煤的油团聚的表面热力学理论

SURFACE THERMODYNAMIC THEORY OF THE OIL AGGLOMERATION OF COALS

本文试图用过程的自由能改变来预言油团聚的热力学稳定性。对具有最低自由能的状态被认为是最稳定状态。本文导出了油团聚过程的自由能，（ｄＦ）Ｔ，Ｐ＝４πｒ１２γ２３［１－ｃｏｓ 由此可见，自由能的降低是由油滴对煤粒大小的比值（ｎ），三相接触角（θ）和油水之间的表面张力（γ（２３））来确定。当ｎ较大和θ较小时，油团聚应能够顺利发生。换言之，热力学上最稳定的油桥是形成在ｎ最大和θ最小时；如果ｎ和θ的数值不落在热力学稳定性的预言范围之内，则考虑油团聚过程未必能实现。

The oil agglomeration of coal is a separation process. It utilizes an immiscible liquid(oil) to form an oil bridge between two coal particles.The oil bridges produce some agglomerate flocs of coal which may subsequently be separated by a screen. The effectiveness with which agglomeration occurs can be assessed by the measurement of agglomerate size.This paper attempts to present a surface thermodynamic theory of the oil agglomeration, Its result is used to predict the thermodynamic stability of the oil agglomeration by free energy change of the process, The state with the lowest free energy is assumed to be the most stable. The free energy change of oil agglomeration process,(dF)T,P, is derived in this paper,i.e. formula(15).The free energy depression is determined by three fundamental system parameters, that is, the ratio of the oil droplet radius to the coal particle radius(n), three phase contact angle,and the surface tension of the oil-water interface(γ23).This theory shows that the ability or inability of a coal sample to be agglomerated by a given oil depends on the ratio of the oil droplet radius to the coal particle radius(n) and the specific three phase contact angle.When n is large and B is small, oil agglomeration of coal will occur readily. In other words,the most thermodynamically stable oil bridges are formed for large n and small.If the specific values of n and do not fall within the predicted ranges for thermodynamic stability, the oil agglomeration process under consideration is unlikely to be feasible.The experimental results of oil agglomeration measured by Guy et al. and Tsutomu Hirose are used to examine the theory in this paper. It has borne out that the surface thermodynamic theory on the oil agglomeration of coal presented in this paper is perfectly correct.