阅读说明：本技术 一种磷石膏分段制备硫酸和矿渣棉纤维的方法及其装置 (Method and device for preparing sulfuric acid and mineral cotton fiber by phosphogypsum in sections ) 是由 张晖 侯翠红 郭旭东 资学民 王好斌 钟晋 谷守玉 宋慧林 王艳语 张建国 于 2021-10-25 设计创作，主要内容包括：本发明公开了一种磷石膏分段制备硫酸和矿渣棉纤维的方法及其装置,涉及磷石膏分段制备硫酸及其烧渣高值化利用技术领域。将磷石膏通过循环流化床还原为硫化钙和硫酸钙的混合物,然后再与经预热后的硅、铝、镁的粉状化合物物料混合后送入高温反应炉焙烧熔融,或者先送入鼓泡流化床焙烧分解,再与经预热后的硅、铝、镁的粉状化合物物料混合后送入高温反应炉熔融,熔融炉渣经喷吹或离心工艺,可制备出附加值高的矿渣棉纤维产品。焙烧过程中制得高浓度SO-(2)烟气,送去制备硫酸。物料以粉状直接进入反应,通过分段法,使得各段反应更加完全,使制得的SO-(2)烟气浓度更高,得到的矿渣棉纤维更细、质量更好,实现磷石膏烧渣的高附加值利用。(The invention discloses a method and a device for preparing sulfuric acid and mineral cotton fiber by phosphogypsum in sections, and relates to the technical field of high-value utilization of sulfuric acid and cinder prepared by phosphogypsum in sections. Reducing phosphogypsum into a mixture of calcium sulfide and calcium sulfate through a circulating fluidized bed, then mixing the mixture with preheated powdery compound materials of silicon, aluminum and magnesium, and then sending the mixture into a high-temperature reaction furnace for roasting and melting, or firstly sending the mixture into a bubbling fluidized bed for roasting and decomposition, then mixing the mixture with the preheated powdery compound materials of silicon, aluminum and magnesium, and then sending the mixture into the high-temperature reaction furnace for melting, and blowing or centrifuging the molten slag to prepare a mineral wool fiber product with high added value. High concentration SO is prepared in the roasting process 2 The flue gas is sent to prepare sulfuric acid. The materials directly enter into the reaction in powder form, and the reaction in each section is more complete through a segmentation method, SO that the prepared SO 2 The flue gas concentration is higher, the obtained mineral cotton fiber is thinner and better in quality, and the high added value utilization of the phosphogypsum cinder is realized.)

1. A method for preparing sulfuric acid and slag cotton fiber by phosphogypsum in a segmented manner is characterized by comprising the following steps: comprises a two-stage method or a three-stage method; wherein, the two-stage method comprises the following steps:

s1-1, adopting powdery raw materials, namely phosphogypsum and coal coke, directly feeding the raw materials into a fluidized bed without compression molding;

s1-2, independently reducing the phosphogypsum in a fluidized bed;

s1-3, supplementing the required preheated powdery raw materials containing silicon, aluminum and magnesium in the powdery hot discharge of the fluidized bed according to the MK and PH value requirements required by the preparation of the slag wool fibers;

s1-4, directly feeding the hot powdery material mixture into a roasting decomposition furnace for roasting decomposition and melting;

high concentration S0 obtained by roasting and decomposing S1-55₂Adding dry air into the flue gas, controlling the gas concentration to be 8.5-12.0%, controlling the oxygen-sulfur ratio at the same time, and sending the flue gas to a sulfuric acid device to prepare sulfuric acid; directly preparing slag cotton fiber products by using molten slag discharged from a roasting decomposition furnace in a liquid state through a blowing or centrifuging process;

the three-stage process comprises the following steps:

s2-1, adopting powdery raw materials, namely phosphogypsum and coal coke, directly feeding the raw materials into a fluidized bed without compression molding;

s2-2, independently reducing the phosphogypsum in a fluidized bed;

s2-3, directly feeding the powdery hot discharge of the fluidized bed into a second-stage roasting decomposition furnace for roasting decomposition to obtain high-concentration S0₂Adding dry air into the flue gas, controlling the gas concentration to be 8.5-12.0%, controlling the oxygen-sulfur ratio, and sending the flue gas to a sulfuric acid device to prepare sulfuric acid;

s2-4, supplementing the required preheated powdery raw materials containing silicon, aluminum and magnesium in the powdery hot discharge material of the roasting decomposition furnace according to the MK and PH value requirements required by the preparation of the slag wool fiber;

s2-5, directly feeding the hot powdery material mixture into a melting furnace for melting, directly preparing slag cotton fiber products by using the molten slag discharged in a liquid state through a blowing or centrifuging process.

2. The method for preparing sulfuric acid and slag wool fibers by sections through phosphogypsum according to claim 1, is characterized in that: the molar ratio of C in the coal coke to S in the raw material phosphogypsum is 0.8-1.2: 1; the coal coke and the raw material phosphogypsum are crushed and uniformly mixed, and are sent into a fluidized bed for rapid reduction, and the reaction time is 2.0-20.0 min at the temperature of 750-850 ℃; the preheating temperature of the powdery raw material containing the components of silicon, aluminum and magnesium in the two-stage method is 600-700 ℃, and the preheating temperature of the powdery raw material containing the components of silicon, aluminum and magnesium in the three-stage method is 1100-1200 ℃; the acidity coefficient Mk of a material system added with the preheated powdery raw materials containing silicon, aluminum and magnesium is 1.1-1.4, and the pH value is 4-5.

3. The method for preparing sulfuric acid and slag wool fibers by sections through phosphogypsum according to claim 1, is characterized in that: the roasting decomposition temperature is controlled to be 1100-1350 ℃, the roasting decomposition time is 5.0-15.0 min, and the decomposition escape rate of sulfur in the phosphogypsum is 95-98%.

4. The method for preparing sulfuric acid and slag wool fibers by sections through phosphogypsum according to claim 1, is characterized in that: the melting temperature is 1350-1550 ℃, the melting time is 20.0-90.0 min, and the viscosity of the generated molten slag is 1-3 pas.

5. The method for preparing sulfuric acid and slag wool fibers by sections through phosphogypsum according to claim 1, is characterized in that: the coal coke is a C reducing agent and is selected from one or more of lignite, anthracite, coke breeze and white coal.

6. The method for preparing sulfuric acid and slag wool fibers by sections through phosphogypsum according to claim 1, is characterized in that: the powdery raw material containing the silicon component is one or more selected from silica powder, fly ash, coke ash, blast furnace slag and potassium feldspar.

7. The method for preparing sulfuric acid and slag wool fibers by sections through phosphogypsum according to claim 1, is characterized in that: the powdery raw material containing the aluminum component is selected from one or more of fly ash, coke ash and blast furnace slag.

8. The method for preparing sulfuric acid and slag wool fibers by sections through phosphogypsum according to claim 1, is characterized in that: the powdery raw material containing the magnesium component is one or two of ludwigite, light-burned magnesium or blast furnace slag.

9. The method for preparing sulfuric acid and slag wool fibers by sections through phosphogypsum according to claim 1, is characterized in that: the production device of the two-stage method comprises a circulating fluidized bed (1), a mixing device (2), a high-temperature reaction furnace (3) and a high-speed centrifuge (4) which are connected in sequence, wherein the mixing device (2) is connected with a preheating device (5); the tail gas outlet discharged by the circulating fluidized bed (1) is sequentially connected with a first dust removal device (6), a combustion device (7) and a tail gas washing system (12), and the outlet of the high-temperature reaction furnace (3) contains high-concentration SO₂The flue gas is sequentially connected with a second dust removal device (8) and a waste heat recovery deviceThe device (9) is connected with a sulfuric acid production device (10), and tail gas at the outlet of the sulfuric acid production device (10) is connected with a tail gas washing system (12).

10. The method for preparing sulfuric acid and slag wool fibers by sections through phosphogypsum according to claim 1, is characterized in that: the production device of the three-stage method comprises a circulating fluidized bed (1), a bubbling fluidized bed (11), a mixing device (2), a high-temperature reaction furnace (3) and a high-speed centrifuge (4) which are connected in sequence, wherein the mixing device (2) is connected with a preheating device (5); the tail gas outlet discharged by the circulating fluidized bed (1) is sequentially connected with a first dust removal device (6), a combustion device (7) and a tail gas purification and washing system (12), and the outlet of the bubbling fluidized bed (11) contains high-concentration SO₂The flue gas is sequentially connected with a second dust removal device (8), a waste heat recovery device (9) and a sulfuric acid preparation device (10), and tail gas at the outlet of the sulfuric acid preparation device (10) is connected with a tail gas washing and purifying system (12).

Technical Field

The invention relates to the technical field of sectional preparation of sulfuric acid by phosphogypsum and high-value utilization of cinder of the sulfuric acid, in particular to a method and a device for sectional preparation of sulfuric acid and mineral cotton fiber by phosphogypsum.

Background

The phosphogypsum is an industrial byproduct of wet-process phosphoric acid production, and 4.5 t-5.5 t of phosphogypsum is produced every 1t of phosphoric acid production. The main component of the phosphogypsum is CaSO₄·2H₂O and contains relatively SiO₂And a small amount of MgO, Al₂O₃、Fe₂O₃、P₂O₅Fluoride, organic matter and the like. At present, the existing phosphogypsum in China is as high as about 7.5 hundred million tons, about 9000 million tons is newly added every year, and the comprehensive utilization and disposal rate is less than 40 percent. Huge amount of phosphogypsum is accumulated in a special slag warehouse in a centralized way, which brings environmental protection and safety risksThe method has the advantages that a new phosphogypsum slag warehouse is not allowed by a family, related departments of national governments and local governments at all levels produce a series of policy documents, higher and higher requirements are put on industrial solid wastes, particularly on the comprehensive utilization rate of phosphogypsum, and enterprises which cannot meet the utilization rate requirements face shutdown risks; on the other hand, a series of policy documents are issued to encourage and strengthen the comprehensive utilization of the large amount of solid wastes and the phosphogypsum. Therefore, the comprehensive utilization problem of the phosphogypsum becomes a major problem which is urgently needed to be solved and restricts the sustainable and healthy development of the wet-process phosphoric acid and high-concentration phosphorus compound fertilizer industry in China.

At present, the byproduct phosphogypsum in the domestic wet-process phosphoric acid and phosphorus compound fertilizer industry is mainly stockpiled in a slag warehouse, the comprehensive utilization rate, especially the resource utilization rate is still in a lower level, and the main utilization way is still in the primary stage of processing low-end products, such as preparing cement retarders, and after modification, the phosphogypsum is used for mine filling and processing building materials (various powder materials and section bars) such as building gypsum. In the aspect of preparing acid by phosphogypsum, compared with a mainstream method for preparing acid by sulfur, the production cost is high, a large amount of cinder can only be used as low-end products such as cement clinker or mixed materials, the quality fluctuation is large, the additional value is low, and the economy and the competitiveness are lacked, so that the large-scale application and popularization are difficult. Except that the individual devices can maintain production due to the consideration of treating industrial waste, other devices for producing acid and co-producing cement by phosphogypsum stop production successively.

The mineral cotton fiber is a kind of cotton silk-like mineral fiber prepared by using molten slag as main raw material and through centrifugal/blowing process, and is a product with high added value. The market selling price of the mineral wool is about 2200 yuan/t or more, and the selling price of part of high-temperature resistant mineral wool heat insulation plate products of metallurgy, chemical industry, electric power and the like is 10000 yuan/t or more. At present, the slag wool is produced by using solid slag such as blast furnace slag, yellow phosphorus slag and the like which are ironed at high temperature in China through the methods of quenching and tempering, homogenizing (heat preservation) and centrifugal fiber forming of the slag.

Patent CN102530886B discloses a method for preparing sulfuric acid and cement from phosphogypsum, which is to add sandy soil, coke, lime, crude salt and ferrous salt into the phosphogypsum for mixing, add the mixture into a rotary kiln for calcining, and decompose the obtained SO₂Flue gas ofSulfuric acid is prepared, and the cinder is used as cement clinker.

The co-production of acid and cement by using phosphogypsum is an important way for realizing the large-scale digestion and utilization of the phosphogypsum in the wet-process phosphoric acid and phosphorus compound fertilizer industry, but is difficult to popularize and apply due to the reasons of large device investment, large occupied area, large clinker quality fluctuation, high production cost, poor economy and the like, and becomes a great problem to be solved urgently.

Disclosure of Invention

The invention aims to provide a method and a device for preparing sulfuric acid and slag cotton fiber by phosphogypsum in sections, which solve the problem of low resource utilization rate of the existing phosphogypsum. The phosphogypsum is quickly reduced into a mixture of calcium sulfide and calcium sulfate by a fluidized bed, calculation and proportioning optimization are carried out, raw materials containing silicon, aluminum, magnesium and the like are added additionally, and the sulfur contained in the phosphogypsum is decomposed by roasting to generate high-concentration SO through roasting decomposition and melting processes₂Flue gas used for preparing sulfuric acid; the slag wool fiber product with high added value can be directly prepared from the molten slag through a blowing or centrifuging process.

In order to solve the technical problems, the invention adopts the following technical scheme: a method for preparing sulfuric acid and slag cotton fiber by phosphogypsum in a segmented manner is characterized by comprising the following steps: comprises a two-stage method or a three-stage method; wherein, the two-stage method comprises the following steps:

s1-1, adopting powdery raw materials, namely phosphogypsum and coal coke, directly feeding the raw materials into a fluidized bed without compression molding;

s1-2, independently reducing the phosphogypsum in a fluidized bed;

s1-3, supplementing the required preheated powdery raw materials containing silicon, aluminum and magnesium in the powdery hot discharge of the fluidized bed according to the MK and PH value requirements required by the preparation of the slag wool fibers;

s1-4, directly feeding the hot powdery material mixture into a roasting decomposition furnace for roasting decomposition and melting;

high concentration S0 obtained by roasting and decomposing S1-55₂Adding dry air into the flue gas, controlling the gas concentration to be 8.5-12.0%, controlling the oxygen-sulfur ratio at the same time, and sending the flue gas to a sulfuric acid device to prepare sulfuric acid; roasting componentDirectly preparing the slag cotton fiber product from the molten slag discharged from the liquid state of the melting furnace by using a blowing or centrifuging process;

the three-stage process comprises the following steps:

s2-1, adopting powdery raw materials, namely phosphogypsum and coal coke, directly feeding the raw materials into a fluidized bed without compression molding;

s2-2, independently reducing the phosphogypsum in a fluidized bed;

s2-3, directly feeding the powdery hot discharge of the fluidized bed into a second-stage roasting decomposition furnace for roasting decomposition to obtain high-concentration S0₂Adding dry air into the flue gas, controlling the gas concentration to be 8.5-12.0%, controlling the oxygen-sulfur ratio, and sending the flue gas to a sulfuric acid device to prepare sulfuric acid;

s2-4, supplementing the required preheated powdery raw materials containing silicon, aluminum and magnesium in the powdery hot discharge material of the roasting decomposition furnace according to the MK and PH value requirements required by the preparation of the slag wool fiber;

s2-5, directly feeding the hot powdery material mixture into a melting furnace for melting, directly preparing slag cotton fiber products by using the molten slag discharged in a liquid state through a blowing or centrifuging process.

The further technical scheme is that the molar ratio of C in the coal coke to S in the raw material phosphogypsum is 0.8-1.2: 1; the coal coke and the raw material phosphogypsum are crushed and uniformly mixed, and are sent into a fluidized bed for rapid reduction, and the reaction time is 2.0-20.0 min at the temperature of 750-850 ℃; the preheating temperature of the powdery raw material containing the components of silicon, aluminum and magnesium in the two-stage method is 600-700 ℃, and the preheating temperature of the powdery raw material containing the components of silicon, aluminum and magnesium in the three-stage method is 1100-1200 ℃; the acidity coefficient Mk of a material system added with the preheated powdery raw materials containing silicon, aluminum and magnesium is 1.1-1.4, and the pH value is 4-5.

The further technical scheme is that the roasting decomposition temperature is controlled to be 1100-1350 ℃, the time is 5.0-15.0 min, and the decomposition and escape rate of sulfur in the phosphogypsum is 95-98%.

The further technical scheme is that the melting temperature is 1350-1550 ℃, the melting time is 20.0-90.0 min, and the viscosity of the generated molten slag is 1-3 Pa · s.

The further technical proposal is that the coal coke is a C reducing agent and is selected from one or more of lignite, anthracite, coke breeze and white coal.

The further technical proposal is that the powdery raw material containing the silicon component is selected from one or more of silica powder, fly ash, coke ash, blast furnace slag and potash feldspar.

The further technical proposal is that the powdery raw material containing the aluminum component is selected from one or more of fly ash, coke ash and blast furnace slag.

The further technical proposal is that the powdery raw material containing magnesium is selected from one or two of ludwigite, light-burned magnesium or blast furnace slag.

The further technical scheme is that the mixture obtained in the step S2 is ground and sieved by a 30-80-mesh sieve, and the particle size of the powdery compound material containing silicon, aluminum and magnesium in the step S3 is 50-100 meshes.

The further technical proposal is that the main component of the slag wool fiber in the step S3 is SiO in percentage by mass₂36-42％、Al₂O₃5-12％、CaO 28-47％，MgO 1-8％、Fe₂O₃1-5％、(K₂O+NaO)0-1.2％。

The further technical proposal is that the acidity coefficient Mk of the slag is the mass ratio of the acid oxide and the basic oxide, and Mk is equal to (W)_SiO2+W_Al2O3)/(W_CaO+W_MgO)。

The further technical scheme is that the calculation method of the slag pH value comprises the following steps:

pH＝-0.0602W_SiO2-0.120W_Al2O3+0.232W_CaO+0.120W_MgO+0.144W_Fe2O3+0.21W_Na2O。

a further technical scheme is that the production device of the two-stage method comprises a circulating fluidized bed, a mixing device, a high-temperature reaction furnace and a high-speed centrifuge which are sequentially connected, wherein the mixing device is connected with a preheating device; the tail gas outlet of the circulating fluidized bed is sequentially connected with a first dust removal device, a combustion device, a tail gas washing system and a high-temperature reaction furnaceThe outlet contains high concentration SO₂The flue gas is connected with a second dust removal device, a waste heat recovery device and a sulfuric acid preparation device in sequence, and tail gas at the outlet of the sulfuric acid preparation device is connected with a tail gas washing system.

A further technical scheme is that the production device of the three-stage method comprises a circulating fluidized bed, a bubbling fluidized bed, a mixing device, a high-temperature reaction furnace and a high-speed centrifuge which are sequentially connected, wherein the mixing device is connected with a preheating device; the tail gas outlet of the circulating fluidized bed is sequentially connected with a first dust removal device, a combustion device and a tail gas purification and washing system, and the outlet of the bubbling fluidized bed contains high-concentration SO₂The flue gas of (2) and be connected with second dust collector, waste heat recovery device and system sulphuric acid device in proper order, system sulphuric acid device export tail gas and tail gas washing clean system are connected.

The working mechanism is as follows:

firstly, the phosphogypsum is reduced into a mixture of calcium sulfide and calcium sulfate through a circulating fluidized bed, preheated silicon, aluminum and magnesium compound raw materials are supplemented to hot materials after reduction reaction, the content of silicon, aluminum and magnesium in the phosphogypsum is further increased, and the batching requirement for preparing slag wool fibers is met.

The reaction principle is as follows;

reduction reaction: CaSO₄+2C＝CaS+CO₂(endothermic reaction)

CaSO₄+4CO＝CaS+4CO₂(endothermic reaction)

Roasting decomposition reaction: 2CaS +3O₂＝＝2CaO+2SO₂(exothermic reaction)

CaS+3CaSO₄＝4CaO+4SO₂(endothermic reaction)

2CaSO₄＝2CaO+O₂+2SO₂(endothermic reaction)

The main component of the phosphogypsum is calcium sulfate dihydrate, the reduction product is a mixture of calcium sulfide and calcium sulfate, and CaO and SiO in silicide, aluminide and magnesium compound and the reduction product are selected according to the formula₂、Al₂O₃And the content of MgO is optimized and determined according to the Mk of the slag of 1.1-1.5 and the pH value of 4-5. The pH value is more accurate to measure the chemical stability of the slag cotton fiberThe index of (1).

The viscosity of the molten slag has a certain relation with the temperature, and at higher temperature, the viscosity is lower and the fluidity is better. When the temperature is lowered to a certain degree, the viscosity is sharply increased and the fluidity is relatively poor. The reasonable and optimized melt viscosity of the prepared mineral wool is 1-3 Pa.s, the corresponding interval temperature is about 1350-1550 ℃, and the requirement for preparing the mineral wool can be met. When the acidity coefficient Mk of the molten slag is 1.1-1.5, the fiber diameters are all smaller than 6.0 mu m, the variation range is not large, and the diameter of the slag wool is slightly increased along with the increase of Mk. Preferably, the reaction temperature of the circulating fluidized bed is 850 ℃, the retention time is 5min, and the reaction products mainly comprise CaS and CaSO₄A mixture of components. The roasting temperature is about 1220 ℃, the retention time is 5min, and the reaction products mainly comprise multi-phase cinder (mainly comprising Ca, Si, Al, Mg and the like) and high-concentration SO₂Flue gas. The melting temperature was 1450 ℃ and the residence time was 30 min.

Compared with the prior art, the invention has the beneficial effects that: reducing phosphogypsum into a mixture of calcium sulfide and calcium sulfate through a circulating fluidized bed, then mixing the mixture with preheated powdery compound materials of silicon, aluminum and magnesium, and then sending the mixture into a high-temperature reaction furnace for roasting and melting, or firstly sending the mixture into a bubbling fluidized bed for roasting and decomposition, then mixing the mixture with the preheated powdery compound materials of silicon, aluminum and magnesium, and then sending the mixture into the high-temperature reaction furnace for melting, and blowing or centrifuging the molten slag to prepare a mineral wool fiber product with high added value. High concentration SO is prepared in the roasting process₂The flue gas is sent to prepare sulfuric acid. The materials directly enter into the reaction in powder form, and the reaction in each section is more complete through a segmentation method, SO that the prepared SO₂The smoke concentration is higher, and the obtained mineral cotton fiber is thinner and has better quality.

In the process, high added value utilization of the phosphogypsum cinder is realized while the S element in the phosphogypsum is recycled, and simultaneously, impurity components such as calcium, higher silicon, aluminum, magnesium and the like contained in the phosphogypsum can be fully utilized to be converted into raw materials for preparing slag wool, so that other solid waste raw materials with higher value, such as wollastonite, other minerals, fly ash and the like, are further reduced and saved, the production cost is reduced, the influence of mining of the minerals such as silicon and the like on the environment is reduced, the phosphogypsum acid preparation has economic benefit and ecological environmental benefit, and the large-scale popularization and application of the phosphogypsum in the chemical field are facilitated.

Drawings

FIG. 1 is a process flow diagram of the present invention.

FIG. 2 is another process flow diagram of the present invention.

In the figure: 1-circulating fluidized bed, 2-mixing device, 3-high temperature reaction furnace, 4-high speed centrifuge, 5-preheating device, 6-first dust removal device, 7-combustion device, 8-second dust removal device, 9-waste heat recovery device, 10-sulfuric acid preparation device, 11-bubbling fluidized bed and 12-tail gas washing system.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

Fig. 1 shows a device for preparing sulfuric acid and slag wool fibers by using phosphogypsum through a two-stage method, which comprises a circulating fluidized bed 1, a mixing device 2, a high-temperature reaction furnace 3 and a high-speed centrifuge 4 which are sequentially connected, wherein the mixing device 2 is connected with a preheating device 5, a tail gas outlet of the fluidized bed 1 is sequentially connected with a first dust removal device 6, a combustion device 7 and a tail gas washing system 12, the high-temperature reaction furnace 3 is sequentially connected with a second dust removal device 8, a waste heat recovery device 9 and a sulfuric acid preparation device 10, and a tail gas outlet of the sulfuric acid preparation device 10 is connected with the tail gas washing system 12.

The preparation method mainly comprises the following steps:

s1, adding a carbon-based reducing material into powdery phosphogypsum; wherein the molar ratio of C in the reducing material to S in the phosphogypsum is 0.8-1.2: 1;

s2, crushing and uniformly mixing the mixed material obtained in the step S1, sending the mixture into a circulating fluidized bed 1 for rapid reduction, and reacting for 2.0-20.0 min at the temperature of 750-850 ℃;

s3, adding powdery compound materials containing silicon, aluminum and magnesium, which are preheated to 600-700 ℃, into the materials discharged from the circulating fluidized bed obtained in the step S2, uniformly mixing in a mixing device 2, controlling the acidity coefficient Mk of a material system to be 1.1-1.4 and the pH value to be 4-5, and feeding the materials into a high-temperature reaction furnace 3 for roasting and melting; wherein the roasting temperature is 1100 ℃, the roasting time is 5.0-15.0 min, the melting temperature is 1350-1550 ℃, the melting time is 20.0-90.0 min, and the generated molten slag is prepared into slag cotton fibers by a high-speed centrifuge 4; the viscosity of the molten slag is 1-3 Pa.s;

s4, carrying out reaction on the high-concentration SO generated in the S3₂The flue gas is added with dry air to control the oxygen-sulfur ratio, and enters a converter for SO₂Conversion to SO₃The decomposition and escape rate of sulfur in the phosphogypsum is 95. After the tail gas from the circulating fluidized bed 1 is dedusted, the incompletely reacted CO is further combusted in the combustion device 7, and then is cleaned and purified and then is discharged.

Example 2

Fig. 2 shows a device for preparing sulfuric acid and slag wool fibers by using phosphogypsum through a three-stage method, which comprises a circulating fluidized bed 1, a bubbling fluidized bed 11, a mixing device 2, a high-temperature reaction furnace 3 and a high-speed centrifuge 4 which are sequentially connected, wherein the mixing device 2 is connected with a preheating device 5, a tail gas outlet of the fluidized bed 1 is sequentially connected with a first dust removal device 6, a combustion device 7 and a tail gas washing system 12, a tail gas outlet of the high-temperature reaction furnace 3 and the bubbling fluidized bed 11 is sequentially connected with a second dust removal device 8, a waste heat recovery device 9 and a sulfuric acid preparation device 10, and a tail gas outlet of the sulfuric acid preparation device 10 is connected with the tail gas washing system 12.

The preparation method mainly comprises the following steps:

s1, adding a carbon-based reducing material into powdery phosphogypsum; wherein the molar ratio of C in the reducing material to S in the phosphogypsum is 0.8-1.0: 1;

s2, crushing and uniformly mixing the materials discharged by the circulating fluidized bed in the step S1, sending the materials into the circulating fluidized bed 1 for rapid reduction, and reacting for 2.0-20.0 min at the temperature of 750-850 ℃;

s3, feeding the material obtained in the step S2 into a bubbling fluidized bed 11 for roasting decomposition at a roasting decomposition temperature of 1150 DEG CThe burning time is 5.0-15.0 min, and high-concentration SO is prepared₂Flue gas and powdery cinder;

s4, adding powdery compound materials containing silicon, aluminum and magnesium, which are preheated to 1100-1200 ℃, into the powdery clinker, uniformly mixing in a mixing device 2, controlling the acidity coefficient Mk of a material system to be 1.1-1.4 and the pH value to be 4-5, and feeding the materials into a high-temperature reaction furnace 3 for melting; the melting temperature is 1400-1550 ℃, the melting time is 30.0-90.0 min, and the generated molten slag is prepared into slag cotton fibers through a high-speed centrifuge 4; the viscosity of the molten slag is 1-3 Pa.s;

s4, carrying out reaction on the high-concentration SO generated in the S3₂The flue gas is added with dry air to control the oxygen-sulfur ratio, and enters a converter for SO₂Conversion to SO₃The decomposition and escape rate of sulfur in the phosphogypsum is 95.6 percent when the sulfuric acid is prepared.

Example 3

The compositions of the raw materials used in the examples and the following examples are shown in Table 1.

Table 1 composition of raw materials used in examples (% by mass)

	CaO	SiO2	Al2O3	MgO	Fe2O3	Na2O	SO3
								Phosphogypsum	28.00	13.50	0.21	0.034	0.13	0.05	38.72
Fly ash	6.09	37.27	26.64	5.19	2.03	0.26
								Iron tailings	3.06	71.93	4.93	4.14	4.75	0.92
Silica	2.22	87.3	3.35	0.36	0.93	0.21

Adding 7.5 parts by mass of coke (the fixed carbon content is 63.62%) into 100 parts by mass of dry phosphogypsum according to the molar ratio of carbon (C) to sulfur (S) in the phosphogypsum of 0.8, feeding the mixture into a circulating fluidized bed, feeding the mixture into the circulating fluidized bed at the temperature of 850 ℃ for 5.0 minutes, crushing 21.5 parts by mass of fly ash, 10 parts by mass of iron tailings and 15 parts by mass of silica, sieving the crushed mixture with a 40-mesh sieve according to the batching requirement of slag wool, preheating the crushed mixture to 800 ℃, mixing the crushed mixture with hot discharge of a fluidized bed, feeding the mixture into a high-temperature reaction furnace, and sequentially carrying out roasting decomposition and melting; controlling the temperature of a roasting decomposition layer to be 1220 ℃, the average residence time of materials to be 5.0 minutes, the temperature of a melting layer to be 1450 ℃, the average residence time of the materials to be 20.0 minutes, and blowing the generated molten slag to prepare slag wool fibers; the molten slag viscosity was 1.8 pas. The decomposition and escape rate of sulfur in the phosphogypsum is 97.0 percent, and SO in the flue gas generated by the reaction₂The mass fraction of the sulfur dioxide is 16.0 percent, the flue gas is discharged from the upper part, is subjected to dust removal, waste heat recovery and washing purification, is added with dry air to control the oxygen-sulfur ratio, and enters a converter for SO₂Conversion to SO₃And (3) preparing sulfuric acid, discharging molten slag through a diversion trench, and preparing mineral wool through an injection process. The prepared slag wool comprises the following components in percentage by weight: 34.58 percent of CaO and SiO₂41.38％、Al₂O₃6.95％、MgO 1.62％、Fe₂O₃1.18％、Na₂0.23 percent of O, 0.19 percent of water content, 4.8 mu m of fiber diameter and 4.49 percent of slag ball.

Example 4

Adding 8.2 parts by mass of coke (fixed carbon content 65.1%) into 100 parts by mass of phosphogypsum according to the molar ratio of carbon (C) to sulfur (S) in the phosphogypsum of 0.9, feeding the phosphogypsum into a circulating fluidized bed, controlling the reduction temperature to be 800 ℃, keeping the average material residence time to be 10.0 minutes, and adding 22.5 parts by mass of coal powder and 25 parts by mass of coal powder according to the proportioning requirement of slag wool, wherein the acidity index MK of slag is 1.39 and the pH value is 4.95Crushing 3 parts by mass of silica and 3 parts by mass of iron tailings, sieving the crushed iron tailings with a 40-mesh sieve, preheating the crushed iron tailings to 800 ℃, thermally mixing the crushed iron tailings with the discharged material of the fluidized bed, feeding the mixture into a high-temperature reaction furnace, and sequentially roasting, oxidizing and melting the mixture; wherein: the temperature of a roasting layer is 1200 ℃, the average residence time of the materials is 10.0 minutes, the temperature of a melting layer is 1400 ℃, the average residence time of the materials is 30.0 minutes, and the generated molten slag is blown to prepare mineral wool fibers; the molten slag viscosity was 2.1 pas. The escape rate of sulfur in the phosphogypsum is 96.8 percent, and SO in the flue gas generated by the reaction₂The mass fraction of the sulfur dioxide is 16.2 percent, the flue gas is discharged from the upper part, is subjected to dust removal, waste heat recovery and washing purification, is added with dry air to control the oxygen-sulfur ratio, and enters a converter for SO₂Conversion to SO₃And (3) preparing sulfuric acid, discharging molten slag through a diversion trench, and preparing mineral wool through an injection process. The prepared slag wool comprises the following components in percentage by weight: CaO 33.67%, SiO₂42.49％、Al₂O₃7.54％、MgO 2.24％、Fe₂O₃1.80％、Na₂0.35 percent of O, 0.61 percent of water content, 4.2 mu m of fiber diameter and 3.18 percent of slag ball.

Example 5

Adding 7.4 parts by mass of coke (with fixed carbon content of 68.21%) into 100 parts by mass of phosphogypsum according to the molar ratio of carbon (C) to sulfur (S) in the phosphogypsum of 0.85, feeding the phosphogypsum into a circulating fluidized bed, controlling the reduction temperature to be 880 ℃, keeping the average material residence time to be 10.0 minutes, crushing 24 parts by mass of coal powder, 20 parts by mass of iron tailings and 6 parts by mass of silica, sieving the crushed materials with a 40-mesh sieve according to the batching requirement of slag wool, preheating the crushed materials to 880 ℃, thermally mixing the crushed materials with the discharged material of the fluidized bed, feeding the mixture into a high-temperature reaction furnace, and sequentially carrying out roasting, oxidation and melting; wherein: the temperature of a roasting layer is 1250 ℃, the average residence time of the materials is 4.0 minutes, the temperature of a melting layer is 1550 ℃, the average residence time of the materials is 35.0 minutes, and the generated molten slag is blown to prepare mineral wool fibers; the molten slag viscosity was 2.3 pas. The escape rate of sulfur in the phosphogypsum is 97.2 percent, and SO in the flue gas generated by the reaction₂The mass fraction of the smoke is 15.3 percent, the smoke is discharged from the upper part, is subjected to dust removal, waste heat recovery and washing purification, is added with dry air to control the oxygen-sulfur ratio, and enters the reactorConverter for SO₂Conversion to SO₃Sulfuric acid is prepared, molten slag is discharged from the lower part, and slag wool is prepared by an injection process. The prepared slag wool comprises the following components in percentage by weight: CaO 33.62%, SiO₂42.21％、Al₂O₃7.89％、MgO 2.15％、Fe₂O₃1.63％、Na₂0.31 percent of O, 2 percent of water content, 2.0 mu m of fiber diameter and 4.21 percent of slag ball.

Example 6

Adding 7.5 parts by mass of coke (with fixed carbon content of 63.62%) into 100 parts by mass of 60 ℃ dried phosphogypsum according to the molar ratio of carbon (C) to sulfur (S) in the phosphogypsum of 0.8, and feeding the phosphogypsum into a circulating fluidized bed at the temperature of 850 ℃ for 5.0 minutes of average material retention time; then feeding the mixture into a bubbling fluidized bed for oxidizing roasting, controlling the roasting temperature to be 1220 ℃, and controlling the average residence time of the materials to be 5.0 minutes; according to the requirement of blending slag wool, the acidity index Mk of slag is 1.35, the pH value is 5.0, 21.5 parts by mass of fly ash, 10 parts by mass of iron tailings and 15 parts by mass of silica are crushed and sieved by a 40-mesh sieve, preheated to 1400 ℃, thermally mixed with hot discharge materials of a fluidized bed, sent into a high-temperature reaction furnace for melting, the temperature is 1450 ℃, the average retention time of the materials is 30 minutes, and the viscosity of molten slag is 1.8 Pa.s. The escape rate of sulfur in the phosphogypsum is 97.2 percent, and SO in the flue gas generated by the reaction₂The mass fraction of the sulfur dioxide is 16.5 percent, the flue gas is discharged from the upper part, is subjected to dust removal, waste heat recovery and washing purification, is added with dry air to control the oxygen-sulfur ratio, and enters a converter for SO₂Conversion to SO₃And (4) preparing sulfuric acid, discharging molten slag from the lower part, and preparing slag wool by using an injection process. The prepared slag wool comprises the following components in percentage by weight: 34.58 percent of CaO and SiO₂41.83％、Al₂O₃6.95％、MgO 1.62％、Fe₂O₃1.18％、Na₂0.23 percent of O, 0.19 percent of water content, 5.8 mu m of fiber diameter and 4.49 percent of slag ball.

Example 7

Adding 8.2 parts by mass of coke (fixed carbon content 65.1%) into 100 parts by mass of phosphogypsum according to the molar ratio of carbon (C) to sulfur (S) in the phosphogypsum of 0.9, feeding the mixture into a circulating fluidized bed, controlling the reduction temperature to be 800 ℃, and stopping the materials on averageThe retention time is 10.0 minutes; feeding the mixture into a bubbling fluidized bed for oxidizing roasting, controlling the roasting temperature to be 1220 ℃, and controlling the average residence time of the materials to be 5.0 minutes; according to the requirement of blending slag wool, the acidity index Mk of slag is 1.39, the pH value is 4.95, 22.5 parts by mass of fly ash, 25 parts by mass of iron tailings and 3 parts by mass of silica are crushed and sieved by a 40-mesh sieve, preheated to 1400 ℃, thermally mixed with the discharged material of a bubbling fluidized bed, and sent into a high-temperature reaction furnace for melting, wherein the temperature is 1400 ℃, the average retention time of the material is 40.0 minutes, and the viscosity of the molten slag is 2.1 Pa.s. The decomposition and escape rate of sulfur in the phosphogypsum is 96.9 percent, and SO in the flue gas generated by the reaction₂The mass fraction of the sulfur dioxide is 15.9 percent, the flue gas is discharged from the upper part, is subjected to dust removal, waste heat recovery and washing purification, is added with dry air to control the oxygen-sulfur ratio, and enters a converter for SO₂Conversion to SO₃And (4) preparing sulfuric acid, discharging molten slag from the lower part, and preparing slag wool by using an injection process. The prepared slag wool comprises the following components in percentage by weight: CaO 33.67%, SiO₂42.49％、Al₂O₃7.54％、MgO 2.24％、Fe₂O₃1.80％、Na₂0.35 percent of O, 2.0 percent of water content, 4.9 mu m of fiber diameter and 3.76 percent of slag ball.

Example 8

Adding 7.4 parts by mass of coke (fixed carbon content is 68.21%) into 100 parts by mass of phosphogypsum according to the molar ratio of carbon (C) to sulfur (S) in the phosphogypsum of 0.85, and feeding the mixture into a circulating fluidized bed, controlling the reduction temperature to be 880 ℃, and controlling the average retention time of materials to be 10.0 minutes; feeding the mixture into a bubbling fluidized bed for oxidizing roasting, controlling the roasting temperature to be 1250 ℃, and controlling the average retention time of the materials to be 4.0 minutes; according to the requirement of blending slag wool, the acidity index Mk of slag is 1.40, the pH value is 4.86, 24 parts by mass of fly ash, 20 parts by mass of iron tailings and 6 parts by mass of silica are crushed and sieved by a 40-mesh sieve, preheated to 1400 ℃, thermally mixed with the discharged material of a bubbling fluidized bed, sent into a high-temperature reaction furnace for melting, the melting temperature is 1550 ℃, the average residence time of the material is 30.0 minutes, and the generated molten slag is blown to prepare slag wool fibers, wherein the viscosity of the molten slag is 2.3 Pa.s. The escape rate of sulfur in the phosphogypsum is 97.5 percent, and SO in the flue gas generated by the reaction₂The mass fraction of the smoke is 15.0 percent, and the smoke is discharged from the upper partAfter being dedusted, waste heat recovered and washed and purified, the effluent is mixed with dry air to control the oxygen-sulfur ratio and enters a converter for SO₂Conversion to SO₃And (4) preparing sulfuric acid, discharging molten slag from the lower part, and preparing slag wool by using an injection process. The prepared slag wool comprises the following components in percentage by weight: CaO 33.62%, SiO₂42.21％、Al₂O₃7.89％、MgO 2.15％、Fe₂O₃1.63％、Na₂0.31 percent of O, 2 percent of water content, 2.0 mu m of fiber diameter and 4.21 percent of slag ball.

The above is merely an example of the preferred embodiments of the present invention and is not intended to limit the present invention, and various modifications and variations of the present invention may occur to those skilled in the art. Any modification, improvement, equivalent replacement, etc. made within the inventive and innovative principles of the present invention shall fall within the protection scope of the present invention.