FI71498C - FILTRERINGSFOERFARANDE OCH DAERVID ANVAENDBAR FILTERTRANSPORTOER. - Google Patents

Description

71498

FILTRATION METHOD AND FILTER CONVEYOR USED THERE

The rise in the price of fuel oil has pushed up the prices of all fuels. This in turn has made the drying of various wet waste fuels economical. Such wet fuels include wet bark, wet torn waste papers and crushed waste wood, tree branches and rhizomes, especially in wood processing plants and sawmills.

When these are dried mechanically, the presses, e.g. when drying the bark, become bark water containing 5-50 g / l of solids, bark and a piece of wood.

Even the smallest bark press dries approx. 40 i-m3 / h of wet bark and then the bark water becomes approx. 16 m3 / h. The amount of bark to be burned is 750 - 800 kg / h, ie 420 -5000 tons of dry matter per year. This fuel, of course, comes at a set price. But the more important point is that if this amount of shell is discharged into a water body, it will cause a very harmful water load. If, on the other hand, this bark water is discharged into the plant or sawmill's wastewater treatment plant 1a, the treatment plant must be dimensioned large and the bark fuel valuable in itself will in most cases have to be driven to landfill with other contaminants separated from the wastewater 11 e I

The book "Manufacture of wood pulp II, part 1" on page 171 shows the method shown in Fig. 28, in which the incoming water _2_ 714 98 is directed to the precipitation conveyor and further to the clarification tank. The peel material left on the conveyor is directed back to the press. However, no fine solid can be filtered here. Along with the water, the fine solids go into the clarifier, from which the sludge and wastewater are diverted separately.

The object of the present invention is to provide a combined filter and conveyor by which a combustible solid is separated from the shell water in a simple manner and immediately dried to a fuel.

The method according to the invention for filtering solids-containing shell water from a shell press is characterized by the features set forth in the characterizing part of claim 1. The characteristics of the filter plant are set out in claim 2.

The invention is described in the accompanying drawings and description.

Figure 1 shows the filter conveyor from the side.

Figure 2 shows the device in section at the shell water inlet.

Figure 3 shows the drying of the casing and the cleaning of the filter conveyor.

Figure 4 is an enlarged side view of the filter conveyor of Figures 1 and 3.

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Figure 1 shows a shell water inlet trough 1 with flow openings 2 at the bottom. From these, water flows over the shell layer 3 'on the wire 3.

Figure 4 shows the filtration procedure. The shell water 2 'from the shell press 14, Fig. 3, along the channel 6, containing solids, pieces of shell 2-5 mm long and a fine shell shape 0-2 mm, flows onto the wire 3, forming a thin but completely dense shell and muff layer about 3-8 mm thick. 3 '. The wire 18 runs quietly in the arrow direction.

The next opening becomes solid water 2 "on the dense layer 3 '. The muju layer 3' filters the solids from the water 2" and the layer 3 "on the wire thickens. The next opening becomes water 2" on the layer 3 "again, which is filtered. Only filtered the water 4 ', 4 ", 4"' comes through the layer 3 ', 3 ", 3"' to be filtered. also cheap and thus economical.

The wire 3 runs slowly, 0.2 to 0.5 m / min, the speed is adjusted according to the solids content of the shell water. Thus, the filtered shell water is solid-free and transparent. The water has turned light brown from the shell.

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The moving wire 3, Fig. 1, carries a solid between the rollers 8 and 9, where a little water is squeezed out so that the filter layer is not water-draining on the conveyor part 9 to 10.

Figure 3 shows the operation of the whole shell drying1 equipment and the flows of the shell water. The wet shell enters the shell drying press 14 by a conveyor 13.

The solid-containing shell water flows from the lower part of the press 14 along the channel 6 to the almost horizontal initial part of the filter conveyor from the flow openings 2. The solid remains on the wire 3 forming a filter layer 3 'and the filter conveyor rollers 8 and 9 squeeze out the running water. In the case shown in Fig. 3, the wet shell rises obliquely upwards into the drying plant to the conveyor 11, which takes the wet incoming shell together with the shredder 12. When the filter bed mixes well with the shell in the shredder, it also dries in a press 14 directly into the furnace of the factory boiler plant for combustion.

The bark water, which has flowed from the openings 2 through the wire 3 to the plate 5 and from there to the trough 17, enters the factory vertical clarifier 7 purified.

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The water coming from the press has a solid size of about 0 to 8 mm. The filter conveyor removes all solids from this water, so the solids content of the shell water entering the vertical clarifier is only about 0.1 to 0.2 g / l. This filter water, purified with a filter conveyor, no longer causes difficulties in the vertical clarifier.

Water treatment of peelers from sawmills, paper and pulp mills is becoming increasingly important as mentioned on the first page of this report.

Today, despite the high costs, even dry peeling is being pursued in order to reduce wastewater problems.

However, wet peeling is cheaper, and during the frost season it is the only viable method of peeling in the Nordic countries when it comes to large quantities of wood. The wet shell can be connected to a completely closed water circuit using Finnish patent application no. 822575 "Procedure and apparatus for water purification" and the continuously renewable filtration method according to this invention. In this case, the water 4 seeping through the filter conveyor is returned to the circulating water of the shell and not to the adventurer 7.

A shell with a fully closed water circuit11a does not cause any environmental damage when the shell water is not discharged into the water bodies at all.

Claims (4)

71498 A method for filtering dried shell-containing shell water from shell presses, the shell water being passed over a moving wire (3) and the filtered solid being fed to the same presses from which the solid water came, characterized in that the shell-containing fines are filtered 3) using solids contained in shell water as a filter aid. A method for filtering dehydrated solids containing dried combustible solids from shell presses according to claim 1, characterized in that the water filtered through the moving wire, from which the solids have been filtered by the renewable filter bed, is returned to the shell circulating water in a completely closed system. Filter conveyor for use in the method according to claim 1, characterized in that the bottom of the shell water inlet chute (1) (Fig. 4) has a plurality of flow openings (21, 2 ", 2" ') through which the shell water flows over the wire (3). Filter conveyor according to claim 3, characterized in that the device comprises a channel (6) leading from the press II 7 71498 (14) with flow openings (2) from which the incoming shell water flows through the wire (3) the device has a plate (5) and a trough (17) to direct the shell water to the clarification tank (7).