Prediction of methanol loss in liquid hydrocarbon phase during natural gas hydrate inhibition using rigorous models

Methanol is the most widely used natural gas hydrate inhibitor and it is only effective as a hydrate inhibitor in the aqueous phase. Methanol is not regenerated in natural gas inhibition process due to its intermittent application in most cases. However, a significant cost is associated with the process because of methanol loss while utilizing this inhibitor. In this work, several intelligent models along with a new mathematical correlation are presented in terms of methanol concentration in aqueous phase and temperature to precisely forecast the methanol loss in the saturated hydrocarbons phase. An excellent match was noticed between the calculated results and literature data.     

二溴海因作用罗非鱼产生的溴离子残留及消解研究

建立了以离子色谱法测定水产品中溴离子质量比的方法,并用该方法检测了二溴海因作用于吉富罗非鱼后所产生的溴离子在肌肉中残留及消解的质量比.检测时采用CsI2A阴离子柱分离,电导检测,溴离子质量比为10～200 mg/kg,决定系数R2=0.9963.结果表明:1)样品添加30 mg/kg和50 mg/kg时,Br-的平均回收率分别为82.58％和86.14％,相对标准偏差为4.61％和6.54％.因此,该方法可以应用于水产品中溴离子的定量分析;2)二溴海因质量浓度为0～0.3 mg/L时,肌肉中未检出溴离子;二溴海因质量浓度为1.5 mg/L时,肌肉中溴离子质量比呈时间-效应关系,即溴离子质量比随时间的延长而增加,第16 d时溴离子在肌肉中质量比达最大21.6 mg/kg,符合国际食品法典的规定.在清水中恢复10 d后,肌肉中溴离子的质量比降低.可见,实际生产中若二溴海因的施药剂量为0.3～0.4mg/L,则肌肉中溴离子对人类几乎没有威胁.     

关于气相色谱法与红外法分析油烟的比较

目前在我国油类监测分析方法中,普遍采用的是红外分光光度法,但是,根据我国在1987年签订的《关于消耗臭氧物质的蒙特利尔议定书》中,四氯化碳被确定为全球禁止使用的试剂,至2014年我国必须全部停用,而四氯化碳正是红外分光光度法监测油类物质的萃取溶剂。所以寻找新的路径来监测油类物质是必须的。实验组通过大量实验对色谱法与红外法分析油类物质进行了比较,并对数据进行了分析,得出结论:色谱法检测油烟理论上可行,但是实际工作中有难度。     

Detection of incipient self-ignition process in solid fuels through gas emissions methodology

The aim of this study is to propose an experimental methodology to detect incipient self-ignition processes in solid fuels. This methodology is based on the gases emissions of different solid fuels, varying the degree of compaction and the grain size of the materials. To achieve this goal, a procedure for the collection and analysis of the gases emitted by samples of various fuels has been developed, analysing the temperatures at which these emissions begin. The results obtained for different materials show that it is possible to detect incipient spontaneous combustion processes using measurements of CO and CO₂ emissions during heating process, and then to set alarm thresholds based on the concentrations of these gases. Those results have been compared with results from conventional thermogravimetry and differential scanning calorimetry tests and it is shown that the proposed methodology detect the self-ignition process start point in advance.     

Lower explosion limit of hybrid mixtures of burnable gas and dust

Hybrid mixtures – mixtures of burnable dusts and burnable gases – pose special problems to industries, as their combined Lower Explosion Limit (LEL) can lie below the LEL of the single substances. Different mathematical relations have been proposed by various authors in literature to predict the Lower Explosion Limit of hybrid mixtures (LEL_hybrid). The aim of this work is to prove the validity or limitations of these formulas for various combinations of dusts and gases. The experiments were executed in a standard 20 L vessel apparatus used for dust explosion testing. Permanent spark with an ignition energy of 10 J was used as ignition source. The results obtained so far show that, there are some combinations of dust and gas where the proposed mathematical formulas to predict the lower explosible limits of hybrid mixtures are not safe enough.     

Analysis of dust distribution in silo during axial filling using computational fluid dynamics: Assessment on dust explosion likelihood

In this study, the dust distribution in a silo during axial filling was modelled using a commercial computational fluid dynamics (CFD) code. The work focused on the dust concentration distribution in the silo, for evaluating the likelihood of a dust explosion in the silo. The simulation was conducted using a combination of renormalized (RNG) k-epsilon and discrete phase models, with standard pressure interpolation and a second order upwind scheme. The predicted dust concentration distribution showed a good agreement with experimental data adopted from the literature. It was found that the dust concentration distribution was influenced by mean velocity and turbulence flow. The simulation results suggest that the cornstarch concentration inside the silo was always above the lower explosion limit (LEL), hence requiring a mitigating action or a control system to reduce the explosion risk.     

拟除虫菊酯气相色谱手性拆分方法及其影响因素分析

拟除虫菊酯具有较强的手性特征,包含多种异构体,不同异构体具有不同的生物活性,因此,其异构体的手性拆分具有重要的意义。气相色谱分析法因其分辨率高,峰容量大,灵敏度高、分析时间短,选择性强等特点,已被广泛应用于拟除虫菊酯的手性拆分中。文章通过阐述基于氢键作用、配位作用、包结络合作用的3种手性固定相的拆分机制,综述了气相色谱用于拟除虫菊酯手性分离的研究状况。此外,文章还分析了有机溶剂、水、温度等对拟除虫菊酯在拆分过程中差向异构现象的影响。     

Dynamic response characteristics and structural optimization of isolation seal under the impact of gas explosion

Either in the chemical process plants or in the underground infrastructures, the isolation seal is regularly used to separate the working sections and inactive sections, or to isolate the possible explosion sites in order to avoid any domino effects. Due to differences in accumulation space or ignition point locations, pressure on the seal can vary when an explosion occurs. Thus, the safety and reliability of seals are crucial to maintaining safety in process industry. This paper focuses on seals constructed with concrete and loess materials, and examines the dynamic response characteristics of the gas explosion wave on the seal through sample experiments and numerical simulation metods. The study proposes an optimized design for the explosion-proof structure of the wedge-shaped and spherical seal, which can provide a technical basis for the explosion-proof and anti-explosion measures of various sealed walls. These research findings can also serve as a basis for improving the construction quality of seals.     

Prediction of gas explosion pressures: A machine learning algorithm based on KPCA and an optimized LSSVM

A gas explosion, as a common accident in public life and industry, poses a great threat to the safety of life and property. The determination and prediction of gas explosion pressures are greatly important for safety issues and emergency rescue after an accident occurs. Compared with traditional empirical and numerical models, machine learning models are definitely a superior approach. However, the application of machine learning in gas explosion pressure prediction has not reached its full potential. In this study, a hybrid gas explosion pressure prediction model based on kernel principal component analysis (KPCA), a least square support vector machine (LSSVM), and a gray wolf optimization (GWO) algorithm is proposed. A dataset consisting of 12 influencing factors of gas explosion pressures and 317 groups of data is constructed for developing and evaluating the KPCA-GWO-LSSVM model. The results show that the correlations among the 12 influencing factors are eliminated and dimensioned down by the KPCA method, and 5 composite indicators are obtained. The proposed KPCA-GWO-LSSVM hybrid model performs well in predicting gas explosion pressures, with coefficient of determination (R²), root mean square error (RMSE), and mean absolute error (MAE) values of 0.928, 26.234, and 12.494, respectively, for the training set; and 0.826, 25.951, and 13.964, respectively, for the test set. The proposed model outperforms the LSSVM, GWO-LSSVM, KPCA-LSSVM, beetle antennae search improved BP neural network (BAS-BPNN) models and reported empirical models. In addition, the sensitivity of influencing factors to the model is evaluated based on the constructed database, and the geometric parameters X1 and X2 of the confined structure are the most critical variables for gas explosion pressure prediction. The findings of this study can help expand the application of machine learning in gas explosion prediction and can truly benefit the treatment of gas explosion accidents.     

原油储罐火灾事故环境风险评价分析

通过运用ADMS模型,对2万m3原油储罐发生火灾爆炸事故时有毒有害气体及燃烧次生污染物的环境影响进行预测。结果表明,其产生的废气污染物对环境影响较大;在火灾持续6h的情况下,产生的主要废气污染物在距离事故中心120m范围内的人员将有半数死亡;距120～240m范围内造成组织缺氧;距240～4725m人员不会有生命危险;距离4725m范围内污染物的浓度超出车间最高允许浓度要求。同时提出了相应的环境风险管理措施,为今后类似事故环境影响评价作借鉴,为环保部门环境管理提供参考。