Authors: Antti Häkkinen, Teemu Kinnarinen, Mehmet Kucuk, LUT University
CHARACTERIZATION AND PRE-TREATMENT OF INDUSTRIAL SIDE STREAMS AT THE FOUNTAINS OF SIDE STREAMS
LOCAL PRODUCERS PREFERRED
There are tens of industrial side streams available in South Karelia; local companies produce a vast variety of ashes, precipitates, sludges, tailings, metal slags and construction wastes. Finnish forest industry has traditionally operated actively in Southeast Finland. It produces large amounts of bioashes, sludges and green liquor dregs and therefore the availability of industrial side streams in the area is good. However, only a small fraction of these side streams has been studied as potential raw materials for new kinds of substances.
The majority of possible raw materials for geopolymer composites were acquired from industry located close to Lappeenranta. The most important sources were biomass boilers, chemical recovery cycles of pulp mills and a local mine that produces large amounts of tailings. After the pre-screening phase, 23 different side streams were selected for more detailed investigations, and 18 of these side streams originated in Southeast Finland. Local production is one of the key aspects in sustainable recycling, because the environmental impacts of transporting raw materials should never exceed the advantages obtained by recycling.
For this reason, we did not have existing paths to follow arising from previous studies and it was necessary for us to start our project by learning to understand the properties of the side streams to be able to reliably predict their suitability as potential raw materials of new innovative composites.
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‘Local’ is a key word for sustainable recycling.
FROM RESULTS TO PRODUCTION The main objective of the characteri-
zation of side streams was to discover what are the different elements and compounds in the side streams and what are their most important physical characteristics. By utilizing the modern selection of analytical equipment at LUT University, it was possible to determine characteristics such as chemical composition, particle size and shape, specific surface area, solubility and heat resistance. In addition to this, numerous close-up images were obtained from the samples using a scanning electron microscope. Some examples of these images are presented in Figure 1. When enough information is collected about the basic building blocks of the geopolymer composites, it is possible to use this information during the actual material development phase as a guideline for making valid decisions. The results from the characterization phase can be considered as a kind of database that enables the producer of the final products to search the background information and then make the adjustments required.
