3-4T/H Straw Pellet Production Line In Vietnam

Vietnam Energy Company has once again partnered with Durable Machinery for the purchase of a straw pellet machine production line. This order includes a straw pellet machine, crusher, crushing equipment, dryer, cooler, packaging equipment, and other necessary supporting machinery.

In order to increase production capacity and expand market share, Vietnam Energy Company customized a 3-4T/H straw pellet production line. Due to the excellent performance of our biomass pellet production line, the Vietnamese customer decided to choose to cooperate with us again.

The production line for our straw pelletizing equipment creates straw pellets that serve as fuel and can be further processed into biomass fertilizer.

Being a national high-tech enterprise, our developed and manufactured straw pelletizer boasts stable operation, low consumption and high energy efficiency, environmental friendliness, energy conservation, and a high molding rate.

Straw

Straw refers to the residual stems and leaves (including ears) of mature crops, typically the remaining portion of wheat, rice, corn, potato, rapeseed, cotton, and sugar cane after the seeds have been harvested. More than half of a crop’s photosynthetic products are found in straw, which is rich in nitrogen, phosphorus, potassium, calcium, magnesium, and organic matter. It serves as a versatile renewable biological resource and is also used as roughage. Straw is characterized by a high crude fiber content (30%-40%) and contains lignin and other components. While pigs and chickens cannot utilize lignocellulose, ruminant cattle, sheep, and other livestock can absorb and utilize it.

The application of straw

In the United States, approximately 45 million tons of straw are collected annually from 24 agricultural states. This straw is utilized as feed and in construction, where high-strength compression is used to fill the walls of new houses with whole bundles of straw. Furthermore, the U.S. actively promotes the use of straw as an alternative fuel, particularly in biofuel production.

In Europe, there has been the development of a new method for power generation using straw.

In Japan, straw is predominantly turned into soil to be used as fertilizer and is also utilized as roughage to feed livestock.

As of 2017, China’s theoretical straw resources reached 1.02 billion tons, showing an increase of nearly 400 million tons compared to the early 1990s. Corn, rice, and wheat straw accounted for 430 million, 240 million, and 180 million tons respectively, with these three major crops making up 83.3% of the straw resources. China’s collectable straw resources amount to 840 million tons, with approximately 700 million tons being utilized. The comprehensive utilization rate of straw stands at over 83%, with fuel, raw material, and base material utilization rates at 47.3%, 12.7%, and 19.4% respectively. Additionally, a comprehensive utilization pattern has been formed, based on fertilizer, feed, and other agricultural uses.

The main characteristics of straw:

Straw typically consists of 80-90% cells and 10-20% lumen, with the internal material containing 5-10% silica and 5-15% extract, predominantly water-soluble. At a molecular level, straw cell walls resemble wood cell walls, comprising cellulose, hemicellulose, and lignin. Cellulose forms aggregates in fibrils surrounded by molecules, while lignin serves as the “glue” connecting individual cells to form plant tissue and fibrils to form cell walls. Straw differs from wood in its cellulose, hemicellulose, and lignin content; it has low cellulose and lignin content but high hemicellulose content.

Due to its wood-like composition, straw can be used to produce straw pulp or be converted into straw pellets. Considering the unique properties of straw, the granulation process can be summarized as follows:

1. Raw material preparation stage:

The potential for high dust content in straw is often influenced by the harvesting method. Therefore, it’s important to screen the straw to remove pollutants such as dust and foreign objects like stones and metals, which could otherwise compromise the quality of the straw pellets and potentially damage the pellet mill during subsequent procedures.

2. Crushing stage:

Straw biomass typically has a tubular structure with a diameter of 4-8 mm and a wall thickness of approximately 0.3-0.6 mm. This tubular structure allows for easy processing to achieve the desired particle size. The process of grinding straw generally involves cutting and crushing it.

Regarding the drying stage, straw is usually transported in the form of air-dried bags with a moisture content of around 15%, which is suitable for producing straw pellets. Therefore, the drying process for straw pellets is not needed. However, if the straw has a high moisture content, the drying step becomes necessary.

3. Modulation

To achieve the ideal hardness, straw requires special conditioning, which involves the application of steam (and/or water) and the addition of binders or additives. Conditioning is necessary to attain the appropriate temperature and humidity for malleability and to melt the lignin in order to act as a binder. Binders are essential to enhance the hardness of the granules and minimize abrasion during granulation.

4. Granulation

In the granulation process, it’s important to consider the impact of material moisture, density, particle size, fiber strength, natural adhesives, and other factors on the quality of granulation.

Common issues encountered during the pelletizing process of straw pellets include clogged and broken pellet molds, overheating, high energy costs, poor pellet quality, and increased pellet mill maintenance. To prevent these problems, a high-quality granulator is essential.

5. Cooling and screenin

After extrusion, the freshly formed straw particles are hot and soft, requiring cooling to achieve the desired hardness. Simultaneously, a sieve is used on the cooling machine to separate out particles that do not meet the required molding standards.

6. Finished product packaging

The cooled granules must be transported to the finished granule bin using a specialized skirt belt conveyor, and subsequently unloaded from the bin and packed using a packaging scale.

Application of straw pellets:

Straw pellets have various practical applications in daily life. They are commonly used as animal bedding, animal feed, and as a source of heating fuel for both domestic and industrial purposes.

The widespread application of straw pellet technology and the global availability of straw pellet machines have contributed to the popularity of straw pellets in heat and power production.

The production process of straw pellets:

The straw solidification molding technology utilizes agricultural waste such as rice straw, wheat straw, and corn straw as raw materials, compressing them into solid biomass fuel for direct burning through specialized equipment like the straw pellet machine using crushing and compression processes.

The process involves:

1. Cutting or pulverizing the straw into lengths below 30mm using a rotary cutting and pulverizing machine.
2. Sending the crushed straw to the drum dryer via a conveyor to control its moisture content within the range of 10-15%.
3. Storing the dried raw materials after unloading sacron, or storing them in a silo.
4. Feeding the material from the storage to the biomass pellet machine through a conveyor. The machine drives the pressure roller to rotate, forcing the material to be extruded from the mold hole into a block, which falls from the exit.
5. Sending the formed pellets to the pellet cooler via a special conveyor.
6. After cooling, packaging the pellets using a packaging scale or ton packing machine for bagging.

The resulting biomass pellet fuel has high specificity, small volume for convenient storage and transportation, and a calorific value of 3200-4500 kcal. It is characterized by flammability, low ash content, and cost-effectiveness, making it a versatile replacement for firewood, raw coal, and other fuels in heating, domestic stoves, industrial boilers, and biomass power plants.

As a new commercial energy source, straw pellet fuel has found widespread application in various industries. Its high density, calorific value, regular shape, and good fluidity enable convenient automatic combustion control, leading to substantial energy cost savings for enterprises.

Precautions for pellet processing:

1. Operators should carefully read the instruction manual and be familiar with the various technological processes of the equipment before using the machine.

2. During the production process, it is necessary to operate strictly in accordance with the regulations and sequence, and perform installation operations according to its requirements.

3. The host equipment needs to be installed and fixed on the horizontal concrete floor, and the screws should be tightened.

4. Smoking and open flames are strictly prohibited in the production site.

5. After each start-up, it needs to idle for a few minutes first, and confirm that the pressure roller fits the mold and rotates before feeding.

6. It is strictly forbidden to add hard debris such as stones and metals to the feeding device, and remove iron before granulation to avoid damage to the granulation chamber.

7. During the operation of the equipment, it is strictly forbidden to use hands or other tools to remove materials to avoid danger.

8. If there is abnormal noise during the production process, the power supply must be cut off immediately, and the machine can be started to continue production after checking and handling the abnormal situation.

9. Before shutting down, first stop the auxiliary feeding, and then put in the oil, and wait until the mold hole is filled with oil and the granulation chamber is empty of oil before shutting down. The purpose of feeding oil is to make it easier to discharge during the next production.

Correctly operate the pellet machine as required, and pay attention to relevant matters as required, not only can improve the output and operating performance of the equipment, but also prolong the service life of the equipment.