Maximum CO2 Concentration Research Articles

Shaped Charge Hydraulic Blasting: An Environmental, Safe, and Economical Method of Directional Roof Cutting

Shaped charge blasting (SCB)—a directional fracture blasting technology—has the disadvantages of low safety, harmful gas, and dust emissions. This study proposes a new type of directional rock-breaking technology called shaped charge hydraulic blasting (SCHB) that uses water as the blasting medium instead of air. To verify the effectiveness of the new method, we performed a theoretical analysis. Twelve groups of on-site directional roof-cutting tests were carried out on SCB and SCHB for comparison in a coal mine. The results showed that, although both blasting methods achieved the goal of directional roof cutting for noncoal pillar mining, SCHB had greater blasting power and produced 8% higher crack rate than SCB for the same charge amount. SCHB required 12.5% less charge than SCB when the crack rate was basically the same. SCHB effectively reduced the concentration of CO. The maximum concentration of CO was reduced by 22–62% compared with SCB. The maximum concentration decreased parabolically with the monitoring distance. In addition, water can absorb high temperature and inhibit sparks from blasting, so SCHB can prevent gas explosions. Therefore, SCHB is an environmental, safe, and economical method of directional roof cutting, which has wide applications in mining and geotechnical engineering.

Quantification of microclimate and its effect on yield of field crops under Agri-horti system in Western plain zone of Uttar Pradesh

Result revealed that diurnal dynamics of temperature was continuously increasing from morning to noon hrs (07:30 hrs to 13:30 hrs) and highest temperature was recorded at 13:30 hrs (afternoon) due to highest light intensity. Thereafter, temperature was decreased and reaching to the lowest at 17:30 hrs irrespective of crops and height from the earth surface. Highest relative humidity was observed at 07.30 hrs morning and lowest relative humidity was recorded in 13:30 hrs to 15:30 hrs. Thereafter, it again increased from evening 17:30 hrs to morning 07:30 hrs. As per study maximum CO2 concentration was found at 07:30 hrs morning and decreased at 15:30 hrs. This decreasing trend of CO2 concentration after afternoon may be due to enhancement in consumption of CO2 for the process of carbohydrate assimilation through photosynthesis which reached to maximum at 15:30 hrs.

Atmospheric air pollution monitoring using flying robotics

This article discusses a method for detecting a source of atmospheric air pollution (for example, carbon monoxide) using flying robotic equipment. The relevance of this study is the autonomy of methods for detecting a source of pollution with a given accuracy. To achieve this goal, the scheme of a mobile instrument platform in the form of an electromechanical system and the problem of finding a source of pollution were considered. By calculation and experiment, the radius of the circle and the speed at which the maximum and minimum CO concentration will be measured were obtained, an algorithm for the method for determining the coordinates of the CO concentration source based on a mobile instrument platform was proposed.

Modeling gaseous emissions and dispersion of two major greenhouse gases from landfill sites in arid hot environment.

As waste production exponentially increases, landfill continues to be the common method of waste disposal. Landfills represent significant anthropogenic sources of methane (CH4) and carbon dioxide (CO2); the main constituents of greenhouse gases (GHGs) resultant from microbial decomposition of organic waste. In the present study, ISC-AERMOD dispersion model was employed to estimate the release and dispersion rates of CH4 and CO2 from major landfill sites across Kuwait under different seasonal conditions. Results revealed that dispersions of CH4 and CO2 were influenced by the dominant northwestern and southeastern wind directions and thus, the dispersion of CH4 and CO2 extended predominantly toward northeastern direction. In terms of seasonal variation, the maximum concentrations of CH4 and CO2 were detected in winter and spring seasons, close to the landfill zone, and the dispersion of CH4 and CO2 fluxes during winter and spring seasons was longer than that during summer and fall seasons. Consequently, residential areas close to the disposal sites were exposed to higher concentrations of CH4 and CO2 gases during winter and spring. The findings of this study can serve as the basis for selecting suitable landfill locations under desert climatic conditions as determined by the distances over which gaseous emissions can diffuse.

Temporal characteristics of carbon dioxide and ozone over a rural-cropland area in the Yangtze River Delta of eastern China

In this study, rural atmospheric carbon dioxide (CO2) and ozone (O3) were measured from January 2015 to December 2018 to investigate characteristics of greenhouse gases in eastern China. Results showed that the annual average CO2 (O3) concentration in 2018 decreased by 2% (increased by 19%) when compared with that in 2015. CO2 concentrations exhibited monthly variability, peaking in February (443.7 ppm) and reaching their lowest levels in July (363.0 ppm); whereas, monthly O3 showed a bimodal pattern with peaks in June (51.3 ppb) and September (34.5 ppb). Regarding the diurnal variation, the maximum CO2 (O3) concentration occurred at nighttime (in the daytime) and a minimum CO2 (O3) in the daytime (at nighttime). As demonstrated by correlation analysis, CO2 and O3 variations were partly modulated by NOx and PM2.5. Furthermore, CO2 showed significant positive correlations with relative humidity in winter, while O3 showed strong positive correlations with temperature in spring. CO2 was accumulated from local sources under calm conditions (< 2 m s−1) and derived from remote sources at high wind speeds (> 4 m s−1), while O3 concentrations were peaking at medium wind speeds of 2–4 m s−1. CO2 was found to derive from long-distance (short-distance transport) transport in spring (the other three seasons), whereas O3 is mainly from long-distance (short-distance) transport in winter (the other three seasons). This work sheds light on the temporal characteristics of CO2 and O3, which has important implications for implementing practices to mitigate source emissions over cropland areas.

Determination of Dissolved CO2 Concentration in Culture Media: Evaluation of pH Value and Mathematical Data

Carbon dioxide is the most influential gas in greenhouse gasses and its amount in the atmosphere reached 412 µmol/mol in August 2020, which increased rapidly, by 48%, from preindustrial levels. A brand-new chemical industry, namely organic chemistry and catalysis science, must be developed with carbon dioxide (CO2) as the source of carbon. Nowadays, many techniques are available for controlling and removing carbon dioxide in different chemical processes. Since the utilization of CO2 as feedstock for a chemical commodity is of relevance today, this study will focus on how to increase CO2 solubility in culture media used for growing microbes. In this work, the CO2 solubility in a different medium was investigated. Sodium hydroxide (NaOH) and monoethanolamine (MEA) were added to the culture media (3.0 g/L dipotassium phosphate (K2HPO4), 0.2 g/L magnesium chloride (MgCl2), 0.2 g/L calcium chloride (CaCl2), and 1.0 g/L sodium chloride (NaCl)) for growing microbes in order to observe the difference in CO2 solubility. Factors of temperature and pressure were also studied. The determination of CO2 concentration in the solution was measured by gas analyzer. The result obtained from optimization revealed a maximum CO2 concentration of 19.029 mol/L in the culture media with MEA, at a pressure of 136.728 kPa, operating at 20.483 °C.

Investigation on the Removal of Carbon Dioxide Exhausted from Industrial Units in a Lab-Scale Fluidized Bed Reactor

In this study, CO2 removal efficiency from flue gas was investigated in a fluidized bed reactor under semi-dry conditions. A lab-scale fluidized bed reactor, filled with inert glass beads, was used to investigate the effect of operating parameters on the CO2 removal efficiency using calcium hydroxide slurry as the absorbent. The Taguchi design method was used to design the experiments. The maximum inlet concentration of CO2 was 3 vol%. The most important factors were the reaction surface area, inlet gas velocity, inlet CO2 concentration, absorbent solution flow rate, inlet gas temperature and calcium hydroxide slurry concentration. The experimental results indicated that the CO2 removal efficiency increased when increasing the effective surface area of the reaction. Moreover, the removal efficiency increased by decreasing the input gas flow rate and inlet CO2 concentration. By performing experiments under optimum conditions, the maximum obtained CO2 removal efficiency was 79%. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Biodegradation of Reactive Orange 16 Dye in Microbial Fuel Cell: An Innovative Way to Minimize Waste Along with Electricity Production.

Microbial fuel cell (MFC) is an attractive green technology which harnesses the power of microorganism for the production of electricity along with bioremediation of waste. However, the bioremediation of the high concentration of dye wastewater in MFC remains unclear. In present study, double-chambered MFC inoculated with mixed bacterial consortium was used for bioremediation of reactive orange 16 (RO-16) dyes at a very high and variable concentration range of 100 to 1000ppm. Maximum voltage was obtained for 100ppm of dye and was found to be 0.5791V along with a power density of 0.0851W/m3. Till 500 ppm concentration of dye COD removal efficiency remains in range of 40 to 100% thereafter it decreases. The maximum concentration of CO2 was found to be 2% at 1000ppm which confirms the biodegradation phenomena in MFC. Kinetics of biodegradation of reactive orange 16 were studied using Haldane inhibitory kinetic model and kinetic constants μmax, Ks, and Ki were calculated and found to be 0.417day-1, 206.2ppm, and 447.12ppm respectively. The experimental results showed inhibitory condition in the MFC after 500ppm and it was supported by the value of inhibitory kinetic constant Ki= 447.12ppm. This study opened the possibility of bioremediation of dyes at high concentrations in MFCs.

Assessment of Heavy Metals in Guinea Sorrel (Hibiscus sabdariffa) Cultivated on Fadama Soils in Maiduguri, Nigeria

River Ngadda is one of the main sources of water used by the resident of Maiduguri Metropolis The proximity of the people to the river encourages a lot of irrigation farming along the river bank during the dry season especially vegetables therefore, concentration values of heavy metals namely Aluminum, Cobalt, Iron, Lanthanum, Manganese, Chromium, Rubidium, Scandium, Samarium, Thorium, Vanadium and Zinc were determined in Guinea Sorrel (Hibiscus sabdariffa) vegetable samples obtained at six different locations on different dry season farming (Fadama) sites along the bank of river Ngadda and Alau dam in Maiduguri, Nigeria. Instrumental neutron activation analysis (INAA) technique which is a sensitive method for determination of major, minor and trace element in a matrix was used to assessed the heavy metal accumulation levels in Guinea Sorrel with the aim to establish the food safety status from heavy metals concentration levels for guinea sorrel cultivated along the bank of river Ngadda and Alau dam and consumed on a daily basis as compared to WHO/FAO recommended maximum permissible limit (MPL) for edible vegetables. The result obtained showed that the concentration values of Al ranged from 932 ± 18 to 3369 ± 54 ppm, Co 0 .12 ± 0.03 to 40 ± 4 ppm, La 1.00 ± 0.03 ppm to 38 ± 4 ppm, Manganese 112 ± 0.4 to 176 ± 1 ppm, Rubidium 4 ± 0.5 to 21 ± 1ppm, Sc 0.10 ± 0.007 to 27 ± 1 ppm Sm 0.106 ± 0.004 to 17.2 ± 0.4 ppm, V 1.10 ± 0.3 to 4 ± 1 ppm and Zn 17 ± 3 to 63 ± 4 ppm, and Fe 379 ± 33 ppm to 2316 ± 65 ppm. This result indicates that the maximum concentrations of Fe, Cr, Mn and Co, in guinea sorrel from most of the sites were above the acceptable limits given by FAO/WHO for edible vegetables. Therefore, it is certain that there is the health risk associated with the continuous consumption of guinea sorrel vegetables cultivated from the study site and authors of this work hereby recommends that investigation of this kind should be carried out from time to time so as to know the buildup or otherwise of heavy metals in guinea sorrel cultivated in the study sites.

Indoor Air Quality Improvement by Simple Ventilated Practice and Sansevieria Trifasciata

Optimum thermal comfort and good indoor air quality (IAQ) is important for occupants. In tropical region offices, an air conditioner is indispensable due to extreme high temperatures. However, the poor ventilation causes health issues. Therefore, the purpose of this study was to propose an improving IAQ method with low energy consumption. Temperature, relative humidity, and CO2 and CO concentration were monitored in a poorly ventilated office for one year to observe seasonal variation. The results showed that the maximum CO2 concentration was above the recommended level for comfort. Simple ventilated practices and placing a number of Sansevieria trifasciata (S. trifasciata) plants were applied to improve the IAQ with the focus on decreasing CO2 concentration as well as achieving energy saving. Reductions of 19.9%, 22.5%, and 58.2% of the CO2 concentration were achieved by ventilation through the door during lunchtime, morning, and full working period, respectively. Placing S. trifasciata in the office could reduce the CO2 concentration by 10.47%–19.29%. A computer simulation was created to observe the efficiency of simple practices to find the optimum conditions. An electricity cost saving of 24.3% was projected for the most feasible option with a consequent reduction in global warming potential, which also resulted in improved IAQ.

Mean Age of Air in Natural Ventilated Buildings: Experimental Evaluation and CO2 Prediction by Artificial Neural Networks

The mean age of air (MAA) is one of the most useful parameters in evaluating indoor air quality in natural ventilated buildings. Its evaluation is generally based on the CO2 monitoring within the environment; however, other methods can be found in the literature, but they have not always led to satisfactory results. In this context, the present paper is focused on two main topics: the effect of the windows airtightness and of the environmental conditions on MAA and the application of artificial neural network (ANN) for the CO2 prediction within the room. Two case studies (case study 1 located in Terni and case study 2 located in Perugia) were investigated, which differ in geometric dimensions (useful area, volume, window area) and in airtightness of windows. The indoor and outdoor environmental conditions (air temperature, pressure, relative humidity, air velocity, and indoor CO2 concentration) were monitored in 33 experimental campaigns, in four room configurations: open door-open window (OD-OW); closed door-open window (CD-OW); open door-closed window (OD-CW); closed door-closed window (CD-CW). Tracer decay methodology, according to ISO 16000-8:2007 standard, was compiled during all the experimental campaigns. A feedforward ANN, able to simulate the indoor CO2 concentration within the rooms, was then implemented; the monitored environmental conditions (air temperature, pressure, relative humidity, and air velocity), the geometric dimensions (useful area, volume, window area), and the airtightness of windows were provided as input data, while the CO2 concentration was used as target. In particular, data of 19 experimental campaigns were provided for the training process of the network, while 14 were only used for testing the reliability of ANN. The CO2 concentration predicted by ANN was then used for the MAA calculation in the four room configurations. Experimental results show that MAA of case study 2 is always higher, in all the examined configurations, due to the higher airtightness characteristics of the window and to the higher volume of the room. When the difference between indoor and outdoor temperature increases, the MAA increases too, in almost all the investigated configurations. Finally, the CO2 concentration predicted by ANN was compared with experimental data; results show a good accuracy of the network both in CO2 prediction and in the MAA calculation. The predicted CO2 concentration at the beginning of experimental campaigns (time step 0) always differs less than 2% from experimental data, while a mean percentage difference of −18.8% was found considering the maximum CO2 concentration. The MAA calculated using the predicted CO2 of ANN was greater than the one obtained from experimental data, with a difference in the 0.5–1.3 min range, depending on the configuration. According to the results, the developed ANN can be considered an alternative and valuable tool for a preliminary evaluation of MAA.

An evaluation of central Iran’s protected areas under different climate change scenarios (A Case on Markazi and Hamedan provinces)

Global climate change poses a new challenge for species and can even push some species toward an extinction vortex. The most affected organisms are those with narrow tolerance to the climatic factors but many large mammals such as ungulates with a wider ecological niche are also being affected indirectly. Our research mainly used wild sheep in central Iran as a model species to explore how the suitable habitats will change under different climatic scenarios and to determine if current borders of protected areas will adequately protect habitat requirements. To create habitat models we used animal-vehicle collision points as an input for species presence data. We ran habitat models using MaxEnt modeling approach under different climatic scenarios of the past, present and future (under the climatic scenarios for minimum (RCP2.6) and maximum (RCP8.5) CO2 concentration trajectories). We tried to estimate the overlap and the width of the ecological niche using relevant metrics. In order to analyze the effectiveness of the protected areas, suitable maps were concerted to binary maps using True Skill Statistic (TSS) threshold and measured the similarity of the binary maps for each scenario using Kappa index. In order to assess the competence of the present protected areas boundary in covering the distribution of species, two different scenarios were employed, which are ensemble scenario 1: an ensemble of the binary maps of the species distribution in Mid-Holocene, present, and RCP2.6; and ensemble scenario 2: an ensemble of binary suitability maps in Mid-Holocene, present, and RCP8.5. Then, the borders of modeled habitats with the boundaries of 23 existing protected areas in two central provinces in Iran were compared. The predicted species distribution under scenario 1 (RCP2.6) was mostly similar to its current distribution (Kappa = 0.53) while the output model under scenario 2 (RCP8.5) indicated a decline in the species distribution range. Under the first ensemble scenario, current borders of the protected areas in Hamedan province showed better efficiency to cover the model species distribution range. Analyzing MaxEnt spatial models under the second climatic scenario suggested that protected areas in both Markazi and Hamedan provinces will not cover “high suitability” areas in the future. Modeling the efficiency of the current protected areas under predicted future climatic scenarios can help the related authorities to plan conservation activities more efficiently.

Distribution of methane and carbon dioxide concentrations in the near-surface zone over regional fault zones and their genetic characterization in the Pszczyna-Oświęcim area (SE part of the Upper Silesian Coal Basin, Poland)

The objective of this paper was to characterize the variability of methane (CH4) and carbon dioxide (CO2) concentrations in the near-surface zone, measured along 4 selected sampling lines positioned perpendicularly to regional fault zones, in the SE part of the Upper Silesian Coal Basin (USCB), Poland. This way it was possible to check the migration activity of these gases to the surface through low-permeable Miocene strata. It was also possible to evaluate the applicability of surface geochemical survey methodology to the identification of potential accumulations of free natural gas in the topmost parts of the Carboniferous formations in the USCB. The results of 319 soil-gas samples were supported by stable isotope analyses and related to the geological setting and the distribution of methane potential at various depths. Moreover, the sampling included the area of the closed and remediated Andrzej VII mining shaft, where 5 soil-gas samples were taken. Additionally, gas flux was evaluated at 3 measurement points at which increased gas concentrations were detected. The maximum concentrations of CH4 and CO2 in soil gases were 15.4 and 9.39 vol%, respectively. Soil gases contain both thermogenic and microbial CH4 and CO2 that migrated from secondary and primary gas zones within the Pennsylvanian coal-bearing strata. In some sites, CO2 was also generated by the oxidation of soil organic matter and/or CH4 in a near-surface zone. Anomalous CH4 concentrations were generally found over elevated fragments of erosional structures of Carboniferous coal-bearing formations. This indicates the presence of free CH4 accumulations beneath the Miocene overburden. However, the surface anomalies did not always correlate with the zones of CH4 secondary accumulations. Anomalous concentrations of CH4 and CO2 correlated with the regional fault zones that cut through the Carboniferous formations. This indicates the potential presence of fault traps saturated with free CH4 in the upper parts of Carboniferous formations. Relatively low values were observed for both CH4 and CO2 emissions (maximum: 25 and 4320 mg m−2 d−1, respectively). This suggests relatively low dynamics of gas migration from the depth to the soil zone.

Self-assembly followed by radical polymerization of ionic liquid for interfacial engineering of black phosphorus nanosheets: Enhancing flame retardancy, toxic gas suppression and mechanical performance of polyurethane

As one of emerging layered nanomaterials, the potential of black phosphorous nanosheets (BP) for fabricating high performance polymer composites was seriously confined by incompatible interface. Herein, interfacial engineering between BP nanosheets and polyurethane (PU) matrix was rationally designed, where employing polymerized ionic liquid as linking bridge between robust BP nanosheets and soft TPU. The ionic liquid (IL) was firstly confined onto the surface of BP nanosheets with the combination of electrostatic-driving self-assembly process and in situ radical polymerization was then performed. The successful preparation of IL-functionalized BP (IL-BP) nanosheets was confirmed by a series of analytic methods, incluing TEM, XPS, FTIR, and so on. The resultant IL-BP nanosheets imparted well mechanical performance and flame retardancy to TPU composites. Compared to the mechanical enhancement reported by other literatures, the break strength of TPU/IL-BP-1.0 was significantly increased by 50%, attributing to strong interfacial regulation of polymerized IL and mechanically robust BP nanosheets, generated by the similar polarity. Meanwhile, significant decreases of 38.2% and 19.7% in peak values of heat release rate and total heat release were achieved for TPU/IL-BP-2.0. With the investigation of combustion residue and pyrolysis products, it was found that a mass of pyrolysis products reacted with IL-BP nanosheets to form mechanically robust protective char and solid products, being no longer used as fuel to support combustion. Meanwhile, the maximum concentration of CO2 and highly toxic CO of TPU/IL-BP-2.0 were effectively decreased by 36.9% and 26.5%, compared to the pure TPU. Such a design route effectively regulates the interfacial interaction between BP nanosheets and polymer matrix and offers a practical route for preparing high performance materials.

Study on propagation characteristics of the secondary explosion of coal dust

Abstract In the era when renewable energy resources are advocated, traditional fuels still account for a dominant proportion. During coal exploitation, coal dust explosion has been one of the most common and serious disasters. Nevertheless, the generated dust can suspend in the air, further leading to a secondary explosion. However, there are limited studies focusing on the propagation characteristics of secondary explosion induced by coal dust. Therefore, this paper aims to detect coal dust explosion in a pipe network and investigate the secondary explosion caused by the first explosion. In specific, this paper numerically analyzed the propagation characteristics of first and secondary explosion of coal dust in aspects of flame temperature, airflow rate and CO mass concentration. The results indicate that the maximum flame temperature of the secondary explosion of coal dust could reach up to 4500 K, which was more intense than the first explosion. After the secondary explosion, the air velocity witnessed a significant increase, compared with the first explosion, but the air velocity at the linear section of the pipe network witnessed the highest because of the air supplement at two sides. Different from the highest CO concentration at the ignition area in the first explosion, the CO concentration in the secondary explosion source area decreased rapidly and the maximum CO concentration appeared in the flame front. Moreover, because of enough oxygen supplement, the explosion reaction was much more sufficient, so that the maximum CO concentration was less than that in the first explosion.

Measuring Regional Atmospheric CO2 Concentrations in the Lower Troposphere with a Non-Dispersive Infrared Analyzer Mounted on a UAV, Ogata Village, Akita, Japan

We have developed a simple measuring system prototype that uses an unmanned aerial vehicle (UAV) and a non-dispersive infrared (NDIR) analyzer to detect regional carbon dioxide (CO2) concentrations and obtain vertical CO2 distributions. Here, we report CO2 measurement results for the lower troposphere above Ogata Village, Akita Prefecture, Japan (about 40° N, 140° E, approximately −1 m amsl), obtained with this UAV system. The actual flight observations were conducted at 500, 400, 300, 200, 100, and 10 m above the ground, at least once a month during the daytime from February 2018 to February 2019. The raw CO2 values from the NDIR were calibrated by two different CO2 standard gases and high-purity nitrogen (N2) gas (as a CO2 zero gas; 0 ppm). During the observation period, the maximum CO2 concentration was measured in February 2019 and the minimum in August 2018. In all seasons, CO2 concentrations became higher as the flight altitude was increased. The monthly pattern of observed CO2 changes is similar to that generally observed in the Northern Hemisphere as well as to surface CO2 changes simulated by an atmospheric transport model of the Japan Meteorological Agency. It is highly probable that these changes reflect the vegetation distribution around the study area.

Characteristic of Possible Obtained Products during the well Underground Coal Gasification

This article is a summarizing of the results of the author's team on the establishment of technological parameters of underground gasification. It provides a justification of the final chemical and energy products that can be obtained as a result of complex physical and chemical transformations of coal. The thermodynamic processes of formation of the gasification source when changing the composition of the blast furnace mixture and the modes of its application to the georeactor are considered. Moreover, the change in the stress-strain state of rocks depending on the composition of the lateral rocks is taken into account. To better ensure the results are consistent with the well-known principles of thermodynamics and phase formation under the influence of the temperature field and the main chemical reactions occurring in complex gasification processes are presented. The main phase transitions in the georeactor are given for the maximum reception of different energy gases. Particular attention is given to the formation of an appropriate relationship between hydrogen and carbon monoxide, which form a synthesis gas. The Anderson-Schultz-Flory reaction is used to determine the maximum CO concentration in the outlet mixture. In general, the system for determining the material and thermal balance is proposed. These approaches were checked both for working out the coal reserves and for utilization of the mining waste products. Results of this investigation were included to the Roman Dychkovskyi thesis of the scientific degree of the Doctor of the Technique Sciences “Scientific Principles of Technologies Combination for Coal Mining in Weakly Metamorphoses Rockmass”. Also, this results were partially presented on international scientific and practical conferences “Forum of Miners” from different years. They contain the researches, which were conducted within the project GP – 489, financed by Ministry of Education and Science of Ukraine.

A steady-state equilibrium-based carbon dioxide gasification simulation model for hydrothermally carbonized cow manure

Abstract A detailed steady-state equilibrium–based simulation model was developed in Aspen Plus to demonstrate the CO2-gasification process of cow manure-derived hydrochar. Simulation was performed at gasification temperature of 700–1000 °C and equivalence ratio of 0.1–0.6 for HTC treatment temperatures between 180 and 260 °C. Various simulation outputs including gas yield, syngas composition, lower heating value, CO/CO2 conversion efficiency, H2/CO ratio, and cold gas efficiency were evaluated. Simulation results revealed that CO concentration was increased with gasification temperature while H2 concentration was initially increased until 950 °C and decreased afterwards. H2 concentration was also decreased with the increasing equivalence ratio. However, CO concentration increased initially but started to decrease after equivalence ratio of 0.3. Gasification temperature of 850 °C and equivalence ratio of 0.3 resulted in the maximum concentrations of both CO and H2 and lower heating value. Replacing CO2 with air increased the lower heating value as the concentration of H2 was increased compared to the concentration of CO.

High-Efficiency Carbon Dioxide Reduction Using Nonthermal Plasma Desorption

We present a highly efficient carbon dioxide (CO2) reduction treatment technique using an adsorbent and nonthermal plasma flow at the laboratory scale. The plasma reactor consists of twelve surface discharge elements, which are energized by a 10-kHz bipolar pulsed high-voltage power supply. As an adsorbent, the molecular sieve zeolite 13X is used, and it is placed downstream of the plasma reactor. In the physical adsorption process, approximately 10% CO2 gas with flow rate 10 L/min is prepared by 99.5% CO2/N2 cylinder and a nitrogen cylinder. It is then introduced into the flow channel, and CO2 is adsorbed by the adsorbent. After the adsorption process, the circulation flow channel is set and the N2 plasma flow is generated with a blower. Consequently, CO2 adsorbed by the adsorbent is desorbed with higher concentration (currently ∼20%) and reduced to CO with high efficiency. The generated CO can be reused as a fuel. We evaluate the experimental results by calculating the conversion efficiency of CO2 to CO and the energy efficiency of the plasma. When the number of repetitions of experiments is 5, a maximum CO concentration of 5% and a maximum CO2 concentration of 20% are reached. The energy efficiency associated with the conversion of desorbed CO2 to CO reaches 14% with the plasma power of 300 W. Discussions are carried out by comparing the value with those obtained in other studies on the plasma reduction of CO2.

Solutal convection in porous media: Comparison between boundary conditions of constant concentration and constant flux

We numerically examine solutal convection in porous media, driven by the dissolution of carbon dioxide (CO2) into water---an effective mechanism for CO2 storage in saline aquifers. Dissolution is associated with slow diffusion of free-phase CO2 into the underlying aqueous phase followed by density-driven convective mixing of CO2 throughout the water-saturated layer. We study the fluid dynamics of CO2 convection in the single aqueous-phase region. A comparison is made between two different boundary conditions in the top of the formation: (i) a constant, maximum aqueous-phase concentration of CO2, and (ii) a constant, low injection-rate of CO2, such that all CO2 dissolves instantly and the system remains in single phase. The latter model is found to involve a nonlinear evolution of CO2 composition and associated aqueous-phase density, which depend on the formation permeability. We model the full nonlinear phase behavior of water-CO2 mixtures in a confined domain, consider dissolution and fluid compressibility, and relax the common Boussinesq approximation. We discover new flow regimes and present quantitative scaling relations for global characteristics of spreading, mixing, and a dissolution flux in two- and three-dimensional media for both boundary conditions. We also revisit the scaling behavior of Sherwood number (Sh) with Rayleigh number (Ra), which has been under debate for porous-media convection. Our measurements from the solutal convection in the range 1, 500<Ra<135, 000 show that the classical linear scaling Sh ~ Ra is attained asymptotically for the constant-concentration case. Similarly linear scaling is recovered for the constant-flux model problem.