Big Repair Shutdown at Aurubis Hamburg in 2013
The latest major shutdown at the primary smelter Aurubis Hamburg was in autumn 2013. This shutdown included the complete relining of the flash smelting furnace (FSF) and the slag cleaning furnace (SCF), both, after 22 years of operation. The shutdown took place from September 2 nd 2013 to October 28 th 2013 (56 days). This shut down also completed the latest expansion project “Future 1,25 Mio. t” that was initiated in December 2011.
Project “Future 1.25 Mio t”
In 2007 the smelter set-up was analyzed with regard to a further increase of concentrate processing capacity. Different expansion options were evaluated. The realized expansion project concept “Future 1,25 Mio. t” increased the budget smelter capacity from 1,15Mio t. to 1,25 Mio t without new furnaces, but with a higher utilization of existing units. A total investment of 40 Mio € compasses:
- substitution of lead-cells with polymer-concrete cells in tankhouse
- constant utilization of acid plant
- changes in off-gas system of PS-converters
- additional auxiliary hoods filter (bag filter with lime addition)
Changes in the PS-converter off-gas system enabled a three-hot-two-blowing mode operation which was the core project for an overall increase of production. This three-hot-two-blowing mode increases production capacity due to the elimination of the idle time between consecutive converter blows. It is possible because the off-gas line manual slide gates were replaced with automatic sickle slide gates allowing switching the off-gas treatment between the converters. Now the second blowing coverter could be operated immediately after the end of the finished converter batch thus increasing the production capacity.
Figure 1: The converter off-gas system before and after the expansions project Future 1.25 Mio t
Major Repair Shutdown 2013
Parallel to the “Future project,” a major repair shutdown was scheduled for autumn 2011. The major repair shutdown total investment of 80 Mio € included:
- FSF: complete relining & intensified cooling
- SCF: complete relining & optimization of off-gas system
- WHB: increased cooling area & legally required inspection
- acid plant: maintenance in washing & cooling section, new contact reactor line 3, new end absorber line 1&2, new process control system
Unfortunately, the FSF suffered a leakage through the hearth bottom on December 3 rd 2010, causing an immediate minor repair shutdown. Due to the run out, the planning of the major shutdown was postponed until autumn 2013. The most critical parts of old FSF design were the old spray cooled reaction shaft and transition area of the reaction shaft to the settler roof. In the new design, reaction shaft spray cooling was changed to a sandwich-type reaction shaft and BIC-cooling elements are used in the reaction shaft and settler transition area. This design allows higher heat extraction from the reaction shaft. BIC-cooling elements have eliminated the high wear of the bricks around the transition area. No problems in these areas have been observed since installation of the new cooling elements.
Figure 2: Design of the FSF at Primary Smelter Aurubis Hamburg
Demolition of the FSF
FSF demolition was known to be the critical path and determining the overall length of the shutdown. The demolition of the FSF was done with several remote-controlled hydraulic hammers. The hammers entered the furnace through the side-wall of the furnace and from the top of the uptake shaft. Several failures of the machines in the uptake, mainly caused by high temperatures, delayed the demolition.
The demolition of the SCF was done with a huge hydraulic hammer and with the application of explosives. Unfortunately, the demolition was severely delayed by about 40 t of bottom build-up in the hearth of the furnace lining. Because of this, the SCF became the critical path for the overall shutdown length.
Figure 3: SCF Metal phases with a thickness of up to 45 cm
Conclusions after Major Repair Shutdown 2013
From the commissioning of the sickle slide gates in December 2011 until the beginning of the shutdown, no significant advantage of the three-hot-two-blowing operation could be realized. Besides infrequent disturbances in other production units, the real bottleneck of the smelter operation was the combined availability of the FSF and the acid plant. In normal operation – also in two-hot-and-blowing mode – the converter section was able to process more matte than the FSF could smelt, or the converter was limited by the available off-gas capacity of the acid plant. After initiating the major repair shutdown, the situation changed. In normal operation the production capacity of the FSF and the acid plant in combined operation is high enough to process significantly more concentrate, resulting in more copper matte. New bottlenecks such as slag discharge capacity, converter processing capacity, availability of the two aisle cranes, casting wheel capacity, etc. have been revealed.
After three months with minor startup problems, the smelter has been running at budget capacity since February 2014.