JP3377152B2 - Hot air circulation device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot air circulation device for circulating air heated by a direct burner to a heat exchanger. 2. Description of the Related Art For example, in a paint drying furnace for painting an automobile body, if high-temperature heated air obtained by burning a direct-burning burner is circulated and supplied to the furnace as it is, the inside of the furnace is not heated. Since the air containing the solvent component is burned and supplied again into the furnace, the air in the furnace is gradually contaminated, and adverse effects such as yellowing of the coating film are caused. For this reason, a heat exchanger is interposed in the hot air circulation path through which hot air is circulated and supplied, and the furnace air is circulated through the heat exchanger to indirectly heat the inside of the furnace, or heat pipes are inserted into the furnace. By forming the drying furnace itself in a heat exchanger by disposing the like, the inside of the furnace is heated without directly introducing high-temperature air heated by a direct-burning burner into the furnace. . FIG. 5 shows a conventional hot air circulating apparatus used in such a coating and drying oven. The air heated by a direct-burning burner 1 is blown by a blowing fan 4 interposed in a hot air circulating path 3. Circulates and supplies the heat as a heat medium to the heat exchanger 2. The heat exchanger 2 is interposed in a flow path 3a from the burner 1 to the blower fan 4 of the hot air circulation path 3, and fresh air is supplied to the flow path 3b from the blower fan 4 to the burner 1 in the path 3. An air inlet 45 for guiding is formed, and an exhaust port 46 for discharging air in the path 3 to the outside is formed between the air inlet 45 and the blower fan 4. The air inlet 45 and the exhaust port 46 are formed to be openable and closable by an intake damper 47 and an exhaust damper 48, and the flow path 3 b of the hot air circulation path 3 is switched between the air inlet 45 and the exhaust port 46 by a switching damper 49. Are provided to switch the flow path. The burner 1 is connected to a combustion air pipe 51 for supplying fresh air for combustion by a blower 50 and a fuel gas pipe 52 for supplying fuel gas. An air flow adjustment damper 53 for maintaining the air flow of the blower 50 at a constant level is provided, and a gas shutoff valve 54 for shutting off the supply of fuel gas to the burner 1 is provided in the fuel gas pipe 52. The pipes 51 and 52 are provided with an air control damper 55 and a gas control valve 56 which are opened and closed in an interlocked manner so as to increase and decrease the supply amount of combustion air and the supply amount of fuel gas while maintaining a constant air-fuel ratio. ing. 57 is the dampers 47, 4
8, 49, a gas shutoff valve 54, an air control damper 55, and a gas control valve 56 are opened and closed at a predetermined timing, and the blower 50 and the blower fan 4 are started / stopped at a predetermined timing. [0005] Before the burner 1 is ignited and after the burner 1 is extinguished, a purging operation for exhausting contaminated air in the hot air circulation path 3 is performed for the purpose of explosion protection. In this case, when the switching damper 49 is closed, the intake damper 47 and the exhaust damper 48 are opened, and the blower fan 4 is operated, fresh air is introduced into the hot air circulation path 3 from the air intake 45 and the hot air circulation path 3 is opened. The contaminated air inside is exhausted from the exhaust port 46, and the air in the hot air circulation path 3 is replaced. When the burner 1 is ignited, after the purge operation is completed, the switching damper 49 is opened to make the hot air circulation path 3 conductive, the intake damper 47 and the exhaust damper 48 are closed, and the burner 1 is connected to the fuel gas pipe 52. The interposed gas shut-off valve 54 is opened to ignite, and then the temperature is controlled by adjusting the supply amounts of the combustion air and the fuel gas by the air control damper 55 and the gas control valve 56. . However, as described above, when the air inlet 45 and the exhaust port 46 are formed in the hot air circulation path 3, at least three dampers 47, 48, 49, and each of the pipes 51 and 52 connected to the direct burner 1
Includes a gas shut-off valve 54, an air control damper 55,
Since the gas control valve 56 is interposed, the number of dampers and valves to be controlled is increased, which not only complicates the control but also increases the equipment cost and the maintenance cost. Therefore, the technical problem of the present invention is to eliminate unnecessary equipment, reduce the number of dampers to be used in the hot air circulation path, make control easier, and reduce equipment and maintenance costs accordingly. I have. [0008] In order to solve this problem, the present invention provides a hot air circulating apparatus for circulating air heated by a direct-burning burner as a heat medium to a heat exchanger.
An openable and closable exhaust port is formed which communicates with a hot air circulation path through which air heated by the burner is circulated and discharges air in the path to the outside.The burner has fresh air for combustion by a blower. A fuel air pipe for supplying fuel gas and a fuel gas pipe for supplying fuel gas are connected, and the fuel gas pipe is provided with a gas shutoff valve for shutting off the supply of fuel gas to the burner. Before the burner is ignited and after the fire is extinguished, fresh air supplied by the blower is introduced into the hot air circulation path from the burner with the exhaust port opened and the gas shut-off valve closed, and the hot air circulation is performed. A control device for performing a purge operation for replacing air in the path is provided. According to the present invention, at the time of the purge operation, the blower for supplying the combustion air to the burner is operated, and the fresh air is supplied to the hot air circulation path through the burner. It is sufficient that an exhaust port is formed so as to communicate with the path, and it is not necessary to form an air intake. Also,
The exhaust port may be opened to discharge the air in the hot air circulation path when performing the purge operation, and may be closed to circulate the hot air when performing the hot air circulation operation, and therefore, it is merely required. It is sufficient to open and close the exhaust port, and there is no need for complicated flow path switching control.
It is not necessary to provide another damper in the hot air circulation path. When performing the purge operation, it is necessary to control the opening and closing of the exhaust port, control the operation of the blower fan, and control the operation of the blower. Therefore, only the start / stop timing of the blower needs to be changed by changing the control program, and the control is extremely simplified. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described based on embodiments shown in the drawings. FIG. 1 is a flow sheet showing an example of a hot air circulation device according to the present invention, FIG. 2 is a flowchart showing a control procedure when a burner is ignited, FIG. 3 is a flowchart showing a control procedure when a burner is extinguished, and FIG. It is a time chart which shows operation | movement at the time. The hot air circulating apparatus of this embodiment is a direct burn type burner 1.
Is circulated and supplied to the heat exchanger 2 as a heat medium by the blower fan 4 interposed in the hot air circulation path 3. The hot air circulation path 3 has an exhaust duct 5
The duct 5 is provided with an exhaust damper 6 whose opening degree is adjustable. The exhaust port 5a formed at the end of the duct 5 through the exhaust duct 5 is connected to the hot air circulation path 3.
Is in communication with The burner 1 is connected to a combustion air pipe 8 for supplying fresh air for combustion by a blower 7 and a fuel gas pipe 9 for supplying fuel gas. Is provided with a blower adjusting damper 10 for maintaining the blower 7 at a constant blower volume.
A gas shut-off valve 11 for shutting off the supply of fuel gas to the fuel tank is provided, and the supply of combustion air and the supply of fuel gas are adjusted in each of the pipes 8 and 9 while maintaining the air-fuel ratio constant. An air control damper 12 and a gas control valve 13 are interposed. The exhaust damper 6 is opened when a purge operation for replacing air in the hot air circulation path 3 is performed, and is closed during hot air circulation for circulating the air heated by the burner 1, but is closed. Even in such a case, the exhaust duct 5 is not completely shut off, but is slightly opened so that the air in the hot air circulation path 3 can be exhausted with a minimum displacement according to the flow rate of the combustion air introduced from the burner 1. I have. A start / stop 14 for the blower fan 4 and the blower 7 at a predetermined timing, an opening / closing of the shutoff valve 11 at a predetermined timing, and an air control damper 1
2, a control device for adjusting the opening of the gas control valve 13 and the exhaust damper 6. The control device 14 controls the burner 1
At the time of ignition and fire extinguishing, with the exhaust damper 6 opened and the gas shut-off valve 11 closed, fresh air is supplied to the hot air circulation path 3 through the burner 1 by the blower 7,
A purge operation for replacing the air in the hot air circulation path 3 is performed. Reference numeral 15 denotes a pilot burner for igniting the burner 1, and reference numeral 16 denotes a pilot shutoff valve interposed in a pipe 17 for supplying fuel gas to the pilot burner 15. Next, a control procedure and operation at the time of ignition of the burner 1 will be described with reference to a flowchart of FIG. 2 and a time chart of FIG. First, a start switch (not shown)
Is turned on, the control of the control device 14 is started according to the flowchart shown in FIG. 2, and it is confirmed in step 1 (STP1) that the gas cutoff valve 11 is closed (FIG. 4:
T ₁ ) In step 2 (STP2), the air control damper 12 and the exhaust damper 6 are fully opened (FIG. 4: T ₂ ). At this time, the air control damper 12 and the gas control valve 13 are operated in conjunction with each other to maintain a constant air-fuel ratio. Therefore, the gas control valve 13 is also fully opened. Is not supplied to the burner 1. Next, in step 3 (STP3), the blower 7 for supplying the combustion air is started to operate at the maximum air flow rate, and the blower fan 4 is started to perform the purge operation (FIG. 4:
T ₃ ). At this time, fresh air is introduced from the blower 7 through the combustion air pipe 8 into the hot air circulation path 3 via the burner 1, and the air in the hot air circulation path 3 is accordingly reduced by the exhaust duct 5.
Thus, the air in the hot air circulation path 3 is completely replaced by introducing, for example, about four times as much fresh air as the total capacity of the hot air circulation path 3. In this example, the amount of fresh air introduced is set according to the time for performing the purge operation. If it takes, for example, 3 minutes to introduce the required amount of fresh air, step 4
In (STP4), after confirming that the operation up to step 3 (STP3) has been performed, the purge operation timer is started, and the purge operation is continuously performed for a predetermined time (for example, 3 minutes). 5 (STP5) (Fig. 4: T ₃
~T _4). Step 5 (STP5) to Step 9 (STP
In step 9), the ignition operation of the burner 1 is performed.
In 5), the air control damper 12 and the gas control valve 13 are throttled to the minimum supply amount, and at the same time, the number of revolutions of the blower 7 is variably controlled by, for example, inverter control of the motor of the blower 7 or a pole change, and the air volume is controlled by the burner. The air volume is reduced to a predetermined air volume required for the combustion of No. 1 (FIG. 4: T ₅ ), and the process proceeds to step 6 (STP6). In step 6 (STP6), the pilot shut-off valve 16 is opened, and at the same time, the spark is skipped by the ignition plug (not shown) and the pilot burner 15 is ignited (FIG. 4:
T ₆ ) Then, in step 7 (STP7), the gas shutoff valve 11
Fuel gas is supplied to the burner 1, the burner 1 is ignited is opened (Figure 4: T _7). Then, step 8 (S
TP8 ignition confirmation timer) is activated, after a predetermined time has elapsed (e.g., 15 seconds), the process proceeds to step 9 (STP9) squeezed exhaust damper 6 to the minimum exhaust volume (Figure 4: T _8), step 10 (STP10 ) And burner operation is continued. In step 10 (STP10), for example, the temperature of the air to be heated, which is heated by the heat exchanger 2 and supplied to the paint drying oven or the like, is detected, and based on the detected temperature, the air control damper 12 and the gas control valve 13 are controlled. Temperature is controlled by adjusting the opening and increasing or decreasing the supply amount of combustion air or fuel gas. Next, the control procedure and operation when the fire of the burner 1 is extinguished will be described with reference to the flowchart of FIG. 3 and the time chart of FIG. First, a fire extinguisher switch (not shown)
When the button is pressed, the control of the control device 14 is started according to the flowchart shown in FIG. 3, and in step 11 (STP11), the shutoff valve 11 and the pilot shutoff valve 16 are closed, and the burner 1 and the pilot burner 15 are extinguished (FIG. 4). : T _11).
Next, the process proceeds to step 12 (STP12), where the air control damper 12 and the exhaust damper 6 are fully opened (FIG. 4:
T ₁₂ ), in step 13 (STP 13), a purge operation is performed with the blower 7 set to the maximum air volume, and fresh air is introduced from the blower 7 through the combustion air pipe 8 to the hot air circulation path 3 via the burner 1. As a result, the air in the hot air circulation path 3 is discharged to the outside through the exhaust duct 5 through the exhaust port 5a. Then, in Step 14 (STP4), Step 13 (STP4)
Ensure that TP3) until operation has been performed a purging operation timer is started (FIG. 4: T _13), after the lapse of a predetermined time required (for example, 30 minutes) to purge and cooling, step 15 (STP15 ) stops the blower 7 and the blower fan 4 shifts to (Figure 4: T _14), narrow the air control damper 12 and the exhaust damper 6 at step 16 (STP16),
The process ends. In the above description, the case where the air control damper 12 and the gas control valve 13 are controlled to open and close in order to maintain the air-fuel ratio constant has been described. Alternatively, the output of the blower 7 and the opening of the gas control valve 13 may be linked and adjusted. Also, the fuel gas pipe 9
Although the case where the gas shut-off valve 11 and the gas control valve 13 are provided in each of the above is described, a case where a single valve having both functions of the gas shut-off valve and the gas control valve may be used. As described above, when the purge operation is performed before the ignition of the burner and after the fire is extinguished, by operating the blower, fresh air is supplied from the combustion air pipe to the hot air circulation path via the burner. Since it is introduced, it is not necessary to provide an air intake and a damper associated therewith in the hot air circulation path, and it is not necessary to provide a damper for switching a flow path when the air intake is provided. Therefore, the control is simplified, and the equipment cost and the maintenance cost can be reduced correspondingly.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow sheet showing an example of a hot air circulation device according to the present invention. FIG. 2 is a flowchart showing a control procedure at the time of ignition. FIG. 3 is a flowchart showing a control procedure at the time of fire extinguishing. FIG. 4 is a time chart showing operations during control and fire extinguishing. FIG. 5 is a flow sheet showing a conventional apparatus. [Description of Signs] 1 ... Burner 2 ... Heat exchanger 3 ... Hot air circulation path 4 ... Blower fan 5 ... Exhaust duct 5a ... Exhaust port 6 ... Exhaust damper 7 ...・ Blower 8 ・ ・ ・ Combustion air pipe 9 ・ ・ ・ Fuel gas pipe 11 ・ ・ ・ Gas shutoff valve 14 ・ ・ ・ Control device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-190620 (JP, A) JP-A-61-96385 (JP, A) JP-A 62-32995 (JP, U) JP-A 61-96 15493 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) F26B 21/04

Claims (1)

Claims: 1. A hot air circulation device for circulating and supplying air heated by a direct burner burner (1) as a heat medium to a heat exchanger (2). ) Communicates with the hot air circulation path (3) through which the air heated in the path (3) is circulated to form an openable and closable exhaust port (5a) for discharging the air in the path (3) to the outside. ), A combustion air pipe (8) for supplying fresh air for combustion by a blower (7) and a fuel gas pipe (9) for supplying fuel gas are connected to the fuel gas pipe (9). 9) is provided with a gas shut-off valve (11) for shutting off the supply of fuel gas to the burner (1), and before the ignition of the burner (1) and after extinguishing, the exhaust port (5a).
While the gas shut-off valve (11) is closed, fresh air supplied by the blower (7) is introduced from the burner (1) into the hot air circulation path (3), and the hot air circulation path is introduced. (3) A hot air circulation device comprising a control device (14) for performing a purge operation for replacing air inside the hot air circulation device.