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.
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)
- Plastics (thermoplastics, elastomers, wax)
- As additive for foam (PU foam, aerogels)
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.
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
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.
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.
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
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
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
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
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
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.
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.
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.
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.
- Flexible setting of granulate size possible
- Stable granulates
- Very low proportion of dust in the granulate
- Stable process
- No addition of additives required
- Low specific energy input
- High system availability
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.
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