The Conventional Power Boiler User Group 2016 conference, run by the Institute of Mechanical Engineers, was held in Nottingham last week. It was an excellent opportunity to find out about the latest developments in conventional boilers used for power generation in the UK and beyond. This year’s programme reflected the rapid changes in the power industry in light of the UK government plans to close all coal generation plants by 2025. To maintain the electricity supply for the UK, the power industry will continue to operate existing coal-fired plants to the end of life or the required closure time, and they will also build new or convert existing boilers to run on other fuel such as biomass or waste.
‘Transitions to a low carbon energy system’ by Mike Colechin from Energy Technology Institute (ETI) was the first day’s keynote presentation. Mike highlighted the energy challenges in the UK to achieve sustainable, secure and affordable energy. The combination of a growing population and energy demand, ageing assets, rising electricity prices and tightening environmental targets means that critical decisions on the future energy mix and investments are needed. These include not only decisions on conventional power plants but also the way these interact with the rest of the system, in particular, the delivery of low carbon heat to homes and work places. Significant levels of innovation are needed over the next ten years, as is the development of a shared understanding of the issues across business, government and the science base. Delays in the launch of major build programmes, whether nuclear, CCS, heat delivery (gas, electricity, biomass, district heating), transport (liquid fuels, electricity, hydrogen), beyond the mid-2020s will lead to an estimated cost increase of around £5 billion/y.
A selective non catalytic reduction (SNCR) system called ‘Umbrella SNCR’ was presented by Marco Re (GE Power). The system can be applied to boilers firing different fuels, including biomass and low quality coals, and is also suitable for different boiler loads and sizes and a variety of burner configurations. Traditional SNCR typically use wall injections or injection grids to inject the reagent (urea or ammonia) into the boiler. The former may have limited reach inside the boiler whereas the latter are expensive. In contrast, the Umbrella system injects the reagent solution in the middle of the boiler using adjustable lances which have a wider reach area. This is because once the reagent is injected in the boiler, the flue gas carries it upwards (‘reagent droplets fly’). The reagent flow injection pressure is pulsated to further improve mixing of flue gas and the reagent. Thus the reagent is sprayed around the nozzle in the shape of an umbrella (cycle), and achieves better penetration of the boiler. The system on its own has a proven NOx reduction rate of up to 50% which can complement the reduction achieved by low NOx burners and other primary NOx control measures.
Plasma ignitor development was discussed by Marcus Whitworth, also from GE Power. Changes in the electricity market in many countries mean that coal power plants no longer operate as baseload plants. Instead, they are required to work with lower capacity factors and have more frequent start-ups in order to back up intermittent renewable energy sources. The start-ups use expensive fuels such as natural gas or oil. The plasma ignitor developed by GE Power Solutions uses a plasma jet which ignites the coal directly, so no starter fuel is required. Tests have shown it is applicable to various solid fuels including biomass, hard coal and lignite as well as coal with low volatile matter content. The system has been commercialised this year and can be installed on the existing burners, which just need to be modified.
There were various presentations on the safety and reliability of coal-fired power plant operation as well as statutory compliance. Paul James (Uniper, formerly EON) gave a paper given on fuelling integrity concerns in modern boiler plant which reviewed boiler plant evolution, the impact of manufacture (defects/faults), operational conditions (pressure, temperature, standby, seasonal and baseload operation) and fuel components on boiler tube integrity as well as proactive and corrective measures such as quality control to mitigate against boiler tube leaks.
Jake Waterhouse from DEKOMTE presented on increasing the life and reliability of expansion joints in ageing conventional boiler plants. Inspection and maintenance of these joints needs to be ongoing and planned in order to ensure smooth plant operation and eliminate various leakages. Examples of DEKOMTE joints were given.
As the UK starts to phase out coal, the number of plants running on alternative fuels such as biomass and waste is increasing. This was reflected in the number of presentations on such plants. Graham Welford from Doosan Babcock, gave a presentation on coal power plant life extension by biomass conversion using the conversion of Lynemouth 3 x 140 MW units as an example. The power plant was a good candidate for conversion for a number of reasons. First, it was closed at the end of 2015 due to a lack of SOx and NOx controls required to meet Industrial Emission Directive (IED) emission limits. Second, most of the plant’s existing systems and components could be used to generate electricity from biomass. Third, the small size of units the made the conversion logistics manageable. This allowed the plant owner (EPH) to apply for a Contract for Difference (CfD) from the UK government and benefit from £105/MWh for 10 years. The project is ongoing and consists of a number of upgrades. These include: a new fuel feeding system, mill modifications and new dynamic classifiers, replacement of existing pulverized fuel pipes or those suitable for more corrosive environment, new low NOx bespoke biomass burners, a new boosted over fire air (BOFA) system for further NOx control, upgraded oil system, new dry bottom ash and fly ash systems as well as ESP upgrade. All of these will allow the plant to maintain 40% plant efficiency and compliance with the IED emission limits. The commercial operation of the plant is expected to be at the end of 2017.
Another example of converting coal-fired plant to biomass by Doosan Babcock was presented by Makesh Kaliyaperumal. Currently under way, the conversion of the 125 MW capacity unit 1 of Yeong Dong power plant in South Korea, is expected to extend the operational life of the unit for another 15 years, improve the thermal efficiency of the existing plant, increase operational and fuel flexibility as well as reduce NOx, SO2, PM and CO2 emissions. The plant is projected to start commercial operation in March 2017.
William Hird, WH Power Ltd gave an excellent overview of energy from waste plants (EfW), which included household waste boiler design, relevant legislation and challenges such as increasing plant efficiency. Roberto Vogel, KRR PROSTREAM, talked about the impact of boiler detonative cleaning in EfW plants.
While there is no denial that the electricity market and power industry are undergoing radical changes in the UK and that a rapid adjustment of the coal-fired power sector is needed, it is clear from this meeting that innovative work is underway and new solutions are being found.
The full programme of the conference can be found here: http://events.imeche.org/ViewEvent?code=CON6369#
