JPH0319479B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling a cleaning nozzle for removing dust or the like adhering to a heat storage body of a rotary heat exchanger by injecting water vapor or high-pressure air to the dust or the like.

A rotary heat exchanger is normally used as a component of a process. For example, a heat storage body consisting of layers formed by processing a metal ribbon into a corrugated shape and accumulated in a disk shape is supported by a casing, and one semicircular side is heated to a high temperature. duct and the other to the cold duct. That is, as shown in FIGS. 1 and 2, the rotary heat exchanger includes a rotating heat storage body 2 that is mounted on a shaft of a casing 1. Sensible heat is supplied to the heat storage body 2 to raise the temperature, and then the stored heat storage body 2 is rotated by the rotary drive device 5 and enters the low temperature side duct 4, and heat exchange is performed by dissipating heat to the low temperature fluid. I'm going.
As the above-mentioned high-temperature fluid is often exhaust gas from a normal process, dust, mist, etc. in the gas adhere to the surface of the heat storage element 2, resulting in an increase in pressure loss, a decrease in heat transfer performance, and heat storage. Disturbances such as body corrosion occur. A fixed cleaner or a reciprocating cleaner is usually installed for the purpose of removing deposits from the heat storage body. However, fixed cleaners require a large number of nozzles to be installed in parallel along the radius of the high-temperature side heat storage element to inject a cleaning medium such as steam or air, which requires large amounts of medium and large equipment. There are problems such as a decrease in heat recovery efficiency due to a decrease in gas temperature due to

As a reciprocating cleaner, as shown in FIGS. 1 and 2, an injection pipe 8 is provided with a nozzle 7 at the tip of the area excluding the central axis of the circular rotating heat storage body 2.
is swung by a drive device 6 provided on the upper part of the body on the high temperature side, and a cleaning medium is injected onto the heat storage body 2 from a nozzle 7 to perform cleaning. By rotating the heat storage body 2 and at the same time periodically reciprocating the nozzle, the nozzle 7 scans the entire surface of the heat storage body 2, thereby cleaning the entire surface.

However, when cleaning is actually performed using such an apparatus, some parts may not be cleaned. This is a case where the reciprocating movement of the nozzle and the rotation of the heat storage body are synchronized such that the scanning locus of the nozzle 7 repeats in a pattern that does not cover the entire surface of the heat storage body 2.

A detailed analysis of this point is as follows. In FIG. 3, if the outer circumferential circle of the heat storage body 2 is Q ₁ , the circle of the central axis part is Q ₂ , the center O, one point of the outer circumferential circle Q ₁ is A, and the intersection of OA and circle Q ₂ is B, the nozzle 7 is It moves back and forth between AB. Although the movement of the nozzle 7 is actually a part of the circumference centered on the root of the injection pipe 8 as shown in FIG. 1, it can be regarded as approximately linear within the range AB. Then, as shown in Figure 4, a straight line
A straight line when point D on the circumference of a circle centered on midpoint C of AB and passing through points A and B rotates on the circumference at a constant speed.
The movement of the intersection point E of the perpendicular line drawn down to AB with the straight line AB is the movement of the nozzle 7. For example, if the rotation speed of the heat storage body 2 is 4.1 times/min, the number of reciprocations of the nozzle is 1.8 times/min, the diameter of the heat storage body D (=) = 2500 mm, and the diameter of the central shaft part α (= DB) = 650 mm, the nozzle The trajectory S drawn by point E in one reciprocating motion is as shown in Figure 3.
The starting point is A′, and the ending point is A′.

The trajectory drawn here becomes the reference, and after this the end point
The same trajectory is drawn with A' as the starting point, and the point that became the ending point also becomes the starting point. After repeating this, synchronization will be achieved when the trajectory starts from A again. Here, if the angle between the starting point A and the ending point A' is α°, the trajectory will be repeated at a natural number multiple of this angle,
When the natural number multiple of α° matches the natural number multiple of 360°, synchronization begins at the least common multiple of these two. Here, when calculating the trajectory under the above conditions, the time required for the trajectory from the start point A to the end point A' is the same as the nozzle moving once in the section, so the time for one revolution is 1/18 = 5/9 minutes. The rotation of the rotor during this period is 4.1×5/9=41/18 rotations.

In other words, if we consider A as a reference, we have made 2 rotations and 5/18 rotations, and this 5/18 rotation represents an angle α°, α/360 = 5/18 α = 360 × 5/18 = 100° Angle 100 The least common multiple of degrees and 360 degrees is 100 degrees × 18 = 1800 degrees 360 degrees × 5 = 1800 degrees The least common multiple is 1800, and when the nozzle moves back and forth 18 times, that is, after 18/1.8 = 10 minutes, point A becomes the starting point again and synchronization occurs. After that, the same trajectory will be scanned repeatedly.

FIG. 5 is a computer-drawn diagram of the locus of the nozzle scanning the heat storage element during continuous operation for 2000 seconds (33 minutes 20 seconds) under the above conditions. As is clear from this figure, the scanning pattern is repeated and the entire surface of the heat storage body is not covered. As a result, there are areas where the nozzle does not spray and cleaning is not performed, and deposits accumulate and cause problems such as clogging.

Next, consider how many times the nozzles must be synchronized to reciprocate to avoid areas that cannot be cleaned.

Assuming that the range that can be effectively cleaned by spraying from the nozzle is 10 mm and the thickness of one layer of corrugated material forming the heat storage body is 2 mm, it is desirable that the scanning interval be 6 mm or less.

Considering the above conditions, the length of AB is = (2500-650)/2 = 925mm The rotor rotation speed during one rotation of the nozzle on the rotor surface is 41/18 rotations, and the trajectory is from the point where it moves while intersecting. When the entire surface is scanned, each surface has been passed twice, so the number of nozzle reciprocations required to scan the entire rotor surface is 925 x 2/6 x 4/18 ≒ 135 times, and the time is 135/1.8 = 75 minutes In other words, in the case of the above-mentioned equipment, it is necessary to control the nozzle so that it does not synchronize during the 135 rotations, which is 75 minutes.

Note that if a pattern is drawn in which the scanning lines are too close together, there will still be areas that cannot be cleaned even if they are not synchronized during this period.

It is difficult to detect whether such synchronization is occurring while the heat exchanger is in operation, and if strong build-up occurs in some areas, the operation must be stopped for a long time to remove it.

In order to solve the above-mentioned problems, the present invention has discovered a method of preventing synchronization by temporarily stopping the reciprocating movement of the cleaning nozzle and cleaning uniformly. That is, in order to break the synchronization, the starting point can be shifted so that it does not start from the same point A in FIG. 3, and the starting point can be shifted by temporarily stopping the reciprocating motion of the nozzle. The cycle of stopping the reciprocating motion may be less than the maximum time required for synchronization, and in the case of the above-mentioned conditions, it is sufficient to shift the nozzle reciprocating motion 18 times within 10 minutes.

For example, when calculating the case where the nozzle rotation is stopped for 0.8 seconds once every 10 minutes to avoid synchronization, the angle at which the starting point shifts during the stop time is 360 x 4.1 x 0.8/60 = 19.68° The angle at which the starting point shifts is 100 x 19.68=119.68° The least common multiple of 360 and 119.68 is 119.68×9000=1077120 360×2992=1077120 In other words, the nozzle will clog until it reciprocates 9000 times.
It will not synchronize for 5000 minutes. If synchronization is not performed for a long time in this way, the entire surface of the heat storage body will be reliably scanned until synchronization is achieved. Calculatedly, in the above example, the nozzle stop time was set at the end of one cycle, but in reality, the stop time would be set in the middle of the cycle, and if some fluctuations in the stop time are considered, synchronization is possible. becomes almost unthinkable.

FIG. 6 shows an example of a circuit for temporarily stopping the reciprocating movement of the nozzle in this manner.

In the circuit diagram of Figure 6, the main switch of all circuits is
S ₁ and sub-switch of heat storage body drive motor M ₁ S ₂ and sub-switch of cleaning device drive motor M ₂
When _S3 is closed and the push button switch _PB1 is closed, the electromagnetic switch _MS1 of _M1 : the holding switch MS1X and the electromagnetic switch _M'S2 of _M2 are closed, and the operation of the heat storage body and cleaning device is started. time switch at the same time
When T ₁ starts and after a predetermined time t ₁ closes, relay R ₁
and time switch _T2 operates, switch _R1 opens, _MS2 opens, and motor _M2 stops. When t ₂ closes after a predetermined time of T ₂ , T ₁ starts again, t ₁ opens, r ₁ and MS ₂ close, and motor M ₂ starts operating, and this operation is repeated thereafter. Also, TR ₁ and TR ₂ are thermal relays for protection of M ₁ and M ₂ , which operate only in the event of an overload to stop the motor.

FIG. 7 shows an example in which the reciprocating motion of the nozzle is stopped for 0.8 seconds every 120 seconds, and FIG. 8 shows a scanning pattern for an example in which the reciprocating motion of the nozzle is similarly stopped for 1.2 seconds every 120 seconds up to 2000 seconds of operation.

In the case of FIG. 7, since the rotation of the nozzle is temporarily stopped, the locus will shift sequentially at point M, and will not be synchronized, and if the operation continues beyond 2000 seconds, the entire area will be filled with scanning lines. In the case of the example shown in FIG. 8, the effect is even more remarkable, and in both cases, the entire surface of the heat storage body can be scanned and cleaned.

Note that the same effect can be obtained by varying the number of rotations (reciprocating) of the heat storage body or the cleaning nozzle and changing the relative speed of the two.
Changing the rotational speed of the heat storage body not only increases equipment costs, but also has the problem that heat exchange is not performed uniformly if the rotational speed is drastically changed. It is also possible to make the swing speed of the nozzle variable using a variable speed motor, an electromagnetic clutch, etc., but this poses a problem of complicating the equipment and increasing costs.
The present invention achieves the object using a relatively simple method, and therefore has extremely great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a front view of the rotary heat exchanger. Second
The figure is a side view showing a partial cross section of the rotary heat exchanger. FIG. 3 is a diagram illustrating a nozzle scanning pattern. FIG. 4 is a diagram illustrating the reciprocating movement of the nozzle. FIG. 5 is a diagram showing the trajectory of a synchronized pattern of nozzle scanning. FIG. 6 is a diagram showing an example of a circuit that controls the reciprocating movement of the nozzle. FIGS. 7 and 8 are diagrams showing trajectories of patterns in which nozzle scanning is not synchronized. Explanation of symbols, 1...Casing, 2...Heat storage body, 3...High temperature duct, 4...Low temperature side duct, 5
... Rotation drive device, 7 ... Nozzle, 8 ... Injection pipe.

Claims (1)

[Scope of Claims] 1. A cleaning nozzle for a rotating heat storage body that sprays fluid and blows off deposits by reciprocating the nozzle at a constant cycle so as to fold back the center and periphery of the rotating heat storage body that rotates at a constant speed. In the control method,
By temporarily stopping the periodic reciprocating motion of the nozzle, the period is exceeded and the rotational motion of the rotating heat storage body and the reciprocating motion of the nozzle are prevented from synchronizing in a short period. A method of controlling a cleaning nozzle, characterized in that the entire surface of the cleaning nozzle can be reliably scanned. 2. In a nozzle control method for cleaning a rotating heat storage body, the nozzle is reciprocated at a constant cycle so as to turn around the center and periphery of the rotating heat storage body rotating at a constant speed to spray fluid and blow off deposits.
By temporarily changing the speed of the periodic reciprocating motion of the nozzle, the period is increased and the rotational motion of the rotary heat storage body and the reciprocating motion of the nozzle are prevented from synchronizing in a short period, thereby causing the nozzle to rotate. A method for controlling a cleaning nozzle, characterized in that the entire surface of a heat storage body can be reliably scanned.