A kind of boiler deslagging and decoking agent and preparation method thereof

Abstract

The present invention relates to a deslagging and decoking agent for boilers and a preparation method thereof, and specifically belongs to the field of deslagging and decoking agents. The deslagging and decoking agent for boilers, according to the total mass as 100%, includes the following raw materials: 5-12% nitrate, 10-18% modified clay, 0.5-1.5% modified carbon powder, 1-2% sulfur powder, 2-3.5% mineral powder, 3-5% borax, 1.5-4% sodium carbonate, 1.5-2.5% metal oxide, 0.1-0.25% combustion-supporting catalyst, 0.05-0.2% dispersant, 0.05-0.2% preservative, and the remainder is water. The effective ingredients in the deslagging and decoking agent prepared in the present invention can make the coking layer on the boiler wall loose and porous, so that it is easy to pulverize and fall off, and has a high decoking efficiency for the coking layer.

Description

Technical Field

[0001] The invention belongs to the field of deslagging and decoking agents, and in particular relates to a deslagging and decoking agent for boilers and a preparation method thereof. Background Art

[0002] High-alkali coal is a type of coal rich in sodium and potassium, such as Zhundong high-alkali coal and Hailar lignite. Among them, Zhundong high-alkali coal has abundant reserves. This type of coal has very special characteristics, such as low ash content, high volatile matter, good ignition and burnout characteristics, strong combustion stability, etc., and has broad development prospects. Because Zhundong high-alkali coal has so many advantages, relevant industry personnel have regarded large-scale blending and pure combustion of Zhundong high-alkali coal as a common industry problem to be solved. However, the content of alkaline oxides in Zhundong high-alkali coal is much higher than that of conventional thermal coal, and the content of acidic oxides, such as silicon dioxide, is significantly lower, and it has a strong tendency to stain and slag. In the process of burning Zhundong high-alkali coal, problems such as slagging of water-cooled walls and severe coking caused by excessive local heat load are prone to occur, which not only reduces the thermal efficiency of the boiler, but also threatens the safe, stable and economic operation of the boiler.

[0003] Boiler decoking agent is a new energy-saving product, mainly for removing coking, slagging, reducing thermal resistance, improving boiler thermal efficiency, reducing energy consumption, slowing down corrosion, extending boiler life, reducing physical labor, extending exercise cycle, and reducing environmental pollution. Patent CN108795534A discloses a boiler decoking agent, which uses zinc powder and flake graphite as raw materials, flake graphite is made into expanded graphene, zinc powder is ground into ultrafine powder by ball milling, and ethanol is used as a dispersant to prepare a well-structured composite material, and a boiler decoking agent with good dispersibility is prepared. Although the decoking agent can play a certain decoking effect, it is not ideal for the removal effect of the thicker coking layer in the boiler, and the viscosity and adhesion of the decoking agent are not enough. When it is sprayed on the coking layer, the decoking agent on the upper part of the boiler will flow downward along the boiler wall under the action of gravity, and a large amount of accumulation is accumulated at the bottom, causing the problem that the decoking effect is not good and the utilization rate of the decoking agent is low.

[0004] Based on the problems existing in the prior art, it is of great significance to develop a decoking agent which is simple and easy to operate, cost-effective, safe, has good combustion-supporting and anti-corrosion properties, and can effectively inhibit boiler coking. It can promote the boiler burning Zhundong high-alkali coal to achieve long-term, high fuel utilization, and full-load stable and safe operation. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a deslagging and decoking agent for boilers and a preparation method thereof. The effective ingredients in the deslagging and decoking agent can make the coking layer on the boiler wall loose and porous, making it easy to pulverize and fall off, and having a high decoking efficiency.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention provides a deslagging and decoking agent for boilers, which comprises the following raw materials based on 100% total mass: 5-12% nitrate, 10-18% modified clay, 0.5-1.5% modified carbon powder, 1-2% sulfur powder, 2-3.5% mineral powder, 3-5% borax, 1.5-4% sodium carbonate, 1.5-2.5% metal oxide, 0.1-0.25% combustion-supporting catalyst, 0.05-0.2% dispersant, 0.05-0.2% preservative, and the remainder is water.

[0008] In some embodiments, the nitrate is one or more of ammonium nitrate, barium nitrate, sodium nitrate, magnesium nitrate, potassium nitrate and calcium nitrate.

[0009] Preferably, the nitrate is ammonium nitrate.

[0010] In some embodiments, the mineral powder is one or more of calcium carbonate powder, andalusite powder, dolomite powder and mullite powder.

[0011] Preferably, the mineral powder is calcium carbonate powder.

[0012] In some embodiments, the metal oxide is one or more of barium oxide, copper oxide, zinc oxide, and magnesium oxide.

[0013] Preferably, the metal oxide is barium oxide.

[0014] In some embodiments, the dispersant is one or more of polyethylene glycol, methyl cellulose and polyacrylamide, and the molecular weight of each of the dispersants is ≤30,000.

[0015] Preferably, the dispersant is polyethylene glycol.

[0016] In some embodiments, the preservative is formaldehyde and / or benzisothiazolinone.

[0017] The deslagging and decoking agent of the present invention has a high decoking efficiency for the coking layer on the boiler. Among them, the metal ions of the nitrate can promote the full combustion of the residual carbon in the coking layer, and can also convert the low melting point material in the coking layer into loose high melting point material, which is helpful for the shedding of the coking layer and prevents high temperature corrosion. In addition, nitrates, sulfur powder and modified carbon powder can produce a high-intensity "micro-explosion" effect at high temperature, so that the coking layer on the boiler wall is disconnected, forming smaller coke blocks, which are easy to fall off. At the same time, part of the oxygen will be released to loosen the ash and coking layers at different parts of the boiler, and then the residual carbon in the coking blocks will be completely burned. The modified clay itself has a high specific surface area and voids, and serves as a carrier of the active ingredients of the deslagging and decoking agent. The dispersant can make the active ingredients of the deslagging and decoking agent uniformly dispersed in the system. The addition of mineral powder can increase the solution viscosity and surface tension, improve adhesion, avoid the deslagging and decoking agent from vaporizing or chemically reacting when it is close to the coking layer, and can also inhibit coking. The combustion-supporting catalyst can act as a carrier for the reaction of oxygen atoms under high temperature conditions, catalyze the re-burning of residual carbon, and cooperate with nitrates, sulfur and modified carbon powder to improve the decoking effect.

[0018] The powders used in the present invention are all powders with mesh sizes of 200-400; the powders include modified clay, modified carbon powder, sulfur powder and mineral powder.

[0019] In some embodiments, the modified clay is prepared by:

[0020] Add iron salt solution and acid to clay to obtain a mixed system, stir the mixed system at 400-450 r / min and 70-80° C. for 3-4 hours, filter and wash, dry and grind the obtained solid to obtain modified clay.

[0021] In some embodiments, the clay accounts for 8-12 wt % of the mixed system; the clay is one or more of bentonite, kaolin, bauxite and clay.

[0022] In some embodiments, the concentrations of the iron salt and the acid in the iron salt solution in the mixed system are 1-1.5 mol / L and 3-4 mol / L, respectively; the iron salt is ferric chloride or ferric nitrate, and the acid is nitric acid or hydrochloric acid.

[0023] In the present invention, iron salt solution and acid are used to modify clay. The applicant has found that the comprehensive performance of the modified clay can be improved by controlling the type and concentration of the iron salt solution and the acid. The reason is that the clay modified by using a certain concentration of ferric chloride solution or ferric nitrate solution and acid has a high specific surface area, abundant macropores, and a proper amount of micropores and mesopores, which is a carrier of the active ingredients of the deslagging and decoking agent; on the other hand, there are a large number of oxygen vacancies on the pore surface, which is conducive to the breaking of macromolecular chemical bonds and functional groups in the coking layer, and promotes the shedding of the coking layer.

[0024] In some embodiments, the modified carbon powder is prepared by:

[0025] (1) dissolving a silane coupling agent and ammonia water in a 90-95wt% ethanol solution, adding carbon powder, ultrasonicating for 30-40 minutes, stirring at room temperature and 300-350 r / min for 20-24 hours, separating, washing, drying and grinding to obtain silane coupling agent coated carbon powder;

[0026] (2) dispersing the sulfonated para-ester in pure water, adding sodium carbonate solution dropwise while stirring, reacting at 2-5°C for 30-40 minutes to obtain suspension 1, dispersing cyanuric chloride in pure water, stirring at 0-4°C for 30-40 minutes to obtain suspension 2, mixing suspension 1 and suspension 2, stirring at 2-5°C for 30-40 minutes, adjusting the pH to 3-4, reacting for 3-4 hours to obtain suspension 3, salting out, washing, suction filtering, and drying the suspension 3 to obtain a powdery substance;

[0027] (3) The powdery substance obtained in step (2) is dissolved in acetone, and the silane coupling agent-coated carbon powder obtained in step (1) is added thereto. The pH is adjusted to 5-6, and the mixture is stirred at 40-45° C. for 3-4 hours. After centrifugation to remove the acetone, the mixture is washed and dried to obtain modified carbon powder.

[0028] In the present invention, the silane coupling agent coated carbon powder is modified by the substance generated by the reaction of sulfonated para-ester and cyanuric chloride, an anion group is introduced on the surface of the carbon powder to improve the hydrophilicity, and the modified carbon powder has good dispersibility under the action of the charge, and can be evenly and stably dispersed in the deslagging and decoking agent system for a long time without sedimentation. In addition, the modified carbon powder can cooperate with nitrate and sulfur powder to produce a high-intensity "micro-explosion" effect at high temperature, so that the coking layer on the boiler wall is broken to form smaller coke blocks that are easy to fall off.

[0029] In some embodiments, the mass ratio of the silane coupling agent to the carbon powder in step (1) is (0.5-0.6):1.

[0030] Preferably, in step (1), the mass ratio of the silane coupling agent to the carbon powder is 0.55:1.

[0031] The applicant has found that strictly controlling the raw material ratio can make the silane coupling agent evenly coated on the surface of the carbon powder, improve the compatibility of the carbon powder and the powdered substance, and promote the chemical reaction between the two.

[0032] In some embodiments, the molar ratio of the sulfonated para-ester to cyanuric chloride in step (2) is 1:(1-1.2).

[0033] Preferably, in step (2), the molar ratio of the sulfonated para-ester to cyanuric chloride is 1:1.1.

[0034] The applicant has found that strictly controlling the molar ratio of the sulfonated para-ester to cyanuric chloride can increase the synthesis rate of the powdery substance.

[0035] In some embodiments, the mass ratio of the powdered substance to the silane coupling agent coated carbon powder in step (3) is (1.5-1.7):1.

[0036] Preferably, in step (3), the mass ratio of the powdery substance to the silane coupling agent coated carbon powder is 1.6:1.

[0037] The applicant has found that strictly controlling the mass ratio of the powdery substance to the silane coupling agent coated carbon powder can increase the yield of the modified carbon powder.

[0038] In some embodiments, the combustion-supporting catalyst is one or more of potassium permanganate, hydrogen peroxide, manganese sulfate, potassium chlorate or manganese oxide.

[0039] Preferably, the combustion-supporting catalyst is potassium permanganate.

[0040] The second aspect of the present invention provides a method for preparing a boiler deslagging and decoking agent, comprising the following preparation steps:

[0041] S1: Dissolve nitrate in half water to obtain nitrate solution;

[0042] S2: Mix modified clay, modified carbon powder, sulfur powder, mineral powder, borax and metal oxide evenly to obtain solid powder, add the solid powder to the remaining water and stir evenly, then add sodium carbonate, dispersant, preservative and combustion catalyst thereto in sequence, stir evenly each time adding a substance, and obtain a mixed solution;

[0043] S3: adding the nitrate solution obtained in step S1 to the mixed solution obtained in step S2, stirring evenly, and obtaining a boiler deslagging and decoking agent.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. The present invention discloses a deslagging and decoking agent for boilers. The preparation process of the deslagging and decoking agent is simple. The effective ingredients therein can make the coking layer on the boiler wall loose and porous, making it easy to pulverize and fall off. It has a high decoking efficiency, is non-corrosive to the boiler, and has a good effect of improving the thermal efficiency of the boiler.

[0046] 2. In the present invention, iron salt solution and acid of specific type and concentration are used to modify clay. The obtained modified clay itself has a high specific surface area and voids. As a carrier of the active ingredients of the deslagging and decoking agent, there are a large number of oxygen vacancies on the surface of its pores, which is beneficial to the breaking of macromolecular chemical bonds and functional groups in the coking layer and promotes the shedding of the coking layer.

[0047] 3. In the present invention, the silane coupling agent coated carbon powder is modified by using the substance generated by the reaction of sulfonated para-ester and cyanuric chloride. The obtained modified carbon powder has good hydrophilicity and can be evenly and stably dispersed in the deslagging and decoking agent system for a long time without sedimentation. In addition, the modified carbon powder can cooperate with nitrate and sulfur powder to produce a high-intensity "micro-explosion" effect at high temperature, so that the coking layer on the boiler wall is broken to form smaller coke blocks that are easy to fall off.

[0048] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0049] In order to better illustrate the specific implementation mode of the present invention, further examples are given below.

[0050] The clay used in the present invention is sodium montmorillonite purchased from Delta Bioreagent; the silane coupling agent used is KH560 purchased from Nanjing Liansi Chemical Co., Ltd.; the carbon powder used is purchased from Junhong Graphite; the nitrate used is ammonium nitrate; the mineral powder used is calcium carbonate powder; the metal oxide used is barium oxide; the dispersant used is polyethylene glycol 4000 purchased from Nantong Lianli; the preservative used is benzisothiazolinone; and the combustion-supporting catalyst used is potassium permanganate.

[0051] Preparation Example 1

[0052] The preparation steps of modified clay are:

[0053] 3.5 kg of 1.25 mol / L ferric chloride solution and 770 g of nitric acid were added to 500 g of clay to obtain a mixed system. The mixed system was stirred at 425 r / min and 75° C. for 3.5 h, filtered, and washed with pure water three times. The obtained solid was dried and ground to obtain modified clay.

[0054] Preparation Example 2

[0055] The preparation steps of modified clay are:

[0056] To 100 g of clay, 1 kg of 1.25 mol / L ferric chloride solution and 220 g of nitric acid were added to obtain a mixed system. The mixed system was stirred at 425 r / min and 75° C. for 3.5 h, filtered, and washed with pure water three times. The obtained solid was dried and ground to obtain modified clay.

[0057] Preparation Example 3

[0058] The preparation steps of modified clay are:

[0059] 1 kg 2 mol / L ferric chloride solution and 220 g nitric acid were added to 140 g clay to obtain a mixed system. The mixed system was stirred at 425 r / min and 75° C. for 3.5 h, filtered, and washed with pure water three times. The obtained solid was dried and ground to obtain modified clay.

[0060] Preparation Example 4

[0061] The preparation steps of the modified clay were the same as those in Preparation Example 1, except that 100 g of nitric acid was added.

[0062] Preparation Example 5

[0063] The preparation steps of modified clay are:

[0064] 1.5 kg of 3.5 mol / L nitric acid solution was added to 140 g of clay to obtain a mixed system. The mixed system was stirred at 425 r / min and 75° C. for 3.5 h, filtered, and washed with pure water three times. The obtained solid was dried and ground to obtain modified clay.

[0065] Preparation Example 6

[0066] The preparation steps of modified carbon powder are:

[0067] (1) 11 g of silane coupling agent and 2.2 g of AR grade ammonia water were dissolved in 420 g of 90 wt% ethanol solution, 20 g of carbon powder was added, ultrasonicated for 35 min, stirred at room temperature and 325 r / min for 22 h, centrifuged, washed with deionized water 3 times, dried, and ground to obtain silane coupling agent coated carbon powder;

[0068] (2) Disperse 1 mol of sulfonated para-ester in 100 mL of pure water, add 4.5 mL of 1.25 mol / L sodium carbonate solution dropwise while stirring, and react at 4°C for 35 min to obtain suspension 1. Disperse 1.1 mol of cyanuric chloride in 100 mL of pure water, and stir at 0°C for 35 min to obtain suspension 2. Mix suspension 1 and suspension 2, stir at 4°C for 35 min, adjust the pH to 3.5 with 1.25 mol / L sodium carbonate solution, and react for 3.5 h to obtain suspension 3. Salt out suspension 3 with saturated NaCl solution, wash the filter cake with ethanol, filter, and dry to obtain a powdery substance.

[0069] (3) Take 16 g of the powdery substance obtained in step (2) and dissolve it in 400 mL of acetone. Then add 10 g of the silane coupling agent-coated carbon powder obtained in step (1) thereto. Adjust the pH to 5.5 with 1.25 mol / L sodium carbonate solution. Stir the reaction at 40°C for 3.5 h. After centrifugation to remove acetone, wash and dry to obtain modified carbon powder.

[0070] Preparation Example 7

[0071] The preparation steps of the modified carbon powder are the same as those in Preparation Example 6, except that the amount of cyanuric chloride used in step (2) is 0.9 mol.

[0072] Preparation Example 8

[0073] The preparation steps of the modified carbon powder are the same as those in Preparation Example 6, except that 10 g of the powdered substance is used in step (3).

[0074] Preparation Example 9

[0075] The preparation steps of the modified carbon powder are the same as those of Preparation Example 6, except for step (3): 16 g of the powdery substance obtained in step (2) is dissolved in 400 mL of acetone, 10 g of ordinary carbon powder is added thereto, the pH is adjusted to 5.5 with 1.25 mol / L sodium carbonate solution, the reaction is stirred at 40°C for 3.5 h, the acetone is removed by centrifugation, and the mixture is washed and dried to obtain the modified carbon powder.

[0076] Preparation Example 10

[0077] The preparation steps of silane coupling agent coated carbon powder are:

[0078] 11 g of silane coupling agent and 2.2 g of AR grade ammonia water were dissolved in 420 g of 90 wt% ethanol solution, 20 g of carbon powder was added, ultrasonicated for 35 min, stirred at room temperature and 325 r / min for 22 h, centrifuged, washed with deionized water for 3 times, dried, and ground to obtain silane coupling agent coated carbon powder.

[0079] Example 1

[0080] A method for preparing a boiler deslagging and decoking agent comprises the following preparation steps:

[0081] S1: Dissolve 25 g of barium nitrate in 188 g of water to obtain a nitrate solution;

[0082] S2: 50g of modified clay, 2.5g of modified carbon powder, 5g of sulfur powder, 10g of mineral powder, 15g of borax, and 7.5g of metal oxide are mixed evenly to obtain a solid powder, the solid powder is added to 188g of water and stirred evenly, and then 7.5g of sodium carbonate, 0.25g of dispersant, 0.25g of preservative and 0.5g of combustion catalyst are added thereto in sequence, each added substance is stirred evenly to obtain a mixed solution;

[0083] S3: adding the nitrate solution obtained in step S1 to the mixed solution obtained in step S2, stirring evenly, and obtaining a boiler deslagging and decoking agent.

[0084] The modified clay used was obtained from Preparation Example 1, and the modified carbon powder used was obtained from Preparation Example 6.

[0085] Example 2

[0086] A method for preparing a boiler deslagging and decoking agent comprises the following preparation steps:

[0087] S1: Dissolve 60 g of barium nitrate in 127 g of water to obtain a nitrate solution;

[0088] S2: 90g of modified clay, 7.5g of modified carbon powder, 10g of sulfur powder, 17.5g of mineral powder, 25g of borax and 12.5g of metal oxide are mixed evenly to obtain a solid powder, the solid powder is added to 127g of water and stirred evenly, and then 20g of sodium carbonate, 1g of dispersant, 1g of preservative and 1.25g of combustion catalyst are added thereto in sequence, each added substance is stirred evenly to obtain a mixed solution;

[0089] S3: adding the nitrate solution obtained in step S1 to the mixed solution obtained in step S2, stirring evenly, and obtaining a boiler deslagging and decoking agent.

[0090] The modified clay used was obtained from Preparation Example 1, and the modified carbon powder used was obtained from Preparation Example 6.

[0091] Example 3

[0092] A method for preparing a boiler deslagging and decoking agent comprises the following preparation steps:

[0093] S1: 40g of barium nitrate was dissolved in 159g of water to obtain a nitrate solution;

[0094] S2: 70g of modified clay, 5g of modified carbon powder, 7.5g of sulfur powder, 12.5g of mineral powder, 20g of borax, and 10g of metal oxide were mixed to obtain a solid powder, and the solid powder was added to 159g of water and stirred evenly, and then 15g of sodium carbonate, 0.5g of dispersant, 0.5g of preservative and 1g of combustion catalyst were added thereto in sequence, and each added substance was stirred evenly to obtain a mixed solution;

[0095] S3: adding the nitrate solution obtained in step S1 to the mixed solution obtained in step S2, stirring evenly, and obtaining a boiler deslagging and decoking agent.

[0096] The modified clay used was obtained from Preparation Example 1, and the modified carbon powder used was obtained from Preparation Example 6.

[0097] Example 4

[0098] A method for preparing a boiler deslagging and decoking agent, the specific implementation method is the same as that of Example 3, except that the modified clay used is obtained from Preparation Example 2.

[0099] Example 5

[0100] A method for preparing a boiler deslagging and decoking agent, the specific implementation method is the same as that of Example 3, except that the modified clay used is obtained from Preparation Example 3.

[0101] Example 6

[0102] A method for preparing a boiler deslagging and decoking agent, the specific implementation method is the same as that of Example 3, except that the modified clay used is obtained from Preparation Example 4.

[0103] Example 7

[0104] A method for preparing a boiler deslagging and decoking agent, the specific implementation method is the same as that of Example 3, except that the modified clay used is obtained from Preparation Example 5.

[0105] Example 8

[0106] A method for preparing a boiler deslagging and decoking agent, the specific implementation method is the same as that of Example 3, except that the modified carbon powder used is obtained from Preparation Example 7.

[0107] Example 9

[0108] A method for preparing a boiler deslagging and decoking agent, the specific implementation method is the same as that of Example 3, except that the modified carbon powder used is obtained from Preparation Example 8.

[0109] Example 10

[0110] A method for preparing a boiler deslagging and decoking agent, the specific implementation method is the same as that of Example 3, except that the modified carbon powder used is obtained from Preparation Example 9.

[0111] Embodiment 11

[0112] A method for preparing a boiler deslagging and decoking agent, the specific implementation method is the same as that of Example 3, except that the silane coupling agent-coated carbon powder obtained in Preparation Example 10 of equal mass is used instead of the modified carbon powder.

[0113] Comparative Example 1

[0114] A method for preparing a boiler deslagging and decoking agent, the specific implementation method is the same as that of Example 3, except that unmodified carbon powder of equal mass is used instead of modified carbon powder.

[0115] Comparative Example 2

[0116] A method for preparing a boiler deslagging and decoking agent, the specific implementation method is the same as that of Example 3, except that unmodified clay of equal mass is used instead of modified clay.

[0117] Performance test of slag and coke removal agent

[0118] 1. Coke removal rate (the deslagging and decoking agents prepared in the embodiments and comparative examples were added to the boiler to test the decoking rate): The weight of the boiler was measured to be W1. The boiler was used normally and calcined at 1200°C for 1 hour. The weight was measured to be W2. A 5wt% deslagging and decoking agent was sprayed on the coked part of the boiler and placed at room temperature for 3 hours. The deslagging and decoking agent was then rinsed with a sponge under running hot water and dried. The weight was measured to be W3. The decoking rate was calculated by the weight method. Decoking rate (%) = 100% × (W2-W3) / (W2-W1).

[0119] 2. Corrosion condition: After testing the decoking rate, observe the corrosion condition of the decoked boiler.

[0120] 3. Thermal efficiency: According to GB / T 10180 standard, the thermal efficiency of a normally operating boiler after adding the decoking agent obtained in the embodiment and the comparative example is tested. The thermal efficiency of the normally operating boiler is 75%. Five samples are tested for each embodiment and comparative example, and the measured values ​​are averaged.

[0121] The specific test results are shown in Table 1.

[0122] Table 1

[0123]

[0124] It can be seen from Table 1 that the deslagging and decoking agents prepared in Examples 1-3 can effectively remove coke on the inner wall of the boiler, with a decoking rate of more than 99%, and are non-corrosive to the boiler and have a good effect of improving the thermal efficiency of the boiler.

[0125] The preparation process of the modified clay used in Examples 4-7 was changed (clay dosage, iron salt solution, acid concentration, no acid added), and the specific surface area, macropores, micropores and mesopores of the prepared modified clay were changed, and the oxygen vacancies in the pores were reduced, which was not conducive to the breaking of the macromolecular chemical bonds and functional groups in the coking layer, and the comprehensive performance was reduced, resulting in a decrease in the decoking effect of the deslagging and decoking agent and the thermal efficiency of the boiler.

[0126] The changes in the preparation process of the modified carbon powder used in Examples 8-10 (raw material dosage and ratio) and the use of an equal mass of silane coupling agent-coated carbon powder instead of the modified carbon powder in Example 11 will both deteriorate the hydrophilicity and dispersibility of the modified carbon powder, weaken the "micro-explosion" synergistic effect on nitrate and sulfur powder, and reduce the decoking effect of the deslagging and decoking agent and the thermal efficiency of the boiler.

[0127] In Comparative Example 1, unmodified carbon powder of equal mass was used to replace modified carbon powder, and the "micro-explosion" synergistic effect of unmodified carbon powder on nitrate and sulfur powder was weakened, and the coking layer could not be broken, resulting in a decrease in the decoking effect of the deslagging and decoking agent and the thermal efficiency of the boiler. In Comparative Example 2, unmodified clay of equal mass was used to replace modified clay, and the internal porosity and comprehensive performance of the unmodified clay were reduced, resulting in a decrease in the decoking effect of the deslagging and decoking agent and the thermal efficiency of the boiler.

[0128] The above is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present application. Although the present application is disclosed as above in the preferred embodiment, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution.

Claims

1. A deslagging and decoking agent for boilers, characterized in that: Based on the total mass of 100%, the following raw materials are included: 5-12% nitrate, 10-18% modified clay, 0.5-1.5% modified carbon powder, 1-2% sulfur powder, 2-3.5% mineral powder, 3-5% borax, 1.5-4% sodium carbonate, 1.5-2.5% metal oxide, 0.1-0.25% combustion catalyst, 0.05-0.2% dispersant, 0.05-0.2% preservative, and the rest is water; The preparation steps of the modified carbon powder are: (1) dissolving a silane coupling agent and ammonia water in a 90-95wt% ethanol solution, adding carbon powder, ultrasonicating for 30-40 minutes, stirring at room temperature and 300-350 r / min for 20-24 hours, separating, washing, drying and grinding to obtain silane coupling agent coated carbon powder; (2) dispersing the sulfonated para-ester in pure water, adding sodium carbonate solution dropwise while stirring, reacting at 2-5°C for 30-40 minutes to obtain suspension 1, dispersing cyanuric chloride in pure water, stirring at 0-4°C for 30-40 minutes to obtain suspension 2, mixing suspension 1 and suspension 2, stirring at 2-5°C for 30-40 minutes, adjusting the pH to 3-4, reacting for 3-4 hours to obtain suspension 3, salting out, washing, suction filtering, and drying the suspension 3 to obtain a powdery substance; (3) dissolving the powdery substance obtained in step (2) in acetone, adding the silane coupling agent-coated carbon powder obtained in step (1) thereto, adjusting the pH to 5-6, stirring and reacting at 40-45° C. for 3-4 hours, centrifuging to remove the acetone, washing, and drying to obtain modified carbon powder; In the step (1), the mass ratio of the silane coupling agent to the carbon powder is (0.5-0.6): 1; In the step (2), the molar ratio of the sulfonated para-ester to cyanuric chloride is 1:(1-1.2); In the step (3), the mass ratio of the powdery substance to the silane coupling agent coated carbon powder is (1.5-1.7): 1; The preparation steps of the modified clay are: Add iron salt solution and acid to clay to obtain a mixed system, stir the mixed system at 400-450 r / min and 70-80° C. for 3-4 hours, filter and wash, dry and grind the obtained solid to obtain modified clay.

2. The deslagging and decoking agent for boilers according to claim 1, characterized in that: The clay accounts for 8-12wt% of the mixed system; the clay is one or more of bentonite, kaolin, bauxite and clay.

3. The deslagging and decoking agent for boilers according to claim 1, characterized in that: The concentrations of the iron salt and the acid in the iron salt solution in the mixed system are 1-1.5 mol / L and 3-4 mol / L respectively; the iron salt is ferric chloride and / or ferric nitrate, and the acid is nitric acid and / or hydrochloric acid.

4. The deslagging and decoking agent for boilers according to claim 1, characterized in that: The combustion-supporting catalyst is one or more of potassium permanganate, hydrogen peroxide, manganese sulfate, potassium chlorate or manganese oxide.

5. A method for preparing a boiler deslagging and decoking agent according to any one of claims 1 to 4, characterized in that: The method comprises the following preparation steps: S1: Dissolve nitrate in half water to obtain nitrate solution; S2: Mix modified clay, modified carbon powder, sulfur powder, mineral powder, borax and metal oxide evenly to obtain solid powder, add the solid powder to the remaining water and stir evenly, then add sodium carbonate, dispersant, preservative and combustion catalyst thereto in sequence, stir evenly each time adding a substance, and obtain a mixed solution; S3: adding the nitrate solution obtained in step S1 to the mixed solution obtained in step S2, stirring evenly, and obtaining a boiler deslagging and decoking agent.

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