Method for reducing content of iron element in coal

Abstract

The invention belongs to the technical field of nonmetal dressing and smelting, and particularly provides a method for reducing the content of an iron element in coal, which comprises the following steps: (1) mixing pulverized coal with water to obtain coal slurry; and (2) sequentially carrying out ultrasonic and high-gradient magnetic separation treatment on the coal slurry. The method for reducing the content of the iron element in the coal has the beneficial effects that an ultrasonic wave-high gradient magnetic separation combined technology is utilized, the adhesive force between iron-containing mineral particles and attached coal is weakened under the action of ultrasonic waves, and dissociation of iron-containing minerals such as pyrite, siderite and hematite in the coal and organic matter is promoted. And separating the coal from the minerals by using a high-gradient magnetic separation technology according to different magnetisms of the coal and the minerals. The method for reducing the content of the iron element in the coal is easy to operate, environmentally friendly, free of pollution and low in economic cost, the iron element in the coal can be effectively removed, and the method has important significance on the coal for industrial silicon smelting.

Description

Technical Field

[0001] The invention belongs to the technical field of non-metallic smelting, and in particular relates to a method for reducing the iron content in coal. Background Art

[0002] Industrial silicon is a basic raw material for semiconductors, medical devices, photovoltaic equipment and other fields, and its demand is increasing. If the iron content in industrial silicon is too high, it will seriously affect the properties and applications of downstream products. Iron is difficult to remove during the smelting process of industrial silicon. Therefore, it is crucial to reduce the introduction of iron from the production raw materials to improve the quality of industrial silicon products.

[0003] Coal, as a carbonaceous reducing agent, is the main raw material in the smelting process of industrial silicon. Therefore, by reducing the iron content in coal, the quality of industrial silicon products can be effectively improved.

[0004] Iron in coal is mostly found in various inorganic minerals, such as pyrite, siderite, illite, etc. At present, the methods for removing iron from coal mainly include physical method, chemical method and physical and chemical method. The use of chemical method to remove iron from coal consumes a large amount of strong acid and strong alkali chemical reagents, and the process is complicated, the production cost is high, and it is easy to produce waste liquid and cause secondary pollution. When using physical and chemical methods to remove iron from coal, neutral oils such as hydrocarbons are often used. The production process conditions are relatively harsh, and the raw materials used also face problems such as difficult recovery and easy pollution. The physical method of removing iron from coal has a simple process flow and relatively low production cost, but the single physical method has problems such as low iron removal rate. Summary of the invention

[0005] The present application provides a method for reducing the iron content in coal, aiming to solve the problems of complex process, high cost, secondary pollution, low iron removal rate, etc. in the prior art of removing iron from coal.

[0006] The present invention provides a method for reducing the iron content in coal, comprising the following steps:

[0007] (1) Mixing coal powder and water to obtain coal slurry;

[0008] (2) The coal slurry is subjected to ultrasonic and high gradient magnetic separation treatments in sequence.

[0009] The method for reducing the iron content in coal described in this application uses a technology combining ultrasound and high gradient magnetic separation to weaken the adhesion between iron-containing mineral particles and organic matter in coal under the action of ultrasound, thereby promoting the dissociation of iron-containing minerals such as pyrite, siderite and hematite from organic matter in coal. According to the difference in magnetic properties between coal and various minerals, high gradient magnetic separation technology is used to separate coal from minerals. High gradient magnetic separation has a stronger magnetic force than ordinary magnetic separation. Due to its stronger magnetic force, there is no need to roast and magnetize the material when separating weakly magnetic minerals, which is beneficial to reducing energy consumption and protecting the environment, with high separation efficiency and achieving fine separation.

[0010] The method for reducing the iron content in coal described in the present application is simple to operate, environmentally friendly and pollution-free, and has low economic cost. It can effectively remove the iron element in coal and is of great significance to coal used for industrial silicon smelting.

[0011] According to some embodiments of the method for reducing the iron content in coal described in the present application, in step (1), the particle size of the coal powder is ≤0.125 mm, wherein the coal powder with a particle size of 0.125-0.074 mm accounts for 30%-90% of the total mass of the coal powder.

[0012] According to some embodiments of the method for reducing the iron content in coal described in the present application, the coal powder with a particle size of 0.125-0.074 mm accounts for 65%-80% of the total mass of the coal powder.

[0013] According to some embodiments of the method for reducing the iron content in coal described in the present application, the concentration of the coal slurry is 60-100 g / L.

[0014] According to some embodiments of the method for reducing the iron content in coal described in the present application, the concentration of the coal slurry is 65-95 g / L.

[0015] According to some embodiments of the method for reducing the iron content in coal described in the present application, in step (2), stirring treatment is performed simultaneously with the ultrasonic treatment.

[0016] According to some implementations of the method for reducing the iron content in coal described in the present application, the stirring temperature is 20-30° C.; and the stirring time is 1-10 min.

[0017] According to some implementations of the method for reducing the iron content in coal described in the present application, the stirring speed is 80-200 r / min.

[0018] According to some embodiments of the method for reducing the iron content in coal described in the present application, in step (2), the operating frequency of the ultrasound is 20-100 kHz.

[0019] According to some embodiments of the method for reducing the iron content in coal described in the present application, the ultrasonic operating frequency is 20-60 kHz.

[0020] According to some embodiments of the method for reducing the iron content in coal described in the present application, the ultrasonic time is 1-10 minutes.

[0021] According to some embodiments of the method for reducing the iron content in coal described in the present application, the ultrasonic time is 2-7 minutes.

[0022] According to some embodiments of the method for reducing the iron content in coal described in the present application, the power of the ultrasound is 150-1000W.

[0023] According to some embodiments of the method for reducing the iron content in coal described in the present application, in step (2), the equipment for implementing the high gradient magnetic separation includes a wet high intensity magnetic separator.

[0024] According to some implementations of the method for reducing the iron content in coal described in the present application, when the wet high-intensity magnetic separator is used for high-gradient magnetic separation, the flow rate of the coal slurry is 2-10 mL / s.

[0025] According to some implementations of the method for reducing the iron content in coal described in the present application, when the wet high-intensity magnetic separator is used for high-gradient magnetic separation, the flow rate of the coal slurry is 3-8 mL / s.

[0026] According to some implementation methods of the method for reducing the iron content in coal described in the present application, when a wet high-intensity magnetic separator is used for high-gradient magnetic separation, the magnetic field strength is 0.5-1.8T.

[0027] According to some implementation methods of the method for reducing the iron content in coal described in the present application, when a wet high-intensity magnetic separator is used for high-gradient magnetic separation, the magnetic field strength is 0.8-1.6T.

[0028] According to some embodiments of the method for reducing the iron content in coal described in the present application, the method also includes a step of preparing coal powder.

[0029] According to some embodiments of the method for reducing the iron content in coal described in the present application, the preparation of the coal powder includes: sequentially crushing, drying and grinding the raw coal.

[0030] According to some embodiments of the method for reducing the iron content in coal described in the present application, the drying temperature is 35-45° C., and the drying time is 2-3.5 hours. DETAILED DESCRIPTION

[0031] Embodiments of the present invention are described in detail below. The described embodiments are intended to explain the present invention but should not be construed as limiting the present invention.

[0032] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0033] The present application provides a method for reducing the iron content in coal, comprising the following steps:

[0034] (1) Mixing coal powder and water to obtain coal slurry;

[0035] (2) The coal slurry is subjected to ultrasonic and high gradient magnetic separation treatments in sequence.

[0036] The method for reducing the iron content in coal described in this application uses a technology combining ultrasound and high gradient magnetic separation to weaken the adhesion between iron-containing mineral particles and attached coal under the action of ultrasound, thereby promoting the dissociation of iron-containing minerals such as pyrite, siderite and hematite from organic matter in coal. According to the difference in magnetic properties between coal and various minerals, high gradient magnetic separation technology is used to separate coal from minerals. High gradient magnetic separation has a stronger magnetic force than ordinary magnetic separation. Due to its stronger magnetic force, there is no need to roast and magnetize the material when separating weakly magnetic minerals, which is beneficial to reducing energy consumption and protecting the environment, with high separation efficiency and achieving fine separation.

[0037] The method for reducing the iron content in coal described in the present application is simple to operate, environmentally friendly and pollution-free, and has low economic cost. It can effectively remove the iron element in coal and is of great significance to coal used for industrial silicon smelting.

[0038] In some embodiments, in step (1), the coal powder particle size is ≤0.125 mm, wherein the coal powder with a particle size of 0.125-0.074 mm accounts for 30%-90% of the total mass of the coal powder, such as 30%, 45%, 50%, 53%, 60%, 68%, 72%, 76%, 81%, 87%, 90%, etc. If the proportion of coal powder with a particle size of 0.125-0.074 mm is too large, the iron-containing minerals will adhere to the organic matter of the coal powder and cannot be fully exposed, and the iron-containing minerals cannot be fully dissociated from the organic matter in the coal powder. If the proportion of coal powder with a particle size of 0.125-0.074 mm is too small, the coal powder is prone to agglomeration, affecting separation. At the same time, to achieve a smaller coal powder particle size, it is necessary to increase the grinding time, increase energy consumption and cost.

[0039] In some embodiments, in step (1), the coal powder with a particle size of 0.125-0.074 mm accounts for 65%-80% of the total mass of the coal powder.

[0040] In some embodiments, in step (1), the concentration of the coal slurry is 60-100g / L, such as 60g / L, 68g / L, 73g / L, 79g / L, 83g / L, 89g / L, 91g / L, 96g / L, 100g / L, etc. A high coal slurry concentration will cause the coal slurry viscosity to be too large, resulting in a relatively large resistance when the iron-containing mineral particles flow in the coal slurry, which is not conducive to the removal of iron. If the coal slurry concentration is too low, the amount of water consumed to process the same amount of coal increases relatively, reducing the processing capacity of the equipment and affecting the economic benefits. Within the coal slurry concentration range of the present application, a high coal yield can be maintained while the iron removal rate is high.

[0041] In some embodiments, in step (1), the concentration of the coal slurry is 65-95 g / L.

[0042] In some embodiments, in step (2), the ultrasonic treatment is performed simultaneously with stirring.

[0043] In some embodiments, the stirring temperature is 20-30° C.; the stirring time is 1-10 min, for example, 1 min, 3 min, 5 min, 7 min, 9 min, 10 min, etc.

[0044] In some embodiments, the stirring speed is 80-200 r / min, for example, 80 r / min, 95 r / min, 100 r / min, 120 r / min, 150 r / min, 180 r / min, 200 r / min, etc.

[0045] In some embodiments, in step (2), the ultrasonic operating frequency is 20-100kHz, such as 20kHz, 30kHz, 38kHz, 45kHz, 53kHz, 65kHz, 78kHz, 82kHz, 88kHz, 91kHz, 96kHz, 100kHz, etc. The lower the ultrasonic operating frequency, the easier it is to produce "cavitation" in the liquid, that is, the mechanical vibration intensity generated by the liquid during the ultrasonic process is greater, which is more conducive to the dissociation of minerals and organic matter. The ultrasonic operating frequency described in the present application is more conducive to the separation of iron-containing minerals and organic matter in coal powder.

[0046] In some embodiments, the operating frequency of the ultrasound is 20-60 kHz.

[0047] In some embodiments, the ultrasonic time is 1-10 minutes, such as 1 minute, 3 minutes, 5 minutes, 7 minutes, 9 minutes, 10 minutes, etc. Properly increasing the ultrasonic time is beneficial to promoting the dissociation of iron-containing minerals from organic matter in coal powder, thereby improving the iron removal rate, but after exceeding a certain ultrasonic time, the iron removal rate remains basically unchanged.

[0048] In some embodiments, the ultrasound duration is 2-7 min.

[0049] In some embodiments, the stirring time is equal to the ultrasonic time.

[0050] In some embodiments, the power of the ultrasound is 150-1000W, for example 150W, 220W, 250W, 300W, 380W, 410W, 490W, 530W, 580W, 600W, 720W, 880W, 930W, 1000W.

[0051] In some embodiments, in step (2), the equipment for implementing the high gradient magnetic separation includes a wet high intensity magnetic separator.

[0052] In some embodiments, the wet high intensity magnetic separator is a wet high intensity magnetic separator XCSQ-50*70.

[0053] In some embodiments, when a wet high-intensity magnetic separator is used for high-gradient magnetic separation, the flow rate of the coal slurry is 2-10 mL / s. If the flow rate is too small, the residence time of the coal slurry during magnetic separation is long, causing some coal particles with weak minerals to be magnetically attracted, resulting in a decrease in coal yield. If the flow rate is too large, the residence time of the coal slurry during magnetic separation is short, and iron-containing minerals with weak magnetism flow out before they have time to be magnetically attracted, resulting in a high iron content in the coal.

[0054] In some embodiments, the flow rate of the coal slurry is 3-8 mL / s.

[0055] In some embodiments, when a wet high-intensity magnetic separator is used for high-gradient magnetic separation, the magnetic field strength is 0.5-1.8T, for example, 0.5T, 0.8T, 1.2T, 1.4T, 1.6T, 1.8T, etc.

[0056] In some embodiments, the magnetic field strength is 0.8-1.6T.

[0057] In some embodiments, the step of preparing coal powder is also included.

[0058] In some embodiments, the preparation of the coal powder includes: crushing, drying and grinding the raw coal in sequence.

[0059] In some embodiments, the drying temperature is 35-45° C., and the drying time is 2-3.5 h.

[0060] The technical solution of the present application is described in detail below in conjunction with specific embodiments.

[0061] The coal sample used in the embodiment of the present application comes from the Balikun mining area in Hami, Xinjiang, and the mass content of iron in the coal sample is 0.65%.

[0062] Example 1

[0063] A method for reducing the iron content in coal comprises the following steps:

[0064] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 30% of the total mass of the coal powder;

[0065] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 60 g / L;

[0066] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 20 kHz, and subjecting the ultrasonic treatment to 1 min under the above conditions;

[0067] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 2 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.5 T. After the magnetic separation, coal with low iron content is obtained.

[0068] Example 2

[0069] The only difference between Example 2 and Example 1 is that the percentage of particles with a size of 0.125-0.074 mm in the coal powder to the total mass of the coal powder is different.

[0070] The specific operations are:

[0071] A method for reducing the iron content in coal comprises the following steps:

[0072] (1) The coal sample was crushed, dried at 40°C for 2 h, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm accounted for 65% of the total mass of the coal powder;

[0073] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 60 g / L;

[0074] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 20 kHz, and subjecting the ultrasonic treatment to 1 min under the above conditions;

[0075] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 2 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.5 T. After the magnetic separation, coal with low iron content is obtained.

[0076] Example 3

[0077] The only difference between Example 3 and Example 1 is that the percentage of particles with a size of 0.125-0.074 mm in the coal powder to the total mass of the coal powder is different.

[0078] The specific operation is: a method for reducing the iron content in coal, comprising the following steps:

[0079] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 80% of the total mass of the coal powder;

[0080] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 60 g / L;

[0081] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 20 kHz, and subjecting the ultrasonic treatment to 1 min under the above conditions;

[0082] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 2 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.5 T. After the magnetic separation, coal with low iron content is obtained.

[0083] Example 4

[0084] The only difference between Example 4 and Example 1 is that in step (2), the concentration of the prepared coal slurry is different.

[0085] The specific operations are:

[0086] A method for reducing the iron content in coal comprises the following steps:

[0087] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 30% of the total mass of the coal powder;

[0088] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 50 g / L;

[0089] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 20 kHz, and subjecting the ultrasonic treatment to 1 min under the above conditions;

[0090] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 2 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.5 T. After the magnetic separation, coal with low iron content is obtained.

[0091] Example 5

[0092] The only difference between Example 5 and Example 1 is that in step (2), the concentration of the prepared coal slurry is different.

[0093] The specific operations are:

[0094] A method for reducing the iron content in coal comprises the following steps:

[0095] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 30% of the total mass of the coal powder;

[0096] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 80 g / L;

[0097] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 20 kHz, and subjecting the ultrasonic treatment to 1 min under the above conditions;

[0098] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 2 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.5 T. After the magnetic separation, coal with low iron content is obtained.

[0099] Example 6

[0100] The only difference between Example 6 and Example 1 is that in step (3), the operating frequency of the ultrasonic treatment is different.

[0101] The specific operations are:

[0102] A method for reducing the iron content in coal comprises the following steps:

[0103] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 30% of the total mass of the coal powder;

[0104] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 60 g / L;

[0105] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 30 kHz, and subjecting the ultrasonic treatment to 1 min under the above conditions;

[0106] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 2 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.5 T. After the magnetic separation, coal with low iron content is obtained.

[0107] Example 7

[0108] The only difference between Example 7 and Example 1 is that in step (3), the operating frequency of the ultrasonic treatment is different.

[0109] The specific operations are:

[0110] A method for reducing the iron content in coal comprises the following steps:

[0111] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 30% of the total mass of the coal powder;

[0112] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 60 g / L;

[0113] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 50 kHz, and subjecting the ultrasonic treatment to 1 min under the above conditions;

[0114] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 2 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.5 T. After the magnetic separation, coal with low iron content is obtained.

[0115] Example 8

[0116] The only difference between Example 8 and Example 1 is that in step (3), the duration of ultrasonic treatment is different.

[0117] The specific operations are:

[0118] A method for reducing the iron content in coal comprises the following steps:

[0119] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 30% of the total mass of the coal powder;

[0120] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 60 g / L;

[0121] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 20 kHz, and subjecting the ultrasonic treatment to 2 min under the above conditions;

[0122] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 2 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.5 T. After the magnetic separation, coal with low iron content is obtained.

[0123] Example 9

[0124] The only difference between Example 9 and Example 1 is that in step (3), the duration of ultrasonic treatment is different.

[0125] The specific operations are:

[0126] A method for reducing the iron content in coal comprises the following steps:

[0127] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 30% of the total mass of the coal powder;

[0128] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 60 g / L;

[0129] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 20 kHz, and subjecting the ultrasonic treatment to 7 min under the above conditions;

[0130] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 2 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.5 T. After the magnetic separation, coal with low iron content is obtained.

[0131] Example 10

[0132] The only difference between Example 10 and Example 1 is that in step (4), the flow rate of the coal slurry is different.

[0133] The specific operations are:

[0134] A method for reducing the iron content in coal comprises the following steps:

[0135] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 30% of the total mass of the coal powder;

[0136] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 60 g / L;

[0137] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 20 kHz, and subjecting the ultrasonic treatment to 1 min under the above conditions;

[0138] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 3 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.5 T. After the magnetic separation, coal with low iron content is obtained.

[0139] Embodiment 11

[0140] The only difference between Example 11 and Example 1 is that in step (4), the flow rate of the coal slurry is different.

[0141] The specific operations are:

[0142] A method for reducing the iron content in coal comprises the following steps:

[0143] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 30% of the total mass of the coal powder;

[0144] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 60 g / L;

[0145] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 20 kHz, and subjecting the ultrasonic treatment to 1 min under the above conditions;

[0146] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 8 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.5 T. After the magnetic separation, coal with low iron content is obtained.

[0147] Example 12

[0148] The only difference between Example 12 and Example 1 is that in step (4), the intensity of the magnetic field is different when high gradient magnetic separation is performed.

[0149] The specific operations are:

[0150] A method for reducing the iron content in coal comprises the following steps:

[0151] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 30% of the total mass of the coal powder;

[0152] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 60 g / L;

[0153] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 20 kHz, and subjecting the ultrasonic treatment to 1 min under the above conditions;

[0154] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 2 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.7 T. After the magnetic separation, coal with low iron content is obtained.

[0155] Example 13

[0156] The only difference between Example 13 and Example 1 is that in step (4), the intensity of the magnetic field is different when high gradient magnetic separation is performed.

[0157] The specific operations are:

[0158] A method for reducing the iron content in coal comprises the following steps:

[0159] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 30% of the total mass of the coal powder;

[0160] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 60 g / L;

[0161] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 20 kHz, and subjecting the ultrasonic treatment to 1 min under the above conditions;

[0162] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 2 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 1.0 T. After the magnetic separation, coal with low iron content is obtained.

[0163] Embodiment 14

[0164] The only difference between Example 14 and Example 1 is that the percentage of particles with a size of 0.125-0.074 mm in the coal powder is different in the total mass of the coal powder, and in step (2), the concentration of the coal slurry prepared is different.

[0165] The specific operations are:

[0166] A method for reducing the iron content in coal comprises the following steps:

[0167] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 75% of the total mass of the coal powder;

[0168] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 90 g / L;

[0169] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 20 kHz, and subjecting the ultrasonic treatment to 1 min under the above conditions;

[0170] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 2 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.5 T. After the magnetic separation, coal with low iron content is obtained.

[0171] Embodiment 15

[0172] The only difference between Example 15 and Example 1 is that in step (3), the operating frequency of the ultrasonic treatment is different and the duration of the ultrasonic treatment is different.

[0173] The specific operations are:

[0174] A method for reducing the iron content in coal comprises the following steps:

[0175] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 30% of the total mass of the coal powder;

[0176] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 60 g / L;

[0177] (3) subjecting the coal slurry obtained in step (2) to ultrasonic treatment while stirring, adjusting the stirring rate to 80 r / min, the stirring temperature to 25° C., the ultrasonic treatment power to 150 W, the operating frequency to 35 kHz, and subjecting the ultrasonic treatment to 2 min under the above conditions;

[0178] (4) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry after ultrasonic treatment. The flow rate of the coal slurry is set to 2 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.5 T. After the magnetic separation, coal with low iron content is obtained.

[0179] Example 16

[0180] The difference between Example 16 and Example 1 is that in step (3), no ultrasonic treatment is performed, and only high gradient magnetic separation treatment is performed.

[0181] The specific operations are:

[0182] A method for reducing the iron content in coal comprises the following steps:

[0183] (1) The coal sample is crushed, dried at 40°C for 2 hours, and ground to obtain coal powder, in which particles with a size of 0.125-0.074 mm account for 30% of the total mass of the coal powder;

[0184] (2) adding water to the coal powder obtained in step (1) to prepare a coal slurry with a concentration of 60 g / L;

[0185] (3) A wet high-intensity magnetic separator XCSQ-50*70 device is used to perform high-gradient magnetic separation on the coal slurry. The flow rate of the coal slurry is set to 2 mL / s, and the magnetic field strength of the wet high-intensity magnetic separator XCSQ-50*70 device is set to 0.5 T. After the magnetic separation, coal with low iron content is obtained.

[0186] The iron removal effect of the method for reducing the iron content in coal described in Examples 1 to 16 of the present application is studied, and the results are shown in Table 1:

[0187] In Table 1, the yield of low iron coal = (mass of low iron coal / mass of coal powder used for slurry preparation) × 100%

[0188] The removal rate of iron in coal = 100% × (iron content in unit mass of pulverized coal for slurry preparation - iron content in unit mass of low-iron coal) / iron content in unit mass of pulverized coal for slurry preparation.

[0189] Table 1

[0190] Yield of low iron content coal / % Removal rate of iron in coal / % Example 1 86.26 75.71 Example 2 88.46 76.50 Example 3 89.65 76.17 Example 4 86.30 75.03 Example 5 90.17 77.96 Example 6 86.45 76.67 Example 7 86.22 76.68 Example 8 86.34 75.97 Example 9 87.56 79.01 Example 10 86.43 77.39 Embodiment 11 89.07 77.45 Example 12 86.37 77.98 Example 13 86.36 78.36 Embodiment 14 91.13 79.20 Embodiment 15 91.04 80.17 Example 16 87.19 70.98

[0191] It can be seen from Table 1 that the removal rate of iron in coal can be significantly improved by ultrasonic pretreatment of high gradient magnetic separation samples. By selecting appropriate treatment parameters, a higher coal yield can be obtained while effectively reducing the iron content in coal.

[0192] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.

Claims

1. A method for reducing the iron content in coal, characterized in that: The following steps are involved: (1) Mixing coal powder and water to obtain coal slurry; (2) The coal slurry is subjected to ultrasonic and high gradient magnetic separation treatments in sequence.

2. The method for reducing the iron content in coal according to claim 1, characterized in that: In step (1), the particle size of the coal powder is ≤0.125 mm, wherein the coal powder with a particle size of 0.125-0.074 mm accounts for 30%-90% of the total mass of the coal powder, preferably 65%-80%.

3. The method for reducing the iron content in coal according to claim 1, characterized in that: In step (1), the concentration of the coal slurry is 60-100 g / L, preferably 65-95 g / L.

4. The method for reducing the iron content in coal according to claim 1, characterized in that: In step (2), stirring is performed simultaneously with the ultrasonic treatment; Preferably, the stirring temperature is 20-30°C; the stirring time is 1-10 min; Preferably, the stirring speed is 80-200 r / min.

5. The method for reducing the iron content in coal according to claim 1, characterized in that: In step (2), the operating frequency of the ultrasound is 20-100 kHz, preferably 20-60 kHz; And / or, the ultrasonic time is 1-10 min; preferably 2-7 min; And / or, the power of the ultrasound is 150-1000W.

6. The method for reducing the iron content in coal according to claim 1, characterized in that: In step (2), the equipment for implementing the high gradient magnetic separation includes a wet high intensity magnetic separator.

7. The method for reducing the iron content in coal according to claim 6, characterized in that: When the wet high-intensity magnetic separator is used for high-gradient magnetic separation, the flow rate of the coal slurry is 2-10 mL / s, preferably 3-8 mL / s.

8. The method for reducing the iron content in coal according to claim 6 or 7, characterized in that: When high gradient magnetic separation is performed using a wet high intensity magnetic separator, the magnetic field strength is 0.5-1.8T, preferably 0.8-1.6T.

9. The method for reducing the iron content in coal according to claim 1, characterized in that: Also included is the step of preparing coal powder; Preferably, the preparation of the coal powder comprises: sequentially crushing, drying and grinding the raw coal.

10. The method for reducing the iron content in coal according to claim 9, characterized in that: The drying temperature is 35-45° C., and the drying time is 2-3.5 hours.