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How many kinds of fillers are used in water treatment?

Time:2013-06-26 Click:2064

      Fillers generally refer to materials filled in other objects.  In chemical engineering, packing refers to inert solid materials, such as bowler ring and raschig ring, which are installed in the packed tower. its function is to increase the gas-liquid contact surface and make them 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 for contact oxidation process. Microbes accumulate on the surface of the filler to increase contact with the surface of sewage and degrade the sewage.


      Fillers are also called fillers and extenders.  Some fillers are also physical pigments.  Micron fillers have good hiding power and are often used in coating industry.


      Fillers can be used in a variety of polyurethane products, such as polyurethane coatings, sealants: polyurethane slurry, special elastomer polyurethane foam.  Melamine plant fiber polymerization, soap and ginseng polyols, organic fillers can be used in polyurethane foam;  Calcium carbonate kaolin (pottery clay, porcelain clay), molecular sieve powder talcum powder wollastonite, titanium dioxide barite powder (barium sulfate) and other fine inorganic powders can be used as fillers for polyurethane sealants, polyurethane soft foam polyurethane elastomers, adhesives, polyurethane coatings and the like.


      Generally refers to materials filled in other objects.  In chemical engineering, packing refers to inert solid materials, such as bowler ring and raschig ring, which are installed in the packed tower. their function is to increase the gas-liquid contact surface and make them 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.  Among them, fillers that can significantly improve the strength of products, such as long fibers and whiskers, are often specially called reinforcing materials, and 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 the dosage and concentration rather than to improve the performance, so they should be called diluents.  Plastic plasticizers, rubber oil extenders and spinning finishes can improve performance and also affect cost, but these liquid materials are customarily regarded as processing aids.


      In polymer chemical industry, filler (filler) is an additive used in a large amount. Almost all plastics (including thermoplastic and thermosetting plastics), natural rubber and coatings use a large amount of filler.  For example, adding wood flour, pottery clay or calcium carbonate when making plastics can not only improve the mechanical properties of the products, increase the hardness, but also reduce the cost.  Using graphite, magnetic powder or mica as filler can improve the conductivity, permeability and heat resistance of plastics.  Adding carbon black or silica (white carbon black) into rubber can significantly improve the physical properties of the product.  Adding titanium dioxide (titanium dioxide) into spinning solution can shade and dye.  White or colored fillers (such as titanium dioxide, talcum powder, calcium carbonate, barium sulfate, etc.) are often added to the coating industry to improve the optical, physical and chemical properties of the coating. Fillers (fillers) for such purposes are called body pigments or pigments.

      Advantages and Disadvantages of Filler Performance


      Mainly depends on:

      (1) has a larger specific surface area (m2/m3 packing layer);

      (2) the liquid has good uniform distribution on the surface of the filler;

      (3) air flow can be evenly distributed in the packing layer;

      (4) Seasoning has larger void ratio (m3/m3 packing layer).


      In addition, factors such as mechanical strength, source, manufacture and price should also be considered when selecting fillers.


      Filler action

      The filler increases the viscosity of the material, especially the fiber filler increases the viscosity obviously.  The filler before adding should be dehydrated to avoid consuming part of isocyanate.  Attention must be paid to the foaming phenomenon of the resin caused by the generation of carbon dioxide, which affects the physical properties of polyurethane resin.

      In order to speed up the filler wetting speed, 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 auxiliary agent with three functions of paint, color paste and mold release agent.  It is evenly sprayed in the mold, and after the paint film is dried, the molded polyurethane sole, self-skinning foam plastic, polyurethane soft foam and hard foam products can be demoulded, and the color paint can be attached to the molded peripheral products.

      The action mechanism of the filler: The filler acts as an additive mainly through its occupied volume. Due to the existence of the filler, the molecular chain of the matrix material can no longer occupy the original entire space, making the connected segments immobilized to some extent and possibly causing the orientation of the matrix polymer.  Due to the dimensional stability of the filler, in the filled polymer, the molecular chain movement in the polymer interface region is limited, which causes the glass transition temperature to rise, the thermal deformation temperature to increase, the shrinkage rate to decrease, and the elastic modulus, hardness, rigidity and impact strength to increase.


      The function of filler:

      (1) reducing the shrinkage rate of molded parts and improving the dimensional stability, surface smoothness, smoothness, flatness or dullness of the products;

      (2) effective regulator of resin viscosity;

      (3) It can meet different performance requirements, improve wear resistance, electrical conductivity and thermal conductivity, etc. Most fillers can improve impact strength and compressive strength of materials, but cannot improve tensile strength;

      (4) the coloring effect of the pigment can be improved;

      (5) Some fillers have excellent light stability and chemical corrosion resistance;

      ⑥ It can increase capacity, reduce costs and improve the competitiveness of products in the market.

      Purpose of Filler in Epoxy Floor Paint

      Filler in epoxy floor paint is also called filler, generally refers to the material added to epoxy resin liquid as a component of epoxy floor paint to change the performance of epoxy resin glue solution and reduce costs.


      The purpose of using fillers in epoxy floor paints is as follows:

      1. Reduce cost, inhibit reaction heat and have brilliant colors.

      2. Extend the service life of the resin mixture.

      3 reduce the shrinkage of the cured resin.

      4. Improve the heat resistance of the cured resin.

      5. Reduce the thermal expansion coefficient of the cured resin, reduce the water absorption of the cured resin, and improve the aging resistance and chemical resistance of the cured resin.

      6 Improve the compressive strength of the cured resin, but the tensile strength and impact toughness will decrease.

      7 Improve the arc resistance and other electrical properties of resin cured products.

      8 Improve the abrasion resistance of resin cured products.


Packing selection criteria

For a particular application, the best standard of filler depends on the desired properties of the composite material, but the following basic principles must be considered.

      1. The filler must maintain its original structure in the processing process, and maintain inertness, insolubility, thermal stability, non-volatility, no catalytic activity and low adsorbability.

      2. The filler must be compatible with the base material and non-corrosive.

      3. Easy to handle, high bulk density, low moisture content, low dust and no toxicity.

      4, must be easy to obtain, sufficient supply, moderate price, stable quality.


      Types of fillers

      There are many kinds of fillers, aluminum powder, zinc powder, copper powder, silver powder and other metal powders can be used as conductive fillers.  Cement, fly ash and the like can also be used as fillers.  Plant powders such as wood flour and starch can also be used as fillers.  Calcium fluoride can be used in polyurethane adhesive and sealant system in small amount.  Has the function of carbon dioxide absorbent.

      Generally speaking, small amount of fine powder filler or modified fine filler, fibrous filler and flake filler can improve the overall performance, for example, it has certain reinforcing effect on elastic polymers (such as rubber and polyurethane elastomer), increases modulus, strength, wear resistance, heat resistance, improves its dimensional stability, and also can appropriately improve strength and aging resistance for hard products.  However, too large an amount of filler will reduce the physical properties and make it difficult to operate when the amount of filler is large.  There are several kinds of packing: according to the different packing methods, they can be divided into bulk packing and regular packing.


      Bulk packing

      Is one by one has a certain geometric shape and size of particles, generally in a random way piled up in the tower, also known as random packing or granular packing.  Bulk packing can be divided into annular packing, saddle packing, annular saddle packing and spherical packing according to different structural characteristics.


      Several typical bulk fillers are introduced:

Raschig ring, Bowler ring, cascade ring, arc saddle packing, rectangular saddle packing, metal ring rectangular saddle packing, spherical packing


      raschig ring

      (1) Raschig ring packing

      Invented by F. Rashching in 1914, it is a circular ring with the same outer diameter and height.  Raschig ring packing has poor gas-liquid distribution, low mass transfer efficiency, large resistance and small flux, and has been less used in industry.


      pall ring

      (2) Bale ring packing

It is an improvement on Raschig ring. Two rows of rectangular window holes are formed in the side wall of Raschig ring. One side of the cut ring wall is still connected with the wall surface, and the other side is bent into the ring to form inwardly extending tongue blades. The side edges of the tongue blades overlap in the center of the ring.  Due to the hole in the ring wall, Bale ring greatly improves the utilization rate of the inner space and the inner surface of the ring, with small airflow resistance and uniform liquid distribution.  Compared with Raschig ring, the gas flux of Bale ring can be increased by more than 50%, and the mass transfer efficiency can be increased by about 30%.  Bale ring is a widely used filler [1].


      cascade ring

      (3) Ladder ring packing

      It is an improvement on the Bale ring. Compared with the Bale ring, the cascade ring has a half-height reduction and a tapered flanging is added at one end.  Due to the reduction of the aspect ratio, the average path of the gas around the outer wall of the packing is greatly shortened, and the resistance of the gas passing through the packing layer is reduced.  Tapered flanging not only increases the mechanical strength of the filler, but also makes the filler change from line contact to point contact, thus not only increasing the gaps between the fillers, but also becoming the collection and dispersion points of liquid flowing along the surface of the filler, which can promote the surface renewal of the liquid film and is beneficial to the improvement of mass transfer efficiency.  The comprehensive performance of cascade ring is better than that of Bauer ring, and it has become one of the excellent ring fillers used.


      Saddle packing

      (4) arc saddle packing

      It is a kind of saddle-shaped filler. It is shaped like a saddle and is generally made of porcelain.  Arc saddle packing is characterized by an open surface, no distinction between inside and outside, uniform flow of liquid on both sides of the surface, high surface utilization rate, arc-shaped flow passage and small flow resistance.  Its disadvantage is that it is easy to overlap, resulting in a part of the filler surface is overlapped, so that the mass transfer efficiency is reduced.  The arc saddle filler has poor strength and capacity of crushing, and is not widely used in industrial production.


      Rectangular saddle packing

      (5) saddle packing

      The arc surfaces at both ends of the arc saddle filler are changed into rectangular surfaces, and the two surfaces have different sizes, thus becoming the rectangular saddle filler.  Rectangular saddle packing does not overlap when stacked, and the liquid distribution is relatively uniform.  Rectangular saddle filler is generally made of porcelain material, and its performance is better than Raschig ring.  The vast majority of domestic applications of porcelain Raschig rings have been replaced by porcelain saddle fillers.


      Metal ring moment saddle packing

      (6) Metal Ring Moment Saddle Packing

      Ring moment saddle filler (called Intalox in foreign countries) is a new type of filler designed taking into account the characteristics of ring and saddle structure. The filler is generally made of metal material, so it is also called ring moment saddle filler.  Ring moment saddle packing integrates the advantages of ring packing and saddle packing, and its comprehensive performance is better than that of Bale ring and cascade ring. It is widely used in bulk packing.


      Spherical packing

      (7) spherical filler

      Generally, it is made of plastic by injection molding, and its structure has many kinds.  The spherical filler is characterized in that the sphere is hollow and can allow gas and liquid to pass through it.  Due to the symmetry of the sphere structure, the packing density is uniform, and it is not easy to generate voids and bridges, so the gas-liquid dispersion performance is good.  Spherical packing is generally only suitable for certain specific occasions and is rarely applied in engineering.

      In addition to the above several typical bulk fillers, new types of fillers with unique configurations have been continuously developed, such as conjugate ring fillers, Haier ring fillers, Nath ring fillers, etc.


      Regular packing

      Structured packing is packing arranged in a certain geometric configuration and piled up neatly.  There are many kinds of structured packing, which can be divided into grid packing, corrugated packing and pulse packing according to their geometric structures.


      Grille packing

      (1) Grille packing

It is formed by combining strip-shaped units with certain rules and has various structural forms.  The very early grid filler used in industry is wood grid filler.  Grics grid filler, mesh grid filler and honeycomb grid filler are widely used, among which Grics grid filler is representative.

Grille packing has low specific surface area and is mainly used for occasions requiring small pressure drop, large load, anti-blocking and the like.


      Corrugated packing

      (2) Corrugated packing

      Most of the structured packing used in industry is corrugated packing, which is a disk-shaped packing composed of many corrugated thin plates. The inclination angles of corrugation and tower shaft are 30 and 45 respectively. When assembling, two adjacent corrugated plates are stacked in reverse.  Each tray of packing is vertically installed in the tower, and the adjacent two trays of packing are staggered at 90 degrees.

      V corrugated packing can be divided into net corrugated packing and plate corrugated packing according to their structures, and their materials are divided into metal, plastic and ceramic.

      Wire mesh corrugated packing is the main form of mesh corrugated packing, which is made of wire mesh.  The pressure of corrugated packing of wire mesh is reduced, and the separation efficiency is very high. It is especially suitable for precision rectification and vacuum rectification devices, and provides an effective means for rectification of difficult-to-separate substances and heat-sensitive substances.  Although its cost is high, it is still widely used due to its excellent performance.

      Corrugated metal plate packing is a main form of corrugated metal plate packing.  The corrugated plate of the filler is punched with many small holes of about f5mm, which can play a role in coarsely distributing liquid on the plate and strengthening transverse mixing.  The corrugated plate is rolled into fine grooves, which can play a role in finely distributing liquid on the plate and enhancing the surface wettability.  Metal orifice corrugated packing has high strength and corrosion resistance, and is especially suitable for large diameter towers and occasions with large gas and liquid loads.

      Metal calendered perforated plate corrugated packing is another representative corrugated packing.  The main difference between it and corrugated filler of metal orifice plate is that the surface of the plate is not punched holes, but punched holes. Very dense small punched holes with a diameter of 0.4 ~ 0.5 mm are rolled on the plate by rolling.  Its separation ability is similar to that of net corrugated packing, but its blocking resistance is stronger than that of net corrugated packing, and it is cheaper and more widely used.

      Corrugated packing has the advantages of compact structure, small resistance, high mass transfer efficiency, large processing capacity and large specific surface area (commonly used are 125, 150, 250, 350, 500, 70