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IEA Clean Coal Centre

IEA Clean Coal Centre

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Microalgal removal of CO2 from flue gas Xing Zhang 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.
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Apr 22 2015
39 mins
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  • 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.
  • Using coal to fuel diesel engines has been investigated previously, but the technology has not yet been commercialised. This presentation reviews the previous R&D programmes on coal-fuelled diesel engines and focuses on the recent developments of the technology in its latest form, the direct injection carbon engine (DICE).
  • Lignite is an important fuel for power generation in many parts of the world. The major issue is that the high moisture content of lignite results in low thermal efficiencies and high CO2 emissions of lignite-fired power plants. An effective way to resolve this issue is to pre-dry the lignite before combustion in the boiler. Several modern pre-drying processes, such as RWE’s WTA dryer and GRE’s DryFining™ systems, have been developed based on this principle, which can be integrated to lignite-fired power plants to continuously pre-dry the feeding run-of-mine lignite. This webinar describes those technologies and their technoeconomic implications for the lignite-fired power plants to which they are integrated. In addition, the webinar also introduces the development of some standalone lignite drying and upgrading technologies.
  • Coal-fired power plants are increasingly required to balance power grids by compensating for the variable electricity supply from renewable energy sources. For this, high flexibility is needed, in terms of possessing resilience to frequent start-ups, meeting major and rapid load changes, and providing frequency control duties. This report reviews the means available and under development for achieving the flexibility. Potential damage mechanisms are well known, and the necessary flexibility can be achieved with acceptable impacts on component life, efficiency and emissions. Designs are being developed to enable flexibility in future plants.
  • Blending of imported and domestic coal is becoming more important. Until recently, coal blending in power stations was adopted mainly to reduce the cost of generation and increase the use of indigenous or more readily available coal. Low-grade (high ash) coal can be mixed with higher grade (imported) coal without deterioration in thermal performance of the boiler, thus reducing the cost of generation. As coal markets change, new reasons for coal blending are becoming apparent. As indigenous coals become less available, of lower quality or more expensive to mine in some regions, blending of imported coals becomes necessary. It can be challenging to ensure that the resulting blend will maintain plant output without damaging the boiler.
    In some cases coal blending is used as a form of pollution control, such as the combination of inexpensive high sulphur coals with more costly low sulphur coals to ensure compliance with sulphur emission limits. It is even possible to blend different coal types to maximise mercury emission reduction.
    Many methods of coal blending are used. Coals can be blended at the coal mine, at the preparation plant, trans-shipment point, or at the power station. The method selected depends upon the site conditions, the level of blending required, the quantity to be stored and blended, the accuracy required, and the end use of the blended coal. Normally in large power stations handling very large quantities of coal, the stacking method with a fully mechanised system is followed.
    In this webinar Lesley discusses the different reasons and priorities for coal blending. She summarises the methods of coal blending, from coal characterisation though to mixing and storage methods, including some case studies of challenging situations.

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