粒径与干燥温度对污泥颗粒干燥特性的影响

为了研究粒径、干燥温度对市政污泥干燥特性的影响,采用恒温干燥的方式对粒径<10 mm污泥颗粒的干燥性能进行实验研究。结果表明,粒径为3～10 mm的污泥颗粒在恒温干燥过程中无破碎现象稳定浓缩,干燥至恒定的时间和干基含水率与粒径大小成正比;粒径<3 mm的污泥颗粒由于吸附水的相互吸附作用形成团聚,对恒温干燥过程呈负面影响。当污泥颗粒粒径一致,干燥至恒重时,干燥温度与时间、干基含水率和挥发分含量成反比。粒径<10 mm的污泥颗粒最佳干燥条件为恒温温度105℃,污泥颗粒粒径3～4 mm。     

快速膜乳化法制备尺寸均一及结构可控聚苯乙烯微粒

以苯乙烯为单体、二乙烯基苯为交联剂,采用快速膜乳化法制备了聚苯乙烯微粒,对其粒径分布、制备重复性、颗粒结构进行了表征,并考察了致孔剂种类及用量对不同粒径颗粒形态结构的影响规律. 结果表明,聚苯乙烯颗粒粒径与所用膜孔径呈线性关系,最佳乳化压力与膜孔径呈反函数关系. 优化工艺条件下所制颗粒粒径为1~6 mm,粒径分布系数均小于0.8,批次相对标准偏差低于3%. 体积效应对小粒径颗粒的成型结构影响较大;粒径越小,颗粒成型时致孔剂与聚合物间的相分离程度越低,颗粒粒径小于2 mm时液体石蜡无法形成完整颗粒,颗粒粒径大于2 mm时十六烷用量在60%(w)以下才能形成大孔结构.     

府谷半焦干燥特性研究

针对炼焦工艺及熄焦方式不同导致焦炭含水率波动较大问题,以府谷半焦为原料,进行半焦干燥实验研究,考察了粒径、干燥温度、有无鼓风、堆积厚度等因素对半焦干燥速率的影响。结果表明,在恒定的干燥条件下,粒径越小,干燥速率越快。若将半焦粒径从50 mm减小到10 mm,则焦炭含水率干燥至1%所需干燥时间由57 min降至31 min;干燥温度降低,干燥初始阶段的调整期延长,干燥速率迅速下降,水脱除量急剧减少。因此,为保证较快的干燥速率,干燥温度应控制在200℃以上为宜;增加鼓风,降低堆积厚度有助于提高干燥速率,通过鼓风方式干燥可将脱水率提高23%。     

掺加橡胶颗粒混凝土材料的性能研究

本文研究橡胶尺寸对橡胶水泥基材料性能的影响,选择三组粒径为6～8mm,3～5mm和0～2mm的橡胶代替骨料制备混凝土,研究制备混凝土材料的稠度和密度、孔径结构、机械强度和干燥收缩性能。结果表明,混凝土材料的稠度和密度随橡胶粒径的增加而降低;对于孔径结构来说,孔体积随着橡胶颗粒粒径尺寸的减小而增加,其中橡胶颗粒粒径尺寸对中孔(50 nm)体积的影响不如橡胶含量因素条件显著;混凝土材料的机械强度随着橡胶颗粒粒径的减小而降低;而混凝土材料干燥收缩率随着橡胶颗粒粒径的减小而增加。     

山核桃等3类果蓬原料制备机制炭工艺

对山核桃果蓬添加比例为10%～100%与木屑共混制备机制棒以及机制炭进行了研究,结果表明,山核桃果蓬的最大添加量以30%为宜,其机制棒的棒形基本完整、平均棒长42.8cm。而从机制炭外形和理化性能来看,山核桃果蓬添加量为10%和20%时制备的机制炭性能较佳,30%次之。同时,对30%油茶果蓬、山核桃果蓬和板栗果蓬制备机制棒和机制炭的性能进行了对比试验,结果表明:山核桃果蓬制备的机制炭灰分含量最高,5.28%;板栗果蓬机制棒密度小、含水率低、呈细纤维状,固化成型得率只有80.85%。从灰分含量、固定碳含量、燃烧值等性能方面对比结果表明,30%板栗果蓬和油茶果蓬制备的机制炭总体性能都强于30%山核桃果蓬制备的机制炭,但30%板栗果蓬制备的机制炭强度较低、易断裂。因此,利用山核桃、板栗和油茶3类果蓬原料制备机制炭具有较高的现实可行性,其中油茶果蓬在机制炭方面应用效果最佳。     

聚合物颗粒气流振动耦合作用干燥效果

针对初始含水率在20%以下,粒径在5～20 mm,密度为1. 2～2 g/cm3的高聚物颗粒的颗粒物料,分阶段对干燥过程中高聚物颗粒含水率变化趋势进行研究,研究气流振动耦合作用对高聚物颗粒物料干燥过程中不同阶段的影响程度,确定物料达到0. 5%～1%的含水率所需要的干燥时间,根据实验结果设计并优化工程实验样机。研究结果表明,在气流振动耦合作用下,含水颗粒物料的干燥过程分为缓慢降速与快速降速2个阶段,分别对应物料表面水与内部结合水的干燥; 5～20 mm的含水颗粒物料的含水率从20%降至0. 5%～1%,所需时间为7～12. 5 min;在气流振动干燥状态下,颗粒物料干燥时间比单一热风情况下减少了20%～30%;设计并加工的气流振动干燥样机可以满足实际生产需求。     

果蓬类原料致密成型特征及其机制炭质量分析

以山核桃、油茶和板栗3类果蓬为原料,研究了此类原料与杉木、松木屑在不同配比条件下对果蓬类致密成型特征及其机制炭质量的影响。证实了果蓬类原料因纤维素含量、木质素含量与杉木、松木存在差异,且因较高的灰分含量限制,需与杉木或松木屑等原料在一定配比条件下才可实现良好的致密成型。而配比选择试验结果则表明,果蓬原料与杉木、松木屑混合原料以3:7比例配料为宜;在此条件下,制备的机制炭外形平直无裂缝,得率为 33.85%~36.73%,固定碳含量 79.80%~86.20%,热值28.96~31.92 MJ/kg。     

制备可再分散苯-丙乳胶粉的干燥温度探讨

采用喷雾干燥法制备苯-丙可再分散乳胶粉.探讨了干燥室进口温度对制备苯-丙可再分散乳胶粉及其性能的影响.结果表明,进口干燥空气的温度对乳胶粉的外观、粒径、含水率、再分散性、成膜性能、吸水率有较大影响.干燥温度升高,可再分散乳胶粉含水率降低,再分散液粒径减小,再分散性、成膜性都变好,吸水率提高.但温度过高(160 ℃)和过低(100 ℃)会使乳胶粒子在干燥过程中形成粒径较大的聚合物颗粒,导致粉体滤渣含量增加,对于苯-丙乳液来说,适当的喷雾干燥温度是120～140 ℃.红外光谱图表明:在100～160 ℃下的干燥没有明显改变乳胶粒子的分子结构.SEM图分析表明:干燥温度越高,再生膜越致密.     

感冒清热颗粒中药渣中试规模循环流化床气化实验

以感冒清热颗粒中药渣为原料,在双回路循环流化床中试设备中进行热解气化实验,研究原料含水率、原料粒径以及空气当量比ER对其气化特性的影响。结果表明：①随着原料含水率的提高,炉内平均温度降低,产生的燃气中焦油含量、CO2含量明显提高;CO含量、气体产率、碳转化率显著降低;H2含量、燃气热值以及气化效率均呈现先增大后减小的趋势。②原料粒径越小,反应炉内平均温度越高,燃气中焦油含量越低,燃气热值和气体产率越高,气化效率以及碳转化率越高;H2、CH4、CO、CnHm含量增加,CO2含量减少。③随着ER的增大,可燃气体尤其是CO的浓度不断降低,CO2含量不断增加;炉内平均温度、气体产率以及碳转化率均逐渐增大;燃气热值和燃气中焦油质量浓度逐渐减小;气化效率则呈现先增大后减小的变化趋势。④当原料含水量<9%、原料粒径<4mm以及ER在0.25~0.27时,气化效率较高,具有较好气化特性。     

超高含水率水泥固化泥炭土压缩模量和固结系数研究

泥炭土具有高含水率、高有机质含量、大孔隙比和低剪切强度等特点。化学固化常用于提升泥炭土地基承载力和抵抗变形能力。通过开展单向固结试验,研究了含水率、有机质含量、pH值、水泥掺量和掺料粒径对水泥固化泥炭土压缩模量和固结系数的影响。研究表明,随着水泥掺量和养护龄期增加,水泥水化反应生成的凝胶不断增长,固化土压缩模量随之增长。泥炭土初始含水率从600%降至300%后,固化土压缩模量增加了3.5倍。有机质含量从40%增至80%(质量分数)时,固化土压缩模量降低了50%。pH值从7.0降至3.5时,固化土压缩模量降低了15.8%。固化泥炭土的压缩模量和固结系数受含水率、水泥掺量影响最大,有机质含量次之,pH值影响最小。掺石英砂能提升固化泥炭土的压缩模量,且石英砂粒径越小,固化土压缩模量增幅越大。     

Screen printing variables and their effect on print paste consumption

This investigation evaluates the effects on print paste consumption of altering screen printing variables in rotary- and flat-screen printing. An analysis of fabric consumption factors for a 100% coverage screen on a number of different substrates is reported. Average factors are calculated for each substrate and the uptake variations brought about by altering squeegee size, magnet pressure, mesh size, machine speed and print fall-on recorded. Paste viscosity remained constant throughout the investigation. The fabric factors, together with screen open area percentages available from the laser engraver, are used to predict the amounts of paste required to print a designated length of fabric. A laboratory Zimmer magnetic rod printer is used under controlled conditions to draw comparisons with the bulk printing results. The data shows that the major influencing variables are squeegee size, machine speed and print fall-on effects.     

聚醚酮熔体过滤装置的建立与改进研究

针对聚醚酮的合成反应会产生细小固体杂质,原料、精制及干燥过程会带入灰尘等杂质,熔体挤出造粒时聚醚酮因长时间塑化和加热会产生残渣等问题,设计、建立了聚醚酮连续过滤生产装置,采用挤出机熔融、加压,再经熔体泵加压,经过高目数过滤网对其进行过滤。对装置试运行后出现的问题进行了改进,确定了适宜的操作条件,加料速度40 kg/h,挤出机加热温度375℃;出口压力12 MPa,熔体泵出口压力22～45 MPa,过滤网304材质,网块直径200 mm、网直径180 mm,网孔直径5μm,换网次数1次/h。测试结果表明,过滤后Ф5μm的颗粒杂质个数<6个/cm2,纯物料收率90.5%。     

Effects of raw material particle size distribution on the characteristics of Scots pine sawdust fuel pellets

In order to study the influence of raw material particle size distribution on the pelletizing process and the physical and thermomechanical characteristics of typical fuel pellets, saw dust of Scots pine was used as raw material for producing pellets in a semi industrial scaled mill (∼ 300 kg h^− 1). The raw materials were screened to a narrow particle size distribution and mixed into four different batches and then pelletized under controlled conditions. Physical pellet characteristics like compression strength, densities, moisture content, moisture absorption and abrasion resistance were determined. In addition, the thermochemical characteristics, i.e. drying and initial pyrolysis, flaming pyrolysis, char combustion and char yield were determined at different experimental conditions by using a laboratory-scaled furnace. The results indicate that the particle size distribution had some effect on current consumption and compression strength but no evident effect on single pellet and bulk density, moisture content, moisture absorption during storage and abrasion resistance. Differences in average total conversion time determined for pellet batches tested under the same combustion conditions was less than 5% and not significant.     

Evaluation of different strategies for pulverization of forest biomasses

The comminution of coarse forest biomass into fine products suitable to feed pulverized fuel burners could be an efficient way to produce usable renewable energy in the short term. However, size reduction of lignocellulosic forest materials is an intensive operation that requires energy. Pulverized fuel burners suitable for biomass usually require that the biomass fuel meet certain particle size specifications. In the present work, the specifications for the comminuted product are set as 95% by weight passing a 1000 μm mesh and 12% weight passing a 125 μm mesh. Three different forest biomasses, namely poplar chips, pine chips and pine bark, have been selected for size reduction study. Four different types of open-circuit processes have been designed and assayed utilizing a pilot plant comprising two hammermills, one screener and one dynamic air separator, in order to obtain the desired fineness for the product. The biomass raw materials and the products obtained have been characterized and the electrical energy requirements recorded. The process consisting of a primary grinding with 4 mm screen size, followed by selection with a dynamic air separator and secondary grinding of the separator reject, has been identified as the process most suitable for obtaining the desired product. The extrapolation to a full-scale plant for processing 10 o.d. t h^− 1 gives estimated energy requirements of 120, 150 and 35 kW h o.d. t^− 1 for poplar chips, pine chips and pine bark, respectively, with initial moisture contents between 10% and 15% (w.b.).     

Experimental casting of multichamotte refractories from slip

Conclusions The possibility of casting refractories from multichamotte slip with a maximum moisture content of 15% has been investigated; a preliminary treatment of the slip under vacuum is recommended as well as a brief vibration of the gypsum molds within a certain period after pouring.The high rate of moisture loss and solidification of multichamotte slip castings allow production on an industrial scale.Multichamotte kaolin mixtures yield castings up to 100 × 80 × 80 mm which acquire the following properties after firing at 1470° C: bulk density –2.17–2.26 g/cm³; porosity –12 to 18%; compressive strength –420 to 800 kg/cm²; loss on ignition –2. 7 to 4. 3; total shrinkage in relation to the size of gypsum molds –4 to 5%.The casting process is of practical value for the manufacture of multichamotte products (including high-alumina refractories) since molding the latter by means of pressing is either impossible or extremely difficult.Industrial tests are conducted for the verification and more accurate determination of technological parameters and the technical and economic effectiveness of the method.     

超临界CO_2流体萃取烟叶中烟碱工艺研究

以烟叶为原料,研究了超临界二氧化碳流体萃取烟碱的工艺条件,以烟碱萃取得率为考察指标,在原料粒度40目,含水率25%,分离釜的压力4～5MPa,温度40℃的条件下,对萃取时间、萃取温度、萃取压力等因素进行了研究,确定了最佳工艺条件为:萃取时间为2h,萃取温度为50℃,萃取压力30MPa。经过验证烟碱萃取得率为2.92%,为工业化生产提供了实验数据。     

Drying behavior of lignite under microwave heating

Because of lignite’s high moisture content, it must be dried before most applications. Microwave radiation may be suitable for efficient drying because of its special heating properties. This study investigated the drying behavior of lignite samples from eastern Inner Mongolia by microwave thermogravimetric analysis. Three stages of microwave drying were observed: preheating, fast weight loss, and falling rate drying periods. Samples’ surface temperatures increased dramatically during preheating, dropped slightly in the second period, and rose again in the final period. The measured surface temperature was <95°C during microwave heating. The overall moisture content decreased more rapidly under higher microwave power. Fine lignite particles (diameter <0.2?mm) and lump samples (particle size 10?mm) dried better than granular lignite (particle size 1–2?mm). The samples also underwent slight natural drying (1–2% point reduction in moisture content) after microwave treatment. The critical moisture content of lignite (11–15% under experimental conditions) was redefined. Energy consumption was analyzed to evaluate the feasibility of the proposed drying process.     

煤焦油中含水量与密度之间的关联研究

以中煤九鑫焦化有限公司煤焦油为样品,探讨了不同温度下煤焦油水分与其密度之间的关联关系。结果表明,在不同温度下,含水质量分数4%焦油的密度随温度升高而不断降低;同一温度下,焦油密度随含水量升高而降低。实际生产中,可利用密度推算出一定温度下的焦油含水量,从而及时调整小氨水澄清槽焦油水分离以及焦油产品储槽自动控制水分脱除程度(≤4%),以减少脱水消耗蒸汽量。     

EFFECTS OF DRYING ON HEAD RICE YIELD USING FLUIDIZATION TECHNIQUE

ABSTRACT

Experimental results of fluidized bed paddy drying using high inlet air temperatures (140 and 150 °C) showed that head rice yield could be increased to a maximum value at a range of paddy final moisture contents of 19 to 22 % wet-basis. In case of reducing moisture content of paddy to lower than 19 % wet-basis, head rice yield of tempered paddy was higher than that of no-tempered one. Initial moisture contents of paddy that could increase head rice yield were in a range of 23 to 31 % wet-basis. As initial moisture content increased head rice yield increased. Whiteness of dried paddy was mostly accepted. However, if tempering temperature was higher than 60 °C, it may cause the problems for trade.     

镀膜电热内墙砖热稳定性的研究

研究了不同材质内墙砖的热稳定性,以及同一材质不同泥浆细度内墙砖的热稳定性.论述了坯粉性能对内墙砖热稳定性的影响.结果显示长石质内墙砖有较高的热稳定性,泥浆的细度控制在万孔筛余0.38%～0.76%,有利于内墙砖热稳定性的提高,使用含水率为6.5%～8.5%,坯粉颗粒以0.25～0.125mm为主,有利于内墙砖热稳定性的提高.