Hospital takes the steam out of carbon emissions

Babcock Wanson, steam generator, DHW
Gas-fired steam generators have replaced boilers fired by heavy fuel oil at Bedford Hospital and reduced carbon emissions by 15% as part of this NHS Trust’s response to the NHS carbon-reduction strategy.

With the NHS aiming to reduce its 2007 carbon footprint by 10% by 2015, Chris Horsley describes how one NHS Trust has considerably reduced its carbon emissions by refurbishing its boiler house and moving from oil to gas for generating steam.

The NHS carbon-reduction strategy for England published early in 2009 identified the NHS as having a carbon footprint of about 18 Mt of CO2 a year. Despite an increase in efficiency, the NHS has increased its carbon footprint by 40% since 1990. To meet the Climate Change Act’s targets of 26% reduction by 2020 and 80% reduction by 2050, the NHS will have to work hard; it aims to reduce its 2007 carbon footprint by 10% by 2015.

Bedford Hospital was one NHS Trust that was quick to react to the figures and to the Carbon Reduction Commitment (CRC) proposals. Its estates team concluded the CRC scheme will require the trust to pay a tax of circa £12/t of carbon dioxide produced by the trust as a direct result of the utilities used on the main site. It is currently estimated that the trust produces around 9000 t of carbon dioxide a year, equal to an additional cost of £108 000 per year.

Working with carbon-reduction specialists, Bedford Hospital identified a number of areas ripe for efficiency improvements, with the boiler house being the priority.

At the time, the hospital’s boiler house housed four enormous oil-fired boilers. They were 30 to 40 years old and did not provide the efficiency expected of current plant. The heavy fuel oil they used is expensive and has to be stored on site and maintained at a constant elevated temperature. So in addition to the cost of the fuel itself, there is the added financial and environmental costs of continual deliveries to site by road, as well as the costs of keeping the oil on the premises at a set temperature. Of course, this also calls for extensive storage facilities which need to be well maintained.

By converting the boiler house to natural gas, costs could be reduced considerably and on-site fuel storage largely eradicated. The trust estimates that converting to gas will reduce its carbon-dioxide emissions by 1500 t a year, while also providing improved efficiency — and security — on site for the trust’s main heating source.

The four heavy-oil boilers have been replaced with three Babcock Wanson steam generators with an output of 2500 kg/h and fitted with high-efficiency exhaust-gas economisers. These new units use coil-type steam-generator technology that gives operating efficiencies of around 94% and low emissions. They utilise modern controls to maintain a close ratio between the burner firing rate and water input — ensuring close control of both steam output and the steam quality. The burner can be supplied to use different gaseous or liquid feeds, but at Bedford Hospital the primary fuel is gas, with one unit configured for dual-fuel operation (gas or oil) as a precautionary measure against failure of the gas supply.

The benefits of using high-efficiency steam generators not only include reduced energy consumption and carbon emissions but also improved safety, simplicity of control, compact size (about half the footprint of the previous fire-tube boilers). They are considerably quieter, cleaner and cooler in operation, making the boiler house a far nicer environment in which to work.

In addition the ESM steam generators, two Babcock Wanson 1200 kg/h vertical coil-type steam generators have been installed in the new building of the sterilisation services department building for use in sterilising processes.

The boiler house refurbishment was largely completed in Summer 2010 and a full review of savings achieved will be carried out shortly. In its annual report for 2009/10, the trust states: ‘A major carbon footprint reduction will be achieved when the scheme currently in progress to change the main boiler fuel from heating oil to gas is completed in summer 2010. This £900 000 project will reduce our carbon emissions via energy usage by around 15% by removing the need to use heavy fuel oil, as the new boiler plant will use natural gas as its main fuel source.’

Bedford Hospital Trust has a proactive and positive attitude to reducing its carbon footprint. It researched the options and possible funding initiatives and put a good team of people together, from inside and outside the Trust, who worked closely together to achieve the smooth transition to a new, efficient steam generation system. It has certainly made a stride towards the NHS’s overall 10% carbon reduction set for 2015.

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