CN218523945U - System for preparing metal oxide powder by stepwise pyrolysis of nitrate and regenerating nitric acid - Google Patents
System for preparing metal oxide powder by stepwise pyrolysis of nitrate and regenerating nitric acid Download PDFInfo
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Abstract
The utility model discloses a system for preparing metal oxide powder and regenerating nitric acid by the step-by-step pyrolysis of nitrate. Comprises a heating and melting device, an atomization pyrolysis furnace, a cyclone dust collector, a dynamic pyrolysis furnace, a dust collector, a draught fan, a heating device and a nitric acid absorption and regeneration device. The nitrate is atomized, pyrolyzed and granulated at low temperature to obtain an alkali nitrate precursor, and then the precursor is sent into a dynamic pyrolysis furnace to be thermally decomposed to obtain metal oxide powder. Two dust gases of cyclone dust removal gas of the atomization pyrolysis furnace and tail gas of the dynamic pyrolysis furnace are subjected to high-temperature deep dust removal, and a small amount of collected materials are returned to the dynamic pyrolysis furnace. The tail gas after dust removal is divided into two parts, one part is sent to the atomization pyrolysis furnace through circulating heat supplementation, and the other part is directly sent to the nitric acid absorption and regeneration device. The system obviously reduces the volume of the atomization pyrolysis furnace, lowers the pyrolysis temperature, avoids unnecessary heat loss, improves the comprehensive heat efficiency, and obviously lowers the comprehensive operation cost, thereby realizing energy conservation and emission reduction.
Description
Technical Field
The utility model provides a system for preparing metal oxide powder and nitric acid regeneration by fractional pyrolysis of nitrate, which belongs to the cross field of inorganic chemical engineering and metallurgical engineering.
Background
In hydrometallurgical production, sulfuric acid, nitric acid are widely used in the leaching stage. The sulfuric acid has low price, wide applicability and larger use ratio. In the impurity removing stage of hydrometallurgy, the overall acidity and alkalinity of the solution is generally adjusted by adopting alkaline substances, so that selective precipitation of certain elements is realized, and the purposes of purification and impurity removal are achieved. The calcium precipitator is selected to produce a large amount of calcium sulfate solid slag, so that the flow is increased and the development concept of flow reduction is contrary to the development concept of flow reduction. If a precipitant such as sodium or magnesium is selected, a large amount of sulfate such as magnesium sulfate or sodium sulfate is produced as a by-product, and the added value of the product is low, the consumption of sulfuric acid is large, and the decomposition temperature is high and recycling is difficult. The physical and chemical properties of nitrates and sulfates are greatly different. The decomposition temperature of the nitrate is low, and metal oxide powder and acid gas can be obtained after decomposition. The metal oxide powder can be effectively separated by a gas-solid separation device, and the acid gas can be absorbed by a regeneration device to obtain nitric acid. Therefore, the method for preparing metal oxide powder and regenerating nitric acid by pyrolyzing nitrate has great application potential.
Chinese patent CN109721038A discloses a method for recovering nitric acid by pyrolyzing nitrate, delivering nitrate to at least two stages of preheating devices, heating and liquefying. And then conveying the nitrate hot fluid into the decomposer, and heating by using high-temperature gas to decompose the nitrate to generate mixed gas and solid powder. Separating the mixed gas and the solid powder, conveying one part of the mixed gas into a nitric acid recovery tank, heating the other part of the mixed gas to 500-800 ℃, and then refluxing the mixed gas into the decomposer for heating the nitrate thermal fluid to decompose the nitrate thermal fluid. The patent successfully realizes the atomization and pyrolysis of nitrate and then realizes the preparation of metal oxide and the cyclic regeneration of nitric acid. However, the degree of the atomized pyrolysis of the nitrates is related to the physicochemical characteristics of the nitrates themselves, the temperature of the pyrolysis furnace, the effective residence time of the particles inside the pyrolysis furnace. Thus, to ensure efficient decomposition of nitrates, pyrolysis furnaces are quite large in volume and the temperature within the furnace is also typically high. This results in large overall capital investment, large heat losses and reduced thermal efficiency of the furnace.
Chinese patent CN 113023695A discloses a method for preparing NO by pyrolyzing metal nitrate 2 The method of the gas oxidant is to pneumatically convey nitrate powder into a microwave pyrolysis device, and nitrate is decomposed under the action of microwaves to obtain metal oxide and high-purity nitrogen oxide gas. The process can also realize the pyrolysis of the nitrate, but the microwave pyrolysis device is used, and the device has high operation cost, high failure rate, high fixed investment and difficult enlargement.
Chinese patent CN 1118474898A discloses a magnesium nitrate pyrolysis furnace device with a high-temperature dust removal function and a method thereof. The pyrolysis furnace device comprises a pyrolysis area for performing pyrolysis reaction on the molten magnesium nitrate and a dust removal area for removing dust from decomposition gas generated after pyrolysis of the magnesium nitrate. The step of entering the pyrolysis furnace by the pyrolysis method comprises the following steps: delivering the magnesium nitrate in a molten state to a pyrolysis zone of a pyrolysis furnace through a delivery pump for carrying out pyrolysis reaction, and discharging powder at the bottom; decomposition gas that pyrolysis magnesium nitrate in pyrolysis district produced gets into the decomposition district, enters into the filling layer through the bending tube, and decomposition gas carries the granule to be adhered to by the high temperature resistant granule on the filling layer, forms the gaseous first draught fan of entering of dust removal. The pyrolysis step also utilizes the dust removal zone of the pyrolysis furnace to simplify the dust removal device. The utility model provides a simple structure, dust collection efficiency is high, the effectual magnesium nitrate pyrolysis furnace device that has high temperature dust removal function of dust removal. The patent is also a nitrate atomization pyrolysis process, so that the decomposing furnace has large volume, large heat loss and low thermal efficiency.
Chinese patent CN 108862218A discloses a method and a device for preparing nitric acid by pyrolyzing metal nitrate, wherein O is generated by pyrolyzing metal nitrate powder in a closed device 2 、NO 2 And metal oxide powder, O obtained 2 、NO 2 The nitric acid is introduced into an absorption tower and circularly absorbed by absorption liquid arranged in the absorption tower to obtain the nitric acid with required concentration. The utility model discloses entire system keeps sealed, keeps the malleation, lets the nitrate fully pyrolyze in the rotary kiln, and the produced gas of this in-process is absorbed completely by the liquid in the absorption tower, and almost no exhaust emission, no wastewater discharge, nitric acid concentration can satisfy hydrometallurgy production needs, and the rate of recovery of nitric acid is high, has greatly reduced the manufacturing cost of nitric acid, has effectively solved metal nitrate's recycle simultaneously. The process realizes the pyrolysis of nitrate, but because the viscosity of the nitrate is high, the nitrate is directly added into a pyrolysis furnace for pyrolysis, so that the phenomenon of wall sticking and ring formation can occur, and the heat conduction efficiency is reduced.
In view of the above problems, there is a need for an improvement of the existing nitric acid regeneration apparatus to reduce the volume of the atomizing pyrolysis furnace and the pyrolysis temperature, and further improve the overall thermal efficiency.
SUMMERY OF THE UTILITY MODEL
The utility model discloses a method and a system for preparing metal oxide powder by stepwise pyrolysis of nitrate and regenerating nitric acid. According to the method, nitrate is atomized, pyrolyzed and granulated at low temperature to obtain an alkali nitrate precursor with controllable particle size and morphology and good fluidity, and the precursor is sent into a dynamic pyrolysis furnace to be thermally decomposed for a long time to obtain metal oxide powder. Two dust gases of cyclone dust removal back gas of the atomization pyrolysis furnace and tail gas of the dynamic pyrolysis furnace are subjected to high-temperature deep dust removal, and a small amount of collected materials are returned to the dynamic pyrolysis furnace for pyrolysis. And after dust removal, tail gas is divided into two parts, and one part is sent to the atomization pyrolysis furnace for low-temperature pyrolysis granulation of nitrate through circulating heat supplementation. The other part is directly sent to a nitric acid absorption and regeneration device to obtain regenerated nitric acid. The system obviously reduces the volume of the atomization pyrolysis furnace, lowers the pyrolysis temperature, avoids unnecessary heat loss, improves the comprehensive heat efficiency, and obviously lowers the comprehensive operation cost, thereby realizing energy conservation and emission reduction.
The utility model discloses a following technical scheme realizes:
the utility model provides a system for nitrate fractional pyrolysis preparation metal oxide powder and nitric acid regeneration, including heating and melting device, atomizing pyrolysis oven, cyclone, dynamic pyrolysis oven, dust remover, draught fan, heating device and nitric acid absorption regenerating unit. Wherein, the first and the second end of the pipe are connected with each other,
the heating and melting device is used as a nitrate carrier to be treated and is used for heating nitrate to a molten state;
the discharge port of the heating and melting device is connected with the feed port of the atomization pyrolysis furnace, and the atomization pyrolysis furnace is provided with an atomization nozzle and is used for atomizing nitrate and pyrolyzing the nitrate at a certain temperature in the atomization pyrolysis furnace to generate basic nitrate precursor;
the discharge port of the atomization pyrolysis furnace is connected with the feed port of the cyclone dust collector, and the cyclone dust collector is used for carrying out gas-solid separation on the output material of the atomization pyrolysis furnace to obtain solid-phase discharge and dust removal tail gas;
the solid-phase discharge port of the cyclone dust collector is connected with the feed port of the dynamic pyrolysis furnace, and the dynamic pyrolysis furnace is used for calcining the basic nitrate output from the atomization pyrolysis furnace at a certain temperature for a long time to obtain metal oxide which is decomposed thoroughly, and outputting the metal oxide from the solid-phase discharge port of the dynamic pyrolysis furnace;
the gas phase outlet of the cyclone dust collector is combined with the gas phase outlet of the dynamic pyrolysis furnace and then connected with the feed inlet of the dust collector, and the dust collector is used for combining the dust-removing tail gas of the cyclone dust collector with the tail gas of the dynamic pyrolysis furnace and then carrying out deep dust removal to obtain deep dust-removed gas;
the inlet of the induced draft fan is connected with the gas phase outlet of the dust remover, the outlet of the induced draft fan is respectively connected with the inlet of the heating device and the inlet of the nitric acid absorption and regeneration device, and the induced draft fan is used for fully mixing the deeply dedusted gas and respectively sending the deeply dedusted gas to the nitric acid absorption and regeneration device and the heating device;
an inlet of the heating device is connected with an outlet of the induced draft fan, an outlet of the heating device is connected with a feed inlet of the atomization pyrolysis furnace, and the heating device is used for heating a part of dedusted gas, then sending the heated gas to the atomization pyrolysis furnace, and supplying heat required by pyrolysis;
the inlet of the nitric acid absorption and regeneration device is connected with the outlet of the induced draft fan, and the nitric acid absorption and regeneration device is used for pressurizing and absorbing part of dedusted gas to obtain regenerated nitric acid.
Preferably, the solid-phase discharge port of the cyclone dust collector is combined with the solid-phase discharge port of the dust collector and then connected with the feed port of the dynamic pyrolysis furnace.
Preferably, the outside of the heating and melting device is provided with a jacket layer and a coil pipe for heating and insulating the heating and melting device.
Preferably, the atomization pyrolysis furnace is one of a two-fluid spray atomization pyrolysis furnace, a pressure type atomization pyrolysis furnace, a two-fluid atomization pyrolysis furnace and a rotary centrifugal atomization pyrolysis furnace or a combination of at least two of the two.
Preferably, the type of the dynamic pyrolysis furnace is various types of rotary kilns and tunnel kilns.
Preferably, the bottom of the dynamic pyrolysis furnace is provided with a slag discharge port for discharging metal oxide powder generated by pyrolysis.
Preferably, the dust remover is one of a cyclone dust remover, an electrostatic dust remover, a high-temperature metal film dust remover, a porous ceramic dust remover and a high-temperature metal wire dust remover or a combination of at least two of the dust removers.
The utility model has the advantages as follows:
(1) The utility model discloses showing the size that has reduced the atomizing pyrolysis oven, having reduced the pyrolysis temperature, having improved whole thermal efficiency, realized energy saving and emission reduction.
(2) Through the two-step pyrolysis, the physical and chemical properties of the metal oxide, such as morphology, granularity, crystal form and the like, can be accurately controlled.
(3) The process is simple, the equipment requirement is low, and the industrial expansion is easy to realize.
Drawings
FIG. 1 is a schematic structural diagram of a system for preparing metal oxide powder by stepwise pyrolysis of nitrate and regenerating nitric acid, according to the present invention:
the mark in the figure is: 1-a heating and melting device, 2-an atomization pyrolysis furnace, 3-a cyclone dust collector, 4-a dynamic pyrolysis furnace, 5-a dust collector, 6-an induced draft fan, 7-a heating device and 8-a nitric acid absorption and regeneration device.
FIG. 2 shows phases of atomized pyrolysis products of magnesium nitrate at different temperatures, wherein 1 is Mg (NO) 3 ) 2 ·6H 2 O,2 is Mg (NO) 3 ) 2 ·2H 2 O,3 is Mg 3 (OH) 4 (NO 3 ) 2 And 4 is MgO.
FIG. 3 (a) is an enlarged view of basic magnesium nitrate 10 obtained in example 4 5 SEM microscopic scanning electron micrograph of magnification, FIG. 3 (b) is 2X 10 magnification of basic magnesium nitrate obtained in example 4 5 SEM microscopic scanning electron micrographs.
Detailed Description
The present invention will be described in further detail with reference to the following drawings and specific embodiments, but the scope of the present invention is not limited to the above description.
The utility model provides a nitrate fractional pyrolysis preparation metal oxide powder and nitric acid regeneration's system, as shown in figure 1, including heating and melting device 1, atomizing pyrolysis oven 2, cyclone 3, dynamic pyrolysis oven 4, dust remover 5, draught fan 6, heating device 7 and nitric acid absorption regenerating unit 8. Wherein, the first and the second end of the pipe are connected with each other,
the heating and melting device 1 is used as a nitrate carrier to be treated and is used for heating nitrate to a molten state, and whether the nitrate is heated or not and the heating temperature are selected according to the situation;
the discharge port of the heating and melting device 1 is connected with the feed port of the atomization pyrolysis furnace 2, and the atomization pyrolysis furnace 2 is provided with an atomization nozzle for atomizing nitrate and pyrolyzing the nitrate at a certain temperature to generate a basic nitrate precursor;
the discharge hole of the atomization pyrolysis furnace 2 is connected with the feed hole of the cyclone dust collector 3, and the cyclone dust collector 3 is used for carrying out gas-solid separation on the output material (namely, mixed dust gas) of the atomization pyrolysis furnace 2 to obtain solid-phase discharge and dust removal tail gas;
the solid-phase discharge port of the cyclone dust collector 3 is connected with the feed port of the dynamic pyrolysis furnace 4, and the dynamic pyrolysis furnace 4 is used for calcining the basic nitrate output from the atomization pyrolysis furnace 2 at a certain temperature for a long time to obtain a metal oxide which is decomposed thoroughly, and outputting the metal oxide from the solid-phase discharge port of the dynamic pyrolysis furnace 4;
the gas phase outlet of the cyclone dust collector 3 is combined with the gas phase outlet of the dynamic pyrolysis furnace 4 and then connected with the feed inlet of the dust collector 5, and the dust collector 5 is used for combining the dust-removing tail gas of the cyclone dust collector 3 with the tail gas of the dynamic pyrolysis furnace 4 and then carrying out deep dust removal to obtain deep dust-removed gas;
the inlet of the induced draft fan 6 is connected with the gas phase outlet of the dust remover 5, the outlet of the induced draft fan 6 is respectively connected with the inlet of the heating device 7 and the inlet of the nitric acid absorption and regeneration device 8, and the induced draft fan 6 is used for fully mixing the deeply dedusted gas and respectively sending the deeply dedusted gas to the nitric acid absorption and regeneration device 8 and the heating device 7;
an inlet of the heating device 7 is connected with an outlet of the induced draft fan 6, an outlet of the heating device 7 is connected with a feed inlet of the atomizing pyrolysis furnace 2, and the heating device 7 is used for heating a part of dedusted gas, and then sending the part of dedusted gas to the atomizing pyrolysis furnace 2 to supply heat required by pyrolysis;
the inlet of the nitric acid absorption and regeneration device 8 is connected with the outlet of the induced draft fan 6, and the nitric acid absorption and regeneration device 8 is used for pressurizing and absorbing part of dedusted gas to obtain regenerated nitric acid.
In an embodiment of the present invention, in order to fully pyrolyze the solid-phase substance obtained by the dust removal, the solid-phase discharge port of the cyclone 3 is combined with the solid-phase discharge port of the dust remover 5 and then connected to the feed port of the dynamic pyrolysis furnace 4.
The utility model also provides a method for preparing metal oxide powder and nitric acid regeneration by fractional pyrolysis of nitrate, the method uses foretell pyrolysis regeneration system, includes following steps:
(1) Adding nitrate into a heating and melting device to obtain nitrate in a molten state.
(2) And spraying the nitrate after heating and melting into an atomization pyrolysis furnace for low-temperature pyrolysis, and performing gas-solid separation on the obtained low-temperature pyrolysis product to obtain the basic nitrate precursor with controllable particle size and morphology and excellent fluidity.
(3) And (3) inputting the basic nitrate precursor into a dynamic pyrolysis furnace for calcination pyrolysis to obtain completely decomposed metal oxide powder.
(4) The tail gas generated after pyrolysis of the atomization pyrolysis furnace and the dynamic pyrolysis furnace is combined and then subjected to dust removal, then the tail gas is fully mixed in an induced draft fan, the tail gas subjected to dust removal is divided into two parts, one part is sent to a heating device for heating and then is input into the atomization pyrolysis furnace for low-temperature pyrolysis of nitrate, and the other part is sent to a nitric acid absorption and regeneration device to obtain regenerated nitric acid.
In one embodiment of the present invention, the nitrate species in step (1) is one or a mixture of calcium nitrate, magnesium nitrate, aluminum nitrate, ferric nitrate, manganese nitrate, nickel nitrate, cobalt nitrate, and scandium nitrate, and the heating temperature range of the melting tank is from room temperature to 150 ℃.
In one embodiment of the present invention, the nitrate is sprayed into the atomization pyrolysis furnace in step (2) to perform low temperature pyrolysis, the temperature range is 200 ℃ to 700 ℃, and the atomization mode is one of two-fluid spray atomization, pressure type atomization, two-fluid atomization and rotary centrifugal atomization or a combination of at least two of them. The shape of the obtained basic nitrate precursor is spherical, and the particle size is 10-300 mu m.
In one embodiment of the present invention, the basic nitrate precursor is input into the dynamic pyrolysis furnace for calcination and pyrolysis in step (3), the temperature range in the dynamic pyrolysis furnace is 200-1500 ℃, and the pyrolysis time is 0.5-3 h. The dynamic pyrolysis furnace is of various types of rotary kilns and tunnel kilns.
In an embodiment of the present invention, step (3) combines the solid phase separation product of the cyclone and the solid phase separation product of the dust remover, and inputs the combined product into the dynamic pyrolysis furnace for pyrolysis. The basic nitrate generated by pyrolysis has two parts, the largest part is generated in the atomization pyrolysis furnace, and the other part is generated in tail gas generated after cyclone dust removal of the atomization pyrolysis furnace. In addition, a small amount of metal oxide and unreacted basic nitrate exist in tail gas generated after the pyrolysis of the dynamic pyrolysis furnace. The solid-phase materials of the two parts of dust collectors are merged and then input into a dynamic pyrolysis furnace, so that the basic nitrate is subjected to complete thermal decomposition reaction.
In an embodiment of the present invention, in the step (4), the tail gas generated by pyrolyzing the atomizing pyrolysis furnace and the dynamic pyrolysis furnace is merged and then dedusted, and then fully mixed in the induced draft fan, wherein the dedusting mode is one of cyclone dedusting, electrostatic dedusting, high-temperature metal film dedusting, porous ceramic dedusting and high-temperature metal wire dedusting or a combination of at least two of the above.
In an embodiment of the present invention, the tail gas after dust removal in step (4) is divided into two parts, one part is sent to the heating device for heating and then input into the atomization pyrolysis furnace for low temperature pyrolysis of nitrate, and the other part is sent to the nitric acid absorption and regeneration device for obtaining regenerated nitric acid. Wherein the gas sent to the heating device accounts for 10-90% of the total amount of the tail gas, the rest gas is sent to a nitric acid absorption and regeneration device, and the concentration of the obtained nitric acid is 20-60%.
The output gas of the draught fan is divided into two parts because the nitric acid absorption device has requirements on the concentration of nitrogen oxides in the gas. The concentration cannot be too low, the concentration of nitrogen oxides in the gas output by the induced draft fan needs to be monitored in real time to determine the amount of gas input into the nitric acid absorption and regeneration device, and the proportion of the two parts of gas can be adjusted by adjusting the air inflow of the valve and the rear-end nitric acid absorption device. This operation may be referred to as recycle gas regenerative pyrolysis, which as the name implies uses the gases produced after pyrolysis as hot gases to exchange heat with the material. This avoids the introduction of air and the overall nitrogen oxide concentration is increased.
The pyrolysis method provided by the utility model is explained as follows: in the prior art, nitrate is mostly dynamically calcined and pyrolyzed in one step, and basically, nitrate is melted and then atomized and sprayed into a pyrolysis furnace for pyrolysis. The method is simple, efficient and quick, but the atomization pyrolysis needs to meet two conditions: 1. a certain residence time; 2. higher temperature. Pyrolysis furnaces are therefore generally bulky and have a high overall temperature. This results in a pyrolysis furnace with high overall heat dissipation, high capital investment and relatively low thermal efficiency.
The applicant found through experiments that nitrate forms a transition state, i.e. a new phase of basic nitrate, after the atomization pyrolysis. This phase can be formed rapidly at lower temperatures. Therefore, the core of the utility model is to convert the original one-step pyrolysis into two-step pyrolysis, namely, the basic nitrate is firstly obtained in the pyrolysis furnace, and then the basic nitrate is calcined in the dynamic calciner for a long time and is thoroughly decomposed to obtain the metal oxide. Therefore, the size of the atomizing pyrolysis furnace can be reduced, the heat efficiency of the whole device can be obviously improved, and the comprehensive cost is reduced.
Taking magnesium nitrate as an example, fig. 2 is a phase diagram of a magnesium nitrate atomized pyrolysis product at different temperatures, wherein the abscissa in the diagram is a 2 theta angle and is an angle scanned by a diffraction spectrometer; the ordinate is the count detected by the receiver in units of CPS (counts per sec.). Wherein 1 is Mg (NO) 3 ) 2 ·6H 2 O,2 is Mg (NO) 3 ) 2 ·2H 2 O,3 is Mg 3 (OH) 4 (NO 3 ) 2 And 4 is MgO. As can be seen from FIG. 2, as the pyrolysis temperature increases, the magnesium nitrate gradually dehydrates to form basic magnesium nitrate at about 550-600 ℃. As the temperature continues to rise, the basic magnesium nitrate slowly decomposes intoAnd (3) magnesium oxide. However, when the temperature is raised to 1100 ℃, basic magnesium nitrate still remains in the product phase, i.e. the decomposition is incomplete. It can be seen that basic magnesium nitrate is easily formed at low temperature, but it is not easy to completely decompose basic magnesium nitrate. The advantages of spray pyrolysis are continuous, rapid, but need to be carried out in a superheated state. For example, the theoretical decomposition temperature of magnesium nitrate is 450-500 ℃, but in the atomized pyrolysis state, a very high temperature is required to ensure complete decomposition, and in addition, the retention time of the product in the pyrolysis furnace must be ensured. Based on the method, the precursor of the basic nitrate can be generated firstly under the low temperature state, and then the basic nitrate can be completely decomposed by long-time calcination.
Table 1 calculates the theoretical residence time of the gas in the furnace at different temperatures. The calculation theory is simple, i.e. the time obtained by dividing the volume of the furnace by the gas flow, where the temperature is a variable, and the contents of table 1 are obtained under simple estimation with the ideal gas state equation (pv = nrt). The pyrolysis apparatus is shown to have a residence time of 83.84 seconds at 550 ℃ and 54.2 seconds at 1000 ℃ in the same volume. The result of combining the upper phase can show that the basic magnesium nitrate is difficult to decompose. When the temperature was raised to 1000 c, basic magnesium nitrate was still present. If the temperature is further increased, the material selection of the atomizing pyrolysis furnace becomes difficult. Therefore, the temperature is no longer the limiting link of the pyrolysis degree, and the furnace body must be enlarged, so that the retention time of the basic magnesium nitrate in the hot zone is increased. Table 2 is a table of the relationship between the retention time at 1000 ℃ and the decomposition rate of magnesium nitrate, and at 1000 ℃ the retention time was 95 seconds, and magnesium nitrate was considered to be substantially completely decomposed. Therefore, to ensure complete decomposition of the magnesium nitrate, the residence time in the atomizing pyrolysis furnace needs to be increased by at least 1.75 times. In other words, by adopting the scheme of the utility model, the volume of the atomizing pyrolysis furnace is reduced by at least 42.9 percent. The fixed investment is reduced, the maintenance cost is reduced, the heat dissipation is obviously reduced, and finally, the comprehensive pyrolysis cost is obviously reduced.
TABLE 1 theoretical relationship between residence time and temperature
| Serial number | Time/s | Volume of gas | Temperature K | Temperature of |
| 1 | 235.50 | 1.00 | 293 | 20 |
| 2 | 184.99 | 1.27 | 373 | 100 |
| 3 | 145.88 | 1.61 | 473 | 200 |
| 4 | 120.42 | 1.96 | 573 | 300 |
| 5 | 102.53 | 2.30 | 673 | 400 |
| 6 | 89.26 | 2.64 | 773 | 500 |
| 7 | 83.84 | 2.81 | 823 | 550 |
| 8 | 79.04 | 2.98 | 873 | 600 |
| 9 | 70.92 | 3.32 | 973 | 700 |
| 10 | 64.31 | 3.66 | 1073 | 800 |
| 11 | 58.82 | 4.00 | 1173 | 900 |
| 12 | 54.20 | 4.34 | 1273 | 1000 |
TABLE 21000 deg.C residence time and degree of decomposition of magnesium oxide
| Serial number | Residence time/s | Decomposition rate of magnesium oxide% |
| 1 | 55 | 95.1 |
| 2 | 65 | 96.7 |
| 3 | 75 | 97.2 |
| 4 | 85 | 98.5 |
| 5 | 95 | 99.8 |
Examples 1 to 5 all employ the system for preparing metal oxide powder by stepwise pyrolysis of nitrate and regenerating nitric acid shown in fig. 1.
Example 1
Firstly, adding aluminum nitrate into a heating and melting device, heating to 90 ℃ to melt the aluminum nitrate, atomizing the aluminum nitrate by a rotary centrifugal atomizer, and feeding the aluminum nitrate into an atomizing pyrolysis furnace, wherein the temperature in the atomizing pyrolysis furnace is 250 ℃. The aluminum nitrate is subjected to rapid low-temperature thermal decomposition in an atomization pyrolysis furnace to obtain an alkali-containing aluminum nitrate precursor and H 2 O、HNO 3 The mixed dust gas is dedusted by a cyclone dust collector to obtain basic aluminum nitrate with the particle size of 75 μm. Then the basic aluminum nitrate is sent to a dynamic pyrolysis furnace (external heating rotary kiln) and calcined for 1h at the temperature of 300 ℃ to obtain the gamma-alumina, wherein the decomposition rate is more than 98%. After the gas decomposed by the dynamic pyrolysis furnace and the gas subjected to the first-step cyclone dust removal are subjected to electrostatic deep dust removal through a dust remover, a small amount of collected mixed materials are returned to the dynamic pyrolysis furnace for pyrolysis, and the gas subjected to dust removal is fully mixed in an induced draft fan. Wherein 20 percent of the aluminum nitrate is sent to a heating device to be heated to 300 ℃ and then sent to an atomization pyrolysis furnace to be used for low-temperature pyrolysis of the aluminum nitrate. And the rest gas is sent to a nitric acid absorption and regeneration device to obtain regenerated nitric acid, wherein the concentration of the nitric acid is 25%.
Example 2
Firstly, adding aluminum nitrate into a heating and melting device, heating to 100 ℃ to melt the aluminum nitrate, atomizing the aluminum nitrate by a two-fluid atomizer, and feeding the aluminum nitrate into an atomizing pyrolysis furnace, wherein the temperature in the atomizing pyrolysis furnace is 300 ℃. The aluminum nitrate is subjected to rapid low-temperature thermal decomposition in an atomization pyrolysis furnace to obtain an alkali-containing aluminum nitrate precursor and H 2 O、HNO 3 The mixed dust gas is dedusted by a cyclone dust collector to obtain the basic aluminum nitrate, and the particle size is 20 mu m. Then the basic aluminum nitrate is sent to a dynamic pyrolysis furnace (external heating type rotary kiln) at the temperature ofCalcining at 1100 deg.C for 0.5h to obtain alpha-alumina with decomposition rate greater than 99.9%. After the gas decomposed by the dynamic pyrolysis furnace and the gas subjected to the first-step cyclone dust removal are subjected to electrostatic deep dust removal through a dust remover, a small amount of collected mixed materials are returned to the dynamic pyrolysis furnace for pyrolysis, and the gas subjected to dust removal is fully mixed in an induced draft fan. Wherein 40 percent of the aluminum nitrate is sent to a heating device to be heated to 350 ℃ and then sent to an atomization pyrolysis furnace to be used for low-temperature pyrolysis of the aluminum nitrate. And the rest gas is sent to a nitric acid absorption and regeneration device to obtain regenerated nitric acid, wherein the concentration of the nitric acid is 30 percent.
Example 3
Firstly, calcium nitrate is added into a heating and melting device and heated to 80 ℃ to be melted, and then the calcium nitrate is atomized and sent into an atomization pyrolysis furnace through a pressure atomizer, wherein the temperature in the atomization pyrolysis furnace is 600 ℃. The calcium nitrate is subjected to rapid low-temperature thermal decomposition in an atomization pyrolysis furnace to obtain an alkali-containing calcium nitrate precursor and H 2 O、NO X The mixed dust gas is dedusted by a cyclone deduster to obtain the basic calcium nitrate, and the particle size is 100 mu m. Then the basic calcium nitrate is sent to a dynamic pyrolysis furnace (external heating rotary kiln) and calcined for 3 hours at the temperature of 700 ℃ to obtain calcium oxide, and the decomposition rate is more than 99%. After the gas decomposed by the dynamic pyrolysis furnace and the gas subjected to the first-step cyclone dust removal are subjected to electrostatic deep dust removal through a dust remover, a small amount of collected mixed materials are returned to the dynamic pyrolysis furnace for pyrolysis, and the gas subjected to dust removal is fully mixed in an induced draft fan. Wherein 60 percent of the aluminum nitrate is sent to a heating device to be heated to 650 ℃ and then sent to an atomization pyrolysis furnace to be used for low-temperature pyrolysis of the aluminum nitrate. And the rest gas is sent to a nitric acid absorption and regeneration device to obtain regenerated nitric acid, wherein the concentration of the nitric acid is 40%.
Example 4
Firstly, adding magnesium nitrate into a heating and melting device, heating to 110 ℃ to melt the magnesium nitrate, atomizing the magnesium nitrate by a rotary centrifugal atomizer, and feeding the atomized magnesium nitrate into an atomizing pyrolysis furnace, wherein the temperature in the atomizing pyrolysis furnace is 500 ℃. Performing rapid low-temperature thermal decomposition on magnesium nitrate in an atomization pyrolysis furnace to obtain an alkali-containing magnesium nitrate precursor and H 2 O、NO x The mixed dust gas is dedusted by a cyclone deduster to obtain the basic magnesium nitrate, and the particle size is 200 mu m. Then the basic magnesium nitrate is sent to a dynamic pyrolysis furnace (outside)A hot rotary kiln) at 400 ℃ for 2h to obtain the magnesium oxide with the decomposition rate of more than 99.9 percent. After the gas decomposed by the dynamic pyrolysis furnace and the gas subjected to the first-step cyclone dust removal are subjected to electrostatic deep dust removal through a dust remover, a small amount of collected mixed materials are returned to the dynamic pyrolysis furnace for pyrolysis, and the gas subjected to dust removal is fully mixed in an induced draft fan. Wherein 80 percent of the aluminum nitrate is sent to a heating device to be heated to 550 ℃ and then sent to an atomization pyrolysis furnace for low-temperature pyrolysis of the aluminum nitrate. The rest gas is sent to a nitric acid absorption and regeneration device to obtain regenerated nitric acid, and the concentration of the nitric acid is 50 percent.
The SEM microscopic scanning electron micrograph of the obtained basic magnesium nitrate is shown in FIG. 3, wherein FIG. 3 (a) is an enlargement 10 5 Magnification, FIG. 3 (b) is a 2X 10 magnification 5 And (4) multiplying. It can be seen that the particles are spherical and therefore the product has very good flowability.
Example 5
Firstly, adding ferric nitrate into a heating and melting device, heating to 120 ℃ to melt the ferric nitrate, and atomizing the ferric nitrate by a pressure atomizer and feeding the ferric nitrate into an atomizing pyrolysis furnace, wherein the temperature in the atomizing pyrolysis furnace is 400 ℃. Carrying out rapid low-temperature thermal decomposition on ferric nitrate in an atomization pyrolysis furnace to obtain an alkali-containing ferric nitrate precursor and H 2 O、HNO 3 The mixed dust gas is dedusted by a cyclone dust collector to obtain the basic ferric nitrate, and the particle size is 250 mu m. Then the basic ferric nitrate is sent to a dynamic pyrolysis furnace (external heating tunnel kiln) and calcined for 1.5h at the temperature of 350 ℃ to obtain the gamma-ferric oxide, and the decomposition rate is more than 99%. After the gas decomposed by the dynamic pyrolysis furnace and the gas subjected to the first-step cyclone dust removal are subjected to electrostatic deep dust removal through a dust remover, a small amount of collected mixed materials are returned to the dynamic pyrolysis furnace for pyrolysis, and the gas subjected to dust removal is fully mixed in an induced draft fan. Wherein 90 percent of the aluminum nitrate is sent to a heating device to be heated to 450 ℃ and then sent to an atomization pyrolysis furnace to be used for low-temperature pyrolysis of the aluminum nitrate. The rest gas is sent to a nitric acid absorption and regeneration device to obtain regenerated nitric acid, and the concentration of the nitric acid is 58 percent.
Comparative example 1
The comprehensive operation cost of the single atomization pyrolysis process and the multi-step pyrolysis process is calculated by taking 1 ton of aluminum nitrate nonahydrate as an example, and the result is shown in Table 2 (the operation cost is reduced by 2.5 yuan/Nm) 3 The natural gas is used as a fuel gas,the calorific value is 8000 kcal/Nm 3 . The single atomization pyrolysis process adopts a nitrate pyrolysis nitric acid recovery device in CN109721038A, compared with the embodiment 1 of the utility model).
TABLE 2
| Energy consumption of atomization pyrolysis | Calcination pyrolysis energy consumption | Total energy consumption | Operating costs | |
| Single atomization pyrolysis process | 187 ten thousand big cards | 0 | 187 ten thousand big cards | 562.5 yuan |
| Multi-step pyrolysis process | 92 ten thousand |
33 ten thousand cards | 125 ten thousand cards | 390.6 membered |
The calculation shows that the pyrolysis cost of aluminum nitrate per ton is reduced from 562.5 yuan to 390.6 yuan, and the operation cost is reduced by 30%. The difference in operating costs for both processes is further magnified if throughput is increased.
The foregoing is a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of improvements and decorations can be made without departing from the principle of the present invention, and these improvements and decorations should also be regarded as the protection scope of the present invention.
Claims (7)
1. A system for preparing metal oxide powder by stepwise pyrolysis of nitrate and regenerating nitric acid is characterized by comprising a heating and melting device, an atomization pyrolysis furnace, a cyclone dust collector, a dynamic pyrolysis furnace, a dust collector, an induced draft fan, a heating device and a nitric acid absorption and regeneration device, wherein,
the heating and melting device is used as a nitrate carrier to be treated and is used for heating nitrate to a molten state;
the discharge port of the heating and melting device is connected with the feed port of the atomization pyrolysis furnace, and the atomization pyrolysis furnace is provided with an atomization nozzle and is used for atomizing nitrate and pyrolyzing the nitrate at a certain temperature in the atomization pyrolysis furnace to generate basic nitrate precursor;
the discharge hole of the atomization pyrolysis furnace is connected with the feed hole of a cyclone dust collector, and the cyclone dust collector is used for carrying out gas-solid separation on the output material of the atomization pyrolysis furnace to obtain solid-phase discharge and dust removal tail gas;
the solid-phase discharge port of the cyclone dust collector is connected with the feed port of the dynamic pyrolysis furnace, and the dynamic pyrolysis furnace is used for calcining the basic nitrate output from the atomization pyrolysis furnace at a certain temperature for a long time to obtain metal oxide which is decomposed thoroughly, and outputting the metal oxide from the solid-phase discharge port of the dynamic pyrolysis furnace;
the gas phase outlet of the cyclone dust collector is combined with the gas phase outlet of the dynamic pyrolysis furnace and then connected with the feed inlet of the dust collector, and the dust collector is used for combining the dust-removing tail gas of the cyclone dust collector with the tail gas of the dynamic pyrolysis furnace and then carrying out deep dust removal to obtain deep dust-removed gas;
the inlet of the induced draft fan is connected with the gas phase outlet of the dust remover, the outlet of the induced draft fan is respectively connected with the inlet of the heating device and the inlet of the nitric acid absorption and regeneration device, and the induced draft fan is used for fully mixing the deeply dedusted gas and respectively sending the deeply dedusted gas to the nitric acid absorption and regeneration device and the heating device;
an inlet of the heating device is connected with an outlet of the induced draft fan, an outlet of the heating device is connected with a feed inlet of the atomization pyrolysis furnace, and the heating device is used for heating a part of dedusted gas, then sending the heated gas to the atomization pyrolysis furnace and supplying heat required by pyrolysis;
the inlet of the nitric acid absorption and regeneration device is connected with the outlet of the induced draft fan, and the nitric acid absorption and regeneration device is used for pressurizing and absorbing part of dedusted gas to obtain regenerated nitric acid.
2. The system for preparing metal oxide powder and regenerating nitric acid through fractional pyrolysis of nitrate according to claim 1, wherein a solid-phase discharge port of the cyclone dust collector is combined with a solid-phase discharge port of the dust collector and then connected with a feed port of the dynamic pyrolysis furnace.
3. The system for preparing metal oxide powder through fractional pyrolysis of nitrate and regenerating nitric acid as claimed in claim 1, wherein: and a jacket layer and a coil are arranged outside the heating and melting device.
4. The system for preparing metal oxide powder through fractional pyrolysis of nitrate and regenerating nitric acid as claimed in claim 1, wherein: the atomization pyrolysis furnace is one of two-fluid spray atomization pyrolysis furnace, pressure type atomization pyrolysis furnace, two-fluid atomization pyrolysis furnace and rotary centrifugal atomization pyrolysis furnace or a combination of at least two of the two.
5. The system for preparing metal oxide powder by fractional pyrolysis of nitrate and regenerating nitric acid according to claim 1, wherein: the dynamic pyrolysis furnace is of various types of rotary kilns and tunnel kilns.
6. The system for preparing metal oxide powder through fractional pyrolysis of nitrate and regenerating nitric acid as claimed in claim 1, wherein: the bottom of the dynamic pyrolysis furnace is provided with a slag discharge port for discharging metal oxide powder generated by pyrolysis.
7. The system for preparing metal oxide powder by fractional pyrolysis of nitrate and regenerating nitric acid according to claim 1, wherein: the dust remover is one of a cyclone dust remover, an electrostatic dust remover, a high-temperature metal film dust remover, a porous ceramic dust remover and a high-temperature metal wire dust remover or a combination of at least two of the cyclone dust remover, the electrostatic dust remover, the high-temperature metal film dust remover, the porous ceramic dust remover and the high-temperature metal wire dust remover.
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| CN115490249B (en) * | 2022-08-17 | 2023-09-29 | 四川顺应动力电池材料有限公司 | Method and system for preparing metal oxide powder and regenerating nitric acid by fractional pyrolysis of nitrate |
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