Low-cost CO2 Research Articles

Experimental Study of SO2 Emission and Sulfur Conversion Characteristics of Pressurized Oxy-Fuel Co-combustion of Coal and Biomass

Pressurized oxy-fuel combustion is a solution to achieve low-cost CO2 capture and higher operating efficiency. The combination of pressurized oxy-fuel combustion technology and biomass combustion t...

Graphene Oxide (GO) Coated Impedimetric Gas Sensor for Selective Detection of Carbon Dioxide (CO2) With Temperature and Humidity Compensation

Design and development of a low-cost, low-power, miniature, highly sensitive, and selective carbon dioxide (CO2) sensor is an active research area due to the rapid rise of CO2 closed to 408 ppm in the atmosphere because of the industrial revolution. This research proposes a highly sensitive planar interdigital sensor coated with graphene oxide (GO) to induce selectivity towards CO2. The performance of the sensor has been analysed with various temperatures, humidities, and different CO2 concentrations. The developed sensor has been characterised using Electrochemical Impedance Spectroscopy (EIS). The calibration standard has been developed for a range of CO2 concentrations from 400 ppm to 4000 ppm. The standard gas chromatography (GC) method is used to validate all the results. The temperature and humidity compensation mechanisms are also included to improve the detection ability for determining the CO2 gas concentration from unknown gas samples. Repeatability, reproducibility, stability, cross-sensitivity, response, and recovery time are also tested. The obtained results are highly encouraging to develop a low-cost smart CO2 gas sensing system for both indoor and outdoor environmental applications.

Low cost CO2 sensing: A simple microcontroller approach with calibration and field use

Understanding the spatial variability of gaseous carbon flux at a landscape scale requires intensive monitoring campaigns necessitating significant and perhaps prohibitive financial investment. Commercially available CO2 sensors may only partially fulfil the requirements of the researcher, thereby generating inadequate data. In this context we present the fully replicable designs for a low-cost, microcontroller-based gaseous CO2 concentration data logger suitable for field deployment at scale. It demonstrates a post-calibration accuracy of 96–99% and large onboard data storage for data collected at user-defined intervals. The sensor can be powered via USB or batteries, assembled by novice users, and produced for approximately £155. Post-calibration it was used to measure CO2 evasion from a peatland stream, environments known to be spatially and temporally variable CO2 sources, although potential applications are much wider in scope. The proliferation of low-cost, open-source, and user-made sensors in physical sciences could allow researchers to answer questions previously unanswerable due to the limitations of existing proprietary equipment. We encourage other research teams to use and adapt this design for a range of purposes and research questions beyond carbon processing in peatlands.

Evaluation of CO2 Hydrogenation in a Modular Fixed-Bed Reactor Prototype

Low-cost iron-based CO2 hydrogenation catalysts have shown promise as a viable route to the production of value-added hydrocarbon building blocks. It is envisioned that these hydrocarbons will be used to augment industrial chemical processes and produce drop-in replacement operational fuel. To this end, the U.S. Naval Research Laboratory (NRL) has been designing, testing, modeling, and evaluating CO2 hydrogenation catalysts in a laboratory-scale fixed-bed environment. To transition from the laboratory to a commercial process, the catalyst viability and performance must be evaluated at scale. The performance of a Macrolite®-supported iron-based catalyst in a commercial-scale fixed-bed modular reactor prototype was evaluated under different reactor feed rates and product recycling conditions. CO2 conversion increased from 26% to as high as 69% by recycling a portion of the product stream and CO selectivity was greatly reduced from 45% to 9% in favor of hydrocarbon production. In addition, the catalyst was successfully regenerated for optimum performance. Catalyst characterization by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), along with modeling and kinetic analysis, highlighted the potential challenges and benefits associated with scaling-up catalyst materials and processes for industrial implementation.

Pressurized oxy-fuel combustion of a char particle in the fluidized bed combustor

Pressurized oxy-fuel combustion of coal in fluidized bed (FB) holds the potential to realize low-cost CO2 capture. However, the fundamental study in this manner is still rare due to the difficult access to the pressurized oxy-FB combustion tests. In this work, the experimental study of single char combustion was firstly conducted in a visualized pressurized FB combustor under various operating conditions. Then an experimentally verified particle-scale char combustion model was developed to reveal the dependence of char combustion on parameters. Results showed that the char conversion was accelerated with the increase of pressure, mainly due to the high oxygen diffusion and char gasification. The gasification played a non-negligible role in pressurized oxy-fuel combustion, especially under high oxygen concentration and bed temperature. Increasing oxygen concentration and bed temperature not only promotes the char oxidation rate and particle temperature, but also increases the gasification rate and the share of char conversion via gasification, resulting in shortening the burnout time of char. In addition, a higher fluidization number lowered both the burnout time and peak temperature of char particle, due to the simultaneous improvement of mass and heat transfer. The influences of char size and fluidization number on char gasification conversion ratio are very weak. In addition, the quantitative analysis of the influence of different operating parameters on the combustion process was obtained by model sensitivity analysis.

Study on microstructure and mechanical properties of Ni60 + WC/Ni35/AISI1040 functional surface gradient structure of remanufacturing chute plate for the mining scraper by a low cost high power CO2 laser cladding technique

CO2 laser cladding is a type of green remanufacturing technology, which is of many technical advantages in repairing and remanufacturing industry, especially for some large-scale key mining equipment or parts due to its characteristics of high quality, high efficiency and environmental protection (e.g. energy and material saving). In this paper, the chute plate of coal mining scraper is fixed and remanufactured by CO2 laser cladding technique. Ni60, WC, Ni35, IG55 and other composite powders are selected to design and build the gradient functional structure for chute plate in order to improve the reproduced lifetime. A lot of high power low cost CO2 laser cladding tests are carried out on the matrix material (AISI 1040 steel plate) of old attrite chute plate. The optical microscope, SEM, XRD, microhardness test and wear experiment are adopted to analyze the relationships among the laser cladding process, the overlaying composite material, gradient functional structure and mechanical properties of the remanufacturing scraper’s chute plate. The research results show that laser power and scanning speed are the dominant cladding process parameters, which have a significant influence on the geometric dimension (including width and height), dilution rate and hardness of the deposited layer. These composite powders (especially including the rare earth metals) are the key factor to form the gradient functional structure. The laser cladding Ni60 + WC/Ni35/AISI1040 composite gradient functional structure has a reasonable toughness and strength of the transition layer structure, and a high hardness and wear-resistant surface functional layer, so the fixed and remanufactured product has formed good ductile plasticity and wear resistance properties as a result of the gradient functional structure. The unique Ni60 + WC/Ni35/AISI1040 gradient functional structure makes sure that the chute plate of mining scraper has excellent comprehensive performance, which is satisfied with the service requirements of mechanical parts or equipment in the harsh working environment of the mining industry. This research work provides technological guidance for the fix and remanufacturing chute plate, and achieves the goal of low cost, high efficiency and long life reproduced chute plate of mining scraper.

Challenges in Monitoring Atmospheric CO2 Concentrations in Seoul Using Low-Cost Sensors

With the increasing importance of monitoring and verifying urban CO2 concentrations to mitigate carbon emissions from cities, a high-resolution ground networks of low-cost CO2 sensors are emerging that have a price advantage over existing high-cost sensors. This study develops a low-cost CO2 instrument called the Seoul National University CO2 Measurement (SNUCO2M) to monitor and analyze intra-city CO2 concentrations over Seoul, Korea. The first step of establishing this low-cost CO2 sensor network involved installing the SNUCO2M at the Yongsan Building (YSB; 113 m MASL) and Namsan Seoul Tower-High (NSTH; 385 m MASL) on October 18, 2018 and July 8, 2019, respectively. For comparison with the SNUCO2M, we utilized CO2 concentrations measured by the Picarro instrument (high-cost CO2 sensor) at Gwanak Mountain (GWA) background measurement site and the lower part of the NST (NSTL). The initial CO2 measurements from the SNUCO2M, show that 1) the SNUCO2M has a 0.71% maximum error range and is sufficient to measure urban atmospheric CO2 concentrations; and 2) the SNUCO2M captures 26.92 and 20.30 ppm of Seoul’s summer and winter time CO2 enhancement compared to the GWA background site. Our results suggest that the low-cost sensors such as SNUCO2M successfully detect urban CO2 characteristics over the megacity and has great potential to replace high-cost sensors with cost and management limitations.

High-Performance Al/PDMS TENG with Novel Complex Morphology of Two-Height Microneedles Array for High-Sensitivity Force-Sensor and Self-Powered Application.

Triboelectric nanogenerators (TENGs) are widely applied to self-powered devices and force sensors. TENGs consist of the electrode-layer frequently made of high-cost conductors (Ag, Au, ITO) and the tribo-layer of rigid negative-triboelectricity fluoropolymers (PTFE, FEP). The surface morpholoy is studied for enhancing performance. Here, a high-performance Al/PDMS-TENG is proposed with a complex morphology of overlapped deep two-height microneedles (OL-DTH-MN) fabricated by the integrated process of low-cost CO2 laser ablation and PDMS casting for self-powered devices and high-sensitivity force/pressure sensors. The high open-circuit voltage and short-circuit current of the OL-DTH-MN-TENG are 167 V and 129.3 µA. Also, the sensitivity of the force/pressure sensor of the OL-DTH-MN-TENG is very high, 1.03 V N-1 and about 3.11 V kPa-1 , at an area of 30 cm2 that is much higher than the sensitivity of about 0.18-0.414 V N-1 and 0.013-0.29 V kPa-1 of conventional TENG sensors. Meanwhile, the high-performance OL-DTH-MN-TENG not only exhibits the energy storage capability of charging a 0.1 µF capacitor to 2.75 V at 1.19 s, to maximum 3.22 V, but also activates various self-powered devices including lighting colorful 226 LEDs connected in series, the "2020-ME-NCKU" advertising board, a calculator and a temperature sensor. Numerical simulation is also performed to support the experiments.

Welding of Cold-Resistant Micro-Alloed Steels 10HSNDA and 15HSNDA in the Atmosphere of Carbon Monoxide (II)

Micro-alloyed steels are widely used in the manufacture of critical welded structures operating under extreme conditions of the North. Microalloying of V, Nb and B is a simple and effective method of transferring known grades of structural steel and alloys to the category of increased and high strength, cold resistance, etc. The possibility of arc welding of steels grade 10CrSiNiAl and 15CrSiNiAl (10, 15ХСНДА in Russian), initially alloyed with trace amounts of niobium and vanadium to increase their cold resistance in carbon monoxide is considered. It is established that the use of the specified reducing atmosphere prevents the oxidation of the weld metal. The thermodynamic substantiation of the chemical reactions of microalloying elements proceeding in the weld pool, leading to the preservation of the steel composition, is presented. The chemical and metallographic analysis of welds was performed. The efficiency of using low-cost CO, or its mixtures with CO2, as substitutes for expensive argon and helium, when welding micro alloyed steels is shown.

Electrolyte-gated transistor for CO2 gas detection at room temperature

The availability of a low-cost CO2 sensor with small package size and low power consumption is crucial to enter market for consumer application. This study is set out to deliver proof-of-concept and a hypothetical mechanism for a new CO2 sensing concept based on an electrolyte-gated transistor (EGT), which consists of the n-semiconducting metal oxide (MOX) In2O3 as channel-forming layer and ionic liquid (IL) [EMIM][BF4] as electrolyte. Gas measurements were performed under typical conditions for indoor and outdoor air quality evaluation, i.e. CO2 in the range 400–4000 ppm. The device behavior was reversible with response and recovery times (t90) of about 20 s in DC mode. Channel conductivity showed a linear CO2 sensitivity of 0.1 %/ppm and resolution ≤200 ppm at low CO2 concentrations (≤1200 ppm). Fitting to the Clifford-Tuma model yielded a sensitivity coefficient of 175ppm−1 in the CO2 range 0–4000 ppm. The sensing mechanism is most likely based on simultaneous electrochemical reactions of H2O, O2, CO2. Basically, the CO2 sensitivity originates from the depletion of O2 in proximity to MOX, which leads to an amplified electrical current. The presented CO2 detection principle synergistically combines advantages of several device classes: Sensitivity of transistors, selectivity of electrochemical sensors, and simplicity of chemiresistors.

Modulated Sn Oxidation States over a Cu2O-Derived Substrate for Selective Electrochemical CO2 Reduction.

Pursuing high catalytic selectivity is challenging but paramount for an efficient and low-cost CO2 electrochemical reduction (CO2R). In this work, we demonstrate a significant correlation between the selectivity of CO2R to formate and the duration of tin (Sn) electrodeposition over a cuprous oxide (Cu2O)-derived substrate. A Sn electrodeposition time of 120 s led to a cathode with a formate Faradaic efficiency of around 81% at -1.1 V vs reversible hydrogen electrode (RHE), which was more than 37% higher than those of the Sn foil and the sample treated for 684 s. This result highlights the significant role of the interface between deposited Sn and the cuprous-derived substrate in determining the selectivity of CO2R. High-resolution X-ray photoelectron spectra revealed that the residual cuprous species at the Cu/Sn interfaces could stabilize Sn species in oxidation states of 2+ and 4+, a mixture of which is essential for a selective formate conversion. Such modulation effects likely arise from the moderate electronegativity of the cuprous species that is lower than that of Sn2+ but higher than that of Sn4+. Our work highlights the significant role of the substrate in the selectivity of the deposited catalyst and provides a new avenue to advance selective electrodes for CO2 electrochemical reduction.

Highly efficient colorimetric CO2 sensors for monitoring CO2 leakage from carbon capture and storage sites

Carbon capture and storage (CCS) technology used for reducing anthropogenic CO2 emissions involves the capture of CO2 from industrial sources and its injection into geological sinks, such as oil reservoirs and abandoned gas fields. To ensure environmental and public safety in implementing CCS technology, efficient CO2-monitoring technology must be developed to detect potential CO2 leakage from CCS sites. Conventional CO2 sensors used for monitoring CCS sites are typically high in cost and require professional staff for maintenance. In this study, we developed a portable and low-cost colorimetric CO2 sensor with high soil CO2 detection efficiency for CCS sites. The sensor consists of a detection solution that contains the pH indicator cresol red encapsulated with a gas-permeable membrane. When CO2 enters the sensor through the membrane, the color of the pH indicator changes and this was quantified using an RGB (red, green, blue) application (app), an app that measures the RGB values of a given color. The change in G and B values of the detection solution showed a significant linear relationship with soil CO2 concentration determined via non-dispersive infra-red (NDIR) CO2 sensor (r2 = 0.98, p = 0.001), and thus these values were used for quantification of CO2 concentration. Tests using CO2-injection chamber showed that the optical CO2 sensors can detect soil CO2 concentration of 0.1 to 30% within a few minutes. Field studies conducted at a natural CO2 vent and an artificial CO2 leakage site showed that the optical CO2 sensors can be applied in analyzing surficial CO2 leakage patterns. The advantage of this optical CO2 sensor when applied to field monitoring is that it is inexpensive and has few installation restrictions. Therefore, this optical CO2 sensor has a strong potential for use in monitoring CO2 leakages from CCS sites.

Bench-Scale Demonstration of Molten Alkali Metal Borates for High-Temperature CO2 Capture

The molten alkali metal borates represent an opportunity for carbon dioxide capture and the on-going challenge of adapting to a carbon-constrained world with the immediacy of climate change. We demonstrate the performance of this new class of materials at the bench scale, highlighting the ability to operate isothermally at high temperatures through the use of steam as a sweep gas. Breakthrough curves for a wide set of conditions are presented and linked to the sorbents’ underlying thermodynamic and kinetic properties. We demonstrate the ability to capture over 99.9% of incoming CO2 even at low concentrations or to capture ∼90% CO2 under high flow rates and utilize a greater portion of the sorbent capacity. The advantages of the molten alkali metal borates scale well, and their unique position as high-temperature liquid phase sorbents may enable new process designs for efficient low-cost CO2 capture facilities.

Hydrogen production via steam reforming of coke oven gas enhanced by steel slag-derived CaO

Steel slag, a waste from steelmaking plant, has been proven to be good candidate resources for low-cost calcium-based CO2 sorbent derivation. In this work, a cheap and sintering-resistance CaO-based sorbent (CaO (SS)) was prepared from low cost waste steel slag and was applied to enhance catalytic steam reforming of coke oven gas for production of high-purity hydrogen. This steel slag-derived CaO possessed a high and stable CO2 capture capacity of about 0.48 g CO2/g sorbent after 35 adsorption/desorption cycles, which was mainly ascribed to the mesoporous structure and the presence of MgO and Fe2O3. Product gas containing 95.8 vol% H2 and 1.4 vol% CO, with a CH4 conversion of 91.3% was achieved at 600 °C by steam reforming of COG enhanced by CaO (SS). Although high temperature was beneficial for methane conversion, CH4 conversion was remarkably increased at lower operation temperatures with the promotion effects from CaO (SS), and CO selectivity has been also greatly decreased. Reducing WHSV could increase methane conversion and reduce CO selectivity due to longer reactants residence time. Reducing C/A could increase methane conversion and hydrogen recovery factor, and also decrease CO selectivity. When being mixed with catalyst during SE-SRCOG, CaO (SS) with a uniform size distribution favored methane conversion due to the high utilization efficiency of catalyst. Promising stability of CaO (SS) in cyclic reforming/calcination tests was evidenced with a hydrogen recovery factor >2.1 and CH4 conversion of 82.5% at 600 °C after 10 cycles using CaO (SS) as sorbent.

Joint-use of activated carbon and carbon black to enhance catalytic stability during chemical looping methane decomposition process

Chemical-looping methane decomposition using activated carbon as a catalyst has been considered a potentially promising approach for high-purity H2 production with low cost and low CO2 emission. However, activated carbon is known to deactivate fast despite its high initial catalytic activity. Oppositely, carbon black has shown stable catalytic methane decomposition that even increases slowly with time of reaction. Considering these two different activity trends, activated carbon and carbon black are jointly used to prepare catalysts and then test for the decomposition of the methane via chemical looping in this study that aimed to examine catalyst and reaction properties which may combine the high initial activity of activated carbon with the steady-and-increasing activity of carbon black. These mixed catalysts are examined using X-ray diffraction analysis (XRD), scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), Brunauer-Emmett-Teller (BET) and high-resolution transmission electron microscopy (HRTEM) before and after reaction testing to reveal chemical and physical constituents which contributed to their reactivities, and the mechanism of long catalytic activity has been discussed. The results point to insights and potential directions for modifying carbonaceous catalysts for chemical looping thermo-catalytic decomposition of methane.

Promoting visible-light photocatalytic activities for carbon nitride based 0D/2D/2D hybrid system: Beyond the conventional 4-electron mechanism

Photocatalysis is regarded as one of promising technology for future clean and sustaniable energy applications. Herein, we have fabricated Au-modified reduced graphene oxide coupled with carbon nitride (Au/rGO/g-C3N4) as novel 0D/2D/2D photocatalytic nanocomposites. The optimized sample 2Au/0.6rGO/g-C3N4 exhibits exceptional visible-light activity for water splititng and CO2 reduction with quantum efficiency of 3.82 % and 1.98 %, respectively. Electrochemistry and ultraviolent photoemission are combined to determine the band alignments and elaborate associated water splitting path-way mechanism. It is validated that due to intrinsic deep valence band position of g-C3N4, the obtained nanocomposites exhibit unusual two-step two-electron way of water oxidization through intermediate H2O2 catalyzed by rGO addition. The exceptional photoactivities are attributed to dual functions of enhanced charge separation and two-electron water oxidization facilitated by rGO and surface plasmon effect of decorated Au. Our work provides illuminations for low cost and high efficiency photocatalytic water splitting and CO2 reduction applications.

Hybrid membrane process for post-combustion CO2 capture from coal-fired power plant

Post-combustion CO2 capture is a promising way to reduce CO2 emissions at the coal-fired power plants. Even though several studies have been conducted regarding a wide variety of CO2 capture techniques, gas separation membrane process has shown potential as an energy-efficient, low-cost CO2 capture option. However, most of the previous researches focused only on CO2-selective membrane, and there's limited literature about the application of N2-selective membrane.In this study, both CO2-selective and N2-selective membranes are considered and relevant issues regarding the CO2-selective membrane, such as pressure ratio, attainability, and multistage configuration, are studied and extended to the N2-selective membrane. Polaris® membrane is served as a typical CO2-selective membrane; on the other hand, membrane properties of N2-selective membrane with selectivity up to 200 are considered. Hybrid membrane process applying both CO2- and N2-selective membranes for capturing at least 90% CO2 from a typical 550 MW subcritical coal-fired power plant is designed, simulated and analyzed using Aspen Plus® simulation software. The optimization and economic analysis are also applied with the cost factor defined in this work, which is a comprehensive index to evaluate the applicability of the membrane, including permeance, membrane lifetime and membrane price. The results reveal the relationship between the optimal design variables and membrane properties. Moreover, the selectivity-limited region is identified, which leads to two different dominant strategies for the cost reduction in a different region, either by the increase in selectivity or the reduction of the cost factor.

Boosting the Peroxidase-like Activity of Cobalt Ions by Amino Acid-based Biological Species and Its Applications.

Enzyme mimics have been widely used as alternatives to natural enzymes, owing to their high stability and low cost. However, the activity and atom economy of enzyme mimics still need to be improved. Herein, we report the boosting effects of amino acids, peptides and proteins on the peroxidase-like activity of Co2+ . Among 20 amino acids, tryptophan (Trp) enhanced the activity of Co2+ approximately 8 times and was identified as the best stimulator. The study revealed the synergy of amino acids-based species and HCO3 - for efficient catalysis. Co2+ is proposed to bind simultaneously to HCO3 - and Trp, and to form a ternary catalyst which facilitates the generation of reactive oxygen species. Based on the selective boosting by Trp, a simple and low-cost Co2+ sensor with high sensitivity was developed, which showed a linear range of 10-300 μM and a limit of detection of 0.4 μM for Co2+ .

Investigation of ordered mesoporous carbon potential as low-cost CO2 adsorbent

<p>In this study, an investigation was carried out in order to determine the potential of ordered mesoporous carbon including high ratio sucrose in its composition as a CO2 adsorbent. Structural characterizations of silica and carbon material were determined by using a scanning electron microscope (SEM), N2 adsorption/desorption and X-ray diffraction (XRD) analysis. CO2 adsorption capacities of developed adsorbent at various temperatures (25°C, 35°C and 50°C) were determined by using a thermogravimetric analyzer under CO2 flow. The maximum adsorption capacity was obtained as approximately 2.27 mmol g CO2 g-1 adsorbent which was remained almost the same in the desorption process. The first order reaction kinetic model was well fitted with the experimental data. Arrhenius equation was used to calculate activation energy which was obtained as -2.86 kJ mol-1 indicating barrier-less type adsorption. Results showed that ordered mesoporous carbon could be a potential source for an efficient and low-cost adsorbent for CO2 capture.</p>

Performance Evaluation of a Cu-Based Oxygen Carrier Impregnated onto ZrO2 for Chemical-Looping Combustion (CLC)

Chemical-looping combustion (CLC) has been introduced as a promising technique with inherent advantages for efficient, low-cost CO2 separation. The type of oxygen carrier employed plays a vital rol...