A method and application for separating low-density coal using a gas-solid separation fluidized bed.

Abstract

The present invention relates to a method and application of separating low-density coal by using a gas-solid separation fluidized bed, which belongs to the technical field of gas-solid separation fluidized beds and solves the problems of low efficiency, high cost and difficulty in separating low-density coal in the prior art. A method of separating low-density coal by using a gas-solid separation fluidized bed comprises: using porous particles as a weighting material to separate low-density coal from the coal to be separated, wherein the average particle size of the porous particles is 70 to 130 μm and the true density is 7.0 to 7.8 g / cm 3 The porosity is 5% to 10%. In the method of the present invention, porous particles are used as weighting materials to form an ultra-low density fluid-like bed layer under the action of airflow, and the gas-solid separation fluidized bed is used to achieve efficient separation of low-density coal based on the density difference of the coal to be separated.

Description

Technical Field

[0001] The invention relates to the technical field of gas-solid separation fluidized bed, and in particular to a method and application of separating low-density coal by using a gas-solid separation fluidized bed. Background Art

[0002] Coal is one of the main energy sources at present, and it is particularly important to develop and utilize coal in a clean, efficient and sustainable manner. Coal preparation is the source technology for realizing clean utilization of coal. It is also one of the important ways to promote the transformation of coal from a single fuel attribute to a fuel and raw material, promote graded and quality-based utilization, and thus realize the low-carbon utilization of high-carbon energy. my country's coal resources are mainly distributed in high-cold and arid areas such as the west and north. The problem of water shortage is serious. Wet sorting technology is prone to secondary water pollution. It requires the configuration of expensive sewage treatment systems and requires the use of a large amount of water resources. It is difficult to promote and use in the above-mentioned areas. Dry sorting technology does not use water, which reduces the use of water resources and has better adaptability in arid and water-scarce areas. Therefore, the development of efficient dry coal preparation technology will help to make up for the shortcomings of existing wet sorting technology and promote the efficient and clean utilization of my country's coal resources.

[0003] Compared with other dry coal sorting technologies, gas-solid fluidized dry coal sorting technology has the advantages of stronger adaptability to coal types, higher sorting accuracy, wider density adjustment range, and lower dielectric loss, and has developed into one of the typical dry sorting technologies. However, the existing gas-solid fluidized dry sorting technology generally has a sorting density between 1.2 and 2.0, and it is difficult to achieve a density lower than 1.2g / cm 3 The ineffective sorting of low-density coal can easily lead to waste of coal resources. Summary of the invention

[0004] In view of the above analysis, the present invention aims to provide a method and application of sorting low-density coal using a gas-solid separation fluidized bed, which is used to solve at least one of the following technical problems: manual sorting has high labor costs and low efficiency; wind sorting has low efficiency, high energy consumption and cost, and poor adaptability to different materials; hydraulic flotation technology is prone to secondary water pollution, requires the configuration of expensive sewage treatment systems, and requires the use of a large amount of water resources; wet coal sorting technology consumes a lot of water; and the existing gas-solid fluidized dry sorting technology is difficult to achieve a density of less than 1.2g / cm 3 Effective separation of low-density coal.

[0005] In the first aspect, the present invention provides a method for separating low-density coal using a gas-solid separation fluidized bed, comprising: using porous particles as a weighting material to separate low-density coal from the coal to be separated, wherein the average particle size of the porous particles is 70 to 130 μm, and the true density is 7.0 to 7.8 g / cm 3 , the porosity is 5% to 10%.

[0006] Furthermore, the method further comprises: forming the porous particles into a particle with a density greater than 1.0 g / cm 3 And not more than 1.3g / cm 3 The sorting bed.

[0007] Furthermore, the density of the separation bed is greater than the density of the target coal in the coal to be separated.

[0008] Furthermore, the gas in the airflow is one or more of air, carbon dioxide, and inert gas.

[0009] Furthermore, the critical fluidization velocity of the porous particles is 4 to 10 cm / s.

[0010] Furthermore, the porous particles are magnetic materials.

[0011] Furthermore, the magnetic material is iron powder.

[0012] Furthermore, the bulk density of the porous particles in the weighting material is 1.2 to 1.5 g / cm 3 .

[0013] Furthermore, the density of the low-density coal is 1.0-1.2 g / cm 3 .

[0014] In a second aspect, the present invention provides an application of the method described in sorting low-density coal.

[0015] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0016] (1) In the method of the present invention, the weighted mass in the gas-solid fluidized bed is selected as porous particles. The porous particles themselves have a relatively low bulk density. At the same time, the pore structure of the particles themselves further promotes the expansion of the particle bed layer. Under the action of the airflow, an ultra-low density separation bed layer can be formed, which can make the fluidized layer density reach 1.3 g / cm 3 The following is something that cannot be achieved by the existing gas-solid fluidized dry separation technology;

[0017] (2) The weighting material of the present invention adopts a porous particle gas-solid fluidized bed, which has a significantly lower minimum fluidization velocity than the gas-solid fluidized bed of solid particles of the same particle size and material, which can save energy and reduce costs; at the same time, compared with the gas-solid fluidized bed of solid particles of the same particle size and material, the emulsified phase dispersion expansion is increased, which reduces the lower limit of the fluidized bed density, so that the density adjustment range is widened, and at the same time, the increase in the emulsified phase dispersion expansion of the fluidized bed can reduce the separation particle size; the present invention adopts porous particles as a weighting material, forms an ultra-low density quasi-fluid bed under the action of airflow, and uses the gas-solid separation fluidized bed to achieve efficient separation of low-density coal based on the density difference of the coal to be selected;

[0018] (3) The porous particles of the present invention include magnetic particles, which facilitate subsequent separation and recovery, thus simplifying the steps;

[0019] (4) The method of the present invention does not require water and is suitable for use in arid and cold regions, thereby saving a large amount of water resources. At the same time, the method of the present invention does not require a sewage treatment system, and the process is simple, further reducing the cost. Therefore, the method of separating low-density coal using a gas-solid separation fluidized bed provided by the present invention can effectively avoid the problems of water waste, high cost, low separation efficiency, and poor adaptability to the selected materials in hydraulic flotation and wind separation in the prior art.

[0020] (5) The density of the fluidized bed in the method of the present invention is greater than 1.0 g / cm 3 And not more than 1.3g / cm 3 , which reduces the lower limit of bed density of the existing coal gas-solid fluidization dry separation fluidized bed, and can be used for the separation of low-density coal in the coal to be separated. 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 explained in the subsequent description, and some advantages may become obvious from the description, or may be understood by implementing the present invention. The objects 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

[0021] 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.

[0022] Figure 1 A schematic diagram of a method for separating low-density coal using a gas-solid separation fluidized bed according to the present invention;

[0023] Figure 2 This is a relationship diagram between the sorting density and the distribution rate in the present invention. DETAILED DESCRIPTION

[0024] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention 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.

[0025] It should be noted that the gas-solid separation fluidized bed in the present invention adopts the existing structure. The specific structure is not within the protection scope of the present invention. As long as the method of separating low-density coal of the present invention can be implemented, the specific fluidized bed structure will not be described in detail in the present invention.

[0026] A specific embodiment of the present invention, as Figure 1 As shown, a method for separating low-density coal by using a gas-solid separation fluidized bed is disclosed, comprising: using porous particles as a weighting material to separate low-density coal from the coal to be separated, wherein the average particle size of the porous particles is 70 to 130 μm, and the true density is 7.0 to 7.8 g / cm 3 , the porosity is 5% to 10%.

[0027] For example, the average particle size of the porous particles is 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm, 130 μm; the true density is 7.0 g / cm 3 , 7.1g / cm 3 , 7.2g / cm 3 , 7.3g / cm 3 , 7.4g / cm 3 , 7.5g / cm 3 , 7.6g / cm 3 , 7.7g / cm 3 , 7.8g / cm 3 ; The porosity is 5%, 5.5%, 6%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, and 10%.

[0028] It should be noted that the porous particles in the present invention are all commercially available raw materials, and as long as the above-mentioned performance conditions are met, they can separate low-density coal from the coal to be sorted.

[0029] Compared with the prior art, the weighted mass selection in the present invention is porous particles, which have a lower bulk density. At the same time, the pore structure of the particles themselves further promotes the expansion of the particle bed, and can form an ultra-low density sorting bed under the action of the airflow; the minimum fluidization velocity of the porous particle gas-solid fluidized bed is significantly reduced compared to the gas-solid fluidized bed of solid particles of the same particle size and material, which can save energy and reduce costs; at the same time, compared with the gas-solid fluidized bed of solid particles of the same particle size and material, the emulsified phase dispersion expansion is increased, which reduces the lower limit of the fluidized bed density and widens the density adjustment range. At the same time, the increase in the emulsified phase dispersion expansion of the fluidized bed can reduce the sorting particle size.

[0030] It should be noted that the size of the porous particles in the present invention may be uniform or non-uniform, the true density of the porous particles may be uniform or non-uniform, the bulk density of the porous particles may be uniform or non-uniform, and the porosity of the porous particles may be uniform or non-uniform.

[0031] In a specific embodiment, the method further comprises: forming a low-density separation bed layer of the porous particles under the action of airflow, wherein the low density is greater than 1.0 g / cm 3 And not more than 1.3g / cm 3 For example, the density is 1.05 g / cm 3 , 1.1g / cm 3 , 1.15g / cm 3 , 1.2g / cm 3 , 1.25g / cm 3 , 1.3g / cm 3 .

[0032] The density of the fluidized bed in the method of the present invention is greater than 1.0 g / cm 3 And not more than 1.3g / cm 3 , which reduces the lower limit of bed density of the existing coal gas-solid fluidization dry separation fluidized bed, and can be used for the separation of low-density coal to be separated.

[0033] In the method of the present invention, the weighted mass in the gas-solid fluidized bed is selected as porous particles, which have a relatively low bulk density. At the same time, the pore structure of the particles further promotes the expansion of the particle bed layer, and an ultra-low density separation bed layer can be formed under the action of the airflow, which can make the fluidized layer density reach 1.3g / cm 3 The following is something that cannot be achieved by the existing gas-solid fluidized dry separation technology.

[0034] In a specific embodiment, the density of the separation bed is greater than the density of the target coal in the coal to be separated.

[0035] In a specific embodiment, the gas in the airflow is one or more of air, carbon dioxide, and inert gas.

[0036] In a preferred embodiment, the gas is air, which is beneficial to reducing costs and environmental pollution.

[0037] In a specific embodiment, the critical fluidization velocity of the porous particles is 4 to 10 cm / s. Exemplarily, the critical fluidization velocity is 4 cm / s, 4.5 cm / s, 5 cm / s, 5.5 cm / s, 6 cm / s, 6.5 cm / s, 7 cm / s, 7.5 cm / s, 8 cm / s, 8.5 cm / s, 9 cm / s, 9.5 cm / s, or 10 cm / s.

[0038] In a specific embodiment, the porous particles are magnetic materials.

[0039] It should be noted that the porous particles include but are not limited to magnetic materials, and the magnetic materials are convenient for subsequent separation and recovery.

[0040] In a specific embodiment, the magnetic material is iron powder.

[0041] In a specific embodiment, the bulk density of the porous particles is 1.2-1.5 g / cm 3 , for example, the bulk density is 1.2 g / cm 3 , 1.25g / cm 3 , 1.3g / cm 3 , 1.35g / cm 3 , 1.4g / cm 3 , 1.45g / cm 3 , 1.5g / cm 3 .

[0042] In a specific embodiment, the density of the low-density coal is 1.0-1.2 g / cm 3 , for example, the density is 1.0 g / cm 3 , 1.05g / cm 3 , 1.1g / cm 3 , 1.15g / cm 3 , 1.2g / cm 3 .

[0043] In a second aspect, the present invention provides an application of the method described in separating low-density coal from coal.

[0044] The method of the present invention does not require water, is suitable for use in arid and alpine areas, and can save a large amount of water resources; at the same time, the method of the present invention does not require a sewage treatment system, has a simple process, and further reduces costs. Therefore, the method of sorting low-density coal using a gas-solid separation fluidized bed provided by the present invention can effectively avoid the problems of water resource waste, high cost, low sorting efficiency, and poor adaptability to selected materials in hydraulic flotation and wind separation in the prior art.

[0045] The technical solution of the present invention is further explained below in conjunction with specific embodiments.

[0046] Example 1

[0047] A method for separating low-density coal using a gas-solid separation fluidized bed in this embodiment is as follows: Figure 1 As shown, the density of the low-density coal is 1.0-1.1 g / cm 3 .

[0048] Specifically, the steps include:

[0049] (1) Select the average particle size d p =125μm, true density ρ=7780kg / m 3 , iron powder with porosity ε = 8.5% is used as porous particles, the critical fluidization velocity of the porous particles is 7.2 cm / s, and the bulk density of the porous particles is 1.4 g / cm 3 , the above iron powder is often used as a weighting material;

[0050] (2) The weighted material is introduced into the fluidized bed separator, and the flow rate of the air flow is adjusted to be greater than the critical fluidization velocity of the porous particles by 0.2 cm / s. Under the action of the gas, the porous particles form a uniform and stable fluidized bed layer, and the bed density of the fluidized bed layer is 1.12 g / cm 3 , the pressure drop fluctuation variance is about 45, and the sorting environment of the bed is relatively stable;

[0051] (3) The coal to be separated is fed into the gas-solid separation fluidized bed. The coal is affected by the overall density of the fluidized bed. The low-density coal and heavy materials in the coal are separated according to the bed density. The low-density coal to be separated floats to the surface of the fluidized bed, thereby achieving separation of the low-density coal.

[0052] Example 2

[0053] The present embodiment provides a method for separating low-density coal in coal by using a gas-solid separation fluidized bed, wherein the density of the low-density coal is 1.1 to 1.15 g / cm 3 .

[0054] The specific steps are as follows:

[0055] (1) Select the average particle size d p =75μm, true density ρ=7780kg / m 3 , iron powder with porosity ε = 7.6% is used as porous particles, the critical fluidization velocity of the porous particles is 5.7 cm / s, and the bulk density of the porous particles is 1.5 g / cm 3 , using the above iron powder as a weighting material;

[0056] (2) The weighted material is introduced into the fluidized bed separator, and the flow rate of the carbon dioxide gas flow is adjusted to be greater than the critical fluidization velocity of the porous particles, 1.52 cm / s. Under the action of the gas, the porous particles form a uniform and stable fluidized bed layer, and the bed density of the fluidized bed layer is 1.18 g / cm 3 , the pressure drop fluctuation variance is about 43, and the sorting environment of the bed is relatively stable;

[0057] (3) The coal to be selected is sent into the gas-solid separation fluidized bed. The low-density coal to be selected is affected by the overall density of the fluidized bed. Coal of different densities is layered according to the bed density. The low-density coal to be separated will float to the surface of the fluidized bed, thereby achieving the separation of the low-density coal.

[0058] Example 3

[0059] A method for separating low-density coal by using a gas-solid separation fluidized bed in this embodiment is as follows: Figure 1 As shown, the density of the low-density coal is 1.15-1.2 g / cm 3 .

[0060] Specifically, the steps include:

[0061] (1) Select the average particle size d p =105μm, true density ρ=7780kg / m 3 , iron powder with porosity ε = 38.2% is used as porous particles, the critical fluidization velocity of the porous particles is 6.4 cm / s, and the bulk density of the porous particles is 1.47 g / cm 3 , using the above iron powder as a weighting material;

[0062] (2) The weighted material is introduced into the fluidized bed separator, and the flow rate of the air flow is adjusted to be greater than the critical fluidization velocity of the porous particles, 1.65 cm / s. Under the action of the gas, the porous particles form a uniform and stable fluidized bed layer, and the bed density of the fluidized bed layer is 1.23 g / cm 3 , the pressure drop fluctuation variance is about 45, and the sorting environment of the bed is relatively stable;

[0063] (3) The coal to be sorted is fed into the gas-solid separation fluidized bed. The coal to be sorted is affected by the overall density of the fluidized bed. Low-density coal and heavy materials in the coal are stratified according to the bed density. The low-density coal to be separated floats to the surface of the fluidized bed, thereby achieving the separation of the low-density coal.

[0064] Comparative Example 1

[0065] The method of separating low-density coal by gas-solid separation fluidized bed in this comparative example is the same as that in Example 1, except that the average particle size of the porous particles is 45 μm, the porosity is 5.5%, and the bulk density of the porous particles is 3.5 g / cm 3 .

[0066] Specifically, the steps include:

[0067] (1) Select the average particle size d p =45μm, true density ρ=7780kg / m 3 , iron powder with porosity ε = 5.5% is used as porous particles, and the bulk density of the porous particles is 3.5 g / cm 3 , using the above iron powder as a weighting material;

[0068] (2) The weighting material is introduced into the fluidized bed separator, and the flow rate of the gas flow is controlled by adjusting the flow meter. However, no matter how the gas flow rate is adjusted, the porous particles cannot reach the fluidized state and separation cannot be achieved.

[0069] This comparative example shows that porous particles that are not within the particle size and bulk density ranges defined in the present invention cannot achieve the purpose of separation.

[0070] Comparative Example 2

[0071] The method of separating low-density coal by gas-solid separation fluidized bed in this comparative example is the same as that in Example 1, except that the average particle size of the porous particles is 450 μm, the porosity is 9.5%, and the bulk density of the porous particles is 2.1 g / cm 3 .

[0072] Specifically, the steps include:

[0073] 1) Select the average particle size d p =450μm, true density ρ=7780kg / m 3 , iron powder with porosity ε = 9.5% is used as porous particles, the critical fluidization velocity of the porous particles is 8.9 cm / s, and the bulk density of the porous particles is 2.1 g / cm 3 , using the above iron powder as a weighting material;

[0074] (2) The weighted material is introduced into the fluidized bed separator, and the flow rate of the flow meter is adjusted to be greater than the critical fluidization velocity of the porous particles, 3.7 cm / s. Under the action of the gas, the porous particles form a fluidized bed layer, and the bed density of the fluidized bed layer is 1.18 g / cm 3 , the pressure drop fluctuation variance is about 85, and the sorting environment of the bed is poor;

[0075] (3) The coal to be sorted is fed into the gas-solid sorting fluidized bed. The coal to be sorted is affected by the overall density of the fluidized bed. The low-density coal and heavy materials in the coal to be sorted are stratified according to the bed density. Some of the low-density coal to be separated floats to the surface of the fluidized bed, while some of the low-density coal to be separated rolls in the middle of the sorting bed due to large bubbles in the sorting bed and unstable bed, making it difficult to float to the surface of the fluidized bed to achieve the sorting purpose.

[0076] This comparative example shows that the porous particles whose particle size is not within the range specified by the present invention and whose packing density is greater than the range specified by the present invention have poor separation effect.

[0077] Comparative Example 3

[0078] The method of separating low-density coal by using a gas-solid separation fluidized bed in this comparative example is the same as that in Example 3, except that the porosity is 0%.

[0079] Specifically, the steps include:

[0080] (1) Select the average particle size d p =75μm, true density ρ=7780kg / m 3 , the porosity ε = 0% iron powder, the critical fluidization velocity is 12.5 cm / s, and the bulk density of the particles is 2.78 g / cm 3 , using the above iron powder as a weighting material;

[0081] (2) The weighted material is introduced into the fluidized bed separator, and the flow rate of the flow meter is adjusted to be greater than the critical fluidization velocity of the porous particles, 4.5 cm / s. Under the action of the gas, the porous particles form a fluidized bed layer, and the bed density of the fluidized bed layer is 4.42 g / cm 3 The bed density is much greater than the density of low-density coal, ranging from 1.0 to 1.2 g / cm 3 , all the coal to be selected will float on the upper part of the bed, and it is impossible to sort the low-density coal in the target density range.

[0082] This comparative example shows that the use of solid particles cannot achieve the purpose of separating low-density coal.

[0083] Test Example 1

[0084] The sorting accuracy of low-density coal in Examples 1-3 and Comparative Examples 1-3 was tested respectively.

[0085] Among them, the sorting accuracy is generally characterized by the possible deviation E. The larger the E value, the lower the sorting accuracy. The possible deviation E of a sorting method is generally determined by floating and sinking experiments. The calculation method of E is: ① Using the data of floating and sinking experiments, the vertical axis is the distribution rate and the horizontal axis is the density to draw the sink distribution curve; ② The density value ρ corresponding to the distribution rate of 75% in the curve 75％ The density value ρ corresponding to the distribution rate of 25% in the curve 25％ The difference divided by 2 is the possible deviation E. The standard for the possible deviation E refers to the "Technical Specification for Dry Coal Preparation" (T / CCT 011-2020) group standard issued by the China Coal Processing and Utilization Association. The sorting equipment used in the present invention is a heavy medium fluidized bed dry sorting machine. For heavy medium fluidized bed dry sorting machines, the "Specifications" stipulate that the processing capacity and main indicators of heavy medium fluidized bed dry sorting machines shall adopt the guaranteed values ​​provided by the manufacturer. That is, the E value is determined according to demand, and there is no exact possible deviation E standard. Therefore, the possible deviation E standard of this test refers to the E value standard for the composite dry sorting machine in the "Specifications". For the sorting of composite dry sorting machines, when the feed particle size is below 25 (13) mm, the maximum allowable range of E is 0.17~0.2g / cm 3 .

[0086] Specific test steps The test takes Example 1 as an example, using ping-pong balls with a diameter of 15 mm to fill mixed particles to prepare standard spherical density balls with different densities, and performing floating and sinking tests in a gas-solid fluidized bed to measure the possible deviation E value. The critical fluidizing gas velocity in the bed is 7.2 cm / s, the apparent gas velocity is 9.2 cm / s, the initial bed height is within the range of 40-300 mm, the sorting time is 60 s, and the floating and sinking test of a single density ball is repeated 30 times, and the number of sinking times is recorded. The results of the floating and sinking test are shown in Table 1. Figure 2 The following table shows the possible deviation E of 0.05 g / cm when the bed height is 180 cm. 3 .

[0087] Table 1

[0088]

[0089] The methods of Examples 1-3 and Comparative Examples 1-3 were respectively used to sort low-density coal, and the sorted low-density coal was respectively subjected to the above-mentioned sorting accuracy test. The results are shown in Table 2.

[0090] Table 2

[0091]

[0092] It can be seen from Table 2 that the separation accuracy of the method of the present invention is relatively high, and the possible deviation E (g / cm 3 ) is 0.045~0.07, which can meet the sorting accuracy requirements.

[0093] 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 sorting low-density coal using a gas-solid separation fluidized bed, characterized in that: include: The porous particles are used as weighting materials to separate the low-density coal in the coal to be sorted. The average particle size of the porous particles is 70-130 μm, and the true density is 7.0-7.8 g / cm 3 , the porosity is 5% to 10%, and the porous particles are magnetic materials; The porous particles are formed into a density greater than 1.0 g / cm under the action of airflow. 3 And not more than 1.3 g / cm 3 The sorting bed; The density of the separation bed is greater than the density of the target coal in the coal to be separated.

2. The method for separating low-density coal using a gas-solid separation fluidized bed according to claim 1, characterized in that: The gas in the air flow is one or more of air, carbon dioxide and inert gas.

3. The method for separating low-density coal using a gas-solid separation fluidized bed according to claim 1, characterized in that: The critical fluidization velocity of the porous particles is 4-10 cm / s.

4. The method for separating low-density coal by using a gas-solid separation fluidized bed according to claim 1, characterized in that: The magnetic material is iron powder.

5. A method for sorting low-density coal using a gas-solid separation fluidized bed according to any one of claims 1 to 3, characterized in that: The bulk density of the porous particles is 1.2-1.5 g / cm 3 .

6. A method for sorting low-density coal using a gas-solid separation fluidized bed according to any one of claims 1 to 3, characterized in that: The density of the low-density coal is 1.0-1.2 g / cm 3 .

7. Application of the method according to any one of claims 1 to 6 in sorting low-density coal.

Images