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![CH4 adsorption isotherms on zeolite 13X. Lines indicate the fitted Sips isotherms. The low pressure region up to 1 bar is shown separately. The dotted lines correspond to literature isotherms on zeolite 13X at 45 °C from [8] (blue), [24] (green), [29] (yellow), and [7] (purple) (Color figure online)](publication/349705726/figure/fig5/AS:996779583610901@1614662180625/CH4-adsorption-isotherms-on-zeolite-13X-Lines-indicate-the-fitted-Sips-isotherms-The.png)
CH4 adsorption isotherms on zeolite 13X. Lines indicate the fitted Sips isotherms. The low pressure region up to 1 bar is shown separately. The dotted lines correspond to literature isotherms on zeolite 13X at 45 °C from [8] (blue), [24] (green), [29] (yellow), and [7] (purple) (Color figure online)
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Reforming of fossil fuels coupled with carbon capture and storage has the potential to produce low-carbon H2 at large scale and low cost. Adsorption is a potentially promising technology for two key separation tasks in this process: H2 purification and CO2 capture. In this work, we present equilibrium adsorption data of H2 and CH4 on zeolite 13X, i...
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Hydrogen as clean energy carrier is expected to play a key role in future low-carbon energy systems. In this paper, we demonstrate a new technology for coupling fossil-fuel based hydrogen production with carbon capture and storage (CCS): the integration of CO 2 capture and H 2 purification in a single vacuum pressure swing adsorption (VPSA) cycle....
The aim of this work is the investigation of several CO2 adsorbents such as three synthetic zeolites (4A, 5A, and 13X), a natural zeolite (clinoptilolite), an activated carbon (AC), and a metal organic framework (MOF‐MIL‐53) for the postcombustion CO2 capture via temperature‐pressure swing adsorption. The adsorbents were evaluated in terms of the C...
The pressure swing adsorption (PSA) process was used to capture carbon dioxide (CO2) from the flue gas of a coal-fired power plant to reduce CO2 emissions. Herein, CO2 was captured from flue gas using the PSA process for at least 85 vol% CO2 purity and with the other exit stream from the process of more than 90 vol% N2 purity. The extended Langmuir...
With the rising level of atmospheric CO2 worsening climate change, a promising global movement toward carbon neutrality is forming urgently. Sustainable CO2 management based on carbon capture and utilization has garnered considerable interest due to its critical role in resolving emission‐control and energy‐supply challenges. Here we present a comp...
The requirement to counter carbon emissions is becoming urgent. Zeolitic Imidazolate Frameworks (ZIFs) have been extensively investigated recently for storing and separating gases, especially carbon dioxide. The present review aims to summarise the state of the art of ZIFs for carbon dioxide capture focusing on the structure, mechanism, optimisatio...
Citations
... The global standalone hydrogen production in 2020 remained at 90 million tons per year (Mt/ y), and with most of it being fossil fuel-based, resulted in 900 Mt/y of carbon dioxide emissions [3]. The share of catalytic steam methane reforming (SMR), coal gasification, and water electrolysis in hydrogen generation is about 76%, 23%, and 1%, respectively [2,4]. With the increasing demand and to achieve a sustainable future, it is vital that hydrogen is generated without associated carbon dioxide emissions. ...
... Further, the syngas with a high concentration of hydrogen generated using oxy-steam gasification of mixed agro-residue pellets (ARP) can be separated downstream for hydrogen production. Swing adsorption technologies are widely applied for this purpose due to their simplicity, low energy consumption [33,34] at a small scale (output < 500 tons per day) [35], and applicability over a wide range of temperatures, pressures, and mixture compositions [4]. Most of the adsorptive separations reported in the literature are performed with the feed gas available at the exit of the fossil SMR-water gas shift (WGS) process, which primarily contains hydrogen (~75 vol%) and has carbon dioxide (20-25 vol%) as the major impurity. ...
The present work reports on the characterization of mixed agro-residue pellets and their subsequent use for
syngas generation in a laboratory-scale downdraft gasifier utilizing the mixture of oxygen and steam as the
gasifying agent (equivalence ratio/steam to biomass ratio: 0.21/2.15). Pure hydrogen is realized in a vacuum
pressure swing adsorption system using zeolite 13X adsorbent. Regarding pellets, the high ash content (11.46 ±
0.38 wt%) and the presence of inorganic elements (potassium, silicon, calcium) dictate gasification process level
interventions. The key requirement established experimentally is maintaining the reactor temperature under
900 ◦C for a clinker-free operation. This prerequisite, accomplished through an optimized char-ash extraction
rate, enables the consistent production of hydrogen-rich (42.2 ± 0.9 vol%) syngas with a lower heating value of
8.3 ± 0.2 MJ/Nm3 at a gross cold gas efficiency of 78.9%. The cyclic separation system operates at a pressure
ratio of 7.5 and continually generates pure hydrogen with minimal contaminants. The oxy-steam gasification of
high ash feedstock in a near-ambient fixed-bed reactor and its integration to a low-pressure swing adsorption
system for practical multi-specie syngas separation with quality assessment of the produced hydrogen are the
main novelty features.
... Several separation technologies, including cryogenic distillation, membranes, absorption, and adsorption, are available. Out of these methods, the latter works on a simple principle, is flexible [17], has low energy consumption [18], is applicable over a wide range of temperatures and pressures [19,20], and is therefore adopted for multi-component gas separation. ...
... Vacuum/pressure swing adsorption (V/ PSA) processes are commonly applied for bulk separation due to their higher productivity, longer adsorbent life, and easy operation. The literature reports the generation of high-purity H 2 , with most of the studies detailing the use of fossil SMR-WGS process stream containing (mol%) H 2 (~75), CO (0-5), CO 2 (15)(16)(17)(18)(19)(20), CH 4 (3)(4)(5), and N 2 (0-3), and utilize either a PSA or a VPSA process for separation which exploits the available high pressure (13-34 bar-abs) of the syngas during adsorption step and desorbs the pre-adsorbed impurities by exposing the columns to ambient or vacuum (0.1-0.9 bar-abs) [21][22][23][24][25]. Additionally, the use of high H 2 -content (83-99 mol%) feeds [1,[26][27][28], coal gas [29], and coke oven gas [30] has also been discussed. The reviewed studies report experimental and/or simulation results, employ various adsorbent types (activated carbons, zeolites, and metal organic frameworks), involve 1 to 10 adsorbers, and primarily use a simulated-dry feed gas mixture. ...
The current work reports on the performance characterization of a VPSA system developed in-house for ISO-quality green hydrogen generation using commercially available zeolite 13X from two practical multi-specie feed streams generated from near-ambient oxy-steam and air gasification of casuarina wood chips. The breakthrough dynamics in a packed column, and the effect of extrinsic and intrinsic decision variables on the separation performance under a cyclic steady state are analyzed. Adsorption pressure and feed flow rate are noted as the most significant influencing factors. The assessment indicates the prevalence of bed thermal gradients and establishes N2 as a limiting gas impurity and CO2 desorption as a rate-determining step. Additionally, Pareto curves signifying the process capability to produce hydrogen of different grades are generated. The average recovery range achieved using syngas feed for obtaining purity >98 mol% (ISO grade A and above) at the lab-scale is noted to be 40.7–74.4%, which is analogous to published literature for fossil streams. Adopting the optimal parameters from the prototype studies and a precise gas contaminant analysis, the technology is practically demonstrated at the pilot scale (feed: 100 Nm3/h) for the continuous generation of fuel cell compliant hydrogen (fuel index ≥ 99.97) and a successful operation at an average recovery of 68.4 ± 3.5% is realized.
... On the other hand, some studies have also considered the use of zeolite 13X as an adsorbent due to its high water adsorption capability [16][17][18]. In this study, for the first time, the synthesis of zeolites 4A and 13X from natural sources (Kankara kaolin) and the mixture optimization for solar adsorption refrigeration application were considered. ...
In a way to overcome challenges with global warming, the use of fossil fuels in producing environmentally friendly energy towards reducing the ozone layer depletion and greenhouse gas emissions by participating countries is of interest. The adsorption refrigeration system has the advantages of a long lifespan and its environmental friendliness; however, its major disadvantage is the low coefficient of performance, which is a function of adsorbent–adsorbate, with zeolite–water as the most common adsorbent–adsorbate working pair. Zeolites 4A and 13X are the most used zeolite classes due to their higher selectivity for separating mixtures of CO2/N2 and CO2/CH4/N2 and their high-water adsorption capability, respectively. In this study, for the first time, the synthesis of zeolites 4A and 13X from natural sources (Kankara kaolin) and the mixture optimization for solar adsorption refrigeration application were considered. Raw Kankara kaolin, beneficiated Kankara kaolin, calcined Kankara kaolin and synthesized zeolites 4A and 13X were characterized using X-ray fluorescence, while the synthesized zeolites 4A and 13X were characterized using X-ray diffraction. Using the mixture simplex lattice design of experiment, mixtures of zeolites 4A and 13X were developed and characterized using Brunauer, Emmett and Teller analysis to obtain their pore size, specific surface area and pore volume. The statistical analysis produced the mathematical models of the response that were significant for pore size and specific surface area. The analysis proposed an optimal solution of 75 wt% zeolite 4A and 25 wt% zeolite 13X, which gave a desirability of 0.944.
... In a DCB experiment, a small column packed with pellets of an adsorbent material is used to adsorb a feed gas. During the dynamic adsorption process, the outlet gas composition and volumetric gas flow rate, the internal temperature (at one or more locations) and the internal adsorption profiles can all be measured as functions of time [4][5][6]. The dynamic adsorption process can be modelled by application of a DCB model, in which material and energy balances are solved, with respect to time, as a coupled system of partial differential equations using a finite-volumes numerical scheme [7]. ...
We have carried out the traditional analysis of a set of dynamic breakthrough experiments on the $$\hbox {CO}_2$$ CO 2 /He system adsorbing onto activated carbon by fitting a 1D dynamic column breakthrough model to the transient experimental profiles. We have quantified the uncertainties in the fitted model parameters using the techniques of Bayesian inference, and have propagated these parametric uncertainties through the dynamic model to assess the robustness of the modelling. We have found significant uncertainties in the outlet mole fraction profile, internal temperature profile and internal adsorption profiles of approximately $$\pm 15\%$$ ± 15 % . To assess routes to reduce these uncertainties we have applied a global variance-based sensitivity analysis to the dynamic model using the Sobol method. We have found that approximately $$70\%$$ 70 % of the observed variability in the modelling outputs can be attributed to uncertainties in the adsorption isotherm parameters that describe its temperature dependence. We also make various recommendations for practitioners, using the developed Bayesian statistical tools, regarding the choice of the isotherm model, the choice of the fitting data for the extraction of system specific parameters and the simplification of the wall energy balance.
... All modelling approaches have in common a thermodynamic inconsistency. Therefore, some research was focussed on transferring approaches from gas to liquid phase adsorption [12,13] and to gain thermodynamically consistence [14][15][16]. Nevertheless, in daily project work, these more sophisticated models were not applied due to numerical complexity and higher efforts of experimental parameter determination. ...
Process chromatography modelling for process development, design, and optimization as well as process control has been under development for decades. Still, the discussion of scientific potential and industrial applications needs is open to innovation. The discussion of next-generation modelling approaches starting from Langmuirian to steric mass action and multilayer or thermodynamic consistent real and ideal adsorption theory or colloidal particle adsorption approaches is continued.
... Unfortunately, such data are rarely reported; even higher pressure studies are mostly limited to modest pressures (e.g., <20 bar [82]). Two exceptions are the report of H2 uptake on LTA and FAU-type zeolites at 77 K up to 70 bar [83], and the report of H2 uptake on an FAU-type zeolite at 298 K up to 35 bar [84]. These data reveal that despite the high volumetric density of micropores, FAUtype zeolites exhibit poor total volumetric hydrogen uptake and delivery at both 298 K and 77 K, in comparison to porous carbons and MOFs (as shown below). ...
Physical adsorption remains a promising method for achieving fast, reversible hydrogen storage at both ambient and cryogenic conditions. Research in this area has recently shifted to focus primarily on the volumetric (H2 stored/delivered per volume) gains achieved within an adsorptive storage system over that of pure H2 compression; however, the methodology for estimating a volumetric stored or delivered amount requires several assumptions related to the ultimate packing of the adsorbent material into an actual storage system volume. In this work, we critically review the different assumptions commonly employed, and thereby categorize and compare the volumetric storage and delivery across numerous different porous materials including benchmark metal-organic frameworks, porous carbons, and zeolites. In several cases, there is a significant gain in both storage and delivery by the addition of an adsorbent to the high-pressure H2 storage system over that of pure compression, even at room temperature. Lightweight, low-density materials remain the optimal adsorbents at low temperature, while higher density, open metal-containing frameworks are necessary for high-density room temperature storage and delivery.
... In eq 4, A represents the surface area per kg of framework, and q i 0 (f) is the pure component adsorption isotherm; the superscript 0 is used to emphasize that q i 0 (f) relates the pure component loading to the bulk fluid fugacity. Since the surface area A is not directly accessible from experimental data, the surface potential, 40,43 ≡ Φ πA RT , with the unit mol kg −1 , serves as a convenient and practical proxy for the spreading pressure π; the surface potential has also been termed the adsorption potential in several recent publications. 49−52 For multicomponent mixture adsorption, each of the equalities on the right side of eq 4 must be satisfied. ...
Microporous crystalline adsorbents such as zeolites and metal–organic frameworks (MOFs) have potential use in a wide variety of separation applications. The adsorption selectivity Sads is a key metric that quantifies the efficacy of any microporous adsorbent in mixture separations. The Ideal Adsorbed Solution Theory (IAST) is commonly used for estimating the value of Sads, with unary isotherms of the constituent guests as data inputs. There are two basic tenets underlying the development of the IAST. The first tenet mandates a homogeneous distribution of adsorbates within the pore landscape. The second tenet requires the surface area occupied by a guest molecule in the mixture to be the same as that for the corresponding pure component. Configurational-bias Monte Carlo (CBMC) simulations are employed in this article to highlight several scenarios in which the IAST fails to provide a quantitatively correct description of mixture adsorption equilibrium due to a failure to conform to either of the two tenets underpinning the IAST. For CO2 capture with cation-exchanged zeolites and MOFs with open metal sites, there is congregation of CO2 around the cations and unsaturated metal atoms, resulting in failure of the IAST due to an inhomogeneous distribution of adsorbates in the pore space. Thermodynamic non-idealities also arise due to the preferential location of CO2 molecules at the window regions of 8-ring zeolites such as DDR and CHA or within pockets of MOR and AFX zeolites. Thermodynamic non-idealities are evidenced for water/alcohol mixtures due to molecular clustering engendered by hydrogen bonding. It is also demonstrated that thermodynamic non-idealities can be strong enough to cause selectivity reversals, which are not anticipated by the IAST.
... In part one [15], we focus on equilibrium isotherm measurements and breakthrough studies to estimate transport parameters, identify a suitable heat transfer model, and validate our column model for relevant mixtures and a variety of temperatures, pressures and flow rates. In this second part, we present cyclic experiments carried out in the same two-column setup for a ternary CO 2 -H 2 -CH 4 stream as feed and using zeolite 13X as adsorbent. ...
... Subsequently, the column was pre-saturated to ensure an initial state that is close to the final state, first with the feed mixture at 25 bar until the temperature front related to CO 2 adsorption reached the middle of the column, then at ambient pressure with the heavy purge mixture until the CO 2 thermal front reached the fifth thermocouple, and finally evacuated and purged with H 2 . This procedure drastically reduced the number of cycles needed to reach steady state from around 50 cycles to [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] cycles. Cyclic steady state (CSS in short) was verified by checking that the composition and temperature profiles for five subsequent cycles do not change. ...
... Process modeling In this work, the same one dimensional model based on mass and energy balance equations as described in part one of this series [15] was used for comparing experimental and simulation results. The gas phase was described using the ideal gas law, the pressure drop was described with the Ergun equation. ...
Hydrogen as clean energy carrier is expected to play a key role in future low-carbon energy systems. In this paper, we demonstrate a new technology for coupling fossil-fuel based hydrogen production with carbon capture and storage (CCS): the integration of CO 2 capture and H 2 purification in a single vacuum pressure swing adsorption (VPSA) cycle. An eight step VPSA cycle is tested in a two-column lab-pilot for a ternary CO 2 –H 2 –CH 4 stream representative of shifted steam methane reformer (SMR) syngas, while using commercial zeolite 13X as adsorbent. The cycle can co-purify CO 2 and H 2 , thus reaching H 2 purities up to 99.96%, CO 2 purities up to 98.9%, CO 2 recoveries up to 94.3% and H 2 recoveries up to 81%. The key decision variables for adjusting the separation performance to reach the required targets are the heavy purge (HP) duration, the feed duration, the evacuation pressure and the flow rate of the light purge (LP). In contrast to that, the separation performance is rather insensitive towards small changes in feed composition and in HP inlet composition. Comparing the experimental results with simulation results shows that the model for describing multi-component adsorption is critical in determining the predictive capabilities of the column model. Here, the real adsorbed solution theory (RAST) is necessary to describe all experiments well, whereas neither extended isotherms nor the ideal adsorbed solution theory (IAST) can reproduce all effects observed experimentally.
