Von Roll flue gas scrubbers make your plant compliant with emission limits because all pollutants generated in combustion are captured by a specially designed multistage process. Every stage is optimized for a particular pollutant. Heavy metals and aerosols, for example, are removed without any need to be concerned about load fluctuations. Stoichiometric metering of reagents results in marginal residue volumes.First stage : From dust collection to quenching.
In the quench stage, scrub water is sprayed into the hot flue gases. As it vaporizes, it cools the gas stream to about 70°C (160°F). The scrub water washes coarse particulate matter out of the flue gases. This stage also handles the absorption of most HCL (hydrochloric acid) and mercury. The scrub water circulates in a closed cycle with low water consumption. The cooled and preconditioned flue gases next go to the scrub tower. Second stage : High-surface-area packing.
The gases pass through a packed bed stage in countercurrent to the scrub water, which cools them to about 60°C (140°F). The Von Roll packing elements offer a large specific surface area, ensuring fast, efficient mass transfer between flue gas and scrub water. Remaining pollutants, such as HCL and HF, are absorbed with good efficiency here, while heavy metal vapors condense to aerosols. If very high sulfur dioxide (SO2) removal efficiencies are needed, caustic soda is added to this stage to elevate the pH. Third stage : Ring jet multiventuri system.
Aerosols and submicron dust particles generated in the cooling and absorption stage are collected in the third stage. The flue gases pass a manifold of ring jets which are part of a multiple venturi configuration that subdivides the gas stream in order to boost separation efficiency. Controlled water supply makes it possible to hold a constant pressure drop and thus a constant removal efficiency over a wide range of loads. The ring jet also offers high efficiency in collecting gaseous contaminants such as sulfur dioxide. Here, caustic soda is used for pH control.
After passing through another demister, the flue gases - now free of all pollutants in gas, particulate and aerosol forms - are routed to the stack or to a downstream process stage, for example, the carbon entrainment process. The scrubber stages can be combined in any way to achieve an optimal solution for individual requirements. Von Roll spray dryer eliminates wastewater.
In situations where no wastewater is acceptable, the scrub water discharged from the scrubber is simply neutralized. The resulting salt solution, laden with particulates and heavy metals, is pumped into the spray dryer and sprayed into the hot flue gases. The water component evaporates completely while cooling the gases to the desired temperature. Only the solid residues remain behind.
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