Water circuit for the wet dedusting system of a cupola furnace

In this basic layout, the plant experienced some operational problems, due to salt accumulation and the low final water quality. An extension was made to the plant, with the aims of increasing the settling velocity, by the use of other flocculants reducing the pollutant content in the scrubbing medium improving sludge dewatering 

For this purpose, a chamber filter press with a voliune of 2 m and a sludge collection tank (30 m in volume) with an agitator were installed. The sludge was passed from the scraper conveyor directly into the storage tank and preconditioned with lime. 

During the trial phase, which lasted several months, it was found that approximately 25 kg of lime per batch were needed to achieve the best result in terms of dewatering and heavy metal removal. The average dry matter content was 70%. Analysis of the filtrate for heavy metals showed values in the range of detection limits. However, the relatively high sulphate concentrations of about 1 g/1 posed a problem for re-use of the filtrate in the scrubbing cycle. 

The filtrate is passed via a turbidity meter into a storage tank in which pH and conductivity are monitored. There are three possibilities for where it goes from there via an equalising tank to slag granulation or dry dust humidification back to the sludge silo (if the turbidity limit is exceeded) to drain (emergency measure only). 

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Figure 4.19 Water circuit for the wet dedusting system of a cupola furnace DSSS double shell sinking separator FA floccniant, M motor [195, UBA, 2003]...

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