The invention relates to a process for preparing peat fibers from peat, such as that process described in U . S. 4 ,261 ,725 , Schmidt, issued April 14, 1981 , and expressly incorporated herein by reference. The process involves preparing a suspension of peat, whereby peat fibers are liberated from the parent material , and further involves separating larger particles in a dewatering step. A peat fiber material having a desired water content is obtained.

Thus far, the above results could only be obtained by the use of large peat processing equipment, which made peat harvest¬ ing economical ly feasible only in peat areas of 100 hectares or more.

It is an object of the present invention to provide a process which can be carried out in simple, mobile equipment; it is a further object to provide a process which may be carried out in relatively small peat areas, on poorly drained terrain , or in areas which were otherwise heretofore unsuitable for peat production , and which may be carried out almost year round.

The process according to this invention is described below, with reference to the drawings. The drawings represent two different installations for earring out the process. Figure 1 shows an installation for obtaining unfractionated fibrous material . Figure 2 shows an installation suitable for obtaining fibrous material of different fiber length.

The installation of Figure 1 comprises a storage tank 1 which is supplied with a peat slurry through a line 2. The slurry may have -a solids content of, for example, 10%. In tank 1 , the slurry is diluted with water to about 3% solids . This suspension is

pumped through a pipeline 4 to a separator 5 by means of a pump 3. In the separator, which may be, for example, a so called Schrotfanger, the suspension is diluted to about 1 % solids, and rocks and other coarse materials are removed . The 1 % peat suspension is conveyed to a sedimentiation tank 7 through line 6 , preferably by gravity , and further diluted to about 0.5% solids. A suitable sedimentation vessel is a lamel ler- type, which is well known in the art ^" In ^" this vessel col loidal particles and then , small fibrous particles (of less than 0.05mm) are separated , without the addition of chemicals. The colloidal suspension, containing the particles of less than 0.05 mm, is fed through a pipeline 8 into a second sedimentation vessel 9. I n this vessel are the colloidal particles precipitated by means of the addition of chemicals. Water from sedimentation vessel 9 is pumped to a distributor 1 1 ,12 ,13 , 14 by means of a pump 10 and used for addition to storage tank 1 , separator 5 and sedimentation vessel 7. The concentrated colloidal dispersion (about 5% solids) from sedimentation vessel 9 is conveyed to a centrifuge 17 by means ^" of a pump 15 and a pipeline 16 , and centrifuged . The resulting colloid fraction (18-20% solids) is removed through pipeline 18. The water phase from the centrifuge is fed through line 19 into the colloid suspension in line 8 which leads to sedimentation vessel 9.

I n addition to this, a peat fiber suspension of about 2% solids is removed from sedimentation vessel 7. This suspension is pumped by means of a pump 20 and a pipeline 21 to a concen¬ tration vessel 22. This vessel may, for example, consist of a rotating screen drum permeable to colloids and particles smaller than 0.05mm. Large particles are retained by the screen and removed from the drum. Water is injected through line 23 which is connected with line 1 1 , in order to dilute the peat fiber sus¬ pension in concentration vessel 22 and to keep the screen open¬ ings free.

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A peat suspension of about 5% solids is obtained from concentration vessel 22; this suspension is conveyed through line 24 to a conventional drying press 25. A fibrous material of about 30% dry solids is removed from the drying press by means of a conveyer belt 26; this material is suitable for burning in a heating plant and for similar purposes.

Water from line 23 , optionally also from line 19, may be used for cleaning of the press. Colloid containing water from concen- tration vessel 22 is removed through line 28 and combined with fiber containing water from the press into line 29; the combined liquid is pumped to separator 5 by means of a pump 31 and a pipeline 30.

The installation described in Figure 2 likewise contains a storage tank 1 to which a peat slurry of, for example, 10% solids is added via line 2. In the storage tank the slurry is diluted with water to about 3% solids . This peat suspension is pumped by means of a pump 3 and a pipeline 4 to a separator (not shown) , where rocks and other coarse materials are removed, and subsequently to a fractionating installation 32. This installation comprises four concentration vessels 33 ,34,35 ,36 , preferably mounted one above the other. Each of these concentration vessels 33 , 34, 35 and 36 can be of the same kind as concentration vessel 22 in Figure 1 , which means that it may consist of a rotary screen drum , capable of separating peat particles of a certain size. The screen drum of concentration vessel 33 in installation 32 has holes of a diameter of about 10 mm. The peat material which passes through the screen has a solids content of about 2.5% and flows by gravity through line 37 to screen drum 34.

Concentration vessel 33 is, for example, suitable for isolating peat material which is suitable for combustion or as a soil im¬ prover. About 10% of the peat starting material arrives at press 40 via lines 38 and 39 in the form of a 12-14% suspension . The

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press is preferably like the one described in Figure 1 . Peat material of about 30% solid content is obtained in this press.

The holes in screen drum 34 have a diameter of 1 mm. The peat suspension of about 1 % which passes through the screen flows by gravity via line 41 to concentration vessel 35. The remaining peat (about 5% solids) is fed into press 40 via lines 39 and 42. This flow amounts to about 60% of the peat starting material . The resulting product is suitable for use in cardboard manufacturing or as a filter medium.

The holes In screen drum 35 have a diameter of about 0.1 mm; the peat suspension of about 0.5% which passes through the screen flows by gravity via line 43 to drum 36 , while the remaining part is fed via line 44 into line 39 of press 40. This peat material suspension , which has a concentration of about 5% solids , comprises about 10% of the peat starting material . The fraction obtained from line 44 is suitable for the manufacture ^' of cardboard or for filter material.

Rotating screen drum 36 has holes of about 0.05mm diameter, so that only colloidal particles and very small fiber particles can pass through. The colloidal suspension which passes through has a concentration of about 0.4% solids and is removed from the installation via line 45 and pump 46. The remaining part of the peat suspension, a 5% suspension which comprises about 10% of the total peat material , is fed via line 47 into line 39 of press 40. This fraction can be used as mulch, or as an additive to the fiber fractions emanating from concentration vessel 33. The various fraction from the different concentration vessels 33 , 34, 35 , and 36 may be fed into press 40 either separately by means of lines 38 , 42 , 44, 47 , 39 and a suitable set of valves (not shown) , or the separate fractions may be mixed prior to pressing . Frac- tionation installation 32 comprises concentration vessels 33 , 34 ,35 and 36 which suitably are located above each other, or otherwise in a way that the suspension flows from one to the other by

gravity . This obviates the need for pumps for the separate concentration vessels , and transport of the suspensions does not involve a mechanical chal lenge of the fibers , which are very prone to disintegration and breaking . The fractionation installa- tion may suitably consist of standard tanks, mounted one above the other. These tanks are equipped with a rotating screen and drums , and each with draining openings for the tank and the drum, and further with a connection line to the next lower tank. A tank system of this type has the advantage that standard tanks can be used, and that the installation , by using suitable staple equipment, can be built within only a small amount of time. It is further possible to dismount the installation within a small amount of time, and to transport it to a next site by means of a truck.

The colloidal suspension , which is obtained from concen¬ tration vessel 36 , is pumped by means of pump 46 and line 45 to a lamellar-type sedimentation vessel , similar to the one described in Figure 1 and having the same function . The colloidal suspen¬ sion from the sedimentation vessel is pumped via pump 50 and line 49 to centrifuge 51 , similar to the centrifuge described in Figure 1 and having the same function. From the centrifuge a 18-20% colloidal material is obtained , which may be used as a peat mulch or as a soil moisture modifier.

The water phase from the centrifuge is removed via pipeline

53 and pump 54 and used for diluting the colloidal suspension in line 45 which leads to sedimentation vessel 48.

The water from sedimentation vessel 48 is distributed over the line system 55 through 62 , and a pump. This water is first used for cleaning of the press 40 and of each of the concen¬ tration vessels 33 and 36 , and subsequently added to storage tank 1 .

The water from press 40 is added to concentration vessel 34 via line 63 and pump 64, for dilution of the suspension .

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The above-described process makes it possible to isolate from peat the fibrous and colloidal materials and to convert these to useful materials without creating polluting byproducts. Moreover, the process can be carried out in a simple installation, which can easily be mounted and dismounted .

Furthermore, all of the water necessary for dilution of the suspensions and for cleaning the equipment can be taken from the process, and no water from other sources is necessary. In view of the large quantities of water which are used in the process, this is an important advantage. The above-described, and in the drawings illustrated , installation can easily be adjusted to other embodiments within the scope of this invention . For example, other types , or a different number, of concentration vessels may be used. More than four concentration vessels may be used for fractionation with respect to fiber size. Or the concentration vessels may be equipped with motor drive units for the drums, level controls, and other elements for propelling and controlling the integrated flow system.