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Ammonia is one of the most widely used chemicals that is commercially produced today given the wide need for fertilizer to sustain the world’s ever-growing populations. Given the high world demand for ammonia, which increases every day, one can see how beneficial to the environment that a zero emission large-scale ammonia plant would be. Through the use of energy from Norwegian wind farms, which produce an excess of energy during off-peak hours, our plant design seeks to turn this wasted energy into useful ammonia products at a production rate of 67.2 kmol/hr.
The design of this ammonia synthesis plant can be split conceptually into two distinct halves. The first is the refinement of the hydrogen and nitrogen that are required for the Haber-Bosch synthesis from the raw inputs of air and water. This is done through the usage of solid oxide electrolytic cells which electrolyze the water into constituent hydrogen and oxygen atoms and separate the oxygen out of the air. The second half of the plant design is a typical Haber-Bosch ammonia synthesis that many plants today are utilizing. This section consists mainly of a reaction vessel at the correct operating conditions for the ammonia synthesis reaction to occur, and a series of separators that recoup the liquid ammonia product at the right conditions for storage while recycling the gaseous hydrogen and nitrogen reactants.
While this plant design provides a layout to accomplish the task of producing ammonia in an environmentally friendly way, it is less friendly to the wallet of the plant owner. Selling the ammonia product at current market rates of $853/ton, it would take roughly 15 years for the plant to overcome the capital investment of the venture and become a monetarily net positive design. Current utility prices are projected to cost the plant over $1.7 million dollars per year, which is another significant consideration why it takes such a large amount of time for the plant to become profitable.
It is our hope that ongoing refinement of solid oxide electrolytic units will enable their purchase at cheaper rates, and that as the environment worsens, a higher premium will be placed on chemical products that have been sourced renewably, both factors that could easily make this plant design a more viable option in the future than it currently is today.
Date Posted: 11 May 2020