Selective Absorption Process Intensification Of Ammonia From Ammonia And Carbon Dioxide Mixture Gas Using A Counter Airflow Shear-rotating Packed Bed

Mixed tail gas containing NH₃ and CO₂ is produced in the production process of many chemical products.Compared with the recovery of single gas,the separation and recovery of mixed gas is an industry conundrum,and it is also an urgent need for enterprises to achieve low-carbon development and resource recovery.The most effective method for the separation and recovery of Ammonia carbon mixtures is the water absorption method,it involves both physical and chemical absorption.The main disadvantages of traditional absorption tower include long residence time,low mass transfer rate,and high energy consumption.What’s more,the long residence time leads to a rapid increase in chemical absorption,and ammonium bicarbonate will be formed in large quantities,which can block the device and pipe.Due to the inability to achieve complete absorption,the residual NH₃ and CO₂ are directly released into the atmosphere,causing serious environmental pollution and waste of resources.The counter airflow shear-rotating packed bed（CAS-RPB）has emerged as a novel process intensification device with the advantages of short residence time（≤0.1 s）,high mass transfer rate,especially it can greatly enhance the gas film-controlled mass transfer.In this study,NH₃from ammonia carbon mixture gas with a molar ratio of 1︰1 or 2.4︰1 was selectively absorbed by water in CAS-RPB,combining the characteristic of intensification on gas-film controlled absorption in CAS-RPB with the solubility difference of NH₃ and CO₂ in water.The effects of different operating conditions on NH₃ selective absorption consequence were elucidated minutely in this paper,to obtain suitable absorption conditions matched to subsequent processing and application operations.And its absorption efficiency is compared with that in RPB.The melamine tail gas was simulated by ammonia-carbon mixture with a molar ratio of2.4︰1.By adjusting the high gravity factor,gas-liquid ratio,and temperature,the NH₃/CO₂ratio in melamine exhaust was reduced to 2︰1 or 1︰1 for coproduction of urea or ammonium bicarbonate.Under both conditions,the selectivity of ammonia was greater than 94%,and the concentration of ammonia in the absorption liquid was greater than 8wt%.NH₃ and CO₂with potential high-added value can be obtained and utilized,and zero-emission of NH₃ and CO₂ can be realized.Compared with Cross-flow rotating packed bed（RPB）,the absorption rate,selectivity,and gas volumetric mass transfer coefficient of NH₃ are increased by 3.34%,8.83%,and 7.02%in CAS-RPB,respectively.The results show that CAS-RPB can significantly enhance the selective absorption process of ammonia from melamine exhaust.The O-Chlorobenzonitrile tail gas was simulated by ammonia-carbon mixture with a molar ratio of 1︰1.When the high gravity factor is 24.44,the gas-liquid ratio is 85.71,the selectivity of ammonia in the ammonia-carbon mixture reaches the highest of 95.81%,the corresponding absorption rate is 22.71%,and the concentration of ammonia in the absorption solution is 0.65wt%.Water is used as an absorbent to absorb ammonia and carbon mixed tail gas,which can reduce the nitrogen content in the tail gas,thereby reducing the subsequent"regenerative thermal incinerator+denitrification"process.The absorbed dilute ammonia water can be used as a raw material denitrifying after being concentrated by liquid ammonia.Data on the selective absorption process of melamine exhaust gases were processed and analyzed,and to speculate on the absorption mechanism using mathematical models.It is concluded that the absorption of ammonia is controlled by gas-film while the absorption of carbon dioxide is looked upon as fast pseudo-first-order reaction is also demonstrated by the study.