These upgrades and new constructions were realised with FLSmidth’s dosing specialist Pfister who has vast experience with dosing all kinds of secondary fuels and has realised a large number of projects. On top of that Pfister could also provide special-design “multifuel” rotor weigh feeders.
As one of the world’s largest manufacturers of building materials, Heidelberg Cement (HC) operates cement plants all over the world. The HC Burglengenfeld cement plant is located close to the global headquarters in Germany. The plant has two production lines and an annual clinker output of 1.1 mill. tonnes. Each of the two preheater kilns has a nominal capacity of 2,000 tato.
Built in 1968 and 1973, respectively, the two kilns were 100% coal fired until 1987 after having been converted from oil to coal in 1981. Due to immensely risen costs for fossil fuels, Burglengenfeld started substituting approximately 8% of the coal with whole tires at the kiln inlet in 1988, which were available virtually for free at that time in this region. Later on waste wood and after that plastics were fed.
Except for tires, all of secondary fuels are used for the main burner today. In the course of the past decades, the plant has gained vast experience in employing different kinds of derived fuels. Up to this day all applications – storage, transportation, weighing and feeding - are running smoothly.
Step-by-step upgrades
A large number of secondary fuel adaptions and configurations have been realised at HC Burglengenfeld. To this day they comprise weighing, dosing and storage:
First upgrade phase:
1997: Construction of a tower silo with Pfister belt weigh feeders
After the positive experiences with feeding secondary fuels to the main burner, a larger primary fuels substitution rate (waste wood instead of coal) was desired. A larger silo was therefore needed to handle an annual consumption of 10,000 t. The new tower silo has a capacity of 1,800 m³. The waste wood was transported, weighed and fed to the kiln with two Pfister belt weigh feeders each of which handled a capacity of 4 t/h.
Even though storage and feeding was functioning smoothly, the burning of wood at the main burner turned out to be challenging: The wood chips had to have a certain grain size in order to avoid residuals in the clinker. This prevented a higher substitution rate. For that reason it was decided to start fuelling RDF (plastics) instead of wood.
Second upgrade phase:
2000: Conversion to firing RDF
In 2000 the same installation was now used for feeding RDF (a mixture of plastics and paper). However the constellation with the belt weigh feeders turned out to be problematic as it was maintenance-intensive due to the high dust content and humidity in the RDF. Thus, in 2002, the belt weigh feeders were substituted by Pfister multi-fuel dosing rotor weigh feeders. which were to come into play later on.
Third upgrade phase:
2002: Installing Pfister multifuel rotor weigh feeders
Substitution of the former belt weigh feeder by state-of-the-art multi-fuel dosing rotor weigh feeders was accomplished with structural modifications: The fundament was adjusted as that a silo and silo despatch could be utilised later on. The rotor weigh feeders are designed as multi-fuel systems. This means that they are capable of dosing a variety of secondary fuels within one system. The dosing capacity of these machines was configured for 6 t/h for each of the two systems.
As compared to formerly fuelled wood chips, RDF has a significantly higher humidity and compression level causing despatch problems. In order to prevent this, the tower silo could only be filled up to a certain level.
Fourth upgrade phase:
2004: Construction of a flat storage for RDF
Due to satisfaction with firing RDF as such but facing the described silo problems, HC Burglengenfeld decided to build a new flat storage for this material. The existing silo was then used as an intermediate storage,which was only filled up to one third. With this solution the compression aspects were solved successfully.
Fifth upgrade phase:
2007: Expansion and retrofitting of the secondary fuels storage
To further increase the coal substitution rate, the secondary fuels storage was retrofitted in 2007. In the meantime, RDF was delivered from nine different suppliers in 20t-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. The intermediary transport was solved with the construction of a new tube conveyor system. To handle this increased capacity two bigger Pfister multi-fuel rotor weigh feeders were installed, each of which handles 12 t/h.
Sixth upgrade phase:
2009: Silo modification for employment of biosolids
To extend the usage of secondary fuels even further, the latest addition to cement plant Burglengenfeld is a modification of the existing tower silo to hold bio solids. 1 t/h of bio solids substitutes 5% primary fuels. Bio fuels are used at the main burner and parallel to RDF. For dosing bio fuels, the existing Pfister rotor weigh feeders, which were formerly employed for wood chips, resp. RDF, were put into service again.
Service technician Klaus Kugler from HC Burglengenfeld (left) and Pfister project engineer Hubert Konrad in front of the two multi-fuel rotor weigh feeders.
For more information on dosing installations and system upgrades for secondary fuels:
Mr Hubert Konrad, Pfister GmbH, Tel. +49 821 794928 364.