Absorption Global Standard - Standardisation of Mass Transfer Parameters in Absorption and Desorption

‘Absorption Global Standard'

Standardization of mass transfer parameters in absorption and desorption

1.    Motivation

Dimensioning of absorption and desorption columns is highly dependent on applied mass transfer parameters, which need to be determined experimentally. However, a partially significant deviation in the value of mass transfer coefficients determined in the past has been observed, thus their comparability is restricted. Based on deficient transparency, reasons for the variation between mass transfer coefficient are often unknown. Consequently, high safety factors for dimensioning of columns are necessary and following high construction costs. Therefore, a standardization of mass transfer measurements in absorption is essential for a consistent database of mass transfer parameters. Hence, increasing application of rigorous mass transfer models for absorption process design will be more effective. Due to the need of standardization the project ‘Absorption Global Standard' was launched in fall 2011. In this project a consortium of universities, producers and users of packings and absorption columns are involved.

2.    Goals

The aim of this project is to develop a method for consistent experimental determination of volumetric mass transfer parameters. In addition to the experimental standardization of measurements, a mathematical method is established that gives the opportunity to designate phase specific mass transfer parameters and effective interfacial area. Based on this, transparency in development of both methods is essential to guarantee global acceptance and comparability of determined mass transfer parameters. For this purpose a detailed description of experimental method will be published at the end of this project. Additionally, a standardized mathematical method is summarized in a tool and will be published along with the experimental method. Thus, database for mass transfer coefficients become more reliable and safety factors decrease. Hence, costs and resources for column design can be optimized. In this work status quo of the project will be shown, with focus on the current state of experimental method development.

3.    Approach

The approach within this project can be classified into three periods. The first period is a qualitative and quantitative analysis of the influence of column configuration parameters and preparation parameters on hydrodynamic and mass transfer results. Thereby, the following configuration parameters are analyzed regarding their influence:

-       Liquid distributor

-       Gas distributor

-       Packing Height

-       Sampling

-       Demister

Additionally, the following preparation parameters are analyzed:

-       Pretreatment of packings

-       Inserting random packings

-       Water quality

In the second period of the project a standardized experimental method is established. Therefore, characterization experiments with respect to the results of the qualitative and quantitative analysis of the first period are arranged. Those are carried out with selected structure packings of Mellapak 250.Y and random packings of Pall Ring 25 M and 50 M at different facility plants. For the estimation of phase specific mass transfer parameters the standardized mathematical method is used. The results will show the comparability of the standardized methods and subsequently the determined mass transfer parameters.

In the third and last period an investigation of interactions between experimental data and calculation pathway of the mathematical method is performed. For this purpose, a detailed local and global sensitivity analysis shows the influence of chemical system data for the standardized calculation method regarding HTU-NTU evaluation.

This project is founded by the “Forschungs-Gesellschaft Verfahrens-Technik e.V.“, IGF-Vorhaben 17116N.