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What is the application of filter washing and drying three-in-one equipment in strong corrosive conditions? Sep 29, 2018

In the past ten years, with the rapid development of the pharmaceutical and chemical industry, Hastelloy materials have become increasingly popular in harsh corrosive environments such as petrochemicals, flue gas desulfurization, fluorine chemicals, pulp and paper, aerospace applications, and acidic environments. The more widely used.


Eliminate traditional anti-corrosion materials on its “three-in-one” multi-function equipment for filtration, washing and drying, and use more advanced Hastelloy corrosion-resistant materials to manufacture key components on “three-in-one” multi-function equipment. . According to the main properties of Hastelloy, it can be widely applied to various unpredictable and harsh environments, and the unplanned maintenance is minimized. At the same time, it also has good processing and welding properties, which is convenient for on-site maintenance.


Filtration, washing and drying The working principle of the “three-in-one” multi-functional equipment: the solid-liquid mixture after crystallization is separated into solid and liquid by the pressure difference before and after the filter cake in a closed container, and then the filtration → slurry washing → filtration is completed → Processes such as slurry washing, filtration or pressure filtration → drying. The initial filtration and the re-filtration process after washing are carried out by pressure filtration or suction filtration, so that the solid-liquid mixed suspension of crystals and liquid after crystallization is passed through the porous sintered mesh plate, so that the crystal (solid particles) is intercepted in the filter medium. Above, while the mother liquor (liquid) is separated by the medium.


At the same time, the drying stage of the three-in-one equipment also heats the filter cake to quickly evaporate the moisture to achieve the drying effect. The evaporation speed is accelerated by the vacuum inside the equipment, and the evaporated moisture is taken away by adding the treated medium such as nitrogen. The material is accelerated to dry and the drying effect is improved. Since the equipment will be widely used in medicine, chemical, pesticide, food and other industries, different companies will process various materials in the equipment. Therefore, the internal construction of the equipment must meet the corrosion resistance of various pharmaceutical and chemical raw materials under high temperature and high pressure. Hastelloy has higher performance than other corrosion-resistant materials, and is most suitable for use in "three-in-one" multi-function equipment.


The current corrosion resistant materials include non-metallic materials and metal materials. Among them, the first type of non-metallic materials are ceramics, glass reinforced plastics, enamels, graphite and plastics, etc., which has the advantage that corrosion will hardly occur, but the disadvantage is that it can only be applied to 200 ° C, is not resistant to high temperatures, and can not withstand high pressure, but can not Welding operations, high maintenance costs, can only produce smaller equipment. Therefore, it is not suitable for the "three-in-one" multi-function device. The second type of metal corrosion-resistant materials are iron-based alloys (stainless steel), nickel-based alloys, and active metals, and Hastelloys are high-grade nickel-based alloys.


Hastelloys are commonly used in Hastelloy B (B-2, B-3) and Hastelloy C (C-22, C-276). They have high corrosion resistance in non-oxidizing inorganic and organic acids. Sexually, such as 70 ° C resistant sulfuric acid, resistant to all concentrations of hydrochloric acid, phosphoric acid, acetic acid and formic acid, especially heat-resistant concentrated hydrochloric acid.


Hastelloy is stable in caustic and alkaline solutions and is completely stable in organic media and seawater.

For iron-based alloys (stainless steel), whether it is ordinary 300 series stainless steel (304, 316L, etc.), it is also austenitic stainless steel (904L, 254SMO, etc.) with strong corrosion resistance, duplex steel (2205, 2507, etc.) and The overall corrosion resistance of the copper 20 alloy series is inferior to that of nickel-based alloys (Halst alloy). This difference in corrosion resistance is particularly pronounced in reducing environments, complex mixed acid environments, and solutions containing halide ions.



Although active metals (titanium, zirconium, hafnium) have very good corrosion resistance, especially titanium has a wide range of applications in China, mainly used to replace some corrosive environments that stainless steel cannot adapt. However, titanium mainly provides protection by forming a dense oxide film, and is susceptible to corrosion in an environment having high reductive property or high airtightness (lack of oxygen) (flange, gasket sealing surface). Moreover, the application temperature of titanium can only reach 300 °C. Although zirconium and hafnium have excellent corrosion resistance, they are expensive because of the high price. All active metals cannot be used in fluorine-containing environments, and their applications are limited.


In comparison, nickel-based alloys have advantages. Since nickel itself is a face-centered cubic structure, its crystallographic stability makes it capable of containing more alloying elements (chromium, molybdenum, etc.) than iron-based alloys to achieve resistance to various environments. Plus nickel itself has a certain degree of corrosion resistance, especially the resistance to chloride corrosion caused by chloride ions is unmatched by all stainless steel. Most Hastelloys can be applied to a wider range of environments and temperature ranges, and are one of the few metal materials that are resistant to fluoride. Hastelloy itself is a nickel-based alloy, but unlike ordinary pure nickel (Ni200) and Monel, it uses chromium-molybdenum as the main alloying element, which is designed to improve the adaptability to various media and temperature, and is applied to different industries. Specialized optimization was carried out.


In summary, the “three-in-one” (filtration, washing, drying) multi-functional equipment produced uses Hastelloy as the main component material to ensure safe filtration of various chemical materials under high temperature and high pressure and strong corrosion. Washing and drying improve the equipment's tolerance and work efficiency, reduce the number of unplanned inspections and various costs, and play an important role in increasing production capacity and creating more profit space for the company. The upgrading and transformation of equipment, innovation and development, occupying more market for pharmaceutical and chemical equipment is of great significance.