Effluent Gas Composition Research Articles

A dynamic control strategy for improving combustion chamber sweep efficiency during the in-situ combustion

Combustion chamber extension is closely associated with oil production efficiency and ultimate oil recovery during in-situ combustion (ISC) process. However, the effective method for controlling combustion chamber extension is is still being explored. This work proposes a novel measure to modify the unfavorable expansion behaviors of combustion chamber while minimizing the impact on variations in pressure difference and combustion stability, and it is implemented by the production well intermittent shutdown (PWIS) method in the heterogeneous porous medium. The variation of effluent gas compositions, spatial distribution of coke zone, swept area of combustion chamber, burning stability, and pressure difference are studied. The results show that the combustion chamber and coke zone develop uniformly and their expansion volume in low and medium permeability regions enlarge noticeably with the PWIS implementation. The PWIS method is able to modify the unfavorable expansion behaviors of combustion chamber with little influence on the burning state, especially as the combustion front propagated in the central section between the injector and producer. The final oil recovery factor can be enhanced by 73.8% after implementing the PWIS method. This work is of significance to the ISC field application and provides an approach to achieving a higher volumetric sweep efficiency of combustion chamber.

Effect of effluent gas composition on characteristics of graphene oxide film based relative humidity sensor

Nitrogen and synthetic air have been used as standard effluent gases in relative humidity (RH) sensing experiments, especially to characterise the dynamic sensing capabilities of RH sensors utilising graphene oxide (GO) as the sensing material. In the present work, we have used GO coated quartz crystal microbalance (QCM) as a tool to investigate the mass adsorption characteristics of samples subjected to multiple humidification-dehumidification cycles using N2 or synthetic air as the effluent gas. We identified that the residual mass adsorbed and retained by the GO film is on average 71.6% higher when using N2 in the initial humidification-dehumidification cycle and this subsequently impacted the hysteresis characteristics until the GO film saturated. To negate the impact of the effluent gas, the GO-based sample should be treated with multiple humidification and dehumidification cycles using either effluent gas.

Role of hydrogen to promote hydrate formation of flue gas mixture of CO2 and N2 in silica nanofluid of single-step origin

This study explores the role of hydrogen as doping agent to enhance CO2 hydrate formation in water and polymer (polyacrylamide, PAM) solution in the presence of varying composition of N2 (0–80 mol%). CO2 storage capacity in clathrate hydrate was explored in the presence of varying quantity of nitrogen (N2) to mimic a flue gas mixture, where N2 composition was gradually increased to simulate effluent gas composition. The silica nanofluids of varying size (35–39 nm, 0.1–1 wt%) were used to accelerate the rate of gas solubility and hydrate formation. All experiments were performed with an initial pressure of 50 bar and ambient temperature while an rpm of 350 was maintained to ensure agitation in the pot. No gas-hydrate was observed in flue gas mixture containing N2 > 45 mol% in both water and PAM solution. To induce hydrate formation in high quantity of N2, the role of hydrogen as a promoter was explored in low dosage volume (1 mol%). The inclusion of hydrogen helped to form gas hydrate for a mixture containing 50 mol% N2. Further, inclusion of silica nanoparticle (1 wt%) increased the rate of gas consumption and hydrate formation for flue gas mixture of 50 mol% N2, indicating positive effect of silica nanoparticle on hydrate formation. From the experimental data, it could be established that silica nanofluid had a positive impact on formation of CO2 hydrate. Gas consumption increased by atleast 12% during dissolution and over 25% during crystallization thus, increasing nanoparticle concentration was beneficial for stimulating gas consumption. The results indicate favorable role of SiO2 nanoparticle and hydrogen on carbon storage of impure gas mixtures exhibiting high amount of N2 (50 mol%).

Reaction model of low asphaltene heavy oil from ramped temperature oxidation experimental analyses and numerical simulations

In situ combustion (ISC) is an advanced thermal recovery technique for crude oil exploitation. The crude oil reaction models with accurate kinetic data are crucial to predict the ISC process. This study investigated the China Xinjiang crude oil reaction kinetics through Ramped Temperature Oxidation (RTO) experiments and numerical simulations. Three different ISC behaviors with low-temperature oxidation (LTO), Negative Temperature Gradient Region (NTGR) reactions and high-temperature oxidation (HTO) were observed from the RTO experiments. The effects of the air injection rate and heating rate on the temperature profile and effluent gas composition were carefully investigated. Experimental results showed that the higher air injection rate and lower heating rate enhanced the heat generation, mainly from the more intensive exothermic HTO reactions. A simplified crude oil reaction model involving LTO, NTGR, and HTO was proposed and implemented with a numerical model to simulate the RTO behaviors. This study also suggested a workflow to build the reaction scheme and calibrate the kinetic data for good predictability and generalization. Acceptable consistency was achieved between the RTO experiments and numerical simulation, which demonstrates the proposed reaction model was predictive to capture the key oxidation mechanism and reproduce the ISC behaviors of the Xinjiang crude oil.

Investigating the role of diffusion in hydrocarbon gas huff-n-puff injection- an Eagle Ford study

Fracture complexity, variation in fluid properties, variations in rock types and diffusion of gas from the fracture into the oil-saturated nano-pores are the main contributing factors in oil recovery using gas huff-n-puff injection. Limited research has been conducted to define diffusion coefficients coupled with rock tortuosity resulting in calculation of effective diffusion. The objective of this work is to conduct a comprehensive experimental and simulation study on lower Eagle Ford rock samples to measure diffusion coefficients for different injection cycles in three representative rock samples from the main flow unit.Three representative rock samples were selected based on their differences in petrophysical properties. Saturated volumes were measured using a low-field nuclear magnetic resonance (NMR) measurement and confirmed with material balance for cores saturated at reservoir conditions. Pressure was recorded during a one-day diffusion process before it was dropped linearly at the end of each cycle for production, and effluent oil and gas compositions were measured. NMR measurement was repeated at the end. Three compositional simulation models were set up for three different samples using tortuosity values from FIB-SEM analysis to simulate experimental diffusion and production. For history matching, relative permeability curves, fracture properties, and tortuosity were tuned to match pressure and production results for three representative samples.Pressure profiles vary significantly between different cycles caused by invasion of the gaseous phase into a new section of the pore network during each cycle. Effective diffusion coefficients were calculated using representative tortuosity values. Diffusion was represented by pressure drop during soaking time. This pressure drop varies across different lithofacies and for different rock samples. For produced oil, the concentration of lighter oil components declined from the first to the last cycle of gas injection while the concentration of the intermediate components increased.Gas huff-n-puff injection into shale oil reservoirs were being investigated from the point of view of diffusion and variations in rock properties for the first time and measurements were validated using numerical simulation. The huff-n-puff experiments, conducted using a constant volume diffusion cell with locally produced hydrocarbon gas and stock-tank oil, show favorable results. Recovery factors for samples A, B, and C are 57.5%, 56.7%, and 51.7%, respectively.

DYNAMIC ADSORPTION OF H2S IN A FIXED BED OF SEWAGE SLUDGE PYROLYSIS CHAR

In this work, sewage sludge char was tested as a H2S adsorbent in a fixed-bed column, at 25 °C. The char was activated physically and chemically (with HCl or KOH) to enhance textural properties. Commercial activated carbon impregnated with iron was also tested for comparison. The column was filled with 18.24 g of char and, then, fed H2S (600 ppm) under 50 mL/min. The effluent gas composition was measured via photocolorimetry and the data was used to plot breakthrough curves. A mathematical modeling was used to estimate parameters such as axial diffusivity, effective intraparticle diffusivity, and external mass transfer coefficient. The main results show that the adsorption capacities varied from 7.2 to 657.60 mgH2S/gads. The percentages of H2S adsorbed varied from 43.36 to 59.04%. HCl proved to be more efficient than KOH. Due to improved textural properties, the commercial activated carbon outperformed (69.15%, 12,527.80 mgH2S/gads) all char samples.

Isotopic Characteristics and Origins of Coalbed Gas of Sijiazhuang Mine Field in Northern Qinshui Basin

There are few studies on the origins of coalbed gas in the northern Qinshui Basin, therefore, the coalbed gas in the Taiyuan Formation of the Sijiazhuang mine field in the northern Qinshui Basin was extracted to test the chemical composition and isotope of effluent gas from six coalbed gas wells, and thus the origins of coalbed gas can be explored. The results show that the average volume fractions of CH4, C2H6, CO2 and N2 in the coal seam of the northern Qinshui Basin are 94.98 %, 0.11 %, 0.25 % and 4.8 %, respectively, with no hydrocarbons heavier than ethane detected. The carbon and hydrogen isotopic values of methane of coalbed gas are within the range of -42.5 ‰ ~ -36.7 ‰ and - 200.06 ‰ ~ -196.33 ‰, respectively; and d13C (CO2) is between -17.1 ‰ and -15.1 ‰. The solution fractionation of groundwater is the main cause of the methane carbon isotope’s becoming lighter with increasing depths. The chemical composition and isotope test data of the Sijiazhuang mine field indicate that the coalbed gas has been subjected to the secondary transformation effect, mainly from coal cracking thermo genesis and supplemented by secondary biogenesis of CH4.

ZnO and Cu-based adsorbents for biogas desulfurization at room temperature

Synthesis and structural characterization of ZnO and Cu based materials were done in order to compare chemical, morphological and microstructural effects in sorbent materials for gas-phase desulfurization reaction at room temperatures as a potential application in biogas cleaning. The materials were synthesized through two wet chemical routes, firstly using zinc nitrate, hexamethylenetetramine and NaOH reagents at 70 and 90 °C for ZnO flower-like and rod-like structures, respectively; and secondly a typical calcination of metallic copper to obtain CuO. Powder X-ray diffraction, X-ray fluorescent spectroscopy analysis were realized. Results showed a unique zincite phase for ZnO and three phases in copper samples: Cu0, Cu2O and CuO (76.3, 18.3 and 5.4 wt%). The size of crystal domains varied from 180 to 1600 nm, while the particle size varied from 660 to 1020 nm. These materials were tested in desulfurization reactions at room temperature using a fixed-bed glass reactor. In order to avoid poisoning and asphyxiation risks a non-desulfurized biogas influent was simulated by a gas mixture of N2 and H2S (100 ppm). The reactor was fed with the gas mixture at rate of 450 ml/min (GHSV 9120 h−1). The composition of effluent gas was determined using a biogas detector, coupled with an electrochemical H2S sensor. Results show that CuO and ZnO could be feasible adsorbents for the removal of hydrogen sulfide; however, they became saturated after 300 s while high surface area materials, evidenced by SEM, showed higher saturation capacity. Characterization of wasted adsorbents using electron microscopy techniques and fluorescence X-ray spectroscopy evidenced the presence of metallic sulfides at amounts less than 0.05 wt%, although no crystalline phases were detected in further analysis.

Industrial catalyst market worth $22.0 bn by 2020

A catalytic Pd76Ag19Cu5 alloy membrane reactor packed with 5% Ni/Ce0.6Zr0.4O2 catalyst was adopted in this study to investigate hydrogen production performance from the dry reforming reaction of methane and carbon dioxide. The 1:1 CH4/CO2 feed was introduced to the reactor with 60 mg of the catalyst at a flow rate of 20 ml/min at 550 °C. The effluent gas compositions were examined using an online gas chromatographer (GC). Compared to a conventional reactor without the membrane, the CH4 and CO2 conversions were significantly increased by 3.5-fold and 1.5-fold, respectively. Correspondingly, the overall H2 yield was greatly improved from about 10–35%. Additionally, the hydrogen selectivity increased from 47 to 53%. It is theorized that the in-situ partial hydrogen withdrawal by the membrane mainly caused the dry reforming reaction equilibrium to shift forward and created a hydrogen-deprived environment unfavorable for the competing reversible water-gas shift reaction to take place.

Improved hydrogen production from dry reforming reaction using a catalytic packed-bed membrane reactor with Ni-based catalyst and dense PdAgCu alloy membrane

A catalytic Pd76Ag19Cu5 alloy membrane reactor packed with 5% Ni/Ce0.6Zr0.4O2 catalyst was adopted in this study to investigate hydrogen production performance from the dry reforming reaction of methane and carbon dioxide. The 1:1 CH4/CO2 feed was introduced to the reactor with 60 mg of the catalyst at a flow rate of 20 ml/min at 550 °C. The effluent gas compositions were examined using an online gas chromatographer (GC). Compared to a conventional reactor without the membrane, the CH4 and CO2 conversions were significantly increased by 3.5-fold and 1.5-fold, respectively. Correspondingly, the overall H2 yield was greatly improved from about 10–35%. Additionally, the hydrogen selectivity increased from 47 to 53%. It is theorized that the in-situ partial hydrogen withdrawal by the membrane mainly caused the dry reforming reaction equilibrium to shift forward and created a hydrogen-deprived environment unfavorable for the competing reversible water-gas shift reaction to take place.

Performance of high temperature PEM fuel cell materials. Part 1: Effects of temperature, pressure and anode dilution

High temperature proton exchange membrane (HT-PEM) fuel cells operate most effectively at temperatures 160 °C or greater and can tolerate high carbon monoxide concentrations in fuel feeds. For practical mobile fuel cell systems, the ability to tolerate high levels of carbon monoxide enables a simplified integrated reformer fuel cell design, where a one-step reforming process can directly feed the fuel cell. This creates the potential for practical fuel cell systems to be designed that are capable of operating using an on-board hydrocarbon fuel. Hydrocarbon reforming processes (i.e., partial oxidation, steam reforming, or autothermal reforming) generate effluent gas compositions that typically contain various amounts of hydrogen, carbon monoxide, carbon dioxide, nitrogen, and water. While there are several studies that have examined the effects of CO dilution on HT-PEM fuel cell performance, there are very few that have examined the effects of other common reformate species, particularly while operating at varying temperatures and pressures. This work aims to fill the research gap in published data through evaluation of the performance exhibited by two HT-PEM membrane-electrode assembly (MEA) types, Advent's TPS©-based MEA and the BASF Celtec series MEA, based on acid-doped polybenzimidazole (PBI). In Part I of this series, the effects of temperature and pressure for various percentages of anode dilution were investigated. Temperatures and pressures were varied from 160 to 200 °C and 101.3–200 kPa, respectively. The effect of hydrogen diluted with nitrogen in the anode feed was examined with nitrogen concentrations up to 70%. Overall, the PBI MEA provided greater performance than the TPS for all tested conditions. Our results show that the performance loss due to high dilution levels can be wholly mitigated through an increase in operating temperature, pressure, or a combination thereof. For example, even at a dilution level containing 70% nitrogen, operating the cell at 200 °C and at 200 kPa provides the same power output as running the cell on pure hydrogen at 160 °C and at atmospheric pressure. This data can be used to model the performance effect of high diluent concentrations in the anode gas feed when developing an integrated reformer/fuel cell system.

A comprehensive analysis of the properties of light crude oil in oxidation experimental studies

The analysis of light crude oil for oxidation reaction experiments is a kind of important technological for evaluating an air injection project in a reservoir. In this study, the paper comprehensively analyzes the variations of Jilin crude oil composition comparing crude oil component’s variations before and after oxidation, and investigates the effluent gas composition and hydrocarbon, analyzes the mechanism of low temperature oxidation reaction (LTO), and rebuilds the light crude oil cracking reaction of intermediate component in a new pattern. In the early stage of the oxidation reaction, firstly, oxygen is captured by forming chemical bond in liquid hydrocarbon. And then oxygen takes part in the free radical chain reaction by forming hyperoxide and decomposes to ketones, aldehydes, alcohols, and so on. Meanwhile, chain scission reaction comes up. Research result shows that the intermediate components (C7–17) of crude oil make great contribution to crude oil cracking. The experimental result shows that Jilin reservoir has the potential of implementing air injection project.

Bio-fuel reforming for solid oxide fuel cell applications. Part 2: Biodiesel

Biodiesel is considered as a renewable hydrogen source for solid oxide fuel cells (SOFCs). This study contributes to a fundamental understanding of biodiesel autothermal reforming (ATR), which has not yet been widely explored in the open literature. Ultra-low sulfur diesel (ULSD) ATR is established as a baseline for this analysis. This work applies a micro-soot meter based on a photo-acoustic method to quantify the condensed carbon from a single-tube reactor, and uses a mass spectrometer to measure the effluent gas composition under different operating conditions (reformer temperature, steam/carbon ratio, oxygen/carbon ratio, and gas hourly space velocity). The key objective is to identify the optimum operating environment for biodiesel ATR with carbon-free deposition and peak hydrogen yield. Thermodynamic analysis based on the method of total Gibbs free energy minimization is used to evaluate the equilibrium composition of effluent from the reformer. The experimental investigations complimented with this theoretical analysis of biodiesel ATR enable effectively optimizing the onboard reforming conditions. This study is one component of a three-part investigation of bio-fuel reforming, also including fuel vaporization and reactant mixing (Part 1) and biodiesel–diesel blends (Part 3).

Isotope exchange between gaseous hydrogen and uranium hydride powder

Isotope exchange between gaseous hydrogen and solid uranium hydride has been studied by flowing hydrogen (deuterium) gas through packed powder beds of uranium deuteride (hydride). We used a residual gas analyzer system to perform real-time analysis of the effluent gas composition. We also developed an exchange and transport model and, by fitting it to the experimental data, extracted kinetic parameters for the isotope exchange reaction. Our results suggest that, from approximately 70 to 700kPa and 25 to 400°C, the gas-to-solid exchange rate is controlled by hydrogen and deuterium transport within the ∼0.7μm diameter uranium hydride particles. We use our kinetic parameters to show that gas chromatographic separation of hydrogen and deuterium using uranium hydride could be feasible.

Stability of In-Situ-Combustion Process to Stoppage of Air Injection

Summary Unlike steam injection for heavy-oil recovery, the in-situ-combustion (ISC)process requires an extra step--namely, the initiation of the process, theso-called ignition operation. During ignition, an ISC front is generated nearthe air-injection well and, thereafter, this front is propagated towardproduction wells. Air-injection interruptions can be unintentional orintentional, including scheduled interruptions for 1 day per month for cleaningoil from air lines exiting the compressors. Regarding air-injectioninterruptions, one question arises: Can the process be resumed withoutinitiating a new ignition operation? This paper attempts to provide answers tothis question. The paper reviews information on 10 cases of air-injectionstoppage in the field, involving well-instrumented dry ISC projects, conductedeither in patterns or in a line-drive system. Most of the cases are from theSuplacu de Barcau (Romania) project, which is the world's largest ISCcommercial project. The duration of air-injection interruptions ranged from afew hours to 42 days. Performance before and after interruptions is analyzed interms of changes in air injectivity, effluent-gas composition, and oilproduction. To support various field observations, essential results fromsimulation of the dry ISC process are also included; temperature distributionsduring air-injection stoppage were determined analytically for a linear systemand numerically for a radial system. In both cases, a specific characteristicof the temperature redistribution was noted: the move/shift of the peaktemperature inside the former burned-out zone. Some additional conclusionsregarding the stability of the process as a function of elapsed time since theinitiation of the process were also formulated. Stability of the process wasinvestigated for air-injection interruptions lasting up to 40 days.

Effects of an environmentally-friendly, inexpensive composite iron–sodium catalyst on coal gasification

The objective of this research is to study the effect of the composite catalyst, FeCO3–Na2CO3, on gasification of a low-sulfur sub-bituminous Wyodak coal from the Powder River Basin (PRB) of Wyoming. The catalytic effects of the composite catalysts were evaluated by comparing their effluent gas compositions and carbon conversion kinetics to those achieved in the presence of either FeCO3 or Na2CO3 catalyst alone or without the presence of any catalyst. All of the evaluation work was conducted in a fixed bed gasifier at atmospheric pressure. Compared to raw coal with no catalyst, the composite catalyst is efficient in increasing the carbon conversion rate constant by as much as two times within the 700–800°C range due to its ability to reduce the activation energy of gasification by about 30–40%. Compared to pure sodium and iron catalysts, the composite catalyst can increase the yields of desired products H2 and CO at 800°C by 15% and 40%, respectively. The composite catalyst can not only synergize the advantages, but also overcome the challenges of pure iron or pure sodium based catalytic coal gasification processes.

Measurement and analysis of carbon formation during diesel reforming for solid oxide fuel cells

Experiments and equilibrium analysis were conducted to study carbon formation during diesel reforming for a solid oxide fuel cell-based auxiliary power unit (APU) application. A photo-acoustic instrument provided direct measurements of solid carbon concentration in the reformer effluent stream, which could be correlated to reformate gas composition (as determined via mass spectrometer) and reformer temperature. These measurements were complimented by equilibrium calculations based upon minimization of total Gibbs free energy. It was determined that oxygen-to-carbon ratio (O/C), fuel utilization fraction and anode recycle fraction all influence the degree of carbon formation, and that once significant carbon concentration is measured, the reformer performance begins to show marked degradation. At a fixed operating point, lowering the reformer temperature produced by far the largest change in effluent carbon concentration. Systematic variation in O/C, fuel utilization and anode recycle revealed the interdependence among reformer temperature, effluent gas composition and carbon concentration, with a strong correlation between carbon and ethylene concentrations observed for [C2H4] > 0.8%. After each experiment, baseline reformer performance could be recovered by operation under methane partial oxidation (POx) conditions, indicating that reformer degradation results at least in part from carbon deposition on the reformer catalyst.

A novel method for sulfonation of microporous polystyrene divinyl benzene copolymer using gaseous SO 2 in the waste air streams

In this study a novel sulfonation method for microporous polystyrene divinyl benzene copolymer (PSDBP) was introduced. In our sulfonation system gaseous SO 2 is used as the sulfonation agent and planned to be obtained from waste gas streams. The proposed method, therefore, combines SO 2 control and clean sulfonation technology in a single compact design. Molded polymeric monoliths of the PSDBP containing imprisoned H 2O 2 solution inside the pores ( PSDBP H 2 O 2 ) were produced in disk shapes. Dry gas mixture containing 3000 ppm SO 2 is fed into PSDBP H 2 O 2 disk reactor with a flow rate of 0.8 L/min and effluent gas composition in terms of SO 2 was measured. Breakthrough curves for varied initial H 2O 2 amount were used to calculate SO 2 adsorption capacity and sulfonation degree of the PSDBP H 2 O 2 disks. Successful sulfonation of PSDBP H 2 O 2 was verified by the changes in its morphological structure and formed sulfone bonds determined by SEM and IR analyses, respectively. Maximum adsorption capacity for PSDBP H 2 O 2 for the initial H 2O 2 volume percentage of 13% was determined as 57 mg SO 2/g polymer. It should be noted that SO 2 adsorption was observed only in H 2O 2 imprisoned polymer disks. Sulfonation degree of PSDBP H 2 O 2 which attained maximum SO 2 amount is calculated as 10%.

Hydrogen production by steam reforming of ethanol over an Ir/CeO 2 catalyst: Reaction mechanism and stability of the catalyst

Steam reforming of ethanol over an Ir/CeO 2 catalyst has been studied with regard to the reaction mechanism and the stability of the catalyst. It was found that ethanol dehydrogenation to acetaldehyde was the primary reaction, and acetaldehyde was then decomposed to methane and CO and/or converted to acetone at low temperatures. Methane was further reformed to H 2 and CO, and acetone was directly converted into H 2 and CO 2. Addition of CO, CO 2, and CH 4 to the water/ethanol mixture proved that steam reforming of methane and the water gas shift were the major reactions at high temperatures. The Ir/CeO 2 catalyst displayed rather stable performance in the steam reforming of ethanol at 650 °C even with a stoichiometric feed composition of water/ethanol, and the effluent gas composition remained constant for 300 h on-stream. The CeO 2 in the catalyst prevented the highly dispersed Ir particles from sintering and facilitated coke gasification through strong Ir–CeO 2 interaction.

Autothermal reforming of ethanol for hydrogen production over an Rh/CeO 2 catalyst

Hydrogen production from ethanol by autothermal reforming over an Rh/CeO 2 catalyst was investigated with a stoichiometric feed composition. Ethanol as well as the reaction intermediates like acetaldehyde and acetone was entirely converted to hydrogen and C1 products at 673 K, and methane steam reforming and reverse water gas shift were the major reactions above 823 K. The Rh/CeO 2 catalyst exhibited stable activity and selectivity during 70 h on-stream operation at 823–923 K without obvious deactivation evidenced by the constant effluent gas composition. Structural analysis of the used catalyst revealed that CeO 2 prevented effectively the highly dispersed Rh particles with sizes of 1–3 nm from sintering and thus maintained sufficient Rh–CeO 2 interfacial areas, which facilitated coke gasification through the high oxygen storage-release capacity.