CN116730366B

CN116730366B - System and method for separating and purifying sodium carbonate and sodium bromide

Info

Publication number: CN116730366B
Application number: CN202310966426.1A
Authority: CN
Inventors: 雷祖磊; 张相; 常涛; 何春晓
Original assignee: Pyneo Co ltd
Current assignee: Pyneo Co ltd
Priority date: 2023-08-02
Filing date: 2023-08-02
Publication date: 2023-10-31
Anticipated expiration: 2043-08-02
Also published as: CN116730366A

Abstract

The application relates to the technical field of separation and purification of sodium salt, in particular to a system and a method for separating and purifying sodium carbonate and sodium bromide, wherein the system comprises a plasma gasification furnace, a first heat exchange part and a second heat exchange part which are sequentially connected, the first heat exchange part comprises a plurality of groups of subassemblies which are connected in series, the subassemblies comprise a first waste heat boiler and a slag catching temperature equalizer which are sequentially connected, the first waste heat boiler is an adiabatic furnace wall, a first heat exchange tube is arranged in an inner cavity of the first waste heat boiler, the first heat exchange tube comprises a pipe wall made of metal and a heat insulation layer made of heat insulation materials from inside to outside, the second heat exchange part comprises a second waste heat boiler and a slag catching temperature equalizer which are sequentially connected, the second waste heat boiler is a water-cooling wall structure, a membrane water-cooling wall is arranged on the wall surface of the second waste heat boiler, and a single heat exchange tube of the membrane water-cooling wall is made of metal materials. The application couples the plasma heating and flue gas cooling device, realizes heat recovery, and utilizes the boiling point difference to condense sodium carbonate and sodium bromide in steps and areas to obtain a high-purity product.

Description

System and method for separating and purifying sodium carbonate and sodium bromide

Technical Field

The application relates to the technical field of separation and purification of sodium salts, in particular to a system and a method for separating and purifying sodium carbonate and sodium bromide.

Background

Terephthalic Acid (PTA) is one of important bulk organic raw materials and is widely used in various industries of national economy such as chemical fiber, electronics, light industry, construction and the like. At present, the most widely applied synthetic PTA in the industry in China is prepared by adopting paraxylene through a series of oxidation-reduction reactions, and a large amount of synthetic wastewater is inevitably generated in the process. According to the related research reports, one ton of PTA is produced to produce 0.6-2 tons of synthetic wastewater. The PTA waste liquid is high-concentration organic waste water containing salt, contains various cyclic organic compounds, and has large fluctuation of pollutant concentration, pH value and temperature.

In recent years, the technology of concentrating and incinerating PTA wastewater is increasingly mature, and the technology has rapid development and industrial application due to high treatment speed, recovery of wastewater heat energy and by-production of a large amount of sodium carbonate and sodium bromide, for example, the prior application CN115371061B of the inventor. The ash produced by the PTA incinerator is a mixture of sodium carbonate and sodium bromide, and in order to improve the utilization value of the ash, the sodium carbonate and the sodium bromide in the ash are required to be separated respectively. The existing separation methods of sodium carbonate and sodium bromide in PTA industry mainly comprise evaporation crystallization, cooling crystallization, membrane separation and the like, such as CN112811444B, CN114380441A and CN113461199A. Whichever of the above separation methods requires a relatively large additional energy consumption.

The operating temperature of the PTA incinerator is generally higher than the melting temperature of sodium carbonate or sodium bromide, ash leaves the incinerator in a molten state, and then the ash needs to be cooled to form solid ash for subsequent separation and recovery, and the ash heat needs to consume additional cooling load and cannot be utilized. The inventor's prior application, publication No.: CN115414692B, name: the application discloses a method and a device for separating sodium carbonate by melting, thermally crystallizing and separating PTA incineration ash, which control the cooling process of liquid slag by utilizing the characteristic of liquid slag discharge of a PTA incinerator, so that sodium carbonate is crystallized from the first-stage cooling of the liquid slag, and after solid-liquid phase separation, impurity-containing parts are melted (sweated) by utilizing the heat of flue gas of the incinerator for further purification. The liquid slag of the separated sodium carbonate is totally converted into solid through secondary cooling crystallization, and the mixture residue is formed and discharged. The recovery rate of sodium carbonate in the fused ash processed by the method is more than or equal to 65%, the solid phase is purified and separated by utilizing the heat of the flue gas, the recovered sodium carbonate can reach the industrial quality standard, the load of the subsequent separation process can be reduced by more than 45%, the energy of the device is mainly from the self-contained fused heat of the fused ash of the incinerator, and the heat of the incineration flue gas is partially used for supplementing, so that the energy consumption of the whole PTA waste liquid and waste gas incineration resource recovery system is reduced.

Disclosure of Invention

Aiming at the technical problems existing in the prior art, the application provides a novel system and a method for separating and purifying sodium carbonate and sodium bromide, wherein the purity of the separated sodium carbonate and sodium bromide is high, and the system energy consumption is economical.

On the one hand, the application provides a system for separating and purifying sodium carbonate and sodium bromide, the system comprises a plasma gasification furnace 3, a first heat exchange part 4 and a second heat exchange part 5 which are sequentially connected, the first heat exchange part 4 comprises at least two groups of first heat exchange components which are connected in series, the first heat exchange components comprise a first waste heat boiler 41 and a first slag-catching temperature equalizer 42 which are sequentially connected, the first waste heat boiler 41 is of a heat insulation furnace wall structure, a plurality of groups of first heat exchange pipes 7 are arranged in an inner cavity of the first heat exchange boiler, the first heat exchange pipes 7 comprise a first heat exchange pipe wall 71 made of metal materials and a first heat exchange pipe heat insulating layer 72 made of heat insulating materials from inside to outside, the distance between the adjacent first heat exchange pipes 7 is d, the distance between the first heat exchange pipes 7 at the edge and the first heat exchange wall 41 is d/2, the inner radius of the first heat exchange pipes is r1, the thickness of the first heat exchange pipe wall 71 is lambda 1, the thickness of the first heat exchange pipe heat insulating layer 72 is lambda 2, d= (3-8) r1, lambda 1 is 4-10 mm, 2= (2-8) lambda 1 is a film type waste heat boiler wall 51, the distance between the second heat exchange pipes 7 at the inner side of the film type heat boiler wall 51 is 2 and the second heat wall 51 is provided with a second heat wall 51, the distance between the second heat exchange wall 51 is between the film type waste heat boiler wall 51 and the second heat wall 51 is provided, and the film type 1 is provided, and the film type wall 51 is provided.

In particular, the system specifically comprises an incinerator bottom slag discharging section 1, an inverted U-shaped connecting pipe 2, a plasma gasification furnace 3, a first heat exchange part 4, a second heat exchange part 5 and a deep treatment part 9 which are connected in sequence, wherein the first heat exchange part 4 and the second heat exchange part 5 are also connected with a double-shaft cooler 6 respectively.

Specifically, the plasma gasification furnace 3 includes a slag inlet 31, a cylinder 32 and a cone section 35 from top to bottom, an air inlet 33 is provided at the lower part of the cylinder 32, a plasma gun 34 is arranged at the middle part of the cone section 35, a crucible 36 is provided at the bottom of the cone section 35, and an air outlet 37 is provided at the upper part of the side wall of the cylinder 32.

In particular, the first slag-capturing temperature equalizer 42 includes a first slag-capturing pipe bundle 421 and a first temperature equalizer 422 which are sequentially connected, and the second slag-capturing temperature equalizer 52 includes a second slag-capturing pipe bundle 521 and a second temperature equalizer 522 which are sequentially connected; the first slag trap pipe beam 421 and the second slag trap pipe beam 521 are made of refractory materials; the first and second temperature equalizers 422 and 522 are internally provided with a honeycomb ceramic heat accumulator.

In particular, the wall 71 of the first heat exchange tube is made of steel, the heat insulating layer 72 of the first heat exchange tube is made of high-temperature ceramic material, and the wall of the single heat exchange tube of the membrane water wall 81 is made of steel.

On the other hand, the application also provides a method for separating and purifying sodium carbonate and sodium bromide, wherein the system is used, molten salt A rich in sodium carbonate and sodium bromide is fed into a plasma gasification furnace 3, a plasma gun 34 heats the molten salt A to be completely changed into a gaseous state, meanwhile, low-temperature carbon dioxide B2 is introduced into the plasma gasification furnace 3, flue gas C containing gaseous salt leaves the plasma gasification furnace 3 and enters a first heat exchange part 4, sodium carbonate in the flue gas C containing gaseous salt is changed into liquid sodium carbonate E to leave the first heat exchange part 4 through the cooling effect of the first heat exchange part 4 and then is cooled into solid sodium carbonate F, flue gas D containing gaseous sodium bromide after separating sodium carbonate enters a second heat exchange part 5 through the cooling effect of the second heat exchange part 5, sodium bromide in the flue gas D containing gaseous sodium bromide is changed into liquid sodium bromide G to leave the second heat exchange part 5 and then is cooled into solid sodium bromide H, high-temperature carbon dioxide B1 containing sodium bromide is changed into low-temperature carbon dioxide B2 after cooling and boosting and is recycled in the furnace 3.

In particular, when the first heat exchange tube 7 works, a first heat exchange tube liquid slag layer 73 is further arranged on the outer side of the first heat exchange tube heat insulation layer 72, and the thickness of the first heat exchange tube liquid slag layer 73 is λ3, and λ3 is 1-5 mm.

In particular, when the second exhaust-heat boiler 51 is in operation, a second heat exchange tube solid slag layer 812 and a second heat exchange tube liquid slag layer 813 are sequentially arranged outside the wall 811 of the second heat exchange tube, the thickness of the second heat exchange tube solid slag layer 812 is λ5, the thickness of the second heat exchange tube liquid slag layer 813 is λ6, λ5=2-8 mm, and λ6 is 1-5 mm.

Particularly, the molten salt A is 860-1200 ℃, the molten salt A enters the plasma gasification furnace 3 from the incinerator bottom slag discharging section 1 of the PTA wastewater through the inverted U-shaped connecting pipe 2, the plasma gasification furnace 3 is an adiabatic hearth, the temperature is 1650-2000 ℃, the temperature of flue gas D containing gaseous sodium bromide is 1400-1580 ℃, the temperature of high-temperature carbon dioxide B1 is 760-1200 ℃, the temperature of low-temperature carbon dioxide B2 is 50-200 ℃, and the system operating pressure is 2-30 bar.

Specifically, the liquid sodium carbonate E leaves the first heat exchange part 4 and then enters the double-shaft cooler 6, the liquid sodium bromide G leaves the second heat exchange part 5 and then enters the double-shaft cooler 6, the double-shaft cooler 6 comprises a jacket shell, a spiral cooling conveying shaft and a driving mechanism, cooling media are introduced into the jacket shell and the cooling conveying shaft, liquid salt materials enter the cooler from a charging port of the cooler, the liquid salt materials are continuously rolled and advance under the pushing of the rotating cooling conveying shaft, the materials are cooled by a cooling main shaft and blades in the advancing process, and heat is replaced and taken away by circulating water; the deep treatment section 9 includes a waste heat boiler and a fan.

On the basis of the common sense in the art, the above preferred conditions can be arbitrarily combined to obtain the preferred examples of the application.

The technical scheme has the following advantages or beneficial effects: the application deeply couples the plasma heating technology and the flue gas cooling device, and separates and purifies sodium carbonate and sodium bromide in the mixed salt while realizing heat recovery. The purity of the sodium carbonate and sodium bromide obtained by separation through the flue gas cooling device is high.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It will be obvious to a person skilled in the art that other figures can be obtained from the figures provided without the inventive effort.

FIG. 1 is a schematic flow diagram of a system for separating and purifying sodium carbonate and sodium bromide according to one embodiment of the application.

Fig. 2 is a schematic structural view of a plasma gasification furnace of a system for separating and purifying sodium carbonate and sodium bromide according to an embodiment of the present application.

Fig. 3 is a schematic diagram of the structure of a first heat exchange section of a system for separating and purifying sodium carbonate and sodium bromide according to one embodiment of the present application.

Fig. 4 is a schematic diagram of the structure of a second heat exchange section of a system for separating and purifying sodium carbonate and sodium bromide according to one embodiment of the present application.

Fig. 5 is a schematic top view of a first waste heat boiler of a system for separating and purifying sodium carbonate and sodium bromide according to one embodiment of the present application.

Fig. 6 is a schematic structural view of a first heat exchange tube of a system for separating and purifying sodium carbonate and sodium bromide according to one embodiment of the present application.

Fig. 7 is a schematic structural view of a first heat exchange tube section of a system for separating and purifying sodium carbonate and sodium bromide according to one embodiment of the present application.

Fig. 8 is a schematic diagram of a first heat exchange tube structure and a temperature distribution of a system for separating and purifying sodium carbonate and sodium bromide according to an embodiment of the present application.

Fig. 9 is a schematic top view of a second waste heat boiler of a system for separating and purifying sodium carbonate and sodium bromide according to one embodiment of the present application.

Fig. 10 is a schematic structural view of a section of a second heat exchange tube of a system for separating and purifying sodium carbonate and sodium bromide according to one embodiment of the present application.

FIG. 11 is a schematic diagram of a second heat exchange tube structure and temperature distribution of a system for separating and purifying sodium carbonate and sodium bromide according to one embodiment of the present application.

Fig. 12 is a schematic view showing an internal temperature distribution of a first group of first heat recovery boilers of the system for separating and purifying sodium carbonate and sodium bromide according to one embodiment of the present application.

Fig. 13 is a schematic view showing an internal temperature distribution of a second group of first heat recovery boilers of the system for separating and purifying sodium carbonate and sodium bromide according to one embodiment of the present application.

Fig. 14 is a schematic view showing an internal temperature distribution of a final set of first heat recovery boilers of the system for separating and purifying sodium carbonate and sodium bromide according to one embodiment of the present application.

Fig. 15 is a schematic view of an internal temperature distribution of a second heat recovery boiler during operation of a system for separating and purifying sodium carbonate and sodium bromide according to an embodiment of the present application.

The device comprises a 1-incinerator bottom slag discharging section, a 2-connecting pipe, a 3-plasma gasification furnace, a 31-slag inlet, a 32-barrel, a 33-air inlet, a 34-plasma gun, a 35-cone section, a 36-crucible, a 37-air outlet, a 4-first heat exchanging part, a 41-first waste heat boiler, a 42-first slag catching temperature equalizer, a 421-first slag catching pipe bundle, a 422-first temperature equalizer, a 5-second heat exchanging part, a 51-second waste heat boiler, a 52-second slag catching temperature equalizer, a 521-second slag catching pipe bundle, a 522-second temperature equalizer, a 6-double-shaft cooler, a 7-first heat exchanging pipe, a 71-first heat exchanging pipe wall, a 72-first heat exchanging pipe heat insulating layer, a 73-first heat exchanging pipe liquid slag layer, a 81-second waste heat boiler membrane water cooling wall, 811-second heat exchanging pipe wall, 812-second heat exchanging pipe solid slag layer, 813-second heat exchanging liquid slag layer, 9-deep heat managing part, A-molten salt, B1-carbon dioxide, B2-low-C-sodium carbonate, D-sodium carbonate, sodium bromide, gaseous sodium bromide, and gaseous sodium bromide. d-first heat exchange tube spacing, r 1-first heat exchange tube inner radius, lambda 1-first heat exchange tube wall thickness, lambda 2-first heat exchange tube heat insulation layer thickness, lambda 3-first heat exchange tube liquid slag layer thickness, T1-first heat exchange tube inner wall temperature, T2-first heat exchange tube outer wall temperature, T3-first heat exchange tube heat insulation layer outer wall temperature, T4-first heat exchange tube liquid slag layer outer wall temperature, T1-first waste heat boiler body flue gas temperature, T2-second group first waste heat boiler body flue gas temperature, tn-last group first waste heat boiler body flue gas temperature, r 2-second heat exchange tube inner radius, d 2-second heat exchange tube bundle spacing, lambda 4-second heat exchange tube wall thickness, lambda 5-second heat exchange tube solid slag layer thickness, lambda 6-second heat exchange tube liquid slag layer thickness, T5-second heat exchange tube inner wall temperature, T6-second heat exchange tube outer wall temperature, T7-second heat exchange tube slag layer outer wall temperature, T8-second waste heat exchange tube solid slag layer outer wall temperature, T8-second waste heat boiler body flue gas temperature, and lambda 2-second waste heat exchange tube body flue gas temperature.

Detailed Description

The technical solutions in the embodiments of the present application are clearly and completely described below with reference to the accompanying drawings. It is obvious that the described embodiments are only some of the embodiments of the present application and are intended to explain the inventive concept. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to fall within the scope of the application.

The terms "center," "longitudinal," "transverse," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," "circumferential," and the like as used in the description are based on the orientation or positional relationship shown in the drawings and are merely for simplicity of description and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operate in a particular orientation.

The terms "first," "second," and the like, as used in the description, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. The term "plurality" means two or more, unless specifically defined otherwise.

The terms "coupled," "connected," and the like as used in the description herein are to be construed broadly and may be, for example, fixedly coupled, detachably coupled, or integrally formed, unless otherwise specifically defined and limited; may be a mechanical connection, an electrical connection; can be directly connected and indirectly connected through an intermediate medium; may be a communication between two elements or an interaction between two elements. The specific meaning of the terms in the embodiments can be understood by those of ordinary skill in the art according to the specific circumstances.

Unless expressly stated or limited otherwise, a first feature "above," "below," or "above" a second feature may be either the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" or "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. A first feature "under", "beneath" or "under" a second feature may be either the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "under", "beneath" or "under" a second feature may be a first feature being directly under or diagonally under the second feature, or simply indicating that the first feature is less level than the second feature.

The terms "one particular embodiment" and "one particular embodiment" as used in this description mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

Referring to fig. 1, a specific embodiment of the present application provides a sodium carbonate and sodium bromide separation and purification system, preferably for separating and purifying sodium salt from PTA incineration molten ash, which comprises an incinerator bottom slag discharging section 1, a connecting pipe 2, a plasma gasifier 3, a first heat exchanging part 4, a second heat exchanging part 5 and a deep processing part 9, which are sequentially connected. The first heat exchanging part 4 and the second heat exchanging part 5 are also respectively connected with a double-shaft cooler 6. The inverted U-shaped connecting pipe 2 is a conveying pipeline of molten salt A, and the inverted U-shaped structure plays a role in liquid sealing, so that mutual cross gas between the plasma gasification furnace 3 and the slag discharging section 1 at the bottom of the incinerator can be prevented.

Referring to fig. 2, a specific embodiment of the present application provides a plasma gasifier for separating and purifying sodium carbonate and sodium bromide, wherein the plasma gasifier 3 comprises a slag inlet 31, a barrel 32 and a cone section 35 from top to bottom, an air inlet 33 is formed at the lower part of the barrel 32, a plasma gun 34 is formed at the middle part of the cone section 35, a crucible 36 is arranged at the center of the bottom of the cone section 35, and an air outlet 37 is formed at the upper part of the side wall of the barrel 32.

Preferably, the slag inlet 31 is in a circular structure and is arranged at the center of the plasma gasification furnace 3, the cylinder 32 is in a cylindrical structure, the cone section 35 is a big end at the top, and the air outlet 37 is in a circular or square structure. A refractory material is provided on the inner wall of the plasma gasification furnace 3. The number of the plasma guns 34 is set to be plural, preferably 3 to 6, and uniformly distributed circumferentially, and the plasma guns 34 are arranged obliquely so that the flames are directed to the middle position of the crucible 36. The air inlets 33 are arranged in multiple paths, preferably 3-6 paths, and are uniformly distributed along the circumference.

Referring to fig. 3, a specific embodiment of the present application proposes a first heat exchange part of a system for separating and purifying sodium carbonate and sodium bromide, the first heat exchange part 4 includes a plurality of groups of first heat exchange components with the same structure and function, a single first heat exchange component includes a first waste heat boiler 41 and a first slag-capturing temperature equalizer 42 which are sequentially connected, and the first slag-capturing temperature equalizer 42 includes a first slag-capturing pipe bundle 421 and a first temperature equalizer 422 which are sequentially connected.

Referring to fig. 4, a specific embodiment of the present application proposes a second heat exchange part of a system for separating and purifying sodium carbonate and sodium bromide, the second heat exchange part 5 includes a second waste heat boiler 51 and a second slag-capturing temperature equalizer 52 which are sequentially connected, and the second slag-capturing temperature equalizer 52 includes a second slag-capturing pipe bundle 521 and a second temperature equalizer 522 which are sequentially connected.

The first slag catching pipe beam 421 and the second slag catching pipe beam 521 are respectively a group of slag supplementing pipe beams formed by pouring refractory materials, and are mainly used for capturing liquid slag carried by flue gas. The first temperature equalizer 422 and the second temperature equalizer 522 are respectively provided with a honeycomb ceramic heat accumulator inside, and are used for adjusting the temperature of the flue gas after heat exchange to be uniform.

Referring to fig. 5 to 8, a specific embodiment of the present application proposes a first waste heat boiler for separating and purifying sodium carbonate and sodium bromide, the first waste heat boiler 41 is an adiabatic furnace wall structure, a water cooling wall is not arranged on the wall surface, and a plurality of groups of serpentine-shaped first heat exchange tubes 7 are arranged in the inner cavity. The first heat exchange tube 7 comprises a first heat exchange tube wall 71 and a first heat exchange tube heat insulation layer 72 from inside to outside. The first heat exchange tube wall 71 is made of steel, and the first heat exchange tube heat insulation layer 72 is made of heat insulation material, preferably high-temperature resistant ceramic. Further, when the first heat exchange tube 7 is in operation, a first heat exchange tube slag layer 73 is also present outside the first heat exchange tube insulating layer 72. Preferably, the distance d between adjacent first heat exchange tubes is d/2, the distance d between the edge first heat exchange tubes 7 and the wall surface of the first waste heat boiler 41 is r1, the wall thickness of the first heat exchange tubes is lambda 1, the thickness of the heat insulation layer of the first heat exchange tubes is lambda 2, the thickness of the liquid slag layer of the first heat exchange tubes is lambda 3, d= (3-8) r1, lambda 1 is 4-10 mm, lambda 2= (2-8) lambda 1, and lambda 3 is 1-5 mm.

Referring to fig. 9 to 11, a specific embodiment of the present application proposes a second waste heat boiler for separating and purifying sodium carbonate and sodium bromide, the second waste heat boiler 51 is a water wall structure, and a second waste heat boiler membrane water wall 81 is disposed on and in the second waste heat boiler 51. The single heat exchange tube of the second waste heat boiler membrane water wall 81 is composed of a second heat exchange tube wall 811, and the second heat exchange tube wall 811 is made of steel material. When the second waste heat boiler 51 operates, a second heat exchange tube solid slag layer 812 and a second heat exchange tube liquid slag layer 813 are sequentially arranged outside the second heat exchange tube wall 811. Preferably, the distance between the adjacent second waste heat boiler film type water walls 81 and the distance between the second waste heat boiler film type water walls 81 and the wall surface of the second waste heat boiler 51 are d2, the inner radius of the second heat exchange tube is r2, the wall thickness of the second heat exchange tube is lambda 4, the thickness of the solid slag layer of the second heat exchange tube is lambda 5, the thickness of the liquid slag layer of the second heat exchange tube is lambda 6, d2= (3-8) r2, lambda 4 is 4-10 mm, lambda 5 = 2-8 mm, and lambda 6 is 1-5 mm.

The double-shaft cooler 6 is used for cooling the liquid molten salt to be changed into a solid product, and the double-shaft cooler 6 mainly comprises a jacket shell, a spiral cooling conveying shaft and a driving mechanism. A cooling medium is introduced into the jacket shell and the cooling conveying shaft. The material enters the cooler from the charging hole of the cooler, is continuously rolled and advanced under the pushing of the rotating cooling conveying shaft, and is cooled by the cooling main shaft and the blades in the advancing process, and the heat is replaced by the circulating water and taken away. The deep treatment part 9 has the functions of deeply cooling the flue gas and providing power for flue gas circulation, the deep treatment part 9 mainly comprises a waste heat boiler and a fan, the waste heat boiler is a water pipe boiler in the prior art, and the fan is a centrifugal fan in the prior art.

The working flow of the method for separating and purifying sodium salt from PTA incineration melting ash is as follows: the molten salt A rich in sodium carbonate and sodium bromide enters the slag inlet 31 of the plasma gasification furnace 3 from the slag outlet section 1 of the bottom of the incinerator through the connecting pipe 2 and falls into the crucible 36 under the action of gravity. The plurality of plasma guns 34 heat the molten salt a to be completely gaseous, and at the same time, the low-temperature carbon dioxide B2 enters the plasma gasification furnace 3 from the gas inlet 33 as a reaction atmosphere. The flue gas C containing the gaseous salt leaves the plasma gasification furnace 3 from the gas outlet 37 and enters the first heat exchange part 4, sodium carbonate in the flue gas C containing the gaseous salt is changed into liquid sodium carbonate E, and the liquid sodium carbonate E leaves the first heat exchange part 4 and enters the double-shaft cooler 6, and is changed into solid sodium carbonate F under the cooling action of the double-shaft cooler 6. The flue gas C containing gaseous salt from which sodium carbonate is separated is changed into flue gas D containing gaseous sodium bromide, the flue gas D containing gaseous sodium bromide enters the second heat exchange part 5, sodium bromide in the flue gas D containing gaseous sodium bromide is changed into liquid sodium bromide G, the liquid sodium bromide G leaves the second heat exchange part 5 and enters the double-shaft cooler 6, and the liquid sodium bromide G is changed into solid sodium bromide H under the cooling action of the double-shaft cooler 6. The high-temperature carbon dioxide B1 from which sodium bromide is separated is cooled and boosted by the deep treatment section 9 to become low-temperature carbon dioxide B2, and is recycled in the plasma gasification furnace 3.

Further, the temperature of the molten salt A is 860-1200 ℃. The plasma gasification furnace 3 is an adiabatic hearth, and the temperature is 1650-2000 ℃. The temperature of the flue gas D containing the gaseous sodium bromide is 1400-1580 ℃. The temperature of the high-temperature carbon dioxide B1 is 760-1200 ℃. The temperature of the low-temperature carbon dioxide B2 is 50-200 ℃. The whole system is operated under the pressure condition, and the operating pressure is 2-30 bar.

The system and the method for separating and purifying the sodium salt by using the PTA incineration melting ash provided by the application have the beneficial effects and the corresponding effectsIs based on the principle of: (1) The application deeply couples the plasma heating technology and the specially designed flue gas cooling device, realizes heat recovery, and simultaneously separates and purifies sodium carbonate and sodium bromide in the mixed salt, and the obtained product meets the industrial quality requirement. (2) The application utilizes the boiling point difference of sodium carbonate and sodium bromide to realize the separation and purification effect, the boiling point of sodium carbonate is 1600 ℃, the boiling point of sodium bromide is 1390 ℃, and the temperature of PTA incineration molten salt is 860-1200 ℃. The application heats the molten salt to 1650-2000 ℃ by utilizing the characteristic of high plasma heat load, so that sodium carbonate and sodium bromide become gaseous. Further, by utilizing multi-section waste heat recovery, firstly, the flue gas containing gaseous salt is cooled to 1400-1580 ℃ to change sodium carbonate into liquid state for separation and recovery, and further, the flue gas is cooled to 760-1200 ℃ to change sodium bromide into liquid state for separation and recovery. (3) The sodium carbonate can undergo decomposition reaction at high temperature, and the decomposition equation is as follows: na (Na) ₂ CO ₃ ⇋Na ₂ O+CO ₂ The application adopts carbon dioxide atmosphere and high pressure condition to promote the reversible reaction to move towards the direction of sodium carbonate generation, thereby preventing the pyrolysis of sodium carbonate.

The application utilizes the boiling point difference of sodium carbonate and sodium bromide to realize separation and purification, but the technical route has the technical difficulty that as the boiling points of sodium carbonate and sodium bromide only have the difference of 210 ℃, the sodium bromide is still in a gaseous state when the sodium carbonate is liquefied and phase-changed, that is, the flue gas temperature in the first heat exchange part 4 can be ensured to be stabilized within the range of more than 1390 ℃, which has a critical influence on the purity of the finally separated products. Once the local temperature of the flue gas is lower than 1390 ℃, the sodium bromide can be liquefied and phase-changed to be mixed with sodium carbonate into a whole, and the purity of the sodium carbonate is seriously affected. In addition, the heat exchange tube is adopted to realize flue gas waste heat recovery and mixed salt separation, so that the high-pressure carbon dioxide atmosphere has strong radiation heat exchange capability, and compared with a conventional coal-fired flue gas waste heat boiler, the heat exchange tube has large heat flux per unit section, so that the temperature difference on a heat exchange surface is large, and the condition that the temperature of a heat exchange wall surface is lower than 1390 ℃ is easy to occur.

The application solves the problems by adopting a plurality of groups of first heat exchange assemblies which are connected in series and have the same structure and function. The first waste heat boiler 41 is of a heat-insulating furnace wall structure, a water cooling wall is not arranged on the wall surface, a plurality of groups of first heat exchange pipes 7 are arranged in the inner cavity, and the first heat exchange pipes 7 are serpentine heat exchange pipes. The distance between the first heat exchange tubes 7 is 3-8 times of the inner radius of the first heat exchange tubes, so that the liquid sodium carbonate can be prevented from bridging between the heat exchange tubes. In addition, the first heat exchange tube 7 includes a first heat exchange tube wall 71 and a first heat exchange tube heat insulating layer 72 from inside to outside. The first heat exchange tube wall 71 is made of steel, and the first heat exchange tube heat insulation layer 72 is made of heat insulation material, preferably high-temperature resistant ceramic. When the first heat exchange tube 7 works, a first heat exchange tube liquid slag layer 73 is arranged outside the first heat exchange tube heat insulation layer 72. The heat conductivity coefficient of the heat exchange tube heat insulation layer 72 is far lower than that of the first heat exchange tube wall 71, the temperature distribution of the first heat exchange tube 7 during operation is t1 for the inner wall temperature of the first heat exchange tube, t2 for the outer wall temperature of the first heat exchange tube, t3 for the outer wall temperature of the heat exchange tube heat insulation layer, and t4 for the outer wall temperature of the liquid slag layer of the first heat exchange tube. t1 is dependent on feed water and drum conditions and ranges from 100 to 300 ℃. The temperature t2 of the outer wall of the first heat exchange tube depends on the thickness lambda 1 of the wall of the first heat exchange tube and the temperature resistance characteristic of the heat exchange tube, lambda 1 is 4-10 mm, and t2 is 400-600 ℃. The outer wall temperature t3 of the heat-exchange tube heat-insulating layer depends on the thickness lambda 2 of the heat-exchange tube heat-insulating layer and the heat transfer characteristic of the heat-exchange layer, lambda 2= (2-8) lambda 1, 1390 ℃ less than t3 less than 1600 ℃. The temperature of the outer wall of the liquid slag layer of the first heat exchange tube is t4, and depends on the thickness lambda 3 of the liquid slag layer of the first heat exchange tube and the heat transfer characteristic, lambda 3 is 1-5 mm, and t3 is less than t4 and less than 1600 ℃.

Referring to fig. 12, the internal temperature distribution diagram of the first group of the first exhaust-heat boilers according to the present application is shown, wherein the temperature of the main body smoke of the first group of the first exhaust-heat boilers is T1, and the distance from the main body smoke to the heat exchange wall is λ. Referring to fig. 13, the internal temperature distribution of the second group of the first exhaust-heat boilers according to the present application is schematically shown, and the temperature of the main body smoke of the second group of the first exhaust-heat boilers is T2. Referring to fig. 14, the internal temperature distribution of the last group of the first waste heat boilers of the present application is schematically shown, and the smoke temperature of the main body of the last group of the first waste heat boilers is Tn. T1 > T2 > 1600 ℃ and Tn > 1390 ℃.

In order to further explain the superiority and superiority of the first heat exchange tube, the comparison and the explanation are made under the condition that the heat insulation layer of the first heat exchange tube is not arranged. When the flue gas containing gaseous salt enters the first waste heat boiler, the distribution condition of the materials on the wall of the heat exchange tube is similar to that of fig. 11, a layer of solid slag is formed outside the wall of the first heat exchange tube, and a layer of liquid slag is formed outside the solid slag. At this time, it is assumed that the temperature of the inner wall of the first heat exchange tube is t1, the temperature of the outer wall of the first heat exchange tube is t2, the temperature of the outer wall of the first solid slag is t3, and the temperature of the outer wall of the first liquid slag is t 4. t1 is dependent on feed water and drum conditions and ranges from 100 to 300 ℃. The temperature t2 of the outer wall of the first heat exchange tube depends on the thickness of the tube wall of the first heat exchange tube and the temperature resistance characteristic of the heat exchange tube, and t2 is 400-600 ℃. The temperature t3 of the outer wall of the first solid slag depends on the thickness of the first layer of solid slag and the heat transfer characteristic of the first layer of solid slag, and t2 is less than t3 and less than 755 ℃ (less than the melting point of sodium bromide). The temperature t4 of the outer wall of the first layer of liquid slag depends on the thickness of the first layer of liquid slag and the heat transfer characteristic of the first layer of liquid slag, and t3 is less than t4 and less than 1600 ℃. Therefore, the temperature distribution interval of t4 at this time comprises an interval lower than 1390 ℃, and the phenomenon that sodium carbonate and sodium bromide are liquefied simultaneously at this time can further cause the failure of the salt separation function of the system. The comparative analysis shows that the heat exchange tube heat insulating layer 72 has a temperature range of less than 1390 ℃ inside the heat exchange tube heat insulating layer, so that the phenomenon that sodium carbonate and sodium bromide are liquefied simultaneously is avoided.

The heat flux is further limited due to the limited heating surfaces arranged in the first waste heat boiler 41 and the presence of the heat insulation layer 72 of the first heat exchange tube, the heat exchange amount of the single first waste heat boiler is limited, and the temperature of the flue gas containing the gaseous salt is reduced and controlled to be 60-100 ℃ after passing through the single first waste heat boiler. In other words, the temperature of the flue gas containing the gaseous salt is reduced slightly after passing through the single first waste heat boiler, and the condition that the temperature of the heat exchange wall surface is lower than 1390 ℃ can be prevented. Further, the uneven temperature of the flue gas at the inlet of the first waste heat boiler is likely to cause the excessively low temperature of the local flue gas, the two adjacent first waste heat boilers are connected through the first slag-capturing temperature equalizer, and the first slag-capturing temperature equalizer is provided with the first slag-capturing pipe bundle and the first temperature equalizer and is used for capturing liquid slag carried by the flue gas and ensuring the uniform temperature of the flue gas entering the lower-level first waste heat boiler. Further, after the multi-stage first waste heat boiler is cooled, the flue gas temperature of the main body of the last group of first waste heat boilers is Tn,1600 ℃ is more than Tn and is more than 1390 ℃, all sodium carbonate is ensured to be separated out in the first heat exchange part 4, and further, the residual sodium carbonate is prevented from entering the second heat exchange part 5.

In summary, the specially designed first heat exchange part can ensure that the temperature of the flue gas in the first heat exchange part is stabilized to be higher than 1390 ℃ and ensure the purity of the separated sodium carbonate.

The flue gas containing gaseous sodium bromide from which sodium carbonate is removed, as it contains substantially only sodium bromide, is directly subjected to waste heat recovery by means of a set of second heat exchange sections 5, while sodium bromide is separated. The second heat exchange part 5 is composed of a second waste heat boiler 51 and a second slag catching temperature equalizer 52 which are sequentially connected, and the second slag catching temperature equalizer 52 comprises a second slag catching pipe bundle 521 and a second temperature equalizer 522 which are sequentially connected.

The second waste heat boiler 51 has a water wall structure, and the second waste heat boiler membrane water walls 81, d2= (3 to 8) r2 are provided in the wall surfaces and the inner cavities of the second waste heat boiler 51, so that the liquid sodium bromide can be prevented from bridging between the membrane water walls. The single heat exchange tube of the membrane water wall of the second waste heat boiler 51 is composed of a second heat exchange tube wall, and the second heat exchange tube wall is made of steel materials. When the second waste heat boiler works, a second heat exchange tube solid slag layer is arranged on the outer side of the tube wall of the second heat exchange tube, and a second heat exchange tube liquid slag layer is arranged on the outer side of the second heat exchange tube solid slag layer. The temperature distribution of the second heat exchange tube is t5 when in operation, t6 when in use, t7 when in use, and t8 when in use. The temperature of the inner wall of the second heat exchange tube is t5, which is 100-300 ℃ according to the conditions of the water supply and the steam drum. The temperature of the outer wall of the second heat exchange tube is t6, and depends on the thickness lambda 4 of the wall of the second heat exchange tube and the temperature resistance characteristic of the heat exchange tube, lambda 4 is 4-10 mm, and t6 is 400-600 ℃. The temperature of the outer wall of the solid slag layer of the second heat exchange tube is t7, and depends on the thickness lambda 5 of the solid slag layer of the second heat exchange tube and the heat transfer characteristic of the solid slag layer of the second heat exchange tube, lambda 5=2-8 mm, t6 is less than t7 and less than 755 ℃ (less than the melting point of sodium bromide). The temperature of the outer wall of the liquid slag layer of the second heat exchange tube is t8, and depends on the thickness lambda 6 of the liquid slag layer of the second heat exchange tube and the heat transfer characteristic, lambda 6 is 1-5 mm, t7 is less than t8 and less than 1390 ℃. Therefore, when the second heat exchange part works, the second heat exchange pipe can form a sodium bromide solid slag layer, and the heat exchange wall surface is protected from being corroded by liquid slag, and meanwhile, the heat of the flue gas is recovered and the sodium bromide is separated. Further, referring to FIG. 15, the internal temperature distribution diagram of the second waste heat boiler is shown, the smoke temperature of the main body of the second waste heat boiler is T, and the temperature T is 1390 ℃ less than or equal to Tn.

Example 1

The mass flow rate of the molten salt A rich in sodium carbonate and sodium bromide is 1000kg/h, wherein the mass fraction of the sodium carbonate is 90%, the balance is sodium bromide, the feeding temperature is 900 ℃, the molten salt A enters a slag inlet 31 of a plasma gasification furnace 3 from a slag discharging section 1 at the bottom of the incinerator through a connecting pipe 2, and the molten salt A further falls into a crucible 36 under the action of gravity. The molten salt A is completely vaporized by heating with the plasma gun 34, and at the same time, low-temperature carbon dioxide B2 (150 ℃ C., 10000m ³ 5 bar) enters the plasma gasification furnace 3 from the gas inlet 33 and serves as a reaction atmosphere. The plasma gasification furnace 3 is an adiabatic hearth, the temperature is 1850 ℃, and the pressure is 5bar. The flue gas C (1850 ℃) containing the gaseous salt leaves the plasma gasification furnace 3 from the gas outlet 37 and enters the first heat exchange part 4, sodium carbonate in the flue gas C containing the gaseous salt is changed into liquid sodium carbonate E which leaves the first heat exchange part 4 and enters the double-shaft cooler 6 through the cooling effect of the first heat exchange part 4, the liquid sodium carbonate E is changed into solid sodium carbonate F under the cooling effect of the double-shaft cooler 6, the mass is 898kg/h, and the purity is more than 99.9%. The flue gas C containing gaseous salt from which sodium carbonate is separated is changed into flue gas D (1450 ℃) containing gaseous sodium bromide, the flue gas D containing gaseous sodium bromide enters the second heat exchange part 5, the sodium bromide in the flue gas D containing gaseous sodium bromide is changed into liquid sodium bromide G which leaves the second heat exchange part 6 and enters the double-shaft cooler 6, the liquid sodium bromide G is changed into solid sodium bromide H under the cooling action of the double-shaft cooler 6, the mass is 102kg/H, and the purity is more than 98%. The high-temperature carbon dioxide B1 (780 ℃) containing gaseous salt from which sodium bromide is separated is cooled and boosted by the deep treatment part 9 to become low-temperature carbon dioxide B2 (150 ℃ and 10000 m) ³ And/h, 5 bar) and is fed into the plasma gasification furnace 3 for recycling.

The first heat exchanging part 4 comprises four groups of first heat exchanging components. The temperature of the flue gas containing the gaseous salt is reduced by 100 ℃ after passing through a single first waste heat boiler. Wherein, for the first group of first heat exchange components, the flue gas temperature T1 of the first group of first waste heat boiler main bodies is 1850 ℃; the temperature t4 of the outer wall of the liquid slag layer of the first heat exchange tube is 1500 ℃, the thickness lambda 3 of the liquid slag layer of the first heat exchange tube is 2mm, and the temperature t3 of the outer wall of the heat insulation layer of the first heat exchange tube is 1450 ℃; the thickness lambda 2 of the heat insulation layer of the first heat exchange tube is 40mm, and the temperature t2 of the outer wall of the first heat exchange tube is 450 ℃; the wall thickness lambda 1 of the first heat exchange tube is 8mm, and the temperature t1 of the inner wall of the first heat exchange tube is 250 ℃. After passing through the first slag-catching temperature equalizer 42, the outlet flue gas of the first group of first waste heat boilers is changed into flue gas with uniform temperature and 1750 ℃ and enters the second group of first waste heat boilers.

For the second group of first heat exchange assemblies, the temperature T2 of the flue gas of the second group of first waste heat boiler main bodies is 1750 ℃; the temperature t4 of the outer wall of the liquid slag layer of the first heat exchange tube is 1500 ℃, the thickness lambda 3 of the liquid slag layer of the first heat exchange tube is 2mm, and the temperature t3 of the outer wall of the heat insulation layer of the first heat exchange tube is 1450 ℃; the thickness lambda 2 of the heat insulation layer of the first heat exchange tube is 40mm, and the temperature t2 of the outer wall of the first heat exchange tube is 450 ℃; the wall thickness lambda 1 of the first heat exchange tube is 8mm, and the temperature t1 of the inner wall of the first heat exchange tube is 250 ℃. After passing through the first slag-capturing temperature equalizer 42, the outlet flue gas of the second group of first waste heat boilers is changed into flue gas with uniform temperature and 1650 ℃ and enters the third group of first waste heat boilers.

For the third group of first heat exchange assemblies, the temperature of the flue gas of the third group of first waste heat boiler main bodies is 1650 ℃; the temperature t4 of the outer wall of the liquid slag layer of the first heat exchange tube is 1500 ℃, the thickness lambda 3 of the liquid slag layer of the first heat exchange tube is 2mm, and the temperature t3 of the outer wall of the heat insulation layer of the first heat exchange tube is 1450 ℃; the thickness lambda 2 of the heat insulation layer of the first heat exchange tube is 40mm, and the temperature t2 of the outer wall of the first heat exchange tube is 450 ℃; the wall thickness lambda 1 of the first heat exchange tube is 8mm, and the temperature t1 of the inner wall of the first heat exchange tube is 250 ℃. After passing through the first slag-capturing temperature equalizer 42, the outlet flue gas of the third group of first waste heat boilers is changed into flue gas with uniform temperature and 1550 ℃ and enters the fourth group of first waste heat boilers.

For the fourth (last) group of first heat exchange assemblies, the fourth group of first waste heat boiler main body flue gas temperature Tn is 1550 ℃; the temperature t4 of the outer wall of the liquid slag layer of the first heat exchange tube is 1420 ℃, the thickness lambda 3 of the liquid slag layer of the first heat exchange tube is 1mm, and the temperature t3 of the outer wall of the heat insulation layer of the first heat exchange tube is 1395 ℃; the thickness lambda 2 of the heat insulation layer of the first heat exchange tube is 40mm, and the temperature t2 of the outer wall of the first heat exchange tube is 420 ℃; the wall thickness lambda 1 of the first heat exchange tube is 8mm, and the temperature t1 of the inner wall of the first heat exchange tube is 230 ℃. After passing through the first slag-capturing temperature equalizer 42, the flue gas at the outlet of the fourth group of the first waste heat boilers becomes flue gas with uniform temperature and 1450 ℃ and enters the second heat exchange part 5.

Further, the inner radius r1 of the first heat exchange tubes is 36mm, the distance d between the adjacent first heat exchange tubes is 180mm, and the distance between the edge first heat exchange tubes 7 and the wall surface of the first waste heat boiler 41 is 90mm.

For the second heat exchange part 5, the second waste heat boiler main body smoke temperature T is 1450 ℃; the temperature of the outer wall of the liquid slag layer of the second heat exchange tube is t8 and 790 ℃, the thickness lambda 6 of the liquid slag layer of the second heat exchange tube is 4mm, and the temperature of the outer wall of the solid slag layer of the second heat exchange tube is t7 and 550 ℃; the thickness lambda 5 of the solid slag layer of the second heat exchange tube is 4mm, and the temperature t6 of the outer wall of the second heat exchange tube is 420 ℃; the wall thickness lambda 4 of the second heat exchange tube is 6mm, and the temperature t5 of the inner wall of the second heat exchange tube is 260 ℃. After passing through the second slag-catching temperature equalizer 52, the outlet flue gas of the second waste heat boiler becomes a flue gas deep treatment part 9 with uniform temperature and 780 ℃.

Further, the inner tube radius r2 of the second heat exchange tube is 36mm, and the second heat exchange tube bundle spacing d2 is 180mm.

In summary, the system and the method for separating and purifying sodium salt from PTA incineration molten ash can separate 1000kg/h of molten salt A (sodium carbonate mass fraction 90% and sodium bromide mass fraction 10%) rich in sodium carbonate and sodium bromide to obtain 898kg/h of sodium carbonate with purity of more than 99.9% and 102kg/h of sodium bromide with purity of more than 98%.

Example 2

The mass flow rate of the molten salt A rich in sodium carbonate and sodium bromide is 2000kg/h, wherein the mass fraction of the sodium carbonate is 80%, the balance is sodium bromide, the feeding temperature is 1100 ℃, the molten salt A enters a slag inlet 31 of a plasma gasification furnace 3 from a slag outlet section 1 at the bottom of the incinerator through a connecting pipe 2, and the molten salt A further falls into a crucible 36 under the action of gravity. The molten salt A is heated by the multiple plasma guns 34 to become completely gaseousAt the same time, low-temperature carbon dioxide B2 (100 ℃,23000 m) ³ /h,10 bar) is introduced into the plasma gasification furnace 3 as a reaction atmosphere from the gas inlet 33. The plasma gasification furnace 3 is an adiabatic hearth, the temperature is 1700 ℃, and the pressure is 10bar. The flue gas C (1700 ℃) containing the gaseous salt leaves the plasma gasification furnace 3 from the gas outlet 37 and enters the first heat exchange part 4, sodium carbonate in the flue gas C containing the gaseous salt is changed into liquid sodium carbonate E which leaves the first heat exchange part 4 and enters the double-shaft cooler 6, the liquid sodium carbonate E is changed into solid sodium carbonate F under the cooling effect of the double-shaft cooler 6, the mass is 1597kg/h, and the purity is more than 99.9%. The flue gas C containing gaseous salt from which sodium carbonate is separated is changed into flue gas D (1460 ℃) containing gaseous sodium bromide, the flue gas D containing gaseous sodium bromide enters into the second heat exchange part 5, the sodium bromide in the flue gas D containing gaseous sodium bromide is changed into liquid sodium bromide G which leaves the second heat exchange part 6 and enters into the double-shaft cooler 6, the liquid sodium bromide G is changed into solid sodium bromide H under the cooling action of the double-shaft cooler 6, the mass is 403kg/H, and the purity is more than 99%. The high-temperature carbon dioxide B1 (800 ℃) containing gaseous salt from which sodium bromide is separated is cooled and boosted by the deep treatment part 9 to become low-temperature carbon dioxide B2 (100 ℃,23000 m) ³ And/h, 10 bar) and is fed into the plasma gasification furnace 3 for recycling.

The first heat exchange part 4 comprises four groups of first heat exchange components which are identical in structure and function. The temperature of the flue gas containing the gaseous salt is reduced by 60 ℃ after passing through a single first waste heat boiler. For the first heat exchange part of the first group, the smoke temperature T1 of the main body of the first waste heat boiler of the first group is 1700 ℃; the temperature t4 of the outer wall of the liquid slag layer of the first heat exchange tube is 1550 ℃, the thickness lambda 3 of the liquid slag layer of the first heat exchange tube is 1.5mm, and the temperature t3 of the outer wall of the heat insulation layer of the first heat exchange tube is 1520 ℃; the thickness lambda 2 of the heat insulation layer of the first heat exchange tube is 50mm, and the temperature t2 of the outer wall of the first heat exchange tube is 400 ℃; the wall thickness lambda 1 of the first heat exchange tube is 8mm, and the temperature t1 of the inner wall of the first heat exchange tube is 220 ℃. After passing through the first slag-catching temperature equalizer 42, the outlet flue gas of the first group of first waste heat boilers is changed into flue gas with uniform temperature and 1640 ℃ and enters the second group of first waste heat boilers.

For the second group of first heat exchange parts, the flue gas temperature T2 of the second group of first waste heat boiler main bodies is 1640 ℃; the temperature t4 of the outer wall of the liquid slag layer of the first heat exchange tube is 1550 ℃, the thickness lambda 3 of the liquid slag layer of the first heat exchange tube is 1.5mm, and the temperature t3 of the outer wall of the heat insulation layer of the first heat exchange tube is 1520 ℃; the thickness lambda 2 of the heat insulation layer of the first heat exchange tube is 50mm, and the temperature t2 of the outer wall of the first heat exchange tube is 400 ℃; the wall thickness lambda 1 of the first heat exchange tube is 8mm, and the temperature t1 of the inner wall of the first heat exchange tube is 220 ℃. After passing through the first slag-catching temperature equalizer 42, the outlet flue gas of the second group of first waste heat boilers is changed into flue gas with uniform temperature of 1580 ℃ and enters the third group of first waste heat boilers.

For the third group of first heat exchange parts, the flue gas temperature of the third group of first waste heat boiler main bodies is 1580 ℃; the temperature t4 of the outer wall of the liquid slag layer of the first heat exchange tube is 1480 ℃, the thickness lambda 3 of the liquid slag layer of the first heat exchange tube is 1.5mm, and the temperature t3 of the outer wall of the heat insulation layer of the first heat exchange tube is 1460 ℃; the thickness lambda 2 of the heat insulation layer of the first heat exchange tube is 45mm, and the temperature t2 of the outer wall of the first heat exchange tube is 400 ℃; the wall thickness lambda 1 of the first heat exchange tube is 8mm, and the temperature t1 of the inner wall of the first heat exchange tube is 220 ℃. After passing through the first slag-capturing temperature equalizer 42, the outlet flue gas of the third group of first waste heat boilers is changed into flue gas with uniform temperature and 1520 ℃ and enters the fourth group of first waste heat boilers.

For the fourth group (last group) of first heat exchange portions, the fourth group of first waste heat boiler main body flue gas temperature T2 is 1520 ℃; the temperature t4 of the outer wall of the liquid slag layer of the first heat exchange tube is 1420 ℃, the thickness lambda 3 of the liquid slag layer of the first heat exchange tube is 1.5mm, and the temperature t3 of the outer wall of the heat insulation layer of the first heat exchange tube is 1400 ℃; the thickness lambda 2 of the heat insulation layer of the first heat exchange tube is 40mm, and the temperature t2 of the outer wall of the first heat exchange tube is 400 ℃; the wall thickness lambda 1 of the first heat exchange tube is 8mm, and the temperature t1 of the inner wall of the first heat exchange tube is 220 ℃. After passing through the first slag-capturing temperature equalizer 42, the flue gas at the outlet of the fourth group of the first waste heat boilers is changed into flue gas with uniform temperature and 1460 ℃ and enters the second heat exchange part 5.

Further, the inner radius r1 of the first heat exchange tubes is 40mm, the distance d between the adjacent first heat exchange tubes is 240mm, and the distance between the edge first heat exchange tubes 7 and the wall surface of the first waste heat boiler 41 is 120mm.

For the second heat exchange part 5, the second waste heat boiler main body flue gas temperature T is 1460 ℃; the temperature of the outer wall of the liquid slag layer of the second heat exchange tube is 810 ℃, the thickness lambda 6 of the liquid slag layer of the second heat exchange tube is 4mm, and the temperature of the outer wall of the solid slag layer of the second heat exchange tube is 580 ℃ at t 7; the thickness lambda 5 of the solid slag layer of the second heat exchange tube is 4mm, and the temperature t6 of the outer wall of the second heat exchange tube is 450 ℃; the wall thickness lambda 4 of the second heat exchange tube is 8mm, and the temperature t5 of the inner wall of the second heat exchange tube is 230 ℃. After passing through the second slag-catching temperature equalizer 52, the outlet flue gas of the second waste heat boiler becomes a flue gas deep treatment part 9 with uniform temperature and 800 ℃.

Further, the inner tube radius r2 of the second heat exchange tube is 40mm, and the second heat exchange tube bundle spacing d2 is 240mm.

In summary, the system and the method for separating and purifying sodium salt from PTA incineration molten ash can separate 2000kg/h of molten salt A (sodium carbonate mass fraction 80% and sodium bromide mass fraction 20%) rich in sodium carbonate and sodium bromide to obtain 1597kg/h of sodium carbonate with purity of more than 99.9% and 403kg/h of sodium bromide with purity of more than 99%.

While embodiments of the present application have been illustrated and described above, it will be appreciated that the above described embodiments are illustrative and should not be construed as limiting the application. The present application is subject to various changes and modifications without departing from the spirit and scope thereof, and such changes and modifications fall within the scope of the application as hereinafter claimed.

Claims

1. The system for separating and purifying sodium carbonate and sodium bromide is characterized in that: the system comprises an incinerator bottom slag discharging section (1), a plasma gasification furnace (3), a first heat exchange part (4) and a second heat exchange part (5) which are sequentially connected, wherein the first heat exchange part (4) comprises at least two groups of first heat exchange components which are connected in series, the first heat exchange components comprise a first waste heat boiler (41) and a first slag catching temperature equalizer (42) which are sequentially connected, the first waste heat boiler (41) is of a heat insulation furnace wall structure, a plurality of groups of first heat exchange pipes (7) are arranged in an inner cavity of the first waste heat boiler, the first heat exchange pipes (7) comprise a first heat exchange pipe wall (71) made of metal materials and a first heat exchange pipe heat insulating layer (72) made of heat insulating materials from inside to outside, the pipe distance between adjacent first heat exchange pipes (7) is d, the distance between the first heat exchange pipes (7) at the edge and the wall surface of the first waste heat boiler (41) is d/2, the pipe inner radius of the first heat exchange pipes is r1, the thickness of the first heat exchange pipe wall (71) is lambda 1, the thickness of the first heat exchange pipe heat insulating layer (72) is 2, d= (3-8) r1, lambda 1 is lambda 1-4 and the water cooling boiler wall (51) is arranged on the inner surface of the second waste heat boiler (51) in sequence, the water cooling wall surface of the second heat boiler (51) is provided with a water cooling film type heat boiler wall (51) and the second heat boiler wall (51) is provided on the wall surface of the second heat boiler wall (51), the pipe wall of a single heat exchange pipe of the film water-cooling wall (81) is made of a metal material, the distance between the film water-cooling wall (81) of the adjacent second waste heat boiler and the wall surface of the second waste heat boiler (51) is d2, the pipe inner radius of the second heat exchange pipe is r2, the pipe wall thickness of the second heat exchange pipe is lambda 4, d2= (3-8) r2, and lambda 4 is 4-10 mm; a plasma gun (34) of the plasma gasification furnace (3) heats the molten salt to be completely changed into a gaseous state, and simultaneously, low-temperature carbon dioxide is introduced into the plasma gasification furnace (3).

2. The system for separating and purifying sodium carbonate and sodium bromide according to claim 1, wherein: the system specifically comprises an incinerator bottom slag discharging section (1), an inverted U-shaped connecting pipe (2), a plasma gasification furnace (3), a first heat exchange part (4), a second heat exchange part (5) and a deep treatment part (9) which are connected in sequence, wherein the first heat exchange part (4) and the second heat exchange part (5) are also connected with a double-shaft cooler (6) respectively.

3. The system for separating and purifying sodium carbonate and sodium bromide according to claim 1, wherein: the plasma gasification furnace (3) comprises a slag inlet (31), a cylinder (32) and a cone section (35) from top to bottom, wherein an air inlet (33) is formed in the lower portion of the cylinder (32), a plasma gun (34) is arranged in the middle of the cone section (35), a crucible (36) is arranged at the bottom of the cone section (35), and an air outlet (37) is formed in the upper portion of the side wall of the cylinder (32).

4. The system for separating and purifying sodium carbonate and sodium bromide according to claim 1, wherein: the first slag catching temperature equalizer (42) comprises a first slag catching pipe bundle (421) and a first temperature equalizer (422) which are sequentially connected, and the second slag catching temperature equalizer (52) comprises a second slag catching pipe bundle (521) and a second temperature equalizer (522) which are sequentially connected; the first slag catching pipe bundle (421) and the second slag catching pipe bundle (521) are made of refractory materials; the first temperature equalizer (422) and the second temperature equalizer (522) are internally provided with honeycomb ceramic heat accumulator.

5. The system for separating and purifying sodium carbonate and sodium bromide according to claim 1, wherein: the wall (71) of the first heat exchange tube is made of steel, the heat insulation layer (72) of the first heat exchange tube is made of high-temperature-resistant ceramic material, and the wall of the single heat exchange tube of the membrane water-cooling wall (81) is made of steel.

6. The method for separating and purifying sodium carbonate and sodium bromide is characterized in that: the system according to claim 1 is used, sodium carbonate and sodium bromide-rich molten salt A is fed into a plasma gasification furnace (3), a plasma gun (34) heats the molten salt A to enable the molten salt A to be completely changed into a gas state, low-temperature carbon dioxide B2 is simultaneously introduced into the plasma gasification furnace (3), gas C containing the gas state salt leaves the plasma gasification furnace (3) and enters a first heat exchange part (4), sodium carbonate in the gas C containing the gas state salt becomes liquid sodium carbonate E and leaves the first heat exchange part (4) through the cooling effect of the first heat exchange part (4), then the gas C is cooled to become solid sodium carbonate F, gas D containing the gas state sodium bromide after the sodium carbonate is separated enters a second heat exchange part (5), sodium bromide in the gas D containing the gas state sodium bromide becomes liquid sodium bromide G leaves the second heat exchange part (5), then the gas C is cooled to become solid sodium bromide H, and the high-temperature carbon dioxide B1 containing the gas C is cooled and boosted to become the low-temperature carbon dioxide B2 and enters the plasma gasification furnace (3) for recycling.

7. The method for separating and purifying sodium carbonate and sodium bromide according to claim 6, wherein: when the first heat exchange tube (7) works, a first heat exchange tube liquid slag layer (73) is arranged on the outer side of the heat exchange tube heat insulation layer (72), the thickness of the first heat exchange tube liquid slag layer (73) is lambda 3, and lambda 3 is 1-5 mm.

8. The method for separating and purifying sodium carbonate and sodium bromide according to claim 6, wherein: when the second waste heat boiler (51) works, a second heat exchange tube solid slag layer (812) and a second heat exchange tube liquid slag layer (813) are sequentially arranged on the outer side of the tube wall (811) of the second heat exchange tube, the thickness of the second heat exchange tube solid slag layer (812) is lambda 5, the thickness of the second heat exchange tube liquid slag layer (813) is lambda 6, lambda 5=2 mm-8 mm, and lambda 6 is 1 mm-5 mm.

9. The method for separating and purifying sodium carbonate and sodium bromide according to claim 6, wherein: the molten salt A is 860-1200 ℃, slag discharging section (1) of the incinerator bottom of the PTA wastewater enters a plasma gasification furnace (3) through an inverted U-shaped connecting pipe (2), the plasma gasification furnace (3) is an adiabatic hearth, the temperature is 1650-2000 ℃, the temperature of flue gas D containing gaseous sodium bromide is 1400-1580 ℃, the temperature of high-temperature carbon dioxide B1 is 760-1200 ℃, the temperature of low-temperature carbon dioxide B2 is 50-200 ℃, and the system operating pressure is 2 bar-30 bar.

10. The method for separating and purifying sodium carbonate and sodium bromide according to claim 6, wherein: the liquid sodium carbonate E leaves the first heat exchange part (4) and then enters the double-shaft cooler (6), the liquid sodium bromide G leaves the second heat exchange part (5) and then enters the double-shaft cooler (6), the double-shaft cooler (6) comprises a jacket shell, a spiral cooling conveying shaft and a driving mechanism, cooling media are introduced into the jacket shell and the cooling conveying shaft, liquid salt materials enter the cooler from a charging hole of the cooler and continuously roll and advance under the pushing of the rotating cooling conveying shaft, the materials are cooled by a cooling main shaft and blades in the advancing process, and heat is replaced by circulating water and taken away; the deep treatment part (9) comprises a waste heat boiler and a fan.