zinc mine operation, UPR, ecoinvent 3.6, Allocation, cut-off
Reference product: sand [kg]
Location: GLO - Global
The multi-output "zinc mine operation" process includes all steps required to produce zinc concentrate (59% Zn by mass), namely mining, comminution, and flotation. The dataset describes the production of zinc concentrate and additional co-products, primarily lead concentrate. Data is based on a study undertaken by the International Zinc Association (IZA) in conjunction with thinkstep (the LCA practitioner) for reference year 2012. Participating companies provided annual primary data on inputs and outputs for each process step, which was aggregated into a single production-weighted dataset. Zinc concentrate is most often used as an input to zinc smelting, either electrometallurgical smelting or the less common pyrometallurgical smelting.
The below image presents the system boundary in relation to the primary product, zinc concentrate.
[To see the image, please follow the link https://db3.ecoinvent.org/images/2b83c8d3-c779-4e64-98f4-60d91c5dd741]
[This dataset has been generated using the system model "Allocation, cut-off by classification". A system model describes how activity datasets are linked to form product systems. The allocation cut-off system model subdivides multi-product activities by allocation, based on a physical properties, economic, mass or other properties. By-products of waste treatment processes are cut-off, as are all by-products classified as recyclable. Markets in this model include all activities in proportion to their current production volume.
Version 3 of the ecoinvent database offers three system models to choose from. For more information, please visit: https://www.ecoinvent.org/database/system-models-in-ecoinvent-3/system-…)]
The technological representativeness of this dataset is considered to be high as mining and concentration methods for zinc are consistent in all regions.
Mining
The mining of zinc ore includes underground and open cast mining processes. Within the global zinc industry, about 80% of zinc ore comes from underground mines and 20% from open pit or combination mines.
- Underground Mining: Access is via vertical shafts or inclined roadways. There are usually two access routes (one for mining personnel and materials, and one for the ore) for safety and for ease of ventilation (fresh air comes in one and is then exhausted out of the other). These are permanent structures and therefore require strong roof supports (often including 'bolts' into the rock to tie the layers together for strength). Once at the correct depth has been reached, horizontal tunnels are driven to reach the ore deposit. These are often temporary, so the support requirements are less substantial. Transport for personnel and materials can be by train, truck or conveyor belts. The largest share of the consumed fuels is diesel followed by electricity. Other major inputs include explosives and water.
- Open Pit Mining: Hard-rock surface mining usually includes drilling, blasting, or a combination of both processes, and then lifting of the broken ore either into trucks or onto conveyors for transportation to the processing plant. This lifting is usually by excavator (electric or hydraulic; with shovel or backhoe configuration) or front-end loader.
Benefication (Comminution and Flotation)
Zinc ore is milled and mixed with water to recover a fine concentrate by gravity and elutriation techniques, creating a slurry. The separation process of the metal from the slurry is realized through the addition of various floatation chemicals.
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