Removal Of Impurities From Exhaust Gas Of Butene Hydration By Absorption-Distillation

The main component in exhaust gas of butene hydration, which comes from butene hydration process of Methyl-Ethyl-Ketone (MEK) production, is butene. Research on the removal of the impurities by absorption-distillation from the exhaust gas is carried out to recycle the butene in the exhaust gas effectively.An absorption-distillation experimental apparatus is designed and setup up, which has the performance of absorption and distillation in the same column with following specifications:the column diameter is Φ57×3.5mm, the packing is "θ" ring of Φ2×2mm by stainless steel, each section height is1200,800,600and600mm, and it has36theoretical stages calibrated by heptane and iso-octane standard system.A gas-chromatography analysis method for the trace amount of impurities in the exhaust gas is established. The effect of separating degree greater than1.5, detection limit less than0.1mg·kg-1and RSD less than5%is get with the self-filled GC column and the liquid-phase injection valve. A model for removal impurities in exhaust gas from butene hydration by absorption-distillation is set up by the process simulation software-Aspen Plus with the module of Radfrac and property method of NRTL-RK. MEK is the best solvent for the process which can meet the requirements of separation by technological and economical analysis.The sensitivity analysis about main operating conditions is carried out to determine the regularity of the absorption-distillation process, and these operating conditions are taken as initial operating conditions for the experiment. The result shows:the two process of absorption and distillation can be combined in one column with the optimized operating conditions: reflux ratio is0.8, recycled solvent to feed flowrate ratio is5with a temperature of54℃, fresh solvent to feed flowrate ratio is0.16, height of fresh solvent liquid level in section II is200mm, top pressure is0.45MPa.Industrial experiment is carried out on the apparatus which process capability of exhaust gas is8000t·a-1by the column of800mm in diameter for three weeks. The concentration of impurities in the purified exhaust gas is less than10mg·kg-1, which circles to butene-concentrating process without any adverse effect on the related process. The recovery of butene is greater than99.5%, so the utilization rate of butene in whole MEK production process increased by13%. As a result, productivity of SBA in hydration reactor increased, and more MEK can be produced with less C4feed.The characteristic of removal impurities from exhaust gas of butene hydration by absorption-distillation are:(1) a column has been set up to remove the impurities efficiently with the performance of absorption and distillation in one column by skilful combination of absorption with distillation.(2) MEK is selected as the best solvent. The rich solvent can be recycled by MEK refining process without additional solvent recycling process.