Method for preparing coal slime collector by using kitchen waste oil

Abstract

The present application relates to a kind of coal slime collector preparation method using kitchen waste oil, comprising the kitchen waste oil after being pretreated with water, emulsifier is mixed, as carbon source configuration first culture medium, Bacillus and Rhodococcus species are inoculated in it and carry out aerobic fermentation, obtain refined oil, and as carbon source configuration second culture medium, Candida species are inoculated in it and carry out aerobic fermentation, obtain mixed fatty acid, and as carbon source configuration third culture medium, Yarrowia species are inoculated in it and carry out micro-aerobic fermentation, obtain alkane mixture;Emulsified oil and / or refined oil are as carbon source configuration fourth culture medium, Pseudomonas species are inoculated in it and carry out aerobic fermentation, obtain rhamnolipid;Alkane mixture is mixed with rhamnolipid, obtain coal slime collector.The present application develops a new type of green, good coal slime collector by constructing multistage series biological transformation process.

Description

Technical Field

[0001] This invention relates to the field of coal slime flotation technology, and specifically to a method for preparing a coal slime collector using waste cooking oil. Background Technology

[0002] Coal mining and processing generate a large amount of fine coal slime. Due to its high water-holding capacity, it is prone to clumping during combustion, affecting boiler operating efficiency. For a long time, it has been considered inferior fuel and rejected by power plants, resulting in resource waste and environmental pollution. Currently, large quantities of fine coal slime are stored in the open, occupying land resources and easily washed away by water and dispersed by wind, causing secondary pollution to water and air. Therefore, achieving large-scale upgrading and resource utilization of fine coal slime has become one of the key bottlenecks in promoting the coal industry towards zero-waste, green, and high-quality development.

[0003] Flotation is the core process for separating and upgrading fine-grained coal slime, and its separation effect is highly dependent on the performance of the collector. Traditional collectors are mainly derived from petroleum-based products, and generally suffer from poor selectivity, large dosage, and poor biodegradability, making it difficult to meet the requirements of green mine construction and clean production. Therefore, developing green and environmentally friendly collectors that are widely available, low in cost, and have excellent flotation performance has become a key direction for technological innovation in the industry.

[0004] On the other hand, my country's catering industry is highly developed, resulting in a large volume and wide distribution of waste cooking oil. Currently, the legal resource utilization of waste cooking oil mainly focuses on the production of bulk chemicals or fuels such as biodiesel and industrial fatty acids, typically employing chemical conversion processes such as transesterification and hydrogenation. However, these processes generally suffer from high energy consumption, large equipment investment, demanding operating conditions, and low product added value, thus limiting the economic viability and widespread adoption of waste cooking oil resource utilization.

[0005] Waste cooking oil has a complex composition, containing impurities such as sulfides, proteins, and colloids. It also has a high freezing point and an unpleasant odor, making it unsuitable for direct use as a collector in coal slime flotation. Although some studies have attempted to use waste oil for flotation after simple treatment or chemical modification, the uncontrollable composition and severe interference from impurities often lead to unstable flotation results, making it difficult to meet the requirements of continuous industrial operation.

[0006] In recent years, technologies utilizing microbial metabolic transformation of waste oils have gradually developed, providing new ideas for the green and efficient utilization of such resources. Microbial transformation has advantages such as mild reaction conditions, high selectivity, and environmental friendliness. However, existing research mostly focuses on the production of single target products (such as lipases, biosurfactants, or biodiesel), lacking systematic design for the synergistic and targeted transformation of functional components required for coal slime flotation (such as alkanes of specific chain lengths and highly efficient biosurfactants). This makes it difficult to achieve efficient utilization of waste cooking oil components and precise control of collector performance.

[0007] Therefore, developing a method to efficiently and controllably convert waste cooking oil into a high-performance collector suitable for the flotation of fine coal slime is of great practical significance and industrial application prospects.

[0008] The above background information is provided only to aid in understanding the concept and technical solution of this application. It does not necessarily belong to the prior art of this application, nor does it necessarily provide technical guidance. In the absence of clear evidence that the above information was disclosed before the filing date of this application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing a coal slime collector using waste cooking oil.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing a coal slime collector using waste cooking oil, comprising the following steps: (1) Pre-treat the waste cooking oil to remove impurities and obtain purified oil; (2) Mix the purified oil obtained in step (1) with water and emulsifier to obtain emulsified oil; (3) Using the emulsified oil obtained in step (2) as a carbon source, prepare a first culture medium, inoculate Bacillus spp. and Rhodococcus spp. into the first culture medium, carry out aerobic fermentation, and obtain refined oil. (4) Using the refined oil obtained in step (3) as a carbon source, prepare a second culture medium, inoculate the Candida species into the second culture medium, carry out aerobic fermentation, and obtain mixed fatty acids; (5) Using the mixed fatty acids obtained in step (4) as a carbon source, prepare a third culture medium, inoculate the Yersinia species into the third culture medium, first carry out aerobic growth, and then carry out micro-aerobic fermentation to obtain a mixture of alkane; (6) Using the emulsified oil obtained in step (2) and / or the refined oil obtained in step (3) as carbon sources, prepare a fourth culture medium, inoculate the Pseudomonas species into the fourth culture medium, and carry out aerobic fermentation to obtain rhamnolipid. (7) The alkane mixture obtained in step (5) is mixed with the rhamnolipid obtained in step (6) to obtain the coal slime collector.

[0011] This invention uses waste cooking oil as raw material and constructs a multi-stage tandem bioconversion process. By leveraging the synergistic effect and targeted metabolism of different functional microorganisms, it sequentially removes impurities from waste oil, degrades macromolecular components, and targets the synthesis of active flotation components. Ultimately, it develops a novel green collector, realizing the high-value resource utilization of waste cooking oil.

[0012] Specifically, this method first pre-treats waste cooking oil to remove solid residues and moisture, providing basic raw materials for subsequent bioconversion. Then, Bacillus and Rhodococcus strains are co-cultured to further remove impurities through a biorefining process, yielding refined oil. This refined oil is then hydrolyzed by Candida strains to generate free fatty acids. Further, Yersinia strains directionally convert the fatty acids into C8-C18 chain alkanes. Finally, using emulsified oil and / or refined oil as substrates, Pseudomonas strains ferment to generate rhamnolipids, which are then compounded with alkane components to prepare a green bio-based collector.

[0013] This collector demonstrates significantly improved separation efficiency in the flotation of fine coal slime, increasing the clean coal yield by approximately 20% compared to traditional collectors (such as the diesel-Span80 compound system). Simultaneously, the ash content of the clean coal is effectively reduced, achieving the dual goals of resource utilization of waste oil and efficient, green upgrading of fine coal slime. This invention effectively overcomes the technical shortcomings of existing collectors, such as poor adaptability and environmental pollution, and possesses significant economic benefits and environmental value.

[0014] In this invention, an imbalance in the ratio of alkane mixture to rhamnolipid will affect the interfacial properties, dispersion stability, and interaction of the collector with the coal slime surface, thereby restricting the improvement of flotation efficiency. When the alkane ratio is too high and the rhamnolipid content is relatively insufficient, the emulsifying and dispersing properties of the collector decrease, making it difficult for it to be uniformly distributed in the aqueous phase, affecting its spreading and adsorption on the coal particle surface, and reducing the collection efficiency. Conversely, when the rhamnolipid ratio is too high and the alkane content is insufficient, although a good emulsion system can be formed, the collecting ability of the non-polar components of alkane is weakened, making it difficult to effectively cover the hydrophobic area on the coal particle surface, resulting in a decrease in flotation selectivity and a possible increase in the ash content of clean coal. In some embodiments of this invention, in step (7), the alkane mixture and rhamnolipid are preferably mixed in a weight ratio of (85~99):(1~15).

[0015] Further, the alkane mixture is mixed with the rhamnolipin at a weight ratio of (92~99):(1~8).

[0016] In this invention, the Bacillus, Rhodococcus, Candida, Yersinia, and Pseudomonas strains used can be selected from typical strains known in the art. As a specific example, the Bacillus strains include, but are not limited to, Bacillus subtilis (…). Bacillus subtilis The species of Rhodococcus mentioned include, but are not limited to, Rhodococcus rubrum (…). Rhodococcus erythropolis ), Rhodococcus turbidus, and the Candida species include, but are not limited to, Candida globosum ( Candida rugosa The *Yersinia* species mentioned include, but are not limited to, *Yersinia lipolytica*. Yarrowia lipolytica The Pseudomonas species mentioned include, but are not limited to, Pseudomonas aeruginosa. Pseudomonas aeruginosa Those skilled in the art should understand that, without departing from the concept of this invention, other strains of the same genus with similar functions may also be selected to achieve the same technical effect.

[0017] In some embodiments, the first culture medium comprises, by weight: The emulsified oil obtained in step (2) is 20-40 parts; Nitrogen source 0.5-2 parts; Phosphorus source 0.1~1 part; Inorganic salts: 0.05~0.5 parts; 70-100 parts water.

[0018] Further, by weight, the first culture medium comprises: 25-35 parts of the emulsified oil obtained in step (2); Nitrogen source: 0.5-1.5 parts; Phosphorus source: 0.3~0.8 parts; Inorganic salts: 0.05~0.15 parts; 70-90 parts water.

[0019] In some embodiments, the second culture medium comprises, by weight: The refined oil obtained in step (3) is 20-40 parts; Yeast extract powder 0.5–2 parts; Phosphorus source 0.1 to 1 part; 70-100 parts water.

[0020] Further, the second culture medium comprises: The refined oil obtained in step (3) is 25-35 parts; Yeast extract powder 0.5–1.5 parts; Phosphorus source: 0.3~0.8 parts; 70-80 parts water.

[0021] In some embodiments, the third culture medium comprises, by weight: The mixed fatty acids obtained in step (4) are 15-25 parts; Nitrogen source: 0.1-0.3 parts; 0.5 to 2 parts of phosphate buffer; 70-100 parts water.

[0022] Further, by weight, the third culture medium comprises: The mixed fatty acids obtained in step (4) are 15-25 parts; Nitrogen source: 0.1-0.3 parts; Phosphate buffer solution: 0.5–1.5 parts; 70-90 parts water.

[0023] In some embodiments, the fourth culture medium comprises, by weight: 20-40 parts of the emulsified oil obtained in step (2) and / or the refined oil obtained in step (3); Nitrogen source: 0.2-0.5 parts; Phosphorus source 0.1~1 part; Inorganic salts: 0.01~0.1 parts; 70-100 parts water.

[0024] Further, 25 to 35 parts of the emulsified oil obtained in step (2) and / or the refined oil obtained in step (3); Nitrogen source: 0.2-0.5 parts; Phosphorus source: 0.3~0.8 parts; Inorganic salts: 0.03~0.1 parts; 70-90 parts water.

[0025] In this invention, the nitrogen source in the culture medium is selected from one or more of ammonium sulfate and sodium nitrate, the phosphorus source is selected from one or more of dipotassium hydrogen phosphate, potassium dihydrogen phosphate, and sodium phosphate, and the inorganic salt is selected from one or more of magnesium salts (such as magnesium sulfate) and calcium salts (such as calcium sulfate).

[0026] In some embodiments, the inoculation of the strains in steps (3) to (6) includes: inoculating the strains into seed culture medium and culturing them with shaking for 10 to 14 hours at 28 to 37°C and pH 6.0 to 8.0 to obtain the logarithmic growth phase, and then inoculating the seed culture medium into its corresponding culture medium.

[0027] The seed culture medium is a commonly used nutrient substrate for culturing microorganisms in the art. Its components typically include a carbon source, a nitrogen source, and inorganic salts. As a specific example, the carbon source may be selected from at least one of glucose, sucrose, soluble starch, or molasses; the nitrogen source may be selected from at least one of yeast extract, peptone, tryptone, beef extract, ammonium sulfate, or urea; and the inorganic salt may be selected from at least one of dipotassium hydrogen phosphate, potassium dihydrogen phosphate, magnesium sulfate, sodium chloride, or manganese sulfate. In a preferred embodiment, the seed culture medium comprises: 5-20 g / L glucose, 5-15 g / L yeast extract, 5-10 g / L peptone, 1-5 g / L sodium chloride, and pH 7.0-7.2.

[0028] The pH range of 6.0 to 8.0 can be maintained and adjusted using conventional methods in the art. Specifically, during the culture medium preparation stage, a phosphate buffer system (such as a sodium dihydrogen phosphate-disodium hydrogen phosphate system) can be used to adjust the initial pH to the desired range. During the culture process, if the pH fluctuates, a sterile acid solution (such as a 1 mol / L hydrochloric acid solution) or an alkaline solution (such as a 1 mol / L sodium hydroxide solution) can be added dropwise for real-time adjustment to ensure the stability of the cell growth environment.

[0029] In some embodiments, step (3) further includes adjusting the OD of the seed liquid of Bacillus and Rhodococcus species. 600 After the values ​​are consistent, they are mixed at a volume ratio of (1~2):1 (Bacillus: Rhodococcus) as co-culture inoculum, and then the co-culture inoculum is inoculated into the first culture medium.

[0030] In some embodiments, in step (2), the mass of emulsifier added is 0.3 to 0.8% of the purified oil, and the mass of water added is 5 to 10% of the purified oil.

[0031] In some embodiments, the emulsifier is Tween (e.g., Tween-80).

[0032] In some embodiments, the pretreatment includes heating, centrifuging, and separating the waste cooking oil.

[0033] In some embodiments, the aerobic fermentation is carried out under the following conditions: the fermentation temperature is controlled at 30~37°C and the dissolved oxygen content is 25~35%.

[0034] The dissolved oxygen concentration can be controlled by referring to conventional techniques in the field. For example, the dissolved oxygen concentration can be maintained above the critical concentration by gradually increasing the aeration rate and stirring speed.

[0035] In some embodiments, the microaerobic fermentation is carried out under the following conditions: the fermentation temperature is controlled at 30~37°C and the dissolved oxygen content is 5~15%.

[0036] Due to the application of the above-mentioned technical solution, the present invention has the following advantages compared with the prior art: This invention uses waste cooking oil as raw material and constructs a multi-stage cascaded bioconversion process. Through the synergistic action and targeted metabolism of different functional microorganisms, it sequentially removes impurities from the waste oil, degrades macromolecular components, and synthesizes the targeted active components for flotation. Ultimately, a novel green collector is developed, achieving high-value resource utilization of waste cooking oil. This collector exhibits superior separation efficiency in the flotation of fine coal slime, increasing the yield of clean coal compared to traditional collectors while effectively reducing coal ash content. This achieves the dual goals of resource utilization of waste cooking oil and efficient, green upgrading of fine coal slime. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the process for preparing a coal slime collector using waste cooking oil provided by the present invention. Detailed Implementation

[0038] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other. Unless otherwise specified, the reagents and instruments used in the following embodiments and comparative examples are commercially available products or can be prepared with reference to existing technology.

[0039] In this invention, unless the context explicitly requires otherwise, the numerical range referred to as "numerical value A to numerical value B" refers to the range including the endpoints A and B. The numerical range referred to as "above" or "below" refers to the numerical range including the stated number. "Optional" or "optional" indicates that certain substances, components, execution steps, application conditions, etc., may or may not be used, and there is no limitation on the manner of use.

[0040] In this invention, unless the context explicitly requires otherwise, all numerical parameters modified by terms such as "about" (including but not limited to time, temperature, pressure, concentration, weight percentage, pH value, and size) should be understood to cover a reasonable range centered on the stated value, based on the fluctuation range of conventional experimental or production equipment. Specifically, this range typically includes ±10% of the stated value, and may be extended to ±20% of the stated value in certain embodiments or where conventional precision in the art allows. Such deviations should be understood as inherent fluctuations caused by differences in measuring instruments, operating methods, environmental conditions, or batch variations of materials, and the technical solutions within this range of fluctuations can achieve the core objectives and beneficial effects of this invention.

[0041] Example 1: This example provides a method for preparing a collector using waste cooking oil, such as... Figure 1 As shown, it includes the following steps: (1) Collect waste cooking oil, heat it to 60°C, and then centrifuge it at 3000 r / min for 15 min to remove residue and water, and obtain purified oil phase. Add water (20%~30% by mass) and Tween-80 (0.5% by mass) to the oil phase, and stir at high speed at 2000 r / min for 5 min to obtain emulsified oil.

[0042] (2) Under aseptic conditions, Bacillus subtilis (purchased from China Industrial Microbial Culture Collection Center (CICC), strain number CICC 21253) and Rhodococcus (purchased from China Industrial Microbial Culture Collection Center (CICC), strain number CICC 10278) were respectively inoculated into seed culture medium (10 g glucose, 5 g peptone, 5 g yeast extract (purchased from Changde Bickman Biotechnology Co., Ltd., product number 110702014), 5 g NaCl, 1000 mL water, pH 7.0-7.3) and cultured for 10-14 h until the logarithmic growth phase to obtain seed solutions. The OD values ​​of the two seed solutions were adjusted. 600 Once the values ​​are consistent, mix them at a volume ratio of 1.5:1 (Bacillus subtilis: Rhodococcus) as a co-culture inoculum.

[0043] Prepare the first fermentation medium by weight: 30 parts of emulsified oil (as carbon source) obtained in step (1), 1 part of ammonium sulfate (as nitrogen source), 0.5 parts of dipotassium hydrogen phosphate, 0.1 parts of magnesium sulfate, and 80 parts of water. Mix them evenly, adjust the pH to 8.0, sterilize and set aside.

[0044] The co-culture inoculum was inoculated into the first fermentation medium at a volume percentage of 10%, and aerobic fermentation was carried out at 37°C and dissolved oxygen >30%. The stirring speed was controlled at 250 r / min during the fermentation process, and the fermentation was carried out at a constant temperature and stirring for 48 hours. After fermentation, the fermentation broth was centrifuged at 3000 r / min for 10 min to remove the lower precipitate, and the upper liquid was collected to obtain refined oil.

[0045] (3) Under aseptic conditions, the Candida species (Candida foldis) were placed in the sterile environment. Candida rugosa The strain (CICC 31280) was purchased from the China Industrial Microbial Culture Collection Center (CICC) and inoculated into seed culture medium (same as step (2)). It was cultured for 10-14 hours until the logarithmic growth phase to obtain seed liquid.

[0046] Prepare the second fermentation medium by weight: 30 parts of refined oil obtained in step (2), 1 part of yeast extract (purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number V34633-500g), 0.5 parts of potassium dihydrogen phosphate, and 80 parts of water. Mix them evenly, adjust the pH to 7.0, sterilize and set aside.

[0047] The seed culture of Candida species was inoculated into the second fermentation medium at a volume percentage of 10%, and aerobic fermentation was carried out at 30°C for 72 hours. The aerobic fermentation conditions other than temperature and fermentation time were the same as in step (2). After fermentation, the mixture of fatty acids in the upper layer was collected by centrifugation.

[0048] (4) Under aseptic conditions, Yersinia species (Yersinia lipolytica) were placed in the sterile environment. Yarrowia lipolytica The culture medium, 0950P, was obtained from the China Industrial Microbial Culture Collection Center (CICC) and was inoculated into seed culture medium (same as step (2)). It was cultured for 10-14 hours until the logarithmic growth phase to obtain the seed liquid.

[0049] Prepare the third fermentation medium by weight: 20 parts of mixed fatty acids obtained in step (3), 0.2 parts of ammonium sulfate, 1 part of 0.1 mol / L phosphate buffer (pH 7.2), and 80 parts of water. Mix them evenly, adjust the pH to 6.5, sterilize and set aside.

[0050] The seed culture of *Yersinia* was inoculated into the third fermentation medium at a volume percentage of 10%. Aerobic fermentation was carried out first at 30°C, followed by microaerobic fermentation for 96 hours. The dissolved oxygen concentration during aerobic fermentation was >30%, and the dissolved oxygen concentration during microaerobic fermentation was controlled at 5%–10%. The stirring speed was 150–250 rpm, and the aeration rate was 0.1–0.3 vvm. After fermentation, the mixture was centrifuged, and the upper alkane mixture was collected.

[0051] (5) Under sterile conditions, a strain of Pseudomonas (Pseudomonas aeruginosa, purchased from China Industrial Microbial Culture Collection Center (CICC), catalog number CICC 10419) was inoculated into seed culture medium (same as step (2)) and cultured for 10-14 hours to the logarithmic growth phase to obtain seed liquid.

[0052] Prepare the fourth fermentation medium by weight: 30 parts of emulsified oil obtained in step (1), 0.4 parts of sodium nitrate, 0.5 parts of dipotassium hydrogen phosphate, 0.05 parts of magnesium sulfate, and 80 parts of water. Adjust the pH to 6.0 and sterilize before use.

[0053] The seed culture of *Pseudomonas* species was inoculated into the fourth fermentation medium at a volume percentage of 10%, and aerobic fermentation was carried out at 30°C for 48 hours. The aerobic fermentation conditions, except for temperature and fermentation time, were the same as in step (2). The fermentation broth was centrifuged or extracted to obtain rhamnolipin products.

[0054] (6) The alkane mixture obtained in step (4) and the rhamnolipin product obtained in step (5) are extracted, concentrated, and purified respectively. The alkane mixture is obtained by centrifugation to collect the upper oil phase, which is then dehydrated with anhydrous sodium sulfate. The rhamnolipin is extracted by acid precipitation (adjusting the pH to 2.0-3.0), and the precipitate or extract phase is collected and concentrated under reduced pressure to remove the solvent, thus obtaining the purified product. Then, 96 parts by weight of the alkane mixture and 4 parts by weight of the rhamnolipin are compounded to obtain the coal slime flotation collector of the present invention.

[0055] In addition, when necessary (such as when the properties of the feed oil fluctuate, the characteristics of the target coal change, or there are special requirements for the dispersibility, stability, and foaming performance of the reagent), a small amount of additives can be added to the coal slime flotation collector. The additives are conventional additives in the field of flotation reagents, including but not limited to one or more of emulsifiers (such as Span-80, Tween-80), dispersants (such as sodium dodecylbenzene sulfonate), stabilizers, pour point depressants, or modifiers. The total amount added shall not exceed 5% of the total mass of the collector, in order to help improve the adaptability, dispersibility, and flotation performance of the reagent.

[0056] The entire process described above employs a multi-stage, series-connected engineered fermentation system, with each reactor linked by sterile pipelines. The effluent from the previous reactor is inactivated through heat treatment (above 120°C for 20 minutes), followed by centrifugation at 8000 rpm for 10 minutes to separate the cells from the product. The separated clear oil or aqueous phase product serves as the designated carbon source or substrate for the next reactor and is pumped into the next stage fermenter via metering pumps.

[0057] Example 2: This example provides a method for preparing a collector using waste cooking oil, which is basically the same as Example 1, except that the purified alkane mixture is compounded with rhamnolipin at a weight ratio of 99:1.

[0058] Example 3: This example provides a method for preparing a collector using waste cooking oil, which is basically the same as Example 1, except that the purified alkane mixture is compounded with rhamnolipin at a weight ratio of 92:8.

[0059] Example 4: This example provides a method for preparing a collector using waste cooking oil, which is basically the same as Example 1, except that the purified alkane mixture is compounded with rhamnolipin at a weight ratio of 85:15.

[0060] Comparative Example 1: This comparative example provides a conventional diesel fuel collector, whose composition by mass percentage is as follows: Diesel 75%, Water 23%, Span80 2%.

[0061] Comparative Example 2: This comparative example provides a method for preparing a collector using waste cooking oil, which is basically the same as Example 1, except that: instead of going through steps (3) and (4), the refined oil obtained in step (2) and the rhamnolipin ester product obtained in step (5) are directly extracted, concentrated and purified in step (6), and then compounded with 96 parts by weight of refined oil and 4 parts by weight of rhamnolipin.

[0062] Comparative Example 3: This comparative example provides a method for preparing a collector using waste cooking oil, which is basically the same as Example 1, except that: instead of step (4), the mixed fatty acids obtained in step (3) and the rhamnolipin ester product obtained in step (5) are directly extracted, concentrated and purified in step (6), and then compounded with 96 parts by weight of mixed fatty acids and 4 parts by weight of rhamnolipin.

[0063] The collectors obtained in each embodiment and comparative example were subjected to the following performance tests.

[0064] (I) Experimental Objective (1) Evaluate the flotation effect of different reagents on a certain fine coal slime; (2) Flotation index requirements: ash content of clean coal <11%, ash content of tailings >65%.

[0065] (II) Flotation Conditions (1) Screening method The coal samples were subjected to sieve analysis according to GB / T 477-2008 "Coal Sieving Test Method". A small-scale sieve method was used, and the main series sieve aperture sizes were selected as follows: 0.500 mm, 0.250 mm, 0.125 mm, 0.075 mm, and 0.045 mm. The specific procedures were performed according to Chapter 7.2 of GB / T 477-2008 "Coal Sieving Test Method".

[0066] (2) Small flotation test Small-scale flotation tests were conducted on coal slime in accordance with GB / T4757-2013 "Coal Slime (Powder Laboratory Unit Flotation Test Method)". The flotation machine used in the test was the XFDM type flotation machine specified in the standard "Coal Preparation Laboratory Unit Flotation Test Method".

[0067] (3) The coal sample used in this test was coal slime from the customer's site. The coal slime was dried, crushed, screened and weighed to obtain the coal sample for the test.

[0068] (4) The foaming agent used in the experiment was FB3532-C, which was produced by Fengbei. The slurry concentration was 80 g / L and the water was tap water.

[0069] Specific test data (1) Sieve test The particle size sieving data of the coal samples are shown in Table 1.

[0070] Table 1. Coal slime particle size screening data

[0071] As shown in Table 1, the content of fine coal slime in this coal slime is >80%, and the ash content of the coal slime is 21.72%, which is typical fine coal.

[0072] (2) Small flotation test The reagent regime for the experiment was as follows: the collector dosage was 600 g / t (600 g per ton of dry coal), and the frother dosage was 200 g / t. Table 2 shows the results of the small-scale flotation test of coal slime. The yield of clean coal, the ash content of clean coal, and the ash content of tailings were all tested according to GB / T 4757-2025 and expressed as percentages. Under the premise of meeting the clean coal ash content requirement (clean coal ash content < 11%), the higher the clean coal yield and the higher the tailings ash content, the better. The combustible gas recovery rate was tested according to GB / T 30047-2013 and expressed as a percentage; the higher the combustible gas recovery rate, the better.

[0073] Table 2 Results of Small Flotation Test

[0074] (IV) Experimental Results and Analysis As shown in Table 2, the collector provided in this embodiment of the invention exhibits superior flotation performance. Specifically, compared to traditional petroleum-based collectors (Comparative Example 1), the collector of this invention not only significantly improves the yield of clean coal but also performs better in terms of comprehensive flotation performance indicators, demonstrating a superior overall flotation effect. In contrast, the collector used in Comparative Example 2 was a direct mixture of refined oil obtained from pretreatment and primary biocatalysis of waste cooking oil and rhamnolipid obtained through biocatalysis. Due to its poor overall hydrophobicity, all flotation indicators were at their lowest. Comparative Example 3 directly combined fatty acids obtained from pretreatment and two-stage biocatalysis of waste cooking oil with rhamnolipid obtained through biocatalysis as the collector. While this combination improved the product structure to some extent, insufficient selectivity led to a significant increase in the ash content of clean coal to 12.17%, indicating that omitting the multi-stage bioconversion steps involved in this invention cannot achieve the desired flotation effect. The multi-stage bioconversion process of this invention plays a crucial role in constructing a highly efficient collector.

[0075] Furthermore, this invention further optimizes the ratio of key components in the collector. By adjusting the relative ratio of the obtained alkane mixture to rhamnolipin, flotation selectivity and efficiency can be effectively improved. Experimental results show that the preferred weight ratio of alkane mixture to rhamnolipin is (85~99):(1~15), within which good flotation performance can be obtained; a further optimized ratio of (92~99):(1~8) yields even better flotation indicators, demonstrating the potential for refined control of the synergistic effect of each component.

[0076] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing a coal slime collector using waste cooking oil, characterized in that, Includes the following steps: (1) Pre-treat the waste cooking oil to remove impurities and obtain purified oil; (2) Mix the purified oil obtained in step (1) with water and emulsifier to obtain emulsified oil; (3) Using the emulsified oil obtained in step (2) as a carbon source, prepare a first culture medium, inoculate Bacillus spp. and Rhodococcus spp. into the first culture medium, carry out aerobic fermentation, and obtain refined oil. (4) Using the refined oil obtained in step (3) as a carbon source, prepare a second culture medium, inoculate the Candida species into the second culture medium, carry out aerobic fermentation, and obtain mixed fatty acids; (5) Using the mixed fatty acids obtained in step (4) as a carbon source, prepare a third culture medium, inoculate the Yersinia species into the third culture medium, first carry out aerobic growth, and then carry out micro-aerobic fermentation to obtain a mixture of alkane; (6) Using the emulsified oil obtained in step (2) and / or the refined oil obtained in step (3) as carbon sources, prepare a fourth culture medium, inoculate the Pseudomonas species into the fourth culture medium, and carry out aerobic fermentation to obtain rhamnolipid. (7) The alkane mixture obtained in step (5) is mixed with the rhamnolipid obtained in step (6) at a weight ratio of (85~99): (1~15) to obtain the coal slime collector.

2. The method for preparing coal slime collector using waste cooking oil according to claim 1, characterized in that, In step (7), the alkane mixture and rhamnolipin are mixed at a weight ratio of (92~99):(1~8).

3. The method for preparing a coal slime collector using waste cooking oil according to claim 1, characterized in that, The first culture medium comprises, by weight: The emulsified oil obtained in step (2) is 20-40 parts; Nitrogen source 0.5-2 parts; Phosphorus source 0.1~1 part; Inorganic salts: 0.05~0.5 parts; 70-100 parts water.

4. The method for preparing a coal slime collector using waste cooking oil according to claim 1, characterized in that, The second culture medium comprises, by weight: The refined oil obtained in step (3) is 20-40 parts; Yeast extract powder 0.5–2 parts; Phosphorus source 0.1 to 1 part; 70-100 parts water.

5. The method for preparing a coal slime collector using waste cooking oil according to claim 1, characterized in that, The third culture medium comprises, by weight: The mixed fatty acids obtained in step (4) are 15-25 parts; Nitrogen source: 0.1-0.3 parts; 0.5 to 2 parts of phosphate buffer; 70-100 parts water.

6. The method for preparing a coal slime collector using waste cooking oil according to claim 1, characterized in that, The fourth culture medium comprises, by weight: 20-40 parts of the emulsified oil obtained in step (2) and / or the refined oil obtained in step (3); Nitrogen source: 0.2-0.5 parts; Phosphorus source 0.1~1 part; Inorganic salts: 0.01~0.1 parts; 70-100 parts water.

7. The method for preparing a coal slime collector using waste cooking oil according to any one of claims 3 to 6, characterized in that, The nitrogen source in each culture medium is selected from one or more of ammonium sulfate and sodium nitrate, the phosphorus source is selected from one or more of dipotassium hydrogen phosphate, potassium dihydrogen phosphate, and sodium phosphate, and the inorganic salt is selected from one or more of magnesium salt and calcium salt.

8. The method for preparing a coal slime collector using waste cooking oil according to claim 1, characterized in that, The inoculation of the strains in steps (3) to (6) includes: inoculating the strains into seed culture medium and culturing them under shaking conditions of 28-37℃ and pH 6.0-8.0 for 10-14 hours to the logarithmic growth phase to obtain seed liquid, and then inoculating the seed liquid into its corresponding culture medium.

9. The method for preparing a coal slime collector using waste cooking oil according to claim 1, characterized in that, In step (2), the emulsifier is added at a mass of 0.3-0.8% of the purified oil, and the water is added at a mass of 5-10% of the purified oil; and / or, The emulsifier is Tween.

10. The method for preparing a coal slime collector using waste cooking oil according to claim 1, characterized in that, The pretreatment includes heating, centrifuging, and separating the waste cooking oil.

11. The method for preparing a coal slime collector using waste cooking oil according to claim 1, characterized in that, The aerobic fermentation is carried out under the following conditions: fermentation temperature controlled at 30-37℃, dissolved oxygen content at 25-35%; and / or, The microaerobic fermentation is carried out under the following conditions: fermentation temperature controlled at 30~37℃, dissolved oxygen content at 5~15%.

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