Off-gas Stream Research Articles

LiAlO2-Melamine for efficient and rapid iodine capture

The search for efficient material to capture iodine from off-gas streams continues. Herein, a novel composite of lithium aluminate and melamine, abbreviated as LiAlO2-Mel, was synthesized and exhibited high vapor iodine capture capacity accompanied by good regeneration ability. The LiAlO2-Mel showed an enormous capture capacity of 1281 mg/g within 4 h towards I2 (g) at 150 °C. The kinetics study showed that the dominant process (at 150 °C) was chemisorption via N∙∙∙I and C–NH∙∙∙I bonding mechanisms. Additionally, LiAlO2-Mel has a low surface area (14.6157 m2/g) yet produced high capacity, suggesting chemisorption played a critical role. However, physisorption was the dominant process at lower temperature values, as proved by kinetics fittings and activation energy (Ea = 23.19 KJ/mol) studies. The kinetics models were validated by statistical error validity models (sum of square error, Chi-square test, and normalized standard deviation). Thermogravimetric analysis and adsorption-desorption experiments showed that the LiAlO2-Mel can be recovered by heat treatment (25–800 °C) in N2 atmosphere and ethanol washout (24 h, 25 °C) of the LiAlO2-Mel-I. The high capture capacity, along with eco-friendly and cost-effectiveness, highlights the promising potential of LiAlO2-Mel for iodine capture.

The behavior of iodine in stabilized granular activated carbon and silver mordenite in cementitious waste forms

Both granular activated carbon (GAC) and silver mordenite (AgM) are utilized for the removal of contaminants and radionuclides (e.g., radioiodine) from off-gas streams in nuclear fuel reprocessing and high temperature immobilization of nuclear waste. Following their service lifetimes, the GAC and AgM contain an inventory of contaminants and radionuclides and require stabilization in a matrix for disposal. GAC and AgM are referred to as solid secondary waste (SSW) materials. Cementitious waste forms can be used as the stabilization matrix for SSW, however, for successful stabilization, the inclusion of GAC and AgM should not negatively impact the physical behavior of the cementitious waste form or increase release of the contaminants/radionuclides compared to the baseline case without stabilization. The present work focuses on evaluation of cement formulations, with and without slag, for the stabilization of iodine-loaded GAC or AgM. The results showed that both a slag-containing and slag-free formulations were able to stabilize GAC and AgM, up to 30 vol%, without deleterious impacts on the bulk physical properties of the encapsulating matrix. When monolithic samples of the GAC or AgM containing cement formulations were subjected to leach tests, it was observed that iodide leached from the SSW) had limited sorption to either of the cement matrices. Nonetheless, the iodine can interact with the SSW materials themselves. Specifically, iodine retention within monolithic samples containing the iodine-loaded GAC or AgM was improved for AgM containing waste forms while no improvement was observed for the GAC containing waste forms. The improvement for the AgM containing waste forms was likely due to an enrichment of Ag at the interface between the AgM particles and the cement matrix that can impede iodine migration out from the waste form. The results are significant in highlighting the potential for long-term retention of iodine in specific cementitious waste forms.

Aging kinetics on silver-functionalized silica aerogel in off-gas streams including dry air, humid air, NO and NO2

Aging impact on silver-functionalized silica aerogel (Ag0-aerogel) in the off-gas streams including dry air, humid air, 1% NO/N2, and 2% NO2/dry air were studied. Aged Ag0-aerogel was prepared through a continuous-flow aging system by exposing Ag0-aerogel (unaged) to the off-gas streams at different aging temperatures and time. Iodine loading capacity on the aged Ag0-aerogel was obtained through a continuous-flow adsorption system. Iodine loading capacity losses were observed after the Ag0-aerogel was exposed to the off-gas streams. Characterization studies were conducted to observe the physical and chemical changes of the Ag0-aerogel after exposed to gas streams. According to iodine adsorption data and analyses, it was revealed that iodine loading capacity on the aged Ag0-aerogel in the off-gas streams decreases with increasing aging temperatures and time. The pseudo reaction model describes experimental data well and the oxidation of Ag0 is the rate determining step in the aging process.

Economic Potential of Bio-Ethylene Production via Oxidative Coupling of Methane in Biogas from Anaerobic Digestion of Industrial Effluents

Brazil’s large biofuels industry generates significant amounts of effluents, e.g., vinasse from bioethanol, that can effectively be used as substrate for production of biogas via Anaerobic Digestion (AD). The Oxidative Coupling of Methane (OCM) is the heterogeneous catalytic oxidation of methane into ethylene, which is a main building block for the chemical industry. This work investigates the potential and competitiveness of bio-ethylene production via OCM using biogas produced by biological anaerobiosis of vinasse as a feedstock. The proposed process can add incentive to treat of vinasse via AD and replace fossil ethylene, thus potentially reducing emissions of Greenhouse Gases (GHG). A process model is developed in Aspen Plus v10 software and used to design an economic Biogas-based Oxidative Coupling of Methane (Bio-OCM) process that consumes biogas and oxygen as educts and produces ethylene, ethane, and light off-gases as products. Operating conditions in the reaction section are optimized and a reaction product yield of 16.12% is reached by applying two adiabatic Packed Bed Reactors (PBRs) in series. For the downstream CO2 removal section, a standalone amine-absorption process is simulated and compared to a hybrid membrane-absorption process on an economic basis. For the distillation section, two different configurations with and without Recycle Split Vapor (RSV) are simulated and compared. The bio-ethylene production cost for a Bio-OCM plant to be installed in Brazil is estimated considering a wide range of prices for educts, utility, side products, and equipment within a Monte Carlo simulation. The resulting average production cost of bio-ethylene is 0.53 ±0.73 USD kgC2H4-1. The production cost is highly sensitive to the sales price assigned to a light off-gas side-product stream containing mostly the un-reacted methane. A sales price close to that of Brazilian pipeline natural gas has been assumed based on the characteristics of this stream. The Monte Carlo simulation shows that a bio-ethylene production cost below or equal to 0.70 USD kgC2H4-1 is achieved with a 55.2% confidence, whereas market values for fossil ethylene typically lie between 0.70USD kgC2H4-1–1.50USD kgC2H4-1. Technical and economic challenges for the industrial implementation of the proposed Bio-OCM process are identified and relevant opportunities for further research and improvement are discussed.

On-Line Monitoring of Gas-Phase Molecular Iodine Using Raman and Fluorescence Spectroscopy Paired with Chemometric Analysis.

Molten salt reactors (MSRs) have the potential to safely support green energy goals while meeting baseload energy needs with diverse energy portfolios. While reactor designers have made tremendous strides with these systems, licensing and deployment of these reactors will be aided through the development of new technology such as on-line and remote monitoring tools. Of particular interest is quantifying reactor off-gas species, such as iodine, within off-gas streams to support the design and operational control of off-gas treatment systems. Here, the development of advanced Raman spectroscopy systems for the on-line analysis of gas composition is discussed, focusing on the key control species I2(g). Signal response was explored with two Raman instruments, utilizing 532 and 671 nm excitation sources, as a function of I2(g) pressure and temperature. Also explored is the integration of advanced data analysis methods to enable real-time and highly accurate analysis of complex optical data. Specifically, the application of chemometric modeling is discussed. Raman spectroscopy paired with chemometric analysis is demonstrated to provide a powerful route to analyzing I2(g) composition within the gas phase, which lays the foundation for applications within molten salt reactor off-gas analysis and other significant chemical processes producing iodine species.

Evaluation of decontamination factor of radioactive methyl iodide on activated carbons at high humid conditions

Radioactive iodine (131I) released from nuclear power plants has been a critical environmental concern for workers. The effective trapping of radioactive iodine isotopes from the off-gas stream generated from nuclear facilities is an important issue in radioactive waste treatment systems evaluation. Numerous studies on retaining methyl iodide (CH3I131) by impregnated activated carbons under the high content of moisture have been extensively studied so far. But there have been no good results on how to remove methyl iodide at high humid conditions up to now. A new challenge is to introduce other promising impregnating chemical agents that are able to uptake enough radioactive methyl iodide under high humid conditions. In order to develop a good removal efficiency to control radioiodine gas generated from a high humid process, activated carbons (ACs) impregnated with triethylene diamine (TEDA) and qinuclidine (QUID) were prepared. In addition, the removal efficiencies of the activated carbons (ACs) under humid conditions up to 95% RH were evaluated by applying the standard method specified in ASTM-D3808. Quinuclidine impregnated activated carbon showed a much higher decontamination factor above 1,000, which is enough to meet the regulation index for the iodine filters in nuclear power plants (NPPs).

Capture of Iodine from Nuclear-Fuel-Reprocessing Off-Gas: Influence of Aging on a Reduced Silver Mordenite Adsorbent after Exposure to NO/NO2.

Iodine radioisotopes released during nuclear fuel reprocessing must be removed from the off-gas stream before discharge. One promising material for iodine capture is reduced silver mordenite (Ag0Z). Nevertheless, the adsorbent's capacity will degrade, or age, over time when the material is exposed to other off-gas constituents. Though the overall impact of aging is known, the underlying physical and chemical processes are not. To examine these processes, Ag0Z samples were prepared and aged in 2% NO2 in dry air and in 1% NO in N2 gas streams at 150 °C for up to six months. Aged samples were then characterized using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray absorption spectroscopy. These techniques show that aging involves two overarching processes: (i) oxidation of the silver nanoparticles present in Ag0Z and (ii) migration of oxidized silver into the mordenite's inner network. Silver on the nanoparticle's surface is oxidized through adsorption of O2, NO, and NO2. Raman spectroscopy and X-ray absorption spectroscopy indicate that nitrates are the primary products of this adsorption. Most of these nitrates migrate into the interior of the mordenite and exchange at framework binding sites, returning silver to its unreduced state (AgZ). The remaining nitrates exist at a persistent concentration without aggregating into bulk-phase AgNO3. X-ray absorption spectroscopy results further indicate that iodine adsorption occurs on not just Ag0Z but also on AgZ and a portion of the nitrates in the system. AgZ adsorbs a sizable quantity of iodine early in the aging process, but its capacity drops rapidly over time. For well-aged samples, nitrates are responsible for up to 95% of mordenite's iodine capacity. These results have enhanced our understanding of the aging process in silver mordenite and are expected to guide the development of superior adsorbents for the capture of radioactive iodine from reprocessing off-gas.

Performance of a Natural Gas Solid Oxide Fuel Cell System With and Without Carbon Capture

Abstract The fuel cell program at the United States Department of Energy (DOE) National Energy Technology Laboratory (NETL) is focused on the development of low-cost, highly efficient, and reliable fossil-fuel-based solid oxide fuel cell (SOFC) power systems that can generate environmentally friendly electric power with at least 90% carbon capture. NETL’s SOFC technology development roadmap is aligned with near-term market opportunities in the distributed generation sector to validate and advance the technology while paving the way for utility-scale natural gas (NG)- and coal-derived synthesis gas-fueled applications via progressively larger system demonstrations. The present study represents a part of a series of system evaluations being carried out at NETL to aid in prioritizing technological advances along research pathways to the realization of utility-scale SOFC systems, a transformational goal of the fuel cell program. In particular, the system performance of utility-scale NG fuel cell (NGFC) systems with and without carbon dioxide (CO2) capture is presented. The NGFC system analyzed features an external auto-thermal reformer (ATR) feeding the fuel to the SOFC system consisting of planar anode-supported SOFC with separated anode and cathode off-gas streams. In systems with CO2 capture, an air separation unit (ASU) is used to provide the oxygen for the ATR and for the combustion of unutilized fuel in the SOFC anode exhaust along with a CO2 purification unit to provide a nearly pure CO2 stream suitable for transport for usage in enhanced oil recovery (EOR) operations or for storage in underground saline formations. Remaining thermal energy in the exhaust gases is recovered in a bottoming steam Rankine cycle while supplying any process heat requirements. A reduced order model (ROM) developed at the Pacific Northwest National Laboratory (PNNL) is used to predict the SOFC performance. The ROM, while being computationally effective for system studies, provides other detailed information about the state of the stack, such as the internal temperature gradient, generally not available from simple performance models often used to represent the SOFC. Such additional information can be important in system optimization studies to preclude operation under off-design conditions that can adversely impact overall system reliability. The NGFC system performance was analyzed by varying salient system parameters, including the percent of internal (to the SOFC module) NG reformation—ranging from 0 to 100%—fuel utilization, and current density. The impact of advances in underlying SOFC technology on electrical performance was also explored.

Sol–gel synthesis of iodosodalite precursors and subsequent consolidation with a glass binder made from oxides and sol–gel routes

Radioiodine accumulates in aqueous solutions and off-gas streams during nuclear fuel reprocessing. In addition, radioiodine is highly mobile in geological environments. Most of the radioiodine can be captured during fuel reprocessing in off-gas streams using solid sorbents and scrubbing solutions. Once iodine is captured, it must be stored in a durable form for eventual disposal. Iodosodalite has been investigated as a waste form for radioiodine, however these synthesis processes often result in mixed products and iodine volatilization during consolidation. This paper proposes a novel approach to synthesizing iodosodalite utilizing a sol–gel method followed by heat treatment. This method was chosen to lower processing temperatures and improve product yield. Preliminary experiments conducted to determine the viability of this synthesis method are presented. In addition, consolidation of sol–gel derived iodosodalite with a glass binder was explored using three different methods: (1) incorporating the glass binder during gel preparation using alkoxide precursors; (2) separately preparing the glass binder using a sol–gel method; and (3) separately preparing the glass binder using a melt-quench technique. Glass-bonded iodosodalite was successfully synthesized using these novel sol–gel-based approaches.

Systematic retrofit method for refinery hydrogen network with light hydrocarbons recovery

Retrofit of the refinery hydrogen network is one of the important issues faced by modern refineries. Refinery off-gas streams are rich in hydrogen and valuable light hydrocarbons. Light hydrocarbons recovery (LHR) process can recover the valuable hydrocarbons and generate the hydrogen-rich stream for reuse and recycle. We firstly propose the systematic procedure for the retrofit of refinery hydrogen network integrated with LHR process. The approach combines the pinch analysis technique and process modelling and simulation. The typical pinch analysis technique (i.e. problem table) is used to determine the flowrate targets. Aspen HYSYS is used for the modelling and simulation of LHR process. The retrofit of an industrial refinery hydrogen network is conducted to illustrate the procedure. Results show that the benefit of retrofit scheme (Integrated Scheme 3) with LHR reaches 7.488 million CNY/y, and the investment payback period is only 8 months.

Intensifying the PC conversion in the raceway by means of coke oven gas

Among numerous measures to accelerate the PC conversion within the blast furnace (BF) raceway, local increase of oxygen concentration is the most common one. On the other hand, the presence of cold media (oxygen) in the vicinity of the coal stream might affect its ignition and combustion negatively. A minor amount of coke oven gas (COG) may increase the temperature and consequently accelerate the coal conversion. To examine this effect, laboratory trials under blast furnace simulating conditions were performed using the Multifunctional Injection Rig for Ironmaking (MIRI). The results of the simulation testified a higher conversion degree of coal while adding the COG. The temperature increase is measurable in the reaction chamber and the off-gas stream. Optical microscopy of the original PC particles and residues after reaction confirm the findings of the off-gas analysis and the increase in temperature during the experiments with addition of COG. The thermogravimetric analysis was applied to determine and to compare the behaviour of coal in different atmospheres including an atmosphere with COG. A stand at one tuyère at a modern BF was erected and tests were performed targeting the observation of the ignition behaviour of coal at different COG rates, using a camera image analysis system. Laboratory trials under blast furnace raceway simulating conditions showed, that even a small amount of COG significantly improves the PC conversion degree. A new technology of PC injection, including addition of small amount of COG to the PC transporting gas, aimed at neutralization of the oxygen local cooling effect, elaborated, justified and tested.

Liquid Antimony Anode for Converting Sulfur-Containing Coal in Direct Carbon Fuel Cells

Liquid antimony anodes (LAAs) are carbon-converting anodes for direct carbon fuel cells (DCFCs), and they have been intensively studied over the last decade because of their decent performance. Though several previous researches have demonstrated the capability of LAAs in carbon oxidation, reaction mechanisms between the LAA and the impurities in the solid carbon fuels, e.g., sulfur, remains largely unknown. In the present research, H2S and pyrite were introduced into the anode, respectively, as the sources of sulfur. The fuel cell was first discharged under 1000 ppm of H2S continuously for over 10 h. At the same time, we used mass spectrometer (MS) to monitor the composition of its flue gas. The performance of the cell remained mostly unchanged under the H2S atmosphere throughout the test, and the lower sulfur concentration in the off-gas stream suggested that the LAA trapped most of the sulfur within itself. In the case of pyrite, the performance of the cell remained stable during the 20-h test, despite the relatively large amount of sulfur fed into the system. The experimental results demonstrated that the LAA is resistive against the sulfur poisoning and able to handle fuels with a high level of sulfur content.

Development of bismuth-mordenite adsorbents for iodine capture from off-gas streams

• Development of bismuth-doped mordenite adsorbents with various bismuth loadings. • Higher surface area and porosity for the bismuth-modernite than that for bare mordenite. • 2.5-fold increase in iodine capacity for bismuth-modernite than that for bare mordenite. • 36% of iodine release to water from the iodine-loaded adsorbents. The search for efficient, cheap, and robust sorbent materials which can effectively remove iodine compounds from off-gas streams in used nuclear fuel reprocessing facilities is still challenging. Herein, we report the development of bismuth-doped mordenite zeolite with different loadings for removal of iodine-129 ( 129 I) from nuclear waste off-gas streams. Of the materials investigated, bismuth-mordenite with 5 wt% bismuth content (Bi 5 @Mordenite) exhibited the highest capture capacity with an iodine uptake capacity up to 538 mg/g after exposure to iodine for 6 h at 200 °C, which was ~2.5 times higher than that of the bare mordenite with relatively fast kinetics. Interestingly, the bismuth-doped mordenite sample exhibited higher surface area and porosity than those of the bare zeolite as a result of mordenite dealumination during bismuth incorporation. Moreover, the leach tests were carried out to determine the degree of iodine leaching from the iodine-loaded Bi 5 @Mordenite upon coming into contact with DI water and the results revealed a maximum iodine amount of 36% that was released from the adsorbent after 24 h exposure, highlighting the necessity of transforming the iodine-loaded adsorbent into a suitable waste form for permanent geological disposal. Overall, the high uptake capacity and fast uptake rate of iodine reveal the potential utility of bismuth-based zeolites as iodine capture materials when consolidated into a waste form for long-term decay storage.

The effect of doping on adsorption of Xe and Kr on graphyne and graphdiyne

Sequestration of radioactive noble gases xenon (Xe) and krypton (Kr) from off-gas streams of nuclear reactors and spent nuclear fuel reprocessing plants are essential. The Generally employed cryogenic distillation process for Xe/Kr separation is expensive and adsorption based techniques using porous materials are viable alternative. Recently, carbon allotropes such as graphynes (Gyn) and graphdiynes (Gdyn) attained importance due to their significance in many applications similar to graphene. In both graphyne and graphdiyne, the carbon atoms are sp-sp2 hybridized where benzene rings are linked through acetylenic and diacetylenic linkages respectively. They are good candidates for gas adsorption/separation due to their chemical stability and large surface area. In this regard, we have investigated the noble gas adsorption properties of doped/undoped graphyne and graphdiyne materials using density functional theory calculations. The graphyne and graphdiyne display enhanced adsorption affinity for Xe and Kr when doped with selective heteroatoms.

Aspen Plus simulation and optimization of industrial spent caustic wastewater treatment by wet oxidation method

Spent caustic is a waste generated by petrochemical refineries, which used to eliminate acid components such as hydrogen sulphide (H2S) and mercaptans from the refined product streams. A study was carried out on simulation and optimization of spent caustic wastewater treatment system by using Aspen Plus based on wet air oxidation (WAO) method. WAO method uses air under elevated temperature and pressure to carry out oxidation in the aqueous phase. Process flow diagram (PFD) of WAO method was drawn and relevant input data was keyed in Aspen Plus according to experimental results on WAO. Both results were validated and the results were match each another as the percentage of allowable error between both the results were less than 5 %. After that, optimization was carried out to determine the optimum ratio of spent caustic feed flow rate to air flow rate and operating temperature of the flash separator unit involved in the process. From the optimization results, it can come to a conclusion that 1: 9.2 is the minimum spent caustic feed flow rate to air flow rate ratio and optimum operating temperature of flash separator unit is 140°C in order for maximum flow rate of CH3SSCH3 in offgas stream in this simulation model of spent caustic wastewater treatment system using WAO method.

Selective removal of CO from hydrocarbon-rich industrial off-gases over CeO2-supported metal oxides

For the selective removal of CO in the off-gas streams from real-life chemical processes, the interfacial interaction between the support and the active metal oxides and the role of active oxygen species are two fascinating problems. Herein, a series of CeO2-supported metal oxide catalysts were synthesized by co-precipitation method and employed for the selective removal of CO from the off-gas stream of propane oxidation process. CuO/CeO2 catalyst exhibits full CO conversion and 100% selectivity for CO removal in off-gas stream within a rather wide temperature window of 140–190 °C, being relatively stable in 200-h long-term time-on-stream experiment. Raman spectra, H2-TPR, CO-TPD and XPS spectra studies revealed that the redox properties and the concentration of active oxygen species varied with supported metal oxide compositions, for which CuO/CeO2 catalyst exhibited the highest surface oxygen vacancy concentration, good low-temperature reduction behavior and the highest adsorption capacity of CO, thus resulting in advanced CO removal performance. This study presents a strategy to design a promising CeO2-supported catalyst for oxidation removal of CO from off-gas of alkane oxidation process.

Online measurement of CO2 and total gas production in parallel anaerobic shake flask cultivations

Online measurements of off-gas streams are often crucial for studying bioconversion processes. However, for anaerobic processes, options for online off-gas analysis are typically restricted to lab-scale bioreactors or larger systems, while gas measurements at smaller scales typically do not discriminate between different gases. In this work, a method for online measurement of CO2 and total gas production in anaerobic fermentations at the shake flask scale is described, extending capabilities of a previously reported device developed for aerobic processes to anaerobic bioprocesses. The novel design allows anaerobic fermentations to be performed in multiple parallel vessels, all of which collect online gas signals. The online gas signals are used to calculate the transfer rates, allowing near real-time visualization of the progress of eight fermentations operating in parallel. Conditions such as carbon source depletion, inhibition of growth, and exhaustion of a single carbon source in a dual-substrate fermentation can all be clearly distinguished. The combination of online signals and offline analysis allowed for carbon balances to be performed with high degrees of closure. The new design allows for higher throughput screening of anaerobic bioprocesses, an area lacking in small-scale options with off-gas analysis capabilities.

Efficient capture of iodine by a polysulfide-inserted inorganic NiTi-layered double hydroxides

Effective capture of radioactive iodine is highly desirable but still remains a significant challenge. We reported here a polysulfide (Sx2−) intercalated inorganic cationic Ni-Ti layered double hydroxide, NiTi-Sx-LDH, which was prepared by coprecipitation method and ion exchange method for efficient capture of iodine. Due to the strong chemical attraction between the soft Lewis base Sx2− and the soft Lewis acid I2, and the reducing property of Sx2−, NiTi-Sx-LDH exhibits highly efficient iodine capture. During the adsorption process, I2 is reduced to I3− by the intercalated Sx2−. In combination with chemical adsorption and physical adsorption, the adsorption capacity of NiTi-Sx-LDH to iodine vapor reaches 52% (wt%). In addition, the adsorption properties of NiTi-Sx-LDH on elemental iodine in organic solvent cyclohexane were also studied, and the maximum adsorption capacity of NiTi-Sx-LDH for iodine reaches up to 527.4 mg/g. Compared with various sorbents for iodine, it is cost-effective, capable of achieving scale-up preparation, and the good performance for the iodine adsorption suggests that NiTi-Sx-LDH may be considered as a promising sorbent for efficient removal of radioactive iodine from reprocessing plant off-gas streams.

Adsorbents and adsorption models for capture of Kr and Xe gas mixtures in fixed-bed columns

Off-gases produced during the reprocessing of used nuclear fuel (UNF) include 129I2, 3HHO, 14CO2, 85Kr, and 135Xe, which are volatilized out into the off-gas. In order to meet regulatory requirements for reprocessing plant emissions, these gases must be captured and removed from the off-gas stream prior to off-gas emission. Of particular interest are the noble gases, Kr and Xe, which can be fairly difficult to remove from the off-gas due to their low chemical reactivity. Thus, this work is focused on utilizing engineered adsorbents, AgZ-PAN and HZ-PAN, to capture Kr and Xe from a mixed-gas stream at relatively low temperatures (191–295 K) and various flow rates (50–2000 mL/min). Isothermal data for Kr and Xe on each adsorbent are analyzed to produce the Langmuir parameters needed to model the mixture adsorption capacities at relevant temperatures using the Extended Langmuir model. Those parameters are then incorporated into a fixed-bed adsorption model developed in this work using the Mulitphysics Object-Oriented Simulation Environment (MOOSE). That model is used to simulate breakthrough times for Kr and Xe in packed columns of AgZ-PAN and HZ-PAN, ranging in length from 6 to 20 in., at relevant temperatures and flow rates. Breakthrough times varied from nearly instantaneous for Kr in AgZ-PAN to 30 h for Xe in HZ-PAN. After the developed model was validated by comparisons with experimental breakthrough data, the model framework was used to simulate the performance of multiple fixed-bed columns connected in series.

Economic assessment of membrane-based power-to-gas processes for the European biogas market

Four different power-to-gas process chains implementing catalytic methanation and membrane upgrading are presented. Their economics for synthetic natural gas production and hydrogen storage are assessed for the first time in the context of multiple different European gas grid standards by simulation. Influence of two different fermentation setups for biogas production as well as pressure levels from 6 to 15 bar and catalyst specific flow rates from 100 to 150 Nl/(h gCAT) were considered. Based on this simulation an economic analysis was done. Capital expenditures and operational expenditures for electrolysis, methanation, membrane gas upgrading, and compressors of each chain are presented.It is shown that the integration of a simple recycle of the off-gas stream can reduce the costs from up to 2.93 €/Nm³ produced synthetic natural gas to at least 1.63 €/Nm³. Hydrogen storage cost can be decreased from up to 1.81 €/Nm³ stored hydrogen to at least 0.95 €/Nm³. Variation of the fermentation setup only leads to savings in the range of 0.03–0.08 €/Nm³ synthetic natural gas if off-gas recycling is included. Catalyst specific gas flow rate is shown to be of neglectable influence, contributing less than 0.01 €/Nm³ produced synthetic natural gas or stored hydrogen. Pressure influence is more pronounced at up to 0.10 €/Nm³ produced synthetic natural gas and up to 0.05 €/Nm³ stored hydrogen. Optimal operation pressure for simple off-gas recycling is shown to be below 10 bar.