(187b) Building Tomorrow’s Mega-scale Ethylene Plants – General Criticality Criteria and Selected Design Aspects for Plate-fin Heat Exchangers and Cracking Furnaces

Authors: Alexander Kromp, Gunther Kracker, Axel Lehmacher, Robert Stegemann
Organization: Linde AG, Engineering Division, Pullach, Germany

After six years of experience in operating 1500 KTA ethylene plants the olefins industry seems poised to take the next step up in capacity. For the design of super-sized plants, two factors become essential: (i) exact understanding of the limitations to the economies-of-scale effect and (ii) the ability to provide tailor-made solutions for mega-scale services.

The size of future mega-scale ethylene plants is determined by the individual plant component breakpoints, beyond which further scale-up becomes disadvantageous. This paper presents a set of criticality criteria for screening of plant components with increasing size. This general approach renders identification of the breakpoints for super-sized ethylene plants on an equipment level. By this means the optimum plant capacity can be determined for project specific boundary conditions.

Considering the developed criticality criteria, this paper further discusses mega-scale design challenges for two selected key elements of ethylene plants:

PFHE - Due to their compactness and their lightweight properties, vacuum brazed plate-fin heat exchangers (PFHEs) are of particular interest when designing super-sized ethylene plants. The breakpoints that limit design of single PFHEs are reported, an overview of design and modularization concepts for further scale-up is given and associated risks and mitigations are discussed.

Cracking Furnaces - As ethylene plants grow, either the number of cracking furnaces or the size of the furnaces must increase. As highly modularized and already parallelized equipment in ethylene plants, they do not represent any limitation for achieving super-sized plant capacities. However, optimization of size and number of cracking furnaces becomes a challenging task for mega-scale crackers. In this context, the interaction of availability, capacity utilization and component costs is discussed in detail.