JP6798249B2 - Boiler efficiency calculation method for latent heat recovery boiler - Google Patents

Description

The present invention relates to a boiler efficiency calculation method for a latent heat recovery boiler.

With the social demand for energy saving and reduction of carbon dioxide emissions, the efficiency of boilers is increasing. It is becoming more and more important to correctly calculate the thermal efficiency of boilers and use them for energy management. As a method for measuring the thermal efficiency of a boiler, there are mainly an exhaust gas loss method described in Patent Document 1 and an input / output heat method described in Patent Document 2.

Here, the exhaust gas loss method is basically an exhaust gas loss calculated by multiplying the difference between the temperature of the exhaust gas discharged from the boiler and the supply air temperature of the air supplied to the boiler by the amount of exhaust gas and the specific heat. This is a method of determining the thermal efficiency of a boiler using the amount of heat. On the other hand, in the heat input / output method, basically, the heat output from the boiler calculated by multiplying the difference between the enthalpy of steam and the enthalpy of water supply by the amount of water supply is the product of the fuel consumption amount and the fuel calorific value. This is a method of obtaining the boiler efficiency by dividing by the heat input to the boiler calculated by.

Japanese Unexamined Patent Publication No. 2012-122640 Japanese Unexamined Patent Publication No. 2011-231968

However, when calculating the boiler efficiency of the latent heat recovery boiler, it has not been possible to easily and accurately measure the boiler efficiency by the conventional method.

Specifically, when the exhaust gas loss method is applied as it is as a method for measuring the boiler efficiency of the latent heat recovery boiler, the amount of latent heat recovered by the latent heat recovery unit is not reflected in the exhaust gas temperature, so the boiler efficiency is calculated to be low. To.
Further, for example, a method of adding the latent heat recovery amount obtained by actually measuring the amount of drain and the temperature to the exhaust gas loss method can be considered. However, it is not realistic to actually measure the amount and temperature of the drain each time the boiler efficiency is measured, because it is a dangerous and laborious task and the amount of drain changes depending on the hydrogen content ratio in the fuel. There is also a method of calculating the above-mentioned latent heat recovery amount using an estimated approximation formula, but there is a deviation from the measured value.

On the other hand, it is possible to measure the boiler efficiency of the entire latent heat recovery boiler using the heat input / output method, but in the heat input / output method, it is necessary to measure the amount of water supplied in order to calculate the amount of heat input / output. However, the error of the flow meter that measures the amount of water supply directly affects the error of the boiler efficiency, which poses a problem in performing accurate measurement.

Therefore, an object of the present invention is to provide a boiler efficiency calculation method for easily and accurately calculating the boiler efficiency of a latent heat recovery boiler.

The present invention is a method for calculating the boiler efficiency of the entire latent heat recovery boiler including the can body and the latent heat recovery unit for recovering the heat of the exhaust gas discharged from the can body, and is supplied to the can body. Latent heat recovery obtained from the difference between the amount of heat lost in the exhaust gas of the can body calculated from the amount of heat of the combustion air and the amount of heat of the exhaust gas discharged from the can body and the amount of heat of the fluid to be heated before and after passing through the latent heat recovery unit. The present invention relates to a boiler efficiency calculation method having a step of subtracting the recovered heat amount of the latent heat recovery unit from the exhaust heat loss heat amount while using the recovered heat amount of the unit.

Further, it is preferable that the latent heat recovery unit is provided with an economizer and / or an air heater.

Further, the boiler efficiency of the entire latent heat recovery boiler is η, the amount of heat loss from exhaust gas in the can body is Q, the amount of heat recovered by the latent heat recovery unit is q, the fuel low calorific value of the fuel used is Hl, heat dissipation and unburned. When the gas loss is α, it is preferable that the boiler efficiency of the entire latent heat recovery boiler is calculated using the formula η = (1- (Q−q) / Hl) × 100−α.

Further, it is preferable that the latent heat recovery boiler further includes a blow heat exchanger and further has a step of calculating the blow loss included in the heat dissipation and the unburned gas loss.

According to the present invention, it is possible to provide a boiler efficiency calculation method for easily and accurately calculating the boiler efficiency of a latent heat recovery boiler.

It is a figure which shows the structural example of the latent heat recovery boiler which concerns on embodiment of this invention, and the measured value by a combustion experiment. It is a figure which shows the structure of the latent heat recovery boiler which concerns on the modification of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration example of a latent heat recovery boiler and an actually measured value obtained by a boiler combustion experiment used when calculating the boiler efficiency using the boiler efficiency calculation method according to the present invention and another calculation method. It is a figure which shows.

Specifically, the latent heat recovery boiler 10 includes a can body 11 and an economizer 12. The can body 11 is a heat source device that converts water into steam by transferring the heat obtained by burning fuel to water, particularly a small once-through boiler. The economizer 12 is a device that raises the boiler efficiency of the latent heat recovery boiler 10 by heating the water supply to the can body 11 with the heat possessed by the exhaust gas discharged from the can body 11.

First, a method of calculating the boiler efficiency by the exhaust gas loss method based on JIS B 8222 will be described.

In order to calculate the boiler efficiency by the exhaust gas loss method, the air ratio m is first obtained. Here, m is when the maximum carbon dioxide concentration [volume%] in the exhaust gas is CO _2max and the carbon dioxide concentration [volume%] in the exhaust gas is CO ₂ .
m = CO _2max / CO ₂ (1)
Can be calculated as.

Using this air ratio m, the actual amount of wet exhaust gas G is obtained. If the theoretical dry exhaust gas quantity G _o, the water vapor content due to moisture vapor and fuel caused by combustion was G _w, the theoretical wet exhaust gas amount can be calculated as G o ₊ G _w. Further, when the theoretical air amount is A _o , the surplus air amount can be calculated as (m-1) × A _o . The actual wet exhaust gas amount G is the sum of these theoretical wet exhaust gas amount and the theoretical air amount, and specifically,
G = _Go + G _w + (m-1) x A _o (2)
Will be.

Next, the exhaust gas loss heat amount Q is calculated using the actual wet exhaust gas amount G described above. Let S be the specific heat of the exhaust gas, and ΔT be the difference Tg-T0 obtained by subtracting the supply air temperature T0 from the exhaust gas temperature Tg.
Q = S × G × ΔT = S × G × (Tg-T0) (3)
Will be.

Using this exhaust gas heat loss Q, fuel low calorific value Hl, heat dissipation and unburned gas loss α [%], the boiler efficiency η [%] is
η = (1-Q / Hl) × 100-α (4)
Can be calculated.
Hl and α are values determined by the type of fuel.

However, for example, when the method for calculating the boiler efficiency using the exhaust gas loss method described above is applied to the latent heat recovery boiler 10 provided with the can body 11 and the economizer 12 as shown in FIG. 1, the exhaust gas temperature is applied. Has a serious drawback that the boiler efficiency is calculated to be low because the amount of latent heat recovered by the latent heat recovery unit is not reflected.

Here, if the exhaust gas heat loss amount of the entire boiler is Q _a , the exhaust gas heat loss heat amount of the can body part is Q _s , and the exhaust gas heat recovery amount of the latent heat recovery part is q.
Q _a = Q _s −q (5)
Will be.

The Q of the above formula (4), substituting the _{Q a} of formula (5),
η = (1-Q _a / Hl) × 100-α = {1- (Q _s −q) / Hl} × 100-α (6)
Will be.

As a result, the exhaust gas heat recovery amount (q), which is the latent heat amount recovered by the latent heat recovery unit, is reflected in the boiler efficiency, and the above-mentioned drawbacks are eliminated.
Here, paying attention to the fact that the exhaust heat recovery amount (q) of the latent heat recovery unit can be calculated from the heat amount received by the heated fluid flowing through the latent heat recovery unit, the flow rate of the heated fluid and the temperature before and after the latent heat recovery unit are measured. Calculate by doing. That is, for Q _s in the equation (6), the amount of heat lost in the exhaust gas is calculated from the temperature difference of the exhaust gas, and for q, the amount of heat recovered is calculated from the temperature difference of the fluid to be heated. As a result, for the right side of the equation (6), it is possible to use the actually measured values for all the numerical values other than the constants.

The applicant of the present invention obtained each measured value shown in FIG. 1 by conducting a combustion experiment for 30 minutes using fuel 13A on a boiler SQ-2000AS manufactured by Miura Co., Ltd., which is an experimental machine. ..
Specifically, the temperature T0 = 35 [° C.] of the air supplied to the can body 11 was obtained.
Further, since the fuel used in the can body 11 is 13A, the lower calorific value of the fuel is Hl = 9406.9 [kcal / m ³ N] = 39377.3 [kJ / m ³ N] and the fuel consumption C. = 112.6 [m ³ N / h].
Further, the pressure P of the steam generated in the can body 11 is 0.5 MPa, the total heat h''= 2756.24 [kJ / kg], the sensible heat h'= 670.87 [kJ / kg], and so on. The degree of dryness X = 0.99.
The temperature of the exhaust gas flowing into the economizer 12 from the can body 11 was the temperature Tgi = 216 [° C.] at the inlet of the economizer 12 and the temperature Tgo = 51 [° C.] at the outlet of the economizer 12. The exhaust gas oxygen concentration O ₂ = 3.7 [%].
Further, the water supply to the latent heat recovery boiler 10, that is, the water supply to the economizer 12, the water supply temperature at the inlet of the economizer 12 is Twi = 14.3 [° C.], and the water supply amount W = 1.722 [m ³ / h] =. It was 1.722 × 998.2 [kg / h] = 1719 [kg / h] (the density of water at a water temperature of 14.3 ° C. was 998.2 [kg / m ³ ]). The water supply temperature at the economizer 12 outlet was Two = 89.2 [° C.], and the water supply amount at the economizer outlet was W = 1719 [kg / h].
Further, the temperature of the drain water discharged from the economizer 12 was T _p = 46.1 [° C.], and the drain amount D = 61.1 [kg / h].
These values were detected by temperature sensors, flow rate sensors, and the like installed at various locations in the latent heat recovery boiler 10.

[Calculation example by the calculation method according to the present invention and comparison with other calculation methods]
As described above, the applicant of the present invention was able to obtain each measured value shown in FIG. 1 by conducting a combustion experiment using a boiler SQ-2000AS manufactured by Miura Co., Ltd., which is an experimental machine. In the following, these measured values will be used, (1) a method of adding the measured value of drain to the exhaust gas loss method, (2) a method of calculating the boiler efficiency of the entire boiler by the input / output heat method, and (3) the present invention. Boiler efficiencies are calculated and compared by the three methods.

(1) Method of adding the measured value of drain to the exhaust gas loss method The boiler efficiency η _e calculated by the method of adding the measured value of drain to the exhaust gas loss method is calculated by the following formula (7).
η _e = (1-Q / Hl) x 100-L _o + (α _s / Hl x 100) (7)
Here, Q is the exhaust gas heat loss, Hl is the lower heating value, L _o other losses, the alpha _s is the latent heat recovery amount.

In the case of the conventional unit, the heat loss Q of the exhaust gas in the right side of the equation (7) is Q = 0.33 × G × ΔT (8) using the specific heat of the exhaust gas 0.33 [kcal / (m ³ N · ° C)].
Is calculated.
Further, the latent heat recovery amount α _s is calculated by using the latent heat recovery amount A and the fuel consumption amount C per hour.
α _s = A / C (9)
Is calculated.
Therefore, by substituting equations (8) and (9), equation (7) becomes
η _e = (1-0.33 × G × ΔT / Hl) × 100-Lo + A / (C × Hl) × 100 (10)
Will be.

となる。 Further, the actual wet exhaust gas amount G in the right side of the equation (10) is a conventional unit because the lower calorific value (Hl) of the fuel is known and the gas fuel 13A is used in this experiment. in the case of,
G = (12.25 x Hl / 10000) + (m-1) x (11.20 x Hl / 10000) (11)
Will be.
Also,
ΔT = Tgo-T0 (12)
Is.
Further, the latent heat recovery amount A per hour is such that the latent heat amount of the drain water is hto and the drain amount is D.
A = hto × D (13)
Will be.
Substituting equations (11), (12), and (13), equation (10) becomes

Will be.

Further, the air ratio m in the right side of the equation (14) is determined by using the residual oxygen concentration O ₂ in the exhaust gas.
m = 21 / (21-O ₂ ) (15)
Similarly, the latent heat amount hto of the drain water in the right side of the equation (14) is calculated assuming that the temperature of the drain water is Tp.
hto = 597.5-0.584 × Tp (16)
Is calculated.
Substituting these equations (15) and (16), the equation (14) becomes the following equation (17).

The measured values shown in FIG. 1, Hl = 9406.9 [kcal / m ³ N], O ₂ = 3.7 [%], Tgo = 51 [° C.], T0 = 35 [° C.], Lo = 0. Substituting 28 [%], Tp = 46.1 [° C.], C = 112.6 [m ³ N / h], and D = 61.1 [kg / h] into equation (17),
η _e = 102.238 [%]
Was calculated.

(2) Method of calculating the boiler efficiency of the entire boiler by the heat input / output method The boiler efficiency η _i calculated by the heat input / output method is calculated by the following formula (18).
η _i = Q _o / Q _i × 100 (18)
Here, Q _o is the amount of heat output and Q _i is the amount of heat input.

Water amount is W, the dryness degree X, the total heat pressure 0.5MPa steam h 'when', the sensible heat of the pressure 0.5MPa steam h ', a water supply enthalpy was hi, exits heat _{Q o} is less It is calculated by the formula (19) of.
Q _o = W × {X × (h''-h') + h'-hi} (19)

Meanwhile, when the fuel consumption C, and Hl a lower heating value, the heat input Q _i is calculated by the following equation (20).
Q _i = C × Hl (20)

Substituting equations (19) and (20), equation (18) becomes the following equation (21).

Furthermore, the water supply enthalpy hi is when the water supply temperature is Twi.
_{h i = Twi × 4.186 (22} )
Therefore, when the equation (22) is substituted, the equation (21) becomes the following equation (23).

Measured values shown in FIG. 1, X = 0.99, h''= 2756.24 [kJ / kg], h'= 670.87 [kJ / kg], Twi = 14.3 [° C.], C = 112.6 [m ³ N / h], Hl = 9406.9 [kcal / m ³ N] = 39377.3 [kJ / m ³ N], and when the water temperature is Twi = 14.3 ° C. Using a value of 998.2 [kg / m ³ ] as the water density and substituting the value converted to W = 1.722 [m ³ / h] = 1719 [kg / h] into equation (23),
ηi = 103.72 [%]
Was calculated.

(3) Calculation method according to the present invention As described above, in the calculation method according to the present invention, where the boiler efficiency of the calculation target is η, the above equation (6) is used.
η = {1- (Q _s −q) / Hl} × 100 − α (6)
It is calculated using the formula.

Here, Q _s is calculated in the same manner as the known exhaust gas loss method. That is, as in the above equation (8),
Q _s = 0.33 x G x ΔT (24)
Will be. Here, as described in the above equation (11),
G = (12.25 x Hl / 10000) + (m-1) x (11.20 x Hl / 10000) (11)
Since ΔT is the difference between the air supply temperature T0 at the inlet of the can body and the exhaust gas temperature Tgi at the outlet of the can body.
ΔT = Tgi-T0 (25)
Is. Substituting Eqs. (11) and (25) into Eq. (24)
Q _s = 0.33 x {(12.25 x Hl / 10000) + (m-1) x (11.20 x Hl / 10000)} x (Tgi-T0) (26)
Will be.
Here, using the numerical values of low calorific value Hl = 9406.9 [kcal / m ³ N], m = 1.2139, Tgi = 216 [° C], and T0 = 35 [° C],
Q _s = 822.9 [kcal / m ³ N]
Was calculated.

Regarding q, assuming that the water supply amount is W, the water supply temperature at the latent heat recovery unit inlet is Twi, the water supply temperature at the latent heat recovery unit outlet is Two, and the fuel consumption is C, the input / output heat method is used.
q = W × (Two-Twi) / C (27)
Is calculated.
The economizer 12 is premised on not changing the state from gas to liquid or from liquid to gas.

Here, the measured values W = 1.722 [m ³ / h] = 1.722 × 998.2 [kg / h] = 1719 [kg / h], Two = 89.2 [° C.], Twi = Substituting 14.3 [° C.] and C = 112.6 [m ³ N / h] into equation (23),
q = 1143.5 [kcal / m ³ N]
Was calculated.

Substituting Hl = 9406.9 and α = 0.28 into the above equation (6) in addition to these calculated values, Q _s = 822.9 and q = 1143.5,
η = 103.13 [%]
Was calculated.

[Effect when the calculation method of the present invention is used]
According to the boiler efficiency calculation method according to the present embodiment described above, for example, the following effects are achieved.

The boiler efficiency calculation method of the present embodiment is a method of calculating the boiler efficiency of the entire latent heat recovery boiler including the can body and the latent heat recovery unit for recovering the heat of the exhaust gas discharged from the can body. The amount of heat lost in the exhaust gas of the can body calculated from the amount of heat of the combustion air supplied to the can body and the amount of heat of the exhaust gas discharged from the can body, and the amount of heat of the fluid to be heated before and after passing through the latent heat recovery unit. It has a step of subtracting the recovered heat amount of the latent heat recovery unit from the exhaust heat loss heat amount while using the recovered heat amount of the latent heat recovery unit obtained from the difference.

As described above, the boiler efficiency η _e = 102.238 [%] calculated by using the exhaust gas loss method plus the measured drain value. In addition, the boiler efficiency of the entire boiler was calculated by using the heat input / output method, and the boiler efficiency was η _i = 103.72 [%]. On the other hand, the boiler efficiency η = 103.13 [%] calculated by using the method according to the present invention.
In the method in which the measured drain value is added to the exhaust gas loss method, the value related to the drain is actually measured, so it is estimated that a value close to the boiler efficiency value can be obtained. Based on this boiler efficiency η _e , the boiler efficiency η calculated by using the method according to the present invention is compared with the boiler efficiency η _i calculated by using the heat input / output method for the entire boiler. The difference with _e was small. That is, it was presumed that the method according to the present invention can obtain a value close to the true boiler efficiency value as compared with the method of applying the heat input / output method to the entire boiler.
As described above, in the heat input / output method, the error of the flow meter that measures the amount of water supply becomes the error of the boiler efficiency as it is, so the error of the calculated boiler efficiency is larger than that of the case of using the exhaust gas loss method. turn into.
Here, in the method according to the present invention, the flow rate of the fluid to be heated flowing through the latent heat recovery unit is measured, but the amount of heat recovered by the latent heat recovery unit is only a part of the amount of heat recovered by the entire boiler. , The influence of the error of the flow meter can be reduced. Specifically, in the method of calculating the boiler efficiency of the entire boiler by the heat input / output method, as can be seen from the equation (19), the error of the water supply amount W affects the entire heat output amount Qo. On the other hand, in the method according to the present embodiment, as can be seen from the equations (6) and (27), the error of the water supply amount W affects only the latent heat recovery q. Therefore, the boiler efficiency calculated by the method according to the present invention has a smaller error than the case where the boiler efficiency of the entire boiler is calculated by using the heat input / output method.

Further, in the simple exhaust gas loss method, the calorific value of the latent heat recovery is not considered in the calculation of the boiler efficiency, but in the present invention, the boiler efficiency can be calculated in consideration of the calorific value of the latent heat recovery. It will be possible.

At the same time, compared to the exhaust gas loss method, which is estimated to obtain a value close to the true boiler efficiency, and the measured drain value is added, it is not necessary to actually measure the value related to the drain, so the boiler efficiency can be easily improved. It is possible to calculate.

Further, when an estimation approximation formula for estimating the value related to the drain is used in addition to the exhaust gas loss method, the larger the boiler of the latent heat recovery unit, that is, the higher the boiler efficiency, the larger the error. Therefore, the calculation according to the present invention. The merit of calculating the boiler efficiency using the method is great.

At the same time, in the present invention, since all the numerical values other than the constants used for the boiler efficiency calculation can be confirmed by actual measurement, the accuracy is higher than the method using the estimation approximation formula.

Further, the boiler efficiency of the entire latent heat recovery boiler is η, the amount of heat loss from exhaust gas in the can body is Q [kcal / m ³ N], and the amount of heat recovered by the latent heat recovery unit is q [kcal / m ³ N]. When the fuel low calorific value of the fuel to be used is Hl [kcal / m ³ N] and the heat dissipation and unburned gas loss are α [%], the boiler efficiency of the entire latent heat recovery boiler is calculated by the formula η = (1- (Q). It may be calculated using −q) / Hl) × 100 −α.

Therefore, again, since all the numerical values other than the constants used for the boiler efficiency calculation can be confirmed by actual measurement, the accuracy is higher than the method using the approximate expression.

[Modification example]
Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be implemented in various forms.

The latent heat recovery unit of the latent heat recovery boiler 10 may include an air heater instead of the economizer 12, or may include both an economizer and an air heater.

Further, the latent heat recovery unit of the latent heat recovery boiler 10 may include a blow heat exchanger in addition to the economizer and / or the air heater. This aspect is shown in FIG.

As shown in FIG. 2, the latent heat recovery boiler 20 includes a can body 21, an economizer 22, and a blow heat exchanger 23. The water supply to the latent heat recovery boiler 20 first passes through the blow heat exchanger 21 and is heated in the blow heat exchanger 23 by the heat of the blow water discharged from the can body 21. After that, the water supply is heated by the exhaust gas discharged from the can body 21 in the economizer 22 via the economizer 22. After that, the water supply is replaced with steam in the can body 21 by the heat of burning the fuel.

At this time, the total heat loss = exhaust gas loss + blow loss + heat dissipation loss = can body exhaust gas loss + can body blow loss + can body heat dissipation loss- (economizer recovery heat amount + blow heat exchanger recovery heat amount).
That is, the total heat loss is Q _A , the can body exhaust gas loss is Q _s , the can body blow loss is Q _B , the can body heat dissipation loss is Q _D , the economizer recovery heat amount is q _e , and the blow heat exchanger recovery heat amount is q _b. Then
Q _A = Q _s + Q _B + Q _D- (q _e + q _b ) (28)
The formula holds. By replacing Q _a = Q _s −q in Eq. (6) with Q _A in Eq. (28), the latent heat recovery boiler is equipped with a blow heat exchanger, and the boiler efficiency is calculated when blow loss is also taken into consideration. It is possible to do.

More specifically, when the blow amount is v _B and the blow enthalpy is h _B , the above-mentioned can body blow loss Q _B is
Q _B = v _B x h _B (29)
Can be calculated.

In addition, when the average heat transfer coefficient of the can body h _m, the area for heat to pass to the A, the heat transfer resistance R of the can body,
R = 1 / h _mA (30)
Can be calculated. T∞ outside air temperature, when the surface temperature of the can body was Ts, can body radiator loss Q _D above,
Q _D = (T∞-Ts) / R (31)
Can be calculated as.

Also, the water supply amount W, economizer 22 the outlet of the enthalpy _{h eo,} economizer 22 the enthalpy of the inlet _{h ei,} blow heat exchanger 23 exit the enthalpy _{h bo,} the enthalpy of the blow heat exchanger 23 inlet and the _{h bi} If
q _e = W × ( _heo- h _ei ) (32)
q _b = W × (h _bo −h _bi ) (33)
However, since the temperature at the outlet of the blow heat exchanger 23 and the temperature at the inlet of the economizer 22 are equal to each other, which are the enthalpies of both h _bo and _hei , the formulas (28) and (29) are the same. ) Is added up
q _e + q _b = W × ( _heo −h _bi ) (34)
Will be.

The equations (29), (31), and (34) are substituted into the equation (28), and Q _a = Q _s −q of the equation (6) is replaced with the Q of the equation (28) as described above. By replacing it with _A , it becomes possible to calculate the boiler efficiency in consideration of the blow loss when the latent heat recovery boiler 20 includes the economizer 22 and the blow heat exchanger 23, using the actually measured values.

In FIG. 2, the economizer 22 and the blow heat exchanger 23 may be in the reverse order when viewed from the can body 21. In this case, since the temperature at the outlet of the economizer 22 and the temperature at the inlet of the blow heat exchanger 23, and the enthalpies of both, _eo and h _bi , are equal, the equations (28) and (29) are added together. Then,
q _e + q _b = W × (h _bo −h _ei ) (35)
Will be. By using this equation (35) instead of the equation (34), it is possible to similarly calculate the boiler efficiency in consideration of the blow loss by using the actually measured value.

10 20 Latent heat recovery boiler 11 21 Can body 12 22 Economizer 23 Blow heat exchanger

Claims (4)

It is a method of calculating the boiler efficiency of the entire latent heat recovery boiler including the can body and the latent heat recovery unit for recovering the heat of the exhaust gas discharged from the can body, and is the calorific value of the combustion air supplied to the can body. And the amount of heat recovered from the latent heat recovery unit obtained from the difference between the amount of heat lost from the exhaust gas of the can body calculated from the amount of heat of the exhaust gas discharged from the can body and the amount of heat of the fluid to be heated before and after passing through the latent heat recovery unit. A method for calculating boiler efficiency, which comprises a step of subtracting the amount of heat recovered by the latent heat recovery unit from the amount of heat lost in exhaust gas. The boiler efficiency calculation method according to claim 1, wherein the latent heat recovery unit includes an economizer and / or an air heater. The boiler efficiency of the entire latent heat recovery boiler is η, the amount of heat lost in exhaust gas in the can body is Q, the amount of heat recovered by the latent heat recovery unit is q, the low calorific value of the fuel used is Hl, heat dissipation and unburned gas loss. The boiler according to claim 1 or 2, wherein the boiler efficiency of the entire latent heat recovery boiler is calculated using the formula η = (1- (Q−q) / Hl) × 100−α. Efficiency calculation method. The latent heat recovery boiler further includes a blow heat exchanger and
The boiler efficiency calculation method according to claim 3, further comprising a step of calculating the blow loss included in the heat dissipation and the unburned gas loss.

Images