Development of High Gravity Process for Integrating Carbon Capture and Utilization with Flue Gas Purification

This study was focused on the development of an innovative integrated high gravity (HiGee) system to deal with carbon capture, air pollution control coupled with alkaline waste treatment. Byproduct lime originated from burnt petroleum coke of circular fluidized bed was used as the reacting agent for carbonation. The research objectives included (1) to investigate the carbonation behavior in rotating packed bed (RPB); (2).to examine the effect of operating conditions on carbonation behavior in RPB; (3) to study the conjunction effect of RPB on air pollution control; (4) to inspect the alteration of properties of cement induced by the introduction of byproduct lime; (5) to comprehensively evaluate the process from the perspective of environmental, economic and engineering aspects. • To investigate the carbonation behavior in RPB The concentration of calcium in slurry and carbonation conversion of byproduct lime was examined by Inductively Coupled Plasma (ICP-OES) and thermal gravimetric analysis (TGA) respectively. The correlation between carbon conversion and time was interpreted and predicted by surface coverage model (SCM). On the hand, a Streeter-Phelps equation liked formula was developed and introduced to describe the variation of calcium concentration in slurry, which has achieved good agreement. From the results of modeling, it was found blowdown wastewater was not favorable for carbonation because the precipitation may be inhibited so that the captured carbon dioxide could not be attached into solid matrix permanently. • To examine the effect of operating conditions on carbonation behavior in RPB Rotating speed, solid-liquid ratio and temperature were chosen to examine the influence on carbonation performance. The results indicated that temperature and rotating speed could exert significant influence on carbonation in tap water. In addition, the effect of solid to liquid ratio was more remarkable for carbonation in blowdown wastewater. • To study the conjunction effect of RPB on air pollution control According to the results of on-site operation in real plant, it was proved that the HiGCarb process is effective and efficient for carbon capture and air pollutant removal. Specifically, the highest removal efficiency could reach up to 95.59%, while the maximum daily capture capacity was nearly 600 kg-CO2/day. With the help of ozone, nitric oxide was successfully oxidized as well as absorbed successfully by slurry. In addition, due to the congenital complex packing structure, the particulate matter in flue gas could be efficiently filtrated and collected. After the installation of HiGCarb system, more than 8000 USD of air pollution penalty could be conserved each year. • To inspect the alteration of properties of cement induced by the introduction of byproduct lime Carbonation is able to transform calcium oxide into calcium carbonate. During this research, both fresh and carbonated byproduct lime was introduced into clinker for substitution. According to the results, with substitution ratio going up, the content of silica decreased which is not favorable for cement deployment. However, calcium carbonate was found to be able to accelerate hydration reaction, resulting in more remarkable strength compared with other specimens at the same curing age. Finally, the substitution ratio at 5% was favorable for both economic benefit and engineering performance. • To comprehensively evaluate the process from the perspective of environmental, economic and engineering aspects In order to evaluate the positive effects and negative impacts from HiGCarb process, 3E analysis was performed. It was found that the introduction of HiGCarb process could drastically reduce negative impact to environment, especially global warming potential and toxicity to ecosystem. With gas flow rate going up, the capture capacity increased, and the process would become more energy efficient. Such phenomenon would be beneficial to economic and environmental aspects. Because at higher gas flow rates, less energy would be consumed for capturing one unit of carbon dioxide, which means less pollutant would be generated. According to the results of graphical solution, the highest achievable amount of daily capture capacity is nearly 600 kg-CO2/day. That could be reached at the acceleration of 63 m/s2, corresponding to the energy consumption of 15 kWh/t-CO2. In addition, the economic benefit is also incredible. It is estimated that around 40 USD could be earned by treating one ton of byproduct lime. Finally, the best scenario is determined where the gas flow rate is 1.84 m3/min and rotating speed is 550 rpm.