CAS OpenIR
生物油关键组分及煤的吸附对生物油煤浆性质的影响
易树萍
Thesis Advisor宋文立
2020-07-01
Degree Grantor中国科学院大学
Degree Name博士
Degree Discipline化学工程
Keyword生物油煤浆,生物油组成,煤种,吸附特性
Abstract

生物油是生物质热解所得液体产物,含水含氧量高、热值低、酸性及腐蚀性强、稳定性差,难以直接利用。将生物油与煤混合制备生物油煤浆,可以代替水煤浆,作为燃料或气化原料。由于生物油与煤的组成、结构都比较复杂,因此,生物油的组成、煤种以及煤对生物油组分的吸附作用决定了生物油煤浆的性质,进而影响生物油煤浆的制备及应用。采用不同变质程度的煤种与生物油制备煤浆,考察了煤种对生物油煤浆流变性、触变性、粘度及稳定性的影响,并分析了影响煤浆性质的主要煤质因素。研究结果表明,无烟煤及变质程度较高烟煤可以制备出稳定且粘度低的生物油煤浆,是适合制备生物油煤浆的煤种;褐煤所制煤浆体系的粘度高且不稳定,不适合制备生物油煤浆;变质程度较低的烟煤能否制备出稳定的生物油煤浆取决于生物油的组成。通过灰度关联法得到影响生物油煤浆特征粘度的主要煤质因素有:总酸性官能团含量、O/C、酚羟基官能团以及羧基官能团含量。该部分研究为选取适宜制备生物油煤浆的煤种提供了理论指导。通过对原始生物油进行减压蒸馏,获得了不同水分含量的生物油样品,考察了生物油中水分含量对煤浆性质的影响。研究结果表明,生物油煤浆根据其流变特性指数是否大于0.800可被分为强假塑性煤浆和弱假塑性煤浆,弱假塑性煤浆大部分可以稳定储存,而强假塑性煤浆能否稳定与制浆煤种及生物油中水分含量有关。水分是影响生物油煤浆性质最大的组分,随制浆用生物油水分含量升高,煤浆逐渐由弱假塑性转变为强假塑性。生物油中存在一特殊的水分含量,CWmin(煤浆特征粘度最小水分含量),由该水分含量生物油所制煤浆特征粘度最低。CWmin的值与制浆煤种和煤粉浓度都有关。因此,可以通过改变生物油中水分的含量而显著改善生物油煤浆的性质。通过向实际生物油中添加共溶组分及糖类的模型化合物,制备了不同共溶组分含量及糖类含量的生物油样品,考察了共溶组分及糖类对生物油煤浆性质的影响。结果表明,生物油中共溶组分及糖类对煤浆的稳定性影响较小;生物油中双亲性共溶组分含量升高可降低生物油粘度和煤浆特征粘度;生物油中疏水性共溶组分含量升高使生物油粘度轻微降低但会使煤浆特征粘度增大;生物油中糖类含量升高使生物油粘度及煤浆特征粘度都增大。因此,双亲性共溶组分含量较高或疏水性共溶组分及糖类含量较低的生物油可以制备出稳定且粘度较低的煤浆。通过测定制浆前后生物油组成变化以及制浆后煤浆体系中可自由流动生物油的量,考察了煤种及生物油组成对煤吸附生物油中各组分的影响;并利用模型化合物配制不同类型的模拟生物油,考察了热解木质素对生物油煤浆稳定性的影响。研究结果表明,煤对生物油中共溶组分的吸附选择性强,对水分及糖类的吸附选择性弱,对热解木质素的吸附选择性取决于生物油的组成,对低水分含量生物油中热解木质素的吸附选择性弱,对高水分含量生物油中热解木质素的吸附选择性强。热解木质素是生物油煤浆保持稳定的必要组分,但当煤浆体系中热解木质素析出量较大时,煤浆也不稳定。当生物油煤浆中可自由流动液体的热解木质素含量超过4.50 wt.%时,煤浆可以保持稳定。由皮尔逊相关性分析得到影响煤吸附生物油组分的主要煤质因素有煤样的O/C、总酸性官能团、酚羟基官能团及羧基官能团含量。而且,煤对生物油组分的吸附特性是影响生物油煤浆体系能否稳定的关键因素,不同煤种所制煤浆的稳定性依赖于煤浆中可自由流动液体的含量。变质程度较低的煤种对生物油中组分的吸附能力强,所制煤浆体系中可自由流动液体含量低;而变质程度较高煤种对生物油中组分的吸附能力弱,所制煤浆体系中可自由流动液体含量较高。综合全文研究结果,获得了生物油煤浆体系的分散及稳定机制。;Bio-oil is the liquid product from biomass pyrolyzing, and exhibits high water and oxygen content, low heating value, strong acidity, corrosiveness and instability. These drawbacks make it difficult for direct utilization. A novel method as a new fuel for combustion and gasification has been proposed to make slurries by blending coal with bio-oil. Both compositions and structure of bio-oil and coal are extremely complex, therefore, bio-oil compositions, coal type and adsorption behavior between coal and bio-oil components would significantly affect CBS properties, which further influence CBS preparation and utilization.Coal samples with different rank were used to prepare CBS, and the effect of coal type on the rheology, thixotropy, apparent viscosity and stability of CBS was studied. Results show that anthracite and high rank bituminous coal can be used to prepare CBS with stable performance and low viscosity, indicating they are suitable for CBS preparation. CBS prepared by lignite coal is unstable and high viscosity, indicating it is not suitable for CBS preparation. The stability of CBS prepared by low rank bituminous coal is closely related to bio-oil compositions. The O/C ratio, total acid functional group, phenolic hydroxyl functional group and carboxyl functional group content of coal are determined as main factors affecting the characteristic viscosity of CBS by the method of grey relational analysis. This research provides foundation for selecting coal samples suitable for CBS preparation.Bio-oil samples with different water content were prepared by vacuum distillation of raw bio-oil,and the influence of water content on CBS properties was investigated. CBS samples can be divided into strong pseudoplastic and weak pseudoplastic CBS based on the rheological index of CBS whether it is larger than 0.800, most of weak pseudoplastic CBS is stable, while the stability of strong pseudoplastic CBS is related to coal type and water content in bio-oil. Water is the most important component in bio-oil affecting CBS properties, and rheological behavior of CBS would change from weak pseudoplastic to strong pseudoplastic with the increase of water content in bio-oil. There is a special water content in bio-oil, CWmin, at which CBS has the minimum characteristic viscosity. The value of CWmin is related to coal type and coal concentration in CBS. Therefore, the properties of CBS could be improved by regulating the water content in bio-oil.Bio-oil samples with different co-solvent and sugar content were prepared by adding model compounds into bio-oil, and the influence of co-solvent and sugar content on CBS properties were investigated. The results show that the stability of CBS is less influenced by the content of co-solvent and sugar in bio-oil. As the content of amphiphilic co-solvent increases, bio-oil viscosity and CBS characteristic viscosity would decrease. While the content of hydrophobic co-solvent in bio-oil increases, bio-oil viscosity would slightly decrease and CBS characteristic viscosity would increase. But as the content of sugar in bio-oil increases, both bio-oil viscosity and CBS characteristic viscosity would increase. Thus, bio-oil with high content of amphiphilic co-solvent or low content of hydrophobic co-solvent and sugar tends to prepare stable CBS with low viscosity.The adsorption characteristic of coal to bio-oil components were studied by measuring the compositions of bio-oil before and after adsorption and the quantity of free liquid in CBS, and the effect of bio-oil compositions and coal type on adsorption behavior of coal to bio-oil components were investigated. Different bio-oil samples prepared by model compounds were used to study the effect of pyrolytic lignin on CBS stability. Results show that coal has strong adsorption selectivity to co-solvent but weak adsorption to water and sugar, and the adsorption behavior of coal to pyrolytic lignin is related to bio-oil compositions, where coal shows weak adsorption selectivity to pyrolytic lignin in bio-oil with low water content but strong adsorption selectivity when in bio-oil with high water content. Pyrolytic lignin is the most important component that keep CBS stable, but CBS would be unstable as the quantity of pyrolytic lignin precipitates in CBS is large. CBS could keep stable during storage when the content of pyrolytic lignin in free liquid of CBS is larger than 4.50 wt.%. The O/C ratio, total acid function group content, phenolic hydroxyl group and carboxyl group content of coal are major factors affecting adsorption quantity of coal to bio-oil components by the method of Pearson correlation analysis. The stability of CBS is closely associated with the adsorption characteristic of coal to bio-oil components and decided by free liquid content in CBS. Strong adsorption ability of lignite and low rank bituminous coal to bio-oil components was observed, and the free liquid content in CBS prepared by these coals is low. Weak adsorption ability of high rank bituminous coal and anthracite to bio-oil components was found, and free liquid content in CBS prepared by these coals is high. Combining results of previous research, the dispersion and stabilization mechanism of CBS is proposed. 

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/49655
Collection中国科学院过程工程研究所
Recommended Citation
GB/T 7714
易树萍. 生物油关键组分及煤的吸附对生物油煤浆性质的影响[D]. 中国科学院大学,2020.
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