HERZOG Recycling

HERZOG offers sample preparation solutions specially tailored to the specifications of the recycling industry. End-of-life processes for recovering valuable components are playing an increasingly important role in the value-added chain of industrial production. At the same time, product-related waste streams of, e.g., WEEE (waste lelctrical and electronic equipment) are increasing. This development is associated with unique quality control requirements towards the recycling process with respect to sample preparation and analysis.

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Sample preparation solutions for the Recycling industry

DetailsTo sample preparation steps

Sample preparation solutions for the Recycling industry

Recycling

HERZOG offers sample preparation solutions specially tailored to the specifications of the recycling industry. End-of-life processes for recovering valuable components are playing an increasingly important role in the value-added chain of industrial production. At the same time, product-related waste streams of, e.g., WEEE (waste lelctrical and electronic equipment) are increasing. This development is associated with unique quality control requirements towards the recycling process with respect to sample preparation and analysis. To some extent, these are different from processes found in other primary industries. Specific aspects of assaying recycling material are:

1. Exposure to potentially hazardous EOL materials has to be minimized. Therefore, in these cases, automation of partial preparation steps or the complete process is an approach to reduce exposition of operational personnel.

2. Aiming at obtaining representative analysis results requires frequent sampling of the inherently inhomogeneous source material. This causes a significantly increased sample load and multiplication of preparation procedures in the laboratory. Laboratory automation allows to build efficient and cost-effective processes.

3. Reproducibility and consistency are the main conditions for establishing a trustful cooperation between business partners and enabling smooth business transactions. Process standardization and automation are the key enabler for reproducible and consistent analysis results.

4. Material loss and cross-contamination during sample preparation have to be avoided, especially for procedures involving PMs, PGMs and other valuable materials. Measures have to be taken for preventing material waste and effective cleaning between each sample batch.

HERZOG components are designed to comply with the stringent technical and analytical requirements of the recycling industry.

Waste Electrical and Electronic Equipment (WEEE) Recycling

Electronic scrap (e.g. circuit boards, batteries, cell phones) is one of the fastest growing secondary metal streams in the world. End processing of the more complex components of WEEE commonly occurs in integrated copper smelters. These smelters use non-ferrous extractive metallurgy to separate complex fractions into their constituent metals. Sampling and assaying are necessary in order to determine the composition and content of precious metals in the e-waste stream, and to ensure that the optimum process is used to recover precious metals. With high metal values and the complex range of forms, these materials present many analytical challenges.
The wide variety of different raw materials requires high adaptability of the sample preparation process in the lab. All machines are designed to set the optimum parameters for each material. At the same time, components are tweaked to minimize material loss and contamination. To this end, HERZOG uses special cleaning mechanisms and coatings for all surfaces coming into contact with the material.

During the recycling process, differing materials like escrap, concentrates, and sulfates are assayed. The specific sample preparation procedures may vary from plant to plant. For escrap, after shredding and sampling, increments are usually incinerated to eliminate plastic content. Following removing of ash the material is fused with aluminum or FeS flux to provide a homogenous matrix which allows fine grinding and final sample preparation. Integral steps of sample preparation are separation of material in specific grain size fractions, crushing, coarse and fine grinding, homogenization, representative splitting, and bagging. For concentrates, particular characteristics like, e.g., low fluidity and high adhesiveness have to be considered and machine parameters to be adjusted accordingly. All sample pathways and parameters like, e.g., exact weights are automatically logged and can be reviewed using the HERZOG PrepMaster.
HERZOG can call on vast experience in sample preparation of recycling material. In our test center we can figure out the optimum preparation for your specific material. Take advantage of our knowledge and step into the automation of sample preparation with all its benefits.

Catalytic Converter Recycling

Automotive catalysts were introduced in the 1970’s to reduce harmful atmospheric emissions. Today, three-way-catalysts are able to decrease the emission of carbon monoxide, hydrocarbons and nitrogen oxides. Those compounds are captured through the catalytic properties of precious metals like platinum, rhodium and palladium. Due to the rising demand, their monetary value and the beneficial environmental influence, PGM have become an important part of industrial processes. Automotive catalysts are generally composed of ceramics. These ceramics are loaded with precious metals which are located on the wash coat. About 50-60% of the precious metals contained in catalysts are recycled worldwide. To achieve recycling rates of spent catalysts of up to 98%, milling, sampling and refining have to be done with modern technologies.

Recycling of spent catalysts is mainly based on pyrometallurgical processes using plasma-type furnaces and top submerged lancing (TSL) furnaces. The catalyst carrier material like alumina, silica and magnesia has major impact on the slag liquidus temperature, furnace function and metal recovery rate. Simultaneously, even small iron slag concentration requires significantly higher furnace temperatures. Precious metals are collected in metal phases and subsequently further refined.
It is well known that deficient sampling and sample preparation can have high financial impact. Therefore, during sub-sampling of the primary lot the integrity of the sample has to be preserved. Additionally, the high prices for precious metals require an analytical accuracy of at least 0.02 %. Representative sampling and sample preparation are also crucial because the PGM credit is an important part of the contract between the refinery and the raw material supplier.
Samples from automotive catalysts are commonly analyzed by AAS, ICP-OES and XRF. Wet chemical sample preparation is time consuming and, due to its complexity, not suitable for industrial applications. For these reasons, samples of catalytic materials are prepared preferentially as pressed pellets. The analysis of pressed powders requires a particle size, which is at least smaller than 70 µm. Crucial for analytical accuracy is the reproducibility of sample preparation to match the matrix of the calibration samples. Additionally, sample loss and cross contamination has to be minimized. Recovering the whole sample is important by the fact that ceramic dust is enriched with PGMs by the factor 2-3.

Catalyst

The fine powdered catalysts are sensitive for re-agglomeration. Therefore, the parameterization for grinding has to be versatile and steplessly adjustable.
Before analysis, the catalyst needs to be dismantled and the steel shell must be removed. Afterwards, the whole carrier is prepared for analysis. The monolith has to be crushed and pulverized down to a suitable size. This can be done with a special mortar crusher (HP-C/M AUT) and an automatic mill like, e.g., the HP-MA. Sometimes drill cores are additionally taken from catalysts. The size of a catalytic monolith can be quite variable so that the automatic mill must provide a batch processing function to allow a convenient and reproducible sample preparation. The automatic mill is either directly connected to an automatic pellet press and spectrometer or provides a magazine for the fine ground samples.
The HP-C/M AUT is a crusher especially designed for automotive catalyst. Entire monoliths can be crushed down to a particle size suitable for fine grinding. The material loss is reduced to a minimum. The material recovery in the HP-C/M AUT is substantially more than 99%. Rigorous cleaning prevents contamination of subsequent samples.

HP-MA: Automatic pulverizing mill

The automatic mill HP-MA is especially suitable for preparing precious metal bearing materials because the machine offers various cleaning options to avoid cross contamination. Three cleaning features namely compressed air, sand cleaning and wet cleaning allow a sufficient material removal. Using the different cleaning functions, cross contamination can be reduced to a low ppm-level. Furthermore, spoon sampling during the material input provides the possibility to pre-contaminate the grinding with the following sample. The final particle size after ± 30 seconds of milling is commonly 90% below 50 µm. The recovery rate of the automatic mills are usually higher than 97%. Grinding vessel, ring and puck are made from chrome steel in order to avoid line overlapping during spectroscopy due to elements introduced by the grinding stones.
Larger amounts of catalytic material can be ground using the HP- M1500. This pulverizer offers the same options as the HP-MA while the volume of the grinding vessel is significantly larger.

In the automatic press HP-PA, almost no additional binding agents are necessary to achieve a high quality pressed pellet with a smooth surface. Cleaning of the automatic press is commonly done by means of compressed air. If cleaning by air is not sufficient, a Mylar foil can be used to cover the pressing tool and prevent it from contamination.

Copper recycling

Copper is obtained from its ores during mining operations or from recycling of copper scrap or smelter residues such as slag, dust and sludges. During recent years, copper recycling has become more and more important. Recently, approximately half of the copper used in the industry originated from recycling of copper components and alloys, which consumes significantly less energy compared to primary copper production.
During the recycling process, copper scrap is smelted in primary and secondary smelters. For oxide scrap material, addition of carbon, iron and fluxes lead to reducing conditions. Depending on the quality of the scrap, electrorefining is necessary. In primary smelters, copper scrap is largely applied as a coolant in ore-based copper production. In the matte-converting process, impure scrap is used for the slag-making stage whereas pure copper is used for the copper-making stage. Cooper scrap can be smelted in a number of different furnaces including blast furnaces, reverberatory, rotary, bath smelting or electrical furnaces.

In addition, electronic scrap (WEEE) enters the copper recycling process. The copper content in electronic scrap may vary between 3 and 27%. The electronic scrap is usually smelted under reducing conditions resulting in so-called black copper, which is further processed under oxidizing atmosphere to remove impurities.
The major challenge for sample preparation in the copper mining and recycling industry is the wide range of element concentrations and varying material properties of the various QC samples. One important focus of sample preparation is therefore to avoid cross-contamination between subsequent samples.

Samples originating during the copper production process include geological samples, leach feeds/ residues, concentrates, slags, matte, anodes, cathodes, ashes, environmental samples, and many more.  Quality control involves many different and complex analyzing methods including XRF, quantitative XRD, ICP- OES, AA, combustion analysis, fire assay, and other more. HERZOG equipment covers all relevant preparation steps including moisture determination, filtration and drying, crushing, pulverizing, pelletizing, fusion, screening, blending/splitting, and bagging.

Aluminium recycling

Aluminum can be recycled any number of times without any detrimental effects on the base metal properties. Recycling provides huge energy savings in the process and consumes only a small fraction of the energy required for initial smelting of the alumina. The smelting process of pre-treated scrap aluminum together with pure aluminum ingots is carefully monitored until all levels of impurities have been removed. Accordingly, frequent sampling and assaying of molten material and slag is required.

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Sample preparation steps

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Crushing

Herzog crushers are designed for the coarse crushing and pre-crushing of sample material. The analytical fineness required for a subsequent spectroscopic examination is normally achieved with the aid of a disk vibration mill.

Jaw Crusher HSC 550

Herzog jaw crushers are designed as jaw crushers equipped with one movable and one fixed breaking jaw. This involves pressing the material to be crushed through the moving jaw and against the fixed jaw and crushing it through the application of pressure and impacts. The moving jaw is moved by an eccentric shaft and is thereby forced into an elliptical movement pattern that crushes the material and moves it downwards. If the grain size is smaller than the width of the bottom gap, the crushed material drops into the collecting container. Using no-rebound funnels prevents material from escaping out of the crushing chamber. IN some automatic machines we also integrate double rocker crushers.
Depending on the material being crushed, the jaw crushers can be supplied with crushing jaws made of different materials. One characteristic of jaws made of manganese steel is that they harden further over time with increased use. Stainless steel is recommended when the formation of rust can be expected due to feed material. Tungsten carbide jaws are particularly hard resistant to wear. Their service life is long even when used on hard materials.

With the cone crusher, the crushing occurs in the gap between the crusher jacket and the crusher cone. This gap opens and closes circumferentially as a result of the eccentric tumbling motion of the crusher cone. The advantage of the cone crusher is that the material is crushed continuously by pressure and friction. There is no alternating working stroke and no-load stroke as occurs with the jaw crusher.
The HP-CM/AUT is a crusher especially designed for automotive catalyst. Entire monoliths can be crushed down to a particle size suitable for fine grinding. The crushed material is captured in a special container (3 l), which can be easily removed by the operator. The material loss is reduced to a minimum and cleaning of the crusher is achieved by compressed air.

Pulverizing

Grinding and pressing is a time-saving and cost-saving sample preparation procedure that is used in the analysis of many inorganic and organic materials. Using powdered samples not only allows the chemical composition to be determined, it also permits the use of X-ray diffraction methods (e.g. cement, salts) for some applications in order to determine the mineral content.

Prior to pressing, the material must be finely ground in order to guarantee sufficient homogeneity. HERZOG offers a wide variety of disk vibration mills in different sizes and configurations for the grinding of sample material. Very hard materials (e.g. silicon carbide) can also be ground down to a grain size that is sufficiently fine to guarantee a high-quality analysis. Along with the program parameters, the attainable fineness is also dependent on the following factors:

  • Material
  • Input quantity
  • Grinfing aids used
  • Grain size when out in

      Generally, a grain size that permits an analysis is obtained after about 60 seconds in the case of most materials. If milling is performed for longer, agglomerations and material accumulations occur in the grinding vessel in the case of specific materials.

      Pulverizing of coarse-grained Material to fine powder, suitable for analysis with RFA, diffractometry and others.

       

      To perform the analysis by means of RFA, it is often necessary for the sample material to be ground to a grain size of < 75 µm. The grinding vessels must be made from wear-resistant materials in order to guarantee sufficient abrasion resistance. This applies particularly when the sample contains very hard mineral phases and has abrasive properties (e.g. clinker, silicon carbide, etc.).

      Grinding vessels

      This means that during grinding, there is inevitably abrasion of the used grinding stones and of the grinding vessel. Depending on the application, the grinding vessel should be suitably hard and should have a chemical composition that does not contain any elements that are of analytical interest. Different grinding vessels are available in order to prevent the entry of elements that are relevant to the analysis.

      The automatic mills are especially suitable for preparing precious metal bearing materials because the machine offers various cleaning options to avoid cross contamination. Three cleaning features namely compressed air, sand cleaning and wet cleaning allow a sufficient material removal. Using the different cleaning functions, cross contamination can be reduced to a low ppm-level. Furthermore, spoon sampling during the material input provides the possibility to pre-contaminate the grinding with the following sample. The final particle size after ± 30 seconds of milling is commonly 90% below 50µm. Grinding vessel, ring and puck have to be made from chrome steel in order to avoid line overlapping by elements introduced by the grinding stones.

      Pelletizing

      Grinding and pelletizing of sample material for XRF and XRD spectroscopy is an established procedure not only within the primary extractive industry but many industrial processes. HERZOG offers a wide range of different equipment from manual machines to fully automatic laboratory solutions.
      For sample pelletizing HERZOG provides manual and automatic machines. For manual applications with small or medium sample loads following models are available: TP20, TP20E, TP40, TP 40/2d, TP60, TP60/2d, HTP40, HTP60. All standard pelletizing procedures can be completed using manual pellet presses. The sample material is filled in manually. Dependending on the used model the pressure is generated manually or by an electrical hydraulic unit.
      The automatic pellet presses HP-MP, HP-P, HP-PA, HP-PD6 are automatically dosing the ground material into the press tool. After pressing excess material and dust is removed from the steel ring. In the HP-P a second press tool can be used as option to avoid cross contamination between two divergent material types.  The ready pellet can be automatically transported to the analyzer. Following analysis the ring is automatically cleaned and stored in a ring magazine.
      The HP- PD6 is a special pellet press for pelletizing of samples for diffractometry analysis. Few grams of sample material is pelletized into a ring using very low pressure. For stabilizing the material within the ring an aluminium button is inserted using a special backloading procedure.

      Depending on the analytical requirements, it is possible to choose between four standard pressing methods:

      Free pressing

      Free pressing is the lowest-cost pressing method because no consumables are required. Precise dosing of the sample material is also not required.

      2- component pressing

      Pressing of 2 components requires an additional work step, but also offers the possibility of preparing small sample quantities for analysis. The refill magazine (e.g. boric acid, Boreox) is dosed and pre-pressed in an initial work step. A special pressing tool cover is used for this. The actual sample material is then pressed into the prepared matrix in a second pressing step. 

      Pressing in aluminium cups

      For pressing in aluminium cups, the plunger should have a suitable venting groove in order to prevent compression of gases in the plunger. Aluminium cups are available in various diameters. Aluminium cups have the advantage that no significant costs are incurred if the samples are to be archived. Nevertheless, aluminium cups offer no guarantee with regard to eruptions occurring on the edges.

      Pressing in steel rings

      Using steel rings offers far-reaching advantages over the other pressing methods with regard to use in automated sample preparation systems. Using steel rings reduces the risk of contamination in the spectrometer by preventing eruptions on the sample edge. However, high costs are incurred if the re-useable rings must be archived. Two rings types are available for pressing in steel rings (Ø 40 mm & Ø 51 mm).

      Cleaning steel rings

      A three-stage brush system can be used to clean used steel rings after the analysis. This can be used with both manual and automatic presses. On manual presses, it is placed manually into the ring and is then removed manually. In automated pressing, the cleaning runs entirely without the operator's intervention. The empty rings are then automatically stored in the internal magazine.

      Almost no additional binding agents for, e.g., catalyst material are necessary to achieve a high quality pressed pellet with a smooth surface. Cleaning of the automatic press is commonly done by means of compressed air. If cleaning by air is not sufficient, a Mylar foil can be used to cover the pressing tool. The pressed pellets can be prepared by using the automatic pelletizing press HP-PA, which can be connected with the pulverizer HP-MA in a linear automation. This allows batch processing of up to 100 samples with a minimum work load.

      Representative splitting

      Representative sampling of secondary raw materials is an important prerequisite to ensure a reliable physical and chemical analysis and in the end lot value determination. After the primary sampling, size-reduction has to be undertaken in such a way that the final aliquot presented to the analytical laboratory displays the lot as much as possible 100 %. The relative sampling variation (RSV) of the sub-sampling to realize the size reduction should be less than 5 %. The prospective RSV has to be determine for each new application with an at least 5-folded simple replication experiment to ensure a full conformity to a representative operation. Representative splitting is of particular importance in PGM recycling but also many other material and commodities sectors like, e.g., mining, food, pharma, secondary raw materials, and agricultural products.

      Fusion

      Fusion process

      Fusion is an extremely efficient method of sample preparation for various analysis methods such as X-ray fluorescence, ICP and AA. The term fusion normally covers the mixing of a sample with a fusion agent, fusing the mixture and pouring in the form of a glass bead or dissolving in an acid solution.
      Fusion is the best method when standards or sample material do not have a consistent matrix. This is normally the case with exploration, environmental and geological samples including mining material, minerals, clay, ores, dusts and waste materials. It is also often used with mixing materials such as cement, catalysts and electronic materials.

      Improving the analysis results

      Preparation with the aid of the fusion process results in a significant improvement in analytical accuracy. There are various reasons for this.
      Firstly, samples that have an identical chemical composition can differ from each other in terms of mineralogy and particle size. This alone can result in different counting rates in the analysis instrument. The fusion process eliminates these factors and thereby increases measuring accuracy.
      Secondly, dilution occurs in fusion through the addition of a fusion agent. This leads to a reduction in the interaction between the elements being analysed and a reduction in the so-called matrix effect.
      Thirdly, fusion makes it significantly easier to perform a calibration. On the one hand it is possible to produce perfect matrix-matched standards for a large number of materials. On the other hand, synthetic standards can be used if no referenced standards are available. Accordingly, synthetic standards can be produced for almost any material without the complex regression analyses for creating calibration curves.

      Avoiding errors

      Fusion is an extremely important part of material analysis by way of X-ray fluorescence, ICP and AA. Fusion is an excellent method for avoiding errors that can have a negative influence on the accuracy of the corresponding measuring method. Fusion is also the simplest and most reliable method for preventing errors arising from inhomogeneous particle distribution, mineralogical effects and insufficient surface quality.

      Improving the sample solution

      Fusion can easily dissolve oxidic samples that are difficult to prepare with the aid of acidulation. Conventional acidulation of resistant material such as silicates aluminium, zirconium etc. takes a long time and often only results in incomplete dissolving. However, complete sample dissolving is an extremely important factor for improving the accuracy and reliability of analysis results.

      Perfectly suited to fluorescence analysis

      The fusion process produces a glass bead that is perfect for X-ray fluorescence instruments. The glass bead has the optimum dimensions, displays excellent homogeneity and has a flat surface.

      Time saving

      A typical fusion process seldom takes longer than ten minutes. In contrast, acidulation takes hours before a satisfactory result can be obtained.

      Safety

      Fusion is a reliable sample preparation process that requires no harmful acids and reagents. Special safety measures are therefore not necessary. The fusion process is especially safe when it is done with apparatus that has automatic sample handling, fusing and pouring of the melt.

      Fusion process

      The most common method is borate fusion. This involves fusing a sample with an excess of lithium borate and in the form of  a glass bead with a flat surface. During the fusion process, the sample's material phases are converted into glass-like borate, which results in a homogeneous fusion bead that is perfectly suited to X-ray fluorescence analysis.
      The finely ground sample material is first mixed in a crucible with a borate fusion agent (usually lithium), consisting of 95% platinum and 5% gold. The crucible is then heated to temperatures in excess of 1000°C until the sample is dissolved in the fusion agent. Movement of the melt during the fusion process improves the homogenisation of the material still further. A wetting agent (bromide, iodide, fluorine) can be added in order to support the separation of the melted material from the wall of the platinum.
      Borate fusion of escrap or catalyst recycaltes in a Pt-crucible is complicated as Pt, Pd and Rh, which are contained in the sample, will alloy with the crucible wall. Nevertheless, the application of fused bead method can improve the accuracy of analysis by the factor 5. Therefore, it should be checked from case to case if fusion is applicable.

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