Shut Down Fans, Save $1/4 Million/Yr and Increase Airflow?

Abstract

In 1994, the fume collection system for the Desulphurization Station at Dofasco Inc., Hamilton, Ontario was studied for energy and maintenance optimization. The existing system consisted of two 600 hp fans on a wet scrubber system for two collection hoods and one 600 hp fan on a baghouse collection system for two more collection hoods. The fans for the wet system had been an ongoing maintenance problem with frequent outages due to build-up problems. The scrubber fans were approximately 20 years old while the dust collector was 14 years old. The two scrubber fans were rated at 50,000 cfm at 55 in.wg (inches water gauge). The baghouse fan was rated at 105,000 cfm at 17.5 in.wg. All fans were controlled by inlet dampers which adjusted to a -4 in.wg inlet pressure set-point depending on whether zero, one or both of the hoods for a particular system pair were open. The engineering feasibility study completed by FLOWCARE Engineering Inc. was able to prove the following. • Through timing changes to the incoming ladle cars, three hoods would be sufficient without affecting production. • By adding tip extensions to the fan wheel, the baghouse was able to handle 3 hoods simultaneously. • Wet scrubber could be shut down.

The entire project was implemented with 100% success within two months after studying. The final result was that $244,115 are now saved annually due to scrubber shutdown. Total implementation costs were $22,000. As an added bonus, hood capture volumes were proved to have been increased slightly. This eliminated a small fugitive emission problem that had existed on the hoods of the scrubber system.