Cord Fricke-Begemann

Fast single piece identification with a 3D scanning LIBS for aluminium cast and wrought alloys recycling

In industrial recycling processes secondary metals need to be separated by material grades before they can be further processed. The identification and separation into different material classes lead to higher value-added industrial feedstock and prevent downgrading processes. Secondary raw materials can be used more efficiently resulting in an increased use of waste products in resource-intensive production processes. Laser-induced breakdown spectroscopy (LIBS) offers a contact free, multi-elemental and fast method for the inline quantitative analysis of single objects in moving particle streams. The LIBS method presented in this paper is based on a 3D object detection combined with a scanning LIBS setup. The optical system consists of a pulsed Nd:YAG laser running at 40 Hz, delivering a 200 mJ double pulse for plasma generation. A high performance three axis galvo-scanner guides the laser beam onto single pieces moving at 3 m s−1 through a measuring volume of 600 × 600 × 100 mm3 with a precision of ±1.5 mm. Twenty channels of a high resolution Paschen–Runge spectrometer are simultaneously processed within a few microseconds enabling multi-elemental analysis of different aluminium (Al) alloys. A dimensionless figure of merit is introduced for the evaluation of the analytical performance. Sorting measurements of Al post-consumer scrap charges, consisting of wrought and cast alloys were carried out. After discarding 20% of the data as outliers low and high silicon alloyed Al pieces were identified with a correctness of >96%. In a second sorting scenario the analytical discrimination of 8 different Al alloys of production scrap, requiring high analytical precision, is investigated. A mean identification correctness of wrought Al alloys >95% is demonstrated successfully for the first time.

Size-resolved analysis of fine and ultrafine particulate matter by laser-induced breakdown spectroscopy

In emissions originating from industrial processes, elemental concentration characteristically depends on particle size. Therefore, not only is the average chemical composition of the particles in the focus of interest but also their size-dependent composition. For industrial applications such as on-line process control, a system using laser-induced breakdown spectroscopy (LIBS) is developed providing the analysis of particulate matter directly in an air stream with a short response time to changes in elemental composition. By using a co-flow in addition to the aersosol flow the time resolution of the system can be enhanced. Investigations are undertaken concerning properties of the laser plasma, the analysis of monodisperse and polydisperse aerosols with regard to the relative elemental concentration and the mass concentration of the particles. The system can be calibrated to either total elemental concentrations or relative compositions. The signal response to a variation of elemental concentration as well as to the particle mass concentration show kinds of saturation effects. Temporal plasma evolution for CaCl2 particles and pure argon are investigated. Different decay times for argon and the particle matter depending on the origin of lines within the plasma are observed. Electron density and temperature are determined using Ca emission lines to describe the temporal evolution of the plasma state for the particle analysis. It has been observed that the electron density increases rapidly for plasma temperatures above 10 000 K. Size-resolved analyses of particles in the size range from 20 nm up to 800 nm are carried out. It has been found that the signal response correlates with the mass distribution of the particles.

Stand-Off Detection of Surface Contaminations with Explosives Residues Using Laser-Spectroscopic Methods

Laser-spectroscopic methods have a high potential for the remote detection of surface contaminations with residues of explosives, since they can operate contactless, fast and sensitive. Laser-induced breakdown spec- troscopy and Raman spectroscopy are two versatile methods which can be employed to identify a wide variety of materials and for which stand-off op- eration has been demonstrated. Since both methods provide complementary spectroscopic information while using a similar instrumentation they can be combined to further increase the selectivity and sensitivity as necessary for security applications.

LIBS analyses for industrial applications : an overview of developments from 2014 to 2018

Measuring distances in the range between a few centimetres and a few metres are of special interest for automated industrial LIBS applications. They allow for a reliable optical access to measuring objects in a process line under harsh industrial environments. In that range a compromise can be found between the conflicting requirements with respect to the protection of the optics facing the measuring object on one side, and sufficiently high laser irradiance and high receiving solid angle of the measuring radiation on the other side. A concise overview about LIBS studies published in the last four years focusing on industrial applications or perspectives therefore is given. Recent RD (b) sorting of refractories; (c) identification of steel blooms in a rolling mill; (d) inverse production scenario for the recovery of valuable materials from end-of-life electronic equipment. For measuring distances of only a few centimetres the size of a LIBS instrument can be downscaled significantly allowing to set up handheld LIBS analysers. Whereas the precursors of such concepts were studied already more than fifteen years ago, quite recently a competitive market arose where various models of handheld LIBS systems are offered. Industrial application fields are mainly positive material identification of metals and sorting of light metal scraps for recycling purposes. A comparative synopsis of features of these LIBS systems will be presented and arising research themes in this context are outlined.