CN111931346A - Real-time calculation method and application of low calorific value of coal as fired in coal-fired boiler - Google Patents

Abstract

A real-time calculation method and application of the low calorific value of the coal as fired of a coal-fired boiler can perform calculation analysis through real-time monitoring and measurement of related production operation data of the coal-fired boiler and evaluate the change of the low calorific value of the coal as fired in real time. And (3) realizing automatic regression and real-time dynamic calculation of the low calorific value of the coal as fired on a calculation software platform by utilizing positive and negative balance efficiency calculation of the boiler, time statistical smoothing of real-time data and a successive approximation iterative method. The short board that the accuracy is not enough, off-line measurement result is untimely is effectively makeed up the on-the-spot actual as-fired coal quality on-line measurement, provides important information support for power plant coal quality real-time supervision and relevant economic index's computational analysis.

Description

A real-time calculation method and application of low-level calorific value of coal fed into a coal-fired boiler

technical field

The invention relates to the technical field of fuel in the energy power industry, in particular to a real-time calculation method and application of the low-level calorific value of coal fed into a coal-fired boiler.

Background technique

At present, the coal quality of coal-fired power stations in my country is complex and changeable, which is quite different from the design coal type, and the measurement of coal calorific value mainly relies on offline manual measurement and manual reporting, so the time for obtaining the measurement results has lagged behind the current time. Actual coal charging time. In addition, the power plant has applied on-line measurement technology of coal calorific value, such as infrared and microwave methods, but the measurement accuracy is still limited and is greatly affected by changes in the external environment. At the same time, these measurement methods are expensive and maintenance-intensive.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a real-time calculation method and application of the low calorific value of the coal fed into the furnace of a coal-fired boiler, which can effectively utilize the real-time data of the power plant to calculate the current low calorific value of the coal fed into the furnace, Provide important and timely coal quality information reference for power plant fuel management and energy saving analysis.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A real-time calculation method for the low calorific value of coal fed into a coal-fired boiler, comprising the following steps;

step 1:

Determine the initial calculated value Q ⁰ _ar,net or the iteratively updated value Q ^i-1 _ar,net of the low calorific value of coal entering the furnace at the i-1th moment;

According to the low calorific value of the designed coal type or the low calorific value of the coal entering the furnace tested yesterday, as the initial value Q ⁰ _ar,net for the calculation of the low calorific value of the coal entering the furnace at the current moment, if the calculation step of this method has been started, the last iteration Calculated real-time low calorific value Q ^i-1 _ar,net of coal entering the furnace at the i-1th moment;

Step 2:

Using the initial value Q ⁰ _{ar,net of} the low calorific value of the coal entering the furnace or the iteratively updated value Q ^i-1 _ar,net at the i-1 th time, the anti-balance efficiency of the boiler at the i-1 th time is calculated by the reverse balance method.

According to the calculated initial value Q ⁰ _ar,net of the low calorific value of the coal entering the furnace or the iteratively updated value Q ^i-1 _ar,net at the i-1 th time, and based on the data platform of the power station plant-level monitoring information system, the anti-balance method is used for the first The heat loss of the boiler at the time i-1 is calculated in real time, and the back-balance efficiency of the boiler at the time i-1 is obtained.

Step 3:

与第i时刻锅炉正平衡效率

相同，通过锅炉正平衡效率计算公式反推第i时刻入炉煤低位热值Qⁱ _ar,net；Assuming the boiler back-balance efficiency calculated at the i-1th time

Efficiency in positive balance with the boiler at time i

In the same way, the low calorific value Q ⁱ _ar,net of the coal entering the furnace at the i-th time is reversed by the calculation formula of the positive balance efficiency of the boiler;

Step 4:

The calculated value Q ⁱ _ar,net of the low calorific value of the coal entering the furnace at the i-th moment is calculated as the new low calorific value of the coal entering the furnace. Continue to repeat steps 2 to 4 in the next real-time calculation cycle to form the real-time iterative calculation results of the low calorific value of the coal entering the furnace on each time section.

Step 5:

Regularly compare and correct the average value of the low-level calorific value of the coal in a period of time and the sampling test value in the period of time.

The step 2 is specifically:

q ₅ =f ₅ (D)

In the formula, η _{b, fph} — boiler anti-balance efficiency, %;

q ₂ ——Boiler exhaust gas loss, %;

q ₃ ——chemical incomplete combustion loss, %;

q ₄ ——Mechanical incomplete combustion loss, %;

q ₅ —— heat dissipation loss, %;

q ₆ — Thermophysical loss of ash, %.

t _py — exhaust gas temperature, °C;

O _{2, py} ——the amount of oxygen in the exhaust flue gas of the boiler, %;

_{tlk ——cold} air temperature, °C;

——第i-1时刻的入炉煤低位热值，kJ/kg；

——The low calorific value of the coal entering the furnace at the i-1th time, kJ/kg;

V _CO , V _H2 , V _CH4 , V _{RO2 ——the} volume fraction of CO/H ₂ /CH ₄ /RO ₂ in the flue gas, %;

_Car , S _ar , A _ar - carbon content, sulfur content and ash content of incoming coal, %;

α _lh , α _yh , α _fh , α _hz — in cold ash/flue ash/fly ash/ash discharge slag, the percentage of each ash in the total ash content of the incoming fuel, %;

C _lh , C _yh , C _fh - the percentage of combustible content in cold ash/flue ash/fly ash, %.

D—— boiler real-time evaporation, t/h;

c _hz ——specific heat capacity of ash, kJ/(kg·℃);

θ _hz — ash temperature, °C;

In the exhaust gas loss q ₃ , except the low calorific value of fuel Q ^i-1 _ar,net , other parameters can be obtained through real-time measurement data, so the q ₃ function only about Qi ^-1 _ar,net can be obtained.

The chemical incomplete combustion loss q ₃ is related to the combustible gas composition in the flue gas, and the loss is very small in large-capacity boilers. If there is real-time measurement data related to the combustible gas composition in the flue gas, it can be substituted into the expression to obtain a function only about Q ^i-1 _ar,net ; if there is no relevant data, the fixed value can also be directly given according to the fuel type and combustion method.

_The parameters related to the ash balance in the mechanical incomplete combustion loss q4 need to be measured offline, and given empirical values during calculation, or given fixed values according to the type of fuel and combustion method.

_The heat dissipation loss q5 is mainly affected by the boiler evaporation, which can be directly obtained from the real-time monitoring parameters.

Among the parameters for calculating the thermal physical loss of ash and slag q ₆ , except for the calorific value of coal entering the furnace, other parameters are determined according to the type of fuel and the method of slagging.

To sum up, the functional relationship between the reverse balance efficiency of the boiler calculated by the reverse balance method and the low calorific value of the coal entering the furnace can be obtained:

The step 3 is specifically:

The formula for calculating the positive balance efficiency of the boiler is:

In the formula, η _{b, zph} — boiler positive balance efficiency, %;

D _gr , D _zr , D _zy , D _pw ,——the amount of superheated steam, reheated steam, self-consumption hot water or steam, sewage discharge, t/h;

i″ _gr , i″ _zr , i′ _zr , i _zy , i′, i _gs — superheated steam enthalpy, hot reheated steam enthalpy, cold reheated steam enthalpy, self-use hot water or steam enthalpy, saturated water enthalpy, feed water Enthalpy value, kJ/kg;

B——fuel consumption, t/h;

i _T ——physical sensible heat of fuel, kJ/kg;

For small-capacity and low-parameter generator sets without reheaters, the reheated steam flow rate is 0.

Except for the low calorific value of incoming coal, other parameters can be obtained through the real-time data platform of the plant-level monitoring information system or set according to on-site conditions. Finally, the functional relationship between the positive balance efficiency of the boiler and the low calorific value of incoming coal can be obtained.

η _{b, zph} = G(Q _{ar, net} )

It also obtains the low calorific value Q ⁱ _ar,net of the coal entering the furnace at the i-th time:

Q _ar,net = G ^-1 (η _{b, zph} )

Since the thermal system of boiler combustion is continuous and the working conditions are stable within seconds, it can be considered that the efficiency of the back-balanced boiler calculated at the previous moment should be equal to the current efficiency of the positive-balanced boiler, let:

Then the low calorific value Q ⁱ _ar,net of the coal entering the furnace at the i-th time can be obtained:

This method is also used for heating boilers, hot water boilers and other units. This method is also used to calculate the low calorific value of the incoming fuel for the boilers burning garbage, biomass, waste, etc., but requires real-time flow measurement of the incoming fuel.

Beneficial effects of the present invention:

The invention can calculate and analyze the real-time monitoring and measurement of the relevant production and operation data of the coal-fired boiler, and evaluate the change of the low-level calorific value of the coal fed into the furnace in real time. Using the boiler's positive and negative balance efficiency calculation, the time statistical smoothing of real-time data and the step-by-step approximation iterative method, the calculation software platform realizes automatic regression and real-time dynamic calculation of the low calorific value of coal into the furnace. It can effectively make up for the shortcomings of insufficient online measurement accuracy of the actual coal quality entering the furnace and untimely offline measurement results, and provide important information support for the real-time monitoring of coal quality in power plants and the calculation and analysis of relevant economic indicators.

With the large-scale production and operation parameters of the power plant connected to the plant-level monitoring information system, a large amount of real-time operating data was collected and the performance of the unit was calculated. In this application, combined with soft sensing technology, through the analysis and modeling of the production process, the collected real-time production data can be effectively used to calculate the calorific value of coal into the furnace in real time, so as to improve the accuracy of the unit performance calculation, and it can be used to master the real-time calorific value of the coal into the furnace. Information and fuel management provide an efficient solution.

Description of drawings

FIG. 1 is a schematic flow chart of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1: a real-time calculation method for the low calorific value of coal fed into a coal-fired boiler, comprising the following steps;

step 1:

Determine the initial calculated value Q ⁰ _ar,net or the iteratively updated value Q ^i-1 _ar,net of the low calorific value of coal entering the furnace at the i-1th moment;

According to the low calorific value of the designed coal type or the low calorific value of the coal entering the furnace tested yesterday, as the initial value Q ⁰ _ar,net for the calculation of the low calorific value of the coal entering the furnace at the current moment, if the calculation step of this method has been started, the last iteration Calculated real-time low calorific value Q ^i-11 _{ar of coal entering the furnace at the i-1th moment, net} ;

Step 2:

Using the initial value Q ⁰ _{ar,net of} the low calorific value of coal entering the furnace or the iteratively updated value Q ^i-1 _ar,net at the i-1th time, calculate the boiler back-balance efficiency at the i-1th time by the back-balance method

According to the calculated initial value Q ⁰ _ar,net of the low-level calorific value of coal entering the furnace or the iteratively updated value Q ^i-1 _ar,net at the i-1th time, the heat loss of the boiler at the i-1th time is analyzed in real time by the anti-equilibrium method. Calculate, and then get the boiler back-balance efficiency at time i-1

q ₅ =f ₅ (D)

In the formula, η _{b, fph} — boiler anti-balance efficiency, %;

q ₂ ——Boiler exhaust gas loss, %;

q ₃ ——chemical incomplete combustion loss, %;

q ₄ ——Mechanical incomplete combustion loss, %;

q ₅ —— heat dissipation loss, %;

q ₆ ——The thermophysical loss of ash, %.

t _py — exhaust gas temperature, °C;

O _{2, py} ——the amount of oxygen in the exhaust flue gas of the boiler, %;

_{tlk ——cold} air temperature, °C;

——第i-1时刻的入炉煤低位热值，kJ/kg；

——The low calorific value of the coal entering the furnace at the i-1th time, kJ/kg;

V _CO , V _H2 , V _CH4 , V _{RO2 ——the} volume fraction of CO/H ₂ /CH ₄ /RO ₂ in the flue gas, %;

_Car , S _ar , A _ar - carbon content, sulfur content and ash content of incoming coal, %;

α _lh , α _yh , α _fh , α _hz — in cold ash/flue ash/fly ash/ash discharge slag, the percentage of each ash in the total ash content of the incoming fuel, %;

C _lh , C _yh , C _fh - the percentage of combustible content in cold ash/flue ash/fly ash, %.

D—— boiler real-time evaporation, t/h;

c _hz ——specific heat capacity of ash, kJ/(kg·℃);

θ _hz — ash temperature, °C;

In the exhaust gas loss q ₃ , except for the low calorific value of fuel Q ^i-1 _ar,net , other parameters can be obtained through real-time measurement data, so the q ₃ function only about Q ^i-1 _ar,net can be obtained;

The chemical incomplete combustion loss q ₃ is related to the combustible gas composition in the flue gas, and the loss is very small in large-capacity boilers. If there is real-time measurement data related to the combustible gas composition in the flue gas, it can be substituted into the expression to obtain a function only about Q ^i-1 _ar,net ; if there is no relevant data, the fixed value can also be directly given according to the fuel type and combustion method;

_The parameters related to ash balance in the mechanical incomplete combustion loss q4 need to be measured offline, and given empirical values during calculation, or given fixed values according to the type of fuel and combustion method;

_The heat dissipation loss q5 is mainly affected by the boiler evaporation, which can be directly obtained from the real-time monitoring parameters;

Among the calculation parameters of ash and slag thermophysical loss q ₆ , except for the calorific value of coal entering the furnace, other parameters are determined according to the type of fuel and the method of slag discharge;

To sum up, the functional relationship between the reverse balance efficiency of the boiler calculated by the reverse balance method and the low calorific value of the coal entering the furnace can be obtained:

Step 3:

与第i时刻锅炉正平衡效率

相同，通过锅炉正平衡效率计算公式反推第i时刻入炉煤低位热值Qⁱ _ar，net。Assuming the boiler back-balance efficiency calculated at the i-1th time

Efficiency in positive balance with the boiler at time i

In the same way, the low calorific value Q ⁱ _ar,net of the coal entering the furnace at the i-th time is reversed by the calculation formula of the positive balance efficiency of the boiler.

The formula for calculating the positive balance efficiency of the boiler is:

In the formula, η _{b, zph} — boiler positive balance efficiency, %;

D _gr , D _zr , D _zy , D _pw ,——the amount of superheated steam, reheated steam, self-consumption hot water or steam, sewage discharge, t/h;

i″ _gr , i″ _zr , i′ _zr , i _zy , i′, i _gs — superheated steam enthalpy, hot reheated steam enthalpy, cold reheated steam enthalpy, self-use hot water or steam enthalpy, saturated water enthalpy, feed water Enthalpy value, kJ/kg;

B——fuel consumption, t/h;

i _T ——physical sensible heat of fuel, kJ/kg;

For small-capacity and low-parameter generator sets without reheaters, the reheated steam flow rate is 0.

Except for the low calorific value of incoming coal, other parameters can be obtained through the real-time data platform of the plant-level monitoring information system or set according to on-site conditions. Finally, the functional relationship between the positive balance efficiency of the boiler and the low calorific value of incoming coal can be obtained.

η _{b, zph} = G(Q _{ar, net} )

It also obtains the low calorific value Q ⁱ _ar,net of the coal entering the furnace at the i-th time:

Q _ar,net = G ^-1 (η _{b, zph} )

Since the thermal system of boiler combustion is continuous and the working conditions are stable within seconds, it can be considered that the efficiency of the back-balanced boiler calculated at the previous moment should be equal to the current efficiency of the positive-balanced boiler, let:

Then the low calorific value Q ⁱ _ar,net of the coal entering the furnace at the i-th time can be obtained:

Step 4:

Continue to repeat steps 2 to 4 in the next real-time calculation cycle with the calculated value Q ⁱ _ar,net of the low calorific value of the coal entering the furnace at the i-th moment, and calculate the low calorific value of the coal entering the furnace as a new one, to form the entering furnace at each time section. Real-time iterative calculation results of coal low calorific value;

Step 5:

Correction of the result of calculating the low calorific value of coal into the furnace

Due to the error of the actual operating parameters, it is necessary to correct the result of calculating the low calorific value of the coal fed into the furnace. The correction method is to regularly compare and linearly correct the average value of the low-level calorific value of the calculated coal entering the furnace within a period of time and the sampling test value within the period of time.

This method is also used for heating boilers, hot water boilers and other units

When used in these cases, the calculation of the boiler's positive balance efficiency requires only the calculation of the actual effective heat output by the boiler.

This method is also used to calculate the low calorific value of the incoming fuel for the boilers burning garbage, biomass, waste, etc., but requires real-time flow measurement of the incoming fuel.

Claims (5)

1. a real-time calculation method for the low calorific value of coal-fired boiler into furnace coal, is characterized in that, comprises the following steps; step 1: Determine the initial calculated value Q ⁰ _ar,net or the iteratively updated value Q ^i-1 _ar,net of the low calorific value of coal entering the furnace at the i-1th moment; According to the low calorific value of the designed coal type or the low calorific value of the coal entering the furnace tested yesterday, as the initial value Q ⁰ _ar,net for the calculation of the low calorific value of the coal entering the furnace at the current moment, if the calculation step of this method has been started, the last iteration Calculated real-time low calorific value Q ^i-1 _ar,net of coal entering the furnace at the i-1th moment; Step 2: Using the initial value Q ⁰ _{ar,net of} the low calorific value of the coal entering the furnace or the iteratively updated value Q ^i-1 _ar,net at the i-1 th time, the anti-balance efficiency of the boiler at the i-1 th time is calculated by the reverse balance method.

According to the calculated initial value Q ⁰ _ar,net of the low calorific value of the coal entering the furnace or the iteratively updated value Q ^i-1 _ar,net at the i-1th time, and based on the data platform of the power station plant-level monitoring information system, the first The heat loss of the boiler at the time i-1 is calculated in real time, and the back-balance efficiency of the boiler at the time i-1 is obtained.

Step 3: Assuming the boiler back-balance efficiency calculated at the i-1th time

Efficiency in positive balance with the boiler at time i

In the same way, the low calorific value Q ⁱ _ar,net of the coal entering the furnace at the i-th time is reversed by the calculation formula of the positive balance efficiency of the boiler; Step 4: The calculated value Q ⁱ _ar,net of the low calorific value of the coal entering the furnace at the i-th time is calculated as the new low calorific value of the coal entering the furnace, and in the next real-time calculation cycle, the steps 2 to 4 are repeated to form the furnace entering the furnace at each time section. Real-time iterative calculation results of coal low calorific value; Step 5: Regularly compare and correct the average value of the low-level calorific value of the coal in a period of time and the sampling test value in the period of time. 2. a kind of real-time calculation method of the low calorific value of coal-fired boiler into the furnace according to claim 1, is characterized in that, described step 2 is specifically:

q ₅ =f ₅ (D)

In the formula, η _{b, fph} —— boiler back-balance efficiency, %; q ₂ ——Boiler exhaust gas loss, %; q ₃ ——chemical incomplete combustion loss, %; q ₄ ——Mechanical incomplete combustion loss, %; q ₅ —— heat dissipation loss, %; q ₆ ——The thermophysical loss of ash, %. t _py — exhaust gas temperature, °C; O _2,py ——the amount of oxygen in the exhaust flue gas of the boiler, %; _{tlk ——cold} air temperature, °C;

——The low calorific value of the coal entering the furnace at the i-1th time, kJ/kg; V _CO , V _H2 , V _CH4 , V _{RO2 ——the} volume fraction of CO/H ₂ /CH ₄ /RO ₂ in the flue gas, %; _Car , S _ar , A _{ar ——the} carbon content, sulfur content and ash content of incoming coal, %; α _lh , α _yh , α _fh , α _hz —— in cold ash/flue ash/fly ash/ash discharge slag, the percentage of each ash in the total ash content of the incoming fuel, %; C _lh , C _yh , C _{fh ——the} percentage of combustible content in cold ash/flue ash/fly ash, %. D—— boiler real-time evaporation, t/h; c _hz ——specific heat capacity of ash, kJ/(kg·℃); θ _hz — ash temperature, °C; In the exhaust gas loss q ₃ , except the low calorific value of fuel Q ^i-1 _ar,net , other parameters can be obtained through real-time measurement data, so the q ₃ function only about Q ^i-1 _ar,net can be obtained. The chemical incomplete combustion loss q ₃ is related to the combustible gas composition in the flue gas, and the loss is very small in large-capacity boilers. If there is real-time measurement data related to the combustible gas composition in the flue gas, it can be substituted into the expression to obtain only about Q ^i-1 The function of _ar,net ; if there is no relevant data, the fixed value can also be directly given according to the fuel type and combustion method. _The parameters related to ash balance in the mechanical incomplete combustion loss q4 need to be measured offline, and given empirical values during calculation, or given fixed values according to the type of fuel and combustion method; _The heat dissipation loss q5 is mainly affected by the boiler evaporation, which can be directly obtained from the real-time monitoring parameters; Among the calculation parameters of ash and slag thermophysical loss q ₆ , except for the calorific value of coal entering the furnace, other parameters are determined according to the type of fuel and the method of slagging; To sum up, the functional relationship between the reverse balance efficiency of the boiler calculated by the reverse balance method and the low calorific value of the coal entering the furnace can be obtained:

3. a kind of real-time calculation method of the low calorific value of coal in a coal-fired boiler according to claim 1, is characterized in that, described step 3 is specifically: The formula for calculating the positive balance efficiency of the boiler is:

In the formula, η _{b, zph} — boiler positive balance efficiency, %; D _gr , D _zr , D _zy , D _pw ,—— boiler superheated steam volume, reheated steam volume, self-use hot water or steam volume, sewage volume, t/h; i″ _gr ,i″ _zr ,i′ _zr ,i _zy ,i′,i _gs — superheated steam enthalpy, hot reheat steam enthalpy, cold reheat steam enthalpy, self-use hot water or steam enthalpy, saturated water enthalpy, feed water Enthalpy value, kJ/kg; B——fuel consumption, t/h; i _T ——physical sensible heat of fuel, kJ/kg; For small-capacity and low-parameter generator sets without reheaters, the reheated steam flow rate is 0. Except for the low calorific value of the coal fed into the furnace, other parameters can be obtained through the real-time data platform of the plant-level monitoring information system or set according to the on-site conditions, and finally the functional relationship between the positive balance efficiency of the boiler and the low calorific value of the coal fed into the furnace can be obtained; η _b,zph = G(Q _ar,net ) It also obtains the low calorific value Q ⁱ _ar,net of the coal entering the furnace at the i-th time: Q _ar,net =G ^-1 (η _b,zph ) Since the thermal system of boiler combustion is continuous and the working conditions are stable within seconds, it can be considered that the efficiency of the back-balanced boiler calculated at the previous moment should be equal to the current efficiency of the positive-balanced boiler, let:

Then the low calorific value Q ⁱ _ar,net of the coal entering the furnace at the i-th time can be obtained:

4. The real-time calculation method of the low calorific value of coal fed into the furnace of a coal-fired boiler based on claim 1 is used for units such as heating boilers and hot water boilers. 5. based on the real-time calculation method of the low calorific value of a kind of coal-fired boiler according to claim 1, it is used for the calculation of the low calorific value of the fuel entering the furnace of the boilers such as burning garbage, biomass, waste, but requires the fuel entering the furnace There is real-time flow measurement.

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