A composition for a salt anti-caking agent, a salt anti-caking agent and its application

Abstract

This invention discloses a salt anti-caking agent composition, the salt anti-caking agent itself, and its application, belonging to the field of saline wastewater treatment technology. The salt anti-caking agent composition comprises ferrocyanide salt, a high-temperature stabilizer, a crystal nucleation dispersant, and a selectively contained nucleating agent, with a weight ratio of 1:(0.3–2.0):(0.05–0.25):(0–0.10), and the composition does not contain a metal chelating agent. This salt anti-caking agent can maximally alter the salt crystallization process and the adhesion force on the salt particle surface in solution, greatly increasing the number of crystal nuclei, making the salt crystals smaller, reducing the binding force between salt particles, and preventing the aggregation into large particles, thereby inhibiting, preventing, or reducing the formation of large salt lumps. This salt anti-caking agent can be applied in the drying and / or crystallization recovery of waste salt from saline wastewater in industries such as fine chemical industry, petrochemical and coal chemical industry, desulfurization and water treatment industry, waste treatment, metallurgical industry, and hazardous waste treatment.

Description

Technical Field

[0001] This invention belongs to the field of saline wastewater treatment technology, and relates to the application of salt anti-caking agents in the drying and / or crystallization recovery of waste salt in saline wastewater processes. Specifically, it relates to a composition for salt anti-caking agents, salt anti-caking agents, and their applications. Background Technology

[0002] MVR evaporation technology is widely used in many fields such as biochemicals, petrochemicals, pharmaceuticals, food manufacturing, environmental protection, and seawater desalination. The MVR process effectively solves the problem of difficult RO concentrate treatment. MVR evaporation technology can further concentrate RO concentrate, and the distillate can be reused, combining wastewater treatment with resource recovery. Concentration to the crystallization stage allows for subsequent treatment to obtain inorganic salts or for spray drying of the wastewater, recovering condensate and waste salts, achieving zero discharge of industrial wastewater. After wastewater concentration, industrial wastewater enters spray drying equipment for salt precipitation. During salt crystallization, inorganic salts, especially sodium chloride and sodium sulfate, often cause the crystals to clump on the inner wall of the drying equipment, resulting in poor salt flow, clogging of equipment pipelines, difficulty in cleaning, and equipment failure or production shutdown. In the hazardous waste incineration industry, when saline wastewater is sprayed back into the quench tower to recover waste salt, the waste salt not only precipitates at the bottom of the quench tower but also forms a dense, hard salt layer tens of centimeters to several meters thick on the inner wall of the tower. This layer easily blocks the channels and causes the unit to shut down. To put the equipment back into operation, manual removal of the accumulated salt is necessary. The formation of accumulated salt not only seriously affects the normal operation of the unit but also creates a harsh working environment for cleaning, posing significant health risks and safety hazards to operators. Therefore, there is a need to find a method to pulverize the crystallized salt, ensuring it has good fluidity, is easy to rinse and self-clean, and is easy to post-process.

[0003] CN112079454A discloses a salt inhibitor for a saline wastewater recirculation quench tower process, the effective component of which includes a water-soluble ferrocyanide salt, preferably any one or a mixture of two or more of potassium ferrocyanide, sodium ferrocyanide, calcium ferrocyanide, or ammonium ferrocyanide. CN112079452A discloses a polycarboxylic acid salt inhibitor for a saline wastewater recirculation quench tower process, the effective component of which includes polycarboxylic acids and / or their salts, including but not limited to any one or a mixture of two or more of ethylenediaminetetraacetic acid, citric acid, tartaric acid, succinic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, and gluconic acid. US3213018 discloses that adding a small amount of a compound MXn with a complex anionic form to a saturated or high-concentration sodium chloride solution can effectively prevent NaCl from crystallizing in large quantities due to temperature decrease. Where M can be Fe or Co, X can be (CN), (NO), (NO2), or (C2O4), and when X is oxalate, n is 3; otherwise, n is 6.

[0004] Zhao Fang [Preparation and Research of Slow-Release Salt Inhibitors [D]. Shandong University, 2006] reported that in the salt inhibition experiment, the use of either ferrocyanide salt or polyacrylic acid polymer alone could change sodium chloride crystals from cubic to loose crystals.

[0005] Liu Renzhi et al. [Inhibitory effect of potassium ferrocyanide on sodium chloride crystallization [J]. Journal of Jinan University (Natural Science and Medicine Edition), 2015, 36(6):448-452] reported the process and mechanism of the inhibitory effect of K4Fe(CN)6 on NaCl crystallization. The results showed that K4Fe(CN)6 inhibited the crystallization of NaCl. + It has an adsorption effect, inhibits the formation of crystal nuclei, and causes NaCl to change from its original cubic crystal form to a dendritic crystal form during the crystallization process, promoting uneven crystal growth and forming a dendritic structure.

[0006] The above patent and literature review indicates that adding ferrocyanide or water-soluble polymers to sodium chloride solutions can significantly increase salt solubility, delay crystallization (effectively requiring a higher concentration of the crystallization brine), and alter the shape of salt crystals. Water-soluble polymers, in particular, often cause difficulty in salt crystallization due to their viscosity, leading to cross-linking of crystals, increased salt caking, reduced crystal flowability, and hindering crystal transport and discharge. Furthermore, the inlet temperature of flue gas from quench towers in hazardous waste incineration plants is often above 500℃, typically ranging from 500℃ to 650℃ depending on process conditions. At such high temperatures, organic salt inhibitors will thermally decompose. Polycarboxylic acid compounds (such as sodium polyacrylate and hydrolyzed polymaleic acid) have a thermal decomposition temperature below 300℃. Even commonly used anti-caking agents, such as potassium ferrocyanide, begin to decompose above 400℃ and almost completely decompose under conventional flue gas operating conditions of 520–620℃, failing to provide effective anti-caking. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a composition for a salt anti-caking agent, a salt anti-caking agent, and the application of the salt anti-caking agent in the drying and / or crystallization recovery of waste salt from saline wastewater.

[0008] To achieve the above objectives, the present invention provides a composition for use as a salt anticaking agent.

[0009] The composition for the salt anti-caking agent does not contain a metal chelating agent, and the composition for the salt anti-caking agent includes a ferrocyanide salt, a high-temperature stabilizer, a crystal nucleation dispersant, and a selectively contained nucleating agent, wherein the weight ratio of the ferrocyanide salt, the high-temperature stabilizer, the crystal nucleation dispersant, and the nucleating agent is 1:(0.3-2.0):(0.05-0.25):(0-0.10), preferably 1:(0.5-1.0):(0.10-0.20):(0-0.05).

[0010] In the above components, the ferrocyanide salt is one of the important components in the composition for salt anti-caking agents. The ferrocyanide salt is at least one selected from potassium ferrocyanide, sodium ferrocyanide, and ammonium ferrocyanide.

[0011] It is well known to those skilled in the art that adding ferrocyanide salts to sodium chloride solutions or solutions with sodium chloride as the main salt component can alter the crystallization morphology of sodium chloride in the solution. The addition of ferrocyanide salts to saline wastewater affects the crystallization process of salts in the wastewater, particularly the crystallization process of sodium chloride. The principle is to change the interface state and growth order of the microcrystals, causing the crystals (especially sodium chloride crystals) to change from a hard, regular cubic structure to a loose, irregular dendritic structure, resulting in smaller salt particles and thus preventing the formation of hard salts. Furthermore, in the hazardous waste treatment industry, in wastewater recirculation processes, the designed flue gas temperature at the inlet of the quench tower is 500℃~650℃; however, according to literature reports, potassium / sodium ferrocyanide decomposes into highly toxic cyanide solids or gases at temperatures above 400℃, and almost completely decomposes at flue gas temperatures ≥520℃, leading to a significant reduction or loss of the anti-salt formation effect. Therefore, it is necessary to add high-temperature stabilizers or lower the operating temperature to alleviate or reduce the decomposition of ferrocyanide salts.

[0012] Among the above components, the high-temperature stabilizer is an important component of the salt anti-caking agent composition. Adding this high-temperature stabilizer can significantly reduce the decomposition of ferrocyanide salts at temperatures above 400°C. The high-temperature stabilizer described in this application is at least one selected from potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, and lithium carbonate.

[0013] The applicant discovered in actual production operations that adding sodium carbonate to potassium ferrocyanide / sodium ferrocyanide can improve the anti-caking performance of the mixture at high temperatures. For example, at the same dosage concentration, under the actual operating inlet temperature of 520-620℃ in the quench tower flue gas of a hazardous waste incineration plant, the salt deposition time on the inner wall of the quench tower was extended from 2 months (without sodium carbonate) to more than 6 months (with sodium carbonate). The applicant also tested potassium hydroxide, sodium hydroxide, potassium carbonate, and lithium carbonate, all of which improved the anti-caking performance of salt under high-temperature conditions. The reason, based on the production process, is speculated to be that the incineration flue gas contains acidic gases. These acidic gases cause the ferrocyanide salt in the solution to form ferrocyanic acid, which is unstable and easily decomposes, leading to the loss of the anti-caking performance of the ferrocyanide salt. Adding a high-temperature stabilizer can neutralize the acidic gases and prevent the formation of ferrocyanic acid and subsequent acidification and decomposition. The applicant further verified this hypothesis through thermogravimetric analysis. Increasing the pH of the anti-caking salt solution to alkaline, especially above 10, significantly reduced the thermal decomposition of ferrocyanide salts. Furthermore, adjusting the solution pH from alkaline to weakly acidic resulted in greater ferrocyanide decomposition. When anti-caking salt was added to saline wastewater and the pH of the wastewater solution was maintained at an alkaline level, the inner wall of the drying equipment was less prone to salt caking compared to neutral or weakly acidic conditions, and the waste salt was more easily kept in a free-flowing powder state.

[0014] In the above components, the nucleation dispersant is one of the important components in the salt anti-caking agent composition. The nucleation dispersant is a copolymer formed from a sulfonic acid-containing olefin and a carbonyl-containing olefin with 3-4 carbon atoms; based on the total amount of the nucleation dispersant, the molar percentage of the structural units formed by the sulfonic acid-containing olefin is 10-25%; and the weight-average molecular weight of the nucleation dispersant is 1500-50000. In the above nucleation dispersant, the carbonyl-containing olefin is acrylic acid and / or maleic acid / anhydride; the sulfonic acid-containing olefin is at least one selected from 2-methyl-2-acrylamidopropanesulfonic acid, vinyl sulfonic acid, styrene sulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, and allyl polyethylene glycol sulfonic acid.

[0015] The dosage of nucleation dispersant should be neither too low nor too high. Too little will not achieve the desired dispersion effect; too much, due to the polymer nature of the dispersant, often hinders salt crystallization, causing cross-linking of crystals, increasing salt caking, reducing the fluidity of salt crystals, and impeding their transport and discharge. The optimal dosage of nucleation dispersant in saline wastewater is maintained at a concentration of 0.02 kg to 2.5 kg / ton of dry salt. When the drying operation temperature exceeds 300℃, the negative impact of the dispersant on salt formation can be disregarded due to the high-temperature decomposition of the polymer. Because saline wastewater often contains trace amounts of heavy metal ions, these ions react with ferrocyanide salts in the anti-caking agent to form insoluble compounds. Adding a nucleation dispersant keeps these insoluble compounds in suspension, preventing precipitation, thus inducing crystallization and promoting crystal refinement during the salt crystallization process.

[0016] In the above components, the nucleating agent is an optional component in the salt anti-caking agent composition. The nucleating agent is a soluble metal ion, such as Zn. 2+ Fe 3+ Cd 2+ Ni 2+ Pb 2+ Co 2+ Cu 2+ Ag + Mn 2+ Al 3+ At least one of the following, other soluble metal ions that can react with ferrocyanide salts to form precipitates in aqueous solution, or soluble metal ions that can form precipitates in alkaline aqueous solution, can be used as nucleating agents.

[0017] In practical applications, when saline wastewater contains heavy metal ions (such as Zn) 2+ Fe 3+ Cd 2+ Ni 2+ Pb 2+ Co 2+ Cu 2+ Ag + Mn 2+ Al 3+ When at least one of the following is present in the salt anti-caking agent, no nucleating agent is needed because the ferrocyanide salt in the salt anti-caking agent reacts with the heavy metal ions to generate a large amount of precipitate, which can serve as heterogeneous nuclei; when the saline wastewater does not contain heavy metal ions, a nucleating agent, such as Zn, can be added. 2+ Fe 3+ Cd 2+ Ni 2+ Pb 2+ Co 2+ Cu 2+ Ag+ Mn 2+ Al 3+ These ions can react with ferrocyanide salts to form precipitates, or they can form insoluble substances under alkaline aqueous conditions, serving as heterogeneous nuclei. The appropriate concentration of nucleating agent in saline wastewater is less than 0.05 kg / ton of dry salt.

[0018] In the above-mentioned components, this invention specifically limits the composition for use as a salt anti-caking agent to be free of metal chelating agents. This is because the use of metal chelating agents would significantly reduce the speed and extent of crystal nucleation, interfere with the formation of small crystal nuclei, and thus reduce the effect of the nucleating agent. The metal chelating agent described herein is an organic compound containing a carboxyl group or a phosphonic acid group that can form a soluble chelate with the aforementioned nucleating agent. This metal chelating agent can be a commercially available metal chelating agent, mainly chelating agents containing aminoacetic acid groups, chelating agents containing glycolic acid groups, chelating agents containing aminoethylphosphonic acid groups, polycarboxylic acid homopolymers, etc., as long as they can form a soluble chelate with the aforementioned nucleating agent (such as Zn). 2+ Fe 3+ Cd 2+ Ni 2+ Pb 2+ Co 2+ Cu 2+ Ag + Mn 2+ Al 3 + Those that form soluble chelates (such as plasma) are not used in this composition. Specifically, such as at least one of the following: nitrotriacetic acid, ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, gluconic acid, citric acid, tartaric acid, succinic acid, aminotriethylene phosphonic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetraethylene phosphonic acid, diethylenetriaminepentamethylene phosphonic acid, triethylenetetraaminehexamethylene phosphonic acid, bis(1,6-methylene)-triaminepentamethylene phosphonic acid, polyamino ether tetramethylene phosphonic acid, polyacrylic acid, polymaleic acid, polyepoxysuccinic acid, polyaspartic acid, and alkaline earth metal salts of the above substances.

[0019] The salt anti-caking agent composition of the present invention further includes an antioxidant and / or a reducing agent, wherein the weight ratio of the antioxidant and / or reducing agent to ferrocyanide is (0.01-0.05):1. The antioxidant and / or reducing agent are used because if the salt anti-caking agent composition is formulated into an aqueous solution, the ferrocyanide salt is easily oxidized and decomposed by light and air in the aqueous solution. Typically, within a few days, the aqueous solution of ferrocyanide salt begins to become cloudy and a brick-red substance precipitates, thereby affecting the salt's anti-caking performance and reducing its effectiveness. To ensure the stability of the ferrocyanide salt in the aqueous solution, an antioxidant and / or reducing agent can be added. There are no particular limitations on the antioxidant and / or reducing agent, but at least one of hydrazine hydrate, carbazide, N,N-diethylhydroxylamine, hydroxylamine hydrochloride, hydroxylamine sulfate, dimethyl ketoxime, sodium isoascorbate, potassium isoascorbate, sodium ascorbate, potassium ascorbate, sodium sulfite, potassium sulfite, sodium dithionite, and potassium dithionite is preferred.

[0020] To achieve the above objectives, the present invention also provides a salt anticaking agent.

[0021] The salt anti-caking agent is an aqueous solution formed by the above-mentioned salt anti-caking agent composition and water.

[0022] In this invention, the content of the salt anti-caking agent composition in the salt anti-caking agent can be selected within a wide range as needed. Generally, the content of the salt anti-caking agent composition accounts for 10-40% of the total weight of the salt anti-caking agent; preferably, the content of the salt anti-caking agent composition accounts for 20-40% of the total weight of the salt anti-caking agent; more preferably, it is 25-35%. In addition, the pH of the aqueous solution of the salt anti-caking agent is greater than 10, more preferably greater than 12.

[0023] In this invention, the salt anti-caking agent described above can be obtained by various existing methods. For example, the raw materials for forming the salt anti-caking agent can be mixed evenly according to the aforementioned required proportions. Therefore, this invention does not have special requirements for the mixing steps and conditions.

[0024] To achieve the above objectives, this invention also provides an application of the aforementioned salt anti-caking agent in the drying and / or crystallization recovery of waste salt from saline wastewater, particularly in the drying and / or crystallization recovery of waste salt from saline wastewater in industries such as fine chemicals, petrochemicals, coal chemicals, desulfurization, water treatment, waste treatment, metallurgy, and hazardous waste treatment. The saline wastewater from the aforementioned industries is one of the following: saline wastewater mainly composed of sodium chloride, saline wastewater mainly composed of sodium chloride and sodium sulfate, or saline wastewater mainly composed of sodium chloride and potassium chloride, wherein the mass percentage of sodium chloride is greater than 85%.

[0025] When using this salt anti-caking agent, the agent is mixed evenly with saline wastewater. The mixture is then fed into a crystallization device, spray dryer, or high-temperature dryer at 25℃ to 620℃ for crystallization or drying, after which the waste salt solids are recovered. The dosage of the salt anti-caking agent in the saline wastewater, based on the effective component, is generally better at 1.0 kg of salt anti-caking agent per ton of dry salt in the wastewater. Higher dosages result in better effects, but considering cost, a dosage of 1.0 to 20.0 kg of salt anti-caking agent per ton of dry salt solids in the wastewater is more suitable; preferably, 1.0 to 10.0 kg of salt anti-caking agent per ton of dry salt solids, i.e., 0.1 to 1.0 kg of salt anti-caking agent per ton of saline wastewater (salt content 10 wt.%). When the dosage of the salt anti-caking agent in the saline wastewater is within the above-mentioned preferred range, it exhibits excellent salt anti-caking performance.

[0026] The beneficial technical effects of this invention are:

[0027] The components in the salt anti-caking agent composition of the present invention can work synergistically with each other. Therefore, the salt anti-caking agent formed by the salt anti-caking agent composition and water has stable chemical properties, meets the requirements of green environmental protection, and has excellent crystallization modification properties. In addition, it has the advantages of low dosage, simple processing and obvious effect, and is easy to promote and apply.

[0028] This invention adds the salt anti-caking agent to the saline wastewater before drying and / or crystallizing, so that the waste salt precipitated during crystallization or drying in the drying equipment can be in a highly dispersed powder state. This significantly reduces the viscosity of the crystallized salt, improves the fineness and flowability of the crystallized salt, and avoids the deposition of large salt blocks on the inner wall of the equipment, thereby avoiding the continuous accumulation and blockage of equipment channels or the shutdown accident caused by large salt blocks falling off and causing blockage. Attached Figure Description

[0029] Figure 1 This is a diagram showing the salt formation effect of the blank sample applied in Scene 1;

[0030] Figure 2 This is one of the salt formation effect diagrams of Example 1 (addition amount 3.0g / kg dry salt) applied in Scenario 1;

[0031] Figure 3 This is the second salt formation effect diagram of Example 1 (addition amount 10.0g / kg dry salt) applied in Scenario 1;

[0032] Figure 4 This is the third salt formation effect diagram of Example 1 (addition amount 20.0g / kg dry salt) applied in Scenario 1;

[0033] Figure 5This is a diagram showing the salt formation effect of Comparative Example 1 of this application in Scenario 1;

[0034] Figure 6 This is a diagram showing the salt formation effect of Comparative Example 3 of this application in Scenario 1;

[0035] Figure 7 This is a diagram showing the salt formation effect of Comparative Example 4 of this application in Scenario 1;

[0036] Figure 8 These are photographs of the crystallization process in Table 2 of this application specification, showing the effect of the nucleation dispersant on the crystallization performance. They are crystallization diagrams of Example 1, Comparative Example 2, and Examples 1-3.

[0037] Figure 9 These are photographs of the crystallization process of the metal chelating agent on the salt crystallization performance in Table 4 of this application specification, specifically crystallization diagrams of Example 1 and Comparative Example 5.

[0038] Figure 10 These are photographs of the crystallization of the salt anticaking agent in the laboratory test in Table 5 of this application specification. They are crystallization diagrams of the blank sample, Example 1 with different dosages, and Examples 2-6. Detailed Implementation

[0039] In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the specific embodiments of the present invention will be described in further detail below with reference to specific examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0040] In the following examples and comparative examples, "effective content" refers to the percentage of the weight of the components other than the solvent to the total weight of the solution; all reagents used in the examples and comparative examples were analytical grade reagents (purchased from Sinopharm Chemical Reagent Co., Ltd.) (all experiments were converted to effective content for calculation).

[0041] The following are the sources and grades of some of the components used in the embodiments and comparative examples of this invention.

[0042] Polyacrylic acid (abbreviated as PAA, number average molecular weight less than 1200, conforming to GB / T 10533-2014 "Water Treatment Agents Polyacrylic Acid") was purchased from Shandong Taihe Water Treatment Co., Ltd.

[0043] Acrylic acid and 2-methyl-2-acrylamidopropanesulfonic acid copolymer (abbreviated as AA / AMPS, conforming to HG / T3642-2016 "Water Treatment Agents Acrylic Acid-2-methyl-2-acrylamidopropanesulfonic Acid Copolymers") was purchased from Shandong Taihe Water Treatment Co., Ltd.

[0044] Acrylic acid-hydroxypropyl acrylate copolymer (abbreviation: AA / HPA, grade T-225) was purchased from Changzhou Wujin Water Quality Stabilizer Factory.

[0045] Acrylic acid and 3-allyloxy-2-hydroxypropanesulfonic acid (AA / AHPS) were purchased from GE Betz, Inc., brand name PY5200.

[0046] Acrylic acid and allyl polyethylene glycol sulfonic acid (AA / APES) were purchased from GE Betz, Inc., brand name AEC3302.

[0047] Salt anticaking agents were prepared according to the following examples and comparative examples.

[0048] Example 1

[0049] Weigh out 1.0g potassium ferrocyanide, 0.75g sodium hydroxide, 0.15g AA / AMPS, 0.025g zinc chloride, and 0.01g hydrazine hydrate. Finally, dilute with water to obtain a solution with an effective content of 25% and stir well (solution pH = 14.0).

[0050] Example 2

[0051] Weigh out 1.0g sodium ferrocyanide, 0.5g potassium carbonate, 0.20g AA / AHPS, and 0.05g sodium isoascorbate, and finally dilute with water to make a solution with an effective content of 25%, and stir well (solution pH=11.0).

[0052] Example 3

[0053] Weigh out 1.0g potassium ferrocyanide, 0.5g sodium carbonate, 0.5g potassium hydroxide, 0.1g AA / APES, 0.05g copper nitrate, and 0.025g diethylhydroxylamine. Finally, dilute with water to prepare a solution with an effective content of 25% and stir well (solution pH = 13.0).

[0054] Example 4

[0055] Weigh out 1.0g potassium ferrocyanide, 0.3g potassium hydroxide, 0.25g AA / AMPS, and 0.05g sodium sulfite, and finally dilute with water to make a solution with an effective content of 25%, and stir well (solution pH=10.0).

[0056] Example 5

[0057] Weigh out 1.0g sodium ferrocyanide, 2.0g potassium carbonate, 0.05g AA / AHPS, 0.1g ferric chloride, and 0.01g carbazide, and finally dilute with water to a solution with an effective content of 25%, and stir well (solution pH=10.5).

[0058] Example 6

[0059] Weigh out 1.0g potassium ferrocyanide, 1.0g sodium carbonate, 0.5g sodium hydroxide, 0.05g AA / APES, 0.01g nickel nitrate, and 0.05g sodium ascorbate. Finally, dilute with water to a solution with an effective content of 25% and stir well (solution pH = 12.0).

[0060] Comparative Example 1

[0061] Referring to the salt inhibitor described in Example 5 of document CN112079454A in the background art, the salt inhibitor aqueous solution (solution pH=9.5) is composed of 0.5% potassium ferrocyanide, 5% hydrolyzed polymaleic anhydride, 5% sodium gluconate, 10% sodium ethylenediaminetetraacetate, and the balance water. It is used as a salt anti-caking agent, and the dosage is 18.75 kg / ton of dry salt after conversion.

[0062] Comparative Example 2

[0063] Salt anticaking agents were prepared according to the components described in Example 1 of this article, except that in Comparative Example 2, 2.0 g AA / AMPS was used instead of 0.15 g AA / AMPS.

[0064] Comparative Example 3

[0065] Salt anticaking agents were prepared according to the components described in Example 1 of this article, except that Comparative Example 3 did not use the high-temperature stabilizer sodium hydroxide (solution pH = 9.5).

[0066] Comparative Example 4

[0067] Salt anti-caking agents were prepared according to the components described in Example 1 of this article, except that Comparative Example 4 did not use the nucleation dispersant AA / AMPS (solution pH>14.0).

[0068] Comparative Example 5

[0069] The salt anticaking agent was prepared according to the components described in Example 1 of this article, except that 0.1 g of the metal chelating agent tetrasodium ethylenediaminetetraacetate (solution pH = 14.0) was also added to Comparative Example 5.

[0070] A. Stability test of high-temperature stabilizers in salt anti-caking agents to ferrocyanide salts

[0071] A salt anti-caking agent solution was prepared according to the components described in Example 1, and the amount of sodium hydroxide, a high-temperature stabilizer, was changed to adjust the pH of the solution to be different from that in Example 1. The corresponding examples are Example 1-1 (same components as Example 1, different pH) and Example 1-2 (same components as Example 1, different pH). After drying the aqueous solution of the examples at 120°C, 1.0 g of the dry basis product was placed in the sample pan of a thermogravimetric analyzer. Under a nitrogen atmosphere, the temperature was rapidly increased to the specified temperatures of 520°C, 620°C, and 650°C at a heating rate of 50°C / min. After reaching the set temperature, the temperature was maintained for 2 minutes, and then the product was removed and rapidly cooled. The content of the remaining ferrocyanide salt was then measured (the decomposition temperature of other organic matter is less than 300°C and is not considered). The results of Comparative Example 1 and Comparative Example 3 were also measured simultaneously (see Table 1). The results show that the salt anti-caking agent at high temperature has better stability under strongly alkaline conditions. When pH>10, within the temperature range of 520-620℃, 45%-28% of the ferrocyanide salt can still remain. However, after exceeding 650℃, the ferrocyanide completely decomposes, indicating that the salt anti-caking agent will completely decompose and become ineffective after 650℃.

[0072] Table 1. Stability test of high-temperature stabilizers for ferrocyanide salts in anti-caking salt agents.

[0073] For example solution pH Temperature / °C Ferrocyanide residue / wt.% Example 1-1 8.0 520 Not detected Comparative Example 1 9.5 520 / 620 2 / Not detected Comparative Example 3 9.5 520 / 620 3 / Not detected Examples 1-2 10.0 520 / 620 / 650 45 / 28 / Not detected Example 1 14.0 520 / 620 48 / 29

[0074] B. Experiment on the effect of nucleation dispersant dosage on salt crystallization performance

[0075] In 250 ml of a saturated sodium chloride solution at 100°C, the amount of salt anti-caking agent listed in Table 2 was added, stirred evenly, and kept at the same temperature for 10 minutes. Then, the saturated solution was poured from the 100°C constant temperature state into a watch glass to cool and observe the crystal shape (see Table 2). Examples 1-3 are salt anti-caking agent solutions prepared according to the components described in Example 1, with the amount of crystal nucleation dispersant added varying to achieve a crystal nucleation dispersant dosage of 2.5 g / kg dry salt.

[0076] Table 2. Effect of nucleation dispersants on crystallization properties

[0077]

[0078]

[0079] The crystallization phenomena observed in Example 1, Comparative Example 2 (referring to Example 1, but with different amounts of AA / AMPS), and Examples 1-3 (referring to Example 1, but with different amounts of AA / AMPS) show that the amount of nucleation dispersant affects salt crystallization. Excessive nucleation dispersant can cause crystals to stick together. Since nucleation dispersants are generally high molecular weight polymers, the viscosity of polymers often makes salt crystallization difficult. The crystals cross-link, increasing salt agglomeration and hindering the refinement of crystals.

[0080] C. The effect of different nucleation dispersants on salt anti-caking agents

[0081] The effects of different nucleation dispersants on the stability of salt anticaking agent solutions were investigated.

[0082] Salt anti-caking agent solutions were prepared according to the components described in Example 1, with variations in the type of nucleation dispersant added. The corresponding examples are Examples 1-4 (referring to Example 1, but using different nucleation dispersants) and Examples 1-5 (referring to Example 1, but using different nucleation dispersants). The stability of the solutions from Examples 1, 1-4, and 1-5 was examined (phenomena are shown in Table 3). No layering indicates good dispersibility; layering / precipitation indicates poor dispersibility.

[0083] Table 3. Effects of different nucleation dispersants on the stability of salt anticaking agent solutions.

[0084] For example Crystal nucleation dispersant type Phenomenon after 24 hours of preparation and standing of solution Examples 1-4 PAA Layered, with a layer of white precipitate at the bottom of the bottle. Examples 1-5 AA / HPA Layered, with a small amount of white precipitate at the bottom of the bottle. Example 1 AA / AMPS Undifferentiated, milky white turbid liquid

[0085] D. Experiment on the effect of metal chelating agents on salt crystallization properties

[0086] A measured amount of anti-caking salt was added to 250 ml of a saturated sodium chloride solution at 100 °C. After stirring evenly, the solution was kept at a constant temperature for 10 minutes. Then, the saturated solution was poured from the 100 °C constant temperature state into a watch glass to cool down, and the crystal shape was observed (see Table 4).

[0087] Table 4. Effect of metal chelating agents on salt crystallization properties

[0088]

[0089] The crystallization phenomena observed in Example 1 and Comparative Example 5 show that, under the same dosage conditions, the salt crystals without the metal chelating agent are more porous than those with the metal chelating agent; and, under the same experimental conditions, the time for crystallization to begin is slower with the metal chelating agent than with the metal chelating agent.

[0090] E. Laboratory testing of salt anti-caking agents

[0091] The laboratory testing methods are as follows:

[0092] A measured amount of anti-caking salt was added to 250 mL of a saturated sodium chloride solution at 100 °C. After stirring thoroughly, the solution was kept at this temperature for 10 minutes. Then, the saturated solution was poured from the 100 °C constant temperature state into a watch glass to cool, and the crystal shape was observed. The test results are shown in Table 5.

[0093] Table 5. Laboratory test results of salt anti-caking agents

[0094]

[0095] As can be seen from the crystallization phenomena observed in Examples 1-6, with the increase of the amount of salt anti-caking agent, the salt crystals change from a small amount of dendritic crystals to a large amount of dendritic crystals, and the crystals also become loose and brittle. In Examples 2 and 4, since no nucleating agent was added, the time for salt crystals to begin precipitating in the experiment was slower than in the examples where a nucleating agent was added.

[0096] F. Industrial trials of salt anti-caking agents

[0097] Industrial trials were conducted on Example 1 and Comparative Examples 1, 3, and 4.

[0098] The results of the industrial field trials are as follows:

[0099] Scenario 1: At a hazardous waste incineration plant in Shandong, approximately 40 tons of wastewater with a salt content of 15-20 wt.% is generated daily (the salt is mainly sodium chloride, with a sodium chloride content greater than 90%). The flue gas inlet temperature of the quench tower is 520-620℃. A quantitative amount of anti-caking agent is added to the brine pipeline before entering the quench water tank. A pipeline mixer is installed on the pipeline to mix the agent and brine evenly before it enters the quench water tank for buffering. Then, the brine is drawn out by the quench water pump at the outlet of the quench water tank and sprayed into the quench tower through the brine pipeline and sprayed at the end of the pipeline using a spray gun.

[0100] Scenario 2: At a hazardous waste incineration plant in Hubei Province, approximately 20 tons of wastewater with a salt content of 20-23 wt% are generated daily (the salts are mainly sodium chloride and sodium sulfate, with sodium chloride exceeding 85% and sodium sulfate exceeding 10%). Supercritical fluid concentration and crystallization are used to precipitate the salt at an operating temperature of 60-90℃. Anti-caking agents are added to the brine. The salt delivery pipelines and concentration equipment are inspected for salt buildup.

[0101] Scenario 3: A waste salt producing company in Jiangsu Province generates wastewater with a salt content of 15-17% daily. The wastewater (mainly sodium chloride and potassium chloride, with sodium chloride greater than 88% and potassium chloride greater than 10%) is dried by spraying hot air at a temperature of 200-280℃. The waste salt is recovered by adding a certain amount of anti-caking agent to the saline wastewater before drying to prevent the waste salt from caking and affecting production.

[0102] The industrial application effects of the salt anti-caking agents in the above embodiments and comparative examples under the three application scenarios are shown in Table 6. The blank sample represents the case without any reagents. Salt deposition analysis in the application effect is used to indicate the high-temperature resistance of the salt anti-caking agent in different scenarios. If the analysis results contain ferrocyanide, it indicates that the salt anti-caking agent has excellent high-temperature resistance; if it does not contain it, it indicates that the salt anti-caking agent is not heat-resistant. The longer the stable operation time of the device, the better the effect and the stronger the performance of the salt anti-caking agent.

[0103] Table 6. Application Effects of Salt Anticaking Agents in Industrial Application Scenarios

[0104]

[0105]

[0106] When Comparative Example 1 was applied in the 520-620℃ environment of Scenario 1, analysis of the deposited salt revealed that it did not contain potassium ferrocyanide, indicating that the anti-caking agent was not heat-resistant and that the potassium ferrocyanide had been decomposed at high temperatures. Therefore, although the anti-caking agent in Comparative Example 1 had a certain anti-caking effect at the same concentration, the effect was poor, resulting in a thicker layer of salt deposits on the inner wall and a large number of fist-sized gray salt lumps. The stable operation time of the device (60 days) was also far shorter than the 240 days in Example 1.

[0107] Comparative Example 3 (lacking only a high-temperature stabilizer compared to Example 1, with a solution pH of 9.5) was applied in the 520-620℃ environment of Scenario 1. Salt deposition analysis revealed that the salt deposits did not contain potassium ferrocyanide, indicating that the anti-caking agent was not heat-resistant and the potassium ferrocyanide had been decomposed at high temperatures. Therefore, without using a high-temperature stabilizer while keeping other components the same, this anti-caking agent exhibited a better anti-caking effect than Comparative Example 1 (the salt deposition thickness was smaller even after a longer period compared to Comparative Example 1). However, its overall effect was still unsatisfactory, specifically manifested in a salt deposition thickness of approximately 40 cm appearing on the inner wall after about 70 days of use, along with numerous fist-sized ash salt lumps. Salt deposition analysis of Examples 1 and 3 shows that adding a high-temperature stabilizer and maintaining a solution pH > 10.0 can effectively stabilize the high-temperature decomposition of ferrocyanide.

[0108] When Comparative Example 4 (lacking only the nucleation dispersant compared to Example 1) was applied in the 520-620℃ environment of Scenario 1, salt deposition analysis revealed the presence of potassium ferrocyanide in the deposited salt. This indicates that the anti-caking agent possesses high-temperature resistance, and that potassium ferrocyanide, one of its main components, was not decomposed or not completely decomposed at high temperatures, thus fully demonstrating its anti-caking effect. However, due to the lack of a nucleation dispersant, it was difficult to disperse the nuclei and fine precipitates in the system. Therefore, although no salt deposits formed on its inner wall, potato-sized salt lumps still appeared.

[0109] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0110] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0111] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A composition for use as a salt anti-caking agent, characterized in that: The composition for the salt anti-caking agent does not contain a metal chelating agent, and the composition for the salt anti-caking agent includes a ferrocyanide salt, a high-temperature stabilizer, a crystal nucleation dispersant, and a selectively contained nucleating agent, wherein the weight ratio of the ferrocyanide salt, the high-temperature stabilizer, the crystal nucleation dispersant, and the nucleating agent is 1:(0.3-2.0):(0.05-0.25):(0-0.10); The high-temperature stabilizer is at least one of potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, and lithium carbonate; The nucleus dispersant is a copolymer of a sulfonic acid-containing olefin and a carbonyl-containing olefin with 3-4 carbon atoms; based on the total amount of the nucleus dispersant, the molar percentage of the structural units formed by the sulfonic acid-containing olefin is 10-25%; and the weight-average molecular weight of the nucleus dispersant is 1500-50000. The nucleating agent is a soluble metal ion that can react with ferrocyanide salt to form a precipitate, or a soluble metal ion that can form a precipitate in an alkaline aqueous solution.

2. The composition for use as a salt anti-caking agent according to claim 1, characterized in that: The ferrocyanide salt is at least one of potassium ferrocyanide, sodium ferrocyanide, and ammonium ferrocyanide.

3. The composition for use as a salt anti-caking agent according to claim 1, characterized in that: The carbonyl olefin having 3-4 carbon atoms is acrylic acid and / or maleic acid / anhydride; the sulfonic acid olefin is at least one of 2-methyl-2-acrylamidopropanesulfonic acid, vinyl sulfonic acid, p-styrene sulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid and allyl polyethylene glycol sulfonic acid.

4. The composition for use as a salt anti-caking agent according to claim 1, characterized in that: The nucleating agent is a soluble metal ion Zn. 2+ Fe 3+ Cd 2+ Ni 2+ Pb 2+ Co 2+ Cu 2+ Ag + Mn 2+ Al 3+ At least one of them.

5. The composition for use as a salt anti-caking agent according to claim 1, characterized in that: The composition for the salt anticaking agent also includes an antioxidant and / or a reducing agent, and the weight ratio of the antioxidant and / or reducing agent to the ferrocyanide is (0.01~0.05):

1.

6. The composition for use as a salt anti-caking agent according to claim 5, characterized in that: The antioxidant and / or reducing agent is at least one of hydrazine hydrate, carbazide, N,N-diethylhydroxylamine, hydroxylamine hydrochloride, hydroxylamine sulfate, dimethyl ketoxime, sodium isoascorbate, potassium isoascorbate, sodium ascorbate, potassium ascorbate, sodium sulfite, potassium sulfite, sodium dithionite, and potassium dithionite.

7. The composition for use as a salt anti-caking agent according to claim 1, characterized in that: The metal chelating agent is an organic compound containing a carboxyl group or a phosphonic acid group that is capable of forming a soluble chelate with the nucleating agent.

8. The composition for use as a salt anti-caking agent according to claim 7, characterized in that: The metal chelating agent is at least one of the following: nitrotriacetic acid, ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, gluconic acid, citric acid, tartaric acid, succinic acid, aminotriethylene phosphonic acid, hydroxyethylenediphosphonic acid, ethylenediaminetetraethylene phosphonic acid, diethylenetriaminepentamethylene phosphonic acid, triethylenetetraaminehexamethylene phosphonic acid, bis(1,6-methylene)-triaminepentamethylene phosphonic acid, polyamino ether tetramethylene phosphonic acid, polyacrylic acid, polymaleic acid, polyepoxysuccinic acid, polyaspartic acid, and alkaline earth metal salts of the above substances.

9. A salt anti-caking agent, comprising an aqueous solution of a salt anti-caking agent composition and water, characterized in that: The pH of the aqueous solution is greater than 10, wherein the salt anticaking agent composition is the salt anticaking agent composition of any one of claims 1 to 8.

10. The salt anti-caking agent according to claim 9, characterized in that: The content of the composition for the salt anti-caking agent is 10-40% of the total weight of the salt anti-caking agent.

11. The application of the salt anti-caking agent of claim 10 in the process of drying and / or crystallizing waste salt from saline wastewater.

12. The application according to claim 11, characterized in that: The saline wastewater is one of the following: saline wastewater mainly composed of sodium chloride, saline wastewater mainly composed of sodium chloride and sodium sulfate, or saline wastewater mainly composed of sodium chloride and potassium chloride, wherein the mass percentage of sodium chloride is greater than 85%.

13. The application according to claim 11, characterized in that: After the salt anti-caking agent is mixed evenly with the saline wastewater, the saline wastewater containing the salt anti-caking agent is fed into a crystallization device, a spray drying device, or a high-temperature drying device, and crystallized or dried at 25℃~620℃ to recover the waste salt solids.

14. The application according to claim 11, characterized in that: The dosage of the salt anti-caking agent in saline wastewater is based on the effective ingredient, and is calculated as 1.0~10.0 kg of salt anti-caking agent per ton of dry salt in the saline wastewater.

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