CN114564833B - Method for determining high alkali coal boiler furnace thermal load parameter - Google Patents
Method for determining high alkali coal boiler furnace thermal load parameter Download PDFInfo
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- 239000003245 coal Substances 0.000 title claims abstract description 79
- 239000003513 alkali Substances 0.000 title claims abstract description 28
- 238000000034 method Methods 0.000 title claims abstract description 28
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000003546 flue gas Substances 0.000 claims abstract description 22
- 230000000630 rising effect Effects 0.000 claims abstract description 19
- 238000002485 combustion reaction Methods 0.000 claims abstract description 7
- 238000010438 heat treatment Methods 0.000 claims abstract description 4
- 239000000779 smoke Substances 0.000 claims description 12
- 238000001816 cooling Methods 0.000 claims description 7
- 239000002585 base Substances 0.000 claims description 4
- 230000014759 maintenance of location Effects 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 claims description 3
- 239000000843 powder Substances 0.000 claims description 3
- 239000007789 gas Substances 0.000 claims 1
- 238000011109 contamination Methods 0.000 abstract description 4
- 239000002817 coal dust Substances 0.000 abstract description 3
- 239000002956 ash Substances 0.000 description 10
- 238000007599 discharging Methods 0.000 description 3
- NAWXUBYGYWOOIX-SFHVURJKSA-N (2s)-2-[[4-[2-(2,4-diaminoquinazolin-6-yl)ethyl]benzoyl]amino]-4-methylidenepentanedioic acid Chemical compound C1=CC2=NC(N)=NC(N)=C2C=C1CCC1=CC=C(C(=O)N[C@@H](CC(=C)C(O)=O)C(O)=O)C=C1 NAWXUBYGYWOOIX-SFHVURJKSA-N 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000002893 slag Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 229910000272 alkali metal oxide Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000010883 coal ash Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000012938 design process Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
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- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
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Abstract
The invention discloses a method for determining a high alkali coal boiler hearth heat load parameter, which comprises the following steps: 1. basic design parameters such as boiler capacity, coal heating value and the like are obtained; 2. the proper width and depth of the boiler are obtained by controlling the rising flow rate of the flue gas; 3. controlling the heat release intensity of the wall surface of the burner zone to be a lower value by adjusting the height of the burner; 4. and determining the vertical distance from the center of the nozzle of the pulverized coal burner at the uppermost layer to the bottom of the screen by controlling the residence time of pulverized coal. 5. And finally obtaining proper boiler furnace heat load parameters according to the key size of the boiler and other empirical sizes. The method ensures that the combustion temperature of the high-alkali coal in the furnace is in a lower level as a whole by coordinately controlling the flue gas flow rate, the height of the burner zone and the residence time of the coal dust in the furnace, thereby improving the adaptability of the boiler to severe slagging and severe contamination of the high-alkali coal, and being applicable to the coal dust boiler with the weight of more than 100MW and having wider application range.
Description
Technical Field
The invention relates to the technical field of power station pulverized coal boiler design, in particular to a method for determining a high-alkali coal boiler hearth heat load parameter, which is suitable for a high-alkali coal solid slag-discharging pulverized coal boiler with a capacity level of more than 100 MW.
Background
In Xinjiang area of China, there are 3900 hundred million tons of eastern coal and 2000 hundred million tons of Hami coal, which are high-alkali coal and are typically characterized by Na in coal ash 2 O, caO, mgO and the like, while SiO is high in alkali oxide content 2 And Al 2 O 3 The content of the equal acid oxide is low, although the ignition and burnout performances are excellent, the slagging and contamination performances are serious, the slagging and contamination prevention design needs to be enhanced in the boiler design process, the adaptability of the boiler to high-alkali coal is improved, and the selection of the heat load parameters of a hearth is critical. The furnace with different combustion modes is definitely specified in the 'DL/831-2015 high-capacity pulverized coal fired boiler furnace selection guide rules', and the selection guide rules can generally adopt the following 4 main characteristic parameters (BMCR working conditions): 1 furnace volume heat release intensity, qv, kW/m 3 (upper limit value), (2) heat release intensity of furnace section, q F ，MW/m 2 (available value); (3) intensity of heat release from burner zone wall, q B ，MW/m 2 (upper limit value); (4) heat release intensity of burnout zone volume, q m ，kW/m 3 (upper limit value). The 4 th characteristic parameter can also be replaced by the vertical distance h from the center of the nozzle of the uppermost pulverized coal burner to the bottom of the screen 1 M (lower limit value).
In recent years, the adaptability of the boiler furnace to the high alkali coal is greatly improved through the optimization of the heat load parameters, and the blending ratio of the high alkali coal is greatly improved, but the heat load parameter selection principle of the boiler furnace specified in the DL/831-2015 high-capacity pulverized coal combustion boiler furnace selection guide rule is not applicable to the high alkali coal, so that the heat load parameters of the high alkali coal boiler furnace with different capacity grades are not specifically specified.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a method for determining the heat load parameters of a high-alkali coal boiler hearth, which is suitable for a high-alkali coal solid slag-discharging pulverized coal boiler with a capacity grade of more than 100 MW.
In order to achieve the above purpose, the invention adopts the following technical scheme,
method for determining heat load parameters of high-alkali coal boiler furnace, wherein the heat load parameters of the boiler furnace under BMCR working conditions comprise (1) furnace volume heat release intensity qv, kW/m 3 (2) furnace section heat release intensity q F ，MW/m 2 The method comprises the steps of carrying out a first treatment on the surface of the (3) Intensity q of heat release from wall surface of burner zone B ，MW/m 2 The method comprises the steps of carrying out a first treatment on the surface of the (4) Vertical distance h from nozzle center of uppermost pulverized coal burner to screen bottom 1 M, the method comprising the steps of:
the first step: the following parameters are obtained from scheme design data or preliminary design data of specific engineering:
unit capacity RL, MW; design of theoretical combustion temperature t of coal a C, controlling the temperature; low-grade heating value Q of received base of design coal net,ar MJ/kg; coal-fired input heat Q of boiler r GJ/h; flue gas volume V in standard state y ，Nm 3 /kg; furnace outlet temperature t out C, controlling the temperature; the number of burner layers n,/; atmospheric pressure P local to the plant d ，kPa；
And a second step of: according to design experience, preliminarily determining the width W, the depth D and the height h of the burner of the hearth 2 Calculating the average rising speed W of the flue gas in the furnace y Width W, depth D and burner height h of furnace 2 In units of m, average rising speed W y Is in units of m/s;
and a third step of: calculating the recommended smoke rising speed W under the unit capacity yt M/s; fluctuation coefficient k,%; recommended maximum smoke rise rate W ytmax M/s; recommended minimum smoke rise rate W ytmin ，m/s；
If W calculated in the second step y Satisfy W ytmin ≤W y ≤W ytmax Determining the width W) and depth D of the hearth preliminarily assumed in the second step as the width and depth of the boiler, otherwise, increasing the width W and depth D of the hearth according to design experience, andreturning to the second step of calculation until W ytmin ≤W y ≤W ytmax Then calculating the heat load q of the section of the boiler furnace F ，MW/m 2 ；
Fourth step: based on the furnace width W, depth D determined in the second step and the burner height h preliminarily determined in the second step 2 Calculating the heat release intensity q of the wall surface of the burner region B ，MW/m 2 If q B ≤0.84MW/m 2 Then enter the fifth step, otherwise increase h 2 And return to the second step until q B ≤0.84MW/m 2 ；
Fifth step: the furnace width W, the depth D determined according to the third step and the burner height h determined according to the fourth step 2 Returning to the second step to calculate and calculate the average rising speed W of the flue gas in the furnace y At the same time, the vertical distance h from the center of the nozzle of the pulverized coal burner at the uppermost layer to the screen bottom is assumed 1 Calculating the residence time t of the pulverized coal in the furnace, wherein a specific calculation formula is shown in a formula (12);
sixth step: if the retention time t of the coal powder calculated in the fifth step in the furnace is more than or equal to 3.4s, determining h assumed in the fifth step 1 The vertical distance from the nozzle center of the uppermost pulverized coal burner to the screen bottom determined for the boiler enters a seventh step, otherwise h is increased 1 Returning to the fifth step until t is more than or equal to 3.4s;
seventh step: burner height h determined in a fourth step from the furnace width W, depth D determined in the final second step 2 The vertical distance h from the nozzle center of the uppermost pulverized coal burner to the screen bottom determined in the fifth step 1 And other empirical parameters of the boiler to obtain the volume V of the hearth, and calculating the volume heat load q of the hearth V ，kW/m 3 The specific calculation is shown in formula (13);
wherein V is the furnace volume, m 3 The calculation formula is as follows:
V＝V 1 +V 2 +V 3 +V 4
wherein V is 1 Is the volume of the screen area, and the calculation formula is as follows:
V 1 ＝W×(D-(h 5 -h 6 )×cotα)×h 4
wherein V is 2 Is the volume of the burnout zone, and the calculation formula is as follows:
V 2 ＝(h 5 ×D-0.5×cotα×(h 5 -h 6 ) 2 )×W
wherein V is 3 The volume from the center of the burner at the uppermost layer to the inflection point on the ash cooling hopper is calculated as follows:
V 3 ＝W×D×(h 2 +h 3 )
wherein V is 4 Is the volume of the cold ash bucket area, and the calculation formula is as follows:
wherein: h is a 3 Is the vertical distance h between the center line of the pulverized coal nozzle of the burner at the lowest row and the break point on the cold ash bucket 4 Is the vertical distance from the bottom of the screen to the top canopy pipe, h 5 Is the burnout height, h 6 The vertical distance between the center of the burner at the uppermost layer and the lower folding point of the folding flame angle is alpha, the lower inclination angle of the folding flame angle is beta, and the included angle between the slope of the ash cooling hopper and the horizontal plane is beta;
therefore, the heat release intensity q of the section of the furnace chamber obtained in the third step F The heat release intensity q of the wall surface of the burner area obtained in the fourth step B The vertical distance h from the nozzle center of the uppermost pulverized coal burner to the screen bottom obtained in the fifth step 1 And the determined heat release intensity qv of the hearth volume in seven steps is a heat load parameter finally determined by the boiler.
The invention is further improved in that in the second step, the calculation formula is as follows:
wherein: q (Q) r -coal fired input heat of boiler GJ/h;
V y flue gas volume in standard state, nm 3 /kg；
W, D, the width and depth of the section of the hearth, m;
t p -average furnace temperature, c, see in particular formula (2);
t p ＝(t 1 ×t 2 ) 0.5 (2)
in the formula (2):
t 1 -average flame temperature of the hearth, c, specific calculation is given in formula (3);
t 1 ＝0.925×(t a ×t out ) 0.5 (3)
t out -furnace exit temperature, DEG C;
t 2 -flame average temperature of the burner region, c, calculated specifically as formula (4);
t 2 ＝1144+249×ln(0.86×q fz )(4)
wherein: q FZ Furnace conversion heat load, MW/m 2 The specific calculation is shown in formula (5);
the invention is further improved in that in the third step, the smoke rising speed W is recommended yt See formula (i) below:
W yt ＝2.1662×RL 0.2037 (6)。
a further improvement of the invention is that in the third step, a maximum flue gas rise rate W is recommended ytmax See formula (i) below:
a further improvement of the invention is that in the third step, a minimum flue gas rise rate W is recommended ytmin See formula (i) below:
the invention is further improved in that in the third step, the fluctuation coefficient k of the rising speed of the smoke is calculated according to the following formula:
k＝7.76×RL -0.232 (9)。
a further improvement of the invention is that in the third step, the heat load q of the boiler furnace section F See formula (i) below:
a further development of the invention is that in the fourth step, the heat release intensity q of the burner zone wall surface B See formula (i) below:
compared with the prior art, the invention has at least the following beneficial technical effects:
1) According to the method provided by the invention, the heat load parameter of the boiler can be controlled at a lower value, meanwhile, the residence time of the pulverized coal in the boiler is ensured, the slag bonding resistance and the contamination resistance of the convection heating surface of the boiler hearth are improved, and the adaptability of the boiler to high-alkali coal is further improved.
2) The method fully reflects the influence of the coal dust residence time as a key core factor on the design of the high-alkali coal boiler.
3) By adopting the method, the highest temperature of the hearth can be controlled at a lower smoke temperature level of about 1250 ℃, the peak temperature of a burner area is reduced, and further, the slagging and the pollution of a boiler are relieved.
4) The invention is applicable to pulverized coal boilers with the power of more than 100MW and has wider application range.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below. It should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other. The present invention will be described in detail with reference to examples.
Case 1 is 1 660MW high alkali coal unit
Method for determining high alkali coal boiler furnace heat load parameters, wherein the furnace heat load parameters (BMCR working conditions) comprise (1) furnace volume heat release intensity qv, kW/m 3 (2) furnace section heat release intensity q F ，MW/m 2 The method comprises the steps of carrying out a first treatment on the surface of the (3) Intensity q of heat release from wall surface of burner zone B ，MW/m 2 The method comprises the steps of carrying out a first treatment on the surface of the (4) Vertical distance h from nozzle center of uppermost pulverized coal burner to screen bottom 1 ，m。
The method comprises the following steps:
the first step: the following parameters are obtained from scheme design data or preliminary design data of specific engineering:
unit capacity RL (MW), theoretical combustion temperature t of coal a Designing the heat productivity Q of the received base low level of the coal net,ar (MJ/kg), the coal-fired input heat Q of the boiler r (GJ/h), flue gas volume V in Standard State y (Nm 3 Per kg), furnace outlet temperature t out (°c), number of burner floors n (/), local atmospheric pressure P of the plant d (kPa)。
Unit capacity rl=660 MW, theoretical combustion temperature t of design coal a =1930 ℃, designed coal received-base low-rank calorific value Q net,ar 18.26MJ/kg, coal input heat Q of boiler r =5600 GJ/h, flue gas volume in furnace V y ＝6.8Nm 3 Kg, furnace outlet temperature t out ＝960℃Burner floor number n=4, atmospheric pressure P local to the plant d ＝95.8kPa；
And a second step of: according to design experience, preliminarily determining the width W (m), the depth D (m) and the height h of the burner of the hearth 2 (m) calculating the average rise rate W of the flue gas in the furnace y (m/s), specifically formula (1):
this preliminary determination w=25.7m, deep d=16.3m, burner height h 2 =19.2m, then the flue gas flow rate calculation is shown in formula (1);
wherein: q (Q) r -coal fired input heat of boiler GJ/h;
V y flue gas volume in standard state, nm 3 /kg；
W, D, the width and depth of the section of the hearth, m;
t p -average furnace temperature, c, see in particular formula (2);
t p ＝(t 1 ×t 2 ) 0.5 ＝(1259×1230) 0.5 ＝1244(2)
in the formula (2):
t 1 -average flame temperature of the hearth, c, specific calculation is given in formula (3);
t 1 ＝0.925×(t a ×t out ) 0.5 ＝0.925×(1930×960) 0.5 ＝1259(3)
t out -furnace exit temperature, DEG C;
t 2 -flame average temperature of the burner region, c, calculated specifically as formula (4);
wherein: q FZ Furnace conversion heat load, MW/m 2 The specific calculation is shown in formula (5);
and a third step of: calculating the recommended smoke rising speed W under the unit capacity yt (m/s), fluctuation coefficient k (%) of the smoke rising speed, the maximum smoke rising speed W is recommended ytmax (m/s), recommended minimum flue gas rise rate W ytmin (m/s), for specific calculations see formulas (6) to (9);
the unit capacity RL=660 MW;
W yt ＝2.1662×RL 0.2037 ＝2.1662×660 0.2037 ＝8.13(6)
k＝7.76×RL -0.232 ＝7.76×660 -0.232 ＝1.721(9)
if W calculated in the second step y (m/s) satisfy W ytmin (m/s)≤W y (m/s)≤W ytmax (m/s), determining the primarily assumed furnace width W (m) and depth D (m) of the second step as the width and depth of the boiler, otherwise, increasing the furnace width W (m) and depth D (m) according to design experience, and returning to the second step for calculation until W ytmin (m/s)≤W y (m/s)≤W ytmax (m/s) and then calculating the heat load q of the boiler furnace section F (MW/m 2 ) The specific calculation is shown in a formula (10);
w calculated in the second step y =8.13 (m/s), W calculated in the third step ytmin ＝8.0m/s，W ytmax =8.27 m/s, thus satisfying W ytmin (m/s)≤W y (m/s)≤W ytmax (m/s), the furnace width w=25.7m and the depth d=16.3m assumed in the second step are the determined boiler width and depth. And calculating the related hearth thermal load parameters according to the formula (10), wherein the calculation is specifically as follows:
fourth step: a furnace width W (m), a depth D (m) determined according to the second step and a burner height h preliminarily determined according to the second step 2 (m) calculating the burner zone wall heat release intensity q B (MW/m 2 ) The specific calculation is shown in the formula (11), if q B ≤0.84MW/m 2 Then enter the fifth step, otherwise increase h 2 And return to the second step until q B ≤0.84MW/m 2 ；
This time q B ＝0.83≤0.84MW/m 2 Entering a fifth step;
fifth step: the furnace width W (m), the depth D (m) and the burner height h determined in the fourth step according to the third step 2 (m) returning to the second step to calculate and calculate the average rising speed W of the flue gas in the furnace y (m/s) assuming a vertical distance h from the center of the nozzle of the uppermost pulverized coal burner to the bottom of the screen 1 (m) calculating the residence time t(s) of the pulverized coal in the furnace, wherein the specific calculation formula is shown in the formula (12);
sixth step: if the retention time t of the coal powder calculated in the fifth step in the furnace is more than or equal to 3.4s, determining h assumed in the fifth step 1 The vertical distance from the nozzle center of the uppermost pulverized coal burner to the screen bottom determined for the boiler enters a seventh step, otherwise h is increased 1 Returning to the fifth step until t is more than or equal to 3.4s;
the calculated retention time t=3.44 s of the pulverized coal in the furnace is entered into the seventh step.
Seventh step: burner height determined from final second step of furnace width W (m), depth D (m) and fourth steph 2 (m) the vertical distance h from the center of the nozzle of the uppermost pulverized coal burner to the bottom of the screen determined in the fifth step 1 And other empirical parameters of the boiler, to obtain the volume V (m 3 ) And calculating q of the heat load of the volume of the hearth V (kW/m 3 ) The specific calculation is shown in formula (13);
the calculation formula of the furnace volume V is as follows:
V＝V 1 +V 2 +V 3 +V 4
wherein V is 1 Is the volume of the screen area, and the calculation formula is as follows:
V 1 ＝W×(D-(h 5 -h 6 )×cotα)×h 4
wherein V is 2 Is the volume of the burnout zone, and the calculation formula is as follows:
V 2 ＝(h 5 ×D-0.5×cotα×(h 5 -h 6 ) 2 )×W
wherein V is 3 The volume from the center of the burner at the uppermost layer to the inflection point on the ash cooling hopper is calculated as follows:
V 3 ＝W×D×(h 2 +h 3 )
wherein V is 4 Is the volume of the cold ash bucket area, and the calculation formula is as follows:
wherein: h is a 3 Is the vertical distance h between the center line of the pulverized coal nozzle of the burner at the lowest row and the break point on the cold ash bucket 4 Is the vertical distance from the bottom of the screen to the top canopy pipe, h 5 Is the burnout height, h 6 Is the vertical distance between the center of the burner at the uppermost layer and the lower folding point of the folding flame angle, alpha is the lower inclination angle of the folding flame angle, and beta is the included angle between the slope of the ash cooling hopper and the horizontal plane.
The final w=25.7m, d=16.3m, h 2 ＝19.2m，h 1 =28m, other empirical parameters: (1) vertical distance h between pulverized coal nozzle center line of lowest burner and break point on cold ash bucket 3 =5m; (2) slag discharging throat net depth d 2 =1.5m; (3) the included angle beta=55 DEG between the slope of the ash cooling hopper and the horizontal plane; (4) vertical distance h between screen bottom and roof pipe 4 =19.5m; (5) the downward inclination angle of the folded flame angle alpha=55°, and (6) the vertical distance h between the center of the burner at the uppermost layer and the downward folding point of the folded flame angle 6 =26m. Calculated boiler volume v=30863m 3 The furnace volume heat load parameters are as follows:
wherein V is the furnace volume, m 3 。
Therefore, the heat release intensity q of the section of the furnace chamber obtained in the third step F (MW/m 2 ) The heat release intensity q of the wall surface of the burner area obtained in the fourth step B (MW/m 2 ) The vertical distance h from the nozzle center of the uppermost pulverized coal burner to the screen bottom obtained in the fifth step 1 (m) seven-step determination of the furnace volume heat release intensity qv (kW/m) 3 ) And finally determining the heat load parameters for the boiler. The final see the table below for this case.
While the invention has been described in detail in the foregoing general description and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that modifications and improvements can be made thereto. Accordingly, such modifications or improvements may be made without departing from the spirit of the invention and are intended to be within the scope of the invention as claimed.
Claims (8)
1. A method for determining the heat load parameters of high-alkali coal boiler furnace is characterized in that the heat load parameters of the boiler furnace under BMCR working condition comprise (1) furnace volume heat release intensity qv,kW/m 3 (2) furnace section heat release intensity q F ，MW/m 2 The method comprises the steps of carrying out a first treatment on the surface of the (3) Intensity q of heat release from wall surface of burner zone B ，MW/m 2 The method comprises the steps of carrying out a first treatment on the surface of the (4) Vertical distance h from nozzle center of uppermost pulverized coal burner to screen bottom 1 M, the method comprising the steps of:
the first step: the following parameters are obtained from scheme design data or preliminary design data of specific engineering:
unit capacity RL, MW; design of theoretical combustion temperature t of coal a C, controlling the temperature; low-grade heating value Q of received base of design coal net,ar MJ/kg; coal-fired input heat Q of boiler r GJ/h; flue gas volume V in standard state y ，Nm 3 /kg; furnace outlet temperature t out C, controlling the temperature; the number of burner layers n,/; atmospheric pressure P local to the plant d ，kPa；
And a second step of: according to design experience, preliminarily determining the width W, the depth D and the height h of the burner of the hearth 2 Calculating the average rising speed W of the flue gas in the furnace y Width W, depth D and burner height h of furnace 2 In units of m, average rising speed W y Is in units of m/s;
and a third step of: calculating the recommended smoke rising speed W under the unit capacity yt M/s; fluctuation coefficient k,%; recommended maximum smoke rise rate W ytmax M/s; recommended minimum smoke rise rate W ytmin ，m/s；
If W calculated in the second step y Satisfy W ytmin ≤W y ≤W ytmax Determining the primarily assumed furnace width W) and depth D of the second step as the width and depth of the boiler, otherwise, increasing the furnace width W and depth D according to design experience, and returning to the second step for calculation until W ytmin ≤W y ≤W ytmax Then calculating the heat load q of the section of the boiler furnace F ，MW/m 2 ；
Fourth step: based on the furnace width W, depth D determined in the second step and the burner height h preliminarily determined in the second step 2 Calculating the heat release intensity q of the wall surface of the burner region B ，MW/m 2 If q B ≤0.84MW/m 2 Then enter the fifth step, otherwise increase h 2 And return to the second step until q B ≤0.84MW/m 2 ；
Fifth step: the furnace width W, the depth D determined according to the third step and the burner height h determined according to the fourth step 2 Returning to the second step to calculate and calculate the average rising speed W of the flue gas in the furnace y At the same time, the vertical distance h from the center of the nozzle of the pulverized coal burner at the uppermost layer to the screen bottom is assumed 1 Calculating the residence time t of the pulverized coal in the furnace, wherein a specific calculation formula is shown in a formula (12);
sixth step: if the retention time t of the coal powder calculated in the fifth step in the furnace is more than or equal to 3.4s, determining h assumed in the fifth step 1 The vertical distance from the nozzle center of the uppermost pulverized coal burner to the screen bottom determined for the boiler enters a seventh step, otherwise h is increased 1 Returning to the fifth step until t is more than or equal to 3.4s;
seventh step: burner height h determined in a fourth step from the furnace width W, depth D determined in the final second step 2 The vertical distance h from the nozzle center of the uppermost pulverized coal burner to the screen bottom determined in the fifth step 1 And other empirical parameters of the boiler to obtain the volume V of the hearth, and calculating the volume heat load q of the hearth V ，kW/m 3 The specific calculation is shown in formula (13);
wherein V is the furnace volume, m 3 The calculation formula is as follows:
V＝V 1 +V 2 +V 3 +V 4
wherein V is 1 Is the volume of the screen area, and the calculation formula is as follows:
V 1 ＝W×(D-(h 5 -h 6 )×cotα)×h 4
wherein V is 2 Is the volume of the burnout zone, and the calculation formula is as follows:
V 2 ＝(h 5 ×D-0.5×cotα×(h 5 -h 6 ) 2 )×W
wherein V is 3 The volume from the center of the burner at the uppermost layer to the inflection point on the ash cooling hopper is calculated as follows:
V 3 ＝W×D×(h 2 +h 3 )
wherein V is 4 Is the volume of the cold ash bucket area, and the calculation formula is as follows:
wherein: h is a 3 Is the vertical distance h between the center line of the pulverized coal nozzle of the burner at the lowest row and the break point on the cold ash bucket 4 Is the vertical distance from the bottom of the screen to the top canopy pipe, h 5 Is the burnout height, h 6 The vertical distance between the center of the burner at the uppermost layer and the lower folding point of the folding flame angle is alpha, the lower inclination angle of the folding flame angle is beta, and the included angle between the slope of the ash cooling hopper and the horizontal plane is beta;
therefore, the heat release intensity q of the section of the furnace chamber obtained in the third step F The heat release intensity q of the wall surface of the burner area obtained in the fourth step B The vertical distance h from the nozzle center of the uppermost pulverized coal burner to the screen bottom obtained in the fifth step 1 And the determined heat release intensity qv of the hearth volume in seven steps is a heat load parameter finally determined by the boiler.
2. The method for determining heat load parameters of a high alkali coal boiler furnace according to claim 1, wherein in the second step, the calculation formula is:
wherein: q (Q) r -coal fired input heat of boiler GJ/h;
V y -signFlue gas volume in quasi-state, nm 3 /kg；
W, D, the width and depth of the section of the hearth, m;
t p -average furnace temperature, c, see in particular formula (2);
t p ＝(t 1 ×t 2 ) 0.5 (2)
in the formula (2):
t 1 -average flame temperature of the hearth, c, specific calculation is given in formula (3);
t 1 ＝0.925×(t a ×t out ) 0.5 (3)
t out -furnace exit temperature, DEG C;
t 2 -flame average temperature of the burner region, c, calculated specifically as formula (4);
t 2 ＝1144+249×ln(0.86×q fz )(4)
wherein: q FZ Furnace conversion heat load, MW/m 2 The specific calculation is shown in formula (5);
3. a method for determining heat load parameters of high alkali coal boiler furnace according to claim 2, wherein in the third step, the flue gas rising speed W is recommended yt See formula (i) below:
W yt ＝2.1662×RL 0.2037 (6)。
4. a method for determining heat load parameters of high alkali coal boiler furnace according to claim 3, characterized in that in the third step, the maximum flue gas rising speed W is recommended ytmax See formula (i) below:
5. the method for determining heat load parameters of high alkali coal boiler furnace according to claim 4, wherein in the third step, the minimum flue gas rising speed W is recommended ytmin See formula (i) below:
6. the method for determining heat load parameters of high alkali coal boiler furnace according to claim 5, wherein in the third step, the fluctuation coefficient k of the rising speed of the flue gas is calculated by the following formula:
k＝7.76×RL -0.232 (9)。
7. a method for determining heat load parameters of high alkali coal boiler furnace according to claim 6, wherein in the third step, heat load q of boiler furnace section F See formula (i) below:
8. the method for determining heat load parameters of high alkali coal boiler furnace according to claim 7, wherein in the fourth step, the heat release intensity q of the wall surface of the burner zone B See formula (i) below:
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