High fuel substitution rates at Lappeenranta

The use of coarse sized alternative fuel gives cement producers and the environment great advantages.

At Finnsementti’s plant in Lappeenranta, Finland, 80% of the calciner fuel has been replaced by coarse Refuse Derived Fuel (RDF). The calciner fuel substitution was reached in one step with optimal integration and low CO levels out of the preheater. With this project FLSmidth sets new standards for use of coarse alternative fuel at high calciner fuel substitution rate.

Finland’s largest cement manufacturer, Finnsementti, had its eye on a new type of alternative fuel for its Lappeenranta plant. The plant already operated a new 1,800 tpd FLSmidth ILC low NOx kiln on coal and pet-coke. When Finnsementti in 2008 decided to implement appropriate technology to burn coarse RDF with particle sizes up to 130mm, FLSmidth was chosen as the full solution provider. Now – in 2010 - the plant operates with RDF as the main calciner fuel.

Guaranteed results
Working with a new fuel standard isn’t easy, and coarse RDF is no exception. The large pieces take time to burn, and their size makes it difficult to get a steady flow of fuel to the kiln. Therefore maintaining sustainable and consistent clinker production can be quite a challenge. FLSmidth based its solution on experience from previous alternative fuel projects, theore­tical knowledge and testing at the FLSmidth Dania research centre. Thereby the cement producer benefitted from all of the already available experience and knowledge – and in addition had a committed partner addressing new challenges specifically related to handling coarse alternative fuel. The result was a reliable and efficient solution meeting the ambitious goals set.

FLSmidth had guaranteed Lappeenranta an unprecedented calciner fuel substitution rate of coarse RDF in the calciner. 80 percent of the calciner fuel was to be coarse RDF on a continuous basis – a degree of substitution that had never been achieved before with such coarse fuel.

The complete solution from FLSmidth
When Finnsementti approached FLSmidth, the cement producer wanted to achieve a large degree of alternative fuel firing as quickly as possible. The ideal way to meet this requirement was to have one solution supplier determining the scope of the plant modifications needed, doing the required engineering work and supplying all of the equipment.

The complete solution and supply was based around two key elements – a system for receiving, storing, dosing and feeding alternative fuels, and a bypass system to remove chloride from the pyro process.

The alternative fuel system consists of a truck unloading station integrated with three storage bunkers with separate extraction units. After the extraction from the storage, a chain conveyor installation brings the fuel to the preheater, where accurate dosing and feeding to the calciner optimally integrates the fuel handling installation with the pyro system. The bypass installation includes FLSmidth’s newly developed quench chamber, a conditioning tower and a fabric filter.

The project was coordinated and executed by FLSmidth’s alternative fuels unit, but it was a truly cross-company project, drawing on FLSmidth’s expertise in project execution and key technological competences. FLSmidth automation systems were integrated in the plant’s existing control system – an efficient FLSmidth air pollution control fabric filter for the bypass was selected – and a robust FLSmidth alternative fuel conveying system was supplied.

High substitution rate – with low CO levels
A key indicator of optimal integration of fuel handling with the pyro process is a high substitution rate with low CO levels in the calciner effluent. This was achieved with the coarse RDF quality specified as fuel. The flexible solution is designed to have a high availability allowing the plant to run constantly, thereby maximising alternative fuel usage and avoiding dis­turbances to clinker production.

Solid foundation for selecting the right solution
When selecting the concept for firing alternative fuels, several aspects have to be taken into consideration. At the same time alternative fuel feed, pyro system properties, kiln process aspects, clinker quality and emissions must be evaluated. Despite it being a rather complex equation to find the right solution, FLSmidth has the knowledge, experience and commitment to address all the required aspects. Thereby it is possible to develop a technically sound solution that fulfils the customers’ requirements while maintaining optimum kiln process conditions and emissions.

Experience and R&D creates the right solutions
The key to creating the right solution is experience and a good fundamental understanding of key parameters. FLSmidth’s active research and development effort has for more than a decade been targeted at aspects of cement production related to using alternative fuels and emissions control. Lately these efforts have been intensified by signing an agree- ment with the Technical University of Denmark and the Danish National Advanced Technology Foundation. This joint effort seeks alternative and optimised processes for cement production – with several active projects aimed at increased use of alternative fuel and reducing emissions.

In 2007, Morten Boberg Larsen of FLSmidth’s alternative fuels business unit published his PhD thesis “Alternative Fuels in Cement Production”. This work elucidated the fundamentals governing combustion of different types of alternative fuels under conditions relevant to cement kilns. Further, it clarified how flow phenomena in calciners and in the HOTDISC interacted with particles, at the same time affecting combustion – and thereby many other process aspects.

In 2008, FLSmidth’s patented HOTDISC received the Global Fuels Award for most innovative technology – and the Duoflex G2 was launched. The Duoflex G2 has a patented inclined nozzle feature which benefits the firing of coarse alternative fuel. Both the HOTDISC and the Duoflex G2 feature have been design optimised using Computational Fluid Dynamics simulations and a range of tests performed at FLSmidth’s Dania research centre.

Together with newly developed fuel characterisation methods and procedures in FLSmidth’s Dania laboratory – as well as experience and operating data from many kilns operating on alternative fuel – FLSmidth experts have a strong platform for selecting the right solutions. Pilot scale tests at Dania have been used to establish appropriate fuel feed configurations for alternative fuel to calciners. This has ensured stable operation and effective control of CO emissions when firing different grades of fuel.

As part of FLSmidth’s overall strategic focus on systematically addressing sustainability and energy conservation, FLSmidth established a business unit with focus on alternative fuels back in 2007 to develop and supply complete solutions that enable cement and minerals producers to use up to 100 percent alternative fuel. Since then, several alternative fuels projects have successfully materialised.

For further information, contact Lars Skaarup Jensen.

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