Feb 2019 – Feb 2020
South Island

Odour extraction and scrubber system installation

Mainstream Engineering Consultants was tasked with reducing the odour to an acceptable level for a manufacturing company.

This project involved the design and installation of an odour extraction and scrubber system for a manufacturing company. The customer had issues with odour levels at their site boundary caused by sections of their manufacturing process being open to the atmosphere. Mainstream Engineering Consultants (MEL) was tasked with reducing the odour to an acceptable level by extracting the odour at the source and processing it through a second-hand scrubber system that had been purchased from the USA.

MEL designed and installed the fume extraction and ducting system from the discharge points to the intended scrubber location. This work was done prior to the scrubber unit arriving on site.

The second-hand scrubber equipment arrived without manuals, assembly drawings or P&ID’s. The equipment had sitting outside, unused for several years and was then roughly dismantled and the ducting cut up for transportation. No photos of the complete unit were provided.

The scrubber layout was reviewed and it was found that a simplified arrangement could be used to achieve the customer’s requirements.  The scrubber units were refurbished and modified to meet the proposed arrangement, pumps and the extraction fan were reconditioned and new sensors sourced. The FRP ducting provided was reconfigured to suit the new scrubber arrangement.

The installed system is a two-stage process passing the extracted air through 2 vertical scrubbers prior to the discharge fan and stack.  Stage 1 uses Sodium Hypochlorite (NaOCl) and stage 2 Sodium Hydroxide (NaOH). Each recirculation system pumps from a basin in the bottom of the scrubber through a spray nozzle and down through the scrubber packing.  Each scrubber has a water make-up and chemical dosing circuit regulated by pH, Conductivity and ORP sensors.

While commissioning scrubber system over the colder winter period it was found that most odours could be reduced to an acceptable level using only water. However during warmer months or when processing specific products, the addition of chemicals was necessary.

The second-hand system was successfully refurbished, reconfigured and integrated into an existing site with minimum disruption and has delivered the required odour reduction with less chemical consumption than originally planned.