To judge the effect of pressure centrifuge is more difficult - Database & Sql Blog Articles

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Pressure Centrifuge - Separation Process

The TA slurry enters the pressure centrifuge through the feed tube at the bottom of the drum. As the drum rotates at about 2000 rpm, centrifugal force causes solid particles to accumulate on the inner wall of the drum. The screw conveyor then pushes the solids downward, mixing them with re-slurry water before entering the re-pulping tank. The liquid overflows from the top and flows into the mother liquor tank by gravity. To prevent clogging of the feed tube, a continuous desalinated rinse-tube flush is installed. The PTA device uses the solubility difference between TA and PT acid for purification. However, if the temperature in the pressure centrifuge causes PT acid to precipitate in the mother liquor, it can affect product quality and the stable operation of the equipment.

3. Analysis of Poor Separation Causes in Pressure Centrifuge

It's difficult to assess the performance of a pressure centrifuge without clear standards. By comparing operational data, when the current increases, the mother liquor temperature drops, the beat tank temperature rises, and the liquid level control valve of the mother liquor tank closes while the beat tank opens more, indicating poor separation efficiency. Combined with sampling and analysis, the following factors were identified as the main reasons:

1) Low temperature of the tube rinse water. Originally, the rinse water was shared with filter cake and beating water via the same heat exchanger. Due to the need to maintain a lower temperature for the re-pulped slurry, the rinse water temperature was too low. This caused PT acid to crystallize and mix with TA in the filter cake, reducing separation efficiency.

2) Poor insulation of the mother liquor pipeline led to PT acid precipitation, causing blockages.

3) Fluctuating rinse water temperature resulted in inconsistent washing performance. This led to high alkaline washing frequency, increased chloride ion corrosion, and higher desalinated water consumption.

4. Improvement Plan

1) Separate the tube rinse water, wash water, and re-slurry water to increase their temperatures. When the centrifuge operates above 140°C, PT acid solubility increases to 4.3 g per 100g of solution, allowing most of it to be carried away with the mother liquor. This improves washing efficiency and reduces the need for frequent alkaline washing.

2) Enhance insulation of the mother liquor system to prevent PT acid crystallization and blockage.

5. Implementation and Results

1) A new heat exchanger was added, using steam from the oxidation process to heat part of the desalinated water to 140°C, which was used for tube rinse and wash water. The mother liquor pipe was also equipped with a steam coil for year-round heating, ensuring stable temperatures.

2) After the improvements, the product qualification rate reached 100%, the premium product rate increased from 95% to 98%, and the alkaline washing frequency was reduced to once a month. Additionally, desalinated water usage was reduced by 0.35 tons per ton of PTA produced.