Air Equivalence Ratio Research Articles

Experimental and simulation study on lean combustion characteristics of passive pre-combustion chamber ignition boosted GDI engine

In order to verify the potential application of passive pre-combustion chamber technology in commercial GDI engines, the efficiency characteristics, combustion characteristics (CA50, Knock Index and COV) and emission characteristics of a pre-combustion chamber ignition engine in a boosted environment were studied by three-stage injection strategy to form a lean burn environment (λ = 1.3). A 3D simulation model of pre-combustion chamber ignition engine is established. Combined with the engine bench test results, the process of intake, mixture formation, combustion and emission generation under different working conditions is simulated by simulation method. The development process of TKE (turbulent kinetic energy), air-fuel ratio, temperature and combustion emissions in the main/pre-combustor is studied. It is found that under high load conditions in boosted pre-combustion chamber engine, the average knock index can be controlled between 2 and 3.4 bar, and the COV can be controlled between 3% and 3.5%. The indicated thermal efficiency reaches over 40% within the load range of IMEP from 10 to 14 bar. When the load increases, NOx and soot emissions show a downward trend, the HC and CO emissions slight increase. The pre-combustion chamber engine exhibits a tumble intake pattern around the cylinder axis perpendicular to the cylinder axis. The TKE reaches its maximum value 20 CAD before the top dead center and then rapidly decreases. The use of a three-injection strategy can form a uniform stratified mixture at the ignition moment. The fuel air equivalence ratio in the ignition area of the pre-combustion chamber is 0.8–0.9, slightly higher than the average fuel air equivalence ratio of 0.75.

Component-based equilibrium modeling of biomass fixed-bed gasifier

In this paper, the process of gasification of rice husk directly with air in a fixed-bed gasifier was modeled using Aspen Plus. Unlike traditional models based on the elemental balance method, this study modeled the decomposition of rice husk into cellulose, lignin, and hemicellulose based on experimental data from the pyrolysis equipment, and the product yields were fitted to obtain the distribution of product yields in the pyrolysis stage of rice husk. In the redox stage, the thermodynamic equilibrium calculation model and the kinetic calculation model were used for the simulation, respectively, and compared and analyzed with the actual plant operation data. In the simulation of the thermodynamic equilibrium calculation model, the error of gas yield was about 5%. While in the kinetic calculation model, the errors of gas production rates of N2, H2 and CH4 were within 5%, the errors of CO and CO2 were larger, which were 13.73% and 17.09%, respectively. The error of the yield of Bio-char, an additional product of gasification, is about 2% in both models, which is close to the actual working conditions. Based on the model, the effects of gasification temperature, air equivalent ratio (ER) and air preheating temperature on the gasification reaction were discussed in this paper. The results concluded that the gasification temperature should be maintained at about 800 °C, the air equivalent ratio at about 0.3, and the air preheating temperature should be increased appropriately when performing rice husk gasification.

Aspen Simulation Study of Dual-Fluidized Bed Biomass Gasification

This article establishes a thermodynamic model of a dual-fluidized bed biomass gasification process based on the Aspen Plus software platform and studies the operational control characteristics of the dual-fluidized bed. Firstly, the reliability of the model is verified by comparing it with the existing experimental data, and then the influence of different process parameters on the operation and gasification characteristics of the dual-fluidized bed system is investigated. The main parameters studied in the operational process include the fuel feed rate, steam/biomass ratio (S/B), air equivalent ratio (ER), and circulating bed material amount, etc. Their influence on the gasification product composition, reactor temperature, gas heat value (QV), gas production rate (GV), carbon conversion rate (ηc), and gasification efficiency (η) is investigated. The study finds that fuel feed rate and circulating bed material amount are positively correlated with QV, ηc, and η; ER is positively correlated with GV and ηc but negatively correlated with QV and η; S/B is positively correlated with GV, ηc, and η but negatively correlated with QV. The addition of CaO is beneficial for increasing QV. In actual operation, a lower reaction temperature in the gasification bed can be achieved by reducing the circulating bed material amount, and a larger temperature difference between the combustion furnace and the gasification furnace helps to further improve the quality of the gas. At the same time, GV, ηc, and η need to be considered to find the most optimized operating conditions for maximizing the benefits. The model simulation results agree well with the experimental data, providing a reference for the operation and design of dual-fluidized beds and chemical looping technology based on dual-fluidized beds.

Modelling and Simulation of Co-Gasification of Chlorella Vulgaris and High-density Polyethylene Using Aspen Plus

A technical innovation that holds promise for producing renewable fuel and decreasing waste disposal is the production of syngas from the co-gasification of waste materials and biomass. In this present study, a new simulation model for co-gasifying high-density polyethylene (HDPE) and microalgae using Aspen plus V10 was built. Several operating parameters, including operating temperature, air equivalence ratio (ER), biomass blending ratio, steam-to-biomass ratio (S/B), and air/steam ratio, were investigated for their influence on the yield and composition of H2, CO, CO2, and CH4. Results indicated that these operating parameters had significant impacts on the gaseous products. High gasifier temperatures (1000°C) for the co-gasification process favored the formation of H2 and CO and increased their yields. Also, the yield of H2 significantly decreased when the value of the equivalence ratio was increased. According to simulation results, increasing the steam-to-biomass ratio favored the synthesis of H2 and CO up to a point. In addition, waste plastic (HDPE) in the feedstock should be kept at a minimum to favor the production of hydrogen-rich gas. The findings show that the model results agree with previous experimental studies. This research study has proven the air-steam co-gasification of microalgae and HDPE as a suitable process for the production of syngas rich in hydrogen.

Numerical simulation analysis of biomass gasification and rich-H2 production process in a downdraft gasifier

Biomass gasification technology offers a sustainable solution for managing agricultural waste, mitigating environmental pollution, and enhancing living standards. This work deploys Aspen Plus to simulate a downdraft gasifier with an integrated H2 reforming module. The impact of key factors, including air equivalence ratio (ER), gasification system pressure, water vapor input, gasification agent temperature, and oxygen content, are considered. Specifically, optimal ER initially improved the gasification efficiency, with a peak followed by a decline. Water vapor addition elevated H2 content, while increased gasifying agent temperature and oxygen concentration enhanced efficiency. However, the increased gasification pressure will lead to a decrease in gasification efficiency. Subsequently, the effect of reforming temperature, CaO, and water vapor input in the hydrogen production model was examined. An appropriate excess of water vapor and calcium oxide were crucial for maximizing H2 concentration. As the reforming temperature increased from 200 °C to 600 °C, the H2 concentration showed an initial increase and then stabilizes. However, beyond 600 °C, there was a rapid decline. Under optimal conditions (H2O/C > 1.3, CaO/C > 1.1, temperature 550–600 °C), the product gas generated during gasification and reforming processes achieved a high H2 concentration of 98%–99%. These findings affirmed the substantial potential of biomass gasification in high-efficiency H2 production.

Characteristics of Molten Salt Gasification of Waste PVC

Molten salt oxidation is a robust thermal process with the inherent capability to catalytically oxidize the organic compounds while retaining the inorganic ingredients in salt bath. In the present study, molten salt gasification was used for the disposal of waste PVC. The characteristics of molten salt gasification of PVC under different temperatures and air equivalence ratios (ERs) on the gasification characteristics, chlorine retention efficiency, PCDD/F generation, and the distribution of heavy metals such as Cu, Pb, and Zn were investigated. The results showed that increasing the temperature and ER could effectively enhance the yield of gasification gas and carbon conversion efficiency. The highest gasification efficiency of 41.2% was achieved at 750 °C and ER = 0.4, with a gas yield of 0.442 Nm3/kg PVC. Molten carbonates showed an absorption and retention efficiency of more than 99.5% for chlorine under all conditions. Increasing temperature resulted in a significant reduction in the generation of PCDD/F. At 750 °C, the PCDD/F generation was less than 19 pg/g PVC with an I-TEQ of less than 1.4 pg/g PVC, and the ER had a minor effect on PCDD/F. During the molten salt gasification process, most of the heavy metals, such as Cu, Pb, and Zn, were retained in the salt bath.

Early flame development characterization of ultra-lean hydrogen–air flames in an optical spark-ignition engine

Hydrogen-fueled internal combustion engines (H2ICEs) represent a promising technology for decarbonizing the transport sector. In pursuit of this goal, research is needed on lean hydrogen–air combustion under engine conditions aiming to mitigate NOx emissions. However, there is a limited amount of experimental data focusing on flame development at high pressure and temperature, especially in ultra-lean mixtures, which are recently considered to play an important role for future H2ICEs. This study investigates the behavior of very-lean to ultra-lean hydrogen–air flames (0.20 <ϕ< 0.55) in an optical spark-ignition engine, focusing on the early flame development phase. Fuel–air equivalence ratio and engine speed (900 <N< 1500 rpm) effects on hydrogen combustion are addressed with pressure-based heat release analysis and chemiluminescence flame imaging techniques. The findings revealed an intrinsic association between these two approaches. Hydrogen flames development measured before 2% of Mass Fraction Burned (MFB) strongly correlates with pressure-based quantities up to 50% MFB, underscoring the critical role of understanding the early flame phase for predicting total combustion duration and in-cylinder pressure traces. A model for hydrogen turbulent flames in the initial combustion stages is formulated based on the Zimont equation and the experimental data. An equation for 0D/1D combustion duration prediction up to 10% MFB is proposed, demonstrating its validity from the wrinkled flame to the well-stirred reactor premixed combustion regimes. Additionally, flame chemiluminescence images for each zone within the Peters–Borghi diagram are presented, offering valuable insights into the diverse characteristics of these flames.

Co‐generation and GHG emission from agricultural waste based on pyrolysis/gasification: Experimental and LCA approaches

AbstractIn this study, co‐generation from rice straw based on pyrolysis and gasification was studied by experimental and modeling approaches. Pyrolysis experiment results show that improving pyrolysis temperature will benefit the yield of gas and bio‐oil, while reducing the yield of bio‐char. The BET (Brunauer, Emmett, and Teller) surface area of bio‐char reached a maximum of 143.26 m2/g when the temperature was increased to 550°C. For co‐generation in this study, an optimized pyrolysis temperature of 500°C was selected. With respect to gasification, air equivalence ratio (ER) largely influenced the syngas yield and composition. At ER = 0.25, the concentration of H2 and CO reached a maximum of 17.8 wt% and 16.2 wt%. Based on the experimental results, an Aspen Plus model was built to evaluate the mass and energy balance during co‐generation. Furthermore, a life cycle assessment method was used to evaluate the greenhouse gas emission during co‐generation process initialed from rice straw planting. Results show that the greenhouse gas emission intensities of the two co‐generation systems were 2.92 and 3.51 g CO2/MJ respectively, which were much lower than traditional fossil fuels.

Effect of air equivalence ratio on the characteristics of biomass partial gasification for syngas and biochar co-production in the fluidized bed

In order to explore the characteristics and mechanism of biomass partial gasification for biochar and syngas co-production in the fluidized bed, a study on the influence of gasification performance and biochar characteristics after partial gasification with different air equivalence ratios was carried out in a self-built small atmospheric bubble fluidized bed. The results indicate that when the air equivalence ratio rises from 0.07 to 0.16, the lower calorific value of wet producer gas keeps decreasing, and the maximum value can reach 9.16 MJ/Nm3. The biochar yield shows a declining trend, and the maximum value is 18.07 %. In addition, when the air-equivalence ratio is lower than 0.14, the rising of air equivalence ratio makes biochar more disordered due to the newly formed C–O structures, and the total Raman intensity will thereby continue to increase.

Experimental investigation of sorted municipal solid wastes producer gas composition in an updraft fixed bed gasifier

Three kinds of municipal solid waste (MSW) from mechanical biological treatment plants, i.e., Fraction after Drum Separator (FDS), Solid Recovered Fuel (SRF) and Plastic Packaging Mixture (PPM), were investigated. These samples were gasified in fixed-bed updraft gasifier under allothermal (800 °C) air supply conditions. Two different air equivalence ratios (ER), i.e., 0.15 ± 0.02 and 0.21 ± 0.04 were created to determine the influence on MSW producer gas properties. Derivative thermogravimetry analysis shows the same volatile release temperatures (330 °C, 500 °C) for all tested MSW kinds. Chromatography analysis of MSW producer gas revealed that the reduction of ER from 0.21 to 0.15 increase the heating value of combustible gases. PPM producer gas contains the highest H2 content – 11.39 %. The highest tar content (47.44 g/m3) was measured in SRF producer gas and primarily consisted of benzene, toluene, naphthalene, and acenaphthylene. The results of the sorted MSW gasification experiments show that the allothermal updraft fixed-bed gasifier is suitable for the production of producer gas that can be used in gas engines.

Thermodynamic modeling and performance analysis on co-gasification of Chlorella vulgaris and petrochemical industrial sludge via Aspen plus combining with response surface methodology

The co-gasification process of Chlorella vulgaris (CV) and petrochemical industrial sludge (IS) was uncoupled and simulated by Aspen Plus. The co-gasification process was considered into drying, pyrolysis, partial oxidation, as well as reduction and reforming. Simulation results showed that, the interactions between IS and CV were found for the differences in CHO, and affected by the IS ratio and gasification temperature. Increasing the temperature could improve the CO content, and get optimal H2 at 700 °C, while decrease CO2 and CH4 contents, thus lead to a higher LHV (lower heating value) of syngas, CGE (cold gas efficiency), and syngas content, CO selection. The higher S/IS-CV (steam to IS-CV blends ratio) value favored H2 production but reduce CO content and CGE. As air equivalent ratio (ER) increased, the H2 content constantly reduced, while CO varied slightly when the ER was lower than 0.10. After the ER value was higher than 0.10, CO reduced and thereby decreasing co-gasification performance. When the drying degree of feedstock increased, the CO content continuously increased, leading to better co-gasification performances. The RSM results showed that the significance factors in the interactions are ER and drying degree, S/IS-CV and ER, gasification temperature and ER, and gasification temperature and ER, respectively for CGE, LHV, Csyngas, and SelCO.

Flame Propagation in Blends of R-152a, R-134a, and R-1234yf with Air

ABSTRACT Some new, low-global warming potential refrigerants will be flammable, and the laminar burning velocity is a useful parameter for quantifying fire risk. Laminar burning velocity measurements have been made using a constant volume experiment with dry air and the refrigerant R-152a (CH3CHF2), pure and blended with R-134a (CH2FCF3), or R-1234yf (CF3CFCH2). The resulting burning velocity data deduced from the pressure rise in the chamber are presented for a range of fuel air equivalence ratio and loading of the less flammable refrigerant, for unburned gases at 298 K and 101 kPa as well as at 375 K and 253 kPa. For comparison, the 1-D, planar laminar burning velocity was numerically simulated using a recently developed kinetic mechanism that includes a wide range of refrigerants with air. The predicted burning velocities agree reasonably well with the experimental values, and the numerical results are used to understand the kinetic mechanism of the reaction of the refrigerants. Uncertainties in the experimental data from radiation heat losses as well as extrapolation to ambient conditions are explored.

Experimental study on pulverized coal swirl-opposed combustion preheated by a circulating fluidized bed. Part A. Wide-load operation and low-NOx emission characteristics

In this study, the operating characteristics and NOx emission patterns are explored under a wide load range based on a 2MWth pulverized coal preheated combustion test platform. Preheated char with high physical sensible heat and preheated gas with high calorific value greatly improve the ignition and stability of the combustion characteristics of pulverized coal at low loads. Moreover, performing pre-denitrification during the preheating process helps to lower NOx emissions. Stable operation at a wide load range of 26%–106% was achieved, and ultralow loads of 40% and 26% were achieved when the pre-circulating fluidized bed (PCFB) was operated in double-/single-sided operation mode, respectively. Meanwhile, uniform concentration and temperature fields were achieved when both/one side of the PCFB were/was in operation. When operating on the double side of the PCFB, ultralow NOx emissions (@6% O2) of 39.9 mg/m3 and 43.7 mg/m3 were achieved at 40% and 50% loads, respectively. When operating on a single side, the NOx emission amount was 28.3 mg/m3 at 26% load. Furthermore, when the swirling air and the bottom air are equally distributed, the secondary air equivalent ratio is appropriately increased, and the injection position of the burnout air is properly delayed, NOx emissions are reduced.

Co-gasification of rural solid waste and biomass in rural areas: Simulation and plant-scale process

Co-gasification technology is considered to be one of the most potential technologies for solid waste treatment, and the co-gasification treatment of rural solid waste (RSW) and biomass can effectively promote waste reduction and resource utilization. In the present study, the co-gasification of RSW and biomass in an updraft fixed bed gasifier was simulated using the Aspen Plus software, where the simulation results were validated via plant-scale experiments. In this scenario, the impacts of biomass source (i.e., rice husk, rice straw, tree bark and corn straw), co-gasification ratio (CGR) (0–40%) and air equivalence ratio (AER) (0.30–0.55) on the performance of the fixed-bed were investigated. Results showed that Aspen Plus could describe the plant-scale co-gasification process well. Besides, the tree bark-RSW system had the highest heat conversion efficiency of 6.00 MJ/kg the simulation temperature of the gasification layer increased greatly from 485 to 913 °C when the AER increased from 0.40 to 0.55. In addition, the co-gasification of RSW and tree bark could achieve the highest efficiency at the AER of 0.45 and CGR of 20% w, in which the gasification temperature reached 799 °C with the gasification efficiency of 57.17%. This study explored the use of co-gasification of RSW and biomass in rural areas by simulation and plant-scale processes, which promotes the commercial application of co-gasification technology and contributes to sustainable waste management in rural areas.

Experimental investigation of heavy fuel oil gasification in an entrained flow gasifier

In order to utilize heavy fuel oil in an effective gasification system, it is necessary to comprehend the phenomena within the gasifier. This study provides a performance evaluation and feasibility study for the gasification of specific heavy fuel oil in an entrained flow gasifier. The experiments are performed in the air equivalence ratio range of 0.29–0.41 to assess gasification characteristics by measuring the gas composition at the reactor outlet and the temperature distribution along the gasifier. The characteristic of fuel spray and burner flame is also discussed based on the temperature and pressure of heavy fuel oil. Moreover, the performance parameters are compared with those calculated from previous studies on heavy fuel oil gasification using equilibrium and kinetics models. The results show that optimum gasification performance is obtained at an equivalence ratio of 0.37 so that syngas yield (CO + H2), cold gas efficiency, and carbon conversion efficiency achieve 76%, 41%, and 63%, respectively. The experiment outcomes give a deep insight into heavy oil gasification in an entrained flow gasifier and indicate its potential for industrial application.

Syngas production from municipal solid waste plasma gasification: A simulation and optimization study

As a greener alternative to traditional combustion systems, thermal plasma gasification has gained a lot of attention in industries including manufacturing and waste management. The primary objective of this research is to enhance the efficiency of the process and boost the quantity and quality of syngas fuel produced through the plasma gasification of MSW. The goal is to find a long-term solution for recycling municipal solid waste into a carbon-free fuel source. Modeling and simulation analysis using Aspen software was used for the prediction of syngas yields from MSW thermal plasma gasification. Eight responses, including syngas fuel output gases and process performance measures including cold gas efficiency (CGE) and carbon conversion (CC), were optimized using response surface methodology (RSM). Three input variables such as air equivalence ratio (ER), steam to fuel ratio (SFR) and oxygen content in the air (O2 %) were examined. Correlations between the primary responses from MSW plasma gasification and the three input variables were developed and shown to be highly accurate. The optimization results for the MSW plasma gasification showed that ER = 0.04, SFR = 0.28, and O2 = 84.31% are the best operating conditions to maximize the hydrogen = 50.66%, carbon monoxide = 44.67, CGE = 57.64% and CC = 86.52%.

The techno-economic-environmental analysis of a pilot-scale positive pressure biomass gasification coupled with coal-fired power generation system

Biomass gasification coupled with coal-fired power generation (BGCPG) is of great significance for alleviating energy shortages and environmental pollution. Here we propose, analyze and validate a BGCPG system under positive pressure for cleaner applications based on a pilot-scale fluidized bed gasification plant and discussed the possibility of higher economic output and operating stability with reduced pollution emissions. Then the effects of temperature, air equivalence ratio and operating pressure were experimentally investigated for parameter optimization. The processes under positive and negative pressure were simulated and compared based on the pilot-scale experimental data, and the effects of the mixing ratio and operating pressure were investigated. Furthermore, the economic and sensitivity analyses were conducted for both a traditional coal-fired power plant and simulated BGCPG systems. The results demonstrated that the gas calorific value, gas yield, and gasification efficiency increased with the gasification temperature increasing, whereas the opposite trend was observed for the gas calorific value with the air equivalence ratio increasing. The positive pressure operation had little influence on the gasification process. The flue gas flow rate increased, and the furnace temperature decreased with an increase in the mixing ratio of biomass and coal. The reduction in fuel NOx and SOx was caused by the decreasing coal content, whereas the decrease in thermal NOx and boiler thermal efficiency was due to the increasing exhaust temperature. Compared with functioning under negative pressure, operation under positive pressure at a 20% mixing ratio could effectively reduce the pollutant emissions of SOx, NOx and dust by 5.64%, 8.8% and 20%, respectively. The generation costs of the BGCPG system under negative and positive pressure conditions were 0.05593 $/kW·h and 0.05582 $/kW·h respectively, indicating that a positive operating pressure would increase the economic benefit of a 660 MW generator by 5.808 × 105 $/year. These findings suggest the effectiveness of clean power generation with a higher economy and lower pollution emissions.

Particle and Phase Analysis of Combusted Iron Particles for Energy Storage and Release

The combustion of metal fuels as energy carriers in a closed-cycle carbon-free process is a promising approach for reducing CO2 emissions in the energy sector. For a possible large-scale implementation, the influence of process conditions on particle properties and vice versa has to be well understood. In this study, the influence of different fuel-air equivalence ratios on particle morphology, size and degree of oxidation in an iron-air model burner is investigated by means of small- and wide-angle X-ray scattering, laser diffraction analysis and electron microscopy. The results show a decrease in median particle size and an increase in the degree of oxidation for leaner combustion conditions. The difference of 1.94 μm in median particle size between lean and rich conditions is twentyfold greater than the expected amount and can be connected to an increased intensity of microexplosions and nanoparticle formation for oxygen-rich atmospheres. Furthermore, the influence of the process conditions on the fuel usage efficiency is investigated, yielding efficiencies of up to 0.93. Furthermore, by choosing a suitable particle size range of 1 to 10 μm, the amount of residual iron content can be minimized. The results emphasize that particle size plays a key role in optimizing this process for the future.

An innovative method for carbonization and activation of low-rank coal via a self-sustaining counter-current combustion process and its reinforcement strategy

Gradation and quality utilization of low-rank coal is promising. In this study, a special counter-current combustion process, characterized by a combustion front traversing the bed against the air supply direction, was innovatively proposed to achieve the carbonization and activation of low-rank coal. This combustion process was first analysed experimentally in a fixed bed test rig. At an air equivalence ratio as low as 0.25, this combustion process was of a front temperature of 889 °C and self-sustainedly traversed the fuel bed at a propagating rate of 0.33 m/h. Accompanied by its propagation, about 82.5% of volatile matter inside the coal was removed. Due to different reaction phases inside the bed, the solids were in-situ activated by self-produced active components. Based on this, intensification experiments of carbonization and activation were carried out in a moving bed test rig. By moving the bed, the heat transfer near the combustion front tended to a quasi-equilibrium state and the residence time of the solids in the high temperature zone was greatly prolonged. The carbonization and activation effects on the solids were promoted. The carbonization effect almost approached the limit because the removal ratio of volatile matter inside the coal was as high as 98.4%. When external heating and active substances intervened, activation reactions of the solids (namely, C–H2O and C–CO2) were intensified in the char reaction phase. The specific surface area and pore volume of the activated char increased up to 594 m2/g and 0.371 cm3/g. Correspondingly, its adsorption values of iodine and methylene blue were 732 and 76 mg/g. This work provides a technical solution for the in-situ high-quality utilization of low-rank coal.

Numerical simulation of plasma gasification of oil-based drilling cuttings

In this paper, ASPEN PLUS commercial software is used to simulate the plasma gasification process of oil-based drilling cuttings, and the numerical simulation results are analyzed in detail. The conclusions can provide theoretical guidance for subsequent experiments and practical engineering applications. A set of reactor models suitable for gasification of such substances was established by using Gibbs? free energy minimization principle, and the accuracy of the model was verified by comparing the numerical simulation results with the experimental results. In this model, the effects of plasma torch power, air equivalent ratio, moisture content of feed, and the amount of CO2 added on the gasification results were simulated. Through systematic analysis, the optimal gasification parameters are determined output power of plasma torch is 27.5 kW, air equivalent ratio is 0.26, moisture content of feed is 6%, and the amount of CO2 added is 6 kg per hour.