A system and method for recovering fluorine and silicon resources from wet-process phosphoric acid tail gas treatment

Abstract

The invention relates to the field of the tail gas treatment technology and in particular relates to a system for recycling fluorine and silicon resources from wet-process phosphoric acid tail gas and a recovery method of the system. Fluorosilicic acid solution is circularly treated in the system, the scale blockage phenomenon of the system can be avoided, fluorosilicic acid can flow out in a solution mode in a cooling process of the tail gas, then fluorosilicic acid is further treated so that the fluorine and silicon resources can be recycled; a small amount of water is adopted for absorption treatment in a tail gas absorption process, then the acquired fluorosilicic acid solution is used for washing tail gas circularly; thus, fluorosilicic acid solution from a fluorine washing tower I has high concentration, the fluorine washing tower I and a fluorine washing tower II are combined to ensure that the fluorine-containing substances during the tail gas empting treatment is low, the recovery rate of the fluorine and silicon resources is improved and the environment pollution rate is reduced.

Description

technical field [0001] The invention relates to the technical field of tail gas treatment, in particular to a system for recovering fluorine and silicon resources from wet-process phosphoric acid tail gas treatment and a recovery method thereof. Background technique [0002] The tail gas of wet-process phosphoric acid is mainly SiF4 gas, and the washing liquid is mainly fluosilicic acid solution and silica gel. Since the washing water is the return water from the slag yard, the solid silica gel is also doped with a small amount of calcium fluoride (CaF 2 ). In the actual operation process, there are the following technical defects: the concentration of fluosilicic acid cannot be used during washing, and the washing water contains metal ions (Na + 、K + , Ca 2+ etc.) makes the system prone to fouling and blockage and needs to be cleaned regularly; when ammonia washing is used, the exhaust gas contains a certain amount of ammonia because the temperature often does not drop; ...

AI Technical Summary

Problems solved by technology

In the actual operation process, there are the following technical defects: the concentration of fluosilicic acid cannot be used during washing, and the washing water contains metal ions (Na + 、K + , Ca 2+ etc.) makes the system prone to fouling and blockage and needs to be cleaned regularly; when ammonia washing is used, the exhaust gas contains a certain amount of ammonia because the temperature often does not drop; when other washing liquids (such as ammonium fluoride, etc.) are used, large-scale Implementation at scale

[0003] Moreover, in the prior art, for the tail gas treatment process after wet phosphoric acid extraction treatment, the technologies adopted include: lime water washing method, quicklime powder and activated carbon dry method for treating fluorine-containing tail gas, ammonia washing method and water washing method; but These techniques are only capable of converting SiF-containing 4 The tail gas is treated up to the standard, and a large amount of fluorine-containing silicic acid-containing washing liquid is treated as wastewater, and the cost of tail washing is quite high.

[0004] Although each of the above-mentioned technologies has some advantages compared to each other, for example, the concentration of the hydrofluorosilicic acid solution brought by the lime washing method is higher than that of the water washing method, so that the obtained hydrofluorosilicic acid solution product is better, but It is more difficult to recover the fluorine resources in the obtained fluorosilicate solution, which leads to higher recovery costs of fluorine resources;

[0005] Quicklime powder and activated carbon dry treatment of fluorine-containing tail gas method is to humidify the fluorine-containing tail gas and mix it with quicklime powder and activated carbon before entering the bag filter for dust removal. The fluorine-containing ash is safely buried in the landfill. The exhaust gas effect is good, but the treatment process is relatively complicated and causes waste of fluorine and silicon resources

The ammonia washing method is to use ammonia water as an absorbent to absorb fluorine-containing gases and generate (NH 4 ) 2 SiF 6 Solution, (NH 4 ) 2 SiF 6 The solution will further decompose and generate NH when it reacts with excess ammonia water 4 F and SiO 2 ·nH 2 O, the ammonia washing method has been affirmed by some researchers, but the NH 4 F has not been purified and has high impurity content, so it cannot be directly used in the production of hydrofluoric acid, and it is necessary to establish a supporting NH 4 F and SiO 2 ·nH 2 O purification treatment device, higher investment

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