Liquefaction process, behavior

Acceptance of these premises would presumably (or, at least, hopefully) facilitate a better understanding of the concepts of coal behavior during utilization, such as in beneficiation, combustion, and gasification processes as well as in liquefaction processes. However, the behavior of coal does not and cannot be represented by an average structure. At best, determining an average structure for a heterogeneous material such as coal is a paper exercise that may bear little relationship to reality. 

In tenns of the physicochemical behavior of coal during the liquefaction process, some mention must also be made of the phenomenon of coal plasticity (Chapter 9). Plasticity is particularly evident in coals of the bituminous rank during the plastic condition (which usually occurs in the tanperature range 325°C-350°C [615 -660 ]), the plastic mass has a tendency to adhere quite strongly to a variety of surfaces. Thus, reactor plugging could be a common result of the tendency of various coals to exhibit plastic behavior and there has been a considerable amount of effort directed to resolving this particular problem. 

We believe that the PFGC equation of state approach will be the most fruitful new route to predicting phase behavior of the diverse systems encountered in the natural gas/petroleum/coal liquefaction gasification process industry. We commend it to your attention. 

Solid soils are commonly encountered in hard surface cleaning and continue to become more important in home laundry conditions as wash temperatures decrease. The detergency process is complicated in the case of solid oily soils by the nature of the interfacial interactions of the surfactant solution and the solid soil. An initial soil softening or "liquefaction", due to penetration of surfactant and water molecules was proposed, based on gravimetric data (4). In our initial reports of the application of FT-IR to the study of solid soil detergency, we also found evidence of rapid surfactant penetration, which was correlated with successful detergency (5). In this chapter, we examine the detergency performance of several nonionic surfactants as a function of temperature and type of hydrocarbon "model soil". Performance characteristics are related to the interfacial phase behavior of the ternary surfactant -hydrocarbon - water system. 

Gas-liquid bubble columns and gas-liquid-solid slurry bubble columns are widely used in the chemical and petrochemical industries for processes such as methanol synthesis, coal liquefaction, Fischer-Tropsch synthesis and separation methods such as solvent extraction and particle/gas flotation. The hydrodynamic behavior of gas-liquid bubble columns and gas-liquid-solid slurry bubble columns are of great importance for the design and scale-up of reactors. Although the hydrodynamics of the bubble and slurry bubble columns has been a subject of intensive research through experiments and computations, the flow structure quantification of complex multi-phase flows are still not well understood, especially in the three-dimensional region. In bubble and slurry bubble columns, the presence of gas bubbles plays an important role to induce appreciable liquid/solids mixing as well as mass transfer. The flows within these systems are divided into two... 

In the process of liquefaction, one must also consider the inversion temperature (-361°F or -183°C or 90°K) of H2, because the behavior of this gas changes (inverses) at that temperature. Below the inversion temperature, when the pressure is reduced, the H2 temperature will drop. Above that temperature the opposite occurs a drop in pressure causes a rise in temperature. Therefore, in the process of liquefaction, H2 first has to be cooled below its inversion temperature—by such means as cooling with LN2—before the Joule-Thomson effect can be utilized. 

The vapor pressure curve forms the basis for the description of vapor-liquid equilibrium for a pure fluid. As the temperature increases, the vapor pressure curve for the vapor-liquid situation ends at the critical pressure. In the case of a binary or multicomponent solution, the critical point is not necessarily a maximum with respect to either temperature or pressure. It is then possible for a vapor or liquid to exist at temperature or pressures higher than the critical pressure of the mixture. At constant temperature, it is then possible for condensation to take place as the pressure is decreased. At constant pressure, condensation may take place as the temperature is increased. Vaporization can take place at constant temperature as the pressure is increased and decreased. This unusual behavior can be useful in some process situations, for example, in the recovery of natural gas from deep wells. If the conditions are right, liquefaction of the product stream is possible. At the same time, the heavier components of the mixture may be separated from the lighter components. 

Kelvin) and performed by J. P. Joule to study departures from ideal gas behavior. The Joule-Thomson expansion, as it is called, is used in the liquefaction of gases and in refrigeration processes (see Chapter 5). ... 

The equation of state fw gas A may be rewritten — (RT/p) Vm — (RTb/p) = 0, which is a quadratic and never has just one real root. Thus, this equation can never model critical behavior. It could possibly model in a very crude manner a two-phase situation, since there are some conditions under which a quadratic has two real positive roots, but not the process of liquefaction. 

The equation of state of gas B is a first-degree equation in Vm and therefore can never model critical behavior, the process of liquefaction, or the existence of a two-phase region. 

Thus, it can be argued (often successfully to a point but not ad nauseam) that an understanding of the chemical nature of coal constituents is, just like an understanding of the chemical and thermal behavior of coal (Chapters 13 and 14), a valuable part of projecting the successful use of coal for conversion and/or utilization processes such as combustion (Chapters 14 and 15), carbonization an briquetting (Chapters 16 and 17), liquefaction (Chapters 18 and 19), gasification (Chapters 20 and 21), or as a source of chemicals (Chapter 24). 

Solvent extraction in coal research (Chapter 10) has been used for isolation and characterization of both soluble and insoluble coal fractions (Van Krevelen, 1957) and fall into four general areas (1) improvement in extraction yields or selectivity, (2) correlation of solvent swelling and extraction behavior to structural models for the insoluble organic portion of coal, (3) analyses of extracts to identify and quantify organic compounds in the raw coal, and (4) use of solvent extraction to predict or influence coal behavior in some other process such as liquefaction. 

Thus, the solvent extraction of coal, far from being a theoretical study, is, in fact, very pertinent to the behavior of coal in a variety of utilization operations. For example, the liquefaction of coal (Chapters 18 and 19) often relies upon the use of solvent and, in addition, the thermal decomposition of coal can also be considered to be an aspect of the solvent extraction of coal. The generation of liquid products during thermal decomposition can be considered to result in the exposure of coal to (albeit coal-derived) solvents with the result that the solvent materials being able to influence the outcome of the process. And there are many more such examples. 

Onozaki M, Namiki Y, Ishibashi H, Takagi T, Kobayashi M, Morooka S. Steady-state thermal behavior of coal liquefaction reactors based on NEDOL process. Energy Fuels 14 355-363, 2000b. 

---