Flash calcination system

Abstract

A flash calcination system of the present invention comprises a first furnace section and a second furnace section, and a fuel inlet tube, a flue gas outlet tube and a furnace chamber communication tube, which are located at the top of each furnace section, wherein each furnace section is provided with a bottom interconnection channel that communicates a first furnace chamber therein with a second furnace chamber therein; each furnace chamber communication tube is configured to be in communication with a fuel inlet tube and a flue gas outlet tube by means of a four-way valve; in the same furnace section, when the first furnace chamber is in communication with the fuel inlet tube, the second furnace chamber is in communication with the flue gas outlet tube, and vice versa; four-way valves of different furnace sections are configured such that when the first furnace chamber of the first furnace section is in communication with the fuel inlet tube thereof, the first furnace chamber of the second furnace section is in communication with the flue gas outlet tube thereof; each furnace chamber is internally provided with spiral reaction tubes, discharge ports of spiral reaction tubes in the first furnace section being connected to feed ports of spiral reaction tubes in the second furnace section; each furnace chamber is internally provided with top regenerative beds and a bottom regenerative bed; primary gas-solid separators are provided at the bottom of each of the first furnace chamber and the second furnace chamber of the second furnace section; and the primary gas-solid separators are both connected to a secondary gas-solid separator arranged outside the second furnace section.

Description

Flash calcination system TECHNICAL FIELD

[0001] The present application relates to a mineral calcination equipment, in particular to a flash calcination system. BACKGROUND

[0002] Conner J. Holly et al. provides a system and method for mineral calcination, and the patent publication number is CN101466461A. The system comprises: a vertically arranged reactor section, an injector unit for receiving particulate feedstock, a reactor heat exchange unit thermally linked with the wall of the reactor section, one or more inlets formed in the reactor section for introducing superheated gas into the reactor section to establish a gas-solid multiphase system environment, and one or more outlets formed in the distillation section for discharging gas products from the reactor section at least partially under the action of the superheated gas stream from the inlet to the outlet.

[0003] The patent technology has the problems of high exhaust gas temperature and low thermal efficiency, and is difficult to be industrialized. Specifically, the heat exchange process between the high-temperature flue gas in the furnace and the heated material in the spiral pipe in the patent technology includes three parts: heat transfer between the high-temperature flue gas and the outer wall of the spiral pipe, heat conduction of the spiral pipe, and heat transfer between the inner wall of the spiral pipe and the gas-solid mixture. The heat transfer rate is low. Under the condition that there is no other carrier to absorb the heat of the high-temperature flue gas in the furnace, the exhaust gas temperature in the furnace is extremely high, which causes great waste of energy, or a waste heat recovery device must be used outside the furnace for heat recovery. SUMMARY

[0004] In order to overcome the above problems, it would be advantageous to provide a flash calcination system with heat storage function to reduce energy consumption.

[0005] To this end, the present application provides a flash calcination system, which comprises: a first furnace section and a second furnace section in which a first furnace and a second furnace are arranged side by side, a fuel inlet pipe and a flue gas outlet pipe at the top of each furnace section, and a furnace communication pipe, each furnace section has a bottom interconnection channel for communicating the first furnace and the second furnace, the furnace communication pipe is arranged to communicate with the fuel inlet pipe and the flue gas outlet pipe through a four-way valve, so that when the first furnace in the same furnace section communicates with the fuel inlet pipe, the second furnace communicates with the flue gas outlet pipe, when the second furnace communicates with the fuel inlet pipe, the first furnace communicates with the flue gas outlet pipe, and the four-way valves of different furnace sections are arranged to communicate the first furnace of the second furnace section with the flue gas outlet pipe when the first furnace of the first furnace section communicates with the fuel inlet pipe, a spiral reaction pipe with a material injection port and a material discharge port is arranged in each furnace, the material discharge port of the spiral reaction pipe in the first furnace section is connected to the material injection port of the corresponding spiral reaction pipe in the second furnace section, a top regenerator and a bottom regenerator are arranged in each furnace, a primary gas-solid separator is arranged at the bottom of the first furnace and the second furnace of the second furnace section, and a secondary gas-solid separator is arranged outside the second furnace section, and the primary gas-solid separators are connected to the secondary gas-solid separator.

[0006] In the present application, since two furnace sections with four furnaces are arranged, a top regenerator and a bottom regenerator are arranged in each furnace, when fuel is introduced into the first furnace, flue gas passes through the second furnace, and when fuel is introduced into one of the two first furnaces of the first furnace section and the second furnace section, flue gas passes through the other one, and the state of the two second furnaces is just the opposite, so that the heat of the fuel after combustion can be absorbed and stored by the furnace through which flue gas passes, and when the furnace is switched to the combustion state, the flue gas temperature at the outlet of the furnace can be reduced to below 200℃ from 800-900℃ when no regenerator is used, and the heat utilization rate is effectively improved.

[0007] Preferably, the top regenerator and the bottom regenerator are ceramic small ball regenerators.

[0008] Preferably, the first furnace and the second furnace of the first furnace section are arranged to be switched between the combustion state of communicating with the fuel inlet pipe and the regenerative state of communicating with the flue gas outlet pipe through the four-way valve, and the first furnace and the second furnace of the second furnace section are arranged to be switched between the regenerative state of communicating with the flue gas outlet pipe and the combustion state of communicating with the fuel inlet pipe through the four-way valve.

[0009] Further preferably, the switching time of the timing switching is 3 minutes.

[0010] Preferably, four groups of spiral reaction pipes are uniformly distributed along the circumference in each furnace, and preferably fins are arranged on the outer wall of the spiral reaction pipe.

[0011] Preferably, the fuel inlet pipe at the top of the first furnace section is arranged to supply fuel to the first furnace section, the fuel being 70% of the total amount of blast furnace gas, and the fuel is supplied together with a mixed gas which is pre-mixed with 45% of the total amount of combustion air, the mixed gas having a temperature of about 700°C and an air coefficient of 0.7, and 25% of the total amount of combustion air is introduced into the first furnace section through the middle and lower part of the first furnace section to further assist combustion, so that the fuel and combustion air in the whole first furnace section is 70% of the total load of the system, and the air coefficient of the first furnace section is 1.1; the fuel inlet pipe at the top of the second furnace section is arranged to supply fuel to the second furnace section, the fuel being 30% of the total amount of blast furnace gas, and the fuel is supplied together with a mixed gas which is pre-mixed with 20% of the total amount of combustion air, the mixed gas having a temperature of about 700°C and an air coefficient of 0.7, and 10% of the total amount of combustion air is introduced into the second furnace section through the middle and lower part of the second furnace section to further assist combustion, so that the fuel and combustion air in the whole second furnace section is 30% of the total load of the system, and the air coefficient of the second furnace section is 1.1.

[0012] Further preferably, the 25% of the total amount of combustion air is preheated by a heat source and introduced into the first furnace section, the heat source being the waste heat of the gas after the secondary gas-solid separator; a spiral reactor outer wall heat exchanger is arranged below the bottom regenerator of the second furnace section to heat the 10% of the total amount of combustion air by heat exchange with the outer wall of the spiral reactor.

[0013] Preferably, the raw material for calcination is injected into the spiral reactor of the first furnace section through the injection port of the spiral reactor, the raw material for calcination being solid powder of metal carbonate and metal hydroxide with a particle size of 50-150 μm and is transported by a transport medium.

[0014] Further preferably, the metal carbonate powder is limestone powder or dolomite powder, the metal hydroxide is carbide slag or magnesium hydroxide, and the transport medium is air or superheated steam.

[0015] Still preferably, the discharge port of the spiral reactor of the first furnace section is connected to the injection port of the corresponding spiral reactor of the second furnace section by a pipeline, and a Venturi ejector is arranged on the pipeline to supplement the air or superheated steam as the transport medium, so as to reduce the CO2 partial pressure in the gas-solid mixture in the spiral reactor of the second furnace section.

[0016] The above aspects and other aspects of the present application will be more clearly illustrated by referring to the following embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0017] The structure of the invention and further objects and advantages will be better understood from the following description, given, purely by way of a non-restrictive example, with reference to the figures enclosed, wherein identical references denote identical elements:

[0018] Figure 1 is a schematic view of the structure of a flash calciner system according to a specific embodiment of the present invention;

[0019] Figure 2 is an enlarged view of section A in Figure 1, in which the Venturi injection device fitted to the duct in Figure 1 is clearly shown. DETAILED DESCRIPTION

[0020] A specific embodiment of the present invention will be described below with reference to the figures enclosed.

[0021] As shown in Figure 1, the flash calciner system according to a specific embodiment of the present invention adopts a regenerative double-muffle double-stage structure, which comprises a first furnace stage 10 and a second furnace stage 30, in which both first and second muffle 21 and 23 are arranged side by side. The top of each furnace stage is provided with a fuel inlet pipe 20, a flue gas outlet pipe 22 and a muffle communication pipe 24. Each furnace stage has a bottom interconnection channel 26 for communicating the first muffle 21 and the second muffle 23. The muffle communication pipe 24 is connected to the first muffle 21 at one end and to the second muffle 23 at the other end, and is arranged to communicate with the fuel inlet pipe 20 and the flue gas outlet pipe 22 through a four-way valve 28, so that when the first muffle 21 of the same furnace stage is connected to the fuel inlet pipe 20, the second muffle 23 is connected to the flue gas outlet pipe 22, and when the second muffle 23 is connected to the fuel inlet pipe 20, the first muffle 21 is connected to the flue gas outlet pipe 22, and the four-way valves 28 of different furnace stages are arranged so that when the first muffle 21 of the first furnace stage 10 is connected to the fuel inlet pipe 20, the first muffle 21 of the second furnace stage 30 is connected to the flue gas outlet pipe 22. In each muffle, a top regenerator 25 and a bottom regenerator 27 are arranged, which in this embodiment are ceramic ball regenerators.

[0022] In this embodiment, through the four-way valve 28 at the top of the first furnace stage 10, the first muffle 21 and the second muffle 23 of the first furnace stage 10 are arranged to switch between the combustion state (i.e. connected to the fuel inlet pipe 20) and the regenerative state (i.e. connected to the flue gas outlet pipe 22) at regular intervals, for example 3 minutes, in other words, when the four-way valve 28 is in position I, fuel enters from the first muffle 21, and flue gas is discharged from the second muffle 23; when the four-way valve 28 is in position II, fuel enters from the second muffle 23, and flue gas is discharged from the first muffle 21.

[0023] The first furnace 21 and the second furnace 23 of the second furnace section 30 are arranged to be switched between the heat storage state (i.e. in communication with the flue gas outlet pipe 22) and the combustion state (i.e. in communication with the fuel inlet pipe 20) by the four-way valve 28 at the top of the second furnace section 30, and the switching time is the same as that of the first furnace section 10. However, the two furnaces of the second furnace section 30 are switched at different times from the two furnaces of the first furnace section 10, that is, in the second furnace section 30, when the four-way valve 28 is in position I, fuel enters the second furnace 23, and flue gas is discharged from the first furnace 21; when the four-way valve 28 is in position II, fuel enters the first furnace 21, and flue gas is discharged from the second furnace 23, that is, the first furnace 21 of the second furnace section 30 and the first furnace 21 of the first furnace section 10 are not in the combustion state or the heat storage state at the same time, but one is in the combustion state and the other is in the heat storage state, and the same is true for the second furnaces of the two furnace sections.

[0024] Each furnace, i.e. the first furnace 21 and the second furnace 23, is provided with four groups of spiral reaction tubes 29, which are evenly distributed in the circumferential direction in the furnace, so that there are eight groups of spiral reaction tubes 29 in each furnace section, i.e. the first furnace section 10 and the second furnace section 30, and each group of spiral reaction tubes 29 has a feeding port 291 and a discharging port 293. The discharging port 293 of the spiral reaction tube 29 of the first furnace section 10 is connected to the feeding port 291 of the corresponding spiral reaction tube 29 of the second furnace section 30.

[0025] A spiral reaction tube outer wall heat exchanger 90 is arranged below the regenerator 27 at the bottom of the second furnace section 30, so that a portion of the air (which can be cooling air) introduced from the middle and lower part of the second furnace section 30 can exchange heat with the spiral reaction tube outer wall heat exchanger 90, thereby raising the temperature of the portion of air and to some extent cooling the spiral reaction tube 29 of the second furnace section 30 that has completed calcination and the raw material in the spiral reaction tube.

[0026] A primary gas-solid separator 50 is provided at the bottom of each of the first and second hearths 21 and 23 of the second furnace section 30, and is used to separate the medium (calcined product powder, superheated steam for conveying raw material, and CO2 generated by decomposition of the raw material during calcination) in the spiral reaction tube 29. A secondary gas-solid separator 70 is provided outside the second furnace section 30, and the primary gas-solid separators 50 are connected to the secondary gas-solid separator 70. The mixed gas (steam, CO2 generated by decomposition, and product powder that has not been completely separated) separated in the primary gas-solid separators 50 is introduced again into the secondary gas-solid separator 70 to be separated. Each of the primary gas-solid separators 50 and the secondary gas-solid separator 70 can be a cyclone gas-solid separator.

[0027] As shown in Fig. 1, the flue gas discharged from the first and second furnace sections 10 and 30 through the flue gas outlet pipe 22 is collected and introduced into a limestone powder storage (not shown) to preheat the raw material limestone powder using the residual heat of the flue gas. Although limestone powder is calcined in this embodiment, other metal carbonate powders such as dolomite powder can be used, and metal hydroxides such as calcium carbide slag or magnesium hydroxide can also be used.

[0028] The 50-150 μm limestone powder used as the raw material is introduced into the spiral reaction tube 29 in the first furnace section 10 through the charging port 291 of the spiral reaction tube 29 by conveying using superheated steam as the conveying medium. After passing through the spiral reaction tube 29 in the first furnace section 10, most of the limestone is decomposed, and is introduced out of the first furnace section 10 through the discharge port 293 of the spiral reaction tube 29 provided at the upper portion of the first furnace section 10. The limestone powder is then introduced into the spiral reaction tube 29 in the second furnace section 30 through the pipe 40 connected to the charging port 291 of the spiral reaction tube 29 in the second furnace section 30 after being supplemented with a portion of the superheated steam through the Venturi jet device 41 provided in the pipe 40 (see the rightward arrow in Fig. 2). The limestone powder discharged from the spiral reaction tube 29 in the second furnace section 30 is calcined, and the mixture (calcined product powder, steam, and CO2 generated by decomposition) is sequentially introduced into the primary gas-solid separator 50 and the secondary gas-solid separator 70.

[0029] Note that the heat of the superheated steam in the first and second furnace sections 10 and 30 is generated from the residual heat of the system. The gas (steam and CO2) separated in the secondary gas-solid separator still has a high temperature and contains a large amount of heat, and is sufficient to satisfy the temperature, pressure, and flow rate requirements of the superheated steam used for conveying.

[0030] As shown in Fig. 1, the fuel inlet pipe 20 at the top of the first furnace section 10 is arranged to deliver fuel to the first furnace section 10, which is 70% of the total amount of blast furnace gas and is delivered together with the pre-mixed gas of 45% of the total amount of combustion air, the temperature of the mixed gas is about 700°C, and the air coefficient is 0.7. The mixed gas first enters the ceramic small ball regenerator at the top of the furnace chamber of the first furnace section 10, and then burns in the furnace chamber. The combustion air of 25% of the total amount is preheated (the heat source is the waste heat of the gas after secondary gas-solid separation) and introduced into the first furnace section 10 through the middle and lower part of the first furnace section 10, moves with the gas flow in the furnace, and continues to burn after contacting with the remaining combustible gas in the fuel in the furnace, that is, further combustion, so as to ensure that the fuel and combustion air in the entire first furnace section 10 are 70% of the total load of the system, that is, the fuel and combustion air in the first furnace section 10 are 70% of the total amount in the flash calcination system, and the mixed gas coefficient in the first furnace section 10 is 1.1.

[0031] The fuel inlet pipe 20 at the top of the second furnace section 30 is arranged to deliver fuel to the second furnace section 30, which is 30% of the total amount of blast furnace gas, that is, the remaining 30% of blast furnace gas, and is delivered together with the pre-mixed gas of 20% of the total amount of combustion air, the temperature of the mixed gas is about 700°C, and the air coefficient is 0.7. The mixed gas first enters the ceramic small ball regenerator at the top of the furnace chamber of the second furnace section 30, and then burns in the furnace chamber. The combustion air of 10% of the total amount is introduced into the second furnace section 30 through the middle and lower part of the second furnace section 30, and the temperature is raised after heat exchange by the spiral reaction tube outer wall heat exchanger 90 at the bottom of the second furnace section 30, and moves with the gas flow in the furnace and continues to burn after contacting with the remaining combustible gas in the fuel in the second furnace section 30, that is, further combustion, so as to ensure that the fuel and combustion air in the entire second furnace section 30 are 30% of the total load of the system, that is, the fuel and combustion air in the second furnace section 30 are 30% of the total amount in the flash calcination system, and the air coefficient in the second furnace section 30 is also 1.1.

[0032] As shown in Fig. 1, the high-temperature gas after secondary gas-solid separation, which has a temperature of about 790°C, first enters the flue gas boiler 60 to heat soft water to generate superheated steam of about 300°C for material conveying; and then enters the air heat exchanger 80 to exchange heat with the above-mentioned combustion air of 25% of the total amount, and preheat the combustion air to about 200°C before being introduced into the furnace chamber for combustion.

[0033] The technical contents and features of the present application have been disclosed above, however, it should be understood that, under the creative thought of the present application, those skilled in the art can make various changes and improvements to the above structure, including the combination of the technical features disclosed or claimed herein alone, and other combinations obviously including these features. These modifications and / or combinations all fall within the technical field to which the present application relates, and fall within the protection scope of the claims of the present application.

Claims

1. A flash calcination system characterized by The application relates to a rotary kiln with two furnace sections, each of which is provided with a first furnace and a second furnace, a fuel inlet pipe and a flue gas outlet pipe at the top of each furnace section, and a furnace communication pipe, each furnace section has a bottom interconnection channel for communicating the first furnace and the second furnace, the furnace communication pipe is arranged to communicate with the fuel inlet pipe and the flue gas outlet pipe through a four-way valve, so that when the first furnace in the same furnace section communicates with the fuel inlet pipe, the second furnace communicates with the flue gas outlet pipe, and when the second furnace communicates with the fuel inlet pipe, the first furnace communicates with the flue gas outlet pipe, and the four-way valves of different furnace sections are arranged to communicate the first furnace of the second furnace section with the flue gas outlet pipe when the first furnace of the first furnace section communicates with the fuel inlet pipe, each furnace is provided with a spiral reaction pipe with a material injection port and a material discharge port, the material discharge port of the spiral reaction pipe of the first furnace section communicates with the material injection port of the corresponding spiral reaction pipe in the second furnace section, a top regenerator and a bottom regenerator are arranged in each furnace, a primary gas-solid separator is arranged at the bottom of the first furnace and the second furnace of the second furnace section, and a secondary gas-solid separator is arranged outside the second furnace section, and the primary gas-solid separators are connected to the secondary gas-solid separator. The top regenerator and the bottom regenerator are both ceramic ball regenerators.

2. The flash calciner system of claim 1, wherein, The first furnace and the second furnace of the first furnace section are arranged to be time-switched between a combustion state of communicating with the fuel inlet pipe and a regenerative state of communicating with the flue gas outlet pipe through the four-way valve, and the first furnace and the second furnace of the second furnace section are arranged to be time-switched between a regenerative state of communicating with the flue gas outlet pipe and a combustion state of communicating with the fuel inlet pipe through the four-way valve.

3. A flash calciner system according to claim 1 or 2, characterised in that, The switching time of the time-switching is 3 minutes.

4. The flash calciner system of claim 3, wherein, Four groups of spiral reaction pipes are uniformly distributed along the circumference in each furnace, and fins are arranged on the outer wall of the spiral reaction pipes.

5. The flash calciner system of claim 1, wherein, The fuel inlet pipe at the top of the first furnace section is arranged to deliver fuel to the first furnace section, the fuel is 70% of blast furnace gas in total and is delivered together after being premixed with 45% of combustion air in total to form a mixed gas, the mixed gas has a temperature of 700 DEG C and an air coefficient of 0.7, 25% of combustion air in total is introduced into the first furnace section through the middle and lower part of the first furnace section to further assist combustion, so that the air coefficient in the whole first furnace section is 1.1, and the fuel inlet pipe at the top of the second furnace section is arranged to deliver fuel to the second furnace section, the fuel is 30% of blast furnace gas in total and is delivered together after being premixed with 20% of combustion air in total to form a mixed gas, the mixed gas has a temperature of 700 DEG C and an air coefficient of 0.7, 10% of combustion air in total is introduced into the second furnace section through the middle and lower part of the second furnace section to further assist combustion, so that the air coefficient in the whole second furnace section is 1.

1.

6. The flash calciner system of claim 1, wherein, ​ 7. The flash calciner system of claim 6, wherein, The combustion air of 25% of the total amount is preheated by a heat source and then introduced into the first furnace section, and the heat source is the waste heat of the gas after the secondary gas-solid separator; a spiral reaction tube outer wall heat exchanger is arranged below the bottom regenerator of the second furnace section to make the combustion air of 10% of the total amount exchange heat with the outer wall of the spiral reaction tube and be heated.

8. The flash calciner system of claim 1, wherein, The calcination raw material is injected into the spiral reaction tube of the first furnace section through the injection port of the spiral reaction tube, and the calcination raw material is the solid powder of metal carbonate and metal hydroxide with a particle size of 50-150 μm and is transported by a transport medium.

9. The flash calciner system of claim 8, wherein, The metal carbonate powder is limestone powder or dolomite powder, the metal hydroxide is carbide slag or magnesium hydroxide, and the transport medium is air or superheated steam.

10. The flash calcination system according to claim 1 or 8 or 9, wherein the discharge port of the spiral reaction tube of the first furnace section is connected to the injection port of the corresponding spiral reaction tube in the second furnace section through a pipeline, and a Venturi ejector device is arranged on the pipeline to supplement the air or superheated steam as the transport medium.

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