A high-calcium vein-type fine-grained cassiterite low-alkalinity flotation combined collector and a flotation separation method thereof

Abstract

The application discloses a high-calcium vein type micro-fine tin stone low-alkalinity flotation combined collector and a flotation separation method thereof, and belongs to the technical field of ore dressing. The combined collector is compounded by a collector A of amido-bishydroxamic acid and a modified oleic acid collector B with the properties of calcium resistance, low-temperature resistance and natural foaming property according to a mass ratio. The collector A has specific adsorption capacity for tin stone. The collector B can stably exist in a high-calcium ore pulp with a pH value of 7.5-9.0, promotes the micro-fine tin stone to target and gather, and provides flotation foam at the same time. The two have synergistic effect, and have weak calcium-containing vein collecting capacity for fluorite, calcite and the like. A small amount of calcium-containing vein inhibitor is matched, a flotation column is used for flotation, no external foaming agent is needed, and a cyclone-static micro-bubble flotation column is used for flotation to obtain tin stone concentrate. The application can improve the recovery rate of micro-fine tin stone, reduce the consumption of reagents, and realize efficient separation of micro-fine tin stone and high-calcium vein.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing technology, specifically relating to a low-alkalinity flotation collector for high-calcium gangue-type fine-grained cassiterite and its flotation separation method. Background Technology

[0002] Cassiterite (SnO2) is the most important mineral raw material for industrial extraction of tin metal, with a theoretical tin content of up to 78.6%. Tin metal has advantages such as being non-toxic, corrosion-resistant, and having a low melting point, and is widely used in soldering, optoelectronics, catalysis, tin chemical products, and tinplate, making it an important resource for technological development. Skarn-type tin deposits are an important type of cassiterite deposit in my country. These deposits are often associated with large amounts of calcium-bearing gangue minerals such as fluorite, calcite, and andradite, and the ore particles are finely disseminated (with a high proportion of -38μm), belonging to the high-calcium gangue type of fine-grained disseminated tin ore. Flotation is the core method for recovering this type of fine-grained cassiterite, but existing flotation technologies still face many challenges in efficiently recovering this type of ore, and resource utilization needs to be further improved. In particular, the tin grade of some low-grade skarn-type tin ores is even as low as below 0.3%, making it almost impossible to achieve economic recovery using traditional processes, resulting in serious resource waste.

[0003] Current cassiterite flotation processes are typically conducted under high-alkalinity pulp conditions (pH > 9.0). This is because the selectivity of traditional collectors (such as benzohydroxyxamic acid, salicylic acid, phosphonates, and arsenoic acids) is easily interfered with by free calcium ions in pulps containing high concentrations of calcium ions. A strongly alkaline environment can enhance the inhibitory effect of depressants such as water glass and sodium hexametaphosphate on calcium-containing gangues like fluorite and calcite, and to some extent reduce the additional reagent consumption caused by side reactions between collectors and calcium ions. However, high-alkalinity flotation systems also have drawbacks: on the one hand, strongly alkaline pulp is corrosive to equipment and increases the burden of neutralization treatment of tailings wastewater; on the other hand, excessively high pH may reduce the surface hydrophobicity of fine-grained cassiterite, which is detrimental to the flotation and recovery of fine-grained cassiterite.

[0004] Regarding reagent formulations, existing technologies also face challenges. The ability of single hydroxamic acid collectors to collect fine cassiterite needs improvement. Combining hydroxamic acid with oleic acid-based reagents is one known approach to improve collecting performance; however, common oleic acid exhibits poor solubility and dispersibility at low temperatures, especially in pulp environments with pH 7.5-9.0 and high calcium ion concentrations, where it easily forms insoluble salts, leading to a reduction in effective components and potentially affecting froth properties. Furthermore, conventional flotation reagent systems typically require the addition of frothers such as No. 2 oil and pine oil to construct a stable froth layer, making reagent formulations and management more complex.

[0005] In terms of separation equipment, traditional mechanically agitated flotation machines produce relatively large bubbles, limiting their efficiency in separating fine-grained minerals. Microbubbles generated by flotation columns are beneficial for increasing the collision and adhesion probability of fine-grained cassiterite, making them a promising separation device. However, to fully leverage the separation advantages of flotation columns, it is necessary to develop flotation reagent systems that can adapt to the unique hydrodynamic environment of flotation columns and possess both high selectivity and good foam stability in low-alkalinity, high-calcium slurries. Existing technologies still have room for improvement in this regard.

[0006] Therefore, developing a novel flotation reagent and its compatible process that can achieve high selective collection of fine-grained cassiterite in a low-alkalinity, high-calcium-ion-concentration slurry environment, while also reducing the amount of frother required, is of great significance for the efficient recovery of this type of cassiterite resource. Summary of the Invention

[0007] The purpose of this invention is to provide a low-alkalinity flotation collector for high-calcium gangue-type fine-grained cassiterite, in order to solve the technical problems of traditional hydroxamic acid collectors having poor selectivity in high-calcium slurry, poor low-temperature resistance when compounded with ordinary oleic acid and easy formation of insoluble calcium salts, and requiring the addition of additional frothers.

[0008] Another objective of this invention is to provide a flotation separation method based on the aforementioned combined collector, thereby eliminating the dependence of traditional processes on a high-alkalinity environment and simplifying the addition of frothers in traditional reagent systems. A reagent system matching the microbubble separation characteristics of the flotation column has been developed, ultimately significantly improving the resource recovery rate of high-calcium gangue-type fine-grained cassiterite.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A high-calcium gangue type fine-grained cassiterite low-alkalinity flotation combined collector, wherein the flotation combined collector is composed of collector A and collector B in a mass ratio of (5~10):1. The collector A is an aminodihydroxyoxime acid compound represented by Formula 1: (Equation 1); Wherein, the two R groups may be the same or different, and each is independently a C1-C10 straight-chain or branched alkylene group, preferably a C2-C6 straight-chain alkylene group.

[0010] Furthermore, the collector B is a modified oleic acid that is calcium resistant and low-temperature resistant. The modified oleic acid is selected from one or more of sulfonated oleic acid, maleic anhydride modified oleic acid, and polyoxyethylene etherified oleic acid. The modified oleic acid remains completely dissolved at 5°C in an aqueous solution with pH=7.5~9.0 and a calcium ion concentration of 300~1000mg / L, without precipitation, and has natural foaming properties. The modified oleic acid has a freezing point ≤5℃ and a solubility in pure water ≥20g / L at 25℃; the modified oleic acid in an aqueous solution at 25℃ and a concentration of 0.1g / L has a foam height ≥80mm and a foam half-life ≥3 minutes, as measured by the Ross-Miles method.

[0011] Furthermore, the mass ratio of collector A to collector B is (6~8):1.

[0012] In this invention's combined collector, collector A exhibits specific recognition and adsorption capabilities for cassiterite surfaces, preferentially adsorbing onto the cassiterite surface even in the presence of calcium-containing gangue minerals. Collector B remains stable in high-calcium slurries with a pH of 7.5–9.0, inducing targeted aggregation of fine cassiterite particles, increasing their apparent particle size, and providing stable froth required for flotation. Through synergistic action, the dihydroxyoxime groups of collector A react with the Sn groups on the cassiterite surface. 4+ A stable five-membered chelate ring is formed, achieving specific adsorption. The hydrophobic long chain of collector B intercalates within the adsorption layer of collector A, enhancing the hydrophobicity of the cassiterite surface. Simultaneously, it induces hydrophobic aggregation of adjacent fine cassiterite particles, significantly increasing the apparent particle size and improving the probability of collision with air bubbles. Ultimately, this significantly improves the flotation rate and recovery of cassiterite, while exhibiting extremely weak collecting activity against calcium-bearing gangue minerals such as fluorite, calcite, and andradite.

[0013] A low-alkalinity flotation separation method for high-calcium gangue-type fine-grained cassiterite, employing the aforementioned flotation collector combination, specifically includes the following steps: (1) Grind the high-calcium gangue-type tin ore containing fluorite, calcite and andradite to obtain a grinding slurry; (2) Add pH adjuster to the grinding slurry to adjust the pH value of the slurry to 7.5~9.0; (3) Add calcium gangue inhibitor to the slurry with adjusted pH value and stir for 2 to 3 minutes; (4) Add the combined collector and stir for 3 to 5 minutes. Do not add any frother during the flotation process. (5) The prepared slurry is fed into the flotation column for flotation, and the froth product is scraped off to obtain cassiterite concentrate.

[0014] Further, in step (1), the content of the -0.038mm particle size after grinding is 30%~60%; in step (2), the pH adjuster is sodium carbonate or sodium hydroxide.

[0015] Further, in step (3), the calcium-containing gangue inhibitor is selected from any one or any combination of two or more of water glass, sodium hexametaphosphate, carboxymethyl cellulose, and tannic acid; the total amount of the calcium-containing gangue inhibitor is 300g / t to 500g / t of raw ore.

[0016] Furthermore, in step (3), sodium fluorosilicate is added to the slurry as an auxiliary inhibitor to help strengthen the surface inhibition of calcium-containing gangue and further improve the grade of the concentrate; the amount of sodium fluorosilicate used is 50g / t~150g / t of raw ore, and its amount is included in the total amount of the calcium-containing gangue inhibitor.

[0017] Further, in step (3), when the calcium gangue inhibitor is a composite inhibitor formed by combining two or more components, the mass ratio between each component is independently 1:(0.5-2); preferably, the composite inhibitor is composed of water glass, carboxymethyl cellulose and tannic acid, with a mass ratio of 2:1:1.

[0018] Furthermore, in step (4), the total amount of the combined collector is 100g / t to 300g / t of raw ore.

[0019] Further, in step (5), the flotation column is a cyclone-static microbubble flotation column, and the diameter of the bubbles generated by the cyclone-static microbubble flotation column is 30~100μm; the process parameters of the flotation operation are: aeration rate of 0.5m³ / h~2.0m³ / h, circulation pressure of 0.1MPa~0.3MPa, pulp concentration of 20%~30%, and flotation residence time of 6 minutes~12 minutes.

[0020] The method of this invention achieves efficient separation of fine-grained cassiterite and high-calcium gangue minerals under low alkalinity conditions by synergistic adaptation of combined collectors and flotation column processes, without the need for additional special frothers, thus significantly simplifying the reagent formulation.

[0021] The significant advantages of this invention are: 1. Strong resistance to calcium ion interference and high selectivity The combined collectors of this invention maintain excellent flotation selectivity in high-calcium slurries (calcium ion concentration 300~1000 mg / L). Collector A, with its aminodihydroxyxamic acid structure, exhibits specific chelating and adsorption capabilities on the cassiterite surface. Collector B, after chemical modification, is less prone to precipitating with free calcium ions. The synergistic effect of these two components increases the cassiterite grade by 6.0~10.9 percentage points compared to the traditional benzyl hydroxamic acid / oleic acid system, while simultaneously increasing the cassiterite recovery rate by 2.9~12.6 percentage points.

[0022] 2. Significantly reduces the dosage of inhibitors, avoiding a series of drawbacks caused by high alkalinity. Because this combined collector exhibits extremely low collecting activity against calcium-bearing gangue such as fluorite, calcite, and andradite, a 50%-70% reduction in inhibitor dosage compared to traditional processes is sufficient to obtain a qualified tin concentrate grade. This not only significantly reduces beneficiation costs but also avoids the corrosion of equipment by high-alkalinity slurry and the burden of neutralizing tailings wastewater. Furthermore, it solves the problem of decreased hydrophobicity and low recovery rate of fine-grained cassiterite under high pH conditions.

[0023] 3. Reduce or eliminate the need for additional foaming agents, simplifying the chemical formulation. The modified oleic acid component in the combined collector of this invention also has certain foaming properties, which can form a stable flotation foam layer without adding or with very little traditional foaming agents such as No. 2 oil. The foam is not sticky, has less gangue entrainment, significantly reduces the types and amounts of reagents used, and lowers the beneficiation cost.

[0024] 4. Excellent low-temperature resistance, suitable for industrial applications in cold regions. The collector B of this invention has a freezing point of ≤5℃ and can still maintain good solubility and dispersion in low-temperature slurry, avoiding the problem of solidification failure of traditional oleic acid at low temperatures. This makes the invention suitable for cassiterite beneficiation operations in high-altitude or cold regions.

[0025] 5. It has good compatibility with flotation column processes and high recovery rate of fine particles. The method of this invention combines a combined collector with a cyclone-static microbubble flotation column, utilizing the efficient collision and adhesion characteristics of microbubbles to fine-grained minerals, and combined with the targeted aggregation effect induced by the combined collector, so that the recovery rate of cassiterite of -19μm fine particles can reach more than 70.5%, which solves the problem of poor recovery effect of fine-grained cassiterite by traditional mechanical stirring flotation machines.

[0026] 6. Environmentally friendly and meets the requirements for green mine development. This invention employs low-alkalinity operation, with the slurry pH close to neutral, significantly reducing the difficulty and cost of tailings wastewater treatment. At the same time, all reagents are free of highly toxic organic arsine substances, avoiding the pollution of soil and water bodies caused by traditional arsine collectors, thus providing good environmental benefits. Attached Figure Description

[0027] Figure 1 This is an X-ray diffraction pattern of the raw ore in an embodiment of the present invention. In the pattern: A-andradite; G-grossular; C-chlorite; Q-quartz; B-biotite; F-fluorite; Ca-calcite; Or-potassium feldspar; Figure 2 This is a diagram showing the intergrowth relationship between cassiterite and gangue minerals in an embodiment of the present invention; Figure 3 This is a process flow diagram of a low-alkalinity flotation separation method for high-calcium gangue-type fine-grained cassiterite according to the present invention. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the present invention. The present invention is not limited to the contents described in the following embodiments. Those skilled in the art should understand that any modifications, equivalent substitutions or improvements made to the technical solution without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

[0029] The "high-calcium system" described in this invention refers to a system in which the soluble calcium ion concentration of the pulp during flotation is 300-1000 mg / L. The soluble calcium ion concentration refers to the calcium ion concentration measured by EDTA titration of the supernatant after the pulp has settled. The ore used in the embodiments of this invention is a typical skarn-type tin ore from my country, and its X-ray diffraction pattern is shown below. Figure 1 As shown, the intergrowth relationship between cassiterite and gangue minerals is as follows: Figure 2 As shown in Table 1, the results of multi-element analysis of the raw ore are shown in Table 2, and the results of tin phase analysis are shown in Table 3.

[0030] Table 1. Results of multi-element analysis of raw ore (%)

[0031] Table 2. Phase analysis results of raw tin ore (%)

[0032] From Table 1, Table 2 and Figure 1 , Figure 2 It is known that tin in this ore mainly exists in the form of cassiterite, accounting for 98.23% of the total tin; the gangue minerals are mainly calcium-containing minerals such as andradite, fluorite, and calcite, with a CaO content as high as 34.01% and a CaF2 content as high as 13.92%, which belongs to a typical high-calcium gangue type fine-grained tin ore.

[0033] In the examples, the foam properties were determined using the Ross-Myers method; after the flotation product was dried, weighed, and sampled, the tin grade was determined using chemical analysis, and the tin recovery rate was calculated.

[0034] The embodiments of the present invention respectively select: Sulfonated oleic acid (industrial grade, freezing point approximately -5℃, solubility in pure water at 25℃ >50g / L); Maleic anhydride modified oleic acid (laboratory-made, freezing point about 3℃, solubility in pure water at 25℃ about 30g / L); Polyoxyethylene etherified oleic acid (industrial grade, freezing point approximately 0°C, solubility in pure water at 25°C >100g / L).

[0035] Tests showed that the three modified oleic acids remained completely dissolved without precipitation in an aqueous solution with pH=8.0 and a calcium ion concentration of 1000 mg / L at 5°C. Furthermore, all three exhibited good natural foaming properties, with foam heights ≥80 mm and foam half-lives ≥3 minutes measured using the Ross-Miles method in an aqueous solution at 25°C and a concentration of 0.1 g / L, meeting the performance requirements of the collector B in this invention.

[0036] Example 1 Preparation method of a combined collector, in which collector A is N-octyltetramethylene dihydroxamic acid (R group is butylene): (1) Preparation of N-octyldi(4-methoxycarbonylbutyl)amine intermediate: 12.9 g n-octylamine (0.1 mol) and 34.5 g anhydrous potassium carbonate (0.25 mol) were added to 200 mL anhydrous acetonitrile. After stirring evenly, the temperature was raised to 60 °C, and 47.0 g methyl 5-bromopentanoate (0.24 mol) was slowly added dropwise. After the addition was completed, the temperature was raised to 80 °C, and the reaction was refluxed for 14 h. After the reaction was completed, the system was cooled to room temperature, and potassium bromide and excess potassium carbonate and other insoluble salts were removed by filtration. The filtrate was collected. The solvent acetonitrile was removed from the filtrate by vacuum distillation to obtain a pale yellow oily crude product. The crude product was purified by vacuum distillation to obtain a colorless and transparent N-octyldi(4-methoxycarbonylbutyl)amine intermediate with a yield of 82%. (2) Preparation of N-octyltetramethylene bishydroxyoxime acid from the intermediate: Dissolve 15.3 g of hydroxylamine hydrochloride (0.22 mol) in 80 mL of deionized water, cool in an ice bath to 0-5 °C, and slowly add 60 mL of an aqueous solution containing 17.6 g of sodium hydroxide (0.44 mol). Control the temperature of the system to not exceed 10 °C during the addition process to obtain a free hydroxylamine alkaline solution. Dissolve 37.4 g of the above N-octyldi(4-methoxycarbonylbutyl)amine intermediate (0.1 mol) in 150 mL of methanol, and slowly add it dropwise to the aforementioned hydroxylamine alkaline solution with stirring. After the addition is complete, raise the temperature to 40 °C and stir the reaction at a constant temperature for 6 h. After the reaction is complete, remove methanol by vacuum distillation at 40 °C, add deionized water to the remaining aqueous phase to a total volume of 200 mL, and adjust the pH of the system to 3-4 with 1 mol / L dilute hydrochloric acid with stirring in an ice bath. A white waxy solid precipitates. Continue stirring for 1 hour to ensure complete precipitation. Filter the mixture, wash the filter cake three times with ice-cold deionized water, and dry it under vacuum at 50°C to obtain N-octyltetramethylene dihydroxyxamic acid, with a yield of approximately 80%.

[0037] (3) Preparation of combined collector: The obtained N-octyltetramethylene dihydroxyoxime acid and sulfonated oleic acid are compounded at a mass ratio of 7:1 to obtain a combined collector; the sulfonated oleic acid is industrial grade, with a freezing point of about -5℃ and a solubility in pure water at 25℃ >50g / L.

[0038] A low-alkalinity flotation separation method for fine-grained cassiterite of high-calcium gangue type includes the following steps: (1) Grind the raw ore to a particle size of -0.038mm with a content of 45% to obtain a grinding slurry. The raw ore is an extremely difficult ore to beneficiate with a tin grade of only 0.30% and a CaO content as high as 34.01%. This grinding fineness can enable more than 90% of cassiterite to achieve individual liberation, while avoiding excessive grinding to produce excessive sludge that affects the flotation effect. (2) Add sodium carbonate to the grinding slurry and adjust the pH of the slurry to 8.0. At this time, the concentration of soluble calcium ions in the slurry is 400 mg / L. (3) Add sodium hexametaphosphate as an inhibitor at a dosage of 500 g / t of raw ore and stir for 2 minutes; (4) Add the combined collector prepared above, with a total dosage of 180 g / t of raw ore, stir for 4 minutes, and do not add any foaming agent; The prepared slurry is fed into a cyclone-static microbubble flotation column for flotation. The flotation column process parameters are: aeration rate of 1.2 m³ / h, circulation pressure of 0.2 MPa, slurry concentration of 25%, and flotation residence time of 8 minutes. Under these conditions, the microbubbles generated by the flotation column have a diameter of approximately 40-80 μm, falling within the 30-100 μm microbubble separation range. The froth product is scraped off to obtain cassiterite concentrate, and the tailings are discharged from the bottom of the flotation column. The process flow of this embodiment is as follows: Figure 3 .

[0039] Flotation results: The tin concentrate grade was 26.8%, and the tin recovery rate was 89.5%, of which the recovery rate of cassiterite in the -19μm particle size was 73.2%.

[0040] Example 2 Preparation method of a combined collector, where collector A is N-octylhexamethylene dihydroxyxamic acid (R group is hexene): (1) Preparation of N-octyldi(6-methoxycarbonylhexyl)amine intermediate: Except for replacing methyl 5-bromopentanoate with an equimolar amount of methyl 7-bromoheptanoate and adjusting the reflux reaction time to 15 h, the other operation steps are the same as step (1) in Example 1, and N-octyldi(6-methoxycarbonylhexyl)amine intermediate is obtained with a yield of about 81%; (2) Preparation of N-octylhexamethylene dihydroxamic acid from intermediate: Except for using the above-mentioned N-octyldi(6-methoxycarbonylhexyl)amine intermediate as raw material and adjusting the reaction time to 7h, the other operation steps are the same as step (2) in Example 1, and N-octylhexamethylene dihydroxamic acid is obtained with a yield of about 79%; (3) Preparation of combined collector: The obtained N-octylhexamethylene dihydroxyoxime acid and maleic anhydride modified oleic acid were compounded at a mass ratio of 6:1 to obtain a combined collector; the maleic anhydride modified oleic acid was prepared in the laboratory, with a freezing point of about 3°C ​​and a solubility of about 30 g / L in pure water at 25°C.

[0041] The flotation steps are the same as in Example 1, except that: the combined collector prepared in this example is used, with a total dosage of 200 g / t of raw ore; the pH of the pulp is adjusted to 7.5; the depressant is a mixture of water glass and carboxymethyl cellulose at a mass ratio of 1:1, with a total dosage of 500 g / t of raw ore; the aeration rate of the flotation column is 1.5 m³ / h, and the circulation pressure is 0.25 MPa; under these process conditions, the microbubbles generated by the flotation column have a diameter of approximately 35~75 μm, falling within the microbubble separation range of 30~100 μm.

[0042] Flotation results: The tin concentrate grade was 25.3%, and the tin recovery rate was 80.5%, of which the recovery rate of cassiterite in the -19μm particle size was 70.5%.

[0043] Example 3 Preparation method of a combined collector, in which collector A is N-octyloctamethylene dihydroxyxamic acid (R group is octylene), as follows: (1) Preparation of N-octyldi(8-methoxycarbonyloctyl)amine intermediate: Except for replacing methyl 5-bromopentanoate with an equimolar amount of methyl 9-bromononanoate and adjusting the reflux reaction time to 16 h, the other operation steps are the same as step (1) in Example 1, and N-octyldi(8-methoxycarbonyloctyl)amine intermediate is obtained with a yield of about 78%; (2) Preparation of N-octyloctamethylene dihydroxamic acid from intermediate: Except for using the above-mentioned N-octyldi(8-methoxycarbonyloctyl)amine intermediate as raw material, adjusting the reaction temperature to 45°C and the reaction time to 8h, the other operation steps are the same as step (2) in Example 1, and N-octyloctamethylene dihydroxamic acid is obtained with a yield of about 77%.

[0044] (3) Preparation of combined collector: The obtained N-octyl octamethylene dihydroxyoxime acid and polyoxyethylene etherified oleic acid are compounded at a mass ratio of 8:1 to obtain a combined collector; the polyoxyethylene etherified oleic acid is industrial grade, with a freezing point of about 0℃ and a solubility in pure water at 25℃ >100g / L.

[0045] The flotation steps are the same as in Example 1, except that: the combined collector prepared in this example is used, with a total dosage of 220 g / t of raw ore; the pH of the pulp is adjusted to 9.0; the inhibitor is a mixture of sodium fluorosilicate and water glass in a mass ratio of 1:1, with a total dosage of 300 g / t of raw ore; the aeration rate of the flotation column is 0.8 m³ / h, and the circulation pressure is 0.15 MPa; under these process conditions, the microbubbles generated by the flotation column have a diameter of approximately 50-90 μm, falling within the microbubble separation range of 30-100 μm.

[0046] Flotation results: The tin concentrate grade was 24.2%, and the tin recovery rate was 77.3%, of which the recovery rate of cassiterite in the -19μm particle size was 68.7%.

[0047] Example 4 The flotation steps are the same as in Example 1, except that: calcium chloride is added to the pulp to adjust the concentration of soluble calcium ions in the pulp to 1000 mg / L (the upper limit of the high calcium system of this invention); the inhibitor is a mixture of water glass, carboxymethyl cellulose and tannic acid in a mass ratio of 2:1:1, with a total dosage of 500 g / t of raw ore.

[0048] Flotation results: The tin concentrate grade was 24.7%, and the tin recovery rate was 90.2%, of which the recovery rate of cassiterite in the -19μm particle size was 80.8%.

[0049] Example 5 The flotation steps are the same as in Example 1, except that: an appropriate amount of deionized water is added to the pulp to dilute it and adjust the concentration of soluble calcium ions in the pulp to 300 mg / L (the lower limit of the high-calcium system of this invention); sodium hexametaphosphate is used as the inhibitor, and the dosage is 300 g / t of raw ore.

[0050] Flotation results: The tin concentrate grade was 29.6%, and the tin recovery rate was 88.2%, of which the recovery rate of cassiterite in the -19μm particle size was 72.6%.

[0051] Comparative Example 1 (Traditional High Alkalinity Process) The flotation steps are the same as in Example 1, except that: benzoic acid is used as the collector at a dosage of 350 g / t of raw ore; ordinary oleic acid is added as an auxiliary collector at a dosage of 60 g / t of raw ore; No. 2 oil is added as a frother at a dosage of 60 g / t of raw ore; the pH of the pulp is adjusted to 10.5; the dosage of water glass is 1000 g / t of raw ore; a mechanically stirred flotation machine is used for flotation, and the generated bubbles are mostly 100~300 μm in diameter, with a flotation time of 5 minutes.

[0052] Flotation results: The tin concentrate grade was 18.7%, and the tin recovery rate was 77.6%, of which the recovery rate of cassiterite in the -19μm particle size was 64.5%.

[0053] Comparative Example 2 (using collector A alone) The flotation steps are the same as in Example 1, except that only N is used. Octyltetramethylene dihydroxamic acid was used as a collector at a dosage of 180 g / t of raw ore; No. 2 oil was added as a foaming agent at a dosage of 60 g / t of raw ore.

[0054] Flotation results: The tin concentrate grade was 22.4%, and the tin recovery rate was 51.9%, of which the recovery rate of cassiterite in the -19μm particle size was 32.1%.

[0055] Comparative Example 3 (using collector B alone) The flotation steps are the same as in Example 1, except that only sulfonated oleic acid is used as the collector, with a dosage of 180 g / t of raw ore.

[0056] Flotation results: The tin concentrate grade was 5.2%, and the tin recovery rate was 73.5%.

[0057] Comparative Example 4 (Used oleic acid instead of modified oleic acid) The flotation procedure is the same as in Example 1, except that ordinary oleic acid is used instead of sulfonated oleic acid, and N is reacted with... Octyltetramethylene dihydroxamic acid was compounded at a mass ratio of 7:1; No. 2 oil was added as a foaming agent at a dosage of 60g / t of raw ore.

[0058] Flotation results: The tin concentrate grade was 16.3%, and the tin recovery rate was 57.9%.

[0059] Comparative Example 5 (Mechanical stirring flotation machine replacing flotation column) The flotation steps are the same as in Example 1, except that a mechanically agitated flotation machine is used for flotation, and the flotation time is 5 minutes. The diameter of the bubbles generated by the mechanically agitated flotation machine is mostly 100~300μm, which is significantly larger than the microbubble size of the flotation column.

[0060] Flotation results: The tin concentrate grade was 23.1%, and the tin recovery rate was 84.6%, of which the recovery rate of cassiterite in the -19μm particle size was 65.7%.

[0061] Comparative Example 6 (with added foaming agent) The flotation steps are the same as in Example 1, except that No. 2 oil is added as a frother at a dosage of 60g / t of raw ore.

[0062] Flotation results: The tin concentrate grade was 23.5%, and the tin recovery rate was 88.7%.

[0063] The results of the above embodiments and comparative examples are analyzed as follows: A comparison of the flotation results of Examples 1-5 and Comparative Examples 1-5 shows that: (1) This invention achieves highly efficient separation with ultra-low inhibitor dosage within the most common high calcium range of 300~1000 mg / L in industry. For extremely difficult-to-process ores with a tin grade of only 0.30% and a CaO content as high as 34.01%, this invention, under low alkalinity conditions of pH 7.5-9.0, requires only 300-500 g / t of inhibitor to achieve excellent tin concentrate grades of 24.7%-29.6% and tin recovery rates of 80.5%-90.2%. Compared with the traditional high-alkalinity process (Comparative Example 1), the inhibitor dosage is reduced by 50%-70%, the tin concentrate grade is increased by 6.0-10.9 percentage points, the total tin recovery rate is increased by 2.9-12.6 percentage points, and the recovery rate of -19μm cassiterite is increased by 6.0-16.3 percentage points.

[0064] (2) The high selectivity of the combined collectors is the core reason for achieving ultra-low inhibitor dosage. The combined collector of this invention exhibits extremely low collecting activity against calcium-bearing gangue minerals such as fluorite, calcite, and andradite, significantly reducing dependence on inhibitors. Traditional processes require large amounts of inhibitors to counteract the collecting effect of the collector on gangue, while this invention requires only a small amount of inhibitor to achieve effective separation, fundamentally resolving the contradiction in high-calcium systems where "large amounts of inhibitor are used while cassiterite is simultaneously inhibited."

[0065] (3) Collector A and collector B have a significant synergistic effect. When collector A is used alone (Comparative Example 2), its ability to collect fine cassiterite is insufficient, with a tin recovery rate of only 51.9%. When collector B is used alone (Comparative Example 3), its selectivity is extremely poor, with a concentrate grade of only 5.2%. However, when the two are used in combination (Example 5), the concentrate grade reaches 26.8%, and the recovery rate reaches 89.5%, achieving both high grade and high recovery rate, which fully demonstrates the synergistic effect of the combined collectors of the present invention.

[0066] (4) Modified oleic acid completely solves the problem of ordinary oleic acid failing in high-calcium systems. When ordinary oleic acid is used instead of modified oleic acid (Comparative Example 4), a large amount of calcium oleate precipitate is formed in the high-calcium slurry at 300 mg / L, leading to reagent inactivation and a significant decrease in concentrate grade and recovery rate. However, the three types of modified oleic acid in this invention can still exist stably under conditions with calcium ion concentrations as high as 1000 mg / L, maintaining good collecting and foaming properties.

[0067] (5) The reagent system of the present invention is well adapted to the flotation column process. Compared to Example 1, when using a mechanically stirred flotation machine (Comparative Example 5), the total tin recovery rate decreased by 0.9 percentage points, and the recovery rate of -19μm cassiterite decreased by 7.5 percentage points. This is because the combined collector of the present invention can induce fine cassiterite particles to form agglomerates of suitable size, which has excellent compatibility with the 30~100μm microbubbles generated by the flotation column, greatly improving the probability of collision and adhesion.

[0068] (6) This invention realizes the integration of harvesting and foaming, simplifying the reagent formulation. The modified oleic acid of this invention possesses excellent natural foaming properties, eliminating the need for additional flotation frothers such as No. 2 oil. This reduces the types of reagents required and lowers the complexity of production management and beneficiation costs. Compared to Example 1, the addition of an additional frother (Comparative Example 6) actually leads to increased gangue inclusions and a 3.3 percentage point decrease in concentrate grade, further demonstrating the superiority of the self-foaming system of this invention.

[0069] The combined collector of this invention has a simple preparation process, readily available raw materials, and low cost; the flotation method is easy to operate, requiring no large-scale modification of existing concentrators, and is easy to promote and apply industrially. For the abundant low-grade, high-calcium gangue-type tin ore resources in my country, this invention has significant economic and environmental benefits.

Claims

1. A high calcium-silicate type fine grained cassiterite low alkalinity flotation combined collector characterized by, The flotation combined collector is composed of collector A and collector B in a mass ratio of (5~10):

1. The collector A is an aminodihydroxyoxime acid compound represented by Formula 1: (Formula 1); Wherein, the two R groups may be the same or different, and each is independently a C1-C10 straight-chain or branched alkylene group, preferably a C2-C6 straight-chain alkylene group.

2. The high-calcium gangue type fine-grained cassiterite low-alkalinity flotation collector according to claim 1, characterized in that, The collector B is a modified oleic acid that is calcium resistant and low-temperature resistant. The modified oleic acid is selected from one or more of sulfonated oleic acid, maleic anhydride modified oleic acid, and polyoxyethylene etherified oleic acid. The modified oleic acid remains completely dissolved at 5°C in an aqueous solution with pH=7.5~9.0 and calcium ion concentration of 300~1000mg / L, without precipitation, and has natural foaming properties. The modified oleic acid has a freezing point ≤5℃ and a solubility in pure water ≥20g / L at 25℃; the modified oleic acid in an aqueous solution at 25℃ and a concentration of 0.1g / L has a foam height ≥80mm and a foam half-life ≥3 minutes, as measured by the Ross-Miles method.

3. The high-calcium gangue type fine-grained cassiterite low-alkalinity flotation collector according to claim 1, characterized in that, The mass ratio of collector A to collector B is (6~8):

1.

4. A method for low-alkalinity flotation separation of high-calcium gangue-type fine-grained cassiterite, employing the flotation combination collector as described in any one of claims 1-3, characterized in that, Specifically, the following steps are included: (1) Grind the high-calcium gangue-type tin ore containing fluorite, calcite and andradite to obtain a grinding slurry; (2) Add pH adjuster to the grinding slurry to adjust the pH value of the slurry to 7.5~9.0; (3) Add calcium gangue inhibitor to the slurry with adjusted pH value and stir for 2 to 3 minutes; (4) Add the combined collector and stir for 3 to 5 minutes. Do not add any frother during the flotation process. (5) The prepared slurry is fed into the flotation column for flotation, and the froth product is scraped off to obtain cassiterite concentrate.

5. The method for low-alkalinity flotation separation of high-calcium gangue-type fine-grained cassiterite according to claim 4, characterized in that, In step (1), the content of the -0.038mm particle size after grinding is 30%~60%; in step (2), the pH adjuster is sodium carbonate or sodium hydroxide.

6. The method for low-alkalinity flotation separation of high-calcium gangue-type fine-grained cassiterite according to claim 4, characterized in that, In step (3), the calcium-containing gangue inhibitor is selected from any one or any combination of two or more of water glass, sodium hexametaphosphate, carboxymethyl cellulose, and tannic acid; the total amount of the calcium-containing gangue inhibitor is 300g / t~500g / t of raw ore.

7. The method for low-alkalinity flotation separation of high-calcium gangue-type fine-grained cassiterite according to claim 4, characterized in that, In step (3), sodium fluorosilicate is added to the slurry as an auxiliary inhibitor to help strengthen the surface inhibition of calcium-containing gangue and further improve the grade of concentrate; the amount of sodium fluorosilicate used is 50g / t~150g / t of raw ore, and its amount is included in the total amount of the calcium-containing gangue inhibitor.

8. The method for low-alkalinity flotation separation of high-calcium gangue-type fine-grained cassiterite according to claim 4, characterized in that, In step (3), when the calcium gangue inhibitor is a composite inhibitor formed by combining two or more components, the mass ratio between each component is independently 1:(0.5-2); preferably, the composite inhibitor is composed of water glass, carboxymethyl cellulose and tannic acid, and the mass ratio is 2:1:

1.

9. The method for low-alkalinity flotation separation of high-calcium gangue-type fine-grained cassiterite according to claim 4, characterized in that, In step (4), the total amount of the combined collector is 100g / t to 300g / t of raw ore.

10. The method for low-alkalinity flotation separation of high-calcium gangue-type fine-grained cassiterite according to claim 4, characterized in that, In step (5), the flotation column is a cyclone-static microbubble flotation column, and the diameter of the bubbles generated by the cyclone-static microbubble flotation column is 30~100μm; the process parameters of the flotation operation are: aeration rate of 0.5m³ / h~2.0m³ / h, circulation pressure of 0.1MPa~0.3MPa, pulp concentration of 20%~30%, and flotation residence time of 6 minutes~12 minutes.

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