Self-heating in acid-producing alum shale

Alum shale is a Cambro-Silurian sedimentary rock commonly found in the Oslo area. When alum shale is exposed to an oxidizing agent (air) and water, sulphides in the rock oxidize with time and may produce acid, possibly resulting in acid rock drainage (ARD). This can cause problems for buildings and infrastructure due to swelling and acid attacks on materials. The release of acidic water, enriched in heavy metals, and naturally occurring radionuclides can affect the downstream environment. Furthermore, the reactions are exothermic, leading to heat production.

Self-heating in piles of alum shale is well-known but not well understood. If there is sufficient access to oxygen and humidity, large piles of alum shale self-heat and smoulder. This is a potential problem with the storage of such masses and can also cause issues with permanent disposal.

In large construction and infrastructure projects in the Oslo area, alum shale is commonly encountered. The Norwegian Public Road Authorities (Statens Vegvesen) has experience with self-heating in alum shale and will contribute with experience and data in a potential master thesis.

Norsk avfallshåndtering (NOAH)'s disposal site for hazardous waste at Langøya receives black shale for disposal and has previously conducted experiments to investigate issues around self-heating. They are interested in more knowledge about this topic and a master thesis can be done in collaboration with NOAH and with access to their resources.

Project aims
The aim of this MSc project is to investigate the self-heating mechanisms in alum shale. Of special interest is the identification of key parameters allowing heating and potential mitigating measures.

The exact content of the master thesis will be defined in discussions with the student but will likely include studying known cases of self-heating. Other possibilities include experiments on relevant masses in collaboration with NOAH, possibilities for modelling the processes and thermodynamic calculations to investigate the exothermic reactions responsible for the self-heating.

Using knowledge from other types of waste where self-heating is a known problem, such as piles of coal or wood chips, can also be useful to illuminate important parameters.

The master's student will have a supervisor from the Norwegian Geotechnical Institute and the project will be in collaboration with the Norwegian Public Road Authorities and NOAH. Since there are several possible scopes of the MSc work this project suits students with a background in geology or chemistry.

What will you learn
This thesis is suitable for students who are interested in learning how to perform geochemical experiments, perform chemical and mineralogical analyses (e.g. XRD, ICP, XRF) to interpret the results. You will learn about environmental geology on a topic that is relevant all over the world.

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Fig. 1 Alum shale formation at Kleggerud, Jevnaker. Photo: Skanska AS. Click here for a bigger version.


Tags: Svartskifer, varme, avfall
Published Sep. 22, 2022 9:34 AM - Last modified Sep. 22, 2022 2:26 PM

Scope (credits)