Method to Liquefy Ammonia Gas

Abstract

An ammonia expander in a liquefaction process, the ammonia expander reducing the resulting vapor from the liquid ammonia expansion and increasing the percentage of both the feed gas input and the process output. Embodiments of the ammonia expander comprise a radial inflow reaction turbine with an induction generator mounted on a generator shaft and a turbine mounted on a turbine shaft, the turbine submerged in the liquid ammonia. The turbine extracts torque from the liquid ammonia as it flows through the turbine. The torque from the turbine is transferred from the turbine shaft to the generator shaft, allowing for energy to be extracted from the liquid ammonia stream.

1 . A process for liquefying ammonia gas, comprising the steps of:
 initially liquefying a first portion of a feed gas and a first portion of a compressed gas to create a liquid ammonia output;   expanding the liquid ammonia output with a liquefied ammonia gas expander to generate a first portion of liquid ammonia output and a first portion of liquid ammonia vapor output; and   removing energy from the liquefied ammonia gas.   
     
     
         2 . An expander for use within an ammonia liquefaction plant to expand liquid ammonia, comprising:
 a vessel having an inlet receiving the ammonia liquid and an outlet outputting expanded ammonia;   a dry side section located within the vessel isolated from the liquid ammonia and expanded ammonia including a generator having a generator shaft, the generator generating energy from rotation of the generator shaft, the dry side section purged with a mostly inert gas; and   a wet side section located within the vessel and submerged within the liquid ammonia including a turbine having a turbine shaft, and a series of one or more runner stages that cause the turbine shaft to rotate as the liquid ammonia flows through the wet side section, the wet side section expanding the liquid ammonia, the turbine shaft driving the generator shaft.   
     
     
         3 . The expander as recited in  claim 2 , wherein the dry side section further includes a first part of a magnetic coupling affixed to the generator shaft, and wherein the wet side section further includes a second part of the magnetic coupling affixed to the turbine shaft, the turbine shaft rotating the second part and transferring rotational power to the first part through the magnetic coupling. 
     
     
         4 . The expander as recited in  claim 2 , wherein the wet side section further includes a set of one or more ball bearings positioned around the turbine shaft and lubricated with the liquid ammonia, and a thrust equalizing mechanism device balancing axial thrust loads on the one or more ball bearings. 
     
     
         5 . The expander as recited in  claim 2 , wherein the dry side section further includes a variable speed constant frequency controller. 
     
     
         6 . The expander as recited in  claim 2 , wherein the wet side section further includes a jet exducer further expanding the expanded ammonia. 
     
     
         7 . An ammonia expander submerged in liquid ammonia, comprising:
 a rotating turbine shaft mounted in one or more bearings in an expander housing with one or more runners, the rotating turbine shaft and the one or more bearings exposed to the liquid ammonia;   a rotating generator shaft mounted in one or more bearings in a generator housing with a generator rotor;   a generator stator mounted in the generator housing, the rotating generator shaft, the one or more bearings, the generator rotor and the generator stator isolated from the liquid ammonia; and   a magnetic coupling with two matching rotating parts, one rotating part mounted on the turbine shaft and one rotating part mounted on the generator shaft next to each other and separated by a non-rotating membrane mounted to the generator housing.