US3449837A - Drying peat - Google Patents

Description

June 17, 1969 QTTMULLER ETAL 3,449,837

DRYING PEAT Sheet Filed July 11 POE June 17, 1969 OTTMULLER ET AL 3,449,837

DRYING FEAT Filed July 11, 1967 Sheet 2 of 4 F|G.1O

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June 17, 1 969 G. OTTMULLER ET m. 3,449,837

DRYING PEAT Filed July 11, 1967 Sheet 4 or 4 FIG. 3

INVEN TOR-'5 United States Patent 3,449,837 DRYING PEAT Gert Ottmuller, Gronepark 19, Ahrensburg 207, Germany, and Wilhelm Jester, Post Wischhafen, Wolfsbruchermoor 2161, Germany Filed July 11, 1967, Ser. No. 652,450 Int. Cl. F26]: 17/10 U.S. CI. 34-57 5 Claims ABSTRACT OF THE DISCLOSURE In drying peat by means of hot air, the peat is brought suddenly into contact with the air, preferably by being thrown centrifugally, and the rate of mixing of the air and peat is varied to hold a constant temperature in air entraining the peat.

The present invention relates more particularly though not exclusively to methods of removing water from peat in which the .peat is passed into an ascending current of hot air, travels with the hot air current, and is then separated from the air current. Before treatment with the hot air to remove water the peat can be dried in the air to a greater or lesser extent and is then comminuted.

Such methods of drying peat using hot air currents have the advantage over methods in which peat, either of the white or black variety, is dried in the atmosphere, that the operation is more rapid, less complicated and is independent of weather conditions. In prior art methods in which a hot air current is used for drying peat in comminuted form, the duration of time for which the peat is exposed to the hot air current is comparatively long and the air current exerts a sorting action on the peat particles so that the lighter, dried out particles are removed from the heavier particles which still contain more water.

The disadvantage of such known methods is the comparatively long time for which the particles are exposed to the hot air current and if the temperature of the current is not comparatively low, that is to say in most cases slightly over 50 C. and certainly not more than 100 C., chemical alteration of the peat particles a so-called coking, results.

One object to the present invention is to provide a method of drying peat, preferably peat that has been predried to a greater or lesser extent in the air, which enables a drying air current with a considerably higher temperature to be used and therefore expel the moisture from the peat rapidly at a faster rate than is possible in the case where the water soaks through the cell walls of the peat substance to evaporate from the surfaces of the particles.

Accordingly, in a method of removing water from comminuted peat in which the peat is mixed with an ascending current of hot air, travels with the hot air current, and is then separated from it, the present invention provides the improvement that the peat is mixed with the air at such a temperature that the peat is suddenly heated by the air, and the rate of mixing of the peat with the air current is varied to keep constant the temperature of the air current entraining the peat and the water vapour in it.

With this method the temperature of the hot air acting on the peat can be comparatively high, the only upper limit to the temperature being the necessity of avoiding coking of the peat. In other words the temperature of the hot air current at the position where the peat is mixed with it and upstream from the position at which the air is separated from the peat can be comparatively high. This is so because the water, which is expelled from the peat particles with considerable violence owing to the high temperature protects the peat from damage.

While with the drying of peat by laying it out on the ground for exposure to the sun and the drying action of the air and with the previously known hot air process water escaped by soaking or permeating through the cell walls of the peat substance, the sudden heating eifect in accordance with the method of the invention, which hardly requires more apparatus than the known hot air process, the cell walls in the peat are burst and this leads to the particles being broken up. As a result of this it is found that the particle size of the final product, that is to say the dried peat, is substantially even. The peat after drying can easily be pressed into bales and such bales have the advantage over known peat bales that they are very easy to break up when the peat is to be spread. Furthermore the peat treated in accordance with the invention has surprisingly large capacity to soak up water and it is not necessary to use Wetting agents for wetting the peat. Another advantage is that the peat is completely sterile and free of live seeds. As will be apparent to those in the art this feature of the method in accordance with the invention may, under certain conditions, enable the winning of the peat from a peat hog to be considerably simplified.

Preferably the method in accordance with the invention employs mechanical means for throwing the peat into the hot air current to mix it with the current.

In accordance with a further preferred feature of the invention the peat is thrown centrifugally in a horizontal plane into the hot air current, the latter having an annular cross-section.

The temperature of the hot air current can conveniently be between approximately 200 and approximately 300 C. the preferred temperature being approximately 250 C.

The invention also consists in an apparatus for removing water from comminuted peat comprising: means for providing a current of hot air, a housing, means for guiding the hot air current into the housing so as to flow upwards in it, downwardly extending conveyor means for passing comminuted peat downwards into the housing, an impeller in the housing arranged below the conveyor for receiving the peat, means for rotating the impeller about a vertical axis so that the peat descending onto it is thrown horizontally into the ascending hot air current and entrained upwards, and at least one separating means for receiving the hot air current and entrained peat coming from the housing and separating off the peat.

The speed of rotation of the impeller can be 3000 rpm. and the throughput can be 2 to 3 tons of peat per hour.

In order to make the invention clear to those in the art, one apparatus for carrying out the method of the invention will now be described with reference to the attached drawings.

FIGURE 1 is a side view;

FIGURE 1a is a side elevation on an enlarged scale with hot air generator and cyclone-type separator removed;

FIGURE 2 is a plan view, and

FIGURE 3 is an end view of the apparatus for carrying out the method in accordance with the invention.

As shown in the drawings the apparatus comprises means for producing a hot air current, generally denoted by reference numeral 1. The means comprises an oil burner 2 for projecting a flame into a jet device mounted in a chamber 3. The hot air produced passes through connecting means leading to a blower 4 driven by a motor 40. The blower drives the air into a tangential inlet fixed 3 to the bottom end of a substantially cylindrical housing 6 with a vertical axis. Between the inlet 5 and the housing 6 there is a perforated plate for distributing the hot air current for flow in upward direction in the housing 6. The plate has a flange 8 as shown in FIGURE 1.

The housing is provided with an upper cover or lid 7 on which there is mounted a feed hopper 9 for guiding comminuted raw peat into a screw conveyor 10. The conveyor is driven by a motor 11 connected with the shaft of the conveyor screw 12 which is coaxially mounted in a housing 11a.

The lower, outlet end 13 of the screw conveyor in the housing 6 is placed above a plate-like impeller 14 serving for throwing the comminuted peat horizontally into the upwardly travelling air current and mixing it with the air current. At this level of the housing 6 the air current is of annular horizontal section since it extends around the impeller. The latter is driven by a motor 15.

The cover 7 of the housing 6 has two connections 16a, 17a connected with ducts 16 and 17 in order to lead oif air from the housing. The two ducts 16 and 17 end in cyclone- type separators 18 and 19 respectively from whose bottom ends 20 dried peat can be discharged when valve means are operated while from the top ends substantially dust-free air is discharged through openings 21.

In operation, peat, comminuted for instance in a mincing machine-type apparatus is fed into the hopper 9 and passed downwards through the screw conveyor on to the impeller 14 which hurls it into the ascending hot air current so that it is mixed with the air, which is preferably at a temperature of 250 C. and entrained upwards. The rate of feed of peat is so controlled that the temperature of the air entraining the peat and the water vapor evolved by the peat is about 100 C. The rate of feed of the peat on to the impeller can be controlled, in order to control the temperature of the air, by varying the amount of peat placed in the hopper 9. That is to say when the temperature rises more peat is fed into the hopper 9 while when it falls less in fed in.

As soon as the peat, with an initial moisture content of about 80%, is fed in a finely comminuted state into the hot air current in the housing, the particles of the peat are immediately subjected to the action of the hot air current from all sides so that there is a sudden vaporization of the water, including the capillary-bound water and the peat substance is ruptured by the high pressure of the escaping vaporized water. The escaping vapour surrounds the particles and protects them against excessively high temperatures in the entraining air.

The peat removed from the cyclone-type separators 19 contains about 60% water though the apparatus can be so operated as to reduce the water content still further. The particles of peat are not damaged by the temperatures to which they are subjected but they are puffed up in size so that the bulkiness of the peat is increased. In this respect the peat treated in accordance with the invention diiTers from peat treated in accordance with conventional methods. The peat can be pressed together into bales just as easily as conventionally treated peat.

The method of the invention has the advantage of being very much more rapid than drying peat in the open air and it is also independent of weather conditions. The peat treated in accordance with the invention also has the advantage of being substantially lighter and being suitable to be spread over larger surfaces.

The best results are obtained with the apparatus shown in the drawings when the speed of rotation of the impeller is 3000 rpm. and the throughput is 2 to 3 tons of peat per hour. The results are also dependent upon the water content of the comminuted peat fed into the apparatus. Variations in water content naturally occur owing to varying conditions under which the peat is predried to a certain extent before being treated. Automatic control means can be provided for varying the rate of feed of the peat into the apparatus in order to achieve a constant temperature in the air entraining the peat.

The predrying of the peat to be treated in the apparatus need only be carried so far as to insure that the peat does not smear and congeal together. It is generally found that a water content of about is suitable. The water content can easily be reduced to this value in a short time by drying in air and the overall process of cutting the peat and drying in accordance with the invention is therefore considerably more time and cost saving than conventional cutting and drying processes.

The peat can be extracted from the peat bog by loosening the top layer of the peat in situ, then subjected to air drying in this condition and finely cleared away by machine or otherwise. A further layer is then treated in this manner so that the winning of the peat proceeds layer by layer.

The thickness of the layer depends on the one hand on the degree to which the peat can be loosened, that is to say from the type of implements used, and on the other hand on the speed of predrying. There are also other factors which may effect the thickness of layer taken. In many cases it is sufiicient to work with a cutting machine having a rotor turning about a horizontal axis, to loosen the peat and then after predrying to clear it away using an implement similar to a plough.

This method of winning has substantial advantages over the conventional method owing to the effect that sods or bricks of peat are not cut and do not have to be piled and then turned over many times before they finally dry out. Owing to the smaller amount of labour required the final product is substantially cheaper although in the drying process there is a considerable requirement for producing the hot drying air.

While the process of the invention has been referred to above as one of drying, it is to be understood that this does not imply that the peat is always treated so as to have a moisture content in the range (20-40%) given in works of reference. The term drying is only intended to mean that there is a reduction in Water content.

The invention is equally applicable to brown and white peat.

What we claim is:

1. Apparatus for drying comminuted peat comprising a source of hot air,

an upright housing,

means for creating a rapid current of hot air from said source to the bottom portion of said housing,

a cover closing the upper end of said housing,

means extending through said cover for delivering comminuted peat into said housing near the bottom thereof,

means within said housing adjacent the bottom thereof for receiving peat from said delivering means and forcefully throwing same horizontally into said hot air current,

duct means leading from said cover providing a passage for hot air and peat, and

means connected to said duct means for separating pea-t from the hot air.

2. Apparatus as claimed in claim 1 in which said hot air creating means comprises a blower, and said force fully throwing means comprises a motor-driven plate-like impeller.

3. Apparatus as claimed in claim 1 comprising a perforated plate in the bottom portion of said housing for distributing hot air current in an upward direction, and in which said housing is cylindrical.

4. Apparatus as claimed in claim 2, in which said peat delivering means comprises a feed hopper in said cover, and a feed screw leading from said hopper to near the bottom of said housing.

5. Apparatus as claimed in claim 2, in which said separating means comprises a cyclone-type separator enabl- 5 6 ing discharge of dried peat from the bottom and substan- FOREIGN PATENTS tially dust-free air from the top 700 1904 Great Britain References Cited UNITED STATES PATENTS 5 1,532,344 4/1925 Plummet 44-33 2,330,545 9/1943 Benoit. 34 59 KENNETH W. SPRAGUE, Primary Examiner.

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