JP5480697B2 - Combustion equipment - Google Patents

Description

The present invention comprises a burner that heats the furnace interior by combustion;
Pattern setting means for setting a combustion control pattern that repeats combustion in the unit cycle time period, while setting the ON time H and OFF time L of combustion within the unit cycle time according to the heat load in the furnace;
The present invention relates to a combustion facility comprising control means for controlling combustion of the burner with a combustion control pattern set by the pattern setting means.

  A typical example of such a combustion facility is an industrial furnace such as a heating furnace or a heat treatment furnace, and it is desired to ensure uniformity of furnace temperature and control responsiveness, and to ensure the life of a burner provided in the facility.

  Inventors proposed the technique of patent document 1 as a combustion installation. On the other hand, Patent Document 2 proposes a combustion control method that can be employed in similar combustion equipment.

  The technologies disclosed in these documents are technologies for controlling the furnace temperature by ON / OFF control of a burner. In these technologies, the cycle time is determined by the output signal (%) of the temperature controller provided in the furnace. The ON time or OFF time in T is set, and the burner is ON-OFF controlled based on the set combustion control pattern. This control is substantially time proportional control.

  In the technique described in Patent Document 1, a set cycle time (cycle time in the present invention) is included as a parameter of the combustion control pattern, and the pattern setting means is configured to respond to the heat load in the furnace in the selected combustion control pattern. When the heat load is greater than or equal to the set value, the burn time of the burner (ON time in the present invention) is maintained constant, the set cycle time is adjusted according to the heat load, and the heat load is set from the set value. If it is smaller, the burn time of the burner is adjusted according to the heat load in such a manner that the set cycle time is kept constant. By adopting such a control mode, combustion control according to the heat load can be realized in a range where the heat load is relatively low.

In the technique described in Patent Literature 2, the output range of the temperature controller is divided, a maximum OFF time is set in advance corresponding to each division, and the normal cycle time and the OFF time calculated from the output signal are set. When the maximum OFF time corresponding to the above category is exceeded, the cycle time when the maximum OFF time is set in the control corresponding to the output signal is calculated instead of the control based on the normal cycle time. Burner ON / OFF control is performed based on the cycle time and the maximum OFF time.
By adopting such a control mode, when the OFF time exceeds the maximum OFF time (when the minimum ON time becomes shorter than the minimum value, that is, on the low combustion side), the OFF time is set to the maximum OFF time. Set the time to calculate the cycle time and ensure the minimum ON time.

Japanese Patent No. 3527035 Japanese Patent No. 4093513

  In the two patent documents described above, both of these patent documents solve the problem on the low heat load side, and hence the problem of the present application will be described below focusing on the invention described in Patent Document 1.

Problem 1 to be solved
The technique described in Patent Document 1 is a kind of time proportional control, and aims to improve both the device life and control responsiveness by making the cycle time variable while the ON time is fixed. In this technique, it is usual to use flow control using a control motor (hereinafter sometimes abbreviated as CM) because it dislikes rapid fluctuations in furnace pressure.
However, in this cycle time variable method, if the ON time is fixed, the OFF time falls below the ON time when the output exceeds 50%. Further, when the thermal load increases, a state occurs in which the OFF time is less than the control motor operating time. Thus, when the OFF time is less than the control motor operating time, the input is different from the input that is actually expected, and the output characteristics are distorted, so that hunting is likely to occur.

This situation will be described with reference to FIG.
FIG. 5 shows the temperature control output of the temperature controller (horizontal axis: ratio% when the temperature control output is 100% when the entire cycle time is ON time) and the input (vertical axis: vertical axis: It is a figure which shows the relationship with the ratio% when input is set to 100% when it becomes ON time in all cycle time.
As can be seen from this figure, in the ideal behavior, as indicated by the solid line in the figure, the input should increase linearly with respect to the temperature control output to reach 100%. In the region where the temperature control output is higher than 50% due to the use of the CM, the actual input moves to the input increasing side with respect to the ideal behavior, and is higher than the temperature control output.

Problem 2 to be solved
Similar to the problem 1, in the method of fixing the ON time, as shown in FIG. 6B, the OFF time becomes shorter as the output becomes higher. For example, when the output is 80% when the ON time is 10 seconds, the cycle time is 12.5 seconds and the OFF time is 2.5 seconds. During this 2.5 seconds, the burner OFF → reignition operation will be performed, but if the afterfire does not disappear during this time, the flame detector provided in the furnace may cause a false detection. It is thought to occur.

Problem 3 to be solved
Under the condition of Problem 2, the cycle time is as extremely short as 12.5 seconds, and the life of the device is remarkably reduced.

  The present invention has been made in view of the above problems, and an object of the present invention is to use a valve that is controlled to open and close by a control motor, for example, in a control region in which the ratio of the ON time in the cycle time is relatively high. Even when the configuration is adopted, a good proportional relationship between the temperature control output and the actual input can be realized, the possibility of erroneous detection by the flame detector can be kept low, and it is also preferable in terms of the life of the equipment. It is to obtain a combustion facility.

A burner for heating the inside of the furnace by combustion according to the present invention for achieving the above object,
Pattern setting means for setting a combustion control pattern that repeats combustion in the unit cycle time period, while setting the ON time H and OFF time L of combustion within the unit cycle time according to the heat load in the furnace;
A characteristic configuration of a combustion facility comprising a control means for controlling combustion of the burner with a combustion control pattern set by the pattern setting means,
Said pattern setting means, said OFF time L becomes the reference minimum OFF time Lmin or more, and such that said cycle time T is equal to or less than the maximum cycle time Tmax, and sets the combustion control pattern for operation control of the burner ,
An ON time ratio that is a ratio (H / T) of the ON time H in the cycle time T, in which the reference shortest OFF time Lmin and the ON time H become longer as the thermal load in the furnace increases. From P, the temporary combustion control pattern (He, Le, Te = He + Le) corresponding to the heat load in the furnace is derived,
The provisional OFF time Le in the derived provisional combustion control pattern (He, Le, Te) is not less than the reference shortest OFF time Lmin, and the provisional cycle time (Te = He + Le) in the provisional combustion control pattern. Is less than the longest cycle time Tmax, the obtained temporary combustion control pattern (He, Le, Te) is set as the combustion control pattern for operation control .

In this combustion facility, a reference shortest OFF time Lmin is set in advance, and this reference shortest OFF time is set from the fully closed state to the fully open state, for example, in relation to the operation time of the control motor. It can be made larger than the time required to
On the other hand, as described above, the problem to be solved in the present invention occurs in a situation where the heat load increases and the ratio of the ON time within a single cycle time needs to be increased. When the cycle time is constant, the OFF time is shortened sequentially, and the opening / closing of the on / off valve that controls the opening / closing of the fuel supply cannot catch up, and there is a gap between the ideal behavior described above and the actual input. To do.

The reason why this problem occurs will be described with reference to FIG.
In the figure, (a) shown on the upper side is a diagram showing a behavior at an output of 50% in which the ON time and the OFF time are the same. The upper side shows the state of the electromagnetic valve opening that allows the valve to be opened and closed instantaneously, and the lower side is the opening of the valve that is controlled to open and close by a control motor that requires a predetermined time (10 seconds in the illustrated case) to open and close the valve. Indicates the situation.
As can be seen from this figure, when the required time from the fully closed state to the fully open state is the same as the ON time and the required time from the fully open state to the fully closed state is the same as the OFF time at 50% output It can be seen that the valve can be opened and closed reliably between the fully closed state and the fully open state.
That is, in this state, no problem occurs in the controllability of the combustion amount.

On the other hand, in the same figure, (b) shown on the lower side is a diagram showing a behavior at an output of 70% in which the ON time increases with respect to the OFF time. This figure also shows the state of the solenoid valve opening that allows the valve to be opened and closed instantaneously on the upper side, and the opening state of the valve that requires a predetermined time (10 seconds in the illustrated case) to open and close the valve on the lower side. ing.
As can be seen from this figure, when the required time from the fully closed state to the fully open state and the required time from the fully open state to the fully closed state becomes shorter than the OFF time at 70% output, The opening operation is started before reaching the closed state, and as a result, it can be seen that the time during which the valve is open deviates from the original control target and the controllability is poor.

  Therefore, even if the OFF time within the cycle time is inevitably shortened due to an increase in the thermal load, the OFF time is provided with a reference that is referred to as the “reference shortest OFF time”. If the OFF time is not shortened, the problem is solved.

In this case, if the OFF time is fixed to the reference shortest OFF time, the ON time becomes longer as the heat load increases, and as a result, the cycle time must be longer.
If the cycle time becomes long in this way, the purpose of setting the cycle time and repeating the combustion control pattern at this cycle time is deviated, and control responsiveness cannot be ensured.
Therefore, the concept of maximum cycle time, which is the upper limit of the cycle time, is introduced, and the OFF time, ON time, and cycle time in the combustion control pattern are set under conditions that satisfy both the requirements of the reference minimum OFF time and the maximum cycle time. Set.

  By providing such a restriction, even when it takes time to open and close the valve, the valve can be reliably operated from the fully closed state to the fully opened state or vice versa. Even when the heat load increases, the amount of input charged into the furnace can be appropriately controlled through the valve for the temperature control output.

As described above, when the combustion control pattern is set by the pattern setting means, it is set by the following procedure .
That is, the reference shortest OFF time Lmin and the ON time H that is the ratio (H / T) of the cycle time T, in which the ON time H becomes longer as the thermal load in the furnace increases, is ON. From the time ratio P, the provisional combustion control pattern (He, Le, Te = He + Le) corresponding to the heat load in the furnace is derived,
The temporary OFF time Le in the temporary combustion control pattern (He, Le, Te) derived in this way is equal to or longer than the reference shortest OFF time Lmin, and the temporary cycle time in the temporary combustion control pattern ( When Te = He + Le) is equal to or shorter than the longest cycle time Tmax, the obtained temporary combustion control pattern (He, Le, Te) is set as the combustion control pattern for operation control.

In such a setting procedure, in relation to the reference shortest OFF time Lmin as a reference, a temporary combustion control pattern (ON = He = OFF time Le and the total value thereof Te = He + Le from the ON time ratio P) He, Le, Te) are first derived.
Then, the relationship between the reference minimum OFF time Lmin and the maximum cycle time Tmax, which are requirements of the present invention, is confirmed. Here, since the OFF time L is selected so as to satisfy the requirement regarding the reference shortest OFF time Lmin, the requirement of the cycle time T is confirmed.
When the requirement is satisfied, the temporary combustion control pattern (He, Le, Te) is adopted as it is, and as a result, even when the heat load is large, the reference shortest OFF time Lmin required in the present invention. In addition, both requirements for the maximum cycle time Tmax can be satisfied, and the relationship between the temperature control output and the input supplied to the furnace can be kept good.

As a more specific method for setting the combustion control pattern by the pattern setting means, the following configuration can be adopted.
When the heat load is high When the ON time ratio P is larger than 0.5,
The pattern setting means includes
The provisional cycle time (Te = He + Le) is obtained as Te = Lmin / (1-P), where the reference shortest OFF time is Lmin,
When the temporary cycle time (Te = He + Le) is shorter than the longest cycle time Tmax, the cycle time T is set as the temporary cycle time Te and the ON time H is set as Te × P.
By adopting this procedure, when the ON time T needs to be longer than the OFF time L, the OFF time L is held as the reference shortest OFF time Lmin, and a provisional cycle time corresponding to the reference shortest OFF time Lmin ( Te = He + Le) is the cycle time T, and the ON time H can also be set appropriately.

On the other hand, when the temporary cycle time (Te = He + Le) is longer than the longest cycle time Tmax, the cycle time T is set as the longest cycle time Tmax, and the OFF time L is set as Tmax × (1−P).
In this case, control responsiveness can be ensured by maintaining the longest cycle time at the expense of consistency between the temperature control output and the actual input.

When the heat load is low Conversely, when the ON time ratio P is smaller than 0.5,
The pattern setting means includes
The provisional cycle time (Te = He + Le) is obtained as Te = Hmin / P, where the reference shortest ON time is Hmin,
When the temporary cycle time (Te = He + Le) is shorter than the longest cycle time Tmax, the cycle time T is set as the temporary cycle time Te, and the OFF time H is set as Le × (1−P).
By adopting this procedure, when the ON time T needs to be shorter than the OFF time L, the ON time is held as the reference shortest ON time Hmin, and the provisional cycle time (Te = He + Le) is the cycle time T, and the OFF time L can be set appropriately.

On the other hand, when the temporary cycle time (Te = He + Le) is longer than the longest cycle time Tmax, the cycle time T can be set as the longest cycle time Tmax, and the ON time H can be set as Tmax × P.
In this case, controllability response can be secured by maintaining the longest cycle time at the expense of consistency between the temperature control output and the actual input.

In the combustion equipment configured so far,
The on / off valve provided in the burner is a control motor control on / off valve whose opening / closing operation is controlled by a control motor,
The reference shortest OFF time Lmin is greater than or equal to the state transition time with respect to the state transition time, which is the time required for the state of the on-off valve to transition from one state between the fully closed state and the fully open state to the other state. It is preferable that the time is set to 1.05 times or less of the state transition time.
Even when adopting a valve that takes a relatively long time to switch between the fully closed state and the fully open state as the on-off valve provided in the burner, the relationship between the temperature control output and the actual input is originally required. You can keep in a relationship.

The figure which shows the structure of a combustion facility. Diagram showing combustion control patterns at different heat loads Explanatory drawing of the configuration of combustion control pattern Diagram showing combustion control pattern setting flow under different heat loads The figure which shows the relationship between the temperature control output and input in this invention and a prior art. The figure which shows the combustion control pattern in the temperature control output 80% in this invention and a prior art Explanatory diagram of the cause of problems in the prior art

Hereinafter, an embodiment of the present invention applied to a combustion facility for heating a box heat treatment furnace will be described with reference to the drawings.
As shown in FIG. 1, four burners 4 for heating a furnace interior 13 of a box-shaped furnace body 11 having an opening / closing door 12 are provided in a distributed manner on the ceiling portion of the furnace body 11. A control unit 7 for controlling each of the burners 4 and an operation panel 8 for sending various control commands to the control unit 7 are provided. Then, the processing object is disposed in the furnace 13 and the four burners 4 are controlled by the control unit 7 so that the furnace 13 is heated to a predetermined target heating condition, and the processing object is heated. It is configured.

  A fuel gas supply path 9 and a combustion air supply path 10 are connected to each burner 4. The fuel gas supply path 9 is provided with a gas on-off valve Vg for intermittently supplying the fuel gas to the burner 4, and the combustion air supply path 10 is intermittently supplied with the combustion air to the burner 4. An on-off valve Va for air is interposed. Although detailed explanation is omitted, the burner 4 is provided with a sub-burner (not shown) for ignition. The gas on-off valve Vg and the air on-off valve Va are on-off valves whose opening and closing is controlled by a control motor CM. By intermittently supplying fuel gas and combustion air to the burner 4, the burner 4 is burned. Or the combustion can be stopped.

  Each of the burners 4 is configured in the same manner, but in order to clarify the positional relationship of each of the burners 4, 4 m, 4 n, 4 o, 4 p and so on are arranged in order from the one located closer to the door 12. Describe.

  Next, the control configuration of the combustion facility will be described. In this combustion facility, the entire inside of the furnace 13 is controlled as one zone. For example, the tempering mode in which the temperature range of the heat treatment is less than 870 ° C. and the temperature range of the heat treatment are It is configured to be able to operate in each operation mode such as a quenching mode of 870 ° C. or higher.

  The operation panel 8 includes a temperature setting unit 81 for setting a target temperature, an automatic / manual switch 82 for switching between an automatic mode for automatically switching the operation mode and a manual mode for manually switching, an operation start / stop switch 83, and the like. Is provided.

The control unit 7 will be described further.
Based on the deviation between the detected temperature of the temperature sensor T3 as temperature detecting means for detecting the temperature in the furnace 13 and the target temperature set by the temperature setting unit 81, the controller 7 outputs a temperature adjustment output. The temperature adjusting means 71, the pattern setting means 72 for setting the combustion control pattern that determines the combustion conditions with the passage of time for each burner 4, and the combustion control pattern set by the pattern setting means 72 are 4 Control means 73 for controlling the burner 4 is provided. The temperature adjustment means 71 outputs a large temperature adjustment output so as to require a larger heating output as the deviation becomes larger.

  The pattern setting unit 72 includes a storage unit 72a that stores basic information of a combustion control pattern for controlling combustion of the burner, and a pattern command unit 72b that generates and commands a combustion control pattern for each burner based on the basic information. The control means 73 controls each of the four burners 4 with the commanded combustion control pattern based on the command information from the pattern command means 72b.

The basic information stored in the storage means 72a includes the order in which the four burners 4 are burned, that is, the combustion start timing at which the burners start combustion within a specific cycle time (from the start timing of the specific cycle time to the combustion start timing). (Hereinafter referred to as “start timing set value” and described as td in FIG. 3), and the maximum allowable cycle time Tmax and ON time H are allowable. The reference shortest ON time Hmin that is the reference value of the shortest time and the reference shortest OFF time Lmin that is the allowable reference value of the shortest time are included.
A setting method for setting the combustion control pattern of each burner using these basic information will be described in detail later.

  In this control unit 7, the pattern setting means 72 is a combustion consisting of a cycle time T, an ON time H, and an OFF time L in accordance with the temperature adjustment output, that is, the temperature adjustment output that becomes a larger value as the thermal load increases. Generate a control pattern. Here, the start timing of the ON time H is adjusted within the determined cycle time T using the start timing set value td described above. In the present invention, the cycle time T changes according to the thermal load. The start timing set value td is set as a standard value corresponding to the longest cycle time Tmax, for example, for each burner. When T is shortened, it is shortened in proportion to the ratio (T / Tmax).

  Hereinafter, generation of a combustion control pattern that is mainly executed in the pattern command unit 72b will be described. In the following description, in order to explain the setting method of the cycle time T, ON time H, and OFF time L for the thermal load (temperature control output) unique to the present application, the heat for a specific single burner is described. First, a method for determining a combustion control pattern for a load (established as a combination of cycle time T, ON time H, and OFF time L) will be described. After the combustion control pattern is determined, the start timing of the ON time H in the combustion control pattern is adjusted based on the combustion order between the burners and the start timing set value td described above.

  FIG. 3 is a diagram showing the relationship between the cycle time T, the ON time H, and the OFF time L in a predetermined combustion control pattern according to the present invention. The cycle time T is established as the sum of the ON time H and the OFF time L. To do. This combustion control pattern is sequentially set according to the input heat load (temperature adjustment output). The cycle time in a specific combustion control pattern is the same among the plurality of burners.

In the combustion facility according to the present application, the longest cycle time Tmax, the reference shortest ON time Hmin, and the reference shortest OFF time Lmin are set for the combustion of each burner.
Here, the longest cycle time Tmax is the maximum cycle time that is allowable when controllability including control responsiveness is considered, and the reference shortest ON time Hmin and the reference shortest OFF time Lmin have a smaller thermal load in the former. In this case, the reference value is the shortest time allowable on the ON time side, and the latter is the shortest time reference value allowable on the OFF time side when the heat load is large. In particular, the latter reference value for the shortest time is unique to the present application, and is set to absorb the deviation from the temperature control output of the actual input, which is a problem on the high heat load side as described above with reference to FIG. As described above with reference to FIG. 7, the time required to open and close the valve between the fully open state and the fully closed state of the valve by the control motor CM provided in the open / close valve (see FIG. 10 times in the case of 7) or longer than that time and close to that time (for example, 1.05 times the time required to control the valve between the fully open state and the fully closed state) ) Is set.
In the embodiment shown in FIG. 2 and FIG. 6A, the longest cycle time Tmax is set to 60 seconds for all burners, the reference shortest ON time Hmin is 10 seconds, and the reference shortest OFF time Lmin is 10 seconds.

  The pattern control means 72 has a relationship between the reference shortest ON time Hmin or the reference shortest OFF time Lmin and the ON time H in the cycle time T, which has a relationship that the ON time H becomes longer as the thermal load in the furnace increases (H / A temporary combustion control pattern (He, Le, Te = He + Le) corresponding to the heat load in the furnace is derived from the ON time ratio P which is T). Here, the ON time ratio P is in the range of 0 to 1, and is determined so that the ON time ratio P increases when the heat load is large, according to the temperature control output (heat load) described above. The ON time ratio P: 0 corresponds to 0% output without heating, and the ON time ratio P: 1 corresponds to heating with 100% output.

FIG. 4 shows a flow for setting the combustion control pattern (H, L, T) by the pattern setting means 72.
When the pattern setting means 72 receives the temperature adjustment output corresponding to the ON time ratio P, P = temperature adjustment output / 100, and it is compared whether or not the ON time ratio P is greater than 0.5 (step # 1). . Here, when the ON time ratio P is larger than 0.5, it means that the ON time H is set longer than half of the cycle time T, and when it is smaller, the OFF time L is set shorter than half of the cycle time T. It means setting to the short side.

[High heat load support]
Hereinafter, first, the setting method on the side where the heat load is high, in other words, the side where the ON time ratio P is larger than 0.5, which is the most problematic of the present application will be described. In FIG. 4, it is a flow on the left side of the same figure. In this process, as the ON time ratio P increases, the cycle time T becomes longer. Therefore, while paying attention to the longest cycle time Tmax, the combustion control pattern (H , L, T).

First, a provisional cycle time (Te = He + Le) is obtained as Te = Lmin / (1-P) from the reference shortest OFF time Lmin (step # 2).
Subsequently, it is compared whether or not the provisional cycle time (Te = He + Le) obtained in step # 2 is longer than the longest cycle time Tmax (step # 3).

  Here, if the provisional cycle time (Te = He + Le) is longer than the longest cycle time Tmax (step # 3: Yes), the cycle time T is set to the longest cycle time Tmax, and the OFF time L is set to Tmax × (1-P ) (Step # 4). Under these conditions, the ON time H is naturally Tmax × P. The region where the combustion control pattern is set in this manner is shown as ZU1 in FIG.

  On the other hand, when the provisional cycle time (Te = He + Le) is shorter than the longest cycle time Tmax (step # 3: No), the cycle time T is a provisional cycle time (Te = He + Le) obtained in advance ( Step # 5). In this case, the ON time H is naturally Te × P, and the OFF time L is the reference shortest OFF time Lmin from the previously selected conditions. The region where the combustion control pattern is set in this way is shown as ZU2 in FIG.

[Compatible with small heat load]
Next, a setting method on the side having a lower heat load, in other words, the side on which the ON time ratio P is smaller than 0.5 will be described. FIG. 4 is a flowchart on the right side of the figure. Regarding this processing, as the ON time ratio P becomes smaller, the OFF time ratio (1-P) becomes larger, and similarly, the cycle time T becomes longer. Therefore, the above explanation was made while paying attention to the longest cycle time Tmax. A combustion control pattern (H, L, T) is set so that the reference shortest ON time Hmin can be observed.

In the processing on the right side, a temporary cycle time (Te = He + Le) is obtained as Te = Hmin / P from the reference shortest ON time Hmin (step # 6).
Subsequently, it is compared whether or not the provisional cycle time (Te = He + Le) obtained in step # 6 is longer than the longest cycle time Tmax (step # 7).

  When the provisional cycle time (Te = He + Le) is longer than the longest cycle time Tmax (step # 7: Yes), the cycle time T is set as the longest cycle time Tmax, and the ON time H is set as Tmax × P. (Step # 9). Here, the OFF time L is naturally Tmax × (1−P). The region where the combustion control pattern is set in this way is shown as ZL1 in FIG.

  On the other hand, when the provisional cycle time (Te = He + Le) is shorter than the longest cycle time Tmax (step # 7: No), the cycle time T is set to the provisional cycle time (Te = He + Le) obtained in advance ( Step # 8). In this case, the OFF time L is naturally Te × (1-P), and the ON time is the reference shortest ON time Hmin from the previously selected conditions. The region where the combustion control pattern is set in this way is shown as ZL2 in FIG.

  When such a combustion control pattern (H, L, T) setting method is used, the burner is set so that the OFF time L is not less than the reference shortest OFF time Lmin and the cycle time T is not more than the longest cycle time Tmax. The combustion control pattern for the operation control is set, specifically, the reference shortest ON time Hmin or the reference shortest OFF time Lmin and the ON time H becomes longer as the heat load in the furnace increases. Temporary combustion control according to the heat load in the furnace from the ON time ratio P (in other words, the OFF time ratio (1-P)) which is the ratio (H / T) of the ON time H in the cycle time T A pattern (He, Le, Te = He + Le) is derived, and the provisional OFF time Le in the provisional combustion control pattern (He, Le, Te) is equal to or greater than the reference shortest OFF time Lmin. When the temporary cycle time (Te = He + Le) in the temporary combustion control pattern is equal to or shorter than the longest cycle time Tmax, the temporary combustion control pattern (He, Le, Te) is set as the combustion control pattern for operation control. It is supposed to be.

In this manner, the combustion control when the combustion control pattern (H, L, T) is the longest cycle time Tmax: 60 seconds, the reference shortest ON time Hmin: 10 seconds, and the reference shortest OFF time Lmin: 10 seconds. The pattern is shown in FIG. FIG. 2 shows examples in which the temperature control output (described as “temperature control output”) is 10%, 20%, 50%, 80%, and 90%. Further, FIG. 5A shows the combustion controllability. Compared with the result of FIG. 5B, the controllability on the high heat load side is also improved.
Further, FIG. 6 shows a comparison of the difference in combustion control pattern at a temperature control output of 80% for the present invention (a) and the prior art (b). In the prior art, since the ON time H is fixed, the OFF time L and the cycle time T are shortened, and there is a problem that the OFF time L described above is shorter than the reference shortest OFF time Lmin. I understand. On the other hand, in the present invention, the OFF time L is made equal to the reference shortest OFF time Lmin, and the ON time H and the cycle time T become long. Therefore, the problem on the side where the heat load is large does not occur. However, as shown in FIG. 5A, when the cycle time T exceeds the longest cycle time Tmax, there is a problem in terms of control responsiveness, so the OFF time L is exceptionally shortened.

[Another embodiment]
In the above embodiment, the present invention has been exemplified for the case where the present invention is applied to a combustion facility for heating a box-type heat treatment furnace. However, the present invention can be applied to a combustion facility for heating various furnaces. Can do.
For example, the present invention can also be applied to a combustion facility that heats a continuous furnace provided with a conveying means that introduces a processed material into the furnace from the inlet, passes the inside of the furnace, and discharges the processed material from the outlet.
In the above embodiment, the case where the pattern setting unit receives the temperature adjustment output and executes a certain arithmetic processing based on the output to set the combustion control pattern is shown. A configuration may be adopted in which the combustion control pattern set according to the technique of the present invention is stored, and the combustion control pattern is set by calling from the storage means corresponding to the temperature control output.

  In the control region where the ratio of ON time in the cycle time is relatively high, a good proportional relationship between the temperature control output and the actual input can be realized even when adopting the control form using CM, and flame detection The possibility of erroneous detection by the vessel can be kept low, and a combustion facility preferable in terms of the life of the device can be obtained.

71 Temperature adjusting means 72 Pattern setting means 72b Pattern command means 73 Control means

Claims (4)

A burner that heats the interior of the furnace by combustion;
Pattern setting means for setting a combustion control pattern that repeats combustion in the unit cycle time period, while setting the ON time H and OFF time L of combustion within the unit cycle time according to the heat load in the furnace;
Combustion equipment comprising a control means for controlling combustion of the burner with a combustion control pattern set by the pattern setting means,
Said pattern setting means, said OFF time L becomes the reference minimum OFF time Lmin or more, and such that said cycle time T is equal to or less than the maximum cycle time Tmax, and sets the combustion control pattern for operation control of the burner ,
An ON time ratio that is a ratio (H / T) of the ON time H in the cycle time T, in which the reference shortest OFF time Lmin and the ON time H become longer as the thermal load in the furnace increases. From P, the temporary combustion control pattern (He, Le, Te = He + Le) corresponding to the heat load in the furnace is derived,
The provisional OFF time Le in the derived provisional combustion control pattern (He, Le, Te) is not less than the reference shortest OFF time Lmin, and the provisional cycle time (Te = He + Le) in the provisional combustion control pattern. Is a combustion facility that sets the calculated temporary combustion control pattern (He, Le, Te) as the combustion control pattern for operation control when the value is equal to or shorter than the longest cycle time Tmax . When the ON time ratio P is larger than 0.5,
The pattern setting means includes
The provisional cycle time (Te = He + Le) is obtained as Te = Lmin / (1-P), where the reference shortest OFF time is Lmin,
The combustion equipment according to claim 1, wherein when the temporary cycle time (Te = He + Le) is shorter than the longest cycle time Tmax, the cycle time T is set as the temporary cycle time Te and the ON time H is set as Te × P. If the temporary cycle time (Te = He + Le) is longer than the maximum cycle time Tmax is the cycle time T and maximum cycle time Tmax, OFF time according to claim 2, wherein the set L as the Tmax × (1-P) Combustion equipment. The on / off valve provided in the burner is a control motor control on / off valve whose opening / closing operation is controlled by a control motor,
The reference shortest OFF time Lmin is greater than or equal to the state transition time with respect to the transition time, which is the time required for the on-off valve to transition from one of the fully closed state and the fully open state to the other state. The combustion facility according to claim 3 , wherein the combustion facility is set to a time not longer than 1.05 times the time.

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