Design method of melt filtering device

Abstract

The invention relates to the technical field of melt filtering devices, in particular to a melt filtering device design method which comprises the following steps: S1, determining the structure of a melt filtering device; s2, performing strength and sealing performance calculation according to design pressure, design temperature and material parameters, calculating the thicknesses of a barrel, an upper end cover and a lower end cover, and selecting a proper sealing gasket; s3, calculating the strength of the supporting disc according to a pressure difference limit value set by a process system, and determining the size of the supporting disc; s4, calculating the pre-tightening compression amount of the sealing gasket, and calculating the depth and width of a mounting groove of the sealing gasket; s5, setting and checking the sizes and types of an inlet connecting pipe and an outlet flange according to the set pipeline load; s6, according to the heat transfer coefficients and heat loss requirements of different heating media, the equivalent heat preservation thickness is calculated, and the size of a heat preservation jacket is determined; the invention provides a method for designing a melt filtering device, which is simple, practical and quick and can ensure that a design calculation result is safe and economical.

Description

Technical Field

[0001] The invention relates to the technical field of melt filtering devices, in particular to a design method of a melt filtering device. Background Art

[0002] In the polyamide device, the filtering effect of the melt filtration device determines the quality of the product; the filtration device needs to overcome harsh operating conditions such as high temperature and high pressure; when designing the melt filtration system, it is necessary to take into account strength, sealing, thermal insulation effect, filtration area, etc., to design a safe and economical filtration device.

[0003] Since the structure of the filtration device is a non-standard structure, there is no completely corresponding calculation model and calculation method in the existing standard system, and there is no systematic design and calculation method for melt filtration devices. In previous design practices, empirical design or finite element method is usually used. The safety and economy of the calculation results of empirical design cannot be guaranteed. As for the finite element method, its modeling and calculation process is cumbersome, and the model needs to be adjusted repeatedly for trial calculation. The scheme determination cycle is long and the calculation efficiency is low, which is not conducive to engineering application and promotion. Summary of the invention

[0004] The main purpose of the present invention is to provide a design method for a melt filtration device to solve the problem in the above-mentioned prior art of how to design a simple, practical, fast and economical melt filtration device design method that can ensure the safety and economical design calculation results.

[0005] In order to achieve the above object, the present invention provides a design method of a melt filtration device, comprising the following steps:

[0006] S1. Determine the structure of the melt filtration device:

[0007] The melt filtering device comprises a cylinder, and the upper and lower ends of the cylinder are connected with an upper end cover and a lower end cover by studs; an inner bolt hole is arranged on the cylinder; a mounting groove is arranged at the top of the cylinder, a support plate is installed in the mounting groove, and the top of the support plate abuts against the upper end cover; sealing gaskets are arranged at the position where the upper end cover and the mounting groove abut against the support plate, and at the position where the lower end cover abuts against the cylinder; a plurality of filter elements are fixedly connected to the lower end of the support plate, and a plurality of filtrate channels opposite to the filter elements are arranged on the support plate; a material outlet and a material inlet are arranged on the upper end cover and the lower end cover; the upper end cover is connected with an outlet flange, and the lower end cover is connected with an inlet pipe; a heat-insulating jacket is arranged on the outer sides of the cylinder, the upper end cover and the lower end cover;

[0008] S2. Calculate the strength and sealing performance according to the design pressure, design temperature and material parameters, calculate the thickness of the cylinder, upper end cover and lower end cover, and select the appropriate sealing gasket;

[0009] S3. Calculate the strength of the support plate according to the pressure difference limit set by the process system and determine the size of the support plate;

[0010] S4, calculating the pre-tightening compression amount of the sealing gasket, and calculating the depth and width of the installation groove of the sealing gasket;

[0011] S5. Set and check the size and type of the inlet pipe and outlet flange according to the set pipeline load;

[0012] S6. Calculate the equivalent insulation thickness and determine the size of the insulation jacket based on the heat transfer coefficient and heat loss requirements of different heat media.

[0013] Furthermore, in step S1, the material outlet and the material inlet both include a tapered hole located near the inside and a round hole located outside; the upper end cover is connected to the outlet flange by bolts, and the upper end cover is provided with an internal threaded hole;

[0014] Step S2 includes:

[0015] S21. Set the stud specifications, quantity and center circle diameter; approximately assume that the thread friction coefficient is the same as the support surface friction coefficient, refer to the VDI 2230 standard and take the upper limit of the corresponding torque tolerance to determine the assembly load F of the stud of the corresponding performance level. MTab And preload torque M A ; Considering the possible overload of the stud caused by the pipeline load during operation, the preload torque is multiplied by the reduction factor 0.88, that is, 80% of the yield strength of the stud is used as the initial preload limit;

[0016] S22, calculate the alternative value of the cylinder thickness - S1, the calculation formula is:

[0017]

[0018] σ ma +σ a =0.8[σ] t

[0019] Where: D1—outer diameter of cylinder, mm;

[0020] D2—Inner diameter of cylinder, mm, is the set value;

[0021] S1—cylinder thickness, mm;

[0022] [σ] t — Allowable material stress of the cylinder, end cover and support plate, MPa;

[0023] S23, calculate the alternative value S2 of the cylinder thickness according to the internal pressure, and the calculation formula is:

[0024]

[0025] Where: e—base of natural logarithm, 2.71828…;

[0026] p c —Design pressure, MPa;

[0027] D2—Inner diameter of cylinder, mm, is the set value;

[0028] S24, determine the matching dimensions of the sealing structure based on the minimum sealing width, the internal thread backing processing dimensions of the cylinder end, the matching tolerance, and the rounding amount, and determine that the minimum cylinder thickness that meets the requirements is S3;

[0029] S25, nominal thickness of cylinder is S=max[S1,S2,S3];

[0030] S26. The force model of the upper end cover and the lower end cover is simplified to a conical shell, and the semi-apex angle of the conical hole of the material outlet and the material inlet is set to α, the maximum diameter is D3, and the minimum diameter is D4; the equivalent cone shell thickness calculation formula is:

[0031]

[0032] ε—dimensionless weighted adjustment coefficient, which is 0.95 when the half apex angle is 75° and 1.05 when the half apex angle is 65°. Other angles are interpolated.

[0033] [σ] t —Allowable material stress of the cylinder, end cover and support plate, MPa;

[0034] p c —Design pressure, MPa;

[0035] Calculate the thickness S6 of the upper and lower end covers using the formula:

[0036]

[0037] Where: S5—the depth of the bolt hole on the upper end cover, mm, is the set value.

[0038] Further, step S3 includes:

[0039] S31. According to the operating requirements of the process system, the pressure difference is set to Δp;

[0040] S32, determining the outer diameter D5 of the support plate according to the size of the sealing gasket;

[0041] S33. Calculate the initial thickness of the support plate using the formula:

[0042]

[0043] S34, set the number of filter elements to n1, the cross-sectional area of ​​the filtrate channel to A1, and the nominal thickness of the filter element support plate to:

[0044]

[0045] Further, step S4 includes:

[0046] S41. The selected gasket is the type without inner and outer reinforcement rings; the calculation assumes that the gasket is always in an elastic state during pre-tightening and operation;

[0047] S42. Calculate the preload compression of the gasket, that is, the reserved initial fit clearance between the two parts in contact with the gasket, using the formula:

[0048]

[0049] Where: S 10 —Thickness of sealing gasket, mm;

[0050] E—equivalent elastic modulus of the sealing gasket, MPa;

[0051] A2—Cross-sectional area of ​​the sealing gasket, mm 2 ;

[0052] S43. Calculate the groove depth of the installation groove of the sealing gasket using the formula:

[0053] S 11 =S 10 -S9

[0054] S44. Calculate the slot width of the gasket installation slot using the formula:

[0055]

[0056] Where: S 12 —Width of sealing pad, mm;

[0057] D G —The diameter of the sealing gasket’s effective center circle shall be determined in accordance with GB / T 150.3, mm.

[0058] Further, step S5 includes:

[0059] S51, the set load of the inlet pipe connected to the inlet pipe is Fx1, Fy1, Fz1, and the set moment is Mx1, My1, Mz1;

[0060] S52. Use the flat cover opening model in the NSAS software to check the overall structure of the lower end cover and the inlet nozzle, and obtain the thickness of the inlet nozzle that meets the requirements;

[0061] S53, the set load of the outlet pipe connected to the outlet flange is Fx2, Fy2, Fz2, and the set moment is Mx2, My2, Mz2;

[0062] S54. Select a suitable outlet flange. The maximum allowable working pressure of the outlet flange is p R The following conditions should be met:

[0063]

[0064] Where: d G —The diameter of the center circle of the outlet flange sealing gasket shall be determined according to GB / T 150.3, mm;

[0065] p e —Equivalent design pressure of outlet flange, Pa.

[0066] Furthermore, in step S1, the heat-insulating jacket comprises an inner shell and an outer shell sleeved on the outer side of the inner shell, and a gap for filling a heat medium material is provided between the inner shell and the outer shell;

[0067] Step S6 includes: the gap size between the inner shell and the outer shell is t i , the gap is t i The formula for approximate calculation based on equivalent insulation thickness is:

[0068]

[0069] h i —Convection heat transfer coefficient between the outer wall of the jacket and the heat medium material, W / [mm 2 ×℃];

[0070] H i —Equivalent heat transfer film coefficient, W / [mm 2 ×℃];

[0071] K i —Thermal conductivity of heat medium material of equivalent insulation thickness, W / [mm×℃];

[0072] λ—Heat loss weighted adjustment coefficient, ranging from 1.05 to 1.15.

[0073] Furthermore, in step S1, a spiral baffle is fixedly connected between the inner shell and the outer shell, and the spiral baffle divides the gap between the inner shell and the outer shell into a spiral channel for the heat medium material to pass through;

[0074] Step S6 includes:

[0075] Calculate the wall thickness δ1 of the inner shell and outer shell using the formula:

[0076]

[0077] L—pitch of spiral baffle, mm;

[0078] p j —Set internal pressure of the insulation jacket, MPa;

[0079] —Allowable stress of the selected insulation jacket material, MPa.

[0080] Further: in step S26, the value range of the cone half apex angle α is 65° to 75°.

[0081] Further: in step S52, when the flat cover opening model in the NSAS software is used to check the overall structure of the lower end cover and the inlet pipe, the allowable coefficient of the primary stress is selected as 2.0, and the allowable combination coefficient of the primary stress + secondary stress is selected as 2.8.

[0082] Furthermore: in step S6, the wall thickness δ1 of the inner shell and the outer shell needs to be no less than 6 mm.

[0083] The present invention provides a simple, practical, fast and economical melt filtration device design method that can ensure the safety and economy of the design calculation results; the design method of the present invention can efficiently design an economical and safe melt filtration device according to different production capacities, different initial melt cleanliness, and the requirements of different downstream fields for finished products. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] The drawings in the specification, which constitute a part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0085] Figure 1 It is a structural schematic diagram of a melt filtration device in an embodiment;

[0086] Figure 2 for Figure 1 The enlarged view of point A in the middle;

[0087] In the figure: 1. Cylinder; 2. Stud; 3. Upper end cover; 301. Material outlet; 4. Lower end cover; 401. Material inlet; 402. Inlet pipe; 5. Support plate; 501. Filtrate channel; 6. Sealing gasket; 7. Insulation jacket; 8. Filter element; 9. Outlet flange. DETAILED DESCRIPTION

[0088] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0089] A method for designing a melt filtration device comprises the following steps:

[0090] S1. Determine the structure of the melt filtration device:

[0091] like Figure 1 and Figure 2 As shown, the melt filtering device comprises a cylinder 1, and the upper and lower ends of the cylinder 1 are connected with an upper end cover 3 and a lower end cover 4 through studs 2; an inner bolt hole is provided on the cylinder 1; a mounting groove is provided at the top of the cylinder 1, and a support plate 5 is installed in the mounting groove, and the top of the support plate 5 abuts against the upper end cover 3; a sealing gasket 6 is provided at the position where the upper end cover 3 and the mounting groove abut against the support plate 5 and at the position where the lower end cover 4 abuts against the cylinder 1; a plurality of filter elements 8 are fixedly connected to the lower end of the support plate 5, and a plurality of filtrate channels 501 opposite to the filter elements 8 are provided on the support plate 5;

[0092] The upper end cover 3 and the lower end cover 4 are provided with a material outlet 301 and a material inlet 401; the material outlet 301 and the material inlet 401 both include a tapered hole located near the inside and a round hole located outside; the upper end cover 3 is connected with an outlet flange 9 by bolts, and an internal threaded hole is provided on the upper end cover 3; the lower end cover 4 is connected with an inlet pipe 402; the outer sides of the cylinder 1, the upper end cover 3 and the lower end cover 4 are provided with a heat preservation jacket 7;

[0093] S2. Calculate the strength and sealing performance according to the design pressure, design temperature and material parameters, calculate the thickness of the cylinder 1, the upper end cover 3 and the lower end cover 4, and select a suitable sealing gasket 6;

[0094] S3, performing strength calculation on the support plate 5 according to the pressure difference limit value set by the process system, and determining the size of the support plate 5;

[0095] S4, calculating the pre-tightening compression amount of the sealing gasket 6, and calculating the depth and width of the installation groove of the sealing gasket 6;

[0096] S5. Setting and checking the size and type of the inlet pipe 402 and the outlet flange 9 according to the set pipeline load;

[0097] S6. Calculate the equivalent insulation thickness according to the heat transfer coefficient and heat loss requirements of different heat media and determine the size of the insulation jacket (7).

[0098] In some embodiments, step S2 specifically includes:

[0099] S21. Set the specification, quantity and center circle diameter of stud 2; approximately assume that the friction coefficient of the thread is the same as the friction coefficient of the supporting surface, refer to the VDI 2230 standard and take the upper limit of the corresponding torque tolerance to determine the assembly load F of stud 2 of the corresponding performance level MTab And preload torque M A; Considering the possible overload of stud 2 caused by the pipeline load in operation, the preload torque is multiplied by the reduction factor 0.88, that is, 80% of the yield strength of the stud is used as the initial preload limit;

[0100] S22, calculate the alternative value of the thickness of the cylinder 1 - S1, the calculation formula is:

[0101]

[0102] σ ma +σ a =0.8[σ] t

[0103] Where: D1—outer diameter of cylinder, mm;

[0104] D2—Inner diameter of cylinder, mm, is the set value;

[0105] S1—cylinder thickness, mm;

[0106] [σ] t — Allowable material stress of the cylinder, end cover and support plate, MPa;

[0107] S23, calculate the alternative value S2 of the thickness of the cylinder 1 according to the internal pressure, and the calculation formula is:

[0108]

[0109] Where: e—base of natural logarithm, 2.71828…;

[0110] p c —Design pressure, MPa;

[0111] D2—Inner diameter of cylinder, mm, is the set value;

[0112] S24. Determine the matching dimensions of the sealing structure based on the minimum sealing width, the internal thread backing processing dimensions of the cylinder end, the matching tolerance, and the rounding amount, and determine that the minimum cylinder 1 thickness that meets the requirements is S3;

[0113] S25, nominal thickness of cylinder 1 is S=max[S1,S2,S3];

[0114] S26, simplify the force model of the upper end cover 3 and the lower end cover 4 into a conical shell, set the cone surface semi-apex angle of the conical hole of the material outlet 301 and the material inlet 401 to α, the maximum diameter to D3, and the minimum diameter to D4; the equivalent cone shell thickness calculation formula is:

[0115]

[0116] ε—dimensionless weighted adjustment coefficient, which is 0.95 when the half apex angle is 75° and 1.05 when the half apex angle is 65°. Other angles are interpolated.

[0117] [σ] t — Allowable material stress of the cylinder, end cover and support plate, MPa;

[0118] p c —Design pressure, MPa;

[0119] The thickness S6 of the upper end cover 3 and the lower end cover 4 is calculated using the formula:

[0120]

[0121] Where: S5—the depth of the bolt hole on the upper end cover, mm, is the set value.

[0122] In some embodiments, in step S26, the value range of the cone half apex angle α is 65° to 75°.

[0123] The high-pressure sealing effect of the melt filtration device depends to a large extent on the pre-tightening effect, that is, ensuring that the pre-tightening force on each stud is the same or similar; the torque table in the "Mechanical Design Manual" is suitable for studs of ordinary strength. For high-strength bolts used for high-pressure sealing, the VDI 2230 standard comprehensively considers various factors. Therefore, step S21 uses the assembly load and pre-tightening torque specified in the standard for the design calculation of high-pressure sealing, which is more scientific and reasonable; and the specific value of the torque given during the design is more conducive to the on-site pre-tightening operation and ensures the sealing effect; considering the possible overload of the stud caused by the pipeline load under high temperature conditions, the pre-tightening torque is multiplied by a reduction factor of 0.88, that is, 80% of the yield strength of the stud is used as the initial pre-tightening limit.

[0124] During operation, heat is transferred between the insulation jacket 7 and the cylinder 1 by radiation heat transfer, which requires that the outer wall of the cylinder 1 should be as close as possible to the inner wall of the insulation jacket 7 and the cylinder 1 should be designed as a straight cylinder structure that is flush up and down. Therefore, in step S21, the straight cylinder structure of the cylinder 1 is equivalent to the end flange, and its mechanical model is reasonable. The calculation result is also conservative and safe. Considering the possible pipeline load at the inlet or outlet, the allowable coefficient of the combined stress is taken as 0.8.

[0125] To ensure the circulation effect of the molten material, the material outlet 301 and the material inlet 401 of the upper end cover 3 and the lower end cover 4 both include tapered holes; the inner sides of the upper end cover 3 and the lower end cover 4 are subjected to the internal pressure of the medium and are also subjected to the reaction force of the sealing gasket 6, and their mechanical model is different from that of a simply supported circular flat cover with an open hole that bears a uniformly distributed load; the reaction force of the sealing gasket 6 generates compressive stress in the upper end cover 3 and the lower end cover 4, and this stress will not cause failure of the upper end cover 3 and the lower end cover 4; the internal pressure acting on the conical surface of the tapered hole causes the upper end cover 3 and the lower end cover 4 to expand and deform, generating a large tensile stress in the circumferential direction, and the tensile stress reaches a maximum value at the thinner part of the port; therefore, step S26 regards the upper end cover 3 and the lower end cover 4 as a conical shell, which is more scientific than regarding the upper end cover 3 and the lower end cover 4 as a simply supported circular flat plate with an opening in the middle that bears a uniformly distributed load.

[0126] Taking into account the bending stress generated by the sealing gasket 6 on the upper end cover 3 and the lower end cover 4, the simplified calculation formula in step S26 takes a load combination coefficient of 1.25 and a weighted adjustment coefficient according to the half-vertex angle to adjust the actual stress state in the actual structure.

[0127] In some embodiments, step S3 specifically includes:

[0128] S31. According to the operating requirements of the process system, the pressure difference is set to Δp;

[0129] S32, determining the outer diameter D5 of the support plate 5 according to the size of the sealing gasket 6;

[0130] S33, calculating the initial thickness of the support plate 5, the formula is:

[0131]

[0132] S34, set the number of filter elements to n1, the cross-sectional area of ​​the filtrate channel 501 to A1, and the nominal thickness of the filter element support plate to:

[0133]

[0134] After the support plate 5 is opened, its strength and rigidity are weakened as a whole; since its opening arrangement is mostly uniformly distributed in concentric circles, it is different from the calculation model of the uniformly weakened simply supported U-shaped tube plate in GB / T 151; therefore, based on the limit calculation formula of the circular plate, a weighted adjustment coefficient is taken according to its structural characteristics to determine the initial thickness; according to the concept of overall reinforcement, the ratio of the metal volume weakened by the opening to the area after the opening is used as the overall reinforcement thickness of the filter element support plate; after comparison and verification of multiple sets of finite element calculation data, the calculation method in steps S33 and S34 is simple, safe and reliable.

[0135] In some embodiments, step S4 specifically includes:

[0136] S41, the selected sealing gasket 6 is a type without inner and outer reinforcement rings; the calculation assumes that the sealing gasket 6 is always in an elastic state during pre-tightening and operation;

[0137] S42, calculating the pre-tightening compression amount of the sealing gasket 6, that is, the reserved initial matching clearance between the two parts in contact with the sealing gasket 6, the formula is:

[0138]

[0139] Where: S 10 —Thickness of sealing gasket, mm;

[0140] E—equivalent elastic modulus of the sealing gasket, MPa;

[0141] A2—Cross-sectional area of ​​the sealing gasket, mm 2 ;

[0142] S43. Calculate the groove depth of the installation groove of the sealing gasket using the formula:

[0143] S 11 =S 10 -S9

[0144] S44, calculating the slot width of the installation slot of the sealing gasket 6, the formula is:

[0145]

[0146] Where: S 12 —Width of sealing pad, mm;

[0147] D G —The diameter of the sealing gasket’s effective center circle shall be determined in accordance with GB / T 150.3, mm.

[0148] The purpose of calculating the pre-tightening compression amount of the sealing gasket 6 in step 3 is to determine the reserved initial fitting clearance between the two components in contact with the sealing gasket 6; in order to minimize the fitting clearance between the sealing surfaces after pre-tightening, minimize the interference of the sealing clearance on the melt flow process, and prevent the passage from being blocked by hanging materials during operation; when a metal gasket is used, its equivalent elastic modulus can be approximately the elastic modulus of the metal material, and when a metal winding gasket is used, its equivalent elastic modulus can be determined by a pre-compression test, provided by the gasket supplier, or by consulting relevant literature with actual use experience; the calculation purpose of steps S41-S44 is to ensure that there is sufficient deformation space during the gasket compression process to ensure the high-pressure sealing effect, and to ensure that after the pre-tightening load determined in step 1 is applied, the sealing gasket 6 will not be over-compressed and leak and fail.

[0149] In some embodiments, step S5 specifically includes:

[0150] S51, the set load of the inlet pipe connected to the inlet pipe 402 is Fx1, Fy1, Fz1, and the set moment is Mx1, My1, Mz1;

[0151] S52, using the flat cover opening model in the NSAS software to check the overall structure of the lower end cover 4 and the inlet pipe 402, and obtain the thickness of the inlet pipe 402 that meets the requirements;

[0152] S53, the set load of the outlet pipe connected to the outlet flange 9 is Fx2, Fy2, Fz2, and the set moment is Mx2, My2, Mz2;

[0153] S54. Select a suitable outlet flange 9. The maximum allowable working pressure of the outlet flange 9 is p R The following conditions should be met:

[0154]

[0155]

[0156] Where: d G —The diameter of the center circle of the outlet flange sealing gasket shall be determined according to GB / T 150.3, mm;

[0157] p e —Equivalent design pressure of outlet flange, Pa.

[0158] The outlet flange 9 is fixed on the upper end cover 3, and the rigidity of the upper end cover 3 is much greater than that of the outlet flange 9. Under the action of the pipeline load, no matter the axial stress is tensile stress or compressive stress, the axial load and torque will not directly damage its seal. In order to simplify the calculation, the influence of the axial load and torque is ignored. Combined with the engineering use effect, the allowable coefficient of the equivalent design pressure of the outlet flange 9 is adjusted to 1.5.

[0159] In some embodiments, in step S52, when the flat cover opening model in the NSAS software is used to check the overall structure of the lower end cover 4 and the inlet pipe 402, the allowable coefficient of the primary stress is selected as 2.0, and the allowable combination coefficient of the primary stress + secondary stress is selected as 2.8.

[0160] In some embodiments, in step S1, the heat-insulating jacket 7 includes an inner shell 701 and an outer shell 702 sleeved on the outer side of the inner shell 701, and a gap for filling a heat medium material is provided between the inner shell 701 and the outer shell 702;

[0161] Step S6 includes: the gap size between the inner shell 701 and the outer shell 702 is t i , the gap is t i The formula for approximate calculation based on equivalent insulation thickness is:

[0162]

[0163] h i —Convection heat transfer coefficient between the outer wall of the jacket and the heat medium material, W / [mm 2 ×℃];

[0164] H i —Equivalent heat transfer film coefficient, W / [mm 2 ×℃];

[0165] K i —Thermal conductivity of heat medium material of equivalent insulation thickness, W / [mm×℃];

[0166] λ—Heat loss weighted adjustment coefficient, ranging from 1.05 to 1.15.

[0167] The determination of the gap size between the inner shell 701 and the outer shell 702 refers to the equivalent calculation method of the insulation thickness, and adds a weighted adjustment coefficient for heat loss on the original basis; this method avoids the cumbersome finite element thermal analysis calculation. During the calculation process, the designer needs to determine the thermal conductivity and convection heat transfer coefficient based on the specific heat medium material. The weighted adjustment coefficient is related to the specific heat capacity of the heat medium material; when heat transfer oil is used as the heat medium material, its value can be 1.1.

[0168] In some embodiments, in step S1, a spiral baffle 703 is fixedly connected between the inner shell 701 and the outer shell 702, and the spiral baffle 703 divides the gap between the inner shell 701 and the outer shell 702 into a spiral channel for the heat medium material to pass through;

[0169] Step S6 includes:

[0170] The wall thickness δ1 of the inner shell 701 and the outer shell 702 is calculated as follows:

[0171]

[0172] L—pitch of spiral baffle, mm;

[0173] p j —Set internal pressure of the insulation jacket, MPa;

[0174] —Allowable stress of the selected insulation jacket material, MPa.

[0175] The insulation jacket 7 is a double-layer cylinder structure. Since the baffle 703 has sufficient rigidity and is welded to the inner shell 701 and the outer shell 702 to form a whole, it is different from the calculation model of a single internal pressure or reinforced external pressure cylinder. Its calculated thickness is determined by a single cavity isolated by the baffle. Therefore, the main bearing annular cavity can be equivalently simplified to a two-dimensional axisymmetric structure, and further simplified to the calculation of the thickness of a flat plate with the pitch as the equivalent diameter. This method fully combines the bearing characteristics of the actual structure, and can reduce the calculated thickness by more than 50% compared with the traditional external pressure cylinder, which can greatly improve the heat transfer efficiency of the insulation jacket.

[0176] In some embodiments, in step S6, the wall thickness δ1 of the inner shell 701 and the outer shell 702 also needs to be no less than 6 mm.

[0177] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for designing a melt filtration device, characterized in that: The following steps are involved: S1. Determine the structure of the melt filtration device: The melt filtering device comprises a cylinder (1), wherein the upper and lower ends of the cylinder (1) are connected to an upper end cover (3) and a lower end cover (4) via studs (2); an inner bolt hole is provided on the cylinder (1); a mounting groove is provided at the top end of the cylinder (1), a support plate (5) is installed in the mounting groove, and the top of the support plate (5) abuts against the upper end cover (3); a sealing gasket ( 6); a plurality of filter elements (8) are fixedly connected to the lower end of the support plate (5); a plurality of filtrate channels (501) opposite to the filter elements (8) are provided on the support plate (5); a material outlet (301) and a material inlet (401) are provided on the upper end cover (3) and the lower end cover (4); the upper end cover (3) is connected to an outlet flange (9), and the lower end cover (4) is connected to an inlet pipe (402); a heat-insulating jacket (7) is provided on the outer side of the cylinder (1), the upper end cover (3) and the lower end cover (4); S2. Calculate the strength and sealing performance according to the design pressure, design temperature and material parameters, calculate the thickness of the cylinder (1), the upper end cover (3) and the lower end cover (4), and select a suitable sealing gasket (6); S3, performing strength calculation on the support plate (5) according to the pressure difference limit value set by the process system, and determining the size of the support plate (5); S4, calculating the pre-tightening compression amount of the sealing gasket (6), and calculating the depth and width of the installation groove of the sealing gasket (6); S5. Setting and checking the size and type of the inlet pipe (402) and the outlet flange (9) according to the set pipeline load; S6. Calculate the equivalent insulation thickness according to the heat transfer coefficient and heat loss requirements of different heat media and determine the size of the insulation jacket (7).

2. The method for designing a melt filtration device according to claim 1, characterized in that: In the step S1, the material outlet (301) and the material inlet (401) both include a tapered hole located near the inside and a circular hole located outside; the upper end cover (3) is connected to the outlet flange (9) by bolts, and the upper end cover (3) is provided with an internal threaded hole; The step S2 comprises: S21. Set the specification, quantity and center circle diameter of the stud (2); approximately assume that the thread friction coefficient is the same as the support surface friction coefficient, refer to the VDI 2230 standard and take the upper limit of the corresponding torque tolerance to determine the assembly load F of the stud (2) of the corresponding performance level. MTab And preload torque M A ; Considering the possible overload of the stud (2) caused by the pipeline load during operation, the preload torque is multiplied by a reduction factor of 0.88, that is, 80% of the yield strength of the stud is used as the initial preload limit; S22, calculate the alternative value of the thickness of the cylinder (1) - S1, the calculation formula is: s ma +s a =0.8[σ] t Where: D1—outer diameter of cylinder, mm; D2—Inner diameter of cylinder, mm, is the set value; S1—cylinder thickness, mm; [σ] t —Allowable material stress of the cylinder, end cover and support plate, MPa; S23. Calculate the alternative value S2 of the thickness of the cylinder (1) according to the internal pressure. The calculation formula is: Where: e—base of natural logarithm, 2.71828…; p c —Design pressure, MPa; D2—Inner diameter of cylinder, mm, is the set value; S24, determine the matching dimensions of the sealing structure by taking into account the minimum sealing width, the internal thread backing machining dimensions of the cylinder end, the matching tolerance, and the rounding amount, and determine that the minimum cylinder (1) thickness that meets the requirements is S3; S25, the nominal thickness of the cylinder (1) is S = max[S1, S2, S3]; S26. The force model of the upper end cover (3) and the lower end cover (4) is simplified to a conical shell, and the cone surface semi-apex angle of the conical hole of the material outlet (301) and the material inlet (401) is set to α, the maximum diameter is D3, and the minimum diameter is D4; the equivalent cone shell thickness calculation formula is: ε—dimensionless weighted adjustment coefficient, which is 0.95 when the half apex angle is 75° and 1.05 when the half apex angle is 65°. Other angles are interpolated. [σ] t —Allowable material stress of the cylinder, end cover and support plate, MPa; p c —Design pressure, MPa; The thickness S6 of the upper end cover (3) and the lower end cover (4) is calculated using the formula: Where: S5—the depth of the bolt hole on the upper end cover, mm, is the set value.

3. The method for designing a melt filtration device according to claim 2, characterized in that: The step S3 comprises: S31. According to the operating requirements of the process system, the pressure difference is set to Δp; S32, determining the outer diameter D5 of the support plate (5) according to the size of the sealing gasket (6); S33, calculating the initial thickness of the support plate (5), the formula is: S34, setting the number of filter elements to n1, the cross-sectional area of ​​the filtrate channel (501) to A1, and the nominal thickness of the filter element support plate to:

4. The method for designing a melt filtration device according to claim 2, characterized in that: The step S4 comprises: S41. The selected sealing gasket (6) is a type without inner and outer reinforcement rings; when calculating, it is assumed that the sealing gasket (6) is always in an elastic state during pre-tightening and operation; S42. Calculate the pre-tightening compression of the sealing gasket (6), that is, the reserved initial fitting clearance between the two parts in contact with the sealing gasket (6), using the formula: Where: S 10 —Thickness of sealing gasket, mm; E—equivalent elastic modulus of the sealing gasket, MPa; A2—Cross-sectional area of ​​the sealing gasket, mm 2 ; S43, calculating the groove depth of the installation groove of the sealing gasket (6), the formula is: S 11 =S 10 -S9 S44. Calculate the slot width of the installation slot of the sealing gasket (6) using the formula: Where: S 12 —Width of sealing pad, mm; D G —The diameter of the sealing gasket’s effective center circle shall be determined in accordance with GB / T 150.3, mm.

5. The method for designing a melt filtration device according to claim 1, characterized in that: The step S5 comprises: S51, the set loads of the inlet pipe connected to the inlet pipe (402) are Fx1, Fy1, Fz1, and the set moments are Mx1, My1, Mz1; S52, using the flat cover opening model in the NSAS software to check the overall structure of the lower end cover (4) and the inlet pipe (402), and obtain the thickness of the inlet pipe (402) that meets the requirements; S53, the set load of the outlet pipe connected to the outlet flange (9) is Fx2, Fy2, Fz2, and the set moment is Mx2, My2, Mz2; S54. Select a suitable outlet flange (9). The maximum allowable working pressure p of the outlet flange (9) R The following conditions should be met: Where: d G —The diameter of the center circle of the outlet flange sealing gasket shall be determined according to GB / T 150.3, mm; p e —Equivalent design pressure of outlet flange, Pa.

6. The method for designing a melt filtration device according to claim 1, characterized in that: In step S1, the heat-insulating jacket (7) comprises an inner shell (701) and an outer shell (702) sleeved on the outer side of the inner shell (701), and a gap for filling a heat medium material is provided between the inner shell (701) and the outer shell (702); The step S6 comprises: the gap size between the inner shell (701) and the outer shell (702) is t i , the gap is t i The approximate calculation is based on the equivalent insulation thickness, and the formula is: h i —Convection heat transfer coefficient between the outer wall of the jacket and the heat medium material, W / [mm 2 ×℃]; H i —Equivalent heat transfer film coefficient, W / [mm 2 ×℃]; K i —Thermal conductivity of heat medium material of equivalent insulation thickness, W / [mm×℃]; λ—Heat loss weighted adjustment coefficient, ranging from 1.05 to 1.

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7. The method for designing a melt filtration device according to claim 6, characterized in that: In the step S1, a spiral baffle (703) is fixedly connected between the inner shell (701) and the outer shell (702), and the spiral baffle (703) divides the gap between the inner shell (701) and the outer shell (702) into a spiral channel for the heat medium material to pass through; The step S6 comprises: The wall thickness δ1 of the inner shell (701) and the outer shell (702) is calculated as follows: L—pitch of spiral baffle, mm; p j —Set internal pressure of the insulation jacket, MPa; —Allowable stress of the selected insulation jacket material, MPa.

8. The method for designing a melt filtration device according to claim 2, characterized in that: In step S26, the value range of the cone half apex angle α is 65° to 75°.

9. The method for designing a melt filtration device according to claim 5, characterized in that: In step S52, when the flat cover opening model in the NSAS software is used to check the overall structure of the lower end cover (4) and the inlet pipe (402), the allowable coefficient of the primary stress is selected as 2.0, and the allowable combination coefficient of the primary stress + the secondary stress is selected as 2.

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10. The method for designing a melt filtration device according to claim 5, characterized in that: In step S6, the wall thickness δ1 of the inner shell (701) and the outer shell (702) needs to be no less than 6 mm.

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