Gas Composition Research Articles

Effect of Hyperthermal Hybrid Gas Composition on the Interfacial Oxidation and Nitridation Mechanisms of Graphene Sheet.

Graphene is one of the most promising thermal protection materials for high-speed aircraft due to its lightweight and excellent thermophysical properties. At high Mach numbers, the extremely high postshock temperature would dissociate the surrounding air into a mixture of atomic and molecular components in a highly thermochemical nonequilibrium state, which greatly affects the subsequent thermal chemical reactions of the graphene interface. Through establishing a reactive gas-solid interface model, the reactive molecular dynamics method is employed in this study to reveal the influences of the thermochemical nonequilibrium gas mixture on the thermal oxidation and nitridation mechanisms of graphene sheet. The results show that three distinctive stages can be recognized during bombardment of various nonequilibrium gas components toward the graphene sheet: (i) collision and surface adsorption stage, (ii) gas-solid heterogeneous reaction stage, and (iii) gas phase homogeneous reaction stage. The surface catalysis effect is found to be dominant during the first two stages, which can influence the following ablation behavior of graphene significantly at high-temperature conditions. Moreover, surface catalysis, oxidation, nitridation, and ablation mechanisms between nonequilibrium gas and graphene interface are revealed, which is of high relevance for future interfacial design and application of graphene as a thermal protection material.

Effect of atmospheric pressure changes on gas transmission through microperforated packages of respiring products

The objective of this work was to quantify the effect of atmospheric pressure changes on gas transmission through microperforations, in order to understand the role of fluctuations in the atmospheric pressure on the headspace composition of microperforated modified atmosphere packages. A 3D numerical model that considers the spatial-time and pressure dependence of the gas composition was adapted to simulate the gas exchange through microperforations at different fixed pressures and at variable pressure due to atmospheric pressure fluctuations (such as those caused by atmospheric tides or by the development of high and low-pressure systems) or to changes in altitude during land or air transport. The model results were successfully verified with experimental data recorded in an experimental system built to measure the CO2 exchange through microperforations affected by pressure changes due to weather conditions (the root mean squared error of the CO2 composition was 0.01%). The results reveal the importance of contemplating the convective flow generated by a change in pressure outside the package. In the simulated routes, the difference in CO2 concentration between considering the pressure-driven flow and neglecting it is one order of magnitude in a 10-h land transport through a medium mountain route, for a 1250 mL container with a single microperforation of 7420.6 μm2 area and initial CO2 concentrations on both sides of the hole of 0.05% and 20.95%. The air transport simulations showed that it is not enough to consider the difference in altitude between the cities of origin and destination, but rather all the pressure fluctuations along the route must be included in the model.

Modeling analysis of water-gas-shift reaction on catalyst-packed ceramic-carbonate dual-phase membrane reactor for hydrogen production

Water-gas shift (WGS) reaction for hydrogen production and CO2 removal/capture in a catalyst-packed CO2-permselective membrane reactor is studied experimentally and simulated with a computational model. The reactor utilizes a tubular dense ceramic-carbonate dual-phase membrane with a commercial high-temperature WGS catalyst. Equations governing CO2 permeation through the membrane and WGS reaction kinetics on the catalyst were obtained through independent CO2 permeation experiments and a fixed-bed reaction kinetic study. The simulation results using the validated model are presented to examine the effects of feed gas composition, steam/CO ratio, gas hourly space velocity, temperature, reactor pressure, sweep to feed molar flow rate ratio, and the membrane area to catalyst volume ratio on the performance of the membrane reactor for WGS with CO2 removal. Under optimized conditions, the catalyst-packed membrane reactor for WGS demonstrates significantly enhanced CO conversion and product H2 purity by effectively removing/capturing CO2 from the WGS reaction side.

Experimental study of the performance of a SI-engine fueled with hydrogen-natural gas mixtures

Green hydrogen has become more attractive as a fuel for engines to reduce greenhouse gas emissions. By mixing it with natural gas (NG), the modification work on the engine can be minimized but the carbon dioxide emissions from combustion can still be decreased. In this paper, an experimental study was accomplished to investigate the performance of a spark-ignition engine fueled with hydrogen-natural gas blends by either keeping a constant ignition timing or changing it. Up to 25 mol-% hydrogen was mixed into natural gases with different compositions and the methane number and Wobbe index were calculated and compared to the requirements set by Euromot. The results show that up to 15 mol-% hydrogen can be blended into NG to meet the limits of Euromot. However, when 25 mol-% hydrogen was mixed into NG the methane number varied between 56 and 64 depending on the gas composition. This would most likely cause knock for a mixture consisting of higher hydrocarbons but during the executed tests knock was never a problem. Furthermore, it was detected that the methane number alone cannot tell the knock tendency of a gas in a certain engine and an additional condition is needed such as the hydrogen level. An adjusted ignition timing was also preferable compared to a constant one to keep the engine component temperature at a moderate level.

Large-scale PANDA facility – radiation experiments and CFD calculations

Abstract CFD modelling of the thermo-hydraulic phenomena in the containment during the various phases of a severe accident necessarily requires consideration of radiative heat transfer – in the presence of steam. These radiative phenomena include (i) energy transfer within the gas mixture and (ii) between the gas and surrounding structures. Preliminary calculations carried out for these types of experiments within the OECD/NEA HYMERES-2 project with the CFD code containmentFOAM using a Monte Carlo solver for thermal radiation, demonstrated that the radiative heat transfer is significant even for very small amounts of vapour in the range of ≈0.1 % to ≈2 %. For this reason, the test matrix was tailored to the two opposite extremes: either gas compositions with a low vapour/steam content, where radiative heat transfer can be neglected, or gas mixtures with higher vapour contents, so that radiative heat transfer plays a dominant role. For the selected experiments of the H2P2 series and the corresponding CFD calculations, a vessel with a diameter of 4 m and a height of 8 m was preconditioned with different air-vapour mixtures (a) at room temperature and (b) elevated temperatures. A stable helium layer was then built-up in the upper part of the vessel. The gas was then compressed by injecting helium from above which resembles with best efforts a compression with a piston in a cylinder. This results in a height-dependent and transient increase of the gas temperature. These experiments and the associated CFD calculations were developed to isolate the phenomena of thermal radiation as good as possible from convective and diffusive effects – within the always present experimental limitations. For the reference experiment with ‘dry conditions’ corresponding to the lowest experimentally possible humidity of ≈0.1 %, we show that the use of a model without radiation provides the best agreement between the experimental and numerical results. For the much higher steam content of ≈60 %, the statistical narrow band correlated-k model (SNBCK), non-gray gas model, is the best candidate for future calculations – with computationally forgivable additional effort. We also provide with the Filtered Rayleigh Scattering technique (FRS) an outlook for a possible future instrumentation approach to better meet the requirements of the CFD community.

Experimental investigation of hydrogen enriched natural gas combustion with a focus on nitrogen oxide formation on a semi-industrial scale

Combustion of hydrogen-enriched natural gas is a valuable short-term strategy for reducing CO2 emissions from high temperature industrial heating. This paper presents several experiments on combustion characteristics and the formation of nitrogen oxides. The experiments included hydrogen contents up to 100% and fuel heat inputs up to 75 kW. Water-cooled lances were used to influence the furnace temperature. The analysis includes the distribution of furnace temperatures, the composition of flue gas, the cooling capacity of the lances under steady-state operating conditions, and OH*-chemiluminescence imaging of the near burner region. The presented results demonstrate the dependence of furnace conditions and NOX formation on various factors, such as different air inlet fluxes, furnace temperature, and fuel composition, for constant heat inputs. Efficiency increased by up to 5.5% and significant changes in flame shaped along with a maximum increase in NOX emissions when comparing natural gas to hydrogen was measured at 167%.

Oxygen Distribution at the Hot Spot in BOF Steelmaking

The distribution of oxygen between the gaseous and liquid oxidation products at the hot spot is modeled. The simplified model accurately describes the interaction of the gas jet exiting the lance nozzles with the gaseous surrounding of the jet. This interaction changes the chemical composition of the gas jet influencing the subsequent interaction with the hot spot. The iterative procedure then calculates the chemical composition of the gas exiting the cavity. The characterization of the exiting gas flowing past the lance head as well as the generation rate of FeO is attained by combining the modeled gas composition exiting the cavity with an oxygen mass balance based on a quasi-stationary BOF operation.

Ionic liquid-ethanol mixed solvent design exemplified for the decarbonization of shale gas and biogas

Shale gas and biogas, recognized as “clean” energy sources, hold the potential to replace fossil fuels, necessitating efficient decarbonization processes. This study proposes a mixed solvent, combining ionic liquid (IL) and ethanol, for a cost- and energy-effective decarbonization approach. Initially, a computer-aided molecular method optimizes the IL molecule structure, identifying 1-hydroxy-3-methyl-pyridinium trifluoroacetate ([OHMPY][CF3COO]) through solving a formulated mixed-integer nonlinear programming (MINLP) problem. The [OHMPY][CF3COO]-ethanol mixed solvent's performance is validated in shale gas and biogas decarbonization across diverse gas compositions and feed conditions. A comprehensive comparison with the traditional MDEA-based CO2 removal process is conducted, evaluating energy, economic, and environmental aspects. Results indicate that the [OHMPY][CF3COO]-ethanol decarbonization process offers 30.65%-41.48% power savings, a 3.68%-17.18% reduction in investment costs, and an 18.08%–22.45% decrease in CO2 emissions. These findings underscore the significant potential of the proposed IL-ethanol binary mixed solvent in decarbonization processes.

Influence of various gases and water vapors on the processes of tritium release from two-phase lithium ceramics

The processes of tritium generation and release in lithium-ceramic breeder blankets are affected by many factors, for example, the presence of impurities in the purge gas. As was shown earlier, oxygen, water vapor and hydrogen have the greatest influence on gas release from lithium ceramics. Hydrogen is planned to be specifically added to the purge gas mixture in breeder blanket to facilitate tritium release.The paper presents data of reactor experiments on irradiation of two-phase lithium ceramics (65 mol% Li4SiO4 /35 mol% Li2TiO3) under conditions of supplying various gases and water vapor into the chamber with samples.We analyzed the sections of experiments in which sequential, step-by-step injection of water, oxygen, hydrogen and deuterium vapors into a continuously pumped chamber with samples at steady-state quasi-equilibrium release of tritium from ceramics was carried out. Using a mass spectrometer, the gas composition in the chamber and, in particular, the release features of tritium-containing molecules, were recorded. Based on the obtained data, the mechanisms of tritium interaction with the investigated gases and water vapor on the ceramic surface were determined, as well as their influence on the processes of tritium release from ceramics.

Effect of syngas recirculation in the pyrolysis zone on the rice husk gasification process using the downdraft reactor

As one of the world's largest rice producers, Indonesia has an abundance of rice husk as a byproduct of rice milling. Rice husks were utilized to examine downdraft gasification with syngas recirculation system. This study attempts to produce better syngas than conventional downdraft gasifier. With an equivalency ratio of 0.20, syngas was recirculated into the reactor in the pyrolysis zone with valve openings at 25%, 50%, and 75%. This study determined the syngas recycling ratio that maximizes H2 and CO gas and decreases tar. Increasing the syngas recirculation valve (25%, 50%, and 75%) accelerates flame propagation and pyrolysis zone temperature. Syngas study showed no recirculation condition produces the maximum CO2 and CH4. Different recirculation valve openings little affect CO and CH4 gas composition. The H2 gas composition demonstrates that valve openings significantly change H2 gas generation and that the peak was at 50% syngas recirculation. Tar content decreased to 30% and 35% at 50% and 75% valve openings. Based on H2/CO comparison and tar concentration, 50% opening syngas recirculation became the optimum case.

Coal conversion to SNG: Thermochemical insights through kinetic-free modeling in entrained flow gasifier

In this study, a kinetic-free thermodynamic equilibrium model consisting of five units was developed to predict SNG production via coal gasification, using two distinct feeding technologies (SFT and DFT) and two coal ranks (BT and BL) in an entrained flow gasifier using Aspen Plus (V10), and comparing results with empirical data. The alignment between simulation outcomes and experimental observations is verified, and analysis of various parameters' impacts on product gas composition and yield is conducted. Sensitivity analysis reveals consistent trends across different coal ranks. The O2/coal ratio emerged as a key factor, demonstrating notable effects on syngas composition and yield. Specifically, increasing the O2/coal ratio from 0.3 to 1.0 enhanced H2 and CO2 proportions in the syngas which are beneficial for SNG production, as hydrogen is a key component for SNG. Elevating the O2/Coal ratio from 0.2 to 0.6 (optimal) favors CGE, facilitating high-quality syngas production. Additionally, increasing the CO2 flow rate up to 3 ton/hr improves the HHV of syngas, beyond which HHV declines. Raising the W/C ratio from 0.3 to 1.0 leads to decreased HHV for BL and BT coal. Additionally, increasing the W/C ratio from 0.3 to 1.0 decreases HHV. Therefore, it is crucial to undergo the production of SNG within the optimal ranges, and these findings provide crucial insights into optimizing gasification parameters for enhanced syngas production across various feed technologies and coal types to produce desired syngas results.

Synergistic effect of green trace K2CO3 and CO2 activation of zhundong coal for high-performance supercapacitors

Porous activated carbons prepared by green trace K2CO3-assisted CO2, H2O, and CO2/H2O activated high-alkali Zhundong coal are being employed as supercapacitor electrode materials. Effects of trace K2CO3 (2 wt% of carbon precursor) and gas composition on physicochemical structure, the morphology and supercapacitor properties of the active carbon are investigated in detail. The results are showing that activated carbon from trace K2CO3-assisted CO2 activation exhibited excellent performance, indicating that CO2 and K2CO3 have synergistic effect in the activation process. It is mainly due to the higher O content in CO2/N2 atmosphere and promotion by K of O transfer from CO2 to the carbon matrix, which produces more active sites. Trace K2CO3-assisted CO2 activated carbon forms a forked hierarchical pore structure, more oxygen-containing functional groups, increases surface free energy of porous carbon, more potassium-containing group structures, and excellent graphitization of amorphous carbon compared with the other carbons. Its corresponding electrode and symmetrical supercapacitor achieve specific capacitance of 277.7 and 114.5 F g−1, respectively. The energy density is 10.54 Wh kg−1 at 209.98 W kg−1 and the material retained 95.89% after 10 000 cycles. A novel method of green trace K2CO3-assisted CO2 activation of high-alkali Zhundong coal is proposed for high-performance supercapacitors.

Post-harvest Biotechnology or Genetic Engineering Solutions: Extending Shelf Life and Reducing Food Waste

Post-harvest losses and food waste have become critical challenges in the global food supply chain, contributing to economic losses, environmental degradation, and food insecurity. This article explores the innovative applications of post-harvest biotechnology and genetic engineering as promising solutions to address these issues by extending the shelf life of perishable products and minimizing food waste. Advancements in genetic engineering techniques have paved the way for the development of crops with enhanced resistance to pests, diseases, and environmental stresses. Additionally, the manipulation of genes associated with ripening and senescence has allowed scientists to engineer fruits and vegetables with extended shelf life. These genetically modified organisms (GMOs) exhibit improved post-harvest characteristics, providing a longer window for transportation, storage, and consumption. Biotechnological interventions also include the use of biocontrol agents and beneficial microorganisms to suppress post-harvest pathogens, thereby reducing spoilage and decay. The development of bio-preservatives, such as antimicrobial peptides and natural compounds, offers an eco-friendly alternative to traditional chemical preservatives, contributing to both food safety and sustainability. Furthermore, the integration of smart packaging technologies with genetic modifications enhances the monitoring and control of environmental conditions during storage and transportation. Intelligent packaging materials equipped with sensors can detect changes in temperature, humidity, and gas composition, enabling real-time adjustments to prolong the freshness of perishable goods.

Experimental study of gas composition in the equilibrium state of a light alkane combustion reaction

Oil field-associated gas is typically a mixture of light alkanes. To ensure production safety, it is essential to investigate the combustion characteristics and the reaction mechanism of light alkane gas mixtures to uncover the underlying mechanisms of the combustion reaction. This paper investigates the equilibrium gas component concentrations resulting from the reaction of a gas mixture of methane, ethane, and propane at specific ratios through experimental tests. The study's results demonstrate that the equilibrium concentrations of methane, ethane, and propane initially decrease and then increase with the rise of the equivalence ratio under the same initial pressure conditions. In oxygen-poor conditions, the equilibrium concentration ratio of methane gradually increases in proportion to the equilibrium ratio, confirming that ethane and propane are the preferred participants in the reaction. Furthermore, a study of the equilibrium concentration of the critical intermediate product, ethylene, revealed that it does not completely oxidize in the combustion reaction. It can persist under both oxygen-rich and oxygen-poor conditions, with an equilibrium concentration of approximately 0.02%. The findings of this paper can serve as a theoretical supplement to the research on explosive gas combustion and explosions.

Carbon and energy balance of biotechnological glycolate production from microalgae in a pre-industrial scale flat panel photobioreactor

Glycolate is produced by microalgae under photorespiratory conditions and has the potential for sustainable organic carbon production in biotechnology. This study explores the glycolate production balance in Chlamydomonas reinhardtii, using a custom-built 10-L flat panel bioreactor with sophisticated measurements of process factors such as nutrient supply, gassing, light absorption and mass balances. As a result, detailed information regarding carbon and energy balance is obtained to support techno-economic analyses. It is shown how nitrogen is a crucial element in the biotechnological process and monitoring nitrogen content is vital for optimum performance. Moreover, the suitable reactor design is advantageous to efficiently adjust the gas composition. The oxygen content has to be slightly above 30% to induce photorespiration while maintaining photosynthetic efficiency. The final volume productivity reached 27.7 mg of glycolate per litre per hour, thus, the total process capacity can be calculated to 13 tonnes of glycolate per hectare per annum. The exceptional volume productivity of both biomass and glycolate production is demonstrated, and consequently can achieve a yearly CO2 sequestration rate of 35 tonnes per hectare. Although the system shows such high productivity, there are still opportunities to enhance the achieved volume productivity and thus exploit the biotechnological potential of glycolate production from microalgae.

Validation of a New Method for Continuous Flare Combustion Efficiency Monitoring

A new method is described for calculating flare combustion efficiency (CE) and destruction and removal efficiency (DRE) using a numerical parametric model. The method combines key variables that affect flare performance including the flare vent gas net heating value (NHV), flare design, flow rate, exit velocity, and inert gas composition, alongside the environmental influence of crosswind speed. Each effect is characterized using a parametric model derived from experimental testing data and computational fluid dynamics (CFD). The inclusion of CFD allows the model to be extended into the high-wind conditions that cannot be adequately controlled for in empirical testing yet represent some of the most challenging conditions in which to maintain good combustion. This new parametric model method (PMM) is coupled with ultrasonic flowmeters from which the molecular weight and net heating value of the flare gas can be derived using the vent gas speed of sound measurement. In doing so, this method provides a reliable continuous flare combustion efficiency measure that can be deployed at scale with minimum hardware updates. The system was verified using an extractive sampling method with tests conducted on three full-scale industrial flares including non-assisted, single-arm pressure-assisted, and multi-arm pressure-assisted flare designs. A total of seventy valid test points were carried out with varying flow rate and flare gas heating value, covering a CE range from 46–100%. The uncertainty of the method was assessed using both traditional error propagation and Monte Carlo methodology. The results from the new method agree with the extractive method to within 0.8% in the ≥98% DRE region where flares are expected to operate to limit the impacts of flaring as a source of methane as a greenhouse gas. Uncertainty analysis revealed that the larger DRE discrepancy for DRE ≤ 98% correlates to the measurement uncertainties for both methods.

Reducing the impact of biomass combustion in residential units on local air quality by using innovative low-loading Pt-based heterogeneous catalyst

There are several published studies evaluating the potential of platinum and palladium-based catalysts for real flue gas purification, however, the need to reduce the mass fraction of precious metals and the effect of this process is often neglected. This study aimed to assess the influence of two catalysts on the overall flue gas composition formed during combustion in a pellet burner operated to mimic the operation of a real wood log stove. Commercial Pt–Pd-based (CAT A) and Pt-based (CAT B) catalysts with innovative sol-gel coatings and a reduced amount of active substance were used. The CO, OGC and PM conversion rates of CAT A reached 87.8%, 37.0% and 25.2%, while the removal efficiency of CAT B reached 85.8%, 37.8% and 18.8%, respectively. The decrease of organic carbon by the catalysts ranged from 28% to 49% in the case of CAT A and from 13% to 60% in the case of Cat B. The concentrations of PAHs emitted seem to indicate a less carcinogenic composition when catalytic converters are used than without these flue gas treatment units.

Coupling coarse‐grained DEM‐CFD and intraparticle model for biomass fast pyrolysis simulation and experiment validation

AbstractThe understanding of complex fluidization hydrodynamics and chemical reactions in biomass fast pyrolysis fluidized bed reactors is lacking and requires further investigation. It is urgent to develop accurate mathematical models capable of describing the complex multiphase reaction system of biomass pyrolysis. A comprehensive multiscale model based on coarse‐grained discrete element method (DEM)‐computational fluid dynamics (CFD) was developed in open‐source MFiX code. It incorporates detailed biomass pyrolysis kinetics and an intraparticle model. To validate the model, measurements were conducted in a fluidized bed pyrolyzer, including quantifying the segmental pressure drop along the height of the bed and determining the yields and compositions of gas, liquid, and solid products. The particle mixing and segregation, axial distribution and residence time, Lacey index, and pyrolysis products were investigated. The study provides experimental and theoretical foundations for designing multiphase fluidized bed reactors and advancing biomass thermochemical conversion.

The effect of CH4 addition on high-H2 syngas combustion characteristics under N2/CO2 dilution

The composition of biomass gas is complex, in order to promote the more extensive and efficient utilization of low-calorific syngas, it is necessary to master the basic combustion characteristics of low-calorific syngas under different compositions. In this paper, the effects of addition of CH4 (0% – 20%) on the combustion characteristics of laminar flow flame of high-H2 syngas (H2:CO = 3:1) were studied by experiments and numerical simulations under the dilution of N2 and CO2 (40%). The laminar burning velocity (LBV) and Markstein length are obtained by experiments. CHEMKIN-PRO software package was used to compare the prediction results of the four mechanisms with the measured data. Finally, GRI3.0 mechanism was selected as the simulation mechanism in this paper. The experimental results indicate that the LBV of N2 dilution is higher than that of CO2 dilution, and the flame is more stable, with adding CH4, the LBV of syngas mixtures is decreased, and the LBV of rich-fuel mixtures is decreased faster, but the stability of premixed flames of syngas is improved. Numerical simulation shows that the dominant branch chain reaction changes from R99 to R38 after CH4 is added, and the mole fraction of H, O decreases while the mole fraction of OH, CH3 increases. The dilution of CO2 results in a lower concentration of active radicals than N2 because CO2 inhibits the important reaction R99. The GRI 3.0 mechanism was used to simulate the formation of NO: the addition of CH4 promoted the formation of hot NO. The NO production of NNH and N2O intermediate mechanism is decreased, and a new way of N2 and CH reaction to HCN is increased. The dilution of CO2 can reduce NO emission more than that of N2. The insights gained from this study have practical implications in a variety of production applications. For example, optimizing mixture equivalence ratios can improve combustion efficiency, thereby increasing energy efficiency and reducing environmental emissions.

Nitrogen isotopes of released gas from rock crushing and implications to origins of molecular nitrogen in Lower Cambrian overmature shale gas in South China

The origin and formation mechanism of N2-rich Lower Cambrian shale gas remain ambiguous, posing serious exploration risks in the Lower Cambrian shale gas in South China. In this study, high-vacuum-pulsed electromagnetic and helium-filled ball-mill rock-crushing methods were developed to measure the released gas contents, compositions and nitrogen isotopes of N2 in shale-crushed gas from Lower Cambrian organic-rich shales in South China. Key factors in N2 enrichment in shale gas and its origins were investigated. Results showed that mineral compositions and thermal maturity affected the contents and compositions of shale-crushed gas. Carbonate cementation, and feldspar dissolution and reprecipitation, formed isolated pores filled with migrated bitumen and thus generated high gas contents with larger CH4/N2 ratios of shale-crushed gas. The thermal maturation of Lower Cambrian organic-rich shale can be further divided into the early and late stages of overmaturation with a boundary of 3.4–3.5%EqVRo. The contents and CH4/N2 ratios of shale-crushed gas continued to increase at the early stage of overmaturation, and then a rapid decrease at the late stage of overmaturation (>3.4–3.5%EqVRo), reflecting the release of large amounts of N2 by intensified aromatization of organic matter. An empirical equation of TONb = 0.0138 × TOC with R2>0.98 was used to estimate the relative contribution of inorganic nitrogen (TINb) and organic nitrogen (TONb) to the bulk of nitrogen content in the overmature Cambrian shale. The EqVRo-δ15NN2 plot allows identification of N2 derived from thermal decomposition of ammonium-bearing clay minerals or residual kerogen. The N2 generated at the early stage of overmaturation (including at wells LX03, EYY1, SNY1 and W001-4) in Lower Cambrian shale gas is characterized by δ15NN2 values ranging from −2 to +2‰, mainly reflecting thermal deammoniation and decomposition of ammonium-bearing clay minerals. In contrast, the N2 generated at the late stage of overmaturation (DQ outcrop) in Lower Cambrian shale gas is characterized by δ15NN2 values greater than +4‰, indicating thermal cracking of pyridinic nitrogen and pyrrolic nitrogen. The N2 generated from thermal transformation of ammonium-bearing clay minerals and pyridinic nitrogen and pyrrolic nitrogen is the main source of N2-rich shale gas in the Lower Cambrian shale of South China.