CN110482605B - Method and device for preparing sodium bichromate by taking chromite as raw material in one step - Google Patents
Method and device for preparing sodium bichromate by taking chromite as raw material in one step Download PDFInfo
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- CN110482605B CN110482605B CN201910805430.3A CN201910805430A CN110482605B CN 110482605 B CN110482605 B CN 110482605B CN 201910805430 A CN201910805430 A CN 201910805430A CN 110482605 B CN110482605 B CN 110482605B
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- C01G37/00—Compounds of chromium
- C01G37/14—Chromates; Bichromates
Abstract
The invention discloses a method and a device for preparing sodium bichromate by taking chromite as a raw material in one step, which specifically comprises the following steps: mixing and stirring chromite, soda ash, sodium hydroxide and water according to the mass ratio of 1: 1-1.1: 0.4-0.5: 5, and heating to 100 ℃ to obtain a mixed liquid material;reacting the mixed liquid material for 2-3 h under the oxygen pressure of 3-3.5 Mpa and the temperature of 200-230 ℃; after the reaction is finished, changing oxygen into carbon dioxide gas, wherein the pressure is 1.2-1.3 Mpa, the temperature is 60-70 ℃, and reacting for 2-3 h to obtain a mixed product; separating supernatant from the mixed product, obtaining white sodium bicarbonate crystals from the supernatant at the temperature of 10-15 ℃, separating the sodium bicarbonate, concentrating the solution, and cooling to obtain a sodium bichromate product; in the present invention, CO obtained by decomposing sodium hydrogencarbonate2And sodium carbonate is recycled, thereby realizing CO2The soda ash and the heat energy are efficiently and automatically recycled, and the waste of energy is reduced.
Description
Technical Field
The invention belongs to the field of preparation of sodium bichromate, and particularly relates to a method and a device for preparing sodium bichromate by one step by taking chromite as a raw material.
Background
Chromite is a mineral with its main components being oxides of iron, magnesium and chromium. Chromite is an indispensable mineral resource for developing the industries of metallurgy, national defense, chemical industry and the like, is mainly used for producing stainless steel, various alloy steels and alloys in the metallurgical industry, and has wide application in the aspects of glass, ceramics, refractory materials and the like. In addition, it is also used for refining metallic chromium, producing ferrochrome, stainless steel, manufacturing dichromate, etc.
The chromium salt is widely applied to the fields of electroplating, coating, wood corrosion prevention and the like, wherein 70-85% of sodium bichromate is used as a mother product of the chromium salt and is used for manufacturing other chromium salt products, so that the chromium salt has very wide application. Chromate products are generally obtained by soda ash roasting processes, which are currently under great pressure due to environmental problems, in the process of roasting alkali ash, lime containing chromite with almost equal mass is added into furnace charge to control siliceous and acidic gangue minerals in the ore, but the addition of lime can generate a large amount of high-alkaline chromite processing slag containing 1-2% of hexavalent chromium (mass fraction), which can cause CaCrO4Generation of, CaCrO4Is volatile and air-borne, poses a significant threat to the health of humans, animals and plants, and the production process is severeThe problems of heavy secondary pollution, resource waste, high energy consumption, low production efficiency and the like, so that a new process technology is urgently needed to solve the defects of the traditional process.
Disclosure of Invention
The invention provides a method for preparing sodium bichromate by taking chromite as a raw material in one step, which realizes the efficient self-recycling of elements and carbon dioxide in the sodium bichromate preparation process, reduces the energy waste, greatly shortens the sodium bichromate preparation process and utilizes byproducts generated in the technical process.
A method for preparing sodium bichromate by taking chromite as a raw material in one step specifically comprises the following steps:
(1) mixing and stirring chromite, soda ash, sodium hydroxide and water according to the mass ratio of 1: 1-1.1: 0.4-0.5: 5, and heating to 100 ℃ to obtain a mixed liquid material;
(2) reacting the mixed liquid material obtained in the step (1) for 2-3 h under the oxygen pressure of 3-3.5 Mpa and the temperature of 200-230 ℃;
(3) after the reaction in the step (2), changing oxygen into carbon dioxide gas, wherein the pressure is 1.2-1.3 Mpa, the temperature is 60-70 ℃, and reacting for 2-3 h to obtain a mixed product;
(4) and (4) separating the supernatant of the mixed product obtained in the step (3), obtaining white sodium bicarbonate crystals at the temperature of 10-15 ℃, separating the sodium bicarbonate, concentrating the residual solution at the temperature of 70-80 ℃, and cooling to obtain the sodium bichromate product.
The mass percentage content of the simple substance Cr in the chromite in the step (1) is 68 percent, the purity of the calcined soda is 99 percent, and the purity of the sodium hydroxide is more than 96 percent.
Decomposing the sodium bicarbonate crystals at 100 ℃ to obtain sodium carbonate and carbon dioxide, returning the carbon dioxide to the step (3) for use, and returning the sodium carbonate to the step (1) for use; washing the residue separated from the mixed product with water for 1-2 times, extracting iron, and returning the washing liquid to step (1)
The invention also provides a device for preparing sodium bichromate by one step by taking chromite as a raw material, which comprises a mixing device 1, a stirring device, a horizontal reaction kettle 7, a waste liquid tank 20, an oxygen tank 23, a carbon dioxide gas tank 24, a decomposition tank 25 and a separation tank 26, the mixing device 1 is internally provided with a stirring device, the mixing device 1 is provided with 4 feed inlets and a discharge outlet, the discharge outlet is connected with a mixed material liquid outlet 8 at the upper part of a horizontal reaction kettle 7 through a pump 6, the horizontal reaction kettle 7 is provided with more than one upper vent hole 10, an oxygen inlet 14, a carbon dioxide inlet 15, a supernatant discharge port 16, a discharge port 18 and more than one lower discharge port 21, each port is provided with a valve, the upper vent hole 10 is used for exhausting and adding water, the lower discharge port 21 is used for discharging washing liquid, the lower discharge port 21 is connected with a waste liquid tank 20, and the waste liquid tank 20 is connected with the water feed inlet of the mixing device 1 through a pump;
the oxygen inlet 14 is connected with an oxygen tank 23, the carbon dioxide inlet 15 is connected with a carbon dioxide tank 24,
the supernatant fluid outlet 16 is connected with a separating tank 26 through a pump, the bottom of the separating tank 26 is connected with the top of a decomposing tank 25, a valve is arranged between the decomposing tank 25 and the separating tank 26, the top of the decomposing tank 25 is connected with a carbon dioxide gas tank 24 through a pump, and the bottom of the decomposing tank 25 is connected with a soda feed inlet of the mixing device 1 through a pump.
Agitating unit is including inhaling formula paddle 2, motor 3, puddler 4, open worm wheel stirring vane 5 certainly, and 4 one ends of puddler are passed 1 tops of mixing arrangement and are connected with motor 3, and 4 middle parts of puddler are equipped with from inhaling formula paddle 2, and 4 bottoms of puddler are equipped with open worm wheel stirring vane 5.
And a heating resistor and a thermometer are also arranged in the mixing device 1.
And a heating resistor, a thermometer 19, a pressure gauge 11 and a liquid level meter 12 are also arranged in the horizontal reaction kettle 7.
A cooling device 17 is arranged outside the horizontal reaction kettle 7, the cooling device 17 wraps the lower part of the horizontal reaction kettle 7, the interior of the cooling device 17 is of a hollow structure, a cooling water inlet 22 is arranged at the lower part of the cooling device 17, and a cooling water outlet 13 is arranged at the upper part of the cooling device; the outside of the separation tank 26 is provided with a cooling device which is the same as the outside of the horizontal reaction kettle 7.
And the horizontal reaction kettle 7 is also provided with an inspection manhole 9.
A heating resistor and a thermometer are arranged in the decomposition tank 25; a heating resistor and a thermometer are provided in the separation tank 26.
The invention has the beneficial effects that:
(1) clean production: the full-flow wet preparation process technology of sodium bichromate is completed, the traditional calcination production mode is thoroughly changed, the simple process flow of the sodium bichromate manufacturing process is realized, no waste is discharged, the environmental pollution is reduced, and the industrial-scale production mode of sodium bichromate is reached.
(2) The method realizes an efficient cyclic comprehensive utilization system of resources: sodium carbonate generated by decomposing the obtained sodium bicarbonate is introduced into the mixing device through a conveying pipeline, and carbon dioxide returns to the horizontal reaction kettle, so that the self-recycling of sodium element and carbon dioxide is realized, the energy waste is reduced, and byproducts generated in the technical process are comprehensively utilized.
(3) The manufacturing cost of sodium bichromate is reduced: the traditional extensive reaction, filtration, evaporation and other modes of the chromium salt are changed, a horizontal reaction kettle, a separation tank and a decomposition tank are introduced, the problems of large equipment abrasion, low chromium yield and the like are systematically solved, and the production of sodium bichromate is greatly improved.
(4) The preparation process is simple: the traditional stepwise reaction of chromium salt is changed, a closed system is adopted in the reaction process, the operation is simple, the process for preparing sodium bichromate is greatly shortened, and the sodium bichromate product can be prepared in one step.
Drawings
FIG. 1 is a schematic view of the structure of an apparatus according to example 1 of the present invention;
in the figure: 1-a mixing device; 2-self-suction type paddle; 3-an electric motor; 4-a stirring rod; 5-open type worm gear stirring blades; 6-a pump; 7-horizontal reaction kettle; 8-mixture liquid port; 9-maintenance manhole; 10-upper vent; 11-pressure gauge; 12-a liquid level meter; 13-a cooling water discharge port; 14-an oxygen inlet; 15-carbon dioxide inlet; 16-supernatant discharge port; 17-a cooling device; 18-a discharge hole; 19-a thermometer; 20-a waste liquid tank; 21-lower discharge port; 22-cooling water inlet; 23-an oxygen tank; 24-a carbon dioxide gas tank; 25-a decomposition tank; 26-separating tank.
Detailed Description
The invention is described in further detail below with reference to the drawings so that those skilled in the art can practice it with reference to the description, which is not specifically described in detail, but is readily available or available to those skilled in the art by conventional means.
Example 1
A device for preparing sodium bichromate by one step by taking chromite as a raw material comprises a mixing device 1, a stirring device, a horizontal reaction kettle 7, a waste liquid tank 20, an oxygen tank 23, a carbon dioxide gas tank 24, a decomposition tank 25, a separation tank 26, a plurality of pumps and valves, wherein a heating resistor and a thermometer are arranged in the mixing device 1 and are used for heating and temperature measurement respectively, the stirring device is arranged in the mixing device 1 and comprises a self-suction paddle 2, a motor 3, a stirring rod 4 and an open type worm stirring blade 5, one end of the stirring rod 4 penetrates through the top of the mixing device 1 and is connected with the motor 3, the self-suction paddle 2 is arranged in the middle of the stirring rod 4, the open type worm stirring blade 5 is arranged at the bottom of the stirring rod 4, the self-suction paddle 2 overturns the material liquid upwards, the open type worm stirring blade 5 downwards presses the material, so that the material is mixed and heated uniformly, the heating time is reduced, 4 feed inlets and a discharge outlet are arranged on the mixing device 1, the 4 feed inlets are a chromite inlet, a soda inlet, a sodium hydroxide inlet and a water inlet respectively,
the discharge port is connected with a mixture liquid port 8 at the upper part of the horizontal reaction kettle 7 through a pump 6, two upper vent ports 10, an oxygen inlet 14, a carbon dioxide inlet 15, a supernatant fluid discharge port 16, a discharge port 18 and a lower discharge port 21 are arranged on the horizontal reaction kettle 7, each port is provided with a valve, the upper vent ports 10 are used for exhausting and adding water, the lower discharge port 21 is used for discharging cleaning solution, the lower discharge port 21 is connected with a waste liquid tank 20, and the waste liquid tank 20 is connected with one of the feed ports of the mixing device 1, namely the water inlet through a pump; the oxygen inlet 14 is connected with an oxygen tank 23, the carbon dioxide inlet 15 is connected with a carbon dioxide tank 24,
the supernatant fluid outlet 16 is connected with a separating tank 26 through a pump, the bottom of the separating tank 26 is connected with the top of a decomposing tank 25, a valve is arranged between the decomposing tank 25 and the separating tank 26, a heating resistor and a thermometer are arranged in the decomposing tank 25 and are both arranged at the bottom of the decomposing tank 25, the upper part of the decomposing tank 25 is connected with a carbon dioxide gas tank 24 through a pump, the bottom of the decomposing tank 25 is connected with one of the feed inlets of the mixing device 1, namely a soda inlet, through a pump, a heating resistor, a thermometer 19, a pressure gauge 11 and a liquid level meter 12 are also arranged in the horizontal reaction kettle 7, the heating resistor and the thermometer 19 are arranged at the bottom of the horizontal reaction kettle 7, the pressure gauge 11 and the liquid level meter 12 are arranged at the top of the horizontal reaction kettle 7, a cooling device 17 is arranged outside the horizontal reaction kettle 7, the cooling device 17 wraps the lower part of the horizontal reaction kettle 7, the inside of the cooling device 17 is of a hollow structure, a cooling water inlet 22 is arranged at the lower part of the cooling device 17, the upper part is provided with a cooling water discharge port 13; a cooling device which is the same as the cooling device arranged outside the horizontal reaction kettle 7 is arranged outside the separation tank 26, and an inspection manhole 9 is also arranged on the horizontal reaction kettle 7 and used for people to enter for inspection when a problem occurs inside the horizontal reaction kettle 7; and a valve is arranged at the joint of each two parts.
The device of the embodiment is used for preparing sodium bichromate by taking chromite as a raw material in one step, and the specific method comprises the following steps:
(1) adding 68 mass percent of chromite containing simple substance Cr, 99 mass percent of soda ash, more than 96 mass percent of sodium hydroxide and water into a mixing device 1 according to the mass ratio of 1:1:0.4:5, starting a motor 3 and a heating resistor, heating while stirring, uniformly mixing, stopping heating and stirring after the temperature measured by a thermometer reaches 100 ℃, and obtaining a mixed liquid material;
(2) pumping the mixed liquid material in the step (1) out of a material liquid outlet of the mixing device 1 by a pressure pump 6, feeding the mixed liquid material into a horizontal reaction kettle 7 from a mixed liquid port 8, closing each port on the horizontal reaction kettle 7 after the liquid level in the horizontal reaction kettle 7 obtained by a liquid level meter 12 reaches a boundary line, opening an oxygen inlet 14 and an upper exhaust port 10, feeding oxygen into the horizontal reaction kettle 7 from an oxygen tank 23, continuously introducing the oxygen for ten minutes, closing each port, opening the oxygen inlet, introducing the oxygen until a pressure gauge 11 displays that the pressure is 3Mpa, closing the oxygen inlet 14, opening a heating resistor in the horizontal reaction kettle 7 to heat the internal material, stopping heating after a temperature gauge 19 displays that the temperature is 200 ℃, and reacting for 3 hours;
(3) after the reaction in the step (2), opening a carbon dioxide inlet 15 and an upper exhaust port 10, introducing carbon dioxide gas for 10 minutes, closing the upper exhaust port 10, continuously introducing the carbon dioxide gas until a pressure gauge 11 displays that the air pressure is 1.2Mpa, simultaneously injecting cold water into a cooling water inlet 22 of a cooling device 17, cooling, and reacting for 3 hours to obtain a mixed product, wherein a temperature thermometer 19 displays that the temperature is 60 ℃;
(4) pumping the supernatant of the mixed product in the step (3) into a separation tank 26 from a supernatant outlet 16 by using a pump, reducing the temperature of the separation tank 26 to 10 ℃ by using a cooling device which is arranged outside the separation tank 26 and outside the horizontal reaction kettle 7 in the separation tank 26, preserving the heat, firstly obtaining white sodium bicarbonate crystals, opening a valve between a decomposition tank 25 and the separation tank 26 when the sodium bicarbonate crystals are not increased any more, separating the sodium bicarbonate crystals from the bottom of the separation tank 26, entering the decomposition tank 25, opening a heating resistor in the separation tank 26, heating the solution left in the separation tank 26 to 70 ℃ for concentration after separation, monitoring by using a thermometer, after the solution is heated to the volume which is not changed any more, filling a liquid level meter in the separation tank 26 for volume observation, and cooling to room temperature by using a cooling device arranged outside the separation tank 26 to obtain a sodium bichromate product;
starting a heating resistor in the decomposition tank 25, heating the sodium bicarbonate in the decomposition tank 25, stopping heating after a thermometer displays that the temperature reaches 100 ℃, decomposing the sodium bicarbonate to obtain sodium carbonate and carbon dioxide, pumping the carbon dioxide into a carbon dioxide gas tank 24 by a pump, and keeping the step (2) for later use; when no carbon dioxide gas is generated, pumping the obtained sodium carbonate into the mixing device 1 from a soda ash inlet by a pump, and returning to the step (1) for use;
adding water from the upper vent 10, cleaning the residue after separating the supernatant of the mixed product for 1 time, opening a valve on the lower discharge outlet 21, allowing the cleaning solution to enter the waste liquid tank 20, pumping the cleaning solution in the waste liquid tank 20 into the mixing device 1 from a water inlet by a pump, and returning to the step (1) for use; the cleaned residue is discharged from the discharge port 18 for iron extraction.
Na in the sodium bichromate product finally obtained in the example2CrO7·H2The O content was 98.32%.
Example 2
By adopting the device of the embodiment 1, the upper vent hole and the lower vent hole are both one, and the sodium bichromate is prepared by taking chromite as a raw material in one step, and the specific method comprises the following steps:
(1) adding 68 mass percent of chromite containing simple substance Cr, 99 mass percent of soda ash, more than 96 mass percent of sodium hydroxide and water into a mixing device 1 according to the mass ratio of 1:1.05:0.45:5, starting a motor 3 and a heating resistor, heating while stirring, uniformly mixing, stopping heating and stirring after the temperature measured by a thermometer reaches 100 ℃, and obtaining a mixed liquid material;
(2) pumping the mixed liquid material obtained in the step (1) out of a material liquid outlet of the mixing device 1 by a pressure pump 6, allowing the mixed liquid material to enter a horizontal reaction kettle 7 from a mixed liquid port 8, closing each port on the horizontal reaction kettle 7 after the liquid level in the horizontal reaction kettle 7 obtained from a liquid level meter 12 reaches a reaction boundary line, opening an oxygen inlet 14 and an upper exhaust port 10, allowing oxygen to enter the horizontal reaction kettle 7 from an oxygen tank 23, continuously introducing oxygen for ten minutes, closing each port, opening the oxygen inlet, introducing oxygen until a pressure gauge 11 displays that the pressure is 3.2MPa, closing the oxygen inlet 14, opening a heating resistor in the horizontal reaction kettle 7 to heat the internal material, stopping heating after a temperature gauge 19 displays that the temperature is 210 ℃, and reacting for 2.5 hours;
(3) after the reaction in the step (2), opening a carbon dioxide inlet 15 and an upper exhaust port 10, introducing carbon dioxide gas for 10 minutes, closing the upper exhaust port 10, continuously introducing the carbon dioxide gas until a pressure gauge 11 displays that the air pressure is 1.25Mpa, simultaneously injecting cold water into a cooling water inlet 22 of a cooling device 17, cooling, and reacting for 2.5 hours to obtain a mixed product, wherein a temperature thermometer 19 displays that the temperature is 65 ℃;
(4) pumping the supernatant of the mixed product in the step (3) into a separation tank 26 from a supernatant outlet 16 by using a pump, reducing the temperature of the separation tank 26 to 12 ℃ by using a cooling device which is arranged outside the separation tank 26 and outside the horizontal reaction kettle 7 in the separation tank 26, preserving the heat, firstly obtaining white sodium bicarbonate crystals, opening a valve between a decomposition tank 25 and the separation tank 26 when the sodium bicarbonate crystals are not increased any more, separating the sodium bicarbonate crystals from the bottom of the separation tank 26, entering the decomposition tank 25, opening a heating resistor in the separation tank 26, heating the solution left in the separation tank 26 to 75 ℃ for concentration after separation, monitoring by using a thermometer, after the solution is heated to the volume which is not changed any more, filling a liquid level meter in the separation tank 26 for volume observation, and cooling to room temperature by using a cooling device arranged outside the separation tank 26 to obtain a sodium bichromate product;
starting a heating resistor in the decomposition tank 25, heating the sodium bicarbonate in the decomposition tank 25, stopping heating after a thermometer displays that the temperature reaches 100 ℃, decomposing the sodium bicarbonate to obtain sodium carbonate and carbon dioxide, pumping the carbon dioxide into a carbon dioxide gas tank 24 by a pump, and keeping the step (2) for later use; when no carbon dioxide gas is generated, pumping the obtained sodium carbonate into the mixing device 1 from a soda ash inlet by a pump, and returning to the step (1) for use;
adding water from the upper vent 10, cleaning the residue after separating the supernatant of the mixed product for 1 time, opening a valve on the lower discharge outlet 21, allowing the cleaning solution to enter the waste liquid tank 20, pumping the cleaning solution in the waste liquid tank 20 into the mixing device 1 from a water inlet by a pump, and returning to the step (1) for use; the cleaned residue is discharged from the discharge port 18 for iron extraction.
Na in the sodium bichromate product finally obtained in the example2CrO7·H2The O content was 96.22%.
Example 3
By adopting the device of the embodiment 1, the upper vent hole and the lower vent hole are both two, and the sodium bichromate is prepared by taking chromite as a raw material in one step, and the specific method comprises the following steps:
(1) adding 68 mass percent of chromite containing simple substance Cr, 99 mass percent of soda ash, more than 96 mass percent of sodium hydroxide and water into a mixing device 1 according to the mass ratio of 1:1.1:0.5:5, starting a motor 3 and a heating resistor, heating while stirring, uniformly mixing, stopping heating and stirring after the temperature measured by a thermometer reaches 100 ℃, and obtaining a mixed liquid material;
(2) pumping the mixed liquid material obtained in the step (1) out of a material liquid outlet of the mixing device 1 by a pressure pump 6, allowing the mixed liquid material to enter a horizontal reaction kettle 7 from a mixed liquid port 8, closing each port on the horizontal reaction kettle 7 after the liquid level in the horizontal reaction kettle 7 obtained from a liquid level meter 12 reaches a reaction boundary line, opening an oxygen inlet 14 and an upper exhaust port 10, allowing oxygen to enter the horizontal reaction kettle 7 from an oxygen tank 23, continuously introducing oxygen for ten minutes, closing each port, opening the oxygen inlet, introducing oxygen until a pressure gauge 11 displays that the pressure reaches 3.5MPa, closing the oxygen inlet 14, opening a heating resistor in the horizontal reaction kettle 7 to heat the internal material, stopping heating after a temperature gauge 19 displays that the temperature is 230 ℃, and reacting for 2 hours;
(3) after the reaction in the step (2), opening a carbon dioxide inlet 15 and an upper exhaust port 10, introducing carbon dioxide gas for 10 minutes, closing the upper exhaust port 10, continuously introducing the carbon dioxide gas until a pressure gauge 11 displays that the air pressure is 1.3Mpa, simultaneously injecting cold water into a cooling water inlet 22 of a cooling device 17, cooling, and reacting for 2 hours to obtain a mixed product, wherein a temperature thermometer 19 displays that the temperature is 60 ℃;
(4) pumping the supernatant of the mixed product in the step (3) into a separation tank 26 from a supernatant outlet 16 by using a pump, reducing the temperature of the separation tank 26 to 15 ℃ by using a cooling device which is arranged outside the separation tank 26 and outside the horizontal reaction kettle 7 in the separation tank 26, preserving the heat, firstly obtaining white sodium bicarbonate crystals, opening a valve between a decomposition tank 25 and the separation tank 26 when the sodium bicarbonate crystals are not increased any more, separating the sodium bicarbonate crystals from the bottom of the separation tank 26, entering the decomposition tank 25, opening a heating resistor in the separation tank 26, heating the solution left in the separation tank 26 to 80 ℃ for concentration after separation, monitoring by using a thermometer, after the solution is heated to the volume which is not changed any more, filling a liquid level meter in the separation tank 26 for volume observation, and cooling to room temperature by using a cooling device arranged outside the separation tank 26 to obtain a sodium bichromate product;
starting a heating resistor in the decomposition tank 25, heating the sodium bicarbonate in the decomposition tank 25, stopping heating after a thermometer displays that the temperature reaches 100 ℃, decomposing the sodium bicarbonate to obtain sodium carbonate and carbon dioxide, pumping the carbon dioxide into a carbon dioxide gas tank 24 by a pump, and keeping the step (2) for later use; when no carbon dioxide gas is generated, pumping the obtained sodium carbonate into the mixing device 1 from a soda ash inlet by a pump, and returning to the step (1) for use;
adding water from the upper vent 10, cleaning the residue after separating the supernatant of the mixed product for 1 time, opening a valve on the lower discharge outlet 21, allowing the cleaning solution to enter the waste liquid tank 20, pumping the cleaning solution in the waste liquid tank 20 into the mixing device 1 from a water inlet by a pump, and returning to the step (1) for use; the cleaned residue is discharged from the discharge port 18 for iron extraction.
Na in the sodium bichromate product finally obtained in the example2CrO7·H2The O content was 97.22%.
Claims (6)
1. A method for preparing sodium bichromate by taking chromite as a raw material in one step is characterized by comprising the following steps:
(1) mixing and stirring chromite, soda ash, sodium hydroxide and water according to the mass ratio of 1: 1-1.1: 0.4-0.5: 5, and heating to 100 ℃ to obtain a mixed liquid material;
(2) reacting the mixed liquid material obtained in the step (1) for 2-3 h under the oxygen pressure of 3-3.5 Mpa and the temperature of 200-230 ℃;
(3) after the reaction in the step (2), changing oxygen into carbon dioxide gas, wherein the pressure is 1.2-1.3 Mpa, the temperature is 60-70 ℃, and reacting for 2-3 h to obtain a mixed product;
(4) separating supernatant of the mixed product obtained in the step (3), obtaining white sodium bicarbonate crystals at the temperature of 10-15 ℃, separating the sodium bicarbonate, concentrating the solution, and cooling to obtain a sodium bichromate product;
decomposing the sodium bicarbonate crystals at 100 ℃ to obtain sodium carbonate and carbon dioxide, returning the carbon dioxide to the step (3) for use, and returning the sodium carbonate to the step (1) for use; washing the residue separated from the mixed product with water for 1-2 times, and then extracting iron, wherein the washing liquid returns to the step (1);
the device used in the method comprises a mixing device (1), a stirring device, a horizontal reaction kettle (7), a waste liquid groove (20), an oxygen tank (23), a carbon dioxide gas tank (24), a decomposition tank (25) and a separation tank (26), the mixing device (1) is internally provided with a stirring device, the mixing device (1) is provided with 4 feed inlets and a discharge outlet, the discharge outlet is connected with a mixture liquid port (8) at the upper part of the horizontal reaction kettle (7) through a pump (6), the horizontal reaction kettle (7) is also provided with more than one upper emptying port (10), an oxygen inlet (14), a carbon dioxide inlet (15), a supernatant discharge port (16), a discharge outlet (18) and more than one lower discharge port (21), each port is provided with a valve, the lower discharge port (21) is connected with a waste liquid tank (20), and the waste liquid tank (20) is connected with one of the feed inlets of the mixing device (1) through a pump;
the oxygen inlet (14) is connected with an oxygen tank (23), the carbon dioxide inlet (15) is connected with a carbon dioxide tank (24),
the supernatant fluid outlet (16) is connected with a separating tank (26) through a pump, the bottom of the separating tank (26) is connected with the top of a decomposing tank (25), a valve is arranged between the decomposing tank (25) and the separating tank (26), the side surface of the decomposing tank (25) is connected with a carbon dioxide gas tank (24) through a pump, and the bottom of the decomposing tank (25) is connected with one of the feed inlets of the mixing device (1) through a pump;
the stirring device comprises a self-suction paddle (2), a motor (3), a stirring rod (4) and an open type worm gear stirring blade (5), one end of the stirring rod (4) penetrates through the top of the mixing device (1) to be connected with the motor (3), the self-suction paddle (2) is arranged in the middle of the stirring rod (4), and the open type worm gear stirring blade (5) is arranged at the bottom of the stirring rod (4);
a cooling device (17) is arranged outside the horizontal reaction kettle (7), the cooling device (17) wraps the lower part of the horizontal reaction kettle (7), the interior of the cooling device (17) is of a hollow structure, a cooling water inlet (22) is arranged at the lower part of the cooling device (17), and a cooling water discharge outlet (13) is arranged at the upper part of the cooling device; the outside of the separating tank (26) is provided with a cooling device which is the same as the outside of the horizontal reaction kettle (7).
2. The one-step preparation method of sodium bichromate from chromite as the raw material according to claim 1, wherein the mass percentage content of the elementary substance Cr in the chromite in the step (1) is 68%, the purity of the soda is 99%, and the purity of the sodium hydroxide is more than 96%.
3. The method for preparing sodium bichromate from chromite by one step according to claim 1, wherein a heating resistor and a thermometer are arranged in the mixing device (1).
4. The method for preparing sodium bichromate from chromite by one step according to claim 1, wherein a heating resistor, a thermometer (19), a pressure gauge (11) and a liquid level meter (12) are further arranged in the horizontal reaction kettle (7).
5. The method for preparing sodium bichromate by using chromite as a raw material in one step according to claim 1, wherein a manhole (9) is further arranged on the horizontal reaction kettle (7).
6. The method for preparing sodium bichromate from chromite by one step according to claim 1, wherein heating resistors and thermometers are arranged in the decomposing tank (25) and the separating tank (26).
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| CN102649584B (en) * | 2011-08-22 | 2014-08-13 | 四川省银河化学股份有限公司 | Preparation method of sodium bichromate |
| CN102897838B (en) * | 2012-11-19 | 2014-12-10 | 四川省银河化学股份有限公司 | One-step preparation method of sodium bichromate |
| CN103193271B (en) * | 2013-04-02 | 2014-12-10 | 四川省银河化学股份有限公司 | Method for producing high-quality sodium bichromate |
| CN105129852B (en) * | 2015-09-15 | 2017-07-11 | 四川省银河化学股份有限公司 | The system that a kind of high-efficiency self-circulation wet method continuously prepares sodium dichromate |
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2019
- 2019-08-29 CN CN201910805430.3A patent/CN110482605B/en active Active
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