Natural Gas-fired Power Plants Research Articles

Determining marginal electricity for near-term plug-in and fuel cell vehicle demands in California: Impacts on vehicle greenhouse gas emissions

California has taken steps to reduce greenhouse gas emissions from the transportation sector. One example is the recent adoption of the Low Carbon Fuel Standard, which aims to reduce the carbon intensity of transportation fuels. To effectively implement this and similar policies, it is necessary to understand well-to-wheels emissions associated with distinct vehicle and fuel platforms, including those using electricity. This analysis uses an hourly electricity dispatch model to simulate and investigate operation of the current California grid and its response to added vehicle and fuel-related electricity demands in the near term. The model identifies the “marginal electricity mix” – the mix of power plants that is used to supply the incremental electricity demand from vehicles and fuels – and calculates greenhouse gas emissions from those plants. It also quantifies the contribution from electricity to well-to-wheels greenhouse gas emissions from battery-electric, plug-in hybrid, and fuel cell vehicles and explores sensitivities of electricity supply and emissions to hydro-power availability, timing of electricity demand (including vehicle recharging), and demand location within the state. The results suggest that the near-term marginal electricity mix for vehicles and fuels in California will come from natural gas-fired power plants, including a significant fraction (likely as much as 40%) from relatively inefficient steam- and combustion-turbine plants. The marginal electricity emissions rate will be higher than the average rate from all generation – likely to exceed 600 gCO 2 equiv. kWh −1 during most hours of the day and months of the year – and will likely be more than 60% higher than the value estimated in the Low Carbon Fuel Standard. But despite the relatively high fuel carbon intensity of marginal electricity in California, alternative vehicle and fuel platforms still reduce emissions compared to conventional gasoline vehicles and hybrids, through improved vehicle efficiency.

Employment benefits of electricity generation: A comparative assessment of lignite and natural gas power plants in Greece

This paper aims at developing an integrated approach for estimating the employment benefits associated with power-generation technologies. The proposed approach exploits the input–output methodology for estimating the direct, indirect and induced employment effects associated with the energy project in question, as well as two different valuation techniques, namely the “opportunity cost of labour” approach and the “public expenditures” approach, for expressing these effects in monetary terms. This framework has been implemented to estimate the employment benefits resulting from the development of a lignite-fired and a natural gas-fired power plant in Greece, taking into account all the stages of the corresponding fuel cycles that are undertaken domestically. The results of the analysis clearly show that lignite-fired electricity generation results in significant employment benefits amounting to 2.9–3.5 €/MWh in the basic scenario. On the other hand, the employment benefits associated with the examined natural gas unit were estimated at 0.4–0.6 €/MWh in the basic scenario. It is also worth mentioning that the significant environmental externalities of the lignite-fired electricity in Greece that have been presented in a number of studies can only be partially compensated by the estimated employment benefits.

Simulation of an oxygen membrane-based combined cycle power plant: part-load operation with operational and material constraints

This paper presents the design and part-load performance of a natural gas-fired oxy-combustion combined cycle power plant for CO2 capture. The combustion chamber of a conventional gas turbine was replaced by a membrane reactor, making it possible to obtain a highly concentrated CO2 stream for long-term storage. The focus was on power plant operation with a view to operational and material constraints of individual process components to ensure their proper performance and required lifetime. In this respect, the mixed-conducting membrane modules were of particular interest. Temperature as well as concentration limitations for CO2 and other chemical species narrowed the operating window. Other critical reactor components added further constraints. For part-load operation of the power plant, two load control strategies were analysed for the gas turbine operating at constant rotational speed. In the first load control strategy, variable guide vanes were used to manipulate the mass flow of air to the gas turbine compressor. This degree of freedom was used to control the turbine exit temperature. In the second control strategy, variable guide vanes were not used and the turbine exit temperature was allowed to vary. For both load control strategies, the mean solid-wall temperature of the membrane modules was maintained close to its design value, which led to improved stability. The load-control strategy using variable guide vanes was superior to the strategy without variable guide vanes due to higher combined cycle efficiencies and increased load-reduction capability. Moreover, the performance of the catalytic combustors in the membrane reactor, operating at near stoichiometric conditions, also improved as a result of increased oxygen concentrations at part-load operation. Relevant process components were based on spatially distributed conservation balances for energy, species, mass, and momentum. A stability diagram was incorporated into the membrane module model to investigate the risk of degradation. Performance maps were used for turbomachinery components.

Kinetics of sulfur dioxide- and oxygen-induced degradation of aqueous monoethanolamine solution during CO 2 absorption from power plant flue gas streams

Studies of the kinetics of sulfur dioxide (SO 2)- and oxygen (O 2)-induced degradation of aqueous monoethanolamine (MEA) during the absorption of carbon dioxide (CO 2) from flue gases derived from coal- or natural gas-fired power plants were conducted as a function of temperature and the liquid phase concentrations of MEA, O 2, SO 2 and CO 2. The kinetic data were based on the initial rate which shows the propensity for amine degradation and obtained under a range of conditions typical of the CO 2 absorption process (3–7 kmol/m 3 MEA, 6% O 2, 0–196 ppm SO 2, 0–0.55 CO 2 loading, and 328–393 K temperature). The results showed that an increase in temperature and the concentrations of MEA, O 2 and SO 2 resulted in a higher MEA degradation rate. An increase in CO 2 concentration gave the opposite effect. A semi-empirical model based on the initial rate, − r MEA = {6.74 × 10 9 e −(29,403/ RT) [MEA] 0.02([O] 2.91 + [SO 2] 3.52)}/{1 + 1.18[CO 2] 0.18} was developed to fit the experimental data. With the higher order of reaction, SO 2 has a higher propensity to cause MEA to degrade than O 2. Unlike previous models, this model shows an improvement in that any of the parameters (i.e. O 2, SO 2, and CO 2) can be removed without affecting the usability of the model.

Source apportionment of PM10 and PM2.5 using positive matrix factorization and chemical mass balance in Izmir, Turkey

Atmospheric particulate matter (PM) fractions (PM10 and PM2.5) were sampled concurrently between June 2004 and May 2005 at two sites (urban and suburban) in Izmir, Turkey. The elemental composition of PM (Al, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, V, and Zn) was determined using inductively coupled plasma-optical emission spectrometer. Elemental compositions of several PM sources were also characterized. Positive matrix factorization (PMF) and chemical mass balance modeling (CMB) were applied to determine the PM sources and their contributions to air concentrations. The major contributors to PM were fossil fuel burning, traffic emissions, mineral industries and marine salt according to the PMF results. However, undetermined parts were more than 40%. On the other hand, the contributions to PM could be determined completely by CMB, and the dominant contributor was traffic with >70% at the two sites. Fossil fuel burning, mineral industries, marine salt and natural gas-fired power plant were the minor contributors.

Investments in liberalised power markets: Gas turbine investment opportunities in the Nordic power system

There is considerable uncertainty in the Nordic electricity system with respect to long-term development in production capacity. The process towards liberalisation of the electricity sector started with a situation of a large capacity margin, which is gradually vanishing. Since potential investors in new production capacity are unaccustomed with investments under the new regime, it is unknown if and when investments will take place. The purpose of this paper is to analyze if and when investors choose to invest in new production capacity depending on their existing portfolio of power producing units. Electricity price scenarios generated with a partial equilibrium model of the Nordic power system are combined with a model of investment decisions. In this, various scenarios for the development in key parameters such as CO 2 emission permit price and development in installed wind power capacity are used to investigate the consequences for investments in a natural gas fired power plant. The main result of the analysis is that new investments are highly sensitive to investors existing power production portfolio, as new production units compete with the existing power plants.

Gas conditioning—The interface between CO 2 capture and transport

Gas conditioning is commonly referred to as the required processing for a produced natural gas to achieve transport and sales specifications. In this paper, gas conditioning as the processing required in the interface between CO 2 capture and transport is studied for nine different natural gas fired power plant concepts and three different CO 2 transport processes. Conditioning processes for both pipeline and ship transport are described and an enhanced process for volatile removal is developed. The energy requirement for the conditioning processes is normally between 90 and 120 kWh/tonne CO 2; however, this depends on the pressure and composition of the captured CO 2-rich stream. The loss of CO 2 in the water purge is small for most capture processes. The waste streams from the gas conditioning processes can contain large amounts of CO 2 and should therefore be further processed or reintroduced at an appropriate point upstream in the capture or gas conditioning process if possible. The integration benefit may vary depending on the composition of the CO 2-rich stream. It could be particularly interesting for processes with “innovative reactors” (membranes, sorbents, chemical looping) to integrate CO 2 capture and gas conditioning.

Effects of SO 2 and NO x control on energy-efficiency power generation

The aim of this paper is to give an overview of the effects of SO 2 and NO x pollution control on the energy efficiency of fossil-fired power generation for the following countries: Australia, China, France, Germany, India, Japan, Nordic countries (Denmark, Finland, Sweden, and Norway aggregated), South Korea, UK and Ireland, and United States. Together these countries generate 65% of fossil-fired power generation worldwide. The level of SO 2 and NO x control seems to vary widely for the included countries. The highest level of desulphurisation and denitrification is present in Japan, Germany, Nordic countries and South Korea. These countries also have the lowest NO x and SO 2 emissions per unit of power generated. Limited pollution control is implemented in India and China, resulting in high specific NO x and SO 2 emissions. The effect of NO x and SO 2 control on net energy efficiency is estimated to be around 2% for coal-fired power plants and 1% for natural gas-fired power plants. The average power use for NO x and SO 2 control for fossil-fired power generation is estimated to be between 1.2% and 1.5% of power generation output for countries with high levels of pollution control; leading to an effect on net efficiency of fossil-fired power generation of 0.5–0.6% points.

Optimizing Short-Term Natural Gas Supply Portfolio for Electric Utility Companies

Natural gas fired power plants (NGFPP) are important electricity generation resources in the United States. Optimizing the natural gas supply portfolio, especially the short-term portfolio, is critical for the day-to-day operations and the financial performance of NGFPPs. Traditionally, such optimization problems are solved using cost-minimization-based frameworks. However, such frameworks are facing challenges due to the lack of consideration of associated financial risks in the current deregulated electricity markets, which the electric utility companies (EUCs) who own and operate NGFPPs now bear. This paper presents a utility-maximization-based framework to optimize the short-term natural gas supply portfolio for the EUC. It considers the financial risks associated with the portfolio and incorporates the risk preferences of the EUCs as decision-maker (DM) in the portfolio optimization process. An application of the proposed framework is provided, and its results show that the proposed framework is more desirable in terms of risk-cost trade-off optimization

Performance and costs of power plants with capture and storage of CO2

This paper assesses the three leading technologies for capture of CO2 in power generation plants, i.e., post-combustion capture, pre-combustion capture and oxy-fuel combustion. Performance, cost and emissions data for coal and natural gas-fired power plants are presented, based on information from studies carried out recently for the IEA Greenhouse Gas R&D Programme by major engineering contractors and process licensors. Sensitivities to various potentially significant parameters are assessed.

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.

Comparison of Coal-fired and Natural Gas-fired Power Plants as Economically Viable and Ecologically Sustainable Power Generation Systems

To achieve a sustainable power generation industry it is necessary to study the environmental impacts and economic costs of all aspects of a power generation plants’ lifecycle - from mining to electricity distribution, and, ultimately, decommission (from cradle to grave). One key component in improving and maintaining quality of life for consumers is the application of the Green Productivity Index (GPI) in order to evaluate the related factors of Life Cycle Assessment (LCA) and Life Cycle Costing (LCC). The goal of this research is to appraise the efficacy of decision-making tools in accurately assessing the potential results of ‘green’ improvements to coal-fired and natural gas-fired power plants in both ecological and economic terms. The recently developed Numerical Eco-load Total Standardization (LCA-NETS) evaluates environmental impacts by identifying and quantifying input energy and output waste released to the environment throughout the life cycle of a power plant. Environmental impacts caused by global and regional environmental issues are numerically calculated in the units of NETS. Environmental assessment tools such as LCA, LCC and GPI can be used to improve the ‘environmental friendliness’ of electricity generation by demonstrating the future sustainability of ‘green’ power generation plants and their contribution to the quality of life of consumer.

PILC-based monolithic catalysts for the selective catalytic reduction of nitrogen oxides by methane in oxygen excess

The aim of this work was the study and development of aluminum-pillared clay (Al-PILC)-based monolithic Pd catalysts for reducing NO x emissions from natural gas-fired power plants using methane as a selective reductant. During preparation of the support, the same raw material used to synthesize the pillared clays was used as a permanent inorganic binder. This confers high surface area and acidity to the extrudates, in addition to high hydrothermal resistance and mechanical strength. The influence of the method used for active phase incorporation on the physico-chemical properties and DeNO x activity and selectivity was studied. Conclusions were drawn from the use of different solution pH values and precursors in relation to the isoelectric point of the solid. Characterization was carried out using X-ray diffraction, inductively coupled plasma-optical emission spectroscopy, X-ray photoelectron spectroscopy, N 2 adsorption, and NH 3 and CO chemisorption.

CO2 Capture from Natural Gas Fired Power Plants by Using Membrane Technology

Simulations of membrane separation were performed for two alternative processes for CO2 removal from an exhaust gas stream at a natural gas fired power plant. One process considered is an integrated membrane separation with pressurized gas (16.5 bar) rich in CO2 (10 vol %), while the other alternative solution is a process for CO2 capture from tail-end flue gas where the content of CO2 is low (4 vol %) and gas is released at 1 bar. A gas stream of 700 000 Nm3/h is considered for both cases. Flux data obtained for a fixed-site-carrier poly(vinylamine) membrane developed within the research group at NTNU were used. This membrane has moderate CO2 flux but very high selectivity in favor of CO2. A favorable process design with a single-stage unit without the extra need for compression, and also use of a sweep gas to meet the process specifications, was recommended for the pressurized gas. For the flue gas lean in CO2, the driving forces are too low for separation unless both a compression of the feed gas (→4 b...

Photochemical Smog Modeling for Assessment of Potential Impacts of Different Management Strategies on Air Quality of the Bangkok Metropolitan Region, Thailand

A photochemical smog model system, the Variable-Grid Urban Airshed Model/Systems Applications International Mesoscale Model (UAM-V/SAIMM), was used to investigate photochemical pollution in the Bangkok Metropolitan Region (BMR). The model system was first applied to simulate a historical photochemical smog episode of two days (January 13-14, 1997) using the 1997 anthropogenic emission database available at the Pollution Control Department and an estimated biogenic emission. The output 1-hr ozone (O3) for BMR, however, did not meet the U.S. Environmental Protection Agency suggested performance criteria. The simulated minimum and maximum O3 values in the domain were much higher than the observations. Multiple model runs with different precursor emission reduction scenarios showed that the best model performance with the simulated 1-hr O3 meeting all the criteria was obtained when the volatile organic compound (VOC) and oxides of nitrogen (NOx) emission from mobile source reduced by 50% and carbon monoxide by 20% from the original database. Various combinations of anthropogenic and biogenic emissions in Bangkok and surrounding provinces were simulated to assess the contribution of different sources to O3 pollution in the city. O3 formation in Bangkok was found to be more VOC-sensitive than NOx-sensitive. To attain the Thailand ambient air quality standard for 1-hr O3 of 100 ppb, VOC emission in BMR should be reduced by 50-60%. Management strategies considered in the scenario study consist of Stage I, Stage II vapor control, replacement of two-stroke by four-stroke motorcycles, 100% compressed natural gas bus, 100% natural gas-fired power plants, and replacement of methyltertiarybutylether by ethanol as an additive for gasoline.

Influence of zirconia raw materials on the development of DeNOx monolithic catalysts

Pd-zirconia-based monolithic catalysts were prepared with various commercial zirconia raw materials and a natural magnesium silicate binder, sepiolite, for the selective catalytic reduction (SCR) of NO with CH4 in oxygen excess. The different textural properties, metastable tetragonal zirconia phase stability, surface acidity, Pd dispersion and catalytic properties of these monoliths were compared to select the most suitable structured catalyst for NOx control in natural gas-fired power plants. The influence of operating temperature in the two reactions, NO reduction and CH4 combustion, with the monolithic catalysts was determined. A 0.4wt.% Pd-zirconia catalyst, manufactured from a sulphated zirconium hydroxide raw material, was selected as the most appropriate in the reaction under study, reaching a maximum NO conversion at 400°C.

Natural Gas Decarbonization to Reduce CO2 Emission From Combined Cycles—Part II: Steam-Methane Reforming

This paper discusses novel schemes of combined cycle, where natural gas is chemically treated to remove carbon, rather than being directly used as fuel. Carbon conversion to CO2 is achieved before gas turbine combustion. The first part of the paper discussed plant configurations based on natural gas partial oxidation to produce carbon monoxide, converted to carbon dioxide by shift reaction and therefore separated from the fuel gas. The second part will address methane reforming as a starting reaction to achieve the same goal. Plant configuration and performance differs from the previous case because reforming is endothermic and requires high temperature heat and low operating pressure to obtain an elevated carbon conversion. The performance estimation shows that the reformer configuration has a lower efficiency and power output than the systems addressed in Part I. To improve the results, a reheat gas turbine can be used, with different characteristics from commercial machines. The thermodynamic efficiency of the systems of the two papers is compared by an exergetic analysis. The economic performance of natural gas fired power plants including CO2 sequestration is therefore addressed, finding a superiority of the partial oxidation system with chemical absorption. The additional cost of the kWh, due to the ability of CO2 capturing, can be estimated at about 13–14 mill$/kWh.

Developing Both the Chicken & the Egg

Published in Oil & Gas Executive Report, Volume 2, Number 3, 1999, pages 18–21,43. The old saying, "What comes first, the chicken or the egg?" is particularly pertinent to the electricity and natural gas business. As developers, we're continually challenged to simultaneously build assets and markets for these assets. When we commit to developing both electricity and natural gas assets, the challenge becomes especially difficult. A company cannot develop a power project until the source of fuel is secured. Nor can an enterprise allocate resources to purchase and deliver fuel without a large, guaranteed customer. Enron's philosophy has been to develop the chicken and the egg simultaneously. It is not an easy task and it requires the ability to envision how energy markets will develop. You also need skills to successfully communicate your conceptualization to partners, governments and lenders. But the risk is that if a company resists undertaking the challenge, it forgoes a chance to make a meaningful difference in how emerging markets can satisfy their huge demands for energy. Enron's experience in India is an excellent example of how successful a two-pronged development strategy can be. We soon will celebrate the opening of phase I of the 826-megawatt (MW) Dabhol power plant in the state of Maharashtra. At about the same time we will reach financial close for phase II of Dabhol, which is scheduled to bring on line 1,624 megawatts more by the end of 2001. Electricity, however, is just one component of Dabhol. Because phase II includes the infrastructure to import and regasify liquefied natural gas (LNG), it instantly creates a beachhead for a major natural gas market in India. Enron in India From the day the Indian government invited Enron to India in 1992, we recognized the existence of a large market for natural gas. The commodity already was in high demand. We knew from our experience that industrial use of natural gas would rise with supply levels, particularly in light of the nation's ambitious program to encourage power development. Natural gas-fired power plants make sense in India. They are quicker and less expensive to build than coal plants and emit far fewer pollutants than other fossil fuel-based generating stations. And, they satisfy India's need for clean energy solutions.

Local Air Quality Impacts due to Downwash Around Thermal Power Plants: Numerical Simulations of the Effect of Building Orientation

One of the primary adverse environmental impacts associated with power generation facilities and in particular thermal power plants is local air quality. When these plants are operated at inland areas the dry type cooling towers used may significantly increase ambient concentrations of air pollutants due to the building downwash effect. When one or more buildings in the vicinity of a point source interrupt wind flow, an area of turbulence known as a building wake is created. Pollutants emitted from relatively low level sources can be caught in this turbulence affecting their dispersion. In spite of the fact that natural gas-fired combined-cycle power plants have lower air emission levels compared to other power plants using alternative fossil fuel, they can still create significant local air pollution problems. In this paper, local air quality impacts of a natural gas-fired combined-cycle power plant located in a coastal area are compared with those of another natural gas-fired combined-cycle power plant having identical air emissions but located in an inland area taking into account differences in topography and meteorology. Additionally, a series of scenarios for the inland site have been envisaged to illustrate the importance of plant lay-out configurations paying particular attention to the building downwash effect. Model results showed that different geometrical configurations of the stacks and cooling towers will cause remarkable differences in ambient air pollutant concentrations; thus it is concluded that when selecting a plant site, a detailed site-specific investigation should be conducted in order to achieve the least possible ambient air pollution concentrations with the given emissions.

Partners in Power

This article focuses on investors who back major power projects throughout in Africa. They are also working jointly with local businesses and governments to improve infrastructures and raise living standards. An African expansion project for CMS Generation involves acquiring and expanding the Takoradi natural gas-fired power plant near Aboadze, Ghana. CMS formed the Takoradi Power Company with the Volta River Authority as a 50-percent partner. CMS Energy’s third major African venture will extend its power generation business into chemical processing. AMPCO has awarded a $300 million engineering, procurement, and construction turnkey contract to Raytheon Engineers & Constructors, Lexington, MA, to construct the methanol plant on Bioko Island. The plant will use a proven, three-stage design. In the first stage, natural gas feedstock and steam are sent to a reformer and are exposed to elevated temperatures and pressure in the presence of a catalyst, forming synthetic gas made of carbon monoxide and hydrogen.