(17c) Revamp of a 50-Year-Old Quench Tower with Modern Internals

In the recent years, a major focus in the process industry has been on transitioning to renewable energy sources and the reduction of environmental impact. A significant aspect within this transition, is the reduction of the energy consumption of existing plants, e.g., by improving the apparatus efficiency using modern internals. At the same time plant availability and robustness must not be compromised.

Linde is involved in many revamps and troubleshooting of various plants, especially steam crackers. These plants are in operation for decades and are typically very challenging from process as well as mechanical point of view. A recent project dealt with a water wash tower built in the early 1970’s, in which internals were already replaced a few times due to several plant load increases. After the client reported operation issues during summertime, the entire process unit has been thoroughly examined. The increased cooling water supply temperature during summertime created limitations in that particular unit. The operation stability of the water quench column is essential for the overall performance of the entire cracker. As modifications on the cooling water side were not favored by client, a solution had to be found to improve the column efficiency and performance to overcome the increased cooling water temperature. The modification works should be cost-optimized and implementable during the already planned shut-down. Therefore, a replacement of the existing column and even welding to the column shell was not an option. Warranty had to be given on pressure drop and gas overhead temperature. The debottlenecking included an optimization of the process conditions, evaluation of possible reuse of existing mass transfer and non-mass transfer internals and a specification of all modification steps needed to fully replace the existing column setup (random packing and trays) with modern high-efficiency internals (structured packing). The limited column height and diameter required tailor made design as well as approaching design limits and general rules for distribution devices including a CFD analysis of most critical areas. Linde was also in charge of procuring and installing the new internals at site. This success story shows that a complex modification of key equipment can be realized even in a challenging environment of a major shutdown. It is also an excellent showcase for the possibility of further improving the performance and energy efficiency of a plant, which had already been revamped several times significantly beyond its original design capacity.

The presentation covers the whole engineering process, starting from the process evaluation and improvement of the column operation stability and optimization of the operating conditions, development of solution as well as identification of risks, internals inspection and modification supervision on site up to the successful performance run.