CZ201262A3 - Method of treating raw material for obtaining biooil by quick pyrolysis of wood - Google Patents

Abstract

An increase in bio-energy yield of up to 26% by the process of rapid wood pyrolysis at 350 to 750 degC is described, at a process pressure of 10 to 1000 kPa, with a residence time of the resulting vapor phase in the hot reaction zone of less than 10 s, in a continuous or a batch arrangement in which wood is used as the raw material, which is treated by the ion exchange method with a solution resulting from the action of a sulfuric acid solution on water-leached wood ash.

Description

The present invention relates to a process for treating a raw material for the production of wood oil. Bio-oil is formed by rapid pyrolysis under the simultaneous catalytic action of one or more catalytically active elements deliberately delivered to the raw material.

State of the art

Classical biomass pyrolysis is a thermal process in which thermolysis reactions take place, it is carried out without air access, its products are both solid residue (charcoal analogue called biochar), liquid fractions (bio-oil and water) and combustible gases. In this text, bio-oil refers to a complex mixture of substances that are in the gaseous state under pyrolysis conditions, after cooling to normal temperature they are in the liquid state. Bio-oil does not include water. Bio-oil can be used as an energy raw material, for example as a specific motor fuel or as a raw material for refinery processing into a part of standard motor fuels. This possibility of using bio-oil has led to the innovation of pyrolysis, which increases the efficiency of wood conversion into bio-oil. The innovation consisted in rapid heating of the raw material to a high temperature, in a short reaction time and in rapid cooling of gaseous products. The innovative process is referred to as rapid pyrolysis or flash pyrolysis or wood liquefaction. In this process, temperatures range from 350 ° C to 750 ° C and the residence time of the vapors in the hot zone is fractions of up to tens of seconds.

The conditions under which the thermolysis of wood takes place, despite the designation, are closer to the industrial cracking process than to petrochemical pyrolysis. In the processing of fossil fuels:: ^, ::: * · · * * * 111 »« «** ** · cracking and pyrolysis aim to obtain useful smaller molecules from high molecular weight substances, but petrochemical pyrolysis is a non-catalytic high temperature process for thermodynamic reasons, while refinery cracking is operated as a catalytic and non-catalytic thermal process. Like cracking, thermal splitting of wood is not a thermodynamically controlled process and both catalytic and non-catalyzed methods of wood thermolysis are known.

The use of catalysts such as alkali metal compounds, Ni, Pt, Zn, Fe, Al, Si, Ti, in the rapid pyrolysis of wood has led to a further increase in the conversion of dry wood to bio-oil.

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The United States Patent (US 20100212215) states that the most important factor influencing the liquid pyrolysis yield is the choice of catalyst added to the pyrolyzed feedstock. The patent further states that the yield of solid residue (biochar) in catalyzed pyrolysis is at the same level as that provided by uncatalyzed rapid pyrolysis of wood. The H-ZSM-5 catalyst accelerates demethoxylation and other hydrogenolysis reactions, so that oxygen is only 21.4% in the oil produced.

A closer look at the application of catalysis in wood thermolysis shows that this area is ambiguous. A catalyst precursor is often added to the wood and its active form is formed only during the thermal process. The catalyst for this process goes beyond the simple definition of a catalyst: “A catalyst is a substance that accelerates specific reactions but does not consume itself. In some configurations, the wood thermolysis catalyst is consumed together with the raw material and exits the process in a biochar stream. This is because the catalyst is usually in solid form, as is the residue from the pyrolysis of wood (biochar), and the two entities cannot simply be separated during pyrolysis. The life of the catalyst is comparable to the mean residence time of the feedstock in the pyrolysis reactor.

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The benefits of the catalytic effect should outweigh the costs of acquiring the catalyst and introducing it efficiently into the pyrolyzed feedstock. In view of this pattern, it follows that the catalyst should be cheap and inexpensive to incorporate into the feedstock.

The essence of the invention

According to the invention, an increase in the energy yield of the bio-oil of up to 26% is achieved by a raw material treatment process for a rapid wood pyrolysis process aimed at obtaining bio-oil carried out at 350 to 750 ° C, process pressure 10 to 1000 kPa, with residence time in a reaction zone of less than 10 s, in a continuous or batch arrangement, which is characterized in that the pyrolyzed feedstock is treated with an ion exchange solution by the action of a sulfuric acid solution on water-leached wood ash.

The energy yield of bio-oil reported here is defined as the ratio of the heat of combustion of bio-oil obtained by rapid pyrolysis of a certain amount of raw material to the heat of combustion of the raw material used. If the energy yield is given as a percentage, this proportion is multiplied by one hundred.

The effect of the processing of the treated raw material is reflected in the energy balance of rapid pyrolysis by:

(a) increasing the weight yield of organic liquids at the expense of solid residue and / or non-condensing pyrolysis products and / or both products;

b) a reduction in the content of organic oxygen in the elemental composition of the bio-oil, which leads to an increase in the energy content (combustion heat) of this product;

c) reducing the process temperature and thus reducing the energy intensity of the wood pyrolysis process.

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The individual points a) to c) or their combinations can manifest the effect of ions in the raw material.

Wood ash is offered as a cheap source of cations, which act catalytically during liquefaction of wood and increase the energy yield of bio-oil. However, simply adding ash to the pyrolyzed feedstock does not increase the energy yield of the bio-oil. However, the inventors have surprisingly found that if the catalytically active cations are introduced into the pyrolyzed feedstock by ion exchange from a suitable solution, and thus evenly distributed in the pyrolyzed feedstock, the energy yield of the bio-oil in the subsequent wood liquefaction process increases rapidly (rapid pyrolysis).

According to the invention, the process for treating the raw material for the rapid wood pyrolysis process consists of two parts:

a) obtaining a solution of ions with which the raw material will be treated; and

b) treatment of the raw material by the ion exchange method.

ad a) Obtaining an ion solution for the treatment of pyrolyzed raw material

The source of the ion solution with which the pyrolysis raw material is treated is wood ash, which, however, contains predominantly calcium ions, which have an inhibitory effect on the liquefaction of wood. The second main component of the ash are potassium compounds, whose effect on wood liquefaction at high concentrations is not positive, and therefore they are added to the ion solution only in such an amount as to reach a suitable pH or limit concentration of potassium in the raw material 0.1 τ 0.15 wt. .%.

The first step in the preparation of the ion solution is preferably the standardization of the raw material, in which the wood ash is annealed at 550 ° C in a stream of air so as to oxidize, i.e. burn, the residues of combustible substances. The next step is leaching

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> ··· «» * * * * · · * · ♦ í í · · «· ** ash with water, part of the resulting aqueous extract can be used to adjust the pH of the ion exchange solution. The ash and water are mixed in a weight ratio of 1: 3 to 1:15 and mixed until the mixture reaches equilibrium, i.e. further mixing does not change the solute concentration. Their concentration can be determined by measuring the pH value. The aqueous extract is basic and the cations dissolved in it are made up of 80-95% alkali metals, another important cation dissolved in the extract is magnesium, calcium is present among the cations of the extract in an amount of less than 1%. 50 <90% of all alkali metal cations contained in the raw material are dissolved in the aqueous extract from the ash. The aqueous extract is separated by filtration.

In the next step, the undissolved part of the ash is subjected to leaching with sulfuric acid diluted to a concentration of, for example, 0.5 4, 2.0 mol / l. The concentration of the acid used can be chosen, which determines the concentration of the ion mixture formed from it. Furthermore, the ratio of acid to ash can be changed during its leaching, which determines the final pH of the obtained cation solution. It is advantageous to add such an amount of sulfuric acid that at steady state the pH of the leachate is around 4. The total amount of sulfuric acid added depends on the ash composition and can reach 7 θ molk. cheese / kPpopeia.

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The next step in the preparation of the ion solution is to adjust the pH of the extract obtained with the sulfuric acid solution (the content of residual sulfuric acid in the ion solution is less than 0.05 mol / kg _{of ash} ). Too acidic pH is adjusted by means of an aqueous ash extract which contains about 0.8 mol _alkali / kg _pO p _e L _a . The pH of the dilute sulfuric acid extract is adjusted to 5 - aqueous extract. .7. When the pH is adjusted, insoluble components, especially silicates, precipitate out of solution. Therefore, the precipitate needs to mature sufficiently (at least 10 hours). Filtration of the precipitate gives an ion solution, which is introduced into the raw material in the next step. By dividing the leaching of the ash into two stages (leaching with water and subsequent:::::,:

As described above), three fractions are obtained as described above:

(i) an aqueous extract which contains mainly alkali metal compounds;

(ii) dilute sulfuric acid extract containing metal compounds such as Fe, Zn, Mn, Ni, Cu, Al;

(iii) a solid residue after partitioning with dilute sulfuric acid, which consists mainly of calcium sulphate.

The ash from which the ion solution is obtained does not have a stable composition. Ash cations are usually made up of 30 x * 60% calcium, 30- <60% potassium, 10-30% magnesium and

Of the other metals, aluminum, copper, iron, manganese, nickel and zinc ions, which are present in fraction (ii), are important. is used to treat the pyrolyzed feedstock after pH adjustment.

ad b) Treatment of raw material by ion exchange method

In general, the introduction of a catalytically active ion solution to the pyrolyzed feedstock can be accomplished in several ways. The wood can be impregnated with an ion solution. A more concentrated ion solution can be applied by spraying. As already mentioned, the disadvantage of both of these methods is the uneven distribution of cations in the raw material (these are located on the surface of the wood particles or partially on the inner surface of the wood), which results in a negligible effect on the energy yield of the bio-oil in the rapid wood pyrolysis process.

The treatment of the raw material by the ion exchange method takes place in a bed of raw material flooded with an ion treatment solution for 1 <48 hours and a temperature of 20,100 ° C. This treatment of the raw material requires its complete flooding, including internal free; ·. ; :. ::::, · ¹ · '* »'« »· t 4 ♦ ♦ · and wood space (trachea and tracheids, transport canals, lumen, porous structure of lignin), which must be targeted. Polyvalent ions preferentially bind polyvalent ions to the volume of wood at the expense of low-polygons. Because the ion solution consists mainly of divalent and trivalent metal cations, the catalytic effect of which has been demonstrated, the monovalent alkali metal cations in the wood are replaced by high-strength cations during ion exchange. In ion exchange, the solution is enriched in alkali metal cations and depleted in catalytically active metal cations, while in wood - the future raw material of pyrolysis, the opposite is true. Ion exchange is an equilibrium process that reaches equilibrium in more than 24 hours at 20 ° C. This time is the minimum to approach equilibrium. The time required to reach the ionic balance between the wood and the solution can be reduced by increasing the temperature in this process.

By increasing the temperature by 10 ° C, the time is usually reduced to 75% of the original time.

Before the actual pyrolysis, it is desirable to adjust the moisture of the raw material. After application of the ion solution, water makes up more than 50% of the raw material. Moisture behaves as an inert substance during pyrolysis, but it affects the parameters of pyrolysis - a higher value slows down the heating of the raw material to the reaction temperature. Adjusting the humidity to the optimum level is usually done by drying. Its conditions are different from the recommendations for wood dryers. It is desirable to dry the pyrolysis feedstock with the lowest possible relative humidity of the drying medium in order to cause stress in the dried wood particles and to crack them. In this way, the effective size of the pyrolyzed particles, especially the largest particles, is reduced, which is desirable.

Because the raw material for the preparation of the ion solution (ash) is not stable, the composition of the ion solution (catalytic ions) is not stable either. For each different mixture of ions and different ways of their application to the pyrolyzed raw material, it is necessary to optimize the pyrolysis conditions in terms of achieving the maximum energy yield of the bio-oil. Pyrolysis conditions are understood primarily as temperature, rate of reaching and cooling of products, as well as reaction time, i.e. the mean residence time of gaseous products in the hot zone, which can be influenced by adjusting the inert gas flow at pyrolysis or raw material humidity or by changing the feed rate.

The conditions of the pyrolysis of the treated raw material must be experimentally optimized on the equipment used.

For rapid pyrolysis of wood to produce bio-oil, it is generally the case that the lower the content of organically bound oxygen in the bio-oil, the higher its heat of combustion. The energy yield of bio-oil is crucial for evaluating the efficiency of the process of converting wood into liquid fuels, the weight yield can only be used in exceptional cases. Only those liquid pyrolysis products whose combustion heat is approximately the same can be compared by weight yield, which is satisfied for samples with the same water content and organically bound elemental oxygen.

Examples of embodiments of the invention

The energy yield was also applied in the evaluation of the raw material treated according to the invention. Three samples were evaluated in the rapid pyrolysis balance test. Samples 1 and 2 are raw materials (wood) treated in such a way as to increase the content of catalytically active cations. Sample 1 was treated according to the method of the invention, the content of ions in sample 2 was increased by impregnation. The third sample is untreated wood with an average cation content. It was found that the energy yield of the wood treated according to the invention (sample 1) is 26% higher than the energy yield of comparative sample 3.

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Example 1

Process for the treatment of the pyrolyzed raw material according to the invention 1a) Preparation of a catalytically active ion mixture (ion treatment solution).

Wood ash was used as a raw material for the preparation of the ion solution, which was annealed in an electrically heated tube furnace at an air flow of about 200 ml / min for 6 hours at a temperature of 550 ° C. This treatment reduced the weight of the ash by 27%.

1500 g of water were added to 300 g of calcined ash. After mixing these components, the suspension was stirred at room temperature for 14 hours. The pH of the solution did not change for the last hour and was 12.8. Titration of the resulting aqueous extract to phenolphthalein revealed that the extract contained 0.56 moles of alkalis. The extract was separated from the insoluble residue by filtration, the residue was dried to constant weight and weighed (287.4 g). 280.0 g of this water-leached residue were mixed with 4200 g of dilute sulfuric acid at a concentration of 0.5014 mol / l, and the resulting suspension was stirred for 16 hours. The pH, which was 4.3, had not changed in the last two hours. The solid residue was then filtered off and dried to constant weight and weighed (348.8 g). The free sulfuric acid in the extract was titrated, the total amount of which in the extract was 0.016 mol. During leaching, 8.27 mol _k reacted. _si rové / kg _popeia .

The aqueous extract contained (as elements): potassium 49.3 g / kg _ash sodium 0.8 g / kg _ash magnesium 0 g / kg _ash calcium 0.06 g / kg ash i _a • _ίο -::. :::. :

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The leachate obtained with the help of 0.5M H ₂ SO ₄ contained (as elements):

iron 1.54 g / kg _{ash and} manganese 2.51 g / kg _ash zinc 4.4 g / kg _ash potassium 26.16 g / kg _ash sodium 0.95 g / kg _ash magnesium 17.58 g / kg _ash calcium 6.16 g / kg _pope4a

Tab. I: Cation content of the ash and two leach residues (as elements) determined by XRF analysis

Element Ash [wt.%] Residue after leaching with water [wt.%] Residue after leaching H ₂ SO ₄ [wt.%] Potassium 8.41 3.58 0, 97 Sodium 0.27 0.20 - Calcium 50.87 50.56 48.71 Magnesium 2.69 2.81 0.29 Aluminium 2, 08 2.06 1.17 Manganese 2.86 3.01 2.22 Iron 0.72 63 1.22 Zinc 0, 15 0, 16 0.10 Chrome - - - Silicon 2.61 3.49 2, 05

The pH of the sulfate solution (obtained with H ₂ SO ₄ solution) was adjusted to 5.5 with aqueous extract and the resulting precipitate was filtered after 14 hours of maturation. The filtrate is referred to as the catalytic ion solution. This solution can be concentrated on an evaporator as needed.

lb) Treatment of pyrolysed raw material with ion solution prepared according to la)

The starting material for pyrolysis (before treatment according to the patent) was white birch wood with an average content

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i «· e« i * ' _t • * · · «* <·· it ··· * · cations in the tissues of this individual (Table II). The log wood was cut with an electric circular saw into sawdust and dried to constant weight. This wood was used to prepare samples 1 and 2, untreated is used as sample 3 (comparative).

Tab. II: Concentration of individual elements in white birch wood

Concentration of elements in white birch wood [mg _element / kg _wood ] AI Ca Cu Fe TO Mg Mn On Ni Zn 40.88 658.14 10.70 84.87 579.88 117.19 135.13 20.14 0.5 ^ 2.37

To 500 g of sawdust in an Erlenmeyer flask was added 5 L of a solution containing an extract of 600 g of ash obtained with 0.5 M H ₂ SO ₄ (for solution preparation see la)). Above this mixture, the pressure was reduced from atmospheric to 5 kPa. This pressure was maintained until air escaped from the sawdust pores, then atmospheric pressure was restored. The mixture was allowed to stand and the operation was repeated after 5 minutes. Again, after 5 minutes of standing, the evacuation was repeated, this time the time required to extract the air escaping from the pores of the wood did not exceed even 1 minute. The goal of pressure pulsation is to completely flood the wood, ie to remove all air from the wood mass. After atmospheric pressure was restored, the flask and mixture were placed on a magnetic stirrer and stirred at 20 ° C for 24 hours. After this time and separation of the liquid and solid phases, the sawdust was rinsed with 200 ml of water and dried at 105 ° C to constant weight. The raw material thus treated - sample 1 - was pyrolyzed in a balance test (see Example 3).

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Example 2

Method of raw material treatment by impregnation

2a) The preparation of the catalytically active ion mixture is identical to the description of Example 1 a)

2b) Impregnation of the pyrolysed raw material with an ion solution prepared according to la)

The starting material was, as in Example 1, white birch wood with an average cation content listed in Table II, cut with an electric circular saw into sawdust, which was dried to constant weight.

To 500 g of sawdust in an Erlenmeyer flask was added 5 L of a solution containing an extract of 600 g of ash obtained with 0.5 M H ₂ SO ₄ (for solution preparation see la)). Above this mixture, the pressure was reduced from atmospheric to 5 kPa. This pressure was maintained until air escaped from the sawdust pores, then atmospheric pressure was restored. The mixture was allowed to stand and the operation was repeated after 5 minutes. Again, after 5 minutes of standing, the evacuation was repeated, this time the time required to extract the air escaping from the pores of the wood did not exceed even 1 minute. The mixture was left for 5 minutes at atmospheric pressure and then the impregnation solution was separated from the chips, which were rinsed with 200 ml of water and dried at 105 ° C to absolutely dry. The raw material thus treated - sample 2 - was pyrolyzed in a balance test (see Example 3) Example 3

Balance pyrolysis

The pyrolysis unit consisted of a cylindrical horizontal reactor of the following dimensions: diameter 290 mm, length of the cylindrical part 890 mm, the reactor was heated from the outside by direct

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* * I * · · ··· · «·· * ·· with a 22 kW flame, both bases of the cylindrical reactor were equipped with an axial tube 200 mm long, which was connected on one side to the feedstock equipment (non-rotating). The reactor was permanently closed by a 90 mm long raw material cylinder, which did not allow the pyrolysis gases to flow through the metering path. The second base was removable, connected to the reaction vessel by a flange. After removing the base with the resulting opening from the reactor, biochar was periodically removed, the base also served to drain the gasified pyrolysis products. Towards the inside of the reactor, the cylinder shell made of stainless steel sieve (stainless steel wire diameter 0.3 mm, mesh size 0.3 x 0.35 mm) was firmly attached to the base, the dimensions of the cylinder surface were diameter 160 mm, height 200 mm. This installation prevented biochar from escaping from the reactor into the air cooler. During the pyrolysis, the reactor was rotated about a longitudinal axis at a frequency of 12 revolutions per minute. The tube, which was firmly connected to the base and thus to the reactor, rotated with it and was inserted into a 4.5 m long static tube, which served as an air cooler. The air cooler was followed by a liquid phase separator (Ξι) with a bottom outlet, gaseous fractions with a temperature lower than 260 ° C were led through a Teflon tube to a glass flask (separator S ₂ ) equipped with efficient reflux coolers, in which the gas phase cooled to less than 50 C. The condensate drained into a flask from which it was periodically drained. The volume of the cooled gas was measured with a flow meter. The temperature was measured at several points on the pyrolysis unit. First, the non-contact thermometer read the temperature of the outer wall of the cylindrical part of the pyrolysis reactor just before the exit of gases from the reactor (TJ), then the temperature of gases at the inlet to the air cooler (T _{2 )} , The temperatures T ₂ , T ₃ and T ₄ were sensed by thermocouples inserted into the gas phase stream _.

The pyrolysis reactor operated in a semi-continuous mode, the raw material was fed continuously, the biochar was from the reactor. :::. :

• · * · tv «« · It ··· * · excluded periodically, always with a change of raw material. The optimal mode was set using the feed rate of the raw material, other parameters were constant. The pyrolysis results were evaluated on the basis of 15 minutes of steady state operation of the unit.

Temperatures reached during the measured pyrolysis period:

Ti = 410 - 500 ° C

T ₂ = 160 230 ° C

T ₃ = 100 - 120 ° C

T ₄ = 20 - 40 ° C

The liquid was taken from the Si and S ₂ separators as a product after reaching the temperature T ₃ = 100 ° C in the steady state operation of the unit. The condensate that had accumulated in these separators before the measurement began was drained and was not part of the product. The resulting liquid was then filtered to remove solids that could cause polymerization. A sample was taken from the filtered liquid phases and the heat of combustion was determined calorimetrically. Based on the known weight of the individual products and their heat of combustion, the energy yield of pyrolysis was calculated (see Table II).

Biooleum samples were comprehensively analyzed. The water content was determined by the Karl Fischer method, the oxygen content was determined by organic elemental analysis, and the organic oxygen content was calculated after deducting the contribution of water.

Balance pyrolysis of samples 12 / a 3.

The prepared raw material samples were pyrolyzed according to the procedure specified above. The raw material of the comparative balance pyrolysis was sample 3, ie native white birch wood dried to constant weight.

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The optimal pyrolysis dosing rate was determined for each sample. This was 45% higher for sample 1 and 30% higher for sample 2 than for sample 3, where it was 18 g / min.

The qualitative and quantitative composition of the bio-oil was determined by the calibrated GC-MS method.

Table III:

Characteristics of wood samples and basic balance characteristics of balance pyrolysis products

Parameter Sample 1 Sample 2 Sample 3 Example 1 Example 2 untreated wood Characterization of pyrolyzed raw materials Dry matter (%) Ashes in 100 100 100 dry matter (%) Concentration 1.27 1, 57 0.44 Ca + Mg (mg / kgs / acid) Concentration 1320 1971 775 K + Na (mg / kg dry matter) Concentration 1920 1395 600 Fe (mg / kg dry matter) Concentration 112 94 85 Z n (mg / kg) Concentration 305 225 42 Mn (mg / kg dry matter) 405 447 135

Pyrolysis products (without water) Mass bio-oils 296 (g / kg _SUEOViny ) Weight of solid residue (9 / ^^ raw material) Combustion heat 290 248 255- ^ 260 bio-oil 29.01 (MJ / kgp _E product _U ) Organic oxygen 16, 84 in bio-oil (%) Energy 28.4 30.6 17.26 16.84 yield 53 bio-oils (%) 48 42

If the yield of comparative sample 3 was indicated as 100%, then the relative energy yield related to this sample is = 114.3% for sample 2 and = 126.2% for sample 3.

Represents:

JUDr. Michal \ Havlík

JUDr Michal HAVLÍK 'lawyer \

120 From PRAGUE2, Hálkovaž -

PATENT CLAIMS

Claims (2)

PATENT CLAIMS Process for the treatment of raw material for a rapid wood pyrolysis process aimed at obtaining bio-oil carried out at a temperature of 350 to 750 ° C, at a process pressure of 10 to 1000 kPa, with a residence time of the resulting gas phase in the hot reaction zone of less than 10 s, in a continuous or batch arrangement, characterized in that the pyrolyzed raw material is treated with an ion exchange solution by the action of a sulfuric acid solution on water-leached wood ash. A method according to claim ¹ , characterized in that a part of the aqueous extract from the leaching of the wood ash is used to adjust the pH of the ion exchange solution. The method according to claim 1, characterized in that the pH of the ion exchange solution is adjusted to 47 by the aqueous leachate from the leaching of wood ash. XV The process according to claim 1, characterized in that the ion exchange takes place in a bed of raw material flooded with an ion treatment solution for 48 hours at a temperature of 20-100 ° C.