CS195669B2 - Method of regulating incinerators for heat treating fine-grained materials - Google Patents

Abstract

1410184 Automatic control KLOCKNERHUMBOLDT-DEUTZ AG 2 Oct 1972 [1 Oct 1971] 45413/72 Heading G3R In a plant for the heat-treatment of granular material and including a furnace and two parallel pre-heating devices through which the furnace exhaust gases pass, the temperatures of the exhaust gases leaving the pre-heating devices are equalized by controlling the flow of exhaust gas and/or material in accordance with those temperatures. In the embodiment shown, cement meal is fed by metering services 6, 7 e.g. weighing conveyors to parallel pre-heaters 2, 3 supplied with hot exhaust gases from rotary kiln 1. The temperatures of the gas from the pre-heaters are measured by short time delay thermocouples 14, 15, any difference between these temperatures being used, by controller 19, to vary the speed of fans 10, 11 in the pre-heater outlet pipes 8, 9 and thus maintain the pre-heater gas output temperatures equal. To regulate these temperatures at a desired value, the output of controller 19 is modified by controller 21 according to a comparison between the average of the measured temperatures and a desired value, that is modified according to the error between the measured oxygen content of the furnace output gas, and a required value. If the speeds of the fans 10, 11 as measured e.g. by tachogenerators exceed a pre-set limit, the difference between the gas outlet temperatures is alternatively switched to controller 27 to vary the material feed from metering devices 6, 7. The pre-heater exhaust gases pass to an electrostatic dust removal apparatus 12 and milling drying plant 13. In an alternative arrangement Fig.3 (not shown) a single fan is used with temperature control by a throttle valve in each pre-heater exhaust pipe.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a combustion apparatus for heat treatment of a fine-grained material, preferably a cement raw meal. which has a furnace and at least wildly paralleled preheating devices in which it is fine-grained. the material is heated by direct contact with the bitter furnace flue gas, wherein the flue gas from the furnace is conveyed by a preheater by means of an artificial draft blower.

Dry clinker production or aluminum hydrate calcination is carried out in a rotary kiln to which a preheating device is connected, for example a so-called cyclone heat exchanger, in which the fine-grained material to be treated, for example cement raw meal, is preheated by direct contact with hot flue gases. · From the furnace. The transition to increasingly kiln output, about 1000 tons or more, requires preheating for fine-grained material, using so-called twin structures, ie hot waste kiln gases that leave the rotary kiln; they are led by two preheating devices connected in parallel. In this case, it is necessary that the ratio of the amount of flue gas to the material always remains approximately the same in the pre-heating devices connected in parallel, so that the material streams, which are separately overrun.

heated, but brought together in the charging region of the rotary kiln, showed approximately the same degree of heat treatment.

The regulation of the amount of hot gases conducted by the two preheating devices in dependence on the measurement of the amount of gases is associated with considerable difficulties. Known instruments, such as gas quantity measurement, such as venturihp tubes, air baffles, “Prandtel boom baffles and similar devices,” are not operationally safe due to the high dust content of the measured flue gases from continuous furnaces and must be constantly monitored by maintenance. In addition, the measuring instruments condition a large amount of gases of this kind due to their flow resistance, a considerable pressure loss, which is economically disadvantageous on the necessary energy load. Measurement errors due to the presence of dust and / or wear do not allow satisfactory control of the flue gas volume during continuous operation. In addition, the nominal value which can be achieved by means of these devices is only valid for a narrowly restricted operating area, but which contradicts the operating requirements imposed on combustion plants of this kind.

Tasks ¹ of the invention is to propose a control method for such combustion plants opatřetaá plurality of parallel přede195889

195689 hřívací. an apparatus to be treated which permits the "safe control" of the parallel-connected preheating devices. also in permanent operation. This object is achieved in accordance with the invention in that the flue gas temperatures are measured for a certain amount of charge predetermined for each preheating device. behind each preheat. the device, wherein, depending on the measured temperatures, it is partial. preferably, the amounts of flue gas fed by the preheating devices automatically regulate relative to each other, so that the partial flue gas streams have no temperature differences between each other. The method according to the invention achieves that in each of the parallel preheating devices there is a ratio of the amount of the material to be preheated to the amount of the flue gas to be determined. For cooling, the same and therefore the 'material streams fed in the furnace' together from the individual preheating devices exhibit the same degree of heat treatment. This also additionally improves the operating conditions for the downstream furnace. An advantage of the method according to the invention is furthermore that the control of the ratio of the amount of material to gas in the individual preheating devices. The temperature sensors can be carried out by known temperature sensors. Temperature sensors of this kind are also 'insensitive' to disturbances caused by the content of dust in the flue gas, such as baking, abrasion, etc., even during a longer period of operation. By using corresponding temperature sensors, for example when using thermocouples, an electrical signal is immediately available, which can be easily done. use a measuring transducer to control the adjusting devices for controlling the amount of flue gas.

In the practice of the invention, the total amount of gas fed by the preheating devices is controlled, whereby the flue gas temperatures measured in the individual sub-streams of the flue gas are controlled. corresponds to a pre-set nominal value. Thus, in the event that the total amount of flue gas is, in particular, reduced by the control action according to the invention affecting the partial flue gas streams, it is achieved that it is. the whole plant again put on its - optimal. gas-to-material ratio. .

Furthermore, in the implementation of the invention, the measurement of the flue gas temperatures is always carried out by means of temperature sensors with a short time delay. For this purpose, thermocouples with a thin protective tube are suitable. By this measure, which causes a regulation intervention - with only a small time delay - when the flue gas temperature changes, it is possible to achieve a substantially uniform operation of the entire plant. This fact is of importance because other separate control circuits are located in the furnace area, on which the flue gas control interventions would have a negative effect if, for example, they caused a change in the amount of flue gas - only at a large time delay.

In addition, when carrying out the process according to the invention, it is in order to comply with it in advance. '. the set nominal values - flue gas temperatures - downstream of the preheating devices, the flue gas flow rate is controlled in dependence on the detected flue gas temperature in the flue gas streams, from the blower speed. In addition to this measure, the preheating devices can be maintained in parallel in a simple manner in an optimal operating area. .

Furthermore, the method according to the invention is applied in order to compensate for the temperature differences between the flue gas streams by controlling the amount of flue gas guided by the individual preheating apparatus by varying the rotational speed of the respective artificial blower. By means of this control measure according to the invention, for each individual parallel heating device, the ratio between the amount of gas and the material is set in a simple manner for the individual pre-heating device. • In the case of control, the material is the same for all preheating devices.

In the - other - implementation of the method of the invention is applied. provided that, to compensate for temperature differences between the flue gas streams, the control of the partial amounts of flue gas guided by the " individual " preheating devices is carried out by means of a throttle valve in the flue gas duct after each preheating device. on the temperature difference found. This embodiment makes it possible to indicate the amount of flue gas conducted by the individual preheating devices to the ratio of the amount between the gas and the material, the optimum for each preheating device, also, if a single blower is used. The plasticizer generates a plurality of parallel-connected pre-casting devices. To achieve - as little pressure loss as possible, the throttles are preferably locked together so that each - one throttle is fully open - and the other causes the necessary resistance equalization. This occurs, for example. in that the temperature sensor - in one flue gas conduit - affects the throttle position - in the second flue gas conduit. Thus, they are in a simple manner automated. different flow resistance variations in the individual preheating devices, which may, for example, occur as a result of the attrition, are regulated. .

Finally, when implementing the method according to the invention, it is provided that, depending on the temperature of the flue gas, the amount of charged material varies for at least one preheating device as long as it is not present. the temperature difference between the flue gas streams. This additional control intervention is necessary when the combustion apparatus is at its highest power limit, i.e., when the most of the feed material is fed to the plant. Aspects with respect to the maximum amount of flue gas; .Due to · . 'it can . , v. in this case, the artificial thrust blowers running downstream of each preheating device are operated with the highest revolutions, respectively. Throttle valves. there are no openings, it is no longer possible to carry out a control action concerning the rotation speed of the blower, the guns, respectively; Throttle valves. In this case, it can be simple. In a manner by equalizing the amount of material to compensate for the temperature difference between the individual flue gas streams after the preheating devices, the charging amount is expediently dosed so that the reduction of the charging amount for a single preheating device at the same time, it corresponds to a corresponding increase in the second preheating device, so that overall the total amount of charge remains approximately 1%. If the predetermined flue gas temperatures are exceeded, in addition to the 'change in relative ratio' of the 'individual amounts' of the material used, the total amount of the charge, in particular, can be varied depending on the flue gas temperatures. be increased if this process no longer occurs by means of a so-called furnace regter.

In the implementation of the method according to the invention, furthermore, a measure is taken that the nominal value of the flue gas temperature is automatically set in dependence on the oxygen content of the flue gas in such a way that the temperature value increases and when the predetermined maximum oxygen content of the flue gas is reached the nominal temperature value. will decrease. By means of this embodiment of the invention, it is possible to achieve an automatic adaptation of the control method according to the invention to those operating conditions given by known control circuits for supplying the amount of fuel, the amount of raw material charge and the furnace speed in such combustion plants. When combustion devices of this kind are used, cooling devices are provided in which the cooling air manifold is supplied with an 'own' blower independent of the preheater blower. The 'artificial draft' device is preferably a cooling system and a combustion device consisting of a preheating device and a furnace, pressure separated by known pressure control circuits, i.e. the artificial draft fan and the cooling fan of the cooling system are matched to each other so that there is ^{1 bar} and a balance in the area of the transition point between the furnace from the cooling system. .

The process according to the invention is explained in more detail. in the form of a flow diagram illustrating an apparatus for firing cement clinkers. The firing devices to be controlled are, from a constructional point of view, still the same, while FIGS. 1 to 3 show, however, different arrangements of control circuits for carrying out the method according to the invention. ·. ·. ·. ·.:,

In an apparatus with a daily output of about 20,000 itUn hen, shown in FIGS. 3 to 3, are two cylindrical rotary heat exchangers located in two rotary heat exchanger systems. 2 and 3, the sterns are connected in parallel to the flue gas flow coming from the rotary kiln. In the flue gas ducts 4, 5 leading to the cycles of the two preheating devices, always the last in the gas flow directions, a cement 'waste gas stream' via a metering device 6, 7, for example 'via a metering weight, is introduced' 's flour. The raw cement meal fed in each case proceeds from the top down to the individual cycles of the respective preheating apparatus. that is, stepwise upstream of the " gas flow, " and " comes in contact " with "

By direct contact of the fine-grained material with hot flue gases having a temperature of about 1000 to 1100 ° C immediately downstream of the rotary kiln, the material is heated and has a temperature at its transition to the furnace. 'about' 800 · to '900¾. During this heat transfer, the flue gas largely releases its heat content of material and leaves the preheating device at a temperature of about 300. up to 400 ° C. In each case after the 'lowest stage of the cycles', the preheated raw meal is passed from the two preheating devices to the feed chamber to the rotary kiln. The 'flue gases coming out of the preheating devices are exhausted by the flue gas lines 8, 9. The two flue gases 8, 9 each open into a single blower 10, 11 producing an artificial draft, which leads the flue gases further to an electrostatic dedusting device 12 and / or to a device 13 for drying the ground material. According to the " operating conditions " the flue gas withdrawn from the preheating device is upstream or downstream of the artificial draft blowers moistened in a corresponding electrostatic working apparatus, not shown. In order to carry out the method according to the invention in the form of a self-regulating circuit, the thermocouples are used as thermocouple temperature sensors in the arrangement according to FIG. . 'which' have the purpose of reducing the time delay in the occurrence of changes. · Flue gas temperatures 'only a thin protective' pipe. The signals coming from the thermocouples are supplied to the control device 18 via the measuring transducer 16, 17 and compared to each other. In a manner corresponding to the temperature difference resulting from their comparison, the rated speed regulator 19 now increases the rotational speed of the artificial draft blower located in the flue gas duct at a lower temperature, while the rotational speed 19 the second dmyc-shaft and e-lower. The total amount of flue gas is normally not affected by this. Since, as mentioned above, the amount of raw meal delivered to each preheater is predetermined on the basis of (operational successes), the ratio of the amount between the gas and the material for each, both ipředehřívacích. device is set to the ratio, • which is ¹ 'considered optimal, -so at the furnace form a uniform level processing - both separately -ohřívaných -di 1čích material streams.

I - - For the purpose. avoiding changes in the total amount of flue gas at stronger control interventions for influencing one of the two partial streams of flue gas, as well as for the combustion plant as a whole not to change the ratio of the total amount of feed material to. the total amount of flue gas against a predetermined optimum ratio and, by means of an additional control circuit, also controls, depending on the temperature of the waste gas, the total amount conveyed by the two artificial air blowers, coming from the two temperature sensors 14, 15, sensed downstream of the two measuring transducers 18, 17, and fed to the measuring transducer 20, in which the formation of the mean value takes place. This mean value is a measure of the temperature of the total waste gas stream behind the preheater. The signal corresponding to the flue gas temperature is now compared in the corresponding regulator 21 with (a predetermined nominal temperature value) .When the actual value deviates from the nominal value, a corresponding signal is sent, which is supplied to the ratio controller. 19. The signals resulting from the flue gas temperature regulator 19 are (controlled by the regulating device 22, 23) for controlling the number of blower drive rotations, which usually have a tachogenerator and a number indicating device. This results in a uniform increase in or decrease in the number of revolutions by the blowers 10, 11 generating an artificial draft, i.e. an increase or decrease in the total amount of flue gas without reducing the total amount of combustion products. changes in mutual ratio of the quantity - both - partial flue gas streams I - Nominal - value of flue gas temperature - The flue gas temperatures are set manually first, since, however, such high-output combustion plants have additional control over the furnace control. the circuits, for example depending on the operating conditions. - inside - combustion zone - controlled - fuel supply, resp. In the case of the charge, the 'fixed setting' of the nominal value in the region - the regulation of the quantity - of the flue gas can have a disadvantageous effect on the operation of the furnace. Since the oxygen content of the flue gas is downstream of the furnace, it is retep. downstream of the preheating devices, according to the invention, the regulation (e ec) can be changed according to the invention by means of this control parameter - the amount of waste gas - according to the inventive method - automatically adapted to the control circuit of the furnace. for the measurement of gases, the 'oxygen content' - in the flue gas is measured - to 19 5 8.8 9, for example, in the inlet orifice, the signal obtained by the measuring device being in the sensor: 25. which is - preferably - embodied as a 'limit alarm', compared to a predetermined nominal value, the deviation of the measured oxygen from the predetermined nominal value is a signal, - the nominal temperature sensor 25, superimposed on the nominal value of the regulator - 21 - - the flue gas temperature, - i.e. k - fixed - set temperature value - is supplied Thus, it is possible that, when the oxygen content in the flue gas decreases below a predetermined minimum value, the nominal temperature or temperature is increased. when the oxygen content of the flue gas increases above a predetermined maximum value, the nominal temperature value is lowered and, accordingly, the blower speed is increased or reduced, and hence the total amount of flue gas guided by the preheater devices. ·

In order to guarantee an optimum operation of the combustion plant, in the event that the plant is regulated within the described control circuit, i. if one of the blowers generating an 'artificial thrust' has reached its / upper power limit, it is according to the invention. - a measure according to which a switch 28, by means of which the output signals of the controller -8 for supplying the temperature difference to the control of the temperature difference, is actuated by means of a speed limit detector of the respective control circuit in the blower motor, is applied. The ratio regulator 27, which appropriately adjusts the dosing scales 8, 7. By this regulator, the ratio of the charge amount to the individual preheating devices is adjusted in a manner analogous to the regulation of the flue gas quantity. In the case of this control, however, it is necessary to take into account the control technique according to the invention. In some circumstances, the dosing scales B, 7 to both preheating devices are set simultaneously by means of the furnace control circuit.

FIG. 2 shows a simplified configuration for carrying out the method according to the invention. A control device having the same function corresponding to the embodiment shown in FIG. 1 are marked with the same reference numerals, but are provided with an index. In this embodiment the measuring signal emanating from -snímače ^1-14 'and the amplified temperature measurement - transducer - 18' is supplied to the controller 28 • temperatures produce combustion gases. s - a predetermined nominal temperature., The nominal value is the 28-temperature controller. flue gas - supplied via - adjuster. 29 - nominal values, automatically adjusted by the i25 'nominal value sensor, which receives a measurement from the device. - a gas content signal corresponding to the oxygen content of the flue gas, - in order to adapt the automatic adaptation to the upstream control circuits. -When the measured flue gas temperature deviates from the pre-heating device against the pre-heating value, which is preset, by means of the flue gas temperature regulator 28, the blower speed 10 is regulated according to the deviation so that it increases and decreases is reduced accordingly, so that the preset nominal temperature is maintained.

An iPro blower 11 is provided with a corresponding control circuit, which is connected to a gas temperature controller 30 whose nominal value is also determined, starting from the temperature sensor 15 * and the measuring transducer 17 *. with the nominal value adjuster 29 '. Depending on the deviation of the gas temperature measured by the temperature sensor 15 * from the preset nominal temperature, the number of revolutions of the blower fan 11 is increased or decreased accordingly. In this way, on both control circuits connected by a common nominal value adjuster 29, the temperature difference between the two partial flue gas streams is equalized and, secondly, a predetermined nominal temperature is set so that both preheating devices can still be operated with a favorable average between the existing amount of charged material and the partial amount of gas to be consumed. individual preheating devices. At the same time, however, in terms of overall facilities ,, this device also 'in ^one operation with a favorable ratio of the amount and the optimum operating point ·.

FIG. 3 shows another control arrangement for implementing the method of the invention for a modified design of a dual combustion plant. Functionally identical control devices corresponding to the embodiment of FIG. 1 are designated with the same reference numerals provided with an index. In this combustion apparatus, the two flue gas lines 8 ' and 9 ' are combined by only one, preferably dual flow, designed artificial air blower 31. move. In order to compensate (temperature differences in the flue gas lines 8 '', 9 '', instead of the two blowers according to the above-mentioned examples, two butterfly valves 132, 33 are driven in the exhaust lines.

Claims (3)

1. A method for regulating a combustion apparatus for heat treatment of ¹ · jemnozmného material, preferably cement, raw mouč- 'Iky having at least .div furnace and connected in parallel předehřfvací device in which ijemnozrnný material is heated in direct contact with the hot kiln exhaust gases, wherein the flue gases from the furnace are conveyed by the preheating device through at least one artificial draft blower, characterized in that for a certain amount of charge predetermined for each preheating device, the flue gas temperatures are measured after each preheating stage, depending on the measured at the flue gas temperatures, a partial amount of flue gas conducted by the pre-heating humidification of the flue gas can be carried out in a corresponding device 34, for example in a spray tower. The arrangement of the control devices is, for analogy to the embodiment of FIG. the difference in the discharge lines 8 ", 9" is compensated by the throttle valves. The throttles are coupled to each other so that one throttle is always fully open, while the other causes the temperature difference to be equalized. This is done by actuating the throttle 14 ' and the throttle 32 ' and the throttle 32 ', and the throttle 33 ' while the throttle valve 32 remains fully open. In the case of stronger control interventions, this leads to a noticeable reduction in the total amount of flue gas, i.e. an unfavorable change in the gas-to-material ratio, for the individual preheating devices or for the respective preheating devices. for the entire device. According to the invention, in this case, to control the total flue gas quantity, because of the constant flue gas temperature, the mean value of the flue gas temperatures existing in both the 8 ', 9' flue gas lines is also produced here by means of a measuring transducer 20 'and 21' In order to control the flue gas temperature, and to control the speed of the flue gas blower 31, a control device analogous to the first embodiment is used. Adjustment of the nominal value of the regulator 21 "of the temperature of flue gas can be carried out analogously to the embodiment of FIG. 1, by measuring the oxygen content: in (ipece input chamber. The same applies to operating the switch 26" for switching the control circuit. 8, 7 for dispensing the insert material. The method according to the invention is not limited to the double device described, but also allows the control of combustion plants with more than two preheating devices. In accordance with the invention, they preferably regulate each other automatically in relation to each other, whereby the partial flue gas streams have no temperature differences between them. . : ' Method according to claim 1, characterized in that the total amount of gas fed by the preheating devices is controlled, whereby the flue gas temperatures measured in the individual flue gas streams correspond to a predetermined nominal value. 13. Method according to Claims 1 or 2, characterized in that the measurement of the flue gas temperatures is always carried out by a temperature sensor with a short time delay. 14. A method according to items 1, 2 or; 3, characterized in that in order to keep predefined 19 5 6 6'9 • Nominal temperature values - flue gas after preheating. By means of a device with a "quantity control", the flue gas is also carried out depending on the detected flue gas temperature, by changing the number of blower revolutions. , 5; A process according to 'claim 1, .2, 3 or ¹ 4, characterized - in -that - for compensation - partial temperature differences -'mezi - flue gas streams were control - quantity -spalin - -jednotlivými- předehřívacíml guided devices being done by the number of turns of the respective artificial draft blower, after the respective preheating device, depending on the detected temperature difference. 3. The method according to claims 1, 2, 3 or 4, characterized in that, in order to compensate for temperature differences between the partial flue gas streams, the regulation of the partial amounts of flue gas conducted by the individual preheating devices is effected by a choke flap in the flue gas duct. after each - the preheating device, which - is adjusted according to the temperature difference detected. 7. "Method - according to points 1, 2, 3, 4, 5 or 6, marked" by:. Additionally, depending on the detected flue gas temperature, the amount of feed material varies for at least one preheating device until the temperature difference between the flue gas streams is equalized. · Method according to claim 7, characterized in that, depending on the detected combustion temperature, the total amount of charged material varies for all preheating devices until a predetermined nominal temperature is set. Method according to one of Claims 1 to 8, characterized in that the nominal value of the flue gas temperature is automatically set in dependence on the oxygen content of the waste gas in such a way that when it is reached in advance The nominal temperature value of the flue gas is increased and the nominal value of the temperature is reduced when a predetermined maximum content is reached (flue gas number in the flue gas).