Sustainable ammonia production through process synthesis and global optimization

Abstract

Current ammonia production technologies have a significant carbon footprint. In this study, we present a process synthesis and global optimization framework to discover the efficient utilization of renewable resources in ammonia production. Competing technologies are incorporated in a process superstructure where biomass, wind, and solar routes are compared with the natural gas‐based reference case. A deterministic global optimization‐based branch‐and‐bound algorithm is used to solve the resulting large‐scale nonconvex mixed‐integer nonlinear programming problem (MINLP). Case studies for Texas, California, and Iowa are conducted to examine the effects of different feedstock prices and availabilities. Results indicate that profitability of ammonia production is highly sensitive to feedstock and electricity prices, as well as greenhouse gas (GHG) restrictions. Under strict 75% GHG reductions, biomass to ammonia route is found to be competitive with natural gas route, whereas wind and solar to ammonia routes require further improvement to compete with those two routes. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16498 2019

Life Cycle Assessment for the Design of Chemical Processes, Products, and Supply Chains

“…Large savings of GWI can be achieved, but only at higher cost, which highlights the need for multi-objective optimization of conflicting objectives. Demirhan et al (95) minimized the costs of ammonia production by solving a process superstructure under strict restrictions on GWI. They found that an optimal process design can reduce both greenhouse gas emissions and cost.…”

“…This type of superstructure optimization often leads to computationally demanding mixedinteger nonlinear programs (MINLPs), in particular when combined with multi-objective optimization. Because the resulting MINLPs are sometimes not solvable with commercial multipurpose solvers, many researchers work not only on the problem formulation but also on tailored solution algorithms (94,95).…”

Energy systems engineering - a guided tour

“…The methodologies listed in the previous section have been applied to various energy systems. Interested readers are encouraged to read the following publications from our research group on the listed topics below: 1) Optimal production of fuels and chemicals through process synthesis [124][125][126][127] 2) Supply chain analysis of fuels and chemicals [128,129] 3) Polygeneration energy systems [130][131][132] [142,143] To show the power of energy systems engineering analyses, we will present a few studies in detail in this chapter. Selected are three examples of an energy systems engineering approach to tackle the multi-faceted and multiscale challenges in the design, supply chain, and operation of producing energy carriers.…”

Renewable production of ammonia and nitric acid

“…Today's ammonia production exhibits a high carbon footprint, thus motivating research on sustainable production methods . Electrified ammonia production dates back to the 1920s, where the Haber‐Bosch process was coupled with a large‐scale hydro‐powered alkaline water electrolysis .…”

“…The new design enables direct production of supercritical steam up to 650°C. Demirhan et al apply a superstructure framework to optimally configure and dimension ammonia production processes based on renewable resources and investigate the options of PEM and alkaline electrolyzers. Allman et al propose to embed operation information into a design problem in order to estimate operating costs under power dynamics; (c) on the supply chain level, recent works analyze the potential of incorporating distributed wind/solar‐powered ammonia plants in the countrywide fertilizer industry .…”