阅读说明：本技术 一种燃煤锅炉褐煤掺烧比例预测方法及装置 (Method and device for predicting lignite blending combustion ratio of coal-fired boiler ) 是由 方军庭 邓中乙 马启磊 潘存华 石军伟 吴戈杨 韩磊 彭志福 洪皓月 于 2021-07-06 设计创作，主要内容包括：本发明提供了一种燃煤锅炉褐煤掺烧比例预测方法,包括,步骤A：根据锅炉使用中处于工作状态的磨煤机数量划分锅炉负荷区间,基于历史运行规律获得下一运行周期内不同负荷区间下的运行时间占比；步骤B：在各负荷区间下,以一台磨煤机使用非褐煤其余磨煤机全部使用褐煤的方式获得掺烧比例；步骤C：以各负荷区间下的运行时间占比与该负荷区间下的掺烧比例的乘积之和作为＝褐煤最大掺烧比例。本发明的优点在于：通过历史数据推测下一周期锅炉的运行工况,并简化锅炉运行模型,直接以适用褐煤和非褐煤的磨煤机数量确定掺烧比例,由此方便计算,通过历史数据计算满足运行要求的最大掺烧比例,为褐煤的采购和使用提供指导,提高电厂运行的经济性。(The invention provides a method for predicting the lignite co-combustion ratio of a coal-fired boiler, which comprises the following steps: dividing boiler load intervals according to the number of coal mills in working states in use of the boiler, and obtaining operation time ratio of different load intervals in the next operation period based on historical operation rules; and B: under each load interval, the blending combustion proportion is obtained in a mode that one coal mill uses non-lignite coal mills to completely use lignite; and C: and taking the sum of the product of the operating time ratio in each load interval and the blending ratio in the load interval as the maximum blending ratio of the lignite. The invention has the advantages that: the operation condition of the boiler in the next period is presumed through historical data, the boiler operation model is simplified, the blending proportion is directly determined according to the number of coal mills suitable for lignite and non-lignite, calculation is facilitated, the maximum blending proportion meeting the operation requirement is calculated through the historical data, guidance is provided for purchasing and using of lignite, and the economical efficiency of power plant operation is improved.)

1. A method for predicting the lignite blending combustion ratio of a coal-fired boiler is characterized by comprising the following steps: comprises that

Step A: dividing boiler load intervals according to the number of coal mills in working states in use of the boiler, and obtaining operation time ratio of different load intervals in the next operation period based on historical operation rules;

and B: under each load interval, the blending combustion proportion is obtained in a mode that one coal mill uses non-lignite coal mills to completely use lignite;

and C: and taking the sum of the product of the operating time ratio in each load interval and the blending ratio in the load interval as the maximum blending ratio of the lignite in the next operating period.

2. The method for predicting the co-combustion ratio of the coal-fired boiler according to claim 1, wherein: further comprises a step of correcting the maximum blending ratio calculated in the step C,

step D: calculating the lower limit of the heat value of the lignite when the blending combustion proportion in the step B is met in different load intervals, and taking the maximum value of the calculated lower limit of the heat value of the lignite in different load intervals as the maximum lower limit of the heat value of the lignite;

step E: if the actual heat value of the lignite is larger than the maximum lower limit of the heat value, outputting the maximum blending combustion ratio of the lignite in the step C; otherwise, turning to the step F;

step F: and D, increasing the number of the non-lignite coal mills used in each load interval in the step B by 1, recalculating the blending combustion ratio in different load intervals, and repeating the steps C-E.

3. The method for predicting the co-combustion ratio of the coal-fired boiler according to claim 2, wherein: the boiler load is divided into four load intervals of 40-50% THA, 50-65% THA, 65-85% THA and 85-100% THA; and taking the average value of historical data of at least 1 previous operating cycle as operating time proportions of each load interval of the next operating cycle, namely a, b, c and d.

4. The method for predicting the co-combustion ratio of the coal-fired boiler according to claim 3, wherein: the number of the coal mills participating in operation in each load interval is m_nAnd n is 1,2,3,4, the blending ratio in different load intervals in the step B is respectivelyThe maximum blending ratio in the step C is

5. The method for predicting the co-combustion ratio of the coal-fired boiler according to claim 4, wherein: the method for calculating the lower limit of the heat value of the lignite in the step D comprises the following steps:

the calculation formula of the coal consumption for power generation is

Q＝R_h×7000

Combining the above three formulas to obtain the final product

Wherein, b_fg/(kW & h) for generating coal consumption; b is_bThe coal consumption in the statistical period is t; w_fIs the generated energy, kW.h; eta_gdFor pipeline efficiency; eta_gThe thermal efficiency of the boiler is shown; q is heat rate, kJ/(kW.h); r_hTaking 4.1868kJ/kcal as a thermal equivalent value; 7000 is standard coal calorific value, kcal; q is the heat value of the fire coal, kJ/kg;

order, Q → Q_net,B_b→m,W_f→ E, obtained

Wherein Q is_netThe heat value of the fire coal, m is the total coal consumption in unit time, and E is the total generated energy in unit time;

according to the formula, calculating the lower limit of the heat value of the fire coal in different load intervals; the lower limit of the heat value of the fire coal is the maximum heat value when the heat consumption rate is maximum and the boiler heat efficiency is minimum in the load interval;

under the condition that the heat value of the non-lignite is basically unchanged, the following relation is satisfied:

lower limit of heat value of fuel coal, non-lignite heat value, non-lignite proportion and lignite heat value, lignite proportion

Therefore, the temperature of the molten metal is controlled,

the lower limit of the heat value of the lignite (lower limit of the heat value of the fuel coal-heat value of the non-lignite) meeting the maximum blending combustion proportion/the proportion of the lignite

Based on the formula, the lower limit of the heat value of the lignite under different load intervals is calculated, and the maximum value of the lower limit of the heat value of the lignite is taken as the maximum lower limit Q_max。

6. The method for predicting the co-combustion ratio of the coal-fired boiler according to claim 2, wherein: and taking the average value of the coal-fired boiler maintenance records of at least one past operation period as the maintenance plan of the coal-fired boiler of the next operation period, when the coal-fired boiler is in the maintenance state, simplifying the coal-fired boiler into one reduced total coal pulverizer number, wherein the normal operation time is p days, the maintenance operation time is (365-p) days, subdividing the load interval and the corresponding operation time ratio, and executing the steps B-F to obtain the maximum blending combustion ratio in the maintenance state.

7. The method for predicting the co-combustion ratio of the coal-fired boiler according to claim 6, wherein: under the condition of considering the maintenance of the coal-fired boiler, the comprehensive maximum blending combustion ratio of the next operation period is

Wherein eta is the maximum mixing combustion ratio of lignite₁Is the maximum mixing burning proportion eta of the lignite under the normal working condition₂Is the maximum blending combustion ratio of the lignite under the maintenance state.

8. The method for predicting the blending combustion ratio of lignite in a coal-fired boiler according to claim 1, wherein the method comprises the following steps: the operating cycle is one year.

9. A coal fired boiler brown coal blending combustion proportion prediction device is characterized in that: comprises that

Load interval divides module: dividing boiler load intervals according to the number of coal mills in working states in use of the boiler, and obtaining operation time ratio of different load intervals in the next operation period based on historical operation rules;

blending combustion ratio determination module: under each load interval, the blending combustion proportion is obtained in a mode that one coal mill uses non-lignite coal mills to completely use lignite;

a calculation module: and taking the sum of the product of the operating time ratio in each load interval and the blending ratio in the load interval as the maximum blending ratio of the lignite in the next operating period.

10. The coal-fired boiler co-combustion ratio prediction device according to claim 9, characterized in that: also comprises the following steps of (1) preparing,

a theoretical heat value calculation module: calculating the lower limit of the heat value of the lignite when the blending proportion determined by the blending proportion determining module is met in different load intervals, and taking the maximum value of the calculated lower limit of the heat value of the lignite in different load intervals as the maximum lower limit of the heat value of the lignite;

a comparison module: if the actual heat value of the lignite is larger than the maximum lower limit of the heat value, outputting the maximum blending combustion proportion of the lignite; otherwise, executing a mixed burning mode updating module;

the mixed burning mode updating module: and increasing the number of the non-lignite coal mills used in each load interval corresponding to the current maximum blending ratio by 1, recalculating the blending ratio in different load intervals, and returning to the calculation module.

Technical Field

The invention relates to the technical field of coal-fired power generation, in particular to a method and a device for predicting the lignite co-combustion ratio of a coal-fired boiler.

Background

In recent years, with the influence of factors such as market environment, coal yield, electric power production and the like, the coal-fired cost of the thermal power plant rises year by year, and coal blending combustion is an effective way for reducing the power generation cost of the thermal power plant. The coal purchasing strategy of the thermal power plant needs to be adjusted flexibly according to the coal market dynamics, and non-designed economic coal types are properly blended. The unit price of the lignite is low, the lignite is suitable for being used as a blended coal type, but the calorific value of the lignite is low and the deviation of the calorific value is large, a reasonable fuel purchasing plan needs to be made on the premise of ensuring the load carrying capacity of a unit, and the economical efficiency of the operation of a power plant is improved. Therefore, the blending combustion proportion of the lignite needs to be predicted and calculated, and the optimal economy is guaranteed.

The existing calculation method estimates the annual data only through the statistical value of the lignite blending combustion amount in the past year, and has no scientific systematic calculation method. And the lignite with different heat values cannot be effectively distinguished, and the heat values of the lignite cannot be pre-judged on the premise of ensuring the loading capacity and the optimal economy of a unit.

The invention patent with publication number CN105135459A discloses a method for calculating the lignite blending capacity of a coal mill, which is implemented by obtaining the maximum blending combustion amount of the coal mill in different states and taking the minimum maximum blending combustion amount as the maximum blending combustion amount. The method is simple in calculation mode, only the operation condition of a single coal mill is considered, and the future blending combustion ratio cannot be predicted from the perspective of a thermal power plant.

Disclosure of Invention

The invention aims to provide a lignite co-combustion ratio prediction method to obtain a co-combustion ratio which ensures the loading capacity and the optimal economic requirement of a unit.

The invention solves the technical problems through the following technical scheme: a method for predicting the lignite co-combustion ratio of a coal-fired boiler comprises

Step A: dividing boiler load intervals according to the number of coal mills in working states in use of the boiler, and obtaining operation time ratio of different load intervals in the next operation period based on historical operation rules;

and B: under each load interval, the blending combustion proportion is obtained in a mode that one coal mill uses non-lignite coal mills to completely use lignite;

and C: and taking the sum of the product of the operating time ratio in each load interval and the blending ratio in the load interval as the maximum blending ratio of the lignite in the next operating period.

The invention conjectures the operation condition of the boiler in the next period through historical data, simplifies the boiler operation model, directly determines the blending proportion according to the number of coal mills suitable for lignite and non-lignite, thereby facilitating calculation, calculates the maximum blending proportion meeting the operation requirement through the historical data, provides guidance for purchasing and using lignite, and improves the economical efficiency of the operation of a power plant.

Preferably, the method further comprises the step of correcting the maximum blending ratio calculated in the step C,

step D: calculating the lower limit of the heat value of the lignite when the blending combustion proportion in the step B is met in different load intervals, and taking the maximum value of the calculated lower limit of the heat value of the lignite in different load intervals as the maximum lower limit of the heat value of the lignite;

step E: if the actual heat value of the lignite is larger than the maximum lower limit of the heat value, outputting the maximum blending combustion ratio of the lignite in the step C; otherwise, turning to the step F;

step F: and D, increasing the number of the non-lignite coal mills used in each load interval in the step B by 1, recalculating the blending combustion ratio in different load intervals, and repeating the steps C-E.

Preferably, the boiler load is divided into four load intervals of 40% -50% THA, 50% -65% THA, 65% -85% THA and 85% -100% THA; and taking the average value of historical data of at least 1 previous operating cycle as operating time proportions of each load interval of the next operating cycle, namely a, b, c and d.

Preferably, the number of the coal mills participating in operation in each load interval is m_nAnd n is 1,2,3,4, the blending ratio in different load intervals in the step B is respectivelyThe maximum blending ratio in the step C is

Preferably, the method for calculating the lower limit of the calorific value of the lignite in the step D comprises the following steps:

the calculation formula of the coal consumption for power generation is

Q＝R_h×7000

Combining the above three formulas to obtain the final product

Wherein, b_fg/(kW & h) for generating coal consumption; b is_bThe coal consumption in the statistical period is t; w_fIs the generated energy, kW.h; eta_gdFor pipeline efficiency; eta_gThe thermal efficiency of the boiler is shown; q is heat rate, kJ/(kW.h); r_hTaking 4.1868kJ/kcal as a thermal equivalent value; 7000 is standard coal calorific value, kcal; q is the heat value of the fire coal, kJ/kg;

order, Q → Q_net,B_b→m,W_f→ E, obtained

Wherein Q is_netThe heat value of the fire coal, m is the total coal consumption in unit time, and E is the total generated energy in unit time;

according to the formula, calculating the lower limit of the heat value of the fire coal in different load intervals; the lower limit of the heat value of the fire coal is the maximum heat value when the heat consumption rate is maximum and the boiler heat efficiency is minimum in the load interval;

under the condition that the heat value of the non-lignite is basically unchanged, the following relation is satisfied:

lower limit of heat value of fuel coal, non-lignite heat value, non-lignite proportion and lignite heat value, lignite proportion

Therefore, the temperature of the molten metal is controlled,

the lower limit of the heat value of the lignite (lower limit of the heat value of the fuel coal-heat value of the non-lignite) meeting the maximum blending combustion proportion/the proportion of the lignite

Based on the formula, the lower limit of the heat value of the lignite under different load intervals is calculated, and the maximum value of the lower limit of the heat value of the lignite is taken as the maximum lower limit Q_max。

Preferably, taking the average value of the coal-fired boiler maintenance records of at least one past operation period as the maintenance plan of the coal-fired boiler of the next operation period, when the coal-fired boiler is in the maintenance state, simplifying the coal-fired boiler into one reduced total coal pulverizer number, wherein the normal operation time is p days, the maintenance operation time is (365-p) days, subdividing the load interval and the corresponding operation time ratio, and executing the steps B-F to obtain the maximum blending combustion ratio in the maintenance state.

Preferably, the comprehensive maximum co-combustion ratio of the next operation period is as follows under the condition of considering the maintenance of the coal-fired boiler

Wherein eta is the maximum mixing combustion ratio of lignite₁Is the maximum mixing burning proportion eta of the lignite under the normal working condition₂Is the maximum blending combustion ratio of the lignite under the maintenance state.

Preferably, the operation period is one year.

The invention also discloses a lignite co-combustion proportion prediction device of the coal-fired boiler, which comprises

Load interval divides module: dividing boiler load intervals according to the number of coal mills in working states in use of the boiler, and obtaining operation time ratio of different load intervals in the next operation period based on historical operation rules;

blending combustion ratio determination module: under each load interval, the blending combustion proportion is obtained in a mode that one coal mill uses non-lignite coal mills to completely use lignite;

a calculation module: and taking the sum of the product of the operating time ratio in each load interval and the blending ratio in the load interval as the maximum blending ratio of the lignite in the next operating period.

Preferably, the method further comprises the following steps,

a theoretical heat value calculation module: calculating the lower limit of the heat value of the lignite when the blending proportion determined by the blending proportion determining module is met in different load intervals, and taking the maximum value of the calculated lower limit of the heat value of the lignite in different load intervals as the maximum lower limit of the heat value of the lignite;

a comparison module: if the actual heat value of the lignite is larger than the maximum lower limit of the heat value, outputting the maximum blending combustion proportion of the lignite; otherwise, executing a mixed burning mode updating module;

the mixed burning mode updating module: and increasing the number of the non-lignite coal mills used in each load interval corresponding to the current maximum blending ratio by 1, recalculating the blending ratio in different load intervals, and returning to the calculation module.

The method and the device for predicting the lignite co-combustion ratio of the coal-fired boiler have the advantages that: the operation condition of the boiler in the next period is presumed through historical data, the boiler operation model is simplified, the blending proportion is directly determined according to the number of coal mills suitable for lignite and non-lignite, calculation is facilitated, the maximum blending proportion meeting the operation requirement is calculated through the historical data, guidance is provided for purchasing and using of lignite, and the economical efficiency of power plant operation is improved. Meanwhile, whether the calculated maximum blending combustion ratio meets the use requirement is determined based on the comparison between the heat value of the lignite and the theoretical maximum lower limit, and the cross combustion ratio is optimized based on the comparison result, so that the normal operation of the unit is ensured. In addition, the overhaul condition is further considered, and the maximum blending combustion ratio close to the real running condition is obtained.

Drawings

Fig. 1 is a flowchart of a method for predicting a lignite co-combustion ratio of a coal-fired boiler according to an embodiment of the present invention.

Detailed Description

To make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention are described below in detail and completely with reference to the accompanying drawings, and it is apparent that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

As shown in fig. 1, the embodiment provides a method for predicting a lignite co-combustion ratio of a coal-fired boiler, which includes the steps of

Step A: dividing boiler load intervals according to the number of coal mills in working states in use of the boiler, and obtaining operation time ratio of different load intervals in the next operation period based on historical operation rules;

and B: under each load interval, the blending combustion proportion is obtained in a mode that one coal mill uses non-lignite coal mills to completely use lignite;

and C: and taking the sum of the product of the operating time ratio in each load interval and the blending ratio in the load interval as the maximum blending ratio of the lignite in the next operating period.

According to the embodiment, the operation condition of the boiler in the next period is presumed through historical data, the operation model of the boiler is simplified, the blending proportion is directly determined according to the number of the coal mills suitable for the lignite and the non-lignite, calculation is facilitated, the maximum blending proportion meeting the operation requirement is calculated through the historical data, and guidance is provided for purchasing and using the lignite.

Further comprises a step of correcting the maximum blending ratio calculated in the step C,

step D: calculating the lower limit of the heat value of the lignite when the blending combustion proportion in the step B is met in different load intervals, and taking the maximum value of the calculated lower limit of the heat value of the lignite in different load intervals as the maximum lower limit of the heat value of the lignite;

step E: if the actual heat value of the lignite is larger than the maximum lower limit of the heat value, outputting the maximum blending combustion ratio of the lignite in the step C; otherwise, turning to the step F;

step F: and D, increasing the number of the non-lignite coal mills used in each load interval in the step B by 1, recalculating the blending combustion ratio in different load intervals, and repeating the steps C-E.

The embodiment also determines whether the calculated maximum blending combustion ratio meets the use requirement or not based on the comparison between the lignite heat value and the theoretical maximum lower limit, optimizes the cross combustion ratio based on the comparison result, and ensures the normal operation of the unit.

The method for predicting the blending combustion ratio provided by the embodiment is explained by taking a common single boiler equipped with 6 coal mills as an example, and a single operation period is a whole year.

Step A: the load interval of the unit is divided, because the load of the unit is hardly lower than 40% THA (turbine heat acceptance) load in the normal operation process of the unit, the load of the unit is divided into four load intervals of 40-50% THA, 50-65% THA, 65-85% THA and 85-100% THA, the division is based on the operation number of coal mills under different load sections, namely the four load intervals are respectively corresponding to 3-6 coal mills to operate. The proportion of the total operation time under different load intervals is referred to the average value of the previous 1-2 years, and is a, b, c and d respectively; and the proportion of each load interval can be adjusted based on the prediction of the electricity consumption of the next year.

And B: according to the purchasing and operating experience of the fire coal, the lignite can not be combusted by a single coal type due to low heat value, and needs to be mixed with the coal. Therefore, the condition that all coal mills are lignite is not considered, and in each load interval, on the basis that 1 coal mill uses common coal, the other coal mills use lignite, and the blending mode is the maximum blending proportion.

And C: and taking the sum of the product of the operating time ratio in each load interval and the blending ratio in the load interval as the maximum blending ratio of the lignite in the next operating period.

The following table is the calculation result of the maximum blending combustion ratio of the lignite under the operation of 6 coal mills under the ideal condition, and the final maximum blending combustion ratio is 0.66a +0.75b +0.80c +0.83 d.

Because different lignite has different heat values, not all lignite heat values can meet the blending combustion proportion under ideal conditions, and lignite heat values. Because the maximum output of the coal mill is fixed, the lower limit of the heat value of the lignite at the blending combustion proportion can be met under different load sections through the reverse calculation of the total coal quantity.

The calculation formula of the coal consumption for power generation is as follows:

Q＝R_hx 7000 in which b_fg/(kW & h) for generating coal consumption; b is_bThe coal consumption in the statistical period is t; w_fIs the generated energy, kW.h; eta_gdFor pipeline efficiency; eta_gThe thermal efficiency of the boiler is shown; q is heat rate, kJ/(kW.h); r_hTaking 4.1868kJ/kcal as a thermal equivalent value; 7000 is standard coal calorific value, kcal; q is the heat value of the fire coal, kJ/kg;

order, Q → Q_net,B_b→m,W_f→ E, obtained

Wherein Q is_netThe heat value of the fire coal, m is the total coal consumption in unit time, and E is the total generated energy in unit time;

according to the formula, calculating the lower limit of the heat value of the fire coal in different load intervals; the lower limit of the heat value of the fire coal is the maximum heat value when the heat consumption rate is maximum and the boiler heat efficiency is minimum in the load interval;

in the embodiment, the pipeline efficiency eta is calculated_gdTaking a unit design value and boiler thermal efficiency eta_gAnd the heat consumption rate q, the coal consumption m in the statistical period and the generating capacity E are determined according to the thermal tests in different load intervals.

Under the condition that the heat value of the non-lignite is basically unchanged, the following relation is satisfied:

lower limit of heat value of fuel coal, non-lignite heat value, non-lignite proportion and lignite heat value, lignite proportion

Therefore, the temperature of the molten metal is controlled,

the lower limit of the heat value of the lignite (lower limit of the heat value of the fuel coal-heat value of the non-lignite) meeting the maximum blending combustion proportion/the proportion of the lignite

Based on the formula, the lower limit of the heat value of the lignite under different load intervals is calculated, and the maximum value of the lower limit of the heat value of the lignite is taken as the maximum lower limit Q_max。

If the actual heat value of the purchased lignite is not less than Q_maxThen, at the current blending ratio, it can be fullThe output requirement of the coal mill is output by taking the currently calculated maximum blending ratio of 0.66a +0.75b +0.80c +0.83d as a final result, if the actual heat value of the purchased lignite is less than Q_maxIf the energy which can be provided by the lignite cannot meet the output requirement of the coal mill under the current blending combustion ratio, the number of the coal mills using non-lignite under each working condition is increased by one, and the maximum blending combustion ratio is calculated again according to the method, which is shown in the following table:

finally, the maximum blending combustion ratio is calculated to be 0.33a +0.50b +0.60c +0.66d, and then the maximum lower limit Q of the heat value of the lignite under the blending combustion ratio is recalculated_maxAnd comparing with the actual heat value, if the output requirement of the coal mill can not be met, continuously increasing the number of the coal mills using the non-lignite until the actual heat value of the lignite is not less than Q_maxAnd outputting the corresponding maximum blending combustion ratio of the lignite.

Example 2

In the long-term operation process of the coal mill, maintenance needs to be arranged, the coal mill cannot operate during the maintenance, and the determination of the lignite mixing combustion ratio can be influenced by the factors.

And for the operation working conditions of 5 coal mills, dividing the load of the unit into three load intervals of 40-50% THA, 50-75% THA and 75-1000% THA, wherein the load intervals respectively correspond to the operation working conditions of 3-5 coal mills. Based on the calculation process of the maximum blending combustion ratio of 6 coal mills, the calculation result is as follows:

for the maximum blending combustion ratio, the maximum lower limit of the theoretical heat value of the lignite is calculated and compared with the actual heat value, and under the condition that the output requirement of the coal mill is not met, the number of the coal mills using non-lignite is increased, so that the maximum blending combustion ratio meeting the requirement is calculated.

After the calculation of the maximum blending proportion of 5 coal mills and 6 coal mills is respectively completed, the comprehensive maximum blending proportion of the whole year needs to be comprehensively determined, and the method comprises the following steps:

wherein eta is the maximum mixing combustion ratio of lignite₁Is the maximum mixing burning proportion eta of the lignite under the normal working condition₂Is the maximum blending combustion ratio of the lignite under the maintenance state.

The embodiment also provides a device for predicting the lignite co-combustion ratio of the coal-fired boiler, which comprises

Load interval divides module: dividing boiler load intervals according to the number of coal mills in working states in use of the boiler, and obtaining operation time ratio of different load intervals in the next operation period based on historical operation rules;

blending combustion ratio determination module: under each load interval, the blending combustion proportion is obtained in a mode that one coal mill uses non-lignite coal mills to completely use lignite;

a calculation module: and taking the sum of the product of the operating time ratio in each load interval and the blending ratio in the load interval as the maximum blending ratio of the lignite in the next operating period.

Furthermore, the method also comprises the following steps of,

a theoretical heat value calculation module: calculating the lower limit of the heat value of the lignite when the blending proportion determined by the blending proportion determining module is met in different load intervals, and taking the maximum value of the calculated lower limit of the heat value of the lignite in different load intervals as the maximum lower limit of the heat value of the lignite;

a comparison module: if the actual heat value of the lignite is larger than the maximum lower limit of the heat value, outputting the maximum blending combustion proportion of the lignite; otherwise, executing a mixed burning mode updating module;

the mixed burning mode updating module: and increasing the number of the non-lignite coal mills used in each load interval corresponding to the current maximum blending ratio by 1, recalculating the blending ratio in different load intervals, and returning to the calculation module.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.