Redwood technology wet air scrubber is a new generation of foam wet scrubbers which is able to use highly mineralized liquid with small impurities. The stable operation of the wet air scrubber even under harsh conditions has made it one of the best air scrubbing solutions available on the market. The wet air scrubber is able to work for extended periods of time using the recirculating cleaning liquid, therefore decreasing the liquid consumption up to 10 times compared to other foam wet scrubbers.

The cleaning liquid used in the scrubber does not have to undergo special treatments as small impurities, such as small rocks and sand, do not interfere with the wet air scrubber operation. It is possible to utilize previously used cleaning liquid thus achieving considerable savings.

The core technology behind the wet air scrubber is the self-cleaning grating made out of plastic (polypropylene) or stainless steel (for high-temperature applications >140°C). The grating doesn’t fray and prevents buildup even when highly mineralized liquid is used (up to 15.6 lb/cf).

The grating itself is composed of standard square-shaped elements. The size of the grating can be changed depending on the required system capacity. Structurally, the grating consists of divergent holes formed by vanes to provide a turbulent stabilization of the foam layer without external stabilizers. The wet air scrubber capacity varies from 600 cfm to 150,000 cfm. Several grating layers can be stacked above one another to achieve the required efficiency.

Redwood technology wet air scrubber is an excellent solution for the gold mining industry as an HCN scrubbing system. We have performed several on-site tests of the wet air scrubber at a gold mining facility to estimate the treatment quality. The achieved treatment quality has exceeded the process requirements and fully satisfied the needs of the client.

HCN concentration1 mg/m3Over 100 mg/m3
Treatment quality 95%97%
Neutralizing reagentNaOH Ca(OH)2 lime milk
Outlet HCN concentrationFrom 0.015 mg/m3 to 0.03 mg/m3 (depending on the inlet HCN concentration)From 6.4 mg/m3 to 10.6 mg/m3 (depending on the inlet HCN concentration)

HCN treatment quality dependence on the circulating NaOH solution pH. The treatment quality shows strong dependence on the circulating liquid pH.

HCN outlet concentration on the inlet concentration dependence with 5% Ca(OH)2 lime milk treatment.

For an effective HCN removal, a neutralizing agent should be mixed in with water. At high HCN concentrations (> 100 mg/m3) and the required treatment quality of 95%, a recommended reagent is 5% Ca(OH)2 lime milk, whereas at low HCN concentrations (< 10 mg/m3) a high pH solution, like NaOH should be used to achieve the treatment quality of 99.9%.