RU2574401C1 - Method of extraction from wood - Google Patents

Abstract

FIELD: woodworking industry.

SUBSTANCE: method comprises the following steps: preparing wood particles of at least a first class and a second class, placement of a thin layer consisting of wood particles of the first class over the next layer consisting of wood particles of the second class, and extraction of the wood particles with liquid extractant. The extractant flows downward first through the thin layer, then through the next layer. At that the wood particles of the first class are thinner than the wood particles of the second class, and thus the thin layer has a lower permeability than the next layer.

EFFECT: use of the proposed method enables to extract energetically efficiently the corresponding substances from wood.

12 cl, 3 dwg

Description

This invention relates to a method of extraction from wood. In particular, taxifolin and / or arabinogalactan are extracted from wood.

Typically, wood is chopped or ground before extraction. The resulting chips or crushed material is loaded into the percolator and the appropriate extraction liquid is introduced.

The objective of the invention is to provide a method of extraction from wood, which, when economically and reliably carried out, makes it possible to quickly, cost-effectively and energy-efficiently extract the corresponding substances from wood. Moreover, in particular, taxifolin is extracted as efficiently as possible with ethanol and / or arabinogalactan is extracted as much as possible with water from wood.

This problem is solved using the distinctive features of paragraph 1 of the claims. The subject matter of the dependent claims are preferred improvements of the present invention. Thus, the problem is solved using the method of extraction from wood, which includes the following stages:

(i) preparing wood particles of at least a first class and a second class,

(ii) laying a thin layer consisting of particles of wood of the first class on top of the next layer consisting of particles of wood of the second class.

(iii) extracting the wood particle with a liquid extracting agent (also: extracting liquid or solvent), wherein the extracting agent flows from top to bottom first through a thin layer and then through the next layer. Particles of wood of two classes according to this invention are distinguished by size reduction. First class wood particles are smaller than second class wood particles. Thus, a thin layer has a lower permeability than the next layer. The “permeability” of a layer describes the amount of extracting agent that passes through the layers at the same layer thickness, the same pressure and at the same time intervals. To compare the permeability of different layers, it is necessary to measure the amount of extracting agent passed through the layers under the condition of the same layer thickness at the same pressure and for the same time intervals. Less fluid passing means less permeability of the corresponding layer. Alternatively, it is also possible to measure the "permeability" of the various layers with a constant amount of fluid passing and variable pressure. The higher pressure required for the same amount of fluid passing through indicates less permeability of the layer. When carrying out the method according to the invention, the individual layers are preferably arranged as horizontal layers in a percolator. In this case, the extracting agent enters the percolator from above. In this case, the thin layer is located so that the extracting liquid inevitably first flows through the thin layer, and then through the next layer with wood particles of the second class. Thus, the lower permeability of the thin layer increases the pressure above the thin layer and reduces the pressure drop along the height of the layers. As a result, the circulation of the extracting agent improves.

Very small particles of wood, in particular less than 1 mm, are undesirable from a technological point of view due to poor permeability, but their appearance is inevitable during grinding. According to this invention, an important advantage of a thin layer is the prevention of too much pressure drop during extraction. In particular, by using a thin layer, the pressure drop in the percolator layer is reduced and, as a result, the circulation of the liquid extracting agent is improved. The liquid extractant passes through the percolator, in particular in several cycles. In this case, the extracting agent passes each time it passes through a thin layer, so that small particles of wood and possibly any impurities are retained in the thin layer. As a result, the extracting agent leaving the percolator ultimately is as free as possible from small particles of wood and contaminants. Preferably, the extracting means after leaving the percolator should no longer be filtered and, accordingly, in the method according to the invention, the operating time or, accordingly, the size of the filter element connected to the percolator is significantly reduced. Thus, a thin layer also serves as a pre-filter.

In a preferred embodiment, fine and coarse wood particles are distinguished by the average particle size distribution. Thus, it is envisaged that the average value (first average value) of the particle size distribution of all particles of wood of the first class is less than the average value (second average value) of the particle size distribution of all particles of wood of the second class.

Particle size, in particular, is the nominal sieve size of wood particles. The nominal particle size of wood is the size of the sieve openings through which at least 95 mass% of the material passes.

It is particularly preferable to determine the nominal sieve size using a sieving method according to DIN EN 15149-1: 2010 or DIN EN 15149-2: 2010. According to these standards, a suitable amount of stacked sieves is used to determine the nominal sieve size and the corresponding particle size distribution. In this case, the diameter of the holes or, accordingly, the mesh size of individual sieves decreases from top to bottom. Horizontal shaking of the sieve stack occurs in one or two directions. Further, according to these standards, the average particle size distribution is also determined. Accordingly, the average value is a value that divides the distribution into two equally sized parts and graphically represents the intersection of the cumulative particle size distribution curve with a 50% horizontal. Preferably, wood particles with the smallest average particle size distribution are considered to be “the thinnest wood particles” and are thus applied to a thin layer.

Particularly preferably, the average value (first average value) of the first class is less than or equal to 3 mm, preferably less than or equal to 2 mm, particularly preferably less than or equal to 1 mm, more preferably less than or equal to 0.5 mm. The lower the average value of the first class, the slower the solvent passes through a thin layer. Thus, by choosing the average value and the height of the thin layer, you can set the pressure drop.

Preferably, the method includes the following steps: to prepare the wood particles, the wood is first crushed into wood particles of various sizes. Grinding occurs using chopping machines and / or machines for grinding and / or crushing. After that, crushed or chopped or crushed wood is sorted. Sorting occurs, in particular, with the help of sieves. In sorting, at least first class wood particles and second class wood particles are distinguished. Of decisive importance in sorting is the separation of sufficiently fine particles of first-class wood. At the same time, it is not necessary that absolutely all the fine particles of wood are separated from the second class.

In addition to sorting the materials obtained by chopping or grinding or crushing, you can add sawdust and / or shavings obtained in another way to the first class. Further, alternatively to sorting, it is also possible that the thin layer consisted only of sawdust and / or shavings and / or wood flour obtained in another way.

In a particularly preferred embodiment, it is provided that the sorting between the first class and the second class takes place using a sieve with a certain mesh size or a certain hole diameter. In this case, the mesh size or hole diameter is preferably from 0.5 mm to 7 mm. The study showed that it is preferable to separate the two classes, in particular, using a sieve with a mesh size or hole diameter of 1 mm to 6 mm, preferably from 1 mm to 4 mm. Depending on the content of water and resins and the type of wood chopping, unsorted materials differ in particle size distributions. Accordingly, screenings of the first class are achieved using the preferred mesh size or hole diameter.

Further, fine and coarse wood particles can vary in the amount of very large wood particles in the class. Preferably, the thin layer does not contain too many very large particles of wood. Thus, it is ensured that permeability is constant throughout the thin layer. Therefore, it is preferable that more than 70 mass% of the wood particles in the first class have a nominal sieve size of at most 4 mm, preferably 2 mm, particularly preferably 1 mm. When chopping wood, the amount of wood particles of the first class depends, for example, on the content of water or resins, as well as on the grinding technology used. Thus, it is not possible to obtain any size distribution of wood particles during milling.

Preferably, the extracting agent passes in a specific manner and is relatively unhindered through the next layer. Therefore, the second class should contain as few fine particles of wood as possible. Preferably, it is provided that more than 30 mass% of the second class wood particles have a nominal sieve size of at least 2 mm, preferably 3 mm.

Further, it is preferably provided that the degree of grinding of the wood particles in the thin layer is sufficient and there are as few as large and very large particles of wood. Therefore, for a nominal sieve size of wood particles of more than 60 mass%, preferably more than 70 mass%, particularly preferably more than 80 mass% of all wood particles that are first class, an upper limit is defined. The next layer should contain a sufficient amount of large particles of wood in order to ensure a certain sufficient flow of the extracting agent. For a nominal sieve size of wood particles of more than 10 mass%, preferably more than 20 mass%, particularly preferably more than 30 mass% of all wood particles of the second class, a lower limit is defined. Preferably, it is provided that the upper boundary of the first class is the same or less than the lower boundary of the second class. Particularly preferably, the upper boundary of the first class is 4 mm, preferably 2 mm, particularly preferably 1 mm.

Depending on the properties of the chopped, chopped or crushed wood, more or less first class material is formed. Preferably, the height of the thin layer is set. On the one hand, the thin layer should not be too high in order to ensure sufficient passage of the extracting agent. On the other hand, a certain height of the thin layer is necessary in order to achieve a sufficient filtering effect and to prevent too large a pressure drop. Preferred was the height of the thin layer from 5% to 70%, preferably from 5% to 50%, particularly preferably from 5% to 40% with respect to the total height of all layers.

Preferably, the layering of wood particle layers occurs in a percolator. The method according to the invention is preferably used in the extraction of very large quantities. The height of the thin layer is preferably 0.5 m, preferably from 1 to 3 m.

Preferably, larch is extracted. Particularly preferably used only the core of the trunk and / or rhizome of larch.

Further, the method according to the invention, in particular the extraction of taxifolin from wood, is carried out using an organic solvent, preferably ethanol. Additionally or alternatively, arabinogalactan is extracted from wood, preferably using water as a solvent.

Sampling from chopped, or chopped, or ground wood is preferably carried out according to DIN EN 14778: 2011, and particle size determination as well as particle size distribution according to DIN EN 15149-1: 2010 or DIN EN 15149-2: 2010.

Further, it is also possible to randomly lay several thin layers or several subsequent layers.

Extraction is theoretically based on Fick's law of diffusion. It follows from this that, firstly, the shorter the required diffusion distance from the material for extraction into the solvent, the faster it is possible to extract the desired product from the material for extraction. From this we can conclude that the smaller the particles of the material used for extraction, the smaller the diffusion distance must be overcome and at the same time the greater the theoretical particle flow into the solvent. In FIG. 1 shows the theoretical flow of a particle stream depending on the particle size.

Secondly, it follows from the law that the greater the difference in concentrations of product particles in a solvent is achieved, the faster the desired product is extracted from the extraction material.

From this we can conclude that the higher the circulation intensity or the amount of solvent used, the higher the difference in concentration caused by diffusion and, at the same time, the greater the theoretical particle flux into the solvent. In FIG. Figure 2 shows the flow of the theoretical particle flux depending on the difference in concentrations.

A number of experiments were conducted to study the extractability of taxifolin from larch wood, depending on the size of the wood particles used. The extraction time, the extraction temperature, the intensity of mixing, as well as the quantitative ratio of the solvent used and the material for extraction, remained constant. In FIG. Figure 3 shows the extractability of taxifolin from larch wood, depending on the nominal sieve size of the wood particles.

Claims (12)

1. The method of extraction from wood, comprising the following stages:
- preparation of wood particles of at least first class and second class,
- laying a thin layer consisting of particles of wood of the first class, on top of the next layer consisting of particles of wood of the second class, and
- extraction of wood particles with a liquid extracting agent, wherein the extracting agent flows from top to bottom, first through a thin layer, and then through the next layer,
- while the wood particles of the first class are thinner than the particles of wood of the second class, and thus a thin layer has lower permeability than the next layer. 2. The method according to p. 1, characterized in that the first average particle size distribution of all particles of wood of the first class is less than the second average particle size distribution of all particles of wood of the second class, in particular, the particle size is the nominal sieve size . 3. The method according to p. 2, characterized in that the first average value is less than or equal to 3 mm, preferably less than or equal to 2 mm, particularly preferably less than or equal to 1 mm. 4. The method according to one of the preceding paragraphs, characterized in that the preparation of wood particles includes the following stages:
- chopping wood into wood particles of various
size, and
- sorting, in particular screening, of wood particles into at least a first class and a second class. 5. The method according to p. 4, characterized in that the first class is sorted from the second class using sieves with a mesh size or hole diameter of from 0.5 mm to 7 mm, preferably from 1 mm to 6 mm, particularly preferably from 1 mm to 4 mm. 6. The method according to p. 1, characterized in that more than 70 wt.% Particles of wood of the first class have a nominal sieve size of at most 4 mm, preferably at most 2 mm, particularly preferably at most 1 mm. 7. The method according to p. 1, characterized in that more than 30 wt.% Particles of wood of the second class have a nominal sieve size of at least 2 mm, preferably at least 3 mm. 8. The method according to p. 1, characterized in that the nominal sieve size of the wood particles is more than 60 wt.%, Preferably more than 70 wt.%, Particularly preferably more than 80 wt. % of all particles of wood of the first class is less than or equal to the first limit value, and the nominal sieve size of the particles of wood is more than 10 wt.%, preferably more than 20 wt.%, particularly preferably more than 30 wt.% of all particles of wood of the second class is greater than or equal to the second limit value wherein the first limit value is equal to or less than the second limit value. 9. The method according to p. 8, characterized in that the first limit value corresponds to a nominal sieve size of 4 mm, preferably 2 mm, particularly preferably 1 mm 10. The method according to p. 1, characterized in that the height of the thin layer is from 5% to 70%, in particular from 5% to 50%, in particular from 5% to 40%, of the total height of all layers. 11. The method according to p. 1, characterized in that the wood particles are laid in layers in a percolator, while the height of the thin layer is at least 0.5 m, preferably at least 1 m 12. The method according to p. 1, characterized in that taxifolin is extracted from the wood, in particular with ethanol as an extractant, and / or arabinogalactan, in particular with water as an extractant.

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