Flow suspension roasting system and method for desiliconizing and purifying coal gangue

Abstract

The invention relates to the technical field of suspension roasting, in particular to a flowing suspension roasting system and method for desiliconizing and purifying coal gangue. The system comprises a multi-stage preheating unit, a multi-stage cooling unit, a flowing suspension roasting furnace and a crystal form control device which are connected in sequence, and the method comprises the steps that coal gangue materials are subjected to multi-stage preheating, so that the materials are heated in stages; performing high-temperature roasting in a flowing suspension roasting furnace, and controlling the retention time of the material and the environment temperature in a crystal form control device so as to regulate and control the crystal form structure of the material. By accurately controlling the roasting process and optimizing material crystal form transformation, efficient removal of silicon in the coal gangue and efficient extraction of aluminum oxide are achieved, and the method has the advantages of being low in energy consumption, high in efficiency and good in environment friendliness and is suitable for large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of suspension roasting, in particular to a flow suspension roasting system and method for desilication and purification of coal gangue. BACKGROUND

[0002] Coal-based solid waste is a rock mixed with organic and inorganic compounds deposited together with coal during coal formation. As a solid waste generated during coal mining, its production amount is about 10% to 15% of the total coal production. After being discarded, the large amount of stacking not only occupies land, but also easily causes environmental pollution and other problems. With the promotion of energy transformation strategy and the increasing requirement of ecological environment protection, the comprehensive and efficient utilization of coal gangue needs further research.

[0003] Research shows that the main components of coal-based solid waste are quartz and kaolinite, which are stable and have complete crystal form at room temperature. High-temperature calcination can effectively purify aluminum resources. In the prior art, although the roasting furnace can realize rapid heating and uniform roasting, it is difficult to dynamically adjust the process parameters in the roasting process according to the physical / chemical properties of the material, and thus it is difficult to obtain an ideal crystal form. SUMMARY

[0004] In view of the above deficiencies in the prior art, the present application aims to provide a flow suspension roasting system for desilication and purification of coal gangue, which realizes precise control of roasting temperature and time through innovation of equipment structure and process parameters, thereby optimizing the crystal form transformation of coal gangue material and laying a foundation for subsequent efficient desilication and high-yield extraction of alumina.

[0005] Another object of the present application is to provide a flow suspension roasting method for desilication and purification of coal gangue, which can adapt to coal gangue raw materials of different components by adjusting the number of preheating units, the roasting temperature and time of the flow suspension roasting furnace, and the parameters of the crystal form controller, and has a wide range of applications.

[0006] The present application is implemented by using the following technical solutions: The flow suspension roasting system for desilication and purification of coal gangue comprises, in sequence: A raw material pretreatment unit for crushing and grinding the coal gangue material to a particle size suitable for roasting, the raw material pretreatment unit comprising a homogenization device, a crusher and a grinding machine; A multi-stage preheating unit for stage-wise preheating of the coal gangue material, the multi-stage preheating unit comprising at least four preheaters connected in series; a flow suspension roasting unit, which is connected with the final discharge port of the multi-stage preheating unit, is used for high-temperature roasting of the preheated material to cause crystal transformation, and then separates the roasted material, and the flow suspension roasting unit comprises a flow suspension roasting furnace and a roasting separator; a crystal type controller, which is connected with the discharge port of the roasting separator, is used for receiving the separated material, and precisely controls the crystal structure of the material by controlling the residence time of the material and controlling the internal temperature of the crystal type control device, so as to obtain active material which is easy to be purified by desilication in the subsequent process; a cooling unit, which directly cools the material by using fluidized air and at least comprises a material cooler for indirectly cooling the material, so as to ensure the stability of the roasted material, and the cooling unit comprises a multi-stage direct cooler and a material cooler; a desilication unit, which intelligently carries out alkali desilication and purification of the cooled active material, and the desilication unit comprises a dynamic pulp adjusting desilication reactor.

[0007] The multi-stage preheating unit comprises at least four preheaters connected in series, i.e., a first-stage preheater, a second-stage preheater and a third-stage preheater, and the material in the material bin is sent into the first-stage preheater by a conveying device and sequentially flows through each preheater, so as to realize step-by-step preheating from low to high temperature.

[0008] The multi-stage preheating unit further comprises a fifth-stage preheater, so as to form a five-stage series preheating structure, thereby further optimizing the preheating effect and energy utilization efficiency.

[0009] The crystal type controller is an elongated pipeline with controllable temperature or an independent heat preservation reaction cavity, which is internally provided with a temperature sensor and an independent heating element and externally connected with a control system, so as to control the residence time of the material by adjusting the temperature in the crystal type control device and the flow rate of the material.

[0010] The multi-stage direct cooler is a fluidized cooler using fluidized air. The feed port of the cooling unit is connected with the discharge port of the crystal type control device, so as to quickly cool the high-temperature material after crystal type control, thereby fixing the active crystal type of the material.

[0011] The cooling unit is a multi-stage cyclone cooler.

[0012] The desilication unit further comprises an alkali liquor storage tank and a central control unit. The dynamic pulp adjusting desilication reactor comprises a strong agitator, a heater, a pH sensor and a temperature sensor.

[0013] The flow suspension roasting furnace is a low-temperature flow suspension roasting furnace.

[0014] The flow suspension roasting method for desilication and purification of coal gangue comprises the following steps: (1) Raw material pretreatment: the coal gangue material is treated by the homogenizing device, crusher and grinder; (2) Preheating: the material is sequentially subjected to staged temperature rising by the multi-stage preheater; (3) Roasting: the preheated material is subjected to roasting in the flow suspension roasting furnace, and separation is performed in the roasting separator (11); (4) Crystal form control: the residence time and temperature of the material are controlled in the crystal form controller to regulate the crystal structure of the material; (5) Cooling: the material is sequentially subjected to cooling by the multi-stage direct cooler and material cooler; (6) Desilication: the cooled material is subjected to alkali desilication purification in the dynamic pulp adjustment desilication reactor.

[0015] In the step (2), the preheating temperature is gradually increased from 200-300℃ to above 500℃.

[0016] In the step (3), the roasting temperature is 750-1000℃, and the roasting time is 5s-30s.

[0017] In the step (4), the control temperature is 800-1200℃, and the residence time is 10min-60min.

[0018] In the step (5), the cooling rate by the multi-stage direct cooler is not less than 20℃ / min.

[0019] The desilication step uses a sodium hydroxide solution with a concentration of 20-25wt%.

[0020] Compared with the prior art, the present application has the following beneficial effects: (1) The present application realizes accurate regulation of the residence time of the material at the key temperature after roasting by adding the crystal form control device, and can directly and effectively roast the material crystal to the best state.

[0021] (2) The present application makes the roasting parameters more easily controllable by the multi-stage ladder type preheating unit and crystal form control, ensures the continuity of the production process and the stability of the product quality, greatly reduces the overall energy consumption, and meets the green production requirements.

[0022] (3) The present application can adapt to different components of the coal gangue raw material by adjusting the number of the preheating unit, the roasting temperature and time of the flow suspension roasting furnace, and the parameters of the crystal form controller, and has a wide application range. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The flow suspension roasting system working flow chart of the present application.

[0024] Figure 2 Structure diagram of the flow suspension roasting system of the present application.

[0025] Figure 3 XRD patterns of coal gangue raw material, examples 1-3 and comparative examples 1-2.

[0026] Figure 4 XRD patterns of example 1 before and after roasting and after desilication.

[0027] In the figure: 1, material bin; 2, homogenizing equipment; 3, crusher; 4, grinder; 5, material separator; 6, first-stage preheater; 7, second-stage preheater; 8, third-stage preheater; 9, fourth-stage preheater; 10, flow suspension roasting furnace; 11, roasting separator; 12, crystal form controller; 13, first-stage cooler; 14, second-stage cooler; 15, third-stage cooler; 16, fourth-stage cooler; 17, material cooler; 18, dynamic slurry preparation desilication reactor; 19, lye storage tank; 20, central control unit; 21, finished product bin. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme of the present application more clear and explicit, the present application is further described in detail as follows.

[0029] As Figures 1-2As shown, the embodiments all employ a fluidized bed roasting system for desilication and purification of coal gangue, including a material silo 1. The outlet of the material silo 1 is connected to the inlet of a homogenization device 2. The outlet of the homogenization device 2 is connected to the inlet of a crusher 3. The outlet of the crusher 3 is connected to the inlet of a grinder 4. The outlet of the grinder 4 is connected to the inlet of a material separator 5. The outlet of the material separator 5 is connected to the inlet of a primary preheater 6. The outlet of the primary preheater 6 is connected to the inlet of a secondary preheater 7. The outlet of the secondary preheater 7 is connected to the inlet of a tertiary preheater 8. The outlet of the tertiary preheater 8 is connected to the inlet of a quaternary preheater 9. The outlet of the quaternary preheater 9 is connected to the inlet of a fluidized bed roasting furnace 10. The outlet of the fluidized bed roasting furnace 10 is connected to a roasting separator 11. The feed inlet of the calcination separator 11 is connected to the feed inlet of the crystal form controller 12. The feed inlet of the crystal form controller 12 is connected to the feed inlet of the primary cooler 13. The feed inlet of the primary cooler 13 is connected to the feed inlet of the secondary cooler 14. The feed inlet of the secondary cooler 14 is connected to the feed inlet of the tertiary cooler 15. The feed inlet of the tertiary cooler 15 is connected to the feed inlet of the quaternary cooler 16. The feed inlet of the quaternary cooler 16 is connected to the feed inlet of the material cooler 17. The feed inlet of the material cooler 17 is connected to the feed inlet of the dynamic slurry desilication reactor 18. The alkali storage tank 19 is connected to the dynamic slurry desilication reactor 18 through a pipeline. The central control unit 20 is signal-connected to the dynamic slurry desilication reactor 18. The feed inlet of the dynamic slurry desilication reactor 18 is finally connected to the finished product silo 21.

[0030] Example 1 like Figures 1-2 As shown, the flow suspension roasting method for desilication and purification of coal gangue has the following workflow: (1) The coal gangue material in the material bin 1 with an initial aluminum-silicon ratio of 0.98 is first transported to the homogenization equipment 2 for homogenization treatment, then crushed by the crusher 3, then sent to the grinding mill 4 for grinding, and finally sent to the material separator 5 for screening to obtain coal gangue raw material with a particle size of 120 mesh.

[0031] (2) The coal gangue raw material obtained in step (1) is sent to the multi-stage preheating unit. The raw material flows through each stage of the preheater in sequence to achieve staged heating: the temperature of the first stage preheater 6 is set at 200℃, the temperature of the second stage preheater 7 is set at 320℃, the temperature of the third stage preheater 8 is set at 410℃, and the temperature of the fourth stage preheater 9 is set at 505℃. The material is kept warm in the fourth stage preheater 9 for 1 hour.

[0032] (3) The coal gangue material obtained in step (2) is sent into the fluidized suspension roaster 10, and roasting is performed in the atmosphere of N2 and H2O (g). The wind speed is set to 3 m / s to form a gas-solid two-phase flow environment. The coal gangue material is preliminarily roasted at 750°C for 15 s in the fluidized suspension roaster. Then, the roasted material is sent into the roasting separator 11 to realize the separation of materials with different particle sizes.

[0033] (4) The roasted and activated coal gangue material obtained in step (3) is sent into the crystal type controller 12. By adjusting the air flow and the fuel gas flow, the temperature inside the crystal type controller is maintained at 1020°C, and the material residence time is controlled to be 55 min, so that the crystal type is fully converted into the target active form, and the minerals such as kaolinite are converted into amorphous active substances.

[0034] (5) The roasted and activated material is sent into the first-stage cooler 13, the second-stage cooler 14, the third-stage cooler 15, and the fourth-stage cooler 16 in sequence for staged cooling. The cooling device is a fluidized cooler, and the cooling rate reaches 100°C / min. Then, the material is sent into a material cooler for indirect cooling. The discharged material is a roasted material with high reactivity, which can be directly used for subsequent alkali desilication and alumina extraction.

[0035] (6) The cooled material is sent into the dynamic slurry desilication reactor 18 for alkali desilication. The sodium hydroxide solution in the alkali storage tank 19 is adjusted to 20wt% by the central control unit 20, and the temperature in the dynamic slurry desilication reactor 18 is adjusted to 80°C. After the reaction starts, the temperature change and the pH change in the dynamic slurry desilication reactor 18 are monitored at all times. When the pH value is detected to be stable, the reaction is ended. The central control unit 20 sends a solid-liquid separation instruction to the dynamic slurry desilication reactor 18 to obtain a desilication product. The aluminum-silicon ratio of the material after roasting and desilication is 5.1. The XRD patterns of the material before and after roasting and desilication in Example 1 are shown in Figure 4 .

[0036] Example 2 As shown in Figure 2 , the working process of the fluidized suspension roasting method for desilication and purification of coal gangue is as follows: (1) The coal gangue material in the material bin 1, with an initial aluminum-silicon ratio of 0.92, is first sent to the homogenizing equipment 2 for homogenization treatment, then sent to the crusher 3 for crushing, then sent to the grinding machine 4 for grinding, and finally sent to the material separator 5 for screening to obtain coal gangue raw material with a particle size of 150 μm.

[0037] (2) The coal gangue raw material obtained in step (1) is sent to a multi-stage preheating unit, and the raw material flows through each stage of preheater in turn to realize staged temperature rise: the temperature of the first-stage preheater 6 is set at 205°C, the temperature of the second-stage preheater 7 is set at 315°C, the temperature of the third-stage preheater 8 is set at 409°C, and the temperature of the fourth-stage preheater 9 is set at 500°C, and the material is kept in the fourth-stage preheater 9 for 1 h.

[0038] (3) The coal gangue material obtained in step (2) is sent to the fluidized suspension roaster 10, and roasting is performed in the atmosphere of N2 and H2O (g), the air speed is set at 5 m / s to form a gas-solid two-phase flow environment, and the coal gangue raw material is preliminarily roasted at 850°C for 20 s in the fluidized suspension roaster, and then the roasted material is sent to the roasting separator 11 to realize separation of materials with different particle sizes.

[0039] (4) The roasting and activating coal gangue material obtained in step (3) is sent to the crystal type controller 12. By adjusting the air flow and the fuel gas flow, the temperature inside the crystal type controller is maintained at 1050°C, the material residence time is controlled for 60 min, the crystal type is fully converted into the target active form, and the minerals such as kaolinite are converted into amorphous active substances.

[0040] (5) The roasted and activated material is sent to the first-stage cooler 13, the second-stage cooler 14, the third-stage cooler 15, and the fourth-stage cooler 16 in turn for staged cooling. The cooling device is a fluidized cooler, and the cooling rate reaches 100°C / min. Then the material is sent to the material cooler to realize indirect cooling of the material. The discharged material is the roasted and activated material with high reactivity, which can be directly used for subsequent alkali desilication and alumina extraction.

[0041] (6) The cooled material is sent to the dynamic slurry desilication reactor 18 for alkali desilication. The sodium hydroxide solution in the alkali storage tank 19 is adjusted to 23wt% by the central control unit 20, and the temperature in the dynamic slurry desilication reactor 18 is adjusted to 85°C. After the reaction starts, the temperature change and pH change in the dynamic slurry desilication reactor 18 are monitored at all times. When the pH value is detected to be stable, the reaction is ended. The central control unit 20 sends a solid-liquid separation instruction to the dynamic slurry desilication reactor 18 to obtain a desilication product. The aluminum-silicon ratio of the material after roasting and desilication is 6.5.

[0042] Example 3 As shown in Figure 2 , the working process of the fluidized suspension roasting method for desilication and purification of coal gangue is as follows: (1) The coal gangue material in the material bin 1 with an initial aluminum-silicon ratio of 0.91 is first conveyed to the homogenizing device 2 for homogenizing treatment, then is crushed by the crusher 3, and then is sent to the grinder 4 for grinding, and finally is sent to the material separator 5 for screening to obtain the coal gangue raw material with a particle size of 200 mesh.

[0043] (2) The coal gangue raw material obtained in step (1) is sent to the multi-stage preheating unit, and the raw material flows through each stage of the preheater in turn to realize staged temperature rising: the temperature of the first-stage preheater 6 is set to 215°C, the temperature of the second-stage preheater 7 is set to 312°C, the temperature of the third-stage preheater 8 is set to 405°C, and the temperature of the fourth-stage preheater 9 is set to 502°C, and the material is kept in the fourth-stage preheater 9 for 1 h.

[0044] (3) The coal gangue material obtained in step (2) is sent to the fluidized suspension roaster 10, and is roasted in the atmosphere of N2 and H2O (g), the air speed is set to 5 m / s to form a gas-solid two-phase flow environment, and the coal gangue raw material is preliminarily roasted at 850°C for 20 s in the fluidized suspension roaster, and then the roasted material is sent to the roasting separator 11 to realize separation of materials with different particle sizes.

[0045] (4) The activated coal gangue material obtained in step (3) is sent to the crystal type controller 12. By adjusting the air flow and gas flow, the temperature inside the crystal type controller is maintained at 1190°C, the material residence time is controlled for 60 min, the crystal type is fully converted to the target active form, and the minerals such as kaolinite are converted into amorphous active substances.

[0046] (5) The activated material after roasting is sent to the first-stage cooler 13, the second-stage cooler 14, the third-stage cooler 15, and the fourth-stage cooler 16 in turn for staged cooling. The cooling device is a fluidized cooler, which realizes direct cooling of the material at a cooling rate of 100°C / min. Then the material is sent to a material cooler to realize indirect cooling of the material. The discharged material is the roasted material with high reactivity, which can be directly used for subsequent alkali desilication and alumina extraction.

[0047] (6) The cooled material is sent to the dynamic slurry desilication reactor 18 for alkali desilication. The sodium hydroxide solution in the alkali storage tank 19 is adjusted to 25wt% by the central control unit 20, and the temperature in the dynamic slurry desilication reactor 18 is adjusted to 80°C. After the reaction starts, the temperature change and pH change in the dynamic slurry desilication reactor 18 are monitored at all times. When the pH value is detected to be stable, the reaction is ended, and the central control unit 20 sends a solid-liquid separation instruction to the dynamic slurry desilication reactor 18 to obtain the desilication product. The aluminum-silicon ratio of the material after roasting and desilication is 6.1.

[0048] Comparative Example 1 The comparative example 1 provides a flow suspension roasting method for desilication and purification of coal gangue, which is different from the example 1 in that the coal gangue material is not subjected to the multi-stage preheating and temperature rising treatment in step (2).

[0049] Comparative example 2 The comparative example 1 provides a flow suspension roasting method for desilication and purification of coal gangue, which is different from the example 1 in that the coal gangue material is not subjected to the multi-stage preheating and temperature rising treatment in step (2). Roasting stage: the ground coal gangue material is sent into a rotary kiln (kiln length 20 m, diameter 2 m) by a feeding machine, stays in the kiln for 3 h, the kiln head temperature is controlled at 1000 ℃, the kiln tail temperature is controlled at 1030 ℃, and the material staying time is adjusted by controlling the cylinder rotating speed (2 r / min); Cooling stage: the roasted coal gangue material is discharged from the kiln tail, enters a water-cooled roller cooler, and the temperature is reduced from 1020 ℃ to 200 ℃ by indirect water cooling, then is sent into a vibrating screen for screening to remove the agglomerates existing in the material caused by sintering, and finally the material is transported to a finished product bin; Wherein, the crystal form control mode: no special crystal form control device.

[0050] The XRD patterns of the coal gangue raw materials of the example 1-3 and the comparative examples 1-2 are shown in Figure 3 .

[0051] Example 1 3 and comparative example 1 The composition of the coal gangue raw materials of the example 1-3 and the comparative examples 1-2 is shown in Table 1.

[0052] Example 1 3 and comparative example 1 The performance test results of the products of the example 1-3 and the comparative examples 1-2 are shown in Table 2.

[0053] Table 1: Composition of coal gangue raw materials of the example 1 3 and comparative example 1 2

[0054] Table 2: Performance test results of the products of the example 1 3 and comparative example 1 2

[0055] From the test results of Table 1, it can be seen that the example 1 3 all show significantly better desilication effect than the comparative examples.

[0056] From the performance test results of Table 2, it can be seen that the example 1 Figure 3It can be seen that the diffraction peak at 16.480° in the sample of Comparative Example 1-2 after calcination disappears, indicating that the sample is in an under-fired state, which shows that without multi-stage preheating and crystal controller control, it is difficult to ensure that the sample is in a fully fired state. Figure 4 It can be seen that the steamed bun peaks in the range of 18.0°-24.35° in the pattern of Example 1 after desilication are obviously flat, indicating that a large amount of irregular quartz has been removed, and the desilication effect is obvious.

Claims

1. A fluidized suspension roasting system for desilication and purification of coal gangue, characterized in that, It comprises sequentially connected: a raw material pretreatment unit, which comprises a homogenizing device (2), a crusher (3) and a grinder (4); a multi-stage preheating unit, which comprises at least four stages of preheaters connected in series; a fluidized suspension roasting unit, which comprises a fluidized suspension roasting furnace (10) and a roasting separator (11); a crystal type controller (12), the feed inlet of which is connected with the discharge outlet of the roasting separator (11); a cooling unit, which comprises a multi-stage direct cooler and a material cooler (17); a desilication unit, which comprises a dynamic pulp-adjusting desilication reactor (18).

2. The fluidized suspension roasting system for desilication and purification of coal gangue according to claim 1, characterized in that, The crystal type controller (12) is a temperature-controllable extended pipeline or an independent heat-insulated reaction cavity.

3. The fluidized suspension roasting system for desilication and purification of coal gangue according to claim 1, characterized in that, The multi-stage direct cooler is a fluidized cooler using fluidized air.

4. The fluidized suspension roasting system for desilication and purification of coal gangue according to claim 1, characterized in that, The desilication unit further comprises a lye storage tank (19) and a central control unit (20).

5. A fluidized suspension roasting method for desilication and purification of coal gangue, using the fluidized suspension roasting system for desilication and purification of coal gangue according to any one of claims 1 to 4, characterized in that, It comprises the following steps: (1) raw material pretreatment: treating coal gangue material through the homogenizing device (2), the crusher (3) and the grinder (4); (2) preheating: sequentially passing the material through the multi-stage preheaters for stage-wise temperature rising; (3) roasting: roasting the preheated material in the fluidized suspension roasting furnace (10) and separating in the roasting separator (11); (4) crystal type control: controlling the residence time and temperature of the material in the crystal type controller (12) to regulate the crystal structure of the material; (5) cooling: sequentially passing the material through the multi-stage direct cooler and the material cooler (17) for cooling; (6) desilication: alkali desilication purification of the cooled material in the dynamic pulp-adjusting desilication reactor (18).

6. The fluidized suspension roasting method for desilication and purification of coal gangue according to claim 5, characterized in that, In the step (2), the preheating temperature is gradually increased from 200-300℃ to above 500℃.

7. The fluidized suspension roasting method for desilication and purification of coal gangue according to claim 5, characterized in that, In the step (3), the roasting temperature is 750-1000℃, and the roasting time is 5s-30s.

8. The fluidized suspension roasting method for desilication and purification of coal gangue according to claim 5, characterized in that, In the step (4), the control temperature is 800-1200℃, and the residence time is 10min-60min.

9. The fluidized suspension roasting method for desilication and purification of coal gangue according to claim 5, characterized in that, In the step (5), the cooling rate through the multi-stage direct cooler is not less than 20℃ / min.

10. The fluidized suspension roasting method for desilication and purification of coal gangue according to claim 5, characterized in that, The desilication step uses a sodium hydroxide solution with a concentration of 20-25wt%.

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