DUST EMISSIONS DURING CRACKING FURNACE DECOKING —REGULATIONS VERSUS THE MEASURED PERFORMANCE

摘要

The BAT (Best Available Techniques) requirements in EU member countries has set very challenging requirements for SO_x, NO_x, CO_2 and dust emissions from olefin unit cracking furnaces. The technologies and target values were set in a so-called BAT BREF (BAT Reference) document, which is same for all EU countries. These targets are a kind of guideline for authorities of individual member countries for setting the local regulations. The BAT target for average dust (particle) emissions during the decoking is < 50 mg/Nm~3. The BATs for particle emissions are cyclone separation and sending the decoke effluent to furnace radiant box to burn the coke particles. When the regulations were imposed, the technologies were available, but only very few ethylene plant operators had measured their particle emissions. Some of the early problems were the interpretation of the requirements, the difficulty in sampling and big variations of particle emissions during the different stages of the decoking. During the transition period, which still seems to continue, an EEPC (European Ethylene Producers Committee) task force – Furnace Emission Issue Group – had an important role in conveying the message to the EU central organization about the difficulties that ethylene producers were facing and by providing information and helping the operators to understand the regulations and their performance ranking compared to best performing plants, which are the pace setters for BAT regulations. This paper concentrates on the comparison of cyclone separation and decoking to firebox from both the operator's and the technology contractor's point of view and compares the pros and cons of operability and performance of the two methods. Information is also provided about sampling methods and actual measurements of particulate emissions.