CN109019645B - Production system and production method of large-particle magnesium nitrate - Google Patents
Production system and production method of large-particle magnesium nitrate Download PDFInfo
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- CN109019645B CN109019645B CN201811115666.6A CN201811115666A CN109019645B CN 109019645 B CN109019645 B CN 109019645B CN 201811115666 A CN201811115666 A CN 201811115666A CN 109019645 B CN109019645 B CN 109019645B
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Abstract
The invention provides a production system and a production method of large-particle magnesium nitrate, wherein the production system comprises a batching reactor, a first filtering device, a filtrate tank, an evaporation concentration device, a second filtering device, a heat preservation tank and a roller granulator which are sequentially connected; wherein, the batching reactor is used for providing the reaction place of magnesium oxide and dilute nitric acid, and first filter equipment and second filter equipment are used for getting rid of insoluble matter, and filtrate tank and heat preservation groove are used for preserving the material, and evaporation concentration device is used for preparing concentrate, and the cylinder granulator is used for realizing the granulation process of large-granule magnesium nitrate; a method for producing large-particle magnesium nitrate, comprising: dissolving solution preparation, primary filtration, evaporation concentration, secondary filtration and roller granulation. The production system and the production method of the large-particle magnesium nitrate can realize continuous production of the large-particle magnesium nitrate on the premise of saving the occupied area and reducing the economic cost.
Description
Technical Field
The invention belongs to the technical field of magnesium nitrate production, and particularly relates to a production system and a production method of large-particle magnesium nitrate.
Background
Modern science holds that magnesium element is a main component of plant chlorophyll, and if the magnesium element is not supplied sufficiently, plant leaves can be yellow, so that the yield of crops is affected. The magnesium nitrate is used as a full nitrate nitrogen fertilizer, can provide magnesium element for crops, improves the chlorophyll content of plants and promotes the plants to carry out photosynthesis. Meanwhile, compared with magnesium sulfate and magnesium chloride, the magnesium nitrate fertilizer does not contain sulfur and chlorine, and is particularly suitable for young plants.
The existing granular magnesium nitrate products are manufactured by a high tower granulation method, but the granulation tower has larger volume and higher investment cost, and is not suitable for small and medium-sized enterprises. And the high tower granulation process needs to convert the raw material mixture into a flowable molten state, thereby improving the difficulty of actual operation. In addition, the granularity of the magnesium nitrate product obtained by the high tower granulation method is smaller, moisture absorption and caking are easy, and meanwhile, the granularity adjusting range of the product of the granulation tower is smaller, so that the magnesium nitrate granules with multiple specifications cannot be produced.
Disclosure of Invention
Therefore, the invention aims to provide a production system and a production method of large-particle magnesium nitrate, which realize continuous production of the large-particle magnesium nitrate on the premise of saving the occupied area and reducing the economic cost.
In order to achieve the above purpose, the technical scheme of the invention is realized as follows:
in a first aspect, a production system of large-particle magnesium nitrate comprises a batching reactor, a first filtering device, an evaporation concentration device, a second filtering device and a roller granulator which are sequentially connected;
the batching reactor is used for providing the reaction place of magnesium oxide and dilute nitric acid, and comprises a shell and a feeding pipeline, wherein the feeding pipeline is arranged at the top of the shell and is used for feeding magnesium oxide and dilute nitric acid into the shell and providing a buffer space for the reaction of the magnesium oxide and the dilute nitric acid, so that the phenomenon of groove overflow is eliminated.
Further, a filtrate tank is arranged between the first filtering device and the evaporation concentration device, and the filtrate tank is used for storing and buffering outlet materials of the first filtering device.
Further, a heat preservation groove is arranged between the second filtering device and the roller granulator, and the heat preservation groove is used for carrying out temperature and buffering on outlet materials of the second filtering device.
Further, evaporation concentration device is the triple effect evaporator, and evaporation concentration device's charge-in pipeline sets up on the second effect evaporator, and discharge pipe sets up on first effect evaporator, and the material flows through second effect evaporator, third effect evaporator and first effect evaporator in proper order in evaporation concentration device inside, is equipped with the delivery pump between third effect evaporator and first effect evaporator.
Further, the feeding pipeline comprises a housing, an inner pipeline and an outer pipeline, the housing is arranged above the shell, the outer pipeline is arranged inside the housing, the lower end of the outer pipeline penetrates out of the bottom surface of the housing and then is inserted into the shell, the inner pipeline is arranged inside the outer pipeline, the upper end of the inner pipeline penetrates out of the top surface of the shell, and a gap exists between the inner pipeline and the outer pipeline; the inner pipeline and the outer pipeline are used for providing places for contact of materials and guiding the materials overflowed by the reaction into the housing.
Further, a feeding connecting pipe is arranged on the outer pipeline, and the free end of the feeding connecting pipe penetrates out of the side wall of the housing.
Further, the part of the inner pipeline, which is exposed out of the housing, is provided with an inclined section, and the inclined section is used for buffering the input materials.
Furthermore, the housing and the shell are communicated through a balance pipeline, a bidirectional pressure release valve is arranged on the balance pipeline, and the balance pipeline is used for balancing the air pressure inside the shell and the air pressure inside the housing.
Further, a circulating pipeline is arranged on the housing and used for guiding materials in the housing into the housing.
Further, the circulation pipeline is provided with an emptying connecting pipe, the emptying connecting pipe is arranged at the lowest part of the circulation pipeline, and the emptying connecting pipe is used for thoroughly emptying residual materials in the housing and the circulation pipeline during shutdown.
Further, a winding type coil pipe is arranged outside the shell, a circulating heat exchange medium is led into the coil pipe, and the coil pipe is used for carrying out heat exchange on the batching reactor, so that the materials in the shell maintain constant temperature.
In another aspect, a method for producing large particle magnesium nitrate includes the steps of:
preparing a dissolving solution: magnesium oxide and dilute nitric acid are put into a batching reactor, wherein the magnesium oxide is fed from an inner pipeline, the dilute nitric acid is fed from a feeding connecting pipe, and the magnesium oxide and the dilute nitric acid enter a shell and are stirred and mixed to obtain a solution;
and (3) primary filtration: filtering the solution by a first filtering device to remove acid insoluble substances, and delivering the filtrate to a filtrate tank for storage.
And (3) evaporating and concentrating: concentrating the filtered solution by an evaporation concentration device;
and (3) secondary filtration: filtering the concentrated solution by a second filtering device, separating out residual solid insoluble matters, and delivering the obtained filtered concentrated solution to a heat preservation tank for preservation;
granulating by a roller: and (5) carrying out roller granulation by a roller granulator to obtain a large-particle magnesium nitrate product.
Further, in the process of preparing the dissolution liquid, the concentration of the added dilute nitric acid is between 37 and 39 percent, and the pH value in the batching reactor is controlled to be between 5 and 7.
Further, in the preparation process of the dissolving solution, the reaction temperature is controlled to be 60-80 ℃ and the reaction time is controlled to be 2.5-3.5 h.
Further, the temperature of the filtrate in the filtrate tank is controlled between 70 ℃ and 80 ℃.
Further, in the evaporation concentration process, the temperature in the evaporator is controlled to be 135-138 ℃, and the concentration of the obtained concentrated solution is ensured to be 96-99%.
Compared with the prior art, the production system and the production method for the large-particle magnesium nitrate have the following advantages:
(1) The production system of the large-particle magnesium nitrate provided by the invention has the advantages that the roller granulator is used for granulating instead of the granulating tower, so that the occupied space is saved, and the economic cost is reduced; meanwhile, the system can improve the granularity of the magnesium nitrate product and produce large-particle magnesium nitrate products with granularity of 3mm-6 mm.
(2) According to the large-particle magnesium nitrate production system, the raw materials are buffered through the batching reactor, the phenomenon of groove overflow is avoided, foam generated by the reaction can be collected through the feeding pipeline, and the utilization rate of raw materials is improved.
(3) The method for producing the large-particle magnesium nitrate, which is created by the invention, utilizes the raw material concentrated solution and the roller granulator to work, can ensure continuous production of the magnesium nitrate, and simultaneously reduces the economic cost.
(4) According to the large-particle magnesium nitrate production method, the dissolved solution is concentrated through the multi-effect evaporator, so that the energy utilization rate is improved, and meanwhile, the production efficiency is improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute an undue limitation on the invention. In the drawings:
FIG. 1 is a schematic flow chart of a large-particle magnesium nitrate production system according to an embodiment of the invention;
FIG. 2 is a schematic diagram of a batch reactor according to an embodiment of the invention;
FIG. 3 is a schematic cross-sectional view of a batch reactor according to an inventive embodiment of the present invention;
FIG. 4 is a schematic view of an evaporation and concentration device according to an embodiment of the present invention;
FIG. 5 is a schematic diagram showing the steps of a method for producing large-particle magnesium nitrate according to an embodiment of the present invention.
Reference numerals illustrate:
1-a batching reactor; 11-a housing; 111-baffle plates; 12-a housing; 121-a circulation pipe; 122-emptying the connecting pipe; 13-an inner pipe; 131-inclined section; 14-an outer pipe; 141-a feed connection tube; 151-stirring motor; 152-stirring shaft; 153-stirring blade; 16-balancing the pipeline; 161-a two-way pressure relief valve; 2-a first filtration device; 21-a first filter-press feed pump; 22-a first filter press device; 3-a filtrate tank; 4-evaporation concentration device; 41-a first effect evaporator; 42-a second effect evaporator; 43-third effect evaporator; 44-a first effect heater; 45-a second effect heater; 46-a third effect heater; 47-a transfer pump; 5-a second filtration device; 51-a second filter pressing feed pump; 52-a second filter pressing device; 6, a heat preservation groove; 7-a roller granulator; 8-cooling packaging equipment; s101-preparing a dissolving solution; s102-primary filtering; s103, evaporating and concentrating; s104, secondary filtration; s105, roller granulation.
Detailed Description
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
In the description of the invention, it should be understood that the terms "center," "longitudinal," "transverse," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships that are based on the orientation or positional relationships shown in the drawings, merely to facilitate describing the invention and simplify the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be configured and operate in a particular orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", etc. may explicitly or implicitly include one or more such feature. In the description of the invention, unless otherwise indicated, the meaning of "a plurality" is two or more.
In the description of the invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the creation of the present invention can be understood by those of ordinary skill in the art in a specific case.
The invention will be described in detail below with reference to the drawings in connection with embodiments.
A production system of large-particle magnesium nitrate comprises a batching reactor 1, a first filtering device 2, an evaporation concentration device 4, a second filtering device 5, a roller granulator 7 and a cooling packaging device 8 which are sequentially connected, wherein the connection relation of the batching reactor 1, the first filtering device 2, the evaporation concentration device 4, the second filtering device 5, the roller granulator and the cooling packaging device 8 can be schematically shown in figure 1. Wherein, the batching reactor 1 is used for fully dissolving the original materials (magnesium oxide and dilute nitric acid) to obtain a magnesium nitrate solution; the first filtering device 2 filters acid insoluble matters in the magnesium nitrate solution to obtain clear filtered solution; the evaporation and concentration device 4 heats and evaporates the filtered solution to obtain a concentrated magnesium nitrate solution with high concentration; the second filtering device 5 filters the concentrated solution again to thoroughly remove solid insoluble substances in the concentrated solution; the roller granulator 7 takes the filtered magnesium nitrate concentrated solution as a gunite raw material for granulation, so as to obtain a large-particle magnesium nitrate product; the cooling and packaging equipment 8 is used for cooling and packaging the magnesium nitrate granules.
In order to ensure the continuous operation of the production system, the system is provided with a filtrate tank 3 and a heat preservation tank 6, wherein the filtrate tank 3 is arranged between the first filtering device 2 and the evaporation concentration device 4, and the dissolution liquid generated in the batching reactor 1 is pumped into the filtrate tank 3 through a centrifugal pump, and a temperature controller is further arranged in the filtrate tank 3. The filtrate tank 3 can accomodate the buffering to the export material of first filter equipment 2, and specifically, when batching reactor 1 gets into the during operation, its first time produced solution only gets into filtrate tank 3 and stores, and when waiting batching reactor 1 to once more output solution, the first time solution flow direction that collects in the filtrate tank 3 filters to first filter equipment 2, and then guarantees the operational continuity of this system.
Since the electric heater and the refrigerator controlled by the temperature controller are arranged in the filtrate tank 3, the temperature of the dissolved solution in the filtrate tank 3 can be controlled. The temperature controller is an automatic control element which can generate physical deformation in the switch according to the temperature change of the working environment, and further control other electronic elements to execute on or off actions. For example, in this embodiment, the temperature controller may be an XMTG-6000 temperature controller of the company ascali, the detection end of the temperature controller is disposed inside the filtrate tank 3, the control panel is disposed outside the filtrate tank 3, and the control output end of the temperature controller is connected to the electric heater and the refrigerator respectively through wires. Before the start of the operation, a suitable storage temperature interval is set, and the temperature controller adjusts the actual temperature in the filtrate tank 3 so as to maintain the actual temperature within the set interval.
The heat preservation groove 6 is arranged between the second filtering device 5 and the roller granulator 7, and the heat preservation groove 6 can preserve heat of the filtered concentrated solution produced by the second filtering device 5, so that the material can conveniently enter the roller granulator 7 for slurry spraying granulation.
As shown in fig. 2 and 3, the batch reactor 1 in the present production system is schematically shown, and as can be seen from the figure, the batch reactor 1 includes a housing 11, a feeding pipe, a stirring motor 151, a stirring shaft 152, and stirring blades 153.
Wherein, the feeding pipeline includes housing 12, inner conduit 13 and outer pipeline 14, housing 12 sets up in casing 11 top, and outer pipeline 14 sets up inside housing 12, and inner conduit 13 sets up inside outer pipeline 14. The lower end of the outer pipe 14 is inserted into the housing 11 through the bottom surface of the cover 12, and the upper end of the inner pipe 13 is contacted with the outside through the top surface of the housing 11. In addition, a gap exists between the inner pipe 13 and the outer pipe 14, and the casing 12 encloses this gap as a closed space.
Because magnesium oxide and dilute nitric acid are contacted in the feeding process, and the dilute nitric acid has certain oxidizing property, the reaction process is more severe. The reaction equation of dilute nitric acid with magnesium oxide is as follows:
MgO+2HNO 3 ＝Mg(NO 3 ) 2 +H 2 O
the heat evolved in this reaction is relatively large and the liquid phase can be brought to boiling point rapidly, so that the water in the product becomes water vapor rapidly. At the same time, part of the dilute nitric acid in the raw material is decomposed by the reaction heat, and nitrogen dioxide gas is generated. And a large amount of gas upwards escapes to upwards blow out the magnesia powder with lighter mass and prevent the subsequent material from entering, so that the phenomenon of channeling is avoided, a large amount of reaction heat moves towards a feeding port along with the phenomenon of channeling, and personnel danger can be generated when the feeding quantity is larger.
In this embodiment, the overflow phenomenon is buffered by the inner pipe 13 and the outer pipe 14, and when a severe reaction occurs, the overflowed gas and liquid flow into the housing 12 through the gap between the two pipes, and the housing 12 collects the materials, so that the risk induced by the overflow phenomenon is avoided, the overflowed materials can be recovered, and the economic cost is reduced.
Preferably, the outer pipe 14 is provided with a feeding connection pipe 141, the height of the inner pipe opening of the feeding connection pipe 141 is lower than that of the bottom end of the inner pipe 13, and the free end of the feeding pipe 141 penetrates out of the side wall of the housing 12. The feed nipple 141 is used to deliver dilute nitric acid into the outer pipe 14 so that the inner pipe 13 becomes a separate passage for magnesium oxide powder, avoiding the reaction of magnesium oxide and dilute nitric acid during the feeding process. In addition, the inner pipe opening of the feeding pipe 141 is lower than the bottom end of the inner pipe 13, so that the contact position of magnesium oxide and dilute nitric acid can be reduced to the inside of the outer pipe 14, the function of a gap between the inner pipe and the outer pipe is fully exerted, and the buffering effect of the feeding pipe is improved.
Preferably, the portion of the inner conduit 13 that exposes the casing 12 is provided with an inclined section 131, the inclined section 131 having an angle of between 30 ° and 60 ° with respect to the horizontal. By providing the inclined section 131, the moving speed of the magnesia powder in the inner pipeline 13 can be reduced, and pipeline blockage caused by excessive input of the magnesia powder is avoided.
In addition, since a large amount of gas is emitted by the reaction of magnesium oxide and dilute nitric acid, the enclosure 12 in a closed state has a safety hazard, and the balance pipe 16 is provided between the enclosure 12 and the housing 11 in this embodiment, and the balance pipe 16 is provided with a bidirectional pressure release valve 161. When the pressure in the housing 12 is too high, the bidirectional pressure release valve 161 is tripped, so that the air flow in the housing 12 flows into the housing, and the air pressure balance between the housing 12 and the housing 11 is ensured; meanwhile, when the air pressure in the housing 12 is low, the bidirectional pressure release valve 161 can allow the air in the housing 11 to flow into the housing 12, so as to avoid the negative pressure environment in the housing 12 to lead to slow feeding.
As a preferred embodiment of the present embodiment, a circulation pipe 121 communicating with the housing 11 is provided on the casing 12, and a vent pipe 122 for evacuating the circulation pipe 121 and the casing 12 is provided on the circulation pipe 121.
Specifically, the upper pipe orifice of the circulation pipe 121 is disposed at the bottom of the casing 12, so as to facilitate drainage of the residual materials in the casing 12; meanwhile, the arrangement height of the pipe orifice at the lower end of the circulation pipe 121 is higher than the bottom end of the outer pipe 4, so as to avoid the backflow of the circulation pipe 121 when the outer pipe 14 is discharged. In order to facilitate the emptying operation of the emptying pipe 122, the connection between the emptying pipe 122 and the circulation pipe 121 should be located at the lowest position of the circulation pipe 121, and a stop valve may be further disposed on the emptying pipe 122 to ensure that the batch reactor 1 is in a closed state during operation.
In order to improve the reaction speed and quality of magnesium oxide and dilute nitric acid, a stirring device is arranged in the batching reactor 1, the stirring device comprises stirring blades 153 arranged in the shell 11 and a stirring motor 151 arranged at the top of the shell 11, and an output shaft of the stirring motor 151 is connected with the stirring blades 153 through a stirring shaft 152. In addition, a baffle 111 is disposed inside the housing 11, an upper end of the baffle 111 is connected to a top surface of the housing 11, and a gap exists between a lower end of the baffle 111 and a bottom surface of the housing 11. The materials thrown into the shell 11 through the material throwing pipeline flow to other positions in the shell 11 through the gap and are stirred through the stirring device, so that the preparation speed of the dissolving liquid is improved.
In addition, in the process of preparing the dissolution solution, the reaction temperature needs to be controlled, preferably, a winding type coil pipe (not shown in the figure) is arranged outside the shell 11, and a heat exchange medium which flows circularly is led into the coil pipe, and can obtain cold energy/heat through an external refrigerator/heater, so that the materials in the shell 11 obtain constant reaction temperature.
When the dissolution liquid is configured, the dissolution liquid enters the first filtering device 2 through a pipeline, and the first filtering device 2 comprises a first filter pressing feeding pump 21 and a first filter pressing device 22. The first filter-press feeding pump 21 pumps the dissolution liquid into the first filter-press device 22, the first filter-press device 22 filters the dissolution liquid in a filter-press manner to remove insoluble substances in the dissolution liquid, and then the filtered dissolution liquid is sent to the filtrate tank 3.
The liquid material flows through the filtrate tank 3 and enters the evaporation and concentration device 4, preferably, the evaporation and concentration device 4 is a three-effect evaporator, and includes a first-effect heater 44, a first-effect evaporator 41, a second-effect heater 45, a second-effect evaporator 42, a third-effect heater 46 and a third-effect evaporator 43, which are sequentially connected through air pipelines. In addition, a feeding pipeline is arranged on the second-effect evaporator 42, a discharging pipeline is arranged on the first-effect evaporator 41, and the second-effect evaporator 42 is sequentially connected with the third-effect evaporator 43 and the first-effect evaporator 41 through the material pipelines. Fig. 4 is a schematic view of the evaporative concentration device 4, wherein the solid lines represent air ducts and the dotted lines represent material ducts.
As shown in fig. 4, for the gas movement in the evaporation concentration device 4: the first effect heater 44 sucks air therein and heats it, and the heated air, as a heat source of the whole evaporation concentration device 4, flows through the first effect heater 44, the first effect evaporator 41, the second effect heater 44, the second effect evaporator 42, the third effect heater 45, and the third effect evaporator 43 in order, and finally flows back to the first effect evaporator 44 for reuse.
For liquid movement in the evaporative concentration device 4: the filtered solution enters the second-effect evaporator 42 through a feeding pipeline, enters the third-effect evaporator 43 after primary concentration, enters the first evaporator 41 after secondary concentration in the third-effect evaporator 43, finally concentrates in the first-effect evaporator 41, and is discharged out of the evaporation concentration device 4 through a discharging pipeline.
Wherein a transfer pump 47 is required between the third effect evaporator 43 and the first effect evaporator 41 for pumping the concentrate, and the concentrate is moved between the second effect evaporator 42 and the third effect evaporator 43 by means of a pressure difference.
Of the three-effect evaporators, the first-effect evaporator 41 has the highest internal temperature and pressure, and the third-effect evaporator 43 has the lowest internal temperature and pressure. The movement of the concentrate from the high energy evaporator to the low energy evaporator does not require the assistance of an external force, while the flow of the concentrate from the third effect evaporator 43 to the first effect evaporator 41 requires the provision of a transfer pump 47 to provide power. In addition, when the concentrated solution flows from the second effect evaporator 42 to the third effect evaporator 43, the flowing direction of the liquid is the same as the flowing direction of the gas, and the heat exchange is performed in the concurrent flow; when the concentrated solution flows from the third effect evaporator 43 to the first effect evaporator 41, the flowing direction of the liquid can be regarded as opposite to the moving direction of the gas, so that the countercurrent heat exchange can be regarded as countercurrent heat exchange, and the countercurrent heat exchange can obtain larger heat exchange temperature difference, so that the concentration effect is improved.
In this embodiment, the filtered solution is concentrated in the second-effect evaporator 42 with medium temperature, so that heat loss caused by too high temperature difference between the material and the air can be avoided, and the heat utilization rate of the hot air can be maximized through the first-effect evaporator 41 with highest temperature before the material leaves the evaporation concentration device 4, so that the concentration rate of the finished product is ensured.
The concentrated material produced by the evaporation and concentration device 4 enters a second filtering device 5, and the second filtering device 5 comprises a second filter pressing feeder 51 and a second filter pressing device 52. The second filtering device 5 can filter the concentrated solution in a pressure filtration mode to remove insoluble residues in the concentrated solution, so that high-quality spray granulation is ensured.
The filtered concentrated solution enters the heat preservation tank 6, and the heat preservation tank 6 can avoid heat loss of the filtered concentrated solution, so that the filtered concentrated solution is ensured to maintain proper slurry spraying temperature before entering the roller granulator 7.
When the filtered concentrated solution enters the roller granulator 7, the spraying granulation process can be started, the roller granulator 7 can be selected from a roller granulator independently developed by the company, the patent publication number is CN203728738U, and the method comprises the following steps: the working process of the drum granulator 7 in the present system is as follows:
after the filtered concentrated solution enters a roller granulator 7, small-particle magnesium nitrate is continuously added from the feeding end of the rotary drum, and the lifting shoveling plate is used for shoveling particles at the bottom of the rotary drum into a cooling bed, so that the particles flow down from an overflow port to form a continuous and uniform curtain. And a nozzle in the rotary drum atomizes the filtered concentrated solution into liquid drops to be sprayed to the material curtain, the liquid drops collide with the moving particles, the surfaces of the particles are coated and solidified, and the enlarged particles fall to the bottom of the rotary drum and are shoveled into the cooling bed again. The above process is continuously repeated in the drum granulator 7 to realize the production of large-particle magnesium nitrate, the granulating and returning materials are derived from small particles and bulk materials after the large particles are crushed, and partial finished products can be used as the granulating and returning materials if necessary.
The production method of the large-particle magnesium nitrate based on the scheme comprises the following steps:
step one, preparing a dissolving solution, namely S101: magnesium oxide and dilute nitric acid are put into a batching reactor 1, wherein the magnesium oxide is put into a batching reactor from an inner pipeline 13, the dilute nitric acid is put into a batching reactor from a feeding connecting pipe 141, and a dissolving solution is obtained after the dilute nitric acid enters a shell 11 and is stirred and mixed;
step two, filtering once S102: filtering the solution by a first filtering device 2 to remove acid insoluble substances, and delivering the filtrate to a filtrate tank 3 for storage;
step three, evaporating and concentrating S103: concentrating the filtered solution by an evaporation concentration device 4;
step four, secondary filtration S104: filtering the concentrated solution by a second filtering device 5, separating residual solid insoluble matters, and delivering the obtained filtered concentrated solution to a heat preservation tank 6 for preservation;
step five, roller granulation S105: and carrying out roller granulation by a roller granulator 7 to obtain a large-particle magnesium nitrate product.
Wherein, in the process of preparing S101 by using the dissolution liquid, the concentration of the dilute nitric acid should be strictly controlled to be between 37 and 39%, and the dissolution liquid is ensured to be in a weak acid environment (namely, the pH is between 5 and 7), preferably, the concentration of the dilute nitric acid is selected to be 38%, and the pH of the dissolution liquid is selected to be 6. The filtering effect of acid insoluble substances can be improved by controlling the concentration of dilute nitric acid, and the working quality of the subsequent steps is improved.
In addition, in the process of preparing S101 by using the dissolution solution, in order to improve the reaction efficiency and the solubility of magnesium nitrate, the reaction temperature should be controlled to be 60-80 ℃, the reaction time should be 2.5-3.5 h, preferably, the reaction temperature is 75 ℃, the reaction time is 3h, the temperature for improving the reaction can be realized by using a winding type coil on the shell 11, and the control of the reaction time can be controlled manually or automatically by using a microcomputer time control switch.
After the dissolved liquid is subjected to a filtering step S102, the dissolved liquid needs to enter the filtrate tank 3 for storage, and preferably, the temperature of the filtrate in the filtrate tank 3 is maintained between 70 ℃ and 80 ℃. The solubility of magnesium nitrate is improved by heating means in the preparation process of the solution, so that the corresponding temperature should be kept in the preservation process after filtration, otherwise, the solubility of solute (magnesium nitrate) in the solution is reduced due to the reduction of the temperature, and crystals are separated out in the solution after filtration.
In the process of evaporating and concentrating S103, the temperature in the evaporator is controlled to be 135-138 ℃, and the concentration of the produced concentrated solution is ensured to be 96-99%. The rapid concentration of the magnesium nitrate solution can be ensured by controlling the internal temperature of the evaporator, and the magnesium nitrate particles produced by spray granulation can have enough magnesium nitrate content by strictly controlling the concentration of the concentrated solution.
The following describes the effects of the above scheme:
the embodiment provides a large-particle magnesium nitrate production system and a production method, which can reduce the occupied area of equipment and the economic cost by replacing the existing high-tower granulation mode with a roller granulation mode; meanwhile, the system can be used for manufacturing magnesium nitrate particles with larger granularity (3-6 mm), and the product is not easy to adhere and agglomerate, thereby being beneficial to storage; the batching reactor 1 in the system eliminates the phenomenon of overflowing of the dissolving solution through the arrangement of the feeding pipeline, and improves the operation safety and the raw material utilization rate. In addition, the magnesium nitrate particles are prepared by the production method without melting raw materials, and continuous production can be ensured by adopting a roller granulation mode, so that the method is more suitable for small and medium-sized enterprises.
The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (3)
1. A production system of large-particle magnesium nitrate, which is characterized in that: comprises a batching reactor (1), a first filtering device (2), a filtrate tank (3), an evaporation concentration device (4), a second filtering device (5), a heat preservation tank (6) and a roller granulator (7) which are sequentially connected;
the batching reactor (1) is used for providing a reaction place of magnesium oxide and dilute nitric acid and comprises a shell (11) and a feeding pipeline, wherein the feeding pipeline is arranged at the top of the shell (11) and is used for feeding the magnesium oxide and the dilute nitric acid into the shell (11) and providing a buffer space for the reaction of the magnesium oxide and the dilute nitric acid, so that the phenomenon of groove overflow is eliminated;
the feeding pipeline comprises a housing (12), an inner pipeline (13) and an outer pipeline (14), wherein the housing (12) is arranged above the shell (11), the outer pipeline (14) is arranged inside the housing (12), the lower end of the outer pipeline (14) penetrates out of the bottom surface of the housing (12) and then is inserted into the shell (11), the inner pipeline (13) is arranged inside the outer pipeline (14), the upper end of the inner pipeline (13) penetrates out of the top surface of the shell (11), and a gap exists between the inner pipeline (13) and the outer pipeline (14); the inner pipeline (13) and the outer pipeline (14) are used for providing places for contact of materials and guiding the materials overflowed by the reaction into the housing (12);
a feeding connecting pipe (141) is arranged on the outer pipeline (14), and the free end of the feeding connecting pipe (141) penetrates out of the side wall of the housing (12); the part of the inner pipeline (13) exposed out of the housing (12) is provided with an inclined section (131), and the inclined section (131) is used for buffering input materials; the housing (12) is communicated with the shell (11) through a balance pipeline (16), a bidirectional pressure release valve (161) is arranged on the balance pipeline (16), and the balance pipeline (16) is used for balancing the air pressure inside the shell (11) and the air pressure inside the housing (12); the casing (12) is provided with a circulating pipeline (121), the circulating pipeline (121) is provided with an emptying connecting pipe (122), and the emptying connecting pipe (122) is arranged at the lowest part of the circulating pipeline (121).
2. A system for producing large particle magnesium nitrate according to claim 1 wherein: the evaporation concentration device (4) is a three-effect evaporator, a feeding pipeline of the evaporation concentration device (4) is arranged on the second-effect evaporator (42), a discharging pipeline is arranged on the first-effect evaporator (41), materials sequentially flow through the second-effect evaporator (42), the third-effect evaporator (43) and the first-effect evaporator (41) in the evaporation concentration device (4), and a conveying pump (47) is arranged between the third-effect evaporator (43) and the first-effect evaporator (41).
3. A system for producing large particle magnesium nitrate according to claim 1 wherein: the outside of the shell (11) is provided with a winding type coil pipe, a circulating heat exchange medium is led into the coil pipe, and the coil pipe is used for carrying out heat exchange on the batching reactor (1) so as to ensure that the materials in the shell (11) maintain constant temperature.
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