Techno-economic analysis of green and blue hybrid processes for ammonia production

Abstract

In a blue ammonia plant, hydrogen required for ammonia synthesis is traditionally produced through steam reforming. This process is cost competitive but has the drawbacks of high CO₂ emissions and excessive energy consumption. On the other hand, in a green ammonia plant, hydrogen production through water electrolysis avoids CO₂ emissions and utilizes renewable energy sources. However, high stack costs and electricity prices degrades the economic viability of the process. Recognizing the potential benefits of both green and blue ammonia production methods, novel hybrid processes have been proposed to integrate these approaches. A thermoneutral tri-reformer has been introduced as a replacement for the energy-intensive steam reforming process, offering a means to eliminate CO₂ emissions. In the green ammonia process, hydrogen generated by a water electrolyzer, along with nitrogen obtained from an air separation unit (ASU), are employed for ammonia synthesis. However, the high-purity oxygen produced as a byproduct from the electrolyzer and ASU has not been utilized thus far. This oxygen can be fed into the tri-reformer to produce blue hydrogen or syngas. To evaluate the technical and economic advantages resulting from the integration of these systems, a techno-economic assessment was conducted on these hybrid processes as well as conventional ones in the literature [3]. The results demonstrate that the proposed processes exhibit superior economic performance compared to conventional approaches, highlighting the potential benefits of system integration.