WO2022222323A1 - 一种高收率水合晶相重构湿法磷酸生产工艺 - Google Patents

一种高收率水合晶相重构湿法磷酸生产工艺 Download PDF

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WO2022222323A1
WO2022222323A1 PCT/CN2021/112634 CN2021112634W WO2022222323A1 WO 2022222323 A1 WO2022222323 A1 WO 2022222323A1 CN 2021112634 W CN2021112634 W CN 2021112634W WO 2022222323 A1 WO2022222323 A1 WO 2022222323A1
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zone
filter
dihydrate
phosphoric acid
filtration
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PCT/CN2021/112634
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English (en)
French (fr)
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郭国清
陈志华
杨培发
赵军
郝易潇
邹文敏
李志刚
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中国五环工程有限公司
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Publication of WO2022222323A1 publication Critical patent/WO2022222323A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/18—Phosphoric acid
    • C01B25/22—Preparation by reacting phosphate-containing material with an acid, e.g. wet process
    • C01B25/222—Preparation by reacting phosphate-containing material with an acid, e.g. wet process with sulfuric acid, a mixture of acids mainly consisting of sulfuric acid or a mixture of compounds forming it in situ, e.g. a mixture of sulfur dioxide, water and oxygen
    • C01B25/228—Preparation by reacting phosphate-containing material with an acid, e.g. wet process with sulfuric acid, a mixture of acids mainly consisting of sulfuric acid or a mixture of compounds forming it in situ, e.g. a mixture of sulfur dioxide, water and oxygen one form of calcium sulfate being formed and then converted to another form
    • C01B25/229—Hemihydrate-dihydrate process
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer

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  • the invention relates to the field of phosphoric acid production, in particular to a high-yield hydrated crystal phase reconstruction wet-process phosphoric acid production process.
  • hemihydrate-dihydrate method The production technology of hemihydrate-dihydrate method is to control the reaction conditions, first crystallize to form calcium sulfate hemihydrate, accompanied by high concentration of phosphoric acid, and then change the reaction conditions, hydrate and recrystallize to form calcium sulfate dihydrate, which is called hemihydrate-dihydrate legal process.
  • the phosphoric acid In the traditional hemi-water-dihydrate wet phosphoric acid process, the phosphoric acid is dissolved and crystallized in turn to obtain hemihydrate gypsum.
  • Publication No. 105036101B discloses a hemihydrate-dihydrate method for producing phosphoric acid by a wet process and a system thereof.
  • a hemihydrate reaction and a filtration process are first performed to obtain the products phosphoric acid and hemihydrate gypsum, and then the hemihydrate gypsum is processed into a hemihydrate gypsum.
  • Dihydrate reaction and filtration process obtains dihydrate dry gypsum.
  • the liquid will not be bumped to ensure the stable operation of the system, and the utilization efficiency and reaction effect of raw materials can be improved by improving the shape of the dissolution tank and the crystallization tank.
  • the dihydrate gypsum transportation is designed as a wet drainage method
  • the hemihydrate gypsum will re-absorb water in the dihydrate re-slurry pipeline and convert it into dihydrate gypsum, and the plate will be fouled and the pipeline will be blocked.
  • the yield of P 2 O 5 needs to be further improved.
  • the slurry drawn from the upper section of the semi-water filter feed tank is sent back to the crystallization area, and the slurry drawn from the lower section is pressurized and then sent to the crystallization zone.
  • the hemihydrate gypsum, back acid and filtered acid are obtained by the hemihydrate filter respectively, and the back acid is respectively returned to the premixing zone, the dissolving zone and the crystallization zone.
  • the sulfate ion concentration in the liquid phase of the premixing zone is controlled to be lower than the CaO concentration by 3.6wt-4.6wt%; in the step A2), the sulfate ion concentration in the liquid phase in the dissolving zone is controlled is lower than the CaO concentration by 2.7wt% to 3.4wt%; in the step A3), the sulfate ion concentration in the crystalline liquid phase is controlled to be higher than the CaO concentration by 1.2wt% to 6%wt%.
  • the slurry that is pressurized and returned to the premix tank adopts a large circulating slurry, and the ratio is 3-5.
  • the conversion zone includes two conversion tanks connected in series, and the slurry in the first conversion tank is pressurized and then sent to the second flash cooler for cooling and then returned to the conversion tank.
  • the sulfate ion concentration in the conversion zone is controlled to be 5wt% to 10wt%, the phosphoric acid concentration to be 12wt% to 25wt% P 2 O 5 , the temperature to be 55°C to 65°C, and the solid content to be 30% to 35wt%. %.
  • the dihydrate filter includes a filter zone, a filter cake washing zone and a filter cloth washing zone; wherein, the filtrate collected below the filtration zone of the dihydrate filter is used as the filter cake washing water after pressurization. Rinse the cake wash area of the semi-aqueous filter.
  • the filter cake washing zone is composed of a washing zone, a second washing zone and a third washing zone, wherein the filtrate collected under the latter washing zone is pressurized as the flushing water of the former washing zone.
  • the filtrate collected under the first washing area is used as the filter cloth washing water after pressurization to wash the filter cloth washing area of the semi-water filter, and the washing liquid in the third washing area comes from the process water.
  • a pre-mixing zone is added, and the phosphate rock is first sent to the pre-mixing zone, mixed with the back acid and decomposed rapidly, and the liquid should be controlled in the pre-mixing zone.
  • the sulfate ion concentration in the phase is lower than the CaO concentration by 3.6wt% to 4.6wt%, which ensures that the back acid can completely dissolve the phosphate rock, and at the same time avoids the encapsulation of the phosphate rock by the calcium sulfate film. ensure.
  • the crystal size of hemihydrate gypsum can be significantly increased (D50 up to 135um) and the number of hemihydrate gypsum fine crystals (less than 1% crystals below 10um) can be significantly reduced through accurate sulfuric acid concentration gradient control.
  • the addition of circulating slurry is considered to dilute the concentration of the added material, so as to avoid the occurrence of encapsulation of phosphate rock.
  • the seed crystals in the circulating slurry inhibit the secondary nucleation of phosphogypsum crystals, which is beneficial to obtain coarse, uniform, and easy-to-filter hemihydrate gypsum crystals. If the ratio is too large, the concentration of sulfuric acid brought into the premixing zone and the dissolution zone by the circulating slurry will be too high, resulting in an excessive increase in the calcium precipitation rate in the premixing zone and the dissolution zone, and the formation of crystal nuclei is too fast. Affect the stable growth of crystals.
  • the other is pressurized and sent to the flash cooler for cooling and then sent to half water. Filter the feeding tank to reduce the heat of reaction and avoid the conversion of the hemihydrate gypsum slurry into anhydrite due to the high temperature After the slurry is pressurized, it is sent to the hemi-water filter, and the slurry drawn from the upper section is sent back to the crystallization zone. It is grown in a stable environment to obtain hemihydrate gypsum crystals with stable and uniform particle size.
  • the filtrate or flushing water collected by the semi-water filter and the di-water filter is reused according to the solid content and P 2 O 5 content, and there is no waste water discharge in the whole process;
  • the pool water contains 1wt% P 2 O 5 , and this part of the pool water is recycled as a flushing liquid to wash the screw unloader of the secondary water filter, the slag hopper below, and the secondary washing area, so as to recycle this part of P 2 O 5, to further improve the total recovery rate of phosphorus.
  • an overflow pipe is set between the filter acid pipeline and the acid return pipeline.
  • the overflow pipe directly enters the inlet of the acid return pump to avoid the accumulation of acid in the filter disc of the filter, causing the filter disc to overflow and the P 2 O 5 concentration of the dihydrate conversion tank to increase beyond the standard, resulting in the increase of soluble phosphorus in dihydrate gypsum.
  • the phosphoric acid is sequentially sent into the premixing zone, the dissolving zone, the crystallization zone and the ripening zone to complete the various stages of the hemi-water reaction, and the gradient control of the relationship between the sulfate ion concentration and the CaO concentration in different stages of the hemi-water reaction is carried out to achieve Increase the crystal size, keep the crystal stable, and obtain hemihydrate gypsum crystals with uniform particle size; control the circulation path of the slurry, which not only increases the reaction residence time, but also ensures that the hemihydrate gypsum crystals grow in a relatively stable environment.
  • a variety of means can be used to obtain coarse, stable and high-strength hemihydrate gypsum crystals.
  • the particle size distribution D50 can reach 135um, and the proportion of hemihydrate gypsum crystals below 10um is less than 1%.
  • the porosity can achieve a large filtration rate, effectively reducing the clogging of the hemihydrate filter cloth by the fine crystals. , reducing the area of the filter, thereby reducing the investment of the device, which is beneficial to the improvement of the driving rate of the entire system, and the hemihydrate gypsum sent to the di-water conversion tank after washing will not bring too much insoluble phosphorus and water-soluble phosphorus.
  • the crystal size distribution D50 of dihydrate gypsum can reach 96um, and the proportion of hemihydrate gypsum crystals below 10um is less than 1%.
  • the dihydrate filtration performance is excellent, reducing the water solubility of dihydrate gypsum after filtration.
  • the phosphorus content increases the final phosphorus recovery rate; the filtrate and flushing water are rationally utilized to reduce waste water discharge and improve the total yield of P 2 O 5 .
  • the method of the invention is simple and easy to control, can effectively obtain coarse and uniform hemihydrate gypsum crystals and dihydrate gypsum crystals, has good filtering effect, high yield, low investment and operating costs, is environmentally friendly and has good operating stability.
  • Fig. 1 is the process flow diagram of the present invention.
  • Embodiment 1 one, semi-aqueous reaction filtration process: A1) comprise that phosphate rock is first sent into premixed zone 1, mixed with returning acid, rapidly decomposed; The sulfate ion concentration in control premixed zone 1 liquid phase is lower than The CaO concentration is 3.6wt% ⁇ 4.6wt%, and the temperature is 90°C ⁇ 100°C; A2) The slurry from the premixing zone 1 is sent to the dissolving zone 2, and fully dissolved in the presence of back acid and sulfuric acid, wherein the liquid phase is controlled The sulfate ion concentration in the solution is lower than the CaO concentration by 2.7wt% to 3.4wt%; A3) The reaction slurry from the dissolution zone 2 is sent to the crystallization zone 3, and the crystallization grows in the presence of concentrated sulfuric acid, wherein the liquid phase is controlled The sulfate ion concentration is higher than the CaO concentration by 1.2wt% ⁇ 6wt%, the temperature is 90°C ⁇ 100
  • the residence time of the reaction slurry in the maturation zone 4 is controlled to be 0.5-1.5h. A5.
  • the slurry exiting the maturing zone 4 is divided into two strands, one is pressurized and returned to the premix tank 1 by the circulating pump 6, and the slurry returned to the premix tank 1 under pressure adopts a large circulating slurry, and the ratio is 3 to 5; the other is pressurized by the flash pump 5 and sent to the flash cooler 6 for cooling, and then sent to the semi-water filter feed tank 7, and the upper part of the semi-water filter feed tank 7 leads out part of the slurry and returns it to the crystallization zone. 3.
  • Part of the slurry drawn from the lower section is pressurized and sent to the filtration area of the hemi-water filter 9, and the filtration acid (containing 36-42wt% P 2 O 5 ) is drawn out from the filtration area 9.1 of the hemi-water filter 9 and pressurized through the filtration acid pipeline 14 Sending out, the returning acid (containing 30-34wt% P 2 O 5 ) drawn from the filter cake washing zone 9.2 is sent back to the premixing zone, the dissolving zone and the crystallization zone respectively through the acid returning line 15, and the hemihydrate gypsum is discharged from the discharge end.
  • the filtration acid containing 36-42wt% P 2 O 5
  • Two, water reaction filtration process: B1) described hemihydrate gypsum is first sent into conversion zone 10 to react with sulfuric acid, and in control conversion zone 10, sulfate ion concentration is 5wt% ⁇ 10wt%, and phosphoric acid concentration is 12wt% ⁇ 25wt%P O 5 , the temperature is 55°C-65°C, and the solid content is 30% to 35% by weight; preferably, the conversion zone 10 includes two conversion tanks connected in series, and the slurry in the first conversion tank is pressurized and then sent to the second conversion tank. The second flash cooler 11 is cooled and returned to the conversion tank.
  • reaction slurry going out of the conversion zone 10 is divided into two strands, one strand is sent to the dihydrate filter 12 for filtering to obtain phosphogypsum, and the other strand is fed back to the screw unloader for flushing the discharge end of the half-water filter 9 and the The slag bucket below it.
  • the dihydrate filter 12 includes a filter zone 12.1, a filter cake washing zone 12.2 and a filter cloth washing zone 12.3; wherein, the filtrate collected under the filter zone 12.1 of the dihydrate filter 12 is pressurized as filter cake washing water
  • the filter cake washing zone 9.1 of the semi-aqueous filter 9 is post-rinsed.
  • the filter cake washing zone 12.2 is composed of a first washing zone, a second washing zone and a third washing zone, wherein the filtrate collected under the latter washing zone is pressurized as the flushing water of the former washing zone, and the filtrate collected under the first washing zone is collected under pressure.
  • the filtrate is used as filter cloth washing water after pressurization to wash the filter cloth washing zone 9.3 of the semi-water filter 9, and the washing liquid in the third washing zone comes from process water.
  • the pool water collected during the subsequent treatment of the phosphogypsum was used as a flushing liquid to flush the screw unloader at the discharge end of the secondary water filter 12 and the slag hopper below, as well as the secondary washing area.
  • An overflow pipe 13 is arranged between the filtering acid pipeline 14 for drawing out the filtered acid and the returning acid pipeline 15 for extracting the returning acid, and the overflow pipe 13 is set with a large inclination angle.
  • the filtrate can be discharged directly from the filter acid line 14 through the overflow pipe 13 into the acid return line 15 to avoid acid accumulation in the filter disc of the semi-water filter.
  • Comparative Example 1 Compared with Example 1 of the present application, the sulfate ion concentration in the liquid phase of the premixing zone 1 is controlled to be 3wt% lower than the CaO concentration, and the sulfate ion concentration in the liquid phase of the dissolving zone 2 is lower than the CaO concentration by 1.5% Except for wt%, the rest are the same as in Example 1.
  • Comparative Example 2 Compared with Example 1 of the present application, without maturing zone 4, two slurries drawn from crystallization zone 3 were sent to premix zone 1 and flash cooler 6 respectively, and the rest were the same as in Example 1.

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Abstract

本发明公开了一种高收率水合晶相重构湿法磷酸生产工艺，包括半水反应过滤工序和二水反应过滤工序，其中半水反应过滤工序包括预混、溶解、结晶、熟化和半水过滤步骤；所述二水反应过滤工序包括转化和二水过滤步骤。本发明通过对半水反应不同阶段硫酸根离子浓度与CaO浓度之间关系的梯度控制，以实现增大结晶尺寸、保持结晶稳定，获得粒径均一的半水石膏结晶；通过改变料浆的循环路径，增加反应停留时间，且保证了半水石膏结晶在相对稳定的环境下生长；通过对二水反应过饱和度的控制，获得粗大均一稳定的二水石膏结晶，过滤性能好，降低二水石膏水溶磷含量，提高过滤收率；通过对滤液和冲洗水合理利用，减少废水排放，提高P2O5总收率。

Description

一种高收率水合晶相重构湿法磷酸生产工艺 技术领域
本发明涉及磷酸生产领域，具体的说是一种高收率水合晶相重构湿法磷酸生产工艺。
 背景技术
半水-二水法生产工艺技术是控制反应条件，先结晶生成半水硫酸钙，同时伴随高浓度磷酸，再改变反应条件，水合重结晶生成二水硫酸钙，称之为半水-二水法工艺。传统的半水-二水湿法磷酸的半水工艺中，磷酸依次经溶解、结晶后得到半水石膏，由于半水-二水法工艺具有P 2 O 5 收率高，磷酸产品浓度高，酸质量好，磷石膏质量好、能耗低和环境污染小等特点，半水-二水法工艺将成为未来湿法磷酸发展的趋势。
如公开号105036101B公开了一种半水-二水法湿法磷酸生产工艺及其系统，以磷矿为原料先进行半水反应及过滤工序得到产品磷酸和半水石膏，再将半水石膏进行二水反应及过滤工序得到二水干石膏。通过采用高位闪蒸冷却器，使液体不会产生暴沸保证系统的稳定运行，通过对溶解槽和结晶槽的形状进行改进提高原料的利用效率和反应效果。上述工艺在实际运行中发现，仍存在以下问题：(1)半水石膏结晶控制不稳定，晶体大小一般为40～60um，半水石膏料浆过滤强度一般为3.0～3.7tP 2 O 5 /m 2 /d,导致过滤速率低下、半水过滤滤布的堵塞，不利于系统开车率的提高。(2)硫酸浓度控制不够精确稳定，磷矿表面容易形成致密的硫酸钙包裹薄膜，阻碍磷矿的分解，恶性循环甚至可能被迫停车进行调整。(3)在运行过程中有时会发生过滤机滤盘积酸的问题，导致过滤机滤盘漫盘而使转化区P 2 O 5 浓度增加超标，从而导致二水石膏拘溶性磷增加。(4)当半水石膏结晶较差时，半水石膏晶体细小，半水滤饼持液量高，二水料浆液相P 2 O 5 浓度容易迅速上升至30％，导致二水转化时间长、石膏中晶间P 2 O 5 损失增大、二水料浆过滤和洗涤困难等。(5)半水结晶吸水转化是放热反应，再加上硫酸稀释热及加入物料的显热，当转化温度和磷酸浓度过高时，如在30％P 2 O 5 浓度下，半水石膏转化为二水石膏的平衡温度点是72℃，若温度超过此值，二水石膏会转化成半水石膏。若二水石膏输送设计为湿排方式，半水石膏在二水再浆输送管道中会重新吸水转化成二水石膏，板结结垢从而导致管道堵塞。(6)P 2 O 5 的收率还有待进一步提高。(7)由于存在大量过滤、洗涤步骤，因此过滤液、洗涤液的合理利用，减少外排，是需要亟待解决的问题。
因此希望能够通过对现有半水-二水法生产工艺的进一步改进，在以获得更高的P 2 O 5 收率，减少设备投资、保证系统的稳定运行。
 技术问题
本发明的目的是为了解决上述技术问题，提供一种方法简单、易于控制，能够有效获得粗大、均一性好的半水石膏晶体、过滤效果好、收率高、对环境友好、运行稳定性好的高收率水合晶相重构湿法磷酸生产工艺。
 技术解决方案
技术方案包括以下步骤：包括半水反应过滤工序和二水反应过滤工序，其特征在于，所述半水反应过滤工序包括以下步骤：A1)将磷矿先送入预混区中，与返酸混合、快速分解；A2)出预混区的料浆送入溶解区中，在返酸和硫酸的存在下充分溶解：A3)出溶解区的反应料浆送入结晶区中在硫酸的存在下结晶长大；A4)出结晶区的反应料浆送入熟化区中，半水石膏结晶进一步长大；A5)出所述熟化区的料浆分为两股，一股加压返回至预混区，另一股加压送入第一闪蒸冷却器冷却后送入半水过滤给料槽，所述半水过滤给料槽上段引出料浆回送结晶区，下段引出料浆加压后送半水过滤机过滤分别得到半水石膏、返酸和过滤酸，所述返酸分别回送预混区、溶解区和结晶区。
所述二水反应过滤工序包括以下工序：B1)所述半水石膏先送入转化区与硫酸反应；B2)出转化区的反应料浆分为两股，一股送入二水过滤机得到二水石膏，另一股回送用于冲洗半水过滤机的螺旋卸料机及其下方的渣斗。
所述A1)步骤中，控制预混区液相中的硫酸根离子浓度低于CaO浓度3.6wt～4.6wt％；所述A2)步骤中，控制所述溶解区液相中的硫酸根离子浓度低于CaO浓度2.7wt％～3.4wt％；所述A3)步骤中，控制所述结晶液相中的硫酸根离子浓度高于CaO浓度1.2wt％～6％wt％。
所述A4)步骤中，控制反应浆料在熟化区中的停留时间为0.5h～1.5h。
所述A1)步骤中，控制的所述预混区温度90℃～100℃；所述A2)步骤中，控制溶解区温度90℃～100℃，磷酸浓度为36％～42wt％P 2 O 5 ，含固量28wt％～37wt％；所述A3)步骤中，控制结晶区温度90℃～100℃，磷酸浓度为36％-42wt％P 2 O 5 ，含固量28wt％～37wt％。
所述A1)步骤中，加压返回至预混槽的料浆采用大循环料浆，比值为3～5。
所述B1)步骤中，所述转化区包括串联的两个转化槽，第一个转化槽内的料浆加压后送第二闪蒸冷却器冷却后回送该转化槽。
所述B1)步骤中，控制转化区中硫酸根离子浓度为5wt％～10wt％，磷酸浓度为12wt％～25wt％P 2 O 5 ，温度为55℃-65℃，含固量30％～35wt％。
所述B2)步骤中，所述二水过滤机包括过滤区、滤饼洗涤区和滤布洗涤区；其中，所述二水过滤机的过滤区下方收集的滤液作为滤饼洗水加压后冲洗半水过滤机的滤饼洗涤区。
所述B2)步骤中，当二水过滤机的过滤区下方收集的滤液中的P 2 O 5 浓度超过25wt％时，则将部分滤液引入罐区缓冲槽中，直至二水过滤机的过滤区下方收集的滤液中的P 2 O 5 浓度降至25wt％以下。
所述B2)步骤中，所述滤饼洗涤区由一洗区、二洗区和三洗区组成，其中，后一级洗区下方收集的滤液加压后作为前一级洗区的冲洗水，一洗区下方收集的滤液作为滤布洗水加压后冲洗半水过滤机的滤布洗涤区，三洗区的冲洗液来自工艺水。
所述B2)步骤中，将磷石膏后续处理过程中的收集的池水作为冲洗液分别冲洗二水过滤机的螺旋卸料机以及下方的渣斗、以及冲洗二洗区。
在过滤酸管线和返酸管线之间设置有溢流管，当半水过滤机超负荷运行或过滤酸泵出口管线出现堵塞时，过滤液可由过滤酸管线经溢流管直接进入返酸管线，避免过滤机滤盘积酸。
针对背景技术中存在的问题，发明人进行了如下改进：1)增加了预混区，通过将磷矿先送入预混区中，与返酸混合快速分解，在预混区时应控制液相中的硫酸根离子浓度低于CaO浓度3.6wt％～4.6wt％，保证返酸能将磷矿彻底溶解，同时避免硫酸钙薄膜对于磷矿的包裹，为获得粗大结晶的半水石膏提供有力保证。
2)严格控制溶解区液相中的硫酸根离子浓度低于CaO浓度2.7wt％～3.4wt％，这是考虑半水石膏结晶环境要求在液相硫酸根不足的条件下进行，在此条件下较低的液相硫酸根浓度，不仅有利于避免磷矿表面形成致密的硫酸钙包裹薄膜而阻碍磷矿的分解、控制适当的钙析率而避免晶核形成过快，提高半水结晶的稳定性。而且意外的发现通过准确的硫酸浓度梯度控制，能够显著提高半水石膏晶体大小(D50高达135um)，且显著减少了半水石膏细晶的数量(10um以下晶体小于1％)。
3)改变了过去由结晶槽输出浆料打循环的常用手段，而是将增设的熟化区出引出的浆料分成两股，一股加压循环返回至预混槽，从而提高了半水反应的有效停留时间，提高半水石膏的晶体尺寸、提高反应收率。从而可以获得粗大、稳定的半水石膏结晶，此处特别采用大循环料浆，比值为3～5，这是考虑利用循环料浆的加入稀释了加入物料的浓度，从而避免磷矿出现包裹，且循环料浆中的晶种抑制了磷石膏晶体的二次成核，有利于获得粗大均匀易于过滤的半水石膏结晶。，比值过大会导致循环料浆带入到预混区和溶解区的硫酸浓度过高，使得预混区和溶解区钙析率过度提高，晶核形成过快，容易造成晶核数量过多，影响晶体的稳定生长。过小会容易形成磷矿的包裹和反应槽中溶液的过饱和度过高，从而晶核数量过多以及临界尺寸过小；另一股加压送入闪蒸冷却器冷却后送入半水过滤给料槽，以降低反应热量，避免半水石膏料浆温度过高转化成无水石膏，冷动后的料浆送入半水过滤给料槽，所述半水过滤给料槽下段引入料浆加压后送半水过滤机，上段引出料浆回送结晶区，料浆从熟化槽去闪冷(然后再去过滤)，不仅增加了反应停留时间，且保证了半水石膏结晶在相对稳定的环境下生长，以获得稳定均一粒径的半水石膏晶体。
4)优化二水转化操作指标：液相硫酸根离子浓度5％-10％，磷酸浓度12％-25％P 2 O 5 ,温度55℃-65℃。控制较高的磷酸浓度，避免半水石膏和二水石膏溶解度差值过大，转化太快，从而导致细晶增多的情况。实际运行过程中发现，二水料浆的液相P 2 O 5 浓度在20％-25％之间时，二水结晶比较粗大(D50高达96um)，过滤性能优异，减少过滤后二水石膏的水溶磷含量至0.2％以下，提高P 2 O 5 总回收率。
4)半水过滤机及二水过滤机收集的滤液或冲洗水，根据固含以及P 2 O 5 含量不同分别回用，整个工艺过程没有废水排放；并且考虑到磷石膏后续处理过程中收集的池水中含有1wt％P 2 O 5 ,将这部分池水回引作为冲洗液分别冲洗二水过滤机的螺旋卸料机以及下方的渣斗、以及冲洗二洗区，从而回收利用此部分P 2 O 5 ，进一步提高磷的总回收率。
5)通过多种手段应对操作过程中的异常情况：在过滤酸管线和返酸管线之间设置有溢流管，当半水过滤机超负荷运行或过滤酸泵出口管线出现堵塞时，可通过溢流管直接进入返酸泵入口，避免过滤机滤盘积酸，导致过滤机滤盘漫盘而使二水转化槽P 2 O 5 浓度增加超标，从而导致二水石膏拘溶性磷增加。
6)当二水过滤机的过滤区下方收集的滤液中的P 2 O 5 浓度超过25wt％时，则将部分滤液引入罐区缓冲槽中，直至二水过滤机的过滤区下方收集的滤液中的P 2 O 5 浓度降至25wt％以下，减少二水过滤酸作为半水过滤滤饼洗水用量，避免磷酸浓度累积最终导致二水反应磷收率降低。
 有益效果
本发明将磷酸依次送入预混区、溶解区、结晶区和熟化区完成半水反应的各个阶段，通过对半水反应不同阶段硫酸根离子浓度与CaO浓度之间关系的梯度控制，以实现增大结晶尺寸、保持结晶稳定，获得粒径均一的半水石膏结晶；通控改变料浆的循环路径，不仅增加了反应停留时间，且保证了半水石膏结晶在相对稳定的环境下生长。采用多种手段，可以获得粗大、稳定、高强度的半水石膏结晶，其粒度分布D50可达到135um，且10um以下的半水石膏晶体占比小于1％，这样形成的滤饼具有很大的孔隙率，能达到较大的过滤速率，有效减少了细小晶体对半水过滤滤布的堵塞，半水石膏晶体的过滤强度高达3.8～4.0tP 2 O 5 /m 2 /d，提高了过滤能力，减小了过滤机面积，从而降低了装置投资，有利于整个系统开车率的提高，而洗涤后送入二水转化槽的半水石膏不会带入过多的不溶性磷和水溶性磷。同时控制二水反应的过饱和度，二水石膏结晶粒度分布D50可达到96um，且10um以下的半水石膏晶体占比小于1％，二水过滤性能优异，降低了过滤后二水石膏的水溶磷含量提高最终的磷回收率；过对滤液和冲洗水合理利用，减少废水排放，提高P 2 O 5 总收率。本发明方法简单、易于控制，能够有效获得粗大、均一性好的半水石膏晶体和二水石膏晶体、过滤效果好、收率高、投资和运行成本低、对环境友好、运行稳定性好。
 附图说明
图1为本发明工艺流程图。
其中，1-预混区、2-溶解区、3-结晶区、4-熟化区、5-闪蒸泵、6-循环泵、7-第一闪蒸冷却器、8-半水过滤给料槽、9-半水过滤机、9.1-过滤区、9.2-滤饼洗涤区、9.3-滤布洗涤区、10-转化区、11-第二闪蒸冷却器、12-二水过滤机、12.1-过滤区、12.2-滤饼洗涤区、12.3-滤布洗涤区、13-溢流管、14-过滤酸管线、15-返酸管线。
 本发明的实施方式
实施例1:一、半水反应过滤工序:A1)包括将磷矿先送入预混区1中，与返酸混合、快速分解；控制预混区1液相中的硫酸根离子浓度低于CaO浓度3.6wt％～4.6wt％，温度90℃～100℃；A2)出预混区1的料浆送入溶解区2中，在返酸和硫酸的存在下充分溶解，其中，控制液相中的硫酸根离子浓度低于CaO浓度2.7wt％～3.4wt％；A3)出溶解区2的反应料浆送入结晶区3中，在浓硫酸的存在下结晶长大，其中，控制液相中的硫酸根离子浓度高于CaO浓度1.2wt％～6wt％、温度90℃～100℃，磷酸浓度为36wt％～42wt％P 2 O 5 ，含固量28wt％～37wt％，温度90℃～100℃，磷酸浓度为36wt％-42wt％P 2 O 5 ，含固量28wt％～37wt％；A4)出结晶区3的反应料浆送入熟化区4中，半水石膏结晶进一步长大，其中，控制反应浆料在熟化区4中的停留时间为0.5～1.5h。A5、出所述熟化区4的料浆分为两股，一股经循环泵6加压返回至预混槽1，加压返回至预混槽1的料浆采用大循环料浆，比值为3～5；另一股经闪蒸泵5加压送入闪蒸冷却器6冷却后送入半水过滤给料槽7，所述半水过滤给料槽7上段引出部分料浆回送结晶区3，下段引出部分料浆加压后送半水过滤机9过滤区，半水过滤机9的过滤区9.1下方引出过滤酸(含36-42wt％P 2 O 5 )经过滤酸管线14加压送出，滤饼洗涤区9.2下方引出返酸(含30-34wt％P 2 O 5 )经返酸管线15分别回送预混区，溶解区和结晶区，卸料端排出半水石膏。
二、水反应过滤工序:B1)所述半水石膏先送入转化区10与硫酸反应，控制转化区10中硫酸根离子浓度为5wt％～10wt％，磷酸浓度为12wt％～25wt％P 2 O 5 ，温度为55℃-65℃，含固量30％～35wt％；优选的，所述转化区10包括串联的两个转化槽，第一个转化槽内的料浆加压后送第二闪蒸冷却器11冷却后回送该转化槽。
B2)出转化区10的反应料浆分为两股，一股送入二水过滤机12过滤后得到磷石膏，另一股回送用于冲洗半水过滤机9卸料端的螺旋卸料机及其下方的渣斗。
其中，所述二水过滤机12包括过滤区12.1、滤饼洗涤区12.2和滤布洗涤区12.3；其中，所述二水过滤机12的过滤区12.1下方收集的滤液作为滤饼洗水加压后冲洗半水过滤机9的滤饼洗涤区9.1。
所述滤饼洗涤区12.2由一洗区、二洗区和三洗区组成，其中，后一级洗区下方收集的滤液加压后作为前一级洗区的冲洗水，一洗区下方收集的滤液作为滤布洗水加压后冲洗半水过滤机9的滤布洗涤区9.3，三洗区的冲洗液来自工艺水。
将磷石膏后续处理过程中的收集的池水作为冲洗液分别冲洗二水过滤机12卸料端的螺旋卸料机以及下方的渣斗、以及冲洗二洗区。
当二水过滤机12的过滤区下方收集的滤液中的P 2 O 5 浓度超过25wt％时，则将部分滤液引入罐区缓冲槽中，直至二水过滤机12的过滤区下方收集的滤液中的P 2 O 5 浓度降至25wt％以下。
在用于引出过滤酸的过滤酸管线14和用于引出返酸的返酸管线15之间设置有溢流管13，溢流管13采用大倾角设置，当半水过滤机9超负荷运行或过滤酸泵出口管线出现堵塞时，过滤液可由过滤酸管线14经溢流管13直接进入返酸管线15排出，避免半水过滤机滤盘积酸。
对比例1：与本申请实施例1相比，控制预混区1液相中的硫酸根离子浓度低于CaO浓度为3wt％，溶解区2液相中的硫酸根离子浓度低于CaO浓度1.5wt％外，其余同实施例1。
对比例2:与本申请实施例1相比，不设熟化区4，由结晶区3引出两股料浆分别送至预混区1和闪蒸冷却器6，余同实施例1。
对比结果如下。
Figure 292584dest_path_image001
。

Claims (12)

  1. 一种高收率水合晶相重构湿法磷酸生产工艺，包括半水反应过滤工序和二水反应过滤工序，其特征在于，
    所述半水反应过滤工序包括以下步骤：
    A1)将磷矿先送入预混区中，与返酸混合、快速分解；
    A2)出预混区的料浆送入溶解区中，在返酸和硫酸的存在下充分溶解：
    A3)出溶解区的反应料浆送入结晶区中在硫酸的存在下结晶长大；
    A4)出结晶区的反应料浆送入熟化区中，半水石膏结晶进一步长大；
    A5)出所述熟化区的料浆分为两股，一股加压返回至预混区，另一股加压送入第一闪蒸冷却器冷却后送入半水过滤给料槽，所述半水过滤给料槽上段引出料浆回送结晶区，下段引出料浆加压后送半水过滤机过滤分别得到半水石膏、返酸和过滤酸，所述返酸分别回送预混区、溶解区和结晶区；
    所述二水反应过滤工序包括以下步骤：
    B1)所述半水石膏先送入转化区与硫酸反应；
    B2)出转化区的反应料浆分为两股，一股送入二水过滤机得到二水石膏，另一股回送用于冲洗半水过滤机的螺旋卸料机及其下方的渣斗。
  2. 如权利要求1所述的高收率水合晶相重构湿法磷酸生产工艺，其特征在于，所述A1)步骤中，控制预混区液相中的硫酸根离子浓度低于CaO浓度3.6wt～4.6wt％；所述A2)步骤中，控制所述溶解区液相中的硫酸根离子浓度低于CaO浓度2.7wt％～3.4wt％；所述A3)步骤中，控制所述结晶液相中的硫酸根离子浓度高于CaO浓度1.2wt％～6％wt％。
  3. 如权利要求1所述的高收率水合晶相重构湿法磷酸生产工艺，其特征在于，所述A4)步骤中，控制反应浆料在熟化区中的停留时间为0.5h～1.5h。
  4. 如权利要求1-3任一项所述的高收率水合晶相重构湿法磷酸生产工艺，其特征在于，所述A1)步骤中，控制的所述预混区温度90℃～100℃；所述A2)步骤中，控制溶解区温度90℃～100℃，磷酸浓度为36％～42wt％P 2 O 5 ，含固量28wt％～37wt％；所述A3)步骤中，控制结晶区温度90℃～100℃，磷酸浓度为36％-42wt％P 2 O 5 ，含固量28wt％～37wt％。
  5. 如权利要求1所述的高收率水合晶相重构湿法磷酸生产工艺，其特征在于，所述A1)步骤中，加压返回至预混槽的料浆采用大循环料浆，比值为3～5。
  6. 如权利要求1或2或3或5任一项所述的高收率水合晶相重构湿法磷酸生产工艺，其特征在于，所述B1)步骤中，所述转化区包括串联的两个转化槽，第一个转化槽内的料浆加压后送第二闪蒸冷却器冷却后回送该转化槽。
  7. 如权利要求6所述的高收率水合晶相重构湿法磷酸生产工艺，其特征在于，所述B1)步骤中，控制转化区中硫酸根离子浓度为5wt％～10wt％，磷酸浓度为12wt％～25wt％P 2 O 5 ，温度为55℃-65℃，含固量30％～35wt％。
  8. 如权利要求6所述的高收率水合晶相重构湿法磷酸生产工艺，其特征在于，所述B2)步骤中，所述二水过滤机包括过滤区、滤饼洗涤区和滤布洗涤区；其中，所述二水过滤机的过滤区下方收集的滤液作为滤饼洗水加压后冲洗半水过滤机的滤饼洗涤区。
  9. 如权利要求8所述的高收率水合晶相重构湿法磷酸生产工艺，其特征在于，所述B2)步骤中，当二水过滤机的过滤区下方收集的滤液中的P 2 O 5 浓度超过25wt％时，则将部分滤液引入罐区缓冲槽中，直至二水过滤机的过滤区下方收集的滤液中的P 2 O 5 浓度降至25wt％以下。
  10. 如权利要求6所述的高收率水合晶相重构湿法磷酸生产工艺，其特征在于，所述B2)步骤中，所述滤饼洗涤区由一洗区、二洗区和三洗区组成，其中，后一级洗区下方收集的滤液加压后作为前一级洗区的冲洗水，一洗区下方收集的滤液作为滤布洗水加压后冲洗半水过滤机的滤布洗涤区，三洗区的冲洗液来自工艺水。
  11. 如权利要求10所述的高收率水合晶相重构湿法磷酸生产工艺，其特征在于，所述B2)步骤中，将磷石膏后续处理过程中的收集的池水作为冲洗液分别冲洗二水过滤机的螺旋卸料机以及下方的渣斗、以及冲洗二洗区。
  12. 如权利要求1-4任一项所述的高收率水合晶相重构湿法磷酸生产工艺，其特征在于，在过滤酸管线和返酸管线之间设置有溢流管，当半水过滤机超负荷运行或过滤酸泵出口管线出现堵塞时，过滤液可由过滤酸管线经溢流管直接进入返酸管线，避免过滤机滤盘积酸。
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