Sinclair Energy Partners Limited, Dundee, Angus, United Kingdom
Abstract
Ammonia is a dense energy carrier with high energy density and established supply chain for transport, and storage of hydrogen. Ammonia is a common commodity used in the fertiliser and chemical sector and has a potential to become an affordable and sustainable energy carrier to meet growing demand for industrial decarbonisation. The transport of hydrogen over long distances require an efficient and cost competitive carrier. Potential options for hydrogen carrier are ammonia, liquid organic hydrogen carrier (LOHC), liquid hydrogen, compressed hydrogen, and methanol. This paper describes an innovative ceramics-based solid oxide fuel cell technology for conversion of ammonia into fossil fuel parity energy at a thermal efficiency of 85%. The technology is based on proton conducting ceramics (PCC) electrochemical pathway which eliminates NOx emissions by design and ammonia slippage by catalyst performance and reactor design. The technology has been developed over 7 years, between 2016 to 2022, and the ammonia utilisation capabilities has been proven through demonstrations conducted for O&G and industrial companies. The technology uses low-cost and widely available ceramics-based catalyst. The technology is particularly suited for industrial decarbonisation because of the ability to yield high efficiency and the ability to produce low-cost heat at 700C and hydrogen as byproducts.
Introduction
There is a rising demand for clean energy as a result of the global drive towards industrial decarbonization and energy security. Ammonia is a commonly used chemical in the fertiliser and chemical sector. Ammonia has the potential of becoming a mainstream clean energy vector in global energy market owing to the high energy density, ease of transportation and storage, and an existing global supply chain. These advantages bridge the gap and offer complementary benefits to the adoption of hydrogen for providing carbon free energy at the point of consumption in industrial facilities.
Even with all the benefits, the adoption of ammonia as an energy carrier or clean fuel faces a few challenges, which deteriorate the economics of energy generation in the form of heat, electricity or hydrogen. The key challenge with converting ammonia into usable power, either by combustion or fuel cells is the abatement of NOx emissions. Combustion of ammonia produces high level of NOx emissions, owing to the low flammability. The removal of NOx emissions requires installation of scrubbers and treatment facilities, which increase both CAPEX and OPEX for the gas separation and treatment process.
The second key challenge associated with using ammonia as a fuel for combustion or with a fuel cell is the risk of ammonia slippage. The risks and consequences associated with slippage of Ammonia into the environment, or the downstream process are high, due to the toxic characteristic of ammonia. There are several ammonia cracking technologies commercially available, however none of these have achieved complete conversion of ammonia into byproducts, such as nitrogen, steam or hydrogen. There is a gap in the market for commercial products which offer complete conversion of Ammonia into usable products, e.g. energy (hydrogen) or by products (nitrogen and steam). The challenge of ammonia slippage can be addressed by installing catalytic converters, however this increases the CAPEX and deteriorates the economics for generating power from Ammonia.
Lastly, there are few emerging ammonia fuel cells and ammonia cracker technologies which solve the above-mentioned challenges, however these technologies use high cost and high carbon intensity catalyst metals such as ruthenium, palladium and cobalt. This increases the CAPEX of the product and also poses challenges in the ability to scale for industrial applications.
There is a growing interest within the United States of America and Europe to reduce the dependence on critical metals imported from developing countries. There is a need for a technological solution which solves the abovementioned challenges with converting ammonia into power and uses catalysts and other critical raw materials which can be sourced economically within the United States of America or Europe.
Development of an affordable and scalable solution is key for industrial decarbonization. Majority of the industrial energy consumption is in the form of heat and there is a need to decarbonise heat in a sustainable and affordable manner.
These challenges prohibit the use of ammonia as an affordable energy carrier. A technological solution which solves these technical challenges and offers strategic alignment with the priorities outlined by G7 countries is the ability to build an Ammonia utilisation system which converts ammonia into fossil fuel parity energy, uniquely positioned to benefit from the large demand for clean energy as well as the abundant supply of ammonia in the global market. There is >10 million tonnes of ammonia production capacity available globally and a large pipeline (>50GW) of green ammonia projects2 coming onstream over the next 10-20 years.
The paper describes a novel technology and a production technique for manufacturing tubular reactors which convert ammonia into grid parity energy in the form of clean energy and high-quality heat (at 700C). The technology has been proven to achieve complete conversion of ammonia into green energy products and does not produce any NOx emissions nor ammonia slippage. The catalyst is made of low-cost ceramics which is manufactured and sourced within the United States of America.
The ammonia utilisation technology is called CAPTAIN (Clean Ammonia To Power Technology For Assets and Industries).
CAPTAIN product is based on solid oxide fuel cell (SOFC) technology. SOFC is among the three key electrochemical processes for hydrogen processes. Electrolysis of water to produce green hydrogen can be obtained by three processes, alkaline electrolysis, PEM (proton exchange membrane), SOEC (solid oxide electrolysis). Solid oxide technologies has two applications, SOEC for electrolysis of water to form hydrogen and SOFC to convert hydrogen into power in the form of electricity and heat. SOFC technology has been used to convert fuels such as ammonia, hydrogen and methanol into energy1.
CAPTAIN technology is well positioned to provide affordable green energy for industrial decarbonization. Industrial end users can directly absorb the energy outputs from the system, without incurring energy losses with subsequent conversions of one form of energy into another. The direct utilisation of the heat from CAPTAIN technology offers an overall thermal efficiency of 85%, which enables delivery of fossil fuel parity energy to industries.
The technology is highly competitive given the global drive towards urgently needed green energy and the move away from fossil fuels. Hydrogen is very rapidly becoming a green energy carrier of choice, mainly as a fuel for electricity generation via fuel cells or industrial heat. CAPTAIN technology eases the burden, high cost and complexities associated with transporting and storage of hydrogen. The ability to transport and store ammonia to the point of consumption and thereafter conversion into hydrogen and heat has the potential to reduce the total cost of hydrogen across the value chain by 45%.
The key strength of the technology is the high efficiency as a result of steady and long-term operation of the high temperature electrocatalytic reaction. This provides fossil fuel parity green energy to the industrial end user. The scale-up of the technology would require access to large storage capacity of ammonia as well as ensuring that the relevant HSE and certifications are in place. The industrial segment is perfectly suited to provide both the large-scale storage of ammonia as well as access state-of-the-art safety equipment and framework adopted in the industrial site.
Figure 1 describes the core advantages and advancements of the technology.
The CAPTAIN technology is well suited for industrial decarbonisation by providing affordable green energy and high-quality heat for high temperature processes. Industries such as steel manufacturing run on processes which require a temperature >1,000C and use hydrogen as a feedstock for reduction of iron, known as direct reduced iron (DRI) process. The CAPTAIN technology provides usable green energy at 700C, which would significantly reduce (at least by 70%) the fossil fuel consumption or green hydrogen, and eliminate equivalent cost of fuel, which could be fossil fuel or hydrogen. The Hydrogen produced can be used to meet the combustion requirements for generation of heat >1,000C, which offers the capability to achieve complete decarbonization of industrial infrastructure. The chemicals, petrochemicals and refining sector also have a high demand for both hydrogen as a feedstock and heat. The application of the technology also stretches to wider industrial portfolio such as utilities, power generation, glass manufacturing, wastewater treatment, cement, and concrete.
Methods, Procedures, Process
The core electrocatalytic reactor for the ammonia utilisation product takes ammonia and air as an input, and provides three outputs namely electricity, hydrogen, heat as an output. Heat is produced in the form of hydrogen, air, steam, and nitrogen at a temperature of 700C.
The process does not produce any NOx or ammonia in the outlet stream.
The hydrogen production can be fed directly to industries such as DRI (direct reduced iron) steel manufacturing. The stream of hot air is fed directly to the industrial end user at 700C.
The combination of hydrogen and heat and a temperature of 700C can be fed to industrial plants which require combustion as an application. Industrial companies require heat in the range of 500C to 1,200C. Heat constitutes 65-85% of the total power demand in an industry. An as example, direct reduced iron (DRI) require a temperature of 1,200C. The ability to provide hydrogen and air at the temperature of 700C as an input to the DRI process reduces the amount of energy input and cost of energy by 58%. This significant reduction in energy and cost structure allows green ammonia to be converted into hydrogen and heat at cost parity with fossil fuels.
The balance of plant requires electricity and water as an input. Electricity is required to run the system and water is needed to extract heat from critical heat sensitive components and is converted to steam as a byproduct. The balance of plant also consists of a pre-heater to heat the inlet Ammonia and air from the outlet gases as well as enable utilisation of any waste heat from the industrial process1.
The CAPTAIN ammonia utilization product is based on an electrocatalytic process, as summarized in Figure 1. Ammonia is fed to the anode and dissociates into nitrogen and hydrogen, and air is fed through a separate cathode channel where the oxygen is combined with protons and thereafter converted to steam.
The SOFC system is based on a tubular stack design as shown in Figure 2.
Figure 3: Form factor and tubular reactor design
Ammonia is converted in the core electrocatalytic reactor to nitrogen and hydrogen as a single-step cracking process. The CAPTAIN technology is based on proton conducting ceramics (PCC), which allows protons to pass through the solid electrolyte, as illustrated in Figure 2. The hydrogen dissociates into proton which goes through the electrolyte and the electron is passed through the current collectors.
The streams of air and ammonia are in two separate compartments. Since there is no mixing between the air and ammonia streams, there is no NOx emissions from the system. The product has been tested that the outlet stream is free of ammonia slippage. The ammonia is completely dissociated into nitrogen and hydrogen in the first half path length of the tubular reactor. The remaining path length converts the energy from hydrogen into heat and electricity.
The overview of electrocatalytical process is summarised in Figure 5. The process consists of three steps for ammonia dissociation and conversion of hydrogen derived from ammonia into heat and electricity.
The CAPTAIN ammonia utilisation product has three outputs, namely electricity, high quality heat and hydrogen. The product can be tuned to meet the requirements of the industrial end user. The amount of electricity generated is expected to be minimal, in the order of 0.0078A against a cell voltage of 970mV, as shown in Figure 3. The heat output is 0.37kWh per kg ammonia, and the remaining energy will be released in the form of hydrogen. The heat losses are in the form of thermal losses to the ambient environment and the energy needed for ammonia endotherm. The combined heat losses are 0.49kWh per kg of ammonia. The outputs can be tuned to maximise hydrogen production or increase the heat output, as per the requirement of the industrial end user. The output can also be tuned during operation, which at scale, would allow the industrial end user to manage any intermittency expected from the use of renewable power.
The technology benefits from a high efficiency of 85% because of the high process temperature at 700C. All the electrical losses and other types of energy losses are contributing to the heat energy coming out from the system at 700C. The mass flow controllers adjust the flow rates to maintain the system at 700C. The only losses in the system are the Ammonia endotherm and the heat losses from the outer casing. The reactor vessel has insulation to retain majority of the heat in the system. The outer casing has a surface temperature of 70C and the low-quality heat (at 70C) is liberated into the environment. Other than these two losses, all the heat energy from Ammonia is converted into power and the high-quality heat at 700C.
This unique phenomenon attributed to the high operating temperature enable the CAPTAIN technology to have an exceptionally high thermal efficiency of 85%. The high thermal efficiency enables us to deliver fossil fuel parity energy from ammonia to decarbonise the iron and steel industrial sector.
The ammonia utilisation technology has been tested extensively over the last 2 years, to ensure the catalyst stability, durability, thermal endurance and performance. The current test rig is based on a capacity of 5.5kg/day of ammonia consumption. There is an ongoing effort to build a system with larger production capacity to 100kg/day in the short-term, followed by an industrial demonstrator of 500kg/day capacity in 2024.
The commercial product deployed in the industrial facility will have a capacity of 5.4Tonnes/day of ammonia. Our roadmap has stacked the development, system integration and certification workstreams in parallel, to deliver a commercial product of 5.4Tonnes/day ammonia consumption capacity and ready for deployment in 2026.
The technology has gone through rigorous testing and development of the core catalyst reactor, backbone manufacturing process and QA for fabricating the ceramics based catalyst and the associated manufacturing process for high temperature electrocatalytic reactions. After a number of iterations, tubular form-factor has been selected as the best design for the reactor to allow the scalability needed for industrial applications.
The tubular reactor product is developed and manufactured in a 7,000 sq ft state-of-the-art laboratory and production facility. The facility is designed to convert the raw catalyst powder into finished tubular reactor product, in seven stages as listed below.
1. Catalyst powder QA/QC
a. Testing porosity, thermogravimetry, differential scanning calorimetry, pore structure and material characterization
2. Catalyst slurry
a. Controlled mixing of catalyst power, binding agents and reagents in a roller mill.
b. Rheology testing
3. Extrusion of tubes
a. Extrusion of the slurry to make tubes for a range of diameters (1cm to 3cm) and length (20cm to 1m)
4. Heat treatment
a. Thermal treatment of the tubes to 1500C
5. Electrode coating
a. Coating of anode layers
6. Heat treatment
a. Intermediate heat treatment is furnace between two successive rounds of coating
7. Assembly
a. Assembly of connectors, seals, current collectors and the housing
The product facility is equipped with equipment and infrastructure to deliver the following capabilities.
· Catalyst formulation and testing capabilities
· Electrolyte and electrode composition optimisation
· Thermogravimetric analysis
· Electrolyte slurry processing
· Catalyst slurry XRD elemental characterisation
· Dip coating facility for electrolyte and electrodes
· Reactor tubes porosity and conductivity
· Large scale heat treatment (5m2 surface area)
· Single cell testing
· Complete tubular product stack testing
The ceramics based proton conducting catalyst have shown high protonic conductivity and good stability under high temperature environment and exposure to a range of industrial gases including ammonia, carbon dioxide, argon, nitrogen and oxygen. The excellent chemical stability of the proton conducting perovskite makes the electrolyte an ideal candidate to be used for the simultaneous cracking of ammonia and electrochemical oxidation of hydrogen. The electrolyte is made of proton conducting solid ceramics.
The technology is based on proton conducting ceramics (PCC). The ammonia utilisation technology has distinct advantages due to the very advanced core technology. We have also tested catalyst material based on ruthenium and other rare earth metals. The proof-of-concept testing concluded that these catalyst recipes can crack ammonia into hydrogen at a temperature range of 250C to 350C, however the evaluation of commercial and supply chain does not suit the requirements for the scale and capabilities needed for industrial decarbonization. Ruthenium is an expensive catalyst and there is uncertainty around the scalability of ruthenium production.
The electrodes have been developed primarily with the goal of achieving long-term durability and stability in an industrial environment. The electrodes compositions have been optimised to improve cell efficiency by reducing total cell resistance (less resistance = higher flow = higher performance). This could be done by optimizing the pore volume ratio of the electrode coating on the electrolyte. The materials composition expertise implemented in the project led to successful pore volume ratio optimization of the electrolyte1.
The tubular reactor has been tested for a total time of 468 hours to ensure the catalyst performance and degradation. The scanning electron microscope (SEM) examination of the catalyst and electrolyte did not show any degradation. The exhaust gases were analysed through an online mass spectrometer to confirm there are no emissions related to NOx and ammonia in the outlet stream.
The tubular reactor has a commissioning and start-up routine which lasts for 24 hours. The commissioning and start-up routine must be followed the first time the system is started. The commissioning operation is not needed for cold starts thereafter. The only procedure for a cold start is a gradual build-up of the temperature at a rate of 10C per minute.
In comparison to another public sector funded project, such as ShipFC project in EU, the proposed technology offers higher process and cost efficiency. The ShipFC project is led by a consortium of 14 companies and institutions. The catalyst module for post processing of the NOx emissions is being developed by the Fraunhofer Institute. The project will deliver a scalable system for decarbonisation of the maritime sector.
During commissioning of the SOFC system, the reactor cell must be reduced by passing a mixture of equal flow rate of Hydrogen and Nitrogen. The exposure to hydrogen results in reduction of the oxide later inside the catalyst tube. The exposure to high temperature and nitrogen results in removing any moisture or in the system and remove any other gaseous impurities. This reduction of the oxide layers inside the electrolyte prepares the cell for ammonia cracking and utilisation. The process ensure that the flow path remains clean of any air or oxygen trapped in the reactor stack or the balance of plant.
The CAPTAIN technology is a perfect fit for technical and commercial needs for industrial decarbonisation, as well as providing a strategic fit in terms of in-country manufacturing and supply chain security. CAPTAIN technology provides affordable green energy and high-quality heat for high temperature process of steel manufacturing which require a temperature >1,000C and use hydrogen as a feedstock for reduction of iron, for direct reduced iron (DRI) process. This would significantly reduce (at least by 70%) the fossil fuel consumption and the associated carbon footprint for DRI steel manufacturing sector. The hydrogen produced can be used to meet the combustion requirements for generation of heat >1,000C, which offers the capability to achieve complete decarbonisation of the iron and steel industries.
Similar to the strategic petroleum reserves held by the Government, the technology offers a long-term strategic opportunity to store ammonia as a power generation source. In specific states with high penetration of renewables and the intermittency on the grid, the ammonia utilisation pathway offers an opportunity to provide stable power near the point of consumption.
Our strategy is to prioritise industrial plants with applications for direct usage of the green energy and heat integration at 700C. These applications will benefit from a net thermal efficiency of 85%. For industrial applications which require conversion of Hydrogen to heat will also benefit from the high efficiency, at the capital expense of installing Hydrogen ready burners. Our goal will be to target demand for industrial heat and hydrogen.
The economics are very attractive for converting ammonia into hydrogen and heat. Assuming a conservative cost of bulk ammonia at $700/ton, the cost Hydrogen generated at the point of consumption is expected to be $3.6/kg. As the cost of ammonia reduces, the cost of hydrogen will decrease proportionally. The cost of hydrogen $3.6/kg at the point of consumption in the industry is highly attractive, as compared to the cost of hydrogen generation, transportation and storage.
The market assessment has concluded that the cost of green ammonia for a long-term (10 year) offtake is in the range of $500-900/Ton. The cost of hydrogen is expected to be in the range of $2.2-3-9/kg.
Although the market price is much higher than the cost of producing ammonia, there is an opportunity for large petrochemical and O&G companies to utilise their ammonia production for decarbonisation their industrial assets such refineries and petrochemical plants.
The CAPEX of manufacturing the tubular reactors is highly competitive at $518,000 per MW, as compared to alternative technologies such as CCGT. The costs have been estimated based on the current equipment, labour and overheads needed for fabrication of 5.4T/day ammonia consumption system. The estimates for the balance of plant and estimated based on preliminary cost estimations by an EPC contractor. With scale-up, factory automation and implementing Industry 4.0 solutions, the CAPEX is expected to reduce by 35% by 2028.
The product will be manufactured and assembled in United Kingdom and United States of America. All critical raw materials sourced, most importantly the catalyst, binders and reagents will be sourced within the United States of America.
The technology offers an attractive, market ready, strategic and cost competitive solution to industrial decarbonisation by providing Hydrogen and high-quality heat.
Results
One of the largest challenges with developing of the Hydrogen economy is that need for large scale Hydrogen storage and transport infrastructure. The production of Green Hydrogen by conventional electrolysis techniques (e.g. PEM, Alkaline, SOEC) needs to be situated in regions with access to large-scale renewable electricity. Due to low density, the transportation of Hydrogen requires low temperatures (-253C) or high pressure (700bar). The business case for using ammonia is the high volumetric density, ease of transportation and the ability of leverage existing standards and supply chain. Ammonia can be stored and transported at -33C or a pressure of 14bar. The ability to use ammonia as the carrier of clean energy has the potential to significantly accelerate the adoption of hydrogen and delivery of high-quality heat for industrial processes. The ammonia solid oxide fuel cell technology offers an opportunity to convert ammonia into hydrogen, heat and electricity at a system level efficiency of 85%. The high efficiency reduces the cost of green energy products and will accelerate the pace of industrial decarbonisation and availability of large-scale hydrogen at the point of consumption.
Next Steps
The next steps in the development, maturation and scale-up of the technology is to deliver a scalable pilot at an industrial site. The key technological gaps are the balance of plant design, complete system level modelling and optimisation, and long-term testing to demonstrate the resilience of SOFC systems.
One of the largest gaps is the lack of regulatory framework on adoption of ammonia as an energy source. The regulations only exists for production and transportation of ammonia. There is a need to build a robust framework for qualification and certification of ammonia SOFC systems for the production of hydrogen and high-quality heat.
The technology will be scaled up to a capacity of 5.4T/day of ammonia for deployment in an industrial environment. The production facility will be designed to fabricate modular products, with the capacity of eaach product being 5.4T/day for first generation product. The second generation product is expected to have a capacity of 25T/day ammonia consumption.
Conclusions
The solid oxide fuel cell technology offers a highly competitive and efficient approach to deliver ammonia driven fossil fuel parity clean energy for industrial decarbonisation and contribute to energy and supply chain security. The technology uses high efficiency leveraging local sourcing of catalysts and in-country manufacturing of reactors. The ability to eliminate the challenges of NOx emissions and ammonia slippage paves the way for rapid penetration in the industrial segment.
The cost of low carbon ammonia produced within the USA has the potential to deliver hydrogen in the range of $1/kg to $3.6/kg at the point of consumption at an industrial facility.
The low cost widely available ceramics based catalyst converts ammonia into high quality heat at 700C and hydrogen at an overall thermal efficiency of 85%.
The technology offers an affordable, scalable, and sustainable pathway towards industrial decarbonization. We plan to deliver a pilot demonstration system in an industrial facility of 500kg/day capacity in 2024 and a commercial product of capacity 5.4T/day in 2026
Acknowledgements
The author would like to acknowledge the support, steer and commercialisation expertise provided by Shell International Exploration and Production at early stages of development. The author would also like to acknowledge the expertise and support provided by Joe Powell from the Energy Transition Institute in the University of Houston.
The author multidisciplinary development team, systems engineering team and scientists involved in the development and maturation of the bioelectrochemical process. The author would also like to express sincere thanks to the industrial partners and water companies who have offered support for initial demonstration and scale-up of the technology.
Abbreviations
· PCC: Proton conducting ceramics
· SOFC: Solid oxide fuel cells
References
1. C. Herradon, L. Le, C. Meisel, J. Huang, C. Chmura, Y. D. Kim. Proton-conducting ceramics for water electrolysis and hydrogen production at elevated pressure; Front. Energy Res., 06 October 2022, Sec. Hydrogen Storage and Production, Volume 10 – 2022
PV Magazine Australia “Historic 50 GW renewable hydrogen hub proposed for WA” https://www.pv-magazine-australia.com/2021/07/13/historic-50-gw-renewable-hydrogen-hub-proposed-for-wa-by-consortium-behind-recently-rejected-project/ (accessed June 28, 2023)
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