CN101776900B - Non-equilibrium energy-saving control system and method for air distillation tower - Google Patents

Abstract

The invention discloses a non-equilibrium energy-saving control system for an air distillation tower, which comprises a field intelligent instrument connected with the air distillation tower, a control station, a database and an upper computer, wherein the upper computer comprises a signal acquisition module and an energy-saving control module. A process comprises the following steps: setting structural parameters and operating parameters of the tower, and specifying an initial value of feeding air flow; assuming components of a liquid-phase main body, the vapor-liquid flow, and the temperature of each tower plate; calculating the mass transfer rate of a liquid phase, the components of a vapor-phase main body, enthalpies of the vapor-phase main body and the liquid-phase main body, effective mass transfer coefficients of the vapor phase and the liquid phase, components of a liquid-phase interface, the equilibrium temperature and the components of a vapor-phase interface; if a judgment condition is met, continuing, otherwise updating the parameters of each tower plate; and if the purity and the yield do not meet the requirement of the current production working condition, finishing iteration and outputting a result, otherwise adding an iteration step to the feeding air flow. The invention also provides a non-equilibrium energy-saving control method for the air distillation tower. The system and the method make the air distillation tower have minimum specific energy consumption and improve the energy-saving property under the current production working condition.

Description

Air separation column non-equilibrium energy-saving control system and method

Technical field

The present invention relates to empty branch field, especially, relate to a kind of air separation column non-equilibrium energy-saving control system and method.

Background technology

The application of oxygen, nitrogen and argon gas very extensively.Oxygen can be used for iron and steel manufacturing, chemical process, metal processing, glass manufacturing, petroleum recovery and refining, papermaking, health care service, space flight national defence etc.Nitrogen is widely used for blanket gas in metallurgical industry, petroleum recovery and refining, Metal Production and processing, electronics industry, chemical industry.Argon gas as protection gas, at electronics, illuminating industry also has very important application simultaneously in aircraft manufacturing, shipbuilding, atomic energy industry and mechanical industry department.Cryogenic air separation process is a difference of utilizing component boiling points such as oxygen in the air, nitrogen, argon, uses the method for rectifying to separate the low temperature liquid air and obtain highly purified oxygen, nitrogen, argon product.It is a current domestic and international air separation sector application method the most widely.In air separation industries, energy cost has accounted for 75% of air products price.Therefore under the situation that energy crisis is constantly deepened, the energy efficiency that improves air separation technology has important society and economic implications.

Non-equilibrium stage model is claimed Rate Models again, is the polynary detachment process model that is based upon on mass transfer and the rate of heat transfer equation.Non-equilibrium stage model has been abandoned the equilibrium stage hypothesis, and has kept the full level hypothesis of mixing, and need not carry out efficiency calculation, presses actual plate to calculate, and can obtain distributions such as accurate more component, efficient and temperature.Air separation column non-equilibrium Energy Saving Control is meant based on the air separation column non-equilibrium stage model, under the prerequisite that satisfies the product purity requirement, constantly calculates and change the feed rate of air separation column, and making air separation process operate in the output maximum all the time is the minimum state of unit consumption of energy.

Summary of the invention

In order to overcome big, the relatively poor deficiency of energy saving of unit consumption of energy of the industrial process of existing empty branch; The present invention provides a kind of air separation column non-equilibrium Energy Saving Control air separation column unit consumption of energy that under current production status condition, makes minimum, and improves the air separation column non-equilibrium energy-saving control system and the method for energy saving.

The technical solution adopted for the present invention to solve the technical problems is:

A kind of air separation column non-equilibrium energy-saving control system comprises the field intelligent instrument and control station, database and the host computer that are connected with air separation column, and intelligence instrument is connected with control station, database, host computer, and described host computer comprises:

Signal acquisition module is in order to gather current production status data;

Energy-saving control module, in order to Energy Saving Control, adopt following process to accomplish:

1) structural parameters and the operating parameter of setting tower are specified feeding air flow initial value;

2) suppose each column plate liquid phase main body composition, vapour-liquid phase flow rate, column plate temperature;

3), calculate the mass transfer in liquid phase flux respectively to each column plate:

$L_{j-1}{x}_{i,j-1}+F_j^L{z}_{i,j}^L-(L_j+S_j^L)x_{i,j}+N_{i,j}^L=0---\left(1\right)$

Wherein, L representes the liquid phase flow, and F representes feed rate; S representes that side carries flow, and x representes that liquid phase forms, and z representes feed composition; N representes the mass transfer flux, and subscript L representes liquid phase, subscript i=1,2,3 expression components; Corresponding successively nitrogen, argon, oxygen, subscript j-1, j represent j-1 and j piece column plate respectively;

4), calculate the vapour phase main body respectively and form to each column plate

$V_{j+1}{y}_{i,j+1}+F_j^G{z}_{i,j}^G-(V_j+S_j^G)y_{i,j}-N_{i,j}^L=0---\left(2\right)$

Wherein V representes the vapour phase flow, and y representes that vapour phase forms, and subscript G representes vapour phase (and revise formula 2, please check);

5), calculate the enthalpy of its vapour-liquid phase main body respectively to each column plate;

6), calculate the effective mutually mass transfer coefficient of vapour-liquid respectively to each column plate;

7), calculate liquid interface respectively and form to each column plate:

$N_i^L=k_{\mathrm{eff},i}^{L}a(x_i^I-x_i)+x_i{N}_t,i=\mathrm{1,2}---\left(3\right)$

$\underset{i=1}{\overset{3}{\mathrm{\Σ}}}{x}_i^I=1---\left(4\right)$

Wherein, k _{Eff, i} ^LRepresent i the effective mass transfer coefficient of component liquid phase, a representes mass transfer area, x _i ^IThe liquid interface composition of representing i component, N _tRepresent total mass transfer flux;

8), form by bubble point method its equilibrium temperature of calculating and vapour phase interface respectively to each column plate;

9) judge that whether following formula (5) satisfies, if satisfy then continue 10), if do not satisfy then updating all column plates liquid phase main body compositions, vapour-liquid phase flow rate, column plate temperature, return 3) the continuation iteration:

$V_{j+1}{H}_{j+1}^G+L_{j-1}{H}_{j-1}^L+F_j^G{H}_j^{\mathrm{FG}}+F_j^L{H}_j^{\mathrm{FL}}-(V_j+S_j^G)H_j^G-(L_j+S_j^L)H_j^L-Q_j<\mathrm{\&epsiv;}---\left(5\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{x}_{i,j}-1<\mathrm{\&epsiv;}---\left(6\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{y}_{i,j}-1<\mathrm{\&epsiv;}---\left(7\right)$

$k_{\mathrm{eff},i}^{G}a(y_i-y_i^I)+y_i{N}_t-N_{i,j}^L<\mathrm{\&epsiv;},i=\mathrm{1,2}---\left(8\right)$

Wherein, H ^FG, H ^FLRepresent vapour-liquid phase charging enthalpy respectively, H ^GAnd H ^LBe respectively vapour-liquid phase enthalpy, subscript j-1, j, j+1 represent j-1, j, j+1 piece plate respectively, and ε is a tolerance, k _{Eff, i} ^GBe the effective mass transfer coefficient of vapour phase, Q representes the heat that column plate spreads out of;

10) judge whether the purity of product nitrogen gas, oxygen and output satisfy current production status requirement; If do not satisfy then finishing iteration; The output result; The feeding air flow of back is maximum air inlet amount, if satisfy then the air feed flow is increased an iteration step length Δ, returns 2) continue iteration.

As preferred a kind of scheme: said host computer also comprises: bubble point method module, and in order to calculate its equilibrium temperature by the bubble point method and the vapour phase interface is formed, its process is following:

8.1) supposition column plate equilibrium temperature;

8.2) calculate the VLE constant, adopt following process to accomplish:

$\ln {\mathrm{\&Phi;}}_i^L=\ln \frac{\mathrm{RT}}{P(v^L-b^L)}-\frac{b_i}{b^L}(1-Z^L)+{\mathrm{\&xi;}}^L{a}^L(\frac{b_i}{b^L}-\frac{2\underset{m}{\mathrm{\&Sigma;}}{x}_m{a}_{i,m}}{a^L})/b^L\mathrm{RT}---\left(9\right)$

$\ln {\mathrm{\&Phi;}}_i^G=\ln \frac{\mathrm{RT}}{P(v^G-b^G)}-\frac{b_i}{b^G}(1-Z^G)+{\mathrm{\&xi;}}^G{a}^G(\frac{b_i}{b^G}-\frac{2\underset{m}{\mathrm{\&Sigma;}}{x}_m{a}_{i,m}}{a^G})/b^G\mathrm{RT}---\left(10\right)$

$K_i={\mathrm{\&Phi;}}_i^L/{\mathrm{\&Phi;}}_i^G---\left(11\right)$

y _i＝K _ix _i (12)

Wherein, Φ representes fugacity coefficient, and subscript L representes liquid phase, and subscript G representes vapour phase, and R is a gas law constant, and T is a temperature, and P is a column plate pressure, subscript m=1,2,3 expression components, corresponding successively nitrogen, argon, oxygen, molar volume v, physical parameter b ^G, b ^L, b _i, a ^G, a ^L, a _{I, m}, ξ ^G, ξ ^L, vapour phase compressibility factor Z ^G, liquid phase compressibility factor Z ^LCalculate by the rerum natura module;

8.3) check $|1-\underset{i}{\mathrm{\&Sigma;}}{y}_i|<0.0001$ Whether set up, set up then finishing iteration, return result of calculation, otherwise, upgrade the column plate equilibrium temperature, return 8.2) the continuation iteration.

As preferred another kind of scheme: said host computer also comprises: the enthalpy module, and in order to calculate vapour-liquid phase enthalpy of mixing, its process is following:

$H_i^{*}=c_i+d_{i}T+e_i{T}^2+f_i{T}^3+h_i{T}^4---\left(13\right)$

$H^{*}=\underset{i}{\mathrm{\&Sigma;}}{y}_i{H}_i^{*}---\left(14\right)$

$H^G=H^{*}-\mathrm{RT}(1-Z^G)-{\mathrm{\&xi;}}^G(a^G-T\frac{d{a}^G}{\mathrm{dT}})/b^G---\left(15\right)$

$H^L=H^{*}-\mathrm{RT}(1-Z^L)-{\mathrm{\&xi;}}^L(a^L-T\frac{d{a}^L}{\mathrm{dT}})/b^L---\left(16\right)$

H wherein _i ^*The enthalpy of representing i pure component ideal gas, H ^*Be potpourri ideal gas enthalpy, c, d, e, f, h are constant.

As preferred another scheme: said host computer also comprises: the rerum natura module, and in order to calculate physical parameter, its process is following:

$a_{i,m}={\mathrm{\&Omega;}}_{\mathrm{ai},m}{R}^2{T}_{\mathrm{ci},m}^2/P_{\mathrm{ci},m}---\left(17\right)$

b _i＝Ω _bRT _ci/P _cia (18)

$T_{\mathrm{ci},m}=\sqrt{T_{\mathrm{ci}}{T}_{\mathrm{cj}}}(1-k_{i,m})---\left(19\right)$

$V_{\mathrm{ci},m}=0.125{(V_{\mathrm{ci},m}^{1/3}+V_{\mathrm{ci},m}^{1/3})}^3---\left(20\right)$

Z _ci，m＝0.5(Z _ci+Z _cm) (21)

P _ci，m＝RT _ci，mZ _ci，m/V _ci，m (22)

Ω _ai，m＝0.5(Ω _ai+Ω _am) (23)

To vapour phase:

$a^G=\underset{i}{\mathrm{\&Sigma;}}\underset{m}{\mathrm{\&Sigma;}}{y}_i{y}_m{a}_{i,m}---\left(24\right)$

$b^G=\underset{i}{\mathrm{\&Sigma;}}{y}_i{b}_i---\left(25\right)$

Order

A ^G＝a ^GP/R ²T ² (26)

B ^G＝b ^GP/RT (27)

α ^G＝2B ^G-1 (28)

${\mathrm{\&beta;}}^G=A^G-3B^G-5B^{G^2}---\left(29\right)$

${\mathrm{\&gamma;}}^G=2(B^{G^3}+B^{G^2})-A^G{B}^G---\left(30\right)$

Getting initial value is 1-0.6P _r, separate following equation with Newton method, promptly obtain vapour phase compressibility factor Z ^G

$Z^{G^3}+{\mathrm{\&alpha;}}^G{Z}^{G^2}+\mathrm{\&beta;}{Z}^G+{\mathrm{\&gamma;}}^G=0---\left(31\right)$

Then,

v ^G＝RT/PZ ^G (32)

${\mathrm{\&xi;}}^G=0.242536\ln \frac{v^G+{3.561553b}^G}{v^G-{0.561553b}^G}---\left(33\right)$

To liquid phase:

$a^L=\underset{i}{\mathrm{\&Sigma;}}\underset{m}{\mathrm{\&Sigma;}}{x}_i{x}_m{a}_{i,m}---\left(34\right)$

$b^L=\underset{i}{\mathrm{\&Sigma;}}{x}_i{b}_i---\left(35\right)$

Order

A ^L＝a ^LP/R ²T ² (36)

B ^L＝b ^LP/RT (37)

α ^L＝2B ^L-1 (38)

${\mathrm{\&beta;}}^L=A^L-3B^L-5B^{L^2}---\left(39\right)$

${\mathrm{\&gamma;}}^L=2(B^{L^3}+B^{L^2})-A^L{B}^L---\left(40\right)$

Getting initial value is P _r(0.106+0.078P _r), separate following equation with Newton method, promptly obtain liquid phase compressibility factor Z ^L

$Z^{L^3}+{\mathrm{\&alpha;}}^L{Z}^{L^2}+\mathrm{\&beta;}{Z}^L+{\mathrm{\&gamma;}}^L=0---\left(41\right)$

Then,

v ^L＝RT/PZ ^L (42)

${\mathrm{\&xi;}}^L=0.242536\ln \frac{v^L+{3.561553b}^L}{v^L-{0.561553b}^L}---\left(43\right)$

Ω _ai＝C _i-D _iτ+E _iτ ²-W _iτ ³ (44)

Ω _b＝0.070721 (45)

τ＝0.01T (46)

Wherein, A, B, α, β, γ, τ are intermediate variables, and C, D, E, W are constants, T _c, P _c, V _c, Z _cBe respectively critical temperature, pressure, volume and compressibility factor, P _rBe reduced pressure, R is a gas law constant, k _{I, m}The mutual coefficient of binary of representing i component and m component, k _{I, m}Be constant, subscript c representes the character of critical point, and subscript r representes reduced state, subscript i, and m representes the two-component mixture of i component and m component, Ω _a, Ω _bIt is intermediate variable.

As preferred another kind of again scheme: said host computer also comprises: the mass transfer coefficient module, and in order to calculate vapour-liquid effective mass transfer coefficient mutually, its process is following:

$k_{\mathrm{eff},i}^{G}a=\frac{1-y_i}{\underset{k=1,k\&NotEqual;i}{\overset{3}{\mathrm{\&Sigma;}}}(y_k/k_{i,k}^{G}a)}---\left(47\right)$

$k_{\mathrm{eff},i}^{L}a=\frac{1-x_i}{\underset{k=1,k\&NotEqual;i}{\overset{3}{\mathrm{\&Sigma;}}}(x_k/k_{i,k}^{L}a)}---\left(48\right)$

$k_{i,k}^{G}a=5.85{\left(\frac{u_h{d}_b{\mathrm{\&rho;}}_m^G}{{\mathrm{\&eta;}}_m^G}\right)}^{-\frac{1}{4}}{\left(\frac{{\mathrm{\&eta;}}_m^G}{{\mathrm{\&rho;}}_m^G{D}_{i,k}^G}\right)}^{-\frac{1}{2}}{\left(\frac{F_a^2}{d_{b}g{\mathrm{\&phi;}}^2{\mathrm{\&rho;}}_m^L}\right)}^{0.17}{\left(\frac{h_{\mathrm{ow}}}{d_b}\right)}^{0.15}{\left(\frac{d_b^{2}g{\mathrm{\&rho;}}_m^L}{{\mathrm{\&sigma;}}_m}\right)}^{0.1}V---\left(49\right)$

$k_{i,k}^{L}a=1.97\&times;{10}^4{D_{i,k}^L}^{0.5}(0.4F_a+0.17)t_{L}L---\left(50\right)$

Wherein, k _{I, k} ^GAnd k _{I, k} ^LBe respectively the vapour liquid phase mass transfer coefficient, u _hBe sieve aperture gas speed, d _bBe the aperture, ρ _m ^GBe vapour phase density, η _m ^GBe vapour phase viscosity, D _{I, k} ^GBe the mutual coefficient of vapour phase binary, F _aBe kinetic energy factor, g is an acceleration of gravity, ρ _m ^LBe density of liquid phase, φ is a percentage of open area, σ _mBe the surface tension of mixing material, h _OWBe plate supernatant floor height, D _{I, k} ^LBe the mutual coefficient of liquid phase binary, t _LIt is the residence time.

Further, described host computer also comprises: display module as a result is used for that the Energy Saving Control result is passed to control station and shows, and through fieldbus the Energy Saving Control result is delivered to operator station and shows.

A kind of air separation column non-equilibrium energy-saving control method, described energy-saving control method may further comprise the steps:

1) structural parameters of setting tower, the production status data of gathering tower are gathered current feeding air flow as initial value;

2) suppose each column plate liquid phase main body composition, vapour-liquid phase flow rate, column plate temperature;

3), calculate the mass transfer in liquid phase flux respectively to each column plate:

$L_{j-1}{x}_{i,j-1}+F_j^L{z}_{i,j}^L-(L_j+S_j^L)x_{i,j}+N_{i,j}^L=0---\left(1\right)$

Wherein, L representes the liquid phase flow, and F representes feed rate; S representes that side carries flow, and x representes that liquid phase forms, and z representes feed composition; N representes the mass transfer flux, and subscript L representes liquid phase, subscript i=1,2,3 expression components; Corresponding successively nitrogen, argon, oxygen, subscript j-1, j represent j-1 and j piece column plate respectively;

4), calculate the vapour phase main body respectively and form to each column plate

$V_{j+1}{y}_{i,j+1}+F_j^G{z}_{i,j}^G-(V_j+S_j^G)y_{i,j}-N_{i,j}^L=0---\left(2\right)$

Wherein V representes the vapour phase flow, and y representes the vapour phase composition, and subscript G representes vapour phase;

5), calculate the enthalpy of its vapour-liquid phase main body respectively to each column plate;

6), calculate the effective mutually mass transfer coefficient of vapour-liquid respectively to each column plate;

7), calculate liquid interface respectively and form to each column plate:

$N_i^L=k_{\mathrm{eff},i}^{L}a(x_i^I-x_i)+x_i{N}_t,i=\mathrm{1,2}---\left(3\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{x}_i^I=1---\left(4\right)$

Wherein, x _i ^IThe liquid interface composition of representing i component, N _tRepresent total mass transfer flux;

8), form by bubble point method its equilibrium temperature of calculating and vapour phase interface respectively to each column plate

9) judge that whether following formula satisfies,,, return step 3) continuation iteration if do not satisfy then updating all column plates liquid phase main body compositions, vapour-liquid phase flow rate, column plate temperature if satisfy then continue step 10):

$V_{j+1}{H}_{j+1}^G+L_{j-1}{H}_{j-1}^L+F_j^G{H}_j^{\mathrm{FG}}+F_j^L{H}_j^{\mathrm{FL}}-(V_j+S_j^G)H_j^G-(L_j+S_j^L)H_j^L-Q_j<\mathrm{\&epsiv;}---\left(5\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{x}_{i,j}-1<\mathrm{\&epsiv;}---\left(6\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{y}_{i,j}-1<\mathrm{\&epsiv;}---\left(7\right)$

$k_{\mathrm{eff},i}^{G}a(y_i-y_i^I)+y_i{N}_t-N_{i,j}^L<\mathrm{\&epsiv;},i=\mathrm{1,2}---\left(8\right)$

Wherein, H ^FG, H ^FLRepresent vapour-liquid phase charging enthalpy respectively, H ^GAnd H ^LBe respectively vapour-liquid phase enthalpy, subscript j-1, j, j+1 represent j-1, j, j+1 piece plate respectively, and ε is a tolerance, k _{Eff, i} ^GBe the effective mass transfer coefficient of vapour phase, Q representes the heat that column plate spreads out of;

10) judge whether the purity of product nitrogen gas, oxygen and output satisfy current production status requirement; If do not satisfy then finishing iteration; The output result; The feeding air flow of back is maximum air inlet amount, if satisfy then the air feed flow is increased an iteration step length Δ, returns step 2) continue iteration.

As preferred a kind of scheme: in the said step 8), the bubble point method is calculated its equilibrium temperature and is formed with the vapour phase interface, adopts following process completion:

8.1) supposition column plate equilibrium temperature;

8.2) calculate the VLE constant, adopt following process to accomplish:

$\ln {\mathrm{\&Phi;}}_i^L=\ln \frac{\mathrm{RT}}{P(v^L-b^L)}-\frac{b_i}{b^L}(1-Z^L)+{\mathrm{\&xi;}}^L{a}^L(\frac{b_i}{b^L}-\frac{2\underset{m}{\mathrm{\&Sigma;}}{x}_m{a}_{i,m}}{a^L})/b^L\mathrm{RT}---\left(9\right)$

$\ln {\mathrm{\&Phi;}}_i^G=\ln \frac{\mathrm{RT}}{P(v^G-b^G)}-\frac{b_i}{b^G}(1-Z^G)+{\mathrm{\&xi;}}^G{a}^G(\frac{b_i}{b^G}-\frac{2\underset{m}{\mathrm{\&Sigma;}}{x}_m{a}_{i,m}}{a^G})/b^G\mathrm{RT}---\left(10\right)$

$K_i={\mathrm{\&Phi;}}_i^L/{\mathrm{\&Phi;}}_i^G---\left(11\right)$

y _i＝K _ix _i (12)

Wherein, Φ representes fugacity coefficient, and subscript L representes liquid phase, and subscript G representes vapour phase, and R is a gas law constant, and T is a temperature, and P is a column plate pressure, subscript m=1,2,3 expression components, corresponding successively nitrogen, argon, oxygen, molar volume v, physical parameter b ^G, b ^L, b _i, a ^G, a ^L, a _{I, m}, ξ ^G, ξ ^L, vapour phase compressibility factor Z ^G, liquid phase compressibility factor Z ^LCalculate by the physical parameter computing method;

8.3) check $|1-\underset{i}{\mathrm{\&Sigma;}}{y}_i|<0.0001$ Whether set up, set up then finishing iteration, return result of calculation, otherwise, upgrade the column plate equilibrium temperature, return 8.2) the continuation iteration.

As preferred another kind of scheme: in the said step 5), the process of enthalpy of calculating vapour-liquid phase main body is following:

$H_i^{*}=c_i+d_{i}T+e_i{T}^2+f_i{T}^3+h_i{T}^4---\left(13\right)$

$H^{*}=\underset{i}{\mathrm{\&Sigma;}}{y}_i{H}_i^{*}---\left(14\right)$

$H^G=H^{*}-\mathrm{RT}(1-Z^G)-{\mathrm{\&xi;}}^G(a^G-T\frac{d{a}^G}{\mathrm{dT}})/b^G---\left(15\right)$

$H^L=H^{*}-\mathrm{RT}(1-Z^L)-{\mathrm{\&xi;}}^L(a^L-T\frac{d{a}^L}{\mathrm{dT}})/b^L---\left(16\right)$

H wherein _i ^*The enthalpy of representing i pure component ideal gas, H ^*Be potpourri ideal gas enthalpy, c, d, e, f, h are constant.

As preferred another scheme: described rerum natura method comprises the steps:

$a_{i,m}={\mathrm{\&Omega;}}_{\mathrm{ai},m}{R}^2{T}_{\mathrm{ci},m}^2/P_{\mathrm{ci},m}---\left(17\right)$

b _i＝Ω _bRT _ci/P _cia (18)

$T_{\mathrm{ci},m}=\sqrt{T_{\mathrm{ci}}{T}_{\mathrm{cj}}}(1-k_{i,m})---\left(19\right)$

$V_{\mathrm{ci},m}=0.125{(V_{\mathrm{ci},m}^{1/3}+V_{\mathrm{ci},m}^{1/3})}^3---\left(20\right)$

Z _ci，m＝0.5(Z _ci+Z _cm) (21)

P _ci，m＝RT _ci，mZ _ci，m/V _ci，m (22)

Ω _ai，m＝0.5(Ω _ai+Ω _am) (23)

To vapour phase:

$a^G=\underset{i}{\mathrm{\&Sigma;}}\underset{m}{\mathrm{\&Sigma;}}{y}_i{y}_m{a}_{i,m}---\left(24\right)$

$b^G=\underset{i}{\mathrm{\&Sigma;}}{y}_i{b}_i---\left(25\right)$

Order

A ^G＝a ^GP/R ²T ² (26)

B ^G＝b ^GP/RT (27)

α ^G＝2B ^G-1 (28)

${\mathrm{\&beta;}}^G=A^G-3B^G-5B^{G^2}---\left(29\right)$

${\mathrm{\&gamma;}}^G=2(B^{G^3}+B^{G^2})-A^G{B}^G---\left(30\right)$

Getting initial value is 1-0.6P _r, separate following equation with Newton method, promptly obtain vapour phase compressibility factor Z ^G

$Z^{G^3}+{\mathrm{\&alpha;}}^G{Z}^{G^2}+\mathrm{\&beta;}{Z}^G+{\mathrm{\&gamma;}}^G=0---\left(31\right)$

Then,

v ^G＝RT/PZ ^G (32)

${\mathrm{\&xi;}}^G=0.242536\ln \frac{v^G+{3.561553b}^G}{v^G-{0.561553b}^G}---\left(33\right)$

To liquid phase:

$a^L=\underset{i}{\mathrm{\&Sigma;}}\underset{m}{\mathrm{\&Sigma;}}{x}_i{x}_m{a}_{i,m}---\left(34\right)$

$b^L=\underset{i}{\mathrm{\&Sigma;}}{x}_i{b}_i---\left(35\right)$

Order

A ^L＝a ^LP/R ²T ² (36)

B ^L＝b ^LP/RT (37)

α ^L＝2B ^L-1 (38)

${\mathrm{\&beta;}}^L=A^L-3B^L-5B^{L^2}---\left(39\right)$

${\mathrm{\&gamma;}}^L=2(B^{L^3}+B^{L^2})-A^L{B}^L---\left(40\right)$

Getting initial value is P _r(0.106+0.078P _r), separate following equation with Newton method, promptly obtain liquid phase compressibility factor Z ^L

$Z^{L^3}+{\mathrm{\&alpha;}}^L{Z}^{L^2}+\mathrm{\&beta;}{Z}^L+{\mathrm{\&gamma;}}^L=0---\left(41\right)$

Then,

v ^L＝RT/PZ ^L (42)

${\mathrm{\&xi;}}^L=0.242536\ln \frac{v^L+{3.561553b}^L}{v^L-{0.561553b}^L}---\left(43\right)$

Ω _ai＝C _i-D _iτ+E _iτ ²-W _iτ ³ (44)

Ω _b＝0.070721 (45)

τ＝0.01T (46)

Wherein, A, B, α, β, γ, τ are intermediate variables, and C, D, E, W are constants, T _c, P _c, V _c, Z _cBe respectively critical temperature, pressure, volume and compressibility factor, P _rBe reduced pressure, R is a gas law constant, k _{I, m}The mutual coefficient of binary of representing i component and m component, k _{I, m}Be constant, subscript c representes the character of critical point, and subscript r representes reduced state, subscript i, and m representes the two-component mixture of i component and m component, Ω _a, Ω _bIt is intermediate variable.

As preferred another kind of again scheme: in the said step 6), effectively the process of mass transfer coefficient is following mutually to calculate vapour-liquid:

$k_{\mathrm{eff},i}^{G}a=\frac{1-y_i}{\underset{k=1,k\&NotEqual;i}{\overset{3}{\mathrm{\&Sigma;}}}(y_k/k_{i,k}^{G}a)}---\left(47\right)$

$k_{\mathrm{eff},i}^{L}a=\frac{1-x_i}{\underset{k=1,k\&NotEqual;i}{\overset{3}{\mathrm{\&Sigma;}}}(x_k/k_{i,k}^{L}a)}---\left(48\right)$

$k_{i,k}^{G}a=5.85{\left(\frac{u_h{d}_b{\mathrm{\&rho;}}_m^G}{{\mathrm{\&eta;}}_m^G}\right)}^{-\frac{1}{4}}{\left(\frac{{\mathrm{\&eta;}}_m^G}{{\mathrm{\&rho;}}_m^G{D}_{i,k}^G}\right)}^{-\frac{1}{2}}{\left(\frac{F_a^2}{d_{b}g{\mathrm{\&phi;}}^2{\mathrm{\&rho;}}_m^L}\right)}^{0.17}{\left(\frac{h_{\mathrm{ow}}}{d_b}\right)}^{0.15}{\left(\frac{d_b^{2}g{\mathrm{\&rho;}}_m^L}{{\mathrm{\&sigma;}}_m}\right)}^{0.1}V---\left(49\right)$

$k_{i,k}^{L}a=1.97\&times;{10}^4{D_{i,k}^L}^{0.5}(0.4F_a+0.17)t_{L}L---\left(50\right)$

Wherein, k _{I, k} ^GAnd k _{I, k} ^LBe respectively the vapour liquid phase mass transfer coefficient, u _hBe sieve aperture gas speed, d _bBe the aperture, ρ _m ^GBe vapour phase density, η _m ^GBe vapour phase viscosity, D _{I, k} ^GBe the mutual coefficient of vapour phase binary, F _aBe kinetic energy factor, g is an acceleration of gravity, ρ _m ^LBe density of liquid phase, φ is a percentage of open area, σ _mBe the surface tension of mixing material, h _OWBe plate supernatant floor height, D _{I, k} ^LBe the mutual coefficient of liquid phase binary, t _LIt is the residence time.

Further, in described step 10), host computer is passed to control station with the Energy Saving Control result and is shown, and through fieldbus the Energy Saving Control result is delivered to operator station and shows.

Beneficial effect of the present invention mainly shows: air separation column is carried out the non-equilibrium Energy Saving Control, can be used for instructing and produce, under the prerequisite that satisfies current production status requirement, improve output, reduce energy consumption of unit product, thereby improve productivity effect.

Description of drawings

Fig. 1 is the hardware structure diagram of non-equilibrium energy-saving control system proposed by the invention.

Fig. 2 is an air separating tower structure synoptic diagram according to the invention.

Fig. 3 is the functional block diagram of host computer of the present invention.

Embodiment

Below in conjunction with accompanying drawing the present invention is further described.

Embodiment 1

With reference to Fig. 1, Fig. 2, Fig. 3; A kind of air separation column non-equilibrium energy-saving control system; Comprise field intelligent instrument 2, data-interface 3, control station 4, database 5 and host computer 6 that air separation column 1 connects, intelligence instrument 2 is connected with fieldbus, and said fieldbus is connected with data-interface 3; Data-interface 3 is connected with control station 4, database 5 and host computer 6, and described host computer 6 comprises:

Signal acquisition module 7 is in order to gather current production status data;

Energy-saving control module 8, in order to Energy Saving Control, adopt following process to accomplish:

1) structural parameters and the operating parameter of setting tower are specified feeding air flow initial value;

2) suppose each column plate liquid phase main body composition, vapour-liquid phase flow rate, column plate temperature;

3), calculate the mass transfer in liquid phase flux respectively to each column plate:

$L_{j-1}{x}_{i,j-1}+F_j^L{z}_{i,j}^L-(L_j+S_j^L)x_{i,j}+N_{i,j}^L=0---\left(1\right)$

Wherein, L representes the liquid phase flow, and F representes feed rate; S representes that side carries flow, and x representes that liquid phase forms, and z representes feed composition; N representes the mass transfer flux, and subscript L representes liquid phase, subscript i=1,2,3 expression components; Corresponding successively nitrogen, argon, oxygen, subscript j-1, j represent j-1 and j piece column plate respectively;

4), calculate the vapour phase main body respectively and form to each column plate

$V_{j+1}{y}_{i,j+1}+F_j^G{z}_{i,j}^G-(V_j+S_j^G)y_{i,j}-N_{i,j}^L=0---\left(2\right)$

Wherein V representes the vapour phase flow, and y representes the vapour phase composition, and subscript G representes vapour phase;

5), calculate the enthalpy of its vapour-liquid phase main body respectively to each column plate;

6), calculate the effective mutually mass transfer coefficient of vapour-liquid respectively to each column plate;

7), calculate liquid interface respectively and form to each column plate:

$N_i^L=k_{\mathrm{eff},i}^{L}a(x_i^I-x_i)+x_i{N}_t,i=\mathrm{1,2}---\left(3\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{x}_i^I=1---\left(4\right)$

Wherein, k _{Eff, i} ^LRepresent i the effective mass transfer coefficient of component liquid phase, a representes mass transfer area, x _i ^IThe liquid interface composition of representing i component, N _tRepresent total mass transfer flux;

8), calculate its vapour phase interface by the bubble point method respectively and form to each column plate;

9) judge that whether following formula (5) satisfies,,, return 3 if do not satisfy then updating all column plates liquid phase main body compositions, vapour-liquid phase flow rate, column plate temperature if satisfy then continue (10)) the continuation iteration:

$V_{j+1}{H}_{j+1}^G+L_{j-1}{H}_{j-1}^L+F_j^G{H}_j^{\mathrm{FG}}+F_j^L{H}_j^{\mathrm{FL}}-(V_j+S_j^G)H_j^G-(L_j+S_j^L)H_j^L-Q_j<\mathrm{\&epsiv;}---\left(5\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{x}_{i,j}-1<\mathrm{\&epsiv;}---\left(6\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{y}_{i,j}-1<\mathrm{\&epsiv;}---\left(7\right)$

$k_{\mathrm{eff},i}^{G}a(y_i-y_i^I)+y_i{N}_t-N_{i,j}^L<\mathrm{\&epsiv;},i=\mathrm{1,2}---\left(8\right)$

Wherein, H ^FG, H ^FLRepresent vapour-liquid phase charging enthalpy respectively, H ^GAnd H ^LBe respectively vapour-liquid phase enthalpy, subscript j-1, j, j+1 represent j-1, j, j+1 piece plate respectively, and ε is a tolerance, k _{Eff, i} ^GBe the effective mass transfer coefficient of vapour phase, Q representes the heat that column plate spreads out of;

10) judge whether the purity of product nitrogen gas, oxygen and output satisfy current production status requirement; If do not satisfy then finishing iteration; The output result; The feeding air flow of back is maximum air inlet amount, if satisfy then the air feed flow is increased an iteration step length Δ, returns 2) continue iteration.

Said host computer 6 also comprises: bubble point method module 9, and in order to be made up of bubble point method its equilibrium temperature of calculating and vapour phase interface, its process is following:

8.1) supposition column plate equilibrium temperature;

8.2) calculate the VLE constant, adopt following process to accomplish:

$\ln {\mathrm{\&Phi;}}_i^L=\ln \frac{\mathrm{RT}}{P(v^L-b^L)}-\frac{b_i}{b^L}(1-Z^L)+{\mathrm{\&xi;}}^L{a}^L(\frac{b_i}{b^L}-\frac{2\underset{m}{\mathrm{\&Sigma;}}{x}_m{a}_{i,m}}{a^L})/b^L\mathrm{RT}---\left(9\right)$

$\ln {\mathrm{\&Phi;}}_i^G=\ln \frac{\mathrm{RT}}{P(v^G-b^G)}-\frac{b_i}{b^G}(1-Z^G)+{\mathrm{\&xi;}}^G{a}^G(\frac{b_i}{b^G}-\frac{2\underset{m}{\mathrm{\&Sigma;}}{x}_m{a}_{i,m}}{a^G})/b^G\mathrm{RT}---\left(10\right)$

$K_i={\mathrm{\&Phi;}}_i^L/{\mathrm{\&Phi;}}_i^G---\left(11\right)$

y _i＝K _ix _i (12)

Wherein, Φ representes fugacity coefficient, and subscript L representes liquid phase, and subscript G representes vapour phase, and R is a gas law constant, and T is a temperature, and P is a column plate pressure, subscript m=1,2,3 expression components, corresponding successively nitrogen, argon, oxygen, molar volume v, physical parameter b ^G, b ^L, b _i, a ^G, a ^L, a _{I, m}, ξ ^G, ξ ^L, vapour phase compressibility factor Z ^G, liquid phase compressibility factor Z ^LCalculate by the rerum natura module;

8.3) check $|1-\underset{i}{\mathrm{\&Sigma;}}{y}_i|<0.0001$ Whether set up, set up then finishing iteration, return result of calculation, otherwise, upgrade the column plate equilibrium temperature, return 8.2) the continuation iteration.

Said host computer 6 also comprises: enthalpy module 10, and in order to calculate vapour-liquid phase enthalpy of mixing, its process is following:

$H_i^{*}=c_i+d_{i}T+e_i{T}^2+f_i{T}^3+h_i{T}^4---\left(13\right)$

$H^{*}=\underset{i}{\mathrm{\&Sigma;}}{y}_i{H}_i^{*}---\left(14\right)$

$H^G=H^{*}-\mathrm{RT}(1-Z^G)-{\mathrm{\&xi;}}^G(a^G-T\frac{d{a}^G}{\mathrm{dT}})/b^G---\left(15\right)$

$H^L=H^{*}-\mathrm{RT}(1-Z^L)-{\mathrm{\&xi;}}^L(a^L-T\frac{d{a}^L}{\mathrm{dT}})/b^L---\left(16\right)$

H wherein _i ^*The enthalpy of representing i pure component ideal gas, H ^*Be potpourri ideal gas enthalpy, c, d, e, f, h are constant.

Said host computer 6 also comprises: rerum natura module 11, and in order to calculate physical parameter, its process is following:

$a_{i,m}={\mathrm{\&Omega;}}_{\mathrm{ai},m}{R}^2{T}_{\mathrm{ci},m}^2/P_{\mathrm{ci},m}---\left(17\right)$

b _i＝Ω _bRT _ci/P _cia (18)

$T_{\mathrm{ci},m}=\sqrt{T_{\mathrm{ci}}{T}_{\mathrm{cj}}}(1-k_{i,m})---\left(19\right)$

$V_{\mathrm{ci},m}=0.125{(V_{\mathrm{ci},m}^{1/3}+V_{\mathrm{ci},m}^{1/3})}^3---\left(20\right)$

Z _ci，m＝0.5(Z _ci+Z _cm) (21)

P _ci，m＝RT _ci，mZ _ci，m/V _ci，m (22)

Ω _ai，m＝0.5(Ω _ai+Ω _am) (23)

To vapour phase:

$a^G=\underset{i}{\mathrm{\&Sigma;}}\underset{m}{\mathrm{\&Sigma;}}{y}_i{y}_m{a}_{i,m}---\left(24\right)$

$b^G=\underset{i}{\mathrm{\&Sigma;}}{y}_i{b}_i---\left(25\right)$

Order

A ^G＝a ^GP/R ²T ² (26)

B ^G＝b ^GP/RT (27)

α ^G＝2B ^G-1 (28)

${\mathrm{\&beta;}}^G=A^G-3B^G-5B^{G^2}---\left(29\right)$

${\mathrm{\&gamma;}}^G=2(B^{G^3}+B^{G^2})-A^G{B}^G---\left(30\right)$

Getting initial value is 1-0.6P _r, separate following equation with Newton method, promptly obtain vapour phase compressibility factor Z ^G

$Z^{G^3}+{\mathrm{\&alpha;}}^G{Z}^{G^2}+\mathrm{\&beta;}{Z}^G+{\mathrm{\&gamma;}}^G=0---\left(31\right)$

Then,

v ^G＝RT/PZ ^G (32)

${\mathrm{\&xi;}}^G=0.242536\ln \frac{v^G+{3.561553b}^G}{v^G-{0.561553b}^G}---\left(33\right)$

To liquid phase:

$a^L=\underset{i}{\mathrm{\&Sigma;}}\underset{m}{\mathrm{\&Sigma;}}{x}_i{x}_m{a}_{i,m}---\left(34\right)$

$b^L=\underset{i}{\mathrm{\&Sigma;}}{x}_i{b}_i---\left(35\right)$

Order

A ^L＝a ^LP/R ²T ² (36)

B ^L＝b ^LP/RT (37)

α ^L＝2B ^L-1 (38)

${\mathrm{\&beta;}}^L=A^L-3B^L-5B^{L^2}---\left(39\right)$

${\mathrm{\&gamma;}}^L=2(B^{L^3}+B^{L^2})-A^L{B}^L---\left(40\right)$

Getting initial value is P _r(0.106+0.078P _r), separate following equation with Newton method, promptly obtain liquid phase compressibility factor Z ^L

$Z^{L^3}+{\mathrm{\&alpha;}}^L{Z}^{L^2}+\mathrm{\&beta;}{Z}^L+{\mathrm{\&gamma;}}^L=0---\left(41\right)$

Then,

v ^L＝RT/PZ ^L (42)

${\mathrm{\&xi;}}^L=0.242536\ln \frac{v^L+{3.561553b}^L}{v^L-{0.561553b}^L}---\left(43\right)$

Ω _ai＝C _i-D _iτ+E _iτ ²-W _iτ ³ (44)

Ω _b＝0.070721 (45)

τ＝0.01T (46)

Wherein, A, B, α, β, γ, τ are intermediate variables, and C, D, E, W are constants, T _c, P _c, V _c, Z _cBe respectively critical temperature, pressure, volume and compressibility factor, P _rBe reduced pressure, R is a gas law constant, k _{I, m}The mutual coefficient of binary of representing i component and m component, k _{I, m}Be constant, subscript c representes the character of critical point, and subscript r representes reduced state, subscript i, and m representes the two-component mixture of i component and m component, Ω _a, Ω _bIt is intermediate variable.

Said host computer 6 also comprises: mass transfer coefficient module 12, and in order to calculate the effective mutually mass transfer coefficient of vapour-liquid, its process is following:

$k_{\mathrm{eff},i}^{G}a=\frac{1-y_i}{\underset{k=1,k\&NotEqual;i}{\overset{3}{\mathrm{\&Sigma;}}}(y_k/k_{i,k}^{G}a)}---\left(47\right)$

$k_{\mathrm{eff},i}^{L}a=\frac{1-x_i}{\underset{k=1,k\&NotEqual;i}{\overset{3}{\mathrm{\&Sigma;}}}(x_k/k_{i,k}^{L}a)}---\left(48\right)$

$k_{i,k}^{G}a=5.85{\left(\frac{u_h{d}_b{\mathrm{\&rho;}}_m^G}{{\mathrm{\&eta;}}_m^G}\right)}^{-\frac{1}{4}}{\left(\frac{{\mathrm{\&eta;}}_m^G}{{\mathrm{\&rho;}}_m^G{D}_{i,k}^G}\right)}^{-\frac{1}{2}}{\left(\frac{F_a^2}{d_{b}g{\mathrm{\&phi;}}^2{\mathrm{\&rho;}}_m^L}\right)}^{0.17}{\left(\frac{h_{\mathrm{ow}}}{d_b}\right)}^{0.15}{\left(\frac{d_b^{2}g{\mathrm{\&rho;}}_m^L}{{\mathrm{\&sigma;}}_m}\right)}^{0.1}V---\left(49\right)$

$k_{i,k}^{L}a=1.97\&times;{10}^4{D_{i,k}^L}^{0.5}(0.4F_a+0.17)t_{L}L---\left(50\right)$

Wherein, k _{I, k} ^GAnd k _{I, k} ^LBe respectively the vapour liquid phase mass transfer coefficient, u _hBe sieve aperture gas speed, d _bBe the aperture, ρ _m ^GBe vapour phase density, η _m ^GBe vapour phase viscosity, D _{I, k} ^GBe the mutual coefficient of vapour phase binary, F _aBe kinetic energy factor, g is an acceleration of gravity, ρ _m ^LBe density of liquid phase, φ is a percentage of open area, σ _mBe the surface tension of mixing material, h _OWBe plate supernatant floor height, D _{I, k} ^LBe the mutual coefficient of liquid phase binary, t _LIt is the residence time.

Described host computer 6 also comprises: display module as a result is used for that the Energy Saving Control result is passed to control station and shows, and through fieldbus the Energy Saving Control result is delivered to operator station and shows.

The hardware structure diagram of the air separation column energy-saving potential optimizing system of present embodiment is shown in accompanying drawing 1; Described optimization system core by comprise signal acquisition module 7, energy-saving control module 8, bubble point method module 9, enthalpy module 10, rerum natura module 11, mass transfer coefficient module 12, the host computer 6 of display module 13 and man-machine interface constitutes as a result; Comprise in addition: field intelligent instrument 2, data-interface 3, control station 4, database 5 and fieldbus.Air separation column 1, intelligence instrument 2, data-interface 3, control station 4, database 5, host computer 6 link to each other through fieldbus successively, realize uploading and assigning of information flow.Energy-saving control system moves on host computer 6, can carry out message exchange with first floor system easily.

The functional block diagram of the optimization system of present embodiment mainly comprises signal acquisition module 7, energy-saving control module 8, bubble point method module 9, enthalpy module 10, rerum natura module 11, mass transfer coefficient module 12, display module 13 etc. as a result shown in accompanying drawing 3.

Described non-equilibrium energy-saving control method is implemented according to following steps:

1) structural parameters of setting tower, the production status data of gathering tower are gathered current feeding air flow as initial value;

2) suppose each column plate liquid phase main body composition, vapour-liquid phase flow rate, column plate temperature;

3), calculate the mass transfer in liquid phase flux respectively to each column plate:

$L_{j-1}{x}_{i,j-1}+F_j^L{z}_{i,j}^L-(L_j+S_j^L)x_{i,j}+N_{i,j}^L=0---\left(1\right)$

Wherein, L representes the liquid phase flow, and F representes feed rate; S representes that side carries flow, and x representes that liquid phase forms, and z representes feed composition; N representes the mass transfer flux, and subscript L representes liquid phase, subscript i=1,2,3 expression components; Corresponding successively nitrogen, argon, oxygen, subscript j-1, j represent j-1 and j piece column plate respectively;

4), calculate the vapour phase main body respectively and form to each column plate

$V_{j+1}{y}_{i,j+1}+F_j^G{z}_{i,j}^G-(V_j+S_j^G)y_{i,j}-N_{i,j}^L=0---\left(2\right)$

Wherein V representes the vapour phase flow, and y representes the vapour phase composition, and subscript G representes vapour phase;

5), calculate the enthalpy of its vapour-liquid phase main body respectively to each column plate;

6), calculate the effective mutually mass transfer coefficient of vapour-liquid respectively to each column plate;

7), calculate liquid interface respectively and form to each column plate:

$N_i^L=k_{\mathrm{eff},i}^{L}a(x_i^I-x_i)+x_i{N}_t,i=\mathrm{1,2}---\left(3\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{x}_i^I=1---\left(4\right)$

Wherein, x _i ^IThe liquid interface composition of representing i component, N _tRepresent total mass transfer flux;

8), form by bubble point method its equilibrium temperature of calculating and vapour phase interface respectively to each column plate;

9) judge that whether following formula satisfies,,, return step 3) continuation iteration if do not satisfy then updating all column plates liquid phase main body compositions, vapour-liquid phase flow rate, column plate temperature if satisfy then continue step 10):

$V_{j+1}{H}_{j+1}^G+L_{j-1}{H}_{j-1}^L+F_j^G{H}_j^{\mathrm{FG}}+F_j^L{H}_j^{\mathrm{FL}}-(V_j+S_j^G)H_j^G-(L_j+S_j^L)H_j^L-Q_j<\mathrm{\&epsiv;}---\left(5\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{x}_{i,j}-1<\mathrm{\&epsiv;}---\left(6\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{y}_{i,j}-1<\mathrm{\&epsiv;}---\left(7\right)$

$k_{\mathrm{eff},i}^{G}a(y_i-y_i^I)+y_i{N}_t-N_{i,j}^L<\mathrm{\&epsiv;},i=\mathrm{1,2}---\left(8\right)$

Wherein, H ^FG, H ^FLRepresent vapour-liquid phase charging enthalpy respectively, H ^GAnd H ^LBe respectively vapour-liquid phase enthalpy, subscript j-1, j, j+1 represent j-1, j, j+1 piece plate respectively, and ε is a tolerance, k _{Eff, i} ^GBe the effective mass transfer coefficient of vapour phase, Q representes the heat that column plate spreads out of;

10) judge whether the purity of product nitrogen gas, oxygen and output satisfy current production status requirement; If do not satisfy then finishing iteration; The output result; The feeding air flow of back is maximum air inlet amount, if satisfy then the air feed flow is increased an iteration step length Δ, returns step 2) continue iteration.

Embodiment 2

With reference to Fig. 1, Fig. 2, Fig. 3, a kind of air separation column non-equilibrium energy-saving control method, described non-equilibrium energy-saving control method may further comprise the steps:

1) structural parameters of setting tower, the production status data of gathering tower are gathered current feeding air flow as initial value;

2) suppose each column plate liquid phase main body composition, vapour-liquid phase flow rate, column plate temperature;

3), calculate the mass transfer in liquid phase flux respectively to each column plate:

$L_{j-1}{x}_{i,j-1}+F_j^L{z}_{i,j}^L-(L_j+S_j^L)x_{i,j}+N_{i,j}^L=0---\left(1\right)$

Wherein, L representes the liquid phase flow, and F representes feed rate; S representes that side carries flow, and x representes that liquid phase forms, and z representes feed composition; N representes the mass transfer flux, and subscript L representes liquid phase, subscript i=1,2,3 expression components; Corresponding successively nitrogen, argon, oxygen, subscript j-1, j represent j-1 and j piece column plate respectively;

4), calculate the vapour phase main body respectively and form to each column plate

$V_{j+1}{y}_{i,j+1}+F_j^G{z}_{i,j}^G-(V_j+S_j^G)y_{i,j}-N_{i,j}^L=0---\left(2\right)$

Wherein V representes the vapour phase flow, and y representes the vapour phase composition, and subscript G representes vapour phase;

5), calculate the enthalpy of its vapour-liquid phase main body respectively to each column plate;

6), calculate the effective mutually mass transfer coefficient of vapour-liquid respectively to each column plate;

7), calculate liquid interface respectively and form to each column plate:

$N_i^L=k_{\mathrm{eff},i}^{L}a(x_i^I-x_i)+x_i{N}_t,i=\mathrm{1,2}---\left(3\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{x}_i^I=1---\left(4\right)$

Wherein, x _i ^IThe liquid interface composition of representing i component, N _tRepresent total mass transfer flux;

8), calculate its vapour phase interface by the bubble point method respectively and form to each column plate;

9) judge that whether following formula satisfies,,, return step 3) continuation iteration if do not satisfy then updating all column plates liquid phase main body compositions, vapour-liquid phase flow rate, column plate temperature if satisfy then continue step 10):

$V_{j+1}{H}_{j+1}^G+L_{j-1}{H}_{j-1}^L+F_j^G{H}_j^{\mathrm{FG}}+F_j^L{H}_j^{\mathrm{FL}}-(V_j+S_j^G)H_j^G-(L_j+S_j^L)H_j^L-Q_j<\mathrm{\&epsiv;}---\left(5\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{x}_{i,j}-1<\mathrm{\&epsiv;}---\left(6\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{y}_{i,j}-1<\mathrm{\&epsiv;}---\left(7\right)$

$k_{\mathrm{eff},i}^{G}a(y_i-y_i^I)+y_i{N}_t-N_{i,j}^L<\mathrm{\&epsiv;},i=\mathrm{1,2}---\left(8\right)$

Wherein, H ^FG, H ^FLRepresent vapour-liquid phase charging enthalpy respectively, H ^GAnd H ^LBe respectively vapour-liquid phase enthalpy, subscript j-1, j, j+1 represent j-1, j, j+1 piece plate respectively, and ε is a tolerance, k _{Eff, i} ^GBe the effective mass transfer coefficient of vapour phase, Q representes the heat that column plate spreads out of;

10) judge whether the purity of product nitrogen gas, oxygen and output satisfy current production status requirement; If do not satisfy then finishing iteration; The output result; The feeding air flow of back is maximum air inlet amount, if satisfy then the air feed flow is increased an iteration step length Δ, returns step 2) continue iteration.

In the said step 8), the bubble point method calculates its equilibrium temperature and the vapour phase interface is formed, and adopts following process to accomplish:

8.1) supposition column plate equilibrium temperature;

8.2) calculate the VLE constant, adopt following process to accomplish:

$\ln {\mathrm{\&Phi;}}_i^L=\ln \frac{\mathrm{RT}}{P(v^L-b^L)}-\frac{b_i}{b^L}(1-Z^L)+{\mathrm{\&xi;}}^L{a}^L(\frac{b_i}{b^L}-\frac{2\underset{m}{\mathrm{\&Sigma;}}{x}_m{a}_{i,m}}{a^L})/b^L\mathrm{RT}---\left(9\right)$

$\ln {\mathrm{\&Phi;}}_i^G=\ln \frac{\mathrm{RT}}{P(v^G-b^G)}-\frac{b_i}{b^G}(1-Z^G)+{\mathrm{\&xi;}}^G{a}^G(\frac{b_i}{b^G}-\frac{2\underset{m}{\mathrm{\&Sigma;}}{x}_m{a}_{i,m}}{a^G})/b^G\mathrm{RT}---\left(10\right)$

$K_i={\mathrm{\&Phi;}}_i^L/{\mathrm{\&Phi;}}_i^G---\left(11\right)$

y _i＝K _ix _i (12)

Wherein, Φ representes fugacity coefficient, and subscript L representes liquid phase, and subscript G representes vapour phase, and R is a gas law constant, and T is a temperature, and P is a column plate pressure, subscript m=1,2,3 expression components, corresponding successively nitrogen, argon, oxygen, molar volume v, physical parameter b ^G, b ^L, b _i, a ^G, a ^L, a _{I, m}, ξ ^G, ξ ^L, vapour phase compressibility factor Z ^G, liquid phase compressibility factor Z ^LCalculate by the physical parameter computing method;

8.3) check $|1-\underset{i}{\mathrm{\&Sigma;}}{y}_i|<0.0001$ Whether set up, set up then finishing iteration, return result of calculation, otherwise, upgrade the column plate equilibrium temperature, return 8.2) the continuation iteration.

In the said step 5), the process of the enthalpy of calculating vapour-liquid phase main body is following:

$H_i^{*}=c_i+d_{i}T+e_i{T}^2+f_i{T}^3+h_i{T}^4---\left(13\right)$

$H^{*}=\underset{i}{\mathrm{\&Sigma;}}{y}_i{H}_i^{*}---\left(14\right)$

$H^G=H^{*}-\mathrm{RT}(1-Z^G)-{\mathrm{\&xi;}}^G(a^G-T\frac{d{a}^G}{\mathrm{dT}})/b^G---\left(15\right)$

$H^L=H^{*}-\mathrm{RT}(1-Z^L)-{\mathrm{\&xi;}}^L(a^L-T\frac{d{a}^L}{\mathrm{dT}})/b^L---\left(16\right)$

H wherein _i ^*The enthalpy of representing i pure component ideal gas, H ^*Be potpourri ideal gas enthalpy, c, d, e, f, h are constant.

Described rerum natura method comprises the steps:

$a_{i,m}={\mathrm{\&Omega;}}_{\mathrm{ai},m}{R}^2{T}_{\mathrm{ci},m}^2/P_{\mathrm{ci},m}---\left(17\right)$

b _i＝Ω _bRT _ci/P _cia (18)

$T_{\mathrm{ci},m}=\sqrt{T_{\mathrm{ci}}{T}_{\mathrm{cj}}}(1-k_{i,m})---\left(19\right)$

$V_{\mathrm{ci},m}=0.125{(V_{\mathrm{ci},m}^{1/3}+V_{\mathrm{ci},m}^{1/3})}^3---\left(20\right)$

Z _ci，m＝0.5(Z _ci+Z _cm) (21)

P _ci，m＝RT _ci，mZ _ci，m/V _ci，m (22)

Ω _ai，m＝0.5(Ω _ai+Ω _am) (23)

To vapour phase:

$a^G=\underset{i}{\mathrm{\&Sigma;}}\underset{m}{\mathrm{\&Sigma;}}{y}_i{y}_m{a}_{i,m}---\left(24\right)$

$b^G=\underset{i}{\mathrm{\&Sigma;}}{y}_i{b}_i---\left(25\right)$

Order

A ^G＝a ^GP/R ²T ² (26)

B ^G＝b ^GP/RT (27)

α ^G＝2B ^G-1 (28)

${\mathrm{\&beta;}}^G=A^G-3B^G-5B^{G^2}---\left(29\right)$

${\mathrm{\&gamma;}}^G=2(B^{G^3}+B^{G^2})-A^G{B}^G---\left(30\right)$

Getting initial value is 1-0.6P _r, separate following equation with Newton method, promptly obtain vapour phase compressibility factor Z ^G

$Z^{G^3}+{\mathrm{\&alpha;}}^G{Z}^{G^2}+\mathrm{\&beta;}{Z}^G+{\mathrm{\&gamma;}}^G=0---\left(31\right)$

Then,

v ^G＝RT/PZ ^G (32)

${\mathrm{\&xi;}}^G=0.242536\ln \frac{v^G+{3.561553b}^G}{v^G-{0.561553b}^G}---\left(33\right)$

To liquid phase:

$a^L=\underset{i}{\mathrm{\&Sigma;}}\underset{m}{\mathrm{\&Sigma;}}{x}_i{x}_m{a}_{i,m}---\left(34\right)$

$b^L=\underset{i}{\mathrm{\&Sigma;}}{x}_i{b}_i---\left(35\right)$

Order

A ^L＝a ^LP/R ²T ² (36)

B ^L＝b ^LP/RT (37)

α ^L＝2B ^L-1 (38)

${\mathrm{\&beta;}}^L=A^L-3B^L-5B^{L^2}---\left(39\right)$

${\mathrm{\&gamma;}}^L=2(B^{L^3}+B^{L^2})-A^L{B}^L---\left(40\right)$

Getting initial value is P _r(0.106+0.078P _r), separate following equation with Newton method, promptly obtain liquid phase compressibility factor Z ^L

$Z^{L^3}+{\mathrm{\&alpha;}}^L{Z}^{L^2}+\mathrm{\&beta;}{Z}^L+{\mathrm{\&gamma;}}^L=0---\left(41\right)$

Then,

v ^L＝RT/PZ ^L (42)

${\mathrm{\&xi;}}^L=0.242536\ln \frac{v^L+{3.561553b}^L}{v^L-{0.561553b}^L}---\left(43\right)$

Ω _ai＝C _i-D _iτ+E _iτ ²-W _iτ ³ (44)

Ω _b＝0.070721 (45)

τ＝0.01T (46)

Wherein, A, B, α, β, γ, τ are intermediate variables, and C, D, E, W are constants, T _c, P _c, V _c, Z _cBe respectively critical temperature, pressure, volume and compressibility factor, P _rBe reduced pressure, R is a gas law constant, k _{I, m}The mutual coefficient of binary of representing i component and m component, k _{I, m}Be constant, subscript c representes the character of critical point, and subscript r representes reduced state, subscript i, and m representes the two-component mixture of i component and m component, Ω _a, Ω _bIt is intermediate variable.

In the said step 6), effectively the process of mass transfer coefficient is following mutually to calculate vapour-liquid:

$k_{\mathrm{eff},i}^{G}a=\frac{1-y_i}{\underset{k=1,k\&NotEqual;i}{\overset{3}{\mathrm{\&Sigma;}}}(y_k/k_{i,k}^{G}a)}---\left(47\right)$

$k_{\mathrm{eff},i}^{L}a=\frac{1-x_i}{\underset{k=1,k\&NotEqual;i}{\overset{3}{\mathrm{\&Sigma;}}}(x_k/k_{i,k}^{L}a)}---\left(48\right)$

$k_{i,k}^{G}a=5.85{\left(\frac{u_h{d}_b{\mathrm{\&rho;}}_m^G}{{\mathrm{\&eta;}}_m^G}\right)}^{-\frac{1}{4}}{\left(\frac{{\mathrm{\&eta;}}_m^G}{{\mathrm{\&rho;}}_m^G{D}_{i,k}^G}\right)}^{-\frac{1}{2}}{\left(\frac{F_a^2}{d_{b}g{\mathrm{\&phi;}}^2{\mathrm{\&rho;}}_m^L}\right)}^{0.17}{\left(\frac{h_{\mathrm{ow}}}{d_b}\right)}^{0.15}{\left(\frac{d_b^{2}g{\mathrm{\&rho;}}_m^L}{{\mathrm{\&sigma;}}_m}\right)}^{0.1}V---\left(49\right)$

$k_{i,k}^{L}a=1.97\&times;{10}^4{D_{i,k}^L}^{0.5}(0.4F_a+0.17)t_{L}L---\left(50\right)$

Wherein, k _{I, k} ^GAnd k _{I, k} ^LBe respectively the vapour liquid phase mass transfer coefficient, u _hBe sieve aperture gas speed, d _bBe the aperture, ρ _m ^GBe vapour phase density, η _m ^GBe vapour phase viscosity, D _{I, k} ^GBe the mutual coefficient of vapour phase binary, F _aBe kinetic energy factor, g is an acceleration of gravity, ρ _m ^LBe density of liquid phase, φ is a percentage of open area, σ _mBe the surface tension of mixing material, h _OWBe plate supernatant floor height, D _{I, k} ^LBe the mutual coefficient of liquid phase binary, t _LIt is the residence time.

In described step 10), host computer is passed to control station with the Energy Saving Control result and is shown, and through fieldbus result of calculation is delivered to operator station and shows.

Air separation column non-equilibrium energy-saving control system and method proposed by the invention; Be described through above-mentioned practical implementation step; Person skilled obviously can be in not breaking away from content of the present invention, spirit and scope to device as herein described with method of operating is changed or suitably change and combination, realize the present invention's technology.Special needs to be pointed out is, the replacement that all are similar and change apparent to one skilled in the artly, they all can be regarded as and be included in spirit of the present invention, scope and the content.

Claims (2)

1. air separation column non-equilibrium energy-saving control system; Comprise the field intelligent instrument and control station, database and the host computer that are connected with air separation column; Field intelligent instrument is connected with control station, database and host computer, it is characterized in that: described host computer comprises:

Signal acquisition module is in order to gather current production status data;

Energy-saving control module, in order to Energy Saving Control, adopt following process to accomplish:

1) structural parameters and the operating parameter of setting air separation column are specified feeding air flow initial value;

2) suppose each column plate liquid phase main body composition, vapour-liquid phase flow rate, column plate temperature;

3), calculate the mass transfer in liquid phase flux respectively to each column plate:

$L_{j-1}{x}_{i,j-1}+F_j^L{z}_{i,j}^L-(L_j+S_j^L)x_{i,j}+N_{i,j}^L=0---\left(1\right)$

Wherein, L representes the liquid phase flow, and F representes feed rate; S representes that side carries flow, and x representes that liquid phase forms, and z representes feed composition; N representes the mass transfer flux, and subscript L representes liquid phase, subscript i=1,2,3 expression components; Corresponding successively nitrogen, argon, oxygen, subscript j-1, j represent j-1 and j piece column plate respectively;

4), calculate the vapour phase main body respectively and form to each column plate

$V_{j+1}{y}_{i,j+1}+F_j^G{z}_{i,j}^G-(V_j+S_j^G)y_{i,j}-N_{i,j}^L=0---\left(2\right)$

Wherein V representes the vapour phase flow, and y representes the vapour phase composition, and subscript G representes vapour phase;

5), calculate the enthalpy of its vapour-liquid phase main body respectively to each column plate;

6), calculate the effective mutually mass transfer coefficient of vapour-liquid respectively to each column plate;

7), calculate liquid interface respectively and form to each column plate:

$N_i^L=k_{\mathrm{eff},i}^{L}a(x_i^I-x_i)+x_i{N}_t,i=\mathrm{1,2}---\left(3\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{x}_i^I=1---\left(4\right)$

Wherein,

Represent i the effective mass transfer coefficient of component liquid phase, a representes mass transfer area,

The liquid interface composition of representing i component, N _tRepresent total mass transfer flux;

8), form by bubble point method calculating column plate equilibrium temperature and vapour phase interface respectively to each column plate;

9) judge that whether following formula (5)～(8) satisfy, if satisfy then continue 10), if do not satisfy then updating all column plates liquid phase main body compositions, vapour-liquid phase flow rate, column plate temperature, return 3) the continuation iteration:

$V_{j+1}{H}_{j+1}^G+L_{j-1}{H}_{j-1}^L+F_j^G{H}_j^{\mathrm{FG}}+F_j^L{H}_j^{\mathrm{FL}}-(V_j+S_j^G)H_j^G-(L_j+S_j^L)H_j^L-Q_j<\mathrm{\&epsiv;}---\left(5\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{x}_{i,j}-1<\mathrm{\&epsiv;}---\left(6\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{y}_{i,j}-1<\mathrm{\&epsiv;}---\left(7\right)$

$k_{\mathrm{eff},i}^{G}a(y_i-y_i^I)+y_i{N}_t-N_{i,j}^L<\mathrm{\&epsiv;},i=\mathrm{1,2}---\left(8\right)$

Wherein, H ^FG, H ^FLRepresent vapour-liquid phase charging enthalpy respectively, H ^GAnd H ^LBe respectively vapour-liquid phase enthalpy, subscript j-1, j, j+1 represent j-1, j, j+1 piece plate respectively, and ε is a tolerance,

Be the effective mass transfer coefficient of vapour phase, Q representes the heat that column plate spreads out of;

10) judge whether the purity of product nitrogen gas, oxygen and output satisfy current production status requirement, if do not satisfy then finishing iteration, the air feed flow of back is maximum air inlet amount, the output result; If satisfy then the air feed flow is increased an iteration step length Δ, return 2) continue iteration;

Bubble point method module, in order to be made up of bubble point method its equilibrium temperature of calculating and vapour phase interface, its process is following:

8.1) supposition column plate equilibrium temperature;

8.2) calculate the VLE constant, adopt following process to accomplish:

$\ln {\mathrm{\&Phi;}}_i^L=\ln \frac{\mathrm{RT}}{P(v^L-b^L)}-\frac{b_i}{b^L}(1-Z^L)+{\mathrm{\&xi;}}^L{a}^L(\frac{b_i}{b^L}-\frac{2\underset{m}{\mathrm{\&Sigma;}}{x}_m{a}_{i,m}}{a^L})/b^L\mathrm{RT}---\left(9\right)$

$\ln {\mathrm{\&Phi;}}_i^G=\ln \frac{\mathrm{RT}}{P(v^G-b^G)}-\frac{b_i}{b^G}(1-Z^G)+{\mathrm{\&xi;}}^G{a}^G(\frac{b_i}{b^G}-\frac{2\underset{m}{\mathrm{\&Sigma;}}{x}_m{a}_{i,m}}{a^G})/b^G\mathrm{RT}---\left(10\right)$

$K_i={\mathrm{\&Phi;}}_i^L/{\mathrm{\&Phi;}}_i^G---\left(11\right)$

y _i＝K _ix _i (12)

Wherein, Φ representes fugacity coefficient, and subscript L representes liquid phase, and subscript G representes vapour phase, and R is a gas law constant, and T is a temperature, and P is a column plate pressure, subscript m=1,2,3 expression components, corresponding successively nitrogen, argon, oxygen, molar volume v, physical parameter b ^G, b ^L, b _i, a ^G, a ^L, a _{I, m}, ξ ^G, ξ ^L, vapour phase compressibility factor Z ^G, liquid phase compressibility factor Z ^LCalculate by the rerum natura module;

8.3) check

whether set up; Set up then finishing iteration; Return result of calculation; Otherwise, upgrade the column plate equilibrium temperature, return 8.2) the continuation iteration;

The enthalpy module, in order to calculate the enthalpy of vapour-liquid phase main body, its process is following:

$H_i^{*}=c_i+d_{i}T+e_i{T}^2+f_i{T}^3+h_i{T}^4---\left(13\right)$

$H^{*}=\underset{i}{\mathrm{\&Sigma;}}{y}_i{H}_i^{*}---\left(14\right)$

$H^G=H^{*}-\mathrm{RT}(1-Z^G)-{\mathrm{\&xi;}}^G(a^G-T\frac{d{a}^G}{\mathrm{dT}})/b^G---\left(15\right)$

$H^L=H^{*}-\mathrm{RT}(1-Z^L)-{\mathrm{\&xi;}}^L(a^L-T\frac{d{a}^L}{\mathrm{dT}})/b^L---\left(16\right)$

Wherein

The enthalpy of representing i pure component ideal gas, H ^*Be potpourri ideal gas enthalpy, c, d, e, f, h are constant;

The mass transfer coefficient module, in order to calculate the effective mutually mass transfer coefficient of vapour-liquid, its process is following:

$k_{\mathrm{eff},i}^{G}a=\frac{1-y_i}{\underset{k=1,k\&NotEqual;i}{\overset{3}{\mathrm{\&Sigma;}}}(y_k/k_{i,k}^{G}a)}---\left(47\right)$

$k_{\mathrm{eff},i}^{L}a=\frac{1-x_i}{\underset{k=1,k\&NotEqual;i}{\overset{3}{\mathrm{\&Sigma;}}}(x_k/k_{i,k}^{L}a)}---\left(48\right)$

$k_{i,k}^{G}a=5.85{\left(\frac{u_h{d}_b{\mathrm{\&rho;}}_m^G}{{\mathrm{\&eta;}}_m^G}\right)}^{-\frac{1}{4}}{\left(\frac{{\mathrm{\&eta;}}_m^G}{{\mathrm{\&rho;}}_m^G{D}_{i,k}^G}\right)}^{-\frac{1}{2}}{\left(\frac{F_a^2}{d_{b}g{\mathrm{\&phi;}}^2{\mathrm{\&rho;}}_m^L}\right)}^{0.17}{\left(\frac{h_{\mathrm{ow}}}{d_b}\right)}^{0.15}{\left(\frac{d_b^{2}g{\mathrm{\&rho;}}_m^L}{{\mathrm{\&sigma;}}_m}\right)}^{0.1}V---\left(49\right)$

$k_{i,k}^{L}a=1.97\&times;{10}^4{D}_{i,k}^{L0.5}(0.4F_a+0.17)t_{L}L---\left(50\right)$

Wherein,

With

Be respectively the vapour liquid phase mass transfer coefficient, u _hBe sieve aperture gas speed, d _bBe the aperture,

Be vapour phase density,

Be vapour phase viscosity,

Be the mutual coefficient of vapour phase binary, F _aBe kinetic energy factor, g is an acceleration of gravity,

Be density of liquid phase, φ is a percentage of open area, σ _mBe the surface tension of mixing material, h _OWBe plate supernatant floor height,

Be the mutual coefficient of liquid phase binary, t _LIt is the residence time;

The rerum natura module, in order to calculate physical parameter, its process is following:

$a_{i,m}={\mathrm{\&Omega;}}_{\mathrm{ai},m}{R}^2{T}_{\mathrm{ci},m}^2/P_{\mathrm{ci},m}---\left(17\right)$

b _i＝Ω _bRT _ci/P _cia (18)

$T_{\mathrm{ci},m}=\sqrt{T_{\mathrm{ci}}{T}_{\mathrm{cj}}}(1-k_{i,m})---\left(19\right)$

$V_{\mathrm{ci},m}=0.125{(V_{\mathrm{ci},m}^{1/3}+V_{\mathrm{ci},m}^{1/3})}^3---\left(20\right)$

Z _ci，m＝0.5(Z _ci+Z _cm) (21)

P _ci，m＝RT _ci，mZ _ci，m/V _ci，m (22)

Ω _ai，m＝0.5(Ω _ai+Ω _am) (23)

To vapour phase:

$a^G=\underset{i}{\mathrm{\&Sigma;}}\underset{m}{\mathrm{\&Sigma;}}{y}_i{y}_m{a}_{i,m}---\left(24\right)$

$b^G=\underset{i}{\mathrm{\&Sigma;}}{y}_i{b}_i---\left(25\right)$

Order

A ^G＝a ^GP/R ²T ² (26)

B ^G＝b ^GP/RT (27)

α ^G＝2B ^G-1 (28)

${\mathrm{\&beta;}}^G=A^G-3B^G-5B^{G^2}---\left(29\right)$

${\mathrm{\&gamma;}}^G=2(B^{G^3}+B^{G^2})-A^G{B}^G---\left(30\right)$

Getting initial value is 1-0.6P _r, separate following equation with Newton method, promptly obtain vapour phase compressibility factor Z ^G

$Z^{G^3}+{\mathrm{\&alpha;}}^G{Z}^{G^2}+\mathrm{\&beta;}{Z}^G+{\mathrm{\&gamma;}}^G=0---\left(31\right)$

Then,

v ^G＝RT/PZ ^G (32)

${\mathrm{\&xi;}}^G=0.242536\ln \frac{v^G+3.561553b^G}{v^G-0.561553b^G}---\left(33\right)$

To liquid phase:

$a^L=\underset{i}{\mathrm{\&Sigma;}}\underset{m}{\mathrm{\&Sigma;}}{x}_i{x}_m{a}_{i,m}---\left(34\right)$

$b^L=\underset{i}{\mathrm{\&Sigma;}}{x}_i{b}_i---\left(35\right)$

Order

A ^L＝a ^LP/R ²T ² (36)

B ^L＝b ^LP/RT (37)

α ^L＝2B ^L-1 (38)

${\mathrm{\&beta;}}^L=A^L-3B^L-5B^{L^2}---\left(39\right)$

${\mathrm{\&gamma;}}^L=2(B^{L^3}+B^{L^2})-A^L{B}^L---\left(40\right)$

Getting initial value is P _r(0.106+0.078P _r), separate following equation with Newton method, promptly obtain liquid phase compressibility factor Z ^L

$Z^{L^3}+{\mathrm{\&alpha;}}^L{Z}^{L^2}+\mathrm{\&beta;}{Z}^L+{\mathrm{\&gamma;}}^L=0---\left(41\right)$

Then,

v ^L＝RT/PZ ^L (42)

${\mathrm{\&xi;}}^L=0.242536\ln \frac{v^L+3.561553b^L}{v^L-0.561553b^L}---\left(43\right)$

Ω _ai＝C _i-D _iτ+E _iτ ²-W _iτ ³ (44)

Ω _b＝0.070721 (45)

τ＝0.01T (46)

Wherein, A, B, α, β, γ, τ are intermediate variables, and C, D, E, W are constants, T _c, P _c, V _c, Z _cBe respectively critical temperature, pressure, volume and compressibility factor, P _rBe reduced pressure, R is a gas law constant, k _{I, m}The mutual coefficient of binary of representing i component and m component, K _{I, m}Be constant, subscript c representes the character of critical point, and subscript r representes reduced state, subscript i, and m representes the two-component mixture of i component and m component, Ω _a, Ω _bIt is intermediate variable.

2. energy-saving control method of realizing with air separation column non-equilibrium energy-saving control system as claimed in claim 1, it is characterized in that: described energy-saving control method may further comprise the steps:

1) structural parameters of setting air separation column, the production status data of gathering air separation column are gathered current feeding air flow as initial value;

2) suppose each column plate liquid phase main body composition, vapour-liquid phase flow rate, column plate temperature;

3), calculate the mass transfer in liquid phase flux respectively to each column plate:

$L_{j-1}{x}_{i,j-1}+F_j^L{z}_{i,j}^L-(L_j+S_j^L)x_{i,j}+N_{i,j}^L=0---\left(1\right)$

Wherein, L representes the liquid phase flow, and F representes feed rate; S representes that side carries flow, and x representes that liquid phase forms, and z representes feed composition; N representes the mass transfer flux, and subscript L representes liquid phase, subscript i=1,2,3 expression components; Corresponding successively nitrogen, argon, oxygen, subscript j-1, j represent j-1 and j piece column plate respectively;

4), calculate the vapour phase main body respectively and form to each column plate

$V_{j+1}{y}_{i,j+1}+F_j^G{z}_{i,j}^G-(V_j+S_j^G)y_{i,j}-N_{i,j}^L=0---\left(2\right)$

Wherein V representes the vapour phase flow, and y representes the vapour phase composition, and subscript G representes vapour phase;

5) to each column plate, calculate the enthalpy of its vapour-liquid phase main body respectively, process is following:

$H_i^{*}=c_i+d_{i}T+e_i{T}^2+f_i{T}^3+h_i{T}^4---\left(13\right)$

$H^{*}=\underset{i}{\mathrm{\&Sigma;}}{y}_i{H}_i^{*}---\left(14\right)$

$H^G=H^{*}-\mathrm{RT}(1-Z^G)-{\mathrm{\&xi;}}^G(a^G-T\frac{d{a}^G}{\mathrm{dT}})/b^G---\left(15\right)$

$H^L=H^{*}-\mathrm{RT}(1-Z^L)-{\mathrm{\&xi;}}^L(a^L-T\frac{d{a}^L}{\mathrm{dT}})/b^L---\left(16\right)$

Wherein

The enthalpy of representing i pure component ideal gas, H ^*Be potpourri ideal gas enthalpy, c, d, e, f, h are constant;

6) to each column plate, calculate the effective mutually mass transfer coefficient of vapour-liquid respectively, process is following:

$k_{\mathrm{eff},i}^{G}a=\frac{1-y_i}{\underset{k=1,k\&NotEqual;i}{\overset{3}{\mathrm{\&Sigma;}}}(y_k/k_{i,k}^{G}a)}---\left(47\right)$

$k_{\mathrm{eff},i}^{L}a=\frac{1-x_i}{\underset{k=1,k\&NotEqual;i}{\overset{3}{\mathrm{\&Sigma;}}}(x_k/k_{i,k}^{L}a)}---\left(48\right)$

$k_{i,k}^{G}a=5.85{\left(\frac{u_h{d}_b{\mathrm{\&rho;}}_m^G}{{\mathrm{\&eta;}}_m^G}\right)}^{-\frac{1}{4}}{\left(\frac{{\mathrm{\&eta;}}_m^G}{{\mathrm{\&rho;}}_m^G{D}_{i,k}^G}\right)}^{-\frac{1}{2}}{\left(\frac{F_a^2}{d_{b}g{\mathrm{\&phi;}}^2{\mathrm{\&rho;}}_m^L}\right)}^{0.17}{\left(\frac{h_{\mathrm{ow}}}{d_b}\right)}^{0.15}{\left(\frac{d_b^{2}g{\mathrm{\&rho;}}_m^L}{{\mathrm{\&sigma;}}_m}\right)}^{0.1}V---\left(49\right)$

$k_{i,k}^{L}a=1.97\&times;{10}^4{D}_{i,k}^{L0.5}(0.4F_a+0.17)t_{L}L---\left(50\right)$

Wherein,

With

Be respectively the vapour liquid phase mass transfer coefficient, u _hBe sieve aperture gas speed, d _bBe the aperture, Be vapour phase density,

Be vapour phase viscosity, Be the mutual coefficient of vapour phase binary, F _aBe kinetic energy factor, g is an acceleration of gravity,

Be density of liquid phase, φ is a percentage of open area, σ _mBe the surface tension of mixing material, h _OWBe plate supernatant floor height, Be the mutual coefficient of liquid phase binary, t _LIt is the residence time;

7), calculate liquid interface respectively and form to each column plate:

$N_i^L=k_{\mathrm{eff},i}^{L}a(x_i^I-x_i)+x_i{N}_t,i=\mathrm{1,2}---\left(3\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{x}_i^I=1---\left(4\right)$

Wherein,

The liquid interface composition of representing i component, N _tRepresent total mass transfer flux;

8) to each column plate, form by bubble point method its equilibrium temperature of calculating and vapour phase interface respectively, adopt following process to accomplish:

8.1) supposition column plate equilibrium temperature;

8.2) calculate the VLE constant, adopt following process to accomplish:

$\ln {\mathrm{\&Phi;}}_i^L=\ln \frac{\mathrm{RT}}{P(v^L-b^L)}-\frac{b_i}{b^L}(1-Z^L)+{\mathrm{\&xi;}}^L{a}^L(\frac{b_i}{b^L}-\frac{2\underset{m}{\mathrm{\&Sigma;}}{x}_m{a}_{i,m}}{a^L})/b^L\mathrm{RT}---\left(9\right)$

$\ln {\mathrm{\&Phi;}}_i^G=\ln \frac{\mathrm{RT}}{P(v^G-b^G)}-\frac{b_i}{b^G}(1-Z^G)+{\mathrm{\&xi;}}^G{a}^G(\frac{b_i}{b^G}-\frac{2\underset{m}{\mathrm{\&Sigma;}}{x}_m{a}_{i,m}}{a^G})/b^G\mathrm{RT}---\left(10\right)$

$K_i={\mathrm{\&Phi;}}_i^L/{\mathrm{\&Phi;}}_i^G---\left(11\right)$

y _i＝K _ix _i (12)

Wherein, Φ representes fugacity coefficient, and subscript L representes liquid phase, and subscript G representes vapour phase, and R is a gas law constant, and T is a temperature, and P is a column plate pressure, subscript m=1,2,3 expression components, corresponding successively nitrogen, argon, oxygen, molar volume v, physical parameter b ^G, b ^L, b _i, a ^G, a ^L, a _{I, m}, ξ ^G, ξ ^L, vapour phase compressibility factor Z ^G, liquid phase compressibility factor Z ^LCalculate by the physical parameter computing method; Described physical parameter computing method comprise the steps:

$a_{i,m}={\mathrm{\&Omega;}}_{\mathrm{ai},m}{R}^2{T}_{\mathrm{ci},m}^2/P_{\mathrm{ci},m}---\left(17\right)$

b _i＝Ω _bRT _ci/P _cia (18)

$T_{\mathrm{ci},m}=\sqrt{T_{\mathrm{ci}}{T}_{\mathrm{cj}}}(1-k_{i,m})---\left(19\right)$

$V_{\mathrm{ci},m}=0.125{(V_{\mathrm{ci},m}^{1/3}+V_{\mathrm{ci},m}^{1/3})}^3---\left(20\right)$

Z _ci，m＝0.5(Z _ci+Z _cm) (21)

P _ci，m＝RT _ci，mZ _ci，m/V _ci，m (22)

Ω _ai，m＝0.5(Ω _ai+Ω _am) (23)

To vapour phase:

$a^G=\underset{i}{\mathrm{\&Sigma;}}\underset{m}{\mathrm{\&Sigma;}}{y}_i{y}_m{a}_{i,m}---\left(24\right)$

$b^G=\underset{i}{\mathrm{\&Sigma;}}{y}_i{b}_i---\left(25\right)$

Order

A ^G＝a ^GP/R ²T ² (26)

B ^G＝b ^GP/RT (27)

α ^G＝2B ^G-1 (28)

${\mathrm{\&beta;}}^G=A^G-3B^G-5B^{G^2}---\left(29\right)$

${\mathrm{\&gamma;}}^G=2(B^{G^3}+B^{G^2})-A^G{B}^G---\left(30\right)$

Getting initial value is 1-0.6P _r, separate following equation with Newton method, promptly obtain vapour phase compressibility factor Z ^G

$Z^{G^3}+{\mathrm{\&alpha;}}^G{Z}^{G^2}+\mathrm{\&beta;}{Z}^G+{\mathrm{\&gamma;}}^G=0---\left(31\right)$

Then,

v ^G＝RT/PZ ^G (32)

${\mathrm{\&xi;}}^G=0.242536\ln \frac{v^G+3.561553b^G}{v^G-0.561553b^G}---\left(33\right)$

To liquid phase:

$a^L=\underset{i}{\mathrm{\&Sigma;}}\underset{m}{\mathrm{\&Sigma;}}{x}_i{x}_m{a}_{i,m}---\left(34\right)$

$b^L=\underset{i}{\mathrm{\&Sigma;}}{x}_i{b}_i---\left(35\right)$

Order

A ^L＝a ^LP/R ²T ² (36)

B ^L＝b ^LP/RT (37)

α ^L＝2B ^L-1 (38)

${\mathrm{\&beta;}}^L=A^L-3B^L-5B^{L^2}---\left(39\right)$

${\mathrm{\&gamma;}}^L=2(B^{L^3}+B^{L^2})-A^L{B}^L---\left(40\right)$

Getting initial value is P _r(0.106+0.078P _r), separate following equation with Newton method, promptly obtain liquid phase compressibility factor Z ^L

$Z^{L^3}+{\mathrm{\&alpha;}}^L{Z}^{L^2}+\mathrm{\&beta;}{Z}^L+{\mathrm{\&gamma;}}^L=0---\left(41\right)$

Then,

v ^L＝RT/PZ ^L (42)

${\mathrm{\&xi;}}^L=0.242536\ln \frac{v^L+3.561553b^L}{v^L-0.561553b^L}---\left(43\right)$

Ω _ai＝C _i-D _iτ+E _iτ ²-W _iτ ³ (44)

Ω _b＝0.070721 (45)

τ＝0.01T (46)

Wherein, A, B, α, β, γ, τ are intermediate variables, and C, D, E, W are constants, T _c, P _c, V _c, Z _cBe respectively critical temperature, pressure, volume and compressibility factor, P _rBe reduced pressure, R is a gas law constant, k _{I, m}The mutual coefficient of binary of representing i component and m component, k _{I, m}Be constant, subscript c representes the character of critical point, and subscript r representes reduced state, subscript i, and m representes the two-component mixture of i component and m component, Ω _a, Ω _bIt is intermediate variable;

8.3) check

whether set up; Set up then finishing iteration; Return result of calculation; Otherwise, upgrade the column plate equilibrium temperature, return 8.2) the continuation iteration;

9) judge that whether following formula satisfies,,, return step 3) continuation iteration if do not satisfy then updating all column plates liquid phase main body compositions, vapour-liquid phase flow rate, column plate temperature if satisfy then continue step 10):

$V_{j+1}{H}_{j+1}^G+L_{j-1}{H}_{j-1}^L+F_j^G{H}_j^{\mathrm{FG}}+F_j^L{H}_j^{\mathrm{FL}}-(V_j+S_j^G)H_j^G-(L_j+S_j^L)H_j^L-Q_j<\mathrm{\&epsiv;}---\left(5\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{x}_{i,j}-1<\mathrm{\&epsiv;}---\left(6\right)$

$\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{y}_{i,j}-1<\mathrm{\&epsiv;}---\left(7\right)$

$k_{\mathrm{eff},i}^{G}a(y_i-y_i^I)+y_i{N}_t-N_{i,j}^L<\mathrm{\&epsiv;},i=\mathrm{1,2}---\left(8\right)$

Wherein, H ^FG, H ^FLRepresent vapour-liquid phase charging enthalpy respectively, H ^GAnd H ^LBe respectively vapour-liquid phase enthalpy, subscript j-1, j, j+1 represent j-1, j, j+1 piece plate respectively, and ε is a tolerance,

Be the effective mass transfer coefficient of vapour phase, Q representes the heat that column plate spreads out of;

10) judge whether the purity of product nitrogen gas, oxygen and output satisfy current production status requirement, if do not satisfy then finishing iteration, the air feed flow of back is maximum air inlet amount, the output result; Simultaneously host computer is passed to control station with the Energy Saving Control result and is shown, and through fieldbus the Energy Saving Control result is delivered to operator station and shows, if satisfy then the air feed flow is increased an iteration step length Δ, returns step 2) continue iteration.

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