More output, less SOx at Poland’s Kozienice20 July 2001
Thanks to extensive modernisation and the recent backfitting of an FGD system (pictured above), Poland’s Kozienice plant aims to reduce emissions while at the same time increasing commercial competitiveness. Staff report
One coal power plant accounts for around 10 per cent of Poland’s installed generating capacity. This is Kozienice, the biggest hard-coal-fired plant in the country. Located on the Vistula river, 80 km southeast of Warsaw, the plant consists of eight units originally rated at 200 MWe apiece and two units originally rated at 500 MWe each. As a result of a steady programme of modernisation work over the past few years, starting in the mid 1990s, the installed capacity of Kozienice is now around 2785 MWe, and is expected to rise to 2820 MW in 2002. Much of the refurbishment has been made possible thanks to long term power contracts for electricity supplied from the refurbished units with PSE SA (Polskie Sieci Elektroenergetyczne), the Polish grid company. These contracts have constituted the guarantee for repayment of the loans taken out to pay for the refurbishment work.
Refurbishment in phases
The first units at Kozienice started supplying electricity to the Polish grid as long ago as 1972, with entry into operation of the first 200 MWe unit. The remaining 200 MWe units started up over the period 1973-75, while the two 500 MWe plants, units 9 and 10, were synchronised with the grid in 1978 and 1979 respectively. But despite their relatively advanced age, plant condition and generation efficiency is generally good, according to Jan Wrona, chairman and MD of the plant.
The first phase of refurbishment, from the mid 1990s to 1998, focused on the 200 MWe units, while major upgrade of the 500 MWe units started in 1999. Unit 10 is now back in operation, while refurbishment of the second of the 500 MWe units, unit No 9, is expected to be completed by December 2001. Jan Wrona points out that as a result of the refurbishment programme on the 500 MWe machines, the same steam flow that produced 500 MWe before refurbishment now produces about 560 MWe.
As well as increasing output and efficiency, there has, at the same time, been a concerted effort to reduce emissions and environmental impact, which is a particularly sensitive issue as the power station is located on the edge of a large environmentally protected forested area. Another driver in the move to clean up Kozienice is Poland’s ambition to join the EU and to meet EU emissions requirements.
The modernisation programme has included the following measures aimed at reducing emissions:
• Replacement of the electrostatic precipitators (ESPs) in the eight 200 MWe units and in one of the 500 MWe units (unit 10). This was done over the period 1988-95. It was the first significant step towards radical reduction in fly ash emissions. Later this year, when modernisation has been done on the second 500 MWe unit, the process of reducing fly ash emissions will have been completed.
• Modernisation of the electrostatic precipitator ash transportation systems, over the period 1998-2000, with the aim of increasing the degree of ash utilisation.
• Modernisation of waste water treatment plant, over the period 1993-98.
• Modernisation of boilers in nine of the units to reduce NOx emissions. This was carried out from 1995 to 2001. Work on the tenth boiler is to due to be completed in 2002.
But perhaps the largest environmental project to date has been a flue gas desulphurisation (FGD) system to serve the 500 MWe units. The new FGD, which was handed over to Elektrownia Kozienice SA on 8 June 2001, is estimated to reduce SO2 emissions from the plant by about 40 000 t/y. From the decision to proceed to guarantee tests the project has taken 30 months.
The contract for supply of the FGD system, which uses the “wet limestone–gypsum process”, was awarded to a consortium of Fortum Engineering (leader) and the Japanese companies Hitachi Ltd and Tomen Corporation.
A particular feature of the FGD plant design selected is its compactness and very tight layout, with short ducts, due to the small area available in the vicinity of the boilers. In fact this was a key factor in the decision to award the contract to Fortum, which, in this instance was offering the FGD technology of Babcock-Hitachi, of which it is a licensee. Also, instead of a rubber coating, the internal lining of the absorber is vinyl-ester resin with glass flakes – a first for Poland
The project comprised: limestone dust unloading system; slurry preparation system; absorption system; flue gas ducts; flue gas reheating; process water feeding system; gypsum dewatering; waste water treatment; electrical systems; instrumentation & control; and civil works. Fortum Engineering carried out the project on a turnkey basis, providing project management, procurement, commissioning, training and after sales services.
The contract for design, delivery and assembly of the gypsum transport, unloading and storage facilities and ancillary infrastructure was placed with Polish company Poltegor-Projekt, based in Wroclaw. The gypsum storehouse in particular is notable for its innovative lightweight structure.
The gypsum byproduct produced by the power plant has good physical and chemical properties, making it attractive to the building industry. With a good deal of building going on in Poland, there is projected to be continuing strong demand for wallboard grade gypsum.
SGS Poland acted on behalf of Elektrownia Kozienice as owner’s engineer and was responsible for technical supervision of the project, ensuring that it met Polish legal requirements and that contracts were complied with, and also providing technical advice to the power plant staff.
The key to financing the FGD installation was a 15 year power-purchase agreement between the plant and PSE for electricity from the modernised 500 MWe units. Powszechny Bank Kredytowy organised the consortium credit for unit 9 modernisation, including 155.5 million zl for construction of the FGD. The Polish National Fund for Water and Environment gave a long term preference loan of 80 million zl for FGD construction. The Helsinki-based Nordic Investment Bank gave long-term preference credit of $30 million for unit 9 modernisation and FGD construction, while the Polish ministry of finance gave guarantees to cover the Nordic Investment Bank credit.
Although space was limited, implementation was achieved on a very tight schedule and without major problems - reflecting good works planning, appropriate design, a high degree of co-operation between client, contractors, and all the other main players, and a generally positive atmosphere.
Construction began in December 1998 and less than three months later, assembly of the absorber grate began along with steel construction on the first building, the circulation pump house.
In November, 23 months after starting, final assembly was completed and commissioning and functional tests could begin.
The particular the challenge of the restricted site area called for some innovative assembly methods for the larger equipment (eg the absorber casing and rotating gas-gas heater) from Polish contractor Energomontaz-Polnoc.
The first start-up of the FGD installation with flue gas from unit 10 took place on 22 February 2001, allowing process and optimisation tests to get underway.
From 9 to 12 April, the 72 hour operation test was performed on the FGD, then, with the Gliwice-based power testing and research organisation Energopomiar acting as contractor to the power plant, guarantee tests for the FGD system were carried out. The tests confirmed that SO2 removal was as specified in the contract. The SO2 concentration at the outlet of the FGD dropped below 200 mg/Nm3 of dry flue gas, with high sulphur coal, maximum exhaust flow at 560 MWe output from the power plant and four circulation pumps in operation. Other values guaranteed in the contract were also confirmed: fly ash concentration in the cleaned flue gas was less than 50 mg/Nm3; cleaned flue gas temperature downstream of the FGD was over 90°C, power consumption by the FGD was less than 8.92 MWh/h, process water consumption was below 93 m3/h; and the gypsum was of the required quality.
Meeting Polish emissions standards
Although there are two 500 MWe units at Kozienice and the FGD system is designed to serve them both, its capacity is 2 300 000 Nm3/h wet flue gas, which corresponds to a single 500 MWe unit. The thinking is that even with the two refurbished 500 MWe units operating at full capacity, and with the FGD system serving only one of them, the plant overall will still be well within Polish emissions standards, both present and projected.
For the period up to 31 December 2005, the Polish emissions standards for power plants of over 500 MWt are as follows (all for dry gases at 6% O2): SO2 - 2350 mg/m3; NO2 - 540 mg/m3; ash - 350 mg/m3; and CO - 250 mg/m3. From 1 January 2006 to 31 December 2010, the figures will be: SO2 - 1200 mg/m3; NO2 - no change; ash - 100 mg/m3; CO - no change.
For the refurbished Kozienice unit 9, as already noted, the new FGD achieves less than 200 mg/m3 (dry) at its outlet (compared with 2900 mg/m3 (wet) at the inlet), giving the plant plenty of margin to expected SO2 emissions requirements, while NOx is less than 500 mg/m3. So the refurbished 500 MWe units at Kozienice can face likely future emission standards with confidence.
In the future a decision will be needed on whether to install an FGD system to serve the newer of the 200 MW plants at the site, units 6, 7 and 8.