جستجوی مقالات مرتبط با کلیدواژه « carbon dioxide (co2) » در نشریات گروه « محیط زیست »

The nickel processing industry has always been related with the issue of carbón dioxide emission. The production of carbon dioxide occurs at different phases of nickel processing, from pretreatment to smelting and refining. In addition to offgas, the nickel processing sector also produces solid waste known as slag, which is a byproduct of both smelting and refining processes. One of the slags in the nickel industry is known to contain iron, which is dominant compared to other elements. The primary objective of this study is to investigate the process of carbon dioxide capture by utilizing iron-rich slag derived from the nickel processing industry. The aim is to assess the feasibility of applying iron-rich slag from nickel smelters in the solid carbonation gas process for carbon dioxide capture, focusing on chemical reactions and overall kinetics. The iron-rich slag analyzed in this study contains a significant amount of iron oxide. It is theoretically anticipated that the iron oxide content in iron-rich slag could potentially sequester carbon dioxide. The study commenced by preparing the materials, undergoing the carbonation process, and then conducting various characterizations including X-ray diffractometer analysis and thermal gravimetric analysis. Additionally, calculations were performed to determine the percentage of carbon dioxide in the sample and the efficiency of carbonation. The kinetics analysis was also carried out using several models, such as mass transport, chemical reaction, and diffusion-controlled model to estimate the carbón dioxide capture mechanism that occurs. The carbon dioxide capture capacity of the iron-rich slag from the ferronickel industry is somewhat limited, albeit still relatively modest. Iron-rich slag was effectively utilized to capture carbon dioxide after thorough analysis. After undergoing a carbonation process for a duration of 4 hours, the percentage of carbon dioxide in the slag witnessed a significant increase, rising from an initial value of 0.28 percent to 1.12 percent. The capture of carbón dioxide gas is due to the reaction between silicate with carbón dioxide gas and water vapor to form siderite. The iron-rich slag operates under the diffusion-controlled model when it comes to capturing carbon dioxide. Iron-rich slag is reported to capture carbón dioxide at 175 degrees celsius with carbón dioxide and water vapor condition, which is proven both from thermodynamic calculations and experiments. Iron(II) carbonate is a carbonate compound generated by the carbón dioxide capture reaction by iron-rich slag. However, the stability of iron(II) carbonate in carbón dioxide and water vapor atmosphere is something that needs to be considered in future research. Further investigation can be conducted in the future to explore the potential of utilizing iron-rich slag for capturing carbon dioxide gas, building upon the findings of this preliminary study.

During this energy transition, research is being done to develop sustainable ways to support the shift to a decarbonized energy and production system. These ways include using renewable energy sources to promote circularity in products, green technologies, and safer procedures. Anaerobic digestion of palm oil mill effluent is a beneficial process for generating biogas, while the waste can also be utilized as fertilizer. The biogas can be further refined into biomethane, a valuable resource commonly used in transportation and power generation. The objective of this study is to examine the enhancement of biogas from Palm oil mill effluent and the elimination of sludge nutrients by utilizing microalgae Chlorella vulgaris. The microalgae will be cultivated in a modified photobioreactor to enhance the capture of carbon dioxide. The study utilized anaerobic batch reactor digesters. A modified photobioreactor, consisting of two columns separated by a membrane, was developed for the technological advancement of biogas upgrading, specifically for carbon dioxide capture and biogas upgrading. A technological gap in biogas upgrade technology innovation is filled by the improved photobioreactor. To optimize the bio-fixation of carbon dioxide from flue gas, it is essential to carefully select a suitable strain of microalgae that possesses both a strong ability to absorb carbon dioxide and a high tolerance to varying concentrations of this gas. By choosing the right strain, the efficiency of carbon dioxide removal can be significantly enhanced. Since Chlorella vulgaris microalgae have demonstrated this potential, they were chosen for this investigation. Microalgae also play a role in removing nutrients contained in the sludge.   Numerous chemical and biological methods have been used to upgrade biogas. Results of biological upgrading of biogas from palm oil mill effluent have been reported, with carbon dioxide removal reaching 89 percent until the methane concentration of the biogas is upgraded to 84 percent. The highest biomass of 1,835 grams per liter was achieved by culturing the microalgae Chlorella vulgaris in laboratory-scale photobioreactors. In this study, the application of 15 percent volume per volume biogas with an optical density of 0.4 was found to be optimal for the growth of the microalgae. The cultivation period lasted for 14 days. The peak biomass production was observed due to the achievement of a remarkable 98 volume per volume efficiency in carbon dioxide removal, which subsequently led to a significant rise in methane content, reaching 60 percent. The enhanced biogas achieved a peak methane content of 98 percent, indicating a significant improvement in quality. The findings of this study, conducted using a modified photobioreactor, indicate that Chlorella vulgaris demonstrated high efficacy in the removal of carbon dioxide, with a rate of up to 90 percent. Additionally, it exhibited remarkable performance in upgrading biogas derived from palm oil mill effluent, achieving a conversion rate of up to 98 percent. The optical density of microalgae at 0.4 played a crucial role in these processes. Furthermore, Chlorella vulgaris showcased its ability to effectively eliminate nutrient nitrogen, reaching a removal rate of 90 percent at an optical density of 0.2. Moreover, it demonstrated a phosphate removal rate of 80 percent at an optical density of 0.4.

Kinetic models which can express the behaviors of hydrolysis and biogas generation more precisely than the conventional models were developed. The developed models were evaluated based on the experimental data of six batch reactors. Anaerobic digestion test was co-digestion of food and vegetable waste with inoculating horse dung by 15% of the total wet weight, at the temperature of 37oC. For hydrolysis, the modified model was developed from an original first-order kinetic model. The modified first-order kinetic model was proved to be better than the original one with the hydrolysis rate constant in the range of 0.22-0.34/day and hydrolyzable rate of 0.80 to 0.84. Kinetics of carbon dioxide and methane were developed from a current potential model. The comparison between experimental data and modeling values had the high correlation of determination (0.9918-0.9998) and low root mean square errors (0.08-4.51) indicating the feasibility of the developed model. In which, the evolution of methane showed the rate constant in the range of 0.031-0.039/day. The carbon dioxide from fermentation accounted for 12-44% of the total observed carbon dioxide. Thus, separation of fermentation and methanogenesis by various reactors may reduce the price of methane enrichment significantly. There was a lag time between methanogenesis and fermentation in reactors (λ = 7-11 days). Also, the biogas yield was in the range of 431.6-596.9 Nml/g-VS with the CH4 concentration of 56.2-67.5%. The best methane yield (393.7 Nml/g-VS) was in a reactor with food waste to the vegetable waste ratio by 1.8:1 (wet basis) and C/N ratio by 25.4.