Grönlutslam och flygaska som tätskiktsmaterial för sluttäckning av sulfidhaltig anrikningssand: Utvärdering efter 5 års användning
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Sweden has a large mining industry compared to the rest of Europe that results in large amounts of mine waste that must be taken care of in an environmentally and economically sustainable way. The mine waste consist of either of waste rock, that is unmineralized/uneconomic that have to be mined for practical reasons to get access to the ore, or tailings, which is a waste product from the enrichment process. The most common oretype to be mined is metal sulfide ore, out of 13 active metal ore mines in the end of 2009 sulfide ore was mined in 11 mines. The sulfide ore often have a metal content of a few percent that results in large amounts of tailings. The tailings are stored in large deposits at the mine site and when the tailings are exposed to oxygen in the air the sulfides in the tailings oxidize. The oxidation of sulfide minerals creates acid mine drainage with high metal content and is considered to be harmful to health and environment. In combination with Sweden’s more and more strict environmental legislation the demands have increased on the mining industry to find good and sustainable solutions to prevent oxidation of sulfide rich tailings. At the same time the heavy industry has become affected by increased costs for landfilling of non-recyclable wastes and has therefore started to search for new alternatives for reusing the waste instead of landfilling it. Two types of wastes that have become interesting to use as cover materials for landfills and tailing deposits are green liquor dregs and fly ashes.To evaluate how green liquor dregs and fly ash ages when used as cover materials in landfills the Rönnskär processing plant and smelter placed two covers on their tailings deposits as pilot study in 2006. One of the covers consisted of green liquor dregs from Smurfit Kappa Kraftliner AB and the other cover consisted of fly ashes from Skellefteå Kraft AB. This study is an evaluation of the two covers after being in use for 5 years.Due to a high water saturation degree both of the covers can be considered to decrease oxygen diffusion to the tailings via air. This has resulted in an oxygen level in the covers to be low according to the mobility of the elements interpreted from the chemical analysis. The covers also have a chemical impact on the tailings where the most noticeable change is the pH. The pH in the tailings under the covers have increased from ca pH 2 to ca pH 3-6 compared to the tailings without cover. The covers also have a negative impact on the tailings where the highest impact is that Zn is leaching from the covers and accumulated in the tailings below.Seen from a technical point of view the green liquor dregs and the fly ashes is not clearly suitable as covers since there are some qualities, for example permeability, that can be improved. But the materials does have several qualities that makes them suitable, for example water saturation degree, buffer capacity etc., and these qualities in combination with how the materials reacts to ageing gives room for additional studies for the purpose of making the materials more suitable to be used as covers.
Place, publisher, year, edition, pages
2012. , 70 p.
Teknik, Grönlutslam, flygaska, tätskikt, anrikningssand
IdentifiersURN: urn:nbn:se:ltu:diva-58312Local ID: ee532738-b001-461a-a8fb-8834609f0649OAI: oai:DiVA.org:ltu-58312DiVA: diva2:1031700
Subject / course
Student thesis, at least 30 credits
Natural Resources Engineering, master's
Hägglund, HansMäkitalo, Maria
Validerat; 20121003 (anonymous)2016-10-042016-10-04Bibliographically approved