JPS6056969B2 - Boiler - combustion air control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a boiler combustion air control method, and more particularly, to a boiler combustion air control method that maintains an appropriate combustion state and controls the amount of air supplied to the boiler to reduce the production of NOx as much as possible. It is related to.

Boilers that burn heavy oil or gas either exclusively or mixedly are widely used in thermal power plants, etc., but the thermal efficiency of such boilers and measures to prevent environmental pollution from exhaust gas are important from the standpoint of resource conservation and pollution control. It is well known that this is the case.

Conventionally, when managing and controlling the above measures,
The necessary information elements for this purpose, such as fuel density, sulfur content, calorific value, etc., are all obtained through manual analysis, which precludes so-called online management and control, and also requires sampling methods. In some cases, this can affect the reliability of the system, and especially during boiler combustion, control errors in the amount of air supplied can lead to undesirable results such as an increase in NOx in the exhaust gas due to the supply of more air than is necessary for combustion. was. This invention has been made in view of the above-mentioned situation, and is aimed at improving the density of the supplied fuel, the sulfur concentration in the fuel, and the total amount of the main composition including sulfur, carbon, and hydrogen in a boiler using heavy oil or gas fuel. By continuously detecting the weight composition concentration of fuel before supplying it to the boiler, and calculating the amount of air required for combustion of the fuel based on each detected value, it is possible to prevent excess air from being supplied to the boiler. The purpose of the present invention is to simultaneously calculate the calorific value of the fuel based on the above-mentioned detection values, and to simultaneously calculate the calorific value of the fuel based on the above-mentioned detection values. The purpose is to enable centralized control of boiler thermal efficiency management.

That is, the boiler combustion air control method of the present invention includes a density detector that detects the density of the fuel as a physically independent value in the fuel supply line to the boiler, and a radiation detector that selectively detects only the sulfur concentration in the fuel. A sulfur concentration detector using radiation and a composition concentration detector using radiation to detect the total gravimetric concentration of the main components of hydrogen, carbon, and sulfur in the fuel are provided, and the output signals of these detectors are Based on this, the minimum amount of air required for complete combustion of the fuel is determined without calculating the hydrogen concentration and carbon concentration of the main components in the fuel, and the actual amount of supplied air is equal to the required amount of air. The system is designed to suppress the concentration of NOO generated in the exhaust gas as much as possible by eliminating the supply of excess air without reducing heat generation efficiency, and to achieve this on-time. be.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a detailed configuration of a detection section and a calculation section of a control system according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the overall configuration of the control system.

In Fig. 1, e is a sample line led from the fuel supply line to the boiler, and the sample line e is equipped with a density meter 1 that physically detects the density of the fuel, and a density meter 1 that selects the concentration of sulfur in the fuel. A sulfur concentration detector 2 that detects the total weight composition of hydrogen, carbon, and sulfur in the fuel. A composition concentration detector 3 for detecting concentration is provided.

The density detector 1 detects the fuel density ρ (g/Cm) as an independent value unrelated to the component ratio using a physical method such as a vibrating density meter. A so-called radiation application device is not used.

Further, the sulfur concentration detector 2 may contain, for example, americium 24
Using a radiation source such as 1, a signal related only to the sulfur concentration Cs is generated using -γ rays with an intensity of, for example, 20 to 23 keV, which equalizes the mass absorption coefficients of hydrogen and carbon and makes the mass absorption coefficient of sulfur different. The sulfur concentration can be selectively detected irrespective of the ratio of other components. Further, the composition concentration detector 3 uses a radiation source such as americium-241 to
A system is used in which a signal related to the total weight composition concentration of each composition is obtained using gamma rays with an intensity of, for example, about 60 keV, which makes the mass absorption coefficients of the required compositions of carbon and sulfur all different. .

The output of the density detector 1 is input to a converter 4 for converting a density signal at a reference temperature into a further normalized voltage signal, and the converter output j is a first signal as a density signal. It will be used for control as an ED.

The output of the sulfur concentration detector 2 is inputted to a combination circuit of a setter 7 and a divider 9 for zero span adjustment of the sulfur concentration via a converter 5 for converting it into a voltage signal.
After temperature correction using the output signal (first signal) of the converter 4 inputted separately and calculations to be described later, the normalized sulfur concentration signal at the reference temperature is calculated from the output of the divider 9. The second signal Es is used for control.

Further, the output of the composition concentration detector 3 is inputted to a combination circuit of a setter 8 and a divider 10 for zero span adjustment of the composition concentration via a converter 6 for converting it into a voltage signal in the same manner as described above, After temperature correction using the output signal (first signal) of the converter 4, which is separately input to the converter 8, and calculations to be described later, the divider 10 outputs the normalized composition concentration signal at the reference temperature. 3 is input to the air amount calculator 11 and the calorific value calculator 12 as the signal Ec.

The air amount calculator 11 receives input from the divider 9 and the divider 10 and generates a composition concentration signal (second signal) as described later.
Then, from the composition concentration signal (third signal), the minimum required air amount necessary for complete combustion of the fuel is calculated, and the fourth signal is calculated.
The calorific value calculator 12 similarly receives input from the divider 9 and the divider 10 and outputs a sulfur concentration signal (second signal) and a composition concentration signal ( The fifth signal EO is output by calculating the calorific value of combustion at that time based on the third signal (third signal).

In FIG. 2, the respective detectors 1, 2, 3 and the first
The arithmetic unit 20 surrounded by a chain line in the figure is indicated by the same reference numeral, and the arrangement of the fuel supply line L to the boiler 18 and the aforementioned sampling line I is also shown.

In FIG. 2, reference numeral 13 denotes a flow meter provided in the fuel supply line L, and the output of this flow meter 13 is input to a multiplier 14. The first signal ED of the arithmetic unit 20 described above is also input to the multiplier 14, and the output of the multiplier 14 is the second signal ED described above.
The fourth and fifth signals Es, Ec, and EQ are input to a multiplication calculator 15, which receives the fourth and fifth signals Es, Ec, and EQ as inputs, respectively. Also boiler 1
The air supply line 17 of No. 8 is provided with a supply air amount regulator 16, and the regulator 16 adjusts the opening degree of the valve or the output of the fan according to the air amount control output A, which is one of the outputs of the multiplier 15. is being controlled. In addition, 19 in the figure is the chimney of the boiler 18. In the above configuration, the density ρ(g/
For example, when the fuel is petroleum, it is known that its density is within the range of 0.65 to 1.0 (g/Cm). In order to use these in a full range corresponding to the range of the calculation system, the difference from the reference value ρo (for example, 0.65 for petroleum) set as the lower limit of the measurement range is calculated by the converter 4. The first signal is in the form of a voltage signal that is converted to density at the reference temperature and normalized to a signal that varies within the measurement range 1 to 5 of the following formula according to the range of the instrument or calculation system used. Output.

(However, ρo and ρMax are the lower and upper limit settings of the density measurement range, respectively).

Furthermore, the ionization current L=I is proportional to the sulfur concentration C, (wt%) at a certain temperature detected by the sulfur concentration detector 2.
OXe-ρt Cs (where ρ is the above-mentioned density, t is a coefficient depending on the measurement path length, and U is a mass absorption coefficient of sulfur S) is obtained from the converter 4 after conversion to a voltage signal by the converter 5 and amplification. Temperature signal at reference temperature (first signal E).

) and the fuel temperature measurement signal in the detector 2, a temperature correction is added in the setter 7, and further, in combination with the divider 9, it is calculated as shown in the following formula, and the signal is normalized to 1 to 5V as described above. It is output as a second signal in the form of a converted voltage signal. (However, C″SO and C″S.nax are the lower and upper limit settings of the sulfur concentration measurement range, respectively.) Similarly, the ionization current 1 proportional to the composition concentration at a certain temperature detected by the composition concentration detector 3 = IOe−ρt(UHCH+Uc
Cc+UsCs) is the density signal (first signal E) at the reference temperature from converter 4 after conversion to a voltage signal and amplification by converter 6.

) and the fuel temperature measurement signal in the detector 3, a temperature correction is added in the setter 8, and then in combination with the divider 10, it is calculated as shown in the following equation to produce a 1 to 5V signal as described above. A third signal is output in the form of a normalized voltage signal. (However, YO is detected by the above detector 3 and EO=μ
HCH+μ.

Compositional concentration values, YcO and Y at which Cc+μSCs holds true
cmu. are the lower limit set value and upper limit set value of the composition concentration measurement range, CH, C. are the weight concentrations (wt%) of hydrogen, carbon, and sulfur, respectively, and CHO, CCOl, and CsO are CHO+CCO+CSO=1 and Y specified by the fuel.
Constants related to hydrogen, carbon, and sulfur, determined so that cO=μHCHO+μCCHO+μ5CS0 holds, CH. ．． aO, Ccma. and Csmax is specified by the fuel) CHmax+Ccmax+Csm
ax:1 and YcrnaxOμCCHmax+μCCla
x+μSClax are constants for hydrogen, carbon, and sulfur, respectively). Now, it is a well-known fact that the elemental composition of petroleum is carbon, hydrogen, and sulfur.

If the constant weight of petroleum is w (g), and the weights of carbon, hydrogen, and sulfur contained therein are Wc, WH, and Ws, the following relationship holds true. W=Wc+WH+Ws On the other hand, the weight composition ratio Cc, CH of carbon, hydrogen, and sulfur,
When Cs is represented by W, the following results are obtained.

Therefore, even if changes, the sum of the ratios will always remain equal to 1.

The high calorific value per unit weight of each element of carbon, hydrogen, and sulfur is QcKcae/KgQHKcae/K9Q.
Supposing that SKCae/K9 is the high calorific value per unit weight of petroleum composed of SKCae/K9, the following relational expression is established between them.

In this way, the calculations of the petroleum calorie meter are based on equations (a) and (b).

Furthermore, the amount of oxygen required for combustion of this petroleum product is determined from the following relationship.

Now, petroleum products Wg (carbon WCgl hydrogen WHgl sulfur Ws
The amount of oxygen G required to burn g) is determined as follows.

The amount of oxygen when burning carbon Wcg is, The amount of oxygen when burning hydrogen Wsg, The amount of oxygen when burning sulfur Wsg, Therefore, the amount of oxygen required when burning Wg of petroleum products The amounts are as follows.

Therefore, the required oxygen amount G per unit weight can be expressed as follows.

8, Wc+8WH+Ws G= っ =? C+8CH+CS In this way, the calculation performed by the air amount calculator 11 using equations (2) and (3) above is such that the required oxygen amount G when burning fuel is, for example, when the fuel is heavy oil. This is known as a theoretical value, and since the amount of oxygen present in the air is K = 23.2wt%, basically the required air amount G is
This is based on the fact that A is determined by GA=G/K.

By the way, the required oxygen amount G is shown using heavy oil as an example.
Since its composition is nearly 100% hydrogen, carbon, and sulfur, the composition concentration YC, sulfur concentration CSl and CH+
Using the relationship Cc+Cs=CHO7+CCO+CSO=1 and the above equation (41), the required oxygen amount G as shown in equation (5) can be determined as follows. That is, if the required oxygen amount corresponding to the lower limit set value YcO is G, then (41
) Equation (43) is derived in the same way as (42).

Equation (44) is derived from (42) and (43).

On the other hand, as mentioned above, the composition concentration value Yc detected by the detector 3
and the lower limit setting of the composition concentration measurement range. CO is determined by the following formula (
45) and (46). Therefore, from these equations (45) and (46), the following equations (45)'' and (4
6)'' is derived, and formula (47) is derived from these formulas (45)" and (46)". This formula (47) is transformed into the above formula (44).
Here, since the constant CsO related to sulfur that gives the lower limit set value YcO and the lower limit set value CsO of the sulfur concentration measurement range are different, the following equation (49) can be derived by adding the correction of this C″SO. I'm scared.

Here, if the required oxygen amount G for the lower limit set value YcO is also corrected by the above C″SO and the required oxygen amount G″O is determined as shown in the formula below, then the following formula (5) is obtained from the formula (49). be guided.

However, G″O=8CHO+?CO+CSO−(7 one arm×In the above equation, the hydrogen concentration CH and carbon concentration speed C as measured values are not necessary for calculation.

That is, by the above-mentioned second signal and third signal,
The air amount calculator 11 performs calculations based on the calculation formula expressed by , and outputs a fourth signal in the form of a voltage signal normalized to a measurement range of 1 to 5V signal.

In addition, in the above, G″Amax is the upper limit setting value Ycn
The air amount corresponding to laX, G″AO is the lower limit setting value Y
It represents the amount of air corresponding to cO. The calculation of the calorific value performed by the calorific value calculator 12 is performed because the ratio of the concentrations of each composition is given by the third signal, and the concentration of sulfur is given by the second signal. , hydrogen theoretical high calorific value QH
=34200kca'/Kg, carbon theoretical high calorific value α=8
080kcae/K9, sulfur theoretical high calorific value α=2500
Since kCae/K9 is known, the theoretical formula Q of the combustion equation
=QHCH+QcCc+QsCs and (g)=QHC
From HO+QcCcO+QsCsO, the theoretical high calorific value Q and lower limit value of calorific value (g) are calculated, and CH+Cc+Cs=
The relationship of CHO+CcO+CsO=1 and the above-mentioned Yc
The calorific value difference ΔQ=Q−QO is obtained from YcO and YcO as follows.

That is, here, CH=1-CC-CS, . CHO=1-
CCO-CSO is Seiko! Therefore, ~ 1, 1- 1-Here, CCO-CC of the above formula (47) =,1+7ぃ× (μH-μs)(Yc-YcO)+? x(
Cs-CsO) as (μH-U,c) ~ノQυ Here, the constant CsO related to sulfur that gives the lower limit set value YcO and the lower limit set value C'' of the sulfur concentration measurement range
Since the SO is different, if this C″SO correction is added, the oil calorific value QO corresponding to the lower limit set value YcO is also corrected for the above C″SO, and the oil calorific value 9 is calculated as shown in the formula below.
When ``0'' is determined, the calorific value difference ΔQ is derived as shown in the following equation.

In the above series of equations, (QH-Qc), (QH-Qs
) (μH−μc) and (μs−μH) are constants, so ΔQ can be calculated based on the signals (Yc−YcO) and (Cs−CsO).

However, for convenience of explanation, it is assumed that the fifth signal as the signal of the amount of heat generated is expressed by a voltage signal normalized to a 1 to 5 V signal in the following formula as described above.

(However, Qmax is the upper limit of the measurement range)
The equation (8) can be established in relation to ΔQ.

What is clear from the above is that by obtaining voltage signals such as equations (1), (2), and (3), it is possible to detect components such as hydrogen and carbon in fuel without having to independently test their concentrations. It is possible to determine the required air amount or calorific value without determining Cc/CH (CH ratio). That is, the ionization current 1=IOe-ρ゛(
μHCH+μCCc+μSCS) to μHCH+PC
CC+PSCS=MoTen Blue is derived. Further, since ρ and Cs are measured by the density detector and the sulfur concentration detector, respectively, METenblue and μScs become constants. Furthermore, Cs in the above formula (a) is also a constant. Therefore, μHCH + μCcc = Me) Enkichi - μSCS = (
CH and Cc are found by solving simultaneous equations consisting of CH+Cc=1−Cs=(constant).
That is, considering the condition that CC+CH+CS=1 in the above equation (a), ρ, μHCH+μ, which are the signals obtained by the density detector, composition concentration detector, and sulfur detector, respectively.
By configuring the calculation system based on CCc+μSCSl and Cs, the oil calorific value Q=QHCH+QC
CC+QSCSL Required oxygen amount G=RCC+8CH+CS
l and required air amount GA=G/K・(However, K=0.2
38) can now be found. Therefore, the configuration of such a calculation system is extremely simple, and the combustion management of the boiler can be performed online based on the obtained signals. That is, as shown in FIG. 2, a flow meter 13 is arranged in the fuel supply line L, and the flow rate signal VCd/
Sec] and the first signal, the density signal ED (Kg/d)
If they are integrated in the multiplier 14, the mass flow rate signal (ED●■
) [K9/Sec] is obtained, and this mass flow rate signal and the fourth
The required air amount ACk9/Sec] required per unit time is obtained by integrating the air amount signal [K9/・K9], which is the signal of By controlling the regulator 16, the amount of air fed into the boiler 18 can be minimized without reducing heat generation efficiency.

In addition, in Fig. 2, S is the mass flow rate signal (EO・■)
The sulfur amount signal [K9/SeO] obtained by integrating and the second signal Es in the multiplier 15, Q is obtained by integrating (ED・■) and the fifth signal EQ in the multiplier 15. This is the calorific value signal [Kcae/Sec] obtained by

As described above, according to the present invention, the circuit configuration of the measurement system calculation system is simplified, the amount of air supplied to the boiler is appropriately controlled, excessive air supply is minimized, and the supplied air is All the oxygen in the fuel is used to burn the hydrogen, carbon, and sulfur in the fuel, preventing the oxidation of nitrogen as much as possible, which greatly reduces the generation of NOx in the exhaust gas. Not only can heat loss due to surplus air be effectively prevented, but also the calorific value and sulfur content can be determined at the same time, which can be used to manage boiler thermal efficiency and SO. Furthermore, since the composition of fuel can be detected before it is combusted, thermal efficiency management and supply air volume control can be carried out on-time without wasting process time. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the detailed configuration of a detection section and a calculation section of a control system according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the overall configuration of the control system. 1... Density detector, 2... Sulfur concentration detector, 3... Composition concentration detector, 4, 5, 6...
・Converter, 7, 8... Setting device, 9, 10...
...Divider, 11... Air amount calculator, 12...
... Calorific value calculation unit, 13 ... Flow meter, 14.
... Multiplier, 15... Multiplication operator, 16...
...Air volume regulator, 18...Boiler.

Claims (1)

[Claims] 1 A first signal is obtained by detecting the density of the fuel as a physically independent value without using radiation, and using radiation of a predetermined intensity to equalize the mass absorption coefficients of carbon and hydrogen. selectively detect the concentration of sulfur in the fuel to obtain a second signal, and detect the concentration of carbon in the fuel using radiation of a predetermined intensity such that the mass absorption coefficients of carbon, hydrogen, and sulfur are different from each other. The total weight composition concentration of each composition of hydrogen and sulfur is detected to obtain a third signal, the first signal is converted to a value at a reference temperature and normalized, and this normalized first signal is correcting the second signal to the reference temperature based on the signal and the fuel temperature at the time of detecting the sulfur concentration, and then normalizing it;
The third signal is corrected to the value at the reference temperature based on the normalized first signal and the fuel temperature at the time of detecting the weight composition concentration, and then normalized, and the third signal is normalized to the normalized second signal. A fourth signal is obtained by calculating the amount of air required for combustion based on the third signal, and the product of the fuel supply amount to the boiler and the normalized first signal and the fourth signal are A boiler combustion air control method characterized in that the amount of air to be supplied to a boiler is controlled based on the amount of air so as not to become excessive.