A 1,500-ton uranium enrichment cascade lean material collecting and pressurizing device and method

Abstract

The present invention relates to the field of uranium enrichment cascade supply and withdrawal, and in particular to a 1,500-ton uranium enrichment cascade lean material receiving and pressurizing device and method. The device comprises two medium passages arranged in parallel between an inlet main pipeline and an outlet main pipeline; each medium passage comprises a large impeller magnetic suspension compressor and at least two small impeller magnetic suspension compressors connected in series; during operation, the frequency ratio of the large impeller magnetic suspension compressor, the front-stage small impeller magnetic suspension compressor and the rear-stage small impeller magnetic suspension compressor is 7~9:14~16:11~14; under abnormal working conditions, after frequency increase, the frequency ratio of the large impeller magnetic suspension compressor, the front-stage small impeller magnetic suspension compressor and the rear-stage small impeller magnetic suspension compressor is 2~4:3~5:2~4. Lean material receiving and pressurizing can be performed using the device. The present invention meets the requirements of the lean material receiving system of the 1,500-ton uranium enrichment cascade for flow rate and pressure increase, and has high continuous operation stability.

Description

Technical Field

[0001] The invention relates to the field of uranium enrichment cascade material supply and withdrawal, and in particular to a 1,500-ton uranium enrichment cascade lean material receiving and pressurizing device and method. Background Art

[0002] The existing uranium enrichment cascade lean material receiving system adopts a pressurized cooling method, in which the pressurization process of the working medium before entering the cooling container is the core of the entire process.

[0003] In the lean material receiving system of the uranium enrichment cascade, a pressurized cooling method is used to enable the working medium to condense from gas to solid and be continuously stored inside the lean material receiving container. In order to ensure the continuous and stable operation of the cascade and the continuity of the pressurized cooling receiving process, high requirements are usually placed on the inlet and outlet pressures of the pressurization system, and the temperature of the delivery pipeline is controlled to ensure that the pressurized working medium can still flow in the pipeline in a gaseous state.

[0004] For the pressurization of lean material collection in the 1,500-ton uranium enrichment cascade, the main process difficulty comes from the pressurization of large flow media and the continuous and stable operation of the entire system. On the one hand, as the production line capacity increases exponentially, the system flow increases exponentially, and it is necessary to select a suitable pressurization method to ensure the efficiency of collecting materials; on the other hand, since the system has a decisive influence on the continuous and stable operation of the cascade system, once the system fails, the entire cascade system will face the risk of complete shutdown, and it is necessary to select a suitable pressurization method to ensure the continuity of collecting materials.

[0005] In the existing pressurized cooling process, a booster is usually used as the front stage and a Roots pump is used as the back stage. Through two pressure increases, the pressure of the working medium is increased by one order of magnitude, that is, the ratio of the outlet pressure to the inlet pressure is 15~20:1 to meet the material collection requirements.

[0006] Roots pump is a mechanical vacuum pump with a pair of synchronously rotating high-speed sole-shaped rotors. It cannot be pumped alone and has no internal compression, so the compression ratio is usually very low, so a fore-stage pump is required. The fore-stage pump needs to be equipped with oil seals, water rings, etc. to discharge directly into the atmosphere. The ultimate vacuum of Roots pump depends not only on the structure and manufacturing accuracy of the pump itself, but also on the ultimate vacuum of the fore-stage pump.

[0007] The booster and Roots pump are connected in series for pressurization. The booster needs to be regularly refueled and maintained to ensure the lubrication effect and sealing of the booster. The added lubricating oil will come into contact with the working medium, thus affecting the purity of the working medium. The Roots pump is a positive displacement pump, and its working compression components require high-precision coordination. However, powder will be produced in the uranium enrichment cascade, which will periodically cause the Roots pump to get stuck, affecting the continuous operation of the cascade system; and it has high power consumption and high operating noise. Furthermore, the Roots pumps used in the uranium enrichment industry are imported pumps, which have a "bottleneck" problem.

[0008] Moreover, after the scale of a single production line is expanded, the lean material flow rate is increased to more than 1.5 times the original amount, and the original pressurization means cannot meet the lean material collection needs of cascades of 1,500 tons and larger. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a 1,500-ton uranium enrichment cascade lean material receiving and pressurizing device and method, which can meet the requirements of the 1,500-ton uranium enrichment cascade lean material receiving system for flow rate and pressure increase and has high continuous operation stability.

[0010] The present invention provides a 1,500-ton uranium enrichment cascade lean material receiving and pressurizing device, wherein a first medium passage and a second medium passage are arranged between an inlet main pipeline and an outlet main pipeline, and the first medium passage and the second medium passage are connected in parallel;

[0011] Each medium passage includes a large impeller magnetic suspension compressor and at least two small impeller magnetic suspension compressors connected in series; the inlet pressure of the inlet main pipeline is not higher than 1.33 kPa, and the outlet pressure of the outlet main pipeline is not higher than 20 kPa;

[0012] During operation, under the condition of maintaining the lowest overall power, the frequency of the front-stage small impeller magnetic suspension compressor is higher than the frequency of the rear-stage small impeller magnetic suspension compressor; the frequency ratio of the large impeller magnetic suspension compressor, the front-stage small impeller magnetic suspension compressor and the rear-stage small impeller magnetic suspension compressor is 7~9:14~16:11~14;

[0013] Under abnormal working conditions, the magnetic levitation compressors are frequency-upgraded at the same time, and the frequency increase value of the front-stage small-impeller magnetic levitation compressor is higher than that of the rear-stage small-impeller magnetic levitation compressor; after frequency upgradation, the frequency ratio of the large-impeller magnetic levitation compressor, the front-stage small-impeller magnetic levitation compressor and the rear-stage small-impeller magnetic levitation compressor is 2~4:3~5:2~4.

[0014] In a specific embodiment of the present invention, it further comprises: a third medium passage; a fourth medium passage;

[0015] The third medium passage is connected in parallel with the first medium passage;

[0016] The third medium passage includes a large impeller magnetic suspension compressor and at least two small impeller magnetic suspension compressors connected in series;

[0017] The fourth medium passage is connected in parallel with the first medium passage;

[0018] The fourth medium passage includes a large-impeller magnetic suspension compressor and at least two small-impeller magnetic suspension compressors connected in series.

[0019] In a specific embodiment of the present invention, the inlet pipe diameter of the large-impeller magnetic levitation compressor is not less than DN300; the inlet pipe diameter of the small-impeller magnetic levitation compressor is not less than DN150.

[0020] In a specific embodiment of the present invention, the medium flow rate of the inlet main pipeline is 100-120 g / s.

[0021] In a specific embodiment of the present invention, all pipes are wrapped with electric heating tapes on the outside, and the heating temperature is 55-65°C.

[0022] In a specific embodiment of the present invention, the maximum compression ratio of the small impeller magnetic levitation compressor is 10.

[0023] In a specific embodiment of the present invention, during operation, the frequency ratio of the large impeller magnetic suspension compressor, the front-stage small impeller magnetic suspension compressor and the rear-stage small impeller magnetic suspension compressor is 8:15:12;

[0024] Under abnormal working conditions, after frequency increase, the frequency ratio of the large-impeller magnetic levitation compressor, the front-stage small-impeller magnetic levitation compressor and the rear-stage small-impeller magnetic levitation compressor is 2:4:3.

[0025] The present invention also provides a method for collecting and pressurizing lean materials in a 1,500-ton uranium enrichment cascade, comprising the following steps:

[0026] Step S1: setting a first medium passage, a second medium passage, a third medium passage and a fourth medium passage in parallel between the inlet main pipeline and the outlet main pipeline;

[0027] Each medium passage includes a large-impeller magnetic suspension compressor and at least two small-impeller magnetic suspension compressors connected in series;

[0028] Step S2: collecting and pressurizing the lean material of the uranium enrichment cascade, the first medium passage and the second medium passage work synchronously, the third medium passage is in standby mode, and the fourth medium passage is used for maintenance;

[0029] The inlet pressure of the inlet main pipeline is controlled to be no higher than 1.33 kPa, and the outlet pressure of the outlet main pipeline is controlled to be no higher than 20 kPa;

[0030] During operation, under the condition of maintaining the lowest overall power, the frequency of the front-stage small impeller magnetic suspension compressor is higher than the frequency of the rear-stage small impeller magnetic suspension compressor; the frequency ratio of the large impeller magnetic suspension compressor, the front-stage small impeller magnetic suspension compressor and the rear-stage small impeller magnetic suspension compressor is 7~9:14~16:11~14;

[0031] Under abnormal working conditions, the magnetic levitation compressors are frequency-upgraded at the same time, and the frequency increase value of the front-stage small-impeller magnetic levitation compressor is higher than that of the rear-stage small-impeller magnetic levitation compressor; after frequency upgradation, the frequency ratio of the large-impeller magnetic levitation compressor, the front-stage small-impeller magnetic levitation compressor and the rear-stage small-impeller magnetic levitation compressor is 2~4:3~5:2~4.

[0032] In a specific embodiment of the present invention, during the operation, the frequency ratio of the large impeller magnetic suspension compressor, the front-stage small impeller magnetic suspension compressor and the rear-stage small impeller magnetic suspension compressor is 8:15:12;

[0033] Under abnormal working conditions, after frequency increase, the frequency ratio of the large-impeller magnetic levitation compressor, the front-stage small-impeller magnetic levitation compressor and the rear-stage small-impeller magnetic levitation compressor is 2:4:3.

[0034] In a specific embodiment of the present invention, the medium flow rate of the inlet main pipeline is 100-120 g / s.

[0035] Compared with the prior art, the 1,500-ton uranium enrichment cascade lean material collecting and pressurizing device and method of the present invention has the following beneficial effects:

[0036] (1) The entire pressurizing device is equipped with multiple medium passages, and each medium passage is combined with the frequency coordination of multiple magnetic suspension compressors to meet the flow and pressure increase requirements of the 1,500-ton uranium enrichment cascade lean material receiving system; it has high continuous operation stability;

[0037] (2) The use of multiple magnetic suspension compressors to cooperate completely replaces the pressurization method of Roots pumps and booster machines. The equipment is oil-free and maintenance-free, achieving the effect of no pollution to the working medium and maintenance-free operation;

[0038] (3) It is not sensitive to the influence of powder, achieving the technical effect of long-term safe, stable and continuous operation;

[0039] (4) The use of magnetic levitation compressor technology achieves the technical effects of low power consumption and low noise;

[0040] (5) The use of magnetic levitation compressor technology has solved the "bottleneck" problem and achieved autonomous and controllable technical effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1A schematic diagram showing the structure of a 1,500-ton uranium enrichment cascade lean material receiving and pressurizing device;

[0042] In the figure, 1 is a large impeller magnetic levitation compressor, 2 is a front-stage small impeller magnetic levitation compressor, 3 is a rear-stage small impeller magnetic levitation compressor, 4 is an inlet main pipeline, and 5 is an outlet main pipeline. DETAILED DESCRIPTION

[0043] In order to further understand the present invention, the embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the present invention.

[0044] In the present invention, a magnetic levitation compressor is used as a pressurizing unit, and through a specific series-parallel design, the requirements for flow rate and pressure increase of a 1,500-ton uranium enrichment cascade lean material receiving system are met.

[0045] In the field of uranium enrichment, the extraction of lean materials requires large flow rate and high pressure ratio.

[0046] The embodiment of the present invention discloses a 1,500-ton uranium enrichment cascade lean material receiving and pressurizing device, such as Figure 1 As shown, a first medium passage and a second medium passage are provided between the inlet main pipeline 4 and the outlet main pipeline 5, and the first medium passage and the second medium passage are connected in parallel;

[0047] Each medium passage includes a large impeller magnetic suspension compressor 1 and at least two small impeller magnetic suspension compressors connected in series;

[0048] The large-impeller magnetic suspension compressor 1 is arranged before the small-impeller magnetic suspension compressor.

[0049] The inlet pipe diameter of the large-impeller magnetic suspension compressor 1 is not less than DN300; the inlet pipe diameter of the small-impeller magnetic suspension compressor is not less than DN150.

[0050] Since the entire running pipeline for lean material extraction is long, the pressure at the front and rear ends of the pipeline may change, and the medium may have sonic flow problems, resulting in the medium flow in the pipeline failing to meet the requirements;

[0051] The inlet pipe diameter of the small impeller magnetic suspension compressor is small. Under the working conditions of large flow and high pressure ratio, the pressure at the inlet of the small impeller magnetic suspension compressor will drop sharply, thus reaching the sonic speed condition, so that the flow rate that the series-connected small impeller magnetic suspension compressor can transport is limited;

[0052] Therefore, the series connection of the large impeller magnetic suspension compressor 1 and the small impeller magnetic suspension compressor effectively avoids the limitation of the sonic flow and provides a suitable working environment for the small impeller magnetic suspension compressor;

[0053] Taking into account the compression requirements, reliability and cost, it is preferred to connect two small impeller magnetic levitation compressors in series.

[0054] The maximum compression ratio of each small impeller magnetic levitation compressor is 10.

[0055] The front-stage small-impeller magnetic suspension compressor 2 is located between the large-impeller magnetic suspension compressor 1 and the rear-stage small-impeller magnetic suspension compressor 3, and the rear-stage small-impeller magnetic suspension compressor 3 is close to the outlet main pipeline 5;

[0056] In order to make the whole device run stably and avoid unnecessary shutdown, it is preferred to further include: a third medium passage and a fourth medium passage;

[0057] The third medium passage, the fourth medium passage, and the second medium passage are all connected in parallel with the first medium passage.

[0058] The third medium passage is for backup, and the fourth medium passage is for maintenance;

[0059] The structure of the third medium passage is the same as that of the first medium passage or the second medium passage, and includes a large impeller magnetic suspension compressor 1 and at least two small impeller magnetic suspension compressors connected in series;

[0060] The structure of the fourth medium passage is the same as that of the first medium passage or the second medium passage, and includes a large-impeller magnetic suspension compressor 1 and at least two small-impeller magnetic suspension compressors connected in series.

[0061] The inlet pressure of the inlet main pipeline 4 is not higher than 1.33 kPa, and the outlet pressure of the outlet main pipeline 5 is not higher than 20 kPa, so as to avoid the subsequent connection hose from rupturing due to excessive outlet pressure;

[0062] The medium flow rate of the inlet main pipeline 4 is 100-120 g / s.

[0063] During the operation of the series-connected small-impeller magnetic levitation compressor, the coupling of the operating frequency is the key to ensuring the process operation.

[0064] Operating frequency coupling needs to obey the following principles:

[0065] 1) The power consumption balance principle: during operation, it is necessary to ensure that the power of the two small impeller magnetic suspension compressors in series is basically the same, so as to ensure the lowest overall power;

[0066] 2) The frequency is high at the front and low at the back. During operation, the frequency of the front-stage small impeller magnetic suspension compressor 2 should be higher than the frequency of the rear-stage small impeller magnetic suspension compressor 3;

[0067] In the centrifugal cascade lean material collection system, there are two main purposes for designing a pressurizing device. One is to extract the lean material generated by the cascade from the cascade in time to prevent the entire cascade from being closed due to excessive pressure at the end of the cascade; the other is to collect the working material from gas to solid by pressurized cooling at the end of the cascade. There are many factors that affect the operating state of the pressurizing device, including the physical and chemical properties of the working medium, the working environment temperature, the length of the pipeline, the radius of the pipeline, the state of the collection container, etc. In the actual frequency determination process, it is difficult to use the established formula to derive and determine the frequency of the large impeller magnetic levitation compressor 1, the front-stage small impeller magnetic levitation compressor 2, and the rear-stage small impeller magnetic levitation compressor 3, and it is usually carried out by experimental methods.

[0068] The test method is divided into the following steps:

[0069] (1) When the magnetic levitation compressor is put into use for the first time, the three magnetic levitation compressors are first started at a lower frequency (such as 20Hz for the large impeller magnetic levitation compressor and 30Hz for the small impeller magnetic levitation compressor) under vacuum;

[0070] (2) Then, a portion of the working substance is slowly charged into the passage;

[0071] (3) As the medium is filled, observe the pressure ratio between the outlet and the inlet of the passage to ensure that the inlet pressure is ≤1.33 kPa and the outlet pressure is ≤20 kPa;

[0072] (4) If the conditions cannot be met, the frequency of each magnetic levitation compressor is appropriately increased to meet the control conditions;

[0073] (5) Special attention should be paid to the pressure of the inlet main pipeline 4. If it is found that the pressure of the main pipeline 4 does not decrease when the frequencies of the front-stage small-impeller magnetic suspension compressor 2 and the rear-stage small-impeller magnetic suspension compressor 3 are increased, the frequency of the large-impeller magnetic suspension compressor 1 should be increased to avoid limiting the flow rate of the sonic flow;

[0074] (6) When the flow rate of the circuit reaches the maximum flow rate, observe the power of the front-stage small impeller magnetic levitation compressor 2 and the rear-stage small impeller magnetic levitation compressor 3. By adjusting the frequencies of the two-stage small impeller magnetic levitation compressors respectively, the power of the front-stage small impeller magnetic levitation compressor 2 and the rear-stage small impeller magnetic levitation compressor 3 are made consistent while ensuring that the pressure ratio between the outlet and the inlet remains unchanged and that the inlet pressure is ≤1.33 kPa and the outlet pressure is ≤20 kPa. During the adjustment process, attention should be paid to the phenomenon in (5) and it should be handled according to the method in (5).

[0075] Through the above test steps, it can be determined that during the operation, that is, the first medium passage and the second medium passage are operating normally, for any medium passage, under the condition of maintaining the lowest overall power, the frequency of the front-stage small impeller magnetic levitation compressor 2 is higher than the frequency of the rear-stage small impeller magnetic levitation compressor 3; the frequency ratio of the large impeller magnetic levitation compressor 1, the front-stage small impeller magnetic levitation compressor 2 and the rear-stage small impeller magnetic levitation compressor 3 is 7~9:14~16:11~14; preferably 8:15:12; at this time, the total power of each magnetic levitation compressor connected in series is the lowest and meets the requirement of outlet pressure ≤20kPa.

[0076] For abnormal working conditions, the test process is similar to that under normal working conditions, except that:

[0077] (1) It is necessary to manually adjust the flow of dual channels to a single channel;

[0078] (2) Simultaneously increase the frequency of the three-stage magnetic levitation compressor to ensure that the control conditions of inlet pressure ≤ 1.33 kPa and outlet pressure ≤ 20 kPa are met;

[0079] (3) When all lean materials pass through a single passage, the power of the large-impeller magnetic levitation compressor 1, the front-stage small-impeller magnetic levitation compressor 2 and the rear-stage small-impeller magnetic levitation compressor 3 is observed. By adjusting the frequencies of the three-stage magnetic levitation compressors respectively, the power of the front-stage small-impeller magnetic levitation compressor 2 and the rear-stage small-impeller magnetic levitation compressor 3 are made consistent while ensuring that the pressure ratio between the outlet and the inlet remains unchanged and that the inlet pressure is ≤1.33 kPa and the outlet pressure is ≤20 kPa. While avoiding the occurrence of sonic flow due to the large-impeller magnetic levitation compressor 1 being too low in frequency, the power of the front-stage small-impeller magnetic levitation compressor 2 and the rear-stage small-impeller magnetic levitation compressor 3 are made consistent.

[0080] Through the above steps, it can be determined that under abnormal working conditions, that is, only one of the first medium passage and the second medium passage is in operation, the magnetic levitation compressors are up-converted at the same time, and the frequency increase value of the front-stage small impeller magnetic levitation compressor 2 is higher than that of the rear-stage small impeller magnetic levitation compressor 3; after the up-conversion, the frequency ratio of the large impeller magnetic levitation compressor 1, the front-stage small impeller magnetic levitation compressor 2 and the rear-stage small impeller magnetic levitation compressor 3 is 2~4:3~5:2~4, preferably 2:4:3.

[0081] In the 1,500-ton uranium enrichment cascade lean material receiving and pressurizing device of the present invention, electric heating belts are wound around the outside of all pipelines, and the heating temperature is 55-65° C. to prevent gas condensation in the pipelines.

[0082] The embodiment of the present invention also discloses a method for collecting and pressurizing lean materials in a 1,500-ton uranium enrichment cascade, comprising the following steps:

[0083] Step S1: a first medium passage, a second medium passage, a third medium passage and a fourth medium passage are provided in parallel between the inlet main pipeline 4 and the outlet main pipeline 5;

[0084] Each medium passage includes a large impeller magnetic suspension compressor 1 and at least two small impeller magnetic suspension compressors connected in series;

[0085] Step S2: collecting and pressurizing the lean material of the uranium enrichment cascade, the first medium passage and the second medium passage work synchronously, the third medium passage is in standby mode, and the fourth medium passage is used for maintenance;

[0086] The inlet pressure of the inlet main pipeline 4 is controlled to be no higher than 1.33 kPa, and the outlet pressure of the outlet main pipeline 5 is controlled to be no higher than 20 kPa;

[0087] The medium flow rate of the inlet main pipeline 4 is 100-120 g / s;

[0088] During operation, under the condition of maintaining the lowest overall power, the frequency of the front-stage small impeller magnetic suspension compressor 2 is higher than the frequency of the rear-stage small impeller magnetic suspension compressor 3; the frequency ratio of the large impeller magnetic suspension compressor 1, the front-stage small impeller magnetic suspension compressor 2 and the rear-stage small impeller magnetic suspension compressor 3 is 7~9:14~16:11~14; preferably 8:15:12;

[0089] Under abnormal working conditions, the magnetic levitation compressors are frequency-upgraded at the same time, and the frequency increase value of the front-stage small-impeller magnetic levitation compressor 2 is higher than that of the rear-stage small-impeller magnetic levitation compressor 3; after frequency upgradation, the frequency ratio of the large-impeller magnetic levitation compressor 1, the front-stage small-impeller magnetic levitation compressor 2 and the rear-stage small-impeller magnetic levitation compressor 3 is 2~4:3~5:2~4, preferably 2:4:3.

[0090] The pressurized material collection device for the 1,500-ton uranium enrichment cascade lean material collection system of the present invention was used to perform pressurized material collection and was operated continuously for 1,000 hours with stable operation and flow and pressure increases meeting requirements.

[0091] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0092] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A 1,500-ton uranium enrichment cascade lean material receiving and pressurizing device, characterized in that: A first medium passage and a second medium passage are arranged between the inlet main pipeline and the outlet main pipeline, and the first medium passage and the second medium passage are connected in parallel; Each medium passage includes a large impeller magnetic suspension compressor and at least two small impeller magnetic suspension compressors connected in series; the inlet pressure of the inlet main pipeline is not higher than 1.33 kPa, and the outlet pressure of the outlet main pipeline is not higher than 20 kPa; During operation, under the condition of maintaining the lowest overall power, the frequency of the front-stage small impeller magnetic suspension compressor is higher than the frequency of the rear-stage small impeller magnetic suspension compressor; the frequency ratio of the large impeller magnetic suspension compressor, the front-stage small impeller magnetic suspension compressor and the rear-stage small impeller magnetic suspension compressor is 7-9:14-16:11-14; Under abnormal working conditions, the magnetic suspension compressors are frequency-upgraded at the same time, and the frequency increase value of the front-stage small-impeller magnetic suspension compressor is higher than that of the rear-stage small-impeller magnetic suspension compressor; after frequency-upgrading, the frequency ratio of the large-impeller magnetic suspension compressor, the front-stage small-impeller magnetic suspension compressor and the rear-stage small-impeller magnetic suspension compressor is 2-4:3-5:2-4; All pipes are wrapped with electric heating tapes on the outside, with a heating temperature of 55 to 65°C.

2. The 1,500-ton uranium enrichment cascade lean material receiving and pressurizing device according to claim 1, characterized in that: Also includes: a third medium passage; a fourth medium passage; The third medium passage is connected in parallel with the first medium passage; The third medium passage includes a large impeller magnetic suspension compressor and at least two small impeller magnetic suspension compressors connected in series; The fourth medium passage is connected in parallel with the first medium passage; The fourth medium passage includes a large-impeller magnetic suspension compressor and at least two small-impeller magnetic suspension compressors connected in series.

3. The 1,500-ton uranium enrichment cascade lean material receiving and pressurizing device according to claim 1, characterized in that: The inlet pipe diameter of the large-impeller magnetic levitation compressor is not less than DN300; the inlet pipe diameter of the small-impeller magnetic levitation compressor is not less than DN150.

4. The 1,500-ton uranium enrichment cascade lean material receiving and pressurizing device according to claim 1, characterized in that: The medium flow rate of the inlet main pipeline is 100-120 g / s.

5. The 1,500-ton uranium enrichment cascade lean material receiving and pressurizing device according to claim 1, characterized in that: The maximum compression ratio of the small impeller magnetic suspension compressor is 10.

6. The 1,500-ton uranium enrichment cascade lean material receiving and pressurizing device according to claim 1, characterized in that: During operation, the frequency ratio of the large impeller magnetic suspension compressor, the front-stage small impeller magnetic suspension compressor and the rear-stage small impeller magnetic suspension compressor is 8:15:12; Under abnormal working conditions, after frequency increase, the frequency ratio of the large-impeller magnetic levitation compressor, the front-stage small-impeller magnetic levitation compressor and the rear-stage small-impeller magnetic levitation compressor is 2:4:

3.

7. A method for collecting and pressurizing lean materials in a 1,500-ton uranium enrichment cascade, characterized in that: The following steps are involved: Step S1: setting a first medium passage, a second medium passage, a third medium passage and a fourth medium passage in parallel between the inlet main pipeline and the outlet main pipeline; Each medium passage includes a large-impeller magnetic suspension compressor and at least two small-impeller magnetic suspension compressors connected in series; Step S2: collecting and pressurizing the lean material of the uranium enrichment cascade, the first medium passage and the second medium passage work synchronously, the third medium passage is in standby mode, and the fourth medium passage is used for maintenance; The inlet pressure of the inlet main pipeline is controlled to be no higher than 1.33 kPa, and the outlet pressure of the outlet main pipeline is controlled to be no higher than 20 kPa; During operation, under the condition of maintaining the lowest overall power, the frequency of the front-stage small impeller magnetic suspension compressor is higher than the frequency of the rear-stage small impeller magnetic suspension compressor; the frequency ratio of the large impeller magnetic suspension compressor, the front-stage small impeller magnetic suspension compressor and the rear-stage small impeller magnetic suspension compressor is 7-9:14-16:11-14; Under abnormal working conditions, the magnetic levitation compressors are frequency-upgraded at the same time, and the frequency increase value of the front-stage small-impeller magnetic levitation compressor is higher than that of the rear-stage small-impeller magnetic levitation compressor; after frequency upgradation, the frequency ratio of the large-impeller magnetic levitation compressor, the front-stage small-impeller magnetic levitation compressor and the rear-stage small-impeller magnetic levitation compressor is 2~4:3~5:2~4.

8. The method for collecting and pressurizing lean materials in a 1,500-ton uranium enrichment cascade according to claim 7, characterized in that: During the operation, the frequency ratio of the large impeller magnetic suspension compressor, the front-stage small impeller magnetic suspension compressor and the rear-stage small impeller magnetic suspension compressor is 8:15:12; Under abnormal working conditions, after frequency increase, the frequency ratio of the large-impeller magnetic levitation compressor, the front-stage small-impeller magnetic levitation compressor and the rear-stage small-impeller magnetic levitation compressor is 2:4:

3.

9. The method for collecting and pressurizing lean materials in a 1,500-ton uranium enrichment cascade according to claim 7, characterized in that: The medium flow rate of the inlet main pipeline is 100-120 g / s.

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