Kinetics of carbon dioxide absorption in aqueous blend of 1-(2-aminoethyl) piperazine using a stirred cell reactor.

Carbon capture utilization and storage (CCUS), the technology for decarbonizing carbon dioxide (CO2) from greenhouse gas emitters such as steel, cement, oil, gas, petrochemicals, chemicals, and fertilizers, has a critical role to play in the world to achieve industrial net zero targets by 2050. CO2 can be separated from industrial exhaust gases/flue gases using amine-based solvents utilizing the post-combustion CO2 Capture process. One most crucial solvent characterization for this application is the kinetics of CO2 absorption. This work identifies aqueous 1-(2-aminoethyl) piperazine (AEPZ) as a potential candidate for CO2 capture solvent. The kinetics of absorption of CO2 in aqueous AEPZ is studied using stirred cell reactor. The experiments are performed at temperatures ranging from 303 to 333 K with weight fractions of AEPZ in an aqueous solution ranging from 0.1 to 0.4. One of the critical parameters of the kinetic study is Henry's constant which is determined experimentally using another stirred cell reactor at a similar temperature and pressure range. The experimental data shows that the overall rate constant is Kov = 2.52987 × 10-4 mol/m2s-kPa for 0.1 wt fr. of AEPZ at 313 K with an initial CO2 partial pressure of 10 kPa. The temperature dependency relation of the second-order reaction rate constant, [Formula: see text] is found to be [Formula: see text] using the Arrhenius equation. The activation energy of 0.3 wt fr. AEPZ is found to be 42.42 kJ/mol. In addition, the density and viscosity of the aqueous solvent are determined at a wide range of temperatures. The diffusivity of CO2 and physical solubility used in the model development has also been determined. The kinetic parameters obtained from this study are helpful in the process design of CO2 capture in a regenerative process with a blended solvent with AEPZ.

Experimental and Computational Investigation upon Combustion Characteristics of Liquid Fuel in a Novel Combustor with Hybrid Swirl and Recirculation Bowl.

In the present study, a novel hybrid swirl combustor is designed to reduce the size and complexity of a conventional gas turbine combustor. In this combustor, a dual-swirl pattern is adopted by providing the central vane swirler (45° vane angle) and circumferential tangential injection scheme to achieve higher recirculation of heat and combustion products inside the combustor. Numerical and experimental studies are carried out to understand the flow patterns and combustion characteristics in this high mass-heat interacting environment. Initially, computational studies were carried out to find the optimum geometry for greater recirculation and interaction among the reacting species inside the combustor. Liquid fuel (kerosene) is sprayed into the combustor for two thermal inputs of 25 and 50 kW. Three cases were studied to analyze the effect of bowl recirculation and tangential air inputs in addition to the swirlers. The hybrid swirl, formed by the counter-flow pattern, helps in achieving low and uniform temperature throughout and assists in flame anchoring. The tangential air flow provides a push to the combustion products from the downstream to the central recirculation zone of the combustor. The combined effect of central and tangential swirlers helps in attaining a more distributed combustion. The CO and NO emissions reduced with the use of hybrid swirl.

Water footprint comparison of a naphtha-fired combined cycle power plant and a coal-fired steam power plant.

The vulnerability of the power generation industries vulnerability to the availability of water is widespread and growing. In this regard, water footprint (WF) is one method to assess this challenge. The present study conducts the WF of a naphtha-fired combined cycle power plant (CCPP) and a coal-fired steam power plant (CSPP). For carrying out WF, it is prudent to look after water consumption during operations and the supply chain stages. Hence, in this regard, two methods have been adopted to investigate the WF of both power plants. The first method deals with the water balance mass diagram (direct WF), and the second method deals with the water supply chain (indirect WF). Evaporation loss appears to be a significant contributing factor to the direct WF. On the other hand, operational WF seems to be an essential contributing factor to indirect WF. Furthermore, the result also shows that specific water consumption in CSPP is 3.54 m3/h, whereas, in CCPP, it is 0.9 m3/h. Finally, some methods have also been suggested to reduce WF in both power plants.

Performance evaluation of a green process for microalgal CO2 sequestration in closed photobioreactor using flue gas generated in-situ.

In the present study, carbon-dioxide capture from in situ generated flue gas was carried out using Chlorella sp. in bubble column photobioreactors to develop a cost effective process for concomitant carbon sequestration and biomass production. Firstly, a comparative analysis of CO2 sequestration with varying concentrations of CO2 in air-CO2 and air-flue gas mixtures was performed. Chlorella sp. was found to be tolerant to 5% CO2 concentration. Subsequently, inhibitory effect of pure flue gas was minimized using various strategies like use of high initial cell density and photobioreactors in series. The final biofixation efficiency was improved by 54% using the adopted strategies. Further, sequestered microalgal biomass was analyzed for various biochemical constituents for their use in food, feed or biofuel applications.