CN102354330A - Method for optimizing parameters of ammonia-spraying device for matching sprayed ammonia with smoke airflow field in smoke denitration system - Google Patents

Abstract

The invention discloses a method for optimizing parameters of an ammonia-spraying device for matching sprayed ammonia with a smoke airflow field in a smoke denitration system. The method comprises the following steps of: establishing a functional relation of an ammonia/nitrogen relative concentration deviation and geometric design parameters of the ammonia-spraying device; selecting m initial sample points and performing numerical calculation on an ammonia-spraying device parameterization model established based on the sample points, thereby acquiring the concentration deviation corresponding to different geometric design parameters; and establishing an optimizing model and calculating a mathematical model, thereby acquiring the geometric parameters of the ammonia-spraying device with a minimum concentration deviation. Combined with an optimizing process, the method also can be used for developing a more efficient and feasible ammonia-spraying device and further promoting the whole running efficiency of an SCR (Selective Catalytic Reduction) denitration system.

Description

The ammonia-gas spraying device parameter optimization method of spray ammonia and flue gas flow field coupling in the flue gas denitrification system

Technical field

The present invention relates to a cover power-plant flue gas denitrating system ammonia-gas spraying device Parameter Optimization method; Especially be directed against in the selective catalytic reduction flue gas denitration system ammonia-gas spraying device Parameter Optimization method of the cover system that spray ammonia situation must propose with the key issue of flue gas Non-uniform Currents coupling.

Background technology

(Selective Catalytic Reduction is under catalyst action SCR) to the selective catalytic reduction denitrating flue gas, is that reductive agent becomes nitrogen and water with decompose nitrogen oxides in the flue gas with ammonia.In the SCR denitrating system, ammonia must can guarantee that just itself and reactant (oxides of nitrogen in the flue gas) fully combine with flue gas mixing fully and uniformly, and to this, good spray ammonia system has played vital role.The main target of SCR denitrating system ammonia-gas spraying device design is: under flue gas design point flow conditions; Particularly to the uneven situation of nitrous oxides concentration field distribution in velocity of flue gas field in the flue and the flue gas; Through to the ammonia-gas spraying device optimization Design of Geometric Parameters; Making that nitrous oxides concentration distributes in spray ammonia and the flue gas is complementary, and realizes that ammonia and flue gas are abundant and mix uniformly in the length of mixing that designs.

Common ammonia-gas spraying device has ammonia-spraying grid or the ammonia-gas spraying device of multi-point injection form such as the spray gun of prewhirling, and typical vortex mixer ammonia-gas spraying device.One of gordian technique of design ammonia-gas spraying device is the interrelated geometrical parameters how spray ammonia point rationally is set, and in the length of mixing of design, fully mixes uniformly with flue gas to realize ammonia.At present mostly be according to engineering experience or numerical experimentation preferred several times; Spray arranging of ammonia point with certain spacing than tentatively being provided with; It is controlled again ammonia-gas spraying device to be designed to the quadrant-type subregion in addition; When promptly in the engineering actual moving process, nitrous oxides concentration being analyzed continuously, the distribution through manual adjustments valve regulation ammonia mixes ammonia and flue gas.But; The distribution of interior velocity of flue gas field of flue and nitrous oxides concentration field is difficult to satisfy uniformity requirement in the actual engineering; And be very complicated; Adopt quadrant-type subregion regulation and control spray ammonia to distribute to be difficult to and guarantee to spray in ammonia and the flue gas nitrous oxides concentration and distribute and be complementary, also abundant and mixed uniformly in the length of mixing that designs with regard to being difficult to realize ammonia and flue gas.In addition, also can know by the above, to spray ammonia situation must with the key issue of flue gas Non-uniform Currents coupling, lack a kind of method for designing of system all the time.

Summary of the invention

Technical matters to be solved by this invention is not enough to above-mentioned prior art, and from the engineering design requirement, in conjunction with agent model technology and optimization method, has proposed a kind of ammonia-gas spraying device Parameter Optimization method of spraying ammonia and flue gas flow field coupling.

For solving the problems of the technologies described above, the technical scheme that the present invention adopts is: the ammonia-gas spraying device parameter optimization method of spray ammonia and flue gas flow field coupling in a kind of flue gas denitrification system is characterized in that containing following steps:

1. make up the funtcional relationship δ=f (g of ammonia/nitrogen relative concentration deviation and ammonia-gas spraying device geometry design parameter ₁, g ₂, L, g _n);

2. choose m initial sample point, and the ammonia-gas spraying device parameterized model of setting up based on this sample point is carried out numerical evaluation, to obtain the corresponding concentration deviation δ of different geometry design parameter:

C _iBe the ammonia/nitrogen concentration ratio of test point, n is the number of test point,

Mathematical mean for all test point ammonia/nitrogen concentration ratio;

3. set up Optimization Model:

MIN：δ＝f(g ₁，g ₂，L，g _n)

$s.t.\left\{\begin{array}{c}{g}_{i,\min }\≤g_i\≤g_{i,\max }(i=\mathrm{1,2},L,n)\\ U_{\min }\≤U\≤U_{\max }\\ L\end{array}\right.$

Ammonia-gas spraying device geometric parameter when calculating with acquisition Cmin deviation to this mathematical model.

Described function f (g ₁, g ₂, L, g _n)=a ₀+ a ₁g ₁+ a ₂g ₂+ a ₃g ₃+ L, g in the formula ₁, g ₂, L, g _nFor describing n geometric parameter of ammonia-gas spraying device, a ₀, a ₁, a ₂, a ₃L is an equation coefficient.

Beneficial effect

1) the present invention is a kind of general ammonia-gas spraying device Parameter Optimization method.Mainly be through to the crucial optimization Design of Geometric Parameters of ammonia-gas spraying device, nitrous oxides concentration distributed be complementary, realize that ammonia and flue gas are abundant and mix uniformly in the length of mixing that designs.Generally be applicable to the ammonia-gas spraying device of multi-point injection forms such as the ammonia-spraying grid or the spray gun of prewhirling, and vortex mixer formula ammonia-gas spraying device.

2) numerical simulation technology has been widely used in spraying in ammonia and the design effort that flue gas mixes, but mostly is based on specific dimensions or specific operation is set up the analytical work that the ammonia-gas spraying device model carries out ammonia/flue gas, inevitably will carry out repeated calculation.And the agent model here technology provides a feasible approach for reducing the computing cost, in addition, combines with optimisation technique and also can develop more efficient, feasible ammonia-gas spraying device, further improves the overall operation efficiency of SCR denitrating system.

Description of drawings

Fig. 1 flue spray ammonia schematic cross-section.

Spray ammonia point spray ammonia and flue gas mixing synoptic diagram in Fig. 2 flue.

Wherein: 1 flue; 2 spray ammonia cross sections; 3 spray ammonia points.

Embodiment

1) designing requirement analysis and initial scheme design.

1. select independently crucial geometric parameter to describe the ammonia spray site and (promptly confirm the geometry design parameter of ammonia-gas spraying device: g ₁, g ₂, L, g _n), and set up parameterized model.

2. set the length of mixing of ammonia/flue gas and after mixing length the blending degree of ammonia and flue gas, represent that with relative concentration deviation δ (concentration deviation δ is defined as

C _iBe the ammonia/nitrogen concentration ratio of test point, n is the number of test point, Mathematical mean for all test point ammonia/nitrogen concentration ratio).

3. flue physical dimension and spray ammonia effluxvelocity U etc. select according to the engineering actual conditions as design constraint.

2) parameterized model optimal design.

1. under SCR denitrating system design point condition, make up the funtcional relationship δ=f (g of ammonia/nitrogen concentration deviation and ammonia-gas spraying device geometry design parameter ₁, g ₂, L, g _n)

(this function can be described as polynomial form: f (g ₁, g ₂, L, g _n)=a ₀+ a ₁g ₁+ a ₂g ₂+ a ₃g ₃+ L, g in the formula ₁, g ₂, L, g _nFor describing n geometric parameter of ammonia-gas spraying device, a ₀, a ₁, a ₂, a ₃L is an equation coefficient);

2. at first; Select for use certain test design method to choose m initial sample point (m organizes geometry design parameter); And the ammonia-gas spraying device parameterized model of setting up based on this sample point carried out numerical simulation calculation, to obtain the corresponding concentration deviation δ of different geometry design parameter.Then, generate funtcional relationship (the coefficient a in promptly definite equation of above-mentioned concentration deviation and ammonia-gas spraying device geometric parameter by this sample ₀, a ₁, a ₂, a ₃L).And with this as the agent model in the follow-up optimal design process.

Need point out; In the general actual engineering on the spray ammonia cross section velocity of flue gas distribute and flue gas in nitrous oxides concentration distribute and be difficult to satisfy uniformity requirement; Therefore; When adopting method for numerical simulation that sample point ammonia-gas spraying device model is carried out numerical evaluation, need velocity of flue gas and nitrous oxides concentration distribution situation are described as boundary value condition accurately.

3. set up Optimization Model:

MIN：δ＝f(g ₁，g ₂，L，g _n)

$s.t.\left\{\begin{array}{c}{g}_{i,\min }\≤g_i\≤g_{i,\max }(i=\mathrm{1,2},L,n)\\ U_{\min }\≤U\≤U_{\max }\\ L\end{array}\right.$

And select for use a kind of optimized Algorithm that this mathematical model is calculated, the ammonia-gas spraying device geometry design parameter during with acquisition Cmin deviation.

3) Performance Evaluation of design result and optimization.

Geometric parameter and ammonia/nitrogen concentration deviation index engineering demands whether in the examination ammonia-gas spraying device design proposal; If can meet design requirement; Then the design of this ammonia-gas spraying device is successful, otherwise revises design proposal, adjustment geometric parameter value; Again be optimized design, until designing the ammonia-gas spraying device that meets design requirement.

Below in conjunction with an example, method for designing and flow process that the present invention is proposed describe.

Fig. 1 and Fig. 2 have provided in the flue spray ammonia point respectively and have arranged and spray the synoptic diagram that ammonia mixes with flue gas.The flue sectional dimension is 3.6m * 1.8m.Flue gas flow rate is linear from the bottom to top in the flue increases, and describes with function u=2.0+8.0y (m/s).

1) designing requirement analysis and initial scheme design

1. be oxides of nitrogen in the effective elimination flue gas, the layout of spray ammonia point needs to adapt with the velocity of flue gas field, needs y among Fig. 2 ₁～y ₃(y ₀, y ₄=(1.8-y ₁-y ₂-y ₃)/2) the spray ammonia spacing of describing is analyzed design.

2. requiring the mixing length of ammonia/flue gas is 6.5m, and ammonia concentration deviation δ is not more than 5% after mixing length.

3. with flue physical dimension and the maximum effluxvelocity 40 of spray ammonia (m/s) as design constraint.

2) parameterized model optimal design

1. make up quadratic polynomial response surface agent model

$\mathrm{\δ}=a_0+a_1{y}_1+a_2{y}_2+a_3{y}_4+a_4{y}_1^2+a_5{y}_2^2+a_6{y}_3^2+a_7{y}_1{y}_2+a_8{y}_2{y}_3+a_9{y}_1{y}_3$

2. obtain 39 groups of sample datas (δ, y through numerical simulation calculation ₁, y ₂, y ₃), and generate above-mentioned agent model by this sample data, it is following promptly to obtain the agent model coefficient:

3. on above-mentioned agent model basis, set up the computation optimization mathematical model:

$\mathrm{MIN}:\mathrm{\δ}-5\%=a_0+a_1{y}_1+a_2{y}_2+a_3{y}_3+a_4{y}_1^2+a_5{y}_2^2+a_6{y}_3^2+a_7{y}_1{y}_2+a_8{y}_2{y}_3+a_9{y}_1{y}_3-5\%$

$s.t.\left\{\begin{array}{c}0m<y_1<1.8m\\ 0m<y_2<1.8m\\ 0m<y_3<1.8m\\ 30m/s\&le;U\&le;40m/s\end{array}\right.$

3) Performance Evaluation of design result and optimization

The optimization results shows: work as y ₁, y ₂And y ₃When value was 0.288m, 0.441m and 0.599m respectively, the ammonia concentration deviation was 5%.

With y ₁, y ₂And y ₃Value is 0.288m, 0.441m and 0.599m respectively, sets up the numerical evaluation model of spray ammonia jet, and result of calculation shows: after the mixing length of design, the ammonia concentration deviation is 2.4%, satisfies it and is not more than 5% designing requirement.

Claims (2)

1. spray ammonia and the ammonia-gas spraying device parameter optimization method that flue gas flow field matees in the flue gas denitrification system is characterized in that containing following steps:

1. make up the funtcional relationship δ=f (g of ammonia/nitrogen relative concentration deviation and ammonia-gas spraying device geometry design parameter ₁, g ₂, L, g _n);

2. choose m initial sample point, and the ammonia-gas spraying device parameterized model of setting up based on this sample point is carried out numerical evaluation, to obtain the corresponding concentration deviation δ of different geometry design parameter:

C _iBe the ammonia/nitrogen concentration ratio of test point, n is the number of test point,

Mathematical mean for all test point ammonia/nitrogen concentration ratio;

3. set up Optimization Model:

MIN：δ＝f(g ₁，g ₂，L，g _n)

$s.t.\left\{\begin{array}{c}{g}_{i,\min }\&le;g_i\&le;g_{i,\max }(i=\mathrm{1,2},L,n)\\ U_{\min }\&le;U\&le;U_{\max }\\ L\end{array}\right.$

Ammonia-gas spraying device geometric parameter when calculating with acquisition Cmin deviation to this mathematical model.

2. the ammonia-gas spraying device parameter optimization method of spray ammonia and flue gas flow field coupling is characterized in that: described function f (g in the flue gas denitrification system according to claim 1 ₁, g ₂, L, g _n)=a ₀+ a ₁g ₁+ a ₂g ₂+ a ₃g ₃+ L, g in the formula ₁, g ₂, L, g _nFor describing n geometric parameter of ammonia-gas spraying device, a ₀, a ₁, a ₂, a ₃L is an equation coefficient.

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