Oxy-fuel Combustion Plant Research Articles

Low-carbon optimal dispatch strategy of power systems considering the combined operation of oxy-fuel combustion and electric hydrogen production

ABSTRACT Oxy-fuel combustion technology offers a promising solution for achieving nearly zero carbon dioxide emissions from coal-fired units, presenting a viable path toward low-carbon dispatch. This study establishes a simulation model for the low-carbon operation of power systems, focusing on the integrated operation of an oxy-fuel combustion plant and electric hydrogen production. By incorporating oxygen generated from electric hydrogen production into the oxy-fuel combustion plant, the primary objective is to minimize system operation costs. Through simulation analysis and verification, a comparative scenario is constructed to evaluate performance. The simulation results indicate that the joint operation approach yields significant benefits. In comparison to separate operation, the joint operation strategy leads to a reduction of approximately 7.38% in total system costs, 18.79% in operating costs, and 23.56% in carbon emissions. This integrated approach not only achieves lower carbon emissions but also results in reduced overall system costs.

Pressurized oxy-fuel combustion with sCO2 cycle and ORC for power production and carbon capture

The pressurization of oxy-fuel combustion presents the opportunity to recuperate more latent heat from the flue gas within the boiler. This study proposed a coal-fired pressurized oxy-fuel combustion plant coupled with the sCO2 Brayton cycle for simultaneous power production and carbon capture. Two configurations, i.e., sCO2 recuperator split and sCO2 bottom cycle, are conceived to fully exploit the flue gas heat from the boiler. Waste heat from various sources, including the air separation unit, the CO2 compression and purification unit and the sCO2 cycle, are recuperated by the organic Rankine cycle (ORC) to augment the net power efficiency. Sensitive analyses, including the turbine parameters, the recuperator split ratio, and the ORC parameters, are conducted to optimize the design and operation conditions of the plant. The plant net power efficiency ranges between 39.4 % and 42.9 %, inclusive of CO2 compression. The levelized cost of electricity (LCOE) is calculated, and the LCOE results are in the range of 101.60 $/MWh and 106.07 $/MWh for different configurations. These findings suggest the system's viability for future coal-fired plant with carbon capture.

CARBON FOOTPRINT COMPARATIVE ANALYSIS FOR EXISTING AND PROMISING THERMAL POWER PLANTS

The power production industry is the main greenhouse gas emitter that makes its contribution to global warming. The greenhouse gas emission takes place in fuel production, transportation, and combustion. A prospective method for emission mitigation is the transition to organic fuel-burning facilities with small emissions by capturing carbon dioxide. Power consumption on the carbon dioxide capture remarkably reduces the efficiency of these facilities, which leads to increasing of fuel consumption and greenhouse gas emission because of the larger fuel production and transportation. Based on the material balance method, taking into account system effect of changes in efficiency and amount of fuel consumed, the paper estimated the carbon footprint over a twenty-year lifecycle for following thermal power plants types: combined cycle and oxy-fuel combustion plants for both natural gas and coal with internal gasification. It is shown that the transition to oxygen-fuel plants can reduce the carbon footprint near 90% for natural gas and near 75% for coal. The study also demonstrates the positive effect of carbon capture and storage system implementation for reducing carbon footprint near 75% for natural gas and near 70% for coal.

Thermoeconomic investigation of pressurized oxy-fuel combustion integrated with supercritical CO2 Brayton cycle

Pressurization is expected to increase the power efficiency of oxy-fuel combustion plant. Supercritical CO2 (sCO2) Brayton cycle could yield higher thermal efficiencies at lower capital cost than the state-of-the-art steam-based power cycles. The coupling of pressurized oxy-fuel combustion and sCO2 cycle could potentially offer higher net power efficiency over its counterparts with CO2 capture. In this paper, pressurized oxy-fuel combustion was integrated with three different sCO2 Brayton cycle layouts, i.e., single reheated recompression, double reheated recompression, and intercooled recompression. The systems were analyzed from the perspective of thermodynamics and economics. The net power efficiencies for the three systems were 39.4%, 40.2%, and 41.3%, respectively. The effect of boiler pressure on the latent heat recovery of the flue gas was analyzed. In the sensitivity analysis, the influence of turbine inlet temperature, turbine inlet pressure, turbine inlet temperature, turbine outlet pressure, recirculated fan pressure boost, and the high-temperature recuperator (HTR) split ratio on the plant net power efficiency was assessed. Finally, the economic analysis was conducted. The levelized cost of electricity (LCOE) of the three systems were 103.18 $/MWh, 108.45 $/MWh, and 110.07 $/MWh, respectively. The results showed that the integrated systems were attractive as potential candidates for the coal-fired power generation with CO2 capture.

Simulation of CO2 Capture Process in Flue Gas from Oxy-Fuel Combustion Plant and Effects of Properties of Absorbent

Oxy-fuel combustion technology is an effective way to reduce CO2 emissions. An ionic liquid [emim][Tf2N] was used to capture the CO2 in flue gas from oxy-fuel combustion plant. The process of the CO2 capture was simulated using Aspen Plus. The results show that when the liquid–gas ratio is 1.55, the volume fraction of CO2 in the exhaust gas is controlled to about 2%. When the desorption pressure is 0.01 MPa, desorption efficiency is 98.2%. Additionally, based on the designability of ionic liquids, a hypothesis on the physical properties of ionic liquids is proposed to evaluate their influence on the absorption process and heat exchanger design. The process evaluation results show that an ionic liquid having a large density, a large thermal conductivity, and a high heat capacity at constant pressure is advantageous. This paper shows that from capture energy consumption and lean circulation, oxy-fuel combustion is a more economical method. Furthermore, it provides a feasible path for the treatment of CO2 in the waste gas of oxy-fuel combustion. Meanwhile, Aspen simulation helps speed up the application of ionic liquids and oxy-fuel combustion. Process evaluation helps in equipment design and selection.

Thermo- economic evaluation of 300 MW coal based oxy-fuel power plant integrated with organic Rankine cycle

Oxy-fuel combustion is currently most potential technology to reduce carbon dioxide emission from coal based power plants. This work describes thermo- economic analysis of CO2 capture technology by assessment of detailed models of a 300 MW steam generation unit, an oxygen separation unit and shock wave CO2 compression unit that are developed using Aspen HYSYS v9. The overall efficiency of the oxy-fuel combustion plant reduced by 10.98% due to implementation of air separation and CO2 sequestration systems. To reduce the efficiency penalty, the waste heat released at different portions of plant is used to boost an organic Rankin cycle for power generation. CO2 compression intercoolers and air separation unit coolers are two low grade heat sources which are utilized in ORCs. By recovering the wasted heats, the unit power consumption of oxygen production decreases from 227.3 to 214.2 kW h/t O2, power plant efficiency drop reduces about 1.51% and cost of electricity decreases from 67.03 to 64.94 €/MWh. The results indicate that proposed ORCs are thermodynamically and economically feasible to integrate with plant to increase the net efficiency.

Impacts of thermos-physical properties on plate-fin multi-stream heat exchanger design in cryogenic process for CO2 capture

Oxy-fuel combustion is one of the most promising technologies for CO2 capture for power plants. In oxy-fuel combustion plants, cryogenic process can be applied for CO2 purification because the main impurities in flue gas are non-condensable gases. The multi-stream plate-fin heat exchanger is one of the most important components in the CO2 cryogenic system. In-depth understanding of the impacts of property on the heat exchanger is of importance for appropriate design. In order to investigate the impacts of properties on sizing the heat exchanger and to further identify the key properties to be prioritized for the property model development, this paper presented the design procedure for the plate-fin multi-stream heat exchanger for the CO2 cryogenic process. Sensitivity study was conducted to analyze the impacts of thermos-physical properties including density, viscosity, heat capacity and thermal conductivity. The results show that thermal conductivity has the most significant impact and hence, developing a more accurate thermal conductivity model is more important for the heat exchanger design. In addition, even though viscosity has less significant impact compared to other properties, the larger deviation range of current viscosity models may lead to higher uncertainties in volume design and annual capital cost of heat exchanger.

Process simulation and optimization of municipal solid waste fired power plant with oxygen/carbon dioxide combustion for near zero carbon dioxide emission

As a new type of high-intensity combustion technology, oxy-fuel combustion technology can effectively reduce the generation and emission of pollutants, particularly near zero emission of carbon dioxide when applied to the waste incineration process. Compared to the conventional air waste-to-energy incineration power generation, the municipal solid waste oxy-fuel combustion power generation system is more complex, resulting in a relatively large space for optimization. In this work, a waste-to-energy incineration power plant in Shenzhen, China, is taken as the original object, and used to establish the process simulation of the conventional plant using Aspen plus. The results are compared and verified with the operation data. Based on the results, models or subsystems are set up for the air separation unit, the municipal solid waste oxy-fuel combustion power system and the flue gas processing compression system, respectively. Then, the subsystems are coupled and connected to establish the whole process simulation of the waste oxy-fuel combustion power plant, and the optimization analyses of the overall plant operating parameters are presented. The results show that the best supplying oxygen concentration is 96%, the carbon dioxide recovery rate of the entire system is 96.24%, and near-zero carbon dioxide emission is basically achieved. The energy consumptions sharing by the flue gas processing compression subsystem, the air separation subsystem, and the others account for 19.82%, 54.29%, and 25.89% of the total energy consumption, respectively. After coupling optimization analysis, the net power generation efficiency of the municipal solid waste oxy-fuel combustion plant increases 2.69%, from 6.88% to 9.57%.

Exergy-based control strategy selection for flue gas recycle in oxy-fuel combustion plant

Control system design is one of the key elements which need to be studied before commercial implementation of oxy-fuel power plants. Among others, the control strategy for flue gas recycle process should be firstly considered as it is one of the major differences between oxy-fuel combustion and traditional power plants. In this paper, a dynamic model combined with exergy analysis was firstly proposed to design the control system and evaluate the performance of potential control schemes for flue gas recycle process. The dynamic model had been extensively validated using static and dynamic data from a 3MWth oxy-fuel combustion facility. Based on the dynamic model, the characteristics of the flue gas recycle system was investigated and two possible control configurations, RR (recycle valve coupled with recycle fan) and SR (stack valve combined with recycle fan), were proposed. The control performances of the two candidates were tested in three typical types of disturbances usually occurred in the operation and further evaluated from the perspective of exergy efficiency. It was shown that both control loops could maintain the target variables (flue gas recycle ratio and recycled flue gas pressure) stable in the disturbances, while the total exergy destruction of flue gas recycle system in RR is 2.4%, 1.7% and 0.6% higher than that in SR during the disturbance tests, respectively. The exergy-based control strategy selection method proposed in this paper provides good insight to obtain the optimum control method for other subsystems in the power plant.

Dynamic modelling of a CO2 capture and purification unit for an oxy-coal-fired power plant

Oxy-combustion is a promising pathway to capture CO2 from coal fired power plants that compete favourably with other CO2 capture technology pathways, such as post-combustion and pre-combustion. Oxy-combustion has attracted attention because it provides a CO2-enriched flue gas stream which can be further purified, if required, using a relatively simple multi-stage compression and cooling processes. Several studies have been published on the capture and purification of CO2 from oxy-combustion. However, knowledge of the dynamic behaviour of the CO2 capture and purification process is very limited. Dynamic insight is key to design suitable control schemes to ensure that this process can be operated at near optimal conditions, while maximizing CO2 recovery and meeting product quality requirements. This study aims to develop and validate a dynamic model of CO2 capture, purification and compression process for integration with oxy-fuel combustion plants. The model was developed and validated based on a study performed by the International Energy Agency Greenhouse Gas (IEAGHG) R&D programme (Dillon et al., 2005). Mathematical models are provided, steady state data are validated and case studies performed to study the transient behaviour of the process in response to process disturbances.

Flue gas cleaning for CO2 capture from coal-fired oxyfuel combustion power generation

Current progress in flue gas cleaning for CO2 capture from oxyfuel combustion has been described based on conceptual development, fundamental understanding and practical tests at the Schwarze Pumpe Oxyfuel Pilot Plant (OxPP). Significant improvement in understanding the characteristics of SOx, NOx, particulate matters (PMs) and non-condensable gas components in flue gas cleaning processes provide a scientific basis for further developments of flue gas cleaning technologies. Testing results from pilot studies have proved that flue gas cleaning systems have reached the achievable performance and have also shown that there is generally no fundamental technical bottleneck for most of the flue gas cleaning technologies. Further developments should focus on comprehensive optimisation of the flue gas cleaning processes combined with boiler and downstream CO2 compression processes. Changes in flue gas cleaning technologies may be excepted if more attractive gas cleaning processes could be successfully developed in the near future; for example, NOx removal and control technologies. The development of a monitoring approach for the mitigation of non-condensable gases is an important operational issue for largescale oxyfuel combustion plant.

Control system for an oxy-fuel combustion fluidized bed with flue gas recirculation

Abstract In oxy-fuel combustion it is generally accepted that fed O2 into the boiler diluted together with CO2 is advantageous when similar combustion conditions as in air-firing case want to be reached. In experimental oxy-fuel combustion plants, auxiliary CO2 from commercial tanks is often used for carrying out experimental tests. However, this fact entails high operational costs in addition to scale prices are not applied in experimental size plants. A reduction of these costs could be achieved by supplying the required CO2 through flue gas recirculation, as it would happen in an industrial oxy-fuel plant. However, transition from air-firing to oxy-firing, and changes in the flue gas composition during operation can vary conditions inside the boiler. This issue becomes particularly important when oxy-fuel combustion takes place inside a fluidized bed boiler, where fluidization conditions must be kept inside a narrow optimum range, i.e. fluidization velocity or oxygen content at inlet, although changes in recirculation rates or flue gas composition could disturb it. With this aim, an efficient recycled flue gas control strategy has been modeled and validated through experiments in a test rig. This system could be easily adapted to any experimental oxy-fuel pilot plant, since it has been designed for controlling conventional instrumentation, valves and drives.