Gas Management Solutions

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Oxygenation/Degassing Equipment 

VATN has un-matched capabilities in the design, development,  testing, modeling and application of oxygenation/degassing equipment used in aquaculture. We have  demonstrated that reactor performance is related to a number of site-specific conditions including both  inlet dissolved oxygen and N2 concentrations, temperature, local BP, alpha, operating pressures, gas feed  rates, gas composition as well as the gas liquid interfacial areas and linked mass transfer coefficients that  are established within a specific reactor type. VATN’s proprietary software and modeling approach is used  to identify reactor operating conditions that act to minimize capital and variable costs while achieving  target levels of dissolved gases and total gas pressures in the reactors discharge. Our extensive  experience in this area includes the development/patenting (1989) of the multi-stage low head oxygenator  (LHO) which has been applied successfully at hundreds of RAS and raceway sites within and outside of  the United States. LHO’s have no moving parts and have been designed to operate with hydraulic  gradients as low as 9 inches. VATN staff has also evaluated/modeled/applied, successfully, the following reactor types (1), spray towers (2), hooded surface agitators (3), packed columns (4), U-tubes and (5),  vacuum degassers. The latter developed by Barnaby in the early 90’s is applied widely given a unique  water jet exhauster component that maintains vacuum and gas venting at target rates despite varying  bulk water -feed rates. His follow-on side-stream designs operate at elevated vacuum levels providing for  an over treated product that with blending with bulk flows reduces equipment scale by about 70%. 

CO2 Control Methods 

VATN staff have extensive experience in CO2 stripping operations  including theory of removal, new equipment designs and evaluations. This includes the use of  forced air packed beds, spray nozzle reactors, surface agitators, and oxygen absorption  equipment modified for concurrent hydroxide base scrubbing of CO2. Scrubber use provides  savings in RAS oxygenation costs given linked reductions in dissolved N2 concentrations.  

VATN Gas Transfer Products Under Development 

VATN In-house research is currently focused on the development of a new class of reactors for  (1) CO2 stripping and (2), side-stream oxygenation or side stream vacuum degassing.  Regarding CO2 stripping, the reactors that have evolved eliminate plastic packing use, operate  efficiently with just 1/3 the footprint and about 40% of the height required by conventional  equipment. Further, air flow for stripping is induced without blower assist over the G/L range of  about 4.5 to 6.0. Higher G/L ratio’s can be accommodated with very low blower back pressure  requirements. Regarding item (2), side-stream treatment, a new very low-profile reactor has  been developed that reduces reactor volume requirements by about 50% while maintaining  packing free pressure or vacuum operation. Volume reductions are made possible by using a new method for controlling bubble carryover. This low-profile reactor is suited for O2, O3 and  CO2 absorption as well as N2 striping. Over treatment of the side-stream flow with blending  reduces dramatically reactor flow rate requirements. 

Vacuum/Degas Column

 Vacuum Degassing has been greatly improved by Barnaby Watten with the computer model he developed to predict performance under each unique application’s water chemistry and other physical plant characteristics. In addition, he simplified the vacuum degasser process by employing a eductor to remove the off gas from the column.

The configuration shown above typically operates at a vacuum level of 3 to 5 feet of water with oxygen addition as per proprietary software predictions based on site operating conditions.  Watten has developed and tested alternative packed bed equipment operating at 13-15 feet of vacuum allowing for side stream treatment with blending given the reactor's ability to reduce Delta P by 200 -300 mmHg.  Typically just 25 - 30% of the bulk flow is needed to be routed through the treatment unit thus reducing equipment scale (costs).  Performance has been automated so as to provide target levels of gas removal at those sites with varying inlet conditions.  Equipment of this type has been designed to be portable (Pennsylvania Fish Commission) allowing for seasonal changes in degassing needs/sites.

Packed Columns