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

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pressure

Separation process

The TA slurry enters the pressure centrifuge through the feed tube at the bottom of the pressure centrifuge, and the centrifugal force generated by the high-speed rotation of the centrifuge drum about 2000r/min is used to accumulate solid particles on the inner wall of the drum, and the solid is forced by the screw conveyor. The drum is sent down, mixed with re-slurry water and then into the re-pulping tank, while the liquid overflows from the top and enters the mother liquor tank by gravity, and the pressure centrifuge realizes solid-liquid separation through this process. To prevent blockage of the feed tube, a continuous desalinated rinse-tube flush is provided at the feed tube. The PTA device utilizes the solubility difference between TA and PT acid to purify the product. The solubility map of PT acid and TA, the temperature of the pressure centrifuge tends to cause the precipitation of PT acid in the mother liquor, affecting the quality of the product and the stable operation of the centrifuge. .

3 analysis of the reasons for poor separation of pressure centrifuge

It is difficult to judge whether the pressure centrifuge is good or bad, and there is no specific standard, only relative comparison value. In combination with the device, in the case of a constant feed amount and a constant total solid content, when the current of the pressure centrifuge rises, the temperature of the mother liquid tank drops, and the temperature of the beat tank rises, the opening degree of the liquid level control valve of the mother liquid tank becomes smaller, and then The opening level of the beating tank liquid level control valve becomes larger, and the torque of the pressure centrifuge rises. Through the above changes, coupled with the sampling and analysis data of the product, it can be judged that the effect of the pressure centrifuge has deteriorated. Combined with operational experience and theoretical analysis, the reasons for the poor effect of the pressure centrifuge of this device are as follows:

1) The tube rinse water temperature is low. In the original design, the tube flushing water of the pressure centrifuge, the filter cake and the beating water and the centrifuge washing water are used to remove the brine from the same heat exchanger. Since the slurry after re-pulping needs to be filtered by the vacuum filter, the temperature cannot be too high. High, and the temperature of the beating water is 9090. The feed rate of a single centrifuge is about 32000kg/h, the temperature is 15000, the tube flushing water flow is 10000kg/h, the temperature is 9090, the temperature of the tube rinse water mixed with the feed is about 13690, and the solubility of PT acid is only about 3 rewards. After 100 g of a saturated solution, the excess PT acid crystallized and entered the filter cake together with TA.

2) The mother liquid system pipeline is not well insulated. The mother liquor tube is easily blocked by the PT acid precipitated by crystallization.

3) The temperature of the flushing water fluctuates, often low, and the washing effect is not in the actual operation of the woman c, exposing the following problems:

1 Product PT has high acid content and unstable quality.

2 The pressure centrifuge has poor washing effect and high alkaline washing frequency. The corrosion of bearings and equipment is caused by chloride ions in the lye, which shortens the life of the equipment.

3 Under the original design conditions, in order to achieve the Pf acid content of the product, the flow rate of the pipe flushing water is high, which increases the consumption of desalinated water.

4 improvement plan

1) Separate the tube rinse water, rinse water and re-slurry from the pressure centrifuge to increase the temperature of the tube rinse water and rinse water.

1 When the operating temperature in the centrifuge is increased to above 140 °C, the solubility of PT acid is increased to a saturated solution of 4.3 g in 4.3 years, and most of the PT acid can be separated with the mother liquor. At the same time, since the temperature of the beating water remains unchanged, the temperature of the slurry after re-pulping is not much improved, and the vacuum filtration process is not adversely affected; 2 the temperature of the washing water is increased and stabilized, thereby improving the washing effect and reducing the frequency of the alkaline washing; Since the PT acid is washed away, the deposition of PT acid and TA in the centrifuge is reduced; 4 the periodic operation of the alkaline washing mother liquor tube is increased (once a week), and the alkaline washing of the pressure centrifuge is changed from once a week to once a month 2) Improve the insulation effect of the mother liquor system and prevent the precipitation of PT acid.

5 Implementation and effect of the program

I) Add a heat exchanger to use a 430 kPa (G) steam produced by the oxidation part to heat a part of the desalted water to 1407 without increasing the external steam supply, as a tube rinse water and rinse of the pressure centrifuge Water and re-slurry are still maintained at the original design temperature. Secondly, steam coil heating is added outside the mother liquor tube, which is kept open all the year round to ensure the heat preservation effect.

2) After the transformation, the product qualification rate reaches 100%, the superior product rate increases from 95% to 98%, the frequency of the alkaline washing pressure centrifuge is reduced to once a month, and the production of PTA per ton can save 0.35t of desalinated water.