In the chemical industry, the complexity, high corrosiveness and high wear of process fluids pose great challenges to equipment used for solid-liquid separation. As one of the main equipment for solid-liquid separation in modern industry, the Decanter Centrifuge is widely used in petrochemical, fine chemicals, chlorine-alkali, pesticides, dyes, intermediates and other sub-sectors due to its advantages of strong continuity, large processing capacity and high degree of automation.
However, since the materials processed in chemical production often contain strong acids, strong alkalis, organic solvents or high-hardness particles, if the material selection is improper, it is very easy to cause equipment corrosion and wear, shorten the service life, and even cause safety accidents. Therefore, the reasonable selection of wear-resistant and corrosion-resistant structural materials is the key to ensure the long-term and stable operation of the decanter centrifuge in the chemical environment.
Typical application scenarios of decanter centrifuges in the chemical industry
The materials in the chemical industry are diverse, and most of them are corrosive and abrasive. The following are typical application scenarios of decanter centrifuges:
Separation of organic chemical raw materials: such as the removal of solid impurities in alcohol, ester, and ketone intermediates.
Inorganic salt crystallization separation: including the separation of crystals such as sodium chloride, sodium sulfate, and ammonium sulfate from mother liquor.
Dye and pigment production: The pigment particles are small and contain a large amount of pigments and additives, which is difficult to separate and has higher material requirements.
Fine chemical production: such as solid by-products produced in the production of pesticides and pharmaceutical intermediates.
Waste liquid and residue treatment: solid-liquid separation process in highly corrosive, high-temperature and high-concentration materials.
The materials involved in these scenarios usually have the following characteristics:
Extreme pH value: strong acid or strong alkalinity;
Various solvents: alcohols, esters, ketones, etc.;
High temperature: some as high as 80℃-150℃;
High content of hard particles: such as oxides, crystalline salts, etc.;
Corrosive ions: such as chloride ions, sulfur ions, and fluoride ions.
Faced with these harsh environments, if the horizontal screw centrifuge does not use suitable materials, its key parts such as the drum, screw pusher, shaft, and discharge port are extremely prone to corrosion and wear, affecting the separation efficiency and equipment life.
Key components and common material configurations of decanter centrifuges
The core components of decanter centrifuges mainly include:
Bowl
Screw conveyor
Shaft and main bearing
Discharge port and sealing part
Shell and cover
The structural material selection of these components must meet the dual requirements of “corrosion resistance” and “wear resistance”. The following is an analysis of common material configurations:
1. Drum material
As the core component of high-speed rotation, the drum is the part that directly contacts the material the most. It bears large centrifugal force and heavy corrosion load.
304 stainless steel: suitable for room temperature and weakly corrosive materials. High cost performance, but not resistant to strong acids and alkalis.
316L stainless steel: adding molybdenum element, enhancing resistance to chloride ion corrosion, is a standard material used more in the chemical industry.
2205 duplex stainless steel: has excellent pitting resistance, stress corrosion and high strength performance, and performs well in high chloride ion environment.
Titanium alloy (Ti): Suitable for extremely corrosive environments, such as fluorine-containing and nitric acid-containing materials, and expensive.
Hastelloy C276: Extremely corrosion-resistant, resistant to harsh environments such as strong oxidants, concentrated hydrochloric acid, and wet chlorine.
2. Screw conveyor materials and wear-resistant treatment
In addition to corrosion, screw conveyors are also subject to extremely high wear, so it is necessary to focus on strengthening wear-resistant design:
Material of the spiral body: usually consistent with the drum, such as 316L or 2205;
Spiral blade coating:
Tungsten carbide spraying: extremely strong wear resistance, suitable for scenes with high solid content and high particle hardness;
Ceramic patch/hard alloy patch: enhance service life;
Overlay alloy: used for local reinforcement of some high-wear parts.
3. Spindle and bearings
The spindle is subject to high force and requires high operating precision. High-strength stainless steel or alloy steel is usually selected and heat-treated; bearings must be selected from high-end brands (such as SKF, FAG) and have a seal and anti-corrosion design.
4. Discharge port, seal and housing
Discharge port: high wear point, high-hardness alloy or ceramic spraying is recommended;
Housing and cover: Most of them are made of 304 or 316L stainless steel, and composite lining design is used in some high-corrosion occasions.
Analysis of corrosion and wear types in the chemical industry
1. Corrosion types
Chemical corrosion: metal dissociation caused by chemicals such as acids and alkalis, such as uniform corrosion in hydrochloric acid and sulfuric acid environments;
Pitting/crevice corrosion: Chloride ion erosion causes local holes, which damages 304 steel very quickly;
Stress corrosion cracking: metal cracks under the combined action of stress and corrosion, which is common in high-chlorine environments;
Intergranular corrosion: intergranular corrosion caused by improper heat treatment, which is more common in austenitic stainless steel.
2. Wear types
Hard particle wear: such as silica sand and crystal salt particles repeatedly scouring the metal surface;
Scrubbing wear: high-speed flowing materials hit the surface, such as high-speed discharge ports;
Sliding friction wear: spiral blades contact the drum wall when pushing materials, causing wear.
In the chemical industry, the material selection of the decanter centrifuge is the core factor that determines the equipment’s operating stability, service life and return on investment. Faced with complex corrosion and wear conditions, a single material is often difficult to balance performance and cost, so it is recommended to adopt a composite configuration strategy of “structural material + surface treatment”. Only through scientific material selection and reasonable configuration can the decanter centrifuge’s operating goal of “taking into account both wear resistance and corrosion resistance” in the chemical industry be truly achieved.
