Production device and method for co-producing alpha-hemihydrate gypsum by two-step wet-process phosphoric acid
阅读说明：本技术 一种两步法湿法磷酸联产α-半水石膏的生产装置及其方法 (Production device and method for co-producing alpha-hemihydrate gypsum by two-step wet-process phosphoric acid ) 是由 朱桂华 何宾宾 魏立军 朱剑峰 欧志兵 张卫红 姜威 彭桦 龚丽 聂鹏飞 于 2021-03-22 设计创作，主要内容包括：本发明公开了一种两步法湿法磷酸联产α半水石膏的生产装置及其方法,涉及湿法磷酸副产半水石膏技术领域。所述装置包括依次连接的压滤机、1#再浆槽、1#反应槽和真空过滤机,真空过滤机磷石膏出口与石膏再浆槽连接,真空过滤机底部渣酸出口与1#反应槽连接,真空过滤机滤液出口与稀酸返酸槽连接,稀酸返酸槽稀酸出口依次连接有2#反应槽、2#再浆槽,2#再浆槽与压滤机连接；2#反应槽的反应料浆出口与1#带式过滤机连接,1#带式过滤机滤液出口与稀酸澄清槽连接,1#带式过滤机磷石膏出口依次连接有调浆槽、3#反应槽、2#带式过滤机,2#带式过滤机滤渣出口依次连接有皮带输送机、烘干机、半水石膏筒仓,生产较高浓度磷酸的同时副产α半水石膏。(The invention discloses a production device and a production method for co-producing alpha hemihydrate gypsum by using wet-process phosphoric acid by a two-step method, and relates to the technical field of by-product hemihydrate gypsum produced by using wet-process phosphoric acid. The device comprises a filter press, a No. 1 repulping tank, a No. 1 reaction tank and a vacuum filter which are sequentially connected, wherein a phosphogypsum outlet of the vacuum filter is connected with a gypsum repulping tank, a slag acid outlet at the bottom of the vacuum filter is connected with the No. 1 reaction tank, a filtrate outlet of the vacuum filter is connected with a dilute acid return tank, a dilute acid outlet of the dilute acid return tank is sequentially connected with a No. 2 reaction tank and a No. 2 repulping tank, and the No. 2 repulping tank is connected with the filter press; the reaction slurry outlet of the No. 2 reaction tank is connected with the No. 1 belt filter, the filtrate outlet of the No. 1 belt filter is connected with the dilute acid clarifying tank, the phosphogypsum outlet of the No. 1 belt filter is sequentially connected with the size mixing tank, the No. 3 reaction tank and the No. 2 belt filter, and the filter residue outlet of the No. 2 belt filter is sequentially connected with the belt conveyor, the dryer and the semi-hydrated gypsum silo, so that the by-product alpha semi-hydrated gypsum is produced while phosphoric acid with higher concentration is produced.)
1. A two-step method wet process phosphoric acid coproduces alpha-hemihydrate gypsum apparatus for production, its characterized in that: the device comprises a filter press (1), a No. 1 repulping tank (2), a No. 1 reaction tank (3) and a vacuum filter (4) which are sequentially connected, wherein a phosphogypsum outlet of the vacuum filter (4) is connected with a gypsum repulping tank (5), a slag acid outlet at the bottom of the vacuum filter (4) is connected with the No. 1 reaction tank (3), a filtrate outlet of the vacuum filter (4) is connected with a dilute acid returning tank (6), a dilute acid outlet of the dilute acid returning tank (6) is sequentially connected with a No. 2 reaction tank (7) and a No. 2 repulping tank (8), and the No. 2 repulping tank (8) is connected with the filter press (1); a reaction slurry outlet of the No. 2 reaction tank (7) is connected with a No. 1 belt filter (9), a filtrate outlet of the No. 1 belt filter (9) is connected with a dilute acid clarifying tank (10), a phosphogypsum outlet of the No. 1 belt filter (9) is sequentially connected with a size mixing tank (11), a No. 3 reaction tank (12) and a No. 2 belt filter (13), and a filter residue outlet of the No. 2 belt filter (13) is sequentially connected with a belt conveyor (14), a dryer (15) and a semi-hydrated gypsum silo (16); the filter press (1) is connected with a phosphorite slurry supply device, and the No. 1 reaction tank (3), the No. 2 reaction tank (7) and the No. 3 reaction tank (12) are respectively connected with a sulfuric acid supply device; the phosphoric acid outlet of the dilute acid clarifying tank (10) is connected with a concentrating device.
2. The production device for co-producing alpha-hemihydrate gypsum by wet-process phosphoric acid with two steps according to claim 1, wherein: an acid returning storage tank (17) is arranged between the slag acid outlet at the bottom of the vacuum filter (4) and the No. 1 reaction tank (3), and the acid returning storage tank (17) is connected with the No. 1 repulping tank (2).
3. The production device for co-producing alpha-hemihydrate gypsum by wet-process phosphoric acid with two steps according to claim 1, wherein: the bottom slag acid outlet of the dilute acid returning tank (6) is connected with the No. 1 reaction tank (3), and the bottom slag acid outlet of the dilute acid clarifying tank (10) is connected with the No. 2 reaction tank (7).
4. The production device for co-producing alpha-hemihydrate gypsum by wet-process phosphoric acid with two steps according to claim 1, wherein: the acid return and filtrate outlets of the No. 2 belt filter (13) are connected with the No. 1 reaction tank (3), the three-washing-liquid outlets of the No. 2 belt filter (13) are connected with the size mixing tank (11), and the size mixing tank (11) is connected with the No. 1 reaction tank (3).
5. The production device for co-producing alpha-hemihydrate gypsum by wet-process phosphoric acid with two steps according to claim 1, wherein: the No. 1 reaction tank (3) is connected with the No. 3 reaction tank (12).
6. The production device for co-producing alpha-hemihydrate gypsum by wet-process phosphoric acid with two steps according to claim 1, wherein: the gypsum repulping tank (5) is connected with a No. 2 belt filter (13).
7. The production device for co-producing alpha-hemihydrate gypsum by using wet-process phosphoric acid through a two-step method according to any one of claims 1 to 6, characterized in that: the production method of the production device comprises the following steps:
s1, dehydrating the phosphorite slurry by using a filter press (1) to control the water content of the phosphorite slurry to be within 20 percent to obtain a filter press cake;
s2.2/3 filter pressing filter cakes enter a No. 1 repulping tank (2), are mixed with returned acid and repulped, are pumped into a No. 1 reaction tank (3), concentrated sulfuric acid is added into the No. 1 reaction tank (3), and the slurry is controlledP2O5Mass concentration of 22-24.5%, solid content of 26-33%, and SO4 2-The mass concentration is 20-30 mg/L, the reaction temperature is 80 +/-2 ℃, the reaction time is 3-4 hours, and coarse crystalline dihydrate phosphogypsum slurry a is obtained after the reaction;
s3, carrying out vacuum filtration on dihydrate phosphogypsum slurry a through a vacuum filter (4), feeding obtained diluted phosphoric acid into a diluted acid returning groove (6), feeding slag acid at the bottom of the diluted acid returning groove (6) into a No. 1 reaction tank (3), carrying out countercurrent washing on phosphogypsum, feeding the phosphogypsum into a gypsum repulping groove (5), and discharging the repulped phosphogypsum into a phosphogypsum yard;
s4, sending part of clear acid on the upper part of the dilute acid return tank (6) into a No. 2 repulping tank (8), pumping part of clear acid into a No. 2 reaction tank (7), mixing the rest 1/3 filter-pressing filter cake in the No. 2 repulping tank (8) to form slurry, sending the slurry into the No. 2 reaction tank (7), continuously adding concentrated sulfuric acid into the No. 2 reaction tank (7), and controlling P in the slurry2O527.5-28% of mass concentration, 26-33% of solid content and SO4 2-The mass concentration is 20-30 mg/L, the reaction temperature is 75 +/-2 ℃, the reaction time is 3-4 hours, and mixed slurry b is obtained after reaction;
s5, pumping the mixed slurry b into a No. 1 belt filter (9), pumping the filtrate obtained by filtering into a dilute acid clarifying tank (10) as a dilute phosphoric acid product, concentrating the clarified dilute phosphoric acid, and returning the bottom slag acid into a No. 2 reaction tank (7) for continuous reaction;
s6.1, filtering phosphogypsum slurry by using a belt filter (9), not washing a phosphogypsum filter cake, sending the filter cake to a slurry mixing tank (11) to be mixed with part of washing liquor from a 2# belt filter (13), pumping part of slurry into a 3# reaction tank (12) after slurry mixing, and pumping the other part of slurry into a 1# reaction tank (3);
s7, feeding dihydrate phosphogypsum slurry a from the size mixing tank (11) and the No. 1 reaction tank (3) into a No. 3 reaction tank (12) for mixing, adding concentrated sulfuric acid, and controlling P in slurry in the No. 3 reaction tank (12)2O5Mass concentration of 18-20%, solid content of 26-31%, and SO4 2-The mass concentration is 8-10.5%, the reaction temperature is 90-95 ℃, the reaction time is 2.5-3 hours, and semi-hydrated gypsum slurry is obtained after the reaction;
s8, conveying the semi-hydrated gypsum slurry to a No. 2 belt filter (13) for filtering and carrying out countercurrent washing to obtain a semi-hydrated gypsum filter cake with the free water being less than or equal to 20%, conveying the semi-hydrated gypsum filter cake to a dryer (15) through a belt conveyor (14) for drying, removing the free water, and conveying the obtained semi-hydrated gypsum to a semi-hydrated gypsum silo (16); the filtrate and washing liquid of the No. 2 belt filter (13) are returned to the No. 1 reaction tank (3).
Technical Field
The invention relates to the technical field of wet-process phosphoric acid byproduct hemihydrate gypsum, in particular to a production device and a production method for co-producing alpha-hemihydrate gypsum by using wet-process phosphoric acid through a two-step method.
Background
At present, domestic phosphoric acid production enterprises mainly adopt a dihydrate method, a semi-hydrate method, a dihydrate-semi-hydrate method and other processes to produce phosphoric acid. The two-water method is adopted by most phosphoric acid production enterprises at present, the technological route of the process is mature, and the localization of large-scale devices is basically realized. However, since the quality of most of domestic phosphate ores is reduced, the phosphoric acid P produced by the wet process of the dihydrate method2O5The mass concentration is low, generally between 21-23%, and in order to obtain phosphoric acid with higher quality, the quality can be improved only by concentration and purification treatment in most cases, the energy consumption of subsequent procedures is increased, and the operation cost is increased. The semi-water process is simple to operate, does not need an evaporation and concentration process under certain conditions, and has low investment; but the operation cost is higher, and the requirement on the quality of the phosphate ore is higher. The dihydrate-hemihydrate process has low energy consumption and can directly produce and obtain P2O5The concentrated phosphoric acid with the mass concentration of about 40 percent has high acid product quality and lower impurity and solid content; the operation is relatively simple, the dry powder of the phosphorite can be directly adopted, the energy consumption is low, and the investment is saved; but P is2O5The recovery rate is low, and SO is generated in the whole process4 2-The method has the advantages that the method has defects and incomplete reaction, and the content of insoluble phosphorus and water-soluble phosphorus in the phosphogypsum is high; has higher requirement on the quality of the phosphate ore, and domestic enterprises have insufficient experience on the control operation of the semi-water flow and the secondary water flow, and the operating rateLow cost and small size.
Dihydrate phosphogypsum is one of the main by-products obtained in the production of phosphoric acid by a dihydrate process. The main component is calcium sulfate dihydrate (CaSO)4·2H2O), the mass fraction of which is more than 85 percent, and also contains a small amount of impurities such as undecomposed phosphorite, unwashed phosphoric acid and the like. The annual emission of phosphogypsum in China is close to 2000 million tons, the cumulative accumulation of the phosphogypsum over 1 hundred million tons over the years becomes a normal state along with the improvement of national environmental protection policies and the development of green enterprises, the comprehensive utilization difficulty of the phosphogypsum is increased, and the sustainable development of the phosphorus chemical industry urgently needs to solve the problem of comprehensive utilization of the phosphogypsum.
The alpha-hemihydrate gypsum has better mechanical property and biocompatibility, is widely applied to the fields of high-grade building materials, precision molds and the like, has a huge market in the field of green building materials, and is the comprehensive utilization direction of the phosphogypsum with the most development potential at present. The alpha-hemihydrate gypsum is prepared by taking the dihydrate phosphogypsum as a raw material, so that the phosphogypsum can be efficiently and greenly consumed, and meanwhile, better economic return is brought to enterprises.
CN110818304B discloses a method for preparing alpha-hemihydrate gypsum, which comprises the steps of preparing dihydrate gypsum by using citric acid as a crystal transformation agent, and then carrying out crystal transformation on the dihydrate gypsum under the excitation effect of alpha-hemihydrate gypsum crystal seeds to prepare the alpha-hemihydrate gypsum. CN108314342B discloses a method for preparing alpha-type high-strength gypsum by using dihydrate phosphogypsum, a phosphoric acid solution and a sulfuric acid solution as raw materials to prepare crystal seeds, and then adding the crystal seeds into mixed slurry of the dihydrate phosphogypsum, the phosphoric acid and the sulfuric acid solution to prepare the alpha-high-strength hemihydrate gypsum. In both methods, dihydrate gypsum is converted into alpha-hemihydrate gypsum under certain conditions, a crystal transformation agent is required to be added to regulate the crystal form of the alpha-hemihydrate gypsum, and the purification and impurity removal treatment of phosphogypsum exists, so that the method is high in energy consumption, high in economic cost, complex in process and poor in continuity.
In conclusion, the phosphoric acid P produced by the existing dihydrate method2O5The mass concentration is low, the concentration needs to be improved through concentration and purification, the production energy consumption is large, the process is complex, and the crystal transformation agent needs to be added in the preparation of the alpha-semi-hydrated gypsum, so that the subsequent purification and impurity removal treatment procedures are complex and the continuity is poor.
Disclosure of Invention
The invention aims to provide a production device and a production method for co-producing alpha-hemihydrate gypsum by using two-step wet-process phosphoric acid, and the two-step method is adopted to further improve P in phosphoric acid2O5The mass concentration, and the recrystallization process, the alpha-hemihydrate gypsum is co-produced without a crystal transformation agent, so that the problems of low utilization rate of phosphogypsum resources, low acid concentration of a dihydrate method and complex preparation procedure of the alpha-hemihydrate gypsum are solved.
In order to solve the technical problems, the invention adopts the following technical scheme: a two-step method wet process phosphoric acid coproduces alpha-hemihydrate gypsum apparatus for production, its characterized in that: the device comprises a filter press, a No. 1 repulping tank, a No. 1 reaction tank and a vacuum filter which are sequentially connected, wherein a phosphogypsum outlet of the vacuum filter is connected with the gypsum repulping tank, a slag acid outlet at the bottom of the vacuum filter is connected with the No. 1 reaction tank, a filtrate outlet of the vacuum filter is connected with a dilute acid return tank, a dilute acid outlet of the dilute acid return tank is sequentially connected with a No. 2 reaction tank and a No. 2 repulping tank, and the No. 2 repulping tank is connected with the filter press; a reaction slurry outlet of the No. 2 reaction tank is connected with a No. 1 belt filter, a filtrate outlet of the No. 1 belt filter is connected with a dilute acid clarifying tank, a phosphogypsum outlet of the No. 1 belt filter is sequentially connected with a size mixing tank, a No. 3 reaction tank and a No. 2 belt filter, and a filter residue outlet of the No. 2 belt filter is sequentially connected with a belt conveyor, a dryer and a semi-hydrated gypsum silo; the filter press is connected with a phosphorite slurry supply device, and the No. 1 reaction tank, the No. 2 reaction tank and the No. 3 reaction tank are respectively connected with a sulfuric acid supply device; the phosphoric acid outlet of the dilute acid clarifying tank is connected with the concentrating device.
A further technical scheme is that an acid returning storage tank is arranged between a slag acid outlet at the bottom of the vacuum filter and the No. 1 reaction tank, and the acid returning storage tank is connected with the No. 1 repulping tank.
The further technical proposal is that the slag acid outlet at the bottom of the dilute acid return tank is connected with the No. 1 reaction tank, and the slag acid outlet at the bottom of the dilute acid clarifying tank is connected with the No. 2 reaction tank.
The further technical scheme is that the acid return and filtrate outlets of the No. 2 belt filter are connected with the No. 1 reaction tank, the three-washing-liquid outlet of the No. 2 belt filter is connected with the size mixing tank, and the size mixing tank is connected with the No. 1 reaction tank.
The further technical proposal is that the No. 1 reaction tank is connected with the No. 3 reaction tank.
The further technical proposal is that the gypsum repulping tank is connected with a No. 2 belt filter.
The further technical proposal is that the production method of the production device comprises the following steps:
s1, dehydrating the phosphorite slurry by using a filter press to control the water content of the phosphorite slurry within 20% to obtain a filter press cake.
S2.2/3 filter pressing filter cakes enter a No. 1 repulping tank, are mixed with return acid and repulped, are pumped into a No. 1 reaction tank, concentrated sulfuric acid is added into the No. 1 reaction tank, and P in the slurry is controlled2O5Mass concentration of 22-24.5%, solid content of 26-33%, and SO4 2-The mass concentration is 20-30 mg/L, the reaction temperature is 80 +/-2 ℃, the reaction time is 3-4 hours, and coarse crystalline dihydrate phosphogypsum slurry a is obtained after the reaction; is beneficial to filtering and washing dihydrate phosphogypsum slurry a and can obtain higher phosphorus yield.
S3, carrying out vacuum filtration on the dihydrate phosphogypsum slurry a through a vacuum filter, feeding the obtained diluted phosphoric acid into a diluted acid returning tank, feeding slag acid at the bottom of the diluted acid returning tank into a No. 1 reaction tank, carrying out countercurrent washing on the phosphogypsum, feeding the phosphogypsum into a gypsum repulping tank, repulping the phosphogypsum, and discharging the phosphogypsum into a phosphogypsum yard.
S4, sending part of clear acid at the upper part of the dilute acid return tank into a No. 2 repulping tank, pumping part of the clear acid into a No. 2 reaction tank, mixing the rest 1/3 filter press cake in the No. 2 repulping tank to form slurry, sending the slurry into the No. 2 reaction tank, continuously adding concentrated sulfuric acid into the No. 2 reaction tank, and controlling P in the slurry2O527.5-28% of mass concentration, 26-33% of solid content and SO4 2-The mass concentration is 20-30 mg/L, the reaction temperature is 75 +/-2 ℃, the reaction time is 3-4 hours, and the mixed slurry b is obtained after reaction.
S5, pumping the mixed slurry b into a No. 1 belt filter, pumping the filtrate obtained by filtering into a dilute acid clarifying tank as a dilute phosphoric acid product, allowing the clarified dilute phosphoric acid to enter a concentration process, and returning the bottom slag acid to the No. 2 reaction tank for continuous reaction. Can obtain dilute phosphoric acid with the concentration of 27.5-28 percent, and is beneficial to reducing the energy consumption of phosphoric acid concentration.
And (3) filtering the phosphogypsum slurry by the S6.1# belt filter, not washing the phosphogypsum filter cake, conveying the filter cake to a size mixing tank to be mixed with part of washing liquid from the 2# belt filter, pumping part of slurry into a 3# reaction tank after size mixing, and pumping the other part of slurry into a 1# reaction tank. Is beneficial to P in slurry in the 3# reaction tank2O5Controlling indexes such as mass concentration, slurry solid content, slurry temperature and the like.
S7, feeding dihydrate phosphogypsum slurry a from the size mixing tank and the No. 1 reaction tank into a No. 3 reaction tank for mixing, adding concentrated sulfuric acid, and controlling P in slurry of the No. 3 reaction tank2O5Mass concentration of 18-20%, solid content of 26-31%, and SO4 2-The mass concentration is 8-10.5%, the reaction temperature is 90-95 ℃, the reaction time is 2.5-3 hours, semi-hydrated gypsum slurry is obtained after the reaction, and the coarse high-strength alpha-semi-hydrated gypsum of the crystal form can be obtained by filtering.
S8, conveying the semi-hydrated gypsum slurry to a No. 2 belt filter (13) for filtering and carrying out countercurrent washing to obtain a semi-hydrated gypsum filter cake with the free water being less than or equal to 20%, conveying the semi-hydrated gypsum filter cake to a dryer (15) through a belt conveyor (14) for drying, removing the free water, and conveying the obtained semi-hydrated gypsum to a semi-hydrated gypsum silo (16); the filtrate and washing liquid of the No. 2 belt filter (13) are returned to the No. 1 reaction tank (3).
The further technical proposal is that the phosphogypsum in the gypsum repulping tank enters a No. 1 belt filter and enters a No. 3 reaction tank together with the phosphogypsum after the two-step wet-process phosphoric acid reaction.
Compared with the prior art, the invention has the beneficial effects that:
1. re-pulping the phosphorus ore pulp, reacting the re-pulped phosphorus ore pulp with concentrated sulfuric acid to generate low-concentration dilute phosphoric acid, reacting the low-concentration dilute phosphoric acid with powdered rock phosphate and concentrated sulfuric acid again to generate higher-concentration phosphoric acid, and producing phosphoric acid by a two-step method to properly improve the P content of the dilute phosphoric acid2O5The concentration, the yield of the phosphoric acid of the device is improved by 33.3 percent, the energy conservation and the consumption reduction are achieved, and the production cost is reduced.
2. In the two-step method, the phosphogypsum reacts with concentrated sulfuric acid on the premise of not using a crystal transformation agent, the reaction temperature is increased by using the dilution heat of the concentrated sulfuric acid, the phosphogypsum is recrystallized, more than 90 percent of dihydrate gypsum can be converted into alpha-hemihydrate gypsum, and the obtained alpha-hemihydrate gypsum has low impurity content, high purity of more than 95 percent and good quality, and is convenient for subsequent industrial processing production.
3. The production device has good continuity and remarkable energy-saving effect, can save steam consumption by 8.6 percent when producing one ton of dilute phosphoric acid, and can save process water by 10.3 percent.
Drawings
FIG. 1 is a process flow diagram of the present invention.
In the figure: the system comprises a 1-filter press, a 2-1# repulping tank, a 3-1# reaction tank, a 4-vacuum filter, a 5-gypsum repulping tank, a 6-dilute acid returning tank, a 7-2# reaction tank, an 8-2# repulping tank, a 9-1# belt filter, a 10-dilute acid clarifying tank, an 11-size mixing tank, a 12-3# reaction tank, a 13-2# belt filter, a 14-belt conveyor, a 15-dryer, a 16-semi-hydrated gypsum silo and a 17-acid returning storage tank.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
FIG. 1 shows a production device for co-producing alpha-hemihydrate gypsum by using wet-process phosphoric acid by a two-step method, which comprises a filter press 1, a 1# repulping tank 2, a 1# reaction tank 3 and a vacuum filter 4 which are sequentially connected, wherein a phosphogypsum outlet of the vacuum filter 4 is connected with a gypsum repulping tank 5, a slag acid outlet at the bottom of the vacuum filter 4 is connected with the 1# reaction tank 3, a filtrate outlet of the vacuum filter 4 is connected with a diluted acid returning tank 6, a diluted acid outlet of the diluted acid returning tank 6 is sequentially connected with a 2# reaction tank 7 and a 2# repulping tank 8, and the 2# repulping tank 8 is connected with the; a reaction slurry outlet of the No. 2 reaction tank 7 is connected with a No. 1 belt filter 9, a filtrate outlet of the No. 1 belt filter 9 is connected with a dilute acid clarifying tank 10, a phosphogypsum outlet of the No. 1 belt filter 9 is sequentially connected with a size mixing tank 11, a No. 3 reaction tank 12 and a No. 2 belt filter 13, and a filter residue outlet of the No. 2 belt filter 13 is sequentially connected with a belt conveyor 14, a dryer 15 and a semi-hydrated gypsum silo 16; the filter press 1 is connected with a phosphorite slurry supply device, and the 1# reaction tank 3, the 2# reaction tank 7 and the 3# reaction tank 12 are respectively connected with a sulfuric acid supply device; the phosphoric acid outlet of the dilute acid clarifying tank 10 is connected with a concentrating device. An acid returning storage tank 17 is arranged between the slag acid outlet at the bottom of the vacuum filter 4 and the No. 1 reaction tank 3, and the acid returning storage tank 17 is connected with the No. 1 repulping tank 2.
The bottom slag acid outlet of the dilute acid returning tank 6 is connected with the No. 1 reaction tank 3, and the bottom slag acid outlet of the dilute acid clarifying tank 10 is connected with the No. 2 reaction tank 7. The 13 acid return and filtrate outlets of the 2# belt filter are connected with the 1# reaction tank 3, the 13 washing liquor outlet of the 2# belt filter is connected with the size mixing tank 11, and the size mixing tank 11 is connected with the 1# reaction tank 3. The reaction tank No. 13 is connected to the reaction tank No. 3 12. The gypsum repulping tank 5 is connected with a No. 2 belt filter 13.
When the device is used, the phosphorite slurry is subjected to pressure filtration by a pressure filter 1 to obtain a pressure filtration filter cake with the water content within 20%, one part of the filter cake is conveyed into a No. 1 repulping tank 2 according to a dihydrate method to be mixed with slurry, the mixed slurry is pumped into a No. 1 reaction tank 3 to react with concentrated sulfuric acid (sulfuric acid with the concentration of 98%) to obtain mixed slurry a, and the mixed slurry a is pumped into a vacuum filter 4 to be subjected to vacuum filtration. The obtained diluted phosphoric acid is sent into a diluted acid returning groove 6, one part of the slag acid is sent into a No. 1 reaction groove 3 for continuous reaction, and the other part of the slag acid is sent into a No. 1 repulping groove 2 for mixing with the filter pressing filter cake; and (3) feeding the filtered phosphogypsum into a gypsum repulping tank 5 after countercurrent washing, discharging one part of repulped phosphogypsum into a phosphogypsum yard, and feeding the other part of repulped phosphogypsum into a No. 1 belt filter 9 to enter a recrystallization process.
And (3) sending one part of clear acid on the upper part of the dilute acid returning groove 6 into a No. 2 repulping groove 8, pumping one part of clear acid into a No. 2 reaction groove 7, enabling the other part of the filter pressing filter cake to enter the No. 2 repulping groove 8 to repulp with dilute phosphoric acid, pumping the filter pressing filter cake into the No. 2 reaction groove 7, reacting with the dilute phosphoric acid returning acid and concentrated sulfuric acid, and obtaining mixed slurry b after reaction. Pumping the mixed slurry b into a No. 1 belt filter 9, pumping the filtrate obtained by filtering into a diluted phosphoric acid clarifying tank 10 as a diluted phosphoric acid product, feeding the clarified diluted phosphoric acid into a concentration process, returning part of the bottom slag acid into a No. 2 reaction tank 7 for continuous reaction, and returning part of the bottom slag acid into a No. 2 repulping tank 8 for size mixing.
The phosphogypsum obtained by filtering with the No. 1 belt filter 9 is not washed, the filter cake and the water fed by the punching cloth are directly conveyed to the size mixing tank 11, and the size is mixed and then pumped into the No. 3 reaction tank 12. Concentrated sulfuric acid and the reacted slurry in the No. 1 reaction tank 3 are added into the No. 3 reaction tank 12, and the semi-hydrated gypsum slurry is obtained after recrystallization reaction.
Conveying the semi-hydrated gypsum slurry to a No. 2 belt filter 13 for filtering and carrying out countercurrent washing to obtain a semi-hydrated gypsum filter cake with crystal water of 4-8% and free water of less than or equal to 20%, conveying the semi-hydrated gypsum filter cake to a dryer 15 through a belt conveyor 14 for drying, removing the free water to obtain semi-hydrated gypsum, and conveying the semi-hydrated gypsum into a semi-hydrated gypsum silo 16; returning acid and filtrate to the No. 1 reaction tank by the No. 2 belt filter 13, and returning part of the three washing liquids to the size mixing tank 11 for size mixing.
Example 2
(1) And (3) dehydrating the phosphate rock slurry by using a filter press 1 to control the water content to be 20% so as to obtain a filter press cake. And conveying the obtained filter-pressing 2/3 ore pulp to a No. 1 repulping tank 2 and 1/3 filter-pressing filter cakes to a No. 2 repulping tank 8.
(2) The pulp obtained from the No. 1 repulping tank 2 is conveyed to the No. 1 reaction tank 3, and concentrated sulfuric acid (sulfuric acid with the concentration of 98%) is added. Controlling the slurry P2O5Mass concentration of 23.5%, SO4 2-The mass concentration is 25mg/L, the solid content of the slurry is 31 percent, and the reaction temperature is 80 ℃, so that the dihydrate phosphogypsum slurry a is obtained.
(3) Pumping the dihydrate phosphogypsum slurry a to a vacuum filter 4 for vacuum filtration to obtain dilute phosphoric acid (P)2O5The mass concentration is 23 percent) is conveyed to a dilute acid returning groove 6 to be used as system returning acid, conveyed to a 2# reaction groove 7 and a 2# repulping groove 8 to be used for size mixing, and the bottom slag acid is returned to a 1# reaction groove 3 to continue to react; and (3) carrying out three-time counter-current washing on the obtained byproduct dihydrate gypsum by using hot water at the temperature of 92-95 ℃, then feeding the dihydrate gypsum into a gypsum repulping tank 5, discharging a part of the repulped dihydrate gypsum into a phosphogypsum yard, and feeding a part of the repulped dihydrate gypsum into a recrystallization process.
(4) Delivering the dilute phosphoric acid obtained in the step (3) to a No. 2 reaction tank 7 and a No. 2 repulping tank 8, mixing 1/3 filter press cakes in the No. 2 repulping tank 8 to form slurry, delivering the slurry to the No. 2 reaction tank 7, continuously adding concentrated sulfuric acid into the No. 2 reaction tank 7, and controlling the slurry P2O5Mass concentration of 27.5%, SO4 2-The mass concentration is 30mg/L, the solid content of the slurry is 30%, the reaction temperature is 75 ℃, the reaction time is 2.5-3 hours, and the mixed slurry b is obtained after the reaction.
(5)The mixed slurry b is sent to a No. 1 belt filter 9 for filtration, and all filtrate obtained by filtration is used as phosphoric acid products (P) of the whole dilute acid making system2O5The mass concentration is 27.3 percent) is conveyed to a dilute acid clarifying tank 10, the clear acid is conveyed to a concentration process for concentration, part of the bottom slag acid returns to a No. 2 reaction tank 7 for continuous reaction, and part of the bottom slag acid returns to a No. 2 repulping tank 8 for size mixing.
(6) The dihydrate phosphogypsum obtained by filtering with the No. 1 belt filter 9 is not washed, the filter cake and the water fed by the punching cloth are directly conveyed to the size mixing tank 11, and the obtained slurry is conveyed to the No. 3 reaction tank 12.
(7) Concentrated sulfuric acid was added to the reaction tank # 3 12 to carry out a recrystallization reaction. Controlling the reaction temperature to be 95 ℃, converting the dihydrate gypsum into the hemihydrate gypsum, controlling the crystallization condition in the process, and controlling the slurry P2O5Mass concentration 20%, SO4 2-The mass concentration is 10.5 percent, and the solid content is 30 percent.
(8) Conveying the reacted dihydrate phosphogypsum slurry a to a No. 3 reaction tank 12 by using a No. 1 reaction tank 3, and heating the slurry in the No. 3 reaction tank 12 by using injected sulfuric acid, wherein the reaction temperature is controlled to be 95 ℃, and the reaction time is controlled to be 2.5 hours. And (3) obtaining semi-hydrated gypsum slurry with good crystallization, conveying the obtained semi-hydrated gypsum slurry to a No. 2 belt filter 13 for filtering, carrying out three times of countercurrent washing to obtain a semi-hydrated gypsum filter cake with 4% of crystal water and 20% of free water, and returning acid and filtrate to a No. 1 reaction tank 3. The obtained semi-hydrated gypsum filter cake is conveyed to a dryer 15 by a belt conveyor 14 for drying, free water is removed, and a semi-hydrated gypsum product is obtained and conveyed to a semi-hydrated gypsum silo 16 after drying and dehydration.
The product performance index is as follows: filtrate diluted phosphoric acid P2O5Mass concentration of 27.3%, SO4 2-The mass concentration is 10.2%; the average crystal particle size was 105.6. mu.m. The obtained alpha-hemihydrate gypsum standard conforms to JC/T2038-2010 alpha 30 grade, and the specific data are shown in attached table 1 and attached table 2.
Example 3
(1) And (3) dehydrating the phosphate rock slurry by using a filter press 1 to control the water content to be 20% so as to obtain a filter press cake. The obtained filter-pressing filter cake 2/3 is conveyed to a No. 1 repulping tank 2, and a No. 1/3 filter-pressing filter cake is conveyed to a No. 2 repulping tank 8.
(2) The pulp obtained from the No. 1 repulping tank 2 is conveyed to the No. 1 reaction tank 3, and concentrated sulfuric acid (sulfuric acid with the concentration of 98%) is added. Controlling the slurry P2O5Mass concentration of 24.5%, SO4 2-The mass concentration is 30mg/L, the solid content of the slurry is 31 percent, and the reaction temperature is 80 ℃, so that the dihydrate phosphogypsum slurry a is obtained.
(3) Pumping the dihydrate phosphogypsum slurry a to a vacuum filter 4 for vacuum filtration to obtain dilute phosphoric acid (P)2O5The mass concentration is 23 percent) is conveyed to a dilute acid returning groove 6 to be used as system returning acid, conveyed to a 2# reaction groove 7 and a 2# repulping groove 8 to be used for size mixing, and the bottom slag acid is returned to a 1# reaction groove 3 to continue to react; and (3) carrying out three-time counter-current washing on the obtained byproduct dihydrate gypsum by using hot water at the temperature of 92-95 ℃, then feeding the dihydrate gypsum into a gypsum repulping tank 5, discharging a part of the repulped dihydrate gypsum into a phosphogypsum yard, and feeding a part of the repulped dihydrate gypsum into a recrystallization process.
(4) Delivering the dilute phosphoric acid obtained in the step (3) to a No. 2 reaction tank 7 and a No. 2 repulping tank 8, mixing 1/3 filter press cakes in the No. 2 repulping tank 8 to form slurry, delivering the slurry to the No. 2 reaction tank 7, continuously adding concentrated sulfuric acid into the No. 2 reaction tank 7, and controlling the slurry P2O528% of SO4 2-The mass concentration is 30mg/L, the solid content of the slurry is 30%, the reaction temperature is 75 ℃, the reaction time is 2.5-3 hours, and the mixed slurry b is obtained after the reaction.
(5) The mixed slurry b is sent to a No. 1 belt filter 9 for filtration, and all filtrate obtained by filtration is used as phosphoric acid products (P) of the whole dilute acid making system2O5The mass concentration is 27.5 percent), the diluted acid is conveyed to a diluted acid clarifying tank 10, the clear acid is conveyed to a concentration process for concentration, part of the bottom slag acid returns to a No. 2 reaction tank 7 for continuous reaction, and part of the bottom slag acid returns to a No. 2 repulping tank 8 for size mixing.
(6) The dihydrate phosphogypsum obtained by filtering with the No. 1 belt filter 9 is not washed, the filter cake and the water fed by the punching cloth are directly conveyed to the size mixing tank 11, and the obtained slurry is conveyed to the No. 3 reaction tank 12.
(7) Concentrated sulfuric acid was added to the reaction tank # 3 12 to carry out a recrystallization reaction. Controlling the reaction temperature to be 93 ℃, converting the dihydrate gypsum into the hemihydrate gypsum, controlling the crystallization condition in the process, and controlling the slurry P2O5Mass concentration 21%, SO4 2-The mass concentration is 10 percent, and the solid content is 31 percent.
(8) Conveying the reacted dihydrate phosphogypsum slurry a to a No. 3 re-reaction tank 12 by using a No. 1 reaction tank 3, and heating the slurry in the No. 3 reaction tank 12 by using injected sulfuric acid, wherein the reaction temperature is controlled to be 93 ℃, and the reaction time is controlled to be 2.5 hours. And (3) obtaining semi-hydrated gypsum slurry with good crystallization, conveying the obtained semi-hydrated gypsum slurry to a No. 2 belt filter 13 for filtering, carrying out three times of countercurrent washing to obtain a semi-hydrated gypsum filter cake with 5% of crystal water and 17% of free water, and returning acid and filtrate to a No. 1 reaction tank 3. The obtained semi-hydrated gypsum filter cake is conveyed to a dryer 15 by a belt conveyor 14 for drying, free water is removed, and a semi-hydrated gypsum product is obtained and conveyed to a semi-hydrated gypsum silo 16 after drying and dehydration.
The product performance index is as follows: filtrate diluted phosphoric acid P2O5Mass concentration of 27.5%, SO4 2-The mass concentration is 9.8%; the average grain size of the crystals was 108.3. mu.m. The obtained alpha-hemihydrate gypsum standard conforms to JC/T2038-2010 alpha 30 grade, and the specific data are shown in attached table 1 and attached table 2.
Example 4
(1) And (3) dehydrating the phosphate rock slurry by using a filter press 1 to control the water content to be 20% so as to obtain a filter press cake. The obtained filter-pressing filter cake 2/3 is conveyed to a No. 1 repulping tank 2, and a No. 1/3 filter-pressing filter cake is conveyed to a No. 2 repulping tank 8.
(2) The pulp obtained from the No. 1 repulping tank 2 is conveyed to the No. 1 reaction tank 3, and concentrated sulfuric acid (sulfuric acid with the concentration of 98%) is added. Controlling the slurry P2O5Mass concentration of 24.5%, SO4 2-The mass concentration is 30mg/L, the solid content of the slurry is 32 percent, and the reaction temperature is 80 ℃, so that the dihydrate phosphogypsum slurry a is obtained.
(3) Pumping the dihydrate phosphogypsum slurry a to a vacuum filter 4 for vacuum filtration to obtain dilute phosphoric acid (P)2O5The mass concentration is 23 percent) is conveyed to a dilute acid returning groove 6 to be used as system returning acid, conveyed to a 2# reaction groove 7 and a 2# repulping groove 8 to be used for size mixing, and the bottom slag acid is returned to a 1# reaction groove 3 to continue to react; the obtained byproduct dihydrate gypsum is washed by hot water at the temperature of 92-95 ℃ for three times in a countercurrent mode and then enters a gypsum repulping tank 5, and a part of the repulped dihydrate gypsum is dischargedAnd (5) entering a phosphogypsum storage yard, and enabling a part of the phosphogypsum to enter a recrystallization process.
(4) Delivering the dilute phosphoric acid obtained in the step (3) to a No. 2 reaction tank 7 and a No. 2 repulping tank 8, mixing 1/3 filter press cakes in the No. 2 repulping tank 8 to form slurry, delivering the slurry to the No. 2 reaction tank 7, continuously adding concentrated sulfuric acid into the No. 2 reaction tank 7, and controlling the slurry P2O528% of SO4 2-The mass concentration is 30mg/L, the solid content of the slurry is 30%, the reaction temperature is 75 ℃, the reaction time is 2.5-3 hours, and the mixed slurry b is obtained after the reaction.
(5) The mixed slurry b is sent to a No. 1 belt filter 9 for filtration, and all filtrate obtained by filtration is used as phosphoric acid products (P) of the whole dilute acid making system2O5The mass concentration is 27.6 percent), the diluted acid is conveyed to a diluted acid clarifying tank 10, the clear acid is conveyed to a concentration process for concentration, part of the bottom slag acid returns to a No. 2 reaction tank 7 for continuous reaction, and part of the bottom slag acid returns to a No. 2 repulping tank 8 for size mixing.
(6) The dihydrate phosphogypsum obtained by filtering with the No. 1 belt filter 9 is not washed, the filter cake and the water fed by the punching cloth are directly conveyed to the size mixing tank 11, and the obtained slurry is conveyed to the No. 3 reaction tank 12.
(7) Concentrated sulfuric acid was added to the reaction tank # 3 12 to carry out a recrystallization reaction. Controlling the reaction temperature to be 92 ℃, converting the dihydrate gypsum into the hemihydrate gypsum, controlling the crystallization condition in the process, and controlling the slurry P2O5Mass concentration 22.5%, SO4 2-The mass concentration is 9.5 percent, and the solid content is 32.5 percent.
(8) Conveying the reacted dihydrate phosphogypsum slurry a to a No. 3 re-reaction tank 12 by using a No. 1 reaction tank 3, and heating the slurry in the No. 3 reaction tank 12 by using injected sulfuric acid, wherein the reaction temperature is controlled to be 92 ℃, and the reaction time is controlled to be 2.5 hours. And (3) obtaining semi-hydrated gypsum slurry with good crystallization, conveying the obtained semi-hydrated gypsum slurry to a No. 2 belt filter 13 for filtering, carrying out three times of countercurrent washing to obtain a semi-hydrated gypsum filter cake with 7% of crystal water and 16% of free water, and returning acid and filtrate to a No. 1 reaction tank 3. The obtained semi-hydrated gypsum filter cake is conveyed to a dryer 15 by a belt conveyor 14 for drying, free water is removed, and a semi-hydrated gypsum product is obtained and conveyed to a semi-hydrated gypsum silo 16 after drying and dehydration.
The product performance index is as follows: filtrate diluted phosphoric acid P2O5Mass concentration of 27.6%, SO4 2-The mass concentration is 9.4%; the average crystal particle size was 110.4. mu.m. The obtained alpha-hemihydrate gypsum standard conforms to JC/T2038-2010 alpha 30 grade, and the specific data are shown in attached table 1 and attached table 2.
Example 5
(1) And (3) dehydrating the phosphate rock slurry by using a filter press 1 to control the water content to be 20% so as to obtain a filter press cake. The obtained filter-pressing filter cake 2/3 is conveyed to a No. 1 repulping tank 2, and a No. 1/3 filter-pressing filter cake is conveyed to a No. 2 repulping tank 8.
(2) The pulp obtained from the No. 1 repulping tank 2 is conveyed to the No. 1 reaction tank 3, and concentrated sulfuric acid (sulfuric acid with the concentration of 98%) is added. Controlling the slurry P2O5Mass concentration of 24.5%, SO4 2-The mass concentration is 30mg/L, the solid content of the slurry is 31 percent, and the reaction temperature is 80 ℃, so that the dihydrate phosphogypsum slurry a is obtained.
(3) Pumping the dihydrate phosphogypsum slurry a to a vacuum filter 4 for vacuum filtration to obtain dilute phosphoric acid (P)2O5The mass concentration is 23 percent) is conveyed to a dilute acid returning groove 6 to be used as system returning acid, conveyed to a 2# reaction groove 7 and a 2# repulping groove 8 to be used for size mixing, and the bottom slag acid is returned to a 1# reaction groove 3 to continue to react; and (3) carrying out three-time counter-current washing on the obtained byproduct dihydrate gypsum by using hot water at the temperature of 92-95 ℃, then feeding the dihydrate gypsum into a gypsum repulping tank 5, discharging a part of the repulped dihydrate gypsum into a phosphogypsum yard, and feeding a part of the repulped dihydrate gypsum into a recrystallization process.
(4) Delivering the dilute phosphoric acid obtained in the step (3) to a No. 2 reaction tank 7 and a No. 2 repulping tank 8, mixing 1/3 filter press cakes in the No. 2 repulping tank 8 to form slurry, delivering the slurry to the No. 2 reaction tank 7, continuously adding concentrated sulfuric acid into the No. 2 reaction tank 7, and controlling the slurry P2O527.5-28% of mass concentration and SO4 2-The mass concentration is 25mg/L, the solid content of the slurry is 30%, the reaction temperature is 75 ℃, the reaction time is 2.5-3 hours, and the mixed slurry b is obtained after the reaction.
(5) The mixed slurry b is sent to a No. 1 belt filter 9 for filtration, and all filtrate obtained by filtration is used as phosphoric acid products (P) of the whole dilute acid making system2O528.2 percent of mass concentration) is conveyed to a dilute acid clarifying tank 10, and the clear acid is conveyed to a concentration processConcentrating, returning part of the bottom slag acid to the No. 2 reaction tank 7 for continuous reaction, and returning part of the bottom slag acid to the No. 2 repulping tank 8 for pulp mixing.
(6) The dihydrate phosphogypsum obtained by filtering with the No. 1 belt filter 9 is not washed, the filter cake and the water fed by the punching cloth are directly conveyed to the size mixing tank 11, and the obtained slurry is conveyed to the No. 3 reaction tank 12.
(7) Concentrated sulfuric acid was added to the reaction tank # 3 12 to carry out a recrystallization reaction. Controlling the reaction temperature to be 90 ℃, converting the dihydrate gypsum into the hemihydrate gypsum, controlling the crystallization condition in the process, and controlling the slurry P2O5Mass concentration 23%, SO4 2-The mass concentration is 9 percent, and the solid content is 33 percent.
(8) Conveying the reacted dihydrate phosphogypsum slurry a to a No. 3 re-reaction tank 12 by using a No. 1 reaction tank 3, and heating the slurry in the No. 3 reaction tank 12 by using injected sulfuric acid, wherein the reaction temperature is controlled to be 90 ℃, and the reaction time is controlled to be 2.5 hours. And (3) obtaining semi-hydrated gypsum slurry with good crystallization, conveying the obtained semi-hydrated gypsum slurry to a No. 2 belt filter 13 for filtering, carrying out three times of countercurrent washing to obtain a semi-hydrated gypsum filter cake with 8% of crystal water and 15% of free water, and returning acid and filtrate to a No. 1 reaction tank 3. The obtained semi-hydrated gypsum filter cake is conveyed to a dryer 15 by a belt conveyor 14 for drying, free water is removed, and a semi-hydrated gypsum product is obtained and conveyed to a semi-hydrated gypsum silo 16 after drying and dehydration.
The product performance index is as follows: filtrate diluted phosphoric acid P2O5Mass concentration of 28.2%, SO4 2-The mass concentration is 9.3%; the average crystal particle size was 112.8. mu.m. The obtained alpha-hemihydrate gypsum standard conforms to JC/T2038-2010 alpha 30 grade, and the specific data are shown in attached table 1 and attached table 2.
TABLE 1 general data for phosphoric acid products
TABLE 2. Combined production of alpha-hemihydrate gypsum product
The table shows that the invention not only improves the quality of the dilute acid to 27.3-28.2%, improves the phosphorus recovery rate and increases the productivity, but also co-produces the high-strength alpha-hemihydrate gypsum and improves the comprehensive utilization of the phosphogypsum.
Although the invention has been described herein with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts or arrangements within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts or arrangements, other uses will also be apparent to those skilled in the art.
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