°Celsius has designed and produced a number of screw heat exchangers for the `Van Bentum Recycling Centrale` in Rotterdam to cool tar asphalt (TAG) in a continuous process from 600°C to 50°C. The `Van Bentum Recycling Centrale`, with nine plants in the Netherlands, is market leader in the field of recycling mineral construction and demolition waste and also a supplier of aggregates to the civil engineering, road construction and hydraulic engineering industry. The Dutch authorities want to remove tar asphalt from `the chain` once and for all, so since 2001, the re-use of uncleaned TAG is no longer permissible. All tar asphalt removed during reconstruction must be thermally cleaned. In theory cleaning tar asphalt is simple. TAG consists of sand, gravel and a pollutant binder, namely tar. The tar is removed from the asphalt by heating at a high temperature. The pollutant gases released are also cleaned. This leaves clean sand, gravel and filler. The thermal cleaning plant on the site in Rotterdam has a cleaning capacity of approximately 750.000 tons per year. Process description A number of screw heat exchangers form part of this cleaning process. In view of the heavy industrial application and the abrasive nature of the product, °Celsius has used highly wear-resistant materials in the engineering and production. This guarantees a long service life. With a capacity of 4000 kg/hour through one of the screw heat exchangers for example the filtered material from the after burner is cooled in a continuous process from 600°C to 50°C to 60°C. Another example is the single screw heat exchanger for cooling mineral filtered material with a temperature of 350°C, with a capacity of 5000 kg/hour this is cooled to 80°C. All the screw heat exchangers use the existing cooling water system of approx. 30°C.

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