Colloquia

Summary

The world is experiencing a transition to sustainability, which is evident from the increasing use of renewable energy technologies and the rise of the circular economy. The circular economy is a major field which accounts for the generation of valuable products either from waste streams from industries or by recycling used materials and products. Waste paper sludge, for example, is such a waste stream in the paper industry, in which minerals (CaCO3) can be recycled. This is done by Alucha Recycling Technologies, by using a pyrolysis and fluidized bed combustion process. The minerals can be reused in the market as fillers in various products, including plastics, paints, rubber and paper.

This research focuses on the fluidized bed combustor. The minerals obtained from the process are used as bed material in the reactor. The particles have ultra-fine particle diameters, Geldart group A or C (d_ST=1.28 micro m). It is not yet known how this group of particles will fluidize. In this report, the fluidization behavior of Alucha’s particles is investigated, based on theory and experiments with a lab BFB scale setup. These results have been combined to create a fluidization behavior model. In addition, a solution to improve the fluidization using oscillating superficial gas velocity is investigated. The oscillating superficial gas velocity will overcome the problems during a run of the BFB, such as agglomerations and channeling. 

The model, based on data from the lab BFB, is translated to the behavior in the pilot BFB (60kg/hr production capacity), to research if the model is also valid for larger setups. In the future, a demo plant with a production capacity more than ten times the capacity of the pilot plant will be build. Data is gathered by running the pilot BFB and is analyzed and compared with the results of the lab BFB. As a result, it is easy to scale up from pilot to demo plant, because the fluidization behavior can be predicted.

Lastly, a theoretical heat transfer model of the pilot BFB is developed to keep the bed temperature below 500 degree C. This will prevent the calcium carbonate from decomposing, rendering it unusable as fillers. The heat transfer model is used to check if the in-bed heat exchanger and cooling wall in the pilot BFB setup have sufficient capacity. The heat transfer model can also be used for the cooling settings during a run.