Modification of gasification fly ash using calcium aluminate cements to produce sorbents for carbon capture

As the link between climate change and carbon dioxide (CO2) emissions becomes increasingly harder to deny, carbon capture and sequestration has been promoted as a potential mitigation tool. One of the more well-established methods of carbon capture involves the use of calcium-based sorbents such as limestone. Gasification fly ash (GFA) has the potential to be used as a calcium-based sorbent in carbon capture applications. Presented as a cheaper alternative to limestone, the implementation of GFA could drastically reduce operational costs. Raw, untreated GFA, however, is unsuitable for use in a fluidised bed reactor due to its corrosiveness and agglomeration under high temperatures. One of the simplest methods of corrosion removal is by washing GFA with water. Washed GFA, however, loses all its mechanical strength and is unable to be fluidised. In this paper, we have investigated the suitability of modifying washed GFA with calcium aluminate cements (CACs) in hopes of improving its mechanical strength. A total of 25 experiments, with varying parameters such as CAC type and calcination gas, were tested. Sorbents were first tested for its fluidisability and mechanical strength in a cold fluidised bed as a preliminary test. Select sorbents were then placed in a hot fluidised bed to test its mechanical strengths under actual conditions, and its capture capacities were also recorded. Results have shown that GFA-CAC sorbents calcined under a nitrogen atmosphere exhibit much greater mechanical strengths than unmodified, washed GFA. The addition of CACs to GFA have also demonstrated greater stability in its carbon capture capacity in the hot fluidised bed. It was also discovered through x-ray diffraction characterisation that the compound mayenite is not solely responsible for contributing to the mechanical strength. Overall, the binding of GFA with CAC for use in carbon capture applications is promising.Bachelor of Engineering (Environmental Engineering

Temporal association of maternal weight gain with early-term and preterm birth and low birth weight babies

Background: Low birth weight and preterm or early-term babies may have a higher risk of poor health. One of the main factors is the weight gain of a pregnant woman during gestational weeks in the second and third trimesters. Changes in weight over a month in a pregnant woman might also have an impact on infant outcomes. This study aimed to investigate the association between maternal weight at different time points and low birth weight and preterm or early-term babies (premature babies). Methods: A total of 156 pregnant women were recruited. Maternal weight was collected at different gestational weeks. Maternal age, body mass index, delivery mode, delivery week, and infant weight were also recorded. Maternal data were restructured into a person-period format before mixed-effects multiple logistic regression was used. Various weight variables with either a fixed effect or time-varying effects were tested in the model. Results: Thirty (19.23%) women had delivered low birth weight or premature babies. Multiple logistic regression model demonstrated that mothers with higher increases in weight at 32 weeks of gestation than that in the predelivery stage had a lower probability of having a low birth weight or premature baby (odds ratio [OR] = 0.64; 95% CI, 0.49-0.85; p < 0.001). Women with a weight increase of more than 2 kg in a 4-week gestation period had a higher probability of having a low birth weight or premature baby than those with an increment of <1 kg (OR = 8.43; 95% CI, 2.90-24.54; p < 0.001). Conclusion: An increase in weight gain after 32 weeks was shown to reduce the risk of low birth weight and premature babies. Maternal weight monitoring was suggested to be conducted every 4 weeks to minimize the chance of having a low birth weight and premature baby

Temporal association of maternal weight gain with early-term and preterm birth and low birth weight babies

Background: Low birth weight and preterm or early-term babies may have a higher risk of poor health. One of the main factors is the weight gain of a pregnant woman during gestational weeks in the second and third trimesters. Changes in weight over a month in a pregnant woman might also have an impact on infant outcomes. This study aimed to investigate the association between maternal weight at different time points and low birth weight and preterm or early-term babies (premature babies). Methods: A total of 156 pregnant women were recruited. Maternal weight was collected at different gestational weeks. Maternal age, body mass index, delivery mode, delivery week, and infant weight were also recorded. Maternal data were restructured into a person-period format before mixed-effects multiple logistic regression was used. Various weight variables with either a fixed effect or time-varying effects were tested in the model. Results: Thirty (19.23%) women had delivered low birth weight or premature babies. Multiple logistic regression model demonstrated that mothers with higher increases in weight at 32 weeks of gestation than that in the predelivery stage had a lower probability of having a low birth weight or premature baby (odds ratio [OR] = 0.64; 95% CI, 0.49-0.85; p < 0.001). Women with a weight increase of more than 2 kg in a 4-week gestation period had a higher probability of having a low birth weight or premature baby than those with an increment of <1 kg (OR = 8.43; 95% CI, 2.90-24.54; p < 0.001). Conclusion: An increase in weight gain after 32 weeks was shown to reduce the risk of low birth weight and premature babies. Maternal weight monitoring was suggested to be conducted every 4 weeks to minimize the chance of having a low birth weight and premature baby