Two-stage ammonia absorption refrigeration system with at least three evaporation stages

Claim 2

A two-stage ammonia absorption refrigeration system comprising a first separation tower for separating strong ammonia water solution into high purity ammonia and weak ammonia water solution, a first condenser to liquefy said high purity ammonia, a second separation tower for separating very high purity ammonia from said high purity ammonia, a first evaporator to receive part of said high purity ammonia after passage through a first pressure-reducing means, a second evaporator to receive the remainder of said high purity ammonia after passage through a second pressure-reducing means, a second condenser to liquefy said very high purity ammonia, a third evaporator to receive said very high purity ammonia after passage through a third pressurereducing means, a first absorber to receive ammonia vapor from said first evaporator and from said third evaporator, a second absorber to receive ammonia vapor from said second evaporator, a pipe for the flow of said weak ammonia water solution from said first separation tower into said second absorber, a first pump to feed said strong ammonia water solution from said first absorber into said first separation tower, and a second pump to feed ammonia water solution from said second absorber into said first absorber.

Claim 3

The refrigeration system of claim 1 wherein first, second and third indirect heat exchangers are associated, respectively, with the first, second and third evaporators, each of said heat exchangers being connected for the countercurrent passage of the ammonia streams flowing to and from its associated evaporator.

Claim 4

The refrigeration system of claim 2 wherein an indirect heat exchanger is connected for the counter-current passage of the weak ammonia water solution flowing from and the strong ammonia water solution flowing to the first separation tower.

Claim 5

The refrigeration system of claim 1 wherein a fourth evaporator is connected to receive part of the very high purity ammonia after passage through a fourth pressure-reducing means, and a pipe is connected for the flow of ammonia vapor from said fourth evaporator to the second absorber.

Claim 6

The refrigeration system of claim 4 wherein an indirect heat exchanger is connected for the counter-current passage of the ammonia streams flowing to and from the fourth evaporator.

Claim 7

In the method of producing refrigeration comprising vaporization of liquid ammonia in two evaporation zones of decreasing pressure and temperature, absorption of the vaporized ammonia from said two evaporation zones in two corresponding absorption zones of decreasing pressure, passage of ammonia water solution from the absorption zone of lower pressure to the absorption zone of higher pressure and from said absorption zone of higher pressure to a generation zone fOr separating ammonia vapor from ammonia water solution, condensing said ammonia vapor and division of the resulting liquid ammonia into two streams discharging through pressure reducing devices, respectively, into said two evaporation zones, the improvement of vaporizing some liquid ammonia in a third evaporation zone of a temperature below the temperatures of said two evaporation zones which comprises separating from said liquid ammonia a portion of higher ammonia purity, passing said portion of high ammonia purity through a pressure reducing device, vaporizing said portion of higher ammonia purity in said third evaporation zone maintained at substantially the higher pressure of one of said two evaporation zones, and absorbing the vaporized ammonia from said third evaporation zone in said absorption zone of higher pressure.

Claim 8

In the method of producing refrigeration comprising vaporization of liquid ammonia in two evaporation zones of decreasing pressure and temperature, absorption of the vaporized ammonia from said two evaporation zones in two corresponding absorption zones of decreasing pressure, passage of ammonia water solution from the absorption zone of lower pressure to the absorption zone of higher pressure and from said absorption zone of higher pressure to a generation zone fOr separating ammonia vapor from ammonia water solution, condensing said ammonia vapor and division of the resulting liquid ammonia into two streams discharging through pressure reducing devices, respectively, into said two evaporation zones, the improvement of vaporizing some liquid ammonia in a third evaporation zone of a temperature below the temperatures of said two evaporation zones which comprises separating from said liquid ammonia a portion of higher ammonia purity, passing said portion of high ammonia purity through a pressure reducing device, vaporizing said portion of higher ammonia purity in said third evaporation zone maintained at substantially the higher pressure of one of said two evaporation zones, and absorbing the vaporized ammonia from said third evaporation zone in said absorption zone of higher pressure.