Addition Of Propane Research Articles

Hydrates production with binary CO2/C3H8 gaseous mixtures (90/10, 85/15, 80/20 vol%) in batch and unstirred conditions: The role of propane on the process thermodynamics

Previous studies revealed that the addition of propane enhances the recovery of methane and the storage of carbon dioxide but, at the same time, the enclathration of propane is limited. In order to deepen the CO2/CH4 replacement mechanism in the presence of contained concentrations of propane, this research experimentally explores the formation of hydrates into an unstirred reactor with binary CO2/C3H8 mixtures at different concentrations (from 90/10 to 80/20 vol%). The lowest pressures reached within the system, together with the thermodynamic trend of both formation and dissociation processes, allowed to explain the previously mentioned low capture of propane during replacement. The results were then explained in terms of cage occupancy and molecular diameter/cavity diameter ratio.

Production of CH4/C3H8 (85/15 vol%) Hydrate in a Lab-Scale Unstirred Reactor: Quantification of the Promoting Effect Due to the Addition of Propane to the Gas Mixture

By itself, propane is capable to form hydrates at extremely contained pressures, if compared with the values typical of “guests” such as methane and carbon dioxide. Therefore, its addition in mixtures with gases such as those previously mentioned is expected to reduce the pressure required for hydrate formation. When propane is mixed with carbon dioxide, the promoting effect cannot be observed since, due to their molecular size, these two molecules cannot fit in the same unit cell of hydrates. Therefore, each species produces hydrates independently from the other, and the beneficial effect is almost completely prevented. Conversely, if propane is mixed with methane, the marked difference in size, together with the capability of methane molecules to fit in the smaller cages of both sI and sII structures, will allow to form hydrates in thermodynamic conditions lower than those required for pure methane hydrates. This study aims to experimentally characterize such a synergistic and promoting effect, and to quantity it from a thermodynamic point of view. Hydrates were formed and dissociated within a silica porous sediment and the results were compared with the phase boundary equilibrium conditions for pure methane hydrates, defined according to experimental values available elsewhere in the literature. The obtained results were finally explained in terms of cage occupancy.

Study on heat transfer characteristics of supercritical CO2/propane mixtures in vertical tube

The performance optimization of the Brayton cycle could be achieved by further investigation of supercritical CO2/propane mixtures. In this paper, the heat transfer characteristics of supercritical CO2/propane mixtures in a vertical tube are numerically analyzed. The addition of propane could reduce or even eliminate heat transfer deterioration. Compared to CO2, the wall temperature peak of CO2/propane mixtures (α = 7 %) could be reduced by 45.5 K. After the pseudo-critical temperature, the effect of heat flux on the wall temperature of CO2 is more significant than that of mixture. Further, new critical heat flux criterion and Nu correlations are proposed for supercritical CO2/propane mixtures. The correlations could accurately reproduce the trend of Nu and capture the onset of heat transfer deterioration in the upward flow. At Re = 40168–84765 and Pr = 1.2–5.4, the maximum prediction deviation of the new correlations is ±14 %. Approximately 98.4 % of the prediction deviations are within ±10 %.

Numerical analysis of wavy PCHEs in supercritical CO2/propane mixture Brayton cycle

The CO2/propane mixtures benefit the safe operation of the Brayton cycle while improving economic efficiency and mitigating environmental impacts. The performance of the heat exchanger has a significant impact on the effective operation of the cycle. However, research on heat exchangers in supercritical CO2/propane mixture Brayton cycles is still in the initial stages. The previous studies were conducted in straight-channel heat exchangers. In this paper, the thermal–hydraulic characteristics of CO2 and CO2/propane mixtures in the wavy printed circuit plate heat exchanger (PCHE) are numerically studied and compared under various operating parameters. In comparison to CO2, the fluid temperature of CO2/propane mixtures is higher, while the pressure loss is smaller. The Nusselt numbers of the cold and hot channel increase by at least 3.1% and 16.8%, respectively. Furthermore, this change becomes more pronounced as cold fluid mass flow and inlet temperature increase. The addition of propane is beneficial to the improvement of the flow and heat transfer performance of the wavy PCHE. New thermal–hydraulic correlations are proposed for these mixture-mixture wavy PCHEs. The prediction deviations of the new correlations are ± 4% for the Nusselt number and ± 2% for the Fanning coefficient.

Optical investigation of methane, ethane, or propane and diesel at low load RCCI conditions

Natural luminosity (NL) imaging diagnostics were employed to investigate the effects of natural gas (NG) components on reactivity-controlled combustion, using an ultra-low sulfur diesel fuel and three NG major components (methane, ethane, and propane). The experiments were performed in a single-cylinder heavy-duty optical compression-ignition (CI) engine at 500 bar diesel injection pressure, 1000 RPM, ∼ 6.6 bar IMEP, and ∼ 64% energy-based diesel substitution ratio. NL confirmed the premixed nature of the combustion, which started inside the squish area and propagated towards the center of the combustion chamber. The high intensity NL regions that appeared towards the end of the premixed combustion were the result of the diffusive combustion of end-of-injection fuel dribble or of the diesel fuel that condensed on the bowl window surface or accumulated in the bowl straight corners (typical of an optical engine piston). The time it took for the spatially integrated NL (SINL) to decrease from its maximum to its minimum was similar for all investigated cases, suggesting that the gas addition did not change the fraction of the diesel fuel that participated in the diffusion-controlled combustion. Differences in oxidation properties between NG components affected the RCCI combustion at these low load conditions. Propane RCCI was characterized by 1 crank angle (CA) to 3 CA more advanced combustion phasing (despite an increased ignition delay) and higher SINL compared to methane and ethane RCCI. However, as NL for the propane RCCI was lower at similar combustion phasing, it suggests that propane addition created a more stratified diesel-gas mixture, with a richer mixture inside the squish volume, supported by faster and more intense combustion compared to the other two RCCI cases. As a result, the flame speed slowed as it progressed from the squish volume towards the center of the combustion chamber, therefore the delay in capturing the premixed combustion in the NL images. The amount of fuel that burned after the premixed combustion completely engulfed the piston bowl was relatively low compared to fraction of the fuel that burned before it. Finally, the results suggest the importance of tailoring the low–high fuel reactivity ratio of the dual-fuel combustion based on the operating condition.

Explosion behaviors of hydrogen-nitrous oxide mixtures with propane addition

In the present work, the explosion of hydrogen-propane-nitrous oxide mixtures with various equivalence ratios (ϕ=0.2-2.4), propane fractions (ωC=0-1.0) and initial pressures (P0=50-100 kPa) at ambient temperature (288 K, room temperature) was experimentally performed in a standard 3.375-L cubic vessel. The maximum explosion pressure (Pmax), maximum pressure rise rate ((dp/dt)max) and explosion time (te) were obtained in light of pressure–time curves, and the normalized maximum explosion pressure (Pmax/P0) and normalized explosion time (td/te) were analyzed as well. Moreover, the adiabatic pressure (Pad) and laminar burning velocity (SL) were also calculated for argumentation. The results indicate that with the increase of ωC, Pmax and (dp/dt)max both present three characteristic variation trends for different ϕ, while the inflections of Pmax-ϕ and (dp/dt)max-ϕ transient gradually from lean to rich mixtures. Besides, te and td/te are monotonously rising with ωC, illustrating that propane addition can remarkably decelerate the explosion process. In addition, with the increase of P0, Pmax/P0 raises monotonously and is asymptotic to Pad/P0 at ωC⩽0.2, demonstrating that heat loss decreases under higher P0. Linear dependence is also found between (dp/dt)max and P0 for any composition. Furthermore, te monotonically decreases with P0, due to the flame acceleration occurring in the combustion period. In general, the presence of nitrous oxide (N2O) with a large content makes the explosion extremely unstable, and a spot of propane can dramatically alter the explosion characteristics of H2-N2O mixtures. These results will be meaningful for the development of explosion-mitigation devices and technology in case of underlying explosion and fire hazards.

Methane replacement by using CO2/C3H8 mixtures for carbon storage and enhanced methane recovery in gas hydrates

The storage of gases via hydrates formation can be enhanced with several different techniques; for instance, the addition of promoting additives helps in reducing the pressures required for the process. However, most of strategies used for gas storage cannot help during replacement processes. This article deals with the hypothesis that the usage of moderate concentrations of small – chain hydrocarbons can absolve both the purposes at the same time. In particular CO2 storage and CH4 replacement were tested with the addition of propane. Three different concentrations of propane in mixture with carbon dioxide were selected, or 0.05, 0.10 and 0.15 mf. Hydrates were formed with each of them and the results discussed in order to identify the better solution in terms of hydrates produced and, mostly, quantity of CO2 stored. The selected concentration was then used for the replacement of methane and the results discussed in order to reveal the benefits obtained in terms of both CO2 stored and CH4 recovered, in comparison with the maximum results theoretically achievable in replacement tests carried out exclusively with pure carbon dioxide.

Experimental and kinetic modeling study on propane enhancing the laminar flame speeds of ammonia

The laminar flame speeds of ammonia/propane in air were investigated in a constant volume combustion bomb at 1–5 atm, over 298–453 K, at the equivalence ratios of 0.7–1.6, with the propane in fuel varying from 0 to 90 vol%. The measured data were provided for the validity of the proposed M-NUIG model. The comparison showed that M-NUIG model could successfully predict the measured data of propane, ammonia and mixtures under wide conditions. The results showed that the addition of 20% propane can enhance the LBV of ammonia by a factor of 3 at 1 atm, 298 K. Based on kinetic analysis, NH2 is mainly consumed by the oxidation of N-contained species in NH3/air flame, and it is completely consumed through reacting with O, OH, H and HO2 in NH3/C3H8/air flame. As for the NH3/C3H8 interactions, NH can react with CH3, forming CH2NH which completely converts to HCN. HNO also reacts with CH3 to generate NO. Thus, the CN interactions are crucial to the formation of harmful emissions. Moreover, with 50% propane addition, the peak concentrations of OH and H radicals are much higher than in NH3/air flame which is the main reason for the higher LBV.

Highly efficient synthesis of cyclic carbonate with CO2 under mild condition catalyzed by deep eutectic solvents in a microreactor

The development of sustainable catalysts for the conversion of carbon dioxide into value-added chemicals is an effective way to alleviate environmental problems. This study examined the cyclic addition of epoxy propane (PO) and carbon dioxide to propylene carbonate (PC) in a microchannel using a range of imidazol-based deep eutectic ionic liquids (DEILs). By examining the effects of various operating circumstances, such as reaction temperature, operating pressure, residence time, and CO2 to PO molar ratio, the performance of the microreactor was evaluated. According to the findings, the residence time was drastically decreased, going from a few hours in a traditional stirring reactor to just over a minute in a microreactor. The yield of PC could reach 94.23%, and the space-time yield could reach 10.063 g/g/h at 80 °C, 1 MPa, and a residence time of 19 min, while they were 92.32% and 0.406 g/g/h, respectively, for 7 h in a traditional reactor under the same circumstances. It was 24.8 times higher in space-time yield for the microchannel.

The effect of 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) Addition on the physical characteristics of β-ionone liposomes

β-ionone (ION) is a cyclic terpenoid compound that demonstrates considerable potential for the prevention and treatment of cancer. However, the water solubility of β-ionone is poor and the compound demonstrates low permeability. Liposomes have been reported as increasing both qualities. In this study, the development of β-ionone liposomes was initiated by adding 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) to produce cationic liposomes as a means of enhancing binding to cancer cells. Liposomes composed of β-ionone, HSPC, cholesterol, and DSPE-mPEG2000 were prepared using the thin layer hydration method. Cellular uptake studies were carried out with HeLa cells incubated with β-ionone liposomes for two hours. The results indicated that the addition of DOTAP increased particle size and affected the spectroscopical and thermogram profiles of the liposomes, thereby confirming reduction in liposome crystallinity, while the zeta potential became positive. Moreover, the calcein release profile further showed that additional DOTAP increased both membrane fluidity and cellular uptake in HeLa cells In conclusion, adding DOTAP affected the physicochemical cationic properties of liposome and improved cellular uptake in HeLa cells.

Concentration‐Flux‐Steered Mechanism Exploration with an Organocatalysis Application

AbstractInvestigating a reactive chemical system with automated reaction network exploration algorithms provides a more detailed picture of its chemical mechanism than what would be accessible by manual investigation. In general, exploration algorithms cannot uncover reaction networks exhaustively for feasibility reasons. They should therefore decide which part of a network is kinetically relevant under some external conditions given. Here, we propose an automated algorithm that identifies and explores kinetically accessible regions of a reaction network on the fly by explicit modeling of concentration fluxes through an (incomplete) reaction network that is emerging during automated first‐principles exploration. Key compounds are automatically identified and selected for the continuation of the exploration. As an example, we explore the reaction network of the multi‐component proline‐catalyzed Michael addition of propanal and nitropropene. Our algorithm provides a mechanistic picture of the Michael addition in unprecedented detail.

Experimental and numerical study on the ignition delay times of methane/propane mixtures diluted in carbon dioxide

Pressurized oxy-fuel combustion has gained great interest owing to its low emission and high efficiency. Methane and propane are important composition of natural gas, which is a clean fossil fuel and widely utilized for combustion applications including gas turbines. In this work, the auto-ignition properties of CH4/C3H8 mixtures in ratios from 90/10% to 70/30% diluted in CO2 were measured at pressures of 1.75 and 10 atm; equivalence ratios of 0.5, 1.0, and 2.0; and temperatures in the range of 1240–1520 K in a shock tube. Four key reactions in the Oxymech 2.0 model were updated and the modified model shows reasonable performance in both the ignition delay time and the laminar flame speed predictions in O2/N2 and O2/CO2 atmospheres. Two kinetic models (NUIG 1.0 and AramcoMech 3.0) were evaluated by present data and the laminar flame speed from the literature. The results of the experiment and calculation show that the addition of propane promotes the ignition significantly in the C3H8 proportion range from 0 to 30% in both cases of CO2 and N2, but has slight effects on the ignition with the C3H8 proportion more than 30%. The effects of CO2 on the promoting effects of C3H8 addition are slight. The ignition delay times increase with the equivalence ratio at 1.75 atm but no statistical difference is observed between the measured data of different equivalence ratios at 10 atm. The influence of C3H8 addition and the equivalence ratio on the ignition delay of CH4/C3H8 mixtures was also analyzed in detail.

Experimental studies on flame propagation and detonation characteristics of premixed nitrous oxide, ammonia, and propane in cylindrical channel

Nitrous oxide fuel blends have been identifiedas a promising propellant to be used as a hydrazine replacement. In this study, the flame propagation and detonation characteristics of nitrous oxide, ammonia, and propane mixtures were investigated experimentally in a cylindrical channel (length, 2000 mm; inner diameter, 15 mm). Tests were performed for five propane mass fractions (0, 2.0, 3.8, 5.7, and 7.4 wt%) to investigate flame behavior and determine the suitablepropellant formulation. The results demonstrated that the flame acceleration rate first increased and then decreased with additional increases of propane. The overpressures and shock velocities exhibited a similar trend and achieved the steady detonation stage except for the mixture with propane fraction of 7.4 wt%. Propane outperformed ammonia as an additive to nitrous oxide, and the addition of 2.0 wt% propane had a positive influence on the flame acceleration process, pressure, and shock buildup for premixed nitrous oxide and ammonia. However, for lower concentrations of nitrous oxide with the addition of excessive propane, a decrease in the aforementioned parameters was observed in the doped flames.

Effects of blending methane, propane, and propylene on soot evolution in ethylene diffusion flames based on optical diagnostics

Soot evolution of the ethylene-based laminar coflow diffusion flame doping with methane, propane, and propylene with the blending ratio ranging from 0 to 50% has been investigated experimentally. These fuels were selected for their different fuel structure. Spatially resolved distribution maps of the flame temperature, soot volume fraction, the fluorescence signals of polycyclic aromatic hydrocarbons (PAHs), and primary soot particle diameter and number density were determined utilizing laser-induced incandescence (LII), laser-induced fluorescence (LIF), and ratio pyrometry (RP). It was found that the flame height surged and the flame temperature dropped dramatically when the propylene blending ratio was 20% while they were almost constant with the increasing addition of methane or propane. The soot/PAHs loading decreased monotonically with the addition of methane and the opposite was true in the cases of blending propylene. The synergistic effect of mixing propane into ethylene was found on both the soot/PAHs loading. The same trends were observed in the percentage of carbon conversion to soot and the primary soot particle diameter. It can be seen from the soot evolution analysis that methane addition suppressed the soot nucleation and surface growth simultaneously. The enhanced soot surface growth for the flames doping with propane at a low addition level and for the whole flame sets doping with propylene were attributed to the earlier inception time and the longer mass growth time. The preferential diffusion and weakened oxidation of soot particles because of the decreased flame temperature perhaps accounted for the transition from a non-smoking flame to a smoking flame when the propylene blending ratio was greater than 40%.

Equilibrium conditions of CO2+C3H8 hydrates in pure and saline water solutions of NaCl

Gas hydrate formation and dissociation have been extensively studied in past decades after introducing hydrate-based technology in the energy and environmental fields. Among all, hydrate-based water desalination (HBWD) has been receiving significant attention because of the shortage in water resources. The present study investigates the equilibrium conditions for gas hydrate formation from propane and carbon dioxide gas mixtures in the presence of pure water and low saline aqueous solutions for the first time. According to the carried out sensitivity analysis on thermodynamic equilibrium conditions of the CO2+C3H8 mixture with different mole fractions of propane (5–50% C3H8 + balanced CO2) it was concluded that the addition of propane above 20% did not significantly affect the hydrate equilibrium condition. Experiments have been carried out with an initial gas molar composition of 20% C3H8 and 80% CO2 in a temperature range of 275.15–280.15 K, at isochoric conditions for the first time. The inhibition effect on the equilibrium conditions is reported in the case of NaCl addition (1, 1.5, 2, and 3 wt%). A reasonable agreement between the experimental data and those calculated from the thermodynamic model applied in this study has been obtained. According to the tests results, the coefficient of determination (R squared) of the final results of the conducted tests and the model predictions are 0.9987 and 0.9950 for pure and saline water, respectively.

Effect of biostimulation and bioaugmentation on biodegradation of high concentrations of 1,4-dioxane.

1,4-Dioxane is a pervasive and persistent contaminant in numerous aquifers. Although the median concentration in most contaminant plumes is in the microgram per liter range, a subset of sites have contamination in the milligram per liter range. Most prior studies that have examined 1,4-dioxane concentrations in the hundreds of milligrams per liter range have been performed with industrial wastewater. The main objective of this study was to evaluate aerobic biodegradation of 1,4-dioxane in microcosms prepared with soil and groundwater from a site where concentrations range from ~ 1500mg·L-1 in the source zone, to 450mg·L-1 at a midpoint of the groundwater plume, and to 6mg·L-1 at a down-gradient location. Treatments included biostimulation with propane, addition of propane and a propanotrophic enrichment culture (ENV487), and unamended. The highest rates of biodegradation for each location in the plume occurred in the bioaugmented treatments, although indigenous propanotrophs also biodegraded 1,4-dioxane to below 25µg·L-1. Nutrient additions were required to sustain biodegradation of propane and cometabolism of 1,4-dioxane. Among the unamended treatments, biodegradation of 1,4-dioxane was detected in the mid-gradient microcosms. An isolate was obtained that grows on 1,4-dioxane as a sole source of carbon and energy and identified through whole-genome sequencing as Pseudonocardia dioxivorans BERK-1. In a prior study, the same strain was isolated from an aquifer in the southeastern United States. Monod kinetic parameters for BERK-1 are similar to those for strain CB1190.

Comparison of natural gas and propane addition to combustion air in terms of engine performance in compression ignition engine

This study aims to examine and compare the effects of natural gas and propane addition to the combustion air of diesel engines on engine performance. Engine tests were carried out at four different loads, 25%, 50%, 75%, and 100%, at 1500 rpm and 2000 rpm. Natural gas and propane have been added separately to the combustion air and sent to the cylinders at 250 g/h and 500 g/h mass flow rates. The results obtained through measurements and calculations (cylinder pressure and temperature, fuel consumption and emissions) have been presented in detail. When the experimental results were examined, maximum pressure of approximately 59 bar was obtained using 500 g/h natural gas at 50% load and 1500 rpm. In terms of BSFC, the best results were obtained at 1500 rpm and full load, and by adding 250 g/h and 500 g/h natural gas to the combustion air, 20% and 21% reduction in BSFC was achieved, respectively, as compared to diesel fuel combusted alone. In the same conditions, by adding 250 g/h propane to the combustion air, approximately 15% reduction was achieved compared to diesel fuel. With the addition of 500 g/h propane at 1500 rpm and 25% load, a 57% reduction in NOx emission was achieved. A 56% reduction in NOx emission was observed with the addition of 500 g/h propane at the same load condition and 2000 rpm.

Results of studies of the direct current generator of low-temperature nitrogen-propane plasma

The effect of propane-butane addition to the plasma-forming gas on the state of cathodes with inserts made from lanthanated tungsten and hafnium is investigated. With a small propane addition (1%), the restorative effect of the insert material is noted, and the propane consumption has an upper limit when it is introduced together with the plasma-forming gas (no more than ∼ 73% of the plasma-forming gas consumption), below which the arc stability is not disturbed.

Effect of steam addition and distance between inlet nozzles on non-catalytic POX process under MILD combustion condition

Moderate or intensive low-oxygen dilution (MILD) combustion is a novel combustion technology with high efficiency and low emissions. Few studies have been performed on the application of this technology for partial oxidation processes. In this research, a Computational Fluid Dynamics study for the effect of different parameters on the natural gas partial oxidation under MILD combustion conditions has been carried out. The combustion chamber was in the form of cylinder with a diameter of 300 mm and a length of 1500 mm. The effect of parameters such as different kinetic mechanisms, adding ethane and propane to methane (shale gas feed), adding steam to the feed and distance (interval) between methane and oxygen nozzles were investigated. Results showed that addition of ethane and propane to methane increased the mole fraction of CO and C2H2 so that, in the case of mixed methane with ethane and propane compared to the case of pure methane, an increase of 18.75% and 12.93% was observed for CO and C2H2, respectively. In addition, with increasing the percentage of steam in the inlet feed at a constant flow rate, methane conversion increased so that it in the case of 30% inlet steam was 77.17%, which showed 11% promotion compared to the pure methane case. Also, increasing the distance between the fuel and oxidizer nozzles led to an increase in the maximum temperature in the combustion chamber.

Development of Natural Gas Chemical Kinetic Mechanisms and Application in Engines: A Review.

In this paper, the brief development of chemical kinetic modeling of natural gas is discussed, with emphasis on the development of chemical kinetic mechanisms describing fuel oxidation. The addition of ethane and/or propane to natural gas not only decreases the ignition delay times but also increases flame speeds. Thus, the mixture of methane, ethane, and propane rather than bare methane obtains more accurate predictions for the combustion and emission characteristics of natural gas. This paper also evaluates different comprehensive mechanisms employed for natural gas engines and pointed out their advantages and disadvantages, giving guidance for the selection of mechanisms during the development of natural gas engines.