Zero Emission Power Plant Research Articles

Stability and Emission Characteristics of a Stratified Hydrogen-Enriched Oxy-Methane Flame on a Multihole Burner: An Experimental Study.

Hydrogen (H2) enrichment is a viable solution to deter the early blowout of oxy-fuel flames at high CO2 dilution levels and to enhance combustor turndown in the supercritical-CO2 cycles of zero-emission power plants. This was already implemented successfully in a previous study by the author, where H2 was premixed with the oxy-reactants upstream of the burner headend in a fully premixed flame stabilized on a micromixer-like burner. The micromixer technology is known for its superior flame stability and inherent fuel/oxidizer flexibility. To avoid the higher risk of flashback when H2 is premixed with the primary reactants, the present study introduces the enrichment H2 in a nonpremixed manner from the enhanced-blowout fuel circuit of the micromixer burner, which comprises circumferential jets that surround the core oxy-flame. This approach aims to enhance combustor turndown even further by benefiting from inducing stratification in the flame. It was found that the blowout limit of the fully premixed (CH4/H2/O2/CO2) flame did not improve by stratification (H2-CH4/O2/CO2); it deteriorated slightly. The present study thus analyzes the stability, morphology, and CO emissions of the stratified flame, in order to explain this behavior and provide recommendations for how hydrogen enrichment should be introduced in oxy-fuel micromixer combustors.

SPECIAL FEATURES OF ENERGY TRANSITION IN ASIAN COUNTRIES

The current stage of development of the world energy industry is taking place in line with the fourth industrial revolution, characterized by the changing ways of life and the introduction of new technologies based on R&D. Environmental pollution has reached a large scale, and as a result it has become necessary to change the structure of modern fuel and energy balance in favor of renewable and non-traditional energy sources. Asian countries vary widely in terms of the level of economic development, making it difficult to create an integrated energy market in Asia. A typology of countries according to the level of economic development was elaborated on the basis of a multi-scale analysis using traditional methods of economic geography. In total these countries rank first in the world in terms of greenhouse gas emissions, accounting for almost 60% of pollutants released into the environment. The fuel and energy balance of Asian countries is characterized by a high proportion of coal, which contributes to the large-scale environment pollution. In accordance with international practice, the countries of the continent adopted energy programs aimed at lesser emissions by reducing the share of coal and switching to low-carbon energy sources. The energy transition can take place primarily in the leading Asian countries that have necessary financial resources. Most Asian countries are at the early stages of industrialization, and the energy transition is almost impossible at this stage because they use energy-intensive industrial technologies. The urgent need to stop climate change comes into conflict with rising energy consumption. Asia has become the world’s leader in energy consumption, as it takes place not only in industry, but also in the utility sector, because 4.2 billion people, or more than 50% of the world’s urban population, live in cities. China has become a leader in the introduction of renewable energy sources, the country has developed and implements new environmental standards that will achieve carbon neutrality by 2060 through the accelerated commissioning of new zero-emission power plants. The rejection of coal could aggravate socio-economic problemsof Asia because of its high share in the fuel and energy balance and the large number of people employed in the industry. In line with the sustainable development goals, the Asian countries try to introduce renewable energy sources based on the local comparative advantages.

Energy efficiency of polyimide membrane modules for air separation in zero-emission power plants: a computational analysis

Energy efficiency of polyimide membrane modules for air separation in zero-emission power plants: a computational analysis

A highly diluted oxy-fuel micromixer combustor with hydrogen enrichment for enhancing turndown in gas turbines

Most burner technologies in past studies were incapable of operating at the high CO2-dilution levels required in the oxy-fuel combustors of zero-emission power cycles. The present study addresses this gap by utilizing the micromixer gas-turbine technology, coupled with hydrogen enrichment, to present an oxy-fuel burner that is capable of sustaining highly diluted flames for application in the zero-emission Allam power. Gas-turbine micromixers have never been tested under oxy-fuel combustion conditions before, which highlights the novelty of the present study. The operability window of the present burner was quantified experimentally over ranges of fuel (CH4/H2) hydrogen fraction and oxidizer (O2/CO2) oxygen fraction. It was found that the micromixer delivers superior stability, allowing for operation at oxygen fractions as low as 21% (by vol.) without hydrogen enrichment, which satisfies the nominal dilution requirements (23%) of the primary reaction zone within the Allam-cycle combustor. Micromixers are thus the technology recommended for oxy-fuel combustion in zero-emission power plants. Enriching the fuel with hydrogen was found to boost flame stability, which allowed for reducing the oxygen fraction further down to a record-low value of 13% at a hydrogen fraction of 65% (by vol.). This offers great operational flexibility and pioneering improvement in the turndown and low-load capabilities of the cycle. The results also showed that hydrogen enrichment has minimal effect on flame temperature and combustor power density (power per unit volume), which facilitates additional operational flexibility in adjusting the hydrogen fraction to sustain flame stability without influencing cycle peak temperature or turbine health.

Thermodynamic analysis and optimization of an oxy-combustion combined cycle power plant based on a membrane reactor equipped with a high-temperature ion transport membrane ITM

This paper presents an advanced zero emission power plant (AZEP) which is a combined cycle power plant with a membrane reactor equipped with a high-temperature ion transport membrane (ITM). The membrane reactor, which is used as a replacement for a combustor in the gas turbine, combines three functions: combustion of fuel, oxygen separation from the air in the ITM, and heating of the oxygen-depleted air. Due to the membrane reactor, the AZEP does not need an energy-consuming external air separation unit, which is a significant advantage over other types of power plants which utilize oxy-combustion technology. The presented thermodynamic model for AZEP with an advanced numeric model of the ITM allows the user to perform thermodynamic analyses for a wide range of AZEP operating parameters and to select their optimal values, without the need to determine the geometric parameters of the ITM and heat exchangers. The obtained results allow one to indicate the basic features of this carbon capture technology. The selection of AZEP operating parameters is related to the balance between the power plant’s efficiency maximization and the limitation of the ITM and heat exchangers surface areas. This manuscript also presents an analysis of the possible AZEP plant development. The development model of the E-AZEP plant assumes a number of improvements in the parameters of the ITM and the entire membrane reactor, with respect to the AZEP plant basic model. The ITM assumes an improvement in the ionic conductivity (σion) by approx. 45%, by changing the value of the conductivity coefficient (C2) as well as increasing the maximum operating temperature of the membrane from 900 °C to 1000 °C. The work demonstrated the great influence of the membrane surface. In the model of the membrane reactor, a higher flue gas temperature was assumed at the combustion chamber outlet, equal to t1g = 1600 °C, which together with the assumption of temperature approximation ΔThe.HHX = 20 K gives an air temperature t3a = 1580 °C. With the current technological possibilities, AZEP plants are competitive compared to alternative solutions, but they do not have a significant advantage over them. However, overcoming the presented limitations may allow us to achieve an advantage in terms of achieved efficiency compared to alternative CO2 capture technologies. Achieving the air temperature at the inlet to the expander, at a level close to the temperatures used in J-class gas turbines (E-AZEP plant case), allows for a decrease in the efficiency when compared to modern combined cycle power plants, at a level of 3% points.

Investigation of Applicability of Polyimide Membranes for Air Separation in Oxy-MILD Zero-Emission Power Plants

Primary element of an oxy-combustion plants is ambient air separation unit. This paper presents the results of experimental research concerning the parameters of the separation of N2/O2 from ambient air, using capillary polymer membranes, potentially applicable in oxy-combustion technology, under variable operational conditions. Collected data were utilized to approximate continuous functions describing the variability of essential parameters of the air separation based on such membranes. The functions were introduced to develop a complete mathematical model of the separation unit, intended to be applied in oxy-Moderate or Intense Low Oxygen Dilution (oxy-MILD) zero-emission plants. Computational analyses were performed for three variants of the unit’s configuration: serial connection of membrane modules, unit with retentate recirculation and unit with permeate recirculation. The results of the research, in the form of sets of characteristic curves, depicting parameters of the separation process as a function of the variable operational conditions, show that crucial differences to the subsequent separation parameters (permeate purity, real selectivity coefficient, recovery coefficient) and with regard to the power consumed, were obtained. The highest parameters of the module were gained for serial connection, whereas the lowest – for permeate recirculation. The lowest energy consumption was acquired for the retentate recirculation variant.

Adapting the zero-emission Graz Cycle for hydrogen combustion and investigation of its part load behavior

A modern energy system based on renewable energy like wind and solar power inevitably needs a storage system to provide energy on demand. Hydrogen is a promising candidate for this task. For the re-conversion of the valuable fuel hydrogen to electricity a power plant of highest efficiency is needed.In this work the Graz Cycle, a zero-emission power plant based on the oxy-fuel technology, is proposed for this role. The Graz Cycle originally burns fossil fuels with pure oxygen and offers efficiencies up to 65% due to the recompression of about half of the working fluid. The Graz Cycle is now adapted for hydrogen combustion with pure oxygen so that a working fluid of nearly pure steam is available. The changes in the thermodynamic layout are presented and discussed. The results show that the cycle is able to reach a net cycle efficiency based on LHV of 68.43% if the oxygen is supplied “freely” from hydrogen generation by electrolysis.An additional parameter study shows the potential of the cycle for further improvements. The high efficiency of the Graz Cycle is also achieved by a close interaction of the components which makes part load operation more difficult. So in the second part of the paper strategies for part load operation are presented and investigated. The thermodynamic analysis predicts part load down to 30% of the base load at remarkably high efficiencies.

Design of a multi-can carbon-free gas turbine combustor utilizing multiple shell-and-tube OTRs for ZEPP applications

Based on 3-D numerical simulations, the present study presents a design of a multi-can carbon-free gas turbine combustor utilizing multiple oxygen transport reactors (OTRs) of the shell and tube type for zero emission power plant (ZEPP) applications. The design of the gas turbine combustor is calculated based on optimizations of flow configuration (co and counter current), shell side and tube side (feed and sweep) flow rates, inlet fuel concentration in the sweep flow (CH4 plus CO2), and membrane tube diameter, pitch (spacing) and length. High-temperature mixed conducting perovskite-type BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3−δ) ceramic membrane tubes are used considering square arrangement of the tubes. A mesh was developed and used by the ANSYS Fluent software. A modified oxygen permeation equation was utilized accounting for reacting flow and sub-step membrane surface reactions. Series of user defined functions (UDFs) written in C++ code are compiled and hooked to the software to account for oxygen permeation across the membrane. A modified two-step oxy-combustion reaction kinetics mechanism for methane is applied. The results showed that co-current flow configuration can fit better the application of OTR in gas turbine combustion applications. Based on required power output in the range from 10 to 15 MWe, the final design of the gas turbine combustor is calculated to have 16 cans (OTRs) with 3000 membrane tubes per can and volume of 5.2272 m3 per can.

Thermodynamic analysis of the advanced zero emission power plant

Abstract The paper presents the structure and parameters of advanced zero emission power plant (AZEP). This concept is based on the replacement of the combustion chamber in a gas turbine by the membrane reactor. The reactor has three basic functions: (i) oxygen separation from the air through the membrane, (ii) combustion of the fuel, and (iii) heat transfer to heat the oxygen-depleted air. In the discussed unit hot depleted air is expanded in a turbine and further feeds a bottoming steam cycle (BSC) through the main heat recovery steam generator (HRSG). Flue gas leaving the membrane reactor feeds the second HRSG. The flue gas consist mainly of CO2 and water vapor, thus, CO2 separation involves only the flue gas drying. Results of the thermodynamic analysis of described power plant are presented.

Design of an ion transport membrane reactor for application in fire tube boilers

A design of an ITM (ion transport membranes) reactor is introduced in a two-pass fire tube boiler furnace to produce steam for power generation toward the ZEPP (zero emission power plant) applications. Oxygen separation, combustion and heat exchange occur in the first pass containing the multiple-units ITM reactor. In the second pass, heat exchange between the combustion gases and the surrounding water at 485 K (Psat = 20 bar) occurs mainly by convection. The emphasis is to extract sufficient oxygen for combustion while maintaining the reactor size as compact as possible. Based on a required power in the range of 5–8 MWe, the fuel and gases flow rates were calculated. Accordingly, the channel width was determined to maximize oxygen permeation flux and keep the viscous pressure drop within a safe range for fixed reactor length of 1.8 m. Three-dimensional simulations were conducted for both counter and co-current flow configurations. Counter-current flow configuration proved its suitability in fire tube boilers for steam generation over the co-current flow configuration. The resultant reactor consists of 12,500 ITM units with a height of 5 m, membrane surface area of 2700 m2 and a total volume of 45.45 m3.

Life Cycle Assessment of Advanced Zero Emission Combined Cycle Power Plants

This study investigated different concepts for natural-gas-fired power plants with the CO2capture, and compared them based on the net plant efficiency and emission of CO2. The cycles were based ona six oxy-fuel, one post-combustion and two pre-combustion capture concept. This paper presented theresults of an environmental evaluation performed by the application of the Life Cycle Analysis (LCA) methodusing SimaPro model to compare an Advanced Zero Emission Power Plant (AZEP) concept with a conventionalcombined cycle power plant from 50MW to 400MW. The LCA study was built upon the calculation and thecomparison of several impacts (emissions of CO2, CO, NOX, and SOX, consumption of water and primaryenergy) and several impact categories (climate change, acid rain, ozone depletion and Ecotoxicity). The workwas developed entirely using the Eco-indicator99 of the LCA method. The results showed that for all studiedimpacts, the AZEP power plants have fewer impacts. However, compared to the conventional combined cyclepower plants, the total primary energy consumption in the AZEP concept is bigger due to the lower electricefficiency.

Zero Emission Power Plant

India is the world’s fourth largest economy and has a fast growing energy market. India’s current power capacity is 30% short of demand. Coal and petroleum are the primary sources of energy. High ash content in Indian coal and inefficient combustion technologies contribute to India’s emission of air particulate matter and other trace gases, including gases that are responsible for the greenhouse effect. Climate change is one of the most serious single challenges faced by humankind today. Probably one of the greatest impacts in reducing CO2 emissions will be made by the introduction of Zero Emission Fossil Fuel Power Plants including carbon dioxide capture and storage. CO2 is the main greenhouse gas due to the very high overall amount emitted by human activities and about one third of the overall human CO2 emissions are produced by the power generation sector. The zero-emission power plant is no longer a fantasy. Filters are becoming increasingly sophisticated; removing dust and other harmful substances from exhaust Gases. And in the future, new power generation technologies should prevent Emissions of carbon dioxide getting into the atmosphere. Enhanced measurement Methods and more efficient power distribution are also helping to ensure cleaner air.

Techno-economical study of the Zero Emission Gas power concept

The objective of this study has been to evaluate the technical and economical feasibility of the novel hybrid Zero Emission Gas power concept (ZEG), featuring production of electrical power from natural gas with integrated CO2 capture, via a close integration of the Sorption Enhanced Steam Methane Reforming process (SE-SMR) with a high temperature Solid Oxide Fuel Cell (SOFC). Technical design, process simulations and the preparation of detailed equipment lists have been carried out to calculate capital expenditure (CAPEX) and operation expenditure (OPEX) of the process. A cost analysis has been carried out for different price scenarios involving natural gas and electrical power prices, as well as CO2-quota cost and CO2 sales value. The ZEG concept has been compared with a more conventional pre-combustion technology alternative as a reference case (REF), involving the coupling of auto-thermal reforming, water gas shift, amine CO2 capture technology and a combined cycle. The results of this study show that the ZEG-case technology is likely to be profitable with relatively high net present values (NPV) in most of the price scenarios chosen, while the REF-case technology, using more conventional pre-combustion available technologies, shows negative NPV-values for all scenarios. Even with no income for the CO2 captured and a quite moderate natural gas price of 19 EUR/MWh, the ZEG-case shows profitability for an electric power price of 50 EUR/MWh or higher. The promising and encouraging results of this study show the potential of the two technologies and of their close integration towards future zero emission power plants on a medium to long term perspective.

Influence of sintering conditions on microstructure and oxygen permeation of Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3− δ (BSCF) oxygen transport membranes

Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3− δ (BSCF) exhibits high oxygen permeability, which is why it is being discussed for gas separation (oxygen transport membrane, OTM) in zero-emission power plants using oxyfuel technology when the membrane is operated in a clean environment, i.e. no flue gas contact. We investigate the influence of membrane processing on microstructure and oxygen permeation. Pure-phase BSCF powder is synthesized using a modified Pechini method. For comparison, commercially available powder is also used, synthesized by a solid-state reaction. Disk-shaped membranes of various microstructures, i.e. closed porosities and grain sizes, are prepared by uniaxial pressing and sintering of the powders processed in different ways. The powders and membranes are characterized by methods including BET, SEM, XRD, and DSC. The microstructures obtained by different sintering conditions are investigated by SEM and TEM. Sintering at 1150 °C leads to incongruent melting of BSCF indicated by DSC. The liquid phase appears at three-phase boundaries grain–grain–air and consists of nearly pure cobalt oxide with small impurities of barium and strontium detected by TEM/EDX analysis. Oxygen permeation of the membranes is measured in an air/Ar gradient depending on temperature and membrane microstructure. The closed porosity of different processed membranes is varied between 2 and 15% with uniform grain sizes in the range of approx. 10 μm. The average grain size is increased from 10 to 45 μm by increasing the sintering temperature. Neither porosity nor the grain size significantly influences the oxygen permeation rate of 1-mm-thick disks in the investigated parameter range.

Development and testing of AZEP reactor components

The advanced zero emissions power plant (AZEP) project addresses the development of a novel “zero emissions,” gas turbine-based, power generation process to reduce local and global CO 2 emissions in a cost-effective way. The key element in AZEP is an integrated MCM-reactor, in which (a) O 2 is separated from air by means of a mixed-conducting membrane (MCM), (b) combustion of natural gas occurs in an N 2-free environment and (c) the heat of combustion is transferred to air by heat exchange. This paper focuses on the development and testing of the ceramic components of the MCM-reactor (air separation membrane and heat exchangers). For compactness and manufacturability, a module design based on extruded square channel monoliths has been chosen. The manifold design enables gas distribution in a checkerboard pattern. Modules with contact area of >500 m 2/m 3 have been produced. Results from testing of the modules under close to realistic process conditions agree with model predictions. Extrapolation to AZEP process conditions gives an oxygen production rate of around 37 mol O 2/(m 3 s), or 15 MW/m 3 power density (per net MCM volume). These values correspond to project targets and confirm the feasibility of the AZEP concept.

A quantitative comparison of gas turbine cycles with [formula omitted] capture

Nine different concepts for natural gas fired power plants with CO 2 capture have been investigated, and a comparison is made based on net plant efficiency and emission of CO 2. The cycles are one post-combustion, six oxy-fuel and two pre-combustion capture concepts. A 400 MW combined cycle plant is applied as a reference case. A common basis for the comparison of all concepts is defined and employed in heat- and mass-balance simulations of the various concepts. As gas turbine cooling impacts the net plant efficiency at high turbine inlet temperatures, a simplified turbine cooling model has been applied in the simulations. It is found that the concepts, in which novel technology (the hydrogen membrane separation reformer—-MSR-H2, the advanzed zero emission power plant—AZEP, the solid oxide fuel cell combined with a gas turbine— SOFC + GT and the chemical looping combustion—CLC concepts) is employed, exhibit the best performance with respect to both efficiency and in most cases also CO 2 capture (capture rates close to 100%). Post-combustion capture and pre-combustion capture with auto-thermal reforming, which are based on more mature technology, show a lower efficiency and a capture rate of typically 90%. The SOFC + GT concept exhibits the best cycle performance and even better than a standard CC plant, however, any realization of a SOFC-GT 400 MW plant has a very distant future perspective. In order to conduct a complete assessment of these diverse concepts, other criteria for comparison such as e.g. technology level and costs should also be considered. This is not, however, included in the present work.

Thermodynamic and Economic Investigation of an Improved Graz Cycle Power Plant for CO2 Capture

Introduction of closed-cycle gas turbines with their capability of retaining combustion generated CO2 can offer a valuable contribution to the Kyoto goal and to future power generation. Therefore, research and development at Graz University of Technology since the 1990s has lead to the Graz Cycle, a zero emission power cycle of highest efficiency. It burns fossil fuels with pure oxygen, which enables the cost-effective separation of the combustion CO2 by condensation. The efforts for the oxygen supply in an air separation plant are partly compensated by cycle efficiencies far higher than 60%. In this work a further development, the S-Graz Cycle, which works with a cycle fluid of high steam content, is presented. Thermodynamic investigations show efficiencies up to 70% and a net efficiency of 60%, including the oxygen supply. For a 100 MW prototype plant the layout of the main turbomachinery is performed to show the feasibility of all components. Finally, an economic analysis of a S-Graz Cycle power plant is performed showing very low CO2 mitigation costs in the range of $10/ton CO2 captured, making this zero emission power plant a promising technology in the case of a future CO2 tax.

99/02651 Environment-friendly energy system

The use of methanol as a medium for transporting hydrogen-based energy offers the possibility of establishing a global system for obtaining and transporting unlimited quantities of sustainable, clean energy. Using various sources of renewable energy (hydroelectric, solar, geothermal, wind), hydrogen can be produced through an efficient electrolytic process. This hydrogen can be combined with CO{sub 2} obtained from power plants in various parts of the world to produce methanol, which can then be transported to areas with high energy consumption for use as fuel in power plants. However, the cost of the methanol synthesized from hydrogen and CO{sub 2} will be nearly four times as high as that of the present commercial methanol. The authors examined a method for the production of methanol or dimethyl ether by a solar thermochemical process using concentrated solar energy. The concentrated solar thermal energy is absorbed by methane reforming and coal gasification, both of which are endothermic reactions that produce carbon monoxide and hydrogen. These gases are then consumed to produce methanol or dimethyl ether. The authors evaluated the amount of CO{sub 2} emission when the methanol or dimethyl ether was used and the cost of the methanol produced by this process. The amountmore » of CO{sub 2} emission using hybridized dimethyl ether (methanol) was estimated to be 60 to 80 % of the amount emitted using coal or natural gas. The cost of the hybridized methanol was estimated to be 2.45/kWh, which is about 20 % of the cost of the liquid hydrogen produced using renewable energy. A preliminary analysis of zero-emission power plants indicated the possibility of achieving 60% gross thermal efficiency (HHV).« less

98/02590 Zero emissions power plant as an incinerator : Iantovski, E. et al. Analysis Util. Oily Wastes, AUZO '96, Int. Conf., 1996, 1, 242–249. Edited by Bokotko, R., Faculty of Chemistry, Technical University of Gdansk, Gdansk, Poland

98/02590 Zero emissions power plant as an incinerator : Iantovski, E. et al. Analysis Util. Oily Wastes, AUZO '96, Int. Conf., 1996, 1, 242–249. Edited by Bokotko, R., Faculty of Chemistry, Technical University of Gdansk, Gdansk, Poland

Stack downward: Zero emission fuel-fired power plants concept

There exists sewerage system for biological wastes in cities and towns, however there are no such systems for technological and energy wastes, released to atmosphere. The real harm to atmosphere and our lungs is evident. A method of evaluation of CO 2 release from fuel-fired power plants and boiler houses based on exergy efficiency is presented. The incremental cost of CO 2 emission reduction is calculated. The main subject of paper is a zero-emissions power plant. The plant is based on air separation unit, combustion of arbitrary fossil fuel in the mixture of oxygen/carbon dioxide, expansion in CO 2 turbines ( 240 60 bar, 600 °C and 60 4 bar, 1200 °C), CO 2 compression and condensation, sequestering of liquid CO 2 in a deep aquifer through depleted gas/oil wells (stack downward). Essentially new, very efficient power plant cycle is presented. It is referred to as quasicombined due to replacement of ordinary bottoming steam Rankine cycle by the topping one, using the same CO 2 as a working substance. The detailed cycle computer simulation (made by Zvagolsky and Gavrilenko) along with the thermodynamic properties of combustion products calculations is discussed. The case studies of the most beneficial versions, such as the use of negative price fuels (used lubricants with forbidden emissions), oil refinery residuals, oil enhancement recovery power/CO 2 supply are the subjects for demonstration. The utility-scale power plant COOPERATE (CO 2 Prevented Emissions Recuperative Advanced Turbines Energy) cycle is outlined. The injection of the CO 2 technology, well known in oil recovery should be used for sequestering of power plant effluents. The hydrolithosphere capacity to store CO 2 is guessed. It seems to be thousand time greater than that of atmosphere. The reliable protection of our lungs from any harm forever due to the development of sewerage system of energy wastes could be achieved. Had the concept been successful, the demand of oxygen production units would have increased manifold.