Rare earth extraction VOC treatment device and method

Abstract

The invention discloses a rare earth extraction VOC treatment device and method. The device comprises an extraction unit, a VOC absorption unit, a first communication unit and a second communication unit, the extraction unit comprises an extractor; the VOC absorption unit is communicated with the extractor through a first communication unit and is arranged to receive VOC gas containing volatile organic matters generated in the extractor and recover the organic matters through water absorption; the VOC absorption unit is also communicated with the extractor through a second communication unit, so that the absorbed residual gas is returned to the extractor through the second communication unit; no vacuumizing equipment is arranged in the device. By adopting the device, all volatile organic matters can be basically recovered, and no waste gas emission in the extraction process can be basically realized.

Description

Technical Field

[0001] The invention relates to a rare earth extraction VOC treatment device and method. Background Art

[0002] During the rare earth hydrometallurgy process, extractants such as P507, P204, N235, and cyclohexane acid are mixed with diluents such as white oil and isooctyl alcohol to prepare organic extractants suitable for production requirements. The rare earth solutions of various systems such as rare earth sulfate solution, rare earth chloride solution or rare earth nitric acid solution containing rare earth elements are mixed and clarified in the extraction tank to achieve separation between rare earth elements and between rare earth and non-rare earth elements.

[0003] During the extraction process, due to various reasons such as process conditions, equipment form, and the properties of organic matter, there is a problem of organic matter volatilizing and overflowing out of the extraction tank during the extraction process.

[0004] In actual production, in order to avoid the unorganized emission of organic matter during the extraction process, the extraction tank is generally sealed, and the tank cover is equipped with a ventilation duct connected to the fan. The fan draws air to form a slight negative pressure inside the extraction tank, and the volatile organic matter is extracted from the extraction tank. Then, the volatilized organic matter is disposed of by adsorption, combustion or catalytic decomposition to ensure that the gas after treatment is discharged in a qualified manner. The treatment idea is to decompose the volatile organic matter into water and carbon dioxide by burning or photolysis after the volatile organic matter is initially recovered. In this way, on the one hand, the use of the fan to form a slight negative pressure increases the volatility of organic matter, which increases the difficulty of treatment; on the other hand, some organic matter is decomposed into water and carbon dioxide, resulting in waste of organic matter.

[0005] CN115069061A discloses a method for treating VOC in P204 and P507 extraction systems by using resin, comprising the following steps: passing the VOC waste gas in the P204 and P507 extraction systems into a washing tower to obtain washed VOC waste gas; passing the washed VOC waste gas into a filtering device to obtain pretreated VOC waste gas; pressurizing the pretreated VOC waste gas and discharging it into a high cross-linked degreasing resin adsorption bed to obtain qualified air and resin after adsorbing the waste gas; desorbing the resin after adsorbing the waste gas to obtain a desorbed mixture and a resolved resin, drying the resolved resin for reuse, passing the desorbed mixture into a condenser to obtain a condensate; separating the condensate into oil and water to obtain a recovered organic solvent and water. This method uses adsorption, and when the adsorbent fails, hazardous waste will be generated, and further treatment of the hazardous waste is required, which increases the cost.

[0006] CN212881763U discloses a treatment system for VOCs by multi-stage extraction with an organic extractant, including a gas buffer tank, a water spray tower, a drying tower, a multi-stage extraction tower, an extractant distillation regeneration tower, and an organic gas waste liquid collection tank; the organic gas waste liquid collection tank is connected to a vacuum buffer tank, and the vacuum buffer tank is connected to a vacuum pump. The treatment system still uses a vacuum pump to form a negative pressure in the system, and the system also needs to burn the residual gas that cannot recover organic matter. In addition, the system uses more components and occupies a large area. Summary of the invention

[0007] In view of this, one object of the present invention is to provide a rare earth extraction VOC treatment device, which can basically achieve the recovery of all volatile organic matter and achieve no waste gas emission during the extraction process. In addition, the vacuum equipment can be omitted to reduce the amount of organic matter volatilization. Another object of the present invention is to provide a method for treating VOC gas generated during rare earth extraction using the above device.

[0008] The present invention adopts the following technical solutions to achieve the above-mentioned purpose.

[0009] In one aspect, the present invention provides a rare earth extraction VOC treatment device, comprising an extraction unit, a VOC absorption unit, a first connecting unit and a second connecting unit;

[0010] The extraction unit comprises an extractor, and the extractor is used for extracting the rare earth solution with an organic extractant;

[0011] The VOC absorption unit is connected to the extractor through the first communication unit, and is configured to receive VOC gas containing volatile organic matter generated in the extractor, and recover the organic matter through water absorption;

[0012] The VOC absorption unit is also connected to the extractor through the second connecting unit, so that the residual gas after absorption returns to the extractor through the second connecting unit;

[0013] Wherein, no vacuum equipment is provided in the device.

[0014] According to the rare earth extraction VOC treatment device of the present invention, preferably, the VOC absorption unit includes a spray tower and a refrigeration device;

[0015] The lower part of the spray tower is connected to the top of the extractor through the first connecting unit; the spray tower is configured to receive VOC gas containing volatile organic matter generated in the extractor, and form droplets of the VOC gas by spraying water, thereby recovering the organic matter by static stratification;

[0016] One side of the refrigeration equipment is connected to the top of the spray tower through a pipeline, and the other side is connected to the top of the extractor through the second connecting unit; the refrigeration equipment is configured to further freeze the residual organic matter in the residual gas after absorption in the spray tower to recover the organic matter, and the frozen residual gas returns to the extractor through the second connecting unit.

[0017] According to the rare earth extraction VOC treatment device of the present invention, preferably, the VOC absorption unit includes a spray tower and a cooling device;

[0018] The lower part of the spray tower is connected to the top of the extractor through the first connecting unit; the bottom and the upper part of the spray tower are also connected to the cooling device through pipelines respectively; the spray tower is configured to receive VOC gas containing volatile organic matter generated in the extractor, and receive water from the cooling device to form spray water, so that the organic matter and water vapor condense into droplets;

[0019] The top of the spray tower is also connected to the top of the extractor through the second connecting unit;

[0020] The cooling device is configured to spray water to the spray tower, and is also configured to receive water obtained after droplet stratification in the spray tower.

[0021] According to the rare earth extraction VOC treatment device of the present invention, preferably, the VOC absorption unit includes a jet pump, a buffer tank and a cooling device;

[0022] The jet pump is connected to the cooling device and the buffer tank respectively; the jet pump is also connected to the first communication unit and is configured to receive VOC gas containing volatile organic matter generated in the extractor and water from the cooling device, and mix the VOC gas with the water from the cooling device, so that the organic matter and water vapor condense into droplets;

[0023] The buffer tank is used to receive the droplets and is configured to recover organic matter by static stratification; the top of the buffer tank is also connected to the top of the extractor through the second connecting unit;

[0024] The cooling device is also connected to the bottom of the buffer tank through a pipeline, and the cooling device is also configured to receive water obtained after stratification in the buffer tank.

[0025] According to the rare earth extraction VOC treatment device of the present invention, preferably, the extractor is provided in plurality, and the plurality of extractors are respectively connected in parallel with the VOC absorption unit through the first connecting unit.

[0026] According to the rare earth extraction VOC treatment device of the present invention, preferably, the extractor is a box-type extractor.

[0027] According to the rare earth extraction VOC treatment device of the present invention, preferably, the first connecting unit includes a first branch connecting tube and a first main connecting tube; the number of the first branch connecting tubes matches the number of the extractors, one end of the first branch connecting tube is respectively connected to the first main connecting tube, and the other end is respectively connected to the corresponding extractor; one end of the first main connecting tube is connected to the VOC absorption unit.

[0028] According to the rare earth extraction VOC treatment device of the present invention, preferably, the second connecting unit includes a second branch connecting pipe and a second main connecting pipe; one end of the second branch connecting pipe is connected to the extractor far away from the VOC absorption unit, and the other end is connected to one end of the second main connecting pipe; the other end of the second main connecting pipe is connected to the VOC absorption unit.

[0029] On the other hand, the present invention also provides a method for treating VOC gas generated in the rare earth extraction process using the rare earth extraction VOC treatment device as described above, comprising the following steps:

[0030] (1) In the extractor, a rare earth solution is extracted using an organic extractant; during the extraction process, VOC gas containing volatile organic matter is generated and flows from the extractor to the VOC absorption unit;

[0031] (2) The VOC absorption unit recovers organic matter through water absorption, and the residual gas after absorption returns to the extractor through the second connecting unit.

[0032] According to the method of the present invention, preferably, the organic extractant comprises a first organic matter and a second organic matter; the first organic matter is selected from one of P507, P204, N235 and cyclohexane acid; the second organic matter is selected from at least one of kerosene, white oil and isooctyl alcohol; the VOCs content in the VOC gas is 1000-5000 mg / m 3 .

[0033] The rare earth extraction VOC treatment device of the present invention can basically realize the recovery of all volatile organic matter, and can achieve no waste gas emission during the extraction process. Furthermore, the rare earth extraction VOC treatment device of the present invention can omit the vacuum equipment, reduce the volatility of organic matter, reduce the volume of VOC gas, and no hazardous waste is generated. In addition, the rare earth extraction VOC treatment device of the present invention has a relatively simple structure, which is conducive to modification on existing equipment, with low investment and small footprint. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic structural diagram of a rare earth extraction VOC treatment device of the present invention.

[0035] Figure 2 This is a schematic diagram of the structure of another rare earth extraction VOC treatment device of the present invention.

[0036] Figure 3 This is a schematic structural diagram of another rare earth extraction VOC treatment device of the present invention.

[0037] The following are the descriptions of the reference numerals:

[0038] 1-extraction unit, 11-extractor, 21-spray tower, 22-refrigeration equipment, 31-first branch connecting pipe, 32-first main connecting pipe, 4-second connecting unit;

[0039] 22'-Cooling equipment,

[0040] 22”-cooling device, 23-jet pump, 24-buffer tank;

[0041] A represents the liquid level of the extractor during extraction, B represents the VOC gas volatilized during extraction, and C represents the organic matter layer after static stratification. DETAILED DESCRIPTION

[0042] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0043] <Rare earth extraction VOC treatment device>

[0044] A rare earth extraction VOC treatment device of the present invention comprises an extraction unit, a VOC absorption unit, a first connecting unit and a second connecting unit. The rare earth extraction VOC treatment device of the present invention does not involve any vacuum equipment, and the vacuum equipment includes a vacuum pump, an exhaust fan, etc. This will not increase the volatilization amount of organic matter. A detailed description is given below.

[0045] Extraction unit

[0046] The extraction unit of the present invention is used for extraction. According to one embodiment of the present invention, the extraction unit comprises an extractor, and the extractor is used for extracting the rare earth solution with an organic extractant.

[0047] In the present invention, the extractor is provided in plurality, and the plurality of extractors are respectively connected in parallel with the VOC absorption unit through the first connecting unit.

[0048] In the present invention, the extractor is a box-type extractor. During extraction, the extractor is sealed, that is, it is not connected to the outside atmosphere.

[0049] The first connected unit

[0050] In the present invention, the first connecting unit is connected to the extraction unit and the VOC absorption unit respectively, and is used to pass the VOC gas containing volatile organic matter from the extraction unit to the VOC absorption unit.

[0051] According to one embodiment of the present invention, the first connecting unit includes a first branch connecting tube and a first main connecting tube; the number of the first branch connecting tubes matches the number of the extractors, and the first branch connecting tubes are respectively connected to the first main connecting tubes in parallel; one end of the first main connecting tube is connected to the VOC absorption unit. Specifically, one end of each of the first branch connecting tubes is respectively connected to the first main connecting tube, and one end of each of the first branch connecting tubes away from the first main connecting tube is respectively connected to the top of the extractor.

[0052] The second connected unit

[0053] In the present invention, the second connecting unit is connected to the VOC absorption unit and the extraction unit respectively, and is used to pass the absorbed residual gas generated by the VOC absorption unit into the extractor to balance the gas pressure in the extractor.

[0054] According to one embodiment of the present invention, the second connecting unit includes a second branch connecting pipe and a second main connecting pipe; one end of the second branch connecting pipe is connected to the extractor far away from the VOC absorption unit, and the other end is connected to one end of the second main connecting pipe; the other end of the second main connecting pipe is connected to the VOC absorption unit. Specifically, one end of the second branch connecting pipe is connected to one end of the second main connecting pipe, and one end of the second branch connecting pipe far away from the second main connecting pipe is connected to the top of the extractor far away from the VOC absorption unit (i.e., the far end is connected to the extractor).

[0055] In the present invention, the diameter of the second connecting unit is smaller than that of the first connecting unit. VOC gas will not enter the VOC absorption unit from the second connecting unit. The first connecting unit is to collect all the generated VOCs gases together and enter the VOC absorption unit from the near end. The pressure is reduced during the treatment process, and the high-concentration gas at the near end naturally flows to the low-pressure direction. The treated gas is connected to the distal extractor by the thinner second connecting unit, and the pressure is basically balanced, and a closed-loop flow direction is formed by using the change in gas pressure.

[0056] VOC absorption unit

[0057] The VOC absorption unit of the present invention is connected to the extractor through the first connecting unit, and is configured to receive VOC gas containing volatile organic matter generated in the extractor, and recover the organic matter through water absorption; the VOC absorption unit is also connected to the extractor through the second connecting unit, so that the residual gas after absorption returns to the extractor through the second connecting unit. In this way, the VOC gas can flow from the extractor to the VOC absorption unit according to its concentration from high to low, and then the organic matter therein can be absorbed by the VOC absorption unit, and the pressure balance in the extractor can be achieved, so that the entire treatment device can continuously treat the VOC gas. Such a treatment device requires little investment in transformation and occupies a small area. The treatment device of the present invention basically does not produce waste liquid, and basically does not emit waste gas into the outside atmosphere, and does not involve burning residual organic matter.

[0058] The inventors believe that the principle of the VOC treatment device of the present invention can be explained by the following two formulas (a) and (b).

[0059]

[0060] In formula (a), G: organic volatilization amount g / h, v: liquid surface wind speed m / s, P: organic saturated vapor pressure, F: organic exposure area m 2 , M: is the molecular weight of the organic compound.

[0061] It can be seen from formula (a) that if the sealed equipment is fixed and the wind speed is zero, the volatility G is only related to the temperature, because the saturated vapor pressure is different at different temperatures.

[0062] Formula PV = nRT, (b);

[0063] In formula (b), P is pressure, in Pascal (Pa). V is gas volume, in cubic meter (m 3 ). n: amount of substance in the gas, in moles (mol). T: temperature, in Kelvin (K). R: molar gas constant, also called universal gas constant, in J / (mol·K) or kPa·L·K-1·mol-1. The value of R under standard conditions is 8.314 J / (mol·K).

[0064] In formula (b), when the temperature remains unchanged, the amount of substance n in the gas decreases during the spraying and freezing process, and the gas turns into liquid, achieving pressure reduction and volume reduction, thereby balancing the pressure increase caused by the volatilization process of the organic matter, and achieving overall pressure balance in the closed circulation system. The recovered organic matter will be used for extraction in the production line, and the organic loss is theoretically zero. However, in the actual spraying absorption process and freezing process, the volatilized water vapor in the system turns into liquid. In order to ensure the balance of the system, the excess water will be discharged from the system. The loss of organic matter is the amount of dissolved organic matter in the discharged water.

[0065] Based on the treatment concept of the present invention, the specific structure of the VOC absorption unit of the present invention is not particularly limited.

[0066] In certain preferred embodiments, the VOC absorption unit includes a spray tower and a refrigeration device; the lower part of the spray tower is connected to the top of the extractor through the first connecting unit; the spray tower is configured to receive VOC gas containing volatile organic matter generated in the extractor, and form droplets of the VOC gas by spraying water, thereby recovering organic matter by standing stratification (and liquid separation); one side of the refrigeration device is connected to the top of the spray tower through a pipeline, and the other side is connected to the top of the extractor through the second connecting unit; the refrigeration device is configured to further freeze the residual gas after absorption from the spray tower to recover organic matter, and the frozen residual gas returns to the extractor through the second connecting unit. The spray tower and the refrigeration device are not particularly limited, and can achieve the functions of the present invention. In this solution, a connecting vessel is formed between the extractor, the spray tower, and the refrigeration device.

[0067] In some other preferred embodiments, the VOC absorption unit includes a spray tower and a cooling device; the lower part of the spray tower is connected to the top of the extractor through the first connecting unit; the bottom and upper part of the spray tower are also connected to the cooling device through pipelines respectively; the spray tower is configured to receive VOC gas containing volatile organic matter generated in the extractor, and to receive water from the cooling device and form spray water, so that the organic matter and water vapor condense into droplets, and the droplets are separated into layers and liquids to recover the organic matter; the top of the spray tower is also connected to the top of the extractor through the second connecting unit; the cooling device is configured to spray water to the spray tower, and is also configured to receive water obtained after the droplets in the spray tower are separated. In this scheme, a connecting vessel is formed between the extractor and the spray tower.

[0068] In some further preferred embodiments, the VOC absorption unit includes a jet pump, a buffer tank and a cooling device; the jet pump is connected to the cooling device and the buffer tank respectively; the jet pump is also connected to the first connecting unit and is configured to receive VOC gas containing volatile organic matter generated in the extractor, and to receive water from the cooling device, and to mix the VOC gas and the water from the cooling device, so that the organic matter and water vapor condense into droplets; the buffer tank is used to receive the droplets, and is configured to recover the organic matter by static stratification; the top of the buffer tank is also connected to the top of the extractor through the second connecting unit; the cooling device is also connected to the bottom of the buffer tank through a pipeline, and the cooling device is also configured to receive water obtained after stratification in the buffer tank. In this scheme, a connecting vessel is formed between the extractor and the buffer tank.

[0069] <Method>

[0070] The present invention also provides a method for treating VOC gas generated in the rare earth extraction process using the rare earth extraction VOC treatment device as described above, comprising the following steps:

[0071] (1) In the extractor, a rare earth solution is extracted using an organic extractant; during the extraction process, VOC gas containing volatile organic matter is generated and flows from the extractor to the VOC absorption unit;

[0072] (2) The VOC absorption unit absorbs organic matter through water, and the residual gas after absorption is returned to the extractor through the second connecting unit.

[0073] In the present invention, the organic extractant includes a first organic matter and a second organic matter; the first organic matter is selected from one of P507, P204, N235 and cyclohexane acid; the second organic matter is selected from at least one of kerosene, white oil and isooctyl alcohol. Based on the treatment concept of the present invention, the flow ratio of the organic extractant to the rare earth solution can be arbitrarily adjusted between 1:100 and 100:1, and the reaction temperature required for the extraction production process can also be adjusted between 18 and 70°C due to different requirements for the characteristics of the extraction substances. The VOCs content in the VOC gas is 1000 to 5000 mg / m 3 .

[0074] According to one embodiment of the present invention, when the organic extractant is a mixture of P507 and white oil, the volatile organic matter in the VOC gas containing volatile organic matter is mainly white oil, and the VOC gas also contains a small amount of P507.

[0075] In the present invention, P507 is 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester, P204 is di(2-ethylhexyl)phosphate, and the main component of N235 is trioctyldecyl tertiary amine.

[0076] In the present invention, the VOCs content in the residual gas after absorption can be less than 500 mg / m 3 , preferably 20 to 500 mg / m 3 , can reach 20~100mg / m 3 The VOCs content in the residual gas after absorption of the present invention does not need to be particularly controlled to a relatively low value, because the residual gas after absorption can be returned to the extractor to balance the pressure therein, so that the VOC gas containing volatile organic matter generated in the extractor continues to flow to the VOC absorption unit and is not discharged to the outside atmosphere.

[0077] In the present invention, since there are various specific schemes of the VOC absorption unit, the specific process of VOC gas absorption in the method needs to be adjusted according to the different specific technical schemes of the VOC absorption unit.

[0078] According to a specific embodiment of the present invention, a method for treating VOC gas generated during rare earth extraction using a rare earth extraction VOC treatment device comprises the following steps:

[0079] (1) In the extractor, an organic extractant is used to extract a rare earth solution; during the extraction process, the VOC gas containing volatile organic matter generated flows from the extractor to the VOC absorption unit, specifically, to a spray tower of the VOC absorption unit;

[0080] (2) The spray tower of the VOC absorption unit recovers organic matter by spraying water, and the residual gas after absorption is cooled again by a refrigeration device to recover some of the remaining organic matter. The final residual gas is returned to the extractor through the second main connecting pipe and the second branch connecting pipe of the second connecting unit.

[0081] According to another specific embodiment of the present invention, a method for treating VOC gas generated during rare earth extraction using a rare earth extraction VOC treatment device comprises the following steps:

[0082] (1) In the extractor, an organic extractant is used to extract a rare earth solution; during the extraction process, the VOC gas containing volatile organic matter generated flows from the extractor to the VOC absorption unit, specifically, to a spray tower of the VOC absorption unit;

[0083] (2) The spray tower of the VOC absorption unit recovers organic matter by spraying water, and the spray water used is provided by a cooling device; the residual gas after absorption in the spray tower is returned to the extractor through the second connecting unit.

[0084] According to another specific embodiment of the present invention, a method for treating VOC gas generated during rare earth extraction using a rare earth extraction VOC treatment device comprises the following steps:

[0085] (1) In the extractor, an organic extractant is used to extract a rare earth solution; during the extraction process, the VOC gas containing volatile organic matter generated flows from the extractor to the VOC absorption unit, specifically, flows to the jet pump of the VOC absorption unit;

[0086] (2) The jet pump of the VOC absorption unit mixes the VOC gas containing volatile organic matter with water from the cooling device to form droplets, which fall into the buffer tank and stand to separate the layers and liquids to recover the organic matter; the residual gas after absorption in the buffer tank returns to the extractor through the second connecting unit.

[0087] In the present invention, the function of the refrigeration equipment is to further recover the residual organic matter. The cooling equipment and the cooling device both provide low-temperature cooling water to absorb the organic matter in the VOC gas. The selection can be made according to actual needs.

[0088] In the present invention, since the entire system is in a sealed state and no external gas is introduced, the process of gas pressure decreasing and concentration decreasing when the gas is liquefied is utilized to realize the active flow of VOC gas from a high-concentration area to a low-concentration area, thereby achieving the control of VOC gas.

[0089] The method of the invention can reduce the volatilization amount of organic matter, and basically no waste liquid is generated and no waste gas is discharged.

[0090] The test methods used in the following examples are described as follows:

[0091] Determination of VOCs content: gas chromatography is used for determination.

[0092] Example 1

[0093] Figure 1 This is a schematic structural diagram of a rare earth extraction VOC treatment device of the present invention.

[0094] like Figure 1 As shown, the rare earth extraction VOC treatment device of this embodiment includes an extraction unit 1, a VOC absorption unit, a first connecting unit and a second connecting unit 4.

[0095] The extraction unit 1 includes an extractor 11. The extractor 11 is used for extracting the rare earth solution with an organic extractant. The extractor 11 is provided in plurality, and the plurality of extractors 11 are respectively connected in parallel with the VOC absorption unit through a first connecting unit. The extractor 11 is a box-type extractor.

[0096] The first connecting unit includes a first branch connecting pipe 31 and a first main connecting pipe 32. The number of the first branch connecting pipes 31 matches the number of the extractors 11, and the plurality of first branch connecting pipes 31 are respectively connected to the first main connecting pipe 32 in parallel. Specifically, one end of each first branch connecting pipe 31 is respectively connected to the first main connecting pipe 32, and the other end of each first branch connecting pipe 31 is connected to the top of a corresponding extractor 11. One end of the first main connecting pipe 32 is connected to the VOC absorption unit. VOC gas containing volatile organic matter flows through the first connecting unit.

[0097] The second connecting unit 4 includes a second branch connecting pipe and a second main connecting pipe. The second main connecting pipe and the second branch connecting pipe are one pipe each. Specifically, one end of the second branch connecting pipe is connected to one end of the second main connecting pipe, and the other end of the second branch connecting pipe is connected to the corresponding extractor 11 far away from the VOC absorption unit (i.e., the extractor 11 is connected at the far end). The other end of the second main connecting pipe is connected to the VOC absorption unit. The diameter of the second connecting unit 4 is smaller than that of the first connecting unit.

[0098] The VOC absorption unit is connected to the extractor 11 through the first connecting unit, and is configured to receive VOC gas containing volatile organic matter generated in the extractor 11, and recover the organic matter through water absorption. The VOC absorption unit is also connected to the extractor 11 through the second connecting unit 4, so that the residual gas after absorption returns to the extractor 11 through the second connecting unit 4. In this way, the pressure in the extractor 11 can be balanced.

[0099] In this embodiment, specifically, Figure 1 As shown, the VOC absorption unit includes a spray tower 21 and a refrigeration device 22 .

[0100] The lower part of the spray tower 21 is connected to the top of the extractor 11 through the first connecting unit. Specifically, the lower part of the spray tower 21 is connected to the top of the extractor 11 through the first main connecting pipe 32 and the first branch connection 31 of the first connecting unit. The spray tower 21 is configured to receive VOC gas containing volatile organic matter generated in the extractor 11, and form droplets of the VOC gas by spraying water. The droplets fall to the bottom of the spray tower 21, and the droplets are left to stand to separate the layers and liquids. After the separation, an organic phase and water obtained by separation are formed. The organic phase is the recovered organic matter, which can be reused as an organic extractant.

[0101] One side of the refrigeration equipment 22 is connected to the top of the spray tower 21 through a pipeline, and the other side is connected to the top of the extractor 11 through the second connecting unit 4. Specifically, the other side of the refrigeration equipment 22 is connected to the top of the extractor 11 through the second main connecting pipe and the second branch connecting pipe of the second connecting unit 4. The refrigeration equipment 22 is configured to further freeze the residual organic matter in the residual gas after absorption in the spray tower 21 to recover the organic matter, and the frozen residual gas returns to the extractor 11 through the second connecting unit 4.

[0102] The rare earth extraction VOC treatment device of this embodiment is not equipped with any vacuum equipment.

[0103] The device can utilize the process of gas pressure decreasing and concentration decreasing after gas liquefaction to realize the active flow of VOC gas from high-concentration area to low-concentration area, thereby treating VOC gas, and does not discharge waste gas to the external atmosphere, nor does it need to burn the residual gas before discharging, and can recover volatile organic matter. Basically no waste liquid is generated.

[0104] During the extraction and VOC gas treatment process, the system is in a sealed state, no external gas is introduced, and there is no need to evacuate to a negative pressure state.

[0105] The following describes a method for treating VOC gas generated during rare earth extraction using the rare earth extraction VOC treatment device of this embodiment, including the following steps:

[0106] (1) In the extractor 11, an organic extractant is used to extract a rare earth solution; during the extraction process, the VOC gas containing volatile organic matter generated flows from the extractor 11 to the VOC absorption unit, specifically, to the spray tower 21 of the VOC absorption unit;

[0107] (2) The spray tower 21 of the VOC absorption unit recovers organic matter by spraying water, and the residual gas after absorption is cooled again by the refrigeration equipment 22 to recover some of the remaining organic matter. The final residual gas is returned to the extractor 11 through the second main connecting pipe and the second branch connecting pipe of the second connecting unit 4.

[0108] like Figure 1 As shown, in this embodiment, a connecting vessel is formed between the extractor 11, the spray tower 21, and the refrigeration equipment 22. In step (1), the organic matter is volatilized at the liquid level of the extractor 11, and the VOCs content in the volatilized VOC gas is generally 1000-5000 mg / m 3 In this embodiment, the organic extractant is a mixture of P507 and white oil, and the rare earth solution is a rare earth sulfate solution. The volatile VOC gas mainly includes white oil and a small amount of P507. Figure 1As shown, the VOC gas flows toward the spray tower 21 with lower concentration due to the continuous increase in concentration. In step (2), in the spray tower 21, water at 0 to 40°C (e.g., water at 10°C) can be used to spray and cool the VOC gas, and the VOCs content in the residual gas after absorption can be controlled to be less than 500 mg / m 3 The oil-water mixture after spraying (i.e. the droplets formed) falls to the bottom of the tower by gravity for clarification, stratification and separation. The separated organic phase is recovered for extraction, and the separated water phase (i.e. the water obtained by stratification) is cooled by a cooling tower and other cooling systems and then recycled as spray water. The VOCs content of the residual gas after absorption is generally 100-500 mg / m 3 , this part of the gas naturally flows to the refrigeration equipment 22, and the temperature of the refrigeration equipment 22 is controlled to be 0-20°C (for example, about 5°C), so that the VOCs gas particles in the gas and the water mist particles brought after the spraying continue to condense into droplets at a lower temperature, and fall into the liquid accumulation pool at the bottom of the refrigeration equipment 22 by gravity. The organic phase and the aqueous phase are allowed to stand for stratification and separation, and the organic phase is recovered and returned for extraction, and the aqueous phase is returned to the spraying system. The final residual gas is a low-concentration VOCs gas (the VOCs content is generally 20-100 mg / m 3 ) returns to the extractor 11 without exhaust gas emission.

[0109] Example 2

[0110] Figure 2 This is a schematic diagram of the structure of another rare earth extraction VOC treatment device of the present invention.

[0111] like Figure 2 As shown, the rare earth extraction VOC treatment device of this embodiment includes an extraction unit 1, a VOC absorption unit, a first connecting unit and a second connecting unit 4.

[0112] The extraction unit 1 includes an extractor 11. The extractor 11 is used for extracting the rare earth solution with an organic extractant. The extractor 11 is provided in plurality, and the plurality of extractors 11 are respectively connected in parallel with the VOC absorption unit through a first connecting unit. The extractor 11 is a box-type extractor.

[0113] The first connecting unit includes a first branch connecting pipe 31 and a first main connecting pipe 32. The number of the first branch connecting pipes 31 matches the number of the extractors 11, and the plurality of first branch connecting pipes 31 are respectively connected in parallel to the first main connecting pipe 32. Each first branch connecting pipe 31 is also connected to the top of a corresponding extractor 11. One end of the first main connecting pipe 32 (the end away from the extractor 11) is connected to the VOC absorption unit.

[0114] The second connecting unit 4 includes a second branch connecting pipe and a second main connecting pipe. The second main connecting pipe and the second branch connecting pipe are one pipe each. Specifically, one end of the second branch connecting pipe is connected to one end of the second main connecting pipe, and the other end of the second branch connecting pipe is connected to the corresponding extractor 11 far away from the VOC absorption unit (i.e., the extractor 11 is connected at the far end). The other end of the second main connecting pipe is connected to the VOC absorption unit. The diameter of the second connecting unit 4 is smaller than that of the first connecting unit.

[0115] The VOC absorption unit is connected to the extractor 11 through the first connecting unit, and is configured to receive VOC gas containing volatile organic matter generated in the extractor 11, and recover the organic matter by spraying water. The VOC absorption unit is also connected to the extractor 11 through the second connecting unit 4, so that the residual gas after absorption returns to the extractor 11 through the second connecting unit 4.

[0116] In this embodiment, specifically, Figure 2 As shown, the VOC absorption unit includes a spray tower 21 and a cooling device 22'. The lower part of the spray tower 21 is connected to the top of the extractor 11 through a first connecting unit. Specifically, the lower part of the spray tower 21 is connected to the top of the extractor 11 through the first main connecting pipe 32 and the first branch connecting pipe 31 of the first connecting unit. The bottom and the upper part of the spray tower 21 are also connected to the cooling device 22' through pipelines, respectively. The spray tower 21 is configured to receive VOC gas containing volatile organic matter generated from the extractor 11, and to receive water from the cooling device 22' and form spray water, so that the organic matter and water vapor are mixed and condensed into droplets. The droplets fall into the bottom of the spray tower 21 and are allowed to stand and stratify.

[0117] The top of the spray tower 21 is also connected to the top of the extractor 11 through the second connecting unit 4. The residual gas after absorption in the spray tower 21 is returned to the extractor 11 through the second connecting unit 4. The cooling device 22' is configured to provide water to the spray tower 21, and is also configured to receive water obtained after the droplets in the spray tower 21 are stratified as circulating water. Basically no waste liquid is generated.

[0118] The rare earth extraction VOC treatment device of this embodiment does not involve any vacuum equipment.

[0119] The following describes a method for treating VOC gas generated during rare earth extraction using the rare earth extraction VOC treatment device of this embodiment, including the following steps:

[0120] (1) In the extractor 11, an organic extractant is used to extract the rare earth solution. During the extraction process, the VOC gas containing volatile organic matter generated flows from the extractor 11 to the VOC absorption unit, specifically, to the spray tower 21 of the VOC absorption unit;

[0121] (2) The spray tower 21 of the VOC absorption unit recovers organic matter by spraying water, and the spraying water is provided by the cooling device 22 ′. The residual gas after absorption in the spray tower 21 is returned to the extractor 11 through the second connecting unit 4 .

[0122] like Figure 2 As shown, in this embodiment, a connecting vessel is formed between the extractor 11 and the spray tower 21. In step (1), during the extraction process, the organic matter in the organic extractant evaporates at the liquid surface of the extractor, and the VOCs content of the volatilized VOC gas is generally 1000-5000 mg / m 3 , the volatilized VOC gas flows towards the spray tower 21 with lower concentration due to the continuous increase in concentration. In this embodiment, the organic extractant is a mixture of P204 and white oil, and the rare earth solution is a rare earth chloride solution. The volatilized VOC gas mainly includes white oil and a small amount of P204. In step (2), the spray tower uses water at 0 to 35°C (for example, 10°C) provided by the cooling equipment 22' to spray and cool the volatilized VOC gas. The oil-water mixture (i.e., droplets) after spraying is clarified, layered and separated at the bottom of the tower, and the separated organic phase is recovered for extraction. The separated water phase is recycled by returning to the cooling equipment 22'. By controlling the water temperature and the amount of spraying water, the VOCs content of the residual gas after absorption is controlled to be less than 500mg / m 3 The low-concentration residual gas returns to the extractor 11 to balance the air pressure in the extractor. No waste gas is discharged.

[0123] Example 3

[0124] Figure 3 This is a schematic structural diagram of another rare earth extraction VOC treatment device of the present invention.

[0125] like Figure 3 As shown, the rare earth extraction VOC treatment device of this embodiment includes an extraction unit 1, a VOC absorption unit, a first connecting unit and a second connecting unit 4.

[0126] The extraction unit 1 includes an extractor 11. The extractor 11 is used for extracting the rare earth solution with an organic extractant. The extractor 11 is provided in plurality, and the plurality of extractors 11 are respectively connected in parallel with the VOC absorption unit through a first connecting unit. The extractor 11 is a box-type extractor.

[0127] The first connecting unit includes a first branch connecting pipe 31 and a first main connecting pipe 32. The number of the first branch connecting pipes 31 matches the number of the extractors 11, and the plurality of first branch connecting pipes 31 are respectively connected in parallel to the first main connecting pipe 32. Each first branch connecting pipe 31 is also connected to the top of a corresponding extractor 11. One end of the first main connecting pipe 32 (the end away from the extractor 11) is connected to the VOC absorption unit.

[0128] The second connecting unit 4 includes a second branch connecting pipe and a second main connecting pipe. The second main connecting pipe and the second branch connecting pipe are one pipe each. Specifically, one end of the second branch connecting pipe is connected to one end of the second main connecting pipe, and the other end of the second branch connecting pipe is connected to the corresponding extractor 11 far away from the VOC absorption unit (i.e., the extractor 11 is connected at the far end). The other end of the second main connecting pipe is connected to the VOC absorption unit. The diameter of the second connecting unit 4 is smaller than that of the first connecting unit.

[0129] The VOC absorption unit is connected to the extractor 11 through the first connecting unit, and is configured to receive VOC gas containing volatile organic matter generated in the extractor 11, and recover the organic matter by water absorption. The VOC absorption unit is also connected to the extractor 11 through the second connecting unit 4, so that the residual gas after absorption returns to the extractor 11 through the second connecting unit 4.

[0130] In this embodiment, specifically, Figure 3 As shown, the VOC absorption unit includes a jet pump 23, a buffer tank 24 and a cooling device 22". The jet pump 23 is respectively connected to the cooling device 22" and the buffer tank 24. The jet pump 23 is also connected to the first main connecting pipe 32 of the first connecting unit. The jet pump 23 is configured to receive VOC gas containing volatile organic matter generated in the extractor 11, and receive water from the cooling device 22", and mix the VOC gas with the water from the cooling device 22", so that the organic matter and water vapor condense into droplets.

[0131] The droplets fall into the buffer tank 24. The buffer tank 24 is used to receive the droplets. Specifically, the droplets fall to the bottom of the buffer tank 24 by gravity, and are left to stand for stratification and liquid separation, and the organic matter (organic phase) and the water (aqueous phase) obtained by stratification are recovered, and the recovered organic matter can be recycled as a raw material for the organic extractant. The top of the buffer tank 24 is also connected to the top of the extractor 11 through the second connecting unit 4. The cooling device 22" is also connected to the bottom of the buffer tank 24 through a pipeline, and the cooling device 22" is also configured to receive the water obtained after stratification in the buffer tank 24, which is used to pass into the jet pump 32 to absorb the organic matter. No waste liquid is generated.

[0132] The rare earth extraction VOC treatment device of this embodiment does not involve any vacuum equipment.

[0133] The following describes a method for treating VOC gas generated during rare earth extraction using the rare earth extraction VOC treatment device of this embodiment, including the following steps:

[0134] (1) In the extractor 11, an organic extractant is used to extract the rare earth solution. During the extraction process, the VOC gas containing volatile organic matter generated flows from the extractor 11 to the VOC absorption unit, specifically, to the jet pump 23 of the VOC absorption unit;

[0135] (2) The jet pump 23 of the VOC absorption unit mixes the VOC gas containing volatile organic matter with water from the cooling device 22" to form droplets, which fall into the buffer tank 24 and are allowed to stand for stratification and liquid separation to recover the organic matter. The residual gas in the buffer tank 24 is returned to the extractor 11 through the second connecting unit 4.

[0136] like Figure 3 As shown, in this embodiment, a communicating vessel is formed between the extractor 11 and the buffer tank 24. In step (1), during the extraction process, the organic matter evaporates at the liquid surface of the extractor 11, and the VOCs content in the volatilized VOC gas is generally 1000-5000 mg / m 3 . In this embodiment, the organic extractant is a mixture of N235 and white oil, and the rare earth solution is a nitric acid rare earth solution. The volatile VOC gas is mainly white oil, and there is a small amount of N235. In step (2), the jet pump 23 is used to efficiently mix the volatile VOC gas with low-temperature water (5-15°C), and the organic matter and water vapor condense into droplets and enter the buffer tank 24. The organic matter floats on the water phase and is used for extraction after recovery. The water phase continues to be recycled as water for the jet pump 23 through the cooling system. The gas that has not formed a liquid (i.e., residual gas) flows out of the buffer tank 24 and returns to the extractor 11 through the second connecting unit 4. The circulation volume of the gas in the system can be controlled by the jet flow rate of the jet pump 23 according to the size of the extractor 11 and the production temperature conditions, and the VOCs content of the residual gas after absorption (i.e., the residual gas after absorption by the jet pump 23) is controlled to be less than 500mg / m 3 , the low-concentration residual gas returns to the extractor 11 to balance the air pressure in the extractor 11 without exhaust gas emission.

[0137] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be conceived by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A rare earth extraction VOC treatment device, characterized in that: It includes an extraction unit, a VOC absorption unit, a first connecting unit and a second connecting unit; The extraction unit comprises an extractor, and the extractor is used for extracting the rare earth solution with an organic extractant; The VOC absorption unit is connected to the extractor through the first communication unit, and is configured to receive VOC gas containing volatile organic matter generated in the extractor, and recover the organic matter through water absorption; The VOC absorption unit is also connected to the extractor through the second connecting unit, so that the residual gas after absorption returns to the extractor through the second connecting unit; Wherein, no vacuum equipment is provided in the device.

2. The device according to claim 1, characterized in that The VOC absorption unit includes a spray tower and a refrigeration device; The lower part of the spray tower is connected to the top of the extractor through the first connecting unit; the spray tower is configured to receive VOC gas containing volatile organic matter generated in the extractor, and form droplets of the VOC gas by spraying water, thereby recovering the organic matter by static stratification; One side of the refrigeration equipment is connected to the top of the spray tower through a pipeline, and the other side is connected to the top of the extractor through the second connecting unit; the refrigeration equipment is configured to further freeze the residual organic matter in the residual gas after absorption in the spray tower to recover the organic matter, and the frozen residual gas returns to the extractor through the second connecting unit.

3. The device according to claim 1, characterized in that The VOC absorption unit includes a spray tower and a cooling device; The lower part of the spray tower is connected to the top of the extractor through the first connecting unit; the bottom and the upper part of the spray tower are also connected to the cooling device through pipelines respectively; the spray tower is configured to receive VOC gas containing volatile organic matter generated in the extractor, and receive water from the cooling device to form spray water, so that the organic matter and water vapor condense into droplets; The top of the spray tower is also connected to the top of the extractor through the second connecting unit; The cooling device is configured to spray water to the spray tower, and is also configured to receive water obtained after droplet stratification in the spray tower.

4. The device according to claim 1, characterized in that The VOC absorption unit includes a jet pump, a buffer tank and a cooling device; The jet pump is connected to the cooling device and the buffer tank respectively; the jet pump is also connected to the first communication unit and is configured to receive VOC gas containing volatile organic matter generated in the extractor and water from the cooling device, and mix the VOC gas with the water from the cooling device, so that the organic matter and water vapor condense into droplets; The buffer tank is used to receive the droplets and is configured to recover organic matter by static stratification; the top of the buffer tank is also connected to the top of the extractor through the second connecting unit; The cooling device is also connected to the bottom of the buffer tank through a pipeline, and the cooling device is also configured to receive water obtained after stratification in the buffer tank.

5. The device according to any one of claims 1 to 4, characterized in that: The extractor is provided in plurality, and the plurality of extractors are respectively connected in parallel with the VOC absorption unit through the first connecting unit.

6. The device according to claim 5, characterized in that The extractor is a box-type extractor.

7. The device according to claim 5, characterized in that The first connecting unit includes a first branch connecting tube and a first main connecting tube; the number of the first branch connecting tubes matches the number of the extractors, one end of the first branch connecting tube is respectively connected to the first main connecting tube, and the other end is respectively connected to the corresponding extractor; one end of the first main connecting tube is connected to the VOC absorption unit.

8. The device according to claim 7, characterized in that The second connecting unit includes a second branch connecting pipe and a second main connecting pipe; one end of the second branch connecting pipe is connected to the extractor far away from the VOC absorption unit, and the other end is connected to one end of the second main connecting pipe; the other end of the second main connecting pipe is connected to the VOC absorption unit.

9. A method for treating VOC gas generated during rare earth extraction by using the rare earth extraction VOC treatment device according to claim 1, characterized in that: The steps include: (1) In the extractor, a rare earth solution is extracted using an organic extractant; during the extraction process, VOC gas containing volatile organic matter is generated and flows from the extractor to the VOC absorption unit; (2) The VOC absorption unit recovers organic matter through water absorption, and the residual gas after absorption returns to the extractor through the second connecting unit.

10. The method according to claim 9, characterized in that The organic extractant comprises a first organic matter and a second organic matter; the first organic matter is selected from one of P507, P204, N235 and cyclohexane acid; the second organic matter is selected from at least one of kerosene, white oil and isooctyl alcohol; the VOCs content in the VOC gas is 1000-5000 mg / m 3 .

Images