Some metallurgical reactors employ cooling elements to conduct heat away from refractory linings in order to provide the safe containment and handling of molten slags, mattes, metals, and fused salts. The cooling elements are manufactured of a high thermal conductivity solid having internal channels through which is pumped a cooling medium for the purpose of extracting heat from the refractory lining by the cooling element. When sufficient heat is extracted by a cooling element, it is possible to maintain some thickness of relatively cool refractory or frozen (i.e. solidified) process material in the area of the cooling element. This is important for providing the necessary integrity for the safe containment of molten materials.
The solid material making up the cooling element may typically be copper and the cooling medium is typically water, though other solid materials and cooling media can be used. Such metallurgical reactor cooling elements may include, for example, a copper cooler built into the sidewall of the reactor or a tapblock for removing (or tapping) the molten process material from the reactor.
Cooling elements may comprise a cast rectanguloid copper block with internal channels to allow for the flow of the cooling medium, with refractory material placed between the cooling element and the molten process material in the reactor. The internal channels are typically pipes that are cast into the copper block during manufacture, that are externally connected to the system providing the cooling medium.
Tapblocks are a variant of a typical cooling element, in that there is a channel through the center of the cooling element lined with a refractory material through which the molten process material flows when the reactor is being tapped. The center channel is typically of small diameter, such as 1 to 4 inches, and is plugged with a hard clay material when it is not required to tap molten process material from the reactor. In order for the reactor to be tapped, the clay plug in the tapblock must be removed by drilling or lancing, or a combination thereof, so as to open the channel and allow the molten process material to flow out of the reactor.
Typical operations for a reactor, including tapping, result in the cooling elements experiencing thermal and mechanical stresses that may cause the condition of the cooling element to deteriorate with time, in effect reducing its ability to extract heat from the reactor. This is undesirable as it reduces the level of reactor integrity and safety provided by the cooling elements. If the cooling element performance is deteriorated below an acceptable safety limit, maintenance is required. Major maintenance may involve shutting down the reactor to replace part or all of the refractory in the tapping channel of a tapblock or replacing the complete tapblock, for example. Major maintenance of cooling elements is generally expensive and time consuming, and the time between major maintenance should be extended as long as possible.
In order for operators of the reactor to assess the current operating condition of the tapblock, the temperature and cooling media flow in certain parts of the cooling element may be monitored, for example, by temperature and flow sensing instruments distributed in and around the cooling element. Simulation by computer modeling in the design phase of the cooling element, using, for example, finite difference methods, may determine the expected temperatures and temperature profiles at the temperature sensing instrument locations.
Using computer models, alarm levels may also be established for each of the temperature and flow sensing instruments to determine whether the cooling element is currently experiencing temperatures or cooling media flows that are beyond what was expected during the design stage.
Such modeling involves comparing the temperature and flow readings at each sampled instant in time with pre-defined alarm levels. Generally two different alarm severities are available, denoted by Hi and HiHi (or Lo and LoLo for coolant flow). The Hi alarm is primarily a notification to the operator that the temperature is above the expected normal operating range. This alarm does not necessarily require any remedial action to be taken. The HiHi alarm indicates that the reactor may be experiencing damaging or dangerous temperature levels. If the HiHi level is exceeded, some automatic action may occur, like tripping the reactor breaker to remove power input and starting the process of reducing the temperature of the process material.
These temperature and flow alarms only provide an indication of temperature or flow excursions outside of what is considered desirable, and do not distinguish between the different particular conditions that could cause a temperature excursion, such as refractory wear, high process operating temperatures, or the deteriorating thermal or mechanical performance of the cooling element.
The described embodiments seek to address or ameliorate one or more shortcomings or disadvantages associated with existing means and methods of assessing the condition of a metallurgical reactor cooling element.