Increasing product quality in recycling applications

In the processing of recycled building materials, the purity of the mineral product grain is decisive for customer acceptance and marketing opportunities. Product quality can be improved by using wind sifting to separate lightweight materials. All Kleemann impact crushers can be optimally equipped with wind sifters for mobile processing in recycling.

In contrast to the processing of pure natural stone, the processing of recycled material is often confronted with the challenge of producing a marketable final product from a variegated mixture of materials. In addition to the mineral components of concrete, brick, asphalt and gypsum, construction demolition waste typically contains other materials such as textiles, wood and plastics. In order to process this material mixture into a certified, recycled aggregate, the separation of lightweight materials is usually essential. On the one hand, the subjective demands of construction material customers in terms of product purity must be met. On the other hand, specifications and technical standards also define maximum proportions for non-mineral impurities.

In Germany, for example, grain mixtures for road substructures may only contain 0.2% by mass of floating lightweight materials. Such low limit values show that the greatest care must be taken when separating lightweight materials. If the quality requirements are not met, the product can only be sold at a lower price or must be used for an inferior purpose. In practice, various processes are used to ensure sufficient product purity through the separation of lightweight materials.

In the video: The function and use of Kleemann wind sifters at the double-deck post screening unit of the impact crusher MOBIREX MR 130i PRO is explained.

Different solutions and procedures

To ensure that no mineral fines are blown out in addition to the lightweight material, these must be screened off before wind sifting. For this reason, mobile impact crushers are usually equipped with a post screening unit and the overflow of the screen can be treated directly with wind sifters.

Kleemann impact crushers with a single-deck post screening unit can be extended accordingly with an oversize grain wind sifter. This separates lightweight materials from the return material flow into the crusher and thus prevents further crushing and contamination of the final product.

If a double-deck post screening unit is installed on the impact crusher, a medium grain wind sifter can be used in addition to the oversize grain wind sifter. This applies a flow of air to the overflow of the screen lower deck and directly ensures that the medium grain is sufficiently clean.

In addition to the product quality, however, the wind sifter also contributes to the smooth running of material processing. If lightweight materials are separated at an early stage, the risk of clogged screen media or material blockages in downstream plants is reduced.