(538y) Electrochemical Conversion of Waste Nitrate to Hydroxylamine

The manufacturing of nitrogen-based chemicals is dependent mainly on the Haber-Bosch process, which produces cheap ammonia (NH₃) from hydrogen (H₂) and atmospheric nitrogen (N₂) gas. However, this process has high energy requirements due to the high process temperature (500 ⁰C) and pressure (100-150 bar). It is also responsible for a significant amount of CO₂ emissions (400 metric tons) and is energy-intensive- it consumes around 2% of the world’s primary energy.

Hydroxylamine is currently produced from ammonia formed by the Haber-Bosch process, followed by the Ostwald process (which generates nitric oxide, NO) and NO reduction by H₂. An alternative reaction mechanism is proposed, involving the electroreduction of nitrate to hydroxylamine. Wastewater from fertilizer run-offs, nuclear power plants, and slaughterhouses is a rich source of nitrates.

Many researchers are now focusing on manufacturing chemicals via electrochemical processes. Electrochemical processes are typically executed at ambient temperature and pressure, thus requiring mild operating conditions and low process energy.

We conduct a techno-economic analysis of this electrochemical conversion system using a general model built by Orella et al., 2020. We performed a sensitivity analysis to calculate the maximum possible reduction in hydroxylamine production cost and to discover the parameters that influence it. The most dominant parameter influencing the cost was the separation factor, followed by lifetime, product Faradaic Efficiency, electricity price, and conversion of nitrite.

We obtained the optimum projected cost of hydroxylamine as $0.12/kg, which is 93% lesser than the market price of hydroxylamine, estimated at $1.72/kg. However, we obtained the base cost, or the current production cost, as $3.27/kg, almost double the current market price. Our analysis suggests an immense potential for cost reduction, which motivates further research.