Industrial-grade polyphosphoric acid production process and system

Abstract

The invention discloses an industrial-grade polyphosphoric acid production process and system and solves the problem that existing methods for producing industrial-grade polyphosphoric acid through wet-process purifying of phosphoric acid are harsh and complex in process condition and low in recovery rate and concentration. The technical scheme includes: feeding circulating acid into an acid heater for heating, feeding the same into a flashing chamber for flashing evaporation, and feeding obtained circulating acid back into the acid heater through a circulating pump for cyclic heating; when concentration of phosphoric acid after being flash-evaporated and concentrated in the flashing chamber is 68-76%P2O5, guiding out part of the circulating acid as finished product acid to be fed into a finished product acid cooler for cooling, and supplementing purified phosphoric acid into the rest of the circulating acid as circulating acid to be sequentially fed into the acid heater for cyclic heating and into the flashing chamber for cyclic flashing evaporation, wherein inlet temperature of the acid heater is controlled to 190-195 DEG C while outlet temperature of the same is controlled to 195-200 DEG C. The process is simple, easy in condition control, high in P2O5 yield and capable of saving energy and lowering consumption. The system is reliable and low in equipment investment and running cost.

Description

technical field [0001] The invention relates to a chemical industry, in particular to an industrial-grade polyphosphoric acid production process and a system thereof. Background technique [0002] Phosphoric acid (H 3 PO 4 ) is also called orthophosphoric acid, theoretically 100% orthophosphoric acid (H 3 PO 4 ) containing 72.4% P 2 o 5 , actually containing 72.4% P2O5 phosphoric acid also contains 12.7% H 4 P 2 o 7 , which is due to the balance of the following equation. [0003] 2H 3 PO 4 →H 4 P 2 o 7 +H 2 o [0004] Phosphoric acid (H 3 PO 4 ) undergoes different degrees of dehydration to form pyrophosphate (H 4 P 2 o 7 ), tripolyphosphoric acid and tetrapolyphosphoric acid, the reaction formula is as follows: [0005] Pyrophosphate: 2H 3 PO 4 -H 2 O→H 4 P 2 o 7 (T=200°C) [0006] Tripolyphosphate: 3H 3 PO 4 -2H 2 O→H 5 P 3 o 10 [0007] Tetrapolyphosphate: 4H 3 PO 4 -3H 2 O→H 6 P 3 o 13 (T=480°C) [0008] In orthophosphoric acid ...

AI Technical Summary

Problems solved by technology

[0010] At present, there is only the process of producing polyphosphoric acid by using thermal phosphoric acid in China, and there is no use of wet process phosphoric acid (i.e. purification of phosphoric acid 56%P 2 o 5 ) report on the process of producing polyphosphoric acid, because the production of polyphosphoric acid by wet phosphoric acid has problems such as harsh and complex process conditions, high requirements for equipment corrosion resistance and pressure resistance, low recovery rate, and low concentration. So far, there is no better way to overcome the above problems

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