CN103455684A - Real-time performance prediction method for industrial steam cracking furnace hearth based on field method - Google Patents

Abstract

The invention relates to a real-time performance prediction method for an industrial steam cracking furnace hearth based on a field method. A hearth radiation model is to adopt a HOTTEL field method to compute the radiation heat transfer rate between areas. A smoke flow model is to compute mass flow rates of a hot area, a cold area and a horizontal surface according to computation results of CFD (computational fluid dynamics). The bottom fuel gas heat-release rate of a fuel gas combustion model is determined by fuel gas consumption rate of each area along the hearth height via CFD computation. The side wall fuel gas heat-release rate is uniformly distributed according to the difference between the height of the area and the height of a nozzle around the side wall nozzle. Therefore, the heat balance equation of each area is established; the nonlinear equation set is performed with iterative computation by a quasi-Newton method until the convergence precision is met; at last, the real-time performance prediction for temperature of smoke and furnace wall of each area and heat flux of each furnace tube in the cracking furnace hearth is carried out, so that reliable model basis and theory supporting are provided for design and operation optimization of the cracking furnace.

Description

Industrial steam pyrolysis furnace burner hearth real-time performance Forecasting Methodology based on field method

Technical field

The present invention relates to a kind of industrial steam pyrolysis furnace burner hearth real-time performance Forecasting Methodology based on field method, the model that utilizes the method to set up can be used for design and the optimization of operating condition of hydrocarbons steam cracking furnace.

Background technology

Ethylene industry is tap and the core of petro chemical industry.The core of ethylene producing device is pyrolysis furnace, and design and the operation of whole ethylene unit benefit and pyrolysis furnace have direct relation.Radiation section is the main positions that cracking reaction occurs, it is also most important part in pyrolysis furnace, the geometry of existing pyrolysis furnace radiation section is huger, and the heat absorptivity due to cracking reaction, need a large amount of fuel combustion heat supplies, therefore the fuel gas of larger flow sprays into burner hearth by burner in the high-speed jet mode, and the mobile of the flue gas in burner hearth made a significant impact, thereby further affect mixing and the combustion process of fuel gas, change the Temperature Distribution in burner hearth.Flue gas is passed to the cracking stock in reaction tube by heat simultaneously, makes it complicated course of reaction occurs, and vice versa.So, along the heat flux distribution of boiler tube length direction, be the tie of contact oil gas and fume side.Due to the restriction that is subject to long period, expensive and limited measurement means, to the experimental study of heat flux distribution, be extremely difficult.Therefore, numerical evaluation is to optimize and design an effective tool of pyrolysis furnace.

The application of Fluid Mechanics Computation (Computational Fluid Dynamics is called for short CFD) technology in the pyrolysis furnace simulation had significant progress, and some has also tentatively carried out commercial Application.But say on the whole, the CFD simulation of pyrolysis furnace also has a segment distance from commercial Application, because itself also having some difficult problems, fail to solve.As: the calculated amount of CFD simulation is large, and computing time is long; Combustion model and part turbulence model are perfect not to the utmost, also need basic theory such as application burning etc. to solve; The industrial pyrolysis furnace actual conditions are very complicated, and influence factor is various, and trickle deviation all can cause calculate occurring very large deviation or not restrain etc.Therefore, in order to make the pyrolysis furnace numerical simulation, in the industrial ethylene pyrolysis furnace, be applied, for the operation optimization of pyrolysis furnace provides guidance, solve in the urgent need to the method for seeking to be more suitable for the industrial operation scene.

Field method (Zone method) is that Huo Teer (H.C.Hottel) proposes in 1954, radiant heat transfer for the tubular furnace burner hearth calculates, because its computing velocity is fast, computational accuracy is high, become now one of most popular method in the Practical Project problem.External ethene business software for example all be take field method, basically as basis, Spyro software.In twenties years of past, there have been many scholars to use field method to do research to the industrial steam pyrolysis furnace.But, during their radiant heat transfer process in calculating burner hearth, fuel combustion process is not simulated, but utilize the rate of heat release of fuel to estimate composition and the temperature of flue gas, but also ignored burning and the impact of flow of flue gas process on conducting heat.The people such as Detemmerman and Froment and Heynderickx for the first time deployment area method and CFD method in conjunction with the radiant heat transfer in pyrolysis furnace is carried out to coupled simulation.H.Barths uses CFD method and zero dimension multizone method coupled simulation Homogeneous Charge Compression Ignition (HCCI) burning.Therefore yet their research need to be used flow model or the combustion model of CFD calculation of complex, computing velocity also can be and slack-off, is not suitable for the actual application of industry.

Summary of the invention

In order to overcome above deficiency, the present invention intends utilizing the method for HOTTEL field method and CFD associating modeling, foundation meets the mathematical model of burner hearth flue gas actual flow, combustion case, and then set up burner hearth field method model, solve that the burner hearth model can obtain that pyrolysis furnace burner hearth Nei Ge district's flue gas and temperature of furnace wall distribute, boiler tube heat flux distribution and flue gas mass rate, flue gas viscosity, coefficient of heat conductivity and the isoparametric distribution of Reynolds number, thereby for the design of industrial pyrolysis furnace and operation optimization provide reliable model according to and theory support.And a kind of industrial steam pyrolysis furnace burner hearth real-time performance Forecasting Methodology based on field method is provided, and this model can be used in design and the optimization of operating condition of pyrolysis furnace, and this model has following characteristics:

1. there is comparatively perfect three-dimensional Radiative heat transfer in furnace model, can comparatively accurately calculate burner hearth Nei Ge district's flue gas and temperature of furnace wall distribution, boiler tube heat flux distribution.

2. consider the impact on conducting heat of flow of flue gas and combustion process, set up the flow model and the combustion model that meet burner hearth flue gas actual flow and combustion case.

According to above characteristics, adopt the method for HOTTEL field method and CFD associating modeling, set up radiation heat-transfer model, flow of flue gas model, fuel gas combustion model and the smoke convection heat transfer model of burner hearth.Set up thus each district's heat balance equation, use quasi-Newton method iterative computation Nonlinear System of Equations, until meet convergence precision.

Particularly, should the industrial steam pyrolysis furnace burner hearth real-time performance Forecasting Methodology based on field method comprise the following steps:

Step 1: determine industrial hydrocarbons steam cracking furnace burner hearth geometry and technological parameter.

Step 2: by burner hearth according to length and width and short transverse zoning.Consider the Radiative heat transfer in furnace model, the flow of flue gas model, fuel gas combustion model, and smoke convection heat transfer model, thus set up each regional energy equilibrium formula.

Step 3: utilize quasi-Newton method iterative computation burner hearth self-energy balance Nonlinear System of Equations, until meet convergence precision, obtain key parameter and the physical parameter distributions such as pyrolysis furnace burner hearth Nei Ge district's flue gas and temperature of furnace wall, boiler tube thermoflux, flue gas mass rate, flue gas viscosity, coefficient of heat conductivity and Reynolds number.

Preferably, described burner hearth geometry comprises the length of burner hearth, the physical dimension of burner and number, the physical dimension of boiler tube and arrangement form etc.; Technological parameter comprises bottom and sidewall fuel gas composition and feed rate, temperature, pressure, excess air coefficient, side/end fuel gas and compares etc.;

Preferably, the subregion of described burner hearth length direction is divided according to boiler tube group number; Subregion on Width is divided according to hot-zone (zone of burner top) and cold-zone (zone of nearly boiler tube); Subregion on short transverse can be divided arbitrarily.Zone is divided more, and result of calculation is more accurate, but amount of calculation is also just larger.

Preferably, described Radiative heat transfer in furnace model is to obtain interborough Direct Exchange Areas according to the HOTTEL field method, total transfer area and oriented flow area, and then try to achieve interborough radiant heat transfer speed.

Preferably, described flow of flue gas model is according to CFD result of calculation output hot-zone surface quality flow, according to its cold-zone of mass balance calculation and lateral surfaces mass rate.

Preferably, the bottom fuel gas rate of heat release of described fuel gas combustion model is that the consumption rate of the fuel gas along each district of furnace height of calculating according to CFD is determined.Sidewall fuel gas rate of heat release is uniformly distributed according to the height at regional place and the difference in height at burner place near burner on sidewall.

Preferably, described smoke convection heat transfer model is according to flue gas, heat transfer coefficient, flue gas and the tube wall temperature difference, the convection heat transfer area of tube wall and furnace wall to be tried to achieve.

Preferably, describedly utilize quasi-Newton method iterative computation burner hearth self-energy balance Nonlinear System of Equations, until the flue gas in each district of burner hearth, temperature of furnace wall distributes and the boiler tube heat flux distribution meets convergence precision, output result of calculation.Recalculate otherwise adjust tube wall temperature, iterate until reach precision.

The invention provides a kind of industrial steam pyrolysis furnace burner hearth real-time performance Forecasting Methodology based on field method.The method that the method adopts burner hearth HOTTEL field method and CFD analog result to combine in modeling, utilize heat balance equation solution burner hearth flue gas, temperature of furnace wall to distribute and boiler tube heat flux distribution situation.This modeling method is applicable to all types of industries hydrocarbons steam cracking furnace, and adaptability is widely arranged.

The accompanying drawing explanation

Fig. 1-1～Fig. 1-2 is that schematic diagram is divided in chamber structure and zone;

Fig. 1-1 is pyrolysis furnace burner hearth 3-D view;

Fig. 1-2 is that schematic diagram is divided in the burner hearth zone;

Fig. 2 is flow of flue gas schematic diagram in burner hearth;

Fig. 3 is the field method solution procedure.

Embodiment

Below in conjunction with drawings and Examples, the present invention is further described.

The burner hearth zone is divided as shown in Figure 1.The length direction number of partitions is boiler tube group number; The Width number of partitions is 2, is respectively hot-zone (zone of burner top) and cold-zone (zone of nearly boiler tube); The short transverse number of partitions can be selected arbitrarily.

(1) radiation heat-transfer model (HOTTEL field method)

1. calculate smoke components, absorption coefficient

The calculating of burning of the composition of based on fuel gas and air and number percent and coefficient of excess air, draw smoke components and exhaust gas volumn; Obtaining on the basis of smoke components, calculated the average stroke length of heat ray by the size of radiation chamber, then estimating a flue gas medial temperature, calculating the absorption coefficient of flue gas.Calculate the absorption coefficient formula referring to formula (20).

2. calculate Direct Exchange Areas

Ash gas abrim in supposing the system, surface is black surface, not reflection, not reflected radiation energy, the net radiation heat exchange between any two black surfaces, only have by the mode of direct radiation and carry out heat exchange.Like this, when having ash gas to exist, the exchange area between two black surfaces is called Direct Exchange Areas.

A. the Direct Exchange Areas between two parallel surfaces:

${\stackrel{\‾}{s_{i}s}}_j=\frac{1}{\mathrm{\π}}\underset{x_i}{\∫}\underset{y_i}{\∫}\underset{x_j}{\∫}\underset{y_j}{\∫}\frac{{\mathrm{\Δz}}^2}{r^4}{e}^{-\mathrm{Kr}}{\mathrm{dy}}_j{\mathrm{dx}}_j{\mathrm{dy}}_i{\mathrm{dx}}_i---\left(1\right)$

B. the Direct Exchange Areas between two vertical surface

${\stackrel{\‾}{s_{i}s}}_j=\frac{1}{\mathrm{\π}}\underset{x_i}{\∫}\underset{y_i}{\∫}\underset{y_j}{\∫}\underset{z_j}{\∫}\frac{\mathrm{\Δx}\·\mathrm{\Δz}}{r^4}{e}^{-\mathrm{Kr}}{\mathrm{dz}}_j{\mathrm{dy}}_j{\mathrm{dy}}_i{\mathrm{dx}}_i---\left(2\right)$

C. gas and surperficial Direct Exchange Areas

${\stackrel{\‾}{g_{i}s}}_j=\frac{K}{\mathrm{\π}}\underset{x_i}{\∫}\underset{y_i}{\∫}\underset{z_i}{\∫}\underset{y_j}{\∫}\underset{z_j}{\∫}\frac{\mathrm{\Δx}}{r^3}{e}^{-\mathrm{Kr}}{\mathrm{dz}}_j{\mathrm{dy}}_j{\mathrm{dz}}_i{\mathrm{dy}}_i{\mathrm{dx}}_i---\left(3\right)$

D. the Direct Exchange Areas of gas and gas

${\stackrel{\‾}{g_{i}g}}_j=\frac{K^2}{\mathrm{\π}}\underset{x_i}{\∫}\underset{y_i}{\∫}\underset{z_i}{\∫}\underset{x_j}{\∫}\underset{y_j}{\∫}\underset{z_j}{\∫}\frac{1}{r^2}{e}^{-\mathrm{Kr}}{\mathrm{dz}}_j{\mathrm{dy}}_j{\mathrm{dx}}_j{\mathrm{dz}}_i{\mathrm{dy}}_i{\mathrm{dx}}_i---\left(4\right)$

3. calculate total transfer area

In engineering calculation, the tube-surface of tubular heater, refractory wall all can be regarded as from the gray surface of Lambert law, are called for short grey body.When radiation energy is mapped to this surface, a part absorbs, and a part reflects, and has considered the exchange area of this character of surface, is called total transfer area.Take into account surface reflection and make used time surface region S _ibiography is to surface region S _jradiant heat flux be defined as:

$Q_{s_i{s}_j}=\stackrel{\‾}{S_i{S}_j}{{\mathrm{\σT}}_{s_i}}^4---\left(5\right)$

Have equally

$Q_{g_i{s}_j}=\stackrel{\‾}{G_i{S}_j}{{\mathrm{\σT}}_{g_i}}^4---\left(6\right)$

$Q_{g_i{g}_j}=\stackrel{\‾}{G_i{G}_j}{{\mathrm{\σT}}_{g_i}}^4---\left(7\right)$

As surface region S _jduring for thermal source, reverberation flow Q _rfor

As gas zone G _iduring for thermal source, have

The reflectivity of supposing surface region is ρ, and absorptivity is α, and blackness is ε.:

A. gas zone is thermal source

Suppose G in system _ifor unique thermal source, to all surface district wherein, comprise refractory wall district S ₁, S ₂, S ₃make the radiation heat balance.As follows by matrix representation:

Separate top system of linear equations, can draw

substitution formula (11), draw the total transfer area between gas zone and surface region; Total transfer area between gas zone and gas zone is shown below:

B. surface region is thermal source

Suppose arbitrary surface region S in system _ifor thermal source, all surface district is made to the radiation heat balance, the corresponding equation of each surface region, as follows by matrix representation:

Separate top system of linear equations, can draw

substitution formula (10) draws the total transfer area of surface region and surface region.

4. calculate the oriented flow area

In formula in front, all suppose that burner hearth is the system that the grey body wall is full of grey gas, and actual flue gas and grey gas different in kind.Contain under fire box temperature the also monatomic and diatomic gas of electromagnetic wave absorption not of non-radiating in flue gas system, also have radiation and absorption to there is optionally water and carbon dioxide.From equivalent angle, flue gas can invent the grey gas different by several absorption coefficients and a transmission gas is formed.So the blackness of real gas is

${\mathrm{\ϵ}}_g=\underset{n=0}{\overset{n}{\mathrm{\Σ}}}{a}_{g,n}\left(T_g\right)[1-\exp (-k_n\mathrm{pL})]---\left(15\right)$

In formula, $\underset{n=0}{\overset{n}{\mathrm{\Σ}}}{a}_{g,n}\left(T_g\right)=1.$

In the engineering application, the blackness of real gas can be similar to an ash gas and a transparent gas, and now, (15) formula can be reduced to:

ε _g=a _g,1[1-exp(-k ₁pL)] (16)

When the ray stroke is L and 2L,

ε _g,L=a _g,L[1-exp(-k ₁pL)] (17)

ε _g,2L=a _g,l[1-exp(-2k ₁pL)] (18)

Above-mentioned two formulas of simultaneous solution, have

$a_{g,1}=\frac{{\mathrm{\ϵ}}_{g,L}^2}{2{\mathrm{\ϵ}}_{g,L}-{\mathrm{\ϵ}}_{g,2L}}---\left(19\right)$

$k_{1}p=-\frac{1}{L}1n(1-\frac{{\mathrm{\ϵ}}_{g,L}}{a_{g,1}})---\left(20\right)$

Calculate thus the oriented flow area as follows:

$\stackrel{\→}{S_i{S}_j}=a_{g,1}{\left(\stackrel{\‾}{S_i{S}_j}\right)}_{k_1}+(1-a_{g,1}){\left(\stackrel{\‾}{S_i{S}_j}\right)}_{k=0}---\left(21\right)$

$\stackrel{\→}{S_i{G}_j}=a_{g,1}{\left(\stackrel{\‾}{S_i{G}_j}\right)}_{k_1}---\left(22\right)$

$\stackrel{\→}{G_i{S}_j}=a_{g,1}{\left(\stackrel{\‾}{G_i{S}_j}\right)}_{k_1}---\left(23\right)$

$\stackrel{\→}{G_i{G}_j}=a_{g,1}{\left(\stackrel{\‾}{G_i{G}_j}\right)}_{k_1}---\left(24\right)$

(2) flow of flue gas model

When calculating the energy equilibrium in each district, need to calculate the enthalpy difference that flue gas passes in and out this district, and the function of the mass rate on surface, this enthalpy difference Shi Gai district.Export according to CFD result of calculation along the mass rate of furnace height on each surface, district, burner hearth hot-zone.Cold-zone and lateral surfaces are tried to achieve according to the mass conservation in this district along the mass rate of furnace height.Be illustrated in figure 2 flow of flue gas schematic diagram in burner hearth.

(3) fuel gas combustion model

The burning of burner hearth fuel gas has been transformed into flue gas, and the fuel gas consumption rate equals the flue gas number percent produced, namely liberated heat number percent.Bottom fuel gas is that the fuel gas consumption rate of calculating according to CFD is determined at the thermal release number percent of each furnace height, 100% the highest flame location of thermal release height correspondence.Sidewall fuel gas rate of heat release is uniformly distributed according to the height at regional place and the difference in height at burner place near burner on sidewall.

(4) smoke convection heat transfer model

Smoke convection heat transfer coefficient calculating formula is as follows:

$h_i=0.33\frac{k_f}{d_{\mathrm{out}}}{\mathrm{Re}}^{0.6}{\mathrm{Pr}}^{0.3}---\left(25\right)$

Flue gas is tube outer surface to the convection heat transfer face of boiler tube, and the radiant heat transfer face has been converted into pipe row plane, for the unification on calculating, also needs to take advantage of a coefficient when tube-surface is converted into to corresponding pipe row plane.

Flue gas to the convection heat transfer' heat-transfer by convection amount on boiler tube surface is:

$q_{c{s}_i}=h_i\·A_{s_i}\·\frac{\mathrm{\π}\·d_{\mathrm{out}}}{\mathrm{\α}\·S_t}\·(T_{g_i}-T_{s_i})---\left(27\right)$

Flue gas to the convection heat transfer' heat-transfer by convection amount on furnace wall surface is:

$q_{c{w}_i}=h_i\·A_{w_i}\·(T_{g_i}-T_{w_i})---\left(28\right)$

(5) set up each district's heat balance equation

The furnace wall district

$\underset{j}{\mathrm{\Σ}}\stackrel{\→}{S_j{S}_i}\mathrm{\σ}{T}_{s_j}^4+\underset{j}{\mathrm{\Σ}}\stackrel{\→}{G_j{S}_i}\mathrm{\σ}{T}_{g_j}^4-A_{s_i}{\mathrm{\ϵ}}_{s_i}\mathrm{\σ}{T}_{s_i}^4+h_i{A}_{s_i}(T_{g_i}-T_{s_i})-Q_{\mathrm{loss}}=0---\left(29\right)$

The boiler tube district

$\frac{1}{n}(\underset{j}{\mathrm{\Σ}}\stackrel{\→}{S_j{S}_i}\mathrm{\σ}{T}_{s_j}^4+\underset{j}{\mathrm{\Σ}}\stackrel{\→}{G_j{S}_i}\mathrm{\σ}{T}_{g_j}^4)-A_{s_i}{\mathrm{\ϵ}}_{s_i}\mathrm{\σ}{T}_{s_i}^4+h_i{A}_{s_i}(T_{g_i}-T_{s_i})-Q_{\mathrm{rec}}=0---\left(30\right)$

The flue gas district

$\underset{j}{\mathrm{\Σ}}\stackrel{\→}{S_j{S}_i}\mathrm{\σ}{T}_{s_j}^4+\underset{j}{\mathrm{\Σ}}\stackrel{\→}{G_j{S}_i}\mathrm{\σ}{T}_{g_j}^4-4K{V}_{g_i}{a}_g\left(T_{g_i}\right)\mathrm{\σ}{T}_{g_i}^4-h_i{A}_{s_i}(T_{g_i}-T_{s_i})+Q_{\mathrm{com}}-\mathrm{\Δ}{H}_i=0---\left(31\right)$

3. field method calculation procedure

Pyrolysis furnace burner hearth field method solution procedure as shown in Figure 3.

(1) divide zoning according to the structure of burner hearth;

(2) rule of thumb or industrial data initialization tube wall temperature;

(3) composition of based on fuel gas and air and number percent and the coefficient of excess air calculating of burning, draw smoke components;

(4) obtaining on the basis of smoke components, calculated the average stroke length of heat ray by the size of radiation chamber, then estimating a flue gas medial temperature, calculating the absorption coefficient of flue gas;

(5) on the basis of zoning and absorption coefficient, according to Gaussian processes, ask definite integral, obtain interborough Direct Exchange Areas;

(6) by the Direct Exchange Areas solve linear equations, calculate total transfer area;

(7) calculate the power of virtual grey gas component, directly ask the oriented flow area;

(8) set up flow of flue gas model, the combustion model of burner hearth, set up the heat balance equation in each district;

(9) utilize quasi-Newton method solution Nonlinear System of Equations according to the furnace tube outer wall Temperature Distribution of hypothesis, until the flue gas in each district of burner hearth, temperature of furnace wall distribution and boiler tube heat flux distribution meet convergence precision, output result of calculation.Recalculate otherwise adjust tube wall temperature, iterate until reach precision.

Model based on above foundation, can calculate each amount of corresponding output according to real-time input quantity.

Only for the preferred embodiment of invention, not be used for limiting practical range of the present invention in sum.Be that all equivalences of doing according to the content of the present patent application the scope of the claims change and modify, all should be technology category of the present invention.

Symbol table

Xi Wen

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Claims (7)

1. the industrial steam pyrolysis furnace burner hearth real-time performance Forecasting Methodology based on field method, is characterized in that,

Step 1: determine industrial hydrocarbons steam cracking furnace burner hearth geometry and technological parameter.

Step 2: by burner hearth according to length and width and short transverse zoning, based on the Radiative heat transfer in furnace model, the flow of flue gas model, fuel gas combustion model, and smoke convection heat transfer model, set up each regional energy equilibrium formula.

Step 3: utilize quasi-Newton method iterative computation burner hearth self-energy balance Nonlinear System of Equations, until meet convergence precision, obtain the parameter distribution of pyrolysis furnace burner hearth Nei Ge district's flue gas and temperature of furnace wall, boiler tube thermoflux, flue gas mass rate, flue gas viscosity, coefficient of heat conductivity and Reynolds number.

2. Forecasting Methodology according to claim 1, is characterized in that, described burner hearth geometry comprises the length of burner hearth, the physical dimension of burner and number, the physical dimension of boiler tube and arrangement form; Technological parameter comprises bottom and sidewall fuel gas composition and feed rate, temperature, pressure, excess air coefficient, side/end fuel gas ratio.

3. Forecasting Methodology according to claim 1, is characterized in that, the subregion of described burner hearth length direction is divided according to boiler tube group number; Subregion on Width is divided according to the distance of distance burner; Subregion on short transverse can be divided arbitrarily.Forecasting Methodology according to claim 1, it is characterized in that, described Radiative heat transfer in furnace model is to obtain interborough Direct Exchange Areas according to the HOTTEL field method, total transfer area and oriented flow area, and then try to achieve interborough radiant heat transfer speed.

4. Forecasting Methodology according to claim 1, is characterized in that, described flow of flue gas model is according to Fluid Mechanics Computation result of calculation output hot-zone surface quality flow, according to its cold-zone of mass balance calculation and lateral surfaces mass rate.

5. Forecasting Methodology according to claim 1, it is characterized in that, the bottom fuel gas rate of heat release of described fuel gas combustion model is that the consumption rate of the fuel gas along each district of furnace height of calculating according to Fluid Mechanics Computation is determined, sidewall fuel gas rate of heat release is uniformly distributed according to the height at regional place and the difference in height at burner place near burner on sidewall.

6. Forecasting Methodology according to claim 1, is characterized in that, described smoke convection heat transfer model is according to flue gas, heat transfer coefficient, flue gas and the tube wall temperature difference, the convection heat transfer area of tube wall and furnace wall to be tried to achieve.

7. Forecasting Methodology according to claim 1, is characterized in that, also further comprising the steps, when described step 3 can't restrain, reaches default precision, adjusts tube wall temperature and re-execute step 3, iterates until reach precision.

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