CN115093152B - Composite chromium-reducing grinding aid and preparation method thereof - Google Patents
Composite chromium-reducing grinding aid and preparation method thereof Download PDFInfo
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- CN115093152B CN115093152B CN202210662687.XA CN202210662687A CN115093152B CN 115093152 B CN115093152 B CN 115093152B CN 202210662687 A CN202210662687 A CN 202210662687A CN 115093152 B CN115093152 B CN 115093152B
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/0028—Aspects relating to the mixing step of the mortar preparation
- C04B40/0039—Premixtures of ingredients
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B7/00—Hydraulic cements
- C04B7/36—Manufacture of hydraulic cements in general
- C04B7/48—Clinker treatment
- C04B7/52—Grinding ; After-treatment of ground cement
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/52—Grinding aids; Additives added during grinding
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding
Abstract
The invention discloses a compound chromium-reducing grinding aid and a preparation method thereof, and relates to the field of building materials, wherein the raw materials comprise 15-30wt% of chromium-reducing components, 5-10wt% of antioxidant components, 20-40wt% of grinding aid components and the balance of water; the chromium-reducing component is thiourea dioxide and/or cyano sodium borohydride; the preparation method comprises adding grinding aid component and water at normal temperature, and stirring; then adding antioxidant components and stirring uniformly; adding the chromium-reducing component while stirring, and stirring uniformly to obtain the finished product of the composite chromium-reducing grinding aid. The composite chromium-reducing grinding aid provided by the invention has the characteristics of good chromium-reducing effect, no rebound, high temperature resistance, oxidation resistance and the like, and can be well adapted to the change of the working condition temperature of cement; the production cost is lower, the mixing amount is lower than that of the common chromium reducing agent, and the chromium reducing agent has the advantages of improving the yield and the consumption, improving the cement performance and reducing the production cost.
Description
Technical Field
The invention relates to the field of building materials, in particular to a chromium-reducing grinding aid and a preparation method thereof.
Background
Hexavalent chromium has the dangerous characteristics of strong oxidability, corrosiveness and the like, and can cause skin eczema after long-term contact, and a large amount of ingestion can even cause adverse consequences such as cancers, mutations and the like; under the environment of long-term rainwater showering, the hidden danger of chromium poisoning can be caused by the pollution of underground water quality and soil chromium. In order to control the content of water-soluble hexavalent chromium in cement, a mandatory standard GB 31893-2015 for limiting and measuring the content of the water-soluble chromium (VI) in cement is issued by China, and the standard clearly specifies that the content of the water-soluble chromium (VI) in the cement is not more than 10mg/kg.
The main method at present has two modes of source control and tail end control for controlling water-soluble chromium (VI) in cement, and under the condition that the raw materials of the cement cannot be changed, a chromium reducing agent is adopted to reduce hexavalent chromium with higher toxicity into trivalent chromium with low toxicity, so that the method is an effective method. However, existing chromium reduction agent products suffer from various drawbacks and problems: the powder chromium-reducing agent generally adopts ferrous sulfate and Sn 2+ Reducing agent such as salt. For example, nowAmong others, chinese patent application CN113480219a provides a chromium reducing agent for reducing water-soluble chromium (vi) in cement, the raw materials of which include chromium reducing agents (sodium thiosulfate, ferrous sulfate, ferrous citrate, nitrilotriacetic acid, anhydrous sodium sulfite), stabilizers (ascorbic acid VC, nitrilotriacetic acid, oligoglucose, polydextrose, sodium oxalate, disodium ethylenediamine tetraacetate), catalysts (anhydrous sodium sulfate, calcium formate) and dispersion carriers (fly ash, heavy calcium carbonate). For example, the cement hexavalent chromium composite reducing agent provided by Chinese patent No. 106365479B comprises sodium sulfite, ferrous sulfate, manganese sulfate and stannous sulfate as raw materials. Some of the chromium reducing agents are easy to oxidize, easy to agglomerate, inaccurate in measurement and poor in high temperature resistance, and some of the chromium reducing agents have the defects of high purchasing cost, uneven dispersion, low cost performance, influence on cement performance and the like, so that the chromium reducing effect is not ideal and cannot be applied to production practice.
Chinese patent application CN111198184a discloses a method for detecting hexavalent chromium ions in soil, adding digestion agent (sodium hydroxide and sodium carbonate), sodium borohydride and phosphoric acid buffer solution into soil, heating and stirring; cooling, adding EDTA disodium salt, continuously heating and stirring, centrifuging to obtain supernatant, adding concentrated nitric acid, fixing volume, and finally detecting hexavalent chromium in the solution to be detected by using a dibenzoyl dihydrazide spectrophotometry method, wherein the sodium hydroxide, sodium carbonate, sodium borohydride, phosphate buffer solution and the like used in the method can cause cement retarding if being used as a cement chromium-reducing agent, and the sodium borohydride can decompose oxygen when meeting water, thus the method belongs to an easily-explosive chemical, has certain danger, is high in purchasing difficulty in the market and high in price, and cannot be considered as the cement chromium-reducing agent.
Too much of these different types of cement chromium-reducing agents can also have an adverse effect on cement performance; the liquid chromium-reducing agent has ideal chromium-reducing effect, but has high price, the cost per 1ppm hexavalent chromium reduction by using the liquid chromium-reducing agent exceeds 1.5 yuan/ton, and the liquid chromium-reducing agent has only a single chromium-reducing effect.
The existing cement grinding aid has only grinding aid and reinforcing effects and has no chromium reducing effect. Therefore, when the common grinding aid is added in the cement grinding process, the chromium reducing agent is additionally added in cement enterprises, so that the production cost is increased greatly.
In the prior art, for example, a composite cement chromium-removing grinding aid provided in Chinese patent application CN109761518A comprises a Cr reducing component (ferrous sulfate or stannous chloride), triethanolamine, glycerol, isooctyl alcohol phosphate, an antioxidant (tannic acid), a surfactant and a reduction enhancer; the reduction enhancer is black particles obtained by extracting pine bark dry powder with hot water to obtain an extracting solution, weighing ferrous sulfate and ferric chloride, mixing to prepare Fe ion solution, mixing with the pine bark extracting solution, stirring for reaction, carrying out suction filtration, adding 3-mercaptopropionic acid into the obtained black solid, adjusting pH to be 8, carrying out ultrasonic treatment, carrying out suction filtration, washing with ethanol, and carrying out suction filtration and drying. Hexavalent chromium is reduced to trivalent chromium and adsorbed on the surfaces of the nano black particles in the form of iron chromium oxide; free and unadsorbed hexavalent chromium can continuously undergo oxidation-reduction reaction with Cr reducing components in the grinding aid, so that the hexavalent chromium is reduced efficiently. However, the tannic acid and other components in the chromium-removing grinding aid also cause cement retarding, and the preparation process is too complex, long in time consumption, high in cost and difficult to implement and apply.
In sum, if the grinding aid is prepared with high cost performance, good chromium reduction effect is achieved, trivalent chromium is prevented from being oxidized again, meanwhile, the coagulation rate of cement is not adversely affected, the cost can be greatly saved, and the efficiency is improved.
Disclosure of Invention
In view of the above deficiencies of the prior art, the present invention provides, in particular, by the following techniques.
The composite chromium-reducing grinding aid is characterized by comprising 15-30wt% of chromium-reducing component, 5-10wt% of antioxidant component, 20-40wt% of grinding-assisting component and the balance of water; the chromium-reducing component is thiourea dioxide and/or cyano sodium borohydride.
Preferably, the raw materials of the composite chromium-reducing grinding aid comprise 25wt% of chromium-reducing components, 8wt% of antioxidation components, 30wt% of grinding aid components and the balance of water.
The composite chromium-reducing grinding aid provided by the invention can be stored for a long time, has obvious chromium-reducing effect and long-term stability, and has grinding-assisting and reinforcing effects; solves the problems of single function, high use cost, poor chromium reducing effect, easy oxidation rebound and the like of the existing chromium reducing agent. Compared with the existing common chromium reducing agents such as thiosulfate, ferrous salt, sulfite, stannous salt, sodium borohydride and the like, the thiourea dioxide is high in reducibility, good in stability and safety performance, does not belong to carcinogenic or dangerous chemicals, and is pollution-free in production and use. Sodium cyanoborohydride also has stronger reducibility, and compared with sodium borohydride, although the reduction effect is slightly poorer, the sodium borohydride is violently reacted and belongs to an explosive product, the use has larger safety risk, and the sodium cyanoborohydride is milder and has better safety performance. Thiourea dioxide is stable under acidic conditions, and is reacted in an alkaline solution to form sulfinic acid with strong reducibility, and sodium cyanoborohydride is acidic after being dissolved in water. Hexavalent chromium is dissolved in alkaline aqueous solution after the cement is contacted with water, and the chromium-reducing component can quickly reduce the hexavalent chromium into trivalent chromium. Therefore, compared with the single use of sodium cyanoborohydride or sodium borohydride, the chromium-reducing grinding aid has higher overall stability and better chromium-reducing effect on cement, and the reduced trivalent chromium is not oxidized into hexavalent chromium again.
More preferably, the mass ratio of thiourea dioxide to sodium cyanoborohydride is 3 (1-2).
Further preferably, the mass ratio of thiourea dioxide to sodium cyanoborohydride is 2:1.
Preferably, the antioxidant component is one or more of formamide, methacrylic acid and sulfosalicylic acid. The antioxidants of formamide, methacrylic acid and sulfosalicylic acid used in the invention can promote hexavalent chromium to be converted into trivalent chromium, and also play a role in stabilizing the trivalent chromium, so that the trivalent chromium is prevented from being oxidized into hexavalent chromium again in a high-temperature oxidation environment; compared with conventional raw materials such as ascorbic acid, nitrilotriacetic acid, glucose oligomer, polydextrose, sodium oxalate, disodium ethylenediamine tetraacetate and the like for the chromium-reducing agent, the formamide, the methacrylic acid and the sulfosalicylic acid have oxidation resistance and have no adverse effect on cement performance, and can promote the reaction reduction of hexavalent chromium to trivalent chromium and inhibit the oxidation of trivalent chromium to hexavalent chromium.
Preferably, the grinding aid component consists of alcohol amine and modified lignosulfonate, wherein the modified lignosulfonate accounts for 2-10% of the total mass of the composite chromium-reducing grinding aid; the preparation method of the modified lignosulfonate comprises the following steps:
p1, dissolving 50-60 parts by weight of lignosulfonate in water, heating to 75-85 ℃, regulating the pH value of the solution to 9-10, and stirring for 20-35min;
p2, adding dilute nitric acid into the mixed solution obtained in the step P1 to adjust the pH value of the solution to 8-9, and adding 5-10 parts by weight of H 2 O 2 Or KMnO 4 And 1-2 parts by weight of FeO or CuO, reacting for 0.5-1h;
p3, adding 40-50% of formaldehyde aqueous solution and fatty amine into the mixed solution obtained in the step P2, wherein the total parts of the formaldehyde aqueous solution and the fatty amine are 20-30 parts by weight, the ratio of the formaldehyde to the fatty amine is 1:1, and reacting for 1-1.5h;
and P4, adding 3-5 parts by weight of 40-50% formaldehyde aqueous solution to react for 0.5-1h, finally adding 3-6 parts by weight of sodium carboxymethyl cellulose and 2-4 parts by weight of sodium sulfate, stirring for 10-30min, and cooling to obtain the modified lignin sulfonate.
The alcohol amine plays roles of assisting grinding, enhancing and improving cement performance, can improve the cement hourly output and reduce the grinding power consumption. The modified lignosulfonate prepared by the modification method has the advantages that the air entraining performance is improved, the retarding effect is obviously weakened, the strength of cement can be increased, the water demand of the cement is reduced, and the comprehensive performance of the cement is improved.
More preferably, the alcohol amine is one or more of triethanolamine, triisopropanolamine, tripropylene glycol, diethanol monoisopropanolamine, and monoethanol diisopropanolamine.
The invention also provides a preparation method of the composite chromium-reducing grinding aid, which comprises the following steps:
s1, adding the grinding aid component and water at normal temperature, and uniformly stirring;
s2, adding the antioxidant component and uniformly stirring; and adding the chromium-reducing component in a stirring state, and continuously stirring uniformly to obtain the finished product of the composite chromium-reducing grinding aid.
Preferably, in the preparation method of the composite chromium-reducing grinding aid, the stirring rotating speeds of the steps S1 and S2 are 60-150rpm; the stirring time of the step S1 is 3-6min, the stirring time after the antioxidant component is added in the step S2 is 5-10min, and the stirring time after the chromium-reducing component is added is 15-30min.
The composite chromium-reducing grinding aid provided by the invention can adjust the proportion of the reducing component and the antioxidant component according to the content of water-soluble chromium (VI) in cement and the required chromium-reducing amplitude, and the doping amount of the composite chromium-reducing grinding aid is generally 0.03-0.1% of the cement mass and can be adjusted.
In general, the chromium-reducing grinding aid is conveyed to a cement grinding workshop, stored in an existing grinding aid storage tank, the mixing amount is controlled through a flow pump, the metering is accurate and stable, the chromium-reducing grinding aid is added into a grinding material, ground through a grinding machine, fully and uniformly mixed with a cement finished product, and conveyed to a cement warehouse for homogenization storage. The composite chromium-reducing grinding aid can be widely applied to the production of low-chromium high-performance cement products.
Compared with the prior art, the invention has the following advantages:
1. the composite chromium-reducing grinding aid provided by the invention has the advantages that the adopted raw materials are good in compatibility and are all dissolved in water, the components of a finished product are uniform, no sediment is generated, and the metering is convenient and accurate; the chromium-reducing agent has the characteristics of long storage time in a closed container, good chromium-reducing effect, no rebound, high temperature resistance, oxidation resistance and the like, and can be well adapted to the change of the working condition temperature of cement;
2. the production cost is lower, the mixing amount is lower than that of the common chromium reducing agent, the cement has the advantages of improving the yield and the consumption, improving the cement performance and reducing the production cost, cement manufacturers do not need to repeatedly purchase and use the cement grinding aid, the production cost is saved, and the economic benefit is better;
3. the preparation method is simple, the formula can be flexibly adjusted according to the requirement of chromium reduction effect, and the operation and quality control are easy; the cement grinding aid storage and addition device is convenient to use, cement enterprises can directly utilize the existing cement grinding aid storage and addition device without adding additional investment, and the cement grinding aid storage and addition device has obvious technical advantages and wide market prospect.
Detailed Description
The following description of the present invention will be made clearly and fully, and it is apparent that the embodiments described are only some, but not all, of the embodiments of the present invention. All other embodiments, which can be made by one of ordinary skill in the art without undue burden on the person of ordinary skill in the art based on embodiments of the present invention, are within the scope of the present invention.
Example 1
The raw materials of the composite chromium-reducing grinding aid provided by the embodiment comprise 25wt% of chromium-reducing component (thiourea dioxide), 8wt% of antioxidant component (methacrylic acid), 30wt% of grinding aid component (triethanolamine 20wt%, diethanol monoisopropanolamine 7wt% and modified calcium lignosulfonate 3 wt%) and the balance of water.
The preparation method of the composite chromium-reducing grinding aid provided by the embodiment comprises the following steps:
s1, adding chromium-reducing component (thiourea dioxide) and water at normal temperature, and stirring at 100rpm for 5min;
s2, adding an antioxidant component (methacrylic acid), and stirring at 100rpm for 8min; and (3) maintaining a stirring state, adding a grinding aid component (triethanolamine and diethanol monoisopropanolamine) firstly, then adding the grinding aid component (modified calcium lignosulfonate), and continuously stirring at 100rpm for 20min to obtain the finished product of the composite chromium-reducing grinding aid.
The preparation method of the modified calcium lignosulfonate comprises the following steps:
p1, dissolving 55 parts of lignosulfonate (calcium lignosulfonate) in water, heating to 80 ℃, regulating the pH value of the solution to 9-10, and stirring for 30min;
p2, adding dilute nitric acid (1 mol/L) into the mixed solution obtained in the step P1 to adjust the pH value of the solution to 8-9, and adding 8 parts of H 2 O 2 2 parts of FeO, and reacting for 1h;
p3, adding formaldehyde aqueous solution (mass fraction 50%) and fatty amine (dodecylamine) into the mixed solution obtained in the step P2, wherein the total parts of the formaldehyde aqueous solution and the fatty amine are 30 parts, the ratio of the formaldehyde to the fatty amine is 1:1, and reacting for 1.5h;
and P4, adding 5 parts by mass of formaldehyde aqueous solution (the mass fraction is 50%) for reaction for 1h, finally adding 5 parts by mass of sodium carboxymethylcellulose and 3 parts by mass of sodium sulfate, stirring for 25min, and cooling to obtain the modified calcium lignosulfonate.
Example 2
The raw materials of the composite chromium-reducing grinding aid provided by the embodiment comprise 15wt% of chromium-reducing components (thiourea dioxide and sodium cyanoborohydride with the mass ratio of 3:1), 10wt% of antioxidant components (methacrylic acid), 40wt% of grinding aid components (triethanolamine 20%, diethanol monoisopropanolamine 10%, modified calcium lignosulfonate 10%) and the balance of water. The preparation method of the composite chromium-reducing grinding aid comprises the following steps:
s1, adding chromium-reducing components (thiourea dioxide and sodium cyanoborohydride) and water at normal temperature, and stirring at 100rpm for 5min;
s2, adding an antioxidant component (methacrylic acid), and stirring at 100rpm for 8min; and (3) maintaining a stirring state, adding a grinding aid component (triethanolamine and diethanol monoisopropanolamine) firstly, then adding the grinding aid component (modified calcium lignosulfonate), and continuously stirring at 100rpm for 20min to obtain the finished product of the composite chromium-reducing grinding aid. The same as in example 1.
Example 3
The raw materials of the composite chromium-reducing grinding aid provided by the embodiment comprise 30wt% of chromium-reducing components (thiourea dioxide and sodium cyanoborohydride with the mass ratio of 2:1), 5wt% of antioxidant components (formamide), 20wt% of grinding aid components (diethanol monoisopropanolamine 10%, triisopropanolamine 8%, modified calcium lignosulfonate 2%) and the balance of water. The preparation method of the composite chromium-reducing grinding aid is the same as that of the example 1.
The preparation method of the composite chromium-reducing grinding aid comprises the following steps:
s1, adding chromium-reducing components (thiourea dioxide and sodium cyanoborohydride) and water at normal temperature, and stirring at 100rpm for 5min;
s2, adding an antioxidant component (formamide), and stirring at 100rpm for 8min; and (3) maintaining a stirring state, adding grinding aid components (diethanol monoisopropanolamine and triisopropanolamine) firstly, then adding the grinding aid components (modified calcium lignosulfonate), and continuously stirring at 100rpm for 20min to obtain the finished product of the composite chromium-reducing grinding aid. The same as in example 1.
Example 4
The raw materials of the composite chromium-reducing grinding aid provided by the embodiment comprise 30wt% of chromium-reducing components (thiourea dioxide and sodium cyanoborohydride are in a mass ratio of 3:2), 8wt% of antioxidant components (formamide and sulfosalicylic acid are in a mass ratio of 1:1), 20wt% of grinding aid components (diethanol monoisopropanolamine 10%, triisopropanolamine 8% and modified calcium lignosulfonate 2%), and the balance of water. The preparation method of the composite chromium-reducing grinding aid is the same as that of the example 1.
The preparation method of the composite chromium-reducing grinding aid comprises the following steps:
s1, adding chromium-reducing components (thiourea dioxide and sodium cyanoborohydride) and water at normal temperature, and stirring at 100rpm for 5min;
s2, adding an antioxidant component (the mass ratio of formamide to sulfosalicylic acid is 1:1), and stirring at 100rpm for 8min; and (3) maintaining a stirring state, adding grinding aid components (diethanol monoisopropanolamine and triisopropanolamine) firstly, then adding the grinding aid components (modified calcium lignosulfonate), and continuously stirring at 100rpm for 20min to obtain the finished product of the composite chromium-reducing grinding aid. The same as in example 1.
Example 5
The raw materials of the composite chromium-reducing grinding aid provided by the embodiment comprise 25wt% of chromium-reducing component (sodium cyanoborohydride), 8wt% of antioxidant component (formamide and methacrylic acid with the mass ratio of 1:1), 30wt% of grinding aid component (triethanolamine 20wt%, diethanol monoisopropanolamine 7wt% and modified calcium lignosulfonate 3 wt%) and the balance of water.
The preparation method of the composite chromium-reducing grinding aid provided by the embodiment comprises the following steps:
s1, adding a chromium reduction component (sodium cyanoborohydride) and water at normal temperature, and stirring at 100rpm for 5min;
s2, adding an antioxidant component (the mass ratio of formamide to methacrylic acid is 1:1), and stirring at 100rpm for 8min; and (3) maintaining a stirring state, adding a grinding aid component (triethanolamine and diethanol monoisopropanolamine) firstly, then adding the grinding aid component (modified calcium lignosulfonate), and continuously stirring at 100rpm for 20min to obtain the finished product of the composite chromium-reducing grinding aid.
Comparative example 1
The raw materials of the composite chromium-reducing grinding aid provided by the comparative example comprise 25wt% of chromium-reducing components (the mass ratio of ferrous sulfate to stannous sulfate is 4:1), 8wt% of antioxidant components (ascorbic acid), 30wt% of grinding aid components (triethanolamine 20wt%, diethanol monoisopropanolamine 7wt% and modified calcium lignosulfonate 3 wt%) and the balance of water. The preparation method of the composite chromium-reducing grinding aid comprises the following steps:
s1, adding chromium-reducing components (ferrous sulfate, stannous sulfate and water) at normal temperature, and stirring at 100rpm for 5min;
s2, adding an antioxidant component (ascorbic acid), and stirring at 100rpm for 8min; and (3) maintaining the stirring state, adding grinding aid components (triethanolamine and diethanol monoisopropanolamine), then adding modified calcium lignosulfonate, and continuously stirring at 100rpm for 20min to obtain the finished product of the composite chromium-reducing grinding aid.
Comparative example 2
The raw materials of the composite chromium-reducing grinding aid provided by the comparative example comprise 15wt% of chromium-reducing components (thiourea dioxide and sodium borohydride are in a mass ratio of 2:1), 40wt% of grinding aid components (triethanolamine 20%, diethanol monoisopropanolamine 10% and modified calcium lignosulfonate 10%), and the balance of water.
The preparation method of the composite chromium-reducing grinding aid provided by the comparative example comprises the following steps:
s1, adding chromium-reducing components (thiourea dioxide and sodium borohydride) and water at normal temperature, and stirring at 100rpm for 5min;
s2, maintaining a stirring state, adding grinding aid components (triethanolamine and diethanol monoisopropanolamine), then adding modified calcium lignosulfonate, and continuously stirring at 100rpm for 20min to obtain a finished product of the composite chromium-reducing grinding aid.
Comparative example 3
The comparative example adopts a commercial liquid chromium reducing agent as a comparison, and the main components of the chromium reducing agent are suspension liquid prepared by uniformly mixing antimony trioxide, stannous sulfate and water, and the price is about 12000 yuan/ton.
Application example: performance comparison of the finished products prepared in examples and comparative examples
The physical properties of the finished products prepared in the above examples and comparative examples were subjected to comparative tests. 9 equal parts of the mythological grade P.O42.5 ordinary Portland cement are taken, 8 parts of blank cement is respectively mixed with the finished product samples of the corresponding examples 1-5 and the comparative examples 1-3, the mixing amounts are 0.05%, and the fluidity of the cement paste is measured according to the method for measuring the fluidity of the cement paste in GB/T8077-2012 test method for the homogeneity of concrete admixture. The standard consistency water consumption, setting time and stability of the cement were measured according to GB/T1346-2011 method for testing the standard consistency water consumption, setting time and stability of Cement. The cement mortar strength was measured according to GB/T17671-1999 method for testing cement mortar Strength (ISO method). The results of the physical properties are shown in Table 1.
TABLE 1 physical Property results of cement mortar incorporating the end products of examples 1-5 and comparative examples 1-3
The mass ratio of the cement is as follows: 76% of clinker (general Portland cement clinker purchased from Yangxin mythology cement Co., ltd.), 10% of slag (purchased from wu-ban steel with particle size smaller than 10 mm), 2.5% of fly ash (purchased from Huangshi Sisai mountain power plant, grade II), 4.5% of desulfurized gypsum (purchased from Kudzuvine shop power plant, grade II) and 7% of limestone (purchased from Yangxin mythology mineral new material Co., ltd.). The materials are uniform samples, the grinding test is carried out on 9 groups according to the same proportion, the total weight of each group of materials is 5kg, the finished products prepared in the examples 1-5 and the comparative examples 1-3 are respectively added according to the mixing amount of 0.05%, and a blank comparative example (namely no grinding aid is added) is additionally arranged; grinding in standard test mill with phi of 500mm multiplied by 500mm for 28min to obtain 9 groups of small-sized cements, and performing grinding-assisting effect comparison test, wherein the results are shown in the following table 2.
TABLE 2 physical Property results of the Portland cements incorporating the end products of examples 1-5 and comparative examples 1-3
The water-soluble hexavalent chromium content in the cement is measured according to GB 31893-2015 limit and measuring method of water-soluble chromium (VI) in cement under different conditions. The hexavalent chromium content of the cement is shown in table 3 below.
TABLE 3 results of hexavalent chromium content testing of cements incorporating the finished products of examples 1-5 and comparative examples 1-3
From the data in tables 1-3, the composite chromium-reducing grinding aid prepared in the embodiment has obviously improved mechanical strength, fluidity and other properties of cement and good grinding-assisting effect. After the compound chromium-reducing grinding aid of examples 1-5 is added, water-soluble chromium (VI) in cement is obviously reduced, the higher the proportion of chromium-reducing components is, the larger the chromium-reducing range is, and the content of hexavalent chromium is not obviously rebounded after the compound chromium-reducing grinding aid is stored at high temperature for a long time, so that the compound chromium-reducing grinding aid is good in chemical stability.
The chromium reducing agent obtained in comparative example 1, which adopts conventional ferrous sulfate and stannous sulfate, has a reduction effect inferior to that of examples 1 to 5, and particularly has obvious rebound after high temperature conditions and long-term storage; comparative example 2, without any antioxidant component added, was identical to the other components of example 2, and had some rebound at high temperature compared with hexavalent chromium upon long-term storage; the chromium reduction effect of comparative example 3 is similar to that of example 5, but the stability is slightly poor and the cost is too high, exceeding 10000 yuan/ton, while the cost of the composite chromium reduction grinding aid of examples 1-5 is 5000-8000 yuan/ton. In combination, the compound chromium-reducing grinding aid has scientific and reasonable formula, various components are indispensable, and the components are matched with each other to play a role together, so that an excellent chromium-reducing grinding aid effect is achieved.
The composite chromium-reducing grinding aid has good chromium-reducing effect, hexavalent chromium does not rebound under the high-temperature condition, water-soluble chromium (VI) is basically stable after long-term storage, the effect is better than that of common chromium-reducing agents in the market, meanwhile, the grinding aid prepared by the invention has no adverse effect on the stability, standard consistency water consumption, paste fluidity and setting time of cement, the cement strength is obviously increased, the grinding aid effect is good, and the composite chromium-reducing grinding aid can simultaneously replace chromium-reducing agents and cement grinding aids, and is beneficial to popularization and application due to lower production cost.
The above detailed description describes in detail the practice of the invention, but the invention is not limited to the specific details of the above embodiments. Many simple modifications and variations of the technical solution of the present invention are possible within the scope of the claims and technical idea of the present invention, which simple modifications are all within the scope of the present invention.
Claims (6)
1. The composite chromium-reducing grinding aid is characterized by comprising 15-30wt% of chromium-reducing component, 5-10wt% of antioxidant component, 20-40wt% of grinding-assisting component and the balance of water; the chromium-reducing component is thiourea dioxide and cyano sodium borohydride;
the mass ratio of thiourea dioxide to cyano sodium borohydride is 3 (1-2);
the antioxidant component is one or more of formamide, methacrylic acid and sulfosalicylic acid;
the grinding aid component consists of alcohol amine and modified lignosulfonate, wherein the modified lignosulfonate accounts for 2-10% of the total mass of the composite chromium-reducing grinding aid; the preparation method of the modified lignosulfonate comprises the following steps:
p1, dissolving 50-60 parts by weight of lignosulfonate in water, heating to 75-85 ℃, regulating the pH value of the solution to 9-10, and stirring for 20-35min;
p2, adding dilute nitric acid into the mixed solution obtained in the step P1 to adjust the pH value of the solution to 8-9, and adding 5-10 parts by weight of H 2 O 2 Or KMnO 4 And 1-2 parts by weight of FeO or CuO, reacting for 0.5-1h;
p3, adding 40-50% of formaldehyde aqueous solution and fatty amine into the mixed solution obtained in the step P2, wherein the total parts of the formaldehyde aqueous solution and the fatty amine are 20-30 parts by weight, the ratio of the formaldehyde to the fatty amine is 1:1, and reacting for 1-1.5h;
and P4, adding 3-5 parts by weight of 40-50% formaldehyde aqueous solution to react for 0.5-1h, finally adding 3-6 parts by weight of sodium carboxymethyl cellulose and 2-4 parts by weight of sodium sulfate, stirring for 10-30min, and cooling to obtain the modified lignin sulfonate.
2. The composite chromium-reducing grinding aid according to claim 1, wherein the raw materials comprise 25wt% of chromium-reducing component, 8wt% of antioxidant component, 30wt% of grinding aid component and the balance of water.
3. The composite chromium-reducing grinding aid according to claim 1, wherein the mass ratio of thiourea dioxide to sodium cyanoborohydride is 2:1.
4. The composite chromium-reducing grinding aid of claim 1, wherein the alcohol amine is one or more of triethanolamine, triisopropanolamine, tripropylene glycol, diethanol monoisopropanolamine, and monoethanol diisopropanolamine.
5. A method for preparing the composite chromium-reducing grinding aid according to claim 1, which is characterized by comprising the following steps:
s1, adding the grinding aid component and water at normal temperature, and uniformly stirring;
s2, adding the antioxidant component and uniformly stirring; and adding the chromium-reducing component in a stirring state, and continuously stirring uniformly to obtain the finished product of the composite chromium-reducing grinding aid.
6. The method for preparing the composite chromium-reducing grinding aid according to claim 5, wherein the stirring speeds of the steps S1 and S2 are 60-150rpm; the stirring time of the step S1 is 3-6min, the stirring time after the antioxidant component is added in the step S2 is 5-10min, and the stirring time after the chromium-reducing component is added is 15-30min.
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