LIBS – A New Approach on Automating Extraction Machinery in Firedamp Atmospheres

Abstract

The efficient extraction of mineral and coal deposits without the presence of humans has been a topic of special interest within the last years. Reasons for that are various. Among them are the efforts to reduce wear and tear of the equipment as well as to optimize extraction processes and the safety of the personnel.

The Institute for Mining and Metallurgical Machinery (IMR) has researched on various methods for automating shearer loaders. The latest development was a system based on thermal infrared cameras to detect boundary layers in structured seam deposits. This project was conducted in cooperation with a shearer loader manufacturer [1]. Now, the IMR is working on a method for utilizing laser-induced breakdown spectroscopy (LIBS) for boundary layer detection. LIBS is a contact-free method which can determine all elements contained in the surface of any sample in any aggregate state.

The major challenge of LIBS for automating coal extraction processes is the constant possibility of firedamp explosions in underground coal mines. If present in a volumetric percentage of 4-14 % in ambient air and exposed to ignition energy of ≥ 0.28 mJ, methane can explode and additionally initiate a following dust explosion. Lasers utilized for LIBS measurements exceed the limitation by more than 160 times. Therefore, an inherent safe method for LIBS analyses in firedamp atmospheres needed to be developed. The ATEX Directives are a guideline for the design of equipment in explosive atmospheres and played a major role in the development of this device.

The paper will describe the development of a test rig which is utilized for sampling wet as well as dry coal and waste rock samples. It will give an insight into the project in greater detail and will describe the current state of research. The project is funded by the German Research Foundation (DFG) and is tagged with the ID NI 631/2-1.