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    Home > Chemicals Industry > Chemical Technology > Stainless steel PTFE tank

    Stainless steel PTFE tank

    • Last Update: 2022-01-31
    • Source: Internet
    • Author: User
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    Stainless steel PTFE tank, the inner liner is made of PTFE material, also known as high-pressure digestion tank, high-pressure tank, synthesis reactor, etc.
    , belongs to the category of pressure vessels, and its pressure performance is designed and manufactured with reference to the reaction pressure vessel in GB1502011 Of

    .

    The stainless steel PTFE tank is an extension of the autoclave, hereinafter referred to as the tank, as shown in Figure 22-30
    .

    Figure 22-30 Stainless steel PTFE tank and its assembly

    The original intention of designing the stuffy tank was to use it as a closed pressure vessel for decomposing insoluble substances, so it is called a high-pressure digestion tank
    .
    The stuffy tank has a PTFE liner, double-layer care, can withstand strong acids and alkalis, has good corrosion resistance, and is a high temperature and high pressure airtight environment, which can achieve the purpose of quickly digesting insoluble substances.
    It is often used in gas and liquid phases.
    , Plasma spectroscopy, mass spectroscopy, atomic absorption and atomic fluorescence and other chemical analysis methods for sample pretreatment

    .
    The high-pressure digestion tank is a powerful assistant for digesting samples when determining trace elements and trace elements.
    It can be used in the determination of heavy metals such as lead, copper, cadmium, zinc, calcium, manganese, iron, mercury, etc.
    , and used as a sample pretreatment Digestion of heavy metals, residual agricultural chemicals, food, sludge, the dilute, aquatic products, the packing containers and the like organic compounds

    .

    The stuffy tank is lined with polytetrafluoroethylene (commonly known as plastic king, melting point is 327℃), with excellent sealing performance.
    Compared with general all-steel autoclaves, it is more resistant to strong acids and alkalis and more corrosion resistance

    .
    The tightly lined stainless steel jacket can make it have high pressure resistance.
    Therefore, in recent years, the stuffy tank has been used as a high temperature, high pressure, and anticorrosive reaction vessel, which has been widely used in chemical laboratories.
    This kind of stuffy tank is often the first thing that comes to mind when some small-scale synthesis reactions are under pressure

    .

    (1) Use

    After placing the reaction sample, close the lid inside the cup tightly
    .
    Put the stainless steel gasket in the stainless steel tank first, then put the Teflon inner cup containing the reaction sample into the stainless steel jacket, attach the stainless steel gasket, pay attention to the front and back of the upper and lower gaskets

    .
    Tighten the stainless steel lid, if necessary, insert a steel rod into the round hole on the lid to help tighten it, and then put it in a water bath or an oil bath for heating reaction

    .

    (2) Safety instructions

    (1) The temperature is inversely proportional to the strength of the lining polytetrafluoroethylene.
    The higher the temperature, the lower the strength of the polytetrafluoroethylene

    .
    Operating temperature: If the dangerous reaction is non-decomposition violent heating or non-polymerization violent heating, the temperature below 150℃ is the safe temperature, 150~200℃ is the relative safety temperature, 200~220℃ is the safety warning temperature, and 220℃ is Limit temperature

    .
    For reactions involving gases such as ammonia or
    hydrogen chloride and low-boiling substances such as ether , the temperature should be controlled below 100°C
    .
    For NH
    3 /MeOH, NH 3 /EtOH, NH 3 /THF solutions, if the concentration of the substance is less than 4mol/L, the limit is below 130°C; if the concentration is greater than 4mol/L, the limit is below 100°C
    .
    If THF is a solvent, it is limited to below 140°C.
    For dangerous reactions that are non-acid corrosive (pH less than 4) over 160°C, non-decomposition violent heating, or non-polymerization violent heating, it is recommended to carry out in a steel autoclave

    .

    (2) Safety pressure: Although the manufacturer promises that the allowable pressure value of the new tank is 4-10MPa, with repeated use, it is easy to fatigue or age, and the pressure resistance will gradually decrease, so the recommended pressure should be below 4MPa
    .
    The higher the pressure, the higher the risk

    .

    There have been many explosion accidents of the stuffy tank, so before the high temperature and high pressure reaction, the physical and chemical properties of the reactants, the reaction solvent, the volume of the reaction liquid, the volume of the space, and the maximum calculated according to the ideal gas state equation should be checked.
    The pressure at the reaction temperature should be well known to prevent an explosion caused by exceeding the limit

    .

    In particular, prevent possible exothermic reactions
    .
    For example, high temperature decomposition caused by the heat of the polymerization reaction may cause carbonization and explosion

    .
    From many explosion cases, almost all reactants are carbonized into black at high temperature, and these black substances are almost insoluble in any solvent

    .

    (3) Before use, check whether the stainless steel tank body and lid have any visible deformation, damage or cracks, observe whether the thread at the screw mouth is damaged, and whether the stainless steel gasket is deformed
    .

    (4) Before use, check whether the cup body and lid of the PTFE inner cup are deformed, damaged or cracked visually, and the tightness of the inner cup should be checked preliminarily: put the inner cup and the jar together in the stainless steel tank, and then Lift the PTFE lid gently by hand.
    If the lid can lift the PTFE cup together smoothly, it means that the inner PTFE cup has good sealing performance; otherwise, it is poor

    .
    After the reaction is over, the lid can only be opened by rotating and lifting.
    If it is difficult, you can only use a tool to rotate it first and then slowly lift it up by hand.
    Do not use a blade to pry the lid, which will easily deform the lid and cause it to be scrapped

    .

    (5) If the oil bath is used for heating, be careful not to directly touch the electric heating ring at the bottom of the tank, so as to avoid the danger of local heating at the bottom of the tank
    .
    If you use an oven to heat, you can only use a sealed electric heating explosion-proof oven, that is, an oven heated by a special porcelain-jacketed electric heater (jacket heating and laminate heating), and the temperature control accuracy is required to reach ±2℃

    .
    It cannot be used in an ordinary oven or muffle furnace with an open flame

    .
    There have been accidents in which the stuffy pot leaked under the high temperature in the oven and exploded when it encountered the heating wire at the bottom of the oven.
    This explosion not only destroyed the glass door of the oven, but also exploded the two sides, back and top of the oven

    .

    (6) It is forbidden to use stuffy tanks as hazardous reactions to explosives such as substances with high nitrogen content, peroxides, etc.
    There have been many explosion cases.

    (7) It is forbidden to use stuffy tanks for violent and exothermic dangerous reactions such as easy polymerization and decomposition at high temperature.
    Reactions involving borane, ethylene oxide, DAST, etc.
    , and reactions in which DMF and DMSO are used as solvents are prohibited

    .
    The exothermic reaction will cause the temperature in the tank to rise, and the temperature in the stuffy tank is difficult to dissipate in time.
    In this way, the higher the temperature, the faster the reaction rate and the more heat generation

    .
    There have been many explosion cases caused by high temperature caused by accelerated self-reaction

    .

    (8) All the stuffy tank reactions need to be isolated by a baffle, and the operation must be carried out with the fume hood door pulled to the end
    .

    (9) Filling factor: The total volume of the reaction liquid generally does not exceed 50% of the total effective volume.
    For reactions where gas is released or the substrate contains volatile substances (ammonia solution, methylamine, ethylamine, etc.
    ), the filling factor shall not be More than 1/3

    .
    Even if it is considered to be the safest response, ensure that the loading factor is less than 4/5

    .

    (10) When heating, the temperature should be raised to the required reaction temperature according to the specified heating rate, which is less than the specified safe use temperature
    .
    It takes at least 0.
    5h to gradually raise the temperature to 100°C.
    On this basis, the temperature can be raised to the required temperature after 1h of constant temperature

    .

    (11) At the end of the reaction, the temperature should not drop sharply.
    It should be operated strictly in accordance with the specified cooling rate to facilitate safety and prolong the service life of the stuffy tank

    .
    First take out the stuffy pot from the oil bath and cool it in the air for more than 0.
    5h, then water cooling, and finally ice water cooling

    .
    After fully cooling and confirming that the temperature of the polytetrazolium inner cup material in the label is lower than the boiling point of the reactants and the solvent, the lid of the kettle can be opened for subsequent operations

    .

    (12) A temperature controller should be used during heating to strictly control the reaction temperature to avoid runaway
    .

    (3) Scrap

    (1) If a large area of ​​the inner wall or outer wall of the steel tank is found to be black and yellow and the threaded mouth is rusted, it shall be scrapped
    .

    (2) If the stainless steel tank body and lid are found to be deformed, damaged or cracked, or the thread at the screw mouth is damaged, or the stainless steel upper and lower gaskets are warped, deformed or have small cracks, they should be scrapped immediately
    .

    (3) If the cup body and lid of the PTFE inner cup are found to be deformed, damaged or cracked, they should be scrapped immediately
    .
    If the sealing is not good, you should find the reason for repair, if it still can not be sealed, it must be resolutely discarded

    .

    (4) If the wall of the lining cup is blackened by more than 2/3 due to high temperature for a long time, extremely blackened, or there is residue that cannot be cleaned up, it should be discarded immediately
    .

    (5) If any user or manager has sufficient reason to believe that it should be scrapped, it should be scrapped decisively
    .

     

     

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