易燃性物料储罐压力惰化过程设计与计算

介绍了可燃气体和易燃液体储罐的压力惰化操作过程及过程中气体组成的变化规律,讨论了惰化操作结束时氧气的控制目标浓度及极限氧气浓度的求取方法,推导出了预测压力惰化过程循环次数的计算公式,并在控制目标浓度从0．0001％-10％、充气压力300—600kPa的参数条件下,100m^3储罐压力惰化所需的循环次数,根据理想气体状态方程,推导了惰化所需氮气用量的计算公式,并计算出在不同操作压力和不同循环次数时的氮气用量。该方法可用于惰化处理过程的设计与计算。     

三元组分图在储罐退役惰性化过程设计中的应用

储罐退役之前,一般要进行惰化处理,以降低可燃气体浓度,避免形成爆炸性混合气体。根据三元组分图,可以方便、直观地设计惰化施工的方案,包括惰化操作的程序设计和危险气体控制目标浓度的确定。本文从理论上研究了在储罐退役惰性化过程设计时,如何用三元组分图表示爆炸极限、最小含氧浓度以及在储罐稀释惰性化过程中气体组成的变化轨迹。提出了两套惰化设计方案,在分析比较的基础上,确定了储罐退役惰化时的最安全实施方案。     

拱顶储罐气相层惰化过程数值模拟及工艺参数研究

针对油罐在检测、维修前须先将气相层可燃气体用氮气惰化到安全浓度,现场凭经验操作效率低且难以掌握氮气合理用量,容易造成氮气浪费或达不到安全浓度引发事故的问题,为确保惰化过程的安全经济,以常见拱顶储罐为例,首先利用改进后的公式法得出多组分可燃气体惰化效果评价指标;然后根据所得指标采用仿真对储罐气相层惰化过程进行数值模拟,并验证了仿真结果的正确性;最后采用仿真计算方法开展储罐气相层氮气惰化工艺参数的影响研究。研究结果表明:惰化效率与进口压力无关,只随进口流速变化,且大于1 m/s流速后,惰化效率已显著变化,此时可以增加进口管道数量,进一步提高惰化效率。理论研究结果可为现场实施提供参考和指导。     

有害因素样品采集的问题

《工作场所有害因素职业接触限值》(GBZ2-2002)已于2002年6月1日起实行。由于GBZ2-2002中,职业接触限值由原来的最高容许浓度(MAC)变更为最高容许浓度、时间加权平均容许浓度(PC-T W A)和短时间接触容许浓度(PC-STEL),对工作场所有害因素的样品采集提出了不同要求。调查中发现,在贯彻和执行工作场所有害因素职业接触限值的样品采集过程中,存在着许多错误和偏差。为了正确地贯彻和执行GBZ2-2002,本文将针对其中的主要问题进行探讨,以便完善和规范职业病危害因素的样品采集。缺乏现场调查和工人的工作写实现场调查和工人的工作写实…     

不同进气方式对某民机中央翼油箱惰化性能的影响

以某运输机中央翼油箱为研究对象,设计了两种惰化气体进气口布置方式,并对燃油箱惰化流场进行了数值模拟,得到了两种不同模型惰化流场氧体积分数的空间分布和平均氧体积分数随时间和体积置换次数的变化规律。通过对计算结果的对比分析,研究了不同进气口布置方式对燃油箱惰化时间和氧体积分数分布的影响,同时得到了不同的进气口布置方式对机载制氮系统设计任务的影响规律。     

丙烯氨氧化制丙烯腈反应器开车过程尾气燃爆危险性研究

丙烯直接氨氧化制丙烯腈工艺由于反应温度高,且反应器内的气相空间存在丙烯、丙烷、丙烯腈、乙腈、氧气、氮气等可燃性气体混合物,极易发生燃爆危险。为研究和评估该工艺装置反应器尾气的燃爆特性,采用11 L爆轰管测试在400℃、40 k Pa (G)工艺条件下,装置开车进料及反应过程中不同进料配比时反应器尾气组成的爆炸极限,并以此绘制爆炸极限三元相图,最终得到爆炸极限和极限氧体积分数。结果表明:反应器内可燃尾气的爆炸上限随氧气体积分数增加而升高,爆炸下限没有明显变化;在开车进料及反应过程中,反应器可燃尾气的极限氧体积分数LOC范围在8. 0%～8. 5%。因此,为避免反应器气相空间在开车过程中发生燃爆危险,需监测反应器内氧气体积分数,并设置氧体积分数报警值小于8. 0%。     

新型茧覆惰化材料对不同体积分数甲烷的吸收性能分析

针对研制出的新型茧覆惰化材料,选择在甲烷爆炸下限以下2%、3%和4%三个体积分数梯度,使用纯水、多体积分数水平的新型复配试剂和参比试剂(国际先进水基灭火溶液F-500)对含有不同体积分数甲烷的混合气体进行喷洒,对比研究新型试剂在不同体积分数甲烷泄漏环境中的吸收性能。结果表明,不同甲烷体积分数环境下,两试剂均表现出良好的吸收包覆甲烷的能力,配方试剂对应曲线较参比试剂的波动小,甲烷体积分数下降速度更快,茧覆吸收效果突出、稳定;随添加量增加,两试剂受到分布不均及包覆饱和的影响,作用后期出现小范围反吸收效应,但不影响甲烷体积分数的整体下降趋势。配方试剂吸收包覆可燃烷烃的能力随试剂添加量及作用时间增长而增强,当添加量超过3%时,作用效果明显,试验初期甲烷体积分数下降迅速,后期逐步趋于稳定。总体而言,新型茧覆惰化材料具有良好的吸收包覆甲烷气体的能力。     

多元混合气体爆炸特性及惰化防爆研究

为了完善常见多元混合气体爆炸特性参数数据库,为安全工程师开展城镇燃气防爆管理、安全操作规程的制定及对废弃管道进行改造、拆除提供依据,采用理论和试验方法对CO2与N2两种惰性气体对液化石油气(LPG)爆炸特性参数的影响规律进行了研究,对比分析了两种惰化剂对LPG的抑爆效果。结果表明:LPG体积分数为4.0%、CO2体积分数为22%时,LPG可燃气退出爆炸区间,此时极限氧体积分数为15.54%;LPG体积分数为3.5%、N2体积分数为32%时,LPG可燃气退出爆炸区间,此时极限氧体积分数为13.545%;两种惰化剂对LPG爆炸特性的抑制规律基本相似,但CO2的抑制效果明显优于N2。当CO2和N2充入的体积分数均为20%时,最大爆炸压力到达时间分别由166 ms延长到1 222 ms和826.30 ms;两种惰化剂用量在体积分数大于10%之前,对最大爆炸压力到达时间的影响均较小,因此在工程应用中采用惰化方式抑爆,惰化剂充入的体积分数需高于10%。     

基于神经网络的数据融合在废气测量中的应用

数据融合方法通过提取各个影响因素之间的特征关系,进行数据之间的融合。针对因传感器故障而失真的数据,综合考虑对畜禽场排放的某一废气测量值的时间、空间和环境等多种影响因素,使用基于神经网络的数据融合方法来估算该废气的浓度,实现失真数据的恢复,从而精确地测量出养殖场连续排放的有害气体的总量,对超标排放进行监控。以氨气(NH3)浓度数据的处理为例,应用MATLAB软件,其仿真结果表明:估算最大相对误差为7.83%,证明基于神经网络的数据融合方法的有效性。     

NH3-H2O2气雾对氰化氢气体的消毒

采用NH_3-H_2O_2气雾对1 m3密闭试验舱内氰化氢气体进行消毒,采用单因素试验研究H_2O_2和NH_3质量浓度对消毒率和消毒反应速率的影响规律。结果表明,NH_3-H_2O_2气雾对HCN的消毒符合一级反应动力学特征,NH_3质量浓度对消毒反应速率有一定影响,但当NH_3质量浓度增加至20 mg/m3以上时,对反应速率几乎没有影响; H_2O_2质量浓度对消毒反应速率有显著影响,反应速率随H_2O_2质量浓度的提高明显增大。NH_3-H_2O_2气雾消毒剂的最佳配方为H_2O_2的质量浓度为120 mg/m3、NH_3的质量浓度为20 mg/m3,在此条件下对HCN进行消毒,在28 min时HCN的残余质量浓度为0. 92 mg/m3,可以达到GBZ 2. 1—2007《工作场所有害因素职业接触限值第1部分:化学有害因素》中有关HCN最高容许质量浓度MAC值(1 mg/m3)的规定。分析消毒机理为H_2O_2首先将HCN氧化为氰酸(HCNO),氰酸不稳定,在NH_3和水的作用下可以水解成碳酸铵,也可以进一步被氧化形成CO2和N2。     

Prediction of flammability limits of fuel-air and fuel-air-inert mixtures from explosivity parameters in closed vessels

Flammability limits of fuel-air and fuel-air-inert gaseous mixtures, especially at non-atmospheric conditions, are essential properties required for establishing safety operating conditions for handling and processing flammable gases. For pure fuels, an important data pool exists, formed by the flammability limits of fuel-air and fuel-air-inert gaseous mixtures at ambient initial conditions measured by standard methods. Such methods can be used for experimental determination of flammability limits for multi-fuels mixed with air, with or without additives, under non-atmospheric conditions. Their use is however a time- and material-consuming process; in addition, the flammability limits obtained by various standard methods may be scattered as a result of different choices in the operating parameters, for each standard method. It appears that a preliminary estimation of the flammability limits for fuel-air and fuel-air-inert gaseous mixtures can minimize the effort of measuring them in specific initial conditions.The present paper describes a new method for estimating the flammability range of fuel-oxidizer gaseous mixtures based on measurements of explosivity properties e.g. the peak explosion pressure and maximum rate of pressure rise recorded during closed vessel laminar explosions of fuel-oxidizer mixtures far from limits. Data obtained for several hydrocarbon-air gaseous mixtures with or without inert gas addition are used to examine the accuracy of estimated flammability limits (LFL – the lower and UFL – the upper flammability limit) as well as of the Limiting Oxygen Concentration (LOC) and the Minimum Inert Concentration (MIC). The predictive ability of the proposed method is examined against the predictive ability of other recently described methods.     

R290制冷剂惰化燃爆特性实验研究

为了研究R290制冷剂惰化燃爆特性,采用带搅拌功能和氧浓度在线测定的20L球试验装置,对R290制冷剂进行了极限氧浓度测定。实验测定了丙烷在CO2和N2惰化气氛中的爆炸极限及极限空气浓度LAC,确定丙烷的极限氧浓度LOC;采用三元图爆炸区、丙烷-O2二维图爆炸区和ASTM标准分布图分析了混合气体爆炸区边界的燃爆特征,给出了极限氧浓度的确定方法和边界爆炸压力分布规律。实验结果表明:常温常压下R290的爆炸极限为2.1%～9.6%,CO2惰化气氛中的极限氧浓度为13.3%,对应的丙烷浓度为3.3%;N2惰化气氛中的极限氧浓度为10.8%,对应的丙烷浓度为2.7%。通过对比分析不同CO2和N2浓度下的爆炸区分布特征,表明CO2对丙烷的惰化效果要优于N2,以氮气和二氧化氮体积分数比为1∶2测试惰化气氛保护能力,惰化效果介于同浓度单种惰性气体之间。     

Effects of initial temperature and pressure on explosion characteristics of propane–diluent–air mixtures

The explosion characteristics of propane–diluent–air mixtures under various temperatures and pressures were investigated using a 20-L apparatus. The explosion limits of propane diluted with nitrogen or carbon dioxide were measured at high temperatures from 25 to 120 °C. The results showed that the upper explosion limit (UEL) increased, and the lower explosion limit (LEL) decreased with the rising temperature. The explosion limits of propane diluted with nitrogen or carbon dioxide were also measured at high pressures from 0.10 to 0.16 MPa. The results showed that the UEL increased, and the LEL almost remainedunchanged along with increased pressure. Under the same initial operating conditions, the concentration of nitrogen required to reach the minimum inerting concentration (MIC) point was higher than the concentration of carbon dioxide. Finally, the study investigated the limiting oxygen concentration (LOC) of propane under various initial temperatures, initial pressures, and inert gases. The LOC of propane decreased approximately linearly with increased temperature or pressure, and the LOC of propane dilution with carbon dioxide was greater than dilution with nitrogen from 25 to 120 °C or from 0.10 to 0.16 MPa, which indicated that the dilution effect of carbon dioxide was better than that of nitrogen.     

Explosion regions and limiting oxygen concentrations of methyl propionate,methyl acetate,dimethyl carbonate with air and inert gas mixtures

New data about explosion regions with special focus on limiting oxygen concentrations for methyl propionate, methyl acetate, dimethyl carbonate with air in the presence of nitrogen, helium and carbon dioxide were determined at ambient initial pressure and 423 K. The measurements were executed according to EN 1839 method T. The changes of the explosion regions with temperature and type of inert gas were also modeled mathematically using an extended calculated adiabatic flame temperature profile (CAFTP) method. The shift of the explosion region boundaries with temperature when switching from nitrogen to carbon dioxide were reproduced well. For a switch to helium a good agreement could be reached only if the very high thermal conductivity of helium had been considered properly by using the Lewis number. This requires the knowledge of the respective Lennard-Jones parameters. The LOC of helium-containing mixtures can, however, be calculated with acceptable accuracy even if the Lennard-Jones parameters of the flammable substance are not known exactly by using reasonable estimations.     

多元混合气爆炸极限的非线性预测研究

根据混合气的爆炸极限与混合气各成分的体积浓度之间具有非线性关系的特点,笔者提出采用神经网络非线性方法来计算含有H2,CH4和CO的多元混合气体的爆炸极限。在模型中,H2,CH4和CO的体积浓度作为输入,爆炸上限和下限作为输出。计算结果表明,该非线性模型预测混合气爆炸下限和上限的最大相对误差为3.90%,3.57%,而模型预测值与计算值的相关系数分别为0.971,0.981;非线性模型的预测结果要好于偏最小二乘回归的预测结果。当H2,CO,CH4在混合气中的体积浓度给定时,非线性模型能够准确预测混合气的爆炸极限。     

受限空间内惰性气体对CH4爆炸抑制特性研究

N2和CO2是常用的惰性抑爆气体,为研究两种气体的抑爆特性,采用20L球形爆炸试验装置,分析了不同浓度配比条件下N2/CH4/空气以及CO2/CH4/空气混合气体的爆炸压力,同时采集爆炸后的气体样品,对比分析爆炸后残留气体的主要成分。结果显示:随CH4浓度从5%增加至12.5%时,完全抑制CH4爆炸需要的惰性气体最小量先增大后降低,CH4浓度在6.5%~7.5%之间时,抑爆需要的惰性气体的量最大;在同一CH4浓度条件下,抑爆需要N2的量大于CO2,并且CH4浓度在5%~6.5%时,抑爆需要两种惰性气体的量值差别最大;当CH4浓度一定时,随着加入惰性气体量的增大,爆炸最大超压逐渐降低,惰性气体浓度和爆炸超压之间基本呈线性关系;在同样条件下,相对于N2,CO2为抑爆气体时,爆炸后腔体内残留的CH4浓度较高。研究成果为惰性气体抑爆技术提供技术支撑,同时为揭示惰性气体抑爆机理有一定作用。     

油页岩含氧干馏工艺流程爆炸极限分析

根据干馏工艺流程配入适量氧气,可以降低载热气体需要预热的温度,以实现低能耗、易于工业生产的特点,设计了一套新型的有氧干馏工艺流程。有氧干馏工艺因其过程中存在可燃性混合物,有发生爆炸事故的可能性,通过实验对所收集的不同温度下的干馏气体的成分与含量进行了分析,结合爆炸极限理论,对该有氧干馏工艺流程的不同温度、不同惰性气体含量条件下可燃气体爆炸极限进行了分析计算。结果表明,可燃气体的浓度在整个反应升温过程中始终没有进入爆炸危险区域,说明该实验装置不具备爆炸危险性;对干馏工艺流程中氧气的输入量的控制,可以防止该工艺流程的火灾爆炸的发生。     

Effects of N2 and CO2 on the flammability of 2,3,3,3-tetrafluoropropene at elevated temperatures

The flammability characteristics of refrigerants are affected by environmental factors, making them prone to flammability and explosion accidents in cooling systems. In this paper, the flammability characteristics of R1234yf–air mixtures with N₂ and CO₂ were investigated comparatively at temperatures between 20 and 50 °C at 80% relative humidity. The lower and upper flammability limits of R1234yf were measured. The limiting oxygen concentration (LOC), critical flammable ratio (CFR), and critical flammable concentration (CFC) of the R1234yf–air mixtures with inert gases were investigated. The paper developed a linear formula between the flammability limit of R1234yf and the temperature. The changes in CFC with different temperatures were negligible for R1234yf. Furthermore, the mixed refrigerant had both non-flammability and the lowest vapor pressure when the CFR of the R1234yf/CO₂ mixture was 2.9. The experimental results were used to propose a new prediction model to estimate the flammability limits of R1234yf. Finally, molecular simulation explained the effect of inert gases on the flammability of R1234yf from a microscopic point of view. The research aimed to provide valid evidence and data for preventing flammable and explosive refrigerant incidents.     

矿井火区可燃性混合气体爆炸三角形判断法及其爆炸危险性分析

矿井火区可燃性混合气体爆炸危险性的判断 ,目前常用单纯的瓦斯爆炸三角形判别法。此法对实际的判断往往未综合考虑火区温度的影响。为此 ,笔者论述了矿井火区多种可燃性气体同时存在时 ,其混合气体爆炸三角形各参数的工程计算方法 :爆炸界限可用 Le Chatelier法 ,但需根据火区实测温度进行修正 ;爆炸时的临界氧浓度 ,则需用另一种三角形图示法予以确定。由此画出的混合气体爆炸三角形分析图 ,可用于矿井火区 ,尤其是矿井大面积火区的密闭和启封过程中 ,作为可燃性混合气体爆炸危险性的综合判断及其防爆措施的制定 ,都具有实用价值和指导意义     

钻具材料疲劳损伤的磁记忆检测试验研究

为及时准确地确定钻具疲劳损伤及应力集中位置,确定疲劳损伤程度,对42CrMo钢缺口试件进行拉扭疲劳试验及磁记忆在线检测。试验中实时采集磁记忆信号的切向分量,分析其梯度变化趋势,并提取Hp(x)max,Hp(x)sub,Kmax,Ksub等4个磁记忆信号特征参量,研究这4个特征参量在整个疲劳循环过程中的变化规律,并比较在线卸载与在线加载检测各特征参量的异同。试验结果表明,在整个疲劳过程中,各磁记忆信号特征参量具有不同的变化规律,很好地诠释了材料的拉扭疲劳过程,表征出不同疲劳阶段材料的应力集中程度。