Coke & Ironmaking
After laboratory studies on the effect of coal type, coal moisture and oil additions, modifications were made to the ASTM D291 procedure to allow for improved coal flow with coal moistures greater than 7%. This allowed operators to measure changes in coal bulk density that were not detected before. Also, routine coal moisture measurements were implemented with bulk density measurements at coal handling to aid operators on when to change oil amounts. With these improvements, new coal bulk density targets were set and adhered to. As a result, less oil is now required to maintain coal bulk density at the new setpoints. New oil sprays were also installed to improve oil-to-coal contact to allow for further improvements.
The cokemaking technology division in a mill in Japan has experienced problems such as price increase and quality deterioration of metallurgical coal, coke oven aging and social demand for environmental friendliness. The Japanese cokemaking industry has struggled to cope with these challenges by developing various new technologies. This paper provides a summary of the recent progress of cokemaking technology such as coal pre-treatment technology for utilizing low-grade, semi-soft coking coal, diagnosis and repair apparatus for coke oven chamber wall, and a method to turn waste plastics into chemical raw materials using coke ovens.
Stickers cause production loss, oven wall damages and reduce the useful life of a coke oven battery. Despite several interrelated causes, stickers are almost always preceded by increased pushing forces. An early warning system has been developed at the ArcelorMittal Burns Harbor coke plant that uses statistical analysis and high-tech programming to warn of impeding problems and take proactive corrective actions. This system helps to avoid stickers, fine-tune coal blend, plan preventive maintenance on deteriorating ovens, repair electrical and mechanical issues on machines, etc. Thus, both batteries (33 and 22 years old) run at full production with all ovens in service.
Monitoring and controlling the above-burden temperature profile of a blast furnace is crucial for process optimization and operation sustainability. At AK Steel – Dearborn Works’ C Blast Furnace, during a period of high productivity, there was a relatively quick, sustained, loss of center temperature. Although still able to operate at high productivity rates there were concerns about implications to furnace stability. A cross functional team including technology, process control, maintenance and operations developed a checklist for potential root causes using a traditional Ishikawa diagram. Potential root causes were identified in areas related to instrumentation, above-burden probes, furnace top water systems, coke chimney, and Bell Less Top® distribution chute. This paper reviews the investigation, including the impact on furnace operation, interpretation of the event from process data, and the consequent return of center temperature profile.
This paper discusses the enhancements in process monitoring capabilities using tuyere camera technology at Stelco’s No. 1 Blast Furnace located at its facility in Nanticoke, Ont., Canada. Tuyere cameras were installed on this blast furnace in 2011 with the initial intent of providing blockage detection, but have since proven useful for tuyere level process monitoring and control, providing an index of stable furnace operation. The cameras incorporate image analysis software that provides real-time output of the burn ratio. Data from the image analysis software is exported to the plant information system. Analytics have been developed that prorate the burn ratio peak frequency during operation at full wind and highlight when there is an increased frequency of peeling due to scab formation and subsequent loss. This information is being used to provide advance warning in conjunction with other process parameters of internal changes that are used to make adjustments to the burden.
Oftentimes, blast furnace hearth wear becomes a bottleneck in lengthening the blast furnace campaign. The hearth’s taphole area, which is severely eroded by the molten iron and intense slag flow, can become a challenge for stable blast furnace operation. This paper presents recent development on taphole clay technology, which has shown excellent results in increasing taphole length, creating a good protection for the hearth. Additionally, it is shown how a high-performance taphole can also reduce costs in the blast furnace operation.