阅读说明：本技术 磷酸生产方法及组合物 (Phosphoric acid production process and composition ) 是由 邱雪平 张磊 于 2019-10-02 设计创作，主要内容包括：湿法磷酸生产方法包括在包含硫酸的浆料中浸提含磷酸盐的矿石,从而形成磷酸和硫酸钙晶体；并且将该磷酸与这些硫酸钙晶体分离；其中,向该浆料中添加消泡剂和聚(羧酸)或其盐,该聚(羧酸)或其盐具有小于1,000,000克/摩尔(g/mol)的重均分子量。该聚(羧酸)可以是聚(丙烯酸)或其盐,并且该消泡剂可以是二烷基磺基琥珀酸盐和脂肪族醇或脂肪酸酯。该方法通过以下中的任一种来增强湿法磷酸生产中磷酸与硫酸钙晶体的分离：增加硫酸钙晶体的体积平均粒度、增加过滤速率和减少泡沫形成。(A wet process phosphoric acid production process includes leaching a phosphate-containing ore in a slurry comprising sulfuric acid, thereby forming phosphoric acid and calcium sulfate crystals; and separating the phosphoric acid from the calcium sulfate crystals; wherein a defoamer and a poly (carboxylic acid) or salt thereof having a weight average molecular weight of less than 1,000,000 grams per mole (g/mol) are added to the slurry. The poly (carboxylic acid) may be a poly (acrylic acid) or a salt thereof, and the defoamer may be a dialkyl sulfosuccinate and a fatty alcohol or fatty acid ester. The method enhances the separation of phosphoric acid from calcium sulfate crystals in wet-process phosphoric acid production by any of the following: increase the volume average particle size of the calcium sulfate crystals, increase the filtration rate, and reduce foam formation.)

1. A wet process phosphoric acid production method, comprising:

leaching the phosphate-containing ore in a slurry comprising sulfuric acid, thereby forming phosphoric acid and calcium sulfate crystals; and

separating the phosphoric acid from the calcium sulfate crystals;

wherein a defoamer and a poly (carboxylic acid) or salt thereof having a weight average molecular weight of less than 1,000,000 grams per mole (g/mol) are added to the slurry.

2. The method of claim 1, wherein the defoamer and poly (carboxylic acid) or salt thereof are added separately to the slurry.

3. The method of claim 1, wherein the defoamer and poly (carboxylic acid) or salt thereof are pre-mixed prior to addition to the slurry.

4. The method of any one of claims 1 to 3, wherein the defoamer and poly (carboxylic acid) or salt thereof are each independently premixed with the phosphate-containing ore, the sulfuric acid, recycled phosphoric acid, or both the sulfuric acid and recycled phosphoric acid prior to addition to the slurry.

5. The method of any one of claims 1 to 4, wherein the poly (carboxylic acid) or salt thereof has a weight average molecular weight of 300 to less than 1,000,000 g/mol.

6. The method of any one of claims 1 to 5, wherein the poly (carboxylic acid) or salt thereof is derived from the polymerization of (meth) acrylic acid, maleic acid, (meth) acrylate, maleate, or a combination comprising at least one of the foregoing monomers.

7. The method of any of claims 1-6, wherein the poly (carboxylic acid) or salt thereof is a poly (acrylic acid), salt thereof, or a combination comprising at least one of the foregoing.

8. The method of any of claims 1-6, wherein the poly (carboxylic acid) or salt thereof is a copolymer of acrylic acid and maleic acid, salt thereof, or a combination comprising at least one of the foregoing.

9. The method of any of claims 1-6, wherein the poly (carboxylic acid) or salt thereof is a copolymer of acrylic acid and polyethylene glycol ether methacrylate, a salt thereof, or a combination comprising at least one of the foregoing.

10. The method of any of claims 1-9, wherein the antifoaming agent is a fatty acid, a fatty acid salt, a fatty acid ester, a sulfonic acid, a sulfonate ester, a fatty alcohol, or a combination comprising at least one of the foregoing antifoaming agents.

11. The method of any one of claims 1 to 10, wherein the defoamer comprises a dialkyl sulfosuccinate.

12. The method of claim 11, wherein the dialkyl sulfosuccinate has the chemical structure:

wherein R is¹And R²Each independently of the others, is a straight-chain or branched C_4-18Alkyl radical, C_5-18Cycloalkyl radical, C_7-18Aralkyl, or C_6-18Aryl, which is unsubstituted or substituted by hydroxy or C_1-18Alkoxy substitution; m is lithium, sodium, potassium or ammonium; and m is 1.

13. The method of claim 11 or 12, wherein the defoamer further comprises an aliphatic alcohol.

14. The method of claim 11 or 12, wherein the defoamer further comprises a fatty acid, a fatty acid salt, a fatty acid ester, or a combination comprising at least one of the foregoing defoamers.

15. The method of any one of claims 1 to 14, wherein a sufficient amount of the poly (carboxylic acid) or salt thereof is added to the slurry to increase the volume average particle size of the calcium sulfate crystals compared to the same method without the addition of the poly (carboxylic acid) or salt thereof.

16. The method of any one of claims 1 to 15, wherein a sufficient amount of the poly (carboxylic acid) or salt thereof is added to the slurry to enhance separation of the phosphoric acid from the calcium sulfate crystals as compared to the same method without adding the poly (carboxylic acid) or salt thereof.

17. The method of any one of claims 1 to 16, wherein a sufficient amount of the defoamer and the poly (carboxylic acid) or salt thereof are added to the slurry to reduce foam formation compared to the same method without the defoamer and the poly (carboxylic acid) or salt thereof.

18. The method of any one of claims 15-17, wherein the sufficient amount of poly (carboxylic acid) or salt thereof is 0.01-10 kg/T P₂O₅。

19. The method of claim 17, wherein the sufficient amount of poly (carboxylic acid) or salt thereof is 0.01 to 10kg/T P₂O₅And the sufficient amount of the antifoaming agent is 0.1 to 20kg/T P₂O₅。

20. A wet process phosphoric acid production method, comprising:

leaching the phosphate-containing ore in a slurry comprising sulfuric acid, thereby forming phosphoric acid and calcium sulfate crystals; and

separating the phosphoric acid from the calcium sulfate crystals;

wherein to the slurry is added a defoamer comprising a dialkyl sulfosuccinate and an aliphatic alcohol, and a poly (acrylic acid) or a salt thereof having a weight average molecular weight of 300 to less than 1,000,000 g/mol.

21. A wet process phosphoric acid production method, comprising:

leaching the phosphate-containing ore in a slurry comprising sulfuric acid, thereby forming phosphoric acid and calcium sulfate crystals; and

separating the phosphoric acid from the calcium sulfate crystals;

wherein to the slurry is added a defoamer comprising a dialkyl sulfosuccinate and a fatty acid ester, and a poly (acrylic acid) or salt thereof having a weight average molecular weight of 300 to less than 1,000,000 g/mol.

22. A composition for enhancing the separation of phosphoric acid from calcium sulfate crystals, the composition comprising:

an antifoaming agent comprising a dialkyl sulfosuccinate and an aliphatic alcohol; and

a poly (acrylic acid) or salt thereof, the poly (acrylic acid) or salt thereof having a weight average molecular weight of 300 to less than 1,000,000 g/mol.

23. A composition for enhancing the separation of phosphoric acid from calcium sulfate crystals, the composition comprising:

an antifoaming agent comprising a dialkyl sulfosuccinate and a fatty acid ester; and

a poly (acrylic acid) or salt thereof, the poly (acrylic acid) or salt thereof having a weight average molecular weight of 300 to less than 1,000,000 g/mol.

Background

About 90% of the world's phosphoric acid is produced according to the wet process, which involves acidifying phosphate ore (which contains calcium phosphate) with sulfuric acid to produce crude wet process phosphoric acid (WPA) and insoluble calcium sulfate (gypsum or phosphogypsum). General description of the manufacture of Phosphoric acid and Phosphates by Becker in "phospholites and Phosphoric Acids [ Phosphates and Phosphates]", Marcel Dekker, Inc. [ Massel Dekker Co. ]]1989; and by Stack in "phosphorus Acid, Part 1and Part 2[ Phosphoric Acid, Part 1and Part 2]", Marcel Dekker, Inc. [ Massel Dekker Co. ]]1968. In the wet process, phosphate ore is washed in a washing apparatus, ground in a ball mill and fed to a series of reactors for leaching (digestion) with sulfuric acid along with recycled phosphoric acid from the process. After leaching, the reaction slurry is filtered to separate the phosphoric acid from the undissolved ore, newly formed gypsum and gangue. The filtered crude WPA was then sent to a clarifier and an evaporator for further purification and concentration. The purified phosphoric acid was sent as commercial grade acid (MGA) or further concentrated to make 69% P₂O₅Superphosphoric acid (SPA). SPA can be converted into a number of end products including chemicals, rust inhibitors, food additives, dental and orthopedic etchants, electrolytes, fluxes, dispersants, industrial etchants, fertilizer raw materials, and components of household cleaning products. For example, crude phosphoric acid is concentrated to 54% (based on P) prior to use in monoammonium phosphate (MAP), diammonium phosphate (DAP), or Ammonium Phosphate (APS) production₂O₅)。

Efficient filtration of phosphoric acid from suspended solids after ore leaching, and efficient clarification of phosphoric acid at various stages, is used to maximize productivity. For equipment limited by filtration capacity, increasing filtration efficiency can have a tremendous commercial impact. High molecular weight flocculants are often used to assist the filtration and clarification process. For example, as noted in U.S. Pat. No. 4,291,005 to Poulos et al and U.S. Pat. No. 4,800,071 to Kaesler et al, conventional organic flocculants such as polyacrylamide and acrylamide/sodium acrylate copolymers can be used to reduce the fine particle solids (fines) content to clarify phosphoric acid and improve filtration rates.

Another way to improve the filtration rate is to reduce the amount of fines formed during phosphate ore leaching. Agents that reduce the amount of fines are called crystal growth regulators. The effect of the crystal growth regulator can be evaluated by measuring the volume average particle size and the filtration time. U.S. patent No. 3,192,014 describes the use of alkyl benzene sulfonic acid, isopropyl naphthalene sulfonic acid and their alkali metal salts to form gypsum crystals with improved filterability. U.S. patent No. 4,140,748 also discloses the use of organic sulfonic acids or derivatives (such as sodium dodecyl sulfate) as crystal growth regulators to improve the growth of calcium sulfate hemihydrate crystals to improve the filtration rate of the phosphoric acid slurry. U.S. patent No. 3,796,790 discloses the use of linear alkylbenzene sulfonic acids, branched alkylbenzene sulfonic acids, linear alkylbenzene sulfonates, branched alkylbenzene sulfonates, linear alkyl sulfates, branched alkyl sulfates, and petroleum sulfonates to assist in the separation of phosphoric acid from gypsum.

U.S. patent No. 5,009,873 describes a method of increasing the filtration rate of a phosphoric acid product slurry using an acrylamide/2-acrylamidomethylpropane sulfonic acid copolymer having a weight average molecular weight of from about 1,000,000 to about 10,000,000 grams per mole (g/mol). The disclosed polymer consists of a major portion of acrylamide units (60-90 mole percent (mol%)) and a minor portion of 2-acrylamidomethylpropane sulfonic acid units (10-40 mol%). It further teaches that "polymers having a weight average molecular weight significantly less than 1,000,000 in the process of the present invention will not be effective crystal modifiers". In "Enhanced Filtration of Phosphogypsum" Florida Institute of Phosphate Research,1995, Publication No. 01-119-.

Several publications "Effect of Surfactants on phosphorus Crystallization and Filtration" by El-Shall et alDuring Wet-Process phosphorus Acid Production "Separation Science and Technology [" influence of surfactant on crystallization and filtration of phosphogypsum During Wet process Phosphoric Acid Production ", Separation Science and Technology]35(2000)395-410, "introducing the Filtration Rate of Phosphogypsum Using surface", Hydrometallurgy [ "use Surfactant to increase Filtration Rate of Phosphogypsum", Hydrometallurgy]85(2007)53-58, and "Effect of phosphoric additive on crystallization of phosphoric and sulfuric acid medium", Crystal Research and Technology [ "Effect of phosphonate additive on crystallization of Gypsum in phosphoric and sulfuric acid medium", Crystal Research and Technology]37(2002)1264-]270(2004)99-105, discussing compounds containing C_6-22The effect of a nonionic surfactant of a mixture of sorbitan ester, aminotri (methylenephosphonic acid) and cetyltrimethylammonium bromide (CMR-100) on modified gypsum crystal growth and improved phosphoric acid filtration.

Foam control is also desirable in WPA production, particularly for the leaching step. Excessive foam (e.g., from carbon dioxide release) generated during the leaching step may occupy large leaching vessel volumes and reduce throughput and productivity. Too much foam can also lead to foam spillage, creating hazardous conditions and safety issues. As used herein, an antifoaming agent is defined as any additive that reduces or prevents the formation of foam, and includes an antifoaming agent (antifoamer). Defoamers may be oil-based, water-based, or powder-based, and include, for example, polysiloxanes (silicones), mineral oils, vegetable oils, surfactants, or other polymers. Fatty acids, fatty acid esters, fatty alcohols and sulfosuccinate surfactants are commercially available and are used to control foam in WPA production. U.S. Pat. No. 4,065,403 discloses a defoamer with a high amount of sulfonated tall oil and a low amount of nonionic additive for use inControlling foam in highly acidic media. U.S. patent No. 4,415,472 discloses the use of a mixture of an alkali metal salt of a dialkyl succinate and a higher linear or branched aliphatic alcohol as an antifoaming agent for mineral acid leaching media. U.S. Pat. No. 6,544,489 discloses a catalyst based on C_12-20Fatty acids and ethoxylated C_1-4Defoamer formulations for highly acidic media of ester condensates of alcohols. U.S. patent application publication No. 2006/0041027 discloses a composition capable of preventing foam formation based on a mixture of a saturated or unsaturated fatty acid or derivative and a rosin acid compound. International publication No. WO2017/006170 discloses the use of reverse microemulsions of anionic surfactants based on alkali metal salts of dialkyl sulfosuccinates, fatty acids, fatty acid esters and oxidizing solvents in WPA production media for foam control.

While the various agents discussed above may have some advantages and applicability in WPA production, the filtration section of the process is still often a bottleneck when the filter cloth forms fluorosilicate type scale that needs cleaning and/or when the particle size and morphology of the gypsum does not allow for efficient filtration. Some devices must physically clean the scale or replace the filter cloth in less than a week. The adverse economic impact of these problems associated with filtration is substantial, and the industry needs more efficient filtration assistance techniques. Accordingly, it would be desirable to improve the compositions and methods that are currently available for filtering phosphoric acid during production. Many factors (e.g., ore type, temperature, agitation, reactor design, acid chemistry, extraneous ions, organic matter, and viscosity of the phosphoric acid medium) can affect the performance of the crystal growth regulator. Thus, there is an unmet need for efficient crystal growth regulators and methods for controlling crystal growth and/or increasing filtration rates under a variety of end-use conditions. Highly effective crystal growth regulators and methods for controlling crystal growth and/or increasing filtration rates would be a useful advance in the art and would quickly gain acceptance in the industry.

Disclosure of Invention

A wet process phosphoric acid production process includes leaching a phosphate-containing ore in a slurry comprising sulfuric acid, thereby forming phosphoric acid and calcium sulfate crystals; and separating the phosphoric acid from the calcium sulfate crystals; wherein a defoamer and a poly (carboxylic acid) or salt thereof having a weight average molecular weight of less than 1,000,000 grams per mole (g/mol) are added to the slurry.

A wet process phosphoric acid production process includes leaching a phosphate-containing ore in a slurry comprising sulfuric acid, thereby forming phosphoric acid and calcium sulfate crystals; and separating the phosphoric acid from the calcium sulfate crystals; wherein to the slurry is added a defoamer comprising a dialkyl sulfosuccinate and an aliphatic alcohol, and a poly (acrylic acid) or salt thereof having a weight average molecular weight of 300 to less than 1,000,000 grams per mole (g/mol).

A wet process phosphoric acid production process includes leaching a phosphate-containing ore in a slurry comprising sulfuric acid, thereby forming phosphoric acid and calcium sulfate crystals; and separating the phosphoric acid from the calcium sulfate crystals; wherein to the slurry is added a defoamer comprising a dialkyl sulfosuccinate and a fatty acid ester, and a poly (acrylic acid) or salt thereof having a weight average molecular weight of 300 to less than 1,000,000 g/mol.

A composition for enhancing the separation of phosphoric acid from calcium sulfate crystals comprising: an antifoaming agent comprising a dialkyl sulfosuccinate and an aliphatic alcohol; and poly (acrylic acid) or a salt thereof having a weight average molecular weight of 300 to less than 1,000,000 g/mol.

A composition for enhancing the separation of phosphoric acid from calcium sulfate crystals comprising: an antifoaming agent comprising a dialkyl sulfosuccinate and a fatty acid ester; and poly (acrylic acid) or a salt thereof having a weight average molecular weight of 300 to less than 1,000,000 g/mol.

This brief description may not list all the necessary features or elements. Accordingly, sub-combinations of these features or elements may also constitute the invention. These and other objects, features and advantages of the present invention will become apparent from the following detailed description of the various aspects of the invention, taken in conjunction with the accompanying examples and drawings.

Drawings

Referring now to the drawings:

figure 1 depicts the cumulative particle size distribution plot of the filter cake from phosphate ore leaching in examples 1-4 obtained using FlowCam. ESD on the x-axis is the "equivalent spherical diameter". These figures show that particle size increases when P (AA-co-MA) (Mw 3000g/mol) is added during leaching without the addition of a defoamer. The increase in particle size depends on the amount used, and an optimum amount of 0.6kg/T P was observed₂O₅(example 3).

Figure 2 depicts the cumulative particle size distribution plot of the filter cakes from phosphate ore leaching in examples 5-8 obtained using FlowCam. ESD on the x-axis is the "equivalent spherical diameter".

Figure 3 depicts the cumulative particle size distribution plot of the filter cakes from phosphate ore leaching in examples 12-15 obtained using FlowCam. ESD on the x-axis is the "equivalent spherical diameter". These figures show the comparison with IONQUEST during phosphate ore leaching^TMEffect of molecular weight of PAA polymer combined with D3001 defoamer. While the low molecular weight polymer promoted crystal growth (examples 13-14 versus example 12), the high molecular weight polymer inhibited crystal growth (example 15 versus example 12).

Figure 4 depicts the particle size distribution plots of the filter cakes from phosphate ore leaching in examples 5, 6, and 8 obtained using FlowCam. ESD on the x-axis is the "equivalent spherical diameter". These figures show that the addition of IONQUEST alone and without additive (example 5)^TMD3001 (example 6) in comparison, P (AA-co-MA) (Mw 3000g/mol) and IONQUEST were added during phosphate ore leaching^TMD3001 (FIG. 8) the particle size distribution shifted upwards.

Figure 5 depicts a visible micrograph collected with FlowCam on the filter cake crystals after phosphate ore leaching. These images show that addition of IONQUEST alone^TMD3001 (example 6) in comparison with IONQUEST^TMP (AA-co-MA) (Mw 3000g/mol) of D3001 combination (example 8) promoted the formation of crystal clusters/aggregates.

FIG. 6 is a photograph depicting the foam level of the slurry after phosphate ore leaching in examples 5-7, with example 6 having 8kg/T P added₂O₅ IONQUEST^TMD3001, and example 7 with 7.2kg/T P₂O₅ IONQUEST^TMD3001 and 0.8kg/T P₂O₅P (AA-Na). Although IONQUEST in example 6 relative to example 5^TMD3001 reduced the amount of foam, but the co-addition of P (AA-Na) (Mw 1200) during the leaching step while maintaining the same total amount of additives (example 7) further reduced the amount of foam.

Detailed Description

The inventors of the present invention have developed an improved wet process phosphoric acid production process that enhances the separation of phosphoric acid from calcium sulfate crystals. The method includes leaching a phosphate-containing ore in a slurry comprising sulfuric acid, thereby forming phosphoric acid and calcium sulfate crystals; and separating the phosphoric acid from the calcium sulfate crystals; wherein a defoamer and a poly (carboxylic acid) or salt thereof having a weight average molecular weight of less than 1,000,000 grams per mole (g/mol) are added to the slurry. Advantageously, it was found that the addition of a defoamer and a poly (carboxylic acid) or salt thereof (having a weight average molecular weight of less than 1,000,000 g/mol) to a wet-process phosphoric acid slurry increases the volume average particle size of the calcium sulfate crystals by improving the filtration rate, enhances the separation of phosphoric acid from the calcium sulfate crystals, and at the same time reduces foam formation.

The antifoaming agent and the poly (carboxylic acid) or salt thereof may be added to the wet-process phosphoric acid slurry in various ways. For example, the defoamer and the poly (carboxylic acid) or salt thereof can be added separately to the slurry. The defoamer and the poly (carboxylic acid) or salt thereof may also be pre-mixed prior to addition to the slurry. Further, in any or all embodiments, the defoamer and poly (carboxylic acid) or salt thereof can each be premixed independently or in combination with sulfuric acid, recycled phosphoric acid, or both sulfuric acid and recycled phosphoric acid prior to addition to the slurry. It is desirable to add the defoamer and the poly (carboxylic acid) or salt thereof during the leaching step.

Despite the contrary teachings in the art, the inventors of the present invention have surprisingly found that low molecular weight poly (carboxylic acids) or salts thereof (i.e., those having a weight average molecular weight of less than 1,000,000 g/mol) are effective in increasing the volume average particle size of calcium sulfate crystals in WPA production. For example, the poly (carboxylic acid) or salt thereof can have a weight average molecular weight of 300 to less than 1,000,000 g/mol. Within this range the weight average molecular weight can be greater than or equal to 500, 700, or 1,000g/mol and less than or equal to 900,000, 700,000, 500,000, 100,000, 50,000, or 20,000 g/mol. In any or all embodiments according to the present disclosure, the weight average molecular weight may be 1,000 to 100,000 g/mol. The weight average molecular weight as reported herein can be measured, for example, by gel permeation chromatography or other suitable methods conventionally known to those skilled in the art.

The poly (carboxylic acid) or salt thereof may be an addition polymer of carboxylic acid functional ethylenically unsaturated monomers. The carboxylic acid functional ethylenically unsaturated monomer can be, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid monoester, fumaric acid monoester, maleic acid monoester, or a combination comprising at least one of the foregoing carboxylic acid functional ethylenically unsaturated monomers. The poly (carboxylic acid) may also be an addition polymer of a carboxylic anhydride functional ethylenically unsaturated monomer, wherein the carboxylic anhydride functionality may be converted to a carboxylic acid functionality, such as maleic anhydride or itaconic anhydride. The carboxylic acid functional ethylenically unsaturated monomer may be (meth) acrylic acid, i.e., acrylic acid, methacrylic acid, or a combination thereof. The poly (carboxylic acid) can be in the form of an acid, a mixed acid and salt, or a salt. Any organic or inorganic cation may be used as the salt, but inorganic counterions are preferred, such as alkali or alkaline earth metals. Thus, in any or all embodiments, the poly (carboxylic acid) or salt thereof is derived from the polymerization of (meth) acrylic acid, maleic acid, (meth) acrylate, maleate, or a combination comprising at least one of the foregoing monomers. The poly (carboxylic acid) or salt thereof can be, for example, poly (acrylic acid) sodium salt, poly (acrylic acid-co-maleic acid) sodium salt, or a combination comprising at least one of the foregoing poly (carboxylic acids). In any or all embodiments, the poly (carboxylic acid) or salt thereof is a poly (acrylic acid), a salt thereof (e.g., a sodium salt thereof), or a combination comprising at least one of the foregoing. The poly (carboxylic acid) or salt thereof can also be a copolymer of acrylic acid and maleic acid, a salt thereof (e.g., a sodium salt thereof), or a combination comprising at least one of the foregoing. The poly (carboxylic acid) or salt thereof can also be a copolymer of acrylic acid and polyethylene glycol ether methacrylate, a salt thereof, or a combination comprising at least one of the foregoing.

The poly (carboxylic acid) or salt thereof may be a copolymer of a carboxylic acid functional ethylenically unsaturated monomer and other ethylenically unsaturated monomers. The other ethylenically unsaturated monomer may be an ionic monomer, such as a sulfonic acid functional monomer, a phosphoric acid functional monomer, a phosphonic acid functional monomer, or a salt thereof. Examples of sulfonic acid functional monomers include 2-sulfoethyl (meth) acrylate, 3-sulfopropyl (meth) acrylate, styrenesulfonic acid, vinylsulfonic acid, and 2- (meth) acrylamido-2-methylpropanesulfonic acid. Examples of the phosphoric acid functional monomer include 2-phosphoethyl (meth) acrylate, 2-phosphopropyl (meth) acrylate, 3-phosphopropyl (meth) acrylate, phosphobutyl (meth) acrylate, and 3-phospho-2-hydroxypropyl (meth) acrylate. The phosphate functional monomer may also be a phosphate ester of an alkoxylated hydroxyalkyl (meth) acrylate, such as an ethoxylate or propoxylate of hydroxyethyl or hydroxypropyl (meth) acrylate having from 1 to 50 ethoxy or propoxy repeating units. The ionic monomer may also be 2- (N, N-dimethylamino) ethyl (meth) acrylate.

The other ethylenically unsaturated monomer may be a nonionic monomer. The nonionic monomer may be a hydrophilic nonionic ethylenically unsaturated monomer, such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, polyethylene glycol (meth) acrylate, or (meth) acrylamide. The nonionic monomer may also be a hydrophobic nonionic monomer, for example, alkyl esters of (meth) acrylic acid, such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, and lauryl (meth) acrylate. The nonionic monomer can also be styrene, or substituted styrenes such as alpha-methylstyrene), alpha-olefins such as ethylene, propylene, 1-decene and diisobutylene, or butadiene. The nonionic monomer may also be a vinyl monomer, such as acrylonitrile, vinyl chloride, vinyl acetate, vinyl butyrate or vinyl esters of branched tertiary alkyl alcohols, which are available under the trade name VeoVa^TMSold, for example, VeoVa available from Momentive Specialty Chemicals, Inc^TM9 monomer, VeoVa^TM10 monomer, VeoVa^TM11 monomer. In any or all embodiments according to the present disclosure, the poly (carboxylic acid) or salt thereof may be derived from the copolymerization of (meth) acrylic acid with at least one other nonionic (meth) acrylic acid or vinyl monomer. For example, the poly (carboxylic acid) or salt thereof can be a copolymer of acrylic acid and polyethylene glycol ether methacrylate, a salt thereof, or a combination comprising at least one of the foregoing. For example, the polycarboxylic acid or salt thereof may be a copolymer of acrylic acid and polyethylene glycol methyl ether methacrylate (MH50) with 50 ethylene glycol (EO) (P (AA-co-MH 50)). The molar ratio of AA to MH50 may be, for example, 80: 20.

Advantageously, an antifoaming agent is combined with the poly (carboxylic acid) or salt thereof to control foaming in the wet phosphoric acid process. Controlling the foam may be achieved by reducing the amount of foam formed or by preventing foam formation in the first place. Although the low molecular weight poly (carboxylic acid) or salt thereof disclosed herein has no defoamer activity, it has been unexpectedly found that the combination of a defoamer and a low molecular weight poly (carboxylic acid) or salt thereof exhibits a synergistic effect on foam control.

The antifoaming agent is a fatty acid, a fatty acid salt, a fatty acid ester, a sulfonic acid, a sulfonate salt, an ester of a sulfonic acid or sulfonate salt, a fatty alcohol, or a combination comprising at least one of the foregoing antifoaming agents. As mentioned above, the defoamer can be in the form of an acid, ester, salt or mixed acid, ester or salt. Any organic or inorganic cation may be used as the salt, for example, an alkali metal, alkaline earth metal, ammonium ion, quaternary ammonium ion, or phosphonium ion. In any or all embodiments according to the present disclosure, the defoamer comprises a dialkyl ester of sulfosuccinate, i.e., a dialkyl sulfosuccinate. The dialkyl sulfosuccinate may have the following chemical structure:

wherein R is¹And R²Each independently of the others, is a straight-chain or branched C_4-18Alkyl (especially C)_4-12Alkyl, more particularly C_4-8Alkyl group), C_5-18Cycloalkyl radical, C_7-18Aralkyl, or C_6-18Aryl, which is unsubstituted or substituted by hydroxy or C_1-18Alkoxy, more particularly C_1-4Alkoxy substitution. In any or all embodiments according to the present disclosure, M is an alkali metal, an alkaline earth metal, an ammonium ion, a quaternary ammonium ion, or a combination comprising at least one of the foregoing cations. When M is an alkaline earth metal, M is 0.5, and when M is an alkali metal or ammonium ion, M is 1. M may be, for example, lithium, sodium, potassium, calcium or ammonium, especially lithium, sodium, potassium or ammonium, and more especially sodium. In any or all of the embodiments according to the invention, R¹And R²Each independently of the others, is a straight-chain or branched C_4-12Alkyl, especially C_4-8An alkyl group. For example, R¹And R²May each independently be pentyl, hexyl, octyl, nonyl, dodecyl or stearyl. Since these alkyl groups may be branched, the octyl group may be 2-ethylhexyl. Thus, in any or all embodiments according to this invention, R¹And R²Are all 2-ethylhexyl groups, M is sodium, and M is 1. This particular dialkyl sulfosuccinate is known as "dioctyl sodium sulfosuccinate".

As mentioned above, combinations of defoaming agents may also be effective. Thus, in any or all embodiments according to the present disclosure, the defoamer comprising a dialkyl sulfonate may further comprise an aliphatic alcohol, such as 2-ethylhexanol. In any or all embodiments according to the present disclosure, the defoamer comprising a dialkyl sulfonate may further comprise a fatty acid, a fatty acid salt, a fatty acid ester, or a combination thereof, such as oleic acid, an oleate salt, an oleate ester, or a combination thereof.

Advantageously, the low molecular weight poly (carboxylic acid) or salt thereof provides increased volume average particle size of calcium sulfate crystals in the production of WPA. Thus, a wet-process phosphoric acid production process includes leaching a phosphate-containing ore in a slurry comprising sulfuric acid, and adding a sufficient amount of a poly (carboxylic acid) or salt thereof to the slurry to increase the volume average particle size of the calcium sulfate crystals as compared to the same process without the addition of the poly (carboxylic acid) or salt thereof.

Advantageously, the increased volume average particle size of the calcium sulphate crystals obtained in the process results in an enhanced separation of phosphoric acid from the calcium sulphate crystals, for example by increasing the filtration rate of the phosphoric acid. Thus, a wet-process phosphoric acid production process includes leaching a phosphate-containing ore in a slurry comprising sulfuric acid, and adding a sufficient amount of a poly (carboxylic acid) or salt thereof to the slurry to enhance separation of phosphoric acid from calcium sulfate crystals as compared to the same process without the addition of the poly (carboxylic acid) or salt thereof.

Advantageously, the combination of the defoamer and the low molecular weight poly (carboxylic acid) or salt thereof also provides reduced foam formation. Thus, the wet process phosphoric acid production process comprises leaching a phosphate-containing ore in a slurry comprising sulfuric acid, and adding a sufficient amount of an antifoaming agent and a poly (carboxylic acid) or salt thereof to reduce the formation of foam compared to the same process without the addition of an antifoaming agent and a poly (carboxylic acid) or salt thereof.

Many factors, including ore type, temperature, agitation, reactor design, acid chemistry, extraneous ions, organic matter, and viscosity of the phosphoric acid medium, may affect the properties of the poly (carboxylic acid) or salt thereof. Thus, the appropriate amount of poly (carboxylic acid) or salt thereof may depend on any of these variables, but can only be determined by conventional methods known to those skilled in the art. P in kg/ton phosphate ore of additive used herein₂O₅Expressed in units and abbreviated as "kg/T P₂O₅". The sufficient amount of poly (carboxylic acid) or salt thereof to increase the volume average particle size of the calcium sulfate crystals and thereby enhance the separation of phosphoric acid from the calcium sulfate crystals may be in the range of 0.01 to 10kg/T P₂O₅Within the range of (1). Within this range a sufficient amount of the poly (carboxylic acid) or salt thereof may be greater than or equal to 0.02, 0.05, or 0.1kg/T P₂O₅And is less than or equal to 5,4, 3, 2 or 1kg/T P₂O₅。

These same factors, including ore type, temperature, agitation, reactor design, acid chemistry, extraneous ions, organic matter, and viscosity of the phosphoric acid medium, may also affect the ability of the combination of the defoamer and the poly (carboxylic acid) or salt thereof to reduce foam formation. However, foot for reducing foam formationThe amount of the antifoaming agent may be 0.1 to 20kg/T P₂O₅Within the range of (1). Within this range the sufficient amount of defoamer can be greater than or equal to 0.2, 0.3, 0.4, or 0.5kg/T P₂O₅And less than or equal to 15, 10, 9,8, 7 or 6kg/T P₂O₅. Further, the sufficient amount of poly (carboxylic acid) or salt thereof in combination with the defoamer to reduce foam formation may be the same amount disclosed in the preceding paragraph sufficient to increase the volume average particle size and enhance separation of phosphoric acid from the calcium sulfate crystals.

Although not intended to limit the scope of the wet process phosphoric acid production process, more specific methods are disclosed herein. For example, a wet phosphoric acid production process may include leaching a phosphate-containing ore in a slurry comprising sulfuric acid, thereby forming phosphoric acid and calcium sulfate crystals; and separating the phosphoric acid from the calcium sulfate crystals; wherein to the slurry is added a defoamer comprising a dialkyl sulfosuccinate and an aliphatic alcohol, and a poly (acrylic acid) or a salt thereof, the poly (acrylic acid) having a weight average molecular weight of 300 to less than 1,000,000 g/mol. In another example of the method, an antifoaming agent comprising a dialkyl sulfosuccinate and a fatty acid ester and a poly (acrylic acid) or salt thereof having a weight average molecular weight of 300 to less than 1,000,000g/mol are added to the slurry.

As noted above, the defoamer and poly (carboxylic acid) can be pre-mixed prior to addition to the slurry. Thus, in any or all embodiments, the composition comprises an antifoaming agent and a poly (carboxylic acid) or salt thereof having a weight average molecular weight of less than 1,000,000 g/mol. For example, a composition for enhancing the separation of phosphoric acid from calcium sulfate crystals comprises an antifoaming agent comprising a dialkyl sulfosuccinate and an aliphatic alcohol; and poly (acrylic acid) or a salt thereof having a weight average molecular weight of 300 to less than 1,000,000 g/mol. The composition for enhancing the separation of phosphoric acid from calcium sulfate crystals may further comprise an antifoaming agent comprising a dialkyl sulfosuccinate and a fatty acid ester; and poly (acrylic acid) or a salt thereof having a weight average molecular weight of 300 to less than 1,000,000 g/mol.

The disclosure is further illustrated by the following aspects, which are not intended to limit the claims.

Aspect 1. a wet process phosphoric acid production method, comprising: leaching the phosphate-containing ore in a slurry comprising sulfuric acid, thereby forming phosphoric acid and calcium sulfate crystals; and separating the phosphoric acid from the calcium sulfate crystals; wherein a defoaming agent and a poly (carboxylic acid) or a salt thereof having a weight average molecular weight of less than 1,000,000g/mol are added to the slurry.

Aspect 2. the method of aspect 1, wherein the defoamer and poly (carboxylic acid) or salt thereof are added separately to the slurry.

Aspect 3. the method of aspect 1, wherein the defoamer and poly (carboxylic acid) or salt thereof are pre-mixed prior to addition to the slurry.

Aspect 4. the method of aspect 3, wherein the defoamer and poly (carboxylic acid) or salt thereof are each independently premixed with the sulfuric acid, recycled phosphoric acid, or both the sulfuric acid and recycled phosphoric acid prior to addition to the slurry.

Aspect 5 the method of any one of aspects 1 to 4, wherein the poly (carboxylic acid) or salt thereof has a weight average molecular weight of 300 to less than 1,000,000 g/mol.

Aspect 6 the method of any of aspects 1-5, wherein the poly (carboxylic acid) or salt thereof is derived from the polymerization of (meth) acrylic acid, maleic acid, (meth) acrylate, maleate, or a combination comprising at least one of the foregoing monomers.

Aspect 7. the method of any of aspects 1-6, wherein the poly (carboxylic acid) or salt thereof is a poly (acrylic acid), a salt thereof, or a combination comprising at least one of the foregoing.

Aspect 8. the method of any of aspects 1-6, wherein the poly (carboxylic acid) or salt thereof is a copolymer of acrylic acid and maleic acid, salt thereof, or a combination comprising at least one of the foregoing.

Aspect 9. the method of any of aspects 1-6, wherein the poly (carboxylic acid) or salt thereof is a copolymer of acrylic acid and polyethylene glycol ether methacrylate, a salt thereof, or a combination comprising at least one of the foregoing.

Aspect 10 the method of any of aspects 1-9, wherein the defoamer comprises a fatty acid, a fatty acid salt, a fatty acid ester, a sulfonic acid, a sulfonate salt, a sulfonate ester, a fatty alcohol, or a combination comprising at least one of the foregoing defoamers.

Aspect 11 the method of any of aspects 1-10, wherein the defoamer comprises a dialkyl sulfosuccinate.

Aspect 12 the method of aspect 11, wherein the dialkyl sulfosuccinate has the following chemical structure:

wherein R is¹And R²Each independently of the others, is a straight-chain or branched C_4-18Alkyl radical, C_5-18Cycloalkyl radical, C_7-18Aralkyl, or C_6-18Aryl, which is unsubstituted or substituted by hydroxy or C_1-18Alkoxy substitution; m is lithium, sodium, potassium or ammonium; and m is 1.

Aspect 13 the method of aspect 12, wherein R¹And R²Are both 2-ethylhexyl groups, and M is sodium.

Aspect 14 the method of any of aspects 11 to 13, wherein the defoamer further comprises an aliphatic alcohol.

Aspect 15 the method of aspect 14, wherein the aliphatic alcohol comprises 2-ethylhexanol.

Aspect 16 the method of any of aspects 11-13, wherein the defoamer further comprises a fatty acid, a fatty acid salt, a fatty acid ester, or a combination comprising at least one of the foregoing defoamers.

Aspect 17. the method of any of aspects 11-13, wherein the defoamer further comprises tall oil fatty acid, tall oil fatty acid salt, oleic acid, oleate salt, or a combination comprising at least one of the foregoing defoamers.

The method of aspect 18. the method of any of aspects 1 to 17, wherein each salt is independently a lithium salt, a sodium salt, a potassium salt, an ammonium salt, or a combination comprising at least one of the foregoing salts.

Aspect 19. the method of any one of aspects 1 to 18, wherein a sufficient amount of the poly (carboxylic acid) or salt thereof is added to the slurry to increase the volume average particle size of the calcium sulfate crystals compared to the same method without the addition of the poly (carboxylic acid) or salt thereof.

Aspect 20 the method of any one of aspects 1-19, wherein a sufficient amount of the poly (carboxylic acid) or salt thereof is added to the slurry to enhance separation of the phosphoric acid from the calcium sulfate crystals as compared to the same method without the addition of the poly (carboxylic acid) or salt thereof.

Aspect 21. the method of any of aspects 1-20, wherein the defoamer and the poly (carboxylic acid) or salt thereof are added to the slurry in sufficient amounts to reduce foam formation as compared to the same method without the defoamer and the poly (carboxylic acid) or salt thereof.

Aspect 22. the method of any of aspects 19 to 21, wherein the sufficient amount of poly (carboxylic acid) or salt thereof is 0.01 to 10kg/T P₂O₅。

Aspect 23. the method of aspect 21, wherein the sufficient amount of poly (carboxylic acid) or salt thereof is 0.01 to 10kg/T P₂O₅And the sufficient amount of the antifoaming agent is 0.1 to 20kg/T P₂O₅。

Aspect 24. a wet process phosphoric acid production method, comprising: leaching the phosphate-containing ore in a slurry comprising sulfuric acid, thereby forming phosphoric acid and calcium sulfate crystals; and separating the phosphoric acid from the calcium sulfate crystals; wherein to the slurry is added a defoamer comprising a dialkyl sulfosuccinate and an aliphatic alcohol, and a poly (acrylic acid) or a salt thereof having a weight average molecular weight of 300 to less than 1,000,000 g/mol.

Aspect 25. a wet process phosphoric acid production method, the method comprising: leaching the phosphate-containing ore in a slurry comprising sulfuric acid, thereby forming phosphoric acid and calcium sulfate crystals; and separating the phosphoric acid from the calcium sulfate crystals; wherein to the slurry is added a defoamer comprising a dialkyl sulfosuccinate and a fatty acid ester, and a poly (acrylic acid) or salt thereof having a weight average molecular weight of 300 to less than 1,000,000 g/mol.

Aspect 26. a composition for enhancing the separation of phosphoric acid from calcium sulfate crystals, the composition comprising: a defoamer and a poly (carboxylic acid) or salt thereof having a weight average molecular weight of less than 1,000,000 g/mol.

A composition for enhancing the separation of phosphoric acid from calcium sulfate crystals, the composition comprising: an antifoaming agent comprising a dialkyl sulfosuccinate and an aliphatic alcohol; and poly (acrylic acid) or a salt thereof having a weight average molecular weight of 300 to less than 1,000,000 g/mol.

A composition for enhancing the separation of phosphoric acid from calcium sulfate crystals, the composition comprising: an antifoaming agent comprising a dialkyl sulfosuccinate and a fatty acid ester; and poly (acrylic acid) or a salt thereof having a weight average molecular weight of 300 to less than 1,000,000 g/mol.

Examples of the invention

The following examples are provided to assist those skilled in the art in further understanding certain embodiments of the present invention. These examples are intended for illustrative purposes and should not be construed as limiting the scope of the invention.

The performance of low molecular weight poly (carboxylic acid) homo-or copolymers and their salts (alone or in combination with conventional defoamers) to increase the average particle size of the gypsum crystals, control foam, and increase the filtration rate of the phosphoric acid slurry was measured by laboratory scale leaching and vacuum filtration tests. The general procedure is outlined below. One skilled in the art will appreciate that different volumes, ratios, and addition rates may be used to produce different phosphoric acid slurries.

General procedure for laboratory-Scale phosphate Ore Leaching

Phosphate ore in powder form was leached using a 500-mL jacketed reactor connected to a hot bath for maintaining the temperature at around 80 ℃. The reactor was also connected to a cooled condenser to avoid water evaporation during leaching. Phosphoric acid and sulfuric acid were added to the reactor continuously by two peristaltic pumps (MasterFlex L/S). The phosphate ore powder was manually added substantially continuously at a corresponding rate. In one embodiment, the feed rate of sulfuric acid (52.4%) is 3.67 g/min; the feed rate of phosphoric acid (37.1%) was 7.67 g/min; and the feed rate of the phosphate ore was 2 g/min. The total feed time was around 30 minutes. After feeding the acid and ore, leaching is continued for an additional 2 to 3 hours to completely leach the ore. When using the reagents of interest (e.g., poly (carboxylic acid) or salts thereof and antifoam), the appropriate amount of reagent is first mixed with the aforementioned phosphoric acid feed and then continuously pumped into the reactor. Alternatively, the reagent has been added directly to the slurry, or first mixed with sulfuric acid or phosphate ore powder. Throughout the process, the leach slurry was stirred with an overhead stirrer (Glas-Col fine speed stirrer) equipped with a propeller impeller operating at 300 rpm.

Filtration test of phosphoric acid slurry

The leached 210g phosphoric acid slurry was transferred to a filter funnel with a 45- μm polypropylene mesh filter (Millipore PP4504700) and vacuum filtration was started immediately. The filtration time reported herein is the time when the filter cake surface is free of phosphoric acid.

Method for analyzing filter cake granularity

The volume average particle size and volume average particle size distribution of the filter cake were determined using a dynamic imaging particle analyzer FlowCam. In this analysis, 1 to 2mg of the dry cake particles were first dispersed in 6mL of propylene glycol. The appropriate amount of the particle dispersion was then transferred to a pipette tip reservoir connected to a flow cell (FC300) supported on a cell holder. The dynamic imaging method is started thereafter, and images of thousands of particles are taken. Finally, the images were analyzed using FlowCam software to generate results such as volume average particle size, volume average particle size distribution, aspect ratio, and aspect ratio distribution.

Examples 1 to 25. Leaching of phosphate ores with or without crystal growth regulators

Poly (acrylic acid) Polymers (PAA), poly (acrylic acid-co-maleic acid) (P (AA-co-MA)), and salts thereof, such as sodium polyacrylate (P (AA-Na)) are available from copolymers of Sigma Aldrich, st louis, mo, or Polyscience, w.n. pa Acrylic Acid (AA) and polyethylene glycol methyl ether methacrylate (having 50EO, MH50) where the molar ratio of AA to MH50 is 80:20 and P (AA-co-MH 50) is obtained from Solvay group (Solvay s.a.). the weight average molecular weights herein are those reported by the suppliers above.

Defoaming agent CYBREAK^TM675HFP (mixture of sulfosuccinate surfactant and fatty alcohol) and IONQUEST^TMD3001 (dialkyl sulfosuccinates and alkali metal salts of fatty acid esters) was obtained from the solvay group. Antifoam #3 was a mixture of dioctyl sodium sulfosuccinate (70% in propylene glycol), a fatty acid ester, a glycol ether, and 2-ethylhexanol in a ratio of 4:4:1: 1. Antifoam #4 was a mixture of oleic acid and 2-ethylhexanol in a 9:1 weight ratio. The efficacy of these polymers (alone and in combination with antifoam) in promoting crystal growth and enhancing filtration rate was investigated using the aforementioned leaching procedure, filtration test and particle size analysis methods. The results of leaching phosphate ores from various sources are shown in tables 1-5. Each table represents a different set of tests. Examples 1, 5, 12, 16, 21 and 26 are controls without any defoamer or poly (carboxylic acid) or salt thereof. The cumulative particle size distributions of the filter cakes of examples 1-4, 5-8, and 12-15 are provided in FIGS. 1, 2, and 3, respectively. The particle size distributions of the filter cakes of examples 5, 6 and 8 are provided in fig. 4.

TABLE 1 Effect of the amount of P (AA-co-MA) on particle size and filtration Rate in the absence of antifoam

a) Comparative example.

TABLE 2 in IONQUEST^TMEffect of the amount and molecular weight of PAA, P (AA-Na) and P (AA-MA) on particle size and filtration Rate in the case of D3001 antifoam

a) Comparative example.

b) PAA and defoamer were added to the slurry after the leaching step and before the filtration step.

TABLE 3 in IONQUEST^TMEffect of molecular weight of PAA homopolymers and copolymers on particle size and filtration Rate in case of D3001 antifoam agent

a) Comparative example.

TABLE 4 in CYBREAK^TMEffect of P (AA-Na) usage on particle size and filtration Rate in the case of 675HFP antifoam

a) Comparative example.

TABLE 5 influence of the amount of P (AA-Na) used on the filtration Rate in the case of antifoam #3 and antifoam #4

a) Comparative example.

b) Antifoam #3 was dioctyl sodium sulfosuccinate (70% in propylene glycol), a fatty acid ester, glycol ether and 2-ethylhexanol in a ratio of 4:4:1: 1.

c) Antifoam #4 was 90% oleic acid + 10% 2-ethylhexanol.

TABLE 6 influence of the amount of PAA used after leaching on the filtration rate without antifoam

a) Comparative example.

b) PAA was added to the slurry after the leaching step and before the filtration step.

High molecular weight (M) is known in the art (e.g., in U.S. Pat. No. 5,009,873)_w>1,000,000) is necessary for the polymer to effectively promote crystal growth. Low molecular weight Polymer (M)_w<1,000,000) are commonly used as dispersants or scale inhibitors to inhibit crystal growth and agglomeration. Thus, it is surprising that low molecular weight poly (carboxylic acid) homopolymers and copolymers and salts thereof (alone or in combination with defoamers) can increase the particle size of the crystals during leaching of phosphate ore from various sources and thereby improve filtration rates. When using high molecular weight PAA (M)_w1,000,000) no increase in particle size and improvement in filtration rate was observed. In contrast, as shown in comparative example 15, high molecular weight PAA is detrimental to crystal growth and filtration rate. The level of low molecular weight poly (carboxylic acid) polymer and its salts used affects particle size and filtration rate. Although about 0.06 to 0.3kg/T P₂O₅In low amounts (as in examples 19 and 2, respectively) and about 1.2kg/T P₂O₅Both provide some improvement in particle size and filtration rate, as in example 4, but between these limits particle size and filtration rate may be optimal. The optimum amount may depend on the particular ore and leaching method used.

Comparison of example 7 with example 11 and example 27 with example 26 shows that poly (carboxylic acid) or its salt should be added during the leaching step, either alone or in combination with an anti-foaming agent, to obtain increased particle size and reduced filtration rate. If they are added after the leaching step, as in examples 11 and 27, there is no improvement in the filtration rate compared to the controls (examples 6 and 26, respectively).

Figure 5 depicts a visible micrograph collected with FlowCam on the filter cake crystals after phosphate ore leaching. These images show that IONQUEST^TMP of D3001 combination(AA-co-MA) (Mw ═ 3,000) promotes the formation of crystal clusters/aggregates. These data are contrary to the expectation that low molecular weight polymers disperse particles and prevent them from forming aggregates. Additionally, it has also been unexpected that a defoamer efficacy (e.g., CYBREAK) when added with a low molecular weight poly (carboxylic acid) or salt thereof during phosphate ore leaching^TM675HFP and IONQUEST^TMD3001) Is also improved. Controlling the foam may be achieved by reducing the amount of foam or preventing foam formation. FIG. 6 is a photograph depicting the foam level of the slurry after phosphate ore leaching in examples 5-7, with example 6 having 8kg/T P added₂O₅ IONQUEST^TMD3001 and example 7 with 0.8kg/T P addition₂O₅P (AA-Na) and 7.2kg/T P₂O₅ IONQUEST^TMD3001. Although IONQUEST in example 6 relative to example 5^TMD3001 reduced the amount of foam, but the co-addition of P (AA-Na) (Mw 1200) during the leaching step (example 7) further reduced the amount of foam. However, low molecular weight poly (carboxylic acids) or salts thereof have no defoamer activity per se. The foam volumes for examples 21-25 are listed in Table 5. Comparison of example 23 with example 22 and example 25 with example 24 also demonstrates the beneficial effect of low molecular weight poly (carboxylic acid) or salt thereof on foaming when used in combination with an anti-foaming agent. In addition, the combination of the defoamer and the low molecular weight poly (carboxylic acid) provides an unexpected synergistic effect in controlling foam. As shown in Table 5, 6.0kg/T P₂O₅Antifoam #3 (example 22) provided 20mL of foam, while 5.4kg/T P₂O₅Antifoam agent #3 and 0.6kg/T P₂O₅The combination of PAA (example 23, same total amount of additives) provided 5mL of foam. Similarly, 6.0kg/T P₂O₅Antifoam #4 (example 24) provided 10mL of foam and 5.4kg/T P₂O₅Antifoam agent #4 and 0.6kg/T P₂O₅The combination of PAA (example 25, same total amount of additives) provided 5mL of foam. The synergistic effect of the combination of the defoamer and the low molecular weight poly (carboxylic acid) on foam control is unexpected.

In summary, the data in tables 1-6 and FIGS. 1-6 show that the addition of effective amounts of an antifoaming agent and a low molecular weight poly (carboxylic acid) or salt thereof increases the volume average particle size, enhances filtration rate, and controls foaming during leaching of phosphate-containing ore.

As used herein, the term "(meth) acrylic" means acrylic acid, methacrylic acid, or a combination of acrylic acid and methacrylic acid. The acronym "PAA" refers in particular to polyacrylic acid. Similarly, the term "(meth) acrylate" refers to an acrylate, a methacrylate, or a combination of an acrylate and a methacrylate.

As used herein, a "salt" may be an alkali metal salt, an alkaline earth metal salt, an ammonium salt, or a quaternary ammonium salt. The salt may be, for example, a lithium salt, a sodium salt, a potassium salt, a calcium salt or an ammonium salt. In any or all embodiments, the salt is a sodium salt.

As used herein, "low molecular weight" refers to a weight average molecular weight of less than 1,000,000 grams per mole (g/mol), and "high molecular weight" refers to a weight average molecular weight of greater than or equal to 1,000,000 g/mol. For example, the phrase "low molecular weight poly (carboxylic acid)" refers to a poly (carboxylic acid) having a weight average molecular weight of less than 1,000,000 g/mol.

P in kg/ton phosphate ore of additive used herein₂O₅Expressed in units and abbreviated as "kg/T P₂O₅”。

This invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. As used herein and in the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

One skilled in the art will appreciate that while preferred embodiments are discussed in greater detail herein, various embodiments of the methods and compositions described herein are also contemplated to be within the scope of the present invention. Thus, it should be noted that any feature described in relation to one aspect or embodiment of the invention is combinable with or interchangeable with another aspect or embodiment of the invention, unless stated otherwise. Those skilled in the art will appreciate that even any description of the present invention described with respect to a particular embodiment or figure may be applicable to and interchangeable with other embodiments of the present invention.

Furthermore, for the purposes of describing the present invention, when an element, component, or feature is said to be included in and/or selected from a list of enumerated elements, components, or features, those skilled in the art will appreciate that in the relevant embodiments of the present invention described herein, the element, component, or feature can also be any of the individually enumerated elements, components, or features, or can also be selected from a group including any two or more of the explicitly enumerated elements, components, or features. Additionally, omissions of any element, component, or feature recited in the list can also be considered part of the disclosure.

It will be further understood by those within the art that any recitation herein of numerical ranges by endpoints, whether explicitly recited or not, includes all numbers subsumed within that range (including fractional numbers) and the endpoints and equivalents of that range. Thus, "1 to 5" includes, for example, 1, 2, 3, 4 and 5 when referring to, for example, the number of elements, and may also include, for example, 1.5, 2, 2.75 and 3.8 when referring to the value of a parameter. The disclosure of a narrower range or a more specific group is not intended to foreclose claims to that broader range or group except that broader range or group. All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. For example, a range of "up to 25 wt.%, or, more specifically, 5 wt.% to 20 wt.%," includes the endpoints and all intermediate values of the range, including "5 wt.% to 25 wt.%," and the like.

The methods and compositions herein can alternatively comprise, consist of, or consist essentially of any suitable step or component disclosed herein separately. The methods and compositions can additionally or alternatively be formulated to be free or substantially free of any steps or materials that are not necessary to the achievement of the function or purpose of the methods and compositions.

"combination" includes blends, mixtures, alloys, reaction products, and the like. Unless expressly stated otherwise, "or" means "and/or. "A and/or B" means "A, B or a combination of A and B".

Unless otherwise specified herein, all test criteria are the most recent validation criteria by the date of filing of the present application or (if priority is required) the date of filing of the priority application.

Unless defined otherwise herein, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

All cited patents, patent applications, and other references are incorporated by reference into this application in their entirety. However, if a term in the present disclosure contradicts or conflicts with a term in the cited reference, the term in the present disclosure takes precedence over the conflicting term in the cited reference.