Application and development prospects of double-reheat coal-fired unitsKyle NicolMost pulverised coal combustion (PCC) plants employ single-reheat cycles. However, double-reheat cycles can significantly improve the electrical efficiency of PCC plants. Surprisingly, no double-reheat units have been commissioned since the 1990s. However, with rising primary energy costs, more stringent emission limits and advances in thermal power engineering, double-reheat cycles are being considered to minimise the cost of electricity, reduce emissions and prolong valuable coal supplies, especially in China. This webinar reviews, analyses and assesses the application and development prospects of coal-fired double-reheat units.Read more >
Recent developments in process waste recycling and biomass utilisation have driven the use of these so-called ‘low value fuels’ for energy generation on a stand-alone basis, and in combination with coal. One particular technology stands out as being particularly well suited to utilising these low value fuels, circulating fluidised bed combustion (CFBC). The upcoming webinar sets out examples of the range of low value fuels, their reserves and properties, with particular emphasis on coal-derived materials, the issues for CFB plant in utilising these fuels and selected examples of manufacturer and operator experience with purpose built, or modified CFB plant.
Coal power plant control systems have progressively evolved to meet the growing demand for efficient and flexible power generation whilst maintaining low emissions. In particular, optimisation of the combustion process has required increased use of online monitoring technologies and the replacement of standard control loops with more advanced algorithms
capable of handling multivariable systems. Improved stoichiometric control can be achieved with
coal and air flow sensors or imaging and spectral analysis of the flame itself, whilst in-situ laser absorption spectroscopy provides a means of mapping CO and O2 distribution in hot regions of the furnace. Modern plant control systems are able to draw on a range of computational
techniques to determine the appropriate control response, including artificial intelligence which
mimics the actions of expert operators and complex empirical models built from operational data.
New sensor technologies are also being researched to further improve control and to withstand the high temperature and corrosive environments of advanced coal plant and gasifiers. Increased use of optical technologies is of particular interest, with sensors based on optical fibres able to perform low noise, highly sensitive, and distributed measurements at high temperatures.
Microelectronic fabrication techniques and newly developed high temperature materials are also being combined to develop miniaturised devices which provide a robust and low cost solution for in-situ monitoring of gases and other parameters. These new sensors can be integrated with wireless communication technology and self-powering systems to facilitate the deployment of distributed sensor networks and monitoring of inaccessible locations. Using principles of self-organisation to optimise their output, such networks may play a growing role in future control systems.
Microalgal removal of CO2 from flue gas
Various methods have been developed to remove CO2 from the flue gas of coal-fired power plants. Biological post-combustion capture is one of these. Microalgae may be used for bio-fixation of CO2 because of their capacity for photosynthesis and rapid growth. The ability of microalgae to withstand the high concentrations of CO2 in flue gas, as well as the potentially toxic accompanying SOx and NOx has been researched. Microalgal strains that are particularly suitable for this application have been isolated. Most of the research on algal bio-fixation has been concerned with carbon fixation strategies, photobioreactor designs, conversion technology from microalgal biomass to bioenergy, and economic evaluations of microalgal energy. This webinar considers current progress in algal technology and product utilisation, together with an analysis of the advantages and challenges of the technologies. It opens with a brief introduction to the theory of algal bio-fixation and factors that influence its efficiency especially in terms of flue gas characteristics, and then discusses culturing, processing technologies and the applications of bio-fixation by-products. Current algae-based CO2 capture demonstration projects at coal-fired power stations around the world are described.
Competition between coal and natural gas for power generation has been observed to occur in North America and Europe in recent years, where the costs of the two fuels have played a key role in determining the relative competitiveness. It is perceived that such a competition could also happen in Asian countries. More importantly, as these countries are expanding their generation capacity to meet growing electricity demand, a key question is raised of whether coal or gas power plants should be built with priority. This webinar is based on a recent report published by IEA CCC, where the authors investigate nine Asian countries to seek to understand the mechanisms that drive the competition between coal and gas for power generation.
Biomass could have an important role in the strategy to reduce greenhouse gas emissions from large coal plants. Amongst the plethora of different biomasses, wood pellets have emerged as one of the most successful and fast growing internationally traded commodities. Wood (and straw) pellets offer a more energy dense and transportable alternative to the traditional wood chip, a product most commonly associated with the paper and pulp industry.
A few large scale projects in Europe have drawn on North American sources to supplement local supplies of biomass without any major problems. At current levels of demand, there appears to be an abundance of wood resource.
However, extending cofiring at low rates (5-10%) to the world’s coal-fired fleet will increase demand for wood pellets significantly. Meeting this demand will offer opportunities and challenges for the entire biomass supply chain, not least forest resources. This presentation accompanies a report by the IEA Clean Coal Centre to review the current understanding of world biomass resources using published forestry data from the UN Forestry and Agricultural Organization (FAO). From these data, the author attempts to identify a global and regional resource figure for wood in the form of residues and waste by-products that arise from the forestry industry; and discusses the broad issues that affect forest resources worldwide.
Legislation for mercury control for coal-fired power plants is emerging in several regions. The US
Environmental Protection Agency (US EPA) has several new rules, including MATS (the Mercury
and Air Toxics Standard) and CSAPR (the Cross-State Air Pollution Rule) both of which will have
a significant impact on coal-fired power plants in terms of retrofitting control technologies for
compliance. Canada has the Canada-Wide Standard which sets caps on mercury emissions for
individual Provinces. Although the EU has not yet set emission limits for mercury from coal-fired
plants, the new IED (Industrial Emissions Directive) has annual monitoring requirements for
mercury emissions. Further, the new BREFs (best available technology reference documents)
include details on options for mercury control. This would imply that, although mercury is not
currently being regulated, emissions are being monitored and control may be required at some
sources in future. China's latest Five-Year Plan includes emission limits for mercury which, for
the moment, are not particularly challenging. However, there is clearly a recent and significant
move in China towards the cleaning up of emissions from the coal sector.
In addition to mercury-specific policies and approaches, these regions have other policies and
regulations which could have a significant effect on mercury emissions. Looking ahead, based on
the consideration that regulations will be enacted for several pollutants simultaneously in these
regions, the outlook for environmental equipment regulations with respect to trace element
emissions is investigated. The webinar covers:
• legislative approaches in the different regions;
• suitable control technologies - co-benefit approaches, mercury specific technologies and
multi-pollutant strategies; and
• summaries of action in each of the target regions.