Judging whether the lignin content of biomass briquette raw materials is suitable mainly depends on the type and content range of raw materials. You can make a quick judgment by the following steps:

First, look at the type of raw materials: qualitative judgment

The lignin content of different raw materials is very different, which directly determines the difficulty of making briquettes(biomass briquette machine):

High-quality raw materials (suitable for briquette making): wood (such as sawdust, shavings, branches). This kind of raw material has high lignin content (usually 25%-30%) and is a natural “glue”, which is easy to soften and bond at high temperature and high pressure, and the prepared bar has high density and good strength.

General raw materials (process needs to be adjusted): straw (such as corn straw and wheat straw). Lignin content is moderate (about 15%-25%). Although it can also be made into briquettes, it usually needs finer crushing and stricter water content control, or needs to add a small amount of adhesive to assist molding.

Difficult raw materials (unsuitable or need to be modified): rice husk, peanut shell, etc. This kind of raw material has low lignin content (about 15%-20%) and high ash content. Ash does not melt at high temperature, which will hinder the bonding of lignin, resulting in loose and fragile bars. Usually, a large number of binders or chemical modifications are needed to form them.

Second, look at the content value: quantitative standard

For briquette making technology, the higher the lignin content, the better, but there is a suitable range:

Ideal range: 20%-30%. Within this range, under the action of high temperature (usually 200-300℃) of the briquette making machine, lignin can be fully softened and melted, generating enough viscosity to bond the fiber particles together, and after cooling, a hard rod is formed.

Critical value: less than 15%. If the lignin content of raw material is less than 15%, it is usually difficult to form by its own viscosity, and the problem of “no stick” or “loose stick” is easy to occur in the process of making sticks, so an external adhesive must be added.

Third, look at the auxiliary indicators: comprehensive evaluation

In addition to lignin content, ash content and moisture content are also key indicators to determine the success or failure of briquette making, which must be evaluated simultaneously:

Ash content: less than 5% is required. Ash is the inorganic substance (such as silicon dioxide, calcium oxide, etc.) left after the combustion of raw materials, and it does not participate in bonding. If the ash content is too high (for example, the ash content of rice husk can reach 15%-20%), it will hinder the bonding of lignin like sand, resulting in extremely poor strength of the briquette.

Moisture content: 10%-15% is required. Moisture is the “catalyst” of lignin softening, but too much moisture will reduce the temperature, affect the melting effect of lignin, and lead to surface cracking of the briquette.

Fourth, simple judgment method

If you don’t have professional testing equipment, you can make a preliminary judgment by the following methods:

Combustion method: ignite a small amount of raw materials and observe the ashes after combustion. If the ash is white or grayish white powder, it means that the ash content is low and the lignin content may be high; If the ash is a black lump or a large number of black particles remain, it means that it is difficult to make briquettes with high ash or low lignin content.

Touch method: rub the raw material powder by hand. If you feel strong fiber sense and toughness, it is usually wood with high lignin content; If it feels crisp, fragile and sandy, it is usually rice husk or peanut shell with high ash content.

Summary: For making briquettes, wood raw materials (sawdust and shavings) are the best choice, and their lignin content is naturally suitable for making briquettes. However, straw requires strict control of technology; rice husk usually needs to be added with adhesive or mixed with other raw materials.