Enhanced drying multi-stage roasting furnace and red mud treatment process

Abstract

The application provides a reinforced drying multi-stage roasting furnace and a red mud treatment process. The reinforced drying multi-stage roasting furnace comprises a multi-stage roasting furnace, and a draft tube, a heating pipe, a hot draft fan and a conveying pipe connected in sequence. The draft tube, the hot draft fan and the conveying pipe are arranged outside the multi-stage roasting furnace, the heating pipe is arranged in a high-temperature furnace layer of the multi-stage roasting furnace, and the leading end of the draft tube and the trailing end of the conveying pipe both penetrate into a low-temperature furnace layer of the multi-stage roasting furnace. The red mud treatment process comprises the steps of pretreatment, roasting treatment, post-treatment and smoke exhaust treatment. The reinforced drying multi-stage roasting furnace and the red mud treatment process solve the problems of insufficient drying capacity of the existing multi-chamber furnace and difficulty in treating red mud.

Description

Technical Field

[0001] This invention relates to the field of multi-hearth furnaces, specifically to an enhanced drying multi-stage roasting furnace and a red mud treatment process. Background Technology

[0002] Multi-hearth furnaces typically consist of six to twelve vertically arranged furnace chambers. Burners are usually installed in the middle chambers to heat the materials inside, meaning the temperature distribution within the furnace is low, high, and low from top to bottom. Since multi-hearth furnaces need to process various materials, the temperature in each furnace chamber needs to be adjusted according to the material type. When processing red mud, due to its high moisture content, the temperature in the upper furnace chambers needs to be higher, while the temperature in the middle chambers needs to be appropriately lowered. This ensures the red mud is thoroughly dried in the upper chambers while preventing material adhesion due to excessively high temperatures in the middle chambers. However, simply adjusting the burner output power is insufficient to meet these temperature control requirements. Furthermore, the pressure within each furnace chamber also needs to be adjusted according to the material type. For example, when processing red mud, a large amount of steam is generated during drying. To ensure smooth steam discharge and maintain drying efficiency, the pressure within the multi-hearth furnace needs to be distributed from top to bottom as a strong negative pressure, slightly negative pressure, and slightly positive pressure. However, existing multi-chamber furnaces lack the ability to accurately adjust the pressure in each chamber, resulting in poor drying performance. Summary of the Invention

[0003] To address the problem of insufficient drying capacity and difficulty in processing red mud in existing multi-hearth furnaces, this invention provides an enhanced drying multi-stage roasting furnace and a red mud treatment process that solves the above problems.

[0004] A multi-stage roasting furnace for enhanced drying includes a multi-stage roasting furnace and sequentially connected induced draft pipe, heating pipe, hot induced draft fan, and conveying pipe. The induced draft pipe, the hot induced draft fan, and the conveying pipe are all located outside the multi-stage roasting furnace. The heating pipe is located inside the high-temperature furnace layer of the multi-stage roasting furnace. The first end of the induced draft pipe and the last end of the conveying pipe both penetrate into the low-temperature furnace layer of the multi-stage roasting furnace.

[0005] In a preferred embodiment of the enhanced drying multi-stage roasting furnace provided by the present invention, multiple sets of heating tubes are respectively disposed in multiple high-temperature furnace layers of the multi-stage roasting furnace, and all heating tubes are connected to the same induced draft pipe and the same conveying pipe. The first end of the induced draft pipe branches and respectively penetrates into multiple low-temperature furnace layers of the multi-stage roasting furnace; the tail end of the conveying pipe branches and respectively penetrates into the same furnace layer.

[0006] In a preferred embodiment of the enhanced drying multi-stage calcining furnace provided by the present invention, the heating tube is connected to the air inlet of the hot draft fan via a temperature control device. The temperature control device includes a temperature-controlled three-way valve and a radiator. The temperature-controlled three-way valve is connected to the heating tube, the air inlet of the hot draft fan, and the air inlet of the radiator simultaneously. The air outlet of the radiator is connected to the air inlet of the hot draft fan via a one-way valve.

[0007] A red mud treatment process using the aforementioned enhanced drying multi-stage roasting furnace is characterized by comprising the following steps:

[0008] Step 1: Pre-treatment, transporting the red mud to one or more silos;

[0009] Specifically, step 1.1 involves unpacking the ton bags of red mud using an unpacking device, and then conveying the unpacked red mud to the pretreatment conveyor using a feeding device.

[0010] Step 1.2: The red mud is transported to one or more silos for temporary storage via a pretreatment conveyor. Each silo is then fed into the enhanced drying multi-stage roasting furnace via a quantitative feeding device.

[0011] Step 2: Calcination treatment. The red mud in the silo is quantitatively transported to the enhanced drying multi-stage calcining furnace to complete the drying, heating, reduction and cooling treatment.

[0012] Step 3: Post-processing, the processed material falls into the cooling tank for quenching;

[0013] Specifically, step 3.1: The material processed in the enhanced drying multi-stage roasting furnace is naturally dropped into the cooling pool at the discharge port for quenching treatment;

[0014] Step 3.2: Use a slag remover to remove the quenched cold slag.

[0015] Step 4: Smoke treatment. The smoke generated by the enhanced drying multi-stage roasting furnace is separated into flue gas and dust. The dust is returned to the silo for recycling.

[0016] Specifically, step 4.1 involves sequentially subjecting the flue gas to settling through a settling device and then subjecting it to dust removal through a dust removal device to obtain separated flue gas and dust.

[0017] Step 4.2: The separated smoke and dust are transported to the pretreatment conveyor via the smoke treatment conveyor and returned to the silo to achieve cyclic processing.

[0018] In a preferred embodiment of the red mud treatment process provided by the present invention, in step 3.2, the cold crushed slag is sent to the beneficiation plant by a post-processing conveyor; in step 4.1, the separated flue gas is sent to the flue gas desulfurization and denitrification plant by a centrifugal induced draft fan.

[0019] Compared to existing technologies, the enhanced drying multi-stage roasting furnace provided by this invention incorporates heating pipes within the high-temperature furnace layer, and an induced draft pipe, a hot induced draft fan, and a conveying pipe are installed between the heating pipes and the low-temperature furnace layer. This enables the transfer of low-temperature air from the low-temperature furnace layer to the high-temperature furnace layer for heating, and then back to the low-temperature furnace layer. This heat transfer from the high-temperature furnace layer to the low-temperature furnace layer raises the temperature in the upper furnace chamber and appropriately lowers the temperature in the middle furnace chamber, ensuring that the red mud is fully dried in the upper layer and does not clump in the middle layer.

[0020] Meanwhile, as the temperature inside the upper furnace rises, the ample heat source and higher temperature cause the moisture in the red mud to evaporate rapidly into water vapor, increasing the airflow velocity. Based on Bernoulli's one-dimensional non-viscous and incompressible equation, the pressure inside the furnace layer decreases as the airflow velocity increases, strengthening the negative pressure, which is conducive to the discharge of water vapor and further enhances the drying effect.

[0021] Compared to existing technologies, the red mud treatment process provided by this invention achieves red mud treatment through an automated process, offering advantages such as high treatment efficiency and minimal manual intervention. Furthermore, the flue gas is recycled into the roasting furnace, providing energy-saving and environmentally friendly benefits. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a multi-stage roasting furnace for enhanced drying;

[0023] Figure 2 yes Figure 1 A magnified view of a portion of the image;

[0024] Figure 3 yes Figure 2 The diagram shown is a structural schematic diagram of the location in Embodiment 2;

[0025] Figure 4 yes Figure 2 The diagram shown is a structural schematic diagram of the location in Embodiment 3;

[0026] Figure 5 This is a flowchart of the red mud treatment process. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0028] Example 1

[0029] Please also refer to Figure 1 and Figure 2 These are schematic diagrams and enlarged views of the multi-stage roasting furnace 1 for enhanced drying provided by the present invention. It includes a multi-hearth furnace 2, and sequentially connected components such as an induced draft pipe 3, a heating pipe 7, a hot induced draft fan 4, and a conveying pipe 5.

[0030] The accompanying drawings are for illustrative purposes only and are not drawn strictly according to the equipment structure and scale, but they do not affect those skilled in the art from understanding and implementing this solution.

[0031] The multi-hearth furnace 2 comprises ten vertically arranged furnace chambers, each 864 mm high and with a net clearance of 722 mm. The total internal space of the furnace is 80 m³, with burners installed in the 4th, 6th, and 8th chambers from the top. Functionally, chambers 1-4 are drying chambers, chambers 5-7 are heating chambers, chambers 8-9 are reduction chambers, and chamber 10 is a cooling chamber.

[0032] The furnace is equipped with a central shaft running vertically through the interior, with a 15 kW AC variable frequency speed-regulating motor at the bottom. The central shaft rotates via a gearbox and bevel gears, simultaneously driving the rake arms and teeth within each layer of the furnace to transport materials through a mixing and conveying process. The central shaft speed is 0.8-1.5 rpm, and the material's journey from entry to exit is 50-90 minutes. The processing time can be adjusted by controlling the AC variable frequency speed of the central shaft and adjusting the rake tooth angle.

[0033] The burner is fed with coal gas produced by the gasifier, and a certain amount of central shaft cooling hot air is mixed in to generate heat. The coal gas flow rate is controlled to stabilize the furnace temperature at each level.

[0034] The water content of red mud is 15%-18%. When treating red mud, carbon monoxide, coal-based reducing agent, hydrogen-based reducing agent, etc. are used. Carbon monoxide comes from the gas produced by the gasifier. Red mud reduction roasting is usually designed with carbon monoxide as the reducing agent.

[0035] A heating pipe 7 is installed inside the fourth furnace chamber. The heating pipe 7 is made of high-temperature resistant material and is arranged in a serpentine pattern around the inner wall of the fourth furnace chamber, with both ends protruding from the right outer wall of the multi-hearth furnace 2. An induced draft pipe 3 is located outside the multi-hearth furnace 2, between the first and fourth furnace chambers, with its first end penetrating into the first furnace chamber and its second end connecting to the first end of the heating pipe 7. The second end of the heating pipe 7 is connected to the air inlet of the induced draft fan 4.

[0036] The conveying pipe 5 is also located outside the multi-hearth furnace 2, between the first and fourth furnace layers. Its first end is connected to the outlet of the hot induced draft fan 4, and its last end extends into the first furnace layer. The hot induced draft fan 4 is fixed outside the multi-hearth furnace 2 by a bracket and is located in the fourth furnace layer. Its air inlet is connected to the last end of the heating pipe 7, and its air outlet is connected to the first end of the conveying pipe 5.

[0037] The beginning of the exhaust pipe 3 and the end of the delivery pipe 5 are both divided into multiple branches, which penetrate into the furnace at multiple locations around the first layer of the furnace to make the airflow more uniform.

[0038] After the hot air blower 4 is started, it can guide the low-temperature air from the first layer to the fourth layer, heat it in the heating pipe 7, and then return it to the first layer through the delivery pipe 5.

[0039] The heat from the fourth layer is directed into the first layer, causing the moisture in the red mud to evaporate rapidly into water vapor, thus increasing the airflow velocity. Based on Bernoulli's equation of one-dimensional inviscidity and incompressibility, the pressure inside the furnace layer decreases as the airflow velocity increases, strengthening the negative pressure. This facilitates the discharge of water vapor (including flue gas) from the top of the furnace through the exhaust pipe, enhancing the drying effect.

[0040] In addition, a control system is included to control the operation of the multi-hearth furnace 2 and the hot induced draft fan 4. The part controlling the operation of the multi-hearth furnace 2 is consistent with existing technology and will not be described in detail here. By controlling the opening and closing of the hot induced draft fan 4, the heating in the first furnace chamber and the cooling in the fourth furnace chamber can be simply controlled and adjusted.

[0041] The combined functions of the two aspects result in the following temperature ranges within the multi-hearth furnace 2: furnace top temperature 200-300℃, layer 1-4 temperature 300-600℃, layer 5-7 temperature 600-800℃, layer 8-9 temperature 600-750℃, layer 10 temperature 500℃, and discharge port temperature 400-500℃.

[0042] In terms of pressure: layers 1-4 are under relatively strong negative pressure, reaching -30Pa; layers 5-7 are under slightly negative pressure, reaching -20Pa; layers 8-10 are under slightly positive pressure, reaching 0Pa to +5Pa. Water vapor is drawn out of the furnace by an external induced draft fan, and the water vapor is recycled to make full use of the waste heat of the gas with a content of <5%.

[0043] In use, the red mud is conveyed by belt conveyor or elevator to a screw feeder with air-blocking function located at the top of the multi-hearth furnace 2. The mud is then fed into the first layer of the furnace through the feed inlet at the top of the furnace 2, where it is dried by hot air introduced through the conveying pipe 5. Simultaneously, the rake arms and teeth continuously tumble the red mud, gradually pushing it from the connection between adjacent furnace layers into the second layer of the furnace, and so on, until it falls continuously. This process of drying, heating, reduction, and cooling is gradually completed, and finally, the mud falls into a water tank for quenching.

[0044] Example 2

[0045] Please see Figure 3 This is a partially enlarged view of the enhanced drying multi-stage roasting furnace 1 provided by the present invention in this embodiment. The difference from Embodiment 1 is that it includes a draft pipe 3, a heating pipe 7, a temperature control device 6, a hot draft fan 4, and a conveying pipe 5 connected in sequence.

[0046] The temperature control device 6 includes a temperature-controlled three-way valve 61, a radiator 62, and a one-way valve. The exhaust duct 3, heating element 7, temperature-controlled three-way valve 61, hot exhaust fan 4, and delivery pipe 5 are connected in sequence. The other port of the temperature-controlled three-way valve 61 is connected to the air inlet of the radiator 62. The air outlet of the radiator 62 is connected to the connecting pipe between the temperature-controlled three-way valve 61 and the hot exhaust fan 4 via the one-way valve.

[0047] Since the high-temperature resistance of the hot draft fan 4 is around 400-500℃, and the required temperature in the first layer of the furnace also falls within this range, the temperature should not be too high. Therefore, the temperature control three-way valve 61 is set as follows: in the default state, it connects the air inlet of the draft duct 3 and the hot draft fan 4; when the temperature reaches 500℃, it automatically switches to connect the air inlet of the draft duct 3 and the radiator 62; when the temperature is below 400℃, it automatically switches to connect the air inlet of the draft duct 3 and the hot draft fan 4. The radiator 62 is a set of coiled tubes with cooling fins, which naturally cools the hot air as it passes through.

[0048] The structure, control, parameters, and other features of the multi-hearth furnace 2, induced draft pipe 3, heating pipe 7, hot induced draft fan 4, and conveying pipe 5 are the same as those in Example 1, and will not be repeated here.

[0049] Example 3

[0050] Please see Figure 4 This is a partially enlarged view of the enhanced drying multi-stage roasting furnace 1 provided by the present invention in this embodiment. The difference from Embodiment 1 is that it includes a sequentially connected air duct 3, two sets of heating tubes 7, a hot air blower 4, and a conveying pipe 5.

[0051] A set of heating tubes 7 is installed in the furnace chambers of the 4th and 6th layers respectively.

[0052] The first end of the induced draft duct 3 is divided into two groups of branches, which pass through the first and second furnace layers respectively; each group of branches includes multiple branches, which pass through the furnace at multiple locations around the first furnace layer and multiple locations around the second furnace layer. The last end of the induced draft duct 3 is divided into two branches, which are connected to the first ends of the two groups of heating pipes 7 respectively.

[0053] The first end of the conveying pipe 5 is connected to the outlet of the hot induced draft fan 4. The tail end is divided into two groups of branches, which pass through the first and second furnace layers respectively; each group of branches includes multiple branches, which pass through multiple locations around the first furnace layer and multiple locations around the second furnace layer. The inlet of the hot induced draft fan 4 is connected to the tail ends of both groups of heating pipes 7, and the outlet is connected to the first end of the conveying pipe 5.

[0054] The structure, control, parameters, and other features of the multi-hearth furnace 2, induced draft pipe 3, heating pipe 7, hot induced draft fan 4, and conveying pipe 5 are the same as those in Example 1, and will not be repeated here.

[0055] Example 4

[0056] Please see Figure 5 This is a flowchart of the red mud treatment process provided by the present invention.

[0057] The system for implementing the red mud treatment process includes a material storage area 11, a ton bag unpacking and feeding device 12, a first buried scraper conveyor 13, a first silo 14, a second silo 15, a first double-screw quantitative feeder 16, a second double-screw quantitative feeder 17, a natural gas source 18, an enhanced drying multi-stage roasting furnace 1, a hot induced draft fan 4, a cooling pool 19, a slag remover 20, a cold crushed slag conveyor 21, a settling box 22, a cyclone dust collector 23, a filter bag dust collector 24, a screw conveyor 25, a second buried scraper conveyor 26, and a centrifugal induced draft fan 27.

[0058] The red mud treatment process includes the following steps:

[0059] S01: Red mud packaged in ton bags is piled up in storage area 11. The ton bags are unpacked and fed by ton bag unpacking and feeding equipment 12, so that the material enters the ton bag unpacking and feeding equipment 12 and is then transported to the first buried scraper conveyor 13.

[0060] S02: Depending on the remaining amount in the silo, the red mud is transported to the first silo 14 or the second silo 15 via the first buried scraper conveyor 13 for temporary storage. Both the first silo 14 and the second silo 15 are equipped with pulse dust collectors, silo wall vibrators, and ash discharge valves, which are used to reduce dust in the silo, ensure smooth unloading, and control the unloading volume, respectively.

[0061] S03: The bottom ends of the first silo 14 and the second silo 15 are respectively connected to the first double-screw quantitative feeder 16 and the second double-screw quantitative feeder 17. The red mud in the first silo 14 and the second silo 15 is quantitatively transported to the enhanced drying multi-stage roasting furnace 1 through the first double-screw quantitative feeder 16 and the second double-screw quantitative feeder 17 respectively.

[0062] S04: According to the process described in Example 1, Example 2 or Example 3, the red mud is placed in the multi-stage roasting furnace 1 for enhanced drying. Under the action of the rake arms and rake teeth, it falls layer by layer and completes the drying, heating, reduction and cooling processes from top to bottom.

[0063] Natural gas is supplied as fuel to the burners in the multi-stage roasting furnace 1 for enhanced drying via natural gas source 18. The drying effect of red mud is enhanced by hot induced draft fan 4.

[0064] S05: The processed red mud falls from the discharge port at the bottom of the enhanced drying multi-stage roasting furnace 1 and falls into the cooling pool 19 for quenching and rapid cooling to form cold slag.

[0065] S06: A slag remover 20 is installed in the cooling pool 19. The slag remover 20 removes the cold slag from the cooling pool 19 and transports it to the cold slag conveyor 21 for delivery to the beneficiation plant.

[0066] S07: The multi-stage roasting furnace 1 for enhanced drying and the exhaust port at the top exhaust the flue gas. The exhaust gas is processed sequentially through the settling box 22, the cyclone dust collector 23 and the filter bag dust collector 24, and then sent to the flue gas desulfurization and denitrification desulfurization degassing ...

[0067] S08: The dust separated in the settling box 22 is fed into the second buried scraper conveyor 26, and the dust separated in the cyclone dust collector 23 is fed into the second buried scraper conveyor 26 via the screw conveyor 25 and then transported to the first buried scraper conveyor 13.

[0068] Subsequently, following the same process as S02, the separated dust and untreated red mud are fed into the first silo 14 or the second silo 15 for recycling.

[0069] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A reinforced drying multi-stage roasting furnace, comprising a multi-stage roasting furnace, the multi-stage roasting furnace comprising ten vertically arranged hearths, and burners are arranged in the fourth, sixth and eighth hearths from top to bottom, characterized in that: It also comprises a draft tube, a heating tube, a hot draft fan and a conveying tube; the fourth layer furnace is provided with the heating tube, the head and tail ends of which are penetrated out of the outer wall of the furnace; the draft tube is arranged outside the furnace, the head end of which is penetrated into the first layer furnace, and the tail end is connected with the head end of the heating tube; the tail end of the heating tube is connected with the air inlet of the hot draft fan through a temperature adjusting device; the conveying tube is arranged outside the furnace, the head end of which is connected with the air outlet of the hot draft fan, and the tail end is penetrated into the first layer furnace; the temperature adjusting device comprises a temperature control three-way valve and a radiator, the temperature control three-way valve is connected with the air inlets of the heating tube, the hot draft fan and the radiator, and the air outlet of the radiator is connected with the air inlet of the hot draft fan through a one-way valve.

2. The enhanced drying multi-stage calciner according to claim 1, characterized in that: The sixth layer furnace is also provided with another group of heating tubes, the head end of which is connected with the tail end of the draft tube, and the tail end is connected with the air inlet of the hot draft fan.

3. The enhanced drying multi-stage calciner of claim 2, wherein: The head end of the draft tube is divided into two groups of branches, which are penetrated into the first layer and the second layer furnace respectively; each group of branches comprises a plurality of branches, which are penetrated into the furnace at a plurality of positions around the first layer furnace and a plurality of positions around the second layer furnace respectively; the tail end of the conveying tube is divided into two groups of branches, which are penetrated into the first layer and the second layer furnace respectively; each group of branches comprises a plurality of branches, which are penetrated into the furnace at a plurality of positions around the first layer furnace and a plurality of positions around the second layer furnace respectively.

4. A process for treating red mud using the enhanced drying multi-stage calciner according to any one of claims 1 to 3, characterised in that, It comprises the following steps: Step 1: pretreatment, conveying the red mud into one or more hoppers; Step 2: roasting treatment, conveying the red mud in the hopper into the enhanced drying multi-stage roasting furnace quantitatively, completing drying, warming, reduction and cooling treatment; Step 3: post-treatment, the treated material falls into the cooling pool for quenching; Step 4: smoke exhaust treatment, separating the exhaust smoke generated by the enhanced drying multi-stage roasting furnace into flue gas and smoke dust, and recycling the smoke dust into the hopper.

5. A red mud treatment process according to claim 4, characterised in that, The pretreatment in the step 1 specifically comprises the following steps: Step 1.1: unpacking the ton bag of red mud through unpacking device, and then conveying the unpacked red mud into the pretreatment conveyor through the feeding device; Step 1.2: conveying the red mud into one or more hoppers for temporary storage through the pretreatment conveyor, and conveying the red mud in the hopper into the enhanced drying multi-stage roasting furnace quantitatively through the quantitative feeding equipment.

6. A red mud treatment process according to claim 5, characterised in that, The post-treatment in the step 3 specifically comprises the following steps: Step 3.1: the treated material in the enhanced drying multi-stage roasting furnace falls into the cooling pool for quenching at the discharge port; Step 3.2: the cold and crushed slag after quenching is fished out by the slag conveyor.

7. A red mud treatment process according to claim 6, characterised in that, The smoke exhaust treatment in the step 4 specifically comprises the following steps: Step 4.1: sequentially performing settlement treatment on the exhaust smoke through the settlement device, and performing dust removal treatment on the exhaust smoke through the dust removal device, to obtain separated smoke dust and flue gas; Step 4.2: conveying the separated smoke dust into the pretreatment conveyor through the smoke exhaust treatment conveyor, and recycling it into the hopper for recycling treatment.

8. A red mud treatment process according to claim 7, characterised in that, In the step 3.2, the cold slag is sent to the concentration plant by a post-treatment conveyor; in the step 4.1, the separated flue gas is sent to the flue gas desulfurization and denitrification by a centrifugal induced draft fan.

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