EXPERIMENTAL STUDIES OF SOLUBILITY OF ELEMENTAL SULPHUR IN SUPERCRITICAL CARBON DIOXIDE

摘要

It is well known that elemental sulphur deposition is a serious problem troubling the production of sour natural gas. This deposit can also occur during transport. In the transport network, natural gas is transported at an average pressure of 5 MPa. However, to enter the distribution network, the gas pressure has to be reduced to 0.5 MPa. Consequently, a solid sulphur accumulation can occur just behind the gas expander. This solid deposit leads to a sealing problem, which regularly compromises the operation of the station. One of the hypotheses proposed to explain the solid accumulation and based on a thermodynamic approach [1] is the desublimation of sulphur. Indeed, during gas expansion, the pressure and the temperature both decrease. Consequently, the gas may become over saturated in sulphur. Because we are below the temperature of the triple point of sulphur, part of the gaseous sulphur can be transformed into solid particles. Thus, it is important to obtain the solubility data of sulphur in natural gases under 373.15 K and 20 MPa. The first step is to determine its solubility in the major gases, which constitute natural gas like CO_2 or CH_4. Several authors measured the solubility of sulphur in pure gases, as well as in synthetic gas with composition approaching natural gas. The experiments were all carried out under conditions of temperature and pressure comparable to the conditions of field. Six groups of authors studied the solid-gas sulphur equilibrium, and determined the solubility of sulphur in natural gas Table 1 summarizes for each paper the nature of the gas considered, the ranges of pressure and temperature conditions for measuring the solubility of sulphur and the volume of the reactor used for the saturation.