A scale inhibitor and dispersant suitable for ultra-high hardness coal gasification ash water and its preparation method

Abstract

The present invention relates to the field of scale inhibitors and dispersants for coal gasification ash water, and more specifically, to a scale inhibitor and dispersant suitable for ultra-high hardness coal gasification ash water. The raw materials of the scale inhibitor and dispersant are calculated by weight percentage, including: 10% to 20% acrylic acid-maleic acid-phosphine copolymer, 35% to 40% phosphine-based sodium polyacrylate, 10% to 20% poly-2-acrylamide-2-methylpropanesulfonate sodium, calculated as 100%, and the rest is deionized water. The patent of the present invention is aimed at ultra-high hardness coal gasification ash water using coal with ultra-high calcium and magnesium ion content as raw material, when the total hardness of the ash water reaches 2400 mg / L or more (calculated as calcium carbonate). The scale inhibitor and dispersant prepared by the present invention can effectively inhibit the scaling of calcium carbonate, calcium sulfate, calcium silicate, etc. in the ash water system to ensure the normal, stable and long-term operation of the ash water system.

Description

Technical Field

[0001] The present invention relates to the technical field of scale inhibitors and dispersants for coal gasification ash water, and more particularly to a scale inhibitor and dispersant suitable for ultra-high hardness coal gasification ash water and a preparation method thereof. Background Art

[0002] Coal gasification is the process in which a water-coal slurry reacts with oxygen in a series of chemical reactions within a gasifier under specific temperature and pressure conditions, converting the solid coal into combustible gases such as CO, H2, and CH4, and non-combustible gases such as CO2. During this process, a large amount of gasification ash water is discharged from the bottom of the gasifier and scrubber. For environmental and economic reasons, this ash water must be recycled. However, due to the wide temperature and pressure range (50-300°C, 1-6 MPa) within the ash water recycling system, operating conditions are complex. As the ash water is continuously reused and concentrated, its hardness, alkalinity, and suspended solids content increase (total hardness around 1000 mg / L), necessitating the addition of scale inhibitors and dispersants to ensure the proper operation of the gasification system.

[0003] The hardness of graywater originates partially from the graywater itself, but most comes from the process medium, coal. When using coal with extremely high calcium and magnesium ion content as raw material, due to the acidic environment of the gasifier, a large amount of calcium and magnesium ions dissolve from the process medium into the graywater, causing the total hardness of the graywater to reach over 2400 mg / L (calculated as calcium carbonate), which is considered ultra-high hardness graywater. At the same time, due to environmental concerns, the hardness cannot be reduced by increasing drainage, which greatly increases the risk of scaling in the system. At this time, ordinary scale inhibitors and dispersants are no longer sufficient for production needs. A more effective scale inhibitor and dispersant is needed for ultra-high hardness graywater from coal gasification to ensure the normal, stable, and long-term operation of the graywater system. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one aspect of the present invention is to provide a scale inhibitor and dispersant suitable for ultra-high hardness coal gasification ash water, which is applied to the coal gasification ash water system. The raw materials of the scale inhibitor and dispersant are calculated in weight percentage and include: 10% to 20% acrylic acid-maleic acid-phosphine copolymer, 35% to 40% phosphine-based sodium polyacrylate, 10% to 20% poly 2-acrylamido-2-methylpropane sulfonate sodium, and the rest is deionized water.

[0005] Preferably, the relative molecular weight of the phosphino sodium polyacrylate is 3000.

[0006] Preferably, the mass ratio of the monomers in the phosphine-based sodium polyacrylate is 7:1, acrylic acid: sodium hypophosphite.

[0007] Preferably, the mass ratio of the monomers in the acrylic acid-maleic acid-phosphine copolymer is 3:3:1 of acrylic acid:maleic acid:sodium hypophosphite.

[0008] Preferably, the scale inhibitor and dispersant is suitable for gray water with a total hardness of 2400 mg / L or above, and effectively inhibits the scaling of calcium carbonate, calcium sulfate and calcium silicate.

[0009] Acrylic acid-maleic acid-phosphine copolymer is produced through the copolymerization of acrylic acid, maleic anhydride, and sodium hypophosphite. It exhibits excellent calcium carbonate and calcium phosphate scale resistance and is particularly suitable for water with high temperatures, high hardness, high pH, ​​high alkalinity, and high turbidity. Containing carboxylic acid and phosphonic acid groups, it combines the strong chelation of organic phosphonic acid with the high dispersibility of carboxylic acid polymers, allowing for use in harsh conditions such as temperatures of 300°C. It exhibits a significant solubility limit at 300°C and high pH.

[0010] Phosphino sodium polyacrylate contains phosphonic acid subunits and carboxyl groups, combining the scale inhibition properties of organic phosphonic acid and polycarboxylic acid. Compared to acrylic acid homopolymers, its most significant advantage is the addition of phosphonic acid groups to the molecule, resulting in a low-molecular-weight electrolyte with excellent stability and integration. The addition of phosphonic acid subunits enhances the polymer's high dispersibility with the strong chelation of organic phosphonic acid, increasing its ability to distort calcium carbonate crystals and improving its temperature resistance. Its scale and temperature resistance are significantly superior to those of acrylic acid homopolymers alone.

[0011] Sodium poly (2-acrylamido-2-methylpropanesulfonate) is produced by the free radical homopolymerization of 2-acrylamido-2-methylpropanesulfonic acid. It effectively inhibits calcium carbonate and calcium sulfate scales and is a sulfonic acid-based scale inhibitor and dispersant. It contains two active groups, sulfonic acid and amide groups. It exhibits synergistic effects when combined with acrylic acid-maleic acid-phosphine copolymer and phosphine-based sodium polyacrylate. The sulfonic acid group further enhances the polymer's water solubility, allowing the molecular chain to fully extend in water, improving its permeability and electrostatic attraction, and endowing the macromolecule with the ability to disperse dirt particles and dissolve insoluble salts. The amide group imparts excellent hydrolytic stability, acid and alkali resistance, and thermal stability, making it suitable for use as a scale inhibitor in water with high hardness and a wide pH range.

[0012] Another aspect of the present invention is to provide a method for preparing a scale inhibitor and dispersant suitable for ultra-high hardness coal gasification ash water. The preparation method comprises weighing phosphine-based sodium polyacrylate, acrylic acid-maleic acid-phosphine-based copolymer, poly (2-acrylamide-2-methylpropanesulfonic acid) sodium and a solvent, and sequentially adding them to a stirring device for stirring and mixing. The finished product is obtained after stirring is completed.

[0013] Preferably, the stirring is completed at normal temperature and pressure, and the stirring time is 2 hours.

[0014] The beneficial effects of the present invention are as follows:

[0015] This patent is aimed at ultra-high hardness coal gasification ash water using coal with ultra-high calcium and magnesium ion content as raw material, with a total hardness of ash water reaching above 2400 mg / L (calculated as calcium carbonate). The scale inhibitor dispersant prepared by this invention can effectively inhibit the scaling of calcium carbonate, calcium sulfate, calcium silicate, etc. in the ash water system to ensure the normal, stable and long-term operation of the ash water system.

[0016] Compared to acrylic acid-maleic acid copolymers and acrylic acid homopolymers, the patented raw materials of this invention, acrylic acid-maleic acid-phosphino copolymers and sodium phosphino polyacrylate, have the greatest advantage of having additional phosphonic acid groups in the molecule. The addition of phosphonic acid subunits enhances the polymer's high dispersibility with the strong chelation of organic phosphonic acid, increasing its ability to distort the calcium carbonate lattice and improving its temperature resistance. Their anti-scaling and temperature resistance are significantly superior to those of acrylic acid-maleic acid copolymers and acrylic acid homopolymers. Sodium poly (2-acrylamido-2-methylpropanesulfonate) is produced by the free radical homopolymerization of 2-acrylamido-2-methylpropanesulfonic acid, without the involvement of carboxylic acid. Compared to an equivalent amount of carboxylic acid-2-acrylamido-2-methylpropanesulfonic acid copolymer, it possesses a greater number of both sulfonic acid and amide groups, increasing the hydrolytic and thermal stability of the scale inhibitor and dispersant, and improving its ability to disperse scale and dissolve insoluble salts.

[0017] Additional aspects and advantages of the invention will become apparent from the description which follows, or may be learned by practice of the invention. DETAILED DESCRIPTION

[0018] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0019] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from the description. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0020] Example 1

[0021] Weigh 15 kg of acrylic acid-maleic acid-phosphine copolymer, 35 kg of phosphine-based sodium polyacrylate, 20 kg of poly (2-acrylamido-2-methylpropanesulfonate), and 30 kg of deionized water, add the materials into a stirring device in sequence, and stir for 2 hours under normal pressure and room temperature. The finished product is obtained after stirring is completed.

[0022] Example 2

[0023] Weigh 20 kg of acrylic acid-maleic acid-phosphine copolymer, 35 kg of phosphine-based sodium polyacrylate, 15 kg of poly (2-acrylamido-2-methylpropanesulfonate), and 30 kg of deionized water, add the materials into a stirring device in sequence, and stir under normal pressure and room temperature for 2 hours. The finished product is obtained after stirring is completed.

[0024] Example 3

[0025] Weigh 20 kg of acrylic acid-maleic acid-phosphine copolymer, 40 kg of phosphine-based sodium polyacrylate, 10 kg of poly (2-acrylamido-2-methylpropanesulfonate), and 30 kg of deionized water, add the materials into a stirring device in sequence, and stir for 2 hours under normal pressure and room temperature. The finished product is obtained after stirring is completed.

[0026] Example 4

[0027] Weigh 10 kg of acrylic acid-maleic acid-phosphine copolymer, 40 kg of phosphine-based sodium polyacrylate, 20 kg of poly (2-acrylamido-2-methylpropanesulfonate), and 30 kg of deionized water, add the materials into a stirring device in sequence, and stir for 2 hours under normal pressure and room temperature. The finished product is obtained after stirring is completed.

[0028] Comparative Example was prepared according to the formula of commercially available ash water dispersant

[0029] Comparative Example 1

[0030] Weigh 20 kg of 2-phosphonobutane-1,2,4-tricarboxylic acid, 20 kg of phosphonocarboxylic acid copolymer, 20 kg of hydrolyzed polymaleic anhydride, 10 kg of acrylic acid-hydroxypropyl acrylate copolymer, and 30 kg of deionized water, add the materials into a stirring device in sequence, and stir at normal pressure and room temperature for 2 hours. The finished product is obtained after stirring is completed.

[0031] Comparative Example 2

[0032] Weigh 20 kg of polyepoxysuccinic acid, 20 kg of polyacrylic acid, 20 kg of maleic acid-acrylic acid copolymer, 10 kg of acrylic acid-acrylate-2-acrylamido-2-methylpropanesulfonic acid polymer, and 30 kg of deionized water, add the materials into a stirring device in sequence, and stir at normal pressure and room temperature for 2 hours. The finished product is obtained after stirring is completed.

[0033] Comparative Example 3

[0034] Weigh 20 kg of hydroxyethylidene diphosphonic acid, 25 kg of 2-phosphonobutane-1,2,4-tricarboxylic acid, 25 kg of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid polymer, and 30 kg of deionized water, add the materials into a stirring device in sequence, and stir at normal pressure and room temperature for 2 hours to obtain the finished product.

[0035] Compare Examples 1 to 4 with Comparative Examples 1 to 3

[0036] According to coal gasification ash water operating requirements, the scale inhibitor and dispersant must remain in the system at approximately 300°C for approximately 30 minutes, so the agent must have good thermal stability. One kilogram of the scale inhibitor and dispersant stock solution from the above test example was added to a 2-liter autoclave. The system was maintained at 6.5 MPa and 350°C for 30 minutes. After cooling to room temperature, the physical and chemical properties of the scale inhibitor and dispersant before and after the test were compared and analyzed. The results are shown in Table 1 below.

[0037] Table 1. Comparison of physical and chemical indicators of scale inhibitors and dispersants

[0038] The results show that the physical and chemical indicators of Examples 1 to 4, Comparative Examples 1 and 2 did not show significant changes, and had good thermal stability. Comparative Example 3 had the greatest changes in appearance, solid content, pH, and density after the test.

[0039] The ash water from the coal gasification system of a Shaanxi Energy Company was collected and its water quality was analyzed. The results are shown in Table 2 below.

[0040] Table 2. Greywater quality analysis results

[0041] Scale inhibitors and dispersants must not only exhibit good thermal stability but, more importantly, possess excellent scale inhibition and dispersancy properties to ensure stable operation of the graywater system and extend the operating cycle of the gasification unit. Based on the graywater's characteristics of high temperature, high hardness, high pH, ​​high alkalinity, and high turbidity, high-pressure equipment was used to conduct scale inhibition and dispersancy tests on graywater samples. Test conditions: Scale inhibitor and dispersant dosages of 80ppm and 120ppm were applied. The temperature was raised to 300°C, the pressure was 6.5MPa, and the sample was allowed to stand for two hours. After cooling to room temperature, the total hardness and turbidity were measured, and the scale inhibition and dispersancy rates were calculated.

[0042] The scale inhibition performance is measured in η and the value is expressed in %. :

[0043] Where: ρ4 is the total hardness value of the test solution after the addition of water treatment agent, the unit is (mg / L); ρ3 is the total hardness value of the blank test solution after the test without the addition of water treatment agent, the unit is (mg / L); ρ is the total hardness value of the water in the actual working conditions, the unit is (mg / L).

[0044] Where: NTU2 is the turbidity value after the test solution with the water treatment agent added, the unit is (NTU); NTU1 is the turbidity value of the actual working water, the unit is (NTU).

[0045] The test results of the scale inhibition and dispersion performance of the agent when the dosage is 80ppm are shown in Table 3 below.

[0046] Table 3. Scale inhibition and dispersion performance test results

[0047] The scale inhibition and dispersion performance test results of the agent when the dosage is 120ppm are shown in Table 4 below.

[0048] Table 4. Scale inhibition and dispersion performance test results

[0049] The above experiments show that the present invention has good scale inhibition performance and dispersion effect. The ash water scale inhibitor dispersant prepared in Examples 1 to 4 can be applied to coal gasification ultra-high hardness ash water to ensure normal, stable and long-term operation of the ash water system.

[0050] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A scale inhibitor and dispersant suitable for ultra-high hardness coal gasification ash water, characterized by: The raw materials of the scale inhibitor and dispersant include, by weight percentage, 10% to 20% acrylic acid-maleic acid-phosphine copolymer, 35% to 40% phosphine-based sodium polyacrylate, and 10% to 20% poly (2-acrylamido-2-methylpropanesulfonate) sodium, with the remainder being deionized water. The mass ratio of the monomers in the phosphine-based sodium polyacrylate is 7:

1.

2. The scale inhibitor and dispersant suitable for ultra-high hardness coal gasification ash water according to claim 1, characterized in that: The mass ratio of the monomers in the acrylic acid-maleic acid-phosphine copolymer is 3:3:1, acrylic acid:maleic acid:sodium hypophosphite.

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