Process for recovery and reuse of ammonia in a liquid ammonia fabric treating system

摘要

The disclosure is directed to a system for the recovery of spent ammonia, in connection with the processing of fabrics and the like with liquid ammonia, and concerns particularly the elimination from the recovered ammonia of undesired water.PPEconomic processing of fabrics by liquid ammonia requires recovery and reuse of substantial quantities of ammonia. In the course of processing, the ammonia unavoidably becomes contaminated with water. Separation of water from ammonia on a laboratory level or, in any kind of batch processing is a theoretically simple matter and can be coped with by conventional differential evaporation techniques, or otherwise. However, in a continuously operating processing line where large quantities of anhydrous liquid ammonia are being used as the treating medium, water accumulates rapidly, not only from the fabric being processed, but also from a certain inevitable amount of air leakage in the system. Because so much of any given increment of the treating medium must be recycled, as compared to that actually "used up" in the treating process, water accumulates rapidly in the system and must be removed on a continuous basis. The specification discloses a unique and highly efficient procedure for removal of water by effecting condensation of water and ammonia vapors, constituting the process effluent, by feeding the effluent to a desuperheating vessel, where it is brought into direct contact with a body of low temperature liquid ammonia. This is done in conjunction with a preliminary low temperature condensation of the effluent in a non- contact heat exchange stage. The condensed body of liquid ammonia in the desuperheater vessel, including residual condensed water from the process effluent combined with re-liquefied ammonia, forms the feed supply of liquid ammonia solution to the process. The condensed water, which in the new process constitutes a portion of the feed supply, is applied to the fabric being treated, along with the liquid ammonia. Typically, some of the water is carried away with the processed fabric as a constituent of its moisture content. The remainder, which is driven off as steam in the process, is recycled.P PA key factor in the new process is that the re-liquefied ammonia, instead of being sent directly back to the process, is directed into the desuperheater vessel, there being combined with the condensed process effluent. The combined solution, containing a minor fraction of condensed residual water is then fed back to the process. In this manner, the total water fraction in the process solution may be kept a satisfactorily low level, typically on the order of two or three percent maximum, under extreme process conditions, and desirably much lower than that under more favorable process conditions.