生物沼气生产利用系统建模分析及可持续性评价

发布时间：2018-01-26 21:14

本文关键词： 生物沼气生物甲烷系统建模单元模拟分析系统综合评价　出处：《中国科学院研究生院(过程工程研究所)》2016年博士论文　论文类型：学位论文

【摘要】：生物质废弃物通过厌氧发酵方式生产生物沼气是生物质高效资源化利用的重要手段之一,具有经济和环境的双重效益,是可再生能源领域的研究热点。现有研究主要针对生物质的厌氧发酵及生物沼气的利用等关键单元技术,从全系统角度的研究较为缺乏,而该体系涉及多种技术、多个单元过程以及多种影响评价指标,是一个复杂拓扑网络系统评价问题。因此,需要借助系统工程的方法对该复杂系统进行深入剖析,了解各单元及变量对系统性能影响的机制,并对影响系统效率的多种技术采用多种指标进行综合评价,筛选出具有代表性的可持续发展路线为生物沼气技术的大规模应用提供指导。基于上述背景,本文对生物沼气全系统进行了能量、环境及经济综合评价,并对系统中的沼气提纯及厌氧发酵关键单元进行了建模与能耗分析。主要研究内容与成果如下：(1)针对粗沼气提纯分离单元,开展了变压吸附法(PSA)粗生物沼气提纯制备生物甲烷工艺的动态模拟与评价研究。分别以13X沸石(Zeolite 13X)、3K碳分子筛(CMS-3K)和508b金属有机骨架材料(MOF-508b)为吸附剂,建立了两塔-六步的改进Skarstrom动态变压吸附模拟流程,对变压吸附过程的关键参数如吸脱附压力、进料吹扫比等进行了灵敏度分析,确定了优化工艺参数；考察了吸附塔内的压力、CH4及CO2组分的浓度随塔高及循环时间的变化：对三种吸附剂装填条件下工艺过程的能耗、设备尺寸及吸附剂装填量进行了计算与比较。结果表明,采用MOF-508b和CMS-3K作为吸附剂时的工艺能耗比Zeolite 13X作为吸附剂时分别低56%和50%;MOF-508b及CMS-3K填充的吸附塔塔径比Zeolite 13X填充的吸附塔塔径分别小13%和27%。(2)针对生物质厌氧发酵单元,建立了容积产气率及单元的热平衡模型。对中温35℃和高温55℃厌氧发酵状态,根据实验数据拟合了三种二元共发酵体系(牛粪与秸秆、鸡粪与秸秆、人粪与秸秆)的容积产气率模型,模型预测结果与实验结果平均偏差在7%以内。对热平衡模型,考察了沼液低温余热的回收对减少过程外供热量的影响。结果表明,发酵过程所需热量的约89%用于加热进口的冷物料,而约11%用于维持发酵罐的恒温。因此,对沼液的低温余热加以回收以减少过程热量供给是十分必要的。以沼气锅炉供热发酵罐方式为例,通过沼液余热回收,在中温发酵和高温发酵状态下,每天可以分别减少42%和49%的沼气消耗。(3)针对生物甲烷生产全系统,开展了物流与能量分析研究。在单元过程模拟基础上,建立了该系统的能耗模型和能量效率评价指标。考虑了2种发酵技术、4种粗沼气提纯技术、2种系统热量供给及是否进行沼液低温余热的利用等因素,设计了32种情景路线：考察了发酵温度、系统热量供给方式及沼液低温余热回收模式对系统能效的影响。结果显示,采用高温发酵技术,粗沼气及生物甲烷转化率比中温发酵分别提高120%及110%,能量的转化效率提高1倍;高温发酵比中温发酵减少了约3.1 wt%沼液及沼渣的处理量及26%的能量损失；对中温及高温发酵情景下系统的能效分析与比较,结果表明,采用高温发酵及加压水洗技术,系统所需的热量由外部热源供给且沼液与发酵原料换热回收低温余热,系统的能效在32种情景中最高(46.5%);采用中温发酵及变压吸附技术,系统所需的热量由燃烧发酵过程自产沼气供给且沼液与发酵原料不进行换热回收低温余热,系统的能量效率在32种情景中最低(15.8%)；在系统的热量供给方式及沼液与发酵原料换热模式相同的情况下,高温条件下系统的能效约为中温条件下的2倍。在对系统能效影响的三个因素中,发酵温度是对系统能效影响最大的因素,其次是系统热量的供给方式,最后是沼液与发酵原料的换热模式。(4)针对三种不同沼气利用方式(提纯制备生物甲烷、热电联产、固体燃料电池)构成的生物沼气生产及利用系统,对其进行了概念设计,并分别对其能效、绿色度及净现值等指标进行了综合评价与比较。结果表明,对于系统的能量效率,为沼气提纯沼气SOFCs沼气CHP,提纯利用方式系统能效最高,SOFCs利用方式系统的能效比CHP利用方式系统的能效高2.5%：对于系统绿色度变化量,沼气SOFCs沼气CHP沼气提纯；对于系统的投资回收期,沼气CHP沼气SOFCs沼气提纯。
[Abstract]:Biomass wastes by anaerobic fermentation to produce biogas is one of the important means of efficient biomass resource utilization, it is benefit to both economy and environment, is a hot research topic in the field of renewable energy. The key technology of the existing research focuses on anaerobic fermentation and biogas biomass utilization, the lack of research from the angle of the system, and this system involves many technologies, multi unit processes and a variety of impact assessment index, is a complex network topology system assessment. Therefore, the need for in-depth analysis of the complex system by using the method of system engineering, understand the influence mechanism of each unit and variables on the performance of the system, and for a variety of techniques affect the efficiency of system using a variety of the comprehensive evaluation index, screening out the large-scale application of representative sustainable development route for biogas technology Provide guidance. Based on the above background, this paper analyzed the energy of biogas system, comprehensive evaluation of environment and economy, and the system of biogas anaerobic fermentation and purification of key unit is analyzed modeling and energy consumption. The main contents and results are as follows: (1) the crude biogas purification unit, carry out the PSA method (PSA) dynamic simulation and evaluation of biological methane preparation technology for purification of crude biogas. Respectively with 13X zeolite (Zeolite 13X), 3K carbon molecular sieve (CMS-3K) and 508b metal organic frameworks (MOF-508b) as adsorbent, establishes an improved Skarstrom dynamic pressure swing adsorption tower two - six step process simulation and the key parameters such as the desorption pressure of the pressure swing adsorption process, the feed ratio of purge and conducted a sensitivity analysis to determine the optimal process parameters; effects of adsorption tower pressure, concentration of CH4 and CO2 components with height and follow The change ring time: consumption of the process of three kinds of adsorbent loading conditions, equipment size and adsorbent loading are calculated and compared. The results show that using MOF-508b and CMS-3K as the adsorbent process energy consumption than the Zeolite 13X as adsorbent respectively 56% and 50%; adsorption and MOF-508b adsorption tower tower CMS-3K filled 13X filling Zeolite diameter ratio diameter respectively, 13% and 27%. (2) for the biomass anaerobic fermentation unit, established the heat balance model of volumetric gas production rate and unit. The temperature of 35 C and 55 C high temperature anaerobic fermentation condition, based on the experimental data of three kinds of a total of two yuan (cow dung fermentation system with straw, chicken manure and straw, manure and straw) volume gas production rate model, the predicted results with experimental results the average deviation is less than 7%. The model of thermal equilibrium, investigated the recovery of low temperature waste heat to reduce the slurry process for The effects of heat. The results showed that the fermentation process about 89% calories for heating cold material imports, and about 11% for the constant temperature fermentation tank. Therefore, low temperature waste heat of the biogas slurry recycled to reduce heat supply is necessary. The biogas boiler heating fermentation tank as an example, the biogas slurry waste heat the recovery in the middle temperature and high temperature fermentation, fermentation condition, every day can be reduced respectively by 42% and 49% of the biogas consumption. (3) for bio methane production system, carried out the research of logistics and energy analysis. Based on the simulation of unit process, established the evaluation index model of energy consumption and energy efficiency of the system. Considering 2 4 kinds of crude fermentation technology, biogas purification technology, 2 kinds of heat supply system and whether the biogas low-temperature waste heat utilization factors, 32 scenarios were designed route: the influences of fermentation temperature, heat supply method and system Effect of biogas slurry waste heat recovery mode on the energy efficiency of the system. The results showed that the high temperature fermentation technology, crude biogas and bio methane conversion rate is increased by 120% and 110% respectively than mesophilic fermentation, energy conversion efficiency is increased by 1 times; high temperature fermentation capacity and energy loss of 26% is about 3.1 wt% and the biogas liquid residue less than the temperature of fermentation; medium temperature and high temperature fermentation conditions of system energy efficiency analysis and comparison, the results show that the high temperature fermentation and pressurized washing technology, the required system heat from the external heat source and heat recovery of low temperature waste heat and biogas fermentation materials, the energy efficiency is highest in the 32 scenario (46.5%); the high temperature fermentation and pressure swing adsorption technology, the required system heat by burning biogas and biogas fermentation production supply and fermentation raw material without heat recovery of low temperature waste heat, the energy efficiency of the system in the 32 scene in the Low (15.8%); in the heat supply system and heat transfer model of biogas slurry and fermentation of raw materials under the same temperature conditions the system efficiency is about 2 times of temperature. In the three factors of system efficiency, the fermentation temperature is the biggest factor affecting the energy efficiency of the system, followed by the the heat supply system, finally hot mode for biogas slurry and fermentation material. (4) according to the three different ways of biogas utilization (purification preparation of bio methane, cogeneration, solid fuel cell) biogas production and utilization system, the concept of design, and the energy efficiency, green and the net present value of the evaluation and comparison. The results show that the energy efficiency of the system, as SOFCs CHP biogas biogas biogas purification, purification by way of system efficiency is highest, SOFCs uses the energy efficiency ratio of the system by CHP The energy efficiency of the system is 2.5%: for the change of system green degree, biogas SOFCs biogas CHP biogas purification, for the system's investment recovery period, biogas CHP methane and SOFCs biogas purification.

【学位授予单位】：中国科学院研究生院(过程工程研究所)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S216.4

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