Chao-Hong He

Tracer diffusion coefficients of solutes in supercritical solvents

Abstract Based on the free-volume-type diffusion model, new correlations are developed to estimate the tracer diffusion coefficients of liquid and solid solutes in supercritical solvents. The correlations are tested to predict various solute–solvent systems with good results. The input data required for the correlations are the solute molecular weight, temperature, density and the solvent basic properties (molecular weight, critical temperature, critical volume and critical pressure).

IMPROVE SAFETY OF INDUSTRIAL PROCESSES USING DYNAMIC OPERATOR TRAINING SIMULATORS

With the increasing complexities and integration of chemical processes, ensuring safety is becoming more difficult and expensive for new and/or modified plants. This inevitably increases the risks of unacceptable environmental impact as well as cost of operation. This is especially true where there is no existing plant to train operators. It is now possible to use design information to build a dynamic operator training simulator (DOTS) which can be used to explore start-up, shutdown and emergency operations procedures, to experience various operations and to evaluate safety. This approach has proved very successful in achieving safe operation of a new MTBE process. The paper reports the experience of developing DOTS and using it to ensure safe operation.

Automatic verification of safety interlock systems for industrial processes

Abstract The safety interlock system (SIS) is one of the most important protective measurements in industrial processes that provide automatic actions to correct an abnormal plant event. This paper considers the use of formal techniques based on symbolic model checking and computation tree logic (CTL) in the specification to automatically verify the SIS for industrial processes. It addresses the problem of modelling industrial processes and presenting the SIS in CTL. It shows how symbolic model checking can be used efficiently in the verification of a SIS. A transferring system for a penicillin process is used as a case study.

Calculation of solid's solubilities in mixed liquid solvents by the λh equation using mixing rules

Abstract Based on the proposed mixing rules for λ and h, the λh equation was extended to calculate the solubilities of solids in mixed liquid solvents. The correlation results for 89 pairs of binary solvent systems and 4 pairs of quaternary solvent systems showed that the extended equation had good agreement with experimental data. Furthermore, a prediction method was given with no parameter adjustment, which was suitable for nonalcohol-solvent systems.

Infinite-dilution diffusion coefficients in supercritical and high-temperature liquid solvents

Abstract A predictive equation, based on the Stokes–Einstein equation, was developed for the determination of infinite-dilution molecular diffusion coefficients in supercritical and high-temperature liquid solvents ( T r ≥0.7). An extensive database on diffusion was collected through the literature in order to evaluate the proposed equation and to determine the accuracy of the predictions with no additional parameter adjustment. The predictions were good, with an average absolute deviation 8.2% for 113 binary systems and 1332 data points. The input data required for the correlations are the solute molecular weight, temperature and density, and the solvent basic properties (molecular weight, critical temperature and critical volume).

Conceptual design of pressure relief systems

Abstract Conceptual design of pressure relief systems is an important stage in the design of a safe process plant. The conceptual design stage consists of the following steps: deciding on the location of pressure relief devices, selecting the general type of pressure relief device for each identified location, i.e. safety valve and/or bursting disc (rupture disc), or other relief device, and selecting the special features for the chosen device type. Some regulations, codes and standards, and a decision tree for the selection of a relief device have been described in the literature. This paper presents four decision trees that have been developed for the different steps in the conceptual design stage. Only positive pressure in pressure vessels is considered here.

Axial dispersion coefficient in high-speed counter-current chromatography.

Experimental measurements of axial dispersion coefficients in high-speed counter-current chromatography have been carried out in the single-phase and two-phase modes. Axial dispersion coefficients were calculated from the residence time distribution curve (or the elution profile). The experimental data obtained were used to develop a model involving Peclet number Pe, Reynolds number and the ratio of flow velocity u to linear angular velocity u(theta) for predicting the axial dispersion coefficient. Furthermore, the models obtained from the single-phase and two-phase modes were compared, and a counterintuitive phenomenon was found in that the effects of the flow rate and the rotation speed on the axial dispersion coefficients are inconsistent: the axial dispersion coefficient decreases with the rotation speed and increases with the flow rate in the single-phase mode, but increases with rotation speed and decreases slightly with the flow rate in the two-phase mode.

Application of alkoxide in catalytic transfer hydrogenation of unsaturated nitrogen compounds

Alcoholate was utilized in catalytic transfer hydrogenation of unsaturated nitrogen compounds. In the reduction of nitro compounds, oximes and imines, alkoxide was used as the promoter, with alcohol as the hydrogen source, while in the reduction of nitriles, alkoxide was used as the hydrogen source.

Synthesis of 1H-indazole: a combination of experimental and theoretical studies

A new practical synthesis of 1H-indazole is presented. A previous mechanism for the cyclization step is proved to be nonfeasible and a hydrogen bond propelled mechanism is proposed. The new mechanism is suitable for similar cyclization, and a new reaction is predicted.