Application of ROTAN magnetic pump in coal tar and coal pitch

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Coal tar and coal pitch – pump solutions that ensure zero leakage and minimal maintenance. Coal tar and coal pitch are usually transported at high temperatures; their vapors are carcinogenic, and the fluid contains small amounts of coke particles. Therefore, pumps used to transport these liquids must be leak-free, seal-less pumps with sufficient resistance to high temperatures and corrosion. Typically, coal tar is transported by cargo ships, where it is then pumped from the ship’s cargo pumps into storage tanks, before being sent to distillation towers for processing. After distillation, about half of the output is coal pitch. In the aluminum industry, coal pitch is used as a raw material for producing electrodes. It is usually circulated in main pipelines using pumps with a diameter of 6 inches (150 mm), while feed to mixers is carried out through pumps with a diameter of 2 inches (50 mm) or 3 inches (80 mm) in the branch pipes. Mass flow meters are installed in the branch pipes, and the feed pumps can be controlled via frequency variation, thereby allowing precise control over the amount of coal pitch supplied. Although this system seems simple, many details related to the reliability and lifespan of the pumps need to be taken into account. The Danish company Koppers is an expert in designing systems for transporting coal pitch. Their systems use ROTAN magnetically driven pumps equipped with tungsten carbide bearings. Today, ROTAN pumps are widely used in such systems across Europe, the Middle East, South Africa, and other regions. If you plan to build a system for pumping coal pitch, choose only professional suppliers with extensive experience in this area. Below we will discuss some of the “details” involved in designing such a system. A complete system should include a storage tank heated at the bottom, with the inlet located in the middle of the tank. The entire inlet pipeline needs to be insulated. The pump needs to be preheated before operation (up to 230°C, using another heating system). If the insulation of the pipeline system is adequate, then no part of the system needs to be heated with oil at temperatures above 250°C. This prevents the formation of “hot spots” that could lead to an excessive amount of coke particles. Two circulation pumps are required in this system (one as a backup). Each circulation pump’s inlet should be equipped with a filter screen with a mesh size of 3 millimeters. However, no filter screen is needed at the inlet of the feed pump. This system is very sensitive to proper preheating and insulation measures. For example, if a valve in the system isn’t properly insulated, the fluid resistance at that valve may increase significantly, even causing the pitch to clump together. We’ve encountered cases where insufficient insulation in the outlet pipes or a poor preheating system led to overload of the magnetic coupling. When pumps need to be used under such conditions, our solution is to run the pump at a frequency of 10 Hz for a few minutes, during which time the “cold spots” can be heated up, allowing the pipes to regain their full flow capacity. After that, the pump can operate normally at a frequency of 50 Hz. Of course, the pipe diameter still needs to be determined based on the pump’s normal operating conditions. The ROTAN pump model used for transporting coal pitch is EDXXXEDK-1U88, and it requires magnetically coupled shafts made of samarium-cobalt material of the highest quality, to ensure sufficient safety margins in case of minor issues in the pipeline system. The pipes of the heating system should be connected using flanges, as tight threaded connections are difficult to achieve in such applications. (Threaded connections are prohibited!) ) Even very minor issues, such as not using the correct method to preheat the piping system, can lead to serious accidents. For example: if you preheat the pump first (you might think this is a good idea, as the center of the pump is farther from the heating system compared to the surrounding pipes), the liquid inside the pump chamber and the pipes adjacent to it begins to melt, but it cannot flow through the pipes because certain sections of the pipes at the pump’s inlet and outlet ends have not yet been heated. The result is shown in the figure below: a damaged seal cover due to excessive pressure, and damaged external magnets. The correct approach is to heat the pipes at the inlet end first, then the pump, and finally the pipes at the outlet end