JP3669638B2 - Concentration blow control method for boiler - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for controlling the concentration blow of a boiler.
[0002]
[Prior art]
In general, in a boiler, if the can water in the boiler is continuously heated at a high temperature for a long time, the concentration of the can water proceeds in proportion to the amount of steam generated, resulting in a high dryness of the generated steam. Is difficult to maintain.
[0003]
In order to avoid this state, the boiler is conventionally provided with an automatic concentration blow device. In this automatic concentrating blow device, a concentrating blow valve is provided via a strainer in the downcomer pipe of the separator of the boiler, and this concentrating blow valve is normally closed and when it is opened, can water is blown into the piping. It is designed to discharge from the outside . And it is the structure which provided the control part in the circuit which connects this concentration blow valve and the electrical conductivity measurement sensor installed in the downstream of the said downcomer. According to the automatic blowdown apparatus, a change in electrical conductivity which is proportional to the concentration of the boiler water on the downstream side of the downcomer by the electric conductivity measuring sensor measures, when the electrical conductivity exceeds a predetermined value The concentrated blow valve is opened to discharge the highly concentrated canned water to the outside. At the same time, the canned water is automatically supplied into the can through the water supply device when the highly concentrated canned water is discharged. Is diluted, the concentration of the entire can water is lowered, and when the electrical conductivity of the can water falls below a specified value, the concentration blow valve is closed. In this way, the automatic concentration blow device maintains the high dryness of the generated steam in the boiler.
[0004]
However, in the automatic concentrating blow device, the electric conductivity of the feed water varies greatly depending on the temperature thereof, so that there are cases where it operates at a position deviating from the reference value depending on the use status of the boiler, its pressure, or the like. Further, when performing maintenance of the boiler, by measuring the ratio of the blow amount to the water supply amount, since the setting of the current electrical conductivity is to check whether correct or not, in setting the electrical conductivity, what The current situation is that an appropriate value is obtained by setting again and again.
[0005]
[Problems to be solved by the invention]
Problems which the present invention is to provide, in response to changes in the water supply of the electrical conductivity, to provide a blowdown control method of a boiler for automatically controlling the enrichment of the boiler water by modifying the blowdown rate set in advance It is.
[0006]
[Means for Solving the Problems]
The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 automatically opens and closes the concentration blow valve 7 based on a preset concentration blow rate to automatically increase the concentration of the can water. In the boiler 1 to be controlled, an operation time until the electric conductivity of the can water becomes substantially constant is set in advance, and the electric conductivity of the can water after the operation time elapses is measured by the electric conductivity measuring sensor 6. When the measured electrical conductivity is compared with the preset electrical conductivity of the can water, if both are different, the water supply is made using the following formula [1] from the measured electrical conductivity and the preset concentration blow rate. Calculate the electrical conductivity, calculate the appropriate concentration blow rate using the following formula [1] from the electrical conductivity of the feed water and the preset electrical conductivity of the can water, and concentrate the blow to the calculated value. Boiler enrichment characterized by correcting the rate Low control method.
E = E ₀ / α …… [1]
E: Electric conductivity of can water E ₀ : Electric conductivity of feed water α: Concentration blow rate
Further, according to the second aspect of the present invention, in the boiler 1 that automatically opens and closes the concentration blow valve 7 based on a preset concentration blow rate and automatically controls the concentration of the can water, The conductivity is measured by the sensor 17, and the measured electrical conductivity of the feed water is compared with the preset electrical conductivity of the feed water. If both are different, the measured electrical conductivity of the feed water and the preset can water A method for controlling the concentration blow of a boiler, wherein an appropriate concentration blow rate is calculated by substituting electric conductivity into the following formula [1], and the concentration blow rate is corrected to the calculated value.
E = E ₀ / α …… [1]
E: Electric conductivity of can water E ₀ : Electric conductivity of water supply α: Concentration blow rate
【Example】
Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. The embodiment shown in the drawings is an example in which the concentrated blow control method according to the present invention is applied to a multitubular once-through boiler.
[0009]
First, an embodiment of claim 1 of the present invention will be described with reference to FIG. As shown in FIG. 1, a water supply pipe 2 of a water supply device (not shown) provided with a check valve, a filter, a chemical injection device, and the like is connected to the lower portion of the boiler 1. The other end of the water supply pipe 2 is connected to a water source (not shown) such as a water supply or a well, and by operation of a water supply pump (not shown), the water of the water source is filtered and the chemical injection water is injected. Then, it is supplied into the boiler of the boiler 1. Further, a separator 3 for separating the generated steam into water is connected to one side of the boiler 1 through a steam communication pipe 4 and a downcomer pipe 5 in communication with the upper and lower parts of the boiler 1. In addition, a blow pipe 8 having an electrical conductivity measuring sensor 6 and an electromagnetic opening / closing type concentrated blow valve 7 is connected to the lower part of the downcomer pipe 5.
[0010]
The operation and stop of the boiler 1 are usually controlled by a combustion controller (not shown) based on the signal of the pressure detector 9 that detects the internal pressure of the boiler 1 based on the load condition. That is, when the internal pressure of the can becomes equal to or higher than a preset pressure value, the combustion is stopped, and when it becomes lower than that, the combustion is started. Further, the burner 16 of the boiler 1 is provided with a combustion detection sensor 10 for detecting combustion in the boiler 1, and the combustion state and combustion time in the boiler 1 are measured. . That is, the pressure detector 9 and the combustion detection sensor 10 constitute detection means for controlling the operation status of the boiler 1.
[0011]
The controller 11 for controlling the opening / closing of the concentration blow valve 7 has, for example, a calculation function built in a microcomputer, and is set in advance with detection signals from detection means such as the pressure detector 9 and the combustion detection sensor 10. The opening / closing timing of the concentration blow valve 7 is calculated according to the concentration blow rate, the time for intermittently opening / closing the concentration blow valve 7 is determined, and the signal is output to the concentration blow valve 7. Yes. Therefore, the controller 11 is connected to the pressure detector 9 and the combustion detection sensor 10 via communication lines 12 and 13, respectively, and is connected to the concentration blow valve 7 via a communication line 14, and the electric The conductivity measuring sensor 6 and the communication line 15 are connected.
[0012]
Generally, the concentration blow rate (ratio between the blow amount and the water supply amount) is set in advance by analyzing the quality (pH, etc.) of the raw water (well water, tap water) to be supplied and supplying the necessary cleanser. Although it is determined in consideration of the amount, etc., it is about 10% to 15%. Here, the water supply amount can also be calculated by the water supply time, but the water supply amount per unit time may fluctuate due to a change in the capacity of the water supply pump, a pressure fluctuation of the boiler 1, etc. Was calculated by evaporation amount × burning time, and the concentration blow rate was defined as the ratio of blow amount and evaporation amount × burning time. That is, it is more accurate to calculate the blow amount based on the detection signals from the pressure detector 9 and the combustion detection sensor 10. This is because the amount of evaporation of the boiler 1 is determined by the rating.
[0013]
According to the above configuration, when the boiler 1 is in operation, the pressure inside the can, the combustion state of the burner 16, the combustion time, etc. are the pressure detector 9, the combustion detection sensor 10, the electrical conductivity measurement sensor 6, etc. The detection means always detects and outputs the detection signal to the controller 11. The controller 11 which has received the output signal, by said detection signal and blowdown rate is set in advance, the closing timing of the blowdown valve 7 is calculated, performed intermittently opening and closing of the blowdown valve 7 The concentration blow valve 7 is automatically opened and closed by determining the time.
[0014]
In the above-described configuration, the concentration blow control method according to the present invention sets in advance the time from the start of operation of the boiler 1 until the electric conductivity of the can water becomes substantially constant, and the electric power of the can water after the lapse of the operation time. The conductivity is measured by the electric conductivity measuring sensor 6, and the corrected concentrated blow rate is calculated from the measured electric conductivity , that is, the actually measured electric conductivity.
[0015]
Here, the concentration of can water is the amount of solute (total evaporation residue) in the solvent (water), but the following relationship is approximately between the total evaporation residue in water and the electrical conductivity. It holds.
[0016]
Total evaporation residue [mg / liter] = 0.7 × electric conductivity [μs / cm]
[0017]
Therefore, the concentration of the can water can be calculated by electric conductivity instead of the total evaporation residue. For example, the electrical conductivity of can water is E [μs / cm], the combustion time is T [h], the actual evaporation is G [kg / h], the retained water is L [liter], and the electrical conductivity of the feed water is E Assuming that ₀ [μs / cm], the concentration blow rate is B [kg / h], and the concentration blow rate is α , the following equation holds.
[0018]
E = {E ₀ × L + E ₀ × (G + B) × T−E × B × T} / L
[0019]
When this equation is transformed, E × {1+ (B × T) / L} = E ₀ × {1+ (G + B) / L × T} .
[0020]
Here, since the multiplication factor is E / E ₀ , E / E ₀ = {1+ (G + B) / L × T)} / {1+ (B × T) / L} .
[0021]
Since α = B / (G + B), E / E ₀ = {1+ (B × T) / (α × L)} / {1+ (B × T) / L} .
[0022]
Accordingly, in this equation, when T increases, E = E ₀ / α (hereinafter referred to as “expression [1] ”).
[0023]
The electrical conductivity measuring sensor 6 constantly measures the electrical conductivity of the can water while the boiler 1 is in operation, and the electrical conductivity E2 of the can water after a predetermined operating time has elapsed and a predetermined predetermined can water. When the electrical conductivity E ₁ is compared and the two are different, the controller 11 calculates the measured electrical conductivity E ₂ of the can water and the preset concentration blow rate α ₁ as described above. Substituting into the equation [1] , the electric conductivity E ₃ of the feed water is calculated (E ₃ = E ₂ × α ₁ ), and then the electric conductivity E _{3 of the} feed water and the electric conductivity of the predetermined can water By substituting the rate E ₁ into the formula [1] , an appropriate concentration blow rate α ₂ is calculated (α ₂ = E ₃ / E ₁ = E ₂ / E ₁ × α ₁ ), and the concentration is added to this value. The concentration of canned water is automatically controlled by correcting the blow rate. Accordingly, it is possible to automatically cope with a change in the electric conductivity of the feed water, and to always control the concentration of the boiler water in the boiler 1 with an appropriate concentration blow rate.
[0024]
Next, a second embodiment of the present invention will be described with reference to FIG. Here, the same members as those in the embodiment of claim 1 are denoted by the same reference numerals, and redundant description is omitted. In the embodiment shown in FIG. 2, a sensor 17 for measuring the electrical conductivity of the water supply is provided in the middle of the water supply pipe 2, and this sensor 17 is connected to the controller 11 via a communication line 18. is there. In this embodiment, a sensor for measuring the electrical conductivity of can water is not required.
[0025]
The sensor 17 constantly measures the electrical conductivity of the feed water, compares the electrical conductivity E ₄ of the predetermined feed water set in advance with the measured electrical conductivity E ₅ of the feed water, and if both are different, The calculation unit of the controller 11 substitutes the measured electric conductivity E ₅ of the feed water and the predetermined electric conductivity E ₁ of the predetermined can water into the formula [1] to obtain an appropriate concentration blow rate. α ₂ is calculated (α ₂ = E ₅ / E ₁ ), and the concentration blow rate is corrected to this value to automatically control the concentration of the can water. Accordingly, it is possible to automatically cope with a change in the electric conductivity of the feed water and to always control the concentration of the boiler water in the boiler 1 with an appropriate concentration blow rate.
[0026]
【The invention's effect】
According to the present invention, in a system that automatically controls the concentration of can water based on a preset concentration blow rate, the electrical conductivity of the predetermined can water and the electrical conductivity of the can water measured after elapse of a predetermined operation time are If it is different, or if the measured electrical conductivity of the specified feed water is different from that of the preset preset water supply, the controller calculates the appropriate concentration blow rate and calculates the appropriate concentration blow rate automatically. Thus, the concentration blow rate can be corrected in accordance with the change in the electrical conductivity of the water supply, and appropriate concentration blow can be performed.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory view showing the arrangement of devices of a multi-tube type once-through boiler in which a concentration blow control method according to claim 1 of the present invention is implemented.
FIG. 2 is an explanatory view showing the arrangement of each device of a multi-tube type once-through boiler in which the concentration blow control method according to claim 2 of the present invention is implemented.
[Explanation of symbols]
1 Boiler 7 Concentration blow valve
6 Electrical conductivity measurement sensor
17 Sensor

Claims (2)

Based on a preset concentration blow rate, in the boiler 1 that opens and closes the concentration blow valve 7 and automatically controls the concentration of the can water, the operation time until the electric conductivity of the can water becomes substantially constant is set in advance. The electrical conductivity of the can water after the operating time is measured by the electrical conductivity measuring sensor 6, and the measured electrical conductivity is compared with the preset electrical conductivity of the can water. The electrical conductivity of the feed water is calculated from the measured electrical conductivity and the preset concentration blow rate using the following formula [1], and the electrical conductivity of the feed water and the preset electrical conductivity of the can water are calculated. A boiler concentration blow control method, wherein an appropriate concentration blow rate is calculated using the following formula [1], and the concentration blow rate is corrected to the calculated value.
E = E ₀ / α …… [1]
E: Electric conductivity of can water E ₀ : Electric conductivity of water supply α: Concentration blow rate Based on a preset concentration blow rate, in the boiler 1 that opens and closes the concentration blow valve 7 and automatically controls the concentration of the can water, the electric conductivity of the water supplied to the boiler 1 is measured by the sensor 17 and measured. When the electrical conductivity of the feed water is compared with the electrical conductivity of the preset feed water , if both are different, the following formula [1] is calculated from the measured electrical conductivity of the feed water and the preset electrical conductivity of the can water. A method for controlling the concentration blow of a boiler, which calculates an appropriate concentration blow rate by using the correction and corrects the concentration blow rate to the calculated value.
E = E ₀ / α …… [1]
E: Electric conductivity of can water E ₀ : Electric conductivity of water supply α: Concentration blow rate

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