固定污染源排气中非甲烷总烃的测定探讨

用气相色谱仪配双氢火焰检测器、双不锈钢填充柱分析固定污染源排气中总烃、甲烷、氧峰从而得到非甲烷总烃(NMHC)含量。当色谱进样量为1.0 mL时,方法的检出浓度为4×10-2mg/m3,方法的定量检定浓度范围为0.12～32 mg/m3。文章着重介绍独特的标准气体的配制方法及进样方法,保证了非甲烷总烃(NMHC)测试的准确性。     

应用气相色谱法检测空气中非甲烷总烃的研究

[0]采用气相色谱法检测空气中的非甲烷总烃需扣除会产生正干扰的氧峰,采用填充GDX-502担体的填充柱测甲烷时,可以将氧峰很好的分离出来,且能保持良好的稳定性,以此得出的氧浓度也可参与非甲烷总烃的计算。     

气相色谱法测定非甲烷总烃的研究

用玻璃注射器(气袋)采集气体样品,以双柱单氢火焰离子化检测器的气相色谱仪直接进行测定。进样1.0 mL样品分别进入汽化室的总烃柱和甲烷柱中,由于这两个柱子填充材料和长短差异,总烃先在FID上产生响应,然后甲烷在FID上产生响应。总烃的浓度扣除甲烷浓度和除烃空气氧的浓度值,即可得到非甲烷总烃(NMHC)的浓度,可以实现单次进样,同时完成总烃、甲烷、非甲烷总烃浓度的测定。文章研究1.37～22.3 mg/m3浓度甲烷标准气,得出甲烷标准曲线方程为Y=715X+829,r=0.9990,相对标准偏差为0.26%～1.8%,总烃标准曲线方程Y=695X+724,相对标准偏差为0.35%～1.4%,除烃空气(O2-N2,20.8%)相对标准偏差为0.75%。该法用于环境空气和固定污染源有组织排放中NMHC含量分析,操作简单,实验结果满意。     

汽油硫含量检测影响因素探讨

选择SH/T 0689-2000轻质烃及发动机燃料和其他油品的总硫含量测定法(紫外荧光法)作为测定依据进行检测实验,对各种影响汽油硫含量检测结果的因素进行分析。结果表明,当裂解温度在1000~1050℃之间时,标样测量结果接近真实值;裂解氧气及载气氩气流量过大或过小,将导致检测结果偏离真实值;不同浓度的样品,其进样量的多少直接影响测试结果的准确性,对硫含量低的样品可适当加大进样量,而硫含量高的样品应适当减小进样量,同时进样速度的快与慢也会影响检测结果的准确性;标准曲线的选取会影响测量结果准确性,当硫含量低于40mg/L时应选择标准曲线0-30-50;当硫含量低于10mg/L时应选择标准曲线0-5-10。     

氧气浓度对好氧甲烷氧化耦合反硝化过程的影响

好氧甲烷氧化耦合反硝化反应是一个重要连接甲烷和氮循环的过程。文中考察了4种氧气浓度(2.5%、5%、10%和21%)对好氧甲烷氧化耦合反硝化反应的影响。试验结果表明,21%的氧气浓度可以促进甲烷氧化,提高体系中溶解性有机碳的浓度,同时一定程度上抑制甲烷氧化耦合反硝化反应。甲烷浓度为6%～8%时,10%氧气浓度下甲烷氧化耦合反硝化反应的脱氮效率最高。     

碳分子筛空气吸附过程的数值模拟

采用Aspen adsorption对空气在碳分子筛上的吸附过程进行了数值模拟,得到了氧气的穿透曲线和氮气出口浓度随时间的变化,考察了吸附压力、原料气流速和原料气中氩气浓度对穿透曲线的影响。研究表明:氧气和氮气出口浓度的模拟值与试验值吻合良好,当压力从0.58 MPa增大到0.98 MPa时,氧气的穿透时间延长了55.6%;穿透时间随原料气流速增大迅速缩短,但变化幅度在流速大于0.004 mol/s后趋于平缓;当原料气中氧气浓度不变时,氩气浓度对氧气的穿透曲线影响甚微。     

甲烷/石墨粉与甲烷/煤粉爆炸特性对比研究

借助20 L球形爆炸系统研究了甲烷/石墨粉和甲烷/煤粉复合体系爆炸特性异同,结果表明：甲烷浓度对甲烷/石墨粉和甲烷/煤粉两相体系的爆炸特性有重要影响,当甲烷的浓度为6%（体积）时,随着石墨粉粒径的增加,甲烷/石墨粉体系的压力曲线由单峰转为双峰,三种粒径的石墨粉（D₅₀：7、18、75 μm）浓度分别在60、200、30 g/m³达到爆炸压力最大值0.691、0.657、0.611 MPa;甲烷/煤粉体系则在400 g/m³达到最大值0.724 MPa,高于甲烷/石墨粉体系。当甲烷浓度接近当量比时,三种粒径石墨粉的爆炸压力峰值均呈现逐渐减小的趋势,石墨粉的粒径越小,甲烷/石墨粉两相体系的爆炸压力峰值越小,甲烷/石墨粉体系在质量浓度为10 g/m³时达到最大值;甲烷/煤粉体系的爆炸压力则在60 g/m³时达到最大值0.776 MPa。甲烷浓度由6%增加至9%时,甲烷/石墨粉和甲烷/煤粉的爆炸火焰由不规则形状转为近似球形发展,火焰表面褶皱消失,同时两相体系的爆燃指数显著增高,当粉尘质量浓度大于30 g/m³时,甲烷/煤粉的爆燃指数大于甲烷/石墨粉体系,这是由于煤粉挥发分含量高,燃烧更为充分,且焦炭参与了爆炸过程;石墨粉本身的挥发分含量低,含碳量远超过煤粉,爆炸中仅有少部分石墨粉参与了爆炸。研究结果将对气粉两相混合物爆炸防治提供指导。     

甲烷/石墨粉与甲烷/煤粉爆炸特性对比研究

借助20 L球形爆炸系统研究了甲烷/石墨粉和甲烷/煤粉复合体系爆炸特性异同，结果表明：甲烷浓度对甲烷/石墨粉和甲烷/煤粉两相体系的爆炸特性有重要影响，当甲烷的浓度为6%（体积）时，随着石墨粉粒径的增加，甲烷/石墨粉体系的压力曲线由单峰转为双峰，三种粒径的石墨粉（D₅₀：7、18、75 μm）浓度分别在60、200、30 g/m³达到爆炸压力最大值0.691、0.657、0.611 MPa；甲烷/煤粉体系则在400 g/m³达到最大值0.724 MPa，高于甲烷/石墨粉体系。当甲烷浓度接近当量比时，三种粒径石墨粉的爆炸压力峰值均呈现逐渐减小的趋势，石墨粉的粒径越小，甲烷/石墨粉两相体系的爆炸压力峰值越小，甲烷/石墨粉体系在质量浓度为10 g/m³时达到最大值；甲烷/煤粉体系的爆炸压力则在60 g/m³时达到最大值0.776 MPa。甲烷浓度由6%增加至9%时，甲烷/石墨粉和甲烷/煤粉的爆炸火焰由不规则形状转为近似球形发展，火焰表面褶皱消失，同时两相体系的爆燃指数显著增高，当粉尘质量浓度大于30 g/m³时，甲烷/煤粉的爆燃指数大于甲烷/石墨粉体系，这是由于煤粉挥发分含量高，燃烧更为充分，且焦炭参与了爆炸过程；石墨粉本身的挥发分含量低，含碳量远超过煤粉，爆炸中仅有少部分石墨粉参与了爆炸。研究结果将对气粉两相混合物爆炸防治提供指导。     

橡胶填料在厌氧-好氧-体式生物反应器处理高浓度有机废水中的作用

采用厌氧-好氧-体式折流板生物反应器，在好氧室添加废旧橡胶作为微生物附着生长填料的情况下，进行了该反应器处理马铃薯淀粉废水中COD和NH，-N的去除试验。试验结果表明：在温度为25-35℃，pH值为5．0-8．5时，出水COD浓度低于200mg／L，反应器COD总去除率最高达到98％，出水氨氮浓度在10mg／L左右，氨氮去除率达到74．7％。     

安庆石化新催化剂治理恶臭气体效果显著

8月9日,安庆石化炼油初级污水处理场催化燃烧装置出口废气跟踪检测数据显示：非甲烷总烃含量最低时每立方米约35mg,最高时每立方米也仅90mg,远低于国家规定标准含量120mg,非甲烷总烃含量直接影响废气的恶臭浓度,这一数据表明,该公司臭气处理效果大幅提升。     

Methanol formation from methane partial oxidation in CH4–O2–NO gaseous phase at atmospheric pressure

The reaction condition for high yield of methanol in a gaseous reaction between methane and oxygen in the presence of NO at atmospheric pressure was explored. Methane partial oxidation without NO (CH₄–O₂) gave only 1% conversion of methane at 966 K. The addition of NO led to a remarkable increase in methane conversion and to high selectivity to C₁-oxygenates. The conversion of methane attained 10% at 808 K in the presence of NO (0.5%) where the selectivities to methanol and formaldehyde were 22.1 and 24.1%, respectively. Nitromethane and carbon oxides were also observed in the product gas. The amount of nitromethane was almost equal and/or near to that of initial NO. The carbon monoxide produced was several times higher than carbon dioxide. Influences of NO concentration, ratio of methane to oxygen, water vapor, and dilution with helium gas on product distribution were measured. Low concentration of NO (0.35–0.55%) was favorable for methanol formation. High selectivity to methanol was obtained at low value of the ratio of methane to oxygen (2.0–3.0) or low concentration of dilution gas (<16%). The NO₂ added promoted methane partial oxidation and selectivity to methanol. Therefore, it was assured that NO_x promoted the formation of CH₃√ and CH₃O√ in the gas phase reaction for CH₄–O₂–NO.     

Effect of Oxygen on Methane Steam Reforming in a Sliding Discharge Reactor

Hydrogen‐rich gas can be efficiently produced in compact plasma reformers by the conversion of a variety of hydrocarbon fuels, including natural gas and gasoline. This article describes experimental and modeling progress in plasma reforming of methane using a sliding discharge reactor (SDR). Experiments have been carried out in a compact device operating at low consumed power (1–2 kW). Previous studies of methane steam reforming using a SDR at atmospheric pressure show promising results (H₂ concentration higher than 55 %). In order to study the effect of oxygen on the methane conversion and thus hydrogen production, a small amount of oxygen in the range of 7–20 % was added to the CH₄‐H₂O mixture. An unexpected result was that under our experimental conditions in the SDR oxygen did not have any influence on the methane conversion. Almost the totality of added oxygen is recovered intact. Moreover, part of the H₂ produced was transformed into water by reaction with O₂. A model describing the chemical processes based on classical thermodynamics is also proposed. The results indicate that the reactor design has to be improved in order to increase conversion and hydrogen production.     

High-yield synthesis of carbon nano-onions in counterflow diffusion flames

High-yield synthesis of carbon nanotubes (CNTs) and nano-onions (CNOs) on a catalytic nickel substrate using counterflow diffusion flames was investigated. With ethylene fixed at 5%, methane varied from 15% to 45% in the upper flow, and air supplied in the lower flow, only a moderate CH₄ concentration (25%) could yield high density CNTs. However, when oxygen was increased to 50% in the lower flow, only CNOs were synthesized. An increase in methane concentration from 15% to 45% led to a higher yield and a greater diameter (ranging from 5 to 60 nm) of CNOs. To examine the role of mixed fuel, it was observed that as ethylene was removed and only 45% methane and nitrogen were supplied in the upper flow, no CNOs could be generated. While, as methane was increased to 50% or 55%, high-yield CNOs were synthesized and the yield increased with methane concentration. Note that the key parameters influencing the formation and yield of CNOs are both the oxygen and fuel concentrations. There was a critical threshold value of oxygen concentration, 30%, for onset of CNOs synthesis. Also, the critical threshold value of methane concentration for onset of CNOs formation decreased with increasing oxygen concentration or ethylene concentration.     

煤层气非催化燃烧除氧实验研究

煤层气由于热值及浓度较低,达不到工业利用要求,工业应用中需进行浓缩。由于煤层气中含有氧,给浓缩过程带来了不安全因素,因此在浓缩前必须将氧除去。简要介绍了煤层气除氧的几种方法,并在除氧反应器装置上对煤层气非催化燃烧除氧进行了实验研究。结果发现,通过非催化燃烧法除氧,O2浓度能够降至1%以下;选用的除氧燃料须具有反应活性好、热值低的特点;除氧温度接近600℃时,CH4损失率小于5%,CH4的裂解是造成CH4损失的主要原因。     

A study on the deposition of pyrolytic carbons from hydrocarbons

A new method for forming isotropic, laminar, and columnar pyrolytic carbons is proposed. For this, a low RPM (below 2.4 rpm) tumbling bed has been used to deposit pyrolytic carbons from hydrocarbon gases. All deposits were made on graphite substrates from propane and methane at a constant temperature of 1200°C. The microstructures of the pyrolytic carbons deposited were dependent on the flow pattern of the reactant gas, the rpm of the reactor, the hydrocarbon concentration, the nature of the hydrocarbon, and the geometry of the bed. Isotropic pyrolytic carbon is formed under deposition conditions where homogeneous nucleation occurs in the gas phase and at the gas flow conditions where the gas-borne droplets can collide on the substrate. Laminar carbon is formed under deposition conditions where homogeneous nucleation does not occur in the gas phase and at gas flow conditions where the carbon species existing in the bulk of the gas phase can collide on the substrate. Columnar carbon is formed when any carbon products existing in the bulk of the gas phase cannot collide on the substrate. The suggested deposition mechanism can also be applied to pyrolytic carbons deposited in a fluidized bed or in a stationary bed. In particular, isotropic carbon can be obtained even in a stationary bed if the requirements for the deposition of the isotropic carbon described above are satisfied.     

Automated analyser for monitoring the contents of hydrocarbons in gas emitted from exploratory bore-holes in the gas and oil industry

An automated analyser for total hydrocarbon contents and hydrocarbon composition (from methane to pentanes) was constructed and tested in both laboratory and field exploitation. It used two-channel analysis: continuous measurements of total hydrocarbon contents and periodic (90 or 150 s) composition analysis after separation of hydrocarbons on a gas chromatographic column. Flame ionization detectors were used in both channels. A simple 16-bit analogue-to-digital converter was used (4.8, practically four orders of magnitude), while the full measuring range (six orders of magnitude) was ensured by automatic dilution of the sample (or standard) with clean air. Full control of the operating (calibration/analyses) cycle was performed by microcomputer. An external programme, based on a computer provided with full information on the instrument operating conditions, presents the results of calibrations/analyses and enables them to be archived in a standard database used in the oil/gas drilling industry (N-LAB) by providing a suitable link. The instrument measuring range was 1 ppm to 100% with precision not worse than 5% at the detection limit. The analyser can operate autonomously for two months, recalibrating itself daily.     

The catalytic oxidative coupling of methane: I. Comparison of experimental performance data from various types of reactor

The methane oxidative coupling performance of a fixed-bed reactor was successfully translated to a bubbling fluidised-bed reactor and this reaction mode was superior to spouted-bed, inclined and mechanically-agitated fluidised-bed units. Also, a two-stage bubbling fluidised-bed reactor with inter-stage addition of oxygen had the same performance as the single-stage unit, for the same total oxygen input, over a wide range of operating conditions. Overall the bubbling fluidised-bed is preferred, catalytic reactions dominate over non-catalytic gas phase reactions in determining the reactor performance, the gas phase exhibited plug-flow behaviour and the performance was independent of the gas phase oxygen partial pressure for a given oxygen input. The best hydrocarbon yield achieved in this study was 19.4%.     

含氧煤层气制LNG产品中含氧量讨论

对含氧煤层气进行直接深冷液化可回收其中的甲烷生产LNG,减少污染排放.产品LNG中主要杂质为氧气,氧气含量对LNG产品的安全性有影响.通过对热量吸入和压力变化导致LNG部分气化的安全性进行分析,得出结论在LNG刚开始气化时气相中氧气浓度最高,并随着气化量增加而减小,LNG产品中氧含量应小于5％.     

Characterization of DLC:Si films by the gas effusion technique

In this work an investigation of hard DLC:Si films by the gas effusion technique is presented. Effusion of hydrogen, methane and higher hydrocarbons was studied for films with silicon contents of up to 40 at%. Three major contributions to the effusion spectra could be identified: (i) a desorption-limited mechanism from the internal surfaces of a network of voids which could be observed even for large hydrocarbon molecules, indicating that low silicon content material possesses a porous structure; (ii) a sharp peak related to the abrupt graphitization of the films which dominates the spectra for hydrogen and methane effusion in the low concentration range and is gradually shifted to high temperatures as the silicon content is increased; and (iii) a diffusion-limited mechanism that appears for high silicon content films, suggesting that the films undergo a transition from porous to a relatively compact structure.