Detection method and application of coal preparation medium

Abstract

The present invention provides a detection method and its application for the medium used in coal preparation. The detection method includes the following steps: performing magnetic separation on the pulp N times in sequence; wherein, the magnetic field intensity of the magnetic separation presents an equal-gradient decreasing mode, and the gradient interval is 25-35 mT; taking the magnetic field intensity value of each magnetic separation as the abscissa, and M N / (M N +m N ) as the ordinate, simulating and establishing a curve function with only one inflection point, taking the magnetic field intensity corresponding to the inflection point as the critical magnetic field intensity of the medium to be detected for coal preparation, denoted as T1; taking the lowest magnetic field intensity in the separation space as the critical magnetic field intensity of the magnetic separation equipment, denoted as T2; using the △T value to evaluate the medium to be detected for coal preparation. The present invention combines the properties of the medium itself and the properties of the magnetic separation equipment, takes the coupling degree between the magnetic property distribution of the medium and the magnetic separation equipment as the detection standard, and break through to propose the above detection method, establishing a two-way corresponding medium detection method for equipment-medium.

Description

Technical Field

[0001] The present invention relates to the technical field of medium coal preparation, and in particular to a detection method for a medium for coal preparation and its application Background Art

[0002] The medium cyclone coal preparation technology is the most efficient one among the current gravity coal preparation methods. With the rapid consumption of coal resources, the quality of raw coal will become worse and worse. In the future coal preparation technology, the medium cyclone coal preparation technology will play a more important role.

[0003] In the prior art, the medium (mainly composed of magnetite powder) is the dominant factor in determining the stability of the suspension, and is also the key to affecting the separation accuracy and efficiency of the coal preparation process. It can be recycled by magnetic separation equipment for repeated use. Therefore, in the production process of the coal preparation plant, whether the quality of the medium recovered by the magnetic separation equipment is qualified has become one of the main indicators of daily inspection. Usually, the magnetic content, true relative density, particle size, moisture and other indicators of the medium can be examined to evaluate whether the quality of the medium is qualified. Among them, the magnetic content is the key indicator to determine the recovery rate of the magnetic separation link. The current enterprise, industry standards and national standards all use the magnetic content as the core indicator. The coal preparation industry has specially formulated a national standard for examining the content of magnetic materials (GB / T18711-2·002 Test method for magnetite powder for coal preparation), which stipulates that the magnetic field strength of 250mT is used to conduct a magnetic separation tube test to detect the magnetic content in the medium, and to evaluate whether the medium is qualified. At present, some coal preparation plants have also proposed improvements to the current medium detection methods. The main idea is to determine the magnetic content of the medium under several excitation currents, and use the relative values ​​of the magnetic content at magnetic field intensities of 150mT and 75mT as indicators to evaluate its quality.

[0004] However, different media and magnetic separation equipment have different matching degrees. When using the above method in the actual test process, there will be a phenomenon that the magnetic attenuation rate or the relative content of intermediate magnetic materials is extremely low or even almost zero. This will further cause part of the medium to be lost in the magnetic separation equipment. A large amount of medium loss in magnetic separation equipment will cause a surge in corporate costs. Such media cannot be considered a qualified product for the company. Therefore, it is not accurate to use only the content of magnetic materials in the medium after magnetic separation as a standard for evaluating whether the medium is qualified.

[0005] In summary, the existing methods for testing whether the medium is qualified are all based on the properties of the medium itself, and the evaluation results are not accurate. Therefore, it is necessary to provide a new method for testing the medium for coal preparation to improve the above problems. Summary of the invention

[0006] The main purpose of the present invention is to provide a method for detecting a coal separation medium and its application, so as to solve the problems of poor accuracy in evaluating whether the coal separation medium is qualified in the prior art.

[0007] In order to achieve the above object, according to one aspect of the present invention, a method for detecting a coal separation medium is provided, the method comprising the following steps:

[0008] Step S1, dispersing the coal separation medium to be tested in a solvent to obtain a slurry;

[0009] Step S2, performing magnetic separation on the slurry N times in sequence; wherein the magnetic field intensity of the magnetic separation is in an iso-gradient descending mode, the magnetic field intensity of the first magnetic separation is 250 mT, the magnetic field intensity of the Nth magnetic separation is 10 mT, and the gradient range is 25 to 35 mT;

[0010] Step S3, drying the concentrate obtained in step S2 and weighing it, the weight is recorded as M N ; After drying the tailings, weigh them and record the weight as m N ;

[0011] Step S4, taking the magnetic field strength value of each magnetic separation as the horizontal coordinate, M N / (M N +m N ) as the ordinate, simulate and establish a curve function y=f(x) with only one inflection point, and take the magnetic field intensity corresponding to the inflection point as the critical magnetic field intensity of the coal preparation medium to be tested, denoted as T1;

[0012] Step S5, measuring the magnetic field strength in the separation space of the magnetic separation device, and taking the lowest magnetic field strength in the separation space as the critical magnetic field strength of the magnetic separation device, recorded as T2;

[0013] Step S6, using △T value to evaluate the coal separation medium to be tested; wherein, △T=T2-T1, when △T≥0, the coal separation medium to be tested is qualified; when △T<0, the coal separation medium to be tested is unqualified.

[0014] Furthermore, M1 / (M1+m1)>95%.

[0015] Furthermore, the particle size of the coal preparation medium to be tested is 200-500 meshes.

[0016] Furthermore, the particle size of the coal preparation medium to be tested is 200-325 meshes.

[0017] Furthermore, the weight ratio of the coal separation medium to the solvent is (10-20):1.

[0018] Furthermore, in step S2, the slurry is placed in a reciprocating oscillator for 5 to 10 minutes before the first magnetic separation.

[0019] Furthermore, the solvent includes a dispersant and water.

[0020] Furthermore, the dispersant is selected from one or more of water glass, sodium hexametaphosphate or sodium lauryl sulfate.

[0021] Furthermore, the volume ratio of the dispersant to water is (1000-500):1.

[0022] In order to achieve the above-mentioned object, according to one aspect of the present invention, there is provided an application of the aforementioned coal separation medium detection method in heavy medium coal separation.

[0023] The present invention combines the properties of the medium itself and the properties of the magnetic separation equipment, takes the coupling degree of the medium magnetic distribution and the magnetic separation equipment as the detection standard, and proposes the above detection method in a breakthrough way, and establishes a medium detection method with bidirectional correspondence between the equipment and the medium. Based on this, the present invention can more accurately evaluate whether the quality of the medium is qualified. Moreover, in the evaluation process, the loss of the medium is also small, and the recovery rate is high, which can further reduce the production cost of the enterprise and achieve better industrial application effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0025] Figure 1 The measured and simulated function diagrams of the medium in Example 1 of the present invention are shown;

[0026] Figure 2 The measured and simulated function diagrams of the medium in Example 2 of the present invention are shown;

[0027] Figure 3 A curve diagram of magnetic field strength in the separation space of the magnetic separation device in Example 1 of the present invention is shown;

[0028] Figure 4 A flow chart of a method for detecting a medium for coal selection in one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0029] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0030] As described in the background of the present invention, the prior art has problems such as poor accuracy in evaluating the quality of coal preparation media. In order to solve this problem, the present invention provides a method for detecting coal preparation media and its application. The detection method comprises the following steps:

[0031] Step S1, dispersing the coal separation medium to be tested in a solvent to obtain a slurry.

[0032] Step S2, magnetic separation is performed on the ore pulp N times in sequence; wherein the magnetic field intensity of the magnetic separation is in an iso-gradient descending mode, the magnetic field intensity of the first magnetic separation is 250mT, the magnetic field intensity of the Nth magnetic separation is 10mT, and the gradient range is 25-35mT.

[0033] Specifically, in step S2, the ore pulp is first subjected to the first magnetic separation to obtain the first concentrate and the second tailings, and then the first concentrate is subjected to the second magnetic separation to obtain the second concentrate and the second tailings, ..., and so on, and then the N-1th concentrate is subjected to the Nth magnetic separation to obtain the Nth concentrate and the Nth tailings; wherein, the magnetic field strength of the first magnetic separation is 250mT, and the magnetic field strength of the second magnetic separation is reduced by a gradient (for example, 25mT, 30mT or 35mT) compared with the magnetic field strength of the first magnetic separation, ..., the magnetic field strength of the Nth magnetic separation is reduced by a gradient compared with the magnetic field strength of the N-1th magnetic separation, and so on, until the magnetic field strength of the Nth magnetic separation is 10mT, and the magnetic separation can be terminated.

[0034] Step S3, drying the concentrate obtained in step S2 and weighing it, the weight is recorded as M N ; After drying the tailings, weigh them and record the weight as m N .

[0035] Specifically, the first concentrate, the second concentrate, ..., and the Nth concentrate obtained in step S2 are mixed, dried, and weighed, and the weights are recorded as M1, M2, ..., M N ; The first tailings, the second tailings, ..., the Nth tailings are mixed and dried and weighed, and the weights are recorded as m1, m2, ..., m N .

[0036] Step S4, taking the magnetic field strength value of each magnetic separation as the horizontal coordinate, M N / (M N +m N ) is used as the vertical coordinate, and a curve function y=f(x) with only one inflection point is simulated and established. The magnetic field intensity corresponding to the inflection point is taken as the critical magnetic field intensity of the coal preparation medium to be tested, which is recorded as T1.

[0037] Specifically, the magnetic field strength values ​​of the first magnetic separation, the second magnetic separation, ..., the Nth magnetic separation are used as the horizontal coordinates, M1 / (M1+m1), M2 / (M2+m2), ..., MN / (M N +m N ) as the ordinate, Matlab software is used to compile the code and perform curve fitting by using the curve fitting toolbox cftool therein, to simulate and establish the curve function y=f(x), and the curve function y=f(x) has only one inflection point, and the magnetic field intensity corresponding to the inflection point is used as the critical magnetic field intensity of the coal preparation medium to be tested, recorded as T1. The following compiled code can be used for curve fitting:

[0038] x = [0.05 0.2 0.3 0.5 1.5];

[0039] y=[36.31 88.93 90.23 91.74 93.00];

[0040] f = fittype('a×log(x)+b');

[0041] fit1=fit(x',y',f,'StartPoint',[x(1)y(1)]);

[0042] a = fit1.a;

[0043] b = fit1.b;

[0044] fdata = feval(fit1,x');

[0045] figure

[0046] plot(x,y); hold on

[0047] plot(x,fdata','r'); hold off

[0048] legend('Ori data','Fitting data');

[0049] Step S5, measuring the magnetic field strength in the separation space of the magnetic separation device, and taking the lowest magnetic field strength in the separation space as the critical magnetic field strength of the magnetic separation device, recorded as T2.

[0050] Step S6, using △T value to evaluate the coal separation medium to be tested; wherein, △T=T2-T1, when △T≥0, the coal separation medium to be tested is qualified; when △T<0, the coal separation medium to be tested is unqualified.

[0051] The present invention combines the properties of the medium itself and the properties of the magnetic separation equipment, takes the coupling degree of the medium magnetic distribution and the magnetic separation equipment as the detection standard, and proposes the above-mentioned detection method in a breakthrough way, and establishes a medium detection method with bidirectional correspondence between the equipment and the medium. Based on this, the present invention can more accurately evaluate whether the quality of the medium is qualified. When △T>0, the medium basically does not incur losses after entering the magnetic separator, and the medium can be fully recovered to reduce medium consumption. Moreover, in the evaluation process, the loss of the medium is also small, and the recovery rate is high, which can further reduce the production cost of the enterprise, and the industrial application effect is better.

[0052] Furthermore, M1 / (M1+m1)>95%. The above detection method of the present invention is particularly suitable for media with a high content of magnetic substances. When evaluating media with a high content of magnetic substances, the accuracy is better, and the loss of high-content media during the evaluation process is also smaller, and then the overall evaluation process is completed, and the recovery rate of the material can be greatly improved.

[0053] In a preferred embodiment, the particle size of the coal preparation medium to be tested is 200-500 mesh. In order to further improve the accuracy of the evaluation, the particle size of the coal preparation medium to be tested is preferably 200-325 mesh. In a preferred embodiment, the coal preparation medium is first sieved into ≥325 mesh and <325 mesh parts; then the medium powder of ≥325 mesh is finely ground to <325 mesh for use.

[0054] In order to further improve the accuracy of the evaluation, the weight ratio of the coal separation medium to be tested to the solvent is preferably controlled to be (10-20): 1. The solvent includes a dispersant and water, the dispersant is selected from one or more of water glass, sodium hexametaphosphate or sodium dodecyl sulfate, and the volume ratio of the dispersant to water is (1000-500): 1. It is further preferred that in step S2, the slurry is first placed in a reciprocating oscillator for 5-10 minutes before the first magnetic separation.

[0055] The present invention also provides an application of the aforementioned detection method for coal separation medium in medium coal separation. Based on the above reasons, the present invention combines the properties of the medium itself and the properties of the magnetic separation equipment, takes the coupling degree of the medium magnetic distribution and the magnetic separation equipment as the detection standard, and proposes the above detection method in a breakthrough manner, and establishes a medium detection method with bidirectional correspondence between equipment and medium. Based on this, the present invention can more accurately evaluate whether the quality of the medium is qualified. Moreover, in the evaluation process, the loss of the medium is also small, and the recovery rate is high, which can further reduce the production cost of the enterprise, and the industrial application effect is better.

[0056] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0057] Example 1

[0058] The medium 1 used in the production of a coal preparation plant in the west has a true density of 4.76g / cm 3 , moisture content is 10.21%, and particle size <325 mesh content is 91.12wt%.

[0059] The evaluation steps of the coal preparation medium are as follows:

[0060] Take 20g of the medium 1 to be tested in the coal preparation plant and pass it through a sieve A with a mesh size of 325, and grind the medium with a mesh size of ≥325 on the sieve to <325 by a rod dry mill;

[0061] Prepare a solvent by mixing water and dispersant water glass in a volume ratio of 1000:1;

[0062] The solvent and the screened magnetic medium are mixed in a ratio of 1:9 to form a 10% slurry;

[0063] Place the above slurry in a reciprocating oscillator B and set it to oscillate and mix for 5 to 10 minutes;

[0064] The ore pulp is subjected to a first magnetic separation to obtain a first concentrate and a second tailing, and the first concentrate is subjected to a second magnetic separation to obtain a second concentrate and a second tailing, ..., and so on, and the N-1th concentrate is subjected to an Nth magnetic separation to obtain an Nth concentrate and an Nth tailing; wherein the magnetic field intensity of the first magnetic separation is 250mT, and the magnetic field intensity of the second magnetic separation is 30mT lower than that of the first magnetic separation, ..., the magnetic field intensity of the Nth magnetic separation is 30mT lower than that of the N-1th magnetic separation, and so on, until the magnetic field intensity of the Nth magnetic separation is 10mT, the magnetic separation can be terminated;

[0065] The first concentrate, the second concentrate, ..., and the Nth concentrate obtained in step S2 are mixed and dried and then weighed. The weights are recorded as M1, M2, ..., M N ; The first tailings, the second tailings, ..., the Nth tailings are mixed and dried and weighed, and the weights are recorded as m1, m2, ..., m N , M N / (M N +m N ) are shown in Table 1;

[0066] Table 1

[0067]

[0068]

[0069] The magnetic field strength values ​​of the first magnetic separation, the second magnetic separation, ..., the Nth magnetic separation are used as the horizontal coordinates, M1 / (M1+m1), M2 / (M2+m2), ..., M N / (M N +m N ) as the ordinate, and the measured line graph is drawn. At the same time, the magnetic field intensity values ​​of the first magnetic separation, the second magnetic separation, ..., the Nth magnetic separation are used as the horizontal coordinates, M1 / (M1+m1), M2 / (M2+m2), ..., M N / (M N +m N ) as the ordinate, the curve function is simulated and obtained as follows: f(x) = 102e -0.0002059x -108.9e -0.02899x , and draw a simulated curve graph. The above measured line graph and simulated curve graph are shown in Figure 1 As shown;

[0070] The magnetic field strength at the inflection point of the above curve function is calculated to be 346.03T, and the magnetic field strength corresponding to the inflection point is taken as the critical magnetic field strength of the coal preparation medium to be tested, which is recorded as T1;

[0071] The gauss meter D was used to measure the magnetic field intensity distribution in the separation space of the magnetic separator in the coal preparation plant. Figure 2 The magnetic field strength curve of the sorting space of the on-site magnetic separator shows that the lowest point of the magnetic field strength in the sorting space is 284.53mT. The lowest magnetic field strength in the sorting space is taken as the critical magnetic field strength of the magnetic separation equipment, recorded as T2.

[0072] Evaluation: ΔT = T2 - T1 = 284.53 mT - 346.03 mT = -61.50 mT < 0. Unqualified.

[0073] Comparison: The magnetic material to be tested in the above coal preparation plant is in accordance with the national standard (GB / T18711-2·002 Test method for magnetite powder for coal preparation), and the magnetic content is 97.63%. According to the determination method of the relative content of intermediate magnetic material (see the following document for details: Ming Lijun. Research on the characteristics and evaluation indexes of magnetite powder for heavy medium coal preparation [J]. Shanxi Coking Coal Science and Technology, 2006 (9): 4.), the intermediate magnetic content is 4.82%. The results obtained by the above two methods both show that the magnetite powder used in the coal preparation plant is of qualified quality. However, the actual medium consumption of the magnetite powder used in the coal preparation plant is relatively high, which is 1.07kg / T. It can be seen that the detection result is more accurate through the above detection method of the present invention.

[0074] Example 2

[0075] In this example, medium 1 of a coal preparation plant in western China is replaced by medium 2, whose true density is 4.68 g / cm 3 The moisture content is 10.42wt%, and the powder content with particle size <325 mesh is 90.98%.

[0076] The evaluation procedure of the coal preparation medium is the same as that of Example 1. N / (M N +m N )See Table 2.

[0077] Table 2

[0078]

[0079] The magnetic field strength values ​​of the first magnetic separation, the second magnetic separation, ..., the Nth magnetic separation are used as the horizontal coordinates, M1 / (M1+m1), M2 / (M2+m2), ..., M N / (M N +m N ) as the ordinate, and the measured line graph is drawn. At the same time, the magnetic field intensity values ​​of the first magnetic separation, the second magnetic separation, ..., the Nth magnetic separation are used as the horizontal coordinates, M1 / (M1+m1), M2 / (M2+m2), ..., M N / (M N +m N ) as the ordinate, the curve function is simulated and obtained as follows: f(x) = 92.79e 0.0001771x -115.3e -0.04324x , and draw a simulation curve graph. The above measured graph and simulation graph are shown in Figure 3 shown.

[0080] The magnetic field strength at the inflection point of the above curve is calculated to be 258.26T, and the magnetic field strength corresponding to the inflection point is taken as the critical magnetic field strength of the coal preparation medium to be tested, recorded as T1;

[0081] Evaluation: △T=T2-T1=284.53mT-258.26mT=26.27mT>0. Pass.

[0082] Comparison: The magnetic material to be tested in the above coal preparation plant is 97.06% according to the national standard (GB / T18711-2·002 Test method for magnetite powder for coal preparation); the intermediate magnetic material content is 4.63% according to the determination method of the relative content of intermediate magnetic material. The results obtained by the above two methods show that the magnetite powder used in the coal preparation plant is of qualified quality.

[0083] like Figure 4 As shown, it can be seen that the method of the present invention takes the sorting characteristics of the on-site magnetic separation equipment as the main detection basis, takes the coupling degree of the medium magnetic distribution and the magnetic separation equipment as the detection standard, and establishes a medium detection method with bidirectional correspondence between the equipment and the medium. On the one hand, it can guide the selection of suitable media according to the characteristics of the equipment, and on the other hand, it can also optimize the performance of the equipment according to the characteristics of the medium. It can not only accurately detect the quality of the medium, but also ensure the recovery effect of the medium, thereby improving the economic benefits of the enterprise.

[0084] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for detecting a medium for coal preparation, characterized in that: The detection method comprises the following steps: Step S1, dispersing the coal separation medium to be tested in a solvent to obtain a slurry; Step S2, sequentially performing magnetic separation on the slurry N times; wherein the magnetic field intensity of the magnetic separation is in an iso-gradient descending mode, the magnetic field intensity of the first magnetic separation is 250 mT, the magnetic field intensity of the Nth magnetic separation is 10 mT, and the gradient range is 25 to 35 mT; Step S3, drying the concentrate obtained in step S2 and weighing it, the weight is recorded as M N , the tailings are dried and weighed, and the weight is recorded as m N ; Step S4, taking the magnetic field strength value of each magnetic separation as the horizontal coordinate, M N / (M N +m N ) as the ordinate, simulate and establish a curve function y=f(x) with only one inflection point, and take the magnetic field intensity corresponding to the inflection point as the critical magnetic field intensity of the coal separation medium to be tested, denoted as T1; Step S5, measuring the magnetic field strength in the separation space of the magnetic separation device, and taking the lowest magnetic field strength in the separation space as the critical magnetic field strength of the magnetic separation device, recorded as T2; Step S6, using ΔT value to evaluate the coal separation medium to be tested; wherein, ΔT=T2-T1, when ΔT≥0, the coal separation medium to be tested is qualified; when ΔT<0, the coal separation medium to be tested is unqualified.

2. The method for detecting a coal separation medium according to claim 1, characterized in that: M1 / (M1+m1)>95%.

3. The method for detecting a coal separation medium according to claim 1 or 2, characterized in that: The particle size of the coal separation medium to be tested is 200-500 meshes.

4. The method for detecting the coal separation medium according to claim 3, characterized in that: The particle size of the coal separation medium to be tested is 200-325 meshes.

5. The method for detecting a coal separation medium according to claim 1 or 2, characterized in that: The weight ratio of the coal selection medium to be tested to the solvent is (10-20):

1.

6. The method for detecting a coal separation medium according to claim 1 or 2, characterized in that: In the step S2, the ore pulp is first placed in a reciprocating oscillator for 5 to 10 minutes before the first magnetic separation.

7. The method for detecting a coal separation medium according to claim 1 or 2, characterized in that: The solvent includes a dispersant and water.

8. The method for detecting the coal separation medium according to claim 7, characterized in that: The dispersant is selected from one or more of water glass, sodium hexametaphosphate or sodium lauryl sulfate.

9. The method for detecting the coal separation medium according to claim 7, characterized in that: The volume ratio of the dispersant to the water is (1000-500):

1.

10. Use of the method for detecting a coal separation medium according to any one of claims 1 to 9 in heavy medium coal separation.

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