What kind of chemicals are used in the pit invasion of oxide ore
Publish: 2021-04-16 10:32:50
1. Verify that the server computer has a working network connection. First, use the basic network and hardware troubleshooting steps to check whether the relevant client hardware (cables and network adapters) is working properly on the client
if the server hardware is ready and working properly, use the ping command to check the network connectivity between other in use and available computers or routers (such as its default gateway) on the same network as the affected DNS server
many users like to use two screens, especially programmers, game players, video procers and so on. It can be said that the two screens display and the game work together. So what's the use of setting up al screen display or multi screen display? How to set up al or multi screen display? Here is a brief introction to its function and specific operation method
What are the advantages of al screen display (computer)
1. Large screen splicing
(splicing computer graphics, splicing dynamic video) projection wall; Command and dispatch systems for public security, military, railway, transportation, aerospace, posts and telecommunications, satellite launching, etc; Graphics and image editing, 3D animation, multimedia design; Process control in instrial field; Information display of securities trading, futures and banks; CAD / CAM design, typesetting editing system, video image editing
2. File editing:
when making planning documents, you should also refer to and search for relevant network information, so as to avoid data confusion caused by switching windows
3. Drawing editing:
when using the drawing software to design a case, the reference document window can be opened at the same time, and the desktop can also be extended to facilitate the processing of large-scale design draft proction, which does not overlap with the proofreading window
4. Film and television entertainment:
(1) watch Internet TV and browse the program introction of other channels at the same time, so that you can not miss the wonderful programs
(2) when playing online games, you can synchronously compare the secret skills of the game strategy< 5. Office:
(1) view large tables (such as Excel charts) across more than two screens
(2) to open multiple programs on the extended desktop space at the same time, there is no need to switch the windows frequently
(3) read the email and open the attachment file on other screens at the same time
6. Program design:
when writing a complex program, another window can view the program execution result screen at the same time to facilitate updating and modification
these are the advantages of al screen computers. Do you know something about al screen computers now? See small make up for everybody to enumerate is the advantage of double screen computer is a little bit excited? Let's take a look at how to set it<
1. Hardware requirements (take win10 system as an example)
1. The computer host must have any two-way output independent graphics interface of VGA / DVI / HDMI (generally supported by entry-level graphics card), as shown in the figure below:
2. Prepare any two VGA / DVI / HDMI cables, and the appearance diagram of the corresponding connection cable of the display output interface is as follows:
3. Two monitors, Support any two interfaces of VGA / DVI / HDMI (otherwise VGA converter connector is needed)
2. Operation steps of al screen
1. First, connect the external display and computer graphics card interface through any two cables of VGA / DVI / HDMI
2. After the connection is successful, enter the desktop of the computer system, right-click the blank space of the desktop, and select display settings
3. If the connection is successful, you can see that there are two displays
4. In the display interface, select expand these displays under multi display settings, and then the two displays can be displayed normally
5. If the line detection is OK and still can't be displayed, right-click the desktop and select NVIDIA control panel
6. Find [set multiple monitors], and then check the monitor we want to use<
3. Multi screen display method
hardware requirements:
in addition to supporting al screen hardware conditions, some computers need to enter BIOS settings to find relevant options. If it cannot be found, it means that the motherboard does not support it, please refer to the following operation
steps to enter BIOS:
1. Turn on the computer to enter BIOS, find the options of [devices] - VIDEO setup], and click enter
2. Select the select active video option and set it to IgD mode, and set the multi monitor support option to enabled mode
3. After setting, click F10 and select Yes to save
4. After restarting the operating system, right-click in the blank space of the desktop, find the integrated graphics card console program from the menu, and set the multi screen display.
if the server hardware is ready and working properly, use the ping command to check the network connectivity between other in use and available computers or routers (such as its default gateway) on the same network as the affected DNS server
many users like to use two screens, especially programmers, game players, video procers and so on. It can be said that the two screens display and the game work together. So what's the use of setting up al screen display or multi screen display? How to set up al or multi screen display? Here is a brief introction to its function and specific operation method
What are the advantages of al screen display (computer)
1. Large screen splicing
(splicing computer graphics, splicing dynamic video) projection wall; Command and dispatch systems for public security, military, railway, transportation, aerospace, posts and telecommunications, satellite launching, etc; Graphics and image editing, 3D animation, multimedia design; Process control in instrial field; Information display of securities trading, futures and banks; CAD / CAM design, typesetting editing system, video image editing
2. File editing:
when making planning documents, you should also refer to and search for relevant network information, so as to avoid data confusion caused by switching windows
3. Drawing editing:
when using the drawing software to design a case, the reference document window can be opened at the same time, and the desktop can also be extended to facilitate the processing of large-scale design draft proction, which does not overlap with the proofreading window
4. Film and television entertainment:
(1) watch Internet TV and browse the program introction of other channels at the same time, so that you can not miss the wonderful programs
(2) when playing online games, you can synchronously compare the secret skills of the game strategy< 5. Office:
(1) view large tables (such as Excel charts) across more than two screens
(2) to open multiple programs on the extended desktop space at the same time, there is no need to switch the windows frequently
(3) read the email and open the attachment file on other screens at the same time
6. Program design:
when writing a complex program, another window can view the program execution result screen at the same time to facilitate updating and modification
these are the advantages of al screen computers. Do you know something about al screen computers now? See small make up for everybody to enumerate is the advantage of double screen computer is a little bit excited? Let's take a look at how to set it<
1. Hardware requirements (take win10 system as an example)
1. The computer host must have any two-way output independent graphics interface of VGA / DVI / HDMI (generally supported by entry-level graphics card), as shown in the figure below:
2. Prepare any two VGA / DVI / HDMI cables, and the appearance diagram of the corresponding connection cable of the display output interface is as follows:
3. Two monitors, Support any two interfaces of VGA / DVI / HDMI (otherwise VGA converter connector is needed)
2. Operation steps of al screen
1. First, connect the external display and computer graphics card interface through any two cables of VGA / DVI / HDMI
2. After the connection is successful, enter the desktop of the computer system, right-click the blank space of the desktop, and select display settings
3. If the connection is successful, you can see that there are two displays
4. In the display interface, select expand these displays under multi display settings, and then the two displays can be displayed normally
5. If the line detection is OK and still can't be displayed, right-click the desktop and select NVIDIA control panel
6. Find [set multiple monitors], and then check the monitor we want to use<
3. Multi screen display method
hardware requirements:
in addition to supporting al screen hardware conditions, some computers need to enter BIOS settings to find relevant options. If it cannot be found, it means that the motherboard does not support it, please refer to the following operation
steps to enter BIOS:
1. Turn on the computer to enter BIOS, find the options of [devices] - VIDEO setup], and click enter
2. Select the select active video option and set it to IgD mode, and set the multi monitor support option to enabled mode
3. After setting, click F10 and select Yes to save
4. After restarting the operating system, right-click in the blank space of the desktop, find the integrated graphics card console program from the menu, and set the multi screen display.
2. Warm water + a certain temperature,
3. In fact, there is a kind of medicament that does not need to use NaCN and sodium cyanide. It is made by Guangxi Desheng gold company. You can check it out. This kind of medicament is called northeast tiger gold selection medicament, and it is an environmental protection and safe gold selection medicament
```
```
4. NaCN, sodium cyanide. The chemical properties of gold are stable, but it is easy to form complexes; For example, aqua regia can dissolve gold. Sodium cyanide reacts with gold to form AGCn complex, which is dissolved in water and then replaced with gold by subsequent treatment. This method is suitable for low content. Zijin Mining is taking this approach, but the pollution is serious.
5. Control what diseases and insect pests with what medicine. Such as apple mold heart disease, is a fungal disease, the pathogen in the flowering period through the stigma invasion, to the ventricular expansion, leading to disease. Spraying 300 times more 1.5% carbendazim or 800 times more 30% carbendazim, tebuconazole or 1000 times more 50% thiophanate methyl plus 800 times more 80% mancozeb on the leaves of 70-80% flowers at the initial flowering stage and flower withering stage. Apple Anthracnose leaf blight. Control with 800 times 80% mancozeb or 600 times 70% propionate or 1000 times 30% tebuconazole carbendazim or 800 times 77% donin or 600 times 66% Tongjia or 1:2:200 times Bordeaux solution, spray once every 7-10 days, spray 2-3 times continuously, the disease can be controlled, and the diseased plants can return to normal growth. Donin, Tongjia and Bordeaux liquid should be used after bagging.
6. The introction of phosphorus removal procts from a company basically covers the relevant knowledge of chemical phosphorus removal ~
1 status quo
e to the extensive use of phosphorus containing detergents, a certain amount of phosphorus is generally contained in urban sewage in China, which is generally 5-10mg / L. Phosphorus is one of the limiting factors for algae reproction. The level of phosphorus in water is closely related to the degree of eutrophication. At the same time, the role of phosphorus is far greater than that of nitrogen in causing water eutrophication. When the concentration of phosphorus in water reaches a certain value, it can cause water eutrophication. Therefore, it is necessary to remove phosphorus in wastewater treatment. China's "discharge standard of common pollutants for urban sewage treatment" (GB18918-2002) clearly stipulates that the first class a discharge standard of total phosphorus index of sewage treatment plants constructed since January 1, 2006 is 0.5mg/l
phosphorus in wastewater can be removed by chemical and biological methods. Biological phosphorus removal is a relatively economic method of phosphorus removal, but at present, the biological phosphorus removal process can not ensure that the effluent total phosphorus can reach the standard of 0.5mg/l, so chemical phosphorus removal measures are often needed<
2 principle of chemical phosphorus removal
chemical phosphorus removal is mainly completed by chemical precipitation process. Chemical precipitation refers to the reaction of adding inorganic metal salts into sewage and soluble salts (such as phosphate) in sewage to proce granular and insoluble substances. In fact, after adding chemicals, not only precipitation reaction but also chemical flocculation takes place in the sewage, that is, the fine insoluble solids are bound together to form larger flocs
3 chemical phosphorus removal agents
in order to generate insoluble phosphate compounds, the main chemical agents used for chemical phosphorus removal are metal salts and calcium hydroxide. Many high priced metal ion reagents will combine with dissolved phosphorus ions in wastewater to form insoluble compounds. However, for economic reasons, the metal salt reagents used for phosphorus precipitation are mainly Fe3 + salt, Fe2 + salt and Al3 + salt, which are used in solution and suspension state. In addition to metal salts, calcium hydroxide is also used as precipitation agent to proce calcium phosphate insoluble in water
see Table 1 for the types of chemicals commonly used in wastewater chemical phosphorus removal<
Table 1 common chemicals for wastewater purification
type
name
molecular formula
state
aluminum salt
aluminum sulfate
Al2 (SO4) 3 · 18H2O
solid
Al2 (SO4) 3 · 14h2o
liquid
nal2 (SO4) 3 · xH2O + mfe2 (SO4) 3 · yh2o
solid
aluminum chloride
AlCl3
liquid
AlCl3 + FeCl3
liquid
polyaluminum chloride
[Al2 (OH) nCl6-n] m
solid Liquid
two ferric salt
/>FeSO4 ferrous sulfate
FeSO4 / 7H2O
solid
FeSO4
liquid
ferric salt
chlorinated ferric sulfate
FeClSO4
liquid (about 40%) f / > liquid iron (/>FeSO4) / > liquid > ca. According to the location of chemical dosing, the commonly used methods are: pre dephosphorization, synchronous dephosphorization and post dephosphorization
4.1 pre dephosphorization
the pre dephosphorization process is characterized by adding chemicals into the grit chamber, the inlet channel (pipe) of the primary sedimentation tank, or the venturi channel (using eddy current). It generally needs to set up devices to generate eddy current or supply energy to meet the needs of mixing. The corresponding precipitated procts (massive flocs) are separated by precipitation in the primary sedimentation tank. If the biofilter is used in the biological section, it is not allowed to use ferric salt to prevent damage to the filler (yellow rust)
the pre phosphorus removal process is more suitable for the reconstruction of the existing sewage treatment plant because it only adds chemical phosphorus removal measures at the front end of the existing process. This process can not only remove phosphorus, but also rece the load of biological treatment facilities. The common chemicals are mainly lime and metal salt. The content of resial phosphate was controlled to be 1.5-2.5mg/l after pre dephosphorization, which could meet the needs of subsequent biological treatment<
4.2 synchronous phosphorus removal
synchronous phosphorus removal is the most widely used chemical phosphorus removal process, accounting for about 50% of all chemical phosphorus removal processes abroad. The process is to add chemicals into the outlet water of aeration tank or the inlet water of secondary sedimentation tank. In some cases, chemicals are also added into the inlet water of aeration tank or the return sludge channel (pipe). At present, it has been determined that the simultaneous chemical phosphorus removal method can be used for the activated sludge process and the biological rotary table process, but it is still worth discussing whether the reagent can be added into the influent of the secondary sedimentation tank in the biological filter process< Post phosphorus removal is a process in which sedimentation, flocculation and separation of flocculated substances are carried out in a facility separated from biological treatment, so it is also called two-stage process. Generally, chemicals are added to a mixing tank after the secondary sedimentation tank, and a flocculation tank and a sedimentation tank (or an air flotation tank) are set behind the tank
for the lax receiving water body, the lime emulsion agent can be used in the post phosphorus removal process, but the pH value of the effluent must be controlled, if CO2 can be used for neutralization.
the flotation tank can remove suspended solids and total phosphorus better than the sedimentation tank, but the operation cost is higher because of the constant supply of air
the advantages and disadvantages of the three phosphorus removal processes are summarized in Table 2
Table 2 Comparison of various chemical phosphorus removal processes
process types
advantages
disadvantages
pre phosphorus removal process
1) can rece the load of biological treatment structures and balance the fluctuation of load, so as to rece energy consumption
2) compared with simultaneous phosphorus removal, the organic components in activated sludge will not increase
3) the existing sewage treatment plant is easy to implement transformation
1) total sludge proction increased
2) affecting denitrification (excessive substrate decomposition)
3) it is unfavorable to improve the sludge index
simultaneous phosphorus removal process
1) phosphorus removal agents can be fully utilized through sludge return
2) if the reagent is added to the aeration tank, the cheaper ferrous salt reagent can be used
3) metal salts can increase the weight of activated sludge and avoid sludge bulking
4) the amount of simultaneous phosphorus removal facilities is small
1) synchronous phosphorus removal process can increase sludge proction
2) the use of acidic metal salts will rece the pH value below the optimal range, which is unfavorable for nitrification
3) it is difficult to recover phosphate when nitrate sludge and excess sludge are mixed together. In addition, phosphorus in sludge will be released again under anaerobic condition
4) the reflux pump will destroy the flocs, but the harm can be reced by adding polymer flocculant AIDS
post phosphorus removal process
1) nitrate precipitation and biological treatment process are separated, and do not affect each other
2) the dosage can be controlled according to the change of phosphorus load
3) the phosphate sludge can be discharged separately and utilized< However, when a new sewage treatment plant is built, the size of the secondary sedimentation tank can be reced by using the post phosphorus removal process.
1 status quo
e to the extensive use of phosphorus containing detergents, a certain amount of phosphorus is generally contained in urban sewage in China, which is generally 5-10mg / L. Phosphorus is one of the limiting factors for algae reproction. The level of phosphorus in water is closely related to the degree of eutrophication. At the same time, the role of phosphorus is far greater than that of nitrogen in causing water eutrophication. When the concentration of phosphorus in water reaches a certain value, it can cause water eutrophication. Therefore, it is necessary to remove phosphorus in wastewater treatment. China's "discharge standard of common pollutants for urban sewage treatment" (GB18918-2002) clearly stipulates that the first class a discharge standard of total phosphorus index of sewage treatment plants constructed since January 1, 2006 is 0.5mg/l
phosphorus in wastewater can be removed by chemical and biological methods. Biological phosphorus removal is a relatively economic method of phosphorus removal, but at present, the biological phosphorus removal process can not ensure that the effluent total phosphorus can reach the standard of 0.5mg/l, so chemical phosphorus removal measures are often needed<
2 principle of chemical phosphorus removal
chemical phosphorus removal is mainly completed by chemical precipitation process. Chemical precipitation refers to the reaction of adding inorganic metal salts into sewage and soluble salts (such as phosphate) in sewage to proce granular and insoluble substances. In fact, after adding chemicals, not only precipitation reaction but also chemical flocculation takes place in the sewage, that is, the fine insoluble solids are bound together to form larger flocs
3 chemical phosphorus removal agents
in order to generate insoluble phosphate compounds, the main chemical agents used for chemical phosphorus removal are metal salts and calcium hydroxide. Many high priced metal ion reagents will combine with dissolved phosphorus ions in wastewater to form insoluble compounds. However, for economic reasons, the metal salt reagents used for phosphorus precipitation are mainly Fe3 + salt, Fe2 + salt and Al3 + salt, which are used in solution and suspension state. In addition to metal salts, calcium hydroxide is also used as precipitation agent to proce calcium phosphate insoluble in water
see Table 1 for the types of chemicals commonly used in wastewater chemical phosphorus removal<
Table 1 common chemicals for wastewater purification
type
name
molecular formula
state
aluminum salt
aluminum sulfate
Al2 (SO4) 3 · 18H2O
solid
Al2 (SO4) 3 · 14h2o
liquid
nal2 (SO4) 3 · xH2O + mfe2 (SO4) 3 · yh2o
solid
aluminum chloride
AlCl3
liquid
AlCl3 + FeCl3
liquid
polyaluminum chloride
[Al2 (OH) nCl6-n] m
solid Liquid
two ferric salt
/>FeSO4 ferrous sulfate
FeSO4 / 7H2O
solid
FeSO4
liquid
ferric salt
chlorinated ferric sulfate
FeClSO4
liquid (about 40%) f / > liquid iron (/>FeSO4) / > liquid > ca. According to the location of chemical dosing, the commonly used methods are: pre dephosphorization, synchronous dephosphorization and post dephosphorization
4.1 pre dephosphorization
the pre dephosphorization process is characterized by adding chemicals into the grit chamber, the inlet channel (pipe) of the primary sedimentation tank, or the venturi channel (using eddy current). It generally needs to set up devices to generate eddy current or supply energy to meet the needs of mixing. The corresponding precipitated procts (massive flocs) are separated by precipitation in the primary sedimentation tank. If the biofilter is used in the biological section, it is not allowed to use ferric salt to prevent damage to the filler (yellow rust)
the pre phosphorus removal process is more suitable for the reconstruction of the existing sewage treatment plant because it only adds chemical phosphorus removal measures at the front end of the existing process. This process can not only remove phosphorus, but also rece the load of biological treatment facilities. The common chemicals are mainly lime and metal salt. The content of resial phosphate was controlled to be 1.5-2.5mg/l after pre dephosphorization, which could meet the needs of subsequent biological treatment<
4.2 synchronous phosphorus removal
synchronous phosphorus removal is the most widely used chemical phosphorus removal process, accounting for about 50% of all chemical phosphorus removal processes abroad. The process is to add chemicals into the outlet water of aeration tank or the inlet water of secondary sedimentation tank. In some cases, chemicals are also added into the inlet water of aeration tank or the return sludge channel (pipe). At present, it has been determined that the simultaneous chemical phosphorus removal method can be used for the activated sludge process and the biological rotary table process, but it is still worth discussing whether the reagent can be added into the influent of the secondary sedimentation tank in the biological filter process< Post phosphorus removal is a process in which sedimentation, flocculation and separation of flocculated substances are carried out in a facility separated from biological treatment, so it is also called two-stage process. Generally, chemicals are added to a mixing tank after the secondary sedimentation tank, and a flocculation tank and a sedimentation tank (or an air flotation tank) are set behind the tank
for the lax receiving water body, the lime emulsion agent can be used in the post phosphorus removal process, but the pH value of the effluent must be controlled, if CO2 can be used for neutralization.
the flotation tank can remove suspended solids and total phosphorus better than the sedimentation tank, but the operation cost is higher because of the constant supply of air
the advantages and disadvantages of the three phosphorus removal processes are summarized in Table 2
Table 2 Comparison of various chemical phosphorus removal processes
process types
advantages
disadvantages
pre phosphorus removal process
1) can rece the load of biological treatment structures and balance the fluctuation of load, so as to rece energy consumption
2) compared with simultaneous phosphorus removal, the organic components in activated sludge will not increase
3) the existing sewage treatment plant is easy to implement transformation
1) total sludge proction increased
2) affecting denitrification (excessive substrate decomposition)
3) it is unfavorable to improve the sludge index
simultaneous phosphorus removal process
1) phosphorus removal agents can be fully utilized through sludge return
2) if the reagent is added to the aeration tank, the cheaper ferrous salt reagent can be used
3) metal salts can increase the weight of activated sludge and avoid sludge bulking
4) the amount of simultaneous phosphorus removal facilities is small
1) synchronous phosphorus removal process can increase sludge proction
2) the use of acidic metal salts will rece the pH value below the optimal range, which is unfavorable for nitrification
3) it is difficult to recover phosphate when nitrate sludge and excess sludge are mixed together. In addition, phosphorus in sludge will be released again under anaerobic condition
4) the reflux pump will destroy the flocs, but the harm can be reced by adding polymer flocculant AIDS
post phosphorus removal process
1) nitrate precipitation and biological treatment process are separated, and do not affect each other
2) the dosage can be controlled according to the change of phosphorus load
3) the phosphate sludge can be discharged separately and utilized< However, when a new sewage treatment plant is built, the size of the secondary sedimentation tank can be reced by using the post phosphorus removal process.
7.
Caustic soda refers to sodium hydroxide, pure proct is colorless and transparent crystal, chemical formula is NaOH, commonly known as caustic soda, caustic soda, caustic soda, is a kind of strong caustic soda, generally in sheet or block form, easy to dissolve in water (exothermic when dissolved in water) and form alkaline solution, and deliquescence, easy to absorb water vapor (deliquescence) and carbon dioxide (deterioration) in the air, Hydrochloric acid can be added to check for deterioration
Sodium hydroxide is used to proce various detergents Papermaking: e to its alkalinity, it is used in the process of boiling and bleaching paper Artificial fiber and textile: cotton fabric treated with caustic soda solution can remove the wax, grease, starch and other substances covered on the cotton fabric, increase the mercerizing color of the fabric, and make the dyeing more uniform Refined petroleum: after washing with sulfuric acid, petroleum procts also contain some acidic substances, which must be washed with sodium hydroxide solution and then washed with water to get refined procts Water treatment: in wastewater treatment plant, sodium hydroxide can rece the hardness of water through neutralization reaction In 1787, doctor Nicolas LeBlanc (1762-1806) invented a suitable process for the preparation of sodium hydroxide from table salt and carried out large-scale proction In 1887, the Swedish chemist Arrhenius founded the acid-base ionization theory (i.e. the acid-base theory of aqueous solution). He proposed that acid is the substance in which all the cations ionized in aqueous solution are hydrogen ions, and alkali is the substance in which all the anions ionized in aqueous solution are hydrogen ions. Since then, the basicity of sodium hydroxide has been clearly definedsource: Internet - sodium hydroxide
8. The main component of gypsum is CaSO4 · 2H2O
soluble in acid, sodium thiosulfate and ammonium salt solution
soluble in acid, sodium thiosulfate and ammonium salt solution
9. 1. The necessity of stainless steel pickling and passivation:
austenitic stainless steel has good corrosion resistance, high temperature oxidation resistance, good low temperature performance and excellent mechanical and energy generation. Therefore, it is widely used in chemical instry, petroleum, power, nuclear engineering, aerospace, marine, medicine, light instry, textile and other departments. Its main purpose is to prevent corrosion and rust. The corrosion resistance of stainless steel mainly depends on the surface passive film. If the film is incomplete or defective, the stainless steel will still be corroded. Pickling and passivation are usually used in engineering to make the corrosion resistance potential of stainless steel play a greater role. In the process of forming, assembling, welding, weld inspection (such as flaw detection, pressure test) and construction marking of stainless steel equipment and parts, surface oil, rust, non-metallic dirt, low melting point metal pollutants, paint, welding slag and spatter are brought. These substances affect the surface quality of stainless steel equipment and parts and damage the oxide film on the surface, The overall corrosion resistance and local corrosion resistance (including pitting corrosion and crevice corrosion) of the steel are reced, and even stress corrosion cracking is caused
stainless steel surface cleaning, pickling and passivation can not only maximize the corrosion resistance, but also prevent proct pollution and obtain beautiful appearance. According to gbl50-1998 "steel pressure vessels", the surface of vessels made of stainless steel and clad steel plates with anti-corrosion requirements shall be pickled and passivated. This regulation is aimed at the pressure vessels used in petrochemical instry, because these equipment are used in the situation of direct contact with corrosive medium. In order to ensure the corrosion resistance, pickling passivation is necessary. For other instrial sectors, if it is not for the purpose of anti-corrosion, it is only based on the requirements of cleaning and aesthetics, and stainless steel is used, acid pickling and passivation are not required. However, pickling and passivation are needed for the weld of stainless steel equipment. In addition to acid pickling and passivation, high-purity medium should be used for final fine cleaning or mechanical, chemical and electrolytic polishing< The corrosion resistance of stainless steel is mainly e to a very thin (about 1nm) dense passivation film on the surface, which is isolated from 1n corrosion medium and is the basic barrier of stainless steel protection. The passivation of stainless steel has dynamic characteristics, which should not be regarded as the complete stop of corrosion, but the formation of diffusion barrier layer, which greatly reces the anodic reaction speed. Generally, it tends to destroy the membrane in the presence of recing agent (such as chloride ion), but it can maintain or repair the membrane in the presence of oxidant (such as air)< However, the protection of this kind of film is not perfect. In order to ensure the integrity and stability of the passive film, it is necessary to clean thoroughly, including alkali washing and acid washing, and then passivate with oxidant. One of the purposes of pickling is to create favorable conditions for passivation treatment and ensure the formation of high quality passivation film. Because the stainless steel surface is 10% on average by pickling μ The chemical activity of the acid solution makes the dissolution rate of the defect part higher than that of other parts on the surface. Therefore, acid pickling can make the whole surface tend to be uniform and balanced, and some hidden dangers that are easy to cause corrosion are removed. But more importantly, through pickling passivation, iron and iron oxides are dissolved preferentially than chromium and chromium oxides, and chromium poor layer is removed, resulting in chromium enrichment on the surface of stainless steel. The potential of this chromium rich passivation film can reach + 1.0V (SCE), which is close to the potential of noble metal, and improves the stability of corrosion resistance. Different passivation treatment will also affect the composition and structure of the film, thus affecting the rust resistance. For example, through electrochemical modification, the passivation film can have multi-layer structure, form CrO3 or Cr2O3 in the barrier layer, or form a glassy oxide film, so as to maximize the corrosion resistance of stainless steel
a lot of researches on the formation of passive film on stainless steel have been carried out by scholars at home and abroad. In recent years, Beijing University of science and technology for 316L steel passivation film photoelectron spectros (XPS) research as an example for a brief description [1]. Passivation of stainless steel is the surface layer dissolved for some reason and absorbed by water molecules. Under the catalysis of oxidant, oxides and hydroxides are formed, and the conversion reaction takes place with Cr, Ni and Mo elements of stainless steel. Finally, a stable phase forming film is formed, which prevents the damage and corrosion of the film. The reaction mechanisms are as follows: < br / < br / < Fe · H2O (Fe · H2O) and [feoh · o *] [feoh · o *] [feoh · o *] [feoh · o *] [FeO · o *] [FeO · o *] [FeO · o *] [FeO · o *] [feoh · o *] [feoh · o *] [feoh · o *] [feoh · o *] [feoh · o *] [FeO · o · o *] [FeO · o · o *] [FeO · o · o *] [FeO · o · o · o *] [FeO · o · o · o · o *] [FeO · o · o · o · o · o · o · · o · O] as [feoh · o · o · o · o · o (FeO · h · H2O] and [FeO · H · h · h · h · h · h · H] and [fe2oh · H2O] and ((where OS is the passivation process Ad is the adsorption intermediate.)[ It can be seen that Fe2O3, Fe (OH) 3, or γ - FeOOH, CR203, crooh or Cr (OH) 3, Mo exist in the form of moo, and the main components of the passive film are CrO3, FeO and NiO
3. Pickling and passivation methods and processes for stainless steel
3.1 comparison of pickling and passivation methods
there are many pickling and passivation methods for stainless steel equipment and parts according to different operations, and their application scope and characteristics are shown in Table 1
Table 1 Comparison of pickling and passivation methods for stainless steel
advantages and disadvantages of application scope of the methods
impregnation method is used for parts that can be put into pickling tank or passivation tank, but it is not suitable for large equipment. Pickling solution can be used for a long time with high proction efficiency and low cost; The large volume equipment is full of acid, and the liquid consumption of impregnation is too large.
the brushing method is suitable for the surface and local treatment of large equipment with poor physical operation, poor working conditions, and acid can not be recovered.
the paste method is used for the installation or maintenance site, especially for the manual operation of welding department, poor labor conditions, and high proction cost.
the spraying method is used for the installation site, However, spray gun and cutting ring system are needed for large-scale equipment, such as heat exchanger and shell treatment. It is convenient for construction and acid liquid can be reused. The circulating system needs to be connected with pipe and pump.
electrochemical method can not only be used for parts, but also can be used for on-site equipment surface treatment by brush method, According to astma380-1999, only 300 series stainless steel is taken as an example,
(1) pickling
reagent hno36% ～ 25% + hf0.5% ～ 8% (volume fraction)
temperature 21-60 ℃; Time as needed
or ammonium citrate 5% - 10% (mass fraction)
temperature 49-71 ℃; The time was 10-60min
(2) passivation
HNO3 20% - 50% (volume fraction)
temperature 49-71 ℃; The time was 10-30 min
or temperature 2L ~ 38 ℃; The time was 30-60 min
or HNO3 20% ～ 50% + na2cr207h2022% ～ 6% (mass fraction)
temperature 49-54 ℃; The time was 15-30 min
or 21-38 ℃; The time was 30-60 min< (3) descaling and pickling
h2so48% ～ 11% (volume fraction)
temperature 66-82 ℃; 6-inch interval, 5-45min
and HNO3 6% ～ 25% + HF 0.5% ～ 8% (volume fraction)
temperature 21-60 ℃
or HNO3 15% ～ 25% + HFL% ～ 8% (volume fraction)< 2.2 paste treatment
(1) take the local passivation of internal surface weld, base metal passivation and maintenance surface grinding weld of new urea stainless steel equipment of Guangzhou Petrochemical Company as an example [3]
pickling paste:
25% HNO ~ + 4% HF + 7L% condensed water (volume fraction) and BaSO, adjust to paste
passivation paste:
Paste with 30% HNO3 or 25% HNO3 + 1% (mass fraction) k2cr207 and baso7
after coating the surface for 5-30min, rinse it with condensed water to pH = 7, or spray hydrogen peroxide for chemical passivation of single equipment
(2) take the patent m of Shanghai Daming iron factory as an example
pickling passivation paste:
hn038% ～ 14% (as passivator)
HFL 0% ～ 15% (as corrosive agent)< 2% ～ 2.7% (as thickener)
magnesium nitrate 60% ～ 70% (as filler to improve adhesion and permeability)[ 3% ～ 2.8% (as corrosion inhibitor)
water (adjust viscosity)
3.2.3 electrochemical treatment
taking Xiamen University Patent [5] as an example, the treatment method is as follows: the stainless steel workpiece to be treated is used as anode and anodized by controlling the constant potential, or the stainless steel workpiece is used as cathode first and anodized by controlling the constant potential, and then the stainless steel workpiece is used as anode and anodized by controlling the constant potential, The electrolyte solution was hn03. After such treatment, the properties of passive film on stainless steel are improved and the corrosion resistance is greatly improved. The critical potential of pitting corrosion (EB) is increased by 1000 MV (in 3% NaCl) and the resistance to uniform corrosion is increased by three orders of magnitude (in 20% - 30% h2s04 at 45 ℃)< The application scope of BR />4. stainless steel is pickled and passivated. The pickling and passivation treatment of
4.1 stainless steel equipment ring the manufacturing process,
4.1.1 cleaning and pickling and passivation after machining, [6]
stainless steel workpiece, after cutting, the surface usually contains iron filings, steel and cooling emulsion, which will cause stains and rust on the surface of stainless steel, so degreasing and degreasing should be carried out. After cleaning with nitric acid, not only iron chips and steel powder are removed, but also passivation is carried out
4.1.2 cleaning and pickling passivation before and after welding [7]
because grease is the source of hydrogen, gas will form in the weld without grease removal, and low melting point metal pollution (such as zinc rich paint) will cause cracking after welding, so the groove and the surface within 20 mm on both sides of stainless steel must be cleaned before welding, and the oil can be wiped with acetone, Paint rust should be removed with emery cloth or stainless steel wire brush, and then cleaned with acetone
no matter what kind of welding technology is used in stainless steel equipment manufacturing, all welding slag, spatter, stain and oxidation color should be removed after welding. The removal methods include mechanical cleaning and chemical cleaning. Mechanical cleaning includes grinding, polishing and sand blasting. Carbon steel brush should be avoided to prevent surface rust. In order to obtain the best corrosion resistance, it can be soaked in the mixture of HNO3 and HF, or acid pickling passivation paste can be used. In fact, it is often used in combination with chemical cleaning
4.1.3 cleaning of forged castings [6]
the surface of stainless steel workpieces after hot working such as forging and casting often has a layer of oxide scale, lubricant or oxide pollution, including graphite, molybdenum disulfide and carbon dioxide. Shot peening, salt bath and multi pass pickling shall be used. For example, the treatment process of stainless steel turbine blades in America is as follows:
salt bath (10min) → water quenching (2.5min) → sulfuric acid washing (2min) → cold water washing (2min) → alkaline permanganate bath (10min) → cold water washing (2min) → sulfuric acid washing (1rain) → cold water washing (1min) → nitric acid washing (1.5min) → cold water washing (1min) → hot water washing (1min) → air drying< 2 pickling and passivation treatment before the new plant is put into operation
pickling and passivation treatment is required for stainless steel equipment and pipelines of many large chemical, chemical fiber and chemical fertilizer plants before they are put into operation. Although the equipment has been pickled in the factory to remove the welding slag and oxide scale, it will inevitably cause the pollution of grease, mud sand and rust in the process of storage, transportation and installation
austenitic stainless steel has good corrosion resistance, high temperature oxidation resistance, good low temperature performance and excellent mechanical and energy generation. Therefore, it is widely used in chemical instry, petroleum, power, nuclear engineering, aerospace, marine, medicine, light instry, textile and other departments. Its main purpose is to prevent corrosion and rust. The corrosion resistance of stainless steel mainly depends on the surface passive film. If the film is incomplete or defective, the stainless steel will still be corroded. Pickling and passivation are usually used in engineering to make the corrosion resistance potential of stainless steel play a greater role. In the process of forming, assembling, welding, weld inspection (such as flaw detection, pressure test) and construction marking of stainless steel equipment and parts, surface oil, rust, non-metallic dirt, low melting point metal pollutants, paint, welding slag and spatter are brought. These substances affect the surface quality of stainless steel equipment and parts and damage the oxide film on the surface, The overall corrosion resistance and local corrosion resistance (including pitting corrosion and crevice corrosion) of the steel are reced, and even stress corrosion cracking is caused
stainless steel surface cleaning, pickling and passivation can not only maximize the corrosion resistance, but also prevent proct pollution and obtain beautiful appearance. According to gbl50-1998 "steel pressure vessels", the surface of vessels made of stainless steel and clad steel plates with anti-corrosion requirements shall be pickled and passivated. This regulation is aimed at the pressure vessels used in petrochemical instry, because these equipment are used in the situation of direct contact with corrosive medium. In order to ensure the corrosion resistance, pickling passivation is necessary. For other instrial sectors, if it is not for the purpose of anti-corrosion, it is only based on the requirements of cleaning and aesthetics, and stainless steel is used, acid pickling and passivation are not required. However, pickling and passivation are needed for the weld of stainless steel equipment. In addition to acid pickling and passivation, high-purity medium should be used for final fine cleaning or mechanical, chemical and electrolytic polishing< The corrosion resistance of stainless steel is mainly e to a very thin (about 1nm) dense passivation film on the surface, which is isolated from 1n corrosion medium and is the basic barrier of stainless steel protection. The passivation of stainless steel has dynamic characteristics, which should not be regarded as the complete stop of corrosion, but the formation of diffusion barrier layer, which greatly reces the anodic reaction speed. Generally, it tends to destroy the membrane in the presence of recing agent (such as chloride ion), but it can maintain or repair the membrane in the presence of oxidant (such as air)< However, the protection of this kind of film is not perfect. In order to ensure the integrity and stability of the passive film, it is necessary to clean thoroughly, including alkali washing and acid washing, and then passivate with oxidant. One of the purposes of pickling is to create favorable conditions for passivation treatment and ensure the formation of high quality passivation film. Because the stainless steel surface is 10% on average by pickling μ The chemical activity of the acid solution makes the dissolution rate of the defect part higher than that of other parts on the surface. Therefore, acid pickling can make the whole surface tend to be uniform and balanced, and some hidden dangers that are easy to cause corrosion are removed. But more importantly, through pickling passivation, iron and iron oxides are dissolved preferentially than chromium and chromium oxides, and chromium poor layer is removed, resulting in chromium enrichment on the surface of stainless steel. The potential of this chromium rich passivation film can reach + 1.0V (SCE), which is close to the potential of noble metal, and improves the stability of corrosion resistance. Different passivation treatment will also affect the composition and structure of the film, thus affecting the rust resistance. For example, through electrochemical modification, the passivation film can have multi-layer structure, form CrO3 or Cr2O3 in the barrier layer, or form a glassy oxide film, so as to maximize the corrosion resistance of stainless steel
a lot of researches on the formation of passive film on stainless steel have been carried out by scholars at home and abroad. In recent years, Beijing University of science and technology for 316L steel passivation film photoelectron spectros (XPS) research as an example for a brief description [1]. Passivation of stainless steel is the surface layer dissolved for some reason and absorbed by water molecules. Under the catalysis of oxidant, oxides and hydroxides are formed, and the conversion reaction takes place with Cr, Ni and Mo elements of stainless steel. Finally, a stable phase forming film is formed, which prevents the damage and corrosion of the film. The reaction mechanisms are as follows: < br / < br / < Fe · H2O (Fe · H2O) and [feoh · o *] [feoh · o *] [feoh · o *] [feoh · o *] [FeO · o *] [FeO · o *] [FeO · o *] [FeO · o *] [feoh · o *] [feoh · o *] [feoh · o *] [feoh · o *] [feoh · o *] [FeO · o · o *] [FeO · o · o *] [FeO · o · o *] [FeO · o · o · o *] [FeO · o · o · o · o *] [FeO · o · o · o · o · o · o · · o · O] as [feoh · o · o · o · o · o (FeO · h · H2O] and [FeO · H · h · h · h · h · h · H] and [fe2oh · H2O] and ((where OS is the passivation process Ad is the adsorption intermediate.)[ It can be seen that Fe2O3, Fe (OH) 3, or γ - FeOOH, CR203, crooh or Cr (OH) 3, Mo exist in the form of moo, and the main components of the passive film are CrO3, FeO and NiO
3. Pickling and passivation methods and processes for stainless steel
3.1 comparison of pickling and passivation methods
there are many pickling and passivation methods for stainless steel equipment and parts according to different operations, and their application scope and characteristics are shown in Table 1
Table 1 Comparison of pickling and passivation methods for stainless steel
advantages and disadvantages of application scope of the methods
impregnation method is used for parts that can be put into pickling tank or passivation tank, but it is not suitable for large equipment. Pickling solution can be used for a long time with high proction efficiency and low cost; The large volume equipment is full of acid, and the liquid consumption of impregnation is too large.
the brushing method is suitable for the surface and local treatment of large equipment with poor physical operation, poor working conditions, and acid can not be recovered.
the paste method is used for the installation or maintenance site, especially for the manual operation of welding department, poor labor conditions, and high proction cost.
the spraying method is used for the installation site, However, spray gun and cutting ring system are needed for large-scale equipment, such as heat exchanger and shell treatment. It is convenient for construction and acid liquid can be reused. The circulating system needs to be connected with pipe and pump.
electrochemical method can not only be used for parts, but also can be used for on-site equipment surface treatment by brush method, According to astma380-1999, only 300 series stainless steel is taken as an example,
(1) pickling
reagent hno36% ～ 25% + hf0.5% ～ 8% (volume fraction)
temperature 21-60 ℃; Time as needed
or ammonium citrate 5% - 10% (mass fraction)
temperature 49-71 ℃; The time was 10-60min
(2) passivation
HNO3 20% - 50% (volume fraction)
temperature 49-71 ℃; The time was 10-30 min
or temperature 2L ~ 38 ℃; The time was 30-60 min
or HNO3 20% ～ 50% + na2cr207h2022% ～ 6% (mass fraction)
temperature 49-54 ℃; The time was 15-30 min
or 21-38 ℃; The time was 30-60 min< (3) descaling and pickling
h2so48% ～ 11% (volume fraction)
temperature 66-82 ℃; 6-inch interval, 5-45min
and HNO3 6% ～ 25% + HF 0.5% ～ 8% (volume fraction)
temperature 21-60 ℃
or HNO3 15% ～ 25% + HFL% ～ 8% (volume fraction)< 2.2 paste treatment
(1) take the local passivation of internal surface weld, base metal passivation and maintenance surface grinding weld of new urea stainless steel equipment of Guangzhou Petrochemical Company as an example [3]
pickling paste:
25% HNO ~ + 4% HF + 7L% condensed water (volume fraction) and BaSO, adjust to paste
passivation paste:
Paste with 30% HNO3 or 25% HNO3 + 1% (mass fraction) k2cr207 and baso7
after coating the surface for 5-30min, rinse it with condensed water to pH = 7, or spray hydrogen peroxide for chemical passivation of single equipment
(2) take the patent m of Shanghai Daming iron factory as an example
pickling passivation paste:
hn038% ～ 14% (as passivator)
HFL 0% ～ 15% (as corrosive agent)< 2% ～ 2.7% (as thickener)
magnesium nitrate 60% ～ 70% (as filler to improve adhesion and permeability)[ 3% ～ 2.8% (as corrosion inhibitor)
water (adjust viscosity)
3.2.3 electrochemical treatment
taking Xiamen University Patent [5] as an example, the treatment method is as follows: the stainless steel workpiece to be treated is used as anode and anodized by controlling the constant potential, or the stainless steel workpiece is used as cathode first and anodized by controlling the constant potential, and then the stainless steel workpiece is used as anode and anodized by controlling the constant potential, The electrolyte solution was hn03. After such treatment, the properties of passive film on stainless steel are improved and the corrosion resistance is greatly improved. The critical potential of pitting corrosion (EB) is increased by 1000 MV (in 3% NaCl) and the resistance to uniform corrosion is increased by three orders of magnitude (in 20% - 30% h2s04 at 45 ℃)< The application scope of BR />4. stainless steel is pickled and passivated. The pickling and passivation treatment of
4.1 stainless steel equipment ring the manufacturing process,
4.1.1 cleaning and pickling and passivation after machining, [6]
stainless steel workpiece, after cutting, the surface usually contains iron filings, steel and cooling emulsion, which will cause stains and rust on the surface of stainless steel, so degreasing and degreasing should be carried out. After cleaning with nitric acid, not only iron chips and steel powder are removed, but also passivation is carried out
4.1.2 cleaning and pickling passivation before and after welding [7]
because grease is the source of hydrogen, gas will form in the weld without grease removal, and low melting point metal pollution (such as zinc rich paint) will cause cracking after welding, so the groove and the surface within 20 mm on both sides of stainless steel must be cleaned before welding, and the oil can be wiped with acetone, Paint rust should be removed with emery cloth or stainless steel wire brush, and then cleaned with acetone
no matter what kind of welding technology is used in stainless steel equipment manufacturing, all welding slag, spatter, stain and oxidation color should be removed after welding. The removal methods include mechanical cleaning and chemical cleaning. Mechanical cleaning includes grinding, polishing and sand blasting. Carbon steel brush should be avoided to prevent surface rust. In order to obtain the best corrosion resistance, it can be soaked in the mixture of HNO3 and HF, or acid pickling passivation paste can be used. In fact, it is often used in combination with chemical cleaning
4.1.3 cleaning of forged castings [6]
the surface of stainless steel workpieces after hot working such as forging and casting often has a layer of oxide scale, lubricant or oxide pollution, including graphite, molybdenum disulfide and carbon dioxide. Shot peening, salt bath and multi pass pickling shall be used. For example, the treatment process of stainless steel turbine blades in America is as follows:
salt bath (10min) → water quenching (2.5min) → sulfuric acid washing (2min) → cold water washing (2min) → alkaline permanganate bath (10min) → cold water washing (2min) → sulfuric acid washing (1rain) → cold water washing (1min) → nitric acid washing (1.5min) → cold water washing (1min) → hot water washing (1min) → air drying< 2 pickling and passivation treatment before the new plant is put into operation
pickling and passivation treatment is required for stainless steel equipment and pipelines of many large chemical, chemical fiber and chemical fertilizer plants before they are put into operation. Although the equipment has been pickled in the factory to remove the welding slag and oxide scale, it will inevitably cause the pollution of grease, mud sand and rust in the process of storage, transportation and installation
10.
Efficacy of Xiaoshiling:
1. It can effectively control or kill microorganisms in water system, such as bacteria, fungi and algae
The effect of fungicide on bacteria was very poor, which destroyed the development of mycelium and the formation of spores It is a kind of pesticide to control plant diseases caused by various pathogenic microorganismsthere have been many disasters in history, such as severe famine caused by the epidemic of some plant diseases, and even a large number of people starved to death. The use of fungicides is an economical and effective method to control plant diseases
extended data:
according to the bactericidal mechanism, it can be divided into two categories: oxidizing bactericides and non oxidizing bactericides. Oxidizing bactericides are usually strong oxidants, which can kill bacteria by oxidizing with metabolic enzymes in bacteria
The common oxidizing bactericides are chlorine, chlorine dioxide, bromine, ozone, hydrogen peroxide, etc. Non oxidizing bactericide is a kind of disinfectant that acts on the special parts of microorganisms in order to destroy the cells or life bodies of microorganisms and achieve bactericidal effect. Common non oxidizing bactericides include chlorophenols, isothiazolinone, quaternary ammonium salts and so onHot content