CN1166813C - A chemical treatment method for stainless steel packing - Google Patents

Abstract

The present invention relates to a chemical treatment method of stainless steel stuffing for separation towers. The chemical treatment method comprises: stainless steel stuffing is immersed in chemical coating working solution of 20 to 100 DEG C for 1 to 5 hours, and then the stainless steel stuffing is flushed with water to neutrality and dried by airing; the chemical coating working solution is prepared from organic acid A, inorganic salt B and additive C. When the chemical treatment method is used for treating stuffing, an oxide film relative to water solution is generated on the stuffing; therefore, the surface damping performance to the water solution is greatly improved, the separation efficiency for substances in the water solution is increased, and meanwhile, the corrosion resistance of the stuffing is greatly increased.

Description

A chemical treatment method for stainless steel packing

The invention relates to a packing used for a separation tower, in particular to a surface treatment method for a stainless steel packing.

Packed separation towers have been widely used in petrochemical, oil refining, chemical fertilizer, environmental protection and many other industries due to their high efficiency, low resistance and high throughput. It has a good separation effect on most chemical systems, especially organic systems, mainly because the filler has a large porosity and specific surface area, and its surface has excellent affinity for organic systems. However, in the actual industrial process, it is often encountered to be separated that contains a large amount of water and is highly corrosive, such as acetic acid-water system, dilute sulfuric acid-water system, etc. Due to the high surface tension of these concentrated aqueous phase systems, the wettability and film-forming properties of the system on the surface of the filler will become particularly poor, resulting in the filler often not being able to fully exert its due high-efficiency separation effect, and due to high corrosion, Generally, stainless steel is in danger of being damaged.

The chemical treatment of stainless steel and other surface modified steel surfaces has been extensively reported. The method adopted is generally electroless copper plating (such as US 5151168, US 5139923), nickel plating (such as US 5019163) and precious metal plating (such as gold plating, US5202151), etc. This method is that there is no external current in the electrolyte solution, and the The surface of the workpiece is catalyzed to form a coating on the surface of the workpiece. Another more convenient chemical treatment method is to treat by chemical conversion coating, such as phosphating treatment (US 5207840, SU 1782997, US 603921) on the surface of steel, passivation treatment (US 5188714, EP 504621), chromium salt treatment (US 5188714, EP 504621). 5399209, DE 4432013) etc. The above chemical treatments are basically done to improve the anti-corrosion and corrosion resistance of the surface of the metal workpiece. There is no report on the surface chemical treatment of fillers, especially stainless steel fillers, to improve their surface wettability and improve their separation efficiency.

The purpose of the present invention is to provide a chemical treatment that improves the affinity of the surface of the stainless steel filler to water, improves the wetting effect of the filler surface, thereby greatly improving the film-forming performance of the water-containing system on the filler surface, and fully exerting the separation efficiency of the filler. method.

The technical scheme of this patent is as follows.

The surface of the stainless steel packing is first degreased and decontaminated, and then the treated packing is soaked in the chemical coating working fluid. The working fluid is composed of inorganic acid A, inorganic salt B and additive C. The composition of inorganic acid A can be concentrated sulfuric acid 0-400g/l, concentrated hydrochloric acid 0-200g/l, concentrated nitric acid 50-700g/l, phosphoric acid 0-500g/l, etc. Inorganic salt B is generally 2-80 g/l of chromate or dichromate, 0-50 g/l of tripolyphosphate, etc. Additive C is generally any one of urea, thiourea, hexamethylenetetramine, etc., with a concentration of 0.5-3 g/l. Make the above three agents into an aqueous solution to obtain a working solution for chemical coating. The method of use is generally to soak the filler in the working fluid, the working temperature is 20-100°C, preferably 35-60°C, and the soaking time is generally 1-5 hours, preferably 2.5-3.5 hours. After the filler is taken out, rinse it with clean water until it is neutral, and then dry it. Through this treatment, the roughness of the filler surface is increased, and a dense layer of oxide film is formed. In this way, the surface wettability of the filler to the aqueous solution is greatly improved, and the corrosion resistance of the filler is also greatly improved.

The packing material that the present invention relates to can be various types of stainless steel (1～4)Cr13, 3Cr13Mo, 1Cr17, 1Cr17Ti, 1Cr18, 1Cr25Ti, 1Cr17Mo2Ti, 1Cr17Ni2, 0Cr18Ni9, 1Cr18Ni9, 2Cr18Ni9, 0Cr18Ni9Ti, 0Cr18Ni12Mo2Ti, 0Cr18Ni12Mo3Ti, 1Cr18Ni132Mo2Ti, etc. . The filler during chemical treatment can be treated as a whole piece of filler, or a piece of filler sheet can be treated separately and then wrapped. The structured packing used is usually of plate corrugated type or wire mesh type. This chemical treatment method is also applicable to other bulk packings of the above materials such as Pall rings, saddle rings, etc.

By adopting the treatment method of the invention, the wettability of the surface of the stainless negative filler to water at room temperature is increased from 25% to over 94%. The filler treated by the invention is used in a rectification tower, and the rectification separation efficiency is increased by 33% to 64%. Corrosion resistance has also been greatly improved.

Description of drawings:

Figure 1 shows the wetting of water on the surface of ordinary stainless steel sheets before and after chemical treatment. A is the part that has been chemically treated, and B is the part that has not been chemically treated.

Figure 2 shows the wetting of water on the surface of the stainless steel filler before chemical treatment.

Figure 3 shows the wetting of water on the surface of stainless steel filler after chemical treatment.

The present invention is further illustrated below with examples.

Embodiment one. After the 316L (US brand) stainless steel plate corrugated structured packing has been degreased and decontaminated, it is immersed in a solution containing concentrated HNO ₃ 650g/l, K ₂ Cr ₂ O ₇ 15g/l and thiourea 2g/l. 70-80°C, soak for 3 hours for chemical coating treatment, then take it out, rinse with clean water, and dry. After the treatment, the wettability of the filler surface to water at room temperature is increased from 25% to 94%. After testing, the rectification separation efficiency of acetic acid-water is increased by 60%. At the same time, when the surface-treated filler is immersed in 60% acetic acid at 105°C for 72 hours, its corrosion weight loss is 1/230 of that of the untreated filler.

Embodiment two. Same as Example 1, wherein the stainless steel corrugated structured packing is 317L, the working fluid contains concentrated H ₂ NO ₃ 100g/l, H ₃ PO ₄ 200g/l, K ₂ Cr ₂ O ₇ 60g/l, hexamethylenetetramine 1g/l. After the treatment, the wettability of the filler surface to water at room temperature is increased from 25% to 96%. After testing, the rectification and separation efficiency of acetic acid-water is increased by 64%. At the same time, the surface-treated filler loses 1/240 of its weight against acetic acid with a concentration of 60%.

Embodiment three. 304 (American brand) stainless steel wire mesh structured packing, after degreasing and decontaminating with cleaning solution, immerse it in a solution containing concentrated HNO ₃ 350g/l, concentrated H ₂ SO ₄ 50g/l, K ₂ Cr ₂ O ₇ 30g/l, Soak in 1.5g/l urea solution at 50°C for 2.5 hours, take it out, rinse it with clean water, and dry it in the air. After testing, the separation efficiency of methanol-water is increased by 33% after the treatment of the screen packing. After immersing the surface-treated filler in dilute sulfuric acid (20% concentration) at 100°C for 48 hours, the corrosion weight loss was reduced to 1/180.

Claims (2)

1. the chemical treatment method of a Stainless Steel Helices, it is characterized in that Stainless Steel Helices after the surface degreasing abatement processes, be placed in the chemical overlay film working fluid and soaked 1～5 hour, the water flushing is to neutral then, described chemical overlay film working fluid is by mineral acid A, inorganic salt B and addition of C are formed, mineral acid A contains the vitriol oil 0～400g/L, concentrated hydrochloric acid 0～200g/L, concentrated nitric acid 50～700g/L and phosphoric acid 0～500g/L, inorganic salt B contains chromic salt or dichromate 2～80g/L and tri-polyphosphate 0～50g/L, addition of C is a urea, or thiocarbamide or hexamethylenetetramine, content is 0.5～3g/L.

2. treatment process according to claim 1 is characterized in that soak time is 2.5～3.5 hours, and temperature is 35～60 ℃.

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