Filter presses are mechanical devices used in industrial and commercial settings to remove liquids from slurries or sludges through the application of pressure. They consist of a series of filter plates, along with a hydraulic or mechanical system to tighten the plates and compress the slurry. Filter presses are an effective and economical choice for the dewatering and filtration needs of many industries.
This blog post will provide an overview of industrial filter presses, including:
- How they work
- Types of filter press plates
- Common filter press applications
- Benefits of filter presses
- Factors to consider when choosing a filter press
- Tips for effective filter press operation
How Do Filter Presses Work?
The basic components and functioning of an industrial filter press is as follows:
- Filter plates – These consist of ribbed filter cloths or filter media sandwiched between two rigid plates.
- Frame – The filter plates are stacked inside a frame that can be tightened using a hydraulic or mechanical mechanism.
- Slurry feed – The slurry or sludge is fed into the space between the plates. As pressure is applied, liquid passes through the filter cloth.
- Filtrate and Cake discharge – The filtrate (filtered liquid) is discharged from one end, while the filter cake (dewatered solid) is discharged from the other end.
- Squeezing cycle – Applying and releasing pressure during the process improves dewatering and solids capture.
Types of Filter Plates
There are two main types of filter press plates:
- Frame plates – Provide structural support to the filter pack and have no filter media.
- Filter plates – Contain the filter cloth or membrane that separates liquids from solids. Common types are:
- Flat plates – Simple and inexpensive with a flat surface area for filtration.
- Tortional plates – Have ridges or grooves to increase the surface area and filtration rate.
- Tubular plates – Long, tube-like filter plates that provide even more surface area.
- Membrane plates – Utilize filter membranes instead of cloth for finer filtration.
Some of the main industrial filter press applications include:
- Wastewater treatment – Removing solids and recovering water from sludge in municipal and industrial plants.
- Mineral processing – Dewatering tailings and concentrates in mining operations.
- Chemical processing – Separating process solids from liquids in chemical manufacturing.
- Food & beverage – Filtration and recovery of process water in food and drink production.
- Pulp & paper – Filtering wood fines and other fibers present in pulping liquors and waste streams.
- Oil & gas – Separating drilling mud and waste fluids from cuttings and drill solids.
- Pharmaceuticals – Recovering water from wet cake in fermentation, recovery and purification.
Benefits of Industrial Filter Presses
- High solid content in filter cake – Up to 70% solids can be achieved, enabling water recovery.
- Fast dewatering rates – Can achieve short filtration cycles times of just a few minutes.
- Low cost per liter of water recovered – Expense is offset by water recycle and reuse.
- Simple and robust design – Require little maintenance and downtime.
- Ability to handle a wide range of slurries – Effective on sludges with varying particle sizes.
- Flexible operation – Can run in batch, continuous or semi-continuous modes.
Factors to Consider When Choosing a Filter Press
- Flow rate and throughput requirements
- Degree of dewatering needed (final solid content)
- Physical and chemical properties of slurry
- Slurry temperature
- Space and footprint considerations
- Required level of automation
- After-treatment of filter cake
Tips for Effective Operation
- Start with a slow squeezing cycle and work up to the maximum operating pressure.
- Allow a dwell time at maximum pressure to achieve the best dewatering.
- Apply vacuum to the filtrate chamber to improve yield where possible.
- Flush and rest the press between cycles for optimal performance.
- Maintain proper sealants and gaskets to minimize leakage.
- Replace filter cloths when needed to avoid blinds and reduced flow rates.