Pure Oxygen Combustion Research Articles

Applications of Oxyhydrogen, Direct Water Injection, and Early-Intake Valve Closure Technologies on a Petrol Spark Ignition Engine—A Path towards Zero-Emission Hydrogen Internal Combustion Engines

This study investigates the performance of a 4-MIX engine utilizing hydrogen combustion in pure oxygen, water injection, and the application of the early-intake valve closure (EIVC) Miller cycle. Transitioning from a standard petrol–oil mix to hydrogen fuel with pure oxygen combustion aims to reduce emissions. Performance comparisons between baseline and oxyhydrogen engines showed proportional growth in the energy input rate with increasing rotational speed. The oxyhydrogen engine exhibited smoother reductions in brake torque and thermal efficiency as rotational speed increased compared to the baseline, attributed to hydrogen’s higher heating value. Water injection targeted cylinder and exhaust temperature reduction while maintaining a consistent injected mass. The results indicated a threshold of around 2.5 kg/h for the optimal water injection rate, beyond which positive effects on engine performance emerged. Investigation into the EIVC Miller cycle revealed improvements in brake torque, thermal efficiency, and brake specific fuel consumption as early-intake valve closure increased. Overall, the EIVC model exhibited superior energy efficiency, torque output, and thermal efficiency compared to alternative models, effectively addressing emissions and cylinder temperature concerns.

Kinetic Study of Pure Oxygen Combustion of Coke Blended with Calcium Oxide

ABSTRACT In order to elucidate the mechanism of CaO on pure oxygen combustion of coke, non-isothermal TGA technique was use to test coke blended CaO samples of varying C/Ca molar ratios (CMCa-2, CMCa-3, and CMCa-4). The characteristic combustion temperatures at varying β were measured. The representative CMCa-2 and CMCa-4 were tested by TG-MS to determine the effect of CaO on coke combustion. Kinetics parameters for the blended samples across various reaction phases were determined using the improved Coats-Redfern method. The results showed that in the pure oxygen atmosphere, the combustion characteristic temperature rise with the increase of β. The material transformations during different reaction stages proceeded as follows: coke combustion generated CO2, CO2 combined with CaO to generate CaCO3, and finally CaCO3 decomposed to release CO2. The E values of three reaction stages were as follows: the highest E was observed in stage 3, ranging from 128.05–151.18 kJ·mol−1, the lowest E in stage 2 was below 46 kJ·mol−1, and the E in stage 1 laid between 99.35–128.71 kJ·mol−1. The C/Ca molar ratio was proportional to the kinetic parameters of the blended sample.

Comparative study on the molecular evolution of changqing petroleum coke during air and pure oxygen combustion: A ReaxFF method analysis

Based on reactive force field (ReaxFF) simulation, the molecular evolution mechanism of air combustion simulation and pure oxygen combustion simulation of Changqing petroleum coke was studied. On the basis of the original petroleum coke molecular model, N2 and O2 molecules were added to construct the air combustion simulation model and the pure oxygen combustion simulation model respectively. The number of molecules, main products, and typical hydrocarbon gases in the two simulation results were analyzed by setting up the LAMMPS in. file. Finally, the molecular changes of pyrrole and pyridine were described. The results show that the main reaction interval of pure oxygen combustion is earlier than that of air combustion. In the main reaction temperature range, the reaction rate of pure oxygen combustion is higher than that of simulated air combustion. At 170 ps, the two simulations reaction speed is the fastest time point; Pyridine is more stable than pyrrole. The research on the distinction and comparison of two kinds of simulation has certain guiding significance for the clean utilization of petroleum coke combustion process in industry.

Simulation of gas–solid flow characteristics of the circulating fluidized bed boiler under pure-oxygen combustion conditions

Simulation of gas–solid flow characteristics of the circulating fluidized bed boiler under pure-oxygen combustion conditions

Space numerical simulation of full oxygen combustion flame in glass melting furnace based on flue gas preheating

This study explores the innovative design of a glass-melting furnace, which incorporates a combustion lance and a flue on one side. The research validates the simulation that the high-temperature flue gas, produced by the pure oxygen combustion of natural gas, can utilize residual heat in a multi-stage process to preheat and burn the fuel natural gas via a jet heat pump. This process significantly reduces energy consumption, thereby decreasing construction costs and energy usage in industries related to glass furnace production. The research focuses on the flame space of a 600 t/day natural gas flat glass all-oxygen combustion furnace. Utilizing numerical calculation methods, a three-dimensional mathematical model of the all-oxygen lance flame space was developed. Numerical simulation methods were employed to examine the temperature field, airflow field, and the distribution pattern of the liquid flow field within the glass space in the furnace. The simulation results reveal that incorporating high-temperature flue gas into the fuel can markedly enhance the performance of the spray gun flame. Additionally, choosing spray gun outlet designs of varying widths can tailor the flame width to better meet the requirements of the glass melting system, thereby significantly improving the waste heat utilization rate of the flue gas. This offers more alternatives for the direct utilization of flue gas. When compared to traditional oxy-combustion glass melting furnaces, this innovative design substantially reduces construction costs and is more energy-efficient and environmentally friendly.

Development of a spray-ejector condenser for the use in a negative CO2 emission gas power plant

One promising solution for developing low-emission power technologies is using gaseous fuel combustion in pure oxygen when the exhaust gas mixture is composed of H2O and CO2, and where CO2 is separated after steam condensation. The paper presents the results of computational analyses providing to the Spray-Ejector Condenser (SEC) development, which is one of the crucial components of the negative CO2 gas power plant (nCO2PP) cycle development. The proposed design of the ejector-condenser to ensure the high effectivity of vapor condensation and CO2 compression with preparation to separation, ready for application in gas power cycle, is a novelty of this research. Different computational techniques leading to the development and better understating of ejector operation were applied. The main operating conditions in the characteristic connected with the developed nCO2pp cycle points were investigated to evaluate the impact of the operating conditions on SEC performances. The amount of motive water needed for the cooling purpose is susceptible to the inlet water pressure and temperature and strongly affects the generated pressure of the suction stream. The preliminary results confirm that the SEC's basic design and geometrical dimensions can be applied in the negative CO2 power plant cycle. Results from CFD modeling give the possibility to investigate the turbulent flow of water/steam/CO2 mixture together with the condensation process occurring at this same time. It is found that the average droplet diameter and motive water supplying method significantly effects the condensation intensity. The further direction of the presented computational research activities and results is to test various designs of Spray-Ejector Condensers that will enable the evaluation of the direct contact condensation process and develop the final geometrical design.

Effect of particle size on the kinetics of pure oxygen combustion of coke

Non-isothermal thermogravimetry technique was used to analyze three groups of coke samples (S-ZD, M-ZD, and L-ZD) of varying particle sizes. The effect of particle size on kinetic parameters was studied in a pure oxygen atmosphere. The ignition (Ti), peak (Tp), and burnout (Tf) temperatures and the flammability (C) and combustion characteristic (Sn) indexes were determined by varying the heating rate (β). The activation energy (Eα) was evaluated following the Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods. Ti, Tp, Tf, C, and Sn correlated positively with the increase in β in a pure oxygen atmosphere. The order of ignition was L-ZD > M-ZD > S-ZD, and the Eα values for the S-ZD, M-ZD, and L-ZD samples were 98.49, 98.35, and 95.17 kJ·mol−1 (FWO) and 90.32, 90.92, and 89.25 kJ·mol−1 (KAS), respectively. Particle size exerted little effect on the kinetics of coke combustion.

A Study on the N2O Reduction Rate According to Temperature and Residence Time in the Exhaust Gas Atmosphere Emitted on Combustion of Air and Oxygen.

N2O is a hazardous greenhouse gas. It should be reduced to solve global warming problems. In this study, experiments of N2O thermal decomposition were conducted by simulating the exhaust gas atmosphere emitted during the combustion of air and pure oxygen in an actual circulating fluidized bed system and incinerator system. As a result of comparing the N2O reduction rate in N2 and CO2 atmospheres, the N2O reduction rate in the CO2 atmosphere was 20% higher than that in the N2 atmosphere. It is judged that the N2O reduction rate is high in a CO2 atmosphere (exhaust gas from pure oxygen combustion) due to complex factors such as the reverse reaction, the diffusion coefficient, and static pressure-specific heat. Therefore, pure oxygen combustion increases the reduction rate of nitrous oxide. In addition, when operated with an appropriate residence time and temperature, a reduction effect of more than 95% can be expected, and the fuel consumption rate is also expected to improve.

Numerical study of a swirl gas turbine combustor for turbulent air and oxy-combustion of ammonia/kerosene fuels

Since ammonia has a carbon-free substance and involves hydrogen atoms per volume unit, many scientists think it could be used as an alternative fuel instead of natural gas or kerosene-based fuels in gas turbine combustors. The main goal of this study is to investigate turbulent swirl combustion ammonia-assisted kerosene fuels with air and pure oxygen combustion conditions in a model gas turbine combustor. For this purpose, numerical modelings have been performed by using a commercial computational fluid dynamics (CFD) code. Ammonia was introduced into the combustor from the different inlets. The ammonia composition was determined until 70% kerosene-30% ammonia mixture in an interval of 10% by heat fraction. During this addition, the total heat load provided was kept constant. The results showed that there was no considerable change over the combustion performance of kerosene. However, the maximum temperature levels and its locations changed somewhat in the combustor with ammonia addition. In addition to temperature distributions of kerosene and ammonia-assisted kerosene fuels, NOX emission levels have been addressed by performing post-processing of the CFD code used in this study. According to the predicted NOX levels, it was seen that the predicted NOX emissions levels increased significantly in the high temperature flame zone due to bound-nitrogen in ammonia (fuel-NOX mechanism). But, the predicted NOx emission levels were not too high at the exit of the combustion chamber. Therefore, it can be concluded that ammonia-assisted kerosene fuels have considerable potential in terms of combustion performance as a new and renewable fuel.

Potential advantages of using compressorless combined cycles in power engineering

Attention of humanity is being increasingly focused on prevention of anthropogenic emissions of greenhouse gases, including CO2 [1]. One of the main contributions to CO2 emissions is associated with the production of electric and thermal energy. Despite great efforts, aimed at developing renewable energy technologies, fossil fuels will dominate in this area of human activity for a very long time. Therefore, the capture of CO2, formed during the combustion of fossil fuels, is of particular importance. If air is used as a fuel oxidizer, the combustion products consist of more than 70% nitrogen. It is very difficult and expensive to separate carbon dioxide from this nitrogen. Promising solutions for carbon capture are associated with air separation and fuel combustion in pure oxygen. Recently, considerable attention has been paid to such cycles [2-4]. The gases temperature of a combustor chamber exit is regulated by the supply of CO2 and H2O to a combustion zone. In this case, a spent working fluid is almost entirely composed of a mixture of carbon dioxide and water vapor, which is easily divided into water and pure carbon dioxide. One of the options for such solutions involves a pressure increase for all components of the working fluid before injection them into a combustion chamber in a liquid phase by pumping equipment [5]. Thermodynamic cycles, in which a pressure of the working fluid is increased in the liquid phase by pumping equipment (without a compressor), can be called compressorless.

NOx emissions for oxy-mild combustion of pulverized coal in high temperature pre-heated oxygen.

Oxy-MILD (Moderate or Intensive Low Oxygen Dilution) combustion is an attractive technology for increasing combustion efficiency and reducing the nitric oxides with respect to the conventional combustion in traditional boilers or furnaces. This technology is a combination of MILD combustion, which exploits the initial preheating of combustion air up to 800÷1300 °C and the simultaneous recirculation of the hot flue gases, and of Oxy-Combustion, which uses pure oxygen (greater than 95% purity) as oxidant instead of air. The combination of both technologies is expected to bring synergetic effects: NOx reduction, CO2 capture possibility, fuel flexibility and uniformity of heat fluxes and species concentrations. This study focuses, in particular, on the analysis, by a CFD approach, of the NOx emissions for Oxy-MILD combustion of pulverized coal in a new concept of industrial boiler. The boiler, fueled with a high-volatile coal, is equipped with five burners and three outlets of the combustion products, localized on the top wall. Each burner is made-up of a central pulverized coal jet surrounded by six preheated oxygen jets. This configuration allows the achievement of the MILD combustion in pure oxygen. Results show that the goal of NOx reduction with this combustion approach is achieved. A value of about 296 mg/Nm3@6%O2 at the boiler exit is obtained under Oxy-MILD conditions, which is significantly lower than 600-800 mg/Nm3@6%O2 obtained in a traditional boiler.

Control of radiative heat transfer in high-temperature environments via radiative trapping—Part I: Theoretical analysis applied to pressurized oxy-combustion

Burning fuels with pure oxygen offers many benefits, including higher efficiency, a CO2-rich flue gas that is suitable for carbon capture, and improved flame stability. However, the extremely high flame temperature that occurs during combustion in pure oxygen is typically assumed to lead to extreme levels of radiative heat flux that are beyond the tolerable limits of boiler materials. This paper presents a unique approach to control wall heat flux under extreme temperatures in particle-laden reacting flows. Fundamental studies were carried out to understand the radiative heat transfer behavior of such systems when temperature and absorption coefficient profiles are dictated by the diffusive–convective characteristics of the system, such as the case of a non-premixed combustion reactor. The results show that if the optical thickness of the particle-laden gas medium is sufficiently large, a considerable amount of emissive power coming from the high temperature sources can be trapped in the medium and the net heat flux on the wall can be managed. An average-temperature approximation (ATA) method is developed to conveniently approximate the wall heat flux when trapping of radiation occurs in an optically dense medium. The ATA method can be utilized to design systems that require manageable wall heat flux via radiative trapping under extremely high flame temperatures.

Analysis of Structure, Extinction and Broadening in Oxygen-Enhanced Non-Premixed Flames

Abstract In the present numerical study laminar oxygen-enhanced and oxy-fuel CH4/N2–O2/N2 non-premixed flames were systematically investigated in counter-flow configuration. The compositions of the fuel and the oxidizer stream were chosen in a way, which allows a study of the flame structure at different flame temperatures in a range of approximately 1800–3000 K at constant stoichiometric mixture fraction of Z st = 0.2. The calculations were performed with the GRI 3.0 as a base kinetic mechanism, while selected cases were also investigated with the Appel et al. mechanism and the GDFkin® 3.0. The flame structure, extinction and flame broadening effects were investigated for various strain rates by analysing the heat release rate and temperature profiles. Four different heat release rate zones were identified, namely the radical chain branching, the main water and carbon dioxide formation, the fuel oxidation and the fuel pyrolysis zone. While those zones overlap in case of air-combustion, a separation accompanied by a flame broadening is found in oxygen-enhanced flames as a result of the higher flame temperatures. The four heat release zones get affected dissimilarly by increased oxygen content and flame temperature, while the flame broadening is dominated by the shift of the radical branching zone towards the oxidizer side. A comparison between air combustion and pure oxygen combustion shows that the flame is broadened by a factor of approximately 10 as long as the flame conditions are not close to the extinction limits. With increasing strain rate flame extinction starts from the oxidizer side. An increased radical pool and temperature level in the chain branching zone extents the extinction limits towards higher strain rates in oxygen-enhanced flames. On the fuel side, the increased oxygen-content with the associated higher temperature level leads to a strong endothermic zone and an intense activation of the C2-pathway.

English

Determining the composition of a mixture of combustion gases at a given temperature is based on chemical equilibrium, when the equilibrium constants are calculated on the assumption of constant pressure and temperature. In this paper, an analysis of changes occurring when combustion takes place at constant volume is presented, deriving a specific formula of the equilibrium constant. The simple reaction of carbon combustion in pure oxygen in both cases (constant pressure and constant volume) is next considered as example of application, observing the changes occurring in the composition of the combustion gases depending on temperature.

순산소 연소용 축열시스템 내에서의 열 유동 수치해석

A pure oxygen combustion technology is crucial in Carbon Capture and Storage (CCS) technology especially in capturing of <TEX>$CO_2$</TEX>, where CCS will reduce 9 <TEX>$GtCO_2$</TEX> by 2050, which is 19% of the total <TEX>$CO_2$</TEX> reduction amount. To make pure oxygen combustion feasible, a regenerative system is required to enhance the efficiency of pure oxygen combustion system. However, an existing air combustion technology is not directly applicable due to the absence of nitrogen that occupies the 78% of air. This study, therefore, investigates the heat and fluid flow in a regenerative system for pure oxygen combustion by using commercial CFD software, FLUENT. Our regenerative system is composed of aluminium packed spheres. The effect of the amount of packed spheres in regenerator and the effect of presence or absence of a bypass of exhaust gas are investigated. The more thermal mass in regenerator makes the steady-state time longer and temperature variation between heating and regenerating cycle smaller. In the case of absence of bypass, the regenerator saturates because of enthalpy imbalance between exhaust gas and oxygen. We find that 40% of exhaust gas is to be bypassed to prevent the saturation of regenerator.

The Multi-Point Temperature Decoupling Control Method and its Realization

There is a strong coupling among the multi-point temperatures of rich- or pure-oxygen combustion ceramic roller kiln. The temperature of ceramic kiln is characterized by large inertia, pure time-delay and nonlinear features. The simple and practical decoupling control method in this kiln is proposed, and the multi-point temperature decoupling controller based on DSP is developed. The traditional PID algorithm is improved. Experimental results show that the decoupling controller of multi-point temperature has high control precision, reliability, and high performance-price ratio. It can meet the control requirements of this kiln.

Methane/oxygen combustion in a rapidly mixed type tubular flame burner

An inherently safe technique of rapidly mixed type tubular flame combustion has been applied to pure oxygen combustion. The flame characteristics under various oxygen mole fractions are experimentally investigated with use of burners of different slit widths, and in addition, with optically accessible quartz burners. To fundamentally understand the requirements for rapidly mixed pure oxygen tubular flame combustion, the characteristic reaction times were calculated with Chemkin code, while the characteristic mixing times were estimated based on the width of mixing layer determined. Results show that the rapidly mixed type tubular flame combustion has been obtained under oxygen-enriched and even pure oxygen conditions. At high oxygen mole fraction, diffusion flames are anchored at the exits of the fuel slits, which restrains mixing between fuel and oxidizer, resulting in a failure of tubular flame combustion. By reducing the slit width, however, the diffusion flame is inhibited and a uniform tubular flame can be obtained from 0.11 to 0.18 in overall equivalence ratio. To quantify the mixing process, the flow field was visualized, and it has been found that there exist two types of flows, a boundary layer type flow near the exits of the slits close to the wall and an axisymmetric potential flow around the axis of rotation. Based on the mixing layer width of the boundary layer type flow, the Damkohler numbers are obtained and it is clearly shown that when the Damkohler number is less than unity, the mixing is completed before the onset of reactions, resulting in establishment of tubular flame combustion.

Technoeconomic Analysis of Microalgae Cofiring Process for Fossil Fuel-Fired Power Plants

The concept of cofiring (algal biomass burned together with coal or natural gas in existing utility power boilers) includes the utilization of CO2 from power plant for algal biomass culture and oxycombustion of using oxygen generated by biomass to enhance the combustion efficiency. As it reduces CO2 emission by recycling it and uses less fossil fuel, there are concomitant benefits of reduced greenhouse gas (GHG) emissions. The by-products (oxygen) of microalgal biomass can be mixed with air or recycled flue gas prior to combustion, which will have the benefits of lower nitrogen oxide concentration in flue gas, higher efficiency of combustion, and not too high temperature (avoided by available construction materials) resulting from coal combustion in pure oxygen. A technoeconomic analysis of microalgae cofiring process for fossil fuel-fired power plants is studied. A process with closed photobioreactor and artificial illumination is evaluated for microalgae cultivation, due to its simplicity with less influence from climate variations. The results from this process would contribute to further estimation of process performance and investment. Two case studies show that there are average savings about $0.264 million/MW/yr and $0.203 million/MW/yr for coal-fired and natural gas-fired power plants, respectively. These cost savings are economically attractive and demonstrate the promise of microalgae technology for reducing GHG emission from fossil fuel-fired power plants.

E221 急速混合型管状火炎バーナによる純酸素燃焼(第2報)(OS-9:燃焼の最近の進展(6))

Pure oxygen combustion has been attempted with using a rapidly-mixed type tubular flame burner. Instead of nitrogen in the previous study, carbon dioxide was used as a diluent and combustion characteristics were investigated as functions the oxygen concentration in the oxygen/carbon dioxide mixtures. Results show that stable combustion can be obtained in wider equivalence-ratio range for carbon dioxide than for nitrogen. Less burning velocities in carbon dioxide mixtures than in nitrogen mixtures seem to be attributed for their wider stable combustion range. Burning velocity control is important to get stable pure oxygen combustion.

Method of Volume Reduction for JET Soft Housekeeping Waste

The need to protect operators and to control the spread of contamination during Joint European Torus (JET) machine maintenance leads to the generation of soft housekeeping materials contaminated with tritium. These materials consist mostly of various plastics. A portion of the material falls into the category of intermediate-level waste and might need to be processed rather then disposed of as waste. This study deals with combustion in pure oxygen as a primary process for waste volume reduction. A mass reduction factor of 13 or greater has been demonstrated. The facility tested is of scale sufficient to meet the JET needs. The results of inactive experimental trials for the individual plastics and their mixtures are presented. The collection of chlorine-containing compounds released into the process gas during decomposition of polyvinylchloride and issues of complying with air pollution prevention regulations in the European Union have been addressed.