A method for recovering fluorine gas from a fluorinated process tail gas

Abstract

This invention belongs to the field of uranium conversion technology, specifically relating to a method for recovering fluorine gas from the tail gas of a fluorination process. The steps are as follows: Excess gas discharge: Excess gas is discharged from the tail gas of the fluorination process before reuse; Gas heating: The gas is heated; Gas dust removal: Dust is removed from the tail gas; Gas pressurization: The tail gas of the fluorination process is pressurized from atmospheric pressure; Buffering and stabilization: The fluorination process tail gas after buffering and stabilization is used as the carrier gas for solid material UF4. This method can realize the recovery and reuse of excess fluorine gas in the tail gas of the fluorination process, reduce the generation of solid waste and fluorine-containing waste liquid, and effectively improve the economic efficiency of the uranium conversion production line.

Description

Technical Field

[0001] This invention belongs to the field of uranium conversion technology, specifically relating to a method for recovering fluorine gas from the tail gas of a fluorination process. Background Technology

[0002] In the production process of uranium hexafluoride from uranium tetrafluoride reacting with fluorine gas, fluorine gas is used in excess by more than 10% to ensure the conversion rate of uranium tetrafluoride. After the uranium hexafluoride condensation and hydrogen fluoride collection of the fluorination furnace gas, the main components of the tail gas are N2, O2, F2, and trace amounts of HF, with fluorine gas accounting for approximately 23%. Currently, uranium conversion plants produce fluorine gas by electrolyzing hydrogen fluoride. The electrolysis feedstock is expensive and consumes extremely high amounts of electricity, resulting in extremely high production costs for fluorine gas. Therefore, improving the utilization rate of fluorine gas and its recovery and reuse are crucial.

[0003] Currently, the fluorine gas in the fluorination tail gas is not recycled; instead, it is treated through charcoal combustion and alkaline scrubbing. This method consumes a large amount of charcoal and generates solid waste carbonized slag and fluorine-containing waste liquid. During the 11th Five-Year Plan period, Plant 404 conducted an experiment to recover fluorine gas using a horizontal stirred furnace as the main recovery equipment. Under certain temperature control, fresh UF4 material reacted with the fluorination tail gas in the horizontal stirred furnace, and the resulting intermediate fluoride was then sent to a vertical fluorination reactor for further reaction. However, in engineering applications, the horizontal stirred furnace frequently experienced gas leaks, causing shutdowns, and this problem remained unresolved, ultimately preventing its application in actual production. Summary of the Invention

[0004] The purpose of this invention is to provide a method for recovering fluorine gas from the tail gas of the fluorination process. The tail gas of the fluorination process is reused as the carrier gas for solid material UF4, replacing nitrogen gas to inject UF4 into the fluorination reactor. This method can realize the recovery and reuse of excess fluorine gas in the tail gas of the fluorination process, reduce the amount of solid waste and fluorine-containing waste liquid generated, and effectively improve the economic efficiency of the uranium conversion production line.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for recovering fluorine gas from the tail gas of a fluorination process includes the following steps:

[0007] Excess gas discharge: Excess gas from the fluorination process is discharged before reuse;

[0008] Gas heating: heating a gas to a higher temperature;

[0009] Gas dust removal: removing dust from exhaust gas;

[0010] Gas pressurization: The tail gas from the fluorination process is pressurized from atmospheric pressure;

[0011] Buffering and stabilizing: The fluorination process tail gas after buffering and stabilizing is used as the carrier gas for solid material UF4.

[0012] Exhaust gas: An electric regulating valve is installed on the exhaust gas pipeline. The valve is adjusted by feedback from the flow meter on the reuse gas pipeline to ensure that the reuse gas volume remains stable at the required flow rate.

[0013] Excess gas discharge: 30% of the volume of excess gas from the fluorination process is discharged before reuse.

[0014] Gas heating: The gas is heated to 20°C using a gas heater.

[0015] Gas dust removal: Dust is removed from the exhaust gas using a gas dust collector equipped with sintered stainless steel filter tubes.

[0016] Gas pressurization: A membrane pressurizer is used to pressurize the fluorinated tail gas from atmospheric pressure to 0.1 MPa.

[0017] Buffer and pressure regulation: A buffer tank is set up for pressure regulation, and a pressure gauge is set up for interlocking.

[0018] When the pressure is <0.09MPa, open the solenoid valve to add fresh nitrogen; when the pressure is >0.11MPa, open the solenoid valve to release excess gas, so that the gas pressure is maintained at 0.1MPa.

[0019] The beneficial effects achieved by this invention are as follows:

[0020] This invention can recycle 70% of the fluorination tail gas, increasing the total fluorine utilization rate to 97%, a 6% improvement over the previous 91%. It also reduces the production cost of uranium conversion production lines. Based on a uranium conversion production capacity of 6000 tU / a, using this method for fluorine recovery and reuse can reduce operating costs by 1.7 million RMB just for the raw materials and electricity used in electrolytic fluorine production. Furthermore, it can further reduce the generation of solid waste and fluorine-containing wastewater. Attached Figure Description

[0021] Figure 1 A simplified flow chart for the reuse of fluorine gas in the tail gas of the fluorination process as a carrier gas.

[0022] In the diagram: Pipeline labels: a-Fluoride tail gas; b-Excess gas; c-Nitrogen; d-Carrier gas (recycled gas). Equipment labels: 1-Electric regulating valve; 2-Flow meter; 3-Gas heater; 4-Gas dust collector; 5-Membrane press; 6-Buffer tank; 7-Pressure gauge; 8-Solenoid valve. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0024] The method employed in this invention is to replace the original nitrogen gas used for blowing the carrier gas of solid material UF4 with fluorinated tail gas. The specific steps are as follows:

[0025] (1) Exhaust gas

[0026] The amount of UF4 carrier gas used for solid material injection is constant, approximately 70% of the fluorination tail gas volume. Fluorination tail gas a needs to have about 30% of its excess gas b discharged before reuse. To prevent fluctuations in the exhaust gas volume from affecting tail gas reuse, an electric regulating valve 1 is installed on the exhaust gas pipeline. Feedback from a flow meter 2 on the reuse gas pipeline adjusts this valve to ensure a stable flow rate for reuse gas.

[0027] (2) Gas heating

[0028] The temperature of the fluorination process tail gas after hydrogen fluoride collection is relatively low, approximately -80°C. However, the temperature of the gas injected into the UF4 carrier belt is required to be at room temperature, so it needs to be heated to room temperature (20°C) by gas heater 3.

[0029] (3) Gas dust removal

[0030] The exhaust gas may contain solid powder, which can damage the subsequent pressurization equipment, the fluorine-specific membrane compressor. To ensure the normal operation of the membrane compressor, the exhaust gas needs to be dusted by a gas dust collector 4 equipped with sintered stainless steel filter tubes.

[0031] (4) Gas pressurization

[0032] The UF4 carrier belt blowing gas pressure requirement is 0.1MPa, while the fluorination tail gas pressure is atmospheric pressure. Therefore, a membrane press 5 is required to increase the pressure of the fluorination tail gas from atmospheric pressure to 0.1MPa.

[0033] (5) Buffer voltage regulation

[0034] To further ensure pressure stability when the fluorinated tail gas is used as the carrier gas, a buffer tank 6 is installed for pressure stabilization, and a pressure gauge 7 is installed for interlocking. When the pressure is <0.09MPa, the solenoid valve 8 is opened to replenish fresh nitrogen c; when the pressure is >0.11MPa, the solenoid valve 8 is opened to discharge excess gas b, thus maintaining the gas pressure around 0.1MPa. The fluorinated tail gas, after buffering and stabilization, can then be used as the carrier gas d for the solid material UF4.

[0035] Because N2 and O2 constitute a large proportion of the fluorination tail gas, while F2 accounts for only 23%, there are currently no good recycling methods in China. This invention treats the fluorination tail gas through steps such as exhaust gas treatment, gas heating, dust removal, pressurization, and buffering and stabilization, replacing pure nitrogen as the carrier gas for the solid material UF4. This fluorine recycling method is applicable to the production system of uranium hexafluoride (UF4) produced by the reaction of uranium tetrafluoride and fluorine in natural uranium conversion plants, and also applicable to post-reactor uranium hexafluoride (UF4) production systems. After recycling the fluorination tail gas using this method, approximately 70% of the fluorine can be recycled, increasing the total fluorine utilization rate of the UF4 production system from 91% to 97%, reducing nitrogen consumption, and reducing the consumption of charcoal and alkali solutions, thereby reducing the generation of carbonization slag and fluorine-containing waste liquid.

[0036] This invention introduces a method for recovering and reusing fluorine gas from the fluorination process tail gas in a uranium hexafluoride production system of a uranium conversion plant. Through steps such as exhaust gas, gas heating, dust removal, pressurization, and buffering and stabilization, the fluorination process tail gas can be reused as a carrier gas to inject solid UF4 into the fluorination reactor. This method enables the reuse of fluorine gas in the fluorination tail gas, reduces waste generation, and improves the economic efficiency of the entire production line.

Claims

1. A method for recovering fluorine gas from the tail gas of a fluorination process, characterized in that: The steps are as follows: Excess gas discharge: 30% of the volume of excess gas from the fluorination process is discharged before reuse. Gas heating: The gas is heated to 20°C using a gas heater; Gas dust removal: Dust removal of exhaust gas is achieved through a gas dust collector equipped with sintered stainless steel filter tubes. Gas pressurization: A membrane pressurizer is used to boost the pressure of the fluorinated tail gas from atmospheric pressure to 0.1 MPa; Buffering and stabilizing: The fluorination process tail gas after buffering and stabilizing is used as the carrier gas for solid material UF4.

2. The method for recovering fluorine gas from the tail gas of the fluorination process according to claim 1, characterized in that: Exhaust gas: An electric regulating valve is installed on the exhaust gas pipeline. The valve is adjusted by feedback from the flow meter on the reuse gas pipeline to ensure that the reuse gas volume remains stable at the required flow rate.

3. The method for recovering fluorine gas from the tail gas of the fluorination process according to claim 1, characterized in that: Buffer and pressure regulation: A buffer tank is set up for pressure regulation, and a pressure gauge is set up for interlocking.

4. The method for recovering fluorine gas from the tail gas of the fluorination process according to claim 3, characterized in that: When the pressure is <0.09MPa, open the solenoid valve to add fresh nitrogen; when the pressure is >0.11MPa, open the solenoid valve to release excess gas, so that the gas pressure is maintained at 0.1MPa.

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