微波辐射对脱水城市污泥穿透性和脱水性的影响

研究了频率2450 MHz、功率500 W的微波在脱水城市污泥中的穿透性及辐射过程中污泥脱水性的变化. 结果表明,微波的穿透深度为8.7 mm,适宜的辐射可显著提高污泥的脱水性. 微波辐射5 min,上层容器中污泥离心后含水率由80.61%降至75.09%. 当温度高于约60℃时,污泥中微生物细胞开始大量破碎,胞内水释出,离心后含水率随温度升高而降低;高于88℃时,胞外聚合物含量无明显增加而亲水性下降,污泥脱水性迅速改善.     

微波连续化学过程研究进展

由于微波在其吸收介质中的穿透深度有限,间歇釜式反应器很难扩大规模,从而使微波化学应用于工业生产受到一定限制。发展微波连续化学过程是实现微波更普遍的应用于工业生产的有效途径。微波连续化学过程克服了吸收介质的穿透深度等问题,显著提高了微波辐射效率,并存在易于控制反应参数,优化实验过程,自动化连续操作等优点。主要介绍了典型的微波连续反应装置及其在微波连续化学过程的应用。     

木材真空干燥设备加热系统理论计算的探讨

将过热蒸汽作为干燥介质,推导了木材真空干燥设备加热系统的理论计算方程,并以厚度为40mm,初含水率从60%干至10%的红松为标准材,对真空干燥设备的加热系统进行了理论计算,比较分析了绝对压力对计算结果的影响。     

微波技术在煤炭加工领域的应用研究进展

微波技术具有清洁、高效、无污染等特点,近年来广泛应用于煤炭清洁高效加工利用领域。介绍了不同物料下微波的穿透、吸收、反射三种响应机理及介电性能、微波穿透深度、非热效应等加热特性,综述了煤与微波相互作用过程的研究现状及微波技术在脱水改质、水煤浆制备、热解和脱硫等煤炭加工领域的应用研究。提出将微波加热实验与煤炭数值模拟相结合,为煤的微波处理工业化提供理论依据。     

微波加热技术在多孔炭处理中的应用

微波加热技术作为一种全新的加热模式在众多领域得到了广泛的应用。本文综述了微波加热的机理、特点及其在多孔炭处理中的应用，包括传统活性炭的制备、再生、改性及活性炭纤维的改性；指出了微波加热在多孔炭处理领域的应用中存在的问题，并对其前景进行了预测。     

微波化学

微波 ( microwarve,MV)指波长 1 μm～ 1 mm,频率从 30 0 MHz～ 30 0 GHz的超高频电磁波。为避免干扰 ,国际上规定民用微波频率一般为 90 0 (± 1 5 )MHz和 2 4 5 0 (± 5 0 ) MHz。作为一种传输介质和加热能源 ,微波已被广泛应用于各学科领域。微波在化学中的应用开辟了微波化学这一化学新领域 ,即微波直接与化学体系发生作用 ,从而促进各类化学反应的进行。本文综述了微波在无机化学、有机化学、分析化学和环境化学等学科的主要应用以及其它一些相关领域的发展 ,并对其反应机理进行了探讨。1　微波在无机化学中的应用1 .1　微波烧结固…     

逾渗多孔介质对固体颗粒吸附过程的影响

研究了悬浮液中的颗粒在通过逾渗多孔介质时的被吸附特性。采用数值计算的方法;通过求解描述低速流体流动的Stokes方程以及简化的颗粒运动方程;初步得到颗粒在逾渗多孔介质中的运动轨迹;并在此基础上;求得颗粒与多孔介质内表面的碰撞概率;进而研究颗粒的被吸附特性。数值结果表明均匀多孔介质和分形多孔介质对颗粒的吸附存在本质差异。颗粒流出概率（实际中常表示为出口悬浮液中的颗粒浓度）与多孔床深度间的指数关系仅对均匀多孔介质成立;而对分形多孔介质并不成立。     

微波硫化

微波是频率在30HDMHz～3000MHz(兆赫)范围内的电磁波，因其频率超高故也被称为超高频(高频频率不低于0．5MHz)，又因其波长(12．5cm)与无线电电波的长度(1～10^3m)相比，相对短而微，故也称微波。微波的最大特点是能穿透导电性能差的物体，使其内部升热，在橡胶制造领域可用于预热，硫化和废胶脱硫。     

频率和功率对轮胎微波加热的影响

在双波导入射功率均为5 k W时,分别对(915±25)MHz频率范围和925 MHz频率时的双波导不同功率分配下的微波加热效率以及轮胎温度场分布进行了模拟。结果表明:微波加热效率随微波频率的变化呈类似于正/余弦曲线波动,在微波作用频率为925 MHz时,微波加热效果最好;双波导功率分配越趋近于一致,微波加热效率越高,轮胎温度场分布越均匀。     

微波加热在毛条烘干中的应用研究

介绍了应用微波加热烘干毛条的基本原理,研究了微波干燥设备的烘干效率、节能效果及烘干效果,结果表明,微波加热可以应用于纺织印染行业,为微波加热在纺织印染行业的推广应用提供了研究基础。通过生产应用,在计算微波加热毛条烘干工艺参数时,微波烘干机的干燥效率可取1.1kg/kW﹒h,微波干燥后,毛条含水率均匀,颜色前后色差无变化,纤维的强度和手感得到改善,微波干燥节能效果,比射频烘干节能约20%。     

Complex Dielectric Properties of the Sapwood of Aspen,White Birch,Yellow Birch,and Sugar Maple

The dielectric properties of four Canadian eastern wood species were measured as a function of moisture content and temperature, at frequencies between 0.4 and 2.47 GHz using the cavity perturbation technique. The temperature was varied from ? 20 to 58°C and moisture content from 40 to 136%. Dielectric properties varied with moisture content, wood temperature, and microwave frequency. However, the influence of moisture content and microwave frequency overshadowed the influence of wood species and wood temperature. The dependencies were established for the selected species and discrepancies are discussed, namely concerning their implication when used in wood industry (nondestructive testing, heating, and drying).     

Complex Dielectric Properties of the Sapwood of Aspen, White Birch, Yellow Birch, and Sugar Maple

The dielectric properties of four Canadian eastern wood species were measured as a function of moisture content and temperature, at frequencies between 0.4 and 2.47 GHz using the cavity perturbation technique. The temperature was varied from - 20 to 58°C and moisture content from 40 to 136%. Dielectric properties varied with moisture content, wood temperature, and microwave frequency. However, the influence of moisture content and microwave frequency overshadowed the influence of wood species and wood temperature. The dependencies were established for the selected species and discrepancies are discussed, namely concerning their implication when used in wood industry (nondestructive testing, heating, and drying).     

Modeling Microwave Heating and Moisture Redistribution in Wood

A finite element model was developed to describe and explain microwave heating of wood and the following moisture redistribution in wood. Dielectric and thermal properties are of great importance, since they are continuously affected during the process by moisture content, density, grain direction, temperature, and more. Computer tomography was used to detect wood density and moisture content. Heat distribution was verified by fiber-optic temperature sensors. The tests were performed in a designed microwave dryer based on 1-kW generators, 2.45 GHz. The results show that finite element modeling is a powerful tool to simulate heat and mass transfer in wood, providing the material is well described.     

Modeling Microwave Heating and Moisture Redistribution in Wood

A finite element model was developed to describe and explain microwave heating of wood and the following moisture redistribution in wood. Dielectric and thermal properties are of great importance, since they are continuously affected during the process by moisture content, density, grain direction, temperature, and more. Computer tomography was used to detect wood density and moisture content. Heat distribution was verified by fiber-optic temperature sensors. The tests were performed in a designed microwave dryer based on 1-kW generators, 2.45 GHz. The results show that finite element modeling is a powerful tool to simulate heat and mass transfer in wood, providing the material is well described.     

Theoretical investigation of temperature distribution uniformity in wood during microwave drying in three-port feeding circular resonant cavity

The temperature distribution within wood samples during microwave drying is significantly influenced by the dimensions of the wood sample, microwave frequency, heating time, and moisture content of the wood. Here, the temperature distribution inside the wood during microwave drying has been studied by finite element analysis in a three-port feeding circular resonant cavity. With an increasing radius of the wood, the calculated temperature variation coefficient decreased from 54.3 to 23.5% and the energy efficiency increased from 18 to 95%. When the radius of the wood was 0.8 times that of the circular cavity, the drying process was optimal. The theoretical calculations indicated that the length of the wood also affects the temperature variation coefficient. When the length of wood was more than the height of waveguide, the temperature variation coefficient was less than 40.5% and the energy efficiency was more than 90%. Other factors such as microwave frequency, heating time, and moisture content also influenced the uniformity of temperature distribution. This study helps to better understand the microwave drying process to facilitate its further applications for wood drying.     

Moisture conditioning of wood using a continuous microwave dryer

Lower moisture content in wood, preferably 5–6%, is desirable for many chemical modification reactions. Economically, it is not feasible to dry timber to such low moisture content by conventional drying without drying degrades. Microwave heating was evaluated and found to be effective in reducing the moisture content of radiata pine from 13% to 6% in a microwave cycle of two minutes. The energy consumption is about 55 kWh/m³. Moisture distribution profiles demonstrate very uniform drying across the sample thickness. The findings suggest that microwave heating can potentially be applied to condition wood in a very short period of time.     

木块微波裂解及产物组成分析

使用2 450 MHz/12 kW微波裂解装置裂解木块并对不同裂解条件下气、液产物进行了分析。结果表明,木块微波裂解生成了极具价值的生物油、合成气等产品;裂解功率对液体产品收率及主要组分的种类产生影响;裂解温度对液态产品各组分相对含量及气态产品的成分构成产生影响。     

Microwave roasting and phospholipids in soybeans (Glycine max. L.) at different moisture contents

The effects of microwave roasting on phospholipids in soybeans were investigated in relation to moisture. Whole soybeans at different moistures (9.6, 38.2, and 51.9%) were roasted by exposure to microwaves at a frequency of 2,450 MHz. During microwave treatments, the lower the moisture content, the higher was the internal temperature in soybeans at the end of microwave roasting. Total lipids were extracted from the beans after microwave treatment, and the phospholipids were separated with thin-layer chromatography. Phosphatidylcholine was the principal phospholipid in the extracted lipids from all unroasted and roasted bean samples. After microwave roasting, phospholipids containing an amino group, especially phosphatidylethanolamine, decreased substantially (P<0.05) in lower-moisture soybeans. However, increasing the moisture content depressed a rise in the internal temperature of soybeans and prevented a reduction in phospholipids and/or polyunsaturated fatty acids in the phospholipids. Based on the changes in the composition and fatty acid distribution of phospholipids in soybeans during microwave roasting, it is necessary to consider the moisture content in soybeans when roasting in a microwave oven.     

Characterization of empty fruit bunch for microwave-assisted pyrolysis

Agricultural waste such as oil palm empty fruit bunch (EFB) is of environmental concern to Malaysia as one of the world’s largest oil palm producers. Pyrolysis can be used to treat biomass waste due to its flexibility in producing solid, liquid and gas products. This study attempts to characterize EFB for pyrolysis using microwaves as an alternative heating source. EFB taken from a local oil palm mill was subjected to fuel, chemical and dielectric property analysis. The findings revealed that high moisture and 47% oxygen gave low calorific value of 16 MJ/kg. Notably, high water content is an advantage in microwave heating as water is a good microwave absorber, which results in fast drying. Further, a high volatile content at 70% gave the EFB an advantage of high reactivity. A moderate potassium content of 12.8% could also positively affect microwave absorption. The dielectric properties of EFB were observed to be proportional to the moisture content. Furthermore, the microwave penetration depth was found highest at 20% moisture, i.e. 3.5 cm. However, low values of both dielectric constant and loss of dried EFBs would require the addition of microwave absorbers for pyrolysis reaction. The fuel and chemical characteristics of EFB were found comparable to other biomasses, which indicated a good candidate for microwave pyrolysis treatment.     

Comparison of Three Different Frequency Drying Methods for Barley Chewable Tablets

The effect of 27 MHz radio-frequency (27 RF), 915 MHz microwave (915 MW), and 2450 MHz microwave (2450 MW) on drying of barley chewable tablets was examined experimentally. It was observed that the dielectric constant was decreased with the moisture content reduction. Penetration depths of samples treated with 27 RF were the highest. The quality of products was evaluated according to color, temperature, ferric-reducing power, and DPPH scavenging. 2450 MW played a positive role in improving antioxidant properties. The comprehensive view is that radio-frequency technology may be a promising drying method for food processing.