China is a large agricultural country, producing approximately 700 million tons of various straws annually, equivalent to about 350 million tons of standard coal. The resources are abundant and can serve as high-quality new energy resources. Compared with fossil energy sources such as coal and oil, its advantage lies in the renewability of straw, low sulfur content, and essentially no sulfur compound pollution during combustion. At the same time, straw utilization is a zero carbon dioxide emission process. Therefore, under the current background of maintaining rapid economic development while promoting energy conservation and emission reduction, the efficient utilization of straw resources is of great practical significance.
Straw is widely distributed, with concentrated production periods, low bulk density, and various shapes. Therefore, using straw directly as fuel still faces some difficulties. In particular, large-scale collection, long-distance transportation, and long-term storage of straw all have high cost issues. Compressing straw into high-density molded fuel is an effective method to solve the above problems. It can achieve fuel standardization and equipment automation, greatly increase fuel transportation radius, improve raw material storage and cleaning performance, and transform scattered, difficult-to-use straw into high-quality, clean, collectible, transportable, and storable commercial energy. Currently, biomass molded fuel utilization has received high attention from the state. China's Renewable Energy Medium and Long-term Development Plan proposed achieving annual consumption of 5 million tons of pellet fuel before 2010, and achieving annual consumption of 50 million tons of pellet fuel by 2020.
Status of Straw Pellet Molding Technology
To achieve commercial utilization and energy substitution of low-quality straw-type biomass resources, many Chinese universities and enterprises have conducted research on biomass molded fuel technology, bringing molded fuel technology and industry into a growth period. A large number of enterprise groups have been formed, beginning to play a role in straw resource energy application and environmental protection. Most of these technologies and products are based on imported foreign products as prototypes, from early rod-shaped fuel molding machines to ring die pellet fuel molding machines and ring die block fuel molding machines, developing very rapidly. Due to the large production capacity and relatively low power consumption of ring die block fuel molding machines, they have become the mainstream of current biomass molding machinery.
Straw Pellet Molding System
The straw pellet molding unit consists of a crusher, material conveyor, compression molding machine, finished product conveyor, cooling air dryer, weighing and bagging machine, etc. First, the straw is naturally dried to a moisture content of 15%-25%, then crushed by the crusher into small particles within 3 centimeters. Through the material conveyor, it is sent to the compression molding machine. Under the action of mechanical pressure, utilizing the viscosity generated by the lignin in the straw when heated under pressure, the straw is compressed into molded fuel. After cooling, it serves as commercial energy that can replace coal.
Economic and Social Benefits
Through continuous improvement, the energy consumption of ring die molding machines has been reduced to within 50 kWh/t, and the continuous working time of ring die and grinding rollers has been improved to 1000 hours, basically meeting the conditions for economic production. In 2011, our province's straw molded fuel output exceeded 1 million tons, replacing more than 500,000 tons of standard coal, reducing carbon dioxide emissions by more than 1.3 million tons, increasing farmers' income by nearly 200 million yuan, and at the same time effectively reducing environmental pollution caused by field burning of straw, making significant contributions to our province's energy conservation and emission reduction.
