US1450107A - Process of preparing peat - Google Patents

Description

2 SHEETS-SHEET l.

1. C. MORRISON.

PROCESS 0F PREPARING FEAT.

FILED Nov.29. |920.

Mar. 27, 1923.

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k Ali Like Cll'toz new Mar. 27', 1923. 1,450,107. 1. c. MORRISON.

PROCESS 0F PREPARING FEAT.

FILED Nov.29,192o. 2 SHEETS- SHEET 2.

Patented Mar. 27, 1923.

UNITED STATES JOHN CAMPBELL MORRISON, OF DETROIT, MICHIGAN.

PROCESS 0F PREPARING FEAT.

Application led November 29, 1920. Serial No. 426,936.

To allwwm it may concern Be it known that I, JOHN CAMPBELL MoR- msoN, a citizen of the United States of America, residing at Detroit, in the county of Wayne and State of Michigan, have invented certain new and useful Improvements in Processes of Preparing Peat, of which the following is a specification, reference being had therein to the accompanying drawings.

My invention relates to a continuous process of mechanical operations whereby peat may be excavated from the bog cheaply and rapidly, reduced in moisture content by pressing in a vacuum, disintegrated, dried with hot peat gases, and pressed into dense blocks or briquettes of fuel rich in volatiles, highly combustible, impervious to water, lasting in fire, and hence approaching hard coal in firing characteristics for all purposes wherein the maximum of heat is to be produced with the minimum replenishment of fuel.

My process has for its object the commercializing of peat fuel, first by reducing the present prohibitive costs of manufacture, and second by facilitating and simplifying each operation as hereinafter described.

A further object of my invention is the production of a dried and finely divided peat of uniform quality, which is not only suitable for briquetting, but which may be used also as a fertilizer or for any other purposes for which it may be desirable.

The process herein to be described is made effective by the employment of a moisture expelling machine which reduces the moisture inherent in the material from eighty per cent to fifty per cent by the mechanical pressing of the peat in an evacuated atmosphere. The removal of a preponderance of moisture without the disruption of the fibers renders the drying process more simple and effective and the material as it issues from the drier is made more uniform in moisture content thereby.

In the drawings:

Figure l, is a diagrammatic representation in plan of the relation of the various mechanisms used in carrying out my process, the course of the material being represented by arrows;

Fig. 2 is a diagrammatic elevation partly in section of the excavating system, representing the removal of the peat from the bog to the factory;

Fig. 3 is a diagrammatic elevation of the moisture expelling, drying, and briquetting system, representing the part of the process carrled on in the factory, and

Fig. 4 is av diagrammatic section of the moisture expelling machine.

I shall now proceed to describe the various steps of my process, referring incidentally to previous ways in which the same problems were solved, and showing where- 1n my present system offers a more economimal and efficient solution of the problem of producing peat fuel commercially.

The first step in my process is the excavation of the wet peat from the bog, which I perform by means of a dragline system. This consists of a mast 1, seventy feet high, securely fastened with guy lines 2, to which is attached a steel cable 8. the other end being anchored at 4, in the bog beyond the point of excavation. On the cable, a steel bucket 5, capable of removing two cubic yards at an operation travels to and from the bog, controlled by an operator at the point of delivery The bucket when filled at the bog is drawn to the point of delivery, and returns to the bog by gravity.

By this means, the material may be excavated to a depth of thirty feet in a complete semicircle around the mast without resetting the machine. By cutting the peat strata obliquely from the bottom to the top, a more uniform material is delivered than is made available by the usual method of excavating from the top downward. rl`hus a single operation of a powerful and readily manipulated device delivers a large quantity of peat to the moisture expelling machine. The complete cycle of operation, including loading, elevating, conveying, dumping. and returning of the bucket to the bog is accomplished in one minute and ten seconds in an actual installation.

Excavation by the drag-line system makes the movement of large bodies of water laden material practical and cheap and the material is' delivered to the moisture expelling machine before the oxygen of the air has time to affect the raw material. This chemical change partially destroys the adhesiveness of the material when it is formed into briquets. When the material is excavated by hand and the peat is left in piles exposed to the sun, the fibers become hard and lose some of their volatile constituents and at the same time oxidization occurs, resulting in considerable variation in the properties of the material. 1V ith the drag-line system the peat is transmitted immediately to the machine with the fibers in a flexible natural condition and containing the natural adhesive substances rendering the dried material suitable for briqueting.

As the bucket is drawn from the bottom upwards across the face of the various strata differing in quality, it gradually scrapes off material until it is filled thus delivering a mixture which is of substantially the average quality of the entire mass, this-material making a better and denser block or briquet than can be produced when only the surface layers are used.

In Fig. 2, a hopper is represented at 6, into Which the bucket 5 may be dumped, the material falling from the hopper upon a suitable conveyor 7. The material from the conveyor 7 is delivered either directly or through an intermediate conveyor 8, into the hopper 9 of the moisture expelling machine.

Moisture' empa-Zafon.

The peat as it comes from the ordinary Wet bog contains four times as much water as the dry Weight of the peat. Each ten thousand pounds lifted from the bog represents eight thousand pounds of Water and two thousand pounds of solid matter. The briquettes When compressed may contain one-fifth as much water as the dry Weight of the peat or four hundred pounds of Water With two thousand pounds of peat. Thus, to obtain a ton of peat in condition for briquetting, it is necessary to remove over seven thousand six hundred pounds of water.

The removal of this large amount of water by mechanical means alone is substantially impossible. The peat is fibrous and the capillary action is so great that rolls and ordinary presses remove only a small portion of the Water, much being immediately reabsorbed by capillary action. Centrifugal machines and filter presses have failed because of the presence of humus with particles so fine that the interstices of the filter sections rapidly become clogged.

By the combined use of compression and suction in my moisture expelling machine later described, I am enabled to remove three-fourths of the Water held by capillary action in the peat. The material remaining is fifty per cent Water, but since the fibers have not been disrupted, the material is in such physical condition that it may be dried in a rotary drier after a simple loosening or beating operation to separate the compact mass that issues from the press into a flaky or granular condition.

Hitherto, it has been believed that, to remove the moisture so tenaciously held by the peat, actual rupture of the cell walls was necessary to release the water Within the cells. In the many processes involving disintegration of the Wet peat before beginning the expulsion of moisture, a highly objectionable condition is brought about. When the cell Walls are broken in the presence of Water, an oily, pasty mass is formed, resembling soft putty, from which it is extremely difiicult to expelthe Water by any physical process. This sticky, semi-liquid substance cannot be dried readily by an air current, because the surface presented to the air has been very much reduced from that of the original fibrous peat. The ruptured cells have yielded paraffin oils, which coat the surfaces exposed to the air, and prevent contact of the air With the Water held Within the pasty masses. The oily substance is practically an emulsion of oils With Water containing the alkaline sap of the fibers, and the solids are completely enclosed Within a salve-like coating.

If the attempt be made to dry this paste by heat, the portion nearest to the heated surface may be raised to the burning point, While the portion only a fraction of an inch away is still a semi-liquid mass. The use of centrifugal machines or filter presses with such pasty mixtures is impracticable, and rolls merely make a smoother and more viscid pulp. Such pasty masses are not suitable for rapid drying in av rotary hot air drier, and briquettes made from such material With excessive moisture are likely to contract and crack. Such fuel is unsatisfactory and has not come into common use, though such processes have been advocated for many years, while the price of coal has continued to advance.

My method of expelling the Water held in the peat by capillary action is to place the material with unbroken fibers into a machine in which horizontal rams 10, 10, having strainer heads 11 are driven against opposite sides of thecrude peat 12 held in a closed compartment. As the rams com` press Athe peat, vacuum ports 13, 13, are simultaneously opened behind them to produce a strong suction. The Water runs out through the ports and the rams are then Withdrawn, opening compressed air ports 14, 14, behind the ram heads. A strong blast of air scavenges the screens or perforations in the strainer heads, thoroughly cleansing them from humus or other fine particles that may have entered with the water. The surfaces are left clean and ready for the next stroke of compression.

By this operation, the peat with its fibers substantially intact has been freed from about three-fourths of the'water it held before compression. The cakes of peat leaving this moisture expeller have still fifty per cent of moisture, but are ready for the macerator or disintegrator 15 designed to loosen the mass into condition for the next operation wherein warm air is used to carry the drying operation to the desired point for the final stage. This moist peat breaks apart in the macerator to a consistency resembling wet bran or wet sawdust. Its open fibrous structure presents large surfaces to the heated air as it falls in loose masses from the lifts of the rotary drier.

This improvement in the most difiicult portion of the treatment of peat has made possible the modification of the other steps in the series. The operation of removing the peat from the bog is made much simpler because the moisture expelling machine can handle it while it is full of water. The air treatment is made simple and effective because of the improved physical structure of the material as it issues from the moisture expelling machine. lThe material issuing from the drier is made uniform in structure and in moisture content and is in the proper condition to be pressed into a. seared briquette which will not crack upon further drying and which will be waterproof and of a hardness to hold its form while in the fire.

Drying.

The loose, porous, bran-like material coming from the macerator that disintegrated the cake produced by the rams of the moisture expeller, is delivered into one end of a rotary," hot air drier 16 which inclines downward toward its exit. Lifts or shelves 17 arranged on the inner walls as is common in such machines raise the material to the top and allow it to fall in a shower. Closely adjacent to the entrance to this rotary drier, I set the boiler 18 used to furnish steam power for the machinery performing the entire series of operations used in my process. The hot, gaseous products of combustion, mixed with the heated air drawn with them through the tubes 19 of the boiler, are driven into the inlet end of the rotary hot air drier and drawn along by the suction fan 20 at the outlet end of the drier. The wet peat falling through this hot blast of super-heated air is heated, and water is driven out, rising as steam to the upper portions of the rotating cylinder. The stack 21 creates a draught, controlled by suitable dampers 22, which draws the saturated upper layer o-f air and steam out of the port 23 at the inlet end of the drier. The inclination of the drier causes a slow movement of the material toward the outlet. A particle of peat carried up by one of the lifts to the top has advanced-a little way toward the lower end of the cylinder. It falls at a point a little nearer the outlet than it was when it Was lifted. By the time it reaches the portion of the cylinder near the outlet, it has lost two-thirds of its moisture. Going in with fifty per cent water, it comes out with six hundred pounds of water to two thousands pounds of peat.

Peat with'this proportion of moisture can be conveyed by a current of air. The exhaust fan 20 at the outlet end is adjusted to remove the particlesl that are light enough several feet before theyl reach the end of the cylinder. The peat removed by an inverted fan at the exit end of each of the driers is carried by the blast of air through pipes 24, 24, to the upper part of a cyclone separator 25, entering tangentially in opposite directions, giving to the material a Cyclonic action. the heavier particles descending down the sides by gravity and the lighter particles of proper size and weight being drawn out at a point 26 above t-he bottom by the action of the fan 27 which delivers' the finished material through the pipe 28 to the hopper 29 over the briquetting machine. 30.

The particles of material that are still too large or heavy to be susceptible to the attraction o-f the finishing fan descend to the bottom of the cyclone separator where they encounter a high-speed pulverizer 31. Tfhis reduces any lumps that no'ay have passed through the rotary drier to proper size. Air jets produced by a fan 32 and entering the casing of the pulverizer blow the particles as soon as disintegrated up into the eddying mass above, where they' are carried off by the current of the fan 27 as soon as they are of proper weight and size.

Thus it will be seen that the function. of the cyclone separator 25 is to insure that the material going into the briquetting machine hopper 29 is of an even grade. At. the same time, it removes a further percentage of moisture by aeration, due to the action of the air currents on the material.

It has become known to me in the art by numerous experiments that in order t-o produce a dense briquette resembling coal, it is necessary that the material going into the press be of an even grade and proper dryness to insure adhesion and density. However, to produce a satisfactory briquet-te the moisture in the peat must be somewhat above the atmospheric degree of moisture.

Peat cannot be successfully or economically dried when macerated to a paste as suggested by other processes. Natural air drying as usually carried on necessitates too many handlings of the material, is slow. is dependent upon climatic and atmospheric conditions, and is possible during only a limited season of the year.

,Drying bv using coal, oil. or other ordinary fuels for the purpose of heating, is too expensive for con'xmercial application. I purpose to utilize the gas which is a byproduct of the coking process, or produced by heating the briquettes in a retort, yielding eighty thousand cubic feet of gas to the t0n, with a caloric value of one hundred and seventy-five B. T. U. to the cubic foot. Or I may prefer to utilize the Waste portions of the gas after it' has passed through the boiler to produce the steam necessary for the operat-ions of the entire plant. The eight thousand cubic feet of gas, with the calor1c value stated, is sufficient: to reduce the moisture content of seven tons of peat from fifty per cent to twenty-five per cent.

The material delivered from the cyclone separato-r into the hopper of the briquetting machine 30 is pressed into seared briquettes by the process set forth in the United States patents to Robert A. Kellond, Nos. 713.11() and 715,271. The form of press used is that shown and described in the United States patent to Robert A. Kellond and John C. Morrison, No. 755,674, which produces a dense briquette, lump, cake, or cylinder of the density and specific gravity of coal, impregnated With the tar, paraffin, and other oily substances contained in the peat. This briquette is impervious to moisture, so that it may be shipped in open cars Without disintegration in Wet or cold Weather. It is hard and dense enough to last in the fire to produce the maximum amount of heat with the minimum replacement of fuel.

In drying the material to the proper degree to produce a commercial briquet, all the volatile constituents except Water must be preserved in the material as it comes from the bog so that there may be sufficient tar and other volatiles in contact with each particle to bind the entire mass into a cohesive re resisting block. A briquet Without sufficient binding materials preserved in its constituents Will disintegrate in a lire at 1800 degrees to 2000 degrees F., or when subjected to rain, snow or other moisture, Will fall apart, the briquet thus being unsatisfactory.

It is also highly important that the vola* tile constituents be entirely preserved since at the point between 500 and 700 degrees F., methane and other gases are released from the bloc-k Which gives a lire of such temperature that the carbon present will be completely burned this resulting in absence of smoke and a high heating value.

The continuous preservation of the volatile hydrocarbons both for their caloriic and for their binding properties has been carefully considered in each operation from the excavation to the delivery of the finished material from the plant.

In the hot processes of briquetting, a considerable loss of the' volatile constituents of the peat occurs and the resultant product is low 1n steaming efficiency. b In the processes 1n which the materials are cold and dry, the product is not waterproof. It breaks up when left inmoist places and vmust be shipped in closed cars. It disintegrates in a hot fire and burns too rapidly. The briquette formed by my system is free from these objections.

As described in Patent No. 715,271 above mentioned, the raw peat material in a finely divided state and containing moisture in excess of the atmos heric degree is compressed 1n suitable moldl; or dies into hard dense blocks and then seared by passing through aheated portion of the machine, usually a dlrect extension of the mold. At a high temperature, the outer surfaces of the blocks become partially carbonized and a portion of the -constituent tar and oil is liberated, produclng an outer coating or crust Which makes the block Water-proof and prevents its disintegration.

Each step of thepresent process is per-l formed mechanically by an economical and highly efficient continuous instrumentality. The drying is rapid and entirely independentof atmospheric or climatic conditions, insuring production at all seasons of the year, the resultant material closely resembling hard coal. It is uniform in quality and free from the defects Which have previously prevented the (general utilization of this W1de-spread an abundant fuel. The savmg of time, labor, and operating expenses makes possible the manufacture at a 10W' cost of a highly desirable product now commercially unavailable from a raw material which is practically neglected in this country.

Substantially all of the peat now being produced in this country is for use as fertilizer or as an ingredient of fertilizing materials. The dried peat delivered into the hopper-29 may if desired be utilized for a. fertilizer instead of being molded into briquettes and it is in a substantially ideal condition for this purpose, being light and of a uniform degree of fineness. By the use of a suitable no-zzle and air pressure, this finely divided fuel may be made to produce a flame in the same manner as is now common With pulverized coal.

In reduction to practice, I have found ,that the various steps, necessary in the carrying 0f my invention into effect, and referred to in the above description are the most effective, yet realizing that the conditions concurrent with the carrying of my method into use will necessarily vary, I desire to emphasize the fact that certain variations from the preciseness in the various steps which I have described may be executed, when necessary, without sacrificing any of the advantages of my invention as defined in the appended claim.

I claim The process of manufacturing peat of heterogeneous grades into briquettes which consists in removing various grades from their original position, delivering them simultaneously for moisture exp111s1on, expelling the water from the crude peat with substantially unbroken fibers by simultaneous compression and suction, reducing the semi-dried peat to a loose, bran-like condition, conveying the peat While in this loose condition to a drier adapted to subject the loose peat to the drying action of currents of unsaturated gases, separating the portion having water not to exceed twenty-five per cent therein by the action of air currents,

separating the dried material into lighter and denser portions, breaking up the denser portions and adding them to the lighter portions, delivering the substantially homogeneous mixture to a briquetting machine, and imparting to each block an outer c0ating or crust composed of fixed carbon and tarry and oily constituents of the peat by a searing operation involving the application of heat to the material only at or near the surface of the block.

In testimony whereof I affix my signature in presence of two witnesses.

JOHN CAMPBELL MORRISON. Witnesses:

KARL H. BUTLER,

ARTHUR MINNIOK.

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