FI20195532A1

FI20195532A1 - A method and an apparatus for recovering chemicals from an alkaline lignin material

Info

Publication number: FI20195532A1
Application number: FI20195532A
Authority: FI
Inventors: Mauno Miettinen; Sami Turunen; Juha Tamper; Meri Ventola
Original assignee: Upm Kymmene Corp
Priority date: 2016-11-17
Filing date: 2016-11-17
Publication date: 2019-06-19

Abstract

In a method and an apparatus for recovering chemicals from an alkaline lignin material, the alkaline lignin material (3) which comprises NaOH or KOH is precipitated in presence of an acid in a precipitation stage (6) for forming a precipitated lignin (7), the precipitated lignin (7) is supplied to a separation stage (8) in which a purified lignin (9) is recovered and from which at least one fraction (10) which comprises Na or K is supplied to a crystallization stage (11), and the fraction (10) which comprises Na or K is treated by crystallization in the crystallization stage (11) for forming a crystallized compound (12). Further, the invention relates to use of the purified lignin, and lignin and chemical products.

Description

A METHOD AND AN APPARATUS FOR RECOVERING CHEMICALS

FROM AN ALKALINE LIGNIN MATERIAL

FIELD

The invention relates to a method and an apparatus for recovering lignin and at least one chemical from an alkaline lignin material. Further, the invention relates to a lignin material and its use. Further, the invention relates to chemical 10 products.

BACKGROUND

Known from prior art is different methods for forming lignin from different raw materials, such as 15 biomass. Many bio-refinery processes, e.g. a hydrolysis, generate crude lignin, such as lignin residue, after water-insoluble significant the hydrolysis of the biomass. This lignin residue usually contains percentage of non-hydrolyzed lignocellulose particles.

Further, known from prior art is to treat lignin chemically by dissolving the lignin in dissolvent, such as in NaOH, alcohol-water mixture or

20195532 prh 19 -06- 2019 organic acid, and to precipitate the lignin, e.g. by 25 sulphuric acid or water. Then the pure lignin can be provided, but known processes suffer from high operating and capital costs. Removing and/or recovering of the dissolvent or formed salt lead to additional costs. A final dewatering of the lignin is usually carried out by a filtration.

OBJECTIVE

The objective of the invention is to disclose a method for forming a lignin fraction and purifying the lignin. Another objective is to produce a purified lignin. Another objective is to recover chemicals after the separation of the lignin.

SUMMARY

The method for recovering chemicals from an alkaline lignin material is characterized by what is presented in claim 1.

The apparatus for recovering chemicals from an alkaline lignin material is characterized by what 10 is presented in claim 17.

The use of the purified lignin is characterized by what is presented in claim 26.

The lignin products are characterized by what are presented in claims 27 and 28.

The chemical product is characterized by what is presented in claim 29.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and constitutes a part of this specification, illustrate some embodiments of the invention and 25 together with the description help to explain the

20195532 prh 19 -06- 2019

principles of the	invention.	In the	drawings :
	Fig. 1	is	a	flow	chart	illustration	of a
method	according	to	one	embodiment,	and
	Fig. 2	is	a	flow	chart	illustration	of a
30 method	according	to	another	embodiment.

DETAILED DESCRIPTION

In a method for recovering chemicals from an alkaline lignin material, wherein the alkaline lignin material (3) which comprises NaOH or KOH is precipitated in presence of an acid in a precipitation stage (6) for forming a precipitated lignin (7), the precipitated lignin (7) is supplied to a separation stage (8) in which a purified lignin (9) is recovered 5 and from which at least one fraction (10) which comprises Na or K is supplied to a crystallization stage (11), and the fraction (10) which comprises Na or K is treated by crystallization in the crystallization stage (11) for forming a crystallized 10 compound (12).

One embodiment of the method is shown in Fig.

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

The apparatus for recovering chemicals from an alkaline lignin material, at least one at least one the alkaline comprises comprising precipitating comprises NaOH or KOH in to form a precipitated wherein the precipitation precipitation lignin materi presence of an acid m c lignin (7), at least comprising at least in which a purified lignin (9) one

20195532 prh 19 -06- 2019 separation separation at least one fraction (10) which comprises Na or K separated and a purified lignin (9) at least one crystallization stage least one crystallization device fraction (10) crystallization compound (12) .

comprises at least the one and are is and which comprises order to form in

In

In one

Na recovered, comprising at treating the or K by crystallized the one embodiment, feeding device for (7) to a separation apparatus comprises supplying the fraction to a crystallization one precipitated lignin one embodiment, the feeding device for which comprises Na or K (11) .

apparatus supplying stage (8).

at least

In this context, (3) means any alkaline an alkaline lignin material lignin based material. The alkaline lignin material may suspension, slurry, solid cake, the like. The alkaline lignin be in the form agglomerates, lump material comprises least lignin and cellulose, and additionally NaOH

KOH. Further, the alkaline comprise also other agents.

alkaline lignin material may of or at or lignin material may

In one embodiment, the comprise carbohydrates, alkaline lignin material may comprise also other carbohydrates and other components. In a preferred material is embodiment, pH of the alkaline lignin

clearly	at an alkaline level, in one embodiment the pH
is at least	9. In	one embodiment pH of the alkaline
lignin materi	al is	10 - 13.8	and in one embodiment 11
- 13.5.
	In	one	embodiment,	the alkaline	lignin
material	(3)	is	formed from a lignin based	start
material	(1) .
	In	this	context,	a lignin based	start
material	(1)	means	any start	material which comprises

at least lignin and cellulose. Further, the lignin based start material (1) may comprise carbohydrates, such as C6 carbohydrates. In one embodiment, the lignin based start material comprises

C6 the lignin based start material may comprise also other

20195532 prh 19 -06- 2019 agents lignin or other carbohydrates. In based start material one embodiment, the comprises C5 carbohydrates below 30 % by weight. The lignin based start material may comprise one or more than one components. The lignin based start material (1) may be in the form of suspension, slurry, solid cake, lump or the like. In one embodiment, the lignin based start material (1) has been formed from raw material, e.g.

wood based raw material and/or other plant based raw material. In one embodiment, the raw material comprises

20195532 prh 19 -06- 2019 at least one of wood based material, wood, lignocellulosic biomass, agricultural residues, bagasse based material, sugarcane bagasse, corn based material, corn stover, wheat straw, rice straw, woody biomass, woody perennials, vascular plants, recycled brown board or deinking pulp, or their mixtures or their combinations. Preferably, the raw material is cellulose based material which comprises lignin. The raw material may comprise lignin, lignocellulose, cellulose, hemicellulose, glucose, xylose and/or extractives. Further, the raw material may comprise other inherent structural components of biomass as well as foreign components such as enzymes or chemicals. In one embodiment, the raw material comprises wood based material or a mixture comprising wood based material. In one embodiment, the raw material is wood based material or a mixture comprising wood based material. In one embodiment, the wood based material is selected from hardwood, softwood or their combination. In one embodiment, the raw material comprises plant pieces, e.g. wood pieces. In one embodiment, the lignin based start material (1) is a fraction which is formed from the raw material and which comprises at least lignin.

In one embodiment, the lignin based start material (1) has been formed from the raw material which preferably has been treated to dissolve at least a part of hemicellulose or a main part of hemicellulose. In one embodiment, the raw material has been pre-treated, preferably by means of a suitable pretreatment. The pre-treatment stage may be selected from the group comprising as milling, extrusion, ultrasound pretreatment chemical pretreatment, alkaline pretreatment, organosolv pretreatment physical pretreatment microwave and such ionic and freeze as acid liquid ozonolysis, , such pretreatment, pretreatment, pretreatment, pretreatment, physico6 chemical pretreatment, such as steam explosion pretreatment, ammonia fiber explosion pretreatment,

CO₂ explosion pretreatment, liquid hot water pretreatment and wet oxidation, biological pretreatment or their combinations. In one embodiment, the raw material is treated by a hydrolysis, e.g. acid hydrolysis, autohydrolysis, thermal hydrolysis, supercritical hydrolysis and/or subcritical hydrolysis, in which at least a part of hemicellulose is separated from the raw material in connection with the hydrolysis. In one embodiment, the raw material is treated by an enzymatic hydrolysis. In one embodiment, the raw material is treated by the steam explosion, in which hemicelluloses are treated and in which at least a part of polysaccharides of the hemicelluloses degrade into monosaccharides and oligosaccharides by means of a hydrolysis and in which pressure is rapidly released. In one embodiment, the raw material is treated by the hydrolysis and by the steam explosion in one or more steps. In one embodiment, the raw material is treated by the catalytic pretreatment, e.g. by using acid or base as catalyst. In the pretreatment stage the raw material enters the reactor unit where the pretreatment takes place.

material can be treated by means of one

The or raw more pretreatment. The treated raw material can be then

20195532 prh 19 -06- 2019 supplied directly, via an additional treatment step storage as a lignin based can be dewatered, washed in one or makes possible to

In one

e.g. by intermediate or via an step, via an intermediate or to the precipitation embodiment, dewatering two or more stages.

separate sugar based the raw material presses, and/or

The dewatering streams .

embodiment, the alkaline lignin formed by a delignification with a base composition which comprises delignification stage (2) before stage ( 6) .

material (1) is (2) in which it which stage

In one embodiment, the the supplied to is treated with

NaOH or KOH in a lignin least comprises material

NaOH or

The but

KOH for

NaOH or KOH, other base components, e.g. one embodiment, waste material.

comprises a embodiment, sulphure-free delignification one embodiment, pulping process, soda pulp process, delignification is carried out at 90 °C. In the precipitation lignin based start delignification stage the base composition forming the alkaline base composition comprises at it may comprise also other or other components. In the base composition is an alkaline Preferably, the lignin dissolving.

the delignification stage. In one comprises the delignification is a conventional such as a dissolving pulp process or In one delignification (2) In a preferred stage (2) is embodiment, a mild alkaline cooking.

the

In carried out one embodiment, the of 110 embodiment, delignification apparatus stages (2) . more than embodiment, the temperature of 70 delignification 145 °C. In is one comprises

In one at least one the embodiment, delignification the apparatus comprises devices in which the than one

20195532 prh 19 -06- 2019 at temperature the apparatus stage (2).

comprises more In one embodiment, one delignification devices are arranged in series. In one apparatus comprises more than one devices. In one embodiment, the devices are arranged sequentially. In the delignification devices In one embodiment, process. In one embodiment, is a continuous device.

delignification is a batch the delignification device embodiment, the delignification delignification one embodiment, are arranged in parallel, the delignification is a continuous the delignification device In one embodiment, the process. In one embodiment, is a batch device. In one embodiment, at least a part of the delignification devices are similar devices. In one embodiment, the delignification devices are different devices. In one embodiment, the alkaline lignin material (3) is a black liquor.

In one embodiment, the method and apparatus comprises which are arranged in series. In one embodiment, the apparatus comprises at least two delignification devices which are arranged in series. Then a continuous process is easy to arrange. Further, a

20195532 prh 19 -06- 2019 better mixing of the process and more equal treatment for the whole material stream can be achieved. Further, a better control of pH can be provided during the alkaline cooking comparing to a single stage or step. Further, a structure of the device, such as a reactor and mixer, can be adjusted to be optimal in each stage or device.

In one embodiment, solid material, e.g. fibers, are separated from the alkaline lignin material (3) after the delignification stage (2) or before the precipitation stage (6). In one embodiment, the apparatus comprises at least one solid material separation stage (22) or separation device, such as a dewatering device or a filtration device, for separating solid material, solid components or fibers from the alkaline lignin material (3) after the delignification stage (2) or before the precipitation stage (6).

In one embodiment, the alkaline lignin material (3) is treated by an evaporation in an evaporation stage (4) for forming a concentrated lignin material (3b) before the precipitation stage (6). In one embodiment, the alkaline lignin material (3,3a) is supplied to the evaporation stage (4) and the treated lignin material (3,3b) is supplied from the evaporation stage (4) to the precipitation stage (6) . In one embodiment, the apparatus comprises at least one evaporation stage (4) before the precipitation stage (6).

In one embodiment, the acid (5) is added to the alkaline lignin material (3) in the precipitation stage (6) in which the alkaline lignin material is precipitated by means of the acid. In one embodiment, the apparatus comprises at least one acid addition 10 device for adding the acid (5) to the alkaline lignin material (3) in the precipitation stage (6) or before the precipitation stage (6) . In one embodiment, the acid (5) comprises sulphuric acid (H₂SO₄) or other inorganic acid, e.g. HC1 or sesquisulphate acid, 15 preferably without an organic acid. In one embodiment, the acid (5) is sulphuric acid (H₂SO₄) or other inorganic acid. Preferably, the acid (5) is not the organic acid. The acid (5) may be an acid composition which comprises at least sulphuric acid or other 20 inorganic acid, but it may comprise also other components. In one embodiment, the acid composition is a waste acid composition. In one embodiment, the acid a base

K₂SO₄.

least added as a stoichiometric compound, such as NaOH or

In one embodiment, the stoichiometric amount amount

KOH acid or to compared with form

Na₂SO₄ or is more added than at

20195532 prh 19 -06- 2019 stoichiometric amount such as NaOH or KOH.

is added more than a with a base embodiment, compared with a base compound,

In one embodiment, the stoichiometric amount compared compound,

NaOH:H₂SO₄ such as NaOH molar ratio is or 2.0:1.0-1.2.

or KOH. In one

In one embodiment,

NaOH:H₂SO₄ molar ratio is 2.0:0.9-1.1 or 2.0:0.9-1.0 or 2.0:1.0-1.1. H₂SO₄ or NaOH can be added also after the 35 precipitation stage, e.g. before an intermediate evaporation (18) or before the crystallization (11) .

20195532 prh 19 -06- 2019

Preferably, majority of acid is added in the precipitation stage. Due to closure of the circulation also H₂SO₄ or NaOH dosed during the crystallization, e.g. in washing stage, add up to total dosage at least 5 partly. Furthermore, fraction of Na and SO₄ present in the pretreated start material (1), which solubilises during the delignification, add up to total Na/SO₄balance. In a preferred embodiment, the precipitation stage (6) does not comprise an addition step of CO₂.

Preferably, the precipitation is performed without an addition of CO₂.

In one embodiment, the process parameters of the precipitation stage (6) are selected so that the precipitated lignin (7) has pH over 1.0, in one 15 embodiment over 1.5 or in one embodiment over 2.0. In one embodiment, pH is 1.0 - 6.0, in one embodiment 1.0 - 4.5, in one embodiment 1.5 - 4.5, or in one embodiment 2.0 - 4.0. In one embodiment, the process parameters of the precipitation stage (6) are selected 20 so that an elevated temperature is used during the precipitation in the precipitation stage (6) . In one embodiment, the temperature is 50 - 85 °C, in one embodiment 55 - 80 °C, or in one embodiment 60 - 75 °C. In one embodiment, the process parameters of the 25 precipitation stage (6) are selected so that a retention time is below 20 hours, in one embodiment below 15 hours, or in one embodiment below 10 hours in the precipitation stage (6) . In one embodiment, the retention time is below 3 hours, in one embodiment below 2 hours, or in one embodiment below 1.5 hours in the precipitation stage (6) . In one embodiment, the retention time is 1 second - 20 hours, in one embodiment 1 minute - 10 hours, or in one embodiment about 0.5 - 1.5 hours in the precipitation stage (6) .

In one embodiment, the process parameters of the precipitation stage (6) are selected so that the pH is

2.0 - 4.0, the temperature is 50 - 85 °C and the retention time is below 3 hours.

In one embodiment, the method and apparatus comprises at least one separation stage (8) after precipitation stage (6) . In one apparatus comprises one embodiment, the than one separation separation stages one embodiment, in parallel.

comprises more the

In the the embodiment, at least one separation device.

and apparatus comprise more (8). In one embodiment, the arranged method stages (8) are separation stages one embodiment, than one separation

In

In one embodiment, sequentially. In (8) are arranged the apparatus devices. In one embodiment, the separation stage comprises at least one separation device. In one embodiment, the separation stage comprises more than one separation devices. In one embodiment, the separation stage comprises one separation device. In one embodiment, the separation devices are arranged sequentially. In one embodiment, the separation devices are arranged 20 sequentially in the separation stage (8). In one embodiment, the separation devices are arranged in parallel. In one embodiment, the separation devices are arranged in parallel in the separation stage (8) .

In one embodiment, the separation device comprises one

20195532 prh 19 -06- 2019 or more separation step, e.g. separation segment. The separation stage may comprise one or more separation steps. In one embodiment, the separation stage comprises different procedures which may be done in one or more separation steps. In one embodiment, the 30 fraction (10) which comprises Na or K is separated in one step. Alternatively, the fraction (10) which comprises Na or K may be separated in more than one steps. In one embodiment, the fraction (10) which comprises Na or K is separated in each separation step.

Preferably, the separation stage (8) comprises the separation of the fraction (10) which comprises Na or K from the purified lignin (9). In one embodiment, the separation comprises the precipitated lignin (7) .

solid-liquid filtration, combinations .

carried out overpressure .

In one a dewatering embodiment, of the separation is centrifugal made treatment by means of or their

In one embodiment, the filtration by pressure, underpressure is or

In one embodiment, the separation device is selected from the group comprising filtration device, vacuum filtration device, press centrifugal combinations .

is selected filtration device,

In one from device, filtration device device based on suitable press, screw embodiment, the group vacuum filter, belt press and the separation comprising filtration based on underpressure, overpressure, centrifugal combinations. In one embodiment, is a pressure filtration device, filtration device press, their device pressure device, filtration filter press, other device the device, based on and their separation device vacuum filtration underpressure or filtration device based on overpressure. In one embodiment, the separation device is a belt press, twin wire press or centrifuge. In one embodiment, the

20195532 prh 19 -06- 2019 separation device is based on centrifugal forces, sedimentation, elutriation, filtration, flotation, screening or their combination. Alternatively, the separation device can be another washing device in which low amount of washing water is used and washing is done in high dry matter content. Then good recovery of the liquid fraction (10) can be achieved. Alternatively, the separation device may be any suitable separation device. In one embodiment, the separation washing.

In device is based on a countercurrent one embodiment, the separation stage (8) filtration in which the fraction (10) purified in the is based comprises a which comprises Na or K is separated from the lignin (9). Preferably, pressure is used filtration. In one embodiment, the separation on a pressure filtration. In one embodiment, the separation is made by a pressure difference, such as by means of vacuum or overpressure. In one embodiment, the separation stage displacement washing is of clean water in order comprises a washing in which a carried out with small amount inhibitors and other to remove majority of sugars, soluble compounds from the to provide good recovery of purified lignin (9) and the fraction (10) which comprises Na or K. Preferably ratio of washing below 4 and more !

water to solid is below 6, preferably

20195532 prh 19 -06- 2019 preferably below 3.

embodiment, the separation stage (8) at least one filtration step and/or washing embodiment, the separation stage (8) least one filtration step and washing embodiment, the separation stage (8) more than one filtration steps and/or In one embodiment, the separation stage comprises two consecutive filtration steps .

In one embodiment, the separation by means of a pressure filtration. In one the apparatus comprises at least one pressure filtration device

In one comprises step. In comprises step. In comprises washing steps.

(8) one at one and washing (8) is made embodiment,

In the comprises as the separation device.

different separation stages the carried out by means of similar or separation can be different separation methods or separation devices.

In one embodiment, the method and apparatus comprise more than one separation stages (8), and the first separation stage or stages are any suitable the group filtration centrifugal separation filtration.

between the may be used made by means of separation device which comprising filtration device, device, stage is

In one press or screw made by is selected from device, vacuum filter, press, means embodiment, separation stages.

as a dilution water in belt press, and of a dilution the last pressure is made recirculated water the first dilution stage or stages. Alternatively, pure water may be used as the dilution water in the first dilution stage or stages. Preferably, pure water is used as the dilution water in the last dilution stage. In one lignin ash content is lowered to d 5 embodiment to d 3 %, or in one embodiment weight during the filtration and washing, embodiment, preferably if the method and apparatus comprise more than one

In one embodiment, the purified lignin (9) is in the form composition, combination embodiment, of suspension, slurry, sludge, particle solid, sediment, cake or their after the separation stage the purified lignin (9) is the particle form. In one embodiment, lignin (9) is recovered in the solid

In one recovered in the purified form. In one embodiment, the purified lignin (9) is recovered in

20195532 prh 19 -06- 2019 the slurry form. In one comprises at least one purified lignin one embodiment, from the group embodiment, the apparatus means for recovering the the means for recovering is selected comprising assembly, outlet, conveyor, screw, belt, pipe, tube, duct, discharge outlet, discharge valve, discharge channel, conduit, other suitable device and their combinations.

In one embodiment, the sodium or potassium liquor which preferably comprises at least

Na₂SO₄ or K₂SO₄. In one embodiment, the sodium based fraction (10) comprises a sodium based salt,

e.g.

sodium sulphate embodiment, the potassium based fraction comprises a potassium based salt,

e.g. potassium sulphate (K₂SO₄) . The fraction (10) which comprises Na or K may comprise also soluble lignin. In one embodiment, the sodium or potassium based fraction (10) comprises soluble lignin and carboxylic acids after the separation stage (8), in one embodiment amount of soluble lignin comprising typically <20 % of dry matter and amount of carboxylic acids comprising typically

100 <50% of dry matter. In one embodiment, 70 one embodiment 80

100 %, in one embodiment % or in one embodiment sodium or potassium in connection with one embodiment, the dry matter content of the sodium or potassium based compound (10) is 2 one embodiment 5

0 %, in one embodiment

TS before the crystallization intermediate one embodiment, the dry matter content of the sodium or potassium based compound (10) is below 30 %, in one embodiment below 20 %, in one embodiment below 15 %

20195532 prh 19 -06- 2019

TS .

In one embodiment, the fraction (10) which comprises Na or K is treated by an intermediate 30 evaporation (18) after the separation stage (8) and/or before the crystallization stage (11) . In one embodiment, the intermediate evaporation is an acidic evaporation step in which pH is below 4.5, in one embodiment below 4.0, or in one embodiment below 3.5.

In one embodiment, the dry matter content of the fraction (10) which comprises Na or K is 20 - 60 % TS,

20195532 prh 19 -06- 2019 in one embodiment 25 - 55 % TS, in one embodiment 25 50 % TS, after the intermediate evaporation (18) . In one embodiment, organic acids, such as volatile carboxylic acids, especially acetic acid and formic 5 acid, are removed or decreased from the fraction (10) which comprises Na or K during the intermediate evaporation (18) when pH is below 4.5. Acetic acid has pKa of 4.75 and formic acid has pKa of 3.75. In one embodiment, at least a part of carboxylic acids are 10 recovered during the intermediate evaporation (18) .

The recovered acetic and formic acids can be further separated, purified and concentrated into commercial grade chemicals, or discharged to for example an anaerobic digestion alone or together with a mother 15 liquor (20,21) from crystallization (11) or with other suitable stream. Other carboxylic acids present in fraction (10), e.g. lactic, oxalic, succinic, levulinic and citric acid, or aldehydes, can be similarly upgraded into commercial grade chemicals or 20 discharged to for example an anaerobic digestion.

Typically, one difficulty for separating carboxylic acids or aldehydes present in lignocellulosic streams, e.g. in sugar hydrolysate, is low concentration of acids leading to high separation costs. In this case, 25 carboxylic acids and aldehydes are concentrated due to closure of the circulation, and are further concentrated in the intermediate evaporation (18) before the crystallization (11).

In one embodiment, an alkali is added in 30 connection with the intermediate evaporation (18) before the crystallization stage (11). Preferably, the alkali is added if the pH of the fraction (10) which comprises Na or K or the pH in the precipitation stage (6) is not at a desired level.

In one embodiment, the fraction (10) which comprises Na or K is filtrated before the

20195532 prh 19 -06- 2019 crystallization stage (11), and in one embodiment solid material is separated and recirculated to the precipitation stage (6), to the fraction (7), i.e. the precipitated lignin, before the filtration of the 5 lignin or out from the process. In one embodiment, an intermediate filtration (19) is performed after the separation stage (8) and/or before the crystallization stage (11) in order to remove solid lignin particles from the fraction (10) which comprises Na or K. In one 10 embodiment, the intermediate filtration (19) is performed after the intermediate evaporation (18). In one embodiment, a flocculation is performed before the intermediate filtration (19) to enhance separation of colloidal and solid lignin material.

In one embodiment, the fraction (10) which comprises Na or K is filtrated and concentrated, e.g. by the evaporation, before the crystallization stage (11) .

Preferably, the fraction (10) which comprises 20 Na or K is supplied to the crystallization stage (11) in order to form the crystallized compound (12), e.g. Na₂SO₄ or K₂SO₄. In one embodiment, the method/apparatus comprises one, two or more than two crystallization stages (11) . In one embodiment, the method/apparatus 25 comprises two or more than two crystallization stages (11). In one embodiment, the crystallization stages (11) are arranged sequentially. In one embodiment, the crystallization stages (11) are arranged in parallel. In one embodiment, the crystallization stage (11) 30 comprises one or more than one crystallization steps.

In one embodiment, the crystallization steps are arranged sequentially in the crystallization stage (11). In one embodiment, the crystallization steps are arranged in parallel in the crystallization stage (11) . In one embodiment, the crystallization is selected from the group comprising a cooling crystallization, evaporation crystallization, e.g.

concentration crystallization, or other suitable crystallization or their combinations. In one embodiment, the crystallization is made by means of 5 the cooling crystallization.

In one embodiment, the cooling crystallization °C, in one embodiment 8 adjusted before is ended at embodiment °C. In the crystallization stage one embodiment, temperature which °C or

is	0 -
in	one
pH	is
11)	to

level of 2 - 7.

In one embodiment, the crystallization stage (11) comprises one crystallization device. In one embodiment, the crystallization stage comprises two or more crystallization devices.

In one embodiment, each crystallization step comprises one crystallization device. In one embodiment, more than one crystallization crystallization crystallization steps are device .

performed by one

In one embodiment, device is the based on a cooling crystallization, evaporation crystallization,

e.g.

concentration crystallization, or other suitable crystallization or their combinations.

In one embodiment, the crystallization stage (11) comprises at least one filtration step (23) after

20195532 prh 19 -06- 2019 the crystallization. In the filtration step (23) the crystallized compound (12) is separated from a mother liquor (20) and/or washing water after the crystallization. In one embodiment, the filtration 30 step (23) is arranged after each crystallization stage, crystallization step or crystallization device.

In one embodiment, the filtration step is based on a solid-liquid filtration. In one embodiment, the filtration is made by means of a vacuum filtration, such as a vacuum filter, belt filter or disc filter with a countercurrent washing, or by means of a decantation, centrifugation or alternatively other suitable filtration method. Preferably, the filtration step is carried out just after the crystallization. In one embodiment, the filtration step is carried out just after the cooling crystallization. Then the crystals of the crystallized compound have not time to become warmer and/or to dissolve significantly before the filtration and/or during the filtration.

In one embodiment, the crystallization stage (11) comprises at least one dissolving step. In the dissolving step the crystallized compound (12) is dissolved before next crystallization stage, crystallization step or crystallization device. In one embodiment, the dissolving step is arranged before each crystallization stage, crystallization step or crystallization device.

In one embodiment, the yield of the crystallized compound (12) is 50 - 95 %, in one embodiment 60 - 93 % or in one embodiment 75 - 90 % in

20195532 prh 19 -06- 2019 connection with the crystallization stage (11).

In one embodiment, the crystallized compound (12) comprises crystal water. In one embodiment, the crystallized compound (12) is an anhydrous crystallized compound.

In one embodiment, at least a part of the crystallized compound (12), e.g. Na₂So₄ or K₂SO₄, is recovered in connection with the crystallization stage (11) or after the crystallization stage (11) . In one embodiment, at least a part of the crystallized compound (12) is recovered as a product, e.g. as a chemical or as a nutrient to a soil improvement.

In one embodiment, the crystallized compound (12) is purified after the crystallization stage (11). In one embodiment, the crystallized compound (12) is washed after the crystallization stage (11) or in connection with the crystallization stage (11). In one embodiment, washing water intermediate evaporation crystallization stage (11). crystallized compound (12) crystallization stage (11).

recycled to before the the

In is

In one embodiment, dried after one embodiment, the the the purity of the crystallized compound (12) is over 98 %, in one embodiment over 99 %, or in one embodiment over 99.5 %.

In one embodiment, at least a part of the 10 mother liquor (20), e.g. primary filtrate, from the crystallization stage (11) is recirculated to the precipitation stage (6) and/or to the fraction (10) which comprises Na or K. In one embodiment, the mother liquor (20) is separated from the crystallized compound (12) after the crystallization stage (11), preferably after the first crystallization stage, the first crystallization step or the first crystallization device. Preferably, the mother liquor comprises an aqueous liquor phase of the crystallization. The mother liquor may comprise dissolved Na₂SO₄ or K₂SO₄. The mother liquor may comprise carboxylic acids. Further, in one embodiment, the mother liquor may comprise washing water from the filtration step (23) after the crystallization. In one 25 embodiment, at least a part of the mother liquor (20)

20195532 prh 19 -06- 2019 from the crystallization stage (11) is recirculated to the precipitation stage (6) . In one embodiment, at least a part of the mother liquor (20) from the crystallization stage (11) is recirculated to the 30 fraction (10) which comprises Na or K, e.g. after the separation stage (8) or before the intermediate evaporation (18). In one embodiment, about 5 - 99 % by volume, in one embodiment about 70 - 98 % by volume or in one embodiment about 80 - 95% by volume, of the mother liquor is recirculated to the precipitation stage (6) and/or to the fraction (10) which comprises

20195532 prh 19 -06- 2019

Na or K. Typically small share of the mother liquor is discharged from the loop in order to prevent too high concentration of carboxylic acids. Typically majority of acetic acid and part of formic acid exit the loop 5 during acidic evaporation (18) . Closing the loop as completely as possible is important for reaching high recovery rate for Na or K salt, and lignin, as well as for minimizing volume of the mother liquor to be discharged from the process. The limit for closing the 10 circulation is defined by functionality of the lignin precipitation (6), lignin filtration (8) and Na or K salt crystallization stages (11) . In one embodiment, the apparatus comprises at least one means or at least one device for recirculating at least a part of the 15 mother liquor (20) from the crystallization stage (11) to the precipitation stage (6) and/or to the fraction (10) which comprises Na or K. In one embodiment, the apparatus comprises at least one means or at least one device for recirculating at least a part of the mother 20 liquor (20) to the precipitation stage (6) . In one embodiment, the apparatus comprises at least one means or at least one device for recirculating at least a part of the mother liquor (20) to the fraction (10) which comprises Na or K.

In one embodiment, the mother liquor (20) from the crystallization stage (11) or a part (21) of the mother liquor (20) is supplied out from the process. In one embodiment, the mother liquor (20) or a part (21) of the mother liquor is supplied to the 30 intermediate evaporation (18) before the crystallization stage (11).

In one embodiment, at least a part of the crystallized compound (12) is supplied to an electrolysis stage (15) in which the crystallized 35 compound is converted into NaOH or KOH (16) and acid (17) by an electrolysis. Preferably, crystals are dissolved in clean water prior to the electrolysis.

This clean water is preferably hot water, and it can be an internal stream, e.g. evaporation condensate or washing filtrate and/or mother liquor from the second 5 crystallization stage. In one embodiment, the apparatus comprises at least one electrolysis stage (15) comprising at least one electrolysis device for converting at least a part of the crystallized compound (12) into NaOH or KOH (16) and acid (17) by 10 an electrolysis. In one embodiment, the apparatus comprises at least one feeding device for supplying the crystallized compound (12) to an electrolysis stage (15) . In one embodiment, at least a part of the crystallized compound (12) is supplied to the 15 electrolysis stage (15) directly or via a suitable additional treatment stage. In one embodiment, water is added to the crystallized compound (12) after the crystallization stage (11).

In one embodiment, the crystallized compound 20 (12) is treated in a purification stage for forming a purified crystallized compound before the electrolysis stage (15), e.g. at least a part of Ca and Mg, optionally K, or other impurities are removed from the crystallized compound (12) . In one embodiment, the crystallized compound (12) is treated by means of a

20195532 prh 19 -06- 2019 cation exchange crystallized stage (15) . compound (12) for forming (13) compound

In one is treated a purified for forming (14) before embodiment, by means of crystallized compound before the the a purified electrolysis crystallized an anion exchange the electrolysis stage (15) .

In one embodiment, the apparatus comprises at least one purification device before the electrolysis stage the apparatus (15)

In one embodiment, comprises at least one cation exchange device before the electrolysis stage (15) . Preferably, crystals are dissolved (24) in clean water prior to the purification stage, such exchange or anion exchange, preferably hot water, and it stream, e.g. evaporation condensate filtrate and/or mother liquor as before the cation

This clean water is can be an internal crystallization stage.

In one embodiment, comprises one or more than (15) . In one embodiment, the sequentially.

(15) are are arranged electrolysis stages one embodiment, the than one or more the in the or from the washing second or apparatus electrolysis stages electrolysis stages (15) In one embodiment, the arranged in parallel. In electrolysis stage one electrolysis electrolysis steps the electrolysis stage (15) electrolysis steps are arranged in the one method (15) comprises

In one steps .

are arranged

In one embodiment, sequentially embodiment, parallel in the electrolysis stage (15). In one embodiment, the electrolysis stage one electrolysis device. In electrolysis stage (15) comprises In one embodiment, device .

one two each

20195532 prh 19 -06- 2019 (15) comprises embodiment, the or more electrolysis devices, electrolysis step comprises one electrolysis In one embodiment, more than one electrolysis steps one electrolysis device.

embodiment, the electrolysis is an In one embodiment, the apparatus ; one electrodialysis device. In one the electrolysis or the electrolysis based on monopolar membranes electrodialysis cell. In one embodiment, electrolysis or the electrolysis device is based bipolar membranes in electrodialysis Alternatively, any suitable electrolysis methods or their combinations can be used in the electrolysis are performed by

In one electrodialysis. :

least comprises at embodiment, device is in the on cell.

In one embodiment, a base compound (16) and an acid compound (17) are formed in the electrolysis stage (15). In one embodiment, NaOH (16) and H₂SO₄ (17) are formed in connection with the electrolysis. In embodiment, KOH (16) and H₂SO₄ (17) are formed connection with the electrolysis.

In one embodiment, NaOH or KOH (16) recovered. In one embodiment, NaOH or KOH (16) embodiment, the acid compound, such as H₂SO₄, (17) one in is is one is recovered. In one embodiment, the acid compound (17) is recirculated to the precipitation stage (6). In one embodiment, the apparatus comprises for recirculating NaOH or KOH

In one apparatus comprises at least at least one embodiment, one means means the the for recirculating the acid compound the electrolysis stage

In one embodiment, the apparatus comprises at least one means for recovering

NaOH or KOH (16) after the electrolysis stage (15).

In one embodiment, the apparatus comprises at means for recovering the for recirculating is least one acid compound (17)

In one embodiment, selected comprising assembly, pump, outlet, after the the means from the inlet, pipe, group tube, duct, discharge outlet, discharge valve, discharge

20195532 prh 19 -06- 2019 channel, suitable compound conduit, other suitable feeding device, other device and their combinations.

In one embodiment, NaOH evaporation after the one embodiment, the apparatus comprises at least one evaporation device

In one embodiment, at least a part of the crystallized compound (12) is supplied to a treatment stage in which the crystallized compound is treated to

20195532 prh 19 -06- 2019 form another chemical compound, e.g. Na or K based compound, and/or sulphate based compound.

Preferably, the purified lignin (9) comprising lignin is formed by means of the method. In 5 one embodiment, the purified lignin comprises lignin and small share of impurities, such as Na-sulphate. Further, the purified lignin may comprise some other residual soluble or insoluble material. In one embodiment, dry matter content of the purified lignin 10 is over 30 % by weight, preferably over 40 % by weight, more preferably over 45 % by weight, after the separation stage. In one embodiment, the purified lignin comprises soluble compounds below 10 %, preferably below 6 %, more preferably below 3 % by dry 15 weight, after the separation stage.

In one embodiment, at least a part of the purified lignin (9) is recovered after the separation stage (8) . In one embodiment, the purified lignin (9) is supplied out after the separation stage (8).

The purified lignin (9) may be used as component in manufacturing a final product. In one embodiment, the purified lignin is used as such. In one embodiment, the purified lignin is supplied to a further processing. In one embodiment, the purified 25 lignin (9) is supplied to an additional lignin purification. In one embodiment, the purified lignin is supplied to a lignin separation for separating lignin from the purified lignin. In one embodiment, the purified lignin is supplied to a hydrolysis which 30 may be selected from the group comprising acid hydrolysis, enzymatic hydrolysis, supercritical hydrolysis and/or subcritical hydrolysis and their combinations, or to a polymerization process, a depolymerization process, a degradation process, a 35 chemical treatment, a manufacture of a composite material, lignin composite, activated carbon, carbon

20195532 prh 19 -06- 2019 fiber, binder material, polymers, resins, phenolic component, dispersion agent or absorbent material, a manufacture of feed or food, or a combustion process or other suitable process or their combinations. The purified lignin may be supplied directly to the hydrolysis, polymerization process, depolymerization process, degradation process, chemical treatment, manufacturing processes of said materials, combustion process or other suitable process, or alternatively 10 via a suitable treatment step or an additional step,

e.g. additional separation step, purification step or dewatering step, to the hydrolysis, polymerization process, depolymerization process, degradation process, chemical treatment, manufacturing processes 15 of said materials, combustion process or other suitable process. In one embodiment, the purified lignin (9) is used as an absorbent for oil, hydrocarbon composition or heavy metals. In one embodiment, the purified lignin is used as combustible 20 matter in energy production.

A lignin product may be formed by means of the method. In one embodiment, the lignin product comprises the purified lignin (9) which has been formed by the method. In one embodiment, the lignin product is 25 the purified lignin (9) .

In one embodiment, a lignin product which is odourless and which has ash content below 5 % by dry weight and comprises carbohydrates less than 1 % by dry weight is formed by means of the method. In one 30 embodiment, the lignin product comprises at least the purified lignin (9). In one embodiment, the lignin product is the purified lignin (9) . In one embodiment, the lignin product has ash content below 3 % by dry weight and in one embodiment below 1 % by dry weight. In 35 one embodiment, the lignin product comprises carbohydrates less than 0.7 % by dry weight and in one

20195532 prh 19 -06- 2019 embodiment less than 0.5 % by dry weight. In one embodiment, the lignin product is substantially a sulphur-free product. In one embodiment, the lignin product is substantially odourless.

Further, in one embodiment a chemical product comprising a crystallized compound (12) is formed by means of the method. Further, in one embodiment a chemical product comprising NaOH or KOH (16) is formed by means of the method. Further, in one embodiment a 10 chemical product comprising an acid (17) is formed by means of the method.

The method and the apparatus provide the purified lignin (9) with good quality. The purified lignin has very high concentration of lignin. Further, 15 the purified lignin has very high purity. Further, the method and the apparatus provide the crystallized compound (12), the acid (17) and NaOH or KOH (16) with good quality. Also the utilization of the acid, NaOH or KOH and/or Na₂SO₄ or K₂SO₄ can be improved.

The method and the apparatus provide an industrially applicable, simple and affordable way of making the purified lignin and recovering the chemicals, such as Na₂SO₄, K₂SO₄, NaOH, KOH and/or H₂SO₄without the need for a recovery boiler. The method or 25 the apparatus is easy and simple to realize as a production process. The method and the apparatus are suitable for use in the manufacture of the different lignin products and chemical products from different raw materials .

EXAMPLES

Some embodiments of the invention are described in more detail by the following examples with reference to accompanying drawings.

Example 1

In this example, a purified lignin produced from an alkaline lignin material chemicals are recovered according to a process

Fig.1.

The alkaline a delignification delignification stage (2) comprises one alternatively at least which are arranged in material (1) is (2) in which forming the based start material so dissolve at is and of lignin material (3) is formed with NaOH or KOH in by (2) . The delignification stage delignification device, or two delignification devices series. A lignin based start supplied to the delignification stage it is treated with NaOH or

KOH for alkaline material that the lignin material (3) .

(1) has been formed raw material has been treated to

A lignin from raw

20195532 prh 19 -06- 2019 least a part of hemicellulose.

The alkaline lignin material (3) which comprises NaOH or KOH is precipitated in presence of an acid in a precipitation stage (6) for forming a precipitated lignin (7) . Solid material, e.g. fibers, may be separated from the alkaline lignin material (3) in a solid material separation stage (22) after the delignification stage (2), e.g. filtration device. Further, the by an forming a concentrated the precipitation stage (3,3a) is supplied (4) and the concentrated (3,3b) is supplied from the the precipitation stage (6) . at least one acid addition material (3) may be treated evaporation stage (4) for lignin material (3b) before (6). The alkaline lignin material to the evaporation stage alkaline lignin material evaporation stage (4) to The apparatus comprises device for adding the acid (5) to the alkaline lignin material (3) in the precipitation stage (6), or of a evaporation lignin in an alternatively before the precipitation stage (6) . In this example, the acid (5) is sulphuric acid (H₂SO₄) without an organic acid.

The precipitated lignin (7) is supplied to a separation stage (8) in which a purified lignin (9) is recovered and at least one fraction (10) which comprises Na or K is recovered. The separation may be made by means of filtration, centrifugal treatment or their combinations. The separation device may be 10 selected from the group comprising filtration device, vacuum filtration device, press filter, belt press, centrifugal device, screw press and their combinations. In this example, the separation is made by means of a pressure filtration device in at least 15 one separation stage (8). Alternatively, the separation is made in at least two separation stages (8) or steps of the separation stage (8).

The fraction (10) which comprises Na or K is supplied to a crystallization stage (10) which comprises Na or K may be treated by an intermediate evaporation before the

Further, which comprises Na or K intermediate filtration may step for be filtrated in an before the removing lignin from the fraction solid material may be

20195532 prh 19 -06- 2019 recirculated precipitated the lignin.

to the lignin (7) before the separation

An alkali or acid may be added connection with the intermediate evaporation it is needed.

of in if

The fraction (10) which comprises Na or K is treated by crystallization, such as by cooling crystallization, in the crystallization stage (11) for forming a crystallized compound (12). The process may comprise two crystallization stages, e.g. cooling crystallization stages, which are arranged sequentially. The crystallization stage (11) comprises a filtration step (23) in which the crystallized is separated after compound (12) and/or washing water crystallized compound (12) next crystallization stage, crystallized compound (12) from the is

At a mother liquor crystallization, dissolved before least a is recovered part of as Na₂SO₄ the the or

K₂SO₄. Further, the crystallized compound (12) may be washed after the crystallization. Further, the crystallized compound (12) may be purified. At least a part of the mother liquor (20) from the first crystallization stage (11) is recirculated to the precipitation stage (6) and/or alternatively to the fraction (10) . A part (21) of mother liquor (20) from the crystallization stage (11) may be supplied out after the crystallization stage (11).

20195532 prh 19 -06- 2019

Example 2

In this example, a purified lignin is produced from an alkaline lignin material and chemicals are recovered according to a process of Fig.2.

The alkaline lignin material (3) is formed by 25 a delignification with NaOH or KOH in a delignification stage (2) . The delignification stage (2) comprises one delignification device, or alternatively at least two delignification devices which are arranged in series. A lignin based start material (1) is supplied to the delignification stage treated with NaOH or

KOH for forming the based start material so dissolve at alkaline material that the lignin material (3) .

A lignin from raw raw material has been treated to least a part of hemicellulose.

20195532 prh 19 -06- 2019

The alkaline lignin material (3) which comprises NaOH or KOH is precipitated in presence of an acid in a precipitation stage (6) for forming a precipitated lignin (7) . Solid material, e.g. fibers, 5 may be separated from the alkaline lignin material (3) in a solid material separation stage (22) after the delignification stage (2), e.g. by means of a filtration device. Further, the alkaline lignin material (3) may be treated by an evaporation in an 10 evaporation stage (4) for forming a concentrated lignin material (3b) before the precipitation stage (6) . The alkaline lignin material (3,3a) is supplied to the evaporation stage (4) and the concentrated alkaline lignin material (3,3b) is supplied from the 15 evaporation stage (4) to the precipitation stage (6) .

The apparatus comprises at least one acid addition device for adding the acid (5) to the alkaline lignin material (3) in the precipitation stage (6), or alternatively before the precipitation stage (6) . In 20 this example, the acid (5) is sulphuric acid (H₂SO₄) without an organic acid.

The precipitated lignin (7) is supplied to a separation stage (8) in which a purified lignin (9) is recovered and at least one fraction (10) which 25 comprises Na or K is recovered. The separation may be made by means of filtration, centrifugal treatment or their combinations. The separation device may be selected from the group comprising filtration device, vacuum filtration device, press filter, belt press, 30 centrifugal device, screw press and their combinations. In this example, the separation is made by means of a pressure filtration device in at least one separation stage (8). Alternatively, the separation is made in at least two separation stages 35 (8) or steps of the separation stage (8).

The fraction (10) which comprises Na or K is supplied to a crystallization stage (11). The fraction (10) which comprises Na oi intermediate evaporation crystallization stage (11). which comprises Na or K intermediate filtration recirculated precipitated the lignin, connection may step for (19) before the removing lignin from solid material (10). The separated to the precipitation stage (6) or lignin (7) before the separation

An alkali or acid may be added with the intermediate evaporation (18) may be to the of in it is needed.

The fraction (10) which comprises Na treated by crystallization, such as by crystallization, in the crystallization stage forming a crystallized compound (12).

comprise two crystallization stages, e.g. crystallization stages, which sequentially. The crystallization s a filtration step (23) in whict if or K is cooling (11) for The process may cooling arranged comprises ie crystallized a mother liquor crystallization, dissolved before are

20195532 prh 19 -06- 2019 compound (12) is sepa and/or washing water crystallized compound next crystallization crystallized electrolysis compound (17) by compound At least from the is (12) stage .

compound (12) stage (15) in converted into the electrolysis.

(12) may be washed is

At the the is an which

NaOH or

Further, the crystallized after the crystallization, the the mother liquor (20) from stage (11) is recirculated to (6) and/or alternatively to t (21) of the mother liquor the the from the crystallization stage (11) may be supplied out after the crystallization

The crystallized in a purification stage, (13) , for forming (14) before the are dissolved (24) stage (11).

compound (12) may be treated of a cation

e.g. by means a purified electrolysis in clean water prior exchange compound

Crystals the cation exchange (13).

In this example, the electrolysis stage (15) is based on an electrodialysis. The apparatus comprises at least one electrodialysis device.

NaOH or KOH (16) is recovered after the electrolysis stage (15), and it may be recirculated to the delignification stage (2). Further, the acid compound (17), such as H₂SO₄, is recovered after the electrolysis stage (15), and it may be recirculated to the precipitation stage (6) . NaOH or KOH (16) and/or the acid compound (17) may be treated by an evaporation after the electrolysis stage (15).

Example 3

In this example, a purified lignin is produced from an alkaline lignin material and chemicals are recovered according to a process of

Fig.1.

The alkaline lignin material (3) is formed by

20195532 prh 19 -06- 2019 a delignification with NaOH in a delignification stage (2) using hemicellulose-lean pre-treated hardwood biomass (1). NaOH was used 75 kg/t BD biomass (1).

The alkaline lignin material (3) is evaporated (4) to concentration of 28% TS. Lignin content in the alkaline lignin material (black liquor) is 61% wt-%. This liquor is then precipitated using sulphuric acid in a precipitation stage (6) for forming a precipitated lignin slurry (7) .

Stoichiometric amount of H₂SO₄ in relation to NaOH is

20195532 prh 19 -06- 2019 dosed to convert into Na₂SO₄ and final pH after the precipitation is 2.8. The precipitated lignin slurry (7) is supplied to a separation stage (8) in which a purified lignin (9) is recovered and a liquid fraction (10) which comprises Na₂SO₄ is recovered using a pressure filter involving a cake washing stage. The purified lignin is further upgraded by re-slurring the filter cakes and then performing another filtration stage .

In first cycle, dry matter of the liquid fraction (10) contains 74 wt-% Na₂SO₄, 15 wt-% total carboxylic acids, 8 wt-% soluble lignin, 1.1 wt-% total carbohydrates, 0.7 wt-% glycolaldehyde, 0.1 wt-% total metals and non-metals other than Na and S, and

0.07 wt-% total furan compounds. Acetic acid represents 65 wt-% of total carboxylic acids. Na₂SO₄based liquor (10) is evaporated (18) to concentration of 32% TS in first cycle. During continuous run the concentration of Na₂SO₄ based liquor was gradually increased in evaporation, being 46% TS in balance. By average, 74% of acetic acid and 30% of formic acid is recovered to steam condensate in each cycle. Other carboxylic acids, e.g. lactic, citric, oxalic, levulinic and succinic acid as well as for example glycolaldehyde, carbohydrates and metals cumulate due to circulation of mother liquor (20), reaching certain concentration levels in balance.

pm automated strainer is used to filtrate (19) solid lignin particles after evaporation (18) and 30 this low-volume slurry is continuously pumped to the precipitated lignin slurry (7) prior to the filtration of lignin. Na₂SO₄ based liquor in 32-46% TS is pumped without pH adjustment to a cooling crystallization stage (11) where temperature is dropped to 12°C.

Formed Na₂SO₄ · 10H₂O (decahydrate) crystals are vacuum filtered, washed with clean water and then conveyed to dissolving stage and crystallized again in subsequent stage. The purified Na₂SO₄ crystals are dried to recover anhydrous Na₂SO₄ crystals.

60% of primary filtrate, i.e. mother liquor (20), from the vacuum filtration is pumped to the precipitation stage (6) and 30% to the evaporation stage (18). The remaining 10% of this Na₂SO₄-lean, but carboxylic acid-rich liquid (21) is discharged to an anaerobic digester together with steam condensate from 10 the acidic evaporation (18).

In balance, so after ca. 40 cycles, dry matter of the liquid fraction (10) contains 45 wt-% Na₂SO₄, 34 wt-% total carboxylic acids, 8 wt-% soluble lignin, 5 wt-% glycolaldehyde, 5 wt-% total carbohydrates, 0.6 wt-% total metals and non-metals other than Na and S, and 0.3 wt-% total furan compounds. In balance, purity for Na₂SO₄ crystals after the first crystallization stage is 99.3 % and after the second crystallization stage 99.95 %. Purity for 20 lignin (9) is 96.1% after the second filtration stage.

Lignin contains 0.7% ash, 0.07% sulphur and 0.6% total carbohydrates on dry basis, and has median (d₅₀) particle size of 6 pm.

In balance, lignin yield as purified lignin 25 (9) from the black liquor (3) is 98.5% and Na₂SO₄ yield as dried crystals from Na/SO₄-balance is 97.2%.

20195532 prh 19 -06- 2019

Despite the high concentration of carboxylic acids in the circulation, runnability of the lignin precipitation, lignin filtration and cooling 30 crystallization stages was on a good level.

The method and apparatus according to the present invention is suitable in different embodiments 35 to be used in different lignin purification processes and/or chemical recovery processes. Further, the method and apparatus according to the present invention is suitable in different embodiments to be used for producing the most different kinds of lignin and chemical products from different raw materials.

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

Claims

1. A method for recovering chemicals from an alkaline lignin material, wherein

5 - the alkaline lignin material (3) which comprises

NaOH or KOH is precipitated in presence of an acid in a precipitation stage (6) for forming a precipitated lignin (7), the precipitated lignin (7) is supplied to a 10 separation stage (8) in which a purified lignin (9) is recovered and from which at least one fraction (10) which comprises Na or K is supplied to a crystallization stage (11), and the fraction (10) which comprises Na or K is 15 treated by crystallization in the crystallization stage (11) for forming a crystallized compound (12).

2. The method according to claim 1, wherein the alkaline lignin material (

3) is formed by a

20 delignification with a base composition which

comprises NaOH or KOH in a delignification stage (2) before the precipitation stage (6). 3 . The method according to claim 1 or 2, wherein the method comprises at least two 25 delignification stages (2) which are arranged in

20195532 prh 19 -06- 2019 series .

4. The method according to any one of claims 1 to 3, wherein the alkaline lignin material (3) is treated by an evaporation in an evaporation stage (4)

30 for forming a concentrated lignin material (3b) before the precipitation stage (6).

5. The method according to any one of claims 1 to 4, wherein the acid (5) is sulphuric acid ( :h₂so₄) or other inorganic acid. 35 6. The method according to any one of claims 1 to 5, wherein the separation is made by means of

20195532 prh 19 -06- 2019 filtration, centrifugal treatment or their combinations in the separation stage (8).

7. The method according to any one of claims 1 to 6, wherein the separation (8) is made by means of a

5 pressure filtration in the separation stage (8).

8. The method according to any one of claims 1 to 7, wherein the fraction (10) which comprises Na or K is filtrated before the crystallization stage (11).

9. The method according to any one of claims 1

10 to 8, wherein the fraction (10) which comprises Na or K is treated by an intermediate evaporation (18) before the crystallization stage (11).

10. The method according to claim 9, wherein at least a part of carboxylic acids is recovered

15 during the intermediate evaporation (18).

11. The method according to any one of claims

1 to 10, wherein at least a part of mother liquor (20) from the crystallization stage (11) is recirculated to the precipitation stage (6) and/or to the fraction 20 (10) which comprises Na or K.

12. The method according to any one of claims

1 to 11, wherein at least a part of the crystallized compound (12) is supplied to an electrolysis stage (15) in which the crystallized compound is converted 25 into NaOH or KOH (16) and acid (17) by an electrolysis .

13. The method according to any one of claims

1 to 12, wherein the crystallized compound (12) is treated in a purification stage, which comprises at 30 least one of a cation exchange (13) or an anion exchange, for forming a purified crystallized compound (14) before the electrolysis stage (15).

14. The method according to any one of claims 1 to 13, wherein NaOH or KOH (16) is recirculated to

35 the delignification stage (2).

15. The method according to any one of claims

1 to 14, wherein the acid compound (17) is recirculated to the precipitation stage (6).

16. The method according to any one of claims

5 1 to 15, wherein the alkaline lignin material (3) is formed from raw material which is wood based material or a mixture comprising wood based material.

17 .

An apparatus from an alkaline lignin apparatus comprises at least one at least precipitating for recovering chemicals material, wherein the precipitation stage one precipitation the alkaline lignin (6) comprising device material for which comprises NaOH or KOH in presence of acid in order to form a precipitated lignin (7) at least one separation stage (8) comprising an at

20195532 prh 19 -06- 2019 least one separation device in which a purified lignin (9) and at least one fraction (10) which comprises Na or K are separated and a purified 20 lignin (9) is recovered, and

- at least one crystallization stage (11) comprising at least one crystallization device for treating the fraction (10) which comprises Na or K by crystallization in order to form a 25 crystallized compound (12).

18. The apparatus according to claim 17, wherein the apparatus comprises at least one delignification stage (2) before the precipitation stage (6).

30

19. The apparatus according to claim 17 or 18, wherein the apparatus comprises at least one evaporation stage (4) before the precipitation stage (6) .

20. The apparatus according to any one of 35 claims 17 to 19, wherein the apparatus comprises at least one acid addition device for adding the acid (5)

20195532 prh 19 -06- 2019 to the alkaline lignin material (3) in the precipitation stage (6) or before the precipitation stage (6).

21. The apparatus according to any one of claims 17 to 20, wherein the separation device is selected from the group comprising filtration device, vacuum filtration device, press filter, belt press, centrifugal device, screw press and their combinations .

22. The apparatus according to any one of claims 17 to 21, wherein the apparatus comprises more than one separation devices which are arranged sequentially.

23. The apparatus according to any one of claims 17 to 22, wherein the apparatus comprises at least one device for recirculating at least a part of mother liquor (20) from the crystallization stage (11) to the precipitation stage (6) and/or to the fraction (10) which comprises Na or K.

24. The apparatus according to any one of claims 17 to 23, wherein the apparatus comprises at least one electrolysis stage (15) comprising at least one electrolysis device for converting at least a part of the crystallized compound (12) into NaOH or KOH (16) and acid (17) by an electrolysis.

25. The apparatus according to claim 24, wherein the apparatus comprises at least one means for recirculating NaOH or KOH (16) and/or at least one means for recirculating the acid compound (17) after the electrolysis stage (15).

26. A Use of the purified lignin (9) obtainable by the method according to any one of claims wherein the purified lignin material in a hydrolysis, depolymerization process,

1 to 16, a source process, process, (9) is used as polymerization degradation chemical treatment, manufacture of a composite material, lignin composite, activated carbon, carbon fiber, binder material, polymers, resins, phenolic component, dispersion agent or absorbent material, manufacture of feed, manufacture of food, combustion 5 process or other suitable process or their combinations .

27. A lignin product comprising the purified lignin (9) which has been formed by the method according to any one of claims 1 to 16.

10

28. A lignin product which is odourless and which has ash content below 5 % by dry weight and comprises carbohydrates less than 1 % by dry weight.

29. A chemical product comprising the crystallized compound (12) which has been formed by the 15 method according to any one of claims 1 to 16.