CN106446436A - Simulation method and device for utility boiler coal dust combustion characteristic under combination of variable coal mill - Google Patents

Abstract

The invention discloses a simulation method and device for utility boiler coal dust combustion characteristic under combination of variable coal mill, which achieves the technical problem that because the furnace size becomes bigger and bigger and the test-bed for manufacturing full scale model has been unrealistic, the entire regular characteristics of burning, flowing and heating in the furnace cannot be measured. The simulation method includes: through a base conservation equation, a turbulence flow model, a turbulent gas-solid two-phase flow model, a gas phase turbulent combustion model, a pulverized coal particle combustion model, a radiative heat transfer model and a NOX building model, the combustion process of the boiler coal dust placed in an after meshing preset boiler burner model under the condition of combination of variable coal mill is simulated; according to the result of simulating under the condition of combination of variable coal mill, the coal burnout rate of the boiler burner, the fly ash carbon content, the NOX emissions and the Lower furnace exit temperature are determined.

Description

Power boiler breeze combustion characteristics analogy method and device under coal pulverizer combination is become

Technical field

The present invention relates to the burning under coal pulverizer combination is become of technical field of electric power, more particularly to a kind of power boiler breeze is special Property analogy method and device.

Background technology

Power boiler breeze burning is the three dimensional process of a complicated turbulent flow, heat transfer and burning.Due to process Complexity and the polytropy of coal-fired boiler fuel, so far, the design to boiler and operation lack ripe theory and warp Test, generally require coldandtest come determine operation and design parameter because test have directly perceived, reliable, can To be used directly to instruct the design of boiler product to produce and manufacture.But Power Plant in China is to high parameter, great Rong at present Develop in terms of amount, size of burner hearth is increasing, and this kind of test period is long, costly, and hardly result in comprehensive, satisfied number According to.The testing stand of manufacture full scale model is unrealistic, directly carries out air to the heavy duty boiler of live actual motion and moves The measurement in the field of force, and burning, flowing, heat transfer global regularity characteristic in stove are measured and be nearly impossible, so, lead to Overtesting instructs boiler design to there is significant limitation.

Therefore, how above-mentioned refer to due to size of burner hearth increasing, the testing stand for manufacturing full scale model is not cut Actual, the technical problem that burning, flowing, heat transfer global regularity characteristic in stove cannot be measured for being caused has become this Skilled person's technical problem urgently to be resolved hurrily.

Content of the invention

Embodiments provide a kind of power boiler breeze become coal pulverizer combination under combustion characteristics analogy method and Device, wherein, power boiler breeze combustion characteristics generates the analogy method of numerical value to be included：Preset boiler-burner model is carried out Multiblock technique is divided；By basal conservation eqution, turbulent flow model, gas-particle two-phase flow movable model, gas phase turbulance burning Model, pulverized coal particle combustion model, radiative heat transfer model and NO_XGeneration model is to the preset boiler-burner mould after stress and strain model Combustion process of the boiler coal-ash in type under coal pulverizer combination condition is become is simulated；According under change coal pulverizer combination condition The result of simulation determines the coal dust burn-off rate of boiler-burner, unburned carbon in flue dust, NO_XDischarge capacity, lower hearth outlet temperature and.This In embodiment, by carrying out multiblock technique division to preset boiler-burner model；By basal conservation eqution, turbulent flow dynamic model Type, gas-particle two-phase flow movable model, gas phase turbulance combustion model, pulverized coal particle combustion model, radiative heat transfer model and NO_XRaw Model is become to become the burning under coal pulverizer combination condition to the boiler coal-ash in the preset boiler-burner model after stress and strain model Process simulation；Determine the coal dust burn-off rate of boiler-burner, fly according to the result in change coal pulverizer combination condition Imitating Grey phosphorus content, NO_XDischarge capacity, lower hearth outlet temperature and, solve at present as size of burner hearth is increasing, manufacture full-scale The testing stand of model is unrealistic, and caused cannot measure to burning, flowing, heat transfer global regularity characteristic in stove Technical problem.

Description of the drawings

In order to be illustrated more clearly that the embodiment of the present invention or technical scheme of the prior art, below will be to embodiment or existing Accompanying drawing to be used needed for technology description is had to be briefly described, it should be apparent that, drawings in the following description are only this Some embodiments of invention, for those of ordinary skill in the art, without having to pay creative labor, may be used also To obtain other accompanying drawings according to these accompanying drawings.

Fig. 1 is a kind of power boiler breeze provided in an embodiment of the present invention combustion characteristics simulation side under coal pulverizer combination is become The schematic flow sheet of one embodiment of method；

Fig. 2 is a kind of power boiler breeze provided in an embodiment of the present invention combustion characteristics simulation dress under coal pulverizer combination is become The structural representation of the one embodiment that puts；

Fig. 3 (a) to (c) is chamber structure and stress and strain model schematic diagram；

Fig. 4 is to become the coal combustion rate under coal pulverizer combination；

Fig. 5 is to become the unburned carbon in flue dust under coal pulverizer combination；

Fig. 6 is to become the NO under coal pulverizer combination_XExhaust air rate；

Fig. 7 is to become the lower hearth outlet temperature under coal pulverizer combination.

Specific embodiment

Embodiments provide a kind of power boiler breeze become coal pulverizer combination under combustion characteristics analogy method and Device, solves at present as size of burner hearth is increasing, and the testing stand of manufacture full scale model is unrealistic, is caused The technical problem that burning, flowing, heat transfer global regularity characteristic in stove cannot be measured.

CFD, software (Computational Fluid Dynamics), i.e., computational fluid dynamicses, are hydromechanical One branch, abbreviation CFD.CFD is modern age hydrodynamics, the product that numerical mathematics and computer science are combined, and is one and has The boundary science of powerful vitality.It applies the mathematical method of various discretizations, Fluid Mechanics with electronic computer as instrument All kinds of problems carry out numerical experiment, computer mould and fit analysis and research, to solve various practical problems.

For enabling the goal of the invention of the present invention, feature, advantage more obvious and understandable, below in conjunction with the present invention Accompanying drawing in embodiment, is clearly and completely described to the technical scheme in the embodiment of the present invention, it is clear that disclosed below Embodiment be only a part of embodiment of the present invention, and not all embodiment.Based on the embodiment in the present invention, this area All other embodiment that those of ordinary skill is obtained under the premise of creative work is not made, belongs to present invention protection Scope.

Fig. 1 is referred to, a kind of power boiler breeze provided in an embodiment of the present invention combustion characteristics under coal pulverizer combination is become One embodiment of analogy method includes：

101st, multiblock technique division is carried out to preset boiler-burner model；

With the development of the subject such as computer technology and Fluid Mechanics Computation, numerical heat transfer, calculating Combustion, calculate Machine analogue technique is developed rapidly.Numerical simulation based on CFD is increasingly becoming the research of various countries' field of energy source power Persons are for studying the important means of boiler boiler flow field.Method for numerical simulation speed is fast, containing much information for acquisition, can be complete and pre- Flowing, heat transfer and combustion process in report stove, is that design, operation and the transformation of boiler provides important reference frame, with weight The engineering application value that wants.Thus, calculated by the full simulation value of boiler flow field, the aerodynamic field in analytical furnace, temperature , come to NO in combustion process_XGeneration give a forecast the research meanses for becoming feasible, it is necessary first to preset boiler-burner Model carries out multiblock technique division.

102nd, by basal conservation eqution, turbulent flow model, gas-particle two-phase flow movable model, gas phase turbulance burning mould Type, pulverized coal particle combustion model, radiative heat transfer model and NO_XGeneration model is to the described preset boiler-burner after stress and strain model Combustion process of the boiler coal-ash in model under coal pulverizer combination condition is become is simulated；

After multiblock technique division is carried out to preset boiler-burner model, need by basal conservation eqution, turbulent flow Flow model, gas-particle two-phase flow movable model, gas phase turbulance combustion model, pulverized coal particle combustion model, radiative heat transfer model And NO_XGeneration model is becoming under coal pulverizer combination condition to the boiler coal-ash in the preset boiler-burner model after stress and strain model Combustion process be simulated.

103rd, according to become coal pulverizer combination condition Imitating result determine the boiler-burner coal dust burn-off rate, Unburned carbon in flue dust, NO_XDischarge capacity, lower hearth outlet temperature.

When by basal conservation eqution, turbulent flow model, gas-particle two-phase flow movable model, gas phase turbulance burning mould Type, pulverized coal particle combustion model, radiative heat transfer model and NO_XGeneration model is to the preset boiler-burner model after stress and strain model In boiler coal-ash combustion process be simulated after, need according to become coal pulverizer combination condition Imitating result determine The coal dust burn-off rate of the boiler-burner, unburned carbon in flue dust, NO_XDischarge capacity, lower hearth outlet temperature.

It should be noted that the above becomes coal pulverizer combination condition refers to that after-flame air quantity is respectively 530,630 and 730t/ In the state of h, and also include after carrying out multiblock technique division to preset boiler-burner model：

Preset boiler-burner model after stress and strain model is simplified, and gets the design parameter after arranging and work Condition condition.

Turbulent flow model is Realizable k- ε two-equation model；

Wherein, k equation is

ε equation is

Gk represents that the Turbulent Kinetic for being caused due to average velocity gradient is produced, and Gb is moved for the turbulent flow that buoyancy effect causes Can produce, YM represents the impact that the expansion of fast turbulence pulsation can be pressed to total dissipative shock wave, σ_k、σ_εIt is Turbulent Kinetic and its dissipation respectively The turbulent prandtl number of rate.

Gas-particle two-phase flow movable model is Lagrangian stochastic particle model trajectory.

Gas phase turbulance combustion model is Hybrid analysis probability density function (PDF) model.

Pulverized coal particle combustion model include for fugitive constituent separate out two-equation model, for coke burning diffusion move Power controls combustion model.

Radiative heat transfer model is P-1 radiation patterns.

NO_XGeneration model is PDF transport equation model.

To be described with a specific embodiment below, application examples includes：

For power station large coal-fired boiler combustion process, basal conservation eqution, turbulent flow model, turbulent flow gas-solid can be used Two-phase flow model, gas phase turbulance combustion model, pulverized coal particle combustion model, radiative heat transfer model lead to carrying out mathematical description Cross and real process is simulated to above-mentioned equation numerical solution, be that actual motion provides reference parameter.This part is just to this report mould Each mathematical model for intending the coal powder boiler combustion process employed in research describes in detail.

Basal conservation eqution

Burning is the turbulent flow process for including very exothermic chemical reaction, and all physical quantitys are all room and times Stochastic variable, but turbulent flow follows continuous media general motion rule.The law of description combustion law has：The conservation of mass, The conservation of momentum, preservation of energy, chemical constituent balance and the chemical element conservation of mass etc..

(1) equation of continuity

(2) equation of momentum

The general type of the equation of momentum can be written as：

σ in formula_ij=p δ_ij-τ_ij

Wherein：τ_ijFor viscous stress.

δ_ijFor Kronecker function：

δ_ijFor stress tensor, S_iVarious body forces and resistance component in i direction is then included.In consideration multiphase flow When, the active force between multiphase flow is also be reflected in this.

(3) energy equation

Energy-balance equation：

The equation equal sign left side：Represent rate of change of the unit fluid gross energy to the time in the unit interval；Equation equal sign The right：1st is surface pressing convection cell infinitesimal work done, typically negligible；2nd unit volume for causing for conduction of heat Energy variation；3rd Φ is to be converted into the part of heat energy, referred to as dissipative function due to viscous effect mechanical energy；4th S_hFor changing Learn reaction heat, radiant heat, alternate heat exchange and self-defining volumetric sources item.

(4) chemical multi-species equation

What chemical multi-species equation embodied is the conservation of mass of each component in combustion process.For any chemical constituent K, its chemical constituent equation of continuity is：

In formula：m_kThe mass fraction of component K, is defined as：

S_kThis component that generation (or consumption) rate of component K for being caused due to chemical reaction and heterogeneous reaction are produced Mass Sources.

Γ_kThe transport coefficient of chemical constituent K：Γ_k=ρ D_k

D_kThe diffusion coefficient of mixed gas is corresponded to for chemical constituent K.

Formula (2-4) is added to whole component K, that is, obtains the equation of continuity of whole fluid：

In formula,The total source item of the quality that causes for particle reaction, when no granule phase reaction

(5) state equation

Contain 6 unknown numbers in aforesaid equation, u, v, w, p, T, and ρ, also need to supplement the state side of contact p, a ρ Journey：

ρ=ρ (p, T) (2-5)

For above-described fundamental equation, its unknown number is equal with equation number, it should say that equation is closing.As long as Boundary condition and initial condition are suitably described, it is possible to solve, but in fact it has been found that in actual nature and engineering stream In dynamic device, flowing is often turbulent flow, and turbulent flow is carried out in the scale of turbulence of a very little.Therefore, this is solved One group of equation of sample is necessary for carrying out in the size of mesh opening of the scale of turbulence, however this to be current computer capacity and speed still can not Realize.Therefore, solve Navier-Stokes equation to set about in terms of other, here it is turbulence model.

Turbulent flow model

Turbulent flow is the common flow phenomenon of nature, and the flowing of fluid in most engineerings is often in turbulence-like State, turbulence characteristic is occupied an important position in engineering.In boiler combustion process, as combustion apparatus size is larger, shape Complicated, air velocity is higher, adds the impact of the chemical reactions such as fuel combustion, and the air current flow in burner and Boiler Furnace is several It is all turbulent flow.

K- ε model in two-equation model, is the turbulence model being most widely used in Practical Project.With regard to turbulent flow On the basis of the equation of kinetic energy k, it has been re-introduced into representing the pulsation that isotropism microvortex rotation mechanical energy changes into heat energy speed Kinetic energy dissipation rate ε.The model is proposed in 1972 by Launder and Spalding.It is now widely used for combustor stream The numerical simulation that field, pipe flow, bluff body backflow and jet flow back, and air current flow, burning, heat transfer, mass transfer in some equipment Deng the gas phase simulation in process synthesis model.

K- ε two-equation model has the advantage that：(1) transport process of turbulent flow physical quantity is considered by seeking partial differential equation, The relation of pulsatile characteristics speed and mean field velocity gradient is determined by solving partial differential equation, rather than directly both is joined System gets up；(2) characteristic length be not by empirically determined, but using dissipative scale as characteristic length, and by solve corresponding partially The differential equation is obtained.

But k- ε model is to buoyant flow, strong eddy flow is dynamic, curved wall flows, bending streamline flows, low Reynolds number turbulent flow And during the flowing such as circular jet, certain distortion can be produced, reason be in the k- ε model of standard, for Reynolds stress Each component, it is assumed that viscosity coefficient μ_tIt is identical, that is, assumes μ_tIt is isotropic scalar.And the situation in bending streamline Under, turbulent flow is anisotropic, μ_tIt should be anisotropic tensor.Therefore, many scholars are for some problems to k- ε model It is corrected, such as consideration nonequilibrium flow, rotation and curvature, compressibility and non-linear etc. develops many improved moulds Type, such as low Reynolds number k- ε model, non-linear k- ε model, multiple dimensioned k- ε model, renormalization group k-ε model, achievable k- ε model etc., and the model after the application enhancements has been achieved for satisfied effect in some respects.

Realizablek- ε (the band rotation is revised) two-equation model that this report is selected carries out numerical simulation calculation. It is to consider turbulent flow physical quantity by seeking partial differential equation that the main feature of Realizable k- ε two-equation model is exactly it Transport process, i.e., determine the relation of pulsatile characteristics speed and mean field velocity gradient by solving partial differential equation, rather than directly Connect and both are connected；In addition, the characteristic length in model is not by empirically determined, but long as feature using dissipative scale Degree, and obtained by corresponding partial differential equation are solved.Therefore the sending out for flat board and round jet of the k- ε model with swirling modification Scattered ratio has a more accurate prediction, and it is for rotational flow, the boundary layer flow of strong adverse pressure gradient, flow separation and secondary Stream has good performance.Comparatively Realizablek- ε both sides journey is more simple, easy to use.Present Realizablek- ε Two-equation model oneself be effectively used for various types of flow simulating, including rotate uniform shear flow, include jet With in the free-flowing of mixed flow, pipeline flowing, boundary layer flow and with detached flowing etc..And all achieve with Test data is than more consistent result, suitable engineering problem research.

K- ε model with swirling modification is that just occur in the recent period, has two main differences compared with standard k-ε model Point：(1) the k- ε model with swirling modification increased a formula for turbulent viscosity；(2) for dissipative shock wave, new transmission side increased Journey, this equation is from an Exact Equation that makees for laminar velocity fluctuates.By revised standard k-ε model, bright The aobvious simulation precision that improve the diffusibility to plane jet and round jet.

Under rectangular coordinate system, the general control equation of the standard k-ε model of stable state is as follows：

Wherein：P is Fluid pressure, and ρ is that fluid density, Φ is general dependent variable, and Г is the transport coefficient of each equation variable (diffusion coefficient), S is shown in Table 1 for corresponding source item in the conservation equation of dependent variable, the particular content of P, ρ, Φ, Г, S.

The expression formula of each variable in 1 general control equation of table

In table 1

μ_e=μ+μ_t,

Wherein：μ_eFor coefficient of virtual viscosity；

μ_tFor coefficient of eddy viscosity；

μ is laminar flow viscosity.

It should be noted that, equal strain rate king-sized situation during standard k-ε model pair, it is possible to cause negative malleation Power.For making flowing meet the physical law of turbulent flow, need to carry out certain mathematical constraint to normal pressure.Calculate turbulent kinetic limit meter C in formula_μShould not be constant, and should connect with strain rate.So as to propose Realizable k- ε model

K equation：

ε equation：

Wherein：G_kRepresent that the Turbulent Kinetic for being caused due to average velocity gradient is produced, G_bIt is the rapids for causing for buoyancy effect The energy of flow is produced；Y_MRepresent the impact that the expansion of fast turbulence pulsation can be pressed to total dissipative shock wave.σ_k、σ_εBe respectively Turbulent Kinetic and its The turbulent prandtl number of dissipative shock wave.

C₂=1.9, σ_k=1.0, σ_ε=1.2, σ_1ε=1.44

In formula, μ_tWith C_μIt is calculated as follows：

Wherein：

A_o=4.0

WhereinIt is ω from angular velocity to be_kReference frame in the when equal slewing rate tensor observed, it is clear that to no The flow field of rotation, U^*Section 2 in formula in radical sign is zero, and this is the impact for being specifically intended for representing rotation, and this mould One of feature of type.

Gas-particle two-phase flow movable model

Process of coal combustion is the dynamic and combustion process of typical gas-particle two-phase flow, the numerical simulation of Gas-solid Two-phase Flow The main simulation for including gas phase turbulance of research, simulation of the gentle solid phase interphase interaction of simulation of granule motion etc., it be in list Grow up on the basis of the simulation of phase turbulent flow.Research to two phase flow has two kinds of different viewpoints at present：One be fluid or Gas is been described by eulerian coordinate system as continuous media, and using particle swarm as discrete system, in Laplace coordinate system It is been described by；And another be in addition to a fluid as continuous media outside, also particle swarm as quasi-continuous medium or fluid analogy, two Coexist in space and interpenetrate, biphase be all been described by eulerian coordinate system.Instantaneous equation to turbulent multiphase flow Group is carried out after Reynolds decomposes and be average, obtaining at that time all equation group, equation according to similar to the method for adopting in single-phase turbulent flow Contain unknown associations during group after homogenizing, it is impossible to close.For this purpose, proposing following simulation and method for simplifying：(1) dynamics of single particles Model；(2) small slip model；(3) no sliding model (one fluid model)；(4) two-fluid model (multi-phase model or sliding Many continuum Model of diffusion)；(5) particle-trajectory model.

Particle-trajectory model, processes granule phase in the Largrangian coordinates, and considers unrelated with particles diffusion, biphase Between big velocity-slip and temperature glide, taken into full account the gas phase interaction alternate with granule.Stochastic Separated Flow Model is adopted Monte-Carlo.Method solves the random orbit of granule motion in this random instantaneous flow field, and the granule for counting fluid turbulent is made With.Particle-trajectory model is easy to simulate the experience of the granule of evaporation, volatilization and out-phase reaction, no numerical value in granule mutually forecasts Diffusion.Therefore, the model is current model most widely used in turbulent flow with combustion simulation.But it cannot meet pulsation The continuity equation of amount, it is impossible to simulate particle fluctuation completely.If obtaining the granule details compared with experimental result, need Amount of calculation that will be very big.

What this report was selected is Lagrangian stochastic particle model trajectory, and a difficult problem for the model solution is concentrated mainly on three Aspect：The coupling of gas-particle two-phase, fluid velocity simulation, boundary condition.Its basic thought is：When the random orbit of granule is calculated The impact that consideration gas-phase fluctuation random velocity is moved to granule, i.e., by the instantaneous equation of momentum of granule, randomly give gas Instantaneous velocity, with Monte-Carlo method calculate the random orbit of granule in random instantaneous flow field with count fluid turbulent to The effect of grain.Its major advantage is to calculate simply, when granule has more complicated change through lasting, can preferably follow the trail of the fortune of granule Dynamic, pseudo- diffusion will not be also produced during numerical computations；It is exactly also the impact for considering fluid turbulent pulsation to granule.Which has the disadvantage It is difficult to simulate the transport process of KεT model completely, it is also difficult to which being given can be with the corresponding granule of granule Euler field feature of actual measurement Speed and the close data of concentration space distribution.

Form (X-direction) of the force balance equation of granule under cartesian coordinate system be：

Right formula Section 1 is stress suffered by granule, and it is additional tension stress that Section 2 is granule gravity, Section 3 itself.

Wherein, u is gas phase velocity, u_pFor particle speed, it is gas density that μ is fluid kinematic viscosity, ρ, ρ_pClose for granule Degree, d_pFor particle diameter.

In (2-13), Re is relative Reynolds number (particle Reynolds number), and expression formula is as follows：

C_DFor stress coefficient, expression formula is as follows：

a₁、a₂、a₃It is ball granule constant, according to its value of Morsi and Alexander et al. view with Re value range And change.

Or, according to the saying of Haider and Levenspiel, can also be expressed as

Wherein, b₁=exp (2.3288-6.4581+2.448 Φ²)

b₂=0.0964+0.5565 Φ

b₃=exp (4.905-13.8944+18.4222 Φ²-10.2599Φ³)

b₄=exp (1.4681+12.2584 Φ -20.7322 Φ²+15.8855Φ³)

The definition of form factor Φ is：Φ=s/S

S is the ball spherome surface product for having same volume with granule, and S is the surface area of granule.In simulation, Φ is set to 1, i.e., It is assumed that pulverized coal particle is spheroidal particle.

Under Lagrange remainder, the instantaneous equation of momentum of granule is：

M in formula_p、V_p, t, F be respectively the quality of granule, speed, movement time and suffered power.Ignore the floating of granule Power, Magnus power, barometric gradient power, effect of Saffman power and false mass force etc..Therefore the equation of momentum of granular mass For：

Wherein, τ_pFor granule slack time, u ', v ', w ' are the fluctuation velocities of gas phase, it is assumed here that gas phase turbulance flow field is Local uniform and isotropic, when granule is located at certain turbulent vortices, u ', v ', w ' are taken as：

In formula,For the mean square root of gas phase turbulance fluctuation velocity, ζ is to meet Gauss to divide The random number of cloth, k is gas phase turbulance kinetic energy.

The equation of locus of granule is：

x_p=∫ u_pdt y_p=∫ v_pdt z_p=∫ w_pdt

Gas phase turbulance combustion model

The appearance of turbulent flow, can not only affect the characteristic in flow field, and influence whether all of transport equation.Turbulent combustion speed Rate is while by being affected in terms of turbulent flow, molecular transport and chemical kineticses three, have not yet to see the rapids for commonly using Stream burn rate formula.The simulation of presently described turbulent flow gas phase combustion process, mainly have k- ε-g model for diffusion flame, Vortex breakdown model (EBU), draw cut sliding formwork type, ESCIMO turbulent combustion theory for premixed flame etc..

In gas phase diffusion flame, fuel and oxidant are in various flows.Before which reacts, both connect Touch and must reach molecular level.When the incorporation time scale ratio response time, yardstick was much bigger, it is necessary to consider turbulent closure scheme in detail Process, but it is transient chemical reaction (fast chemical reaction) that assume that, can calculate course of reaction using balanced algorithm.? Have in comprehensive combustion model and plant easily widely used method, i.e. the Hybrid analysis method that assumes based on this.

Hybrid analysis probability density function (PDF) model need not solve the transport equation of each component, only solve one The transport equation of individual or two conserved quantities (Hybrid analysis), the concentration of single component is asked according to the distribution of the Hybrid analysis of prediction Solution.The impact of turbulent flow in the solution procedure of conserved quantity, is considered using probability density function.Suitable for incompressible turbulent flow Flow field and diffusion combustion response system, it is impossible to for premix or partly-premixed combustion system.

The binary system constituted by a kind of fuel and a kind of oxidant, the definition of Hybrid analysis f is represented by：

In formula：Z_iElement mass fraction for element i.Subscript ox represents the value of oxidant stream porch, and fuel represents combustion The value of stream porch.

Under the hypothesis of identical diffusibility, composition equation can be reduced to a single equation with regard to blending ingredients f. F is a conserved quantity, and time average Hybrid analysis equation is：

Source item S_mOnly refer to quality by the incoming gas phase of reaction particles (as coal).S_userSource item is defined for any user.

Except solve Hybrid analysis when equal equation in addition to, there is also a need for solving average Hybrid analysis mean-square valueConservation equation：

In formula：Constant σ_t、C_g、C_d0.85,2.86,2.0 are taken respectively.

Hybrid analysis analogy method benefit is the Hybrid analysis that chemical reaction is reduced to one or two conservation.Institute There is heat chemistry scalar (constituent mass fraction, density and temperature) all uniquely relevant with Hybrid analysis.Given reaction coefficient chemical Matter and chemical reaction, in flow field, the instantaneous conservation fractional value of any point can be used for calculating each component molar fraction, density And temperature value.Can just simulate in the middle of in turbulent reacting flows as Hybrid analysis method need not solve substantial amounts of mass transfer equation The interaction of the formation of product, turbulent flow and chemical reaction, and its computational efficiency height, can draw than finite rate method more accurate Average fluid density, so be widely used at present.

Coal dust firing model

Process of coal combustion is divided into several stages：Pulverized coal preheating, fugitive constituent are separated out and combustion process, coke burning were waited Journey.The fugitive constituent for producing during pyrolysis of coal and the burning of fugitive constituent have important impact for whole burning of coal process, sometimes Even conclusive impact.In order to obtain the differential equation group that closes, the source item master in energy equation and component balanced equation Be given by volatile matter devolatilization model and coke granule combustion model jointly.

(1) fugitive constituent precipitation model

There is pyrolytic reaction in coal, separate out fugitive constituent, the then volatilization of remaining coke and precipitation at high temperature first Part is reacted with the oxygen of in the air respectively:

Raw coal：Y fugitive constituent+(1-y) coke

On the basis of numerical computations test, researcher establishes different devolatilization model.Mainly there is fixed volatilization speed Rate model, single reaction model, two-equation model, multistep parallel reaction model, functional group's devolatilization model, consideration non-dynamics control Devolatilization model of factor etc..

The double parallel reaction model for being proposed in 1975 by Stickler et al. is currently the more extensive model of application, should Model thinks there is rate constant

In the model, E₂＞ E₁, A₂＞ A₁.In lower temperature, first reaction plays a major role, during high temperature, second Reaction plays a major role.

Discharge fugitive constituent ratio and be respectively α₁And α₂, control activation energy numerical value so that first reaction is carried out at low temperature, the Two reactions are carried out at high temperature, and the Mass lost amount of the coal caused by pyrolysis is：

Fugitive constituent mass change：

Wherein：m_cFor unreacted raw coal quality；A₁,A₂,E₁,E₂For fugitive constituent pyrolysis Kinetics Parameter, by measuring.By Simple in calculating, result of calculation has certain accuracy, and therefore two-equation model is applied very wide in realistic simulation.

(2) combustion simulation of coke

In the combustion process of pulverized coal particle, the burning of coke is a complicated process (belonging to gas-solid heterogeneous combustion), The process include oxidation material to the diffusion process of particle surface and these materials particle surface and coke course of reaction, one As think, the two processes are while carry out under a quasi-equilibrium reactive state.Coke granule inhomogeneous reaction process Simulation be complicated, it be subject to the fragmentation of coke, endoporus diffusion, the change of surface area and change of temperature and pressure etc. these The impact of uncertain factor.

As the burning of coke is not only relevant with diffusion, also relevant with kinetics factor.Thus coke burning at present Modal in the model for using is exactly eddy diffusion combustion model.Burn rate R of coke_cCoke table is diffused into by oxygen Speed K in face_dChemical reaction rate K with coke surface_cThe co- controlling of these two aspects, is represented by：

In formula, P_O2Partial pressure for oxygen；D_O2Diffusion coefficient for oxygen；S_kFor Sherwood number, 2.0 are taken as；Mc is carbon Molal weight.

In the present embodiment, fugitive constituent is separated out and uses two-equation model, and coke burning uses diffusion kinetics Control combustion model.In a model, it is assumed that coal grain is the spheroidal particle of single particle size, and in any moment of reaction, coal grain is by water Divide, raw coal, coke and this four part of ash constitute.The rising of coal grain temperature causes the moisture evaporation in coal grain, enters gas phase change Become water vapour.Raw coal is consumed as fugitive constituent is separated out, and remaining solid combustible is that coke, coke occurs out-phase anti-with oxygen Should and gradually after-flame.Ash is gradually intended to 1 with the after-flame of coke.The composition of the fugitive constituent that hypothesis is separated out is nytron Thing (CH_X), it exhausts in gas-phase combustion reaction rapidly.

Radiative heat transfer model

Radiant heat transfer process is the main heat transfer type in high-temperature burner hearth, therefore in Combustion simulation system, to radiation The simulation of the transmission of energy is extremely important, while being also an extremely complex task.Such as in a typical coal dust firing In stove, radiation is while include granule, coal dust, coke, soot particle, bituminous coal and gas phase (mainly CO₂And H₂O effect).Radiation is calculated Degree of accuracy depending on adopted computational methods levels of precision and for radiation medium and the degree of understanding of surrounding wall property. Currently for different applicable elements, the computation model of a lot of radiation heat transfers is had been developed, the method master that these models are adopted Heat flow method (Heat Flux) to be had, Monte Carlo method (Monte-Carlo) and region analysis method (Zone Analysis).

The feature of heat flow method be by complicated uneven multinomial interface radiant heat flux with uniform interface radiant heat flux To replace, and average.The advantage of heat flow method is that calculating is simple and amount of calculation is little.But for the area with intense radiation Domain, the hypothesis of heat flow method is clearly present in true discrepancy.But as the method calculates easy, the model that error is allowed in engineering In enclosing, therefore apply more at present in boiler flow field numerical simulation, develop more ripe perfect.

The model that this report is selected is the P-1 radiation patterns based on heat flow method.P-1 method is that a simplest bulb is humorous Function method, it assumes that the radiant intensity in medium is along the distribution of space angle orthogonal thereto spheric harmonic function, and by containing differential, integration Emittance equation of transfer is converted into one group of partial differential equation, and simultaneous energy equation and corresponding boundary condition just can obtain spoke Penetrate the spatial distribution of intensity and temperature.Compared with DO method, P-1 method considers the effect of radiating scattering, is more suitable for optical thickness The combustion apparatus of big and geometry complexity, and the time for solving required for emittance equation is short, is relatively suitable for solving coal Burn in powder stove.Researcher both domestic and external this model multiplex when coal-powder boiler burning is simulated.

For radiant heat flux q_r,

Wherein：α is absorptance, σ_sFor scattering coefficient, it is linear anisotropic phase function system that G is incident radiation, C Number.Introduce parameter：

Equation can be turned to：

q_r=-Γ G

The transport equation of G is：▽(Γ▽G)-αG+4ασT⁴=S_G(2-27)

Wherein：σ is Stefan Boltzmann constant, S_GFor user-defined radiation source phase.During using P-1 model, ask This equation is solved to obtain local radiant intensity.

Merge two formula above, equation below is obtained：

-▽q_r=α G-4 α σ T⁴(2-28)

-▽q_rExpression formula can be brought directly to energy equation, so as to obtain the calorie source (converge) caused due to radiation.

When granule dispersion phase is included in model, the impact of granule can be considered in P-1 radiation patterns.For including There is the grey body medium of absorption, transmitting, scattering nature granule, the transport equation of incident radiation is：

Wherein, E_PFor the radiation-emitting amount of equal value of granule, α_pEquivalent absorption coefficient for granule.

Wherein, ε_pn, A_pn, T_pnThe blackness of respectively n-th granule, projected area (vertical radiation direction) and temperature.

The definition of Γ is：

Wherein, equivalent particle dispersion factor is defined as：

It obtains during granule following calculation, f_pnScattering coefficient for n-th granule.

Radiant heat strength q in P-1 method_rWall boundary condition be：

If it is assumed that wall is diffusion grey body surface, then ρ_w=1- ε_w, above formula can be expressed as：

This equation is used for calculating the q in energy equation_r,wAnd the boundary condition of radiation equation.

NO_XFormation mechanism and model

(1)NO_XFormation mechanism

The NO for generating in coal combustion process is thought in research at present_XIt is divided into three types, respectively heating power type, Quick-type and combustion Material type.NO in impact burning_XThe factor of generation has fuel characteristic such as coal, nitrogen content, nitrogen substance structure, grain diameter etc.； Service condition such as boiler form, load, temperature, oxygen amount, response time (time of staying) etc..

(2) thermal NO_X(Thermal NO_X) formation mechanism

Thermal NO_XRefer to the N in combustion air₂The nitrogen oxides for aoxidizing at high temperature and generating.Its formation mechanism It is that Zeldovich was proposed in nineteen forty-six, its generating process can be described by following reaction：

When fuel concentration is excessive, in addition it is also necessary to consider that following formula reacts：

Thermal NO_XHigh-temperature region mainly more than 1500 DEG C produces, the relation of its formation speed and temperature be by According to Ah 's Li Wusi law：With the rising of temperature, NO_XFormation speed exponentially increase sharply.Its growing amount is permissible Estimated by Zeldovich kinetic model：

In formula：[O₂], [N₂], [NO] is respectively O₂, N₂, the concentration (mol/cm of NO³)；

T is absolute temperature (K)；

T is the time (s)；

R is universal gas constant (J/ (mol K)).

Thermal NO_XFormation speed have exponent relation with temperature, when ignition temperature less than 1800K when, thermal NO_XRaw Become few, when temperature is higher than 1800K, reaction is gradually obvious, and the rising with temperature, NO_XGrowing amount drastically raise, Temperature is in 1800K or so, and temperature often raises 100K, and reflection speed will increase 6-7 times.In combustion, if there is office Portion high-temperature region, then can generate more NO in these regions_X, the NO that it may be indoor to whole burning_XKey work is generated With therefore should avoiding the effect in area of localized hyperthermia in real process as far as possible.

Excess air coefficient is to heating power NO_XImpact be also obviously, in theory for heating power NO_XGrowing amount and oxygen The square root of concentration is directly proportional, i.e., oxygen concentration increases the concentration of oxygen atoms that oxygen molecule can be made at relatively high temperatures to decompose gained and increases Plus, make heating power NO_XGrowing amount increase.And situation can be more more complicated in real process, because excess air coefficient increases On the one hand oxygen concentration, another aspect O are increased₂The increase of concentration can cause ignition temperature to decline due to the diluting effect of oxygen, cause NO_XGenerating rate reduce.In a word, NO_XGenerating rate and O₂Concentration has the relation of an extreme value, and this extreme value is α in theory =1, deviateing α=1 can all make NO_XGrowing amount reduce.

(3) Quick-type NO_XFormation mechanism

Quick-type NO_XIt is found through experiments in 1971 by Fenimore (Fenimore) earliest.In rich hydrocarbonization On the flame front face of compound fuel combustion, the substantial amounts of quick NO of generation can be reacted_X, the CH that gone out due to hydrocarbon fuel pyrolytic from By base and the N of in the air₂Reaction generates HCN and N, and then in O₂In the presence of form NO at a terrific speed_X, required for reaction Time be about 60ms, 0.5 power of growing amount and furnace pressure is directly proportional, little with the relation of temperature.Due to quick NO_X Hydrocarbon is needed to start and N₂Reaction, so growing amount is more in fuel-rich flame, the multiple combustion for being born in internal combustion engine Burning process, for coal combustion equipment, Quick-type NO_X5% or so is only accounted for.

(4) fuel type NO_XFormation mechanism

Fuel type NO_XIn the NO that coal dust firing is generated_XIn account for very big ratio.Either fugitive constituent burning or coke combustion The burning stage all defines substantial amounts of NO_X, coal fuel type NO during pyrolysis and combustion_XGeneration and reduction process extremely complex, it With after coal characteristic, the structure of nitrogen content of coal, nitrogen decomposes in fugitive constituent and coke ratio, nitrogen-containing products composition and combustion Burning condition is closely related.Burning type NO_XGeneration reduction process can substantially divide following three step：(a) pyrolysis devolatilization process：Wave Send out the precipitation of part N；(b) oxidizing process：The course of reaction of fugitive constituent N and coke N and in the air oxygen；(c) double competitive reaction processes： The nitrogenous intermediate product of fuel N conversion generates NO_XOxidation reaction and generate NO_XN is reduced into containing oxygen intermediate₂Also The process that former reaction occurs and vie each other simultaneously.

(5)NO_XGeneration model

NO in combustion process_XGenerating process and its complexity, mainly have following NO at present_XGeneration model：Elementary reaction De ' Soete model of model, PDF transport equation model, De ' Soete model and extension etc..

(6) elementary chemical reaction model

Elementary chemical reaction model have ignored the feature during Actual combustion, emphasize NO_XThe balancing response of generation, it is considered to system Interior all possible elementary reaction and reacting substance, are solved by equilibrium equation.Elementary chemical reaction model precision is higher, but due to being related to Reaction a lot, calculate more complicated.

(7) De ' Soete model

De ' Soete model is set to HCN all intermediate products, in coal the rate of release of N be proportional to pulverized coal pyrolysis and Mass attenuation rate during coal char combustion.

Wherein, f_NMass fraction for nitrogen content of coal；M_HCN,Respectively HCN, N₂Molecular weight.

(8) De ' the Soete model for extending

De ' Soete model only accounts for fuel NO_XThe NO that the fugitive constituent HCN of the inside is produced_XAnd thermal NO_X, do not consider NH in fugitive constituent₃Etc. the NO that component and coke are generated.

(9) PDF transport equation model

NO_XIn generating process, not only relevant with the chemical reaction mechanism of itself, and and Turbulent Flow Field and its between Dependent interaction is relevant.Xiang Douyong closing form related with chemical reaction rate for turbulent transport expressed by PDF transport equation model, Without the need for simulation, any complicated chemical reaction mechanism accurately can be calculated, and therefore it is in the simulation of pollutant generating process It is used widely in journey.

NO in process of coal combustion_XThe growing amount of pollutant is few, mainly NO, and it will not be to other local mean fields Variable, such as temperature, speed, key component concentration produce large effect.Therefore, the numerical simulation calculation that NO is generated can be from meter Calculate in stove and decouple out in the program of Gas-solid Two-phase Flow, heat transfer and coal dust firing, that is, adopt postpositive disposal (post- Processor method) is simulated very little, can typically ignore.Therefore, herein consideration is not given to the reaction of Quick-type NO.

NO in coal-powder boiler_XGenerating process betides turbulent gas particle flows disorder of internal organs, and during its turbulent flow, equal reaction rate is different from changing Learn the instantaneous reaction rate that mechanism model is provided, it is therefore necessary to consider impact of the turbulence pulsation to its chemical reaction rate.Coke The reduction reaction of NO is reacted for out-phase, speed is slower, can ignore impact of the turbulence pulsation to its chemical reaction rate, at that time All reaction rates can be directly calculated by average variable.Rate of release for HCN in coal can also ignore turbulence pulsation Impact.However, for NO generation and each homogeneous reaction in reduction process, during due to its response time yardstick with turbulent closure scheme Between yardstick be the same order of magnitude, it is therefore necessary to consider impact of the turbulence pulsation to its chemical reaction rate.At present, apply and must compare Universal method is to simulate the impact of turbulent flow using setting PDF (Probability Density Function) model method, Compared with PDF transport equation model method, the model is difficult to simulate the phase between detailed limited chemical kineticses and turbulent flow Interaction, but for NO_XThe general simulation of generation is suitable, and amount of calculation is less, and with higher computational accuracy.This Research sets instantaneous reaction rate as two variable-temperature, the function of oxygen concentration, using the setting beta function shape of limited response speed The PDF model of formula, i.e. p (T), p (Y_O2), instantaneous reaction rate is multiplied by p (T) p (Y_O2) be integrated, it is possible to draw average Reaction rate.Temperature T is carried out nondimensionalization for θ, while assuming θ and Y_O2It is the variable of two statistical iteration, concrete model is：

Method of value solving

By to the conservation of mass in combustion process, preservation of energy, the conservation of momentum, component balanced and kinetics base The research of this rule, establishes the mathematical model of flowing in combustion process, heat transfer, mass transfer and combustion phenomena and each subprocess. The governing equation of combustion process is complicated non-linear partial differential Fang Yicheng, in addition to indivedual simple case, it is difficult to directly solution Method obtains the accurate solution of these partial differential equation, can only seek its approximate solution with iterative method, therefore, sets up correct physical model Afterwards, it is critical only that whether can set up appropriate method for solving.

(1) discretization in region

Before numerical simulation is carried out to boiler combustion, first have to carry out the discretization of zoning, its essence is exactly Replace original continuous space, i.e. gridding with limited discrete point.Before the discretization in region carries out numerical computations Carry.The method of gridding is a lot, has fixed mesh and floating grid, orthogonal grid and non-orthogonal mesh, be uniformly distributed grid and Non-uniform Distribution grid, staggered-mesh etc..

According to dependent variable in distribution hypothesis and the method for deriving discrete equation of node, mainly there are following several discrete sides Method：Finite difference calculus, FInite Element and finite volume method.Finite volume method (Finite Volume is used herein Method abbreviation FVM) also known as control volume mothod.The basic ideas of finite volume method：Zoning is divided into grid, and is made every There is a mutually unduplicated control volume around individual mesh point, the differential equation to be solved is controlled volume integral to each, so as to Draw one group of discrete equation.From the choosing method of integral domain, finite volume method belongs to the SUBDOMAIN METHOD in weighted residual method, From the approximation method of Unknown Bound, finite volume method belongs to the discrete method using Local approximation.

Additionally, the position regarding node in control volume, can be divided into interior nodes method and exterior node method.The mode shadow of gridding Ring the discrete difficulty or ease of the differential equation.Also it is related to the precision of solution, convergence and economy

(2) several discrete scheme

When discrete equation is set up using finite volume method, it is important that a step be exactly will control volume interface on physics Amount and its derivative are obtained by node physical quantity interpolation.Mainly there are following several discrete scheme at present：Central difference schemes, single order Upstreame scheme, mixed format, exponential scheme, power law scheme, Second-order Up-wind form and QUICK form.

Central difference schemes (Central Differencing Scheme), are exactly the physical quantity on interface using linear Formula for interpolation is calculating.Central difference schemes can be only applied to speed very little or mesh spacing very little.

Monovalence upstreame scheme (First Order Upwind Scheme) considers the impact of flow direction, at any All without the concussion for causing solution under part, can obtain forever physically it appear that suitably solving.Therefore, single order upstreame scheme is obtained To being widely applied.

Mixed format (Hybrid Scheme) combines centered difference and acts on the factor of two side's one sides windward.Therefore, mix Qualified formula is widely adopted in CFD software.Have the disadvantage only single order precision.

Exponential scheme (Exponential Scheme) will spread with the effect of convection current and together with considering.Exponent arithmetic Can accurately be solved, but computing expense is time-consuming, in the problem of two and three dimensions, and the situation that source item is not zero, calculate not Accurately.

Power law scheme (Power-law Scheme) and a kind of exponential scheme discrete scheme closely.

Second-order Up-wind form is with single order upstreame scheme it is identical in that physical quantity all by upstream units point is determining control The physical quantity at volume interface processed.But Second-order Up-wind form not only uses the value of a nearest point of upstream, other one will be also used The value of individual point upstream.

QUICK (Quadratic Upwind Interpolation of Connective Kinematics) form is A kind of method for improving discrete equation intercept.

This report adopts monovalence upstreame scheme.

(3) flow field numerical algorithm

The basic process of Flow Field Calculation is spatially with finite volume method, computational fields to be separated into many little volume lists Unit, solves to the governing equation group after discrete in each elementary volume, volume element.Coupling type solution and separate type solution can be divided into Method, wooden literary grace separate type solving method.Separate type solving method is sequentially, seriatim to solve each equation (with regard to u, v, w, p and T Equation).After namely first an equation (as the u equation of momentum) being solved on total-grid, then solve another equation (as v The equation of momentum).Due to governing equation be nonlinear, and each other be coupling, therefore, before convergence solution is obtained, Through excessive wheel iteration.Each wheel iteration is made up of following steps：1st, according to the result of current solution, all flowing momentum are updated, such as Fruit calculates and just starts, then updated with initial value；2nd, solve u, v and w equation of momentum respectively in order, velocity field is obtained, note When being intended to calculate, the mass flow of pressure and unit interface uses current given value；3rd, because the speed that the 2nd step is obtained is likely to Continuity equation is unsatisfactory for, and the pressure correction side of a Poisson type therefore, is constructed with continuity equation and the linearizing equation of momentum Journey, then solves the pressure correction equation, obtains the correction value of pressure field and velocity field；4th, using the velocity field for newly obtaining and pressure The field of force, solves the governing equation of other scalars (such as temperature, tubulence energy and group are graded)；5th, for the simulation comprising discrete phase, when The source item of continuous phase when inside has Coupling Between Phases, is updated according to the trajectory calculation result of discrete phase；6th, equation group is checked whether Convergence.If not restraining, the 1st step is returned to, is repeated.

SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) is current engineering In a kind of wide variety of Flow Field Calculation method, it belongs to one kind of pressure-type cable.Mainly include SIMPLE and derived from by it SIMPLER, SIMPLEST and PISO out.

The present embodiment adopts SIMPLE algorithm.

Stove combustion process numerical simulation

Calculate grid

Turbulent burner is single only tissue burning, and therefore the burner of swirl-opposed boiler has very big shadow to boiler combustion Ring.As burner is for boiler, size is comparatively small, and the grid of burner region can be very big, and this is to computer Performance requirement is very high.Coal dust firing in burner hearth is had no effect in view of the process in horizontal flue and back-end ductwork, and coal dust When grain moves to flue, burning terminates substantially, and flue gas does not substantially occur chemical reaction in flue, does not therefore have herein To the process simulation in back-end ductwork, and have ignored the impact of superheater stream field in horizontal flue.According to upper one section The flow behavior of burner outlet, as boiler-burner entrance boundary condition, builds domain and carries out stress and strain model, Furnace outlet increases the horizontal segment of 10m, to obtain fully developed flow in exit.In order to obtain high-quality calculating grid, adopt Multiblock technique division methods are used, using structuring hexahedral mesh, for accurate simulation burner outlet aerodynamic field, is burnt Device entrance area needs to carry out grid local cypher, and total grid number is 1,500,000.Chamber structure and grid such as Fig. 3 (a) to (c) Shown.

Simulated condition and computational methods

Burner body is simplified, and burner inlet model is built according to burner dimensions；Centre wind and First air Using speed entrance boundary condition, inner second air and outer second air adopt quality entrance boundary condition；Porch wind speed, pathogenic wind-warm, Mass flow is configured according to the burner outlet flow behavior of design parameter, variable working condition condition and a upper section.To after-flame Wind and side burnout degree body are simplified, and build its entrance model according to burner dimensions；Burnout degree and side burnout degree adopt matter Amount entrance boundary condition, mass flow values are calculated according to design parameter and variable working condition condition.In the condition of entrance boundary, The definition of velocity component adopts partial cylindrical coordinate system, sets the velocity component of each spout respectively.Export boundary condition is adopted Pressure export, pressure is set to -80Pa；Burner hearth wall adopts standard law of wall equation, no slip boundary condition, and heat exchange adopts the Two class boundary conditions, i.e. temperature boundary condition, given wall surface temperature and radiance, wall surface temperature is that 700K, Wall Radiation rate is 0.6.In simulation, it is contemplated that upper furnace screen superheater and high temperature superheater must be affected on afterbody flow field and heat exchange.

Pulverized coal particle diameter is distributed according to Rosin-Rammler method.Rosin-Rammler distribution is assumed in particle diameter The d and mass fraction Y of the granule more than this diameter_dBetween there is exponential relationship：

For average diameter, n is profile exponent

The coal dust sample obtained by phenomenon carries out laser particle size analysis, obtains coal particle size distributed data：5 μ of minimum grain size M, 250 μm of maximum particle diameter, 63.8 μm of mean diameter, profile exponent 1.008.

Carry out cold conditions calculating first, then carry out hot calculating again, until convergence.Pressure and speed for discrete equation group Degree coupling is using SIMPLE Algorithm for Solving, and solving equation is using by-line iterative method and underrelaxation factor, and convergence is energy, spoke Penetrating heat transfer, NO and HCN residual error is calculated less than 10^-6, remaining items calculating residual error is less than 10^-3.

Become the analysis of coal pulverizer combine analog

Fig. 4 to Fig. 7 is to become the lower coal dust burn-off rate of coal pulverizer combination, unburned carbon in flue dust, NOx discharge and lower hearth to export Temperature.

In the operation of ACDEF coal pulverizer, the operation of BCDEF coal pulverizer and the operation of ABCDE coal pulverizer, coal dust burn-off rate is respectively 99.66%th, 99.59% and 99.62%, unburned carbon in flue dust is respectively 1.97%, 2.40% and 2.19%.Compare ACDEF coal-grinding Machine runs, and during the operation of BCDEF coal pulverizer, coal dust burn-off rate reduces 0.07%, and unburned carbon in flue dust increased 0.43%；ABCDE During coal pulverizer operation, coal dust burn-off rate reduces 0.04%, and unburned carbon in flue dust increased 0.22%.After due to A layer burner being Wall lower floor burner, F layer burner is Hou Qiang middle level burner, and B layer burner is Hou Qiang upper strata burner；Negative in 600MW During lotus, when ACDEF coal pulverizer runs, A layer and F layer burner enter the coal dust of burner hearth have in stove longer stop distance and The longer tail-off time, the burn-off rate of coal dust can increase, and unburned carbon in flue dust can reduce.The operation of ACDEF coal pulverizer is compared, when When BCDEF coal pulverizer is run with ABCDE coal pulverizer, B layer burner enters stop distance and after-flame of the coal dust of burner hearth in stove Time is relatively shorter, and the burn-off rate of coal dust can reduce, and unburned carbon in flue dust can increase.

In the operation of ACDEF coal pulverizer, the operation of BCDEF coal pulverizer and the operation of ABCDE coal pulverizer, NO_XDischarge capacity is respectively 281st, 321 and 308mg/m^3 (6%O₂).This shows, different coal pulverizers are combined to NO_XDischarge capacity has a certain impact.As described above Analysis, it is Hou Qiang middle level burner that A layer burner is Hou Qiang lower floor burner, F layer burner, and B layer burner is on rear wall Layer burner；When ACDEF runs, A layer is farthest with a distance from burnout degree region with F layer burner, air classification degree maximum, The effect that the NOx for generating in burner region is reduced is strengthened, and reduces NO_XEffect is best, furnace outlet NO_XDischarge capacity Minimum；When BCDEF coal pulverizer is run with ABCDE coal pulverizer, sky is weakened equivalent on the basis of the operation of ACDEF coal pulverizer Gas grading effect, in the NO that burner region is generated_XThe effect being reduced has been weakened, furnace outlet NO_XDischarge capacity has also risen High.

In the operation of ACDEF coal pulverizer, the operation of BCDEF coal pulverizer and the operation of ABCDE coal pulverizer, lower hearth exiting flue gas temperature Degree is respectively 1209,1226 and 1214 DEG C.This shows, stoppage in transit upper strata burner, and lower hearth exit gas temperature can reduce, favorably In the tendency for reducing pendant superheater dust stratification dross.

Above analysis shows, stoppage in transit upper strata burner is conducive to improving efficiency of combustion and reduces NOx discharge, is also beneficial to Reduce the tendency of pendant superheater dust stratification dross.

Fig. 2 is referred to, a kind of power boiler breeze provided in an embodiment of the present invention combustion characteristics under coal pulverizer combination is become One embodiment of analog includes：

Division unit 201, for carrying out multiblock technique division to preset boiler-burner model；

Unit 202 reprocessed by model, for simplifying to the preset boiler-burner model after stress and strain model, and obtains Design parameter and working condition to after arrange.

Analogue unit 203, for passing through basal conservation eqution, turbulent flow model, gas-particle two-phase flow movable model, gas Phase turbulent combustion model, pulverized coal particle combustion model, radiative heat transfer model and NO_XGeneration model is to the preset pot after stress and strain model Combustion process of the boiler coal-ash in burner model under coal pulverizer combination condition is become is simulated；

Determining unit 204, for according to the coal for determining boiler-burner in the result for becoming coal pulverizer combination condition Imitating Powder burn-off rate, unburned carbon in flue dust, NO_XDischarge capacity, lower hearth outlet temperature.

Those skilled in the art can be understood that, for convenience and simplicity of description, the system of foregoing description, Device and the specific work process of unit, may be referred to the corresponding process in preceding method embodiment, will not be described here.

In several embodiments provided herein, it should be understood that disclosed system, apparatus and method are permissible Realize by another way.For example, device embodiment described above is only schematic, for example, the unit Divide, only a kind of division of logic function, can have other dividing mode, such as multiple units or component when actually realizing Can in conjunction with or be desirably integrated into another system, or some features can be ignored, or not execute.Another, shown or The coupling each other for discussing or direct-coupling or communication connection can be the indirect couplings of device or unit by some interfaces Close or communicate to connect, can be electrical, mechanical or other forms.

The unit that illustrates as separating component can be or may not be physically separate, aobvious as unit The part for showing can be or may not be physical location, you can be located at a place, or can also be distributed to multiple On NE.Some or all of unit therein can be selected according to the actual needs to realize the mesh of this embodiment scheme 's.

In addition, each functional unit in each embodiment of the present invention can be integrated in a processing unit, it is also possible to It is that unit is individually physically present, it is also possible to which two or more units are integrated in a unit.Above-mentioned integrated list Unit both can be realized in the form of hardware, it would however also be possible to employ the form of SFU software functional unit is realized.

If the integrated unit is realized and as independent production marketing or use using in the form of SFU software functional unit When, can be stored in a computer read/write memory medium.Based on such understanding, technical scheme is substantially The part in other words prior art being contributed or all or part of the technical scheme can be in the form of software products Embody, the computer software product is stored in a storage medium, use so that a computer including some instructions Equipment (can be personal computer, server, or network equipment etc.) executes the complete of each embodiment methods described of the present invention Portion or part steps.And aforesaid storage medium includes：USB flash disk, portable hard drive, read only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disc or CD etc. are various can store journey The medium of sequence code.

The above, above example only in order to technical scheme to be described, rather than a limitation；Although with reference to front State embodiment to be described in detail the present invention, it will be understood by those within the art that：Which still can be to front State the technical scheme described in each embodiment to modify, or equivalent is carried out to which part technical characteristic；And these Modification or replacement, do not make the essence of appropriate technical solution depart from the spirit and scope of various embodiments of the present invention technical scheme.

Claims (10)

1. a kind of power boiler breeze is becoming combustion characteristics analogy method under coal pulverizer is combined, it is characterised in that include：

Multiblock technique division is carried out to preset boiler-burner model；

By basal conservation eqution, turbulent flow model, gas-particle two-phase flow movable model, gas phase turbulance combustion model, coal dust Particle burning model, radiative heat transfer model and NO_XGeneration model is in the described preset boiler-burner model after stress and strain model Boiler coal-ash become coal pulverizer combination condition under combustion process be simulated；

The coal dust burn-off rate of the boiler-burner, flying marking is determined according in the result for becoming coal pulverizer combination condition Imitating Amount, NO_XDischarge capacity, lower hearth outlet temperature.

2. power boiler breeze according to claim 1 is becoming combustion characteristics analogy method under coal pulverizer is combined, its feature Being, also includes after multiblock technique division being carried out to preset boiler-burner model：

Described preset boiler-burner model after stress and strain model is simplified, and gets the design parameter after arranging and work Condition condition.

3. power boiler breeze according to claim 1 is becoming combustion characteristics analogy method under coal pulverizer is combined, its feature It is, the turbulent flow model is Realizable k- ε two-equation model；

Wherein, k equation is

ε equation is

Gk represents that the Turbulent Kinetic for being caused due to average velocity gradient is produced, and Gb is produced for the Turbulent Kinetic that buoyancy effect causes Raw, YM represents the impact that the expansion of fast turbulence pulsation can be pressed to total dissipative shock wave, σ^k、σ_εIt is Turbulent Kinetic and its dissipative shock wave respectively Turbulent prandtl number.

4. power boiler breeze according to claim 1 is becoming combustion characteristics analogy method under coal pulverizer is combined, its feature It is, the gas-particle two-phase flow movable model is Lagrangian stochastic particle model trajectory.

5. power boiler breeze according to claim 1 is becoming combustion characteristics analogy method under coal pulverizer is combined, its feature It is, described gas phase turbulance combustion model is Hybrid analysis probability density function (PDF) model.

6. power boiler breeze according to claim 1 is becoming combustion characteristics analogy method under coal pulverizer is combined, its feature Be, the pulverized coal particle combustion model include for fugitive constituent separate out two-equation model, for coke burning diffusion Dynamic Control combustion model.

7. power boiler breeze according to claim 1 is becoming combustion characteristics analogy method under coal pulverizer is combined, its feature It is, the radiative heat transfer model is P-1 radiation patterns.

8. power boiler breeze according to claim 1 is becoming combustion characteristics analogy method under coal pulverizer is combined, its feature It is, the NO_XGeneration model is PDF transport equation model.

9. a kind of power boiler breeze is becoming combustion characteristics analog under coal pulverizer is combined, it is characterised in that include：

Division unit, for carrying out multiblock technique division to preset boiler-burner model；

Analogue unit, for passing through basal conservation eqution, turbulent flow model, gas-particle two-phase flow movable model, gas phase turbulance Combustion model, pulverized coal particle combustion model, radiative heat transfer model and NO_XGeneration model is to the described preset boiler after stress and strain model Combustion process of the boiler coal-ash in burner model under coal pulverizer combination condition is become is simulated；

Determining unit, for according to the coal dust combustion for determining the boiler-burner in the result for becoming coal pulverizer combination condition Imitating Most rate, unburned carbon in flue dust, NO_XDischarge capacity, lower hearth outlet temperature.

10. power boiler breeze according to claim 9 is becoming combustion characteristics analog under coal pulverizer is combined, its feature It is, also includes：

Unit reprocessed by model, for simplifying to the described preset boiler-burner model after stress and strain model, and gets Design parameter and working condition after setting.