Retreatment of Polymer Wastes by Disintegrator Milling

Global introduction of waste utilization techniques to the polymer market is currently not fully developed but has enormous potential. Before reintegration of used material into a new product, it normally requires grinding, that is shredding, crushing, or milling. In traditional grinders, the generated stresses in the material to be ground are equal to or less than the strength of the material. If by traditional methods, the stresses generated are compressive + shift, so by milling based on collision are tension + shift. Due to the high stress-material strength ratio at collision, it is possible to crush not only brittle materials but also ductile materials. This process allows easily combining the grinding of composite materials with their separation into individual constituents. In the current study, the mechanical recycling of the following groups of polymer materials was studied: pure brittle and soft polymers (PMMA, HDPE and IER), blends of plastics (ABS+PMMA, PC + ABS), reinforced plastics (PMMA+GFP); elastomers (rubber and tyres), and printed circuit boards (PCB)

STUDY OF THE APPLICATION OF PELLETS FROM TEXTILE MATERIAL WASTE AND BIOMASS MIXTURE IN INDUSTRIAL AND RESIDENTAL HEATING SYSTEMS

The efficient waste management hierarchy is based on four priorities, reuse, recycle, energy recovery, deposit.Efficient energy recovery from non-recyclable textile materials (waste to energy) principles we study in this paper. Energy recovery from the fuel pellets consisting of waste textile materials and biomass depends on many factors. One of the main is to create a competitive form for the newly offered fuel (pellets from a mixture of biomass and textile), as well using a new generation of small-scale energy production facilities. Using already existing applications for efficient waste management is one of the circular economy aspects we lay on in this paper.Roughly estimated that the quantities of textiles separately collected will increased from 65 000 to 90 000 tons per year across the EU-27 from 2025. Reuse and recycling outlets will need to be created, as the current sorting and recycling capacities are not sufficient to process the anticipated volumes. However, it is also expected that at least half of these additional volumes will comprise non-reusable textile waste with specific flame retardant (FR) treatment. It is known that flame retardant is hazard by its adverse environmental impacts of FRs in their production and disposal phases.The objective of the paper is to review opportunities of elaboration a new type of the fuel pellets, and using them in industrial heat pellet boilers and combined heat and power CHP systems.Elaborated the new pellets from biomass (prepared by plasticization method) and chopped textile waste sized till 2-3 mm (by method separative milling) were tested in controlled combustion processes.Experiments were carried out by adding different proportions of textile waste to biomass pellets and the results obtained are summarized in the article

Selective Disintegration–Milling to Obtain Metal-Rich Particle Fractions from E-Waste

This research was supported by ERDF project no. 1.1.1.1/20/A/139 “Development of sustainable recycling technology of electronic scrap for precious and non-ferrous metals extraction”. The project was co-financed by REACT-EU funding to mitigate the effects of the pandemic crisis. The article was published with the financial support from the Riga Technical University Research Support Fund. This research was also supported by the Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Program H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2. The authors would also like to mention the support from the “Innovation Grants for Maritime Students” performed at Latvian Maritime Academy (project no: 1.1.1.3/18/A/006, funded by the European Regional Development Fund—ERDF, Republic of Latvia).Various metals and semiconductors containing printed circuit boards (PCBs) are abundant in any electronic device equipped with controlling and computing features. These devices inevitably constitute e-waste after the end of service life. The typical construction of PCBs includes mechanically and chemically resistive materials, which significantly reduce the reaction rate or even avoid accessing chemical reagents (dissolvents) to target metals. Additionally, the presence of relatively reactive polymers and compounds from PCBs requires high energy consumption and reactive supply due to the formation of undesirable and sometimes environmentally hazardous reaction products. Preliminarily milling PCBs into powder is a promising method for increasing the reaction rate and avoiding liquid and gaseous emissions. Unfortunately, current state-of-the-art milling methods also lead to the presence of significantly more reactive polymers still adhered to milled target metal particles. This paper aims to find a novel and double-step disintegration–milling approach that can provide the formation of metal-rich particle size fractions. The morphology, particle fraction sizes, bulk density, and metal content in produced particles were measured and compared. Research results show the highest bulk density (up to 6.8 g·cm−3) and total metal content (up to 95.2 wt.%) in finest sieved fractions after the one-step milling of PCBs. Therefore, about half of the tested metallic element concentrations are higher in the one-step milled specimen and with lower adhered plastics concentrations than in double-step milled samples. © 2022 by the authors.--//-- This is an open access article Blumbergs E., Serga V., Shishkin A., Goljandin D., Shishko A., Zemcenkovs V., Markus K., Baronins J., Pankratov V. "Selective Disintegration–Milling to Obtain Metal-Rich Particle Fractions from E-Waste" (2022) Metals, 12 (9), art. no. 1468, DOI: 10.3390/met12091468 published under the CC BY 4.0 licence.Latvian Maritime Academy (project no: 1.1.1.3/18/A/006); ERDF project no. 1.1.1.1/20/A/139; REACT-EU; Institute of Solid-State Physics, University of Latvia has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2

PERFORMANCE EVALUATION OF CEMENT MORTAR AND CONCRETE WITH INCORPORATED MICRO FILLERS OBTAINED BY COLLISION MILLING IN DISINTEGRATOR

This research focuses on natural quartz and natural quartz-limestone sand mechanoactivation with the high energy milling by collision in disintegrator using different energy rates (8.4 and 25.2 kWh/t) and its application effectiveness as microfiller in Portland cement composites. The obtained microfiller was used to partially replace sand in mortar and to partially replace cement in high performance self-compacting concrete (SCC). The activity factor of disintegrated microfillers in time was investigated to detect the potential changes of sand particle properties during milling and the subsequent storage. XRD, BET, morphological investigation and grading analysis was performed for disintegrated sand. Mechanical, physical and durability properties regarding to chloride penetration and freeze-thaw resistance were determined to prepared cement composites. The results indicate that cement mortar which was prepared with disintegrated microfillers right after their disintegration provides compressive strength increase up to 20% comparing to the reference mixture and the time factor has significant effect on the activity of disintegrated sand. The SCC strength slightly decreased, if cement was replaced by the disintegrated sand up to 15 wt%, while the results of durability test indicate that resistance to freeze-thaw damage and chloride penetration could remain in the level of the reference mixture

Mechanical and Pyrometallurgical Recycling of Electronic Wastes

In this paper, the mechanical milling of the electronic wastes was carried out. The metal parts and plastic parts were roughly separated. The final plastic powder size could be as small as ∼100 μm. Then the pyrometallurgical recycling Printed Circuit Boards (PCB) was executed. The mechanisms of thermal degradation and combustion are investigated using TG/DTA and MS. Some chemical powders, such as Na2CO3, NaHCO3, NaOH and CaCO3 are used to control the exhausted toxic gas such as Br2

Metal-Matrix Hardmetal/Cermet Reinforced Composite Powders for Thermal Spray

Recycling of materials is becoming increasingly important as industry response to public demands, that resources must be preserved and environment protected. To produce materials competitive in cost with primary product, secondary producers have to pursue new technologies and other innovations. For these purposes different recycling technologies for composite materials (oxidation, milling, remelting etc) are widely used. The current paper studies hardmetal/cermet powders produced by mechanical milling technology. The following composite materials were studied: Cr3C2-Ni cermets and WC-Co hardmetal. Different disintegrator milling systems for production of powders with determined size and shape were used. Chemical composition of produced powders was analysed.  To estimate the properties of recycled hardmetal/cermet powders, sieving analysis, laser granulometry and angularity study were conducted. To describe the angularity of milled powders, spike parameter–quadric fit (SPQ) was used and experiments for determination of SPQ sensitivity and precision to characterize particles angularity were performed. Images used for calculating SPQ were taken by SEM processed with Omnimet Image Analyser 22. The graphs of grindability and angularity were composed. Composite powders based on Fe- and Ni-self-fluxing alloys for thermal spray (plasma and HVOF) were produced. Technological properties of powders and properties of thermal sprayed coatings from studied powders were investigated. The properties of spray powders reinforced with recycled hardmetal and cermet particles as alternatives for cost-sensitive applications were demonstrated.DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1348</p