恒浓点与水硫比

Identical concentration point and water-sulphur ratio

恒浓点是一系列的,共沸点只是其中之一。恒浓点为水逃逸性转折点、酸腐蚀性分界点。水硫比是H_(2)O与SO_(3)分子数量的比值,统一了气体与硫酸浓度间的关系。相对水硫比为气液平衡状态下的气相水硫比与硫酸中的水硫比之比值,随硫酸温度升高呈扇状展开。在恒浓点相对水硫比等于1;硫酸浓度低于恒浓点时相对水硫比大于1,酸中H_(2)O易逃逸;硫酸浓度越过恒浓点则相对水硫比小于1,SO_(3)更易逃逸,酸中H2O与SO_(3)的化学键弱于H_(2)O与H_(2)SO_(4)间的氢键。酸热回收第2级流下的酸与1级上塔酸混合呈区域不均,2级酸多处相对水硫比上移、气中水分含量大增而引起空间冷凝。半干法制酸用吸湿塔去除水汽,再由吸收塔完成吸收。湿法制酸亦可用两个填料塔——先吸收再吸湿。图示了两种工艺的相对水硫比与硫酸温度的关系,半干法与湿法制酸间是质的不同。

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 H_(2)O to SO_(3),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 H_(2)O in the acid is prone to escape.Crossing the identical concentration point is less than 1,and SO_(3) is more prone to escape because the chemical bond between H2O and SO_(3) in the acid is weaker than the hydrogen bond between H_(2)O and H_(2)SO_(4).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.