Improved RDF Quality and Combustion Due to the Drum Drier, Chelm, Poland

Jarosław Sawecki Cemex Poland, Chełm Cement Plant

CEMEX Poland is one of the leading producers of cement, concrete, aggregates and construction chemicals in Poland. It has a large production base, which comprises two cement plants with a total production capacity of 3.1 million tons of cement, a grinding plant in Gdynia, 10 aggregates quarries and 40 concrete plants located throughout Poland.

Chelm cement plant is the CEMEX’s leading plant in Poland. The clinker kiln at Chelm works with the semidry method. The plant has specialized in the production of pure Portland cement, including HSR/NA type used in large structural projects, and cement with fly ash addition. CEMEX has pursued a series of projects at Chelm in recent years that have affected the improvement and efficiency of its processes and that are related to the usage of alternative fuels. The most important ones include the construction of a Refuse Derived Fuel (RDF) dryer (Figure 1).

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Figure 1: The RDF dryer, Chełm Plant

The use of alternative fuels at Chelm Cement Plant

Chelm cement plant is the leader in Poland in terms of substituting coal with alternative fuels. The level of substitution exceeds 80 %. As part of fuel diversification, a variety of alternative fuels, such as shredded tires, dry stabilized sewage sludge, meat and bone meal, secondary liquid fuels and biomass. However, the main alternative fuel is that of segregated and shredded waste of municipal and, to a small extent, industrial origin (RDF).

Recent years have seen intensive development of the alternative fuel market in Poland, contributed to by the changing regulations following the requirements of the European Union

Figure 2: A chart of the RDF dryer

but also by the cement plants, which were the first ones to reach for this type of fuel. In the wake of the waste market growth, increasing volumes of alternative fuels are produced. This does not have a positive effect on fuel quality. The quantity of industrial waste that RDF can be produced of is small. As a result, most of the alternative fuel is made of wet municipal waste, which translates into an increased water content of RDF and a reduced calorific value as well as increased specific heat consumption to make clinker. The average water content of RDF reaches 30 %.

In the long term, the use of RDF with such low quality parameters on such a large scale as at Chelm Cement Plant could not be maintained. Therefore, CEMEX decided in 2011 to build a dryer for fuel of municipal origin in order to reduce the water content and increase the calorific value. The construction of the dryer was completed at the end of 2012.

RDF drum dryer

A drum dryer with a capacity of 40 tph of RDF and capable of evaporating up to 8 tph of water was used. The dryer uses excess air from the clinker cooler filter at a temperature of 260 °C and cleaned hot air from the cooler cold section for very wet RDF (figure 2).

CALC

AINER

C1

C2

C3

Disk and magnetic separator RDF dryer

Alternative fuel store including wet

RDF

Activated carbon bed for odor

reduction

Dry RDF feeder to kiln

Cleaned air with steam

Cleaned hot air from cooler

filter

260°C

50 - 60°CBag filter

Dry RDF feeder to calciner

The dryer works on-line with the kiln. The dried fuel from the dryer is sent directly to the feeders of the calciner and the main burner. The possibility of storing the dry RDF has been excluded due to fire hazards.

Downstream of the dryer bag filter there is an activated carbon bed for odor reduction. After this treatment, the exhaust air leaves the dryer system.

The benefits from the dryer’s operation are more than satisfactory. The RDF water content is reduced to 10-15 % of total content. At the same, a significant decrease, close to 10%, in specific heat consumption to make clinker has been observed.

The dryer fire protection

When planning the construction of the dryer, the fire hazards as posed by the direct contact between RDF and hot air from the cooler were considered. Therefore, an automatic fire detection and extinguishing system was constructed at the same time as the dryer, The fire protection system covers all the alternative fuel stores, conveyors, feeders and the dryer. The system comprises a water tank with a capacity of 1,000 m³, a pumping station with independent power supply, water sprinklers and an extensive system of fire, temperature, smoke and spark detectors inside the dryer.