WO2013076362A1

WO2013076362A1 - Method for treating biomass

Info

Publication number: WO2013076362A1
Application number: PCT/FI2012/051113
Authority: WO
Inventors: Tom Grahn
Original assignee: Kemira Oyj
Priority date: 2011-11-21
Filing date: 2012-11-14
Publication date: 2013-05-30
Also published as: FI20116156L

Abstract

The present invention provides a method for treating biomass, comprising treating said biomass with first hot water stream to release minerals, treating said biomass with second hot water stream to release hemicellulosic fraction, and treating obtained biomass matrix with third hot water stream to torrefy the biomass to produce high energy solid product. The present invention also provides a mineral product, a hemicellulosic product, and a high energy solid fuel product obtained with said method.

Description

Method for treating biomass

Field of the invention The present invention relates to method for treating biomasses wherein said biomass is subjected to hot water streams.

Background of the invention Fuels are divided into fossil or renewable depending on their origin. Historically fossil fuels have been the mainstream in energy production. In the future renewable fuels for energy production will grow in general, and specifically after the Fuku- shima catastrophe 2011. The most promising areas of renewable fuels growth are the production technologies of fossil and renewable fuels where these can be uti- lized side by side without any major investments. This is called cofiring or cocum- bustion. Fossil coal is the largest source of energy worldwide. It is therefore evident that technologies where a renewable solid fuel can be cofired with coal on equal terms over a wide ratio of fossil/renewable fuel are of high commercial and political interest. To a large extent these coal fired heat and power plants are situ- ated near sea close to or in harbors worldwide.

Lignocellulosic biomasses and agribiomasses consist basically of three groups of ingredients from the biggest one to the smallest: holocellulose (celluloses + herni- celluloses), lignin, minerals, not forgetting water i.e. the water content of the bio- mass. Each of these groups has a definite impact on the properties of the biomass or agribiomass in question from the point of combustion.

The heat values of the holocellulosic components are the same. The heat value of lignin is the highest. The heat value of minerals is practically nonexistent as ash components. To increase the heat value of a biomass the most essential feature is to separate one of the main components that as per se has an economic value. The separation of minerals will increase the heat value, but only slightly.

The mineral components, their volume and their composition, are crucially im- portant to cofiring a biomass/agribiomass with fossil coal. In the industry the following rule of thumb is known. Each 10°C in peak steam boiler temperature has a +2% impact on the power yield of a plant. It is easy to understand the fundamental difference of firing a fossil coal plant steam boiler at 580°C, and a pure unrefined biomass steam boiler at 480°C. The key reason why a biomass fired boiler is fired at essentially lower temperatures is the volume and the composition of the ash forming minerals. The water content i.e. the moisture content of a biomass/agribiomass has a direct impact on the heat value of that biomass due to the heat of evaporation of water. The drier the biomass is the higher is the heat value of the biomass. Any biomass is hydrophilic by nature. If a biomass could be hydrophobic, it would not absorb water, but repel it. In practice this would mean that such a biomass could be stored outdoors in piles in the same manner as fossil coal. Hydrophilic biomasses must be stored under roof once they are dry or dry enough. Moist biomasses have little uses as fuels.

Fossil coal is a bulk volume commodity. Coal is transported in large vessels from ports near to coalmines to coal power plants located logistically at shores. This coal is stored in large piles. For utilization the stored coal is milled to coal powder to be fed to the incinerator and steam boiler. Due to low or very low slagging, fouling and corrosive chemicals, primarily chlorine and potash, the boiler firing temperatures of coal power plants are normally in the range of 550 to 600°C.

Any biomass-based fuel cofireable with coal should at least fulfill similar handling basic criteria as coal. These so-called prerequisites for such a biofuel include: transport in bulk in large vessels to point of use, the fuel must be hydrophobic, the degree of hydrophobicity must tolerate rain and humidity without impairing the heat value, logistically such a fuel is stored like fossil fuels in large piles, and the grinding energy for powdering the fuel must be less or comparable to coal.

It is therefore basically clear that wood products like wood chips, bark, saw dust, forest residues, peat, straw etc. lose out commercially already due to fuel handling and fuel storage behavior, not to mention pulverization and wettability.

Such a listing of prerequisites is, however, not enough. Nowadays fuel and combustion chemistry is playing a crucial role in screening out candidates for cofirea- bility with fossil coal. The efficiency of a coal power plant is based on its steam boiler characteristics, which are temperature and pressure, as well as long life and low maintenance and service periods and cost of standing. Slagging, fouling and corroding elements in a biofuel reduce its attractiveness and economy. Especially potash (K) and chlorine (CI) are elements that the industry especially looks out for. Biofuels with low potash and low chlorine content are in principle cocombustible with coal. Biofuels with higher contents of either or both are not cofireable, or, they become cofirebale but at essentially lower efficiencies of the boiler. Recently, since the turn of the millennium, dry torrefaction of woody biomasses has been developed, and historically the method is known to be internally used industrially by Pechiney in France since the 1980's. It is only during the past five years that woody biomass demonstration plants and pilot plants have been or are being commercially tested (Global Bio-Coal Energy Ltd, BC, CA; Topell Energy NL; ECN, NL; Tora Ab, SE, and the like). Especially when major energy companies like RWE, Vattenfall, etc. have entered the dry torrefaction processing of woody biomass, the commercial outcome of industrially dry torrefied biofuels will be set. One of the major obstacles is certainly not met by dry torrefaction. By its definition dry torrefaction takes place at 250-300°C in non-oxygen (e.g. nitrogen) atmosphere aided by the hemicelluloses fraction enthalpy volatilization as "torgas" below 200°C. Three considerable wood matrix changes take place. The energy density is increased 10-20% due to loss of more C than O. The mass balance loss is alto- gether 20-30% and the density remains at the same level. The woody matrix turns blackish brown and hydrophobic. The ash-forming minerals densify to the same degree as volatilized carbon is evaporated. Hence, in dry torrefaction of biomass the slagging, fouling and corroding chemistry is even more prominent in the product than in the feedstock.

With the best current and available industry and scientific information of today any lignocellulosic or agribiomass, whether fired as is or mildly pyrolyzed (dry torrefied), will be cofireable with fossil coal neither on terms of fossil coal fuel characteristics, nor on fossil coal power plants efficiency.

It is also imperative that the hemicellulose fraction of holocellulose be lost in the mass balance. The loss of the hemicellulose fraction as gasified "torgas" is responsible for the increase in energy density, and loss in mass balance. It is relevant to ask, is it possible to recover the hemicelluloses fraction for further value added processing, and still increase the energy density, and still achieve a hydrophobic renewable fuel. It is also easy to understand that the minerals in the biomass/agribiomass are the results of the water transport from the soil into the tree/plant whether it is fertilized or not. The mineral composition of a biomass/agribiomass corresponds to the water solution of the soil absorbed, transported and accumulated in the tree/plant at point of photosynthesis and evaporation.

As a summary, there are at least the following problematic issues to overcome before claiming to be able to produce a true renewable fuel completely cofireable with fossil coal:

·> separation of mineral volume and composition to a point where the minerals do not demand a deduction in steam boiler temperature of fossil coal plant;

separation of hemicelluloses fraction in a way where the hemicellulose (from 20 to 30%) is not lost as energy but preserved for valued added processing.

It is desired to create a method by which the problems of prior art in cofiring with fossil coal in existing coal power plants with a biomass-based product are solved in a feasible way. The reaction of water with woody biomass knowledge and know-how goes back to 1965 (Rydholm). The process of disintegration by extraction of hemicelluloses from lignocellulosic biomatrix is called autohydrolysis. Several attempts during the decades since 1965 have been made to design and build know-how on this basic platform of autohydrolysis of biomasses. One example is below.

WO2009/122018 discloses a method of treating biomass containing a fibrous structure and polysaccharides, comprising subjecting the biomass to extractive treatment in which it is heated in aqueous phase at a pressure in excess of 5 bar and at a temperature over 160°C in order to separate the polysaccharides from the mass; wherein the pH of the biomass subjected to the extractive treatment is not actively lowered during the extractive treatment; after the treatment the pressure is reduced in a controlled fashion so as not to decompose significantly the fibrous structure of the biomass; polysaccharides separated from the mass are recovered as a first fraction; the fibrous structure of the biomass is recovered as a second fraction; and at least one of these fractions is subjected to further treatment.

US2011129886A discloses a process of extraction of useful biochemicals from a non-food plant biomass, the process comprising: a) hot-water extraction carried out by contacting a charge of the non-food plant biomass material with water, in a pressurized vessel at an elevated temperature up to about 250°C and at a pH below about 7.0, to yield an aqueous extract containing hemicellulosic components and other lignocellulosic derived compounds and a lignocellulosic residue; b) sep- arating the lignocellulosic residue and other coarse materials from the aqueous extract; c) processing the aqueous extract to remove larger aromatic and oligo- meric molecules; d) deriving a more pure, concentrated sugar solution from the aqueous extract remaining after step c) by sundering of oligomeric sugars into a concentrated sugar stream and fermentation inhibitory compounds into a perme- ate stream; e) hydrolyzing of the concentrated sugar stream of step d) into mono- meric and/or dimeric sugars; f) removing inhibitory components from the hydro- lyzed monomeric and/or dimeric sugar solution of step e) as a permeate stream; g) concentrating the monomeric/dimeric saccharides after step f); h) separating the permeate stream after steps d) and/or f) into individual components; and i) recov- ering water from the sugar solution after step f) and from the permeate stream in step h),

Lundgren and Helmerius (Integration of a hemicellulose extraction process into a biomass based heat and power plant, Proceedings of ECOS 2009) describe the hot-water extraction of hemicellulose. Hardwood hemicelluloses consist of mainly glucuronoxylan, while galactoglucomannan is the major part of softwood hemicelluloses. Glucuronoxylan in hardwood contributes 15-30% of the total dry weight and softwood contains 7-12% arabinoglucuronoxylan. Hot water pre-treatment of wood materials is less severe compared to acid or alkali pre-treatment. Hot water pre-treatment of wood increases the accessible surface area, removes hemicelluloses and alters the lignin structure to a minor degree. Diluted acid treatment has similar effects on wood, but alters the lignin structure to a significant extent. Hot water pre-treatment is a self-catalytic process and the mechanism of hydrolysis lies in cleavage of O-acetyl and uronic acid substitutions that result in the for- mation of acetic and other organic acids, with further hydrolysis of polysaccharides to oligomers and monomers possible. If hemicelluloses are to be extracted from wood, it is important to obtain high final sugar concentration in extracted liquid that can be utilised by organisms in fermentation processes. However, the generation of compounds that are inhibitory to microbial processing, such as acetic acid, hy- droxymethylfurfural (HMF) and furfural, need to be considered in the extracted liquid. Summary of the invention

The present invention directly and clearly targets a renewable biomass-based fuel with dominant cofireable properties with fossil coal.

The core of the present invention is the following. Biomass of lignocellulosic character is extracted by hot water in a reactor in two or three steps at two or three different temperatures. The resulting products are a solid phase which is a washed biofuel compatible with co-combustion in existing coal power plants, a liquid or solid product containing extracted hemicelluloses, and optionally a liquid or solid product containing the extracted minerals which in itself is a fertilizer for new biomass production.

The present invention provides a method for treating biomass, comprising

(i) treating said biomass with first hot water stream in temperature T1 in the range of 100-170°C to release minerals,

(ii) treating said biomass with second hot water stream in temperature T2 in the range of 140-200°C to release hemicellulosic fraction, and

(iii) treating obtained biomass matrix with third hot water stream in tem- perature T3 in the range of 200-300°C to torrefy the biomass to produce high energy solid product.

The method is commercially and industrially applicable. The basic equipment for a suitable reactor is in part used in the pulp and fiber industry today. Each hot water stream may be engineered for energy efficiency and isolation of the product component, and the process water may be reused. When using water streams no substantial amounts of undesired gases, such as oxygen, are left in the chamber and there is no need to remove such gases. It is an advantage of the invention that the treatment of the biomass may be done in a concentrated way. The different treatment steps may for example be carried out in the same reactor or chamber, which saves energy and time. Both the end product and the by-products are of good quality and useful and can be easily recovered. No flushing of the reactor for example with gas between the steps is re- quired. No extra chemicals are required, such as acids or catalysts. This makes the method both simple and economic. It is another advantage of the invention that the end product is a commercially viable biofuel fully compatible with fossil coal cofireable in existing boilers or coal power plants. Preferably the end product is hydrophobic mass. It is another advantage of the invention that no dry torrefaction is required. This helps maintaining the hemicellulose fraction which would otherwise be burnt and lost in the dry torrefaction.

It is still another advantage of the invention that the useful minerals may be recov- ered and used as fertilizers in the nature and agriculture. It is still another advantage of the invention that the hemicellulose fraction is recovered. It may be used for example as a commercial hemicellulose product ready for animal feed, ruminant feed, and a feedstock for products from water treatment technology to pharmaceutical products. Further, products such as succinic acid, propionic acid, methanol, ethanol, butanol etc. may be produced from the hemicellulose fraction via fermentation or by other processes.

Detailed description of the invention In practical terminology lignocellulosic and agribiomasses refer mainly to wood, straw and husks. General examples of such material include wood chips, bark, saw dust, forest residues, peat and the like. Biomass refers to any suitable renewable energy source. Lignocellulosic material includes constituents of hemicellulose, cellulose and lig- nin.

"Agri" as used herein is an abbreviation for agricultural i.e. it refers to cultivated biomasses.

Hot water extraction refers to separation of a substance from its matrix by hot water over or under 100°C.

"Minerals" as used herein refer to any ash-forming elements, such as potassium, phosphor, magnesium, calcium and manganese.

"Hemicellulosic fraction" or "hemicellulose fraction" as used herein refers to extracted hemicelluloses and derivatives thereof, which may be polysaccharide pol- ymers or may for example be hydrolyzed into mono-, di- and oligosaccharides, and may be recovered as useful biochemicals or as raw material thereof. The hemicellulosic fraction may also contain other molecules and coarse material. Examples of molecules contained in this fraction include short-chain sugars, such as xylose, mannose, arabinose, rhamnose, galactose, and glucose (5 and 6-carbon sugars), and chemicals such as acetic acid, formic acid, furfural, lignin and methanol.

"Torrefaction" refers to a mild pyrolysis of biomass at a temperature in the range of 200 to 300°C. "Dry torrefaction" refers to torrefaction performed in gaseous state. "Wet torrefaction" refers to torrefaction performed in liquid state.

The present invention provides a method for treating biomass to release, recover and obtain useful products. Generally the method comprises

(i) optionally treating said biomass with first hot water stream in temperature T1 to release minerals,

(ii) treating said biomass with second hot water stream in temperature T2 to release hemicellulosic fraction, and

(iii) treating obtained biomass matrix with third hot water stream in tem- perature T3 to torrefy the biomass to produce high energy solid product, i.e. the torrefaction is wet torrefaction.

The water streams are different, separate streams. In one embodiment the different streams in each step have different temperatures. In one embodiment the dif- ferent streams in each step have different durations. The released fractions, mineral fraction or hemicellulose fraction, are removed and optionally recovered.

In one embodiment step (i) is omitted. In such a case the method comprises two steps (i)-(ii) as referred to below (the two-step method), and it may be defined as a method for treating biomass, the method comprising

(i) treating said biomass with first hot water stream in temperature T2 to release hemicellulosic fraction, and

(ii) treating obtained biomass matrix with second hot water stream in temperature T3 to torrefy the biomass to produce high energy solid product.

If step (i) is included, the present invention provides a method for treating biomass, the method comprising (i) treating said biomass with first hot water stream in temperature T1 to release minerals,

(iii) treating obtained biomass matrix with third hot water stream in temperature T3 to torrefy the biomass to produce high energy solid product.

In one exemplary embodiment of the method a fractionated biomass in a bioreac- tor is first treated with a hot water stream of 120-150°C to release the minerals absorbed by the biomass tree/plant from the soil. When 80-90% of the minerals are extracted into its own product stream, this mineral hot water loop is closed. A second hot water stream at 160- 80°C is released into the reactor and the hemicellulosic fraction is extracted. When approximately 95% of the hemicellulose is extracted into the hot water, the hemicellulose hot water stream is closed. A final hot water stream is released into the reactor at 220-240°C and within a relatively short time of 5-10 min the biomass matrix is torrefied into a washed high energy density biofuel solid product compatible with cofiring of fossil coal in existing coal power plants. The pH or the pressure are generally not controlled or adjusted. They may be monitored, but for example over-pressure is not required to carry out the treatment. The pressure may rise during the treatment, but the reactor or process unit does not need to be pressurized. The reactor is generally not flushed with gases, such as nitrogen gas or any other inert gas. No additional chemicals are generally added, for example catalysts, such as lithium chloride, or acids, such as acrylic acid, sulfuric acid, acetic acid or citric acid.

The method of the invention can be used for any lignocellulosic or agribiomasses. Generally the time and temperature differ in each of the two or three extraction processes in series. Each of the two product streams are treated and handled for to recover the product in solution. These are the absorbed minerals from the soil and the hemicelluloses created by the tree/plant species. The solid product from the third stream may be dried to a moisture content of 6-8% and is as such ready for cofiring with coal as it fulfills all the prerequisites and especially, after the ex- traction-washing-procedure, it fulfills the requirement of low levels of all and any slagging, fouling and corroding elements. The water system in each step may be a closed loop system. The energy required for this process is viable from commercial production. 100- 150 kWh/t feedstock is needed for fractionation of the biomass. Theoretically the three-step hot water treatment requires approximately 300 kWh/t of water and about 80-90% of this energy is recuperated and reused in the process. One such major use is the drying of the washed and hydrophobic biofuel solid phase.

In one embodiment the temperature T1 is in the range of 100-170°C, preferably in the range of 120-155°C. In one example the temperature T1 is in the range of 135-155°C. In another example the temperature T1 is in the range of 145-155°C.

In one embodiment the temperature T2 is in the range of 140-200°C, preferably in the range of 160-190°C, for example 165-175°C.

In one embodiment the temperature T3 is in the range of 200-300°C, preferably in the range of 220-240°C, for example about 220°C.

In one example at least 60% by weight of the minerals of the biomass are removed, preferably at least 80% by weight. The extracted minerals may be recovered and used for example as fertilizers for new biomass production. The minerals may be recovered as an aqueous solution. In one embodiment the treatment of step (i) in temperature T1 is continued until at least 80%, such as 80-90%, of the minerals are extracted, and then the mineral hot water loop may be closed.

In one example at least 70% by weight of the hemicelluloses of the biomass are removed, preferably at least 90% by weight. The extracted hemicelluloses and derivatives thereof, which may be polysaccharide polymers or may for example be hydrolyzed into mono-, di- and oligosaccharides, may be recovered as useful bio- chemicals. The hemicelluloses and derivatives thereof may be recovered as an aqueous solution. The hemicellulose fraction may also contain other molecules and coarse material. The hemicellulose fraction may be further processed to purify and/or concentrate any of said components or compounds.

In one embodiment the treatment of step (ii) in temperature T2 is continued until at least 90%, preferably at least 95% of the hemicellulose is extracted, and then the hemicellulose hot water stream may be closed.

In one embodiment steps (i) and (ii) are carried out in the same process unit, such as a reactor. In one embodiment all the steps (i)-(iii) are carried out in the same process unit. Every stream may have its own circulation. The matrix remains in the reactor during the process in steps (i) and (ii) and in step (iii) it will be turned into biocoal. The process may be run as a continuous process or as a batch process. In one embodiment at least one of the steps (i), (ii) and (iii) is carried out continuously. In another embodiment at least one of the steps (i), (ii) and (iii) is carried out as a batch process.

In one embodiment the time t1 of step (i) is in the range of 1-180 minutes, prefer- ably in the range of 10-60 minutes, for example about 30 minutes.

In one embodiment, wherein the method comprises three steps (i)-(iii), the time t2 of step (ii) is in the range of 1-120 minutes, preferably in the range of 10-80 minutes, for example about 20 minutes. In another embodiment, wherein the method comprises two steps (i)-(ii) (two-step process), the time t2 of step (i) is in the range of 1-120 minutes, preferably in the range of 10-80 minutes, for example about 20 minutes.

In one embodiment wherein the method comprises three steps (i)-(iii), the time t3 of step (iii) is in the range of 1-20 minutes, preferably in the range of 3-10 minutes, for example about 5 minutes. In another embodiment wherein the method comprises two steps (i)-(ii) (two-step process), the time t3 of step (ii) is in the range of 1-20 minutes, preferably in the range of 3-10 minutes, for example about 5 minutes.

In one embodiment said biomass is non-food biomass.

In one embodiment said biomass comprises lignocellulosic biomass. In one embodiment said biomass contains hemicellulose at least 10% by weight, preferably 10-40% by weight.

In some examples, chemical additives, such as catalysts or acids, may also be added to the process. One example of such an additive is acetic acid, which cata- lyzes degradation of hemicellulose. Another example is lithium chloride (LiCI) which reduces vapor pressure of hot water. It may be used as a tool to reduce reactor pressure. The present invention also provides a mineral product derived from hydrothermal treatment with water, i.e. obtained with any of the methods described herein. Said product may be in aqueous solution. The present invention also provides a hemicellulosic product derived from hydro- thermal treatment with water, i.e. obtained with any of the methods described herein. Said product may be in aqueous solution.

The present invention also provides a high energy solid fuel product derived from hydrothermal treatment with water, i.e. obtained with any of the methods described herein. The moisture content of the dried end product may be in the range of about 6-8% (w/w).

Examples

Examples 1-6: the first treatment

800 g saw dust of spruce wood, with dry content of about 49%, and 2800 ml distilled water was charged at ambient temperature into 5 I gas tight reactor after which the mixture was heated, 5°C/min, with continuous mixing to desired temperature T and held at this for the desired time t. Thereafter the reactor was cooled and filtrate was separated from wood fraction by centrifuge. The metal content was analyzed with ICP and hemicelluloses with acidic methanolysis. Examples 7-11 : the second and the third treatment

In the second and the third treatment steps the separated solid residue from previous step was treated with water in a similar way as described above (first treatment). Solid dry content/liquid ratio was 1 :8, (liquid includes added water together with moisture of the saw dust residue).

The composition of the untreated saw dust is shown in Table 1 and temperatures and treatment times in Table 2. Ash, metal and hemicellulose contents are presented in Tables 3 to 5. Table 1 : Saw dust before treatment.

Table 2: Experimental conditions

Experiment: 1 2 3 4 5 6 7 8 9 10 1 1 step i T1 (°C) 135 135 145 155 135 135 135 135 t1 (min) 30 120 30 20 30 120 30 120 step ii T2 (°C) 165 174 165 165 165 165 165 t2 (min) 20 20 20 20 20 20 20 step iii T3 (°C) 220 220 220 t3 (min) 5 5 5 Table 3: Result, ash contents

5 Table 4: Results, metal contents

Experiment: 1 2 3 4 5 6 7 8 9 10 11

Ca [mg/kg] 290 223 236 184 124 93 83 58 26 20 15

K [mg/kg] 35 31 32 30 24 22 9 13 6 7 5 g [mg/kg] 28 21 22 17 12 8 7 5 <5 <5 <5

Na [mg/kg] 6 10 10 9 7 8 6 26 10 15 10

Al [mg/kg] <5 28 <5 5 <5 <5 <5 11 <5 7 6

B [mg/kg] 6 13 10 9 6 8 7 38 10 25 15

Ba [mg/kg] 5 <5 <5 <5 <5 <5 5 <5 <5 <5 <5

Fe [mg/kg] 6 <5 <5 5 6 8 6 9 7 11 <5

Mn [mg/kg] 27 21 22 17 11 7 7 <5 <5 <5 <5

Ni [mg/kg] <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 <5

Si [mg/kg] 9 15 10 9 8 8 8 10 9 17 15

S [mg/kg] 21 24 22 23 23 24 21 22 19 16 17

Total [mg/kg] 432 383 362 306 219 183 158 191 86 116 83

Total metal reduction 50% 56% 58% 65% 75% 79% 82% 78% 90% 87% 90%

Table 5: Results, Hemicellulose contents

After examples 10 and 1 1 the dry content of the solid residue was measured and the total reduction of solid mass during the tree step process were calculated as 28 and 32 w-%, respectively. This is well in line with the original hemi content of the untreated saw dust (27%) and shows that the saw dust was fully torrefied. From the results it can also be seen clear temperature correlations in the reductions of both metal and hemicellulose contents. Significant reduction in ash and metal contents can be seen at lower temperatures compered to hemicellulose. From table 5, filtrate analyses show increased hemicellulose extraction above 160°C. This shows that metals and hemicellulose can be separated from saw dust selectively in to own aqueous streams for further processing before the final torre- fication.

Claims

1. Method for treating biomass, characterized in that said method comprises

(ii) treating said biomass with second hot water stream in temperature 12 in the range of 140-200°C to release hemicellulosic fraction, and

(iii) treating obtained biomass matrix with third hot water stream in temperature T3 in the range of 200-300°C to torrefy the biomass to produce high energy solid product.

2. The method of claim 1 , characterized in that the temperatures in each step (i) to (iii) are different temperatures.

3. The method of claim 1 or 2, characterized in that the temperature T1 is in the range of 120-155°C.

4. The method of any of the preceding claims, characterized in that the temperature T2 is in the range of 160-190°C.

5. The method of any of the preceding claims, characterized in that the temperature T3 is in the range of 220-240°C.

6. The method of any of the preceding claims, characterized in that at least 60% by weight of the minerals of the biomass are removed, preferably at least

80% by weight.

7. The method of any of the preceding claims, characterized in that at least 70% by weight of the hemicelluloses of the biomass are removed, preferably at least 90% by weight.

8. The method of any of the preceding claims, characterized in that at least one of the steps (i), (ii) and (iii) is carried out continuously.

9. The method of any of the claims 1-7, characterized in that at least one of the steps (i), (ii) and (iii) is carried out as a batch process.

10. The method of any of the preceding claims, characterized in that steps (i) and (ii) are carried out in a same process unit.

11. The method of any of the preceding claims, characterized in that all the steps (i)-(iii) are carried out in a same process unit.

12. The method of any of the preceding claims, characterized in that the time t1 of step (i) is in the range of 1-180 minutes, preferably in the range of 10-60 minutes.

13. The method of any of the preceding claims, characterized in that the time t2 of step (ii) is in the range of 1-120 minutes, preferably in the range of 10-80 minutes.

14. The method of any of the preceding claims, characterized in that the time t3 of step (iii) is in the range of 1-20 minutes, preferably in the range of 3-10 minutes.

15. The method of any of the preceding claims, characterized in that said bio- mass comprises lignocellulosic biomass.

16. The method of any of the preceding claims, characterized in that said biomass contains hemicellulose at least 10% by weight, preferably 10-40% by weight.

17. A mineral product obtained with the method of any of the preceding claims.

18. A hemicellulosic product obtained with the method of any of the claims 1-16.

19. A high energy solid fuel product obtained with the method of any of the claims 1-16.