Complete Combustion Research Articles

ANALISIS KANDUNGAN SULFUR, NITROGEN, DAN KLORIN DALAM BIOPELLET BERBASIS LIMBAH PADAT KAYU PUTIH DAN GONDORUKEM

In recent years, a transition towards renewable energy sources has begun to reduce fossil energy usage. One alternative renewable energy source is biopellets, which have gained public interest as an environmentally friendly fuel. Biopellets are a type of renewable energy derived from biomass, which, if it emits too much carbon, can lead to pollution. Carbon emissions are also related to combustion efficiency, as complete combustion can help reduce carbon emissions. This study aims to determine combustion emissions and combustion efficiency of biopellets made from eucalyptus solid waste with the addition of rosin to optimize the use of raw materials as renewable energy. The study employs an experimental laboratory approach with a factorial design to test the impact of sulfur, chlorine, and nitrogen content on the combustion efficiency of biopellets made from eucalyptus waste and rosin. Results indicate that the sulfur and chlorine content remain above the French standard (ITEBE), at 0.31% and 1.12%, respectively, while nitrogen content is below the standard at 0.48%. The resulting combustion efficiency ranges between 9.569% and 9.701%.

Spray characteristics and combustion mechanism influence on combustion stability of UDMH/NTO pre-combustor under external excitation

To study the combustion stability of liquid rocket engines with hypergolic propellant more comprehensively, external pressure pulse excitation was applied to the UDMH (unsymmetrical dimethylhydrazine)/NTO (methylhydrazine) pre-combustor. The effects of pressure pulse intensity, spray characteristics (droplet diameter and spray cone angle), and combustion mechanism on combustion stability characteristic frequencies and attenuation characteristics after excitation were investigated. The simulation results show that all operation conditions capture the first three longitudinal frequencies of the pre-combustor, and all factors have a greater impact on frequencies with higher orders. Increasing the pulse intensity and reducing the droplet diameter are not conducive to combustion stability. The influence of the spray cone angle on the combustion stability is not monotonous. The pre-combustor has good stability when the spray cone angle is 70°. Different combustion mechanisms have a significant effect on the results before and after pressure pulses, and considering a more complete combustion process may increase the attenuation time in the pre-combustor. The obtained rules can provide a reference for the design and simulation of hypergolic liquid rocket engines, which is beneficial for predicting and evaluating the combustion stability of liquid rocket engines.

Effect of Methane on Combustion of Glycerol and Methanol Blends Using a Novel Swirl Burst Injector in a Model Dual-Fuel Gas Turbine Combustor

Glycerol, a byproduct of biodiesel, has moderate energy but high viscosity, making clean combustion challenging. Quickly evaporating fine fuel sprays mix well with air and burn cleanly and efficiently. Unlike conventional air-blast atomizers discharging a jet core/film, a newly developed swirl burst (SB) injector generates fine sprays at the injector’s immediate exit, even for high-viscosity fuels, without preheating, using a unique two-phase atomization mechanism. It thus resulted in ultra-clean combustion for glycerol/methanol (G/M) blends, with complete combustion for G/M of 50/50 ratios by heat release rate (HRR). Lower combustion efficiencies were observed for G/M 60/40 and 70/30, representing crude glycerol. Hence, this study investigates the effect of premixed methane amount from 0–3 kW, and the effect of atomizing gas to liquid mass ratio (ALR) on the dual-fuel combustion efficiency of G/M 60/40-methane in a 7-kW lab-scale swirl-stabilized gas turbine combustor to facilitate crude glycerol use. Results show that more methane and increased ALR cause varying flame lift-off height, length, and gas product temperature. Regardless, mainly lean-premixed combustion, near-zero CO and NOx emissions (≤2 ppm), and ~100% combustion efficiency are enabled for all the cases by SB atomization with the assistance of a small amount of methane.

To Study the Effects of Microemulsion Based Hybrid Biofuel on Emission Characteristics of CI Engine: A Short Review

AbstractMicroemulsion based fuels (MBF) have gained significant attention in recent years due to their potential to enhance combustion efficiency, reduce emissions, and improve overall engine performance. This research paper enlightens the effects of physiochemical properties on the emission characteristics of CI engine. The microemulsions are formulated using surfactants, co‐surfactants, water or alcohols, and fuel components. The effects of density, viscosity, calorific value, cold flow properties, and cetane number along with the stability and the multi‐component characteristics of (MBF) has been taken into consideration to examine its effects on Emission characteristics such as nitrogen oxides (NOx), sulfur oxides (SOx), carbon monoxide (CO), particulate matter (PM), and unburned hydrocarbons (UHC). Microemulsion‐based fuels lower emissions of NOx and PM, recognized to the more complete combustion. The review highlights various studies that have investigated the benefits of microemulsion fuels, including reduced emissions of different pollutants and thus reduce the adverse effect on environment.In conclusion, microemulsion‐based fuels show likely physiochemical properties, as well as favorable emission characteristics, with reduced NOx, SOx, CO, PM, and UHC emissions. This study highlights the potential of microemulsion‐based fuels as environment friendly alternatives, flagging the way for further research.

Analysis of the Effect of More Fuel and Air Variations Excess Air on Combustion Process Simulation at a 10 kW Biomass Power Plant Using ASPEN PLUS

Abstract The utilization of biomass as an alternative energy can support the achievement of Net Zero Emissions. Each type of biomass fuel can provide different combustion effects from one another. This is due to the different heating values of each fuel. The calorific value is one of the things that affect the combustion performance of the biomass power plant. The main purpose of this study is to examine how different amounts of excess air used during the combustion process affect the outcomes. Combustion is a chemical reaction involving decomposition and gasification that simultaneously occurs in a space where a large amount of energy is released. The modeling and simulation of the decomposition and gasification processes were carried out using Aspen Plus. In this simulator, the decomposition process takes place in the Yields Reactor, while the gasification process occurs in the Gibbs Reactor. The biomass and ash components are characterized by their ultimate, proximate, and sulfur analysis. Then the excess air is varied to analyze its impact on the flame temperature from the reaction. The simulation findings emphasize crucial considerations for achieving complete combustion and reducing harmful gas emissions. Maintaining excess air close to the stoichiometric level ensures maximum combustion temperature at 1616.15 °C while minimizing excess air reduces NOx gas concentration. Approaching stoichiometric air level decreases CO gas and increases CO2, indicating more thorough combustion. However, excess air leads to lower adiabatic flame temperature due to nitrogen formation.

Analysis of the Influence of Variation in Medical Waste Heating Value on the Electrical Energy Output of Generator in Medical Waste Cogeneration Incinerator System using Gatecycle Solver

Abstract Medical waste incinerator is a technology capable of processing and exterminating hazardous medical waste through combustion at temperatures exceeding 800°C. Medical waste exhibits a range of heating values depending on its material composition. The heating value represents the potential heat energy released when a substance undergoes complete combustion. A cogeneration incinerator is designed to treat medical waste while also harnessing the heat of the flue gas that emanates from the combustion process. The flue gas acts as a hot fluid that transfers its heat, causing the water temperature inside the boiler to increase and transform into high-temperature steam. This steam drives a steam turbine connected to a generator to generate electrical energy. The amount of electrical energy generated is influenced by the steam quality produced through the boiler’s water-heating process. This study aims to investigate the influence of variation in the heating value in medical waste on the electrical energy output of the generator in a medical waste cogeneration incinerator system. The range of heating value variations used in the testing varies from 25 MJ/kg to 35 MJ/kg. The variation is tested through thorough simulations using GateCycle software to obtain data on the electrical energy generated. To achieve a maximum electrical energy output of 200 kW, fuel with a total heating value of 32.25 MJ/kg is required. This study is beneficial to be implemented as renewable energy sources based on biomass powerplant systems.

Nitrogen migration and gasification characteristics of pulverized coal using the novel gasification-combustion technology

This study proposes a feasible gasification-combustion technology for coal-fired boilers operating at low loads for the purpose of providing strong support for stable output of the power grid system that accommodates more renewable energy power. In this technology, a multi-nozzle impinging entrained-flow gasifier is used for the first time to preheat pulverized coal (PC), and the gasified fuel enters a down-fired combustor (DFC) for complete combustion with air-staged method. A 75 kW novel self-sustained gasification-combustion test rig was constructed. The stability and feasibility of the test rig were verified, and the gasification characteristics and nitrogen migration mechanism of PC under loads of 45 kW, 55 kW, 65 kW and 75 kW were investigated. The results demonstrated that the gasifier could continuously and steadily provide high-temperature gasified gas-char mixture to the combustor. The gas-char mixture, consisting of coal gas which was rich in high-concentration flammable gases (CO, H2, and CH4) and char with enlarged specific surface area, was easy to ignite, which could enhance the flame stability of boilers operating at low loads. Additionally, more than 61.6 % of coal-N was released in the gasifier. The liberated coal-N primarily transformed to N2 and NH3 instead of NOx, while the amount of NH3 produced was influenced by the gasification temperature. The gasified gas-char mixture entering the combustor achieved stable combustion with uniform temperature distribution. Before the injection of tertiary air, the released char-N and the NH3 in coal gas transformed primarily to N2, and there was no production of NO due to the strong reducing environment. The lowest NOx emission was 122.31 mg/Nm3 (@6% O2) at 65 kW, and the combustion efficiencies under all loads exceeded 99.62%, indicating that the gasification-combustion technology could enable efficient combustion and reduce NOx emission. Hopefully, the proposed technology could provide an innovative solution for the stable combustion of PC boilers at low loads and provide a feasible way to achieve clean combustion.

Numerical investigation of NOx emission characteristics in air-staged combustion system fueled by premixed ammonia/methane

For the purpose of achieving global CO2 reduction, decarbonization at the source of fuels is a practical approach. The transition phase of blending fossil fuels with carbon-free fuels for combustion is a hot topic in the current carbon emission reduction process. In order to achieve efficient and low-pollution combustion of NH3/CH4, the combustion and emission characteristics of NH3/CH4 under single-stage and air-staged combustion methods were numerically investigated in this work. The emissions were compared for different equivalence ratios and different ammonia content conditions. rate of production (ROP) and sensitivity analysis were performed for NOx, and the reaction path of NH3/CH4 was analyzed. The results indicate that the C-N interaction of the NH3/CH4 mixed combustion process is not significant and turns weaker in the lean flames. HNO intermediate is an important specie for NO generation, and HCN together with HNO intermediate, are essential species for NO generation. NH2 and NH almost dominate the promotion and inhibition of NO generation. Given that the contrasting NOx and CO emission behavior of NH3/CH4 in rich and lean flames, the single-stage combustion approach is not suitable. Air-staged combustion achieves both ensuring complete burning of NH3 and CH4 while reducing NOx and CO emissions. Moreover, the results suggest that Φpri=1.2/Φtotal=0.6 is the optimal NH3/CH4 combustion staging method for controlling NOx emissions.

CFD Simulation of the Influence of the Type of Gas Distribution in the Burners on Thermal Aerodynamic Processes in the DKVR 10-13 Boiler

Topics related to fuel combustion and its impact on the environment will never lose their relevance, as the issues of efficient combustion and emission reduction are key in power generation and environmental protection. The countries of the European Union are massively abandoning the use of natural gas as a fuel for thermal power stations. However, in Asian countries, the ease of using natural gas as the main fuel and its environmental friendliness compared to coal made it possible to widely use natural gas in industry and energy sector. Comparing natural gas with alternative combustible gases (generator, blast furnace, mine, biogas), the main conclusion that it has the most attractive characteristics for its use in industry, including energy facilities, can be drawn. Therefore, it is impossible to replace it with alternative fuels in the chemical, heavy industry and energy sector in the near future. The paper is devoted to CFD modeling of stabilized combustion without premixing in a burner with low swirl for two operating modes of the boiler unit - nominal one and at 60% capacity. The study was carried out using numerical methods with the ANSYS-Fluent application program package. The object of the study is a burner built according to the technology based on the use of jet-niche systems with gas distribution of fuel by circular jets fed perpendicularly into the flow of the oxidizer through a single-row system of holes. Hydrodynamics and heat exchange processes were chosen as the subject of research, based on the analysis of which a model of NOx generation in jet-niche systems was obtained. The authors of the paper believe that replacing the regular burners of the DKVR-10-13 water heating boiler with a jet-niche ones can contribute to better mixing of fuel and air and ensure more complete combustion. In this paper, two types of burners are considered. In one of the burners, fuel is supplied through rectangular slits, in the other – through round holes arranged in a row. Air is supplied to both burners through rectangular slits. It was determined that gas distribution through round holes increases the spraying of the mixture and increases the area of combustion products spraying. Visualization of the distribution of pressure, temperature, kinetic energy profiles of turbulent pulsations and vorticity was carried out. The obtained results indicate that there are no changes in the flow regime, flame displacement or its instability. It was determined that both the axial velocity and the tangential velocity of the flow affect the distribution of combustion products and harmful impurities such as NOx. Gas distribution in circular jets stabilizes combustion and reduces flame expansion.

Evaluating Engine Performance, Emissions, Noise, and Vibration: A Comparative Study of Diesel and Biodiesel Fuel Mixture

This study investigates the performance, emissions, noise, and vibration characteristics of a single-cylinder, air-cooled, four-stroke diesel engine running on pure diesel (D100) and biodiesel blends (B10: 90% diesel, 10% biodiesel; B20: 80% diesel, 20% biodiesel) at 1800 rpm, where the engine delivers maximum torque. Key metrics such as torque, power, brake specific fuel consumption (BSFC), exhaust gas temperature, noise, vibration, and emissions (CO, CO2, HC, O2, NOx, and smoke opacity) were analyzed. The findings indicate that B10 enhances torque, power output, and overall fuel efficiency, especially at low to medium loads, with a significant 17.54% reduction in BSFC compared to D100 at 40% engine load. Vibration levels generally increased with biodiesel addition, while B10 and B20 both reduced smoke opacity, with B20 having a more substantial effect. HC emissions decreased at idle with B10 but increased at higher loads, suggesting more complete combustion with potential thermal stress on engine components. Noise and vibration results were mixed; B20 reduced noise at higher loads but increased vibration. At 100% load, B20 decreased noise by 1.42% compared to D100. Despite benefits such as improved torque and reduced particulate emissions, biodiesel blends, particularly B20, led to increased NOx and CO2 emissions, emphasizing the need for further op-timization of blend formulations and emission control strategies. This study provides valuable insights into the tradeoffs and potential of biodiesel blends as sustainable diesel alternatives.

Determination of the effect of low concentration titanium dioxide nano fuel additive in biodiesel on performance and emissions

In this study, the effect of nanoparticle addition into rapeseed methyl ester (R0) produced by the transesterification method on engine performance and emissions was experimentally investigated. Titanium dioxide was used as a nano fuel additive and was added to the test fuels at rates of 50 ppm (RTi50) and 75 ppm (RTi75) using an ultrasonic mixer. The effect of titanium dioxide on engine performance and exhaust emissions was experimentally determined by taking advantage of its photocatalysis effect and chemical reaction accelerator properties. Additionally, titanium dioxide additive reduced the viscosity and density of biodiesel fuel, resulting in higher micro explosion. According to the test results carried out at 4 different engine loads, brake specific fuel consumption decreased by 7.51% and 8.62% in RTi50 and RTi75 fuels compared to R0 fuel. Brake thermal efficiency increased by 2.47% and 6.21%, respectively. The improvement in combustion achieved by the nano additive increased the conversion of CO emissions into CO2, increased NOX emissions, reduced smoke emissions and caused more complete combustion products to come out of the exhaust.

TO THE ISSUE OF NON-PROJECT FUEL COMBUSTION

Nowadays, the issues of ecology and sustainable development are becoming more and more urgent, and the scientific community is actively looking for ways to more efficient and environmentally friendly use of renewable energy sources. One of such directions is the development and improvement of coal combustion technologies in aerodynamic furnaces. This paper offers a detailed analysis of this topic, looking at both theoretical aspects and practical applications. Aerodynamic furnaces are specialised devices designed to burn solid fuels such as coal with maximum efficiency and minimum environmental impact. The basic principle of operation of such furnaces is to create optimum conditions for complete combustion of the fuel, which is achieved through carefully designed aerodynamics and process control. The operation of the boiler on the coal of Karazhyra deposit is considered. This coal belongs to non-project fuel and improvement of its combustion processes is required to reduce harmful emissions and increase combustion efficiency. For the energy sector of the Republic of Kazakhstan, the conducted research is important, and the results obtained can be used to regulate and improve the operation of similar equipment, which contributes to improving environmental performance and overall efficiency of the country's energy systems.

Hydrochar from co-hydrothermal carbonization of sewage sludge and sunflower stover: Synergistic effects and combustion characteristics

This study carried out co-hydrothermal carbonization (Co-HTC) on sewage sludge (SS) and sunflower straw (SFS) at various ratios (1:0, 3:1, 1:1, 1:3, 0:1) to prepare hydrochar. The raw samples and produced hydrochar were characterized using ultimate analysis, proximate analysis, Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The potential synergistic impact during the reaction process were analyzed. As the SFS ratio increased, the fuel ratio of hydrothermal carbons rose from 0.29 to 0.37, while the higher heating value (HHV) improved from 7.44 (MJ/kg) to 20.86 (MJ/kg). The co-hydrothermal synergistic effect resulted in enhanced the hydrochar yield, energy yield, carbon sequestration rate and organic retention rate. Compared to raw sample, the surface of hydrochar exhibits a rougher and more fragmented structure, with an increased number of microspheres and micropores, resulted in an increased specific surface area. Thermogravimetric analysis (TGA) demonstrated that, in comparison to HTC of sludge alone, the Co-HTC of SS with SFS enhances the ignition temperature and delays the completion of combustion. Therefore, Co-HTC with SFS is an effective method for converting SS into clean solid fuel for energy applications.

Combination of high cetane diesel fuel and post injection mode in a diesel engine: A path towards lower exhaust emissions

The major objective of the presented work is to explore the effect of post injection (PI) strategy using neat diesel fuel (D100) blended with cetane number enhancer (CNE). The motive behind adding CNE in diesel fuel was to lower its self-ignition temperature and hence delay period subsequently. This can lead to more efficient combustion of post injected fuel which leads to lower incomplete combustion losses. The CNE used was Di-Tert-Butyl Peroxide (DTBP) which was blended with D100 in proportion of 1 % by volume. Initially experiments were conducted with D100 under various PI modes where variation of post injection timing (PIT) as well as post quantity (PQ) was considered. The experimental results showed that implementing PI resulted in lower smoke, unburned hydrocarbon (UHC), carbon monoxide (CO) and nitrogen oxides (NOx) emissions compared to single injection while affecting fuel consumption negatively. Then after similar experiments under various PI modes were repeated using blends of D100 and DTBP (D/DTBP) and results were compared with D100 case. It was found that addition of CNE in D100 resulted in more complete combustion of post fuel which further reduced CO and UHC emissions. The shorter delay period in case of D/DTBP blend compared to D100 case led to lower NOx emissions as well as higher smoke emissions. The obtained results revealed that PI mode with 3 mg PQ and 20° after top dead center (ATDC) PIT with D/DTBP blend offered 41.18 %, 17.55 %, 64 % and 62.5 % reduction in smoke, NOx, UHC and CO emissions respectively compared to single injection mode using D100 fuel.

Smoke Emissions and Buoyant Plumes above Prescribed Burns in the Pinelands National Reserve, New Jersey

Prescribed burning is a cost-effective method for reducing hazardous fuels in pine- and oak-dominated forests, but smoke emissions contribute to atmospheric pollutant loads, and the potential exists for exceeding federal air quality standards designed to protect human health. Fire behavior during prescribed burns influences above-canopy sensible heat flux and turbulent kinetic energy (TKE) in buoyant plumes, affecting the lofting and dispersion of smoke. A more comprehensive understanding of how enhanced energy fluxes and turbulence are related during the passage of flame fronts could improve efforts to mitigate the impacts of smoke emissions. Pre- and post-fire fuel loading measurements taken during 48 operational prescribed burns were used to estimate the combustion completeness factors (CC) and emissions of fine particulates (PM2.5), carbon dioxide (CO2), and carbon monoxide (CO) in pine- and oak-dominated stands in the Pinelands National Reserve of southern New Jersey. During 11 of the prescribed burns, sensible heat flux and turbulence statistics were measured by tower networks above the forest canopy. Fire behavior when fire fronts passed the towers ranged from low-intensity backing fires to high-intensity head fires with some crown torching. Consumption of forest-floor and understory vegetation was a near-linear function of pre-burn loading, and combustion of fine litter on the forest floor was the predominant source of emissions, even during head fires with some crowning activity. Tower measurements indicated that above-canopy sensible heat flux and TKE calculated at 1 min intervals during the passage of fire fronts were strongly influenced by fire behavior. Low-intensity backing fires, regardless of forest type, had weaker enhancement of above-canopy air temperature, vertical and horizontal wind velocities, sensible heat fluxes, and TKE compared to higher-intensity head and flanking fires. Sensible heat flux and TKE in buoyant plumes were unrelated during low-intensity burns but more tightly coupled during higher-intensity burns. The weak coupling during low-intensity backing fires resulted in reduced rates of smoke transport and dispersion, and likely in more prolonged periods of elevated surface concentrations. This research facilitates more accurate estimates of PM2.5, CO, and CO2 emissions from prescribed burns in the Pinelands, and it provides a better understanding of the relationships among fire behavior, sensible heat fluxes and turbulence, and smoke dispersion in pine- and oak-dominated forests.

Study on Explosion Mechanism of Dimethyl Ether/H2-Blended Gas Based on Chemical Kinetics Method

In order to reveal the deflagration mechanism of DME/H2-blended gasses, the micro-mechanism was studied based on the constructed UC San Diego 2016 pyrolysis oxidation mechanism model. The results show that adiabatic flame temperature and laminar flame speed increase with the increase in the equivalence ratio (Φ); they first increase and then decrease with the increase in the hydrogen (H2)-blended ratio (λ), and with the increase in λ, the Φ corresponding to the peak laminar flame speed of the blended gas increases. The addition of H2 increases the consumption of O2, and H2 reacts with CO to form H2O and CO2, promoting complete combustion. When Φ = 1.0–1.2, the equilibrium mole fraction of H and OH-activated radicals reach the maximum, and with the addition of H2, the concentration of activating radicals gradually increases, while the number of promoted elementary reactions increases by two, and the number of inhibited elementary reactions does not increase. Meanwhile, the addition of H2 increases the reaction rate of most reactions on the main chemical reaction path CH3OCH3→CH3OCH2→CH2O→HCO→CO→CO2 of DME and increases the risk of the deflagration of DME/H2-blended gas.

Assessment of the Energy Potential of Plastics as a Component of ANFO-type Explosives

Many methods have been developed to reduce the environmental impact of plastic waste. New technologies have been developed to make high-temperature utilisation of these wastes possible. A promising method for the unconventional disposal of plastics by detonation was identified. The popular explosive ANFO (Ammonium Nitrate Fuel Oil) is a component mixture of oxidiser (ammonium nitrate) and fuel (diesel fuel). The optimal composition is 94.5% oxidiser and 5.5% fuel – a guarantee of complete and total combustion. Plastics have a chemical composition and oxygen balance similar to fuel oil. It is possible to replace the fuel share in ANFO by adding plastics and using the energy they contain. The amount of energy that can be recovered is high for PE and PP (at the level of 0.6) and PS – 0.5. Using polymers as ANFO components is advantageous for economic reasons – plastic waste will be eliminated during blasting works.

Comparative experimental study on the co-firing characteristics of water electrolysis gas (HHO) and lean coal/lignite with different injection modes in a one-dimensional furnace

Zero-carbon fuels (H2/NH3) replacing coal co-firing is a promising way to address carbon emissions. Hydrogen co-firing helps improve combustion stability at low loads and control pollutant emissions. This study used a safer water electrolysis gas (HHO) for the multi-coal co-firing adaptability test. The effects of HHO injection mode and flow rate on combustion intensity, flue gas emissions, and fly ash characteristics were investigated. The results showed that HHO and lean coal/lignite co-firing could significantly increase the combustion temperature. The maximum temperature increases after co-firing were 108 °C and 95 °C. As the HHO increased, the CO2 in lignite co-firing increased, and CO and unburnt carbon decreased, while the opposite results were observed for lean coal (LC). At the 2200L/h HHO co-firing, CO2 decreases by 14.46 % and 27.22 % for LC premixed co-firing (PC) and staged co-firing (SC). Compared to SC, PC is more conducive to promoting the complete combustion of coke. The NOX emissions of HHO/LC co-firing are lower than those of pure coal, reaching the lowest value of ∼ 9 ppm under SC. As the HHO increases, the NOX of Lignite-PC first increases and then slowly decreases, while Lignite-SC has the opposite effect. Although various NOX emission trends are observed under different conditions, the results are dominated by a common mechanism − the competition between NOX reduction caused by HHO gas and the increase in co-firing temperature on NOX generation. The NOX of SC is all lower than that of PC. The SO2 emission from the LC co-firing decreases with the increase of HHO, while the SO2 from lignite increases. The SO2 of LC-SC can be reduced from ∼ 142 ppm to 0 ppm. HHO gas injection inhibits the release and oxidation of sulfur in lean coal. The differences in coal types lead to different changes in SO2 of co-firing. HHO gas reduced the SO3 content of lignite fly ash by 38.01 %. The high-temperature reduction atmosphere promotes the decomposition of sulfates and increases SO2 emissions. HHO co-firing refines the particle size of fly ash. The ultra-fine and micron particle matter (PM) increases, and the content of PM>100μm in Lignite-SC decreased by 10.32 %.

An approach of analyzing gas and biomass combustion: Positioned of flame stability and pollutant reduction

Biomass, as a renewable energy source, has gained attention as a sustainable alternative to conventional fuels due to its global availability and usability in rural areas. However, biomass combustion presents challenges such as flame instability and pollutant emissions. This study compares the use of methane gas, wood shavings, and a combination of these two fuels, examining the effects of preheating and flame stability in the combustion of natural gas, biomass, and their co-firing using numerical methods. An equivalence ratio of 1 has been used to avoid a rich-fuel mixture, and an air mass flow rate of 0.0001 kg/s are considered to ensures a sufficient supply of oxygen for the combustion process. Biomass fuel particles are injected from the surface of the fuel and its particle diameter ranging between 5 and 10 μm. The results showed that using the combined fuel not only increased the flame temperature at the beginning of the combustion chamber but also achieved more complete and stable combustion, with over 97 % of the fuel consumed at the start of combustion. As a result of this complete combustion, the emissions of toxic gases CO and NOx in the combustion products reached zero. Additionally, preheating the air increased the flame temperature by 14 %, while preheating the fuel reduced NOx emissions by 24 %.

Effect of airflow velocity in vessel-pipelines on dust explosion during pneumatic conveying

In order to investigate the flame propagation and pressure characteristics of dust particles during airflow transportation, a dust explosion experimental apparatus simulating dust handling processes was designed. The system is supplied with a stable airflow by a high-pressure fan, capable of continuously transferring dust from the vessel to the pipeline at a controllable speed. Dust explosion experiments were meticulously executed by applying 1 kJ of ignition energy to the transported dust particles at airflow velocities of 5, 10, and 15 m/s. This study examines the effects of airflow velocity, pipe diameter, and ignition position on explosion characteristics and delves into the mechanisms of these effects through a detailed analysis of experimental results. For the maximum explosion pressure, an increase in airflow velocity causes the maximum explosion pressure to rise. As the pipe diameter increases, the maximum explosion pressure first rises and then falls. The maximum explosion pressure occurs in the case of bottom ignition. The range of maximum explosion pressure values is expected to provide a reference for explosion detection and explosion venting. For flame propagation, the flame undergoes five processes within the vessel, including ignition of dust particles, spherical flame development, flame stretching towards the mouth of the pipe, complete combustion of particles, and near exhaustion of particle combustion. The higher the airflow velocity and the larger the pipe diameter, the more pronounced the flame stretching and development towards the pipe opening become. Within the pipe, two distinct flame propagation behaviors were observed under conditions of high and low airflow velocities. Compared with the experimental results of high-pressure pneumatic powder spraying forming a dust cloud within a vessel-pipeline, this study measures the maximum explosion pressure at specific turbulence levels and establishes a quantitative relationship between airflow velocity and explosion characteristics. Utilizing this correlation can provide a reference for predicting industrial-grade dust explosion characteristics at different airflow velocity levels, thereby offering a more optimized design basis for the design and safety protection of industrial equipment.