阅读说明：本技术 提高湿法磷酸浓度并联产半水石膏的方法 (Method for increasing concentration of wet-process phosphoric acid and coproducing hemihydrate gypsum ) 是由 兰洲 李兵 梅胜明 王建秋 郑永红 于 2019-11-07 设计创作，主要内容包括：本发明公开了一种提高湿法磷酸浓度并联产半水石膏的方法,包括磷矿浆预处理,磷矿浆与磷酸、混酸浆料混合反应获得预处理料,将预处理料与浓硫酸反应获得混酸浆料,并进一步将混酸浆料熟化、过滤分离得到磷酸和半水石膏,本发明利用磷酸和返回的混酸酸化溶解磷矿浆,溶解过程中带入的水分非常少,有利于提高最终获得的磷酸的浓度,减少后期石膏和二水石膏的生成量。(The invention discloses a method for increasing the concentration of wet-process phosphoric acid and co-producing semi-hydrated gypsum, which comprises the steps of pretreating phosphoric ore pulp, mixing and reacting the phosphoric ore pulp with phosphoric acid and mixed acid slurry to obtain a pretreated material, reacting the pretreated material with concentrated sulfuric acid to obtain mixed acid slurry, further curing the mixed acid slurry, filtering and separating to obtain phosphoric acid and semi-hydrated gypsum.)

1. A method for increasing the concentration of wet-process phosphoric acid and co-producing hemihydrate gypsum is characterized by comprising the following steps:

s1: pretreating the phosphorite slurry;

s2: stirring and reacting the phosphorus ore pulp, the phosphoric acid and the mixed acid slurry returned in the step S3 for not less than 60min to obtain a pretreated material, wherein the mass ratio of the phosphorus ore pulp to the phosphoric acid is 1:2.5-3, and the mass of the mixed acid slurry returned in the step S3 is 9-12% of that of the phosphoric acid;

s3: mixing the pretreatment material and concentrated sulfuric acid according to the mass ratio of 2.5-3:1 for 45-60min to obtain mixed acid slurry, returning part of the mixed acid slurry to the step S2, and entering other mixed acid slurries to the step S4;

s4: further curing the mixed acid slurry for 60-90min to obtain a mixture of semi-hydrated gypsum and phosphoric acid;

s5: and filtering and separating the mixture of the semi-hydrated gypsum and the phosphoric acid to obtain a finished product of the semi-hydrated gypsum and the phosphoric acid.

2. The method for increasing the concentration of wet-process phosphoric acid and co-producing hemihydrate gypsum as claimed in claim 1, wherein: the phosphoric acid of the step S2 is obtained from the phosphoric acid obtained in the step S5, and the phosphoric acid pulp, the phosphoric acid and the mixed acid pulp react for 60min at 94-98 ℃, so that the pretreated material is obtained.

3. The method for increasing the concentration of wet-process phosphoric acid and co-producing hemihydrate gypsum as claimed in claim 1 or 2, wherein: and (4) reacting the pretreatment material obtained in the step S3 with concentrated sulfuric acid at 88-93 ℃ for 60min to obtain the mixed acid slurry.

4. The method for increasing the concentration of wet-process phosphoric acid and co-producing hemihydrate gypsum as claimed in claim 3, wherein: and (5) curing the mixed acid slurry obtained in the step (S4) at 88-93 ℃ for 90min, and filtering and separating to obtain the semi-hydrated gypsum and the phosphoric acid with the concentration not lower than 45%.

5. The method for increasing the concentration of wet-process phosphoric acid and co-producing hemihydrate gypsum as claimed in claim 1, wherein: p in the phosphoric ore pulp before pretreatment in step S1₂O₅The content is 32-36%, the water content is below 35%, and the balance is impurities.

6. The method for increasing the concentration of wet-process phosphoric acid and co-producing hemihydrate gypsum as claimed in claim 1 or 5, wherein: the phosphorite slurry pretreatment of step S1 is carried out in phosphorite slurry pretreatment device, and this phosphorite slurry pretreatment device includes phosphorite slurry holding vessel (13), phosphorite pump (14), first filter equipment (15) and measurement belt weigher (16) that connect gradually along the direction of transportation of material, its moisture content is 8-10% after phosphorite slurry is through first filter equipment (15) filtering separation.

7. The method for increasing the concentration of wet-process phosphoric acid and co-producing hemihydrate gypsum as claimed in claim 6, wherein: steps S2, S3, S4 and S5 are performed in the pretreatment tank (1), the hemihydrate reaction tank (2), the aging tank (3) and the second filtering device (4), respectively;

the pretreatment tank (1), the semi-hydrated reaction tank (2) and the ageing tank (3) are respectively wound with steam heating pipes, wherein the pretreatment tank (1) is provided with a phosphate slurry adding port (6), a phosphoric acid adding port (7), a mixed acid adding port (5) and a pretreatment liquid outlet (9), the semi-hydrated reaction tank (2) is provided with a pretreatment liquid inlet (10), a concentrated sulfuric acid adding port (22), a returned acid outlet (11) and a reaction material outlet (12), the discharge end of the metering belt scale (16) is connected with the phosphate slurry adding port (6), the pretreatment liquid outlet (9) is connected with the pretreatment liquid inlet (10), the returned acid outlet (11) is connected with the mixed acid adding port (5), the reaction material outlet (12) is connected with the feed inlet of the ageing tank (3), the discharge outlet of the ageing tank (3) is connected with a second filtering device (4), the liquid outlet of the second filtering device (4) is connected with a phosphoric acid storage tank (21), the phosphoric acid storage tank (21) is connected with the phosphoric acid adding port (7), and the solid outlet of the second filtering device (4) is connected with a semi-hydrated gypsum bin (20).

8. The method for increasing the concentration of wet-process phosphoric acid and co-producing hemihydrate gypsum as claimed in claim 7, wherein: the second filtering device (4) is a tilting disk type filter, a washing water inlet of the tilting disk type filter is connected with the same washing water pipe (23), a washing water flowmeter is arranged on the washing water pipe (23), the second filtering device (4) is used for filtering and separating phosphoric acid and semi-hydrated gypsum and simultaneously introducing washing water through the washing water pipe (23) for washing, and the mass ratio of the mixture of the semi-hydrated gypsum and the phosphoric acid to the washing water is 1: 1.

9. The method for increasing the concentration of wet-process phosphoric acid and co-producing hemihydrate gypsum as claimed in claim 7, wherein: the exhaust ports of the semi-water reaction tank (2) and the aging tank (3) are connected with a cooling absorption tower (17), and the top of the cooling absorption tower (17) is provided with a soft water inlet.

10. The method for increasing the concentration of wet-process phosphoric acid and co-producing hemihydrate gypsum as claimed in claim 1, wherein: the mass of the mixed acid slurry returned in step S3 was 10% of the mass of phosphoric acid.

Technical Field

The invention relates to the technical field of phosphoric acid production, in particular to a method for increasing the concentration of wet-process phosphoric acid and co-producing hemihydrate gypsum.

Background

The production process for producing wet-process phosphoric acid by a semi-aqueous method has the advantages of short production flow, low investment and high concentration of the produced phosphoric acid, and the obtained phosphoric acid can be directly used for producing DAP or feed monocalcium phosphate without concentration and is used by a plurality of enterprises. Although the production process for producing wet-process phosphoric acid by the semi-water method has the advantages, if the water content in the production process is not well controlled, the washing water consumption in the filtering link is increased, and the like, the obtained semi-water gypsum can be quickly reacted with water to generate gypsum and dihydrate gypsum, pure semi-water gypsum is difficult to obtain, the subsequent filtering difficulty is large, pipelines are easy to block, great difficulty is caused to subsequent processes, for example, the blocked pipelines must be cleaned regularly, and even the phosphoric acid concentration is reduced.

Disclosure of Invention

In view of the above, the invention provides a method for increasing the concentration of wet-process phosphoric acid and co-producing hemihydrate gypsum.

The technical scheme is as follows: the method for increasing the concentration of wet-process phosphoric acid and co-producing hemihydrate gypsum is characterized by comprising the following steps: s1: pretreating the phosphorite slurry;

s2: stirring and reacting the phosphorus ore pulp, the phosphoric acid and the mixed acid slurry returned in the step S3 for not less than 60min to obtain a pretreated material, wherein the mass ratio of the phosphorus ore pulp to the phosphoric acid is 1:2.5-3, and the mass of the mixed acid slurry returned in the step S3 is 9-12% of that of the phosphoric acid;

s3: mixing the pretreatment material and concentrated sulfuric acid according to the mass ratio of 2.5-3:1 for 45-60min to obtain mixed acid slurry, returning part of the mixed acid slurry to the step S2, and entering other mixed acid slurries to the step S4;

s4: further curing the mixed acid slurry for 60-90min to obtain a mixture of semi-hydrated gypsum and phosphoric acid;

s5: and filtering and separating the mixture of the semi-hydrated gypsum and the phosphoric acid to obtain a finished product of the semi-hydrated gypsum and the phosphoric acid.

By adopting the technical scheme, phosphoric acid and returned mixed acid slurry are utilized to acidify and dissolve the phosphoric ore slurry, the water brought in the dissolving process is very little, the concentration of the finally obtained phosphoric acid is favorably improved, and the generation amount of gypsum and dihydrate gypsum in the later period is reduced; concentrated sulfuric acid reacts with calcium ions, phosphate ions and a small amount of water in a semi-hydrated reaction tank to produce semi-hydrated gypsum and phosphoric acid; after the semi-hydrated gypsum and the phosphoric acid are filtered and separated, the target product is obtained.

As further preferred:

the phosphoric acid of the step S2 is obtained from the phosphoric acid obtained in the step S5, and the phosphoric acid pulp, the phosphoric acid and the mixed acid pulp react for 60min at 94-98 ℃, so that the pretreated material is obtained. The reaction is best at 95 ℃, and in the process, because the amount of the returned sulfuric acid is insufficient and the phosphoric acid is redundant, the phosphorus in the phosphorus ore pulp is ionized, so that sufficient preparation is made for obtaining better effect and reaction speed of the next sulfuric acid extraction reaction.

And (4) reacting the pretreatment material obtained in the step S3 with concentrated sulfuric acid at 88-93 ℃ for 60min to obtain the mixed acid slurry. The reaction is preferably carried out at 90 deg.C, during which the sulfuric acid is in excess, which facilitates the formation of hemihydrate gypsum and prevents the conversion of hemihydrate gypsum to gypsum and dihydrate gypsum.

And (5) curing the mixed acid slurry obtained in the step (S4) at 88-93 ℃ for 90min, and filtering and separating to obtain the semi-hydrated gypsum and the phosphoric acid with the concentration not lower than 45%. The process is preferably at 90 deg.C, and the aging reaction time is longer than that in step S3, so that the insufficiently reacted materials in step S3 are sufficiently reacted at this stage, thereby increasing the yield of phosphoric acid and hemihydrate gypsum.

P in the phosphoric ore pulp before pretreatment in step S1₂O₅The content is 32-36%, the water content is below 35%, and the balance is impurities. The selected phosphate rock slurry is used as a preparation raw material, which is beneficial to reducing the impurity amount in the later period.

The phosphorite slurry pretreatment of the step S1 is performed in a phosphorite slurry pretreatment device, the phosphorite slurry pretreatment device comprises a phosphorite slurry storage tank, a phosphorite slurry pump, a first filtering device and a metering belt scale which are sequentially connected along the conveying direction of the material, and the moisture content of the phosphorite slurry is 8-10% after the phosphorite slurry is filtered and separated by the first filtering device.

Steps S2, S3, S4 and S5 are performed in the pretreatment tank, the hemihydrate reaction tank, the aging tank and the second filtering device, respectively;

the pretreatment tank, the semi-water reaction tank and the ageing tank are respectively wound with steam heating pipes, wherein the pretreatment tank is provided with a phosphorite slurry adding port, a phosphoric acid adding port, a mixed acid adding port and a pretreatment liquid outlet, the semi-water reaction tank is provided with a pretreatment liquid inlet, a concentrated sulfuric acid adding port, an acid return outlet and a reaction material outlet, the discharge end of the metering belt scale is connected with the phosphorite slurry adding port, the pretreatment liquid outlet is connected with the pretreatment liquid inlet, the acid return outlet is connected with the mixed acid adding port, the reaction material outlet is connected with the feeding port of the ageing tank, the discharge port of the ageing tank is connected with a second filtering device, the liquid outlet of the second filtering device is connected with a phosphoric acid storage tank, the phosphoric acid storage tank is connected with a phosphoric acid adding port, and the solid outlet of the second filtering device is connected with a semi-hydrated gypsum bin.

The second filtering device is a tilting disk type filtering machine, a washing water inlet of the tilting disk type filtering machine is connected with the same washing water pipe, a washing water flowmeter is arranged on the washing water pipe, the second filtering device is used for filtering and separating phosphoric acid and semi-hydrated gypsum and simultaneously introducing washing water through the washing water pipe for washing, and the mass ratio of the mixture of the semi-hydrated gypsum and the phosphoric acid to the washing water is 1: 1. The dosage of the washing water is strictly controlled, which is beneficial to improving the concentration of the phosphoric acid and preventing the semi-hydrated gypsum from being converted into the gypsum and the dihydrate gypsum.

The exhaust ports of the semi-water reaction tank and the ripening tank are connected with a cooling absorption tower, and the top of the cooling absorption tower is provided with a soft water inlet. By adopting the structure, the hydrogen fluoride and the silicon tetrafluoride which are escaped from the semi-water reaction tank and the ageing tank can be absorbed by the cooling absorption tower to obtain the fluosilicic acid, so that on one hand, the waste gas can be discharged up to the standard, and on the other hand, the obtained fluosilicic acid also has certain economic value.

The mass of the mixed acid slurry returned in step S3 was 10% of the mass of phosphoric acid. This ratio is the optimum ratio.

Compared with the prior art, the invention has the beneficial effects that: the system utilizes phosphoric acid and returned mixed acid to acidify and dissolve the phosphorus ore pulp, the water brought in the dissolving process is very little, the concentration of the finally obtained phosphoric acid is favorably improved, the generation amount of later gypsum and dihydrate gypsum is reduced, favorable conditions are created for subsequent filtration, the phosphoric acid, sulfuric acid and the phosphorus ore pulp fully react in the semi-hydrated reaction tank and the aging tank to generate semi-hydrated gypsum and phosphoric acid, and the phosphoric acid and the semi-hydrated gypsum can be obtained after filtration and separation.

Drawings

FIG. 1 is a schematic structural diagram of the present invention.

Detailed Description

The present invention will be further described with reference to the following examples and the accompanying drawings.

As shown in fig. 1, embodiment 1, a system for increasing the concentration of wet-process phosphoric acid and producing hemihydrate gypsum comprises a pretreatment tank 1, a hemihydrate reaction tank 2, a maturation tank 3 and a second filtering device 4;

the device comprises a pretreatment tank 1, a pretreatment tank 6, a phosphorite slurry adding port 6, a phosphoric acid adding port 7, a mixed acid adding port 5 and a pretreatment liquid outlet 9, wherein the phosphorite slurry adding port 6 is connected with a phosphorite slurry pretreatment device, the phosphorite slurry pretreatment device comprises a phosphorite slurry storage tank 13, a phosphorite slurry pump 14, a first filtering device 15 and a metering belt scale 16 which are sequentially connected along the conveying direction of materials, a discharge port of the metering belt scale 16 is connected with the phosphorite slurry adding port 6, the phosphorite slurry pump 14 is connected with a frequency converter, and the first filtering device 15 is a disc type filter;

be equipped with pretreatment liquid import 10, concentrated sulfuric acid on the semi-water reaction tank 2 and add mouth 22, return sour export 11, reaction material export 12, pretreatment liquid export 9 is connected with pretreatment liquid import 10, return sour export 11 through the sour pipeline of anti-acid with mix sour interpolation mouth 5 and be connected, it has return acid pump, anti-acid flowmeter and anti-acid control valve to establish ties on the anti-acid pipeline, reaction material export 12 with the feed inlet of ageing groove 3 is connected, the discharge gate of ageing groove 3 pass through the discharge conduit with the feed inlet of second filter equipment 4 is connected, wherein be equipped with ejection of compact control valve and ejection of compact flowmeter on the discharge conduit, second filter equipment 4 is the tilting disk filter, and the washing water entry of this tilting disk filter is connected with same root wash water pipe 23, is equipped with washing water flowmeter and washing water control valve on this wash water pipe 23, the solid exit linkage of tilting disk filter has belt conveyor 19, the discharge end of this band conveyer 19 is connected with half water gypsum storehouse 20, the liquid outlet connection of second filter equipment 4 has phosphoric acid holding vessel 21, this phosphoric acid holding vessel 21 pass through the phosphoric acid pipeline with phosphoric acid adds mouthful 7 and connects, be equipped with phosphoric acid pump, phosphoric acid flowmeter and phosphoric acid control valve on the phosphoric acid pipeline.

The exhaust ports of the semi-water reaction tank 2 and the aging tank 3 are connected with a cooling absorption tower 17, and the top of the cooling absorption tower 17 is provided with a soft water inlet.

Pretreatment tank 1, semi-water reaction tank 2 and ageing tank 3 are outer respectively spiral winding have steam heating pipe, all steam heating pipe's import is connected with the boiler 18 of same supply steam through the gas supply line respectively, the last air feed control valve that has of gas supply line, all steam heating pipe's exit linkage has same comdenstion water to gather groove 19.