Abstract

The possibility of using high efficiency structured packing in CO2 absorption processes with a newly proposed solvent, 2-amino-2-methyl-l-propanol (AMP) was investigated. The evaluation of packing performance was performed by CO2 absorption into sodium hydroxide solutions and aqueous AMP solutions in 1.77 m high and 0.019 in ID absorption column. The performance of structured packing representing in term of the overall mass transfer coefficient (KGa) is reported as junctions of the main operating variables, namely CO2 partial pressure, gas flow rate liquid flow rate, and liquid composition. An excellent performance of structured packing over random types in CO2 absorption process was found in this study.

Introduction

Carbon dioxide (CO2) absorption is an essential step in many industrial processing operations such as natural gas purification manufacture of hydrogen and coal gasification. For industrial purposes the absorption process helps in removing CO2, from gas streams so that higher quality gas stream products can be achieved and operational difficulties can be minimized. Environmentally this process can alleviate the global warming problem by reducing net CO2 emission from waste gases which would otherwise be vented to the atmosphere.

In the absorption process. CO2 in gas streams is basically absorbed into liquid solvents. The used solvents can be simply classified as physical and chemical solvents. Chemical solvents are however, preferred for the processes because of their higher absorption capacity at a low partial pressure of CO2. Alkanolamines are considered the most commonly used chemical solvents for CO2 removal applications. [1] Among these monoethanolamine (MEA) belonging to the primary class is the most popular absorption solvent. [2]

A new class of acid gas absorbents, the sterically hindered amines has recently been disclosed by EXXON Research and Engineering Company. [3] Among these chemicals. 2amino- 2-mcthyl-l-propanol (AMP) is the most promising solvent since it provides higher CO2, absorption capacity on a molecular basis when compared with that of MEA. the most commonly used conventional alkanolamine. [3] In addition absorption of CO2, in AMP solutions causes less corrosion (which is considered the most severe operational problem in alkanolamine plants). [4]

The above considerations show that the replacement of conventional alkanolamine MEA with the hindered amine AMP is very attractive. One limitation for use of AMP is that its absorption rate is lower than that of MEA, by approximately 10 times. [5] To make the replacement feasible, the rate of CO2 absorption into the new AMP solution must be improved. An approach that might lead to the improved efficiency of a CO2 absorption process using AMP solution is modification of the interior of the absorber. Previous experiences in using structured packing for distillation and gas dehydration application [6,7] show that use of structured packing may improve mass transfer performance in the new CO2-AMP absorption system.

The primary objective of this study was therefore to investigate the possibility of using high efficiency structured packing in CO2 absorption processes with a newly proposed solvent 2-amino-2-methyl-l-propanol (AMP). The performance of the studied packing was evaluated by performing CO2 absorption into sodium hydroxide (NaOH) solutions which are commonly used to characterize

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