METHOD FOR ACQUIRING THERMAL EFFICIENCY OF A BOILER

Abstract

The present invention discloses a method for acquiring thermal efficiency of a boiler, comprising: acquiring effective output heat and total output heat of the boiler, and obtaining the thermal efficiency of the boiler according to the effective output heat and total output heat. In the method provided by the present invention, by acquiring the thermal efficiency of the boiler according to the obtained effective output heat and total output heat, the thermal efficiency of the boiler can be acquired without performing coal quality testing, thus the thermal efficiency of the boiler is conveniently obtained, and the real-time capability and accuracy are satisfied.

Claims

1. A method for acquiring thermal efficiency of a boiler, wherein the method for acquiring the thermal efficiency of the boiler comprises: acquiring effective output heat and total output heat of the boiler, and obtaining the thermal efficiency of the boiler according to the effective output heat and total output heat.

2. The method for acquiring the thermal efficiency of the boiler according to claim 1, wherein the method for acquiring the thermal efficiency of the boiler comprises: acquiring energy Q.sub.gq absorbed by superheated steam of the boiler, heat Q.sub.zq absorbed by reheated steam, energy Q.sub.py output from flue gas at a thermal boundary outlet of the boiler, energy Q.sub.fh output from fly ash at the thermal boundary outlet of the boiler, heat Q.sub.lz output from slag at the thermal boundary outlet of the boiler, heat loss Q.sub.sr of the boiler, energy Q.sub.pw output from discharged sewage of the boiler, heat Q.sub.sm output from pebble coal discharged from a coal pulverizer, and energy Q.sub.xl output from boiler side leakage steam and water; and obtaining the thermal efficiency .sub.gl of the boiler through the following formula: ${}_{\mathrm{gl}}=\frac{Q_{\mathrm{gq}}+Q_{\mathrm{zq}}}{Q_{\mathrm{gq}}+Q_{\mathrm{zq}}+Q_{\mathrm{py}}+Q_{\mathrm{fh}}+Q_{\mathrm{lz}}+Q_{\mathrm{sr}}+Q_{\mathrm{pw}}+Q_{\mathrm{sm}}+Q_{\mathrm{xl}}}100.Math.\%$ where Q.sub.gp is the energy absorbed by superheated steam, Q.sub.zq is the heat absorbed by reheated steam, Q.sub.py is the energy output from flue gas at the thermal boundary outlet of the boiler, Q.sub.fh is the energy output from fly ash at the thermal boundary outlet of the boiler, Q.sub.lz is the heat output from slag at the thermal boundary outlet of the boiler, Q.sub.sr is the heat loss of the boiler, Q.sub.pw is the energy output from discharged sewage of the boiler, Q.sub.sm is the heat output from pebble coal discharged from the coal pulverizer, and Q.sub.xl is the energy output from boiler side leakage steam and water.

3. The method for acquiring the thermal efficiency of the boiler according to claim 2, wherein the step of acquiring the energy absorbed by the superheated steam comprises: acquiring a flow D.sub.gqc of steam at an outlet of a last-stage superheater of the boiler, an enthalpy value h.sub.gqc of steam at the outlet of the last-stage superheater of the boiler, a flow D.sub.gjw-i of desuperheating water at each stage injected into a water side of the boiler before a measuring point of a flow of feed water at an inlet of an economizer, a stage number n of desuperheating water injected into the water side of the boiler before the measuring point of the flow of feed water at the inlet of the economizer, an enthalpy value h.sub.fw of feed water at the inlet of the economizer and an enthalpy value h.sub.gjw-i of desuperheating water at each stage injected into the water side of the boiler before the measuring point of the flow of feed water at the inlet of the economizer; and calculating the heat Q.sub.gq absorbed by the superheated steam according to the following formula: $Q_{\mathrm{gq}}=D_{\mathrm{gqc}}.Math.h_{\mathrm{gqc}}-\left(D_{\mathrm{gqc}}-\underset{i=1}{\overset{n}{.Math.}}.Math.D_{\mathrm{gjw}.Math.\text{-}.Math.i}\right).Math.h_{\mathrm{fw}}-\underset{i=1}{\overset{n}{.Math.}}.Math.D_{\mathrm{gjw}.Math.\text{-}.Math.i}.Math.h_{\mathrm{gjw}.Math.\text{-}.Math.i}$ where i is a current stage number and n is a stage number of desuperheating water injected into the water side of the boiler before the measuring point of the flow of feed water at the inlet of the economizer.

4. The method for acquiring the thermal efficiency of the boiler according to claim 2, wherein the step of acquiring the heat Q.sub.zq absorbed by reheated steam comprises: acquiring a flow D.sub.zqj of steam at an inlet of a reheater, an amount D.sub.zjw of desuperheating water injected into a water side of the reheater, an enthalpy value h.sub.zqc of steam at an outlet of the reheater, an enthalpy value h.sub.zqj of steam at the inlet of the reheater and an enthalpy value h.sub.zjw of desuperheating water of the reheater, and calculating the heat Q.sub.zq absorbed by reheated steam according to the following formula:
Q.sub.zq=(D.sub.zqj+D.sub.zjw)h.sub.zqcD.sub.zqjh.sub.zqjD.sub.zjwh.sub.zjw where D.sub.zqj is the flow of steam at the inlet of the reheater, D.sub.zjw is the amount of desuperheating water injected into the water side of the reheater, h.sub.zqc is the enthalpy value of steam at the outlet of the reheater, h.sub.zqj is the enthalpy value of steam at the inlet of the reheater and h.sub.zjw is the enthalpy value of desuperheating water of the reheater.

5. The method for acquiring the thermal efficiency of the boiler according to claim 3, wherein the step of acquiring the energy Q.sub.py output from flue gas at the thermal boundary outlet of the boiler comprises: calculating the energy Q.sub.py output from flue gas at the thermal boundary outlet of the boiler according to the following formula:
Q.sub.py=(V.sub.py1.24D.sub.ch)CP.sub.py(t.sub.pyt.sub.0)+126.36V.sub.py(CO)+D.sub.ch(h.sub.pychsh.sub.fw) where V.sub.py is an amount of flue gas at the thermal boundary outlet of the boiler, D.sub.ch is a flow of soot blowing steam, t.sub.0 is air temperature at a thermal boundary inlet of the boiler, t.sub.py is flue gas temperature at the thermal boundary outlet of the boiler, CP.sub.py is average specific heat at constant pressure of flue gas from t.sub.0 to t.sub.py after deducting the influence of soot blowing steam at the thermal boundary outlet of the boiler, (CO) is volume concentration of CO gas in flue gas at the thermal boundary outlet of the boiler, h.sub.pychs is water vapor enthalpy under conditions of 1.24D.sub.ch/V.sub.py flue gas partial pressure and t.sub.py flue gas temperature, and h.sub.fw is the enthalpy value of feed water at the inlet of the economizer; wherein CP.sub.py is calculated according to the following formula: ${\mathrm{CP}}_{\mathrm{py}}^{}=\frac{{\left({\mathrm{CO}}_2\right)}^{}}{100}.Math.{\mathrm{CP}}_{{\mathrm{CO}}_2}+\frac{{\left(H_2.Math.O\right)}^{}}{100}.Math.{\mathrm{CP}}_{H_2.Math.O}+\frac{{\left(O_2\right)}^{}}{100}.Math.{\mathrm{CP}}_{O_2}+\frac{{\left(\mathrm{CO}\right)}^{}}{100}.Math.{\mathrm{CP}}_{\mathrm{CO}}+\frac{{\left({\mathrm{SO}}_2\right)}^{}}{100}.Math.{\mathrm{CP}}_{{\mathrm{SO}}_2}+\frac{{\left(N_2\right)}^{}}{100}.Math.{\mathrm{CP}}_{N_2}$ where CP.sub.CO2, CP.sub.H2O, CP.sub.O2, CP.sub.CO, CP.sub.SO2 and CP.sub.N2 are respectively average specific heat at constant pressure of CO.sub.2, H.sub.2O, O.sub.2, CO, SO.sub.2 and N.sub.2 from t.sub.0 to t.sub.py; (Xi) is flue gas composition of X.sub.i after deducting the dilution of soot blowing steam to tail flue gas, X.sub.1 is CO.sub.2, X.sub.2 is O.sub.2, X.sub.3 is CO, X.sub.4 is SO.sub.2 and X.sub.5 is N.sub.2; and (H.sub.2O)=100.sub.i=1.sup.5(X.sub.i) wherein the flue gas composition (Xi) of X.sub.i after deducting the dilution of soot blowing steam to tail flue gas is calculated according to the following formula: ${\left(X_i\right)}^{}=\frac{V_{\mathrm{py}}}{V_{\mathrm{py}}-1.24.Math..Math.D_{\mathrm{ch}}}.Math.\left(X_i\right)$ $\left(N_2\right)=100-\left({\mathrm{CO}}_2\right)-\left(H_2.Math.O\right)-\left(O_2\right)-\left(\mathrm{CO}\right)-\left({\mathrm{SO}}_2\right)$ where (X.sub.i) is volume concentration of gas X.sub.i in the flue gas at the thermal boundary outlet of the boiler.

6. The method for acquiring the thermal efficiency of the boiler according to claim 5, wherein the step of acquiring the flow D.sub.ch of soot blowing steam comprises: acquiring the flow D.sub.ch through a measurement device; or acquiring the flow of feed water at the inlet of the economizer, the flow of steam at the outlet of the last-stage superheater of the boiler and the flow of desuperheating water at each stage injected into the water side of the boiler before the measuring point of the flow of feed water at the inlet of the economizer; and calculating the flow D.sub.ch of soot blowing steam according to the following formula: $D_{\mathrm{ch}}=D_{\mathrm{fw}}+\underset{i=1}{\overset{n}{.Math.}}.Math.D_{\mathrm{gjw}.Math.\text{-}.Math.i}-D_{\mathrm{gqc}}$ where D.sub.fw is the flow of feed water at the inlet of the economizer, D.sub.gqc is the flow of steam at the outlet of the last-stage superheater of the boiler and D.sub.gjw-i is the flow of desuperheating water at each stage injected into the water side of the boiler before the measuring point of the flow of feed water at the inlet of the economizer.

7. The method for acquiring the thermal efficiency of the boiler according to claim 2, wherein the step of acquiring the energy Q.sub.fh output from fly ash at the thermal boundary outlet of the boiler and the heat Q.sub.lz output from slag at the thermal boundary outlet of the boiler comprises: acquiring concentration of fly ash in flue gas at the thermal boundary outlet of the boiler, an enthalpy value of fly ash in flue gas at the thermal boundary outlet of the boiler, an enthalpy value of fly ash under a condition of raw coal temperature at an inlet of the coal pulverizer, a mass ratio of fly ash to slag at the thermal boundary outlet of the boiler, an enthalpy value of slag at the thermal boundary outlet of the boiler, an enthalpy value of slag under the raw coal temperature at the inlet of the coal pulverizer, content of combustible substances in fly ash at the thermal boundary outlet of the boiler and an amount of flue gas at the thermal boundary outlet of the boiler; and calculating according to the following formula: $Q_{\mathrm{fn}}+Q_{\mathrm{lz}}=\mathrm{.Math.}\left(\mathrm{ash}\right).Math.V_{\mathrm{py}}\left(h_{\mathrm{fn}}-h_{\mathrm{fh}.Math..Math.0}\right)+\frac{1}{a}.Math.\mathrm{.Math.}\left(\mathrm{ash}\right).Math.V_{\mathrm{py}}\left(h_{\mathrm{lz}}-h_{\mathrm{lz}.Math..Math.0}\right)+0.33727.Math.\left(1+\frac{1}{a}\right).Math.\mathrm{.Math.}\left(\mathrm{ash}\right).Math.V_{\mathrm{py}}.Math.C_{\mathrm{fh}}$ where (ash) is the concentration of fly ash in flue gas at the thermal boundary outlet of the boiler; h.sub.fh is the enthalpy value of fly ash in flue gas at the thermal boundary outlet of the boiler; h.sub.fh0 is the enthalpy value of fly ash under the condition of raw coal temperature at the inlet of the coal pulverizer; a is the mass ratio of fly ash to slag at the thermal boundary outlet of the boiler; h.sub.lz is the enthalpy value of slag at the thermal boundary outlet of the boiler; h.sub.lz0 is the enthalpy value of slag under the raw coal temperature at the inlet of the coal pulverizer; C.sub.fh is the content of combustible substances in fly ash at the thermal boundary outlet of the boiler; and V.sub.py is the amount of flue gas at the thermal boundary outlet of the boiler.

8. The method for acquiring the thermal efficiency of the boiler according to claim 2, wherein the step of acquiring the energy Q.sub.pw output from discharged sewage of the boiler comprises: acquiring an amount of discharged sewage of the boiler, an enthalpy value of discharged sewage of the boiler and the enthalpy value of feed water at the inlet of the economizer; and calculating according to the following formula: Q.sub.pw=D.sub.pw(h.sub.pwh.sub.fw), where D.sub.pw is the amount of discharged sewage of the boiler; h.sub.pw is the enthalpy value of discharged sewage of the boiler; and h.sub.fw is the enthalpy value of feed water at the inlet of the economizer.

9. The method for acquiring the thermal efficiency of the boiler according to claim 2, wherein the step of acquiring the heat Q.sub.sm output from pebble coal discharged from the coal pulverizer comprises: acquiring an amount of pebble coal discharged from the coal pulverizer, a calorific value of pebble coal, a sensible enthalpy value of discharged pebble coal and a sensible enthalpy value of pebble coal under the condition of raw coal temperature at the inlet of the coal pulverizer; and calculating the heat Q.sub.sm output from pebble coal discharged from the coal pulverizer according to the following formula:
Q.sub.sm=M.sub.sm(Q.sub.smfr+h.sub.smh.sub.sm0) where M.sub.sm is the amount of pebble coal discharged from the coal pulverizer; Q.sub.smfr is the calorific value of pebble coal; h.sub.sm is the sensible enthalpy value of discharged pebble coal; and h.sub.sm0 is the sensible enthalpy value of pebble coal under the condition of raw coal temperature at the inlet of the coal pulverizer.

10. The method for acquiring the thermal efficiency of the boiler according to claim 2, wherein the step of acquiring the heat loss Q.sub.sr of the boiler comprises: acquiring a rated flow of steam at the outlet of the last-stage superheater of the boiler and the flow of steam at the outlet of the last-stage superheater of the boiler; and calculating the heat loss Q.sub.sr of the boiler according to the following formula: $Q_{\mathrm{sr}}=\frac{1}{17.18.Math.{D_{\mathrm{gqc}}\left(D_{\mathrm{gqc}}^e\right)}^{-0.62}-1}.Math.\left(Q_{\mathrm{gq}}+Q_{\mathrm{zq}}+Q_{\mathrm{py}}+Q_{\mathrm{fh}}+Q_{\mathrm{lz}}+Q_{\mathrm{pw}}+Q_{\mathrm{sm}}+Q_{\mathrm{xl}}\right)$ where D.sub.gqc.sup.e is the rated flow of steam at the outlet of the last-stage superheater of the boiler; and D.sub.gqc is the flow of steam at the outlet of the last-stage superheater of the boiler.

Description

DESCRIPTION OF THE DRAWINGS

[0051] In order to describe more clearly the embodiments of the present invention or the technical solutions in the prior art, a brief introduction of the drawings to be used in the embodiments or the description of the prior art will be given below. Obviously, the drawings described below are merely the embodiments of the present invention, and one skilled in the art may also obtain other drawings according to the provided drawings without contributing any inventive labor.

[0052] The sole FIGURE illustrates a flowchart of a method for acquiring efficiency of a boiler provided in the present invention.

DESCRIPTION OF THE EMBODIMENTS

[0053] A clear and complete description of the technical solution in the embodiment of the present invention will be given below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention instead of all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by one skilled in the art without contributing any inventive labor shall fall within the scope of the present invention.

[0054] The core of the present invention is to provide a method for acquiring thermal efficiency of a boiler, which does not involve coal quality acquisition in the acquisition process and is convenient and accurate.

[0055] The method for acquiring the thermal efficiency of the boiler provided by the present invention comprises:

[0056] acquiring energy Q.sub.gq absorbed by superheated steam of the boiler, heat Q.sub.zq absorbed by reheated steam, energy Q.sub.py output from flue gas at a thermal boundary outlet of the boiler, energy Q.sub.fh output from fly ash at the thermal boundary outlet of the boiler, heat Q.sub.lz output from slag at the thermal boundary outlet of the boiler, heat loss Q.sub.sr of the boiler, energy Q.sub.pw output from discharged sewage of the boiler, heat Q.sub.sm output from pebble coal discharged from a coal pulverizer, and energy Q.sub.xl output from boiler side leakage steam and water, and obtaining the thermal efficiency .sub.gl of the boiler through the following formula:

[00008]${}_{\mathrm{gl}}=\frac{Q_{\mathrm{gq}}+Q_{\mathrm{zq}}}{Q_{\mathrm{gq}}+Q_{\mathrm{zq}}+Q_{\mathrm{py}}+Q_{\mathrm{fh}}+Q_{\mathrm{lz}}+Q_{\mathrm{sr}}+Q_{\mathrm{pw}}+Q_{\mathrm{sm}}+Q_{\mathrm{xl}}}100.Math.\%$

[0057] where Q.sub.gp is the energy absorbed by superheated steam, Q.sub.zq is the heat absorbed by reheated steam, Q.sub.py is the energy output from flue gas at the thermal boundary outlet of the boiler, Q.sub.fh is the energy output from fly ash at the thermal boundary outlet of the boiler, Q.sub.lz is the heat output from slag at the thermal boundary outlet of the boiler, Q.sub.sr is the heat loss of the boiler, Q.sub.pw is the energy output from discharged sewage of the boiler, Q.sub.sm is the heat output from pebble coal discharged from the coal pulverizer, and Q.sub.xl is the energy output from boiler side leakage steam and water.

[0058] It needs to be noted that, in order to know the thermal efficiency of the boiler in real time, the thermal efficiency is acquired according to the following formula:

[00009]$.Math.\mathrm{Thermal}.Math..Math.\mathrm{efficnecy}.Math..Math.\mathrm{of}.Math..Math.\mathrm{boiler}=\frac{\mathrm{Effective}.Math..Math.\mathrm{output}.Math..Math.\mathrm{heat}}{\mathrm{Total}.Math..Math.\mathrm{output}.Math..Math.\mathrm{heat}}100.Math.\%$$.Math.\mathrm{or}$$\mathrm{Thermal}.Math..Math.\mathrm{efficnecy}.Math..Math.\mathrm{of}.Math..Math.\mathrm{boiler}=1-\frac{\mathrm{Ineffective}.Math..Math.\mathrm{output}.Math..Math.\mathrm{heat}}{\mathrm{Total}.Math..Math.\mathrm{output}.Math..Math.\mathrm{heat}}100.Math.\%$

[0059] where the thermal efficiency of the boiler is .sub.gl (%), wherein the effective output heat Q.sub.yx (MJ/h) of the boiler and the total output heat Q.sub.tot (MJ/h) of the boiler are specifically calculated as follows.

[0060] Specifically, please refer to the following formulas:

Q.sub.yx=Q.sub.gq+Q.sub.zq

Q.sub.tot=Q.sub.gq+Q.sub.zq+Q.sub.py+Q.sub.fh+Q.sub.lz+Q.sub.sr+Q.sub.pw+Q.sub.sm+Q.sub.xl

[0061] where Q.sub.gp is the energy absorbed by superheated steam, unit: MJ/h;

[0062] Q.sub.zq is the heat absorbed by reheated steam, unit: MJ/h;

[0063] Q.sub.py is the energy output from flue gas at the thermal boundary outlet of the boiler (including sensible heat and combustion energy), unit: MJ/h;

[0064] Q.sub.fh is the energy output from fly ash at the thermal boundary outlet of the boiler (including sensible heat and combustion energy), unit: MJ/h;

[0065] Q.sub.lz is the heat output from slag at the thermal boundary outlet of the boiler (including sensible heat and combustion energy), unit: MJ/h;

[0066] Q.sub.sr is the heat loss of the boiler, unit: MJ/h;

[0067] Q.sub.pw is the energy output from discharged sewage of the boiler, unit: MJ/j;

[0068] Q.sub.sm is the heat output from pebble coal discharged from the coal pulverizer (including sensible heat and combustion energy), unit: MJ/h; and

[0069] Q.sub.xl is the energy output from boiler side leakage steam and water, unit: MJ/h.

[0070] To sum up, the formula for calculating the thermal efficiency .sub.gl of the boiler can be obtained. In the acquisition method provided by the present invention, by employing the calculation formula of the boiler thermal efficiency .sub.gl, the thermal efficiency of the boiler can be acquired without performing coal quality testing, the thermal efficiency of the boiler can be conveniently obtained, and the and accuracy can be satisfied.

[0071] It needs to be noted that the unit labeled after the physical quantity in the description of the present invention is a unit applicable in the formula, but the unit is not limited to this unit. As long as the use of the formula is satisfied, the whole adjustment may be made.

[0072] On the basis of the above-mentioned embodiments, the step of acquiring the energy absorbed by the superheated steam may specifically comprise:

[0073] acquiring a flow D.sub.gqc of steam at an outlet of a last-stage superheater of the boiler, an enthalpy value h.sub.gqc of steam at the outlet of the last-stage superheater of the boiler, a flow D.sub.gjw-i of desuperheating water at each stage injected into a water side of the boiler before a measuring point of a flow of feed water at an inlet of an economizer, a stage number n of desuperheating water injected into the water side of the boiler before the measuring point of the flow of feed water at the inlet of the economizer, an enthalpy value h.sub.fw of feed water at the inlet of the economizer and an enthalpy value h.sub.gjw-i of desuperheating water at each stage injected into the water side of the boiler before the measuring point of the flow of feed water at the inlet of the economizer; and calculating the heat Q.sub.gq absorbed by the superheated steam according to the following formula:

[00010]$Q_{\mathrm{gq}}=D_{\mathrm{gqc}}.Math.h_{\mathrm{gqc}}-\left(D_{\mathrm{gqc}}-\underset{i=1}{\overset{n}{.Math.}}.Math.D_{\mathrm{giw}.Math.\text{-}.Math.i}\right).Math.h_{\mathrm{fw}}-\underset{i=1}{\overset{n}{.Math.}}.Math.D_{\mathrm{giw}.Math.\text{-}.Math.i}.Math.h_{\mathrm{gjw}.Math.\text{-}.Math.i}$

[0074] where i is a current stage number and n is a stage number of desuperheating water injected into the water side of the boiler before the measuring point of the flow of feed water at the inlet of the economizer.

[0075] Herein, D.sub.gqc is the flow of steam at the outlet of the last-stage superheater of the boiler, unit: t/h;

[0076] h.sub.gqc is the enthalpy value of steam at the outlet of the last-stage superheater of the boiler, unit: kJ/kg;

[0077] D.sub.gjw-i is the flow of desuperheating water at each stage injected into the water side of the boiler before the measuring point of the flow of feed water at the inlet of the economizer, unit: t/h;

[0078] n is the stage number of desuperheating water injected into the water side of the boiler before the measuring point of the flow of feed water at the inlet of the economizer;

[0079] h.sub.fw is the enthalpy value of feed water at the inlet of the economizer, unit: kJ/kg; and

[0080] h.sub.gjw-i is the enthalpy value of desuperheating water at each stage injected into the water side of the boiler before the measuring point of the flow of feed water at the inlet of the economizer, unit: kJ/kg.

[0081] On the basis of any one of the above-mentioned embodiments, the step of acquiring the heat Q.sub.zq absorbed by reheated steam may specifically comprise:

[0082] acquiring a flow D.sub.zqj of steam at an inlet of a reheater, an amount D.sub.zjw of desuperheating water injected into a water side of the reheater, an enthalpy value h.sub.zqc of steam at an outlet of the reheater, an enthalpy value h.sub.zqj of steam at the inlet of the reheater and an enthalpy value h.sub.zjw of desuperheating water of the reheater,

[0083] and calculating the heat Q.sub.zq absorbed by reheated steam according to the following formula:

Q.sub.zq=(D.sub.zqj+D.sub.zjw)h.sub.zqcD.sub.zqjh.sub.zqjD.sub.zjwh.sub.zjw

[0084] where D.sub.zqj is the flow of steam at the inlet of the reheater, unit: t/h;

[0085] D.sub.zjw is the amount of desuperheating water injected into the water side of the reheater, unit: kJ/kg;

[0086] h.sub.zqc is the enthalpy value of steam at the outlet of the reheater, unit: kJ/kg;

[0087] h.sub.zqj is the enthalpy value of steam at the inlet of the reheater, unit: kJ/kg; and

[0088] h.sub.zjw is the enthalpy value of desuperheating water of the reheater, unit: kJ/kg.

[0089] On the basis of any one of the above-mentioned embodiments, the step of acquiring the energy Q.sub.py output from flue gas at the thermal boundary outlet of the boiler may specifically comprise:

[0090] calculating the energy Q.sub.py output from flue gas at the thermal boundary outlet of the boiler according to the following formula:

Q.sub.py=(V.sub.py1.24D.sub.ch)CP.sub.py(t.sub.pyt.sub.0)+126.36V.sub.py(CO)+D.sub.ch(h.sub.pychsh.sub.fw)

[0091] where V.sub.py is an amount of flue gas at the thermal boundary outlet of the boiler, unit: km.sup.3/h;

[0092] D.sub.ch is a flow of soot blowing steam, unit: t/h;

[0093] t.sub.0 is air temperature at a thermal boundary inlet of the boiler, unit: C.;

[0094] t.sub.py is flue gas temperature at the thermal boundary outlet of the boiler, unit: C.;

[0095] CP.sub.py is average specific heat at constant pressure of flue gas from t.sub.0 to t.sub.py after deducting the influence of soot blowing steam at the thermal boundary outlet of the boiler, unit: kJ/m.sup.3 k;

[0096] (CO) is volume concentration of CO gas in flue gas at the thermal boundary outlet of the boiler, unit: %;

[0097] h.sub.pychs is water vapor enthalpy under conditions of 1.24D.sub.ch/V.sub.py flue gas partial pressure and t.sub.py flue gas temperature, unit: kJ/kg; and

[0098] h.sub.fw is the enthalpy value of feed water at the inlet of the economizer, unit: t/h.

[0099] Herein, CP.sub.py is calculated according to the following formula:

[00011]${\mathrm{CP}}_{\mathrm{py}}^{}=\frac{{\left({\mathrm{CO}}_2\right)}^{}}{100}.Math.{\mathrm{CP}}_{{\mathrm{CO}.Math.}_2}+\frac{{\left(H_2.Math.O\right)}^{}}{100}.Math.{\mathrm{CP}}_{H_2.Math.O}+\frac{{\left(O_2\right)}^{}}{100}.Math.{\mathrm{CP}}_{O_2}+\frac{{\left(\mathrm{CO}\right)}^{}}{100}.Math.{\mathrm{CP}}_{\mathrm{CO}}+\frac{{\left({\mathrm{SO}}_2\right)}^{}}{100}.Math.{\mathrm{CP}}_{{\mathrm{SO}}_2}+\frac{{\left(N_2\right)}^{}}{100}.Math.{\mathrm{CP}}_{N_2}$

[0100] where CP.sub.CO2, CP.sub.H2O, CP.sub.O2, CP.sub.CO, CP.sub.SO2 and CP.sub.N2 are respectively average specific heat at constant pressure of CO.sub.2, H.sub.2O, O.sub.2, CO, SO.sub.2 and N.sub.2 from t.sub.0 to t.sub.py, unit: kJ/m.sup.3k;

[0101] (Xi) is flue gas composition of X.sub.i after deducting the dilution of soot blowing steam to tail flue gas, unit: %, X.sub.1 is CO.sub.2, X.sub.2 is O.sub.2, X.sub.3 is CO, X.sub.4 is SO.sub.2 and X.sub.5 is N.sub.2; and (H.sub.2O)=100.sub.i=1.sup.5(X.sub.i),

[0102] wherein the flue gas composition (X.sub.i) of X.sub.i after deducting the dilution of soot blowing steam to tail flue gas is calculated according to the following formula:

[00012]${\left(X_i\right)}^{}=\frac{V_{\mathrm{py}}}{V_{\mathrm{py}}-1.24.Math..Math.D_{\mathrm{ch}}}.Math.\left(X_i\right)$$\left(N_2\right)=100-\left({\mathrm{CO}}_2\right)-\left(H_2.Math.O\right)-\left(O_2\right)-\left(\mathrm{CO}\right)-\left({\mathrm{SO}}_2\right)$

[0103] where (X.sub.i) is volume concentration of gas X.sub.i in the flue gas at the thermal boundary outlet of the boiler, unit: %.

[0104] On the basis of the above-mentioned embodiments, the step of acquiring the flow D.sub.ch of soot blowing steam may specifically comprise:

[0105] acquiring the flow D.sub.ch through a measurement device;

[0106] or acquiring the flow of feed water at the inlet of the economizer, the flow of steam at the outlet of the last-stage superheater of the boiler and the flow of desuperheating water at each stage injected into the water side of the boiler before the measuring point of the flow of feed water at the inlet of the economizer; and calculating the flow D.sub.ch of soot blowing steam according to the following formula:

[00013]$D_{\mathrm{ch}}=D_{\mathrm{fw}}+\underset{i=1}{\overset{n}{.Math.}}.Math.D_{\mathrm{gjw}.Math.\text{-}.Math.i}-D_{\mathrm{gqc}}$

[0107] where D.sub.fw is the flow of feed water at the inlet of the economizer, unit: t/h; D.sub.gqc is the flow of steam at the outlet of the last-stage superheater of the boiler, unit: t/h; and D.sub.gjw-i is the flow of desuperheating water at each stage injected into the water side of the boiler before the measuring point of the flow of feed water at the inlet of the economizer, unit: t/h.

[0108] On the basis of any one of the above-mentioned embodiments, the step of acquiring the energy Q.sub.fh output from fly ash at the thermal boundary outlet of the boiler and the heat Q.sub.lz output from slag at the thermal boundary outlet of the boiler comprises:

[0109] acquiring concentration of fly ash in flue gas at the thermal boundary outlet of the boiler, an enthalpy value of fly ash in flue gas at the thermal boundary outlet of the boiler, an enthalpy value of fly ash under a condition of raw coal temperature at an inlet of the coal pulverizer, a mass ratio of fly ash to slag at the thermal boundary outlet of the boiler, an enthalpy value of slag at the thermal boundary outlet of the boiler, an enthalpy value of slag under the raw coal temperature at the inlet of the coal pulverizer, content of combustible substances in fly ash at the thermal boundary outlet of the boiler and an amount of flue gas at the thermal boundary outlet of the boiler; and calculating according to the following formula:

[00014]$Q_{\mathrm{fn}}+Q_{\mathrm{lz}}=\mathrm{.Math.}\left(\mathrm{ash}\right).Math.V_{\mathrm{py}}\left(h_{\mathrm{fn}}-h_{\mathrm{fh}.Math..Math.0}\right)+\frac{1}{a}.Math.\mathrm{.Math.}\left(\mathrm{ash}\right).Math.V_{\mathrm{py}}\left(h_{\mathrm{lz}}-h_{\mathrm{lz}.Math..Math.0}\right)+0.33727.Math.\left(1+\frac{1}{a}\right).Math.\mathrm{.Math.}\left(\mathrm{ash}\right).Math.V_{\mathrm{py}}.Math.C_{\mathrm{fh}}$

[0110] where (ash) is the concentration of fly ash in flue gas at the thermal boundary outlet of the boiler, unit: g/Nm.sup.3;

[0111] h.sub.fh is the enthalpy value of fly ash in flue gas at the thermal boundary outlet of the boiler, unit: kJ/kg;

[0112] h.sub.fh0 is the enthalpy value of fly ash under the condition of raw coal temperature at the inlet of the coal pulverizer, unit: kJ/kg;

[0113] a is the mass ratio of fly ash to slag at the thermal boundary outlet of the boiler;

[0114] h.sub.lz is the enthalpy value of slag at the thermal boundary outlet of the boiler, unit: kJ/kg;

[0115] h.sub.lz0 is the enthalpy value of slag under the raw coal temperature at the inlet of the coal pulverizer, unit: kJ/kg;

[0116] C.sub.fh is the content of combustible substances in fly ash at the thermal boundary outlet of the boiler, unit: %; and

[0117] V.sub.py is the amount of flue gas at the thermal boundary outlet of the boiler, unit: km.sup.3/h.

[0118] On the basis of any one of the above-mentioned embodiments, the step of acquiring the energy Q.sub.pw output from discharged sewage of the boiler comprises:

[0119] acquiring an amount of discharged sewage of the boiler, an enthalpy value of discharged sewage of the boiler and the enthalpy value of feed water at the inlet of the economizer; and calculating according to the following formula: Q.sub.pw=D.sub.pw(h.sub.pwh.sub.fw), [0120] where D.sub.pw is the amount of discharged sewage of the boiler, unit: t/h; h.sub.pw is the enthalpy value of discharged sewage of the boiler, unit: kJ/kg; and h.sub.fw is the enthalpy value of feed water at the inlet of the economizer, unit: kJ/kg.

[0121] On the basis of any one of the above-mentioned embodiments, the step of acquiring the heat Q.sub.sm output from pebble coal discharged from the coal pulverizer comprises:

[0122] acquiring an amount of pebble coal discharged from the coal pulverizer, a calorific value of pebble coal, a sensible enthalpy value of discharged pebble coal and a sensible enthalpy value of pebble coal under the condition of raw coal temperature at the inlet of the coal pulverizer; and

[0123] calculating the heat Q.sub.sm output from pebble coal discharged from the coal pulverizer according to the following formula:

Q.sub.sm=M.sub.sm(Q.sub.smfr+h.sub.smh.sub.sm0)

[0124] where M.sub.sm is the amount of pebble coal discharged from the coal pulverizer, unit: t/h;

[0125] Q.sub.smfr is the calorific value of pebble coal, unit: kJ/kg;

[0126] h.sub.sm is the sensible enthalpy value of discharged pebble coal, unit: kJ/kg; and

[0127] h.sub.sm0 is the sensible enthalpy value of pebble coal under the condition of raw coal temperature at the inlet of the coal pulverizer, unit: kJ/kg.

[0128] On the basis of any one of the above-mentioned embodiments, the step of acquiring the heat loss Q.sub.sr of the boiler comprises:

[0129] acquiring a rated flow of steam at the outlet of the last-stage superheater of the boiler and the flow of steam at the outlet of the last-stage superheater of the boiler; and calculating the heat loss Q.sub.sr of the boiler according to the following formula:

[00015]$Q_{\mathrm{sr}}=\frac{1}{17.18.Math.{D_{\mathrm{gqc}}\left(D_{\mathrm{gqc}}^e\right)}^{-0.62}-1}.Math.\left(Q_{\mathrm{gq}}+Q_{\mathrm{zq}}+Q_{\mathrm{py}}+Q_{\mathrm{fh}}+Q_{\mathrm{iz}}+Q_{\mathrm{pw}}+Q_{\mathrm{sm}}+Q_{\mathrm{xl}}\right)$

[0130] where D.sub.gqc.sup.e is the rated flow of steam at the outlet of the last-stage superheater of the boiler, unit: t/h; and D.sub.gqc is the flow of steam at the outlet of the last-stage superheater of the boiler, unit: t/h.

[0131] Under normal operation conditions, the leakage amount Q.sub.xl and the pebble coal amount M.sub.sm of the boiler are very small, and can often be neglected. In addition, the item Q.sub.pw is generally only used for drum boilers, its quantity is generally a certain proportion of evaporation, the proportion is generally very small and can be ignored, and for once-through boilers, there is no item Q.sub.pw.

[0132] On the basis of any one of the above-mentioned embodiments, with respect to data acquisition, all of the above-mentioned data except the directionally acquired data related to t.sub.py, V.sub.py, (CO.sub.2, H.sub.2O, O.sub.2, CO, and SO.sub.2 volume concentrations), (ash) and C.sub.fh can be acquired in real time by direct or indirect calculation through the unit DCS database, the related material parameter database and the directionally acquired data mentioned above. The exhaust gas temperature is measured in real time by a plurality of arranged thermocouples. The amount of flue gas can be measured in real time by an arranged flue gas measuring device. The flue gas composition can be measured in real time by an arranged multi-function flue gas analyzer. The concentration of fly ash can be measured in real time by an arranged fly ash concentration meter. The content of fly ash combustible can be measured in real time by an arranged fly ash combustible measuring device.

[0133] Optionally, the above-mentioned acquisition method is not unique, and the corresponding values or measurements can be acquired by adopting other monitoring and acquisition methods.

[0134] The various embodiments in the description are described in a progressive manner. Each embodiment highlights the differences from other embodiments, and for the same and similar parts of the various embodiments, a mutual reference can be made.

[0135] The method for acquiring the thermal efficiency of the boiler provided by the present invention is introduced above in detail. Specific examples are used to illustrate the principle and implementation of the present invention. The description of the above-mentioned embodiments is only intended to help understand the method and core idea of the present invention. It should be pointed out that, for one skilled in the art, without departing from the principle of the present invention, a number of improvements and modifications can be made to the present invention, which fall within the protective scope of the claims of the present invention.