Studies On a Newly Developed Modular Packed Absorption Column

Studies on a newly developed modular packed absorption column

1.    Motivation

Increasing product differentiation and changing from commodities to specialized products are reasons for shortened product life circles in chemical engineering. Traditionally, large scale-plants possess inadequate flexibility in capacity and product portfolio based on their ‘one purpose' development. Therefore apparatus with increased flexibility, like modular devices, becomes necessary to handle fluctuating customer demands. Due to modular assembly capacity can be increased either by equaling up modules from general structures or by numbering up equipment. Hence, a ‘smart scale-up' of the complete modular apparatus becomes possible. In favor of smart scale-up only the operating parameters of the single module are necessary and thus reduced time-to-market periods for the products (see figure 1). In fact the challenge on scaling-up modular devices is an equal feed flow for every single module.

Modular devices are state of the art in chemical engineering. Apparatus types like plate heat exchangers or filter presses are established technologies with a long history of development. Nevertheless, most of other apparatus principles are not modular in terms of adaptable capacity and operational flexibility. Even continuously working multiphase reactors and separation units are scale-up by the traditional similarity analysis. Therefore our chair is running several research projects presently dealing with the modularization of multiphase units like packed columns and bubble column reactors for example.

In this contribution first experimental studies on a newly developed packed absorption module are compared with the operation behavior of a conventional packed column.

2.    Experimental Studies

For the experimental studies a packed absorption module with rectangular cross-section was developed (see figure 2). Firstly, experimental studies regarding hydrodynamics and mass transfer efficiency of the module have been performed. Those studies have been performed with dumped and structured packings for liquid and gas loads up to the flooding point. In detail, this work presents results of measurements with Pall Ring 25 M and Raschig Super-Pak 250. A comparison of experimental results between a packed absorption module and conventional packed columns shows the practicality of this new apparatus (see figure 3). With regard to identical packings, the module's results are comparable to conventional packed columns. Although the single module shows the expected losses in capacity for the gas and liquid load, it shows comparable results for the mass transfer efficiency in consideration of the reduced cross-section. Particularly with regard to the distribution of the fluids in the module, experimental studies have been performed to show the influence of the rectangular cross section and thus the shortened distance for liquid and gas to the wall. For   qualitative and quantitative investigations of the wall effect a new in-situ measurement method for the   thickness of the wall near liquid film in packed columns will be developed. By a detailed examination of the wall effect inside the module, internals will be designed to minimize the wall film thickness and increase the mass transfer efficiency.

For an investigation of the gas distribution, studies have been performed with fog to visualize the stream of the gas inside the rectangular absorption module. The tests with fog will show the need of a gas distributor and the behavior of gas stream inside the newly module.

3.    Interconnection of the modules

As aforementioned the utilization of the packed absorption module can be increased by a multiple connection of single modules, the so-called numbering-up. Purpose of this work is to show possible design studies to connect single modules (see figure 4). These studies indicate the conduction of gas and liquid flows and possible integration of the modules into existing modular concepts like frames of plate heat exchangers.