Tube Settlers vs. Plate Settlers: Comparing Lamella Technologies


The sedimentation process in both water and wastewater treatment is a physical process which relies on gravity to settle and remove suspended solids. Advanced solids settling processes typically utilize lamella, commonly referred to as tube settlers or plate settlers, to reduce the vertical distance solids particles must fall until hitting a “settling surface”. Higher flow rates, better effluent quality, and more compact sedimentation basins can all be achieved with both types of lamella sedimentation equipment. Although both operate on the same principles of solids settling and can be used as basis of design in many cases, there are several notable differences between the two technologies.


Characteristics of Tube Settlers and Plate Settlers


Tube settlers utilize multiple adjacent tubular channels that are sloped at a nominal 60° angle and combine to form an increased effective settling area. The size and shape of the tubular channels vary by manufacturer. Brentwood’s tube settler design features a trapezoidal shape created by thermoforming PVC sheets. You can learn more about our design process by reading our Thermoformed vs. Extruded Tube Settlers blog.


In contrast, plate settlers use a series of inclined plates, typically constructed of steel, which are spaced two to three inches apart from each other on a 55° to 60° angle to form an increased effective settling area. As a result of these design differences, typical design parameters for these two types differ.



Comparing Design Parameters


It is important to note that there is a difference in application rate (flow rate/coverage area, expressed in gpm/ft2) between tube settlers and plate settlers as a result of different effective settling area terms used, despite settling principles being similar for the two technologies. To provide a more direct comparison, the application rates of tube settlers can be converted to an equivalent “plate” application rate by taking into account the projected surface area of tubes:


As illustrated in the above table, the equivalent maximum “plate” application rates of Brentwood tube settlers are in the same range as a generic plate settler, which has an average application rate of 0.30. IFR6041 tube settlers are the most comparable to plate settlers in regard to coverage area because settler length is similar. However, Brentwood’s other tube settler modules are capable of treating required flow just as effectively with appropriate coverage area. Tube settlers also eliminate cross-flow and eddy currents, which makes flow hydraulics more stable and efficient.


In addition to varying design approaches, there are other advantages and disadvantages to consider when comparing tube settlers or plate settlers for your application:


Tube Settlers


Advantages:




Lightweight PVC results in easy installation and does not require heavy lifting equipment




Lower capital cost due to materials of construction




Applicable in shallow tanks with underflow velocity concerns




Twenty to twenty-five year service life, provided proper maintenance is performed




Only PVC tube settlers are replaced at the end of their useful life typically supporting structures and effluent troughs can remain




Tube settlers are strong enough to walk on top of for proper maintenance




Highly customizable to accommodate varying basin configurations




Disadvantages:




Maximum module vertical height is 41 inches, resulting in a maximum application rate of 3.5 gpm/ft2




PVC must be protected from extensive UV exposure. Brentwood tube settlers do contain UV inhibitors. AccuGrid protective surface grating is also available for additional UV protection.




Plate Settlers


Advantages:




Less limitation on depth




Longer lifespan due to material of construction




Disadvantages:




Two to three times higher capital cost




Higher installation cost due to required heavy lifting equipment




Deeper basin requirements to accommodate underflow velocities




Risk of corrosion in certain environments (certain industrial wastewater applications)








Polyhedral Hollow Ball packing is made from heat resistant and chemical corrosion resistant plastics, and the application temperature in media ranges from 60 to 150 degrees.


Plastic Polyhedral Hollow Ball (PP, PE, PVC, CPVC, RPP ) is also called plastic multi-aspect hollow ball, polyhedral hollow ball packing composed of two hemispheres which will form into a ball. And each hemisphere consists of a number of half fan-shaped leaves, the upper and lower leaves in a staggered arrangement. The design concept is advanced and the structure is reasonable. Plastic Polyhedral hollow balls have the virtue of light weight, wide free space, small wind resistance, and good surface hydrophilic, big full wet surface area and convenient filling in the equipment and sound usage effect.


Plastic polyhedral Hollow Ball can be used in sewage treatment, desulfurization of CO2 in power plant, desulfuration and purified water tower packing. Plastic multi-aspect hollow ball is a new type of high-efficiency tower packing applied in water treatment equipment.


Pall rings: made in various materials, used in massive applications


Pall rings are the most frequently used form of random packaging. They are made of metal and plastic. They also have different applications. Our experts will give you the most beneficial info about pall rings through this blog at Linquip. To find more, read on.


What are Pall Rings?


As said above, pall Rings are a random ring-type packaging with a well-established success background and a globally distributed base. They try to increase the use of packaging by disrupting the flow by providing an increased number of edges while reducing the volume of the ring packing medium itself. Pall rings have identical cylindrical dimensions but have window rows that improve the surface area size. They are ideal for low-pressure drops and applications with high power. They have randomness and relatively high liquid retention that promotes high absorption, especially if the reaction rate is slow. Pall rings’ cross structure makes them mechanically robust and ideal for deeply packed beds.


What are Pall Rings Used for?


Pall ring is applied in a variety of areas, including:




Different Separation and Absorption




Absorption and Stripping Services




Steam Stripping




Quench Towers




Direct Contact Cooling




Reaction Towers




Distillation Columns




Tower Packing




Plastic pall rings


Random packaging has been used for over 50 years to boost the efficiency of a tower.


In comparison with high-performance packing, plastic pall rings are less sensitive to liquid distribution quality and have a higher hold-up and residence time. Although plastic pall rings do not have “high performance” characteristics, they are well known for their performance.


Plastic pall rings, as one type of pall rings, can be made of different shapes for different applications. In gas and liquid separators applications, for example, they are increasingly popular. They have excellent chemical resistance, the stability of the temperature, and mechanical strength. They are made of polypropylene pall ring, Polyethylene pall ring, RPP pall ring, PVDF pall ring, PVC pall ring, and CPVC pall ring.


The composition of plastic pall rings varies from the ceramic pall ring and metallic pall ring. Two levels of windows on the cylinders wall and ligules bend inside the ring axes on the cylinders’ wall for the metal and ceramic ring. The plastic cylinder wall is fitted with two layers of windows and the fingers or webs bow inward and form different forms. The handling efficiency of the pall ring is 50 percent greater than the ring with the same decompression condition. The mass pressure is meanwhile at the same treatment half below the Raschig ring. Moreover, the efficiency of transfer will increase by 20%.


Metal Pall Rings


Metal pall rings are a significant type of pall rings. Metal pall rings can be customized into different sizes. In very hostle environments, they are more resistant to corrosion and rust compared with plastic pall rings. Metal pall rings are made primarily from carbon steel, galvanized steel, and other materials. There are two layers of windows on the cylinder wall close to the ceramic pall ring. And there are five ligules in each sheet, which bend inwards into the ring axis.


Metal pall rings are used in quench towers, direct contact cooling applications, atmospheric pressure separation, and absorption applications, places in which vacuum is critical to the low-pressure drop, and applications of steam stripping.


Overview About Mist Eliminators


Mist eliminators, also known as demisters, are devices that remove liquid droplets or vapor from the work atmosphere. This device has found some applications in many industries where such vapors are released as a by-product of the different chemical processes. Manufacturers produce standard or specialized devices to work as an important part of various industrial operations which include absorption towers, distillation towers, separation tanks, gas separators, evaporators, and so on. Various industries like metallurgy, petroleum, medicine manufacturing use demisters in their production processes or environmental protection measures.



Working Principle of a Mist Eliminator


Standard demisting devices work on the principles of inertia and dispersion. The liquid vapor rises with the gas and passes through the eliminator pads. These pads are fitted with wire meshes with openings that correspond to the predetermined average vapor droplet size, which is generally in the range of 3 to 5 micrometers. Due to the increasing inertia of these droplets, they get attached to the wire meshes. With subsequent passes, these collected droplets get heavier and heavier due to the tensile and adhesive properties of liquids, ultimately falling off the pads. In this manner, the vapor liquid is essentially separated from the gaseous emissions passing through standard eliminator pads.


Advantages


Eliminator manufacturers of today produce demisters of various sizes and capillary openings based on the above principle. A standard mist eliminator has various advantages as listed below.


· It is an essentially simple device; its size is only dependent on the gaseous emission pathway dimensions


· For such a basic device, it is highly efficient in removing liquid vapors with minimum disturbance to the actual process


· Eliminators improve the output by removing vaporized impurities; they also make gaseous emissions, safer by helping to separate potentially harmful compounds


· With no external power needed for its operation, it is a cost-saving device


· The liquid deposits may be collected and re-processed


Types


According to the requirements of specific industries, there are various types of these devices produced and operating in several industrial applications. However, we may segregate mist eliminator devices into three basic categories as discussed below.


Standard Mist Eliminator


These are the basic demisters that may be used in normal work environments. These devices can work efficiently in standard gaseous emissions, separating liquefied vapors. The mesh sizes of these devices are bigger, and they can sustain low to moderate amounts of gas pressure.