Gas cofiring in coal-fired stokers for emissions reduction and performance improvement
Adding gas burners above the grate of a coal-fired stoker can be an economical method of reducing gaseous and particulate emissions and improving efficiency and operational flexibility. With this cofiring configuration, the improved heat distribution and mixing with the stoker combustion products can give reduced opacity, reduced emissions of particulate, NO{sub x} and SO{sub 2}, improved carbon burnout and lower overall ash, reduced excess air, faster load response, cleaner and quicker lightoffs, improved turndown at both lower and upper capacity limits, and improved performance with problematic coals. To develop and validate the cofiring technology, three cofire field experiments have been conducted. A 165,000 lb/hr spreader stoker and mass feed chain grate stokers rated at 40,000 and 75,000 lb/hr have been retrofit with gas burners and tested in the field. The two larger units used dual, opposed burners, while the smaller unit was retrofit with a single burner. With the spreader stoker, the primary benefits of gas cofire was reduction in opacity episodes with coal quality variability and recovery of lost derate. With the larger chain grate unit, the primary benefit was reduction of NO{sub x} and SO{sub 2} to within Title V limits and elimination of opacity episodes during startup and load swings. With the smaller chain grate, the primary benefit was ability to operate at low loads without unacceptable opacity excursions which had previously required a backup boiler. In all cases, the economics justified the capital burner system retrofit cost and incremental fuel costs.
- OSTI ID:
- 549632
- Report Number(s):
- CONF-960954--
- Country of Publication:
- United States
- Language:
- English
Similar Records
Refuse-derived fuel evaluation in an industrial spreader-stoker boiler
Reducing operating costs in stoker boilers with natural gas cofiring