The LoTOxTM process uses ozone to oxidize insoluble NOx to higher oxides that are then captured in a wet or semi-dry FGD process. The low temperature process allows stable and constant NOx control regardless of load or concentration.
AECOM Process Technologies is the licensee of Linde LLC's patented LoTOx process for power industry applications. LoTOx involves the injection of ozone into low-temperature flue gas (optimally ≤300°F) to oxidize NO and NO2 to N2O5, which is highly soluble. The flue gas moisture and the liquid in the downstream wet or semi-dry FGD process easily and quickly converts N2O5 to nitric acid (HNO3). The conversion of the N2O5 into the aqueous phase is rapid and irreversible, allowing for near-complete removal of NOx.
In LoTOx applications, the amount of ozone production capacity is determined by the amount of NOx present in the flue gas and the targeted removal efficiency. During operation, the ozone is generated “on demand” based on the incoming NOx level, so that no onsite ozone storage is required – ozone is produced by passing oxygen through a conventional ozone generator.
There are different ozone delivery models available, depending on the client’s preference. The utility may elect to procure the equipment necessary for onsite oxygen and ozone generation. Alternatively, Linde provides an “over-the-fence” ozone supply model, in which they own and operate a plant that purchases power from the utility and supplies ozone for the LoTOx process on a contract basis. These contracts can be tailored to a particular need and significantly reduce the capital investment.
When used in combination with combustion tuning or SNCR, LoTOx provides a cost-effective alternative for achieving emissions comparable to SCR. This approach ha a number of advantages over SCR, including:
- Higher potential NOx removal (>90%)
- Lower capital cost
- No catalyst poisoning
- No catalyst deactivation or periodic outages for replacment
- No minimum operating temperature restriction
- No air heater fouling
- Minimal increase in pressure drop
- Shorter outage required for implementation