WO2000009629A1 - Continuous production closed retort charcoal reactor - Google Patents

Abstract

This is a process, with the entailing equipment arrangement and machinery designed to produce charcoal and graphite of selectable varying degrees of volatile content from all types of waste wood, bark and vegetable matter. The procedure used in the past, or those current or planned for the future are obsolete, time consuming, inefficient, and dangerous, and require vast amounts of investment capital to bring into production. The process I have outline is continuous, 24 hrs. per day seven days a week, safe, non-pollutant, profitable and requires the minimum capital expenditure necessary to produce a commodity of highest quality. Instead of the huge vertical, gravity feed retorts, and the attendant costs and dangers they generate, this process is not reliant on gravity in vertical retorts but uses horizontal force fed, oxygen negligent tubes arranged in tiers of rows across the width of the refractoried oven, each tube independently controlled, vented and monitored and small enough to prohibit massive volumes of exhaust gases at extreme temperatures thus eliminating dangerous conditions. With the requirement of only two people per shift to operate it, the machine is extremely cost efficient. Because it can use any and all organic material, including wood waste, mixed up with bark in any ratio it is also a complete solution to the forest industry waste proliferation problem in any region with forest based industries. It can use the waste from the harvesting in the bush, to the manufacturing of finished products. It can use various other types of vegetable waste with minor modifications to the raw material handling procedures.

Description

CONTINUOUS PRODUCTION CLOSED RETORT CHARCOAL REACTOR

DESCRIPTION:

The machine and equipment arrangement as well as the process they are designed to improve is for the purpose of producing charcoal in a continuous manner. The production of charcoal today is a stop and start procedure entailing cooling down periods and time consuming renewed start up. This new process eliminates that, since once it is started it is run continuously , twenty four hours a day and seven days a week. The only other continuous process that I'm aware of, involved at least ten times the invested capital, emitted exhaust gases steadily, was difficult to service and maintain, and at times very dangerous to operate. It was abandoned thirty-eight years ago rather than develop any improvements.

The reactor, as it was called then and I have called mine now, was at that time a vertical retort machine reaching fifty feet into the air and relying solely on gravity to feed the sawdust through the retorts inside the heated chamber. This caused the the sawdust to hang up within, creating super hot spots, and extremely perilous conditions when it was finally freed and fell into the hot empty space, the first batch to hit literally vaporized on contact and all control was temporarily lost. This new reactor has horizontal retorts (D), and is force fed by the injection screw (Z) canceling any possibility of an empty retort, over heating, and the subsequent violent potential.

The distillate gases then were simply released into the open air, where they burned freely when hot enough. These now will be collected and confined in the recovery pipes (L) and circulated into the combustion chamber through the burner (B) draft ports as a supplementary fuel; or if a precipitation recovery assembly is installed the alcohol, turpentine, and tar will be removed as a by-product first .

With the previous reactors the entire roof had to be torn off to replace or service one retort, removing it one half section at a time, the lower half hanging suspended in the reactor while the upper was lowered to the ground, and then the lower pulled out and lowered also. With these you need only remove the split slip plates (14), FIG:7, (they are shown on the drawing in the backed away from the reactor wall position), from the front and rear of the particular retort needing service and pull it out on rollered jacks. The reactor can then be easily re-started after covering the hole with a solid dummy plate, limiting the shut down time of the facility. The previous system was crippled until the missing retort was replaced.

The greatest advantage of these horizontal retorts lies in retort screws. Since their speed can be precisely controlled, so can the quality and chemical composition of the charcoal produced; while maintaining a constant temperature in the enclosure. Pushing the raw material faster through the retorts will give higher volatiles in the finished product; slowing them down will give more carbon in relation to other the elements, allowing the production of graphite, or very near it, if desired. Previously, to exercise what little control could be had over the finished material, the temperature around the retorts had to be varied between such extremes that the continued expansion and contraction of the equipment induced unnecessary fatigue in the metals and shortened the service life throughout.

Here, that is eliminated by the design of the screws (Z) shown in FIG: 7. Having the flight removed before and after each gas vent (Y) vastly improves the capacity to control quality, making this innovation, in conjunction with the horizontal arrangement of, and the forced progression in the retorts, the mainstay of the entire process. This is, in fact the new process, the rest is mere improvements in control mechanisms all down the production line, to reduce wear and tear, and the emission recovery pipes. It is due to this fact that once the temperature is reached to reduce the raw material to charcoal, it need not be altered, thus improving the efficiency of the combustion fuel and the life of the machine .

ASSEMBLY:

The sawdust dryer assembly (Fig: 10), with its feed screw conveyer (4) from the sawdust pile, and the four foot diameter blower (3), with the twenty foot high, six foot diameter cone (6) mounted on it, the 75HP motor (1) are bolted to a reinforced concrete pad at least ten feet square in dimension and two feet thick, with the appropriate conduit for for supply and control power installed before pouring. The circuits for the thermal-couples, (e) located one at the top of cone, one at the bottom of the same and one directly in front of the air intake shut-off gate, (8) must be run in asbestos wire or its equivalent temperature rating.

Intake hot air pipe (5) and the sawdust and air exhaust pipe (7) are both twenty-two inches in diameter made from ten or eight gauge mild steel, the former should be insulated with two inches of fiber-glass wool wrapped over with flexible heavy aluminum foil.

The blower housing and dryer cone are made of three sixteenth inch thick mild steel, but the drive shaft and the impeller, (2) should be of 316 stainless steel.

The reactor (Figs: 1-4 incl.), in its entirety is constructed on a heavily re-inforced concrete pad, four feet thick, measuring twenty-five feet square. Again all appropriate conduit is run in before pouring, as are the mounting bolts and steel bases for the reactor pillars, (9) and the sawdust return blower (H).

The four corner pillars (9) are ten inch steel I beams measuring twelve feet from each other at ninety degree angles and and nineteen feet high. These are tied together every four feet in height with six inch by six inch angle members, (left off patent drawings for clarity), and to these the three eighths inch thick steel sheathing of the housing is slot-bolted for expansion. On the inside of the reactor it is coated with castable refractory four inches thick, from the floor to the stack, this must be tolerant of temperatures ranging to a maximum of 1000°C. All thermal-couples (ς) must be installed before this is poured. The stack shown is for the use of hog fuel burners. If bunker fuel burners are applied it must be modified according to the burner manufacturer's specification.

All reactor components are made from mild steel but it is strongly recommended that the closed retorts (D) and that part of the gas venting system (L) that are inside the heated enclosure be of 316 Stainless Steel, except the retort screw (Z) Fig: 7, cutaway, it can be mild steel for cost efficiency if necessary since it is easily replaced. (It has been found that mild steel subjected to those temperatures inside the reactor does not survive beyond six months.) Retorts, (tubes) (D) are twelve inch diameter, outside with a wall thickness of three-eights of an inch. Flanges on both ends are one half inch thick, drilled with six i" holes each, to bolt on the two end pieces with the one half inch thick asbestos ring gaskets (S) between the tube and each end assembly portion of the retort .

The heat exchanger for the sawdust dryer Fig: 5, items (V) and (Q) can be mild steel since the steady volume of air passing through them will prohibit a heat build-up and prolong the life substantially. The manifold (Q) is of twenty-four inch diameter, one quarter inch thick wall pipe, the inside five exchanger tubes (V) are eight inch diameter three eighths thick wall.

The top receiving cyclone, (C) is four feet in diameter, and six feet high. The discharge pipe (13) at the bottom is of twelve inch diameter and sixteen AWG wall.

All electric motors throughout the entire plant are three phase, 550-600 Volt. Those adjacent to the reactor must be of the totally enclosed dust proof type, and those mounted on metal components of the reactor itself, such as the retort screw motors (T) , the sawdust feed cross-conveyer motor (X), and the collection conveyer motor (10) should be rated for hazardous locations, (explosion proof). This is not in anticipation of any explosions but to protect the motors themselves from heat conducted through the metal mountings from the reactor, and from the incessant abrasion they may be subjected to internally from any charcoal dust that could be drifting around. It is my experience that these ultra fine particles are next to impossible to contain or eliminate during the course of production. All supply circuit, control, and monitoring wiring attached to the reactor housing is of the asbestos insulation or equivalent type and enclosed in rigid conduit. All other wiring to C.S.A., and regional codes standards or better.

The bearings for the retort screw shafts are: on the input end S.K.F. or similar, sealed ball with lubricating fittings as per their specifications. On the output end they shall be an oilite casing lined with one half inch graphite bushing mounted in a flange housing. These may now be available commercially, we had to have them made up in years previous. The screw shaft must be free to slide in the graphite for linear expansion of the screws.

All screw conveyers carrying charcoal from where it exits the reactor (G) and (M) must be water jacketed to prolong their life because of the heat they will be subjected to and the bearings must also be able to tolerate higher than normal temperatures. For the delivery to bin conveyer (M) it is recommended that split shell graphite bushings be used for the screw shaft. If for any reason the user of this facility deems it necessary to cool the charcoal before pressing it into briquettes, although I can not at this time imagine why, fog nozzles can be installed at the reactor end of the bin conveyer (M) to do this. Water for cooling these conveyers is re-circulated from, and to, any storage tank that's convenient.

The sawdust overflow and return blower (H) is thirty six inches in diameter, powered by a thirty horsepower motor of six to seven hundred RPM with intake and outlet pipes being 16"-18" diameter and standard blowpipe thickness.

CONVEYER AND BLOWER SIZES, SPEEDS, and MOTOR HP. and RPM: All the specifications here are for an average application to a plant using sawdust with a particle size equal to that coming from a sawmill head rig, roughly one quarter inch cube, with an initial moisture content of forty to sixty per-cent by weight.

Sawdust Feed Conveyer (E): twelve inch trough; screw one turn in ten inches driven at variable RPM with 3 hp motor.

Dryer Blower ( 3) :

Forty-eight inch diameter housing, twenty-four inch intake and outlet, powered by 90 HP motor at 650 RPM, fixed.

Sawdust Cross Feed Conveyers (E) three in all:

These have ten inch trough, screw one turn in ten inches and all driven with one 5 HP at variable speed. (60-120

RPM)

Closed Retorts (D) : Eighteen in total are twelve inch outside diameter with a wall thickness of .375" and made preferably of 316 stainless steel with one half inch thick flanges on both ends, drill to accept six half inch bolts used to secure the feed and exhaust portions on to them with the one half inch asbestos gaskets in place. These retorts are installed in the reactor with slip plates (14) FIG:7, on either end and in holes with allowance for radial expansion. The slip plates cover the allowance cracks but must be free to slide on the retort tube at all times and manually pushed to the wall of the housing when expansion pulls them away. These plates are made in two pieces, backed with 1/2" thick asbestos on the reactor side, and put on once the retorts are laid in. The retorts nor their drive motors and mechanisms are nowhere secured to anything that will prevent their free expansion in both radial and linear directions. The sawdust receiving slot in the tubes is larger than the delivery one in the cross conveyer for expansion, as is the charcoal out-put smaller than the one in the collection conveyer for the same reason. The chutes (F) are made from thin sheet metal and are flexible enough to allow for what small difference in the length may occur between one layer of retorts and the other.

Retort Screws (Z) Eighteen in Total, see Fig: 7. The diameter of these is ten and one half inches with a twist of one in six or eight inches. The flight is cut out on two feet of either side of the first vent hole, to slow the progress through the tube and allow gas venting as well as to compensate for the shrinking of the sawdust due to the same. This is done again at the second vent but only for eighteen inches on either side for the same reason. This is one of the designs critical to a steadier and more efficient operation of the entire closed retort production principal. These are powered in sets of three by a 5HP motor for each set, (T) at RPMs that will have to be varied by the reactor operators according to the inside temperature, the moisture content of the wood delivered to the retort screws, and the degree of volatiles they wish to achieve in the final product. Suggest for start-up, 30RPM.

Charcoal Collection Conveyer (G):

Eight inch water jacketed trough with a screw of one twist in ten inches powered by 2HP at 120 RPM.

Charcoal to Bin Conveyer (M) :

Ten inch trough, (added cap. for future second reactor running in tandem), water jacketed, screw twist of one in ten inches, powered by 3HP, Depending on distance to bin, at 60 RPM. All conveyers will be tightly covered and their drive mechanisms guarded safely.

The Dryer Air Heat Exchangers (V):

These are bolted securely to the manifold (Q) which is in turn secured to the reactor framing. The pipes (V) are left un-secured at the opposite end and are free to expand and contract here.

Distillate Gas Collection System (L) :

That portion of them that is inside the reactor are preferably made of 316 stainless steel but should be of the same type of material as the retort tubes themselves. The collection pipes are mounted on the vents (Y) with asbestos gaskets to prevent gas from escaping into the reactor combustion chamber at these points. They exit the reactor through slots, for linear expansion of the tubes, equipped with slip plates similar to those on the tubes but smaller of course and then are bolted, again with asbestos gaskets to the outside portions of the gas system. Then the entire system, through a low volume fan or simply by the draft suction on the burners combined with the pressure in the gas expulsion system, conveys these gases back into the burner chamber as a supplementary fuel. This whole contraption can be adapted easily to the recovery of these gases as liquid or solid such as they may occur by modifying the bottom end before it returns to the burners. These are 2" diameter pipes inside changing to 3" diameter that the vertical outside consist of.

Gas Monitoring Vents (K):

These are fitted with lids to prevent the escape of any distillate gases to the atmosphere, unnecessarily; but can be allowed to open for sampling and inspection of those gases so as to enable the operator to tell what's going on inside the retort. The colour, density, and even the smell of this smoke will reveal at what stage the wood is in its transformation to charcoal, only seconds are needed for this and then they close again. These are small stubs of one inch diameter pipe.

CONTROL ROOM & THE SWITCH ROOM BELOW:

The control room should be one story up to give the operator a better view of the reactor and equipment he's meant to control and have the front and two sides in glass. It must be of convenient size to house all remote motor stop-start buttons and their control lights, read-out dial for the three thermal couples on the dryer and a minimum of twelve on the reactor, and a four pen, twenty-four hour circular polygraph for the four point burner temperature monitors. Insulated and heated in cold locations.

Electrical Switch Room, (below control room):

Total capacity for incoming supply of 1000KW to allow for future expansion to tandem reactors. It must also be large enough for all safety switches, splitter enclosures, magnetic starters, timers, and a whole array of control paraphernalia .

WIRING NOTE:

The wiring of all in feed equipment is interlocked, as is that handling the actual production of charcoal and its delivery to the bin. Such as: The retort screw motors (T) cannot be started until the until the collection conveyer motor (10) is going and this cannot be started until the storage conveyer motor (11) is on. The starting sequence of this system is from the destination back to the source. The in-feed system is similarly interlocked starting with the over flow sawdust blower (H), then the feed conveyers motor (X), then the dryer motor (1) and finally the sawdust conveyer from the bin. This wiring plan makes it absolutely impossible to plug up any portion of the system.

Although throughout, sawdust has been specified as the raw material, the machine and process will convert any and all vegetable matter provided it is of a consistent particle size. Household vegetable waste must be run through a centrifuge first to remove excessive moisture and be completely free of any synthetic fiber, polymer plastics, or plastics of any sort.

Operation :

Since all motors are interlocked they must be started from the final destination, the storage conveyer (11) first, then the collection conveyer (10), then the six retort screw motors (T) , then the sawdust feed cross conveyer motor (X), then the dryer blower (3), and finally the sawdust from the bin conveyer (4).

While all this is running the burners are lighted and the reactor is now heating up as the retorts are filled. The retort motors are left running until sawdust comes from the output end then they are shut down, until the charcoal is ready to extract. Periodic inspections at the gas monitoring vents ( ) will give an indication of this and testing of ejected material at the product sampling holes (N) will confirm the status of the reaction taking place. The sawdust feed from the bin and the dryer equipment is left running, the over flow blower will return it to the bin .

When the charcoal reaches the desired state, the retort screw motors can run steady, until such time as it starts coming out raw again. Then each set of retorts must rest and cook for a while, according to the condition of the product within. Initial lab analysis and growing operator experience will train all concerned in the most effective way of manipulating the relationships between the level of heat in the reactor, speed of the retort screws, and the duration of their running time. While the charcoal is cooking the sawdust drying and feeding apparatus is left running steady, the overflow return blower (H) sends it back to the feed conveyer of the sawdust bin and it goes a second time through the drying cone. Now the raw material should be as dry as it can get and this will allow a more continuous operation of the retort screws, a considerable increase in production, and a general settling down of the operation into routine checks, lubrication, and monitoring. When it becomes necessary to shut the reactor down the first thing done is trim the burners to gradually cool the inside gear and then shut them off entirely. The retorts must remain full until the machine has cooled to body temperature, your own, even if if means running a little raw sawdust into the charcoal bins. This creates no problem, since it's loaded into the bin from the bottom and will be mixed adequately enough with the hot material stored to convert it also. If not it can be returned to the sawdust pile and used during the next start-up.

At NO TIME NOR UNDER ANY CONDITIONS, can the reactor temperature at any of the thermal couples be allowed to exceed 600° Celsius.

At NO TIME NOR UNDER ANY CONDITIONS, can the dryer cone temperatures be allowed to exceed 150° Celsius at any of the thermal couples.

It is with respect to the retorts shown in figs: 6, 7, 9, & 11; their orientation and size, and the screw configuration contained within, that particular protection is sought through patenting procedures. Nowhere has the application of these combinations been used before for the purpose of charcoal manufacture.

CONTINUOUS PRODUCTION CLOSED RETORT CHARCOAL REACTOR

DRAWING TITLES DIRECTORY

FIG : 1 Front on View (From control room)

FIG : 2 Right Side View

FIG : 3 Rear View

FIG : 4 Left Side View

FIG : 5 Dryer Heat Exchanger Detail, top view

FIG : 6 Top View: inside with roof and dryer exchanger taken taken off; and front on elevation showing exhaust gas collection system in detail. Screws removed.

Flanges left off for clarity FIG: 7 Closed Retort Cutaway Detail, (one of up to 24 that can be installed in the reactor's heated enclosure. FIG: 8 Closed Retort end view from sawdust intake end. FIG: 9 Closed Retort end view from charcoal exhaust end,

( less flange) . FIG:10 Dryer Cone showing sawdust feed converyer, front on C/W Blower and intake and exhaust pipes. FIG:11 Split Slip Plate Detail c/w asbestos seals against reactor wall and around retort tube, (front on and top views)

Scale: All drawings except figs: 7, 8, 9, & 11, 1/4" = 1ft Figs: 7, is 1/4" = 6 inches Figs: 8, 9, & 11, is 1/4" = 3 inches

LEGEND :

Reactor Housing & Stack

Burners

Sawdust Receiving Cyclone

Closed Retorts (see Fig. 7 detailed cutaway) 18 Total

Sawdust Feed Conveyers

Charcoal Chutes

Charcoal Collection Conveyer (water jacket)

Sawdust Return Blower

Inspection Window

Service Doors

Gas Monitoring Vents (open only when needed)

Exhaust Gas Collection System

Charcoal to Storage Bin Conveyer (water jacket)

Product Sampling Holes

Concrete Foundation (4 feet thick reinforced)

Finished Grade Level

Hot Air Manifold for Dryer

Four Inch Lining of 1400°F Refractory Inside

Asbestos Gaskets 1/2" thick min. all Retorts, both ends

Retort Screw Motors ( 6 driving 3 screws each)

Graphite Bushings on all Retort Screws exhaust end

Dryer Heat Exchanger Tube (8" Diameter)

Feed Conveyers Motor

Distillate Gas Vent

Retort Screw (flight cut away over gas vents)

Thermal Couples, Reactor

Thermal Couples, Dryer

Blower Motor 60-90HP 650 RPM Blower Impeller Shaft Blower Sawdust Feed Converyor from bin

Hot Air Intake Pipe 22"

Dryer Cone

Exhaust Air and Sawdust Pipe

Air Shut-Off gate and Handle

Main Corner Pillars of Reactor Frame

Collection Conveyor Motor

Storage Conveyor Motor

Sawdust Over-flow Pipe

Sawdust Feed Pipe

Split Slip Plates c/w asbestos backing seal

Asbestos Seal (on slip plate)

Claims

THE EMBODIMENT OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. I claim a method of producing granular charcoal continuously in a safe and non-pollutant manner from forest industry residue or other clean organic material after grinding and drying; comprised of an enclosure heated to 600°C equipped with a number of closed horizontal tubular retorts containing motor driven Archimedean screws for the entire length of the retort and exit section and designed particualrly to prevent compression of the material while allowing the distillate gases to escape through hermetically sealed manifolds to be delivered to the burner area of the oven for complete combustion, after recovery of by-product liquids, if a system for such is installed.

2. I claim the method according to Claim 1, whereby the tubes are fed and the Archimedean screws within are designed to prevent the introduction of outside air into the tubes so as to maintain an anaerobic condition within said tubes.

3. I claim the method according to Claim 1, whereby the Archimedean screws are constructed with the flight, (drive flanges) removed at the precise intervals to slow the material within to allow for adequate gas venting while preventing the compression of said material but maintaining a continuous flow to the collection conveyer.

4. I claim the method according to Claim 1, wherein said tubular retorts are provided with ports at the proper intervals to allow the distillate gases to be collected and isolated in a manifold system preventing their accumulation and subsequent possible explosion in the upper reaches of the overall enclosure oven or being exhausted as pollutants out the stack.

5. I claim the method according to Claim 1, wherein provision is made for the closed manifold system to deliver the residual distillate gases safely to that location where complete combustion of these same gases can be achieved.