Para-xylene crystallization technology
The process of separating p-xylene by crystallization is an older process still in use. Before the emergence of adsorption separation technology, the separation of p-xylene by crystallization was the only technology for refining p-xylene. Due to the development of adsorption technology, the existing crystallization technology for the separation of mixed xylenes for equilibrium components no longer has advantages, but the separation of mixed xylenes for high-concentration p-xylene is still attractive.
Our company has conducted in-depth research on p-xylene refining and successfully developed a complete set of process and engineering treatment technology for p-xylene crystallization and refining, forming unique technical characteristics.
Para-xylene crystallization technology adopts a two-stage crystallization process, which is suitable for high-efficiency and energy-saving recovery of PX from mixed xylene materials with high concentration of para-xylene (including o-xylene, meta-xylene, and para-xylene). The process reliability is high, the cost is low, the feed composition requirement is low, and the investment is lower.
Process feature advantages
01 Process characteristics: innovative crystallization process
02 Process advantages: crystallization technology adopts two-stage crystallization process.
(1) A two-stage crystallization process is adopted, the first stage is used to ensure the purity of p-xylene, and the second stage is used to ensure the yield of p-xylene;
(2) The scraped surface falling film crystallizer is used for the primary crystallization, which can effectively control the purity and particle size of the crystals and facilitate separation;
(3) The secondary crystallizer adopts static crystallizer, intermittent operation, simple and reliable structure, no need to set up low-temperature centrifuge;
(4) The purity of p-xylene product>99.7%, and the yield of p-xylene>90%.
(5) The heat exchange network is optimized and the energy consumption of the device is reduced.
(6) The minimum requirement of p-xylene content is >70%. If it is a balanced composition, the product can also be operated, but more energy is required.
(7) No special chemicals or adsorbents are required.
(8) Small footprint.
(9) Low fixed cost and low operating cost.
The feed is sent to the buffer tank buffer, pumped into the crystallization feed tank, and the washing liquid from the centrifuge, enters the crystallization feed tank. The material in the tank is pumped into the primary crystallizer. Para-xylene can achieve satisfactory purity of para-xylene product through primary crystallization.
After p-xylene is crystallized in the primary crystallizer, the p-xylene crystals and mother liquor flow into the centrifuge. After separation, the crystals are washed and pushed into the finished product melting tank by the centrifuge. After the crystals in the tank are heated and melted, the pressure is boosted by a pump, and then divided into two strands, one strand is sent out as a product, and the other strand is sent to the centrifuge to wash the p-xylene crystals, and the washing liquid after washing is returned and sent Crystal feed tank.
The mother liquor discharged from the centrifuge enters the primary mother liquor tank, and the mother liquor in the tank is sent to the static crystallizer to recover the p-xylene in the mother liquor. The separated mother liquor is mixed with xylene as a by-product, and the crystals are returned to the crystallization feed tank.
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