CN-122007129-A - Red mud gradient temperature pyrolysis-melting vitrification integrated treatment device and process

CN122007129ACN 122007129 ACN122007129 ACN 122007129ACN-122007129-A

Abstract

The invention relates to the technical field of solid waste harmless and recycling equipment, in particular to a red mud gradient temperature pyrolysis-melting vitrification integrated treatment device and process. The device directly couples the electromagnetic heating rotary kiln pyrolysis section and the electrode melting section with the material transfer device through high-temperature atmosphere isolation. The technological process includes pelletizing red mud, reductant and flux, feeding the pelletized red mud, reductant and flux into a rotary kiln with multiple groups of electromagnetic induction coils to complete dewatering, selective reduction and iron particle polymerization successively to produce high temperature pyrolysis slag of over 1000 deg.c, and separating molten iron from stable glass body in the electric smelting bath. The invention solves the problems of high energy consumption and complex flow in the traditional process by the design of 'hot slag direct melting' and 'energy closed loop', and realizes the efficient recovery of iron resources in the red mud and the thorough harmless and high-value utilization of residues.

Inventors

LIU MENGJIE
MIAO LINFENG
Pan Saifei
LI QINGLIN
DUAN YIHANG
WANG SHAOWEI
CHEN QIANGBO
WANG XUETAO
Pan kunming
XING LILI
REN YONGPENG
LI YARU
LI HAOJIE
LI XIAOCHUAN

Assignees

龙门实验室

Dates

Publication Date: 20260512
Application Date: 20260403

Claims (10)

1. The red mud gradient temperature pyrolysis-melting vitrification integrated treatment device is characterized by comprising a feeding and pretreatment unit, a gradient temperature pyrolysis unit, a high-temperature atmosphere isolation and material transfer device, an electrode melting and vitrification unit and a product collection and flue gas treatment system; the gradient temperature pyrolysis unit comprises a rotary kiln, wherein the feeding and pretreatment unit is connected with the kiln head of the rotary kiln through a screw feeder, and the kiln tail of the rotary kiln is connected with an inlet positioned on the side surface of the cyclone separator; The rotary kiln is an inclined electromagnetic heating rotary kiln, a barrel of the rotary kiln adopts a multilayer composite structure, and comprises an inner liner, an induction heating layer, an insulating layer and an outer protective shell from inside to outside in sequence, wherein an electromagnetic induction coil is arranged on the outer side of the outer protective shell along the axial direction of the kiln body, is a sectional induction coil and comprises a first group of coils, a second group of coils and a third group of coils which are sequentially distributed along the axial direction of the rotary kiln, the first group of coils correspond to a preheating dewatering area, the second group of coils correspond to a medium-temperature reduction area, the third group of coils correspond to a high-temperature final reduction area, an external induction heating power supply is electrically connected with the electromagnetic induction coil and supplies power for the electromagnetic induction coil, and a PLC is electrically connected with the external induction heating power supply; The cyclone separator is positioned at the outlet of the bottom and is connected with a feed inlet positioned at the top of the material transferring device, an upper flashboard bin, a transition cavity and a lower flashboard bin which are distributed from top to bottom are arranged in the high-temperature atmosphere isolation and material transferring device, an upper valve seat is arranged at the top of the transition cavity, an inverted round table-shaped pit is arranged at the upper part of the upper valve seat, a first through hole which is communicated with the pit and the transition cavity is arranged at the central position of the upper valve seat, the first through hole is in an inverted round table shape, an upper flashboard is arranged at the bottom of the upper flashboard bin, a convex part matched with the pit is arranged at the bottom of the upper flashboard, an inverted round table-shaped blanking port is arranged in the upper flashboard, the large diameter end of the blanking port is communicated with the upper flashboard bin, the small diameter end of the blanking port is larger than the large diameter end of the first through hole, a partition plate is arranged in the lower part of the partition plate, a blocking piece protruding out of the small diameter end of the blanking port is arranged at the bottom of the partition plate, the blocking piece is matched with the first through hole, the upper flashboard is connected with a first hydraulic driving device, and when the piston rod moves close to or moves towards the upper flashboard, and is far away from the first valve seat; The top of the lower flashboard bin is provided with a lower valve seat, the bottom of the transition cavity is provided with a lower flashboard, the lower flashboard is connected with a piston rod of a second hydraulic driving device, the second hydraulic driving device is electrically connected with a PLC, and when the PLC controls the piston rod in the second hydraulic driving device to act, the lower flashboard moves towards a direction approaching or far away from the lower valve seat, and the structures of the lower valve seat and the lower flashboard are the same as those of the upper valve seat and the upper flashboard; The high-temperature atmosphere isolation and material transfer device is also provided with a purge gas inlet, an exhaust port, a pressure sensor, a high-temperature charge level indicator, an oxygen sensor and a water cooling jacket, and the PLC is respectively and electrically connected with a first electromagnetic valve at the purge gas inlet, a second electromagnetic valve at the exhaust port, the pressure sensor, the high-temperature charge level indicator and the oxygen sensor; the electrode melting and vitrification unit comprises an electric melting pool, a discharge hole positioned at the bottom of the high-temperature atmosphere isolation and material transfer device is connected with the electric melting pool, a graphite electrode is arranged in the electric melting pool, a molten iron outlet is arranged at the bottom of the electric melting pool, a glass melt outlet is arranged on the side surface of the electric melting pool, a gas inlet and a gas outlet are arranged at the top of the side surface of the electric melting pool, and the gas outlet of the electric melting pool is connected with a product collection and flue gas treatment system through a pipeline.
2. The integrated treatment device for red mud gradient temperature pyrolysis and melting vitrification according to claim 1, wherein the feeding and pretreatment unit comprises a proportioning bin, a mixer and a granulator, an outlet of the proportioning bin is connected with an inlet of the mixer, an outlet of the mixer is connected with an inlet of the granulator, an outlet of the granulator is connected with an inlet of a screw feeder, an outlet of the screw feeder is connected with a kiln head of the rotary kiln, a rotary motor is used for driving the rotary kiln to rotate, a supporting device is arranged at the lower part of the rotary kiln, an inner liner of the rotary kiln is made of refractory materials, an induction heating layer is made of conductive magnetic materials, and a shell protecting shell is made of nonmagnetic stainless steel.
3. The red mud gradient temperature pyrolysis-melting vitrification integrated processing device of claim 1, wherein a red mud bin, a reducing agent bin and a flux bin are arranged in the proportioning bin, the screw feeder is a sealed screw feeder, an outlet of the cyclone separator at the bottom is connected with a feed inlet of the material transferring device at the top through a first flange connection interface, a discharge outlet of the material transferring device at the bottom is connected with an electric melting pool through a second flange connection interface, and high-temperature flexible graphite sealing rings are embedded on the wall surface of the upper valve seat pit and the wall surface of the first through hole.
4. The integrated treatment device for red mud gradient temperature pyrolysis and melting vitrification according to claim 1, wherein a water cooling jacket is arranged on the outer sides of the upper flashboard bin, the transition cavity and the lower flashboard bin, circulating cooling water is communicated in the water cooling jacket, and the purge gas inlet, the exhaust port, the pressure sensor, the high-temperature level gauge and the oxygen sensor are all arranged at positions corresponding to the transition cavity.
5. The integrated treatment device for red mud gradient temperature pyrolysis and fusion vitrification according to claim 1, wherein the product collection and flue gas treatment system comprises an air preheater, a steam turbine, a generator, a quenching tower, a bag-type dust collector and a desulfurization and denitrification device, wherein a gas outlet of an electric melting pool is connected with the air preheater through a pipeline, the air preheater is connected with the steam turbine, the steam turbine is connected with the generator, a gas outlet of the steam turbine is connected with an inlet of the quenching tower, the quenching tower is connected with the bag-type dust collector, the bag-type dust collector is connected with the desulfurization and denitrification device, the generator supplies power for a graphite electrode, and an output end of the generator is connected with an external induction heating power supply.
6. The integrated treatment device for red mud gradient temperature pyrolysis and fusion vitrification according to claim 5, wherein an outlet of a pyrolysis gas pipeline is connected to a pipeline between a gas outlet of an electric melting pool and an air preheater, a hot air drying pipeline is connected to a pipeline between the air preheater and a steam turbine, an outlet of a cyclone separator positioned at the top is respectively connected with an inlet of the pyrolysis gas pipeline and an inlet of a reflux pipeline through a flow regulating valve, an outlet of the reflux pipeline is connected with a reducing atmosphere inlet of a kiln head of the rotary kiln, and an outlet of the hot air drying pipeline is connected with a proportioning bin.
7. A red mud gradient temperature pyrolysis-melting vitrification integrated treatment process, which adopts the device as set forth in any one of claims 1-6, and is characterized by comprising the following steps: (1) Firstly, the PLC correspondingly closes an upper flashboard and a lower flashboard through a first hydraulic driving device and a second hydraulic driving device respectively, namely the upper flashboard and the lower flashboard are in a closed state, a purge gas inlet is opened, inert gas is filled into a transition cavity until a pressure sensor shows that the cavity pressure in the transition cavity is stable at a set value, then, the rotary kiln is driven to rotate, then, the electromagnetic induction coil of the rotary kiln is powered on in a partitioning manner, the temperature is gradually increased to the working temperature, and meanwhile, an external power supply is powered on for a graphite electrode of an electric molten pool, and the flux in the pool is melted to form an initial molten pool; The rotary kiln is divided into three temperature control areas along the length direction of the kiln, ① a preheating and dehydrating area, ② a medium-temperature reduction area, and ③ a high-temperature final reduction area, wherein the temperature is 500-700 ℃, the temperature is 750-950 ℃, and the temperature is 1000-1100 ℃; (2) Metering red mud, a carbonaceous reducing agent and a flux, controlling the blanking amount through a feeding and pretreatment unit according to a preset formula, and preparing compact pellets; (3) Feeding the granulated mixture into a kiln head of a preheated rotary kiln by a screw feeder, enabling the material to enter a region heated by a first group of coils of an electromagnetic induction coil, enabling the material to sequentially enter a region controlled by a second group of coils and a third group of coils, and finally discharging the reacted iron-slag composite pyrolysis slag and gas from the kiln tail; (4) The gas-solid mixture discharged from the kiln tail immediately enters a cyclone separator, high-temperature dust-containing combustible gas is tangentially separated, purified pyrolysis gas is sent to a product collection and flue gas treatment system from an outlet at the top of the cyclone separator, and separated high-temperature solid pyrolysis slag directly falls into a feed inlet of a high-temperature atmosphere isolation and material transfer device through an outlet at the bottom of the cyclone separator; (5) The PLC automatically operates the high-temperature atmosphere isolation and material transfer device according to a preset program to perform a working cycle: The receiving and isolation are that the PLC firstly confirms that the upper flashboard and the lower flashboard are in a closed state, inert gas is filled in the transition cavity in advance, and the pressure is normal; when the high-temperature bin level gauge detects that the material reaches a preset full material position, the PLC immediately sends a signal to the PLC, and then the PLC commands the first hydraulic driving device to move so as to enable the upper flashboard to descend, the channel is closed, the first mechanical sealing isolation is completed, and the atmosphere of the pyrolysis section is sealed outside; After the upper flashboard is closed, the PLC controls to open the exhaust port, meanwhile, inert gas is injected into the transition cavity through the purge gas inlet to perform purge replacement, after the purge is finished, the exhaust port is closed, the PLC adjusts the air inflow of the purge gas inlet according to real-time feedback of the pressure sensor, the pressure in the transition cavity is stabilized in a micro-positive pressure state slightly higher than the feeding port of the melting section, and the water-cooling jacket runs in the whole course; The PLC instructs the second hydraulic driving device to move, the lower flashboard is lifted, the material channel is exposed, the high-temperature pyrolysis slag material directly falls into the electric melting pool through the lower flashboard bin, after the material in the transition cavity is emptied, the high-temperature material level meter sends a 'blank' signal, and the PLC immediately instructs to close the lower flashboard; Then, the PLC fills inert gas into the transition cavity through the purge gas inlet again, so that the transition cavity is restored to an initial protection state of micro-positive pressure, and the preparation is made for the next material receiving cycle; (6) The high-temperature pyrolysis slag material continuously and directly falls into an electric melting pool through the high-temperature atmosphere isolation and material transfer device; The graphite electrode is immersed in the melt, heated and maintained at high temperature, the high-temperature pyrolysis slag falling into the molten pool is rapidly assimilated by the high-temperature melt, molten iron is settled and accumulated at the bottom of the electric molten pool to form a molten iron layer, silicate melt floats at the upper part of the electric molten pool and is homogenized into glass melt, a small amount of air or oxygen is introduced into the upper part of the electric molten pool through a gas inlet, the molten iron at the bottom is periodically siphoned and discharged through a molten iron outlet, the glass melt at the upper part continuously overflows through an overflow weir of the glass melt outlet, high-temperature flue gas generated at the top is led out from a gas outlet at the side surface of the top of the electric molten pool and then enters a product collecting and flue gas treatment system, and the treated molten iron is discharged after reaching standards.
8. The integrated treatment process for red mud gradient temperature pyrolysis and melting vitrification according to claim 7, wherein in the step (1), inert atmosphere is adopted as background gas in a rotary kiln, meanwhile, reducing atmosphere required by reduction reaction is provided by CO generated by a carbonaceous reducing agent at high temperature in situ, the residence time of materials in the rotary kiln is 60-120 minutes, the rotating speed of the rotary kiln is 0.5-3rpm, and the inclination angle is 2-5 degrees.
9. The integrated treatment process for the gradient temperature pyrolysis and the molten glass of the red mud according to claim 7, wherein the water content of the red mud in the step (2) is less than or equal to 25 percent, the granularity of a carbonaceous reducing agent is less than or equal to 2mm, the addition amount of the carbonaceous reducing agent is 1.1 to 1.3 times of the carbon amount required by theoretical reduction, the solvent comprises SiO 2 and CaO, the addition amount of the solvent is such that the final slag phase binary basicity CaO/SiO 2 is preferably 0.8 to 1.2, the grain size of dense pellets is 8 to 12mm, one part of pyrolysis gas purified in the step (4) is sent to an air preheater in a product collection and flue gas treatment system through a pyrolysis gas pipeline from the outlet of the top of a cyclone, and then sent to a generator for power generation through a steam turbine, and the other part of pyrolysis gas is recycled as reducing gas to a reducing atmosphere inlet of a kiln head of a rotary kiln.
10. The integrated treatment process for red mud gradient temperature pyrolysis and melting vitrification according to claim 7, wherein the temperature of the electric melting pool in the step (6) is maintained at 1350-1450 ℃, high-temperature flue gas generated at the top of the electric melting pool is led out from a gas outlet on the side surface of the top of the electric melting pool and then enters a product collection and flue gas treatment system, firstly air for supporting combustion is preheated to be more than 500 ℃ from normal temperature through an air preheater, then the flue gas is connected into a steam turbine to generate electricity and then is converged into a main waste gas treatment system, and finally tail gas is treated by a quenching tower, a cloth bag dust removing and desulfurization and denitrification device and then is discharged up to the standard.

Description

Red mud gradient temperature pyrolysis-melting vitrification integrated treatment device and process Technical Field The invention relates to the technical field of solid waste harmless and recycling equipment, in particular to a red mud gradient temperature pyrolysis-melting vitrification integrated treatment device and process. Background With the development of industrialization and urbanization, the yield of national solid waste rises year by year. Red mud is a strongly alkaline solid waste discharged in the process of producing alumina by using a Bayer process. About 0.8 to 1.5 tons of red mud is produced per 1 ton of alumina produced. Global red mud stockpiling has exceeded 40 hundred million tons and continues to increase at a rate of over 1.5 hundred million tons per year. The red mud has high pH value (pH value is 10-13), contains residual caustic alkali and various heavy metal elements, occupies a large amount of land after long-term storage, and has serious environmental and safety risks such as underground water pollution by percolate, atmosphere pollution by dust emission, dam break and the like. Therefore, the large-scale, harmless and recycling treatment of the red mud is a great environmental and technical problem of the alumina industry and even global attention. The pyrometallurgical recovery of iron is the most widely used direction of red mud treatment and resource research, but the energy consumption is high, the reduction product is a mechanical mixture of metallic iron and gangue slag, the separation of iron and slag is very incomplete, fine grinding and strong magnetic separation are needed, the iron recovery rate is low (generally < 85%), the iron powder grade is low (< 80%), and a large amount of tailings needing secondary treatment are generated. The wet method is often adopted for extracting valuable metals, but the method generally has the problems of long process, huge consumption of chemical reagents, serious equipment corrosion, large amount of acidic or alkaline waste liquid which is difficult to treat, and the like, has poor economical efficiency and environmental protection, and is difficult to industrialize and amplify. Red mud can also be used for producing cement, bricks, roadbed materials and the like, but alkali metals (Na, K) in the red mud can seriously influence the long-term strength and durability of building materials. The red mud and SiO 2 are mixed and then can be melted to prepare glass ceramic, the method can realize complete harmless treatment, but has the fatal defects of huge energy consumption, failure in recovering valuable iron resources in the red mud and difficult bearing of operation cost. In order to achieve both resource recovery and harmlessness, a combined process of reduction and iron extraction and residue vitrification has been explored in recent years. The red mud is pyrolyzed and reduced, the iron is recovered by magnetic separation, and then the magnetic separation tailings are melted and vitrified at high temperature. But the energy efficiency is extremely low, the flow is complex, the cost is high, the pyrolysis and the melting are designed as independent units, and the materials are required to be subjected to the intermittent processes of cooling, storing and reheating, so that the efficient coupling of energy and the continuous transfer of the materials cannot be realized. The prior art fails to provide a red mud treatment scheme which can synchronously and continuously realize the efficient recovery of valuable metals, is thoroughly harmless, and has industrial feasibility in energy consumption and cost. The invention discloses a method for recovering iron and tailings in red mud, which is characterized in that a rotary kiln and an electric melting pool are loosely coupled, and the cooling and storing in an intermediate link not only cause energy and material loss, but also destroy the continuity of a reducing atmosphere, so that the surface of iron particles is oxidized, and finally the yield and quality of molten iron are reduced. The process does not actively regulate slag components and atmosphere to form a stable vitreous network, but forms a gel material through water quenching, drying and the like, has the problems of long flow, high energy consumption, low added value and the like, and the product is inferior to a real vitrified solid in the aspects of heavy metal solidification stability and environmental safety. The China patent with the application number 202210577975.5 discloses a method for cooperatively utilizing high-iron red mud and molten steel slag, wherein reduction and melting are completed in the same space and at the same time, the strong reducing atmosphere is unfavorable for forming chemically stable glass bodies, and the strong gas stirring in a molten pool can cause iron drops to be dispersed in slag, so that the iron sedimentation efficiency is reduced. The Chinese patent with the application number 2021210