Shiao-Hung Chiang

Hydrogen solubility in coal liquid (SRC-II)

Abstract Experimental results are presented for hydrogen solubility in hydrogenated coal liquid (SRC-II) and coal-liquid partial pressure in the hydrogen-coal-liquid system, over temperature and pressure ranges of 420–680 K and 4–11 MPa. Two in situ hydrogen probes were used to determine the hydrogen partial pressure in the system. No coking was observed at these temperature levels. The results are in good agreement with hydrogen solubility data for similar hydrogen-bearing systems reported in the literature. The hydrogen solubility exhibits an inversion with increasing temperature at constant total pressure, which can be interpreted in terms of the strong dependence of the coal-liquid partial pressure on temperature.

DETERMINATION OF THE FRACTAL DIMENSIONS OF COAL FILTER CAKES AND THEIR RELATIONSHIP TO CAKE PERMEABILITY

ABSTRACT The permeabilities of various fine coal filter cakes were related to cake microstructure through micrographically measured fractal dimensions. Two other porous systems, consolidated glass beads and CaCO3 crystal filter cake, were also analyzed for comparison. A variety of coal mesh sizes were examined spanning a reasonable range of permeability The fractal dimension was determined using the dilation function of the image analyzer. This fractal dimension was then related to the Kozeny parameter, K″, using experimentally measured porosity and permeability, and micrographically measured specific surface. Finally, with K″ as a unique function of fractal dimension, permeabilities were estimated using the Carman-Kozeny equation. Calculated values were in good agreement with experimentally determined values considering the simplicity and direct nature of the approach.

Diffusion model for simultaneous mass and heat transfer in partially miscible liquid systems: experimental findings and numerical simulation

Abstract A coupled diffusion model has been numerically solved to obtain temperature profiles when two partially miscible liquids are contacted at a planar interface. The proposed model includes the presence of a heat source at the interface due to the heat of solution which is considered to have a non-linear relationship with concentration. As a result, a system of four partial differential equations is obtained which is numerically solved with the DISPL software package. This DISPL package solves systems of PDEs by means of a Galerkin procedure. This procedure reduces these PDE systems to ODEs which are, in turn, solved by a multistep stiff ODE solver. The basis of the method of solution involves defining new variables to transform the domain so that the interface conditions can be treated as boundary conditions. The temperature difference predictions calculated with this model were compared to experimental data obtained for eight partially miscible liquid systems. The agreement proved to be remarkable in some instances and only qualitatively adequate in others. Further improvements in the predictions would be expected if a microconvection mechanism close to the interface and heat losses were incorporated into the model.

Tetralin vapour pressure at elevated temperatures

Abstract Vapour pressure of tetralin was measured at elevated temperatures up to 661 K. The experimental vapour pressure data obtained from this work and the literature have been correlated by multiple regression resulting in the equation: log P = −2549 T−1.022 × 10 −3 T + 7.804 . This equation can be used to predict tetralin vapour pressure between the normal boiling point and the critical point with maximum error of ≈3%.

LICADO Process for Fine Coal Cleaning – Mechanism

Abstract The mechanism of the LICADO process has been investigated in terms of the surface and interfacial properties of gaseous CO2, liquid CO2, and water in contact with feed coal, clean coal products, and refuse materials. Contact angles of water on the coal surface measured utilizing two different drop-deposition techniques were used to simulate the wetting characteristics of coal in the LICADO process under various mixing conditions. The clean coal particles show a strong hydrophobic behavior which results in their agglomeration and transfer to the liquid CO2 phase while the refuse particles, being more hydrophilic, remain in the water phase. The results also showed that an optimum mixing speed is necessary in order to provide enough shearing force to expose the clean coal particles to the CO2 droplets. The CO2 adsorption on coal surfaces at pressures up to 6.2 MPa and the Dubinin-Polanyi coal surface area measurements indicate that the clean coal samples have higher adsorption isotherms and larger s...

Use of image intensification for mass transfer studies in liquid-liquid systems☆

Abstract An experimental method based on electro-optical image intensification of radiotracer compounds coupled with low-light-level photography was developed for concentration measurements of an organic solute in an aqueous phase. Experimental concentration profiles as a function of time were obtained in the aqueous phase of the water/ethyl acetate and water/isobutanol partially miscible systems. The results obtained for both liquid systems suggest the presence of interfacial activity and microconvection in the region close to the interface. In addition, the relationship between the solute concentration in the aqueous phase and the time elapsed since the contacting of the phases showed an oscillatory behavior with a period of 50–60 min.

Hydrogen solubility of hydrogen-methane-tetralin and hydrogen-ethane-tetralin systems at elevated temperatures and pressures

Abstract Expanding on previous studies on hydrogen solubility in model coal liquids and coal liquids, this work concentrates on the solubility of hydrogen in the presence of the light hydrocarbons methane and ethane that are often produced in coal liquefaction operations. Pressures and temperatures to 7 MPa and 700 K were explored using a hydrogen meter which relied on the permeation of hydrogen through thin nickel tubing. Operation of the meter was made automatic by sensing elements with electrical outputs coupled to a computer for control. The presence of methane and ethane in the system affected the solubility of hydrogen in tetralin. At a constant temperature and hydrogen partial pressure the solubility of hydrogen in tetralin first increased, as the methane and ethane partial pressures increased, and then decreased. The hydrogen solubility also increased with the system temperature and pressure.

HEAT TRANSFER IN PARTIALLY MISCIBLE TERNARY SYSTEMS

In the study of mass transfer between partially miscible liquids, temperature perturbations have been found to have an important effect in the generation of interfacial activity. Micro- and macro-generated interfacial convection usually occurs in combination with one another even in fairly simple heat or mass transfer events. These combinations are responsible for the enhancement of mass transfer rates. In an effort to acquire a better understanding of the heat transfer effects in ternary liquid-liquid systems, temperature difference profiles were measured when contacting two partially miscible phases. A vertical and a rotational transfer cell were designed to contact the partially miscible phases without inducing external disturbances. Five thermocouples were immersed in the bottom liquid phase at predetermined positions below the interface. In order to understand the influence of the convection generated, the vertical cell was designed to hinder convection in one phase, while the rotational cell permits...

TEMPERATURE MEASUREMENTS DURING MASS TRANSFER IN PARTIALLY MISCIBLE LIQUID-LIQUID SYSTEMS†

In a study of interfacial activity, temperature measurements were made with ten partially miscible systems. In all cases the interfacial temperature showed a fast decrease upon the contact of the two phases, passing through a minimum. Temperature differences of the order of 1 (K) were obtained. In an analysis of the experimental data with two pure heat conduction models, the existence of microconvection currents close to the interface has been suggested.

Development of a Computer Controlled Continuous System for the LICADO Process

A common challenge to coal cleaning technologies is the development of suitable mechanical equipment together with the necessary instrumentation and control devices. This challenge was encountered in the design of a continuous unit for the LICADO (LIquid CArbon DiOxide) process for fine coal cleaning. A microcomputer-based control system was developed for the operation. The computer is equipped with A/D and D/A converter modules which accept input data from pressure transducers, Coriolis type mass flowmeters, a capacitance type liquid-liquid interface position probe, and liquid level switches while transmit control signals to pumps, pneumatic ball valves and regulating valves. Simple strategies were implemented to manage the feed and discharge from the process unit, to control operating variables, and to perform on-line data acquisition.