Effluent pump for alkylation device

Abstract

According to the effluent pump for the alkylation device, a gap between a throat shaft sleeve and a throat lining, a gap between a first-stage shell wear ring and a first-stage impeller wear ring, a gap between an interstage shaft sleeve and an interstage lining and a gap between a balance shaft sleeve and a balance sleeve are arranged; and gaps between the secondary shell wear ring and the secondary impeller wear ring are modified, so that heat generated by an overflowing part can be dissipated in an accelerated manner, the situation that equipment is damaged due to the fact that a rotating part and the wear rings are heated to expand and stick to each other due to short-time flow insufficiency is effectively avoided, and meanwhile, the service life of the equipment is prolonged. And the situation that equipment is damaged due to local overheating caused by partial flow channel blockage due to too small interstage gaps of large-particle impurities carried in a medium can be avoided.

Description

Technical Field

[0001] This invention belongs to the field of petroleum refining, and specifically relates to an effluent pump for an alkylation unit. Background Technology Alkylation units react isobutane and C4 olefins to produce high-octane alkylate oil. This product is characterized by: zero aromatics, zero benzene, zero olefins, high octane number, low sulfur, and low vapor pressure. Alkylate oil also exhibits good stability, low toxicity, and non-corrosiveness, making it easy to store and transport. As a gasoline blending component, it improves vehicle starting performance and ensures complete combustion, making it an ideal blending component for high-octane gasoline. It plays a crucial role in the production of high-octane gasoline and has significant economic value.

[0002] The key pumps in the alkylation unit are two effluent pumps. Their main function is to extract the reaction effluent from the flash tank and send it to the effluent refining and product fractionation sections for further processing. The flash tank is a horizontal vessel with an intermediate partition and a common separation space. The hydrocarbon gas exiting the flash tank's gas phase space goes directly to the refrigeration compressor. If the effluent pumps malfunction, it will trigger a high liquid level alarm in the flash tank. If not handled promptly, it will cause the refrigeration compressor to shut down, leading to a shutdown of the alkylation unit. The effluent pumps use a dual-support, two-stage impeller pressurization design. The seal employs a PLAN11+PLAN53B flushing scheme. In the PLAN11 scheme, the medium flows from the pump outlet to the sealing chamber, providing cooling for the seal and expelling gas from the sealing chamber before flowing into the pump as the process medium. The PLAN53B scheme uses a pressurized isolation fluid circulation system with a bladder-type accumulator, suitable for highly hazardous, flammable, and explosive media, requiring zero discharge of the process medium; therefore, the pressure is higher than that of the PLAN11 scheme. The above two sealing flushing solutions provide circulating flushing fluid for the mechanical seal, removing heat from the sealing cavity and ensuring normal operation of the seal. Since its commissioning, the alkylation effluent pump has frequently experienced mechanical seal leakage and damage to flow components within the pump body, resulting in high maintenance frequency and costs, short operating cycles, and significantly impacting safe and stable production. Summary of the Invention

[0003] The purpose of this invention is to provide an effluent pump for an alkylation unit, which solves the problems of frequent mechanical seal leakage and damage to the flow parts inside the pump body in existing alkylation effluent pumps, resulting in high maintenance frequency and cost, and short operating cycle.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention provides an effluent pump for an alkylation unit, comprising a shaft, on which a pump body is fitted. Within the cavity of the pump body, from the non-driving end to the driving end, a throat sleeve, an interstage sleeve, and a balance sleeve are sequentially arranged, wherein: The throat bushing is fitted with a throat bushing and a first-stage impeller, and the gap between the throat bushing and the throat bushing is 0.45mm-0.5mm. Both ends of the first-stage impeller are provided with first-stage impeller inlet rings, and first-stage housing inlet rings are fixedly installed on the pump body at the corresponding positions of the first-stage impeller inlet rings. The first-stage housing inlet ring and the first-stage impeller inlet ring are in sliding and rotating fit; the gap between the first-stage housing inlet ring and the first-stage impeller inlet ring is 0.6mm-0.65mm. An interstage bushing is provided between the interstage bushing and the pump body, and the gap between the interstage bushing and the interstage bushing is 0.45mm-0.5mm; A balance sleeve is fitted onto the balance shaft sleeve, with a gap of 0.45mm-0.5mm between them; A secondary impeller is provided between the interstage bushing and the balance bushing, and the secondary impeller is fitted onto the shaft. Secondary impeller end rings are installed at both ends of the secondary impeller, and secondary housing end rings are fixedly installed on the pump body corresponding to the secondary impeller end rings. The secondary housing end rings and the secondary impeller end rings are in sliding and rotating fit; the gap between the secondary housing end rings and the secondary impeller end rings is 0.6mm-0.65mm.

[0005] Preferably, a nitrided layer is formed on the surface of the interstage bushing.

[0006] Preferably, a nitrided layer is formed on the surface of the interstage bushing.

[0007] Preferably, the transition channel exhaust port N1 on the effluent pump and the reserved port N2 on the pump inlet pipeline are both connected to the gas phase zone of the flash tank via pipeline N4.

[0008] Preferably, the shaft is further provided with a mechanical seal device, which has an inlet and an outlet for a release fluid, and the included angle between the inlet and the outlet for the release fluid is 270°.

[0009] Preferably, the bushing is further provided with a wave spring, which is arranged between the push ring and the transmission seat, and the wave spring is made of NS3303 material.

[0010] Preferably, the bushing is provided with a primary dynamic and static ring, wherein the primary dynamic and static ring includes a primary dynamic ring and a primary static ring, and the primary dynamic ring and the primary static ring are prepared by pressureless sintering silicon carbide.

[0011] Preferably, the bushing is provided with a secondary stationary ring, which is prepared by Toyo Carbon.

[0012] Preferably, the first fully enclosed O-ring disposed between the bushing and the shaft is a perfluoroether ring.

[0013] Preferably, the second fully enclosed O-ring disposed between the bushing and the first-stage moving ring is a perfluoroether ring; an inner pressure cap assembly is disposed on the first-stage stationary ring, and the third fully enclosed O-ring disposed between the first-stage stationary ring and the inner pressure cap assembly is a perfluoroether ring.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention provides an effluent pump for an alkylation unit. By modifying the gaps between the throat bushing and throat liner, the gap between the first-stage housing ring and the first-stage impeller ring, the gap between the interstage bushing and interstage liner, the gap between the balance bushing and balance sleeve, and the gap between the secondary housing ring and the secondary impeller ring, the following improvements are made: First, it accelerates the dissipation of heat generated by the flow components; second, it effectively avoids damage to the equipment caused by insufficient flow or cavitation leading to thermal expansion and sticking of rotating parts and rings; and third, it prevents damage to the equipment caused by localized overheating due to blockage of flow channels caused by large particulate impurities carried in the medium due to excessively small interstage gaps.

[0015] Furthermore, a nitrided layer is formed on the surface of both the interstage bushing and the interstage liner to increase surface hardness and strengthen the material strength of the flow components, thereby mitigating the situation where the flow components easily stick together due to the untimely dissipation of heat caused by the vaporization of the medium.

[0016] Furthermore, the exhaust port N1 of the transition channel on the effluent pump and the reserved port N2 on the pump inlet pipeline are both connected to the gas phase zone of the flash tank through pipeline N4. When cavitation occurs in the effluent pump, the gas phase in the medium can be promptly and tightly discharged into the flash tank to prevent cavitation from damaging the flow components of the effluent pump.

[0017] Furthermore, the mechanical seal device is provided with an isolation fluid inlet and an isolation fluid outlet, and the included angle between the isolation fluid inlet and the isolation fluid outlet is 270°; the cross-sectional area of ​​the sealing flushing end face is increased from the original 180° to 270°, in order to enhance the flushing fluidity and the stability of the liquid film on the end face of the moving and stationary rings, and to remove more heat in a timely manner. Attached Figure Description

[0018] Figure 1 This is a cross-sectional view of the effluent pump structure described in this application; Figure 2 This is a schematic diagram of the gas phase connection of the effluent pump described in this application; Figure 3 This is a schematic diagram of the mechanical seal device described in this application; Figure 4 This is a schematic diagram for direction A; Figure 5 A comparison of the main operating parameters of alkylation effluent pump A before and after the technical upgrade; Figure 6 A comparison of the main operating parameters of alkylation effluent pump B before and after the technical upgrade; The components include: 1. O-ring seal; 2. Retention washer for round nut; 3. Oil slinger ring; 4. Oil separator; 5. Bearing housing; 6. Angular contact ball bearing; 7. Non-drive adjusting ring; 8. Bracket; 9. Water-cooled water cover; 10. Non-drive end pump cover; 11. Throat bushing; 12. First stage casing inlet ring; 13. First stage impeller; 14. First stage impeller inlet ring; 15. Pump body; 16. Interstage bushing; 17. Secondary stage casing inlet ring; 18. Secondary impeller; 19. Secondary impeller... 20. Wheel flange; 21. Balance sleeve; 22. First O-ring; 23. Second O-ring; 24. Bearing isolator; 25. Drive adjusting ring; 26. Deep groove ball bearing; 27. Drive oil slinger sleeve; 28. Retaining washer for round nut; 29. ​​Bearing isolator; 30. Oil mist driving bearing cover; 31. Round nut; 32. Constant position oil cup with metal protective cover; 33. Shaft; 34. Drive end cartridge mechanical seal; 35. Lock nut; 36. Drive pump cover; 37. Metal spiral wound gasket; 37. Balance bushing; 38. Interstage bushing; 39. Throat bushing; 40. Non-drive end cartridge mechanical seal; 41. Oil level indicator; 42. Oil slinger ring sleeve; 43. Round nut; 44. Non-drive bearing gland; 45. Bushing; 46. Drive ring; 47. First fully enclosed O-ring; 48. First O-ring; 49. First set screw; 50. Inner gland assembly; 51. Drive end outer gland assembly; 52. Gland gasket; 53. Retaining ring; 54. Snap ring; 55. Limiting plate 56. Pressure cover gasket; 57. Screw; 58. Bolt; 59. Transmission seat; 60. Push ring; 61. First-stage moving ring; 62. First-stage stationary ring; 63. Second fully enclosed O-ring; 64. Third fully enclosed O-ring; 65. Wave spring; 66. Second set screw; 67. Spring box assembly; 68. Second-stage moving ring; 69. Second-stage stationary ring; 70. Second O-ring; 71. Third O-ring; 72. Third set screw; 73. Pumping ring; 74. Plug. Detailed Implementation

[0019] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0020] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0021] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0022] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0023] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0024] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0025] Example 1 like Figure 1 As shown, this embodiment provides an effluent pump for an alkylation apparatus, including a shaft 32, on which a pump body 15 is fitted. The pump body 15 has a throat sleeve 39, an interstage sleeve 38, a balance sleeve 37, and a pump drive cover 35 arranged sequentially from the non-driving end to the driving end within its cavity. The throat sleeve 39, the interstage sleeve 38, the balance sleeve 37, and the pump drive cover 35 are all fitted onto the shaft 32.

[0026] The throat bushing 39 is fitted with a throat bushing 11 on the side near the non-driving end, and a non-driving end pump cover 10 is fitted on the throat bushing 11; the throat bushing 39 is fitted with a first-stage impeller 13 on the side near the driving end.

[0027] The gap between the throat bushing 39 and the throat bushing 11 is 0.45mm-0.5mm.

[0028] Both ends of the first-stage impeller 13 are provided with first-stage impeller mouth rings 14.

[0029] The pump body 15 is fixedly installed with a first-stage housing ring 12 corresponding to the first-stage impeller ring 14, and the first-stage housing ring 12 and the first-stage impeller ring 14 are in sliding and rotating fit.

[0030] The gap between the first-stage housing ring 12 and the first-stage impeller ring 14 is 0.6mm-0.65mm.

[0031] An interstage bushing 16 is provided between the interstage bushing 38 and the pump body 15, and the gap between the interstage bushing 38 and the interstage bushing 16 is 0.45mm-0.5mm.

[0032] The balance shaft sleeve 37 is fitted with a pump drive cover 35.

[0033] A balance sleeve 20 is provided between the balance shaft sleeve 37 and the pump cover 35.

[0034] The gap between the balance sleeve and the balance shaft sleeve 34 is 0.45mm-0.5mm.

[0035] A metal spiral wound gasket 36 is provided between the pump drive cover 35 and the pump body 15.

[0036] A secondary impeller 18 is provided between the interstage bushing 38 and the balance bushing 37, and the secondary impeller 18 is fitted onto the shaft 32.

[0037] Secondary impeller 18 is equipped with secondary impeller inlet rings 19 at both ends. Secondary housing inlet rings 17 are fixedly installed on the pump body 15 corresponding to the secondary impeller inlet rings 19. The secondary housing inlet rings 17 and the secondary impeller inlet rings 19 are in sliding and rotating fit.

[0038] The gap between the secondary housing ring 17 and the secondary impeller ring 19 is 0.6mm-0.65mm.

[0039] The shaft 32 is also provided with a drive end container seal 33, and the drive end container seal 33 and the balance shaft sleeve 37 are fixedly connected by a lock nut 34.

[0040] In this embodiment, by setting the gaps between the interstage bushing 38 and the pump body 15, the gap between the interstage bushing 38 and the interstage bushing 16, the gap between the first-stage housing ring 12 and the first-stage impeller ring 14, and the gap between the secondary housing ring 17 and the secondary impeller ring 19, the following are used for: Firstly, it accelerates the dissipation of heat generated by the current-carrying components; Secondly, it effectively avoids the situation where the rotating parts and the mouth ring stick due to thermal expansion caused by insufficient flow in a short period of time, which could damage the equipment. Third, it can avoid the situation where large particles of impurities carried in the medium cause blockage of some flow channels due to insufficient interstage gaps, resulting in local overheating and equipment damage.

[0041] Example 2 like Figure 2 As shown in Example 1, this embodiment provides an effluent pump for an alkylation unit. Both the interstage bushing 38 and the interstage liner 16 undergo particle nitriding treatment to form a nitrided layer on their surfaces, increasing surface hardness. The upgraded interstage liner has a hardness of HB330-375, and the interstage bushing has a hardness of HB241-285. The hardness after nitriding is essentially equivalent to that of ordinary carbon steel, strengthening the material strength of the flow components and mitigating the risk of flow components sticking due to insufficient heat dissipation caused by medium vaporization.

[0042] Example 3 like Figure 2 As shown, based on Example 1, this example provides an effluent pump for an alkylation unit. The transition channel exhaust port N1 on the effluent pump and the reserved port N2 on the pump inlet pipeline are both connected to the gas phase zone of the flash tank through pipeline N4.

[0043] When cavitation occurs in the effluent pump, the gas phase in the medium can be promptly and tightly discharged into the flash tank to prevent cavitation from damaging the flow parts of the effluent pump.

[0044] Example 4 like Figure 3 , Figure 4 As shown, based on Example 1, this embodiment provides an effluent pump for an alkylation device. The shaft 32 is also provided with a mechanical seal device. The mechanical seal device includes a bushing 45, which is fitted onto the shaft 32. The first fully enclosed O-ring 47 between the bushing 45 and the shaft 32 is a perfluoroether ring.

[0045] The bushing is provided with a primary dynamic and static ring and a secondary dynamic and static ring. The primary dynamic and static ring includes a primary dynamic ring 61 and a primary static ring 62, which are prepared by pressureless sintering of silicon carbide. The secondary dynamic and static ring includes a secondary dynamic ring 68 and a secondary static ring 69, wherein the secondary static ring 69 is prepared by Toyo Carbon.

[0046] The material of the primary dynamic and static rings was changed from reaction-bonded silicon carbide (SiC) to pressureless sintered silicon carbide because reaction-bonded silicon carbide is produced by reacting silicon with carbon and graphite, resulting in a free silicon content typically between 8% and 12%. This free silicon is susceptible to corrosion by strong acids and alkalis, and API 682 recommends a pH value between 4 and 11 for use. Pressureless sintered silicon carbide, on the other hand, is composed entirely of silicon carbide, formed from pure silicon carbide powder using a non-oxidizing sintering agent. It has a homogeneous silicon carbide structure and contains no free silicon. This characteristic gives pressureless sintered silicon carbide chemical stability in all corrosive environments.

[0047] The second fully enclosed O-ring between the bushing 45 and the primary moving ring 61 is a perfluoroether ring.

[0048] An inner pressure cap assembly 50 is provided on the primary stationary ring 62, and a third fully enclosed O-ring 64, which is a perfluoroether ring, is provided between the primary stationary ring 62 and the inner pressure cap assembly 50.

[0049] A wave spring 65 is also provided on the bushing 45, and the wave spring 65 is arranged between the push ring 60 and the transmission seat 59. The wave spring is made of NS3303 material.

[0050] The mechanical seal device is provided with a separator fluid inlet and a separator fluid outlet, and the included angle between the separator fluid inlet and the separator fluid outlet is 270°.

[0051] The cross-sectional area of ​​the sealing flushing end face was increased from 180° to 270°, increasing the flushing cross-sectional area and further enhancing the flushing fluidity and the stability of the liquid film on the dynamic and static ring end faces. This allows for the timely removal of more heat and impurities, protecting the seal for long-term stable operation.

[0052] The operation control method of the mechanical seal device: Through the above technical improvements, the calculated sealing chamber pressure of the mechanical seal device is 0.43 MPa. According to the technical requirements for seal operation and long-term practical experience, the atmospheric side sealing oil pressure should be controlled between 0.68 MPa and 0.84 MPa.

[0053] Since the alkylation unit's effluent pumps began operation in April 2019, they have frequently experienced problems such as mechanical seal leakage and damage to flow components. Before the technical upgrade, the pumps were overhauled on average every 30 days, with a total of 16 overhauls, including 2 factory return overhauls and replacement of 25 mechanical seals, resulting in low work efficiency and high costs.

[0054] After targeted technical modifications, and following two years and two months of practical operation, it has been proven that the system effectively avoids frequent seal leaks and damage to flow components caused by severe operating conditions such as short-term cavitation, insufficient flow, low load operation, and cavitation in the alkylation unit's effluent pumps. As of June 1, 2024, the two alkylation effluent pumps had accumulated 11,260 hours and 7,460 hours of maintenance-free operation (the two pumps had accumulated over 24 months of maintenance-free operation). This effectively ensures long-term safe and stable operation of key pumps in the alkylation unit, significantly reduces maintenance costs, guarantees the safe and environmentally friendly long-term operation of the unit, and improves work efficiency.

[0055] Figure 5 and Figure 6 The figure shows the operating parameters of the alkylation effluent pump before and after the implementation of the technical optimization measures. As can be seen from the figure, after the optimization and adjustment of the above measures, the main operating parameters of the effluent pump, such as vibration, bearing temperature, and sealing gland temperature, have been greatly improved, laying a solid foundation for the long-term operation of key pumps.

[0056] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. An effluent pump for an alkylation unit, characterized by, The shaft is sleeved with a pump body, and a cavity of the pump body is sequentially provided with a throat sleeve, an inter-stage sleeve and a balance sleeve from a non-driving end to a driving end. The throat sleeve is sleeved with a throat bushing and a first-stage impeller, and a gap between the throat sleeve and the throat bushing is 0.45mm-0.5mm. Both ends of the first-stage impeller are provided with first-stage impeller port rings, and the pump body is respectively fixedly provided with first-stage casing port rings corresponding to the first-stage impeller port rings, and the first-stage casing port rings and the first-stage impeller port rings are in sliding and rotating fit; a gap between the first-stage casing port rings and the first-stage impeller port rings is 0.6mm-0.65mm. The inter-stage sleeve and the pump body are provided with an inter-stage bushing, and a gap between the inter-stage sleeve and the inter-stage bushing is 0.45mm-0.5mm. The balance sleeve is sleeved with a balance sleeve, and a gap between the balance sleeve and the balance sleeve is 0.45mm-0.5mm. The inter-stage sleeve and the balance sleeve are provided with a second-stage impeller, and the second-stage impeller is sleeved on the shaft. Both ends of the second-stage impeller are provided with second-stage impeller port rings, and the pump body is respectively fixedly provided with second-stage casing port rings corresponding to the second-stage impeller port rings, and the second-stage casing port rings and the second-stage impeller port rings are in sliding and rotating fit; a gap between the second-stage casing port rings and the second-stage impeller port rings is 0.6mm-0.65mm.

2. An effluent pump for an alkylation unit as defined in claim 1, wherein, A surface of the inter-stage sleeve is formed with a nitriding layer.

3. An effluent pump for an alkylation unit as defined in claim 1, wherein, A surface of the inter-stage bushing is formed with a nitriding layer.

4. An effluent pump for an alkylation unit as defined in claim 1, wherein, Transition flow passages of the effluent pump and a reserved port on a pump inlet pipeline are connected with a gas phase zone of a flash tank through pipelines.

5. An effluent pump for an alkylation unit as defined in claim 1, wherein, The shaft is further provided with a mechanical sealing device, and the mechanical sealing device is provided with a barrier liquid inlet and a barrier liquid outlet, and an included angle between the barrier liquid inlet and the barrier liquid outlet is 270°.

6. An effluent pump for an alkylation unit as defined in claim 5, wherein, The shaft sleeve is further provided with a wave spring, and the wave spring is arranged between a push ring and a transmission seat, and the wave spring is prepared from NS3303 material.

7. An effluent pump for an alkylation unit as defined in claim 5 wherein, The shaft sleeve is provided with a primary dynamic and static ring, wherein the primary dynamic and static ring comprises a primary dynamic ring and a primary static ring, and the primary dynamic ring and the primary static ring are prepared from pressureless sintered silicon carbide.

8. An effluent pump for an alkylation unit as defined in claim 5 wherein, The shaft sleeve is provided with a secondary static ring, and the secondary static ring is prepared from Oriental Carbon.

9. An effluent pump for an alkylation unit as defined in claim 5 wherein, A first full-cover O-shaped ring between the shaft sleeve and the shaft is a perfluoroether ring.

10. An effluent pump for an alkylation unit as defined in claim 5 wherein, A second full-cover O-shaped ring between the shaft sleeve and the primary dynamic ring is a perfluoroether ring; the primary static ring is provided with an inner pressure cover assembly, and a third full-cover O-shaped ring between the primary static ring and the inner pressure cover assembly is a perfluoroether ring.

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