Kymin Voima Oy’s Kuusankoski cogeneration plant, completed in 2002, can be regarded as the very model of a modern European power station. Located on the Kuusanniemi industrial estate, the biofuelled plant (running principally on forest industry wastes) produces electricity, process steam and heating for the nearby Kymi paper mill, as well as heat and electricity for a local energy company. Installed capacity is approximately 80 MW of electricity, 125 MW of process steam and 60 MW of district heat.
The new plant has a Kvaerner supplied 269 MW bubbling fluidised bed boiler, while the steam turbine synchronised to the grid in June 2002 was manufactured by Alstom (and was the biggest machine to be produced by that company’s Brno facility). The dual casing turbine, directly coupled to a 2-pole generator, is equipped with an internally controlled extraction connected to the 5 bar steam network of the paper mill and an externally controlled extraction connected to its 15 bar network; steam can be supplied simultaneously to both networks depending on need. Steam is also extracted for the heating of feed water, for two high-pressure preheaters, three low-pressure preheaters and a deaerator. The turbine also generates district heat. Maximum power output of the steam turbine is 85 MW at 3000 rpm, inlet steam 114 bar / 541°C, with maximum flow of internally controlled steam extraction 45t/h at 5 bar and back pressure in the range 0.3- 0.9 bar.
The mill’s pulp and paper processes had previously relied on two 40 year old boilers for their steam supply. According to the plant management, the power generation technology is now on par with that used for the mill’s pulp and paper production.
Process automation
The plant’s process automation system covers all operations from fuel handling to steam distribution. The system consists of four operator workstations, eight process stations with 7000 I/Os and connections to boiler protection, turbine controls and electricity distribution.
A comprehensive package of metsoDNA information management applications extends from condition and production monitoring to performance and environmental monitoring, and includes specialised tools for cost calculations and fuel management, including a calculation program that allocates costs and payments.
The plant is a joint effort between UPM-Kymmene’s Kymi paper mill, power company Pohjolan Voima Oy (in which UPM-Kymmene is a shareholder) and the local energy company Kouvolan Seudun Sähkö Oy. The sharing of costs and profits between these partners, who each have a share of Kymin Voima Oy (the entity that owns and operates the power plant) is a complicated business. So the metsoDNA based cost calculation application is tailored to divide the costs and profits automatically in accordance with the real production and consumption figures.
“The system is based on the idea that each owner pays for what that owner actually gets,” says Lasse Elojärvi, Chief Engineer at Kymin Voima. “This solution meets our extremely detailed cost allocation requirements. For instance, it calculates the distribution of produced electricity between the partners in proportion to their steam consumption, based on the amount of extracted steam flows. In addition, another special application predicts the electricity supplied to the partners based on calculations from their heat demands,” Elojärvi explains.
“It would be almost impossible to carry out such calculations manually and would also require too many staff. Now, the cost calculation application allocates the shares automatically, and also provides the partners with real-time information about the facts behind this allocation.”
“The only difficulty we’re having is to make people believe in the system. It’s not that easy to accept that you’re being paid and invoiced by a program!”
Kymi annually uses 2.3 million cubic meters of wood for its pulping process, and bark is the major fuel for the power generation. Another biofuel is sludge. Biofuels make up 75 per cent of the fuels, the rest is peat and natural gas (used for start-ups and as reserve fuel).
As fuels amount to a considerable part of the operating costs at today’s power plants, Kymin Voima wanted to pay special attention to this factor. Their customised fuel management application registers the fuels coming from outside suppliers and Kymi, monitors fuel quality based on laboratory analysis, and then a special heat power compensator tool defines the real heat value of the delivered fuel. “As a result, our fuel costs are directly proportional to energy production,” Elojärvi points out. “The advanced reporting system provides both plant owners and fuel suppliers with accurate information about fuel amounts, energy contents and costs.”
The information system is also crucial in enabling the plant to fulfil and improve on exacting environmental requirements. The plant’s emission monitoring system reports both absolute and specific emissions automatically in the required units and helps to ensure that flue gas limits are not exceeded.
Sharing information
A comprehensive ePower plant management solution provides important plant reports to all partners through the Internet. This way, the owners can share the same information flexibly and at the same time without investing in expensive fixed networks still maintaining modern security requirements. The partners can also follow real-time information from certain displays through their office computers.
“ePower opens an entirely new dimension of credibility for our shareholders,” Kerkelä says. “The energy company, Kouvolan Seudun Sähkö Oy, for instance, is able to access on-line information about heat and electricity production. They can also further analyse this information and supply facts to their partners and customers.”
“Open communication and information that is easily available to all partners is the most essential requirement in creating trust between the owners – and thus is a cornerstone for our profitable operation. There is no reason to hide information – especially when everything runs smoothly,” he notes.
Optimised solutions of the kind being pursued at the Kymin Voima plant are essential for success in today’s cogeneration plants. Effective optimisation is in turn based on versatile and comprehensive information management and active operations monitoring. Automation and information applications as exemplified by those installed at Kymin Voima offer various tools that can reveal the ‘weak links in the chain’ and help improve process efficiency.
