Various methodologies have been proposed in literatures to simulate pure steam filmwise/dropwise condensation and filmwise condensation in the presence of non-condensable gas (NCG). However, simulation methodology for dropwise condensation in the presence of NCG is rarely to be studied. In this paper, theories related to chemical gas-liquid absorption are referred, coupling with the widely used pure steam dropwise condensation model, a new methodology for heat transfer calculation of dropwise condensation in the presence of NCG is finally developed. After comparing experimental data from literatures with simulation results based on the proposed model, the new developed methodology gets validated. Heat transfer performance is found to be coordinately controlled by capacities of absorption mass transfer and surface condensation. Then, the effect of two practical easy to be controlled operation variables of Re number and sub-cooling degree on dropwise condensation process in the presence of NCG are investigated. Results indicate that sub-cooling degree is more sensitive than Re number, and the key to improve total heat flux is to accelerate the rate-determining step. Finally, 133° is found to be the optimal contact angle, under which the maximum heat flux could be achieved.

In this work, a process with no reflux rate (R) of distillate product in heterogeneous extractive distillation (HED) for the separation of close boiling compounds is proposed. The effects of pressure in HED and flowrate of solvent on controllability and economic performance are investigated. Close loop sensitivity tests show that an increase in flowrate of solvent can enhance the controllability but increases the annual total cost (TAC). Simulation shows that higher pressure in HED leads to lower flowrate ratio of solvent (EG) to feed. A lower pressure is preferred for economic index, but has worse controllability. There is trade-off between controllability and economic performance. The interaction between units is analyzed theoretically based on mass balance principle. The analysis can help further design of control structure. A basic control structure (CS1) based on modified alternative process with increased solvent flowrate is proposed first. Then an improved control structure (CS2) based on CS1 is proposed to reject the flowrate disturbance and address the interaction between units. Dual temperatures are applied in the recovery column (C2). The temperatures of two stages are controlled by the ratio of reflux rate to feed (R/F) and reboiler duty in C2, respectively. Pressure-compensated temperature control is applied to compensate temperature in the presence of flowrate disturbance. Dynamic responses show the improved control structure can handle +/- 10% feed flowrate and +/- 20% composition disturbances.

Waste heat recovery for wet flue gas desulfurization (WFGD) system is quite necessary so that both heat and water consumption can be saved. However, formerly, there existed no clear concept about the upper limit quantity of waste heat that can be recovered for a target WFGD system, and where the final operation status of WFGD system after waste heat recovered will be located is also absent. Therefore, in the current paper, a methodology is developed first to simulate the magnesium method desulfurization system with circulating water considered using Aspen Plus V8.4. After validation, the methodology with slight modification is then used to investigate the theoretical maximal quantity of waste heat that can be recovered under different conditions and study the corresponding variation tendencies of updated thermal and water equilibrium states. Desulfurization efficiency is also discussed qualitatively. Results indicate that there exist maximal 1.41 to 2.27 MW heat that can be recovered at WFGD system for an 80 t/hr coal-fired boiler, equivalent to save standard coal from about 1,385 to 2,230 t/a. All the streams temperature are reduced after recovering waste heat, but different streams behave different variation tendency. Water consumption and desulfurization efficiency also could get improved.

The crystal structure, thermodynamic phase diagram, and polymorphic transformation behaviors of CL-20 acetonitrile solvate are systematically investigated.

The solution-mediated polymorphic transformation (SMPT) of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) from form β to form ε was investigated in ethyl acetate-chloroform mixed solvent. The transformation process was revealed by using on-line tools including attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and in-situ Raman spectroscopy combined with off-line analysis of the solid phase using optical microscopy and powder X-ray diffraction (PXRD). Thermodynamic driving force of the SMPT process was evaluated through solubility determination of the two forms. The results demonstrate that the SMPT process consists of three stages, which are the dissolution of form β, the nucleation and the growth of form ε, and the rate-determining step is the nucleation and growth of form ε. The transformation experiments were also performed under different solvent compositions, solid loadings, percentages of seeds and particle sizes of seeds to give deeper insights into the SMPT process. Besides, the transformation kinetics were further investigated by Avrami-Erofeev model to access the effect of temperature on the SMPT process. This study enriches the research of SMPT mechanism for CL-20 and provides a good guidance for obtaining particles with superior crystal form purity.

In this work, the dissolution behaviors of a series of sodium alkylbenzenesulfonates (NaLAS) tablets with different moisture contents and neutralization degrees were investigated in aqueous solution. The ANOVA-based, model-independent and model-dependent methods were employed to perform comparison analyses on dissolution profiles. The measurements of powder X-ray diffraction patterns and mechanical properties elucidate distinct differences in each formula. The results show that ANOVA provides a possibility for finding the source of differences among different variables, and the model-independent methods including the k values and mean dissolution time are easy to interpret and perform comparison analyses. The Hixson–Crowell model gives satisfactory correlation results for the dissolution data and the dissolution kinetics parameters are obtained. The inhibition effects of neutralization degree and moisture content on NaLAS dissolution were examined, which reveals that the increase in lamellar phase proportion leads to the reduction of dissolution rate. The comparison analyses performed in this work form part of a methodology for dissolution profile prediction and comparison.

Various methodologies have been proposed in literature on modeling microwave drying process. However, in these methodologies moisture diffusion is normally considered in the presence of intensive microwave energy. In the present study, a new theoretical model was developed to simulate microwave drying of thin layer particulate solids, based on the consideration that moisture diffusion along material layer could be ignored due to rapid evaporation under intensive microwave energy. The model was solved numerically by using finite difference method and validated against experimental data. Results indicated good agreement between the model and experimental data, thus providing confidence in the modeling approach. For the system investigated in this study, it was demonstrated that an 80% reduction in drying time was achieved with approximately fivefold increase in microwave power (109–543W). Furthermore, it was also demonstrated that the drying rate was the maximum corresponding to the optimal layer thickness in microwave thin layer drying process. Qualitative analysis explained the optimal thickness phenomenon using principles of heat and mass transfer. Finally, the validated model was used to predict moisture and temperature distributions along the entire material layer.