The impact of tower internals on column performance

Full scale testing and analysis of operation demonstrate the importance of tower internals on the performance of mass transfer packings

Fractionation Research Inc. (FRI) is the most modern independent test institute in the world for performing tray, random packing, and structured packing tests under rectification conditions on an industrial scale test column (see Figure 1). In 1998, Raschig Super- Ring No. 2 was tested at FRI for the first time, and FRI high performance tower internals were selected for this test. However, in 2012, Raschig elected to retest Super-Ring No. 2. In this retest, the company used state of the art tower internals. This article shows the impact of tower internals on packing performance, comparing both FRI test results.

In addition to the FRI test results, the article provides information about Raschig’s large scale liquid distributor test facility. The test facility was built to improve large and small scale distributor designs as a development project and to demonstrate their performance after fabrication for industrial columns. Finally, the article describes an industrial design example for which modern tower internals were applied.

Tests with two sets of tower internals

The development over the past few decades of the most modern packing generations and tower internals, such as distributors, hold-down plates and support plates, have seen pronounced and noticeable design improvements.

High performance tower internals used 10 to 20 years ago in mass transfer columns are currently often considered to be low or standard performance devices, especially Full scale testing and analysis of operation demonstrate the importance of tower internals on the performance of mass transfer packings MICHAEL SCHULTES Raschig GmbH when they are used with high performance packings. When Raschig Super-Ring No. 2 was tested at FRI in 1998 for the first time, the FRI high performance tubed drip pan (TDP) distributor and the FRI support plate and hold-down plate were selected for the test (see Figure 2).

However, in 2012, Raschig elected to retest Super-Ring No. 2. In this retest, the company used a more modern, narrow trough type distributor that is very open to the gas phase compared to FRI’s TDP distributor. In addition to the high performance DT-S distributor which Raschig used in 2012, FRI employed a modern Raschig SP-1 support system and HP-1 holddown device.