How to avoid blocky walls as much as possible? (PTA)
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In PTA production, starting from the oxidation stage, a layer of lumps forms on the walls of the reactor; this also occurs in the crystallization tank and the dryer. How do you manage to avoid this as much as possible? Our company features: 1. All reactors are equipped with baffle plates. 2. Add a decanting tray at the top; the reflux liquid returns to this tray via wall flow, washing against the walls to prevent crystallization. This post was last edited by uway on 2008-6-7 19:21]
That’s probably about it; however, the baffle serves to assist the mixer.
For a typical PTA plant, the most important thing is to strictly control the operating parameters in order to avoid scaling caused by PTA crystallization resulting from temperature fluctuations! The crystallizers are connected in series; due to the high pressure and temperature in the earlier ones, the concentration of PTA crystals is not very high, so scaling basically does not occur. However, the subsequent crystallizers have relatively lower temperatures and pressures; the concentration of PTA crystals begins to increase, and there is still a certain distance between the bottom of the agitator and the bottom of the tank, which makes scaling and even material accumulation very likely! Scaling problems in dryers are almost inevitable; the most important thing is to avoid rapid cooling when the dryer is shut down. Try to empty the materials as much as possible if conditions permit. Turn the equipment at normal speed (to prevent deformation of the equipment due to localized heating and caking of materials). Scaling in PTA production lines is a common occurrence; generally, the company should schedule a major maintenance session once a year and a minor maintenance session every six months, in order to remove the scaled deposits from within the tanks and pipelines as much as possible.
What does “turn the crank at normal time” mean, as mentioned upstairs? Thank you~~~
Isn’t scaling related to concentration as well as temperature? If the concentration is too low, doesn’t that make crystallization more likely?
This is a reactive process, not a reversible one; if the concentration is not controlled, the yield cannot be guaranteed.
I think this is a matter of experience; it mainly comes down to the proportional control of pressure and temperature. After operating for a while, one develops a sense for it
Regularly adjusting the liquid level in the oxidation reactor can also help reduce scaling on the reactor walls. However, in most PTA plants, the operating load is kept very high, so there are few opportunities to raise the liquid level. Nevertheless, taking advantage of the periods of reduced load during routine maintenance tasks to adjust the reactor’s liquid level several times can be beneficial in preventing scaling. Add floor 4: “Turning the machine at normal speed” should refer to the fact that today’s PTA plants are very large, and so are their oxidation dryers – they are large in size and long in length. To prevent deformation of the dryers due to uneven heating when the machines stop operating, modern TA/PTA dryers are equipped, in addition to the main drive motor, with a separate motor for turning the machine, which operates at a very low speed, thereby enabling the machine to be turned. If there is no automatic barring device, one has to do it manually, and that’s very tedious! If the operator feels pain, they might not turn the equipment at a time close to normal, and that could lead to problems with the equipment!
The discharge temperature of the dryer is controlled above 150 degrees, preventing wall formation in the dryer
Controlling the process operating conditions is important; large fluctuations should be avoided as much as possible, as this can reduce the degree of wall formation