(72c) Maximize Ethylene Gain In Acetylene Removal Units - Optimization Strategies and New Generation Catalysts to Increase Production, Profit and Flexibility

Acetylene is a troublesome byproduct in the manufacture of ethylene.  It must be removed from the ethylene product before it can be sold, as it is considered a poison to downstream users even in very low concentrations.  Selective hydrogenation of acetylene to ethylene is the industry preferred method of removing acetylene.  Maximizing the conversion of acetylene to ethylene and minimizing side reactions (specifically the hydrogenation of ethylene to ethane) maximizes production and increases plant profitability.

This paper will address details on improving operation of tail-end acetylene converters to maximize profit.  There are several parameters in operation of a tail-end converter that can be optimized to improve ethylene make, as well as plant reliability and flexibility; these operating parameters will be reviewed.

 Additionally, the paper will discuss several common operational problems with tail-end acetylene converters.  The most common of these operational problems is rapid deactivation, which leads to premature acetylene breakthrough in the reactor effluent and short cycles.  Another common problem with many reactors is non selective operation, which can actually result in off-spec product if not recognized early in the operating cycle.  Lack of flexibility is also cited by ethylene producers as problematic; operators need to be free to make changes to feed slate and production rate without concern that the changes will negatively affect the operation of the acetylene converter.

One key area to enable achievement of optimum performance and avoid operational problems is through proper catalyst selection to match the specific site operational needs (e.g., high activity, flexibility, CO-free operation, etc.).  Recent improvements in tail-end acetylene converter catalyst now allow ethylene manufacturers to operate with a highly stable, selective catalyst that also provides enough activity to fully hydrogenate the acetylene despite feed slate or production rate changes.  There is no longer a need to sacrifice selectivity for activity with these new catalysts.  Included in the discussion will be a review of latest generation catalyst offerings from Süd-Chemie detailing laboratory test results, commercial operational experience and the benefits users have realized due to operation of these catalysts.