A coal dry flotation process

Abstract

The invention discloses a coal dry flotation process, the main steps of which are as follows: 1) loading bed material particles into an upper bed and a lower bed, adjusting the gas velocity of the two beds to make the particles circulate and fluidize; 2) sending crushed raw coal particles into the middle of the upper bed, and the heavier gangue particles gradually sink to the bottom and are mined; 3) the lighter coal particles gradually float up and enter the lower bed through the upper orifice with the bed material particles, and the coal particles are enriched at the upper part and mined; 4) the bed material particles continue to sink in the lower bed and return to the upper bed through the lower orifice to continue to participate in the next cycle of raw coal flotation. The process requires simple equipment, decouples the simultaneous separation process of gangue and coal particles into two relatively independent separation processes, firstly mining the gangue particles, and then mining the coal particles, and can take into account the mining purity of both at the same time. In addition, the process has good versatility and can realize continuous and efficient sorting of different types of raw coal.

Description

Technical Field

[0001] The invention relates to the field of coal processing, in particular to a coal dry flotation process. Background Art

[0002] Raw coal mined from coal mines often contains a large amount of gangue. Separating gangue from raw coal (i.e. coal sorting) is the first step to achieve efficient and clean utilization of coal resources. Furthermore, sorting coal at the coal production site (rather than the site of use) can not only save transportation costs, but also backfill the sorted gangue on site to prevent environmental and ecological problems such as surface collapse in the mining area.

[0003] The current coal separation process mainly uses the density difference between gangue and coal (the former has a higher density than the latter), so it is also called flotation process. The earliest coal flotation process used water as a medium: when the raw coal particles were poured into the water, the heavier gangue particles would sink to the bottom, while the lighter coal particles would float on the water surface, thus separating the two. However, this wet flotation process consumes a lot of water resources and causes serious environmental pollution.

[0004] Based on this, people have developed a coal dry flotation process, which uses a particle group in a bubbling fluidized state as a flotation medium. Figure 1 As shown in the figure, firstly, specific bed material particles (such as magnetite particles) are loaded into the fluidized bed, and air is introduced into the lower part to make the bed in a bubbling fluidized state. Then, the operating gas velocity is reasonably adjusted to make the bed density between the density of gangue and coal. After that, the crushed raw coal particles are sent into the bubbling fluidized bed from the middle. The heavier gangue particles will gradually settle to the bottom of the bed and be mined, while the lighter coal particles will float to the surface of the bed and be mined. In this way, continuous dry flotation of raw coal can be achieved.

[0005] Compared with the wet flotation process, the dry flotation process does not require precious water resources, and has a natural advantage in my country's arid areas rich in coal. However, the current dry flotation process has the following disadvantages: 1) The separation of gangue and coal particles is carried out in a bubbling fluidized bed, and the purity of the gangue particles mined from the bottom and the coal particles mined from the top cannot be taken into account at the same time. In other words, either the coal mined from the top is mixed with bed particles, or the gangue mined from the bottom is mixed with bed particles, and the subsequent separation of gangue or coal and bed materials will have to be faced. 2) Since the structure and size of the fluidized bed are difficult to change, the axial distribution of gas velocity and bed density is fixed, resulting in poor versatility. It is necessary to customize and process a dedicated fluidized bed according to the coal production characteristics of a specific coal mine (creating a unique axial distribution of bed density), which invisibly increases the investment cost.

[0006] In summary, up to now, there is still no dry flotation process with wide adaptability to various types of coal that can take into account the extraction purity of both coal and gangue particles. Summary of the invention

[0007] The purpose of the present invention is to solve the above technical problems and propose a new coal dry flotation process.

[0008] The technical solution mainly includes the following steps: 1) loading bed material particles into the upper bed and the lower bed, and adjusting the gas velocity of the two beds to make the particles circulate and fluidize; 2) sending the crushed raw coal particles into the middle of the upper bed, and the heavier coal gangue gradually sinks to the bottom and is mined; 3) the lighter coal particles gradually float up and enter the lower bed through the upper orifice with the bed material particles, and the coal particles are enriched in the upper part and are mined; 4) the bed material particles gradually sink in the lower bed and return to the upper bed through the lower orifice to continue to participate in the next cycle of raw coal flotation.

[0009] The technical solution decouples the simultaneous separation process of gangue and coal particles into two separation processes, firstly selecting the gangue particles in the ascending bed, and then realizing the separation of coal and bed material particles in the descending bed.

[0010] The operating gas velocity of the ascending bed needs to be greater than the operating gas velocity of the descending bed. The bed density of the former is smaller than that of the latter, and the bed material particles can circulate between the ascending bed and the descending bed.

[0011] The purpose of the ascending bed is to sort out the gangue particles. The smaller bed density is conducive to all the gangue particles sinking to the bottom, thereby improving the gangue sorting yield.

[0012] The purpose of the descending bed is to separate the coal particles from the bed material particles. The higher bed density is very beneficial to the enrichment of all the coal particles in the upper part, thereby improving the sorting yield of the coal particles. In short, the natural difference in bed density between the ascending bed and the descending bed is beneficial to improving the sorting yield of both the gangue and the coal particles.

[0013] The operating gas velocity of the ascending bed and the operating gas velocity of the descending bed can both be regulated relatively independently, so the extraction purity of the gangue particles in the descending bed and the extraction purity of the coal particles in the ascending bed can be taken into account at the same time without losing one for the other.

[0014] The beneficial effects of the present invention are: 1) the process flow is simple, the required equipment is simple, and the investment is small; 2) the operating gas speed of the ascending bed and the descending bed can be adjusted relatively independently, so that the extraction purity of coal gangue and coal can be taken into account and improved at the same time; 3) during normal operation, the bed density of the ascending bed is less than the bed density of the descending bed. Such bed density distribution is not only beneficial to the sinking sorting of coal gangue particles in the ascending bed, but also beneficial to the floating sorting of coal particles in the descending bed, and finally improves the sorting yield of coal gangue and coal particles at the same time; 4) as long as the bed density of the ascending bed is less than the bed density of the descending bed, the device can operate normally, so the operating gas speed of the two beds has greater operating flexibility, which ultimately makes the process have good versatility and can process raw coal particles with different properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The current dry flotation process for raw coal

[0016] Figure 2 The process of the present invention is used for separation of coal gangue and coal. DETAILED DESCRIPTION

[0017] Implementation Method 1

[0018] The following is combined with Figure 2 The method of the present invention is further described:

[0019] The bed material particles are loaded into the upper bed 1 and the lower bed 2, and the bed heights in the two beds are controlled to be substantially flush with the lower edge of the upper orifice 5. Air is respectively pumped into the upper bed 1 and the lower bed 2 from the gas distribution plates 3 and 7 as the fluidizing medium. The operating gas velocity in the upper bed 1 is controlled to be greater than the operating gas velocity in the lower bed 2, and the particles in the upper bed 1 will enter the lower bed 2 through the upper orifice 5. Afterwards, the particles in the lower bed 2 return to the upper bed 1 through the lower orifice 4. In this way, the bed material particles can continuously circulate between the upper bed 1 and the lower bed 2.

[0020] When the circulating flow of bed material particles between the upper bed 1 and the lower bed 2 reaches a steady state, the crushed raw coal particles are fed into the upper bed 1 from the middle. The heavier gangue particles gradually sink to the bottom of the upper bed 1 and are mined, while the lighter coal particles continue to float up and enter the lower bed 2 through the upper orifice 5 with the bed material. In the lower bed 2, the lighter coal particles are enriched on the bed surface and are mined, while the heavier bed material particles relative to the coal particles continue to sink and return to the upper bed 1 through the lower orifice 4 to continue to participate in the next cycle of raw coal flotation. In this way, the raw coal particles can be continuously separated into heavier gangue particles and lighter coal particles.

[0021] In principle, as long as the operating gas velocity in the upper bed 1 is greater than the operating gas velocity in the lower bed 2, the bed material particles can circulate between the two beds. Therefore, there is a lot of room for independent changes in the operating gas velocity of the upper bed 1 and the operating gas velocity of the lower bed 2. This makes it possible to simultaneously improve the purity of the extracted coal gangue and coal carbon particles. Specifically, the operating gas velocity of the upper bed 1 is first changed to ensure that the coal gangue particles extracted from the lower part have a high purity, and then the operating gas velocity of the lower bed 2 is adjusted to ensure that the coal particles extracted from the upper part also have a high purity.

[0022] The design of the baffle 8 can improve the purity of the mined coal particles and prevent the coal particles that have floated to the surface from being "contaminated" by the materials from the upper bed 1. In addition, the height of the gas distribution plate 3 is controlled to be lower than the gas distribution plate 7, so that there will be an extra space at the bottom of the upper bed 1 to further separate the coal gangue and bed material particles, ultimately improving the purity of the mined coal gangue.

[0023] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A coal dry flotation process, characterized in that: The steps include: 1) Load the bed material particles into the upper bed and the lower bed, and adjust the gas velocity of the two beds to make the particles circulate and fluidize; 2) The crushed raw coal particles are sent to the middle of the upper bed, and the heavier gangue particles gradually sink to the bottom and are mined; 3) The lighter coal particles gradually float up and enter the descending bed through the upper holes together with the bed material particles. The coal particles are enriched in the upper part and mined out; 4) The bed material particles gradually sink in the descending bed and return to the ascending bed through the lower orifice to continue to participate in the next cycle of raw coal flotation; The operating air speed of the upper bed needs to be greater than the operating air speed of the lower bed; Air is pumped into the upper bed and the lower bed from the upper bed gas distribution plate and the lower bed gas distribution plate as the fluidizing medium, and the height of the upper bed gas distribution plate is controlled to be lower than that of the lower bed gas distribution plate.

2. A coal dry flotation process according to claim 1, characterized in that: The simultaneous separation of gangue and coal particles is decoupled into two separation processes. First, the gangue particles are sorted out in the ascending bed, and then the coal and bed material particles are separated in the descending bed.

3. A coal dry flotation process according to claim 1 or 2, characterized in that: The two separation processes can be controlled relatively independently, thereby taking into account the extraction purity of coal gangue and coal particles at the same time.

4. A coal dry flotation process according to claim 1, characterized in that: The bed density of the ascending bed is less than that of the descending bed. This natural density difference can improve the sorting yield of the gangue particles in the descending bed, as well as the sorting yield of the coal particles in the ascending bed.

5. A coal dry flotation process according to claim 1, characterized in that: The operating gas velocities of the ascending bed and the descending bed have high operating flexibility. The process has good versatility and can process raw coal particles with different properties.

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