TWI573965B - Modification method of oxygen concentration for combustion system - Google Patents

Description

Method for correcting oxygen concentration of combustion system

The present disclosure relates to a method of modifying the oxygen concentration of a combustion system, and more particularly to an oxygen concentration correction method for a combustion system that can correct the original oxygen concentration.

Boilers can burn coal to generate heat to convert water into steam, which can be powered by steam. In order to obtain a certain combustion efficiency and reduce air pollution, it is necessary to manually set the oxygen rate required by the boiler in the combustion process. However, each batch of coal has a large variation in coal quality, such as its composition and water content, which makes it difficult for each batch of coal to be artificially controlled.

The disclosure relates to a method for correcting the oxygen concentration of a combustion system, which can automatically correct the oxygen concentration, taking into account low air pollution and high combustion efficiency.

In accordance with an embodiment of the present disclosure, a method of modifying an oxygen concentration of a combustion system is presented. The oxygen concentration correction method of the combustion system includes the following steps. The combustion system determines an original oxygen concentration according to a load versus original oxygen concentration curve, wherein the load versus the original oxygen concentration curve indicates that the load is required under different loads. Raw oxygen concentration; burning at the original oxygen concentration; determining whether the concentration of nitrogen oxides discharged is higher than a first critical value; if the nitrogen oxide concentration is higher than the first critical value, determining a clamping oxygen concentration; Oxygen concentration for combustion; determining a predicted concentration of nitrogen oxides; determining whether the predicted concentration of nitrogen oxides is lower than the first critical value in a first time interval; if the predicted concentration of nitrogen oxides is low in the first time interval At the first critical value, the combustion is performed at the original oxygen concentration; and if the predicted concentration of nitrogen oxides in the first time interval is not lower than the first critical value, the original oxygen concentration of the load versus the original oxygen concentration is lowered.

In order to better understand the above and other aspects of the present disclosure, the preferred embodiments are described below in detail with reference to the accompanying drawings.

100‧‧‧Combustion system

105‧‧‧fuel

110‧‧‧Boiler

120‧‧‧Control Module

121‧‧‧ Controller

122‧‧‧Timer

130‧‧‧Air blower

D‧‧‧ Revised ratio

D _{out, COx} , (D _{out, COx} ) ₇ , (D _{out, COx} ) ₉ ‧‧‧Carbon oxide concentration

D _{out, NOx} ‧ ‧ NOx concentration

D _{out, O2} ‧‧‧Oxygen concentration

D _O2 , (D _O2 ) ₂ , (D _O2 ) _2' , (D _O2 ) ₃ , (D _O2 ) _3' , (D _O2 ) ₇ , (D _O2 ) _7' ‧‧‧ Original Oxygen Concentration

D _{r, O2} ‧ ‧ clamp oxygen concentration

D _{in, O2} ‧‧‧Input oxygen concentration

D _{p, NOx} , (D _{p, NOx} ) ₂ , (D _{p, NOx} ) ₃ , (D _{p, NOx} ) ₅ ‧ ‧ NOx predicted concentration

ΔD1, ΔD2‧‧‧ total correction

L1‧‧‧ first critical value

L2‧‧‧ second threshold

L3‧‧‧ third threshold

ΔL1, ΔL2‧‧‧ difference

M2‧‧‧ second time-varying model

M1‧‧‧ first time-varying model

P‧‧‧load

S1, S1'‧‧‧ load versus original oxygen concentration curve

S2‧‧‧ Time vs. clamped oxygen concentration curve

S3‧‧‧ time vs. oxygen concentration curve

S4‧‧‧ Time vs. predicted concentration of nitrogen oxides

Steps S105, S110, S115, S120, S127, S125, S130, S135, S140, S145, S150, S155, S160, S162, S165, S180‧‧

T1, t2, t3, t4, t5, t6, t7, t8, t9‧‧

T‧‧‧ time

T1‧‧‧ first time interval

T2‧‧‧ first time interval

T3‧‧‧ third time interval

T4‧‧‧ fourth time interval

1A and 1B are flow charts showing a method for correcting the oxygen concentration of a combustion system according to an embodiment of the present disclosure.

2 is a schematic view of a combustion system in accordance with an embodiment of the present disclosure.

FIG. 3 is a graph showing load versus oxygen concentration in accordance with an embodiment of the present disclosure.

FIG. 4 is a schematic view showing the determination of the oxygen concentration of the clamp according to an embodiment of the present disclosure.

FIG. 5 is a schematic diagram showing the predicted concentration of nitrogen oxides according to an embodiment of the present disclosure.

FIG. 6A is a schematic diagram showing a method of adjusting the original oxygen concentration according to an embodiment of the present disclosure.

Figure 6B is a graph showing the change in nitrogen oxide concentration after down-regulating the original oxygen concentration.

Figure 7 is a graph showing the relationship between the corrected load and the original oxygen concentration.

Figure 8 is a graph showing the relationship between time and carbon oxide concentration in accordance with an embodiment of the present disclosure.

Figure 9 is a graph showing the relationship between the corrected load and the original oxygen concentration.

1A and 1B are flow charts showing a method for correcting the oxygen concentration of a combustion system according to an embodiment of the present disclosure.

In step S105 (shown in FIG. 1A), please refer to FIGS. 2 and 3 simultaneously. FIG. 2 is a schematic diagram of a combustion system according to an embodiment of the present disclosure. The combustion system 100 includes a boiler 110, a control module 120, and a blower 130. The blower 130 sends oxygen-containing air into the boiler 110, and the fuel 105 fed into the boiler 110 participates in combustion to generate heat to heat the water, converts the water into steam, and drives the turbine to generate electricity. The fuel 105 is, for example, coal fired. The control module 120 is, for example, a distributed control system (DCS), and includes at least one controller 121 and a timer 122. One of the controllers 121 controls the blower 130 to send air into the boiler 110.

FIG. 3 is a graph showing load versus oxygen concentration in accordance with an embodiment of the present disclosure. In this step, the control module 120 determines the original oxygen concentration D _O2 (the unit is, for example, %) according to the load and the original oxygen concentration relationship S1, wherein the load versus the original oxygen concentration curve S1 represents the original oxygen required for the different load P. Concentration D _O2 . In actual operation, the same or different load P may be required at different time points, and the control module 120 may determine the original oxygen concentration D _O2 from the load and oxygen concentration relationship curve S1 according to the load required at different time points. The load P herein refers to, for example, the amount of coal burned per unit time (e.g., a ton/hour), although the disclosed embodiment does not limit the unit of the load P. The original oxygen concentration herein refers to the initial oxygen concentration used at the beginning of each batch of coal combustion in the boiler, and the load versus raw oxygen concentration curve S1 can be automatically corrected in the present disclosure method, as will be described in detail below.

In step S110 (shown in FIG. 1A), the control module 120 uses the original oxygen concentration D _O2 as the input oxygen concentration D _{in, O2} input to the boiler 110 (the input oxygen concentration D _{in, O2 is} shown in the second Figure) and to determine the amount of air required (its oxygen concentration is roughly equal to the original oxygen concentration D _O2 ). After determining the required amount of air, the control module 120 controls the blower 130 to act to deliver the required amount of air to the boiler 110 for combustion. The boiler 110 emits nitrogen oxides, carbon oxides (such as carbon monoxide) and/or oxygen during combustion, which have a nitrogen oxide concentration D _{out, NOx} (unit is, for example, ppm), and carbon oxide concentration D _{out, respectively. COx} (unit is, for example, ppm) and oxygen concentration D _{out, O2} (unit is, for example, ppm). The nitrogen oxide concentration D _{out, NOx} , carbon oxide concentration D _{out, COx} and oxygen concentration D _{out, O2} can be measured in the stack of the boiler 110 or outside the boiler 110.

During the combustion process, if the original oxygen concentration D _{O2 is} too high, the exhausted nitrogen oxide concentration D _{out, NOx} may be too high to cause air pollution; conversely, if the original oxygen concentration D _{O2 is} insufficient, it is easy to cause combustion efficiency. Good and excessively high carbon oxide concentration D _{out, COx} . However, according to the oxygen concentration correction method of the disclosed embodiment, the relationship between the load and the original oxygen concentration can be automatically corrected according to the exhausted nitrogen oxide concentration D _{out, the NOx} and the carbon oxide concentration D _{out, COx} during the combustion process. To balance high combustion efficiency with low air pollution. The following is further explained.

In step S115 (as shown in FIG. 1A), the control module 120 determines whether the nitrogen oxide concentration D _out discharged from the boiler 110 is greater than the first critical value L1 (the first critical value L1 is shown in FIG. 4). If yes, go to step S120; if no, go to step S165.

In step S120 (as shown in FIG. 1A) _{, NOx is} greater than the first critical value L1 due to the nitrogen oxide concentration _Dout (the first critical value L1 is shown in FIG. 4), indicating combustion under the current oxygen setting. It may or may be expected to cause air pollution. Therefore, the control module 120 determines a clamped oxygen concentration D _{r, O 2} is a set point (the clamped oxygen concentration D _{r , O 2 is} shown in FIG. 4 ), thereby controlling the nitrogen oxide concentration D _{out, NOx} at the first critical value. Under L1, avoid possible subsequent air pollution. The following is a further description of how to determine the clamped oxygen concentration D _r,O2 .

Please refer to FIG. 4, which is a schematic diagram of determining the concentration of oxygen in the clamp according to an embodiment of the present disclosure. The control module 120 takes the first critical value L1 as an upper limit and inputs the critical value to the first time-varying model M1 according to the timing, and obtains a timely corresponding output value, and the output value is the clamped oxygen concentration D _{r, O2} . After a period of observation, several clamped oxygen concentrations D _{r, O2} may constitute a curve S2 of time versus clamped oxygen concentration. The time vs. clamped oxygen concentration curve S2 represents the clamped oxygen concentration _{Dr, O2} at different time points. Since the continuously updated time-varying model M1 can conform to the instantaneous relationship between the nitrogen oxide concentration and the oxygen concentration, if the oxygen concentration D _{r, O 2 is} clamped as the input oxygen concentration D _{in, O 2} input to the boiler 110 _{, the} boiler 110 is controlled. The combustion can be expected to produce a nitrogen oxide concentration D _{out, which is} also limited below the first critical value L1, thus preventing excessive air pollution from occurring.

The first time-varying model M1 can be a time-series model of one m-order, and its structure is as shown in the following formula (1), and the model parameters can be changed with time and thus become time-varying. In the formula (1), x(n) is an input variable indicating the nitrogen oxide concentration D _out at the time point n _{, and} the upper limit L1 of _NOx , y(n) represents the clamped oxygen concentration D _{r, O2} at the time point n, z ^-1 is a unit time delay operation unit, and the parameters c ₁ , _... , c _m , d ₀ , d ₁ , _... , d _m can be obtained from the past m unit time to the current nitrogen oxide concentration D _{out, The} measurement information of _NOx and oxygen concentration D _{out, O2} is determined by an algorithm, wherein the algorithm can adopt a recursive form algorithm for parameters c ₁ , _... , c _m , d ₀ , d ₁ , _... , d _m performs on-line estimation, and performs model update, wherein the iterative formal algorithm can adopt a method such as a least squares with forgetting factor method or a projection method.

In step S125 (as shown in FIG. 1A), the control module 120 controls the boiler 110 to perform combustion to clamp the oxygen concentration D _{r, O 2} as the input oxygen concentration D _{in, O 2} to set the nitrogen oxide concentration D _{out, NOx.} It is confined below the first critical value L1, thereby reducing excessive air pollution.

In step S127 (as shown in FIG. 1A), the control module 120 determines whether the accumulated total correction amount ΔD1 (the following formula (3), detailed later) of the load and the original oxygen concentration relationship curve S1 has reached an allowable level. The correction amount; if yes, the process proceeds to step S115, and the corrected load and the original oxygen concentration relationship curve S1 are not considered; if not, the process proceeds to step S130, and the corrected load and the original oxygen concentration relationship curve S1 are considered. The above allowable correction amount is, for example, a value between about 50% and about 90% of the original curve. Further, if the original oxygen concentration relationship curve S1 has not been corrected or the flow is executed for the first time, step S130 may be directly proceeded from step S127.

In step S130 (as shown in FIG. 1A), the timer 122 of the control module 120 begins to count from zero after or at the same time controlling the boiler combustion with the clamped oxygen concentration _{Dr, O2} .

In step S135 (as shown in FIG. 1A), the control module 120 determines the predicted concentration of nitrogen oxides D _{p, NOx} to predict the initial oxygen concentration D _O2 as the input oxygen concentration D _{in, O 2} . Simulate the predicted predicted concentration of nitrogen oxides D _p, whether _NOx will fall below the first critical value L1. The following is a further description of how to determine the predicted concentration of nitrogen oxides D _{p, NOx} .

Please refer to FIG. 5, which is a schematic diagram of estimating the concentration of nitrogen oxides according to an embodiment of the present disclosure. In this step, the original oxygen concentration set point at a certain time can be obtained according to the load change with time according to the load-to-oxygen relationship curve, and the set point is input to the second time-varying model M2, and the instant nitrogen oxidation can be obtained. The predicted concentration D _{p, NOx} . The time vs. oxygen concentration curve S3 represents the original oxygen concentration D _{O2 at} different time points and the time vs. NOx predicted concentration curve S4 represents the predicted concentration of nitrogen oxides D _{p, NOx at} different time points.

The second time varying model M2 can be a time series model of one order m, and its structure is as shown in the following formula (2). In equation (2), y(n) is an input variable representing the original oxygen concentration D _O2 at time n (as shown in Figure 5), and x(n) is the output variable, indicating nitrogen oxidation at time n The predicted concentration D _{p, NOx} (as shown in Figure 5), and the parameters a ₁ , _... , a _m , b ₀ , b ₁ , _... , b _m can be used from the past m time points to the present The oxygen concentration D _{out, O2} and the nitrogen oxide concentration D _{out, NO} are determined by an algorithm, wherein the algorithm can adopt an iterative form algorithm for the parameters a ₁ , _... , a _m , b ₀ , b ₁ , _... , b _m performs on-line estimation and model update, wherein the iterative formal algorithm can adopt a method such as a forgetting factor least square method or a projection method.

Whether or not the load and the original oxygen concentration relationship curve S1 need to be corrected can be judged by the predicted concentration D _{p, NOx} of the nitrogen oxide obtained by the second time-varying model M2.

Further, in step S140 (as shown in FIG. 1B), please refer to FIGS. 6A and 6B. FIG. 6A is a schematic diagram showing a method of adjusting the original oxygen concentration according to an embodiment of the present disclosure, and FIG. 6B A graph showing changes in nitrogen oxide concentration after down-regulating the original oxygen concentration. In this step, the control module 120 determines whether the predicted concentration of nitrogen oxides _{Dp, NOx} (as shown in FIG. 6B) in the first time interval T1 (as shown in FIG. 6A) is less than the first critical value L1 ( If it is shown in FIG. 6B); if yes, go to step S145; if no, go to step S155. The first time interval T1 is, for example, an arbitrary time value between 5 minutes and 15 minutes, but may be other time values.

In step S145 (as shown in FIG. 1B), if the NOx predicted concentration _{Dp in the} first time interval T1 _{, NOx is} less than the first critical value L1, for example, the predicted concentration of nitrogen oxides at several time points D _{p, NOx} are lower than the first critical value L1, indicating that if the control module 120 continues to use the load and the original oxygen concentration relationship S1 to determine the input oxygen concentration Di _{n, O2} , the expected concentration of nitrogen oxides D _{p, NOx} Will fall. Accordingly, the control module 120 can determine the original oxygen concentration D _O2 with the original load and the original oxygen concentration relationship S1 without correcting the load and the original oxygen concentration relationship S1, and determine the original oxygen concentration D _O2 as the input oxygen concentration. D _{in , O 2} to control the combustion of the boiler 110.

In step S150 (as shown in FIG. 1B), the control module 120 determines to control the combustion of the boiler 110 with the original oxygen concentration D _O2 as the input oxygen concentration D _{in, O 2} , and the timer 122 is reset to zero in order to In S130, the timer 122 can start counting by resetting to zero.

In step S155 (as shown in FIG. 1B), if the NOx predicted concentration D _{p in the} first time interval T1 _{, NOx is} not less than the first critical value L1, for example, the NOx prediction at several time points The concentration D _{p, the NOx} changes up and down in the vicinity of the first critical value L1 or the predicted concentration of nitrogen oxides D _{p and NOx} at several time points are higher than the first critical value L1, indicating that the control module 120 continues to use the load and the original The oxygen concentration relationship curve S1 determines the input oxygen concentration D _{in, O2} , and then the expected concentration of nitrogen oxides D _{p , NOx} will be greater than the first critical value L1, resulting in excessive air pollution. Accordingly, the control module 120 lowers the original oxygen concentration D _O2 , and further describes the down regulation method below.

As can be seen from Fig. 6B, after the first time interval T1 has elapsed, as at time t1, the predicted concentration of nitrogen oxides _{Dp, NOx is} still higher than the first critical value L1. Accordingly, the control module 120 reduces the original oxygen concentration D _{O2 by} a correction ratio d every second time interval T2 until the nitrogen oxide predicted concentration D _{p , NOx is} lower than the first critical value L1 and shows a downward trend. The correction ratio d is, for example, an arbitrary value between 0.05% and 5%, and the second time interval T2 is, for example, an arbitrary time value or other time value between 5 minutes and 15 minutes.

Further, as shown in FIG. 6A, after the time interval t1 passes the second time interval T2, that is, at the time point t2, the control module 120 reduces the original oxygen concentration D _{O2 by} 0.1%, so that the original time point t2 is obtained. The oxygen concentration (D _O2 ) ₂ drops to (D _O2 ) _2' ; then, the adjusted original oxygen concentration (D _O2 ) _{2' is} input to the second time-varying model M2 to obtain the corresponding predicted concentration of nitrogen oxides. (D _{p, NOx} ) ₂ (as shown in Fig. 6B); Next, in step S160, the control module 120 determines whether the predicted concentration of nitrogen oxides (D _{p , NOx} ) ₂ is decreasing.

There are several ways to determine whether there is a downward trend. The following two methods are listed below. In the first method, if the predicted decrease in the concentration of nitrogen oxides (D _{p, NOx} ) ₂ is less than a certain ratio, it is judged that the predicted concentration of nitrogen oxides (D _{p, NOx} ) _{2 does} not show a downward trend. For example, as shown in FIG. 6B, the ratio of the difference ΔL1 between the predicted concentration of nitrogen oxides (D _{p, NOx} ) ₂ and the first critical value L1 at time t2 to the first critical value L1 (ΔL1/L1) If it is less than a first ratio, it is judged that the predicted concentration of nitrogen oxides (D _{p, NOx} ) _{2 does} not show a downward trend; conversely, if the ratio ΔL1/L1 is equal to or greater than the first ratio, the predicted concentration of nitrogen oxides is judged ( When D _{p, NOx} ) ₂ shows a downward trend, the process proceeds to step S162. The first ratio here is, for example, an arbitrary value between 5% and 10%. In the second method, if the NOx predicted concentration D _{p and the NOx} decrease trend for several consecutive time points (for example, a value between three and ten time points), the nitrogen oxidation is judged. The predicted concentration D _{p, NOx} showed a downward trend.

In step S160 (shown in FIG. 1B), it is judged whether or not the _NOx predicted concentration _{Dp, NOx} is in a downward trend; if so, the process returns to step S162; if not, the process returns to step S155.

In step S155 (as shown in Fig. 1B) _{, the NOx does} not show a downward trend due to the predicted concentration of nitrogen oxides _Dp, and the original oxygen concentration D _O2 is continuously lowered. For example, since the predicted concentration of nitrogen oxides (D _{p, NOx} ) ₂ (as shown in Fig. 6B) at the time point t2 does not show a downward trend, as shown in Fig. 6A, at the next time point t3 The control module 120 continues to reduce the original oxygen concentration by 0.1%, so that the original oxygen concentration (D _O2 ) _{3 at} the time point t3 is decreased to (D _O2 ) _{3 '} ; then, the original oxygen concentration after the reduction (D _{O2 ) 3' is} input to the second time-varying model M2 to obtain a corresponding predicted concentration of nitrogen oxides (D _{p, NOx} ) ₃ (shown in FIG. 6B); then, in step S160, the control module 120 determines the nitrogen Whether the oxide concentration D _{p and NOx} are in a downward trend; if not, returning to step S155, the original oxygen concentration D _{O2 is} continuously lowered; if yes, the process proceeds to step S162.

As shown in FIGS. 6A and 6B, in the present embodiment, at the time points t1, t2, t3, and t4, the predicted concentrations of nitrogen oxides _{Dp and NOx do} not show a downward trend until the time point t5. The predicted initial concentration of oxygen (D _O2 ) _5' predicted by the reduced oxygen concentration (D _{p, NOx} ) ₅ has shown a downward trend (for example, the magnitude of the decrease ΔL2 exceeds the first ratio). Accordingly, the process proceeds to step S162, where the correction of the load versus the original oxygen concentration curve S1 is started.

In step S162 (as shown in FIG. 1B), as shown in FIG. 7, a graph showing the relationship between the corrected load and the original oxygen concentration is shown. Calculate the total correction amount ΔD1 according to the following formula (3); then, the control module 120 corrects the total correction amount ΔD1 by the entire load and the original oxygen concentration relationship curve S1, and obtains the relationship between the corrected load and the original oxygen concentration. Curve S1'. The corrected curve S1' allows the combustion of the boiler 110 to achieve both low air pollution and high combustion efficiency. Further, the oxygen concentration correction method of the combustion system of the embodiment of the present disclosure can correct the original oxygen concentration D _O2 according to the variation of each batch of coal (for example, the water content and composition of each batch of coal) to meet the empty Pollution standards and high combustion efficiency.

In the formula (3), the correction ratio d _i represents the correction ratio of the i-th time (each time corresponding to a different time point), which may be a proportional value between 0.05% and 5%, and D _O2,i represents the i-th time. The correction ratio d _i corresponds to the original oxygen concentration D _O2 , and n represents the number of corrections, which may depend on the actual situation. In the present embodiment, as shown in Figs. 6A and 6B, the number of corrections n is four times (four times from time point t2 to t5). Further, the i-th original oxygen concentration D _O2,i can be obtained from the load versus the original oxygen concentration curve S1. For example, at time point t2 of FIG. 6A, since the control module 120 knows a specific load corresponding to the time point t2, it can be known from the time and the original oxygen concentration relationship curve S1 (as shown in FIG. 3). The original oxygen concentration D _{O2 for} a particular load.

After the correction of the load and the original oxygen concentration relationship curve S1 is completed, the process returns to step S115 to continue monitoring the combustion state of the boiler. Subsequent combustion control and correction basis can be modified to use the corrected load versus raw oxygen concentration curve S1'.

In step S115, if the control module 120 determines the nitrogen oxide concentration D _out discharged from the boiler 110 _{, and the NOx is} less than the first critical value L1 (as shown in FIG. 4), the process proceeds to step S165 to monitor the carbon oxide concentration. D _out, the concentration of _COx changes.

In step S165 (shown in FIG. 1A), as shown in FIG. 8, a graph showing the relationship between time and carbon oxide concentration according to an embodiment of the present disclosure is shown. In this step, the control module 120 determines whether the carbon oxide concentration D _out discharged from the boiler 110 _{, COx} is greater than the second critical value L2; if yes, proceeds to step S180; if not, returns to step S115 to continue monitoring the combustion state of the boiler . For example, the control module 120 can determine whether the carbon oxide concentration D _out, the time T at _{which the COx is} greater than the second threshold L2 (as shown in FIG. 8 ) continues to exceed the third time interval T3 , wherein the third time interval T3 For example, a time value between 10 minutes and 30 minutes; if yes, the control module 120 determines the carbon oxide concentration D _out discharged from the boiler 110 _{, and the COx is} greater than the second critical value L2, and proceeds to step S180. The load is compared with the original oxygen concentration curve S1 to reduce the carbon oxide concentration.

In step S180 (as shown in FIG. 1A), please refer to FIGS. 8 and 9. FIG. 9 is a graph showing the relationship between the corrected load and the original oxygen concentration. As shown in FIG. 8, at time t6, when the carbon oxide concentration _{Dout, COx is} greater than the second critical value L2, the control module 120 compares the entire load to the original oxygen concentration curve S1 according to the following formula (4). Correct the correction amount ΔD2 upward as shown in Fig. 9.

Δ D 2= u × D _{O 2} .........................(4)

In the formula (4), the correction ratio u may be a proportional value between 0.05% and 10%, and D _O2 represents the corresponding original oxygen concentration. For example, at time point t6 of FIG. 8, since the control module 120 knows a specific load corresponding to the time point t6, it can be time-supplied with the original oxygen concentration curve S1 (as shown in FIG. 3) or newly corrected. The oxygen concentration relationship curve S1' is known to correspond to the original oxygen concentration D _{O2 of} a specific load, and then taken into the above formula (4) to obtain the correction amount ΔD2.

After step S180 (as shown in FIG. 1A), the process returns to step S115 to continue monitoring the change in the nitrogen oxide concentration _{Dout, NOx} . Subsequent combustion control and correction basis can be changed to use the corrected load versus raw oxygen concentration curve S1'.

As shown in FIG. 8, the control module 120 determines the carbon oxide concentration D _out at the time point t7 in step S165 (as shown in FIG. 1A), _{and the COx is} still greater than the second threshold L2, so the process proceeds to step S180. (As shown in Fig. 1A), continue to correct the entire load and the original oxygen concentration relationship curve S1' upward by a correction amount ΔD2 according to the above formula (4), and then return to step S115 (as shown in Fig. 1A). It is judged whether or not the nitrogen oxides have passed the first critical value, and if not, returning to step S165 (as shown in FIG. 1A), the carbon oxide concentration D _{out and} the concentration of _COx are continuously monitored. Next, the control module 120 determines the carbon oxide concentration D _out at the time point t8 in step S165 (as shown in FIG. 1A), _{and the COx is} still greater than the second threshold L2, and proceeds to step S180 again (as shown in FIG. 1A). Further, the entire load and the original oxygen concentration relationship curve S1' are further corrected by a correction amount ΔD2 according to the above formula (4), and then the process returns to step S115 (as shown in FIG. 1A). Until time t9, the carbon oxide concentration D _{out, COx is} lower than the second critical value L2, indicating the carbon oxide concentration D _{out, COx} has been effectively controlled, so return to step S115 (as shown in FIG. 1A), The overall combustion condition of the boiler 110 is continuously monitored.

As shown in Fig. 9, the corrected load versus the original oxygen concentration curve S1' allows the combustion of the boiler 110 to achieve both low air pollution and high combustion efficiency. Further, the oxygen concentration correction method of the combustion system of the embodiment of the present disclosure can correct the original oxygen concentration according to the variation of each batch of coal (such as the water content and composition of each batch of coal) to meet the air pollution standard and High combustion efficiency.

In the above, the disclosure has been disclosed in the above preferred embodiments, and is not intended to limit the disclosure. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the disclosure. Therefore, the scope of protection of this disclosure is subject to the definition of the scope of the appended claims.

Steps S105, S110, S115, S120, S125, S127, S130, S135, S165, S180‧‧

Claims (11)

A method for correcting oxygen concentration of a combustion system is applicable to a combustion system, comprising: determining an original oxygen concentration according to a load versus original oxygen concentration curve, wherein the load versus raw oxygen concentration curve indicates that the load is required under different loads Raw oxygen concentration; burning at the original oxygen concentration; determining whether the concentration of nitrogen oxides discharged is higher than a first critical value; if the nitrogen oxide concentration is higher than the first critical value, determining a clamped oxygen concentration; Compressing with the oxygen concentration; determining an estimated concentration of nitrogen oxides; determining whether the predicted concentration of nitrogen oxides is lower than the first critical value in a first time interval; if the first time interval is within the first time interval The predicted concentration of nitrogen oxides is lower than the first critical value, and the combustion is performed at the original oxygen concentration; and if the predicted concentration of the nitrogen oxides is not lower than the first critical value in the first time interval, the original is lowered The oxygen concentration; wherein the step of determining the clamping oxygen concentration further comprises: using the first critical value as an upper limit and inputting to a first time-varying model The decision to suppress the oxygen concentration. The oxygen concentration correction method of the combustion system of claim 1, wherein the oxygen concentration correction method further comprises: starting timing; wherein, in the first time interval, After the estimated concentration of the nitrogen oxide is lower than the first critical value, after the step of burning the original oxygen concentration, the oxygen concentration correction method further comprises: timing zeroing. The method for correcting the oxygen concentration of the combustion system according to claim 1, wherein the step of determining the predicted concentration of the nitrogen oxides further comprises: obtaining a relationship between the time and the oxygen concentration, wherein the time versus oxygen concentration is expressed by a curve. The original oxygen concentration at different time points; the time-oxygen concentration relationship curve is input to a second time-varying model, and the relationship between the time and the predicted concentration of nitrogen oxides is determined, wherein the time is related to the predicted concentration of nitrogen oxides. The relationship curve represents the predicted concentration of nitrogen oxides at different time points. The method for modifying an oxygen concentration of a combustion system according to claim 1, wherein the step of lowering the original oxygen concentration further comprises: if the predicted concentration of the nitrogen oxide is not lower than the first in the first time interval The critical value is used to adjust the relationship between the load and the original oxygen concentration every second time interval. The original oxygen concentration of the curve is a corrected ratio until the predicted concentration of nitrogen oxides is lower than the first critical value and exhibits a downward trend. The method for correcting the oxygen concentration of the combustion system according to claim 1, further comprising: if the concentration of the nitrogen oxide is not lower than the first critical value, determining whether the concentration of the one carbon oxide discharged is higher than a first a second critical value; and if the carbon oxide concentration is higher than the second critical value, the load is adjusted to a relationship with the original oxygen concentration. The method for modifying an oxygen concentration of a combustion system according to claim 5, wherein if the carbon oxide concentration is higher than the second critical value, the step of adjusting the load to the original oxygen concentration curve further comprises: determining the carbon Whether the time when the oxide concentration is higher than the second critical value lasts for a third time interval; and if the time when the carbon oxide concentration is higher than the second critical value has continued for the third time interval, the load is increased and the original Oxygen concentration curve. The method for correcting the oxygen concentration of the combustion system according to claim 6, wherein the step of up-regulating the relationship between the load and the original oxygen concentration further comprises: adjusting the load to the original oxygen concentration curve every other fourth time interval. Correcting the ratio until the carbon oxide concentration is lower than the second critical value and decreasing Potential. The method for modifying an oxygen concentration of a combustion system according to claim 5, wherein if the carbon oxide concentration is higher than the second critical value, the step of adjusting the load to the original oxygen concentration curve further comprises: adjusting the upper strip The load is related to the original oxygen concentration curve. The method for modifying an oxygen concentration of a combustion system according to claim 8, wherein the combustion system determines the original oxygen concentration according to a curve of the load and the original oxygen concentration, the combustion system is based on the adjusted load. The original oxygen concentration is determined by the relationship with the original oxygen concentration. The method for modifying the oxygen concentration of the combustion system according to claim 1, wherein the step of lowering the original oxygen concentration further comprises: adjusting the load to the original oxygen concentration curve of the lower adjustment bar. The method for modifying an oxygen concentration of a combustion system according to claim 10, wherein in the step of determining the original oxygen concentration according to the load and the original oxygen concentration curve, the combustion system is based on the adjusted load. The original oxygen concentration is determined by the relationship with the original oxygen concentration.