Lower Explosion Limit Research Articles

Effect of CO2 on the explosion limit parameters and kinetic characteristics of ammonia-hydrogen-air mixtures

To explore the effect of CO2 on the explosion limit parameters and kinetic characteristics of the NH3-H2-air mixtures, the standard combustible gases explosion limits device was utilized to test and analyze the explosion limit, critical oxygen concentration, and explosion triangle. Based on the CHEMKIN software, the suppression mechanism of CO2 on NH3-H2-air mixtures explosion with 0.4 R (hydrogen ratio) and a near-inerting critical concentration was simulated and analyzed. The results indicated that increasing F (volume fraction of CO2) led to a decrease in the upper explosion limit (UEL) of NH3-H2-air mixtures and an increase in the lower explosion limit (LEL). When F increased to 36%, the explosion of the NH3-H2-air mixtures with 0.4 R was completely suppressed. As R increased, the UEL and LEL decreased and increased linearly, respectively, the critical explosion-suppression concentration of CO2 increased, the critical oxygen concentration decreased, and the explosive zone area also increased. In addition, based on the analysis of the changing characteristics of the UEL and LEL, prediction models for the UEL and LEL of NH3-H2-air mixtures with different hydrogen ratios under the effect of CO2 were provided. Reaction kinetics analysis found that less CO2 had a more pronounced impact on ·H and ·OH. However, when F increased to 20-30%, the maximum mole fraction of ·O decreased the most. At this point, the sensitivity of·NH2 towards decreasing oxygen concentrations became comparable to that of ·H and ·OH. When F increased to a near-critical explosion-suppression concentration of 30%, ·H, ·OH, ·O, and ·NH2 were in a critical state of disappearing, and the chain initiation of the explosion was destroyed. Sensitivity analysis indicated that ·H+O2(+M)<=>HO2(+M) and ·NH2+·NH=N2H3 performed a more significant inerting effect on ·H and ·NH2, which ultimately led to the termination of the explosive chain reactions.

Consequence modeling and analysis of ethanol leakage from storage tank using the ALOHA program

Chemical spills pose a significant threat to the safety of people living nearby, as well as to air quality and occupational safety. Therefore, preventing chemical spills has become a key issue in environmental protection and process safety. This study aims to evaluate the effects of ethanol released from a tank at a chemical plant in Istanbul, Türkiye. The Areal Location of Hazardous Atmospheres model (ALOHA) version 5.4.7 estimates the storage tank's leakage radius and spread risk under three scenarios. ALOHA can assess the area affected by chemical hazards. The model shows that if the spill occurs 10 centimeters from the base of the tank, the toxic concentration of ethanol exceeds the Immediately Dangerous to Life or Health (IDLH) threshold (i.e., 3300 parts per million) at a distance of 31 meters from the place of release. In addition, when the ethanol concentration exceeds 60% of the Lower Explosive Limit (LEL) (i.e., 19800 parts per million), the flammable vapor cloud extends up to 31 meters from the place of release. For a Boiling Liquid Expanding Vapor Explosion (BLEVE), the mass of the fireball is assumed to be 100%, resulting in the worst possible scenario. During BLEVE, it is estimated that the fireball's diameter and time duration, determined by the amount of Ethanol present, would be 141 meters and 10 seconds, respectively. The results show that the thermal radiation effects caused by Ethanol BLEVE are extremely dangerous.

Ultra-sensitive liquefied petroleum gas (LPG) sensor based on monometallic Ag nanospheres synthesized via microwave-assisted facile approach

We present the synthesis, analysis, and utility of polyvinylpyrrolidone (PVP) stabilized monometallic silver nanospheres for liquefied petroleum gas sensing at room temperature. We have synthesised silver nanospheres (Ag-NSs) in the diameter range of 13–21 nm using a microwave assisted method, which is both easy and fast, because microwave irradiation only takes 30 s. A solution of 0.1 M silver nitrate (AgNO3) in an ethanolic medium was microwave-irradiated to produce Ag-NSs. PVP was used as a stabilising agent throughout the process. Spin coating method was used to produce thin films of synthesised monometallic Ag-NSs. X-ray diffraction (XRD), scanning electron microscopy (SEM), acoustic particle sizer (APS), UV–visible absorption (UV–visible) and Fourier Transform Infrared (FT-IR) spectroscopy were used for characterising Ag-NSs. Based on the acoustic attenuation of the prepared sample, the acoustic particle sizer estimated the diameter of Ag-NSs to be around 17 nm. The deposited films were examined for LPG leakage detection at ambient temperature. This is the first report on monometallic Ag-NSs for leakage detection of LPG at room temperature operation below its lower explosive limit (LEL). The significant finding of the developed sensor is that it prompts the quick response (∼16 s) and recovery (∼64 s) as Ag enhances the reaction rate between the sensing film surface and adsorbed LPG, thereby, augments the sensitivity of sensor even below LEL. Moreover, the fabricated LPG sensor shows noteworthy reproducibility (measured up to six cycles) and stability up to 06 months after fabrication.

Acquisition Study of Downhole Explosion Limit in Air Drilling

Summary Downhole explosions adversely affect air drilling; however, the explosion limit can facilitate the adjustment of the flow rate to prevent downhole explosions. The downhole explosion limit, comprising lower and upper limits, can be determined through diverse methodologies. In this study, the interrelation between absolute enthalpy and adiabatic flame temperature (AFT) enabled the deduction of the lower explosion limit (LEL) prediction method, and an equilibrium between heat generation and heat transfer formed the basis for the upper explosion limit (UEL) prediction method. Additionally, a variable-volume apparatus was established to measure the explosion limit and adjust the pressure precisely without changing the amount of gas. The explosion limit of methane in the air was determined using both predicted and experimental methods, mirroring the scenarios of natural gas entering the wellbore during air drilling. The theoretical model exhibited the same reliability as the experimental results, and the prediction method for the explosion limit proved more efficient. Moreover, the effects of initial temperature and pressure on the explosion limit are discussed. The LEL decreased by an average of 15.5% when the initial pressure increased from 0.1 MPa to 2 MPa, while the UEL experienced a significant increase by an average of 152%. The UEL exhibited a logarithmic dependence on the initial pressure. The effect of the initial temperature on the explosion limit was noticeably less pronounced than that of the initial pressure. This study provides the essential theoretical basis and experimental results for avoiding downhole explosions during air drilling.

Dual functionality of cathode microporous layers: Reducing hydrogen permeation and enhancing performance in proton exchange membrane water electrolyzers

Hydrogen permeation and cell performance are critical factors for the safe and efficient operation of proton exchange membrane (PEM) water electrolysis. In this study, the effects of a cathode microporous layer (MPL) on water transport, hydrogen permeation, and cell performance in a proton exchange membrane water electrolyzer (PEMWE) were investigated. Results reveal that adding an MPL between the catalyst layer (CL) and the porous transport layer (PTL) at the cathode reduces interfacial contact resistance by approximately 60 % under 400 N cm−2, leading to superior performance. The wettability of the MPL plays a crucial role in water transport and hydrogen permeation in PEMWEs. The hydrophobic MPL-P-CB4, which uses polytetrafluoroethylene (PTFE) as a binder with a carbon black (CB) loading of 4 mgCB cm−2, enhances the crossover of water and hydrogen from the cathode to the anode through back diffusion, exceeding the technical safety criterion of 2 vol% H2 in the anode product gas (50 % lower explosion limit) at 2.0 A cm−2. However, the hydrophilic MPL with Nafion ionomers as binders (MPL-N-CB4) facilitates efficient removal of water and hydrogen from the cathode CL to the cathode flow field via capillary pressure, resulting in only 0.2 vol% H2 in O2 at 2.0 A cm−2. Consequently, a hydrophilic MPL is optimal for achieving superior performance and low-hydrogen-crossover in a PEMWE cathode. This study provides valuable insights for designing the PTL/CL interface in next-generation PEMWE cathodes.

Time-dependent variations in desorbed gas composition: methodological analysis of asphaltite vein investigation results

In this study, a phenomenon that can have significant technical and economic impacts in the mining and unconventional gas production of hydrocarbon resources is discussed, change of gas composition during desorption period. The change is analyzed, related findings are obtained and engineering tools are forged. In this scope, a member of the Southeastern Turkey asphaltite’s gas content and composition character was examined. 12+1 samples were collected at equal intervals from an inclined drillhole that cut through the asphaltite vein. The United States Bureau of Mines (USBM) direct method was employed to determine the gas content. Gas composition analysis was performed on gas samples, which were collected four times throughout the desorption period. Residual gas composition is determined as well. During desorption period, methane and hydrogen ratios exhibited decreasing trends, while others have increasing trends. In evaluating of the collected data, the desorption order between gas compounds are revealed. Logarithmic trend functions are generated to estimate the concentrations of gas compounds at specific time points. With these functions and gas content measurement data, weighted average concentrations for gas compounds are determined. These concentration functions and the weighted average results are used to create engineering tools showing unit energy content of desorbed gas through desorption period both instantaneous and cumulative. Similarly, change in lower explosive limit and auto-ignition temperature during desoption period is shown. The weighted average gas concentrations obtained are used to interpret geological insights as they are the actual gas composition of the samples. In the study, gas content characteristic properties of Üçkardeşler asphaltite vein is comprehensively presented. Accordingly, the mean gas content, excluding one sample with a value of 2.78 m3/t at a location near a fault intersection, was found to be 1.66 m3/t. The average volumetric concentrations of methane, ethane, propane, and acetylene in the desorbed gas were determined as 61.6%, 24.5%, 10.7%, and 2.3%, respectively. The remaining part primarily consisted of heavier hydrocarbons, with low amounts of carbon dioxide and hydrogen.

Thermal energy propagation characteristics and hazard effects of hydrogen cloud explosion

Hydrogen has advantages such as high energy density and zero carbon emissions, but it poses a risk of generating explosion fireballs in the air. The gas explosion process not only involves thermal radiation from the fireball but also heat conduction and convection caused by the diffusion of high-temperature products. In this work, the thermal parameters of hydrogen cloud explosion with different equivalence ratios and gas cloud radius in an unconfined space were investigated. The results show that the flame temperature-distance curve of a hydrogen explosion exhibited a ’Z’ type. The maximum distance of flame propagation is positively correlated with the peak thermal radiation flux and cloud radius and increases first and then remains steady with the equivalence ratio. When only considering thermal convection, the minimum injury distance of flame temperature is achieved, and the thermal radiation effect can promote the flame propagation speed. Under the q-t criterion, the effective thermal radiation radius of first-level damage at a gas cloud size of 1 m was 6.11 m at φ = 1.2, which was 1.89 times that of φ = 0.6. Compared with the thermal dose criterion, the thermal flux-time criterion results in a larger thermal injury radius. The propulsion effect of hydrogen explosion products can cause the hydrogen cloud in the premixed zone to diffuse outward. The critical distance of hydrogen diffusion within the lower explosion limit was also analyzed. This study provides significant guiding implications for preventing hazards in people and buildings.

Development of Next Generation Membranes for PEM Water Electrolysis in AGC

AGC’s FORBLUETM product family has over 70 years of experience in ion-exchange membranes (IEMs). S-SERIES, a FORBLUETM member, is a per-fluorinated sulfonic acid polymer (PFSA) membrane utilized in various electrochemical devices and industrial electrolysis. AGC’s IEM technology had a lot of experience in the chlor-alkali application and was further developed for the PEM water electrolysis industry.AGC R&D has developed S-SERIES membranes with a smaller thickness, improved reinforcement, and high ion exchange capacity (IEC) that enhanced not only an electrochemical performance but also dimensional stability.A membrane electrode assembly (MEA) was fabricated using a developed membrane with high IEC polymer (IEC 1.25 meq/g). As a result, IV characterization of a single cell with 25 cm2 electrode area at 80°C showed a significant voltage reduction compared to a commercial membrane in the PEM water electrolysis market. In addition, H2 crossover during the electrolysis was evaluated in a single cell with a 25 cm2 electrode area at 80°C and ambient pressure, and the H2 concentration in O2 at the anode side was compared at a current density of 1.0 A/cm2. The developed membrane showed 0.3 vol% H2 crossover, whereas the commercial membrane showed 0.5 vol%.Furthermore, next-generation membranes with gas recombination catalysts (GRC) and radical scavengers leading to lower gas crossover and higher chemical stability are under development. Recently, high-pressure electrolyzers have been getting more attention and the increase of H2 crossover is a concern against the lower explosive limit (LEL) for hydrogen in oxygen. In general, PFSA membranes are considered to have high chemical durability, however, F ion release is observed, that indicate that this PFSA polymer is attacked by OH radicals generated in the PEM water electrolysis system. AGC has been investigating the application of GRC and radical scavengers to the newly developed membranes. It was evaluated in a single cell with 25 cm2 electrode area at 80°C and 2.0 A/cm2. As a result, the H2 crossover and F ions release rate (FRR) were reduced compared to the membrane without both additives. The data will be presented on these improved performances.

Critical risks with the permeability dimension to describe the hydrogen crossover phenomenon

Hydrogen crossover in water electrolyzer systems equipped with ion exchange membranes (IEM) poses significant safety risks and reduces overall process efficiency. This communication identifies and addresses two critical errors in current hydrogen crossover literature: inaccurate measurement methods and the inappropriate use of permeability (e.g., barrer) to quantify hydrogen crossover. Accurate evaluation of hydrogen crossover through an IEM can be challenging because it is a two-phase material fully hydrated in liquid water. We propose a standardized protocol for accurately measuring hydrogen crossover in fully hydrated IEMs and emphasize the necessity of using flux (e.g., mole∙m−2∙s−1) instead of permeability (e.g., barrer) dimension. The obtained data reveal that normalizing hydrogen crossover by transmembrane pressure and membrane thickness can result in significant errors, with relative errors reaching up to 25%. When applied to the actual electrolysis operation, using the permeability data to predict hydrogen crossover at a current density of 0.4 A cm−2 results in 47% error, with the actual system reaching the lower explosion limit (LEL) while the predicted value does not. Additionally, hydrogen crossover data provides insights into the internal ion channel morphology of IEMs. This communication article intends to convey the current existing safety hazards to the hydrogen research community with a detailed transport models and validation.

Facile Abatement of Oxygenated Volatile Organic Compounds via Hydrogen Co-Combustion over Pd/Al2O3 Catalyst as Onsite Heating Source

Catalytic combustion of volatile organic compounds (VOCs) usually requires external energy input to hold the desired reaction temperature via electric heating. This work presents an example of internal onsite heating of the catalytic active sites via hydrogen catalytic combustion with air over a conventional Pd/Al2O3 catalyst. Hydrogen combustion was ignited by the catalyst at room temperature without electric heating, and thus the temperatures were readily varied with the concentrations of H2. Representative oxygenated VOCs such as methanol, formaldehyde and formic acid can be completely oxidized into CO2 and water by co-feeding with H2 below its low explosion limit of 4% using Pd/Al2O3 as shared catalyst. The catalytic performance apparently is not sensitive to the sizes of Pd nanoparticles in fresh and spent states, as revealed by XRD and STEM. This provides an option for using renewable green hydrogen to eliminate VOC pollutants in an energy-efficient way.

Dynamics of gas composition and thermal behavior post explosions: An experimental investigation across varied initial concentrations

Gas explosion accidents are a leading cause of casualties in underground coal mines. This study investigates the variation patterns of explosion temperature and pressure under different initial gas concentration conditions using a 20 L explosion characteristic test system and high-precision sensors. Accurate post-explosion gas analyses were conducted using a GC9560 gas chromatograph. Our research aligns with global research, finding that initial gas concentrations within the range of 5.8%–13.3% generate maximum explosion pressures between 0.3 and 0.9 MPa, posing a significant overpressure hazard to humans. Comprehensive fitting analyses of various post-explosion gases reveal that at an initial gas concentration of 10.6%, the produced H2 can reach its lower explosion limit, indicating a risk of secondary explosions. Furthermore, post-explosion CO levels can peak at 9.87%, potentially causing poisoning or death, while elevated CO2 levels and diminished O2 concentrations could lead to asphyxiation. A unique observation at a 9.5% concentration was a secondary temperature rise, with the relationship between temperature delay, heating time, and initial gas concentration presenting a U-shaped pattern that mirrors theoretical expectations. This study advances the field by addressing research gaps in post-explosion gas analysis and emphasizing the necessity of precise monitoring and control of gas concentrations, thereby offering novel insights and substantial theoretical and practical contributions to the prevention of gas explosion incidents in underground coal mines.

Inhibition effect of inert gas jet on gas and hybrid explosions caused by thermal runaway of lithium-ion battery

When lithium-ion batteries undergo thermal runaway in a confined space, the released gases and/or vapors or dust particles can lead to an explosion. An 8L cylindrical experimental vessel was constructed to study the inert effect of inert gases on battery-vented gas (BVG) in a confined vessel. Firstly, the inhibition effect and inert mechanism of CO2 and N2 on BVG explosion were analyzed by experiments and simulation software. The results show that the inert effect of CO2 on the BVG is significantly better than that of N2. This is because CO2 is not only better than N2 in physical explosion inhibition, but also participates in the chemical reaction. Secondly, the effect of the release of high-pressure CO2 gas on the explosion of the BVG in a closed container was simulated, showing that when the BVG is near the lower explosive limit, the CO2 jet will significantly increase the rate of explosion pressure rise of the BVG. This suggests that the inhibition effect of the CO2 jet is not as good as in premixed conditions. Finally, it is found that the inhibition effect of CO2 on the hybrid explosion is better than that of CO2 jet on the BVG. Since CO2 makes oxygen insufficient, leading to a reduction in the amount of graphite dust burned. The graphite dust and CO2 have a synergistic inhibition effect on the hybrid explosion. The above findings can provide a reference for the lithium-ion battery explosion inhibition method in the process industry.

The gas production characteristics and catastrophic hazards evaluation of thermal runaway for LiNi0.5Co0.2Mn0.3O2 lithium-ion batteries under different SOCs

Lithium-ion batteries (LIBs) are widely used as electrochemical energy storage systems in electric vehicles due to their high energy density and long cycle life. However, fire accidents present a trend of frequent occurrence caused by thermal runaway (TR) of LIBs, so it is especially important to evaluate the catastrophic hazards of these LIBs. This study conducted the adiabatic TR test coupled gas production test, Gas Chromatography-Mass Spectrometry test, and explosion limit test on a commercial LIB with Ni0.5Co0.2Mn0.3 as the cathode material at different states of charge (SOCs). The results show that the TR temperature and the maximum temperature at low SOC are lower compared to that at a high SOC. The probability of LIBs TR at less than SOC = 50 % is small and also causing less harm. For the gas production characteristics, the lower the SOC of the battery, the lower the gas production volume. The peak and steady-state gas production increase with the increase of SOC. For the mixed gases generated during TR, the content of CO2 shows a trend of decreasing with the increasing of battery SOC, while that of H2 and CO increase with the increasing of SOC. For the explosion limit of the mixed gas, the lower explosion limit and upper explosion limit decrease and increase with the increasing of SOC, respectively. Finally, based on the seven parameters related to the TR gas production of LIBs and so on, the analytic hierarchy process method was used to establish a LIB TR disaster-causing hazard evaluation system. The evaluation system can quantitatively evaluate the thermal safety of a LIB. This is instructive for establishing a comprehensive quantitative evaluation method for battery safety in practical engineering applications.

Numerical simulation of gas diffusion and explosion limit of VOCs in containment integrated leak rate test

CILRT is an important work in the overhaul of nuclear power plants. VOCs from paints and cleaners used in the containment during the overhaul will migrate inside the containment, and the numerous rooms and compartments inside the containment make the air flow impeded, and the VOCs may be enriched to bring combustion risk. The complete fire risk analysis method includes volatilization kinetics of chemicals, mixture explosion limits, and numerical simulation of VOCs diffusion and migration. The volatilization rate at the lowest room temperature of 20°C is used as a conservative input, the complement of CAITA realistic model is used as the flow domain, and the geometry is appropriately simplified, and the steady ventilation process, the internal flow and the laws of diffusion and agglomeration of 12 kinds of VOCs gases in the 9-h pressure-holding process are investigated by Computational Fluid Dynamics. The simulation results of steady ventilation show that the VOCs gases are almost uniformly carried by the air to all spaces inside the containment, and the explosion risk is low. The concentration field of the steady ventilation process was taken as the initial boundary condition and unsteady state simulation of the 9-h holding pressure process was performed. The results show that the gas flow inside the containment basically stops after 3456 s of pressure holding. With the extension of time, the VOCs gases accumulate at the bottoms of the three lower layers of the containment under the effect of laminar diffusion and gravitational settling, where the total concentration of the mixed gases reaches the highest at the bottom of the lowest layer. The total concentration of the VOCs gas mixture was below the lower explosion limit throughout the 9-h pressure-holding process, and the explosion risk was low.

Unveiling the Air Quality Impacts of Municipal Solid Waste Disposal: An Integrative Study of On-Site Measurements and Community Perceptions

This study examines air quality conditions in and around a classroom located in the Sarıçam/Adana region of Türkiye, near the campus of Adana Alparslan Türkeş Science and Technology University and the Sofulu municipal solid waste (MSW) facility. This academic setting was strategically chosen due to its proximity to the waste facility. The study aims to provide a comprehensive view of the environmental and social impacts of solid waste management through a methodological approach that combines quantitative on-site measurements and qualitative survey studies. Findings from measurements and surveys underline the significant and measurable impacts of MSW facilities on the ambient air quality of university residents. The analysis revealed a marked increase in concentrations of key pollutants, including carbon monoxide (CO), hydrogen sulfide (H2S), dust, and methane (CH4). At sampling point N1, H2S levels rose from 0 ppm in July to 13 ppm in November. Methane increased from 0.2% to 2.5% of the Lower Explosive Limit (LEL) at the same point, although it remained within safety limits. Additionally, CO levels showed a 40% increase, and dust concentration levels rose from 0.21 mg/m3 to 2.36 mg/m3 from summer to winter, indicating a seasonal variation likely influenced by the landfill’s operational dynamics, as well as changes in temperature and relative humidity. In particular, the results indicate high concentrations of CO, H2S and dust, which are directly related to air quality degradation. The study also sheds light on the impacts of these waste disposal facilities on the general well-being and health of the university community, particularly on students and staff. In addition to these findings, the study highlights a general lack of awareness in the university community about the impacts of MSW facilities on air quality. This highlights the need for increased education and information dissemination. The results support the development of comprehensive and effective strategies, including technical solutions and public awareness initiatives, to mitigate the impacts of these facilities on residential areas. In conclusion, the impacts of MSW facilities on air quality should be seen as a multidimensional issue that requires a holistic approach addressing environmental, health, social, and educational dimensions.

Investigation of gas explosion hazards and characteristics during overcharged behavior of nickel-cobalt-manganese (523) lithium-ion battery

Compared with hard-shell lithium batteries, the obvious thermal runaway (TR) characteristic of nickel‑cobalt‑manganese pouch cell (NPC) is that it cannot release a large amount of gas in time. Therefore, the fire risk during the TR process of NPC is centralized by gas explosion hazard. The overcharged TR process of nickel‑cobalt‑manganese (523) NPC (NCM523) was explored in this work. The jetting flame phenomenon still occurs during the TR process of NCM523 in the absence of air, indicating that it is primarily attributed to self-reaction and exhibits spontaneous properties. Moreover, the air environment can increase the intensity of jetting and gas explosion hazards. The gases produced during the TR process of NCM523 in the air and nitrogen are mainly CO, H2, N2, CO2, CH4, C2H6, C2H4, and C3H6. The volume percentages of combustible gases in the air and nitrogen are 64.87 % and 46.24 %, respectively. The lower explosion limit (volume ratio) of gases in the air environment is between 10 % and 11.25 %, while the upper is between 39.37 % and 40 %. The maximum flammable intensity of gases generated from the TR process of NCM523 is 25 %. As revealed by CHEMKIN simulations, H∙, O∙, and OH∙ are the most important key radicals that catalyze the entire chain reaction and gas explosion during the TR process of NCM523. The interaction and mutual promotion of reactions R1, R2, and R3 are crucial for the generation of free radicals. Therefore, the combustion and explosion risk during the TR process of NCM523 can be reduced by increasing inert gases and suppressing the free radical reaction chemically during gas phase combustion.

Research on High Performance Methane Gas Concentration Sensor Based on Pyramid Beam Splitter Matrix.

Methane gas concentration detection faces the challenges of increasing accuracy and sensitivity, as well as high reliability in harsh environments. The special design of the optical path structure of the sensitive element provides an opportunity to improve methane gas concentration detection. In this study, the optical path structure of the sensitive element was newly designed based on the Pyramidal beam splitter matrix. The infrared light source was modulated by multi-frequency point-signal superimposed modulation technology. At the same time, concentration detection results and confidence levels were calculated using the four-channel methane gas concentration detection algorithm based on spectral refinement. Through the experiment, it was found that the sensor enables the full-range measurement of CH4; at the lower explosive limit (LEL, CH4 LEL of 5%), the reliability level is 0.01 parts-per-million (PPM), and the limit of detection is 0.5 ppm. The sensor is still capable of achieving PPM-level detections under extreme conditions in which the sensor's optical window is covered by two-thirds and humidity is 85% or dust concentration is 100 mg/m3. Those improve the sensitivity, robustness, reliability, and accuracy of the sensor.

Research on high performance combustible gas concentration sensor based on pyramid beam splitter matrix.

Combustible gas concentration detection faces challenges of increasing accuracy, and sensitivity, as well as high reliability in harsh using environments. The special design of the optical path structure of the sensitive element provides an opportunity to improve combustible gas concentration detection. In this study, the optical path structure of the sensitive element was newly designed based on the Pyramidal beam splitter matrix. The infrared light source was modulated by multi-frequency point signal superimposed modulation technology. At the same time, concentration detection results and confidence levels were calculated using the 4-channel combustible gas concentration detection algorithm based on spectral refinement. Through experiment, it is found that the sensor enables full-range measurement of CH4, at the lower explosive limit (LEL, CH4 LEL of 5%), the reliability level is 0.01 parts-per-million (PPM), and the sensor sensitivity is up to 0.5PPM. The sensor is still capable of achieving PPM-level detections, under extreme conditions in which the sensor's optical window is covered by 2/3, and humidity is 85% or dust concentration is 100mg/m3. Those improve the sensitivity, robustness, reliability, and accuracy of the sensor.

Flowline Modification of Vapour Closed Drain to Acid Flare at Matindok CPP in Reducing CO2 Emission

Pertamina EP Donggi Matindok Field produces gas and condensate by transforming natural raw gas to sweet gas through several processes. LP Vent Stack is a facility to release non-hazardous gas such as N2 and O2 excess to ambient air. However, waste gaseous in Matindok Central Processing Plant (CPP) that comes from Condensate Tank, Closed Drain, and Produced Water Tank causing vapour release, where this vapour release is mainly detected from Closed Drain. Gaseous release from Closed Drain which contains high hydrocarbon and H2S with characterization of high Lower Explosive Limit (LEL) can cause potential explosive when contacted with heat source, electricity, or lightning. On January 20th 2022 and February 15th 2022, flame occurred in LP Vent Stack located in Matindok CPP. Flowline modification of Closed Drain to Acid Flare is conducted to prevent potential flame and reduce emission in LP Vent Stack. The gaseous release from Closed Drain is being modified to Acid Flare as purge, hence reducing the usual purge needed from fuel gas and able to reduce 352.86 kg of CO2 emission in 2022.

Comparison Between Wet and Dry Transfer Fe2O3-CNT Hybrid Thin Films as Room-Temperature Liquefied Petroleum Gas (LPG) Sensors

Fe2O3-CNT hybrid thin films are promising candidates for room-temperature gas sensors with high sensitivity, rapid response, and recovery times. In this work, we reported the suitable fabrication strategies of Fe2O3-CNT hybrid thin films as liquefied petroleum gas (LPG) sensors by comparing the dry (without using aqueous solutions) and wet processes. Fe-CNT hybrid thin films were used as the primary material for synthesizing Fe2O3-CNT hybrid thin films, which were then annealed in air at 350oC to create α-Fe2O3. Characterizations by X-ray photoelectron spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy (FE-SEM) confirmed the decoration of α- Fe2O3 nanoparticles on CNT surfaces. The transfer process had effects on the surface morphology and sensor characteristics. FE-SEM presents that the surface morphology of the wet-transfer Fe2O3-CNT films was web-like structures with a highly porous morphology. Whereas the surface morphology of the dry-transferred Fe2O3-CNT films was a branch-like structure. The I-V relationship of both annealed wet- and dry- films was non-linear indicating the present of n-type α- Fe2O3. Under 5 vol.% of LPG, the wet-transferred Fe2O3- CNT films have higher sensitivity (S = ~ 3% Tresp.= 10 s, trec.= 59s) compared to the dry- transferred Fe2O3-CNT films (S = ~ 1.4%, Tresp.=90s, trec.= incomplete recovery). Moreover, the wet-transferred Fe2O3-CNTs could detect LPG concentration at a lower value than 25% of LEL (Lower Explosive Limit) with rapid response and recovery time of 23 s and 49 s, respectively.