POWER GENERATION INDUSTRY
November 2010
This month I will be looking at applications for water filtration in the power generation industry.
In such a critical environment where efficient operation of all plant and equipment must be maintained continually, any filtration systems installed must also be extremely durable and reliable. As a result, Boll & Kirch automatic, self cleaning filters are often specified for power stations - both for raw water filtration and to provide protection of high capital plant. Raw water for subsequent cooling or process water is often sourced from rivers or the sea and stored in large reservoirs or lagoons in remote parts of the site. In this case, it is vital that the filtration system can operate on an unmanned basis - without the need for regular cleaning or maintenance.
At Bollfilter UK, we have been involved in designing and supplying a number of filtration systems for the UK Power Industry, both for applications at individual power stations or working with other OEM manufacturers to supply stand-alone, integrated power generation equipment.
COOLING WATER FILTRATION: Hinkley Point Power Station
British Energy Generation owns and runs nuclear power stations in the UK and supplies energy businesses with electricity.
Based near Bridgwater in Somerset, Hinkley Point B is a British Energy Advanced Gas-cooled Reactor (AGR) nuclear power station. The plant, which was built in 1967, has two reactors with a combined electrical output of 1220 Mega Watts - capable of supplying electricity to over 1 million households.
Nuclear power stations harness the energy released from continuous fission of the atoms to produce steam, which is then used to drive the turbines that produce electricity. As part of the process, the nuclear reactors require large quantities of cooling water.
At Hinkley Point B, seawater from the Bristol Channel is used to provide the reactor cooling water. However, in order to protect the system from risk of blockage by particulates, it is necessary to continuously filter the raw water.
As part of a major refurbishment programme to replace cast iron pipework, the old filters were removed and replaced with the latest Bollfilter systems. Two Boll automatic seawater filters - one Duty, one Standby - with Super Duplex Stainless Steel internals have been installed on the water supply to each reactor.
FLUE GAS DESULPHURISATION
Flue Gas Desulphurisation (FGD) is a technique designed to reduce emissions generated by coal-fired power stations. It requires large quantities of clean water as part of the process.
CASE STUDY: Eggborough Power Station
Also operated by British Energy, Eggborough Power Station has been generating electricity for over 30 years, producing a maximum output of 2000 Megawatts - sufficient to meet the demands of 2 million homes.
A FGD (Flue Gas Desulphurisation) plant has been installed to significantly reduce sulphur dioxide (SO2) emissions and ensure that the National Air Quality Standards are met. Within the FDG plant, limestone slurry is sprayed into the hot flue gases. The flue gas reacts with the limestone to remove at least 90% of the SO2, creating a gypsum slurry which is dewatered and sold for plasterboard manufacture.
Water used in the process is taken from Eggborough's cooling water system which is fed by the nearby River Aire. Before use in the FGD plant, this water must be filtered to 100 microns in order to prevent blockages in various spray nozzles within the FGD plant.
A constant supply of water at up to 100 tonnes per hour is required by the FGD plant. However, after heavy rainfall the run-off from nearby arable land - especially at harvest time - can lead to a dramatic increase in particulates in the river and cause blockages in the FGD water filter. This is a major concern as the FGD plant must be shut-down within 20 minutes of an interruption to its water supply. Under EA regulations the associated generating unit may not be allowed to operate without the FGD plant also in service.
A Boll 6.18.2 Heavy Duty Automatic Filter System with 6.18 Automatic Stand-by Filter has been installed on the FGD water inlet from the Power Station water intake. This removes any particulates over 100 microns, preventing the risk of blockages in the FGD plant.
Rob Welborn, responsible for FGD Operations, was responsible for specifying the new filter system. "I liked Boll's self-cleaning technology and the new heavy duty automatic filter has proven effective. Since the system has been installed we have not lost any days operation due to water filter blockages."
TURBINE PROTECTION
As I have already mentioned, Boll & Kirch filters may be installed directly on-site or as part of other OEM equipment, such as Steam or Gas Turbines. There are two types of applications - the use of automatic water filters to protect the plant cooling systems or the use of manual lube oil or fuel oil filters within an integrated skid-mounted Steam Turbine.
CASE STUDY: Glendoe Power Station
Two Bollfilter Automatic self-cleaning back-flushing filters have been installed at the Glendoe Hydro Power Scheme - the flagship project of Scottish & Southern Energy (SSE).
Currently Scotland's largest civil engineering project and the first large scale conventional hydro electric power station to be built there for 50 years, the Glendoe Hydro Power Scheme is designed to generate up to 100MW of clean, green energy. Set in the mountainside beside Loch Ness, the Scheme features a reservoir formed by a 905m long dam on the River Tarff, an underground cavern housing the power station and an extensive network of tunnels. The tunnels channel water from the reservoir to the 'Powerhouse' and then into Loch Ness. Glendoe will be the UK's most efficient hydro electric scheme thanks to the height drop between reservoir and turbine.
The Powerhouse cavern, which has been created deep underground is 38m long, 18m wide and 32m high. It contains the turbine, which is turned by the force of water flowing through the tunnels, and generator.
In order to protect the power generation plant, a plant protection system has been installed by Weir Services. This incorporates a Boll automatic water filtration system to remove potentially damaging particulates from the raw river water. The system operates continually (one filter duty/one standby), with a pre-set back-flushing programme to ensure efficient filtration without the need for regular cleaning or maintenance.
The interior of the Glendoe Powerhouse Cavern during construction of the turbine hall, which features a Bollfilter water filtration system to protect the turbines.
CASE STUDY: Dresser Rand Steam Turbines
Dresser Rand specialises in the design and manufacture of steam turbines, offering a complete package comprising the turbine, gearbox, generator, instrumentation, control and monitoring systems, and associated ancillary equipment - usually mounted on a single fabricated baseplate.
Dresser Rand Steam Turbines are employed throughout the world in a variety of power generation applications, many involving renewable and sustainable energy. They are also widely used in the oil, gas and marine industry, generating power for FPSO (Floating Production Storage & Offloading) Vessels, on and offshore facilities and large container ships.
In order to protect the moving parts of such high value capital equipment, Boll Simplex or Duplex filtration systems are specified to remove particulates down to 10 microns from the closed loop system supplying Control Oil and Lube Oil.
Boll filters can be fitted as part of the main turbine baseplate or skid, or installed alongside with other ancillary equipment. In marine applications, space is particularly critical and it is important that all the equipment can be contained on a single skid. The latest Boll BFD Duplex filters are ideal for skid-mounted applications thanks to their compact size.
John Dow can be contacted at:
Bollfilter UK Ltd
Unit 9, Station Road
Tolleshunt D'arcy
Essex CM9 8TY
Tel: 01621 862180
Fax: 01621 869257
E-mail:
john@bollfilter.co.uk
web:
www.bollfilter.co.uk
To view previous issues of John Dow's Filtration Column click on the links below:
