Regenerating used sand in the foundry

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Foundry Corporate News Topic Plant Technology, Equipment Topic Green Sand

15. April 2024

FSP offers the right service to reduce costs

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The regeneration of used sand in foundries involves a great deal of effort and considerable costs. In addition, energy prices will continue to rise in the long term and new sand is not endlessly available. The solution is cost- and resource-saving sand regeneration by a specialised supplier.

For reasons of sustainability alone, the primary objective when treating used sand must be to use it again and again as a regenerate, and thus reduce the proportion of new sand purchased. However, investing in new plant technology for regeneration is expensive and therefore out of the question for many foundries. In addition, existing disposal routes for used sand - for example via cement works - will become obsolete in the next few years. Furthermore, the available landfill space for sand in Germany will become less and less. Options such as filling mines or topping up open-cast lignite mines will also become significantly fewer in the future.

Sand processing at FSP is largelyCO2-neutral

FSP GmbH (Foundry Sand Processing) offers the regeneration of used sand as a service. This not only saves foundries the cost of purchasing new sand. The new operator model also relieves them of investment, energy, and labour costs. By outsourcing, the foundries are also making an important contribution to the implementation of the circular economy: not only is the sand reused again and again during casting, but energy, water and process air also move in a permanent cycle in the recycling process. And last but not least, the processing of the sand at FSP is largelyCO2-neutral.

FSP in a pioneering role: synthesis gas from wood pellets instead of natural gas

FSP is taking on a pioneering role here: to minimise the use of natural gas, synthesis gas made from wood pellets is used in the plants. In addition, alternative fuels, such as plastic granulate from sports fields, are used and FSP also generates its own electricity using photovoltaic systems.

Block diagram of mechanical-thermal regeneration

Regeneration plants close to foundry sites

The service model is simple: FSP operates regeneration plants near foundry sites, collects the used sand from the foundries, regenerates it and returns the sand to its customers. The process technology used ensures that there is no mixing of the regenerates, and that each customer receives the regenerate from their used sand.

Sand in the cycle

The basis of regeneration at FSP is the wet regeneration process for used sand bound to water glass. Used sand, which has been in use in the pilot plant at the Stuttgart site since 2022 and has and has passed the acid test. For the regeneration of organically bound sands, FSP will also operate an additional pilot plant from May 2024, which will which has mechanical-thermal stages. The quality of both regenerates is equal to that of virgin sand: they substitute it by around 95 per cent.

On the one hand, FSP's service model relieves customers of the need to invest in the plant components required for the connection to the regeneration process. Depending on the process and binder system used, these include sand dryers, lump breakers, screens, magnets for removing metallic particles or cooling systems for the regenerated material after regeneration. On the other hand, many activities associated with the disposal of untreated used sand, waste and, above all, the dumping of dust are eliminated. Compared to an in-house plant, the operator model frees up personnel capacities in the area of plant operation and avoids cost-intensive maintenance and stockpiling of spare parts. In addition, the foundries do not have to go through any authorisation procedures.

FSP takes over the disposal of all residual materials

In contrast to models where plants are built on the premises of a foundry or for which a price is payable per month for a tonne of processed sand (pay-per-use) in addition to a rental fee, FSP also takes care of the delivery and removal of both the used sand and the regenerated sand. In addition, FSP takes care of the disposal of all residual materials produced during regeneration, in particular the dust produced. It is analysed at FSP and, if possible, supplied to other industries as replacement material. In this way, the dust also becomes recycled material.

Overall, FSP significantly reduces the material flow in the customer's plants, not only in terms of the amount of waste, but also in terms of plant transport. In addition, the model avoids empty runs for the delivery and removal of materials, as every lorry and every freight wagon that collects used sand from a foundry is loaded with reclaimed material. At the Stuttgart site, it can even be supplied by rail and ship.

FSP disposes of all waste produced during reclamation via a certified disposal route via Heinrich Feess GmbH & Co. KG in Kirchheim/Teck, the shareholder of FSP. This reliefs customer of the need to build up and maintain their own personnel capacities for waste disposal. Customers are also relieved of the burden of working with environmentally harmful materials.

Both the reclaimed material and the fines produced during regeneration correspond to landfill classes DK 01 or DK 02, which can be disposed of at lower costs. This means that the operator model also pays off for foundries that cannot reuse the sand due to special processes.

The reclaimed material also offers the possibility of utilising other disposal methods: The EU standards that will apply in the future state that reclaimed sand can be reused more easily in road construction, as an additive in the production of cement and gypsum or in the glass industry. Nevertheless, the primary aim of regenerating used sand must be to reuse the regenerate in a continuous cycle - this is the only way to ensure responsible and future-proof handling of sand as a natural resource.

The operator model in practice

FSP is pursuing a concrete roadmap: The pilot plant for wet reclamation, which has been in operation since 2022, will be expanded to a throughput of 2.5 tonnes per hour, i.e., around 20,000 tonnes per year. A further pilot plant for mechanical-thermal regeneration with a capacity of around one tonne per hour is under construction and will be available to customers for test series and open-loop processes from May 2024.

FSP will also install a mechanical-thermal system with a throughput of six tonnes per hour, i.e., around 70,000 to 75,000 tonnes per year, at its headquarters in Stuttgart in the course of this year. It will be ready for series production at the beginning of 2025 and will primarily supply foundries in the greater Stuttgart area and the rest of Baden-Württemberg.

FSP is also planning to open two to three further sites in the near future, each of which will serve other foundries within a radius of 200 to 300 kilometres. They will each have a capacity of around 180,000 to 200,000 tonnes of used sand per year.

Both test facilities will be available to foundries from May 2024. They can be used to test and analyse the regenerability of inorganically or organically bound sands, or even mixed sands. FSP offers interested customers a range of different tests - from a simple test series with up to 1 tonne of sand to a complete free-running process with determination of the best possible ratio of reclaimed and new sand in core production. At the end of the tests, the customers receive the reclaim, dust and waste backpacked in big bags. This allows them to draw conclusions about the composition of the reclaim, for example the ratio of reclaim to fines and residual materials.

The main quality characteristics relevant to both binder systems (inorganic and organic) are determined in the in-house sand laboratory: Fines content and AFS number, active clay and slurry content, pH value, residual alkalinity, electrical conductivity, loss on ignition, strengths, and core weight.

For the test series and in subsequent series operation, sand samples are analysed on delivery of the used sand and on delivery of the reclaimed sand. The quality is recorded and documented online during series operation of the reclamation plants. This prevents deviations from the agreed quality criteria of the reclaimed sand. External laboratory facilities can also be consulted.

INFO: The technology in detail

The following applies to both reclamation variants: the used sand can be delivered in both silo and skip lorries. The complex plant and process technology ensures that the used sand - before it is fed into the actual reclamation process - is free of foreign materials, scrap metals and lumps and is dry and free-flowing. After reclamation, the reclaimed material is conveyed into outdoor silos and is ready for transport in silo lorries for collection.

In order to minimise the customer's handling costs, any necessary adjustments at the customer's plant to ensure a smooth and consistent supply of reclaim are clarified together on a case-by-case basis and implemented on site.

FSP's globally patented process for the wet regeneration of inorganically bonded core sands washes 98 per cent of adhering residues from the used sand. All common water glass-bonded used sands as well as special sands from 3D printing can be fully processed.

In the patented drying system, the sand is not dried with air, but the moisture is extracted from it in an energy-efficient manner through condensation. The sand is then cooled in a separator with patented fluidisation and additionally dedusted.

In principle, washing is the gentlest option for regenerating inorganic binders, as there is no direct mechanical impact on the sand grain. As a result, no additional dust is formed apart from the fines that are already contained in the used sand and are washed out. The process water required for the washing process is 100% treated and kept in a closed circuit. Binder components and waste from the casting process are completely washed out and removed from the process as sludge via the water treatment system. The resulting waste is disposed of in a certified process and the correct treatment is documented.

With mechanical-thermal regeneration, FSP is also setting new standards in the field of regeneration using series systems with medium and high throughput rates. The process can be used for both bentonite-bound green sand and organically bound core sand (cold box, hot box, shell sand, furan). Compared to conventional mechanical or purely thermal regeneration processes, the process technology reduces the dust content to a minimum.

Thermal-mechanical regeneration is characterised by the high efficiency of the three-stage system. After pre-treatment of the used sand, the sand is fed dry and free-flowing to the first - mechanical - stage, in which sand grain by sand grain and thus the binder is removed.

In the second stage, the sand is fed to the thermal stage. Gas and air mix in a sand bed, it fluidises, and the organic binder and fines are burnt. The effect of the quartz cracking loosens any remaining binder from the natural recesses of a grain of sand or even blasts it off. In the third, also mechanical stage, the last residues are rubbed off the grain; it works in the same way as stage one.

Providing information on site

In June 2024, FSP will be organising an "open week" at the Stuttgart site: Interested parties can visit all the plants and see for themselves both the efficiency of the two regeneration processes and find out about the advantages of the operator model.

About the FSP Gmbh

Founded in Stuttgart in May 2022, FSP GmbH Foundry Sand Processing develops and sells systems and solutions for the regeneration and processing of bulk materials. The basis is decades of experience in the recycling of raw materials and the mechanical-thermal or wet regeneration of used foundry sands. The founding partners are Heinrich Feess GmbH & Co. KG in Kirchheim/Teck and DEANTEC GmbH in Kirchhundem.

Feess, which was awarded the German Federal Environmental Prize in 2016, proved its expertise in the recycling of mineral waste, while DEANTEC contributes its experience with its unique, patented wet regeneration and drying process - a plant technology that uses exclusively renewable energy in the processing of used sand.

The merger to form FSP GmbH offers customers the complete, almost CO2-neutral sand processing chain. The regenerated material replaces up to 95 per cent of new sand and makes an important contribution to the conservation of resources and sustainable production.

Author: Dipl.-Oec. Stefan Zimmermann, Managing Director, FSP GmbH Foundry Sand Processing, Stuttgart