A method for preparing a composite collector for high-ash difficult-to-clean coal using waste cooking oil

Abstract

The present invention relates to a method for preparing a composite collector for high-ash difficult-to-clean coal using waste cooking oil, which belongs to the technical field of fine coal flotation and solves the problems of low selectivity, low collection performance, large dosage of reagent, low clean coal yield and low clean coal grade in the prior art. A method for preparing a composite collector for high-ash difficult-to-clean coal using waste cooking oil comprises the following steps: (1) filtering and removing impurities and dehydrating the waste cooking oil; (2) preparing an intermediate aqueous solution at room temperature; (3) adding the waste cooking oil treated in step (1) to the intermediate aqueous solution, and adjusting the pH of the mixed solution of the waste cooking oil and the intermediate solution to 7.5-8.5; (4) stirring the mixed solution in step (3) to obtain a composite collector with a Gemini-like structure. The method achieves the goal of reducing the ash content of the clean coal and the dosage of the collector while ensuring the clean coal yield.

Description

Technical Field

[0001] The invention relates to the technical field of fine-particle coal flotation, and in particular to a method for preparing a composite collector for high-ash difficult-to-separate coal by utilizing waste cooking oil. Background Art

[0002] The development and utilization of high-quality coal resources and the improvement of mechanized coal mining technology have led to a trend of coal becoming finer. At the same time, a large amount of gangue is mixed into the coal, resulting in higher ash content, increased intergrowth content, and poor floatability of the coal slime, which further highlights the problem of difficult selection of coal slime. The typical characteristics of high-ash difficult-to-select coal flotation are high clean coal yield and poor flotation selectivity. Excessive ash content seriously restricts the quality of the final clean coal product.

[0003] Research shows that the main reasons for the high ash content of high-ash hard-to-clean coal are the adsorption cover of fine mud on the surface of clean coal, water entrainment and the existence of coal-mineral intergrowth (such as floatable components). To address the problem of high ash content of high-ash hard-to-clean coal, the existing technology is mainly the flotation process intensification method, including efficient pulping, selective flocculation, adding inhibitors, etc.

[0004] During the flotation process, pollutants such as fine-grained clay minerals will be adsorbed and covered on the surface of coal, reducing the hydrophobicity of the coal surface, thereby reducing the adhesion efficiency of particles and bubbles, hindering the adsorption of collectors, and resulting in reduced flotation efficiency. Clay minerals are fine colloidal particles, which can easily enter the flotation clean coal foam with water flow under stirring, resulting in an increase in the ash content of the clean coal. Slurry adjustment before flotation helps to achieve the dispersion of coal particles and ash particles, enhance the selective adsorption of flotation agents on the coal surface, and improve the flotation separation effect of high-ash and difficult-to-separate coal. Flotation slurry adjustment requires a certain amount of turbulence and shear to achieve mineral dispersion and agent adsorption, which can promote the recovery of clean coal in flotation and reduce the ash content of clean coal, but the inhibitory effect of flotation slurry adjustment on the ash content of flotation clean coal is limited and may further break up the coal particles.

[0005] Selective flocculation refers to the addition of flocculants such as polyaluminium chloride and polyacrylamide in flotation slurry to achieve flocculation of fine-grained clay minerals, thereby reducing mineral entrainment and fine mud cover during flotation. However, since coal often undergoes hydrophobic flocculation before clay minerals, it is difficult to achieve selective flocculation of clay minerals in coal flotation. Inhibitors such as modified starch, water glass and sodium hexametaphosphate can also be added to the slurry to destroy or weaken the adsorption of minerals on collectors, enhance the hydrophilicity of the mineral surface, and achieve the purpose of improving flotation, but there are high requirements for the type and amount of inhibitors.

[0006] The existing flotation process intensification methods are difficult to adapt to the requirements of separation and quality improvement of difficult-to-select coal slimes with high ash content and complex embedding, and the flotation process lacks adaptability to changes in material properties. Summary of the invention

[0007] In view of the above analysis, an embodiment of the present invention aims to provide a method for preparing a composite collector for high-ash difficult-to-clean coal using waste cooking oil, so as to solve at least one of the problems of existing collectors, such as low selectivity, low collection performance, large dosage of reagents, low clean coal yield, and low clean coal grade.

[0008] On the one hand, an embodiment of the present invention provides a method for preparing a composite collector for high-ash difficult-to-clean coal using waste cooking oil, comprising the following steps:

[0009] (1) Filter, remove impurities and dehydrate the kitchen waste oil;

[0010] (2) preparing an intermediate aqueous solution at room temperature;

[0011] (3) adding the waste cooking oil treated in step (1) to the intermediate aqueous solution, and adjusting the pH of the mixed solution of the waste cooking oil and the intermediate solution to 7.5 to 8.5;

[0012] (4) Stirring the mixed solution in step (3) to obtain a composite collector with a Gemini-like structure.

[0013] Specifically, the concentration of the intermediate aqueous solution in step (2) is less than 0.05 mM.

[0014] It should be noted that the molar concentration ratio of the waste cooking oil and the intermediate in step (3) is 2:1.

[0015] Furthermore, the waste cooking oil is used as the tail chain molecule of the composite collector, and the Gemini-like structure is formed by one intermediate and two tail chain molecules under the action of electrostatics.

[0016] Furthermore, the intermediates and tail chain molecules in the Gemini-like structure are depolymerized under acidic conditions.

[0017] It is worth noting that the molecular structures of the two tail chains are the same or different, and are one or more combinations of the following:

[0018]

[0019] Specifically, the intermediate structural formula is R1 in the intermediate structure contains some atoms of N, S, O, and C atoms, and the total number of non-hydrogen atoms in R1 is 2 to 8; R2 contains N atoms or both N and C atoms, and the total number of atoms is 1 to 3.

[0020] Exemplarily, the composite collector of the Gemini-like structure comprises:

[0021]

[0022]

[0023] On the other hand, an embodiment of the present invention further provides a composite collector for high-ash and difficult-to-clean coal, which is prepared by the method for preparing a composite collector for high-ash and difficult-to-clean coal by using waste cooking oil.

[0024] On the other hand, the embodiment of the present invention also provides a flotation process for high-ash difficult-to-separate coal, wherein the prepared composite collector is applied to the flotation of high-ash difficult-to-separate coal, comprising the following steps:

[0025] (1) Primary flotation: The pH of the ore pulp is adjusted to be weakly alkaline, so that the composite collector forms a Gemini-like structure, and roughing is performed to obtain the tail coal of the primary flotation and the ore pulp containing clean coal. The ore pulp containing clean coal enters the secondary flotation;

[0026] (2) Secondary flotation: adjust the pH of the slurry to be weakly acidic to depolymerize the composite collector and perform flotation to produce clean coal and medium coal;

[0027] (3) Separation and re-selection of intergrowths: The medium coal produced by the second stage flotation enters the ball mill for grinding to fully dissociate the intergrowths of the medium coal, and the coal slurry returns to the first stage flotation.

[0028] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0029] 1. In view of the high ash content and complex components of high-ash difficult-to-select coal, the present invention adopts waste cooking oil to prepare tail chain molecular substances for obtaining composite collectors. Waste cooking oil is rich in unsaturated acids such as oleic acid, linoleic acid, and linolenic acid. The adsorption effect of unsaturated carboxylic acids on the coal surface is stronger, which is more conducive to flotation separation. In addition, the preparation of tail chain molecular substances from waste cooking oil has certain economic efficiency and obvious environmental benefits.

[0030] 2. The present invention designs a pH-sensitive composite collector. Under alkaline conditions, the intermediate and tail chain molecules are fully mixed and form a Gemini-like structure under the action of electrostatics. The polar groups of the intermediate structure are combined with the hydrophilic sites on the coal surface, so that the two tail chain molecules can better play a hydrophobic role and enhance the floatability of the coal. In particular, when the intermediate structure is a disulfide bond, a sulfoxide group, etc., it has a strong surface activity and improved solid affinity compared to other traditional collectors, thereby improving its collection performance and greatly improving the clean coal yield;

[0031] Under acidic conditions, the intermediates and tail chain molecules depolymerize, and only the tail chain molecules play a role. The tail chain molecules exist in the form of hydrocarbon oil and are selectively adsorbed on the coal surface, which improves the selectivity of the collector, helps to reduce the ash content of the flotation clean coal, and improves the grade of the clean coal.

[0032] The composite collector designed by the present invention can enhance the hydrophobicity of the coal surface through the strong hydrophobicity of the tail chain molecules in the assembled or depolymerized state, thereby ensuring the flotation separation effect.

[0033] 3. The pH-sensitive composite collector used in the present invention is combined with the two-stage flotation + intergrowth dissociation and reselection process to timely adjust the collector's collection capacity according to the changes in the physical properties of the slurry, thereby reducing the clean coal ash content while ensuring the clean coal yield;

[0034] In the first stage of flotation, the pH of the pulp is adjusted to be weakly alkaline, so that the collector forms a Gemini-like structure for roughing, ensuring that more clean coal products are obtained; in the second stage of flotation, the pH of the pulp is adjusted to be weakly acidic, which enhances the selectivity of the collector, obtains good separation indicators without adding other reagents, and improves the grade of clean coal;

[0035] For the tail coal of the second flotation, the present invention adopts a grinding process to release the clean coal in the medium coal body, maximizes the recovery and utilization of coal resources, and combines it with the pH-sensitive agent flotation process to form a high-ash and difficult-to-separate coal flotation recovery technology system based on selective dissociation-interface regulation, thereby realizing the precise separation of coal gangue.

[0036] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0038] Figure 1 This is a working principle diagram of the present invention for preparing a composite collector using waste kitchen oil as raw material.

[0039] Figure 2 This is a process flow chart of deep flotation of high-ash difficult-to-clean coal according to the present invention;

[0040] Figure 3 This is a connection diagram of the deep flotation process equipment for high-ash difficult-to-clean coal of the present invention;

[0041] Figure 4 This is a working principle diagram of the composite collector of the present invention in an assembled state;

[0042] Figure 5 This is a working principle diagram of the composite collector of the present invention in a depolymerization state;

[0043] Reference numerals:

[0044] 1-feeding tank; 2-feeding pump; 3-collector stirring barrel; 4-collector dosing pump; 5-foaming agent barrel; 6-foaming agent dosing pump; 7-alkaline solution barrel; 8-alkaline solution dosing pump; 9-acidic solution barrel; 10-acidic solution dosing pump; 11-first stage automatic dosing machine; 12-second stage automatic dosing machine; 13-slurry preprocessor; 14-slurry pump; 15-first stage flotation machine; 16-second stage flotation machine; 17-ball mill. DETAILED DESCRIPTION

[0045] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0046] High-ash difficult-to-clean coal has the characteristics of high ash content and contains more fine-grained coal slime. Fine-grained clay minerals and other pollutants are easily adsorbed and covered on the coal surface, reducing the hydrophobicity of the coal surface, thereby reducing the adhesion efficiency of particles and bubbles, hindering the adsorption of collectors, resulting in low separation efficiency of high-ash fine-grained coal slime in conventional washing processes. The presence of some medium coal intergrowths will also affect the flotation indicators, making it difficult to obtain high-yield and low-ash clean coal at the same time.

[0047] A specific embodiment of the present invention discloses a method for preparing a composite collector for high-ash and difficult-to-clean coal using waste cooking oil, comprising the following steps:

[0048] (1) Filter, remove impurities and dehydrate the kitchen waste oil;

[0049] (2) preparing an intermediate aqueous solution at room temperature;

[0050] (3) adding the waste cooking oil treated in step (1) to the intermediate aqueous solution, and adjusting the pH of the mixed solution of the waste cooking oil and the intermediate solution to 7.5 to 8.5;

[0051] (4) Stirring the mixed solution in step (3) to obtain a composite collector with a Gemini-like structure.

[0052] Specifically, the kitchen waste grease is pre-treated. For the use of coal slime flotation, the kitchen waste grease only needs to be physically filtered and impurities removed according to the density difference, and then heated and precipitated for further dehydration and impurity removal, so that it can be mixed with the intermediate solution as a tail chain molecular substance;

[0053] Waste cooking oil is mainly composed of vegetable oil, rich in carboxylic acid substances, mainly oleic acid, linoleic acid, linolenic acid, etc. The preparation of tail-chain molecular substances from waste cooking oil is economical and has obvious environmental benefits. Moreover, unsaturated acids such as oleic acid, linoleic acid, linolenic acid, etc. have a stronger adsorption effect on the coal surface, which is more conducive to flotation separation.

[0054] Furthermore, the waste cooking oil is used as the tail chain molecule of the composite collector, and the Gemini-like structure is formed by one intermediate and two tail chain molecules under the action of electrostatics.

[0055] It should be noted that the concentration of the intermediate aqueous solution in step (2) is less than 0.05 mM; the appropriate concentration of the intermediate aqueous solution is controlled to make the intermediate better dissolved and dispersed, and the composite collector is formed after the tail chain molecules are added; if the concentration of the intermediate aqueous solution is too high, the added tail chain molecules must also be increased accordingly, and the tail chain molecules are mainly hydrocarbon oils, which makes dissolution and dispersion difficult.

[0056] Specifically, the molar concentration ratio of the waste cooking oil and the intermediate in step (3) is 2:1.

[0057] In step (4), the mixed solution is fully stirred, dispersed and mixed to make the intermediate and the tail chain material fully contact, so that adsorption and assembly occur, and a composite collector in an assembled state is obtained. The molar concentration of the collector solution is equal to the molar concentration of the intermediate aqueous solution in step (2).

[0058] Furthermore, the intermediates and tail chain molecules in the Gemini-like structure are depolymerized under acidic conditions.

[0059] like Figure 1 As shown, under alkaline conditions, the intermediate and two tail chain molecules of the composite collector are assembled through electrostatic action to form a Gemini-like structure, which has strong collection performance and can be efficiently adsorbed on the coal surface, thereby improving the flotation recovery rate; under acidic conditions, when the composite collector is not assembled or depolymerized, the intermediate with cationic groups at both ends has little effect on flotation, and only the tail chain molecules play a role. Because the tail chain molecules exist in the form of hydrocarbon oil, they form micro-oil droplets in the slurry and spread on the surface of coal particles, which has strong selectivity and is conducive to reducing the ash content of flotation clean coal; the composite collector can enhance the hydrophobicity of the coal surface through the strong hydrophobicity of the tail chain molecules in the assembled or depolymerized state, thereby ensuring the flotation separation effect;

[0060] The assembly and depolymerization of the composite collector are affected by the pH of the solution, and the pH required for the assembly and depolymerization of composite collectors with different anionic and cationic groups is quite different;

[0061] In a possible design, when the solution pH is 7.5-8.5, the composite collector is in an assembled state, and when the solution pH is 5.5-6.0, the composite collector is in a depolymerized state.

[0062] Furthermore, the molecular structures of the two tail chains are the same or different, and are one or more combinations of the following:

[0063]

[0064] The intermediate structure is R1 in the intermediate structure contains some atoms of N, S, O, and C atoms, and the total number of non-hydrogen atoms in R1 is 2 to 8; R2 contains N atoms or both N and C atoms, and the total number of atoms is 1 to 3.

[0065] Further, R1 in the intermediate structure is one of -(CH2)2-, -CH2C(O)CH2-, -SS-, -(CH2)2NH(CH2)2-, -(CH2)2NH(CH2)2NH(CH2)2-, -CH=CH-, and -N=N- structures;

[0066] When R1 in the intermediate structure is a strong polar group such as a disulfide bond or a sulfoxide group, the sulfur or oxygen atom can undergo hydrogen bonding and other adsorption reactions with the polar sites on the surface of the coal or the surface of the coal intergrowth. Compared with other traditional collectors, it has strong surface activity, improved solid affinity, and thus higher capture performance.

[0067] Specifically, R2 in the intermediate structure is a protonated group of -NH2 or -C(NH)NH2.

[0068] Preferably, the intermediate structure comprises:

[0069] Exemplarily, the composite collector of the Gemini-like structure comprises:

[0070]

[0071] On the other hand, an embodiment of the present invention further provides a composite collector for high-ash and difficult-to-clean coal, which is prepared by the method for preparing a composite collector for high-ash and difficult-to-clean coal by using waste cooking oil.

[0072] In one possible design, the tail chain molecule uses The two tail chain molecules are the same or different, wherein R3 is the polar group of the tail chain molecule, which is deprotonated -COOH or -SO3H; n is the carbon chain length of the tail chain molecule, which is 6 to 18, and the CC bond in the tail chain is a single bond or an unsaturated bond. R2 is a cationic group, and R3 is an anionic group; its chemical structure is generally formulated as follows: The commonly used tail chain molecular structure is Its working principle is as follows Figure 4 , Figure 5 shown.

[0073] On the other hand, the embodiment of the present invention also provides a flotation process for high-ash difficult-to-clean coal, such as Figure 2 As shown, the prepared composite collector is applied to the flotation of high-ash difficult-to-clean coal, comprising the following steps:

[0074] (1) preparing flotation reagents: adding tail chain molecular substances and intermediate solution into a collector stirring barrel according to a molar ratio and stirring and mixing them uniformly, inputting the composite collector into a first-stage automatic dosing machine through a collector dosing pump, inputting the frother in the frother barrel and the alkaline solution in the alkaline solution barrel into a first-stage automatic dosing machine through a frother dosing pump and an alkaline solution dosing pump respectively, and adding reagents in a first-stage flotation process by a first-stage automatic dosing machine and automatically adjusting the dosage;

[0075] The acid solution in the acid solution barrel is added to the second-stage automatic dosing machine through the acid dosing pump. The reagents in the second-stage flotation process are added by the second-stage automatic dosing machine and the dosage is automatically adjusted;

[0076] (2) Primary flotation: The slurry in the feed tank is transported to the slurry pre-processor by the feed pump. After the slurry and the reagents from the primary automatic dosing machine are fully slurried, the alkaline slurry is pumped into the primary flotation machine for flotation by the slurry pump. The flotation machine scrapers scrape out the flotation clean coal, and the primary flotation clean coal a and tail coal b are obtained after roughing. The flotation clean coal a continues to enter the secondary flotation machine for cleaning, and the flotation tail coal b enters the dehydration system as the final tail coal product;

[0077] (3) Secondary flotation: The clean coal a produced by the primary flotation machine is fed into the secondary flotation machine, and the pH value of the pulp is adjusted to weak acid by adding acidic solution through the secondary automatic dosing machine. Clean coal d and medium coal c are produced by flotation in the secondary flotation machine. The clean coal d produced by the secondary flotation machine enters the dehydration stage and becomes a clean coal product.

[0078] (4) Separation and reselection of intergrowths: The secondary flotation machine selects the medium coal c and sends it to the ball mill for selective grinding and dissociation, so that the intergrowths of the medium coal are fully dissociated. The coal slurry returns to the primary flotation machine to be mixed with the feed for flotation.

[0079] Preferably, the collector is a pH-sensitive composite collector, the frother is an alcohol frother, the amount of the first-stage flotation collector is 500-1500 g / t, and the amount of the frother is 100-250 g / t.

[0080] Preferably, the pH of the first-stage flotation pulp is 7.5-8.5, and the pH of the second-stage flotation pulp is 5.5-6.0.

[0081] Preferably, the grinding time in the ball mill is 2 to 3 minutes.

[0082] In a possible design, the tail chain molecule substance and the intermediate solution in step (1) are in a molar ratio of 2:1.

[0083] The pH-sensitive composite collector is combined with the two-stage flotation + intergrowth dissociation and reselection process to timely adjust the collector's collection capacity according to the changes in the physical properties of the ore pulp, thereby reducing the clean coal ash content while ensuring the clean coal yield;

[0084] In the first stage of flotation, the pH of the pulp is adjusted to be weakly alkaline, so that the collector forms a Gemini-like structure for roughing, ensuring that more clean coal products are obtained; in the second stage of flotation, the pH of the pulp is adjusted to be weakly acidic, which enhances the selectivity of the collector, obtains good separation indicators without adding other reagents, and improves the grade of clean coal;

[0085] For the tailings of the second-stage flotation, the grinding process is adopted to release the clean coal in the medium coal conglomerate, so as to recover and utilize the coal resources to the maximum extent. Combined with the pH-sensitive agent flotation process, a high-ash and difficult-to-separate coal flotation recovery technology system based on selective dissociation-interface regulation is formed, thus realizing the precise separation of coal gangue.

[0086] High ash difficult coal flotation system Figure 3 As shown, it includes a flotation dosing system, a feeding system, a first-stage flotation machine 15, a second-stage flotation machine 16 and a ball mill 17 connected in sequence through pipelines;

[0087] The outlet of the feeding system is connected to the inlet of the first stage flotation machine 15, the first outlet of the first stage flotation machine is connected to the inlet of the second stage flotation machine, the first outlet of the second stage flotation machine 16 is connected to the inlet of the ball mill 17, the outlet of the ball mill 17 is connected to the inlet of the first stage flotation machine 15, and the second outlets of the first stage flotation machine and the second stage flotation machine are both product outlets;

[0088] The feeding system comprises a feed pool 1, a feed pump 2, a slurry preprocessor 13 and a slurry pump 14 which are connected in sequence through pipelines, the feed pool outlet is connected to the feed pump inlet, the slurry preprocessor inlet is connected to the feed pump outlet, and the slurry pump suction port is connected to the slurry preprocessor outlet;

[0089] The flotation dosing system includes a first-stage flotation dosing system and a second-stage flotation dosing system, wherein the outlet of the first-stage flotation dosing system is connected to the slurry preprocessor through a pipeline, and the second-stage flotation dosing system is connected to the second-stage flotation machine through a pipeline;

[0090] The first stage flotation dosing system comprises a first stage automatic dosing machine 11, a collector stirring barrel 3, a frother stirring barrel 5, and an alkaline solution barrel 7, wherein the collector stirring barrel 3, the frother stirring barrel 5, and the alkaline solution barrel 7 are respectively connected to the first stage automatic dosing machine 11 through a collector dosing pump 4, a frother dosing pump 6, an alkaline solution dosing pump 8, and pipelines;

[0091] The two-stage flotation dosing system comprises an acid solution barrel 9, an acid solution dosing pump 10 and a two-stage automatic dosing machine 12 which are sequentially connected through pipelines.

[0092] In summary, the present invention designs a pH-sensitive composite collector, cooperates with a two-stage flotation + intergrowth dissociation and reselection process, and timely adjusts the collection capacity of the collector according to the changes in the physical properties of the ore pulp, thereby reducing the ash content of the clean coal while ensuring the clean coal yield; in view of the high ash content and complex components of high-ash difficult-to-select coal, the tail chain molecular substances of the composite collector are prepared using kitchen waste oil, which are mainly oleic acid, linoleic acid, and linolenic acid with unsaturated bonds. These unsaturated carboxylic acids have a stronger adsorption effect on the coal surface, reduce the dosage of the agent, and greatly improve the adsorption strength and spreading rate of the collector. In addition, the preparation of tail chain molecular substances from kitchen waste oil has certain economy and obvious environmental benefits.

[0093] The composite collector and deep flotation process of the present invention are described below in conjunction with specific embodiments.

[0094] Example 1

[0095] The coking coal of a coal preparation plant in Shanxi was flotated and ash reduced by using the process of one-stage roughing and two-stage cleaning. The ash content of the raw coal was 23%.

[0096] The steps of preparing the composite collector are as follows:

[0097] (1) Pre-treating the waste cooking oil by filtering, removing impurities and dehydrating until there is no visible water and impurities. For the use of coal slime flotation, the waste cooking oil only needs to be physically filtered and removed impurities according to the density difference, and then heated and precipitated for further dehydration and impurity removal, so that the tail chain molecular substance can be mixed with the intermediate solution;

[0098] (2) Preparation of intermediates at room temperature Solution, solution concentration is 0.04mM;

[0099] (3) adding the pretreated cooking oil to the intermediate solution to prepare a pH-sensitive composite collector, wherein the molar concentration ratio of the cooking oil to the intermediate is 2:1 (the cooking oil adopts an average molecular weight according to its specific composition analysis);

[0100] The average molecular weight of cooking oil in this preparation process was calculated as 278;

[0101] (4) using sodium hydroxide to adjust the solution pH to pH = 7.5-8.5, and fully stirring the mixed solution to mix it evenly to obtain an assembled composite collector, wherein the tail chain molecule can be linoleic acid or linolenic acid in the waste cooking oil, or the two tail chain molecules can be a combination of two of oleic acid, linoleic acid, and linolenic acid;

[0102] One possible structural formula is:

[0103]

[0104] The composite collector prepared by the above method adopts the process of one-stage roughing-two-stage cleaning to flotation and ash reduction of coking coal from a coal preparation plant in Shanxi Province as follows:

[0105] (1) Preparing a first-stage flotation reagent: The assembled composite collector, frother, and alkaline solution are respectively input into a first-stage automatic dosing machine. The reagents in the first-stage flotation process are added by the first-stage automatic dosing machine and the dosage is automatically controlled;

[0106] The dosage of collector in the first stage of flotation is 500g / t, the dosage of frother is 150g / t, and the dosage of alkaline solution is adjusted according to the pH value of the pulp;

[0107] Using pinene alcohol as a foaming agent, sodium hydroxide is used to prepare an alkaline solution;

[0108] (2) Primary flotation: The slurry in the feed tank is transported to the slurry preprocessor by the feed pump. After the slurry and the reagents from the primary automatic dosing machine are fully slurried, the pH of the slurry is maintained at 7.5-8.5. The alkaline slurry is pumped into the primary flotation machine for flotation by the slurry pump. The flotation clean coal is scraped out by the flotation machine scraper. After roughing, the primary flotation clean coal a and tail coal b are obtained. The flotation clean coal a continues to enter the secondary flotation machine for cleaning. The flotation tail coal b enters the dehydration system as the final tail coal product.

[0109] (3) Secondary flotation: The clean coal a produced by the primary flotation machine is fed into the secondary flotation machine, and an acid solution (prepared with sulfuric acid) is added through the secondary automatic dosing machine to adjust the pH of the pulp to 5.5-6.0. Clean coal d and medium coal c are produced by flotation in the secondary flotation machine. The clean coal d produced by the secondary flotation machine enters the dehydration stage and becomes a clean coal product.

[0110] (4) Separation and reselection of coal aggregates: The selected medium coal c from the second-stage flotation machine enters the ball mill for selective grinding and dissociation. The grinding time in the ball mill is 2 to 3 minutes, so that the medium coal aggregates are fully dissociated. The coal slurry returns to the first-stage flotation machine to mix with the feed for flotation.

[0111] The indicators of the obtained products are shown in Table 1.

[0112] Example 2

[0113] The process of one-stage roughing and two-stage cleaning was used to flotation and ash reduction of anthracite from a coal preparation plant in Henan Province. The ash content of the raw coal was 26%.

[0114] The steps of preparing the composite collector are as follows:

[0115] (1) Pre-treating the waste cooking oil by filtering, removing impurities and dehydrating until there is no visible water and impurities. For the use of coal slime flotation, the waste cooking oil only needs to be physically filtered and removed impurities according to the density difference, and then heated and precipitated for further dehydration and impurity removal, so that the tail chain molecular substance can be mixed with the intermediate solution;

[0116] (2) preparing an intermediate triethylenetetramine solution at room temperature, wherein the solution concentration is 0.04 mM;

[0117] (3) adding the pretreated cooking oil to the intermediate solution to prepare a pH-sensitive composite collector, wherein the molar concentration ratio of the cooking oil to the intermediate is 2:1 (the cooking oil adopts an average molecular weight according to its specific composition analysis);

[0118] The average molecular weight of cooking oil in this preparation process was calculated as 278;

[0119] (4) using sodium hydroxide to adjust the solution pH to pH = 7.5-8.5, and fully stirring the mixed solution to mix it evenly to obtain an assembled composite collector, wherein the tail chain molecule can be linoleic acid or linolenic acid in the waste cooking oil, or the two tail chain molecules can be a combination of two of oleic acid, linoleic acid, and linolenic acid;

[0120] One possible structural formula is:

[0121]

[0122] The composite collector prepared by the above method adopts the process of one-stage roughing-two-stage cleaning to flotation and ash reduction of coking coal from a coal preparation plant in Shanxi Province as follows:

[0123] (1) Preparing a first-stage flotation reagent: The assembled composite collector, frother, and alkaline solution are respectively input into a first-stage automatic dosing machine. The reagents in the first-stage flotation process are added by the first-stage automatic dosing machine and the dosage is automatically controlled;

[0124] The dosage of collector in the first stage of flotation is 500g / t, the dosage of frother is 150g / t, and the dosage of alkaline solution is adjusted according to the pH value of the pulp;

[0125] Using pinene alcohol as a foaming agent, sodium hydroxide is used to prepare an alkaline solution;

[0126] (2) Primary flotation: The slurry in the feed tank is transported to the slurry preprocessor by the feed pump. After the slurry and the reagents from the primary automatic dosing machine are fully slurried, the pH of the slurry is maintained at 7.5-8.5. The alkaline slurry is pumped into the primary flotation machine for flotation by the slurry pump. The flotation clean coal is scraped out by the flotation machine scraper. After roughing, the primary flotation clean coal a and tail coal b are obtained. The flotation clean coal a continues to enter the secondary flotation machine for cleaning. The flotation tail coal b enters the dehydration system as the final tail coal product.

[0127] (3) Secondary flotation: The clean coal a produced by the primary flotation machine is fed into the secondary flotation machine, and an acid solution (prepared with sulfuric acid) is added through the secondary automatic dosing machine to adjust the pH of the pulp to 5.5-6.0. Clean coal d and medium coal c are produced by flotation in the secondary flotation machine. The clean coal d produced by the secondary flotation machine enters the dehydration stage and becomes a clean coal product.

[0128] (4) Separation and reselection of coal aggregates: The selected medium coal c from the second-stage flotation machine enters the ball mill for selective grinding and dissociation. The grinding time in the ball mill is 2 to 3 minutes, so that the medium coal aggregates are fully dissociated. The coal slurry returns to the first-stage flotation machine to mix with the feed for flotation.

[0129] The indicators of the obtained products are shown in Table 1.

[0130] Example 3

[0131] The process of one-stage roughing and two-stage cleaning was used to flotation and ash reduction of anthracite from a coal preparation plant in Henan Province. The ash content of the raw coal was 26%.

[0132] The steps of preparing the composite collector are as follows:

[0133] (1) Pre-treating the waste cooking oil by filtering, removing impurities and dehydrating until there is no visible water and impurities. For the use of coal slime flotation, the waste cooking oil only needs to be physically filtered and removed impurities according to the density difference, and then heated and precipitated for further dehydration and impurity removal, so that the tail chain molecular substance can be mixed with the intermediate solution;

[0134] (2) preparing an intermediate ethylenediamine solution at room temperature, wherein the solution concentration is 0.04 mM;

[0135] (3) adding the pretreated cooking oil to the intermediate solution to prepare a pH-sensitive composite collector, wherein the molar concentration ratio of the cooking oil to the intermediate is 2:1 (the cooking oil adopts an average molecular weight according to its specific composition analysis);

[0136] The average molecular weight of cooking oil in this preparation process was calculated as 278;

[0137] (4) using sodium hydroxide to adjust the solution pH to pH = 7.5-8.5, and fully stirring the mixed solution to mix it evenly to obtain an assembled composite collector, wherein the tail chain molecule can be linoleic acid or linolenic acid in the waste cooking oil, or the two tail chain molecules can be a combination of two of oleic acid, linoleic acid, and linolenic acid;

[0138] One possible structural formula is:

[0139]

[0140] The composite collector prepared by the above method adopts the process of one-stage roughing-two-stage cleaning to flotation and ash reduction of coking coal from a coal preparation plant in Shanxi Province as follows:

[0141] (1) Preparing a first-stage flotation reagent: The assembled composite collector, frother, and alkaline solution are respectively input into a first-stage automatic dosing machine. The reagents in the first-stage flotation process are added by the first-stage automatic dosing machine and the dosage is automatically controlled;

[0142] The dosage of collector in the first stage of flotation is 500g / t, the dosage of frother is 150g / t, and the dosage of alkaline solution is adjusted according to the pH value of the pulp;

[0143] Using pinene alcohol as a foaming agent, sodium hydroxide is used to prepare an alkaline solution;

[0144] (2) Primary flotation: The slurry in the feed tank is transported to the slurry preprocessor by the feed pump. After the slurry and the reagents from the primary automatic dosing machine are fully slurried, the pH of the slurry is maintained at 7.5-8.5. The alkaline slurry is pumped into the primary flotation machine for flotation by the slurry pump. The flotation clean coal is scraped out by the flotation machine scraper. After roughing, the primary flotation clean coal a and tail coal b are obtained. The flotation clean coal a continues to enter the secondary flotation machine for cleaning. The flotation tail coal b enters the dehydration system as the final tail coal product.

[0145] (3) Secondary flotation: The clean coal a produced by the primary flotation machine is fed into the secondary flotation machine, and an acid solution (prepared with sulfuric acid) is added through the secondary automatic dosing machine to adjust the pH of the pulp to 5.5-6.0. Clean coal d and medium coal c are produced by flotation in the secondary flotation machine. The clean coal d produced by the secondary flotation machine enters the dehydration stage and becomes a clean coal product.

[0146] (4) Separation and reselection of coal aggregates: The selected medium coal c from the second-stage flotation machine enters the ball mill for selective grinding and dissociation. The grinding time in the ball mill is 2 to 3 minutes, so that the medium coal aggregates are fully dissociated. The coal slurry returns to the first-stage flotation machine to mix with the feed for flotation.

[0147] The indicators of the obtained products are shown in Table 1.

[0148] Comparative Example 1

[0149] The process of one-stage roughing and two-stage cleaning was used to flotation and ash reduction of anthracite from a coal preparation plant in Henan Province. The ash content of the raw coal was 26%.

[0150] The steps of preparing the composite collector are as follows:

[0151] (1) preparing an intermediate triethylenetetramine solution at room temperature, wherein the solution concentration is 0.04 mM;

[0152] (2) adding linolenic acid to the intermediate solution to prepare a pH-sensitive composite collector, wherein the molar concentration ratio of linolenic acid to triethylenetetramine is 2:1;

[0153] (3) Using sodium hydroxide to adjust the pH of the solution to pH = 7.5-8.5, the mixed solution is fully stirred and mixed evenly to obtain an assembled composite collector.

[0154] The composite collector prepared by the above method adopts the process of one-stage roughing-two-stage cleaning to flotation and ash reduction of anthracite in a coal preparation plant in Henan Province as follows:

[0155] (1) Preparation of first-stage flotation reagents: The assembled composite collector, frother and alkaline solution are respectively input into a first-stage automatic dosing machine. The reagents in the first-stage flotation process are added by a first-stage automatic dosing machine and the dosage is automatically adjusted; the dosage of the first-stage flotation collector is 600 g / t, the dosage of the frother is 150 g / t, and the dosage of the alkaline solution is adjusted according to the pH value requirement of the slurry;

[0156] Using pinene alcohol as a foaming agent, sodium hydroxide is used to prepare an alkaline solution;

[0157] (2) Primary flotation: The slurry in the feed tank is transported to the slurry pre-processor by the feed pump. After the slurry and the reagents from the primary automatic dosing machine are fully slurried, the alkaline slurry is pumped into the primary flotation machine for flotation by the slurry pump. The flotation machine scrapers scrape out the flotation clean coal, and the primary flotation clean coal a and tail coal b are obtained after roughing. The flotation clean coal a continues to enter the secondary flotation machine for cleaning, and the flotation tail coal b enters the dehydration system as the final tail coal product;

[0158] (3) Secondary flotation: The clean coal a produced by the primary flotation machine is fed into the secondary flotation machine, and an acid solution (prepared with sulfuric acid) is added through the secondary automatic dosing machine to adjust the pH of the pulp to 5.5-6.0. Clean coal d and medium coal c are produced by flotation in the secondary flotation machine. The clean coal d produced by the secondary flotation machine enters the dehydration stage and becomes a clean coal product.

[0159] (4) Separation and reselection of coal aggregates: The selected medium coal c from the second-stage flotation machine enters the ball mill for selective grinding and dissociation. The grinding time in the ball mill is 2 to 3 minutes, so that the medium coal aggregates are fully dissociated. The coal slurry returns to the first-stage flotation machine to mix with the feed for flotation.

[0160] The indicators of the obtained products are shown in Table 1.

[0161] Comparative Example 2

[0162] The process of one-stage roughing and two-stage cleaning was used to flotation and ash reduction of anthracite from a coal preparation plant in Henan Province. The ash content of the raw coal was 26%.

[0163] The steps of preparing the composite collector are as follows:

[0164] (1) Preparation of intermediates at room temperature Solution, solution concentration is 0.04mM;

[0165] (2) Adding linolenic acid to the intermediate solution to prepare a pH-sensitive composite collector, linolenic acid and The molar concentration ratio is 2:1;

[0166] (3) Using sodium hydroxide to adjust the pH of the solution to pH = 7.5-8.5, the mixed solution is fully stirred and mixed evenly to obtain an assembled composite collector.

[0167] The composite collector prepared by the above method adopts the process of one-stage roughing-two-stage cleaning process to flotation and ash reduction of anthracite in a coal preparation plant in Henan Province as follows:

[0168] (1) Preparation of first-stage flotation reagents: The assembled composite collector, frother and alkaline solution are respectively input into a first-stage automatic dosing machine. The reagents in the first-stage flotation process are added by a first-stage automatic dosing machine and the dosage is automatically adjusted; the dosage of the first-stage flotation collector is 600 g / t, the dosage of the frother is 150 g / t, and the dosage of the alkaline solution is adjusted according to the pH value requirement of the slurry;

[0169] Using pinene alcohol as a foaming agent, sodium hydroxide is used to prepare an alkaline solution;

[0170] (2) Primary flotation: The slurry in the feed tank is transported to the slurry pre-processor by the feed pump. After the slurry and the reagents from the primary automatic dosing machine are fully slurried, the alkaline slurry is pumped into the primary flotation machine for flotation by the slurry pump. The flotation machine scrapers scrape out the flotation clean coal, and the primary flotation clean coal a and tail coal b are obtained after roughing. The flotation clean coal a continues to enter the secondary flotation machine for cleaning, and the flotation tail coal b enters the dehydration system as the final tail coal product;

[0171] (3) Secondary flotation: The clean coal a produced by the primary flotation machine is fed into the secondary flotation machine, and an acid solution (prepared with sulfuric acid) is added through the secondary automatic dosing machine to adjust the pH of the pulp to 5.5-6.0. Clean coal d and medium coal c are produced by flotation in the secondary flotation machine. The clean coal d produced by the secondary flotation machine enters the dehydration stage and becomes a clean coal product.

[0172] (4) Separation and reselection of coal aggregates: The selected medium coal c from the second-stage flotation machine enters the ball mill for selective grinding and dissociation. The grinding time in the ball mill is 2 to 3 minutes, so that the medium coal aggregates are fully dissociated. The coal slurry returns to the first-stage flotation machine to mix with the feed for flotation.

[0173] Table 1 Product indicators of the first stage roughing-second stage cleaning process

[0174]

[0175] Examples 1, 2, and 3 use kitchen waste oil as the source of tail chain molecular substances, and Comparative Examples 1 and 2 use linolenic acid as the tail chain molecular substance; It can be seen from Table 1 that Examples 1, 2, and 3 all achieve better sorting effects, wherein the first-stage roughing clean coal yield is higher than 85.7%, and the collector has higher collecting performance than Comparative Examples 1 and 2, thereby increasing the first-stage clean coal yield; the second-stage clean coal ash content is lower than 9.7%, and the clean coal yield is higher than 73.5%, and the collector has higher selectivity than Comparative Examples 1 and 2, which is beneficial to reducing the flotation clean coal ash content and improving the clean coal grade;

[0176] On the other hand, the clean coal yields of Examples 1, 2, and 3 in both stages were significantly higher than those of Comparative Examples 1 and 2 when using less collectors. This shows that the hydrophobic modification effect of unsaturated carboxylic acids in waste cooking oil is more obvious, and the dosage of the agent can be reduced.

[0177] In summary, the present invention designs a pH-sensitive composite collector, cooperates with a two-stage flotation + intergrowth dissociation and reselection process, and timely adjusts the collection capacity of the collector according to the changes in the physical properties of the slurry, thereby reducing the ash content of the clean coal while ensuring the clean coal yield; in view of the high ash content and complex components of high-ash difficult-to-select coal, the tail chain molecular substances of the composite collector are prepared by using waste kitchen oil, which has a stronger adsorption effect on the coal surface, reduces the dosage of the agent, and greatly improves the adsorption strength and spreading rate of the collector. In addition, the preparation of the tail chain molecular substances from waste kitchen oil has certain economy and obvious environmental benefits.

[0178] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a composite collector for high-ash and difficult-to-clean coal using waste cooking oil, characterized in that: The steps include: (1) Filter, remove impurities and dehydrate the waste cooking oil; (2) preparing an intermediate aqueous solution at room temperature; (3) adding the waste cooking oil treated in step (1) to the intermediate aqueous solution, and adjusting the pH of the mixed solution of the waste cooking oil and the intermediate solution to 7.5 to 8.5; (4) Stirring the mixed solution in step (3) to obtain a composite collector with a Gemini-like structure.

2. The method according to claim 1, characterized in that The concentration of the intermediate aqueous solution in step (2) is less than 0.05 mM.

3. The method according to claim 1, characterized in that The molar concentration ratio of the waste cooking oil and the intermediate in step (3) is 2:

1.

4. The method according to claim 1, characterized in that: The kitchen waste oil is used as the tail chain molecular substance of the composite collector, and the Gemini-like structure is formed by one intermediate and two tail chain molecules under the action of electrostatics.

5. The method according to claim 4, characterized in that The intermediates and tail chain molecules in the Gemini-like structure are depolymerized under acidic conditions.

6. The method according to claim 4, characterized in that The molecular structures of the two tail chains are the same or different, and are one or more combinations of the following:

7. The method according to claim 4, characterized in that The intermediate structure is R1 in the intermediate structure contains some atoms of N, S, O, and C atoms, and the total number of non-hydrogen atoms in R1 is 2 to 8; R2 contains N atoms or both N and C atoms, and the total number of atoms is 1 to 3.

8. The method according to claim 1, characterized in that: The composite collector of the Gemini-like structure comprises:

9. A composite collector for high-ash and difficult-to-clean coal, characterized in that: The composite collector is prepared by the method for preparing high-ash and difficult-to-select coal by utilizing waste cooking oil as described in any one of claims 1 to 8.

10. A flotation process for high-ash difficult-to-clean coal, characterized in that: The composite collector prepared by the method according to any one of claims 1 to 8 is applied to the flotation of high-ash difficult-to-separate coal, comprising the following steps: (1) Primary flotation: The pH of the ore pulp is adjusted to be weakly alkaline, so that the composite collector forms a Gemini-like structure, and roughing is performed to obtain the tail coal of the primary flotation and the ore pulp containing clean coal. The ore pulp containing clean coal enters the secondary flotation; (2) Secondary flotation: adjust the pH of the slurry to be weakly acidic to depolymerize the composite collector and perform flotation to produce clean coal and medium coal; (3) Separation and re-selection of intergrowths: The medium coal produced by the second stage flotation enters the ball mill for grinding to fully dissociate the intergrowths of the medium coal, and the coal slurry returns to the first stage flotation.

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