CN102779203A - Industrial unit dichloroethane cracking furnace coupled modeling method and application - Google Patents

Abstract

The invention relates to an industrial unit dichloroethane cracking furnace coupled modeling method and application. In the method, during modeling, a dichloroethane cracking furnace is divided into a hearth model and a furnace tube model, a one-dimensional partition method in combination with method is used for the hearth, the smoke temperature distribution condition of the hearth is solved by a heat balance equation, for the furnace tube model, the furnace tube is partitioned according to the amount of straight tube sections of a radiant section, and the reaction and the heat absorption capacity in the tube are calculated section by section. The hearth model and the furnace tube model are mutually iterated through a quasi-newton method according to the calculated smoke temperature and heat transfer rate information, until meeting the convergence precision and the model precision. The model is based on the dynamical model and the energy conservation relation, and is corrected by real-time data so as to further measure the relevant parameters of the cracking furnace in a soft sensing manner. The accurate model is the basis of optimization, provides reliable model basis for optimization of field important economic indicators, such as the outlet temperature of the furnace tube of the cracking furnace, the dichloroethane cracking conversion rate, the selectivity, the unit consumption and so on, and realizes real-time soft sensing of relevant parameters.

Description

Commercial plant ethylene dichloride pyrolysis furnace coupling modeling method and application

Technical field

The present invention relates to a kind of commercial plant modeling method, especially a kind of commercial plant ethylene dichloride pyrolysis furnace coupling modeling method and application.

Technical background

To commercial plant especially reaction unit Modeling Research is the basis of carrying out technology, engineering development and optimization.Especially the Pintsch process furnace apparatus belongs to the energy consumption rich and influential family in the device; Quantitatively understand ethylene dichloride (EDC) boiler tube heat flux distribution; The pyrolysis gas Temperature Distribution, pyrolysis gas is formed distribution, burner hearth and boiler tube heat coupled relation; Be familiar with its rule and mechanism; Set up dynamics and thermodynamical model, thus for the optimization of the design of ethylene dichloride pyrolysis furnace, production operation condition, and the transformation of production technology etc. foundation and means are provided, therefore set up can accurate description ethylene dichloride pyrolysis furnace operation characteristic mechanism model significant.

Vinyl chloride (VCM) can be made by ethene or acetylene.Vinyl chloride be colourless, be prone to liquid gas, boiling point-13.9 ℃, 142 ℃ of critical temperatures, emergent pressure 5.22MPa.Vinyl chloride and air form explosive mixture, explosion limits 4%～22% (volume).Frenchman V. Le Niao in 1835 handles ethylene dichloride with potassium hydroxide and at first obtains vinyl chloride in ethanolic solution.The thirties in 20th century, German Ge Lisihaimu electronics corporation has at first realized the commercial production of vinyl chloride based on hydrogen chloride and acetylene addition.At the initial stage, vinyl chloride adopts calcium carbide, and the method production of acetylene and hydrogen chloride catalysis addition is called for short acetylene method.After, along with the development of petrochemical complex, synthetic the turning to rapidly with ethene of vinyl chloride is the process route of raw material.1940, U.S. combinating carbide company developed dichloroethane law.For the utilization of balance chlorine, Japanese Wu Yu chemical industrial company has developed the combination method with acetylene method and dichloroethane law Joint Production vinyl chloride again.Nineteen sixty, Dow Chemical company has developed the method for ethene through the oxychlorination synthesizing chloroethylene, and cooperates with dichloroethane law, and being developed to ethene is the complete method of raw material production vinyl chloride, and this method has obtained developing rapidly.Additive methods such as acetylene method, mixing eneyne method are in the status that progressively is eliminated owing to energy consumption is high.

Seeing also Fig. 1, is the process chart that existing ethylene oxychlorination balancing method is produced TOWER OUTLET IN VINYL CHLORIDE UNIT, and TOWER OUTLET IN VINYL CHLORIDE UNIT comprises: oxychlorination unit 1; Ethylene dichloride refined unit 2; Ethylene dichloride cracking unit 3, vinyl chloride refined unit 4, hydrogen chloride (HCL) reclaims unit 5 formants such as grade.Wherein the ethylene dichloride pyrolysis furnace of ethylene dichloride cracking unit 3 is one of nucleus equipments of preparation vinyl chloride technology, is the high tube process stove of technology content.At present only there is fewer companies grasping complete manufacturing technology in the world, particularly important as the usefulness ability rich and influential family of a whole set of TOWER OUTLET IN VINYL CHLORIDE UNIT.Seeing also Fig. 2, is aforementioned ethylene dichloride pyrolysis furnace synoptic diagram.Ethylene dichloride from refined unit 2 is preheated to 170 ℃ through feeder pump entering ethylene dichloride primary heater; EDC after the preheating gets into the ethylene dichloride convection section and is preheated to 225 ℃; Downtake through gas bag pyrolysis gas of 480 ℃ in the shell side of ethylene dichloride evaporator and tube side carries out heat exchange again; The EDC of liquid phase heats in evaporator; Through evaporating, separate in the tedge entering ethylene dichloride gas bag, through the further gas-liquid separation of wire mesh demister, the ethylene dichloride of gas phase gets into convection section in cracking furnace again and is superheated to 260 ℃.Directly to get into radiation section further overheated for gas phase EDC in the overheated back of convection section, when the temperature of EDC begins cracking about 390 ℃, finishes until cracking.The cracking outlet temperature is controlled at 480 ℃.The pyrolysis gas that comes out from pyrolysis furnace ℃ gets into quenching unit through EDC evaporator cools to 278.

Research shows that ethylene dichloride cracking reaction initial temperature reacts completely and carries out at the pyrolysis furnace radiation section about 390 ℃, therefore modeling of the present invention is primarily aimed at the modeling of radiation section burner hearth and boiler tube.Ethylene dichloride Pintsch process course of reaction is extremely complicated, has multiple subsidiary reaction.And there is serious heat coupling in boiler tube and burner hearth, up to the present also is not applicable to the accurate model of industrial ethylene dichloride pyrolysis furnace.

Summary of the invention

In order to solve the problem of above-mentioned acomia accurate description ethylene dichloride Pintsch process course of reaction, the present invention proposes a kind of modeling method.

This method is divided into burner hearth modeling and boiler tube modeling:

Wherein, burner hearth adopts the method that one dimension subregion method combines with Luo Boyiwansifa.The fuel gas burning supposes that based on combustion model (1) respectively distinguishing fuel gas distinguishes perfect combustion at this.Follow energy conservation equation (2)～(4) in the burner hearth, distribute thereby calculate chamber flue gas temperature.

And; The boiler tube modeling is carried out subregion according to boiler tube straight tube hop count; Boiler tube satisfies conservation of matter equation (6)～(7), boiler tube momentum conservation equation (8) in tandem reaction kinetics equation (5), the boiler tube, energy conservation equation (9)～(11), thereby pyrolysis gas temperature in the computer tube; Pressure is formed important indicators such as distribution.

The coupling of burner hearth boiler tube heat utilizes intends Newton iteration method, and the burner hearth boiler tube model that iterates is until satisfying convergence precision and modeling accuracy.

Particularly, comprise following scheme:

A kind of commercial plant ethylene dichloride pyrolysis furnace coupling modeling method, said method comprises following steps:

Step 1: confirm on-the-spot ethylene dichloride pyrolysis furnace industry service data; Comprise ethylene dichloride feed rate, pressure and temperature, the pyrolysis gas outlet is formed, pressure and temperature, fuel gas feed rate, temperature; Air and fuel gas mass ratio; Ethylene dichloride cracking conversion ratio, ethylene dichloride cracking selectivity, the ethylene dichloride cracking generates the fuel gas quality that vinyl chloride per ton consumes;

Step 2: the modeling of ethylene dichloride pyrolysis furnace comprises reaction boiler tube modeling and burner hearth modeling:

Step 2.1: based on boiler tube internal reaction kinetics equation, boiler tube self-energy and momentum conservation relation are carried out the reaction boiler tube modeling; Utilize the subregion method boiler tube to be carried out subregion and draw pyrolysis gas Temperature Distribution in the pipe by boiler tube straight tube hop count, pipe inside and outside wall Temperature Distribution, pyrolysis gas pressure distribution in managing, pyrolysis gas is formed distribution, pyrolysis gas coil outlet temperature, pressure and composition in the pipe;

Step 2.2: the method that burner hearth utilizes the subregion method to combine with Luo Bo-Yi Wansifa; Based on burner hearth fuel gas firing model, the flow of flue gas heat transfer model, and burner hearth is to boiler tube pipe row's convection heat transfer' heat-transfer by convection and radiant heat transfer model; Through calculating burner hearth heat balance equation; Obtain distributing along furnace height direction flue-gas temperature, burner hearth exhanst gas outlet temperature, burner hearth is to the rate of heat transfer of boiler tube;

Step 3: the heat coupled relation based on burner hearth and boiler tube existence, utilize method of value solving to find the solution:

Step 3.1: initialization boiler tube and burner hearth feed conditions and chamber flue gas temperature distribute;

Step 3.2: utilize quasi-Newton method, iterate boiler tube and burner hearth model satisfy convergence precision up to the chamber flue gas temperature distribution, and iterative process is following:

Step 3.2.1: distribute based on chamber flue gas temperature, calculate the boiler tube model, obtain every boiler tube caloric receptivity and each burner hearth subregion rate of heat transfer to boiler tube;

Step 3.2.2: to furnace tube heat transfer speed, calculate the burner hearth model based on step 3.2.1 gained burner hearth, distribute thereby obtain new boiler tube flue-gas temperature;

Step 3.3: further adjust boiler tube intake pressure and temperature, thus iteration burner hearth boiler tube coupling model again, up to satisfying the model accuracy requirement.

Further, in the step 2.1 boiler tube internal reaction dynamics adopt ethylene dichloride-vinyl chloride-the tandem reaction mechanism of accessory substance.

Further, momentum conservation relation in the boiler tube described in the step 2.1, for the process atmospheric pressure changes and process gas mean molecular weight, temperature, mass flux, tube inner diameter and straight tube are relevant with the bend pipe resistance, and concrete pressure drop calculation formula is following:

$\frac{\mathrm{dP}}{\mathrm{dL}}=\frac{{\mathrm{<figure-callout\; id="2"\; label="G"\; filenames="HDA00001750666400011.png"\; state="\{\{state\}\}">G</figure-callout>}}^2\mathrm{<figure-callout\; id="2"\; label="RTP\; G"\; filenames="HDA00001750666400011.png"\; state="\{\{state\}\}">RTP</figure-callout>}}{G^{}}\&CenterDot;(\frac{1}{\mathrm{G\&Omega;}}\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\frac{d{N}_j}{\mathrm{dL}}+\frac{1}{T}\frac{\mathrm{dT}}{\mathrm{dL}}+\frac{1}{G}\frac{\mathrm{dG}}{\mathrm{dL}}+2\&CenterDot;f\&CenterDot;E\left(L\right))$

Wherein: f is a Fanning friction factor, and P is a process gas stagnation pressure, kgf/cm ²G is the mass flux that comprises material in the pipe, kg/ (m ²S); Ω is an infinitesimal section cross-sectional area, m ²M is a process gas mean molecular weight, kg/kmol; E (L) is the equivalent conversion coefficient of reaction tube infinitesimal section L position; ρ is the process air tightness, kg/m ³D is a reaction tube actual circulation internal diameter, m; Re is a Reynold's number; R is a gas constant; T is that process is drawn last breath to temperature; G is an acceleration of gravity.

Further, boiler tube self-energy conservation relation is in the step 2.1: heat absorption of boiler tube internal procedure gas lift temperature and the required heat Q of endothermic heat of reaction _p, equal to react the heat Q that tube wall transmits _t, and equal the heat Q that gas radiation and smoke convection in the radiation chamber are passed to the reaction tube outer wall _r

Further, the burner hearth model adopts the method simulated hearth that one dimension subregion method combines with Luo Bo-Yi Wansifa in the step 2.2, and the said burner hearth heat balance equation that draws is: $Q_{\mathrm{Si}}+\mathrm{\&sigma;}{A}_0[T_{\mathrm{Gm}(i-1)}^4-T_{\mathrm{Gmi}}^4]+\mathrm{\&sigma;}{A}_0[T_{\mathrm{Gm}(i+1)}^4-T_{\mathrm{Gmi}}^4]-Q_{\mathrm{Ri}}-\mathrm{\&Delta;}{H}_i-Q_{\mathrm{Li}}=0,$ Q wherein _SiBe i district fuel thermal discharge; T _GmiBe i district flue gas medial temperature, K; σ is Si Difen-Boltzmann constant; A ₀Be the vertical radiation useful area in i district; Q _RiFor burner hearth i district to furnace tube heat transfer speed; Δ H _iFor the flue gas in turnover i district is taken away net heat; Q _LiBe the thermal loss of i district through approach such as furnace wall heat radiations; I is the partition number along radiation chamber short transverse boiler tube, and span is [1, N].

Further, burner hearth spreads heat and radiant heat transfer model and is in the step 2.2: $Q_{\mathrm{Ri}}=\mathrm{\&sigma;}{a}_D{A}_{\mathrm{Cpi}}{F}_i(T_{\mathrm{Gmi}}^4-T_{\mathrm{Wi}}^4)-h_{\mathrm{Rc}}{A}_{\mathrm{Ri}}(T_{\mathrm{Gmi}}-T_{\mathrm{Wi}}),$ Wherein: Q _RiFor burner hearth i district to furnace tube heat transfer speed; a _DBe pipe row angle factor; σ is Si Difen-Boltzmann constant, W/m ².K ⁴A _CpiBe i district cold-smoothing area; F _iBe i district built-up radiation exchange factor; T _GmiBe i district flue gas medial temperature, K; T _WiBe i district pipe outer wall medial temperature; h _RcBe convective heat-transfer coefficient; A _RiBe i district reaction tube external surface area, i is the partition number along radiation chamber short transverse boiler tube, and span is [1, N].

Further; Said step 3.2 adopts the plan Newton iteration method that burner hearth and boiler tube are carried out the heat The Coupling: the variable that transmits each other in boiler tube and the stove model is that burner hearth is respectively distinguished flue-gas temperature to the rate of heat transfer and the burner hearth of boiler tube, wherein respectively distinguishes flue-gas temperature and calculates iterative formula T _Gmi(k+1)=(T _Gmi(k)+T _Gmi(new))/2, T _GmiBe i district chamber flue gas temperature, i is the subregion along radiation chamber short transverse boiler tube, and span is [1, N].

Further, also comprise step 4: the model that obtains based on step 3 is input with the real-time parameter numerical value of actual device, calculates and obtains all the other parameters.

Further, input parameter is: boiler tube burner hearth physical dimension, boiler tube intake pressure, boiler tube inlet temperature, boiler tube import mass flux, fuel gas consumption, excess air coefficient, fuel gas load distribution ratio, and convergence precision index; Output parameter is: the conversion ratio of coil outlet temperature or boiler tube top hole pressure or ethylene dichloride cracking reaction.The present invention provides ethylene dichloride pyrolysis furnace burner hearth boiler tube coupling modeling method in a kind of commercial production TOWER OUTLET IN VINYL CHLORIDE UNIT; The method is divided into burner hearth model and boiler tube model with the ethylene dichloride pyrolysis furnace in modeling; The method that burner hearth adopts one dimension subregion method to combine with Luo Boyiwansifa; Utilize heat balance equation solution chamber flue gas temperature distribution situation, the boiler tube model according to radiation section straight tube hop count with boiler tube subregion computer tube internal reaction and caloric receptivity piecemeal.Flue-gas temperature that burner hearth and the utilization of boiler tube model are calculated and rate of heat transfer information adopt the mutual iteration of quasi-Newton method up to satisfying convergence precision and model accuracy.This model is based on kinetic model and energy conservation relation, and the correction through real time data, with further soft measurement pyrolysis furnace correlation parameter.This accurately model be the basis of optimizing; For on-the-spot principal economic indicators optimizations such as cracking furnace tube outlet temperature, ethylene dichloride cracking conversion ratio, selectivity, unit consumption provide reliable model foundation and theory support, and realized the real-time soft measurement of each parameter based on this model.And this modeling method is applicable to all kinds of high-temperature cracking furnaces, and adaptability is widely arranged.

Description of drawings

Fig. 1 is an ethylene oxychlorination balancing method preparing chloroethylene device schematic flow sheet.

Fig. 2 is a Mitsui device ethylene dichloride pyrolysis furnace synoptic diagram.

Fig. 3 is that burner hearth and boiler tube heat transferred concern synoptic diagram.

Fig. 4 is pyrolysis furnace burner hearth and boiler tube simulation iteration convergence graph of a relation

The reference numeral explanation

Among Fig. 3, Tgm is a chamber flue gas temperature, and Tw is a tube wall temperature, and Twi is the inside pipe wall temperature, and Tci is burnt layer inner wall temperature, and T is pyrolysis gas temperature in the pipe.

Embodiment

Below in conjunction with accompanying drawing and embodiment the present invention is further specified.

The basis of implementing advanced control of ethylene dichloride pyrolysis furnace and real-time optimization is not only in ethylene dichloride pyrolysis furnace simulation accurately and reliably, and production operation guidance and pyrolysis furnace design optimization are also had vital role.The ethylene dichloride modeling divides from framework: can be divided into reaction boiler tube modeling and burner hearth modeling, but the two is not isolated each other, but heat coupling closely, modeling more complicated are arranged.Cracking reaction is carried out at radiation section in the radiation section of the burner hearth that the pyrolysis furnace burner hearth has the greatest impact for boiler tube, ethylene dichloride pipe.So the simulation of ethylene dichloride pyrolysis furnace is to the burner hearth of radiation section and boiler tube modeling respectively.Fuel gas adopts C4 fuel gas in the present embodiment, but not as limit.

1. be directed against the burner hearth modeling of radiation section:

The pyrolysis furnace radiation chamber is that flue-gas temperature distributes to the most important variable of reaction tube, and ethylene dichloride pyrolysis furnace burner hearth all heat supply adopts the burner on sidewall heat supply, along the furnace height direction, four arranges the sidewall nozzles altogether.Boiler tube is simulated the radiation of burner hearth chamber along the method that short transverse adopts one dimension subregion method to combine with Luo Bo-Yi Wansifa, according to sidewall nozzle location and radiant coil straight tube hop count burner hearth is divided into N district, is 4 districts in the present embodiment.Combustion model is mainly considered its thermal effect, supposes burner on sidewall perfect combustion in this district:

Q _si=G _siQ _sl (1)

Q _Si: sidewall fuel produces heat, W in the i district;

G _Si: sidewall fuel combustion mass rate, Kg/hr;

Q _Sl: sidewall lower calorific value of fuel, J/kg;

According to Luo Bo-Yi Wansi method, with the rate of heat transfer Q of arbitrary district flue gas to reaction tube pipe row _RiSimplify and calculate as follows:

$Q_{\mathrm{ri}}=\mathrm{\&sigma;}{a}_D{A}_{\mathrm{cpi}}{F}_i(T_{\mathrm{gmi}}^4-T_{\mathrm{wi}}^4)-h_{\mathrm{Rc}}{A}_{\mathrm{Ri}}(T_{\mathrm{gmi}}-T_{\mathrm{wi}})---\left(2\right)$

In the formula:

Q _Ri: the rate of heat transfer in i district, its value should with each infinitesimal section caloric receptivity summation Q in the i district _iEquate W;

σ: Si Difen-Boltzmann constant, W/m ².K ⁴

a _D: pipe row angle factor;

A _Cpi: i district cold-smoothing area, m ²

F _i: i district built-up radiation exchange factor;

T _Gmi: i district flue gas medial temperature, K;

T _Wi: i district tube wall medial temperature, K;

h _Rc: convective heat-transfer coefficient, W/m ².K;

A _Ri: i district reaction tube external surface area, m ²

Suppose to be divided into N district along the radiation chamber short transverse; The energy that gets into i district comprises the fuel thermal discharge; Heat that flue gas is brought into and axial radiations heat energy three parts that get into by the adjacent area, the energy that leaves this district comprises the caloric receptivity of the corresponding reaction in this district pipeline section, furnace wall dispersed heat; The heat that flue gas is taken away and to the axial radiations heat energy of adjacent area can get N energy-balance equation thus:

$\left\{\begin{array}{c}{Q}_{s1}+\mathrm{\&sigma;}{A}_0[T_{\mathrm{gm}2}^4-T_{\mathrm{gm}1}^4]-Q_{r1}-\mathrm{\&Delta;}{H}_1-Q_{l1}=0\\ Q_{s2}+\mathrm{\&sigma;}{A}_0[T_{\mathrm{gm}1}^4-T_{\mathrm{gm}2}^4]+\mathrm{\&sigma;}{A}_0[T_{\mathrm{gm}3}^4-T_{\mathrm{gm}2}^4]-Q_{r2}-\mathrm{\&Delta;}{H}_2-Q_{l2}=0\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ Q_{\mathrm{si}}+\mathrm{\&sigma;}{A}_0[T_{\mathrm{gm}(i-1)}^4-T_{\mathrm{gmi}}^4]+\mathrm{\&sigma;}{A}_0[T_{\mathrm{gm}(i+1)}^4-T_{\mathrm{gmi}}^4]-Q_{\mathrm{ri}}-\mathrm{\&Delta;}{H}_i-Q_{\mathrm{li}}=0\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ Q_{s(N-1)}+\mathrm{\&sigma;}{A}_0[T_{\mathrm{gm}(N-2)}^4-T_{\mathrm{gm}(N-1)}^4]+\mathrm{\&sigma;}{A}_0[T_{\mathrm{gm}\left(N\right)}^4-T_{\mathrm{gm}(N-1)}^4]-Q_{r(N-1)}-\mathrm{\&Delta;}{H}_{(N-1)}-Q_{l(N-1)}=0\\ Q_{\mathrm{si}}+\mathrm{\&sigma;}{A}_0[T_{\mathrm{gm}(N-1)}^4-T_{\mathrm{gm}\left(N\right)}^4]-Q_{\mathrm{rN}}-\mathrm{\&Delta;}{H}_N-Q_{\mathrm{lN}}=0\end{array}\right.---\left(3\right)$

Wherein:

Q _Si: i district fuel thermal discharge, W;

A ₀: the vertical radiation useful area in i district, m ²

Δ H _i: the flue gas in turnover i district is taken away net heat, W;

Q _Li: the i district is through the thermal loss of approach such as furnace wall heat radiation, W;

And the total amount of heat balance of whole radiation chamber provides an equation for finding the solution flue-gas temperature:

∑Q _si+∑Q _ri+∑Q _li+∑H _i=0 (4)

First ∑ Q in the formula _SiBe the thermal discharge of the total fuel of radiation chamber (sidewall), second ∑ Q _RiFor reaction tube totally recepts the caloric, the 3rd ∑ Q _LiBe the loss of radiation chamber overall thermal, the 4th ∑ H _iTake away heat for flue gas leaves radiation chamber, formula (3) constitutes the heat balance Nonlinear System of Equations in the radiation chamber with formula (4), and simultaneous solution can obtain the average flue-gas temperature in each district of radiation chamber.

2. be directed against the boiler tube modeling of radiation section:

For ethylene dichloride Pintsch process course of reaction, main reaction is that the ethylene dichloride cracking generates target product vinyl chloride and hydrogen chloride, absorbs the heat of 19kcal simultaneously.

Meanwhile, subsidiary reaction also can take place generate ethene, benzene, butadiene, chlorbutadiene, chloromethanes, propane, carbon, chloropropene etc. in the ethylene dichloride cracking furnace pipe.Subsidiary reaction will cause the productive rate of the reaction product vinyl chloride of needed main reaction to reduce, and influence economic benefit.For ethylene dichloride cracking reaction process, with one-level cascade reaction models treated, wherein by-products content is lower, and is less for the whole rerum natura influence of pyrolysis gas, with the rerum natura approximate substitution of acetylene, as accessory substance:

Wherein make the concentration of ethylene dichloride, vinyl chloride, hydrogen chloride, accessory substance be respectively C respectively ₁, C ₂, C ₃, C ₄, then can set up kinetics equation, as shown in the formula:

$\left\{\begin{array}{c}{r}_1=-\frac{d{c}_1}{\mathrm{dt}}=-k_1{e}^{-\frac{E_1}{\mathrm{RT}}}{C}_1\\ {\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HDA00001750666400011.png"\; state="\{\{state\}\}">r</figure-callout>}}_2=\frac{d{c}_1}{\mathrm{dt}}-\frac{\mathrm{<figure-callout\; id="2"\; label="d\; c"\; filenames="HDA00001750666400011.png"\; state="\{\{state\}\}">d</figure-callout>}{c}_{}{}_2}{\mathrm{dt}}=k_1{e}^{-\frac{E_1}{\mathrm{RT}}}{C}_1-k_2{e}^{-\frac{{\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="HDA00001750666400011.png"\; state="\{\{state\}\}">E</figure-callout>}}_2}{\mathrm{RT}}}{C}_2\\ {\mathrm{<figure-callout\; id="3"\; label="r"\; filenames="HDA00001750666400011.png"\; state="\{\{state\}\}">r</figure-callout>}}_3=\frac{d{c}_1}{\mathrm{dt}}+\frac{d{c}_2}{\mathrm{dt}}=k_1{e}^{-\frac{E_1}{\mathrm{RT}}}{C}_1+k_2{e}^{-\frac{{\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="HDA00001750666400011.png"\; state="\{\{state\}\}">E</figure-callout>}}_2}{\mathrm{RT}}}{C}_2\\ {\mathrm{<figure-callout\; id="4"\; label="r"\; filenames="HDA00001750666400011.png"\; state="\{\{state\}\}">r</figure-callout>}}_4=\frac{d{c}_2}{\mathrm{dt}}=k_2{e}^{-\frac{{\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="HDA00001750666400011.png"\; state="\{\{state\}\}">E</figure-callout>}}_2}{\mathrm{RT}}}{C}_2\end{array}\right.---\left(6\right)$

Wherein, kinetic parameter k ₁, k ₂, E ₁, E ₂Can proofread and correct acquisition through industrial service data, in applicating example of the present invention, k ₁=5.719 * 10 ⁷s ^-1, E ₁=123.9kJ/mol; k ₂=5.607 * 10 ⁷s ^-1, E ₂=137.8kJ/mol, gas constant R=8.314J/ (molK), T are that process is drawn last breath to temperature (K).Based on cracking reaction dynamics, each component changes formula along pipe range infinitesimal section:

$\frac{d{N}_i}{\mathrm{dL}}=\frac{S}{V}{r}_i---\left(7\right)$

N wherein _i: be the mole flow velocity of component i, mol/s;

L: be infinitesimal segment length, m;

S: process gas amasss flow rate, m ³/ s;

r _i: be the reaction rate of component i, mol/s ²

V: process gas amasss flow rate, m ³/ s.

Usually, tube drop calculates and all adopts short-cut method, and a kind of is the straight tube that is converted to the bent tube section in each pipeline equivalent length, all assigns to and does pressure drop calculation in the pipeline; Another kind is that local pressure is considered separately, and the former can't embody the local pressure variation, though the latter has considered local pressure, has ignored process gas self character and has changed the influence to pressure, makes can only descend along the pressure of pipe range.In fact, the process atmospheric pressure changes and process gas mean molecular weight, temperature, and mass flux, tube inner diameter and straight tube are relevant with the bend pipe resistance, with the peaceful equality substitution of model Bernoulli equation, obtain following pressure drop calculation formula:

$\frac{\mathrm{dP}}{\mathrm{dL}}=\frac{{\mathrm{<figure-callout\; id="2"\; label="G"\; filenames="HDA00001750666400011.png"\; state="\{\{state\}\}">G</figure-callout>}}^2\mathrm{<figure-callout\; id="2"\; label="RTP\; G"\; filenames="HDA00001750666400011.png"\; state="\{\{state\}\}">RTP</figure-callout>}}{G^{}}\&CenterDot;(\frac{1}{\mathrm{G\&Omega;}}\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\frac{d{N}_j}{\mathrm{dL}}+\frac{1}{T}\frac{\mathrm{dT}}{\mathrm{dL}}+\frac{1}{G}\frac{\mathrm{dG}}{\mathrm{dL}}+2\&CenterDot;f\&CenterDot;E\left(L\right))---\left(8\right)$

Fanning friction factor wherein, concrete value is following:

f=0.0356+0.264·Re ^-0.42

P: process gas stagnation pressure, kgf/cm ²

G: comprise the mass flux of material in the pipe, kg/ (m ²S);

Ω: infinitesimal section cross-sectional area, m ²

M: process gas mean molecular weight, kg/kmol;

E (L): the equivalent conversion coefficient of reaction tube infinitesimal section L position;

ρ: process air tightness, kg/m ³

D: reaction tube actual circulation internal diameter, m;

Re: Reynold's number;

R: gas constant;

T: process is drawn last breath to temperature;

G: acceleration of gravity;

Four in formula (8) bracket characterize molecular weight, temperature, mass flux (because of confluxing or shunting the mass change that causes; The area change that causes greatly because of the unexpected change of caliber) variation; And the frictional resistance effect of straight length and elbow section, more fully reflected the variation characteristic of process atmospheric pressure.

Infinitesimal section energy delivery has following relation in the reaction tube: heat absorption of reaction tube internal procedure gas lift temperature and the required heat Q of endothermic heat of reaction _p, equal to react the heat Q that tube wall transmits _t, equal the heat Q that interior gas radiation of radiation chamber and smoke convection are passed to the reaction tube outer wall _r, occur in the heat transfer capacity in the reaction tube and concern as shown in Figure 3.

Pipe internal procedure gas lift temperature reaction heat:

$Q_p=\left(\underset{k}{\mathrm{\&Sigma;}}{C}_{\mathrm{pk}}{N}_k\right)\mathrm{dT}+\underset{k}{\mathrm{\&Sigma;}}\left(\mathrm{\&Delta;}{H}_{\mathrm{fk}}^0\right)\frac{d{N}_k}{\mathrm{dL}}---\left(9\right)$

Tube wall conducts heat:

Q _t=KπD _o(T _w(L)-T)·dL (10)

By Q _p=Q _tCan get:

$\frac{\mathrm{dT}}{\mathrm{dL}}=\frac{\mathrm{K\&pi;}{D}_0(\mathrm{Tw}\left(L\right)-T)-\underset{K=1}{\mathrm{\&Sigma;}}\left(\mathrm{\&Delta;}{H}_{\mathrm{fk}}^0\right)\frac{d{N}_k}{\mathrm{dL}}}{\underset{k}{\mathrm{\&Sigma;}}{C}_{\mathrm{pk}}{N}_k}---\left(11\right)$

In the formula:

C _Pk: the isobaric molar heat capacity of k component, J/ (mol.K);

k component is at 288.15K; Standard heat of formation under the 1atm, J/mol;

T _w(L): the tube wall temperature of reaction tube infinitesimal section L position, K;

Consider not have the expression formula of overall heat transfer coefficient K of the cleaning pipe of burnt layer and dirt:

$\frac{1}{K}=\frac{1}{\mathrm{\&alpha;}}\frac{D_o}{D_i}+\frac{{\mathrm{<figure-callout\; id="2"\; label="D\; o"\; filenames="HDA00001750666400011.png"\; state="\{\{state\}\}">D</figure-callout>}}_o}{2{\mathrm{\&lambda;}}_w}\ln \frac{D_o}{D_i}---\left(12\right)$

In the formula:

K: with the external surface area is the overall heat transfer coefficient of benchmark, W/ (m ².K);

D _i, D _o: be respectively how much internal diameters of pipe, how much external diameters, m;

α: reaction tube internal procedure gas convective heat-transfer coefficient, W/ (m ².K);

λ _w: tube wall heat conduction coefficient, W/ (m.K);

Have serious heat coupling between burner hearth and the boiler tube heat, burner hearth offers the heat of boiler tube will want balance with the heat that the boiler tube internal reaction is absorbed on the boiler tube direction.Because burner hearth and boiler tube are modelings respectively, the iterative concrete steps that therefore must be coupled are as shown in Figure 4:

Step 1: set simulated input condition, calculate convergence index and precision: boiler tube import mass flux; The boiler tube inlet temperature, boiler tube intake pressure, fuel gas consumption; Excess air coefficient; Fuel gas load distribution ratio, flue-gas temperature computational accuracy, the computational accuracy of reaction tube outlet temperature and pressure, and suppose inlet pressure and radiation chamber fuel quantity in one group of flue-gas temperature, the pipe;

Step 2: distribution of Yi Ge district flue-gas temperature and inlet pressure are found the solution the reaction tube model as boundary condition, obtain along the heat flux distribution of pipe range direction;

Step 3: will manage the inner model gained and distribute as boundary condition, the Nonlinear System of Equations of heat balance model in the radiation chamber is found the solution calculating, and obtain new flue-gas temperature and distribute along the rate of heat transfer of pipe range direction;

Step 4: the new flue-gas temperature that will calculate and last group of temperature compare, if the unmet accuracy requirement, the new flue-gas temperature that radiation chamber is calculated distributes as boundary condition, changes step 2, as if satisfying accuracy requirement, changes step 5;

Step 5: whether inspection outlet temperature and top hole pressure satisfy the convergence index, if the unmet condition then reappraises fuel quantity and inlet pressure, change step 2, if satisfy condition, calculating stops.

The ethylene dichloride pyrolysis furnace is except coil outlet temperature; Outside the visible index directly perceived such as boiler tube top hole pressure; Also comprise index: the conversion ratio of ethylene dichloride cracking reaction through the ethylene dichloride pyrolysis furnace operating condition of secondary calculating gained; The selectivity of ethylene dichloride cracking reaction, and generate the spent fuel gas consumption of vinyl chloride per ton.

The defined formula of conversion ratio does

Optionally defined formula does

The defined formula of fuel gas unit consumption:

Through an actual industrial device is carried out modelling verification, ethylene dichloride cracking furnace tube outlet temperature during the full load of Model Calculation, the conversion ratio of top hole pressure and ethylene dichloride cracking reaction; Selectivity, the relative error of important indicator such as unit consumption and actual operating mode data comparative simulation value and industry value is respectively: 0.19%, 1.4%; 1.16%; 1.02%, 0.44%, can know that this model reaches the modeling accuracy requirement fully.

Being merely the preferred embodiment of invention in sum, is not to be used for limiting practical range of the present invention.Be that all equivalences of doing according to the content of claim of the present invention change and modification, all should be technological category of the present invention.

Claims (9)

1. commercial plant ethylene dichloride pyrolysis furnace coupling modeling method is characterized in that said method comprises following steps:

Step 1: confirm on-the-spot ethylene dichloride pyrolysis furnace industry service data; Comprise ethylene dichloride feed rate, pressure and temperature, the pyrolysis gas outlet is formed, pressure and temperature, fuel gas feed rate, temperature; Air and fuel gas mass ratio; Ethylene dichloride cracking conversion ratio, ethylene dichloride cracking selectivity, the ethylene dichloride cracking generates the fuel gas quality that vinyl chloride per ton consumes;

Step 2: the modeling of ethylene dichloride pyrolysis furnace comprises reaction boiler tube modeling and burner hearth modeling:

Step 2.1: based on boiler tube internal reaction kinetics equation, boiler tube self-energy and momentum conservation relation are carried out the reaction boiler tube modeling; Utilize the subregion method boiler tube to be carried out subregion and draw pyrolysis gas Temperature Distribution in the pipe by boiler tube straight tube hop count, pipe inside and outside wall Temperature Distribution, pyrolysis gas pressure distribution in managing, pyrolysis gas is formed distribution, pyrolysis gas coil outlet temperature, pressure and composition in the pipe;

Step 2.2: the method that burner hearth utilizes the subregion method to combine with Luo Bo-Yi Wansifa; Based on burner hearth fuel gas firing model, the flow of flue gas heat transfer model, and burner hearth is to boiler tube pipe row's convection heat transfer' heat-transfer by convection and radiant heat transfer model; Through calculating burner hearth heat balance equation; Obtain distributing along furnace height direction flue-gas temperature, burner hearth exhanst gas outlet temperature, burner hearth is to the rate of heat transfer of boiler tube;

Step 3: the heat coupled relation based on burner hearth and boiler tube existence, utilize method of value solving to find the solution:

Step 3.1: initialization boiler tube and burner hearth feed conditions and chamber flue gas temperature distribute;

Step 3.2: utilize quasi-Newton method, iterate boiler tube and burner hearth model satisfy convergence precision up to the chamber flue gas temperature distribution, and iterative process is following:

Step 3.2.1: distribute based on chamber flue gas temperature, calculate the boiler tube model, obtain every boiler tube caloric receptivity and each burner hearth subregion rate of heat transfer to boiler tube;

Step 3.2.2: to furnace tube heat transfer speed, calculate the burner hearth model based on step 3.2.1 gained burner hearth, distribute thereby obtain new boiler tube flue-gas temperature;

Step 3.3: further adjust boiler tube intake pressure and temperature, thus iteration burner hearth boiler tube coupling model again, up to satisfying the model accuracy requirement.

2. according to the commercial plant ethylene dichloride pyrolysis furnace shown in the claim 1 coupling modeling method, it is characterized in that, in the step 2.1 boiler tube internal reaction dynamics adopt ethylene dichloride-vinyl chloride-the tandem reaction mechanism of accessory substance.

3. according to the coupling of the commercial plant ethylene dichloride pyrolysis furnace shown in the claim 1 modeling method; It is characterized in that momentum conservation relation in the boiler tube described in the step 2.1 is for the process atmospheric pressure changes and process gas mean molecular weight; Temperature; Mass flux, tube inner diameter and straight tube are relevant with the bend pipe resistance, and concrete pressure drop calculation formula is following:

$\frac{\mathrm{dP}}{\mathrm{dL}}=\frac{G^2\mathrm{RTP}}{G^2\mathrm{RT}-P^2\mathrm{Mg}}\&CenterDot;(\frac{1}{\mathrm{G\&Omega;}}\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}\frac{d{N}_j}{\mathrm{dL}}+\frac{1}{T}\frac{\mathrm{dT}}{\mathrm{dL}}+\frac{1}{G}\frac{\mathrm{dG}}{\mathrm{dL}}+2\&CenterDot;f\&CenterDot;E\left(L\right))$

Wherein: f is a Fanning friction factor, and P is a process gas stagnation pressure, kgf/cm ²G is the mass flux that comprises material in the pipe, kg/ (m ²S); Ω is an infinitesimal section cross-sectional area, m ²M is a process gas mean molecular weight, kg/kmol; E (L) is the equivalent conversion coefficient of reaction tube infinitesimal section L position; ρ is the process air tightness, kg/m ³D is a reaction tube actual circulation internal diameter, m; Re is a Reynold's number; R is a gas constant; T is that process is drawn last breath to temperature; G is an acceleration of gravity.

4. according to the coupling of the commercial plant ethylene dichloride pyrolysis furnace shown in the claim 1 modeling method, it is characterized in that boiler tube self-energy conservation relation is in the step 2.1: heat absorption of boiler tube internal procedure gas lift temperature and the required heat Q of endothermic heat of reaction _p, equal to react the heat Q that tube wall transmits _t, and equal the heat Q that gas radiation and smoke convection in the radiation chamber are passed to the reaction tube outer wall _r

5. according to the coupling of the commercial plant ethylene dichloride pyrolysis furnace shown in the claim 1 modeling method; It is characterized in that; The burner hearth model adopts the method simulated hearth that one dimension subregion method combines with Luo Bo-Yi Wansifa in the step 2.2, and the said burner hearth heat balance equation that draws is: $Q_{\mathrm{Si}}+\mathrm{\&sigma;}{A}_0[T_{\mathrm{Gm}(i-1)}^4-T_{\mathrm{Gmi}}^4]+\mathrm{\&sigma;}{A}_0[T_{\mathrm{Gm}(i+1)}^4-T_{\mathrm{Gmi}}^4]-Q_{\mathrm{Ri}}-\mathrm{\&Delta;}{H}_i-Q_{\mathrm{Li}}=0,$ Q wherein _SiBe i district fuel thermal discharge; T _GmiBe i district flue gas medial temperature, K; σ is Si Difen-Boltzmann constant; A ₀Be the vertical radiation useful area in i district; Q _RiFor burner hearth i district to furnace tube heat transfer speed; Δ H _iFor the flue gas in turnover i district is taken away net heat; Q _LiBe the thermal loss of i district through approach such as furnace wall heat radiations; I is the partition number along radiation chamber short transverse boiler tube, and span is [1, N].

6. according to the commercial plant ethylene dichloride pyrolysis furnace shown in the claim 1 coupling modeling method, it is characterized in that burner hearth spreads heat and radiant heat transfer model and is in the step 2.2: $Q_{\mathrm{Ri}}=\mathrm{\&sigma;}{a}_D{A}_{\mathrm{Cpi}}{F}_i(T_{\mathrm{Gmi}}^4-T_{\mathrm{Wi}}^4)-h_{\mathrm{Rc}}{A}_{\mathrm{Ri}}(T_{\mathrm{Gmi}}-T_{\mathrm{Wi}}),$ Wherein: Q _RiFor burner hearth i district to furnace tube heat transfer speed; a _DBe pipe row angle factor; σ is Si Difen-Boltzmann constant, W/m ².K ⁴A _CpiBe i district cold-smoothing area; F _iBe i district built-up radiation exchange factor; T _GmiBe i district flue gas medial temperature, K; T _WiBe i district pipe outer wall medial temperature; h _RcBe convective heat-transfer coefficient; A _RiBe i district reaction tube external surface area, i is the partition number along radiation chamber short transverse boiler tube, and span is [1, N].

7. commercial plant ethylene dichloride pyrolysis furnace coupling modeling method according to claim 1; It is characterized in that; Said step 3.2 adopts the plan Newton iteration method that burner hearth and boiler tube are carried out the heat The Coupling: the variable that transmits each other in boiler tube and the stove model is that burner hearth is respectively distinguished flue-gas temperature to the rate of heat transfer and the burner hearth of boiler tube, wherein respectively distinguishes flue-gas temperature and calculates iterative formula T _Gmi(k+1)=(T _Gmi(k)+T _Gmi(new))/2, T _GmiBe i district chamber flue gas temperature, i is the subregion along radiation chamber short transverse boiler tube, and span is [1, N].

8. the application of commercial plant ethylene dichloride pyrolysis furnace according to claim 1 coupling modeling method is characterized in that, also comprises step 4: the model that obtains based on step 3 is input with the real-time parameter numerical value of actual device, calculates and obtains all the other parameters.

9. the application of commercial plant ethylene dichloride pyrolysis furnace coupling modeling method according to claim 8 is characterized in that input parameter is: boiler tube burner hearth physical dimension; The boiler tube intake pressure, boiler tube inlet temperature, boiler tube import mass flux; The fuel gas consumption; Excess air coefficient, fuel gas load distribution ratio, and convergence precision index; Output parameter is: the conversion ratio of coil outlet temperature or boiler tube top hole pressure or ethylene dichloride cracking reaction.

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