PROCESS AND APPARATUS FOR TREATING AMMONIA-CONTAINING WASTE WATER

摘要

A process for treating an ammonia-containing wastewater, which comprises the steps of contacting an ammonia-containing wastewater A with steam C (carrier gas) in a stripping column (7) to transfer NH3 to a gas phase from the ammonia-containing wastewater A; heating the resultant gas containing NH3 in a preheater (11)and then contacting the gas with a catalyst layer (13) to decompose NH3 into nitrogen and water; measuring the NOx (or N2O) content of the gas generated in the above decomposition step; and adjusting, based on the measured values of the NOx (or N2O) content, one or more of (a) the feed rate of the ammonia-containing wastewater, (b) the NH3 content of the ammonia-containing wastewater and (c) the flow rate of the gas containing NH3 to be contacted with the catalyst layer [when the N2O content is measured, one or more of the flow rate of the carrier gas, the flow rate of an added gas such as air, and the flow rate of the part of the gas generated in the above decomposition step to be recycled to the catalyst layer]. The process is advantageous in that an extremely small amount of hazardous substances such as NOx is discharged even at the start of an apparatus for the process or when the NH3 content of a gas is considerably changed.