WO2009125058A1

WO2009125058A1 - Method and apparatus for recovering of liquids

Info

Publication number: WO2009125058A1
Application number: PCT/FI2009/050255
Authority: WO
Inventors: Reino Pendikainen
Original assignee: Wood-Neste Oy
Priority date: 2008-04-07
Filing date: 2009-04-06
Publication date: 2009-10-15
Also published as: FI20080271A0; FI20090043A0

Abstract

The invention relates to a method for the recovering of liquids of wood particularly or other material containing capillaries, in which method, liquid is driven along the capillaries of wood (3) with vapour which is substantially formed of the inherent liquid of the wood (3) with electric energy (2) by conducting the electric energy (2) in the wood (3) being treated substantially directly with electrodes (1) fastened in the side surfaces of the wood (3) and by recovering the liquid. Furthermore, the invention relates to an apparatus for applying the method, which apparatus includes electrodes (1), a current source (2), wood (3) to be dried and means (4) for recovering wood liquids.

Description

METHOD AND APPARATUS FOR RECOVERING OF LIQUIDS

The invention relates to a method and an apparatus for the recovering of liquids of wood particularly or other material containing capillaries directly with electric energy, by conducting electric energy directly to the material being treated which simultaneously dries. However, recovered liquids are the main product here. The examination focuses mostly on wood, even though other materials containing capillaries exist in addition to wood.

It is previously known to recover wood liquids by mechanical compression, by dry distillation and by tapping from a living tree, e.g. raw rubber from rubber trees, sap from birches and resin from conifers. Traditionally, tar has been separated from conifers in tar kilns, which is closest to a pyrolysis process. Liquids generated when producing coal gas have also been recovered if required.

Conventionally, timber has only been dried and the recovery of wood liquids has not been considered necessary. Despite that, specification PCT/FI2007/000214 introduces an apparatus provided with liquid recovery. This liquid recovery has now been further developed with the explicit object of stressing the importance and possibilities of the recovery of wood liquids. Liquid is well applicable for the purposes of chemicals industry, for pharmaceuticals, cosmetics and perfumes etc.

The object of the invention is thus to introduce a method and an apparatus by means of which the recovery of wood liquids takes place in connection with the drying of wood, because the drying of wood is still a common operation in the utilisation chain of timber. An object of the invention is also to provide a liquid recovering apparatus which is well integratable in various kinds of production lines in the sawmill and wood product industries, with other products such as sawn timber, round logs and finished wooden objects.

The object of the invention will be achieved with a method and an apparatus the characteristic features of which are described in more detail in the enclosed claims.

The invented method is based on vaporising liquid contained by wood by means of electricity, by conducting an electric current through the wood. Then, electricity flowing through wood heats up liquid in the wood and/or converts part of liquid to vapour the high pressure of which drives liquid out of the wood along wood - capillaries and the liquid is recovered. Finally, only vapour exits, which can be condensed for recovery. It is worth noticing that quite a part of wood liquid exits the wood explicitly as liquid, whereby a considerable amount of energy is saved compared to the total vaporisation required by previous methods. It should be noted that the apparatus according to the invention is designed to operate in normal conditions, i.e. in normal air pressure and mostly in a space warmer than the temperature of 0⁰C. Naturally, these easily providable conditions incur a lot of savings compared to that one would have to provide e.g. negative or positive pressure, high temperatures etc. Nothing prevents from utilising the method together with other liquid removal or drying methods.

In conventional wood drying, wood materials contained by vapour have not been utilised, but the vapour has been led to the open air. After the recovery of liquid, wood can be used totally like previously as dry for building and other conventional purposes. According to tests, the volume of wood will not change much in the process and the shrinkage differs only slightly from zero.

Next, the invention will be examined in the light of an advantageous embodiment to which it will not, however, be limited.

Fig. 1 schematically shows an arrangement for implementing a method according to the invention.

The figure shows electrodes 1, a current source 2, wood 3 to be dried and a means 4 for recovering wood liquids which means 4 is in this embodiment a trough-like means located below the wood to be dried.

When conducting a high-voltage electric current obtained from the current source 2 via the elastic electrodes 1 to the sides of the wood 3, moisture inside the wood 3 starts to separate as the wood 3 heats up. Wood is typically driest from the centre, whereby the centre has the highest electric resistance. Thus, the centre of the wood 3 starts to heat up first. When water in the centre vaporises, it drives water out of the wood 3 via wood capillaries. Finally, there is only a little of vapour which is hotter and drier in the centre of the wood 3 than father out. The hotter and drier vapour is also in higher pressure and drives the moister vapour of surface layers out. After the vapour has exited, the wood has dried and its resistance has increased so high that the current supplied by the current source 2 decreases substantially, due to which the energy consumption of the apparatus decreases automatically. It is easy to monitor the progress of drying by suitably observing the change of the electric current with an ampere meter. The drying result can be affected by changing voltage, whereby increasing the voltage provides a better drying result. On the other hand, in the initial stage of drying when a lot of liquid comes out of the wood, it can even be necessary to decrease the power.

For controlling the output of liquid, it is possible to use various ways of controlling power known as such, e.g. periodic on/off control and/or power control by changing voltage and/or current. Electricity can be alternating or direct current of different form. Used voltage is typically a few kilovolts.

A considerable part of the liquids of the wood 3 exits without boiling in the form of liquids. Liquid having come out in the form of liquid flows in the recovery trough 4 below. If wanting to recover the part of liquid coming out in the form of vapour, the apparatus is provided with a traditional condensation apparatus (not shown in the figure).

In practical arrangements, it is possible to use several different alternatives for implementing the invention. Fig. 1 shows the drying of a round piece of wood, e.g. a pole. Two conventional versions are shown of the electrode 1, an annular one and an electrode divided into two or more parts in the circle. Other versions are also possible. A more important utilisation area might still be the drying of sawn timber. Then, the electrodes 1 can be plate-like and the pieces of sawn timber to be dried can be between them adjacently, spaced with small air gaps from which an airflow can be blown in order to lead moisture out. In the other electrode, located farther down, or in its immediate vicinity, a trough 4 can be constructed to collect liquid from which liquid is let run for recovery. Liquid is well applicable for the purposes of chemicals industry, for pharmaceuticals and perfumes. If a quite exhaustive recovery of wood liquids is required, the drying can be arranged to take place in a hydrophobic light liquid, whereby the wood liquids sink to the bottom of the trough and are easily collectable from there. Naturally, the liquid in question cannot conduct electricity or be inflammable. The electrodes can also be perforated in order to enhance the exit of vapour and liquid. To assure the flow of electricity, the contact surface of the electrodes against the wood can be provided with a spongy surface and a moisturising apparatus. If required, it is also possible to use liquid more electrically conductive, such as e.g. saline water, for the moisturising.

It is also possible to consider using some paste- or gel-type material for conducting electricity.

If desiring to increase the exit of liquid from the wood without increasing the voltage, it is possible to divide the electrode into several successive part-electrodes the coupling of which enables keeping the voltage reasonably low. Then, the electrode has been divided into part-electrodes in the longitudinal direction of the wood or equivalent.

The exit of liquid in a desired direction can also be increased by constructing at least one electrode movable along the surface of the wood or equivalent. Then, e.g. the upper electrode can be made crawler-like with rotating rollers with which the wood surface is 'rolled' in the desired direction.

The trough 4 is advantageously large enough in order to contain so much hydrophobic, electrically non-conductive, fire-proof liquid that the whole apparatus can be operated sunk in the liquid.

Pre-heating can be utilised in drying the material. If there is extra or inexpensive heat energy available, the pieces of wood to be dried can be pre-heated to some extent, which reduces the electricity costs of the actual drying apparatus.

The efficiency of the apparatus is expected to be excellent, because no unnecessary heating of drying chambers or similar spaces takes place and the drying is only exerted on the wood to be dried. Besides, no heat is transferred in pipelines in the factory area.

As it is evident from the above description, the invention can be implemented in many different ways. It is still possible to consider using the invention together with other liquid recovery and/or drying methods known previously. Thus, the invention is not limited to the above-described examples, but it can vary within the scope of the inventive idea presented in the claims.

Claims

1. A method for the recovering of liquids of wood or other material containing capillaries, characterised in that liquid is driven along the capillaries of wood (3) or other material containing capillaries with vapour which is substantially formed of the inherent liquid of the wood or equivalent (3) with electric energy (2) by conducting the electric energy (2) in the wood or equivalent (3) being treated substantially directly with electrodes (1) fastened in the side surfaces of the wood or equivalent (3) and that the liquid is recovered.

2. A method according to claim 1, characterised in that a considerable part of the liquids of the wood or equivalent (3) exits without boiling as liquids which are recovered in a trough (4).

3. A method according to claim 1, characterised in that, for controlling the output of liquid, various ways of controlling power known as such are used, e.g. periodic on/off control and/or power control by changing voltage and/or current.

4. A method according to claim 1, characterised in that pre-heating is utilised in drying the material.

5. An apparatus implementing the method according to claim 1, characterised in that it includes electrodes (1), a current source (2) and means (4) for recovering wood liquids, and that the electrodes (1) are permeable to vapour and/or liquid and elastic.

6. An apparatus according to claim 5, characterised in that at least one electrode (1) is constructed movable along the surface of the wood or equivalent (3).

7. An apparatus according to claim 5, characterised in that for liquid separating of wood or equivalent (3) is constructed a recovery by a trough (4) in the lower part of the apparatus, and that for liquid separating as vapour is constructed a condensation device known as such.

8. An apparatus according to claim 5, characterised in that the trough (4) is large enough in order to contain so much hydrophobic, electrically non- conductive, fire-proof liquid that the whole apparatus can be operated sunk in the liquid.

9. An apparatus according to claim 5, characterised in that the electrode (1) is divided into part-electrodes in the longitudinal direction of the wood or equivalent (3).

10. An apparatus according to claim 5, characterised in that the used voltage is typically a few kilovolts.