基于RGB三波段消光法和单帧单曝光图像法的汽轮机湿蒸汽测量实验研究

为了揭示汽轮机内湿蒸汽两相流动机理,提出了基于RGB三波段消光法和单帧单曝光图像法(SFSEI)的湿蒸汽测量探针系统,并采用2 100nm和960nm聚苯乙烯标准颗粒以及粒径范围为50~400μm的标准圆图像标定板对探针系统测量准确性进行了实验验证.利用该探针对某330 MW汽轮机在277 MW定压运行时末级后湿蒸汽进行了测量.结果表明:沿叶高方向,一次水滴的粒径分布在0.7~0.9μm,湿度在6%~9%,二次水滴的最大速度可达225.7m/s,最大粒径约200μm,并且二次水滴的速度、粒径和运动方向角随叶高变化不同;该探针系统可实现汽轮机湿蒸汽参数的有效测量,为湿蒸汽研究提供依据.     

燃煤过程中亚微米颗粒生成及影响因素的研究

通过沉降炉燃煤实验,讨论了燃煤过程中亚微米颗粒的形成机理,研究了炉膛温度、煤粉粒径及氧浓度对亚微米颗粒生成的影响.实验选择平顶山烟煤、六盘水烟煤和合山烟煤,每种煤的煤粉粒径范围分别是100～200 μm、63～100 μm和小于63μm.煤粉在不同条件下燃烧后,用13级低压撞击器按不同粒径收集可吸入颗粒物进行研究.结果表明:粒径小于0.377 μm的颗粒是通过气化-凝结机理形成,而粒径大于0.377μm的颗粒是通过矿物质的破碎、聚结机理形成;随着炉膛温度的升高、煤粉粒径的降低及氧浓度的提高,亚微米颗粒生成量会有不同程度的增加;炉膛温度是最主要的影响因素,煤粉粒径及气氛次之.     

毛豆秆热解实验研究

以毛豆秆为实验原料,研究不同热解温度、物料粒径和金属氧化物催化剂对毛豆秆热解产生的可燃气(CO、H2)生成特性和最终失重率的影响。实验发现,提高热解温度,可燃气的产量和最终失重率增大;高温热解时,毛豆秆粒径对热解的影响很小,最终失重率维持在约93%;金属氧化物Al2O3、Fe2O3、Ni2O3和CaO催化热解毛豆秆,可提高可燃气的产量,但会减小最终失重率,减小率最大可达9.84%。     

岔河集油田岔15断块柔性微球调驱适应性实验评价

针对华北岔河集油田岔15断块高温(74℃)、高盐(地层水矿化度为15200mg/L),平面和纵向上非均质性强,一般三采方法提高采收率不理想的现状,开展了岔15断块微球调驱适应性分析。研究结果表明,3μm微球和3μm+500nm混合微球(质量比为1∶1)具有理想封堵岩心孔隙喉道的作用和能力。其中,3μm+500nm混合微球(质量比为1∶1)的封堵能力大于单一的3μm微球的封堵能力;大粒径(3μm)微球的有效作用时间(200d)大于3μm+500nm混合微球(质量比为1∶1)的有效作用时间(100d)。实验结果表明,选用柔性微球驱替原油,在一定程度上提高了原油的采出程度,效果较为理想。影响微球颗粒是否成功最为关键的因素,是颗粒大小与孔隙喉道直径的匹配。根据搭桥堵塞原理,颗粒直径为孔道直径的1/8～1/3,才能产生有效搭桥作用。     

石灰石煅烧产物CaO的孔隙特征模拟及实验研究

为了研究石灰石煅烧产物 CaO 的孔隙特征与脱硫过程的关系,建立了 CaO 孔结构特征的数学模型,利用模型计算了 CaO 内部孔的比表面积和孔容积,计算值与实测值吻合良好.重点对0～5 nm,5～20 nm,20～100 nm及>100 nm 4个孔径范围进行了分析,结果表明:在 3 种试样中,试样 A 的粒径最大,孔径分布最宽,函数峰值所对应的孔半径及平均孔半径最大;试样 B 的粒径居中,但是孔径分布最窄,函数峰值所对应的孔半径及平均孔半径最小;粒径最小的试样 C,煅烧时可能部分烧结,导致函数峰值所对应的孔半径及平均孔半径比试样 B 大.在 3 种试样中,试样 B 的有效孔径(5～20 nm)所占的比例最大,由此预测其脱硫效果最好,选取上述 3 种粒径石灰石煅烧产物进行脱硫实验,实验结果与预测结果一致.     

静止气氛中单碳粒燃烧非稳态过程的影响因素

针对单个碳颗粒在静止气氛中的燃烧过程,进行了包括详细的物理和化学模型在内的瞬态数值模拟。研究了粒径收缩、初始粒径(50～200μm)、环境氧气的体积分数(9%～21%)和气相温度(1 200～1 600 K)对燃烧过程的影响。结果表明：碳粒燃烧过程中,碳粒表面温度先逐渐升高后迅速下降至环境温度,峰值温度出现在碳粒半径为35～45μm的范围内;碳粒收缩过程符合d₂定律,推导得到的碳粒单位面积燃烧速率?与粒径r_s的反比例关系式可用于对碳粒燃烧速率的预测计算;碳粒燃烧过程的特征值只取决于当前的颗粒直径,与其先前的演变过程无关;碳粒粒径越小,温度越低,化学动力学对燃烧过程的控制能力越强;初始碳粒半径相同时,升高气相温度或环境氧气的体积分数不会改变燃烧过程特征值的基本变化趋势,燃烧速率和碳粒表面温度均随气相温度或环境氧气体积分数的增大而增大,其中气相温度升高会导致碳粒表面温度达到峰值时的粒径减小。     

新型扩散式气固分离器PDA的实验研究

通过实验方法(三维粒子动态分析实验)研究了扩散式气固分离器流场分布，粒径分布等，从为研究扩散式气固分离器的结构，降低阻力，提高分离效率提供依据。从实验得出该气固分离器分离粒子的粒径分布主要在30μm--40μm，即对该粒径范围的粒子的分离效率很高。图5参3     

翅片管换热器积灰对空气侧传热和压降影响的实验研究

文章选取室外实际运行的翅片管换热器,在采样分析其表面沉积粉尘粒度的基础上,搭建换热器积灰实验台,以平直翅片管换热器为测试样件,研究积灰对换热器空气侧传热和压降的影响。结果表明,换热器表面不同位置沉积粉尘的粒径分布规律相近,沉积粉尘的粒径集中分布在1～100μm;换热器空气侧积灰对压降的影响大于对换热的影响;高风速能够减小积灰对换热器空气侧传热和压降的影响,当风速从1.5 m/s增大到3.0m/s,空气侧污垢热阻减小54%,压降增幅减小18.3%;换热器稳定后的空气侧污垢热阻及压降增幅,在低风速时随粉尘粒径的增大而减小,高风速时随粉尘粒径的增大而增大。     

柴油机燃用乙醇-柴油含氧燃料时微粒特性的分析

研究了一台增压柴油机燃用乙醇一柴油时的微粒总质量排放及粒径分布特性,并对微粒中可溶性有机物(SOF)、干碳烟(DS)和硫酸盐的质量百分比及SOF中的组分进行了分析。结果表明：使用含氧燃料后柴油机排气烟度大幅度降低而微粒总排放量降低幅度要小一些;微粒中DS排放降低;SOF排放增加,与未燃甲酯的产生导致HC排放增加有关;多环芳香烃比例随发动机负荷增大而减小;含氧燃料使得粒径分布在0．2～0．5μm范围内的比重在小负荷时降低,大负荷时升高。     

湿式电除尘器充电模型建立与收集效率的数值研究

本研究采用有限体积法对湿式电除尘器内部颗粒运动轨迹和颗粒收集效率进行了计算,利用某330 MW燃煤发电机组湿式电除尘器的实验数据来建立其颗粒充电模型,并分析不同循环水量下的颗粒收集效率。应用欧拉多相流方法计算气液两相流,结合DPM(离散相模型)追踪离子轨迹来模拟湿式电除尘器内部三相流动。结果显示,数值计算模型与实验数据匹配程度较好,能一定程度上体现湿式电除尘器内部特性。研究发现,在一定范围内随着循环水量的增加,收集效率随之增大;同时发现,在高循环水量的情况下,收集效率随着粒径的增大而增大;但是,在低循环水量下,随着粒径增大,收集效率下降,然后随着粒径的增大而升高。     

Enzymatic hydrolysis of pretreated soybean straw

In order to produce lactic acid, from agricultural residues such as soybean straw, which is a raw material for biodegradable plastic production, it is necessary to decompose the soybean straw into soluble sugars. Enzymatic hydrolysis is one of the methods in common use, while pretreatment is the effective way to increase the hydrolysis rate. The optimal conditions of pretreatment using ammonia and enzymatic hydrolysis of soybean straw were determined. Compared with the untreated straw, cellulose in straw pretreated by ammonia liquor (10%) soaking for 24 h at room temperature increased 70.27%, whereas hemicellulose and lignin in pretreated straw decreased to 41.45% and 30.16%, respectively.The results of infrared spectra (IR), scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis also showed that the structure and the surface of the straw were changed through pretreatment that is in favor of the following enzymatic hydrolysis. maximum enzymatic hydrolysis rate of 51.22% was achieved at a substrate concentration of 5% (w/v) at 50 °C and pH 4.8 using cellulase (50 fpu/g of substrate) for 36 h.     

Optimizing thermomechanical pretreatment conditions to enhance enzymatic hydrolysis of wheat straw by response surface methodology

Wheat straw was pretreated with a thermomechanical process developed in our laboratory to improve the enzymatic hydrolysis extent of potentially fermentable sugars. This process involves subjecting the lignocellulosic biomass for a short time to saturated steam pressure, followed by an instantaneous decompression to vacuum at 5 kPa. Increasing of the heat induced by saturated steam result in intensive vapour formation in the capillary porous structure of the plant material and the subsequent release of the pressure to vacuum allows fixing the expanded structure. Response surface methodology (RSM) based on central composite design was used to optimize three independent variables of the pretreatment process: processing pressure (300-700 kPa), initial moisture contents of wheat straw (10-40%) and processing time (3-62 min). The process was optimised for hydrolysis yield and initial hydrolysis rate obtained by enzymatic hydrolysis on the pretreated solids by Celluclast (1.5 L). The analysis of variance (ANOVA) revealed that, among the process variables, processing pressure and processing time have the most significant effect on the hydrolysis yield and on initial rate of hydrolysis whereas initial moisture content observed significantly lower effect on the two responses. The predicted hydrolysis yield and in a lesser extent the predicted initial rate of hydrolysis agreed satisfactorily with the experimental values with R² of 96% and 86% respectively.     

Tandem-ring mill pulverization benefits for enzymatic saccharification of biomass

A vibration mill, called a “tandem-ring mill”, which has cog-ring media in place of the ball medium of a conventional vibration mill, was developed to achieve high-impact pulverization of lignocellulosic biomass for bio-ethanol production. This study investigated pulverization characteristics of various biomass samples of Japanese cedar, eucalyptus, rice straw, rice husk, and reeds using a batch-type tandem-ring mill for 60 min and 100 min pulverizations. The pulverized biomasses were characterized by the mean particle diameter, crystallinity index, and enzymatic saccharification. The mean particle diameter of biomass was decreased rapidly in the first 20 min. Then the biomass mean particle diameter reached around 40 μm by flocculation. Furthermore, the crystallinity indexes of biomasses were decreased by pulverization. Especially, woody biomasses of cedar and eucalyptus were decreased rapidly around 10%, nearly a non-crystalline state. Woody biomasses, Japanese cedar, and eucalyptus showed high saccharification efficiency. Similarly, grass biomasses, rice straw, and rice husks showed high saccharification, aside from reeds. Therefore pretreatment of various biomasses using a tandem-ring mill was suitable for enzymatic saccharification.     

Screening of steam explosion conditions for glucose production from non-impregnated wheat straw

The conversion of wheat straw to fermentable sugar for bioethanol production typically involves a thermal pretreatment step, followed by enzymatic hydrolysis. In this study we have investigated the effect of steam explosion parameters on wheat straw digestibility using a newly designed steam explosion unit and a process without acid impregnation. The wheat straw was steam pretreated using 18 different conditions in the temperature range of 170-220 °C and the resulting material was used directly (i.e. without washing) for enzymatic hydrolysis and fermentation in either a separate hydrolysis and fermentation (SHF)-type or a simultaneous saccharification and fermentation (SSF)-type set-up. Maximum glucose yields upon enzymatic hydrolysis were obtained after pretreatment at 210 °C for 10 min and yields were similar at harsher conditions. Xylose yields increased with temperature and residence time up to 190 °C, but decreased at harsher pretreatment conditions since these led to xylan degradation and concomitant production of furfural. In an SHF-type set-up ethanol formation did not follow enzymatic glucose release and was inversely correlated with furfural levels. An SFF-type set-up displayed a straightforward correlation between the expected amount of released glucose and the ethanol yields. The highest saccharification yields corresponded to about 90% of the cellulose in the substrate. Overall, this study shows that steam explosion without an acid catalyst is a good pretreatment method for saccharification of wheat straw. Optimal steam explosion conditions need to be a compromise between sugar accessibility and sugar degradation.     

Batch-based enzymatic saccharification of sweet sorghum bagasse

To improve enzymatic digestibility and sugar concentration, sweet sorghum bagasse was pretreated with alkali and liquid hot water, and then subjected to fed-batch enzymatic hydrolysis. Scanning electron microscopy assay suggested that different pretreatment methods resulted in different composition and structure of residues; these changes had a significant influence on cellulose hydrolysis. Fresh substrate was pretreated and then added at different amounts during the first 48 h to yield a final dry matter content of 30% (w/v). For liquid hot water pretreatment, a maximal glucose concentration of 95.71 g/L, corresponding to 52.85% xylan removal, was obtained with the sweet sorghum bagasse pretreated at 184°C for 18 min. NaOH soaking at ambient conditions removed lignin up to 60%, and the subsequent hydrolysis with cellulase loading of less than 10 FPU/g DM, and substrate supplementation every few hours yield the high glucose and xylose concentrations of 114.89L and 29.93 g/L, respectively after 144 h.     

Effect of enzyme addition on fermentative hydrogen production from wheat straw

Wheat straw is an abundant agricultural residue which can be used as raw material to produce hydrogen (H₂), a promising alternative energy carrier, at a low cost. Bioconversion of lignocellulosic biomass to produce H₂ usually involves three main operations: pretreatment, hydrolysis and fermentation. In this study, the efficiency of exogenous enzyme addition on fermentative H₂ production from wheat straw was evaluated using mixed-cultures in two experimental systems: a one-stage system (direct enzyme addition) and a two-stage system (enzymatic hydrolysis prior to dark fermentation). H₂ production from untreated wheat straw ranged from 5.18 to 10.52 mL-H₂ g-VS⁻¹. Whatever the experimental enzyme addition procedure, a two-fold increase in H₂ production yields ranging from 11.06 to 19.63 mL-H₂ g-VS⁻¹ was observed after enzymatic treatment of the wheat straw. The high variability in H₂ yields in the two step process was explained by the consumption of free sugars by indigenous wheat straw microorganisms during enzymatic hydrolysis. The direct addition of exogenous enzymes in the one-stage dark fermentation stage proved to be the best way of significantly improving H₂ production from lignocellulosic biomass. Finally, the optimal dose of enzyme mixture added to the wheat straw was evaluated between 1 and 5 mg-protein g-raw wheat straw⁻¹.     

Enhanced enzymatic conversion with freeze pretreatment of rice straw

Production of bioethanol by the conversion of lignocellulosic waste has attracted much interest in recent years, because of its low cost and great potential availability. The pretreatment process is important for increasing the enzymatic digestibility of lignocellulosic materials. Enzymatic conversion with freeze pretreatment of rice straw was evaluated in this study. The freeze pretreatment was found to significantly increase the enzyme digestibility of rice straw from 48% to 84%. According to the results, enzymatic hydrolysis of unpretreated rice straw with 150 U cellulase and 100 U xylanase for 48 h yielded 226.77 g kg⁻¹ and 93.84 g kg⁻¹ substrate-reducing sugars respectively. However, the reducing sugar yields from freeze pretreatment under the same conditions were 417.27 g kg⁻¹ and 138.77 g kg⁻¹ substrate, respectively. In addition, hydrolyzates analysis showed that the highest glucose yield obtained during the enzymatic hydrolysis step in the present study was 371.91 g kg⁻¹ of dry rice straw, following pretreatment. Therefore, the enhanced enzymatic conversion with freeze pretreatment of rice straw was observed in this study. This indicated that freeze pretreatment was highly effective for enzymatic hydrolysis and low environmental impact.     

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。     

Hydrolysis of pretreated rice straw by an enzyme cocktail comprising acidic xylanase from Aspergillus sp. for bioethanol production

The most crucial enzyme involved in xylan hydrolysis is endoxylanase which cleaves the internal glycosidic bonds of xylan. The aim of this work was to study the production of extracellular xylanase by a locally isolated strain of Aspergillus sp. under solid-state fermentation (SSF) and to evaluate the potential of the enzyme in enzymatic hydrolysis of pretreated rice straw. Xylanase production reached maximum with incubation period (96 h), moisture level (80%), inoculum size (3 × 10⁶ spores/mL), pH (4.8), temperature (25 °C), carbon source (wheat bran) and nitrogen source (yeast extract). Under optimized conditions, xylanase production reached to 5059 IU/gds. Crude xylanase was used for supplementing the enzyme cocktail comprising cellulases (Zytex, India), β-glucosidase (In-house) and xylanase (In-house) for the saccharification of alkali-pretreated rice straw to get the maximum reducing sugar production. The cocktail containing the three enzymes resulted a maximum of 574.8 mg/g of total reducing sugars in comparison to 430.2 mg/g sugars by the cocktail without xylanase. These results proved that the crude xylanase preparation from Aspergillus sp. could be a potent candidate for the enzyme cocktail preparation for biomass hydrolysis in lignocellulosic bioethanol program.     

Pretreatment of sweet sorghum bagasse for hydrogen production by Caldicellulosiruptor saccharolyticus

Pretreatment of sweet sorghum bagasse, an energy crop residue, with NaOH for the production of fermentable substrates, was investigated. Optimal conditions for the alkaline pretreatment of sweet sorghum bagasse were realized at 10% NaOH (w/w dry matter). A delignification of 46% was then observed, and improved significantly the efficiency of enzymatic hydrolysis. Under hydrolysis conditions without pH control, up to 50% and 41% of the cellulose and hemicellulose contained in NaOH-pretreated sweet sorghum bagasse were converted by 24 h enzymatic hydrolysis to soluble monomeric sugars. The extreme thermophilic bacterium Caldicellulosiruptor saccharolyticus showed normal growth on hydrolysates of NaOH-pretreated biomass up to a sugar concentration of 20 g/L. Besides hydrogen, the main metabolic products detected in the fermentations were acetic and lactic acid. The maximal hydrogen yield observed in batch experiments under controlled conditions was 2.6 mol/mol C6 sugar. The maximal volumetric hydrogen production rate ranged from 10.2 to 10.6 mmol/(L h). At higher substrate concentrations the production of lactic acid increased at the expense of hydrogen production.