Bulk material handling for melting operations frequently leads to complaints from neighboring residents or businesses, who are reacting to precipitants in the surrounding air.
In addition to posing a hazard to the residents, managing the dust may become very costly for the plant that is perceived to be the source. It may be expensive, as well as annoying, for a company to be held liable for damages that it has not caused, simply because the source of the emissions cannot be clearly identified.
|Three measuring stations situated on the plant site recorded heavy dust emissions with westerly winds (green arrows) during the hours indicated on the top graph. The wind speed is plotted in the lower graph. |
The ADIM3 system developed by the Metal Consulting Agency (www.kva-international.com/index.php/en.html), measures and documents emissions in such a way that emission sources are “unequivocally” identified — so targeted countermeasures can be taken.
Dust emissions are unavoidable during handling and processing of bulk materials. For example, at transfer stations for coal and ores, during crushing and transporting of slag, in steel mills or foundries, among others. The causes of these emissions must be eliminated as much as possible.
To date stationary or mobile measuring instruments have been able to deliver only cumulative day values for the dust fall ,or at best hourly averages. Often, these data are not reliable or acceptable for documenting the source of an emission. As a result, the plant operators are unable to take targeted countermeasures and eliminate the reasons for complaints. In particular, short-time events are affected, for example, events such as loading and unloading of trucks or ships, vehicles driving gravel roads, operations in constructionwaste recycling, and various other examples.
The new ADIM3 system (Automated Dust Immission Measurement) has already proven successful in coal and ore handling operations. It takes continuous weight measurements of the dust contained in the air and sends the measured values to an evaluation and monitoring module, which indicates the current dust load. In this way it is able to document short-time events reliably, such as loading/unloading of a truck or slag treatment operations. The system computes the source and quantity of the emissions through a flow-dynamic simulation of the dust transport based on meteorological data, such as wind direction and speed.
Video recordings by cameras installed at suitable positions on the site help to identify emission sources. In one case at a steel mill, it was possible to see that under certain conditions heavy momentary emissions of dust occurred during slag treatment. The operator eliminated the emission source – and avoided future complaints simply by installing common spray nozzles.
Another operator was to use the ADIM3 system to prove that a certain emission did not originate from its operations. This relieved the company from the obligation of cleaning and painting several dozen vehicles — and returned the investment.
ADIM3 dust monitoring is based on the process of direct deposition. The dust falls through a funnel onto gel-covered discs, the weight of which is measured by a scale calibrated to +/- 1 mg, or an emission of +/- 10 mg/m″/day.
The system contains up to 32 discs. These discs are inserted into the scale at defined intervals by an automatic transport mechanism. The fact that the discs are retained inside the measuring unit provides the basis for reliable, long-term documentation of emissions. Moreover the discs do not require daily replacement.
While the initial commercial applications in basic manufacturing have been made at steelmaking plants, the developers are optimistic about its prospects in foundries. According to a source, “This topic is of great interest for foundries, as during unloading of the molding sand and knocking out of the castings from the molds large amounts of dust arise. This dust is often laden with furan resins. Therefore, German foundries have signaled much interest in the new system. According to our information, the European Union is working on a new dust-pollution standard for foundries, setting limit values for allowable dust emissions. Therefore, it will become necessary to measure the dust load.”