Ongoing upgrade of alternative fuel systems at German cement plant

For more than two decades, Heidelberg Cement’s Burglengenfeld plant in Germany has been firing its two kilns partly with alternative fuels. Pfister, the FLSmidth Group’s dosing specialist, has played an important role in the phased upgrading and retrofitting of the alternative fuel firing systems.

The HC Burglengenfeld cement plant has two production lines and an annual clinker output of 1.1 million tonnes. Each of the two preheater kilns has a nominal capacity of 2,000 tpd.

Built in 1968 and 1973, the two kilns were originally oil fired and later converted to coal in 1981. Due to the rapidly rising cost of fossil fuels, in 1988 HC Burglengenfeld started replacing some 8% of the coal with whole car tyres that were introduced at the kiln inlet. In those days used car tyres were obtainable virtually for free in that part of Germany.

Over the past years, HC Burglengenfeld has gained vast experience in employing different kinds of waste derived fuels. To this date, all the necessary installations – storage, transportation, weighing and feeding – have been running smoothly.

1997: Introducing Pfister belt weigh feeders

After the successful experience of feeding car tyres to the kiln, HC Burglengenfeld decided to use chipped waste wood to replace a higher portion of the coal firing. A 1,800 m3 silo was built to hold the 10,000 tpy of wood chip fuel. To weigh and feed the wood chips to the kiln, HC Burglengenfeld ordered two 4 tph belt weigh feeders from Pfister.

Even though storage and feeding of the new alternative fuel continued to function smoothly, burning the wood chips in the main burner turned out to be challenging: The wood chips need to have a certain grain size to avoid residuals in the clinker. This put a limit to the obtainable fuel substitution rate.

2000: Conversion to RDF

In 2000, RDF (a mixture of plastic and paper) was introduced as alternative fuel instead of wood chips, and the existing fuel handling and feeding system was used for this new fuel. However, it turned out that the high dust content and humidity of the RDF required intensive maintenance of the belt weigh feeders. So it was decided to replace the belt weigh feeders by state-of-the art Pfister multi-fuel dosing rotor weigh feeders.

2002: New Pfister multifuel rotor weigh feeders installed

Installing the new rotor weigh feeders necessitated certain structural modifications: The foundation was modified to enable using a silo and a silo despatch system later on. The rotor weigh feeders are capable of dosing a variety of alternative fuels within one system. Each of the two dosing systems is configured for a capacity of 6 tph. The higher humidity and compression of the RDF, compared to wood chips, made it necessary to keep the filling of the silo below a certain level.

2004: Construction of a flat storage for RDF

HC Burglengenfeld was satisfied with the RDF feeding system, but to overcome the silo limitations they decided to build a new flat storage. The existing silo was then used as an intermediate storage, utilising up to one third of its capacity. This solution successfully solved the issue of a high compression level.

2007: Expansion and retrofitting of the alternative fuels storage

To further increase the coal substitution rate, the alternative fuels storage was retrofitted in 2007. RDF was now being delivered from different suppliers in walking-floor trailers, up to 28 trailers per day, six days a week. To detect debris, a magnetic separator and a disc screen were added to the storage system. A new FLSmidth KOCH Pipe Conveyor system was installed to handle in-plant transportation. Two larger Pfister multi-fuel rotor weigh feeders, each capable of handling 12 tph, were installed to cope with the higher RDF feed rate. After som minor modifications the weigh feeders are now running smoothly.

2009: Silo modification for employment of biosolids

To extend the use of alternative fuels even further, Burglengenfeld has recently modified the existing tower silo to hold bio solids (dried sewage sludge). Bio fuels are used at the main burner, parallel to RDF. The existing Pfister rotor weigh feeders, which were originally installed for wood chips, and later RDF, have reentered service for the dosing of bio fuels.

Complete alternative fuel solutions from FLSmidth

FLSmidth supplies complete alternative fuel solutions to the cement and minerals industries, integrating experience from hundreds of alternative fuel projects – such as the HC Burglengenfeld plant. FLSmidth Alternative Fuels was established in 2007 to integrate the technology and experience accumulated throughout the FLSmidth Group into reliable and guaranteed solutions.

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