US-20260125273-A1 - SYSTEMS AND METHODS FOR THE PRODUCTION OF AMMONIA

US20260125273A1US 20260125273 A1US20260125273 A1US 20260125273A1US-20260125273-A1

Abstract

Systems and methods for ammonia synthesis integrating an ammonia absorption refrigeration cycle and an ammonia synthesis cycle. The ammonia synthesis cycle includes a multistage non-adiabatic reactor system formed of multiple non-adiabatic reactors for converting a synthesis gas containing hydrogen and nitrogen into ammonia. The ammonia is chilled and stored as a cold ammonia product. Lean solution from the ammonia absorption refrigeration cycle can be used as a heat exchange utility fluid for the reactors, and the refrigeration cycle can also be used to chill the ammonia from the synthesis cycle for cold storage. Almost all of the syngas is converted in a single pass through the multistage non-adiabatic reactor system, eliminating the need for recycle streams and associated energy consumption.

Inventors

Muhamad F. FOUAD
Matthew J. DUHE
Joshua S. BALDASSARO
Joel R. VOGEL

Assignees

THE MOSAIC COMPANY

Dates

Publication Date: 20260507
Application Date: 20251105

Claims (14)

1 . A system for producing ammonia, comprising: an ammonia absorption refrigeration cycle, wherein a refrigerant comprises ammonia, wherein the ammonia absorption refrigeration cycle comprises: an evaporator configured to convert liquid ammonia to gaseous ammonia, an absorber configured to combine the gaseous ammonia with water to form an ammonia-rich solution, a generator configured to heat the ammonia-rich solution to convert the ammonia contained therein to gaseous ammonia while the remaining solution remains liquid to be returned to the absorber, and a condenser for condensing the gaseous ammonia from the generator into liquid ammonia to be returned to the evaporator; and an ammonia synthesis cycle comprising a non-adiabatic reactor system comprising at least one ammonia synthesis reactor and a reboiler, wherein the non-adiabatic reactor system is configured to receive a synthesis gas containing hydrogen and nitrogen to be reacted in the presence of a catalyst to produce a reaction mixture containing an ammonia in a single pass, wherein the system is configured such that: a lean ammonia solution exiting the reboiler is combined with an ammonia vapor exiting the ammonia synthesis cycle to form an enriched solution for introduction into the absorber; and lean ammonia solution from the ammonia absorption refrigeration cycle is supplied to the reactor system as a heat exchange fluid.
2 . The system of claim 1 , wherein the ammonia absorption refrigeration cycle is configured to supply the lean ammonia solution to the non-adiabatic reactor system to control a thermal condition of the reactor system.
3 . The system of claim 2 , wherein the non-adiabatic reactor system comprises a plurality of reactors, and the lean solution from the ammonia absorption refrigeration cycle is supplied to and returned each reactor of the non-adiabatic reactor system.
4 . The system of claim 1 , wherein the lean solution exiting the reboiler is introduced into a low-pressure absorber to absorb the ammonia vapor.
5 . The system of claim 1 , wherein the reaction mixture exits the ammonia synthesis cycle and is directed to an ammonia chiller system.
6 . The system of claim 1 , wherein a nitrogen conversion of the ammonia synthesis cycle is at least 85%.
7 . The system of claim 6 , wherein the nitrogen conversion of the ammonia synthesis cycle is at least 90%.
8 . The system of claim 7 , wherein the nitrogen conversion of the ammonia synthesis cycle is at least 95%.
9 . The system of claim 1 , wherein the ammonia synthesis cycle is completely free of a recycled syngas stream.
10 . The system of claim 1 , wherein the lean solution exiting the reboiler is at a temperature in a range of from about 300-390 degrees Fahrenheit.
11 . The system of claim 1 , wherein the ammonia absorption refrigeration cycle further comprises: a pump configured to pump the ammonia-rich solution to the generator; a pressure reducing valve positioned between the generator and the absorber and configured to reduce a pressure of the remaining solution returning from the generator to the absorber; and an expansion valve positioned between the condenser and the evaporator and configured to reduce a pressure of the liquid ammonia returning from the condenser to the evaporator.
12 . A method of providing an ammonia refrigeration system for an ammonia synthesis process, the method comprising: introducing a synthesis gas comprising hydrogen and nitrogen to an ammonia synthesis cycle comprising a multistage, non-adiabatic reactor system to produce a reaction mixture containing ammonia product and unreacted synthesis gas; separating the ammonia product from the unreacted synthesis gas; introducing the ammonia product into an ammonia-water distillation column to produce a pure liquid ammonia and ammonia vapor; condensing the ammonia vapor to produce an ammonia refrigerant; and introducing a portion of the ammonia refrigerant to the ammonia synthesis process.
13 . The method of claim 12 , wherein heat required by the ammonia-water distillation column is provided by heat generated from the ammonia synthesis process.
14 . The method of claim 12 , further comprising: combining a cooled lean ammonia solution collected from a reboiler of the ammonia synthesis process and ammonia vapor from the ammonia synthesis process into a low pressure absorber to produce an enriched intermediate ammonia solution; and pumping the enriched intermediate ammonia solution to the ammonia-water distillation column to produce pure liquid ammonia and ammonia vapor.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present disclosure claims the benefit of U.S. Provisional Application No. 63/716,597, filed Nov. 5, 2024, which is hereby fully incorporated by reference in its entirety. FIELD OF INVENTION The present disclosure relates generally to ammonia synthesis, and more particularly to methods and systems for efficiently producing ammonia. BACKGROUND Ammonia production (NH3) accounts for approximately 80% of the fertilizer industry's total energy consumption globally. Producing ammonia requires a multistep, energy intensive process, known as the Haber-Bosch process. The Haber-Bosch process converts atmospheric nitrogen (N2) to ammonia (NH3) by a reaction with hydrogen (H2) using an iron metal catalyst under high temperatures and pressures. Ammonia synthesis reaction can generally be written as follows: This reaction is slightly exothermic (i.e. it releases energy), meaning that the reaction is favored at lower temperatures and higher pressures, and is reversible. It decreases entropy, complicating the process because it produces fewer molecules than with which it started. Although the Haber-Bosch process has undergone various degrees of optimization, ammonia production still remains limited by thermodynamics to typically less than 20% conversion in a single pass. Generally, the process requires that hydrogen is produced via steam reforming, followed by an iterative closed cycle to react hydrogen with nitrogen to produce ammonia. More particularly, steam reforming of light hydrocarbons, such as natural gas, is the most used method for the large-scale ammonia production, where natural gas is purified, then converted to hydrogen via steam reforming or partial oxidation of the natural gas, thereby forming of synthesis gas, or syngas. The syngas in turn is utilized in the synthesis of ammonia in the presence of nitrogen per the above reaction. The total energy consumption of the production of ammonia in these large-scale steam reformers is approximately 50% greater than the theoretical thermodynamic minimum. This elevated energy consumption is largely contributed to compression losses throughout these steam reforming processes. Once the ammonia is produced, it is separated from unreacted N2 and H2, which must then be repressurized, reheated, and recycled. The process utilizes vapor compression cycles during ammonia synthesis to compress unreacted nitrogen and hydrogen into recycle streams directed back into the ammonia synthesis process. Because the nitrogen conversion rates of these processes are typically less than 20%, the recycle streams are large and therefore require large amounts of compression work before the unreacted nitrogen and hydrogen can be directed back into the synthesis process. All of this in addition to the steam reforming step contributes to high energy consumption and greenhouse gas emissions. There is a need in the industry for an improvement to the currently ammonia production process to address this elevated energy consumption and greenhouse gas emissions. SUMMARY The problems described above are largely addressed by the process described herein. A method for ammonia synthesis and system comprises integrating an ammonia absorption refrigeration cycle and an ammonia synthesis cycle, the ammonia synthesis cycle comprising a multistage non-adiabatic reactor system, supplying waste heat from the ammonia synthesis cycle to the ammonia absorption refrigeration cycle, and supplying lean solution from the ammonia absorption refrigeration cycle to the ammonia synthesis cycle as a heat exchange utility fluid. In embodiments, a system for producing ammonia includes an ammonia absorption refrigeration cycle, wherein a refrigerant comprises ammonia, and an ammonia synthesis cycle comprising a multistage, non-adiabatic reactor system. The multistage, non-adiabatic reactor system is a series of reactors, each of which is configured to receive a synthesis gas containing hydrogen and nitrogen to be reacted in the presence of a catalyst to produce a gaseous reaction mixture containing an ammonia. The gaseous reaction mixture is condensed and the ammonia product is separated and further chilled for storage. The unreacted mixture (if present) is converted to syngas and enters the next reactor in the series of reactors of the system until almost all the syngas has been converted in a single pass through the entire system. Waste heat from the ammonia synthesis cycle is supplied to the ammonia absorption refrigeration cycle, and lean ammonia solution from the ammonia absorption refrigeration cycle is supplied to the reactor system as a heat exchange fluid. In embodiments, the ammonia absorption refrigeration cycle is configured to supply lean ammonia solution to the multi-stage, non-adiabatic reactor system to control a thermal condition of the reactor system. For example, the lean ammonia solution can cool the non-adiabatic reactors to a temperature that favors nitrogen conve