Background Information K+S Challenge

Transcription

1 Experience growth. Brine Challenge Background Information K+S Challenge

2 About K+S K+S considers itself a customer-focused, independent minerals company for the Agriculture, Industry, Consumers, and Communities segments and wants to grow the EBITDA to 3 billion by Our approximately 15,000 employees enable farmers to provide nutrition for the world, solutions that keep industries going, improve daily life for consumers and provide safety in the winter. We continually meet the growing demand for mineral products from production sites in Europe, North and South America as well as a worldwide sales network. We strive for sustainability because we are deeply committed to our responsibilities to people, the environment, the communities and the economy in the regions in which we operate. Learn more about K+S at 1

3 Potash and Magnesium Products Production Sites in Germany Potash mining in the Werra Fulda Region Kassel Potash Seam Hesse Share of annual production capacity (in %) 1. Wintershall 2. Unterbreizbach Integrated Werra Plant ~ Hattorf 4. Zielitz ~ Neuhof-Ellers ~ Sigmundshall (until ) ~ Bergmannssegen-Hugo ~ 5 (pure production site, no mining) Potash Seam Thuringia 2

4 Waste Management The mined raw materials only contain a limited share of valuable resources (max. 30%), therefore the tailings formation is inevitable. This challenge is shared among all potash producing companies in the world! The reutilization of tailings is performed as effective as possible. The techniques and the technology of constructing tailings piles (heaps) are proved and tested. In total 4 different ways of disposing solid and liquid tailings are used world wide: Tailings piles Underground disposal River injection Deep well injection These ways of disposal - depending on the corresponding site - are used also in combination. They currently represent the best available technique. 3

5 Aim of the challenge The goal is to find materials, coatings or any other material technology that can strongly reduce the brine production and/or protect the tailings from rainfall. The solutions ideally allow for permanent reduction/elimination of brine run-off. Currently K+S is developing and applying different techniques to cover potash tailings piles that are still operated. The approaches are further described below. One of these approaches is currently under further development for an application at the Werra site. We see this approach as a viable solution to the challenge of brine reduction but we want to seek alternative techniques that might be applicable. 4

6 Tailings piles K+S currently operates six large tailings piles at different sites. This challenge focuses on the two tailings piles operated at the Werra Site. For the challenge consider that the tailings piles are still operated during covering measures (the tailings piles are expanding in one direction). Characteristics of the piles: - Large dimension (some piles cover more than 100 ha) - Large heights (some are more than 200 m above ground) - Annual formation of approximately 620 liter brine per m² - Steep and long slopes approximately Slope length > 400 m Example of tailings composition 5

7 Structure and movement of the piles The tailings pile structure consist of two different natural formed structural elements: a high density core structure and a mantle structure of a lower density. The tailings pile shows a viscoplastic behavior, meaning that over the time it will lose height but will expand in width. This movement does not occur equally to all sites, certain areas are subject to movement more than others. Therefore covering measures need to be able to cope with these movements for example by showing a certain flexibility. mantle core 6

8 Vicoplasticity and solving of the tailings piles Dissolving of the salt as well as the movement of the tailings will lead to the failure of any inflexible cover as depicted here (concrete like cover tested at the Zielitz site). Testing has shown that non-flexible covers will fail sooner or later. Local structures might lead to the dissolving of salt. This should be avoided due to work safety. 7

9 Brine forming due to rainfall rainfall tailings pile basal structure collecting ditch collected brine solution Rainfall on potash tailings piles leads to the formation of salt brines, by solving the excavation residues. These brines need to be collected in ditches at the base of the tailings piles and properly disposed A small part of these brines percolates within the underground of the tailings pile. To minimize percolation a basal structure below the tailings is applied where possible, and further developed beyond the current best available technology. (not depicted in the following schemes) 8

10 Brine Reduction by Covering One way to reduce brine formation is by covering the pile Aim of the cover: Reduction of the amount of brine water, that needs to be disposed Depending on the location the aim is to reduce the amount of brine water up to the possible maximum by ideally creating a maintenance free tailings pile. 9

11 Current covering approaches K+S is using and/or developing several techniques to cover potash tailings piles to reduce the amount of brine solution formed by preventing rainfall from having contact with the salt deposited. The idea is that a cover is either preventing the contact by collecting and disposing the fresh water or by using evaporation or evapotranspiration to minimize the brine forming. Vegetative as well as non-vegetative covers are a way to reduce the amount of salt being dissolved. In the following slides the different solutions that are currently being used are described. Several other techniques have been tested as well and have created a picture of the limiting factors that have to be considered when covering large tailings piles. 10

12 Existing Approaches: Vegetative Covers 1. Direct vegetation: Old and rather small tailings piles, where insoluble materials (like anhydrate) have enriched on the top layer, can be vegetated directly. This technique is an exception since it requires a certain composition of the tailings, which is not given at most of the sites. However there are few examples where this technique was used. The approximate efficiency of this cover is an evapotranspiration rate of 30%. 111

13 Existing Approaches: Vegetative Covers 2. Common covering: Small to medium sized tailings piles can be covered using common soil materials and/or recycling materials from construction or deconstruction works. Similar techniques are used to cover waste disposal sites. Since there is a difference between the slope angle of the salt deposits and the soil materials, large amounts of material are required and the technique leads to a rather high land use. Therefore this technique is not suitable for the covering of large tailings piles. The approximate efficiency of this cover is an evapotranspiration rate of 80%. Enormous land use is required for covering with soil material due to different slopes. 12

14 Existing Approaches: Vegetative Covers 3. Thin layer cover: This technique was developed to cover large tailings piles. A layer (several meters) of soil and/or soil like materials (recycling materials) is conditioned with a pozzolan (binding) additive and then applied almost hang parallel to the tailings pile. This approach is being applied at the Sigmundshall Site. The same approach is under development for the Werra Site using different materials. The approximate efficiency of this cover is an evapotranspiration rate of 80%. Extra land use is limited to only a few meters. 133

15 Existing Approaches: Non-Vegetative Covers 4. Technical evaporation cover: Technical evaporation covers use the solubility of the salt to enrich a thin cover at the top layer of the tailings piles. Additives are added to the newly produced salt tailings (usually within the last top 10 meters of salt that is deposited). The insoluble additives enrich on the top layer after the salt is dissolved (same effect that is used at the direct vegetation, by artificially raising the amount of insoluble material). Water retention and evaporation rate are raised compared to the salt tailings. The approximate efficiency of this cover is an evapotranspiration rate of 50%. A follow up vegetation might be possible. 144

16 Existing Approaches: Non-Vegetative Covers 5. Temporary ponds at plateau areas: At plateau sites it is possible to build temporary ponds to collect rainfall. By using synthetic liners to build pond structures 100% of the rainfall within the covered area can be collected before solving any salt. However these measures are only temporary due to the life span of the used materials. 155