共查询到19条相似文献,搜索用时 109 毫秒
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褐煤干燥脱水是实现其高效利用、节能减排的重要技术措施。基于不同热风温度(60℃,80℃,100℃)和煤样粒度(小于2 mm, 2 mm~5 mm, 5 mm~7 mm, 7 mm~10 mm, 10 mm~13 mm)对高西沟低阶褐煤单一热风干燥特性进行探讨,依次采用单一热风干燥、热风-红外串联和热风-红外并联联合干燥方式,通过实验分析了干燥过程褐煤水分比和干燥速率的变化特征,应用比能耗(QSEC)和能效(ηe)对比了三种干燥方式的能耗,采用SEM和FTIR分别分析了煤样表观形貌和官能团。结果表明:单一热风干燥温度越高,煤样与空气温差越大,煤样获得的热量越高,干燥速率越快;煤样粒度越小,煤样水分比下降越快,结束时的水分比越低;热风-红外串联联合干燥转换时间节点越早,所需干燥时间越短,在热风与红外干燥阶段干燥速率各出现一次最大值;并联干燥中褐煤水分比呈指数下降,并以降速期为主要阶段;三种干燥方式按比能耗由大到小依次为单一热风干燥(334.54 MJ/kg)、热风-红外并联干燥(273.89 MJ/kg)、热风-红外串联干燥(121.18 MJ/... 相似文献
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为降低生物质型煤干燥成本,提高干燥效率,研究热风干燥风速和温度对热风干燥特性的影响,拟合了生物质型煤在不同热风干燥条件下水分随时间变化的模拟曲线。结果表明:生物质型煤与多数多孔介质类似,干燥过程可分为加速干燥、恒速干燥、降速干燥3个阶段,其中恒速干燥阶段的干燥时间约25 min;热风温度越高,风速越大,生物质型煤的干燥速率越大,干燥时间越短,干燥时的裂纹率也越高。当干燥温度180℃,风速1.2 m/s时,生物质型煤热风干燥效果较好,干燥热效率最高为48.34%。通过对不同温度、风速条件下的生物质型煤干燥试验数据与常用干燥模型进行拟合分析,发现Sabbet干燥模型拟合度最好,当干燥温度180℃,风速1.2 m/s时相关性系数为0.997,二者相关性显著,因此Sabbet干燥模型可较好地反映生物质型煤在不同温度、风速下的干燥特性。 相似文献
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采用静态法研究了明胶的平衡含湿质量分数,得到了20℃下吸湿和解吸等温线,结果表明,当空气相对湿度在16%—39%,存在吸湿滞后现象。在对流干燥实验台上进行了明胶干燥特性的实验,以不同厚度的明胶块为实验对象研究了热风温度、风速、湿度对干燥过程的影响。实验结果表明:明胶的干燥过程只有降速阶段,提高热风温度、加大风速均可以在前期提高干燥速率,但在干燥后期干燥速率反而降低;明胶块中心温度受胶块厚度、热风温度影响较大,而在实验范围内空气相对湿度的变化对明胶中心温度影响甚微;明胶的相对含湿质量分数随时间呈指数规律下降,提高风温、加大风速后明胶含湿质量分数在开始阶段下降较快,但最终含湿质量分数反而偏高。 相似文献
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针对褐煤水分高、发热量低、易风化自燃等特点,以内蒙古褐煤为研究对象,进行了褐煤静态干燥实验和褐煤提质多因素实验。以O2体积分数10.5%的烟气为干燥介质,在分析褐煤流化床提质干燥机理的基础上,对褐煤进行流化床动态提质实验。结果表明:褐煤提质水分控制在5%左右为宜。褐煤粒级小于3 mm时,温度对煤样干燥速度影响最大,其次是煤样粒度,风速对干燥速度影响最小。确定全粒级、0.5~1.25、1.25~2、2~3 mm褐煤临界流化风速分别为38、20、40和50 m3/h。褐煤适宜提质温度和时间分别为200~240℃和5~8 min。最后建立了褐煤提质模型,说明褐煤提质规律与提质介质温度、风速密切相关,该模型对褐煤提质生产具有指导作用。 相似文献
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褐煤深度脱水的实验研究 总被引:1,自引:0,他引:1
针对褐煤低温烟气干燥技术脱水幅度难以提高,发热量增加不多等问题,提出了低温干燥与深度脱水的联合工艺。研究了不同干燥温度、干燥时间和煤样粒度对褐煤深度脱水效果的影响,结果表明:褐煤深度脱水适宜的干燥温度为500~800℃,较为适宜的干燥时间为80 s左右,当粒度小于50 mm时,干燥产物发热量随粒度变化不大。最后提出了褐煤深度脱水最佳工艺条件和参数,即当预干燥煤的Mar约为18%,煤样粒度为-50 mm,干燥温度为700℃,干燥时间为80 s时,深度脱水产物的Mar为8%,Vdaf在46%左右,折算Qnet,ar约为21 kJ/g。褐煤深度脱水促进了褐煤发热量的进一步提高,实现了褐煤资源的增值,研究结果为褐煤低温干燥与深度脱水联合工艺技术方案的确定奠定了基础。 相似文献
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将微波干燥和热风干燥应用于新鲜金萱茶叶的干燥,在3个不同的微波功率(350 W,470 W,800 W)和4个不同的空气温度(70 ℃,80 ℃,90 ℃,100 ℃)下,研究了干燥参数即微波功率或温度对干燥时间、失水量的影响,同时还考察了茶叶中茶多酚总量和儿茶素含量的变化、干茶叶的复水性。实验得出,与热风干燥相比,微波干燥的时间缩短了76%~95%,而且干燥后的茶叶有很好的复水性,但干燥后茶多酚总量少于热风干燥;同时随着功率增加,微波干燥时间由11 min降为6 min,随着温度升高,热风干燥时间由127 min缩短为45 min。这两种方法的茶叶干燥动力学模型均满足Page’s半经验公式。 相似文献
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为优化盐泥颗粒干燥设备及结构参数,搭建热风干燥实验装置对盐泥颗粒进行热风干燥实验,研究不同风温、风速和堆积厚度对盐泥颗粒热风干燥特性的影响。对不同条件下的干燥特性曲线,通过比较决定系数R2、卡方x2和标准误差ESME等指标,评价5种常用干燥动力学模型对干燥曲线的拟合结果。结果表明:Midilli模型可以预测盐泥颗粒热风干燥过程水分的变化规律,模型预测的干燥曲线与实验干燥曲线有较高的拟合度。盐泥颗粒热风干燥过程中干燥速率逐渐下降,热风干燥特性与风温和堆积厚度密切相关。当温度从50℃增加到80℃时,有效水分扩散系数由2.038 39×10-9 m2·s-1增加到8.137 643×10-9 m2·s-1。 相似文献
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2种方式干燥的天然橡胶干燥特性之研究 总被引:2,自引:0,他引:2
为探讨微波干燥天然橡胶新技术,分别在温度115℃下,采用电热烘箱产生热空气和微波干燥装置干燥湿天然橡胶胶粒,对二者的干燥特性及硫化胶性能进行对比分析研究。结果表明,微波干燥只需13.467min就可使胶料含水量降至0.791%,热空气干燥则需211min。天然橡胶微波干燥和热空气干燥主要包含失水率加速期、失水率减速期、失水率相对恒速期3个失水阶段。整个干燥过程中,微波干燥失水率较大,而热空气干燥失水率比较小。微波干燥天然橡胶硫化胶的耐热氧老化性能得到显著提高:其老化前后拉断伸长率变化率(-35%)和拉伸强度变化率(-59%)明显高于热风干燥天然橡胶硫化胶的拉断伸长率变化率(-62%)和拉伸强度变化率(-89%)。 相似文献
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《Drying Technology》2013,31(7):1173-1184
Abstract Combination of microwave-vacuum drying and air drying was investigated as a potential mean for drying garlic slices. The sample was dried by microwave-vacuum until the moisture content reached 10% (wet basis), and then by conventional hot-air drying at the temperature of 45°C to final moisture content less than 5% (wet basis). Pungency, color, texture, and rehydration ratio of garlic slices dried by this method were evaluated and compared with those dried by freeze drying and conventional hot-air drying. The comparison showed that the quality of garlic slices dried by the current method was close to that of freeze dried garlic slices and much better than that of conventional hot-air dried ones. The lab microwave-vacuum dryer which the materials to be dried could be rotated in the cavity was developed by the authors. 相似文献
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Dehydration of Garlic Slices by Combined Microwave-Vacuum and Air Drying 总被引:10,自引:0,他引:10
Combination of microwave-vacuum drying and air drying was investigated as a potential mean for drying garlic slices. The sample was dried by microwave-vacuum until the moisture content reached 10% (wet basis), and then by conventional hot-air drying at the temperature of 45°C to final moisture content less than 5% (wet basis). Pungency, color, texture, and rehydration ratio of garlic slices dried by this method were evaluated and compared with those dried by freeze drying and conventional hot-air drying. The comparison showed that the quality of garlic slices dried by the current method was close to that of freeze dried garlic slices and much better than that of conventional hot-air dried ones. The lab microwave-vacuum dryer which the materials to be dried could be rotated in the cavity was developed by the authors. 相似文献
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Effect of Microwave-Vacuum Drying on the Carotenoids Retention of Carrot Slices and Chlorophyll Retention of Chinese Chive Leaves 总被引:3,自引:0,他引:3
Microwave-vacuum drying, and combined microwave-vacuum with air or vacuum drying were investigated as potential methods for drying green and high-carotenoid vegetables of Chinese chive leaves and carrot slices. The samples were dried by microwave-vacuum until the moisture content reached about 20% (wet basis), and then by conventional air drying at the temperature of 45-50°C or conventional vacuum drying at the temperature of 55-60°C or by continued microwave-vacuum drying at lower power level to final moisture content about 6% (wet basis). The carotenoid retention of carrot slices and chlorophyll retention of Chinese chive leaves, dried by these methods, was evaluated and compared with those dried by freeze-drying and conventional hot-air drying. The comparison showed that the carotenoid retention of carrot slices and chlorophyll retention of chive leaves, dried by the current methods, was very close to or even as much as those dried by freeze-drying and much better than those dried by conventional hot-air. Blanching was not necessary when using microwave-vacuum drying or combined microwave-vacuum with conventional hot-air drying or vacuum drying, because the activity of enzymes which were responsible for the degradation of color was greatly reduced with extremely rapid decreasing of moisture, and because oxygen was absent in microwave-vacuum drying. 相似文献
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为了发展丹参叶绿茶产品,本文研究了不同干燥方法对丹参叶有效成分的影响。以丹酚酸B和叶绿素含量等指标确定了热风干燥和真空冷冻干燥的最佳工艺参数,并与丹参叶中的有效成分进行比较。最终确定的热风干燥的最佳工艺参数为温度60℃,风速0.6m/s,物料厚度为2层。真空冷冻干燥的最佳工艺参数为采用-25℃进行预冻,保持2h左右的时间,50Pa升华22h左右,20℃解析14h。结果表明真空冷冻干燥是丹参叶绿茶保质干燥的最佳方法,其对丹参叶中的丹酚酸B和叶绿素含量保留率分别为98.76%和82.21%。 相似文献