The Role Of Thickeners And Filter Presses In Aggregate Processing.
Edited by Mark S. Kuhar
Water plays a crucial role in the aggregate industry, particularly in washing and classifying processes. However, traditional methods of water management often result in substantial water waste and environmental impact.
Thickeners and filter presses offer a modern solution by facilitating the recycling of process water for reuse, therefore minimizing water waste, and reducing the environmental footprint of aggregate processing plants.
Thickeners: Enhancing Water Recycling
Thickeners are essential in the aggregate industry for the efficient separation of solid particles from water. They can be used to recover immediately reusable process water from an aggregate waste stream. Thickeners can also concentrate and thicken solids in the waste stream to help reduce the volume of slurry going into the settling pond.
Thickeners operate by introducing a flocculating agent that allows fine particles to clump together and settle at the bottom of the tank, leaving clean water at the surface, which can be reused in the plant as process liquid. A rotating rake moves the settled solids toward the discharge cone located in the center of the tank, where the solids are then discharged to the pond or to downstream processing equipment.
Applications of Thickeners
Water Clarification: Thickeners are used to clarify process water by removing suspended solids. This clean water can then be recycled back into the wash plant, reducing the need for fresh water. This is beneficial in areas where the water supply may be scarce or the water is costly.
Sludge Concentration: In the same process, thickeners also concentrate the sludge, making it easier to handle and dispose. This is particularly important for meeting environmental regulations and minimizing the volume of waste reporting to settling ponds or downstream processing equipment.
Benefits of Thickeners
Reduced Freshwater Consumption: By recycling process water, thickeners significantly reduce the need for fresh water.
Cost Savings: Reduced freshwater consumption and lower wastewater treatment costs result in substantial operational savings.
Higher Liquid Recovery Rates (85% or greater): Thickeners generate a virtually solids-free liquid overflow, which can then be reused as process water in the wash plant or for dust suppression on site.
Reduce Volume of Waste Material: By separating out the liquid from the solids, thickeners generate a denser solids underflow. Because of this, the volume of material going to storage is reduced, as well as the load on downstream equipment such as filter presses.
Filter Presses: Maximizing Water Recovery
Filter presses are another critical component in the sustainable management of water in aggregate processing. They offer the highest level of liquid-solid separation without the use of chemicals. Filter presses generate a solids product that is drip-free and easily transported with mechanical handling equipment. They also generate an immediately reusable process water.
Filter presses are composed of a heavy-duty support framework holding a series of polypropylene plates that are lined with a synthetic filter cloth. The plates feature recesses on each side so that when the plates are clamped together, the recesses form chambers between the plates.
A high-pressure pump fills the chambers with slurry, and the solids in the slurry become trapped on the filter cloths. The cloths allow the liquid to flow through and discharge through the filtrate ports to be reused within the plant. When the filtration cycle has ended, the plates separate, allowing the drip-free filter cakes to fall. These cakes can be easily managed with mechanical handling equipment, such as loaders and conveyor belts, and can be potentially used or sold as backfill material.
Applications of Filter Presses
Dewatering Sludge: Filter presses are used to dewater sludge produced by thickeners, reducing the volume of waste reporting to settling ponds or eliminating them altogether, and producing a solid cake that is easier to handle and transport.
Recycling Process Water: The filtrate water from filter presses is typically of high quality and can be reused in the processing plant, further reducing the demand for fresh water.
Benefits of Filter Presses
Maximized Water Recovery: Filter presses achieve high levels of water recovery, ensuring that the maximum amount of water can be recycled back into the process.
Reduced Waste Volume: By separating the liquid from the solids in the waste stream, filter presses significantly reduce the volume of waste that needs to be managed, lowering disposal costs and environmental impact.
Driest Cakes: Compared to other dewatering technologies, filter presses offer the highest level of solids concentration in the resulting filter cakes.
Because of the above benefits, filter presses have proven to be the best equipment option to help reduce or even eliminate settling ponds.
A combination of both thickeners and filter presses offers a complete solution for water management in the aggregate industry. By working together, these technologies ensure that water is recycled and reused to the greatest extent possible, minimizing waste and environmental impact.
Benefits of Using a Filter Press and Thickener Together
Enhanced Water Recycling: Thickeners and filter presses work together to recycle virtually all process water, significantly reducing the need for fresh water.
Efficient Sludge Management: Thickeners concentrate sludge, which is then efficiently dewatered by filter presses, reducing waste volume and disposal costs.
Compliance with Environmental Regulations: The use of thickener and filter press technologies helps aggregate plants meet stringent environmental regulations by minimizing wastewater discharge and reducing the environmental footprint of their operations.
As the aggregate industry strives toward more sustainable practices, the role of thickeners and filter presses in water management becomes even more important. These technologies not only enhance the efficiency and sustainability of aggregate processing plants, but also provide significant cost savings and environmental benefits.
By integrating thickeners and filter presses into their operations, aggregate producers can achieve optimal water management, ensuring a more sustainable and responsible approach to aggregate processing.
Information for this article courtesy of Eagle Iron Works, which offers filter presses through a partnership with Diefenbach.