FI129929B - A method for forming a lignin fraction and a lignin composition - Google Patents

Abstract

The invention relates to a method and an apparatus for forming a lignin fraction from crude lignin which has been processed by means of a treatment step selected from enzymatic treatment, treatment with ionic liquid and their combinations. The method comprises treating the crude lignin (1) by a lignin liberation in at least one lignin liberation step (3), and separating a lignin fraction (6) in at least one separation step (5). Further, the invention relates to a lignin composition and its use.

Description

A METHOD FOR FORMING A LIGNIN FRACTION AND A LIGNIN

COMPOSITION

FIELD OF THE INVENTION

The invention relates to a method for forming a lignin fraction. Further, the invention relates to a lignin composition.

BACKGROUND OF THE INVENTION

Known from prior art is different methods for forming lignin from different raw materials, such as biomass. Many bio-refinery processes, e.g. a hydroly- sis, generate crude lignin, such as lignin residue, after the hydrolysis of the biomass. This water- insoluble lignin residue usually contains significant percentage of non-hydrolyzed lignocellulose particles.

Further, known from prior art is to treat lignin chemically by dissolving the lignin in a dis- solvent, such as in NaOH, alcohol-water mixture or or- ganic acid, and to precipitate the lignin, e.g. by sulphuric acid or water. Then the pure lignin can be provided, but known processes suffer from high operat- ing and capital costs. Removing and/or recovering of

N the dissolvent or formed salt lead to additional

O costs. A final dewatering of the lignin is usually 00 carried out by a filtration. Size of precipitated lig- 2 nin particles are generally rather small, which has

N 30 negative effect on a filtration rate and dry solids

E content of a filter cake. = From WO 2014/143657, EP 2796561 and WO 2 2012/056872 are known different methods for producing = saccharification products and lignin products.

N 35

OBJECTIVE OF THE INVENTION

The objective of the invention is to disclose a new method for forming a lignin fraction. Another objective of the invention is to disclose a new method for purifying lignin. Another objective of the inven- tion is to produce a purified lignin composition with improved properties.

SUMMARY OF THE INVENTION

The method for forming a lignin fraction ac- cording to the present invention is characterized by what is presented in claim 1.

The lignin composition according to the pre- sent invention is characterized by what is presented in claim 15.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are included to provide a further understanding of the invention and constitutes a part of this specification, illus- trate some embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings:

N Fig. 1 is a flow chart illustration of a

N method according to one embodiment of the present in-

S vention,

N 30 Fig. 2 is a flow chart illustration of a

E method according to another embodiment of the present > invention, 3 Fig. 3a shows the crude lignin before the 00 liberation, and

N 35 Fig. 3b shows the crude lignin after the lib- eration.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a method for forming a lignin fraction (6) from crude lignin (1), and pref- erably for purifying the crude lignin in order to form a pure lignin fraction. The crude lignin (1) has been processed by means of a treatment step (24) selected from enzymatic treatment, treatment with ionic liquid and their combinations. The method comprises treating the crude lignin (1) by a lignin liberation in at least one lignin liberation step (3) for liberating lignin of the crude lignin (1) so that the lignin is liberated for forming two solid phases, lignocellulose and free lignin particles, and separating a lignin fraction (6) by means of at least one separation step (5). In a preferred embodiment, the lignin fraction (6) is a purified crude lignin.

One embodiment of the method of the present invention is shown in Fig. 1. Another embodiment of the method of the present invention is shown in Fig. 2.

The apparatus comprises at least one libera- tion reactor (3) for liberating the crude lignin (1) in at least one liberation step, at least one separa- tion device (5) for separating the lignin fraction (6) in at least one separation step, at least one first feeding device for feeding the crude lignin (1) into

N the liberation reactor (3), and at least one second

N feeding device for feeding the treated crude lignin 3 30 (4) from the liberation reactor (3) to the separation

N device (5). = Preferably, the crude lignin (1) has been > formed from starting material (20). In this context, o starting material (20) means any wood or plant based 3 35 raw material. The starting material may contain lignin, lignocellulose, cellulose, hemicellulose, glucose, xy- lose, extractives and other inherent structural compo-

nents of biomass as well as foreign components such as enzymes or chemicals. In one embodiment, the starting material is selected from the group consisting of wood based raw material, woody biomass, lignin containing biomass such as agricultural residues, bagasse and corn stover, woody perennials, vascular plants, recy- cled brown board, deinking pulp and their combina- tions.

In this context, crude lignin (1) refers any material or composition containing lignin, substan- tially without free lignin. In one embodiment, the crude lignin contains below 20 wt-% free lignin. Fur- ther, the crude lignin contains also lignocellulose, which has glucan units. Lignocellulose, such as glucan units, and lignin are bound into each other in hetero- genous structure meaning that typically lignin is not evenly distributed in the material. Mainly, the crude lignin comprises lignin and lignocellulose, but may contain also hemicelluloses. The crude lignin may con- tain one or more lignin material components. The crude lignin may contain different contents of lignin and glucan. Further, the crude lignin may contain enzymes, especially after an enzymatic treatment. Typically, the crude lignin is in the form of suspension which contains water, acid, e.g. formic acid, acetic acid or sulfuric acid, alcohol or other liquid, or in the form

N cake, lump or the like. In one embodiment, the crude

O lignin is in the form of suspension. Preferably, the © crude lignin is a lignin residue from the hydrolysis, 2 30 e.g. cellulignin.

N In one embodiment, especially after the enzy- = matic treatment and/or treatment with ionic liquid,

O the crude lignin (1) contains high share carbohydrates 3 in the form of solid lignocellulose. After the enzy- o 35 matic treatment and/or treatment with ionic liquid

N lignin is tightly bound in lignocellulose of the crude lignin. Then further processing step is needed to lik- erate lignin. The separation of lignin particles can be facilitated by means of the invention. Preferably, the separation is based on a solid-solid separation. 5 Simultaneously the crude lignin is purified to obtain lignin material more suitable for utilization in vari- ous applications. In the invention the lignocellulose fraction may be circulated back to the enzymatic treatment, such as enzymatic hydrolysis, and/or treat- ment with ionic liguid. An alternative option is to utilize the recovered lignocellulose fraction in an external application.

In one embodiment, the crude lignin has been diluted with liquid, e.g. with water. In one embodi- ment, WIS% (water insoluble solids) of the crude lignin is between 1 - 50 %, or between 20 — 40 %, in the lik- eration step. In one embodiment, WIS% (water insoluble solids) of the crude lignin is between 1 - 35 %, or between 10 - 30 %, or between 15 - 30 %, in the sepa- ration step. Water insoluble solids, WIS%, can be cal- culated: WIS% = (weight of washed and dried materi- al) / (weight of the wet slurry for washing). Low con- sistency of suspension aids mechanical separation of free lignin particles and lignocellulose particles. In one embodiment, weight average particle size of the crude lignin is below 1000 jm, preferably below 500

N um.

O In one embodiment, the cellulose content, 00 i.e. glucan content, of the crude lignin (1) is 3 — 70 2 30 % by weight, preferably 5 - 60 % by weight and more

N preferably 10 - 60 % by weight, analyzed as glucose. = In one embodiment, the lignocellulose parti-

O cles are in the form of fiber sticks in the crude lig- 3 nin. In one embodiment, weight average particle size > 35 of the lignocellulose particle is below 1000 pm, in one embodiment below 500 pm and in one embodiment be- low 300 pm.

The crude lignin has been processed by means of an enzymatic treatment and/or treatment with ionic liquid (24). In one embodiment, the crude lignin has been processed by means of the enzymatic treatment and/or treatment with ionic liquid after the hydroly- sis (21) in which the crude lignin has been formed from the starting material (20).

In one embodiment, the crude lignin has been processed by means of the enzymatic treatment (24). In one embodiment, the enzymatic treatment is an enzymat- ic hydrolysis. In one embodiment, the crude lignin has been formed from the starting material and processed by means of the enzymatic hydrolysis.

In one embodiment, the crude lignin (1) is treated by dewatering, washing, filtrating and/or cen- trifuging in at least one washing and separation step (2) before the lignin liberation (3). Preferably, the crude lignin (1) is washed and soluble carbohydrates are separated before the lignin liberation (3). Pref- erably, soluble carbohydrates, such as soluble Cs car- bohydrates, (14) can be separated from the crude lig- nin during the washing and separation step (2). In one embodiment, the apparatus comprises at least one de- vice, e.g. a filter or centrifuge, for treating the

AN crude lignin (1) by dewatering, washing, filtrating

O and/or centrifuging in at least one washing and sepa- © ration step (2) before the lignin liberation (3). 2 30 In one embodiment, the crude lignin (1) is

N treated by liberating in the presence of acid. In one = embodiment, the crude lignin (1) is treated by liber-

O ating without acid. In one embodiment, the crude lignin 3 (1) is liberated by means of a heat treatment, such as

DO 35 hydrothermal treatment, in the lignin liberation step

N (3). In one embodiment, the crude lignin is liberated by means of an autohydrolysis. In one embodiment, the crude lignin is liberated by means of a dilute acid hydrolysis. In one embodiment, the crude lignin is liberated in two stages. In one embodiment, one stage is performed without acid and another stage with acid.

In one embodiment, the liberation reactor (3) is a di- gester. In one embodiment, the liberation reactor (3) is a glass-lined digester, e.g. a batch glass-lined digester, or a standard continuous digester. In one embodiment, the liberation reactor (3) is a Continuous pipe reactor with short retention time and involving sudden release of pressure after reactor phase. In one embodiment, the liberation reactor (3) is a percola- tion or flow-through reactor.

In one embodiment, temperature is 130 — 400 °C during the lignin liberation (3). In one embodi- ment, temperature is at least 170 °C during the lignin liberation (3). In one embodiment, temperature is 170 — 240 °C during the lignin liberation (3). In the lib- eration, free lignin is liberated from the crude lig- nin and two solid phases, lignocellulose and free lig- nin particles, are formed. In one embodiment, when the crude lignin is treated by liberating, a steam explo- sion effect is achieved during the lignin liberation to aid formation of the free lignin particles and to decrease particle sizes of the lignocellulose parti-

N cles. The most effective lignin liberation is accom-

O plished by short retention time in high temperature, 0 i.e. to produce so called flash effect for liberating 2 30 lignin. Properties of the crude lignin, target proper- - ties for the purified lignin and lignocellulose frac- a. tion as well as economical and ecological values set

O the optimal process conditions. 3 In one embodiment, water is added before the > 35 lignin liberation (3). Temperature of water may be about 20 - 100 °C.

In one embodiment, the apparatus comprises at least two parallel liberation reactors (3) for liber- ating lignin of the crude lignin (1). Preferably, the parallel reactors facilitate the continuous process.

In one embodiment, the apparatus comprises at least two sequential liberation reactors (3) for liberating lig- nin of the crude lignin (1).

In one embodiment, the severity of the liber- ation treatment is between standard hemicellulose (Cs) and cellulose (Cg) hydrolysis, so the lowest possible severity to liberate lignin. Typical pH adjusted com- bined severity (CS) or severity index (SI) is between 1.5 and 2.5 (defined by an equation presented below), where t is time in minutes and T is temperature in de- grees Celsius. log (CS) = tog|t exp(—)| —pH

The low severity is advantageous in order to dissolve as low percentage of cellulose as possible, since this improves Cg-carbohydrate yield in an enzy- matic process. Additional benefits are preservation of natural reactivity of the lignin and higher selectivi- ty of the liberation treatment leading to cleaner sug- ar solution.

In one embodiment, below 70 %, preferably be-

AN low 60 %, more preferably below 50 % and most prefera-

O bly below 40 %, of glucan is dissolved during the lig- © nin liberation (3). 2 30 Fig. 3a presents one embodiment of the crude

N lignin before the lignin liberation, and Fig. 3b pre- = sents one embodiment of the crude lignin after the

O lignin liberation. Darker round shapes in Fig. 3b are 3 liberated lignin particles and lighter colour material > 35 is lignocellulose.

In one embodiment, cooking liquor from the lignin liberation may be removed during or after the lignin liberation. Soluble carbohydrates of the cook- ing liquor may be recovered. Alternatively the cooking liquor may be supplied to a waste water treatment plant as such or after a subsequent treatment.

In one embodiment, carbonate is added before the lignin liberation. In one embodiment, carbonate is added during the lignin liberation. In one embodiment, carbonate is in the form of sodium carbonate, sodium bicarbonate, carbon dioxide, other suitable carbonate or their derivatives or their combinations. Lignin particle size can be increased by means of adding the carbonate. When CO, is generated during the liberation step, softened lignin particles swell due to expanding gas inside the pores. Then lignin particles with in- creased particle size can be separated more easily from the crude lignin.

In one embodiment, the treated crude lignin (4) is cooled after the lignin liberation (3).

In one embodiment, the treated crude lignin (4) is washed after the lignin liberation (3).

In one embodiment, the lignin fraction (6) is separated in one or more separation step (5), after the lignin liberation step (3). In one embodiment, the lignocellulose fraction (7) is separated in one or

AN more separation step (5). In one embodiment, the sepa-

O ration is carried out by means of a mechanical separa- 00 tion. In one embodiment, a separation method is se- 2 30 lected from the group consisting of centrifugal forc-

N es, sedimentation, elutriation, filtration, flotation,

E: screening and their combinations. In one embodiment,

O the separating is made by means of centrifugal forces. 3 In one embodiment, the separating is made by means of

DO 35 sedimentation. In one embodiment, the separating is

N made by means of elutriation. In one embodiment, the separating is made by means of filtration. In one em- bodiment, the separating is made by means of flota- tion. In one embodiment, the separating is made by means of screening. In one embodiment, each separation step is made by similar methods. Alternatively, every separation step is made by different methods. In one embodiment, the lignin fraction (6) is separated from the treated crude lignin (4) so that remaining crude lignin is the lignocellulose fraction (7). In one em- bodiment, the lignocellulose fraction (7) is separated from the treated crude lignin (4) so that remaining crude lignin is the lignin fraction (6). Preferably, the lignin fraction (6) is the purified lignin.

In one embodiment, the apparatus comprises at least one separation device (5) for separating the lignin fraction (6) from the treated crude lignin (4), and preferably for purifying the lignin fraction (6).

In one embodiment, the apparatus comprises at least two separation devices (5). In one embodiment, the separation device is based on centrifugal forces, sed- imentation, elutriation, filtration, flotation, screening or their combinations. The separation device may be reactor, vessel, tank, bowl, cyclone, filter, column, cell, basin, thickener or the like. In one em- bodiment, at least one separation step for separating the lignin fraction is made by means of centrifugal

AN forces, e.g. by basket centrifuge or decanter centri-

O fuge such as solid bowl centrifuge, or flotation, e.g. 0 by froth flotation or column flotation. 2 30 In one embodiment, the separation of the lig- - nin fraction (6) is carried out in one or more separa- = tion step. In one embodiment, the separation is car-

O ried out in one separation step. In one embodiment, 3 the separation is carried out in more than one separa-

DO 35 tion step. In one embodiment, the separation is car-

N ried out in three separation steps. In one embodiment,

the separation device (5) comprises one or more sepa- ration step. In one embodiment, the separation step comprises one or more separation device. In one embod- iment, the lignin fraction (6) is separated in the last separation step. In one embodiment, the lignin fraction (6) is separated between two separation steps. In one embodiment, the lignin fraction (6) is separated in the first separation step. In one embodi- ment, the lignin fraction (6) is separated in the first separation step and after that the lignin frac- tion is purified the later separation steps. In one embodiment, the lignin fraction (6) is separated in each separation steps. In one embodiment, the ligno- cellulose fraction (7) is separated in the first sepa- ration step. In one embodiment, the lignocellulose fraction (7) is separated in more than one separation step. In one embodiment, the lignocellulose fraction (7) is separated in each separation steps. In one em- bodiment, at least one separated lignocellulose flow is circulated to a desired step of the separation.

In one embodiment, the lignin fraction (6) is further purified by screening, preferably by vibrating screen, to remove char and sugar decomposition prod- ucts.

The separation can be carried out in wide temperature range, e.g. at temperatures between O -

N 100°C. Higher temperature usually aids the separation

O due to lower viscosity. Generally near natural process 0 temperature is utilized to avoid heating or cooling. 2 30 In one embodiment, a stabilizing chemical (8)

N is added into the treated crude lignin (4) in connec-

E: tion with the separation step (5). In one embodiment,

O the stabilizing chemical (8) is added into the treated 3 crude lignin (4) before the separation step (5). In o 35 one embodiment, the stabilizing chemical (8) is added

N into the treated crude lignin (4) during the separa-

tion step (5). In one embodiment, the apparatus com- prises at least one feeding device for adding a stabi- lizing chemical (8) into the treated crude lignin (4).

The stabilizing chemical (8) is added into the treated crude lignin (4) in at least one step. In one embodiment, the stabilizing chemical (8) is added into the treated crude lignin (4) in one step. In one embodiment, the stabilizing chemical (8) is added into the treated crude lignin in more than one step. In one embodiment, the stabilizing chemical (8) is added into the treated crude lignin in connection with each sepa- ration step. In one embodiment, the stabilizing chemi- cal (8) is added into the treated crude lignin in the first separation step and/or in at least one later separation step. Preferably, the chemical stabiliza- tion and mechanical separation are made.

In one embodiment, the stabilizing chemical is added into the treated crude lignin and the crude lignin is mixed, preferably by high-shear mixing. The high-shear mixing is beneficial to facilitate adsorp- tion of chemical on surfaces. The stabilizing chemical predominantly adsorbs on lignocellulose particles.

In one embodiment, the stabilizing chemical (8) is polysaccharide as such or modified polysaccha- ride. In this context, the stabilizing chemical is typically hydrophilic chemical. In one embodiment, the

N stabilizing chemical is selected from the group con-

O sisting of carboxymethyl cellulose (CMC), polyanionic 00 cellulose (PAC), other cellulose derivatives, e.g. 2 30 ethylhydroxyethyl cellulose and methyl cellulose, guar

N gum, such as native guar gum or modified guar gum, na- = tive starch, modified starch, pectin, glycogen, cal-

O lose, chrysolaminarin, native hemicellulose, modified 3 hemicellulose, xylan, mannan, gJgalactomannan, galac-

DO 35 toglucomannan (GGM), arabinoxylan, glucuronoxylan and

N xyloglucan, fucoidan, dextran, alginate, other poly-

saccharide and their combinations. Said stabilizing chemical may be in native form or in modified form. In one embodiment, the stabilizing chemical is carboxyme- thyl cellulose (CMC). In one embodiment, the stabiliz- ing chemical is guar gum. Preferably, function of the stabilizing chemical is to keep suspended lignocellu- lose particles stable through chemical interaction.

Therefore, treated lignocellulose particles remain in suspension while free lignin particles are separated from suspension.

In one embodiment, washing water (9), e.g. at temperature between 20 — 70 °C, may be added into the separation device (5), preferably in the last separa- tion step, for washing the lignin fraction (6). Alter- natively, the lignin fraction (6) is washed after the separation (5). In one embodiment, the lignin fraction is washed by a displacement washing. The purified lig- nin can be easily neutralized in washing stage without negatively affecting dewatering performance. In this context, the washing water means any washing liquid or washing water. The washing water may be fresh washing water or recycled washing water. Washing water can be physically and/or chemically cleaned raw water as well as clean side stream from biorefinery process, e.g. condensate from evaporation of sugar. The separation process does not require ultra clean water, e.g. ob-

N tainable by ion exchange, distillation or reverse os-

O mosis. © In one embodiment, the lignin fraction (6) is 2 30 in the form of suspension, solid, sediment, sludge, - cake or the like after the separation step. The lignin = fraction (6) may contain also other components or

O agents than lignin particles. Preferably, the lignin 3 fraction contains free lignin. In one embodiment, the

DO 35 lignin fraction contains over 80 %, preferably over 85

N %, more preferably over 90 %, most preferably over 95

%, lignin and below 20 %, preferably below 15 %, more preferably below 10 %, most preferably below 5 %, glu- can. Lignin content is specified to be combination of acid-insoluble and acid-soluble lignin.

In one embodiment, the lignin fraction (6) is treated after the separation by dewatering the lignin fraction in at least one dewatering step (10) which may be selected from the separation methods described above or other suitable methods. In one embodiment, the dewatering is carried out in the separation step.

In one embodiment, the lignin fraction (6) is treated by dewatering in at least one filtration step, e.g. by a pressure filter or vacuum filter. In one embodiment, the lignin fraction (6) is treated by dewatering in at least one cleaning separation step. In one embodiment, the lignin fraction is treated in the cleaning separa- tion step by means of centrifugal cleaning e.g. by hy- drocyclone, sedimentation, e.g. by thickener, elutria- tion, aggregation, flotation, flocculation and/or screening. In one embodiment, the lignin fraction (6) is treated by grinding.

In one embodiment, the apparatus comprises at least one filtration device, e.g. a pressure filter or vacuum filter, for filtering and purifying the lignin fraction (6). In one embodiment, the apparatus com- prises at least one dewatering device for dewatering

N the lignin fraction (6). < The dewatering of the lignin can be improved 0 by means of the present invention. Removal of the lig- 2 30 nocellulose particles clearly improves the dewatering - of the lignin, evidenced by increased filtration rate = and/or higher solids content. The higher solids con-

O tent means that the lignin is more suitable for down- 3 stream applications as such and less energy is needed > 35 in drying.

In one embodiment, at least a part of the lignocellulose fraction (7) including lignocellulose particles is circulated back to the enzymatic treat- ment, such as enzymatic hydrolysis, and/or treatment with ionic liquid. In one embodiment, at least a part of the lignocellulose fraction (7) is circulated from the separation step (5) to the enzymatic treatment, such as enzymatic hydrolysis, and/or treatment with ionic liquid. In one embodiment, at least a part of the lignocellulose fraction (7) is circulated to a stage before treatment step (24), preferably before the enzymatic treatment or treatment with ionic lig- uid. In one embodiment, the lignocellulose fraction (7) is circulated to a stage between the hydrolysis process (21) and treatment step (24). In one embodi- ment, the lignocellulose fraction (7) is circulated into a re-slurry tank (23) which is arranged prior the treatment step (24). Alternatively, at least a part of the lignocellulose fraction (7) may be circulated to a separate hydrolysis process. In one embodiment, the ap- paratus comprises a circulation means for circulating the lignocellulose fraction (7). In one embodiment, a feeding system is used for circulating the lignocellu- lose fraction (7) from the separation device (5) to the enzymatic treatment, such as enzymatic hydrolysis, and/or treatment with ionic liquid.

N Preferably, in the case of enzymatic process,

O the raw material, e.g. wood material, can be more ef- 0 fectively utilized in the process when the lignocellu- 2 30 lose fraction (7) is recirculated to the enzymatic - treatment, such as enzymatic hydrolysis. = When the lignocellulose fraction (7) is cir-

O culated, the conversion may be lowered in the enzymat- 3 ic treatment or treatment with ionic liquid. In one o 35 embodiment, the conversion is lowered by at least 10

N 2, or by at least 20 %, of the prior optimal conver-

sion level. An enzyme dosage is chosen so that desired glucan to glucose conversion is achieved in the enzy- matic treatment. The lower conversion enables decrease in the enzyme dosage. Properties of the circulated lignocellulose fraction, especially small particle size, low hemicellulose content and low lignin con- tent, potentially decrease the enzyme dosage further.

In one embodiment, feed consistency can be increased in the enzymatic treatment. This compensates otherwise lower sugar concentration and higher volume of the en- zymatic treatment tanks, such as enzymatic hydrolysis tanks, when the lower conversion is applied. The high- er feed consistency is facilitated by lower viscosity of mixture of pretreated starting material and ligno- cellulose in comparison with pretreated starting mate- rial alone. In conventional process the lower conver- sion would result in equivalent drop in Ce-sugar yield, but when the recovered lignocellulose fraction is circulated to the enzymatic hydrolysis the combined

Ce-yield is typically higher than in a reference case with normal conversion level.

The lignocellulose fraction (7) may contain also other components or agents than carbohydrates, such as glucan. In one embodiment, the lignocellulose fraction (7) is in the form of suspension. This sus- pension contains liguid, such as water. In one embodi-

AN ment, lignocellulose fraction (7) contains 40 - 90 %,

O preferably 50 —- 90 %, more preferably about 60 - 90 %, © glucan and 10 — 60 %, preferably 10 - 50 %, more pref- 2 30 erably about 10 - 40 %, lignin after the separation - step (5). = In one embodiment, the lignocellulose frac-

O tion (7) is dewatered, e.g. by filtering, after the e separation (5). = 35 In one embodiment, the lignocellulose frac-

N tion (7) is diluted for forming a diluted lignocellu-

lose fraction (13) after the separation step (5). In one embodiment, liquid in the lignocellulose fraction replaces partly or totally fresh water needed in dilu- tion of pretreated starting material prior to enzymat- ic hydrolysis.

According to present invention a lignin compo- sition can be formed. The lignin composition includes lignin fraction which has been formed by the method described in this context. The lignin composition may be used as component in manufacturing a product, such as a final product, selected from the group consisting of activated carbon, carbon fiber, lignin composite, binder material, polymers, resins, phenolic component, dispersion agent, feed, food or their combination. In one embodiment, the lignin composition is used as an adsorbent for oil, hydrocarbon composition or heavy metals. In one embodiment, the lignin composition is used as combustible matter in energy production.

In one embodiment, a lignocellulose composi- tion can be formed. The lignocellulose composition in- cludes lignocellulose fraction which has been formed by the method described in this context. The lignocel- lulose composition may be used as component in manu- facturing a product selected from the group consisting of composites, wood composites, lignin-wood compo- sites, wood-plastic composites comprising composites

N formed from plastic, synthetic polymers, biopolymers,

O rubber or their combinations together with wood, res- 0 ins, preferably as filler in resins, wood based mate- 2 30 rials, wood based fillers, construction materials, - building boards, glue boards and/or other wood based = boards, such as a particle board, an oriented strand

O board, a chip board, an intrallam, a gluelam, a hard- 3 board, corrugated board, a wafer board, a fiber board,

DO 35 a plywood, an insulation material, a packaging materi-

N al, a barrier material or a foam material. In one em-

bodiment, the lignocellulose composition is used as combustible matter in energy production. In one embod- iment, the lignocellulose composition is used as raw material in a production of microcrystalline cellu- lose, nanocrystalline cellulose or nanofibrillated cellulose. High crystallinity index and small particle size promote usage of the lignocellulose in the pro- duction of microcrystalline cellulose or nanocrystal- line cellulose.

In the present invention the separation of the lignin fraction may be optimized. The method ac- cording to the present invention provides the lignin fraction and lignin composition with good quality. Es- pecially, purity of the lignin fraction can be im- proved. When improving purify of the lignin and in- creasing dry solids content in the lignin fraction so then it may be provided better properties of the final product. Further, the lignocellulose fraction can be recovered. Thanks to the invention usage of raw mate- rials and enzymes can be reduced. The invention pro- vides feasible way to lower conversion in the enzymat- ic treatment, such as in the enzymatic hydrolysis (EH) , without having negative impact on sugar yield, sugar concentration or size of enzymatic hydrolysis tanks. Further, Ce-sugar yield can be improved in the process.

AN Thanks to the invention, preferably improved

O filterability is achieved. Further, thanks to the in- 0 vention heat wvalue of the lignin composition can be 2 30 increased so that the heat value without drying may im- - prove at least 50 %. a. The present invention provides an industrial-

O ly applicable, simple and affordable way of making the 3 purified lignin based composition and also the ligno-

DO 35 cellulose based composition. The method according to

N the present invention is easy and simple to realize as a production process. The method according to the pre- sent invention is suitable for use in the manufacture of the different lignin and lignocellulose based prod- ucts and final products from different starting mate- rials. Preferably, the crude lignin is purified by separating the lignocellulose particles. Further, the lignin composition can be used as sources of energy.

EXAMPLES

The invention is described in more detail by the following examples with reference to accompanying drawings.

Example 1

In this example a lignin fraction (6) is formed according to a process of Fig.l.

The pretreated starting material is formed from starting material (20), such as biomass, by means of for example hemihydrolysis (21). The formed pre- treated starting material (22) is processed in a treatment step (24) which is an enzymatic treatment, such as an enzymatic hydrolysis, or treatment with ionic liquid in order to form the crude lignin (1).

The crude lignin (1) is fed by means of a first feeding device into a liberation reactor (3), e.g. into a digester, preferably based on autohydroly-

N sis or dilute acid hydrolysis, for treating the crude

O lignin by a liberation. Water may be added into the 00 liberation reactor (3). 2 30 The treated crude lignin (4) is fed by means

N of a second feeding device from the liberation reactor

E (3) into the separation device (5) for separating a

O lignin fraction (6). Carboxymethyl cellulose (8) may 3 be added as a stabilizing chemical into the crude lig-

DO 35 nin during the separation. Preferably, the separation

N is carried out in more than one separation step. The lignin fraction (6) from the separation device (5) is recovered. Also a lignocellulose fraction (7) is sepa- rated. The lignocellulose fraction (7) may be circu- lated back to the enzymatic treatment, such as enzy- matic hydrolysis, or treatment with ionic liquid.

Example 2

In this example a lignin fraction (6) is formed according to a process of Fig.2.

The pretreated starting material is formed from starting material (20), such as biomass, by means of for example hemihydrolysis (21). The formed pre- treated starting material (22) is fed via a re-slurry tank (23) to a treatment step (24) which is an enzy- matic treatment, such as an enzymatic hydrolysis, or treatment with ionic liquid. The pretreated starting material (22) is processed in the treatment step (24) in order to form the crude lignin (1).

The crude lignin (1) is filtrated in a fil- tration device (2) in which soluble carbohydrates (14) may be removed. Optionally the crude lignin can be washed with water during or after filtration, prefera- bly using displacement washing. After that the crude lignin (1) is fed by means of a first feeding device into a liberation reactor (3), e.g. into a digester, preferably based on autohydrolysis or dilute acid hy-

N drolysis, for treating the crude lignin by a libera-

O tion. Preferably, the apparatus comprises a steam ex- © plosion stage in the end. Water may be added into the 2 30 liberation reactor. Liquid phase containing solubil-

N ised carbohydrates (15) may be separated during or af- = ter the liberation. Preferably, the treated crude lig-

O nin (4) is washed after the lignin liberation. 3 The treated crude lignin (4) is fed by means o 35 of a second feeding device from the liberation reactor

N (3) into the optional washing stage and further to separation device (5) for separating a lignin fraction (6). Also a lignocellulose fraction (7) is separated.

Carboxymethyl cellulose (8) may be added as a stabi- lizing chemical into the crude lignin during the sepa- ration. Preferably, the separation is carried out in more than one separation step. Washing water (9), e.g. at temperature between 20 — 60 °C, may be added into the separation device (5), preferably in the last sep- aration step, for washing the lignin fraction (6).

The lignin fraction (6) from the separation device (5) is fed to the second filtration unit (10) for further treating the lignin fraction (6), e.g. by a pressure filter. The lignin fraction (6) can be filtrated and purified for forming a final lignin composition (11).

The lignocellulose fraction (7) is circulated back to the enzymatic treatment, such as enzymatic hy- drolysis, or treatment with ionic liquid. The ligno- cellulose fraction (7) may be diluted in a dilution step (12) for forming a diluted lignocellulose frac- tion (13). The diluted lignocellulose fraction (13) is fed the re-slurry tank (23) and circulated to the treatment step (24).

Example 3

In this example, lignin and lignocellulose fractions were formed.

N Pre-treated biomass (PTB) was subjected to an

O enzymatic hydrolysis with a commercial enzyme using 0 16% TS (total solids) feed. An enzyme dosage was cho- 2 30 sen so that 80% glucose conversion was achieved after

N 48 h hydrolysis time. Residual solid material, i.e.

E: crude lignin, was separated from Cs-carbohydrates by a

O pressure filtration. The crude lignin was exposed to 3 dilute acid treatment in a liberation step. The crude > 35 lignin was liberated in a digester using following conditions: 20.9% TS, time 210 min, temperature 181°C and sulphuric acid dosage 6 kg/t TS PTB. After the liberation treatment slurry was cooled down in the re- actor. After cooling pH of slurry was 3.0.

A pressure filtration and displacement wash- ing was used to separate water soluble material from solid particles. The liberated lignin particles and residual lignocellulose particles were separated se- quentially in four stages. The first stage (rougher stage) provided a lignocellulose fraction and a semi- purified lignin fraction. The following stages (clean- er stages) were used to further purify the lignin fraction. The standard procedure was to circulate lig- nocellulose fractions from stages 2-4 upstream to op- timal stages in the separation process. Optionally there can be one or several stages to further purify the lignocellulose fraction (scavenger stages). The treated crude lignin was re-slurried to provide 7% TS feed for the rougher stage. CMC (carboxymethyl cellu- lose) was added 10 kg/t TS, and temperature was 55 °C.

The slurry was pumped through GEA Westfalia UCD205 de- canter centrifuge at feed rate of 23 kg/min using bowl speed of 2800 rpm. Separated lignin (heavy) fraction was further re-slurried, CMC was added 3 kg/t TS, and the formed slurry was processed in the first cleaner stage using a decanter centrifuge. Two subsequent cleaner stages were based on sedimentation. CMC was

AN added 1.5 kg/t TS in the second cleaner stage, and the

O third cleaner stage was performed without CMC. Under- © flow was collected after 2 h sedimentation time in the 2 30 both stages. - Lignin and carbohydrates were analysed using & TAPPI-methods T-222 and T-UM 250. Results are present-

O ed in table 1. 3 > 35

Table 1 nin

CL1 = crude lignin before digester

CL2 = crude lignin after digester

LC/SS1 = lignocellulose fraction after separation stage 1

L/SS4 = lignin fraction after separation stage 4 15% of glucan was hydrolysed (solubilised) during the liberation step meaning that 85% of glucan is available for the enzymatic hydrolysis after 100% recovery in the separation stage. The lignin fraction

L/SS4 was significantly cleaner than the crude lignin after the digester (CL2) demonstrating that lignin is at least partially liberated from the crude lignin during the dilute acid hydrolysis. Mechanical separa- tion is not able to purify the crude lignin before the digester. Large biomass particles present in PTB com- plicated purification of the lignin, since bigger lig- nocellulose particles tend to drift into the heavy fraction (lignin fraction). For this reason a hot

N blow, e.g. a steam explosion, after the liberation

S step is a preferred option providing a practical way s to decrease particle size. More severe conditions © leading to higher degree of the glucan hydrolysed - 25 would significantly contribute to the lignin libera-

E tion and conseguent separation. © The laboratory scale enzymatic hydrolysis was 3 performed for the mixture of the PTB and circulated > lignocellulose LC/SS1 with ratio 87:13 on total solids basis. Reference was a similar enzymatic hydrolysis with 100% PTB material. Results are presented in table 2.

Table 2 mera |s7:13 a [mers [87:38 hours, %

Eafe EII hours, % md FFo hours, %

Results indicate that recycled lignocellulose (glucan) was converted to glucose as efficiently as virgin PTB.

Example 4

In this example, an effect of a circulated lignocellulose fraction on rheology of formed slurry was demonstrated. The separated lignocellulose frac- tion from example 3 was used in the experiment. Pre- treated biomass (PTB material) was re-slurried with the lignocellulose material to provide a suspension having total solids (TS) of 16.8% and water-insoluble solids content (WIS) of 16.5%. Ratio of the PTB and

N circulated lignocellulose was set to 70:30 on total

S 20 solids basis. Viscosity of suspension was 306 mPas s (Brookfield 50 rpm). As a reference the same pre-

O treated biomass (PTB) was re-slurried with clean water r to provide a suspension having total solids (TS) of

E 16.8% and water-insoluble solids content (WIS) of 2 25 16.5%. Viscosity of suspension was 1876 mPas 3 (Brookfield 50 rpm). This example demonstrates that > the mixing of the lignocellulose with the pre-treated biomass leads to unexpected rheological properties.

This addresses mainly the effect of the bipolar parti- cle size distribution, but also altered surface prop- erties may play a role. Lower viscosity enables use of higher solids content, for example when the enzymatic hydrolysis is performed with low conversion, i.e. low carbohydrate yield, thus enabling compensation for otherwise lowered sugar concentration and increased tank volume. Even if there is no benefit to reach higher solids content lower viscosity facilitates use of a less intensive mixing stage.

The method according to the present invention is suitable in different embodiments to be used for forming lignin fractions and lignocellulose fractions from the most different kinds of crude lignin.

The invention is not limited merely to the example referred to above; instead many variations are possible within the scope of the inventive idea de- fined by the claims.

N

N

O

N

© <Q ©

N

I a a oO

Oo © 00

O

N

Claims (15)

1. A method for forming a lignin fraction from crude lignin which has been formed by processing by means of a treatment step selected from enzymatic treatment, treatment with ionic liquid and their com- binations, wherein the method comprises - treating the crude lignin by a lignin liberation in at least one lignin liberation step such that the lignin is liberated, and temperature is 170 — 240 °C during the lignin liberation, and - separating a lignin fraction and a lignocellu- lose fraction in at least one solid-solid separa- tion step after the lignin liberation.

2. The method according to claim 1, wherein the crude lignin is liberated by means of a hydrother- mal treatment.

3. The method according to claim 1 or 2, wherein the crude lignin is liberated by means of a dilute acid hydrolysis.

4. The method according to any one of claims 1 to 3, wherein below 70 %, preferably below 60 %, more preferably below 50 % and most preferably below 40 %, of glucan is dissolved during the lignin liberation.

5. The method according to any one of claims 1 to 4, wherein the crude lignin is treated by dewater- N ing, washing, filtrating and/or centrifuging in at N least one washing and separation step before the lig- & nin liberation. © 30

6. The method according to any one of claims 1 I to 5, wherein the treated crude lignin is cooled after + the lignin liberation.

=

7. The method according to any one of claims 1 O to 6, wherein the treated crude lignin is washed after > 35 the lignin liberation.

8. The method according to any one of claims 1 to 7, wherein a lignocellulose fraction is separated in at least one separation step.

9. The method according to any one of claims 1 to 8, wherein the separation of the lignin fraction is carried out in more than one separation step.

10. The method according to any one of claims 1 to 9, wherein a stabilizing chemical is added into the treated crude lignin in connection with the sepa- ration step.

11. The method according to claim 10, wherein the stabilizing chemical is carboxymethyl cellulose (CMC) or guar gum.

12. The method according to any one of claims 1 to 11, wherein at least a part of the lignocellulose fraction is circulated from the separation step to the enzymatic treatment or treatment with ionic liquid.

13. The method according to any one of claims 1 to 12, wherein a lignin composition consisting of the lignin fraction is used as component in a product se- lected from the group consisting of activated carbon, carbon fiber, lignin composite, binder material, poly- mers, resins, phenolic component, dispersion agent, feed, food or their combination.

14. The method according to any one of claims 1 to 12, wherein a lignin composition consisting of the N lignin fraction is used as an adsorbent for oil, hy- O drocarbon composition or heavy metals. 0

15. A lignin composition, wherein the lignin 2 30 composition consists of the lignin fraction which is N obtained by the method according to any one of claims = 1 to 14. 2 3 S 35