Process and apparatus for carbonizing wood

May 21, 1963

A. R. KEIL

3,090,731

PROCESS AND APPARATUS FOR CARBONIZING WOOD

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Fig. 7

INVENTOR.

ALVIN R. KEIL

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ATTORNEYS

May 21, 1963 a. r. keil 3,090,731

PROCESS AND APPARATUS FOR CARBONIZING WOOD

Filed Aug. 31, 1959 3 Sheets-Sheet 2 &gt;54

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INVENTOR.

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ATTORNEYS

May 21, 1963 a. r. keil 3,090,731

PROCESS AND APPARATUS FOR CARBONIZING WOOD

Filed Aug. 31, 1959 3 Sheets-Sheet 3

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United States Patent Office

3,090,731

Patented May 21, 1963

3,090,731

PROCESS AND APPARATUS FOR CARBONIZING WOOD

Alvin R. Keil, Rochester, N.Y., assignor to Pfaudler Permutit Inc., Rochester, N.Y., a corporation of New York 5

Filed Aug. 31, 1959, Ser. No. 837,172

Claims. (CI. 202—19)

This invention relates to a retort for the distillation of wood or other carbonaceous material to produce charcoal.

The by-products of the distillation of wood are quite valuable, and in the past, provision has usually been made for their recovery. In fact, in some cases the charcoal that was obtained by the distillation of wood was an important, but nevertheless a secondary, product.

The most important by-products of the distillation of wood for charcoal are acetic acid, acetone, methanol, gas and tar. Acetic acid is now manufactured cheaply from acetylene; acetone is made economically by a fermenta- ₂o tion process and by a synthetic process; methanol is produced in large quantities by synthetic means; and the gas and tar have relatively little value. At the present time, in order to be economical, a process for the production of charcoal must utilize the by-products, but 25 their recovery and sale often is not practicable.

One object of the present invention is to provide a practical charcoal retort that has as its essential purpose the production of high grade charcoal.

Another object of the invention is to provide a prac- 30 tical charcoal retort that consumes a substantial proportion of the by-products as fuel.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims. 35

FIG. 1 is a side elevation, partly broken away, of a charcoal retort and its accessory equipment, constructed and arranged according to one embodiment of this invention;

FIG. 2 is a top plan view thereof; 40

FIG. 3 is a side elevation of the retort alone, partly broken away, and showing the retort from a vantage point that is 90° removed from that of FIG. 1;

FIG. 4 is a bottom view thereof;

FIG. 5 is a schematic diagram illustrating the flow of 45 gas during operation of the retort; and

FIG. 6 is an enlarged fragmentary cross section taken along line 6—6 of FIG. 1.

Referring now in detail to the drawings by numerals of reference, and particularly to FIG. 1, 11 denotes a 50 generally cylindrical steel shell that constitutes the body of the retort. This shell 11 is supported on a plurality of equiangularly spaced legs 12. A pair of curved steel plate segments 14 is secured to the lower end of the shell 11, as shown in FIGS. 1, 3, and 4, to provide the ³³major parts, respectively, of a pair of spaced, generally conical discharge chutes that communicate with the interior of the shell 11 at their upper ends.

Referring to FIGS. 3 and 4, a pair of generally triangular plates 16, of V-shaped cross-section, is secured be- 50 tween the segments 14, to close the confronting sides of these segments. A flat plate 17 is secured along its shorter sides (FIG. 4) to the plates 16. A pair of generally triangular plates 18 is secured, respectively, to the two longer sides of the plate 17, and to the plates 16, to provide, between the two plates 16, the two plates 18, and the horizontal plate 17, a chamber 19 (FIG. 3).

A pipe 21 is secured to the plate 17 to communicate with the chamber 19. The pipe 21 is connected at its lower end to an L 22, that is connected to a header 24 that leads away from the shell 11.

A baffle 27 is secured by two of its sides (FIG. 4) to the two triangular plates 18, above and substantially in parallelism with the plate 17. The two other sides of the plate 17 are spaced from the surfaces of the triangular plates 16, to permit the free passage of gas around these two sides of the baffle, between the edges of the baffle 27 and the surfaces of the plates 16.

A large diameter pipe 28 is mounted within the shell 10, substantially coaxially therewith. The pipe 28 is supported at its lower end by three pipes 31 (FIG. 3) that are equiangularly spaced from each other and that are secured at their inner ends to the pipe 28 and at their outer ends to the inner surface of the shell 11. The pipe 28 is supported in a similar manner at its upper end by three similarly arranged pipes 32. At its lower end, the pipe communicates only with the chamber 19. At its upper end, the pipe communicates with the interior of the shell 11.

A generally U-shaped frame 34 is mounted about the open lower end of each chute, and a plate 36 (FIG. 4) is mounted in each frame for sliding movement across and away from the open lower end of its respective chute. Two U-shaped brackets 35 are secured to the ends of the plates 36, respectively, and a pair of levers 37 are pivotally mounted on pins 38 that are secured to the segments 14, and project through the brackets 35, respectively, to permit movement of a closure plate 36 upon movement of its respective associated lever 37.

A dome 41 is secured to the upper end of the shell 11, to close it. A generally conically shaped baffle 42 is secured to the inner surface of the dome 41, with its apex aligned with the axis of the pipe 28, to divert radially outwardly the upward flow of gas from the pipe 28. A thermometer well 44 is mounted on the upper surface of the baffle 42, with its upper end projecting above the upper surface of the dome 41. Referring now particularly to FIG. 2, a pair of charge doors 46 are pivotally mounted on hinges 47 on the dome 41, to cover openings that are formed in the dome 41. A sight glass 48 is mounted on a pipe 49 that is mounted on the dome 41, and that communicates with the interior of the shell 11.

A guard rail 51 is mounted around the top of the dome 41, and a platform and guard rail 52 are secured to the upper end of the shell 11 and extend about 180° around the shell. A ladder 54 is provided that extends from the ground level up to the platform and guard rail 52, to permit access to the dome 41.

A scroll or bustle pipe 56 is mounted around the lower end of the shell 11. This bustle pipe has a closed end 57, and it is preferably disposed so that it has a gentle downward slope from its closed end 57, to permit drainage of any condensate. This slope is not shown in the drawings. The bustle pipe 56 preferably is generally rectangular in cross-section. At approximately equally spaced intervals along the length of the bustle pipe 56, it is formed with openings 58 that coincide with and communicate with similarly shaped openings in the shell 11, to permit communication between the shell and the bustle pipe.

The accessory equipment for the retort, which is disposed immediately adjacent the retort, includes a supporting platform 61 (FIGS. 1 and 2). A fan 62 is mounted on this platform, and is connected by pipe fittings generally denoted by the numeral 64 (FIG. 2) to withdraw gas from the lower end of the bustle pipe 56. The fan 62 is connected through a pipe 66 (FIG. 1) to discharge into the upper part of a generally box-shaped tar trap 67 that is supported on legs 68 on the platform 61. The tar trap 67 is formed with a pair of downwardly converging bottom walls 69. A drain line 70 (FIGS. 2 and 5) communicates with the tar trap at the lowest point thereof, to

3,090,731 permit periodic drainage of accumulated condensate. A baffle 72 is hung from the top of the tar trap 67 and is secured to its front and back walls, to form a somewhat tortuous path, in a downward and then in an upward direction, for gas that is discharged by the fan 62 through 5 the pipe 66, into the tar trap. A pipe 74 is mounted to communicate with the tar trap adjacent its upper front side, opposite the side with which the pipe 66 communicates. ^; The pipe 74 is mounted with its center line spaced forward, relative to FIG. 2, of the center line of 10 the pipe 66, further to complicate the path of the gas through the tar trap.

A large combustion chamber 76 is mounted on a supporting saddle 77 (FIG. 1) beneath the platform· 61. This combustion chamber 76 is generally cylindrical in 15 shape. The pipe 74 communicates with this combustion chamber adjacent the front end of the chamber.

A controlled-atmosphere burner assembly 78 is mounted . at the front end of the combustion chamber 76. The burner assembly 78 is connected through a line 79 with a 20 source of fluid fuel (not shown). A blower 81 is mounted on the platform 61, and is connected to the burner assembly 78 through a line 82, a valve 84, and another line 86.

A large pipe 87 is mounted to communicate with the 25 combustion chamber 76. A flutter valve 88 is connected to the line 87. .This valve 88 is connected to a pipe 89, that communicates with the lower end of a stack 91. The upper end of the stack 91 projects above the dome 41.

A pipe 92 is -also disposed to communicate with the 30 combustion chamber 76. A slide valve 94 is interposed between the pipe 92 and the pipe 24, to complete communication between the combustion chamber 76 and the shell 11, through the line 92, the valve 94, the tine 24, the L 22, the line 21, the chamber 19, and the pipe 28. 35

A T-shaped fitting 96 is mounted on top of the tar trap 67, in communication with the tar trap. A by-pass valve 97 is mounted on one arm. of the T 96. The valve 97 is connected to a line 102 (FIG. 5). A condenser 104 is mounted in the line 102, to condense volatile materials. ⁴⁰The line 102 is connected to communicate with the combustion chamber 76, or alternatively, it can discharge directly to the atmosphere. The other arm of the T 96 is connected to a line 98. A second by-pass valve 99 is connected to the line 98, and it is also connected to a line 45 101 that communicates with the stack 91.

To use this retort, the doors 36, at the bottom of the chutes, are closed. The doors 46 in the dome 41 are opened, and a charge of wood is placed in the retort. When the retort 11 is filled with _wood, the doors 46 are 50 closed. Gas or other fuel is admitted to the burner assembly 78 through the line 79, and the blower 81 is operated to blow air through the line 82, the open valve 84, and the line 86 into the burner assembly 78. Hot gaseous products of combustion are formed in the combustion 55 chamber 76, and pass through the pipe 92, the slide valve 94, the pipe 24, the elbow 22, and the pipe 21, into the chamber 19. The hot gas that is discharged from the pipe 21 is forced to pass around the left and right sides of the baffle plate 27, referring to FIG. 3, and thus flow 60 over the confronting surfaces of the two plates 16. The hot gas then passes into the pipe 28. The gas travels up the pipe 28, is discharged from its upper end, impinges against the baffle 42, and is caused to flow radially outwardly and then downwardly through the stack of wood. 65

As the pipe 28 is heated, it heats the wood by radiation and conduction. Heat exchange also occurs between the downflowing hot gas and the wood, with the result that volatile materials are given off by the wood. The character of these volatile materials depends, to a large extent, 70 upon the stage of the distillation at which the evolution of the volatile material occurs. During the early stages of distillation, water is driven off. Later, pyroligneous acid is driven off.

The mixture of hot input gas and evolved gas or vapor 75 escapes from the shell 11 into the bustle pipe 56 through the openings 58. The gaseous mixture is withdrawn from the bustle pipe 56, through the piping 64, by the fan· 62, and is discharged through the line 66 into the tar trap 67. In the tar trap, the gas is forced to travel downwardly, then upwardly, around the baffle 72.

In the early stages of operation, when water vapor is being given off by the wood, it is preferred that the value 97 be open and that the valve 99 be closed. A part of the gas, that enters the tar trap 67, escapes through the T 96 and the open valve 97 into the line 102, and is passed over the condenser 104, to trap out the water vapor and other volatile materials. The gas is then returned to the combustion chamber 76, or, particularly if the condenser 104 is not operated, it can be discharged to the atmosphere. As the operation proceeds further, the valve 97 is closed.

The main flow of gas, that enters the tar trap 67, passes through the line 74 back to the combustion chamber 76. In the combustion chamber 76, the combustible volatile gases, that are given off by the wood, pass into contact with the burning fuel from the burner assembly 78, and are burner to recover their heating value and to produce additional hot gases that, in turn, are passed from the combustion chamber 76, by means already described, into the retort 11. The amount of oxygen, that is admitted to the combustion chamber, is carefully controlled, either by adjusting the blower 81 or by adjusting the valve 84, so that the hot gases leaving the combustion chamber are substantially oxygen-free.

In the operation of the retort, the progress of the carbonization may be followed by means of temperature measurements at various parts of the retort. As the hot gas passes into the retort through pipe 21, it is at a temperature in excess of 700° F., but by the time it passes through the charge of wood its temperature drops considerably. The temperature of a thermometer in well 44 is observed, thereby measuring the temperature of the gases at the top of the retort. These gases gradually rise in temperature as the carbonization proceeds, and when these gases reach a temperature of between 650° and 700° F., the batch is finished.

It has been found that if the unit is shut down when the dome temperature reaches between 300 and 340° F., and the furnace is allowed to “coast” for a period of about eight hours or overnight, that the charcoal batch will be thoroughly carbonized. However, if it is desired to obtain maximum production and to run on a 24 hour basis, the retort is run until the temperature in the dome as measured by the thermometer in thermometer well 44 reaches between 400 and 500° F. prior to shutting down. This finishes the batch of charcoal much more quickly. When this has been done, the batch of charcoal may be dumped approximately half an hour after the furnace is shut off by cooling the charcoal by means of a water spray described above.

At all times during operation of the retort, the circulating gas, in the retort and in the accessory equipment and piping, is maintained under positive pressure, preferably equal to or greater than two inches of water. To maintain the operating pressure on the order of about 2 inches of water, the valve 99 is adjusted to permit some part of the gas flow to escape from the tar trap 67, through the T 96, the line 98, the open valve 99, and the line 101, into the stack 91. The flutter valve 88 preferably is adjusted to open at pressures on the order of 4 inches or 5 inches of water, to act as a high pressure relief valve, to permit gas to escape from the combustion chamber, through the line 87, the open valve 88, the line 89, into the stack 91, for discharge to the atmosphere. The gas that is vented from the top of the stack 91 can be ignited, to avoid disagreeable odors in the vicinity of the retort.

Gas that passes through the tar trap 67 undergoes a sharp change in velocity and in direction, and may be

3,000,731 slightly cooled, and the tars from the wood tend to condense from the gas and collect in the trap. The deposited tars can be drained ofi periodically through the line 70.

When the wood has been converted into premium grade of charcoal, the burner is turned off, and the retort may 5 be permitted to cool. However, it has been found that this cooling requires a number of hours, and during that time the furnace stands idle. It has been found economically desirable to expedite this cooling process to shorten the process cycle in order to increase the number of 10 batches of charcoal that can be produced by a unit. This is accomplished by injecting a measured amount of water into bustle pipe 56 as shown schematically at 108 in FIG. 5. Since the bustle pipe is hot at the end of a cycle, this water immediately flashes into steam absorbing a con- 15 siderable amount of heat. Since the volume of the steam is much greater than the water injected, this steam forces its way through the bustle pipe back through ports 58 and into the charge of charcoal. Since this steam is considerably cooler than the contents of the charcoal, it serves to 20 cool the charcoal rapidly. Further, since this steam contains no oxygen, it has no deleterious effects on the hot charge of charcoal. By this means, the charcoal charge may be cooled to a temperature suitable for discharging in a period of half an hour. 25

After cooling, the charcoal is readily removed from the retort by opening doors 34, and permitting the charcoal to drop out into carts or other receptacles. After the retort is empty, it may be used immediately for another cycle.

Excellent heat exchange is obtained with all of the wood in the retort, because of the forced circulation of hot gas in the retort. The gas that passes around the two sides of the baffle 27 heats the plates 16, and insures that the wood in the chutes 14 is heated substantially to the same degree as the rest of the wood in the retort. If desired, openings 58 may be covered or protected by means of inwardly and downwardly extending channels 106 (FIG. 6) which prevent the charcoal from rolling into openings and into bustle pipe 56. These inwardly and downwardly extending channels also have the advantage of forcing the hot gases passing downwardly through the charge to go down below the level of the openings 58 prior to passing out through the openings into the bustle pipe 56, thereby assuring full carbonization of the wood 45 in cones 14. The downward flow of the hot gas through the wood charge insures intimate contact between the hot gas and all of the charge.

Should it be found that the charcoal in any particular portion of the retort or in cones 14 is not properly 50 carbonized, additional heat may be supplied to these particular places by drilling holes in the appropriate places in plate 16 or in pipe 28. These holes will allow a small amount of hot gases to pass directly into the regions where carbonization is not complete, and will increase 55 the temperature and rate of carbonization in these particular areas to correct this condition.

When wood is herein mentioned in this application, it is to be understood that while the preferred raw material for manufacturing charcoal is wood, any other suit- 60 able carbonaceous matter could serve equally well. It is contemplated that the charcoal furnace herein described could be used to carbonize corn husks, peanut shells, coconut husks, and any other carbonaceous material which can be reduced to charcoal by heating out of contact with ^5 oxygen.

While this invention has been described in connection with a specific embodiment thereof, it will be understood that it is capable of further modification, and this application is intended to cover any variations, uses, or adapta- ⁷⁰tions of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as 75 may be applied to the essential features hereinbefore set forth, and as fall within the scope of the invention or in the limits of the appended claims.