绿色环保绝缘材料应用——天然酯绝缘油发展回顾

天然酯绝缘油的属性与矿物油相比,在安全性、环保性和对变压器运行方面的优势和缺点广受议论.回顾标准、测试的现状和天然酯绝缘油在电力行业高压变压器的应用,重申ASTM标准规范,新的IEEE指导值和推荐均被检测,并与矿物油标准比较,同时也介绍了IEC规范发展的现状和天然酯绝缘油市场经济发展的需要.     

植物绝缘油中抗氧化剂的PDSC评价和选用

文章采用加压差示扫描量热法(PDSC)和旋转氧弹法(RBOT)对比评价了4,4’-亚甲基双(2,6-二叔丁基苯酚)(抗氧化剂702)、2,6-二叔丁基酚(DTBP)、2,6-二叔丁基对甲酚(BHT)和叔丁基对苯二酚(TBHQ)4种抗氧化剂在大豆植物绝缘油中的作用及其适宜添加量。试验结果表明,两种方法得出的结果相一致,均是抗氧化剂702对大豆植物绝缘油抗氧化性能的提升效果最好,添加0.8%的抗氧化剂702后,大豆植物绝缘油的抗氧化性能与25~#矿物变压器油相当。     

水分对天然酯变压器油热老化特性的影响

水分被认为是除温度外影响变压器油纸绝缘寿命最主要的因素,为研究水分对天然酯变压器油热老化特性的影响,通过设计不同初始水分含量油纸绝缘试品在130℃下进行加速热老化试验,测试分析天然酯变压器油在不同老化时间下的介电性能和油色谱特性.结果 表明,初始水分含量越高,天然酯变压器油热老化过程中相对介电常数增加的速率越快、介质损...     

质子辐照对甲基硅橡胶电性能的影响

利用空间辐照环境模拟设备对甲基硅橡胶进行了质子辐照试验。辐照能量为150keV，辐照剂量范围为10^14～10^16cm^-2。对辐照后样品进行了电子自旋共振(ESR)分析和电性能测试。研究发现，当质子辐照剂量小于10^15cm^-2时，交流击穿电压上升，体积电阻率、介电常数及介电损耗角正切无明显变化。当质子辐照剂量大于10^15cm^-2后，体积电阻率及交流击穿电压下降，介电常数及介电损耗角正切上升。残存自由基和微观结构的变化是引起电性能改变的主要原因。     

微氧和铜对植物绝缘油热老化特性的影响

在变压器运行过程中因储油罐与空气作用或密封设备发生泄漏,会导致绝缘油中溶解微量的氧气,且因植物绝缘油不饱和脂肪酸含量较高而更易氧化。植物绝缘油酸值远高于矿物绝缘油,油中低分子有机酸对金属材料有腐蚀作用,且油中过渡金属离子对绝缘油的氧化有一定的催化作用。为此,研究了微氧和铜作用下植物绝缘油的热老化特性,分析了不同老化时间下油样的电气性能、油色谱特性。结果表明,相较于微氧作用,铜对植物绝缘油的热老化促进作用更为明显;植物油纸绝缘热老化特征气体为CO2、C2H6。     

高酸值废油萃取反应耦合脱酸、酯化工艺的研究

以高酸值餐饮废油和甲醇为原料,强酸性阳离子交换树脂同时作为固体酸催化剂和萃取填料,在自制的固定床反应器中进行了萃取一反应的耦合过程,成功降低了高酸值油脂的酸值,并合成了脂肪酸甲酯。考察了流量、醇油比对酸值和游离脂肪酸酯化率的影响,得到了优化参数：醇油质量比1：1、反应温度60℃、流量2．6mL／min,该实验条件下,原料油酸值从52．45mgKOH／g油降低到3．22mgKOH／g;过柱次数对油相脱酸效果的影响很小。     

质子与热循环协同效应对硅太阳电池电性能的影响

通过空间环境地面模拟实验方法,研究了低能质子辐照及其与热循环效应协同作用下背场硅太阳电池电性能的变化。试验结果表明,在2×1013cm-2-2×1016cm-2辐照剂量范围内,能量为60~180keV质子辐照可使硅太阳电池的开路电压、短路电流和最大输出功率产生不同程度的衰退,衰退的程度随辐照能量和辐照剂量而变化。对150keV质子辐照后的硅太阳电池单体片进行200次和360次热循环实验,热循环温度范围取-120℃-+120℃。电池的电性能随着循环次数的增加有着不同程度的增幅,其增幅的程度与质子辐照剂量密切相关。通过DLTS测试结果表明,上述试验结果与辐照引入的深能级缺陷HI及其退火特性有关。     

几种因素对天然焦-H_2O气化反应活性的影响

在Thermax500型加压热重分析仪上进行了天然焦-H2O气化反应试验,分析了常压下气化温度、水流量、氧气分压、反应气氛和灰分等因素的影响.结果表明,气化温度升高,天然焦-H2O气化反应明显加快;随着水流量加大,碳转化率有所增大,但水流量达到0.07 mL/min后,碳转化率不再随水流量的进一步增加而变化;在气化剂中加入少量纯氧能有效促进气化反应;天然焦-H2O的气化速率明显大于天然焦-CO2的气化速率;天然焦脱灰后碳转化率略有降低.     

天然采光对建筑能耗影响的研究

在定性分析天然采光对建筑能耗影响的基础上,以一天窗建筑为研究对象,利用eQUEST能耗模拟软件为工具,分析了结合照明控制的天窗采光对夏季供冷峰值负荷及建筑各用能项如照明、供冷、供热的能耗影响,探讨了天窗透光率、照明密度、照明控制方式对建筑能耗的影响,并针对不同气候地区的典型城市探讨了昼光照明的气候差异性。     

环氧化菜籽绝缘油的制备及性能研究

菜籽油与双氧水在乙酸参与和硫酸铝的催化下通过环氧化反应制得环氧化菜籽绝缘油。试验结果表明,环氧化反应的最佳工艺条件为菜籽油∶30%双氧水∶乙酸∶硫酸铝=1∶1.11∶0.25∶0.09(质量比),反应温度为60℃,反应时间为8 h,此条件下环氧值为4.73%。精炼后环氧化菜籽绝缘油的主要理化和电气性能可以达到10#变压器油GB/T 2536-90标准。经过环氧化反应后,菜籽油的抗氧化安定性大大提高,环氧化程度越高,抗氧化安定性越好。     

Effect of natural antioxidants on the oxidation stability of methyl ester of rubber seed oil

Biodiesel has been proved as a promising solution amidst other alternate fuels in terms of its characteristics compared to diesel. The oxidation property of biodiesel results in the degradation of its quality. This problem can be solved by the addition of suitable antioxidants which improves the oxidation stability of the fuel. Usage of natural antioxidants offsets the defects in synthetic antioxidants, because they are renewable, nontoxic as well as cost effective. The effect of natural antioxidant additives on the oxidation stability of the Methyl Ester of non-edible Rubber Seed oil (MERB) has been experimentally investigated in this study. Natural antioxidants Ginger, Moringa oleifera Lam, Basil and Oregano have been mixed in varying proportions (500, 1000, 1500 and 2000 ppm) and the antioxidant characteristics of the additives were identified by using Fourier Transform Infra-Red (FTIR) analysis. The induction period, which denotes the oxidation stability was worked out with Rancimat apparatus. From this study it was found out that the oxidation stability of MERB increased when natural antioxidant additives were added. Among the antioxidants used, Ginger was found to be more effective in enhancing the oxidation stability, with induction period values of 11.5 h, 18.5 h, 23 h and 26.5 h for proportions 500, 1000, 1500 and 2000 ppm respectively.     

大豆绝缘油的制备与性能研究

以市售大豆油为原料,通过活性白土减压吸附、碱性Al2O3降酸、微孔滤膜真空抽滤和减压蒸馏深度净化等精炼工艺过程,制备出一种环保型植物绝缘油。理化与电气性能测试结果表明,其闭口闪点达230℃,水分含量低于10 mg/L,酸值(KOH)降低至0.02 mg/g,90℃介质损耗因数tanδ为0.23%,体积电阻率ρ达8.66×1010Ω.m,击穿电压大于60 kV,关键性能指标满足"变压器油(GB2536-90)"标准对500 kV超高压电气设备用油的要求。     

Enhancing the oxidation stability of Mahua oil methyl ester with the addition of natural antioxidants

A rapid decrease in the availability of non-renewable fossil fuels has initiated the search for alternative fuels. Biodiesel obtained from various feedstocks has proved to be an effective alternative source for diesel engines due to its convincing fuel characteristics. The oxidation property of biodiesel is influenced by external factors such as sunlight and exposure to atmosphere.The oxidation stability of biodiesel can be improved by the addition of antioxidants which may be synthetic or natural. Natural antioxidants are more effective than synthetic ones in terms of economic value as well as prevention of adverse carcinogenic effects. Natural antioxidants, namely, ginger, Moringa oleifera, oregano, basil, and clove were extracted and used for the present study. The antioxidant activity of the additives was analyzed by DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging activity. The DPPH scavenging effect was calculated in terms of % by using absorbance values recorded with UV spectrophotometer. Among the antioxidants used, clove additive was found to be more efficient in enhancing the oxidation stability, with scavenging effect of 42.23%, 47.67%, 51.62%, and 55.61% for 500, 1000, 1500, and 2000 ppm, respectively. It was also observed that the scavenging activity increased with the concentration of antioxidant additives, and the maximum value was recorded at a concentration of 2000 ppm. Mahua oil methyl ester (MOME) was selected as biodiesel for the present study for which the oxidation stability has to be evaluated. The oxidation stability of MOME was measured in terms of induction period using the Rancimat method which does not meet the required standards. The oxidation stability of MOME, MOME + ginger 2000, MOME + M. oleifera 2000, MOME + oregano 2000, MOME + basil 2000, and MOME + clove 2000 was evaluated. The highest induction period was observed to be 38.44 h for MOME + clove 2000 blend. Hence, clove additive was found to be more effective among the selected natural antioxidants in terms of increasing the scavenging effect as well as increasing the oxidation stability of MOME. Thus, the addition of natural antioxidants can be recommended to improve the oxidation stability of biodiesel based on their scavenging effect which can be further validated by means of the Rancimat method in terms of the induction period     

大豆绝缘油的热老化特性与分解产物研究

以大豆油为原料,通过活性白土吸附、碱性氧化铝降酸和减压蒸馏等工艺得到精炼大豆绝缘油,其主要理化性能与进口库柏油相当,能满足电气设备对绝缘油的要求。以库柏油为参照,对大豆绝缘油进行了加速热老化试验,研究了其老化特性。试验结果表明:两种植物绝缘油在热老化过程中产生了大量的烃类气体和较多的CO和CO2,不产生C2H2气体;随着热老化时间的延长,两种植物绝缘油的酸值和介质损耗因数均呈增大趋势。     

低酸价菜籽油一步法制备生物柴油工艺的研究

以低酸价菜籽油为原料,采用一步法工艺制备生物柴油,对低酸值原料的酯化-醇解反应进行了考察及分析.试验结果表明,加入适量的水有利于酯化-醇解耦合过程的进行.在对产物组成进行分析和计算的基础上,提出了耦合反应过程的机理,并得出反应的最佳工艺条件:水的加入量为菜籽油质量的2.5%,催化剂加入量为菜籽油质量的1%,98%浓硫酸加入量为菜籽油质量的1%,醇油物质的量比为4:1,反应时间为5.5 h,最高反应温度为93℃.在以上条件下,脂肪酸甘油脂转化率达95%以上.     

圆柱形储罐合理选择保温层厚度的探讨

为减少热损失 ,存储载热介质的储罐通常要包敷保温层 ,而保温层厚度的大小将直接影响保温效果的优劣。本文从建立圆柱形储罐导热的数学模型入手 ,通过对该数学模型的求解 ,探讨了圆柱形储罐保温层合理厚度的确定方法 ,结论认为本文所提出的确定方法可用于工程实际。     

Effect of ethanol addition on the properties of Jatropha ethyl ester

Fossil fuels are available in limited quantity and may extinct in future. Moreover, pollutant emission from diesel engines affects the ecological systems. Biodiesel, derived from vegetable oil, is a renewable and green source of fuel. In this study, biodiesel produced from base catalyzed transesterification was blended with different diesel volumes. The diesel–biodiesel blends showed varied flash point (168–42°C), viscosity (4.34–3.31 mm²/s), density (0.872–0.8351 g/cm³), acid value (0.3–0.4 mg KOH/g), and cetane number (51.6–49.5). The results showed that alcohol addition helped in reducing viscosity and density of biodiesel by almost half. These provide explanation on engine performance, combustion, and emission characteristics.     

Environmental effect of rapeseed oil ethyl ester

Exhaust emission tests were conducted on rapeseed oil methyl ester (RME), rapeseed oil ethyl ester (REE) and fossil diesel fuel as well as on their mixtures. Results showed that when considering emissions of nitrogen oxides (NO_x), carbon monoxide (CO) and smoke density, rapeseed oil ethyl ester had less negative effect on the environment in comparison with that of rapeseed oil methyl ester. When fuelled with rapeseed oil ethyl ester, the emissions of NO_x showed an increase of 8.3% over those of fossil diesel fuel. When operated on 25–50% bio-ester mixed with fossil diesel fuel, NO_x emissions marginally decreased. When fuelled with pure rapeseed oil ethyl ester, HC emissions decreased by 53%, CO emissions by 7.2% and smoke density 72.6% when compared with emissions when fossil diesel fuel was used. Carbon dioxide (CO₂) emissions, which cause greenhouse effect, decreased by 782.87 g/kWh when rapeseed oil ethyl ester was used and by 782.26 g/kWh when rapeseed oil methyl ester was used instead of fossil diesel fuel. Rapeseed oil ethyl ester was more rapidly biodegradable in aqua environment when compared with rapeseed oil methyl ester and especially with fossil diesel fuel. During a standard 21 day period, 97.7% of rapeseed oil methyl ester, 98% of rapeseed oil ethyl ester and only 61.3% of fossil diesel fuel were biologically decomposed.     

Comparative assessment of a biogas run dual fuel diesel engine with rice bran oil methyl ester,pongamia oil methyl ester and palm oil methyl ester as pilot fuels

The present study tries to explore the potential of three different types of biodiesel viz. Rice bran oil methyl ester (RBME), Pongamia oil methyl ester (PME) and Palm oil methyl ester (POME) as pilot fuels for a biogas run dual fuel diesel engine designed for power generation. The results indicated that under dual fuel mode, RBME-biogas produced a maximum brake thermal efficiency of 19.97% in comparison to 18.4% and 17.4% respectively for PME-biogas and POME-biogas at 100% load. The emission study divulged that under dual fuel mode, on an average, there was an increase of CO emission by 25.74% and 32.58% for PME-biogas and POME-biogas, respectively in comparison to RBME-biogas. Furthermore, on an average, the HC emissions for PME-biogas and POME-biogas increased by 11.73% and 16.27%, respectively in comparison to RBME-biogas. On the other hand, on an average, there was a decrease in NO_X emission by 5.8% and 14%, respectively for PME-biogas and POME-biogas respectively in comparison to RBME-biogas.