Sensor for operational control of oxygen and combustible gases concentration in waste gases of thermal units

A new sensor has been developed for continuous monitoring of oxygen and combustible gases content in the waste gases of thermal units. The target application of the sensor is its installation in shunt pipes of thermal units, directly into the waste gas flow. The sensor is characterized by one reference gas electrode and three measuring electrodes applied on the surface of a solid electrolyte tube made of a zirconia electrolyte (e.g., 8YSZ). The reference gas electrode and one of the measuring electrodes were made of silver, the second measuring electrode was made of platinum, the third measuring electrode was made of a mixture of zinc oxide (95 wt %) and lanthanum-strontium manganite (5 wt %). The oxygen content in the gas mixture was determined by the well-known potentiometric method in accordance with the Nernst equation, i.e. an Ag|8YSZ|Ag electrochemical cell was used. To determine the products of incomplete combustion of fuel, the method of mixed potential between Pt- and Zn-based electrodes was used; the obtained potential value was determined by the difference in the oxidation rate of carbon monoxide as the main component of unburned fuels, on different materials of measuring electrodes. The experimental results of the sensor for the determination of carbon monoxide, hydrogen, and methane in a gas mixture are presented.https://doi.org/10.15826/elmattech.2023.2.01

Electrochemical detection of simple alkanes by utilizing a solid-state zirconia-based gas sensor

Solid-state gas sensors composed of complex oxide electrolytes offer great potential for analyzing various atmospheres at high temperatures. While relatively simple gas mixtures (H2O+N2, O2+N2) have been successfully studied by means of ZrO2-based sensors, the precise detection of more complex compounds represents a challenging task. In this work, we present our findings regarding the analysis of lower alkanes (CH4, C2H6, and C3H8) mixed with nitrogen as an inert gas, utilizing an amperometric ZrO2-based sensor. This sensor, serving as an electrochemical cell with a diffusion barrier, was tested at 500–600 °C to measure the limiting current, which depends on the gas composition and can be further used as a basis for calibration curves. In addition, the diffusion coefficients of the specified gas mixtures were successfully found and compared with references, confirming the applicability of the fabricated sensor for studying diffusion processes in wide concentration and temperature ranges

Stability and reproducibility of solid electrolyte amperometry sensors at the analysis of hydrogen in nitrogen-containing gas mixtures

This paper illustrates the results of long-term tests on the stability of the output signal of the solid electrolyte amperometry sensor when measuring the hydrogen concentration in the H2 + N2 gaseous mixture. The obtained experimental data verify the stability and reproducibility of the sensor output signal for hydrogen concentration measurements in the nitrogen-containing gaseous mixture during  8000 h of operation. The output signal drift, i.e., the limiting current value, was insignificant, less than ± 5 %. The sensor operation was performed at 3 temperature shifts with different time intervals; these changes did not have any impact either on the sensor integrity or on its operation. The structure of the solid electrolyte sensor, intermediate solid electrolyte / electrode layer and electrodes did not undergo any significant changes during operation. The dynamic characteristics of the sensor, the response time in particular, remained stable during the operation.https://doi.org/10.15826/elmattech.2024.3.02

Stability and Reproducibility of the Amperometric Sensors for Oxygen Concentration Analysis in the Nitrogen Gas Mixtures

Received: 26 December 2023. Accepted: 4 March 2024. Published online: 12 March 2024.The paper presents experimentally obtained results on the long-term stability tests of the solid electrolyte amperometric sensor output signal during the operation in the O2 + N2 gas mixtures. These data prove the stability and reproducibility of the output signal when measuring the oxygen concentration in air for 8000 hours. The output signal variation during the tests did not exceed ± 2 %. We performed four heating / cooling cycles of different durations, which did not influence either sensor integrity or operation characteristics. The structure of the solid electrolyte sensor and the solid electrolyte/electrode interfacial layer remained unchanged during the tests. Dynamic characteristics of the sensor, including the response time, were stable.The present research was performed within the budget plan of the Institute of High Temperature Electrochemistry

Stability and Reproducibility of Solid Electrolyte Amperometry Sensors at the Analysis of Hydrogen in Nitrogen-Containing Gas Mixtures

Received: 9 November 2023. Accepted: 13 December 2023. Published online: 12 January 2024.This paper illustrates the results of long-term tests on the stability of the output signal of the solid electrolyte amperometry sensor when measuring the hydrogen concentration in the H2 + N2 gaseous mixture. The obtained experimental data verify the stability and reproducibility of the sensor output signal for hydrogen concentration measurements in the nitrogen-containing gaseous mixture during > 8000 h of operation. The output signal drift, i.e., the limiting current value, was insignificant, less than ± 5 %. The sensor operation was performed at 3 temperature shifts with different time intervals; these changes did not have any impact either on the sensor integrity or on its operation. The structure of the solid electrolyte sensor, intermediate solid electrolyte / electrode layer and electrodes did not undergo any significant changes during operation. The dynamic characteristics of the sensor, the response time in particular, remained stable during the operation.The present research was performed within the budget plan of the Institute of High Temperature Electrochemistry

Development of oxygen sensor for pyrochemical reactors of spent nuclear fuel reprocessing

The problem of closing the nuclear fuel cycle is not only related to the development of new types of nuclear fuel and the operation of fast neutron reactors, but also to the complex schemes for the pyrochemical reprocessing of spent nuclear fuel (SNF), which, in turn, require adherence to strict process parameters. In particular, this concerns the operation of the reduction of oxidized SNF mainly by metallic lithium. The paper presents the basic scientific principles and the results of experimental verification of the operation of an electrochemical sensor for measuring oxygen in molten salts in pyrochemical reactors for the reprocessing of spent nuclear fuel. The sensor design consists of two combined electrochemical cells based on the solid electrolyte ZrO2-Y2O3 with a common reference electrode. The sensor allows continuous measurement of the oxygen activity in the oxide-chloride melt and the partial pressure of oxygen in the gas atmosphere above the melt directly during the process of pyrochemical processing. Experimental verification of the sensor performance was performed in a reactor with LiCl-Li2O melts at a temperature of 650 ° C. The resource of continuous sensor operation exceeded 500 hours, and the number of thermal cycles without destruction was at least 20. The sensor readings were found to depend on the specified Li2O content in the LiCl melt. © Published under licence by IOP Publishing Ltd

Hilbert-Huang versus Morlet wavelet transformation on mismatch negativity of children in uninterrupted sound paradigm

Background. Compared to the waveform or spectrum analysis of event-related potentials (ERPs), time-frequency representation (TFR) has the advantage of revealing the ERPs time and frequency domain information simultaneously. As the human brain could be modeled as a complicated nonlinear system, it is interesting from the view of psychological knowledge to study the performance of the nonlinear and linear time-frequency representation methods for ERP research. In this study Hilbert-Huang transformation (HHT) and Morlet wavelet transformation (MWT) were performed on mismatch negativity (MMN) of children. Participants were 102 children aged 8–16 years. MMN was elicited in a passive oddball paradigm with duration deviants. The stimuli consisted of an uninterrupted sound including two alternating 100 ms tones (600 and 800 Hz) with infrequent 50 ms or 30 ms 600 Hz deviant tones. In theory larger deviant should elicit larger MMN. This theoretical expectation is used as a criterion to test two TFR methods in this study. For statistical analysis MMN support to absence ratio (SAR) could be utilized to qualify TFR of MMN. Results. Compared to MWT, the TFR of MMN with HHT was much sharper, sparser, and clearer. Statistically, SAR showed significant difference between the MMNs elicited by two deviants with HHT but not with MWT, and the larger deviant elicited MMN with larger SAR. Conclusion. Support to absence ratio of Hilbert-Huang Transformation on mismatch negativity meets the theoretical expectations, i.e., the more deviant stimulus elicits larger MMN. However, Morlet wavelet transformation does not reveal that. Thus, HHT seems more appropriate in analyzing event-related potentials in the time-frequency domain. HHT appears to evaluate ERPs more accurately and provide theoretically valid information of the brain responses.peerReviewe

Justification of an asymptotic expansion at infinity

A family of asymptotic solutions at infinity for the system of ordinary differential equations is considered. Existence of exact solutions which have these asymptotics is proved.Comment: 8 page

Replacement of Sarcocystis orientalis Zaman and Colley, 1975 by Sarcocystis singaporensis sp.n.

10.1007/BF00380536Zeitschrift für Parasitenkunde51113