CN104850755A - Combustion stability determining method based on thermal decomposition - Google Patents

Abstract

The invention relates to a combustion stability determining method based on thermal decomposition. The pulverized coal combustion stability determination condition is acquired by the raw coal thermal decomposition method, the boiler design parameters are combined additionally, and the combustion stability of one power plant boiler is predicted previously. Compared with the prior art, the method has the advantages that the target of preventing and intervening power plant boiler blended combustion previously is achieved, the hysteresis and randomness caused by real-time monitoring are avoided, the full-load prediction of pulverized coal combustion stability can be implemented, and the applicability of combustion stability determination is improved.

Description

A kind of combustion stability determination methods based on thermal decomposition

Technical field

The present invention relates to a kind of power boiler burning stability analysis technology, especially relate to a kind of combustion stability determination methods based on thermal decomposition.

Background technology

The jumbo station boiler of ultra supercritical becomes the trend of domestic power industry, and its efficient performance, lower pollutant emission and lower unit capacity cost have obvious advantage.Heavy duty boiler is huge on power grid security impact, and therefore, the security requirement of heavy duty boiler is also more and more higher.But by the impact of coal market, changeable coal and ature of coal and mixing are mixed the as-fired coal of joining and caused significant impact to the security that heavy duty boiler burns, show that the fluctuation of combustion instability, furnace pressure is large, steam superheat change is violent.If combustion instability, the burning efficiency of flame can be reduced on the one hand, waste a large amount of energy, increase production cost, the security incident of the impact safety in production such as burner hearth booster, detonation can be caused on the other hand, time serious, cause security incident.

Therefore be necessary very much to carry out anticipation to the stability of power boiler burning, take technical measures to guarantee Actual combustion process safety in advance, avoid the generation of calamity.Judge that power boiler burning is whether stable and mainly comprise 2 directions at present: furnace pressure signal when 1, monitoring hearth combustion, by minute-pressure fluctuation diagnosing combustion operating mode; 2, carry out characteristics extraction by digital image processing techniques team flame combustion image, judge whether burning stablizes.

There are 3 weak points in the method for current hearth combustion stability distinguishing: 1, boiler combustion always exists pressure fluctuation, and the pressure fluctuation signal of this state is difficult to when there is random fluctuation monitor preferably; 2, the flame kernel offset distance utilizing image analysis technology process image to obtain exists that fluctuation range is large, vibration frequency is fast, is unfavorable for the overall condition reflecting burning; 3, monitor judged result delayed, often after monitoring is pinpointed the problems, fault also there occurs in the lump, has little time to take preventive measures, and Operating Guideline is not strong.

Summary of the invention

Object of the present invention be exactly in order to overcome above-mentioned prior art exist defect and a kind of combustion stability determination methods based on thermal decomposition is provided.

Object of the present invention can be achieved through the following technical solutions:

Based on a combustion stability determination methods for thermal decomposition, it is characterized in that, obtained the judgement of stability condition of coal dust firing by the method for raw coal thermal decomposition, auxiliary with boiler design parameter, prejudge the combustion stability on some station boilers.

The method is specially:

1) as-fired coal is processed, division, drying, sample preparation, obtain moisture, sample that fineness is qualified;

2) obtain representative coal sample according to as-fired coal, carry out technical analysis and thermal decomposition experiment, obtain coal characteristic eigenwert;

3) basicly stable temperature of combustion surplus Δ T1 is calculated according to technical analysis and thermal decomposition experimental result;

4) correction smooth combustion temperature margin Δ T2 is calculated according to boiler capacity and structural parameters;

5) obtain by basicly stable temperature of combustion surplus Δ T1 and correction smooth combustion temperature margin Δ T2 the smooth combustion temperature margin Δ T being suitable for this coal;

6) the Theoretical combustion medial temperature Tc of raw coal in station boiler is obtained according to technical analysis result and coal burning caloricity;

7) judge the hot degree of raw coal combustion, be specially:

If Tc>Tf+ Δ T, then burning is in stable region,

If Tc=Tf+ Δ T, then burning is in critical section,

If Tc<Tf+ Δ T, then burning is in explosive area

Wherein Tf is maximum temperature of reaction.

Described step 1) be specially: grind to form particle diameter after being dried by the raw coal sample of set amount at the granule of 90 μm ~ 200 μm, the constant temperature oven being placed in 80 DEG C is slowly dried, Pulverized Coal after drying is sieved again, obtains the pulverized coal particle sample that particle diameter, moisture are all moderate.

Described step 2) be specially:

Technical analysis is carried out to as-fired coal former state, obtains total moisture Mt, fugitive constituent Vdaf, fixed carbon FCar, ash content Aar; Be placed in thermogravimetric analyzer to as-fired coal sample, carry out thermal decomposition according to the ambiance set, heating curve, obtain TG, DTG and DSC change curve and eigenwert weightless temperature Ts, maximum temperature of reaction Tf, burn temperature Te, maximum reaction velocity Vf, heat flow density qrz.

Described step 3) be specially, with fugitive constituent Vdaf, ash content Aar and weightless temperature Ts, maximum reaction velocity Vf, heat flow density qrz for characteristic quantity calculates basicly stable temperature of combustion surplus Δ T1, formula is Δ T1=(5.67*10 ^-8/ qrz*1000000/30) ^1/4* Aar/Vdaf*1000+Ts/Vf*3.

Described step 4) be specially, calculate with boiler capacity Qr, Thermal load of cross-section qA, volume heat load qV and revise smooth combustion temperature margin Δ T2, formula is Δ T2=qV/qA*4* (2000/Qr) ^1/2.

Described Δ T is specifically calculated as follows Δ T=a* Δ T1+b* Δ T2, and a, b are respectively modifying factor.

Described step 6) be specially:

(1) calculate oxygen, carbon dioxide, nitrogen gas component in flue gas according to coal elemental composition total moisture Mt, fugitive constituent Vdaf, fixed carbon FCar, ash content Aar and flue gas oxygen content, set up flue gas enthalpy temperature table;

(2) primary zone temperature Tzr is determined according to coal-fired mean calorie and flue gas enthalpy temperature table;

(3) furnace outlet gas temperature Tltc is calculated according to the furnace height of object boiler, width, the degree of depth, number of burners and position, inflow temperature, separator outlet steam temperature;

(4) medial temperature Tc when determining that burner hearth inside is surely fired with primary zone temperature Tzr and outlet cigarette temperature Tltc.

Described Tltc and Tc is specifically calculated as follows:

$Tltc=\frac{T_a^3}{M{\left(\frac{{\mathrm{\&sigma;}}_0{a}_l{\mathrm{\&psi;}}_{pj}{F}_{CT}{T}_a^3}{{\mathrm{\&psi;B}}_j{\mathrm{Vc}}_{pj}}\right)}^{0.6}+1}-273,$

Tc＝(Tzr+Tltc)/2，

In formula, T _afor theoretical temperature combustion, K; M is the parameter considering furnace flame maximum temperature relative position; σ ⁰for Boltzmann constant, 5.67 × 10 ^-11kJ/ (m ²sK ⁴); a _lfor furnace emissivity; B _jfor calculated fuel consumption, kg/s; Vc _pjfor the mean specific heat of hearth combustion product between furnace exit temperature and theoretical temperature combustion, kJ/ (kgK); ψ is burner hearth errors; ψ _pjfor burner hearth thermal effective coefficient; F _cTfor furnace heating surface amasss, m ².

Compared with prior art, the present invention is by adopting the mode of thermolysis process and boiler structure and technical parameter, obtain temperature levels and the reaction rate of coal dust smooth combustion, obtain the smooth combustion temperature margin of coal, the judgement of stability conclusion that stokehold just obtains coal dust firing can be entered at raw coal, achieve advance preventing, burning target mixed by prior station boiler of intervening, the hysteresis quality avoiding Real-Time Monitoring to bring and randomness, and the full load prediction of coal dust firing stability can be realized, improve the applicability that combustion stability judges.

Accompanying drawing explanation

Fig. 1 is particular flow sheet of the present invention.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.

For the combustion stability of coal burning boiler of power station can be judged earlier, make use whether judgement early, or take related measure early, improve the security of Boiler Stable Combustion, the invention process case provides a kind of determination methods of combustion stability, flow process is see Fig. 1, described below:

(1) grind to form particle diameter after being dried by a certain amount of raw coal sample at the granule of 90 μm ~ 200 μm, the constant temperature oven being placed in 80 DEG C is slowly dried, and the Pulverized Coal after drying again is sieved, obtains the pulverized coal particle sample that particle diameter, moisture are all moderate.

(2) technical analysis is carried out to as-fired coal former state, obtain total moisture Mt, fugitive constituent Vdaf, fixed carbon FCar, ash content Aar; Be placed in thermogravimetric analyzer to as-fired coal sample, carry out thermal decomposition according to the ambiance set, heating curve, obtain TG, DTG and DSC change curve and eigenwert weightless temperature Ts, maximum temperature of reaction Tf, burn temperature Te, maximum reaction velocity Vf, heat flow density qrz.

(3) calculate oxygen, carbon dioxide, nitrogen gas component in flue gas according to coal elemental composition total moisture Mt, fugitive constituent Vdaf, fixed carbon FCar, ash content Aar and flue gas oxygen content, set up flue gas enthalpy temperature table.

(4) primary zone temperature Tzr is determined according to coal-fired mean calorie and flue gas enthalpy temperature table.

(5) furnace outlet gas temperature Tltc is calculated according to the furnace height of object boiler, width, the degree of depth, number of burners and position, inflow temperature, separator outlet steam temperature.

(6) medial temperature Tltpj when determining that burner hearth inside is surely fired with primary zone temperature Tzr and outlet cigarette temperature Tltc.

(7) with Vdaf, Aar and Ts, Vf, qrz for characteristic quantity calculates basicly stable temperature of combustion surplus Δ T1;

(8) correction smooth combustion temperature margin Δ T2 is calculated with boiler capacity Qr, Thermal load of cross-section qA, volume heat load qV;

(9) obtain by basicly stable temperature of combustion surplus Δ T1 and correction smooth combustion temperature margin Δ T2 the smooth combustion temperature margin Δ T being suitable for this coal.

(10) utilize and realize medial temperature Tltpj, smooth combustion temperature margin Δ T and maximum temperature of reaction Tf when the inside that calculates surely is fired and carry out threshold value and compare, hot degree and the degree of stability of raw coal combustion can be judged according to comparison function f (x, y).

The combustion stability being achieved coal burning boiler of power station by above-mentioned steps 1 ~ 10 is judged, judges combustion stability from the angular advance of combustion mechanism and type of furnace characteristic, improves the science and perspective of combustion stability judgement.

Claims (9)

1. based on a combustion stability determination methods for thermal decomposition, it is characterized in that, obtained the judgement of stability condition of coal dust firing by the method for raw coal thermal decomposition, auxiliary with boiler design parameter, prejudge the combustion stability on some station boilers.

2. a kind of combustion stability determination methods based on thermal decomposition according to claim 1, it is characterized in that, the method is specially:

1) as-fired coal is processed, division, drying, sample preparation, obtain moisture, sample that fineness is qualified;

2) obtain representative coal sample according to as-fired coal, carry out technical analysis and thermal decomposition experiment, obtain coal characteristic eigenwert;

3) basicly stable temperature of combustion surplus Δ T1 is calculated according to technical analysis and thermal decomposition experimental result;

4) correction smooth combustion temperature margin Δ T2 is calculated according to boiler capacity and structural parameters;

5) obtain by basicly stable temperature of combustion surplus Δ T1 and correction smooth combustion temperature margin Δ T2 the smooth combustion temperature margin Δ T being suitable for this coal;

6) the Theoretical combustion medial temperature Tc of raw coal in station boiler is obtained according to technical analysis result and coal burning caloricity;

7) judge the hot degree of raw coal combustion, be specially:

If Tc>Tf+ Δ T, then burning is in stable region,

If Tc=Tf+ Δ T, then burning is in critical section,

If Tc<Tf+ Δ T, then burning is in explosive area

Wherein Tf is maximum temperature of reaction.

3. a kind of combustion stability determination methods based on thermal decomposition according to claim 2, it is characterized in that, described step 1) be specially: grind to form particle diameter after being dried by the raw coal sample of set amount at the granule of 90 μm ~ 200 μm, the constant temperature oven being placed in 80 DEG C is slowly dried, Pulverized Coal after drying is sieved again, obtains the pulverized coal particle sample that particle diameter, moisture are all moderate.

4. a kind of combustion stability determination methods based on thermal decomposition according to claim 3, is characterized in that, described step 2) be specially:

Technical analysis is carried out to as-fired coal former state, obtains total moisture Mt, fugitive constituent Vdaf, fixed carbon FCar, ash content Aar; Be placed in thermogravimetric analyzer to as-fired coal sample, carry out thermal decomposition according to the ambiance set, heating curve, obtain TG, DTG and DSC change curve and eigenwert weightless temperature Ts, maximum temperature of reaction Tf, burn temperature Te, maximum reaction velocity Vf, heat flow density qrz.

5. a kind of combustion stability determination methods based on thermal decomposition according to claim 4, it is characterized in that, described step 3) be specially, with fugitive constituent Vdaf, ash content Aar and weightless temperature Ts, maximum reaction velocity Vf, heat flow density qrz for characteristic quantity calculates basicly stable temperature of combustion surplus Δ T1, formula is Δ T1=(5.67*10 ^-8/ qrz*1000000/30) ^1/4* Aar/Vdaf*1000+Ts/Vf*3.

6. a kind of combustion stability determination methods based on thermal decomposition according to claim 4, it is characterized in that, described step 4) be specially, calculate with boiler capacity Qr, Thermal load of cross-section qA, volume heat load qV and revise smooth combustion temperature margin Δ T2, formula is Δ T2=qV/qA*4* (2000/Qr) ^1/2.

7. a kind of combustion stability determination methods based on thermal decomposition according to claim 4, is characterized in that, described Δ T is specifically calculated as follows Δ T=a* Δ T1+b* Δ T2, and a, b are respectively modifying factor.

8. a kind of combustion stability determination methods based on thermal decomposition according to claim 4, is characterized in that, described step 6) be specially:

(1) calculate oxygen, carbon dioxide, nitrogen gas component in flue gas according to coal elemental composition total moisture Mt, fugitive constituent Vdaf, fixed carbon FCar, ash content Aar and flue gas oxygen content, set up flue gas enthalpy temperature table;

(2) primary zone temperature Tzr is determined according to coal-fired mean calorie and flue gas enthalpy temperature table;

(3) furnace outlet gas temperature Tltc is calculated according to the furnace height of object boiler, width, the degree of depth, number of burners and position, inflow temperature, separator outlet steam temperature;

(4) medial temperature Tc when determining that burner hearth inside is surely fired with primary zone temperature Tzr and outlet cigarette temperature Tltc.

9. a kind of combustion stability determination methods based on thermal decomposition according to claim 8, it is characterized in that, described Tltc and Tc is specifically calculated as follows:

$Tltc=\frac{T_a^3}{M{\left(\frac{{\mathrm{\&sigma;}}_0{a}_l{\mathrm{\&psi;}}_{pj}{F}_{CT}{T}_a^3}{{\mathrm{\&psi;B}}_j{\mathrm{Vc}}_{pj}}\right)}^{0.6}+1}-273,$

Tc＝(Tzr+Tltc)/2，

In formula, T _afor theoretical temperature combustion, K; M is the parameter considering furnace flame maximum temperature relative position; σ ⁰for Boltzmann constant, 5.67 × 10 ^-11kJ/ (m ²sK ⁴); a _lfor furnace emissivity; B _jfor calculated fuel consumption, kg/s; Vc _pjfor the mean specific heat of hearth combustion product between furnace exit temperature and theoretical temperature combustion, kJ/ (kgK); ψ is burner hearth errors; ψ _pjfor burner hearth thermal effective coefficient; F _cTfor furnace heating surface amasss, m ².