Water Vapor In Flue Gas Research Articles

Study of SO2 oxidation over V2O5/activated carbon catalyst using in situ diffuse reflectance infrared Fourier transformation spectroscopy

The SO2 oxidation over V2O5/AC catalyst was studied using an in situ diffuse reflectance infrared Fourier transformation spectroscopy technique at 120 °C. Results reveal that the surface oxygen groups could neither act as active sites for SO2 oxidation nor supply the oxygen needed for VV↔VIV redox cycle. The vanadia species and gas phase oxygen are essential for SO2 oxidation. During SO2 oxidation over V2O5/AC, the surface hydroxyl groups involve in the formation of sulfate species. The role of water vapor in flue gas might be to supplement the hydroxyl groups consumed so that the SO2 oxidation could continue.

Efficiency and Flexibility Potential of Calcium Looping CO2 Capture

Abstract The Calcium Looping (CaL) is a proven technology for efficient post combustion CO2 capture from fossil fuel fired power plants. The technology is applied in Dual Fluidized Bed (DFB) systems and offers CO2 capture rates of 90% and above with low electric efficiency penalty. Early process feasibility studies for Calcium Looping were performed to identify the process potential by means of simplified process simulations based on assumptions and experimental data from lab scale. Now, existing experimental data from pilot scale investigations provide a substantial data base for reliable calculation of process efficiency and efficiency penalty for CO2 capture. Therefore the results of parametric investigations at pilot scale were incorporated into the simulations and new findings like the process improvement potential by natural flue gas water vapor considered. Moreover, the process simulation model was extended with a flue gas recycle for a more realistic process design and a CO2 capture model to predict CO2 capture efficiencies based on the operated process parameters. These novelties were used to identify optimum process operating points and further process optimization potential and process efficiency penalty calculated, considering expenditures for oxygen production by an air separation unit and CO2 compression for storage. The process simulation model is capable to be used as a design tool for process scale-up. Besides efficiency improvement, load flexibility is a major challenge for CCS plants of the future. In the second part of this publication, concepts to increase load flexibility of Calcium Looping CO2 capture systems are presented. For small size power plants up to 200 MWel or industrial CCS plants a turbulent carbonator design with a bottom link to the sorbent calciner represents an interesting option for highest plant flexibility. Both, a fast fluidized carbonator and a turbulent carbonator design was tested at IFK with high capture efficiency and flexibility in operation.

A parametric study of the impact of membrane materials and process operating conditions on carbon capture from humidified flue gas

Membranes are among a suite of technologies being considered for post-combustion carbon capture. Recent studies have shown the importance of process design in optimizing membrane system performance and setting guidelines for membrane materials development. In this study, the simulated performance of membranes based on a rubbery poly(ethylene oxide) block copolymer, a polyvinylamine/polyvinyl alcohol blend that shows facilitated CO2 transport, and a glassy thermally-rearranged polybenzimidazole is compared for a single-stage membrane operation treating humidified flue gas. Parametric studies were conducted to investigate the impact of different operating modes and conditions. For all cases, high membrane CO2 permeance minimizes membrane area requirements, while high CO2/N2 selectivity improves the CO2 purity and reduces the energy needed for CO2 purification. The benefits of higher selectivity are accentuated at higher feed-to-permeate pressure ratios, at the expense of increased energy cost. The advantages of higher permeance are most pronounced at a lower pressure ratio. The effects of water vapor in flue gas on CO2 capture with membranes can be complex depending on possible interactions of sorbed water with the membrane. From a process standpoint, a slight positive sweep effect is generated from the co-permeation of water vapor which increases the CO2 separation degree at a fixed membrane area.

Method for the control of NOx emissions in long-range space travel.

The wheat straw, an inedible biomass that can be continuously produced in a space vehicle has been used to produce activated carbon for effective control of NOx emissions from the incineration of wastes. The optimal carbonization temperature of wheat straw was found to be around 600 degrees C when a burnoff of 67% was observed. The BET surface area of the activated carbon produced from the wheat straw reached as high as 300 m2/g. The presence of oxygen in flue gas is essential for effective adsorption of NO by activated carbon. On the contrary, water vapor inhibits the adsorption efficiency of NO. Consequently, water vapor in flue gas should be removed by drying agents before adsorption to ensure high NO adsorption efficiency. All of the NO in the flue gas was removed for more than 2 h by the activated carbons when 10% oxygen was present and the ratio of carbon weight to the flue gas flow rate (W/F) was 30 g min/L, with a contact time of 10.2 s. All of NO was reduced to N2 by the activated carbon at 450 degrees C with a W/F ratio of 15 g min/L and a contact time of 5.1 s. Reduction of the adsorbed NO also regenerated the activated carbon, and the regenerated activated carbon exhibited an improved NO adsorption efficiency. However, the reduction of the adsorbed NO resulted in a loss of carbon which was determined to be about 0.99% of the activated carbon per cycle of regeneration. The sufficiency of the amount of wheat straw in providing the activated carbon based on a six-person crew, such as the mission planned for Mars, has been determined. This novel approach for the control of NOx emissions is sustainable in a closed system such as the case in space travel. It is simple to operate and is functional under microgravity environment.

The use of rice hulls for sustainable control of NOx emissions in deep space missions.

The use of the activated carbon produced from rice hulls to control NOx emissions for future deep space missions has been demonstrated. The optimal carbonization temperature range was found to be between 600 and 750 degrees C. A burnoff of 61.8% was found at 700 degrees C in pyrolysis and 750 degrees C in activation. The BET surface area of the activated carbon from rice hulls was determined to be 172 m2/g when prepared at 700 degrees C. The presence of oxygen in flue gas is essential for effective adsorption of NO by activated carbon. On the contrary, water vapor inhibits the adsorption efficiency of NO. Consequently, water vapor in flue gas should be removed by drying agents before adsorption to ensure high NO adsorption efficiency. All of the NO in the flue gas was removed for more than 1.5 h when 10% oxygen was present and the ratio of the carbon weight to the flue gas flow rate (W/F) was 15.4 g min/L. Reduction of the adsorbed NO to form N2 could be effectively accomplished under anaerobic conditions at 550 degrees C. The adsorption capacity of NO on the activated carbon was found to be 5.02 mg of NO/g of carbon. The loss of carbon mass was determined to be about 0.16% of the activated carbon per cycle of regeneration if the regeneration occurred when the NO in the flue gas after the carbon bed reached 4.8 ppm, the space maximum allowable concentration. The reduction of the adsorbed NO also regenerated the activated carbon, and the regenerated activated carbon exhibited an improved NO adsorption efficiency.