【作者】 王永江；

【导师】 韩鲁佳；

【作者基本信息】 中国农业大学 ， 农业工程， 2014， 博士

【摘要】 有机质降解动力学模型是建立好氧堆肥过程数学模型的重要基础。好氧堆肥过程中生物化学形式的产热量、产水量和耗氧量模拟的数学模型往往基于有机质降解动力学而建立。为深入开展有机质降解动力学模型研究,本研究主要包含以下内容：1、自由空域对猪粪好氧堆肥过程有机质降解的影响研究自由空域对堆肥过程有机质的降解有重要的影响,现有文献鲜见基于数学模型量化表征自由空域对好氧堆肥过程有机质降解影响的报道。本部分研究考虑3种不同自由空域水平对堆肥过程温度变化、氧气浓度变化和有机质降解速率的影响,采用相同质量但不同物料配比的方式获得不同的堆肥自由空域水平,基于实验室小型好氧堆肥反应器进行了好氧堆肥对比试验研究,并进一步基于Matlab软件平台编写、建立了基于温度、氧浓度等多因素堆肥过程有机质降解动力学模型。试验测量、化学分析和模拟结果表明自由空域对堆肥过程中温度、氧气浓度、含水率、有机质的降解速率的变化均有重要的影响。2、好氧堆肥过程不同有机质成分的降解规律试验研究为对猪粪堆肥过程中不同有机质成分(例如：粗蛋白、粗脂肪、纤维素和可溶性糖含量)的降解规律进行研究,根据目前比较通用的化验测试手段,研究选取猪粪好氧堆肥过程中可挥发性固体、粗蛋白、粗脂肪、纤维素和可溶性糖含量等成分的变化作为表征有机质降解规律的指标,为猪粪好氧堆肥有机质降解动力学的研究提供数据支持。试验研究采用等粒径且等体积的塑料管或麦秸作为膨胀剂与等质量的猪粪混合堆肥,利用实验室小型好氧堆肥反应器进行了3组好氧堆肥试验,研究了3种不同情况下猪粪好氧堆肥过程中温度、含水率、氧气体积分数、挥发性固体含量、粗蛋白、粗脂肪、纤维素、可溶性糖的变化。研究发现不同有机质成分的降解存在梯次性差异。3、基于有机质降解动力学的堆肥过程热量和水分平衡数学模型研究基于有机质降解的热量平衡数学模型研究中,依据有机质降解一级动力学方程和系统热量平衡方程,充分考虑堆肥有机质降解的梯次性对数学建模的影响,建立了反应器好氧堆肥过程有机质降解模型和热量平衡模型。水分平衡数学模型研究中,基于水分平衡质量守恒模型和水分蒸发一级动力学方程分别建立了两种不同的猪粪麦秸好氧堆肥水分平衡模型。4、基于可溶/不可溶性有机质的猪粪堆肥降解动力学模型构建本研究将堆肥有机质划分为可溶性有机质(可溶性糖、脂肪和蛋白质)和不可溶性有机质(纤维素、半纤维素和木质素),基于可溶性和不可溶性有机质建立降解数学模型,并在此基础上,建立了温度、氧气浓度和水分含量变化的数学模型,研究了可溶性和不可溶性有机质降解动力学模型的适用性。结果表明,基于可溶性和不可溶性有机质建立降解数学模型可增加模型对有机质降解特征的描述能力,并可较好的适用于好氧堆肥过程中热量平衡、氧气浓度和水分含量平衡模型的建立和模拟。更多还原

【Abstract】 Degrading kinetics of aerobic composting process is one of the fundamental factors for composting simulation including modeling of biological heat production, biological water production as well as biological oxygen demand. In other words, mathematical modelings of heat production, water production and biological oxygen demand are often based on degrading kinetics. In addition, the changes of organic maters during composting process makes a significant influence on degradation yields for heat, water as well as carbon oxygen. Therefore, studies of degrading kinetics are of great interest. In order to get a better understanding on degradation kinetics of composting, the following studies were performed with experimental analysis and mathematical simulation.1. Analysis the influence of free airspace to substrate degradationTo study the effects of different initial free air space (FAS) on composting degradation of pig slurry-wheat straw with lab-scale reactor system, three levels of FAS (56.70%,62.67%,68.36%) were obtained by mixing pig slurry and wheat straw with the same mass ratio but in different wheat straw sizes (<lcm,2-5cm,-7cm). Oxygen concentration and temperature were monitored by sensors during the whole composting period, while moisture and volatile solid (VS) content were measured by chemical analysis method at the beginning and the end of composting. In addition, a Monod model was employed to simulate VS content during composting period. According to the results of composting test, changes of oxygen concentration, temperature, moisture and VS based on different initial FAS levels were significantly different, which indicated that the effects of FAS had influence on substrate degrading and those effects should be took into account for degrading simulation.GUIs were developed to facilitate FAS study based on the model developed.2. Degrading analysis of different types of substrate during composting of swine manure in a laboratory-scale reactorIn order to study the degrading characteristic of volatile solid content, soluble carbohydrate content, cellulose content, crude fat content and crude protein content for processing of swine manure composting, three parallel composting experiments were conducted with laboratory scale composting reactors. Same amount of swine manure was mixed with equal volume of wheat straw or plastic bulking agents. Temperature, oxygen concentration, moisture content, volatile solid content, soluble carbohydrate content, cellulose content, crude fat content and crude protein content were monitored and recorded respectively. Mathematical models were employed to detect changes of free air space and its effect on substrate decomposition. According to the results of composting experiments, temperature of composting pile using wheat straw as bulking agents raise faster than the one with plastic bulking agents at the beginning of the composting. Meanwhile wheat straw bulking agents showed better performance on water-holding capacity. However, plastic bulking agents was better at keeping free air space of the composting pile. Degrading data of soluble carbohydrate content, cellulose content, crude fat content and crude protein content were recorded for next-step studies.3. Thermal and moisture balancing models based on substrate degradation kineticsIn the study regarding thermal balance, simulation models for organic matter content and composting temperature were developed based on the first order assumption with respect to the quantity of biodegradable volatile solid (BVS) and the law of thermal conservation, respectively, during composting. Different kinds of organic matter were mainly degraded in different composting stages and this was considered importantly for constructing models. For the modeling of organic matter degradation, temperature, moisture content, oxygen content and free air space were considered as key influence factors to degeneration rate. Regarding the model for thermal balance, forced convention and conduction were considered as main heat removal forms. In order to verify the models constructed, aerobic co-composting experiment of pig slurry and wheat straw was conducted. Temperature, oxygen content, moisture content and organic matter concentration were monitored during composting. Degrading kinetics constituted important role for thermal-balance modeling.Simulation models regarding moisture content were developed respectively by law of conversation of mass and first order assumption with respect to the moisture content. Approaches by law of conversation of mass to moisture content prediction was based on an analysis of biologically produced water, exit gaseous moisture content and inlet gaseous moisture content. The approach for moisture content prediction based on first order moisture evaporation kinetics was developed by an analysis of composting substrate moisture content and aeration rate. An aerobic composting process of pig slurry and wheat straw was conducted in order to verify the models constructed. The experimental results showed that modeling results gave good accuracy, and the relative standard errors were8.01%and8.86%for the models developed, respectively.4. An integrated mathematical model of composting process developed to test the feasibility of integrating degradable-substrate distinction into composting modelsDifferential equations regarding to heat balances, moisture content, oxygen concentrations, substrate decomposition and microbe growth were developed. Degradable substrates were divided into soluble substrate and insoluble substrate. Consequently, heat conversion factor was described as a state variable related to soluble substrate content. The model was validated against observed data obtained from lab-scale composting experiments with swine manure and wheat straw, regarding temperature, water and oxygen contents as well as substrate variations. Based on the experimental results, distinct substrate degradation model could be integrated with other physical and biological models. Further studies should be continued to build up a more generalized and structured substrate degradation model.更多还原