Issues

　　Mainly, it produces polymers, changes in color and produces impurities.

The main factors triggering these problems and styrene storage should be taken when the following important measures

　　1、Rational storage tank selection

　　Line standard SH/T3007 & mdash; 2007 article 4.2.5 notes: “ Some A A, B B chemicals have special storage needs, can not be used inside the floating top tank. Such as styrene, in order to inhibit polymerization needs to contact with oxygen, although styrene is a class A liquid, but its tanks can only be used to fix the top of the tank. ” Fixed top tank internal structure to be simple, the internal surface of the tank to be smooth, clean, no scars, weld tumors, minimize crossbeams, tie rods, etc., to avoid the accumulation of styrene vapor condensation. And the tank structure design must be considered to prevent styrene polymerization when hanging on the wall of the tank measures.

　　2、Control the storage temperature

　　Under normal storage conditions, styrene self-polymerization is slow, but the rate of self-polymerization is accelerated with the increase in temperature, so the temperature is the most important of the many factors that should be controlled when storing styrene. At higher temperatures, the rate of polymer production is significantly accelerated, the consumption of polymer inhibitors is significantly increased, and the storage time of styrene is greatly reduced. Table 2 lists the effects of polymerization inhibitors and oxygen concentration on the storage period of styrene at different temperatures.

　　3、Add the appropriate amount of polymerization inhibitor

　　For styrene the most suitable TBC content is 10-15 mg / kg and 45-55 mg / kg (for different specifications), but in practice the application can be adjusted according to the specific temperature and oxygen content. The right amount of TBC will not make styrene due to the addition of TBC and increase the color, but the TBC content of more than 40 & mdash; 50 mg / kg, it is possible to increase the color of styrene, but also to the late removal of TBC increased the difficulty and cost.

　　The minimum value of TBC (dangerous value) is 4—5mg/kg, below this value there will be the possibility of exothermic or violent aggregation, and according to the experimental data and the actual operation of the measurement data, at any time the increase in TBC content gradually The higher the storage temperature, the more the TBC content is reduced.

　　4、Add the right amount of oxygen

　　From the data in Table 2, it can be seen that the interaction between TBC and dissolved oxygen in styrene can only achieve the effect of effective storage period, and when the oxygen content is insufficient, even if the TBC content is high, the coalescence-blocking effect is still very unsatisfactory. The mechanism of TBC is that the free radicals of styrene polymerization monomer combine with oxygen and then seize the H in TBC bisphenol to oxidize TBC to quinone, thus preventing the formation of free radicals and playing a role in the blocking of aggregation. When the content of styrene monomer is insufficient, the blocking ability decreases. When the oxygen content is lower than 15mg/kg, it will even lose the ability to block aggregation, so it is necessary to maintain sufficient oxygen content in styrene monomer.

　　5、Set up nitrogen seal protection system

　　The complete absence of oxygen (dissolved) in styrene causes TBC to lose its blocking effect. But the presence of excess oxygen (mainly in the gas phase) poses another set of problems. This is because the styrene vapor in the gas phase above the styrene storage tank does not contain a polymerization inhibitor. This styrene vapor and the styrene droplets it forms after condensation are rapidly oxidized by oxygen in the air and tend to adsorb to the rusty or porous surfaces of the storage tank. In addition, if the fall of these deposits containing oxidation products or dissolved into the styrene in the tank, it will also increase the color and polymer content of styrene. At the same time, it is also one of the factors that contribute to the polymerization of styrene. Therefore it is necessary to seal the styrene with an inert gas above the liquid level with nitrogen to reduce the adverse effects caused by oxygen in the gas phase. During styrene storage, the inert gas in the gas phase gradually displaces the oxygen in the styrene, allowing oxygen to enter the gas phase and gradually increasing the oxygen content in the gas phase. When the oxygen content in the gas phase reaches 8% ((p), an explosive gas mixture may form a hazard. Therefore, the oxygen content in styrene should be supplemented with air frequently to ensure the effective blocking effect of TBC. At the same time, the inert gas in the gas phase space should be changed frequently to ensure that the oxygen content in the gas phase is kept below 8%.

　　6、Improve the storage process to optimize the operation

　　In order to ensure the safety and quality of styrene storage, if necessary, the existing process needs to be improved, the existing operating procedures and other optimization. Styrene storage tanks into and out of the tank opening should be close to the bottom of the tank, styrene pipeline to avoid “dead oil section ” the appearance. Storage tanks and pipelines and other equipment on a variety of instrumentation to insulate the pilot tube, and regular discharge to prevent the polymerization of styrene in the pilot tube. To prevent the occurrence of explosive aggregation, the storage tanks and accessories should be at various locations (the bottom of the pipe, the top of the tank, breathing valve, nitrogen sealing valve, emergency relief hole, etc.) styrene in the polymer inhibitor, polymer analysis, and detection of styrene, styrene vapor temperature.