Q-Chem Steam Boilers NOx Emissions Reduction

摘要

Q-Chem Plant in Mesaieed has three steam boilers. They run on fuel gas that is 90% mol methane and are also designed to co-fire C4-C11 liquid fuel which is a by-product from the De-Propanizer tower. The boilers design and actual efficiency is ～ 90%. Based on the 1999 Qatar state environmental regulations, they were designed for maximum NOx emissions of 250 mg/Nm~3. However, the new Ministry of Environment (MOE) regulations limited the NOx emissions to 125 mg/Nm~3 maximum from December 2008. Modifying the existing boilers to produce 125 mg/Nm~3 max NOx was a big challenge for the technical group especially with a running plant. The steam system is very critical to the plant and its outage leads to a total plant outage. This paper will discuss and reflect the different technical options and how the boilers modification was carried out. Special emphasis will be presented on the required technical modifications, value engineering and operational flexibility to grant the outage on the boilers for a month each.. Some final actual NOx emissions will be presented where the modification resulted in superior NOx reductions up to 90 mg/Nm~3 at full firing mode.