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Ammonia

Dig into how FastOx gasification produces ammonia, a crucial fertilizer ingredient.

Production

Sierra Energy’s FastOx gasification system utilizes hydrogen, nitrogen, and the Haber-Bosch reaction to produce ammonia (NH3). For ammonia production, syngas is treated via a water-gas shift (WGS) reaction to sequester out the hydrogen. Once it has run through the WGS reactor and the appropriate purity has been obtained, nitrogen is introduced and the following catalytic reaction takes place:
 

3 H2 + N→ 2 NH3

 

Sometimes called the Haber ammonia process, the Haber-Bosch process was the first industrial chemical process to make use of extremely high pressures of approximately 5,000 PSI. In addition to high pressures, the process also uses high temperatures of about 400°-650°C (750-1,200°F). The efficiency of the reaction is a function of pressure and temperature in that greater yields can be produced at higher pressures and lower temperatures within the necessary range.
 

The Process

In order to produce ammonia, pure nitrogen gas and hydrogen gas must be obtained and cleaned of impurities. Nitrogen can be obtained from ambient air, which is 78% nitrogen by volume, and the hydrogen is be provided by the syngas generated from gasification.
 

Next, these two gases are mixed and the mixture is compressed until the pressure reaches roughly 200 atmospheres. The compressed gas is then pumped into the converter, where it flows over beds of iron catalysts kept around at least 450°C (840°F). The reaction listed above is reversible, so these catalysts push the reaction towards the production of ammonia. The exact pressure and temperature requirements vary for every individual process and are system-specific.
 

Only 15% of the total mixture is converted into ammonia in a gaseous state. The mixture of ammonia gas with the unreacted nitrogen and hydrogen gases then flows into a cooler, where the ammonia gas condenses into a liquid and separates from the stream. The liquid ammonia is collected and the remaining nitrogen and hydrogen gases are recycled back to the converter to create more ammonia. This recycling practice within the Haber-Bosch process is called the ammonia synthesis loop. With the collection of liquid ammonia and recycling of remaining gases from the ammonia synthesis loop, an overall conversion of 97% can be achieved.

Production via FastOx Gasification

The ammonia output of a FastOx system depends on many factors such as the feedstock, plant configuration, and other plant specifics. For post-recycled municipal solid waste, FastOx systems would produce an estimated 300-450 metric tons of ammonia per metric ton of feedstock in small scale projects.
 

It is recommended to use our online calculator to see other ammonia outputs for different waste materials and capacities.

 

Impact and Potential

Ammonia is an important chemical compound because it is the primary ingredient in chemical fertilizers. Without it modern agricultural yields would be unattainable. Currently, over 400 million metric tons of ammonia are produced every year. The major source of hydrogen required for the process to operate currently comes from the methane in natural gas via steam reforming conducted with air deoxygenated by the combustion of natural gas.
 

Using FastOx gasification to produce hydrogen gas instead of relying on methane from natural gas (a fossil fuel) helps reduce greenhouse gas emissions. In addition, ammonia production requires energy-intensive processing conditions, the likes of which are typically only achievable at large-scale, centralized facilities. The scaling capabilities of FastOx gasification allow for the production of ammonia to happen at small scales in a localized, distributed manner, ultimately helping to reduce the transportation and operating costs behind conventional ammonia synthesis.
 

In essence, our system provides a more environmentally-friendly solution for ammonia production.

 

Equipment

The production of ammonia from FastOx gasification is essentially an expansion of a hydrogen production back-end system. The Haber-Bosch process requires high purity hydrogen gas as primary ingredient. FastOx gasification can readily provide high purity hydrogen, and nitrogen is readily produced onsite via an air separation unit. The full FastOx system for ammonia production will include a FastOx gasifier, a back end system for hydrogen production, and additional Haber-Bosch equipment.
 

The Haber-Bosch process requires the use of the following equipment:

  • Pumps
  • Compressors
  • Catalysts
  • Coolers (Heat Exchangers/Condensers)
  • Storage tanks