Application of Melt Pump in Polyester Production Line
The production process of most plastics today began with crude oil. When it comes to crude oil, we usually think of the gasoline that comes from it. In fact, only about 40% of the yield of a barrel of crude oil is gasoline. In order to obtain gasoline and many other useful by-products, petrochemical plants heat crude oil in tanks and separate it according to the different boiling points of various components. These components are called "fractions", and this process is called "distillation". When the temperature reaches around 150 ℃, gasoline is separated from crude oil, and the gas phase by-products ethylene and propylene are "cracked" from the residue when heated to 840 ℃, becoming raw materials for plastics.
reactor kettle melt pump
These gas components, also known as monomers, will enter a reactor. The temperature and pressure inside the reactor vary depending on the polymer produced. Monomer molecular chains polymerize under the action of heat and pressure to form long chains, which we call polymers. As the reaction progresses, heavy polymers settle to the bottom of the reaction vessel, making polyester melt gear pumps suitable for high temperature, high pressure, and high viscosity useful.
china melt pump for reactor kettle
Because most of the reactor is in a vacuum state, the polyester melt pump is often directly connected to the bottom of the reactor by bolts to reduce the required cavitation margin. At this point, due to the presence of a large amount of solvents in the polymer, the material viscosity is not particularly high, around 150000 cP. The bottom discharge melt pump needs to have a special design to adapt to the low pressure and high temperature resistance of the inlet, in order to offset the thermal expansion of steel at a high temperature of 200 ℃. The inlet of the melt pump for reactor kettle is designed as a conical large opening, which can help materials enter the pump, and the jacket can be used to heat the pump body with steam or heat medium.
melt pump for polymer reaction kettle/reactor
In some processes, the polymer is pumped into a second reactor or tray tower, and the solvent is separated, leaving a more viscous material with a viscosity of 500000 cP and a temperature of 340 ℃. This requires another gear pump to extract the material from the bottom of the tower. Because the melt needs to be pushed out to other equipment with high pressure drop before entering the pelletizer, this pump needs to have a higher design than this pump to adapt to more extreme working conditions and higher pressures. It is normal to have an outlet pressure of up to 250kpa. Therefore, there must be tight and precise clearance design between the moving parts of the pump. These clearances need to be carefully calculated by the pump manufacturer considering factors such as high temperature, high pressure, high viscosity, different thermal expansion coefficients of materials, and the characteristics of non Newtonian fluid materials.
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