生物质闪速热裂解制取生物油的试验研究

基于生物质资源的高效清洁能源化利用目的，对生物质热裂解制取生物油这一具有重要应用前景的技术开展研究。结合流化床的优质和生物质的特殊性，自行研制成功给料速达5kg/h的流化床热裂解反应器，并制取得到产率高达60％的生物油。同时针对木屑和秸秆的系统试验研究得出了反应温度和原料种类等主要参数对生物质闪速热裂解制油的影响规律。     

基于逐级裂解气质联用和热重质谱联用技术的杉木热解特性研究

利用逐级裂解气质联用(stepwise Py-GC/MS)和热重质谱联用技术(TG/MS)对杉木的热解特性进行了研究。结果表明,杉木热解主反应温度为250～430℃,随着升温速率的增大,热解起始温度和终止温度均向高温侧移动。对杉木慢速热解过程进行了动力学分析,得到3种升温速率下对应的活化能分别为83.99,88.87,91.98kJ/mol。杉木逐级裂解主要液体产物有乙酸、1-羟基-丙酮、糠醛、雪松醇、左旋葡萄糖和4-羟基-2-甲氧基肉桂醛等,各温度段产物分布各不相同。在杉木慢速热解条件下,左旋葡萄糖发生二次反应,液体产物中存在很多芳香类物质。     

基于裂解设备的连杆裂解加工质量影响分析

连杆裂解方法是近些年发展起来的一种连杆加工新技术,目前正在逐步取代传统加工方法,利用裂解连杆自动化生产线,针对A型连杆完成了激光切割裂解槽工序和定向裂解加工工序,并进行了系统的裂解试验研究。首先讨论了影响激光裂解槽加工质量的因素,其次讨论了裂解槽对于裂解质量的影响,最后讨论了定向裂解工序中,夹具、加载速度及背压力等因素对于裂解质量的影响。系统地介绍了裂解连杆开发过程中出现的各种质量缺陷,并给出了相应缺陷的解决方案,为进一步提高裂解连杆产品的质量提供了可靠的理论与实践基础。     

连杆厚度对裂解的影响分析

结合理论分析与数值模拟研究了连杆厚度对裂解加工的影响,给出了断裂韧性、裂纹区塑性区状态与连杆厚度的关系,并讨论了连杆厚径比对裂解的影响.结果表明:在启裂工步,随连杆厚度的增加,裂纹区的Von Mises应力由狭长的、多个分散集中状态逐渐过渡到趋向中面唯一分布的集中状态,裂尖附近的最大主应力均值逐渐增加,分析了连杆厚度及厚径比与裂解力的关系,得出某规格连杆的厚径比D/R最佳设计范围为3.312～3.438.     

生物质及其热裂解产物生物油的特性分析

以红松、白松、落叶松、玉米秸秆等不同生物质为原料,对流化床反应器热裂解制取的生物油进行了研究试验,通过对生物油的物理特性及其成分的分析,得出的实验结果表明:红松制取的生物油品质最好,热值高,含水率低,更适合进一步改性研究和应用,并利用现代精密仪器GC-MS对生物油进行了组分分析,解释了生物油高含氧和高含水特性。     

基于热红联用分析的木质素热裂解动力学研究

利用热重红外联用系统对生物质的主要组分木质素进行了热裂解动力学研究.在用红外固体压片法研究木质素结构的基础上得到不同升温速率下木质素热裂解的热重曲线.实验结果表明,随着升温速率的增加,各个阶段的起始和终止温度向高温侧轻微移动,主反应区间增加;计算得到的木质素两阶段活化能分别为58.41 kJ/mol和119.98 kJ/mol.与纤维素热解气的联机红外分析谱图相比可知木质素热解过程中气体析出机理复杂,主要生成CO、CH4和呋喃等产物.     

不同烘焙条件对纤维素热裂解机理的影响研究

通过红外固体压片法对不同烘焙处理的纤维素的微观结构进行分析,发现烘焙处理并没有改变纤维素基本结构框架,但能改变官能团的数量,如473K下15h处理样品在消耗结晶水的同时生成了羟基使得羟基振动明显增强.利用热重红外联用技术研究烘焙处理后纤维素的热裂解行为,结果表明:不同样品失重量因水分、CO和CO2等气体析出强度降低而减少.高温和长时间烘焙利于纤维素经过活性纤维素生成焦油,低温和短时间烘焙则易发生低温焦炭化作用获得CO、CO2等小分子气体和残炭.     

结构不对称对斜切口连杆裂解影响分析

分析了斜切口连杆结构不对称对裂解加工中两侧裂解槽起裂时序及裂解质量的影响.建立了斜切口裂解连杆有限元模型,以试验确定的斜切口连杆材料断裂韧性参数为起裂判据,变化斜切口裂解连杆有限元模型的两侧裂解槽深差,进行了斜切口连杆裂解起裂准静态有限元分析.模拟结果表明,通过优化斜切口连杆两侧裂解槽深度参数可以减小由于结构不对称引起的斜切口连杆裂解加工中两侧裂解槽的起裂时间差.进行了不同槽深情况的斜切口连杆裂解试验研究,通过电测方法测定了试验中斜切口连杆两侧裂解起裂时间差,试验结果与数值模拟结果相比有较好的一致性.     

生物油催化裂解的动力学分析

以CaO·MgO混合物为催化剂,采用热重分析法探讨了混合物中MgO含量对生物油催化裂解反应速度和最终残留率的影响.实验结果显示,生物油的热重变化过程可以分为室温～200℃范围内的挥发阶段和200～520℃范围内的热裂解阶段.在热裂解阶段中,反应速率常数和温度的关系可以用Ardaenius方程式表示.在MgO含量为50%的CaO·MgO混合物的催化作用下,生物油热裂解反应活化能从无催化剂时的20.9kJ/mol降低到16.5kJ/mol,最终相对残留率降低到0.75.MgO含量为38.7%的煅烧白云石是有效的生物油裂解催化剂.     

粒径和氧浓度对烟梗燃烧产物析出特性的影响

为探究粒径和氧浓度对烟梗燃烧产物析出特性的影响,文章采用热重-质谱联用技术对烟梗进行燃烧实验,重点研究了烟梗在4种粒径和3种氧浓度条件下燃烧时的挥发性有机化合物(VOCs)析出特性。研究结果表明:烟梗燃烧析出的VOCs主要包括乙炔、丙烯、乙腈、丙烯腈、苯、甲苯和氯甲烷,其中,乙炔和乙腈的相对累积量较大,其次是丙烯和氯甲烷;VOCs在纤维素和木质素燃烧阶段均有析出,而氯甲烷在半纤维素燃烧阶段也表现出明显的析出特性;粒径和氧浓度的改变对VOCs的析出有明显影响,随着烟梗粒径的减小,VOCs的析出峰值温度均向低温区移动,乙腈、丙烯腈和氯甲烷的相对累积量先减小后增大,而其余4种VOCs均减小;当烟梗粒径为140目时,VOCs在木质素燃烧阶段达到最大析出强度;随着氧浓度的增加,VOCs的析出峰值温度向低温区移动,VOCs的相对累积量逐渐增大,当氧浓度为21%时,VOCs在木质素燃烧阶段达到最大析出强度。     

Investigation of wheat straw biodegradation by Phanerochaete chrysosporium

Production of renewable fuels and chemicals from biomass requires an efficient pretreatment technology, which further depends on better understanding of biodegradation process of such lignocellulosic biomass. The biodegradation of wheat straw by Phanerochaete chrysosporium was investigated in this study. The fungal secretomes and compositional, functional groups and structural changes of the fungal spent wheat straw lignin were determined. The result showed ∼ 30% loss of total lignin within three weeks of biopretreatment by P. chrysosporium. Detailed structural analysis through two dimentional heteronuclear multiple quantum coherence nuclear magnatic resonance (2D HMQC NMR) of the pretreated lignin (acetylated) revealed low abundance of substructures D (dibenzodioxacin) and E (cinnamyl alcohol). Further, analysis of lignin by Fourier Transmission Infrared (FTIR) and Pyrolysis Gas Chromatography/Mass Spectrometry (Py-GC/MS) demonstrated the significant decrease of guaiacyl (G) units. The results support the previous findings in the biodegradation of wheat straw analyzed by ¹³C cross polarization magic angle spinning (CPMAS). Revealing the characteristic behavior of P. chrysosporium mediated biomass degradation, the information presented in this paper offers new insights for understanding the biological lignin degradation of wheat straw by P. chrysosporium.     

麦秆水热炭化水溶液循环对碳及水溶物分布的影响

以农业废弃物麦秆为原料,通过水溶液循环利用的水热炭化实验,对麦秆水热炭化过程中碳及水溶有机物主要组分浓度的分布进行了深入研究。结果表明:在220℃、120 min、液固比为30∶1的水热条件下,随水循环次数的增加,水溶产物产率及碳质量分数逐渐减少,水循环第6次以后,水溶产物产率和碳质量分数变化不大,分别约为15%和5%;水溶产物中还原糖、糠醛和5-羟甲基糠醛(5-HMF)的浓度均随循环次数的增加而减少,而乙酸浓度一直呈逐渐增加趋势,并催化了水热炭化反应,水循环第10次时,乙酸浓度达到18.32 g/L。     

The application of pyrolysis-molecular beam mass spectrometry for characterization of bark phenolysis products

Barks from four common Mediterranean trees subjected to phenolysis under acidic conditions at moderate temperature (130°C or 150°C) were evaluated with pyrolysis-molecular beam mass spectrometer (py-MBMS). The results indicated that both concentration of acid catalyst and the phenolysis temperature have an impact on the chemical composition of both the isolated oils and the solid residue, with the acid concentration having the greatest influence. The primary phenolysis reaction products included phenolics and furans. As expected, at higher acid concentrations the phenolysis products contained less carbohydrate and included more phenolic fragments. These phenolysis oils should be useful as feedstocks for the production of phenol formaldehyde resins. The py-MBMS method was found to be an effective and convenient method to understand bark phenolysis.     

Reprint of: Pelletizing properties of torrefied wheat straw

Combined torrefaction and pelletization are used to increase the fuel value of biomass by increasing its energy density and improving its handling and combustion properties. However, pelletization of torrefied biomass can be challenging and in this study the torrefaction and pelletizing properties of wheat straw have been analyzed. Laboratory equipment has been used to investigate the pelletizing properties of wheat straw torrefied at temperatures between 150 and 300 °C. IR spectroscopy and chemical analyses have shown that high torrefaction temperatures change the chemical properties of the wheat straw significantly, and the pelletizing analyses have shown that these changes correlate to changes in the pelletizing properties. Torrefaction increase the friction in the press channel and pellet strength and density decrease with an increase in torrefaction temperature.     

Combustion characteristics of wheat straw in a fixed bed

Combustion of wheat straw was investigated in a fixed-bed reactor for two air flow rates, 1,151 and 2,125 kg/m²h. Measured temperatures, mass loss, and gas composition were used to evaluate the combustion characteristics in terms of ignition front speed, burning rate, and quality of combustion in general. At lower value of air flow rate difference between the ignition rate and burning rate was significant, which can be easily noticed by the measurement results. At higher value of air flow rate, there was still a small difference between the ignition and burning rate, while the content of oxygen in the flue gas was 10%, which leads to the conclusion that a change in the method of delivering the combustion air is necessary.     

小麦秸秆转化为可发酵糖的研究

对小麦秸秆水解转化为可发酵糖进行了研究，考察了小麦秸秆预处理方法以及温度、pH值、酶用量、底物浓度和反应时间等因素对小麦秸秆酶水解的影响。试验结果表明，汽蒸加蒽醌方法是较好的预处理方法。酶解最佳工艺为：温度48℃，pH值5．2，酶解时间24h，酶用量与底物的最佳配比0．160：1；底物浓度≥1％，以1．5％～2．5％为宜，此时还原糖得率达32．4％。     

麦秸催化热解的TG-FTIR分析

在升温速率为20℃/min,催化剂为纯CaO和煅烧后的白云石（CaO/MgO）,氮气气氛下进行麦秸的热解和催化热解试验。由TG曲线可见麦秸催化热解可以提高其最大失重率,由DTG曲线可见催化热解有两个挥发分析出峰,通过比较说明添加催化剂有利于热解反应的进行,并且CaO/MgO催化效果更明显;对挥发分最大吸光率和第二大吸光率的红外谱图进行分析,再次证明了催化剂的效果;对挥发分大量析出阶段的主要气体CO2、CO、CH4、SO2的表观生成过程进行了研究分析;通过热解反应动力学的计算,采用Ozawa-Doyle法进行数据处理,表明添加催化剂后麦秸的热解活化能降低,有利于热解反应的进行。     

Modelling solid-convective flash pyrolysis of straw and wood in the Pyrolysis Centrifuge Reactor

Less than a handful of solid-convective pyrolysis reactors for the production of liquid fuel from biomass have been presented and for only a single reactor a detailed mathematical model has been presented. In this article we present a predictive mathematical model of the pyrolysis process in the Pyrolysis Centrifuge Reactor, a novel solid-convective flash pyrolysis reactor. The model relies on the original concept for ablative pyrolysis of particles being pyrolysed through the formation of an intermediate liquid compound which is further degraded to form liquid organics, char, and gas. To describe the kinetics of the pyrolysis reactions the Broido–Shafizadeh scheme is employed with cellulose parameters for wood and modified parameters for straw to include the catalytic effect of its alkali-containing ash content. The model describes the presented experimental results adequately for engineering purposes for both wood and straw feedstock even though conditions for ablative pyrolysis from a reaction engineering point of view are not satisfied. Accordingly, even though the concept of an ablatively melting particle may constitute a limiting case, it can still be used to model flash pyrolysis provided that the reacting particle continuously shed the formed char layer.     

Ozone pretreatment of wheat straw for enhanced biohydrogen production

Ozonation was tested as a pretreatment method for enhanced biohydrogen production from wheat straw. Ozone pretreatment effectively degraded wheat straw lignin, and the delignification increased with increase in the applied ozone dose. Results of reducing sugar measurement showed that under our experimental conditions ozone pretreatment significantly increased reducing sugar yields. A simultaneous enzyme hydrolysis and dark fermentation experiment was then conducted using a mixed anaerobic consortium, and the results demonstrated that ozone pretreatment significantly increased biohydrogen production. Compared to the untreated one, hydrogen production in the samples ozonated for 15, 30, 45 and 90 min increased 107%, 134%, 158% and 138%, respectively. Slight inhibitory effect on the dark fermentation was observed with the sample ozonated for 90 min, and the inhibitory effect was due to prolonged ozonation. These results proved that enhancement of biohydrogen production from lignocellulosic biomass using ozone as a pretreatment method is technically feasible.     

Harvest index and straw yield of five classes of wheat

Wheat straw is a potential cellulosic feedstock for bioethanol. This study was conducted to evaluate straw yield potential and its relationship with grain yield for wheat (Triticum spp.) grown in the United States. The specific objective was to determine if differences in straw yield and harvest index (HI) exist between and within regions and/or wheat classes. Using on-going variety performance trials in eight states, a total of 255 varietal trial entriess from five classes of wheat were surveyed for above-ground biomass. Averaged over all wheat classes and regions the HI was 0.45. Soft red winter wheat in Kentucky had, on average, the highest HI and lowest straw yield among regions and wheat classes. Soft white winter wheat under irrigation in the Pacific Northwest produced the highest straw yield. Hard red winter wheat in the southern plain states of Texas and Oklahoma had, on average, the lowest HI. Differences in the amount of precipitation and cultivars were the major contributors to the variation detected within wheat classes. The amount of wheat straw available as cellulosic feedstock in a state or wheat class can be estimated using the grain yield estimates provided by the National Agricultural Statistics Service and the class specific HI.