DE1751615A1 - Device for regulating a furnace - Google Patents

Description

Device for controlling a furnace The invention relates to a device for controlling a furnace, in particular such a furnace, of one or more groups of burners which, for whatever reason, are fired for short intervals is interrupted: Examples of this are regenerative furnaces or blast furnaces: -It was Up until now it was common practice to melt a batch of glass in a furnace and the molten one Material in a preheating. Oven to direct the glass in a flowable state to one or more feed devices connected to the preheating furnace was. The feeding devices are provided with numerous small openings, from which.glass.jets from.the preheating furnace flow out, where.glass bodies. educated that could easily be pulled out into threads. The Rays or vitreous can be drawn into threads in various ways, e.g. hot gas streams at high speed in contact with the off the Primary filaments formed by glass rays are moved, or by directing the glass rays be brought into contact with streams of steam or compressed air. Are continuous if continuous threads are desired, the rays can be drawn out that the threads are brought into contact with rapidly rotating tension or press rollers or the threads or ropes or teats formed from threads become fast wound on a cylindrical sleeve or a mandrel in the form of a winding, where the very fast winding creates the power to thin or pull the glass rays are produced in the form of threads.

The uniformity and quality of the fibers or threads that are produced from the glass rays or the primary threads formed from them by pulling out the latter largely depend on the homogeneity of the glass mixture in which the components are evenly distributed, and also on the correct regulation of the . Temperature and viscosity of the glass at each feeder connected to the preheater. The development of methods and devices for drawing glass fibers with extremely small diameters has meant that great care has to be taken on the points mentioned, because the diameter of the fibers depends on the above properties. The diameter and the uniformity of the fibers also depend on the height of the glass in the feeding devices and thus on the level of the glass in the furnace that supplies the preheating furnaces and the feeding devices. A change in the level of the glass leads to greater or lesser pressure on the glass body to be pulled out, which influences its diameter. A number of glass level controls have been developed which allow the level of the glass to be varied by changing the amount of solid glass to be melted into the furnace. However, such a control does not allow fine regulation of the glass height, since the pressure inside the furnace can be different from that outside the furnace to which the molten glass is transported, which causes the glass height to rise or fall and the formation of waves in the preheating furnaces to be supplied will. An increase in the pressure in the furnace compared to the pressure outside the furnace, for example, presses the glass level in the furnace downwards, while the level of the molten glass in the preheating furnaces and the feeding devices is raised. Conversely, a drop in pressure in the furnace leads to an increase in the level of the glass in this furnace and to a decrease in the level of the glass in the associated preheating furnaces and feeding devices. For ovens where the operation. If the burner is interrupted and restarted after a certain period of time, the pressure in the furnace changes. For example, when regulating a regenerative oven, it is necessary to switch the air supply to the hot air heaters on each side of the oven alternately, in some ovens about every 20 minutes, in order to create a new heating source to preheat the incoming air used as combustion air. This means that while one of the wind heaters is heating the incoming combustion air, the exhaust gases are introduced into the other, which heats it up. If the air supply is switched over, a malfunction occurs in that combustion air and gas are now supplied to the furnace. This leads to a considerable cooling of the air and thus also of the glass in the furnace, which can be 38 to 660 C. Furthermore, there are considerable pressure changes in the furnace when the burners are switched over. When using a regenerative furnace, the pressure changes in the furnace and the cooling of the glass or a melt other than the furnace's own operating phenomena must be accepted.

The invention is therefore based on the object, a device of the type mentioned at the outset to create an exact Temperature- and pressure control inside the furnace within predetermined limits and thus a more precise controls of the melt allowed. Starting from a furnace that has a fuel supply device for burners as well as a device for recording the furnace temperature and for generation a temperature signal proportional to this and a device for interruption and to resume firing of the burners after a predetermined period of time this object is achieved by a restart of the burner firing Attractive device for generating a counter signal during an initial part a burner period the burner whose size is at least approximately equal to the current one Deviation of the temperature signal from its value before the combustion was interrupted is, as well as by an addition device for adding the counter signal and the Temperature signal and a fuel supply control device that responds to this sum signal for controlling the fuel supply device. The furnace according to the invention can therefore controlled so that the pressure and temperature changes have exact values and occur in a predetermined manner. This is by predictive or thermal Vortex, the course of the convection etc. a relative stability reached the melt. In addition, fuel is saved and the temperature in regulated to the desired extent.

It is noted that the invention, which is here based on a regenerative furnace used for batch melting of glass is described in the same Way is applicable to high ovens or other ovens in which the operation of a Group of burners interrupted and resumed after a certain period of time will.

The exponential counter signal is expediently signed vice versa, but practically equal in size to a predetermined deviation of the instantaneous temperature signal from one at the time of resumption of combustion given size. The exponential counter signal and the one proportional to the temperature Temperature signals are added and sent to the control device that supplies the Regulates the amount of fuel.

The exponential counter signal @ is a dummy signal that corresponds to the Regulator indicates that the oven temperature is actually higher than it is stated. The controller thus supplies the burners with a constant amount of fuel, which means the stability of temperature and pressure inside the furnace and thus the stability the melt can be improved. The device for generating the counter signal can be set so that each time a new fire is fired, a counter-signal of the same Size is generated, as the operational characteristics of such a furnace at each renewed combustion, i.e. each time the burners are started up again, in general stay the same. However, in the event of malfunctions that change the operating characteristics of the furnace or if the new combustion period is to be regulated more precisely a device for measuring the temperature drop in the furnace between the lower. refraction and the resumption of burner operation and further equipment is provided responsive to the device for measuring the temperature drop and the is used to control the initial size of the counter signal. In this way, size becomes of the counter signal with each new burn. .period precisely set One special preferred device according to the invention is used the regulation of one Furnace having first and second groups of burners, further comprising a Device for the supply of fuel to the burner groups and a device is provided for measuring the furnace temperature, which emits a signal that of the measured Temperature is proportional. There is also provided a device for Ignition of the first burner group, to interrupt the operation of the first group, to ignite the second burner group, namely a certain period of time later, further to interrupt the operation of the second group and to repeat it Cycle after a second period of time has elapsed. A device for generating a signal that responds to the ignition or start-up of a burner group, generates an exponential counter-signal that is reversed in sign, but in the size practically equal to a predetermined deviation of the temperature proportional Signal is of a predetermined size at the @ time of ignition. It is still means for adding the counter signal and the the temperature proportional signal provided. The embodiment described has adjustable Supply valves on, which respond to the added signals to the the burners to regulate the amount of fuel supplied. furthermore are again a device for Measure the temperature drop in the furnace between the interruption of operation of the one group and the ignition of the other burner group and another device provided, which responds to the device for measuring the temperature drop and is used to control the initial size of the counter signal.

The regulating device can have valves for regulating the supply, by means of which the fuel flowing through can be measured. There is also a device for setting the control valves in selected metering positions. seen. The device for igniting and interrupting is preferably equipped with a timer, the ignition and Interrupt signals generated. This facility can also have first and second shut-off valves, which on the time address the transmitter and switch between the device for burning fuel supply and the first and second burner group speaking in a first and a second fuel supply line are arranged. Ignition devices for the first and the second burner group are correspondingly in these groups arranged and are loaded for ignition by the timer makes. To avoid the big changes that usually occur when the new burn period starts too early, can. A device can be provided to control the control valves hold for the feed in the same metering position, and in the period between an interrupt signal and an ignition signal, so that these control valves initially the same amount of fuel during the burning period as before feed refraction. This facility is advantageous switched so that it responds to the timer that the Circulatory controls. The device for generating the counter signals can respond to an interrupt signal from the timer: or set again speak and thereby reset / become. For example, embodiments of the invention are explained below with reference to the drawing in which 1 schematically shows a device for controlling a furnace. shows according to the invention.

Fig. 2 shows in a diagram the relationship between temperature and time in the furnace of FIG. 1.

Fig. 3 shows in a diagram the relationship between voltage and time with the device according to the invention.

1 shows a furnace 10 which has two burners or groups of burners 11 and 12. A fuel tank 20 is connected via a main line 21 to branch lines 22, 23 which carry fuel to the first or left burner group 11 and to the second or right burner group 12. A device for regulating the amount of fuel supplied to the burners is designated generally by 30 and comprises an adjustable supply valve 31, a motor 32 and a temperature controller 33. The motor 32 is mechanically coupled to the supply valve 31 and controls it in a fully open, fully closed or in a selected position between open and closed in order to meter the fuel flowing through. The motor 32 responds: to the temperature controller 33. A signal can be given to the motor 32 via the newspaper 34, as a result of which the latter opens the supply valve further. The motor receives a signal via the newspaper 55 , as a result of which it closes the supply valve 31 more. The newspaper 36 is a common return line of the signal lines 34 and 35 to the temperature controller 33. In a preferred embodiment of the invention, a Re12? S40, which has an excitation winding 41 and a set of contacts 42, is arranged so that the contacts 42 interrupt the return line 36 so that the motor 32 remains in the position selected by the last signal that the motor 32 received via the newspaper 34 or line 35. A thermocouple T1 measures a furnace temperature and outputs a signal proportional to the temperature measured in the furnace to the temperature controller 33. The measured furnace temperature can be the temperature of the atmosphere in the furnace, the temperature of the melt or any other temperature which serves as an indicator for the desired operation can.

A timer 70 controls the cycle of operation of the oven 10.

That is to say, the timer 7U sends a signal via the lines 75 to a shut-off valve 51 for the burner 11, which is located in the supply line 22. The ignition signal coming via the newspaper 75 is applied to a solenoid 52 which controls the valve 51, whereby the valve 51 is opened and fuel is supplied to the burner 11 via the newspaper 22. The ignition signal is also given from the solenoid 52 via newspapers 75a to an ignition device 13 which is arranged at the burner 11. In a similar manner, the firing of the burner 11 is interrupted by a signal which is given by the timer 70 via the newspapers 75 to the solenoid 52, whereby this is switched off and the shut-off valve 51 is closed. In addition, the ignition 13 is switched off via the lines 75a by the interruption signal.

The timer 7U may further provide an ignition signal via the newspapers 7 6 on a check valve 61 which is actuated by a solenoid 62nd Upon receipt of the ignition signal, the solenoid 62 opens the valve 61, whereby the right or second burner group 12 is supplied via the line 23 fuel. In addition, a signal is sent to an ignition device 14 via the lines 76a in order to ignite the fuel emerging from the burner 12.

An operating cycle of the furnace 10 has so far proceeded as follows. It is assumed that the left or first burner group 11 is burning. The solenoid 52 is therefore energized by a signal from the timer 70 to hold the left shutoff valve 51 open. The temperature controller 33 responds to the temperature in the oven 10 via the signals it receives from the thermocouple T1. The temperature controller 33 then sends a signal to the motor 32 which brings the valve 31 into a position which allows a sufficient fuel supply through the line 22 to the left burner group 11 in order to keep the temperature in the furnace 10 at a level that this Toaperaturreglere-33 is determined by a Sinatolluxg.

If a switchover of the burners is desired, the burning period of the left group ends when the timer 70 gives an interrupt signal via the newspapers 75 to the solenoid 52, whereby the latter is switched off and the shut-off valve 51 is closed. After a predetermined transition time, for example after 20 seconds, the timer 70 sends a signal to the newspapers 76 to energize the solenoid 62 and open the valve 61, so that fuel can flow through the supply line 23 to the burner or burners 12 can flow. At the same time, an ignition signal is sent to the ignition device 14 for the right-hand or second burner group 12 via the newspapers' j6a.

The above-described operating sequence has hitherto continued to be repeated in order to maintain the temperature conditions in the furnace which were necessary for melting the charge fed to the furnace.

A temperature-time diagram of a furnace according to FIG. 1 is shown in FIG. The time period X is the time span between the interruptions of the combustion in one burner or separate burner groups, and it is, for example, 20 minutes. The time Y indicated in FIG. 2 is the transition period between the interruption of combustion in one burner and the resumption of combustion in this burner, or between the interruption of combustion in a first burner group and ignition and the start of combustion in a second Burner group. During this period of time, the temperature in the furnace drops significantly and can affect the temperature of the glass or other batch to be melted so that the batch cools by the high value of about 38 to 66 ° C. At the end of the transition period or time period Y, the other group of burners in Fig. 1 begins to burn and: the temperature rises along a curve characteristic of this particular furnace until it reaches the desired level set in the temperature controller. This period of time is denoted by Z in FIG. 2 and can be approximately 3 to 4 minutes in the example described here. The thermocouple T1 has picked up the sharp drop in temperature and gives a relatively strong signal to the temperature controller 33. The temperature controller 33 gives a signal to the motor 32 to open the solenoid-controlled valve 31 further to supply the required fuel. in order to bring the temperature back to the selected standard as quickly as possible. This wastes considerable amounts of fuel and greatly disturbs the stability of the melt in the furnace, causing the undesirable effects described above are connected to energize a control relay 40. At the beginning of the transition period Y, a signal is sent via the newspapers 74 to the control relay = 40, as a result of which the excitation winding 41 is excited and the contacts 42 which are in the common return line 36 are opened. As a result, the motor 32 retains its last position, since it cannot receive any signals from the temperature controller 33, which, following the signals it has received from the thermocouple T1, would quickly open the valve 31 further in accordance with the relatively sharp temperature drop in the furnace. Thus, the valve 31 remains in its metering position last selected at the time of the interruption of the combustion: At the end of the transition period Y a signal is given by the timer 70 via newspapers 78 to the signal generator 80 to indicate that the ignition resp. combustion begins at one of the burner groups. The timer 70 also switches off the relay 40 in order to close the contacts 42 so that the motor 32 can be operated again by the temperature controller 33.

FIG. 3 shows the voltage-time diagram of the signals that the temperature controller 33 receives. The dashed curve 100 indicates the temperature drop that was recorded by the thermocouple T1 and the information that the = oil element T1- passed on to the temperature controller 33. 13th in Pig. 2, the drop in temperature over time from a certain temperature level, such as 8 ..., 142500 (26000F) in the atmosphere in the furnace to a lower temperature at which re-combustion begins in one of the burner groups, is a Exponential curve. Likewise, the increase from the lower temperature back to the desired temperature level has an exponential character. This exponential decrease and increase is represented by the curves 100a and 100b of the curve 100, which represents the signal obtained from the thermocouple T1.

In order to regulate the furnace within narrow limits and thereby to create the desired stability, the signal generator 80 is used to generate an exponential counter signal, which is shown in FIG. 3 is indicated as a dashed curve 101, and that, conversely, in the preceding sign, but practically equal in size to a predetermined deviation of the signal 100 proportional to the temperature from a level predetermined at the time of ignition or renewed combustion. The counter signal and the signal proportional to the temperature are added at the time of ignition before they are sent to the temperature controller 33: At the end of the transition period Y, the temperature controller therefore receives a resulting signal 102 (FIG. 3) which is similar or identical to the signal that he received from the thermocouple T1 before the interruption of the combustion in one of the burner groups. Thus, neither the D: otor 32 nor the valve 31 need to fluctuate greatly in order to try to reach the desired height. Rather, the temperature controller 33 and thus the valve 31 are under the control of the .Kurvenabfall 101b of the blind signal 101, which is generated by the signal generator 80. The furnace is brought evenly to the desired temperature without the fluctuations, without wasting fuel and without vibrations, which are normally associated with extreme malfunctions in a servo system. The control cycle is repeated for each combustion.

The signal generator 80 may be any of the well known resistance-capacitance circuits in which the components are chosen so that the falling exponential curve 101b arises.

When the next transition period comes, the timer 70 gives a signal to the newspapers 78 to reset the signal generator 80, where it emits an interrupt signal at the same time. The signal generator 80 can the Charging voltage, which at the time of the interruption on the capacitor, must be present must already have in order to achieve the size or height of curve 101 in FIG. 3. However, the capacitor can also run along the start-up side during the transition period Y 101a of curve 101 can be loaded quickly. This is done so that an adjustment occurs when the signal 1u0a falls, the relay 40 does not need to be used because the added signals 100a and 101a cause the valve-31 in remains in its last selected position. On the other hand, -by using Switching devices the R-C circuit can be charged to the desired level, whereupon the signal from the signal regenerator is delivered through contacts in the circuit is, so that the exponentially increasing curve 101-a of the curve 101 of the Temperature controller 33 is not noticed. Though using an R-C circuit in which the signal regenerator can be advantageous, other means, e.g. motorized rheostats, can be used to generate the desired signal. Since the characteristics of the temperature drop according to FIG. 2 and of the signal 100 of the Thermocouple in Fig. 3 between the transition periods normally. very similar remain, the signal generator 80 can be adjusted once to the desired Generate the size of the input counter signal 101. However, to have a more precise scheme to achieve and in transitional conditions where the individual setting of the signal generator would be inexpedient, the signal generator 80 can have a thermocouple T2 to measure the temperature drop in the furnace between the interruption of the combustion in a group -and the beginning. the burn in the other. Burner group. The signal generator 80 in this case has a device that the device for measuring the temperature drop responds and for regulating the The initial size of the counter signal is used. That is, with the help of known circuits the thermocouple T2 can have a temperature drop expressed in the form of a voltage register, whereby through this voltage the initial size of the input counter signal 101 is selected, with the normal temperature indicating signal from the Thermocouple T1 is added and given to the temperature controller 33. To this Way, the counter signal is precisely set for each transition interval and it regulated in very much. tight limits the operation of the furnace 10.

Although FIG. 1 shows a separate thermocouple T2 which those for setting the initial size of the counter signal for each transition interval provides necessary information, this is mainly for the sake of clarity he follows. The thermocouple T1 also provides this information and it can be used with proper connection, not just a continuous signal to the temperature controller 33, but also to the readjustment the initial size of the counter signal necessary to provide the information during every transition interval. So if an exponential Counter signal 701b is generated, which is complementary to the signal 100 of the thermal element is, the temperature controller 33 takes during the beginning, i.e. the initial burning period Burner, practically constant signal on. Accordingly, the fuel flow becomes through the valve 31, which would otherwise rise, during start-up on a kept practically constant ornament. The temperature regulator 33 limits the flow of fuel through the valve 31 to the amount that passed through the valve before the interruption while the temperature of the furnace is continuously being built up. The thermocouple T1, which decreases the shell temperature, gives a steadily increasing control signal from, corresponding to the reduction in the influence of the signal generator 80 generated counter signal. This allows the furnace to operate when switching over, when restarting or be controlled extremely precisely during the first burning period, whereby the temperature of the ufens and the melt is kept within very narrow limits.

In the embodiment of FIG. 1, a timer is specified as the preferred device for the regulation of the switching cycle, or i interruption and resumption of the operation of the combustion burner. However, this regulation can also be implemented with the help of other facilities. For example, a controller can deliver the necessary signals as a function of the temperatures in the 1, 'inderheaterern when the temperature of a first heater reaches a predetermined value, or when the temperature difference between the first and a second heater reaches a predetermined value. If the furnace is fired from the opposite direction, the critical temperature to be measured can be the temperature of the second heater or, again, the temperature difference between the two heater.

The invention is not limited to the illustrated and described embodiment limited, but modifications are possible without departing from the scope of the invention to deviate.

Claims (1)

P atentansprühe device for controlling a furnace, which has a BrehnstQffzufuhreineinrichtung for burners as well as a device for receiving the furnace temperature and for generating a temperature signal proportional to this temperature and a device for interrupting and resuming the firing of the burners after a predetermined period of time by a device ($ 0) responsive to the resumption of burner firing for generating a counter signal during an initial part of a burning period of the burners, the size of which is at least approximately equal to the current deviation of the temperature signal from its value before the. Firing is interrupted, as well as by an addition device for adding the counter signal and the temperature signal and a fuel supply control device (31, 32, 33) responsive to this sum signal for controlling the fuel supply device (21, 22, 23). 2. Apparatus according to claim 1, characterized in that the fuel supply control device has a supply control valve (31) for metering the amount of fuel flowing through. 3. Apparatus according to claim 2, characterized by a servo device, in particular a motor (32) for setting this valve (31) in predetermined metering positions. 4. Apparatus according to claim 3, characterized by a device (33) for driving this motor (32) as a function of the furnace temperature measuring device (T 1). 5. Apparatus according to claim 1, characterized in that the device for interrupting the burner operation comprises a timer (70) for generating an interruption signal and a resume signal. 6. Apparatus according to claim 5, characterized in that this device for interrupting the burner operation has shut-off valves (, 51 =, 61) which can be controlled by this timer (70) and downstream of the feed control valve (31) lie in a fuel supply line. '. Device according to Claim 5, characterized in that the device ($ Ö) for generating the counter signal by this interrupt signal. can be reset or re-adjusted. $ @ Device according to claim. 5, characterized in that the device ($ G) for generating the counter signal initiates the majority of this counter signal as a function of this resume signal. j. Device according to claim 1, characterized by a Einrchtung (T 2) for measuring the Temperaturabfalleä in the furnace zwisehen interruption and resumption of firing the burner and means for regulating the initial size of the counter signal, responsive to said means for measuring the temperature drop 10. Apparatus according to claim 1, characterized in that the furnace has a first and a second burner group and that the device for interrupting the burner operation to interrupt the firing of both burner groups, to switch on the first burner group, to interrupt the firing of this first burner group, in particular the second burner group :,; to be switched on a certain period of time later and the firing of the second burner group to be interrupted in a repeating cycle. 11. Device according to claims 9 and 10, characterized by a device (T 2) for measuring the temperature drop in the furnace between the interruption of the firing of one group and the ignition or commissioning of the other burner group, through which the device for regulating the initial size this counter signal is controllable. 12. Device according to claims 6 and 10, characterized in that the device for interrupting and resuming burner operation is provided with a first and a second shut-off valve (51, -61) which can be controlled by the "timer" (70) -and between this fuel supply device and. the first (11) or: the second burner group (12). 13 .-- Device according to claims 5 and 10, characterized in that the device for switching on and interrupting the burner operation is provided with a first and a second ignition device (13, 14) which can be controlled by the timer (70) and accordingly are arranged at the first and the second burner group. 14. Device according to claims 2, 6 and 10, characterized by a device (41, 42) for fixing the supply-Re-- gel valve (31) in the interval between an interruption signal and an ignition signal in the same metering position -15. Device according to claim 14, characterized in that this retaining device (41, 42) can be controlled by the timer (70).