Preparation method of dextrin for iron ore reverse flotation inhibitor

Abstract

The invention discloses a preparation method of dextrin for an iron ore reverse flotation inhibitor. According to the method, insoluble starch is converted into soluble dextrin capable of being used as the iron ore reverse flotation inhibitor by using alpha-amylase under the conditions of certain agent, temperature and concentration, the production and preparation time is greatly shortened compared with that of a traditional enzyme method dextrin production process, and the process is simpler. Compared with the traditional inhibitor such as corn starch, the dextrin for the iron ore reverse flotation inhibitor prepared by the method has a weak inhibition effect on silicate or iron-containing gangue, but has a strong inhibition effect on magnetic and hematite minerals, and the flotation index, especially the iron ore concentrate grade, is obviously improved; compared with the conventional soluble starch, the use amount of the inhibitor measured by dry weight in the reverse flotation operation is reduced by 20%, and the use cost is reduced by 50%.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and in particular relates to a method for preparing dextrin used as an iron ore reverse flotation inhibitor. Background Art

[0002] In the reverse flotation of iron ore, insoluble starch such as corn starch and sweet potato starch is usually used as an iron ore inhibitor. When the slurry is in an alkaline environment and the content of silicate or iron-containing gangue is high, the inhibitor not only inhibits the floatability of magnetite and hematite, but also inhibits silicate or iron-containing gangue, resulting in the inability to distinguish between the concentrate and the tail, making it difficult to obtain ideal separation indicators. The selectivity of the inhibitor has an important influence on the quality of the reverse flotation indicators. Experiments show that small molecular weight soluble dextrins of disaccharides to tetrasaccharides have only a weak inhibitory effect on silicates or iron-containing gangue in iron ore, but have sufficient inhibitory effect on magnetite and hematite, so better separation indicators can be obtained, but monosaccharides have basically no inhibitory effect, and starch with more than four sugars has poor selectivity. However, the standard process for making soluble starch (dextrin) is: using acid method, acid enzyme method or enzyme method to liquefy ordinary starch or grain in solution at high temperature, decompose by heat preservation, purify, inactivate enzymes, filter, decolorize, ion exchange, dry, inspect and package (see Figure 2 ), there are many processes, so the production cost is high, the market source is limited, the transportation cost is high, and the DE value (glucose content) of soluble dextrin on the market is 15-20%. Due to the small molecular weight and high content of low sugar, after NaOH causticization, although the newly prepared solution has a good selective inhibition effect, as time goes by, the solution will change color from light to dark, indicating that the solution is unstable, and the polysaccharide is continuously hydrolyzed into monosaccharide. Excessive dextrin needs to be added to produce sufficient inhibition. If this type of dextrin is directly used in iron ore reverse flotation, it means high cost. Summary of the invention

[0003] In view of the above problems, the object of the present invention is to provide a method for preparing dextrin used as an iron ore reverse flotation inhibitor.

[0004] The object of the present invention is achieved by a method for preparing dextrin as an iron ore reverse flotation inhibitor, which is achieved by the following steps: 1) Add a certain weight of common insoluble commercial starch to a pharmaceutical mixing barrel, first add about the same weight of cold water, start stirring, stir evenly, add 3 to 6 times the weight of starch and 90 to 100°C hot water and continue stirring to obtain a suspension with a starch weight concentration of 12 to 20% and a temperature of 60 to 70°C; 2) Add industrial soda ash to adjust the pH to 6.0-6.5, then add 0.5-1 kg / t 淀粉The weight of medium-temperature α-amylase and 0.5-1% of calcium chloride by weight of starch are stirred for enzymolysis for 20-40 minutes, and then 5-12 times the weight of starch are added with 90-100°C hot water to obtain a dextrin liquid with a dextrin concentration of 5-10% and a temperature of 75-85°C; 3) At a temperature of 75-85°C, add industrial caustic soda to the dextrin liquid to causticize the dextrin liquid for 20-40 minutes. The amount of NaOH added is 700-1000g / t. 淀粉 , and obtain a dextrin solution with a pH of 9.5 to 11, which can be directly used as a depressant for reverse flotation of iron ore; The DE value of dextrin in the dextrin solution is 10-17%.

[0005] The beneficial effects of the present invention are as follows: the present invention utilizes α-amylase to convert insoluble starch into soluble dextrin that can be used as an iron ore reverse flotation inhibitor under certain reagent, temperature and concentration conditions, and the production and preparation time is greatly shortened compared with the traditional enzymatic dextrin production process, and the process is more concise. Compared with traditional inhibitors such as corn starch, the dextrin used as an iron ore reverse flotation inhibitor prepared by the method of the present invention has a weak inhibitory effect on silicates or iron-containing gangue, but a strong inhibitory effect on magnetic and hematite minerals, and the flotation index, especially the grade of iron concentrate, is significantly improved; compared with the conventionally used soluble starch, the amount of inhibitor used in reverse flotation operations measured by dry weight is reduced by 20%, and the use cost is reduced by 50%. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 The process flow chart of the dextrin used as an iron ore reverse flotation inhibitor of the present invention; Figure 2 This is a traditional process flow chart for the production of dextrin used as an iron ore reverse flotation inhibitor. DETAILED DESCRIPTION

[0007] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited in any way. Any changes or improvements made based on the teachings of the present invention fall within the protection scope of the present invention.

[0008] The present invention provides a method for preparing dextrin used as an iron ore reverse flotation inhibitor, which is achieved by the following steps: 1) Add a certain weight of common insoluble commercial starch to a pharmaceutical mixing barrel, first add about the same weight of cold water, start stirring, stir evenly, add 3 to 6 times the weight of starch and 90 to 100°C hot water and continue stirring to obtain a suspension with a starch weight concentration of 12 to 20% and a temperature of 60 to 70°C; 2) Add industrial soda ash to adjust the pH to 6.0-6.5, then add 0.5-1 kg / t 淀粉The weight of medium-temperature α-amylase and 0.5-1% of calcium chloride by weight of starch are stirred for enzymolysis for 20-40 minutes, and then 5-12 times the weight of starch are added with 90-100°C hot water to obtain a dextrin liquid with a dextrin concentration of 5-10% and a temperature of 75-85°C; 3) At a temperature of 75-85°C, add industrial caustic soda to the dextrin liquid to causticize the dextrin liquid for 20-40 minutes. The amount of NaOH added is 700-1000g / t. 淀粉 , and obtain a dextrin solution with a pH of 9.5 to 11, which can be directly added as a depressant to the slurry stirring tank in the reverse flotation operation for iron ore reverse flotation; The DE value of dextrin in the dextrin solution is 10-17%.

[0009] In step 1), the starch is one or more of corn starch, potato starch, sweet potato starch or cassava starch.

[0010] In step 1), the activity of the mesophilic α-amylase is ≥ 2000 U / g.

[0011] The iron ore is magnetite or hematite.

[0012] The iron ore reverse flotation is anion reverse flotation or cation reverse flotation.

[0013] The invention also provides dextrin used as an iron ore reverse flotation inhibitor obtained based on the preparation method and application of the dextrin as an iron ore reverse flotation inhibitor.

[0014] The present invention uses any common starch with wide sources and low prices as raw materials, and converts it into a soluble dextrin solution through enzymatic action, which can be realized in a conventional flotation reagent preparation stirring barrel. Under stirring, starch raw materials, cold water, hot water, medium-temperature α-amylase, and calcium chloride are added in stages to convert the paste starch into low-viscosity soluble dextrin, and finally the selectivity and stability of inhibiting iron ore are improved through the causticization of NaOH.

[0015] The starch in the present invention refers to corn starch, potato starch, sweet potato starch, cassava starch and other starches prepared from plants, whether industrial grade or food grade, and is characterized by being cheap and easy to obtain.

[0016] The raw materials in the present invention, such as starch, calcium chloride, medium-temperature alpha-amylase, industrial soda ash and industrial caustic soda flakes, are all non-toxic industrial products that are easy to transport, store and use.

[0017] Example 1 A preparation process of soluble dextrin as an iron ore reverse flotation inhibitor, the specific method is as follows: 10 tons of cassava starch is added to a reagent stirring barrel, 10 tons of cold water is added first, stirring is started, and 30 tons of hot water at a temperature of 93°C is added after stirring evenly to obtain a suspension with a starch weight concentration of 20% and a temperature of 66°C, then Na2CO3 (industrial soda ash) is added to adjust the pH of the suspension to 6.0, and finally 10 kg of medium-temperature α-amylase (activity 2000 U / g) and 100 kg of calcium chloride are added, and stirred in the reagent stirring barrel for 30 minutes to decompose the sticky insoluble starch into low-viscosity, small-molecular-weight dextrin to obtain a dextrin liquid, and then 50 tons of 93°C hot water is added to dilute the dextrin liquid, and finally 800 kg of NaOH (industrial flake caustic soda) is added when the temperature of the dextrin liquid is 83°C to causticize the soluble dextrin, and the causticization time is 30 minutes. After causticization, a dextrin solution with a pH of 10.5 is obtained, which can be directly added to the reverse flotation operation as an iron ore reverse flotation inhibitor. The dextrin weight concentration is 10%. After testing, the DE value of the dextrin solution is 15%. The starch content is 0 when measured with iodine solution, indicating that the starch has been completely converted into dextrin of the same weight. The solution remains stable and does not change color within 48 hours.

[0018] Example 2 A preparation process of soluble dextrin as an iron ore reverse flotation inhibitor, the specific method is as follows: 5 tons of corn starch are added to a reagent stirring barrel, 5 tons of cold water are added first, stirring is started, and 30 tons of hot water at a temperature of 85°C are added after stirring evenly to obtain a suspension with a starch weight concentration of 12.5% ​​and a temperature of 70°C, then Na2CO3 (industrial soda ash) is added to adjust the pH of the suspension to 6.5, and finally 5 kg of medium-temperature α-amylase (activity 2000 U / g) and 50 kg of calcium chloride are added, and stirred in the reagent stirring barrel for 40 minutes to decompose the sticky insoluble starch into low-viscosity, small-molecular-weight dextrin to obtain a dextrin liquid, and then 60 tons of 85°C hot water are added to dilute the dextrin liquid, and finally 400 kg of NaOH (industrial flake caustic soda) is added when the temperature of the dextrin liquid is 80°C to causticize the soluble dextrin, and the causticization time is 25 minutes. After causticization, a dextrin solution with a pH of 9.5 was obtained, which can be directly added to the reverse flotation operation as an iron ore reverse flotation inhibitor. The dextrin weight concentration was 5%. After testing, the DE value of the dextrin solution was 17%. The starch content was measured by iodine solution and was 0, indicating that the starch had been completely converted into dextrin of the same weight. The solution remained stable and did not change color within 48 hours.

[0019] Experimental Example 1 The dextrin solution prepared in Example 1 was used as an iron ore reverse flotation inhibitor to perform anion reverse flotation on a mixed maghemite ore (mainly hematite, containing 20% ​​silicate minerals, and iron silicate accounting for 8% of the total iron) with a TFe grade of 45%. In a stirring barrel with a pulp concentration of 35-45%, 800 g / t of NaOH (industrial flake caustic soda) as a pH adjuster were added in sequence.矿石 , dextrin solution prepared in Example 1 800g / t 矿石 , Gangue activator CaO 400g / t 矿石 , Anion collector GH-HL 600g / t 矿石 ; The flotation operation adopts a three-stage scavenging process of one roughing, one cleaning, and one cleaning. In the cleaning operation, an anion collector GH-HL 100g / t is added 矿石 , no other reagents are added. After flotation operation, the iron ore is not captured by the collector and enriched in the flotation tank to become iron concentrate, while the gangue is captured by the collector and floats up with the foam as tailings, and finally the separation indicators of TFe grade of 62% and recovery rate of 83% can be obtained.

[0020] Compared with the commercially available dextrin inhibitor with a price of 6,500 yuan / t, the commercially available dextrin inhibitor can achieve similar separation indicators only when the consumption is 1kg / t of ore and the dosage of other reagents is the same.

[0021] Cost calculation: With cassava starch with a factory price of 3,000 yuan / t as raw material, this process needs to consume the following reagents to prepare 1 t of iron ore reverse flotation inhibitor: 5 kg of industrial soda ash, priced at 3,000 yuan / t; 10 kg of calcium chloride, priced at 5,000 yuan / t; 1 kg of medium-temperature α-amylase (2000U / g), priced at 10,000 yuan / t. The water, electricity and NaOH added in the causticizing process used in this method also need to be added and consumed in equal amounts in the preparation of iron ore reverse flotation inhibitor starch (including directly purchased soluble starch, dextrin, etc.), and are not considered as additional costs. After calculation, the additional cost of preparing 1 t of inhibitor in Experimental Example 1 is 3,165 yuan, while the cost of using commercially available dextrin inhibitor is 6,500 yuan / t. When the flotation scale is 2.2 million t / a, the anion reverse flotation operation consumes 1,760 tons of Example 1 inhibitor per year, or consumes 2,200 tons of commercially available dextrin.

[0022] Compared with the commercially available dextrin inhibitor, the inhibitor of Example 1 can reduce the cost by: 2200×6500-1760×3165=8.7296 million yuan / a.

[0023] Experimental Example 2 The inhibitor prepared in Example 2 was used as an iron ore reverse flotation inhibitor to perform cationic reverse flotation on 45% of the mixed hematite ore (mainly hematite, containing 20% ​​silicate minerals, and iron silicate accounting for 8% of the total iron): in a stirring barrel with a pulp concentration of 35-45%, 400 g / t of NaOH (industrial flake caustic soda) as a pH adjuster was added in sequence. 矿石 , dextrin solution prepared in Example 2 800g / t 矿石 , Cationic collector 986 mixed amine 300g / t 矿石; The flotation operation adopts a three-stage sweeping process of one roughing, one cleaning, and an additional collector of 100g / t is added in the cleaning operation. 矿石 , no other reagents are added. After flotation, the iron ore is not captured by the collector and enriched in the flotation tank to become iron concentrate, while the gangue is captured by the collector and floats with the foam as tailings. During the flotation process, the inhibitor prepared in Example 2 is added in an amount of 800g / t 矿石 After flotation, an iron concentrate with a TFe grade of 60% (yield of 60.75%) and a recovery rate of 81% can be obtained.

[0024] Cost calculation: Cationic reverse flotation scale is 2.2 million t / a Using corn starch with a factory price of 3500 yuan / t as raw material, the following reagents are required to prepare 1 ton of inhibitor in Example 2: 5 kg of industrial soda ash, priced at 3000 yuan / t; 10 kg of calcium chloride, priced at 5000 yuan / t; 1 kg of medium-temperature α-amylase (2000U / g), priced at 10000 yuan / t. The consumption of the inhibitor obtained by this method is 800 g / t of ore, and an iron concentrate with a TFe grade of 60% (yield 60.75%) and a recovery rate of 81% can be obtained. The consumption of corn starch directly used as an inhibitor is 600 g / t of ore, and an iron concentrate with a TFe grade of 57% (yield 63.16%) and a recovery rate of 80% can be obtained through cationic reverse flotation (other conditions are the same). The price of 60% grade iron concentrate is 600 yuan / t, and the price is reduced by 20 yuan / t when the grade is reduced by 1%.

[0025] Increased cost: 1760×3665-(600÷800)×1760×3500=1.8304 million yuan / a.

[0026] The benefits generated by improving the sorting indicators are: 220×0.6075×600-220×0.6316×540=51.5592 million yuan / a.

[0027] New profit: 5155.92-183.04=49728800 yuan / a.

[0028] Compared with the corn starch inhibitor, the use of the inhibitor in Example 2 can increase profits by 49.7288 million yuan / a.

Claims

1. A method for preparing dextrin as an iron ore reverse flotation inhibitor, characterized in that: To do this, follow these steps: 1) Add a certain weight of common insoluble commercial starch to a pharmaceutical mixing barrel, first add about the same weight of cold water, start stirring, stir evenly, add 3 to 6 times the weight of starch and 90 to 100°C hot water and continue stirring to obtain a suspension with a starch weight concentration of 12 to 20% and a temperature of 60 to 70°C; 2) Add industrial soda ash to adjust the pH to 6.0-6.5, then add 0.5-1 kg / t 淀粉 The weight of medium-temperature α-amylase and 0.5-1% of calcium chloride by weight of starch are stirred for enzymolysis for 20-40 minutes, and then 5-12 times the weight of starch are added with 90-100°C hot water to obtain a dextrin liquid with a dextrin concentration of 5-10% and a temperature of 75-85°C; 3) At a temperature of 75-85°C, add industrial caustic soda to the dextrin liquid to causticize it for 20-40 minutes. The amount of NaOH added is 700-1000g / t. 淀粉 , and obtain a dextrin solution with a pH of 9.5 to 11, which can be directly used as a depressant for reverse flotation of iron ore; The DE value of dextrin in the dextrin solution is 10-17%.

2. The method for preparing dextrin as an iron ore reverse flotation inhibitor according to claim 1, characterized in that: In step 1), the starch is one or more of corn starch, potato starch, sweet potato starch or cassava starch.

3. The method for preparing dextrin as an iron ore reverse flotation inhibitor according to claim 1, characterized in that: In step 1), the activity of the mesophilic α-amylase is ≥ 2000 U / g.

4. The method for preparing dextrin as an iron ore reverse flotation inhibitor according to claim 1, characterized in that: The iron ore is magnetite or hematite.

5. The method for preparing dextrin as an iron ore reverse flotation inhibitor according to claim 1, characterized in that: The iron ore reverse flotation is anion reverse flotation or cation reverse flotation.

6. A dextrin used as an iron ore reverse flotation inhibitor obtained based on the preparation method of claim 1.

7. Use of the dextrin according to claim 6 as an iron ore reverse flotation inhibitor.

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