Recovery of Ammonia from Liquid Digestate for NOx Removal

A new process including ammonia preconcentration via ion exchangers (zeolite) followed by air stripping should solve this problem (ion exchanger-loop-stripping). Through the preconcentration step a separate, NH 4 + -containing stream is produced, wherefore operating respectively investment costs as well as the scale of the following air stripping process are decreased. In the end, a purified process water stream and a concentrated ammoniumsulfate-solution should be generated, latter can be used for NOx-removal at cement works. In laboratory experiments, required contact times, performance and exchange capacities as well as various desorption and pretreatment conditions for natural zeolite (klinoptilolite) are tested. Exchange capacities up to 8 mg NH 4 + /g zeolite can be achieved if the regeneration/pretreatment is performed with concentrated NaCl-solutions. Given these capacities, even under ideal laboratory conditions a high amount of zeolite is necessary for preconcentration. Nevertheless, ion exchanger-loop-stripping can be a practicable process for partial digestate treatment.