Long-term Cyclic Operation Research Articles

Effects of competitive cations and dissolved organic matter on ammonium exchange and up-concentration properties of ion exchangers from domestic wastewater under multicycle exchange - regeneration operation

This study aimed to investigate the impact of competitive cations and dissolved organic matter (DOM) on ammonium exchange and up-concentration properties of ion exchangers for domestic wastewater treatment during the multicycle exchange - regeneration operations. Three ion exchangers, including zeolite, strong acid cation resin and 4A molecular sieve (MS), all showed good NH4+ separation and up-concentration properties in 30 exchange - regeneration cycles. The exchange capacities of zeolite, resin, and MS decreased by 8.2 %, 10.4 %, and 4.8 % in the presence of Ca2+ and Mg2+, while DOM only impaired the exchange ability of zeolite. The up-concentration factors of zeolite, resin, and MS were 5.1, 11.5, and 5.0, respectively. Isothermal tests and breakthrough curves confirmed that long-term salt regeneration slightly reduced the exchange capacity, and the presence of competitive cations and DOM shortened the breakthrough time. Elemental mass balance further demonstrated that Ca2+ and Mg2+ were easily trapped by ion exchangers and could be released into the regeneration solution, which should be precipitated to avoid accumulation for long-term cyclic operation. Morphological analysis indicated that the presence of Ca2+ and Mg2+ would cause the resin to crack. Overall, for domestic wastewater treatment, the resin exhibited the highest NH4+ capture ability and up-concentration properties with low resistance to Ca2+ and Mg2+ contamination, while silicate exchangers with a regular and compact structure had higher durability but lower up-concentration properties.

Lithium-ion battery pack thermal management under high ambient temperature and cyclic charging-discharging strategy design

To ensure the stable operation of lithium-ion battery under high ambient temperature with high discharge rate and long operating cycles, the phase change material (PCM) cooling with advantage in latent heat absorption and liquid cooling with advantage in heat removal are utilized and coupling optimized in this work. Based on the preferred hybrid cooling scheme, the two layers cold plates and fins are arranged, and the cold plate structure is redesigned to optimize cooling system. The coupling effects of composite PCM and water flow rate, as well as charging and discharging strategy, are numerically studied. The results show that the hybrid cooling is more suitable to high discharge rate of 5C and long-term cyclic operation at 40 °C. The two layers cold plate and fins arranged in hybrid cooling system can mitigate the temperature non-uniformity of batteries along the axis, and the maximum temperature Tmax and temperature difference ΔTmax are reduced by 4.44 °C and 4.17 °C, respectively. Also, the optimized cold plate can mitigate the temperature non-uniformity caused by battery dispersion, and the standard deviation of temperature of batteries is reduced from 0.48 to 0.37. Then, the composite PCM added with expanded graphite can further decrease the Tmax and ΔTmax by 2.18 °C and 1.79 °C, respectively. Lower charging rate offers more reliable cooling performance during continuous cyclic operations. In general, the designed fin-enhanced hybrid cooling system with composite PCM and two layers cold plate can control the Tmax and ΔTmax within 45.85 °C and 3.39 °C at 40 °C ambient temperature and 5C discharge respectively, and offers a reliable and desired cooling performance during continuous charging and discharging of 1C, 2C and 3C. During cyclic operation with 3C discharging and 1C charging, the Tmax and ΔTmax can be controlled below 44.39 °C and 2.64 °C, respectively.

Hydrogen production by isothermal thermochemical cycles using La0.8Ca0.2MeO3±δ (Me = Co, Ni, Fe and Cu) perovskites

Solar-driven thermochemical water splitting has the potential to transform concentrated solar energy into green hydrogen and other solar fuels. In this work, La0.8Ca0.2MeO3±δ (Me = Co, Ni, Fe and Cu) perovskites have been synthesised by a modified Pechini method and evaluated as materials for hydrogen production by two step thermochemical water splitting cycles. Performing the thermal reduction at temperatures of 1200 and 1000 °C, while the oxidation is done at 800 °C, allows a remarkable and stable hydrogen production after 5 consecutive cycles. However, the perovskites suffer changes in the structure after each redox cycle, with potential effects in the long-term cyclic operation. On the contrary, the isothermal thermochemical cycles at 800 °C produce a stable amount of hydrogen with each consecutive cycle maintaining the perovskite structure. This hydrogen production ranges from 3.60 cm3 STP/gmaterial·cycle for the material with the lowest productivity (La0.8Ca0.2FeO3±δ) to 5.02 cm3 STP/gmaterial·cycle for the one with the highest activity (La0.8Ca0.2NiO3±δ). Particularly the Ni-based material shows the highest H2 productivity accompanied by very good material stability after 15 consecutive cycles, being possible to combine with current solar thermal facilities based on concentrated solar power technologies like plants with central receivers.

Reservoir gas losses at UGS facilities in aquifers

Experience shows that in the process of creating and long-term cyclic operation of underground gas storage facilities (UGS) in reservoirs of aquifers, reservoir gas losses can occur. Losses can reach tens of percent of the injected volumes of gas into the reservoir and have a significant impact on the reliability and safety and efficiency of operation of UGS. In this regard, the issues of the organization of field control and methodology for assessing reservoir gas losses at UGS are relevant. The article proposes the structuring of the gas injected into the reservoir into possible reservoir components, taking into account the state of the gas phase and participation in filtration mass transfer processes. The main factors determining the formation of different reservoir components are given. The basic concepts are considered and the definition of reservoir gas losses at UGS in aquifers is given. The main features of one or another type of reservoir gas losses are shown. Reservoir losses from free gas currents from an artificial gas deposit, which can occur as a result of vertical leaks from the storage facility and lateral gas escapes through the reservoir beyond the trap, are briefly described. Formation losses associated with gas adsorption by rocks, gas phase transitions and gas saturation of low-permeable sections of reservoirs; gas dissolution in invading reservoir water and its convective-diffusion entrainment by displaced water into the aquifer region of the reservoir are also considered. Using the example of a UGS created in an aquifer, the system of geological and commercial monitoring of a subsurface area within a mining branch in conditions of vertical interplastic flows of free gas is considered. It is shown that the implemented system of observation and control wells allows for adequate monitoring of the gas storage facility and control of the tightness of UGS throughout the section above the storage facility. The following components of reservoir gas losses at the storage facility are considered: dissolved gas in residual water within the gas reservoir; gas adsorbed by rocks within the gas reservoir; dissolved gas diffused from the gas reservoir into the contact aquifer region of the reservoir; dissolved and free gas in the control horizons. Using a geological model of the formation, as well as the results of modeling the convective-diffusion transfer of dissolved gas into the aquifer region of the formation, the assessment of the components of reservoir gas losses in a direct way by their locations is given.

Promoting effects of Li3PO4 and CaCO3 on the intermediate-temperature CO2 adsorption over molten NaNO3-promoted MgO-based sorbents

Molten nitrate-promoted MgO-based sorbents represent a potential class of materials for CO2 capture at intermediate temperatures. However, their poor stability under harsh but realistic regeneration conditions (e.g., at high temperatures in pure CO2) is a challenge for the application of CO2 capture. In this work, a series of NaNO3 and/or Li3PO4 promoted MgO and MgO-CaCO3 sorbents were prepared, characterized, and evaluated. The results showed that the NaNO3-Li3PO4 promoted MgO-CaCO3 sorbents had high CO2 adsorption performance in terms of rate, capacity and stability, which was attributed to the promoting effect of Li3PO4 and CaCO3. Li3PO4 can enhance the surface adsorption of CO2 by providing some extra moderate basic sites, while CaCO3 can accelerate the carbonation reaction of bulk MgO via the formation of CaMg(CO3)2. In addition, Li3PO4 can hinder the sintering of sorbent particles, and consequently improve the stability of the sorbent. The optimized sorbent had a stable CO2 uptake of 0.12 (or 0.26) gCO2/gsorbent when 30% (or pure) CO2 was used at the adsorption stage in long-term cyclic operation (desorption at 500 °C in pure CO2 for both cases), showing promising applications in intermediate-temperature CO2 capture and thermochemical energy storage.

Achieving no spent brine discharge in an anion exchange resin-based fixed-bed process for typical DOM removal

The anion exchange resin (AER) process successfully removed dissolved organic matter (DOM) from various water matrices. To restore AER capacity by routine DOM removal from the regenerant is an attractive strategy to solve the spent brine disposal problem. This study investigated the long-term removal (from the feed) and accumulation (in the inorganic regenerant) characteristics of typical DOM molecules (including anionic pharmaceuticals, short-chain aliphatic acids, humic substances and amino acids) during ˜50 adsorption–regeneration cycles of an AER-based fixed-bed process with the routine physico-chemical purification treatment of the regenerant. All anionic DOM molecules complied with common long-term removal and accumulation mechanisms driven by both electrostatic and non-electrostatic interactions in a multicomponent system, regardless of aromatic structure, hydrophobicity/hydrophilicity, or water solubility. A high anionic DOM removal (˜90%) from the feed could be stably achieved after anionic DOM accumulated in the regenerant was effectively removed (˜80%) by more frequent regenerant-purification treatments. The AER presented here did not selectively remove aromatic and/or hydrophobic DOM molecules from water matrices during the long-term cyclic operation. These findings will enable the development of new designs of AER-based fixed-bed processes for DOM removal from various water matrices.

Investigations on a Mesoporous Glass Membrane as Ion Separator for a Redox Flow Battery

This article reports extensive studies of a Vycor® porous glass (VPG) membrane as an ion separator for an all-vanadium redox flow battery (VRFB). The VPG membrane had an average pore size of 4 nm and porosity of ~28%. The VPG ion separator exhibited higher proton diffusivity but lower conductivity than the Nafion® 117 membrane because the former is intrinsically nonionic. The VRFB equipped with the VPG ion separator (VPG-VRFB) exhibited much better stability during long-term cyclic operation than the VRFB equipped with the Nafion-117 membrane (Nafion-VRFB) because the ionic Nafion membrane could be contaminated by vanadium ions exchanged into the water channels. This increases its area specific resistance, while the VPG does not have ion exchange capacity and hence has less vanadium ion contamination. The VPG-VRFB was found to outperform the Nafion-VRFB in energy efficiency (EE) during long-term cyclic operation although the former underperformed the latter in the initial period of continued operation. The VPG ion separator also showed markedly better thermal stability and temperature tolerance than the Nafion membrane as indicated by the significantly smaller losses of EE and discharge capacity for the VPG-VRFB than for the Nafion-VRFB after operating at 45 °C. The outstanding temperature tolerance of the VPG ion separator is due primarily to its rigid and non-swelling pore structure and nonionic nature, which are highly resistant to thermal distortion and vanadium ion contamination. The excellent temperature tolerance of the VPG may be useful for applications where temperature control is difficult.

Material Characterization of a Magnetorheological Fluid Subjected to Long-Term Operation in Damper.

This paper investigates the field-dependent rheological properties of magnetorheological (MR) fluid used to fill in MR dampers after long-term cyclic operation. For testing purposes, a meandering MR valve was customized to create a double-ended MR damper in which MR fluid flowed inside the valve due to the magnetic flux density. The test was conducted for 170,000 cycles using a fatigue dynamic testing machine which has 20 mm of stroke length and 0.4 Hz of frequency. Firstly, the damping force was investigated as the number of operating cycles increased. Secondly, the change in viscosity of the MR fluid was identified as in-use thickening (IUT). Finally, the morphological observation of MR particles was undertaken before and after the long-term operation. From these tests, it was demonstrated that the damping force increased as the number of operating cycles increases, both when the damper is turn on (on-state) and off (off-state). It is also observed that the particle size and shape changed due to the long operation, showing irregular particles.

Centrifuge model test on the retrogressive landslide subjected to reservoir water level fluctuation

Geological disasters have occurred frequently in the Three Gorges Reservoir area. Therefore, the stability and failure mode research on riverside landslides has become increasingly important. Taking the toe of Liangshuijing landslide as a case study and combining the geological conditions of the Three Gorges Reservoir area, a centrifuge slope model is constructed. In addition, the fluctuation of the water level is simulated in the centrifuge model test. Based on the digital photography, laser displacement sensors (LDS), pore pressure transducers (PPT) and earth pressure sensors (E), multi-physical data are obtained. Finally, numerical simulation is carried out to analyze the stability and deformation characteristics of the slope model. The results indicate that: (1) At the water level rise stage, the model is dominated by the vertical displacement. And the horizontal displacement is much larger than the vertical displacement at the drainage stage. (2) Cracks first appear at the toe of the slope and extend to the middle and rear of the model gradually. Then, deformation occurs in the middle platform of the slope. (3) At the water level rise stage, the factor of safety increases rapidly. When the reservoir water level remains stable, the stability of the slope decreases slowly. And at the drainage stage, the factor of safety decreases first and then increases. (4) There is a significant positive linear correlation between the decline rate of the safety factor and the drainage rate over a certain test range. And the stability of the landslides on the reservoir banks would become worse gradually during the long-term cyclic operation of the Three Gorges Reservoir.

Triboelectric nanogenerators with gold-thin-film-coated conductive textile as floating electrode for scavenging wind energy

We report triboelectric nanogenerators (TENGs) composed of a flexible and cost-effective gold-coated conductive textile (CT) to convert wind energy into electricity. The Au-coated CT is employed because of its high surface roughness resulting from Au nanodots distributed on microsized fibers. Thus, the Au-coated CT with nano/microarchitecture plays an important role in enhancing the effective contact area as well as the output performance of the TENG. Moreover, the surface roughness of the Au-coated CT is controlled by adjusting the Au thermal deposition time or tailoring the diameter of the Au nanodots. At an applied wind speed of 10 m·s–1, a wind-based TENG (W-TENG) with dimensions of 75 mm × 12 mm × 25 mm produces an open-circuit voltage (V OC) of ∼39 V and a short-circuit current (I SC) of ∼3 μA by using the airflow-induced vibrations of an optimized Au-coated CT between two flat polydimethylsiloxane (PDMS) layers. To further specify the device performance, the electric output of the W-TENG is analyzed by varying several parameters such as the distance between the PDMS layer and Au-coated CT, applied wind speed, external load resistance, and surface roughness of the PDMS layers. Introducing an inverse micropyramid architecture on the PDMS layers further improves the output performance of the W-TENG, which exhibits the highest V OC (∼49 V) and I SC (∼5 μA) values at an applied wind speed of 6.8 m·s−1. Additionally, the reliability of the W-TENG is also tested by measuring its output current during long-term cyclic operation. Furthermore, the rectified output signals observed by the W-TENG device are used as a direct power source to light 45 green commercial light-emitting diodes connected in series and also to charge capacitors (100 and 4.7 μF). Finally, the output performance of the W-TENG device in an actual windy situation is also investigated.

Extended performance analysis of polyurethane–iron oxide nanocomposite for efficient removal of arsenic species from water

A polyurethane (PU) foam nanocomposite impregnated with iron oxide nanoparticles (IONPs) was developed to remove arsenic (As) from drinking water at ppb concentrations. The effect of synthesis and application parameters such as the size of IONPs, pH levels, weight of adsorbents, and arsenic concentrations on the performance of PU-IONP adsorbents in removing arsenic were studied. The prepared adsorbents were characterized by scanning electron microscopy and energy dispersive X-ray microscopy to evaluate the microstructure of PU-IONPs and the surface adsorption of arsenic species, respectively. Atomic absorption spectrometry was conducted to measure the concentration of arsenic in the treated solutions in order to calculate the removal capacity of PU-IONPs. The experimental results revealed that decreasing the size of IONPs from 50–100 nm to 15–20 nm yields a higher removal capacity. Increasing the weight of the used adsorbents and the contact time led to an increase in the removal capacity as well. As the arsenic species (III and V) concentration increased in the solution, the removal capacity of PU-IONPs decreased. In a column study, a long-term cyclic operation mode was found to be very effective in removing arsenic; 100% removal capacity was achieved when 500 ml of As solution (100 ppb) was treated.

Development of Al-stabilized CaO–nickel hybrid sorbent–catalyst for sorption-enhanced steam methane reforming

In this work, Al-stabilized CaO–Ni hybrid sorbent–catalysts integrated in a single particle with various nickel loadings (12, 18 and 25 wt% NiO) were developed and tested in cyclic hydrogen production by sorption-enhanced steam methane reforming (SESMR) process. A simple wet-mixing technique based on limestone acidification and two-step calcination was employed to produce hybrid materials with different nickel loadings. All developed materials were characterized by BET, XRD, SEM and TEM and studied during 25 CO 2 sorption/regeneration cycles as well as for 10 SESMR cycles. Based on both CO 2 sorption and SESMR results, it was concluded that the proposed hybrid sorbent–catalyst with NiO loading of 25 wt% led to the best performances: (i) CaO molar conversion is 41.2% at the end of the 25th sorption cycle and (ii) average CH 4 conversion and H 2 production efficiency during 10 SESMR cycles are remarkable (99.1% and 96.1%, respectively). For the most efficient hybrid sorbent–catalyst (25 wt% NiO), the influence of CH 4 flow rate and steam to carbon ratio (S/C) was also investigated, as well as its behavior during long-term cyclic operation of SESMR (30 cycles), where the H 2 production time was just limited to pre-breakthrough period. The very efficient performance (average of H 2 yield 97.3%) of the proposed hybrid sorbent–catalyst material in long-term operation confirmed its high potential for use in SESMR process. • Al–stabilized CaO–nickel hybrid sorbent–catalyst prepared by limestone acidification. • The hybrid sorbent–catalyst with 25 wt% NiO provided the best results. • CH 4 conversion of 99.1% in cyclic SESMR operation (10 cycles). • H 2 production efficiency of 96.1% (10 cycles) and 97.3% (30 cycles).

CO2 Sorbents with Scaffold‐like CaAl Layered Double Hydroxides as Precursors for CO2 Capture at High Temperatures

A highly stable high-temperature CO₂ sorbent consisting of scaffold-like Ca-rich oxides (Ca-Al-O) with rapid absorption kinetics and a high capacity is described. The Ca-rich oxides were prepared by annealing Ca-Al-NO₃ layered double hydroxide (LDH) precursors through a sol-gel process with Al(O(i)P)₃ and Ca(NO₃)₂ with Ca(2+)/Al(3+) ratios of 1:1, 2:1, 4:1, and 7:1. XRD indicated that only LDH powders were formed for Ca(2+)/Al(3+) ratios of 2:1. However, both LDH and Ca(OH)₂ phases were produced at higher ratios. Both TEM and SEM observations indicated that the Ca-Al-NO₃ LDHs displayed a scaffold-like porous structure morphology rather than platelet-like particles. Upon annealing at 600 °C, a highly stable porous network structure of the CaO-based Ca-Al-O mixed oxide (CAMO), composed of CaO and Ca₁₂Al₁₄O₃₃, was still present. The CAMO exhibited high specific surface areas (up to 191 m(2)g(-1)) and a pore size distribution of 3-6 nm, which allowed rapid diffusion of CO₂ into the interior of the material, inducing fast carbonation/calcination and enhancing the sintering-resistant nature over multiple carbonation/calcination cycles for CO₂ absorption at 700 °C. Thermogravimetric analysis results indicated that a CO₂ capture capacity of approximately 49 wt% could be obtained with rapid absorption from the porous 7:1 CAMO sorbents by carbonation at 700 °C for 5 min. Also, 94-98% of the initial CO₂ capture capability was retained after 50 cycles of multiple carbonation/calcination tests. Therefore, the CAMO framework is a good isolator for preventing the aggregation of CaO particles, and it is suitable for long-term cyclic operation in high-temperature environments.

Ca‐Rich Ca–Al‐Oxide, High‐Temperature‐Stable Sorbents Prepared from Hydrotalcite Precursors: Synthesis, Characterization, and CO2 Capture Capacity

We present the design and synthesis of Ca-rich Ca-Al-O oxides, with Ca(2+)/Al(3+) ratios of 1:1, 3:1, 5:1, and 7:1, which were prepared by hydrothermal decomposition of coprecipitated hydrotalcite-like Ca-Al-CO(3) precursors, for high-temperature CO(2) adsorption at 500-700 °C. In situ X-ray diffraction measurements indicate that the coprecipitated, Ca-rich, hydrotalcite-like powders with Ca(2+)/Al(3+) ratios of 5:1 and 7:1 contained Ca(OH)(2) and layered double hydroxide (LDH) phases. Upon annealing, LDH was first destroyed at approximately 200 °C to form an amorphous matrix, and then at 450-550 °C, the Ca(OH)(2) phase was converted into a CaO matrix with incorporated Al(3+) to form a homogeneous solid solution without a disrupted lattice structure. CaO nanocrystals were grown by thermal treatment of the weakly crystalline Ca-Al-O oxide matrix. Thermogravimetric analysis indicates that a CO(2) adsorption capacity of approximately 51 wt. % can be obtained from Ca-rich Ca-Al-O oxides prepared by calcination of 7:1 Ca-Al-CO(3) LDH phases at 600-700 °C. Furthermore, a relatively high CO(2) capture capability can be achieved, even with gas flows containing very low CO(2) concentrations (CO(2)/N(2) = 10 %). Approximately 95.6 % of the initial CO(2) adsorption capacity of the adsorbent is retained after 30 cycles of carbonation-calcination. TEM analysis indicates that carbonation-promoted CaCO(3) formation in the Ca-Al-O oxide matrix at 600 °C, but a subsequent desorption in N(2) at 700 °C, caused the formation CaO nanocrystals of approximately 10 nm. The CaO nanocrystals are widely distributed in the weakly crystalline Ca-Al-O oxide matrix and are present during the carbonation-calcination cycles. This demonstrates that Ca-Al-O sorbents that developed through the synthesis and calcination of Ca-rich Ca-Al LDH phases are suitable for long-term cyclic operation in severe temperature environments.

Development and optimization of two-stage cyclic fed-batch culture for h G-CSF production using L-arabinose promoter of Escherichia coli

The long-term process for producing human granulocyte-colony stimulating factor (hG-CSF) was developed using two-stage cyclic fed-batch culture, in which hG-CSF expressing-recombinant Escherichia coli was directed by an L-arabinose promoter system. For the optimization, the preinduction growth rate during the growth stage and the feeding strategy during the production stage were investigated. The maximum harvest volume during the production stage was predicted before long-term cyclic operation. Based on those optimized strategies, the two-stage cyclic fed-batch culture was performed for 12 cycles (86 h). The cell growths in both stages were maintained at 45–50 g/L and 71–77 g/L, respectively. hG-CSF was stably produced at a level of 8–9 g/L and the plasmid stability was maintained at more than 90%. Volumetric productivity by the two-stage cyclic fed-batch culture was 0.643 g/L/h, which was about 280% higher than that of conventional DO-stat fed-batch culture.

A Regenerable Copper-Based Sorbent for H2S Removal from Coal Gases

Much of the sulfur sorbent research and development work has focused considerably on zinc-based sorbents. Because of concern over the gradual loss of reactivity and physical deterioration in long-term cyclic operation at elevated temperature, extensive research is still being conducted to improve the performance of zinc-based sorbents; justifiably, however, investigation of non-zinc-based materials has also been pursued as a logical approach to develop more effective alternatives. This paper reports on research conducted for the development of copper-based sorbents for hot coal gas desulfurization applications in the temperature range of 550−650 °C. A thermodynamic analysis is given to rationalize the selection of chromia (Cr2O3), and its potential superiority to alumina (Al2O3), for the stabilization of copper oxide (Cu2O) against complete reduction to elemental copper (Cu) upon exposure to a fuel gas in the indicated temperature range. The results of packed-bed experiments carried out for the determinat...