Field of the invention

The invention relates to an apparatus for separating one or more compounds from and/or for reducing the content of one or more compounds in source material. The invention also relates to a method and a system for separating one or more compounds from and/or for reducing the content of one or more compounds in source material.

Background of the invention

There is often a need in industry to remove various compounds, such as impurities, from a material to be produced. According to the need, the material used as the starting material can be, for example, mechanically refined and/or sorted for reducing the content of impurities.

One possibility to remove impurities from the material used as the starting material is extraction. For example, in supercritical extraction, the extraction is typically performed by using carbon dioxide in such a way that the carbon dioxide is under supercritical conditions during the extraction. Carbon dioxide is commonly used, among other things, because of its relatively low supercritical conditions (pressure 73 bar, temperature 31 °C). One example of supercritical extraction in industrial scale is column extraction with carbon dioxide for decaffeinating coffee beans, wherein the final product is so- called decaffeinated coffee. Another example of supercritical extraction in industrial scale is degreasing with carbon dioxide, wherein the final products are low-fat products.

However, there is still a need in industry for novel approaches for removing impurities from starting material. Brief summary of the invention

It is an aim of the principle of the invention to separate one or more compounds from source material and/or to reduce the content of one or more compounds in source material, for example to reduce the content of impurities in the material to be purified. Therefore, we present a new method, system and apparatus for separating one or more compounds from source material, and/or for reducing the content of one or more compounds in source material. According to the principle of the invention, it is possible to obtain a substantially odourless and applicable product to be refined to a final product.

For achieving the aim of the invention, the apparatus according to the invention for reducing the content of, and/or for separating one or more compounds from source material is primarily characterized in what will be presented in the appended claim 1. The method according to the invention for reducing the content of, and/or for separating one or more compounds from source material is primarily characterized in what will be presented in the appended claim 3. The system according to the invention for reducing the content of, and/or for separating one or more compounds from source material is primarily characterized in what will be presented in the appended claim 10.

The method according to the invention for reducing the content of, and/or for separating one or more compounds from source material comprises at least one extraction step, in which one or more compounds, such as impurities, are transferred from the source material to an extraction solution, i.e. solvent, used in the extraction.

According to the principle of the invention, said extraction solution, i.e. solvent, advantageously comprises water, an acid, a base, a solution of salt, an ionic liquid, and/or an organic solution. Preferably, the extraction solution consists, in whole or substantially in whole (advantageously, at least 90 wt%, preferably at least 95 wt%), of one or more of the above mentioned substances. Advantageously, the extraction solution is selected according to the impurities to be removed. The selection of the extraction solution is influenced, among other things, by the polarity and the solubility of the substance to be removed from the source material. Furthermore, the source material is preferably taken into account in the selection of the extraction solution so that the extraction solution does not unnecessarily destroy the source material and/or unnecessarily change the properties of the source material. The source material is preferably in solid state.

In an example, the extraction solution comprises one or more acids selected from mineral acids, such as e.g. HCI, HNO3, H2SO4, and/or from organic acids, such as e.g. acetic acid, formic acid, aromatic acids, and anionic surface active compound solutions.

In an example, the extraction solution comprises one or more bases selected from NaOH, carbonate solutions, ammonia, amine solutions, and cationic so-called GOOD buffers, i.e. cationic organic buffers used in biochemistry.

In an example, the extraction solution comprises one or more solutions of salts selected from NaCI, KCI, K ₂ CO ₃ , and NaSO ₄ .

In an example, the extraction solution comprises one or more ionic liquids selected from the following: "salt melt solutions", i.e. solutions formed by liquid salt, quaternary solutions prepared from ammonium, imidazole, pyridine, and phosphonium derivatives.

In an example, the extraction solution comprises one or more organic solutions selected from: hexane, toluene, acetone, ethyl acetate, and isopropanol.

In an advantageous example, said extraction solution comprises water.

In the method and system according to the invention, an extraction apparatus is used, comprising a reactor in which the source material is extracted. Said reactor preferably comprises a stirring device for stirring the material during the extraction. Stirring of the sample has been found to substantially improve the final result obtained.

Preferably, the reactor can be pressurized; in other words, it is a so-called pressure reactor. Typically, the pressure applied in the reactor during the extraction depends on, inter alia, the material from which impurities are removed, as well as on the properties of the impurities to be removed.

In an advantageous example, the principle of the invention is applied to reduce impurities in an inorganic compound. In an example, the principle of the invention is applied to reduce impurities in a carbonate, such as calcium carbonate or magnesium carbonate.

In an example, the principle of the invention can be applied to reduce

the content of volatile sulphur compounds, and/or

the content of volatile nitrogen compounds, and/or

the content of volatile organic compounds, and/or

the content of one or more metals, and/or

metal species.

Possible examples of extraction according to the invention include

- the extraction of volatile sulphur compounds and/or organic sulphur compounds by alcohols from a starting material, such as coal,

- the extraction (i.e. removal) of volatile nitrogen compounds and/or nitro-PAH compounds from a starting material, such as tea, wherein due to the formation of nitrogen gas (N ₂ ) it is possible to remove ammonia, nitric acid, TNT compounds, and fertilizer residues that contain nitrogen, from a sample, for example food,

- the extraction of volatile organic compounds and/or drug impurities from a starting material,

- the reduction of an excessive content of a starting material, such as fats and/or fatty acids from the starting material, in order to achieve a low-fat product by supercritical extraction with carbon dioxide in the case of a food or drug product, and by liquid extraction with hexane in the case of a product not used for the above-mentioned cases, - the purification of one or more metals and/or the extraction for recovery of valuable metals by a treatment with nitric acid from a starting material, such as rock material,

- the purification of glass by extraction with an acidic aqueous solution,

- the extraction of metal species, for example the purification of waste, the purification of a soil sample, and desalination by extraction with pressurized water.

In an example, the principle of the invention is used for reducing the content of organic compounds, such as carcinogens (PAH, PCN), dioxins, and/or furans, from a starting material. Thus, in an example, the solvent used is an organic solvent.

In an example, the principle of the invention is applied to reduce nitrogen and/or nitric compounds in the material to be purified, by extraction with pressure and heat. In an example, the principle of the invention is applied to reduce nitrogen and/or nitric compounds in an inorganic material. Thus, in an example, the solvent used is water, if the compounds are hydrophilic, and an organic solvent, such as hexane and/or acetone, if they are hydrophobic.

In an advantageous example, the principle of the invention is used for purification of so-called side flows, i.e. waste material, produced in industry, and thereby for improving the recyclability of such materials. Thus, in an example, the solvent used is water and/or hexane and/or ethanol.

In an example, the principle of the invention can be applied in the extraction process of valuable metals in the mining industry. Thus, in an example, acetone is used as the solvent.

In an example, the principle of the invention can be used to purify burnt ash from heavy metals in the paper and pulp industries. Thus, in an example, the solvents used are mineral acids and/or organic ligands in an organic solvent.

The processing according to the invention may stabilize the source material. The principle of the invention may be applicable for the purification of a raw material to be processed further in another process, wherein chemical residues from the previous process are removed before the further processing.

By means of the invention, it may be possible to purify materials whose purification by methods of the state of art is difficult and/or expensive, because the extraction used in the invention can be implemented by a principle that saves the material to be extracted. When the principle of the invention is implemented at a relatively low temperature and/or at a relatively low pressure, the energy efficiency of the principle is typically improved.

The principle of the invention can be utilized in such a way that one or more impurities in the form of a volatile compound can be obtained in a gaseous form from the inside of particles of a source material, such as an inorganic material. Thus, said compound brought to said gaseous form is preferably absorbed into the extraction solution, such as water, used as the liquid for extraction. Said compound absorbed in the extraction solution can be converted to a solution form after normal conditions have been established. Said at least one volatile compound (for example, volatile impurities in source material) may comprise at least one inorganic compound and/or at least one organic compound. In an example, said at least one volatile compound comprises a nitrogen compound and/or a sulphur compound and/or an organic compound. In an example, said at least one volatile compound (impurity) comprises ammonia.

By the principle of the invention, it is also possible to remove impurities from relatively small sample quantities in a cost-effective way. The presented solution is particularly energy friendly when a relatively low pressure and/or temperature is applied.

The principle of the invention is suitable for a variety of source materials so that the matrix of the source material is not substantially changed during the process in which compounds are separated from the source material. In other words, in the presented novel approach it is possible to reduce the content of one or more compounds, such as impurities, in a source material in such a way that the matrix structure of said material remains unchanged or substantially unchanged. Thus, the principle of the invention may also be applicable for the purification of inorganic materials, such as carbonate. Typically, it has not been possible to apply e.g. the supercritical extraction method according to the state of art, in which carbon dioxide is used, for e.g. said carbonate without substantially changing the matrix structure of the original material during the extraction.

In an advantageous example of the principle according to the invention, impurities are removed from calcium carbonate. It has been challenging to remove e.g. ammonia from calcium carbonate, because when e.g. heat is used for removing ammonia, calcium carbonate starts to decompose when the temperature exceeds 550°C. This naturally limits the processing at higher temperatures. On the other hand, the removal of ammonia by e.g. refining calcium carbonate has turned out to be insufficient. Also, the removal of ammonia by washing calcium carbonate with water under normal pressure would require far too many washing steps and a large amount of water to be a cost-effective alternative. In the presented new method, it is possible to reduce impurities from carbonate in a cost-effective way so that the material matrix can remain substantially unchanged.

In an embodiment of the invention, the content of ammonium in calcium carbonate is decreased, whereby, among other things, the odour problem caused by calcium carbonate is reduced. Preferably, substantially odourless calcium carbonate is obtained as the final result. In an example, the invention is applied for decreasing the content of impurities in such calcium carbonate that originates from waste material. Thus, after the reduction of impurities, said calcium carbonate may be suitable for reuse, for example in the food industry or the pharmaceutical industry. Without the method of the invention, for example calcium carbonate that contains ammonia may be considered unusable and taken to a waste disposal site.

The material which has been produced as the final product of the process and from which impurities have been removed, can be processed further. It can be, for example, dried and/or refined and/or surface treated and/or granulated and/or briquetted. For example, calcium carbonate, from which impurities have been removed, may be suitable for, inter alia, the paper industry, the plastics industry, the paint industry, the glass industry, and/or products of the construction industry.

Description of the drawings

In the following, the invention will be described in more detail with reference to the appended drawings, in which:

Figs. 1 a to 1 c show reduced schematic charts of systems according to some embodiments for separating one or more compounds and/or for reducing the content of one or more compounds, from source material.

Fig. 2 shows a reduced view of a pressure reaction according to an embodiment,

Fig. 3 shows a sample container of a pressure reactor according to an embodiment,

Fig. 4 shows the cover of a pressure reactor according to an embodiment, and Fig. 5 shows a pressure reactor according to an embodiment, as well as a heater for the pressure reactor.

Detailed description of the invention In this application, reference is made to Figs. 1 to 5, in which the following reference numerals are used:

1 source material, for example material, from which impurities are reduced,

2 reactor,

3 sample container for the reactor,

4 cover for the reactor, 5 temperature control devices for the reactor,

6 stirring device for the reactor,

7 material, from which one or more compounds have been removed, i.e. so-called purified material,

8 extract solution, i.e. extraction solution containing impurities,

10 extraction, extraction step,

1 1 extraction solution, i.e. solvent,

12 measuring device for measuring the temperature,

13 measuring device for measuring the pressure,

14 gas,

15, 15a valves,

15a safety valve,

20 pre-processing of material 1 , and

21 processing of the extract solution 8.

In the present application, the terms "solvent" and "extraction solution" refer to the solution used for extraction, into which one or more compounds are transferred from the source material during the extraction.

In the present application, the term "extract solution" relates to a solution that contains said extraction solution as well as one or more compounds transferred from the source material.

The solubility of a substance in the extraction process is normally improved by raising the pressure in the processing space. A substance is in a supercritical state when its temperature and pressure exceed the critical point of liquid/steam. Said critical point refers to the point at which the gaseous and liquid phases are combined and their specific latent heat of vaporization is zero. At high pressures, the properties of supercritical fluids are changed, and the fluid typically starts to behave like a liquid solvent. A substance in a supercritical state typically has gas-like carrying properties and a liquid-like solvent power. In an advantageous embodiment of the method according to the invention, supercritical extraction is used for separating one or more compounds and/or for reducing the content of one or more compounds from source material. Figures 1 a to c show reduced schematic charts on some examples of the principle of the invention for reducing impurities. The figures show source material 1 , an extraction solution 1 , a reactor 2 for extracting the source material 1 in at least one extraction step 10, so-called purified material 7, pre-processing 20 of the material 1 , an extract solution 8, as well as processing 21 of the extract solution 8. the apparatus according to the invention for separating one or more compounds and/or for reducing the content of one or more compounds from source material comprises an extracting apparatus comprising a reactor 2. The method according to the invention for separating compounds from source material comprises one or more extraction steps 10, for example 1 to 3 extraction steps, which can be performed in a batch process, in a continuous process, or in a semi-continuous process. Advantageously, the approach according to the invention comprises one or two extraction steps 10. When several extraction steps are used, the same solvent can be used in different extraction steps, or different solvents can be used in one or more extraction steps. During the extraction 10, one or more compounds are separated from and/or the content of one or more compounds is reduced in the source material.

The source material 1 , from which impurities are removed, can be pre- processed 20 before the extraction 10. The pre-processing 20 may comprise, for example, refining of the source material 1 into smaller particles by a refiner, and/or dissolving and/or mixing of the source material 1 in a liquid, such as water.

The selection of the pressure, the temperature, and the stirring rate applied during the extraction step 10 are preferably . influenced by i.e. the source material 1 to be processed, the particle size of the source material 1 to be processed, said one or more compounds whose content in the source material is to be reduced, the content of said one or more compounds in the source material to be processed, and/or the extraction solution used. Advantageously, the pressure and the temperature applied in the invention are selected according to the extraction solution so that said extraction solution is in a supercritical state. The approach according to the invention preferably comprises at least one extraction step 10, in which the pressure is at least 2 bar or at least 3 bar, more preferably at least 4 bar or at least 5 bar. In said at least one extraction step 10, the pressure is advantageously not higher than 100 bar or not higher than 50 bar, more preferably not higher than 20 bar or not higher than 15 bar, more advantageously not higher than 13 bar or not higher than 11 bar, and most advantageously not higher than 9 bar or not higher than 7 bar. In an example, the extraction apparatus according to the invention can be used for extracting at a pressure of at least 200 bar, at least 300 bar or at least 400 bar.

In at least one extraction step 10 according to the invention, the temperature used is advantageously at least 20°C, at least 30°C, at least 50°C, at least 70°C, or at least 80°C. In said at least one extraction step 10, the temperature is suitably not higher than 150°C, not higher than 130°C, not higher than 110°C, or not higher than 100°C. In an example, the apparatus according to the invention can be used for extraction by applying a temperature higher than 200°C or higher than 250°C.

In view of energy efficiency, the best extraction time is typically as short as possible. However, the extraction time should be sufficiently long to achieve the desired effect. In at least one extraction step 10 according to the invention, the extraction time at the desired pressure and temperature may be, for example, at least 10 min, at least 15 min, at least 20 min, at least 25 min, or at least 30 min. Furthermore, or alternatively, the extraction time at the desired pressure and temperature may be, for example, not longer than 120 min, not longer than 90 min, not longer than 60 min, not longer than 50 min, or not longer than 40 min. In an example, the apparatus according to the invention can be used for extracting source material 1 in such a way that the extraction time is at least 1 day.

In the approach according to the invention, stirring is preferably applied during the extraction. The stirring has a substantial effect on the efficiency of the apparatus. The stirring rate influences the yield in such a way that the yield is normally improved when the stirring rate is increased. In an example, the stirring device is a so-called anchor agitator. During at least one extraction step 10, the stirring rate is advantageously at least 100 rpm, at least 200 rpm, at least 300 rpm, or at least 400 rpm. In said at least one extraction step 10, the stirring rate is preferably not higher than 000 rpm, not higher than 800 rpm, not higher than 600 rpm, or not higher than 500 rpm.

In an example, the method according to the invention comprises one or more of the steps listed hereinbelow:

Introducing source material 1 in the system.

Introducing extraction solution 11 in the system.

Introducing gas 14 in the system.

Admixing source material 1 into the extraction solution 1 in such a way that a mixture is formed which comprises said source material 1 and extraction solution 11.

Pre-processing 20 the source material 1 before the extraction 10. Extracting 10 impurities from the source material 1 to be processed into the extraction solution 11 in such a way that the mixture is stirred with an agitator 6 during the extraction, wherein at least so-called purified material 7 and extract solution 8 are formed.

Processing 21 the extract solution 8.

In an example, the system according to the invention comprises one or more of the following devices:

First devices for introducing source material 1 into the system.

Second devices for introducing extraction solution 11 into the system.

Third devices for introducing gas into the system.

Pre-processing devices 20 for pre-processing the source material 1 before the extraction.

Devices for mixing the extraction solution and the solution material 1 together.

Pre-processing devices for pre-processing the source material before the extraction.

Devices for extracting the source material 1 into the extraction solution in such a way that at least so-called purified material 7 and extract solution 8 are formed, said devices comprising at least a reactor 2 and an agitator 6 for the reactor.

Devices 20 for processing the extract solution 8. Preferably, the ratio between the sample quantity and the solvent is at least 1 :10, for example 1 : 0 to 1 :700, advantageously 1 :50 to 1 :250, or 1 :100 to 1 :200. When the sample is a solution, the total solution volume of 150 ml is used in an advantageous example. In an example, the ratio used in at least one extraction step 10 between the quantity of solvent, such as water, and the sample quantity is 1 g of the dry sample and about 10 g of the solvent. According to the invention, it is possible to achieve a low solvent consumption.

In an example, the content of the solvent used is not higher than 2/3 of the (empty) volume of the sample vessel 3 of the pressure reactor 2 in use. In an example, the total content of the solvent used and the sample adds up to 2/3 of the (empty) volume of the sample vessel 3 of the pressure reactor 2 in use.

In the method according to the invention, it is possible to use a gas 14 for removing impurities. The function of the gas is to carry away the compounds which gasify when heated, and/or to stabilize the process conditions. The gas 14 used is preferably inert and does not react with the sample. The gas used in the method according to the invention preferably comprises at least:

- argon,

- nitrogen,

- helium,

- air,

- oxygen, and/or

- a mixture of these.

In aerobic extraction, air or oxygen is preferably used as the gas. Oxygen and air are typically the most affordable gas alternatives, and they are particularly suitable for samples which are not easily oxygenated. In anaerobic extraction, argon, nitrogen or helium are preferably used as the gas. The approach according to the invention also makes recovery in the gas phase possible.

Figure 2 shows a reduced view of a pressure reactor 2 according to an example; Fig. 3 shows a sample vessel 3 for a pressure reactor according to an embodiment; and Fig. 4 shows a cover 4 for a pressure reactor according to an embodiment.

The reactor 2 of the extraction apparatus preferably comprises at least one agitator 6 for the reactor. The agitator 6 for the reactor may be provided in connection with the cover 4 of the reactor.

Advantageously, the reactor 2 comprises one or more measuring devices 13 for measuring the pressure during the extraction, and/or one or more measuring devices 12 for measuring the temperature during the extraction. Furthermore, the reactor preferably comprises one or more valves 15, 15a which can be used, inter alia, for controlling the pressure.

In the approach according to the invention, thanks to the agitator 6 which is preferably used, the extraction 10 can be performed from a mixture that is mixed substantially uniformly and comprises extraction solution 1 1 and source material 1. Furthermore, by the principle of the invention, it is possible to obtain a substantially homogeneous extract.

The reactor 2 preferably comprises a reactor sample vessel 3, a reactor cover 4, and reactor temperature control devices 5. The temperature control devices 5 preferably comprise one or more heating pipes and/or one or more cooling pipes for controlling the temperature of the reactor 2. Furthermore, the reactor 2 preferably comprises a heatable reactor mantle which is preferably heated by means of the temperature control devices 5. The reactor 2 may also comprise one or more glass coils. In an example, the heating coil is used to replace possible baffle plates, which approach may be particularly advantageous when a separate coil is used.

The reactor 2 is preferable heated by using one or more of the alternatives hereinbelow:

1 ) The reactor 2 is provided with a mantle, wherein the heating and the cooling are preferably implemented by circulating a liquid in the mantle.

2) A separate heating coil and/or heating device is provided inside the reactor 2 and preferably placed in the structure of the inner surface of the reactor, most advantageously in an integrated manner.

3) The reactor 2 is heated by microwave radiation. Figure 5 shows a reactor 2 according to an embodiment, equipped with pressure, temperature and gas sensors. Furthermore, Fig. 5 shows temperature control devices 5 which in Fig. 5 comprise a so-called LAUDA temperature control unit which is based on water.

The reactor 2 should be made of materials which are resistant to the pressure and the temperature used in the extraction 10, and it is preferably cladded. The materials for the core part of the sample vessel 3 of the reactor 2 (shown e.g. in Fig. 2) are preferably selected so that they are inert with respect to the materials involved in the extraction. Advantageously, at least the core parts of the reactor 2 and the agitator are either coated with a coating suitable for the extraction conditions, or made of a material that is resistant to the extraction conditions, i.e. the chemical and/or mechanical loadings. Such materials may include, among other things, Teflon and steel. The sample vessel 3 of the reactor may comprise, for example, Teflon and/or steel as the production material. In an example, the sample vessel 3 is made entirely or substantially entirely of Teflon and/or steel.

The reactor according to the invention is applicable in both laboratory scale and industrial scale. The volume of the reactor can be selected according to the use.

Advantageously, recirculation by pumping of the material of the extracting solvent is applied in the reactor 2, which may make the process more efficient and/or which can be utilized in the management of the process. Thus, the system comprises devices for providing recirculation by pumping. Recirculation by pumping is particularly advantageous in large reactors, i.e. reactors of industrial scale, but it can also be applied in connection with small reactors.

Advantageously, the apparatus according to the invention also comprises devices for emptying the reactor, which devices may comprise e.g. a pump and/or a discharge outlet.

Preferably, the system comprises a control system for controlling the process. The control system preferably comprises electronic data capture. In an embodiment of the invention, the source material 1 , from which impurities are removed, comprises carbonate, such as calcium carbonate or magnesium carbonate. In an advantageous example, the content of nitrogen in said carbonate is reduced, for example in the form of nitrogen compounds. For example, calcium carbonate may comprise small amounts of impurities, such as nitrogen in different forms, wherein particularly the ammonia form of nitrogen (NH ₃ ) may cause odour problems in possible uses unless its content is reduced in said source materials 1. In an example, the invention is applied for reducing the ammonium content in carbonate. In an example, impurities are removed from calcium carbonate which has been obtained as a side product from the fertilizer industry where apatite has been used as the raw material.

In an example, the principle of the invention is applied to reduce at least 50 wt% or at least 60 wt%, more advantageously at least 70 wt% or at least 80 wt%, and most advantageously at least 90 wt% or at least 95 wt% of nitrogen compounds in the source material 1 (percentages of dry product). In an example, the principle of the invention is applied to reduce the nitrogen content in a material having a nitrogen content of at least 1 g per kg of said material.

The method according to the invention can be implemented in such a way that the matrix of the source material 1 is not essentially changed; that is, the particle size and shape of the source material 1 remain substantially constant, the source material 1 is not dissociated, and no more impurities appear in the source material 1.

The extract solution 8 separated in at least one extraction step 10 according to the invention can be processed and/or analyzed after the extraction step 10. The processing of the extract solution 8 for e.g. analyzing can comprise, for example, filtering and/or evaporation of liquid. The filtering can be implemented with a filter material of the state of art. The evaporation of the liquid can be implemented, for example, by heating. The analysis of the extract solution 8 advantageously comprises an elemental analysis, a separation analysis, and/or a quantitative analysis. Said analysis may comprise, for example, one or more of the following methods:

- flame atomic absorption spectroscopy, FAAS;

- inductively coupled plasma atomic emission spectroscopy, ICPAES;

- ion chromatography, IC;

- capillary electrophoresis, CE;

- scanning electron microscopy, SEM;

- fluorescence electron microscopy, FEM;

- thermogravimetric analysis, TMA; and

- differential scanning calorimetry, DSC:

Thanks to the principle of the invention, both the source material 1 and the extract solution 8 can be utilized for further processing after the extraction, because the new method according to the invention makes it possible that the source material 1 is not substantially destroyed.

The principle of the invention can be implemented for example in the following way:

If the source material comprises carbonate, such as calcium carbonate, an extraction pressure of 2 to 8 bar and/or an extraction temperature of 70 to 120°C is advantageously used for extraction; more advantageously, an extraction pressure of 3 to 7 bar and/or an extraction temperature of 80 to 1 10°C is used.

If the source material comprises wood chips, totarol compound can be extracted with e.g. carbon dioxide, wherein the conditions may be, for example, the following: pressure 300 bar and temperature 313 K. If the pressure used is, for example, 70 bar, and the temperature is 298 K, it is possible to extract 1 g of totarol from 1 kg of wood chips.

If the source material is of plant origin, for example the heavy metals Pb, Cd, Cu, Fe, Zn, As, and Hg can be extracted by supercritical extraction by using e.g. carbon dioxide CO2. Thus, the conditions may be, for example, pressure 150 bar and temperature 60°C. Advantageously, very polar or non-polar solvents are used for extracting in the invention. Preferably, the temperatures used in the invention are relatively low and the pressures are relatively low.

EXAMPLE

In the following, the invention will be explained by way of an example with a series of empirical tests.

The aim of the empirical tests was to reduce the content of impurities in samples. A particular aim was to reduce the content of ammonium (total nitrogen content) in the samples. During the tests, the chemical and physical composition of four different calcium carbonate samples was examined. The samples 1 to 4 used are presented in Table I.

Table I Sam les

At the beginning, the unprocessed samples 1 to 4 were analyzed by the so- called Kjeldahl method to find out the total nitrogen contents of the samples before the extraction according to the invention. For analysis of the solid samples, scanning electron microscopy (SEM) was also applied to determine the contents by weight percent of elements in the extracted samples. For analysis of aqueous phases in the extraction tests, capillary electrophoresis (CE) was primarily used to determine the ammonium contents in the aqueous phases. The capillary electrophoresis results indicated how much ammonium was removed from the sample by extraction. The anions separated in the extractions can also be analyzed from the aqueous samples by ion chromatography. For the extraction, a pressure reactor was designed which could apply a pressure of 10 bar and a relatively high temperature (+120°C) in the extraction. The apparatus comprised primarily of an extraction vessel (V = 750 ml), a cover, a board for heating the vessel (by heating oil), an agitator motor, and a gas cylinder (in these tests, argon).

In the extraction tests, the sample was extracted with Millipore water (MilliQ), which is very pure water having a particle size of 0.22 pm. The extraction was performed in a ratio of (50 g of sample)/(500 ml of milliQ). At the beginning of each extraction, the sample and the water were weighed.

Raising the temperature inside the reactor to a desired extraction temperature took about 1.5 h. The extraction was performed at the extraction temperature (± 1 °C) for 30 minutes. During the extraction, the sample was stirred. Upon expiry of the extraction time, cooling was started by dropping the temperature of the board to +20°C. After the temperature inside the reactor had dropped down to a level of about +30°C, the extraction apparatus was turned off. The cooling of the extraction apparatus took about 1.5 h.

After the extraction had been finished, the sample was first poured into a beaker of 800 ml, from which the sample was transferred through a filter paper (VWR international, filter, papers 474, d 1 1 cm) in a funnel to a small plastic sample bottle (VWR international, bottle wide neck + cap round, LDPE, 100 ml). The dry matter residue from the extraction was recovered by filtering through the filter paper by applying an underpressure. The filtered dry matter was not dried but the dry sample was tipped from the filter paper into a glass crucible and taken directly into an oven of about 00°C for drying overnight.

The actual extraction tests were started by first testing the effect of pressure on the ammonium content, maintaining the other factors constant. Other factors than the pressure included temperature, extraction time, and stirring rate. The scheme for the first extraction series (pressure extractions) is presented in Table II. Furthermore, the first extraction (5 bar) of the first extraction series was performed twice to test the repeatability of the extractions.

Table II Scheme for the first extraction series sam le 1.

The samples of the series were analysed by capillary electrophoresis. The best pressure (5 bar) for removal of ammonium content was selected as the constant for the next series of extractions, in which the effect of temperature on the ammonium content was tested, the other factors being constant. The scheme for the second series is presented in Table III.

The second series was also analyzed by capillary electrophoresis. After the best extraction pressure and temperature had been found out on the basis of the ammonium content results obtained by capillary electrophoresis, sample 3 was extracted with the values of these best variables (5 bar, +90°C, 30 min, 450 rpm). Reference samples

In addition to the extraction tests according to the invention, microwave extraction was tested (apparatus: GWB Pressurized microwave decomposition, GWB Exhaust and cooling unit), as well as extraction under free pressure, and the effect of these two methods on the total nitrogen content and ammonium content in the samples.

Microwave extraction was tested on four samples in the project, and also on commercial calcium carbonate (MERCK). In microwave extraction, about 200 mg of samples were weighed into microwave extraction vessels, in addition to which 5 ml of Millipore water was added into the vessels. In the extraction, 8 PMD degrees were applied (total duration of PMD was 10 min), the duration of the extraction was 10 min (High Intensity), and the duration of the cooling was also 10 min (Low intensity 10). After the extraction, the extraction solution was filtered through a filter paper (VWR international, filter, papers 474, d 1 1 cm) into a measuring flask of 50 ml. The samples left on the walls of the extraction vessel were carefully rinsed with Millipore water and poured through the filter paper into the measuring flask which was filled up to the mark with Millipore water. The extraction vessel was carefully washed after each extraction.

The extraction tests carried out under free pressure were taken in a reactor with a larger volume (V = 4 L). In these extractions, the ratio between the sample quantity and water was (50 g of sample)/(L of MilliQ). The extractions were carried out for all samples in Table I. The extraction temperature used was +85°C and the extraction time was 30 min. The agitator was an anchor agitator with a stirring rate of 200 rpm.

Results and description of the results

From the microwave extractions (reference samples), anions were analyzed: chloride, fluoride, nitrite and nitrate, by using ion chromatography. The results of ion chromatography are presented in Table IV. Table IV Anion contents from microwave extractions.

From the aqueous phase of samples of the first series of extractions, ammonium contents were analyzed by capillary electrophoresis, the results being presented in Table V. Table IV also gives the result on the ammonium content of sample 1 extracted under free pressure. Solid extraction samples of the first series of extractions were also analysed with SEM, the results being presented in Table VI.

Table V Ammonium contents of the first series of extractions

(extraction according to the invention, pressure variations) determined with CE.

Extraction mg/L w-% g/kg

SAMPLE 1 13.40 0.0134 0.1340

5 bar, rep 1

SAMPLE 1 1 1.20 0.01 12 0.1 120

5 bar, rep 2

SAMPLE 1 8.20 0.0082 0.0824

7 bar

SAMPLE 1 8.35 0.0083 0.0834

9 bar

SAMPLE 1 0.292 0.0006 0.0058

free pressure Table VI The contents of elements in solid samples of the first series of extractions anal sed b SEM, in wei ht ercent.

Ammonium contents were also determined from the aqueous phase of the extraction samples of the second series of extractions by capillary electrophoresis, presented in Table VII below. Table VII Ammonium contents of the second series of extractions (samples according to the invention, temperature variations) determined with CE.

On the basis of Tables V to VII, the best extraction pressure and extraction temperature was 5 bar and +90°C (30 min, 450 rpm), respectively, so that the last extraction test on sample 3 was carried out with the values of the above-mentioned variables. The extraction sample was also analyzed by capillary electrophoresis, and the result is presented in Table VIII, where also the first and second repetitions of sample 1 under the best extraction variables were analyzed.

Table VIII Ammonium contents of extractions on repetitions of sample 1

During the empirical tests, all the four samples of Table I and a commercial calcium carbonate (MERCK) were analyzed by the Kjeldahl method, for determining the total nitrogen contents of the samples. The total nitrogen content results of unprocessed samples are presented in Table IX. Total nitrogen contents of unprocessed samples, determined by the Kjeldahl method (analyses carried out

The dry matter recovered from both pressure and temperature extractions were also analysed by the Kjeldahl method, the results being presented in Table X.

Table X Total nitrogen contents of dry matter samples recovered from extractions, determined by the Kjeldahl method (analyses carried out twice .

On the basis of the Kjeldahl results, the total nitrogen content measured from the unprocessed sample was reduced by about 0, 15 to 0.2 g/kg, thanks to the extraction of the invention. On the basis of the Kjeldahl measurements on extractions (Table X), extraction at the pressure of 5 bar and at a temperature of +100°C gives the best result for the reduction of total nitrogen content (ammonia + nitrate + nitrite).

On the basis of analyses by capillary electrophoresis, the best extraction for the reduction of ammonia is extraction applied at 5 bar and +90°C. On the basis of capillary electrophoresis results shown in Table VII, almost twice as much ammonia is reduced from sample 1 under the conditions of 5 bar and +90°C as in extraction at 5 bar and +100°C. The different total nitrogen contents in these two extractions may be due to the fact that more ammonia can be reduced in one of the extractions, and in the other extraction, not only ammonia but also nitrogen-containing anions, such as nitrite and nitrate, are released from the matrix.

The invention is not limited solely to the examples presented in Figs. 1 to 5 and the above description, but it may be modified within the scope of the appended claims.

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