Large Volume Inorganic Chemicals - Ammonia ... - ammk-rks.net

Chapter 99.4.4 Steam purification and treatment/recycling of condensatesDescriptionWhatever the process, some water is fed along with HNO 3 and, as only a part of this water canend up in the ANS, there is an important remaining quantity to be removed from the process asprocess steam or from the evaporation section. Depending on the process conditions and thetreatment of the process steam, the resulting condensate can be polluted by various amounts ofAN, HNO 3 or NH 3 .Table 9.9 shows an example for a combination of steam purification and condensate treatment.According to [148, EFMA, 2000], contaminated condensate can be re-used or purified usingvarious techniques including:• stripping with air or steam with the addition of alkali to liberate ionised ammonia if required• distillation• membrane separation techniques, such as reverse osmosis.Another option is ion exchange but there are safety risks about using organic material that needto be taken into account. The recycling of organic resins to the ammonium nitrate process mustbe prevented, and the exchange resin must not be allowed to become nitrated.Options for discharging the condensate, arising from the steam leaving the neutraliser, includethe following ways [148, EFMA, 2000]:• to biological treatment (on-site or joint treatment with municipal waste water)• to a nitric acid plant for use as absorption water, if the quality is acceptable for production• to other users on the site, such as in fertiliser solution manufacturing• as boiler feed-water, after further purification• to the scrubbing section of AN/CAN prilling or granulation.InputVenturi scrubberCyclonic columnFilter candlesEvaporatorCondenserOutputProcess steam from neutraliserAcidic scrubbing with ANS to neutralise NH 3Removal of remaining AN dropletsIn a shell and tube, a part of the process steam is used to produce a “clean”steam and a concentrated condensate, by heating the tubes and evaporationin the shellCondensation of the “clean” steamConcentrated condensate for recycling as scrubbing liquid in the ANSplant, to HNO 3 plant absorption tower, or elsewhere“Clean” condensate with a AN content of