Ejectors for the introduction of gaseous oxygen are similar in construction form and mode of operation to apparatus supplied with compressed air. They are installed principally within the aeration tank and are operated by dryor wet-installed centrifugal pumps. The difference to the ejectors supplied with compressed air is that the gaseous oxygen is injected between the pressure side of the pump and the entrance to the ejector by a nozzle system in the connecting pipeline. So intermixing takes place at the highest pressure level, even before entry into the ejector.
The intermixing is intensified during perfusion of the ejector – whereby a considerable portion of the gas is dissolved already in the waste water. In the ejector, static pressure energy is converted into kinetic energy so that the two-phase mixture enters the aeration tank with high turbulence.
Fields of application
Apart for oxygen introduction, ejectors can also be designed for the complete intermixing of an aeration tank – without gas supply – so that their utilisation facilitates an intermittent nitrification/de-nitrification – without additional agitators. The action of flow over the tank floor by the ejectors prevents deposits. The oxygen transfer system is optimised by means of individual adaption of the maintenance-free ejectors to the respective operating conditions, power consumption and numbers of necessary pumps are reduced.
Ejectors are applied
- for peak load coverage
- for basic load coverage
- for introduction of gaseous oxygen occurring as off-gas in ozone plants
Layout
Apart from multi-path ejectors, single-path jet ejectors find application as well. Installation can take place on the aeration tank floor as well as through the tank wall. All ejectors are manufactured in chrome-nickel steel whereby the material quality depends on the respective waste water composition.Furthermore, their compact construction form permits a later installation on a base frame as a mobile oxygen transfer system.Reference projects
Aeration tank at a paper mill
Description
Oxygen transfer system in one of the two 3400 m³ sized aeration tanks belonging to the Lang paper mill in Ettringen. Eight six-path ejectors each are supplied with oxygen generated as off-gas in a downstream ozone plant.Aeration tank at a refinery
Aeration tank at a food maker
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