FI126765B

FI126765B - A process for the preparation of a lignin component, a lignin component and its use, and a product

Info

Publication number: FI126765B
Application number: FI20125703A
Authority: FI
Inventors: Mauno Miettinen
Original assignee: Upm Kymmene Corp
Priority date: 2012-06-25
Filing date: 2012-06-25
Publication date: 2017-05-15
Also published as: FI20125703A

Description

A METHOD FOR MAKING A LIGNIN COMPONENT, A LIGNIN COMPONENT AND ITS USE AND A PRODUCT

FIELD OF THE INVENTION

The invention relates to a method for manufacturing a lignin component. Further, the invention relates to a lignin component and a use of the lignin component. Further, the invention relates to a product .

BACKGROUND OF THE INVENTION

Known from publication WO 2006/031175 is a method for separation of lignin from black liquor.

OBJECTIVE OF THE INVENTION

The objective of the invention is to disclose a new method for manufacturing a lignin component. Another objective of the invention is to produce a lignin component with improved properties and a product comprising the lignin component.

SUMMARY OF THE INVENTION

The method for making a lignin component from a lignin material according to the present invention is characterized by what is presented in claim 1.

The lignin component according to the present invention is characterized by what is presented in claim 16.

The use of the lignin component according to the present invention is characterized by what is presented in claim 17.

The product according to the present invention is characterized by what is presented in claim 18.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying figures, 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 together with the description help to explain the principles of the invention. In the figures:

Fig. 1 is a flow chart illustration of a method according to one embodiment of the present invention,

Fig. 2 is a flow chart illustration of a method according to another embodiment of the present invention, and

Fig. 3 shows a SEM-picture of lignin structure in cake of one lignin component according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to optimization of acid treating in lignin separation process. In the method of the present invention a lignin component is formed from a lignin material by an acid treatment, the method comprising: forming a lignin component of lignin material by treating the lignin material in an acid treatment stage by means of an acid composition; and optimizing process conditions in the acid treatment stage so that high temperature over 70 °C, long retention time, such as delay time, over 6 hours and pH level between 4.5-7 are used during the acid treatment in order to remove undesired substance from the lignin component and to purify the lignin component and to reduce acid consumption in the acid treating of lignin.

In a preferred embodiment the lignin material 1 is treated by an acid washing 2 to form a lignin component 3. The lignin material 1 is treated in an acid washing stage 2. Long retention time over 6 hours, high temperature over 7 0 °C, and pH level between 4.5 and 7 are used in the acid washing.

One embodiment of the method of the present invention is shown in figure 1. Another embodiment of the method of the present invention is shown in figure 2. A structure of one lignin component is shown in figure 3.

The invention is specially based on improving properties of the lignin component. When the lignin material is acid treated by optimizing process conditions and parameters, e.g. retention time and temperature, then higher pH level, e.g. 4.5 - 7 instead of about 2.5, can be used, and then the properties, such as purity, dry solids content and filterability of the lignin component are good. Further, acid such as virgin acid consumption can be decreased. Preferably, destabilisation of lignin happens before the filtration thanks to high temperature and long retention time in the acid treatment. Further, odour in the lignin component can be decreased. Then it is provided the lignin component which is suitable to use in typical and special applications.

In this context, a lignin material refers any material or composition containing lignin. The lignin material may contain one or more material components. In one embodiment suitable and desired additives can be added into the lignin material to form a desired lignin component.

In one embodiment the lignin material includes material which is selected from a group consisting of lignin from alkaline pulping process, kraft lignin, lignin from soda process, lignin coming from a process in which lignin is separated the raw material by a solution including suitable chemicals and their combinations .

In one embodiment the lignin material includes flash precipitated lignin. In one embodiment flash precipitated lignin is obtained after C02-precipitation. Preferably, flash precipitated lignin is formed as disclosed in patent application PCT/FI2011/050896.

In one embodiment the lignin is precipitated from the black liquor by a continuous process with C02 at 6 - 10 bar overpressure. In one embodiment the lignin is separated by a flash precipitation lignin separation method, such as disclosed in patent application PCT/FI2011/050896. In one embodiment of the present invention the lignin is flash precipitated lignin. The term "flash precipitated lignin" should be understood in this specification as lignin that has been precipitated from black liquor in a continuous process by decreasing the pH of a black liquor flow, under the influence of an over pressure of 200 - 1000 kPa, down to the precipitation level of lignin using a carbon dioxide based acidifying agent, preferably carbon dioxide, and by suddenly releasing the pressure for precipitating lignin. The residence time in the above method is under 300 s. The flash precipitated lignin particles, having a particle diameter of less than 2 pm, form agglomerates, which can be separated from black liquor using e.g. filtration. The flash precipitated lignin can be purified and/or activated if needed for the further processing. The flash precipitated lignin has many advantages, e.g. activity, dispersability, solubility, drainability and preservability. In one embodiment of the present invention, the lignin component is a flash precipitated kraft lignin. Preferably, the flash precipitated kraft lignin is undrained. Therefore the lignin has higher activity, and the lignin can be re-dissolved. The lignin needs only a very simple re-dispersing stage when it is added e.g. into an adhesive mixture. Also control of the amount of water in the lignin based composition is easier when the redispersing is easier. Further, the lignin is easier to handle in the process because the lignin is not dusty. Preferably, the flash precipitated kraft lignin has dry matter content of 50 - 80 %.

In one embodiment the lignin material is treated chemically and/or mechanically before the acid treatment stage of the present invention. In one embodiment the lignin material is precipitated before the acid treatment stage. In one embodiment the lignin material is re-slurried before the acid treatment.

In this context, a lignin component means product formed from lignin material in one or more stages. Term "lignin component" is already used after the first treatment stage.

In this context, the acid washing refers to any acid washing method. In one embodiment the acid washing is performed with an acid composition containing sulphuric acid (H2S04) , other acid or other suitable acidifying chemical or their combination. The optimization of the process affects positively consumption of H2S04 or other acid or other acidifying chemical .

In one embodiment the acid composition contains sulphuric acid, which can be virgin acid or recycled acid. Without any process improvements according to the invention consumption of sulphuric acid is rather high. Sulphuric acid is cheap, but high amount of sodium hydroxide is needed to fulfil Na/S balance of pulp mill. Furthermore, all extra sulphur added to process must be dumped from recovery boiler meaning extra cost.

In a preferred embodiment the acid composition contains other acid or other acidifying chemical containing salt. Salt can be selected from group K-,

Na-, Mg-, Al-, Ca-salt or other suitable salt. In one embodiment the acid composition contains sulphate compound with salt. In one embodiment the acid composition contains sodium sesquisulphate. Sodium sesquisul-phate (SSS) is a waste fraction from chlorine dioxide plant in pulp mill. In one embodiment waste acid is used as other acid or other acidifying chemical.

Preferably the acid composition contains sulphuric acid, and other acid or other acidifying chemical with salt. In one embodiment the acid composition contains sulphuric acid and sodium sesquisulphate. In one embodiment the acid composition contains sulphuric acid about 10 - 90 w-%, in one embodiment 60 - 70 w-%, and sodium sesquisulphate about 10 - 90 w-%, in one embodiment 30-40 w-%. The high pH saves acid or other acidifying chemical containing salt which is good for the pulp mill and brings less salt to process, and then less water is needed for washing.

Preferably, in the acid treatment stage of the invention a suitable combination of temperature, retention time and pH level is selected. The selected combination varies based on acid washing method, lignin material, acid composition and desired product.

Preferably, long retention time is used in the acid treatment according to the invention. In one embodiment the retention time is over 6 hours, preferably over 10 hours, and more preferable between 10 and 20 hours.

In this context, retention time means time of the treatment stage. The retention time does not include a filtration time.

In one embodiment the temperature is over 80 °C during the acid treatment stage, preferably over 85 °C, and more preferable between 80 - 90 °C.

In a preferred embodiment pH level is sufficient high during the acid treatment stage. In one em bodiment the pH level is over 4.5, preferable over 5. In one embodiment the pH level is under 7, preferably under 6. In a preferred embodiment the pH level which is between 5 and 6 can be used. When high pH is used according to the invention, so it leads to non-corrosive lignin as a product. Then stainless steel instead of more expensive acid-proof steel can be used in the process devices.

In one embodiment the pH level is between about 4.5 - 7, preferably about 5-6, the temperature is between 70 - 100 °C, preferably 80 - 90 °C, and the retention time is over 1 hour, preferably 6-30 hours and more preferable between 10 and 20 hours, at the acid treatment stage.

Increasing temperature and/or retention time and/or pH level dry solid content and filterability may be improved. Improved dry solid content of filter cake leads to lower energy consumption in drying and to lower consumption of water in washing to reach same purity. Also dryer can be smaller, which leads to savings in investment. Savings in water consumption is important, since likely washing water must be circulated back to evaporation plant. Also certain dry solid content is needed to maintain processability of lignin cakes. For applications requiring no drying, for example burning, the low content of water in filter cake is a benefit.

In the present invention it has been noticed that use of high temperature and long delay time combined with high pH, e.g. 5 - 7, and use of sodium ses-quisulphate can reduce acid consumption even by about 65 %, which means acid consumption of about 7 0 kg/t lignin. In the process of the invention normal cake washing with water after the acid treatment is enough to raise or keep pH of final lignin to between 5 and 7.5, preferably 6 - 7. Then lignin is non-corrosive.

Production of neutral lignin is necessity for most applications. If lignin has pH of 2.5, so an additional process stage is needed to neutralize lignin.

The method of the invention can be used in connection with any acid treatment process containing one or more acid treatment stages. In one embodiment the acid treatment process comprises acid hydrolysis stage before or after the acid washing stage.

The method of the invention can be used in connection with the acid treatment process described in patent application FI20116253.

In one embodiment the method of the present invention comprises a pre-treatment step 5 before the acid treatment stage 2. In one embodiment the lignin material is re-slurried in the pre-treatment step. In a preferred embodiment the pre-treatment step is a softening step of lignin in which the lignin is softened and structure of the lignin is modified.

In one embodiment, when the pre-treatment 5 is made before the acid treatment so in the pretreatment retention time is below 2 hours, temperature is between 55 - 70 °C and pH is between 9 and 10.5.

It is important for the invention that long retention time is used at the acid treatment. Alternatively, the long retention time can be used also in other stage such as in the pre-treatment stage. The long retention time can be used in the acid washing and/or in the pre-treatment step.

In one embodiment the formed lignin component 3 is filtrated at the filtration stage 4 after the acid treatment stage 2.

In this context, the filtration refers to any filtration method which can be used in the filtration of the lignin. Preferably, in the filtration the lignin component is washed by water and pressed and optionally air-dried. The filtration can be performed by any suitable filtration device. In one embodiment the formed lignin component is filtrated by pressure filtration or vacuum filtration. In one embodiment pressure is between 10 - 20 bar, preferably 13 - 17 bar and more preferable about 15 bar in the pressure filtration.

Preferably improved filterability, especially better filtration rate, achieved by means of the invention leads to smaller pressure requirement in the filtration and to shorter filtration time. Then cheaper filters, e.g. based on size and type of device, may be used.

In one embodiment temperature is over 50 °C and pH is between 5 and 7 during the filtration. In one embodiment the pH level is re-adjusted just before the filtration.

In one embodiment the process comprises at least two filtration stages. In one embodiment there is one filtration stage after each acid treatment stage. In one embodiment there is the first filtration stage before the acid washing of the invention and the second filtration stage after the acid washing of the invention. In the first filtration stage the lignin material or lignin component washed is filtrated at pH about 10, and then sulphuric acid can be saved in the acid washing.

In one embodiment the additional oxidation is made after the filtration in which an acidic filtrate is additionally oxidized. In one embodiment the lignin component is additionally oxidized during the acid treatment stage. The additional oxidation may be performed by means of air, oxygen, other oxidizing agent or their combinations in order to stabilize structure of the lignin component, to increase purity of lignin and to remove odour.

The lignin component 3 obtainable by the method of the present invention can be used as component in manufacturing a final product selected from activated carbon, carbon fiber, lignin composite, e.g. lignin-plastic composite or lignin-fiber composite, binder material, phenolic component, dispersion agent and their combinations.

The final product or product comprises the lignin component of the present invention. Preferably, pure lignin component according to the present invention is needed in the manufacturing of the activated carbon and carbon fibers.

The method according to the present invention provides the lignin component with good quality. When improving the purify and increasing dry solids content of the lignin component so then it may be provided better properties of the lignin product and the final product.

The present invention provides an industrially applicable, simple and affordable way of making the lignin component from the lignin material. The method according to the present invention is easy and simple to realize as a production process. The method according to the present invention is suitable for use in the manufacture of the different lignin components from different lignin materials.

EXAMPLES

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

Example 1

In this example and in figure 1, a lignin component 3 is formed by an acid treatment on a laboratory scale. A starting lignin material 1, which was flash precipitated lignin, was re-slurred and treated by an acid washing stage 2. Process conditions were following at the acid washing stage: temperature about 87 °C, retention time about 12 hours and pH level about 5.6. The acid washing was performed with an acid composition containing H2S04 and sodium sesquisulphate (SSS) so that mixture of H2S04:SSS was 1:6. SSS was 20 % liquid.

The lignin component 3 was filtrated after the acid washing stage 2 by pressure filtration 4. Temperature was about 82 °C and pH was 6.5 - 7 during the filtration. Filtration rate was about 207 kg/m3/h. Dry solids content of filter cake was about 78 %.

In these tests it was discovered that it may be produced the lignin component with good properties. It was discovered that dry solids content of the final lignin component cake and filterability and filtration rate time needed were in good level. Further, sulphuric acid can be saved by means of the invention.

Further, it was discovered that lignin structure in the cake of the lignin component was in the form of big-single particles. This explains good filterability and high dry solids content.

Example 2

In this example a lignin component 3 is formed by an acid washing according to figure 1 on a pilot scale. A starting lignin material 1, which was flash precipitated lignin, was slurred and was treated at an acid washing stage 2 by an acid composition in order to produce a lignin component. The acid washing was performed with an acid composition containing H2S04 and sodium sesquisulphate (SSS) so that mixture of H2S04: SSS was 1: 6 .

The lignin component 3 was filtrated after the acid washing stage 2 by pressure filtration 4. Temperature was about 82 °C and pH was 6.5 - 7 during the filtration.

Process conditions are described in table 1.

Table 1

in which T1 is temperature of the acid washing tl is retention time of the acid washing

Process results are described in table 2.

Table 2

in which DS is dry solids

Filtration rate is defined during feeding.

In the tests it was surprisingly discovered that filterability of the lignin component was good even though lignin component was treated in high pH level in the acid washing. In the tests it was discovered that to enable practical filtration rate, slurry of the lignin material 1 must stay at pH 5-6 for sufficiently long time, over 6 hours and at sufficiently high temperature, over 70 °C, in the acid washing. Further, it was discovered that it may be produced the lignin component with good cake dry solids and quality. Further, it was discovered that high sodium concentration in the acid washing generally improves filtration, but usually raises final ash content in lignin component. However, ash content was at an adequate level.

Further, it was discovered that lignin structure in the cake of the lignin component was in the form of big-single particles. One lignin component of test 2 is shown in figure 3, SEM image.

From the all tests it was discovered that it is important for the invention that long retention time and high temperature together with high pH level are used in the acid washing stage. Further, it was important that at least part of sulphuric acid is substituted by other acid or other acidifying chemical with salt. Sulphuric acid consumption can be decreased due to high pH level and substitution of sulphuric acid.

The method according to the present invention is suitable in different embodiments to be used for making the most different kinds of lignin components from different lignin materials. The lignin component according to the present invention is suitable in dif ferent embodiments to be used in different final products .

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

A process for the preparation of a lignin component from a lignin material by acid treatment comprising: - forming a lignin component from a lignin material by treating the lignin material in an acid treatment step with an acid composition; and - optimizing the process conditions in the acid treatment step using a high temperature, above 70 ° C, a long retention time, greater than 6 hours, and a pH between 4.5 and 7 during the acid treatment.

The process of claim 1, wherein the acid treatment step is acid washing.

The process of claim 1 or 2, wherein the acid composition contains H 2 SO 4.

The process of any one of claims 1 to 3, wherein the acid composition contains an acidification chemical including a salt.

The process of any one of claims 1 to 4, wherein the acid composition contains sodium sesquisulfate.

The process according to any one of claims 1 to 5, wherein the pH is between 5 and 6.

The method of any one of claims 1 to 6, wherein the retention time is greater than 10 hours.

The process according to any one of claims 1 to 7, wherein the temperature is above 80 ° C.

The process according to any one of claims 1 to 8, wherein the lignin material is precipitated before the acid treatment step.

The method of any one of claims 1 to 9, wherein the lignin material comprises a material selected from the group consisting of an alkaline pulp lignin, a kraft lignin, a soda lignin process, a process lignin, wherein the lignin is separated from the raw material by a solution. containing a suitable chemical and combinations thereof.

The method of any one of claims 1 to 10, wherein the lignin material comprises flash-precipitated lignin.

The method of any one of claims 1 to 11, wherein the method comprises: filtering the lignin component after the acid treatment step.

The method according to any one of claims 1 to 12, wherein the lignin component is filtered by pressure filtration or vacuum filtration.

The method of any one of claims 1 to 13, wherein the pH is readjusted just before filtration.

A process according to any one of claims 1 to 14, wherein the temperature is above 50 ° C and the pH is between 5 and 7 during filtration.

A lignin component formed from a lignin material by an acid treatment, wherein - the lignin component is formed from the lignin material so that the lignin material is treated in an acid treatment step with an acid composition; and - the acid treatment step is optimized by process conditions such that a high temperature, above 70 ° C, a long retention time, greater than 6 hours, and a pH between 4.5 and 7 are used during the acid treatment.

Use of a lignin component obtained by a method according to any one of claims 1 to 15, wherein the lignin component is used as a component in the preparation of a final product selected from the group consisting of activated carbon, carbon fiber, binder material, phenol, dispersant.

A product containing a lignin component obtained by the process of any one of claims 1 to 15.

The product of claim 18, wherein the product is selected from the group consisting of: activated carbon, carbon fiber, lignin composite such as lignin plastic composite and lignin fiber composite, binder material, phenolic component, dispersant and combinations thereof.