Process Description
Waste gases from tobacco processing or odour waste chemical can be cleaned in multi ventury crossflow scrubber with a high degree of efficiency. The best result are achieved with a multi-stage crossflow system such scrubber offer high efficiency combined with a low space demand.

The air to be cleaned is led into the first washing stage containing packing elements which are easily to clean. In this pre scrubbing stage dust and solid particles are removed. The packing elements are continuously rinsed with washing water. Generously dimensioned circulating pumps guarantee are evenly distributed and sufficient wetting of the packing.

After that the air is led into the second scrubbing stage which is equipped with special packing material. This packing are continuously rinsed from top in that way that the washing liquid is dripping through the packings into the built in washing water pumps. This arrangement provide the lowest pressure drop as well as low running cost.

Fresh water will be filled into the second stage. Through an over flow the washing water will first be used in the last and then in the first scrubbing stage in order to reduce the water consumption. Each washing stage has its own droplet separator. This to prevent washing liquid droplet to be transferred from one stage to the next. Salination is avoided by conductivity control and automatic blow down.

Expecting higher NH3 emissions the second stage is equipped with a chemical dosing station. By adding sulphuric acid to the washing liquid the NH3 absorption can be increased.

The waste gases having an original dew point temperature of >60º C high odour emissions can be expected because of the relative high vapour pressure of the odour components. Therefore the washing liquid from the second stage will be cooled down by plate heat exchanger for decreasing the waste gas temperature to 40 - 45° C. Here the heat is transferred to the water of secondary circuit. This is helpful for increasing the removal efficiency of odorous pollutants.

The secondary circuit is driven by centrifugal pump with sufficient pressure to over pressure the pressure loss of the system. At the working tower the absorbed energy is transferred to the atmosphere by evaporation of the cooling water. Hereby the cooling water is fused over an air cooled packing. Evaporation losses are replaced automatically.