【作者】 罗炉林；

【导师】 刘建忠； 黄镇宇；

【作者基本信息】 浙江大学 ， 工程热物理， 2011， 硕士

【摘要】 我国煤炭种类繁多,其中褐煤产量丰富,价格低廉,但由于褐煤“二高三低”的特点,目前在国内开采较少,利用不广。如何降低褐煤水分,提高褐煤的利用效率,成为减低褐煤利用成本,增强褐煤市场竞争力的有效方法。本文结合褐煤高吸收率的自身的特性和我国褐煤产地丰富的太阳能资源的特点,提出利用太阳能对褐煤进行干燥处理,并从以下几个方面开展了相关工作。采用褐煤空气干燥法,对褐煤在等温条件下的干燥特性进行研究分析,得出褐煤在等温干燥下,干燥过程主要发生在降速干燥阶段。设计并构建两套太阳能干燥系统：温室型太阳能干燥系统和温室-集热型太阳能干燥系统。在温室型太阳能干燥系统上进行了褐煤太阳能干燥技术研究,得出在同等条件下,平衡时褐煤可达到比水和空气更高的温度,因此褐煤较适合太阳能干燥。对于预热和不预热干燥系统的条件下,褐煤太阳能干燥具有不同的干燥性质。研究中还对太阳辐射强度、煤粒大小、煤层厚度等影响因素对褐煤太阳能干燥效果进行了探索,研究表明辐射强度越强、煤粒越小、煤层越薄,越有利于褐煤的干燥。在温室.集热型太阳能干燥系统内主要研究了薄层褐煤的干燥特性,以及辐射强度、煤粒大小、通风量等因素对褐煤太阳能干燥影响。研究结果表明太阳能干燥薄层褐煤主要发生在降速干燥阶段,干燥曲线和干燥速率曲线呈指数变化。在实验的基础上,本文还对褐煤太阳能干燥进行了数学拟合,通过几个干燥模型的比较,选择了精确度较高,模拟效果较好的Logarithmic模型对褐煤的太阳能干燥进行模拟。实验和计算结果表明无论是室内人工太阳能装置下的干燥还是室外真实太阳光下的干燥,实验数据和干燥模型计算值的拟合较好,相关系数为0.99左右。因此Logarithmic模型可作为褐煤的太阳能的干燥模型,并由此得到褐煤太阳能干燥方程。文章在最后利用热平衡的原理计算两种干燥器的效率,结果表明在于燥前期,两种干燥器效率都较高,,其中温室-集热型太阳能干燥器对褐煤干燥效果较好,太阳能热利用效率较高,效率为19.7%,而温室型为14.5%。从整个实验阶段来看,两种装置的效率差距较小,均在11%左右。更多还原

【Abstract】 Lignite has low price and worldwide abundant minable reserves. However, due to the high moisture content and low heat value, lignite is not widely used. Dewatering and improving efficiency of lignite when lignite is transported to be utilized is an effective way of reducing costs and enhancing the market competitiveness.Solar drying of lignite is originally proposed here based on high absorptivity of lignite due to its black brown color and rich, clean and renewable solar energy in lignite producing areas. A series of work were performed as follows:Using an oven, the drying characteristics of lignite under isothermal conditions was investigated. It can be concluded that drying process occurred mainly in falling rate drying period when isothermal drying of lignite.Two sets of solar drying systems were designed and built:direct-mode type solar drying systems and mixed type solar drying systems. In the former one, feasibility and preliminary study on solar drying of lignite was conducted. It concluded that the temperature of lignite was much higher than water and air under the same experimental conditions. Therefore, the technology of solar drying is good for lignite. Lignite has different drying characteristics in solar drying preheating and without preheating. Moreover, influencing factors in solar drying of lignite, including the effect of solar radiation intensity, the particle size of lignite and the thickness of lignite layer, were investigated. The results indicated that strong solar radiation, small lignite particles and thin lignite layer are good for the increase of the performance of solar drying of lignite.Thin layer drying characteristics of lignite was studied in the mixed type solar drying systems. It concluded that thin layer solar drying lignite mainly occurred in the falling rate drying period. Besides drying curve and drying rate curves expressed as exponential function.Characteristics of Solar drying lignite were simulated using origin software. Six mathematical models of thin layer drying are selected in order to estimate the suitable model for describing the drying curves. Logarithmic model gives the best prediction of the drying curves. Experimental and computational results show that Logarithmic model can fit the data of indoor experiment under artificial solar systems and outdoor experiment under real sunlight very well with a correlation coefficient R of about 0.99.Therefore logarithmic model can be considered as model of solar drying of ignites.The efficiency of two kinds of drying systems was calculated at last. Both of them have higher efficiency in the earlier period of drying than efficiency in the later period. As a comparison, the efficiency of mixed type solar drying systems is 19.7%, while 14.5% for direct-mode type solar drying systems in the earlier period of drying. the efficiency of the two in whole Stage has little gap, were around 11%.更多还原