The Haber-Bosch Process - Methane
On Sept. 9, 1913, BASF constructed the first commercial ammonia plant based on the Haber process in Oppau, Germany. This invention ushered in a new era in human history, and in the century since its inception, over 175 million metric tons of ammonia are produced annually, with an estimated market cap of over $100 billion.
This process is comprised of six major steps which include: reforming, gas-shifting, carbon dioxide scrubbing, dehydration, methanation, and ammonia synthesis.
Reforming – natural gas is reacted with steam at high temperatures to form syngas, which is a mixture of carbon monoxide, carbon dioxide, and hydrogen. This is typically conducted in two phases, with the remaining methane being reacted with air in the secondary reformer. The secondary reformer is also when nitrogen is introduced into the process.
Gas-shifting – carbon monoxide is shifted to carbon dioxide through the use of both a high temperature and low temperature water-gas shift reaction. This allows for an easier separation of carbon from the process as carbon dioxide can be readily scrubbed from the gas stream.
Carbon dioxide scrubbing – carbon dioxide is removed from the stream, as both carbon dioxide and carbon monoxide have the potential to form solid carbamates in the ammonia synthesis reaction. Amine circuits are commonly used to remove carbon dioxide from these gas streams.
Dehydration – the stream undergoes a dehydration step to remove excess moisture.
Methanation – residual traces of carbon monoxide and carbon dioxide are reduced to methane in the presence of a metal catalyst to ensure neither will be present in the synthesis reaction.
Ammonia synthesis – N2 is reacted with H2 at high pressures to form NH3. A separation unit combined with a purge and recycle stream is employed in this operation to increase the plant’s overall yield.
This process is both energy intensive and costly to run; therefore, ensuring that the process operates within specifications is crucial to maintaining a plant’s overall bottom line. Sulfur for example, is a catalyst poison for most water-gas shift reactions, therefore ensuring that sulfur is not present in the stream is crucial to the longevity of the catalyst found in the water-gas shift reactor. Continuously monitoring this with inline solutions such as ultraviolet absorption spectroscopy that enable plant operators to correct for sulfur breakthroughs as soon as possible. For example, Applied Analytics’ OMA-300 has a response time of 1-5 seconds depending on the application, whereas a GC option could be as much as 20 minutes. That is almost 250 times longer.
Moreover, spectrometers, like AAI’s OMA-300-InGaAs, which include multicomponent functionality, can measure multiple components at once with a near instant response time. This is particularly helpful for locations after the reformers or water-gas shift reactors, where it can be used to monitor carbon monoxide, carbon dioxide, and moisture levels at once. This allows plant staff to have a real-time window into their reactor and make any adjustments as needed without delay.
Other measurements such as carbon dioxide levels found after gas-scrubbing and methanation can help ensure that no potential poisons will enter the ammonia reactor. An NDIR photometer, like Applied Analytics’ MCP-200, is both a proven and reliable solution for measuring this reactor poison. Likewise, if catalysts do lose performance, an ammonia analyzer like Applied Analytics’ OMA-300, is an excellent tool to detect a loss in conversion across an ammonia reactor. These trends can also be further corroborated with hydrogen measurement after the reactor. A good example of this type of system would be AAI’s APG-710. If you would like to learn more about one of these applications or have one in mind that is not listed here, then reach out to the AAI team today, and let us provide you with a window into your process.
