Claus waste heat boiler economics Part 1: process considerations The design of the waste heat boiler has a critical role to play in determining process operations,reliability and economic performance in the sulphur recovery unit

摘要

Higher sulphur feedstocks offer margin advantages to refiners and gas producers but with challenges to uptime metrics and environmental constraints as downsides.To meet economic objectives,such competing requirements must all be met reliably without equipment failure.One key piece of equipment that can impact uptime is the Claus waste heat boiler(WHB).The WHB operates under harsh conditions with serious reliability challenges.It is one of the most fragile equipment items in the sulphur recovery unit(SRU).Not only does it provide heat recovery from the thermal section of the SRU,but it also affects the unit's hydrogen balance and COS levels because of recombination reactions.Peak heat flux at the front end of the boiler tubes can lead to over-heating and reliability problems.The design of the WHB plays a critical role in determining the extent of the recombination reactions as well as the peak heat flux,all while balancing capital cost and operational reliability.Part 1 of this two-part series discusses general process considerations including the effects of tube length,pressure drop,and COS/H2 reactions on sulphur recovery.Part 2 examines details of how operating conditions and WHB design affect tube wall temperature and the important reliability implications of that relationship.