Turn waste into treasure: make pellet with forestry residues

With the continuous improvement of agricultural production modes, the agricultural production level is gradually raised, and the change of idea, a large number of forestry residues, firewood, and crop stalk backlog in rural areas. Idle or burning forestry residues not only cause serious pollution to the environment, but also cause huge waste of resources. How to make full use of forestry residues?

Forest residues pellet fuel is a new type of modern biomass fuel that is compressed by a biomass pelletizer (pellet mill and briquette machine) to compress residues from harvesting residues, bucking residues, and wood processing residues.

Market demand of biofuel pellet

1.     Domestic market:

Industrial raw materials: Many chemical companies, iron and steel enterprises, and electronics industries in China directly or indirectly use biomass pellet fuel as raw materials, and multi-party purchase can meet production needs.

2.     International market:

Japan, South Korea, Singapore, the United States, the United Kingdom, France, Australia and other countries have imported a large amount of charcoal and biomass pellet fuel, so the sales of the pellets are guaranteed.

3.     living needs:

Living heating can use biomass pellet fuel instead of coal burning, mechanism charcoal. The demand and prospect is promising.

Make pellets from forestry residues

At the beginning of the 20th century, biomass fuel technology has attracted widespread attention at home and abroad, and began related research and development. At present, China's processing technology for making pellet fuels from agricultural biomass such as straw, straw, and peanut shells has matured and has been initially industrialized. Forestry biomass materials are mainly woody, the internal structure is harder than agricultural biomass, and press forming is much more difficult. The forestry residue is mostly used to make biomass briquettes or bars, what about biomass pellet? In china, forestry biomass pellet forming technology is mainly based on sawdust and other processing residues, and some technologies need to add additives such as softeners and binders, and some technologies will use industrial waste such as sawdust, bamboo chips and papermaking waste liquid or agricultural biomass mixed into a mixture. 

Generally, pellets is made from forestry residues with pellet mill or pellet plant. As we all know, pellet mill is the core equipment of pellet production line, flat-die pellet mill and ring die pellet mill are two typical types of pellet making machine, we takes ring die pellet mill as an example.

Working principle of ring die pellet mill: The roller type ring die pellet machine consists of a pressure roller and a ring die. The ring die is driven to rotate by the driving mechanism, the ring die, material and pressure roller are mutually rubbed, the ring die drives the material to rotate, and the material drives the pressure roller to rotate around the pressure roller shaft. A tooth or groove on the outer circumference of pressure roller for increasing the friction between the pressure roller and the material, and simultaneously extruding the material into the formed hole in the ring die. The material extruded from the forming hole becomes a biomass pellet and is finally cut to the desired length with a cutter.

Notes for forestry residues pellet making

• The length-to-diameter ratio of ring die determines the forming pressure of the forestry residue. The larger length-to-diameter ratio of the ring die, the higher the forming rate. The lignin and cellulose content of the forestry residue are different, and the molding pressure of the pellet fuel is also different. The lignin content is proportional to the cellulose content.
• Within a certain range, the higher the water content is, the higher the molding rate is, but the excessive moisture content will deteriorate the molding effect.
• Within a certain range, with the increase of feed speed, the forming rate will increase, and the production efficiency will gradually increase, but the electricity consumption per ton of material will also increase gradually. However, the feed speed is not as high as possible. When the feed speed is too high, the molding machine is easily clogged, the power load is too high, and the molding machine is easily stuck. The feed rate during the formation of forestry residues is generally between 550 and 800 r / min.
• Different forestry residues are different, and the optimum molding process conditions for pellet fuel are various.
• The density of forestry residual pellet fuel is 1. 1 g/cm3 or more. In terms of calorific value, pellet fuels made from fir and pine has highest value, exceeding 17 800 kJ/kg. 

Advantages of forestry residues pellet making

• First of all, due to the shape of the pellets, compress the volume, save the storage space, the transportation is also facilitated, and reduce the transportation cost.
• Secondly, the combustion efficiency is high, it is easy to burn out, and the amount of residual carbon is small. Compared with coal, the volatile content is high and the ignition point is low, easy to ignite; the density is increased, the energy density is large, and the combustion duration is greatly increased, which can be directly applied to the coal-fired boiler.
• In addition, the biomass pellets have extremely low levels of harmful gas components when burned, and emit less harmful gases, which is environmentally friendly. And the burned ash can also be used directly as potash, saving money.
• Finally, the forestry residues are commonly recognizes as waste things, occupy the area and pollute the environment. Forestry residue pellet is an effective way to solve this problem, turn waste into wealth.