JP5408149B2 - Boiler system - Google Patents

Description

  The present invention relates to a boiler system including a boiler and a combustion amount control unit that sets a combustion mode and controls a combustion amount of the boiler.

  Conventionally, when steam or hot water is generated by burning a plurality of boilers, for example, the number of boilers to be burned and the combustion amount are calculated so that the steam pressure becomes a target value, and the combustion amount of the target boiler is calculated. A technique related to control of an increasing / decreasing boiler is disclosed (see, for example, Patent Document 1).

JP 2002-130602 A

  In the boiler system as described above, it is desired to appropriately change the combustion mode related to the combustion amount of the boiler, appropriately increase or decrease the combustion amount, and further improve the boiler efficiency.

  The present invention provides a boiler system including a boiler and a combustion amount control means for controlling a combustion amount by setting a combustion mode, appropriately changing the combustion mode, appropriately increasing / decreasing the combustion amount, and further improving boiler efficiency. It aims at providing the boiler system which can be improved.

The present invention is a boiler system including a boiler and a combustion amount control means for controlling a combustion amount of the boiler, wherein the boiler includes a boiler body in which combustion is performed, and water supply supplied to the boiler body A feed water temperature measuring means for measuring a feed water temperature that is a temperature, and the combustion amount control means burns as a mode related to the combustion amount of the boiler based on the feed water temperature measured by the feed water temperature measuring means Based on the combustion mode setting means for setting the mode, the combustion mode set by the combustion mode setting means and / or the feed water temperature measured by the feed water temperature measuring means, a feed water temperature threshold is set as a threshold for the feed water temperature A feed water temperature threshold setting means that performs the combustion mode when the feed water temperature measured by the feed water temperature measurement means is equal to or lower than the feed water temperature threshold. Constant means, the combustion mode is set to a minimum combustion mode the amount of combustion is the smallest of the boiler, wherein when the feed water temperature measured by the feedwater temperature measuring means exceeds the feedwater temperature threshold value, the combustion mode setting unit Sets the combustion mode to the second combustion mode in which the combustion amount of the boiler is larger than the combustion amount of the boiler in the minimum combustion mode, and when the combustion mode is the second combustion mode, the feed water temperature measurement The combustion mode setting means sets the combustion mode to the minimum combustion mode only when the feed water temperature measured by the means becomes equal to or lower than the second temperature threshold that is lower than the feed water temperature threshold by a differential value. About the system.

  Further, when the combustion mode is the second combustion mode, the combustion mode setting means is only when the state where the feed water temperature measured by the feed water temperature measuring means is below the feed water temperature threshold continues for a predetermined time, It is preferable to set the combustion mode to the minimum combustion mode.

  Moreover, it is preferable that the said water supply temperature threshold value is preset before it is set by the said water supply temperature threshold value setting means.

  The boiler is a discharge section that discharges combustion gas generated in the boiler body, and a discharge passage that allows the combustion gas to flow through the boiler body and the discharge section, and is disposed above and below at least a part thereof. A discharge path having a circulation part extending in the direction, a heat exchange part that is disposed in the circulation part and through which feed water supplied to the boiler body circulates, and the heat exchange by the combustion gas that circulates through the circulation part A feed water preheater that preheats the feed water in the section and then feeds the feed water to the boiler body, and the feed water temperature measuring means uses the feed water temperature as the feed water temperature. It is preferable to measure the temperature.

  Moreover, it is preferable to provide a plurality of the boilers.

  According to the present invention, in a boiler system including a boiler and a combustion amount control means for setting the combustion mode and controlling the combustion amount, the combustion mode is appropriately changed, the combustion amount is appropriately increased and decreased, and the boiler efficiency is increased. The boiler system which can improve further can be provided.

It is a figure showing the outline of boiler system 1 concerning a 1st embodiment of the present invention. 1 is a longitudinal sectional view of a boiler 20 in a boiler system 1. FIG. It is a graph which shows the relationship between the load factor in case feed water temperature is 15 degreeC, and boiler efficiency. It is a graph which shows the relationship between a load factor in case a feed water temperature is 45 degreeC, and boiler efficiency. It is a flowchart which shows operation | movement of the boiler system 1 which concerns on 1st Embodiment. It is drawing which shows the 1st specific example which concerns on control of the combustion amount of a boiler. It is drawing which shows the 2nd specific example which concerns on control of the combustion amount of a boiler. It is a flowchart which shows operation | movement of the boiler system which concerns on 2nd Embodiment.

[First Embodiment]
Hereinafter, with reference to FIG.1 and FIG.2, the boiler system 1 which concerns on 1st Embodiment of this invention is demonstrated. FIG. 1 is a diagram showing an outline of a boiler system 1 according to the first embodiment of the present invention. FIG. 2 is a longitudinal sectional view of the boiler 20 in the boiler system 1.

  As shown in FIG. 1, the boiler system 1 of 1st Embodiment is the boiler group 2 comprised from the several boiler 20, and the combustion amount control part (combustion amount control means) which controls each combustion amount of the several boiler 20 ) 4, a feed water temperature measuring unit (feed water temperature measuring means) 50 provided in each of the plurality of boilers 20, a steam header 6 for storing steam generated in the boiler body 21 of the boiler 20, and the inside of the steam header 6 A vapor pressure measuring unit (vapor pressure measuring means) 7 for measuring the vapor pressure of

The boiler system 1 according to the first embodiment is capable of supplying steam generated in the boiler group 2 to the steam using facility 18.
In the boiler system 1, the required load is the amount of steam consumed in the steam use facility 18. The boiler system 1 measures the steam pressure P inside the steam header 6 to be controlled by the steam pressure measuring unit 7, and the measured steam pressure P and the feed water temperature T measured by the feed water temperature measuring unit 50 (for details, see FIG. The number of boilers 20 to be burned, the amount of combustion of the boiler 20 and the like are controlled by the combustion amount control unit 4 based on the following.

The boiler group 2 is composed of, for example, five boilers 20.
In the first embodiment, the boiler 20 is composed of a step value control boiler. A step-value control boiler controls the amount of combustion by selectively turning combustion on and off, adjusting the size of the flame, etc., and gradually increasing or decreasing the amount of combustion according to the selected combustion position. It is a possible boiler. The stage value control boiler is a boiler whose combustion position can be sufficiently secured with respect to the proportional control boiler in terms of equipment structure and cost.

The combustion amount at each combustion position is set so as to generate an amount of steam corresponding to the pressure difference of the steam pressure (control target) in the steam header 6 to be controlled.
The five boilers 20 composed of stage value control boilers are set to have the same combustion amount and combustion capacity (combustion amount in a high combustion state) at each combustion position.

Stage value control boiler
1) Combustion stopped state (first combustion position: 0%)
2) Low combustion state EL (second combustion position: 20%)
3) Medium combustion state EM (third combustion position: 45%)
4) High combustion state EH (4th combustion position: 100%)
The so-called four-position control is made possible to control the combustion state in four stages (combustion position, load factor).
The N position control means that the combustion amount of the step value control boiler can be controlled stepwise to the N position including the combustion stop state.

  The combustion amount control unit 4 relates to the combustion amount of the boiler 20 based on the steam pressure P inside the steam header 6 measured by the steam pressure measuring unit 7, the feed water temperature T measured by the feed water temperature measuring unit 50, and the like. A combustion mode is set as a mode, and the combustion amount of each of the plurality of boilers 20 is controlled.

  The combustion amount control unit 4 includes an input unit 4A, a calculation unit 4B, a database 4D, and an output unit 4E. The combustion amount control unit 4 calculates the required combustion amount GN of the boiler group 2 and the combustion state of each boiler corresponding to the required combustion amount GN in the calculation unit 4B based on the required load input from the input unit 4A, A control signal is output from the output unit 4E to each boiler to control the combustion of the boiler 20.

The input unit 4 </ b> A is connected to the vapor pressure measuring unit 7 through a signal line 13. A signal (steam pressure signal) of the steam pressure P inside the steam header 6 measured by the steam pressure measuring unit 7 is input to the input unit 4A via the signal line 13.
The input unit 4 </ b> A is connected to each boiler 20 by a signal line 14. Information such as the combustion state of each boiler 20, the number of boilers 20 that are burning, the feed water temperature T measured by the feed water temperature measurement unit 50, and the like are input to the input unit 4 </ b> A via the signal line 14. It is like that.

  In the database 4D, for example, the boiler group 2 necessary for adjusting the steam pressure P inside the steam header 6 measured by the steam pressure measuring unit 7 within the allowable range of the set steam pressure (target steam pressure) PT. A required combustion amount GN, an initial value of a feed water temperature threshold Ta described later, a combustion mode M, a table indicating a correspondence relationship between the feed water temperature T and the feed water temperature threshold Ta, and the like are stored.

  The calculation unit 4B performs a predetermined calculation related to the setting of the combustion amount of the boiler 20. Specifically, the calculation unit 4B reads a control program stored in a storage medium (not shown) (for example, a ROM (Read Only Memory)), executes this control program, and the vapor pressure from the vapor pressure measurement unit 7 Based on the signal, the vapor pressure P inside the vapor header 6 is calculated, and the vapor pressure P and the database 4D are made to correspond to each other so that the vapor pressure P is set within the allowable range of the set vapor pressure PT (set values of the upper and lower pressure limits). ) To obtain the required combustion amount GN.

  Specifically, the calculation unit 4B includes a combustion mode setting unit 41 as a combustion mode setting unit and a feed water temperature threshold setting unit 42 as a feed water temperature threshold setting unit.

  The combustion mode setting unit 41 sets the combustion mode M as a mode related to the combustion amount of the boiler 20 based on the feed water temperature T measured by the feed water temperature measuring unit 50. In the first embodiment, the combustion mode M includes a low combustion mode ML as a minimum combustion mode, a medium combustion mode MM as a second combustion mode, and a high combustion mode MH.

The low combustion mode ML is a combustion mode in which the combustion amount of the boiler 20 is the smallest, and is a mode corresponding to the low combustion state EL.
The middle combustion mode MM and the high combustion mode MH are combustion modes in which the combustion amount of the boiler 20 is larger than the combustion amount of the boiler 20 in the low combustion mode MLL. The middle combustion mode MM is a mode corresponding to the middle combustion state EM. The high combustion mode MH is a mode corresponding to the high combustion state EH.
In the first embodiment, the combustion amount of the boiler 20 in the middle combustion mode MM is next to the combustion amount of the boiler 20 in the low combustion mode ML. The combustion amount of the boiler 20 in the high combustion mode MH is next to the combustion amount of the boiler 20 in the medium combustion mode MM.

The feed water temperature threshold setting unit 42 sets a feed water temperature threshold Ta as a threshold for the feed water temperature T based on the combustion mode M set by the combustion mode setting unit 41 and the feed water temperature T measured by the feed water temperature measurement unit 50. To do. The feed water temperature threshold Ta is associated with the combustion mode M and the feed water temperature T by a table stored in the database 4D. Therefore, the feed water temperature threshold setting unit 42 reads the feed water temperature threshold Ta associated with the measured combustion mode M and feed water temperature T with reference to the database 4D. Thereby, the feed water temperature threshold Ta is set.
The feed water temperature threshold Ta is set to be lower as the combustion mode M approaches the lower one, and as the feed water temperature T is lower.

  When the feed water temperature threshold Ta is not set, the feed water temperature threshold setting unit 42 reads the initial value of the feed water temperature threshold Ta with reference to the database 4D. Thus, the water supply temperature threshold Ta is set in advance before being set by the water supply temperature threshold setting unit 42.

Further, when the feed water temperature T measured by the feed water temperature measuring unit 50 is equal to or less than the feed water temperature threshold Ta, the combustion mode setting unit 41 sets the combustion mode M to the low combustion mode ML as the minimum combustion mode.
However, in the first embodiment, when the combustion mode M is the middle combustion mode MM, the feed water temperature T measured by the feed water temperature measuring unit 50 is lower by the differential value Td than the feed water temperature threshold Ta. Only when the temperature becomes equal to or lower than the temperature threshold Tb, the combustion mode setting unit 41 sets the combustion mode M to the low combustion mode ML. The differential value Td is appropriately set and is, for example, 5 to 10 ° C.

When the feed water temperature T measured by the feed water temperature measuring unit 50 exceeds the feed water temperature threshold Ta, the combustion mode setting unit 41 sets the combustion mode M to the middle combustion mode MM as the second combustion mode. .
Further, the combustion mode setting unit 41 determines whether or not the combustion mode M is the middle combustion mode MM, that is, whether or not the combustion mode M is the middle combustion mode MM or the low combustion mode ML.

  The output unit 4 </ b> E is connected to each boiler 20 by the signal line 16. The output unit 4E outputs the combustion control signal calculated by the calculation unit 4B to each boiler 20. The combustion control signal includes the number of boilers that are burning, the combustion state (combustion amount) of the boiler, and the like.

The upstream side of the steam header 6 is connected to the boiler group 2 (each boiler 20) via a steam pipe 11. The downstream side of the steam header 6 is connected to the steam use facility 18 via the steam pipe 12. The steam header 6 adjusts the mutual pressure difference and pressure fluctuation of each boiler 20 by collecting the steam generated in the boiler group 2, and supplies the steam whose pressure is adjusted to the steam using equipment 18. ing.
The steam use facility 18 is a facility operated by steam from the steam header 6.

Next, the details of the configuration of the boiler 20 will be described.
As shown in FIG. 2, the boiler 20 is combusted by communicating a boiler body 21 in which combustion is performed, a discharge unit 25 that discharges combustion gas G4 generated in the boiler body 21, and the boiler body 21 and the discharge unit 25. As a water supply preheater for supplying the feed water W3 to the boiler body 21 after preheating the feed water W1 after preliminarily heating the feed water W1 to W3 to the discharge passage 24 through which the gases G2 to G4 are circulated, the boiler body 21 An economizer 40 and a feed water temperature measuring unit 50 as a feed water temperature measuring means are provided.

  In the boiler body 21, the fuel supplied from the fuel supply unit 22 is burned by a burner (not shown) provided in the boiler body 21, and the combustion gas G <b> 1 generated by this combustion is a can body ( The water inside (not shown) is heated and discharged into the discharge passage 24 as combustion gas G2.

  About combustion gas, what is located in the boiler main body 21 is called "combustion gas G1." The combustion gas G1 discharged from the boiler body 21 and introduced into the discharge path 24 is referred to as “combustion gas G2”. The combustion gas G2 passing through a heat exchanging portion 44 (described later) of the economizer 40 and having a temperature lowered is referred to as “combustion gas G3”. The thing located in the vicinity of the discharge part 25 in the inside of the discharge path 24 is called "combustion gas G4." What is discharged from the discharge unit 25 and diffused and mixed in the atmosphere near the discharge unit 25 is referred to as “combustion gas mixed air (combustion gas) G5”.

  As for the water supply, the water before being distributed to the heat exchanging unit 44 of the economizer 40 is referred to as “water supply W1”, and the water after being heated in the heat exchanging unit 44 is referred to as “water supply W2”, which is supplied to the boiler body 21. The water just before the water supply is called “water supply W3”.

  The combustion gas is a concept including at least one of a fuel gas that has undergone a combustion reaction and a fuel gas that is undergoing the combustion reaction. Combustion gas is generated from the boiler main body 21 and is present in the boiler main body 21. The combustion gas is discharged from the discharge unit 25 and mixed with the atmosphere. Even those existing in the vicinity of are included. The fuel is made of, for example, a fuel gas obtained by mixing raw gas and combustion air. Instead of fuel gas, liquid fuel such as heavy oil may be used as the fuel.

  The fuel supply unit 22 includes, for example, a blower fan (not shown) that supplies combustion air, and a nozzle (not shown) that supplies raw gas to the combustion air. The fuel supply unit 22 burns fuel gas, in which combustion air blown from a blower fan and raw gas supplied from a nozzle are mixed, with a burner.

The discharge path 24 is a passage for transferring the combustion gas G2 generated by combustion in the boiler body 21 from the boiler body 21 to the discharge unit 25 and discharging it into the atmosphere.
The discharge path 24 has a descending circulation part 24D as a circulation part extending in the vertical direction at least in part. In the downward circulation part 24D, the combustion gases G2, G3 descend and flow downward from above.

  In detail, the discharge path 24 is connected to the terminal side of the boiler body 21, and is connected to the first horizontal circulation part 24A and the first horizontal circulation part 24A formed in the horizontal direction in a side view. And a first upward circulation part 24B extending upward, a second horizontal circulation part 24C connected to the first upward circulation part 24B and extending in the horizontal direction, and connected to the second horizontal circulation part 24C and downward. A downward circulation part 24D extending, a third horizontal circulation part 24E connected to the downward circulation part 24D and extending in the horizontal direction, and a second upward circulation part 24F connected to the third horizontal circulation part 24E and extending upward It is equipped with.

  The discharge part 25 is formed at the end of the second ascending flow part 24F and opens to the atmosphere.

The economizer 40 includes an air passage 46 through which the combustion gas G2 passes and a heat exchange unit 44 that contacts the combustion gas G2 and exchanges heat.
The ventilation path 46 is configured by a descending flow part 24 </ b> D of the discharge path 24.

The heat exchanging part 44 is arranged in the descending circulation part 24D, and the feed water W1 supplied to the boiler body 21 circulates. The economizer 40 preheats the feed water W1 in the heat exchanging part 44 with the combustion gas G2 discharged from the boiler body 21 and flowing through the descending circulation part 24D, and then supplies the feed waters W2 and W3 to the boiler body 21.
For example, the heat exchanging unit 44 can recover the sensible heat of the combustion gas G2 or recover the latent heat of the combustion gas G2 to condense the water vapor contained in the combustion gas G2 and recover it as water. ing.

Next, the operation of the economizer 40 will be described.
1) The combustion gas G1 generated by the combustion of fuel in the boiler body 21 is heated to the water in the can of the boiler body 21 and then discharged to the discharge passage 24 to become the combustion gas G2.
2) The combustion gas G <b> 2 that has moved to the discharge path 24 passes through the heat exchange unit 44 that is disposed in the descending flow part 24 </ b> D of the discharge path 24. The water inside the heat exchanging unit 44 is heated by the sensible heat of the combustion gas G2, and the temperature of the combustion gas G2 decreases. Further, the water vapor contained in the combustion gas G2 is condensed and separated as water, and the temperature of the combustion gas G2 is reduced to a state of the combustion gas G3.
3) The combustion gas G3 (G4) whose temperature has decreased via the heat exchanging section 44 is mixed with the atmosphere in the vicinity of the discharge section 25 to become the combustion gas mixed air G5.
Thus, since the heat exchanging part 44 is arranged in the descending flow part 24D, the moisture (drain water) condensed in the heat exchanging part 44 can be easily recovered below the heat exchanging part 44.

  The water supply device 30 is a device that supplies water to the boiler body 21 via the economizer 40. The water supply device 30 includes a water supply tank (not shown), a first water supply line 31, a heat exchange unit 44, a second water supply line 32, and a water supply pump 33.

The first water supply line 31 connects the water supply tank and the lower end of the heat exchange unit 44, and distributes the water supply W <b> 1 stored in the water supply tank to the lower end of the heat exchange unit 44.
The 2nd water supply line 32 connects the upper end part of the heat exchange part 44, and the lower header (not shown) of the boiler main body 21, and supplies the water supply W2 which passed the heat exchange part 44 to the said lower pipe of the boiler main body 21 Make it available for distribution.
The water supply pump 33 is provided in the middle of the 1st water supply line 31, and sends out the water supply W1 located in the 1st water supply line 31 to the downstream (boiler main body 21 side).

  The feed water temperature measurement unit 50 is connected to the vicinity of the heat exchange unit 44 in the first feed water line 31 and measures the feed water temperature T that is the temperature of the feed water W <b> 1 before flowing through the heat exchange unit 44.

Next, among the functions of the combustion amount control unit 4, functions related to control of the combustion amounts of the plurality of boilers 20 based on the feed water temperature T measured by the feed water temperature measurement unit 50 will be described.
In the combustion amount control unit 4, a water supply temperature threshold Ta is set as a threshold for the water supply temperature T.
For example, the water supply temperature threshold Ta is preferably in the range of 40 ° C. or higher, and can be appropriately set in the range of 40 to 50 ° C. (for example, 45 ° C.). , Can be set to any range. When the feed water temperature threshold Ta in the first embodiment is 45 ° C., the feed water temperature threshold Ta is a temperature near the dew point of the combustion gas in the first embodiment.

In the first embodiment, the heat dissipation loss of the boiler 20 is preferably 1% or less, and more preferably 0.6% or less.
The “heat dissipation loss” here is the total amount of heat dissipation loss from the boiler 20, for example, loss from combustion gas (exhaust gas), loss from the boiler body 21, loss from the discharge path 24, fuel non-combustion component Loss due to incomplete combustion gas, drainage from each part, loss due to leakage of steam or hot water, etc.
When the heat dissipation loss of the boiler 20 is 1% or less, the tendency (described later) that the boiler efficiency gradually increases as the boiler load factor decreases as shown in FIG.

In the first embodiment, the boiler (instantaneous) efficiency of the boiler 20 is preferably 96% or more, and more preferably 97%.
Here, “boiler efficiency” means the ratio of the total absorbed heat amount of the output steam to the total supplied heat amount, and is the instantaneous efficiency (design efficiency) at 100% load.
When the boiler efficiency is 96% or more, a tendency (described later) that the boiler efficiency gradually increases as the boiler load factor as shown in FIG. 3 decreases.

  As in the boiler system 1 in the first embodiment, a configuration in which the heat exchanging portion 44 of the economizer 40 is arranged in the descending circulation portion 24D where the combustion gases G2, G3 descend downward from above (downflow type) In this case, the dew condensation water (drain water) generated in the upper part of the heat exchanging part 44 flows in the same direction as the descending combustion gas, and improves the latent heat recovery effect by the condensation effect.

In accordance with the feed water temperature T, the combustion conditions of the boiler 20 at which the boiler efficiency becomes maximum change. For example, the degree to which the temperature of the combustion gas decreases differs depending on the feed water temperature T, and the ease of generating condensed water (drain water) differs.
Therefore, in the first embodiment, the combustion amount control unit 4 controls the combustion amount of each of the plurality of boilers 20 based on the feed water temperature T measured by the feed water temperature measurement unit 50.

Specifically, when the feed water temperature T measured by the feed water temperature measuring unit 50 is equal to or lower than the feed water temperature threshold Ta, the combustion amount control unit 4 sets the combustion amount of each of the plurality of boilers 20 to the smallest.
When the feed water temperature measured by the feed water temperature measurement unit 50 is 5 to 35 ° C., the combustion amount control unit 4 preferably sets the combustion amount of the boiler 20 to 5 to 35% of the maximum combustion amount. . For example, when the feed water temperature measured by the feed water temperature measuring unit 50 is 10 to 20 ° C., the combustion amount control unit 4 sets the combustion amount of the boiler 20 to 10 to 20% of the maximum combustion amount. Specifically, when feed water having a feed water temperature T of 15 ° C. (ordinary temperature) is supplied and combustion gas G 2 having a temperature of about 350 ° C. is introduced into the heat exchange unit 44, the combustion amount control unit 4 includes a plurality of combustion amount control units 4. The combustion amount of each boiler 20 is set to the smallest. In the first embodiment, the smallest combustion amount is the low combustion state EL (second combustion position: 20%). Therefore, in the first embodiment, the combustion amount control unit 4 sets the combustion state of the boiler 20 to the low combustion state EL (second combustion position: 20%).

The combustion amount in the case of “setting the combustion amount of the boiler 20 to be the smallest” does not include, for example, the combustion amount in pilot combustion (including continuous pilot combustion) and purge (including light wind purge).
Pilot combustion is combustion that is smaller than low combustion in a gas-fired boiler and does not increase the vapor pressure. Pilot combustion maintains a pilot-fired state (continuous pilot combustion state) with a pilot burner, thereby enabling a quick transition when it is desired to increase the combustion amount to a combustion state of low combustion or higher. .
In the oil-fired boiler, the slight wind purge is used to reduce the blower rotation speed so that unburned gas does not stay in the can so that it can be ignited as soon as a combustion signal is output. It means to maintain the air blowing state.

If pilot combustion and light wind purge are not set, heat dissipation loss due to pre-purge increases, which disadvantageously reduces boiler efficiency. The reason is that the boiler is temporarily stopped and the boiler is restarted, so that it is necessary to start combustion after pre-purging the inside of the boiler can.
The pre-purge is a process of automatically turning the blower before ignition of the boiler, sending the wind into the combustion chamber, and expelling the gas remaining in the combustion chamber to the outside.

The reason for setting in this way is as follows. FIG. 3 is a graph showing the relationship between the load factor and the boiler efficiency when the feed water temperature is 15 ° C.
When the feed water temperature T is low (15 ° C.) (when the feed water temperature T is much lower than the dew point of the combustion gas), the temperature of the combustion gas G2 is greatly reduced. A lot of drain water) is likely to occur. Further, the lower the load factor, the smaller the latent heat loss of the combustion gas (exhaust gas). Due to these factors, as shown in FIG. 3, the boiler efficiency tends to gradually increase as the boiler load factor decreases. Moreover, if the amount of combustion is made as small as possible, the temperature of the combustion gas G3 after circulating the economizer 40 can be reduced. Therefore, the combustion amount control unit 4 sets the combustion state of the boiler 20 to the low combustion state EL (second combustion position: 20%).

On the other hand, when the feed water temperature T measured by the feed water temperature measurement unit 50 exceeds the feed water temperature threshold Ta, the combustion amount control unit 4 preferably sets the combustion amount of each of the boilers 20 to 40% of the maximum combustion amount. For example, 40% to 70% is set.
Specifically, when hot water supply water having a water supply temperature T of 45 ° C. is supplied and combustion gas G 2 of about 350 ° C. is introduced into the heat exchange unit 44, the combustion amount control unit 4 includes a plurality of combustion amount control units 4. The combustion amount of each boiler 20 is set to 40 to 70% of the maximum combustion amount. In the first embodiment, the middle combustion state EM (third combustion position: 45%) corresponds to 40 to 70% of the maximum combustion amount. Therefore, in the first embodiment, the combustion state of the boiler 20 is set to the middle combustion state EM (third combustion position: 45%).

The reason for setting in this way is as follows. FIG. 4 is a graph showing the relationship between the load factor and boiler efficiency when the feed water temperature is 45 ° C.
When the feed water temperature T is high (45 ° C.) (close to the dew point of the combustion gas), the lower the load factor, the greater the effect of heat dissipation loss, while the higher the load factor, the latent heat loss of the combustion gas (exhaust gas). Becomes larger. Due to these factors, as shown in FIG. 4, when the combustion state of the boiler having an intermediate load factor is the middle combustion state EM (third combustion position: 45%), the boiler efficiency becomes maximum (peak). Therefore, the combustion amount control unit 4 sets the combustion state of the boiler 20 to the middle combustion state EM (third combustion position: 45%).

In addition, the combustion amount control unit 4 controls the combustion amount of each of the plurality of boilers 20 so that the number of boilers 20 to be burned with the set combustion amount is increased one by one.
For example, when the combustion state of the boiler 20 is set to the low combustion state EL (second combustion position: 20%), the combustion amount control unit 4 first sets one boiler 20 to the low combustion state EL (second combustion state). Burn at position: 20%). In the combustion of one boiler 20, when the amount of steam (necessary steam amount) to be generated by the boiler system 1 is insufficient, the second boiler 20 is placed in a low combustion state EL (second combustion position: 20%). Burn with. The boiler 20 to be burned in the low combustion state EL (second combustion position: 20%) is increased until the necessary steam amount is obtained. If the required steam amount cannot be obtained even if all the boilers 20 are burned in the low combustion state EL (second combustion position: 20%), the combustion state of one boiler 20 is changed to the middle combustion state EM (third Combustion position: 45%). Thereafter, the boiler 20 to be burned in the middle combustion state EM (third combustion position: 45%) is increased until the necessary steam amount is obtained.

Even when the combustion state of the boiler 20 is set to the middle combustion state EM (third combustion position: 45%) from the beginning, the control is performed in the same manner as described above.
Note that a plurality of boilers 20 to be burned at a set combustion amount may be increased at a time.

  Next, in the boiler system 1 of 1st Embodiment, control of the combustion amount of the boiler 20 based on the feed water temperature T which is the temperature of the feed water W1 before distribute | circulating to the heat exchange part 44 is demonstrated, referring FIG. . FIG. 5 is a flowchart showing the operation of the boiler system 1 according to the first embodiment.

  As shown in FIG. 5, in step ST <b> 11, the feed water temperature measurement unit 50 measures the feed water temperature T that is the temperature of the feed water W <b> 1 before flowing into the heat exchange unit 44. Information on the feed water temperature T measured by the feed water temperature measurement unit 50 is input to the calculation unit 4B via the input unit 4A of the combustion amount control unit 4.

  In step ST12, the water supply temperature threshold Ta is set in advance. Specifically, the feed water temperature threshold setting unit 42 of the calculation unit 4B of the combustion amount control unit 4 reads the initial value of the feed water temperature threshold Ta from the database 4D. Thereby, the feed water temperature threshold Ta is set in advance.

  In step ST13, the combustion mode setting unit 41 of the calculation unit 4B of the combustion amount control unit 4 determines whether or not the feed water temperature T is equal to or lower than the feed water temperature threshold Ta. If the feed water temperature T is equal to or lower than the feed water temperature threshold Ta (YES), the process proceeds to step ST14. If the feed water temperature T exceeds the feed water temperature threshold Ta (NO), the process proceeds to step ST15.

  When the feed water temperature T is equal to or lower than the feed water temperature threshold Ta (YES), the boiler efficiency can be maximized by setting the combustion amount of each of the plurality of boilers 20 to the smallest. In the first embodiment, the smallest combustion amount is the low combustion state EL (second combustion position: 20%). Therefore, in step ST14, the combustion mode setting unit 41 sets the combustion mode M of each of the plurality of boilers 20 to the low combustion mode ML, and sets the combustion amount to the low combustion state EL (second combustion position: 20%). To do.

  On the other hand, when the feed water temperature T exceeds the feed water temperature threshold Ta (NO), for example, if the combustion amount of each of the plurality of boilers 20 is set to 40 to 70% of the maximum combustion amount, the boiler efficiency is maximized. Can be high. In the first embodiment, the middle combustion state EM (third combustion position: 45%) corresponds to 40 to 70% of the maximum combustion amount. Therefore, in step ST15, the combustion mode setting unit 41 sets the combustion mode M of each of the plurality of boilers 20 to the middle combustion mode MM, and sets the combustion amount to the middle combustion state EM (third combustion position: 45%). To do.

  After step ST14 or step ST15, the combustion amount of the boiler 20 is controlled by the combustion amount control unit 4 based on the steam pressure P or the like inside the steam header 6 measured by the steam pressure measurement unit 7.

  Next, in step ST <b> 21, the feed water temperature measurement unit 50 measures the feed water temperature T that is the temperature of the feed water W <b> 1 before flowing into the heat exchange unit 44. Information on the feed water temperature T measured by the feed water temperature measurement unit 50 is input to the calculation unit 4B via the input unit 4A of the combustion amount control unit 4. The measurement of the feed water temperature T in step ST21 is for comparing the magnitude of the feed water temperature T and the feed water temperature threshold Ta, and for resetting the feed water temperature threshold Ta in the next step, step ST22.

  In step ST22, the feed water temperature threshold setting unit 42 sets the feed water temperature threshold Ta based on the combustion mode M set by the combustion mode setting unit 41 and the feed water temperature T measured by the feed water temperature measurement unit 50. The feed water temperature threshold setting unit 42 reads the feed water temperature threshold Ta associated with the measured combustion mode M and feed water temperature T with reference to the database 4D. Thereby, the feed water temperature threshold Ta is set.

In step ST24, the combustion mode setting unit 41 determines whether or not the feed water temperature T measured by the feed water temperature measurement unit 50 is equal to or lower than a second temperature threshold Tb that is lower than the feed water temperature threshold Ta by the differential value Td. To do. If the feed water temperature T is equal to or lower than the second temperature threshold Tb (YES), the process proceeds to step ST26. If the feed water temperature T exceeds the second temperature threshold Tb (NO), the process proceeds to step ST27.
In step ST24, frequent switching (hunting) of the combustion mode M can be suppressed by setting the differential value Td to the feed water temperature threshold Ta.

In step ST26, the combustion mode setting unit 41 sets the combustion mode M to the low combustion mode ML.
On the other hand, in step ST27, the combustion mode setting unit 41 sets the combustion mode M to the middle combustion mode MM.
After step ST26 or step ST27, the process returns to step ST21. In step ST21, the feed water temperature T is measured again, and in step ST22, the feed water temperature threshold Ta is set again. Thereafter, steps ST24 to ST27 are executed again.

Next, specific examples (a first specific example and a second specific example) of controlling the combustion amount will be described with reference to FIGS. 6 and 7. FIG. 6 is a drawing showing a first specific example relating to the control of the combustion amount of the boiler. FIG. 7 is a drawing showing a second specific example relating to the control of the combustion amount of the boiler.
In this specific example, the following conditions are assumed. As shown in FIG.6 and FIG.7, the boiler system is comprised from four boilers (NO.1-NO.4). The steam generation capacity of one boiler is 2 t / h, and the required steam amount is 2 t. The steam generation capacity of the boiler when set to the low combustion state EL (second combustion position: 20%) is 400 kg / h. The steam generation capacity of the boiler when it is set to the middle combustion state EM (third combustion position: 45%) is 1 t / h.

Under the above conditions, when feed water having a feed water temperature T of 15 ° C. (normal temperature) is supplied and combustion gas having a temperature of about 350 ° C. is introduced into the heat exchange section, four boilers are used as shown in FIG. For all, the combustion amount is set to a low combustion state EL (second combustion position: 20%). Since there are four boilers with a steam generation capacity of 400 kg / h, the steam generation capacity of the entire boiler system is 1.6 t / h, which is close to the required steam volume.
By controlling the combustion amount in this way, the boiler efficiency can be maximized.

Further, under the above conditions, when hot water having a feed water temperature T of 45 ° C. is supplied and combustion gas having a temperature of about 350 ° C. is introduced into the heat exchange section, as shown in FIG. Of the boilers, only two boilers (NO.1, NO.2) set the combustion amount to the middle combustion state EM (third combustion position: 45%). The other two boilers (NO.3, NO.4) are in a combustion stopped state. Since there are two boilers having a steam generation capacity of 1 t / h, the steam generation capacity of the entire boiler system is 2 t / h, which is the same as the required steam amount.
By controlling the combustion amount in this way, the boiler efficiency can be maximized.

According to the boiler system 1 of the first embodiment, for example, the following effects are produced.
In the first embodiment, the combustion amount control unit 4 is set by a combustion mode setting unit 41 that sets the combustion mode M based on the feed water temperature T measured by the feed water temperature measurement unit 50 and the combustion mode setting unit 41. A feed water temperature threshold setting unit 42 for setting a feed water temperature threshold Ta based on the feed water temperature T measured by the combustion mode M and the feed water temperature measuring unit 50, and the feed water temperature measured by the feed water temperature measuring unit 50 When T is equal to or lower than the feed water temperature threshold Ta, the combustion mode setting unit 41 sets the combustion mode M to the low combustion mode ML that is the minimum combustion mode.

Therefore, according to the first embodiment, it is possible to appropriately change the combustion mode M, appropriately increase or decrease the combustion amount, and further improve boiler efficiency.
For example, when the feed water temperature threshold Ta is set to an average fixed value without dynamically changing based on the feed water temperature T, the feed water temperature threshold Ta is generally stable when the boiler system 1 is operated. Then, the hot drain water is supplied as a part of the water supply, and is set in accordance with the increase of the water supply temperature T. On the other hand, generally, in the morning when the boiler system 1 is started and the first combustion of the boiler 20 is performed in one day, there is no drain water and the feed water temperature T is low. Therefore, in the morning, the water supply temperature threshold Ta is too high for the low water supply temperature T, which is inefficient in terms of boiler efficiency.

  However, in the first embodiment, the feed water temperature threshold setting unit 42 is based on the combustion mode M set by the combustion mode setting unit 41 and the feed water temperature T measured by the feed water temperature measurement unit 50. Set. Therefore, since the feed water temperature threshold Ta suitable for the feed water temperature T can be set, the combustion mode M is appropriately changed, the combustion amount is appropriately increased / decreased, the boiler efficiency is further improved, and the fuel cost is further suppressed. can do.

  In the first embodiment, when the combustion mode M is the middle combustion mode MM, the feed water temperature T measured by the feed water temperature measuring unit 50 is lower than the feed water temperature threshold Ta by the differential value Td. Only when the temperature becomes equal to or lower than the temperature threshold Tb, the combustion mode setting unit 41 sets the combustion mode M to the low combustion mode ML. Therefore, according to the first embodiment, compared to the case where the differential value Td is not set, the combustion mode setting unit 41 can be suppressed from setting the combustion mode M to the low combustion mode ML. Switching (hunting) can be suppressed.

  Moreover, in the boiler system 1 of 1st Embodiment, the boiler 20 is the discharge path 24 which connects the boiler main body 21 and the discharge part 25, and distribute | circulates the combustion gas G2-G4, Comprising: Up-down direction is carried out to one part. A discharge gas 24 having a downward circulation part 24D extending to the bottom, and a heat exchange part 44 that is disposed in the downward circulation part 24D and through which the feed water W1 supplied to the boiler body 21 circulates, and flows through the downward circulation part 24D And an economizer 40 that supplies the water supply W3 to the boiler body 21 after the water supply W1 is preheated in the heat exchanging unit 44 by G2. The feed water temperature measurement unit 50 measures the temperature of the feed water W <b> 1 flowing through the heat exchange unit 44 as the feed water temperature T.

  Therefore, according to 1st Embodiment, in order to control the combustion amount of each of the several boilers 20 based on the feed water temperature T which is the temperature of the feed water W1 before distribute | circulating to the heat exchange part 44, the heat loss of the boiler 20 is reduced. It is easy to set the boiler efficiency of the boiler 20 to 96% or more. Therefore, according to the first embodiment, the heat dissipation loss of the boiler 20 can be reduced and the boiler efficiency can be improved.

  Next, a second embodiment of the present invention will be described. The second embodiment will be described mainly focusing on differences from the first embodiment. For the points not particularly described in the second embodiment, the description of the first embodiment is applied as appropriate. Also in the second embodiment, the same effects as in the first embodiment are achieved.

[Second Embodiment]
Next, a second embodiment will be described. In the first embodiment, in order to suppress frequent switching (hunting) of the combustion mode M, the differential value Td is set to the feed water temperature threshold Ta. In contrast, in the second embodiment, in order to suppress frequent switching (hunting) of the combustion mode M, instead of setting the differential value Td to the feed water temperature threshold Ta, switching to the combustion mode M is performed. Delay times Te and Tf are set.

In the second embodiment, when the combustion mode M is the middle combustion mode MM, the state where the feed water temperature T measured by the feed water temperature measuring unit 50 is equal to or lower than the feed water temperature threshold Ta continues for a predetermined time (delay time Te). Only occasionally, the combustion mode setting unit 41 sets the combustion mode M to the low combustion mode ML.
Further, the combustion mode setting unit 41 sets the combustion mode M to the middle combustion mode only when the state where the feed water temperature T measured by the feed water temperature measurement unit 50 exceeds the feed water temperature threshold Ta continues for a predetermined time (delay time Tf). Set to MM.

  The delay time Te and the delay time Tf may be the same or different. The delay time Te and the delay time Tf are, for example, 5 to 10 minutes. In the second embodiment, the delay time Te and the delay time Tf are 10 minutes.

  Next, in the boiler system 1 of 2nd Embodiment, control of the combustion amount of the boiler 20 based on the feed water temperature T which is the temperature of the feed water W1 before distribute | circulating to the heat exchange part 44 is demonstrated, referring FIG. . FIG. 8 is a flowchart showing the operation of the boiler system according to the second embodiment.

  In the flowchart in the second embodiment, the processes (steps) up to step ST14 and step ST15 are the same as the processes (steps) up to step ST14 and step ST15 in the flowchart in the first embodiment shown in FIG. Therefore, in the flowchart in the second embodiment, the description of the processes before step ST14 and step ST15 is omitted, and only the processes after step ST31 are described.

  In 2nd Embodiment, after step ST14 or step ST15, in step ST31, the feed water temperature measurement part 50 measures the feed water temperature T which is the temperature of the feed water W1 before distribute | circulating to the heat exchange part 44. FIG. Information on the feed water temperature T measured by the feed water temperature measurement unit 50 is input to the calculation unit 4B via the input unit 4A of the combustion amount control unit 4. The measurement of the feed water temperature T in step ST31 is for comparing the magnitude of the feed water temperature T and the feed water temperature threshold Ta, and for resetting the feed water temperature threshold Ta in the next step, step ST32.

  In step ST <b> 32, the feed water temperature threshold setting unit 42 sets the feed water temperature threshold Ta based on the combustion mode M set by the combustion mode setting unit 41 and the feed water temperature T measured by the feed water temperature measurement unit 50. The feed water temperature threshold setting unit 42 reads the feed water temperature threshold Ta associated with the measured combustion mode M and feed water temperature T with reference to the database 4D. Thereby, the feed water temperature threshold Ta is set.

  In step ST33, the combustion mode setting unit 41 determines whether or not the state where the feed water temperature T measured by the feed water temperature measuring unit 50 is equal to or less than the feed water temperature threshold Ta continues for a predetermined time (delay time Te). When the state where the feed water temperature T is equal to or lower than the feed water temperature threshold Ta continues for a predetermined time (delay time Te) (YES), the process proceeds to step ST34. If the state where the feed water temperature T is equal to or less than the feed water temperature threshold Ta has not continued for a predetermined time (delay time Te) (NO), the process proceeds to step ST35.

  In step ST34, the combustion mode setting unit 41 sets the combustion mode M to the low combustion mode ML.

  In step ST35, the combustion mode setting unit 41 determines whether or not the state where the feed water temperature T measured by the feed water temperature measurement unit 50 exceeds the feed water temperature threshold Ta continues for a predetermined time (delay time Tf). If the state where the feed water temperature T exceeds the feed water temperature threshold Ta continues for a predetermined time (delay time Tf) (YES), the process proceeds to step ST36. If the state where the feed water temperature T exceeds the feed water temperature threshold Ta does not continue for a predetermined time (delay time Tf) (NO), the process returns to step ST31.

In step ST36, the combustion mode setting unit 41 sets the combustion mode M to the middle combustion mode MM.
After step ST34 or step ST36, the process returns to step ST31.

According to the second embodiment, the same effects as those of the first embodiment are achieved.
In the second embodiment, when the combustion mode M is the middle combustion mode MM, the state where the feed water temperature T measured by the feed water temperature measuring unit 50 is equal to or lower than the feed water temperature threshold Ta is a predetermined time (delay time Te). Only when it continues, the combustion mode setting part 41 sets the combustion mode M to the low combustion mode ML. Therefore, according to the second embodiment, the combustion mode setting unit 41 can be suppressed from setting the combustion mode M to the low combustion mode ML as compared with the case where the delay time Te is not set. Switching (hunting) can be suppressed.

  In the second embodiment, only when the state where the feed water temperature T measured by the feed water temperature measurement unit 50 exceeds the feed water temperature threshold Ta continues for a predetermined time (delay time Tf), the combustion mode setting unit 41 The combustion mode M is set to the middle combustion mode MM. Therefore, according to the second embodiment, compared to the case where the delay time Tf is not set, the combustion mode setting unit 41 can be suppressed from setting the combustion mode M to the middle combustion mode MM. Switching (hunting) can be suppressed.

As mentioned above, although preferred embodiment was described, this invention is not limited to embodiment mentioned above, It can implement with a various form.
For example, the feed water temperature threshold setting unit 42 serving as the feed water temperature threshold setting unit sets the feed water temperature threshold Ta based on both the combustion mode M and the feed water temperature T in the present embodiment, but is not limited thereto. . The feed water temperature threshold setting unit 42 may set the feed water temperature threshold Ta based on only one of the combustion mode M and the feed water temperature T.
In the embodiment, the second combustion mode in which the combustion amount of the boiler is larger than the combustion amount of the boiler in the minimum combustion mode (low combustion mode ML) is the middle combustion mode MM, but is not limited to this, and the high combustion mode Mode MH may be used.

  Further, in the embodiment, the circulation part where the heat exchange part 44 is arranged in the discharge path 24 is provided in the descending circulation part 24D in which the combustion gas descends from above to circulate. Not limited to. The circulation part may be provided in an ascending circulation part where the combustion gas rises from below to circulate.

  Moreover, in the said embodiment, as the boiler 20, a combustion stop state (1st combustion position: 0%), a low combustion state EL (2nd combustion position: 20%), a middle combustion state EM (3rd combustion position: 45) %) And high combustion state EH (fourth combustion position: 100%), which uses a four-position control stage value control boiler that can be controlled in four stages of combustion state (combustion position, load factor), but is limited to this. Not.

As a four-position control stage value control boiler, combustion stopped state (first combustion position: 0%), low combustion state EL (second combustion position: 20%), middle combustion state EM (third combustion position: 60%) In addition, a four-position control stage value control boiler that can be controlled to four combustion states (combustion position, load factor) of the high combustion state EH (fourth combustion position: 100%) can be used.
The control of the combustion position in the step value control boiler is not limited to the 4-position control, and may be 3-position control, 5-position control, or the like.

The feed water temperature threshold is preferably 40 ° C. or higher, and preferably 40 to 50 ° C. (for example, 45 ° C.) as an embodiment. can do.
The number of boilers in the boiler system may be one.
In the boiler system, boilers having different steam generation capacities may be provided together (for example, a boiler with a steam generation capability of 2 t / h and a boiler with 3 t / h).

A proportional control boiler can be used instead of the step value control boiler.
The proportional control boiler is capable of continuously controlling the combustion amount in the range of 0% (no combustion) to 100% (maximum combustion amount) with respect to the combustion capacity (combustion amount in the maximum combustion state), For example, it is adjusted by controlling the opening degree (combustion ratio) of the proportional control valve.
The combustion amount of the proportional control boiler is obtained by the product of the combustion capacity of the proportional control boiler and the valve opening (combustion ratio).

Continuously controlling the combustion amount in the proportional control boiler is not only when the combustion amount is controlled without permission, but also when the calculation and signal in the control unit are handled digitally and handled in stages, For example, the amount of control by a control mechanism such as a valve is set to a smaller value (for example, 1% or less) than the fluctuation of the combustion amount due to variations in combustion air, fuel gas, etc., and is controlled continuously in practice. Shall be included.
The present invention can also be applied to gas-fired boilers and oil-fired boilers.

1 Boiler system 4 Combustion amount control section (combustion amount control means)
20 Boiler 21 Boiler body 24 Discharge path 24D Downflow distribution section (distribution section)
25 Discharge unit 40 Economizer (Water supply preheater)
41 Combustion mode setting unit (combustion mode setting means)
42 Water supply temperature threshold setting unit (water supply temperature threshold setting means)
44 Heat exchange part 50 Feed water temperature measuring part (feed water temperature measuring means)
G1, G2, G3, G4 Combustion gas W1, W2, W3 Water supply

Claims (5)

A boiler system comprising a boiler and a combustion amount control means for controlling a combustion amount of the boiler,
The boiler is
A boiler body in which combustion is performed, and a feed water temperature measuring means for measuring a feed water temperature which is a feed water temperature supplied to the boiler body,
The combustion amount control means includes
Combustion mode setting means for setting a combustion mode as a mode related to the combustion amount of the boiler based on the feed water temperature measured by the feed water temperature measuring means;
Supply water temperature threshold setting means for setting a feed water temperature threshold as a threshold related to the feed water temperature based on the combustion mode set by the combustion mode setting means and / or the feed water temperature measured by the feed water temperature measuring means. And
When the feed water temperature measured by the feed water temperature measuring means is less than or equal to the feed water temperature threshold, the combustion mode setting means sets the combustion mode to the minimum combustion mode with the smallest combustion amount of the boiler ,
When the feed water temperature measured by the feed water temperature measuring unit exceeds the feed water temperature threshold, the combustion mode setting unit sets the combustion mode, and the combustion amount of the boiler is greater than the combustion amount of the boiler in the minimum combustion mode. Is set to a larger second combustion mode,
When the combustion mode is the second combustion mode, only when the feed water temperature measured by the feed water temperature measuring means is equal to or lower than the second temperature threshold value which is lower than the feed water temperature threshold value by a differential value. The combustion mode setting means is a boiler system that sets the combustion mode to the minimum combustion mode . In the case where the combustion mode is the second combustion mode, the combustion mode setting means is configured so that the combustion mode setting means can The boiler system according to claim 1 , wherein is set to the minimum combustion mode. The boiler system according to claim 1 or 2 , wherein the feed water temperature threshold is set in advance before being set by the feed water temperature threshold setting means. The boiler is
A discharge unit for discharging combustion gas generated in the boiler body;
An exhaust path that allows the combustion gas to flow through the boiler body and the exhaust section, the exhaust path having a flow section extending in the vertical direction at least at a part thereof,
It has a heat exchange part which distributes the feed water which is arranged in the circulation part and is supplied to the boiler body, and after heating water in the heat exchange part beforehand with combustion gas which circulates through the circulation part, A feed water preheater for supplying to the boiler body,
The boiler system according to any one of claims 1 to 3 , wherein the feed water temperature measuring unit measures a temperature of feed water flowing through the heat exchange unit as the feed water temperature. The boiler system in any one of Claims 1-4 provided with two or more of the said boilers.

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