CN102866240B - Online soft measurement method of magnetite oxygenation efficiency distribution in grate pellet material layer - Google Patents

Abstract

The invention provides an online soft measurement method of magnetite oxygenation efficiency distribution in a grate material layer in a production process of an iron ore oxidized pellet. The online soft measurement method comprises the following steps of: dividing the pellet material layer on the grate into virtual elements to be calculated and analyzed; establishing a magnetite oxygenation efficiency distribution model in the pellet material layer according to an unreacted core model theory of a solid product layer and the phenomenon of heat transfer and mass transfer in the grate pellet production process by taking the green-ball magnetite content, the green-ball radius, the material layer temperature and the gas temperature as instrumental variables; and by considering the time sequence of parameters, calculating the material layer oxygenation efficiency in each calculating element on the grate. The method is applied to the production of the grate-rotary kiln iron ore oxidized pellet and capable of realizing the online detection of the oxygenation efficiency distribution in the grate material layer.

Description

A kind of online soft sensor method that drying grate pelletizing bed of material magnetic iron ore oxygenation efficiency distributes

Technical field

The present invention relates to a kind of online soft sensor method that drying grate pelletizing bed of material magnetic iron ore oxygenation efficiency distributes.

Background technology

China's steel and iron industry develop rapidly in recent years, within 2010, crude steel output reaches 6.27 hundred million tons, and blast furnace iron output reaches 5.90 hundred million tons, world rankings first.Blast furnace maximizes, modernization is more and more higher to furnace charge requirement, and Proper Burden Constitution of Blast Furnace more and more comes into one's own.

Iron ore acid pellet meets the reasonable furnace charge requirement of blast furnace, adapts to China's iron ore deposit feature, compares sintering process and is conducive to energy-saving and emission-reduction, day by day causes concern, just progressively developed.As a kind of important iron ore acid pellet production method, grate kiln technique is applicable to China's iron ore acid pellet development, occupies leading position in output.

Ferrous oxide content [pelletizing production raw material generally contains magnetic iron ore, and magnetic iron ore oxidation is that pelletizing ferrous content reduces] is the important quality index of iron ore oxide pellet, to blast furnace process important.It is generally acknowledged, the every raising 10% of reduction degree of feed stock for blast furnace, coke ratio can reduce by 8% ~ 9%; The every reduction by 1% of ferrous oxide content, coke ratio reduces by 1%.According to GB 50491-2009 regulation, finished ball nodulizing FeO content should be less than or equal to 1.0%.

In grate kiln production technology, the oxidizing process of pelletizing magnetic iron ore significantly betides drying grate preheating section.Theoretical research and production practices have all proved the necessity that guarantees preheated pellets oxygenation efficiency on drying grate.First, it is themopositive reaction that magnetic iron ore is oxidized to haematite, and fully the carrying out of oxidation reaction can guarantee that pre-hot-bulb obtains sufficient heat under lower burnup condition, has enough physical strengths and meets the requirement of rotary kiln production run; The second, can be remaining at pellet center if preheating section magnetic iron ore oxidation is insufficient, when pelletizing enters high-temperature roasting band, magnetic iron ore will with gangue SiO ₂reaction, generates low-melting compound, in pellet inside, occurs liquid slag phase, when cooling, shrinks, and makes the concentric crackle of the inner appearance of pellet, not only affects the intensity of pellet, and worsens its reductibility; In addition, bad mechanical strength, the pre-hot-bulb that oxygenation efficiency is low enter rotary kiln and easily produce pelletizing wearing and tearing and break, and may cause the generation of the accidents such as ring formation of rotary kiln because FeO in these dust exists the liquid phase producing.Therefore on drying grate, preheated pellets magnetic iron ore oxygenation efficiency has material impact to pelletizing production.

At present in pelletizing production, generally finished ball nodulizing FeO content has been carried out to regular inspection by sampling, but on drying grate, the oxidation situation of warm pelletizing because causing the reasons such as sample representation is poor, grate kiln closed system sampling difficulty and oxygenation efficiency skewness in the bed of material not yet realizes online detection.

Therefore, develop a kind of technology that can detect online drying grate bed of material magnetic iron ore oxygenation efficiency distribution in iron ore acid pellet production run, grate kiln iron ore acid pellet is produced to tool and be of great significance.

Summary of the invention

Technical matters to be solved by this invention is to provide a kind of online soft sensor method that drying grate pelletizing bed of material magnetic iron ore oxygenation efficiency distributes, and the online soft sensor method energy fast detecting that this drying grate pelletizing bed of material magnetic iron ore oxygenation efficiency distributes goes out drying grate bed of material magnetic iron ore oxygenation efficiency in pelletizing production process and distributes.

The technical solution of invention is as follows:

The online soft sensor method that drying grate pelletizing bed of material magnetic iron ore oxygenation efficiency distributes, comprises the following steps:

Step 1: grid is divided:

It is L that the pelletizing bed of material on drying grate is divided into range of size ₁* L ₂* L ₃virtual calculating infinitesimal, wherein, L ₁for 0.1% ~ 1% of drying grate effective length, unit is cm; L ₂for pelletizing bed of material width, unit is cm; L ₃for 5% ~ 10% of real-time bed depth, unit is cm;

Step 2: the value of obtaining auxiliary variable:

Auxiliary variable comprises green-ball magnetic iron ore content, green-ball radius, material layer temperature and gas temperature;

Step 3: model is set up and solved: the unreacted core model of solid product layer is theoretical according to having, and sets up pelletizing bed of material magnetic iron ore oxygenation efficiency computation model equation, calculates pelletizing bed of material magnetic iron ore oxygenation efficiency in infinitesimal to each and solves.

In step 2, the obtain manner of 4 auxiliary variables is respectively:

1) green-ball magnetic iron ore content

Green-ball magnetic iron ore content is calculated by following equation:

$p=\frac{\mathrm{\Σ}{m}_i{p}_i(1-w_i)}{232(m_{\mathrm{greenpellet}}+m_{\mathrm{return}})}$ Formula 1

Wherein, p is green-ball magnetic iron ore content, and unit is mol/g green-ball; m _ibe i kind raw material unit interval discharge quantity, unit is t/h; p _ibe i kind raw material FeO mass percentage content, unit is %; w _ibe i kind raw material water cut, unit is %; 232 is magnetic iron ore molar weight, and unit is g/mol; m _greenpelletfor green-ball pelletizing amount, t/h; m _returnfor green-ball returning charge amount, t/h.Gather m _i, p _i, w _i, m _greenpelletand m _returnduring data, consider sequential.

[raw material moisture and chemical composition check, and be t at raw material ore tank storage duration ₁hour; From batching, mixing, pelletizing until green-ball belt transport duration sum is t ₂hour; Mixing duration is t ₃hour; Mixture ore trough storage duration is t ₄hour; Pelletizing duration is t ₅hour; Green-ball and return conveyer scale stoichiometric point to cloth process belt transport duration is t ₆hour; Drying grate rotating speed is v m/h.For the infinitesimal apart from drying grate inlet end L rice, while calculating the interior pelletizing green-ball magnetic iron ore content of this infinitesimal, raw material blanking amount m _ifor ((L/v)+t ₆+ t ₅+ t ₄+ t ₃+ t ₂) hour before detection data; Raw material FeO content p _iwith raw material moisture w _ifor ((L/v)+t ₆+ t ₅+ t ₄+ t ₃+ t ₂+ t ₁) hour before detection data; Green-ball material amount m _greenpelletwith green-ball returning charge amount m _returnfor ((L/v)+t ₆) hour before detection data.】

2) green-ball radius

Green-ball radius is carried out to timing sampling detection, obtain green-ball radius r ₀, unit is cm.

3) material layer temperature

Utilize following solid-phase thermal balance equation to calculate each and calculate the pelletizing bed of material temperature T in infinitesimal _s:

${\mathrm{\ρ}}_s(1-{\mathrm{\ϵ}}_2)C_s\frac{T_s(x_m,t_n)-T_s(x_m,t_{n-1})}{t_n-t_{n-1}}=\mathrm{hA}[T_g(x_m,t_{n-1})-T_s(x_m,t_{n-1})]-q_1(x_m,t_{n-1})+Q_1(x_m,t_{n-1})$

Formula 2

Wherein, ρ _sfor ore density, unit is g/cm ³; ε ₂for pelletizing feed layer porosity, unit is that %[pelletizing feed layer porosity refers to that pelletizing is on drying grate in stacking volume in bulk, and the voidage between particle accounts for the ratio of cumulative volume, in specific production technology, according to flow scheme design, is certain value, can pass through formula calculate, wherein ρ _tand ρ _bbe respectively pelletizing real density and bulk density.]; C _sfor pelletizing specific heat, unit is J/g.K; X is bed depth, and unit is cm; T is the time, and unit is s; M and n are respectively the grid position on bed depth and drying grate length direction, and m is from gas feed layer end to going out bed of material end meter, and n is from drying grate cloth end to delivery end meter; T _sfor calculating pelletizing material layer temperature in infinitesimal, unit is K, and initial value is got room temperature; T _gfor calculating gas temperature in infinitesimal, unit is K, and initial value is got gas and entered the temperature before the pelletizing bed of material; H is the heat transfer coefficient between gas and pelletizing, and unit is J/cm ².K.s; A is unit volume pelletizing bed of material heat transfer area, and unit is cm ²/ cm ³, A=1/ infinitesimal height; q ₁for moisture evaporation endothermic speed, unit is J/s.cm ³, initial value gets 0; Q ₁for magnetic iron ore exothermic heat of reaction amount, unit is J/cm ³.s, initial value gets 0;

In formula 2,

(1) pelletizing specific heat C _saccording to laboratory under different temperatures, detecting data fitting formula calculates:

$C_s=\left\{\begin{array}{cc}0.1605+1.5000\&times;{10}^{-4}[T_s(x_m,t_{n-1})-273]& T_s<973K\\ 0.2140& T_s\&GreaterEqual;973K\end{array}\right.$ Formula 3

(2) between gas and pelletizing, heat transfer coefficient h calculates according to following formula:

H=NuK _a/ (2r ₀) formula 4

Wherein, Nu is Nusselt number, dimensionless; K _afor Measurement of Gas Thermal Conductivity, unit is J/cm.K.s;

K _abe respectively with Nu computing formula:

K _a=16.6670 * [1.7187 * 10 ^-6+ 7.3645 * 10 ^-9t _g(x _m, t _n-1)] formula 5

Nu=2.0+0.6P _r ^1/3r _e ^1/2formula 6

Wherein, P _rfor Prandtl number, μ is that gas viscosity [detects data fitting formula according to laboratory under different temperatures and calculates μ=16.67 * (5.28 * 10 ^-6+ 1.82 * 10 ^-8* T _g)], g/cm.s; C _gfor the specific heats of gases, unit is J/g.K, and computing formula is as follows:

C _g=1.0868 * 10 ^-7[T _g(x _m-1, t _n)-273] ²-0.5097 * 10 ^-10[T _g(x _m-1, t _n)-273] ³formula 7

-1.7065×10 ^-5[T _g(x _m-1,t _n)-273]+0.2452

(3) magnetic iron ore exothermic heat of reaction amount Q ₁according to following formula, calculate:

Q ₁(x _m, t _n)=Δ Hr _mag(x _m, t _n-1) N formula 8

Wherein, Δ H is magnetic iron ore oxidation reaction enthalpy change, gets 260kJ/mol; N is pelletizing amount in unit volume, and unit is 1/cm ³, r _magfor magnetic iron ore oxidizing reaction rate, unit is mol/s, and initial value gets 0;

[r _magcomputing formula see formula 18]

(4) moisture evaporation endothermic speed q ₁according to following formula, calculate:

Q ₁(x _m, t _n)=hA[T _g(x _m, t _n)-T _s(x _m, t _n)] a (x _m, t _n) formula 9

Wherein, a is that the bed of material obtains the scale-up factor evaporating for moisture in heat; [a computing formula is with reference to English

People's achievements in research such as state R.W.Young are prior art:

$a(x_m,t_n)=\left\{\begin{array}{cc}1-[373-T_s(x_m,t_{n-1})]/100& W_s(x,t)\&GreaterEqual;W_c,T_s(x,t)<373K\\ \{1-[3730-T_s(x_m,t_{n-1})]/100\}{W}_s(x_m,t_n)/W_c& W_s(x,t)<W_c\end{array}\right.$

Formula 10

Wherein, W _cfor pelletizing water cut critical value, get 2.0%; W _sfor pelletizing biodiversity degree, initial value is green-ball water cut, and unit is %;

W _saccording to following formula, calculate:

$\frac{W_s(x_m,t_n)-W_s(x_m,t_{n-1})}{t_n-t_{n-1}}=\frac{q_1(x_m,t_{n-1})}{{\mathrm{\&lambda;\&rho;}}_s(1-{\mathrm{\&epsiv;}}_2)}$ Formula 11

Wherein, λ is evaporation of water latent heat, and value is 2260J/g.】

4) gas temperature

Utilize following gas phase thermal balance equation to calculate each and calculate the gas temperature T in infinitesimal _g:

$M_g{C}_g\frac{T_g(x_m,t_n)-T_g(x_{m-1},t_n)}{x_m-x_{m-1}}=\mathrm{hA}[T_s(x_{m-1},t_n)-T_g(x_{m-1},t_n)]+q_2(x_{m-1},t_n)$

Formula 12

Wherein, M _gfor the matter flow of gas, unit is g/cm ².s; [Mg is that the unit interval is interior by the gaseous mass of unit area, detects by flowmeter] q ₂for condensate moisture rate of heat release, unit is J/s.cm ³, initial value gets 0;

Q ₂by following formula, calculated:

Q ₂(x _m, t _n)=λ M _g[W _g(x _m, t _n)-W _gs(x _m, t _n)] formula 13

Wherein, W _gfor gas moisture mass percentage content, unit is %; W _gsfor biodiversity degree in saturated air, unit is %; λ is evaporation of water latent heat, and value is 2260J/g;

W _gand W _gscomputing formula is respectively:

$\frac{W_g(x_m,t_n)-W_g(x_{m-1},t_n)}{x_m-x_{m-1}}=-\frac{q_1(x_{m-1},t_n)}{{\mathrm{\&lambda;M}}_g}$ Formula 14

$W_{\mathrm{gs}}(x_m,t_n)=e^{-5.49269+0.0549269[T_g(x_{m-1},t_n)-273]}$ Formula 15

Current time (t _n) q ₁(x _m, t _n) be by a upper moment (t _n-1) q ₁(x _m, t _n-1) calculate successively W _s(x _m, t _n), a(x _m, t _n) obtain.

Current height (x _m) q ₂(x _m, t _n) be by a upper height (x _m-1) q ₁(x _m-1, t _n) calculate W _g(x _m, t _n) obtain.

Computation sequence provides with target form under x and t, arranges as shown in Figure 5.

Pelletizing bed of material magnetic iron ore oxygenation efficiency computation model equation described in step 3 is:

$\mathrm{\&chi;}(x_m,t_n)=1-{\left[\frac{r_m(x_m,t_n)}{r_0}\right]}^3$ Formula 16

Wherein, χ is magnetic iron ore oxygenation efficiency in pelletizing, and unit is %; r ₀for magnetic iron ore original radius, unit is cm; r _mfor magnetic iron ore unreacted core radius, unit is cm, and initial value is pelletizing radius r ₀[illustrate: along with oxidation reaction is carried out, unreacted core dwindles, r _mchanging value], by following reaction interface translational speed equation, calculate:

$\frac{r_m(x_m,t_n)-r_m(x_m,t_{n-1})}{t_n-t_{n-1}}=-\frac{r_{\mathrm{mag}}(x_m,t_n)}{4p{r}_m{(x_m,t_{n-1})}^2{\mathrm{\&rho;}}_s(1-{\mathrm{\&epsiv;}}_1)\mathrm{\&pi;}}$ Formula 17

Wherein, ε ₁for pelletizing porosity, unit is %, according to pelletizing sample examination, obtains; P is green-ball magnetic iron ore content in formula 1;

Magnetic iron ore oxidizing reaction rate r _magcomputing formula is as follows:

$r_{\mathrm{mag}}(x_m,t_n)=\frac{16\mathrm{\&pi;}{r}_0^2{C}_{O_2}}{\frac{1}{k_{g\left(O_2\right)}}+\frac{1}{k_r}{\left[\frac{r_0}{r_m(x_m,t_{n-1})}\right]}^2+\frac{r_0}{D_{O_2}}[\frac{r_0}{r_m(x_m,t_{n-1})}-1]}$ Formula 18

Wherein, for the O in gas phase ₂concentration, unit is mol/cm ³, get air oxygen concentration conduct for O in gas phase ₂by the mass transfer coefficient of gas boundary layer, unit is cm/s; k _rfor magnetic iron ore chemical reaction velocity, unit is cm/s; for O in pelletizing ₂by the effective diffusion cofficient of product layer, unit is cm ²/ s;

k _rwith computing formula is respectively:

$k_{g\left(O_2\right)}=\frac{\mathrm{Sh}\&CenterDot;D}{2r_0}$ Formula 19

$k_r=3000\&times;e^{-6000/T_s(x_m,t_{n-1})}$ Formula 20

$D_{O_2}=\frac{D{\mathrm{\&epsiv;}}_1}{\mathrm{\&tau;}}$ Formula 21

Wherein, Sh is Sherwood number, dimensionless; D is O ₂coefficient of diffusion in gas, unit is cm ²/ s; τ is the bent joint factor, and dimensionless, gets 5 according to drying grate acid pellet working condition;

(1) Sherwood counts Sh and calculates according to the research of Ranz and Marshall, belongs to prior art:

Sh=2.0+0.6Re ^1/2sc ^1/3formula 22

Wherein, Re is Reynolds number, sc is Schmidt number, ρ is fluid density, and unit is g/cm ³; V is the relative velocity between pelletizing and gas, and unit is cm/s; L is characteristic line size, and unit is that cm[gets pelletizing diameter 1.3cm]; Other symbolic significances are the same, and μ is gas viscosity, and μ is in formula 6 explanations above;

(2) O ₂diffusion coefficient D in gas is calculated according to following formula:

D=9.71 * 10 ^-6t _g(x _m-1, t _n) ^1.75formula 23

It should be noted that according to hot air flow to difference, blasting drying period infinitesimal computation sequence is for from top to bottom, and down-draft drying zone, preheating I section and preheating II section are from top to bottom.

Beneficial effect:

The online soft sensor method that drying grate pelletizing bed of material magnetic iron ore oxygenation efficiency of the present invention distributes, has following characteristics:

(1) quick

Pre-hot-bulb ferrous oxide content has impact to pellet strength and rotary kiln production status, but drying grate is the system of a relative closure, in producing at present, cannot detect drying grate pelletizing bed of material magnetic iron ore oxygenation efficiency, general only to finished ball nodulizing sample examination ferrous oxide content,, hysteresis indirect to pre-hot-bulb magnetic iron ore oxidation situation reflection.The present invention passes through the soft measurement of pelletizing bed of material magnetic iron ore oxygenation efficiency on model realization drying grate, and calculates by computer software programming, and required time is short, can realize production on-line operation, guarantees the real-time of testing result.

(2) abundant information

The present invention carries out grid division by the drying grate pelletizing bed of material, infinitesimal height is close with individual layer pelletizing height, therefore the model calculation not only can reflect along the situation of carrying out of drying grate traffic direction magnetic iron ore oxidation reaction, and can reflect each layer of difference that pelletizing oxidation reaction is carried out in bed depth direction.

(3) improve productivity effect

Use the present invention to carry out drying grate pelletizing bed of material magnetic iron ore oxidizing process and detect control, can optimize drying grate production run, guarantee pre-hot-bulb intensity and ferrous content, reduce the generation of the phenomenons such as the interior ring formation of the concentric crackle of pelletizing and rotary kiln, make full use of magnetic iron ore oxidation heat liberation, reduce power consumption, energy consumption, improve productivity effect.

Accompanying drawing explanation

Fig. 1 is that grid is divided schematic diagram;

Fig. 2 is drying grate-rotary kiln-circular cooler pelletizing production system construction drawing;

Fig. 3 is the visual demonstration that drying grate bed of material magnetic iron ore oxygenation efficiency is distributed;

Fig. 4 is the pelletizing averaged oxygen rate curve along drying grate traffic direction;

Fig. 5 is intermediate variable cycle calculations schematic diagram.

Embodiment

Below with reference to the drawings and specific embodiments, the present invention is described in further details:

The online soft sensor method that drying grate pelletizing bed of material magnetic iron ore oxygenation efficiency distributes, comprises the following steps:

Step 1: grid is divided:

It is L that the pelletizing bed of material on drying grate is divided into range of size ₁* L ₂* L ₃virtual calculating infinitesimal, wherein, L ₁for 0.1% ~ 1% of drying grate effective length, unit is cm; L ₂for pelletizing bed of material width, unit is cm; L ₃for 5% ~ 10% of real-time bed depth, unit is cm;

Step 2: the value of obtaining auxiliary variable:

Auxiliary variable comprises green-ball magnetic iron ore content, green-ball radius, material layer temperature and gas temperature;

Step 3: model is set up and solved: the unreacted core model of solid product layer is theoretical according to having, and sets up pelletizing bed of material magnetic iron ore oxygenation efficiency computation model equation, calculates pelletizing bed of material magnetic iron ore oxygenation efficiency in infinitesimal to each and solves.

In step 2, the obtain manner of 4 auxiliary variables is respectively:

1) green-ball magnetic iron ore content

Green-ball magnetic iron ore content is calculated by following equation:

$p=\frac{\mathrm{\&Sigma;}{m}_i{p}_i(1-w_i)}{232(m_{\mathrm{greenpellet}}+m_{\mathrm{return}})}$ Formula 1

Wherein, p is green-ball magnetic iron ore content, and unit is mol/g green-ball; m _ibe i kind raw material unit interval discharge quantity, unit is t/h; p _ibe i kind raw material FeO mass percentage content, unit is %; w _ibe i kind raw material water cut, unit is %; 232 is magnetic iron ore molar weight, and unit is g/mol; m _greenpelletfor green-ball pelletizing amount, t/h; m _returnfor green-ball returning charge amount, t/h.Gather m _i, p _i, w _i, m _greenpelletand m _returnduring data, consider sequential.

[raw material moisture and chemical composition check, and be t at raw material ore tank storage duration ₁hour; From batching, mixing, pelletizing until green-ball belt transport duration sum is t ₂hour; Mixing duration is t ₃hour; Mixture ore trough storage duration is t ₄hour; Pelletizing duration is t ₅hour; Green-ball and return conveyer scale stoichiometric point to cloth process belt transport duration is t ₆hour; Drying grate rotating speed is v m/h.For the infinitesimal apart from drying grate inlet end L rice, while calculating the interior pelletizing green-ball magnetic iron ore content of this infinitesimal, raw material blanking amount m _ifor ((L/v)+t ₆+ t ₅+ t ₄+ t ₃+ t ₂) hour before detection data; Raw material FeO content p _iwith raw material moisture w _ifor ((L/v)+t ₆+ t ₅+ t ₄+ t ₃+ t ₂+ t ₁) hour before detection data; Green-ball material amount m _greenpelletwith green-ball returning charge amount m _rentrnfor ((L/v)+t ₆) hour before detection data.】

2) green-ball radius

Green-ball radius is carried out to timing sampling detection, obtain green-ball radius r ₀, unit is cm.

3) material layer temperature

Utilize following solid-phase thermal balance equation to calculate each and calculate the pelletizing bed of material temperature T in infinitesimal _s:

${\mathrm{\&rho;}}_s(1-{\mathrm{\&epsiv;}}_2)C_s\frac{T_s(x_m,t_n)-T_s(x_m,t_{n-1})}{t_n-t_{n-1}}=\mathrm{hA}[T_g(x_m,t_{n-1})-T_s(x_m,t_{n-1})]-q_1(x_m,t_{n-1})+Q_1(x_m,t_{n-1})$

Formula 2

Wherein, ρ _sfor ore density, unit is g/cm ³; ε ₂for pelletizing feed layer porosity, unit is that %[pelletizing feed layer porosity refers to that pelletizing is on drying grate in stacking volume in bulk, and the voidage between particle accounts for the ratio of cumulative volume, in specific production technology, according to flow scheme design, is certain value, can pass through formula calculate, wherein ρ _tand ρ _bbe respectively pelletizing real density and bulk density.]; C _sfor pelletizing specific heat, unit is J/g.K; X is bed depth, and unit is cm; T is the time, and unit is s; M and n are respectively the grid position on bed depth and drying grate length direction, and m is from gas feed layer end to going out bed of material end meter, and n is from drying grate cloth end to delivery end meter; T _sfor calculating pelletizing material layer temperature in infinitesimal, unit is K, and initial value is got room temperature; T _gfor calculating gas temperature in infinitesimal, unit is K, and initial value is got gas and entered the temperature before the pelletizing bed of material; H is the heat transfer coefficient between gas and pelletizing, and unit is J/cm ².K.s; A is unit volume pelletizing bed of material heat transfer area, and unit is cm ²/ cm ³, A=1/ infinitesimal height; q ₁for moisture evaporation endothermic speed, unit is J/s.cm ³, initial value gets 0; Q ₁for magnetic iron ore exothermic heat of reaction amount, unit is J/cm ³.s, initial value gets 0;

In formula 2,

(1) pelletizing specific heat C _saccording to laboratory under different temperatures, detecting data fitting formula calculates:

$C_s=\left\{\begin{array}{cc}0.1605+1.5000\&times;{10}^{-4}[T_s(x_m,t_{n-1})-273]& T_s<973K\\ 0.2140& T_s\&GreaterEqual;973K\end{array}\right.$ Formula 3

(2) between gas and pelletizing, heat transfer coefficient h calculates according to following formula:

H=NuK _a/ (2r ₀) formula 4

Wherein, Nu is Nusselt number, dimensionless; K _afor Measurement of Gas Thermal Conductivity, unit is J/cm.K.s;

K _abe respectively with Nu computing formula:

K _a=16.6670 * [1.7187 * 10 ^-6+ 7.3645 * 10 ^-9t _g(x _m, t _n-1)] formula 5

Nu=2.0+0.6P _r ^1/3re ^1/2formula 6

Wherein, P _rfor Prandtl number, μ is that gas viscosity [detects data fitting formula according to laboratory under different temperatures and calculates μ=16.67 * (5.28 * 10 ^-6+ 1.82 * 10 ^-8* T _g)], g/cm.s; C _gfor the specific heats of gases, unit is J/g.K, and computing formula is as follows:

C _g=1.0868 * 10 ^-7[T _g(x _m-1, t _n)-273] ²-0.5097 * 10 ^-10[T _g(x _m-1, t _n)-273] ³formula 7

-1.7065×10 ^-5[T _g(x _m-1,t _n)-273]+0.2452

(3) magnetic iron ore exothermic heat of reaction amount Q ₁according to following formula, calculate:

Q ₁(x _m, t _n)=Δ Hr _mag(x _m, t _n-1) N formula 8

Wherein, Δ H is magnetic iron ore oxidation reaction enthalpy change, gets 260kJ/mol; N is pelletizing amount in unit volume, and unit is 1/cm ³, r _magfor magnetic iron ore oxidizing reaction rate, unit is mol/s, and initial value gets 0;

[r _magcomputing formula see formula 18]

(4) moisture evaporation endothermic speed q ₁according to following formula, calculate:

Q ₁(x _m, t _n)=hA[T _g(x _m, t _n)-T _s(x _m, t _n)] a (x _m, t _n) formula 9

Wherein, a is that the bed of material obtains the scale-up factor evaporating for moisture in heat; [a computing formula is with reference to English

People's achievements in research such as state R.W.Young are prior art:

$a(x_m,t_n)=\left\{\begin{array}{cc}1-[373-T_s(x_m,t_{n-1})]/100& W_s(x,t)\&GreaterEqual;W_c,T_s(x,t)<373K\\ \{1-[3730-T_s(x_m,t_{n-1})]/100\}{W}_s(x_m,t_n)/W_c& W_s(x,t)<W_c\end{array}\right.$

Formula 10

Wherein, W _cfor pelletizing water cut critical value, get 2.0%; W _sfor pelletizing biodiversity degree, initial value is green-ball water cut, and unit is %;

W _saccording to following formula, calculate:

$\frac{W_s(x_m,t_n)-W_s(x_m,t_{n-1})}{t_n-t_{n-1}}=\frac{q_1(x_m,t_{n-1})}{{\mathrm{\&lambda;\&rho;}}_s(1-{\mathrm{\&epsiv;}}_2)}$ Formula 11

Wherein, λ is evaporation of water latent heat, and value is 2260J/g.】

4) gas temperature

Utilize following gas phase thermal balance equation to calculate each and calculate the gas temperature T in infinitesimal _g:

$M_g{C}_g\frac{T_g(x_m,t_n)-T_g(x_{m-1},t_n)}{x_m-x_{m-1}}=\mathrm{hA}[T_s(x_{m-1},t_n)-T_g(x_{m-1},t_n)]+q_2(x_{m-1},t_n)$

Formula 12

Wherein, M _gfor the matter flow of gas, unit is g/cm ².s; [Mg is that the unit interval is interior by the gaseous mass of unit area, detects by flowmeter] q ₂for condensate moisture rate of heat release, unit is J/s.cm ³, initial value gets 0;

Q ₂by following formula, calculated:

Q ₂(x _m, t _n)=λ M _g[W _g(x _m, t _n)-W _gs(x _m, t _n)] formula 13

Wherein, W _gfor gas moisture mass percentage content, unit is %; W _gsfor biodiversity degree in saturated air, unit is %; λ is evaporation of water latent heat, and value is 2260J/g;

W _gand W _gscomputing formula is respectively:

$\frac{W_g(x_m,t_n)-W_g(x_{m-1},t_n)}{x_m-x_{m-1}}=-\frac{q_1(x_{m-1},t_n)}{{\mathrm{\&lambda;M}}_g}$ Formula 14

$W_{\mathrm{gs}}(x_m,t_n)=e^{-5.49269+0.0549269[T_g(x_{m-1},t_n)-273]}$ Formula 15

Current time (t _n) q ₁(x _m, t _n) be by a upper moment (t _n-1) q ₁(x _m, t _n-1) calculate successively W _s(x _m, t _n), a(x _m, t _n) obtain.

Current height (x _m) q ₂(x _m, t _n) be by a upper height (x _m-1) q ₁(x _m-1, t _n) calculate W _g(x _m, t _n) obtain.

Computation sequence provides with target form under x and t, arranges as shown in Figure 5.

Pelletizing bed of material magnetic iron ore oxygenation efficiency computation model equation described in step 3 is:

$\mathrm{\&chi;}(x_m,t_n)=1-{\left[\frac{r_m(x_m,t_n)}{r_0}\right]}^3$ Formula 16

Wherein, χ is magnetic iron ore oxygenation efficiency in pelletizing, and unit is %; r ₀for magnetic iron ore original radius, unit is cm; r _mfor magnetic iron ore unreacted core radius, unit is cm, and initial value is pelletizing radius r ₀[illustrate: along with oxidation reaction is carried out, unreacted core dwindles, r _mchanging value], by following reaction interface translational speed equation, calculate:

$\frac{r_m(x_m,t_n)-r_m(x_m,t_{n-1})}{t_n-t_{n-1}}=-\frac{r_{\mathrm{mag}}(x_m,t_n)}{4p{r}_m{(x_m,t_{n-1})}^2{\mathrm{\&rho;}}_s(1-{\mathrm{\&epsiv;}}_1)\mathrm{\&pi;}}$ Formula 17

Wherein, ε ₁for pelletizing porosity, unit is %, according to pelletizing sample examination, obtains; P is green-ball magnetic iron ore content in formula 1;

Magnetic iron ore oxidizing reaction rate r _magcomputing formula is as follows:

$r_{\mathrm{mag}}(x_m,t_n)=\frac{16\mathrm{\&pi;}{r}_0^2{C}_{O_2}}{\frac{1}{k_{g\left(O_2\right)}}+\frac{1}{k_r}{\left[\frac{r_0}{r_m(x_m,t_{n-1})}\right]}^2+\frac{r_0}{D_{O_2}}[\frac{r_0}{r_m(x_m,t_{n-1})}-1]}$ Formula 18

Wherein, for the O in gas phase ₂concentration, unit is mol/cm ³, get air oxygen concentration conduct for O in gas phase ₂by the mass transfer coefficient of gas boundary layer, unit is cm/s; k _rfor magnetic iron ore chemical reaction velocity, unit is cm/s; for O in pelletizing ₂by the effective diffusion cofficient of product layer, unit is cm ²/ s;

k _rwith computing formula is respectively:

$k_{g\left(O_2\right)}=\frac{\mathrm{Sh}\&CenterDot;D}{2r_0}$ Formula 19

$k_r=3000\&times;e^{-6000/T_s(x_m,t_{n-1})}$ Formula 20

$D_{O_2}=\frac{D{\mathrm{\&epsiv;}}_1}{\mathrm{\&tau;}}$ Formula 21

Wherein, Sh is Sherwood number, dimensionless; D is O ₂coefficient of diffusion in gas, unit is cm ²/ s; τ is the bent joint factor, and dimensionless, gets 5 according to drying grate acid pellet working condition;

(1) Sherwood counts Sh and calculates according to the research of Ranz and Marshall, belongs to prior art:

Sh=2.0+0.6Re ^1/2sc ^1/3formula 22

Wherein, Re is Reynolds number, sc is Schmidt number, ρ is fluid density, and unit is g/cm ³; V is the relative velocity between pelletizing and gas, and unit is cm/s; L is characteristic line size, and unit is that cm[gets pelletizing diameter 1.3cm]; Other symbolic significances are the same, and μ is gas viscosity, and μ is in formula 6 explanations above;

(2) O ₂diffusion coefficient D in gas is calculated according to following formula:

D=9.71 * 10 ^-6t _g(x _m-1, t _n) ^1.75formula 23

It should be noted that according to hot air flow to difference, blasting drying period infinitesimal computation sequence is for from top to bottom, and down-draft drying zone, preheating I section and preheating II section are from top to bottom.

Embodiment 1:

In the typical grate kiln iron ore acid pellet technological process of production of take as shown in Figure 2, online detection of drying grate production run bed of material magnetic iron ore oxygenation efficiency distribution is example, by reference to the accompanying drawings, the specific embodiment of the invention is described further.This example is to further illustrate of the present invention, rather than restriction scope of invention.

In example, study drying grate effective length 50m, width 4.5m, design cloth height 0.2m, is divided into blasting drying period, down-draft drying zone, preheating I section, preheating II section.Raw material comprises haematite, magnetic iron ore, bentonitic clay and dedusting ash.

Level-sensing device is 188mm to the detection data of Cloth height on drying grate, and therefore, it is the virtual calculating infinitesimal of 0.2m * 4.5m * 1.88cm that the pelletizing bed of material on drying grate is divided into size, amounts to 2500.

Consider time-lag effect, magnetic iron ore, haematite, bentonitic clay and dedusting ash water cut that current drying grate porch green-ball is corresponding are respectively 11%, 5.2%, 3.5% and 0.2%, FeO content is respectively 27.88%, 7.38%, and 0.21% and 0.34%, it is front through super-dry that segment magnet ore deposit participates in batching, and dry rear water cut is 6.1%.In blending process, the real-time discharge quantity of each raw material adopts belted electronic balance to detect online, and the data of homogeneous raw material are summed up to calculating, the instantaneous discharge quantity that obtains the dry magnetic iron ore of current drying grate entrance green-ball correspondence, dry rear magnetic iron ore, haematite, bentonitic clay and dedusting ash is respectively 161.13t/h, 132.06t/h, 127.03t/h, 6.55t/h and 11.52t/h.Green-ball and green-ball returning charge amount sum total are 443t/h.By formula, calculating green-ball magnetic iron ore content is 0.002618mol/g-pellet.Green-ball radius is about 6.5mm, green-ball temperature in is 25 ℃, bed of material porosity is 0.4, green-ball moisture is 10.1%, it is 3.43m/min that online detection obtains drying grate machine speed, cloth height is 188mm, and blasting drying period, down-draft drying zone, preheating I section, the preheating II section unit area bed of material enter hot blast air quantity and be respectively 0.1144g/cm ².s, 0.1430g/cm ².s, 0.0918g/cm ².s and 0.1290g/cm ².s, blasting drying period 17# and 16# bellows hot blast temperature are respectively 235 ℃ and 233 ℃, and down-draft drying zone, preheating I section and preheating II section petticoat pipe temperature are respectively 294 ℃, 867 ℃ and 1067 ℃.

Data substitution soft-sensing model equation is calculated, obtain all infinitesimal internal magnets of drying grate bed of material ore deposit oxygenation efficiency.By data-the reflection of graphics, carry out the corresponding conversion of oxygenation efficiency and bitmap rgb value, by the visual demonstration that distributes of each material layer oxidation rate of drying grate, as shown in Figure 3.As seen from Figure 3, on drying grate in pelletizing magnetic iron ore significantly oxidation start from preheating section, because preheating section hot blast passes through the bed of material from top to bottom, so upper strata pelletizing is compared and is had higher oxygenation efficiency with lower floor pelletizing.To drying grate pelletizing exit position, in the pelletizing of upper strata, magnetic iron ore oxygenation efficiency is 98.65%, and lower floor's oxygenation efficiency is 66.24%, and magnetic iron ore oxygenation efficiency distributes along bed depth direction, and there is some difference.Take drying grate length as horizontal ordinate, on drying grate, the mean value of 10 layers of pelletizing oxygenation efficiency of identical horizontal ordinate bed depth direction is ordinate, drafting is along the pelletizing averaged oxygen rate curve of drying grate traffic direction, and on reflection drying grate, pelletizing magnetic iron ore is oxidized situation, as shown in Figure 4.As seen from Figure 4, the averaged oxygen rate of the pre-hot-bulb in drying grate pelletizing exit reaches 85.27%.

Claims (2)

1. the online soft sensor method that drying grate pelletizing bed of material magnetic iron ore oxygenation efficiency distributes, is characterized in that, comprises the following steps:

Step 1: grid is divided:

It is L that the pelletizing bed of material on drying grate is divided into range of size ₁* L ₂* L ₃virtual calculating infinitesimal, wherein, L ₁for 0.1%～1% of drying grate effective length, unit is cm; L ₂for pelletizing bed of material width, unit is cm; L ₃for 5%～10% of real-time bed depth, unit is cm;

Step 2: the value of obtaining auxiliary variable:

Auxiliary variable comprises green-ball magnetic iron ore content, green-ball radius, material layer temperature and gas temperature;

Step 3: model is set up and solved: the unreacted core model of solid product layer is theoretical according to having, and sets up pelletizing bed of material magnetic iron ore oxygenation efficiency computation model equation, calculates pelletizing bed of material magnetic iron ore oxygenation efficiency in infinitesimal to each and solves;

In step 2, the obtain manner of 4 auxiliary variables is respectively:

1) green-ball magnetic iron ore content

Green-ball magnetic iron ore content is calculated by following equation:

$p=\frac{\mathrm{\&Sigma;}{m}_i{p}_i(1-w_i)}{232(m_{\mathrm{greenpellet}}+m_{\mathrm{return}})}$ Formula 1

Wherein, p is green-ball magnetic iron ore content, and unit is mol/g green-ball; m _ibe i kind raw material unit interval discharge quantity, unit is t/h; p _ibe i kind raw material FeO mass percentage content, unit is %; w _ibe i kind raw material water cut, unit is %; 232 is magnetic iron ore molar weight, and unit is g/mol; m _greenpelletfor green-ball pelletizing amount, t/h; m _returnfor green-ball returning charge amount, t/h; Gather m _i, p _i, w _i, m _greenpelletand m _returnduring data, consider sequential;

2) green-ball radius

Green-ball radius is carried out to timing sampling detection, obtain green-ball radius r ₀, unit is cm;

3) material layer temperature

Utilize following solid-phase thermal balance equation to calculate each and calculate the pelletizing bed of material temperature T in infinitesimal _s:

${\mathrm{\&rho;}}_s(1-{\mathrm{\&epsiv;}}_2)C_s\frac{T_s\left(x_m{,t}_n\right)-T_s(x_m,t_{n-1})}{t_n-t_{n-1}}=\mathrm{hA}[T_g(x_m,t_{n-1})-T_s(x_m,t_{n-1})]-q_1(x_m,t_{n-1})+Q_1(x_m,t_{n-1})$

Formula 2

Wherein, ρ _sfor ore density, unit is g/cm ³; ε ₂for pelletizing feed layer porosity, unit is %; C _sfor pelletizing specific heat, unit is J/g.K; X is bed depth, and unit is cm; T is the time, and unit is s; M and n are respectively the grid position on bed depth and drying grate length direction, and m is from gas feed layer end to going out bed of material end meter, and n is from drying grate cloth end to delivery end meter; T _sfor calculating pelletizing material layer temperature in infinitesimal, unit is K, and initial value is got room temperature; T _gfor calculating gas temperature in infinitesimal, unit is K, and initial value is got gas and entered the temperature before the pelletizing bed of material; H is the heat transfer coefficient between gas and pelletizing, and unit is J/cm ².K.s; A is unit volume pelletizing bed of material heat transfer area, and unit is cm ²/ cm ³, A=1/ infinitesimal height; q ₁for moisture evaporation endothermic speed, unit is J/s.cm ³, initial value gets 0; Q ₁for magnetic iron ore exothermic heat of reaction amount, unit is J/cm ³.s, initial value gets 0;

In formula 2,

(1) pelletizing specific heat Cs detects the calculating of data fitting formula according to laboratory under different temperatures:

$C_s=\left\{\begin{array}{cc}0.1605+1.5000\&times;{10}^{-4}[T_s(x_m,t_{n-1})-273]& T_s<973K\\ 0.2140& T_s\&GreaterEqual;937K\end{array}\right.$ Formula 3

(2) between gas and pelletizing, heat transfer coefficient h calculates according to following formula:

H=NuK _a/ (2r ₀) formula 4

Wherein, Nu is Nusselt number, dimensionless; K _afor Measurement of Gas Thermal Conductivity, unit is J/cm.K.s;

K _abe respectively with Nu computing formula:

K _a=16.6670 * [1.7187 * 10 ^-6+ 7.3645 * 10 ^-9t _g(x _m, t _n-1)] formula 5

Nu=2.0+0.6P _r ^1/3r _e ^1/2formula 6

Wherein, P _rfor Prandtl number, μ is gas viscosity, g/cm.s; C _gfor the specific heats of gases, unit is J/g.K, and computing formula is as follows:

C _g=1.0868 * 10 ^-7[T _g(x _m-1, t _n)-273] ²-0.5097 * 10 ^-10[T _g(x _m-1, t _n)-273] ³formula 7

-1.7065×10 ^-5[T _g(x _m-1,t _n)-273]+0.2452

(3) magnetic iron ore exothermic heat of reaction amount Q ₁according to following formula, calculate:

Q ₁(x _m, t _n)=△ Hr _mag(x _m, t _n-1) N formula 8

Wherein, △ H is magnetic iron ore oxidation reaction enthalpy change, gets 260kJ/mol; N is pelletizing amount in unit volume, and unit is 1/cm ³, r _magfor magnetic iron ore oxidizing reaction rate, unit is mol/s, and initial value gets 0;

(4) moisture evaporation endothermic speed q ₁according to following formula, calculate:

Q ₁(x _m, t _n)=hA[T _g(x _m, t _n)-T _s(x _m, t _n)] a (x _m, t _n) formula 9

Wherein, a is that the bed of material obtains the scale-up factor evaporating for moisture in heat;

4) gas temperature

Utilize following gas phase thermal balance equation to calculate each and calculate the gas temperature T in infinitesimal _g:

$M_g{C}_g\frac{T_g(x_m,t_n)-T_g(x_{m-1},t_n)}{x_m-x_{m-1}}\mathrm{hA}[T_s(x_{m-1},t_n)-T_g(x_{m-1},t_n)]+q_2(x_{m-1},t_n)$

Formula 10

Wherein, M _gfor the matter flow of gas, unit is g/cm ².s;

Q ₂for condensate moisture rate of heat release, unit is J/s.cm ³, initial value gets 0;

Q ₂by following formula, calculated:

Q ₂(x _m, t _n)=λ M _g[W _g(x _m, t _n)-W _gs(x _m, t _n)] formula 11

Wherein, W _gfor gas moisture mass percentage content, unit is %; W _gsfor biodiversity degree in saturated air, unit is %; λ is evaporation of water latent heat, and value is 2260J/g;

W _gand W _gscomputing formula is respectively:

$\frac{W_g(x_m,t_n)-W_g(x_{m-1},t_n)}{x_m-x_{m-1}}=-\frac{q_1(x_{m-1},t_n)}{{\mathrm{\&lambda;M}}_g}$ Formula 12 $W_{\mathrm{gs}}(x_m,t_n)=e^{-5.49269+0.0549269[T_g(x_{m-1},t_n)-273]}$ Formula 13

2. the online soft sensor method that drying grate pelletizing bed of material magnetic iron ore oxygenation efficiency according to claim 1 distributes, is characterized in that, the pelletizing bed of material magnetic iron ore oxygenation efficiency computation model equation described in step 3 is:

$\mathrm{\&chi;}(x_m,t_n)=1-{\left[\frac{r_m(x_m,t_n)}{r_0}\right]}^3$ Formula 14

Wherein, χ is magnetic iron ore oxygenation efficiency in pelletizing, and unit is %; r ₀for magnetic iron ore original radius, unit is cm; r _mfor magnetic iron ore unreacted core radius, unit is cm, and initial value is pelletizing radius r ₀[illustrate: along with oxidation reaction is carried out, unreacted core dwindles, r _mchanging value], by following reaction interface translational speed equation, calculate:

$\frac{r_m(x_m,t_n)-r_m(x_m,t_{n-1})}{t_n-t_{n-1}}=-\frac{r_{\mathrm{mag}}(x_m,t_n)}{{4\mathrm{pr}}_m{(x_m,t_{n-1})}^2{\mathrm{\&rho;}}_s(1-{\mathrm{\&epsiv;}}_1)\mathrm{\&pi;}}$ Formula 15

Wherein, ε ₁for pelletizing porosity, unit is %, according to pelletizing sample examination, obtains; P is green-ball magnetic iron ore content in formula 1;

Magnetic iron ore oxidizing reaction rate r _magcomputing formula is as follows:

$r_{\max }(x_m,t_n)=\frac{{16\mathrm{\&pi;r}}_0^2{C}_{O_2}}{\frac{1}{k_{g\left(O_2\right)}}+\frac{1}{k_r}{\left[\frac{r_0}{r_m(x_m,t_{n-1})}\right]}^2+\frac{r_0}{D_{O_2}}[\frac{r_0}{r_m(x_m,t_{n-1})}-1]}$ Formula 16

Wherein, for the O in gas phase ₂concentration, unit is mol/cm ³, get air oxygen concentration conduct ; for O in gas phase ₂by the mass transfer coefficient of gas boundary layer, unit is cm/s; k _rfor magnetic iron ore chemical reaction velocity, unit is cm/s; for O in pelletizing ₂by the effective diffusion cofficient of product layer, unit is cm ²/ s;

k _rwith computing formula is respectively:

$k_{g\left(O_2\right)}=\frac{\mathrm{Sh}\&CenterDot;D}{{2r}_0}$ Formula 17

$k_r=3000\&times;e^{-6000/T_s(x_m,t_{n-1})}$ Formula 18

$D_{O_2}=\frac{{\mathrm{D\&epsiv;}}_1}{\mathrm{\&tau;}}$ Formula 19

Wherein, Sh is Sherwood number, dimensionless; D is O ₂coefficient of diffusion in gas, unit is cm ²/ s; τ is the bent joint factor, and dimensionless, gets 5 according to drying grate acid pellet working condition.