Innovations in Liquid Filtration
Filtering is a valuable technology that has prevented many water-borne diseases from spreading. Now, researchers are experimenting with sheets of graphene, a form of carbon just one atom thick, to filter seawater.
Eaton’s LifeTec depth and membrane filters help beverage and liquid food manufacturers lower production costs and increase process reliability. Watch the videos below to learn more.
1. Hybrid Particulate Collection (HPC)
Providing safe drinking water to all the world’s people has become a critical goal, but the current technology used to treat surface and groundwater is often too costly or complicated for impoverished communities. Some technologies, such as desalination and sedimentation, have been deemed impractical or unaffordable, but innovative advancements in the area of filtration are bringing hope to this global issue.
One such solution comes from a Tanzanian chemical engineer who developed a low-cost customizable filter that uses natural biological channels to filter and purify water. His invention uses aquaporins, which are small membrane proteins that act as semi-porous gates through which water molecules pass via diffusion or osmosis. These channels naturally occur in the kidneys of mammals and plants, and they can be found in nature as well.
This new filtration method can be used in conjunction with other methods, such as water chlorination and UV disinfection, to create an inexpensive, user-friendly system that is more effective than traditional treatments, according to the company. The technology has the potential to transform water treatment in many developing countries, where access to clean, potable water remains a challenge, and may help reduce deaths due to preventable waterborne diseases.
In another promising development, researchers from the Massachusetts Institute of Technology are experimenting with using sheets of graphene — a form of carbon that is just a single-atom thick — to filter seawater. The filters contain holes that block salt particles, but allow water to pass through. The process is faster and cheaper than desalination, and requires less energy.
Other new innovations include a process that separates crude oil components at a refinery, which could help to reduce emissions and energy consumption. The process uses pressure instead of heat to separate naphtha and kerosene, the primary ingredients in gasoline and jet fuel, from light crude oil. It may also be able to replace some heat-based distillation processes in oil refineries.
Ahlstrom, a Finnish manufacturer of fibre-based products with an emphasis on renewable materials, has introduced a new line of filter media made from lignin, a waste byproduct from pulp production that has only recently been valorised. The new ECO filtration media reduces formaldehyde emissions from air intake and engine oil filters, without affecting performance or durability.
2. Membrane Filter Bags
Membrane filtration technology uses molecular size and charge to separate particles. This non-thermal technology can remove up to 100% of the germs and pathogens found in food products, resulting in better product quality and compliance with strict regulatory requirements. It also eliminates the need for chemical additives and reduces temperature-induced protein denaturation and changes in product sensory qualities. In addition, membrane filtration is extremely energy efficient. It requires lower operating pressures than conventional MF, UF, and nanofiltration, and is far more effective than reverse osmosis.
Most industrial membrane filtration is conducted as cross-flow filtration. Unlike media, cartridge and bag filtration, which are dead-end technologies that require constant halting of the process to backwash or change out the filter medium, membrane technology utilizes a cross-flow filtration process that allows the bulk solution to flow continuously over and parallel to the membrane surface. This helps to minimize the formation of a foulant filter cake and enables the filtration process to be interrupted only for maintenance or cleaning.
PTFE membrane filter bags are ideal for applications such as oil removal and paint dewatering. They are composed of a specialized high-performance polytetrafluoroethylene (PTFE) fiber that resists acid and alkali corrosion, withstands a wide range of temperatures, and does not absorb moisture or lubricants. These high-performance bags are manufactured with a proprietary, patented, high-flow pore structure that prevents surface collapse and breakthrough of gelatinous particles and contaminants, which leads to less downtime and improved filtration efficiency.
The performance of a membrane filter depends on several key properties such as porosity, pore size distribution and morphology. Research has demonstrated that the use of carbon-based nanomaterials such as graphene oxide (GO) and carbon nanotubes can be used to modify polymer membranes to increase their hydrophilicity and porosity, thereby improving the water flux. This allows for increased oil rejection while maintaining a low-energy requirement. A hybrid GO/aminated polyacrylonitrile electrospun membrane showed significantly improved oil rejection with water flux as high as 10,000 L/m2hbar. As a result, membrane technology is becoming increasingly popular for its oil removal capabilities.
3. Seamless Filter Bags
Bag filters are used for liquid filtration to remove particles from the product. They are a common form of industrial filter and can be found in most chemical plants. The design of the filter is simple and consists of a number of long thin bags that are placed in a filter vessel. The liquid flows through the bag under gravity, and the solids are collected inside the bag. The solids are then removed from the bag and can be reused or sent for disposal. Bag filters have been largely superseded by other types of filters, although they are still in use in some industries.
Traditionally, bag filter construction has relied on stitched seams to prevent fluid bypass. However, these are vulnerable to leaks. A new technology is reducing the need for stitching in this type of filter. The latest generation of bag filters are seamless and can be made from needle punched non-wovens, melt blown fiber or spun bonded web that are welded together. This reduces the risk of pinholes in the seam and provides a much higher level of debris holding capacity to prevent clogs. These welded filter bags also have high integrity, which allows them to withstand changes in pressure.
Seamless filters are a good choice for applications where absolute rated filtration is required. These can be manufactured from a variety of materials, including PTFE film and other fluoropolymers, polypropylene or polyester. They can be supplied as either a single bag in a container, or they can be combined to make a duplex filter system. The flow through a duplex system can be controlled so that the bags are online, filtering, or offline, being cleaned.
One example of a new innovation in this type of bag filter is the BOS MAX heavy-duty seamless filter bag. This provides extended life and improved efficiency for absolute rated filtration in pharmaceutical production, food processing and chemical applications. The seamless design eliminates bypass, and the composition of thermally bonded 100% pure polypropylene microfibers excludes bonding agent contaminates from entering the process stream. The bag also offers high levels of oil adsorption, which is critical for removing gelatinous contaminants from the filtered liquid.
4. Electrostatic Precipitator (ESP) Filter Bags
An electrostatic precipitator (ESP) uses electrical forces to remove particulate matter from flue gas. A high-voltage source generates a corona current that charges the particles and moves them toward grounded collecting plates where they are deposited. The majority of ESPs use plate collectors, which require periodic or continuous rapping to keep the surfaces clean. https://ztfilterbag.com/ The remaining ESPs use membrane filter bags to capture the particles that remain after rapping. ESP technology provides high and stable dust collection efficiency, low capital costs, and a small footprint.
ESPs are available with efficiencies of up to 99.9% for submicron particles. This performance can be increased by increasing the discharge electrode voltage, lengthening the electric field length, and improving power supply quality. Indicators of ESP performance include particulate matter outlet concentration, which can be measured with a particulate matter continuous emissions monitoring system (CEMS), opacity, and secondary corona power.
The quality factor of ESP-equipped bag filters can also be improved by selecting the right filter medium and enhancing the design of the ESP discharge electrodes. Bag filters with a larger pore size and shorter fiber diameter provide higher filtration efficiency than those with smaller pore sizes and longer fibers. The ESP discharge electrodes are also more efficient when their diameter is smaller and the discharge area is maximized.
Electrostatic precipitator systems can be designed with various types of discharge electrodes, including plates and tubular designs. Plate ESPs are more common than tubular ESPs, which are typically used to collect fly ash from coal-fired power plants. They can have a flat-plate or wire-plate structure. A popular type of plate ESP is the “plate-wire” configuration, which has a grid of parallel plates of thin metal wires with a high-voltage long-distance discharge electrode.
A hybrid electrostatic / bag-filter is a combination of two processes that improves filtration efficiency by reducing dust reentrainment. In addition, the unipolar charge of the bag filter improves the ESP’s ability to attract and hold particles, resulting in better overall performance. A recent study [26] compared the performance of a hybrid electrostatic / bag-filter with an ESP and traditional bag filters in a large coal-fired power plant. The results showed that the hybrid was capable of achieving a much higher quality factor than the ESP and the bag filters alone, with lower pressure drop increase per minute and electricity consumption, and a comparable total dust removal efficiency.