Lignin

Individual processes for compacting and grinding

Lignin is an organic polymer and, alongside cellulose and hemicellulose, a component in wood. Here it has an impact on the lignification of the cell and the compressive strength and durability of the plant tissue. Overall lignin accounts for around 20 to 30 percent of the dry matter of ligneous plants. Previously, this natural raw material was regarded as a by-product produced during the manufacture of pulp or bioethanol and has scarcely been used industrially to date. In fact lignin is versatile and can actually be used for the various end products – from batteries to cosmetics. For this, the lignin must be present either in the form of fine powder or granulate so that it can be ground or compacted. Hosokawa Alpine has developed innovative processes for both these procedures.

What types of lignin are there?

Kraft lignin and sulphur-free lignin and their uses

Lignin can be acquired by means of various different chemical procedures including the sulphate and sulphite procedure, the soda procedure, Acetocell procedure or the organosolv procedure. Depending on the process, the lignin acquired has different chemical and procedural properties. For the subsequent processing, a primary distinction is made between kraft lignin from the sulphate and sulphite process and sulphur-free lignin from other procedures. Depending on the manufacturing procedures and quality of the lignin, it can be used in the following application areas:

Carbon fibres
Hard carbon for battery anodes
Animal feed
As a building block for the chemical industry
Replacement carbon black for rubber (tyres)
Resin
Plastics (thermoplastics, elastomers, wax)
As additive for foam (PU foam, aerogels)
Cosmetics

Processing lignin

Individual solutions necessary

Lignin is therefore an extremely versatile raw material Its natural source however means that its quality is subject to strong fluctuations – since not all woods are identical. The manufacturing process also influences the properties of the raw material: Its properties will vary depending on whether the lignin is acquired during the manufacture of pulp or paper or in bio refineries.

For the processing of lignin this means: There is no standard solution for the grinding or compacting of lignin. Depending on the initial product and end usage, an individual process is therefore required and Hosokawa Alpine would be delighted to be able to develop this for you.

Different types of lignin in transparent jars — Lignin is a natural raw material whose quality is subject to strong fluctuations.

For the processing of raw lignin, there are various processes, which lead to different lignin qualities and depend not just on the desired application but on the type of lignin too: By grinding with a classifier or jet mill and subsequent classification, customers will obtain a premium quality lignin powder. By compacting (granulation/briquetting) a dust-free granulate or briquette will arise with good flow characteristics and a high bulk density

Which process for which lignin?

	Kompaktor	Classifier mill	Jet mill	Classifier
Kraft-Lignin	✓	×	×	×
Biorefined Lignin	✓	✓	✓	✓
Carbonised Lignin	×	×	✓	✓

Cooperation with Lignopure

Working together for a strong solution

The Hamburg start-up Lignopure GmbH is a pioneer for the incorporation of lignin into consumer products. We are bundling our knowledge together with this application expert and will develop a specific process for you for your required application

For this, Lignopure analyses the initial material but also the requirements of its end use. Based on this, they will determine how lignin has to be modified in terms of its particles in order to obtain an optimal end product. In turn, Hosokawa Alpine, as a machine and system builder, possesses the required know-how and technologies to process lignin with the required properties as best as possible. In this way we will support you in finding the right technology for your requirements and obtaining an optimal lignin granulate or powder.

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Grinding of lignin

Powder with outstanding properties

To grind lignin, there are two types of suitable mill: With the jet mill AFG, you will obtain a high degree of fineness where d₉₇ = 5–15 µm. By the use of high grinding energy, fibrous raw materials can also be milled. With a classifier mill like the ACM, you will obtain a coarser target product with a fineness of d₉₇= 10–25 µm. Mechanical milling is a highly energy-efficient process.

Grinding with jet mill AFG

1 Material feed 2 AFG Fluidised bed opposed jet mill 3 Filter 4 Blower 5 Final product

Your benefits with AFG jet mill:

High degrees of fineness
Sharp and easily adjustable separation line
Fibrous materials can be ground
Low wear
Contamination-free product handling possible due to the ceramic lining of the complete system

Grinding with classifier mill ACM

1 Material feed 2 Classifier mill ACM 3 Process air 4 Filter 5 Blower 6 Final product

Your benefits with ACM classifier mill:

Low specific grinding energy
Sharp and easily adjustable separation line
Flexible production parameters for setting the grinding fineness
Compact, space-saving construction

Grinding with jet mill Microburst AMB

Microburst AMB jet mill is ideal for use in a lab and can also grind coarse or fibrous products extremely finely without any preliminary crushing.

Your benefits with jet mill AMB:

Also suitable for coarse and fibrous products
Extra fine grinding is possible without any preliminary crushing
Very high degrees of fineness can be obtained
Simple explosion protection concept
Modular set-up
Easy to clean
Baseline version also available for stand-alone use

De-dusting with wind classifier ATP

In order to obtain a steeper particle size distribution, classification with wind classifier ATP is recommended for:

De-dusting at 2-3 µm
Top grain classification at 20-30 µm

De-dusting ensures you obtain a dust-free product with optimised flow capabilities. In addition you can ensure a sharp separation line by classification of top grain and remove the agglomerates. The steep separation curve also leads to a high product yield This premium value powder is ideal, among other things, for premium quality plastics, foams or cosmetics.

1 Material feed 2 ATP air classifier 3 Process air 4 Filter 5 Blower 6 Coarse fraction 7 Fine fraction

Why Hosokawa Alpine?

Machines and systems by Hosokawa Alpine ensure stable processes and a high level of system availability. This reduces downtime considerably and ensures smooth-running production with a high level of product quality. Our many years of experience in processing involving natural products and explosives means we possess a high level of expertise in the area of explosion protection

Up-valuation of lignin

Optimisation of product characteristics by compacting

Fine lignin powder is explosive, has poor flow characteristics and a low bulk density. For this reason product handling is complex, occupational health and safety is cost-intensive and large warehousing areas are required. The solution to these challenges lies in the granulation or briquetting of liginin powder.

Granulation of lignin with a special compactor design

By using a roller press, you will obtain a dust-free ligin granulate or briquette with a constant, very high product quality, higher bulk density and good flow characteristics. This is subsequently not only better for further processing but for storage and transport too. In addition, there is less risk of a dust explosion or contamination meaning fewer measures are required for employee and environmental protection. Due to this refinement of lignin, a higher market price can then be attained.

During granulation, the material is initially dosed evenly into the compactor. In the compactor, it is compressed to a scab by two counter-rotating wheels. Subsequently the scab is broken down to the desired particle size by an optional pre-crusher and a roller crusher.

Briquetting lignin

During briquetting, the raw material is compressed to the desired shape. Subsequently, dust and bars are sifted out and fed back into the process. Should water or other additives be necessary to manufacture stable briquettes, a mixing unit will have to be switched upstream of the compactor.

Your benefits with compactor systems by Hosokawa Alpine

With our compactor systems, you obtain the best from product and system. Since all system components are obtained from a single source, machines and processes are perfectly coordinated to one another.

Application-related advantages:

Flexible setting of granulate size possible
Stable granulates
Very low proportion of dust in the granulate

System-related benefits:

Stable process
No addition of additives required
Low specific energy input
High system availability

Explosion protection

Lignin typically occurs in dust explosion class St 2, meaning there is a considerable risk of explosion during processing. To protect personnel and system and comply with safety standards, three basic measures are suitable:

1. Avoiding effective ignigion sources

Equipment and measuring devices are designed in such a way that sources of ignition cannot occur. Whether this method can be used depends on the material and equipment.

2. Pressure-shock-resistant design

With its pressure-shock-resistant design, the design of the system is so stable that no external damage can arise even in case of the maximum explosion pressure. In case of large systems, a lower explosion pressure is possible via a pressure-relief or extinguishing system. The advantage of this is that no nitrogen is required and subsequently running costs can be reduced.

3. Inertisation

During inertisation, the oxygen content inside the system is reduced so greatly that no explosion can occur. Oxygen concentration can be continually monitored. By means of a circulating gas process, nitrogen consumption can be reduced.

Explore more: Hosokawa Alpine and Lignopure announce collaboration | Case Study: Lignin - from process consulting to turnkey systems