CN112744792A - Method for preparing metal oxide powder and nitric acid by decomposing nitrate - Google Patents
Method for preparing metal oxide powder and nitric acid by decomposing nitrate Download PDFInfo
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Abstract
The invention discloses a method for preparing metal oxide powder and nitric acid by decomposing nitrate, belonging to the field of inorganic chemical industry. The method comprises the steps of firstly, pyrolyzing molten nitrate to generate high-temperature dust gas; collecting dust at high temperature to obtain metal oxide powder; one part of the gas after dust collection enters a nitric acid absorption system, and the other part of the gas is used as circulating gas; part of the circulating gas is mixed with the combustion-supporting gas to form oxygen-enriched combustion-supporting gas, the oxygen-enriched combustion-supporting gas is combusted with the combustion gas to release high-temperature fuel gas, the high-temperature fuel gas is mixed with the rest of the circulating gas to form high-temperature gas, and the high-temperature gas is circulated to the pyrolysis furnace for pyrolyzing nitrate melt again; the mixed gas entering the nitric acid absorption system is cooled by a waste heat boiler, then is subjected to multistage cooling and deep condensation to remove water, and is pressurized by a compressor to enter an absorption tower to prepare nitric acid; and the absorbed tail gas is subjected to carbon dioxide recovery to produce carbon dioxide. The method is simple and efficient, basically has no waste gas emission in the whole process, is green and environment-friendly, has strong operability and is easy to realize industrialization.
Description
Technical Field
The invention belongs to the field of inorganic chemical industry, relates to the technical field of preparing metal oxide by pyrolyzing nitrate, and particularly relates to a method for preparing metal oxide powder and nitric acid by quickly decomposing nitrate with high efficiency, energy conservation and environmental protection.
Background
The nitrate can be generated by the reaction of metal oxide and nitric acid, and common nitrate is potassium nitrate, sodium nitrate, calcium nitrate, magnesium nitrate, aluminum nitrate, zinc nitrate, ferric nitrate and the like. The nitrate has various kinds and properties, and is widely applied to the fields of fertilizer generation, catalyst synthesis, nano material preparation and the like.
Most nitrates are unstable at high temperatures and are prone to decomposition reactions, the type of which can vary due to differences in the metal mobility of the cations. For example, potassium nitrate, sodium nitrate, calcium nitrate, etc. are decomposed at high temperatures to generate nitrites and oxygen; magnesium nitrate, aluminum nitrate, zinc nitrate, copper nitrate and the like are decomposed at high temperature to generate metal oxides, oxygen and nitrogen dioxide; silver nitrate, mercury nitrate and the like can generate metal simple substances, oxygen and nitrogen dioxide after being heated and decomposed.
In the decomposition process of the nitrate, because gas is released, a large amount of porous structures are formed on the surface of the nitrate, so that the specific surface area of the product is larger and the activity is higher. Meanwhile, the crystal structure of the product metal oxide can be changed by controlling the decomposition temperature. Based on the above two points, the process for preparing metal oxide by pyrolyzing nitrate is receiving more and more attention. However, thermal decomposition of nitrates requires a large amount of energy, and the decomposition produces a large amount of nitric oxide gas to be disposed of. These two points severely restrict the application of the process in industrialization, and a great deal of research is only in the laboratory stage at present.
Chinese patent application CN109721038A discloses a method for recovering nitric acid by pyrolysis of nitrate. Firstly, conveying nitrate into at least two stages of preheating devices for heating and liquefying, then conveying a nitrate hot fluid into a 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, indirectly exchanging heat of the other part of the mixed gas to 800 ℃ through a tube array, and refluxing the mixed gas to the decomposer for heating the nitrate thermal fluid to be heated and decomposed. The method realizes rapid decomposition of nitrate, dust collection and nitric acid regeneration. However, the heater used in the process is an indirect heater, such as a coil type heater, an electric heater, etc., the heating mode effectively avoids the mixing of air, and the concentration of the nitrogen oxides entering the absorption device is increased (up to 35-45%), but the indirect heater has low heating efficiency, generally only 70%, and the heat transfer rate is slow, so that the device is not beneficial to the upsizing of the device, and needs to be further improved.
Chinese patent application CN201921626702.5 discloses a device system for preparing nitric acid by thermal decomposition of metal nitrate, which comprises a raw material tank, a pyrolysis furnace, a cyclone separator, a heat accumulating type heater, an absorption tower and a nitric acid recovery tank. In the whole nitrate thermal decomposition and recovery process, mixed gas generated by decomposing nitrate is used as a heat source, and finally, nitrogen oxide compound gas can be completely absorbed to prepare nitric acid. The heater of the process is a heat accumulating type heater, the problem of large-scale equipment is solved, but the problem of low heat transfer efficiency of a heat accumulating type indirect heat exchanger still exists, and the heat efficiency is only about 70%. Meanwhile, the heat storage heater discharges a large amount of high-temperature tail gas in the heating process, if the recycling of part of heat is not considered, the thermal efficiency is further reduced, and the part of tail gas may contain a small amount of nitrogen oxide gas, so that the part of tail gas needs to be treated by an environment-friendly facility. In addition, the fixed investment of the heat accumulating type heater is huge, and depreciation are large.
Chinese patent application CN201410437034.7 discloses a device for preparing magnesium oxide by spray pyrolysis of saturated brine, which comprises a pyrolysis furnace, a hot air system and a feeding system. Wherein, the pyrolysis oven is for self-control brick mixes and two unification structures of carborundum furnace, and hot air system contains air compressor, liquefied petroleum gas jar, controller, air liquefied gas and mixes pipe, burning firearms, some firearm and instrument system in advance, and feeding system comprises storage tank, diaphragm pump, pipeline, nozzle. The device is heated by means of a direct fired heater which is extremely thermally efficient, typically 95%. However, this process is not very suitable for the pyrolytic regeneration of nitrates: firstly, the mixing of air will greatly reduce the concentration of nitrogen oxide gas therein, and once the concentration is lower than 10%, the standard of nitric acid production will not be met; secondly, the nitrogen oxide absorption gas amount absorbed by the nitric acid at the rear end becomes huge, the scale of the compressor also becomes large, and the fixed investment cost is increased; and the production cost of the nitric acid is greatly increased. If the oxygen-enriched direct-fired heating is adopted, although the mixing of nitrogen in the air can be reduced to a certain extent, and the content of nitrogen oxide in the absorbed gas can be improved, the flame temperature of the oxygen-enriched direct-fired heating is extremely high, the temperature of a combustion chamber can reach above 2000-3000 ℃, the high temperature can lead refractory materials to be difficult to select, so that the fixed investment is increased, and the large-scale operation is hindered. In addition, oxygen-enriched direct-fired heating is not beneficial to controlling the temperature of the decomposing furnace, and high combustion temperature and high oxygen concentration can cause damage to a furnace lining, thereby causing safety accidents. For these reasons, the process is also not suitable for the pyrolysis of nitrates.
Disclosure of Invention
Aiming at the defects and shortcomings of the process method for preparing the metal oxide by pyrolyzing the nitrate in the prior art, the invention provides a method for preparing the metal oxide powder and the nitric acid by quickly decomposing the nitrate with high efficiency, energy conservation, environmental protection and environment protection. The method overcomes the defects of low thermal efficiency and large equipment investment in an indirect heat exchange mode by utilizing the circulating gas, and simultaneously avoids the problems of overhigh temperature of a combustion chamber, low concentration of nitrogen oxides in the absorbed gas, high nitric acid absorption cost and large equipment investment in a complete direct combustion type heating mode. The process method disclosed by the invention can ensure that the concentration of the nitrogen oxide in the absorption gas is maintained at a higher level, thereby meeting the requirement of nitric acid absorption; meanwhile, the whole system has extremely high thermal efficiency and low energy consumption, and has the advantages of no waste gas emission, small fixed investment, strong operability, easy realization of large-scale industrial production and the like.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for preparing metal oxide powder and nitric acid by decomposing nitrate comprises the following steps:
(1) adding the molten nitrate into a pyrolysis furnace for pyrolysis to generate high-temperature dust gas;
(2) the high-temperature dust gas passes through a high-temperature dust collecting device, and gas-solid separation is carried out to obtain metal oxide powder;
(3) allowing part of the mixed gas after high-temperature dust collection to enter a nitric acid absorption device through a hot air blower to prepare nitric acid, and allowing the other part of the mixed gas to be used as circulating gas; one part of the circulating gas is mixed with oxygen-enriched air in a mixing chamber to form oxygen-enriched combustion-supporting gas, the oxygen-enriched combustion-supporting gas is fully combusted with combustion gas in a combustion chamber to release high-temperature fuel gas, the high-temperature fuel gas and the other part of the circulating gas are mixed in the mixing chamber to form high-temperature gas with a certain temperature, and the high-temperature gas are circularly led into a pyrolysis furnace to pyrolyze nitrate melt;
(4) the gas entering the nitric acid absorption device is firstly cooled by a waste heat boiler to generate steam, and then is subjected to deep condensation to remove water and multistage cooling to a specific temperature; pressurizing and thickening the cooled nitric oxide gas by a compressor, absorbing the nitric oxide gas in an absorption tower, and finally obtaining finished nitric acid at the bottom of the absorption tower;
(5) and the absorbed tail gas enters a carbon dioxide recovery system to prepare carbon dioxide.
Further, the nitrate in the step (1) comprises one or more of calcium nitrate, aluminum nitrate, magnesium nitrate, ferric nitrate, scandium nitrate, nickel nitrate, cobalt nitrate, manganese nitrate, chromium nitrate and zinc nitrate; the melting temperature of the nitrate is 50-200 ℃.
Further, the high-temperature dust gas in the step (1) is a mixed gas containing metal oxide powder, nitrogen oxide gas, water vapor and oxygen; the pyrolysis temperature range is 300-1500 ℃, and the form of the pyrolysis furnace comprises any one or the combination of rotary kiln decomposition, rotational flow dynamic calcination decomposition and fluidized bed furnace type thermal decomposition.
Further, the high-temperature dust collecting device in the step (2) comprises any one or a combination of high-temperature metal film dust collection, high-temperature metal wire dust collection and high-temperature porous ceramic dust collection.
Further, the temperature of the mixed gas after the high-temperature dust collection in the step (3) is 300-700 ℃, and the mixed gas has a large amount of heat energy and can be recycled.
Further, 10-70% of the mixed gas after high-temperature dust collection in the step (3) enters a nitric acid absorption device to prepare nitric acid.
Further, the oxygen content of the oxygen-enriched air in the step (3) is 30-100%; the oxygen content of the oxygen-enriched combustion-supporting gas is 15-30%.
Further, the combustion gas in the step (3) comprises any one of natural gas, coal gas and coke oven gas or a combination form thereof; the mixing ratio of the oxygen-enriched combustion-supporting gas to the combustion gas is 2-20: 1.
Further, the temperature of the combustion chamber in the step (3) is controlled at 900-1500 ℃; the temperature of the high-temperature gas formed by mixing the high-temperature fuel gas and the circulating gas in the mixing chamber is 500-1300 ℃.
Further, the burners used in the step (3) are high-efficiency energy-saving burners, including a direct-flow burner, a cyclone burner and a flat-flame burner.
Further, the temperature of the gas in the step (4) is reduced to 200 ℃ through a waste heat boiler, and the temperature after multi-stage temperature reduction is 35-50 ℃.
Further, the pressure of the compressor in the step (4) is 0.3MPa-1.2 MPa.
Further, the concentration of the finished nitric acid in the step (4) is 45-65%.
Further, the method for recovering carbon dioxide used in step (5) comprises any one of physical adsorption method, chemical adsorption method, membrane separation method and cryogenic distillation method or a combination form thereof.
Further, the carbon dioxide prepared in the step (5) is in industrial grade or food grade, has the purity of more than 99.9 percent, can be directly sold and can also be used as a raw material for producing carbonate and bicarbonate.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
(1) the oxygen-enriched concurrent heating type combustion heating device used in the invention has extremely high thermal efficiency, small occupied area and low fixed investment, and compared with other processes, the operation cost is obviously reduced.
(2) The invention innovatively adopts a mixed gas which is formed by mixing a part of circulating gas and oxygen-enriched air in a mixing chamber into a new component as a combustion-supporting gas, and then the mixed gas and the combustion gas are fully and completely combusted in a combustion chamber. The mixing of a large amount of invalid gas nitrogen in the air is reduced, the concentration of nitrogen oxide in the gas entering the nitric acid absorption device is avoided to be too low, the problem that high-temperature refractory materials of a combustion chamber are difficult to select due to a pure oxygen direct combustion type heating mode is avoided, and the temperature control performance of the decomposing furnace is enhanced.
(3) The use of the oxygen-enriched combustion in the invention ensures that the concentration of carbon dioxide in the absorbed tail gas is higher, has recovery value, can be used as a good raw material for producing carbonate, and can also be directly sold as a commodity, thereby realizing zero pollution emission of the whole process flow.
Drawings
FIG. 1 is a schematic view of the apparatus involved in the process flow of decomposing nitrate to prepare metal oxide powder and nitric acid according to the embodiment of the present invention.
The labels in the figure are: 1-a nitrate heating and melting device, 2-a pyrolysis furnace, 3-a high-temperature dust collection device, 4-a fan, 5-an oxygen preparation device, 6-a combustion-supporting gas mixing chamber, 7-a combustion chamber, 8-a combustor, 9-a waste heat boiler, 10-a multistage cooling device, 11-a deep dust remover, 12-a deep water remover, 13-a nitrogen oxide compressor, 14-an absorption tower, 15-a carbon dioxide recovery system and 16-a temperature-control air mixing chamber.
Detailed Description
The invention is described in further detail below with reference to the figures and the examples, but the scope of the invention is not limited to the description.
The invention discloses a method for preparing metal oxide powder and nitric acid by quickly decomposing nitrate with high efficiency, energy conservation, environmental protection and environment protection. Firstly, adding molten nitrate into a pyrolysis furnace for pyrolysis to generate mixed gas containing metal oxide powder, nitrogen oxide gas and water vapor; collecting dust of the dust-containing gas at high temperature to obtain metal oxide powder; passing the gas after high-temperature dust collection through a hot air blower, and preparing nitric acid by a part of nitric acid removal absorption system; the other part of the gas is used as circulating gas, wherein a certain proportion of the gas and the combustion-supporting gas are mixed into oxygen-enriched combustion-supporting gas in a new proportion in a mixing chamber, the oxygen-enriched combustion-supporting gas and the combustion gas (natural gas, coal gas and the like) are combusted in a combustion chamber to release high-temperature gas, then the high-temperature gas and the residual circulating gas are mixed into high-temperature gas with a certain temperature in the mixing chamber, and the high-temperature gas and the residual circulating gas are circulated into the pyrolysis furnace again. The mixed gas entering the nitric acid absorption system is firstly cooled by a waste heat boiler and steam is produced, then is pressurized by a compressor after multi-stage cooling and deep condensation dewatering, and is absorbed in an absorption tower, and finally, the finished product nitric acid is obtained at the bottom of the tower; and the absorbed tail gas passes through a carbon dioxide recovery device to produce high-quality carbon dioxide. The method is simple and efficient, basically has no waste gas emission in the whole process flow, is green and environment-friendly, has strong operability and is easy to realize industrialization.
Example 1
Heating calcium nitrate hydrate to 50 ℃ for melting, and introducing the calcium nitrate hydrate into a pyrolysis furnace, wherein the temperature of the pyrolysis furnace is 850 ℃. The calcium nitrate melt is heated in the furnace and rapidly decomposed to generate NOx and O2、H2O, CaO are provided. The mixed dust-containing gas is sent to a high-temperature dust collecting device, high-activity CaO powder is obtained after gas-solid separation, and the decomposition rate of calcium nitrate is 98%. The temperature of the gas after high-temperature dust collection is 650 ℃ after passing through the hot air blower, wherein 20% of the gas enters the nitric acid absorption device, and the other 80% of the gas enters the circulating heating device, and part of the circulating gas enters a special mixing chamber to be mixed with oxygen-enriched air with the oxygen content of 95% to form new combustion-supporting gas, and the oxygen content is 27%; the combustion-supporting gas and natural gas are mixed in a ratio of 10: the proportion of 1 is fully and completely combusted in a combustion chamber, the temperature of the combustion chamber is 1400 ℃, the combustion gas and the rest of the circulating gas are mixed in an air mixing chamber for controlling the temperature, the temperature of the mixed gas is controlled to be 850 ℃, and the mixed gas is circularly led into a pyrolysis furnace to be used as a heat source for pyrolyzing the calcium nitrate melt. The gas absorbed by the nitric acid passes through a waste heat boiler, and the gas after condensation, dust absorption and collection is cooled to 150 ℃ through the waste heat boiler, and steam is produced. After multi-stage temperature reduction, the temperature is reduced to 45 ℃, then deep dust removal and deep condensation are carried out to remove water, the nitrogen oxide is sent to a nitrogen oxide compressor to be pressurized and thickened under the pressure of 0.5Mpa, and then the nitrogen oxide enters an absorption tower, and finally nitric acid with the concentration of 50% is obtained at the bottom of the tower. The concentration of the carbon dioxide in the tail gas after absorption is 90 percent, and the concentration of the nitrogen oxide is less than 50ppm, and then the tail gas is sent to a carbon dioxide recovery device to prepare the food-grade carbon dioxide with the purity of 99.95 percent.
And (3) carrying out an industrial expansion test according to the process conditions, wherein the addition amount of the calcium nitrate hot molten salt is 10 t/h.
Comparative example 1
In order to further explain the technical effect of the invention, an industrial scale-up test is carried out according to the process method and the device system of the Chinese patent application CN 109721038A. Comparative example 1 employs an indirect heater such as electric heating, heat radiation heating, regenerative heating, etc., and the other devices are the same as in example 1. The indirect heating has the advantages that air is not introduced into the circulating gas, so that the content of nitrogen oxide in the decomposed gas is reduced, the content of nitrogen oxide in the decomposed gas is higher, and the requirement of decomposing and absorbing nitric acid can be met. However, the heat transfer efficiency of indirect heating is very low, typically only around 70%. In example 1, direct heating was used by mixing natural gas and combustion-supporting gas in a ratio of 1: the proportion of 10 is fully combusted and then directly mixed into the circulating flue gas, and the heat exchange efficiency is extremely high, usually 95%. The concentration of nitrogen oxides after thermal decomposition can also meet the requirement of nitric acid absorption.
The addition amount of the calcium nitrate hot molten salt in comparative example 1 was also 10 t/h. The operating costs of the two sets of equipment under the same standard feeding amount were calculated, and the results are shown in table 1.
Table 1 industrial production of example 1 and comparative example 1
The comprehensive calculation result shows that compared with the comparative example 1, the operation cost of the embodiment 1 is saved by 4665600 yuan every year, the fixed investment is saved by 10530000 yuan, the fixed investment equipment is saved by 1053000 yuan every year, and the economic benefit is remarkable. In addition, if the feeding amount of calcium nitrate is enlarged, the difference of the comprehensive operation cost of the two sets of equipment is multiplied.
Example 2
Heating the aluminum nitrate hydrate to 80 ℃ for melting, and introducing the aluminum nitrate hydrate into a pyrolysis furnace, wherein the temperature of the pyrolysis furnace is 600 ℃. The aluminum nitrate melt is heated in the furnace and rapidly decomposed to generate NOx and O2、H2O、Al2O3. The mixed dust-containing gas is sent to a high-temperature dust collecting device, and gamma-Al is obtained after gas-solid separation2O3The decomposition rate of the powder was 99% for aluminum nitrate. The temperature of the gas after high-temperature dust collection is 600 ℃ after passing through the hot air blower, wherein 10% of the gas enters the nitric acid absorption device, and the other 90% of the gas enters the circulating heating device. Part of the circulating gas enters a special mixing chamber to be mixed with oxygen-enriched air with the oxygen content of 80 percent to form new combustion-supporting gas with the oxygen content of 25 percent; the aidGas and natural gas in a 12: the proportion of 1 is fully and completely combusted in a combustion chamber, the temperature of the combustion chamber is 1300 ℃, the combustion gas and the rest of the circulating gas are mixed in an air mixing chamber for controlling the temperature, the temperature of the mixed gas is controlled to be 600 ℃, and the mixed gas is circularly led into a pyrolysis furnace to be used as a heat source for pyrolyzing the aluminum nitrate melt. The gas absorbed by the nitric acid passes through a waste heat boiler, and the gas after condensation, dust absorption and collection is cooled to 180 ℃ through the waste heat boiler, and steam is produced. After multi-stage temperature reduction, the temperature is reduced to 40 ℃, then deep dust removal and deep condensation are carried out to remove water, the nitrogen oxide is sent to a nitrogen oxide compressor to be pressurized and concentrated under the pressure of 0.6Mpa, then the nitrogen oxide enters an absorption tower, and finally nitric acid with the concentration of 53% is obtained at the bottom of the tower. The concentration of the carbon dioxide in the absorbed tail gas is 85 percent, and the concentration of the nitrogen oxide is less than 50ppm, and then the tail gas is sent to a carbon dioxide recovery device to prepare industrial-grade carbon dioxide with the purity of 99.93 percent.
Example 3
Heating the aluminum nitrate hydrate to 80 ℃ for melting, and introducing the aluminum nitrate hydrate into a pyrolysis furnace, wherein the temperature of the pyrolysis furnace is 1400 ℃. The aluminum nitrate melt is heated in the furnace and rapidly decomposed to generate NOx and O2、H2O、Al2O3. The mixed dust-containing gas is sent to a high-temperature dust collecting device, and alpha-Al is obtained after gas-solid separation2O3The decomposition rate of the powder and aluminum nitrate was 99.98%. The temperature of the gas after high-temperature dust collection is 550 ℃ after passing through the hot air blower, wherein 25% of the gas enters the nitric acid absorption device, and the other 75% of the gas enters the circulating heating device. Part of the circulating gas enters a special mixing chamber to be mixed with oxygen-enriched air with the oxygen content of 75 percent to form new combustion-supporting gas with the oxygen content of 23 percent; the combustion-supporting gas and the natural gas are mixed in a ratio of 9: the proportion of 1 is fully and completely combusted in a combustion chamber, the temperature of the combustion chamber is 1400 ℃, the combustion gas and the rest of the circulating gas are mixed in an air mixing chamber for controlling the temperature, the temperature of the mixed gas is controlled to be 550 ℃, and the mixed gas is circularly led into a pyrolysis furnace to be used as a heat source for pyrolyzing the aluminum nitrate melt. The gas absorbed by the nitric acid passes through a waste heat boiler, and the gas after condensation, dust absorption and collection is cooled to 200 ℃ through the waste heat boiler, and steam is produced. After multi-stage temperature reduction, the temperature is reduced to 38 ℃, and then deep dust removal and deep condensation are carried out to remove waterThe nitric acid is sent to a nitrogen oxide compressor to be pressurized and concentrated at the pressure of 0.6Mpa, and then enters an absorption tower, and finally, nitric acid with the concentration of 53% is obtained at the bottom of the tower. The carbon dioxide concentration of the absorbed tail gas is 83 percent, the nitrogen oxide concentration is less than 50ppm, and then the tail gas is sent to a carbon dioxide recovery device to prepare industrial-grade carbon dioxide with the purity of 99.93 percent.
Example 4
Heating magnesium nitrate hydrate to 100 ℃ for melting, and introducing the magnesium nitrate hydrate into a pyrolysis furnace, wherein the temperature of the pyrolysis furnace is 700 ℃. The magnesium nitrate melt is heated in the furnace and rapidly decomposed to generate NOx and O2、H2O, MgO are provided. The mixed dust-containing gas is sent to a high-temperature dust collecting system, high-activity MgO powder is obtained after gas-solid separation, and the decomposition rate of magnesium nitrate is 97.8%. The temperature of the gas after high-temperature dust collection is 500 ℃ after passing through the hot air blower, wherein 30% of the gas enters the nitric acid absorption device, and the other 70% of the gas enters the circulating heating device. Part of the circulating gas enters a special mixing chamber to be mixed with oxygen-enriched air with oxygen content of 70 percent to form new combustion-supporting gas with oxygen content of 21 percent; the combustion-supporting gas and the coke oven gas are mixed in a ratio of 15: the proportion of 1 is fully and completely combusted in a combustion chamber, the temperature of the combustion chamber is 1100 ℃, the combustion gas and the rest of the circulating gas are mixed in an air mixing chamber for controlling the temperature, the temperature of the mixed gas is controlled to be 700 ℃, and the mixed gas is circularly led into a pyrolysis furnace to be used as a heat source for pyrolyzing the magnesium nitrate melt. The gas absorbed by the nitric acid passes through a waste heat boiler, and the gas after condensation, dust absorption and collection is cooled to 160 ℃ through the waste heat boiler, and steam is produced. After multi-stage temperature reduction, the temperature is reduced to 41 ℃, then deep dust removal and deep condensation are carried out to remove water, the nitrogen oxide is sent to a nitrogen oxide compressor to be pressurized and thickened under the pressure of 0.8Mpa, and then the nitrogen oxide enters an absorption tower, and finally, the nitric acid with the concentration of 56% is obtained at the bottom of the tower. The concentration of the carbon dioxide in the tail gas after absorption is 78 percent, and the concentration of the nitrogen oxide is less than 50ppm, and then the tail gas is sent to a carbon dioxide recovery device to prepare the food-grade carbon dioxide with the purity of 99.98 percent.
Example 5
Heating cobalt nitrate hydrate to 65 ℃ for melting, and introducing the cobalt nitrate hydrate into a pyrolysis furnace, wherein the temperature of the pyrolysis furnace is 1300 ℃. The cobalt nitrate melt is heated in the furnace and rapidly decomposed to generate NOx and O2、H2O, CoO are provided. The mixed dust-containing gas is sent to a high-temperature dust collecting system, and CoO powder is obtained after gas-solid separation, wherein the decomposition rate of the cobalt nitrate is 99%. The temperature of the gas after high-temperature dust collection is 450 ℃ after passing through the hot air blower, wherein 50% of the gas enters the nitric acid absorption device, and the other 50% of the gas enters the circulating heating device. Part of the circulating gas enters a special mixing chamber to be mixed with oxygen-enriched air with oxygen content of 45 percent to form new combustion-supporting gas with oxygen content of 21 percent; the combustion-supporting gas and the coal gas are mixed in a ratio of 6: the proportion of 1 is fully and completely combusted in a combustion chamber, the temperature of the combustion chamber is 1400 ℃, the combustion gas and the rest part of circulating gas are mixed in an air mixing chamber for controlling the temperature, the temperature of the mixed gas is controlled to be 1300 ℃, and the mixed gas is circularly led into a pyrolysis furnace to be used as a heat source for pyrolyzing the cobalt nitrate melt. The gas absorbed by the nitric acid passes through a waste heat boiler, and the gas after condensation, dust absorption and collection is cooled to 170 ℃ through the waste heat boiler, and steam is generated. After multi-stage temperature reduction, the temperature is reduced to 35 ℃, then deep dust removal and deep condensation are carried out to remove water, the nitrogen oxide is sent to a nitrogen oxide compressor to be pressurized and concentrated under the pressure of 0.9Mpa, then the nitrogen oxide enters an absorption tower, and finally the nitric acid with the concentration of 59% is obtained at the bottom of the tower. The concentration of the carbon dioxide in the tail gas after absorption is 58 percent, and the concentration of the nitrogen oxide is less than 50ppm, and then the tail gas is sent to a carbon dioxide recovery device to prepare the food-grade carbon dioxide with the purity of 99.98 percent.
Example 6
Heating the copper nitrate hydrate to 50 ℃ for melting, and introducing the copper nitrate hydrate into a pyrolysis furnace, wherein the temperature of the pyrolysis furnace is 300 ℃. The copper nitrate melt is heated in the furnace and rapidly decomposed to generate NOx and O2、H2O, CuO are provided. The mixed dust-containing gas is sent to a high-temperature dust collecting system, CuO powder is obtained after gas-solid separation, and the decomposition rate of copper nitrate is 99%. The temperature of the gas after high-temperature dust collection is 400 ℃ after passing through the hot air blower, wherein 70% of the gas enters the nitric acid absorption device, and the other 30% of the gas enters the circulating heating device. Part of the circulating gas enters a special mixing chamber to be mixed with oxygen-enriched air with the oxygen content of 30 percent to form new combustion-supporting gas with the oxygen content of 15 percent; the combustion-supporting gas and natural gas are mixed in a ratio of 20:1 is fully and completely combusted in a combustion chamber, and the temperature of the combustion chamberThe temperature of the combustion gas is 1000 ℃, the combustion gas and the rest of the circulating gas are mixed in an air mixing chamber for controlling the temperature, the temperature of the mixed gas is controlled to be 300 ℃, and the mixed gas is circularly led into a pyrolysis furnace to be used as a heat source for pyrolyzing the copper nitrate melt. The gas absorbed by the nitric acid passes through a waste heat boiler, and the gas after condensation and dust absorption is cooled to 190 ℃ through the waste heat boiler, and steam is generated. After multi-stage temperature reduction, the temperature is reduced to 39 ℃, then deep dust removal and deep condensation are carried out to remove water, the nitrogen oxide is sent to a nitrogen oxide compressor to be pressurized and concentrated under the pressure of 1.1Mpa, then the nitrogen oxide enters an absorption tower, and finally nitric acid with the concentration of 62% is obtained at the bottom of the tower. The concentration of the carbon dioxide in the absorbed tail gas is 35 percent, and the concentration of the nitrogen oxide is less than 50ppm, and then the tail gas is sent to a carbon dioxide recovery device to prepare industrial-grade carbon dioxide with the purity of 99.93 percent.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A method for preparing metal oxide powder and nitric acid by decomposing nitrate is characterized by comprising the following steps:
(1) adding the molten nitrate into a pyrolysis furnace for pyrolysis to generate high-temperature dust gas;
(2) the high-temperature dust gas passes through a high-temperature dust collecting device, and metal oxide powder is obtained after gas-solid separation;
(3) allowing part of the mixed gas after high-temperature dust collection to enter a nitric acid absorption device through a hot air blower to prepare nitric acid, and allowing the other part of the mixed gas to be used as circulating gas; one part of the circulating gas is mixed with oxygen-enriched air in a mixing chamber to form oxygen-enriched combustion-supporting gas, the oxygen-enriched combustion-supporting gas is fully combusted with combustion gas in a combustion chamber to release high-temperature fuel gas, the high-temperature fuel gas and the other part of the circulating gas are mixed in the mixing chamber to form high-temperature gas with a certain temperature, and the high-temperature gas are circularly led into a pyrolysis furnace to pyrolyze nitrate melt;
(4) the gas entering the nitric acid absorption device is firstly cooled by a waste heat boiler to generate steam, and then is subjected to deep condensation to remove water and multistage cooling to a specific temperature; pressurizing and thickening the cooled nitric oxide gas by a compressor, absorbing the nitric oxide gas in an absorption tower, and finally obtaining finished nitric acid at the bottom of the absorption tower;
(5) and the absorbed tail gas enters a carbon dioxide recovery system to prepare carbon dioxide.
2. The method for preparing metal oxide powder and nitric acid by decomposing nitrate according to claim 1, wherein the nitrate of step (1) comprises one or more of calcium nitrate, aluminum nitrate, magnesium nitrate, ferric nitrate, scandium nitrate, nickel nitrate, cobalt nitrate, manganese nitrate, chromium nitrate, and zinc nitrate; the melting temperature of the nitrate is 50-200 ℃.
3. The method for preparing metal oxide powder and nitric acid by decomposing nitrate according to claim 1, wherein the high temperature dust gas in the step (1) is a mixed gas containing metal oxide powder, nitrogen oxide gas, water vapor and oxygen gas; the pyrolysis temperature range is 300-1500 ℃, and the form of the pyrolysis furnace comprises any one or the combination of rotary kiln decomposition, rotational flow dynamic calcination decomposition and fluidized bed furnace type thermal decomposition.
4. The method for preparing metal oxide powder and nitric acid by decomposing nitrate according to claim 1, wherein the high temperature dust collecting device in step (2) comprises any one of or a combination of high temperature metal film dust collection, high temperature metal wire dust collection and high temperature porous ceramic dust collection.
5. The method for preparing metal oxide powder and nitric acid by decomposing nitrate according to claim 1, wherein the temperature of the mixed gas after the high-temperature dust collection in step (3) is 300-700 ℃; and (3) enabling 10-70% of the mixed gas after high-temperature dust collection to enter a nitric acid absorption device to prepare nitric acid.
6. The method for preparing metal oxide powder and nitric acid by decomposing nitrate according to claim 1, wherein the oxygen content of the oxygen-enriched air in the step (3) is 30-100%; the oxygen content of the oxygen-enriched combustion-supporting gas is 15-30%; the combustion gas comprises any one mode or a combination mode of natural gas, coal gas and coke oven gas; the mixing ratio of the oxygen-enriched combustion-supporting gas to the combustion gas is 2-20: 1.
7. The method for preparing metal oxide powder and nitric acid by decomposing nitrate according to claim 1, wherein the temperature of the combustion chamber in step (3) is controlled at 900-1500 ℃; the temperature of the high-temperature gas formed by mixing the high-temperature fuel gas and the circulating gas in the mixing chamber is 500-1300 ℃; the used burners are high-efficiency energy-saving burners, including a direct-flow burner, a cyclone burner and a flat flame burner.
8. The method for preparing metal oxide powder and nitric acid by decomposing nitrate according to claim 1, wherein the temperature of the gas in the step (4) is reduced to 120-200 ℃ by a waste heat boiler, and the temperature after multi-stage temperature reduction is 35-50 ℃; the pressure of the compressor is 0.3MPa-1.2 MPa.
9. The method for preparing metal oxide powder and nitric acid by decomposing nitrate according to claim 1, wherein the concentration of the finished nitric acid in the step (4) is 45-65%.
10. The method for preparing metal oxide powder and nitric acid by decomposing nitrate according to claim 1, wherein the method for recovering carbon dioxide used in the step (5) comprises any one or a combination of physical adsorption, chemical adsorption, membrane separation and cryogenic distillation; the prepared carbon dioxide is in industrial grade or food grade, and the purity is more than 99.9%.
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| CN113479926A (en) * | 2021-08-06 | 2021-10-08 | 四川顺应动力电池材料有限公司 | Method for preparing metal oxide powder by heating and decomposing nitrate in fluidized bed furnace |
| CN113636530A (en) * | 2021-07-22 | 2021-11-12 | 四川顺应动力电池材料有限公司 | Method for directly realizing one-step conversion from nitrogen to nitric acid by utilizing air |
| CN114484872A (en) * | 2022-01-12 | 2022-05-13 | 四川顺应动力电池材料有限公司 | System for decomposing metal salt through electromagnetic induction heat accumulation type self-circulation and metal salt decomposition treatment method |
| CN115092901A (en) * | 2022-07-04 | 2022-09-23 | 四川顺应动力电池材料有限公司 | Method for preparing battery-grade iron phosphate by decomposing phosphate ore with nitric acid |
| CN115215309A (en) * | 2022-07-11 | 2022-10-21 | 四川顺应动力电池材料有限公司 | Method for producing industrial-grade phosphoric acid and recycling industrial-grade phosphoric acid by phosphorite-nitric acid method |
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| CN115092901A (en) * | 2022-07-04 | 2022-09-23 | 四川顺应动力电池材料有限公司 | Method for preparing battery-grade iron phosphate by decomposing phosphate ore with nitric acid |
| CN115092901B (en) * | 2022-07-04 | 2023-11-03 | 四川顺应动力电池材料有限公司 | Method for preparing battery-grade ferric phosphate by decomposing phosphorite with nitric acid |
| CN115215309A (en) * | 2022-07-11 | 2022-10-21 | 四川顺应动力电池材料有限公司 | Method for producing industrial-grade phosphoric acid and recycling industrial-grade phosphoric acid by phosphorite-nitric acid method |
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