生物质热解油处理工艺优化实验研究

为了提高生物热解油的利用效率,使用固定床反应器开展了生物质热解油催化裂化反应实验,在加入催化剂的条件下,开展了不同类型催化剂、质量空速、反应温度、反应时间以及反应压力对催化裂化各产物产率的影响实验。结果表明：当催化剂类型为分子筛催化剂B、质量空速为3 h^-1、反应温度为400℃、反应时间为4 h以及反应压力为2 MPa时,生物质热解油催化裂化处理效果最好,此时的产油率为45.36%、产炭率为28.94%、产气率为11.32%。生物质热解油催化裂化反应后油相的主要成分以单环芳烃和多环芳烃为主,气相组分中CO和CO₂的含量较高,说明该处理工艺对生物质热解油中的含氧化合物达到了良好的催化裂化处理效果。     

生物质快速热解流化床反应器气力进料特性

为探究不同工况下热解流化床反应器的气力进料特性,设计并搭建了流化床反应器气力进料冷态试验装置。生物质原料和床料分别采用落叶松颗粒和石英砂颗粒,通过试验测得了本装置的最小流化速度,研究了流化气速、喷动气速、流量比、初始静床高、石英砂粒径、落叶松粒径对流化床反应器气力进料特性的影响。试验结果表明：流化气速和喷动气速的增加均会提高进料率;流化气使床料流化并为落叶松颗粒提供进料空间,喷动气为落叶松颗粒提供动能,并平衡一部分床层压力;落叶松与石英砂粒径的增加对进料效果不利;流量比在1.9~2.7范围内进料率高且稳定性好。本文构建了生物质、床料与气体的三相流物理及数学模型,开展试验对模型进行验证,结果表明其预测误差为±13%。     

生物质热裂解实验研究

介绍了用于生物质热解的试验装置及试验方法,研究了升温速率、加热终温两种因素对秸秆和锯末热解产物的产率及其质量的影响,试验结果表明两种不同生物质热解产物得率的变化规率基本一致,热解温度控制在300℃～400℃温度内,热解气产率最大,热解温度越高,热解产气量越大,测验结果还表明,常见热解条件下的生物质热解表现为四个阶段的反应特点。     

稻壳快速热解制取生物质油的试验研究

目前生物质快速热解高温热解气主要利用间壁式冷却器进行冷凝,容易造成冷却管道的结焦堵塞问题,本试验根据流化床稀相输送特点、生物质的热解特性以及生物质油的冷凝收集特点,设计了生物质快速热解反应装置,改进生物质物快速冷凝系统,以稻壳为原料进行快速热解制取生物质油的试验研究,分别考察单因素反应温度、流化气量以及进料速度对生物质油产率的影响。试验表明:稻壳热解气能够快速顺利地得到冷凝,反应系统能够连续顺利运行,随着反应温度、流化气量、进料速度的增大,生物质油的产率都呈现先增大后减小的趋势。另外对产出的生物质油用气质联用设备进行了成分分析,得出了生物质油的主要成分,其中酸类、酮类、脂类以及酚类的含量相对较高。     

固体热载体外循环逆流移动床生物质气化工艺

基于实验室外循环逆流移动床(ECCMB)催化气化反应体系进行了生物质气化实验研究。该反应系统由移动床热解反应器、气固逆流移动床气化反应器和提升管燃烧反应器组成。以白松木屑为生物质原料、煅烧橄榄石为热载体(催化剂)进行气化实验,考察了热解器温度、水蒸气质量/生物质质量(S/B)、原料粒度以及气化器床层高度对气化结果的影响。实验结果表明:反应器温度和S/B是影响气化产品分布的重要因素;随热解温度的升高,气体产率和化学效率显著提高,氢气含量也有所增加;水蒸气的加入不仅提高了产气率,焦油含量明显降低;原料颗粒粒度和气化器床层高度均对产品分布和化学效率产生不同程度的影响。     

褐煤与秸秆共热解的研究

选用小麦秸秆与褐煤进行共热解实验。主要考察生物质掺混比对共热解产物及热解特征参数的影响。结果表明:生物质与煤具有不同的热解温度范围。从DTG曲线可知,共热解过程中生物质先于煤进行热解。随着生物质掺混比的增加,生物质的热解特征增强,且共热解产物收率与掺混比呈线性关系。因此可初步判断:在慢速热解条件下,生物质与煤在共热解过程中不存在协同作用。     

不同种类生物质热解炭的特性实验研究

在管式炉上进行了生物质热解实验研究,分析了热解温度对生物质热解炭产量的影响规律,对比研究了农作物类和木材类生物质在相同热解条件下热解炭产量的差异,对生物质热解炭进行了电镜扫描分析,分析了不同热解温度下炭的表面结构特征。结果表明,生物质热解炭产量随热解温度升高而降低, 芸香木和稻壳的炭产量分别由300℃时的28.38%和45.84%降低到600℃时的7.55%和15.45%。在相同热解条件下,农作物热解炭产量普遍高于木材热解炭, 在400℃时稻壳糠热解得到的炭产量最高为30.32%,红胡桃热解得到的炭产量最低为19.23%。SEM分析表明,热解炭产物呈现多孔结构。     

热解条件对秸秆生物质炭性质的影响研究

为优化秸秆生物质炭的制备工艺,以小麦和玉米秸秆为原料制备生物质炭,研究不同热解温度和热解时间对秸秆生物质炭性质的影响.结果表明,同样热解温度(400℃、450℃和500℃)条件下,不同热解时间(0.5、1.0、2.0、3.0、5.0 h)的秸秆生物质炭pH值均为碱性.随着热解温度升高,秸秆生物质炭产率和有机碳含量下降,...     

生物质焦对甲苯的催化裂解实验研究

为降低生物质气化气中焦油含量,在小型固定床反应器上,进行了生物质焦对焦油模型化合物甲苯的催化裂解反应的实验研究,考察了热解焦粒径、裂解温度、气相停留时间和反应气氛对甲苯裂解率的影响.结果表明,高温条件下,热解焦对甲苯的裂解具有明显的催化作用.950℃时,所用的两种热解焦对甲苯的转化率分别达到了98%以上,同时发现,较长的气相停留时间更有利于甲苯的裂解.水蒸气或CO2能与甲苯和碳发生反应,提高甲苯的转化率,延长焦的催化活性;另外,动力学计算得出,生物质焦对甲苯催化裂解的活化能约为73 kJ/mol.     

橄榄废弃物低温热解过程中氯的析出规律

生物质直燃是生物质能利用的主要方式,而含氯化合物的释放则影响了生物质锅炉的结渣与腐蚀。低温热解作为一种有效的预处理手段可以解决由氯化物导致的锅炉结渣、腐蚀问题。利用水平管式炉试验系统,测量了不同热解温度下橄榄废弃物HCl、CH₃Cl等含氯物质的释放情况,分析了不同热解温度下上述污染物的释放规律。通过分析发现：HCl和CH₃Cl是生物质热解过程中氯的主要析出产物,热解温度的升高有助于氯等元素分别向HCl和CH₃Cl的转化,低温热解条件下氯的释放主要以CH₃Cl为主,随着温度的升高,二者的差距逐渐减小,当温度达到400℃时,HCl取代CH₃Cl成为生物质热解过程中主要的含氯气态产物。     

Pyrolytic characteristics of Jatropha seedshell cake in thermobalance and fluidized bed reactors

Pyrolytic kinetic parameters of Jatropha seedshell cake (JSC) were determined based on reaction mechanism approach under isothermal condition in a thermobalance reactor. Avrami-Erofeev reaction model represents the pyrolysis conversion of JSC waste well with activation energy of 36.4 kJ mol^?1 and frequency factor of 9.18 s^?1. The effects of reaction temperature, gas flow rate and feedstock particle size on the products distribution have been determined in a bubbling fluidized bed reactor. Pyrolytic bio-oil yield increases up to 42 wt% at 500 °C with the mean particle size of 1.7 mm and gas flow rate higher than 3U _mf , where the maximum heating value of bio-oil was obtained. The pyrolytic bio-oil is characterized by more oxygen, lower HHVs, less sulfur and more nitrogen than petroleum fuel oils. The pyrolytic oil showed plateaus around 360 °C in distribution of components’ boiling point due to high yields of fatty acid and glycerides.     

Fast pyrolysis of rice husk under different reaction conditions

In this work, rice husk, an agricultural waste in Korea, was pyrolyzed under different reaction conditions (temperature, flow rate, feed rate, and fluidizing medium) in a fluidized bed with the influence of reaction conditions upon characteristics of the bio-oil studied. The optimal pyrolysis temperature for bio-oil production was found to be between 400 and 450 °C. Higher flow rates and feeding rates were more effective for its production. The use of the product gas as the fluidizing medium led to the highest bio-oil yield. With the exception of temperature, no single operation variable largely affected the physicochemical properties of the bio-oil.     

Pyrolysis characteristics of Oriental white oak: Kinetic study and fast pyrolysis in a fluidized bed with an improved reaction system

The kinetic parameters for the pyrolysis of Oriental white oak were evaluated by thermogravimetric analysis (TGA). The white oak was pyrolyzed in a fluidized bed reactor with a two-staged char separation system under a variety of operating conditions. The influence of the pyrolysis conditions on the chemical and physical characteristics of the bio-oil was also examined. TGA showed that the Oriental white oak decomposed at temperatures ranging from 250 to 400 °C. The apparent activation energy ranged from 160 to 777 kJ mol^− 1. The optimal pyrolysis temperature for the production of bio-oil in the fluidized bed unit was between 400 and 450 °C. A much smaller and larger feed size adversely affected the production of bio-oil. A higher fluidizing gas flow and higher biomass feeding rate were more effective in the production of bio-oil but the above flow rates did not affect the bio-oil yields significantly. Recycling a part of the product gas as a fluidizing medium resulted the highest bio-oil yield of 60 wt.%. In addition, high-quality bio-oil with a low solid content was produced using a hot filter as well as a cyclone. With exception of the pyrolysis temperature, the other pyrolysis conditions did not significantly affect the chemical and physical characteristics of the resulting bio-oil.     

A study on the deposition of pyrolytic carbons from hydrocarbons

A new method for forming isotropic, laminar, and columnar pyrolytic carbons is proposed. For this, a low RPM (below 2.4 rpm) tumbling bed has been used to deposit pyrolytic carbons from hydrocarbon gases. All deposits were made on graphite substrates from propane and methane at a constant temperature of 1200°C. The microstructures of the pyrolytic carbons deposited were dependent on the flow pattern of the reactant gas, the rpm of the reactor, the hydrocarbon concentration, the nature of the hydrocarbon, and the geometry of the bed. Isotropic pyrolytic carbon is formed under deposition conditions where homogeneous nucleation occurs in the gas phase and at the gas flow conditions where the gas-borne droplets can collide on the substrate. Laminar carbon is formed under deposition conditions where homogeneous nucleation does not occur in the gas phase and at gas flow conditions where the carbon species existing in the bulk of the gas phase can collide on the substrate. Columnar carbon is formed when any carbon products existing in the bulk of the gas phase cannot collide on the substrate. The suggested deposition mechanism can also be applied to pyrolytic carbons deposited in a fluidized bed or in a stationary bed. In particular, isotropic carbon can be obtained even in a stationary bed if the requirements for the deposition of the isotropic carbon described above are satisfied.     

Heat transfer of bio-oil in a direct contact heat exchanger during condensation

Rapid quenching of volatiles in fast pyrolysis is important for achieving high yield and quality of the bio-oil product, but few studies have examined the condensation of volatiles and their related heat exchangers. Accordingly, we have studied the condensation characteristics of volatiles by varying heat transfer conditions in a direct contact heat exchanger. As the mass flow rate ratio of quenching oil to pyrolysis gas increased, the heat transfer rate and yield of bio-oil increased. The heat transfer rate and yield of bio-oil reached a maximum value at an intermediate air-to-quenching oil mass flow rate ratio. Additionally, the heat transfer rate and yield of bio-oil decreased as the temperature of the quenching oil increased. Experiments were also conducted to derive an empirical relationship for the volumetric heat transfer coefficient for direct contact heat exchangers.     

Investigation of the liquid recycle in the reactor cascade of an industrial scale ebullated bed hydrocracking unit

One of the commercial means to convert heavy oil residue is hydrocracking in an ebullated bed. The ebullated bed reactor includes a complex gas–liquid–solid backmixed system which attracts the attention of many scientists and research groups. This work is aimed at the calculation of the internal recycle flow rate and understanding its effect on other parameters of the ebullated bed. Measured data were collected from an industrial scale residual hydrocracking unit consisting of a cascade of three ebullated bed reactors. A simplified block model of the ebullated bed reactors was created in Aspen Plus and fed with measured data. For reaction yield calculation, a lumped kinetic model was used. The model was verified by comparing experimental and calculated distillation curves as well as the calculated and measured reactor inlet temperature. Influence of the feed rate on the recycle ratio(recycle to feed flow rate) was estimated. A relation between the recycle flow rate, pump pressure difference and catalyst inventory has been identified. The recycle ratio also affects the temperature gradient along the reactor cascade. Influence of the recycle ratio on the temperature gradient decreased with the cascade member order.     

Influence of reaction conditions and the char separation system on the production of bio-oil from radiata pine sawdust by fast pyrolysis

Radiata pine sawdust was pyrolyzed in a bubbling fluidized bed equipped with a char separation system. The influence of the reaction conditions on the production of bio-oil was investigated through the establishment of mass balance, and the examination of the products' chemical and physical characteristics. The optimal reaction temperature for the production of bio-oil was between 673 and 723 K, and the yield was above 50 wt.% of the product. An optimal feed size also existed. In a particle with a size that was less than 0.3 mm, the bio-oil yield decreased due to overheating, which led to gas formation. A higher flow rate and feeding rate were found to be more effective for the production of bio-oil, but did not significantly affect it. The main compounds of bio-oil were phenolics, including cresol, guaiacol, eugenol, benzendiol and their derivatives, ketones, and aldehydes. In addition, high-quality bio-oils, which contained less than 0.005 wt.% of solid, no ash and low concentrations of alkali and alkaline earth metals, were produced due to the char removal system.     

芳烃抽余油磺化工艺的研究

以气相三氧化硫为磺化剂,芳烃抽余油为原料,通过气体SO3和芳烃抽余油液膜进行连续的管式气-液反应,考察了SO3气体流量、夹套的水温、进料温度和流量对抽余油磺化收率的影响.实验结果表明,SO3气相膜式磺化反应的条件为：抽余油的进料流量为77 g/min,进料温度为30℃、SO3气体流量为2.5 L/min、干燥空气流量为l00 L/min、改变夹套水温35℃时,抽余油磺化产率最高,最高产率为52.7％.     

The pyrolysis of waste mandarin residue using thermogravimetric analysis and a batch reactor

A study on the pyrolysis of waste mandarin residue, with the aim of producing bio-oil, is reported. To elucidate the thermodynamics and temperature-dependency of the pyrolysis reaction of waste mandarin residue, the activation energy was obtained by thermogravimetric analysis. Mass loss occurred within the temperature range 200–750 °C, and the average activation energy was calculated to be 205.5 kJ/mol. Pyrolysis experiments were performed using a batch reactor, under different conditions, by varying the carrier gas flow rate and temperature. When the carrier gas flow rate was increased from 15 to 30 and finally to 50ml/min, the oil yield slightly increased. Experiments performed within the temperature range 400–800 °C showed the highest oil yield (38.16 wt%) at 500 °C. The moisture content in the bio-oil increased from 35 to 45% as the temperature increased from 400 to 800 °C, which also resulted in reduction of the oxygenates content and increase in the phenolics and aromatics content, indicating that temperature is an important operating parameter influencing the yield and composition of bio-oil.