机械搅拌厌氧消化池流态研究

发布时间：2018-01-07 15:11

本文关键词：机械搅拌厌氧消化池流态研究　出处：《清华大学》2015年硕士论文　论文类型：学位论文

【摘要】：厌氧消化工艺可以同时实现固体废物处理和能源回收利用,在市政污泥、城市生活垃圾、餐厨垃圾、农业垃圾、禽畜粪便等固体废物处理中具有广泛的应用。厌氧消化过程是一个复杂的生物反应过程,混合效果对厌氧消化具有重要影响。目前对厌氧消化的研究主要集中在预处理、物料共消化,分级分相等旨在提高厌氧消化效率的技术手段方面,对厌氧消化反应器流场特性研究较少。在厌氧消化池设计中,对消化池池型和搅拌强度的选择主要依靠设计经验。本课题结合示踪实验和计算流体力学(CFD),对小试规模的反应器以及工程运行中的生产规模消化池,进行停留时间分布(RTD)和流态模拟研究。以机械搅拌厌氧消化池作为研究对象,通过对多种污泥浓度、搅拌方式、消化池池型条件下厌氧消化反应器的流态特征进行研究,揭示机械搅拌厌氧消化池内部流场的流态特征和变化规律,明确影响厌氧消化池流场的主要因素。为工程设计提供指导和依据。其中CFD模拟过程中以水作为模拟介质,因此模拟结果仅对低浓度消化物料有效。在小试实验中,通过对进料TS浓度分别为2.5、5.0和10.0 g/L的污泥厌氧消化反应器进行示踪实验,发现污泥浓度以及采用连续或间歇两种搅拌方式,对消化池运行和内部流态特征没有影响。通过CFD模拟对不同高径比(H/D)圆柱形和卵形消化池模型进行研究。结果表明,搅拌器形式和消化池高径比H/D对消化池流场特征具有显著影响。中心搅拌的圆柱形消化池,H/D增加时,消化池平均流速降低;侧入搅拌消化池H/D提高时,平均流速也随之提高。卵形消化池流态特征基本不受高径比影响。对四座运行中的大、中型厌氧消化池进行示踪实验。各厌氧消化池的示踪曲线和RTD曲线与理想CSTR曲线一致,消化池内部流态特征完全混合状态。各消化池内均存在一定比例的死区,但是物料的分散度都较高,基本不发生短流。顶入式中心搅拌厌氧消化池更接近CSTR反应器,侧入搅拌消化池偏离CSTR的程度高。CFD模拟结果显示,卵形消化池在中部混合效果较弱,圆柱形消化池内流场分布更加均匀。大型厌氧消化池宜采用大扭矩慢速搅拌器,不宜采用过高的搅拌转速和搅拌功率。
[Abstract]:Anaerobic digestion process can simultaneously achieve solid waste disposal and recycling of energy, in the municipal sludge, city garbage, food waste, agricultural waste, livestock manure is widely used in solid waste treatment. Anaerobic digestion process is a complex biological process, the mixing effect has important influence on the current research on anaerobic digestion. Anaerobic digestion is mainly concentrated in the pretreatment, CO digestion of material, technique means the classification phase. It is aimed at improving the efficiency of anaerobic digestion, anaerobic digestion of the reactor flow characteristics of less. In the anaerobic digester in the design of digestion tank and stirring intensity selection mainly depends on the design experience. The research combined with the tracer experiment and the computational fluid dynamics (CFD), the scale of production of digestion tank reactor of lab scale and project operation, of the residence time distribution (RTD) and flow simulation In order to study. Mechanical stirring anaerobic digester as the research object, through a variety of sludge concentration, stirring method, study on flow characteristics of anaerobic digestion reactor digestion pool conditions, reveal the mechanical pattern and the variation characteristics of the internal flow field of anaerobic digester mixing, clear main factors influencing anaerobic digester flow to provide guidance. And the basis for the engineering design. The simulation process of CFD simulation in water as medium, so the simulation results only for low concentration digestion materials effectively. In laboratory experiments, conducted by tracer experiment of sludge anaerobic digestion reactor to feed TS concentration were 2.5,5.0 and 10 g/L, sludge concentration and found that continuous or intermittent two mixing methods, has no effect on the digester operation and internal flow characteristics. Through CFD simulation of different ratio of height to diameter (H/D) and cylindrical digester model for research Study. The results showed that the agitator types and digestion tank height to diameter ratio of H/D had significant effects on the flow characteristics of the digester. Cylindrical digester mixing center, H/D increases, the average flow rate decrease digester; improve the mixing side into the digester H/D, the average flow velocity increases. Digestion pool pattern ovate no the ratio of height to diameter. On four in the operation of large, medium-sized anaerobic digester of the anaerobic digester tracer experiments. The tracer curve and the RTD curve is consistent with the ideal CSTR curve, the internal flow characteristics of digester completely mixed state. The digester are kept in a certain proportion of the dead, but the material dispersion high, basically no short flow. Top entry type anaerobic digester mixing center closer to the CSTR reactor side into a mixing digester from CSTR high degree of.CFD simulation results show that the digester in the middle part of the mixing effect is weak, cylindrical The distribution of the flow field in the digestible pool is more uniform. The large anaerobic digestion tank should adopt the large torque and slow speed agitator, which is not suitable to use high stirring speed and stirring power.

【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703

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