Method for preparing ferric phosphate and by-product fertilizer using ammonium phosphate

Abstract

To provide a method of producing ferric phosphate and a byproduct fertilizer using ammonium phosphate.SOLUTION: A byproduct fertilizer production granulator used in the method, comprises a housing comprising a storage space. The storage space of the housing is successively divided into a granulation chamber, a screening chamber and a material storage chamber from top to bottom. A blow assembly is provided between the granulation chamber and the screening chamber. A vibration screen reciprocally movable in the vertical direction is provided between the screening chamber and the material storage chamber. A material discharge pipe is connected to the material storage chamber. A top cap is detachably attached on the upper end of the housing. A plurality of sprayers are provided on the top cap to spray a molten material into the housing. An exhaust pipe is connected to the top cap. The blow assembly includes mutually connected distribution pipes arranged in a zigzag shape. A plurality of air-ducts are connected to the upper end of the distribution pipes. An air introduction pipe is connected to one side of a distribution pipe.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the technical field of ferric phosphate production, and in particular to a method for preparing ferric phosphate and by-product fertilizers using ammonium phosphate. [Background technology]

[0002] In the process of preparing ferric phosphate using a phosphate concentrate, it is necessary to remove acid-insoluble matter by acid decomposition of the phosphate concentrate. However, existing acid decomposition methods have a problem in that the removal rate of acid-insoluble matter is low. The remaining acid-insoluble matter not only affects the quality of the subsequent ferric phosphate, but also affects the quality of the nitrate phosphate fertilizer produced from the by-product preparation of ferric phosphate. Therefore, there is an urgent need to develop a method for increasing the removal rate of acid-insoluble matter in phosphate concentrate. Summary of the Invention [Problem to be solved by the invention]

[0003] Based on the technical problems of the background art, the present invention proposes a method for preparing ferric phosphate and by-product fertilizer with ammonium phosphate. The method for preparing ferric phosphate using ammonium phosphate according to the present invention comprises the steps of: S11: Decomposing the phosphate concentrate with nitric acid, and adding an antifoaming agent during the decomposition process to defoam the mixture. After the decomposition, filtering and removing the acid insoluble matter to obtain a first solution; S12: adding sulfuric acid to the first solution in S11 to react with it, and after the reaction, filtering and removing calcium sulfate precipitate to obtain a crude phosphoric acid solution; S13: Adding ammonia to the crude phosphoric acid solution in S12 to carry out a neutralization reaction, and filtering after the reaction to obtain precipitate A and a second solution; S14: Adding an iron source to the second solution in S13 to react, and filtering after the reaction to obtain precipitate B iron phosphate and a by-product third solution.

[0004] Preferably, the concentration of the nitric acid solution in S11 is 55-65%, and the ratio of the mass of the nitric acid to the mass of the phosphate concentrate is 1.2-1.4:1.

[0005] Preferably, the antifoaming agent in S11 contains polysiloxane, polyoxyethylene glycol, and lauryl polyoxyethylene ether in a mass ratio of 1:0.5-1.5:0.5-1.5.

[0006] Preferably, the concentration of sulfuric acid in the S12 is 98%, and the amount of the sulfuric acid is 90-96% of the theoretical amount of calcium in the frozen mother liquor.

[0007] Preferably, the amount of ammonia added in S13 is 105-110% of the theoretical amount of ammonia required for forming ammonium phosphate in the crude phosphoric acid solution, and the reaction pH is 7-8.

[0008] Preferably, in S14, the iron source is one or more of iron powder, iron oxide, ferrous oxide, or ferric nitrate, and the amount of the iron source added is 90 to 95% of the theoretical amount required to completely react with the phosphoric acid in the second solution.

[0009] The method for preparing ferric phosphate by-product preparation fertilizer with ammonium phosphate using the above method provided by the present invention includes the steps of mixing, concentrating and melting the precipitate A in S13 and the by-product third solution in S14, and granulating the molten material with a granulator to obtain nitrate phosphate fertilizer.

[0010] Preferably, the granulation apparatus comprises a housing having an accommodation space, the accommodation space of the housing being partitioned successively from top to bottom into a granulation chamber, a sieve chamber and a material storage chamber, a blow assembly is provided between the granulation chamber and the sieve chamber, a vibrating sieve capable of vertically reciprocating displacement is provided between the sieve chamber and the material storage chamber, a material discharge pipe is connected to the material storage chamber, a top cap is detachably provided at an upper end of the housing, a number of material spray devices for spraying molten material into the housing are provided in the top cap, and an exhaust pipe is further connected to the top cap.

[0011] Preferably, the blower assembly includes a number of distribution pipes arranged in a staggered pattern and connected to each other, a number of air ducts are connected to upper ends of the distribution pipes, and an air introduction pipe is further connected to one side of the distribution pipes.

[0012] Preferably, a vibrating telescopic rod for driving the reciprocating displacement of the vibrating sieve is connected to a lower end of the vibrating sieve, an elastic isolation sleeve is fitted on the outside of the vibrating telescopic rod, both ends of the elastic isolation sleeve are connected to a bottom of the housing and the lower end of the vibrating sieve, respectively, the elastic isolation sleeve includes a sliding sleeve slidably connected to a reference sleeve, and a spring is further provided between the reference sleeve and the sliding sleeve. Effect of the Invention

[0013] The present invention has the following beneficial effects: (1) In the present invention, a defoamer is added during the acid decomposition of phosphate concentrate to suppress the generation of foam. In the present invention, the defoamer made of polysiloxane, polyoxyethylene glycol, and lauryl polyoxyethylene ether not only has a certain synergistic effect on defoaming, but also improves the removal rate of acid-insoluble matter, thereby ensuring the quality of the ferric phosphate and nitrate phosphate fertilizer prepared thereafter.

[0014] (2) The present invention enables the sufficient reuse of the by-products of ferric phosphate preparation by mixing impurity metal phosphates (precipitate A) with a mixed solution (third solution) of ammonium nitrate and ammonium phosphate resulting from the preparation of ferric phosphate to prepare nitrate phosphate fertilizer.

[0015] (3) The granulating device of the present invention generates an ascending air current by the blow assembly, which acts on the falling material and rotates the material while it falls, thereby preparing fertilizer particles that are more uniform and have a smoother surface, and the material can be sieved by the vibrating sieve installed in the housing to obtain nitrate-phosphate fertilizer with the required particle size. [Brief description of the drawings]

[0016] [Figure 1] 1 is a flow chart of the method of preparing ferric phosphate and by-product fertilizer using ammonium phosphate as presented in the present invention. [Diagram 2] FIG. 2 is a structural schematic diagram of the granulation device proposed by the present invention. [Diagram 3] FIG. 2 is an enlarged view of a portion AA of the granulation device proposed by the present invention. [Figure 4] FIG. 2 is a structural schematic diagram of the blow assembly proposed by the present invention. [Explanation of symbols]

[0017] 1. Housing 2 Top Cap 3. Exhaust pipe 4 Material spraying device 5 Granulation chamber 6 Blow Assembly 7 Vibrating sieve 8 Elastic isolation sleeve 9. Vibrating Telescopic Rod 10 Material discharge pipe 11 Material Storage Room 12 Sieve Room 13 Air intake tube 14 Reference sleeve 15 Spring 16 Sliding sleeve 17 Distribution piping 18 Air duct DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The components of the phosphate concentrates used in the examples of the present invention were measured and the results are shown in Table 1.

[0019] [Table 1]

[0020] Example 1 The method for preparing ferric phosphate using ammonium phosphate according to the present invention includes the following steps: S11: Decompose phosphate concentrate with nitric acid, and add antifoaming agent during the decomposition process to defoam. After decomposition, filter and remove acid insolubles to obtain a first solution, the concentration of nitric acid solution is 60%, the mass ratio of the nitric acid to the phosphate concentrate is 1.3:1, the antifoaming agent includes polysiloxane, polyoxyethylene glycol, lauryl polyoxyethylene ether, and the mass ratio of the antifoaming agent is 1:1:1, and the amount of the antifoaming agent is 1% of the amount of the phosphate concentrate. S12: Add sulfuric acid to the first solution in S11 to react, and after the reaction, filter and remove calcium sulfate precipitate to obtain a crude phosphoric acid solution, in which the concentration of sulfuric acid is 98%, and the amount of said sulfuric acid is 93% of the theoretical amount of calcium in the frozen mother liquor. S13: Ammonia is added to the crude phosphoric acid solution in S12 to carry out a neutralization reaction, and after the reaction, it is filtered to obtain precipitate A and a second solution, the amount of ammonia added is 108% of the theoretical value of ammonia required for the formation of ammonium phosphate in the crude phosphoric acid solution, and the reaction pH is 7.5. S14: Add an iron source to the second solution in S13 to react, and filter after reaction to obtain precipitate B ferric phosphate and by-product a third solution, the iron source is ferrous oxide, and the amount of said iron source added is 92% of the theoretical amount required to completely react with the phosphoric acid in the second solution.

[0021] Example 2 The method for preparing ferric phosphate using ammonium phosphate according to the present invention includes the following steps: S11: Decompose phosphate concentrate with nitric acid, and add antifoaming agent during the decomposition process to defoam. After decomposition, filter and remove acid insolubles to obtain a first solution, the concentration of nitric acid solution is 55%, the mass ratio of the nitric acid to the phosphate concentrate is 1.2:1, the antifoaming agent contains polysiloxane, polyoxyethylene glycol, lauryl polyoxyethylene ether, and the mass ratio of the antifoaming agent is 1:0.5:0.5, and the amount of the antifoaming agent is 1% of the amount of the phosphate concentrate. S12: Add sulfuric acid to the first solution in S11 to react, and after the reaction, filter and remove calcium sulfate precipitate to obtain a crude phosphoric acid solution, in which the concentration of sulfuric acid is 98%, and the amount of said sulfuric acid is 90% of the theoretical amount of calcium in the frozen mother liquor. S13: Ammonia is added to the crude phosphoric acid solution in S12 to carry out a neutralization reaction, and after the reaction, it is filtered to obtain precipitate A and a second solution, the amount of ammonia added is 105% of the theoretical value of ammonia required for the formation of ammonium phosphate in the crude phosphoric acid solution, and the reaction pH is 7. S14: Add an iron source to the second solution in S13 to react, and filter after reaction to obtain precipitate B ferric phosphate and by-product, a third solution, the iron source is ferric oxide, and the amount of said iron source added is 90% of the theoretical amount required to completely react with the phosphoric acid in the second solution.

[0022] Example 3 The method for preparing ferric phosphate using ammonium phosphate according to the present invention includes the following steps: S11: Decompose phosphate concentrate with nitric acid, and add antifoaming agent during the decomposition process to defoam. After decomposition, filter and remove acid insolubles to obtain a first solution, the concentration of nitric acid solution is 65%, the mass ratio of the nitric acid to the phosphate concentrate is 1.4:1, the antifoaming agent includes polysiloxane, polyoxyethylene glycol, lauryl polyoxyethylene ether in a mass ratio of 1:1.5:1.5, and the amount of antifoaming agent is 1% of the mass of the phosphate concentrate. S12: Add sulfuric acid to the first solution in S11 to react, and after the reaction, filter and remove calcium sulfate precipitate to obtain a crude phosphoric acid solution, in which the concentration of sulfuric acid is 98%, and the amount of said sulfuric acid is 96% of the theoretical amount of calcium in the frozen mother liquor. S13: Ammonia is added to the crude phosphoric acid solution in S12 to carry out a neutralization reaction, and after the reaction, it is filtered to obtain precipitate A and a second solution, the amount of ammonia added is 110% of the theoretical value of ammonia required to form ammonium phosphate in the crude phosphoric acid solution, and the reaction pH is 8. S14: Add an iron source to the second solution in S13 to react, and filter after reaction to obtain precipitate B ferric phosphate and by-product third solution, the iron source is a mixture of iron powder and iron oxide, and the amount of said iron source added is 95% of the theoretical amount required to completely react with the phosphoric acid in the second solution.

[0023] Example 4 The method of preparing fertilizer from the by-product of ferric phosphate with ammonium phosphate using the above method proposed by the present invention includes the steps of mixing, concentrating and melting the precipitate A in S13 and the by-product third solution in S14, and granulating the molten material by a granulator to obtain nitrate phosphate fertilizer.

[0024] 2 to 4, the granulation apparatus of the present invention includes a housing 1 having a storage space, and the storage space of the housing 1 is partitioned in order from top to bottom into a granulation chamber 5, a sieve chamber 12, and a material storage chamber 11. A blow assembly 6 is provided between the granulation chamber 5 and the sieve chamber 12, and a vertically reciprocating vibrating sieve 7 is provided between the sieve chamber 12 and the material storage chamber 11. A material discharge pipe 10 is connected to the material storage chamber 11. A top cap 2 is detachably provided at the upper end of the housing 1. A number of material spray devices 4 are provided on the top cap 2 to spray molten material into the housing 1. The material spray devices achieve atomization of the material, and conventional technology can be used. An exhaust pipe 3 is further connected to the top cap 2, and the exhaust pipe can be connected to an exhaust treatment device to reduce environmental pollution.

[0025] Specifically, the blower assembly 6 includes a number of distribution pipes 17 arranged in a staggered pattern and connected to each other, a number of blower pipes 18 are connected to the upper ends of the distribution pipes 17, and an air inlet pipe 13 is further connected to one side of the distribution pipes 17, and the gas in the air inlet pipe is an inert gas.

[0026] Furthermore, a vibrating telescopic rod 9 for driving the reciprocating displacement of the vibrating sieve 7 is connected to the lower end of the vibrating sieve 7, and an elastic isolating sleeve 8 is fitted onto the outside of the vibrating telescopic rod 9, and both ends of the elastic isolating sleeve 8 are connected to the bottom of the housing 1 and the lower end of the vibrating sieve 7, respectively. The elastic isolating sleeve 8 includes a reference sleeve 14 and a sliding sleeve 16 slidably connected thereto, and a spring 15 is further provided between the reference sleeve 14 and the sliding sleeve 16.

[0027] In the granulating device of the present invention, the blower assembly 6 generates an ascending air current, which acts on the falling material and rotates the material while it falls, so that the prepared fertilizer particles are more uniform and have a smoother surface. The vibrating sieve 7 installed in the housing 1 can sieve the material to obtain nitrate-phosphate fertilizer with the required particle size.

[0028] Comparative Example 1 The method for preparing ferric phosphate using ammonium phosphate according to the present invention includes the following steps: S11: Use nitric acid to decompose phosphate concentrate, and add antifoaming agent during the decomposition process to defoam. After decomposition, filter and remove acid insolubles to obtain a first solution, the concentration of nitric acid solution is 60%, the mass ratio of the nitric acid to the phosphate concentrate is 1.3:1, the antifoaming agent contains polysiloxane, polyoxyethylene glycol in a mass ratio of 1:1, and the amount of antifoaming agent is 1% of the mass of the phosphate concentrate. S12: Add sulfuric acid to the first solution in S11 to react, and after the reaction, filter and remove calcium sulfate precipitate to obtain a crude phosphoric acid solution, in which the concentration of sulfuric acid is 98%, and the amount of said sulfuric acid is 93% of the theoretical amount of calcium in the frozen mother liquor. S13: Ammonia is added to the crude phosphoric acid solution in S12 to carry out a neutralization reaction, and after the reaction, it is filtered to obtain precipitate A and a second solution, the amount of ammonia added is 108% of the theoretical value of ammonia required for the formation of ammonium phosphate in the crude phosphoric acid solution, and the reaction pH is 7.5. S14: Add an iron source to the second solution in S13 to react, and filter after reaction to obtain precipitate B ferric phosphate and by-product a third solution, the iron source is ferrous oxide, and the amount of said iron source added is 92% of the theoretical amount required to completely react with the phosphoric acid in the second solution.

[0029] Comparative Example 2 The method for preparing ferric phosphate using ammonium phosphate according to the present invention includes the following steps: S11: Decompose phosphate concentrate with nitric acid, and add antifoaming agent during the decomposition process to defoam. After decomposition, filter and remove acid insolubles to obtain a first solution, the concentration of nitric acid solution is 60%, the mass ratio of nitric acid to phosphate concentrate is 1.3:1, the antifoaming agent contains polysiloxane, lauryl polyoxyethylene ether in a mass ratio of 1:1, and the amount of antifoaming agent is 1% of the mass of phosphate concentrate. S12: Add sulfuric acid to the first solution in S11 to react, and after the reaction, filter and remove calcium sulfate precipitate to obtain a crude phosphoric acid solution, in which the concentration of sulfuric acid is 98%, and the amount of said sulfuric acid is 93% of the theoretical amount of calcium in the frozen mother liquor. S13: Ammonia is added to the crude phosphoric acid solution in S12 to carry out a neutralization reaction, and after the reaction, it is filtered to obtain precipitate A and a second solution, the amount of ammonia added is 108% of the theoretical value of ammonia required for the formation of ammonium phosphate in the crude phosphoric acid solution, and the reaction pH is 7.5. S14: Add an iron source to the second solution in S13 to react, and filter after reaction to obtain precipitate B ferric phosphate and by-product a third solution, the iron source is ferrous oxide, and the amount of said iron source added is 92% of the theoretical amount required to completely react with the phosphoric acid in the second solution.

[0030] Comparative Example 3 The method for preparing ferric phosphate using ammonium phosphate according to the present invention includes the following steps: S11: Decompose phosphate concentrate with nitric acid, and add antifoaming agent during the decomposition process to defoam. After decomposition, filter and remove acid insolubles to obtain a first solution, the concentration of nitric acid solution is 60%, the mass ratio of the nitric acid to the phosphate concentrate is 1.3:1, the antifoaming agent includes polyoxyethylene glycol, lauryl polyoxyethylene ether in a mass ratio of 1:1, and the amount of antifoaming agent is 1% of the mass of the phosphate concentrate. S12: Add sulfuric acid to the first solution in S11 to react, and after the reaction, filter and remove calcium sulfate precipitate to obtain a crude phosphoric acid solution, in which the concentration of sulfuric acid is 98%, and the amount of said sulfuric acid is 93% of the theoretical amount of calcium in the frozen mother liquor. S13: Ammonia is added to the crude phosphoric acid solution in S12 to carry out a neutralization reaction, and after the reaction, it is filtered to obtain precipitate A and a second solution, the amount of ammonia added is 108% of the theoretical value of ammonia required for the formation of ammonium phosphate in the crude phosphoric acid solution, and the reaction pH is 7.5. S14: Add an iron source to the second solution in S13 to react, and filter after reaction to obtain precipitate B ferric phosphate and by-product a third solution, the iron source is ferrous oxide, and the amount of said iron source added is 92% of the theoretical amount required to completely react with the phosphoric acid in the second solution.

[0031] Comparative Example 4 The method for preparing ferric phosphate using ammonium phosphate according to the present invention includes the following steps: S11: Decomposing the phosphate concentrate with nitric acid, and after decomposition, filtering and removing the acid insoluble matter to obtain a first solution, the concentration of the nitric acid solution is 60%, and the mass ratio of the nitric acid to the phosphate concentrate is 1.3:1. S12: Add sulfuric acid to the first solution in S11 to react, and after the reaction, filter and remove calcium sulfate precipitate to obtain a crude phosphoric acid solution, in which the concentration of sulfuric acid is 98%, and the amount of said sulfuric acid is 93% of the theoretical amount of calcium in the frozen mother liquor. S13: Ammonia is added to the crude phosphoric acid solution in S12 to carry out a neutralization reaction, and after the reaction, it is filtered to obtain precipitate A and a second solution, the amount of ammonia added is 108% of the theoretical value of ammonia required for the formation of ammonium phosphate in the crude phosphoric acid solution, and the reaction pH is 7.5. S14: Add an iron source to the second solution in S13 to react, and filter after reaction to obtain precipitate B ferric phosphate and by-product a third solution, the iron source is ferrous oxide, and the amount of said iron source added is 92% of the theoretical amount required to completely react with the phosphoric acid in the second solution.

[0032] As can be seen from the test results of Example 1 and Comparative Examples 1 to 3, the defoaming effect of the defoaming agent of Example 1 is far superior to the defoaming effects of Comparative Examples 1 to 3, which indicates that the defoaming agent of the present invention has a certain synergistic effect on defoaming in the acid decomposition process.

[0033] In addition, the measurement results showed that after 1000 g of phosphate concentrate was acid-decomposed by the method of Example 1, the mass of acid-insoluble matter was 68.71 g, whereas after acid-decomposition by the method of Comparative Example 4, the mass of acid-insoluble matter was as high as 87.48 g. Therefore, the defoaming agent added according to the present invention not only has a defoaming effect, but also improves the removal rate of acid-insoluble matter, and ensures the quality of the subsequently prepared ferric phosphate and nitrate phosphate fertilizer.

[0034] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and any modifications, equivalent replacements, improvements, etc. made without departing from the spirit and principles of the present invention are all included in the scope of protection of the present invention.

Claims

1. S11: Decomposing the phosphate concentrate with nitric acid, and adding an antifoaming agent during the decomposition process to defoam the mixture. After the decomposition, filtering and removing the acid insoluble matter to obtain a first solution; S12: adding sulfuric acid to the first solution in S11 to react with it, and after the reaction, filtering and removing calcium sulfate precipitate to obtain a crude phosphoric acid solution; S13: Adding ammonia to the crude phosphoric acid solution in S12 to carry out a neutralization reaction, and filtering after the reaction to obtain precipitate A and a second solution; S14: Adding an iron source to the second solution in S13 to react, and filtering after the reaction to obtain precipitate B iron phosphate and a by-product third solution; The method for preparing iron(III) phosphate using ammonium phosphate, wherein the amount of ammonia added in S13 is 105 to 110% of the theoretical amount of ammonia required for forming ammonium phosphate in the crude phosphoric acid solution, and the reaction pH is 7 to 8.

2. 2. The method for preparing ferric phosphate using ammonium phosphate according to claim 1, wherein the concentration of the nitric acid solution in S11 is 55-65%, and the ratio of the mass of the nitric acid to the mass of the phosphate concentrate is 1.2-1.4:

1.

3. The method for preparing iron(III) phosphate using ammonium phosphate according to claim 1, wherein the defoaming agent in S11 contains polysiloxane, polyoxyethylene glycol, and lauryl polyoxyethylene ether in a mass ratio of 1:0.5-1.5:0.5-1.

5.

4. The method for preparing ferric phosphate using ammonium phosphate according to claim 1, wherein the concentration of sulfuric acid in the S12 is 98%, and the amount of the sulfuric acid is 90-96% of the theoretical amount of calcium in the frozen mother liquor.

5. 2. The method for preparing ferric phosphate using ammonium phosphate according to claim 1, wherein in S14, the iron source is one or more of iron powder, iron oxide, ferrous oxide, or ferric nitrate, and the amount of the iron source added is 90 to 95% of the theoretical amount required to completely react with the phosphoric acid in the second solution.

6. 13. A method for preparing fertilizer from the by-product of ferric phosphate with ammonium phosphate using the method of claim 1, comprising the steps of mixing, concentrating and melting precipitate A in S13 and the by-product third solution in S14, and granulating the molten material using a granulator to obtain nitrate phosphate fertilizer.

7. 7. The method for preparing a fertilizer from a by-product of ferric phosphate using ammonium phosphate according to claim 6, wherein the granulating apparatus comprises a housing having an accommodation space, the accommodation space of the housing being partitioned successively into a granulating chamber, a sieve chamber and a material storage chamber from top to bottom, a blow assembly is provided between the granulating chamber and the sieve chamber, a vibrating sieve capable of vertically reciprocating displacement is provided between the sieve chamber and the material storage chamber, a material discharge pipe is connected to the material storage chamber, a top cap is detachably provided at an upper end of the housing, a number of material spraying devices are provided in the top cap for spraying molten material into the housing, and an exhaust pipe is further connected to the top cap.

8. 8. The method for preparing fertilizer from a by-product of ferric phosphate using ammonium phosphate according to claim 7, wherein the blower assembly includes a number of distribution pipes arranged in a staggered manner and connected to each other, a number of air blowing pipes are connected to upper ends of the distribution pipes, and an air inlet pipe is further connected to one side of the distribution pipes.

9. 8. The method for preparing fertilizer from ferric phosphate by-product using ammonium phosphate as claimed in claim 7, wherein a vibrating telescopic rod is connected to a lower end of the vibrating sieve for driving the reciprocating displacement of the vibrating sieve, an elastic isolation sleeve is fitted on the outside of the vibrating telescopic rod, both ends of the elastic isolation sleeve are connected to a bottom of the housing and the lower end of the vibrating sieve, respectively, the elastic isolation sleeve includes a sliding sleeve slidably connected to a reference sleeve, and a spring is further provided between the reference sleeve and the sliding sleeve.

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