What are the types of fillers used in water treatment? What are the types of fillers used in water treatment? Fillers refer to materials that are filled into other objects. In chemical engineering, packing refers to inert solid materials, such as Bauer rings and Raschig rings, that are packed inside a packed tower. Their function is to increase the contact surface between air and liquid, allowing them to mix strongly with each other. In chemical products, fillers, also known as fillers, refer to solid materials used to improve processing performance, mechanical properties of products, and/or reduce costs. In the field of sewage treatment, it is mainly used in contact oxidation processes, where microorganisms accumulate on the surface of the packing material to increase surface contact with the sewage and degrade it.
Fillers are also known as fillers or extenders. Some fillers are also physical pigments. The filler of micro knobs has good covering power and is commonly used in the coating industry.
Fillers can be used for a variety of polyurethane products, such as polyurethane coatings, sealants: polyurethane slurry, elastomer polyurethane foam. Melamine plant fiber polymerization, soap polyol, etc., organic filler can be used for polyurethane foam; Calcium carbonate kaolin (clay, porcelain clay), molecular sieve powder talc powder, wollastonite powder, titanium dioxide barite powder (barium sulfate) and other fine inorganic powders can generally be used as fillers for polyurethane sealants, polyurethane soft foam polyurethane elastomers, adhesives, polyurethane coatings, etc.
Refers to materials filled in other objects. In chemical engineering, packing refers to inert solid materials, such as Bauer rings and Raschig rings, that are packed inside a packed tower. Their function is to increase the contact surface between air and liquid, allowing them to mix strongly with each other. In chemical products, fillers, also known as fillers, refer to solid materials used to improve processing performance, mechanical properties of products, and/or reduce costs. Fillers that can significantly improve the strength of the product, such as long fibers and whiskers, are commonly referred to as reinforcing materials, while carbon black is called reinforcing filler. Solid materials and calcium carbonate are often added as fillers in pharmaceutical tablets, cosmetics, and detergents, but their purpose is to adjust dosage and concentration rather than improve performance, so they should be called diluents. Plastic plasticizers, rubber oil fillers, and spinning oil additives can improve performance and affect costs, but these liquid materials are commonly regarded as processing aids.
In polymer chemistry, fillers are the most commonly used additives, and almost all plastics (including thermoplastic and thermosetting plastics), rubber, and coatings use large amounts of fillers. For example, adding wood powder, clay, or calcium carbonate when manufacturing plastics can not only improve the mechanical properties of the product, increase hardness, but also reduce costs; Using graphite, magnetic powder, or mica as fillers can improve the conductivity, magnetization, and heat resistance of plastics; Adding carbon black or silica (white carbon black) to rubber can significantly improve the physical properties of the product; Adding titanium dioxide (TiO2) to the spinning solution can block light and dye. White or colored fillers (such as titanium dioxide, talcum powder, calcium carbonate, barium sulfate, etc.) are often added in the coating industry to improve the optical, physical, and chemical properties of the coating. These fillers (fillers) used for this purpose are called pigments or pigments.
Performance advantages and disadvantages of fillers
Mainly depends on:
① Has a large specific surface area (m2/m3 filler layer);
② The liquid has good uniform distribution performance on the surface of the packing material;
③ The airflow can be evenly distributed in the packing layer;
④ Seasoning has a high porosity (m3/m3 filling layer).
In addition, when selecting fillers, factors such as mechanical strength, source, manufacturing, and price should also be considered.
Packing function
Fillers increase the viscosity of materials, while fiber fillers significantly increase the viscosity. The filler before addition needs to undergo dehydration treatment to avoid consuming some isocyanates. It should be noted that the generation of carbon dioxide can cause foaming of the resin, affecting the physical properties of polyurethane resin.
In order to accelerate the wetting speed of fillers and reduce the viscosity of the system or add more fillers to polyurethane resin, it is sometimes necessary to add wetting and wetting dispersants to the resin in advance.
In mold paint is an additive with three functions: coating, color paste, and release agent. It is evenly sprayed in the mold. After the paint film is dry, the molded polyurethane sole, self skinning foam, polyurethane soft foam and hard foam products can be demoulded, and the color paint can be attached to the molded products.
The mechanism of action of fillers: As additives, fillers mainly exert their effects by occupying volume. Due to the presence of fillers, the molecular chains of the matrix material can no longer occupy all the original space, causing the connected segments to be fixed to some extent and possibly causing the orientation of the matrix polymer. Due to the dimensional stability of the filler, the molecular chain movement within the polymer interface region is restricted in the filled polymer, resulting in an increase in glass transition temperature, thermal deformation temperature, shrinkage rate, and an increase in elastic modulus, hardness, stiffness, and impact strength.
The function of fillers:
① Reduce the shrinkage rate of molded parts, improve the dimensional stability, surface smoothness, smoothness, and flatness or non gloss of the products;
② Resin viscosity modifier;
③ Can meet different performance requirements, improve wear resistance, enhance conductivity and thermal conductivity, etc. Most fillers can increase the impact strength and compressive strength of materials, but cannot increase tensile strength;
④ Can improve the coloring effect of pigments;
⑤ Some fillers have good photostability and chemical corrosion resistance;
⑥ It has a capacity increasing effect, can reduce costs, and improve the competitiveness of products in the market.
The purpose of fillers in epoxy floor paint
The filler in epoxy floor paint, also known as filler, generally refers to a material added to the epoxy resin liquid as a component of the epoxy floor paint to change the properties of the epoxy resin adhesive and reduce costs.
The purpose of using fillers in epoxy floor paint is twofold:
1. Reduce costs, suppress reaction heat, and create vibrant colors.
Extend the shelf life of the resin mixture.
Reduce the shrinkage of resin cured products.
4. Improve the heat resistance of resin cured products.
5. Reduce the thermal expansion coefficient of resin cured materials, lower their water absorption, and improve their aging and chemical resistance.
6. Improve the compressive strength of resin cured materials, but the tensile strength and impact toughness will decrease.
7. Improve the arc resistance and other electrical properties of resin cured materials.
Improve the wear resistance of resin cured products.
Packing selection criteria
For a certain application, the optimal standard for filler materials is determined based on the expected performance of the composite material, but the following basic principles must be considered.
1. The filler must maintain its original structure during the processing, and maintain inertness, insolubility, thermal stability, non volatility, non catalysis, and low adsorption.
2. The filler must be compatible with the substrate and non corrosive.
3. Easy to handle, high packing density, low moisture content, and low dust.
4. Easy to obtain, sufficient supply, moderate price, and stable quality.
Types of fillers
There are many types of fillers, and metal powders such as aluminum powder, zinc powder, copper powder, silver powder, etc. can be used as conductive fillers. Cement, fly ash, and other materials can also be used as fillers. Plant based powders such as wood powder and starch can also be used as fillers. Calcium fluoride can be used in small amounts for polyurethane adhesives and sealant systems; It also serves as a carbon dioxide absorbent.
Generally speaking, the use of small amounts of fine powder fillers or modified fine fillers, as well as fibrous and sheet-like fillers, can improve their overall performance, such as reinforcing elastic polymers (such as rubber and polyurethane elastomers), increasing modulus, strength, wear resistance, heat resistance, and improving their dimensional stability. It can also appropriately increase the strength and aging resistance of hard products. However, excessive use can lead to a decrease in physical properties, and it is difficult to operate when the filler content is high. There are several types of fillers: depending on the filling method, they can be divided into bulk fillers and regular fillers.
random packing
It is a collection of particles with geometric shapes and sizes, usually randomly stacked inside the tower, also known as random packing or granular packing. Bulk fillers can be divided into annular fillers, saddle shaped fillers, annular saddle shaped fillers, and spherical fillers according to their structural characteristics.
Here are several typical bulk fillers:
Rascal ring, Ball ring, Step ring, Arc saddle packing, Rectangular saddle packing, Metal ring Rectangular saddle packing, Spherical packing
Raschig Ring
(1) Lacy ring packing
Invented by F. Rashching in 1914, it is a circular ring with an outer diameter equal to its height. The gas-liquid distribution of Rascal ring packing is poor, the mass transfer efficiency is low, the resistance is high, and the flux is small. It has been rarely used in industry.
Pall Ring
(2) Ball ring packing
It is an improvement on the Rascal ring, with two rows of rectangular windows opened on the side wall of the Rascal ring. One side of the cut ring wall is still connected to the wall surface, while the other side bends inward into the ring, forming an inward extending tongue leaf. The side edges of each tongue leaf overlap at the center of the ring. Due to the openings on the ring wall, the utilization efficiency of the space and surface inside the ring is greatly improved, resulting in low airflow resistance and uniform liquid distribution. Compared with the Raschig ring, the gas flux of the Bauer ring can be increased by more than 50%, and the mass transfer efficiency can be improved by about 30%. Ball ring is a widely used filler [1].
Cascade ring
(3) Ladder ring packing
It is an improvement on the Ball ring. Compared with the Ball ring, the height of the stepped ring has been reduced by half and a tapered flange has been added at one end. Due to the reduction in aspect ratio, the average path of gas around the outer wall of the packing is greatly shortened, reducing the resistance of gas passing through the packing layer. Conical flanging not only increases the mechanical strength of the packing, but also changes the main contact between the packing from linear contact to point contact. This not only increases the gap between the packing, but also becomes a collection and dispersion point for the liquid flowing along the packing surface, which can promote the surface renewal of the liquid film and improve the mass transfer efficiency. The comprehensive performance of the stepped ring is superior to that of the Bauer ring, making it an excellent type of annular packing used.
Arc saddle packing
(4) Arc saddle packing
A type of saddle shaped filler that resembles a saddle and is generally made of porcelain material. The characteristics of saddle packing are that the surface is completely open, without distinction between inside and outside, the liquid flows evenly on both sides of the surface, the surface utilization is high, the flow channel is arc-shaped, and the flow resistance is low. Its disadvantage is that it is prone to overlapping, resulting in some of the packing surfaces being overlapped, which reduces the mass transfer efficiency. The strength of the saddle packing is poor, it can withstand breakage, and is not widely used in industrial production.
Intalox saddle
(5) Rectangular saddle packing
Change the curved surfaces at both ends of the saddle packing to rectangular surfaces, with unequal sizes on both sides, to become the saddle packing. When the saddle packing is stacked, it will not overlap and the liquid distribution is relatively uniform. The saddle packing is generally made of ceramic material, which has better performance than the Rascal ring. In the vast majority of applications where ceramic Raschig rings are used, they have been replaced by ceramic saddle fillers
Metal ring saddle packing
(6) Metal ring saddle packing
Intalox, also known as metal ring saddle packing, is a new type of packing designed to balance the characteristics of both circular and saddle structures. It is generally made of metal material and is therefore also known as metal ring saddle packing. The annular saddle packing combines the advantages of both annular packing and saddle packing, and its comprehensive performance is superior to that of the ball ring and stepped ring, making it widely used in bulk packing.
Spherical filling material
(7) Spherical filling material
It is generally made of plastic injection molding and has various structures. The characteristic of spherical packing is that the sphere is hollow, allowing gases and liquids to pass through its interior. Due to the symmetry of the spherical structure, the packing density is uniform, and it is not easy to produce voids and bridging, so the gas-liquid dispersion performance is good. Spherical fillers are generally only suitable for certain specific situations and are less commonly used in engineering applications.
In addition to the typical bulk fillers mentioned above, new types of fillers with various configurations are constantly being developed, such as conjugated ring fillers, Haier ring fillers, Nut ring fillers, etc.
structured packing
Regular packing is a packing material arranged in a geometric configuration and neatly stacked. There are many types of regular packing, which can be divided into grid packing, corrugated packing, pulse packing, etc. based on their geometric structure.
Grid Packing
(1) Grid filling material
It is composed of regular combinations of strip-shaped unit cells and has various structural forms. The earliest industrial application of grid fillers is wooden grid fillers. The commonly used types of fillers include Gritch grid fillers, mesh grid fillers, honeycomb grid fillers, etc. Among them, Gritch grid fillers are representative.
The specific surface area of grid packing is relatively low, mainly used in situations where low pressure drop, high load, and anti blocking are required.
Corrugated packing
(2) Corrugated packing
The vast majority of regular packing used in industry is corrugated packing, which is a disc-shaped packing composed of many corrugated thin plates. The angle between the corrugation and the tower axis is 30 ° and 45 °, and adjacent corrugated plates are stacked in reverse during assembly. Each tray of packing is vertically installed inside the tower, with adjacent trays of packing arranged in a 90 degree staggered manner.
Corrugated fillers can be divided into two categories based on their structure: mesh corrugated fillers and plate corrugated fillers, with materials such as metal, plastic, and ceramic.
Metal wire mesh corrugated packing is the main form of mesh corrugated packing, which is made of metal wire mesh. The pressure reduction of metal wire mesh corrugated packing results in high separation efficiency, making it suitable for accurate distillation and vacuum distillation devices, providing a means for the distillation of difficult to separate and thermosensitive systems. Despite its high cost, it has been widely used due to its excellent performance.
Metal plate corrugated packing is a major form of plate corrugated packing. There are many small holes with a diameter of about 5mm punched on the corrugated plate of this filler, which can play a role in roughly distributing the liquid on the plate and strengthening the lateral mixing. Rolling fine grooves on the corrugated sheet can help to finely distribute the liquid on the sheet and enhance the surface wetting performance. Metal orifice plate corrugated packing has high strength and strong corrosion resistance, and is suitable for large diameter towers and situations with high gas-liquid loads.
Metal rolled perforated plate corrugated packing is another representative type of plate corrugated packing. The main difference between it and the corrugated packing of metal orifice plates is that the surface of the plate is not punched holes, but rather pierced holes. Small piercing holes with a diameter of 0.4-0.5mm are rolled out on the plate by rolling. Its separation ability is similar to that of corrugated packing, but its anti blocking ability is stronger than that of corrugated packing, and it is cheaper and widely used.
The advantages of corrugated packing are compact structure, low resistance, high mass transfer efficiency, large processing capacity, and large specific surface area (commonly used include 125, 150, 250, 350, 500, 700, etc.). The disadvantage of corrugated packing is that it is not suitable for handling materials with high viscosity, easy polymerization, or suspended solids, and it is difficult to load, unload, and clean, resulting in high cost.
Pulse packing
(3) Pulse packing
It is a regular packing made up of hollow prismatic individuals with necking, assembled in a certain way. After the assembly of pulse packing, a porous prismatic channel with necking will be formed, and the longitudinal flow channel will alternately shrink and expand, generating strong turbulence when gas-liquid phases pass through. In the necking section, high gas velocity and intense turbulence enhance mass transfer. In the expansion section, the gas velocity is reduced to a small value to achieve the separation of the two phases. The alternating repetition of channel contraction and expansion achieves a "pulse" mass transfer process.
The characteristics of pulse packing are large processing capacity and low pressure drop, making it an ideal packing for vacuum distillation. Due to its excellent liquid distribution performance, the amplification effect is reduced, making it suitable for situations with large tower diameters.
PTFE filler
Polytetrafluoroethylene valve stem packing is a soft product made from polytetrafluoroethylene fine powder and processed using a new technology. White, continuous rope shaped, with a circular cross-section. It has high flexibility, good filling, self-lubricating, low friction coefficient, corrosion resistance and other properties.
Technical parameters:
Operating temperature -260 to+260
Use pressure<20MPa
Applicable media include all chemical substances except elemental fluorine and molten alkali metals.
advantage:
Easy and fast loading. When filling, it is generally not necessary to disassemble the valve. Simply wrap the rope shaped packing around the valve stem, push it into the packing box, tighten the box cap, and the packing will be compressed into a dense whole.
Excellent sealing performance. The microstructure of expanded polytetrafluoroethylene endows this product with excellent flexibility and moldability, allowing it to easily fill the gaps inside the packing box, and even all the pits and grooves on the valve stem and body. This also prevents the replacement or repair of corroded and worn old valves.
Long service life. Due to its long-term soft plasticity, the leakage gap can be filled at any time, and because it is not corroded or aged, it can be used for a long time.
The valve is flexible and lightweight in opening and closing. Because polytetrafluoroethylene has a low coefficient of friction and excellent self-lubricating properties.
Do not contaminate the fluid in the pipeline. Because it is pure and clean, it will not peel off due to corrosion and aging, making it suitable for industries such as pharmaceuticals, fine chemicals, and food.
Good universality of specifications, reducing the storage capacity of fillers and saving expenses. Just prepare a few sizes of stem packing to meet the needs of most valves. Generally, large-sized fillers that can be embedded by hand are selected, but finer fillers can also be used in large-sized valves. After compression, they will also undergo plastic deformation to obtain a dense sealing body.
plastic filler
Plastic filler is a filler formed by mold pressing, which does not need to be cut and coiled into a ring like braided filler when used, and is made into a ring according to the size of the shaft neck. Plastic fillers come in two forms: cotton like and layered.
(1) Cotton like filling material
Cotton like filler is a mixture of fibers, graphite, mica, metal powder (or metal flakes), grease, and elastic binder, molded into a ring shape, and then a layer of stone cotton yarn (metal wire can also be used as needed) is woven on the outer layer. Another way of use is to directly place the mixture into the packing chamber, press it tightly with a cover, and use it directly. Due to the lack of fixed size of the packing, improper packing can easily affect the sealing performance, so this method is less commonly used. The types and ratios of various mixtures in the sponge packing can be adjusted according to working conditions, such as adding copper powder to high-pressure steam seals, adding lead particles or sheets to acidic medium seals, and adding more elastic binders when the shaft vibrates. Due to the absence of lubricants, this type of packing has minimal volume change under high pressure and can be used for sealing high-speed pumps and high-pressure valves. If solid lubricants are added, it can ensure good self-lubricating performance, and the structure is dense, which helps to improve sealing performance. In addition, sponge fillers have plastic flowability and can also be used in combination with metal fillers.
(2) Layered filling material
This type of filler is coated with rubber on the surface of asbestos cloth or canvas, and is formed by hot pressing and vulcanization after stacking or winding. It can also be filled with soft fillers such as rubber cores or embedded in springs, and has several layered filler structures. Layered packing has good sealing performance and can be used for low-pressure steam, water, and ammonia liquids below 120 ℃. It is mainly used as a shaft seal and valve stem seal for reciprocating motion. Non interface ring mounted layered packing can also be used as a piston ring for reciprocating pumps. Due to insufficient lubricant in the layered packing, lubricant needs to be added during use.
