JP6424725B2 - Boiler system - Google Patents

Description

  The present invention relates to a boiler system in which a plurality of boiler groups are mixed, which includes a first boiler group having one or more boilers and a second boiler group having one or more boilers not belonging to the first boiler group.

  In a boiler system that collects steam generated in a boiler group consisting of a plurality of boilers in a steam header and supplies steam from the steam header to a load device, the boiler group is roughly divided into two types, and these are controlled Boiler systems are known. For example, Patent Document 1 roughly divides into an eco-operation boiler group in which the boiler group is burned at a combustion rate at which the boiler efficiency increases, and a load following boiler group in which the combustion rate is changed and burned according to the fluctuation of required load. It has been described that.

  Conventionally, when two types of boiler groups are individually subjected to target pressure value control, usually, one boiler group is mainly burned (hereinafter, also referred to as "first boiler group") and the other boiler group is Is generally burned to compensate for the shortfall (hereinafter, also referred to as "second boiler group").

  For example, each boiler belonging to the first boiler group, as a waste heat recovery boiler, is a control in which an in-can pressure value (hereinafter also referred to as "in-can pressure value") which is a pressure value in a can of the boiler is preset. The amount of heat recovery is controlled so as to be within the range of the pressure zone, and the boilers belonging to the second boiler group have steam pressure values inside a steam header where steam generated in a plurality of When the combustion state is controlled so that the header pressure value becomes “a target pressure value set in advance” and the two boiler groups are individually controlled, the target pressure value of the second boiler group is It is preferable to set the value lower than the upper limit value of the control pressure band of the in-can pressure value of the group of boilers.

By doing so, when the overall load is low, the in-can pressure of each boiler of the first boiler group is stabilized at a pressure value higher than the target pressure value of the second boiler group, and the header pressure value is It becomes stable in the vicinity of the pressure value calculated taking into consideration the pressure loss in the steam pipe of each boiler of the first boiler group.
Then, the header pressure value of the second boiler group largely exceeds the target pressure value preset in itself, so the combustion amount of the second boiler group is basically zero.

Unexamined-Japanese-Patent No. 2014-98529

In this case, load deviation occurs in the boiler group. As a result, for example, when the overall load is low and the overall required amount is satisfied by the first boiler group, the boilers of the second boiler group may be stopped in combustion, and all the units may be on standby. In this case, there is a risk of boiler can corrosion due to low load. In addition, since the load deviation between the boiler groups is too large, there is also a problem that the boiler load becomes uneven.
For this reason, even when the target pressure value of the header pressure value of the second boiler group is set to a value smaller than the upper limit value of the control pressure band of the in-can pressure value of the boiler of the first boiler group, It is desirable to burn the boilers of the second boiler group to some extent.

  The present invention includes a boiler group including a first boiler group including one or more waste heat recovery boilers and a second boiler group including one or more boilers, and each waste heat recovery boiler belonging to the first boiler group Each of the boilers belonging to the second boiler group has a header pressure value equal to a preset target pressure value so that the in-can pressure value falls within the preset control pressure zone. In a boiler system in which one boiler group is controlled individually and the target pressure value of the second boiler group is set to a value smaller than the upper limit value of the control pressure band of the in-can pressure value of the boilers of the first boiler group The boilers of the boiler group can be easily burned to correct the load non-uniformity among the boiler groups, and a combustion amount of a predetermined amount or more can be secured for the second boiler group regardless of the amount of steam used. Providing a boiler system For the purpose.

  The present invention combines a boiler group comprising a first boiler group comprising one or more waste heat recovery boilers, a second boiler group comprising one or more auxiliary boilers, and steam generated in the boiler group A boiler system comprising: a steam header to be controlled; steam pressure measuring means for measuring a header pressure value which is steam pressure inside the steam header; and a control unit for controlling a combustion state of the second boiler group, In the waste heat recovery boiler belonging to the first boiler group, an in-can pressure measuring means for measuring an in-can pressure value, which is a pressure value in the can body of the waste heat recovery boiler, and the in-can pressure value are preset. And a local control unit for controlling the heat recovery amount of the first boiler group so as to fall within the range of the control pressure zone, wherein the control unit controls the header pressure value measured by the vapor pressure measuring unit, Preset Calculated by the required steam volume calculation unit that calculates the required steam volume by the PI algorithm or PID algorithm so as to match the target pressure value that is smaller than the upper limit value of the control pressure zone, and the required steam volume calculation unit When the required amount of steam is less than the preset first amount of steam, the first amount of steam is output, and when the required amount of steam is equal to or more than the first amount of steam, the required amount of steam is output. And a power control unit configured to control a combustion state of the second boiler group.

  The output control unit may burn the number of auxiliary boilers set in advance in the second boiler group at a predetermined fixed combustion rate when outputting the first amount of steam.

  Further, the fixed combustion rate can be set to the highest combustion rate of the combustion efficiency of the auxiliary boiler to be burned.

  Further, the fixed combustion rate can be a minimum combustion rate of the auxiliary boiler to be burned.

  Further, the target pressure value may be smaller than an intermediate value between the upper limit value and the lower limit value of the control pressure band, and may be equal to or higher than the lower limit value of the control pressure band.

  The target pressure value may be smaller than the lower limit value of the control pressure zone.

  According to the boiler system of the present invention, the first boiler group is provided with the first boiler group including the one or more waste heat recovery boilers and the second boiler group including the one or more auxiliary boilers. In each of the waste heat recovery boilers to which the boiler belongs, the boilers belonging to the second boiler group have target pressure values for which header pressure values are preset so that the in-can pressure value falls within the range of the control pressure zone set in advance. The two boiler groups are individually controlled so that the target pressure value of the second boiler group is set to a value smaller than the upper limit value of the control pressure zone of the in-can pressure value of the boilers of the first boiler group. In the boiler system, even if the overall load is low, the second boiler group can be burned by a fixed amount, so that load unevenness among the boiler groups can be corrected and the overall load is low. Praise the overall need Even when the boiler of the second boiler unit does not become Zendai standby, thereby preventing the boiler body corrosion caused by low load, it is possible to improve the load non-uniformity between the boiler group.

It is a figure showing an outline of boiler system 1 concerning a 1st embodiment of the present invention. It is a figure which shows the outline of a boiler group. It is a functional block diagram showing composition of control part 4B. It is a flow chart which shows operation of boiler system 1 concerning a 1st embodiment. It is a flow chart which shows operation of boiler system 1 concerning a 1st embodiment. It is a figure which shows transition of the amount of vapor | steam generated in the 1st boiler group and the 2nd boiler group in, when conventional control is implemented. It is a figure which shows transition of the amount of generated steam in the 1st boiler group and the 2nd boiler group in, when control concerning a 1st embodiment is carried out.

First Embodiment
Hereinafter, a boiler system 1 according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a boiler system 1.

  As shown in FIG. 1, the boiler system 1 includes a boiler group 2 including a first boiler group 2A including one boiler 20A, and a second boiler group 2B including two boilers 20B, and a plurality of boilers 20A. And 20B, the steam pressure sensor 7 for measuring the pressure inside the steam header 6 (hereinafter also referred to as "header pressure"), and the combustion state of the second boiler group 2B. And a number control device 3B having a control unit 4B to control. The steam pressure value inside the steam header 6 measured by the steam pressure sensor 7 is hereinafter also referred to as "header pressure value PV".

The boiler group 2 generates steam to be supplied to the steam using facility 18.
The steam header 6 is connected to the plurality of boilers 20A and 20B that constitute the boiler group 2 via the steam pipe 11. The downstream side of the steam header 6 is connected to a steam using facility 18 via a steam pipe 12.
The steam header 6 collects and stores the steam generated by the boiler group 2 to adjust the pressure difference and the pressure fluctuation between the plurality of boilers 20A and 20B, and the steam using the steam whose pressure is adjusted Supply 18

The boiler 20A of the first boiler group 2A is configured of a waste heat recovery boiler (exhaust gas utilizing boiler). The waste heat recovery boiler, for example, refers to a boiler that generates steam using exhaust gas such as high-temperature combustion gas generated when supplying fuel to drive a generator in a plant facility as a heat source.
The boiler 20A includes a boiler body 21A, a boiler pressure detection unit 23A that measures an in-can pressure value of the boiler 20A, and a local control unit 22A.
The boiler main body 21A exchanges heat between the exhaust gas introduced from the exhaust gas supply pipe (not shown) and the water supplied from the water supply pipe (not shown) to generate steam. Exhaust gas used for heat exchange in the boiler main body 21A is discharged to the outside from an exhaust pipe (not shown).

Boiler pressure detector 23A measures the in-can pressure value PV _A boiler 20A, and transmits the measured in-can pressure value PV _A to the local control unit 22A.
The local control unit 22A, based on the in-can pressure value PV _A measured by the boiler pressure detector 23A, controlling the heat recovery amount of the boiler 20A. Specifically, the local control unit 22A controls the heat recovery amount of the boiler 20A by controlling the amount of exhaust gas introduced into the boiler main body 21A.
The adjustment of the amount of exhaust gas introduced into the boiler main body 21A is, for example, the flow rate of the exhaust gas flowing from the exhaust gas supply pipe to the bypass pipe (not shown) connecting the exhaust gas supply pipe and the exhaust pipe to the boiler 20A. And a switching damper (not shown) for adjusting, and the opening degree of the switching damper is adjusted.

  In the boiler system 1, the boiler 20A functions as a main output boiler (base load boiler). For example, when the heat recovery amount is 100%, the boiler 20A is configured to enable steam output of 10 to 30 t / h as a corresponding evaporation amount.

On the other hand, the boiler 20B of the second boiler group 2B is, for example, a continuous control boiler configured of a multi-tube type once-through boiler. The boiler 20B includes a boiler body 21B in which combustion is performed, and a local control unit 22B that controls the combustion state of the continuous control boiler 20B.
In the boiler system 1, the boiler 20B functions as a sub output boiler (peak load boiler). The boiler 20B is configured, for example, to be able to produce a steam output with an equivalent evaporation amount of 2 to 3 t / h when the combustion amount is 100%.

  The vapor pressure sensor 7 is electrically connected to the number control device 3 B via the signal line 13. The vapor pressure sensor 7 measures the header pressure, and transmits a signal (vapor pressure signal) relating to the measured header pressure value PV to the number control device 3B via the signal line 13.

  The number control device 3B is electrically connected to the plurality of boilers 20B via the signal line 16B. The number control device 3B controls the combustion state of the boiler 20B based on the header pressure value PV measured by the steam pressure sensor 7.

  As described above, the boiler system 1 can supply the steam generated by the first boiler group 2A and the second boiler group 2B to the steam using facility 18 through the steam header 6.

Specifically, if the demand load (steam consumption) increases due to the increase in the demand for the steam using facility 18 and the amount of steam supplied to the steam header 6 is insufficient, the in-can pressure and the header pressure of the boiler 20A are respectively It will decrease. On the other hand, the demand load (steam consumption) decreases due to the decrease in the demand for the steam using facility 18, and if the amount of steam supplied to the steam header 6 becomes excessive, the in-can pressure and the header pressure of the boiler 20A increase. It will be. Therefore, the boiler system 1, based on the variation of the header pressure value PV measured by the can internal pressure values PV _A and the vapor pressure sensor 7 of the boiler 20A measured by the boiler pressure detector 23A, monitor the variation of the required load can do.
More specifically, the boiler 20A constituting the first boiler group 2A, based on the in-can pressure value PV _A boiler 20A, is required in accordance with the consumption amount of steam of the steam-using facility 18 (required load) The required amount of steam MV _A , which is the amount of steam, is calculated.
The second boiler group 2B calculates a required steam amount MV, which is a steam amount required in accordance with the consumed steam amount (required load) of the steam using facility 18, based on the header pressure value PV.

  Here, several boilers 20A and 20B which comprise the boiler system 1 are demonstrated. FIG. 2 is a schematic view of the boiler group 2.

[About the boiler 20A]
In the boiler 20A constituting the first boiler group 2A, the amount of heat recovery (for example, the opening of the switching damper is set by the proportional distribution control method so that the in-can pressure value PV _A falls within the range of the control pressure zone set in advance. Control).
Specifically, the boiler pressure detector 23A measures the in-can pressure value PV _A boiler 20A, and transmits the measured in-can pressure value PV _A to the local control unit 22A.
The local control unit 22A is, in-can pressure value PV _A measured by the boiler pressure detector 23A is to fall within a range of the control pressure zone, to control the heat recovery amount by the boiler 20A.

The local control unit 22A stores the content of the instruction given to the boiler 20A, the information on the heat recovery state received from the boiler 20A, and the information on the amount of output steam in a local storage unit (not shown).
Further, in the local storage unit (not shown), as the setting condition according to the in-can pressure value PV _A measured by the boiler pressure detector 23A, and the upper limit value P _max of the control pressure zone of the combustion control of the boiler 20A The lower limit value P _min can be set in advance.
Details of the proportional distribution control method will be described later.

[About the boiler 20B]
On the other hand, the boiler 20B is, for example, a continuous control boiler capable of burning while continuously changing the amount of combustion, such as a multi-tube type once-through boiler.
A continuous control boiler is a boiler in which the amount of combustion can be continuously controlled at least in the range from the minimum combustion state S1 (for example, the combustion state at a combustion amount of 20% of the maximum combustion amount) to the maximum combustion state S2. It is. The continuous control boiler adjusts the amount of combustion by controlling, for example, the opening (combustion ratio) of a valve that supplies fuel to a burner and a valve that supplies combustion air.

  Also, to continuously control the amount of combustion means that the calculation and signals in the local control unit 22B are digitally processed and handled in stages (for example, the output (amount of combustion) of the boiler 20B is controlled in 1% steps) Even if the output can be controlled virtually continuously.

The change of the combustion state between the combustion stop state S0 and the minimum combustion state S1 in the boiler 20B in the first embodiment is controlled by turning on / off the combustion of the boiler 20B (burner). And in the range from the minimum combustion state S1 to the maximum combustion state S2, the amount of combustion can be controlled continuously.
More specifically, a unit steam flow rate U, which is a unit of variable steam flow rate, is set for each of the plurality of boilers 20B. Thereby, the boiler 20B is capable of changing the amount of steam in units of the unit amount of steam U in the range from the minimum combustion state S1 to the maximum combustion state S2.

The unit steam flow U can be appropriately set according to the steam flow (maximum steam flow) in the maximum combustion state S2 of the boiler 20B, but from the viewpoint of improving the followability of the output steam flow in the boiler system 1 to the required steam flow, It is preferably set to 0.1% to 20% of the maximum steam flow of 20B, and more preferably set to 1% to 10%.
The output steam volume indicates the steam volume output by the first boiler group 2A and the second boiler group 2B, and this output steam volume is the sum of the steam volumes output from the plurality of boilers 20A and 20B. Is represented by

  Further, in the first embodiment, an eco-driving point, which is a load factor at which the boiler efficiency is the highest, is set in each of the plurality of boilers 20B.

Moreover, the priority is set to each of the plurality of boilers 20B. The priority order is used for the number control device 3B to select the boiler 20B that issues a combustion instruction or a combustion stop instruction. The priority can be set, for example, using an integer value such that the smaller the numerical value, the higher the priority.
As shown in FIG. 2, for example, when the priorities of "1" and "2" are assigned to the second and third units of the boiler 20B of the second boiler group 2B, respectively, the priority of the second unit is highest High, the lowest priority for Unit 3. In the normal case, the priority is changed at predetermined time intervals (for example, 24 hour intervals) under the control of the control unit 4B described later.

  As described above, the boiler 20B includes the boiler body 21B and the local control unit 22B that controls the combustion state of the boiler 20B. The local control unit 22B changes the combustion state of the boiler 20B according to the steam consumption.

  Specifically, in the boiler 20B constituting the second boiler group 2B, the local control unit 22B is input by the control signal transmitted from the number control device 3B via the signal line 16B or the manual operation of the driver The combustion state of the boiler 20B is controlled based on the control signal. Further, the local control unit 22B transmits a signal used by the number control device 3B to the number control device 3B via the signal line 16B. As a signal used by number control device 3B, the actual combustion state of boiler 20B, and other data etc. are mentioned.

  The number control device 3B calculates the combustion state of each boiler 20B according to the required load based on the steam pressure signal from the steam pressure sensor 7, and transmits a number control signal to each boiler 20B (local control unit 22B). . As shown in FIG. 1, the number control device 3B includes a storage unit 5B and a control unit 4B, and is electrically connected to each boiler 20B via a signal line 16B.

The control unit 4B transmits various instructions to the boiler 20B via the signal line 16B, receives various data from each boiler 20B, and executes control of the combustion state and the number of operating boilers 20B. . When each boiler 20B receives a signal indicating a change instruction of the combustion state from the number control device 3B, it controls the amount of combustion of the corresponding boiler 20B according to the instruction. The control unit 4B receives information on the combustion state of the boiler 20B via the signal line 16B.
The detailed configuration of the control unit 4B will be described later.

The storage unit 5B is controlled by the number control device 3B (control unit 4B), the contents of the instruction given to the boiler 20B, the information such as the combustion state received from each boiler 20B, unit steam of each boiler 20B Information on setting of the amount U, information on setting of priority of the plurality of boilers 20B, information of setting on changing of the priority (rotation), and the like are stored.
Further, in the storage unit 5B, a target pressure value P1 related to the combustion control of the second boiler group 2B can be set in advance as a setting condition related to the header pressure value PV measured by the vapor pressure sensor 7.
Further, in the storage unit 5B, a fixed steam rate corresponding to the base load is set in advance in the second boiler group 2B, and a fixed combustion rate for each boiler 20B of the second boiler group 2B for outputting a constant steam rate And the number of boilers can be set in advance.
By doing so, as will be described later, the output control unit 41B of the second boiler group 2B compares the required steam flow MV _n calculated based on the header pressure value PV with the first steam flow V1, thereby making it necessary. The number of boilers set in advance in the second boiler group 2B is preset so as to control the combustion state of the second boiler group 2B or output the first steam amount V1 based on the steam amount MV _n. It can be determined whether to burn at a fixed combustion rate.

  In the boiler system 1 configured as described above, the steam generated by the first boiler group 2A and the second boiler group 2B is supplied to the steam using facility 18 via the steam header 6.

Next, control of the heat recovery amount in the first boiler group 2A and combustion control in the second boiler group 2B will be described.
First, the detailed configuration of the local control unit 22A that executes the heat recovery amount control of the boiler 20A configuring the first boiler group 2A will be described.

Proportional distribution control method
The local control unit 22A determines the control pressure band by setting the set pressure and the control width in advance. Here, the control pressure zone, the pressure zone between the lower limit value P _min is the minimum allowable value of the upper limit value P _max and the pressure is the maximum allowable value of the can internal pressure the amount value PV _A boiler 20A.
The local control unit 22A, the control pressure the pressure value of the can body of the steam generated from the boiler 20A constituting the first boiler group 2A, i.e. the can internal pressure values PV _A measured by the boiler pressure detector 23A is set in advance The control amount is calculated by a proportional distribution control algorithm in which the required vapor amount is uniquely determined by the in-can pressure value PV _A so as to fall within the band range, and the heat recovery amount of the boiler 20A is controlled based on this control amount. .

The local control unit 22A calculates the required vapor amount MV _An based on the pressure deviation P _D1 that is the difference between the in-can pressure value PV _A and the upper limit P _max of the control pressure zone for each control cycle. Here, the subscript n indicates the number of operations (n: n = 1, 2,..., N is a positive integer value) of the repetitive operation performed for each control cycle.
More specifically, the local control unit 22A has a control width which is a difference between the pressure deviation P _D1 of the in-can pressure value PV _A and the upper limit P _max of the control pressure zone and the lower limit P _{min in} each control cycle. Based on the ratio P _R1 divided by P ₁ , the amount of steam to be generated by the boiler 20A (hereinafter, also referred to as “necessary amount of steam MV _An ”) is calculated by (Equation 1).

Required steam volume MV _An = maximum steam volume JG × P _R1 ··············· (Equation 1)

Here, the maximum amount of steam JG is the maximum amount of steam when waste heat (or waste heat) is recovered at the maximum heat recovery rate preset in the boiler 20A constituting the first boiler group 2A.

The local control unit 22A determines, for each control cycle, the deviation between the required steam flow MV _An calculated by Equation 1 and the output steam flow JT calculated for each control cycle and the fluctuation state of the in-can pressure value PV _A. The heat recovery amount of the boiler 20A can be controlled.
The local control unit 22A that controls the boiler 20A that configures the first boiler group 2A has been described above.

Next, the detailed configuration of the control unit 4B that executes the combustion control of the second boiler group 2B will be described.
As shown in FIG. 3, the control unit 4B is configured to include a required steam amount calculation unit 41B and an output control unit 42B.

The required steam amount calculation unit 41B is configured to calculate the header pressure based on a predetermined PI algorithm or PID algorithm with respect to the deviation between the header pressure value PV and the target pressure value P1 of the second boiler group 2B preset in the storage unit 5B. A required vapor amount MV _n necessary for the value PV to become the target pressure value P1 is calculated.
More specifically, it is calculated as follows.

The required steam amount calculation unit 41B calculates the current required steam amount MV _n to be generated from the plurality of boilers 20B that constitute the second boiler group 2B using the following velocity equation (equation 1B).
MV _n = MV _n-1 + ΔMV _n (Equation 1B)
In (Formula 1B), MV _n: necessary steam amount of current (current required steam quantity), _{MV n-1:} necessary steam amount of the control cycle time of the latest (last necessary steam amount), .DELTA.MV _n: from the previous to the current It is the required amount of steam change. Here, the subscript n indicates the number of operations of the repetitive operation (nth time: positive integer value of n = 1, 2,..., N).

The required steam flow variation ΔMV _n from the previous time to the current time is calculated by the following (Equation 2B).
ΔMV _n = ΔP _n + ΔI _n + ΔD _n (Equation 2B)
In Equation (2), ΔP _n : P control output (change), ΔI _n : I control output (change), and ΔD _n : D control output (change), each of the following (Equation 3B) to It is obtained by the equation 5B).
ΔP _n = K _P × (e _n −e _n−1 )... (Equation 3B)
_{ΔI n = K P × (Δt} / T I) × e n ············ ( formula 4B)
ΔD _n = K _P × (T _D / Δt) × (e _n −2 e _n−1 + e _n −2)
(Equation 3B) to (Equation 5B), Δt: control period, K _P : proportional gain, T _I : integration time, T _D : differentiation time, e _n : deviation amount at the present time, e _{n -1} : previous control Deviation of cycle time, en _-2 : Deviation of control cycle time before last.
Deviation e _n at the present time is, the second target pressure value P1, a difference between the header pressure value PV measured by the vapor pressure sensor 7, it is determined by the following equation (6B).
e _n = P 1-PV ······················ (Equation 6B)

The necessary vapor amount calculation unit 41B sums the outputs (changes) calculated by (Equation 3B), (Equation 4B), and (Equation 5B) according to (Equation 2B), and thus the need from the previous time to this time The amount of change in vapor amount ΔMV _n is calculated.
The necessary steam amount calculating section 41B, as shown in (Formula 1B), by adding the required amount of steam variation .DELTA.MV _n the last necessary steam amount _{MV n-1,} to calculate the time required steam amount MV _n it can.

The output control unit 42B outputs the first steam flow rate V1 when the required steam flow rate MV _n calculated by the required steam flow rate calculation unit 41B falls below the first steam flow rate V1 set in advance. The number of boilers set in advance in 2B is burned at a fixed combustion rate set in advance.
Further, the output control unit 42B determines that the required steam calculated by the required steam volume calculation unit 41B when the required steam volume MV _n calculated by the required steam volume calculation unit 41B is _equal to or more than the first steam volume V1 set in advance. Control to output the quantity MV _n .
By doing so, even if the overall load is low, the second boiler group 2B can be burned by a fixed amount, so that boiler can corrosion is prevented, and the first boiler group 2A and the second boiler group 2B Load non-uniformity can be improved.

The fixed combustion rate is preferably set to the highest combustion rate of the combustion efficiency of the boiler 20B to be burned in the second boiler group 2B. The fixed combustion rate can also be the minimum combustion rate of the boiler 20B to be burned in the second boiler group 2B.
As described above, the fixed combustion rate is set in advance for each boiler 20B of the second boiler group 2B so that the second boiler group 2B outputs the first steam amount V1 corresponding to the base load in the storage unit 5B. can do.

<Output Steam Amount Control by Output Control Unit 42B>
The control unit 4B causes the output control unit 42B to output the first vapor amount V1 when the required vapor amount MV _n calculated by the required vapor amount calculation unit 41B is less than the first vapor amount V1 serving as a preset base load. As a result, the number of boilers set in advance in the second boiler group 2B is burned at a fixed combustion rate set in advance.
Further, when the required steam volume MV _n calculated by the required steam volume calculation unit 41B is _equal to or more than the first steam volume V1 which is a preset base load, the control unit 4B determines the required steam volume by the output control unit 42B. Control is performed so as to output the required vapor amount MV _n calculated by the calculation unit 41B.

By doing so, when the load in the second boiler group 2B is low (for example, the first required steam amount MV _n calculated based on the header pressure value PV in the second boiler group 2B corresponds to the preset base load) Even if it is less than the steam amount V1), the boiler for the base load allocated to the second boiler group 2B can be fixedly burned at the fixed combustion rate corresponding to the first steam amount V1 set in advance, so the boiler It is possible to prevent can corrosion and improve load non-uniformity in the first boiler group 2A and the second boiler group 2B.

Conversely, if the overall load rises and the first boiler group 2A can not meet the required load alone, and the load in the second boiler group 2B becomes high (for example, calculated by the required steam amount calculation unit 41B In the case where the required steam volume MV _n is equal to or more than the constant steam volume corresponding to the preset base load), the load following is performed in all the boilers belonging to the second boiler group 2B including the fixed combustion boiler that burns at the fixed combustion rate It can be performed.

Next, the flow of processing for realizing the operation of the boiler system 1 of the first embodiment will be described with reference to FIGS. 4 and 5. FIG.4 and FIG.5 is a flowchart which shows the flow of a process of 1st boiler group 2A and 2nd boiler group 2B, respectively.
First, the flow of processing in the first boiler group 2A will be described with reference to FIG.

As preparation for the process, the control pressure zone range setting of the in-can pressure value PV _A which is the pressure value in the can for the boiler 20A constituting the first boiler group 2A (upper limit P _max and lower limit P _min ) And store them in the local storage unit (not shown).

  In step ST1, combustion control of the boiler 20A is started by the local control unit 22A.

In step ST2, the local control unit 22A controls the combustion state of the boiler 20A for each control cycle.
More specifically, the local control unit 22A sets the in-can pressure value PV _A (feedback value) of the boiler 20A measured by the boiler pressure detection unit 23A at each control cycle and the boiler set in advance in the local storage unit. the pressure deviation P _D1 of the can internal pressure values PV _a of 20A, based on the ratio P _R1 divided by the control width P ₁ of the control pressure zone, by performing feedback control based on a predetermined proportional distribution control algorithm, boiler 20A in-can pressure value PV _a calculates the amount of steam MV _an needed to fit within the range of the control pressure zone, to control the heat recovery amount of the boiler 20A to generate the calculated amount of steam MV _an.

  The local control unit 22A repeats step ST2 for each control cycle.

Next, the flow of the process in the second boiler group 2B will be described with reference to FIG.
As preparation for processing, a target pressure value P1 is set for the second boiler group 2B and stored in the storage unit 5B.
Here, set to be smaller than the upper limit value P _max of the control pressure zone of the can internal pressure values PV _A boiler 20A of the target pressure value P1 of the second boiler unit 2B constituting the first boiler group 2A. Specifically, it is preferable to set the target pressure value P1 lower than the pressure value (P _max −α) calculated by taking the pressure loss α in the steam pipe 11 into consideration.
In addition, the second boiler group 2B is configured to set in advance a fixed steam amount (first steam amount V1) corresponding to the base load in the second boiler group 2B and to output the first steam amount V1 corresponding to the base load. The fixed combustion rate and the number of boilers for each boiler 20B are set and stored in the storage unit 5B. Regarding the relationship between the first vapor amount V1 and the fixed combustion rate, the first vapor amount V1 can be set so as to be generated not by burning all the units but by burning an arbitrary number of units. . (As above, not shown).

  In step ST11, combustion control of the second boiler group 2B is started by the number control device 4B.

In step ST12, the control unit 4B determines, for each control cycle, whether or not the required steam volume MV _n calculated by the required steam volume calculation unit 41B is less than the first steam volume V1 serving as a preset base load. Do. If the required vapor amount MV _n is less than the first vapor amount V1 (Yes), the process proceeds to step ST13. If the required vapor amount MV _n is _equal to or greater than the first vapor amount V1 (No), the process proceeds to step ST14.

  In step ST13, the output control unit 42B burns a predetermined number of boilers in the second boiler group 2B at a preset fixed combustion rate so as to output the first steam flow V1.

  Thereafter, the process proceeds to step ST12.

In step ST14, the control unit 4B (the output control unit 42B) controls the boiler 20B that configures the second boiler group 2B so as to generate the calculated required steam amount MV _n .

  Thereafter, the process proceeds to step ST12.

Next, referring to FIGS. 6 and 7, upper limit value P _max of the control pressure band of in-can pressure value PV _A of boiler 20A constituting second boiler group 2A with target pressure value P1 of second boiler group 2B The second boiler group 2B is based on a predetermined PI algorithm or PID algorithm by setting smaller than the pressure value (P _max −α) more preferably taking into consideration the pressure loss α in the steam pipe 11 The operation in the case where the combustion control according to the first embodiment is performed will be described in comparison with the case where feedback control is performed (hereinafter referred to as “conventional combustion control”).

Here, FIG. 6 is a figure which shows transition of the header pressure at the time of the 2nd boiler group 2B performing "the conventional combustion control." On the other hand, FIG. 7 is a figure which shows transition of the header pressure at the time of implementing combustion control which concerns on 1st Embodiment of this invention.
Here, in each of (B) to (D) in FIG. 6 and (B) to (D) in FIG. 7, the vertical axis is the amount of steam, and the horizontal axis is time. Therefore, the first boiler group generated steam amount in FIGS. 6 and 7 is the generated steam amount of the boiler 20A that constitutes the first boiler group 2A. Further, MAX of the first boiler group generated steam amount is the maximum output steam amount of the boiler 20A constituting the first boiler group.
The second boiler group generated steam amount in FIGS. 6 and 7 is the sum of the generated steam amounts of the boilers 20B that constitute the second boiler group 2B. Further, MAX of the boiler 20B constituting the second boiler group 2B is the sum of the maximum output steam amount of the boiler 20B constituting the second boiler group 2B.

<Conventional combustion control>
When the conventional combustion control is performed, as shown in FIG. 6, when the overall load is low (t _{0 to} t ₁ ), the in-can pressure value PV _A of the boiler 20A constituting the first boiler group 2A is the control pressure The amount of steam required to _reach a pressure value close to the upper limit _{Pmax of the} band is generated. At this time, the header pressure value is a value (PV _A −α) calculated by adding the pressure loss α in the steam pipe 11 to the in-can pressure value PV _A of the boiler 20A, which is higher than the target pressure value P1. For this reason, all the 2nd boiler groups 2B will be in a stand-by state.

Thereafter, even if the increased use steam total amount of the load rises, the in-can pressure value PV _A boiler 20A is lowered, until the time t ₁ ~t _2, fall within the range of the control pressure zone, In addition, it is possible to cover the necessary amount of steam with its own output steam amount so that the value (PV _A −α) calculated by taking into consideration the pressure loss α in the steam pipe 11 still becomes the target pressure value P1 or more. For this reason, all the 2nd boiler groups 2B will be in a stand-by state.

Thereafter, the entire load is increased, the time t ₂ later, the header pressure value PV becomes the target pressure value P1, the second boiler group 2B, the steam quantity required for the header pressure value PV becomes the target pressure value P1 Is calculated and feedback control is started to generate the calculated amount of steam.
Thus, when the overall load increases and the amount of steam used increases, the boiler 20A outputs the maximum amount of steam X that can be output by itself (before reaching the lower limit P _min of the control pressure band), The second boiler group 2B starts feedback control.
As described above, when the conventional combustion control is performed, the second boiler group 2B is in the standby state for all the vehicles until the header pressure value PV becomes the target pressure value P1.

<Combustion control according to the first embodiment>
On the other hand, when the combustion control according to the first embodiment is performed, as shown in FIG. 7, when the overall load is low (t _{0 to} t ₁ ), the boiler 20A constituting the first boiler group 2A cans The internal pressure value PV _A generates the amount of steam required to be a pressure value close to the upper limit value P _max of the control pressure zone. At this time, the header pressure value is a value (PV _A −α) calculated by adding the pressure loss α in the steam pipe 11 to the in-can pressure value PV _A of the boiler 20A, which is higher than the target pressure value P1.
On the other hand, in the second boiler group 2B, the required steam flow calculated by the required steam flow calculation unit 41B is zero, and falls below the preset first steam flow V1. Output

Thereafter, even if the increased use steam total amount of the load rises, the in-can pressure value PV _A boiler 20A is lowered, until the time t ₁ ~t _2, fall within the range of the control pressure zone, And the amount of steam necessary for the pressure value (PV _A -α) calculated with pressure loss α in the steam pipe 11 still to be equal to or higher than the target pressure value P1 can be covered by the output steam amount of the boiler 20A itself it can.
For this reason, the second boiler group 2B still has the required steam volume calculated by the necessary steam volume calculator 41B at zero, and falls below the preset first steam volume V1, so the output controller 42B produces the first steam volume Output V1.

Thereafter, the entire load is increased, the time t ₂ later, the header pressure value PV becomes the target pressure value P1, the second boiler group 2B, the steam quantity required for the header pressure value PV becomes the target pressure value P1 Is calculated and feedback control is started to generate the calculated amount of steam.
Thus, when the overall load increases and the amount of steam used increases, the boiler 20A reaches the lower limit P _min of the control pressure band (that is, before outputting the maximum amount of steam X that can be output by itself). , And the second boiler group 2B starts feedback control.
As described above, when the conventional combustion control is performed, the second boiler group 2B is in the standby state for all the vehicles until the header pressure value PV becomes the target pressure value P1.
As described above, when the combustion control according to the first embodiment is performed, the second boiler group 2B can burn a predetermined amount or more regardless of the amount of steam used.

According to the boiler system 1 of the first embodiment, for example, the following effects are achieved.
In the boiler system 1 according to the first embodiment, the boiler 20A constituting the first boiler group 2A has the heat recovery amount of the boiler 20A such that the in-can pressure value PV _A falls within the range of the control pressure zone set in advance. Is controlled by the local control unit 22A.
On the other hand, in the second boiler group 2B, the header pressure value PV is a preset target pressure value P1 (here, the target pressure value P1 is the in-can pressure value PV _{A of} the boiler 20A constituting the first boiler group 2A. Set to a value smaller than the pressure value (P _max −α) calculated by adding the pressure loss α in the steam pipe 11 to the upper limit P _max of the control pressure zone , And an output control unit 42B that controls the combustion state of the second boiler group 2B based on the required steam amount MV _n calculated by the required steam amount calculation unit 41B, and the output control unit 42B calculates the required steam amount When the required steam volume MV _n calculated by the unit 41B falls below the preset first steam volume V1, the number of boilers preset in the second boiler group 2B is set to output the first steam volume V1. Preset It is burned at a constant firing rate, if necessary steam amount MV _n is a first steam quantity V1 above, so as to output the required amount of steam MV _n, controls the combustion state of the second boiler unit 2B.

  Therefore, according to the first embodiment, since it is possible to secure a combustion amount of a predetermined amount or more with respect to the second boiler group 2B regardless of the amount of steam used, it is possible to prevent boiler can corrosion and Load non-uniformity can be improved.

  Further, in the boiler system 1 of the first embodiment, the fixed combustion rate set in advance can be set to the highest combustion rate (eco operation point) of the combustion efficiency of the boiler 20B to be burned in the second boiler group 2B.

  Therefore, according to the first embodiment, when the overall load is low, the second boiler group 2B can be burned efficiently.

  Further, in the boiler system 1 of the first embodiment, the fixed combustion rate set in advance can be set to the minimum combustion rate of the boiler 20B to be burned in the second boiler group 2B.

  Therefore, according to the first embodiment, when the second boiler group 2B compensates for the shortage of the output steam amount of the first boiler group 2A when the entire load increases, the boiler system 1 excellent in load following property is provided. can do.

As mentioned above, although demonstrated per preferable embodiment of the boiler system of this invention, this invention is not restrict | limited to the above-mentioned embodiment, It can change suitably.
For example, the target pressure value P1 of the second boiler group 2A may be smaller than an intermediate value between the upper limit value P _max and the lower limit value P _min of the control pressure band, and may be equal to or more than the lower limit value P _min .
Further, the target pressure value P1 of the second boiler group 2A may be set to a value smaller than the lower limit value P _min of the control pressure band.

Moreover, in 1st Embodiment, this invention was applied to the boiler system 1 provided with the boiler group 2 which consists of the 1st boiler group 2A which consists of 1 boiler 20A, and the 2nd boiler group 2B which consists of 2 boilers 20B. But it is not limited to this.
That is, in the first boiler group 2A including two or more boilers 20A according to the present invention, each boiler 20A belonging to the first boiler group 2A has an in-can pressure value PV _A that is a pressure value in a can of the boiler 20A. within the can internal pressure values PV _a boiler pressure detector 23A and boiler 20A is preset control pressure zone to measure the heat recovery amount to fit (between the upper limit value P _max and the lower limit value P _min) It is good also as what is provided with local control part 22A which controls.
Similarly, the present invention may be applied to a boiler system 1 in which the second boiler group 2B includes three or more boilers 20B, and the second boiler group 2B includes the single boiler 20B. It may apply.

  Further, in the first embodiment, the boiler capacity of each of the boilers 20B of the second boiler group 2B is not particularly limited. Even if the minimum combustion amount, the unit steam amount, and the combustion capacity as the maximum combustion amount are the same or different for each boiler 20B, it is applicable.

Further, in the first embodiment, only the required amount of change in vapor amount ΔMV _{n for} each control cycle is calculated as a PI (or PID) control algorithm of the second boiler group 2B, and the required amount of vapor MV _n−1 last time In addition, PI or PID control by the velocity type PI (or velocity type PID) algorithm for calculating the required vapor amount MV _n is applied, but the present invention is not limited to the velocity type PI (or position type PID) algorithm. Alternatively, PI or PID control based on a position-type PI (or position-type PID) algorithm may be applied which directly calculates the currently required vapor amount MV _n every control cycle.

  In the first embodiment, the change of the combustion state between the combustion stop state S0 and the minimum combustion state S1 in the boiler 20B is controlled by turning on / off the combustion of the boiler 20B, respectively, and the minimum combustion state S1. In the range from the maximum combustion state S2 to the continuous control boiler 20B capable of continuously controlling the amount of combustion, the invention is not limited thereto. That is, the boiler 20B may be configured by a continuous control boiler capable of continuously controlling the amount of combustion in the entire range from the combustion stop state to the maximum combustion state.

In the first embodiment, the boiler 20A, like fall within the scope of the control pressure zone can internal pressure values PV _A is set in advance, a proportional distribution control system, the heat recovery amount (e.g., open switching damper Although described as controlling the degree), it is not limited thereto. Boiler 20A, like fall within the scope of the control pressure zone can internal pressure values PV _A is set in advance, by the on / off control scheme, may be configured to control the heat recovery amount.

1 boiler system 2 boiler group 2A first boiler group 2B second boiler group 20 boiler 20A waste heat recovery boiler 22A local control unit 23A boiler pressure detection unit 20B continuous control boiler 3B number control device 4B control unit 41B necessary steam amount calculation unit 42B Output control unit 5B storage unit 6 steam header (steam collecting unit)
7 Steam pressure sensor (steam pressure measuring means)
18 Steam using equipment (load equipment)

Claims (6)

A boiler group comprising a first boiler group comprising one or more waste heat recovery boilers, and a second boiler group comprising one or more auxiliary boilers;
A steam header for collecting steam generated in the boiler group;
Vapor pressure measuring means for measuring a header pressure value that is vapor pressure inside the vapor header;
A control unit that controls a combustion state of the second boiler group;
A boiler system comprising
The waste heat recovery boiler belonging to the first boiler group includes in-can pressure measuring means for measuring an in-can pressure value which is a pressure value in a can of the waste heat recovery boiler.
A local control unit that controls the heat recovery amount of the first boiler group so that the in-can pressure value falls within the range of a control pressure zone set in advance;
The control unit
The required amount of steam by the PI algorithm or PID algorithm so that the header pressure value measured by the vapor pressure measuring means matches the target pressure value which is smaller than the preset upper limit value of the control pressure zone. A required steam amount calculation unit for calculating
When the required steam volume calculated by the required steam volume calculation unit is less than the first steam volume set in advance, the first steam volume is output, and the required steam volume is equal to or more than the first steam volume, And b. An output control unit configured to control a combustion state of the second boiler group so as to output the necessary amount of steam.   The boiler system according to claim 1, wherein the output control unit burns a predetermined number of auxiliary boilers in the second boiler group at a predetermined fixed combustion rate when outputting the first steam flow. .   The boiler system according to claim 2, wherein the fixed combustion rate is the highest combustion rate of the combustion efficiency of the auxiliary boiler to be burned.   The boiler system according to claim 2, wherein the fixed combustion rate is a minimum combustion rate of the auxiliary boiler to be burned.   The boiler according to any one of claims 1 to 4, wherein the target pressure value is smaller than an intermediate value between the upper limit value and the lower limit value of the control pressure zone, and is equal to or higher than the lower limit value of the control pressure zone. system.   The boiler system according to any one of claims 1 to 4, wherein the target pressure value is a value smaller than a lower limit value of the control pressure zone.

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