Generalized tray solution method and apparatus for distillation columns

Abstract

This application discloses a general method and apparatus for solving distillation tray temperature, which allows the initial value of the tray temperature in iterations to be set to a value that, during iterative calculations, only requires comparing the total specific enthalpy of the gas-liquid two-phase system and the total specific enthalpy of the feed to determine the next iteration. For different convergence errors ε, the maximum number of iterations for the tray temperature is log2((T)). n,d -T n,b The method (ε) is applicable to solving mixtures with wide and narrow boiling ranges. The initial values ​​for iteration are easy to determine, and it has good convergence and stability.

Description

Technical Field

[0001] This application relates to the field of distillation column simulation modeling technology, specifically to a general method and apparatus for solving distillation column trays. Background Technology

[0002] Distillation is a separation process that separates components in a mixture by utilizing their different volatility. The calculation of distillation trays is very complex. The usual method for solving distillation trays is based on the Rachford-Rice flash equation and the heat balance equation, which includes two independent variables, temperature T and vaporization rate R, and uses an adiabatic flash algorithm that iterates between the inner and outer layers.

[0003] For wide-boiling-range mixtures, the flash evaporation equation combined with the vaporization rate R is used as the inner iteration layer, and the heat balance equation combined with the temperature T is used as the outer iteration layer. For narrow-boiling-range mixtures, the flash evaporation equation combined with the temperature T is used as the inner iteration layer, and the heat balance equation combined with the vaporization rate R is used as the outer iteration layer. This makes the calculation more complex, has poor versatility, and may fail to converge if the initial values ​​of the iteration are not chosen appropriately. Summary of the Invention

[0004] Therefore, this application provides a general method and apparatus for solving distillation trays, in order to solve the problems of computational complexity, poor versatility, and potential convergence failure due to inappropriate selection of initial values ​​in the prior art.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] Firstly, a general method for determining distillation trays includes:

[0007] S1: Obtain tray pressure P n Where n is the tray number;

[0008] S2: Calculate the total feed composition of the trays Total feed enthalpy of tray Where i is the component number;

[0009] S3: Calculate the tray pressure P n and the total feed composition of the tray The bubble point temperature T n,b and dew point temperature T n,d ;

[0010] S4: Order Let the initial value of the tray temperature be... but

[0011] S5: Calculate the tray pressure P n and tray temperature The liquid phase component x n,i and gas phase component y n,i ;

[0012] S6: Calculate the liquid flow rate L on the tray n and gas phase flow rate V n ;

[0013] S7: Calculate the tray temperature according to the first formula. Total enthalpy of gas and liquid phases

[0014] The first formula is: Among them, h n For liquid phase enthalpy, H n Compared to enthalpy;

[0015] S8: Determine the overall specific enthalpy of the gas-liquid two-phase system. and the total feed enthalpy of the tray Size;

[0016] S9: If Then the iteration exits and the calculation ends, where ε is the convergence error;

[0017] S10: If and Then let Return to step S5 and perform iterative calculations;

[0018] S11: If and Then let Return to step S5 and perform iterative calculations.

[0019] Preferably, the bubble point temperature T n,b The dew point temperature T n,d The liquid phase component x n,i and the gas phase component y n,i It is calculated based on the phase equilibrium equation and the component normalization equation.

[0020] Preferably, the phase equilibrium constant of the phase equilibrium equation is K. n =f(T) n ,P n ).

[0021] Preferably, the liquid phase component x n,i and the gas phase component y n,i It is calculated based on the material balance equation.

[0022] Preferably, the material balance equation is:

[0023] (F·xF,i +L n-1 ·x n-1,i +V n+1 ·y n+1,i ) = L n ·x n,i +V n ·y n,i ,

[0024] F+L n-1 +V n+1 =L n +V n ,

[0025] Where F is the tray feed flow rate, and x is the feed component. F,i L n-1 The liquid flow rate of the upper tray is given by x, and the liquid phase composition is given by x. n-1,i V n+1 The gas flow rate of the lower tray is given by y, and the gas composition is given by y. n+1,i .

[0026] Preferably, the total feed composition of the tray for:

[0027]

[0028] Preferably, the total feed enthalpy of the tray is... for:

[0029]

[0030] Secondly, a universal distillation tray solver includes:

[0031] The parameter acquisition module is used to obtain the tray feed flow rate F and feed composition x. F,i Enthalpy of feed ratio h F Liquid flow rate L on the upper tray n-1 Liquid phase component x n-1,i Liquid phase enthalpy h n-1 Gas flow rate V in the lower tray n+1 Gas phase component y n+1,i enthalpy of gases H n+1 and tray pressure P n , where n is the tray number and i is the component number;

[0032] The first calculation module is used to calculate the total feed composition of the trays. Total feed enthalpy of tray Bubble point temperature T n,b and dew point temperature T n,d ;

[0033] The iterative initial value determination module is used to set... Let the initial value of the tray temperature be... but

[0034] The second calculation module is used to calculate the liquid phase component x. n,i Gas phase component y n,i Liquid flow rate (L) on tray n Gas phase flow rate V n Specific enthalpy of gas and liquid phases

[0035] The judgment module is used to determine the overall specific enthalpy of the gas-liquid two-phase system. and the total feed enthalpy of the tray Size;

[0036] like Then the iteration exits and the calculation ends, where ε is the convergence error;

[0037] like and Then let Return and perform iterative calculations;

[0038] like and Then let Return and perform iterative calculations.

[0039] Compared with the prior art, this application has at least the following beneficial effects:

[0040] This application provides a general method and apparatus for solving distillation tray temperature problems, where the initial value for iterative tray temperature is... Furthermore, during iterative calculations, only the overall specific enthalpy of the gas and liquid phases needs to be compared. Enthalpy of total feed The next iteration can then be determined. For different convergence errors ε, the maximum number of iterations for the tray temperature is log2((T n,d -T n,b The method (ε) is applicable to solving mixtures with wide and narrow boiling ranges. The initial values ​​for iteration are easy to determine, and it has good convergence and stability. Attached Figure Description

[0041] To more intuitively illustrate the prior art and this application, several exemplary figures are provided below. It should be understood that the specific shapes and structures shown in the figures should not generally be regarded as limiting conditions for implementing this application; for example, based on the technical concept disclosed in this application and the exemplary figures, those skilled in the art are able to easily make conventional adjustments or further optimizations to the addition / reduction / classification, specific shapes, positional relationships, connection methods, size ratios, etc. of certain units (components).

[0042] Figure 1 A flowchart illustrating a general method for solving distillation trays, as provided in this application embodiment. Detailed Implementation

[0043] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] In the description of this application: unless otherwise stated, "a plurality of" means two or more. The terms "first," "second," "third," etc., in this application are intended to distinguish the objects referred to and do not have any special meaning in terms of technical connotation (e.g., they should not be construed as an emphasis on importance or order). Expressions such as "comprising," "including," and "having" also mean "not limited to" (certain units, components, materials, steps, etc.).

[0045] The terms used in this application, such as "upper," "lower," "left," "right," and "middle," are generally used to facilitate intuitive understanding by referring to the accompanying drawings, and are not absolute limitations on the positional relationships in the actual product. Changes in these relative positional relationships, without departing from the technical concept disclosed in this application, should also be considered within the scope of this application.

[0046] Please see Figure 1 The embodiments of this application provide a general method for solving distillation trays, including:

[0047] S1: Obtain tray pressure P n Where n is the tray number;

[0048] S2: Calculate the total feed composition of the trays Total feed enthalpy of tray Where i is the component number;

[0049] Specifically, the total feed composition of the trays for:

[0050]

[0051] Total feed enthalpy of tray for:

[0052]

[0053] Wherein, the tray feed flow rate F, and the feed component x F,i Enthalpy of feed ratio h F Liquid flow rate L on the upper tray n-1 Liquid phase component x n-1,i liquid relative enthalpy h n-1 Gas flow rate V in the lower tray n+1 gas phase component y n+1,iCompared to enthalpy H n+1 Where n is the tray number and i is the component number;

[0054] S3: Calculate the tray pressure P based on the phase equilibrium equation and the component normalization equation. n The total feed composition of the tray is as follows: The bubble point temperature T at that time n,b and dew point temperature T n,d ;

[0055] Specifically, the equilibrium equation is: y n,i =K n,i ·x n,i ;

[0056] The component normalization equation is: ∑ i x n,i =1

[0057] ∑ i y n,i =1;

[0058] Wherein, the phase equilibrium constant of component i is K n =f(T) n ,P n );

[0059] S4: Order Assume the initial value of the tray temperature during iteration is but

[0060] S5: Calculate the tray pressure P based on the phase equilibrium equation and the component normalization equation. n tray temperature The liquid phase component x n,i and gas phase component y n,i ;

[0061] Specifically, the equilibrium equation is: y n,i =K n,i ·x n,i ;

[0062] The component normalization equation is: ∑ i x n,i =1

[0063] Σ i y n,i =1;

[0064] Wherein, the phase equilibrium constant of component i is K n =f(T) n ,P n );

[0065] S6: Calculate the liquid flow rate L on the tray based on the material balance equation. n and gas phase flow rate V n ;

[0066] The material balance equation is: (F·x) F,i +L n-1 ·x n-1,i +V n+1 ·y n+1,i ) = L n ·x n,i +V n ·y n,i ;

[0067] F+L n-1 +V n+1 =L n +V n ;

[0068] S7: Calculate the tray temperature according to equation (1) Total enthalpy of gas and liquid phases

[0069]

[0070] S8: Compare the overall specific enthalpy of the gas and liquid phases Enthalpy of total feed

[0071] S9: If (ε is the convergence error), then exit the iteration and the calculation ends;

[0072] S10: If and Then let Return to step S5 and perform iterative calculations;

[0073] S11: If and Then let Return to step S5 and perform iterative calculations.

[0074] Embodiments of this application provide a universal distillation tray solver, comprising:

[0075] The parameter acquisition module is used to obtain the tray feed flow rate F and feed composition x. F,i Enthalpy of feed ratio h F Liquid flow rate L on the upper tray n-1 Liquid phase component x n-1,i Liquid phase enthalpy h n-1 Gas flow rate V in the lower tray n+1 Gas phase component y n+1,i enthalpy of gases H n+1 and tray pressure Pn , where n is the tray number and i is the component number;

[0076] The first calculation module is used to calculate the total feed composition of the trays. Total feed enthalpy of tray Bubble point temperature T n,b and dew point temperature T n,d ;

[0077] The iterative initial value determination module is used to set... Let the initial value of the tray temperature be... but

[0078] The second calculation module is used to calculate the liquid phase component x. n,i Gas phase component y n,i Liquid flow rate (L) on tray n Gas phase flow rate V n Specific enthalpy of gas and liquid phases

[0079] The judgment module is used to determine the overall specific enthalpy of the gas-liquid two-phase system. and the total feed enthalpy of the tray Size;

[0080] like Then the iteration exits and the calculation ends, where ε is the convergence error;

[0081] like and Then let Return and perform iterative calculations;

[0082] like and Then let Return and perform iterative calculations.

[0083] This application provides a general method and apparatus for solving distillation tray temperature problems, where the initial value for iterative tray temperature is... Furthermore, during iterative calculations, only the overall specific enthalpy of the gas and liquid phases needs to be compared. Enthalpy of total feed The next iteration can then be determined. For different convergence errors ε, the maximum number of iterations for the tray temperature is log2((T n,d -T n,b The method (ε) is applicable to solving mixtures with wide and narrow boiling ranges. The initial values ​​for iteration are easy to determine, and it has good convergence and stability, making it suitable for the field of distillation column simulation modeling.

[0084] The technical features of the above embodiments can be combined in any way (as long as there is no contradiction in the combination of these technical features). For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; these embodiments not explicitly written should also be considered to be within the scope of this specification.

[0085] The present application has been described in a relatively specific and detailed manner above through general descriptions and specific embodiments. It should be understood that, based on the technical concept of the present application, several conventional adjustments or further innovations can be made to these specific embodiments; however, as long as they do not depart from the technical concept of the present application, the technical solutions obtained by these conventional adjustments or further innovations also fall within the protection scope of the claims of the present application.

Claims

1. A general method for solving distillation tray calculations, characterized in that, include: S1: Obtain tray pressure P n Where n is the tray number; S2: Calculate the total feed composition of the trays Total feed enthalpy of tray Where i is the component number; S3: Calculate the tray pressure P n and the total feed composition of the tray The bubble point temperature T n,b and dew point temperature T n,d ; S4: Order Let the initial value of the tray temperature be... but S5: Calculate the tray pressure P n and tray temperature The liquid phase component x n,i and gas phase component y n,i ; S6: Calculate the liquid flow rate L on the tray n and gas phase flow rate V n ; S7: Calculate the tray temperature according to the first formula. Total enthalpy of gas and liquid phases The first formula is: Among them, h n For liquid phase enthalpy, H n Compared to enthalpy; S8: Determine the overall specific enthalpy of the gas-liquid two-phase system. and the total feed enthalpy of the tray Size; S9: If Then the iteration exits and the calculation ends, where ε is the convergence error; S10: If and Then let Return to step S5 and perform iterative calculations; S11: If and Then let Return to step S5 and perform iterative calculations.

2. The general method for solving distillation trays according to claim 1, characterized in that, The bubble point temperature T n,b The dew point temperature T n,d The liquid phase component x n,i and the gas phase component y n,i It is calculated based on the phase equilibrium equation and the component normalization equation.

3. The general method for solving distillation trays according to claim 2, characterized in that, The phase equilibrium constant of the phase equilibrium equation is K. n =f(T) n ,P n ).

4. The general method for solving distillation trays according to claim 1, characterized in that, The liquid phase component x n,i and the gas phase component y n,i It is calculated based on the material balance equation.

5. The general method for solving distillation trays according to claim 4, characterized in that, The material balance equation is as follows: (F·x F,i +L n-1 ·x n-1,i +V n+1 ·y n+1,i )=L n ·x n,i +V n ·y n,i , F+L n-1 +V n+1 =L n +V n , Where F is the tray feed flow rate, and x is the feed component. F,i L n-1 The liquid flow rate of the upper tray is given by x, and the liquid phase composition is given by x. n-1,i V n+1 The gas flow rate of the lower tray is given by y, and the gas composition is given by y. n+1,i .

6. The method for solving the general distillation tray problem according to claim 5, characterized in that, The total feed components of the tray for:

7. The general method for solving distillation trays according to claim 5, characterized in that, The total feed enthalpy of the tray for:

8. A universal distillation tray solver, characterized in that, include: The parameter acquisition module is used to obtain the tray feed flow rate F and feed composition x. F,i Enthalpy of feed ratio h F Liquid flow rate L on the upper tray n-1 Liquid phase component x n-1,i Liquid phase enthalpy h n-1 Gas flow rate V in the lower tray n+1 Gas phase component y n+1,i enthalpy of gases H n+1 and tray pressure P n , where n is the tray number and i is the component number; The first calculation module is used to calculate the total feed composition of the trays. Total feed enthalpy of tray Bubble point temperature T n,b and dew point temperature T n,d ; The iterative initial value determination module is used to set... Let the initial value of the tray temperature be... but The second calculation module is used to calculate the liquid phase component x. n,i Gas phase component y n,i Liquid flow rate (L) on tray n Gas phase flow rate V n Specific enthalpy of gas and liquid phases The judgment module is used to determine the overall specific enthalpy of the gas-liquid two-phase system. and the total feed enthalpy of the tray Size; like Then the iteration exits and the calculation ends, where ε is the convergence error; like and Then let Return and perform iterative calculations; like and Then let Return and perform iterative calculations.

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