Industrial by-product phosphogypsum reprocessing sulfuric acid system and acid production process

Abstract

A system and process for preparing sulfuric acid by reprocessing industrial byproduct phosphogypsum, including a furnace reactor, a gaseous carbon generating device and a high-temperature combustion gas device arranged outside the furnace reactor, wherein a reduction zone and an oxidation zone separated by the upward pressure of high-temperature flue gas are arranged from bottom to top in the furnace reactor, the gaseous carbon generating device is used to generate gaseous carbon and then pass it into the reduction zone; the high-temperature combustion gas device controls the oxygen content of the high-temperature flue gas after combustion to be below a threshold and then passes it into the reduction zone; the raw material pretreatment component is connected to the reduction zone through a solid material inlet. Compared with the prior art, the present invention does not need to add solid coke to the raw materials, and during the raw material pretreatment process, multiple processing processes for solid coke are eliminated, simplifying the production process, and the reduction zone realizes the reduction reaction between gaseous carbon and solid materials. The reaction rate of the gas-solid reaction is dozens of times higher than that of the solid-solid reaction, which greatly improves the decomposition efficiency of phosphogypsum and also reduces energy consumption.

Description

Technical Field

[0001] The invention relates to the technical field of chemical product processing, and in particular to a system for preparing sulfuric acid by reprocessing industrial by-product phosphogypsum and an acid-making process. Background Art

[0002] Phosphogypsum is a byproduct of the wet-process phosphoric acid industry. Every ton of phosphorus (calculated as P2O5) produced produces about 4.5 to 5.5 tons of phosphogypsum. According to statistics, my country produces about 16.6993 million tons of phosphate fertilizers throughout the year, and the accumulated amount of phosphogypsum has exceeded 300 million tons over the years. Enterprises spend a lot of money on the construction of slag yards and their operation and management every year. At the same time, phosphogypsum contains impurities such as undecomposed phosphate ore, sulfide, fluoride, etc. Large-scale stacking will cause environmental problems and pollute the soil, air and water.

[0003] There are three main types of existing comprehensive utilization technologies for phosphogypsum. The first is to make phosphogypsum into gypsum building materials such as gypsum powder, gypsum board, and gypsum blocks; the second is to make phosphogypsum into cement retarders; the third is to decompose phosphogypsum to produce sulfuric acid and cement. However, since most natural gypsum resources are abundant and the quality of phosphogypsum is not high and it contains impurities such as phosphorus, fluorine, and sulfide, the amount of phosphogypsum consumed as cement retarders and gypsum building materials is quite limited; and the process flow of phosphogypsum to produce sulfuric acid and cement is complicated, the equipment is numerous, the energy consumption is high, and the economic benefits are not high. Therefore, the domestic technology of phosphogypsum to produce sulfuric acid and cement is slowly promoted. The invention patent No. CN102442650A discloses a method for producing sulfuric acid and calcium carbide from phosphogypsum, which uses primary air and secondary air directly introduced into the reactor for reduction reaction and oxidation reaction. , due to the introduction of air into the reduction zone, it is basically difficult to ensure a reducing atmosphere in this scheme, and the decomposition rate of phosphogypsum is extremely low; in addition, the Chinese invention patent application with application number 2021115407909 also discloses a process for making sulfuric acid from phosphogypsum, and its scheme is also to directly introduce primary air and combustion gas into the reduction zone, and then the secondary air in the oxidation zone will also enter the reduction zone, which is difficult to ensure a reducing atmosphere, and solid coke and phosphogypsum are used in the reduction zone for solid-solid reaction. The contact area between the reactants is small, resulting in low reaction efficiency, which not only causes a low decomposition rate of phosphogypsum, but also increases energy consumption, making the comprehensive utilization rate of phosphogypsum only about 30%. The use of phosphogypsum, such as the preparation of building materials, lacks an economical and applicable pretreatment process, and still has defects such as difficult purification and high energy consumption. The technology of producing sulfuric acid and cement from phosphogypsum has the problems of complex production process, high energy consumption, large investment, low decomposition rate, and small production scale. Summary of the invention

[0004] The purpose of the present invention is to provide a system for preparing sulfuric acid by reprocessing industrial by-product phosphogypsum and an acid production process, so as to solve the technical defects of the prior art of producing sulfuric acid using phosphogypsum, such as low decomposition rate of phosphogypsum, low sulfur dioxide concentration, and excessively high production energy consumption.

[0005] The technical solution of the present invention is achieved in this way:

[0006] A system for preparing sulfuric acid by reprocessing industrial by-product phosphogypsum comprises a raw material pretreatment component, a reaction furnace component and an acid production component. The reaction furnace component comprises a furnace reactor and a gaseous carbon generating device and a high-temperature combustion gas device arranged outside the furnace reactor. A reduction zone and an oxidation zone separated by the upward pressure of high-temperature flue gas are arranged from bottom to top in the furnace reactor. The gaseous carbon generating device is used to generate gaseous carbon and then pass it into the reduction zone to provide a gaseous reducing agent for the reduction reaction; the high-temperature combustion gas device controls the oxygen content of the high-temperature flue gas after combustion to be lower than a set threshold value and then passes it into the reduction zone to provide energy for the reduction reaction; the raw material pretreatment component is connected to the reduction zone through a solid material inlet to provide solid material for the reduction reaction, and the oxidation zone is connected to the acid production component through a SO2 gas outlet above the furnace reactor.

[0007] Preferably, the gaseous carbon generating device comprises a plasma catalytic device connected to a natural gas tank, and the plasma catalytic device catalyzes the natural gas into gaseous carbon and hydrogen by high-temperature and high-speed electrons and then introduces the gaseous carbon and hydrogen into the reduction zone.

[0008] Preferably, the bottom of the reduction zone is configured as a cone, and the cone is provided with a high-temperature combustion gas inlet through which the high-temperature flue gas can enter the reduction zone by cutting into the inner side of the cone and rise in a spiral form. The high-temperature combustion gas inlet is connected to a high-temperature combustion gas device. The high-temperature combustion gas inlet is configured in multiple numbers and is equidistantly arranged around the cone. The upper part of the reduction zone is configured as a long cylinder, and the upper part of the long cylinder is connected to the oxidation zone.

[0009] Preferably, the high-temperature burner device includes an air-fuel mixer and a combustion chamber, the air-fuel mixer is provided with a primary air inlet, a combustion gas inlet and a mixer outlet, the combustion gas inlet is connected to a natural gas tank, the mixer outlet is connected to the combustion chamber, the combustion chamber is connected to the high-temperature combustion gas inlet through a high-temperature flue gas duct to provide high-temperature flue gas with an oxygen content lower than a set threshold for the reduction zone, the high-temperature burner device is provided with a gas distributor, a flow meter, and a regulating valve for controlling the oxygen content of the high-temperature flue gas to be lower than the set threshold, the regulating valve is connected to an external PLC controller, and the oxidation zone is provided with a secondary air inlet.

[0010] Preferably, the raw material pretreatment component includes three groups of crushing mills and single-material silos for crushing the raw materials. The raw materials include silica, phosphogypsum, and bentonite. The material outlets of the crushing mills for each raw material are connected to the corresponding single-material silos, and the material outlets of all single-material silos are connected to a mixer for uniformly mixing the raw materials. The discharge port of the mixer is connected to a granulator, and the discharge port of the granulator is connected to a preheater for preheating the raw materials to 200-400°C. The discharge port of the preheater is connected to a mixing silo, and the discharge port of the mixing silo is connected to the solid material inlet of the reduction zone through a continuous feeder.

[0011] Preferably, the raw material pretreatment component also includes a dehydration dryer for dehydrating phosphogypsum, and the material outlet of the dehydration dryer corresponds to the inlet of the phosphogypsum crushing mill.

[0012] Preferably, the acid-making component includes a purification system for converting SO2 gas into SO3, a contact chamber, an absorption tower, and a finished product silo. The air inlet of the purification system is connected to the SO2 gas outlet of the oxidation zone. The purification system is provided with a venturi, a foam tower and an electric precipitator. The air inlet of the absorption tower is connected to the SO3 gas outlet of the contact chamber, and the liquid outlet of the absorption tower is connected to the finished product silo through a pipeline.

[0013] Preferably, the primary air inlet is connected to a primary air device, the secondary air inlet is connected to a secondary air device, both the primary air device and the secondary air device are provided with a gas distributor, a flow meter, a regulating valve and a fan, the regulating valve is connected to an external PLC controller, the continuous feeder is provided with a weighing sensor and a variable frequency motor, the variable frequency motor is connected to an external PLC controller, and the weighing sensor and the variable frequency motor constitute a closed-loop controlled loss-in-weight scale.

[0014] Preferably, the inner wall of the furnace reactor is provided with a refractory heat-insulating layer.

[0015] Preferably, the solid slag outlet of the furnace reactor is connected to a rotary kiln for producing cement, and the exhaust gas from the rotary kiln is connected to a preheater through a pipeline.

[0016] Preferably, the reaction temperature in the furnace reactor is set at 1280-1600°C.

[0017] The present invention also discloses a process for preparing sulfuric acid, comprising the following steps:

[0018] 1) Prepare solid raw materials of silica, phosphogypsum and bentonite in proportion, crush and mix them;

[0019] 2) The mixed solid raw materials are granulated and sent to the reduction zone of the furnace reactor for reduction reaction;

[0020] 3) The gaseous carbon generation device catalyzes natural gas into gaseous carbon and hydrogen and then introduces them into the reduction zone, wherein the gaseous carbon and solid raw materials are introduced in proportion, and the gaseous carbon and solid raw materials undergo gaseous and solid reduction reactions. The high-temperature burner device introduces the high-temperature flue gas in its combustion chamber that meets the oxygen content lower than the set threshold into the reduction zone in the furnace, and after providing energy for the phosphogypsum reduction reaction, the high-temperature flue gas rises in a spiral form, exerting an upward impulse on the mixed gas in the oxidation zone, thereby forming independent reduction zones and oxidation zones;

[0021] 4) SO2 gas, the product of the reduction reaction, floats up under the high-pressure impact of the high-temperature flue gas and is discharged from the SO2 gas outlet above the furnace body to the acid-making component. A certain amount of air is introduced into the oxidation zone to oxidize the hydrogen rising from the reduction zone and the remaining fuel gas in the high-temperature flue gas. The heat generated by the oxidation reaction is transferred downward to the reduction zone in the form of thermal radiation and is used in the reduction reaction;

[0022] 5) After the SO2 gas is cooled, dusted and impurity-free by the venturi, foam tower and electrostatic precipitator, it enters the contact chamber, where it is catalyzed by vanadium pentoxide to generate SO3, which is then absorbed and hydrated by the absorption tower to produce sulfuric acid, which enters the finished product silo, completing the sulfuric acid preparation process.

[0023] Preferably, in step 2), the solid material is preheated to 200-400° C. and then fed into the reduction zone.

[0024] Preferably, the step 5) further includes a process for making cement from the solid slag in the furnace reactor, specifically: the solid reaction residue in the reduction zone is discharged from the residue discharge port below the furnace body, enters the rotary kiln and conveys the corresponding ingredients from the batching port, and is calcined in the rotary kiln at 1300-1450°C to obtain cement clinker, which is input into the finished product silo, and at the same time, the furnace gas can enter the preheater through the gas outlet above the rotary kiln to preheat the solid raw materials.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The system for preparing sulfuric acid by reprocessing the industrial by-product phosphogypsum of the present invention does not need to add solid coke to the raw materials. In the process of raw material pretreatment, a series of processing processes such as cleaning, crushing and granulation of solid coke are eliminated, thereby simplifying the production process. The reduction reaction between gaseous carbon and solid materials is achieved by catalyzing natural gas into gaseous carbon and entering the reduction zone for reduction reaction. The reaction rate of the gas-solid reaction is dozens of times higher than that of the solid-solid reaction in the prior art, which greatly improves the decomposition efficiency of the phosphogypsum and also reduces energy consumption. In addition, the present invention does not use solid coke as a raw material, and the solid reaction residue in the reduction zone is also greatly reduced, which is more environmentally friendly.

[0027] The industrial byproduct phosphogypsum reprocessing system of the present invention is to supply energy by introducing high-temperature flue gas with extremely low oxygen content into the reduction zone, and the high-temperature flue gas enters in the form of a tangent and rises in the form of a spiral to form an upward positive pressure of the gas in the furnace, thereby ensuring that the secondary air in the oxidation zone will not penetrate downward into the reduction zone and affect the reducing atmosphere, and completely isolate the reduction zone and the oxidation zone to ensure that the combustion reduction reaction of the phosphogypsum can be carried out in an independent reduction zone, thereby improving the decomposition rate of the phosphogypsum. In addition, the reactor introduces secondary air into the oxidation zone, which can cause hydrogen and the combustion gas remaining in the high-temperature flue gas to be oxidized and burned. Although the gas in the oxidation zone cannot penetrate into the reduction zone, more than half of the heat generated by the oxidation reaction in the oxidation zone will be transferred to the reduction zone in the form of thermal radiation for utilization, thereby reducing energy consumption and production costs, while reducing the impurity content in the residue and improving the quality of the final product.

[0028] The furnace reactor of the present invention has a conical bottom structure in the reduction zone, which can produce a high speed limit, so that the incoming substances are suspended and fluidized, thereby preventing agglomeration and improving the reaction efficiency.

[0029] The furnace reactor of the present invention can significantly improve the decomposition rate of phosphogypsum and the reaction heat transfer efficiency. Compared with the prior art, it can reduce the heat energy consumption by 30% and the electric energy consumption by 40%. At the same time, the device is easily compatible with the existing sulfur concentrate production line of sulfuric acid, with low investment and maintenance cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The equipment layout diagram of the sulfuric acid preparation system for the reprocessing of the industrial by-product phosphogypsum of the present invention.

[0031] In the figure: furnace reactor 1, reduction zone 2, oxidation zone 3, natural gas tank 4, plasma catalytic device 5, cone 6, high-temperature combustion gas inlet 7, fuel mixer 8, combustion chamber 9, primary air inlet 10, combustion gas inlet 11, mixer outlet 12, secondary air inlet 13, crushing mill 14, single material silo 15, mixer 16, granulator 17, preheater 18, mixing silo 19, continuous feeder 20, dehydration dryer 21, contact chamber 22, absorption tower 23, finished product silo 24, venturi 25, foam tower 26, electric demister 27, rotary kiln 28, PLC controller 29, long cylinder 30. DETAILED DESCRIPTION

[0032] The present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0033] like Figure 1As shown, a system for preparing sulfuric acid by reprocessing industrial by-product phosphogypsum includes a raw material pretreatment component, a reactor component and an acid-making component. The reactor component includes a furnace reactor 1 and a gaseous carbon generating device and a high-temperature combustion gas device arranged outside the furnace reactor 1. The furnace reactor 1 is provided with a reduction zone 2 and an oxidation zone 3 isolated by the upward pressure of high-temperature flue gas from bottom to top. The gaseous carbon generating device is used to generate gaseous carbon and then pass it into the reduction zone 2 to provide a gaseous reducing agent for the reduction reaction; the high-temperature combustion gas device controls the oxygen content of the high-temperature flue gas after combustion to be lower than a set threshold value and then passes it into the reduction zone 2 to provide energy for the reduction reaction, and the set threshold value is 0.5%; the raw material pretreatment component is connected to the reduction zone 2 through a solid material inlet to provide solid materials for the reduction reaction, and the oxidation zone 3 is connected to the acid-making component through the SO2 gas outlet above the furnace reactor. The SO2 gas generated in the furnace reactor 1 enters the acid-making component to prepare sulfuric acid.

[0034] The gaseous carbon generating device comprises a plasma catalytic device 5 connected to a natural gas tank 4. The plasma catalytic device catalyzes natural gas into gaseous carbon and hydrogen through high-temperature and high-speed electrons and then introduces them into the reduction zone 2. According to the formula ratio, the introduced gaseous carbon is excessive, and the gaseous carbon reacts with solid phosphogypsum (CaSO4) in the reduction zone 2. The solid phosphogypsum is granular, and the excessive gaseous carbon will fill the entire space of the reduction zone 2, thereby maximizing the contact area between the solid phosphogypsum and the gaseous carbon, thereby achieving a violent reaction, maximizing the reaction efficiency, and reducing energy consumption; the present invention uses natural gas to convert into gaseous carbon as a reducing agent, which also reduces the process flow of pretreatment of this part of the raw materials and reduces the generation cost; in addition, no residue will be left after the gaseous carbon reaction, which also facilitates the subsequent treatment of the residue. The basic principle of the catalysis of the above-mentioned plasma catalytic device is that after the chemical molecules obtain sufficient energy in the electric field, the high-temperature and high-energy ions collide with the methane molecules to crack them into highly active carbon and hydrogen elements (gaseous carbon and gaseous hydrogen), thereby improving the overall chemical reaction activity and rate.

[0035] The bottom of the reduction zone 2 is set as a cone 6, and a high-temperature combustion gas inlet 7 is set on the cone 6, through which the high-temperature flue gas can enter the reduction zone 2 by cutting the inner side of the cone and rise in the form of a spiral. The high-temperature combustion gas inlet 7 (burner) has a certain upward inclination angle with the connected cone surface, so that the high-temperature flue gas flows obliquely upward along the side wall of the cone 6 when entering (side cutting), forming an upward cyclone, so that the high-temperature flue gas rises in the form of a spiral. The huge cyclone can bring the gas after the reaction in the reduction zone 2 into the upper oxidation zone 3, and can ensure that the gas in the oxidation zone 3 will not flow to the bottom reduction zone 2. Specifically: since the furnace reactor is only provided with one outlet (i.e., the SO2 gas outlet) at the top, the high-temperature burner device will introduce a large amount of high flue gas at a set angle for heating the lowermost reduction zone 2, and a large amount of high-temperature flue gas will flow from bottom to top to the outlet in the form of a spiral, thereby increasing the positive pressure of the bottom gas. The force will drive various gases to rise together in the process of flue gas rising, thereby blocking the gas (especially oxygen-containing air) in the oxidation zone 3 from diffusing downward, isolating the reduction zone 2 from the oxidation zone 3, ensuring that the oxygen content in the reduction zone 2 approaches 0, and at the same time, it will not affect the heat of the oxidation zone 3 radiating downward to provide heat for the reduction reaction in the reduction zone 2, ensuring the physical isolation of the oxidation zone 3 and the reduction zone 2 in the reactor, that is, ensuring the reducing atmosphere in the reduction zone. The high-temperature combustion gas inlet is arranged in multiple numbers and is arranged around the vertebral body at equal distances. The high-temperature flue gas can enter the furnace from each high-temperature combustion gas inlet without any difference in air pressure, ensuring that the air pressure from the bottom of the furnace body is relatively balanced. The upper part of the reduction zone 2 is arranged as a long cylinder 30, and the upper part of the long cylinder 30 is connected to the oxidation zone 3. Since the materials for the reduction reaction are concentrated in the vertebral part of the reduction zone 2, the long cylinder 30 plays a certain buffering and isolating role in the reduction reaction and the oxidation reaction.

[0036] The high temperature burner device includes an air-fuel mixer 8 and a combustion chamber 9. The air-fuel mixer 8 is provided with a primary air inlet 10, a combustion gas inlet 11 and a mixer outlet 12. The combustion gas inlet 11 is connected to the natural gas tank 4, and the mixer outlet 12 is connected to the combustion chamber 9. The combustion chamber 9 is connected to the high temperature combustion gas inlet 7 through a high temperature flue gas duct to provide high temperature flue gas with an oxygen content lower than a set threshold for the reduction zone 2. The high temperature burner device is provided with a gas distributor, a flow meter, and a regulating valve for controlling the oxygen content of the high temperature flue gas to be lower than the set threshold. The regulating valve is connected to an external PLC controller 29. The oxidation zone 3 is provided with a secondary air inlet 13. The high temperature burner device is controlled by PLC to adjust the air-fuel ratio to 1:17-1:20. The combustion chamber is under-oxygenated. If the oxygen content of the high-temperature flue gas is detected to be lower than the set threshold, the high-temperature flue gas is introduced into the furnace reactor to ensure the reducing atmosphere of the reduction zone 2 and ensure a high conversion rate. The reduction zone 2 is provided with a high-temperature combustion gas inlet 7 and a solid material inlet, and the oxidation zone 3 is provided with a secondary air inlet. The solid material inlet is connected to the material outlet of the raw material pretreatment component, and the top of the furnace reactor is provided with a SO2 gas outlet. Since the high-temperature combustion gas inlet 7 is arranged at the bottom of the furnace body and the SO2 gas outlet is arranged at the top of the furnace body, the high-temperature combustion gas inlet 7 and the SO2 gas outlet constitute a positive pressure gas channel from bottom to top in the furnace body, ensuring that the gas in the oxidation zone 3 does not sink, and the SO2 gas outlet is connected to the gas inlet of the acid-making component.

[0037] The raw material pretreatment component includes three groups of crushing mills 14 and single-material silos 15 for crushing the raw materials. The raw materials include silica, phosphogypsum, and bentonite. The material outlets of the crushing mills 14 for each raw material are connected to the corresponding single-material silos 15, and the material outlets of all single-material silos 15 are connected to a mixer 16 for uniformly mixing the raw materials. The discharge port of the mixer 16 is connected to a granulator 17, and the discharge port of the granulator 17 is connected to a preheater 18 for preheating the raw materials to 200-400°C. The discharge port of the preheater 18 is connected to a mixing silo 19, and the discharge port of the mixing silo 19 is connected to the solid material inlet of the reduction zone 2 through a continuous feeder 20.

[0038] The raw material pretreatment component also includes a dehydration dryer 21 for dehydrating phosphogypsum, and the material outlet of the dehydration dryer 21 corresponds to the inlet of the crushing mill 14 of the phosphogypsum.

[0039] The acid production component includes a purification system for converting SO2 gas into SO3, a contact chamber 22, an absorption tower 23, and a finished product silo 24. The air inlet of the purification system is connected to the SO2 gas outlet of the oxidation zone 3. The purification system is provided with a venturi 25, a foam tower 26 and an electric precipitator 27. The air inlet of the absorption tower 23 is connected to the SO3 gas outlet of the contact chamber 22, and the liquid outlet of the absorption tower 23 is connected to the finished product silo 24 through a pipeline.

[0040] The primary air inlet 10 is connected to a primary air device, and the secondary air inlet 13 is connected to a secondary air device. Both the primary air device and the secondary air device are provided with a gas distributor, a flow meter, a regulating valve and a fan. The regulating valve is connected to an external PLC controller 29. The continuous feeder 20 is provided with a weighing sensor and a variable frequency motor. The variable frequency motor is connected to the external PLC controller 29. The weighing sensor and the variable frequency motor constitute a closed-loop controlled loss-in-weight scale.

[0041] The inner wall of the furnace reactor 1 is provided with a refractory insulation layer, which is used to prevent the heat in the furnace from radiating to the outside of the furnace. Since the reduction and oxidation reactions are completed in the furnace reactor 1, and the reduction reaction is an endothermic reaction, the heat is mostly provided by the high-temperature flue gas provided by the high-temperature burner device, and the oxidation reaction in the oxidation zone 3 is an exothermic reaction (the oxidation reaction is surplus natural gas, gaseous carbon and hydrogen, etc., so a large amount of heat will be generated). The heat in the oxidation reaction area of ​​the furnace reactor 1 will be transferred to the reduction zone 2 for reduction reaction by radiation, and nearly half of the heat will be used, thereby greatly reducing the consumption of fuel gas.

[0042] The solid slag outlet of the furnace reactor 1 is connected to the rotary kiln 28 for producing cement, and the exhaust gas of the rotary kiln 28 is connected to the preheater 18 through a pipeline. The solid slag from the furnace reactor 1 contains very little sulfur, fluorine and other elements, and the cement produced by the rotary kiln 28 has a high purity and can be directly used in industrial construction. The reaction temperature in the furnace reactor is set at 1280-1600°C.

[0043] The present invention also discloses a process for preparing sulfuric acid, comprising the following steps:

[0044] 1) Solid raw materials of silica, phosphogypsum and bentonite are prepared in proportion, crushed and mixed. The solid raw materials can be prepared in the following weight ratio: phosphogypsum 1000 parts, silica 120 parts and bentonite 1 part. After the phosphogypsum is sent to a dehydration dryer for dehydration, it is sent to respective crushing mills together with silica and bentonite by a grab bucket for crushing and grinding to produce fine powder particles with a particle size of <0.2 mm. The ground phosphogypsum, silica and bentonite are respectively sent to respective single material silos. After the phosphogypsum, silica and bentonite are weighed again in their respective single material silos according to the preparation ratio, they are sent to a mixer for uniform mixing;

[0045] 2) Granulation and feeding: The mixed material is sent to the granulator for granulation. The granulated material is sent to the preheater for preheating and then sent to the mixing bin and continuous feeder. The continuous feeder uses a loss-in-weight scale to transport the raw materials into the furnace reactor according to the set feed flow rate for reduction and oxidation reactions;

[0046] 3) The gaseous carbon generating device catalyzes the natural gas into gaseous carbon and hydrogen and then introduces them into the reduction zone 2, wherein the gaseous carbon and the solid raw material are mixed and introduced in proportion, and the weight ratio of the gaseous carbon to the phosphogypsum is greater than 60 to 1000, that is, the gaseous carbon can be surplus, and the gaseous carbon and the solid raw material undergo gaseous and solid reduction reactions, and the high-temperature burner device introduces the high-temperature flue gas in its combustion chamber with an oxygen content lower than a set threshold into the reduction zone in the furnace, and the set threshold is 0.5%, and after providing energy for the phosphogypsum reduction reaction, the high-temperature flue gas rises in a spiral form, exerting an upward impulse on the mixed gas in the oxidation zone, thereby forming an independent reduction zone and oxidation zone;

[0047] 4) SO2 gas, the product of the reduction reaction, floats up under the high-pressure impact of the high-temperature flue gas and is discharged from the SO2 gas outlet above the furnace body to the acid-making component. A certain amount of air is introduced into the oxidation zone to oxidize the hydrogen rising from the reduction zone and the remaining fuel gas in the high-temperature flue gas. The heat generated by the oxidation reaction is transferred downward to the reduction zone in the form of thermal radiation and is used in the reduction reaction;

[0048] 5) After the SO2 gas is cooled, dusted and impurity-free by the venturi, foam tower and electrostatic precipitator, it enters the contact chamber, where it is catalyzed by vanadium pentoxide to generate SO3, which is then absorbed and hydrated by the absorption tower to produce sulfuric acid, which enters the finished product silo, completing the sulfuric acid preparation process.

[0049] In step 2), the solid material is preheated to 200-400° C. and then fed into the reduction zone. The preheating energy can be provided by the high temperature gas discharged from the rotary kiln 28 .

[0050] The step 5) also includes a process for making cement from the solid slag in the furnace reactor, specifically: the solid reaction residue in the reduction zone is discharged from the residue discharge port at the bottom of the furnace body, enters the rotary kiln and conveys the corresponding ingredients from the batching port, and is calcined in the rotary kiln at 1300-1450°C to obtain cement clinker, which is input into the finished product silo. At the same time, the furnace gas can enter the preheater through the gas outlet above the rotary kiln to preheat the solid raw materials.

[0051] Based on the system equipment structure and production process of the present invention, it can be known that in the system for preparing sulfuric acid by reprocessing the industrial by-product phosphogypsum of the present invention, there is no need to add solid coke to the raw materials. In the process of raw material pretreatment, a series of processing processes such as cleaning, crushing, and granulation of solid coke are eliminated, thereby simplifying the production process. The reduction reaction between gaseous carbon and solid materials is achieved by catalyzing natural gas into gaseous carbon and entering the reduction zone for reduction reaction. The reaction rate of the gas-solid reaction is dozens of times higher than that of the solid-solid reaction in the prior art, which greatly improves the decomposition efficiency of phosphogypsum and also reduces energy consumption. In addition, the present invention does not use solid coke as a raw material, and the solid reaction residue in the reduction zone is also greatly reduced, which is more environmentally friendly.

[0052] The present invention provides energy by introducing high-temperature flue gas with extremely low oxygen content into the reduction zone, and the high-temperature flue gas enters in the form of a tangent and rises in the form of a spiral to form a positive pressure upward in the furnace gas, thereby ensuring that the secondary air in the oxidation zone will not penetrate downward into the reduction zone and affect the reducing atmosphere, and completely isolate the reduction zone and the oxidation zone to ensure that the combustion reduction reaction of phosphogypsum can be carried out in an independent reduction zone, thereby improving the decomposition rate of phosphogypsum. In addition, the reactor introduces secondary air into the oxidation zone, which can cause hydrogen and the combustion gas in the high-temperature flue gas to undergo oxidative combustion. Although the gas in the oxidation zone cannot penetrate into the reduction zone, more than half of the heat generated by the oxidation reaction in the oxidation zone will be transferred to the reduction zone in the form of thermal radiation for utilization, thereby reducing energy consumption and production costs, while reducing the impurity content in the residue and improving the quality of the final product.

[0053] The furnace reactor of the present invention has a conical bottom structure in the reduction zone, which can produce a high speed limit, so that the entering solid matter is suspended and fluidized, thereby preventing agglomeration and improving the reaction efficiency.

[0054] The furnace reactor of the present invention can greatly improve the decomposition rate of phosphogypsum and the reaction heat transfer efficiency, and can reduce the heat energy consumption by 30% and the electric energy consumption by 40% compared with the prior art. At the same time, the device is easily compatible with the existing sulfur concentrate production line for sulfuric acid, with small investment and low maintenance cost.

Claims

1. A system for preparing sulfuric acid by reprocessing industrial byproduct phosphogypsum, comprising a raw material pretreatment component, a reactor component and an acid production component, characterized in that: The reaction furnace assembly includes a furnace reactor, a gaseous carbon generating device and a high-temperature combustion gas device arranged outside the furnace reactor. The furnace reactor is provided with a reduction zone and an oxidation zone separated by the upward pressure of high-temperature flue gas from bottom to top. The gaseous carbon generating device is used to generate gaseous carbon and then pass it into the reduction zone to provide a gaseous reducing agent for the reduction reaction; the high-temperature combustion gas device controls the oxygen content of the high-temperature flue gas after combustion to be lower than the set threshold and then passes it into the reduction zone to provide energy for the reduction reaction; the raw material pretreatment component is connected to the reduction zone through a solid material inlet to provide solid materials for the reduction reaction, and the oxidation zone is connected to the furnace reactor through a solid material inlet. The SO2 gas outlet at the top is connected to the acid-making component. The gaseous carbon generating device includes a plasma catalytic device connected to a natural gas tank. The plasma catalytic device catalyzes the natural gas into gaseous carbon and hydrogen through high-temperature and high-speed electrons and then passes them into the reduction zone. The bottom of the reduction zone is set as a cone, and the cone is provided with a high-temperature combustion gas inlet through which the high-temperature flue gas can enter the reduction zone by cutting the inner side of the cone and rise in a spiral form. The high-temperature combustion gas inlet is connected to the high-temperature combustion gas device. The high-temperature combustion gas inlet is set in multiple numbers and is arranged around the cone at equal distances. The upper part of the reduction zone is set as a long cylinder, and the upper part of the long cylinder is connected to the oxidation zone.

2. The system for preparing sulfuric acid from phosphogypsum, an industrial by-product, according to claim 1, characterized in that: The high-temperature combustion gas device includes an air-fuel mixer and a combustion chamber. The air-fuel mixer is provided with a primary air inlet, a combustion gas inlet and a mixer outlet. The combustion gas inlet is connected to a natural gas tank, and the mixer outlet is connected to the combustion chamber. The combustion chamber is connected to the high-temperature combustion gas inlet through a high-temperature flue gas duct to provide high-temperature flue gas with an oxygen content lower than a set threshold for the reduction zone. The high-temperature combustion gas device is provided with a gas distributor, a flow meter, and a regulating valve for controlling the oxygen content of the high-temperature flue gas to be lower than the set threshold. The regulating valve is connected to an external PLC controller. The oxidation zone is provided with a secondary air inlet.

3. The system for preparing sulfuric acid from industrial by-product phosphogypsum by reprocessing according to claim 2, characterized in that: The raw material pretreatment component includes three groups of crushing mills and single-material silos for crushing the raw materials. The raw materials include silica, phosphogypsum, and bentonite. The material outlets of the crushing mills of each raw material are connected to the corresponding single-material silos, and the material outlets of all single-material silos are connected to a mixer for uniformly mixing the raw materials. The discharge port of the mixer is connected to a granulator, and the discharge port of the granulator is connected to a preheater for preheating the raw materials to 200-400°C. The discharge port of the preheater is connected to a mixing silo, and the discharge port of the mixing silo is connected to a solid material inlet of a reduction zone through a continuous feeder.

4. The system for preparing sulfuric acid from industrial by-product phosphogypsum by reprocessing according to claim 3, characterized in that: The raw material pretreatment component also includes a dehydration dryer for dehydrating phosphogypsum, and the material outlet of the dehydration dryer corresponds to the inlet of the phosphogypsum crushing mill.

5. The system for preparing sulfuric acid from industrial by-product phosphogypsum by reprocessing according to claim 1, characterized in that: The acid-making component includes a purification system for converting SO2 gas into SO3, a contact chamber, an absorption tower, and a finished product silo. The air inlet of the purification system is connected to the SO2 gas outlet of the oxidation zone. The purification system is provided with a venturi, a foam tower, and an electric precipitator. The air inlet of the absorption tower is connected to the SO3 gas outlet of the contact chamber, and the liquid outlet of the absorption tower is connected to the finished product silo through a pipeline.

6. The system for preparing sulfuric acid from industrial by-product phosphogypsum by reprocessing as claimed in claim 3, characterized in that: The primary air inlet is connected to a primary air device, the secondary air inlet is connected to a secondary air device, both the primary air device and the secondary air device are provided with a gas distributor, a flow meter, a regulating valve and a fan, the regulating valve is connected to an external PLC controller, the continuous feeder is provided with a weighing sensor and a variable frequency motor, the variable frequency motor is connected to an external PLC controller, and the weighing sensor and the variable frequency motor constitute a closed-loop controlled loss-in-weight scale.

7. The system for preparing sulfuric acid from industrial by-product phosphogypsum by reprocessing according to claim 2, characterized in that: The inner wall of the furnace reactor is provided with a refractory heat-insulating layer.

8. The system for preparing sulfuric acid from industrial by-product phosphogypsum by reprocessing according to claim 2, characterized in that: The solid slag outlet of the furnace reactor is connected to a rotary kiln for producing cement, and the exhaust gas of the rotary kiln is connected to a preheater through a pipeline.

9. The system for preparing sulfuric acid from industrial by-product phosphogypsum by reprocessing according to claim 2, characterized in that: The reaction temperature in the furnace reactor is set at 1280-1600°C.

10. A process for preparing sulfuric acid, using the system for preparing sulfuric acid by reprocessing the industrial byproduct phosphogypsum according to any one of claims 1 to 9, characterized in that: The following steps are involved: 1) Prepare solid raw materials of silica, phosphogypsum and bentonite in proportion, crush and mix them; 2) The mixed solid raw materials are granulated and sent to the reduction zone of the furnace reactor for reduction reaction; 3) The gaseous carbon generation device catalyzes natural gas into gaseous carbon and hydrogen and then introduces them into the reduction zone, wherein the gaseous carbon and solid raw materials are introduced in proportion, and the gaseous carbon and solid raw materials undergo gaseous and solid reduction reactions. The high-temperature combustion gas device introduces the high-temperature flue gas in its combustion chamber that meets the oxygen content lower than the set threshold into the reduction zone in the furnace, and after providing energy for the phosphogypsum reduction reaction, the high-temperature flue gas rises in a spiral form, exerting an upward impulse on the mixed gas in the oxidation zone, thereby forming independent reduction zones and oxidation zones; 4) SO2 gas, the product of the reduction reaction, floats up under the high-pressure impact of the high-temperature flue gas and is discharged from the SO2 gas outlet above the furnace body to the acid-making component. A certain amount of air is introduced into the oxidation zone to oxidize the hydrogen rising from the reduction zone and the remaining fuel gas in the high-temperature flue gas. The heat generated by the oxidation reaction is transferred downward to the reduction zone in the form of thermal radiation and is used in the reduction reaction; 5) After the SO2 gas is cooled, dusted and impurity-removed by the venturi, foam tower and electrostatic precipitator, it enters the contact chamber, where it is catalyzed by vanadium pentoxide to generate SO3, which is then absorbed and hydrated by the absorption tower to produce sulfuric acid, and then enters the finished product silo, completing the sulfuric acid preparation process.

11. The process for preparing sulfuric acid according to claim 10, characterized in that: In step 2), the solid material is preheated to 200-400°C and then sent to the reduction zone.

12. The process for preparing sulfuric acid according to claim 10, characterized in that: The step 5) also includes a process for making cement from the solid slag in the furnace reactor, specifically: the solid reaction residue in the reduction zone is discharged from the residue discharge port at the bottom of the furnace body, enters the rotary kiln and conveys the corresponding ingredients from the batching port, and is calcined in the rotary kiln at 1300-1450°C to obtain cement clinker, which is input into the finished product silo, and at the same time, the furnace gas enters the preheater through the gas outlet above the rotary kiln to preheat the solid raw materials.

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