CN212581525U - Device system for recovering nitric acid through thermal decomposition of nitrate - Google Patents
Device system for recovering nitric acid through thermal decomposition of nitrate Download PDFInfo
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- CN212581525U CN212581525U CN202021711940.9U CN202021711940U CN212581525U CN 212581525 U CN212581525 U CN 212581525U CN 202021711940 U CN202021711940 U CN 202021711940U CN 212581525 U CN212581525 U CN 212581525U
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Abstract
The utility model relates to a device system for recovering nitric acid by thermal decomposition of nitrate, which comprises a heating and melting tank, a pyrolysis furnace, an atomizer, a dust collector, a fan, a tail gas heat exchanger and a nitric acid absorption device; the heating and melting tank is used for heating and melting nitrate to obtain a nitrate thermal fluid; the pyrolysis furnace is used for decomposing nitrate hot fluid from the heating melting tank; decomposing the mixed gas, and separating dust entrained in the mixed gas; cooling and conveying the mixture to a nitric acid absorption device; the pyrolysis furnace is divided into an inner shell and an outer shell, and the inner shell forms a decomposition channel of the pyrolysis furnace; and a heating body is arranged between the inner shell and the outer shell, and the heating body is a resistance wire, a microwave magnetron or a radiant heating pipe. The device system can effectively reduce the heating cost, simultaneously simplify the whole process of recovering the nitric acid by thermal decomposition, has strong controllability, and simultaneously, the prepared metal oxide has uniform particle size.
Description
Technical Field
The utility model relates to an inorganic chemical industry resource recovery processing technology field, concretely relates to device system for nitric acid is retrieved in nitrate thermal decomposition.
Background
Most of metal nitrates can be decomposed into metal oxides, nitrogen dioxide and oxygen under heated conditions, the released oxygen and nitrogen dioxide can be absorbed by water under certain conditions to generate nitric acid, the metal oxides can also be recycled in the fields of nonferrous metal hydrometallurgy and other chemical industries, the low-cost production process is realized, and the mode of recovering the nitric acid and the metal oxides by thermal decomposition of the metal nitrates draws more and more attention.
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 device2、NO2And metal oxide powder, O obtained2、NO2The 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 whole system keeps sealed and positive pressure, so that nitrate is fully pyrolyzed in the rotary kiln, and the generated gas is absorbed by liquid in the absorption tower to prepare nitric acid solution. However, the nitrate decomposition requires a high temperature, and if the nitrate is directly conveyed into a rotary kiln for heating decomposition, the nitrate is heated unevenly, and the decomposition is insufficient. Therefore, the operation energy consumption of the system is high, and the recovery rate of nitric acid in nitrate is not high.
Chinese patent CN109721038A discloses a method for recovering nitric acid by pyrolyzing nitrate, which is to convey nitrate into at least two stages of preheating devices for 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 from the solid powder, conveying one part of the mixed gas to a nitric acid recovery tank, heating the other part of the mixed gas to 800 ℃, and then refluxing the mixed gas to the decomposer for heating the nitrate thermal fluid to efficiently decompose the nitrate thermal fluid by heating. However, the method has some disadvantages that firstly, the high-temperature gas used by the method needs additional equipment for heating, and the operation cost is high due to large heat loss in the heating process; secondly, the whole production flow is complicated by additional heating equipment, the manual control difficulty is high, and the operability is poor; finally, the high-temperature gas is utilized to decompose the nitrate, and the influence of dynamic gas flow or device switching can cause the prepared metal oxide particles to be uneven, and the sale price to be greatly reduced.
Disclosure of Invention
The utility model aims to provide a: aiming at the technical problems of low utilization rate of uneven heating of nitrate, high heating cost, complex flow, poor operability, uneven metal oxide particles and the like in the process of recovering nitric acid by thermal decomposition of nitrate in the prior art, the device system for recovering nitric acid by thermal decomposition of nitrate is provided. The device system can effectively reduce the heating cost, simultaneously simplify the whole process of recovering the nitric acid by thermal decomposition, has strong controllability, and simultaneously, the prepared metal oxide has uniform particle size.
In order to realize the purpose, the utility model discloses a technical scheme be:
a device system for recovering nitric acid by thermal decomposition of nitrate comprises a heating and melting tank, a pyrolysis furnace, an atomizer, a dust collector, a fan, a tail gas heat exchanger and a nitric acid absorption device;
a discharge hole of the heating and melting tank is connected to a feed hole at the top end of the pyrolysis furnace, and a discharge hole in the middle of the pyrolysis furnace is connected to a feed hole on the side surface of the dust collector; an exhaust port at the top end of the dust collector is connected to an air inlet of a tail gas heat exchanger through a fan, and an exhaust port of the tail gas heat exchanger is connected to a nitric acid absorption device;
the pyrolysis furnace comprises an inner shell and an outer shell, wherein the inner shell is nested in the outer shell, and the inner shell surrounds a decomposition channel of the pyrolysis furnace; a closed heat source space is formed between the inner shell and the outer shell; a heating body is arranged in the heat source space; the heating body is a resistance wire, a microwave magnetron or a radiation heating pipe;
the top of the pyrolysis furnace is provided with an atomizer, and the atomizer is used for spraying nitrate hot fluid input from a top feed inlet of the pyrolysis furnace into a decomposition channel of the pyrolysis furnace;
the utility model provides a device system for recovering nitric acid by thermal decomposition of nitrate, which comprises a heating and melting tank, a pyrolysis furnace, an atomizer, a dust collector, a fan, a tail gas heat exchanger and a nitric acid absorption device, wherein the heating and melting tank is used for heating and melting nitrate to obtain nitrate hot fluid; the pyrolysis furnace is used for decomposing nitrate hot fluid from the heating melting tank; the dust collector is used for receiving decomposed mixed gas discharged by the pyrolysis furnace and separating dust carried in the mixed gas; and the tail gas heat exchanger is used for receiving the mixed gas which is discharged by the dust collector and subjected to dust separation, cooling and conveying the mixed gas to a nitric acid absorption device for nitric acid recovery.
Wherein, the heating melting jar is earlier to metal nitrate heating melting, then spout into the pyrolysis oven with the mode of hot-fluid, simultaneously, the utility model provides a pyrolysis oven, its inner shell constitutes the pyrolysis passageway, is provided with heating element between inner shell and the shell, and forms inclosed heat source space, what the pyrolysis oven adopted is that intermediate layer formula self-heating mode, spouts the pyrolysis passageway of this pyrolysis oven with the metal nitrate hot-fluid for nitric acid can abundant pyrolysis, can not receive the influence of air current at the pyrolysis in-process, also can not have heating device to switch, the particle size distribution of the metal aluminium oxide of preparation is even, and the quality improves greatly. And simultaneously, the utility model discloses a pyrolysis oven need not extra external natural gas heating system, need not to utilize circulation high temperature gas heating, through the selection to pyrolysis oven shell material, the adjustment of thickness and arranging of heating member for there is not great heat loss in whole heating process, and heat cost greatly reduced does not have extra firing equipment and makes whole production flow simplification, more is favorable to manual control, and maneuverability improves greatly.
As a preferable scheme of the utility model, the heating and melting tank is used for heating and melting the nitrate to obtain a nitrate hot fluid; the pyrolysis furnace is used for decomposing nitrate hot fluid from the heating melting tank; the dust collector is used for receiving decomposed mixed gas discharged by the pyrolysis furnace and separating dust carried in the mixed gas; and the tail gas heat exchanger is used for receiving the mixed gas which is discharged by the dust collector and subjected to dust separation, cooling and conveying the mixed gas into the nitric acid absorption device.
As the preferred proposal of the utility model, a stirring device is arranged in the heating and melting tank. The metal nitrate can further accelerate the melting efficiency through the stirring of the stirring device in the heating and melting process.
As the preferred scheme of the utility model, the shell is a structural member made of heat-insulating refractory materials. As a preferable scheme of the utility model, the heat-insulating refractory material is one or more of alumina, magnesia and silica.
As a preferable aspect of the present invention, the thickness of the housing is at least 20 cm. Researches show that when the thickness of the shell is less than 20cm, the heat preservation effect of the shell is poor, and unnecessary waste is caused by heat.
As a preferable proposal of the utility model, the thickness of the shell is 20 cm-50 cm. The main effect of shell is used for keeping warm fire-resistant, and is different according to the handling capacity of equipment, and the thickness of shell can suitably be adjusted, and utility model people discovers, and in practical application, according to the consideration in aspects such as calorific loss condition, material cost, heat cost, bearing, the thickness setting of shell is suitable and practical relatively at 20cm ~ 50 cm. Preferably, the thickness of the shell is 30 cm-40 cm.
As a preferable scheme of the present invention, the inner shell is a structural member made of stainless steel or alloy steel material.
As the preferred scheme of the utility model, the inner shell is stainless steel with high temperature resistant effect, and the high temperature is 200 ℃ -1000 ℃.
As the preferable proposal of the utility model, the thickness of the inner shell is 1 mm-10 mm. The main effect of inner shell is used for heat-resisting, the sparse heat, and interior thickness undersize can not guarantee the quality of inner shell under the high temperature condition, and the thickness of inner shell too big can cause the thermal effect of sparse not good, can not reach good mating reaction with the heat preservation of shell, causes calorific loss easily. Utility model people discover, in practical application, according to the consideration in aspects such as calorific loss condition, material cost, heat cost, bearing, the thickness setting of inner shell is better at 1mm ~ 10 mm. Preferably, in the pyrolysis furnace, the thickness of the outer shell is 4mm to 8 mm.
As the preferred scheme of the utility model, the heating member evenly distributed in the heat source space.
As the preferred scheme of the utility model, be provided with temperature-sensing ware in the decomposition passageway in the pyrolysis oven, temperature-sensing ware is arranged in detecting the temperature in the decomposition passageway. As the preferred scheme of the utility model, still be provided with cooling element in the heat source space, cooling element is connected with the single-machine piece, the single-machine piece still is connected the temperature-sensing ware. The single chip is used for receiving the temperature information transmitted by the temperature sensor and controlling the heating body and the cooling body according to the temperature so as to adjust the temperature of the decomposition channel. The device system can accurately adjust the temperature in the decomposition channel, promote the decomposition rate and simultaneously produce metal oxides of different crystal forms according to the adjustment of the temperature.
As a preferable embodiment of the present invention, the nitrate is one or more of magnesium nitrate, aluminum nitrate, zinc nitrate, iron nitrate, tin nitrate, lead nitrate, and copper nitrate. According to research, nitrates such as aluminum nitrate, magnesium nitrate, ferric nitrate, zinc nitrate and the like are found to generate oxides with higher activity when heated. The reason is that nitrogen oxide, oxygen and other gases are generated when nitrate is antipyretic and decomposed, and the oxide surface is promoted to form a porous structure, so that the oxide has a large specific surface area and activity. The decomposition temperature has great influence on the properties of the product, and oxides with different crystal forms can be obtained by controlling the decomposition temperature. Such as decomposition of ferric nitrate, at lower temperatures, magnetic iron oxides, i.e., gamma-Fe, may be formed2O3When the temperature is increased, more stable alpha-Fe can be generated2O3。
As the preferred scheme of the utility model, the bottom of pyrolysis furnace is provided with first cinder notch for discharge the solid powder that produces when metal nitrate thermal decomposition.
As the preferred scheme of the utility model, the bottom of dust collector is provided with the second and arranges the cinder notch for discharge the solid powder of dust collector separation.
As the preferred scheme of the utility model, be provided with devices such as compressor, nitric acid absorbing device, tail gas heat exchanger, nitric acid system, waste heat utilization system of starting to work among the nitric acid absorbing device.
Further, the use method of the device system for recovering the nitric acid by the thermal decomposition of the nitrate comprises the following steps:
step 1, heating metal nitrate in a heating melting tank to form metal nitrate hot fluid;
2, conveying the metal nitrate thermal fluid obtained in the step 1 to a top feed inlet of a pyrolysis furnace, and spraying the metal nitrate thermal fluid into a decomposition channel of the pyrolysis furnace through an atomizer for thermal decomposition to obtain metal oxide powder and mixed gas; conveying the mixed gas with the metal oxide powder obtained by decomposition in the pyrolysis furnace to a dust collector;
and 3, separating solid and gas by using a dust collector, sending the gas into a tail gas heat exchanger through a fan for heat exchange and cooling, and then conveying the cooled gas into a nitric acid absorption device for absorption reaction to obtain nitric acid.
The method for recovering nitric acid by thermal decomposition of nitrate has the advantages of simple process and relatively simplified device, the gas after dust collection is cooled to an acid making system to prepare nitric acid, the nitric oxide tail gas is changed into valuable, and the comprehensive economic index of the system is improved. In the pyrolysis process of the method, the particle size distribution of the prepared metal alumina is uniform, the quality is greatly improved, and metal oxide powder with different particle sizes, activities and crystal forms can be obtained by controlling the temperature through controlling the spraying amount and the constant temperature of the pyrolysis furnace.
Further, in the step 1, the temperature in the heating and melting tank is the melting point temperature of the metal nitrate. Further, in the step 1, the temperature of the heating and melting tank is 50 ℃ to 300 ℃.
Further, in the step 2, the pressure in the pyrolysis furnace is-0.01 to-0.1 MPa. When the pyrolysis furnace is used for pyrolysis operation, the pressure in the furnace is interlocked with the rotating speed of a fan in the dust collector in a variable frequency manner, and the nitrogen oxide gas can be prevented from leaking by keeping a micro-negative pressure state.
Furthermore, the dust collector adopts one or more of electrostatic dust collection, high-temperature cloth bag dust collection, high-temperature metal film dust collection, cyclone dust collection and gravity settling dust collection.
To sum up, owing to adopted above-mentioned technical scheme, the beneficial effects of the utility model are that:
1. the utility model provides a device system of nitric acid is retrieved in thermal decomposition of nitrate, including heating melting jar, pyrolysis oven, atomizer, dust collector, fan, tail gas heat exchanger, nitric acid absorbing device, heating melting jar can heat the nitrate and melt, later utilizes the atomizer to spout and carries out the pyrolysis in the pyrolysis oven, and the metal oxide that the pyrolysis obtained and mist carry out gas-solid separation through the dust collector, then utilize the fan to carry and carry out the nitric acid recovery in letting in nitric acid absorbing device after the heat transfer of tail gas heat exchanger. Heating melting jar is earlier to metal nitrate heating melting, then spout into the pyrolysis oven with the mode of hot-fluid, the utility model provides a pyrolysis oven, its inner shell constitutes the pyrolysis passageway, is provided with heating element between inner shell and the shell, and forms inclosed heat source space, what the pyrolysis oven adopted is that the intermediate layer formula is from the heating mode for nitric acid can abundant pyrolysis, and nitric acid recycle rate can reach more than 99.5%.
2. The utility model discloses a pyrolysis oven need not extra external natural gas heating system, through the selection to pyrolysis oven shell material, the adjustment of thickness and arranging of heating member, need not to utilize the heating of circulation high temperature gas for there is not great heat loss in whole heating process, thermal cost greatly reduced decomposes the thermal cost of per ton aluminium nitrate and only controls for 350 yuan.
3. The utility model discloses the device system does not have extra firing equipment to make whole production flow simple in the heating process, more is favorable to manual control, and maneuverability improves greatly.
4. The utility model discloses the device system can not receive the influence of air current at the pyrolysis in-process, also can not have the heating device to switch, can not only make the particle size distribution of the metallic alumina of preparation even through the control of the constant temperature who spouts material volume and pyrolysis oven among the pyrolysis process, and the quality improves greatly, can obtain the metallic oxide powder of different particle diameters, activity, crystal form moreover through control temperature.
Drawings
FIG. 1 is a schematic structural diagram of a device system for recovering nitric acid by thermal decomposition of nitrate.
Icon: 1-heating and melting tank; 2-a pyrolysis furnace; 3-an atomizer; 4-a dust collector; 5, a fan; 6-tail gas heat exchanger; a 7-nitric acid absorption device; 8-inner shell; 9-a housing; 10-heating body.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the invention.
Example 1
As shown in fig. 1, a device for recovering nitric acid by thermal decomposition of nitrate comprises a heating and melting tank 1, a pyrolysis furnace 2, an atomizer 3, a dust collector 4, a fan 5, a tail gas heat exchanger 6 and a nitric acid absorption device 7;
a discharge hole of the heating and melting tank 1 is connected to a feed hole at the top end of the pyrolysis furnace 2, and a discharge hole in the middle of the pyrolysis furnace 2 is connected to a side feed hole of the dust collector 4; an exhaust port at the top end of the dust collector 4 is connected to an air inlet of a tail gas heat exchanger 6 through a fan 5, and an exhaust port of the tail gas heat exchanger 6 is connected to a nitric acid absorption device 7;
an atomizer 3 is arranged at the top of the pyrolysis furnace 2, and the atomizer 3 is used for spraying nitrate thermal fluid into the pyrolysis furnace 2; wherein the pyrolysis furnace 2 is divided into an inner shell 8 and an outer shell 9, and the inner shell 8 forms a decomposition channel of the pyrolysis furnace 2; and a resistance wire heating body 10 is arranged between the inner shell 8 and the outer shell 9, and the resistance wires are uniformly distributed outside the inner shell 8. The outer shell 9 is made of an alumina material and has a thickness of 50cm, and the inner shell 8 is made of stainless steel and has a thickness of 8 mm.
The bottom of the pyrolysis furnace 2 is provided with a first slag discharge port for discharging solid powder generated in the thermal decomposition of the metal nitrate. And a second slag discharge port is formed in the bottom of the dust collector 4 and used for discharging the solid powder after dust collection. A stirring device is arranged in the heating and melting tank 1. The metal nitrate can further accelerate the melting efficiency through the stirring of the stirring device in the heating and melting process.
Heating ferric nitrate hydrate to 90 ℃ in a heating and melting tank 1 to melt the ferric nitrate hydrate, and then adding the ferric nitrate melt to pyrolysisThe furnace 2 is heated and pyrolyzed, the heating mode is resistance wire indirect heating, and the temperature in the decomposing channel of the pyrolyzing furnace 2 is controlled to be 330 ℃; conveying the mixed gas carrying the metal oxide powder in the pyrolysis furnace 2 to a dust collector 4; fe obtained2O3The crystal form of the gas is gamma-shaped, the granularity is 3.0 mu m, the particle size is uniform, the gas after dust collection is cooled by a tail gas heat exchanger 6, and then the cooled gas is conveyed to a nitric acid absorption device 7. The heat cost for decomposing each ton of ferric nitrate is 360 yuan, the concentration of the obtained nitric acid is 48.2 percent, and the decomposition rate of the ferric nitrate is 98 percent.
Example 2
Heating ferric nitrate hydrate to 90 ℃ in a heating and melting tank 1 by using the same device system as in the embodiment 1 to melt the ferric nitrate hydrate, adding the ferric nitrate melt into a pyrolysis furnace 2 for heating and pyrolysis, wherein the heating mode is resistance wire indirect heating, and the temperature in a decomposition channel of the pyrolysis furnace 2 is controlled to be 550 ℃; conveying the mixed gas carrying the metal oxide powder in the pyrolysis furnace 2 to a dust collector 4; fe obtained2O3The crystal form of the gas is a mixture of gamma type and alpha type, the granularity is 7.2 mu m, the uniformity is good, the gas after dust collection is cooled by a tail gas heat exchanger 6, and then the cooled gas is conveyed to a nitric acid absorption device 7. The calculated heat cost for decomposing each ton of ferric nitrate is 610 yuan, the concentration of the obtained nitric acid is 48.7 percent, and the decomposition rate of the ferric nitrate is 98.9 percent.
Example 3
Heating ferric nitrate hydrate to 90 ℃ in a heating and melting tank 1 to melt the ferric nitrate hydrate, then adding the ferric nitrate melt into a pyrolysis furnace 2 for heating and pyrolysis, wherein the heating mode is resistance wire indirect heating, and the temperature in a decomposition channel of the pyrolysis furnace 2 is controlled to be 600 ℃; conveying the mixed gas carrying the metal oxide powder in the pyrolysis furnace 2 to a dust collector 4; fe obtained2O3The crystal form of the gas is alpha type, the granularity is 9.8 mu m, the particle size is uniform, the gas after dust collection is cooled by a tail gas heat exchanger 6, and then the cooled gas is conveyed to a nitric acid absorption device 7. The calculated heat cost for decomposing each ton of ferric nitrate is 680 yuan, and the concentration of the obtained nitric acid is 49.7 percentThe decomposition rate of ferric nitrate was 99.9%.
Example 4
As shown in fig. 1, a device for recovering nitric acid by thermal decomposition of nitrate comprises a heating and melting tank 1, a pyrolysis furnace 2, an atomizer 3, a dust collector 4, a fan 5, a tail gas heat exchanger 6 and a nitric acid absorption device 7;
a discharge hole of the heating and melting tank 1 is connected to a feed hole at the top end of the pyrolysis furnace 2, and a discharge hole in the middle of the pyrolysis furnace 2 is connected to a side feed hole of the dust collector 4; an exhaust port at the top end of the dust collector 4 is connected to an air inlet of a tail gas heat exchanger 6 through a fan 5, and an exhaust port of the tail gas heat exchanger 6 is connected to a nitric acid absorption device 7;
an atomizer 3 is arranged at the top of the pyrolysis furnace 2, and the atomizer 3 is used for spraying nitrate thermal fluid into the pyrolysis furnace 2; wherein the pyrolysis furnace 2 is divided into an inner shell 8 and an outer shell 9, and the inner shell 8 forms a decomposition channel of the pyrolysis furnace 2; microwave magnetrons are arranged between the inner shell 8 and the outer shell 9 and are uniformly distributed outside the inner shell 8. The outer shell 9 is made of an alumina material and has a thickness of 30cm, and the inner shell 8 is made of stainless steel and has a thickness of 3 mm.
The bottom of the pyrolysis furnace 2 is provided with a first slag discharge port for discharging solid powder generated in the thermal decomposition of the metal nitrate. And a second slag discharge port is formed in the bottom of the dust collector 4 and used for discharging the solid powder after dust collection. A stirring device is arranged in the heating and melting tank 1. The metal nitrate can further accelerate the melting efficiency through the stirring of the stirring device in the heating and melting process.
Heating zinc nitrate hydrate to 100 ℃ in a heating and melting tank 1 to melt the zinc nitrate hydrate, then adding the zinc nitrate melt into a pyrolysis furnace 2 for heating and pyrolysis, wherein the adopted heating mode is microwave heating, and the temperature in a decomposition channel of the pyrolysis furnace 2 is controlled to be 350 ℃. Conveying the mixed gas carrying the metal oxide powder in the pyrolysis furnace 2 to a dust collector 4; the obtained ZnO has the particle size of 3.5 mu m and uniform particle size, the gas after dust collection is cooled to an acid making system, the heat cost for decomposing zinc nitrate per ton is 370 yuan by calculation, the concentration of the obtained nitric acid is 45.4 percent, and the decomposition rate of the zinc nitrate is 91 percent.
Example 5
The same apparatus system as in example 4 was used to heat zinc nitrate hydrate to 100 ℃ in the heating and melting tank 1 to melt it, and then the zinc nitrate melt was added to the pyrolysis furnace 2 for pyrolysis by microwave heating, and the temperature in the decomposition path of the pyrolysis furnace 2 was controlled to 400 ℃. Conveying the mixed gas carrying the metal oxide powder in the pyrolysis furnace 2 to a dust collector 4; the obtained ZnO has the particle size of 4.7 mu m and uniform particle size, the gas after dust collection is cooled to an acid making system, the heat cost for decomposing zinc nitrate per ton is 440 yuan through calculation, the concentration of the obtained nitric acid is 48.4 percent, and the decomposition rate of the zinc nitrate is 98.9 percent.
Example 6
As shown in fig. 1, a device for recovering nitric acid by thermal decomposition of nitrate comprises a heating and melting tank 1, a pyrolysis furnace 2, an atomizer 3, a dust collector 4, a fan 5, a tail gas heat exchanger 6 and a nitric acid absorption device 7;
a discharge hole of the heating and melting tank 1 is connected to a feed hole at the top end of the pyrolysis furnace 2, and a discharge hole in the middle of the pyrolysis furnace 2 is connected to a side feed hole of the dust collector 4; an exhaust port at the top end of the dust collector 4 is connected to an air inlet of a tail gas heat exchanger 6 through a fan 5, and an exhaust port of the tail gas heat exchanger 6 is connected to a nitric acid absorption device 7;
an atomizer 3 is arranged at the top of the pyrolysis furnace 2, and the atomizer 3 is used for spraying nitrate thermal fluid into the pyrolysis furnace 2; wherein the pyrolysis furnace 2 is divided into an inner shell 8 and an outer shell 9, and the inner shell 8 forms a decomposition channel of the pyrolysis furnace 2; electric radiant tube heating elements are arranged between the inner shell 8 and the outer shell 9, and the electric radiant tubes are uniformly distributed outside the inner shell 8. The outer shell 9 is made of a magnesium oxide material and has a thickness of 20cm, and the inner shell 8 is made of an alloy steel material and has a thickness of 1 mm.
The bottom of the pyrolysis furnace 2 is provided with a first slag discharge port for discharging solid powder generated in the thermal decomposition of the metal nitrate. And a second slag discharge port is formed in the bottom of the dust collector 4 and used for discharging the solid powder after dust collection. A stirring device is arranged in the heating and melting tank 1. The metal nitrate can further accelerate the melting efficiency through the stirring of the stirring device in the heating and melting process.
Heating copper nitrate hydrate to 110 ℃ in a heating and melting tank 1 to melt the copper nitrate hydrate, then adding the copper nitrate melt into a pyrolysis furnace 2 for heating and pyrolysis, wherein the adopted heating mode is electric radiation heating, and the temperature in a decomposition channel of the pyrolysis furnace 2 is controlled to be 200 ℃; the mixed gas in which the metal oxide powder is entrained in the pyrolysis furnace 2 is sent to a dust collector 4. The particle size of the obtained CuO is 2.7 mu m, the particle size is uniform, the gas after dust collection is cooled by a tail gas heat exchanger, and then the cooled gas is conveyed to a nitric acid absorption device 7. The calculated heat cost for decomposing each ton of copper nitrate is 240 yuan, the concentration of the obtained nitric acid is 46.3 percent, and the decomposition rate of the copper nitrate is 97.6 percent.
Example 7
Heating the copper nitrate hydrate in the heating and melting tank 1 to 110 ℃ by using the same device system as in the embodiment 6 to melt the copper nitrate hydrate, adding the copper nitrate melt into the pyrolysis furnace 2 for heating and pyrolysis, wherein the heating mode is electric radiation heating, and the temperature in a decomposition channel of the pyrolysis furnace 2 is controlled to be 250 ℃; the mixed gas in which the metal oxide powder is entrained in the pyrolysis furnace 2 is sent to a dust collector 4. The particle size of the obtained CuO is 3.5 μm, the particle size is uniform, the gas after dust collection is cooled by a tail gas heat exchanger, and then the cooled gas is conveyed to a nitric acid absorption device 7. The calculated heat cost for decomposing each ton of copper nitrate is 290 yuan, the concentration of the obtained nitric acid is 48.3 percent, and the decomposition rate of the copper nitrate is 99.5 percent.
Example 8
Heating aluminum nitrate hydrate to 100 ℃ in a heating and melting tank 1 by using the same device system as in the embodiment 6 to melt the aluminum nitrate hydrate, adding the aluminum nitrate melt into a pyrolysis furnace 2 for heating and pyrolysis, wherein the heating mode is electric radiation heating, and the temperature in a decomposition channel of the pyrolysis furnace 2 is controlled to be 450 ℃; the mixed gas in which the metal oxide powder is entrained in the pyrolysis furnace 2 is sent to a dust collector 4. The obtained alumina had a particle size of 3.5 μm and a uniform particle diameter, and the dust-collected gas was cooled by a tail gas heat exchanger, and then the cooled gas was sent to a nitric acid absorption apparatus 7. The calculation shows that the thermal cost for decomposing each ton of aluminum nitrate is 350 yuan, the concentration of the obtained nitric acid is 48.5 percent, and the decomposition rate of the aluminum nitrate is 99.3 percent.
Comparative example 1
The nitric acid is recycled according to the method for preparing the nitric acid by pyrolyzing the metal nitrate disclosed in the Chinese patent CN 108862218A. The same starting material used in example 8 was aluminum nitrate and was pyrolysed in a rotary kiln to produce oxygen, nitrogen dioxide and metal oxide powder. After the device system for recovering nitric acid by pyrolyzing aluminum nitrate runs for a period of time, the aluminum nitrate in the rotary kiln is not decomposed sufficiently due to non-uniform temperature, the recovery rate of the aluminum nitrate is only 64.7%, and the produced particle size is non-uniform. And the rotary kiln needs to be regularly maintained and treated, so that the operation efficiency of the nitrate recovery system is influenced. And the rotary kiln is maintained in a severe working environment and has high working difficulty, and the inner wall of the rotary kiln is easy to damage, so that the cost for recovering the nitric acid is increased.
Comparative example 2
According to the method for recovering nitric acid by pyrolyzing nitrate disclosed in Chinese patent CN109721038A, aluminum nitrate is conveyed into at least two stages of preheating devices for heating and liquefying. And then conveying the aluminum nitrate hot fluid into the decomposer, and heating by using high-temperature gas to decompose the nitrate to generate mixed gas and solid powder. And separating the mixed gas from the solid powder, conveying one part of the mixed gas into a nitric acid absorption device 7, heating the other part of the mixed gas to 650 ℃, and then refluxing the mixed gas into the decomposer for heating the aluminum nitrate hot fluid to efficiently decompose the aluminum nitrate hot fluid by heating.
In the practical application process, the high-temperature gas used by the method needs additional equipment for heating, and has larger heat loss in the heating process, so that the operation cost is high, and the heat cost for decomposing each ton of aluminum nitrate can reach 850 yuan; secondly, the whole production flow is complicated by additional heating equipment, the manual control difficulty is high, and the operability is poor; the high-temperature gas is possibly influenced by dynamic gas flow or device switching in the nitrate decomposition process, so that the prepared alumina particles are uneven, and the sale price is greatly reduced.
The utility model discloses a single-stage preheating process and pyrolysis oven direct heating decomposition technology coordinate each other and promote, match each other, greatly reduced the heat cost, finally realize better nitrate thermal decomposition technological effect.
Comparative example 3
The enclosure 9 of the apparatus system in example 6 was set to a thickness of 15cm, and aluminum nitrate was recovered by thermal decomposition in the same manner as in example 8, and the thermal cost for decomposing each ton of aluminum nitrate was calculated to rise to 400 yuan.
Comparative example 4
In the same apparatus for recovering nitric acid by thermal decomposition of nitrate as in example 6 except for setting the housing 9 of the apparatus system in example 6 to a thickness of 10cm, aluminum nitrate was thermally decomposed and recovered in the same manner as in example 8, and the thermal cost for decomposing each ton of aluminum nitrate was calculated to rise to 460 yuan.
From the test results of comparative examples 3 and 4, it can be seen that the outer shell 9 of the pyrolysis furnace 2 has a heat-insulating effect, and the heat loss is caused by the excessively small thickness, and the heat cost for decomposing the metal nitrate is correspondingly increased.
The device system provided by the utility model utilizes the heating melting tank to heat and melt the metal nitrate, and then sprays the metal nitrate into the pyrolysis furnace in a hot fluid mode, the pyrolysis furnace adopts a sandwich type self-heating mode, and the combination of the hot fluid and the non-rotary kiln mode ensures that the nitric acid can be fully pyrolyzed, and the recovery rate of the nitric acid is increased; furthermore, the utility model discloses a pyrolysis oven need not extra external natural gas heating system, need not to utilize the heating of circulation high temperature gas, through the selection to pyrolysis oven shell material, the adjustment of thickness and arranging of heating member for there is not great heat loss in whole heating process, and heat cost greatly reduced does not have extra firing equipment and makes whole production flow simplification, more is favorable to manual control, and maneuverability improves greatly. The utility model discloses can not receive the influence of air current at the pyrolysis in-process, also can not have the heating device switching, the particle size distribution of the metallic alumina of preparation is even, and the quality improves greatly.
The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, as any modifications, equivalents, improvements and the like made within the spirit and principles of the present invention are intended to be included within the scope of the present invention.
Claims (9)
1. A device system for recovering nitric acid by thermal decomposition of nitrate is characterized by comprising a heating and melting tank (1), a pyrolysis furnace (2), an atomizer (3), a dust collector (4), a fan (5), a tail gas heat exchanger (6) and a nitric acid absorption device (7);
a discharge hole of the heating and melting tank (1) is connected to a feed hole at the top end of the pyrolysis furnace (2), and a discharge hole in the middle of the pyrolysis furnace (2) is connected to a feed hole on the side surface of the dust collector (4); an exhaust port at the top end of the dust collector (4) is connected to an air inlet of a tail gas heat exchanger (6) through a fan (5), and an exhaust port of the tail gas heat exchanger (6) is connected to a nitric acid absorption device (7);
the pyrolysis furnace (2) comprises an inner shell (8) and an outer shell (9), the inner shell (8) is nested in the outer shell (9), and the inner shell (8) encloses a decomposition channel of the pyrolysis furnace; a closed heat source space is formed between the inner shell (8) and the outer shell (9); a heating body (10) is arranged in the heat source space; the heating body (10) is a resistance wire, a microwave magnetron or a radiation heating pipe;
the atomizer (3) is arranged at the top of the pyrolysis furnace (2), and the atomizer (3) is used for spraying nitrate hot fluid input from a top end feed inlet of the pyrolysis furnace (2) into a decomposition channel of the pyrolysis furnace (2).
2. The plant for the thermal decomposition recovery of nitric acid according to claim 1, wherein said housing (9) is a structural member made of insulating refractory material; the heat-insulating refractory material is one or more of aluminum oxide, magnesium oxide and silicon oxide.
3. The apparatus for the thermal decomposition recovery of nitric acid of claim 1, wherein said inner shell (8) is a structural member made of stainless steel or alloy steel material.
4. Plant system for the thermal decomposition recovery of nitric acid according to claim 1, wherein said shell (9) has a thickness of at least 20 cm.
5. The apparatus for the thermal decomposition recovery of nitric acid of claim 1, wherein the thickness of said inner shell (8) is 1mm to 10 mm.
6. Device system for the thermal decomposition recovery of nitric acid from nitrates according to claim 1, characterized in that the heating bodies (10) are uniformly distributed in the heat source space.
7. The apparatus system for recovering nitric acid through thermal decomposition of nitrate according to claim 1, wherein the bottom of the pyrolysis furnace (2) is provided with a first slag discharge port for discharging solid powder generated during thermal decomposition of metal nitrate,
and/or the presence of a gas in the gas,
and a second slag discharge port is formed in the bottom of the dust collector (4) and used for discharging solid powder separated by the dust collector (4).
8. The apparatus for recovering nitric acid through thermal decomposition of nitrate according to any one of claims 1 to 7, wherein a temperature sensor is provided in the decomposition passage in the pyrolysis furnace (2) for detecting the temperature in the decomposition passage.
9. The apparatus system for recovering nitric acid through thermal decomposition of nitrate according to claim 8, wherein a cooling element is further disposed in the heat source space, and the cooling element is connected with a single chip, and the single chip is further connected with the temperature sensor.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111847405A (en) * | 2020-08-17 | 2020-10-30 | 眉山顺应动力电池材料有限公司 | Device system for recovering nitric acid through thermal decomposition of nitrate and use method thereof |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111847405A (en) * | 2020-08-17 | 2020-10-30 | 眉山顺应动力电池材料有限公司 | Device system for recovering nitric acid through thermal decomposition of nitrate and use method thereof |
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