An Integrated Evaluation Method with Application to a New Ammonia Synthesis Process Design

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Abstract

While keeping the traditional centralized large-scale chemical production, the increasing market volatility and the rising use of renewable resources will require new production ways such as distributed, modularized, and small-scale production. The new emerging processes are expected to provide more flexibility, shorter time to market, and better use of distributed renewable raw materials (e.g. biomass) and energy (e.g. solar and wind). However, the traditional process evaluation methods such as TEA (Techno-Economic Analysis) tend to lower the value of the new processes since the small-scale would make higher capital cost and lower operation efficiency. Therefore, a new evaluation method is required to fully address the features in a holistic way including environment, renewable resources, supply chain, modular design and manufacturing, control and safety, as well as traditional economic analysis.

In this study, an integrated evaluation method is proposed to evaluate the novel wind energy based distributed ammonia synthesis process and compare to the traditional ones. The new process applies wind-based electricity to produce hydrogen via water electrolysis, separates nitrogen from air, and produces ammonia as the product. With process simulation, the integrated evaluation method extends the traditional TEA with emission penalty, renewable resource credit, transportation cost, modular manufacturing discount, as well as safety/control concerns. The proposed method has accomplished a meaningful evaluation and comparison not only to the traditional technology, but also to different air separation methods (e.g. cryogenic vs. membrane) and ammonia synthesis technologies (e.g. Haber-Bosch vs. low pressure synthesis). The method has also provided the foundation for design parameter sensitivity study and technical route selection. The quantitative results show that if only traditional TEA is applied, the wind energy based distributed process could not compete with the traditional one. However, the new evaluation method shows that the new process could have a competitive breakeven price when all the evaluation factors are taken into account.

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