Assessment of Explosion Risks in the Presence of Hydrocarbon Mixtures Procedia Engineering 168 ( 2016 ) 493 – 496 Available online at www sciencedirect com 1877 7058 © 2016 The Authors Published by El[.]
Available online at www.sciencedirect.com ScienceDirect Procedia Engineering 168 (2016) 493 – 496 30th Eurosensors Conference, EUROSENSORS 2016 Assessment of explosion risks in the presence of hydrocarbon mixtures Alexander M Baranova, Andrey Somovb,*, Alexey Karelinc, Evgeny E Karpovc, Sergey Mironovc, Elena Karpovad b a Moscow Aviation Institute (National Research University), Russia College of Engineering, Mathematics and Physical Sciences - University of Exeter, UK c NTC-IGD Research Center, Russia d STANKIN – Moscow State Technological University, Russia Abstract The most of gas associated industries face with the risks of explosion and fire which may lead to dire consequences We present an approach for assessing the explosion risks in the presence of hydrocarbon mixtures when the chemical composition and concentration of gases in the mixture are unknown The core idea is the measurement of warm dissipated during the combustion of hydrocarbons in the reaction chamber of the sensor To evaluate this approach we use a catalytic planar sensor with limited gas diaphragm in the reaction chamber We demonstrate the feasibility of our approach experimentally © Authors Published by Elsevier Ltd This ©2016 2016The The Authors Published by Elsevier Ltd.is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the organizing committee of the 30th Eurosensors Conference Peer-review under responsibility of the organizing committee of the 30th Eurosensors Conference Keywords: catalitic sensor; combustible gases; hydrocarbons; gas detection; gas mixture; sensor system Introduction A number of industries worldwide (oil and gas, mining, offshore, underground water management) deal with combustible gases directly or indirectly Their leak or release may result in accidents, financial losses and fatalities * Corresponding author Tel.: +44(0)1392 723623 E-mail address: a.somov@exeter.ac.uk 1877-7058 © 2016 The Authors Published by Elsevier Ltd This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the organizing committee of the 30th Eurosensors Conference doi:10.1016/j.proeng.2016.11.142 494 Alexander M Baranov et al / Procedia Engineering 168 (2016) 493 – 496 Even negligible continuous leaks may lead to occupational diseases The major problem is to quickly identify the potential risk from gas mixture appeared in the environment and take measures against its leak A widely used gas in industry is methane which has Lower Explosive Limit (LEL) 4.4% [1] Other gases, e.g propane (1.7%), have less LELs Gases with less LELs together with methane reduce the total LEL of hydrocarbon mixture Therefore, the assessment of the explosion risks at the industrial facilities is an important task Typically, assessing the explosion hazard requires (i) the predefined composition of gas mixture which is a challenging task itself or (ii) multi sensor monitoring system [2] which is challenging in terms of power consumption in the context of autonomous monitoring systems such as Wireless Sensor Networks (WSN) [3] and calibration periods which may differ for each sensor type We propose an approach for the analysis of the total explosiveness of gas mixture in the atmosphere using just one sensor when the mixture components are not predefined This approach helps to estimate the possibility of reaching the LEL of hydrocarbon gas mixture using a planar catalytic sensor [4] Approach The cornerstone of the approach is the phenomena of combustion gas heat multiplied by %LEL The resultant value is rather equal for most gases (9.5±15% max., see Table 1) Table Widely used hydrocarbons in the oil and gas producing industry Gas Methane ɋɇ Concentration CLEL, %vol 4,4 Standard combustion heat Q0, kcal/mole 191,554 CLEL Â Q0 , kcal/mole 8,428 Ethane C H 2,5 376,421 9,411 Propane C H 1,7 488,201 8,299 Benzol C H 1,2 756,998 9,084 Toluol C H 1,1 900,898 9,910 Cyclohexane C H 1,2 881,103 10,573 Methyl alcohol CH O 5,5 182,43 10,034 Acetone C H O 2,5 435,029 10,876 6 12 For calculating the amount of emitted warm on the sensor it is essential to limit the gas diffusion to the sensor reaction chamber for ensuring the burn of fixed gas volume For effectuating this task we use the catalytic sensor DTK-3 by NTC-IGD with a small hole diaphragm in the sealed cap to control the speed of gas flow into the reaction chamber The diaphragm diameter is defined empirically This speed must be much higher than the speed of gas burning in the package According to industrial standards [5] the speed of chamber filling must be less than the sensor response time to gas detection in the atmosphere Fig Gas burning and resultant response signal w.r.t hole diameter Fig Testbed used in this work 495 Alexander M Baranov et al / Procedia Engineering 168 (2016) 493 – 496 Fig demonstrates that for proper flow, the hole diameter must be 0.3 mm or bigger For detecting % LEL of combustible gases we measure the sensor voltage response in the Wheatstone circuit [6] using and compare it with reference voltage The response corresponds to the amount of warm dissipated during the gas burning process in the sensor The reference voltage levels are defined during the calibration process when predefined gas concentration is supplied to the sensor and its response (reference value) is recorded in the Micro Controller Unit (MCU) memory located on the measurement board (see Fig 2) Function for calculating % LEL is given by: ĐU UT0 C = ăă T` U T1 − U T 0 © T Ã áá dt (1) where C is gases concentration in %LEL, UT0 is the sensor response without the presence of gases in the atmosphere, U`T1 is the sensor response in the presence of gases with known concentrations, UT1 is the sensor response in the presence of gases with unknown concentrations The testbed shown in Fig is the gas measurement board built around the MCU ATMega256 and consists of sensing unit with DTK-3 sensor and integrated gas chamber For experimental and debugging reasons the board is equipped with the data acquisition connector for the board interfacing with a PC Experimental Results To realize this idea into practice, we first put the sensor in the atmosphere without gases and measure the amount of warm Q01-2 emitted on the catalytic element during the measurement procedure in the time interval IJ1 - IJ2 We conduct the same experiment to measure the amount of warm Q1-2 in the presence of gas in the same time interval Fig Current variation at gas burning process in the sensor package Fig Transition state for typical hydrocarbons ‘1’ – 0,1% CH4; ‘2’ – 1% CH4; ‘3’ – 1,4% CH4; ‘4’ – 2,5% CH4, ‘5’ – 1% C3H8; ‘6’ – 0,6% C4H10; ‘7’ – 0,5% C6H14 Both processes are accompanied by different response current (Fig 3) The duration of burning process is around seconds To ensure effective filling of reaction chamber we use the sealed caps with the hole diameter 0.5 mm Since the amount of emitted warm is almost equal for most gases at the concentrations corresponding to LEL, the calculation of %LEL is simplified to the monitoring of the sensor response voltage (Fig 4) and its comparing with a threshold value which is defined during the calibration procedure 496 Alexander M Baranov et al / Procedia Engineering 168 (2016) 493 – 496 Table Experimental results for gas mixtures Mixture composition Gas Mixture concentration Gas Gas Gas Formula LEL, % vol Mixture concentration LEL, % vol (% LEL) Measured LEL, % vol H2 0.96%vol CH4 1.47%vol H2 0.384%vol CH4 0.882%vol 4.270 ɋɇ4+ɇ2 1.266 (30) 32 CH4 1.47%vol C3H8 1.01%vol CH4 0.882%vol C3H8 0.404%vol 2.935 ɋɇ4+C3ɇ8 1.286 (44) 44 CH4 1.47%vol C4H10 1.01%vol CH4 1.187%vol C4H10 0.128%vol 3.641 ɋɇ4+C3ɇ10 1.315 (36 ) 38 Table demonstrates the experimental results on total explosiveness of three gas mixtures Each mixture consists of two gases in air where methane presents in all mixtures The experiment is conducted in the following way: the mixtures H2+air and CH4+air (see rows ‘1’, ‘2’ and ‘3’ in Table2) are flown through measurement chamber using the inlet valves The valves set constant gas flow through the chamber As a result, there is a stable gas mixture (see column mixture concentration in Table 2) and air concentration in the chamber In all cases shown in Table the mixture concentration is less than standard LEL which means that there are no explosion risks from the gas mixtures presented in the environment The last two columns in Table show that the experimental results (measured LEL) are in line with calculated values (mixture concentration LEL, % vol) It is worth noting that the first case, i.e mixture of H2 and CH4, is the most difficult one in terms of the evaluation of explosive risks since in practice it is not a trivial task to detect H2 in the presence of hydrocarbon(s) Conclusion In this work we have proposed and experimentally evaluated the approach for the assessment of explosion risks in the presence of hydrocarbon mixtures when the concentrations of gases in the mixture are unknown The approach is based upon the measurement of warm dissipated during the combustion of hydrocarbons in the reaction chamber of the catalytic sensor We have demonstrated the feasibility of our approach and shown that the experimental results on the assessment of the total explosiveness of gas mixtures are in agreement with the calculated values (% vol.) The experiments are conducted for the mixtures of different hydrocarbons and the mixture of H2 and CH4 Acknowledgements This work was supported by the grant No RFMEFI57714X0133 from the Ministry of Education and Science of Russian Federation References [1] J Leis, D Buttsworth, A temperature compensation technique for near-infrared methane gas threshold detection, IEEE Transactions on Industrial Electronics 63 (2016) 1813-1821 [2] A Oprea, J Courbat, D Briand, N Bârsan, U Weimar, N.F de Rooij, Environmental monitoring with a multisensor platform on polyimide foil, Sensors and Actuators B: Chemical 171–172 (2012) 190-197 [3] A Somov, E F Karpov, E Karpova, A Suchkov, S Mironov, A Karelin, A Baranov, D Spirjakin, Compact low power wireless gas sensor node with thermo compensation for ubiquitous deployment, IEEE Transactions on Industrial Informatics 11 (2015) 1660-1670 [4] A Somov, A Baranov, A Suchkov, A Karelin, S Mironov, E Karpova, Improving interoperability of catalytic sensors, Sensors and Actuators, B: Chemical 221 (2015) 1156-1161 [5] Standard RD BT 39-0147171-003-88, Requirements for setting up stationary gas analyzers at industrial premises and outdoor areas of oil and gas enterprises [6] A Somov, A Baranov, D Spirjakin, R Passerone, Circuit design and power consumption analysis of wireless gas sensor nodes: one-sensor versus two-sensor approach, J IEEE Sensors 14 (2014) 2056-2063 ... presence of hydrocarbon( s) Conclusion In this work we have proposed and experimentally evaluated the approach for the assessment of explosion risks in the presence of hydrocarbon mixtures when the. .. methane reduce the total LEL of hydrocarbon mixture Therefore, the assessment of the explosion risks at the industrial facilities is an important task Typically, assessing the explosion hazard... noting that the first case, i.e mixture of H2 and CH4, is the most difficult one in terms of the evaluation of explosive risks since in practice it is not a trivial task to detect H2 in the presence