Neutral descaling decoking agent for boiler of sugar refinery and preparation method of neutral descaling decoking agent

Abstract

The invention discloses a neutral descaling and decoking agent for a boiler of a sugar refinery and a preparation method of the neutral descaling and decoking agent, and belongs to the technical field of descaling and decoking agents. The neutral descaling decoking agent is prepared from 5 to 15 parts of permeation activation component, 2 to 4 parts of butyl cellosolve, 5 to 10 parts of mild oxidant, 10 to 15 parts of sodium glucoheptonate, 8 to 10 parts of etidronic acid, 0.5 to 5 parts of phosphorylated vegetable tannin, 1 to 3 parts of sodium polyacrylate, 1 to 2 parts of borax, 1 to 3 parts of sodium citrate and 30 to 50 parts of deionized water. According to the neutral descaling decoking agent provided by the invention, the phosphorylated vegetable tannin is introduced as a key synergistic bridging component and forms a synergistic system with the glycosyl penetrant, the mild oxidizing agent and the multi-element chelating agent, and the neutral descaling decoking agent can be used for descaling and decoking under a neutral condition. The special inorganic salt-silicate-biomass tar multi-component composite scale layer of the boiler of the sugar refinery is efficiently and safely removed, the scale removal efficiency is obviously superior to that of a traditional cleaning agent, meanwhile, the corrosion rate in the whole process is extremely low, and the industrial problem that efficient cleaning and equipment safety are difficult to consider at the same time is solved.

Description

Technical Field

[0001] This invention belongs to the technical field of descaling and slag removal agents, specifically relating to a neutral descaling and slag removal agent for sugar factory boilers and its preparation method. Background Technology

[0002] Scale and char buildup on boiler heating surfaces is a common and serious problem affecting thermal efficiency and operational safety during boiler operation. For boilers in the sugar industry, which extensively use biomass such as bagasse as fuel, the scale problem is particularly complex and persistent. This type of scale is not a single component but a typical "quaternary composite scale," consisting of: scale formed by inorganic salts from fuel and water; hard silicate scale formed by elements such as silicon and magnesium at high temperatures; viscous biomass tar produced by incompletely burned bagasse; and carbon black formed by carbonization. This complex scale layer, with its interwoven organic and inorganic components and extremely strong adhesion, leads to a significant decrease in boiler heat transfer efficiency, increased fuel consumption, and even safety accidents such as localized overheating and tube rupture.

[0003] Currently, the main technical methods for boiler cleaning can be divided into two categories: strong chemical cleaning and neutral / weak chemical cleaning. Strong chemical cleaning, such as cleaning with hydrochloric acid, nitric acid, and citric acid, while rapidly dissolving some inorganic scale, has significant inherent drawbacks: the acidic media are highly corrosive to the boiler's metal structure, and even with the addition of corrosion inhibitors, risks such as hydrogen embrittlement and pitting corrosion remain. The cleaning process requires shutdown, and wastewater treatment is complex and environmentally challenging. More importantly, strong acids have very weak dissolving power for silicate scale and are almost ineffective against biomass organic tar. Neutral or weakly alkaline chemical cleaning, on the other hand, has gained attention due to its low corrosivity and high operational safety. Common products on the market are often formulated with organophosphonates, polymer dispersants, and small amounts of surfactants. However, these general-purpose neutral cleaning agents exhibit significant limitations when dealing with the special complex scale found in sugar mill boilers: their formulations are often designed for common scale, lacking effective penetrating, emulsifying, and chemically converting components for biomass tar, and also failing to effectively break down and disperse the hard silicate scale network structure. The result is incomplete cleaning, long cleaning cycles, and often no solution for tightly adhered organic / inorganic mixed layers.

[0004] Therefore, there is an urgent need in this field to develop a new type of cleaning agent that maintains an absolutely neutral working pH value, ensures zero risk of corrosion to boiler equipment, and can effectively remove different types of dirt components such as inorganic salt scale, silica scale, organic tar and carbon black. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a neutral descaling and slag-removing agent for sugar factory boilers and its preparation method. The neutral descaling and slag-removing agent of this invention has both extremely low corrosion rate and good cleaning effect.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a neutral descaling and slag-removing agent for sugar factory boilers, comprising the following components in parts by weight: 5-15 parts of penetrating activating component, 2-4 parts of ethylene glycol butyl ether, 5-10 parts of mild oxidant, 10-15 parts of sodium gluconate, 8-10 parts of hydroxyethylidene diphosphonic acid, 0.5-5 parts of phosphonyl tannin, 1-3 parts of sodium polyacrylate, 1-2 parts of borax, 1-3 parts of sodium citrate, and 30-50 parts of deionized water.

[0007] Preferably, the permeation activation component includes one or more of alkyl polyglucosides, fatty acid glucamides, and sucrose esters.

[0008] In this invention, the molecular structure of the alkyl polyglucoside glycoside surfactant exhibits "like dissolves like" properties with the residual sugar derivatives in bagasse tar, enabling it to preferentially wet and penetrate deep into the hydrophobic tar layer. Ethylene glycol butyl ether, as a highly efficient solvent and penetration aid, further reduces the surface tension of the system, synergistically promoting the penetration of the cleaning solution into the gaps of the dense scale layer. This achieves deep wetting and deep penetration into the scale layer, especially the sticky organic tar layer, opening channels for subsequent reactions.

[0009] Preferably, the mild oxidant includes one or more of sodium percarbonate, sodium peracetate, and sodium perborate. In this invention, the mild oxidant slowly releases active oxygen in a neutral aqueous solution, which mildly oxidizes and breaks down the large molecules and viscous organic matter in biomass tar, reducing their molecular weight and adhesion, transforming them from a stubbornly adhered state into easily peelable fragments, while avoiding the corrosion of the metal matrix by strong oxidants.

[0010] Preferably, the method for preparing the phosphonylated plant tannin is as follows: Tannic acid and anhydrous pyridine were mixed and phosphorus oxychloride was added dropwise while stirring in an ice-water bath. After the addition was complete, the mixture was heated to reflux. After the reaction was completed, the reaction mixture was cooled to room temperature and poured into deionized water to collect the precipitate. The precipitate was then washed, filtered, and dried to obtain phosphonylated plant tannins.

[0011] Preferably, the mass ratio of tannic acid, anhydrous pyridine, and phosphorus oxychloride is 100:20-30:40-60.

[0012] Preferably, the reflux reaction is carried out at a temperature of 50-60°C for 4-6 hours.

[0013] In this invention, sodium gluconate, with its multi-hydroxyl structure, exhibits a strong chelating effect on calcium, magnesium, and iron ions, and can specifically penetrate and insert into the network structure of silicate scale, causing it to swell and loosen. Hydroxyethylidene diphosphonic acid can efficiently chelate scale-causing metal ions and has excellent dispersion and scale-inhibiting capabilities for detached solid particles, preventing secondary deposition. Phosphonylated plant tannins, through chemical modification, introduce phosphonic acid groups onto natural tannin molecules, giving them both the affinity of tannins for biomass scale and the strong chelating power of organophosphonic acids for metal ions. These three components work synergistically to form a "loosening-chelating-dispersion" cleaning pathway, demonstrating excellent removal and inhibition effects, especially on silica and iron scale that are difficult to treat with conventional cleaning agents.

[0014] This invention provides a method for preparing the above-mentioned neutral descaling and descaling agent, comprising the following steps: Weigh the raw materials according to the stated mass ratio; Deionized water, permeation activation component, phosphonylated plant tannin, and ethylene glycol butyl ether are mixed evenly to obtain component A; Sodium gluconate, sodium citrate, and borax were mixed evenly and then slowly added to an aqueous solution of hydroxyethylidene diphosphonic acid and a sodium polyacrylate solution under stirring to obtain component B. Mix component A and component B evenly, then slowly add a mild oxidant and continue stirring until completely dissolved to obtain a neutral descaling and descaling agent.

[0015] It contains at least the following beneficial technical effects: This invention utilizes a penetrating and activating component in synergy with phosphonylated plant tannins. The network macromolecules of tannins act as carriers, helping other components to be more stably and deeply adsorbed and penetrate into the scale layer. Simultaneously, the penetrated, mild oxidant begins to break down and transform the tar. The phosphonylated plant tannins synergistically interact with the polyhydroxy groups of sodium gluconate, enhancing penetration and loosening of silica scale; their own phosphonic acid groups can also form a chelating network with hydroxyethylidene diphosphonic acid, thus improving the absorption and loosening of calcium carbonate. 2+ Mg 2+ Fe 3 + The capture capacity and stability of plasma far exceed those of single chelating agents. This invention significantly improves the removal efficiency of silica scale and organic coke specific to sugar factory boilers through the synergistic effect of phosphonylated plant tannins, sugar-based surfactants, and chelating agents, achieving highly efficient cleaning while ensuring zero corrosion to boiler metals throughout the entire process. Detailed Implementation

[0016] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0017] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0018] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0019] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0020] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0021] Unless otherwise specified, "room temperature" and "normal temperature" in this invention refer to 25±2℃.

[0022] Unless otherwise specified, all raw materials or instruments used in the following embodiments of the present invention are commercially available.

[0023] Example 1 In a four-necked flask equipped with a stirrer, thermometer, dropping funnel, and reflux condenser, 100 g of tannic acid and 25 g of anhydrous pyridine were added, and stirring was started to form a suspension. The system was cooled in an ice-water bath and maintained at 1 °C. 50 g of phosphorus oxychloride was slowly added dropwise over 2.5 hours with continuous stirring. After the addition was complete, the ice-water bath was removed, and the reaction system was slowly heated to 55 °C. The mixture was then stirred and refluxed at this temperature for 5 hours. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was slowly poured into 1.2 L of deionized water with stirring, resulting in a yellowish-brown precipitate. After standing, the supernatant was discarded, and the precipitate was filtered and washed with plenty of deionized water until the filtrate tested negative for chloride ions using silver nitrate. Finally, the precipitate was washed twice with a small amount of acetone and dried under vacuum at 55 °C for 10 hours to obtain a light yellowish-brown powder of phosphonylated plant tannin with a yield of 78%.

[0024] Weigh the raw materials according to the following parts by weight: 8 parts alkyl polyglucoside, 3 parts ethylene glycol butyl ether, 7 parts sodium percarbonate, 12 parts sodium gluconate, 14.2 parts hydroxyethylidene diphosphonic acid, 2 parts phosphonyl tannin, 5 parts sodium polyacrylate, 1.5 parts borax, 2 parts sodium citrate, and 40 parts deionized water.

[0025] The preparation steps are as follows: (1) Mix deionized water, alkyl polyglucoside, phosphonylated plant tannin, and ethylene glycol butyl ether in a stirred tank and stir for 30 minutes until completely dissolved and homogeneous to obtain component A.

[0026] (2) Mix sodium gluconate, sodium citrate and borax, and slowly add aqueous solution of hydroxyethylidene diphosphonic acid and sodium polyacrylate solution while stirring. Stir until completely dissolved to obtain clear component B.

[0027] (3) Add component B to component A under stirring. After mixing evenly, control the system temperature below 35°C, slowly add sodium percarbonate solid, and continue stirring for 60 minutes until all solids are completely dissolved to obtain a light amber transparent liquid product with a pH value of 7.1.

[0028] Example 2 In a four-necked flask equipped with a stirrer, thermometer, dropping funnel, and reflux condenser, 100 g of tannic acid and 20 g of anhydrous pyridine were added, and stirring was started to form a suspension. The system was cooled in an ice-water bath and maintained at 3 °C. Under continuous stirring, 40 g of phosphorus oxychloride was slowly added dropwise over 2.5 hours. After the addition was complete, the ice-water bath was removed, and the reaction system was slowly heated to 50 °C. The reaction was then stirred and refluxed at this temperature for 5 hours. After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was slowly poured into 1.2 L of deionized water under stirring, resulting in a yellowish-brown precipitate. After standing, the supernatant was discarded, the precipitate was filtered, and washed with plenty of deionized water until the filtrate was free of chloride ions when tested with silver nitrate. Finally, the mixture was washed twice with a small amount of acetone and dried under vacuum at 55 °C for 10 hours to obtain a light yellowish-brown powder of phosphonylated plant tannin with a yield of 73%.

[0029] Weigh the raw materials according to the following parts by weight: 5 parts fatty acid glucamide, 3 parts sucrose ester, 3.5 parts ethylene glycol butyl ether, 8 parts sodium peracetate, 10 parts sodium gluconate, 15 parts hydroxyethylidene diphosphonic acid, 1 part phosphonyl tannin, 3.75 parts sodium polyacrylate, 1.2 parts borax, 2.5 parts sodium citrate, and 45 parts deionized water.

[0030] The preparation steps are as follows: (1) Mix deionized water, alkyl polyglucoside, phosphonylated plant tannin, and ethylene glycol butyl ether in a stirred tank and stir for 30 minutes until completely dissolved and homogeneous to obtain component A.

[0031] (2) Mix sodium gluconate, sodium citrate and borax, and slowly add aqueous solution of hydroxyethylidene diphosphonic acid and sodium polyacrylate solution while stirring. Stir until completely dissolved to obtain clear component B.

[0032] (3) Add component B to component A under stirring. After mixing evenly, control the system temperature below 35°C, slowly add sodium percarbonate solid, and continue stirring for 60 minutes until all solids are completely dissolved to obtain a light amber transparent liquid product with a pH value of 7.2.

[0033] Example 3 In a four-necked flask equipped with a stirrer, thermometer, dropping funnel, and reflux condenser, 100 g of tannic acid and 30 g of anhydrous pyridine were added, and stirring was started to form a suspension. The system was cooled in an ice-water bath and maintained at 3 °C. 60 g of phosphorus oxychloride was slowly added dropwise over 2.5 hours with continuous stirring. After the addition was complete, the ice-water bath was removed, and the reaction system was slowly heated to 60 °C. The mixture was then stirred and refluxed at this temperature for 6 hours. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was slowly poured into 1.2 L of deionized water with stirring, resulting in a yellowish-brown precipitate. After standing, the supernatant was discarded, and the precipitate was filtered and washed with plenty of deionized water until the filtrate tested negative for chloride ions using silver nitrate. Finally, the precipitate was washed twice with a small amount of acetone and dried under vacuum at 55 °C for 10 hours to obtain a light yellowish-brown powder of phosphonylated plant tannin with a yield of 70%.

[0034] Weigh the raw materials according to the following parts by weight: 10 parts alkyl polyglucoside, 2.5 parts ethylene glycol butyl ether, 6 parts sodium percarbonate and sodium perborate mixed in a 1:1 mass ratio, 14 parts sodium gluconate, 15.8 parts hydroxyethylidene diphosphonic acid, 3.5 parts high phosphorylation degree phosphonyl tannin, 6.25 parts sodium polyacrylate, 1.8 parts borax, 1.5 parts sodium citrate, and 35 parts deionized water.

[0035] The preparation steps are as follows: (1) Mix deionized water, alkyl polyglucoside, phosphonylated plant tannin, and ethylene glycol butyl ether in a stirred tank and stir for 30 minutes until completely dissolved and homogeneous to obtain component A.

[0036] (2) Mix sodium gluconate, sodium citrate and borax, and slowly add aqueous solution of hydroxyethylidene diphosphonic acid and sodium polyacrylate solution while stirring. Stir until completely dissolved to obtain clear component B.

[0037] (3) Add component B to component A under stirring. After mixing evenly, control the system temperature below 35°C, slowly add sodium percarbonate solid, and continue stirring for 60 minutes until all solids are completely dissolved to obtain a light amber transparent liquid product with a pH value of 7.2.

[0038] Comparative Example 1 This comparative example uses the same method as Example 1, except that it does not contain phosphonylated plant tannins.

[0039] Comparative Example 2 The method used in this comparative example is the same as that in Example 1, except that an equal amount of phosphonylated plant tannins are replaced with ordinary tannic acid.

[0040] Example 1 (1) Static cleaning efficiency test of simulated mixed scale samples Test method: Refer to the static immersion method in "HG / T2387-2007 Quality Standard for Chemical Cleaning of Industrial Equipment". Prepare simulated mixed scale flakes (40% calcium carbonate, 30% magnesium silicate, 20% simulated bagasse tar, and 10% iron oxide, bonded together) with a composition similar to that of a sugar factory boiler. Prepare a 3% test solution by mixing each example and the comparative example, and immerse in a constant temperature water bath at 65±2℃ for 24 hours. After immersion, remove the flakes, clean, dry, and weigh them using the same procedure.

[0041] Evaluation index: Descaling rate = (weight of scale before cleaning - weight of scale after cleaning) / weight of scale before cleaning × 100%. Simultaneously, the integrity of scale flake removal and the state of surface residue can be qualitatively observed and recorded.

[0042] (2) Corrosion test Test method: Refer to GB / T18175-2014 "Determination of Corrosion Inhibition Performance of Water Treatment Agents - Rotary Suspended Plate Method". Standard 20# carbon steel test pieces (commonly used in boilers) were suspended in the 3% test solution prepared for each example and comparative example, and immersed at a constant temperature of 60±1℃ for 48 hours.

[0043] Evaluation indicators: corrosion rate (unit: g / (m²·h)) and corrosion inhibition rate.

[0044] The test results are shown in Table 1.

[0045] Table 1

[0046] The lack of phosphonylated plant tannins or the use of unmodified tannic acid significantly reduces cleaning efficiency, particularly in removing stubborn silica scale and organic coke, demonstrating a non-obvious synergistic effect among the components of this invention.

[0047] This invention achieves highly efficient and comprehensive removal of complex scale unique to sugar factories while maintaining an extremely low corrosion rate, and its overall performance is significantly superior to commercially available general-purpose neutral products.

[0048] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A neutral descaling and coking agent for use in sugar factory boilers, characterized in that, It comprises the following components by weight: 5-15 parts of penetrating activation component, 2-4 parts of ethylene glycol butyl ether, 5-10 parts of mild oxidant, 10-15 parts of sodium gluconate, 8-10 parts of hydroxyethylidene diphosphonic acid, 0.5-5 parts of phosphonyl tannin, 1-3 parts of sodium polyacrylate, 1-2 parts of borax, 1-3 parts of sodium citrate, and 30-50 parts of deionized water.

2. The neutral descaling and descaling agent according to claim 1, characterized in that, The permeation-activating component includes one or more of alkyl polyglucosides, fatty acid glucamides, and sucrose esters.

3. The neutral descaling and descaling agent according to claim 1, characterized in that, The mild oxidant includes one or more of sodium percarbonate, sodium peracetate, and sodium perborate.

4. The neutral descaling and descaling agent according to claim 1, characterized in that, The method for preparing the phosphonylated plant tannin is as follows: Tannic acid and anhydrous pyridine were mixed and phosphorus oxychloride was added dropwise while stirring in an ice-water bath. After the addition was complete, the mixture was heated to reflux. After the reaction was completed, the reaction mixture was cooled to room temperature and poured into deionized water to collect the precipitate. The precipitate was then washed, filtered, and dried to obtain phosphonylated plant tannins.

5. The neutral descaling and descaling agent according to claim 4, characterized in that, The mass ratio of tannic acid, anhydrous pyridine, and phosphorus oxychloride is 100:20-30:40-60.

6. The neutral descaling and descaling agent according to claim 4, characterized in that, The reflux reaction is carried out at a temperature of 50-60°C for 4-6 hours.

7. The method for preparing the neutral descaling and descaling agent according to claim 1, characterized in that, Includes the following steps: Weigh the raw materials according to the stated mass ratio; Deionized water, permeation activation component, phosphonylated plant tannin, and ethylene glycol butyl ether are mixed evenly to obtain component A; Sodium gluconate, sodium citrate, and borax were mixed evenly and then slowly added to an aqueous solution of hydroxyethylidene diphosphonic acid and a sodium polyacrylate solution under stirring to obtain component B. Mix component A and component B evenly, then slowly add a mild oxidant and continue stirring until completely dissolved to obtain a neutral descaling and descaling agent.

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