JP6220255B2 - Multi-can boiler - Google Patents

Description

In the present invention, a plurality of boilers that adjust the combustion value stepwise such as high combustion, medium combustion, low combustion, and standby for combustion are installed, and each boiler is based on the pressure value of steam supplied by the boiler. The present invention relates to a multi-can boiler that controls the combustion value of the boiler.

As disclosed in Japanese Patent Application Laid-Open No. 2012-251721, a multi-can installation boiler including a plurality of boilers and a number control device for controlling the number of combustion of the boilers is widely used. The unit control device controls the amount of combustion in the entire boiler so that the pressure value of the steam supplied by the boiler is kept within the pressure adjustment range. When the amount is increased and the steam pressure value is increased, the combustion amount in the entire boiler is reduced. In the number control device, the combustion value in each boiler is determined from the combustion amount in the entire boiler, and a combustion command for the determined combustion value is output to each boiler. The adjustment of the combustion value in the boiler described in Japanese Patent Application Laid-Open No. 2012-251721 is such that each boiler performs four-position combustion control of high combustion, medium combustion, low combustion, and combustion standby, The apparatus determines which combustion value is set for each boiler and outputs the combustion command.

FIG. 8 shows a unit control pattern in the case where unit control is performed with four boilers that perform combustion control at four positions of high combustion, medium combustion, low combustion, and combustion standby. In the figure, the combustion state of the boiler is indicated by “H” for high combustion, “M” for intermediate combustion, “L” for low combustion, and “−” for standby for combustion. The figure shows a combustion pattern that represents the combustion value of each boiler at a certain steam pressure value, and a unit control pattern that represents a state in which the combustion pattern is changed.

The amount of combustion in the boiler ranges from the state of "----" where all the boilers are on standby for combustion, to "HHHH", where high combustion is achieved in all boilers. Here, a 13-stage combustion pattern is set. ing. This combustion amount is set corresponding to the pressure value of the steam supplied from the boiler. The higher the steam pressure value, the smaller the combustion amount of the boiler, and the lower the steam pressure value, the more the combustion amount of the boiler. Keep getting bigger. In the actual number control pattern, a case where the combustion amount is reduced is set as described in FIGS. However, if the number control pattern when the combustion amount is reduced is described, the figure becomes complicated, and it becomes difficult to compare the number control patterns with different settings. Therefore, here, the number control pattern in the case where the state is changed in one direction from the state where all the boilers are set to the combustion standby state to the state where all the boilers are set to the high combustion is described.

In FIG. 8, three number control patterns are set. The three unit control patterns are different in the maintenance target number of boilers that burn with low combustion or medium combustion, which is a boiler capable of increasing the amount of immediate combustion. When the set value of the maintenance target number is two, Four cases are listed side by side. This maintenance target number setting value is set based on the fluctuation state of the steam usage on the steam usage side.

When the fluctuation of the steam usage is steep, it is necessary for the boiler to increase the steam supply amount in a short time according to the change of the steam usage. When the combustion value is changed by the boiler, the change in the direction of decreasing the combustion value can be performed in a short time because only the supply amount of fuel and combustion air is reduced or stopped. Even in the direction of increasing the combustion value, in the case of changing from low combustion to medium combustion or changing from medium combustion to high combustion, only the supply amount of fuel and combustion air is increased. Can change with time. However, when combustion is started from a state where combustion is stopped, it is necessary to perform a preparation process such as furnace ventilation. Furthermore, when the boiler is cold, steam cannot be supplied until the temperature rises to the steam generation temperature. Therefore, a relatively long time is required from the output of the combustion command to the start of steam supply.

Therefore, if the amount of steam used may increase rapidly, a certain number of boilers that can immediately increase the amount of steam supplied by increasing the combustion value should be secured. To prepare. In other words, if a certain number of low-burning or medium-burning boilers that can increase the amount of immediate combustion are secured, an increase from low combustion to medium combustion and an increase from medium to high combustion can be performed in a short time. Therefore, even when the amount of steam used increases rapidly, the amount of steam supply can be increased immediately. The more the number of low-burning or medium-burning boilers that can increase the amount of immediate combustion is maintained, the better the followability to the load.

The number of boilers that can immediately increase the steam supply amount by increasing the combustion value is required as the change in the amount of steam used is rapid (rapid load). If the maintenance target number of boilers capable of increasing the combustion amount is set to a large value and the change in steam consumption is moderate (slow load), the number of low combustion or medium combustion may be small. The maintenance target number is set to a small number. Of the three unit control patterns shown in Fig. 8, the setting is when the change in steam usage is the slowest when the maintenance target number is 2, and the steam usage is the case when the maintenance target number is 4 The setting is made when the change in amount is sudden, and the maintenance target number of three in the middle is set when the change in the amount of steam used is in the middle. The set value of the maintenance target number is the minimum one and the maximum is the number of boilers subject to unit control, and can be arbitrarily set between them.

The number control pattern when the set number of maintenance target numbers is two will be described with reference to the drawing. The number of maintenance target units set to two is to set the maintenance target number of boilers to be maintained at low combustion or medium combustion in order to increase the combustion amount in a short time. In this case, when increasing the combustion amount in the state where there are two or more boilers that are already low-burning or medium-burning boilers capable of increasing the instantaneous combustion amount, the boilers that are already burning without changing the number of combustion Increase the combustion value by increasing the combustion value. When the combustion amount is increased in a state where there are less than two boilers capable of increasing the immediate combustion amount, the number of combustion units is increased if the number of combustion units can be increased. When increasing the combustion amount from "---" where all the boilers have stopped combustion, first change the first boiler from "combustion standby" to "low combustion" to "L ---" Become. When the next combustion amount is increased, the number of boilers capable of increasing the immediate combustion amount has not reached the target value of two, so the number of combustion is increased. By changing the second boiler from standby to low combustion, the combustion value of the boiler becomes “LL-”. Next, when increasing the combustion amount, the number of boilers that can increase the immediate combustion amount at this point has reached the set value of two, so this time, without increasing the number of combustion units, Increase combustion value. When the combustion value is increased by changing the combustion value of the first boiler from low combustion to medium combustion, the combustion state becomes “ML--”. Next, when increasing the combustion amount, the number of boilers that can increase the immediate combustion amount has reached the set value of 2, so this time the combustion number of the first boiler is further increased without increasing the number of combustion. To increase. If the combustion value is increased by changing the combustion value of the first boiler from medium combustion to high combustion, the combustion state becomes “HL—”.

Next, when increasing the combustion amount, the number of boilers capable of increasing the immediate combustion amount is less than the set value of two, so the combustion amount is increased by increasing the boiler capable of increasing the immediate combustion amount. . In other words, combustion is started in the third boiler that is in a combustion standby state, and the combustion amount is increased to “HLL−” by setting the combustion to low. After that, when the combustion value is increased when there are two or more boilers capable of increasing the immediate combustion amount, the combustion value is increased by one step with the boiler capable of increasing the instantaneous combustion amount without increasing the number of combustion. However, when the combustion amount is increased in a state where the number of boilers capable of increasing the immediate combustion amount is less than two, the combustion amount is increased by increasing the number of combustion. When the combustion state reaches “HHHL”, all the boilers subject to unit control are already combusting, and the number of combusted units cannot be increased. Therefore, the combustion amount increase from this state is performed by increasing the combustion value of the fourth boiler. The combustion amount can be increased until the combustion amount reaches the maximum combustion amount that is “HHHH”.

When the set number of maintenance target units is 3, the number of boilers capable of increasing the immediate combustion amount is aimed to be 3. In this case as well, when the combustion amount is increased with more than the set number of boilers capable of increasing the immediate combustion amount, the combustion amount is increased by increasing the combustion value without increasing the number of combustion units. When the combustion amount is increased in a state where the number of boilers that can be increased is less than the set number, the number of combustion units is increased if the number of combustion units can be increased. When the set number is three, it changes only where the number of boilers that can increase the amount of immediate combustion increases to three. When the combustion amount is increased from "----" where all boilers have stopped burning, up to "L ---" and "LL--" The same.

In the case of 2 maintenance target units, the next increase was “ML--”, but in the case of 3 maintenance target units, the number of boilers capable of increasing the immediate combustion amount reached the set 3 units at this stage. Therefore, the number of boilers capable of increasing the immediate combustion amount is set to 3 as “LLL-”. Here, the number of boilers that can increase the amount of immediate combustion has reached the set number of three, so the next combustion amount increase does not increase the number of combustion units, and the combustion value of the first boiler is changed from low combustion to medium combustion. “MLL-”. Next, when increasing the combustion amount, the number of boilers capable of increasing the immediate combustion amount is 3 or more, which is the set value. Therefore, the combustion value of the first boiler is increased without increasing the number of combustion again. . When the combustion value is increased by changing the combustion value of the first boiler from medium combustion to high combustion, the combustion state becomes “HLL-”. As a result of this increase, the number of boilers capable of increasing the amount of immediate combustion is less than the target of three, so the next increase will increase the number of combustion. Similarly, if the number of boilers capable of increasing the immediate combustion amount is less than the set number, increase the number of combustion units, and if the number of boilers capable of increasing the immediate combustion amount is greater than the set number, combustion of the boiler that is burning Increase the value.

The idea is the same even if the number of maintenance target units is set to four. In this case as well, if the combustion amount is increased with less than four boilers capable of immediate combustion increase, the number of combustion increases If it is possible, increase the number of combustion units, and if the combustion value is increased when there are already four or more boilers that can increase the immediate combustion amount, increase the combustion value without increasing the number of combustion units. Increase.

As described above, if the number of boilers that can increase the amount of immediate combustion is maintained up to the set number, if a rapid increase in the amount of steam supply becomes necessary, the boiler that burns with low combustion is switched to medium combustion. Or since the boiler which is burning by medium combustion can increase a combustion value to high combustion in a short time, it can respond also at the time of the sudden increase in steam usage. When the increase in the amount of steam used increases, it is possible to cope with large fluctuations by setting a large maintenance target number.

By the way, in the boiler used for such a unit control, the capacity and turndown are increasing in recent years. In the most popular small multi-tube once-through boilers, the conversion evaporation has been up to 2t / h for a long time. Boilers are on sale. And for boilers with 2t / h of converted evaporation, the standard turndown was 2: 1. However, when entering the era of 3t / h of converted evaporation, turndown increased to a large ratio of 5: 1 or 7: 1. It is changing. In other words, when the combustion amount of high combustion is 100%, low combustion is a value such as 20% or 15%. Therefore, the combustion amount in the conventional boiler varies between 1 t / h and 2 t / h in terms of steam generation. What is done is that in a boiler with a converted evaporation amount of 3 t / h, the combustion amount changes between 0.6 t / h and 3 t / h in terms of steam generation. For this reason, the combustion state is greatly different between high combustion and low combustion, and the heating state in the boiler greatly changes depending on the combustion value.

In a once-through boiler in which the water level is set in the middle of the water pipe, there may be inconvenience if the set water level is the same in the high combustion where the boiling of the boiler water is large and the low combustion where the boiling of the boiler water is small. In the boiler, since the generated steam is a mixture of liquid components, it is separated into steam and boiler water by an attached steam separator, and steam with high dryness is taken out. However, if the amount of boiler water that reaches the steam separator increases due to an increase in the amount of boiler water that rises, and the boiler water level in the steam separator increases, the effective volume in the steam separator Becomes smaller. And if the volume of the part which isolate | separates the steam and boiler water in a steam-water separator becomes small, and it becomes impossible to fully isolate | separate boiler water, the dryness of a steam will fall. Moreover, although the heat exchanger tube which heats boiler water is heated with the high temperature combustion gas which flows outside, since the boiler water inside absorbs heat, it is prevented that temperature rises to some extent or more. However, if the amount of boiler water that rises decreases and the amount of boiler water that cools the heat transfer tube at the top of the heat transfer tube decreases, cooling may be insufficient. If the heat transfer tube is insufficiently cooled, the heat transfer tube temperature becomes higher than expected, and if the heat transfer tube temperature becomes normal, the life of the boiler is shortened.

Therefore, the water level in the boiler is changed according to the combustion value. At the time of high combustion where the amount of boiling of boiler water increases, the dryness of the boiler is prevented from decreasing by lowering the set water level. On the other hand, at the time of low combustion when the amount of boiler water boiling up is low, the boiler life is prevented from being shortened by increasing the set water level.

The water level in the boiler is adjusted by installing multiple electrode rods with different heights at the bottom and detecting whether or not the electrode rods are in contact with the boiler water by energizing each electrode rod. This is done by controlling the operation of the feed pump based on the above. When the water level in the boiler decreases to the water supply start water level, the water supply pump is operated to raise the water level, and when the water level rises to the water supply stop water level, the operation of the water supply pump is stopped. Since the boiler water is reduced by the amount of steam generated in the boiler, the water level decreases when the operation of the feed water pump is stopped.

In a boiler that has lowered the set water level due to high combustion, when a change is made to raise the set water level by reducing the combustion value, the water level is raised by operating the feed water pump. On the other hand, in a boiler that has been set low with low combustion and the set water level is high, if the change is made to lower the set water level by increasing the combustion value, the feed water pump will not operate until the low water supply start water level is reached. Thus, it waits for the water level to drop due to evaporation.

The above-mentioned inconvenience can be solved by setting the water level according to the combustion value, but when the combustion value is changed from low combustion to medium combustion and then changed to high combustion in a short time The adjustment of the water level may not be in time for the change of the combustion value. Looking at the portion surrounded by a dotted line in FIG. 8, the combustion value is changed to high combustion immediately after changing from low combustion to medium combustion. This change occurs even when the set value of the maintenance target number is changed, and is generated in each number control pattern.

The change from low combustion to medium combustion or change from medium combustion to high combustion can be completed in a short time because it can be performed simply by changing the fuel supply amount and the combustion air supply amount as described above. . However, when lowering the set position in the boiler, it is necessary to wait for the actual water level to evaporate in the boiler, and changing the water level takes a longer time than changing the combustion value. Due to this time difference, if a time zone in which the combustion value is high but the water level remains high is generated, the amount of boiler water that rises increases and the dryness of the steam decreases.

JP 2012-251721 A

The problem to be solved by the present invention is to install a plurality of boilers that can adjust the combustion value in stages, and to maintain the pressure value of the steam supplied from the boiler within the adjustment range. In a multi-can installation boiler that controls the combustion value of each boiler, a multi-can installation boiler that controls the number of units that can prevent the steam dryness from decreasing when the combustion value is changed by increasing the change speed of the combustion value Is to provide.

The invention described in claim 1 is provided with a plurality of boilers that adjust the combustion value stepwise such as high combustion, medium combustion, low combustion, and standby for combustion, and the pressure value of steam supplied by the boiler It is a multi-can installation boiler with a unit control device that controls the combustion value of each boiler based on
The number control device should be able to detect the number of low-combustion boilers, and set the maintenance target number of low-combustion boilers to an arbitrary value up to the number of boilers subject to unit control minus one. Every
When increasing the amount of combustion in the entire boiler, first confirm whether it is necessary to ensure intermediate combustion based on whether there is one or more boilers that are at or above medium combustion at the present time. Priority is given to securing the boiler of the above, and when there is one or more boilers of medium combustion or higher, control is performed with the aim of setting the number of low combustion boilers next,
In the control with a low combustion boiler as the set number, when the current number of low combustion boilers is less than the maintenance target number, priority is given to increasing the number of low combustion boilers,
When the number of low-fired boilers exceeds the maintenance target number, priority is given to the increase to low-burning boilers for medium combustion. It is characterized in that it takes a number control pattern to be performed after becoming.

According to the second aspect of the present invention, in the multi-can boiler, the maintenance target number of low combustion is set to a larger number as the steam usage changes more rapidly, and the steam usage changes more slowly. The multi-can installation boiler is characterized in that the number of boilers is set to be as small as possible.

By carrying out the present invention, when changing the amount of steam, it is possible to prevent the occurrence of a situation in which the balance between the combustion value and the water level in the can becomes unbalanced and the steam dryness decreases.

Flow diagram of a multi-can installation boiler performing an embodiment of the present invention Number control pattern creation flowchart in one embodiment of the present invention Explanatory drawing of the number control pattern at the time of the combustion amount increase in the time of the maintenance target number of the low combustion maintenance boiler in one embodiment of the present invention from 1 to 3 Number control pattern explanatory drawing at the time of one low combustion maintenance target number in one embodiment of the present invention Number control pattern explanatory diagram when the low combustion maintenance target number is 2 in one embodiment of the present invention Number control pattern explanatory drawing at the time of 3 low combustion maintenance target numbers in one embodiment of the present invention Number control pattern explanatory drawing at the time of zero low combustion maintenance target number in one embodiment of the present invention The number of boilers that can increase the amount of immediate combustion with conventional unit control Boiler maintenance target unit control pattern explanation from 2 to 4 units

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart of a multi-can installation boiler implementing an embodiment of the present invention, FIG. 2 is a flow chart for creating a unit control pattern in an embodiment of the present invention, and FIG. FIG. 6 is an explanatory diagram of a unit control pattern when the combustion amount is increased from one to three combustion boiler maintenance target units. FIG. 4 is an explanatory diagram of the number control pattern when the low combustion maintenance target number is one in one embodiment of the present invention, and FIG. 5 is the number of low combustion maintenance target numbers when the number of low combustion maintenance target number is two in one embodiment of the present invention. FIG. 6 is an explanatory diagram of the control pattern, and FIG. 6 is an explanatory diagram of the number control pattern when the low combustion maintenance target number is three in one embodiment of the present invention.

In FIG. 1, boilers 1 to 4 can be installed in parallel, and steam headers 4 for collecting steam generated in each boiler 1 are provided. The steam pipes 5 are connected between the boilers 1 and the steam headers 4, and the steam generated in the boilers 1 is collected in the steam headers 4 and then sent to a steam use section (not shown). The steam header 4 is provided with a pressure detection device 6 that detects a steam pressure value, and the steam pressure value detected by the pressure detection device 6 is sent to the number control device 3. In the number control device 3, a number control pattern that determines the number of combustion of boilers is set according to the steam pressure value, and the number control device 3 determines the presence / absence of combustion and the combustion value in each boiler. Each boiler is provided with an operation control device 2, and the operation control device 2 receives the combustion request signal from the number control device 3 and burns the boiler.

Each boiler performs four-position combustion control of high combustion, medium combustion, low combustion, and combustion standby. Combustion values in each boiler are between high combustion and medium combustion, such as 50% for medium combustion and 20% for low combustion when high combustion is 100%. The difference in combustion value is set larger than the difference in combustion value between medium combustion and low combustion, and the difference in combustion value between low combustion and combustion standby.

In the number control device 3, a priority order is set for each boiler 1, and it is determined which combustion value is assigned to which boiler from the highest priority order. The number control patterns set in the number control device are those described in FIGS. The number control of the boiler performed by the number control device 3 is performed based on the number control pattern set in the number control device 3, and the combustion amount of the boiler is increased as the steam pressure value detected by the pressure detection device 6 is lower. The higher the steam pressure value, the lower the combustion amount. When the amount of steam generated is larger than the amount of steam used, the steam pressure value increases, and when the amount of steam generated is smaller than the amount of steam used, the steam pressure value decreases. Therefore, the number control device 3 reduces the combustion amount of the boiler if the steam pressure value is high, and increases the combustion amount of the boiler if the steam pressure value is low so as to keep the steam pressure value within the control pressure range. Implement control.

In the number control device, as described side by side in FIG. 3, a low combustion maintenance target number is set, and a number control pattern is determined for each set target number. The set number of the low combustion maintenance target number is determined on the basis of the steam usage status of each user. The set value of the low combustion maintenance target number is set to 0 at the minimum, and the maximum can be set to an arbitrary value between the number of boilers subject to unit control minus one. The set number of low combustion maintenance target units is the number of units aimed at maintaining a low combustion boiler, which is a combustion value that can increase the combustion value in two steps in a short time. The more it keeps, the more it can cope with the rapid increase in steam consumption. The maintenance target number is set to a large value when a rapid increase in steam usage occurs, and to a small value when a rapid increase in steam usage does not occur.

In the figure, the combustion state of the boiler is indicated by “H” for high combustion, “M” for intermediate combustion, “L” for low combustion, and “−” for standby for combustion. The concept of setting the number control pattern in the present invention is as follows. First, secure the early combustion of the boiler that burns with medium combustion, Second, secure the set number of low combustion boilers, Third, from low combustion to medium combustion The change to high combustion is set based on the three principles of prevention in a short time. The first principle is to secure the boiler that burns with medium combustion at the early stage. At the start of combustion from the state where all cans are stopped, until the combustion command for medium combustion is output to the boiler with the first operation priority No combustion command is given to other boilers, and the number of combustion units is increased after a medium combustion boiler is secured. In the unit control pattern, if the combustion amount is increased from “——” to “L——”, the next combustion amount increase will not be “LL—” but “M——”. And This setting is common regardless of the setting of the number of low combustion maintenance target units, which is the second principle, and must be set.

When starting combustion with a boiler that has stopped combustion, a series of preparatory steps are required, so the steam supply cannot be started immediately. However, when the combustion value is increased in a boiler that is burning at low combustion or medium combustion, the combustion value can be increased in a short time because the fuel supply amount and the combustion air supply amount can be increased. If the difference in combustion value between medium combustion and high combustion is greater than the difference between combustion values between low combustion and medium combustion, change from medium combustion to high combustion rather than change from low combustion to medium combustion. The steam supply amount can be changed more greatly. If the number of combustion units is large, when the required amount of steam increases rapidly, it can be handled by changing from low combustion to medium combustion for a plurality of units. However, if the amount of steam used increases rapidly when the number of combustion units is small and a low-combustion boiler cannot be secured sufficiently, if the number of low combustion units is increased at that time, it will not be in time for the increase in steam requirements. There was a thing. In that case, the number of combustion is not increased until the boiler that first started combustion is changed to medium combustion, so that a medium combustion boiler is secured at an early stage. If it is necessary to increase the steam supply amount with a small number of combustion units, it is possible to increase the steam supply amount more quickly by increasing the combustion value with a burning boiler than by increasing the number of combustion units. . In addition, the change from medium combustion to high combustion can be performed in almost the same time as the change from low combustion to medium combustion, but the change range becomes larger, so the steam supply amount can be increased more. Therefore, if there is a medium combustion boiler, the increase in the amount of steam supply from the boiler can be increased in a short time.

The second principle, securing low-combustion boilers, is for boilers with the second highest priority in operation. This sets a low combustion maintenance target number, compares the current number of low combustion boilers with the low combustion maintenance target number, and maintains an appropriate number of low combustion boilers. When increasing the amount of combustion, if the number of low combustion boilers is not enough for the target number of low combustion maintenance, priority is given to changing from combustion stop to low combustion. Further, if the number of low combustion boilers is equal to or greater than the maintenance target number at the time of increase in the combustion amount, one of the low combustion boilers is changed to medium combustion. Low combustion (20%) boilers can increase the combustion value to medium combustion (50%) in a short time and further increase from medium combustion to high combustion (100%). If there is, it can cope with a sudden increase in steam consumption. And the more sudden the load change is, the more the number of low combustion maintaining units is increased to prepare for the sudden load change.

The third principle of preventing the change from low combustion to high combustion via medium combustion in a short time is to increase the combustion value from low combustion to medium combustion in each boiler, It prevents the increase to high combustion. For this reason, priority is given to an increase to medium combustion in a low combustion boiler, and an increase from medium combustion to high combustion is performed after all the boilers burning at low combustion become medium combustion. If this mechanism was not adopted, a unit control pattern such as “LL-” → “ML-” → “HL--” was taken as shown in FIG. In this case, the combustion value at the left end is L → M → H. Since the change from low combustion to medium combustion and from medium combustion to high combustion can be performed in a short time as described above, it may change from low combustion to high combustion in a short time. In that case, when changing from low combustion, which is 20% combustion value, to high combustion, which is 100% combustion value in a short time, the combustion amount is greatly different, so the pressure change / water level change in the boiler is large. There was a problem that occurred. Therefore, “L ——” → “M ——” → “ML ——” → “MM ——” → “MML—” → “MMM—” → “HMM—”. By doing in this way, changing from low combustion to high combustion in a short time is prevented. If this mechanism is adopted, it is possible to prevent the combustion value from being changed from low combustion to high combustion in a short time in a certain boiler.

In the number control program, the low combustion maintenance target number can be set to zero. When the low combustion maintenance target number is set to 0, the second principle and the third principle are not performed. If the low combustion maintenance target number is zero, priority is given to increasing the combustion value in the burning boiler rather than starting combustion in the boiler that has stopped combustion. You will be off.

A specific determination procedure is in the flowchart of FIG. 2 and will be described based on the flowchart. In this flowchart, which combustion value is increased when the combustion amount is increased is calculated. First, in S1, which is the first step in the flowchart, it is confirmed whether it is necessary to ensure medium combustion in principle 1. In step S1, it is detected whether there is one or more boilers of medium combustion or high combustion at present. If there are one or more boilers with medium combustion or high combustion, the period of securing medium combustion due to the small number of combustion is over, but there is no boiler with medium or high combustion. In this case, priority should be given to securing a medium-combustion boiler. In step S1, the number of medium combustion or high combustion boilers is less than one, and in the NO-side route for securing the medium combustion boiler, the presence or absence of a low combustion boiler is confirmed in S2, which is the next step. If there is a low combustion boiler, one low combustion boiler is secured by changing the low combustion boiler to medium combustion in step S3. Here, since the purpose of increasing the combustion value is achieved by changing the combustion value from low combustion to medium combustion, the flowchart ends. If there is no low combustion boiler in step S2, the combustion stopped boiler is activated in step S4 to make low combustion. Since the combustion cannot be suddenly started after the combustion is stopped, the low combustion is set to one stage before, and the combustion value is increased here. Therefore, the increase in the combustion amount is the end.

If there is a medium-burning or high-burning boiler in the previous step S1, it means that securing of a medium-burning boiler when the number of combustion units is small is over, and therefore the process proceeds to step S5. When proceeding to this route, control is performed with the aim of reducing the low combustion rate in principle 2 to the set number. In step S5, the number of low combustion boilers at this time is confirmed. If the number of low combustion boilers is YES, which is less than the set value, the route of step S6 aiming to increase the number of low combustion boilers, the number of low combustion boilers is greater than the set value. If NO, branch to the route of step S12 where the increase in the number of low combustion boilers is not intended. Note that when the low combustion maintenance target number is set to 0, even if the low combustion is 0, the set value is not less than the set value. In this case as well, the process proceeds to step S12.

When it is necessary to increase the number of low-combustion units, the increase in the number of low-combustion boilers can be achieved by setting the combustion stop boiler to low combustion. Therefore, it is confirmed whether there is a combustion stop boiler in the route of step S6. If there is a combustion stop boiler, the combustion value is increased by changing the combustion stop boiler to low combustion in step S7. If there is no combustion stop boiler in step S6, it means that the number of low combustion units cannot be increased at the present time, and therefore the combustion amount is increased by another means. In the next step S8, the control that gives priority to the increase from low combustion to medium combustion in principle 3 is performed, and it is confirmed here whether there is a low combustion boiler. If there is a low combustion boiler, the combustion value is increased by changing the low combustion boiler to medium combustion in step S9. If there is no low combustion boiler in step 8, increasing the combustion value means that the medium combustion boiler can only be changed to high combustion. Note that even when all the operation target boilers are already in high combustion, there is no low combustion boiler, so the NO route is set in step S8. In step S10, the number of high combustion boilers and the number of operation target boilers are compared. This means that when the number of high combustion boilers is equal to the number of operation target boilers, the combustion amount cannot be increased because the combustion amount has already been maximized. The difference between the number of high combustion boilers and the number of operation target boilers is that there are medium combustion boilers. In that case, the combustion amount is changed by changing from medium combustion to high combustion in step S11. Make an increase.

Also, if the NO route is taken because the number of low combustion boilers exceeds the set number in step S5, this means that there is no need to increase the number of low combustion boilers. Prioritize changes to combustion. In the next step S12, the presence or absence of the low combustion boiler is confirmed. If there is a low combustion boiler, the combustion amount is increased by changing the low combustion to the medium combustion in step S13. When there is no low combustion boiler in S12, the presence or absence of a medium combustion boiler is confirmed in step S14. If there is a medium combustion boiler, the combustion amount is increased by changing the medium combustion to high combustion in step S15. If there is no medium combustion boiler, the process proceeds to step S16. Step S16 is a step for confirming whether or not all of the operation target boilers are in high combustion, and if all of the operation target boilers are in high combustion, there is no room for increase in the combustion amount, so the combustion amount is not increased. End. If the number of high combustion boilers and the number of control target boilers are different in step S16, it means that there is a combustion stop boiler, and the combustion amount is increased by setting the combustion stop boiler to low combustion.

The number control patterns created by this procedure are shown in FIGS. In FIG. 3, when the setting of the low combustion maintenance target number is 1 unit, when 2 units are set, when 3 units are set, the combustion amount increase route from the standby state for all cans to the high combustion mode for all cans is set. Number control patterns are listed side by side. FIG. 3 shows a case where the combustion amount continues to increase in one direction, and is an excerpt from FIGS. 4 to 6. First, the number control pattern on the left side of the figure in which the set number of maintenance target numbers is one will be described with reference to the flowchart of FIG. When the combustion amount is increased from "---" for all cans, the number of boilers with medium or high combustion is less than one, but there is no low combustion boiler. Change one of the boilers to low combustion and become "L ---". Even in the next increase in fuel amount, the number of boilers with medium combustion or high combustion is less than one and there are low combustion boilers. In step S3, one of the low combustion boilers is changed to medium combustion, and “M- ―― ”. The control up to this point performs a common operation even if the low combustion maintenance target number is different.

After the increase in the combustion amount, the medium combustion or high combustion boiler satisfies one or more conditions unless the combustion amount is decreased. When the amount of combustion from “M ---” is increased, the number of low combustion boilers is less than the set number, and there is a combustion standby boiler. In step S7, one of the combustion standby boilers is present. Is changed to low combustion and becomes “ML--”.

Prior to this increase, the number of low-fired boilers was less than the set number, so priority was given to increasing the number of low-fired boilers, and if the increase was not possible, the low-fired boiler was changed to medium combustion. However, since the number of low-combustion boilers has reached one of the set number, the next increase in the combustion amount takes the NO route on the side that does not aim at increasing the number of low-combustion boilers in step S5. Since there is a low combustion boiler at this stage, the combustion amount is increased by setting the low combustion boiler to medium combustion in step S13, and “MM-” is set.

Since the number of low combustion boilers has become less than one low combustion maintenance target number due to this increase in the combustion amount, the next increase in the combustion amount involves an operation to increase the low combustion boiler, and in step S7 the combustion stop boiler One of these is set to low combustion and "MML-". After that, if one or more low combustion boilers are present, the low combustion boiler is changed to medium combustion in step S13, and if there are less than one low combustion boiler, the combustion stop boiler is changed to low combustion in step S7. Do as much as possible. In this example, the number of boilers subject to unit control is four, and the number of combustion units cannot be increased further up to “MMMM”. Therefore, the increase in the combustion amount from “MMMM” goes to step S6 because the number of low combustion boilers is less than the set number in step S5, but because there is no combustion stop boiler, there is no low combustion boiler. Proceed to step S10. At this time, since the number of high combustion boilers is smaller than the number of boilers subject to unit control, the process proceeds to step S11, and the medium combustion boiler is changed to high combustion. After that, until all the boilers become high combustion, an operation of changing the medium combustion boilers to high combustion one by one in step S11. Therefore, the subsequent combustion patterns are “HMMM”, “HHMM”, “HHHM”, and “HHHH”. When all of the boilers subject to unit control have high combustion, the combustion amount cannot be increased further, and the combustion amount becomes maximum here. It should be noted that the operation for increasing the combustion amount after becoming “MMMM” is a common movement even if the target number for maintaining low combustion changes.

When the set value of the maintenance target number becomes two, the increase in the combustion amount becomes the number control pattern described in the middle of FIG. Even when the set number of maintenance target units is 2, securing the middle combustion boiler first is the same as when the low combustion maintenance target unit number is 1, and “――――” “L -――” The same unit control pattern is used up to “M ---” and “ML--”. In the next increase, when the low combustion maintenance target number set value described above is 1, the number of low combustion maintenance boilers has reached the set number, and therefore the number of low combustion boilers need not be increased. Therefore, when it was set to “MM--”, when the low combustion maintenance target number of set values is 2, the number of low-burning boilers has not yet reached the set number of 2 at this point. Therefore, here, one of the combustion standby boilers is changed to low combustion to be “MLL−”. After that, when the set value of the maintenance target number is 2, when the number of low combustion boilers is less than 2, priority is given to the increase in the number of low combustion boilers, and the number of low combustion boilers has reached 2 Continues as much as possible to change the low combustion boiler to medium combustion. Although the low combustion maintenance target number is different from the previous example, the idea is the same even if the number is different. Similarly, the combustion patterns are “MML-”, “MMLL”, and “MMML”. In the next increase in combustion amount, the number of low combustion boilers is less than the set value, but there is no combustion stop boiler and the number of low combustion boilers cannot be increased. Since there is a low combustion boiler, the low combustion boiler is changed to high combustion in step S9 to become “MMMM”. The subsequent increase is common even if the set value of the low combustion maintenance number is different, and becomes “HMMM”, “HHMM”, “HHHM”, and “HHHH”.

And even if the number of low combustion maintenance target number is set to 3, the concept is the same as above, and how many low combustion maintenance boilers are increased will change, but how to increase the number is the same. Become. As the set number of low combustion maintenance target units increases, the number of low combustion boilers increases. In a low-combustion boiler, the combustion value can be increased in a short time and the amount of steam generated can be increased immediately. Therefore, if a large number of low-combustion boilers are held, it is possible to cope with a rapid increase in the amount of steam used. . By maintaining the number of low-combustion boilers at an arbitrary number, the number of units can be controlled in accordance with the load fluctuation.

4 is an overall view of the unit control pattern when the set number of low combustion maintenance target units is one, FIG. 5 is two low combustion maintenance target units, and FIG. 6 is a low combustion maintenance target number of three units. Both the movement when the combustion amount increases and the movement when the combustion amount decreases are shown. The reason why the route for increasing the combustion amount and the route for decreasing the combustion amount are made different in FIGS. 4 to 6 is to reduce the frequency of increase / decrease in the number of combustion, that is, to reduce the number of start / stop of combustion.

In the control of the number of multi-can boilers, the efficiency decreases as the number of combustion starts and stops increases, and the followability to the load also decreases. Therefore, it is better not to stop the combustion of boilers that are already burning. Therefore, the number control pattern is determined so that the change in the number of combustion is reduced. For example, in FIG. 5, when the combustion amount is increased by one step from “MML−”, “MMLL” is set. However, when the combustion amount is decreased by one step from “MMLL”, it is not returned to “MML−” and “ MLLL ". In this case, if the "MMLL" is returned to "MML-", if the combustion amount increases thereafter, combustion of one boiler that has stopped combustion must be started, and steam is immediately supplied. Since this is not possible, the increase in steam supply will be delayed. There is a period during which the combustion is stopped, and when the combustion is stopped and when the combustion is started, the amount of heat released increases to ventilate the inside of the furnace. However, when “MLLL” is set, even if it is necessary to increase the combustion amount, the combustion amount can be increased by setting one of the low combustion units to the middle combustion. In this case, the steam supply amount can be quickly increased. Since it can increase, the fall of a steam pressure value can be suppressed. Therefore, the change of the combustion amount is dealt with only by changing the combustion value within the same number of combustion as much as possible, and the number of combustion is changed only when the change of the number of combustion is unavoidable.

In the present invention, the target number of low combustion maintenance is set, and the operation state of the boiler is determined so as to maintain the number of low combustion boilers at the target value. The required amount of steam varies depending on the conditions on the steam usage side. In an environment where the steam usage may increase rapidly, it is necessary to change the steam supply amount accordingly. In this case, by making it possible to set the low combustion maintenance target number to an arbitrary value, and to allow the predetermined number of low combustion boilers to exist, it is possible to cope with load fluctuations. And the low combustion maintenance target number is set to a larger number as the increase of the steam supply amount is larger. If there are many boilers that are maintained at low combustion, there will be many boilers that can increase the amount of combustion in a short time, which means that the followability to the load will be high, and steam is required When the quantity increases rapidly, the steam supply quantity can be greatly increased.

For boilers that perform four-position combustion control of high combustion, medium combustion, low combustion, and combustion stop, changing the combustion value from medium combustion to high combustion is the same as changing from low combustion to medium combustion The amount of combustion can be increased in a short time. If that is the case, it is conceivable to secure a certain number of medium combustion boilers, but there is room for an increase from two stages of increase from low combustion to medium combustion and increase from medium combustion to high combustion if low combustion. On the other hand, in the middle combustion, only an increase of one stage can be performed. Under the condition that a certain number of fuels are combusted, it is possible to increase the amount of steam supply by securing a certain number of low combustions having room for two stages of increase.

For users who use only a small amount of steam and rarely perform high-combustion operation with all installed boilers subject to unit control, for example, from the amount of steam generated in "L ----" (20%), "MM If you use steam for the amount of steam generated in "-" (50% x 2 = 100%), the number of combustion units will start and stop repeatedly between one and two. In the boiler, the inside of the furnace is ventilated when combustion is started and stopped. Therefore, the amount of heat release increases as the number of start and stop increases, and the overall efficiency decreases. If the number of combustion is reduced and “L ---” (for 20%) and “H ---” (for 100%) are repeated, a decrease in efficiency due to start / stop can be prevented. For this reason, if the target number of low combustion maintenance is increased, it may be counterproductive and is set to an appropriate value according to the situation.

When the low combustion maintenance target number is set to 0, that is, the control that does not perform low combustion maintenance is performed, the number control pattern is as shown in FIG. In this case, since the fixed number of low-combustion boilers is not maintained, when the combustion amount is increased in a state where there is a low-combustion boiler, the low-combustion boiler is changed to medium combustion. Operations that prioritize the change from low combustion to medium combustion are performed in all states.

The point to be noted in the number control pattern in the present invention is that it is surrounded by a dotted-line square in FIG. In the present invention, when the combustion value is changed from low combustion to medium combustion in a certain boiler, the combustion value is increased next in the boiler after the combustion value in another boiler is increased. Therefore, it does not increase to high combustion immediately after increasing from low combustion to medium combustion.

In the conventional case, for example, in the case of 33% low combustion, 66% medium combustion, and 100% high combustion, if the time in medium combustion is short, the combustion value is substantially suddenly changed from 33% to 100% combustion value. was there. In addition, when the low combustion is 20%, the middle combustion is 60%, and the high combustion is 100%, when the time in the middle combustion is short, the combustion value suddenly becomes 100% from the 20% combustion value, and the variation range is widened. The impact was even greater. When such a rapid change of the combustion value is performed, the water level in the boiler may deviate from an appropriate position determined according to the combustion value. Although the combustion value is high and the boiling of the boiler water is large, if the water level in the boiler remains at a high position for low combustion, the steam dryness is due to the water level being too high. Was supposed to decline. As in the present invention, after increasing from low combustion to medium combustion, after increasing the time to maintain medium combustion, increase to high combustion, and do not immediately increase to high combustion. Therefore, it is possible to prevent the balance between the combustion amount and the water level in the boiler from being greatly broken.

In this embodiment, when the combustion standby mode is changed to low combustion mode, the combustion mode is immediately changed to intermediate combustion mode. Therefore, it is not necessary to provide a time for maintaining an intermediate combustion value in this portion. Not. However, in this embodiment, the difference in the combustion value from the combustion standby to the low combustion and from the low combustion to the medium combustion, such as low combustion 20%, medium combustion 50%, and high combustion 100%, respectively, is from the medium combustion to the high combustion. It is smaller than the difference in combustion value. Here, since the difference in the combustion value from the standby to the low combustion and from the low combustion to the middle combustion is small, it is possible to change the combustion value without greatly losing the balance between the combustion value and the water level. I can do it.

In addition, as a unit control pattern, the target number of low combustion maintenance is zero, that is, a unit control pattern that does not aim to maintain a low number of low combustion boilers is set. For users who use only a small amount of steam and rarely perform high-combustion operation in all installed boilers subject to unit control, for example, from the amount of steam generated by "L ---" (20%), "MM--" If the steam is used for the amount of steam generated (50% × 2 = 100%), the number of combustion units will be repeatedly started and stopped between one and two. In a boiler, when the combustion starts and stops, the inside of the furnace is ventilated, so the amount of heat release increases, and increasing the number of starts and stops leads to a decrease in efficiency. If the number of combustion is reduced and “L ---” (for 20%) and “H ---” (for 100%) are repeated, a decrease in efficiency due to start / stop can be prevented.

For users whose steam consumption varies greatly depending on the season, the target number of low combustion maintenance is set to 0 rather than preventing a short-time transition from low combustion to high combustion by taking the above unit control pattern depending on the required amount of steam. In some cases, it may be desirable to reduce the frequency of combustion start / stop depending on the number control pattern used as a base. When the target number of low combustion maintenance is set to 0, the above-mentioned number control pattern cannot be taken, but more preferable number control can be performed by providing options.

The present invention is not limited to the embodiments described above, and many modifications can be made by those having ordinary knowledge in the art within the technical idea of the present invention.

1 boiler
2
Operation control device
3 Number control device 4 Steam header 5 Steam piping 6 Pressure detection device

Claims (2)

Multiple boilers that adjust the combustion value in stages, such as high combustion, medium combustion, low combustion, and combustion standby, are installed, and the combustion value of each boiler is set based on the pressure value of the steam supplied by the boiler. A multi-can installation boiler with a unit control device to control,
The number control device should be able to detect the number of low-combustion boilers, and set the maintenance target number of low-combustion boilers to an arbitrary value up to the number of boilers subject to unit control minus one. Every
When increasing the amount of combustion in the entire boiler, first confirm whether it is necessary to ensure intermediate combustion based on whether there is one or more boilers that are at or above medium combustion at the present time. Priority is given to securing the boiler of the above, and when there is one or more boilers of medium combustion or higher, control is performed with the aim of setting the number of low combustion boilers next,
In the control with a low combustion boiler as the set number, when the current number of low combustion boilers is less than the maintenance target number, priority is given to increasing the number of low combustion boilers,
When the number of low-fired boilers exceeds the maintenance target number, priority is given to the increase to low-burning boilers for medium combustion. The multi-can installation boiler is characterized in that it takes a number control pattern to be performed after becoming. In the multi-can boiler according to claim 1, the maintenance target number of low combustion is set to a larger number as the steam usage changes rapidly, and less as the steam usage changes more slowly. A multi-can installation boiler characterized in that the number of boilers is set.

Images