Low Concentrations Of Carbon Dioxide Research Articles

Study on competitive adsorption characteristics of CO/CO2/CH4 multi-component low concentration gases in coal

ABSTRACT Coal spontaneous combustion indicator gases are one of the important indicators to judge coal spontaneous combustion, but coal spontaneous combustion is not the only source of these gases, the coal will also absorb these gases. Therefore, the study of gas adsorption characteristics in coal is of great significance for the prevention of coal fire. In this work, the adsorption characteristics of the low concentrations of carbon monoxide (CO), carbon dioxide (CO2) and methane (CH4) in coal were studied and the competitive adsorption relationships among these three gases were identified by sorption isotherms. Experiments were performed on two coal samples from the Linnancang Coal Mine (LNC coal sample, named after the first word of the mine name) and Xixizhuang Coal Mine (XXZ coal sample, same as above), which were submitted to different gas atmosphere. A mathematical approach for calculating the adsorptive volume of each gas component under four experimental conditions was proposed, and the relationship between the adsorption capacities of CO, CO2 and CH4 and pressure was obtained during the adsorption and desorption. The results show that for the XXZ coal sample, the adsorption volume of CO under the maximum pressure conditions during the standard gas adsorption and desorption process is 7.7×10−2 mL/g, while the comparable values in gas-He, gas-CH4 and gas-CO2 are 3.5×10−2 mL/g, 1.9×10−2 mL/g, and 1.2×10−2 mL/g, respectively. The adsorption volumes of CO, CO2 and CH4 decrease with increasing pressure, but the decreasing trend is lower than that of standard gas adsorption under low-concentration conditions. The adsorption capacity of the desorption process under the same pressure conditions is greater than that of the adsorption process. In the adsorption state composed of CO, CO2, and CH4 gases, there are mutual constraints and influences between the gases, showing competitive adsorption behavior. Both CO2 and CH4 have obvious inhibitory effects on CO, while He does not inhibit CO adsorption.

Effect of packaging design with two functional films on the quality of figs stored at ambient temperature

This work aims to study the effect of a new packaging design with two functional films on the postharvest preservation of figs under ambient temperature (T = 25 ± 1°C, RH = 60 ± 5%). Water vapor permeable film, oxygen-permeable film, and polyethylene terephthalate tray were used to make the packaging. During the experiment, the gas composition in the packaging, water loss rate, hardness, appearance, and nutrient contents of figs were tested and recorded. The atmosphere with low oxygen composition and high carbon dioxide concentration was formed in the packaging. New packaging could reduce the water loss of figs and slow down the decrease of hardness and the loss of nutrients. The shelf life of figs was prolonged to 4 days under ambient temperature by functional films, while the control group was only 2 days. Practical applications Two kinds of functional films (Water vapor permeable film and oxygen-permeable film) were used to make a new packaging design for figs. The packaging could effectively prolong the storage time of fresh figs to 4 days under ambient temperature. It was of great significance to the storage, transportation, and sale of figs after harvest. Two kinds of functional films can also be used to preserve other fresh fruits and vegetables that are difficult to store.

A new multivariable benchmark for Last Glacial Maximum climate simulations

Abstract. We present a new global reconstruction of seasonal climates at the Last Glacial Maximum (LGM, 21 000 years BP) made using 3-D variational data assimilation with pollen-based site reconstructions of six climate variables and the ensemble average of the PMIP3—CMIP5 simulations as a prior (initial estimate of LGM climate). We assume that the correlation matrix of the uncertainties in the prior is both spatially and temporally Gaussian, in order to produce a climate reconstruction that is smoothed both from month to month and from grid cell to grid cell. The pollen-based reconstructions include mean annual temperature (MAT), mean temperature of the coldest month (MTCO), mean temperature of the warmest month (MTWA), growing season warmth as measured by growing degree days above a baseline of 5 ∘C (GDD5), mean annual precipitation (MAP), and a moisture index (MI), which is the ratio of MAP to mean annual potential evapotranspiration. Different variables are reconstructed at different sites, but our approach both preserves seasonal relationships and allows a more complete set of seasonal climate variables to be derived at each location. We further account for the ecophysiological effects of low atmospheric carbon dioxide concentration on vegetation in making reconstructions of MAP and MI. This adjustment results in the reconstruction of wetter climates than might otherwise be inferred from the vegetation composition. Finally, by comparing the uncertainty contribution to the final reconstruction, we provide confidence intervals on these reconstructions and delimit geographical regions for which the palaeodata provide no information to constrain the climate reconstructions. The new reconstructions will provide a benchmark created using clear and defined mathematical procedures that can be used for evaluation of the PMIP4–CMIP6 entry-card LGM simulations and are available at https://doi.org/10.17864/1947.244 (Cleator et al., 2020b).

CO2 reduction in a microchannel electrochemical reactor with gas-liquid segmented flow

Abstract Electrochemical CO2 reduction is suffered from mass transfer limitation at high current densities, owing to the low carbon dioxide concentration over the surface of the catalyst. To enhance mass transfer, a novel annular microchannel electrochemical reactor was established, which consists of a cylindrical cation exchange membrane at the outside and an oxide-derived Cu foam rod as the electrode in the middle. The results show that, due to the enhanced gas–liquid mass transfer of CO2 in the channel, the limiting current density can increase by 49.3% from 6.7 mA cm−2 to 10.0 mA cm−2 and CO2 reduction rate increase by 55.3% from 21.5 × 10−9mol s−1 cm−2 to 33.4 × 10−9mol s−1 cm−2, compared when Cu electrode is in the open space. It further shows the limiting current density is influenced by the annulus channel width and gas–liquid ratio, and width of 1 mm gives the best performance at a gas–liquid ratio of 2:1. This work demonstrates the great potential of utilizing microchannel to intensify the mass transfer for efficient electrochemical CO2 reduction.

Comparative analysis on temperature swing adsorption cycle for carbon capture by using internal heat/mass recovery

Due to relatively high energy consumption of absorption technology, adsorption carbon dioxide capture is gathering the momentum in recent years. This paper aims to further improve the thermal performance of a 4-step temperature swing adsorption cycle by integrating internal mass recovery and heat recovery. Exergy efficiency is evaluated by using adsorption characteristics of activated carbon and compared in terms of four different situations i.e. basic cycle, heat recovery cycle, mass recovery cycle, heat and mass recovery cycle, which could illustrate the advantages and disadvantages of different recovery technologies. Results demonstrate that heat recovery and mass recovery technologies are quite conducive to improve the up limit of cycle thermal efficiency. Under the conditions of different desorption/adsorption temperatures and pressures, exergy efficiencies using recovery technologies could be improved by up to 2.86 times when compared with that of basic cycle. Besides, in real application unused percentage of adsorption reactor and metal ratio have large influence on the cycle performance while mass recovery rate has a relatively small influence. One potential application of the proposed recovery technologies is direct air capture in building ventilation system since a largest improvement could be achieved at a low carbon dioxide concentration.

DETECTION OF CAMPYLOBACTER SPP. WITH REAL-TIME POLYMERASE CHAIN REACTION

Bacteria of Campylobacter genus are ones of the main zoonotic pathogens causing human and animal diseases. Campylobacter organisms are microaerophiles and, therefore, require low oxygen concentration (3–5%) and high carbon dioxide concentration (3–10%) for their growth. They use amino acids rather than carbons as a source of energy. Classical bacteriological methods for Campylobacter spp. detection are not always successful due to diffi culties in creating optimal conditions for their growth. Therewith, development and implementation of molecular methods for Campylobacter detection and identifi cation are of current importance. Assay for qualitative Campylobacter spp. detection with real-time polymerase chain reaction using CFX-96 thermocycler was optimized. Highly specifi c segment of 16S rRNA gene allowing identifi cation of 6 Campylobacter species: C. jejuni, C. coli, C. lari, C. upsaliensis, C. helveticus и C. hyointestinalis was selected as an amplifi cation target. Optimal magnesium ion concentration (2.5 мМ) and primer annealing temperature (58 °С) were determined. Eighteen reference strains of various bacteria were tested. Only tests of Campylobacter genus strains gave positive results. The method sensitivity was 40 target molecules. The said method was used for testing 76 samples of raw materials of animal origin. Campylobacter spp. genome was detected in 18 samples. Obtained results showed that the optimized variant of real-time polymerase chain reaction based on 16S rRNA gene amplifi cation was a specifi c, sensitive, rapid, reproducible and accurate method for qualitative detection of Campylobacter spp. in samples of raw animal materials.

New sensor measures biological activity in soil at field scale in real time

New sensor measures biological activity in soil at field scale in real time

Insights into Carbonate Fuel Cell Operation Under Carbon Dioxide Capture Conditions

Providing for increasing global energy needs while managing carbon dioxide emissions is the dual energy challenge the modern world faces. In order to meet this challenge, reliable and dispatchable low carbon energy sources are a likely component. For many scenarios, this suggests that cost effective carbon dioxide capture will be a key technology.[1] Carbon capture with carbonate fuel cells (CFCs) may be one such technology option.[2]Carbonate fuel cells concentrate carbon dioxide from the cathode to the anode as part of their normal operation, effectively doing both carbon capture and low carbon power generation in a single process. (see Figure 1) When generating power, typical carbon dioxide concentrations fed to the CFC cathode tend to be higher than carbon dioxide emissions of many industrial processes. This means that if we want to capture that carbon dioxide, we need the fuel cell to operate at lower carbon dioxide concentrations than it typically does. For carbon capture operations, cathode inlet carbon dioxide concentrations could be as low as 4%. Additionally, under typical power generation operations, CFCs only capture a fraction of the carbon dioxide (<50%) fed to the cathode, where for carbon capture rates may be as high as 90%. Together these two constraints (low initial concentration and higher capture) results in very low carbon dioxide concentrations in the cell, particularly at the cathode outlet. This may impact the fundamental chemistry of the process. Carbon dioxide capture at 4% and lower was tested in a fuel cell, specifically designed to minimize mass transport effects external to the active cell components. Carbon capture was demonstrated at a range of carbon dioxide concentrations ranging from standard operation for power generation (>10%) to <1%. Additionally, oxygen concentrations and current densities were varied over likely operational ranges. We demonstrate that under most circumstances, operations under carbon capture conditions proceed via a similar mechanism to those under power generation conditions. However, in harsh or extreme conditions, where carbon dioxide concentrations are low (<0.5%) and/or current densities high, alternative mechanisms appear. We demonstrate how the CFC performs when these alternative mechanisms are present. Additionally, our findings suggest that they appear to utilize water in place of carbon dioxide and allow the cell to operate at conditions beyond theoretical complete carbon capture. [1] IEA World Energy Outlook 2018; Bloomberg New Energy Finance, New Energy Outlook 2018 [2] Ghezel-Ayagh H., Jolly S., Patel D., Hunt J., Steen W., Richardson C., Marina O., (2013) A Novel System for Carbon Dioxide Capture Utilizing Electrochemical Membrane Technology ECS Transaction Vol 51 (1) 265-272 Figure 1

Purificación de biogás usando Cianobacterias

&#x0D; Objetivo: Investigar técnicas biológicas para purificar biogás. Metodología: El biogás con bajo contenido de dióxido de carbono fue burbujeado en dos soluciones acuosas que contenían cianobacterias filamentosas de diferentes cepas de Leptolyngbya sp. Luego, los resultados obtenidos fueron comparados contra un blanco. Resultados y Concluiones: El biogás que fue parcialmente purificado redujo su contenido de dióxido de carbono en una proporción de 20 % a &lt; 10 % luego de estar en contacto con cianobacterias. A la vez, el oxígeno producido durante la fotosíntesis se mantuvo por debajo de los límites de explosión para la mezcla metano-oxígeno. En contraste, el blanco usado en el ensayo se saturó de dióxido de carbono, causando una caída en el pH conforme pasaba el tiempo. El contenido de metano en el biogás purificado, cuya pureza fue medida con un método volumétrico, superó el 90 %. Las dos cepas de cianobacteria usadas tenían una composición en base seca de proteína ? 25 % y en lípidos &lt; 2 %.&#x0D;

Effects of alkalinity, extremely low carbon dioxide concentration and irradiance on spectral properties, phycobilisome, photosynthesis, photosystems and functional groups of the native cyanobacterium Calothrix sp. ISC 65

Effects of alkalinity, extremely low carbon dioxide concentration and irradiance on spectral properties, phycobilisome, photosynthesis, photosystems and functional groups of the native cyanobacterium Calothrix sp. ISC 65

Optimization of microalgae Scenedesmus SP. growth rate using a central composite design statistical approach

In this research, growth rate of microalgae Scenedesmus sp. was modified by optimizing four effective factors. The operational energy efficiency factor (OEEf) of the photobioreactor was also considered in parallel. A central composite design statistical approach was implemented to evaluate the results. These factors were carbon dioxide concentration (0.038 (air), 2.0, 5.0, 7.0, 10.0%), aeration rate (0.2, 0.5, 1.5, 3.0, 4.0 vvm), initial inoculum concentration (0.140–0.430 g/l) and gas diffuser diameter (0.4, 1.0, 2.6, 4.0, 5.0 mm). All the factors were very significant at the defined ranges. The diffuser diameter also showed different effect when either low or high carbon dioxide concentration was applied. The optimized values (6.02% CO2, 0.39 vvm flow rate, 3.7 mm diffuser diameter and 0.180 g/l initial inoculation) would result the maximum growth rate of 0.525 g/l.d and high OEEf of 19.5 which was very significant. It was concluded that microalgae technology is a promising solution for carbon dioxide sink in large scale and biofuel production after optimizing the biomass production rate.

Methane number measurements of hydrogen/carbon monoxide mixtures diluted with carbon dioxide for syngas spark ignited internal combustion engine applications

A comprehensive analysis of the autoignition tendency of binary mixtures of hydrogen and carbon monoxide diluted with carbon dioxide is carried out in this paper. Methane Number (MN) measurements of these mixtures were performed by using a method analogous to the standard method for Octane Number (ON) measurement. The experimental MNs ranged from 46.0 to 139.1 according to experimental data. These results are compared with the MNs calculated by programs released for natural gas MN estimations. A comparative analysis concluded that these programs are not suitable to calculate MN of syngas. A method to isolate the effect of carbon dioxide on the autoignition tendency of binary mixtures of hydrogen and carbon monoxide is proposed. Results reveal that increments of carbon dioxide concentration in the mixtures, exponentially increase the MN of the mixtures. At low carbon dioxide concentration, the MN of the ternary mixtures can be approximated by the MN of their equivalent binary mixtures of hydrogen and carbon monoxide. Based on this observation, the MNs of coal gases reported in the literature are estimated.

Реакция цианобактерии Calothrix sp. ISC 65 из загрязненных нефтью регионов на комплексное воздействие солености, дефицита углерода и низкой освещенности

Реакция цианобактерии Calothrix sp. ISC 65 из загрязненных нефтью регионов на комплексное воздействие солености, дефицита углерода и низкой освещенности

Microstructure of cement paste at different carbon dioxide concentrations

Numerous studies have been performed on the carbonation model based on the boundary (carbonation front line) between the partially carbonated and non-carbonated zones. However, a significant difference exists between the traditional phenolphthalein spray test results and the prediction model results on carbonation depth. The difference is mainly caused by the partially carbonated zone. In this study, the changes in the microstructure of cement paste during the carbonation process at different carbon dioxide (CO2) concentrations (0·03, 3 and 20%) were determined through the phenolphthalein spray test, thermogravimetric analysis and mercury intrusion porosimetry (MIP). The results showed that carbonation depth and the square root of carbonation time have a linear relationship. Compared with that in the natural carbonation condition, the effect of 20% carbon dioxide concentration on the size of the partially carbonated zone was significant. However, no effect was seen for 3% carbon dioxide concentration. MIP showed that, in the same carbonation zone, low carbon dioxide concentration led to low total porosity; there was a clear refinement in the pore size and there was a high degree of carbonation.

Samples of Cyanobacterium Calothrix sp. ISC 65 Collected from Oil Polluted Regions Respond to Combined Effects of Salinity, Extremely Low-Carbon Dioxide Concentration and Irradiance

Samples of Cyanobacterium Calothrix sp. ISC 65 Collected from Oil Polluted Regions Respond to Combined Effects of Salinity, Extremely Low-Carbon Dioxide Concentration and Irradiance

Effect of accelerated carbonation conditions on the characterization of load-induced damage in reinforced concrete members

Reinforced concrete is widely used in the construction of buildings, historical monuments and also nuclear power plants. For various reasons, many concrete structures are subject to unavoidable cracks that accelerate the diffusion of atmospheric carbon dioxide to the steel/concrete interface. Carbonation at the interface induces steel corrosion that may cause the development of new cracks in the structure, and this is a determining factor for its durability. It is therefore important to accurately characterize the length of the load-induced damage along the steel/concrete interface in order to understand the effect of cracking on corrosion initiation and propagation. The aim of this paper is to present an experimental procedure that allows the load-induced damage length to be assessed. The procedure consists in subjecting specimens to accelerated carbonation and determining the length of the carbonated steel/mortar interface, which is assumed to be equal to the length of the damaged steel/mortar interface. Suitable conditions should therefore be found for the accelerated carbonation in order to obtain an accurate characterization of the damaged steel/mortar interface length. To this end, two carbonation concentrations (3, 50%) and several carbonation durations were tested. The results indicate that a strong carbonation shrinkage phenomenon develops at high carbon dioxide concentration and leads to new cracking along the steel/mortar interface. These cracks allow the carbon dioxide to spread along the interface over a length greater than the damaged length. This is not the case when the accelerated carbonation test is performed at lower carbon dioxide concentration. Consequently, accelerated carbonation at high carbon dioxide concentration (50%) cannot be used neither for the estimation of the length of the mechanically damaged steel/mortar interface nor for the carbonation-induced corrosion studies because it will lead to an overestimation of the size of the corroded area.

Changes in the chloroplastic CO2 concentration explain much of the observed Kok effect: a model.

Mitochondrial respiration often appears to be inhibited in the light when compared with measurements in the dark. This inhibition is inferred from the response of the net CO2 assimilation rate (A) to absorbed irradiance (I), changing slope around the light compensation point (Ic ). We suggest a model that provides a plausible mechanistic explanation of this 'Kok effect'. The model uses the mathematical description of photosynthesis developed by Farquhar, von Caemmerer and Berry; it involves no inhibition of respiration rate in the light. We also describe a fitting technique for quantifying the Kok effect at low I. Changes in the chloroplastic CO2 partial pressure (Cc ) can explain curvature of A vs I, its diminution in C4 plants and at low oxygen concentrations or high carbon dioxide concentrations in C3 plants, and effects of dark respiration rate and of temperature. It also explains the apparent inhibition of respiration in the light as inferred by the Laisk approach. While there are probably other sources of curvature in A vs I, variation in Cc can largely explain the curvature at low irradiance, and suggests that interpretation of day respiration compared with dark respiration of leaves on the basis of the Kok effect needs reassessment.

Cyanuric Acid‐Based Organocatalyst for Utilization of Carbon Dioxide at Atmospheric Pressure

A organocatalytic system based on economical and readily available cyanuric acid has been developed for the synthesis of 2-oxazolidinones and quinazoline-2,4(1H,3H)-diones from propargylamines and 2-aminobenzonitriles under atmospheric pressure carbon dioxide. Notably, a low concentration of carbon dioxide in air was directly converted into 2-oxazolidinone in excellent yields without an external base. Through mechanistic investigation by in situ FTIR spectroscopy, cyanuric acid was demonstrated to be an efficient catalyst for carbon dioxide fixation.

Preoperative EUS-guided tattooing of the pancreas with a minuscule amount of marking solution utilizing a newly designed injector

To our knowledge, here we report the first case of nonischemic priapism following penile tattooing.To report the first case of nonischemic priapism following penile tattooing.A case with tattooing‐induced priapism is presented including subjective reporting, physical examination, and laboratory/radiologic evaluations.A 21‐year‐old man, presented with partially rigid penis of 3‐month duration. On examination, the penis was half rigid, with a tattoo on its dorsal surface, and a smaller tattoo on the glans (Figure 1). The patient initially stated that the tattoo had been created years ago, but later admitted that he had it created just before the occurrence of priapism. A traditional tattooist created the tattoo manually, using a handheld needle. Bleeding from deep penile tissue for several days complicated the tattooing.Known etiologies of priapism were investigated and ruled out. Specifically, perineal injury, leukemia, sickle cell trait, thalassemia, urinary tract infection, neurogenic, neoplastic, infectious, toxic, and pharmacological causes were actively investigated and ruled out. There was no history of alcohol consumption or smoking. Aspirated penile blood was bright red. Cavernous blood gas measurements confirmed high oxygen and low carbon dioxide content, diagnostic of arterial priapism.There was no embolization facility in Kermanshah. In fact, there are few experts in superselective embolization in Iran. We referred the patient for superselective embolization. However, he underwent a nonindicated Sacher procedure. Predictably, the procedure was unsuccessful. At present, the patient continues to have priapism. Because of the painless nature of erections, moderately good preservation of erectile function during intercourses, and disappointment with former surgery, the patient declined further therapies, and he lives with his condition.Tattooing should be added to the etiologies of nonischemic priapism. Considering this case, we discourage penile tattooing. Zargooshi J, Rahmanian E, Motaee H, and Kohzadi M. Nonischemic priapism following penile tattooing. J Sex Med 2012;9:844–848.

Control of a recuperative vapor- recompression air separation process

The use of oxy-combustion for producing furnace stack gases with low nitrogen and high carbon dioxide concentrations is a potential method for economical sequestration of green house gases. A conventional air separation unit to provide oxygen compresses all the air feed and operates with one of the two cryogenic distillation columns at elevated pressure so heat integration can be employed.The use of recuperative vapor recompression has been recently proposed in which only a portion of a nitrogen stream is compressed to provide liquid reflux to two columns, which both operate at low pressure where the separation is easier. Steady-state designs have been developed and economically optimized.The purpose of this paper is to explore the dynamic controllability of this type of vapor recompression system for air separation.