DE1934597A1 - Switching system for regenerative ovens - Google Patents

Description

Leeds & Northrup Company 8 »July 1969 Our file BA-K491 (Caw 1 * 567) ' φΑ / SB / * Umflobalteystea for Regenerative ^ en

(Priority * 8 July 1968, U ₀ S ₀ A,, ffr _o 74? 176)

Begenerativufen generally comprise chambers pass through the fuel, combustion air and the Verbrorätmgsprodulct ·, to be then gesundet in the furnace to reach "ü" maximum efficiency in furnace operation ", it is desirable" to increase zn the temperature of the combustion air prior to combustion within the furnace For this purpose, regenerative or heat storage chambers are provided at opposite ends of the furnace! absorb the alternating heat from the furnace ITerbrennungsprodufcten AEEA · and alternately emit the heat to the combustion air *

The operation of the furnace must be switched over periodically to prevent excessive cooling or overheating of the material from which the hegenerative casamers are built which the oven is turned around "For example, U & UF &tentsohrif" ITr * 2 287 186 well-known techniques for determining the changeover "· 'time for hegenerative substances are described" Perhaps the

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The most uncomplicated of these techniques is to switch the oven over after certain time intervals «.

Further more complicated techniques for determining the switching point in time are given in the USA patent no. 2 851 221, 2 177 805, 2 531 200 and 2 804 268 described

In a system in which the stove is switched periodically nothing prevents the possibility of one side of the hearth takes up a major part of the total burning time This can lead to a large temperature difference on the grating between the two sides of the stove. known systems of the type described above see a system that responds to a temperature difference in the chambers ο Many systems of this type switch over at periodic time intervals, unless there is an overload caused by an excessive temperature difference between the two, especially those with a temperature difference working systems give a good safety factor, they are basically not the same as the caloric one

SUB

Heat input on both sides of the furnace / · Dh _o , every temperature measurement is delayed compared to the calorie input, so that there is never a good balance of the caloric heat input on both sides if this input power is only temperature-controlled also not the mean grid temperature, but only the temperature of a hot or cold zone in the vicinity of the thermocouple «· Standing detailed description results _o

The invention relates to an improved control system for

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Regenerative ovens and a device for providing a Display, if the load is evenly to the desired Heated up to temperature and ready to be removed from the oven isto

An important © object of the present invention is thus j verbessert® output at Regenerativb'fen to provide characterized in that the cahrge be Heist uniform and the temperature of the regenerative checker bricks is compensated for by controlling the power supplied from both sides Ealorienmengen to the same value _e The Gesamtheizsyklus will be shortened ,, that the stove then ₉ when the fuel is switched off ₀ and not a simple time base is shifted longitudinally, in which the switching can also take place if the Brennstoffaufuhr is turned on _o in this case, an analog signal for the Äriderungsgeschwindigköit of at generated ehargenweiee heated ovens zugeführfcan fuel flow and ₉ when check approaches a constant value of this Signsl, indicated that the "charge uniformly heated to a desired temperature and ready for demoulding system from the furnace is _o Further, should a signal be generated which the ratio of the ² time during which the fuel ufuhr is switched on, reproduces the entire cycle time, the switching of the firing direction depending on the signal above a certain adjustable point, if the burner has been switched on for a certain time ₉ and also depending on the signal below the certain adjustable point occurs _β if the fuel supply to the furnace is switched off «

Further details emerge from the following description of an A _US management example based on the drawing

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voltages; in these show:

1 shows an embodiment of the changeover system according to the invention in connection with a regenerative hearth furnace;

, 1a shows the temperature profile in the furnace over time according to ffigo 1f

Figo 2 shows the time course of the relationship between Burning time and total time to visualize the operating * wise a furnace according to the state of the art ι

3 shows a diagram similar to that of FIGS. 2 and is shown a mode of operation according to the invention «in which the switchover always takes place when the fuel supply is switched off is; and

FIG. 3 is a diagram similar to FIG. 3 to illustrate a modified mode of operation according to the invention.

In its preferred embodiment, the invention is shown applied to the control of a regenerative underground furnace Λ , which has regenerative chambers or latticework rooms 2, 3 at both ends the air is preheated for the supply of heated air for the combustion. A flap 6 arranged at the junction of the supply and suction lines directs the air to and from the other end of the furnace

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vlrd swiveled by 90 ° to switch the furnace operation. Suitable fuel is eye to the furnace by means of a · conduit 7, the β to the burners and each having 9 leading branch lines} of the burner 8, 9 and n is the ends of the furnace at a position fitted on the check the incoming air with the fuel can mix and thus ensured combustion. A switch valve 10 is used to feed fuel to one or the other of the burners. The flap 6 and valve 10 are operated in a conventional manner to switch over the furnace operation *

What has been described above "is a conventional regenerative furnace _t which also includes a relay set 11 for actuating the furnace switchover Valve 10 reverses

A Seehennetswerk is provided, the integrating amplifier 12 and 13 as well as a Division or quotient network 14 includes

The ivy network generates a signal at the output of the quotient network 14, which corresponds to the ratio of the time during that the fuel supply is switched on (the burning time) is proportional to the total time between the individual switchings * This signal is shown as the burning time signal. net ο

Integrating amplifier 12 produces an output signal indicative of the duration that one of the burners is

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8 or 9 is in operation «The burners 8 and 9 are temperature-controlled _v d» h. _t a thermocouple 15 measures the temperature in the furnace, and a contact in accordance with variations in temperature around a set point operated "As shown in the particular embodiment shown, the contact 16 in the Teiiperatursehreiber 1? The output of the thermocouple is fed to the temperature recorder 17, which has a conventional adjustment circuit under the action of the adjustment circuit the pen is moved up and down depending on the temperature with respect to the scale At a certain point of its movement the contact 16 open or closed, this contact can be used to switch the burners 8 and 9 on or off. In an alternative solution, the actuation of the contact 16 can also only give an indication of the point in time at which the burners 8 and 9 are switched on and off _{or the like}

If the contact 16 is closed, which indicates that one of the burners is in operation, then there is a potential at the integrating amplifier 12 which determines the burning time of this burner indicating output signal produced · Simultaneously with the When contact 16 closes, a timer 18 starts running Timer 18 starts every time one of the burners is switched on

Assume that the ratio of burning time to total time between two switchings is above a certain value Value, about a 50 ^ value, the timer runs 18 after a given interval, for example 4 minutes, off and actuates the switch-over belay system 11

Sss Umsehalt Relaissystera 11 takes about 20 seconds for complete switchover, d. H. in order to carry out the sequence of relay operations that switch the flap 6

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and of the valve 10 _o At the end of this switching time, a relay contact is closed, which applied a voltage to the integrating amplifier 13

The integrating amplifier 13 generates a linearly increasing output voltage · At the beginning of the next changeover period, the hot contact in the system 1Ü is opened and the input signal is thereby separated from the integrating amplifier 13 between the switchings. indicates · During the switching period (takes in the illustrated example, these 20 seconds) the calculation of the firing time · Here, the signal from the integrating amplifier 12 _for the fuel feed time is proportional, by which the time between the more conversations proportional signal from the This division is divided into the integrating amplifier 13. the integrators 12 and 13 are reset so that they are ready for the next calculation. Although the sampling and reset functions for the Beohennetzwerk are not shown in FIG. 1, it is within the ability of a person skilled in the art to provide these punctures at the times indicated «

If the continuous burning signal falls below a certain adjustable value If (in the case under discussion under 50 #), then another technique used to make the switchings "" The recorder 19 operates to set the Pointer 20 to the correct position over the usual self-

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balance circle at a certain point in its movement with «in this case at the point that has a £ 50 -1« · Indicates the burning time, a separate indicator of the pointer 20 is displayed Mechanism the working contact 22. So the burning time falls below the £ 50 value, * o this changes the criteria for the actuation of the Umeehavior · The Uaaebjdt Relalasystem 11 is no longer normal via the tent generator 18, but then acted upon when the contact 16 opens nndrdabel indicating that the burners are turned off · this means "that the stove vird switched whenever 4 * r oven ron the state" at DTE Brennstoffsufuhr is eingeredhaltet * passes into the state in the the fuel supply is switched off.

The application dee-Üneteuer Relaissyeteee under this condition, by so-called "automatic * Control or" manual · done ^'1 Stuerung. In the case of automatic control, the application takes place via a circle which comprises the contact 16, the closed contact 22 and the contact 27 *, which is only closed with automatic control is when the temperature is about 20 ° below the set point, as well as via the contact -27o, which is only closed for manual control:

The operation of the furnace under these conditions is shown in FIG. 1a, which shows the furnace temperature as a function of the time _o However, if the fuel supply runs for 4 minutes »without being switched off, the side sender initiates» switchover of all upper inflation rates _o

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In the circuit between the switchover stem and the integrating amplifier 13 there is a deodorant locking device holder 28 which opens "when the stove cover is removed. If the cover is closed again, the formation of the total signal time continues ο this «* interlocking is required? as furnaces of this type have another lock that prevents firing of the oven is open Seckel allow · If you that the uee _a mtzeit continue while the interruption ds & .Je & eiimgskreisee, the recorded data were defective during this period.

In summary, the system of FIG _o 1 is the furnace switching in response to two different criteria regulated If the signal that represents the ratio .of burning time to total time greater than 550 #, the switching is · controlled by the timer 18 is at umt operation a previously set total time has elapsed in the timer 18 during which a burner is in operation, a switchover is effected. During this period the furnace is under high fire Oven over, a calculation is carried out and the relationship between the burning time and the total time is recorded ο The main thing about this operating mode is that both sides of the stove are sure to have the same burning time *.

The second criterion for hes & posture is during the periods in which the ratio of burning time to total time is less than £ 50 ". The change from the first

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Criterion to the second is brought about by actuation of the contact · »22 in the recording device 19 when applying the second criterion dee delivers the switchover de * furnace every · times then a" when the burners are switched off »B _# h _o" which the ümschaltrelaissystem 11 heaufsehlagt as often as the switch 16 is actuated «.

As a further feature of the invention, a display 23 is provided which indicates when the steel in the furnace "softened" is has de h »evenly reaches the gewünsehte! Temperature _P base for the operation of this display is the approach of the ratio of burning time to Total time to a constant value and thus the closer to the "Aufweieh ™ - points in time" The burners are only in operation until the input is supplied with the amount of heat that was lost during the burner switch-off time If there is an indication that the "softening" has occurred »To determine the presence of such a condition, the burning duration signal for a season period is compared with the burning duration signal of the previous calculation period Abgleiohs-Sehleif-, wire 24 of the Aufzeiehnungsgeräts 19 to Is available _o This signal is at a Vergleichaverstärker 25, the "network 14 is supplied further to the straight existing value of the firing time signal from the Division * that both signals are within a certain Tolerans" If the comparison Ever amplifier 25 to _9, a counter 26 is to kept one step further. If the counter 26 has counted a certain number of cycles during which the previous burning duration signal is within the tolerance of the current burning duration range, it actuates the indicator lamp 23, which indicates that the "softening" has occurred.

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The advantages of the present invention over the prior art, can see based on 91g · 2 to 4 "cowardly," FIG. 2 is a Betriebeart nafth the prior art again when the oven is switched periodically _o Xa the example shown was the äerd every 4- minutes uogeeohalt · Piß. 2 is a diagram showing the relationship ψ & η burning time to the total time as a function of the time. The diagram according to FIG. 2 was created for a furnace that was turned over every * minutes as often as the oven has been switched

In the lower one, labeled A (Peil des Dlagraaa * according to Fig. 2, both burners are over 100%, the stove is turned over every M minutes in operations Ba, problems occur, both burners have the same duration, and Both regenerative chambers are heated equally At point B, however, the burning time drops to about 60 $ of the time. The left burner running during this time is therefore only in operation for about € 0 $ of the time. At point 0, on the other hand, the right burner is about 96 % of ^ eit in operation ₀ the portion D of the diagram shows dl "switched time after the switching, d · h _o the combustion duration for the burner in the left ventricle · If one follows the Umsshaltungen along the graph, it is found that the right burner is always in operation for longer periods than the left burner This is a highly undesirable condition

Fig. 3 shows the relationship sswisohen burning time and de ~ samtseit in the case that switching is carried out every time when the Brennstoffsufuhr is turned off · It can be seen that no large SEHW _a ONS exist in the recording

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are, which means «that between the burning time of the one Branner and that of the other burner, there are no large fluctuations *

Tig, 4 is a diagram similar to FIG. 3 with the exception "that the switchover"! ₀ This means that calculations have been carried out in which the calculated values of the heat ratios have been averaged for both combustion chambers and not separately calculated for the right and left combustion chambers.This is an advantageous modification in order to better display it obtained ₉ when the steel is "softened" Note that the relatively rapid changes in the diagram of Fig. 3 make it difficult to obtain successive scale values with close tolerances. However, if the fluctuations between the two burners are averaged like this When the recording is made, it is possible to obtain a number of successive scale values for which the duration signal is constant

Claims (1)

Expectations 1 “Device for controlling the switching of the flow of combustion air and combustion products through one Regenerative furnace with regeaerative chambers on both sides and an arrangement that alternates the combustion air through the chambers and the burners in each of the chambers - 13 - 909883/1358 BATH ORIGINAL guides »s β k e η η β β i ο h η et through a temperature« sensitive binary direction (17) to control the on and off Switching of the burner firing as well as a device (16) responding to a change in the combustion conditions of the burners ($ * 9) for switching the flow of combustion air and combustion products 2 »Device according to claim 1, characterized by a timer (18) to determine the burning time during! * time representing each firing cycle, means (14) for generating a signal indicative of the ratio τοη burning time to total cycle, one on this ^ö ignal above a specific adjustable point responsive means (11) for switching the flow of combustion air and Verbrennungeprodukten whenever the timer exceeds a set time interval, the device (16) responding to a change in the burning state of the burners (8, 9) can only be actuated if the said signal is below the specific adjustable function o 3 · Device according to one of claims 1 or 2, characterized marked that the on a change in Burning state of the burner (8, 9) responsive device comprises a relay contact (16) which, when the burner is switched off is operated to reduce the flow of combustion air and products of combustion - 14. - 909883/1358 4 _{β A} method for controlling the switching of the flow of combustion air and combustion gases through a regenerative furnace, characterized in that the reserve of burning time and total cycle time is determined and that the flow of combustion air and combustion products, if this ratio over a certain adjustable function according to the set time intervals and, if the ratio is below this point, the burner is switched over when switching off 5e Procedure for indicating the point in time at which the steel, is heated evenly to the desired temperature in a batch-operated furnace, characterized in that an electrical signal is generated, which represents the change in the rate of fuel flow into the furnace and that an indicator is actuated when this signal approaches a constant value to indicate that the steel is heated evenly to the desired temperature 60 Method according to Claim 5 _f, characterized in that, for actuating the display device, the said signal for a previous cycle is compared with the signal for the current cycle, so that a counter is actuated each time the signal for the previous cycle - 15 - 909883/1368 DA-K491 - 15 - essentially the same as the signal for the current one Cycle is, and that the display device is acted upon if the counter continued to hold a certain number of steps batο 7ο Method for operating a Hegenerativ-Qfena, in which the combustion air flow is passed alternately through ßegenerativkammern, characterized in that an electrical signal is generated which represents the change in the rate of fuel flow into the furnace, that a display device is actuated when it is this signal approaches a constant value to indicate that the steel in the furnace has been heated uniformly to the desired temperature, and that the flow of combustion air and combustion products, if this signal is above a certain adjustable point, after set time intervals and , if the signal is below this puck, the burner is switched when switching off «, 909883/13 5 8 Lee on the side