Jiang Yang, Qu Jingxia, Guo Jun, Liu Rixin, Zhang Dalei
Abstract: The technical conditions, equipment system and actual operation of biomass fuel pellets produced at ambient temperature were analyzed. The effects of compression ratio, raw material type and moisture content of raw material on the density of pellet fuel were studied. Density pellet fuel under the condition of lower energy consumption.The research work laid the foundation for the development and industrial application of biomass pellet fuel technology.
0 Foreword
In the recent years, biomass pellet fuel production has attracted great attention and widespread concern, the national renewable energy industry development plan And related policies have also played a huge role in promoting the application of biomass pellet fuel.
The key to produce biomass pellet fuel is to have a good performance and simple operation of pellet fuel production equipment.In this paper, homemade biomass pellet fuel equipment, the study of corn stalks, bean stalks, rice husk, reed and other four kinds of raw materials at room temperature molding Conditions, access to a series of development of production equipment and the production of particulate fuel has the guiding significance of the law.
1 test
1.1 test equipment and sources of raw materials
Test equipment used in Liaoning Province Institute of Energy developed BIO-C37 biomass pellet machine.
According to the production capacity of molding equipment and the requirement of raw material granularity, the material of corn stalks, bean stalks, reeds and other materials are crushed, the size of the crushed material is less than 10mm; the sawdust, rice husk and other materials can be directly molded without further crushing. The four kinds of raw materials of corn stalk, bean stalk, rice husk and reed were taken from Yingkou area of Liaoning Province and the sawdust was the waste of wood processing plant in Dalian. The corn straw, rice husk and bean stalk were all produced from the previous year, Are produced in the current year.
1.2 test content
① Five kinds of raw materials, corn stalks, rice hulls, sawdust, reed, and bean stalks, were used to test the effects of various raw materials under the conditions of ring compression ratio (pressure 25 ~ 65Mpa) of 3.5, 4.0, 4.5, Molding conditions, projected particulate fuel molding trend.
② The appearance quality, density and drawing characteristic curve of molded pellets were tested under the condition of 3.5, 4.0, 4.5, 5.0, 5.5 of compression ratio of ring mold with corn stalks, rice hulls, sawdust, reed and bean stalks , To determine the quality of various types of raw materials molding, density and ring compression ratio relationship.
③To determine the optimum molding ring compression ratio, the energy consumption of the plant system was tested by using 9%, 12%, 15%, 18%, 21% corn stalks and reeds as raw materials, Appearance quality, density, draw the characteristic curve, to determine the most appropriate moisture range of this type of crop straw molding.
(4) The corn stalks and reeds with 4 kinds of particle size (more than 10mm, 5 ~ 10mm, 1 ~ 5mm, less than 1mm) were tested under the conditions of determining the optimum molding ring compression ratio and the optimum moisture content. Appearance of the product quality, density, to determine the most suitable crop straws forming the size range.
2 results and discussion
2.1 biomass pellet fuel forming principle analysis
Loosely structured, less dense biomass materials subjected to external forces, the material will undergo rearrangement position, mechanical deformation, elastic deformation, plastic deformation phase of non-elastic or viscoelastic cellulose molecules intertwined and twisted between, So that the material is reduced in size and density (Figure 1).
2.2 Different biomass materials under the same compression ratio molding conditions
Figure 2 is the corn stalk, reed, bean stalk, sawdust particle fuel density and compression ratio of the relationship between the material can be seen from Figure 2, corn stalks and reeds forming particles required to achieve a higher density of the same compression ratio; sawdust Larger compression ratios are required for the shaped particles to reach higher densities, reflecting the differences in the organizational structure and composition of different types of biomass materials, which are mainly composed of cellulose, hemicellulose, lignin and the like, Lignin is a natural polymer compound with three-dimensional structure composed of benzenepropane structure monomer, lignin hardly dissolves in water and common organic solvent and does not soften under heating condition at room temperature, and its content Which has little effect on material forming.Cellulose is one of the main components of plant cell wall and it is a linear polymer composed of glucose.The higher the content of cellulose, the more advanced the mechanical organization of plant cells, the greater the need of particle formation pressure.
The cellulose content in the biomass determines the ease of forming at room temperature.The analysis of the cellulose content of the biomass material validates the test results (Table 1).
Ring mold compression ratio determines the size of the molding pressure of corn stalks, reeds and other raw materials less cellulose content by the external force easily deformed when squeezed, so the molding ring mold required for compression ratio is small, that is, forming pressure than Small; sawdust cellulose content is high, the molding ring mold required when the compression ratio is large, that is, the molding pressure is greater.Therefore, the use of different biomass raw material for the production of pellet fuel should be used in the ring compression ratio, the raw material fiber Biomass material close to the content of the same compression ratio ring mold.
2.3 The same biomass in different compression ratio ring mold forming analysis
Various materials in different compression ratio ring mold forming test and calculation data in Table 2 ~ 4.
As can be seen from Tables 2 to 4, with the increase of the ring mold compression ratio, the particle density increases, the energy consumption increases, and the yield increases for several of the above raw materials. When a certain compression ratio is reached, the density of the shaped particles increases Small, energy consumption increased correspondingly, but the yield decreased.Experiments showed that soybean straw as raw material, the compression ratio of 4.0 ring mold; corn stalks as raw material, the compression ratio of 4.5 ring die; sawdust Raw materials, the use of compression ratio of 5.0 ring mode, the density of particulate fuel can meet the quality requirements, and equipment, lower energy consumption.
The same raw material in different compression ratio ring mold, the density of particulate fuel increases with the compression ratio increases gradually, and in a certain range of compression ratio, the density remained relatively stable, when the compression ratio increased to a certain extent, Due to the pressure is too large, the raw material can not be discharged easily and can not be formed. Due to the large size of the rice husk and the high ash content, the rice husk is hard to form granules. For the same material, to obtain larger particle density, Larger ring die compression ratio.
2.4 raw material size of the molding conditions
As shown in Table 5, with the increase of particle size of corn stalks and reed raw materials, the density of the formed particles gradually decreases, and when the particle size of raw materials is more than 10mm, the forming effect is very poor , Even if the raw material particle size is too small, it will also affect the density of the particles.Therefore, it is more appropriate to keep the particle size at 1 ~ 5mm when the biomass fuel such as corn stalks and reeds is used as raw material.
2.5 Raw material moisture on the density of particulate fuel
Material particle density and moisture content of the relationship shown in Figure 3, Figure 4. Can be seen from Figure 3, Figure 4, with the increase of moisture content of the material, the density of the formed pellet fuel increases, when reaching a certain appropriate At the moisture content range, the density of the pellet fuel reaches the maximum and remains relatively stable. When the moisture content of the feedstock increases to a certain extent, the density of the pellet fuel begins to drop, eventually resulting in un-shaping.
The organism has an appropriate amount of bound water and free water in the body, which has the function of a lubricant to reduce the internal friction between the particles and enhance the fluidity so as to promote sliding and fitting of the particles under the pressure. When the water content of the biomass raw material When the rate is too low, the particles are not fully extended, and the particles are not close enough to the surrounding particles, so the particles can not be formed. When the water content is too high, the particles can extend between the particles in a direction perpendicular to the maximum principal stress, As the raw material more water is squeezed out, distributed between the particle layers, making the particle layer can not be close fit, and therefore can not be molded.
Therefore, with corn stalks, reeds and other biomass as raw material for pellet fuel production, the moisture content of raw materials should be maintained at 12% to 18% is more appropriate, the best moisture content of 15%.
3 Conclusion
At room temperature, biomass materials in the compression molding process, the particles after deformation in the form of intermeshing with each other, and particle layers in the form of mutual bonding between the combination of raw materials in the cellulose content determines the ease of molding , The higher the content of cellulose, the easier the forming.The particle size and moisture content of raw materials have a significant impact on the molding conditions, particle size of 1 ~ 5mm, moisture content of 12% ~ 18%, the maximum production of particulate fuel density.
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