Sand reclamation has become a necessity in no-bake operations, particularly given the current challenges regarding the cost and availability of new sand. Foundries can no longer afford to operate with new sand alone and most are exploring how best to economically integrate sand reclamation systems into their processes.
For a reclamation plant to realise the full value of a sand reclamation system, it must operate at optimal efficiency. Without the careful monitoring of outputs and control parameters in place, the foundry could risk an unacceptably high level of casting defects as well as lost production – and thus revenue.
Cost reductions after installing sand reclamation are made by re-using the sand after casting, buying less new sand and with some systems actually reducing the binder content at the mixer.
Due to less sand being dumped there is an obvious reduction to the impact on the environment.
Primary attrition can be further broken down into three main types: primary attrition low-level, primary attrition high-level and combined shake-out/attrition
Casting quality is improved by using less resin at the mixer and improving the sand grain’s characteristics so that it becomes more rounded. A more rounded sand grain leads to better compaction after mixing, greater strength and better surface finish.
In order to reclaim the sand, the equipment used must first of all reduce the lumps back to grain size, remove all coarse grains, agglomerated sand grains as well as dust and fine particles. The sand must be cooled before re-use but more importantly, as much binder should be removed as possible.
There are three main options for sand reclamation: Primary attrition, secondary attrition and thermal.
Primary attrition can be further broken down into three main types: primary attrition low-level, primary attrition high-level and combined shake-out/attrition.
High-level refers to the loading height of the attrition unit. This type would typically be positioned in a pit and fed via a separate shake out and vibratory feeder. It would not have its own shakeout deck and would be used where heavy castings or high throughputs would be processed.
Secondary attrition can be employed after the primary attrition unit to enable further binder removal
Low-level units are floor mounted requiring no special foundations and can be used as a shake out as well as attrition unit. This type of plant is usually more compact, easier to maintain and has a low investment cost. The main limitation is the maximum load capacity of three tons and a maximum throughput of 15 tons per hour.
Combined shakeout attrition units are usually mounted in a pit but can take much higher load capacities.
Secondary attrition can be employed after the primary attrition unit to enable further binder removal. These units are especially suitable for the no-bake process and gives up to 60% reduction in loss on ignition (LOI) and thereby giving better quality reclaimed sand. Secondary attrition is also not as costly to purchase or operate as thermal so can be considered a more cost-effective alternative to thermal.
The ultimate in sand reclamation has to be thermal, whereby 100% of all binder and other organic material is removed. The sand is generally better quality than when it was first bought.
Sand cooling and classification
The final section is regarding the cooling of the sand and the removal of dust and fines. Often overlooked, the sand cooler/classifier is equally as important as the attrition unit because unless we remove all of the dust and fine particles from the sand we will not see a reduction in the LOI at the mixer.
Whilst no two foundries are the same and all have different sand systems and requirements, there are many variations of sand reclamation plants available. All that has to be determined is the amount of binder removal required and the level of investment.
The ultimate in sand reclamation has to be thermal, whereby 100% of all binder and other organic material is removed. The sand is generally better quality than when it was first bought
Modern sand reclamation plants have evolved in such a way that even the smallest foundry can be accommodated in terms of floor space required by the plant but also in terms of investment and running costs. Essentially, there is a sand reclamation plant to suit every foundry requirement and budget.
Endeco Omega Sinto equipment
Endeco Omega Sinto has a full range of mechanical sand reclamation equipment suitable for all no-bake processes. These mechanical reclamation plants range from 1 ton per hour up to 30 tons per hour and Omega’s unique low-level range of mechanical reclamation plants mean that they can be installed without pits or special foundations. The low-level range is also very compact in design and can fit into very small areas inside or outside of the foundry.
Endeco Omega Sinto’s mechanical reclamation plants use the non-aggressive, dry attrition method of binder removal, this means that fragile sand grain structures can be effectively reclaimed without sand degradation. In fact, the scrubbing action of the attrition units will round the sand grains and make them more suitable for no-bake moulding. Also, due to four stages of sand scrubbing, a good reduction in LOI can be achieved.