Synergistic blue and green ammonia process

Abstract

An integrated blue-green ammonia process that avoids the need for air separation is disclosed. Water electrolysis, to produce hydrogen, produces oxygen as a co-product. Natural gas (methane) is reacted in a reformer with steam and air to create a mixture composed primarily of hydrogen, steam, nitrogen and carbon dioxide. The oxygen from electrolysis drives this process, either directly inside an autothermal reformer, or indirectly by oxycombustion in the furnace of a steam methane reformer. The steam is removed by cooling the gas, the carbon dioxide is removed, leaving a purified stream comprising hydrogen and nitrogen. This stream can be combined with additional hydrogen from the electrolyzer to yield a 3:1 mixture of hydrogen and nitrogen for the Haber-Bosch process to make ammonia. The disclosed blue-green process is two-fold less expensive than the conventional green ammonia process and emits about half as much greenhouse gas as the conventional blue ammonia process.

Description

[0001] SYNERGISTIC BLUE AND GREEN AMMONIA PROCESS

[0002] This application claims priority of U . S . Provisional Patent Application Serial No . 63 / 673 , 846 , filed July 22 , 2024 , the disclosure of which is incorporated herein by reference in its entirety .

[0003] Background

[0004] Ammonia is one of the most important chemicals produced in the world, finding uses in a multitude of applications such as agriculture , textile manufacturing, plastic production, refrigeration, and more . Today, 183 million metric tons of ammonia is produced annually making it the second-most produced chemical by mass and is estimated to account for 15 - 20% of the greenhouse gas (GHG) emissions from the chemical sector . Additionally, the use of ammonia as a carbon- free liquid fuel is gaining momentum which will only increase its future demand . Therefore, designing and building renewable and low-carbon intensity ammonia production facilities is pivotal to achieve future GHG emission targets .

[0005] The long-established Haber-Bosch process which uses nitrogen and hydrogen feedstock mixtures with an iron catalyst is used to produce ammonia . The nitrogen is typically sourced from an on-site air separation unit (ASU) that conducts the Linde process to generate pure oxygen and nitrogen gases . Hydrogen, on the other hand, can be produced by a variety of methods , which are typically designated colors to indicate the feedstock and carbon intensity . The two main processes considered in a future low-carbon industrial standard are "blue" hydrogen, which typically makes use of natural gas as a feedstock but includes on-site carbon capture and sequestration processes to reduce direct GHG emissions, and "green" hydrogen, which uses electrolysis of water powered by renewable electricity. Blue hydrogen is thought to be a mid-term solution to reduce emissions when using fossil fuel feedstocks, whilst green hydrogen is the expected long-term solution when electricity grids are sufficiently decarbonized. Blue hydrogen and green hydrogen have several potential subprocesses. Blue hydrogen processes include modifying steam methane reforming to use oxycombustion as the primary heat source, and autothermal reforming (ATR) , which has somewhat better performance. The green hydrogen process uses low temperature electrolysis (LTE) , often using proton exchange membrane (PEM) electrolyzers which can safely handle fluctuating loads.

[0006] The overall blue and green ammonia production processes are illustrated in FIGs. 1A-1B. Both processes have drawbacks despite their well-established status. A typical blue process, shown in FIG. 1A, includes a pre-former 20 (also called a pre-reformer) which accepts natural gas (or methane) and steam to produce carbon monoxide and hydrogen. The pre-former 20 preferentially converts heavier hydrocarbons in the natural gas (e.g. propane and butane) into lighter gases including methane, making the overall system more robust to variations in the natural gas composition. The preformer effluent also includes unconverted natural gas and steam. These outputs are supplied to an ATR reactor 30. The ATR reactor 30 also requires oxygen from the air separation unit (ASU) 10. The ATR reactor 30 is configured to produce the following reaction: 4 CH4+ 02+ 2 H20 10 H2+ 4 CO. Next, the output from the ATR reactor 30, which may include carbon monoxide, hydrogen, steam, and carbon dioxide, is provided to a water-gas shift (WGS) reactor 40. The WGR reactor 40 is configured to achieve the following reaction: CO + H2O CO2+ H2. Thus, the output of the WGS reactor 40 includes a gaseous mixture of hydrogen, carbon dioxide , steam, and any impurities . The output of the WGS reactor 40 is delivered to a carbon dioxide capture unit 50 . This unit first condenses the steam to water, and then removes the carbon dioxide from the gaseous stream . The remaining gaseous stream is sent to a pressure swing adsorption ( PSA) unit 60 . The PSA unit 60 is used to remove any gasses that are not hydrogen from the gaseous stream such that the output from the PSA unit 60 is pure hydrogen, which is then supplied to the Haber-Bosch reactor 70 . The air separation unit (ASU) 10 also creates nitrogen for the Haber-Bosch process 70 . The Haber-Bosch reactor 70 then performs the following reaction : N + 3H22NH3. However, creation of both nitrogen and hydrogen by the ASU 10 results in excess nitrogen being produced as the ASU si zing is oxygen-limited . This results in large capital and operating expenses .

[0007] On the other hand, in the green process , shown in FIG . IB, an electrolyzer 80 is used to produce hydrogen and oxygen from water . Additionally, as described above , an air separation unit (ASU) 10 is used to separate air into nitrogen and oxygen . The nitrogen from the ASU 10 and the hydrogen from the electrolyzer 80 serve as inputs to the Haber-Bosch reactor 70 . However, both the electrolyzer 80 and the ASU 10 produce oxygen that is not used elsewhere . The oxygen typically has low value where it is produced, so most of it is vented to the atmosphere .

[0008] Therefore , both processes have byproducts that are currently being wasted and include air separation units that are expensive and underutili zed . Additionally, the green process is limited by the capacity of existing proton exchange membrane ( PEM) electrolyzers , meaning that they can only be used for small-scale ammonia production, which is cost-inef ficient due to the lack of economies of scale .

[0009] Therefore , an improved low-GHG system and method for the production of ammonia would be beneficial .

[0010] Summary

[0011] An integrated blue-green ammonia process that avoids the need for air separation is disclosed . Water electrolysis , to produce hydrogen, produces oxygen as a co-product . Natural gas (methane ) is reacted in a reformer with steam and air to create a mixture composed primarily of hydrogen, steam, nitrogen and carbon dioxide . The oxygen from electrolysis drives this process , either directly inside an autothermal reformer, or indirectly by oxycombustion in the furnace of a steam methane reformer . The steam is removed by cooling the gas , then the carbon dioxide is removed, leaving a purified stream comprising hydrogen and nitrogen . This stream can be combined with additional hydrogen from the electrolyzer to yield a 3 : 1 mixture of hydrogen and nitrogen for the Haber-Bosch process to make ammonia . The disclosed blue-green process is two-fold less expensive than the conventional green ammonia process . The disclosed blue-green process emits only about hal f as much greenhouse gas as the conventional blue ammonia process . This reduction in greenhouse gas emissions comes at a moderate cost of about $ 100 per tonne of CO2e avoided .

[0012] According to one embodiment , a system for producing ammonia is disclosed . The system comprises an electrolyzer to electrolyze water into hydrogen and oxygen; a reforming system configured to receive natural gas , air, and steam, plus the oxygen from the electrolyzer, and output a gaseous stream that comprises at least nitrogen, carbon monoxide , and hydrogen; at least one component downstream from the reforming system to convert the carbon monoxide into carbon dioxide , separate the carbon dioxide from the gaseous stream for sequestration, and puri fy the gaseous stream such that the puri fied gaseous stream comprises hydrogen and nitrogen; and a Haber-Bosch reactor configured to receive the purified gaseous stream and the hydrogen from the electrolyzer and output ammonia, wherein at least 95% of the nitrogen used by the Haber-Bosch reactor is provided by the air introduced into the reforming system .

[0013] In some embodiments , the reforming system includes an autothermal reforming reactor (ATR) . In certain embodiments , a compressor is in communication with an input air stream from an ambient environment to increase a pressure of the air introduced to the ATR reactor . In certain embodiments , an oxygen compressor is used to increase a pressure of the oxygen from the electrolyzer prior to its introduction into the ATR reactor . In certain embodiments , the system includes a pre- former, wherein the natural gas and the steam are supplied to the pre- former and the preformer produces an output that includes natural gas that was not converted, steam, hydrogen and carbon monoxide ; and wherein the output is supplied to the ATR reactor .

[0014] In some embodiments , the at least one component comprises a water-gas shi ft (WGS ) reactor to convert the carbon monoxide into the carbon dioxide . In some embodiments , the at least one component comprises a carbon dioxide capture unit to separate the carbon dioxide from the gaseous stream for sequestration . In some embodiments , the at least one component comprises a pressure swing adsorption ( PSA) unit to puri fy the gaseous stream. In some embodiments, a hydrogen compressor is used to increase a pressure of the hydrogen from the electrolyzer prior to its introduction into the Haber-Bosch reactor.

[0015] According to another embodiment, a method of producing ammonia is disclosed. The method comprises using an electrolyzer to produce oxygen and hydrogen; introducing air, the oxygen, steam and natural gas into a reforming system to create a gaseous stream comprising at least nitrogen, hydrogen, and carbon monoxide; reacting the carbon monoxide to create carbon dioxide; sequestering the carbon dioxide; purifying the gaseous stream such that the purified gaseous stream comprises hydrogen and nitrogen; and using a Haber-Bosch reactor to react the hydrogen from the electrolyzer and the hydrogen and the nitrogen from the purified gaseous stream to produce ammonia, wherein at least 95% of the nitrogen used in the Haber-Bosch reactor is introduced as air in the reforming system.

[0016] In some embodiments, the reforming system utilizes an autothermal reforming reactor (ATR) . In certain embodiments, a pre-former is used, wherein the natural gas and the steam are introduced into the pre-former, and the pre-former reacts the natural gas and steam to produce an output gas stream comprising natural gas, steam, carbon monoxide and hydrogen, which are then introduced into the ATR reactor. In certain embodiments, the method comprises using an oxygen compressor to increase a pressure of the oxygen exiting the electrolyzer prior to its introduction into the ATR reactor. In certain embodiments, the electrolyzer is controlled such that at least 95% of the oxygen produced by the electrolyzer is consumed by the ATR reactor. In some embodiments , the gaseous stream is purified using a pressure swing adsorption ( PSA) unit . In some embodiments , the carbon monoxide is reacted using a water-gas shi ft (WGS ) unit to create the carbon dioxide . In some embodiments , the method comprises using a hydrogen compressor to increase a pressure of the hydrogen exiting the electrolyzer prior to its introduction into the Haber-Bosch reactor .

[0017] Brief Description of the Drawings

[0018] For a better understanding of the present disclosure , reference is made to the accompanying drawings , in which like elements are referenced with like numerals , and in which :

[0019] FIG . 1A shows the production of blue ammonia according to the prior art ;

[0020] FIG . IB shows the production of green ammonia according to the prior art ;

[0021] FIG . 2 shows the production of ammonia using one embodiment of the disclosed integrated blue-green production process ;

[0022] FIG . 3 shows the leveli zed cost of ammonia (LCOA) for blue , green and integrated blue-green ammonia;

[0023] FIG . 4 shows leveli zed CCye emissions of the blue, green and integrated blue-green ammonia processes ; and

[0024] FIG . 5 shows the cost per tonne CO2e avoided for both green and integrated blue-green processes .

[0025] Detailed Description

[0026] A new system and process is disclosed which integrates the blue and green ammonia production processes into a less expensive combined process with lower greenhouse gas emissions . The oxygen produced from the electrolyzer is used to supply the 02needed by the blue H2 production process . In one embodiment , this 02is fed into an autothermal reformer (ATR) reactor . In another embodiment, the O2is used for oxycombustion in the furnace of a steam methane reformer . In either embodiment , the reformer is fed with air, and once the oxygen in that air is consumed, the remaining nitrogen is used in the subsequent Haber-Bosch process . Therefore, this integration eliminates the need for the expensive air separation units (ASUs ) and provides means to use all by-products within the process . Only a single large-scale Haber-Bosch process is required, meaning the small but expensive Haber-Bosch plant for a stand-alone green plant is also avoided . A schematic for an embodiment of this integrated process is illustrated in FIG . 2 .

[0027] In this embodiment, natural gas ( such as CH4) and steam are provided to a pre-former 20 . As described above , the pre-former 20 is used to convert any heavier hydrocarbons in the natural gas into methane , and to produce some carbon monoxide and hydrogen . The pre- former ef fluent also includes natural gas components that were not converted and steam . These outputs are supplied to an ATR reactor 30 . Unlike the prior art blue ammonia production process described above, air is also provided to the ATR reactor 30 . This air is inj ected in an amount necessary to provide substantially all of the nitrogen that is needed by the Haber-Bosch reactor 70 . In certain embodiments , at least 95% of the nitrogen used by the Haber-Bosch reactor 70 is provided by the air that is introduced into the ATR reactor 30 . In certain embodiments , all of the nitrogen is provided by this air . In some embodiments , an air compressor 31 is used to compress the air prior to its introduction into the ATR reactor 30 . Additionally, an electrolyzer 80 is used to split water into oxygen and hydrogen ( 2 H O 2 H2+ O2) . The oxygen is also provided to the ATR reactor 30 . An oxygen compressor 32 may be used to compress the oxygen prior to its introduction into the ATR reactor 30 . In some embodiments , the air compressor 31 and the oxygen compressor 32 may compress the respective gasses to about 30 atmospheres .

[0028] The ATR reactor 30 is configured to produce the following reaction : 4 CH4+ O2+ 2 H2O 10 H2+ 4 CO . This reaction may occur at a pressure of about 30 atm. Next, the gaseous stream from the ATR reactor 30 , which may include carbon monoxide , hydrogen, steam, carbon dioxide , nitrogen and other impurities is provided to a water-gas shi ft (WGS ) reactor 40 . Note that , in certain embodiments , substantially all of the oxygen (which may be at least 95% ) introduced into the ATR reactor 30 from both the electrolyzer 80 and the air is consumed in the ATR reactor 30 .

[0029] The WGS reactor 40 is configured to achieve the following reaction : CO + H2O CO2+ H2. In other words , the WGS reactor 40 is used to convert the carbon monoxide into carbon dioxide . Thus , the output of the WGS reactor 40 includes a gaseous stream of hydrogen, nitrogen (which was introduced into the ATR reactor 30 via the air stream) , carbon dioxide , steam, and any impurities . The output of the WGS reactor 40 is delivered to a carbon dioxide capture unit 50 . The carbon dioxide capture unit 50 may utili ze adsorption, absorption or membrane separation, including processes such as amine scrubbing, Selexol , and Rectisol , as are known in the art . Often the first step in the CO2capture process is to cool the stream to condense the water . Then the CO2capture unit 50 removes the carbon dioxide from the gaseous stream, which may then be sequestered, and supplies the remaining gaseous stream to a pressure swing adsorption (PSA) unit 60. Note that the numbers shown in FIGs. 3, 4, and 5 were computed for an embodiment where the CO2capture unit was the Selexol process.

[0030] The pressure swing adsorption (PSA) unit 60 is used to further remove CO2 and other impurities from the gaseous stream, leaving a stream that is nearly pure nitrogen and hydrogen, with some residual impurities of methane, CO, and argon. The impurity-rich stream from the PSA (i.e. the flue gas) typically contains some combustible gases (e.g. H2, CO, CH4) , which may be burned to provide heat or electrical power (CHP: combined heat and power) for the process. The purified gaseous stream (which comprises hydrogen and nitrogen, which is more than 99% pure) from the PSA unit 60 is provided to the Haber-Bosch reactor 70. Small amounts of argon may be present in the purified gaseous stream, along with trace amounts of C02, CH4and CO. Thus, substantially all of the nitrogen (95% or more) supplied to the Haber-Bosch reactor 70 is provided by the air introduced into the ATR reactor 30.

[0031] The Haber-Bosch reactor 70 also receives additional hydrogen from the electrolyzer 80. In some embodiments, the hydrogen from the electrolyzer 80 is compressed using a hydrogen compressor 33. This may be compressed to the same pressure as the purified gaseous stream exiting the PSA unit 60. In some embodiments, the combined N2 / H2stream is further compressed at the inlet of the Haber-Bosch unit to achieve the high pressure needed by that process. As is well known, the Haber-Bosch reactor 70 produces ammonia typically at pressures at between 200 and 400 atmospheres and at temperatures of between 400°C - 450°C. The ratio of hydrogen to nitrogen entering the Haber-Bosch reactor 70 may be controlled so as to be 3: 1. Note that this production process does not require the use of an air separation unit (ASU) , which are typically expensive .

[0032] A controller 100 may be used to control the operation of the system of FIG . 2 . Speci fically, the controller 100 may control the introduction rate of natural gas and steam into the pre-former 20 . Further, the controller 100 may control the rate that air is introduced into the ATR reactor 30 . The controller 100 may also control the energy supplied to the electrolyzer 80 , which in turn controls the amount of oxygen and hydrogen produced . The controller 100 will also control the CO2capture process and the PSA unit , and adj ust the compressors as needed to compensate for any variability in the process . The controller 100 may employ an open loop or a closed loop control system to control these various parameters . For example , sensors , such as temperature sensors , oxygen sensors , pressure sensors , flow sensors , composition sensors , or other types of sensors may be employed to monitor the system . The output from these sensors may be used by the controller 100 . Several additional units not shown in FIG . 2 , and matching sensors and control elements , may be needed to ensure safe operation and to facilitate start-up and shut-down of this ammonia production plant . Many of these additional units and controllers are used commercially for ammonia or H2production units , and others have been presented in the patent and engineering literature, so they are known to someone reasonably skilled in the art .

[0033] Further, FIG . 2 shows j ust one embodiment . In certain embodiments , the pre- former 20 may not be employed . Rather, the natural gas and steam may be introduced directly into the ATR reactor 30 . In this embodiment, the controller 100 may control the introduction rate of steam and natural gas into the ATR reactor 30 .

[0034] In certain embodiments , the ATR reactor 30 may be replaced by a steam methane reformer and its furnace , providing heat by oxycombustion of some of the natural gas with the oxygen from the electrolyzer 80 . The oxycombustion process and how it is used to avoid CO2emissions to the atmosphere has been thoroughly explained in the patent and scienti fic literature . Thus , any reforming system that coverts natural gas , air and oxygen into carbon monoxide , nitrogen and hydrogen may be used . Additionally, as was described for the ATR reactor 30 , more than 95% of the nitrogen used by the Haber-Bosch reactor 70 is introduced as air into this reforming system .

[0035] Further, in certain embodiments , the components located downstream from the ATR reactor 30 may be modi fied . Speci fically, the components located downstream from the ATR reactor 30 (which in FIG . 2 include the WGS reactor 40 , the carbon dioxide capture unit 50 , and the PSA unit 60 ) may be replaced with other components that provide the same functionality . For example , other components may be used to convert the carbon monoxide from the ATR reactor 30 to carbon dioxide, separate the carbon dioxide from the gaseous stream output for sequestration, and purify the gaseous stream such that the puri fied gaseous stream comprises the hydrogen and the nitrogen . For example , in another embodiment , sorbents or membranes may be used instead of the PSA unit 60 to purify the gaseous stream that enters the Haber-Bosch reactor 70 . In some embodiments , CO2capture technologies such as amines or Rectisol may be used instead of Selexol . Having described the operation of the integrated blue-green production process , its performance will be described below .

[0036] The blue production process of FIG . 1A, the green production process of FIG . IB and the integrated production process of FIG . 2 were simulated using the ASPEN Plus vl2 . 1 simulation software . The models were used to calculate the mass and energy flows through the respective processes , necessary utility requirements , system ef ficiency, and equipment si zing . The models were validated by comparing key performance metrics for each model subprocess against industry numbers . For standalone blue ammonia and the combined blue-green production processes , both meet the two most common reported standards : >90% of the direct CO2emissions are captured and the levelized emissions are within the range 0 . 1 - 0 . 2 kg CO2emitted / kg NH3produced . For green ammonia, the leveli zed electricity usage in the hydrogen production process is taken to be 55 kWh / kg H2in line with industry standards . For all three processes , the feedstock conversion ef ficiencies of the Haber-Bosch process were confirmed to be >90% for H2and >96% for N2.

[0037] Using the outputs from the ASPEN models , the capital and operating costs associated with each production process were computed using the National Energy Technology Laboratory (NETL ) framework and the established NETL and National Renewable Energy Laboratory (NREL) reports as a reference values . Next , the capital and operating costs were fed into the NREL' s Hydrogen Analysis Production Models : H2A model to perform a discounted cash- flow analysis to calculate the levelized cost of ammonia production .

[0038] Emissions are also estimated for each production process and include three maj or components : direct emissions , life cycle feedstock emissions , and life cycle emissions from electricity use . Direct emissions are derived from the ASPEN models , the electricity emissions are derived using the United States Environmental Protection Agency grid distribution data and NREL' s li fe cycle analysis of different electricity sources . For green electricity, emissions are estimated assuming onshore wind as the primary source . Finally, li fe cycle feedstock emissions include accounting for methane leaks when using natural gas . A range of values are considered based on literature reports .

[0039] The leveli zed cost of ammonia ( LCOA) from each process is shown in FIG . 3 . The breakdown into constituent components is displayed as is the impact of green electricity price . In each grouping, the first column represents the conventional blue production process ("ATR CCS" ) ; the second column represents the conventional green production process ("LTE" ) ; the third column represents the new integrated blue-green process ("ATR-LTE Green" ) powered by green electricity . Additionally, the cost of running individual ( separated) blue ammonia and green ammonia plants matching the ratio of the combined blue-green process (pie chart on right ) is also shown in the last column of each grouping for comparative purposes (" Individual ATR and LTE" ) . In the grouping on the left , the fourth column ("ATR-LTE Split" ) represents the embodiment wherein the electrolyzer 80 of FIG . 8 is powered by green electricity but the other components are powered by grid electricity .

[0040] In this graph, "High Green Electricity Cost" refers to $78 / MWh ( an estimate of current industrial price of clean electricity) , "Base Green Electricity Cost" refers to $ 62 / MWh (which is roughly current industrial grid price ) and "Low Green Electricity Cost" refers to $39 / MWh (an optimistic projected future price of green electricity) .

[0041] The cost analysis shows the benefits of the new integrated synergistic design that doesn't require an ASU : in all scenarios, the combined process is less expensive than running individual conventional plants with the same ratio of blue to green ammonia. This can be seen by comparing the third column with the last column for each grouping. The savings are 15.5%, 12.5%, and 10.5% for high, base, and low green electricity costs, respectively. FIG. 3 also highlights the high cost of conventional green ammonia, which is likely to significantly slow deployment. The new synergistic integrated process provides a less-costly way to build industrialscale green ammonia capacity in the mid-term.

[0042] The levelized CO2e emissions are shown in FIG. 4, using the 100-year value when computing the GHG value of methane, and current USA grid intensity when computing the greenhouse gas emissions associated with grid electricity. Levelized CO2e emissions for the conventional blue production process ("ATR CCS Grid") , the conventional green production process ("LTE Green") , and the new integrated blue-green production process (ATR-LTE) are shown. For the blue and integrated blue-green processes, the options of using grid electricity (e.g. "ATR-LTE Grid") or renewable (green) electricity are considered ("ATR CCS Green" and "ATR-LTE Green") . An additional case, where green electricity is used for electrolyzer, but grid electricity is used for the rest of the process is called "ATR-LTE Split". The breakdown into constituent components is displayed as well as the impact of methane leak rate. "High Methane Leak" refers to 35 kgCO2e / MMBTU (5.4 % leak) , "Base Methane Leak" refers to 15 kgCO2e / MMBTU (2.3 % leak) and "Low Methane Leak" refers to 3 kgCO2e / MMBTU (0.45 % leak) . FIG . 4 shows the importance of controlling methane leaks as the viability of blue ammonia as a low-GHG production process depends on this . Both the blue and integrated blue-green production processes have substantial sensitivity to this parameter and have order of magnitude higher emissions than the green ammonia production process i f the methane leak rate is high . However, for low methane leak rates , the emissions of the blue and integrated blue-green production processes are within a factor of two of the green ammonia production process , i f green electricity is used to power those plants .

[0043] A way to simultaneously consider both cost and emissions benefits and tradeoffs is to compute the $ / tonne of CO2e avoided . This metric can be directly compared to other decarbonization alternatives such as direct air capture ( DAG ) to assess the practicality of the integrated blue-green ammonia production process disclosed herein . FIG . 5 most clearly shows the benefits of the integrated blue-green production process . Regardless of the methane leak rate , the additional cost of the new integrated bluegreen production process compared to the conventional blue ammonia production process using grid electricity is always in the range of $ 100 / tonne CO2e avoided, well below the $ 600 - $ 1000 / tonne CO2e avoided reported for DAC . This means that the integrated bluegreen production process is a much more economical way of achieving a desired tonne CO2e / tonne ammonia than running the standard blue ammonia process and using DAC for additional carbon capture .

[0044] As shown in FIG . 5 , with the conventional blue ammonia production process as the baseline , pure green ammonia ("LIE" ) has a very high $ / tonne CO2e avoided, comparable to or more expensive than DAG in two of the scenarios . The high cost is due primarily to the large amount of electricity required and current high electrolyzer prices . This is expected to change with future reductions in renewable electricity cost and electrolyzer / green hydrogen production costs , but these cost reductions are likely to require learning-by-doing at industrial scale . The integrated blue-green production process ("ATR-LTE" ) can provide a valuable transition option, since it involves industrial-scale deployment of electrolyzers and further build out of the 24x7 green electricity system, while simultaneously providing signi ficantly improved environmental performance relative to conventional blue ammonia at a modest cost per tonne of C02e avoided .

[0045] The present system has many advantages . First , by eliminating the air separation unit , a maj or capital expenditure is eliminated . Additionally, this system of fers other benefits . As shown in FIG . 3 , the leveli zed cost of ammonia produced using this integrated blue-green production process is within 10% of the cost of blue ammonia, and substantially less expensive than green ammonia . Further, as shown in FIG . 4 , i f green electricity is used, the total emissions from this integrated blue-green production process are about 10% lower than a blue ammonia process using only green electricity, and almost a factor of two lower than the GHG emissions from conventional blue ammonia using grid electricity . Lastly, as seen in FIG . 5, the cost per tonne of CO2 avoided is far lower (more than 9x at base or low methane leak rates ) for the integrated blue-green system than for the conventional green ammonia production process .

[0046] The present disclosure is not to be limited in scope by the specific embodiments described herein . Indeed, other various embodiments of and modi fications to the present disclosure , in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings . Thus , such other embodiments and modifications are intended to fall within the scope of the present disclosure . Furthermore , although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose , those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes . Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein .

Claims

What is claimed is :1 . A system for producing ammonia, comprising : an electrolyzer to electrolyze water into hydrogen and oxygen; a reforming system configured to receive natural gas , air, and steam, plus the oxygen from the electrolyzer, and output a gaseous stream that comprises at least nitrogen, carbon monoxide , and hydrogen; at least one component downstream from the reforming system to convert the carbon monoxide into carbon dioxide , separate the carbon dioxide from the gaseous stream for seguestration, and purify the gaseous stream such that the puri fied gaseous stream comprises hydrogen and nitrogen; and a Haber-Bosch reactor configured to receive the puri fied gaseous stream and the hydrogen from the electrolyzer and output ammonia, wherein at least 95% of the nitrogen used by the Haber-Bosch reactor is provided by the air introduced into the reforming system .2 . The system of claim 1 , wherein the reforming system includes an autothermal reforming reactor (ATR) .3 . The system of claim 2 , further comprising a compressor in communication with an input air stream from an ambient environment to increase a pressure of the air introduced to the ATR reactor .4 . The system of claim 2 , further comprising an oxygen compressor to increase a pressure of the oxygen from the electrolyzer prior to its introduction into the ATR reactor .5 . The system of claim 2 , further comprising a pre- former, wherein the natural gas and the steam are supplied to thepre-former and the pre-former produces an output that includes natural gas that was not converted, steam, hydrogen and carbon monoxide; and wherein the output is supplied to the ATR reactor.

6. The system of claim 1, wherein the at least one component comprises a water-gas shift (WGS) reactor to convert the carbon monoxide into the carbon dioxide.

7. The system of claim 1, wherein the at least one component comprises a carbon dioxide capture unit to separate the carbon dioxide from the gaseous stream for sequestration.

8. The system of claim 1, wherein the at least one component comprises a pressure swing adsorption (PSA) unit to purify the gaseous stream.

9. The system of claim 1, further comprising a hydrogen compressor to increase a pressure of the hydrogen from the electrolyzer prior to its introduction into the Haber-Bosch reactor .

10. A method of producing ammonia, comprising using an electrolyzer to produce oxygen and hydrogen; introducing air, the oxygen, steam and natural gas into a reforming system to create a gaseous stream comprising at least nitrogen, hydrogen, and carbon monoxide; reacting the carbon monoxide to create carbon dioxide; sequestering the carbon dioxide; purifying the gaseous stream such that the purified gaseous stream comprises hydrogen and nitrogen; and using a Haber-Bosch reactor to react the hydrogen from the electrolyzer and the hydrogen and the nitrogen from the purified gaseous stream to produce ammonia, wherein at least 95% of the nitrogen used in the Haber-Bosch reactor is introduced as air in the reforming system.

11. The method of claim 10, where the reforming system utilizes an autothermal reforming reactor (ATR) .

12. The method of claim 11, further comprising using a pre-former, wherein the natural gas and the steam are introduced into the pre-former, and the pre-former reacts the natural gas and steam to produce an output gas stream comprising natural gas, steam, carbon monoxide and hydrogen, which are then introduced into the ATR reactor.

13. The method of claim 11, further comprising using an oxygen compressor to increase a pressure of the oxygen exiting the electrolyzer prior to its introduction into the ATR reactor.

14. The method of claim 11, wherein the electrolyzer is controlled such that at least 95% of the oxygen produced by the electrolyzer is consumed by the ATR reactor.

15. The method of claim 10, wherein the gaseous stream is purified using a pressure swing adsorption (PSA) unit.

16. The method of claim 10, wherein the carbon monoxide is reacted using a water-gas shift (WGS) unit to create the carbon dioxide.

17. The method of claim 10, further comprising using a hydrogen compressor to increase a pressure of the hydrogen exiting the electrolyzer prior to its introduction into the Haber-Bosch reactor.

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