Optimizing Reaction-Absorption Process for Lower Pressure Ammonia Production

Abstract

Ammonia separation using metal halide absorbents has been shown to be a viable path for ammonia production at lower pressure. This work reports on optimizing the operating parameters of the reaction−absorption process that can be adapted for large-scale processing. The experiments were executed in three different modes. First, the effect of reaction parameters on the production rate was studied. Then, the absorption conditions were investigated in a single-pass reaction-then-absorption mode to evaluate the effectiveness of the absorbent at different temperatures, pressures, and space velocities. Finally, fed-batch reactionabsorption tests were conducted in constant pressure to evaluate the process performance with optimized conditions and gain more in-depth understanding of the transient behavior of this process. Results suggest that the recycle flow rate and absorber temperature significantly influence the ammonia production rates. These findings were then used to optimize the performance of a continuous fed-batch ammonia production process at constant pressure. A production rate upward of 27 μmol g cat s −1 was obtained under the most optimized conditions, which is a factor of 14 greater than the best result reported earlier. The optimized conditions were then used to study the cyclic operation of the fed-batch reaction− absorption process in a cyclic process. A transient behavior was observed for the ammonia production, which could be attributed to the partial saturation of the absorber column. Stable performance of reaction-absorption process was demonstrated for more than nine cycles, with no decay in the performance of the absorber after relatively short regeneration cycles.

Simulation Analysis for Design of H2/N2 Ratio of Feed Gas to Ammonia Synthesis Process Using Ru/CeLaTiOx Catalyst

“…As seen in Figure , specific energy consumption associated with the NH 3 separation constitutes up to ∼68% of total synthesis loop energy requirement. Replacing the flash separator with other low-energy technologies such as ammonia absorber/adsorber has potentials to bring down energy consumption of the loop further below 4 GJ/ton-NH 3 , , and this step will be considered for a next course of action. Nevertheless, the proposed design with novel Ru/CeLaTiO x catalyst presents a greener and economically viable and flexible alternative for commercial renewable-derived NH 3 production.…”

Perspective on Intensification of Haber−Bosch to Enable Ammonia Production under Milder Conditions

“…Overall, the results suggest that the regeneration temperature and time are important factors affecting the loading capacity in the subsequent cycles. The optimal conditions for absorption and desorption have been studied to achieve higher ammonia production rates using different supported and unsupported absorbents and different configurations. − Recent work on ammonia absorption was dedicated to implementing the cyclic uptake and release of ammonia. , Efforts were also made to optimize absorption/desorption conditions to achieve higher ammonia purity via a dynamic flow breakthrough test . Much more research is needed to develop stable absorbents and understand the uptake-release cyclic operation.…”

Improving Absorbent-Enhanced Ammonia Separation For Efficient Small-Scale Ammonia Synthesis

“…In this way, the use of supported metal halides (e.g., MgCl 2 ) to capture ammonia in an ammonia synthesis process offers potential for a more sustainable and economical renewable ammonia synthesis at a small production scale. 6,10,17,18 While capturing ammonia using metal halides can be more economical and efficient compared to the condensation approach, 19,20 the use of absorbents presents other challenges. In most ammonia absorbents, the equilibrium absorption of ammonia in the solid salt absorbent (as represented by absorption isotherms) is nonlinear with varying temperature.…”

“…While capturing ammonia using metal halides can be more economical and efficient compared to the condensation approach, , the use of absorbents presents other challenges. In most ammonia absorbents, the equilibrium absorption of ammonia in the solid salt absorbent (as represented by absorption isotherms) is nonlinear with varying temperature.…”