An Initial Analysis of Slurry Transportation in Subarctic Environment

Sammanfattning: In today’s economy, it is important to have a sustainable business model where as little as possible goes to waste or finding solutions to create something useful out of by-products. Therefore, LKAB are looking to make a large investment into creating an infrastructure of several plants to turn tailings from the production of iron ore into usable products for several industries which LKAB has designated project ReeMAP (Rear Earth Elements and MonoAmmonium Phosphate). These products include phosphorus used in the production of food, gypsum used in the building industry and fluorine used in the chemical industry. One of the key ingredients in making these products is apatite, a calcium-phosphate crystal which is extracted from the tailings. The plant where the apatite is to be produced will be located close to the mining sites in Kiruna and Malmberget and then transported to the coast. The transportation can be caried out by rail carts which is how the iron ore is transported. Depending on the quantity of apatite that will be transported, a new rail track would need to be built which is a huge investment on top of the investment for the ReeMAP infrastructure. An alternative transportation method for the apatite is to use a pipeline that is pressurized by a series of pumps known as slurry transportation. This method of transporting material has been utilized in many countries around the world as it has shown to be a cost effective and more environmentally cautious method of transportation.  Slurry transportation comes with its own unique challenges, the major ones are making sure the slurry is well mixed and the solid particles do not deposit inside the pipeline and the other is the risk of freezing during a longer system shutdown. This has been studied using Computational Fluid Dynamics analysis in the software ANSYS Fluent. In addition, an overview calculation of the pressure losses to determine the number of pumps needed for the transportation has been conducted. The software ANSYS Fluent Multiphase was used to model the interaction of solid apatite particles with water and determine the volume concentration of apatite inside the pipeline. For the freezing of water inside the pipeline during a shutdown and stationary flow, the software ANSYS Fluent Solidification/Melting was used for the modelling.  The results from the flow model show that the apatite becomes pseudo-homogenous during the transportation, given that the particle size remains within a certain interval, which will deposit the correct amount of apatite at the outlet of the pipeline. The results from the freezing model shows that a shutdown of a few hours is possible without the risk of the water freezing inside the pipeline. With insulation, this time may be extended.