Ammonia Transfer Research Articles

Research on modularized design and parameter matching of dual-fuel pre-cooler for chemically precooled engine

Precooling technology is a widely used method for increasing the flight speed of aero-engine by installing a precooler in front of compressor. However, the traditional precooler is difficult to meet the precooling requirement in a wide range because of the fixed geometric structure. In this paper, a novel precooling strategy based on multi-module is proposed, in which the precooler is divided into multiple identical modules and the number of modules cooled by different fuels could be regulated, so as to meet the precooling requirement under different working conditions. To evaluate the performances of this scheme, a one-dimensional model of precooler is established. Besides, the characteristics of heat transfer and decomposition of ammonia are experimentally studied to support the precooler design. The study shows that the heat sink of ammonia reaches 4.59 MJ/kg at 629 °C, and the fitted heat transfer correlation equation matches well with the experimental values within the error of 15 %. Further, in the range of Ma2.5 – 2.88, the precooling demand can be satisfied by using only RP-3, and above Ma2.88, it is necessary to use both NH3 and RP-3 simultaneously. Moreover, the optimal number of precooler module division is 5, and the modular precooling scheme could improve the specific impulse by 24.06 % at Ma3.4 compared to non-modular precooling scheme.

Safe Transfer of Ammonia in Pipelines: An Analysis of Risk

Humanity is currently confronted with unprecedented environmental challenges, prompting an urgent shift toward the widespread adoption of clean energy. Among the diverse alternatives, ammonia stands out as a highly promising candidate due to its relatively high volumetric energy density, advanced technical readiness level, and a well-established infrastructure with established standards. However, the safety of ammonia transport via pipelines demands particular attention, as several past accidents have shown. Given the inherent risks associated with ammonia pipeline accidents, a thorough safety analysis is essential, especially for densely populated countries like Singapore. While Singapore explores using ammonia, a detailed assessment of potential pipeline leaks is currently lacking. To address this, this study employed Computational Fluid Dynamics (CFD) simulations using Phast software. Simulations modeled ammonia leaks at various pressures and weather conditions and the results highlighted the significant hazards of ammonia leaks, including toxicity and flammability. Notably, the potential hazardous zone resulting from these leaks could span up to 1,000 meters. Furthermore, the study proposes effective countermeasures based on insights derived from the simulations, offering valuable perspectives to enhance safety and efficiency in clean energy applications. These measures include the implementation of safety instrumented systems, among others. The results from this study lay the groundwork for future laboratory-based experiments aimed at improving the safety of ammonia pipelines.

Alkali-driven Donnan dialysis for efficient ammonia recovery from wastewater: Performance, mechanism and optimization

Recovery of ammonia from wastewater is of practical importance toward a sustainable society. To this end, concentration-driven Donnan dialysis (DD) is a promising recovery method especially for its simplicity and negligible energy consumption. Upon the traditional salt-driven DD, the conceptive alkali-driven DD significantly enhanced mass transfer and removal efficiency, yet their performance in terms of key process parameter were not deeply understood and further optimization remained unclear. Models for salt (NaCl) and alkali (NaOH)-driven DD processes were thus established and the ammonia transfer was theoretically investigated. The results showed that a fluctuated Donnan equilibrium constant was found responsible for the superior performance of alkali-driven DD (mass transfer accelerated by 90 % than control). Interestingly, there was an optimal ammonia recovery mode via adjusting ratios of alkali/ammonia and cation/ammonia, two key parameters governing the process efficiency, based on which the salt-alkali coupling-driven DD process was further proposed. It was verified that the coupling-driven DD process achieved the ammonia removal kinetic value of 0.1632 h−1 under insufficient alkali conditions (accounting for 50 % ammonia concentration in feed) with lowest CO2 emissions of 3.49 kg CO2/kg NH4+. The descending overall efficiency of ammonia removal, following alkali-driven (0.2943 h−1) > coupling-driven (0.1632 h−1) > salt-driven (0.1228 h−1), was ascribed to the variations in the electrochemical potential of ions involved in the respective processes. In addition, the cost of chemical consumption for a coupling-driven DD process (3.99 $/kg NH4+) was close to that of a salt-driven process, but much lower than that of an alkali-driven process (14.81 $/kg NH4+). These finding insight the low-carbon and efficient recovery of ammonia from wastewater.

Aluminium in der Chemie der Frustrierten Lewis‐Paare

AbstractDieser Übersichtsartikel beschreibt die Entwicklung der Verwendung von Aluminiumverbindungen in der Chemie der frustrierten Lewis‐Paare (FLPs) in den letzten 14 Jahren. Es werden die Synthese, die Reaktivität und die katalytischen Anwendungen von intermolekularen, intramolekularen und sogenannten versteckten FLPs mit Phosphor‐, Stickstoff‐ und Kohlenstoff‐Lewis‐Basen erörtert. Die intrinsisch höhere Acidität von Aluminiumverbindungen im Vergleich zu ihren Bor‐Analoga eröffnet unterschiedliche Reaktionswege. Die Ergebnisse werden in einer mehr oder weniger chronologischen Reihenfolge präsentiert. Es wird gezeigt, dass Al‐FLPs mit einer Vielzahl von polaren und unpolaren Substraten reagieren und sowohl stabile Addukte bilden als auch reversibel Bindungen aktivieren. Folglich werden einige katalytische Anwendungen der Titelverbindungen vorgestellt, wie z. B. die Dimerisierung von Alkinen, die Hydrierung von tert‐butylethylen und Iminen, die Aktivierung von C−F‐Bindungen, die Reduktion von CO2, die Dehydrierung von Aminboran und der Transfer von Ammoniak. Darüber hinaus wurden verschiedene Al‐FLPs als Initiatoren in Polymerisationsreaktionen eingesetzt.

Aluminum in Frustrated Lewis Pair Chemistry.

This review article describes the development of the use of aluminum compounds in the chemistry of frustrated Lewis pairs (FLPs) over the last 14 years. It also discusses the synthesis, reactivity and catalytic applications of intermolecular, intramolecular and so-called hidden FLPs with phosphorus, nitrogen and carbon Lewis bases. The intrinsically higher acidity of aluminum compounds compared to their boron analogs opens up different reaction pathways. The results are presented in a more or less chronological order. It is shown that Al FLPs react with a variety of polar and non-polar substrates and form both stable adducts and reversibly activate bonds. Consequently, some catalytic applications of the title compounds were presented such as dimerization of alkynes, hydrogenation of tert-butyl ethylene and imines, C-F bond activation, reduction of CO2, dehydrogenation of amine borane and transfer of ammonia. In addition, various Al FLPs were used as initiators in polymerization reactions.

Pool boiling heat transfer of ammonia outside enhanced tubes with various fin structures

Pool boiling heat transfer of ammonia on a smooth tube and three enhanced tubes was investigated at the saturation pressure ranging from 6.15 to 11.7 bar, which corresponds to the saturation temperature from 10 to 30 °C. The test tube with a length of 796 mm was immersed in the liquid pool of ammonia inside a cylindrical chamber having an internal diameter of 254.4 mm, and convection or pool boiling heat transfer outside the test tube was generated by flowing hot water through the tube. Three enhanced tubes of a low-finned tube (Low-fin), a low-finned tube with oblique cuttings (Turbo-C), and a finned tube having re-entrant cavities (Turbo-E) were prepared to examine the pool boiling enhancement on various finned tubes. Boiling hysteresis on the smooth tube was observed between when the heat flux increases and when the heat flux decreases, which resulted in the deviation of the heat transfer coefficients from the previous correlations when the heat flux decreases. A suitable correlation was suggested to compensate for the deviation of the heat transfer coefficients in case of decreasing the heat flux by modifying the Stephan-Abdelsalam correlation. Three enhanced tubes exhibited considerable enhancement in the heat transfer coefficients compared with the smooth tube, and boiling performance on the Turbo-E tube having re-entrant cavities was highly affected by the variation of the bubble diameter according to the saturation pressure. Enhancement factors of the enhanced tubes were obtained from the ratio of thermal conductance on the enhanced tube to that on the smooth tube.

Vacuum ammonia stripping from liquid digestate: Effects of pH, alkalinity, temperature, negative pressure and process optimization

High ammonia-nitrogen digestate has become a key bottleneck limiting the anaerobic digestion of organic solid waste. Vacuum ammonia stripping can simultaneously remove and recover ammonia nitrogen, which has attracted a lot of attention in recent years. To investigate the parameter effects on the efficiency and mass transfer, five combination conditions (53 °C 15 kPa, 60 °C 20 kPa, 65 °C 25 kPa, 72 °C 35 kPa, and 81 °C 50 kPa) were conducted for ammonia stripping of sludge digestate. The results showed that 80% of ammonia nitrogen was stripped in 45 min for all experimental groups, but the ammonia transfer coefficient varied under different conditions, which increased with the rising of boiling point temperature, and reached the maximum value (39.0 mm/hr) at 81 °C 50 kPa. The ammonia nitrogen removal efficiency was more than 80% for 30 min vacuum stripping after adjusting the initial pH to above 9.5, and adjustment of the initial alkalinity also affects the pH value of liquid digestate. It was found that pH and alkalinity are the key factors influencing the ammonia nitrogen dissociation and removal efficiency, while temperature and vacuum mainly affect the ammonia nitrogen mass transfer and removal velocity. In terms of the mechanism of vacuum ammonia stripping, it underwent alkalinity destruction, pH enhancement, ammonia nitrogen dissociation, and free ammonia removal. In this study, two-stage experiments of alkalinity destruction and ammonia removal were also carried out, which showed that the two-stage configuration was beneficial for ammonia removal. It provides a theoretical basis and practical technology for the vacuum ammonia stripping from liquid digestate of organic solid waste.

Vibrational energy transfer in ammonia-helium collisions.

While the rotational energy transfer of ammonia by rare gas atoms and hydrogen molecules has been the focus of many studies, little is known about its vibrational relaxation, even though transitions involving the umbrella bending mode have been observed in many astrophysical environments. Here we explore the vibrational relaxation of the umbrella mode of ammonia induced by collisions with helium atoms by means of the close-coupling method on an ab initio potential energy surface. We compute cross sections up to kinetic energies of 1500 cm-1 and rate coefficients up to a temperature of 300 K for vibrational, rotational, and inversion transitions involving the lowest two vibrational states. We show that vibrational relaxation is much less efficient than rotation-inversion relaxation, although the rate coefficients for vibrational relaxation strongly increase with the temperature. We also observe important differences for vibrationally-elastic transitions within the lowest two vibrational states, i.e., for rotation-inversion transitions. These are a direct consequence of the difference in the tunnelling splitting of the lowest inversion levels.

Recyclable ammonia uptake of CuCl2/graphite composite adsorbents with high adsorption capacity

Ammonia is considered a good hydrogen storage material due to its advantages of high hydrogen content density. At the same time, the characteristic of efficient heat transfer of ammonia makes it develop rapidly in many energy industries. However, unutilized NH3 can cause corrosion and poisoning, therefore, NH3 must be captured in time. Metal chloride is a green, efficient and sustainably utilized material for NH3 adsorption and capture. In this paper, a novel composite adsorbent was proposed by loading graphite to CuCl2 to enhance the NH3 adsorption·NH3 adsorption–desorption experiments of composite adsorbents were performed on the fixed bed. The results showed that the optimal loading of graphite on CuCl2 was 20 wt% and the optimal adsorption temperature was 25 ℃. The optimal adsorption of CuCl2-G (20) was 0.64 g NH3/g adsorbent. Moreover, the composite adsorbents showed good stability in NH3 adsorption properties during long-term cycling. The cumulative NH3 adsorption capacity of CuCl2-G (20) in the 10 cycles was up to 5.8 g NH3/g adsorbent, which was 0.07 g NH3/g adsorbent higher than that of CuCl2. Notably, all graphite-loaded composite adsorbents showed a stronger NH3 adsorption capacity than a single CuCl2 in the 2nd and subsequent cycles. Thus, CuCl2-G (20) is a promising adsorbent with potential application in the removal and enrichment of excess NH3 produced in industrial processes.

Pool boiling heat transfer of ammonia outside a single tube with fin structures: Hysteresis phenomena and boiling enhancement

Pool boiling heat transfer of ammonia outside a single tube was investigated at three saturation pressures of 6.15, 8.57, and 11.7 bar (saturation temperature of 10, 20, and 30 °C) at the heat fluxes ranging from 1.2 to 72.9 kW/m2. Hysteresis in a boiling curve and boiling enhancement were examined on both the smooth tube with machined roughness and two enhanced tubes with low fins and re-entrant cavities. All three tubes have outermost diameters from 15.68 to 15.87 mm and the same length of 796 mm. A large hysteresis between increasing the heat flux and decreasing the heat flux was observed on the smooth tube, and the hysteresis increased as the saturation pressure decreased. The boiling hysteresis of ammonia was reasonably explained from the thermodynamic analysis based on Clausius-Clapeyron and Young-Laplace equations. Heat transfer coefficients on the enhanced tubes were increased by 47% to 105% (Low-fin) and 103% to 159% (Turbo-E) compared with the smooth tube at the saturation pressure of 8.57 bar. However, the hysteresis itself was increased on the enhanced tubes owing to the wall temperature decrease along the fin. Hydrophobic coating and the enhanced tube having re-entrant cavities with cavity mouths of a few micrometers were suggested to mitigate the hysteresis phenomena in the pool boiling of ammonia.

Novel membrane contactor-like bioreactor for selective separation and biodegradation of phenol and ammonium from coal chemical wastewater

The development of coal chemical industry usually generates high-concentrated wastewater containing phenol and ammonium, which requires deep treatment before disposal. Herein, a novel combined process of membrane contactor and bioreactor (MCBR) was established for the efficient treatment of phenol-ammonium wastewater for the first time. When pH was in the range of 8–13, the increase of pH weakened the transmembrane mass transfer of phenol and enhanced the mass transfer of ammonia, owing to their different existing forms at different pH values. At a temperature of 20–30 ℃, the transmembrane mass transfer of phenol and ammonia both increased with temperature increasing. Meanwhile, the established transmembrane mass transfer model reflected the same tendencies of phenol and ammonium recovery rates between experiment and theory. The precise control of concentrations of phenol and ammonium by membrane contactor ensured the safety and effectiveness of subsequent biodegradation process. After biodegradation, the concentrations of phenol and ammonium reduced from 120.1 and 78.9 mg/L to 7.8 and 2.5 mg/L, respectively. The volatile solid content of activated sludge remained relatively constant, while the settling ratio decreased from 39 % to 29 %. Overall, this study established a novel MCBR system for green and cost-effective treatment of high-concentrated coal chemistry wastewater.

A crystalline aluminium-carbon-based ambiphile capable of activation and catalytic transfer of ammonia in non-aqueous media.

Despite recent achievements in the field of frustrated Lewis pairs (FLPs) for small molecule activations, the reversible activation and catalytic transformations of N-H-activated ammonia remain a challenge. Here we report on a rare combination of an aluminium Lewis acid and a carbon Lewis base. A so-called hidden FLP consisting of a phosphorus ylide featuring an aluminium fragment in the ortho position of a phenyl ring scaffold is introduced. Although the formation of the Lewis acid/base adduct is observed in the solid state, which at first glance leads to formally quenched FLP reactivity, we show that the title compound readily reacts with non-aqueous ammonia thermoneutrally and splits the N-H bond reversibly at ambient temperature. In addition, NH3 transfer reactions mediated by a main-group catalyst are presented. This proof-of-principle study is expected to initiate further activities in utilizing N-H-activated ammonia as a readily available, atom-economical nitrogen source.

A pH-based control system for nitrogen recovery using hollow fibre membrane contactors

Nitrogen is accumulated in wastewater being the main sink of this nutrient. As consequence, wastewater appears as a relevant source to recover this nutrient. Current wastewater treatment are focused on nitrogen removal instead of recovering it. However, different technologies have been appeared in the last decade. Hollow fibre membrane contactor is one of them and its capacity has been demonstrated with different feedstock and conditions. In this work a pH- based control system has been developed using the pH slope as a variable to control the performance of these membranes operated for nitrogen recovery. This is a novelty low-cost control tool for recovery process automation and optimization which offers the possibility of process monitoring without the drawbacks of maintenance, costs and time of lab analysis and more complex sensors. During the nitrogen recovery process pH in the feed solution decreases because of free ammonia transfer across the membrane. pH measurements cannot be correlated with nitrogen concentration (usually pH is controlled to maintain the driving force of the recovery process). However, the pH slope varies with the ammonia transfer rate representing the ammonia nitrogen concentration remaining in the feed solution. Since the membrane contactors are operated in batch mode, the developed control system stops the recovery process when the pH slope is below a threshold value for four minutes. Three different threshold values were evaluated (−0.06, −0.03 and −0.015 pH·min−1) demonstrating that the nitrogen recovery efficiency desired can be achieved by selecting an appropriate threshold value for the pH slope.

Efficient recovery of ammonia from digestate by membrane distillation: Nano-FeOOH re-entry structure modification, anti-fouling, and anti-wetting performance

The recovery of resources from wastewater has drawn worldwide attention, and digestate has the potential to produce amino fertilizers as an ammonia-rich carrier. Membrane distillation (MD) is an effective process to recover ammonia from digestate, but membrane fouling and wetting are identified as major challenges faced. However, the research to enhance membrane fouling resistance and ammonia transfer efficiency through membrane modification has seldom been explored. Herein, we fabricated FeOOH grafted membranes with superior resistance to wetting by simple hydrothermal synthesis and fluorination. The grafted re-entrant FeOOH nanoparticles and fluorosilanes were confirmed by SEM, EDS, FTIR, and XRD. The superior hydrophobicity of the modified film was confirmed by contact angle (CA = 152.9 ± 2.8°) analysis. The fouling growth behavior of the membrane surface was monitored in situ by optical coherence tomography (OCT), and the anti-fouling performance was proved to be superior to that of commercial polyvinylidene fluoride membrane (PVDF) (no fouling accumulation was detected for 6 h). The modified membrane achieved ammonia recovery flux of 3.89 ± 0.18 g/m2 h and high ammonia recovery of 95.2 ± 2.3% without wetting occurrence. Our research illustrates that the grafting of nano-FeOOH re-entrant structures facilitates the recovery of ammonia from highly concentrated ammonia wastewater without wetting and fouling, revealing its promising prospect in MD resource recovery.

Ammonia recovery from source-separated hydrolyzed urine via a dual-membrane distillation in-series process

This study presents a dual membrane distillation (MD) in-series process to recover ammonia from source-separated hydrolyzed urine. The first MD stage separates and recovers ammonia from the hydrolyzed urine using an acid solution, while the second MD stage helps dewater the acid solution with captured ammonia and maintain its solution pH. The feed temperature and pH were optimized for operational conditions. The specific ammonia transfer (SAT) value was evaluated to obtain comparative results. While the water fluxes of both the single and dual-MD in-series set up systems were similar, the dual-MD in-series module showed higher SAT values and ammonia fluxes. At pH = 6, the ammonia flux values were minimal, but at pH = 13.2, they significantly increased to over 180 g/m2 h for the dual-MD in-series setup, which was approximately twice as much as the single MD setup (about 100 g/m2 h). In addition, the ammonium concentration in dual-MD in-series setup rose to over 200 mg/L at pH around 9, which is twice higher than that of a single MD setup. The results demonstrated that during the experiment, the dual-MD in-series configuration could help maintain the acid collector pH around 3 while for a single setup it continuously increased and reached to over 8 after 4 h. This innovative design not only preserves the desired pH range but also minimizes the amount of acid consumed, making it a promising approach in advancing nutrient recovery from human urine.

Effect of chemical speciation in boundary layer on performance of ammonia recovery in membrane contactor

Membrane contactor is a promising option for ammonia recovery from wastewater due to its high selectivity and efficiency. We employed an ammonia mass transfer model that tracks and reflects chemical speciation in the boundary layer (BL) of a membrane contactor, a mechanism that may be involved in the ammonia recovery process but has very rarely been addressed. Simulation and experimental results, which agreed well with each other, indicated that ammonia mass transfer in a membrane contactor could occur via two significant pathways: i) direct transfer of free ammonia from feed bulk to strip side and ii) ammonium-ion supply from feed bulk to feed BL followed by deprotonating at the feed BL and passing through the membrane to the strip side. The contribution of the latter relative to the overall mass transfer rate increased when the feed was strongly buffered in pH, less basic, and flowing slower, reaching up to 78.9 % for conditions tested in this study. These results demonstrate for the first time that chemical speciation in the BL plays a significant role in the performance of a membrane contactor for ammonia recovery under typical operating conditions.

Decoupling Electron‐ and Phase‐Transfer Processes to Enhance Electrochemical Nitrate‐to‐Ammonia Conversion by Blending Hydrophobic PTFE Nanoparticles within the Electrocatalyst Layer

AbstractElectrochemical upcycling of nitrate into ammonia at ambient conditions offers a sustainable synthesis pathway that can complement the current industrial NH3 production from the Haber–Bosch process. One of the key rate‐limiting steps is the effective desorption of gaseous or interfacial bubble products, mainly NH3 with some minor side products of nitrogen and hydrogen, from the electrode surfaces to sustain available sites for the NO3− reduction reaction. To facilitate the gaseous product desorption from the catalytic sites, hydrophobic polytetrafluoroethylene (PTFE) nanoparticles are blended within a CuO catalyst layer, which is shown to eliminate the undesirable accumulation and blockage of electrode surfaces and largely decouples the electron‐ and phase‐transfer processes. The NH3 partial current density normalized by the electrochemically active surface area (ECSA) increases by nearly a factor of 17.8 from 11.4 ± 0.1 to 203.3 ± 1.8 mA cm−2ECSA. The DFT and ab‐initio molecular dynamics simulations suggest that the hydrophobic PTFE nanoparticles may serve as segregated islands to enhance the spillover and transport the gaseous products from electrocatalysts to the PTFE. Thus, a higher ammonia transfer is achieved for the mixed PTFE/CuO electrocatalyst. This new and simple strategy is expected to act as inspiration for future electrochemical gas‐evolving electrode design.

The characteristics of forced convective boiling heat transfer of ammonia in microchannel heat exchanger

The characteristics of forced convective boiling heat transfer of ammonia in microchannel heat exchanger

Heat Transfer Coefficient Calculation for Developed Ammonia Boiling in the Evaporator Channel of a Thermal Sink

The subject of this article is the heat transfer of ammonia in the channels of thermal sink evaporators. The objective was to determine a sufficiently simple correlation acceptable for engineering practice, which could be used to calculate the heat transfer in cylindrical channels of a thermal sink, designed for two-phase systems of thermal control systems of uncrewed spacecraft. For this purpose, experiments were performed on two thermal sink having an evaporator channel of ~7 mm diameter made of aluminum alloy and stainless steel, with channel surface roughness Ra 3.33 µm and 0.12 µm. The experiments were carried out with a subcooled liquid or two-phase flow at the channel inlet. The results of the experiments were compared with Kupriyanova's formula obtained under markedly different conditions: with ammonia boiling in a large volume on the external surface of 5...6 mm diameter tubes at –40 °C...+20 °C. It is shown that Kupriyanova's formula can be used on the ground and in microgravity conditions to calculate heat transfer coefficients during the developed boiling of ammonia in the range of flow parameters: saturation temperature +35 °C...+75 °C; mass velocity 27...200 kg/(sec-m²); liquid subcooling to saturation temperature at thermal sink inlet 0 °C...30 °С; mass vapor quality at the inlet 0...0.7. Difference of calculated and experimental values of heat transfer coefficients did not exceed 30 %.

Ammonium removal by metakaolin-based geopolymers from municipal and industrial wastewaters and its sequential recovery by stripping techniques

In this study, a technical scheme of an ammonium recovery process from diluted municipal or industrial wastewaters was developed, and the main operational parameters of adsorption/desorption and air-stripping/acid-scrubbing or membrane units were examined. The proposed approach combines the removal of ammonium nitrogen by an ion-exchange mechanism on metakaolin-based geopolymers (MKGPs) followed by adsorbent regeneration. A regeneration agent was purified by the air-stripping technique or membrane technology. A ready-to-use market-grade fertilizer or industrial-grade ammonia water could be obtained as the final product. The properties and regeneration ability of MKGP, prepared from activated kaolinite clay, were compared with new geopolymer adsorbents based on papermill sludge (FS MKGP). Adsorption fixed-bed column experiments with continuously circulated regeneration solution purified by air-stripping or the membrane approach were conducted to determine the limits of the regeneration solution’s application. Sodium and potassium salts were tested as regeneration agents, and the influence of regeneration solution composition on ammonium removal and recovery rates was investigated. Based on a breakthrough curve analysis, the removal rate of ammonium N by FS MKGP was found to be 3.2 times higher than that by MKGP for actual wastewater samples. Moreover, there were substantial differences in the regeneration regime between the two adsorbents. For the air-stripping technique, a liquid-phase temperature of 45°C was minimal and enough for efficient ammonia transfer to the gaseous phase. For the membrane technique, a feed-phase temperature of 40°C was enough for removing ammonia from the regeneration solution, while no heating of a receiving phase was required.