto in a direction so as to intersect the surfaces thereof.

2. The process of carbonizing solid fuel which comprises, compacting and reshaping to a selected conformation under pressure a thin layer of finely divided solid carbonizable fuel while preheating the same but while preventing substantial carbonization of the fuel, continuously moving the compacted and reshaping fuel layer through a carbonization zone while carbonizing it by heat applied to two opposite surfaces of the layer during such movement and while continuously subjecting the fuel layer being carbonized to a low shape of the fuel layer during carbonization, and at a point in the said path releasing the pressure and reversing the curvature of the said path for discharging the carbonized fuel from the carbonization zone.

4. The process of carbonizing solid fuel which comprises preheating a body of finely-divided solid fuel to a temperature below its carbonization temperature, thereafter disposing the hot fuel in a uniform thin layer having a free surface, compacting the fuel layer and shaping the free surface thereof to a selected configuration, then moving the compacted and shaped fuel into and through a carbonization zone, and carbonizing the fuel while continuously exerting a regulated low pressure upon the fuel layer and while preventing both substantial change in the surface shape of the layer and substantial disturbance of the individual fuel particles during the carbonization, and thereafter concurrently removing the carbonized fuel from the carbonizing zone and releasing the said pressure.

5. The process of carbonizing solid fuel which comprises disposing solid carbonizable material in a regulated uniform thin layer having a free surface, compacting under pressure the fuel in the said layer while heating the same to temperatures below the carbonization temperature thereof, moving the compacted fuel into a carbonization zone and carbonizing the said fuel layer under low pressure,. and maintaining the said pressure upon the fuel layer substantially throughout the carbonization independently of any volume changes occurring therein during such carbonization.

6. The process of carbonizing solid carbonizable fuel which comprises disposing a fuel mixture in a uniform thin layer of regulated thickness having a free surface, compacting the said fuel layer while shaping the free surface thereof to a selected configuration, carbonizing the compacted and shaped fuel layer while continuously maintaining the latter under a low pressure maintained substantially throughout the said carbonization, and shielding the thin fuel layer from carbonizing heat until the.layer is about to be subjected to the said pressure.

7. The process of carbonizing solid carbonizable fuel which comprises forming a thin uniform layer of the said fuel having a free surface and concurrently moving the said layer to a carbon ization zone, compacting the said fuel layer and providing the same with a selected surface conformation prior to the beginning of carbonization thereof, thereafter concurrently carbonizing the thin fuel layer while continuously maintaining the same under a low regulated compresa temperature below the low temperature carbonization range, quickly compacting the said fuel layer while shaping both the said free surface of the layer and the opposite surface thereto to form selected configurations corresponding to the opposite surfaces of the briquette to be formed, carbonizing the said thin layer while continuously maintaining thereon a regulatedlow degree of pressure independently of volume changes in the layer during the carbonization and while preventing substantial disturbance of the individual fuel particles during the carbonization, and shielding the preheated fuel layer from carbonizing heat until shortly before the latter is subjected to the last-named pressure.

10. The carbonization process which comprises preheating solid bituminous fuel to a temperature near but below its carbonization temperature, disposing the preheated fuel in a thin unconfined layer having a free surface, quickly compactirig the said fuel layer under a pressure of from 1 to 100 pounds pe'rsquare inch while concurrently shaping the free surface of the fuel layer to'a selected configuration, thereafter moving the compacted and-shaped'fuel layer into a carbonization zone thereby carbonizing the same, continuously maintaining the fuel layer under a low regulated pressure maintained throughout the carbonization substantially independent of volume changes occurring in the layer while preventing substantial disturbance in the arrangement of the individual fuel particles until the carbonization is substantially completed, and thereafter concurrently releasing the pressure and removing the carbonized fuel from the carbonization zone.

11. The process of carbonizing solid fuel which comprises disposing finely divided solid carbonizable fuel in a thin layer having a free surface, compacting and shaping to a selected configuration under pressure a surface of the fuel layer while the fuel'is at temperatures below the carbonization temperature, moving the compacted and shaped fuel into and through a carbonization zone thereby carbonizing the fuel while continuously exertinga regulated low compression pressure upon the fuel throughout the said carbonization applied transversely of the free surface thereof, and preventing substantial change in the surface configuration of the fuel layer during the said carbonization.

12. The process for the production of carbonized fuel briquettes which comprises, preheating a finely divided mixture of petroleum coke and pitch to a temperature near but below its carbonization temperature, continuously forming the preheated mixture in a thin uniform layer having a free surface, compacting the layer under a pressure of from 1 to pounds per square inch prior to substantial carbonization, forming the same into a plurality of separate portions while reshaping the free surface of the layer to a selected configuration, moving the thus compacted and shaped fuel into and through a;high temperature heat-radiating-and-conducting zone thereby carbonizing the said fuel, maintaining a low regulated pressure upon the layer of fuel and applied in a direction intersecting the free surface thereof substantially throughout the said carbonization, gradually increasing the said pressure during at least the early stages of the carbonization, and concurrently releasing the said pressure and removing the carbonized bri- 100 quettes from the carbonizing zone...

13. The carbonization process which comprises carbonizing solid bituminous fuel in a thin uniform layer having a free surface while moving the thin layer en masse along a curved path without substantial disturbance of the individual fuel particles during the said carbonization, and continuously applying a regulated low compression pressure transversely upon the said free surface of the fuel layer substantially throughout the carbonization.

14. The process of carbonizing bituminous fuel which comprises forming a thin uniform layer of the said fuel having a free surface, subdividing the said layer into a plurality of shallow portions, passing the said portions so subdivided in succession through a carbonizing zone thereby carbonizing the portions, and exerting a regulated low compression pressure transversely upon the free surface of the said fuel portions substantially throughout the carbonization.

15. The process of producing carbonized fuel briquettes, which comprises continuously carbonizing finely divided solid bituminous fuel while the latter is divided into a plurality of thin briquette-shaped portions each having a free surface, continuously applying a low regulated pressure transversely upon the free surface of the said portions substantially throughout the carbonization independently of volume changes occurring in the fuel portions during such carbonization, and subsequently releasing the said pressure and continuously discharging in bri- .quette form the thus carbonized fuel.

/ ALBERT LUDWIG KLEES.

HENRY O. LOEBELL.

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