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玉米秸秆炭和典型农业废弃物混合成型与燃烧特性试验

Experiment on combustion characteristic and densified biomass pellets from maize stalk char mixing typical agricultural wastes

  • 摘要: 以玉米秸秆炭和玉米秸秆、苹果枝、沼渣、菌渣为原料,在成型压力为6 MPa的条件下,研究了不同混配比例混合燃料的成型特性,并在此基础上探讨了特定混配比例下的混合样品燃烧特性。研究结果表明:农业废弃物质量分数、种类对混合成型燃料稳定性均有影响,农业废弃物占70%比例时混合成型燃料的抗跌碎强度均大于99.50%;玉米秸秆对成型燃料的稳定性影响最为明显,其质量分数大于30%时,成型燃料抗跌碎强度达到99.68%以上,而沼渣和菌渣质量分数大于50%时,其成型燃料的抗跌碎强度分别超过99.11%和99.71%;苹果枝质量分数大于60%,其成型燃料抗跌碎强度超过99.34%;4种成型燃料的能量密度与原料相比分别提高14.93、11.36、11.74、14.53 GJ/m3;堆积密度分别提高792.99、596.92、605.63、820.12 kg/m3。该研究为农业废弃物新型成型燃料的开发提供了基础支撑。

     

    Abstract: Renewable energy, often referred to as clean energy, become necessary in recent years, as the consumption of fossil energy has worsened the environment and global climate. The rich agriculture resources in China can be expected to achieve the typical renewable energy for the sustainable development. Normally, biochar can be used as adsorbing materials, catalyst carrier and fuel, due to its abundant pore structure. This study aims to investigate the combustion characteristic of a molding fuel that fabricated by maize straw char and agricultural wastes. Four kinds of agriculture wastes were selected as adhesive, including the maize stalk, apple tree branch, biogas residue and mushroom dreg, and then molded with maize stalk char to manufactured by a hydraulic granulating machine. The maize stalk char was produced by the slow pyrolysis at 550℃, with the heating rate of 3℃/min. The pressure of all the pellets was 6 MPa, while the content of agriculture waste was 10%-70% in weight. The drop test machine was used to examine the crush resistance of molding fuel and agriculture waste pellets. The results showed that the combination properties of molding fuel depended strongly on the type and content of agricultural wastes during densification. Furthermore, the mechanical strength of molding fuel increased with the increase of agricultural waste content. The durability of molding fuel particles reached 99.68%, when the content of agriculture waste was 70%, with an emphasis on the content of maize stalk. In addition, a chamber with constant temperature and humidity was used to explore the water absorption characteristics of the densified biomass pellets. The water absorption characteristics of molding fuel can be ranked in order, AB70, MD70, MS70, BR70, lower than four kind of agriculture waste pellets. Scanning electron microscope was used to characterize the binding mechanism of molding fuel. The surface of molding fuel became more smoothly as the combustion proceeded. The lignin was regarded as the major component of binder in the process of molding. The thermogravimetric analyzer was used to analyze the combustion characteristics of the molding fuel. The energy density and bulk density of MS70 improved by 4.25 times and 5.06 times, respectively, compared with other agriculture wastes. It infers that the molding fuel can be beneficial to the storage and transportation of agriculture wastes. The energy density of molding fuel MS70, AB70, BR70, MD70 improved to 14.93, 11.36, 11.74, 14.53 GJ/m3, respectively, compared with AW materials. Two kind of ideal molding fuel MS70 and BR70 were achieved the optimal performance. The combustion characteristic index of all the molding fuel were higher than that of biochar, whereas, the ignition temperature of each molding fuel was lower than that of biochar. Therefore, the mix molding of agricultural wastes and biochar can be a great efficient approach to improve the utilization of agriculture wastes. The research can provide a new promising reference for the comprehensive utilization of agricultural waste, as well as molding fuels.

     

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