天然气组分的水合常数、水合热及理论溶解度

天然气在水中的溶解度是天然气地球化学定量研究中的基础参数。欲应用理论公式计算天然气组分在水中的溶解度,关键在于建立天然气组分的水合平衡常数与温度的关系。本文利用天然气组分的溶解度数据,标定了甲烷、乙烷、丙烷、N₂、CO₂和H₂S的水合常数与温度的关系,从而建立了上述组分的理论溶解度公式。经验证,至少在下述分压范围内,上述气体的溶解度计算值与实测值基本吻合:甲烷≤60MPa;乙烷≤5MPa;丙烷≤3MPa;N₂≤50MPa;CO₂≤5MPa;H₂S≤5MPa.天然气的水合热是研究气水合物形成的重要参数。研究表明,天然气组分的水合反应符合一般的化学反应规律。根据计算,上述气体的水合热分别为:甲烷,-17.741;乙烷,-10.471;丙烷,-9.441;CO₂,-17.520;N₂,-15.418;H₂S,-11.845(负号表示水合反应为放热反应,水合热的单位:kJ/mol).从理论上证明了当压力趋向无穷大时,气体的溶解度趋向一极限值。

AQUO CONSTANT, AQUO HEAT OF GAS COMPONENTS AND THEIR THEORETICAL SOLUBILITIES

The solubility of gas in water is one of the basic parameters on quantitative study in natural gas geochemistry.To calculate the solubility of natural gas component, it is necessary to establish the equations of the aquo constants with temperature of these gases. In this paper, aquo equilibrium constants (kp) of natural gas component, in which CH₄, C₂H₆, C₃H₈, N₂, CO₂, and H₂S, have been calibrated by solubility of data.These equations of the aquo constants with temperature of the gases above have been respectively established, which makes it possible to calculate the solubility of these gases from theoretical equation.According to verification, at least, in the following range of partial pressure: CH₄, ≤60Mpa; C₂H₆,≤5MPa; C₃H₈,≤3MPa; N₂≤50MPa; CO₂,≤5MPa; H₂S,≤5MPa, the theoretical solubilities of the gases were coincided with their experimental data.
The aquo heat of the gas is an important parameter for studying aquo-compound of the gas.Based on our investigation, the aquation of the gas is in accordance with general law of chemical reaction. The aquo heat of the gas have been calculated, which are CH₄－17.741; C₂H₆, －10.471; C₃H₈, －9.441; －CO₂, －17.52; H₂S, －11.845; N₂, －15.418 (negative sign indicate that these reactions give out heat, kj/mol).
The fact that when pressure of a gas tents to infinitely great, the solubility of the gas tents to a limit value have been proved in theory.