Case Study: Filtration of Scrubber Dust

Background

The Client’s smelter consists of a furnace that produces dust which is very harmful to the environment, so a scrubber is used to capture the dust, which forms a slurry. This slurry is then pumped to a slurry storage facility. However, this handling method creates environmental challenges.

Filtaquip offered a solution to dewater the scrubber slurry into a dry filter cake, which is then returned to the furnace, enabling the valuable metals to be recovered. As these solids have commercial value, the Client’s overall revenue is improved, whilst at the same time significantly reducing environmental impact.

Objectives of the test work

• To assess: filtration behaviour, cake formation time, and final moisture content.
• Assess optimal operating conditions: chamber depth, membrane squeeze and air-blow.

It was essential to obtain a cake as dry as possible, as it will be fed back to the furnace.

Why a filter press?

• High capture efficiency of solids: particles are retained by a filter cloth, producing clear filtrate.
• Low final cake moisture: the use of membrane squeeze plates reduces cake moisture significantly.
• Water recovery and re-use: filtrate can be recycled back into the process, reducing overall water consumption.

Filtration test results

The filter press pilot plant test work assessed three different operating configurations by varying the pre-squeeze chamber depth and the dewatering sequence.

Across all tests, firm, dry-to-the-touch cakes were produced with consistently low final moisture contents with an average of 25% w/w, confirming effective dewatering under all tested conditions, which includes clear filtrate production.

Before & after filtration

Conclusions

• Pilot test work confirmed that a filter press is effective for dewatering the scrubber dust sludge, consistently producing firm, stable cakes with moisture contents of ~25% w/w.
• Membrane squeezing was the primary driver for moisture reduction, with air-blowing providing additional dewatering benefits.
• Variations in chamber depth influenced final cake thickness and cycle times.
• Initial filtrate quality was poor, however, this was easily addressed in the design of a full-scale filter press plant.
• The results provide a reliable technical basis for the selection and design of a full-scale filter press plant, with membrane plates for clarification and dewatering, as well as materials handling.