Automated analyser for monitoring trace amounts of volatile chloro-organic compounds in recirculated industrial water

An automated analyser of volatile chloro-organic compounds in water was constructed and tested using standard mixtures of dichloromethane and dichloroethane. It was based on continuous, countercurrent gas stripping of the liquid sample followed by periodic trapping of the analytes on two traps alternately connected to the bubbler outlet, and thermal desorption. When one trap performed adsorption, the other underwent desorption and cooling. Analytes were detected by an ECD detector. Integration, calibration, calculations and overall operating cycle control was performed by a microcomputer. The instrument guarantees a 0.02 ppm Cl (w/w) detection limit, a 0-2 ppm detection range and 2 months of autonomous operation. Results are reported every 13 min.     

Separation of instrumental and chemical errors in the analysis of oils by gas chromatography—A collaborative evaluation

Thirty-five analysts studied the concept that, in the gas chromatographic (GC) analysis of fatty acid composition, errors can be separated into those caused by poor chromatograph optimization and those related to inefficient conversion of triacylglycerols (TAG) to fatty acid methyl esters (FAME). A primary standard mixture of FAME was used to determine how well the participants had optimized their chromatographs. A primary standard of the equivalent TAG was used to determine total error of analysis. “Chemistry error” was calculated as the difference between the absolute errors found for the FAME and the TAG standards. Grades of analysis were computed for the FAME and TAG results and for the chemistry errors calculated from these analyses. Only four analysts achieved grades of analysis for the FAME standard that can be considered excellent or good. These four analysts used different injector/column configurations, indicating that, when properly optimized, a GC with a flame ionization detector is an extremely accurate instrument. Conversely, it is evident that there is the potential for most analysts to improve their instrumental optimization. In agreement with published information, AOCS method Ce 2-66 and AOAC method 969.33 gave low chemistry grades, but a number of analysts used modifications of these methods, and some achieved much better grades. It would appear that many of the standard methods that are in common use are capable of producing improved results, but that critical parameters need to be better specified to ensure minimization of error. The concept of separating errors into those of instrument origin and those caused by the chemical component of the total method would appear to be a useful concept for the validation of analytical methods.     

NOx reduction from a large bore natural gas engine via reformed natural gas prechamber fueling optimization

Lean combustion is a standard approach used to reduce NO_x emissions in large bore (35–56 cm) stationary natural gas engines. However, at lean operating points, combustion instabilities and misfires give rise to high total hydrocarbon (THC) and carbon monoxide (CO) emissions. To counteract this effect, precombustion chamber (PCC) technology is employed to allow engine operation at an overall lean equivalence ratio while mitigating the rise of THC and CO caused by combustion instability and misfires. A PCC is a small chamber, typically 1–2% of the clearance volume. A separate fuel line supplies gaseous fuel to the PCC and a standard spark plug ignites the slightly rich mixture (equivalence ratio 1.1–1.2) in the PCC. The ignited PCC mixture enters the main combustion chamber as a high energy flame jet, igniting the lean mixture in the main chamber. Typically, natural gas fuels both the main chamber and the PCC. In the current research, a mixture of reformed natural gas (syngas) and natural gas fuels the PCC. Syngas is a broad term that refers to a synthetic gaseous fuel. In this case, syngas specifically denotes a mixture of hydrogen, carbon monoxide, nitrogen, and methane generated in a natural gas reformer. Syngas has a faster flame speed and a wider equivalence ratio range of operation than methane. Fueling the PCC with Syngas reduces combustion instabilities and misfires. This extends the overall engine lean limit, enabling further NO_x reductions.Research results presented are aimed at quantifying the benefits of syngas PCC fueling. A model is developed to calculate the equivalence ratio in the PCC for different mixtures and flowrates of fuel. An electronic injection valve is used to supply the PCC with syngas. The delivery pressure, injection timing, and flow rate are varied to optimize PCC equivalence ratio. The experimental results show that supplying the PCC with 100% syngas improves combustion stability by 21% compared to natural gas PCC fueling. A comparison at equivalent combustion stability operating points between 100% syngas and natural gas shows an 87% reduction in NO_x emissions for 100% syngas PCC fueling compared to natural gas PCC fueling.     

溶剂型胶粘剂中多环芳烃的气相色谱-质谱法检测

建立了溶剂型胶粘剂中16种PAHs(多环芳烃)含量的GC-MS(气相色谱-质谱)检测方法。分别优化了样品的萃取溶剂、净化方式和浓缩过程。研究结果表明:样品经过前处理后,可采用SIM(选择离子扫描)模式和内标法对PAHs进行定量分析;该检测方法的线性相关系数均大于0.999,检出限为0.001~0.020 mg/kg,用加标回收率法确定了该检测方法的精密度为1.54%~8.91%(n=7),16种物质的回收率为83.13%~104.32%;该检测方法具有准确、高效之特点,适用于胶粘剂中PAHs含量的定量检测。     

用气相色谱法测定甲醛中甲醇含量

以Ｐｏｒａｐａｋ－Ｎ为固定相,以Ｈ２为载气,用热导检测器气相色谱法－水－甲醇三组分分离,以色谱柱的分离度作分离效率的指标,研究柱温及载气流速对分度的影响,确定最佳的操作条件,在此基础上要用标准曲线时进行了定量。     

气相色谱法检测煤气中氧气含量的测量不确定度评定

利用气相色谱法对煤气中氧气含量进行检测,通过应用现代数理统计方法对煤气中氧气含量测量不确定度来源进行分析,同时从标准样品、标准样品峰面积和混合气体样品峰面积等几大方面对测量不确定度来源进行了分析和量化评定,指出主要的不确定度来源是标准物质、测量重复性和仪器校准时的示值误差.并计算出相对合成不确定度,得出煤气中氧气体积分数为Ψ(O2)=(0.87±0.04)％,(k=2).     

Membrane system design for multicomponent gas mixtures via mixed-integer nonlinear programming

An optimal design strategy for membrane networks separating multicomponent gas mixtures based on an approximate permeator model and mixed-integer nonlinear programming (MINLP) is proposed. A permeator system superstructure is used to embed a very large number of possible network configurations and allows the permeator feed-side pressure to be fixed or a design variable. A MINLP design model is developed to minimize the total annual process cost by simultaneous optimization of the permeator configuration and operating conditions. Case studies for the separation of acid gases (CO₂ and H₂S) from crude natural gas mixtures with spiral-wound permeators are presented. Permeator configurations are derived for different number of separation stages for both continuous and discrete membrane areas. The method is sufficiently robust to handle product compositions that vary five orders of magnitude. The proposed approach provides an efficient methodology for preliminary screening of multi-stage membrane separation systems for multicomponent gas mixtures.     

An instrument for determining the total water content in air when extinguishing fires

An instrument suitable for measuring the total water content both as small liquid droplets and as vapour in the air, in water mist total flooding extinguishing tests, is presented. The instrument consists of a heater and a Vaisala humidity meter. The Vaisala humidity meter is capable of measuring relative humidity at temperatures up to 180°C. The instrument has a measuring range of 0–600g/m³, a sample rate of 1 L/min, a time constant of 5–10 s and an accuracy of ±40 g/m³. Accurate results are obtained when used outside the direct spray from a nozzle. If the instrument is placed in the spray the total water content can be either over‐ or underdetermined, depending on which part of the instrument faces the spray. Copyright © 1999 John Wiley & Sons, Ltd.     

Evaluation of a new instrument offering sodium,potassium, and ionized calcium in combination with haematocrit,pH and blood gas analysis; the performance of the Nova Stat Profile 1

The Nova Stat Profile 1 analyser, a combined sodium, potassium, ionized calcium, haematocrit and conventional blood gas analyser, was evaluated over a four month period. In addition to assessing and demonstrating that the instrument met analytical requirements, an appreciation of the use of ionised calcium (iCa) was made. Prospective costs were characterised and practical problems of iCa measurement addressed.     

Theoretical and experimental assessment of a novel method to establish the complete measurement range of the calorimeter and its limit of detection and quantification

For determining the accuracy of a calorimeter over the instrument’s entire measuring range, a novel method has been established. For this new approach, (a) benzoic acid (C₆H₅CO₂H) as a certified reference material (CRM), (b) SiO₂ and (c) a mixture of CRM benzoic acid and SiO₂ have been used. To illustrate the essential difference between 1) the novel analytical method for control of the entire measurement range and 2) the calorimeter calibration, both applications of benzoic acid (BA) have been demonstrated. An experimental result showed that BA was successfully used to check the whole calorimeter measurement range. The results also showed that the same new method was successfully applied to determine the limit of detection and quantification. A new instrument testing process and a new measurement technique have thus been established. In this way, the cost of using CRM to control the accuracy of measuring the entire measuring range of the calorimeter, as shown in this paper, is minimized. The requirements of the ISO/IEC 17025:2017 standard are satisfied. ISO/IEC 17025:2017, together with ISO 9001:2015 (quality management systems), ISO 14001:2015 (relate to environmental protection) and ISO 45001:2018 (occupational safety), constitute an integrated quality system by which a testing laboratory may also accredit.     

工业苯酚丙酮装置氧化尾气的气相色谱分析

采用质量分数2.5%的邻苯二甲酸二壬酯和质量分数2.5%的硅藻土,以chromsorb G·DMCX(150~180μm)为担体的色谱填充柱进行分离,氢火焰离子化检测器进行检测,用峰面积外标法进行定量分析,同时对工业苯酚丙酮装置氧化尾气组成进行气相色谱分析。对色谱柱的选择、操作条件的优化、定性、定量分析,进样量和线性范围、最低检测限等实验项目进行了考察,实验结果表明此方法具有操作简单、分析速度快、分析成本低、重复性与准确性好等特点。     

Evaluation of the use of different hydrocarbon fuels for gas reburning

Gas reburning is a NO_x reduction technique that has been demonstrated to be efficient in different combustion systems. An experimental study of gas reburning performance in the low temperature range (at and under 1100°C) has been carried out. An evaluation of the use of different hydrocarbon fuels, such as natural gas, methane, ethane, ethylene and acetylene was performed and the influence of the temperature and stoichiometry is considered. The results show that the reburning process is effective under appropriate conditions at the low temperatures used in this work. However, as the temperature diminishes, the influence of the reburn fuel becomes more marked and the use of acetylene or ethane and ethylene leads to better performance than natural gas or methane, the classical reburn fuels for high temperature applications.     

Isobaric measurement of gas permeability of polymers

The principles and design of a gas permeability measuring instrument based on thermal conductivity measurement are described. Since the thermal conductivity of a gas mixture is dependent upon the partial pressure fraction rather than absolute partial pressure of sample gas, and the permeation rate of reference and sample gases through polymer films differe considerably, a pressure-equalizing device is necessary for the accurate measurement of gas permeability. The three types of measurements—integral, differential (flow method), and decay rate measurements—can be used with the instrument. The results of permeability constants and diffusion constants obtained with the methods showed good agreement with the conventional vacuum-type method. With proper selection of methods, the instrument can measure the gas flux through the range of 10^?10 to 10^?3 cm³ (STP)/cm² sec cm Hg. Some advantages of the methods are discussed.     

天然气制油循环气脱碳活化剂和烃类损失研究

针对天然气制油（GTL）循环尾气组成在脱碳过程中对活化剂的降解损失以及烃类的损失进行了试验研究,报道了有机胺类活化剂与含氧有机气体以及烃类气体接触的降解试验数据。在模试装置上测定了原料气中烃类在GTL循环气脱碳溶剂中的损失,最高为0．69％,最低为0．08％。在溶液循环量不变的情况下,改变循环气的流量,在单位体积溶液溶解的烃类有随气量增高的趋势,但变化比较平缓,在5～8L／m3内缓慢上升。     

Numerical simulation of the two-dimensional flow in high pressure catalytic combustor for gas turbine

The objective of this paper is modeling the mechanism of high pressure and high temperature catalytic oxidation of natural gas, or methane. The model is two-dimensional steady-state, and includes axial and radial convection and diffusion of mass, momentum and energy, as well as homogeneous (gas phase) and heterogeneous (gas surface) single step irreversible chemical reactions within a catalyst channel. Experimental investigations were also made of natural gas, or methane combustion in the presence of Mn-substituted hexaaluminate catalysts. Axial profiles of catalyst wall temperature, and gas temperature and gas composition for a range of gas turbine combustor operating conditions have been obtained for comparison with and development of a computer model of catalytic combustion. Numerical calculation results for atmospheric pressure agree well with experimental data. The calculations have been extended for high pressure (10 atm) operating conditions of gas turbine.     

Performance analysis of NiO cathode using a molten carbonate fuel cell with gas recycle

The effect of oxidant gas composition on the polarization of NiO cathode has been investigated in a benchscale molten carbonate fuel cell operating at 650 °C. Cathode gas recycling has been applied to minimize the gradient of oxidant gas composition within the cell. The performance of NiO cathode was analyzed at a number of gas recycling ratios and a variety of inlet gas compositions to investigate the relation between cathode polarization and partial pressure of oxidant gas. It was found that the correlation equation based on superoxide mechanism could be used to estimate the cathode performance in a broad partial pressure range of oxidant gas.     

Electrochemical reduction of vinyl chloride on a Au/porous alumina plate/Pt electrode assembly in nonaqueous electrolytes: Toward the development of gas sensors

A novel configuration consisting of one porous alumina plate, two electrodes sputtered on both sides and an organic electrolyte, was developed to analyse in situ vinyl chloride in the gaseous phase. Gold and platinum with several solvents (e.g., 1,4-dioxane aqueous solution, acetonitrile and toluene/DMF mixtures) were applied to investigate the suitability for the analysis of vinyl chloride gas in the concentration range of 13–44.5%. The effect of solvent composition on the response behavior was discussed. The analyser with 20% toluene/80% DMF (v/v) mixture had the largest sensitivity at –2.3 V vs Ag/Ag⁺. The content of residual water in the electrolyte affected not only the background current but also the reduction current of vinyl chloride.     

Determination of fatty acid composition by gas chromatography: I. Analysis with use of thermal conductivity detector

For the purpose of establishing a standard method for the gas chromatographic determination of fatty acid composition, a collaborative study team has carried out replicate analyses of specified samples using gas chromatographs equipped with thermal conductivity detectors and has examined the entire set of experimental data by a statistical method. From the results of the four collaborative works it was found that deviation of analytical values from exact composition and interlaboratory scattering of data may be considerably decreased by the following means: (a) enlarging the size of narrow peaks (less than 5 mm at a half height) or peaks with low height by adjusting the attenuator range or chart speed; (b) correcting the analytical values by using correction factors determined from analysis of known mixtures having composition similar to that of an unknown sample. Presented at the JOCS-AOCS Joint Meeting, Los Angeles, April 1972.     

An optimization framework for the integration of water management and shale gas supply chain design

This study presents the mathematical formulation and implementation of a comprehensive optimization framework for the assessment of shale gas resources. The framework simultaneously integrates water management and the design and planning of the shale gas supply chain, from the shale formation to final product demand centers and from fresh water supply for hydraulic fracturing to water injection and/or disposal. The framework also addresses some issues regarding wastewater quality, i.e., total dissolved solids (TDS) concentration, as well as spatial and temporal variations in gas composition, features that typically arise in exploiting shale formations. In addition, the proposed framework also considers the integration of different modeling, simulation and optimization tools that are commonly used in the energy sector to evaluate the technical and economic viability of new energy sources. Finally, the capabilities of the proposed framework are illustrated through two case studies (A and B) involving 5 well-pads operating with constant and variable gas composition, respectively. The effects of the modeling of variable TDS concentration in the produced wastewater is also addressed in case study B.     

Soot oxidation in gas turbines using heavy fuels. 2

Most of the work carried out, so far, in the study of soot oxidation has used laboratory flames and shock tubes in connection with graphite to avoid the difficulty in determining the history of soot particles in complex practical flames such as those of the gas turbine. Therefore, a soot oxidation model is developed to calculate the soot burning rate in the secondary zone of a gas turbine combustor operating with heavy fuels including blends of gas oil and residual fuel oil. The combustor pressure is raised to 1.0 MPa, inlet air temperature to 460 K, primary air/fuel mass ratio to 25 and total air/fuel mass ratio to 120. The capability of the model is found to be favourable when evaluated at the exhaust plane. Furthermore, it is noted that, at full power, the soot level in the primary zone can decrease ≈ 1000 times in its travel through the secondary zone before emerging as smoke. A disparity in the peak soot burning rate is noted between fuels at the idle condition. At full power this disparity disappears.