Process for separating ammonia and acid gases from waste waters containing fixed ammonia salts

摘要

A water purification process is described for the removal of ammonia and optionally one or more acid gases from waste waters such as coke- plant or coal conversion waste waters. The process involves adding lime to these waste waters in amounts sufficient to react with fixed ammonia salts present in the waste water and to enable substantial amounts of the ammonia to be evolved upon distillation, adding a threshold amount of a scale inhibitor compound chosen from the class of certain organic phosphonates and subjecting the thus treated waste water to distillation to remove substantial amounts of the ammonia and acid gases present from the waste water. Preferably, this process is achieved by two separate and successive distillations. In this preferred process, the first distillation substantially reduces the amount of the acid gases and free ammonia and is conducted at a pH of more than 9. In the second distillation, the amount of fixed ammonia is substantially reduced. To conserve energy, the stripping vapors from the second distillation are reused as stripping vapors for the first distillation.