CN103148508A - Secondary air distribution method and system for pulverized coal boiler with swirling combustion of front-back hedging - Google Patents

Abstract

The invention discloses a secondary air distribution method for a pulverized coal boiler with swirling combustion of front-back hedging. The method comprises the steps of establishing a mesh structure model of the boiler; according to the mesh structure model, establishing a mathematical model of each process which is formed by the pulverized coal combustion; according to the established mathematical model, simulating the process of the pulverized coal combustion, and obtaining a number range of the secondary air swirling intensities inside and outside a swirling combustor when the boiler is made to meet a preset performance; and when the boiler is in operation, executing air distribution for the secondary air inside and outside the swirling combustor according to the number range of the swirling intensity. In addition, the invention further discloses a secondary air distribution system for the pulverized coal boiler with swirling combustion of front-back hedging. According to the method and the system provided by the invention, the problem that the accuracy caused by manual air distribution is not high to lead to unstable combustion inside the boiler is overcome. Therefore, the combustion efficiency of the boiler is increased. Meanwhile, the contaminants which are produced during the combustion process are greatly reduced.

Description

Before and after the liquidate Secondary Air air distribution method and system of swirl flow combustion pulverized-coal fired boiler

Technical field

The swirl flow combustion pulverized-coal fired boiler technical field that liquidates before and after the present invention relates to relates in particular to a kind of front and back liquidate Secondary Air blowing system of swirl flow combustion pulverized-coal fired boiler of the Secondary Air air distribution method of swirl flow combustion pulverized-coal fired boiler and a kind of front and back that liquidates.

Background technology

The energy resource structure of China within the long term still take coal as main.Because a large amount of fire coals are used to generating, the NO that discharges _X(nitrogen oxide) accounts for the significant proportion of national total displacement, and environment has been caused serious destruction.Therefore, the NO in boiler combustion process _XDischarge capacity is answered reduce.For a long time by exhaustive exploitation, coal reserve begins to manifest deficiency due to coal in China, and pressure appears in coal supply.Therefore, reducing NO _XHow discharging time allows the burning of fuel-efficient, and boiler combustion efficiency is improved, and is also the major issue that power plant is concerned about.

In thermal power generation, the boiler operatiopn quality is closely connected with the Furnace Aerodynamic Field situation.Furnace Aerodynamic Field can guarantee that not only boiler safety moves reliably, has guaranteed again the economy of power plant preferably.Burner is the key equipment that affects Furnace Aerodynamic Field, and dissimilar burner generates different aerodynamic fields in stove.Burner is divided into two kinds: DC burner and turbulent burner.DC burner generally is applied to Process In A Tangential Firing, is applicable to Pump for Medium and Small Power Generating Set; The swirl flow combustion boiler and turbulent burner generally is applied to liquidate is applied to large-scale unit.Compare with DC burner, the aspects such as the steady combustion of turbulent burner is good, combustion economization is high, cigarette temperature deviation is little, unit maximization have unique advantage, but NO _XGrowing amount is higher, and some unit does not still reach discharging standards.Turbulent burner mixes with air-flow strongly due to coal dust, and the temperature rise that fluid field in furnace is too fast and local excessive oxygen make coal dust firing intensity higher, cause nitrogen oxide to generate in a large number.

In the actual motion of power plant, realize low NO by the mode that changes the Secondary Air partition _XDischarging and improving efficiency of combustion is a kind of important means.At present to carry out according to artificial experience for the liquidate common practices of Secondary Air air distribution of swirl flow combustion pulverized-coal fired boiler of front and back, because the degree of accuracy of artificial experience is not high, cause that sometimes the stove internal combustion is unstable, cause burner outlet to be burned, or local heating's face coking, also can cause boiler extinguishment when serious, the security and the economy that reduce power plant reduce; In addition, present way can't configure rational Secondary Air to boiler, thereby has affected the efficiency of combustion of boiler; And the mode of artificial air distribution can cause a large amount of pollutant of generation in combustion process, and environment is caused very large destruction.

Summary of the invention

Based on this, the invention provides a kind of front and back liquidate Secondary Air blowing system of swirl flow combustion pulverized-coal fired boiler of the Secondary Air air distribution method of swirl flow combustion pulverized-coal fired boiler and a kind of front and back that liquidates.

A kind of the liquidate Secondary Air air distribution method of swirl flow combustion pulverized-coal fired boiler of front and back comprises the following steps:

According to the liquidate design parameter of swirl flow combustion pulverized-coal fired boiler of front and back, according to the structure in turbulent burner, furnace hopper zone, burner region, burner upper area and pendant superheater zone, set up the gridding structural model of described boiler;

According to described gridding structural model, set up the Mathematical Modeling of the formed gas-phase turbulent flow process of coal dust firing, two flow process of gas-solid, radiant heat transfer process, Volatile process, coke combustion and nitrogen oxide generative process;

According to the described Mathematical Modeling of setting up, process of coal combustion is simulated the number range of the inside and outside secondary wind swirl intensity of turbulent burner when obtaining described boiler and satisfying default capabilities;

When described boiler operatiopn, according to the number range of described swirl strength, the inside and outside Secondary Air of turbulent burner is carried out air distribution.

Compare with general technology, the Secondary Air air distribution method of swirl flow combustion pulverized-coal fired boiler of liquidating before and after the present invention is set up the Mathematical Modeling corresponding with formed each physical and chemical processes of coal dust firing, adopt the method for numerical simulation to obtain the number range of the inside and outside secondary wind swirl intensity of turbulent burner when making described boiler satisfy default capabilities, and according to the number range of described swirl strength, the inside and outside Secondary Air of turbulent burner is carried out air distribution.The present invention is consuming time short in numerical simulation, assesses the cost low, do not need the regulation and control at power plant scene to coordinate in implementation procedure, and analog result has good visuality.Overcome the degree of accuracy that artificial air distribution produces not high, easily can cause the unsettled problem of stove internal combustion, improved the efficiency of combustion of boiler, can greatly reduce the pollutant that produces in combustion process simultaneously.

The liquidate Secondary Air blowing system of swirl flow combustion pulverized-coal fired boiler of a kind of front and back, configuration model module, Mathematical Models module, analog module and air distribution module;

Described configuration model module, design parameter for the swirl flow combustion pulverized-coal fired boiler that liquidates according to front and back, according to the structure in turbulent burner, furnace hopper zone, burner region, burner upper area and pendant superheater zone, set up the gridding structural model of described boiler;

Described Mathematical Models module, be used for according to described gridding structural model, set up the Mathematical Modeling of the formed gas-phase turbulent flow process of coal dust firing, two flow process of gas-solid, radiant heat transfer process, Volatile process, coke combustion and nitrogen oxide generative process;

Described analog module is used for according to the described Mathematical Modeling of setting up, process of coal combustion being simulated, the number range of the inside and outside secondary wind swirl intensity of turbulent burner when obtaining described boiler and satisfying default capabilities;

Described air distribution module is used for according to the number range of described swirl strength, the inside and outside Secondary Air of turbulent burner being carried out air distribution when described boiler operatiopn.

Compare with general technology, the Secondary Air blowing system of swirl flow combustion pulverized-coal fired boiler of liquidating before and after the present invention is set up the Mathematical Modeling corresponding with formed each physical and chemical processes of coal dust firing, adopt the method for numerical simulation to obtain the number range of the inside and outside secondary wind swirl intensity of turbulent burner when making described boiler satisfy default capabilities, and according to the number range of described swirl strength, the inside and outside Secondary Air of turbulent burner is carried out air distribution.The present invention is consuming time short in numerical simulation, assesses the cost low, do not need the regulation and control at power plant scene to coordinate in implementation procedure, and analog result has good visuality.Overcome the degree of accuracy that artificial air distribution produces not high, easily can cause the unsettled problem of stove internal combustion, improved the efficiency of combustion of boiler, can greatly reduce the pollutant that produces in combustion process simultaneously.

Description of drawings

Fig. 1 is the schematic flow sheet of Secondary Air air distribution method of swirl flow combustion pulverized-coal fired boiler of liquidating before and after the present invention;

Fig. 2 is the boiler structure front view;

Fig. 3 is the boiler structure front view;

Fig. 4 is the turbulent burner structural representation;

Fig. 5 is the grid zoning schematic diagram of boiler;

Fig. 6 is the structural representation of Secondary Air blowing system of swirl flow combustion pulverized-coal fired boiler of liquidating before and after the present invention.

The specific embodiment

For further setting forth the technological means that the present invention takes and the effect that obtains, below in conjunction with accompanying drawing and preferred embodiment, to technical scheme of the present invention, know and complete description.

See also Fig. 1, be the schematic flow sheet of the Secondary Air air distribution method of the swirl flow combustion pulverized-coal fired boiler that liquidates before and after the present invention.Liquidate before and after the present invention Secondary Air air distribution method of swirl flow combustion pulverized-coal fired boiler comprises the following steps:

S101 is according to the liquidate design parameter of swirl flow combustion pulverized-coal fired boiler of front and back, according to the structure in turbulent burner, furnace hopper zone, burner region, burner upper area and pendant superheater zone, sets up the gridding structural model of described boiler;

S102 sets up the Mathematical Modeling of the formed gas-phase turbulent flow process of coal dust firing, two flow process of gas-solid, radiant heat transfer process, Volatile process, coke combustion and nitrogen oxide generative process according to described gridding structural model;

S103 simulates process of coal combustion according to the described Mathematical Modeling of setting up, the number range of the inside and outside secondary wind swirl intensity of turbulent burner when obtaining described boiler and satisfying default capabilities;

S104 carries out air distribution according to the number range of described swirl strength to the inside and outside Secondary Air of turbulent burner when described boiler operatiopn.

Take DG2060/26.15-II2 type boiler as example, according to the actual operating data of power plant, set up the Mathematical Modeling of whole burner hearth.On the basis that guarantees coal dust smooth combustion and safe operation of the boiler, change the swirl strength of the inside and outside Secondary Air of turbulent burner, burner is carried out the cold conditions simulation in full burner hearth zone, draw the adjustable extent of inside and outside secondary wind swirl intensity; Under the prerequisite of safe operation of the boiler, namely improved boiler combustion efficiency, guarantee again NO _XDischarge capacity is in critical field.

As one of them embodiment, in the step of the described gridding structural model of setting up described boiler, described design parameter comprises that furnace width, furnace height, ceiling flex point absolute altitude, horizontal flue are dark, the number of turbulent burner, the spacing of adjacent turbulent burner, the boundary condition of burner hearth entrance and the boundary condition of furnace outlet.

The complete network structure chart of boiler can be set up like this, and the accuracy of modeling can be guaranteed according to the setting parameter modeling.

In step S101, whole boiler is carried out modeling.To the 660MW of power plant boiler BMCR(Boiler Maximum Continuous Rate, boiler maximum continuous rating) operating mode is carried out modeling, when building model, turbulent burner, burner hearth, pendant superheater and enter, the condition such as export boundary condition is the boiler design parameter.

Take Shanwei, the Guangdong Province DG2060/26.15-II2 of power plant type boiler as example, this power plant is equiped with 2 660MW coal-burning steam turbine generator groups.Boiler is ultra supercritical parameter, transformation Once-through Boiler, opposed firing mode (vortex burner), solid deslagging, single burner hearth, single reheat, balanced draft, outdoor layout, all steel framework, full suspention, п type structure.Boiler main wants limiting size to see Table 1.

Table 1 boiler main is wanted limiting size

Title	Unit	Data
			Furnace width	mm	22162.4
Furnace depth	mm	15456.8
			Ceiling flex point absolute altitude	mm	72500
Horizontal flue is dark	mm	5486.4

Upper furnace has been arranged steam, pendant superheater and high temperature superheater; Horizontal flue is comprised of water-cooling wall extension and rear Yan Jing extension, internal placement high temperature reheater; After rear vertical shaft, the wall top is provided with enclosure wall superheater; Before rear vertical shaft, flue is provided with low-temperature reheater, and rear pass is provided with low temperature superheater and economizer successively.Boiler structure front view, boiler structure front view and boiler main want operational factor to see respectively Fig. 2, Fig. 3 and table 2.

Table 2 boiler main is wanted operational factor

Title	Unit	The BMCR operating mode
			The furnace outlet excess air coefficient	-	1.14
Primary air flow	Kg/s	137
			Secondary air flow (not containing after-flame wind)	Kg/s	385.6
The after-flame air quantity	Kg/s	111.2
			Primary air ratio	%	21.62
Secondary air ratio	%	78.38
			Air temperature of burner	℃	77
Burner Secondary Air temperature	℃	335
			Wind wind speed of burner	m/s	22.4
Burner inner second air wind speed	m/s	35.2
			Burner outer second air wind speed	m/s	36.4
Burnt wind direct current wind wind speed	m/s	43.3
			Burnt wind eddy flow wind wind speed	m/s	30.8

The turbulent burner structure as shown in Figure 4, coal burner is divided into four parts with combustion air: centre wind, wind, inner second air and an outer second air.Wherein, centre wind and a wind are direct current, and inside and outside Secondary Air is eddy flow, and inner second air is designed to the axial rotational flow blade, outer second air is designed to the tangential swirl blade.

This model is Opposite Firing Boiler, comprises the turbulent burner of whole burner hearth and 36 same structures, and front-back wall is arranged respectively 3 layers, and every layer has the spacing of 6 burners and adjacent burner identical.

Whole model meshes adds up to 2,270,000 left and right, design feature according to model, adopt the method for independent grid division, burner hearth is divided into 5 zones, be respectively: turbulent burner, furnace hopper zone, burner region, burner upper area and pendant superheater zone.In the process of dividing, model all adopts structured grid, turbulent burner and hearth combustor zone are suitably encrypted, in order to improve the precision of calculating, the joint face of each burner outlet and burner hearth is set to interface, prevents that the mesh quality of two two faces and mesh shape from differing greatly and causing error.

Because the turbulent burner structure is comparatively complicated, during grid division with centre wind, a wind, inside and outside secondary air channel is divided separately.It is less that the furnace hopper zone reaches the coal dust firing impact to flowing of fluid field in furnace, so this area grid is comparatively loose.Burner region is the main region of coal dust firing, and is connected with turbulent burner, and coupling part grid difference should not be too large, so burner region adopts the thin grid configuration in close centre, two ends.The grid zoning schematic diagram of boiler is seen Fig. 5.The setting of model coordinate direction can be found out, the X-axis positive direction is along the burner hearth front wall to rear wall direction, the Y-axis positive direction is along the furnace height direction, the Z axis positive direction is along the left wall of burner hearth to right wall direction, because all numerical simulations of the present invention are all to carry out on same foundation, so all coordinate directions of the present invention are all unified.

The entrance of burner hearth mainly is divided into three parts: turbulent burner, side after-flame wind, after-flame wind, the entry condition of each several part is obtained by actual operating data.Each porch turbulence intensity is stronger, so turbulence intensity is set as 10%.The line size of each entrance represents with the water conservancy equivalent diameter, and the hydraulic equivalent diameter computing formula is:

$D_H=\frac{4A}{S}$

In following formula: D _HBe the water conservancy equivalent diameter; A is the wetted perimeter area; S is the wetted perimeter diameter; The burner inlet boundary condition sees Table 3.

Outlet and wall boundary condition: in actual motion, furnace outlet is under state for little negative pressure, and therefore in simulation, furnace outlet adopts the pressure export type, and outlet pressure is set as-200pa.Furnace heating surface is set to without the static wall of slippage, and owing to carrying out the cold conditions simulation, main result is velocity field in stove, and is uncorrelated with wall surface temperature, so wall surface temperature adopts default setting, namely 77 ℃.

Table 3 burner inlet boundary condition

In step S102, the combustion process of coal dust is a comparatively complicated process, although this process is complicated, still observes three large basic law of conservation, that is: mass conservation law, the law of conservation of momentum and laws of conservation of energy in process.Relate to wherein that two of gas-phase turbulent flows, gas-solid flow, pulverized coal particle heating, coal dust Volatile, volatile matter and coke burning, the interior radiant heat transfer of stove and NO _xGeneration and the process such as reduction, this chapter has set up the required Mathematical Modeling of each process for the subject study object, model is as follows.

(1) governing equation

The numerical simulation coal dust firing is the steady-flow process of a three-dimensional, follows mass-conservation equation, momentum conservation equation and energy conservation equation, and for arbitrary chemical constituent M, the mass-conservation equation of its component is:

$\frac{\∂\mathrm{\ρ}}{\∂t}+\frac{\∂\mathrm{\ρ}{\stackrel{\‾}{u}}_i}{{\∂x}_i}=S_m$

Momentum conservation equation:

$\frac{\∂\left(\mathrm{\ρ}{\stackrel{\‾}{u}}_i\right)}{\∂t}+\frac{\∂}{{\∂x}_j}\left(\mathrm{\ρ}{\stackrel{\‾}{u}}_i{\stackrel{\‾}{u}}_j\right)=\frac{\∂}{{\∂x}_j}[\mathrm{\μ}\frac{\∂{\stackrel{\‾}{u}}_i}{{\∂x}_j}-\mathrm{\ρ}\stackrel{\‾}{u_i^{\′}{u}_j^{\′}}]-\frac{\∂p}{{\∂x}_i}+{\mathrm{\ρg}}_i$

Energy conservation equation:

$\frac{\∂\left({\mathrm{\ρc}}_p\stackrel{\‾}{T}\right)}{\∂t}+\frac{\∂}{{\∂x}_j}\left({\mathrm{\ρc}}_p\stackrel{\‾}{u_{j}T}\right)=\frac{\∂}{{\∂x}_j}[\mathrm{\λ}\frac{\∂\stackrel{\‾}{T}}{{\∂x}_j}-{\mathrm{\ρc}}_p\stackrel{\‾}{u_j^{\′}{T}^{\′}}]+S_f+S_R$

State equation:

$\mathrm{\ρ}=\mathrm{\ρ}(p,\stackrel{\‾}{T})$

In above-mentioned formula: S _m, S _f, S _RRepresent the source phase;

Average speed for reference axis x, y, three directions of z; U ' is the fluctuation velocity of reference axis x, y, three directions of z;

Be mean temperature; g _iBe i direction gravitational acceleration component; The coefficient of kinetic viscosity of μ for being caused by molecular thermalmotion; ρ is density; P is pressure.

(2) vapor phase stream movable model

Simulation use both sides' journey turbulence model can be used for the comparatively complicated Fluid Flow in A of simulation, and simulate effect is better during gas-phase turbulent flow, and on limited computer resource basis, amount of calculation is less, and is therefore comparatively general in application.

Both sides' journey turbulence model is divided into by the fluid-flow mode difference: standard k-ε model, RNG k-ε model and realizable k-ε model.Standard k-ε model is fit to be applied to the general of fluid and flows, and RNG k-ε model is fit to be applied to that rotating machinery produces flows, realizable k-ε model be fit to be applied to the flow field problem such as the rotating jet, backflow of fluid,

Object of the present invention comprises flowing of turbulent burner and opposite-flushing type boiler furnace gas thereof, in Fluid Flow in A, the phenomenons such as rotating jet and backflow can appear, therefore turbulence model is selected the realizable k-ε model with swirling modification, considered the impact of swirl flow, can flow by the simulate eddy flow.

$\frac{\∂\left(\mathrm{\ρk}\right)}{\∂t}+\frac{\∂\left({\mathrm{\ρku}}_i\right)}{{\∂x}_i}=\frac{\∂}{{\∂x}_j}\left[(\mathrm{\μ}+\frac{{\mathrm{\μ}}_t}{{\mathrm{\σ}}_k})\frac{\∂k}{{\∂x}_j}\right]+G_k-\mathrm{\ρ\ϵ}$

$\frac{\∂\left(\mathrm{\ρ\ϵ}\right)}{\∂t}+\frac{\∂\left({\mathrm{\ρ\ϵu}}_i\right)}{{\∂x}_j}=\frac{\∂}{{\∂x}_j}(\mathrm{\μ}+\frac{{\mathrm{\μ}}_t}{{\mathrm{\σ}}_{\mathrm{\ϵ}}})+{\mathrm{\ρC}}_1\mathrm{S\ϵ}-{\mathrm{\ρC}}_2\frac{{\mathrm{\ϵ}}^2}{k+\sqrt{\mathrm{v\ϵ}}}$

$C_1=\max [0.43,\frac{\mathrm{\η}}{\mathrm{\η}+5}]$

η＝Sk/ε

In above-mentioned formula: k is the turbulent flow energy; ε is dissipative shock wave; μ _tBe coefficient of eddy viscosity; σ _kAnd σ _εIt is respectively the turbulent prandtl number of turbulent flow energy and dissipative shock wave thereof; G _kThe turbulent flow that expression causes due to average velocity gradient can produce item; C ₂Be constant; S is the mean strain rate; V is the molecular motion viscosity.

(3) Dual-Phrase Distribution of Gas olid movable model

Turbulent burner is the entrance of air, is also the entrance of coal dust, therefore needs to consider the gas-solid phase flow model.In process of coal combustion, fluid turbulent needs to consider on the randomness impact of pulverized coal particle, so the orbiting motion of pulverized coal particle adopts Stochastic Separated Flow Model.The equation of motion of pulverized coal particle is as follows:

$\frac{{\mathrm{du}}_p}{\mathrm{dt}}=F_D(u-u_p)+\frac{g_x({\mathrm{\ρ}}_p-\mathrm{\ρ})}{{\mathrm{\ρ}}_p}+F_x$

In following formula: F _D(u-u _p) be the suffered tractive force of particle unit mass; U is gaseous substance speed; ρ _pBe grain density; ρ is gaseous substance density; F _xSummation for suffered other power of particle.

(4) radiation model

Furnace heat transfer mainly contains radiant heat transfer and heat convection, and because temperature in stove is higher, heat convection only accounts for the very little part of total heat exchange amount, can ignore, so furnace heat transfer can be seen the radiant heat transfer process as.For coal dust firing, this model has adopted P-1 radiation model.

Radiant heat flux:

$q_r=-\frac{1}{3(a+{\mathrm{\σ}}_s)-{\mathrm{C\σ}}_s}\▿G$

In following formula: C is linear each diversity phase function coefficient; A is absorption coefficient; σ _sBe scattering coefficient; G is incident radiation;

Introduce parameter Γ:

$\mathrm{\Γ}=\frac{1}{3(a+{\mathrm{\σ}}_s)-{\mathrm{C\σ}}_s}$

The radiant heat flux formula can be converted into:

q _r＝-Γ▽G

The Boltzman transport equation Boltzmann of G is:

-▽(Γ▽G)-aG+4aσT ⁴＝0

In following formula: σ is this Boltzmann's constant;

Merge two formulas, obtain following formula:

-▽q _r＝aG-4aσT ⁴

General-▽ q _rBring energy equation into, thereby obtain due to the caused calorie source of radiation.

(5) Volatile model

The coal dust decomposes is the process of a complexity, and the thermal decomposition product temperature influence is larger, selects appropriate Volatile model, can improve the accuracy of coal dust firing numerical simulation.Volatile of the present invention adopts two step competitive precipitation models, and reactional equation is:

$\frac{\mathrm{dV}}{\mathrm{dt}}=\frac{{\mathrm{dV}}_1+{\mathrm{dV}}_2}{\mathrm{dt}}(a_1{K}_1+a_2{K}_2)$

$\frac{\mathrm{dC}}{\mathrm{dt}}=-(K_1+K_2)C$

In formula: a ₁, a ₂Be coefficient, determined by experiment; C is the ratio of unconverted coal in residual carbon; K ₁, K ₂Be constant;

When temperature was low, first formula played a major role, and when temperature was higher, second formula played a major role.

(6) coke combustion model

Coke is the remainder that fugitive constituent is separated out rear coal dust, coal dust is in temperature during less than 1000 ℃, burning velocity depends mainly on the chemical reaction kinetics factor, after temperature is greater than 1400 ℃, burning depends mainly on the diffusion velocity of O2, therefore power/diffusing surface rate process model is adopted in the burning of this paper coke, and coke burning global rate constant is:

$k=\frac{1}{1/k_s+1/k_d}$

k _s＝A _cT ^Nexp[-E _c(RT)]

k _d＝φShD ₀δ _p

In formula: k _sBe kinetic constant; k _dBe the volume diffusion constant; A _cBe pre-exponential factor; E _cBe activation energy; φ is the chemical equivalent factor; Sh is the particle mass tranfer coefficient; D ₀Be diffusion coefficient; δ _pBe particle diameter.

(7) NOx generation model

In the stove combustion process, the ratio that the growing amount of NOx accounts for the total growing amount of gas phase is very little, the generation reduction reaction process of NOx can not exert an influence substantially to temperature field in furnace, velocity field and each material concentration field computation result substantially, therefore the present invention adopts the method for post processing to the simulation of NOx, namely first whole burner hearth is carried out thermal simulation, utilize the fluid field in furnace that calculates after restraining to carry out generation-reduction reaction of NOx.Studies show that, utilize NOx result and the actual conditions that this method obtains to meet better, therefore proved the reasonability that adopts the NOx generation model.The present invention has ignored Quick-type NOx, adopts the Desoete mechanism model, thinks that fugitive constituent N first is converted into intermediate product NH3 and HCN, and then further reaction generates NOx, and char N is directly reacted generation NOx.

As one of them embodiment, after the described step of setting up Mathematical Modeling, comprise the step that adopts cold test that the described Mathematical Modeling of setting up is verified:

Described boiler is carried out cold test, obtain cold state experimental results;

Adopt described Mathematical Modeling to carry out the cold conditions simulation to described boiler, obtain the cold conditions analog result;

Described cold conditions analog result and described cold state experimental results are compared, verify whether described Mathematical Modeling satisfies default index.

The Mathematical Modeling of setting up is verified, can be guaranteed the accuracy of model before numerical simulation.Only have in the situation that has satisfied default index, just carry out numerical simulation, avoided the unnecessary wasting of resources.

Under former design conditions, the swirl strength Ω 1=0.58 of the inner second air of burner, the swirl strength Ω 2=0.58 of outer second air, the angle that is inner second air axial blade and axis direction is 30 °, the angle of outer second air tangential vane and center of circle direction is 60 °, and along with the increase of inner second air angle, the swirl strength of inner second air strengthens gradually, and outer two wind present opposite trend.

Identical and be equally spaced due to burner structure, therefore only need the analog result of adjacent two burners of comparative analysis and near burner hearth thereof, according to the cold flow field analog result of certain two adjacent burner, wherein the swirl strength of inside and outside Secondary Air is 0.58.Hence one can see that, and on the burner axis direction, the recirculating zone, center appears in the burner outlet distance scope of rear wall 0.8 to 2.2m, and wherein distance is that backflow phenomenon in 1.4 to 2m zones is the most obvious.

In order to verify the feasibility of cold conditions numerical simulation, the cold test of having carried out under identical operating mode is measured.Place long ribbon at burner outlet, observe the flow field situation by the deflection of ribbon.Cold test finds that primary air jet rigidity is more intense in the zone of distance burner nozzle 1 to 2m; In distance spout 2 to 5m zones, ribbon deflects, and ribbon end off-axis is 600mm approximately.This shows that cold conditions numerical simulation result of the present invention is consistent with test aspect qualitative, thereby has verified the feasibility of method for numerical simulation.

As one of them embodiment, if the gap between described cold conditions analog result and described cold state experimental results is less than or equal to preset difference value, judge that described Mathematical Modeling satisfies default index.

Judge that by preset difference value Mathematical Modeling satisfies default index, make deterministic process that the standard that quantizes arranged, improved efficient.

The effect of recirculating zone, center is entrainment the high-temperature flue gas that has caught fire and it is refluxed, near the breeze airflow burner outlet provides ignition heat and activation energy.If center, recirculating zone and burner outlet apart from each other can not provide stable thermal source, easily cause the coal dust firing wild effect.

The recirculating zone, center plays an important role to steady combustion in coal powder ignition process and stove, analyzes and studied wind swirl strength to inside and outside secondary by changing the recirculating zone, center.Result and the cold conditions experiment of simulation are compared analysis, see Table 4, two kinds of data results substantially identical, show that the result of modeling is comparatively accurate, can be used for the sunykatuib analysis that the inside and outside Secondary Air eddy flow of burner flows.

The result contrast of table 4 numerical simulation and cold conditions experiment

Title	Numerical simulation	The cold conditions experiment
			Recirculating zone, center scope	0.8 to 2.2	0.5 to 2
The recirculating zone scope is stablized at the center	1.4 to 2	1.4 to 2
			Almost without range of circulating flow	>3	>3

To the BMCR condition model, carry out the cold conditions simulation, the verification model reliability on this basis, changes the swirl strength of the inside and outside Secondary Air of turbulent burner, carries out the cold conditions simulation of different operating modes.Analyze the adjustable extent separately of inside and outside secondary wind swirl intensity.

In step S103, the effect of outer second air is to provide the air that coal dust completing combustion needs, and cool burner outlet simultaneously and near water-cooling wall thereof prevent that burner is burned or the water-cooling wall coking.The outer second air swirl strength of this burner is controlled by tangential vane, and blade has the effect of switch air door, and aperture is less, and swirl strength is larger, and the area that forms the recirculating zone, center is larger, more is beneficial to coal dust and fully mixes with air-flow in stove.May cause that gas stream in the stove produces finning yet swirl strength is excessive, undercompounding during due to coal dust firing, the mobility of breeze airflow is affected, the hot-spot phenomenon can appear in the burner near zone, cause that water-cooling wall burns out or coking, thereby bring extremely adverse influence to boiler operatiopn.Therefore, when Ω 1=0.58, the parameter of outer second air changes as shown in table 5, and wherein the Secondary Air inclination angle is the angle of tangential vane airflow direction and vertical direction.

The parameter of table 5 outer second air

Operating mode	Ω2	The outer second air inclination angle/(°)
			1	0.58	60
2	0.84	50
			3	1	45
4	1.2	40

When Ω 1=0.58, can obtain the flow field track of the different swirl strengths of outer second air, the situation of change of recirculating zone when table 6 is the different swirl strength of outer second air.By operating mode 1～3 as can be known, the center, recirculating zone is gradually away from burner axis, and the length of recirculating zone increases gradually, and the area of recirculating zone increases.Yet in operating mode 4, the recirculating zone, center has been displaced near two water-cooling walls between burner, and the recirculating zone of formation is unstable, and most of air-flow is adherent to flow, begin to occur finning in stove, this moment, coal dust firing can cause the accident that in stove, water-cooling wall is burned.This shows, the recirculating zone, center is subjected to the impact of outer second air swirl strength, the swirl strength adjustable range of outer second air can only be 0.58～1, when swirl strength greater than 1 the time, can not form fluid field in furnace preferably, this is larger on the boiler operatiopn impact, may cause the accident that water-cooling wall coking and burner outlet are burned.

The situation of change of recirculating zone during the different outer second air swirl strength of table 6

The effect of inner second air is recirculating zone, formation center, entrainments the furnace high-temperature flue gas and it is delivered near burner outlet coal powder ignition zone, is used for firing coal-dust and smooth combustion.The inner second air of this burner is formed by the axial rotational flow blade, and blade tilt is the angle between axial direction and blade.When Ω 2=0.58, the parameter of inner second air is as shown in table 7.Angle is larger, and the swirl strength of inner second air is larger.

When Ω 2=0.58, can obtain the flow field track of the different swirl strengths of inner second air, the situation of change of recirculating zone when table 8 is the different swirl strength of inner second air.By operating mode 1,5～7 as can be known, along with the inner second air swirl strength increases, the center, recirculating zone begins away from the burner outlet axis, reflux area length increases, recirculation area increases, and has simultaneously a swirl strength limiting value, and swirl strength is crossed conference generation finning.The adjustable extent of inner second air swirl strength is 0.58～2.74, as Ω 1〉2.74 the time, the gas stream in the stove finning easily occurs.

The parameter of table 7 inner second air

Operating mode	Ω1	The inner second air inclination angle/(°)
			1	0.58	30
5	1	45
			6	2.74	70
7	3.27	75

The situation of change of recirculating zone during the different inner second air swirl strength of table 8

By operating mode 1～7 as can be known, when changing swirl strength separately, the adjustable extent of the swirl strength of inner second air and outer second air is respectively 0.58～2.74 and 0.58～1.00.Because the inside and outside Secondary Air of burner is all eddy flow, the recirculating zone, center is formed by adjacent swirl jet, determines but the formation of recirculating zone, center is average swirl strength by Secondary Air.Inner second air is the internal layer eddy flow wind of burner, is subject to the factor impacts such as centre wind, wind and outer second air, and when increasing the swirl strength of inner second air, outer second air plays the effect on a swirl strength border, is restricting the change of inner second air.Yet outer second air is the outer eddy flow wind of burner, only is subjected to the impact of inner second air, and the restraining factors that are subject to are less, when increasing the swirl strength of outer second air, although inner second air can produce to outer second air the effect of a gravitation, affects less.Therefore, the swirl strength outer second air adjustable extent of this turbulent burner is less, and the adjustable extent of inner second air is larger.

In step S104, those of ordinary skills can adopt the whole bag of tricks to carry out air distribution to the inside and outside Secondary Air of turbulent burner after reading this patent.For example, adopt computer software directly to set, perhaps by the operation of boiler being set etc.

As one of them embodiment, described number range according to described swirl strength is carried out the step of air distribution to the inside and outside Secondary Air of turbulent burner, comprise the following steps:

Choose the numerical value of inside and outside secondary wind swirl intensity in described number range, turbulent burner is carried out the air distribution of inside and outside Secondary Air.

The number range that obtains according to numerical simulation is carried out the air distribution of Secondary Air, can improve the accuracy of air distribution.Make the result of numerical simulation be used by engineering practice, the series of problems of having avoided artificial air distribution to cause.

As one of them embodiment, after the step of the described air distribution that turbulent burner is carried out inside and outside Secondary Air, comprise the following steps:

In the running of described boiler, during greater than the maximum of described number range or less than the minimum of a value of described number range, send alarm signal when the swirl strength of the inside and outside Secondary Air of turbulent burner.

The number range that numerical simulation obtains also can be used for the running status of boiler is monitored, if the swirl strength of inside and outside Secondary Air has been broken through described number range, illustrates that problem might appear in boiler operatiopn.

The present invention is directed to certain 660MW of power plant face-fired boiler and carried out numerical simulation, and compare with measurement data, verified the reliability that having of analog result is higher.On the basis of former design conditions, by changing the swirl strength of the inside and outside Secondary Air of turbulent burner, can obtain:

When the swirl strength of inside and outside Secondary Air increased separately, the trend that the recirculating zone, center changes was identical.Increase along with swirl strength, the recirculating zone, center begins away from the burner outlet axial location, reflux area length increases, recirculation area increases, but swirl strength is during greater than a certain numerical value, can not form recirculating zone, good center, finning easily occurs, and brings adverse influence to boiler operatiopn;

Will form stable recirculating zone, center in stove and finning does not occur, the adjustable extent of inner second air and outer second air swirl strength is respectively 0.58～2.74 and 0.58～1.00;

The swirl strength of outer second air is larger on the impact of recirculating zone, and adjustable range is less, and the adjustable extent of inner second air is larger.In the adjusting of reality, should be take the swirl strength of adjusting inner second air as main, and the swirl strength of outer second air tries not to adjust.

Compare with general technology, the Secondary Air air distribution method of swirl flow combustion pulverized-coal fired boiler of liquidating before and after the present invention is set up the Mathematical Modeling corresponding with formed each physical and chemical processes of coal dust firing, adopt the method for numerical simulation to obtain the number range of the inside and outside secondary wind swirl intensity of turbulent burner when making described boiler satisfy default capabilities, and according to the number range of described swirl strength, the inside and outside Secondary Air of turbulent burner is carried out air distribution.The present invention is consuming time short in numerical simulation, assesses the cost low, do not need the regulation and control at power plant scene to coordinate in implementation procedure, and analog result has good visuality.Overcome the degree of accuracy that artificial air distribution produces not high, easily can cause the unsettled problem of stove internal combustion, improved the efficiency of combustion of boiler, can greatly reduce the pollutant that produces in combustion process simultaneously.

See also Fig. 6, be the structural representation of the Secondary Air blowing system of the swirl flow combustion pulverized-coal fired boiler that liquidates before and after the present invention.

Liquidate before and after the present invention Secondary Air blowing system of swirl flow combustion pulverized-coal fired boiler comprises configuration model module 601, Mathematical Models module 602, analog module 603 and air distribution module 604;

Described configuration model module 601, design parameter for the swirl flow combustion pulverized-coal fired boiler that liquidates according to front and back, according to the structure in turbulent burner, furnace hopper zone, burner region, burner upper area and pendant superheater zone, set up the gridding structural model of described boiler;

Described Mathematical Models module 602, be used for according to described gridding structural model, set up the Mathematical Modeling of the formed gas-phase turbulent flow process of coal dust firing, two flow process of gas-solid, radiant heat transfer process, Volatile process, coke combustion and nitrogen oxide generative process;

Described analog module 603 is used for according to the described Mathematical Modeling of setting up, process of coal combustion being simulated, the number range of the inside and outside secondary wind swirl intensity of turbulent burner when obtaining described boiler and satisfying default capabilities;

Described air distribution module 604 is used for according to the number range of described swirl strength, the inside and outside Secondary Air of turbulent burner being carried out air distribution when described boiler operatiopn.

As one of them embodiment, described design parameter comprises that furnace width, furnace height, ceiling flex point absolute altitude, horizontal flue are dark, the number of turbulent burner, the spacing of adjacent turbulent burner, the boundary condition of burner hearth entrance and the boundary condition of furnace outlet.

The complete network structure chart of boiler can be set up like this, and the accuracy of modeling can be guaranteed according to the setting parameter modeling.

As one of them embodiment, described air distribution module is used for choosing the numerical value of inside and outside secondary wind swirl intensity in described number range, turbulent burner is carried out the air distribution of inside and outside Secondary Air.

The number range that obtains according to numerical simulation is carried out the air distribution of Secondary Air, can improve the accuracy of air distribution.Make the result of numerical simulation be used by engineering practice, the series of problems of having avoided artificial air distribution to cause.

As one of them embodiment, also comprise alarm module, described alarm module is used for the running at described boiler, during greater than the maximum of described number range or less than the minimum of a value of described number range, sends alarm signal when the swirl strength of the inside and outside Secondary Air of turbulent burner.

The number range that numerical simulation obtains also can be used for the running status of boiler is monitored, if the swirl strength of inside and outside Secondary Air has been broken through described number range, illustrates that problem might appear in boiler operatiopn.

Compare with general technology, the Secondary Air blowing system of swirl flow combustion pulverized-coal fired boiler of liquidating before and after the present invention is set up the Mathematical Modeling corresponding with formed each physical and chemical processes of coal dust firing, adopt the method for numerical simulation to obtain the number range of the inside and outside secondary wind swirl intensity of turbulent burner when making described boiler satisfy default capabilities, and according to the number range of described swirl strength, the inside and outside Secondary Air of turbulent burner is carried out air distribution.The present invention is consuming time short in numerical simulation, assesses the cost low, do not need the regulation and control at power plant scene to coordinate in implementation procedure, and analog result has good visuality.Overcome the degree of accuracy that artificial air distribution produces not high, easily can cause the unsettled problem of stove internal combustion, improved the efficiency of combustion of boiler, can greatly reduce the pollutant that produces in combustion process simultaneously.

The above embodiment has only expressed several embodiment of the present invention, and it describes comparatively concrete and detailed, but can not therefore be interpreted as the restriction to the scope of the claims of the present invention.Should be pointed out that for the person of ordinary skill of the art, without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection domain of patent of the present invention should be as the criterion with claims.

Claims (10)

1. the front and back Secondary Air air distribution method of swirl flow combustion pulverized-coal fired boiler that liquidates, is characterized in that, comprises the following steps:

According to the liquidate design parameter of swirl flow combustion pulverized-coal fired boiler of front and back, according to the structure in turbulent burner, furnace hopper zone, burner region, burner upper area and pendant superheater zone, set up the gridding structural model of described boiler;

According to described gridding structural model, set up the Mathematical Modeling of the formed gas-phase turbulent flow process of coal dust firing, two flow process of gas-solid, radiant heat transfer process, Volatile process, coke combustion and nitrogen oxide generative process;

According to the described Mathematical Modeling of setting up, process of coal combustion is simulated the number range of the inside and outside secondary wind swirl intensity of turbulent burner when obtaining described boiler and satisfying default capabilities;

When described boiler operatiopn, according to the number range of described swirl strength, the inside and outside Secondary Air of turbulent burner is carried out air distribution.

2. the front and back according to claim 1 Secondary Air air distribution method of swirl flow combustion pulverized-coal fired boiler that liquidates, it is characterized in that, in the step of the described gridding structural model of setting up described boiler, described design parameter comprises that furnace width, furnace height, ceiling flex point absolute altitude, horizontal flue are dark, the number of turbulent burner, the spacing of adjacent turbulent burner, the boundary condition of burner hearth entrance and the boundary condition of furnace outlet.

3. the front and back according to claim 1 Secondary Air air distribution method of swirl flow combustion pulverized-coal fired boiler that liquidates, it is characterized in that, after the step of the described Mathematical Modeling of setting up the formed gas-phase turbulent flow process of coal dust firing, two flow process of gas-solid, radiant heat transfer process, Volatile process, coke combustion and nitrogen oxide generative process, comprise the step that adopts cold test that the described Mathematical Modeling of setting up is verified:

Described boiler is carried out cold test, obtain cold state experimental results;

Adopt described Mathematical Modeling to carry out the cold conditions simulation to described boiler, obtain the cold conditions analog result;

Described cold conditions analog result and described cold state experimental results are compared, verify whether described Mathematical Modeling satisfies default index.

4. the front and back according to claim 3 Secondary Air air distribution method of swirl flow combustion pulverized-coal fired boiler that liquidates, it is characterized in that, if the gap between described cold conditions analog result and described cold state experimental results is less than or equal to preset difference value, judge that described Mathematical Modeling satisfies default index.

5. the front and back according to claim 1 Secondary Air air distribution method of swirl flow combustion pulverized-coal fired boiler that liquidates, is characterized in that, described number range according to described swirl strength is carried out the step of air distribution to the inside and outside Secondary Air of turbulent burner, comprise the following steps:

Choose the numerical value of inside and outside secondary wind swirl intensity in described number range, turbulent burner is carried out the air distribution of inside and outside Secondary Air.

6. the front and back according to claim 5 Secondary Air air distribution method of swirl flow combustion pulverized-coal fired boiler that liquidates, is characterized in that, after the step of the described air distribution that turbulent burner is carried out inside and outside Secondary Air, comprises the following steps:

In the running of described boiler, during greater than the maximum of described number range or less than the minimum of a value of described number range, send alarm signal when the swirl strength of the inside and outside Secondary Air of turbulent burner.

7. the front and back Secondary Air blowing system of swirl flow combustion pulverized-coal fired boiler that liquidates, is characterized in that, comprises configuration model module, Mathematical Models module, analog module and air distribution module;

Described configuration model module, design parameter for the swirl flow combustion pulverized-coal fired boiler that liquidates according to front and back, according to the structure in turbulent burner, furnace hopper zone, burner region, burner upper area and pendant superheater zone, set up the gridding structural model of described boiler;

Described Mathematical Models module, be used for according to described gridding structural model, set up the Mathematical Modeling of the formed gas-phase turbulent flow process of coal dust firing, two flow process of gas-solid, radiant heat transfer process, Volatile process, coke combustion and nitrogen oxide generative process;

Described analog module is used for according to the described Mathematical Modeling of setting up, process of coal combustion being simulated, the number range of the inside and outside secondary wind swirl intensity of turbulent burner when obtaining described boiler and satisfying default capabilities;

Described air distribution module is used for according to the number range of described swirl strength, the inside and outside Secondary Air of turbulent burner being carried out air distribution when described boiler operatiopn.

8. the front and back according to claim 7 Secondary Air blowing system of swirl flow combustion pulverized-coal fired boiler that liquidates, it is characterized in that, described design parameter comprises that furnace width, furnace height, ceiling flex point absolute altitude, horizontal flue are dark, the number of turbulent burner, the spacing of adjacent turbulent burner, the boundary condition of burner hearth entrance and the boundary condition of furnace outlet.

9. the front and back according to claim 7 Secondary Air blowing system of swirl flow combustion pulverized-coal fired boiler that liquidates, it is characterized in that, described air distribution module is used for choosing the numerical value of inside and outside secondary wind swirl intensity in described number range, turbulent burner is carried out the air distribution of inside and outside Secondary Air.

10. the front and back according to claim 9 Secondary Air blowing system of swirl flow combustion pulverized-coal fired boiler that liquidates, it is characterized in that, also comprise alarm module, described alarm module is used for the running at described boiler, during greater than the maximum of described number range or less than the minimum of a value of described number range, send alarm signal when the swirl strength of the inside and outside Secondary Air of turbulent burner.

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