One Question per Day: Methanol Technology Exchange Edition 20180522
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Learn from the advanced practices of the *Brothers section; there are rewards for correct answers – any answer earns a reward, allowing us to grow and mature through these Q&A sessions. Short answer: What is the absorption principle of low-temperature methanol washing? Answer: By utilizing the principle of different solubilities of various components in a solvent. H2S and CO2 in the feed gas are selectively absorbed by the solvent, and then under conditions of increased temperature and reduced pressure, H2S and CO2 are gradually desorbed from the solution.
The basic principles of low-temperature methanol washing: Raoult’s law and Henry’s law are two fundamental laws used to study gas-liquid phase equilibrium. The gas-phase and liquid-phase equilibrium of the absorbed gas in methanol is also governed by these two laws. According to Raoult’s law, the vapor pressure of a solvent in a solution is equal to the vapor pressure of the pure solvent multiplied by its mole fraction. Expressed in formula form as: (1-1), where: PA is the vapor pressure of the solvent in the mixed solution; PA is also the vapor pressure of the pure solvent; XA is the mole fraction of the solvent. If the mole fraction of the solute is XB, then since XA = 1-XB, the above formula (1-1) can be rewritten as: Henry’s law states that, at a constant temperature and under equilibrium conditions, the solubility of a gas in a solution is directly proportional to its equilibrium partial pressure. Expressed in formula form as: where PB is the equilibrium partial pressure of the solute gas, XB is the molar fraction of the solute gas in the solution, and H is the Henry constant. Experiments have shown that in dilute solutions, if the solute obeys Henry’s law, then the solvent must obey Raoult’s law. Absorption separation utilizes the difference in solubility of various components in a gas mixture by a solvent, to selectively absorb those gases with higher solubility, thereby achieving the removal of such gases from the gas mixture or their further recovery