System for flash production of anhydrite from phosphogypsum

Abstract

The invention relates to a system for flash production of anhydrite from phosphogypsum. The system comprises a chimney, an induced draft fan, a bag collector and a vertical cylinder furnace, the vertical cylinder furnace is composed of a furnace body, a furnace cover, a furnace bottom and a material scattering device. The furnace body comprises a green electric heating body, a heat insulation material and a furnace body shell. The green electricity is used as an energy source, the anhydrous gypsum is produced by adopting a vertical suspension calcination technology, and the carbon neutralization of the anhydrous gypsum industry is favorably realized.

Description

Technical Field

[0001] The present invention relates to the field of phosphogypsum resource utilization, and in particular to a flash production anhydrous gypsum system. Background Art

[0002] Gypsum is a widely occurring sulfate mineral resource in nature. It is also a long-standing cementitious material, one of the three pillars of inorganic cementitious materials, along with lime and cement. Gypsum is divided into natural gypsum and industrial gypsum. Currently, industrial gypsum mainly includes phosphogypsum and desulfurized gypsum.

[0003] Phosphogypsum is a byproduct of the wet-process phosphoric acid industry. Its comprehensive utilization rate is low, and the remaining phosphogypsum is often dumped nearby. This results in significant annual expenditures for the construction and operation of slag dumps. Phosphogypsum contains impurities such as undecomposed phosphate rock, free phosphoric acid, and fluoride. Large amounts of this material can pose environmental risks.

[0004] Anhydrous gypsum has high strength and water resistance and is widely used. Flash production of anhydrous gypsum using phosphogypsum offers high production efficiency and low energy consumption, facilitating the resourceful utilization of phosphogypsum.

[0005] Wind power, photovoltaic power generation, and hydropower, also known as green electricity, are renewable, clean energy sources that ensure zero carbon emissions from the system's electricity consumption. This green electricity is stored in a sodium-ion battery system, which offers low cost and stable power. Photovoltaic power generation is located at photovoltaic power plants, wind power generation at wind farms, and hydropower at hydropower stations. Green electricity from these power plants and hydropower stations is connected to the sodium-ion battery energy storage system within the phosphogypsum plant via metal conductors. The sodium-ion battery energy storage system is then connected to the electrical equipment in the production system via metal conductors.

[0006] Currently, there is no system for efficiently producing anhydrous gypsum using green electricity. This system also has the characteristics of high production efficiency, low equipment investment and small site usage. Summary of the Invention

[0007] In order to solve the problems existing in the prior art, the present invention provides a system for flash producing anhydrous gypsum from phosphogypsum. The system has high production efficiency and achieves carbon neutrality in the anhydrous gypsum production process.

[0008] The technical solution adopted by the present invention to solve its technical problem is:

[0009] A system for flash-producing anhydrous gypsum from phosphogypsum comprises a chimney, an induced draft fan, a bag dust collector, and a vertical tube furnace; the vertical tube furnace comprises a furnace body, a furnace cover, a furnace bottom, and a spreader; the furnace body comprises a green electric heating element, a heat insulating material, and a furnace shell.

[0010] The electric energy used by the vertical drum furnace is one of photovoltaic power generation, wind power generation and hydropower.

[0011] The green electric heating element is composed of a heating element, a protection tube, a motherboard and a cover plate.

[0012] The heat insulating material is one of mullite fiber and alumina fiber.

[0013] The furnace cover and furnace bottom are composed of high-alumina cement refractory casting material and a shell.

[0014] Compared with the existing technology, the advantages of this patent are:

[0015] The chimney is made of a hollow cylinder made of steel pipe. The inner and outer walls of the steel pipe are sprayed with a high-temperature resistant paint. The working temperature of the high-temperature resistant paint is 100-180℃. The high-temperature resistant paint can extend the service life of the chimney. The high-temperature resistant paint can be one of epoxy phenolic paint and silicone high-temperature resistant paint, which can achieve the desired effect.

[0016] The induced draft fan is a centrifugal boiler induced draft fan with an operating temperature of 150-250℃. It is made of stainless steel and is corrosion-resistant. It also has the characteristics of stable operation and low energy consumption.

[0017] The bag dust collector is a high-temperature air box pulse bag dust collector. The filter bag is made of high-temperature resistant basalt fiber. The working temperature is 150-250℃ and the dust concentration at the outlet is less than 10mg / Nm 3 The exhaust gas can meet the emission standards.

[0018] The elevator is a belt bucket elevator with an operating temperature of 100-150℃. It has the characteristics of stable operation and low equipment cost.

[0019] A screw conveyor is a machine that uses a motor to drive the screw to rotate and push the material to move to achieve the purpose of conveying. It has the advantages of simple structure, small cross-sectional area, easy operation, easy maintenance, and convenient closed transportation.

[0020] The vertical tube furnace consists of a furnace body, a furnace cover, a furnace bottom, and a material spreading tray. The furnace body includes a green electric heating element, thermal insulation, and a furnace shell. The cover, furnace body, and furnace bottom are bolted together for easy installation. The cover and furnace bottom are constructed of high-alumina cement refractory castables and the shell is welded from carbon steel, making it simple to manufacture and low-cost. Materials move downward from the top under gravity, with a residence time of less than 10 seconds within the furnace, resulting in high production efficiency.

[0021] The spreader is fixed on the furnace cover and is manufactured based on the principle of the ceiling fan in the electric fan. The material transported from the elevator is sent to the spreader and is evenly thrown into the furnace to fully exchange heat with the furnace wall and hot air. It has the characteristics of simple structure and easy maintenance.

[0022] The furnace body is a hollow cylinder. From the inner chamber to the outer chamber, it consists of the green electric heating element, the insulation material, and the furnace shell. A constriction in the furnace, formed by a raised motherboard, prolongs the material's residence time within the furnace and facilitates efficient heat exchange between the material and the hot air. The insulation material is either mullite fiber or alumina fiber, both of which achieve the desired effect. They are lightweight and highly efficient, keeping the furnace shell temperature below 50°C. The shell is made of carbon steel, offering low cost.

[0023] The green electric heater consists of a heating element, a protective tube, a motherboard, and a cover. The heating element is made of either an iron-chromium-aluminum alloy or a nickel-chromium alloy, offering oxidation and corrosion resistance, along with a long service life, all of which achieve the invention's objectives. The heating element is spiral-shaped and housed within the protective tube. Its operating temperature is 500-1100°C.

[0024] The protective tube is made of either mullite or cordierite, which has low expansion coefficient and thermal shock resistance, both of which achieve the invention's objectives. The heating element is located within the protective tube. When the surface of the heating element oxidizes, blast furnace gas is introduced into the tube to reduce the oxides, regenerating the heating element and extending its service life by 50-100%, while reducing costs.

[0025] The motherboard, cover plate, and T-bar are all made from a composite ceramic sintered from a mixture of silicon carbide (15-33%), silicon nitride (4-12%), zirconium silicate (20-50%), and quartz (10-15%). These ceramics exhibit high strength, high-temperature resistance, corrosion resistance, and anti-scaling properties. The three-point bending strength of the composite ceramics, regardless of their formulation, exceeds 800 MPa. They also exhibit excellent thermal shock resistance and can withstand 20 cycles of heating to 750°C and immediate water cooling without damage. The heating element is housed in a protective tube, placed in the cavity between the motherboard and cover plate. This prevents corrosion from contact between the furnace material and the tube, extending the life of both the tube and the heating element, providing a double layer of protection for the heating element.

[0026] The motherboard of the green electric heating element is a rectangular block with grooves on the front and back, which is built into the vertical tube furnace. The T-shaped head of the T-shaped rod is dovetail-shaped, and there is a round hole at the tail of the T-shaped rod. The material of the T-shaped rod is the same as that of the motherboard to avoid damage caused by different materials during operation. The T-shaped head of the T-shaped rod is placed in the T-shaped rod keying groove on the motherboard furnace wall, and the round hole at the tail of the T-shaped rod is hung on the metal hook on the inner wall of the furnace shell to connect the motherboard to the furnace shell and fix the motherboard in the furnace; the gap between the furnace wall surface of the motherboard and the furnace shell is filled with insulation material, and the surface temperature of the furnace wall is lower than 50°C; the insulation material is one of mullite fiber and alumina fiber, both of which can achieve the purpose and have a service life of more than 10 years. The furnace surface of the motherboard is a dovetail groove, and the cover plate is dovetail-shaped, which facilitates the installation, disassembly and maintenance of the protective tube and electric heating element, reducing the difficulty and cost of maintenance.

[0027] The cover plate and T-bar are installed from the side of the motherboard. The remaining space that cannot be installed by the cover plate and T-bar is filled with castable material. The dovetail design of the motherboard, cover plate and T-bar facilitates installation and replacement, reducing costs.

[0028] The vertical tube furnace uses green electricity as energy. During the phase change of phosphogypsum to anhydrous gypsum, only water vapor is emitted. All auxiliary equipment used in the production system uses green electricity, achieving zero carbon emissions in the production of anhydrous gypsum. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of this patent or the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the prior art descriptions; obviously, the drawings described below are only one embodiment recorded in this patent, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 This is a flow chart of a system for flash production of anhydrous gypsum from phosphogypsum provided in an embodiment of the present invention.

[0031] Figure 2 It is a schematic structural diagram of a vertical tube furnace provided in an embodiment of the present invention.

[0032] Figure 3 It is a schematic cross-sectional view of the structure of a green electric heating element provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] To help those skilled in the art better understand this patent, the following further describes this patent with reference to the accompanying drawings and examples. Obviously, the described embodiment is only one example of this patent, not all examples. The embodiments and features within these embodiments may be combined with each other unless there is a conflict.

[0034] See also Figure 1 The embodiment of this patent provides a system for flash production of anhydrous gypsum from phosphogypsum, and its working principle is as follows:

[0035] 1. Take the flow direction of gas as an example to illustrate, where: Figure 1 The dotted line indicates the flow direction of gas; cooling air enters from the bottom of the vertical tube furnace to cool the material and then heat it. The hot cooling air enters the middle of the vertical tube furnace, exchanges heat with the furnace wall and the material, and is discharged from the top of the furnace. It enters the bag dust collector, the induced draft fan, and finally enters the chimney to meet the emission standards.

[0036] 2. Take the flow of phosphogypsum materials as an example to illustrate, Figure 1The solid line in the figure indicates the flow direction of the materials; the phosphogypsum materials and the dust materials collected by the bag dust collector enter the vertical tube furnace together through the elevator; after being heated in the vertical tube furnace, the materials are discharged from the bottom of the vertical tube furnace to obtain anhydrous gypsum products.

[0037] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the scope of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A system for flash production of anhydrous gypsum from phosphogypsum, comprising a chimney, an induced draft fan, a bag dust collector, and a vertical tube furnace; the vertical tube furnace comprises a furnace body, a furnace cover, a furnace bottom, and a spreader; the furnace body comprises a green electric heating element, a heat insulating material, and a furnace shell.

2. A system for flash production of anhydrous gypsum from phosphogypsum according to claim 1, characterized in that: The electric energy used by the vertical drum furnace is one of photovoltaic power generation, wind power generation and hydropower.

3. The system for producing anhydrous gypsum by flash phosphogypsum according to claim 1, characterized in that: The green electric heating element is composed of a heating element, a protection tube, a motherboard and a cover plate.

4. The system for producing anhydrous gypsum by flash phosphogypsum according to claim 1, characterized in that: The heat insulating material is one of mullite fiber and alumina fiber.

5. The system for producing anhydrous gypsum by flash phosphogypsum according to claim 1, characterized in that: The furnace cover and furnace bottom are composed of high-alumina cement refractory casting material and a shell.

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