Method for automatically monitoring the fouling resistance of a target shell-and-tube heat exchanger of a distillation column

Abstract

The present application relates to a kind of rectifying column target shell-and-tube heat exchanger fouling thermal resistance automatic monitoring method, according to the thermodynamic property parameter of the obtained rectifying column target shell-and-tube heat exchanger industrial stream obtains its stream phase transition interval, stream phase transition interval is pre-divided into corresponding preset number of substream phase transition interval, i.e. strict division stream phase transition interval is strictly divided, to each substream phase transition interval is evaluated, and the thermodynamic property of gas-liquid phase of each substream phase transition interval is respectively obtained, heat exchanger heat transfer model matched with the corresponding substream phase transition interval of target shell-and-tube heat exchanger is established, the clean total heat transfer coefficient and actual fouling total heat transfer coefficient of target shell-and-tube heat exchanger are calculated, and then the total fouling thermal resistance value of target shell-and-tube heat exchanger under current working condition is obtained, realizes the condenser and reboiler fouling thermal resistance automatic monitoring method of rectifying column, improves calculation accuracy.

Description

Technical Field

[0001] This invention relates to the field of distillation columns and steam networks, and more particularly to an automatic monitoring method for fouling thermal resistance of target shell-and-tube heat exchangers in distillation columns. This method aims to provide gas flow rate and liquid reflux to the distillation column through gas boiling and vaporization, condensation and liquefaction, and steam regeneration for industrial waste heat recovery, thereby enabling automatic monitoring of fouling thermal resistance in shell-and-tube reboilers and condensers. Background Technology

[0002] A distillation column, as a tower-type vapor-liquid contact device, separates mixtures to purify target components through a distillation process. Its working principle utilizes the different vapor pressures (i.e., relative volatility) of the components in the mixture at the same temperature, causing lower-boiling-point components in the liquid phase to transfer to the vapor phase, and higher-boiling-point components in the vapor phase to transfer to the liquid phase, thus achieving separation. Distillation columns are widely used in petrochemical production and are important mass and heat transfer separation equipment. A distillation column mainly consists of a preheater, a condenser, and a reboiler, with the condenser and reboiler both being shell-and-tube heat exchangers.

[0003] The separation efficiency of a distillation column primarily depends on the vapor-liquid phase equilibrium and mass transfer of the trays. The reboiler at the bottom of the column vaporizes a portion of the bottom product to provide the vapor flow within the column. The condenser at the top of the column condenses a portion of the top product, which flows into the reflux reflux tank and back into the column to provide the liquid flow. Therefore, efficient heat transfer and safe operation of the condenser and reboiler are crucial to the normal operation of the distillation column.

[0004] During the operation of a distillation column, fouling continuously forms due to the erosion and deposition of fluids. The accumulation of this fouling reduces the operating efficiency of the condenser and reboiler, and may even lead to structural damage, thus posing a significant safety hazard to the normal operation of the distillation column.

[0005] Therefore, how to automatically and accurately monitor the fouling thermal resistance of the shell-and-tube condenser and reboiler in a distillation column, thereby ensuring the efficient and safe operation of the distillation column, has become an important technical problem that needs to be solved in the safety management of distillation columns. Solving this problem can not only improve the operating efficiency of the distillation column and reduce the equipment failure rate, but also provide greater safety assurance for petrochemical production. Summary of the Invention

[0006] To address the technical problems described above, this invention provides an automatic monitoring method for fouling thermal resistance of a target shell-and-tube heat exchanger in a distillation column. This automatic fouling thermal resistance monitoring method can automatically and accurately detect the fouling thermal resistance of a target shell-and-tube heat exchanger in a distillation column, thereby improving the operating efficiency of the distillation column and reducing equipment failure rate.

[0007] The technical solution adopted by this invention to solve the above-mentioned technical problems is: an automatic monitoring method for fouling thermal resistance of a target shell-and-tube heat exchanger in a distillation column, characterized by comprising the following steps:

[0008] To obtain the industrial material properties of a target shell-and-tube heat exchanger on a distillation column; wherein the target shell-and-tube heat exchanger is a shell-and-tube condenser and / or a reboiler;

[0009] Establish a heat transfer model for a shell-and-tube heat exchanger that matches the target type of shell-and-tube heat exchanger.

[0010] Based on the industrial material properties of the target shell-and-tube heat exchanger and the heat transfer model of the shell-and-tube heat exchanger, the overall clean heat transfer coefficient of the target shell-and-tube heat exchanger under clean conditions is calculated.

[0011] The heat load, heat transfer temperature difference, and heat transfer area of ​​the target shell-and-tube heat exchanger under the current operating conditions are obtained, and the actual total fouling heat transfer coefficient of the target shell-and-tube heat exchanger under the current operating conditions is calculated based on the obtained heat load, heat transfer temperature difference, and heat transfer area.

[0012] Based on the calculated clean total heat transfer coefficient and the actual fouling total heat transfer coefficient of the target shell-and-tube heat exchanger, the total fouling thermal resistance of the target shell-and-tube heat exchanger under the current operating conditions is obtained.

[0013] In an improved version, in the automatic monitoring method for fouling thermal resistance of the target shell-and-tube heat exchanger in the distillation column, the target shell-and-tube heat exchanger is the reboiler of the distillation column; wherein, the process of establishing the heat transfer model of the heat exchanger is as follows:

[0014] Step a1: Obtain the structural parameters of the reboiler of the distillation column;

[0015] Step a2: Determine the reboiler type based on the reboiler structural parameters.

[0016] When the reboiler type is a kettle reboiler, a nucleus boiling heat transfer model is established to estimate the shell-side boiling heat transfer performance; when the reboiler type is a thermosiphon reboiler, proceed to step a3.

[0017] Step a3: Determine whether boiling occurs on the tube side of the thermosiphon reboiler:

[0018] When the boiling occurs on the tube side of a thermosiphon reboiler, a convective boiling heat transfer model is established to estimate the tube-side boiling heat transfer performance; otherwise, a nucleus boiling heat transfer model is established to estimate the shell-side boiling heat transfer performance.

[0019] In a further improvement, in the automatic monitoring method for fouling thermal resistance of the target shell-and-tube heat exchanger in the distillation column, the target shell-and-tube heat exchanger is the shell-and-tube condenser of the distillation column; wherein, the process of establishing the heat transfer model of the heat exchanger is as follows:

[0020] Step b1: Obtain the structural parameters of the shell-and-tube condenser for the distillation column;

[0021] Step b2, determine whether condensation occurs on the pipe side:

[0022] When condensation occurs on the tube side, a tube-side condensation two-phase model is established; otherwise, a shell-side condensation two-phase model is established.

[0023] Furthermore, in the automatic monitoring method for fouling thermal resistance of the target shell-and-tube heat exchanger in the distillation column, when the target shell-and-tube heat exchanger is a tube-side condenser, the process of establishing the tube-side condensation two-phase model is as follows:

[0024] Based on the obtained industrial material properties of the target shell-and-tube heat exchanger, the material condensation phase change range of the tube-side condenser is obtained.

[0025] The material condensation phase change zone of the tube-side condenser is divided into a preset number of sub-material condensation phase change zones;

[0026] Obtain the gas-liquid phase thermodynamic properties of each sub-login condensation phase transition region;

[0027] Based on the obtained thermodynamic properties of each sub-stream's gas-liquid phase, a tube-side condensation two-phase model corresponding to the condensation phase transition zone of each sub-stream is established. Improvedly, in the automatic monitoring method for fouling thermal resistance of the target shell-and-tube heat exchanger in the distillation column, the structural parameters of the target shell-and-tube heat exchanger include the heat exchanger's geometric parameters.

[0028] Improvedly, in the automatic monitoring method for fouling thermal resistance of the target shell-and-tube heat exchanger in the distillation column, the thermodynamic property parameters of the industrial stream of the target shell-and-tube heat exchanger obtained include the temperature data and liquid flow properties of the target shell-and-tube heat exchanger under actual operating conditions, as well as the thermodynamic property parameters obtained by process simulation technology based on actual test data.

[0029] Furthermore, the thermodynamic physical properties include viscosity, thermal conductivity, density, and specific heat.

[0030] In a further improvement, the method for automatically monitoring the fouling thermal resistance of the target shell-and-tube heat exchanger in the distillation column is as follows: The overall clean heat transfer coefficient of the target shell-and-tube heat exchanger is calculated as follows:

[0031]

[0032] h T =(h TB ·y STHT +h TL y kettle )y re +(hTL ·y Jshell +h TC y Ishell )y con ;

[0033] h S =(h SL ·y STHT +h NB y kettle )y re +(h SC ·y Jshell +h SL y Ishell )y con ;

[0034] Among them, U C This represents the overall clean heat transfer coefficient of the target shell-and-tube heat exchanger. Wherein, when the target shell-and-tube heat exchanger is a condenser, y con =1, y re =0; When the target shell-and-tube heat exchanger is a reboiler, y con =0, y re =1;

[0035] When the condenser is a shell-side condenser, y Jshell =1, y Ishell =0; when the condenser is a tube-side condenser, y Jshell =0, y Ishell =1;

[0036] When the reboiler is a shell-side boiling kettle-type reboiler, y kettle =1, y STHT =0; when the reboiler is a thermosiphon reboiler with tube-side boiling, y kettle =0, y STHT =1;

[0037] Heat transfer coefficient h without phase change tube TL The calculation method is as follows:

[0038]

[0039]

[0040] The heat transfer coefficient h of the shell side without phase change SL The calculation method is as follows:

[0041]

[0042]

[0043]

[0044]

[0045] The shell-side heat transfer coefficient h of a reboiler NB The calculation is as follows:

[0046]

[0047]

[0048]

[0049] Among them, Qf T For heat flow, h NB,S The heat transfer coefficient for single-tube bubble nucleus boiling is hm. NB,m h is the heat transfer coefficient of the mixture during nucleation boiling. NB PC is the shell-side nucleus boiling heat transfer coefficient of the reboiler. NB For critical pressure, PO NB For operating pressure, T dew T is the dew point in the boiling phase transition range. bub D represents the bubble point within the boiling phase transition range. SB P is the diameter of the reboiler tube bundle. T D is the reboiler tube spacing. O The outer diameter of the reboiler tube;

[0050] The tube-side convective boiling heat transfer coefficient h of the thermosiphon reboiler TB The calculation method is as follows:

[0051]

[0052] Among them, Xtt T,z The Lockhart-Martinelli parameters represent the boiling phase transition range, in μL. T,z The viscosity of the liquid phase in the boiling phase transition region is expressed in μV. T,z ρL represents the gas phase viscosity in the boiling phase transition region. T,z ρV represents the liquid phase density during the boiling phase transition. T,z This represents the gas phase density during the boiling phase transition phase.

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060] Where, ρ tp,z E represents the two-phase density during the boiling phase transition region. z F z and H z Calculate the empirical coefficients, Fr, for the two-phase product parameters respectively. z For the boiling phase transition interval Froude number, We z φ is the Weber number for the boiling phase transition range. LO,z is the product parameter of the two phases in the boiling phase transition range, g is the gravitational constant, and ST is the surface tension of the liquid phase;

[0061]

[0062]

[0063]

[0064] h L,z =(KL T / D i Nu L,z ;

[0065] Among them, Ret L,z Prt represents the liquid phase Reynolds number (Prt) in each boiling phase change zone on the tube side of the shell-and-tube heat exchanger. L,z Nu represents the Prandtl number of the liquid phase in each boiling phase change zone on the tube side of the shell-and-tube heat exchanger. L,z h represents the liquid phase Nusselt number in each boiling phase change zone on the tube side of the shell-and-tube heat exchanger. L,z This represents the liquid phase heat transfer coefficient in each boiling phase change zone on the tube side of the shell-and-tube heat exchanger.

[0066] Among them, when Xtt T,z <10 o'clock, When Xtt T,z When ≥10, FXtt z =1;

[0067]

[0068] Among them, FXtt z SCH represents the liquid phase heat transfer enhancement coefficient. z ReChen represents the heat transfer attenuation coefficient of nucleation boiling. z Indicates the two-phase corrected Reynolds number;

[0069] h TB,z =SCH z ·h NB+FXtt z h L,z ;

[0070]

[0071] Among them, h TB,z The heat transfer coefficient between the tube sides of the shell-and-tube heat exchanger represents the two-phase heat transfer coefficient of the boiling phase change zone, where Z is the total number of phase change zones; h TB This represents the tube-side average convective boiling heat transfer coefficient of the shell-and-tube heat exchanger.

[0072] Condenser-shell side condensation heat transfer coefficient h SC The calculation method is as follows:

[0073]

[0074] Condenser-tube side condensation heat transfer coefficient h TC The calculation method is as follows:

[0075]

[0076] Further improvements are made to the automatic monitoring method for fouling thermal resistance of the target shell-and-tube heat exchanger in the distillation column, wherein the actual total fouling heat transfer coefficient of the target shell-and-tube heat exchanger in its current state is calculated as follows:

[0077]

[0078] Wherein, U represents the actual total fouling heat transfer coefficient of the target shell-and-tube heat exchanger in the current state, Q represents the heat load of the target shell-and-tube heat exchanger in the current state, and T... LMTD,eff For effective logarithmic heat transfer temperature difference, S represents the heat transfer area of ​​the target shell-and-tube heat exchanger.

[0079] Furthermore, in the automatic monitoring method for fouling thermal resistance of the target shell-and-tube heat exchanger in the distillation column, the total fouling thermal resistance value of the target shell-and-tube heat exchanger in the current state is calculated as follows:

[0080]

[0081] Among them, R f The total fouling thermal resistance of the target shell-and-tube heat exchanger in its current state.

[0082] Compared with the prior art, the advantages of the present invention are as follows: The invention fully considers the vaporization phase change and condensation phase change effects of cold and hot flow in the heat exchanger of the distillation column during heating and cooling. Based on the thermodynamic property parameters of the industrial stream of the target shell-and-tube heat exchanger on the distillation column, the phase change interval of the industrial stream of the target shell-and-tube heat exchanger is obtained, and the phase change interval of the stream is pre-divided into a corresponding preset number of sub-stream phase change intervals. The gas-liquid phase thermodynamic properties of each sub-stream phase change interval are obtained, and a heat exchanger heat transfer model matching the sub-stream phase change interval of the target shell-and-tube heat exchanger is established. Then, the overall clean heat transfer coefficient of the target shell-and-tube heat exchanger under clean conditions and the actual fouling heat transfer coefficient under the current operating conditions are calculated, thereby obtaining the total fouling thermal resistance value of the target shell-and-tube heat exchanger on the distillation column under the current operating conditions. This invention, by strictly dividing the phase change intervals of the industrial stream in the target shell-and-tube heat exchanger on the distillation column, evaluates the phase change process of each sub-stream in order to assess the phase change intervals of the target shell-and-tube heat exchanger (such as condenser and reboiler). It realizes an automatic monitoring method for fouling thermal resistance of the target shell-and-tube heat exchanger in the distillation column, improves the calculation accuracy, ensures the safe operation of the distillation column, and avoids additional energy consumption losses. Attached Figure Description

[0083] Figure 1 This is a schematic diagram of the automatic monitoring method for fouling thermal resistance of the target shell-and-tube heat exchanger in a distillation column, as described in an embodiment of the present invention. Detailed Implementation

[0084] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0085] This embodiment provides an automatic monitoring method for fouling thermal resistance of a target shell-and-tube heat exchanger in a distillation column, used to automatically monitor the shell-and-tube condenser and reboiler of the distillation column. Specifically, see [link to documentation]. Figure 1 As shown, the automatic monitoring method for fouling thermal resistance of the target shell-and-tube heat exchanger in this embodiment includes the following steps 1 to 6:

[0086] Step 1: Obtain the industrial material properties of the target shell-and-tube heat exchanger on the distillation column; wherein the target shell-and-tube heat exchanger is a shell-and-tube condenser and / or a reboiler.

[0087] Specifically, in this embodiment, the thermodynamic property parameters of the industrial logistics include temperature data and liquid flow properties of the target shell-and-tube heat exchanger under actual operating conditions, as well as thermodynamic property parameters obtained by process simulation technology based on actual experimental data of the target shell-and-tube heat exchanger. Temperature and flow data are used as basic data and are collected from the actual operating conditions of the target shell-and-tube heat exchanger in the enterprise factory. The thermodynamic property parameters include viscosity, thermal conductivity, density, and specific heat, which are obtained from actual experimental data of the logistics products or raw materials themselves. The process simulation technology used in this embodiment is a mature existing technology in the field, and the thermodynamic property parameters are obtained by performing process simulation on the obtained thermodynamic property parameters.

[0088] Step 2: Establish a heat transfer model for a shell-and-tube heat exchanger that matches the target type of shell-and-tube heat exchanger.

[0089] Step 3: Based on the industrial material properties of the target shell-and-tube heat exchanger and the heat transfer model of the shell-and-tube heat exchanger, calculate the overall clean heat transfer coefficient of the target shell-and-tube heat exchanger under clean conditions.

[0090] Step 4: Obtain the heat load, heat transfer temperature difference, and heat transfer area of ​​the target shell-and-tube heat exchanger under the current operating conditions, and calculate the actual total fouling heat transfer coefficient of the target shell-and-tube heat exchanger under the current operating conditions based on the obtained heat load, heat transfer temperature difference, and heat transfer area.

[0091] Step 5: Based on the calculated total clean heat transfer coefficient and the actual total fouling heat transfer coefficient of the target shell-and-tube heat exchanger, obtain the total fouling thermal resistance of the target shell-and-tube heat exchanger under the current operating conditions.

[0092] Regarding step 2 in this embodiment:

[0093] When the target shell-and-tube heat exchanger is the reboiler of a distillation column, the process of establishing the heat transfer model for this heat exchanger is as follows: steps a1 to a3:

[0094] Step a1: Obtain the reboiler structural parameters of the distillation column; wherein, in this embodiment, the reboiler structural parameters include reboiler geometric parameters, such as common geometric parameters like inner tube diameter, outer tube diameter, tube spacing, number of tube passes, inner shell diameter, area of ​​the reboiler heat exchanger, and number of shell passes; industrial streams are raw material streams within a plant that need to be heated to specific temperatures required for separation or reaction processes, and that need to be cooled to specific temperatures for separation, storage, etc., such as crude oil, or product streams such as diesel, reactor products, etc.

[0095] Step a2: Determine the reboiler type based on the reboiler structural parameters.

[0096] When the reboiler type is a kettle reboiler, a nucleus boiling heat transfer model is established to estimate the heat transfer based on the shell-side boiling; when the reboiler type is a thermosiphon reboiler, proceed to step a3.

[0097] Step a3: Determine whether boiling occurs on the tube side of the thermosiphon reboiler:

[0098] When the boiling occurs on the tube side of a thermosiphon reboiler, a convective boiling heat transfer model is established to estimate the tube-side boiling heat transfer; otherwise, a nucleus boiling heat transfer model is established to estimate the shell-side boiling heat transfer.

[0099] When the target shell-and-tube heat exchanger is a shell-and-tube condenser of a distillation column, the process of establishing the heat transfer model for this heat exchanger is as follows: steps b1 to b2:

[0100] Step b1: Obtain the structural parameters of the shell-and-tube condenser for the distillation column;

[0101] Step b2, determine whether condensation occurs on the pipe side:

[0102] When condensation occurs on the tube side, a tube-side condensation two-phase model is established; otherwise, a shell-side condensation two-phase model is established.

[0103] For example, when the target shell-and-tube heat exchanger is a tube-side condenser, the process of establishing the tube-side condensation two-phase model is as follows:

[0104] Based on the obtained industrial material properties of the target shell-and-tube heat exchanger, the material condensation phase change range of the tube-side condenser is obtained.

[0105] The material condensation phase change zone of the tube-side condenser is divided into a preset number of sub-material condensation phase change zones;

[0106] Obtain the gas-liquid phase thermodynamic properties of each sub-login condensation phase transition region;

[0107] Based on the obtained thermodynamic properties of each sub-stream gas-liquid phase, a pipe-side condensation two-phase model corresponding to the condensation phase transition interval of each sub-stream is established.

[0108] It should be noted that the more sub-stream condensation phase transition intervals there are, the smaller the temperature difference between each sub-stream condensation phase transition interval, and the more accurate the calculation. The gas-liquid phase thermodynamic properties of each sub-stream condensation phase transition interval can be sensitively analyzed based on the experimental data of the stream. For the target stream, changing its temperature can further obtain the results.

[0109] In this embodiment, the calculation method for the overall clean heat transfer coefficient of the shell-and-tube condenser and the reboiler is as follows:

[0110]

[0111] h T =(h TB ·y STHT +h TL y kettle )y re +(h TL ·y Jshell +h TC y Ishell )y con ;

[0112] h S =(h SL ·y STHT +h NB y kettle )y re +(h SC ·y Jshell +h SL y Ishell )y con ;

[0113] Among them, U C This represents the overall clean heat transfer coefficient of the target shell-and-tube heat exchanger. Where the target shell-and-tube heat exchanger is a condenser, y... con =1, y re =0; When the target shell-and-tube heat exchanger is a reboiler, y con =0, y re =1;

[0114] When the condenser is a shell-side condenser, y Jshell =1, y Ishell =0; when the condenser is a tube-side condenser, y Jshell =0, y Ishell =1;

[0115] When the reboiler is a shell-side boiling kettle-type reboiler, y kettle =1, y STHT =0; when the reboiler is a thermosiphon reboiler with tube-side boiling, y kettle =0, y STHT =1;

[0116] Heat transfer coefficient h without phase change tube TL The calculation method is as follows:

[0117]

[0118]

[0119] The heat transfer coefficient h of the shell side without phase change SL The calculation method is as follows:

[0120]

[0121]

[0122]

[0123]

[0124] The shell-side heat transfer coefficient h of a reboiler NB The calculation is as follows:

[0125]

[0126]

[0127]

[0128] Among them, Qf T For heat flow, h NB,S The heat transfer coefficient for single-tube bubble nucleus boiling is hm. NB,m h is the heat transfer coefficient of the mixture during nucleation boiling. NB PC is the shell-side nucleus boiling heat transfer coefficient of a reboiler. NB For critical pressure, PO NB For operating pressure, T dew T is the dew point in the boiling phase transition range. bub D represents the bubble point within the boiling phase transition range. SB P is the diameter of the reboiler tube bundle. T D is the reboiler tube spacing. O The outer diameter of the reboiler tube;

[0129] The tube-side convective boiling heat transfer coefficient h of the thermosiphon reboiler TB The calculation method is as follows:

[0130]

[0131] Among them, Xtt T,z The Lockhart-Martinelli parameters represent the boiling phase transition range, in μL. T,z The viscosity of the liquid phase in the boiling phase transition region is expressed in μV. T,z ρL represents the gas phase viscosity in the boiling phase transition region. T,z ρV represents the liquid phase density during the boiling phase transition. T,z This represents the gas phase density during the boiling phase transition phase.

[0132]

[0133]

[0134]

[0135]

[0136]

[0137]

[0138]

[0139] Where, ρ tp,z E represents the two-phase density during the boiling phase transition region. z F z and H z Calculate the empirical coefficients, Fr, for the two-phase product parameters respectively. z For the boiling phase transition interval Froude number, We z φ is the Weber number for the boiling phase transition range. LO,z is the product parameter of the two phases in the boiling phase transition range, g is the gravitational constant, and ST is the surface tension of the liquid phase;

[0140]

[0141]

[0142]

[0143] h L,z =(KL T / D i Nu L,z ;

[0144] Among them, Ret L,z Prt represents the liquid phase Reynolds number in each boiling phase change zone on the tube side of a shell-and-tube heat exchanger. L,z Nu represents the Prandtl number of the liquid phase in each boiling phase change zone on the tube side of a shell-and-tube heat exchanger. L,z h represents the liquid Nusselt number in each boiling phase change zone on the tube side of a shell-and-tube heat exchanger. L,z This represents the liquid phase heat transfer coefficient in each boiling phase change zone on the tube side of a shell-and-tube heat exchanger.

[0145] Among them, when Xtt T,z <10 o'clock, When Xtt T,z When ≥10, FXtt z =1;

[0146]

[0147] Among them, FXtt z SCH represents the liquid phase heat transfer enhancement coefficient. z ReChen represents the heat transfer attenuation coefficient of nucleation boiling. zIndicates the two-phase corrected Reynolds number;

[0148] h TB,z =SCH z ·h NB +FXtt z h L,z ;

[0149]

[0150] Among them, h TB,z Z represents the two-phase heat transfer coefficient of the tube-side boiling phase change zone in a shell-and-tube heat exchanger, where Z is the total number of phase change zones; h TB This represents the tube-side average convective boiling heat transfer coefficient of a shell-and-tube heat exchanger.

[0151] Condenser-shell side condensation heat transfer coefficient h SC The calculation method is as follows:

[0152]

[0153] Condenser-tube side condensation heat transfer coefficient h TC The calculation method is as follows:

[0154]

[0155] In this embodiment, the actual total fouling heat transfer coefficient of each target shell-and-tube heat exchanger in its current state is calculated as follows, for both shell-and-tube condensers and reboilers:

[0156]

[0157] Where U represents the actual total fouling heat transfer coefficient of the target shell-and-tube heat exchanger in the current state, Q represents the heat load of the target shell-and-tube heat exchanger in the current state, and T LMTD,eff For effective logarithmic heat transfer temperature difference, S represents the heat transfer area of ​​the target shell-and-tube heat exchanger. It should be noted that the heat load referred to here is the actual operating data of the target shell-and-tube heat exchanger in the factory. The heat load Q of the target shell-and-tube heat exchanger in the current state is obtained based on the actual test data of the target shell-and-tube heat exchanger and processed using process simulation technology.

[0158]

[0159]

[0160]

[0161] T LMTD,eff For effective logarithmic heat transfer temperature difference, T HI T represents the inlet temperature of the heat flow. HOT represents the outlet temperature of the heat flow. CO T represents the outlet temperature of the cold flow. CI Indicates the inlet temperature of the cold flow, F T The logarithmic temperature difference correction coefficient is given by R, P, α, and S1, which are transient parameters, respectively. shells F represents the number of shell passes in series; TC This represents the correction factor for the average logarithmic heat transfer temperature difference, and the effective logarithmic heat transfer temperature difference T. LMTD,eff The mean logarithmic temperature difference and F TC The product between them.

[0162] In this embodiment, the total fouling thermal resistance of each target shell-and-tube heat exchanger in its current state is calculated as follows:

[0163]

[0164] Among them, R f The total fouling thermal resistance of the target shell-and-tube heat exchanger in its current state.

[0165] For example, a boiling phase change heat transfer model that matches the selected target shell-and-tube heat exchanger can be selected based on the detected gas phase mass fraction. When the detected gas phase mass fraction is 0, a convection heat transfer model is used; when the detected gas phase mass fraction is greater than 0 or less than 1, a phase change correction model and a nucleation boiling correction model are used to calculate the heat transfer coefficient.

[0166] Although preferred embodiments of the present invention have been described in detail above, it should be clearly understood that various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An automatic monitoring method for fouling thermal resistance of a target shell-and-tube heat exchanger in a distillation column, characterized in that, Includes the following steps: To obtain the industrial material properties of a target shell-and-tube heat exchanger on a distillation column; wherein the target shell-and-tube heat exchanger is a shell-and-tube condenser and / or a reboiler; Establish a heat transfer model for a shell-and-tube heat exchanger that matches the target type of shell-and-tube heat exchanger. Based on the industrial material properties of the target shell-and-tube heat exchanger and the heat transfer model of the shell-and-tube heat exchanger, the overall clean heat transfer coefficient of the target shell-and-tube heat exchanger under clean conditions is calculated. The heat load, heat transfer temperature difference, and heat transfer area of ​​the target shell-and-tube heat exchanger under the current operating conditions are obtained, and the actual total fouling heat transfer coefficient of the target shell-and-tube heat exchanger under the current operating conditions is calculated based on the obtained heat load, heat transfer temperature difference, and heat transfer area. Based on the calculated clean total heat transfer coefficient and the actual fouling total heat transfer coefficient of the target shell-and-tube heat exchanger, the total fouling thermal resistance of the target shell-and-tube heat exchanger under the current operating conditions is obtained. In the process of establishing a heat transfer model for a shell-and-tube heat exchanger that matches the target type of shell-and-tube heat exchanger: When the target shell-and-tube heat exchanger is a reboiler of a distillation column, the process of establishing the heat transfer model of the heat exchanger is as follows: Step a1: Obtain the structural parameters of the reboiler of the distillation column; Step a2: Determine the reboiler type based on the reboiler structural parameters. When the reboiler type is a kettle reboiler, a nucleus boiling heat transfer model is established to estimate the shell-side boiling heat transfer performance; when the reboiler type is a thermosiphon reboiler, proceed to step a3. Step a3: Determine whether boiling occurs on the tube side of the thermosiphon reboiler: When the boiling occurs on the tube side of a thermosiphon reboiler, a convective boiling heat transfer model is established to estimate the tube-side boiling heat transfer performance; otherwise, a nucleus boiling heat transfer model is established to estimate the shell-side boiling heat transfer performance. When the target shell-and-tube heat exchanger is a shell-and-tube condenser of a distillation column, the process of establishing the heat transfer model of the heat exchanger is as follows: Step b1: Obtain the structural parameters of the shell-and-tube condenser for the distillation column; Step b2, determine whether condensation occurs on the pipe side: When condensation occurs on the tube side, a tube-side condensation two-phase model is established; otherwise, a shell-side condensation two-phase model is established.

2. The method for automatic monitoring of fouling thermal resistance in a target shell-and-tube heat exchanger of a distillation column according to claim 1, characterized in that, When the target shell-and-tube heat exchanger is a tube-side condenser, the process of establishing the tube-side condensation two-phase model is as follows: Based on the obtained industrial material properties of the target shell-and-tube heat exchanger, the material condensation phase change range of the tube-side condenser is obtained. The material condensation phase change zone of the tube-side condenser is divided into a preset number of sub-material condensation phase change zones; Obtain the gas-liquid phase thermodynamic properties of each sub-login condensation phase transition region; Based on the obtained thermodynamic properties of each sub-stream gas-liquid phase, a pipe-side condensation two-phase model corresponding to the condensation phase transition interval of each sub-stream is established.

3. The method for automatic monitoring of fouling thermal resistance in the target shell-and-tube heat exchanger of a distillation column according to claim 1, characterized in that, The structural parameters of the target shell-and-tube heat exchanger include the heat exchanger's geometric parameters.

4. The method for automatic monitoring of fouling thermal resistance of a target shell-and-tube heat exchanger in a distillation column according to claim 1, characterized in that, The thermodynamic property parameters of the target shell-and-tube heat exchanger industrial flow include temperature data, liquid flow properties, and thermodynamic property parameters obtained by process simulation technology based on actual test data under actual operating conditions.

5. The method for automatic monitoring of fouling thermal resistance in a target shell-and-tube heat exchanger of a distillation column according to claim 4, characterized in that, The thermodynamic physical properties include viscosity, thermal conductivity, density, and specific heat.

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