SE1350282A1 - Method and apparatus for reducing variations in the sweep steam flow in a combustion boiler. - Google Patents

Abstract

The present invention relates to a system and a method for reducing variations in the flow of soot steam in a combustion boiler (8) with soot blowing systems comprising a plurality of steam operating soot blowers (1, 1), which are run in succession and control means for controlling the soot stalls. and the spraying of steam through them '(1, 1'), a central computer-controlled control system (71) being arranged to control the start (3,3 '') on the basis of individual programmed values (11, 13, 11 ', 13') for the the individual soot beehives, or groups of the same, in such a way that the steam consumption (100) is substantially kept at a predetermined level when changing from a soot blower (1), or group, to a next soot blower (1 '), respectively group.

Description

The steam flow to the soot blower is controlled by a steam valve, which in turn is usually controlled by a mechanical linkage, which mechanically opens the valve, when the position and direction mechanism of the soot blower has passed an opening mechanism. The point where the steam valve opens is mechanically determined by the position of the opening mechanism and the position of the position and direction mechanism.

The sootblower's cleaning principle is based on a cleaning cycle in which the sootblower's steam valve (14) and the sootblower's position and direction mechanism for the steam nozzles interact.

Collaboration normally takes place mechanically through a steam control mechanism.

On lance blowers, e.g. of type IK-525, the steam control mechanism is normally designed so that the steam valve is connected to the position and direction mechanism of the nozzles by the steam control mechanism opening the steam valve when the position and direction mechanism has passed a mechanical position at a mechanically determined distance from the rest position.

On rotary soot blowers only, eg Clyde Bergemann DSE, the steam control mechanism is normally designed so that the steam control mechanism is mechanically coupled to the position and direction mechanism performing all or parts of rotated revolutions of the steam nozzles.

A common way of achieving the steam control mechanism is to use a pin coupled to the steam valve, as well as an eccentric mechanically coupled to the rotation of the steam nozzles.

The design of the mechanics means that there is a certain delay between the rest position of the position and direction mechanism with closed steam fl fate and the rotational position where the valve opens, and a certain delay between the shutdown of the steam fl fate and after further rotation the arrival to the position and direction mechanism rest position.

Sootblowers are usually controlled by a control computer and electrical drives connected to the sootblower's motor drives and to one or more sensors on the sootblower. The sensors are usually limit position sensors, which are used for position indication for the position and directional mechanics of the sootblower. Usually there are limit position sensors for sleep mode and any end positions. Lance sootblowers and wall sootblowers are usually equipped with end limit position sensors, which are used to reverse the direction of operation of the position and direction mechanism of the sootblower 10 (15). Reversal of the operating direction usually takes place by phase reversing the current supply to the motor drives of the position and direction mechanism.

A soot blower is normally at rest for most of the time with off steam fl desolate. During sooting, the sootblower is started, which cleans the heating surfaces according to an established procedure called the sootblower's cleaning cycle. The cleaning cycle is mainly determined by the mechanical design of the sootblower, the position sensor of the sootblower, and the control of the sootblower. A sootblower's clean cleaning cycle normally takes place according to the following sequence.

The position and direction mechanism of the Sofa phase Sootblower is at rest and in a defined rest position. The steam control mechanism closes the steam med fate with the steam valve.

Limit position sensor on the soot blower signals sleep to the soot blower control.

Starting phase The position and direction mechanism of the sootblower is in operation. The steam control mechanism has not yet opened the steam valve. No steam flows through the sootblower.

Cleaning phase The valve mechanism of the steam control mechanism opens the steam valve and steam flows out of the nozzles of the sootblower.

The position and direction mechanism of the sootblower is in operation.

The stop phase steam control mechanism closes the steam valve.

The position and direction mechanism of the sootblower is in operation until the rest position is reached.

When the sootblower has reached its dormant position, the motor drives are stopped and the sootblower goes into dormant phase.

Both the start phase and the stop phase normally last 1-5 seconds, which means that the steam flow through the soot blower is switched off for 2-10 seconds of a soot blower's total operating time.

The time for the start phase and the stop phase is mainly determined by the mechanical design of the individual sootblower, the location of the limit position sensors and the speed of the sootblower's position and direction mechanism. The time of the starting phase and the stopping phase often varies between different soot blowers installed in the boiler depending on the type of soot blower used, and variations in the mechanical settings of the individual soot blowers. In addition, the soot blowers can be equipped with electric drives with controllable speed of the soot blower by changing the speeds of the drive motors of the soot blowers.

Usually several soot blowers are run in groups, e.g. to soot a superheater. The driving method is normally based on the principle that sootblowers are run directly one after the other based on an alternating procedure between sootblowers, so that when the working sootblower indicates that the position and direction mechanism has reached its rest position, the next sootblower starts, directly or with some delay.

The driving method means that pulsations are created in the common steam fl fate when changing soot blowers in operation, which creates unwanted stresses in the system and can lead to disturbances in other equipment connected to the steam system, e.g. lost efficiency in steam turbines. The pulsations are caused by the shut-off soot plume fl fate during the stop phase of the soot blower in operation, as well as the start phase of the next soot blower operation. The total time with off steam fl fate at a change is mainly the sum of the previous sootblower stop time and the next soot blower start time as well as a possible start delay between the soot blowers.

The time with off steam fl fate varies with shifts for different soot blowers, and depends on the stopping time of the previous soot blower and the start time of the next soot blower. Usually, the speed of the position and direction mechanism is also controllable by using a frequency converter, which means that stop time and start time can be changed without the need for mechanical interventions or changes.

An existing method of reducing the steam shocks is to equip the sootblowers with an extra position sensor that gives a physical signal at a certain position for the sootblower, before the sootblower's steam fl fate is turned off, where the sensor signal is used to give start order to the next sootblower. signal that creates a steam fl fate-synchronized change with the normally subsequent sootblower steam start time.

The disadvantages of the method are that it is laborious and expensive as it requires installation of extra sensors on the soot blower, and that the method does not take into account whether the next soot blower is of a different type, with a different steam start time, and that the method can not handle cases where soot blower speeds are changeable. 10 15 20 25 30 35 5 (14) Another existing method is to give a start order to the next sootblower a fixed time after the sootblower starts in the forward or reverse direction. The time is then adjusted so that the normally trailing soot blower is started with steam fl fate-synchronized change with the normally trailing soot blower's steam start time.

The disadvantages of the method are that it does not take into account whether the next sootblower is of a different type, with a different steam start time, and that the method cannot handle cases where the speeds of the sootblowers are changeable.

BRIEF SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for eliminating or at least substantially reducing pulsations in the common steam flow of soot steam when switching from a soot blower in a soot sequence to a subsequent one.

This object is achieved in a method of the kind specified in the first paragraph above by according to the invention a central computer-controlled control system, preferably software-controlled, is arranged to control start and / or stop based on individual programmed values for the individual soot blowers or groups thereof in such a manner. that the steam consumption is kept constant as far as possible when switching from one sootblower to the next. The object is also achieved in a device of the type specified in the second paragraph above in that according to the invention a central computer-controlled control system is arranged to control start and / or stop based on individual programmed values for the individual soot blowers or groups thereof in such a way that the steam consumption in as far as possible kept constant when switching from one sootblower to the next.

As a result, not only can the pulsations of soot vapor be avoided as far as possible, but also no laborious and expensive installation of extra sensors on the soot blowers is required. Furthermore, the method according to the invention takes into account whether the next sootblower is of a different type, with a different steam start time, and the method can handle cases where the speeds of the sootblowers are changeable.

Preferably, the control system is arranged to start supplying soot steam in a next soot blower or group of soot blowers synchronously with switching off the supply of soot steam in a immediately preceding soot blower or group of soot blowers. 10 15 20 25 30 35 6 (14) Usually the soot blowers operate with a starting phase between the start of a position and direction mechanism included in each soot blower and the start of the supply of soot steam and a stop phase between the shut-off of the supply of soot steam and the stop of the position and direction mechanism . It is then suitable that the control system is arranged to cause the starting phase in the next sootblower or group of sootblowers to at least partially overlap the stopping phase in the immediately preceding sootblower or group of sootblowers.

Furthermore, the start phase is followed in turn by a cleaning phase, the stop phase and a rest phase.

It is then appropriate that the values programmed into the control system include measured, calculated or estimated times for the beginning and end of the phases.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention will be described in more detail with reference to preferred embodiments and the accompanying drawings.

Fig. 1 shows a schematic view of an embodiment of a soot blower in accordance with the invention in a rest position, Fig. 2 shows the soot blower according to Fig. 1 at a later stage when the opening of the steam valve takes place, Fig. 3 shows the soot blower according to Fig. 1 an outermost , turning position, Fig. 4 shows an overview of a soot system consisting of fl your soot blowers connected to the same steam supply.

Fig. 5 is an illustration of the steam fate through a soot blower during the entire execution of the soot blower, Fig. 6 is an illustration of the common steam fate during an execution of your soot blowers in succession.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Fig. 1 shows a schematic embodiment of a sootblower arrangement in accordance with the invention, the sootblower lance 60 being in a rest position. The sootblower arrangement includes a frame 59, a movable carriage 54 and a motor 54 not supported by the frame. ) to surface the trolley (in a known manner) by means of a transmission 57.

The sootblower lance 60 is mounted to the carriage 54 to be movable in and out of the boiler 63, 70 and it is provided with at least one preferably two nozzles 64 for steam. The sootblower lance 60 encloses an internal steam tube 61 to which external feed steam is supplied via a steam line 50. An on / off valve 51 is arranged between the steam line 50 and the steam tube 61. Thus steam will be supplied to the steam tube 61 when the on / off valve 51 is in its open position.

A first opening device 56 is arranged at the frame 59 of the soot blower arrangement, which opening device 56 has the task of placing the on / off valve 51 in the open and closed position, respectively. For this purpose, a mechanical abutment element 55 is arranged at the carriage 54 which, on contact with an opening device 56, acts on a mechanical arm 53 to put the valve 51 in the open position, and to leave it in the open position. Alternatively, a first indicator element 55 can be used, which is sensed by an opening device 56 which then gives a signal to a central control unit 71, which in turn initiates a control device 53 (eg electrically) to open and close the valve 51. As shown in Fig. 1 the sensor device 55 is suitably arranged centrally at the carriage.

A first end position sensor 58 is located at the bottom near a rear end of the frame 59 of the soot blower and a second end position sensor 62 is arranged in the vicinity of the front end of the frame 59. The frame 59, which may also be referred to as a housing, extends to the boiler wall 63 Centrally arranged, in the extension of the ramp, there is a hole in the boiler wall 63 where the sootblower lance 60 can move freely in and out to reach the interior 70 of the boiler. The first end position sensor 58 is positioned in a first transverse plane 80 near the rear end of the frame and the second position sensor 62 is relatively close to the boiler wall 63. At the carriage 54 there is arranged a second indicator means 57 which triggers a signal when it comes to level with the first and second position sensor 58, 62, respectively, which signal is transmitted to the control unit 71. FIG. 1, as already mentioned, the soot blower 9 is in a rest position and the valve 51 is therefore closed, meaning that no steam is supplied to the steam tube 61. Figs. 2 shows that the control unit 71 has given a signal to the carriage 54 to move towards the boiler wall 63, and that it reached an activating position 81 where the opening member 56 is actuated by the stop element 55, causing the valve 51 to be set in its open position.

When the valve is in its open position, steam 65 will squirt out of the nozzles 64 inside the boiler 70.

Fig. 3 shows a turning position where the carriage 54 in the sootblower arrangement moves to a position 83 where the second indicator 57 is level with the second position sensor 62. The carriage 54 has then moved the entire distance 84 from that end position 50 and to the turning position 83. Fig. 4 shows diagrammatically and in summary a sootblower system with a number of sootblowers 1 connected to the same steam supply 7. Steam is supplied from a suitable source through a first line 74 to a reduction valve 75, where the pressure is reduced. to a level suitable for soot blowing. From the valve 75 the steam is led through a main line 7 to a number of normally suitably vertical branch lines, 71, 72, 73. In the example shown there are three branch lines, e.g. a first 71 for the superheater, a second 72 for the convection section and a third 73 for the economizer. A number of steam supply lines 50 are connected to the branch lines 71, 72, 73 for supplying steam to each of the sootblower arrangements 1. As shown in Fig. 3, it may be convenient for manually operable valves to be arranged between the on / off valve 51 and the branch line 73. 5. In the example shown, there are fifteen sootblowers in the section relating to the superheater, nine sootblowers in the convection section and eight sootblowers in the economizer section. It is realized that it can of course be varied within a wide range depending on wishes and needs. At the bottom of the branch lines 71, 72, 73, they are interconnected to a common outlet line 77, with an outlet valve 78.

The outlet valve 78 may suitably be controlled by a temperature controlled sensor unit 79, e.g. in the form of Standard Equipment.

Fig. 5 shows an illustration of the steam flow through a soot blower during the entire execution of the soot blower. The upper graph in Fig. 5 shows the entire active operating time of a soot blower 1 from start time 3 to stop time 6, while the lower graph illustrates the active steam med fate with start time 4 and stop time 5, presented along a timeline 10. It appears that there is a time 11 of delay from the start time of the sootblower 3 until the steam starts at the time of start of the steam 4. Correspondingly, it appears that there is a time period 13 from the time 5 when the steam stops spraying to the time 6 when the soot blower is at rest. The total time 7 for the execution of the sootblower is thus greater than the time 8 for steam supply. This delay leads to difficulties in controlling the total steam fl fate effectively.

Fig. 6 illustrates a common steam fl fate during an execution of three soot blowers A, B, C in sequential order. In the case shown, the soot blowers are controlled in the usual way with opening means 56, which entails a delay and thus time slots between start and steam activation.

Thanks to the invention, an even vapor distribution distribution 100 is obtained over time when using sequential control of soot blowers regardless of the activation procedure, i.e. for example when using activation according to the principle known above. This is obtained by using the central control unit 71 for timely start 3 of each of the soot blowers, based on the start-up lead time 11, 11 ", 11" of each soot blower, respectively, its shut-down lead time 13, 13 ”.

INDUSTRIAL APPLICATION Figure 6 shows schematically how three soot blowers 1, 1 °, 1 ”are controlled sequentially in order to obtain a steam de fate 100 over time which becomes as even as possible. At a first time 3 according to the figure, the central control unit 71 will start the first soot blower 1, whereby its carriage 54 begins to move towards the boiler wall 63, (see above). Thus, after some movement of the carriage 54, the opening device 56 will be activated by the stop element 55, steam activation taking place, i.e. after a certain, known start-up lead time 11, and some known a shut-down lead time 13. Thus, it is known to the control unit 71 that the steam fl fate will begin at a certain predetermined time 4, which is after the start time 3 with the start-up lead time 11. For the central control system 71 it is also known that the next soot blower 1 "to be started has a certain own start-up lead time 11" and a certain own shut-off lead time 13 ". With the help of knowledge of the lead times 11 ", 13" which are present at the sequential start-up of the next sootblower 1 "after the final sootblowing of the first sootblower 1, a change can be made where the steam consumption change 48 at the change can be optimized to be basically zero.

This is done by the central control system 71 being aware that the steam fl fate 8 through the first soot blower 1 will cease at a certain given time 5. Based on this time 5 known to the control system 71, the control system can select a start time 3 "for the next the sootblower 1 "having a lead time 11" which exactly matches the time 5 for shutting off the steam fl fate by the first sootblower 1. In other words, the central control unit 71 regulates the system in such a way that the time 5 when the steam fl fate by the first sootblower 1 ceases coincides with the time 4 "for starting steam fl destiny through the second sootblower 1". In the same way, the central control unit 71 controls the changeover between the second soot blower 1 "and the third soot blower 1", i.e. so that the time 5 ° for the cessation of steam igenom fate through the second soot blower 1 ”coincides with the time 4” for the start of steam fl fate through the third soot blower 1 ”.

As can be seen from Figure 6, this principle according to the invention offers the possibility of achieving an even steam fl fate 100, without significant pressure spikes in the steam system, regardless of how much lead time 11, 13 is present in each of the soot blowers 1, since the starting time 3 for each subsequent soot blower 1 is adapted so its start lead time 11 is adapted to the stop lead time of the previous soot blower. Due to the fact that the system is centrally controlled, and thus controls all steam blowers included in a sequence, and that the total steam flow 100 (10) is preferably repeatedly sensed, preferably continuously, a simple and efficient manner can be continuously achieved. adaptation so that the steam fl fate 100 is kept in principle completely even, even when changing lead times 11, 13 by individual soot blowers 1. The principle of such a recurring, preferably continuous, adaptation can e.g. based on the system 71 reading / sensing any fl fate and / or pressure variation 48, 49 at the time of switching between two soot blowers.

As an example, reference may be made to the changeover between the first sootblower 1 and the second sootblower 1 ”in Figure 6, where the system 71 has experienced a smaller increase in pressure 48. This smaller increase in pressure is an expression that some reversal has occurred in the changeover between the first 1 and the other 1 ”sootblower. An example of a reason why such a pressure variation can take place may be that wear in the control system of the first soot blower has caused its shut-off lead time 13 to increase slightly. The control system 71 can, on the basis of the measured ök destiny search, by means of a suitable adaptation algorithm in software (eg including iterative looping), have the (known) lead time 13 adjusted to a higher value until a change is again made without flow change. According to the same principle, with inverse adjustment, equalization is achieved when reading the fl reduction of fate 49.

Thanks to the invention, there is thus no need to make costly and complicated adjustments of control components in the individual control systems of the soot blisters 1, but instead the control is handled entirely centrally via the central control system 71, which thus also makes it possible to use software to automate a recurring / continuous control of the sequential control so that in principle a constant, even steam flow is achieved.

The invention is not limited by the above described but can be varied within the scope of the appended claims. Thus, it is understood, for example, that the person skilled in the art based on what has been described above that the principles according to the invention are also applicable when the steam flow is switched off or started, as shown in Figures 5 and 6. The person skilled in the art knows that in some cases, depending on valve and valve actuators, there may be a more gradual start-up resp. shutdown of steam fl fate. The person skilled in the art realizes that in such circumstances it means that there should be some reversal in order to obtain even steam fl fate 100 at the shifts. On the other hand, it should be noted that the invention, thanks to adaptive control based on steam output 100, can effectively allow adjustment to be accomplished by the control system 71 regardless of the cause of a pressure nail (output reduction), or pressure reduction (output output).

Furthermore, it is understood that the principles according to the invention can be used even when the pressure in the steam system is measured, instead of steam fl fate, since the pressure is dependent on fl fate, ie 11 (14) pressure changes can also be used to control according to the invention. It is thereby realized that instead of controlling the system so that even steam fl fate is obtained, it can also be controlled from the outside to maintain an even pressure in the steam system, which may. may mean that the steam fl fate may vary over time if different soot blowers have different pressure drops. Furthermore, it is understood that a combination of pressure and fl fate can also be used for the control.

Claims (1)

1. 0 15 20 25 30 35 12 (14) PATENT REQUIREMENTS A method for reducing variations in the fate of soot steam in an incinerator (8) with a soot blowing system comprising a number of steam operating soot blowers (1, 1), which are run in succession and control means for controlling the soot blowers and the spraying of steam through dem '(1, 1'), characterized in that a central computer-controlled control system (71) is arranged to control start (3, 3 '°) based on individual programmed values (11, 13, 11 °, 13 °) for the the individual sootblowers, or groups of them, in such a way that the steam consumption (100) is substantially kept at a predetermined level when switching from a sootblower (1), or group, to a next sootblower (1 ”), respectively group. Method according to claim 1, characterized in that the control system (71) is arranged to start (4) supply of soot steam in a next soot blower (1 °), or group of soot blowers, substantially synchronously with shut-off (5) of supply of soot steam in a immediately preceding sootblower (1), or group of sootblowers. A method according to claim 2, wherein the soot blowers (1, 1 °) operate with a starting phase (11, 11 ") between starting (3, 3 °) of a position and direction mechanism included in each soot blower and starting (4, 4 °) of the supply of soot steam and a stop phase (13, 13 °) between the shut-off of the supply of soot steam and the stop of the position and direction mechanism, characterized in that the control system (71) is arranged to bring the start phase (1 1 ”) into the next soot blower or the group of sootblowers to at least partially overlap the stop phase (13) in the immediately preceding sootblower or the group of sootblowers. Method according to claim 3, wherein the start phase is followed in turn by a cleaning phase, the stop phase and a rest phase, characterized in that times for the phases beginning (11, 11 ") and end (13, 13 °) are measured, calculated and / or estimated. , after which the values obtained are programmed into the control system (71). Device for reducing variations in the fate of soot steam in a combustion boiler (8) with a soot blowing system comprising a number of steam-operating soot blowers (1, 1 °), which are run in succession and control means (71) for controlling the soot blowers and the spraying of steam through them, characterized in that a central computer-controlled control system (71) is arranged to control start (3, 3 "), and / or stop, based on individual programmed values for the individual soot blowers (1, 1"), or groups of the same, in such a way that the steam consumption (100), and / or the vapor pressure, are substantially kept substantially at a predetermined level, when switching from a soot blower (1), or group, to a next soot blower ( 1 ”), respectively group. Device according to claim 5, characterized in that the control system is arranged to start supply of soot steam in a next soot blower or group of soot blowers synchronously with shut-off of supply of soot steam in a immediately preceding soot blower or group of soot blowers. Device according to claim 6, in which the soot blowers operate with a starting phase between the start of a position and direction mechanism included in each soot blower and the start of the supply of sooting steam and a stop phase between the shut-off of the supply of sooting steam and the stop of the position and direction mechanism. that the control system is arranged to cause the starting phase in the next sootblower or group of sootblowers to at least partially overlap the stopping phase in the immediately preceding sootblower or group of sootblowers. Device according to claim 7, in which the start phase is followed in turn by a cleaning phase, the stop phase and a rest phase, characterized in that the values programmed into the control system include measured, calculated or estimated times for the beginning and end of the phases.