Coal-fueled Power Plants Research Articles

Dynamic learning of flue gas desulfurization process using deep LSTMs neural network

SO2 emissions are known to pose great harm to both human health and atmospheric air, and flue gas generated from coal-fueled power plant is the prime source of sulfur dioxide. For this reason, flue gas desulfurization (FGD) technology has found wide applications in most coal-fired power stations. Correctly describe the dynamic behavior of an FGD process is the precondition of controlling it effectively. However, FGD process modeling is by no means an easy task, as the underlying process dynamics are highly nonlinear in nature, meanwhile time-delay effect is significant therein. Long short-term memory (LSTM) network possesses remarkable long-term memory capability, hence it is anticipated to have a powerful identification capability. In this paper, the connection between deep learning and system identification is established, further a unidirectional/bidirectional LSTM deep network is designed and employed to identify a real FGD process. Simulation results clearly demonstrate the effectiveness of deep learning-based identification approach, and the superiority of deep LSTMs over other conventional identification models is also verified.

An Updated Look at the Costs, Economics, and Business Case for Co2 Capture from Retrofit of Natural Gas Combined-Cycle and Coal-Fueled Power Plants: Two New Case Studies

An Updated Look at the Costs, Economics, and Business Case for Co2 Capture from Retrofit of Natural Gas Combined-Cycle and Coal-Fueled Power Plants: Two New Case Studies

An Updated Look at the Costs, Economics, and Business Case for CO2 Capture from Retrofit of Natural Gas Combined-Cycle and Coal-Fueled Power Plants: Two New Case Studies

An Updated Look at the Costs, Economics, and Business Case for CO2 Capture from Retrofit of Natural Gas Combined-Cycle and Coal-Fueled Power Plants: Two New Case Studies

Who Cares about Jellyfish? An Environmental Legacy of the Suez Canal Begins to Surface

On June 24, 2015, a huge swarm of jellyfish clogged the cooling system of an Israeli coal-fueled power plants located on the Mediterranean shoreline, almost forcing a shutdown. Images from the event displayed tons of pale blue, translucent jellies, lumped together in a container and spread over the factory floor after being removed from the cooling system filter. The spectacular incident prompted speculation that the jellyfish were foreign agents sent from Egypt to sabotage Israeli security. It may seem laughable, but this is not the first time that non-humans have figured as agents and national security threats in geopolitical dramas in the Middle East. In 2010, following repeated shark attacks on tourists in one of Egypt's Red Sea resorts, Sharm El-Sheikh, the governor of South Sinai told the media he could not rule out the possibility of the attacking shark being remotely controlled by the Israeli intelligence agency Mossad. In this context, foreign, underwater jellyfish armies are nothing out of the ordinary.

Improvement in efficiency of thermal power plant using optimization and robust controller

This paper briefs on some of the most effective control configurations that can be used to improve the efficiency of coal fueled thermal power plant, thus practically saving coal and increasing energy produce at a significant level. Our control theory is based on the real time data we collected at the 500 MW capacity unit of NPTL Thermal Power Plant Tuticorin. The collected data helped us to design an accurate model of coal, air and feed water flow rate. With the use of evolution and optimization technique the controllers for all the three loops were adjusted to perfection. The best features of the controllers are highlighted as to give the readers an educated opinion to choose between the discussed controller types.

Analysis of the Dependence of the Observed Urban Air Pollution Extremes in the Vicinity of Coal Fuelled Power Plants on Combined Effects of Anthropogenic and Meteorological Drivers

Analysis of the Dependence of the Observed Urban Air Pollution Extremes in the Vicinity of Coal Fuelled Power Plants on Combined Effects of Anthropogenic and Meteorological Drivers

Coal to Biomass Conversion as a Path to Sustainability: A Hypothetical Scenario at Pego Power Plant (Abrantes, Portugal)

Energy consumption is associated with economic growth, but it comes with a toll regarding the environment. Renewable energies can be considered substitutes for fossil fuels and may contribute to reducing the environmental degradation that the world is presently facing. With this research, we aimed to offer a broader view of the state-of-the-art in this field, particularly regarding coal and biomass. The main objective is to present a viable and sustainable solution for the coal power plants still in operation, using as a hypothetical example the Pego Power Plant, the last operating coal fueled power plant in Portugal. After the characterization of land use and energy production in Portugal, and more particularly in the Médio Tejo region, where the power plant is located, the availability of biomass was assessed and it was concluded that the volume of biomass needed to keep the Pego power plant working exclusively with biomass is much lower than the yearly growth volume of biomass in the region, which means that this transition would be viable in a sustainable way. This path is aligned with policies to fight climate change, since the use of biomass for energy is characterized by low levels of GHGs emissions when compared to coal. The risk of rural fires would be reduced, and the economic and social impact for this region would be positive.

Solid Oxide Cell Technology for Supply, Recovery, and Storage Energy

Fuel Cell Energy, Inc. (FCE) is advancing the current state of Solid Oxide Fuel Cell (SOFC) technology towards commercial deployment for efficient and nonpolluting generation of electric power from natural gas and biomass derived fuels. Additionally, FCE is utilizing the same solid oxide cell and stack technology in electrolysis of steam for production of hydrogen from renewable sources and other electric power sources, such as nuclear power plants during the curtailment periods. Additionally, FCE’s SOFC technology has shown to be a viable technology for storage of energy by cyclic charge and discharge operation.FCE’s SOFC technology is based on anode supported thin electrolyte planar cell platform chosen for its higher power density at reduced operating temperature (700-800°C). Traditional materials, such as Ni/YSZ anodes, YSZ electrolytes and perovskite cathodes have been utilized in a basic cell structure. Research and development focus has been placed on developing better electrochemical functional areas at both cathode/electrolyte and anode/electrolyte interfaces. This was achieved through material advancements, microstructure optimization, and manufacturing process integration.The solid oxide stack is comprised of planar solid oxide fuel cells with glass ceramic seals and sheet metal, bipolar plate interconnects; and has a mix of internal and external gas manifolds. Each cell is a 0.30 mm thick annular (donut shaped), cell with 81 cm2 active area made in a process consisting of tape casting, screen printing, and firing cell components. The full height stack consists of 350 repeat units and a set of non-repeat parts. A repeat unit includes one ceramic cell, inner and outer seals, and a metallic interconnect which incorporates flow fields for both fuel and oxidant. Non-repeat parts include the end plates, manifolds, and compression components. The stack is capable of producing 7kW power when fueled with natural gas, biogas, hydrogen, or other fuels. The same stack is capable of operating at higher power density in electrolysis mode, producing 25 kg/day hydrogen with 36 kW power input.FCE’s SOFC system design philosophy is based on using factory-assembled stack building blocks, which in turn may be used to fabricate larger multi-stack modules for applications in centralized natural gas and coal fueled power plants. An attractive pathway to deployment of SOFC systems is through near-term market opportunities in natural gas fueled distributed generation (DG) applications. FCE is planning to take the advantage of the scalability, modularity, and fuel flexibility of the SOFC technology to transition the technology from small (sub-MW) systems to megawatt class power plants for distributed generation, and ultimately (through aggregation of fuel cell modules) to large stationary power plants for base-load utility applications using coal and/or natural gas fuel.FCE has recently designed, fabricated, and tested a 200kW natural gas fueled packaged system. This autonomous unit is an outdoor rated power system with capabilities for both grid-connection as well as island operation.Electricity storage is a growing need given the increasing penetration of intermittent renewable sources of solar and wind. Traditional battery storage technology uses rare materials that could pose sourcing challenges and depletion with widespread adoption. Hydrogen based energy storage is the only practical way to store the GWh of energy that will need to be stored to enable significant penetration of intermittent renewable energy on the electricity grid. Another advantage of hydrogen based energy storage is that once hydrogen is stored it can be used to make power, or exported for another use such as vehicle fueling or industrial uses.

Comparative Environmental, Economic, and Jobs Impacts in the USA of Renewable Energy Compared to Carbon Capture, Utilization, and Storage

This paper assesses the relative economic and jobs benefits of retrofitting an 847 MW USA coal power plant with carbon capture, utilization, and storage (CCUS) technology compared to replacing the plant with renewable (RE) energy and battery storage. The research had two major objectives: 1) Estimate the relative environmental, economic, and jobs impacts of CCUS retrofit of the coal plant compared to its replacement by the RE scenario; 2) develop metrics that can be used to compare the jobs impacts of coal fueled power plants to those of renewable energy. The hypotheses tested are: 1) The RE option will reduce CO2 emissions more than the CCUS option. We reject this hypothesis: We found that the CCUS option will reduce CO2 emissions more than the RE option. 2) The RE option will generate greater economic benefits than the CCUS option. We reject this hypothesis: We found that the CCUS option will create greater economic and jobs benefits than the RE option. 3) The RE option will create more jobs per MW than the CCUS option. We reject this hypothesis: We found that the CCUS option will create more jobs per MW more than the RE option. We discuss the implications of these findings.

Improving the Business Case for CCS in the Electric Power Generation Industry

Supporting new, high impact energy and environmentally friendly initiatives has been a regular and important component of US tax policy. A production tax credit (PTC) of up to 2.3 cents per kWh (now reduced) was available for electricity generated by wind. Solar photovoltaic projects receive a 30% investment tax credit (ITC). These tax credits, along with state-level renewable performance standards, have significantly increased investments in renewables and supported their growth in the electricity generation sector. A similar opportunity now exists for supporting accelerated installation of large-scale Carbon Capture and Storage (CCS) in the US electric power generation industry. Section 45Q of the US tax code represents a first, but still insufficient, step for covering the costs of using CCS with electric power generation. It provides a $50 per metric ton (mt) tax credit for captured CO2 stored in geological formations and a $35 per mt tax credit for captured CO2 used and stored with enhanced oil recovery. However, the 45Q tax credits contain limitations, including-- a rapidly approaching “commence construction” deadline, limited years for claiming the tax credit, a tax credit level insufficient for economically viable installation of CCS by natural gas-fueled power plants, and little support for first-of-a-kind (FOAK), higher CO2 capture rate facilities. In a previous paper (Esposito, et al., 2019), the authors illustrated the basic arithmetic for assessing the economic viability of CCS in the electric power generation industry with availability of the Section 45Q tax credits, including an extensive look at the business case for installing CCS by coal-fueled power plants. This paper discusses a series of modifications to the Section 45Q tax credit, as well as additional steps, that would improve the business case for installing CCS on natural gas-fueled power plants. The paper addresses the following topics: • Extending the Commence Construction Date for the Section 45Q Tax Credit. Given a fast-approaching deadline, the paper provides a series of arguments for extending the “commence construction” date for eligibility for the Section 45Q tax credit. • Increasing the Time Period for Eligibility for the Section 45Q Tax Credit. The paper examines how the business case for CCS would be improved by increasing the time of eligibility for the Section 45Q tax credit to 20 years from the current 12 years. • Increasing the Value of the Tax Credit for Natural Gas-Fueled Power Generation. The overall CO2 capture costs at a natural gas-fueled plant are about 60% as much as at an equivalent generation capacity coal-fueled power plant. However, the volume of CO2 produced from a natural gas-fueled power plant is about 40% as much as from a coal-fueled plant. As such, the per-ton costs of capturing CO2 at a natural gas power plant are 1.5 times higher than the per-ton costs of capturing CO2 at a coal-fueled power plant. Since the Section 45Q tax credit rate was designed to approximately cover the cost of CO2 capture at a coal-fueled power plant, it needs to be increased by about 50% to cover the cost of CO2 capture at a natural gas-fueled power plant. • Providing Incentives for Higher Capture Rate, FOAK Plants. The paper also examines how a more robust set of incentives, including modified Section 45Q tax credits and other options, could help overcome the barriers facing first-of-a-kind (FOAK), high (95%+) CO2 capture rate plants. • Providing Section 48A Investment Tax Credits for Natural Gas-Fueled Power Plants. The paper examines how expansion of the eligibility for the Section 48A investment tax credit could support installation of CCS at natural gas-fueled power plants.

Estimation of various radiological parameters associated with radioactive contents emanating with fly ash from Sahiwal coal-fuelled power plant, Pakistan.

The release of natural radioactive materials with the emission of fly ash as a result of coal burning in power generation plants is considered amongst the sources that elevate the technologically environmental radioactivity level. This research mainly concerns the assessment of various radiological parameters including excess lifetime cancer risk due to natural radioactive contents associated with fly ash emitted to the surrounding environment from the stack of 1320 Mw Sahiwal coal-fuelled power generation plant (CFPP). For this purpose, fifty-four soil samples were collected in a radius of 4 Km from CFPP and a highly background radiation-shielded HPGe system is used to measure radioactivity in the collected samples. The activity concentrations of radium-226, potassium-40, and thorium-232 in collected samples was found to be in the range of 20 to 138, 43 to 860, and 27 to 127 Bq/kg with average values of 66, 409, and 67 Bq/kg respectively. Activity concentrations of radium-226 and thorium-232 were observed significantly higher than UNSCEAR reported typical global average values. A significant decrease in the level of the aforementioned radionuclides in the collected soil samples was observed with increasing distance from the power plant, which is a clear indication for the elevation of radioactivity concentrations in the surrounding environment as a result of the operation of the CFPP. To assess the radiation dose delivered to the occupational workers and inhabitants living next to Sahiwal CFPP, absorbed γ-dose rate (Dγ), outdoor annual effective dose rate (EOutdoor), and excess lifetime cancer risk (ELCR) were estimated and these were found higher than the UNSCEAR recommended values of 59 nGy/h, 0.07 mSv/y, and 2.9 × 10-4 respectively. The outcome of this first systematic study is the assessment of potential radiological health risk to the occupational workers as well as the inhabitants living in the proximity of this CFPP.

Torrefied Biomass as an Alternative in Coal-Fueled Power Plants: A Case Study on Grindability of Agroforestry Waste Forms

The use of biomass as a renewable energy source is currently a reality, mainly due to the role it can play in replacing fossil energy sources. Within this possibility, coal substitution in the production of electric energy presents itself as a strong alternative with high potential, mostly due to the possibility of contributing to the decarbonization of energy production while, at the same time, contributing to the circularization of energy generation processes. This can be achieved through the use of biomass waste forms, which have undergone a process of improving their properties, such as torrefaction. However, for this to be viable, it is necessary that the biomass has a set of characteristics similar to those of coal, such that its use may occur in previously installed systems. In particular, with respect to grindability, which is associated with one of the core equipment technologies of coal-fired power plants—the coal mill. The objective of the present study is to determine the potential of certain residues with agroforestry origins as a replacement for coal in power generation by using empirical methods. Selected materials—namely, almond shells, kiwifruit pruning, vine pruning, olive pomace, pine woodchips, and eucalyptus woodchips—are characterized in this regard. The materials were characterized in the laboratory and submitted to a torrefaction process at 300 °C. Then, the Statistical Grindability Index and the Hardgrove Grindability Index were determined, using empirical methods derived from coal analysis. The results obtained indicate the good potential of the studied biomasses for use in large-scale torrefaction processes and as replacements for coal in the generation of electrical energy. However, further tests are still needed, particularly relating to the definition of the ideal parameters of the torrefaction process, in order to optimize the grindability of the materials.

Evaluation of the potential for energy recovery from olive oil industry waste: Thermochemical conversion technologies as fuel improvement methods

The search for new sources of energy is one of the demands of current times. Traditional lignocellulosic biomass sources, used by Man since immemorial times, begin to suffer the effects of overuse, which is why to find new sources is so urgent, especially if those are associated with industrial or agroforestry waste sources. In this context, several options arise, some of which are object of concern, given the large volumes produced, and the environmental impacts associated with them. Olive pomace is one of these cases. Portugal assumes a prominent role in the production of olive oil and is, therefore, also a major producer of waste related with olive oil industry. Energy recovery of olive pomace is something that has been referenced in the bibliography since long ago. However, traditional forms of recovery, such as direct combustion, did not shown to be the best option, given the high content of volatiles of the product, and the problems associated with its storage and transportation. Thermochemical conversion technologies, such as torrefaction or pyrolysis, can play a decisive role here, since in addition to the increment in energy density, allow a very significative volume reduction, facilitating storage and transportation. In the present study, torrefaction and pyrolysis tests were carried out on olive pomace samples at different temperatures, respectively, 300, 400 and 500 °C, followed by the characterization of the obtained materials. There was a significative improvement in the energy content of the materials. The characterization of the Hardgrove Grindability Index (HGI) was also carried out, allowing comparison with coal grindability, and leaving an open door for the possibility of these residues being used as coal substitutes in coal-fueled power plants.

Determination of PM10 and deposited dust dispersion on the settlement areas from Aksa Göynük coal (lignite) fueled thermal power plant

With the growing population and rapidly developing industrialization in Turkey, energy demand is also increasing. The majority of the energy is produced using imported products, which increase the current account deficit in Turkey. The use of coal from domestic sources are encouraged for economic reasons. One of the coal (lignite) fueled thermal power plants established for this purpose is operating in the province of Bolu Göynük. In order to determine the environmental effect of the plant on the settlement areas in the area, air quality monitoring studies have been conducted. In the study, the periodic PM10 and deposited dust parameters have been monitored monthly at four points between 2013 and 2019, including before and after installation of the plant. As a result of the study; the mean PM10 measurement were obtained as 36.48 ± 0.73; 37.61 ± 0.75; 42.70 ± 0.85 and 38.72 ± 0.77 μg/m3 for four points. Meanwhile, the mean values of the deposited dust were found as 70.81 ± 2.12; 35.55 ± 1.07; 79.50 ± 2.39 and 29.38 ± 0.88 mg/m2/day. Despite the providing current limit values of the dust parameter for power plant where the electrostatic precipitator (ESP) filter and flue gas desulfurization (FGD) systems are applied, it is observed that the dust emissions from activities such as coal extraction, crushing, sieving and ash storage in the area show different cases depending on meteorological conditions.

A study on the CO2 marginal abatement cost of coal-fueled power plants: is the current price of China pilot carbon emission trading market rational?

This paper aims to analyze the trading mechanism of China pilot carbon emission trading market and figure out whether the current market price is rational and valid. By applying directional distance function and stochastic frontier analysis method, we estimated the CO2 marginal abatement cost of 92 coal-fueled generators belonging to 27 power plants located in Shanghai which is one of the pilot carbon emission trading market cities in China. The result indicates that the market price will greatly affect the trading activities within carbon emission trading market. We conclude that the current market price is not rational for coal-fueled power industry which is high-carbon and high CO2 MAC industry. When the exchange of nationwide carbon trading market formally start, policymakers should impose carbon tax or carbon emission quota to adjust the market price and stimulate the CO2 emission reduction willingness of coal-fueled power plants.

Creation Care as Caring for Human Beings: An Environmental Justice Case Study

A special ORU Student study directed by Dr. Jeff Lamp. Caring for God’s creation is a burgeoning area of interest among Christians in recent decades. In many Christian circles, however, caring for creation is not given high priority in rankings of the duties of Christian disciples in the world. This article will argue that caring for creation is a biblically mandated call for God’s people in the world and derives from the role of human beings as caretakers of creation, creation’s status as a recipient of God’s salvation in Christ, and the connection between human beings and the other-than-human creation. If creation care is understood as an act of healing creation, then given the relationship between human beings and the rest of creation, healing creation will frequently result in healing human beings. The case study of mercury emissions from coal-fueled power plants and the health of fetuses will provide a point of entry into this discussion.

Advances on power system oscillation

Power system is one of the largest man-made systems, which over the years has become the vital infrastructure for modern life. The foundation of today’s power system is three-phase alternating current (AC), which is adopted as the main stream technology for its advantages in voltage transforming, wide-area networking and long-distance power transmitting. The AC power system is a self-sustained oscillatory system operating at nominal frequency, i.e., 50 or 60 Hz. However, the multi-time-scale dynamics in a power system, mechanical, electrical or their coupled are prone to cause the exchange of energy at wide range of frequencies other than the nominal one, which is collectively known as the oscillation issues in a power system. Such oscillations would lead to power quality degradation, equipment failure, or even worse, system instability. Actually, the development history of power system is also a history of continuous “battle” against the oscillation problems. This article reviews the basic concepts and classification of the classical as well as emerging power system oscillations. The mechanism, origin and research advances of various oscillations are re-visited and discussed, from the earlier and long-standing low frequency oscillation (LFO), and then subsynchronous oscillation/resonance (SSO/SSR) associated with turbo-generators and wind turbine generators, to the latest wide-band oscillations involving the sophisticated dynamics of increasing renewables and power electronics in a power system. LFO incident was reported for the first time in 1964 in American Western Interconnection, where the formation of a larger power system by combining two smaller one, i.e., Northwest and Southwest systems, caused power oscillation at about 0.1 Hz. Later studies showed that the multiple machines with mechanical inertial but electrically connected through networks function like a mass-spring system, leading to LFOs at a frequency ranging from 0.01 to 2.5 Hz, depending on the size of the system. Initially, excitation control was improved by adding the function of power system stabilizer (PSS) to mitigate LFO. Later, advanced control, including linear optimal control, nonlinear control and optimal decentralized coordinated control, were developed to solve the problem. Since 2000, the continuous increase of system size and coverage causes very-low-frequency oscillation issues, to address which, several new technologies, for instance, wide-area monitoring and control, flexible AC transmission system (FACTS) control, has been commissioned in China and around the world. SSR/SSO is induced by the interactions between the multi-mass shaft of a turbo-generator and the series-compensated AC or HVDC transmissions. The frequency of power oscillation is subsynchronous, or less than the nominal frequency but generally above the 2.5 Hz. The first SSR incident was captured at Mohave Power generating Station in 1970. In China, however, SSR/SSO has been a severe stability concern since 2000, the time witnessing the widely usage of series compensation and HVDC to transfer electricity from remote coal-fueled power plants. After more than ten years’ continuous research, we have developed effective tools and countermeasures, for instance, multi-dimensional analysis, optimized control and coordinated protection, to solve practical SSR/SSO problems in China and some other countries. The integration of wind power introduces new interactive dynamics that involve wind turbine converters and AC grids. It is called sub-/super-synchronous control interaction (SSCI), which would result in a different type of oscillation from several Hz to double nominal frequency. Such sub/super-synchronous oscillations associated with wind power has entered people’s vision since 2009 and gained widespread attention after the occurrence of several actual incidents in US and China. To address this new issue, we have developed novel frequency-domain modeling and analysis methods to quantify the risk first, and then control strategies on either generator/converters side or grid side to modify the interaction to stabilize SSCI. These methods and strategies have been put into practice, for instance in Guyuan and Hami systems in China, to verify their effectiveness. At this moment, power system is undergoing profound changes, one of which is the rapid growth of renewables and power electronics in all sections, including generation, transmission and consumption of electricity. Such a change is triggering power system oscillations in a very wide band, i.e., from several Hz to several thousand Hz. The underlying reason is the multi-time-scale dynamic interactions among the huge number of converters and the increasingly complicated power grid. This leads to open challenges that are yet to be solved, including the need of: (1) Wide-spectrum models to represent the multi-time-scale dynamics; (2) advanced analysis methods to quantify the stability of wide-band oscillations; and (3) adaptive and coordinated controls to mitigate the oscillation under varying system conditions. In a nutshell, systematic and in-depth researches are required to establish new theories and methodologies for this emerging issue so as to promote the sustainable growth of renewable energy and the low-carbon development of power system.

Performance evaluation of a new conceptual combustion air preheating system in a 1000 MW coal-fueled power plant

An innovative design of combustion air preheating for large-scale coal-fueled power plants was proposed. Differing from the conventional air preheating system using a rotary regenerative air preheater, a cascade heating concept is adopted in the new configuration, where the air obtains heat from the feedwater, circulating water and flue gas in several tubular heat exchangers, which significantly diminishes the air leakages and the exergy destruction. The results of a detailed thermodynamic analysis show that, for a typical 1000 MW coal-fueled power plant, the net thermal efficiency increment can reach 0.49% points with a net heat rate reduction of 86.77 kJ/kWh, if the novel air preheating design is adopted instead of the conventional one. This is because the exergy efficiency of the air preheating process is promoted from 77.88% to 91.77% owing to the proposal, and the total exergy efficiency of the power plant rises by 0.48% points. The economic performance of the new design was examined as well, indicating that the dynamic payback period is only 5.30 years when the proposed air preheating system is employed to replace the conventional one. This work may be beneficial for enhancing the air preheating system and advancing coal-fired power production.

Flue Gas Desulphurization in Circulating Fluidized Beds

Sulphur dioxide (SO2) is mostly emitted from coal-fueled power plants, from waste incineration, from sulphuric acid manufacturing, from clay brick plants and from treating nonferrous metals. The emission of SO2 needs to be abated. Both wet scrubbing (absorption) and dry or semi-dry (reaction) systems are used. In the dry process, both bubbling and circulating fluidized beds (BFB, CFB) can be used as contactor. Experimental results demonstrate a SO2-removal efficiency in excess of 94% in a CFB application. A general model of the heterogeneous reaction is proposed, combining the external diffusion of SO2 across the gas film, the internal diffusion of SO2 in the porous particles and the reaction as such (irreversible, 1st order). For the reaction of SO2 with a fine particulate reactant, the reaction rate constant and the relevant contact time are the dominant parameters. Application of the model equations reveals that the circulating fluidized bed is the most appropriate technique, where the high solid to gas ratio guarantees a high conversion in a short reaction time. For the CFB operation, the required gas contact time in a CFB at given superficial gas velocities and solids circulation rates will determine the SO2 removal rate.

Urban pollution in the Danube and Western Balkans regions: The impact of major PM2.5 sources

The SHERPA tool was used to assess the major pollution sources and the geographical areas impacting on the PM2.5 of the main cities in the Danube and Western Balkans regions. The activity sectors influencing most the PM2.5 levels in the study area are energy production (22%), agriculture (19%), residential combustion (16%) and road transport (7%). The energy production in inefficient coal-fuelled power plants was identified as one of main source of PM2.5 in the Western Balkans. As for the geographical origin of PM2.5, the transboundary pollution is confirmed as the main origin of PM2.5 (44%) in the investigated cities, while the city own emissions and the national sources outside the concerned city impact on average 22% and 15%, respectively. An association was observed between the long-range transport and the impact of agriculture and energy production, while both local urban emissions and long-range transport were associated with the residential sector. A special attention is given in this study to biomass, a renewable source, which use is often promoted in the frame of climate and energy policies. Nevertheless, the combustion of biomass in inefficient small appliances has considerable particulate matter emissions and therefore this type of practice impacts negatively on air quality. Considering that biomass is traditionally used in South-East Europe as fuel for residential heating, the interpretation of the model results was supported with the estimation of biomass burning contributions to PM2.5 obtained with receptor models and data on biomass fuel consumption from the literature. The analysis of the contributions from biomass burning derived from receptor models suggests that biomass burning is the dominant source within the residential heating sector in the studied area and that the emissions from this source are likely underestimated. This study concludes that more effort is needed to improve the estimations of biomass burning emissions and that policies to improve air quality in the cities should involve a geographic context wider than the city level.