A dual purpose, low flow scrubber is needed for a facility that extracts lithium from geothermal brine. The scrubber treats a chlorine (Cl2) rich stream from a chlor-alkali process and HCl from a caustic storage tank vent line. The scrubber is installed outdoors in a desert environment with significant seismic and wind requirements. Temperatures reach 113oF in the summer. The furthest emission source is 70 ft away. The scrubber will use and induced draft (ID) fan to pull exhaust gas from the upstream sources. The fan must be corrosion resistant and capable of pulling a low flow rate draft across the pressure drop of the inlet ductwork and scrubber.
The customer selected an Envitech packed bed scrubber. The scope of supply includes a fiber reinforced plastic (FRP) packed bed absorber, instruments, control system with HMI display, pre-assembled recirculation pump, piping, valves, and fittings, interconnect duct, and an FRP ID fan. Instruments are pre-mounted in the piping and pre-wired to the control system.
The Cl2 scrubbing reaction is exothermic. A dilution air damper on the HCl tank vent line dilutes pollutant concentrations to a range that keeps the scrubber from getting too hot. It also provides enough flow for the minimum cross-sectional area needed to house the packing. The packed bed vessel and ductwork are self-supporting for wind and seismic. A high-performance mesh pad at the top of the scrubber removes acid aerosol droplets formed in the scrubber. The recirculation liquid operates at a high pH. The scrubber needs to achieve 99.98% removal for the worst-case loading conditions. The scrubber height and mesh pad work together to achieve performance guarantees.
The scrubber will be delivered in the first quarter of 2022 and is designed to meet the following design conditions:
- Inlet flow rate – 400 acfm
- Inlet temperature – Ambient
- Max HCl and Cl2 discharge limit < 5 ppmv
- Removal efficiency > 99.98%