CN113378394A - Intelligent soot blowing algorithm based on Guerweiqi heat balance - Google Patents

Abstract

The invention relates to an intelligent soot blowing algorithm based on Guerweiqi heat balance, which is based on a soft measurement technology of a local heat balance principle, wherein the soft measurement technology is used for calculating to obtain an actual heat transfer coefficient, a theoretical heat transfer coefficient and a cleaning factor by calculating to obtain a flue gas inlet temperature when a check error between heat absorption capacity and heat release capacity is less than 2% under the condition that outlet flue gas temperature, inlet working medium temperature, outlet working medium temperature and working medium mass flow are known through an iterative algorithm. The algorithm solves the problems of incomplete measuring points and the like, and saves the cost. The algorithm can effectively monitor the pollution state of the heating surface of the boiler, determine the optimal soot blowing time, further maintain the cleanliness of the heating surface and improve the operation efficiency of the boiler. Meanwhile, soot blowing media are saved, corrosion and abrasion of the tube wall of the heating surface are reduced, and the service efficiency of each heating surface of the boiler is indirectly prolonged.

Description

Intelligent soot blowing algorithm based on Guerweiqi heat balance

Technical Field

The invention relates to an intelligent soot blowing algorithm based on Guerweiqi heat balance, and belongs to the field of intelligent algorithms.

Background

Electric energy is one of the most important energy sources in human civilization at present. At present, most of the electric energy production in China is from coal-fired power generation, however, during the combustion process of the coal-fired power generation unit, ash content in the coal-fired power generation unit can cause ash accumulation and slag bonding on the heating surface of the boiler, so that the heat transfer coefficient of the heating surface is reduced, the heat transfer efficiency of the heating surface is influenced, the temperature of main steam and reheated steam is reduced, the temperature of exhaust smoke is increased, the efficiency of the boiler is reduced, energy waste is caused, and even the safe operation of the unit can be damaged in severe cases. Therefore, in order to maximize the utilization of coal combustion energy, the heating surfaces of the boiler tubes must be cleaned and sootblown in time. The most reasonable and scientific soot blowing optimization strategy is formulated, so that the maximization of the heat transfer efficiency of the heating surface within a period of time can be ensured, and the energy conservation and emission reduction and the safe operation of the unit are realized.

At present, soot blowing operation of large power station boilers in China generally adopts a timed and quantitative program control mode. Because the operation mode is carried out under the condition that the actual soot-dirt state of the heating surface is not known, insufficient soot blowing or excessive soot blowing is inevitably generated, the soot blowing time and the soot blowing position are mostly determined by experience, and the soot blowing process has artificial subjectivity, thereby causing more coal consumption. The energy conservation and emission reduction at the present stage provides higher requirements for soot blowing optimization, and the coal-fired power plant can have better economic benefits only by predicting the future state and preparing in advance.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide an intelligent soot blowing algorithm based on Guerweiqi heat balance.

In order to achieve the purpose, the invention adopts the technical scheme that:

an intelligent soot blowing algorithm based on Guerweiqi heat balance comprises the following steps:

(1) calculating theoretical Heat transfer coefficient K₀

Wherein:

a₁＝a_d+a_f

in the formula: a is₁The heat release coefficient of the flue gas to the pipe wall is shown;

a₂the heat release coefficient of the working medium to the pipe wall is shown;

a_dis the surface heat release coefficient;

a_fis the radiative heat transfer coefficient;

C_z、C_srespectively the correction coefficients of the longitudinal and transverse tube rows in the airflow flowing direction;

lambda is the heat conductivity coefficient at the average temperature of the flue gas, W/(m DEG C);

d is the outer diameter of the pipe, m;

re and Pr are respectively the Relode number and the Plantt number of the smoke;

C_la correction coefficient for the relative length of the heating surface of the scour;

C_tand the correction coefficients are fluid temperature T and pipe wall temperature Tb.

σ₀Boltzmann constant;

ε_sthe system blackness is obtained;

T_gband T is the tube wall temperature and the system temperature, K, respectively;

(2) determining the temperature of the flue gas at the inlet of the heat exchanger through a Guerweiqi heat balance intelligent algorithm;

calculating to obtain the heat absorption capacity and the heat release capacity of the working medium through the outlet flue gas temperature, the inlet working medium temperature, the outlet working medium temperature, the working medium mass flow and the assumed inlet flue gas temperature value, wherein each temperature can be converted into a corresponding enthalpy value, and when the checking error of the heat absorption capacity and the heat release capacity is less than 2% through an iterative algorithm based on a local heat balance principle, the assumed inlet flue gas temperature is the finally determined inlet flue gas temperature;

(3) calculating the actual heat transfer coefficient K_sj

Wherein:

Q_z＝D_z(h”-h')

in the formula: q_zThe heat absorption capacity of the working medium is kJ/kg;

D_zthe mass flow of inlet working medium is kg/s;

h and h' are enthalpy values of the working medium outlet and the working medium inlet respectively, and kJ/kg;

a is the heat transfer area, m²；

Δt_maxAnd Δ t_minRespectively representing large temperature pressure and small temperature pressure;

wherein, during the counter flow, the temperature and pressure delta t are high_maxJ' -t "; at downstream, the large temperature and pressure Δ t_max＝J′-t′；

At the time of countercurrent, the small temperature pressure Deltat_minJ "-t'; at downstream, the small temperature and pressure Δ t_min＝J″-t″；

J': flue gas inlet temperature, deg.C; t': working medium outlet temperature, DEG C; j': flue gas exit temperature, deg.C; t': working medium inlet temperature, DEG C;

(4) calculating the cleaning factor CF

When CF is 1, the heated surface is in an ideal clean state, namely the clean factor of a smooth pipe; a CF of less than 1 indicates that the heated surface is contaminated with soot, and the smaller the CF, the more serious the contamination.

The specific method of the step (2) is as follows:

1) economizer inlet flue gas temperature algorithm

The economizer is divided into a superheater side and a reheater side through a flue gas baffle;

economizer (reheater side)

The flue gas temperature and the flue gas enthalpy value are in one-to-one correspondence, the known temperature can obtain the enthalpy value through table lookup, and the known enthalpy value can obtain the temperature; assuming that the economizer (reheater side) flue gas inlet temperature is J';

economizer (reheater side) working medium heat absorption: q_z＝D_z(h”-h')

Economizer (reheater side) flue gas heat release: q_y＝m_z(H'-H”)

Wherein: d_zThe mass flow of the working medium at the inlet of the economizer is kg/s;

h and h' are enthalpy values of the working medium outlet and the working medium inlet respectively, and kJ/kg;

m_zthe side-burning coal amount of the reheater is kg/s;

h 'and H' are respectively the enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

calculating a checking error: q_z-Q_y

If Q is_z-Q_yIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

② economizer (superheater side)

Assuming that the temperature of a flue gas inlet of an economizer (on the superheater side) is J';

heat absorption capacity of working medium on the economizer (superheater side): q_z＝D_z(h”-h')

Economizer (superheater side) flue gas heat release: q_y＝m_g(H'-H”)

Wherein: d_zThe mass flow of the working medium at the inlet of the economizer is kg/s;

h and h' are enthalpy values of the working medium outlet and the working medium inlet respectively, and kJ/kg;

m_gthe amount of coal is burned on the side of the superheater in kg/s;

h 'and H' are respectively the enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

calculating a checking error: q_z-Q_y

If Q is_z-Q_yIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

2) algorithm for inlet flue gas temperature of horizontal section of low-temperature superheater

The outlet flue gas temperature of the horizontal section of the low-temperature superheater is equal to the inlet flue gas temperature of an economizer (on the superheater side), and the inlet flue gas temperature of the horizontal section of the low-temperature superheater is assumed to be J';

heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m_g(H'-H”)

Wherein: d_zThe mass flow of the inlet working medium of the low-temperature superheater is kg/s;

h and h' are enthalpy values of the working medium outlet and the working medium inlet respectively, and kJ/kg;

m_gthe amount of coal fired on the superheater side is kg/s;

h 'and H' are respectively the enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj，

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.02Q_z

If Q is_y-Q_z-Q_fjIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

3) algorithm for temperature of flue gas at vertical section inlet of low-temperature superheater

The temperature of the vertical section flue gas outlet of the low-temperature superheater is equal to the temperature of the horizontal section flue gas inlet of the low-temperature superheater, and the temperature of the vertical section flue gas inlet of the low-temperature superheater is assumed to be J';

heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Wherein D is_z: the mass flow of the working medium at the inlet of the low-temperature superheater is kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": respectively the enthalpy values of the flue gas inlet and the flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj，

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.05Q_z

If Q is_y-Q_z-Q_fjIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

4) algorithm for inlet flue gas temperature of horizontal section of low-temperature reheater

The temperature of the flue gas outlet of the horizontal section of the low-temperature reheater is equal to the temperature of the flue gas inlet of an economizer (on the reheater side), and the temperature of the flue gas inlet of the horizontal section of the low-temperature reheater is assumed to be J';

heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Heat release of flue gas: q_y＝m_z(H'-H”)

Wherein D is_z: mass flow of the low-temperature reheater inlet working medium is kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m_z: the side-burning coal amount of the reheater is kg/s;

h', H ": respectively the enthalpy values of the flue gas inlet and the flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.015Q_z

If Q is_y-Q_z-Q_fjIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

5) algorithm for inlet flue gas temperature of vertical section of low-temperature reheater

The temperature of a flue gas outlet of the vertical section of the low-temperature reheater is equal to the temperature of a flue gas inlet of the horizontal section of the low-temperature reheater, and the temperature of the flue gas inlet of the vertical section of the low-temperature reheater is assumed to be J';

heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Wherein D is_z: mass flow of the low-temperature reheater inlet working medium is kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": respectively the enthalpy values of the flue gas inlet and the flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.04Q_z

If Q is_y-Q_z-Q_fjIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

6) algorithm for inlet flue gas temperature of high-temperature reheater

The temperature of a flue gas outlet of the high-temperature reheater is equal to the temperature of a flue gas inlet of a vertical section of the low-temperature reheater, and the temperature of the flue gas inlet of the high-temperature reheater is assumed to be J';

heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Wherein: d_z: reheater steam flow, kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.06Q_z

If Q is_y-Q_z-Q_fjIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

7) algorithm for inlet flue gas temperature of high-temperature superheater

The temperature of the flue gas outlet of the high-temperature superheater is equal to the temperature of the flue gas inlet of the high-temperature reheater, and the temperature of the flue gas inlet of the high-temperature superheater is assumed to be J';

heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Wherein D is_z: main steam flow, kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": respectively the enthalpy values of the flue gas inlet and the flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.06Q_z

If Q is_y-Q_z-Q_fjIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

8) algorithm for inlet flue gas temperature of platen superheater

The temperature of the flue gas outlet of the platen superheater is equal to the temperature of the flue gas inlet of the high-temperature superheater, and the temperature of the flue gas inlet of the platen superheater is assumed to be J';

heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Total heat absorbed by the screen: q_p＝Q^d _p+Q^f _p

Convective heat absorption of the heated surface: q^d _p＝Q_y-Q^d _fj，

Convection heat absorption of additional heating surface: q^d _fj＝0.15Q_z

Radiant heat absorbed by the screen: q^f _p＝Q_f-Q^f _fj

Direct radiation inside the furnace absorbed by the screen: q_f＝Q_f′-Q_f″

Direct radiation in the furnace obtained by the additional heating surface:

direct radiation in the furnace falling into the screen area:

direct radiation in the furnace penetrating the screen area:

furnace outlet heat flow falling into the screen area:

heat absorption capacity of the hearth:

in the formula, D_z: the steam flow entering the platen superheater is kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

f': the area of a smoke window at the outlet of the hearth and the square meter;

a: the blackness of the smoke;

x' p is the angular coefficient of the outlet cross section;

A_chthe area of a smoke window at the outlet of the screen and the square meter;

T_pj: average temperature of flue gas, K;

B_j: total coal combustion amount, kg/s;

beta: the heat exchange coefficient between the hearth and the screen is increased;

eta: a coefficient of non-uniformity along the height of the hearth;

H₁: the effective radiation heating area of the hearth and the square meter;

the heat preservation coefficient;

Q₁: low calorific value, kJ/kg;

I₁", the smoke enthalpy at the outlet of the hearth, kJ/kg;

A_fj: adding a heated area and a square meter;

s: the total heating area and the square meter;

calculating a checking error: q_p-Q_z

If Q is_p-Q_zIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met.

The invention has the beneficial effects that:

the cleaning factor CF (CleanlinessFactor) can represent the pollution state of the convection heating surface, is a mark of the cleaning degree of the heating surface and is defined as the ratio of the actual heat transfer coefficient to the theoretical heat transfer coefficient. The dust deposition condition of each heating surface is usually monitored by calculating a cleaning factor, however, the calculation of the cleaning factor requires knowing the temperature of a flue gas inlet and outlet of each heating surface, and many power plants have no measuring point, so that the calculation of the cleaning factor is limited.

The invention utilizes an intelligent soot blowing algorithm of Guerweiqi heat balance, a soft measurement technology based on the principle of local heat balance, and an iterative algorithm, under the condition that the temperature of outlet flue gas, the temperature of inlet working medium, the temperature of outlet working medium and the mass flow of working medium are known, when the checking error of heat absorption and heat release is less than 2%, the inlet temperature of the flue gas is calculated, and then the actual heat transfer coefficient, the theoretical heat transfer coefficient and the cleaning factor are calculated. The algorithm solves the problems of incomplete measuring points and the like, and saves the cost.

The intelligent soot blowing algorithm based on Guerweiqi heat balance can effectively monitor the pollution state of the heating surface of the boiler, determine the optimal soot blowing time, further maintain the cleanliness of the heating surface and improve the operation efficiency of the boiler. Meanwhile, soot blowing media are saved, corrosion and abrasion of the tube wall of the heating surface are reduced, and the service efficiency of each heating surface of the boiler is indirectly prolonged.

Drawings

FIG. 1 is a block diagram of an economizer (reheater side) inlet flue gas temperature algorithm;

FIG. 2 is a block diagram of an economizer (superheater side) inlet flue gas temperature algorithm;

FIG. 3 is a block diagram of an algorithm for the inlet flue gas temperature of the horizontal section of the low-temperature superheater;

FIG. 4 is a block diagram of a low-temperature superheater vertical section inlet flue gas temperature algorithm;

FIG. 5 is a block diagram of a low temperature reheater horizontal section inlet flue gas temperature algorithm;

FIG. 6 is a block diagram of a low temperature reheater vertical section inlet flue gas temperature algorithm;

FIG. 7 is a block diagram of a high temperature reheater inlet flue gas temperature algorithm;

FIG. 8 is a block diagram of a high temperature superheater inlet flue gas temperature algorithm;

FIG. 9 is a block diagram of a platen superheater inlet flue gas temperature algorithm;

FIG. 10 is a flowchart of the Golviki heat balance intelligent algorithm of the present invention.

Detailed Description

The following examples further illustrate the embodiments of the present invention in detail.

The units of heat and enthalpy values related in the formula of the invention are kJ/kg.

Examples

An intelligent soot blowing algorithm based on Guerweiqi heat balance comprises the following steps:

(1) calculating theoretical Heat transfer coefficient K₀

Wherein:

a₁＝a_d+a_f

in the formula: a is₁The heat release coefficient of the flue gas to the pipe wall is shown;

a₂the heat release coefficient of the working medium to the pipe wall is shown;

a_dis the surface heat release coefficient;

a_fis the radiative heat transfer coefficient;

C_z、C_srespectively the correction coefficients of the longitudinal and transverse tube rows in the airflow flowing direction;

lambda is the heat conductivity coefficient at the average temperature of the flue gas, W/(m DEG C);

d is the outer diameter of the pipe, m;

re and Pr are respectively the Relode number and the Plantt number of the smoke;

C_la correction coefficient for the relative length of the heating surface of the scour;

C_tand the correction coefficients are fluid temperature T and pipe wall temperature Tb.

σ₀Boltzmann constant;

ε_sthe system blackness is obtained;

T_gband T is the tube wall temperature and the system temperature, K, respectively;

(2) determining the temperature of the flue gas at the inlet of the heat exchanger through a Guerweiqi heat balance intelligent algorithm;

calculating to obtain the heat absorption capacity and the heat release capacity of the working medium through the outlet flue gas temperature, the inlet working medium temperature, the outlet working medium temperature, the working medium mass flow and the assumed inlet flue gas temperature value, wherein each temperature can be converted into a corresponding enthalpy value, and when the checking error of the heat absorption capacity and the heat release capacity is less than 2% through an iterative algorithm based on a local heat balance principle, the assumed inlet flue gas temperature is the finally determined inlet flue gas temperature;

(3) calculating the actual heat transfer coefficient K_sj

Wherein:

Q_z＝D_z(h”-h')

in the formula: q_zThe heat absorption capacity of the working medium is kJ/kg;

D_zthe mass flow of inlet working medium is kg/s;

h and h' are enthalpy values of the working medium outlet and the working medium inlet respectively, and kJ/kg;

a is the heat transfer area, m²；

Δt_maxAnd Δ t_minRespectively representing large temperature pressure and small temperature pressure;

wherein, during the counter flow, the temperature and pressure delta t are high_maxJ' -t "; at downstream, the large temperature and pressure Δ t_max＝J′-t′；

At the time of countercurrent, the small temperature pressure Deltat_minJ "-t'; at downstream, the small temperature and pressure Δ t_min＝J″-t″；

J' is the temperature of the flue gas inlet, DEG C;

t': working medium outlet temperature, DEG C;

j' is the temperature of the smoke outlet at DEG C;

t': working medium inlet temperature, DEG C;

(4) calculating the cleaning factor CF

When CF is 1, the heated surface is in an ideal clean state, namely the clean factor of a smooth pipe; CF less than 1 indicates a heated surface

The pollution is caused by ash dirt, and the smaller the pollution is, the more serious the pollution is.

The specific method for determining the temperature of the inlet flue gas of the heat exchanger through the Gulviki heat balance intelligent algorithm in the step (2) is as follows:

1) economizer inlet flue gas temperature algorithm

The economizer is divided into a superheater side and a reheater side by a flue gas baffle.

Economizer (reheater side)

The flue gas temperature and the flue gas enthalpy value are in one-to-one correspondence, the known temperature can obtain the enthalpy value through table lookup, and the known enthalpy value can obtain the temperature. Assume that the economizer (reheater side) flue gas inlet temperature is J'.

Economizer (reheater side) working medium heat absorption: q_z＝D_z(h”-h')

Economizer (reheater side) flue gas heat release: q_y＝m_z(H'-H”)

Wherein: d_zThe mass flow of the working medium at the inlet of the economizer is kg/s;

h and h' are enthalpy values of the working medium outlet and the working medium inlet respectively, and kJ/kg;

m_zthe side-burning coal amount of the reheater is kg/s;

h 'and H' are respectively the enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

calculating a checking error: q_z-Q_y

If Q is_z-Q_yIf the calculated smoke temperature is less than 2%, the assumed smoke inlet temperature is the finally determined inlet smoke temperature, otherwise, the smoke inlet temperature is assumed again to be calculated until the calculation error is met (as shown in FIG. 1).

② economizer (superheater side)

Assume that the economizer (superheater side) flue gas inlet temperature is J'.

Heat absorption capacity of working medium on the economizer (superheater side): q_z＝D_z(h”-h')

Economizer (superheater side) flue gas heat release: q_y＝m_g(H'-H”)

Wherein: d_zThe mass flow of the working medium at the inlet of the economizer is kg/s;

h and h' are enthalpy values of the working medium outlet and the working medium inlet respectively, and kJ/kg;

m_gthe amount of coal is burned on the side of the superheater in kg/s;

h 'and H' are respectively the enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

calculating a checking error: q_z-Q_y

If Q is_z-Q_yIf the calculated smoke temperature is less than 2%, the assumed smoke inlet temperature is the finally determined inlet smoke temperature, otherwise, the smoke inlet temperature is assumed again to be calculated until the calculation error is met (as shown in FIG. 2).

2) Algorithm for inlet flue gas temperature of horizontal section of low-temperature superheater

The outlet flue gas temperature of the horizontal section of the low-temperature superheater is equal to the inlet flue gas temperature of the economizer (on the superheater side), and the inlet flue gas temperature of the horizontal section of the low-temperature superheater is assumed to be J'.

Heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m_g(H'-H”)

Wherein: d_zThe mass flow of the inlet working medium of the low-temperature superheater is kg/s;

h and h' are enthalpy values of the working medium outlet and the working medium inlet respectively, and kJ/kg;

m_gthe amount of coal fired on the superheater side is kg/s;

h 'and H' are respectively the enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj，

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.02Q_z

If Q is_y-Q_z-Q_fjIf the calculated smoke temperature is less than 2%, the assumed smoke inlet temperature is the finally determined inlet smoke temperature, otherwise, the smoke inlet temperature is assumed again for calculation until the calculation error is met (as shown in FIG. 3).

3) Algorithm for temperature of flue gas at vertical section inlet of low-temperature superheater

The temperature of the vertical section flue gas outlet of the low-temperature superheater is equal to the temperature of the horizontal section flue gas inlet of the low-temperature superheater, and the temperature of the vertical section flue gas inlet of the low-temperature superheater is assumed to be J'.

Heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Wherein D is_z: the mass flow of the working medium at the inlet of the low-temperature superheater is kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": respectively the enthalpy values of the flue gas inlet and the flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj，

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.05Q_z

If Q is_y-Q_z-Q_fjIf the calculated smoke temperature is less than 2%, the assumed smoke inlet temperature is the finally determined inlet smoke temperature, otherwise, the smoke inlet temperature is assumed again for calculation until the calculation error is met (as shown in FIG. 4).

4) Algorithm for inlet flue gas temperature of horizontal section of low-temperature reheater

The outlet temperature of the flue gas at the horizontal section of the low-temperature reheater is equal to the inlet temperature of the flue gas at the economizer (on the reheater side), and the inlet temperature of the flue gas at the horizontal section of the low-temperature reheater is assumed to be J'.

Heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Heat release of flue gas: q_y＝m_z(H'-H”)

Wherein D is_z: mass flow of the low-temperature reheater inlet working medium is kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m_z: the side-burning coal amount of the reheater is kg/s;

h', H ": respectively the enthalpy values of the flue gas inlet and the flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.015Q_z

If Q is_y-Q_z-Q_fjIf the calculated smoke temperature is less than 2%, the assumed smoke inlet temperature is the finally determined inlet smoke temperature, otherwise, the smoke inlet temperature is assumed again for calculation until the calculation error is met (as shown in FIG. 5).

5) Algorithm for inlet flue gas temperature of vertical section of low-temperature reheater

The temperature of the flue gas outlet of the vertical section of the low-temperature reheater is equal to the temperature of the flue gas inlet of the horizontal section of the low-temperature reheater, and the temperature of the flue gas inlet of the vertical section of the low-temperature reheater is assumed to be J'.

Heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Wherein D is_z: mass flow of the low-temperature reheater inlet working medium is kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": respectively the enthalpy values of the flue gas inlet and the flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.04Q_z

If Q is_y-Q_z-Q_fjIf the calculated smoke temperature is less than 2%, the assumed smoke inlet temperature is the finally determined inlet smoke temperature, otherwise, the smoke inlet temperature is assumed again for calculation until the calculation error is met (as shown in FIG. 6).

6) Algorithm for inlet flue gas temperature of high-temperature reheater

The temperature of the flue gas outlet of the high-temperature reheater is equal to the temperature of the flue gas inlet of the vertical section of the low-temperature reheater, and the temperature of the flue gas inlet of the high-temperature reheater is assumed to be J'.

Heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Wherein: d_z: reheater steam flow, kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.06Q_z

If Q is_y-Q_z-Q_fjIf the calculated smoke temperature is less than 2%, the assumed smoke inlet temperature is the finally determined inlet smoke temperature, otherwise, the smoke inlet temperature is assumed again for calculation until the calculation error is met (as shown in FIG. 7).

7) Algorithm for inlet flue gas temperature of high-temperature superheater

The temperature of the flue gas outlet of the high-temperature superheater is equal to the temperature of the flue gas inlet of the high-temperature reheater, and the temperature of the flue gas inlet of the high-temperature superheater is assumed to be J'.

Heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Wherein D is_z: main steam flow, kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": respectively the enthalpy values of the flue gas inlet and the flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.06Q_z

If Q is_y-Q_z-Q_fjIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is determined againThe flue gas inlet temperature is assumed to be calculated until the calculation error is met (as shown in fig. 8).

8) Algorithm for inlet flue gas temperature of platen superheater

The temperature of the flue gas outlet of the platen superheater is equal to the temperature of the flue gas inlet of the high-temperature superheater, and the temperature of the flue gas inlet of the platen superheater is assumed to be J'.

Heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Total heat absorbed by the screen: q_p＝Q^d _p+Q^f _p

Convective heat absorption of the heated surface: q^d _p＝Q_y-Q^d _fj，

Convection heat absorption of additional heating surface: q^d _fj＝0.15Q_z

Radiant heat absorbed by the screen: q^f _p＝Q_f-Q^f _fj

Direct radiation inside the furnace absorbed by the screen: q_f＝Q_f′-Q_f″

Direct radiation in the furnace obtained by the additional heating surface:

direct radiation in the furnace falling into the screen area:

direct radiation in the furnace penetrating the screen area:

furnace outlet heat flow falling into the screen area:

heat absorption capacity of the hearth:

in the formula, D_z: the steam flow entering the platen superheater is kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

f': the area of a smoke window at the outlet of the hearth and the square meter;

a: the blackness of the smoke;

x' p is the angular coefficient of the outlet cross section;

A_chthe area of a smoke window at the outlet of the screen and the square meter;

T_pj: average temperature of flue gas, K;

B_j: total coal combustion amount, kg/s;

beta: the heat exchange coefficient between the hearth and the screen is increased;

eta: a coefficient of non-uniformity along the height of the hearth;

H₁: the effective radiation heating area of the hearth and the square meter;

the heat preservation coefficient;

Q₁: low calorific value, kJ/kg;

I₁", the smoke enthalpy at the outlet of the hearth, kJ/kg;

A_fj: adding a heated area and a square meter;

s: the total heating area and the square meter;

calculating a checking error: q_p-Q_z

If Q is_p-Q_zIf the calculated smoke temperature is less than 2%, the assumed smoke inlet temperature is the finally determined inlet smoke temperature, otherwise, the smoke inlet temperature is assumed again for calculation until the calculation error is met (as shown in FIG. 9).

Claims (2)

1. An intelligent soot blowing algorithm based on Guerweiqi heat balance is characterized by comprising the following steps:

(1) calculating theoretical Heat transfer coefficient K₀

Wherein:

a₁＝a_d+a_f

in the formula: a is₁The heat release coefficient of the flue gas to the pipe wall is shown;

a₂the heat release coefficient of the working medium to the pipe wall is shown;

a_dis the surface heat release coefficient;

a_fis the radiative heat transfer coefficient;

C_z、C_srespectively the correction coefficients of the longitudinal and transverse tube rows in the airflow flowing direction;

lambda is the heat conductivity coefficient at the average temperature of the flue gas, W/(m DEG C);

d is the outer diameter of the pipe, m;

re and Pr are respectively the Relode number and the Plantt number of the smoke;

C_la correction coefficient for the relative length of the heating surface of the scour;

C_tand the correction coefficients are fluid temperature T and pipe wall temperature Tb.

σ₀Is BoltzmannA constant;

ε_sthe system blackness is obtained;

T_gband T is the tube wall temperature and the system temperature, K, respectively;

(2) determining the temperature of the flue gas at the inlet of the heat exchanger through a Guerweiqi heat balance intelligent algorithm;

calculating to obtain the heat absorption capacity and the heat release capacity of the working medium through the outlet flue gas temperature, the inlet working medium temperature, the outlet working medium temperature, the working medium mass flow and the assumed inlet flue gas temperature value, wherein each temperature can be converted into a corresponding enthalpy value, and when the checking error of the heat absorption capacity and the heat release capacity is less than 2% through an iterative algorithm based on a local heat balance principle, the assumed inlet flue gas temperature is the finally determined inlet flue gas temperature;

(3) calculating the actual heat transfer coefficient K_sj

Wherein:

Q_z＝D_z(h”-h')

in the formula: q_zThe heat absorption capacity of the working medium is kJ/kg;

D_zthe mass flow of inlet working medium is kg/s;

h and h' are enthalpy values of the working medium outlet and the working medium inlet respectively, and kJ/kg;

a is the heat transfer area, m²；

Δt_maxAnd Δ t_minRespectively representing large temperature pressure and small temperature pressure;

wherein, during the counter flow, the temperature and pressure delta t are high_maxJ' -t "; at downstream, the large temperature and pressure Δ t_max＝J′-t′；

At the time of countercurrent, the small temperature pressure Deltat_minJ "-t'; at downstream, the small temperature and pressure Δ t_min＝J″-t″；

J': flue gas inlet temperature, deg.C; t': working medium outlet temperature, DEG C; j': flue gas exit temperature, deg.C; t': working medium inlet temperature, DEG C;

(4) calculating the cleaning factor CF

When CF is 1, the heated surface is in an ideal clean state, namely the clean factor of a smooth pipe; a CF of less than 1 indicates that the heated surface is contaminated with soot, and the smaller the CF, the more serious the contamination.

2. The intelligent soot blowing algorithm as claimed in claim 1, wherein the specific method of the step (2) is as follows:

1) economizer inlet flue gas temperature algorithm

The economizer is divided into a superheater side and a reheater side through a flue gas baffle;

economizer (reheater side)

The flue gas temperature and the flue gas enthalpy value are in one-to-one correspondence, the known temperature can obtain the enthalpy value through table lookup, and the known enthalpy value can obtain the temperature; assuming that the economizer (reheater side) flue gas inlet temperature is J';

economizer (reheater side) working medium heat absorption: q_z＝D_z(h”-h')

Economizer (reheater side) flue gas heat release: q_y＝m_z(H'-H”)

Wherein: d_zThe mass flow of the working medium at the inlet of the economizer is kg/s;

h and h' are enthalpy values of the working medium outlet and the working medium inlet respectively, and kJ/kg;

m_zthe side-burning coal amount of the reheater is kg/s;

h 'and H' are respectively the enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

calculating a checking error: q_z-Q_y

If Q is_z-Q_yLess than 2%, the assumed flue gas enters at this timeThe port temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

② economizer (superheater side)

Assuming that the temperature of a flue gas inlet of an economizer (on the superheater side) is J';

heat absorption capacity of working medium on the economizer (superheater side): q_z＝D_z(h”-h')

Economizer (superheater side) flue gas heat release: q_y＝m_g(H'-H”)

Wherein: d_zThe mass flow of the working medium at the inlet of the economizer is kg/s;

h and h' are enthalpy values of the working medium outlet and the working medium inlet respectively, and kJ/kg;

m_gthe amount of coal is burned on the side of the superheater in kg/s;

h 'and H' are respectively the enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

calculating a checking error: q_z-Q_y

If Q is_z-Q_yIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

2) algorithm for inlet flue gas temperature of horizontal section of low-temperature superheater

The outlet flue gas temperature of the horizontal section of the low-temperature superheater is equal to the inlet flue gas temperature of an economizer (on the superheater side), and the inlet flue gas temperature of the horizontal section of the low-temperature superheater is assumed to be J';

heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m_g(H'-H”)

Wherein: d_zThe mass flow of the inlet working medium of the low-temperature superheater is kg/s;

h and h' are enthalpy values of the working medium outlet and the working medium inlet respectively, and kJ/kg;

m_gthe amount of coal fired on the superheater side is kg/s;

h 'and H' are respectively the enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj，

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.02Q_z

If Q is_y-Q_z-Q_fjIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

3) algorithm for temperature of flue gas at vertical section inlet of low-temperature superheater

The temperature of the vertical section flue gas outlet of the low-temperature superheater is equal to the temperature of the horizontal section flue gas inlet of the low-temperature superheater, and the temperature of the vertical section flue gas inlet of the low-temperature superheater is assumed to be J';

heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Wherein D is_z: the mass flow of the working medium at the inlet of the low-temperature superheater is kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": respectively the enthalpy values of the flue gas inlet and the flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj，

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.05Q_z

If Q is_y-Q_z-Q_fjIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

4) algorithm for inlet flue gas temperature of horizontal section of low-temperature reheater

The temperature of the flue gas outlet of the horizontal section of the low-temperature reheater is equal to the temperature of the flue gas inlet of an economizer (on the reheater side), and the temperature of the flue gas inlet of the horizontal section of the low-temperature reheater is assumed to be J';

heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Heat release of flue gas: q_y＝m_z(H'-H”)

Wherein D is_z: mass flow of the low-temperature reheater inlet working medium is kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m_z: the side-burning coal amount of the reheater is kg/s;

h', H ": respectively the enthalpy values of the flue gas inlet and the flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.015Q_z

If Q is_y-Q_z-Q_fjIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

5) algorithm for inlet flue gas temperature of vertical section of low-temperature reheater

The temperature of a flue gas outlet of the vertical section of the low-temperature reheater is equal to the temperature of a flue gas inlet of the horizontal section of the low-temperature reheater, and the temperature of the flue gas inlet of the vertical section of the low-temperature reheater is assumed to be J';

heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Wherein D is_z: mass flow of the low-temperature reheater inlet working medium is kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": respectively the enthalpy values of the flue gas inlet and the flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.04Q_z

If Q is_y-Q_z-Q_fjIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

6) algorithm for inlet flue gas temperature of high-temperature reheater

The temperature of a flue gas outlet of the high-temperature reheater is equal to the temperature of a flue gas inlet of a vertical section of the low-temperature reheater, and the temperature of the flue gas inlet of the high-temperature reheater is assumed to be J';

heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Wherein: d_z: reheater steam flow, kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.06Q_z

If Q is_y-Q_z-Q_fjIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

7) algorithm for inlet flue gas temperature of high-temperature superheater

The temperature of the flue gas outlet of the high-temperature superheater is equal to the temperature of the flue gas inlet of the high-temperature reheater, and the temperature of the flue gas inlet of the high-temperature superheater is assumed to be J';

heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Wherein D is_z: main steam flow, kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": respectively the enthalpy values of the flue gas inlet and the flue gas outlet, kJ/kg;

calculating a checking error: q_y-Q_z-Q_fj

Wherein Q is_fjFor additional heat transfer surface convection heat absorption, Q_fj＝0.06Q_z

If Q is_y-Q_z-Q_fjIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met;

8) algorithm for inlet flue gas temperature of platen superheater

The temperature of the flue gas outlet of the platen superheater is equal to the temperature of the flue gas inlet of the high-temperature superheater, and the temperature of the flue gas inlet of the platen superheater is assumed to be J';

heat absorption capacity of the working medium: q_z＝D_z(h”-h')

Flue gas heat release: q_y＝m(H'-H”)

Total heat absorbed by the screen: q_p＝Q^d _p+Q^f _p

Convective heat absorption of the heated surface: q^d _p＝Q_y-Q^d _fj，

Convection heat absorption of additional heating surface: q^d _fj＝0.15Q_z

Radiant heat absorbed by the screen: q^f _p＝Q_f-Q^f _fj

Direct radiation inside the furnace absorbed by the screen: q_f＝Q_f′-Q_f″

Direct radiation in the furnace obtained by the additional heating surface:

direct radiation in the furnace falling into the screen area:

direct radiation in the furnace penetrating the screen area:

furnace outlet heat flow falling into the screen area:

heat absorption capacity of the hearth:

in the formula, D_z: the steam flow entering the platen superheater is kg/s;

h ', h': respectively the enthalpy values of the working medium outlet and the working medium inlet, kJ/kg;

m: total coal combustion amount, kg/s;

h', H ": enthalpy values of a flue gas inlet and a flue gas outlet, kJ/kg;

f': the area of a smoke window at the outlet of the hearth and the square meter;

a: the blackness of the smoke;

x' p is the angular coefficient of the outlet cross section;

A_chthe area of a smoke window at the outlet of the screen and the square meter;

T_pj: average temperature of flue gas, K;

B_j: total coal combustion amount, kg/s;

beta: the heat exchange coefficient between the hearth and the screen is increased;

eta: a coefficient of non-uniformity along the height of the hearth;

H₁: the effective radiation heating area of the hearth and the square meter;

the heat preservation coefficient;

Q₁: low calorific value, kJ/kg;

I₁", the smoke enthalpy at the outlet of the hearth, kJ/kg;

A_fj: adding a heated area and a square meter;

s: the total heating area and the square meter;

calculating a checking error: q_p-Q_z

If Q is_p-Q_zIf the temperature is less than 2%, the assumed flue gas inlet temperature is the finally determined inlet flue gas temperature, otherwise, the flue gas inlet temperature is assumed again for calculation until the calculation error is met.

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