阅读说明：本技术 一种微波强化流态化磷石膏脱水的装置及其方法 (Microwave-enhanced fluidized phosphogypsum dehydration device and method ) 是由 张晖 李恒 钟晋 李�瑞 于 2021-11-04 设计创作，主要内容包括：本发明公开了一种微波强化流态化磷石膏脱水的装置及其方法,通过螺旋给料机将磷石膏加入到体系中,利用热风炉提供的热空气经过文丘里干燥和旋风预热器脱除磷石膏中的附着水后与吸波粉体物质共同进入流化床透波加热段中混合流化；微波在谐振腔体中穿过透波加热段被吸波粉体物质与磷石膏吸收,利用分子高速运动产生的热量通过固－固、气－固以及微波加热方式同时实现磷石膏结晶水的脱除。由于脱除结晶水的磷石膏流化高度改变实现与吸波粉体物质分离。本方法和装置适用性广能够实现一套装置连续化生产两种产品、热效率高、加热速度快、物料加热均匀,证产品稳定性高,半水石膏分子表面极性成分加强,接触角减小,尾气温度低,热量损失小。(The invention discloses a device and a method for dehydrating microwave-reinforced fluidized phosphogypsum, wherein phosphogypsum is added into a system through a screw feeder, and hot air provided by a hot blast stove is utilized to remove attached water in the phosphogypsum through Venturi drying and a cyclone preheater and then enters a wave-transmitting heating section of a fluidized bed together with wave-absorbing powder substances for mixing and fluidizing; microwaves pass through the wave-transparent heating section in the resonant cavity and are absorbed by the wave-absorbing powder substance and the phosphogypsum, and heat generated by high-speed movement of molecules is utilized to simultaneously remove crystal water of the phosphogypsum in a solid-solid, gas-solid and microwave heating mode. The separation from the wave-absorbing powder material is realized due to the change of the fluidization height of the phosphogypsum for removing the crystal water. The method and the device have wide applicability, can realize continuous production of two products by one set of device, and have the advantages of high thermal efficiency, high heating speed, uniform material heating, high product stability, strengthened polar components on the surfaces of the semi-hydrated gypsum molecules, reduced contact angle, low tail gas temperature and small heat loss.)

1. A microwave reinforced fluidized phosphogypsum dehydration device is characterized in that: the device comprises a screw feeder (1), a Venturi dryer (2), a cyclone preheater (3), a microwave fluidized bed (4), a cyclone separator (5) and a bag-type dust remover (6) which are connected in sequence, wherein air inlets of the Venturi dryer (2) and the cyclone preheater (3) are connected with an air outlet of a hot blast stove (10);

the microwave fluidized bed (4) comprises a material main chamber (401), a material auxiliary chamber (402), a feeding pipe (403), a microwave resonant cavity (404), a wave-transparent heating section (405), an air inlet pipe (406), an expansion section (407) and a discharging pipe (408); air inlets at the bottoms of the material main chamber (401) and the material auxiliary chamber (402) are connected with an air supply device, feed inlets are formed in the tops of the material main chamber (401) and the material auxiliary chamber (402), the material main chamber (401) and the material auxiliary chamber (402) are communicated, the material auxiliary chamber (402) is communicated with the wave-transparent heating section (405) through a feed pipe (403), and the feed inlet of the material main chamber (401) is connected with a discharge outlet of the cyclone preheater (3);

the wave-transparent heating section (405) is arranged in the microwave resonant cavity (404), and the microwave resonant cavity (404) is connected with a microwave generator (409) through a waveguide tube; an air distribution plate is arranged in the air inlet pipe (406), one end of the air inlet pipe (406) is connected with the bottom of the wave-transparent heating section (405), the other end of the air inlet pipe (406) is connected with a gas supply device, the top of the wave-transparent heating section (405) is connected with the expansion section (407) through a flange, and a discharge pipe (408) is arranged on the side surface of the expansion section (407) and connected with the material receiving tank (7); the top exhaust port of the expanding section (407) is connected with the cyclone separator (5) and the bag-type dust collector (6) in sequence.

2. The device of claim 1, wherein the microwave-enhanced dehydration of fluidized phosphogypsum is characterized in that: the outer side wall of the material receiving tank (7) is provided with a water-cooling jacket, a water inlet of the water-cooling jacket is connected with a cooling water tank (9) through a variable frequency water pump (8), and a water outlet of the water-cooling jacket is connected with the cooling water tank (9).

3. The device of claim 1, wherein the microwave-enhanced dehydration of fluidized phosphogypsum is characterized in that: a temperature sensor is arranged in the material receiving tank (7), and a vibrator is arranged at a discharge outlet at the bottom.

4. The device for microwave-enhanced dehydration of fluidized phosphogypsum according to any one of claims 1 to 3, characterized in that: the microwave-enhanced fluidized phosphogypsum dehydration method of the device comprises the following steps:

s1, allowing phosphogypsum to enter a Venturi dryer (2) through a screw feeder (1), allowing hot air provided by a hot blast stove (10) to enter from the lower end of the Venturi dryer (2), removing part of attached water in the phosphogypsum, scattering the agglomerated phosphogypsum, allowing the treated phosphogypsum to enter a cyclone preheater (3), and further removing the attached water by controlling the temperature of the hot air entering the cyclone preheater (3) from the hot blast stove (10) to maintain the content of the attached water in the phosphogypsum at 1-3%;

s2, removing the phosphogypsum with attached water, entering a material main chamber (401), enabling wave-absorbing powder substances to enter a material auxiliary chamber (402), continuously inputting the wave-absorbing powder substances into a wave-transparent heating section (405) through airflow, and uniformly mixing the wave-transparent heating section and the material auxiliary chamber left and right to form a fluidized state;

s3, setting different microwave frequencies for different products, starting a microwave generator (409), and reflecting the microwaves in a resonant cavity (404) to pass through a wave-transparent heating section (405) to be absorbed by the wave-absorbing powder material and the phosphogypsum; because the removal of the phosphogypsum crystal water leads the fluidization height of the phosphogypsum crystal water to be increased in the microwave fluidized bed (4) and the fluidization height of the wave-absorbing powder substance to be unchanged, the separation of the phosphogypsum crystal water from the wave-absorbing powder substance is realized; then the dehydrated phosphogypsum enters a material receiving tank (7), and tail gas is purified and dedusted by a cyclone separator (5) and a bag-type deduster (6) and then is discharged; the material in the material receiving tank (7) is cooled to be made into a finished product.

5. The device of claim 4, wherein the microwave-enhanced dehydration of fluidized phosphogypsum is characterized in that: the temperature of hot air entering the Venturi dryer (2) is 250-350 ℃, and the temperature of hot air entering the cyclone preheater (3) is 150-250 ℃.

6. The device of claim 4, wherein the microwave-enhanced dehydration of fluidized phosphogypsum is characterized in that: the wave-absorbing powder substance is Fe₃O₄、SiC、Si₃N₄At least one of the materials has the mass of 500-1000 g, the particle size distribution of 30-220 microns, 20-170 microns and 15-140 microns, and the mass ratio of the phosphogypsum to the wave-absorbing powder material in the wave-transparent heating section (405) is 5-10: 1.

7. The device of claim 4, wherein the microwave-enhanced dehydration of fluidized phosphogypsum is characterized in that: when the product is building gypsum powder, the flow of compressed air at the air inlet pipe (406) at the bottom of the microwave fluidized bed (4) is 4-9m³H; when the product is II type anhydrous gypsum, the flow of compressed air at the bottom of the microwave fluidized bed (4) is 2-4m³/h。

8. The device of claim 4, wherein the microwave-enhanced dehydration of fluidized phosphogypsum is characterized in that: the discharging temperature of the material receiving tank (7) is 30-40 ℃, and the vibration frequency of the vibrator is 2-5 cpm.

9. The device of claim 4, wherein the microwave-enhanced dehydration of fluidized phosphogypsum is characterized in that: the material of the wave-transparent heating section (405) of the fluidized bed is one of wave-transparent ceramics, polycrystalline mullite fiber products and high-temperature-resistant glass.

10. The device of claim 4, wherein the microwave-enhanced dehydration of fluidized phosphogypsum is characterized in that: the power of the microwave generator (409) is 100W-1000W and can be continuously adjusted, when the product is building gypsum powder, the microwave frequency generated by the microwave generator (409) is 500-1500MHz, and the heating temperature of the phosphogypsum in the wave-transparent heating section (405) is 130-160 ℃; when the product is II type anhydrous gypsum, the frequency of the microwave generated by the microwave generator (409) is 2000-3000MHz, and the heating temperature of the phosphogypsum in the wave-transparent heating section (405) is 750-850 ℃.

Technical Field

The invention relates to a device and a method for dehydrating microwave-enhanced fluidized phosphogypsum, and belongs to the field of resource utilization of phosphogypsum.

Background

The phosphogypsum is a byproduct waste residue in the wet-process phosphoric acid production process, the slurry after the reaction of preparing the phosphoric acid by the wet process is filtered and washed to prepare the phosphoric acid, and simultaneously the byproduct phosphogypsum is generated, and the byproduct phosphogypsum of 4.5-5.5 t is usually produced for 1t of phosphoric acid. With the development of the phosphorus chemical industry, the emission of the phosphogypsum is increased year by year. At present, the annual output of phosphogypsum in China is about 8000 weight, and because the phosphogypsum contains phosphorus impurities, fluorine impurities, organic matters, alkali metal salt and SiO₂And the like, and the impurity components are complex and various, so that the phosphogypsum which is not subjected to purification treatment cannot be effectively recycled. The comprehensive utilization rate of China is only about 30%, phosphogypsum stacking occupies a large amount of land, and great threat is caused to the ecological environment around the stacking land. The utilization approach of the domestic phosphogypsum mainly focuses on 3 aspects of building material industry, industry and agriculture. In recent years, the method has rapidly developed in the aspects of preparing building gypsum cementing materials by calcining phosphogypsum and replacing calcium carbonate with II type anhydrous gypsum as chemical fillers.

The main component of the phosphogypsum is CaSO₄·2H₂O, calcining gypsum is prepared by calcining CaSO₄·2H₂And O, heating and dehydrating to form plaster of paris. CaSO4 & 2H₂When the temperature reaches 120-140 ℃, 1.5 crystal water is removed from the calcium sulfate dihydrate and converted into beta-hemihydrate gypsum, and when the temperature is continuously raised to 190 ℃ of 170-190 ℃, the hemihydrate gypsum is further dehydrated and converted into CaSO₄(III)，CaSO₄(III) unstable conversion to CaSO when the temperature reaches 320 ℃ and 360 DEG C₄(II)。

At present, the common calcining process technology and equipment for phosphogypsum mainly comprise a frying pan calcining process, a rotary kiln calcining process, a two-section fluidized bed furnace calcining process, an air flow type calcining process, a hammer type drying and grinding and calcining integrated process and the like. However, the calcining mode has the advantages of small reaction area, uneven heating, large occupied area and small single set of capacity; the heat efficiency is low, the equipment volume is large, the internal components are complex, the exhaust emission temperature is high, the heat loss is large, and the energy consumption is high; the single set has small productivity, low production efficiency and easy over-burning or under-burning of the product; large one-time investment, high energy consumption, secondary pollution caused by the emission of calcination tail gas, other pollution and the like.

Disclosure of Invention

Aiming at the limitations of the existing phosphogypsum calcining and dehydrating technology, namely the existing phosphogypsum calcining technology has low thermal efficiency, unstable product, low production efficiency and CO fuel₂Secondary pollution caused by discharge and the like. The invention provides a method for stably, efficiently and continuously removing crystal water in phosphogypsum, namely a device and a method for dehydrating microwave-reinforced fluidized phosphogypsum.

The invention relates to a method and a device for dehydrating microwave-enhanced fluidized phosphogypsum, which specifically comprise the following steps:

(1) and (3) a water desorption stage: the phosphogypsum treated by washing and filter pressing enters a Venturi tube through spiral feeding, hot air at a certain temperature provided by a hot blast stove enters from the lower end of the Venturi tube to remove part of attached water in the phosphogypsum and break up agglomerated phosphogypsum, and then the phosphogypsum enters a cyclone preheater and is further removed of the attached water by controlling the temperature of the hot blast stove, so that the attached water content in the phosphogypsum is maintained within a fluidizable range.

(2) A mixing and fluidizing stage: the wave-absorbing powder material with certain mass and particle size distribution and the preheated phosphogypsum are continuously conveyed into a fluidized bed by airflow according to a certain proportion. After compressed air is introduced into the bottom of the fluidized bed, the phosphogypsum and the wave-absorbing powder are uniformly mixed and form a fluidized state in a wave-transparent heating section of the fluidized bed.

(3) Microwave heating dehydration stage: the microwave generator is used for transmitting high-frequency electromagnetic waves with certain frequency into the fluidized bed resonance cavity. Microwaves are reflected in the cylindrical resonant cavity and penetrate through the wave-transparent heating section of the fluidized bed, the microwaves are fully absorbed by wave-absorbing powder substances, the temperature is rapidly and sharply increased in a short time, the wave-absorbing powder substances transmit heat to phosphogypsum and air in a solid-solid or gas-solid mode, and the heated hot air enables the temperature of the phosphogypsum to be increased, so that the dehydration of the phosphogypsum is accelerated. The phosphogypsum and organic impurities contained in the phosphogypsum can also absorb microwave energy and convert the microwave energy into heat energy, so that the temperature of the phosphogypsum is increased. When the temperature in the fluidized bed reaches a certain value, the dihydrate gypsum is dehydrated and converted into semi-hydrated gypsum, and the semi-hydrated gypsum is further dehydrated to form anhydrous gypsum.

(4) And (3) material separation stage: the air flow speed introduced into the fluidized bed is kept unchanged, and meanwhile, the mass of the wave-absorbing powder substance is not changed along with the temperature. Therefore, the fluidization height of the wave powder substance in the fluidized bed can be controlled by changing the particle size distribution of the wave powder substance. But the phosphogypsum has lighter weight because of removing crystal water. Therefore, the fluidization height of the phosphogypsum without the crystal water is increased in the fluidized bed, the fluidization height of the wave-absorbing powder substance is unchanged, and the phosphogypsum without the crystal water is layered with the wave-absorbing powder substance. And when the fluidization height of the phosphogypsum without crystal water reaches the height of the discharge port, discharging the phosphogypsum from the discharge port. The flow of compressed air at the bottom of the microwave fluidized bed is controlled aiming at different products, so that the fluidization height is controlled while the phosphogypsum is fully dehydrated.

(5) Material cooling and tail gas treatment: the material enters the material receiving tank after being discharged from the discharge hole, and the material receiving tank contains a water-cooling interlayer. And the variable frequency water pump conveys cooling water from the open water tank to an interlayer at the lower end of the material receiving tank to flow in for cooling the phosphogypsum, and then the cooling water flows out from the upper end and enters the water tank for circulation. The cooling circulating water after temperature rise is naturally cooled in the open water pool and is continuously used for the circulating cooling system. A temperature detector is arranged in the material receiving tank, when the temperature of the dehydrated phosphogypsum is lower than a set temperature, an outlet at the lower end of the material receiving tank is automatically opened to shake and discharge materials, and a discharge hole is automatically closed after the materials are discharged. The introduced compressed air is discharged from the top of the fluidized bed, enters a cyclone cooler for cooling and then enters a bag-type dust collector for further purification and dust removal. The fine dehydrated phosphogypsum mixed in the air is collected from cyclone dust collection and cloth bag dust collection.

In microwave heating, the coupling ability of a material to microwaves is expressed by a loss tangent (ratio of loss factor to dielectric constant), and the larger the loss tangent, the stronger the coupling ability of the material to microwaves. In the invention, the electron cloud of molecules of a strong absorption microwave substance with a large loss tangent value is deflected under the action of microwaves to cause the movement of dipoles, and the dipoles present positive and negative polarities. Due to the high-frequency change of the electromagnetic field, molecules move at high speed, violent collision friction is generated among the molecules to generate heat, the temperature is quickly increased, and the heat is transferred to the phosphogypsum through contact transfer heat to remove crystal water. Although phosphogypsum belongs to a substance which absorbs microwaves weakly and has a small relative dielectric constant, the phosphogypsum can also absorb a certain amount of microwaves to increase the temperature of the phosphogypsum. And when the temperature is higher than 500 ℃, the relative dielectric constant of the phosphogypsum is increased, the microwave absorption capacity is enhanced, and the temperature rising speed is accelerated. The phosphogypsum contains a small amount of attached water and organic matter, which have large dielectric loss and can absorb a large amount of microwave energy and convert the microwave energy into heat energy, so that the temperature rise of the phosphogypsum is realized by simultaneously evaporating water and decomposing organic matter in the whole volume. The traditional phosphogypsum heating dehydration only can input energy in a heat transfer mode, the dehydration speed is slow, and the direct energy input action of microwaves and the thermal contact transfer action of high-loss tangent wave-absorbing substances are combined in the invention, so that the dehydration speed of the phosphogypsum is increased by a plurality of times compared with the ordinary heating speed. Compared with the traditional ardealite heating dehydration mode, the method combines three modes of solid contact heat transfer, gas-solid heat transfer and microwave direct heating of ardealite and a high-loss tangent wave-absorbing substance to simultaneously remove crystal water from ardealite.

The phase change process of the dehydration of the phosphogypsum by microwave heating in the invention. After the free moisture in the phosphogypsum is completely evaporated or decomposed, when the overall temperature of the phosphogypsum gradually reaches the dehydration temperature, the thermal fluctuation causes the water layer vacancy with weak binding force to migrate to the vacancy, distortion, peritectic, cleavage, crack, impurity and the like on the crystal of the phosphogypsum, and the vacancy disappears after migrating to the surface of the phosphogypsum and forms a dew point, thus forming the crack. After the water molecule dew point is formed, semi-hydrated gypsum crystal blanks are formed around the dew point quickly. After forming stable crystal nucleus, the dihydrate gypsum is continuously decomposed, and Ca is excited by heat²⁺And SO₄ ^2-The ions continuously migrate to the position of the new phase nucleus, so thatThe crystal nucleus is rapidly grown and diffused to the periphery until the crystal nucleus is completely converted into beta-hemihydrate gypsum.

In the invention, because the main component of the phosphogypsum is calcium sulfate dihydrate, the crystal of the phosphogypsum has commonized electrons. After the commonized electrons absorb electromagnetic waves with certain frequency, hydrogen bond chemical bonds with lower bond energy are broken, oxygen forming calcium sulfate becomes a dangling bond, and the acting force of the hydrogen bond is stronger than that before the hydrogen bond is broken, so that the polar component of the surface energy of the calcium sulfate is enhanced. Therefore, after the phosphogypsum is irradiated by microwaves, the polar components on the surface are strengthened, so that the contact angle is reduced, and the wetting tendency is strengthened. The method is favorable for reducing the standard thickness of the phosphorus building gypsum prepared by the fluidization microwave dehydration of the phosphogypsum, thereby improving the compression strength and the breaking strength of the phosphorus building gypsum hardened body. On the other hand, the microwave has non-thermal effects of promoting the densification of the crystal structure of the phosphogypsum, influencing the growth of crystal grains, accelerating chemical reaction and the like, and the microwave removes the crystal water of the phosphogypsum and simultaneously improves the hydration activity of the produced phosphorus building gypsum and anhydrous gypsum.

The temperature of the hot air introduced into the Venturi dryer is 250-350 ℃, and the temperature of the hot air introduced into the cyclone preheater is 150-250 ℃.

The content of the attached water of the phosphogypsum after the preheating treatment is 1 to 3 percent.

The high loss tangent substance is Fe₃O₄、SiC、Si₃N₄The mass is 500g-1000g, the particle size distribution is 30-220 μm, 20-170 μm and 15-140 μm respectively, the wave-transparent heating section of the fluidized bed is phosphogypsum and Fe₃O₄、SiC、Si₃N₄The mass ratio of (A) to (B) is 5:1-10: 1.

The fluidized bed wave-transparent heating section material is wave-transparent ceramic, a polycrystalline mullite fiber product and high-temperature-resistant glass.

When the product is building gypsum powder, the flow rate of compressed air at the bottom of the microwave fluidized bed is 4-9m³H; when the product is II type anhydrous gypsum, the flow rate of compressed air at the bottom of the microwave fluidized bed is 2-4m³/h。

The power of the microwave generator is 100W-1000W and can be continuously adjusted, and the microwave frequency generated by the microwave generator is 500-1500MHz when the product is building gypsum powder; when the product is II type anhydrous gypsum, the microwave frequency generated by the microwave generator is 2000-3000 MHz.

The microwave resonant cavity is cylindrical and made of stainless steel

The vibration discharging vibration frequency is 2-5cpm, and the automatic discharging temperature of the material receiving tank is 30-40 ℃. The flow rate of the cooling water is determined according to the finished product, and when the product is building gypsum powder, the flow rate is 3-5 m/s; when the product is type II anhydrous gypsum, the flow rate is 10-18 m/s.

The invention also aims to provide a device for completing the dehydration of the microwave reinforced fluidized phosphogypsum, which comprises a screw feeder, a venturi dryer, a cyclone preheater, a microwave fluidized bed, a cyclone separator and a bag-type dust collector which are connected in sequence, wherein the air inlets of the venturi dryer and the cyclone preheater are both connected with the air outlet of a hot blast stove. The microwave generator is connected with the waveguide tube and respectively installed on two sides of the cylindrical resonant cavity, the wave-transparent heating section is arranged in the microwave resonant cavity, the upper end of the wave-transparent section is connected with the fluidized bed expansion section through a flange, the lower part of the wave-transparent section is connected with the air inlet pipe through a flange, and the other end of the air inlet pipe is connected with the gas supply device. The upper end of the fluidized bed expansion section is connected with a cyclone cooler through a tail gas pipeline, and the cyclone cooler is connected with a bag-type dust collector. The fluidized bed is provided with a feeding pipe and a discharging pipe, the feeding pipe is connected with the material chambers, the discharging pipe is connected with the upper end of the material receiving tank, and the material main chamber and the material chambers are respectively connected with the pneumatic control cabinet through air ducts. The inside water-cooling intermediate layer that is equipped with of material receiving tank, material receiving tank top are passed through the water pipe and are connected with the cooling trough, and the bottom is passed through variable frequency water pump and cooling trough intercommunication.

The method and the device have the following advantages and effects:

(1) the two products can be continuously produced by one set of device through the adjustment of the microwave frequency.

(2) The heat efficiency is high, the inside and the outside of the material are heated simultaneously, the heating speed is high, and the heat and mass transfer speed is high;

(3) the heating is uniform, the phenomena of surface hardening and unevenness easily caused in the conventional heating process are avoided, and the product stability is effectively ensured;

(4) compared with the semi-hydrated gypsum prepared by the traditional heating method, the semi-hydrated gypsum has the advantages that the surface polar component is strengthened, the contact angle is reduced, and the standard thickness of the semi-hydrated gypsum is favorably reduced.

(5) The tail gas temperature is low, and the heat loss is small. Compared with the traditional heating mode, the heat source does not generate CO₂And S0₂And the like.

Drawings

FIG. 1 is a schematic structural diagram of the present invention.

FIG. 2 is a schematic structural view of a microwave fluidized bed in the present invention.

FIG. 3 is a schematic view showing the internal structure of the microwave fluidized bed of the present invention.

In the figure: the method comprises the following steps of 1-a screw feeder, 2-a Venturi dryer, 3-a cyclone preheater, 4-a microwave fluidized bed, 401-a material main chamber, 402-a material auxiliary chamber, 403-a feeding pipe, 404-a microwave resonant cavity, 405-a wave-transparent heating section, 406-an air inlet pipe, 407-an expansion section, 408-a discharging pipe, 409-a microwave generator, 5-a cyclone separator, 6-a bag dust collector, 7-a material receiving tank, 8-a water pump, 9-a cooling water tank and 10-a hot blast furnace.

Detailed Description

The present invention will be described in detail with reference to the following embodiments, but the scope of the present invention is not limited to the above-described embodiments.

Example 1: in this example, the object to be treated was phosphogypsum produced in the wet process of producing phosphoric acid in a certain phosphoric acid plant, and the analysis results are as follows.

Detecting items	Attached water	Crystal water	Grade (L) of a material	pH
					Results	22	17.3	85	3.4

(1) And (3) a water desorption stage: washing and filter-pressing phosphogypsum coming out of a rotary disc of a filter, feeding the phosphogypsum into a Venturi tube through spiral feeding, and supplying hot air with the temperature of 330 ℃ by a hot air furnace at the temperature of 12m³The flow of the flow is that partial attached water in the phosphogypsum is removed from the lower end of a Venturi tube, simultaneously the agglomerated phosphogypsum is scattered, the residence time of the phosphogypsum in the Venturi tube is 90s, then the phosphogypsum enters a cyclone preheater, and a hot air furnace provides hot air with the temperature of 210 ℃ and takes 8m³And (4) further removing the attached water at the flow rate of/h, wherein the retention time of the phosphogypsum is 120s, and finally, the content of the attached water in the phosphogypsum is maintained to be about 1-3%.

(2) A mixing and fluidizing stage: fe with the mass of 700g and the particle size distribution of 30-220 mu m₃O₄After the powder is added into the fluidized bed, the phosphogypsum after the preheating treatment is continuously conveyed into the fluidized bed through air flow. The bottom of the fluidized bed is introduced with a flow of 6m³H post-air-compression phosphogypsum and Fe₃O₄Uniformly mixing and forming a fluidization state in a wave-transparent heating section of the fluidized bed, wherein phosphogypsum and Fe₃O₄The mass ratio is 8: 1.

(3) Microwave heating dehydration stage: setting the power of a microwave generator to be 280W, setting the microwave frequency to be 750MHZ, and conveying high-frequency electromagnetic waves into the fluidized bed resonant cavity by the microwave generator. The microwave is reflected in the cylindrical resonant cavity and passes through the wave-transparent heating section of the fluidized bed to be heated by Fe₃O₄Full absorption, rapid rise of temperature in a short time, Fe₃O₄Transferring heat to phosphogypsum and air by heat transfer mode, and heating the heated airThe gas can increase the temperature of the phosphogypsum and accelerate the dehydration of the phosphogypsum. The phosphogypsum and organic impurities contained in the phosphogypsum can also absorb microwave energy and convert the microwave energy into heat energy, so that the temperature of the phosphogypsum in a wave-transparent heating section of the fluidized bed reaches 130 ℃, and dihydrate gypsum is dehydrated and converted into building gypsum.

(4) And (3) material separation stage: fe₃O₄The quality does not change with the temperature, but the phosphogypsum becomes light after the crystal water is removed and is transformed into building gypsum, the fluidization height is increased, and the Fe is added₃O₄Constant fluidization height, building gypsum and Fe₃O₄Layering is formed. When the beta-hemihydrate gypsum fluidization height reaches the discharge port height, discharging from the discharge port.

(5) Material cooling and tail gas treatment: and the dehydrated phosphogypsum is discharged from a discharge hole and then enters a material receiving tank, and the material receiving tank contains a water-cooling interlayer. And the variable-frequency water pump conveys cooling water from the open water tank to the interlayer at the lower end of the material receiving tank at the flow speed of 3m/s for phosphogypsum cooling, and then the cooling water flows out from the upper end and enters the water tank for circulation. The cooling circulating water after temperature rise is naturally cooled in the open water pool and is continuously used for the circulating cooling system. And a temperature detector is arranged in the material receiving tank, when the temperature of the dehydrated phosphogypsum is lower than the set temperature of 35 ℃, an outlet at the lower end of the material receiving tank is automatically opened, the vibration frequency is 3cpm, and the discharge port is automatically closed after the discharge is finished. The introduced compressed air is discharged from the top of the fluidized bed, enters a cyclone cooler for cooling and then enters a bag-type dust collector for further purification and dust removal. The fine dehydrated phosphogypsum mixed in the air is collected from cyclone dust collection and cloth bag dust collection.

The three-phase analysis and detection results of the building gypsum after microwave-enhanced dehydration treatment are shown in the following table.

Detecting items	Attached water	DH/％	HH/％	AIII/％	pH
						Results	0	1.4	80	3.1	5.5

As shown in figures 1-3, the device for completing the method comprises a screw feeder 1, a Venturi dryer 2, a cyclone preheater 3, a microwave fluidized bed 4, a cyclone separator 5 and a bag-type dust collector 6 which are connected in sequence, wherein air inlets of the Venturi dryer 2 and the cyclone preheater 3 are connected with an air outlet of a hot blast stove 10.

The microwave fluidized bed 4 comprises a material main chamber 401, a material auxiliary chamber 402, a feeding pipe 403, a microwave resonant cavity 404, a wave-transparent heating section 405, an air inlet pipe 406, an expansion section 407 and a discharging pipe 408; the air inlets at the bottom of the material main chamber 401 and the material auxiliary chamber 402 are connected with an air supply device. The gas supply device mainly comprises a control cabinet and an air compressor. The top of the material main chamber 401 and the top of the material auxiliary chamber 402 are both provided with feed inlets, the material main chamber 401 and the material auxiliary chamber 402 are communicated, the material auxiliary chamber 402 is communicated with the wave-transparent heating section 405 through a feed pipe 403, and the feed inlet of the material main chamber 401 is connected with the discharge outlet of the cyclone preheater 3.

The wave-transparent heating section 405 is disposed in the microwave resonant cavity 404, and the microwave resonant cavity 404 is connected to the microwave generator 409 through a waveguide. The microwave resonant cavity 404 is cylindrical, the cavity body is made of stainless steel, the wave-transparent heating section is respectively connected with the air inlet pipe 406 and the expanding section 407 through flanges, and the wave-transparent heating section 405 is made of wave-transparent ceramics, polycrystalline mullite fiber products or high-temperature-resistant quartz glass materials. Intake pipe 406 one end is connected with wave-transparent heating section 405 bottom, and the intake pipe 406 other end is connected with gaseous providing device, for make compressed air more even get into wave-transparent heating section 405 in, is provided with gas distribution plate in the intake pipe 406.

The top of the wave-transparent heating section 405 is connected with an expansion section 407 through a flange, and the powdery material in the expansion section 407 is connected with a material receiving tank 7 through a discharge pipe 408; the top exhaust port of the expanding section 407 is connected with the cyclone separator 5 and the bag-type dust collector 6 in sequence. In order to cool the materials as soon as possible and facilitate packaging, the outer side wall of the material receiving tank 7 is provided with a water-cooling jacket, a water inlet of the water-cooling jacket is connected with a cooling water tank 9 through a variable frequency water pump 8, and a water outlet of the water-cooling jacket is connected with the cooling water tank 9. The cooling water tank 9 is filled with normal temperature clear water which circulates in the water cooling jacket to rapidly cool the gypsum finished product in the water cooling jacket. In order to facilitate discharging, a temperature sensor is arranged in the material receiving tank 7, and a vibrator is arranged at a discharge outlet at the bottom. When the finished product is cooled to a certain temperature, the material receiving tank 7 automatically vibrates to discharge materials.

The phosphogypsum is conveyed by a screw feeder 1 to enter a Venturi dryer 2 for removing attached water, then enters a cyclone preheater 3, is further dried and then enters a material main chamber 401 in a microwave fluidized bed 4, and Fe is added in advance₃O₄Into material subchamber 402. Compressed air generated by an air compressor passes through the pneumatic control cabinet to mix phosphogypsum and Fe₃O₄Blowing the gas from a feed pipe 406 into a wave-transparent heating section 405 in the microwave fluidized bed 4, and on the other hand, entering compressed air into the fluidized bed from a gas inlet pipe 406 through a gas distribution plate to mix phosphogypsum and Fe₃O₄Uniformly mixed and formed into a fluidized state. Microwaves generated by a microwave generator 409 enter the cylindrical resonant cavity 404 through a three-way waveguide tube, pass through a wave-transparent heating section 405, and simultaneously realize the removal of phosphogypsum crystal water through solid-solid, gas-solid and microwave direct heating modes, and then are mixed with Fe₃O₄The separation is carried out from the discharge pipe 408 into a material receiving tankIn step 7, the building gypsum is cooled by a cooling water circulation formed by an inverter water pump 8 and a cooling water tank 9.

Example 2: in this example, the treatment object is phosphogypsum stockpiled in a phosphogypsum slag warehouse, and the analysis result is as follows.

Detecting items	Attached water	Crystal water	Grade (L) of a material	pH
					Results	12	18.6	89	4.8

(1) And (3) a water desorption stage: washing and filter-pressing phosphogypsum in a slag warehouse, feeding the phosphogypsum into a Venturi tube through spiral feeding, and supplying hot air with the temperature of 280 ℃ by a hot blast stove at 12m³The flow of the flow is that partial attached water in the phosphogypsum is removed from the lower end of a Venturi tube, simultaneously the agglomerated phosphogypsum is scattered, the residence time of the phosphogypsum in the Venturi tube is 110s, then the phosphogypsum enters a cyclone preheater, hot air of 195 ℃ is provided by a hot air furnace, and the hot air is 8m³And (4) further removing the attached water at the flow rate of/h, wherein the retention time of the phosphogypsum is 130s, and finally the content of the attached water in the phosphogypsum is maintained to be about 1-3%.

(2) A mixing and fluidizing stage: mass of600g of SiC powder with the particle size distribution of 20-170 mu m is added into the fluidized bed, and then the phosphogypsum subjected to preheating treatment is continuously conveyed into the fluidized bed through air flow. The bottom of the fluidized bed is introduced with a flow of 6.5m³H post-compressed air phosphogypsum and SiC₄Uniformly mixing and forming a fluidized state in a wave-transparent heating section of the fluidized bed, wherein the mass ratio of the phosphogypsum to the SiC is 6.5: 1.

(3) Microwave heating dehydration stage: setting the power of a microwave generator to be 350W, setting the microwave frequency to be 900MHZ, and conveying high-frequency electromagnetic waves of the microwave generator into the fluidized bed resonant cavity. Microwaves are reflected in the cylindrical resonant cavity and penetrate through the wave-transparent heating section of the fluidized bed, the microwaves are fully absorbed by SiC, the temperature is sharply increased in a short time, the SiC transmits heat to phosphogypsum and air in a solid-solid or gas-solid mode, and the heated hot air can increase the temperature of the phosphogypsum and accelerate the dehydration of the phosphogypsum. The phosphogypsum and organic impurities contained in the phosphogypsum can also absorb microwave energy and convert the microwave energy into heat energy, so that the temperature of the phosphogypsum in the wave-transparent heating section of the fluidized bed reaches 140 ℃, and the dihydrate gypsum is dehydrated and converted into beta-hemihydrate gypsum.

(4) And (3) material separation stage: the SiC quality does not change with temperature. The grain size of SiC is controlled. After the phosphogypsum is removed and converted into the building gypsum by crystal water, the weight is lightened, the fluidization height is increased, the SiC fluidization height is unchanged, and the building gypsum and SiC form layering. And when the building gypsum fluidization height reaches the height of the discharge port, discharging from the discharge port.

(5) Material cooling and tail gas treatment: and the dehydrated phosphogypsum is discharged from a discharge hole and then enters a material receiving tank, and the material receiving tank contains a water-cooling interlayer. And the variable-frequency water pump conveys cooling water from the open water pool to the interlayer at the lower end of the material receiving tank at the flow velocity of 3.5m/s for phosphogypsum cooling, and then the cooling water flows out from the upper end and enters the water pool for circulation. The cooling circulating water after temperature rise is naturally cooled in the open water pool and is continuously used for the circulating cooling system. And a temperature detector is arranged in the material receiving tank, when the temperature of the dehydrated phosphogypsum is lower than the set temperature of 35 ℃, an outlet at the lower end of the material receiving tank is automatically opened, the vibration frequency is 4cpm, and the discharge port is automatically closed after the discharge is finished. The introduced compressed air is discharged from the top of the fluidized bed, enters a cyclone cooler for cooling and then enters a bag-type dust collector for further purification and dust removal. The fine dehydrated phosphogypsum mixed in the air is collected from cyclone dust collection and cloth bag dust collection.

The three-phase analysis and detection results of the building gypsum after microwave-enhanced dehydration treatment are shown in the following table.

Detecting items	Attached water	DH/％	HH/％	AIII/％	pH
						Results	0	1.3	84	2.5	5.7

The structure of the device of this embodiment is the same as that of embodiment 1.

Example 3: the object to be treated in this example was desulfurized gypsum produced by flue gas desulfurization in a chemical plant, and the analysis results are as follows.

Detecting items	Attached water	Grade (L) of a material	pH
				Results	8	92	5.1

(1) And (3) a water desorption stage: feeding desulfurized gypsum into venturi tube by spiral feeding, and supplying hot air with temperature of 250 ℃ at 12m by hot blast stove³The flow of the flow is that partial attached water in the phosphogypsum is removed from the lower end of a Venturi tube, simultaneously the agglomerated phosphogypsum is scattered, the residence time of the phosphogypsum in the Venturi tube is 80s, then the phosphogypsum enters a cyclone preheater, hot air of 180 ℃ is provided by a hot air furnace, and the hot air is 8m³And (4) further removing the attached water at the flow rate of/h, wherein the retention time of the phosphogypsum is 100s, and finally the content of the attached water in the phosphogypsum is maintained to be about 1-3%.

(2) A mixing and fluidizing stage: si with the mass of 500g and the particle size distribution of 15-140 mu m₃N₄After the powder is added into the fluidized bed, the phosphogypsum after the preheating treatment is continuously conveyed into the fluidized bed through air flow. The bottom of the fluidized bed is introduced with a flow of 2m³H post-air compression phosphogypsum and Si₃N₄Uniformly mixing and forming a fluidized state in a wave-transparent heating section of the fluidized bed, wherein phosphogypsum and Si are mixed₃N₄The mass ratio is 5: 1.

(3) Microwave heating dehydration stage: setting the power of a microwave generator to 800W and the frequency of microwave to 2450MHZ, and feeding high-frequency electromagnetic waves into fluidization by the microwave generatorIn the bed resonance cavity. Microwave is reflected in the cylindrical resonant cavity and passes through the wave-transparent heating section of the fluidized bed to be heated by Si₃N₄Full absorption, rapid rise of temperature in a short time, and Si₃N₄The heat is transferred to the phosphogypsum and the air in a solid-solid and gas-solid mode, and the heated hot air can increase the temperature of the phosphogypsum and accelerate the dehydration of the phosphogypsum. The phosphogypsum and the organic impurities contained in the phosphogypsum can also absorb microwave energy and convert the microwave energy into heat energy, so that the temperature of the phosphogypsum in the wave-transparent heating section of the fluidized bed reaches 800 ℃. The dihydrate gypsum is dehydrated and converted into II type anhydrous gypsum.

(4) And (3) material separation stage: si₃N₄The mass does not change with temperature. After the phosphogypsum is converted into II type anhydrous gypsum by removing crystal water, the weight is lightened, the fluidization height is increased and Si is contained₃N₄Constant fluidization height, anhydrous gypsum type II and Si₃N₄Layering is formed. And when the fluidization height of the type II anhydrous gypsum reaches the height of the discharge port, the anhydrous gypsum is discharged from the discharge port.

(5) Material cooling and tail gas treatment: and the dehydrated phosphogypsum is discharged from a discharge hole and then enters a material receiving tank, and the material receiving tank contains a water-cooling interlayer. And the variable-frequency water pump conveys cooling water from the open water tank to the interlayer at the lower end of the material receiving tank at the flow speed of 12m/s to flow in for cooling the phosphogypsum, and then the cooling water flows out from the upper end and enters the water tank for circulation. The cooling circulating water after temperature rise is naturally cooled in the open water pool and is continuously used for the circulating cooling system. And a temperature detector is arranged in the material receiving tank, when the temperature of the dehydrated phosphogypsum is lower than the set temperature by 40 ℃, an outlet at the lower end of the material receiving tank is automatically opened, the vibration frequency is 5cpm, and the discharge port is automatically closed after the discharge is finished. The introduced compressed air is discharged from the top of the fluidized bed, enters a cyclone cooler for cooling and then enters a bag-type dust collector for further purification and dust removal. The fine dehydrated phosphogypsum mixed in the air is collected from cyclone dust collection and cloth bag dust collection.

The content of AII type anhydrous gypsum in the phosphogypsum after microwave reinforced dehydration treatment is 95 percent.

The structure of the device of this embodiment is the same as that of embodiment 1.

Although the invention has been described herein with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More specifically, various variations and modifications are possible in the component parts or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts or arrangements, other uses will also be apparent to those skilled in the art.