Yeo Il Yoon

A kinetic study on medium temperature desulfurization using a natural manganese ore

Abstract Natural manganese ores were selected as raw materials for the desulfurization sorbent because of economical efficiency and high reactivity on hydrogen sulfide. Initial reaction rates between H 2 S and desulfurization sorbent of natural manganese ores were determined in a temperature range of 400–800°C using a thermobalance reactor. All reactions were first order with respect to H 2 S and were expressed by the Arrhenius relation. When the sulfidation reaction was controlled by diffusion, the temperature dependence of the effective diffusivity was given by the Arrhenius equation. Activation energies and frequency factors were obtained from the product layer diffusion coefficient of various sorbents by plotting as an Arrhenius equation form. Several additives were mixed to improve the sulfidation capacity, and NiO was the best additive.

CO2 absorption characteristics of a piperazine derivative with primary, secondary, and tertiary amino groups

Thermodynamic and kinetic data are important for designing a CO2 absorption process using aqueous amine solutions. A piperazine derivative, 1-(2-aminoethyl)piperazine (AEP), was blended with aqueous amine solutions due to its thermal degradation stability, high CO2 loading (mole of CO2-absorbed per mole of amine) and high solubility in water. In this study, the vapor liquid equilibrium (VLE), absorption rate, and species distribution of aqueous AEP solutions were studied to develop an optimum amine solution in a post-combustion capture process. The VLE and apparent absorption rate of the aqueous 30wt% AEP solution were measured using a batch-type reactor at 313.15, 333.15, and 353.15 K. The AEP exhibited approximately twice higher CO2 loading compared with monoethanolamine (MEA) at all temperatures. The apparent AEP absorption rate (kapp=0.1 min−1) was similar to that of diethanolamine (DEA) at 333.15 K. Speciation of the CO2-absorbed AEP was analyzed using 13C NMR. Although AEP featured a primary amino group and secondary amino group, it did not form bicarbamate upon reaction with CO2 based on analysis results. AEP-1-carbamate was primarily formed by reactions between AEP and CO2 during the initial reaction. Bicarbonate species formed as the quantity of absorbed CO2 increased.

CO2 capture using aqueous solutions of K2CO3+2-methylpiperazine and monoethanolamine: Specific heat capacity and heat of absorption

The specific heat capacity, heat of CCO2 absorption, and CCO2 absorption capacity of aqueous solutions of potassium carbonate (K2CO3)+2-methylpiperazine (2-MPZ) and monoethanolamine (MEA) were measured over various temperatures. An aqueous solution of K2CO3+2-MPZ is a promising absorbent for CCO2 capture because it has high CCO2 absorption capacity with improved absorption rate and degradation stability. Aqueous solution of MEA was used as a reference absorbent for comprison of the thermodynamic characteristics. Specific heat capacity was measured using a differential scanning calorimeter (DSC), and heat of CCO2 absorption and CCO2 absorption capacity were measured using a differential reaction calorimeter (DRC). The CCO2-loaded solutions had lower specific heat capacities than those of fresh solutions. Aqueous solutions of K2CO3+2-MPZ had lower specific heat capacity than those of MEA over the temperature ranges of 303-353 K. Under the typical operating conditions for the process (CCO2 loading=0.23mol-CCO2·mol−1-solute in fresh solution, T=313 K), the heat of absorption (−ΔHabs) of aqueous solutions of K2CO3+2-MPZ and MEA were approximately 49 and 75 kJ·mol-CO2, respectively. The thermodynamic data from this study can be used to design a process for CCO2 capture.

CO2 absorption, density, viscosity and vapor pressure of aqueous potassium carbonate+2-methylpiperazine

The physical properties of the absorbent are important for designing a CO2 capture process. The density and viscosity are used to calculate the mass transfer coefficient that determines the height of the absorber. Furthermore, these physical data affect the selection of liquid pump and pipe lines. Vapor pressure is a factor that estimates absorbent loss and condenser size. In this study, the physical properties of the aqueous potassium carbonate (K2CO3)+2-methylpiperazine (2MPZ) solution were obtained in a temperature range from 303.15 K to 343.15 K. The physical properties of the different aqueous K2CO3+2MPZ solutions (various amine concentrations and amounts of CO2 absorbed) were measured to obtain the parameters for process design. A regression analysis was conducted for the experimental data. The densities of the aqueous K2CO3+2MPZ solutions increased when the amounts of absorbed CO2 or 2MPZ concentrations were increased. The densities and viscosities of the absorbents decreased according to the increase in temperature. The viscosities of the absorbent increased when 2MPZ concentrations were increased. The temperature dependency of vapor pressure follows the Antoine equation; the CO2 gas and aqueous solution of a base follows the vapor pressure variation of the mixed solution.

Electrocatalytic Stability of Tin Cathode for Electroreduction of CO2 to Formate in Aqueous Solution

The electrocatalytic stability of tin (Sn) nanoparticle for electrochemical reduction of CO2 to formate was measured using an H-type cell during electrolysis for 40 h. The Faradaic efficiency (FE) and partial current density (PCD) of formate formation reduced as much as 10% and 13% of the maximum values, respectively. To elucidate the decrease in FE and PCD, the changes in the morphology, chemical composition, the crystalline structure were investigated. The spherical Sn nanoparticles were pulverized after electrolysis. Furthermore, the crystal structure of the fresh Sn electrocatalyst was collapsed and changed into amorphous phase after 40 h electrolysis. The decrease in FE and PCD of formate production on the Sn/CFP electrode could be mainly originated from the reduction of the SnOx to Sn on the cathode surface during electrolysis.

Post-combustion CO 2 capture with potassium L-lysine

Carbon dioxide is one of the main causes of global warming. In order to develop a novel absorbent, the characteristics of amino acid salts solution as a solvent for capture in continuous process were investigated. The cost of capture is almost 70% of total cost of CCS (carbon dioxide capture and storage). In the carbon dioxide capture process, process maintenance costs consist of the absorbent including the absorption, regeneration, degradation, and etc. It is very important to study the characteristics of absorbent in continuous process. In this study, we have investigated the properties of potassium L-lysine (PL) for getting scale-up factors in continuous process. To obtain optimum condition for removal efficiency of in continuous process by varying liquid-gas (L/G) ratio, concentration of and absorbent (PL) were tested. The stable condition of absorber and regenerator (L/G) ratio is 3.5. In addition, PL system reveals the highest removal efficiency of with 3.5 of L/G and 10.5 vol% ().