CA1217971A - Process and apparatus for the dewatering of peat - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The invention concerns a process as well as an apparatus, such as a press, for the mechanical dewatering of peat to a predetermined degree of humidity, for example about 70%. For this purpose, there is carried out a progressive compression of peat on a certain distance by continuously bringing closer pressure elements and elements loaded with humid peat. A series of pressure blocks whose forward movement is dependent on the forward movement of a series of molds is adapted to increasingly penetrate in the molds, thereby increasing gradually the pressure within the peat. In a second step, the penetration of the pressure blocks in the molds is maintained substantially constant for a certain distance, after which the pressure is released as a result of a progressive decrease of the penetration of the pressure blocks in the molds until contact between the latter ceases, which provides for a decompression of the peat. In this manner, it is possible to obtain a partially dewatered peat in which the degree of humidity is homogeneous and substantially constant, such as about 70%.

Description

37~

This invention relates to a process and an apparatus for the mechanical detouring of peat More particularly, the invention is directed to the progressive compression of peat for a certain distance, such as about six feet, by allowing two conveyors to converge towards one another. One of the conveyors may carry molds to contain raw peat while the other has pressure elements, both working in pairs.
There is presently a marked interest to use peat as a binding agent for poulticing iron ore, as a substitute for bentenite. Although this latter mentioned material gives pellets of excellent quality, it is a substance which is expensive mainly because it is only available from specific areas of the world, such as the state of Wyoming in the U.S.A. and Greece. Furthermore, it contains silica which has the disadvantage of mixing with the iron ore when preparing the pellets. Tests made with peat have given good results and as long as a good supply can be found it is only necessary to give it a suitable treatment to make it readily acceptable as a binder.
When carrying out tests with peat it was found that shredded peat containing between about 70 - OWE water, preferably 72%, was highly suitable as a binder. Since the deposits of peat always contain a large amount of water and because this amount is not consistent, there is a need for an apparatus which can debater peat on a continuous basis and to a specific degree of humidity any forms of mechanical detouring have been disclosed in the prior art: roll and belt presses, filter presses, screw presses, centrifuges and screens. High pressure is required to reduce the water to a level of about OWE. An optimum combination of high capacity and pressure is therefore needed.

I

'row well known presses are the Ingersoll-Rand Vari-NipTM press and the Solacer Belt Press. Both can reduce water content to the 65%-70/~ level.
The Vari-Nip press consists of two horizontal rolls mounted in a sealed vat. One roll is fixed, and the other is movable to allow for variable nip openings.
If the mat thickness varies, the variable roll automatically-lye follows this change and maintains a constant nip load, resulting in a constant discharge of solids.
The slurry, at an incoming solids concentration of approximately 3% to 5%, enters the sealed vat at a pressure of approximately 3 to 5 prig. The slurry then drains by pressure filtration and forms a mat on the roll surfaces, which is carried forward into the nip by the rotation of the rolls. In the nip, the mat is further detoured to the desired dryness of up to OWE solids.
Immediately beyond the nip, the solids are scraped off the rolls and guided into a top-mounted, screw-type shredder conveyor. The detoured material is then gravity-discharged at the rear end of the machine for ultimate disposal. The priest flows through the roll faces and is discharged at the bottom of the press.
In the Solacer "multi-nip" press, the peat is moved through the machine on belts. The press has a large number of pairs of rollers, which apply progressively increasing pressure as the peat passes through the machine. In the inlet zone the peat is stabilized by application of moderate pressures. This feature minimizes rejection of the peat at the nip of the rolls In the later stages, higher pressures (approximately 600 psi) are applied to maximize the extract-ion of water from the stabilized "cake" of peat.

The belt system consists of a total of four belts.

Two are polyester sieves between which the peat travels through the machine. Above the upper sieve belt is a resilient rubber belt, a key element in stabilizing the peat in the pressing zone, which allows for foreign material that might find its way into the press with the feed. Below the lower sieve belt is a harder rubber belt provided with diagonal channels on a herringbone pattern, through which the water is expelled. Both presses are expensive and complicated to operate.
According to the present invention, there is provided an apparatus for the mechanical detouring of peat to a predetermined degree of humidity which comprises con-voyeur means, means for continuously feeding peat to the conveyor means' pressure means engage able with the conveyor means when the latter are subjected to continuous circular lion, means enabling the pressure means to cause the peat to undergo a gradual increase of pressure while it travels along an initial part of the conveyor means to thereby remove water from the peat' means for gradually decreasing the pressure while the peat travels along a remaining part of the conveyor means, means for continuously removing peat dried to the pro-determined degree from the conveyor means; and means for collecting the dried peat.
Preferably, there are provided means for keeping the peat at a constant pressure at the end of said gradual increase of pressure and before decreasing the pressure.
The conveyor means preferably comprises a chain of receptacles.
According to the invention, there is also provided a process which comprises providing a continuous circulation of receptacles on a conveyor, continuously feeding raw peat to the receptacles, subjecting peat contained in the 7~7~

receptacles to a gradual increase of pressure along an initial part of the conveyor, gradually decreasing the pressure while the peat travels along a remaining part of the conveyor, continuously removing peat dried to the predetermined degree of humidity from said conveyor, and collecting the dried peat.
Preferably, there is an intermediate step after the gradual increase of pressure and before decreasing the pressure, during which peat is kept at a constant pressure.
The invention will now be illustrated by means of the annexed drawings which are only given for the purpose of illustration and are not intended to be limiting.
In the drawings:
EGO. 1 is an elevation view of an apparatus for detouring peat according to the invention, FIG, 2 is a view taken along line 2-2 of Fig l;
FIG. 3 is a view in elevation showing the feeding as well as the first stage of drying of the same apparatus FIG. 4 is a view in elevation showing the last stages of drying as well as the peat collector of the same apparatus, FIG. 5 is a view showing the pressure members in pressing position while fully engaged in the receptacles of the lower conveyor, FIG. 6 is a view taken along line 6-6 of FIG 5, FIG. 7 is a view taken along line 7-7 of FIG. 1, FIG. is an end view of a mold receptacle, FIG. 9 is a side view of the same mold, and FIG. 10 is a partial view taken along line 10-10 of FIG. 9, Foxily and 12 show alternatives for the receptacles.

~797~

The second sheet of drawings contains FOX, 8, 9, 10, 11 and 12.
Referring to the drawings, there is shown a peat press 1 which is mounted on a trailer 3. The press 1, which is an apparatus for the mechanical detouring of peat to a predetermined degree of humidity, essentially consists of a feeder 5, a lower conveyor 7, an upper con-voyeur 9, a peat collector 11, the whole being mounted on a frame 13.
The frame 13 can be designed in any manner which is suitable to mount the two conveyors 7 and 9 as well as the feeder 5 and the collector 11. In the model which has been illustrated, it merely consists of a pair of Beams 15, 17, which are disposed over a plurality of transverse I-beams 19, all as particularly shown in Fig. 1 of the drawings. The transverse beams 19 sit on corresponding bases 21 which rest on the trailer 3.
As illustrated, the rear end of the trailer 3 is the forward end of the apparatus 1 and the front end of the trailer constitutes the rear end of the apparatus 1. At the front end of the apparatus 1, there is a sprocket wheel 23 which is mounted on a suitable shaft 25 while at the rear end of the apparatus there is a sprocket wheel 27 which is mounted on a corresponding shaft 29. A sprocket chain 31 carrying receptacles 33, which will be described more fully hereinafter, is rotatable mounted around both sprocket wheels 23 and 27. It should be noted that while the sprocket wheel 23 is freely rotatable around its shaft 25, the sprocket wheel 27 is, on the other hand, operatively connected to a motor (not shown in the drunks In opera-I I

lion, the motor will cause rotation of the sprocket chain around both sprocket wheels 23 and 27.
As shown in FOX and 7, over the pair of I-beams 15, 17, which are mounted in parallel fashion and extend sub-staunchly along the entire length of the apparatus, there are a series of staggered roller bearings 35, 379 which are mounted over each lower I-beam. It will be noted that a roller bearing 35, which is mounted on one I-beam, corresponds to a roller bearing 37, which is mounted on the other lower I-beam. These roller bearings are staggered-lye arranged and are mounted on the beams 15, 17, in a manner known to those skilled in the art. Each pair of bearings 35, 37, receives a roller 39, and because of the staggered arrangement of the roller bearings, the rollers are staggeredly arranged on the frame constituted by the I-beams 15, 17.
As shown, the staggeredly mounted rollers 39 are evenly distributed along the entire length of the frame so as to constitute a support for the receptacle containing sprocket chain 31. The staggered arrangement of the rotatable rollers 39 enables to maintain a constant and non-pulsating pressure in the sprocket chain 31 as the latter rotates along the frame, around both sprocket wheels 23, 27.
For a better description of the receptacles 33, and the mounting thereof on the sprocket chain 31, refer-once is made to Figs. 4 and 6 to 10 inclusive. As shown, each receptacle 33 comprises two vertical sides 41, 43, which are parallel to each other, and a bottom 45 which connects the two sides 41, 43, in the particular manner shown in Fig. 6 of the drawings. Preferably, the bottom 45 is welded to the sides 41, 43. Also as shown 9 the bottom 45 is provided with perforations 47 to permit water I
to escape from the receptacle 33 when the peat is under pressure as will be discussed later. Each perforation 47 has a first portion 49 of smaller cross-section followed by a second portion 51 of larger cross-section. This particular arrangement is intended to prevent the peat from escaping through the perforations.
Returning to the two sides 41, 43, each has a downward extension 53, 55 past the bottom 45, thereby defining parallel flanges. Bolts 57, 59, are disposed, as shown in the bottom 45, for mounting the receptacle on the chain 31 as will now be explained. AS shown in Fig. 6, the receptacle 33 sits over the sprocket chain 31 by means of its flanges 53, 55, and the receptacles 33 are attached to the chain by means of the bolts 57, 59. For this purpose, the bolts 57, 59 extend through links 61 of the sprocket chain 31 and are screwed tightly thereon by means of nuts 63, 65.
In the embodiment illustrated, the sides 41, 43, have been shown with perforations 67 which are identical to perforations 47 provided in the bottom 45 of the receptacle 33. However, in most cases, it has been found that the perforations 67 in the sides 41, 43, are not necessary and, therefore, it may be completely satisfactory to have receptacles wherein the perforations are only provided in the bottom 45.
Turning now to the second conveyor 9, there are provided sprocket wheels 69 and 71 which are respectively mounted at both. ends of the frame 1, at a higher level than the sprocket wheels 23 and 27. In the case of conveyor 9, both sprocket wheels 69, 71 are freely rotatable. A sprocket chain 73 is rotatable mounted around both sprocket wheels 69, 71 in the particular manner shown in Figs. 3 and 4 of the ~797~

drawings, and a series of pressure members 75 are attached in a manner which will be described later to the sprocket chain 73.
It was mentioned above that the idea of the invention is to create an increasing pressure on the peat as it advances on the lower conveyor, optionally followed by a treatment at constant pressure, and, finally, by a period wherein the pressure of the peat is gradually decreased. This is made possible by causing the chain 73 to first of all gradually approach sprocket chain 31 followed by a stage wherein the sprocket chain 73 causes the pressure in the receptacle 33 to be constant for a certain distance along the conveyor 31; after which the pressure is gradually decreased by allowing the sprocket chain 73 to gradually move away from the sprocket chain 31. For this purpose, the chain 73 is guided by three guides 77, 79 and 81. Referring to Fig. 3, it will be seen that guide 77, which is in the form of an I-beam, is adjustable connected to guide 79 to be downwardly inclinable in order to gradually bring the sprocket chain 73 from the sprocket wheel 69 closer to the first sprocket chain 31, thereby, as a result of the contact of the two conveyors 7 and 9, inducing rotation of the sprocket chain 73 and enabling the pressure members 75 to penetrate deeper and deeper into the receptacles 33, as particularly shown in Figs. 6 and 7 of the drawings, to gradually increase the pressure of the peat contained in the receptacles 33. The guide 79 is nearly horizontal and is mounted to provide a very slowly decreasing distance between the sprocket chain 31 and the sprocket chain 73, consequently causing such a perpetration of the pressure members 75 in the receptacles 33 as to keep the peat under constant pressure while the platter is traveling underneath the guide 79. Finally there is a .~2~7~

guide 81 which is connected to the guide 79 to be upwardly inclinable in order to gradually bring the sprocket chain 73 further away from the sprocket chain 31 until the sprocket chain 73 reaches the sprocket wheel 71. This will cause the pressure members 75 to penetrate less and less into receptacles 33, thereby gradually decreasing the pressure of the peat contained in the receptacles. It will be noted that the connection between the guides 77, 79 and 81 does not form part of the invention and can be carried out in any manner known to those skilled in the art. The way shown in the drawings is only for illustrative purposes Of course, the chain 73 cannot be allowed to slide along the guides 77, 79, 81, per so. Suitable sliding means must be provided end in the embodiment illustrated, this is made possible by using transverse rollers 83. These rollers are held by the guides 77~ 79 and 819 as shown in the draw-ins and as will be explained in more detail hereinafter.
For the time being, it is merely sufficient to mention that the chain 73 rests against the rotatable rollers 83 and that the latter are staggeredly arranged to maintain a constant and non-pulsating pressure in the chain 73.
It was mentioned above that the guides 77 and 81 are adjustable with respect to the guide 79. This is essential in order to be able to vary the angles of incline-lion of the guides 77, 79, depending on the nature of the peat to be detoured, especially if the water content of the raw peat varies to a large extent.
Returning to the upper conveyor 9, we shall now describe the pressure members 75 in greater detail. Each pressure member 75 comprises a base plate 85, a holding plate 87 which is spaced from the base plate 85 and is parallel thereto, and two side plates 89, 91, which are _ g ~7~7~

joined together by means of the base plate 85 and the hold-in plate 87, all as shown in FIG. 6 of the drawings. The pressure member 75 is obviously shaped to sit substantially exactly in the receptacle 33. It will be noted that the lower edges of the side plates 89, 91, are pointed as at 93, 95, in order to prevent peat from accumulating between the sides 41, 43, of the receptacle 33 and the side plates 89, 91, of the pressure member 85. The two side plates 89, 91, each have an upward extension 97, 99, past the holding plate 87, to define parallel flanges. It will be noted that bullet, 103 are provided in the holding plate 87 for connection of the pressure member 75 to the sprocket chain 73. For this purpose, the sprocket chain 73 is disposed above the pressure members US between the flanges defined by the extensions 97, 9g, and the pressure members are attached to links 105 of the sprocket chain 73 by means of nuts 107, 109, screwed onto the bolts 101, 103.
It has been pointed out before, that the sprocket chain 73 is allowed to slide along the guides 77, 79 and 81 by means of the rollers 83. Before further describing the arrangement of the rollers, it should first of all be pointed out that, as in the case o-f the lower I-beams 15~
17, the guides 77, 79 and 81 also appear as pairs of I-beams which are parallel to one another. Underneath each pair of I-beams 77, 79 and 81, there is a series of staggeredly arranged roller bearings 111, 113, so that a roller bearing 111 underneath one specific I-beam 77, 79 or 81, corresponds to another roller bearing 113 which is disposed underneath the other parallel upper I-beam 77, 79 or 81 of a specific pair. As the rollers 83 are mounted in the roller bearings 111, 113, in known manner, there is provided a staggered arrangement of the rollers 83 on the upper I-beams 77, 79 iota or 81, which will make sure that there will be constant and non-pulsating pressure in the chain 73.
The mounting of the guides 77, 79 and 81 on the frame will now be described. A number of transverse members 19 are disposed underneath the lower I-beams 15, 17, to maintain the latter mentioned I-beams in horizontal post-lion. In other words, the parallel longitudinal beams 15, 17 rest on a plurality of I-beams 19. Bases 21, as mentioned above, are provided on the frame to mount the transverse members 19. A number of additional transverse members 115 are disposed above each pair of upper I-bearns 77, 79 and 81 in the particular manner shown in Fig. 1 of the drawings. As shown, some of the transverse members 19 are connected to corresponding transverse members 115 by means of holding rods 117. Preferably, there is a first pair of holding rods to hold the first pair of downwardly inclinable I-beams 77, there is a plurality of holding rods 117 to hold the second pair of horizontal I-beams 79, and there is a last pair of holding rods 117 to hold the third pair of upwardly inclinable I-beams 81.
In order to make sure that the upper turn of the sprocket chain 73 remains horizontal without touching the upper ends of some of the holding rods 117 and the guides 77, 79 and 81, a roller 119 is mounted in known manner between the upper end of the first pair of holding rods 117 and a second roller 121 is mounted between the upper ends of the last pair of holding rods 117. As shown, these two rollers 119, 121, will be used to support the sprocket chain 73 during its return pass.

As mentioned above, feeding of the apparatus according to the invention is carried out by means of a hopper 5, of known construction, into which peat is loaded 3LZ17~7~

for filling the receptacles 33 as they pass underneath the hopper 5. The collector 11 is made of a hood 123 and an impeller 125 which is operatively connected to a driving means (not shown) so as to remove the peat dried to a predetermined degree and throw it to a suitable container trot shown).
Preferably, the pressure members 75 are made of two identical steel blocks which are welded side to side, as shown in Fig. I
In order to make sure that the pressure remains constant while the lower conveyor passes underneath the guide 79, the distance between the upper and the lower roller increases at the rate of I inch on a distance of 12 feet.
The preferred distance between the perforations to make sure that there is a satisfactory escape of water is between 1/2 to 1 inch, or less than 1 inch.
The operation of the device is of course self-understood. It is merely sufficient to mention that the motor is operated to drive the sprocket wheel 27 so that the lower conveyor moves in the direction indicated by the arrow 133. As the upper conveyor becomes closer to the lower conveyor, the upper conveyor will be moved along by the action of the lower conveyor.
The peat which is filled into the receptacles 33 is gradually pressed by the pressure members 75 until it is discharged from the apparatus by moans of the impeller 125.
The perforations 47, can also be in the form of conic eel holes not shown in the drawings alternatively, with role-fence to FIGURES 11 and 12, there may be provided tapered slots 127 which permit the evacuation of water. In addition the both Tom 45 may be covered with a screen 129 to prevent small part-ales from escaping through the perforation or through the ~Z17~7~

tapered slots.
Other rollers 131 may also be associated with rods 117 to further help in keeping the chain 73 horizontal.

Claims (16)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. Apparatus for the mechanical dewatering of peat to a predetermined degree of humidity which comprises:
a frame, first and second sprocket wheels respectively mounted at both ends of said frame, a first sprocket chain rotatably mounted around said sprocket wheels, said second sprocket wheel being freely rotatable, a motor operatively connected to said first sprocket wheel to cause rotation of said sprocket chain around said first and second sprocket wheels, a continuous series of receptacles mounted on said sprocket chain, each receptacle comprising two vertical sides which are parallel to one another, a bottom connecting said two sides and provided with means to permit water to escape from said receptacle when said peat is under pressure, said two sides each having a downward extension past said bottom to define first parallel flanges, first bolts being provided in said bottom, said first sprocket chain being disposed under-neath said receptacles between said first flanges, said receptacles being attached to links of said first sprocket chain by means of nuts screwed onto said first bolts, a plurality of first transverse freely rotatable rollers evenly distributed along the length of said frame and which are adapted to support said receptacle containing sprocket chain as the latter moves along said frame, pressure means engageable with said receptacles when said receptacles are subjected to continuous circulation, means enabling said pressure means to engage with said receptacles and to cause said peat to undergo a gradual increase of pressure while said peat travels along an initial part of said first sprocket chain to thereby remove water from said peat, means for gradually decreasing said pressure while said peat travels along a remaining part of said first sprocket chain, means for keeping said peat at a constant pressure at the end of said gradual increase of pressure and before decreasing said pressure, means for continuously removing peat dried to said predetermined degree from said receptacles; and means for collecting said dewatered peat.

2. Apparatus according to claim 2, which comprises third and fourth sprocket wheels respectively mounted at both ends of said frame, at a higher level than said first and second sprocket wheels, both said third and fourth sprocket wheels being freely rotatable, a second sprocket chain rotatably mounted around said third and fourth sprocket wheels, a series of pressure members attached to said second sprocket chain, a down-wardly inclinable first guide to gradually bring the second sprocket chain from the third sprocket wheel closer to the first sprocket chain thereby inducing rotation of said freely rotatable sprocket chain and enabling the pressure members to penetrate deeper and deeper into said receptacles to gradually increase the pressure of the peat contained in said receptacles, a second guide adapted to provide a very slowly decreasing distance between the first and second sprocket chains and consequently causing such a penetration of said pressure members in said receptacles to keep the peat under constant pressure while said peat is traveling underneath said second guide, and an upwardly inclinable third guide to gradually bring the second sprocket chain further away from the first sprocket chain until it reaches the fourth sprocket wheel, so as to cause the pressure members to penetrate less and less into said receptacle to gradually decrease the pressure of the peat containd in the receptacles.

3. Apparatus according to claim 2, which comprises a plurality of second transverse freely rotatable rollers held by said first, second and third guides, said second sprocket chain resting against said second rotatable rollers.

4. Apparatus according to claim 3, wherein said first and third guides are adjustable with respect to the second guide so as to vary their angles of incli-nation depending on the nature of the peat to be dewatered.

5. Apparatus according to claim 2 , wherein said pressure member comprises a base plate and a holding plate spaced from said base plate and parallel thereto, two side plates joined together by means of said base plate and said holding plate, said pressure member being shaped to fit substantially exactly in said receptacle, the lower edges of said side plates being pointed to prevent peat from accumulating between the sides of said receptacle and the side plates of said pressure member, said two side plates each having an upward extension past said holding plate to define second parallel flanges, second bolts being provided in said holding plate, said second sprocket chain being disposed above said pressure members between said second flanges, said pressure members being attached to links of said second sprocket chain by means of nuts screwed onto said second bolts.

6. Apparatus according to claim 5, wherein said first, second and third guides each comprises a pair of upper I-beams.

7. Apparatus according to claim 6,wherein said frame comprises a pair of lower I-beams mounted in parallel fashion and extending substantially along the entire length of the appa-ratus, a series of staggeredly arranged roller bearings mounted over each said lower I beams, a roller bearing on one lower I-beam corresponding to another roller bearing on the other lower I-beam so as to provide a staggered arrangement of said rollers on said lower I-beams, another series of staggeredly arranged roller bearings mounted underneath each said pair of upper I-beams, a roller bearing underneath one upper I-beam corresponding to another roller bearing on the other upper I-beam of one specific pair, so as to provide a staggered arrangement of said rollers on said upper I-beams, a plurality of first transverse members disposed underneath said lower I-beams to maintain said lower I-beams in horizontal position, bases on said frame to mount said first transverse members, a plurality of second transverse members disposed above said pairs of upper I-beams, said upper and lower member being connected by means of holding rods.

8. Apparatus according to claim 7, which comprises a first pair of holding rods to hold said first pair of downwardly inclinable I-beams, a plurality of holding rods to hold said second pair of horizontal I-beams, and a last pair of holding rods to hold said third pair of upwardly inclinable I-beams.

9. Apparatus according to claim 8, which comprises a first roller mounted between the upper ends of said first pair of holding rods and a second roller mounted between the upper ends of said last pair of holding rods, said first and second rollers to support the second sprocket chain during its return pass.

10. Apparatus according to claim 9, which comprises perforations in the bottom of said receptacles to allow for the escape of water from peat under treatment.

11. Apparatus according to claim 10, which also comprises perforations in the sides of said receptacles for additional water to escape from said peat under treatment.

12. Apparatus according to claim 11, wherein each perforation has a first portion of smaller cross-section followed by a second portion of larger cross-section to prevent peat from escaping therethrough.

13. Apparatus according to claim 12, wherein each pressure member is made of two identical steel blocks welded side to side.

14. Apparatus according to claim 13, wherein the distance between the upper and lower rollers, at the stage where peat passes opposite the second guide, decreases at the rate of 1/4" on a distance of twelve feet so as to keep the pressure constant within the peat.

15. Apparatus according to claim 14,wherein the distance between the perforations varies between 1/2 to 1 inch.

16. Apparatus according to claim 15, which comprises an impeller mounted on said frame in a position to remove the dewatered peat from the last receptacle, and a hood to cover said impeller and to direct said dewatered peat in a collector.