Fluid flow patterns with a gel reaction in a circular flow pipe are investigated experimentally. Solutions of 10 mass% polyvinyl alcohol (PVA) and 3 mass% borax are used as the working fluids. The flow channel consists of a transparent main flow pipe and a transparent branch flow pipe that is connected vertically to the main flow pipe. The solution of 10 mass% PVA flows in the main flow pipe under steady-state conditions. The Reynolds number (Rem) based on the mean velocity and the diameter of the main flow pipe is less than 30. The borax solution is colored with blue dye to visualize the flow patterns and is injected once only from the branch flow pipe. The experimental results show three distinct flow patterns, namely, capsule, capsule+stretched, and capsule+stretched+fingering flow. Rem and the ratio of the volume flow rate (β) are used to predict quantitatively the flow patterns with gel reaction. The results show that, in the region in which β is less than unity, capsule flow forms and β is the governing parameter. In the region in which β is greater than unity, Rem is dominant for determining the flow pattern with gel reaction.
Neutralization reaction crystallization is useful for manufacturing drugs that require high bioavailability (i.e., high solubility). Because drug crystals must be of high quality, with the optimal form and particle size, the development of procedures that can produce high quality crystals by reaction crystallization is important. In cooling crystallization, analysis of the supersaturation profile (SSP) is an effective way to improve the crystal quality. SSP analysis is also important in reaction crystallization. However, the changes in the operation parameters (e.g., pH) necessary for crystallization strongly depend on the deposition of the crystals. Thus, solution pH also changes with deposition of the crystals. The purpose of this study is to propose an optimal crystallization point for the improvement of crystal quality through SSP analysis in reaction crystallization. The experimental system involved the reaction of hydrochloric acid and L-arginine to crystallize L-arginine hydrochloride monohydrate. The SSP was computed using HPLC and a pH meter. The relationship among the amount of feed added, crystal size distribution (CSD), and the crystal morphology was investigated through SSP analysis. Control of minute crystals was found to be crucial for CSD improvement. Moreover, operation at a neutral pH and the use of seed crystals were found to effectively inhibit the formation of minute crystals. Furthermore, operation at basic pH effectively produced good crystal morphology. Finally, using these results to modulate the addition technique in the reaction crystallization process, quality crystals with the desired CSD and morphology have been produced.
We prepared Ni nanoparticle-deposited silica (SiO2) microspheres using a method based on the collision of Ni nanoparticles, which were generated by hydrogen reduction of NiCl2, with SiO2 microspheres. SiO2 microspheres were heated in a gas-phase reactor to a temperature sufficiently high to soften their surfaces. Notably, when SiO2 microspheres were heated to temperatures higher than 973 K before collision with Ni nanoparticles, the nanoparticles showed no signs of sintering on the SiO2 microsphere surfaces during heat treatment at a high temperature of 1,073 K. In addition, we independently controlled the diameter and content of Ni nanoparticles on the SiO2 microspheres by changing NiCl2 evaporation temperature and NiCl2-carrier gas flow rate.
Three kinds of coal with different ranks and sulfur contents were extracted using 1-methyl naphthalene at 350°C. The sample coals were fractionated into three fractions: a solvent-soluble fraction, a deposited fraction from the solvent-soluble fraction at room temperature, and the solvent-insoluble fraction. The forms of sulfur in the raw coals and the extracted products were determined by X-ray adsorption near edge structure analysis. Most of the inorganic sulfur was transferred to the solvent-insoluble fraction and the organic sulfur was distributed among the three fractions. Interestingly, the solvent-soluble fraction contained organic sulfur without inorganic sulfur, and only thiophenic sulfur was detected independent of coal type. Because of the high selectivity of imidazolium type ionic liquid for thiophenic sulfur, dimethyl imidazolium methyl sulfate was applied to extract the sulfur contained in the solvent-soluble fraction. The extractive experiment using ionic liquid showed that the sulfur content decreased linearly with the number of extraction stages. A high extent of desulfurization was obtained with a high concentration of ionic liquid.
The quasi-steady state heat and mass transfer around a single coal char particle with and without CO oxidation was numerically analyzed to investigate the effect of CO oxidation on the reaction process of char. With CO oxidation, the gas temperature around the particle is increased by the exothermic heat of CO oxidation, and the particle itself also experiences a temperature increase due to the heat transfer between high-temperature gas and the particle. In addition, the generation of additional CO2 by CO oxidation promotes the CO2 gasification of char, whereas the consumption of O2 suppresses the char oxidation. As a result of balancing among these factors, the net reaction rate of char, which is the sum of the partial oxidation rate and CO2 gasification rate, with CO oxidation became larger than that without CO oxidation. Under conditions of a higher temperature and larger particle size, the net reaction rate with CO oxidation was larger than that without CO oxidation, though the partial oxidation rate with CO oxidation was smaller than that without CO oxidation because of the promoted consumption of O2 by CO oxidation. This result indicates that CO2 gasification compensates for the decrease in the net reaction rate due to the suppression of char oxidation. Therefore, CO oxidation should greatly affect the heterogeneous reaction rates of char, especially CO2 gasification, through changes in the temperature and compositions of the gas-phase near a coal char particle.
CO2 separation using an amine, in particular monoethanolaimne (MEA), is widely used in the carbon capture and storage (CCS) applications. Despite its technical and economic merits, new amines and improved systems, such as small-size processes that consume less utilities, must be developed to reduce capital and operating costs. Therefore, we aim to i) investigate the technical feasibility of new CO2 separation processes using different amines, focusing on piperazine-mixed amines, and ii) comparatively analyze its economic competitiveness against conventional systems. In achieving this goal, we first perform process modeling and simulation for CO2 separation processes using nine different amines: three single amines (MEA, diethanolamine and methyldiethanolamine) and six mixed amines by mixing the single amines with different amounts of piperazine. Using process models, we then estimate capital and operating costs of the processes, and comparatively analyze the economics of the processes based on the CO2 processing cost. We also discuss the sensitivity of major parameters to the process economics with various technical and market scenarios.
This paper proposes a novel reactor–separator network in the Bunsen process for high hydrogen production thermal efficiency. Six case studies were conducted to investigate the effect of reactants on the Bunsen reaction. The key classification of the case studies was the location of the SO2–O2 stream to avoid oxygen contact in the Bunsen reaction and the use of an HIX purifier instead of the SO2 absorber to reduce iodine. The thermal efficiency in the best case was 48.91%. The main criteria for high efficiency were low iodine flow, high HI flow, and higher amount of SO2 recycling to avoid hindrance and maintain low iodine flow.
Since methanol is an attractive fuel and chemical for various applications, its demand will continue to increase. To satisfy this increased demand, new methanol synthesis plants have been built in Asian, Middle Eastern, and South American countries. Self-heat recuperation and a pressure swing system were recently developed as an energy-saving process design, in which overall-process internal energy caused by condition changes is recirculated within the process without the need for heat addition. In this study, the feasibility of applying self-heat recuperation technology and a pressure swing system to the industrial methanol synthesis process which possesses both temperature and pressure changes was investigated from energy-saving and process design points of view, based on actual plant data. Based on simulation results, it was concluded that the use of self-heat recuperation technology and pressure swing system is an attractive alternative for sustainable future development of the methanol synthesis process.
The present study investigates microwave irradiation to develop the recycling technology of any kind of plastic waste containing organic chlorine, dechlorination. Polyvinyl chloride (PVC) was used as a typical organic chlorine. Under constant sample temperature, the PVC dechlorination properties were compared between microwave irradiation and conventional heating. It was clarified that microwave irradiation induced much faster dechlorination than conventional heating. It was also found that the dechlorination reaction by microwave irradiation progressed at a lower temperature than that by convention heating. Moreover, the efficiency of dechlorination, defined as the ratio of dechlorination to total weight loss, using microwave irradiation was higher than that by conventional heating. This result shows the possibility of selective dechlorination by using microwave irradiation.
The interactions between cesium ions and two kinds of 2 : 1 clay minerals (kaolin and vermiculite) were investigated under batch conditions and dynamic equilibrium using the electrokinetic (EK) process. The adsorption capacities of kaolin and vermiculite were 1.2 and 18.8 mg/g, respectively, at pH 6 after 24 h in the batch system. Because the basal spacing of kaolin is 0.93 nm, Cs+ ions cannot enter the interlayers. On the other hand, the basal spacing of vermiculite is 1.01 nm, and vermiculite can adsorb Cs+ ions in the interlayers. Four kinds of model soils with different ratios of vermiculite to kaolin were prepared by mixing these two types of clay minerals, and the migration behaviors of Cs+ ions in these soils on the application of the EK process were determined. The Cs+ ion migration efficiency decreased with an increase in vermiculite content. The content of vermiculite in the soil was an important factor determining the migration behavior of Cs+ ions under the dynamic equilibrium conditions produced by the EK process. The applications and limitations of the EK process for the removal of cesium from contaminated soil are discussed.