Heinrich Wagner Sinto Maschinenfabrik GmbH (HWS) is one of the leading international suppliers of machinery and equipment for the foundry industry and part of the Sintokogio group of companies with its headquarter in Japan. The company employs more than 300 skilled workers at its site at Bad Laasphe. The focus is on the manufacture and sale of moulding machines and moulding plants as well as pouring units for sand and die casting. The portfolio is supplemented by machines and plants for the mechanical reclamation of used sands in green sand foundries.
The disposal and landfilling of foundry sand are causing steadily rising costs. Reducing the quantities of used sand and reusing it in the material cycle are more important today than ever before. The reuse of raw materials has always been a core competence of the foundry industry. In this context, the use of used sand as a recyclable material is the logical extension of internal recycling management. It offers opportunities for improving economic efficiency and conserving natural resources. The reclamation of used sand contribute to the long-term security of the site, ensures greater sustainability by increasing the recycling rate, reducing the volume of transport and lowering the CO2 emissions. The question is not if we are able and willing to reclaim, but when we start. There is a consensus that the disposal of one of the world's most used and valuable resources, sand, is not a sustainable model.
Introduction sand reclamation
The reclamation of moulding material serves to break down and remove the binder shells and other non-sand constituents in order to obtain a reusable basic moulding material . The aim is to use this basic moulding material (reclaim) as a substitute of new sand, mostly in core production. In a green sand foundry, it can be assumed that the used sand to be reclaimed is in most cases a mixture of bentonite-bonded moulding sand and organically bonded core sand (cold box). Various processes exist for their reclamation, which can be divided primarily into main groups (variants/combinations not taken into account).
More diverse than the number of processes are the properties of the specific used sand to be reclaimed, which usually varies from foundry to foundry. The appropriate solution should ideally be sought in close coordination with the machine and binder suppliers. An optimum design of the overall process can only be made after determining the initial situation and the planned reuse of the reclaim. Further consideration here will concentrate on mechanical reclamation. Unless explicitly stated otherwise, the term "reclamation" in the following always refers to mechanical reclamation.
Mechanical sand reclamation
The mechanical reclamation processes can be divided into various subgroups. The reclamation of used sand must always be regarded as an interlinked overall process. This consists of several stations for sand pre-treatment and sand post-treatment as well as the cleaning process on the sand grains themselves. Depending on the choice of the reclamation process and the available starting material (used sand), appropriate conditions for efficient cleaning, such as residual moisture or grain separation, must always be ensured. These conditions are set by sand pretreatment and ensure that the required reclaim properties are achieved. They are also largely determined by the reclamation unit selected for the cleaning process and the process parameters set. The correct ratio of the degree of reclamation (reduction of the signal components compared to the used sand) and the reclaim output (ratio of reclaim to used sand quantity) should be observed (cf. ). For the economic operation of a sand reclamation plant, the following applies in a simplified way: "Reclaim as clean as necessary and output as high as possible!". Depending on the reuse case, an associated reclaim aftertreatment ensures compliance with further target parameters, such as the target temperature, which are not directly set by the reclamation unit.