JPS5848494B2 - Control method for cement firing equipment with composite ventilation system - Google Patents

Description

[Detailed Description of the Invention] This invention solves the ventilation control in the composite ventilation system C, sets the optimum calcining rate of the raw material fed to the rotary kiln, stabilizes the raw material advancing speed in the rotary kiln, and prevents internal disturbance. The present invention relates to a method of controlling a cement incineration equipment having a composite ventilation system.

In the production of cement and the like, a burning method has been developed in which a rotary kiln equipped with a suspension preheater that floats and preheats the powder raw material is attached with a raw material calcination device having a combustion mechanism independent of the rotary kiln.

A device using this burning method generally consists of a multi-stage cyclone type Sanupension preheater (hereinafter referred to as cyclone) installed at the end of a rotary kiln connected to a clinker cooler via a mixing chamber and a calcining device. The calcination device and the lower end of the clinker cooler are connected by a duct for transmitting high-temperature air, and the exhaust gas is exhausted by a main exhaust fan via a cyclone.

The calcination equipment performs high-efficiency combustion and heat transfer calcination to the raw material at the same time. Fuel and high-temperature air are introduced into the calcination equipment, and the powdered raw material to be calcinated is suspended. It is responsible for maintaining stable combustion in suspension.

On the other hand, the rotary kiln is responsible for sintering the raw material that has been almost completely calcined, so it is naturally necessary to maintain stable combustion, and for this reason, it is necessary to constantly discharge the rotary kiln exhaust gas.

In addition, the exhaust gas from the calcination equipment and the rotary kiln and the gas generated during the sintering of the raw materials are exhausted by the main exhaust fan. The two ventilation systems are arranged in parallel, and after merging in the mixing chamber, they are connected to the preheater system and connected to the main exhaust fan, so it is necessary to balance both ventilation systems.

Next, as a problem in controlling the process until the raw material is sintered in the rotary kiln, it may be difficult to detect the progress of the process until the raw material is sintered.

Variations in external disturbances entering the sintering completion process in the rotary kiln, such as feed rate of raw materials, chemical and physical composition of raw materials, rotation speed of the rotary kiln, and fuel feed rate, are reduced to the greatest extent possible. However, the current situation is that it is difficult to detect disturbances that occur internally, and there is no way to determine what to target.

There are various possible causes of this internal disturbance, but the most common cause is a change in the speed at which the raw material moves inside the rotary kiln.

This change in the advancing speed of the raw material changes the temperature distribution of the raw material and gas in the rotary kiln, and each process up to the tarinka sintering step interferes with each other, making the process extremely unstable.

As long as the rotational speed of the rotary kiln remains constant, changes in the advancing speed of the raw material are due to changes in the passage resistance of the raw material in the rotary kiln and the resistance between the raw material particles. This is due to changes in the adhesion state of the coning or ring, as well as changes in the chemical and physical properties of the raw materials in the rotary kiln from their steady state.

It is theoretically and empirically known that the higher the calcining rate of the raw material supplied to the rotary kiln, the smaller the change in the advancing speed of the raw material.

That is, a powder raw material with a high calcination rate has an increased stickiness, which increases the resistance to passing through the rotary kiln and the adhesion between raw material particles.

Therefore, the higher and more constant the calcining rate of the raw materials supplied to the rotary kiln, the higher the rotational speed of the rotary kiln, and the more stable and highly efficient operation becomes possible.

However, since the powder raw material has a fixed particle size distribution, it is necessary to raise the temperature of the raw material supplied to the rotary kiln considerably in order to achieve a true calcination rate of 100%. This causes the raw material to adhere to the joint between the upper end of the rotary kiln and the lowermost cyclone, promoting coagulation and impeding operation.

The upper limit of the temperature of the raw material fed to the rotary kiln, that is, the upper limit of the calcination rate, is determined from the relationship between the raw material temperature at which this raw material starts to adhere and condense and the exhaust gas temperature of the rotary kiln, and the optimum calcination rate exists at a calcination rate below this value. .

Furthermore, the permissible range of fluctuations in the calcination rate of the raw material around this optimum calcination rate must be within a range that can absorb fluctuations in the calcination rate due to the rolling of the raw material in the rotary kiln. is the lower limit value.

From the above, in a rotary kiln with a suspension preheater equipped with a calcination device, a method for controlling the optimum calcination rate of the raw material supplied from the lower cyclone to the rotary kiln for operational control, and (b) combustion air and combustion in the calcination device. The gas ventilation system is parallel to the ventilation system of the rotary kiln, and both systems are connected in series with the main exhaust fan through the suspension preheater to form a series-parallel ventilation system (referred to as a composite ventilation system). The problem is how to control ventilation.

Among these, a method of measuring the calcination rate of the raw material itself that is supplied to the tally kiln related to (@) can be considered.

However, this method is extremely difficult to average sampling, requires input or special measuring equipment to measure the calcination rate, and takes a long time to measure, so the control signal is based on the raw material itself. Measuring the calcination rate is not a good idea.

This invention was made in consideration of these points, and includes a composite ventilation system 6 formed between the rotary kiln and the calcination device, and the opening degree of the calcination device combustion air duct, the opening! Ventilation balance is controlled by a ventilation balance control loop based on the opening degree of the condenser mechanism installed in the flue of the tally kiln, and at the same time, combustion is controlled by adding oxygen concentration in the exhaust gas, etc. to determine the optimum feedstock for the rotary kiln. The present invention provides a method for controlling a cement baking apparatus having a composite ventilation system that sets the burning rate, stabilizes the rate of progress of raw materials in a rotary kiln, and prevents and effectively quiets internal disturbances during steady state.

An embodiment of the present invention will be described below with reference to the drawings.

First, the structure of a cement burning apparatus having a composite ventilation system to which the present invention is applied will be explained with reference to FIG.

11 is a rotary kiln, one end of which is connected to a clinker cooler 12, and the other end to which a mixing chamber 13 is connected.

A calcination device 14 is provided in parallel with this mixing chamber 13, and the upper end of this calcination device 14 and the clinker cooler 12
A duct 15 is interposed between the two.

Above the mixing chamber 13 and the calcining device 14, there are, for example, four stages of cyclone type suspension preheaters (hereinafter referred to as cyclones) 161, 162, 163,
164 is provided, and this uppermost cyclone 164 is connected to the main exhaust fan 18 via the duct 17.

? To explain this on the premise of the structure, this invention focuses on a method of controlling the calcination rate of the raw material by using the temperature of the raw material supplied to the rotary kiln 11 as a control signal as an alternative method of measuring the calcination rate of the raw material itself. As shown in FIG. 2, we found a characteristic curve of the temperature T of the rotary kiln feedstock and the calcination rate.

From this characteristic curve, if the heat transfer efficiency to the raw material in the calcination device is determined in the rotary kiln, it is possible to fix the calcination rate of the raw material supplied to the rotary kiln at high nW, and therefore the calcination rate of the raw material itself can be fixed. If the calciner 14 is operated so that the temperature of the raw material fed to the rotary kiln is kept within predetermined upper and lower limits as an alternative index for the rate, disturbance to the rotary kiln can be reduced and highly efficient and stable operation can be achieved.

Next, the part ζ related to the present invention of the combustion control of the calcination device 14 accompanying the control of the calcination rate (material temperature as an alternative index) of the raw material fed to the rotary kiln will be explained.

That is, the temperature of the raw material fed to the rotary kiln is controlled in a steady state by controlling the combustion state of the calciner 14.

This has advantages such as the gain of the heat transfer process of the calciner for the rotary kiln feedstock is much larger than the gain of the heat transfer process of the rotary kiln, and the response speed is large and there is almost no wasted time. This is because there is.

However, in a rotary kiln with a suspension preheater attached to a calcination device, unlike a normal rotary kiln with a suspension preheater, combustion of fuel takes place in two places, the rotary kiln and the calcination device, while the air for combustion is exhausted from the main exhaust. It is given only by the ventilation force of the wind machine.

As is clear from FIG. 1, since this structure forms a composite ventilation system, it is necessary to control the ventilation balance of the rotary kiln and the calcining device.

Therefore, in this invention, the fixed value control based on the minor loop O of the amount of fuel used, the amount of raw material supplied, and the kiln lower end foot pressure, which was implemented in the conventional rotary kiln with a suspension preheater attached to the calcination device, has been improved. By adding a ventilation balance control loop and organically linking these loops, we solved the problem of ventilation balance associated with the combustion control of a rotary kiln with a suspension preheater attached to a calcination device.

Here, the control system will be explained with reference to FIG.

First of all, the control system of this invention is capable of controlling controlled variables and manipulated variables such as openings of dampers and flow contraction mechanisms in addition to general continuous control for reasons such as improving equipment economy, efficiency, and safety. The basic function is to set an upper limit value, a lower limit value, or an upper and lower limit value for a quantity, and to selectively control this according to a certain logic.

First, the raw material is supplied from the raw material quantitative feeder 19 to the duct connected to the cyclone 164 at the top stage, and the actuator 2 is supplied to the rotary kiln 11 and the calcining device 14, respectively.
Fuel is supplied through valves 22 and 23 which are opened and closed by valves 0 and 21.

These actuators 20 and 21 each have a flow rate controller 24
, 25 from the control system 26, and the raw material metering feeder 19 is also controlled by the control system 26.

Then, the total amount of fuel used F that corresponds to the amount M of raw material supplied from the raw material quantitative feeder 19 is determined, and the ratio α between the amount of fuel used by the rotary kiln FK and the amount used by the calciner Fs is determined.

The value of α is related to the efficiency of the system and is 0.4 to 0.6.
That's about it.

Furthermore, the air ratio nK at the upper end of the rotary kiln 11 and the air ratio ns at the outlet of the calcining device 14 are determined.

The value of each of these air ratios ns should be determined to be an appropriate value for improving the thermal efficiency of the entire system.

In reality, the air ratio ns of the calciner 14 is controlled to a fixed value in a minor loop by the fuel amount Fs used and the high temperature air amount Q8 from the tarinka cooler 12.

The air ratio nK at the upper end of the rotary kiln 11 is determined by measuring the oxygen gas concentration in the exhaust gas at the upper end of the rotary kiln 11, and this is used as a representative index of the air ratio nK.

The oxygen concentration in the exhaust gas of the rotary kiln 11 is detected by the oxygen concentration meter 27c, converted into an electrical signal, and guided to the control system 26.

The amount of fuel used in the calciner 14 and the amount of high temperature air Q8 are controlled by the air-fuel ratio in a minor loop, but the amount of high temperature air Qs is controlled by the adjustment damper 28 provided in the duct 15 to a maximum opening of 60%, for example. An upper limit value is set by the limiter and inputted to the control system 26.

The upper limit of the opening degree of the damper 28 is determined by the type of damper, the pressure loss in the wind pipe, and the pressure loss allowable for the damper.

On the other hand, an upper limit value for the opening degree of the flow contraction mechanism 29 interposed between the rotary kiln 11 and the mixing chamber 13 is also input to the control system 26 .

This opening degree differs depending on the scale 6 of the device. In addition, each of the adjustment damper 28 and the contraction mechanism 29 has a Kucheta 30
, 31 are connected, and the opening degree is controlled by a signal from the control system 26.

Next, from the bottom cyclone 161 to the rotary kiln 11
The temperature T of the raw material supplied to the rotary kiln is inputted to the control system 26, and the upper and lower limits of the raw material temperature determined from the temperature T and the characteristic curve of the rotary kiln feedstock temperature and the calcination rate of the feedstock shown in FIG. A comparison is made.

Similarly, the rotary kiln exhaust gas temperature T2 at the upper end of the rotary kiln 11 is input to the control system 26,
A comparison is made with predetermined upper and lower limits of rotary kiln exhaust gas temperature.

This upper limit value of the rotary kiln exhaust gas temperature is to prevent raw materials from adhering to and condensing on the conduit at the joint between the lowermost cyclone 161 and the rotary kiln 11. Normally, if the exhaust gas temperature exceeds 1050°C, adhesion and condensation will occur rapidly. It is said to promote

Therefore, in the example, the temperature was set at 900° C. with allowance in mind.

In addition, the lower limit value must be at a level that does not interfere with the operation of the rotary kiln 11.
In the example, the temperature was determined empirically from the relationship with the temperature T of the raw material supplied to No. 1, and was set at 850°C.

Next, the rotary kiln 1 is controlled at a constant value by the ventilation pressure P at the upper end of the rotary kiln 11 and another minor, - loop.
.

The control system 264 will now be explained with reference to FIG.

First, from the lowest stage Cyclone 161 to Roguery Kiln 11
The raw material temperature T supplied to is input to a high selector 35 where an upper limit value TIH is set and a low selector 37 where a lower limit value TIL is set.

On the other hand, the upper limit value TIH is input as a setting value of the simultaneous I/O calculation controller 38.

The measured rotary kiln feedstock temperature T is then compared with respective set values TIH, T by a high selector 35 and a low selector 37.

At this time, if T>TIH, the output of the high IL selector 35 becomes T and is input to the arithmetic controller 36, and if TζT, TIH is input and becomes 1-IH.

Similarly, in the low selector 37, when T,<T, the output is T, and when T≧TIL, the output is T.
ITIL is input to the arithmetic controller 364.

This calculation controller 36 calculates T and the set upper limit value TIH, and its output is input to the temperature check circuit 536. It will be done.

Similarly, the calculation controller 38 calculates T and the set lower limit value TIL, and its output is input to the temperature check circuit 53.

Further, the rotary kiln exhaust gas temperature T2 is inputted to a high limiter 40 in which an upper limit value is set in advance and a low limiter 41 in which a lower limit value is set in advance, where it is compared with the upper limit value T2H and lower limit value T2L of the exhaust gas temperature, respectively, and the output is are respectively input to the temperature check circuit 53.

This temperature check circuit 53 functions as shown in FIG. 4, that is, in the case of T>TIH, T>T and T2>=T2L, the output 2 2H is sent to the feed material amount calculator 39. This is input, and calculations are performed in the direction of increasing the amount of raw material to be fed, changing the set value of the raw material controller.

Further, when T>TIH and T2≦T2L, the output of the temperature check circuit 53 is input to the arithmetic unit 44, which performs a calculation in the direction of α reduction, that is, the fuel amount F8 used by the calciner 14, and the output is It is input to the fuel regulator (consisting of valve 23, etc.) of the calcining device 14.

At this time, the amount of fuel F used in the entire system is held constant by the calculator 43.

Furthermore, when T≦TIL and T2>T2H and T2>T2L, the output of the temperature check circuit 53 is input to the calculator 42, and the output of the temperature check circuit 53 is inputted to the calculation unit 42 to increase the amount of fuel F used in the entire system. Input to the calciner fuel controller and rotary kiln fuel controller (consisting of valve 22, etc.).

At this time, the fuel usage rate α is kept constant by the calculator 44.

The gains of these computing units and controllers and the parameters of the control elements are related to the gain and characteristics of the heat transfer process of the system.

Although the gain and characteristics of this heat transfer process are nonlinear, they can be considered linear in the range of minute fluctuations from steady operating conditions. The parameters were determined.

Next, the control of the ventilation amount accompanying the control of combustion will be explained with reference to FIGS. 3 and 5.

First, regarding combustion control, if the total fuel amount is F, calculation is performed in the calculator 43 based on the value of the fuel ratio α mentioned above, and the amount of fuel used in the rotary kiln 11 is FK.
==F(1-α), the amount of fuel used in the calciner 14 is F8-
αF, and each is input as a set value to the minor loop controller.

On the other hand, calcining? The amount of fuel used F8 in No. 14 is input to a minor loop calculator (ratio setting device), and is calculated between it and the predetermined air ratio n3, and as a result, the amount of high-temperature air Qs for combustion in the temporary combustion device 14 is determined. The damper 28 is operated by a minor loop of air amount control to control the air-fuel ratio to a constant value.

Here, control of the ventilation system of the rotary kiln system will be explained.

An upper limit value and a lower limit value are set for the oxygen concentration detected by the oxygen concentration meter 27 shown in FIG.

This upper limit value is determined based on the combustion and thermal efficiency of the rotary kiln 11, and the lower limit value is determined including prevention of incomplete combustion.

The set value nK of the air ratio of the rotary kiln 11 (oxygen concentration as an alternative index) is input to the oxygen concentration controller 46.

That is, the measured oxygen concentration 02 is determined by a high limiter 47 to which an upper limit value 02H is set in advance, a low limiter 48 to which a lower limit value 02L is set, and the oxygen concentration controller 46.
is input.

The output of this oxygen concentration controller 46 is the opening check circuit 54.
The outputs of the high limiter 47 and the low limiter 48 are also input to the opening degree check circuit 54.

This opening check circuit 54 has a function as shown in FIG.
2L and rotary kiln exhaust gas oxygen concentration measurement value 02
If 02≦02L, the opening degree θ of the contraction mechanism 29
2, and find its opening degree and the predetermined upper limit value θ of the opening degree.
A comparison with 2H will be made.

At this time, when θ2≦θ2H, the rotary kiln lower end foot pressure P increases.

When the absolute value of the difference between the pressure P and the pressure P at the upper end of the rotary kiln, that is, the value of; An action is taken.

The upper limit of IP to Po described above changes depending on the rotary kiln size, ventilation amount, and coating adhesion state.

Additionally, the upper limit value PH is set to avoid the inability to control the ventilation volume due to an abnormality occurring within the rotary kiln 11.
This is a signal for transitioning to a separately provided abnormality operation.

In the example, P H =30 ("Ag).

Therefore, if 0 OL and θ2≦θ2H and 2-2 l P,~PoI exceeds the upper limit PH, the output of the oxygen concentration controller 46 is held at the value at that time, and no operation is performed.

Next, if 02≦OL, is the opening degree θ2 of the contraction mechanism 29 upward? value θ2
When IP~Po1≦PH exceeds H, the output of the oxygen concentration controller 46 is input to the actuator 56 of the damper 55 of the main exhaust fan 18 in order to ensure the ventilation amount of the kiln system.

Also, in the case of 0>0 2 H, it means that the air ratio of the rotary kiln 11 exceeds the set value. If so, the output of the oxygen concentration meter 46 is input to the actuator 31 of the trickle mechanism 29.

As described above, the opening degree of the ventilation amount adjusting damper 28 of the next C calcining device 14 is set to the upper limit value θ1H, which is set by the high selector 51 and the opening degree controller 5'2.

When the opening degree θ of the damper 28 exceeds the upper limit value θH, that is, when θ>θH, the output of the opening degree controller 52 is input to the actuator 56 of the main exhaust inlet damper 55.

In this case, there is a concern about interference with the rotary kiln system, but this will not be a problem at all if the relationship between the upper limit 02H and lower limit 02L of oxygen concentration and θH are set to appropriate values.

In the example, everything was controlled using analog control, but if the arithmetic function and logic selection function are replaced with a digital computer,
Furthermore, easier and better control results can be expected.

As described above, according to the present invention, the optimum calcination rate of the raw material to be fed to the rotary kiln is set, and in particular, the ventilation of the composite ventilation system is controlled by controlling the opening degree of the air duct damper for calcination equipment combustion and the condenser mechanism. To provide a control method for a cement burning equipment having a composite ventilation system that solves the problem and enables stable control of the amount of combustion air, stabilizes the rate of progress of raw materials in a rotary kiln, and reduces and quickly calms internal disturbances. be able to.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing cement firing having a composite ventilation system to which the control method according to the present invention is applied, Fig. 2 is a characteristic curve of rotary kiln feed material temperature versus rotary kiln feed material calcination rate, and Fig. 3 is Figure 4 is a flowchart of the temperature check circuit in the control system shown in Figure 3. Figure 5 is the same diagram as shown in Figure 3. It is a flowchart of the opening degree check circuit in a control system. 11... Rotary kiln, 12...
Clinker cooler, 13...Mixing chamber, 14...
...Calcination device, 15...Duct, 161
, 162, 163, 164...Cyclone, 1
7...Duct, 18...Main exhaust fan, 1
9... Raw material quantitative feeder, 20, 21...
・Actuator, 22, 23...Valve, 2
4, 25...Flow rate controller, 26...Control system, 27...Oxygen concentration meter, 28...
...Damper, 29... Contraction mechanism, 30, 31
... Actuator, 35 ... High selector, 36 ... Arithmetic controller, 37... Low selector, 38... Arithmetic controller, 39 ...
...Arithmetic unit, 40...High limiter, 41.
...Low limiter, 42...Arithmetic unit, 4
3... Arithmetic unit, 44... Arithmetic unit, 45
......Calculator, 46...Oxygen concentration controller, 4 7--High limiter, 48...
Low limiter, 49... Arithmetic unit, 50...
...Arithmetic unit, 51...High selector, 52...
...Opening degree controller, 53... Temperature check circuit, 54... Opening degree check circuit, 55...
... Damper 56... Actuator.

Claims (1)

[Claims] 1. When controlling a cement sintering device in which a rotary kiln and a clinker cooler are successively combined with a calcination device that forms a composite ventilation system with a main exhaust fan, a suspension preheater, and the above-mentioned sanupunjung preheater, the rotary kiln feedstock Upper and lower limits are set for the temperature, and the above gas temperature is set using the total amount of fuel used, the fuel ratio of the calciner and rotary kiln, and the amount of raw material supplied as manipulated variables so that the gas temperature of the suspension preheater system falls within the upper and lower limits. At the same time, the upper and lower limits are set for the oxygen concentration in the rotary kiln exhaust gas, and the opening of the calcination device combustion air duct damper and the opening of the rotary kiln exhaust flue are set so that the oxygen concentration falls within the upper and lower limits. A method for controlling a seven-ment incinerator having a composite ventilation system, characterized in that the amount of combustion air is controlled using the opening of a flow contraction mechanism and the opening of a main exhaust fan artificial damper as manipulated variables.