微波预处理稻壳对纤维素酶固态发酵的影响

以稻壳为原料,通过微波预处理后用于固态发酵生产纤维素酶,研究了微波处理对后续发酵过程的影响。采用正交试验与单因素试验确定了微波处理的条件,并分析了微波功率与处理时间对发酵过程中纤维素酶活性及戊糖、还原糖含量的影响。试验结果表明,用功率为300W的微波处理稻壳7min后进行发酵,可以得到最高的纤维素酶酶活,其中滤纸酶活（干基质）可达7．09 IU／g,CMC酶活（干基质）可达87．24 IU／g,分别比未经处理的稻壳提高了21％和15％。若以单位能耗产生的酶活增加量计算,微波处理稻壳5min后发酵,可以得到最高的酶活性增加量。     

Optimization of microwave pretreatment on wheat straw for ethanol production

An orthogonal design (L₉(3⁴)) was used to optimize the microwave pretreatment on wheat straw for ethanol production. The orthogonal analysis was done based on the results obtained from the nine pretreatments. The effect of four factors including the ratio of biomass to NaOH solution, pretreatment time, microwave power, and the concentration of NaOH solution with three different levels on the chemical composition, cellulose/hemicellulose recoveries and ethanol concentration was investigated. According to the orthogonal analysis, pretreatment with the ratio of biomass to liquid at 80 g kg⁻¹, the NaOH concentration of 10 kg m⁻³, the microwave power of 1000 W for 15 min was confirmed to be the optimal condition. The ethanol yield was 148.93 g kg⁻¹ wheat straw at this condition, much higher than that from the untreated material which was only 26.78 g kg⁻¹.     

Effects of hot water extraction pretreatment on physicochemical changes of Douglas fir

Hot water extraction (HWE) is an autocatalytic pretreatment that can be effectively integrated into most of the conversion technologies for extracting hemicelluloses from woody biomass. The objective of this study was to understand the influence of pretreatment factors on removal of hemicelluloses from Douglas fir chips. Compositional change in biomass was analyzed with ion chromatography and further confirmed with Fourier transform infrared spectroscopy (FT-IR). Highest hemicellulose extraction yield (HEY) was estimated to be 67.44% at the optimum reaction time (79 min) and temperature (180 °C) by using response surface methodology (RSM). Experimental results show that the HEY increased from 19.29 to 70.81% depending on the reaction time (30–120 min) and the temperature (140–180 °C). Effects of the severity factor (SF) on the mass removal and compositional changes were also evaluated. Hygroscopicity and thermal stability of wood were improved after HWE pretreatment. Colorimetric analysis showed that temperature has a greater influence on color of the wood chips during HWE pretreatment than dwell time. HWE pretreatment shows great potential for extracting hemicelluloses and altering physicochemical properties of wood in an integrated biorefinery for diversification of product portfolio.     

Effect of different grinding conditions on the dissociation and flotation of difficult-to-float coal

The recovery of clean coal can be improved through grinding. In this study, grinding and flotation experiments were conducted on difficult-to-float coal. Results show that the particle size obtained from ball milling is finer than that obtained from rod milling. However, the particle size distribution obtained from rod milling is more evenly distributed than that obtained from ball milling. The contact styles of steel rod and steel ball are “line contact” and “point contact,” respectively. Results from the flotation experiments are consistent with those from the orthogonal experiments.     

微波辅助NaOH预处理提高油菜秸秆酶解效率的研究

为提高油菜秸秆的酶解效率,试验借助于常压微波加热技术辅助NaOH预处理,并对处理条件进行了优化。结果表明,与未处理比较,经微波预处理的油菜秸秆致密结构明显破坏,利于被纤维素酶水解。微波辅助预处理的最优化条件:微波功率600 W,时间5 min,NaOH 0.1 mol/L,温度80℃,经预处理后的油菜秸秆酶解率可达28.09%,较未处理前增加2.75倍,显著提高了酶解效果。     

Microwave pretreatment on microalgae: Evolution of gas and char in chemical looping gasification

Chemical looping gasification (CLG) of Chlorella vulgaris was investigated by TGA and FTIR technology. The release characteristic and evolution behavior of gaseous products and bio‐char in different conditions were analyzed to evaluate the effects of CLG and microwave pretreatment. The results indicated that the gas production of CLG was higher than that of SiO₂:Chlorella, and it would be higher after microwave pretreatment. CO, CO₂, and CH₄ were mainly produced in the pyrolysis and gasification stages. After adding Fe₂O₃, C―O, C═O, and C═C compounds decreased by 3.75%, 20.86%, and 24.72%, respectively. But more CO, CO₂, and CH₄ were produced. Microwave pretreatment was helpful for reducing the degrees of hydrogen‐rich, aliphatic structure, aromatization, and oxygen‐rich in char. Moreover, microwave pretreatment promoted the reduction of C―O, C═O, and C═C compounds. However, CO increased by 55.63%, and CO₂ decreased by 2.31% in this condition. Therefore, microwave pretreatment was beneficial to CLG reaction.     

不同煤化程度煤的可磨性指数变化和破碎特性

可磨性是煤加工利用过程中的一个重要指标，可磨性指数与煤的破碎机理、煤粒破碎后的粒度分布均有关系。运用哈氏可磨性指数测定仪和马尔文激光粒度仪对几种不同煤化程度的单煤进行了可磨性指数测定和激光粒度分析试验，分析了煤种的破碎过程以及破碎后的粒度分布规律。试验结果表明，经过哈氏可磨性测定仪后，各煤种的工业分析都发生了不同程度的变化，而煤粉破碎后的粒度分布取决于煤种的煤化程度，而与煤种的可磨性指数相关性较小。     

不同预处理对玉米芯酶解特性和形态结构的影响研究

研究了硫酸、氢氧化钠、双氧水和碱性双氧水预处理玉米芯对其纤维素酶解率的影响,并利用扫描电镜、红外光谱仪和X射线衍射仪分析处理前后的玉米芯显微结构、官能团和结晶性。结果表明,4种预处理方法对玉米芯结构都有不同程度的破坏,能够有效提高玉米芯的酶解产糖率;其中含有1.5%氢氧化钠的碱性双氧水预处理玉米芯,酶解率最高为46.08%,玉米芯质量损失率为29.84%;预处理后木质素特征峰基本消失,玉米芯的结晶指数和结晶度显著提高,分别为1.527和49.35%。     

Effects of ultrasonic pretreatment on the flotation performance and surface properties of coking middlings

The effects of ultrasonic pretreatment on the flotation performance of coking middlings were investigated through a flotation cell. The surface properties of coking middlings before and after ultrasonic pretreatment were indicated using X-ray fluorescence analyzer (XRF), scanning electron microscope (SEM) and DSA100 contact angle analyzer. The flotation results demonstrated that the combustible recovery increased by 7.18%, while the ash value of flotation tailings decreased by 2.74% at most after ultrasonic pretreatment. Flotation results were supported by XRF analysis, SEM analysis, and contact angle measurements results. These results show that the ultrasonic pretreatment has a beneficial influence on the flotation of coking middlings.     

Effect of NaOH on pretreatment of Gossypium herbaceum

In present study, the substrate Gossypium herbaceum (cotton stalks) was treated with sodium hydroxide to investigate its greatest promising use as an economical substrate for bioethanol production. Initially, 2 mm mesh size cotton stalks were soaked in various concentrations of NaOH (1–3%) for different soaking intervals of 2, 4, 6, 12, 24, and 48 h. The results showed that the cellulose content and delignification increased with the increase in the concentration of alkali and soaking time. However, the maximum cellulose and delignification (60.6% and 51.5%) were observed with 2.5% NaOH after 24 h of soaking. In physiochemical pretreatment, the maximum cellulose content (73.19%) was achieved with 2.5% NaOH at 121°C after 60 min while delignification was found to be 77.7%. All these results of the present study indicate that a suitable concentration of alkali as well as an autoclaving period at specific temperature are very much crucial to expose the maximum cellulosic contents prior to employing cotton stalks as substrates for bio-fuel production.     

碱性胍预处理水稻秸秆研究

以水稻秸秆为研究对象,采用有机强碱——胍进行预处理,考察了催化剂用量、预处理时间和温度对预处理效果的影响。以扫描电镜(SEM)、X-射线衍射仪(XRD)、红外光谱仪(FTIR)、热重分析仪(TG)对预处理前后样品进行了表征。结果表明:胍用量为3%、温度为60℃、时间为6 h是较适宜的预处理条件,催化剂用量是预处理水稻秸秆最关键的因素。SEM照片显示,预处理后秸秆表面呈现不规则的层片状皱褶、裂缝和孔洞;XRD表征显示,预处理后纤维素结晶度均提高;FTIR表征显示,胍对去除木质素和降解氢键作用明显;TG表征表明预处理前后水稻秸秆具有不同的热稳定特性。     

Hydrothermal pretreatment of fresh forest residues: Effects of feedstock pre-drying

Hydrothermal pretreatment has become an attractive method for upgrading biomass fuel because of its capacity to work effectively with various types of low cost wet feedstock. However, most of the past studies in the field dried the feedstock prior to the pretreatment without being aware of the effect of high temperature drying. In this study, fresh forest residues (Norway spruce and birch branches) were used as feedstocks to utilize the advantage of the hydrothermal pretreatment method. More importantly, the present work aims at investigating the effects of the pre-drying process on the solid product via a direct comparison on the fuel and physicochemical properties of hydrochars produced from fresh and dried forest residues. This assessment helps to identify differences when fresh and dried feedstocks are used for hydrothermal pretreatment study. The results showed that these differences were considerable with respect to solid and energy yields; and the use of dried feedstocks will be less representative for a commercially feasible hydrothermal process, using wet feedstock directly.     

Effects of oxygen concentration on the macroscopic characteristic indexes of high-temperature oxidation of coal

To explore the macroscopic characteristic indexes for oxidation of coal under high-temperature conditions, an XKGW-1-type high-temperature-programmed heating experimental system was constructed. Tests on high-temperature oxidation of coal under high-temperature conditions at five oxygen concentrations of 21, 17, 13, 8, and 3 vol% were independently conducted. Laws of variation in high-temperature oxidation of coal indices, such as the coal temperature, gas ratios, rate of oxygen consumption, and exothermic strength from indoor temperature to 500 °C, were investigated at those oxygen concentrations. The results showed that the variation tendencies of characteristic indices for high-temperature oxidation of coal at different oxygen concentrations were extremely intricate. At the five oxygen concentrations, the rate of oxygen consumption increased rapidly with an increase in coal temperature and eventually remained at a higher range. The rate of oxygen consumption increased with temperature with an approximate exponential trend at the five oxygen concentrations tested. For the same coal temperature, the rate of oxygen consumption decreased with the oxygen concentration. The variation tendencies of the CO and CO₂ production rates were similar, both increased rapidly with an increase in coal temperature in the early stages and reached a maximum at a coal temperature of 380 °C. They decreased slightly with an increase in coal temperature at first and increased promptly thereafter. The concentrations of CH₄, C₂H₄, and C₂H₆ first increased with an increase in the coal temperature and markedly decreased after the maximal value. The temperatures for the extreme points were 480, 410, and 420 °C for CH₄, C₂H₄, and C₂H₆, respectively. The trends of the macroscopic characteristic indexes throughout the process of high-temperature oxidation of coal in a certain temperature range at various oxygen concentrations can be used for temperature prediction and fire prevention during coal mining.     

稀酸处理对秸秆厌氧发酵产氢的影响

以稻草秸秆为纤维素原料,先利用稀硫酸对其进行预处理,再利用活性污泥进行厌氧发酵产氢。试验研究了压力、温度、硫酸浓度、加压时间、固液比以及原料粒度对预处理结果的影响,并根据产氢量优化了预处理条件。试验结果表明:在硫酸浓度为0.7%、处理压力为0.1MPa、加压时间为60min、固液比为1∶12,秸秆原料过60目筛的情况下预处理效果最好,此时每克秸秆产氢量为113ml,秸秆中半纤维素、纤维素的利用率为87.47%,秸秆的有效利用率为52.38%。     

玉米秸秆预处理对厌氧发酵制氢影响的研究

为提高玉米秸秆的产氢能力,实验研究了蒸汽爆破预处理、硫酸预处理、氢氧化钠预处理、盐酸预处理和酸化(碱化)气爆预处理5种预处理方法对玉米秸秆发酵产氢能力的影响。结果表明,预处理可以将秸秆中相当一部分纤维素和半纤维素水解生成还原糖,其中质量分数为0.8%的H2SO4酸化汽爆预处理对秸秆的水解效果最好。在固-液比1∶10、H2SO4质量分数0.8%、保持微沸状态30min的处理条件下,秸秆的糖含量达到最大值24.57%,最大氢气产量为141mL/g。     

NaOH固态预处理对稻草中纤维素结构特性的影响

通过NaOH固态预处理,提高稻草厌氧消化产气量,从而实现稻草的高效能源转化.采用傅立叶变换红外光谱(FTIR)、X射线衍射光谱(XRD)研究了未处理与经过6%NaOH固态处理后稻草中纤维素结构的变化情况.结果表明:NaOH固态预处理使稻草中纤维素的形态结构发生了变化,纤维素中的部分B-(1→4)-糖苷键与氢键发生断裂;纤维素的晶体类型与002面微晶位置虽然没有改变,但是纤维素的结晶度与002面微晶尺寸增大.这些变化是导致稻草厌氧消化产气量提高的原因之一.     

有机钙盐预处理纤维素的热解试验研究

摘要：在管式炉上进行了预处理纤维素（CaFA纤维素）的热解实验,研究了预处理对纤维素热解特性的影响。样品红外压片分析显示预处理影响了纤维素组成单元吡喃环的稳定性,且CaFA纤维素出现了明显的羧酸根官能团振动。热解实验表明：预处理使得纤维素的半焦和气体产率增加,生物油产率下降。CaFA纤维素最大生物油产率为0.496(g/g),相比未处理纤维素最大生物油产率降低19.1%。CaFA纤维素的气体产物中,CO含量减少,而CO2、CH4和H2含量增加,一定程度上提高了热解气相产物中的氧含量。GC-MS分析表明预处理对纤维素生物油组分具有明显的选择性,CaFA纤维素生物油中,大分子糖类及其衍生物的相对含量显著减少,而小分子酮类物质明显增加。     

机械活化预处理对蔗渣酶解产糖影响的研究

采用机械活化方法对蔗渣进行预处理,研究其对蔗渣酶解产糖的影响。用红外光谱、X-射线衍射和扫描电镜测定预处理前后蔗渣结构及表面形态的变化,并分析其作用机理。研究结果表明,机械活化用于蔗渣预处理,可明显提高预处理后蔗渣的酶解产糖率。酶解时间为48 h时,蔗渣酶解产糖率从未处理时的19.86%提高到59.34%。蔗渣酶解产糖率的提高是由于机械活化处理使得蔗渣纤维素分子间部分氢键发生断裂、结晶度下降、表面有序结构被破坏的所致。     

超声波预处理对污泥干燥速率影响研究

在超声波预处理污泥干燥实验基础上,分析了超声波预处理技术对污泥干燥速率的影响,并对污泥干燥过程进行了指数拟合,结果表明.超声波预处理能有效提高污泥干燥效率,其改善的程度取决于不同的实验条件;超声波预处理能够加速表面自由水分蒸发和快速结束污泥恒速干燥阶段;增大超声波功率可以更好地改善污泥的干燥特性,但改善的程度随着十燥时间的延长而放缓;超声波处理时间过长可能会增大污泥的黏度,反而不利于污泥脱水干燥.     

微波热解生物质废弃物的研究

利用微波热裂解生物质废弃物,使其转化为可直接利用的能源,是一种非常重要的处理工艺。运用自行研发的单模谐振腔微波设备对生物质废弃物进行热解反应试验,考察了微波功率、反应时间、含水率和物料粒径对木屑热解的影响,得到较优的反应工艺条件:微波功率为2.0 kW,反应时间为8 min,含水量为20%,物料粒径为0.5~0.8 mm。分析研究了固、液、气3种热解产物:固体产物(炭)的性质得到了改善;生物油主要是芳香烃类化合物和呋喃类化合物的复杂混合物;热解气体产物主要为CO,CO2,甲烷等,热值相对较高。