Green and Blue Ammonia

January 2019
Blue Ammonia
Ammonia has been manufactured for the past century using the Haber-Bosch process into which are fed nitrogen and hydrogen gas streams. At the right temperature and pressure, and in the presence of a catalyst, ammonia is produced. Traditionally, Haber-Bosch processes are fueled by hydrocarbons and release a lot of carbon dioxide. Blue ammonia is defined as ammonia produced by this traditional process however with the addition of CCS (Carbon Capture and Storage) to sequester all of the carbon dioxide generated rather than allowing it to enter the atmosphere. Achieving effective and permanent CCS will be very challenging due to the technical issues, energy consumption and high cost. There are some proposals to “sequester” the CO2 into existing oil wells and in doing so, achieve enhanced oil recovery (EOR) however this would seem to be counterproductive from an environmental point of view as it releases more hydrocarbons to be burnt in the future. Therefore blue ammonia production will probably be an interim solution only, until green ammonia production can be brought on line.
Green Ammonia
Green ammonia can be manufactured in the Haber-Bosch process using renewable energy rather than hydrocarbons. This will result in no CO2 emissions. Renewable electrical energy is used to separate hydrogen from water with electrolysers and separate nitrogen from air with air separation units. The bulk of the energy input is used to generate the hydrogen whilst a minor part is used for the air separation and Haber-Bosch processes. There are a number of pilot green ammonia plants operating in several countries.
It is likely that any new large scale green ammonia production plants will operate on the Haber-Bosch system. These systems operate most efficiently and produce lowest cost ammonia when they are continuously supplied with renewable electrical energy. Therefore the best forms of continuous renewable energy for green ammonia production are likely to be hydroelectricity, geothermal electricity or similar. Manufacturing ammonia from intermittent forms of renewable electrical energy (solar, wind, wave, tidal etc.) will be viable, but less efficient. It may be possible to use a combination of two or more of these intermittent sources to provide a virtually continuous supply and thereby improve the efficiency.
Green ammonia is the most likely contender to fulfil future global non-nuclear, carbon-free energy requirements in areas including:
– A vector to transport hydrogen over long distances
– An internationally traded energy commodity
– Grid scale energy storage
In the next instalment we will discuss ammonia as an internationally traded energy commodity.
Until then
Kind Regards

Ammonia & Fuel Cells

January 2019

PEM Fuel Cell Electric Vehicles
A number of the world’s leading automobile manufacturers have commenced making Fuel Cell Electric Vehicles (FCEV’s) in recent years. These vehicles have PEM (Proton Exchange Membrane) fuel cells which are fueled by hydrogen gas carried on board in high pressure gas tanks. The fuel cells provide a very efficient conversion of the energy contained in the hydrogen fuel, into electricity to propel the vehicle. This conversion efficiency is much higher than that achieved using the hydrogen fuel in an internal combustion engine and it is therefore likely that the FCEV’s will be the carbon free way forward rather than hydrogen fueled combustion engines. The leading manufacturers of FCEV’s are:
– Toyota with their Mirai
– Hyundai with their Nexo
These FCEV’s have high pressure 700 bar hydrogen gas tanks on board to achieve a reasonable energy density. The vehicles can be re fueled from a hydrogen filling station in several minutes and when full, hold around 5 or 6 Kg of hydrogen, which gives them a range of 500 to 800 km.
Liquid hydrogen fuel is generally not commercially viable due to the amount of energy it takes to liquefy it. Liquefaction consumes about one third of the hydrogen energy stream which means only about 66% comes out as liquid and the rest is lost. This is due to the fact that it must be cooled to well below the critical point (-240C) to about -253C (20K) and this process is very energy hungry and expensive. Consequentially the hydrogen FCEV’s use high pressure compressed hydrogen gas tanks rather than cryogenic liquid hydrogen tanks.
Ammonia is a very good carrier of hydrogen and is easily and cheaply liquefied (+132C critical point) to provide a much higher transportable energy density than hydrogen gas. In August 2018, the CSIRO in Australia demonstrated it’s groundbreaking technology which is able to provide high purity hydrogen gas derived from ammonia to re fuel the FCEV’s. This technology provides a system to crack the hydrogen out of the ammonia then put it thru a metal membrane filter to achieve very high purity hydrogen to comply with the FCEV manufacturers specifications.
This CSIRO development paves the way for hydrogen to be shipped , stored , transported and distributed to the fueling stations as ammonia liquid, and then the hydrogen is cracked and filtered from the ammonia at the fueling station to re fuel the FCEV’s. This will be a far more efficient and cost effective way of distributing the hydrogen than the existing system of using hydrogen gas tube tankers.
Solid Oxide Fuel Cells
In 2017 the Green Ammonia Consortium was formed in Japan and now involves 28 companies. One of the priorities of this consortium is the development of a solid oxide fuel cell which will run directly on ammonia. There is rapid progress on this project and they already have prototypes operating in the lab. The aim is to produce a commercially viable fuel cell with at least similar efficiencies to the PEM fuel cells. Once this new fuel cell is developed, it will open a multitude of options for ammonia energy in areas including transport and electricity generation. We will watch this exciting development with great interest.
In the next instalment we will discuss the manufacture of green and blue ammonia.
Until then
Kind Regards