Cofiring high ratios of biomass with coal

Hermine Nalbandian presents her latest research

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.

Latest research from Dr Qian Zhu

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.

Turkey has one of the world’s fastest growing economies. Rapid economic expansion, rising population, and growing industrialisation have triggered a general increase in energy demand. Over the next ten years energy demand is expected to double. In order to meet this, significant investment in the energy sector will be required.

Turkey's indigenous energy resources are limited almost exclusively to lignite and smaller amounts of hard coal, so there is a heavy
dependence on imported sources of energy. More than 90% of Turkey’s oil and 98% of its natural gas is imported, as is much of the hard coal consumed, as a considerable cost. The government aims to reduce this,
partly through the greater use of domestic lignite, widely available in many parts of the country. Thus, the government has a ‘coal strategy’ and has introduced incentives to encourage the its greater utilisation. Many new power generation projects are in the pipeline, some fired on ligniteand others that will rely on imported hard coal.

Many existing state-owned coal-fired power assets (and coalfields) are in the process of being transferred to the private sector. Some power plants require modernising and this is being factored into their selling price. The current coal-based generating fleet comprises plants based on conventional pulverised coal or fluidised bed combustion technology. Some newer projects plan to use supercritical steam conditions and all major power plants will be required to install effective emission control systems.

The further development and application of a range of clean coal technologies is being pursued by a number of Turkish utilities, technology developers, and universities. There is increasing involvement
with international projects and, in many cases, growing links with overseas counterparts.

This study examines the role of HELE (high efficiency, low emission) coal-fired power plant in helping to meet the goal of reduced carbon dioxide emissions by setting out an overview of the prospects for the role of HELE technologies in a number of major coal user countries. Ten countries have been selected for study and are (in alphabetical order); Australia, China, Germany, India, Japan, Poland, Russia, South Africa, South Korea and the USA. The target countries have differing coal-plant fleet ages and efficiencies, and different local conditions and policies which impact on the scope for HELE implementation.
The profile of the coal fleet for each country has been calculated to meet future electricity demand under three scenarios with progressively greater replacement of lower efficiency capacity with HELE technology, and the consequent emissions of carbon dioxide and costs of implementation determined. The results are discussed in terms of potential carbon dioxide savings and the prospects for adopting a HELE upgrade pathway in the context of current energy policy.

First Asia-Pacific webinar from the IEA CCC. Presented by Toby Lockwood and Kyle Nicol.

Pulverised coal combustion (PCC) power plant with supercritical (SC) steam parameters have been operational for over forty years and ultra-supercrital (USC) PCC plant have been operational for just over twenty years. This significant amount of operating experience is valuable regarding the performance of high temperatures steels. For example 9-12% chromium martensitic steels have had problems with cracking and some have not been as strong as they were projected to be. Additionally, PCC power plant have been operated outside of design parameters, such as severe cyclic operation, which has resulted in unforeseen problems for high temperature steels. This webinar reviews the performance, problems, solutions and research efforts for high temperature steels used in SC and USC technology.

There are many items to include when considering the sustainability of biomass for cofiring, and some of them are hard to quantify. The focus of this webinar is on the greenhouse gas emission aspects of sustainability. The reduction of greenhouse gas emissions achieved by substituting biomass for coal depends on a number of factors such as the nature of the fossil fuel reference system, the source of the biomass, and how it is produced. Relevant issues in biomass production include the energy balance, the greenhouse gas balance, land use change, non-CO2 greenhouse gas emission from soils, changes to soil organic carbon, and the timing of emissions and removal of CO2 which relates to the scale of biomass production. Certification of sustainable biomass is slow to emerge at the national and international level, so various organisations are developing and using their own standards for sustainable production. The EU does not yet have sustainability standards for solid biomass, but the UK and Belgium have developed their own.

Coal gasification for chemicals, gaseous and liquid fuels production can fulfil an important strategic need in those developing countries where coal is the primary fuel source and oil and gas energy security is an issue. At the same time, the establishment of major projects in such countries can be problematical for a number of technical and economic reasons, although it is encouraging that some projects appear to be moving forward. There are two developing countries where coal conversion projects to produce chemicals, gaseous and liquid fuels have been taken forward strongly. The first is South Africa, which established the world’s only commercial-scale coal-to-liquids and coal-tochemicals facilities at Secunda and Sasolburg respectively. The other is China, where there is a major gasification-based coal conversion development and deployment programme that is set to become a significant, large-scale commercial element in the nation’s energy development plans. This will provide further major opportunities for the deployment of large-scale coal gasification technologies, various syngas conversion units and catalysts for the subsequent production of the required products. The role of China is likely to be critical in the dissemination of such technologies to other developing countries as it can not only provide the technical expertise but also financially underpin such projects, including the associated infrastructure needs.

Xing Zhang presents the results of her research

Paul Baruya presents the findings of his recent research

Kyle Nicol presents the findings of his latest report

Toby Lockwood presents the results of his latest research

Dr Stephen Mills presents the findings of his latest report