FI117451B - Fluidised bed condition monitoring method - Google Patents

Description

117451 "CONSTRUCTION MANAGEMENT METHOD FOR FLOATING LAYER

The invention relates to a method for monitoring the condition of a fluidized bed boiler according to the preamble of claim 1.

The invention also relates to a fluid bed boiler fluid bed condition monitoring system according to the preamble of claim 6 and to a fluid bed boiler using a condition monitoring system according to the preamble of claim 11.

10 Fluidized bed combustion and gasification techniques are based on the use of sand or similar material as fluidizing medium. The purpose of the fluidizing material is to dry, pyrolyse, ignite solid fuel, and to aid in the "evacuation" of the coarse material from the fluidized bed. Fluidized bed material is an essential part of a fluidized bed boiler and has a significant effect on the operation of the 15 boilers.

The grain size of the pure and / or unused fluidized bed material is typically in the range of 0.5-1.2 mm in sandwich applications and typically in the range of 0.1-0.6 mm in circulating fluidized bed applications. In the fluidized bed material, the body 20 twists and forms during the combustion a so-called. coarse material, i.e. large solid particles such as rocks, metals and: y; sintered songs. Typically, coarse material is classified as coarse material with grain size greater than 1.5 mm and circulating fluidized bed. . * Material exceeding 0.8 mm in applications. In part, the occurrence of these particles is affected by the unevenness of the combustion process in the fluidized bed: and by the impurities in the fuel. Then you can, for example. lumps of sand formed at the hot spots of the fluidized bed. One of the basic prerequisites for the smooth operation of a fluidized bed boiler is that the particle size of the fluidized bed material remains within the desired range. If the particle size of the fluidized bed material 30 becomes too large, i.e. the amount of coarse material, * ·: * ', the fluidization properties of the fluidized bed material diminish, resulting in: [**] interference with the combustion process and, at worst, stopping the boiler. ? • · *. Due to the smooth operation of the fluidized bed boiler, coarse material must be removed from the fluidized bed material t ···: 35, and typically this is accomplished gradually during the combustion process. The rough removal may be performed in advance 2 1 17451; at regular intervals, whereby a certain proportion of the fluidized bed material is removed regardless of the actual amount of coarse material in the fluidized bed material. As a rule, this results in wastage due to excessive consumption of the Lei fluidised bed material, since it is safer to change too much than too little fluidized bed material.

To reduce the "unnecessary" loss of fluidized bed material, various methods have been developed to determine the amount of coarse material. The basic idea is to sample and analyze the fluidized bed material. Based on the result, the coarse amount is known and if the concentration of fluidized bed material is exceeded. One problem with this sampling method is its slowness and laboriousness, particularly when it comes to continuously monitoring the condition of the fluidized-15 bed material.

The main object of the present invention is to provide a method for monitoring the fluidized bed of a fluidized bed boiler which provides continuous condition monitoring information on the state of the fluidized bed.

20 i · * ·.: To accomplish this purpose, a condition monitoring system according to the invention; the drawing method is essentially characterized by what is disclosed in the characterizing part of independent claim 1. The condition monitoring system of the invention according to the invention is essentially characterized by what is disclosed in the characterizing part of independent claim 6.

The fluidized bed boiler of the invention, in turn, is essentially characterized by what is disclosed in the characterizing part of independent claim 11. In other dependent claims, f are preferred embodiments of the invention. , 30 • ♦ * ·: ** One of the main ideas of the invention is to monitor the temperature of the fluidized bed from at least two levels, and to provide information about the condition of the fluidized bed as a function of the temperature variation of these levels.

The invention is based on the simultaneous monitoring of fluidised bed temperatures at different points in the fluidized bed, since different areas of the fluidized bed have been observed; 3 117451 exhibits measurable temperature changes as the coarse material content of the fluidized bed material changes. The temperature of the fluidized bed has been observed to decrease as the amount of coarse material increases. It has also been found that the temperature of the lower part of the fluidized bed first decreases and the temperatures of the upper parts begin to decrease later. With typical boilers, the time difference between lower and upper temperatures starts several hours to days. Indeed, the increase of coarse material in the fluidized bed material can be detected by measuring the temperature of the fluidized bed and in one embodiment of the invention the temperature is measured at the bottom and top of the fluidized bed and comparing these temperatures with the increase in coarse material.

In one embodiment, the upper temperature of the fluidized bed is measured from the upper portion of the fluidized bed 15, e.g., at a height of 300 to 350 mm from the fluidizing nozzles. The lower temperature, in turn, is measured in one embodiment at a height of 30-50 mm from the fluidizing nozzles. The highest temperature measurement level should be located at the top of the fluidized bed and the lowest temperature measurement level should be located as low as possible in the 20 fluidization zone. A sufficient difference is then achieved between the lower level and the upper level (s). Lowest measurement level * *? however, as a rule, shall be located above the nozzles. The placement of the lowest temperature measurement is affected by e.g. air from the nozzles,, *. *, which, when cool, distorts the result of a measuring element placed too close. This would also easily measure the temperature of the fluidized air rather than the temperature of the fluidized bed • · · * V material. Because temperatures are measured inside the boiler for a variety of purposes, such as determining combustion lock conditions, calculating fluid bed thickness, and controlling bed temperature, in some embodiments, it is preferable to select a temperature measurement level that can be used for both condition monitoring and other purposes. .

• * «• · • ·

However, since it is possible that the difference between the lower and upper temperatures will increase. for reasons other than the propagation of coarse material, some embodiments of the invention have shown some ways to reduce the susceptibility to ·: ··· interference. One way is to measure temperatures as much as possible; 4 117451 at the point of the fluidized bed and compare these values with each other. In practice, temperatures are measured from the inside of the boiler for a number of purposes, such as the above-mentioned determination of the combustion locking conditions, the calculation of the fluidized bed thickness and the control of the bed temperature. Some of these measurements are made at altitudes such that they do not necessarily give the best value for measurements at only two altitudes. By using this temperature data, which is primarily intended for other purposes, as additional information for condition monitoring, the reliability of the condition monitoring according to the invention can be very simply improved.

In another embodiment of the invention, the above-described detection of the amount of coarse material based on temperature measurement and additionally the detection of the content of coarse material based on sampling. For example, a fluidized bed material can be sampled when a temperature measurement indicates that the amount of coarse material has increased above a given threshold. The fluidized bed material can be sampled in many different ways and sample analysis can also be performed in a number of different ways. One way is to take the sample through the door in the bottom of the boiler, after which the sample is cooled. The sample can then be passed through a suitable sieve, leaving coarse material in the sieve. Replacement of fluidised bed material * · ** '. can be turned on, if necessary, based on the result of the heat measurement and / or screening.

: 25 1 * 4 ·

Typically, fluidised bed material exchange is controlled manually; * ··. by the operating staff, but it is also possible to perform the material exchange automatically. In this case, the material exchange is performed sil -...; I created when the measurement value obtained from the heat measurement result and / or the screening result • l ·: 30 exceeds the limit value.

* ♦ * · ···. · * ·. The condition monitoring according to the invention provides continuously * 9 information on the state of the fluidized bed. In addition, by measuring the different temperatures of the fluidized bed, a prediction of the rate of growth of the coarse material · 35 content of the fluidized bed can be made, so that the required operating procedures can be better predicted and known than known solutions.

In one embodiment of the invention, a measurement information is provided to the graphical user interface to facilitate decision-making by the operating personnel. This makes it easier for operating personnel to detect changes in the boiler and to anticipate potential disturbances.

The invention will now be described in more detail with reference to the accompanying principal drawings, in which Figure 1 illustrates an embodiment of a fluidized bed boiler condition monitoring system, 15 '_ "Figure 2 shows an embodiment of a condition control system, and' Figure 3 shows dimensions of a fluidized bed boiler condition monitoring system.

• · ♦ · · • · «t« • * ·

For the sake of clarity, only the details necessary for an understanding of the invention are given in the drawings. Unnecessary to the understanding of the invention, structures and details unnecessary to those skilled in the art will be omitted from the drawings in order to emphasize the features of the invention. . ·.

• · ·

Figure 1 shows, in principle, the lower part of a fluidized bed boiler in which the fluidized bed 6 **: ** subject to the condition monitoring according to the invention is located. The picture has omitted e.g. structures related to the supply of fuel and combustion air, as well as ducts and structures related to the exhaust •; Figure 1 shows the fluidizing air nozzles 4 and ·. the lower temperature measuring level L1 and the upper temperature measuring level L2 disposed in accordance with the invention. The fluidizing air nozzles 4 and the measuring points 1, 2 forming the temperature measuring plane L1, L2 may be more than 6, 117451, but for the sake of clarity of the picture, there is only one measuring point for each measuring plane. ;;

The function of the fluidizing nozzles 4 is to fluidize with a fluidized bed material 5 which, when fluidized, forms fluidized bed 6. In the example, the temperature measuring levels L1, L2 are arranged such that the upper level L2 is located at the top of the fluidized bed 6, whereby the measurement results in the temperature of the top of the fluidized bed. In a conventional boiler, where the top temperature is measured at a height of about 300 mm, the temperature at that point is typically from 10,750 to 930 ° C with optimal combustion.

An attempt should be made to place the low temperature level L1 as low as possible in the fluidized bed 6. This provides a sufficient difference between the lower temperature level L1 and the upper temperature level L2 (as well as the 15 levels that may be shown later).

However, the lowest temperature measurement level L1 must be the general rule!

just above the nozzles 4. The placement of the lowest temperature measurement is influenced by e.g. air from the nozzles 4 which, when cool, distorts the result of the measuring element 1 placed too close. A measuring element 1 placed too close to the nozzle 20 4 would measure mainly the temperature of the fluidizing air and not the temperature of the lower part of the fluidized bed 6. Typically, the lower temperature measurement backing plane L1 is preferably positioned at a height of 15-50 mm (preferably 20-50 mm) from the upper surface of the nozzle 4. In this case, in a conventional boiler, the temperature at that point is typically 700-890 ° C, when: 25 combustion is optimal and the fluidized bed material does not contain * coarse material to disturb the combustion process.

* · · • «··. * ··· • · -j

Figure 2 shows an embodiment different from the embodiment of Figure 1, e.g. in that it comprises a third temperature measurement plane 30 L3 disposed between the lower L1 and the upper L2. This * ··· ** third temperature measurement level L3 can often be combined with another boiler temperature measurement, since in practice the temperature inside the boiler is measured for a variety of purposes, such as • ·. Therefore, for determining the locking conditions for the combustion, for calculating the thickness 35 of the fluidized bed 6 and for adjusting the bed temperature. Some of these measurements *: ··· are performed at an altitude stabilized or at an altitude of 7 1 17451 such that the result obtained from that altitude may not give the best value for measurements at only two altitudes. By using this temperature data, which is primarily intended for other purposes, as additional information for condition monitoring, the reliability of condition monitoring according to the invention can be very simply improved. For example, in a conventional boiler, where the temperature is measured at a height of about 100 mm, the temperature at that point 3 is typically 740 to 930 ° C when combustion is optimal (i.e., the temperature is closer to upper 10 than lower temperature). These additional temperature measurement levels may also be several and may be located differently than shown in the example.

Figures 1 and 2 show, for the sake of clarity, one measuring point 1,2,3 at the temperature measurement level L1, L2, L3 of the cap 15. Especially in larger boilers it is sometimes useful to use more than one measuring point 1,2,3 at a single temperature measurement level L1, L2, L3. This allows a more accurate measurement of the temperatures of the various locations of the fluidized bed 6, while at the same time better detecting the local decrease in heat transfer 20 caused by the coarse material. The type and position of the measuring members 1,2,3 may vary, and: Figures 1 and 2 only show in principle the positioning of the measuring members on a kind of arms. In one embodiment, a single arm or similar suspension member may also be used to accommodate one or more measuring members 1,2,3. It is also possible to use the measuring element 1,2,3 for other purposes. At the same time ~: * · *: 1 • ♦ of several measuring points on the temperature measuring plane L1, L2, L3. ···. 1,2,3 measurement data can be used in different applications depending on the application. For example, when generating control data or information aggregation ..., the value of some measurement point can be weighted.

• · ·:. · 30 ···

In the examples shown in Figures 1 and 2, the measurement of the temperature is · · · ··. cartilage, in addition to coarse material recognition, the ability to • • determine the amount of coarse material based on sampling. Thus, for example, fluidized bed material f "· \ · 35 can be sampled whenever needed, such as when a temperature measurement indicates that the amount of coarse material has increased beyond a predetermined limit. The sample can be sampled in many different ways and sample analysis can also be performed. One way is to take a sample through the door 5 or other suitable structure in the bottom of the boiler Because the fluidized bed material is very hot, the sample is typically cooled before analysis. For example, the sample may be passed through a suitable sieve to evaluate the coarse material. by measuring the proportion of coarse material in the sample taken, for example by weighing, it is possible to refine the estimate of the proportion of coarse material) obtained through temperature measurement. sufficiently reliable from the point of view of congratulation, in particular where a register of measurement results is available, by comparing the measured values with the result, a prediction can be made.

Figure 3 shows the values of temperatures T from the measurement levels of the condition monitoring arrangement according to one embodiment, with respect to time t. The condition monitoring system of the example comprises three measurement levels L1, L2, L3, each of which provides its own value curve T1, T2, T3. The value curve T2 of the highest temperature measurement level L2 is also at the top of the figure and the value curve T1 of the lowest temperature measurement level L1 is: the lowest. Between them is the value curve T3 of the third temperature measurement plane L3, and in this example the third temperature measurement plane * \ is located at a height of 100 mm. In addition, the figure shows a curve K, * * · · * 'representing the relative proportion of coarse material to the fluidized bed material.

* · · * »· * · •»: ***; In Figure 3, all three value curves T1, T2, T3 start in essentially the same direction, that is, the temperature T varies at different points in the boiler ... # under normal operation and at approximately the same level · * .. · '30 different fluidized beds 6 sections. The increase in coarse material in the fluidized bed * 6 produces a noticeable temperature change (in the figure. '. · * · * "· From t1 onwards), since the accumulation of coarse material weakens the heat transfer locally. , as the coarse material tends to be located .. 'S 35 at the bottom of the fluidized bed As shown in Figure 3, the temperature curve T1 of the lowest temperature measurement level L1 starts to drop at t1 and 117451 9.> l The temperature curves T2 of the higher temperature levels at substantially previous levels. '·' ^ V · |

The increase in coarse material expands the heat drop range upwardly in the fluidized bed 6 of the bogie bogies. In Figure 3, at the time t2, the coarse material has caused the temperature of the upper part of the fluidized bed 6 to decrease, as a result of which the temperature curves T2, T3 of the upper temperature measuring levels L2, L3 start to decrease quite sharply. In this case, the fluidized bed material must be replaced almost immediately if the boiler is to be kept on. Unless the fluidized bed material is replaced, its fluidization properties will be impaired to such an extent that the process cannot be continued.

As shown in Figure 3, there is a clear time difference between the lowest temperature measurement level L1 at the indi-15 detection time t1 and the highest temperature measurement level L2 at the detection time t2, which for conventional boilers has several hours up to several days. This time difference is dependent e.g. boiler size and fuel used, and the time difference can be determined with sufficient precision for each application.

20 ...: According to the invention, by monitoring the change in the lowest temperature measurement level L1 / temperature T1, it is possible to monitor the increase in coarse material from the bucket before the amount of coarse material causes problems in the incineration process, so it may not be practical to wait t2, where the fluidized bed material exchange should be performed · * · *: almost immediately. Because the temperature varies even under normal use «Λ. ···. slightly, it is practically useful to compare the temperature of the lowest temperature measurement level * · L1 with at least one, preferably more, temperature T2, T3 of the upper temperature measurement level L2, L3. In this case, the change in the difference between the temperature T1 of the lowest temperature: V 30 space measuring level L1 and the other temperature measuring levels L2, L3 is measured roughly. ···. material reproduction.

· ♦ *. .. ··?

Since the temperature T1 of the lower part of the fluidized bed 6 drops significantly before the combustion process is substantially disturbed, the necessary maintenance operations can be planned and initiated in good time. Form 10 ;; ; 117451 'tl By recording the measurement results and, if necessary, supplementing the sampling data with information available, it is possible to form a highly reliable prediction method for boiler condition monitoring. The information in the register need not necessarily be that obtained from the particular power plant 5, but the data otherwise produced for that power plant may also be used as the data in the register.

The condition monitoring system can also be used to automatically control the boiler. Thus, for example, when the amount of coarse material 10 according to the measurement results increases above the limit, the exchange of fluidized bed material is automatically turned on. The exchange of fluidized bed material can be controlled based on the result of the heat measurement and / or the screening result, depending on the application and the various functions therein.

15 '

In one embodiment of the invention, the results of the measurement of the temperature measurement levels L1, L2, L3 provide a graphical user interface to facilitate the decision-making of the operating personnel. Preferably, the temperatures T1, T2, T3 of the various temperature measurement levels L1, L2, L3 are displayed as graphs in the same coordinate system. Different alarm limits, alarms and * · other boiler operating information can also be displayed on an application-specific basis. Using the information in the register, it is also possible to generate a rough estimate on the screen. the proportion of material K and the forecast for the exchange of fluidized bed material * · · j “: 25 times. The compilation of information makes it easier for operating staff to: V detect changes in the boiler and anticipate possible disturbances.

By combining the operating modes and structures presented in connection with the various embodiments of the invention described above in various ways, various embodiments of the invention may be obtained which conform to the spirit of the invention. Therefore, the foregoing examples should not be construed but embodiments of the invention may freely vary within the scope of the inventive features set forth in the claims below.

*

• · 4I

Claims (13)

11k 117451 A method for monitoring the condition of the fluidized bed of a fluidized bed boiler to control the amount of coarse material in the fluidized bed (6), characterized by; 5, at least determining the temperature (T2) of the upper part of the fluidized bed (6), determining the temperature (T1) of the lower part of the fluidized bed (6), and monitoring the difference in said temperatures (T1, T2). Method according to claim 1, characterized in that a third temperature (T3) is also determined, the change in difference of which between the lower part temperature (T1) and / or the upper part temperature (T2) is monitored. Method according to claim 1 or 2, characterized in that the change in temperature (T1, T2, T3) changes the sampling. Method according to one of the preceding claims 1 to 3, characterized in that a change in the temperature (T1, T2, T3) difference and / or sampling is used to control the material change of the fluidized bed (6). * * * · · * ·· · · Method according to claim 1 or 2, characterized in that the temperatures (T1, T2, T3) are displayed as curves in the same coordinate. . tossa. • · · ·····: 25 * * ·: V 6, a fluid bed boiler fluid bed condition monitoring system for controlling the amount of coarse material in a fluidized bed, characterized in that the system comprises at least - a first member (1) for determining the temperature of the lower part of the fluidized bed (6), 30 Ian (T1); * '- for determining the temperature (T2) of the upper part of the fluidized bed (6) of the second member (2). ** *. * ···· * · The condition monitoring system according to claim 6, characterized in that the system further comprises a third element (3) for determining the floatation, T%, of a fluidized bed boiler. ': 117451 The condition monitoring system according to claim 6 or 7, characterized in that the system further comprises means for determining differences in temperatures (T1, T2, T3). A condition monitoring system according to claim 6, characterized in that the first member (1) is arranged to monitor the temperature (T1) of the lower part of the fluidized bed (6) at a height of 20-50 mm from the nozzles (4) for fluidizing the fluidized bed. X. The condition monitor according to any one of claims 6 to 9? system, characterized in that the system also comprises a screen. A fluidized bed boiler comprising at least a condition monitoring system for controlling the amount of coarse material in the fluidized bed, characterized in that the condition monitoring system comprises at least a first member (1) for determining the lower temperature of the fluidized bed (T1) and a second member (2). (6) to determine the temperature of the upper part (T2). 20: \ i A fluidized bed boiler according to claim 11, characterized in that: 1. the first member (1) is arranged to monitor the temperature (T1) of the lower part of the fluidized bed * 1. (6) at a height of 20-50 mm; «·· the nozzles for storing (4). -: 25 * 1 ': Fluidized bed boiler according to claim 11 or 12, characterized in that the condition monitoring system also comprises a sieve. • 1 · · 1 1 • ♦ · • · 30 * · · • • • «Ml • ·«, * · * · ** # ** ··· * · · «117451 O