The performance of a CO2 double-pipe evaporator was studied through experiments and a simulation model that was established by the steady-state distribution parameter method and experimentally verified while using a CO2 transcritical water‒water heat pump system. The effects of different operating parameters on heat transfer performance were studied over a range of evaporation temperatures (−5 to 5 °C), mass velocity (100‒600 kg/m2s), and heat flux (5000‒15,000 W/m2). It was found that the dryout quality increased at a small evaporation temperature, a large mass velocity, and a small heat flux. The simulation yield means relative error (RE) of heat transfer for the evaporation temperature and that of the CO2 pressure drop for the chilled water inlet temperature were 5.21% and 3.78%, respectively. The effect of tube diameter on the performance of CO2 double-pipe evaporator is probed through simulations. At the same time, this paper defines a parameter α , which is the proportio... [more]

Reducing the emissions of greenhouse gas is a worldwide problem that needs to be solved urgently for sustainable development in the future. The solubility of CO2 in ionic liquids is one of the important basic data for capturing CO2. Considering the disadvantages of experimental measurements, e.g., time-consuming and expensive, the complex parameters of mechanism modeling and the poor stability of single data-driven modeling, a multi-model fusion modeling method is proposed in order to predict the solubility of CO2 in ionic liquids. The multiple sub-models are built by the training set. The sub-models with better performance are selected through the validation set. Then, linear fusion models are established by minimizing the sum of squares of the error and information entropy method respectively. Finally, the performance of the fusion model is verified by the test set. The results showed that the prediction effect of the linear fusion models is better than that of the other three optima... [more]

The treatment of nitrate and phosphate ions in fresh water such as streams, rivers, lakes, reservoirs, and wetlands through biological treatment has been getting more crucial and popular in recent years. This paper reports the reduction of nitrate and phosphate ions in modified low salinity fresh water via the cultivation of a microalgae strain, e.g., Tetraspora sp. and Spirogyra sp. The low salinity fresh water (9054 to 9992 ppm) was modified with the addition of organic fertiliser (VermiCompost Tea) and used as the cultivation medium to grow microalgae. The microalgae strains were grown under controlled conditions in an indoor laboratory for 14 days. The initial concentrations of nitrate and phosphate ions in the modified fresh water sample were 1.17 mg/L and 0.10 mg/L, respectively. The reduction of nitrate and phosphate ions associated with the effect of cultivation of Tetraspora sp. and Spirogyra sp. in ambient air (0.03% of CO2) and 15% of CO2 was investigated. In ambient air, th... [more]

Reduction of carbon dioxide emission from natural and industrial flue gases is paramount to help mitigate its effect on global warming. Efforts are continuously deployed worldwide to develop efficient technologies for CO₂ capture. The use of environment friendly amino acids as rate promoters in the present amine systems has attracted the attention of many researchers recently. In this work, the reaction kinetics of carbon dioxide with blends of N-methyldiethanolamine and L-Arginine was investigated using stopped flow technique. The experiments were performed over a temperature range of 293 to 313 K and solution concentration up to one molar of different amino acid/amine ratios. The overall reaction rate constant (kov) was found to increase with increasing temperature and amine concentration as well as with increased proportion of L-Arginine concentration in the mixture. The experimental data were fitted to the zwitterion and termolecular mechanisms using a nonlinear regression techniqu... [more]

Polyimides with excellent physicochemical properties have aroused a great deal of interest as gas separation membranes; however, the severe performance decay due to CO₂-induced plasticization remains a challenge. Fortunately, in recent years, advanced plasticization-resistant membranes of great commercial and environmental relevance have been developed. In this review, we investigate the mechanism of plasticization due to CO₂ permeation, introduce effective methods to suppress CO₂-induced plasticization, propose evaluation criteria to assess the reduced plasticization performance, and clarify typical methods used for designing anti-plasticization membranes.

The widespread raising of swine in farms becomes a serious problem in terms of the emission of carbon dioxide (CO₂) and methane (CH₄). This study aims to measure concentrations of carbon dioxide and methane, which account for the largest percentage of carbon emissions, to temporally estimate the carbon emitted during the pig-manure composting process. The research subject was a farmhouse raising 3000 growing pigs and 100 mother pigs. The capacity of the composting facility for pig manure treatment was 330 m², and the daily treatment was about 6 tons. After the pig manure discharged from the pig farm was delivered to the composting facility, for the 8 days including 6 before mixing and 2 after mixing, the concentrations of CO₂ and CH₄ were measured. The result shows that the CO₂ and CH₄ concentrations in the composting facility were 1208 ± 385 ppm and 95 ± 10 ppm, respectively. In the comparison of concentrations before and after mixing at the composting facility, the values of both CO₂... [more]

Rapid economic development has resulted in a significant increase in energy consumption and pollution such as carbon dioxide (CO₂), particulate matter (PM2.5), particulate matter 10 (PM10), SO₂, and NO₂ emissions, which can cause cardiovascular and respiratory diseases. Therefore, to ensure a sustainable future, it is essential to improve economic efficiency and reduce emissions. Using a Meta-frontier Non-radial Directional Distance Function model, this study took energy consumption, the labor force, and fixed asset investments as the inputs, Gross domestic product (GDP) as the desirable output, and CO₂ and the Air Quality Index (AQI) scores as the undesirable outputs to assess energy efficiency and air pollutant index efficiency scores in China from 2013⁻2016 and to identify the areas in which improvements was necessary. It was found that there was a large gap between the western and eastern cities in China. A comparison of the CO₂ and AQI in 31 Chinese cities showed a significant dif... [more]

This article presents gas hydrate experimental measurements for mixtures containing methane (CH₄), carbon dioxide (CO₂) and nitrogen (N₂) with the aim to better understand the impact of water (H₂O) on the phase equilibrium. Some of these phase equilibrium experiments were carried out with a very high water-to-gas ratio that shifts the gas hydrate dissociation points to higher pressures. This is due to the significantly different solubilities of the different guest molecules in liquid H₂O. A second experiment focused on CH₄-CO₂ exchange between the hydrate and the vapor phases at moderate pressures. The results show a high retention of CO₂ in the gas hydrate phase with small pressure variations within the first hours. However, for our system containing 10.2 g of H₂O full conversion of the CH₄ hydrate grains to CO₂ hydrate is estimated to require 40 days. This delay is attributed to the shrinking core effect, where initially an outer layer of CO₂-rich hydrate is formed that effectively s... [more]