Fluidized bed-based system for preparing yellow phosphorus through phosphorite carbothermal reduction

Abstract

The utility model discloses a system for preparing yellow phosphorus through phosphorite carbon thermal reduction based on a fluidized bed. The system comprises a feeding device, a fluidized bed reactor, a high-temperature cyclone separator, a material returning device, a dust remover, a hydration absorption tower, a phosphoric acid pool and an air blower, the feeding device comprises two raw material bins which are respectively a pulverized coal bin and a ground phosphate rock bin, the two raw material bins are connected with the lower part of the fluidized bed reactor through feeding pipes, the upper part of the fluidized bed reactor is connected with a high-temperature cyclone separator, a top outlet of the high-temperature cyclone separator is connected with a dust remover, and a bottom outlet of the high-temperature cyclone separator is connected with a material returning device; a bottom outlet of the hydration absorption tower is connected with the phosphoric acid pool; the return device outlet is connected with the bottom of the fluidized bed reactor; the air blower is arranged around the bottom of the fluidized bed reactor and feeds air from the bottom of the fluidized bed reactor; the system is used for implementing a process for preparing yellow phosphorus through phosphorite carbothermal reduction based on the fluidized bed, the phosphorite utilization rate is high, and the system is economical and efficient.

Description

Technical Field

[0001] The utility model relates to a system for preparing yellow phosphorus by carbon thermal reduction of phosphate rock based on a fluidized bed. Background Art

[0002] Phosphate rock is an important mineral resource that can be used to produce yellow phosphorus and phosphoric acid. Currently, there are two production processes: wet-process phosphoric acid and thermal-process phosphoric acid. Wet-process phosphoric acid is not suitable for processing my country's phosphate rock resources due to its extremely high phosphate rock grade requirements, low product concentration, and the production of phosphogypsum as a byproduct. Thermal-process phosphoric acid not only fully utilizes low- and medium-grade phosphate rock, but also produces a high-purity product without byproducts.

[0003] Thermal phosphoric acid production processes are currently divided into fixed-bed and kiln processes. The fixed-bed process uses a fixed-bed reactor, with coal char as a reducing agent and silica added to react with phosphate rock to produce carbon monoxide and yellow phosphorus vapor. After heat recovery, dust removal, washing, condensation, and subsequent refining and separation, the finished phosphorus is obtained. This method has extremely high reaction temperatures, long residence time in the furnace, high energy consumption, low phosphate rock utilization, and high production costs. The kiln process uses a kiln as a reactor. The raw materials are first pressed into pellets, where the phosphate rock and coal char undergo a reduction reaction to produce yellow phosphorus vapor and carbon monoxide. Oxygen is introduced outside the pellets to combust the carbon monoxide and provide heat for the reduction reaction. This method suffers from problems such as material blockage and ringing, kiln gas purification, and severe kiln wear, and has therefore not yet been industrialized. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art such as high production cost and low utilization rate of phosphate rock, the utility model provides a system for preparing yellow phosphorus by carbon thermal reduction of phosphate rock based on a fluidized bed.

[0005] The technical solution of the utility model is as follows:

[0006] A system for preparing yellow phosphorus by carbon thermal reduction of phosphate rock based on a fluidized bed, comprising: a feeding device, a fluidized bed reactor, a high-temperature cyclone separator, a material return device, a dust collector, a hydration absorption tower, a phosphoric acid tank, and a blower;

[0007] The feeding device includes two raw material bins, namely a coal powder bin and a phosphate rock powder bin. The two raw material bins are connected to the lower part of the fluidized bed reactor through a feeding pipe. The upper part of the fluidized bed reactor is connected to a high-temperature cyclone separator. The top outlet of the high-temperature cyclone separator is connected to a dust collector, and the bottom outlet of the high-temperature cyclone separator is connected to a return device; the dust collector outlet is connected to the top inlet of a hydration absorption tower, and the bottom outlet of the hydration absorption tower is connected to a phosphoric acid tank; the return device outlet is connected to the bottom of the fluidized bed reactor; a blower is arranged around the bottom of the fluidized bed reactor to send air into the fluidized bed reactor from the bottom.

[0008] Furthermore, the exteriors of the fluidized bed reactor, the high-temperature cyclone separator, and the material return device are all provided with a thermal insulation layer;

[0009] Furthermore, the fluidized bed reactor is divided into a heating zone and a reduction zone from bottom to top.

[0010] Furthermore, a slag collection device is provided below the fluidized bed reactor.

[0011] Furthermore, a first expansion device is provided on the connection passage between the bottom outlet of the high-temperature cyclone separator and the material return device.

[0012] Furthermore, a second expansion device is provided on the connecting passage between the outlet of the recirculator and the bottom of the fluidized bed reactor.

[0013] The method for preparing yellow phosphorus by carbon thermal reduction of phosphate rock based on a fluidized bed using the system of the utility model comprises:

[0014] A mixed raw material of phosphate rock powder, silica, and additives is added to a phosphate rock silo, and raw coal powder is added to a coal powder silo. The raw materials are fed into a fluidized bed reactor through a feeding device. Air is fed into the fluidized bed reactor through a blower. The phosphate rock powder undergoes a reduction reaction with the coal powder under the promotion of silica and additives. The gas-solid mixture generated by the reaction enters a high-temperature cyclone separator. The separated solid phase passes through a return device and re-enters the fluidized bed reactor to continue the reaction. The separated gas phase enters a dust collector for purification and then passes into a hydration absorption tower. After the hydration reaction, a phosphoric acid solution is generated and collected in a phosphoric acid tank.

[0015] Wherein, the additive is selected from one or more of Na2SO4, K2SO4, MgSO4, Al2(SO4)3; preferably, the additive is added according to 3 to 12% of the molar amount of Ca in the phosphate rock powder;

[0016] Raw materials such as phosphate rock powder and coal powder are pre-ground to less than 150μm before being fed into the fluidized bed reactor. The silicon-calcium molar ratio of the raw materials added to the reactor is controlled to be 1.8-2.2, and the carbon excess coefficient is 4.0-5.0. The reactor operates at atmospheric pressure, and the temperature of the heating zone and the reduction zone is controlled at 1200-1300℃.

[0017] The raw materials are mixed and heated in the heating zone. When the temperature rises to 1200-1300℃, a reduction reaction occurs in the reduction zone. A small amount of pulverized coal is burned to provide the heat required for the reduction reaction, and the remaining pulverized coal is used to reduce the phosphate rock, generating yellow phosphorus vapor, carbon monoxide and slag.

[0018] Unreacted phosphate rock powder will be sent into a high-temperature cyclone separator along with the reacted slag by the airflow, where it will be centrifugally separated. The solid particles will be sent back to the heating zone through a return device to be heated, and then enter the reduction zone to continue the reaction, forming a cycle of phosphate rock powder; the slag and fly ash will be discharged from the reactor through continuous or intermittent slag discharge; the yellow phosphorus vapor can be hydrated to produce an extremely pure phosphoric acid solution, thereby preparing a high-purity phosphoric acid product.

[0019] Description of the principle of this utility model:

[0020] The utility model adopts electric heating to provide the heat required for the reaction. The phosphate rock absorbs heat in the fluidized bed reactor and undergoes a carbon thermal reduction reaction with coal powder and the like. The generated yellow phosphorus vapor and carbon monoxide are separated by the fluidized gas through a cyclone separator and then enter a hydration absorption tower to separate and purify the yellow phosphorus in the synthesis gas for use in the production of phosphoric acid or other yellow phosphorus products. The by-product high-quality synthesis gas can be used as a chemical raw material after purification.

[0021] Compared with the prior art, the advantages of this utility model are:

[0022] 1. Conventional fixed-bed reactors require long reaction times and temperatures, resulting in high production costs, large amounts of coke, and low utilization of phosphate rock resources. The present invention utilizes a fluidized bed reactor, which can maintain a high conversion rate of phosphate rock at relatively low temperatures, with shorter reaction times, lower costs, and better economics.

[0023] 2. The wet-process phosphoric acid process requires high-grade phosphate rock with a P2O5 content exceeding 30%. Only 7% of my country's phosphate rock reserves meet the requirements for wet-process phosphoric acid. Furthermore, the resulting phosphoric acid product is of low purity and requires a complex separation process. The present invention has no restrictions on the grade of the phosphate rock, and the yellow phosphorus produced can be directly used in the preparation of phosphoric acid or other phosphorus-containing chemicals. The product is extremely pure and has a wide range of applications.

[0024] 3. During the phosphate rock reduction process, the reducing agent coal or coke is converted into a by-product CO, which has a large output and high purity. It can be applied to other chemical industries, thereby achieving efficient utilization of phosphate rock at a lower cost while realizing synthesis gas production.

[0025] 4. Adding sulfate additives during the reduction process can promote the defluorination reaction of calcium fluorophosphate in phosphate rock, reduce the activation energy of the reaction system, and significantly reduce the reaction temperature, thereby achieving the purpose of improving the utilization rate of phosphate rock resources while being more energy-saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 : Diagram of fluidized bed phosphate rock reduction device.

[0027] Among them, there are coal powder bin 1, phosphate rock powder bin 2, fluidized bed reactor 3, insulation layer 4, high-temperature cyclone separator 5, first expansion device 6, second expansion device 8, return device 7, dust collector 9, hydration absorption tower 10, phosphoric acid tank 11, slag collection device 12, and blower 13. DETAILED DESCRIPTION

[0028] The present invention will be further described below through specific embodiments in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited thereto.

[0029] Example 1

[0030] like Figure 1 As shown, a system for preparing yellow phosphorus by carbon thermal reduction of phosphate rock based on a fluidized bed includes: a feeding device, a fluidized bed reactor 3, a high-temperature cyclone separator 5, a return device 7, a dust collector 9, a hydration absorption tower 10, a phosphoric acid tank 11, and a blower 13.

[0031] The feeding device includes a pulverized coal bin 1 and a phosphate rock powder bin 2. The two raw material bins are connected to the lower part of the fluidized bed reactor 3 through a feeding pipe; the outlet of the fluidized bed reactor 3 is connected to a high-temperature cyclone separator 5; the top outlet of the high-temperature cyclone separator 5 is connected to a dust collector 9, and the bottom outlet is connected to a return device 7; the outlet of the return device 7 is connected to the bottom of the fluidized bed reactor 3; the outlet of the dust collector 9 is connected to the inlet of a hydration absorption tower 10, and the outlet of the hydration absorption tower 10 is connected to a phosphoric acid tank 11.

[0032] The fluidized bed reactor 3 is divided into a heating zone and a reduction zone from bottom to top. A slag collection device 12 is provided below the fluidized bed reactor 3 . A blower 13 is provided around the bottom of the fluidized bed reactor 3 to send air into the fluidized bed reactor 3 from the bottom.

[0033] A first expansion device 6 is provided on the connection passage between the bottom outlet of the high-temperature cyclone separator 5 and the recycler 7 , and a second expansion device 8 is provided on the connection passage between the outlet of the recycler 7 and the bottom of the fluidized bed reactor 3 .

[0034] The exteriors of the fluidized bed reactor 3 , the high-temperature cyclone separator 5 , and the material return device 7 are all provided with a heat-insulating layer 4 .

[0035] Process flow:

[0036] (1) Phosphate rock, pulverized coal and other raw materials are fed into the fluidized bed reactor through a raw material feeder, the raw material particle size is controlled to be below 150 μm, the silicon-calcium molar ratio is 1.8-2.2, and the carbon excess coefficient is 4.0-5.0. The reactor is operated under normal pressure, the operating temperature is controlled within the range of 1200-1300°C, the temperature difference between the heating zone and the reduction zone is controlled within 100°C, and the fluidization wind speed is controlled within the range of 450-550 L / h. The raw materials undergo a carbon thermal reaction in the reduction zone in the furnace to generate a large amount of yellow phosphorus gas, synthesis gas and slag.

[0037] (2) The slag is discharged from the reactor through the slag discharge port, and the generated product gas enters the high-temperature cyclone separator from the upper part of the furnace. The solid phase separated in the high-temperature cyclone separator enters the lower part of the fluidized bed reactor through the return feeder to react again, and the separated gas phase enters the bag dust collector for dust removal.

[0038] (3) The product gas after dust removal enters the hydration absorption tower to separate the synthesis gas and yellow phosphorus. The generated phosphoric acid product will be passed into the phosphoric acid pool.

Claims

1. A system for preparing yellow phosphorus by carbon thermal reduction of phosphate rock based on a fluidized bed, characterized in that: include: Feeding device, fluidized bed reactor, high temperature cyclone separator, return device, dust collector, hydration absorption tower, phosphoric acid tank, blower; The feeding device includes two raw material bins, namely a coal powder bin and a phosphate rock powder bin. The two raw material bins are connected to the lower part of the fluidized bed reactor through a feeding pipe. The upper part of the fluidized bed reactor is connected to a high-temperature cyclone separator. The top outlet of the high-temperature cyclone separator is connected to a dust collector, and the bottom outlet of the high-temperature cyclone separator is connected to a return device; the dust collector outlet is connected to the top inlet of a hydration absorption tower, and the bottom outlet of the hydration absorption tower is connected to a phosphoric acid tank; the return device outlet is connected to the bottom of the fluidized bed reactor; a blower is arranged around the bottom of the fluidized bed reactor to send air into the fluidized bed reactor from the bottom.

2. The system for preparing yellow phosphorus by carbon thermal reduction of phosphate rock based on a fluidized bed as claimed in claim 1, characterized in that: The exteriors of the fluidized bed reactor, high-temperature cyclone separator, and return material container are all provided with thermal insulation layers.

3. The system for preparing yellow phosphorus by carbon thermal reduction of phosphate rock based on a fluidized bed as claimed in claim 1, characterized in that: The fluidized bed reactor is divided into a heating zone and a reduction zone from bottom to top.

4. The system for preparing yellow phosphorus by carbon thermal reduction of phosphate rock based on a fluidized bed as claimed in claim 1, characterized in that: A slag collection device is provided below the fluidized bed reactor.

5. The system for preparing yellow phosphorus by carbon thermal reduction of phosphate rock based on a fluidized bed as claimed in claim 1, characterized in that: A first expansion device is provided on the connecting passage between the bottom outlet of the high-temperature cyclone separator and the material return device.

6. The system for preparing yellow phosphorus by carbon thermal reduction of phosphate rock based on a fluidized bed as claimed in claim 1, characterized in that: A second expansion device is provided on the connecting passage between the outlet of the return device and the bottom of the fluidized bed reactor.

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