Tunable diode laser measurement of pressure-induced shift coefficients of CO2 around 2.05 μm for Lidar application

Atmospheric carbon dioxide (CO₂) is one of the main contributors to the greenhouse effect. A global monitoring of CO₂ from space is foreseen as a key issue to quantify its sources and sinks at a regional scale and to better predict future levels of CO₂ and their effect on climate change. Differential Absorption Lidar (DiAL) is a promising and novel spectroscopic technique for remote sensing CO₂ spatial and temporal concentration distribution with a high level of accuracy. However, a precise knowledge of spectroscopic parameters of CO₂ molecular transitions and their dependence with temperature and pressure is required for reducing the uncertainty on DiAl measurements. Hence, to support remote sensing of carbon dioxide in the troposphere, we report on the accurate determination of air pressure-induced shift coefficients for eight absorption lines belonging to the R branch of (20⁰1)_III←(00⁰0)_I band of CO₂ at 2.05 μm. Purposely, a high-resolution tunable diode laser absorption spectrometer (TDLAS) coupled to a cryogenically cooled optical cell was implemented. From these measurements, we have further determined the temperature-dependencies of the air pressure-induced shift coefficients.     

Realization of oxyfuel combustion for near zero emission power generation

Oxyfuel combustion is one of the promising carbon capture and storage (CCS) technologies for coal-fired boilers. In oxyfuel combustion, combustion gas is oxygen and recirculating flue gas (FGR) and main component of combustion gas is O₂, CO₂ and H₂O rather than O₂, N₂ in air combustion. Fundamental researches showed that flame temperature and flame propagation velocity of pulverized cloud in oxyfuel combustion are lower than that in air with the same O₂ concentration due to higher heat capacity of CO₂. IHI pilot combustion test showed that stable burner combustion was obtained over 30% O₂ in secondary combustion gas and the same furnace heat transfer as that of air firing at 27% O₂ in overall combustion gas. Compared to emissions in air combustion, NOx emission per unit combustion energy decreased to 1/3 due to reducing NOx in the FGR, and SO_x emission was 30% lower. However SO_x concentration in the furnace for the oxyfuel mode was three to four times greater than for the air mode due to lower flow rate of exhaust gas. The higher SO₃ concentration results that the sulphuric acid dew point increases 15–20 °C compared to the air combustion. These results confirmed the oxyfuel pulverized coal combustion is reliable and promising technology for coal firing power plant for CCS.In 2008, based on R&D and a feasibility study of commercial plants, the Callide Oxyfuel Project was started in order to demonstrate entire oxyfuel CCS power plant system for the first time in the world. The general scope and progress of the project are introduced here. Finally, challenges for present and next generation oxyfuel combustion power plant technologies are addressed.     

Qualitative and quantitative determination of human biomarkers by laser photoacoustic spectroscopy methods

The hypothesis that blood, urine and other body fluids and tissues can be sampled and analyzed to produce clinical information for disease diagnosis or therapy monitoring is the basis of modern clinical diagnosis and medical practice. The analysis of breath air has major advantages because it is a non-invasive method, represents minimal risk to personnel collecting the samples and can be often sampled. Breath air samples from the human subjects were collected using aluminized bags from QuinTron and analyzed using the laser photoacoustic spectroscopy (LPAS) technique. LPAS is used to detect traces of ethylene in breath air resulting from lipid peroxidation in lung epithelium following the radiotherapy and also traces of ammonia from patients subjected to hemodialysis for treatment of renal failure. In the case of patients affected by cancer and treated by external radiotherapy, all measurements were done at 10P(14) CO₂ laser line, where the ethylene absorption coefficient has the largest value (30.4 cm⁻¹ atm⁻¹), whereas for patients affected by renal failure and treated by standard dialysis, all measurements were performed at 9R(30) CO₂ laser line, where the ammonia absorption coefficient has the maximum value of 57 cm⁻¹ atm⁻¹. The levels of ethylene and ammonia in exhaled air, from patients with cancer and renal failure, respectively, were measured and compared with breath air contents from healthy humans. Human gas biomarkers were measured at sub-ppb (parts per billion) concentration sensitivities. It has been demonstrated that LPAS technique will play an important role in the future of exhaled breath air analysis. The key attributes of this technique are sensitivity, selectivity, fast and real time response, as well as its simplicity.     

Role of Purging Gases in the Analysis of Polycarbonate With Laser-Induced Breakdown Spectroscopy

Polycarbonate is a strong, durable, and high-transparent material. It is being used extensively in electronics applications, eyewear lenses, exterior automotive components, construction industry, and manufacturing of containers. Laser-induced breakdown spectroscopy (LIBS) is a well-known and widely-used technique in quantitative and qualitative analysis of materials. The analysis is based on the spectra obtained in the LIBS process. We investigate the LIBS spectrum of polycarbonate (C₁₂H₁₈O₇)_n polymer in the presence of air, helium, argon, neon, and mixed-gas atmospheres using a Spectrolaser-7000 system. We investigate the peak intensities of hydrocarbon fragments like C₂, C, and CN in He, Ar, and Ne atmospheres. Moreover, we observe the CN molecular lines in the LIBS spectrum of polycarbonate in air only. We show that, in the He and Ne atmospheres, the peak intensity of the hydrogen (656 nm) line increases 1.85 and 4.5 times, and the peak intensity of the carbon (247 nm) line increases 1.46 and 2.6 times, respectively, as compared to that in air. These results are very useful and will help in the analysis and detection of polymers and bio-samples, which are mostly comprised of carbon and hydrogen.     

Combustion processes for carbon capture

A review of the technologies for coal-based power generation closest to commercial application involving carbon capture is presented. Carbon capture and storage (CCS) developments are primarily adaptations of conventional combustion systems, with additional unit operations such as bulk oxygen supply, CO₂ capture by sorbents, CO₂ compression, and storage. They use pulverized coal combustion in entrained flow—the dominant current technology for coal-based power, or gasification in entrained flow, although similar concepts apply to other solid-gas contacting systems such as fluidized beds. Currently, the technologies have similar generation efficiencies and are associated with efficiency penalties and electricity cost increases due to operations required for carbon capture. The R&D challenges identified for the combustion scientist and engineer, with current understanding being detailed, are those of design, optimisation and operational aspects of new combustion and gasification plant, controlling the gas quality required by CCS related units and associated emission compliance, and gas separations. Fundamental research needs include fuel reactions at pressure, and in O₂/CO₂ atmospheres, as few studies have been made in this area. Laboratory results interpreted and then included in CFD models of combustion operations are necessary. Also identified, but not detailed, are combustion issues in gas turbines for IGCC and IGCC-CCS. Fundamental studies should be a component of pilot-plant and demonstrations at practical scale being planned. Concepts for new designs of combustion equipment are also necessary for the next generation of technologies. The challenges involved with the design and operation of these integrated systems, while supplying electricity on demand, are considerable.     

Assessment of LIBS for Spectrochemical Analysis: A Review

Abstract

This review assesses the applications of laser-induced breakdown spectroscopy (LIBS) for the analysis of a variety of samples, including biomaterials (teeth, nail, hair, gallstones, and kidney stones, etc.), food materials (fruits and vegetables, milk, salt, nutritional supplements, etc.), medicinal plants, industrial waste, liquid samples, etc. In addition, for the first time the identification of cholesterol and pigment stones was performed on the basis of atomic lines of different elements and molecular bands of C₂ molecules present in the LIBS spectra of gallstones. Chemometric techniques such as principal component analysis (PCA) was also applied to LIBS data for rapid identification/classification of different gallstone samples. LIBS analysis of toxic/heavy elements present in vegetables (spinach, tomato) and rice is also presented in this review. It was observed that vegetables grown near industrial areas are rich in several toxic metals like Pb and Cr. The wastewater samples from different industries were also analyzed by recording their spectra using a liquid jet. These results clearly demonstrate the ability of LIBS technique as an instant monitoring device to detect heavy metals present in liquid samples. Finally, this review shows that LIBS is a versatile analytical technique with unlimited applications.     

Analysis of Minerals and Rocks by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) technique was applied for rapid analysis of major and minor elements composing geological samples including minerals, rocks, and a soil sample. The plasma was produced in air at atmospheric pressure by focusing on the targets a pulsed infrared Nd:YAG laser in open-path configuration. The emitted light in the UV-Vis was analyzed by a compact LIBS system to measure spectral emission lines of Si, Al, Fe, Ca, Na, K, Mg, C, Cu, Mn, and Ti. The experimental issues relevant for the analysis of the different samples were investigated by taking into account their peculiar features: drilling through a weathered layer, roughness and grain-size considerations, statistical averaging, and accuracy of the measurements. In this approach, the characterization of the samples was achieved by studying the relative variations of the emission intensities of each element normalized with respect to an internal standard. The present study shows the usefulness of LIBS as a tool for reliable identification of field samples.     

基于激光诱导击穿光谱技术的土壤泥浆中Pb元素检测

激光诱导击穿光谱(LIBS)作为一种新兴的元素分析技术,具有实时在线、非接触、多元素同时探测等渚多优点.将LIBS技术引入土壤泥浆重金属污染的检测分析,力图发展一种针对泥浆重金属污染监测的原位传感技术.实验选择Pb作为探测元素,Mn为内标元素;采用重复频率10 Hz的Nd:YAG调Q激光器的二倍频(532 nm)输出作为激发光源,OCD收集信号,对实验室配制的不同浓度Pb泥浆样品的LIBS信号进行了探测分析.获得了各种浓度下Pb泥浆样品在Pb 405.78 nm和Mn 403.07 nm处的原子线强度比IPb/IMn及其随浓度变化的规律.结果显示IPb/IMn与样品的含铅浓度有着很好的线性关系,线性拟合相关系数R2达到0.994 9.初步证实了采用内标法对土壤泥浆中重金属Pb进行LIBS检测分析的可行性.文章还对泥浆重金属LIBS检测的影响因素进行了讨论.     

Diurnal variability of δ13C and δ18O of atmospheric CO2 in the urban atmosphere of Kraków,Poland

This article presents the results of measurements of the isotopic composition and concentration of atmospheric carbon dioxide, performed on air samples from Kraków (Southern Poland) in different seasons of the year. A simple isotope mass balance model has been applied to determine the contributions of different sources of CO₂ to the urban atmosphere of Kraków city: the latitudinal/regional background, biospheric contributions and anthropogenic emissions. The calculations show that during the summer and early autumn the dominant contribution to local CO₂ peaks is the biosphere, making up to 20% of atmospheric CO₂ during the nocturnal temperature inversion in the lower troposphere. During early spring and winter, anthropogenic emissions are the main local source.     

Microcombustion of ng Amounts of Carbon in Non-Volatile Materials for isotope Ratio Evaluation

Abstract

A novel microcombustion technique for carbon isotopic analysis of nanogram amounts of carbon in non-volatile materials based on isotope ratio monitoring (irm) mass spectrometry is described. Liquid or solid samples placed in a quartz sleeve are combusted at 1000°C in a continuous stream of helium and oxygen. CO₂ removed from the carrier gas stream by cryogenic trapping is transferred onto a GC column. Following GC separation, the CO₂ is transferred via an open split to the ion source of a gas isotope ratio mass spectrometer. Reproducibility for samples >25 nmol carbon is <1‰. Problems associated with blanks from various sources and with reproducible deposition of small sample amounts led to variable accuracy, which was dependent on the compound class being analysed. Minimum sample size was in the range from 5 to 10 nmol carbon. Measurements of dissolved organic carbon (DOC) of groundwater from Germany yielded consistent values of δ¹³C = -28.8‰.     

Contaminant concentration in environmental samples using LIBS and CF-LIBS

The present paper deals with the detection and quantification of toxic heavy metals like Cd, Co, Pb, Zn, Cr, etc. in environmental samples by using the technique of laser-induced breakdown spectroscopy (LIBS) and calibration-free LIBS (CF-LIBS). A MATLAB^TM program has been developed based on the CF-LIBS algorithm given by earlier workers and concentrations of pollutants present in industrial area soil have been determined. LIBS spectra of a number of certified reference soil samples with varying concentrations of toxic elements (Cd, Zn) have been recorded to obtain calibration curves. The concentrations of Cd and Zn in soil samples from the Jajmau area, Kanpur (India) have been determined by using these calibration curves and also by the CF-LIBS approach. Our results clearly demonstrate that the combination of LIBS and CF-LIBS is very useful for the study of pollutants in the environment. Some of the results have also been found to be in good agreement with those of ICP-OES.     

Recent improvements on atmospheric CO2 measurements at Mt. Cimone observatory, Italy

Summary Continuous atmospheric CO₂ measurements have been carried out at Mt. Cimone from 1979 up to the present. Omitting here a measurement presentation, in this paper we show the current experimental procedures adopted and NDIR apparatus performances. Quality measurements have been recently improved by introducing an ULTRAMAT-5E (SIEMENS) NDIR analyzer controlled, for operating mode, by computer: the routine precision attained is ±0.1 p.p.m. An interesting performance of the analyzer is its nondetectable sensitivity to water vapour infrared absorption, enabling us also to determine CO₂ measurements in wet air. A flask sampling technique and an investigation of the flask deterioration risk, against storing time, are presented. Results of the investigation validate the use of electropolished stainless-steel flasks for high-quality measurements.     

Photoacoustic multicomponent gas analysis using a Levenberg–Marquardt fitting algorithm

2 laser photoacoustic spectrometer has been developed for the in-situ monitoring of atmospheric trace gases in different environments. Numerous air pollutants, such as ammonia, ethene, ozone and alcohols, can be monitored with a time resolution of a few minutes. A new fitting algorithm based on the numerical method of Levenberg–Marquardt is discussed and applied to the derivation of individual gas concentrations from measured photoacoustic signal amplitudes and phases at selected CO₂ laser wavelengths. The algorithm has been tested with artificially generated multicomponent gas mixtures exhibiting gas concentrations in the ppb to ppm range. Furthermore, its potential is demonstrated with the analysis of an air sample from a fruit storage chamber and with ambient air measurements during a field study in a rural environment. Received: 23 March 1998/Revised version: 18 June 1998     

Laser-induced plasma in methane and dimethyl ether for flame ignition and combustion diagnostics

In this paper we report the investigation of the laser-induced breakdown and ignition behaviour of methane/air and dimethyl ether (DME)/air mixtures. Moreover, the optical emission from the induced plasma is utilized for determining the mixture composition quantitatively by means of laser-induced breakdown spectroscopy (LIBS). To the best of the authors’ knowledge, LIBS and laser ignition of DME have not been reported in literature before. The technique under investigation is finally employed for combustion diagnostics in laminar as well as turbulent flames. In the laminar premixed and non-premixed flames the LIBS spectra allow spatially resolved measurements of the equivalence ratio and enable studying the mixing of gases provided through the burner with the surrounding room air. In addition, the breakdown threshold of the applied laser pulse energy yields an estimate for the local temperature. In the turbulent cases single-shot LIBS spectra are recorded at fixed position allowing the derivation of local statistical fluctuations of the equivalence ratio in partially premixed jet flames. The results show that laser-induced breakdowns have a strong potential for flame diagnostics and, under suitable conditions, for the ignition of combustible mixtures.     

Analysis of Ti in textile stippled by TiO<Subscript>2</Subscript> nanoparticle sol using double-pulse LIBS and ED XRF spectrometry

Double-pulse LIBS and ED XRF usabilities for quantitative analysis of Ti in samples of cotton, wool, and viscose fabrics were compared to each other. The analyzed samples were prepared by stippling a particular fabric with TiO₂ nanoparticle sol (particle size 100 nm). Both spectrometers were calibrated with the aid of the same sets of authentic fabric samples previously analyzed by ICP OES after the microwave digestion. Average values of the Ti concentration calculated from five repeated measurements of the same sample obtained by LIBS and ED XRF were comparable for all types of the tested materials (100∙(C_Ti-LIBS/C_{Ti-ED XRF})) ≅ 96–109%), but the precision of analysis expressed as RSD (relative standard deviation) was usually better for ED XRF (RSD_LIBS from 9 to 25%, RSD_{ED XRF} from 3 to 17%). Poor RSD values of LIBS measurements were observed mainly in the case of samples with lower areal weights. Limits of detection calculated as a triple standard deviation of five repeated measurements of Ti in a sample with the low concentration of the analyte were comparable for both methods (LOD_LIBS = from 15 to 97, and LOD_{ED XRF} = from 21 to 64, all in mg/kg).     

激光诱导击穿光谱技术分析土壤中的Cr和Sr

采用波长1 064 nm的调Q脉冲Nd:YAG激光器和多通道小型光纤光栅光谱仪,建立了一套激光诱导击穿光谱分析装置.记录了系列土壤标准样品的激光诱导等离子体发射光谱,详细研究了重金属原子Cr和Sr的特征辐射谱线信号强度、标准偏差与数据采样方式以及采样平均次数的关系,首次采用300个激光脉冲轰击样品表面同一点,并取其中最大光谱信号后的200次激光轰击等离子体发射光谱的平均值进行分析的取样平均方式,发现能较好地把对重金属Cr和Sr浓度分析测量的相对标准偏差(RSD)分别减小到9.02%和10.5%,并得到了定量分析Cr和Sr等金属的定标曲线,对Cr和Sr元素的检测灵敏度分别为25.3和15.2 μg·g-1,优于目前国内外报道的结果.研究表明我们的采用的数据采集、分析定标方法对提高了LIBS技术在土壤中金属检测检测灵敏度和精密度具有很好的应用价值.     

On carbon dioxide storage based on biomineralization strategies

This study focuses on the separation and storage of the global warming greenhouse gas CO₂, and the use of natural biocatalysts in the development of technologies to improve CO₂ storage rates and provide new methods for CO₂ capture. Carbonic anhydrase (CA) has recently been used as a biocatalyst to sequester CO₂ through the conversion of CO₂ to HCO^? in the mineralization of CaCO₃. Biomimetic CaCO₃ mineralization for carbon capture and storage offers potential as a stable CO₂ capture technology. In this report, we review recent developments in this field and assess disadvantages and improvements in the use of CA in industrial applications. We discuss the contribution that understanding of mechanisms of CO₂ conversion to CO₃^? in the formation and regeneration of bivalve shells will make to developments in biomimetic CO₂ storage.     

LIBS used as a diagnostic tool during the laser cleaning of ancient marble from Mediterranean areas

The use of laser ablation for cleaning stone is a tried-and-tested method for preserving outdoor artwork surfaces exposed to environmental stresses. However, it is of interest to spectroscopically characterize the sample surface before and during the laser ablation in order to implement automatic control of the cleaning process. To this aim, we have undertaken systematic LIBS analysis on various clean and dirty surfaces of marble fragments collected from ancient quarries in Mediterranean areas, without the characteristic patina that comes from the protective layers usually deposited on the final artwork. The effectiveness of the cleaning process was then monitored by following the disappearance from the LIBS spectra of the encrustation elements during successive laser shots. The LIBS analysis of the clean surfaces of the samples examined confirmed that main bulk composition is based on calcium and magnesium carbonates, with the addition of strontium and, to a minor extent, of manganese and copper substituents. On the other hand, the encrustations were rich in sodium, aluminum, iron, silicon, titanium, lithium, manganese, and chromium, probably coming from sand/soil deposition and, only to a minor extent, from atmospheric pollution. Although SEM imaging and SEM-EDX analyses performed on the same samples at different resolutions showed remarkable surface inhomogeneities from the crustal region deep into the bulk material, the work demonstrates the possibility of a quantitative, minimally invasive, LIBS stratigraphy. The results from the technique are suitable for monitoring cleaning processes by determining appropriate elemental markers present on the surface at trace level (of the order of 100 ppm). PACS 52.25.Kn; 7.60.Rd; 32.30.Jc; 42.62.Fi     

The importance of longer wavelength reheating in dual-pulse laser-induced breakdown spectroscopy

Dual-pulse laser-induced breakdown spectroscopy (LIBS) provides improved sensitivity compared to conventional single-pulse LIBS. We used a combination of Nd: yttrium aluminum garnet (YAG) and CO₂ lasers to improve the sensitivity of LIBS. Significant emission intensity enhancement is noticed for both excited neutral lines and ionic lines for dual-pulse LIBS compared to single-pulse LIBS. However, the enhancement factor is found to be dependend on the energy levels of the lines, and resonance lines provided maximum enhancement. Our results indicate that IR reheating will cause significant improvement in sensitivity, regardless of the conditions, even with an unfocused reheating beam. The improved sensitivity with a YAG-CO₂ laser combination is caused by the effective reheating of the pre-plume with a longer wavelength laser is due to efficient inverse Bremsstrahlung absorption. The role of the spot sizes, inter-pulse delay times, energies of the preheating and reheating pulses on the LIBS sensitivity improvements are discussed.     

激光等离子体光谱分析技术的发展现状

综述了近几年来应用激光等离子体光谱分析技术在不同领域所取得的研究成果,包括利用激光诱导击穿光谱学(LIBS)和激光诱导等离子体光谱学(LIPS)方法对固体样品(如金属合金、土壤、混凝土、矿物、化石、药品等)、液体样品(溶液、纯净水、液体喷射流等)和气体样品(大气、纯净气体、水蒸气和气溶胶等)中物质成分和相关特性的分析研究,以及在其他方面的研究应用;讨论了影响检测性能的因素,如激光波长、脉冲能量、功率密度、环境气氛、外加电场、样品表面涂层以及样品材料性能等对分析精确度和检出限的影响;对一些改进的实验装置及方法也进行了简单介绍。激光等离子体光谱分析技术的发展,为许多科学和应用研究创造了方便和快捷的有利条件,对科技进步有深远影响。