What is Hydrogen
Hydrogen, with element symbol H, or commonly represented by H2, is a gaseous substance which is the simplest and most abundant element in the universe. Currently, hydrogen is increasingly recognized for its potential to serve as a clean energy carrier [1,2].
The earliest known important chemical property of hydrogen, is it’s capability to burn with Oxygen to form water (H2O).
“Colors” of hydrogen refers to their production method, the most common ones are ‘Grey’ Hydrogen when it’s produced using the SMR process, ‘Blue’ hydrogen when it’s SMR + an accomopanying Carbon Capture Unit (CCS/CCUS), and ‘Green’ hydrogen when it’s produced using renewable energy, such as electrolysis with electricity produced from Solar PV.
Hydrogen production can be classified according to energy source, or it’s main feedstock. [9]
Steam-Methane Reforming (SMR)
Today, 95% of the hydrogen produced in the United States utilizes natural gas, which contains methane (CH4); that can be used to produce hydrogen through thermal processes such as Steam Methane Reformation (SMR) or Partial Oxidation. [13]
The process utilizes high-temperature steam (700°C – 1,000°C) which reacts with methane under 3 – 25 bar pressure. The output of SMR includes production of hydrogen and emissions of carbon monoxide and carbon dioxide.
Additionally, in “water-gas shift reaction”, the carbon monoxide and steam reacts using a catalyst, which produces carbon dioxide and more hydrogen. The final process, which is called “pressure-swing adsorption” removes carbon dioxide and other impurities from the gas stream, which essentially leaves pure hydrogen.
Reaction of SMR and water-gas shift reaction can be seen below:
Steam-methane reforming reaction
CH4 + H2O (+ heat) -> CO + 3H2
Water-gas shift reaction
CO + H2O -> CO2 + H2 (+ small amount of heat)
Electrolysis
Green hydrogen production is commonly associated with hydrogen production from electrical energy, specifically renewable energy. The main method would be water electrolysis. Water (H2O), can be split into both components, hydrogen and oxygen. This reaction requires energy, and it occurs by breaking the molecules apart. [9]
Currently, commercial electrolysers are grouped based on temperature ranges, Alkaline Water Electrolysis (AWE) and Proton Exchange Membrane (PEM) electrolysers operate at temperatures below 100°C ; and for temperatures above 500°C, Solid Oxide Electrolyser Cell (SOEC) is utilized to handle water vapor. [9]
What is Ammonia
Ammonia (NH3), is a chemical compound of nitrogen and hydrogen. About 70% of ammonia is used for synthesis of agricultural fertilizers; and the rest is used in a wide array of industrial chemicals, including plastics and explosives.
When it comes to renewable energy or hydrogen to ammonia, however, ammonia is commonly used as energy storage or carrier. After the process of combining hydrogen gas with nitrogen gas to make ammonia, the reverse is done when Hydrogen is needed. hydrogen can be extracted by heating ammonia to high temperatures. [10]
Ammonia Synthesis
Ammonia produced on an industrial scale has been done for more than 100 years, and yet improvements are always done with efficiency in mind, as its production process is complex and energy intensive. [3]
Ammonia can also be found in nature, almost exclusively in the form of ammonium salts and decomposition of organic matter. In 1908, the Haber-Bosch process was developed, and it still sees use in the industry even today. [4]
In 1913, the first commercial Haber-Bosch synthesis loop was built by BASF in Germany with a production capacity of 30 ton NH3/d. [5]
Haber-Bosch Process
This well known ammonia synthesis loop is currently used for over 96% of ammonia production facilities worldwide, with all the nitrogen obtained in this process coming from air, and the hydrogen from fossil fuels, using natural gas, oil, or coal as feedstock. The sources of hydrogen doesn’t really matter as they can be obtained from green sources as well, and this process won’t be changed for different sources of hydrogen or nitrogen. [3, 6, 8]
The average diagram of ammonia production process can be seen in figure 1. Below:
Figure 1: Ammonia synthesis loop, from [9]
Three main steps are shown above, which are compression, ammonia condensation, and reaction.
Depending on the purity of raw materials, which are hydrogen and nitrogen, continuous purging may be needed in order to stabilize pressure as there may be accumulation of inert in the loop, consisting of methane and argon.
The main challenge for this process is in aligning both the continuous Haber-Bosch process with the intermittency of renewable energy [11] as the ammonia synthesis reactor needs stable operating conditions, where pressure and temperature cycling induce failure modes akin to fatigue, and temperature cycling raises catalyst damage.
JGC has been involved in several projects to produce ammonia from hydrogen, most notable , in collaboration with Japan’s National Institute of Advanced Industrial Science and Technology, utilizing solar PV for water electrolysis, and synthesis of ammonia at low temperature and pressure, generating 47 kW by an ammonia gas turbine. [15]
Additionally, JGC has also developing in collaboration with Asahi Kasei utilizing alkaline water electrolysis system. [16]
Ammonia Storage and Transport
As we’ve already established in the earlier paragraphs, ammonia has many uses, including as a medium for storage of energy. The adaptability of ammonia and ability to store and transport Hydrogen is the true potential.
The containers that can be used to store ammonia ranges from small containers to large storage tanks. The containers can be spherical or cylindrical depending on the storage capacity needed and other requirements such as standards, or safety requirements.
Commonly, storage for ammonia in ammonia production facilities can hold a minimum of 15 days of production, which helps as a buffer capacity to compensate for fluctuations in production and demand between the production unit, and the downstream or distribution units [12].
For long distances and large quantities of ammonia, transport by pipeline is more suitable when compared to transport by barge or rail, although it would be limited to certain locations with existing pipelines.
When means of transport are not available, for distances of less than 150 km, truck transportation is commonly considered although it counts as the most expensive method. In general, the current options for Ammonia transport are ship, barge, pipeline, rail, and truck; with infrastructure, access, and cost as the main considerations.
Sources:
[1] https://ijtech.eng.ui.ac.id/article/view/7171
[2] https://www.britannica.com/science/hydrogen
[3] F. B. Juangsa, A. R. Irhamna and M. Aziz, “Production of ammonia as potential hydrogen carrier: Review on thermochemical and electrochemical processes,” International journal o f hydrogen energy, vol. 46, pp. 14455-14477, 2021.
[4] B. Wang, T. Li, F. Gong, M. H. D. Othman and R. Xiao, “Ammonia as a green energy carrier: Electrochemical synthesis and direct
ammonia fuel cell - a comprehensive review,” Fuel Processing Technology, vol. 235, 2022.
[5] V. Pattabathula and J. Richardson, “Introduction to Ammonia Production,” American Institute of Chemical Engineers (AIChE), pp. 69-75, 2016.
[6] A. K. Hill, C. Smith and L. Torrente-Murciano, “Current and future role of Haber-Bosch ammonia in a carbon-free energy landscape,” Energy Environ. Sci., 2020.
[7] https://www.sciencedirect.com/science/article/pii/S0016236123015132
[8] K. H. R. Rouwenhorst, P. M. Krzywda, N. E. Benes, G. Mul and L. Lefferts, “Ammonia, 4. Green Ammonia Production,” Ullmann's Encyclopedia of Industrial Chemistry, pp. 1-20, 2020.
[11] IRENA and AEA, “Innovation Outlook: Renewable Ammonia,” International Renewable Energy Agency, Abu Dhabi, Ammonia Energy Association, Brooklyn., 2022.
[12] https://ptx-hub.org/publication/ammonia-paper-2-ammonia-transport-and-storage/
[13] https://www.energy.gov/eere/fuelcells/hydrogen-production-natural-gas-reforming
[14] O. ELISHAV, B. M. LIS, A. VALERA-MEDINA and G. GRADER, “Storage and Distribution of Ammonia,” in Techno-Economic Challenges of Green Ammonia as an Energy Vector, 2021, pp. 85-103.
[15] https://www.jgc.com/en/business/hydrogen/#3
[16] https://www.jgc.com/en/news/2023/20230322-3.html#:~:text=3.,for%20fiscal%202027%20and%20beyond.
This article is written by
Fauzaan Radinka Sudrajat
Sales & Marketing staff
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