Window of opportunity

Siàƒ¢n Green

Deregulation of Europe’s electricity industry over the past two years has brought change for most countries – perhaps none more so than in Germany in recent months. The region’s largest power market has seen price wars and mergers like no other since it opened its market, creating opportunity for new and old players – both foreign and domestic.

Figure 1. Wacker-Chemie’s Burghausen works, Germany, is approximately 100 km east of Munich
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Among the new players in Europe’s competitive markets are industrial companies able to benefit from developing their own on-site power assets, using the power and heat generated, and selling excess power to the grid. According to UK consultants Datamonitor, an estimated 10.3 GW of new industrial capacity was ordered across the EU between 1993 and 1998.

One such industrial company is Germany-based Wacker-Chemie GmbH, which produces a range of specialist products from facilities in Germany, Singapore and the USA. In 1998 the company decided to install a combined heat and power plant at its works in Burghausen, Germany, in order to meet electricity and steam demand.

Wacker-Chemie signed a contract with Fortum Energie GmbH, the German subsidiary of Finland’s Fortum, in late 1998 for the turnkey development of a 120 MWe CHP plant, making Fortum the first foreign independent power producer (IPP) in Germany. A project company, Fortum Kraftwerk Burghausen GmbH has now been established. The plant will supply electricity and 350 t/h of process steam to the Burghausen chemical works, and is scheduled for commercial operation in early 2001. The project has presented Fortum with several challenges, including a tight time schedule and limited site space.

On-site expansion

The Burghausen chemical works is located approximately 100 km east of Munich, near to the Austrian border. Employing 10 000 of Wacker-Chemie’s 16 000 workforce – including 3000 Austrians – it produces a range of products including semiconductors and silicon wafers. At around 2.5 km2 in area and with an annual electricity demand of nearly 1.5 TWh/year, it is the company’s largest site. It buys 60 per cent of its electricity needs from Bayernwerk.

Existing energy generating facilities at Burghausen include a hydropower plant commissioned in 1918, which generates around 20 per cent of the site’s electricity needs, and a natural gas-fired cogeneration plant dating back to 1917. The latter consists of five natural gas-fired boilers – four high pressure and one low pressure, five steam turbines and two compressors, and generates 20 per cent of the site’s electricity and all of its steam demand. The steam production of the high pressure boilers and heat recovery steam generator (HRSG) is connected to one high pressure network. The five existing steam turbines supply the three pressure level steam network consisting of 15, 5 and 1.2 bar grids.

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The decision to increase the generating capability of the Burghausen works was taken largely due to the high industrial electricity prices which existed in Germany prior to deregulation. Wacker-Chemie felt that by being able to meet its entire electricity demand with on-site facilities, it would save money. It therefore decided to add a gas turbine generator and HRSG to the existing cogeneration plant to convert it to a combined cycle cogeneration plant.

Lacking the expertise to construct and operate power plants, and following deregulation in Germany in April 1998, Wacker-Chemie held an international tender for the power project. It received six bids, and then shortlisted three bids: Finland’s Fortum, and Bayernwerk and Steag of Germany.

According to Wacker-Chemie’s Gàƒ¼nter Keilitz, Fortum won the bid not just on price; the German chemical company was also impressed with Fortum’s technical capabilities, its experience with CHP plants and knowledge of liberalized markets. “[Fortum has] a very good knowledge of running such power plants,” said Keilitz.

Figure 2. inset
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Financing was also a factor in choosing a partner for the project, according to Keilitz. Fortum was able to offer financing for the project, and has done so based on its own balance sheet. “Wacker was not ready to finance a power plant because our key business is the chemical field,” said Keilitz. “Fortum was therefore the right partner.”

Figure 2. The heat recovery steam generator will have a vertical arrangement and will be placed on top of the GE Frame 9E gas turbine (inset is a photomontage of the finished plant)
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Fortum has approximately 9070 MW of generating capacity worldwide in operation – experience it says that the other bidders for the project did not possess. It sees itself as a leader in the cogeneration field, able to offer packaged turnkey delivery without ties to any particular equipment suppliers. When the German market deregulated, and Wacker-Chemie invited bids for Burghausen, Fortum saw a good opportunity to enter an important market.

Germany is one of Fortum’s ‘target’ markets. It was initially attracted by the margins offered by the high industrial prices as well as the market’s size. Even though electricity prices have fallen dramatically over the past year, it will remain committed there and has forecast gradual price increases in the long term. Fortum was also the first foreign company to obtain an electricity supply license in Germany, and recently took full ownership of power utility Elektrizitatswerk Wesertal.

Under the engineering, procurement and construction contract, Fortum Engineering is supplying the equipment for the CHP plant development and is responsible for construction and commissioning of the facility and its connection to the existing plant. Fortum Service will operate and maintain the ‘new’ section of the plant, i.e. the gas turbine and the HRSG, while Wacker-Chemie will continue to manage the existing sections of the plant.

Fortum will sell process steam from the plant directly to Wacker-Chemie. Power sales, however, presented both Fortum and Wacker-Chemie with a challenge. Electricity demand at the Burghausen works varies from day to day, with peaks and troughs caused by changes in the outside temperature, production rates and so on. Such variances are difficult to manage with a combined cycle cogeneration plant where process steam output must be kept nearly constant.

To overcome these challenges, Wacker-Chemie reached a ‘three-way’ agreement whereby Fortum sells the entire electrical output of the plant to Bayernwerk, which will continue to supply part of Wacker-Chemie’s electricity needs as it did prior to the construction of the new plant.

Figure 3. The extension to the existing plant will supply high and medium pressure steam to Wacker-Chemie’s steam network, and will export power to Bayernwerk
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Under this arrangement, the power that Wacker-Chemie buys from Bayernwerk is the same price as the chemical company would have paid Fortum for direct supplies from the power plant. The three-way deal also removes a great deal of risk; Wacker will not be concerned about gas turbine trips resulting in lost production time, and the problem of managing peaks and troughs in demand at the site is also solved. “I think it was a very good combination to cooperate with Fortum on the one side and Bayernwerk on the other,” commented Keilitz.

Saving space

Fortum will therefore operate the plant as a baseload unit. In its original bid, Fortum envisaged a 2 x 70 MW gas turbine configuration but later changed this to a 1 x 120 MW, not only to closely match the site’s steam requirements, but also for economic reasons – installing two gas turbines would have required the demolition of an adjacent building.

The footprint for the new plant has therefore been minimized. An old storage building has been removed for the new unit, and the available area necessitated use of a vertical arrangement for the HRSG, with the gas turbine unit directly beneath it. This has resulted in a specific place demand of 0.25 MW(e+th)/m2.

The gas turbine selected for the project is a GE Frame 9E manufactured in France by GE Energy Products Europe. This machine is particularly well suited to the project due to its compact footprint and vertical outlet stub which will allow a vertical connection to the boiler inlet duct. It was also attractive from a reliability viewpoint, according to Fortum.

The turbine has a 17-stage compressor and a three stage turbine section. The exhaust mass flow of the machine is 400 kg/s at 542à‚°C. The combustion system is of the Dry Low NOx type consisting of 14 combustion chambers arranged around the periphery of the compressor discharge casing. The natural gas is supplied to each combustion chamber through a nozzle designed to disperse and mix the fuel with air.

The pumps and process equipment of the balance of plant will be located around the gas turbine, and the blowers, wash skid and the fuel gas skid will be located on an additional 3 m level. The gas turbine and its auxiliary equipment is to be housed in an acoustic enclosure to ensure that the average sound pressure level of the package is less than 82 dB(A) at 1 m distance.

The HRSG is a two-pressure unit with supplementary firing manufactured by Foster Wheeler at its Sosnowiec works in Poland. It uses the exhaust gases of the gas turbine to produce steam of 120 bar/528à‚°C and 7 bar/190à‚°C. The feed water inlet temperature is 73à‚°C and there is a low pressure economizer extraction of 20 t/h at 150-160à‚°C for preheating natural gas.

The HRSG uses natural gas for supplementary firing, and the supplementary firing capacity corresponds to the maximum steam demand of the Burghausen site during winter. The maximum emission values for the whole operating range of the gas turbine and HRSG supplementary firing are 100 mg/Nm2 NOx and 100 mg/Nm3 CO. Actual emissions will be lower than these values.

Steam guaranteed

In the event of a gas turbine trip or boiler malfunction, steam supplies must be secured to ensure the continued operation of the chemical works. Wacker-Chemie is therefore in the process of converting two of the five existing natural gas-fired high pressure boilers to quick-starting reserve boilers. Three steam accumulators will also be installed, each around 30 m in length and 3 m diameter, giving enough time for the five existing natural gas-fired boilers to be started so that production at the chemical works is not interrupted.

High pressure steam from the high pressure steam network is expanded through the existing steam turbines to produce low and medium pressure steam. The steam turbines will continue to generate electricity for the site’s local network as they did prior to the construction of the new sections of the plant.

The electric power is generated at 15 kV and is transformed into 110 kV in a 155 MVA generator transformer.

The power plant is connected to the site’s 110 kV network with a 500 m long underground cable. The existing 110 kV gas insulated indoor switchgear is being extended for connection to the main local grid. In the event of a grid disturbance, the power plant can be operated in island mode, supplying local industrial loads only.

The power plant will be equipped with ABB Utility Automation GmbH’s Procontrol P distributed control system (DCS). This will include the protection system of the HRSG and an interface with GE’s Mark V Speedtronic gas turbine control system. Operators will supervise and control the plant via visual display units and process operator stations, which permit a certain level of intuitive control under computer guidance by the operator.

The main control console consists of two operator work stations, four VDU monitors and operator log and alarm printers, and is located in the control room of the existing cogeneration plant. The DCS cabinets housing the control processor, I/O equipment and terminations are located in the electronic room in the new plant. The DCS has functionally distributed architecture composed of groups of similar processing units linked to a group of intelligent workstations by redundant highways. Each processor is programmed to perform a specific dedicated task for control information and data acquisition applications, and all plant I/O interface is through the termination cabinets.

On track

Fortum Engineering is working under a tight time schedule – 20 months from contract signing to plant commissioning – to complete the project.

While this schedule called for parallel running tasks, the limited space available on site and the layout of the gas turbine and HRSG called for sequentially running activities. Therefore, during the planning period, many of the activities overlapped, and at contract signing, all site activities were started at the same time. Any delays would cost Wacker-Chemie, which is importing additional power from Bayernwerk during construction of the CHP plant.

Site work began in late summer 1999 and Fortum is on track to take delivery of the boiler in mid-2000. It will then start commissioning at the end of 2000 in preparation for commercial operation, which is scheduled for mid-2001.

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