两种机械处理方式对生物质原料反应性能的影响

Effects of two different mechanical pretreatment methods on reactivity of biomass raw materials

减小生物质原料粒径是提高生物质精练过程中组分分离效率的关键步骤,生物质粒径的大小以及不同机械处理方式对原料反应性能的影响尚不明确。本研究对比了机械粉碎与双螺杆挤压机联合盘磨处理获得物料的反应性能,结果表明:机械粉碎物料受到剪切力作用,长度变短导致粒径变小,纤维仍然呈紧密的束状结构;随着粒径减小,比表面积与吸液能力随之增加,反应性能越好,粒径小于0.18 mm的物料反应性能最优。双螺杆挤压机联合盘磨机利用剪切力、摩擦力、挤压力使物料纤维微纤丝化,打开了部分闭合纹孔。与粒径小于0.18 mm的粉碎机粉碎物料相比,双螺杆挤压联合盘磨获得的物料比表面积提高了31.54%,吸液能力提高了43.46%;过氧化氢预处理时,木质素去除率提高31.93%,预处理后酶解葡萄糖得率提高54.19%。实验表明,双螺杆挤压机联合盘磨处理比机械粉碎更利于提高生物质反应性能。

Lignocellulosic biomass is composed of carbohydrates(cellulose and hemicellulose), lignin, and other extraneous components(proteins, lipids, and inorganic substances). It is a renewable and abundant resource suitable for production of bio-based products such as biofuels and chemicals. The recalcitrance nature of biomass hampers its chemical reaction property, as well as polysaccharide accessibility for enzymes and microbes. Several pretreatment methods have been developed for the conversion of lignocellulosic biomass into value-added products. In order to achieve high efficiency of pretreatment technology, wood flour with particle size less than 850 μm is mostly crushed by a pulverizer and the specific surface area of biomass is improved by reducing particle size. However, it is difficult to use a pulverizer to smash on the industrial scale production. To overcome this difficulty, useful lessons can be learned from the traditional thermo-mechanical pulp industry, which has been combined a twin screw extruder with a disc mill to reduce the size and dissociate fibers of biomass. The size reduction of biomass is an energy extensive operation for biorefinery, and the effect of size and physical pretreatment process on biomass fractionation is pressing to be un-raveled. Herein, the reaction properties of wood particle size produced by the pulverizer and materials produced by two-screw extruder combined with a disc refiner were investigated. The fiber length of materials produced from the pulverizer was cut by shear force, and then particle size became smaller, while fibers still presented a compact structure. Smaller size had better reaction performance due to their large specific surface area and favorable liquid absorbability. Particle size less than 0.18 mm had the best reaction performance, and the degradation rates of the three chemical components were the highest after the same chemical pretreatment. Materials produced by a twin screw extruder combined with a disc mill(TSE-DM) could promote micro-fibrillation, some fine fractures were found at the weak parts of the cells, followed by the shear force, friction force, and extrusion force, which increased specific surface area and liquid absorption capacity. Compared with the particle size of less than 0.18 mm, the specific surface area of materials from the TSE-DM process increased by 31.54%, and the liquid absorption capacity increased by 43.46%. While alkaline hydrogen peroxide was used for pretreatment, the removal rate of lignin increased by 31.93%, and the glucose yield increased by 54.19% during the enzymatic hydrolysis process after the alkaline hydrogen peroxide pretreatment. Compared with the pulverizing process, the TSE-DM process could improve the reaction performance of biomass, which is beneficial to the separation and application of biomass components.