Oxy-fuel System Research Articles

Technological, economic, and emission analysis of the oxy-combustion process

AbstractThe high concentration of polluting emissions, and in particular of CO2 in the atmosphere, determines the greenhouse effect, therefore it is necessary to reduce its quantity as much as possible. For this reason, a strong commitment is underway to obtain effective technological improvements and to study adequate operational measures. One measure among these may be the oxy-combustion process.Many researchers have studied this process, its characteristics, and operating conditions but what is not known in the literature is the economic feasibility of a plant employing this technology and its environmental impact. There are few plants powered by oxy-combustion and many of these are still pilot plants, for this reason using Retscreen it was possible to evaluate and optimize the technical and financial feasibility of an oxy-fuel cogeneration plant for a university campus in such a way as to demonstrate the cost-effectiveness and lower environmental impact that an oxy-fuel system causes compared to a traditional system. It was evaluated the return on investment for the cogeneration plant as the economic parameters varied: in almost all cases analyzed the investment turned out to be convenient and the minimum calculated payback time was 2.5 years.With this software, it was also possible to determine the environmental impact of this technology which corresponds to a reduction of approximately 3700 tons/year of carbon dioxide compared to a traditional type of system. This work will encourage the investors and corporate sector to embrace this alternative technology for decreasing polluting emissions from the process.

Advanced exergy and exergoeconomic analyses to evaluate the economy of LNG oxy-fuel combined cycle power plant

Oxy-fuel combustion has attracted wide attention since it is thought to be an advanced technology for CO2 capture from the power generation plant on a large scale. An oxy-fuel combustion system is proposed to raise system energy efficiency utilizing cold energy from liquefied natural gas (LNG). The quantitative research on the exergy consumption, economic feasibility, and optimization strategies of the LNG oxy-fuel combustion system is conducted by advanced exergetic and exergoeconomic analyses. The results show the oxy-fuel system has an exergy efficiency of 46.83 %. The exergy destruction of the oxy-fuel system is 445.51 MW, of which the avoidable part accounts for 81.68 %. In terms of economic feasibility, the oxy-fuel system costs approximately 4.44 × 106$/h, which is considerably higher than the value of 1.99 × 106$/h in the air system. Moreover, more than 78.21 % of the cost in the oxy-fuel system is avoidable, 36.05 % higher than that of the air system. The work discovers that in the combustor of the oxy-fuel system, the improvement of the flue gas treatment unit (FGU) has a significant impact on promoting its net efficiency, and increasing its investment cost rate is not an economic limitation to save the system economy. The study is crucial for the application of oxy-fuel combustion electricity generation technologies.

The Effect of Water Content on the Combustion Characteristics of Methanol in the Oxy-fuel System

The Effect of Water Content on the Combustion Characteristics of Methanol in the Oxy-fuel System

Oxy-fuel Combustion Power Cycles: A Sustainable Way to Reduce Carbon Dioxide Emission

The energy generation from the fossil fuels results to emit a tremendousamount of carbon dioxide into the atmosphere. The rise in the atmosphericcarbon dioxide level is the primary reason for global warming and other cli-mate change problems for which energy generation from renewable sourcesis an alternative solution to overcome this problem. However, the renewablessources are not as reliable for the higher amount of energy production andcannot fulfil the world’s energy demand; fossil fuels will continue to beconsumed heavily for the energy generation requirements in the immediatefuture. The only possible solution to overcome the greenhouse gas emissionfrom the power plant is by capturing and storing the carbon dioxide within thepower plants instead of emitting it into the atmosphere. The oxy-fuel combus-tion power cycle with a carbon capture and storage system is an effective wayto minimize emissions from the energy sectors. The oxy-fuel power cycle canreduce 90–99% of carbon dioxide emissions from the atmosphere. Moreover,the oxy-fuel power cycles have several advantages over the conventionalpower plants, these include high efficiency, lesser plant footprint, much easiercarbon-capturing processes, etc. Because of these advantages, the oxy-fuel combustion power cycles capture more attention. In the last decades, thenumber of studies has risen exponentially, leading to many experimental anddemonstrational projects under development today. This paper reviews theworks related to oxy-fuel combustion power generation technologies withcarbon capture and storage system. The cycle concepts and the advancementsin this technology have been briefly discussed in this paper.

Emission of typical pollutants (NOX, SO2) in the oxygen combustion process with air in-leakages

Oxygen combustion, being an alternative to air combustion, is distinguished in a variety of modern coal management technologies by quick and easy removal of CO2 from the combustion process, which is the key merit of this oxy-fuel technology. The laboratory work conducted so far has not directly addressed the issue of air in-leakages in the oxy-fuel system. The previous studies showed that air in-leakages in the combustion system (both under the air and oxygen regime) occur and affect the combustion process. However, there are no direct research studies on the volume of air in-leakages and their impact on the individual stages of combustion, including the emission of gaseous pollutants. This article focuses on the assessment of the impact of air in-leakages on NOx and SO2 emissions for a single-stage coal-dust combustion system. Moreover, these studies were supplemented with measurements on the rate of devolatilisation of volatile matters and, in particular, on the rate of nitrogen compounds released from fuel. The obtained results of combustion in the oxy-fuel atmosphere with the following air in-leakage levels: 10, 15 and 20% were compared to combustion conditions in the air. Air in-leakages in the oxygen combustion system create an additional flow of oxygen and nitrogen appearing in the combustion area, which affects the course of pollutants and their emission. The conducted studies have shown that when adequate tightness of the combustion system is provided, it contributes to the reduced emission of nitrogen compounds.

Comparative Analysis of the Oxyfuel and Calcium Looping Processes for Low-Carbon Cement Production

In this work, the performance of a cement plant with the integrated calcium-looping (CaL) system being developed in the H2020 CLEANKER project are simulated and benchmarked against alternative CO2 capture options, namely: (i) Tail-end CaL configuration (an end-of-pipe CaL option, with circulating fluidized bed reactors) (ii) Full Oxyfuel configuration (where both the pre-calciner and the rotary kiln are operated in oxy-combustion mode), and (iii) Partial Oxyfuel configuration (where only the pre-calciner is converted to oxy-combustion). Both CaL and oxyfuel options are integrated with a CO2 purification unit (CPU). The analysis performed shows that CaL systems provide greater CO2 reductions (both direct and indirect) than oxyfuel systems, but are subject to greater fuel consumption. The integrated CaL system shows better energy performance than the tail end CaL system (which is the most fuel consuming system) thanks to the presence of a single calciner. The full oxyfuel system shows the lowest SPECCA value among the systems studied but is penalized by the high electric energy demand. Finally, the partial oxyfuel system has lower electricity consumption than the full oxyfuel system, but it is the system with the highest CO2 emissions.

Update of project to develop high-efficiency oxy-fuel IGCC system

Update of project to develop high-efficiency oxy-fuel IGCC system

Numerical study on an original oxy-fuel combustion power plant with efficient utilization of flue gas waste heat

In this work, an original oxy-fuel combustion natural gas power plant with two-stage power generation subsystems is proposed to realize the high-efficiency power generation with low-cost carbon capture. H2O and CO2 derived from flue gas is used as diluent to moderate the high temperature in oxy-fuel system. N2 Brayton cycle as the primary subsystem is utilized to generate electricity from GT exhaust heat. Organic Rankine cycle and transcritical CO2 cycle is used as the secondary subsystem for the low-grade power generation. Accordingly, organic Rankine cycle system and transcritical CO2 cycle system are established and simulated. The cryogenic LNG provides cold energy for the two-stage power generation subsystems and CO2 capture to reduce the power consumption of compression. The numerical results show that when 94.8% of CO2 with 97.2% purity is captured, the power consumption of carbon capture is approximately 0.57 kWh/kg-CO2 and 0.07 kWh/kg-CO2 in O2/CO2 and O2/H2O combustion atmosphere. Transcritical CO2 cycle is revealed to be more efficient for the utilization of flue gas waste heat (including the latent heat of flue gas) than organic Rankine cycle. The net power generation efficiency of transcritical CO2 cycle system is 58.78% in O2/CO2 atmosphere and 54.87% in O2/H2O atmosphere.

Chemical, thermal and dilution effects of carbon dioxide in oxy-fuel combustion of wood in a fixed bed

Experimental and numerical modeling was performed on eucalyptus wood combustion under oxy-fuel conditions using a fixed bed reactor in order to isolate the role of various carbon dioxide effects on the burning rate. Wood combustion was investigated under four different mixtures of O2 and Ar/CO2/N2: 21 % O2/79 % N2; 21 % O2/22.5 % CO2/56.5 % Ar; 40 % O2/60 % CO2; and 40 % O2/47 % CO2/13 % Ar. The first three mixtures were designed to have the same peak temperatures in order to isolate chemical and dilution effects of CO2. This was achieved by substituting some percentage of CO2 with Ar in O2/CO2 mixture while maintaining a constant concentration of O2. The fourth mixture was meant to isolate the thermal effect of CO2. The results were obtained from both the experimental rig and numerical simulation for a fixed bed configuration. Wood combustion in the fixed bed was modeled using Lagrange-Euler method, where gas-phase was calculated using computational fluid dynamics (CFD), that is Euler phase, while solid-phase was tracked in Lagrange phase using discrete element method (DEM). The results show that ignition time in CO2 environment decreases gradually as O2 concentration is increased. On the other hand, burning rate and flame front speed increase as O2 concentration is increased. It was established that dilution effect is the most influential parameter on the burning rate of wood combustion in an oxy-fuel system.

Sliding wear performance of thermally sprayed Ni-Cr based alloy deposited on SAE 1045 steel

ABSTRACTThe present work has been carried out in order to investigate the sliding wear performance of a Ni-Cr based alloy, containing boron, carbon, silicon and iron, deposited onto a SAE 1045 steel substrate. The coatings were thermally sprayed by means of a High Velocity Oxy-Fuel system and post heat-treated for one hour at 760°C in an argon atmosphere. The relative sliding performance was evaluated under unlubricated dry conditions at different applied normal loads and sliding velocities, in order to analyze the influence of these parameters on the wear response. Test results are discussed and interpreted on the basis of both microstructural evaluations and mechanical properties measurements. The surface morphology and topography of the wear scars have been studied through of a Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) techniques. The results have shown an improved wear resistance of the coated steel samples as compared to the uncoated ones.

Gas-fired chemical looping combustion with supercritical CO2 cycle

Oxy-fuel combustion is currently gathering attention as one of the promising options for capturing CO2 efficiently, when applied to power plants, for subsequent carbon sequestration. However, this option requires a large quantity of high-purity oxygen that is usually produced in an energy-intensive air separation unit (ASU). Chemical looping combustion (CLC) is a technology with the potential of reducing the costs and energy penalties associated with current state-of-the-art cryogenic ASUs. In this work, the techno-economic performance of a natural gas-fired oxy-combustion cycle with cryogenic ASU is compared with that based on CLC. Two natural gas-fired cycles are considered: (i) staged oxy-fuel natural gas combined cycle as a reference; and (ii) gas-fired CLC with supercritical CO2 cycle. The process models were developed in Aspen Plus® in order to evaluate the thermodynamic performance of the proposed system and to benchmark it against the reference cycle. The results show that the net efficiency of the proposed cycle, including CO2 compression, is more than 51%, which is comparable to that of a conventional natural gas combined cycle with CO2 capture and 2.7% points higher than that of the reference cycle. Moreover, the economic evaluation indicates that a reduction in levelised cost of electricity from £38.3/MWh to £36.1/MWh can be achieved by replacement of the ASU-based oxy-fuel system with CLC. Hence, gas-fired CLC with a supercritical CO2 cycle has high potential for commercialisation.

Current Activites for Commercialization of Oxyfuel Power Plant

IHI has been developing oxyfuel technology as one of the CO2 capture technologies from coal fired power plants since 1989. For the demonstration of oxyfuel combustion technology, IHI jointly formed and participated in “Callide Oxyfuel Project” with Australian and Japanese partners in 2008. In the Project, the applicability of the technology to an existing power plant, the reliability and the effectiveness for CCS were demonstrated through achievement of more than 10,000 hours oxyfuel operation and underground injection of CO2 that captured from oxyfuel coal power plant. After completion of the demonstration, additional tests were carried out in the laboratory and at the pilot-scale combustion test facilities in IHI’s Aioi Works. The additional test purpose is to check the performance of the equipment mostly used in current power plants in order for the technology to be flexibly applied to them. For example, the vertical type roller mill and the ESP were tested. In vertical type roller mill test, it was made clear that the effect of moisture concentrated in the flue gas in oxyfuel system was not so big for the pulverization of coal. In ESP test, it was clearly found that the dust collection efficiency in oxyfiring combustion is higher than that in airfiring combustion.

Update of Project to Develop High-Efficiency Oxy-Fuel IGCC System

Update of Project to Develop High-Efficiency Oxy-Fuel IGCC System

Verification of applicability to wide range coal property of O<sub>2</sub>/CO<sub>2</sub> –blown gasification technology for Oxy-fuel IGCC system

Verification of applicability to wide range coal property of O<sub>2</sub>/CO<sub>2</sub> –blown gasification technology for Oxy-fuel IGCC system

Verification of O<sub>2</sub>/CO<sub>2</sub> –blown gasification technology for oxy-fuel IGCC system

Verification of O<sub>2</sub>/CO<sub>2</sub> –blown gasification technology for oxy-fuel IGCC system

Effects of Purity and Phase Content of Feedstock Powder on Thermal Durability of Zirconia-Based Thermal Barrier Coatings

The thermal durability of thermal barrier coatings (TBCs) obtained using feedstock powders with different purity and phase content was investigated by cyclic thermal testing, including the effects on the sintering and phase transformation behaviors. Three kinds of 8 wt.% yttria-stabilized zirconia, namely regular purity (8YSZ), high purity (HP), and no monoclinic phase (nMP), were employed to prepare top coats by atmospheric plasma spraying on a NiCoCrAlY bond coat using a high-velocity oxy-fuel system. Use of 8YSZ, HP, and nMP for plasma spraying affected the microstructure and lifetime of the TBC in furnace cyclic testing (FCT) at 1100 °C and the sintering rate during annealing at 1400 °C for 50, 100, 200, and 400 h. In FCT, the TBC formed from nMP showed the longest durability, while that formed from HP showed lifetime performance similar to that obtained with regular-purity 8YSZ. The TBC obtained with nMP also exhibited the lowest monoclinic phase transition rate, followed by those obtained using HP and 8YSZ.

Numerical Study on the Effect of Lambda Value (Oxygen/Fuel Ratio) on Temperature Distribution and Efficiency of a Flameless Oxyfuel Combustion System

The flameless oxyfuel combustion technology has been proven to be a promising new method to reduce the fuel consumption and pollutants in industrial applications [...]

CO<sub>2</sub>回収型クローズドIGCCシステム検討と実証計画

CO<sub>2</sub>回収型クローズドIGCCシステム検討と実証計画

Sliding Wear Behavior of High Velocity Oxy-Fuel Sprayed WC-CO Coatings

The Thermal spraying techniques are coating processes in which melted materials are sprayed onto a surface and the feedstock is heated by electrical or chemical means. High velocity oxy-fuel (HVOF) spraying is seen as the pre-eminent process for deposition of such coatings. The coating that is formed is not homogenous and typically contains a certain degree of porosity, and, in the case of sprayed metals, the coating will contain oxides of the metal. This paper examines the effect of WC–Co coatings on the wear behaviour, WC were thermally sprayed by a high-velocity oxy-fuel (HVOF) system from WC–12% Co powder. Sliding wear resistance of this coating was calculated using pin-on-disk tribometer (ASTM G99-90). The morphologies of WC-Co coating were observed by X-ray diffraction (XRD), Energy dispersive analysis and Scanning electron microscope (SEM). Micro hardness is calculated by using Vickers Hardness test. And it was found that WC-Co coatings show better wear resistant properties.

A Comparative CFD Study on Simulating Flameless Oxy-Fuel Combustion in a Pilot-Scale Furnace

The current study presents a method to model the flameless oxy-fuel system, with a comparative approach, as well as validation of the predictions. The validation has been done by comparing the predicted results with previously published experimental results from a 200 kW pilot furnace. A suction pyrometer has been used to measure the local temperature and concentrations of CO, CO2, and O2at 24 different locations. A three-dimensional CFD model was developed and the validity of using different submodels describing turbulence and chemical reactions was evaluated. The standardk-εmodel was compared with the realizablek-εmodel for turbulence, while Probability Density Function (PDF) with either chemical equilibrium or the Steady Laminar Flamelet Model (SLFM) was evaluated for combustion. Radiation was described using a Discrete Ordinates Model (DOM) with weighted-sum-of-grey-gases model (WSGGM). The smallest deviation between predictions and experiments for temperature (1.2%) was found using the realizablek-εmodel and the SLFM. This improvement affects the prediction of gaseous species as well since the deviation between predictions and experiments for CO2volume percentages decreased from 6% to 1.5%. This provides a recommendation for model selections in further studies on flameless oxy-fuel combustion.