Filter residue dispersing agent for blast furnace slag flushing system

Abstract

The invention discloses a filter residue dispersing agent for a blast furnace slag flushing system, and relates to the technical field of industrial wastewater treatment. The preparation raw materials comprise hexamethylenediamine tetra (methylene phosphonic acid), itaconic acid-maleic acid-allylsulfonic acid copolymer, sodium humate and sodium hydroxide. The preparation method comprises the following steps: dissolving sodium hydroxide in water to obtain liquid caustic soda; the preparation method comprises the following steps: putting hexamethylenediamine tetra (methylene phosphonic acid) into water, and dropwise adding liquid caustic soda to obtain a hexamethylenediamine tetra (methylene phosphonic acid) dissolving solution; dropwise adding liquid alkali into the itaconic acid-maleic acid-sodium allylsulfonate copolymer to obtain an itaconic acid-maleic acid-sodium allylsulfonate copolymer; dissolving sodium humate in water to obtain a sodium humate solution; and mixing and stirring the hexamethylenediamine tetra (methylene phosphonic acid) dissolving solution, the itaconic acid-maleic acid-sodium allylsulfonate copolymer and the sodium humate dissolving solution. According to the method, the phenomenon of filter layer hardening formed by salt precipitation in the blast furnace slag flushing water system can be effectively broken, and the slag filtering effect of the filter layer is recovered and maintained, so that stable operation of the blast furnace slag flushing water system is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of industrial wastewater treatment, in particular to a dispersant acting on filter slag of a blast furnace slag flushing system. Background Art

[0002] Steel companies generate large quantities of wastewater during their production processes. Directly discharging this wastewater without effective treatment can cause serious pollution to the surrounding aquatic environment. Against this backdrop, zero wastewater discharge has become an inevitable trend in the steel industry. Achieving zero wastewater discharge not only helps companies comply with environmental regulations but also reduces their reliance on external water resources, improving resource efficiency and sustainable development.

[0003] The steel production process generates a wide variety of wastewater types. Among these, high-concentration wastewater, such as reverse osmosis high-salt wastewater and wastewater from coking biochemical treatment, is characterized by high salt content and a strong tendency to corrosiveness. These wastewaters have complex compositions, containing large amounts of inorganic salts, organic matter, heavy metal ions, and other pollutants. Traditional wastewater treatment technologies struggle to treat them to reuseable standards, and the high cost of treatment results in low reuse value. To achieve zero wastewater discharge, steel companies typically dispose of these wastewaters during the steel production process. Common disposal methods include using them as blast furnace slag flushing water, steel slag soaking water, and sinter ore moisturizing water.

[0004] Among wastewater disposal methods such as blast furnace slag flushing, steel slag soaking, and sinter ore humidification, blast furnace slag flushing represents the largest wastewater disposal method for steel companies. Blast furnace slag flushing utilizes water to cool and granulate high-temperature blast furnace slag. Heat exchange between the slag flushing water and the blast furnace slag rapidly cools the blast furnace slag and forms a slag with a defined particle size, facilitating subsequent transportation and utilization. However, the blast furnace slag flushing process presents numerous technical challenges that severely impact the proper operation of the slag flushing water system.

[0005] For example, blast furnace slag flushing uses a dead-end water system. This means that the slag flushing water is circulated and reused, with no wastewater discharged except for a small amount of water carried away by the slag. Due to the extremely high temperature of blast furnace slag, typically reaching 1400-1600°C, the slag flushing water that comes into contact with it evaporates and is consumed in large quantities. To maintain the water balance in the slag flushing water system, new water must be continuously added. This new water is often highly salty. As this highly salty water circulates continuously, the salts gradually accumulate and concentrate within the system as they evaporate. When the salt concentration reaches a certain level, salts precipitate from the water and adhere to pipes, equipment, and filter surfaces, forming a scale layer. The formation of this scale layer causes the filter layer of the slag flushing water system to compact, reducing its porosity and partially losing its slag filtering function. This not only affects the water quality of the slag flushing water but also increases system resistance, reducing slag flushing efficiency. In severe cases, it can even cause blockage in the slag flushing water system, disrupting normal blast furnace operations.

[0006] Currently, steel companies have implemented measures to address the problem of filter layer compaction in blast furnace slag flushing systems, such as regular filter layer cleaning and filter media replacement. However, these methods have numerous limitations. Regular filter layer cleaning requires downtime, which can impact normal blast furnace production and increase production costs. Furthermore, the cleaning effect is often suboptimal, making it difficult to completely remove scale from the filter layer. Replacing filter media is costly, and frequent changes can also impact production continuity. Furthermore, some companies have attempted to use traditional water treatment agents to address filter layer compaction, but these agents are mostly designed for general water treatment systems and are not particularly effective in addressing filter layer compaction in the specialized operating conditions of blast furnace slag flushing. Some dispersants may not effectively penetrate the compacted filter layer, failing to break the bond between the scale layer and the filter media. Other dispersants may corrode the equipment and piping in the blast furnace slag flushing system, shortening the equipment's service life.

[0007] In summary, the development of a dispersant suitable for slag filter in blast furnace slag flushing system has important practical significance. Summary of the Invention

[0008] The purpose of the present invention is to provide a slag dispersant for a blast furnace slag flushing system. This dispersant can effectively break the filter layer compaction phenomenon formed by salt precipitation in the blast furnace slag flushing water system, restore and maintain the slag filtering effect of the filter layer, thereby ensuring the stable operation of the blast furnace slag flushing water system and helping steel enterprises achieve the goal of zero wastewater discharge.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is: The raw materials for its preparation include the following components: Hexamethylenediaminetetramethylenephosphonic acid, itaconic acid-maleic acid-propylene sulfonic acid copolymer, sodium humate and sodium hydroxide; The preparation method comprises the following steps: A. Preparation of liquid caustic soda: Dissolve sodium hydroxide in water to obtain liquid caustic soda, which is then set aside. B. Dissolving hexamethylenediaminetetramethylenephosphonic acid: first, put hexamethylenediaminetetramethylenephosphonic acid into water, and add dropwise the liquid caustic soda prepared in step A above under stirring conditions to dissolve all the hexamethylenediaminetetramethylenephosphonic acid in water to obtain a hexamethylenediaminetetramethylenephosphonic acid solution for standby use; C. Sodium alkalization of itaconic acid-maleic acid-propylene sulfonic acid copolymer: under stirring, the liquid caustic soda prepared in step A above was added dropwise to the itaconic acid-maleic acid-propylene sulfonic acid copolymer to alkalize it to obtain sodium itaconic acid-maleic acid-propylene sulfonate copolymer for later use; D. Dissolving sodium humate: dissolving sodium humate in water to obtain sodium humate solution for later use; E. Preparation: Mix and stir the hexamethylenediaminetetramethylenephosphonic acid solution prepared in step B, the itaconic acid-maleic acid-sodium propylene sulfonate copolymer prepared in step C, and the sodium humate solution prepared in step D.

[0010] In the above technical solution, a more specific technical solution may also be: the mass fraction of the liquid caustic soda is 30%.

[0011] Furthermore, the mass fraction of the hexamethylenediaminetetramethylenephosphonic acid solution is 50%.

[0012] Furthermore, the mass fraction of the sodium humate solution is 15%.

[0013] Furthermore, the specific method for dissolving hexamethylenediaminetetramethylenephosphonic acid in step B is as follows: First, add hexamethylenediaminetetramethylenephosphonic acid into water in portions, and then add the liquid alkali prepared in step A dropwise under stirring. The pH value of the solution is controlled at 10-10.5 to dissolve all the hexamethylenediaminetetramethylenephosphonic acid in water.

[0014] Furthermore, the specific method for alkalizing the itaconic acid-maleic acid-propylene sulfonic acid copolymer in step C is as follows: Under stirring conditions, the liquid alkali prepared in the above step A is added dropwise to the itaconic acid-maleic acid-propylene sulfonic acid copolymer, and the pH value thereof is adjusted to 10-11 for reaction to obtain the sodium alkalized itaconic acid-maleic acid-propylene sulfonate copolymer.

[0015] Furthermore, the specific method of preparing the step E is as follows: The hexamethylenediaminetetramethylenephosphonic acid solution prepared in step B, the itaconic acid-maleic acid-sodium propylene sulfonate copolymer prepared in step C and the sodium humate solution prepared in step D are mixed and stirred at 40° C. to 50° C. for 30 to 60 minutes.

[0016] Furthermore, in the preparation of step E, by weight, the hexamethylenediaminetetramethylenephosphonic acid solution prepared in step B is 40 parts, the itaconic acid-maleic acid-sodium propylene sulfonate copolymer prepared in step C is 32 parts, and the sodium humate solution prepared in step D is 28 parts.

[0017] Due to the adoption of the above technical solution, the present invention has the following beneficial effects compared with the prior art: The present invention has analyzed the test data of blast furnace slag and slabs of several steel mills, and the analysis is as follows: 1) The crust is mainly composed of sulfate and sulfite; 2) Some steel mills have experienced a certain amount of burn-off of compacted materials. Analysis suggests that this is due to the presence of coking wastewater in the blast furnace slag flushing system feed water, causing organic matter to gel at high temperatures and form compacted materials. 3) Some steel mills have calcium fluoride and other aggregates in their aggregates.

[0018] The above values ​​show that sulfate and sulfite together account for more than 50% of the scale. Therefore, solving the problem of sulfate and sulfite scaling can greatly alleviate the problem of filter layer compaction in blast furnace slag flushing systems.

[0019] To this end, the present invention determines the dispersant composition by accurately analyzing the scaling factors of blast furnace slag flushing water. The phenomenon of caking and scaling of blast furnace slag flushing water is mainly attributed to the precipitation of substances such as sulfates and sulfites in the water. Therefore, alleviating sulfate scaling becomes the key to solving the problem of filter layer caking. The dispersant components used in the present invention each have unique advantages and significant synergistic effects. Hexamethylenediaminetetramethylenephosphonic acid and sodium itaconic acid-maleic acid-propylene sulfonate are alkalized by sodium hydroxide to form a co-salt. This co-salt structure cleverly combines scale inhibition efficiency and dispersing effect. Compared with the use of each component alone, its efficiency is improved by more than 20%. Combined with sodium humate with excellent temperature resistance, the three work synergistically to significantly alleviate the problem of filter layer caking of slag flushing water, ensure the stable operation of the blast furnace slag flushing water system, and provide strong support for steel enterprises to achieve the goal of zero wastewater discharge. Among them, hexamethylenediaminetetramethylenephosphonic acid exhibits excellent temperature resistance. It can cleverly occupy the high potential energy points of scale microcrystals, effectively prevent the growth of sulfate crystals, and prevent sulfate precipitation from forming scale bodies from the root, providing a strong guarantee for solving the scaling problem; itaconic acid-maleic acid-propylene sulfonic acid, as a high-molecular organic dispersant, has a unique long-chain molecular structure with abundant active groups distributed on its molecular chain. These active groups can adsorb microcrystalline scale particles, reduce the packing density of scale, make the scale structure loose, and difficult to form a hard scale layer, thereby effectively alleviating the problem of filter layer compaction; sodium humate, as a traditional dispersant, has good temperature resistance. It is not only not easy to pyrolyze, but also can maintain good dispersion effect in a high temperature environment of 100°C. It will not pyrolyze even at an extremely high temperature of 800°C. This excellent temperature resistance enables it to function stably in high-temperature environments such as blast furnace slag flushing. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with examples; Among them, the raw material components used in the following examples: Hexamethylenediaminetetramethylenephosphonic acid: white crystalline powder, chemical formula C 10 H 28 N2O 12 P4; Itaconic acid-maleic acid-propylene sulfonic acid copolymer: yellow liquid, general structural formula [C5H6O4-C4H4O4-C3H5SO3]n; Sodium humate: black shiny particles, molecular formula R-(COONa)n, molecular weight 2000~50000; Sodium hydroxide: white flaky solid, chemical formula NaOH.

[0021] Example - A slag dispersant for blast furnace slag flushing system The raw materials for its preparation include the following components: Hexamethylenediaminetetramethylenephosphonic acid, itaconic acid-maleic acid-propylene sulfonic acid copolymer, sodium humate and sodium hydroxide; The preparation method comprises the following steps: A. Preparation of liquid caustic soda: Dissolve 30 parts of sodium hydroxide in 70 parts of water to obtain a 30% liquid caustic soda by weight, and set aside. B. Dissolving hexamethylenediaminetetramethylenephosphonic acid: First, by weight, add 50 parts of hexamethylenediaminetetramethylenephosphonic acid into water in portions, and add the liquid caustic soda prepared in step A above dropwise under stirring. Control the pH value of the solution to 10-10.5 until the hexamethylenediaminetetramethylenephosphonic acid is completely dissolved in the water. Add water to make up the total solution volume to 100 parts, and the mass fraction of the hexamethylenediaminetetramethylenephosphonic acid solution is 50%, and set aside. C. Sodium alkalization of itaconic acid-maleic acid-propylene sulfonic acid copolymer: under stirring, the liquid caustic soda prepared in step A above was added dropwise to the itaconic acid-maleic acid-propylene sulfonic acid copolymer, and the pH value thereof was adjusted to 10-11 to alkalize the itaconic acid-maleic acid-propylene sulfonic acid copolymer to obtain sodium itaconic acid-maleic acid-propylene sulfonate copolymer, which was set aside; D. Dissolving sodium humate: Dissolve 15 parts of sodium humate in 85 parts of water to obtain a sodium humate solution with a mass fraction of 15%, and set aside. E. Preparation: Mix 40 parts by weight of the hexamethylenediaminetetramethylenephosphonic acid solution prepared in step B above, 32 parts of the itaconic acid-maleic acid-sodium propylene sulfonate copolymer prepared in step C, and 28 parts of the sodium humate solution prepared in step D, and stir at 40°C to 50°C for 30 to 60 minutes to ensure uniform mixing.

[0022] Implementation effect: Application case of a 2000m³ blast furnace: The filter layer hardening period was extended from 14 days to 87 days; The pressure difference of the slag flushing water system was reduced by 39% (from 1.8MPa→1.1MPa).

[0023] Table 1 Analysis of the composition of filter residue agglomerates (comparison before and after application of the present invention) .

[0024] Note: 1) The compacted material before use is the compacted material collected after the slag flushing water system has been running for 14 days without adding dispersant. The compacted material after use is the compacted material collected after the slag flushing water system has been running for 87 days with the dispersant of the present invention added.

[0025] 2) Other components are mainly blast furnace slag components.

[0026] Table 2 Comparison of water treatment agent performance .

[0027] Note: In Table 2 above, commercially available product A is Nalco OSM60 scale inhibitor from the United States; commercially available product B is Ciba EFKA® HPMA, a high-efficiency scale inhibitor under BASF (formerly Ciba) - hydrolyzed polymaleic anhydride (HPMA).

[0028] The above tests refer to: HG / T4541-2013 "Determination of scale inhibition performance of water treatment agents - Limiting carbonate method"; GB / T16632-2019 "Determination of scale inhibition performance of water treatment agents - Calcium carbonate deposition method".

[0029] From the above test results, we can see that: ① After using the present invention, the amount of compacted matter remaining on the filter layer of the slag flushing water system is significantly reduced, proving that the present invention can effectively break the compaction phenomenon of the filter layer formed by salt precipitation in the blast furnace slag flushing water system.

[0030] ② After using the present invention, the proportion of sulfate, fluoride and organic matter with high viscosity in the compacted material is greatly reduced.

[0031] ③ Compared with existing water treatment agents, the present invention has an excellent dispersing effect, which can effectively prevent substances such as sulfates and sulfites from precipitating from the blast furnace slag flushing water system and prevent the occurrence of calcification of the filter layer of the blast furnace slag flushing water system.

[0032] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A slag dispersant for a blast furnace slag flushing system, characterized by: The raw materials for its preparation include the following components: Hexamethylenediaminetetramethylenephosphonic acid, itaconic acid-maleic acid-propylene sulfonic acid copolymer, sodium humate and sodium hydroxide; The preparation method comprises the following steps: A. Preparation of liquid caustic soda: Dissolve sodium hydroxide in water to obtain liquid caustic soda, which is then set aside. B. Dissolving hexamethylenediaminetetramethylenephosphonic acid: first, put hexamethylenediaminetetramethylenephosphonic acid into water, and add dropwise the liquid caustic soda prepared in step A above under stirring conditions to dissolve all the hexamethylenediaminetetramethylenephosphonic acid in water to obtain a hexamethylenediaminetetramethylenephosphonic acid solution for standby use; C. Sodium alkalization of itaconic acid-maleic acid-propylene sulfonic acid copolymer: under stirring, the liquid caustic soda prepared in step A above was added dropwise to the itaconic acid-maleic acid-propylene sulfonic acid copolymer to alkalize it to obtain sodium itaconic acid-maleic acid-propylene sulfonate copolymer for later use; D. Dissolving sodium humate: dissolving sodium humate in water to obtain sodium humate solution for later use; E. Preparation: Mix and stir the hexamethylenediaminetetramethylenephosphonic acid solution prepared in step B, the itaconic acid-maleic acid-sodium propylene sulfonate copolymer prepared in step C, and the sodium humate solution prepared in step D.

2. The slag dispersant for blast furnace slag flushing system according to claim 1, characterized in that: The mass fraction of the liquid caustic soda is 30%.

3. The slag dispersant for blast furnace slag flushing system according to claim 2, characterized in that: The mass fraction of the hexamethylenediaminetetramethylenephosphonic acid solution is 50%.

4. The slag dispersant for blast furnace slag flushing system according to claim 3, characterized in that: The mass fraction of the sodium humate solution is 15%.

5. The slag dispersant for blast furnace slag flushing system according to claim 1, 2, 3 or 4, characterized in that The specific method of dissolving hexamethylenediaminetetramethylenephosphonic acid in step B is as follows: First, add hexamethylenediaminetetramethylenephosphonic acid into water in portions, and then add the liquid alkali prepared in step A dropwise under stirring. The pH value of the solution is controlled at 10-10.5 to dissolve all the hexamethylenediaminetetramethylenephosphonic acid in water.

6. The slag dispersant for blast furnace slag flushing system according to claim 5, characterized in that The specific method for alkalizing the itaconic acid-maleic acid-propylene sulfonic acid copolymer in step C is as follows: Under stirring conditions, the liquid alkali prepared in the above step A is added dropwise to the itaconic acid-maleic acid-propylene sulfonic acid copolymer, and the pH value thereof is adjusted to 10-11 for reaction to obtain the sodium alkalized itaconic acid-maleic acid-propylene sulfonate copolymer.

7. The slag dispersant for blast furnace slag flushing system according to claim 6, characterized in that The specific method of the preparation in step E is as follows: The hexamethylenediaminetetramethylenephosphonic acid solution prepared in step B, the itaconic acid-maleic acid-sodium propylene sulfonate copolymer prepared in step C and the sodium humate solution prepared in step D are mixed and stirred at 40° C. to 50° C. for 30 to 60 minutes.

8. The slag dispersant for blast furnace slag flushing system according to claim 7, characterized in that: In the preparation of step E, by weight, the hexamethylenediaminetetramethylenephosphonic acid solution prepared in step B is 40 parts, the itaconic acid-maleic acid-sodium propylene sulfonate copolymer prepared in step C is 32 parts, and the sodium humate solution prepared in step D is 28 parts.