Identical concentration point and water-sulphur ratio
The identical concentration point is a series,and the azeotropic point is just one of them.The identical concentration point is the turning point for water escape and acid corrosion.The water-sulphur ratio is the ratio of the molecular number of H2O to SO3,which unifies the relationship between gas and sulphuric acid concentration.The relative water-sulphur ratio is the ratio of gas phase water-sulphur ratio to water-sulphur ratio of sulphuric acid in gas-liquid equilibrium state,which unfolds in a fan-shaped pattern as the temperature of sulphuric acid increases.At the identical concentration point,the relative water-sulphur ratio is equal to 1.When the concentration of sulphuric acid is below the identical concentration point,the relative water-sulphur ratio is greater than 1,and H2O in the acid is prone to escape.Crossing the identical concentration point is less than 1,and SO3 is more prone to escape because the chemical bond between H2O and SO3 in the acid is weaker than the hydrogen bond between H2O and H2SO4.The acid from the second stage packing of acid heat recovery tower mixed unevenly with the acid from the first stage inlet.The relative water-sulphur ratio of the second stage acid shifted upwards,and the water content in the gas increased significantly,causing space condensation.The semi-drying sulphuric acid process uses a moisture absorption tower to remove water vapor,which is then absorbed by the absorption tower.Wet sulphuric acid process can also use two packed towers:absorb first and then absorb moisture.The relationship between the relative water-sulphur ratio and sulphuric acid temperature for two processes is illustrated,and there is a qualitative difference between the semi-drying and wet sulphuric acid process.
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