Hydraulic Mass Transfer Reactor
HMTR is a hydraulic reactor for dissolving air and process gases in water and other liquids. It uses the energy of liquid flow and water-column pressure to create effective gas–liquid contact. Depending on the configuration and project requirements, undissolved gas can be recovered and reused, carried into the liquid as microbubbles, or made available as compressed air.
HMTR is Koohub’s proprietary technology, with an independent architecture and development history. Its mechanism differs from ejectors, diffusers and conventional microbubble and nanobubble generators: gas–liquid contact, dissolution and separation of remaining gas are managed inside the device.
The device operates through the head difference between inlet and outlet, supplied by pumping or natural elevation. The 1 m minimum applies to suitable passive conditions. Typical head of 2.5–3 m applies to surface discharge or injection up to 7.5 m deep at a gas-to-water volume ratio around 0.3. Deeper injection may require more head. Final head depends on flow and losses and is not the same as total device height.
The inlet header guides the liquid into a less turbulent, directed flow. A relative pressure reduction at the gas inlet draws gas into the device.
The gas–water mixture travels downward. Hydrostatic pressure and intensive bubble contact promote dissolution; water can become supersaturated relative to external ambient conditions.
Depending on configuration, excess gas is carried as microbubbles through zone 6 or separated from water as compressed gas in zone 4.
Under suitable conditions without strong gas or liquid reactions, the outlet generally lies in the saturation range appropriate to the conditions. Actual concentration depends on temperature, pressure, gas composition and liquid properties. The calculator provides a theoretical equilibrium estimate.
Two manufactured variants with different connection arrangements: deep-tank discharge and external installation. The plate identifies water and air connections, compressed-air outlets, sampling ports and header connections.
The device core has no moving parts. Its body is designed for a minimum 25-year life under specified environmental conditions. Composite construction simplifies handling and installation.
Pressurised contact and intensive bubble interaction allows the liquid to approach local saturation. A large tank is not needed solely for contact, though dilution or process residence time may require volume. Deep discharge can preserve a higher equilibrium concentration.
Gas remaining after dissolution can be separated, reinjected or reused, or carried with the flow as microbubbles at a deep outlet.
Passive or pumped, inside or outside the tank: all configurations can be installed without auxiliary support or protective structures.
The HMTR core has no moving parts and requires no periodic servicing. Maintenance costs concern the pumping unit and any installed measurement or monitoring equipment.
In purpose-designed deep tanks, recovered gas is reused for dilution and microbubble injection with the aim of reducing whole-system energy demand.
Reduced depth and hydrostatic pressure limit dissolution benefits and microbubble contact time. Shallow or external arrangements approach surface-pressure equilibrium, reducing the benefit of pressurised dissolution.
For example, ozone produced by an air-fed generator has a lower partial pressure and may require more water flow for comparable mass transfer. Increased pumping flow can reduce the system’s energy advantage.
HMTR is at least 10 m tall. Where excavation or a deep tank is unavailable, pumping costs may increase and reduce the system’s energy advantage. Device height is not the same as pump head.
Initial cost can exceed that of some conventional gas-injection equipment. Small installations and traditional aquaculture require an economic assessment of flow, available energy and whole-life operating cost.
In every arrangement, zone 1 remains above the water surface. Surface discharge uses zone 2, while deep discharge follows zone 3. Zones 4 to 6 remain within the enclosed core.
Using elevation difference to compress air
Can be designed for large flows according to available head, site conditions and structure: diverted river water can gain dissolved oxygen while producing compressed air. A suitable distribution line can supply lake and water-body management several kilometres away. This arrangement can be assessed for large-scale compression and energy conversion, following the approach of historical hydraulic compressors.
Compressed air for pneumatic equipment
This configuration can be assessed for pneumatic equipment and deep-mine applications. Pressure depends on effective water-column height: approximately 10 m of water produces a 1 bar pressure difference. Direct water contact removes compression heat and brings the process closer to isothermal compression. Cooler water reduces the water vapour carried in the outlet air. The device core is oil-free.
Reusing air for circulation
After gas dissolution, recovered air supplies an airlift or pneumatic equipment for dilution, circulation and tank mixing. A principal intended application is oxygen transfer from air in biological wastewater treatment alongside flow management.
Prioritising effective gas transfer
Unused gas is separated and recirculated to the injection path to minimise losses. Corrosive, hazardous or valuable process gases require a designed closed circuit and gas-compatible components.
Theoretical dissolved-oxygen equilibrium
At the water surface
| Water depth | Concentration, mg/L |
|---|---|
| 0 m | 7.7 |
| 1 m | 8.5 |
| 2 m | 9.3 |
| 3 m | 10.0 |
| 5 m | 11.6 |
| 8 m | 13.9 |
| 10 m | 15.5 |
Instantaneous gas consumption, gas–liquid reactions and salinity are excluded. This is a theoretical equilibrium reference; actual output depends on gas and liquid conditions and system performance.