Showing papers in "Journal of Chemical Engineering of Japan in 2014"

Thermal Stability of Oxygen-Containing Functional Groups on Activated Carbon Surfaces in a Thermal Oxidative Environment

Abstract: The thermal stability of oxygen-containing functional groups on activated carbon surfaces in a thermal oxidative environment was studied. The raw activated carbon (AC0) was rst treated with nitric acid, and the resulting nitric acid-treated activated carbon (ACn) was further oxidized under 2.5% O2 (in N2) atmosphere at di erent temperatures. The types and the amount of oxygen-containing functional groups were analyzed by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Boehm titration, and X-ray photoelectron spectroscopy (XPS). Both oxygenand nitrogen-containing functional groups were introduced onto the ACn surface. Under thermal oxidative conditions, hydroxyl was oxidized to the corresponding carboxyl group in the temperature range of 378–473 K, and epoxy groups and lactones were generated between 573 to 773 K via oxidation reactions between graphitized carbon and oxygen. In contrast, carboxyl decomposition occurred at around 573 K. Lactones, ketones, and quinones exhibited better thermal stability, undergoing decomposition between 773 to 973 K. Ether and epoxy groups exhibited the best thermal stability, decomposing only at temperatures above 973 K.

Present Status and Points of Discussion for Future Energy Systems in Japan from the Aspects of Technology Options

Abstract: Michihisa Koyama1,2, Seiichiro Kimura2, Yasunori Kikuchi2,3, Takao Nakagaki4 and Kenshi Itaoka2 1 Inamori Frontier Research Center, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka-shi, Fukuoka 819-0395, Japan 2 International Institute for Carbon-Neutral Energy Research, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka-shi, Fukuoka 819-0395, Japan 3 Presidential Endowed Chair for “Platinum Society,” e University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan 4 Department of Modern Mechanical Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan

Application of Taylor Vortex to Crystallization

Abstract: This study summarizes crystallization technology when using a Taylor vortex ow. A Taylor vortex is created in the gap between two co-axially positioned cylinders based on the rotation of the inner cylinder. Due to its unique periodic ow motion, a Taylor vortex has a signi cant in uence on the processes of nucleation, growth, and agglomeration breakage in various crystallizations, including reaction recrystallization, drowning-out crystallization, and cooling crystallization. In the gas–liquid reaction crystallization of calcium carbonate, the mass transfer at the gas–liquid interface is greatly facilitated by a Taylor vortex, resulting in small crystals with a uniform size and morphology. Further, due to molecular alignment by the periodic Taylor vortex motion, the polymorphic nucleation of stable crystals is also promoted. This e ect of molecular alignment by a Taylor vortex is demonstrated by the phase transformation of sulfamerazine. Furthermore, the Taylor vortex ow in a Taylor crystallizer improves the productivity of crystallization when compared with the random turbulent eddy ow in an MSMPR crystallizer. Consequently, the high performance of a Taylor crystallizer using a Taylor vortex has strong potential for application to various crystallizations.

Synthesis of an Optimizing Control Structure for Dual Mixed Refrigerant Process

Abstract: This study was aimed to investigate the best control structure that provides optimal operation for dual mixed refrigerant (DMR) process. The steady-state operational map that correlates the refrigerant flow rate and the total compressor duty was drawn to locate the region the optimal operation of DMR process. This map also encompasses information of state variables in DMR process that in particular combinations provide the optimum solution. The steady-state operational map of DMR process was developed by conducting steady-state behavior analysis in a rigorous dynamic simulation of DMR process built in Aspen Hysys. The resulting steady-state operational map suggests that when the flow rate ratio of the two mixed refrigerants (WMR/CMR ratio) is kept constant, the operational of DMR process will remain within optimum region. From several control tests, the control structure that consists of WMR/CMR ratio loop has better performance on recovering the process after propagated by disturbances

Stable Phase Equilibrium of Aqueous Quaternary System Li+, K+, Mg2+//Borate–H2O at 348 K

Abstract: The solubility values and physicochemical properties such as densities, refractive indices, and pH values of the equilibrium solution in the quaternary system Li+, K+, Mg2+//borate–H2O at 348 K were measured by isothermal dissolution method. The phase diagram, water content diagram, and the diagrams of the physicochemical properties versus composition were constructed using the measured data. Results show that this quaternary system at 348 K is of a simple type, no double salt or solid solution formed. The stable phase diagram of this quaternary system consists of one invariant point, three univariant curves, and three crystalline phase areas. The invariant point saturated with three salts corresponding to lithium tetraborate trihydrate (Li2B4O7·3H2O), potassium tetraborate tetrahydrate (K2B4O7·4H2O), and hungchaoite (MgB4O7·9H2O). The crystallization field of MgB4O7·9H2O is the maximum, meaning that the salt magnesium borate has the smallest solubility among the coexisting salts. Comparisons between the ...

Recovery and Enrichment of Phosphorus from the Nitric Acid Extract of Dephosphorization Slag

Abstract: A method for the recovery and enrichment of the phosphate from dephosphorization slag was examined. First, the elution of aqueous phosphate from dephosphorization slag using aqueous HNO3 was examined using both the batch and flow methods. With the batch method, 82% of the dephosphorization slag could be dissolved within 30 min using 1.0 mol/L HNO3, indicating that the batch method could be used for mass processing to extract phosphorus in the bulk phase, but all components contained in the slag were unselectively dissolved. In contrast, by using 0.05 mol/L HNO3 via the flow method, 22% of the slag was dissolved in 100 min giving a more selective dissolution of phosphate from the slag compared with the batch method, which indicated that this method would be incompatible with mass processing for the purpose of extracting phosphorus in the bulk phase. In order to remove the Fe-species in the aqueous solution obtained by the batch method using 1.0 mol/L HNO3, which has been referred to as the “slag solution,” it was necessary to add calcium hydroxyapatite (CaHAp) to the slag solution. The optimal conditions for the removal of Fe-species using CaHAp were observed at a solution pH of ca. 1.5, which resulted in 100% removal of the Fe-species after 4 h. When the pH of the slag solution was adjusted to 7.0 after removing the Fe species, a pale pink solid sample was precipitated. The amounts of phosphate in the slag solution and in the pink solid were 3.5 and 42.0 mol%, respectively, indicating that the treatment suggested in the present study could be used for the recovery and enrichment of phosphate, that is, phosphorous, from dephosphorization slag.

Modeling of Heat Transfer in Single Cell of Polymer Electrolyte Fuel Cell by Means of Temperature Data Measured by Thermograph

Abstract: The aim of this study is to construct a simple heat-transfer model to present the temperature of the interface between the polymer electrolyte membrane (PEM) and the catalyst layer at the cathode, i.e., the reaction surface, in a single cell of polymer electrolyte fuel cell (PEFC). The model is based on the temperature data of the separator measured by thermograph in a power-generation experiment. In addition, this study also aims to investigate the e ect of the operation condition on the temperature of the reaction surface using the heat-transfer model developed. The heat-transfer model is constructed by assuming multi plate heat transfer for components of a single cell of PEFC. In this model, the temperature of the reaction surface under the rib of separator and that under the gas channel of the separator are assumed to be the same. The result shows that the temperature of the reaction surface is higher with increasing gas channel pitch. The impact of the ow rate of the supply gas on the temperature of the reaction surface is small when O2 is used as the cathode supply gas. When air is used as the cathode supply gas, the temperature of the reaction surface is higher than that when O2 is used. The temperature of the reaction surface at the inlet is lower than that at the middle and outlet of the cell. This study can explain these temperature characteristics under several conditions by power-generation performance and energy conversion of the fuel cell.

Application of a drag reduction phenomenon caused by surfactant solutions

Abstract: In 1994, the first commercial application of su rfactant drag reduction was conducted in Japan for the air conditioning system in the Shunan Regional Industry Promotion Center building. A commercially available drag-reducing additive (LSP-01) based on the mixture of a cationic surfactant, a co unter ion, and corrosion inhibitors was developed based on the results of the project. Sinc e 1995, LSP-01 has been used at more than 180 sites in building air conditioning systems throughout Japan. The drag-reducing technique was adopted recently for an air condition ing system in a skyscraper in Tokyo. Here, I measured the drag reduction and heat transf er characteristics during the cooling operation of a heat exchanger for a surfactant and a counter ion system, Ethoquad O/12 and NaSal. The analogy between the momentum and hea t transfer for the drag-reducing flow is also discussed.

Novel Nickel Catalysts Based on Spinel-Type Mixed Oxides for Methane and Propane Steam Reforming (Special Issue for the International Symposium on Innovative Materials for Processes in Energy Systems 2013 (IMPRES2013))

Abstract: Novel nickel catalysts based on magnesium aluminate spinel-type mixed oxides are developed as hydrocarbon reforming catalysts for hydrogen supply to polymer electrolyte fuel cells. The spinel catalysts were prepared by co-precipitation and the Pechini method, and the spinels prepared by the former method exhibited higher activity for methane steam reforming. The e ect of spinel composition, Mg1−xNixAl2O4 (x=0.17, 0.35, 0.50, 0.70, 1) was investigated on the activity and resistance to carbon deposition in steam reforming reaction. The turnover frequency for methane steam reforming at a steam-to-carbon (S/C) ratio of 2 increased with increase in the x value from 0.17 to 0.35, and then gradually decreased with further increase in the nickel content. The carbon deposition tolerance of the spinel catalysts was examined in propane steam reforming at S/C=1 and 600°C. The propane conversion during the reaction was ca. 98% over all catalysts tested, and the amount of deposited carbon, determined as carbon dioxide by temperature programmed oxidation, was least at x=0.17, which is 1/8 of that deposited on a conventional Ni/γ-Al2O3 catalyst. The spinels with x≤0.5 exhibited smaller amounts of carbon deposition, and thus superior tolerance to deactivation.