Control of the ammonia-recovery system

The type of apparatus that can be used for the recovery of the excess ammonia may be varied within wide limits. The physical properties of the amine and the compound from which it is derived, along with the means utilized to effect the separation of the amine, are the principal guides in the selection of the proper apparatus. 

Absoipfion Systems. When anhydrous ammonia is used, the essentials of a refrigeration assembly will serve for the recovery of the excess ammonia (Fig, 8-28). In recent years, the use of liquid ammonia, frequently in, conjunction with an organic solvent, has increased markedly, and the use of high-pressure ammonia-recovery systems is destined to become more prevalent. 

In liquid-phase ammonolysis with aqueous ammonia, the ammonia-recoveiy syst m may consist of a number of submerged coils or double-pipe condensers, fiwwed by a series of vertical absorbers. The submerged coils are cooled by circulating water, and the temperature of the vapors is 

The vertical absorbers contain aqueous ammonia of varying concentrations, and a standpipe suspended from the top supplies the NH gas, which is distributed at the base by means of suitable perforated fittings. Any unabsorbed gas scapes at the top and k then led to the bottom of the following absorber. The heat of solution is removed either by internal cooling coils or by an outtide spray astern. 

Ammonia recovery system. Absorbers operate at atmospheric pressure. Rectifiers operate at approximately 200 psi. 

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