CAJ | 학술논문

为了解污泥常压过热蒸汽薄层干燥特性，搭建了常压过热蒸汽干燥试验台，进行了2、4、6和10 mm厚度污泥在不同过热蒸汽温度160～280℃下薄层干燥试验，并分段对试验数据进行拟合分析，得到了模型参数与过热蒸汽温度、污泥厚度之间的关系。结果表明：污泥在较高温度过热蒸汽干燥后没有氧化燃烧，且裂纹密集，表面粗糙，利于干燥的进行。污泥薄层在干燥初始阶段存在凝结过程，过热蒸汽凝结在物料表面使其质量不降反而增加，导致干燥时间延长，凝结水质量和干燥时间的增幅受过热蒸汽温度的影响较大，过热蒸汽温度越高，增幅越小，而污泥的厚度对污泥质量和干燥时间的增幅影响较小。根据斐克第二定律，得到2、4、6和10 mm厚度污泥在160～280℃过热蒸汽干燥水分有效扩散系数分别为2.0641×10-9～8.8527×10-9、4.3738×10-9～1.6626×10-8、6.6082×10-9～2.46×10-8和1.1916×10-8～4.0806×10-8 m2/s，由Arrhenius方程建立有效扩散系数的对数与温度倒数的线性关系，得到水分的活化能分别为26.250、22.032、21.894和20.961 kJ/mol。试验结果可为污泥过热蒸汽干燥工艺参数优化及干燥设备研制提供参考。
위료해오니상압과열증기박층간조특성，탑건료상압과열증기간조시험태，진행료2、4、6화10 mm후도오니재불동과열증기온도160～280℃하박층간조시험，병분단대시험수거진행의합분석，득도료모형삼수여과열증기온도、오니후도지간적관계。결과표명：오니재교고온도과열증기간조후몰유양화연소，차렬문밀집，표면조조，리우간조적진행。오니박층재간조초시계단존재응결과정，과열증기응결재물료표면사기질량불강반이증가，도치간조시간연장，응결수질량화간조시간적증폭수과열증기온도적영향교대，과열증기온도월고，증폭월소，이오니적후도대오니질량화간조시간적증폭영향교소。근거비극제이정률，득도2、4、6화10 mm후도오니재160～280℃과열증기간조수분유효확산계수분별위2.0641×10-9～8.8527×10-9、4.3738×10-9～1.6626×10-8、6.6082×10-9～2.46×10-8화1.1916×10-8～4.0806×10-8 m2/s，유Arrhenius방정건립유효확산계수적대수여온도도수적선성관계，득도수분적활화능분별위26.250、22.032、21.894화20.961 kJ/mol。시험결과가위오니과열증기간조공예삼수우화급간조설비연제제공삼고。
Generally, sludge exists with high moisture content. De-water is the first and crucial step in disposal processes such as land filling, composting, building materials, and incineration. Currently, there are many studies on sludge drying by different heat transfer modes such as conduction and convection. But in most studies, the sludge drying was carried out under an atmosphere of air, which had disadvantages in high-energy consumption and an abundant quantity of exhaust. Superheated steam drying has been used to dehydrate a variety of products, including meat, grain stillage, lignite, and wood, because of environmental protection, non-oxidation, and higher drying efficiency advantages. The purpose of this study was to investigate the drying characteristics of superheated-steam on a thin layer of sludge. Thin layer drying experiments of sludge samples with different thicknesses under a series of superheated steam temperatures were carried out. Sludge samples were collected in a local wastewater treatment plant after mechanical dewatering. The size of the sludge samples were taken over an area of 100 mm×100 mm, having thicknesses of 2, 4, 6, and 10 mm, respectively. The temperatures of superheated steam were controlled by the amount of the access heaters. The experiments of superheated steam drying were conducted at 160, 200, 240, and 280℃, respectively. Relations between the model parameters and temperature and thickness for the moisture ratio of sludge in relation to drying time were determined. The results showed that sludge samples were not oxidized or burnt after superheated steam drying even at high temperatures. The dense crack and rough surface of sludge during superheated steam drying were beneficial to the drying process. At the beginning of the drying process, the mass of the samples increased due to superheated steam coming in contact with the cold surface of the sludge as the initial temperature of the sludge is close to room temperature (around 20℃). As a result, the drying time of sludge samples to reach a certain moisture content increased. The increase in the mass of condensation water and drying time was greatly influenced by the temperature of superheated steam. As a result, the higher the temperature, the smaller the increase. However, the increase was hardly influenced by the thickness of sludge. The Effective moisture diffusivity was calculated by using Fick’s second law. Thin layers of sludge formed by superheated steam drying having thicknesses of 2, 4, 6, and 10 mm had effective diffusion coefficient variations of 2.0641×10-9-8.8527×10-9, 4.3738×10-9-1.6626×10-8, 6.6082×10-9-2.46×10-8, and 1.1916×10-8-4.0806×10-8 m2/s at the temperature 160-280℃. The linear relationship between the natural logarithm of the effective diffusion coefficient and reciprocal of temperature was built based on the Arrhenius empirical formula. The activation energy values of 2, 4, 6, and 10 mm thicknesses of sludge were 26.250, 22.032, 21.894, and 20.961 kJ/mol. A valuable reference for the parameter optimization and equipment design of sludge superheated steam drying was provided by the experimental results.