CN111854372A - Ammonium chloride drying system and drying process - Google Patents
Ammonium chloride drying system and drying process Download PDFInfo
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- CN111854372A CN111854372A CN202010728823.1A CN202010728823A CN111854372A CN 111854372 A CN111854372 A CN 111854372A CN 202010728823 A CN202010728823 A CN 202010728823A CN 111854372 A CN111854372 A CN 111854372A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B11/00—Machines or apparatus for drying solid materials or objects with movement which is non-progressive
- F26B11/02—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles
- F26B11/04—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis
- F26B11/0463—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis having internal elements, e.g. which are being moved or rotated by means other than the rotating drum wall
- F26B11/0477—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis having internal elements, e.g. which are being moved or rotated by means other than the rotating drum wall for mixing, stirring or conveying the materials to be dried, e.g. mounted to the wall, rotating with the drum
- F26B11/0486—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis having internal elements, e.g. which are being moved or rotated by means other than the rotating drum wall for mixing, stirring or conveying the materials to be dried, e.g. mounted to the wall, rotating with the drum the elements being held stationary, e.g. internal scraper blades
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B11/00—Machines or apparatus for drying solid materials or objects with movement which is non-progressive
- F26B11/02—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles
- F26B11/04—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis
- F26B11/0445—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis having conductive heating arrangements, e.g. heated drum wall
- F26B11/045—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis having conductive heating arrangements, e.g. heated drum wall using heated internal elements, e.g. which move through or convey the materials to be dried
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B23/00—Heating arrangements
- F26B23/10—Heating arrangements using tubes or passages containing heated fluids, e.g. acting as radiative elements; Closed-loop systems
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
- F26B25/001—Handling, e.g. loading or unloading arrangements
- F26B25/002—Handling, e.g. loading or unloading arrangements for bulk goods
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
- F26B25/005—Treatment of dryer exhaust gases
- F26B25/007—Dust filtering; Exhaust dust filters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
- F26B25/06—Chambers, containers, or receptacles
- F26B25/14—Chambers, containers, receptacles of simple construction
- F26B25/16—Chambers, containers, receptacles of simple construction mainly closed, e.g. drum
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B3/00—Drying solid materials or objects by processes involving the application of heat
- F26B3/18—Drying solid materials or objects by processes involving the application of heat by conduction, i.e. the heat is conveyed from the heat source, e.g. gas flame, to the materials or objects to be dried by direct contact
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- Combustion & Propulsion (AREA)
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- Drying Of Solid Materials (AREA)
Abstract
In the embodiment of the invention, the materials are discharged in a flash mode, and the retention time of the materials in a steam rotary dryer is adjusted by controlling the flash capacity, so that the drying quality of the materials can be effectively adjusted. The amount of the moisture-carrying gas depends on the drying amount of the material, the moisture-carrying gas is only used as moisture-carrying working gas, the drying is completed in an indirect mode, the amount of the moisture-carrying gas is very small, the burden of a subsequent tail gas purification system is reduced, and the pollution to the atmosphere is reduced.
Description
Technical Field
The invention relates to an ammonium chloride drying system and an ammonium chloride drying process.
Background
Ammonium chloride is colorless crystal or white crystalline powder, and has hygroscopicity. The powdered ammonium chloride is very deliquescent, the moisture absorption point is generally about 76%, and when the relative humidity in air is higher than the moisture absorption point, the ammonium chloride generates moisture absorption phenomenon and is easy to agglomerate, so that the use of the ammonium chloride is influenced, and therefore, the ammonium chloride needs to be dried before packaging, for example, to avoid agglomeration.
Further, ammonium chloride is relatively weak in chemical stability, and starts to decompose at 100 ℃ and can completely decompose into ammonia gas and hydrogen chloride gas at 337.8 ℃, and therefore, the drying temperature is not too high when ammonium chloride is dried.
It is to be noted that in the field of material drying, the material before drying is generally referred to as wet material, as indicated by reference numeral 3 in fig. 1; the dried material is generally referred to as a dry material, such as a dry product, as indicated by reference numeral 16 in fig. 1. It is to be understood that dry and wet materials are collectively referred to as materials. In the drying process, the gas used to carry away the components volatilized from the drying, such as water vapor, ammonia gas, ammonium chloride dust, is generally referred to as moisture-carrying gas, which is used as a working gas in the drying process.
Fig. 1 shows a schematic diagram of a known internal heating fluidized bed drying system, which is also a conventional ammonium chloride drying system. In the figure, the fluidized bed 4 is configured such that the heating air for drying the material is supplied to the front stage by the drying blower 23 and the cooling air for cooling the material is supplied to the rear stage by the cooling blower 24. The heated air and the cooling air are used as functional gases for heating or cooling materials and are used as moisture-carrying gases, and the gases are used as dry tail gas, subjected to two-stage dust removal by the cyclone dust collector 6 and the bag-type dust collector 9, subjected to ammonia removal by the wet dust collector and directly discharged into the atmosphere 11. In contrast, the functional gas is used as moisture carrying gas, which is seriously excessive in terms of the requirement of carrying moisture, is easy to carry away a larger amount of ammonia gas and ammonium chloride dust generated by drying, inevitably increases the difficulty of treating the dried tail gas, and is difficult to remove and easy to cause environmental pollution because of more harmful gases.
In addition, the working gas used for drying has a higher temperature than the moisture-carrying gas, and the temperature of the working gas used for drying at the end of drying is still high, so that the drying tail gas tends to take away more heat, resulting in higher overall drying energy consumption. Meanwhile, once the types of the fluidized bed 4 and the airflow dryer are determined, the fluidization wind speed and the air inlet temperature are not allowed to fluctuate greatly due to the characteristics of fluidization drying of the materials, the air inlet amount and the energy consumption are determined, and the elasticity of the product is small. Meanwhile, the ammonium chloride particles are in a fluid state by fluidization through airflow, are in a turbulent flow state, are easy to generate violent collision with drying and circulating process equipment, damage crystal forms and generate fine dust materials, so that the particle size distribution of the ammonium chloride is poor, and the dust materials are easy to be carried out by dry tail gas to generate loss.
Chinese patent document CN207849900U discloses a closed-cycle fluidization system for ammonium chloride drying, which employs two fluidized beds 4, one of which is configured as a fluidized bed dryer and the other of which is configured as a fluidized bed cooler, and uses carbon dioxide as a moisture-carrying and heated working gas. Most of the working gas is recycled after cloth bag dust removal and water washing deamination. The carbon dioxide can be combined with ammonia gas to generate ammonium carbonate, so that the content of the ammonia gas in the working gas can be reduced. However, the dual-purpose of the working gas is an inherent characteristic of the fluidized bed, the problem of large amount of dry tail gas cannot be solved all the time, and even if the internal circulation is adopted, the environmental friendliness is good, but the workload of the process equipment for removing ammonia gas is increased. Meanwhile, the problems that the ammonium chloride has poor particle size distribution and more materials are carried away by working tail gas cannot be avoided. In particular, the carbon dioxide needs to be supplied continuously, so that the problem of 'cycle gas expansion' is easily caused in a process system, and accidents are easily caused when the load of process equipment is exceeded.
Chinese patent document CN208419545U discloses a steam rotary drying system for ammonium salts, in which the moisture-carrying gas is independently distributed, and the water vapor for heating is not in direct contact with the material, but exchanges heat by means of physical isolation. The carrying capacity of the moisture-carrying ammonia gas and dust can be greatly reduced due to the small amount of the moisture-carrying gas and the slow flow rate. This patent document relies on a rotary drum, installs the pipeline that is used for circulating saturated vapor in the rotary drum, and along with the rotation of rotary drum, the material is gradually removed from the one end of inclined rotary drum to the other end when being stirred, and the rotational speed of rotary drum is lower relatively, is difficult to make ammonium chloride granule breakage or wearing and tearing to make ammonium chloride's particle size distribution better, carry the moisture gas flow rate in addition slower, the volume of the ammonium chloride particle that can be taken away by carrying the moisture is less relatively. In this patent document, the cooling still requires a large amount of cold air as the cooling air and the fluidizing air, and the consumption of the working gas is still large, and the burden of the subsequent process is increased. At the same time, the presence of a fluidized bed also limits its capacity.
Disclosure of Invention
The invention aims to provide an ammonium chloride drying system which can fully dry ammonium chloride and has relatively less tail gas emission; the invention also provides an ammonium chloride drying process.
In an embodiment of the present invention, there is provided an ammonium chloride drying system comprising:
one end of the steam rotary dryer is a feeding end, and the other end of the steam rotary dryer is a discharging end; the discharge end is blocked by an end plate, the end plate is provided with a flash port, and the flash port is provided with an adjusting mechanism for adjusting the opening degree of the flash port;
the moisture-carrying assembly is connected into the steam rotary dryer from the feed end;
a feed assembly for introducing wet material into the steam rotary dryer at a feed end;
the discharging assembly is used for guiding the dry materials out of the steam rotary dryer from the discharging end;
and the tail gas purification system is used for guiding out moisture-carrying gas from the discharge end and discharging the moisture-carrying gas into the atmosphere after purification.
Optionally, the adjustment mechanism is configured to:
the two opposite sides of the flash opening are provided with slots for providing insertion plates guiding the slots so as to adjust the opening of the flash opening through the positions of the insertion plates in the slots.
Optionally, the edge of the end plate is provided with at least one discharge opening with a sealing gate.
Optionally, the center of the flash port is located at one half to two thirds of the end plate from the center of the circle in the radial direction.
Optionally, at least one and no more than three separation points are arranged in a rotary cylinder of the steam rotary dryer, each separation point is provided with a plurality of material baffle groups perpendicular to the axis of the rotary cylinder, and the interior of the rotary cylinder is divided into a plurality of drying areas;
a pipe support body for supporting the axial pipe of the saturated steam pipe is arranged between the baffle plate groups;
and a discharge gap is determined between the material baffle group and the pipe support body and is used for the circulation of materials in the front-stage drying area to the rear-stage drying area.
Optionally, the tail gas purification system comprises a cyclone dust collector at the front stage and a wet dust collector at the rear stage;
wherein the wet dust collector is based on spraying;
correspondingly, a circulating pipeline and a matched spray pump are provided for circulating spray water; the circulating pipeline is provided with a bypass for discharging concentrated liquid, and the wet dust collector is provided with a liquid supplementing branch for supplementing liquid.
Optionally, the feed assembly comprises a blender;
correspondingly, the steam rotary dryer or the discharging assembly is provided with a material returning structure or a material returning mechanism for guiding a given amount of dry materials into the mixer so as to mix the given amount of dry materials and wet materials and then feed the mixed materials into the steam rotary dryer.
Optionally, when the material returning mechanism is used for returning materials, the feeding end of the material returning mechanism is connected with the vibrating screen matched with the discharging assembly;
when a material returning structure is adopted, the material returning structure is configured as follows:
the outer surface of a rotary cylinder of the steam rotary dryer is provided with a spiral feed back channel.
Optionally, the material returning mechanism and the material returning channel are both provided with flow control devices.
Optionally, the discharge assembly is provided with a cooler;
the cooler is provided with a loosening air device which comprises a compressed air system;
a chamber of the cooler for circulating the dry materials is provided with a loosening air hole or an aeration head;
loosening the air holes or the aeration heads to be connected with the compressed air system;
and an exhaust port is arranged on the cooler and is connected to the tail gas purification system.
In an embodiment of the present invention, there is also provided an ammonium chloride drying system, including the steps of:
1) drying the introduced wet material by using a steam rotary dryer, and introducing moisture from the feed end of the steam rotary dryer in the drying process; discharging in a flash mode at a discharging end in the drying process, and adjusting the retention time of the material in the steam rotary dryer by adjusting the flash speed;
2) the moisture-carrying gas is led out from the discharge end of the steam rotary dryer;
3) the discharged moisture-carrying gas is purified and discharged.
Optionally, the material gradually increases drying capacity during the drying cycle.
Optionally, the drying time of the material is 15-25 min.
Optionally, before the moisture-carrying gas is introduced into the steam rotary dryer, the moisture-carrying gas is heated to reach a temperature of 110-160 ℃.
Optionally, a given amount of dry material is mixed into the wet material before it is introduced into the steam rotary dryer;
the amount of wet material mixed into the dry material is directly related to the amount of caking in the dry material.
Optionally, screening the dry materials, and then cooling the screened dry materials;
the amount of caking was determined by the reject fraction.
Optionally, compressed air is introduced to turn the dry materials over to avoid sticking while the dry materials are cooled.
In the embodiment of the invention, the material is discharged in a flash mode, and the retention time of the material in the steam rotary dryer is adjusted by controlling the flash capacity, so that the drying quality of the material can be effectively adjusted. The amount of the moisture-carrying gas depends on the drying amount of the material, the moisture-carrying gas is only used as moisture-carrying working gas, the drying is completed in an indirect mode, the amount of the moisture-carrying gas is very small, the burden of a subsequent tail gas purification system is reduced, and the pollution to the atmosphere is reduced.
Drawings
Fig. 1 is a schematic diagram of a known internal heating fluidized bed drying system.
Fig. 2 is a schematic diagram of an ammonium chloride drying system in a first embodiment.
Fig. 3 is a schematic diagram of an ammonium chloride drying system in a second embodiment.
FIG. 4 is a schematic diagram of an exemplary embodiment of a tail end of a steam rotary dryer.
FIG. 5 is a schematic cross-sectional view of the middle portion of the steam rotary dryer in one embodiment.
Fig. 6 is a schematic diagram of a first striker plate structure in an embodiment.
Fig. 7 is a schematic structural diagram of a second retainer plate in an embodiment.
In the figure: 1. condensed water discharge, 2 saturated steam, 3 wet materials, 4 fluidized bed, 5 returning material screw conveyer, 6 cyclone dust collector, 7 cyclone discharge valve, 8 returning material discharge valve, 9 bag dust collector, 10 induced draft fan, 11 exhaust into atmosphere, 12 wet dust collector, 13 screw conveyer, 14 bag discharge valve, 15 spray pump, 16 drying product, 17 circulating water return, 18 circulating water upper water, 19 bucket elevator, 20 vibrating screen, 21 discharging discharge valve, 22 air preheater, 23 drying blower, 24 cooling blower, 25 heating front-loading moisture, 26 gear ring, 27 saturated steam connection, 28 powder flow cooler, 29 loosening air interface, 30 product discharge valve, 31 star discharge valve, 32 discharging screw conveyer, 33 discharging cover, 34 steam rotary dryer, 35. the device comprises a heating and moisture-carrying unit, 36 a mixer, 37 a return material screw, 38 soft water supplement, 39 a concentrated liquid discharge unit, 40 a guide cover, 41 a pipe through hole, 42 a discharge end plate, 43 a discharge hole, 44 a cover plate, 45 a discharge hole, 46 a pipe support body, 47 a first baffle plate, 48 a second baffle plate, 49 a pipe support groove, 50 an assembly hole, 51 a plate body, 52 an assembly hole and 53 a plate body.
Detailed Description
It will be appreciated that the gas discharged directly into the atmosphere by a system may be referred to as tail gas. However, as the environmental requirements increase, the application system is usually equipped with an exhaust gas purification system, in other words, the exhaust gas can be referred to as exhaust gas before being purified after being generated, and thus the portion discharged into the atmosphere 11 after being purified is referred to as purified exhaust gas.
In the embodiment of the present invention, the core processing equipment is a steam rotary dryer 34, and the steam rotary dryer 34 disclosed in chinese patent documents CN 204944086U, CN 204757589U, CN201014901Y, CN201377966Y, CN 201575669U, etc. can be selected. This type of steam rotary dryer 34 differs from conventional dryers in that the medium that provides the heat energy for drying is saturated steam 2. The heat exchange is realized by adopting an indirect mode, no direct contact is generated between a heat supply medium and materials, generally speaking, the heat exchange tubes are distributed in the steam rotary dryer 34, saturated steam circulates in the heat exchange tubes, the materials move axially in the rotary drum of the steam rotary dryer 34, and meanwhile, the materials can be turned by the rotary drum, so that indirect drying is realized.
Further, a separate moisture carrying assembly is provided, moisture carrying is circulated from one end of the rotary drum to the other end, and a relatively small amount of moisture is required.
In general, the rotary drum of the steam rotary dryer 34 is of a typical cylindrical construction, but has a defined one end and the other end, and in general, material is fed from one end and discharged from the other end. One end for feeding is marked as a feeding end, and one end for discharging is marked as a discharging end.
A rotary drum of the steam rotary dryer 34 has an installation inclination angle of 2-3 degrees from a feeding end to a discharging end, and the discharging end is lower than the feeding end. When the rotary drum is in a working state, the rotary drum rotates at the rotating speed of 3-5 rpm, and materials move from the feeding side to the discharging side along with the rotation of the rotary drum. In the steam rotary dryer 34, the material is indirectly contacted with heating steam, the temperature is gradually increased for dehydration, and evaporated moisture is taken away by moisture-carrying gas. The retention time of the materials in the dryer is 15-25 min, so that sufficient drying is achieved. The dried material is discharged from the bottom of the discharging cover 33, and is conveyed and lifted by the discharging screw conveyor 32, the star-shaped discharging valve 31 and the bucket elevator 19. The dried product is screened by a vibrating screen 20 to remove lumps. Most of the sieved powder is cooled by a powder flow cooler 28 and discharged by a product discharge valve 30 to obtain a dry product.
The vibrating screen 20 is arranged to obtain a dry material of a desired particle size, the reject fraction is often lumps due to caking or the like, and the wet material tends to cake during drying. In this connection, reference will be made hereinafter to reducing lumps in dry material, for example by mixing a certain amount of dry material into the wet material.
The steam rotary dryer 34 generally uses saturated steam with pressure of 0.35-1.0 MPa as a drying heat source and is connected to a heat exchange tube assembly in a rotary cylinder of the steam rotary dryer 34 through rotary sealing.
In an embodiment of the present invention, the moisture-laden air assembly is pumped into the original moisture-laden air from the feed end into the steam rotary dryer 34 in fig. 2 and 3, for example, using a blower. The moisture-laden air is also preheated prior to introduction into the steam rotary dryer 34, and for the same purpose, the heated moisture-laden air 35 mixes with the wet material, helping to reduce the amount of caking and also reducing the adhesion between the wet material and the drying equipment. The preheating of the moisture-carrying substances is required to be 110-160 ℃ in a preferred embodiment.
Specifically, the introduction of the preheated moisture-laden air at the mixer 36 helps to quickly carry away some of the water vapor and reduces the likelihood of binding of the wet material during transport. The method has the advantages that moisture is carried through preheating, so that the temperature of the moisture is increased, the drying efficiency of the material at the feeding section is improved, the wet material is dehydrated as soon as possible, and the viscosity is reduced.
In fig. 2 and 3, the front end of the fixed discharging cover 33 is in dynamic sealing fit with the rotary cylinder, the tail gas purification system is connected out from the top of the discharging cover 33, and tail gas on the side of the rotary cylinder can be sucked and discharged by adopting an induced air mode.
In fig. 2 and 3, the exhaust gas purification system comprises two stages of purification, it being apparent that in the art at least one stage, generally no more than four stages, is involved in the purification of exhaust gas, and relatively many two stages and three stages are involved.
The first-stage purification device is a cyclone dust collector 6, working media such as filtering and spraying are not needed for dust removal of the cyclone dust collector 6, dust particles are separated from tail gas by means of centrifugal force, the dust particles are settled, and settled materials can be recovered.
The lower part of the cyclone dust collector 6 consists of an ash bucket and a cyclone discharge valve 7 arranged at the lower end of the ash bucket, and materials can be recovered through the cyclone discharge valve 7.
For example, the device discharged into the atmosphere 11 in fig. 2 is an induced draft fan, and the induced draft fan is a subsequent device of the wet dust collector 12. The draught fan directly discharges the purified tail gas into the atmosphere, and the material is heated in an indirect mode, so that the moisture-carrying gas is only used as moisture-carrying working gas, the total amount of the moisture-carrying gas is relatively less, the treatment amount is relatively less, and the better purification is easy to realize.
In addition, as a basic configuration, the ammonium chloride drying system further comprises a feed assembly for introducing wet material into the steam rotary dryer at a feed end and a discharge assembly for discharging dry material from the discharge end.
In fig. 2 and 3, the feed assembly employs a blender 36 for mixing wet material and partially dry material and feeding the steam rotary dryer 34. If the dry materials are not mixed, they may be fed to the steam rotary dryer 34 using, for example, a screw conveyor, or other conveying mechanism.
Feeding using a screw conveyor in that the screw conveyor has a cylindrical housing facilitates a relatively good seal with the steam rotary dryer 34.
As can also be seen in fig. 3, the mixer 36 is connected to the rotary steam dryer 34 via a tubular introduction hood 40, the introduction hood 40 being coaxial with the mixer 36 and introducing the moisture-laden air coaxially.
In some embodiments, the cartridge of the blender 36 of FIG. 2 may have an air inlet to which the air preheater 22 is connected by piping to introduce moisture-laden air.
The discharging assembly is in the structure shown in fig. 2 and fig. 3, is adapted to the lower end of the discharging cover 33, and is provided with a discharging screw conveyor 32, and further provided with a star-shaped discharging valve 31, a bucket elevator 19 for elevating the dry material to a given height, a vibrating screen 20 for receiving the bucket elevator 19, and a powder flow cooler 28 for receiving the material screened by the vibrating screen 20, wherein the lower end of the powder flow cooler 28 is provided with a product discharging valve 30 for discharging the finished product.
The steam rotary dryer 34 can be adjusted in output by changing the rotational speed relative to the fluidized bed 4, and the flow rate of the moisture-carrying gas can be adapted accordingly.
In the steam rotary dryer 34 shown in fig. 2 and 3, the same material is dried by 100-120 m per ton3The amount of exhaust gas discharged; for the traditional fluidized bed drying, the thickness is 800-1000 m3From this, it is understood that the ammonium chloride drying system according to the embodiment of the present invention can greatly reduce the amount of exhaust gas treated and the amount of exhaust gas discharged.
In addition to air as the moisture carrier, compressed air, nitrogen, carbon dioxide, or the like may be used as the moisture carrier.
For the tail gas exhausted into the atmosphere 11, the ammonia concentration before tail gas treatment is 950-5000 mg/m3The concentration of the ammonia after dust removal and ammonia removal is 53-66 mg/m3The net emission of ammonia is in direct proportion to the emission of tail gas, and the net emission of ammonia can be greatly reduced according to the calculation of the same emission concentration because the emission of tail gas is reduced.
Fig. 2 and 3 respectively show a material returning mode, fig. 2 shows an external circulation material returning structure, fig. 3 shows a self-returning material of a rotary drum, and the returning of partial dry materials can solve the problems of wall sticking, caking and low thermal efficiency of wet materials. The rotary drum can simplify the material returning equipment by self material returning, and the occupied area of the equipment is reduced.
The rotary drum realizes the returning charge from the returning charge through the mode of constructing the returning charge structure on the outer surface of the rotary drum, specifically, a spiral returning charge channel is arranged on the outer surface of the rotary drum, and a small amount of dry materials can return to the feeding end through the returning charge channel in the rotating process of the rotary drum through the adaptation of turning.
The material returning mechanism can be seen from the structure shown in fig. 2, an independent conveying mechanism needs to be provided, and the occupied area is relatively large. In fig. 2, the return mechanism is configured as a return screw conveyor 5.
The material returning positions of the two material returning modes are different, in fig. 2, the material returning position is taken from the dry material sieved by the vibrating screen 20, and in the structure shown in fig. 3, the material returning position is the discharging end of the rotary drum.
The dry material and the wet material of this given volume are mixed the back and are fed to steam rotary dryer 34, can effectively avoid the material to glue the pipe, glue the wall problem, improve production stability.
Because of the difference of wet material water content, and the behavior can change in the course of the work, for the convenient suitable material returning ratio of adjustment, material returning mechanism and feed back passageway all are equipped with flow control device.
The simplest control method for flow control is through a flow control valve.
Regarding the control point for determining the return material ratio, the water content of the wet material can be selected and designed in some embodiments. The higher the water content, the more dry materials need to be returned, and conversely, the less dry materials need to be returned.
In the configuration shown in fig. 2 and 4, the cooling assembly is provided with a powder flow cooler 28 to cool the dried dry material for packaging.
The powder flow cooler 28 is equipped with a loosening air device comprising a compressed air system;
the powder flow cooler 28 is provided with loose air holes or an aeration head in a cavity for circulating dry materials;
and the loose air holes or the aeration heads are connected with the compressed air system.
The loosening air is discharged inevitably, the dried dry materials still maintain a certain temperature, the ammonia gas still volatilizes, the loosening air forms another type of moisture-carrying gas, and therefore the air discharged from the powder flow cooler 13 is guided into a tail gas purification system to be purified together with the tail gas directly discharged from the steam rotary dryer 34. Solves the secondary pollution problem of 'gas stripping ammonia removal' and the problem of 'circulating gas expansion'.
When the powder flow is cooled, the loose air volume is far less than the dry air volume, and the powder flow cooler exhausts air in positive pressure, so that the air is easy to distribute, and the operation and the adjustment are simple.
In fig. 2 and 3, the powder flow cooler 28 is a material tank structure, the middle upper part is a cylindrical tank, the lower part is a conical can, and the conical can is provided with a loosening air delivery port, so that loosening is completed at the position.
The discharge of the loose wind is finished at the upper end of the cylindrical tank, and the air flow has longer crossing distance, thereby fully playing the conveying role.
In a preferred embodiment, the drying capacity of the steam rotary dryer 34 increases from the feed end to the discharge end. Aiming at the material characteristics, the rotary cylinder is axially divided into a feeding section and a drying section, and the intervals of the annular heat exchange tubes at different positions are different. The feeding section is located the feed end of rotary drum, and its length is 1.5~3m, and the centre-to-centre spacing of its annular heat exchange tube is 150~300 mm. The drying section is located between the feeding section and the discharging cover 33, and the center distance of the annular heat exchange tube is 100-130 mm. The feeding adopts larger space, which can prevent the wet material from adhering between the heat exchange tubes. The drying section adopts smaller space, can improve effective heat exchange area, increases the barrel utilization ratio.
Fig. 4 shows a schematic structural view of the tail end, i.e., the discharge end, of the rotary drum of the steam rotary dryer 34, in which the discharge end is blocked by an end plate to form a discharge end plate 42 shown in the figure, and the discharge end plate 42 is provided with a discharge opening, i.e., a discharge opening 43 shown in fig. 6.
The discharge port 43 is substantially in the radial middle of the discharge end plate 42 from the center of the circle, and the center thereof is substantially one half to two thirds from the center of the circle.
The flash port is provided with an adjusting mechanism for adjusting the opening degree of the flash port, so that the opening degree of the discharge port 43 is changed by adjusting the adjusting mechanism, and the layer thickness of the material in the rotary cylinder is changed to adapt to different applications.
In the structure shown in fig. 4, the adjustment mechanism is configured to:
the two opposite sides of the flash opening are provided with slots for providing insertion plates guiding the slots so as to adjust the opening of the flash opening through the positions of the insertion plates in the slots.
In fig. 4, the cover plate 44 is a fixed plate, a plurality of adjusting holes are provided on both sides of the discharge hole 43, and the position of the cover plate 44 is adjusted by assembling on different adjusting holes.
In addition, the edge of the discharging end plate 42 is provided with at least one discharging opening 45 with a sealing door, the sealing door can be normally opened or normally closed, and even if the sealing door is normally opened, the influence on the whole drying stroke is not great. The discharge opening 45 is mainly used for the clean discharge operation of the dry materials before the shutdown.
Fig. 5 is a schematic cross-sectional structure view of the middle of a rotary drum, specifically, at least one and no more than three separation points are arranged in the rotary drum of the steam rotary dryer 34, each separation point is provided with a plurality of baffle plate groups perpendicular to the axis of the rotary drum, and the interior of the rotary drum is divided into a plurality of drying zones;
a pipe support body 46 for supporting the axial pipe of the saturated steam pipe is arranged between the baffle plate groups;
a discharge gap is defined between the baffle group and the pipe support 46 for the material in the front stage drying area to flow to the rear stage drying area.
The retention time of the material in a certain drying area can be prolonged by blocking the material through the material baffle plate group, so that the drying effect is improved.
As for the striker plate group, as shown in fig. 5, it is assembled by a plurality of first striker plates 47 and second striker plates 38.
It should be noted that the tightness of the assembly of the striker plate group is not required to be very high.
The striker plate can be assembled on a pipe shaft at the center of the rotary cylinder or assembled with each other to form an annular structure.
In the configuration shown in fig. 2 and 3, the subsequent purification device for purifying the exhaust gas is a wet dust collector 12, and the wet dust collector 12 is a dust collector for performing dust fall by a spray method. In fig. 1, the part for supplying the shower water includes a circulation line and a spray pump equipped thereto, and the concentration of the shower water is inevitably increased gradually by the circulation spray, and for this purpose, the circulation line is equipped with a bypass for discharging the concentrate, that is, a line corresponding to the concentrate discharge 39 shown in fig. 3. The wet scrubber 12 is also provided with a fluid replacement branch for replacement fluid, such as the line corresponding to the soft water replacement 38 shown in fig. 3.
From the above description, the flow of the ammonium chloride drying method is roughly clear, and it includes the following steps:
1) drying the introduced wet material by using a steam rotary dryer 34, and introducing moisture-carrying gas from the feed end of the steam rotary dryer 34 in the drying process; discharging in a flash mode at a discharging end in the drying process, and adjusting the retention time of the material in the steam rotary dryer 34 by adjusting the flash speed;
2) moisture-laden air is led out from the discharge end of the steam rotary dryer 34;
3) the discharged moisture-carrying gas is purified and discharged.
In a preferred embodiment, the material is gradually increased in drying capacity during the drying cycle to avoid hardening due to too fast drying in the early stage.
The drying time of the materials is 15-25 min.
Before the moisture-carrying gas is introduced into the steam rotary dryer 34, the moisture-carrying gas is heated to a temperature of 110 to 160 ℃.
A given amount of dry material needs to be mixed into the wet material before the wet material is introduced into the steam rotary dryer 34;
the amount of wet material mixed into the dry material is directly related to the amount of caking in the dry material.
Screening the dry materials, and then cooling the screened dry materials;
the amount of caking was determined by the reject fraction.
The method of claim 16, wherein compressed air is introduced to tumble the dry materials while cooling the dry materials to avoid binding.
Furthermore, in step 4), the moisture-laden air is cooled before being dehumidified.
Before the moisture-carrying gas is introduced into the steam rotary dryer 34, the moisture-carrying gas is heated to a temperature of 110 to 160 ℃.
Before the purified moisture-carrying gas is introduced into the steam rotary dryer 34, if the gas supply quantity or the gas supply pressure is insufficient, the gas supply quantity or the gas supply pressure is balanced in a gas supply mode;
if the gas supply amount or the gas supply pressure before gas supply exceeds a set value, balancing the gas supply amount or the gas supply pressure in a discharging mode;
the discharge point is located before the equipment for dehumidification in step 4).
The wet material is mixed with a predetermined amount of dry material before being introduced into the steam rotary dryer 34.
The drying capacity of the material is gradually enhanced in the drying circulation process.
The drying time of the materials is 15-25 min.
Screening the dry materials, and then cooling the screened dry materials;
when the dry materials are cooled, compressed air is introduced to turn over the dry materials to avoid bonding.
The compressed air used to tumble the dry material is collected into an exhaust gas purification system after tumbling the dry material to incorporate the moisture laden.
The method for purifying the moisture-carrying gas is to carry out cyclone dust removal and then spray decontamination.
The decontamination solution for spraying decontamination is used based on an internal circulation mode or a mode of discharging after spraying;
if the internal circulation mode is adopted, concentrated solution with the concentration reaching the given requirement is discharged at regular time, and then diluted solution is supplemented.
The weak solution is softened water or filtered mother solution of ammonium chloride;
when the filtered mother liquor is used as decontamination liquor, the filtered mother liquor is discharged after being sprayed.
Claims (17)
1. An ammonium chloride drying system, comprising:
one end of the steam rotary dryer is a feeding end, and the other end of the steam rotary dryer is a discharging end; the discharge end is blocked by an end plate, the end plate is provided with a flash port, and the flash port is provided with an adjusting mechanism for adjusting the opening degree of the flash port;
the moisture-carrying assembly is connected into the steam rotary dryer from the feed end;
a feed assembly for introducing wet material into the steam rotary dryer at a feed end;
the discharging assembly is used for guiding the dry materials out of the steam rotary dryer from the discharging end;
and the tail gas purification system is used for guiding out moisture carried by the discharge end and discharging the purified moisture into the atmosphere.
2. The ammonium chloride drying system of claim 1, wherein the adjustment mechanism is configured to:
the two opposite sides of the flash opening are provided with slots for providing insertion plates guiding the slots so as to adjust the opening of the flash opening through the positions of the insertion plates in the slots.
3. Ammonium chloride drying system according to claim 1 or 2, wherein the edge of the end plate is provided with at least one discharge opening with a sealing gate.
4. The ammonium chloride drying system of claim 1, wherein the center of the flash port is located between one half and two thirds of the end plate from the center of the circle in the radial direction.
5. The ammonium chloride drying system of claim 1, wherein at least one and no more than three separation points are provided in the rotary drum of the steam rotary dryer, each separation point is provided with a plurality of baffle groups perpendicular to the axis of the rotary drum to separate the interior of the rotary drum into a plurality of drying zones;
a pipe support body for supporting the axial pipe of the saturated steam pipe is arranged between the baffle plate groups;
and a discharge gap is determined between the material baffle group and the pipe support body and is used for the circulation of materials in the front-stage drying area to the rear-stage drying area.
6. The ammonium chloride drying system of claim 1, wherein the tail gas purification system comprises a cyclone dust collector at a front stage and a wet dust collector at a rear stage;
wherein the wet dust collector is based on spraying;
correspondingly, a circulating pipeline and a matched spray pump are provided for circulating spray water; the circulating pipeline is provided with a bypass for discharging concentrated liquid, and the wet dust collector is provided with a liquid supplementing branch for supplementing liquid.
7. The ammonium chloride drying system of claim 1, wherein the feed assembly comprises a blender;
correspondingly, the steam rotary dryer or the discharging assembly is provided with a material returning structure or a material returning mechanism for guiding a given amount of dry materials into the mixer so as to mix the given amount of dry materials and wet materials and then feed the mixed materials into the steam rotary dryer.
8. The ammonium chloride drying system of claim 7, wherein when the material is returned by the material returning mechanism, the feed end of the material returning mechanism is connected to the vibrating screen of the discharging assembly;
when a material returning structure is adopted, the material returning structure is configured as follows:
the outer surface of a rotary cylinder of the steam rotary dryer is provided with a spiral feed back channel.
9. The ammonium chloride drying system of claim 8, wherein the return mechanism and the return channel are each provided with a flow control device.
10. The ammonium chloride drying system of claim 1, wherein the discharge assembly is provided with a cooler;
the cooler is provided with a loosening air device which comprises a compressed air system;
a chamber of the cooler for circulating the dry materials is provided with a loosening air hole or an aeration head;
loosening the air holes or the aeration heads to be connected with the compressed air system;
and an exhaust port is arranged on the cooler and is connected to the tail gas purification system.
11. An ammonium chloride drying system, comprising the steps of:
1) drying the introduced wet material by using a steam rotary dryer, and introducing moisture-carrying gas from the feed end of the steam rotary dryer in the drying process; discharging in a flash mode at a discharging end in the drying process, and adjusting the retention time of the material in the steam rotary dryer by adjusting the flash speed;
2) carrying moisture out of the discharge end of the steam rotary dryer;
3) and purifying the derived moisture-carrying gas and then discharging the purified gas.
12. The ammonium chloride drying system of claim 11, wherein the material gradually increases drying capacity during the drying cycle.
13. The method for drying ammonium chloride according to claim 11 or 12, wherein the drying time of the material is 15-25 min.
14. The method of claim 11, wherein the moisture-laden air is heated to a temperature of 110-160 ℃ before being introduced into the steam rotary dryer.
15. The method of claim 11, wherein a predetermined amount of dry material is mixed into the wet material before the wet material is introduced into the steam rotary dryer;
the amount of wet material mixed into the dry material is directly related to the amount of caking in the dry material.
16. The method of claim 15, wherein the dried material is first sieved and then cooled;
the amount of caking was determined by the reject fraction.
17. The method of claim 16, wherein compressed air is introduced to tumble the dry materials while cooling the dry materials to avoid binding.
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CN112794347A (en) * | 2021-02-04 | 2021-05-14 | 中国天辰工程有限公司 | By using CO2Combined device and process for preparing heavy alkali by drying and carbonizing ammonium chloride in concentrated gas |
CN114646207A (en) * | 2022-03-21 | 2022-06-21 | 江苏国信协联能源有限公司 | Wet blue algae drying method |
CN114877637A (en) * | 2022-07-07 | 2022-08-09 | 山东天力能源股份有限公司 | Steam rotary dryer |
CN115615177A (en) * | 2022-07-14 | 2023-01-17 | 金川集团股份有限公司 | Steam drying method for nickel-copper bulk concentrate |
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