Nondispersive Infrared Gas Analyzer Research Articles

Comparison of saturator designs for delivery of low-volatility liquid precursors

Numerous low-volatility precursors are utilized in chemical vapor deposition and atomic layer deposition processes. Such precursors are often delivered from one of two common saturator designs: a bubbler or a flow over vessel. Previous reports concerning precursor delivery from such vessels have focused primarily on continuous delivery of moderate to high volatility liquids and solids. Few reports have focused on cyclical delivery of low volatility precursors at reduced pressures. This lack of knowledge concerning such processes can be a hindrance to efficient selection of deposition conditions and vessel design. The objective of this investigation was to compare the performance of these two saturator designs for pulsed injection at reduced pressures using the low volatility liquid precursor μ2-η2-(tBu-acetylene) dicobalthexacarbonyl (CCTBA). The basis of this comparison was the measurement of CCTBA mass carryover per injection as a function of injection number, injection time, carrier gas flow rate, system pressure, and vessel idle time. The mass carryover was determined from absorbance measurements performed using a non-dispersive infrared gas analyzer. The measured mass carryover for both vessels was compared to the theoretical mass carryover determined using a simple analytical model based upon the “bubbler equation”. In the case of the bubbler, this model described the vessel performance well with knowledge of the precursor vapor pressure and vessel head space pressure. In the case of the flow over vessel, this model described the overall vessel performance poorly unless an additional vessel efficiency factor was included, a factor that is difficult to predict a priori. Furthermore, the efficiency factor was not necessarily constant for a series of injections: the efficiency factor tended to decrease from the first injection until a stable value was achieved, a value that depended on the process conditions. This limitation of the model was attributed to the specific flow dynamics associated with the flow over vessel design. Computational fluid dynamics simulations were able to reproduce the mass carryover of the flow over vessel, after estimating the CCTBA-carrier gas binary diffusion coefficient. These simulations also showed that a larger binary diffusion coefficient and a higher vapor pressure both led to an increase in mass carryover but vessel efficiency could not equal that of the bubbler. While these results were obtained with CCTBA, the general relationships between mass carryover and the various process parameters in these saturators are expected to be similar for other low-volatility precursors.

Physicochemical Parameters and Microbial Community in Anaerobic Digestion of Organic Wastes

The demand for an alternative source of energy and challenge of increase in wastes pollution initiates the need for renewable energy and management of waste using anaerobic digestion (AD). Anaerobic digestion is an effective and efficient method of waste treatment and energy generation. The study focused on investigating the physicochemical parameters and microbial community in anaerobic digestion of organic wastes and was conducted using chicken wastes and food wastes as organic substrate under semi-continuous conditions at hydraulic retention time (HRT) of forty-two (42) days in fifteen liter (15L) fabricated digesters labeled D1, D2 and D3 at 37OC. The pH, volatile fatty acid (VFA), moisture content (MC), total ammonia, total solid, volatile solid, alkalinity was assessed before and after digestion while the microbial community diversity was analyzed using 16S rRNA amplicon-based nextgeneration sequencing (NGS). The results indicated a pH value of 6.65 ± 0.12, 7.27 ± 0.13, 6.43 ± 0.27, volatile fatty acid of 72.17 ± 1.42, 58.35 ± 2.58, 40.56 ± 0.38 and moisture content of 98.9 ± 2.65, 92.3 ± 1.81, 96.4 ± 3.60 at day 42 for D1 (Chicken waste and food wastes), D2 (Chicken wastes+), D3 (control) respectively. A collective biogas yield of 686±17.00 kpa for D1, 700±11.00kpa for D2 and 521±21.00 kpa for D3 were recorded. The characterization of biogas analyzed with nondispersive infrared (NDIR) gas analyzer (gas board 3100p) revealed a percentage methane content of 46.11±1.11, 52.4±1.05, 50.31±1.33 for D1, D2 and D3 respectively. The microbial community identified phylum Bacteroidetes, Firmicutes, proteobacteria, Tenericutes, Verrucomicrobia, Actinobacteria, Euryarchaeota among others. The study shows that physicochemical properties and microbial community diversity are useful tools to indicate digester performance and also to enhance anaerobic digestion process.

Identification and characterization of microbial community of anaerobic digested poultry litter

Livestock farming have resulted in the release of excessive wastes which, contains abundant organic matter and microbial population. The need to develop an alternative and sustainable methods to minimize the waste generated and it effects on the environment led to the application of anaerobic digestion (AD) for the treatment of waste and generation of methane gas. The study focused on investigation of the microbiome involve in AD of poultry litter and was conducted using poultry litter as organic substrate under batch conditions at hydraulic retention time (HRT) of fifty-six (56) days in fifteen (15) liter fabricated digesters at 37OC. The pH, total solid (TS), moisture content (MC) total ammonia nitrogen, volatile solid (VS) was assessed before and after digestion while the microbial community diversity was analyzed using 16S rRNA amplicon-based next-generation sequencing (NGS). The results indicated a pH of 7.91±0.04 before digestion and 7.33±0.06 after digestion and a TS value of 56.40±0.6% before digestion and 6.30±0.34% after digestion. A collective biogas yield of 5.21±21.00 bars were recorded. The characterization of biogas analyzed with non-dispersive infrared (NDIR) gas analyzer (gas board 3100p) revealed a percentage methane content of 50.31±1.33. The microbial community indicate Bacteroidetes (46.37%), Firmicutes (48.37%), Proteobacteria (8.17%), as the most dominant phylum. This study suggests the importance of molecular analysis as a fundamental tool to gain insight and deeper understanding of anaerobic digester performances.

Characterization of vapor draw vessel performance for low-volatility solid precursor delivery

Low volatility precursors are widely utilized in chemical vapor deposition (CVD) and atomic layer deposition (ALD) processes. Compared to gases and high volatility liquid precursors, delivery of low volatility liquid and solid precursors can be problematic, with solid precursors being particularly so. To investigate some of these delivery issues, the performance of a vapor draw vessel was characterized for the delivery of pentakis(dimethylamido) tantalum (PDMAT), a low-volatility solid precursor at preferable delivery temperatures, for reduced-pressure cyclical CVD and ALD processes. Vessel characterization involved determining (1) a source efficiency as a function of process conditions and (2) the degree of PDMAT decomposition as a function of temperature and vessel idle time. The PDMAT partial pressure, flow rate, and mass per injection used to determine the source efficiency were determined from measurements obtained using a custom-designed non-dispersive infrared gas analyzer. For a series of injections after an idle/purge sufficiently long to saturate the vessel head space, the source efficiency decreased from a maximum slightly less than unity for the first injection until a consistent value was reached that was approximately one half to one third of the maximum value. A comparable trend was observed for mass delivered per injection. For the conditions used in this investigation, the source efficiency decreased when the injection time was increased to longer than 1 s, when pressure was decreased, and when the carrier gas flow rate was increased. Although the corresponding mass per injection increased with these changes, the increase in mass was less than that predicted had the carrier gas been saturated. The source efficiency did not depend strongly on temperature and only moderately on vessel idle durations (4–16 s). The degree of PDMAT decomposition was evaluated by measuring the partial pressure of dimethylamine (the primary PDMAT decomposition product under the conditions of this investigation) using the same gas analyzer. For a given idle time, the amount of dimethylamine delivered more than doubled as vessel temperature was increased from 68 to 78 °C.

Electrochemical Pumping Behavior of an Anion Exchange Membrane CO2 Separation Device

Anion exchange membranes (AEM) are well studied in the context of fuel cells and water electrolyzers, as they permit the use of non-noble catalysts. However, such alkaline systems have a notable drawback of carbonation when they are operated using atmospheric air, which is known to reduce the anion conductivity of the membrane. The (bi)-carbonate ions are removed from the membrane through the migration of hydroxide ions, also known as the self-purging mechanism. This carbonation effect of AEMs can be utilized to selectively remove CO2 from a dilute gas mixture (e.g., flue gas or air) and transport it across the membrane, as shown in Figure 1.Effective CO2 transport across the membrane can be enabled using hydrogen evolution and oxidation reactions in the presence of CO2 and alkaline media. This methodology differentiates itself from other membrane-based separation techniques, as it allows for low concentrations (<1%) of CO2 to be removed at a high fraction (>90%) from a gas stream. Significant developments are required to optimize such a system, reduce material costs and cell overpotentials, and allow for long-term operation.We performed preliminary experiments proving the concept of an electrochemical CO2 separation device utilising AEMs. Steady-state galvanostatic experiments with on-line non-dispersive infrared gas analysis have demonstrated the clear relationship between current density, cell potential, and CO2 pumped across the membrane for a wide range of inlet CO2 concentrations. Faradaic efficiencies for CO2 transport are strongly dependent on the inlet CO2 concentration and current density. Considerations for further development are discussed.Figure Caption: Schematic of AEM CO2 separator Figure 1

Nondispersive Infrared Gas Analyzer for Partial Pressure Measurements of a Tantalum Alkylamide During Vapor Deposition Processes.

A nondispersive infrared gas analyzer was demonstrated for investigating metal alkylamide precursor delivery for microelectronics vapor deposition processes. The nondispersive infrared analyzer was designed to simultaneously measure the partial pressure of pentakis(dimethylamido) tantalum, a metal precursor employed in high volume manufacturing vapor deposition processes to deposit tantalum nitride, and dimethylamine, the primary decomposition product of pentakis(dimethylamido) tantalum at typical delivery conditions for these applications. This sensor was based on direct absorption of pentakis(dimethylamido) tantalum and dimethylamine in the fingerprint spectral region. The nondispersive infrared analyzer optical response was calibrated by measuring absorbance as a function of dimethylamine and pentakis(dimethylamido) tantalum density. The difference between the mass of material removed from the ampoule during flow tests as measured gravimetrically and as determined optically, by calculating flow rates from the nondispersive infrared analyzer measurements, was only ≈2 %. The minimum detectable molecular densities for pentakis(dimethylamido) tantalum and dimethylamine were ≈2 × 1013 cm-3 and ≈5 × 1014 cm-3, respectively (with no signal averaging and for a sampling rate of 200 Hz), and the corresponding partial pressures were ≈0.1 Pa and ≈2 Pa for pentakis(dimethylamido) tantalum and dimethylamine, respectively (for an optical flow cell temperature of 93 ℃). Pentakis(dimethylamido) tantalum could be detected at all conditions of this investigation and likely the majority of conditions relevant to high volume manufacturing tantalum nitride deposition. Dimethylamine was not detected at all conditions in this study, because of a lower nondispersive infrared analyzer sensitivity to dimethylamine compared to pentakis(dimethylamido) tantalum and because conditions of this study were selected to minimize DMA production. While this nondispersive infrared gas analyzer was specifically developed for pentakis(dimethylamido) tantalum and dimethylamine, it is suitable for characterizing the vapor delivery of other metal alkylamide precursors and the corresponding amine decomposition products, although in the case of some metal alkylamides a different bandpass filter would be required.

Characterization of bubbler performance for low-volatility liquid precursor delivery.

The performance of a bubbler to deliver the low-volatility, liquid cobalt precurso - -(tBu-acetylene) dicobalthexacarbonyl (CCTBA) for reduced-pressure chemical vapor deposition and atomic layer deposition processes was characterized. A relatively large process window was investigated by varying carrier gas flow rate, system pressure, and bubbler temperature. For this range of conditions, the CCTBA partial pressure was measured using a custom-designed non-dispersive infrared gas analyzer, and the CCTBA flow rates were derived from these partial pressure measurements. The dependence of CCTBA flow rate on these process parameters was modeled to obtain a deeper understanding of the factors influencing bubbler performance. Good agreement between measured and modeled CCTBA flow rates was obtained using a model in which a constant CCTBA partial pressure in the bubbler head space for a given bubbler temperature was assumed and in which the pressure drop between the bubbler head space and the pressure measurement location was included. The dependence of CCTBA head space partial pressure on temperature was parameterized in the form of the August equation, which is commonly used to describe the temperature-dependence of vapor pressure. While this report was focused specifically on CCTBA, the results are expected to apply to other low-volatility, liquid precursors of interest in vapor deposition processes.

Nondispersive Infrared Gas Analyzer for Vapor Density Measurements of a Carbonyl-Containing Organometallic Cobalt Precursor.

A nondispersive infrared (NDIR) gas analyzer was demonstrated for measuring the vapor-phase density of the carbonyl-containing organometallic cobalt precurso μ2-η2-(tBu-acetylene) dicobalthexacarbonyl (CCTBA). This sensor was based on direct absorption by CCTBA vapor in the C≡O stretching spectral region and utilized a stable, broadband IR filament source, an optical chopper to modulate the source, a bandpass filter for wavelength isolation, and an InSb detector. The optical system was calibrated by selecting a calibration factor to convert CCTBA absorbance to a partial pressure that, when used to calculate CCTBA flow rate and CCTBA mass removed from the ampoule, resulted in an optically determined mass that was nominally equal to a gravimetrically-determined mass. In situ Fourier transform infrared (FT-IR) spectroscopy was performed simultaneously with the NDIR gas analyzer measurements under selected conditions in order to characterize potential spectroscopic interferences. Interference due to CO evolution from CCTBA was found to be small under the flow conditions employed here. A CCTBA minimum detectable molecular density as low as ≈3 × 1013 cm-3 was calculated (with no signal averaging and for a sampling rate of 200 Hz). While this NDIR gas analyzer was specifically tested for CCTBA, it is suitable for characterizing the vapor delivery of a range of carbonyl-containing precursors.

Correct calculation of CO2 efflux using a closed‐chamber linked to a non‐dispersive infrared gas analyzer

Summary Improved understanding of the carbon (C) cycle is essential to model future climates and how this may feedback to affect greenhouse gas fluxes. We summarize previous work quantifying respiration rates of organic substrates and briefly discuss how advances in technology, specifically the use of chambers linked to a non‐dispersive infrared gas analyzer (NDIR), can be applied to assess carbon dynamics from short‐term field measurements. This technology hastens measurement and is relatively inexpensive, enabling researchers to increase replication and investigate temporal and spatial variation. We describe the theory behind calculations of CO2 efflux released through organic substrates, when using a closed‐chamber linked to a NDIR. These methods can in principle be extended to any chamber‐based measurement of gas fluxes, including partially closed chambers as used for soil surface CO2, nitrous oxide or methane effluxes and stem CO2 respiration, although additional assumptions may apply. We show that incorrect application of formulae in some earlier studies resulted in either under‐ or over‐estimation of CO2 effluxes. Of the studies, we reviewed measuring the respiration of woody debris, leaf litter or woody stems using closed chambers linked to a NDIR, only 22% (11 of 51) provided the equations used to calculate CO2 efflux, and 72% (8 of 11) of those provided contained basic errors. Using our data on the decomposition of woody debris as an example, we found that such mistakes resulted in anywhere from 8% underestimation to 22% overestimation of CO2 efflux. The errors varied among studies and hence may limit understanding of the factors affecting emissions of CO2 and our ability to incorporate this knowledge into global carbon models. We provide formulae for the correct calculation of respiration rates in future studies using closed chambers and thus provide a basis for comparative studies of factors affecting CO2 efflux from woody debris, leaf litter and other substrates. Ultimately, this will contribute to improved parameterization of forest respiration.

Measurements of metal alkylamide density during atomic layer deposition using a mid-infrared light-emitting diode (LED) source.

A nondispersive infrared (NDIR) gas analyzer that utilizes a mid-infrared light emitting diode (LED) source was demonstrated for monitoring the metal alkylamide compound tetrakis(dimethylamido) titanium (TDMAT), Ti[N(CH3)2]4. This NDIR gas analyzer was based on direct absorption measurement of TDMAT vapor in the C-H stretching spectral region, a spectral region accessed using a LED with a nominal emission center wavelength of 3.65 μm. The sensitivity of this technique to TDMAT was determined by comparing the absorbance measured using this technique to the TDMAT density as determined using in situ Fourier transform IR (FT-IR) spectroscopy. Fourier transform IR spectroscopy was employed because this technique could be used to (1) quantify TDMAT density in the presence of a carrier gas (the presence of which precludes the use of a capacitance manometer to establish TDMAT density) and (2) distinguish between TDMAT and other gas-phase species containing IR-active C-H stretching modes (allowing separation of the signal from the LED-based optical system into fractions due to TDMAT and other species, when necessary). During TDMAT-only delivery, i.e., in the absence of co-reactants and deposition products, TDMAT minimum detectable molecular densities as low as ≈4 × 10(12) cm(-3) were demonstrated, with short measurement times and appropriate signal averaging. Reactions involving TDMAT often result in the evolution of the reaction product dimethylamine (DMA), both as a thermal decomposition product in a TDMAT ampoule and as a deposition reaction product in the deposition chamber. Hence, the presence of DMA represents a significant potential interference for this technique, and therefore, the sensitivity of this technique to DMA was also determined by measuring DMA absorbance as a function of pressure. The ratio of the TDMAT sensitivity to the DMA sensitivity was determined to be ≈6.0. To further examine the selectivity of this technique, measurements were also performed during atomic layer deposition (ALD) of titanium dioxide using TDMAT and water. During ALD, potential interferences were expected from the evolution of DMA due to deposition reactions and the deposition on the windows of species containing IR-active C-H stretching modes. It was found that the interfering effects of the evolution of DMA and deposition of species on the windows corresponded to a maximum of only ≈6% of the total observed TDMAT density. However, this level of interference likely is relatively low compared to a typical chemical vapor deposition process in which co-reactants are introduced into the chamber at the same time.

Comparison of continuous in situ CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; observations at Jungfraujoch using two different measurement techniques

Abstract. Since 2004, atmospheric carbon dioxide (CO2) is being measured at the High Altitude Research Station Jungfraujoch by the division of Climate and Environmental Physics at the University of Bern (KUP) using a nondispersive infrared gas analyzer (NDIR) in combination with a paramagnetic O2 analyzer. In January 2010, CO2 measurements based on cavity ring-down spectroscopy (CRDS) as part of the Swiss National Air Pollution Monitoring Network were added by the Swiss Federal Laboratories for Materials Science and Technology (Empa). To ensure a smooth transition – a prerequisite when merging two data sets, e.g., for trend determinations – the two measurement systems run in parallel for several years. Such a long-term intercomparison also allows the identification of potential offsets between the two data sets and the collection of information about the compatibility of the two systems on different time scales. A good agreement of the seasonality, short-term variations and, to a lesser extent mainly due to the short common period, trend calculations is observed. However, the comparison reveals some issues related to the stability of the calibration gases of the KUP system and their assigned CO2 mole fraction. It is possible to adapt an improved calibration strategy based on standard gas determinations, which leads to better agreement between the two data sets. By excluding periods with technical problems and bad calibration gas cylinders, the average hourly difference (CRDS – NDIR) of the two systems is −0.03 ppm ± 0.25 ppm. Although the difference of the two data sets is in line with the compatibility goal of ±0.1 ppm of the World Meteorological Organization (WMO), the standard deviation is still too high. A significant part of this uncertainty originates from the necessity to switch the KUP system frequently (every 12 min) for 6 min from ambient air to a working gas in order to correct short-term variations of the O2 measurement system. Allowing additional time for signal stabilization after switching the sample, an effective data coverage of only one-sixth for the KUP system is achieved while the Empa system has a nearly complete data coverage. Additionally, different internal volumes and flow rates may affect observed differences.

An Experimental Comparison of the Emissions Characteristics of Standard Jet A-1 and Synthetic Fuels

Emissions characteristics of lean, turbulent, partially premixed swirled flames of synthetic fuels along with a standard Jet A-1 fuel are studied. The investigated synthetic fuels are (a) Fully synthetic jet fuel (FSJF), (b) Fischer Tropsch synthetic paraffinic kerosene (FT-SPK), (c) FT-SPK+20 % hexanol, and (d) FT-SPK+50 % naphthenic cut. The measurements are performed in a tubular combustor equipped with a burner based on the principle of air-blast atomization. The exhaust gas compositions are measured using a non-dispersive infrared gas analyzer for carbon dioxide (CO2) and carbon monoxide (CO), a flame ionization detector for unburned hydrocarbons (UHC), and a chemical luminescence detector for nitric oxides (NO and NO2). The emissions indices (EI) of CO and NOX of the investigated fuels are calculated using guidelines provided by the Society of Automotive Engineers (SAE). Measurements are performed at several combustor pressure levels, i.e., 0.3, 0.54 and 0.8 MPa, to compare the emissions behavior of the investigated fuels at varied operating conditions. At 0.3 MPa of combustor pressure, the order of fuels with their increasing formation of NOX are FSJF, FT-SPK+20 % hexanol, Jet A-1, FT-SPK+50 % naphthenic cut and neat FT-SPK. Differences in the observed NOX formation behavior of the investigated fuels are attributed to their probable different degrees of mixing with air in the combustor. At 0.8 MPa, no significant differences in their emissions characteristics are observed due to very low absolute values; hence we report that at higher pressure conditions which prevail in the aero-engine combustion systems, the emissions characteristics of tested synthetic fuels are very close to that of standard Jet A-1 fuel.

Optical methods for monitoring harmful gas in animal facilities

Animal facilities produce large amounts of harmful gases such as ammonia, hydrogen sulfide, and methane, many of which have a pungent odor. The harmful gases produced by animal housing not only affect the health of people and livestock but also pollute the air. The detection of the harmful gases can effectively improve efficiency of livestock production and reduce environmental pollution. More and more optical detection methods are applied to the detection of the harmful gases produced by animal housing. This summarizes optical detection methods for monitoring the harmful gases in animal housing recently, including nondispersive infrared gas analyzer, ultraviolet differential optical absorption spectroscopy, Fourier transform infrared spectroscopy, and tunable diode laser absorption spectroscopy. The basic principle and the characteristics of these methods are illustrated and the applications on the detection of harmful gases in animal housing are described. Meanwhile, the research of harmful gases monitoring for livestock production based on these methods were listed. The current situation and future development of the detection methods for harmful gases generated by animal housing were summarized by comparing the advantages and disadvantages of each method.

Measuring daytime CO2 fluxes from the inter-tidal mangrove soils of Indian Sundarbans

The aim of this research was to measure the rate of carbon dioxide (CO2) exchange between the soil and atmosphere in the inter-tidal forest floor of the Indian Sundarbans mangrove ecosystem and to study its response with soil temperature and soil water content. Soil CO2 effluxes were monitored every month at two stations (between April, 2011 and March, 2012); one situated at the land–ocean boundary of the Bay of Bengal (outer part of the mangrove forest) and the other lying 55 km inshore from the coast line (inner part of the mangrove forest). The static closed chamber technique was implemented at three inter-tidal positions (landward, seaward and bare mudflats) in each station. Fluxes were measured in the daytime every half an hour by circulating chamber headspace air through a sampling manifold assembly and a closed-path non-dispersive infrared gas analyser. The fluxes ranged between 0.15 and 2.34 μmol m−2 s−1 during the annual course of sampling. Effluxes of higher magnitude were measured during summer; however, it abruptly decreased during the monsoon. CO2 flux from the forest floor was strongly related to soil temperature, with the highest correlation found with temperature at 2 cm depth. No such significant relationship between soil water content and CO2 efflux could be properly ascertained; however, excessively high soil water content was found to be the only reason which hampered the rate of effluxes during the monsoon. On the whole, landward (LW) sites of the mangrove forest emitted more than the seaward (SW) sites. Q 10 values (obtained from simple exponential model) which denote the multiplicative factor by which the efflux rate increases for a 10 °C rise in temperature ranged between 2.07 and 4.05.

Spatial and short-term temporal distribution of fugitive methane and nitrous oxide emission from a decentralised sewage mining plant: a pilot study

The decentralisation of wastewater treatment operations exposes several environmental consequences. This includes the fugitive emission of two greenhouse gases, nitrous oxide (N2O) and methane (CH4). The magnitude of these emissions is presently unclear. Therefore, it is necessary to measure the extent of the release of N2O and CH4 gas from decentralised wastewater treatment plants (WWTPs) in order to quantify the impact these emissions will have on the environment and to determine strategies to reduce them. Specifically, this pilot study employed an online non-dispersive infrared (NDIR) gas analyser and flux hood to evaluate the spatial and short-term temporal distribution of N2O and CH4 flux over half a day, from an aeration tank system within a decentralised sewage mining plant. The aeration tank system was able to emit N2O fluxes of up to 11.6 g N2O m−2 day−1 and CH4 fluxes of up to 1.1 g CH4 m−2 day−1. The N2O and CH4 fluxes varied rapidly over short time intervals in the same position (as high as 45% for N2O and 36% for CH4) and could almost triple in magnitude between two different positions across the surface of the aeration tank (within a distance no greater than 1.5 to 2 m).

Particle and gaseous emissions from individual diesel and CNG buses

Abstract. In this study size-resolved particle and gaseous emissions from 28 individual diesel-fuelled and 7 compressed natural gas (CNG)-fuelled buses, selected from an in-use bus fleet, were characterised for real-world dilution scenarios. The method used was based on using CO2 as a tracer of exhaust gas dilution. The particles were sampled by using an extractive sampling method and analysed with high time resolution instrumentation EEPS (10 Hz) and CO2 with a non-dispersive infrared gas analyser (LI-840, LI-COR Inc. 1 Hz). The gaseous constituents (CO, HC and NO) were measured by using a remote sensing device (AccuScan RSD 3000, Environmental System Products Inc.). Nitrogen oxides, NOx, were estimated from NO by using default NO2/NOx ratios from the road vehicle emission model HBEFA3.1. The buses studied were diesel-fuelled Euro III–V and CNG-fuelled Enhanced Environmentally Friendly Vehicles (EEVs) with different after-treatment, including selective catalytic reduction (SCR), exhaust gas recirculation (EGR) and with and without diesel particulate filter (DPF). The primary driving mode applied in this study was accelerating mode. However, regarding the particle emissions also a constant speed mode was analysed. The investigated CNG buses emitted on average a higher number of particles but less mass compared to the diesel-fuelled buses. Emission factors for number of particles (EFPN) were EFPN, DPF = 4.4 ± 3.5 × 1014, EFPN, no DPF = 2.1 ± 1.0 × 1015 and EFPN, CNG = 7.8 ± 5.7 ×1015 kg fuel−1. In the accelerating mode, size-resolved emission factors (EFs) showed unimodal number size distributions with peak diameters of 70–90 nm and 10 nm for diesel and CNG buses, respectively. For the constant speed mode, bimodal average number size distributions were obtained for the diesel buses with peak modes of ~10 nm and ~60 nm. Emission factors for NOx expressed as NO2 equivalents for the diesel buses were on average 27 ± 7 g (kg fuel)−1 and for the CNG buses 41 ± 26 g (kg fuel)−1. An anti-relationship between EFNOx and EFPM was observed especially for buses with no DPF, and there was a positive relationship between EFPM and EFCO.

Fast Measurement of Dissolved Inorganic Carbon Concentration for Small-Volume Interstitial Water by Acid Extraction and Nondispersive Infrared Gas Analysis

We developed a system for measuring the total dissolved inorganic carbon (DIC) concentrations in interstitial water and hydrothermal fluid, which are hard to obtain in large volumes. The system requires a sample volume of only 500 μL, and it takes only 150 s per one sample. The detection limit of this system was estimated to be 66.6 μmol/kg with repeated analysis of CO(2)-free ultrapure water (n = 9). The precision of this nondispersive infrared (NDIR) system was ±3.1% of the relative standard deviations (2σ) by repeated CRM batch 104 (n = 10). This result is much larger than the required precision for oceanographic studies, but is comparable to a previous result of interstitial water analysis. An on-site trial showed a significant DIC enrichment in interstitial water of hydrothermally altered sediment, and is considered to occur by the mixing of hydrothermal fluid. This procedure will achieve carbon dioxide flux calculations from hydrothermal activities, and will bring a more accurate feature on the global carbon cycle.

Development of pilot WGS/multi-layer membrane for CO2 capture

For pre-combustion CO2 capture processes, a 1Nm3/h water gas shift (WGS)/multi-layer membrane system has been developed. Simulated syngas (H2: 25–35, CO: 60–65, CO2: 5–15 vol.%) was used in these experiments. The 1Nm3/h WGS/multi-layer membrane system consisted of mass flow controllers, water gas shift reactors, gas/steam separators, five layer Pd–Cu membrane module, back pressure regulator, gas chromatograph (GC) analyzers and nondispersive infrared (ND-IR) gas analyzers. The operation conditions of WGS/multi-layer membrane system were 200–400°C, 10–20bar and steam/carbon ratios in WGS were between 2.0 and 5.0. In the experiments of WGS/multi-layer membrane system, the average gas concentration before membrane module was H2: 57–58, CO2: 42–43, CO: 0.2–0.3 vol.%. The CO2 concentration of retentate flow reached up to 80 vol.% and the H2 concentration of permeate flow was over 99 vol.%.

Method of sensitivity improving in the non-dispersive infrared gas analysis system

A method of interference correction for improving the sensitivity of non-dispersive infrared (NDIR) gas analysis system is demonstrated. Based on the proposed method, the interference due to water vapor and carbon dioxide in the NDIR NO analyzer is corrected. After interference correction, the absorbance signal at the NO filter channel is only controlled by the absorption of NO, and the sensitivity of the analyzer is improved greatly. In the field experiment for pollution source emission monitoring, the concentration trend of NO monitored by NDIR analyzer is in good agreement with the differential optical absorption spectroscopy NO analyzer. Small variations of NO concentration can also be resolved, and the measuring correlation coefficient of the two analyzers is 94.28%.

Transport of Carbon Dioxide through a Biomimetic Membrane

Biomimetic membranes (BMM) based on polymer filters impregnated with lipids or their analogues are widely applied in numerous areas of physics, biology, and medicine. In this paper we report the design and testing of an electrochemical system, which allows the investigation of CO2 transport through natural membranes such as alveoli barrier membrane system and also can be applied for solid‐state measurements. The experimental setup comprises a specially designed two‐compartment cell with BMM connected with an electrochemical workstation placed in a Faraday cage, two PH meters, and a nondispersive infrared gas analyzer. We prove, experimentally, that the CO2 transport through the natural membranes under different conditions depends on pH and displays a similar behavior as natural membranes. The influence of different drugs on the CO2 transport process through such membranes is discussed.