Measurement Of SO Research Articles

Temperature measurement of SO2 based on mid‐infrared laser absorption spectroscopy

AbstractThe temperature measurement of Sulfur dioxide (SO2) is a crucial parameter for accurately determining its concentration, particularly in high‐temperature environment. Herein, it is realized by using three different techniques, which are direct absorption spectroscopy, wavelength modulation spectroscopy and non‐calibration wavelength modulation spectroscopy based on the bispectral lines temperature measurement method. The bispectral lines of SO2 locates at 1396.844 and 1396.921 cm−1, respectively. The gas temperature in the absorption cell was also measured with K‐type thermocouple and compared with these three spectral measurements. The linearities corresponding to these three techniques are 99.71%, 99.8%, and 99.88%, respectively. Their average relative error between the spectral measurement results and the linear fitting value of the three techniques is 1.15%, 0.86%, and 0.57%, respectively. It is illustrated the feasibility of the bispectral lines method for high‐temperature measurement. These investigations provide methods for temperature measurement in high‐temperature coal‐fired boilers, potentially for investigating other sulfide gas molecules such as SO3 and H2S.

Portable Spectroscopy System for Environmental Monitoring: An SO2 Case Study

In this work, a compact, portable, extended operating life, maintenance-free and remotely operable apparatus for optical absorbance measurements in the ultraviolet region is proposed. The system is useful for concentration measurement of chemical species or biological agents that exhibit ultraviolet light absorption. An apparatus prototype was developed using a commercial LED as photons source at the desired wavelength and a photo-detector with low noise, high sensitivity and visible blindness, opportunely fabricated using Silicon Carbide technology. A suitable electronic for handling the very low-level current of the detector has been designed and built to be robust, portable, low-power, low-cost and with a WiFi user interface. The ultraviolet spectroscopy apparatus application to which this work is aimed, is the low-level concentration measurement of SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in volcanic environment, while it can be easily adapted to other molecules detection and higher concentration level. While in previous Authors’ work the system feasibility has been explored using laboratory instrumentation, in this work the focus is to design a system that can be used in real harsh volcanic environment, where system lightweight, endurance and chemical strength against aggressive compounds are paramount. Resolution of approximately 1 ppm, compactness, robustness and insensitivity to humidity and temperature variations are required for this kind of environment. The performed laboratory tests and calibration for SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> monitoring, are reported and discussed. The system shows good sensitivity as high as 8 pA/ppm, a resolution < 1 ppm for SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> detection and low cross-sensitivity to main components usually present in volcanic gases.

Analysis of Potential on Measurement of SO 2 and NO 2 using Radiative Transfer Model and Hyperspectral Sensor

Analysis of Potential on Measurement of SO 2 and NO 2 using Radiative Transfer Model and Hyperspectral Sensor

Measurement of SO2 gas in Miyake-jima Island, Japan

Measurement of SO₂ gas in Miyake-jima Island, Japan

In situ measurements of SO 2, NO x, NO y, and O 3 in Beijing, China during August 2008

The measurement of SO 2, O 3, NO, NO 2, and NO y mixing ratios was conducted from Jul 28, 2008 to Sep 2, 2008 at the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP, CAS) station, which is 2 km southwest to the Beijing National Stadium (Bird's Nest/Olympic Stadium). Photochemical pollution was detected during the measurement on Aug 2, 2008, and the maximum hourly average [O 3] reached 128 ppbv, caused by both the local photochemical reactions and regional transportation of pollutants. The NO x Ozone Production Efficiency (OPE (NO x)) values were 6.9 and 20.2 on Aug 2 and Aug 24, 2008 respectively, which were the two days with highest O 3 pollution. The OPE (NO x) of 6.9 on Aug 2 was within a typical range in city area, and it implied that the high O 3 could be due to local sources. While OPE (NO x) of 20.2 on Aug 24 was larger than the typical value in the region, but lower than that of the surrounding clean area during 2008 Beijing Olympics Closing Ceremony. It indicated that the pollution was because of regional transportation of pollutants. In addition, 60% of the extent of the Smog Production Model (SPM) data was less than 0.6 and the rest was slightly larger than 0.6, with maximum of 0.78. It indicated that the sensitivity of O 3 generated was volatile organic compounds (VOCs) control during the observation period. The SPM results also implied that O 3 product in high-O 3 day is a transition state from VOCs sensitivity to NO x sensitivity. Lastly, the analysis of the wind direction and extent of SPM showed that the photochemical pollution of this region was mostly subject to the influence of southeastern air flow in the summer.

High temporal resolution SO 2 flux measurements at Erebus volcano, Antarctica

The measurement of SO 2 flux from volcanoes is of major importance for monitoring and hazard assessment purposes, and for evaluation of the environmental impact of volcanic emissions. We propose here a novel technique for accurate and high time resolution estimations of the gas flux. We use two wide field of view UV spectrometers capable of collecting, instantaneously, light from thin parallel cross-sections of the whole gas plume, obviating the need for either traversing, scanning or imaging. It enables tracking of inhomogeneities in the gas cloud from which accurate evaluation of the plume velocity can be made by correlation analysis. The method has been successfully applied on Mt. Erebus volcano (Antarctica). It yields estimations of the plume velocity and gas flux at unprecedented time resolution (1 Hz) and high accuracy (uncertainty of 33%). During a ∼ 2 h experiment on 26 December 2006, SO 2 flux varied between 0.17 and 0.89 ± 0.2 kg s − 1 with a vertical plume velocity varying between 1 and 2.5 ± 0.1 m s − 1 . These measurements provide insight into the short-term variations of the passive degassing of this volcano renowned for its active lava lake. A cyclicity in flux, ranging from about 11–24 min, is evident. We propose two physical mechanisms to explain this degassing pattern, associated to periodic supply of either gas-rich magma or gas alone into the lake. The dual-wide field of view DOAS technique promises better integration of geochemical and geophysical observations and new insights into gas and magma dynamics, as well as processes of magma storage and gas segregation at active volcanoes.

Principle, calibration, and application of the in situ alkali chloride monitor

The extended use of biomass for heat and power production has caused increased operational problems with fouling and high-temperature corrosion in boilers. These problems are mainly related to the presence of alkali chlorides (KCl and NaCl) at high concentrations in the flue gas. The in situ alkali chloride monitor (IACM) was developed by Vattenfall Research and Development AB for measuring the alkali chloride concentration in hot flue gases (less than or approximately 650 degrees C). The measurement technique is based on molecular differential absorption spectroscopy in the UV range. Simultaneous measurement of SO(2) concentration is also possible. The measuring range is 1-50 ppm for the sum of KCl and NaCl concentrations and 4-750 ppm for SO(2). This paper describes the principle of the IACM as well as its calibration. Furthermore, an example of its application in an industrial boiler is given.

Reliability of Lightguide Spectrophotometry (O2C®) for the Investigation of Skin Tissue Microvascular Blood Flow and Tissue Oxygen Supply in Diabetic and Nondiabetic Subjects

Skin microvascular assessment has progressed to an important evaluation in patients with diabetes mellitus. This study was done to evaluate a new device using micro-lightguide spectrophotometry in the assessment of skin microvascular function. Twenty nondiabetic subjects (age 46.6 +/- 14.8 years; mean +/- SD) and 20 diabetic patients (age 59.4 +/- 8.4 years) participated in repeated microvascular measurements using micro-lightguide spectrophotometry. This technique allows simultaneous, noninvasive measurement of microvascular blood flow and hemoglobin oxygenation (SO(2)) at the same anatomical area in different tissue layers. A skin probe was placed on nonhairy skin at the thenar eminence of the left hand for the measurement of SO(2), and the postischemic reactive hyperemia response (PRH) was measured in skin and underlying muscle tissue. Repeated measurements in PRH revealed a good correlation at the superficial skin layer (r = 0.97, p < 0.0001) with a coefficient of variation at 9.2 +/- 1.7% and at the superficial muscle layer (r = 0.80, p < 0.0002) with a coefficient of variation at 9.7 +/- 1.5%. A slightly weaker correlation was observed for the SO(2) measurement at the skin layer (r = 0.69 +/- p < 0.0001) with a coefficient of variation at 17.5 +/- 3.8% and at the muscle layer (r = 0.48; p = 0.0016) with a coefficient of variation at 18.1 +/- 10.5%. Lightguide spectrophotometry is an easy, noninvasive, and reliable method for simultaneous measurement of superficial microvascular blood flow by laser Doppler fluxmetry and skin oxygenation by spectrophotometry. Further studies are required to clarify the validity of these measures in special patient populations such as diabetes mellitus with specified microvascular complications.

Broadband spectroscopic sensor for real-time monitoring of industrial SO_2 emissions

A spectroscopic system for continuous real-time monitoring of SO(2) concentrations in industrial emissions was developed. The sensor is well suited for field applications due to simple and compact instrumental design, and robust data evaluation based on ultraviolet broadband absorption without the use of any calibration cell. The sensor has a detection limit of 1 ppm, and was employed both for gas-flow simulations with and without suspended particles, and for in situ measurement of SO(2) concentrations in the flue gas emitted from an industrial coal-fired boiler. The price/performance ratio of the instrument is expected to be superior to other comparable real-time monitoring systems.

Development of an automatic continuous analyzer for water-soluble gases in air by combining an artificial lung with an ion chromatograph

An automatic measurement system for the simultaneous monitoring of sulfur dioxide (SO 2) and ammonia (NH 3) in air was developed by combining an artificial lung and an ion chromatograph. An artificial lung was used as a new technique for concentrated collection of trace amounts of gaseous pollutants in air. It was found that SO 2 and NH 3 were effectively absorbed into ultra-pure water in the artificial lung. Collection efficiencies for SO 2 and NH 3 were 100% and 98%, respectively, at a gas flow rate of 1 l min –1, and material balances >90% were obtained. No interference from the simultaneous collection of SO 2 and NH 3 was found. When a 400 ppb standard NH 3 gas was measured automatically with this system, the recovery rate was 98%, and the relative standard deviation was 2.7% ( n=8). In the case of a 200 ppb standard SO 2 gas, the recovery rate was 87%, and the relative standard deviation was 1.6% ( n=7). Results from the simultaneous measurement of SO 2 and NH 3 with the automatic system were equally as good as those obtained by measuring a single component at a time. Calibration curves for SO 2 and NH 3 showed good relationships between concentration and peak intensity. The linear correlation coefficients were 0.997 and 0.998 for SO 2 and NH 3, respectively. The detection limits of SO 2 and NH 3 were 0.06 and 0.1 ppb, respectively, in a 40 l air volume. The system was tested in air and found to be capable of simultaneous measurement of SO 2 and NH 3 with a 20 min cycle.

Development of disposable amperometric sulfur dioxide biosensors based on screen printed electrodes

The possibility of developing amperometric biosensors for the measurement of SO 2 in flowing gas streams has been examined. Screen-printed carbon electrodes (SPCEs) were tailored with the enzyme sulfite oxidase and cytochrome c and the response is generated through the resulting enzymatic and electrocatalytic reactions involving SO 3 2−, formed when SO 2 gas is dissolved in the supporting electrolyte. Two methods of integrating the enzyme and cytochrome c with the SPCE were investigated. In one design (b-type biosensor), the components were mixed thoroughly with the same ink used to produce the SPCEs, then the modified ink was spread over the working electrode. In the second approach the bio-components were dissolved in the supporting electrolyte and simply deposited on top of the transducer (s-type biosensor). Both devices gave linear responses over the range 4–50 ppm but the sensitivity of the s-type was approximately twice that of the b-type biosensor. In addition, the time taken to reach 90% of the maximum response ( t 90%) was 110 s for the s-type biosensor compared with 200 s for the b-type biosensor. These studies illustrate the successful use of biosensors for the detection of sulfur dioxide at the relatively low potential of +0.3 V versus Ag.AgCl and should provide useful alternatives for decentralised environmental studies.

Compact, open and general purpose cell of variable effective pathlength: direct absorption measurement of SO(4)(2-) in water.

The use of an optothermal window (OW) was proposed for the direct (no need for sample preparation) spectroscopic, non-destructive measurement of SO(4)(2-) in water at 1078 cm(-1). The presently determined limit of detection (LOD) of 1 mmol/L is comparable to that provided by CO(2) laser photoacoustic spectroscopy, but about one order of magnitude superior to that obtainable by the ATR method.

A fully solid-state SO x ( x = 2,3) gas sensor utilizing Ag-ß″-alumina as solid electrolyte

A galvanic-cell-type SO x ( x = 2,3) gas sensor with Ag-ß″-Al 2O 3 solid electrolyte, porous Pt as working electrode and Ag as reference electrode has been constructed and tested. The electromotive force (e.m.f.) responses are in good agreement with theoretical values for SO x concentrations from 10 to 10 4 ppm in the temperature range 550–750 °C. The experimental results show that CO 2 and NO 2 did not disturb the measurement of SO x .

Some properties of sulfate ion-selective PVC membranes based on a neutral carrier and ion-exchanger

For the measurement of SO 4 ion activity in aqueous solutions sulfate-selective PVC membranes with different concentrations of ion-exchanger and netural carrier were prepared and tested. The sulfate ion-selectivity electrodes (SO 4-ISE) were then examined in terms of their response curves and slope in the linear part, selectivity coefficients, and the effect of the pH. Experimental results on selectivity are discussed and compared with those calculated from a mathematical model described earlier.

Capacitive thin film gas sensor with signal processing system for determination of SO 2

The SO 2 gas sensor presented consists of a thin film capacitor with an SO 2-sensitive dielectric and a signal processing circuit constructed on the basis of SC technology (i.e. using switched capacitor techniques) making use of hybrid technology. The measuring limit of the sensor developed lies between the MAK value (MAK value of SO 2: 2 vpm). The sensors described are distinguished by good reproducibility and reversibility, short response time (<20 s) and low cross-sensitivity to other gases. A battery-powered measuring unit was developed for measurement of SO 2 at changing locations of use.

B35 雲仙火山における火山ガス中の SO2,HCI の遠隔測定

B35 雲仙火山における火山ガス中の SO2,HCI の遠隔測定

Thin-film gas sensors with organically modified silicates for the measurement of SO 2

Gas sensors based on interdigital capacitors (IDC), with organically modified silicates as a sensitive layer, have been developed for the measurement of SO 2 concentrations between 0.5 vpm and some 6000 vpm. The gas-sensitive coating is produced with the sol-gel process and spin-on technique. These sensors are distinguished by good reproducibility and reversibility, a short response time (<20 s), low cross-sensitivity to other gases, and low dependence on temperature and humidity. The sensor concept, design, manufacture and measurements in a gaseous atmosphere as well as the cross-sensitivity to humidity are discussed.

Evaluation of improved inlets and annular denuder systems to measure inorganic air pollutants

Modifications were made to various components of an annular denuder system for the collection of ambient SO 2, HNO 3, HNO 2, NH 3, SO 4 2−, and NO 3 −. The annular denuder was modified to incorporate a laminar restoration section as part of the annular denuder itself in order to reduce construction costs and to minimize leaks in the system during field operation. Teflon-coated glass impactors and cyclone inlets for the annular denuders were developed and evaluated for their inertness to acidic gases collected in the annular denuders. Paired samples were collected over a period of several months on the roof of the EPA laboratory in Research Triangle Park, NC, in order to compare the new inlets. For 17 sampling runs when two different types of inlets were compared, average differences for the measurement of SO 2, HNO 3 and HNO 2 were 3.4, 6.4 and 8.3%, respectively. For five sampling runs using pairs of identical impactor inlets, duplication for SO 2 and HNO 3 improved slightly. Annular denuder systems using cyclone and impactor preseparators yielded no significant differences in their abilities to collect HNO 3 and SO 2. The results are supported by the laboratory data of Appel et al. (1987, EPA/APCA Symp., Research Triangle Park), which indicate that no HNO 3 is retained in the inlets tested. Coarse-particle bounce through the system was shown to be a potential problem, although this had no apparent effect on acidic gas collection.

Contribution of foliar leaching and dry deposition to sulfate in net throughfall below deciduous trees

Experiments were conducted at Walker Branch Watershed, TN, in 1986 with radioactive 35S (87 day half-life) to quantify the contribution of foliar leaching and dry deposition to sulfate (SO 2− 4) in net throughfall (NTF). Two red maple ( Acer rubrum) and two yellow poplar ( Liriodendron tulipifera) trees (12–15 m tall) were radiolabeled by stem well injection. Total S and 35S were measured in leaves; 35S and SO 2− 4 were measured in throughfall (THF). The contribution of foliar leaching to SO 2− 4 in NTF, THF minus incident precipitation, was estimated by isotope dilution of 35S in NTF arising from nonradioactive S in dry deposition. The per cent contribution of foliar leaching to SO 2− 4 in NTF was greatest during the week following isotope labeling and during the period of autumn leaf fall. During the growing season, foliar leaching accounted for < 20% and dry deposition accounted for > 80% of the SO 2− 4 in NTF beneath the study trees. Dry deposition of S to these tree species can be reasonably approximated during summer from the measurement of SO 2− 4 flux in NTF.

Distribution of sulphur in one-dimensional pulverized-coal flames

Results of experiments to determine the distribution of fuel sulphur in one-dimensional pulverized-coal flames are presented for two high volatile A bituminous coals, one pulverized into three size fractions, and one subbituminous A coal. A complete determination of the sulphur fed into the flame was obtained through measurement of SO 2, H 2S, COS, CS 2, and solids sulphur. SO 2 is the predominant gas-phase species followed by H 2S with COS and CS 2 being present in smaller amounts. Sulphur is released from smaller particles more rapidly than from larger ones. Sulphur release parallels, to some extent, nitrogen release except at the longer residence times for the subbituminous coal and one of the bituminous coals. A substantial fraction of the sulphur contained in these coals is inorganic. First-order rate constants for sulphur release from the solid are presented. The effects of internal mass transfer on the kinetics are presented for one of the bituminous coals by considering the sulphur release process to consist of a first-order devolatilization reaction occurring in parallel with diffusion of the sulphur to the particle surface and first-order deposition back to the solid matrix. Particle size effects are accounted for in the model, and the data on solids sulphur are used to obtain activation temperatures for the devolatilization reaction and the deposition reaction of 29 900 and 31 400 K, respectively.