Modeling and simulation of ammonia removal from purge gases of ammonia plants using a catalytic Pd-Ag membrane reactor

Advances and Perspectives of H2 Production from NH3 Decomposition in Membrane Reactors

Hydrogen is often regarded as an ideal energy carrier. Its use in energy conversion devices does in fact not produce any pollutants. However, due to challenges related to its transportation and storage, liquid hydrogen carriers are being investigated. Among the liquid hydrogen carriers, ammonia is considered very promising because it is easy to store and transport, and its conversion to hydrogen has only nitrogen as a byproduct. This work focuses on a review of the latest results of studies dealing with ammonia decomposition for hydrogen production. After a general introduction to the topic, this review specifically focuses on works presenting results of membrane reactors for ammonia decomposition, particularly describing the different reactor configurations and operating conditions, membrane properties, catalysts, and purification steps that are required to achieve pure hydrogen for fuel cell applications.

The benefits of autotrophic nitrogen removal from high concentration of urea wastewater through a process of urea hydrolysis and partial nitritation in sequencing batch reactor

For the sake of high efficiency and saving operational cost for high-concentration urea wastewater treatment, a novel two-stage partial nitritation (PN)-anammox process containing simultaneous urea hydrolysis and PN in sequencing batch reactor (SBR) was investigated. Although the influent urea concentration increased from 500 to 1200 mg/L, the SBR simultaneously achieved urea removal efficiency higher than 98% and stable PN with effluent NO₂^--N/NH₄⁺-N ratio of 1.0-1.3 without any extra alkalinity addition. The intracellular hydrolysis was the dominant mechanism for urea removal and persistent free ammonia inhibition on nitrite-oxidizing bacteria was the main reason for nitrite accumulation of 97.92% in SBR. The subsequent anammox reactor showed efficient nitrogen removal performance with average ammonium removal efficiency, nitrogen removal efficiency and maximum nitrogen removal loading rate of 98.08%, 81.45% and 1.05 kg N·m^-3·d^-1 respectively. High-throughput sequencing results indicated Gemmatimonadetes became the most abundant bacterial phylum related to potential intracellular urea hydrolysis and displayed obvious ammonium-oxidizing bacteria enrichment and nitrite-oxidizing bacteria inhibition in SBR, and the dominant anammox bacteria (Candidatus_Kuenenia) in anammox reactor. The proposed process was proven to be promising for high-concentration urea wastewater treatment, facilitating the sustainable development of the urea industry in the future.

Chemical dual-site capture of NH3 by unprecedentedly low-viscosity deep eutectic solvents

It is found that ethylamine hydrochloride (EaCl) and phenol (PhOH) can form a new type of deep eutectic solvent (DES) with quite low viscosity, and two active sites for chemical absorption of NH₃.

Simultaneous Increase of H2 and Gasoline Production by Optimizing Thermally Coupled Methanol Steam Reforming with Fischer-Tropsch Synthesis

The worldwide growing of gaseous pollutions amount has attracted a great deal of attention for development of clean energy resources like hydrogen. Recently, methanol steam reforming (MSR) has been considered as an effective method for hydrogen production compared to other fuels for reforming. Indeed, advantages of methanol such as its good accessibility and properties like its low boiling point and low probability of coke formation as well as high hydrogen to carbon ratio encourage utilizing this substance in reforming process. Therefore, in this work, MSR as an endothermic reaction has been innovatively coupled with Fischer-Tropsch (FT) exothermic synthesis in order to enhance the yield of hydrogen and gasoline production. Presence of membrane in the proposed thermally coupled membrane reactor (TCMR) promotes H2 separation as the desired product. A homogeneous one-dimensional steady- state model was considered in the present work. Differential evolution (DE) optimization technique was used to optimize feed molar flow rates and inlet temperatures in both endothermic and exothermic reaction sides with the aim of maximizing gasoline and H2 yields (in both sides). Results show 42.1 % increase in gasoline yield production and simultaneously high H2 production yield of 68.5 % in exothermic side compared with the industrial FT reactor that is considered as conventional reactor (CR). Moreover, the suggested configuration can be considered as an energy and cost effective strategy as a result of supplying required energy for endothermic section by generated heat in the exothermic side.

Analysis of ammonia separation from purge gases in microporous hollow fiber membrane contactors

In this study, a mathematical model was developed to analyze the separation of ammonia from the purge gas of ammonia plants using microporous hollow fiber membrane contactors. A numerical procedure was proposed to solve the simultaneous linear and non linear partial differential equations in the liquid, membrane and gas phases for non-wetted or partially wetted conditions. An equation of state was applied in the model instead of Henry's law because of high solubility of ammonia in water. The experimental data of CO₂-water system in the literature was used to validate the model due to the lack of data for ammonia-water system. The model showed that the membrane contactor can separate ammonia very effectively and with recoveries higher than 99%. SEM images demonstrated that ammonia caused some micro-cracks on the surfaces of polypropylene fibers, which could be an indication of partial wetting of membrane in long term applications. However, the model results revealed that the membrane wetting did not have significant effect on the absorption of ammonia because of very high solubility of ammonia in water. It was also found that the effect of gas velocity on the absorption flux was much more than the effect of liquid velocity.