Application of the longest range water sootblowers

2022-10-22
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Application of long-range water sootblowers in modern large-scale coal-fired boilers

Abstract: with the progress of the times, modern large-scale utility boilers are developing in the direction of large capacity and high parameters, but with the improvement of boiler parameters, the heat load of furnace section is increasing, and the possibility of coking of furnace water-cooled wall is increasing This seriously affects the economy and safety of boiler operation, causing the unit to sometimes have to limit the load or even shut down. If serious coke drop occurs, it will also endanger the safety of unit operators. Many power plants have encountered such problems, while some furnace wall soot blowers previously used mostly use steam as the medium, which have problems such as low soot blowing efficiency, complex operation and maintenance, and low input rate, Therefore, modern large utility boilers need a safe, reliable and effective furnace coking method

I. operation status of large power station boilers

with the progress of the times, modern large power station boilers are developing in the direction of large capacity and high parameters, but with the improvement of boiler parameters, the heat load of furnace section is increasing, and the possibility of coking of furnace water wall is increasing This seriously affects the economy and safety of boiler operation, causing the unit to sometimes have to limit the load or even shut down. If serious coke drop occurs, it will also endanger the safety of unit operators. Many power plants have encountered such problems, while some furnace wall soot blowers previously used mostly use steam as the medium, which have problems such as low soot blowing efficiency, complex operation and maintenance, and low input rate, Therefore, modern large utility boilers need a safe, reliable and effective furnace coking method

at present, the "Jett" long-range water soot blower installed on the Russian produced in KT (n-76) supercritical pressure once through boiler of XX power plant in Russia is a relatively advanced technology in the world, and it is rarely used in China at present

two 5oo MW supercritical pressure units produced in Russia are installed in XX power plant in Russia, with a rated continuous output of 1650T/h The main steam pressure is 25MPa, the boiler is arranged in T-shape, the cross-section size of the furnace is 23*13.8m, the combustion mode is opposed combustion on both sides of the wall, and a total of 32 swirl burners are arranged in four layers

"Jett" type water sootblowers are arranged in two layers at the elevation of 18.6m and 33m. There are 4 sets in each layer. The water consumption of a single sootblower is 40t/h, and the water pressure 5MPa, each working time 10min In addition, 18 OBM type short-range retractable wall type water sootblowers are arranged as a supplement to the "Jett" type water sootblowers

II. Application of long-range water sootblowers in large coal-fired boilers

2.1 working principle of sootblowers

"Jett" type long-range water sootblowers are arranged on the side wall water-cooled walls at the four corners of the furnace, which can spray high-pressure water to the opposite and adjacent corners of the furnace By changing the angle of the nozzle in the left-right and up-down directions, the water flow will follow a toothed track in the approximately square area on the opposite wall, which can clean an area of nearly 400m2, and the efficiency is much higher than that of general soot blowers The ash deposited on the furnace wall is cracked by the cold water flow. In addition, the water flow can penetrate into the gap of the ash, and then evaporate by heating. Because the vaporization speed is very fast, it is equivalent to a micro explosion, loosening the ash, and finally washing the ash away with the help of the impact of the liquid flow

2.2 commissioning and operation of "Jett" type long-range water sootblowers in Russian power plants

it is necessary to have circulating air in the experimental box.

the whole set of equipment of the furnace water sootblowers of the power plant, including the control system, are self-produced. The control equipment of the boiler is composed of relays, which is easy to fail, and the purging program is realized by hardware, which is not easy to change Despite these problems, the operation effect of "Jett" water sootblower is still good

the boiler burner of the power plant is a spiral case swirl burner, and the oil is placed in the center of the burner. In the early stage of unit startup, the coking near the burner is relatively serious, and in the loaded stage of the unit, there is coking in the water wall and other areas to varying degrees

first, the cold state test of the water soot blowing system was carried out before the unit was started, and the hot state operation test was carried out under the high load of the unit. During the test, various operating parameters of the boiler were monitored At that time, the boiler was running close to full load. What was the effect of "Jett" water sootblower lubrication on Jinan assaying concrete pressure testing machine? Lubrication plays an important role in the concrete pressure testing machine. When entering, the negative pressure of the furnace, the flue gas temperature at the outlet of the furnace and the temperature along the water-cooled wall have no significant changes, which indicates that when the water sootblowers, a slight coke falling sound can be heard at the zero meter of the boiler After purging, the coke deposited on the water wall has been basically cleaned through the observation hole, and the soot blowing effect is good

2.3 introduction to similar water sootblowers in the world

the "Jett" water sootblowers made in Russia are produced with the patent of German Bergemann Due to the gap of the whole labor level, there is still a considerable gap between Russian products and German products, especially in its control system

"Jett" type water sootblower has the technical advantage that the sedimentation area is controlled by the travel switch, which is not accurate enough and is easy to change due to external factors. Moreover, the water flow path can only be a simple tooth type, and it is likely that some areas are not purged thoroughly The WLB type water soot blower of German Bergman company is completely controlled by microcomputer. The direction of the nozzle is controlled by two motors of x-axis and y-axis. The soot blowing trajectory can be designed arbitrarily The water flow path of wlb30 water soot blower installed on the 1805t/h boiler of welsweiler power plant in Germany is shown in Figure 2 During soot blowing, the water flow can bypass some areas that do not want to be sprayed by water, such as combustion burners, fire viewing holes, etc. for places that need soot blowing, it can be done without letting go. Moreover, because the soot blowing trajectory is controlled by software, it can be easily modified according to the actual operation

2.4wlb advantages of long-range water sootblowers

2.4.1 good soot blowing effect

previously, domestic sootblowers used steam or compressed air as the medium, which was very suitable for burning some coals with weak coking tendency But for those ash deposits with high viscosity, which are difficult to remove, it seems that they are somewhat inadequate

the new soot blower uses water as the medium. Due to the large temperature difference between water and ash, the ash can be loosened when it is violently vaporized in the ash gap, and the momentum of water flow is much larger than that of steam, which can easily wash away the ash, so the soot blowing effect of the new soot blower is better than that of the old one

2.4.2 high working efficiency and investment saving

the new remote injection water sootblower wlb90 can sweep nearly 400m2 of the furnace area at a time when working, and its efficiency is much higher than that of general blowers

in weisweiler power plant in Germany, sk85 slow expansion wall soot blower was originally installed. In the above Russian power plant, the nozzle was slowly pushed into the furnace in a spiral shape, which can purge the water-cooled wall in a circular plane centered on itself Because the area of this kind of water sootblowers is limited, the whole furnace needs to be equipped with multiple sets, and the system is relatively complex

since 1991, this boiler has been equipped with wlb30 type long-range water sootblowers. One of the new water sootblowers can purge all the water-cooled walls within the elevation range of 42m-62m. However, 15 sk85 type water sootblowers were originally required in these areas, which greatly simplifies the system and saves future operation and maintenance costs

2.4.3 the uniform water flow of fire blowing and shooting has little effect on the temperature of the surface of the water-cooled wall.

sk85 soot blower works with uneven water flow in its own purging area. The water flow is strong near the center of the circle, and the water flow will be greatly weakened far away from the center of the circle, which may make the water flow in some areas too strong, causing harm to the water-cooled wall, while the water flow in some areas is too strong, and the purging is not clean

for wlb30 soot blower, since the water flow is sprayed to the opposite side of the furnace, the water flow range in the whole area is similar, so the purging is relatively uniform

as for the damage of water flow to the water-cooled wall, people are mainly worried that the temperature stress of cold water spray on the water-cooled wall is too large, resulting in the cracking of the water-cooled wall. For this, Germany Bergman company has made a targeted test

they first installed many thermocouples in the water wall area where sk85 and wlb30 soot blowers work together. The specific installation method is shown in Figure 3, and then recorded the temperature difference of the thermocouples before and after purging For sk85 soot blower The temperature difference under different nozzle sizes is shown in the attached table

for wlb30 water sootblowers, the maximum temperature difference of the thermocouple before and after cleaning is 5 degrees Celsius, which shows that the cleaning effect of the new long-range water sootblowers is relatively uniform and has little impact on the temperature of the water wall surface Attached table measurement record

nozzle size

minimum temperature

maximum temperature difference

4

5

6

11

12

13

142

210

168

note: the larger temperature difference is caused by the direct injection of water onto the thermoelectric coupling

2.4. The layout is convenient, Flexible adjustment

because the new long-range water sootblower wlb90 only needs to open a hole in the appropriate area of the water wall to clean all the water wall on the opposite side, the system layout is very flexible. The old soot blower is difficult to arrange in some special areas, such as near the burner, which may cause some areas, such as near the burner, which may cause some areas to be unable to purge, which is light and easy to lift for the long-range water soot blower

since the water flow trajectory during soot blowing is designed by software, it is very convenient to modify, so it can be flexibly adjusted according to the actual operation effect

2.5 explanation of two doubts about the new water soot blower

2.5.1 whether it will affect the normal combustion conditions in the furnace

as mentioned above, from the operation of the "Jett" type water sootblowers of XX power plant in Russia, as long as certain input conditions are guaranteed, such as requiring the boiler load to be more than 80% and appropriately increasing the furnace negative pressure to PA, the water sootblowers will not affect the normal combustion conditions in the furnace

2.5.2 whether long-term use of water sootblowers will cause cracks in the water wall

sk85 water sootblowers have been installed in the boilers of welsweiler power plant in Germany since 1975; In 1991, the power plant detected the 3.0*1.5m water wall in the working area of sk85 water sootblower, and no cracks were found. This shows that after being put into operation three times a day for 17 years, the sk85 water sootblower has not caused cracks in the water wall due to temperature stress

as mentioned above, wlb30 long-range water sootblowers have a much smaller impact on the surface temperature of the water wall than sk85, so there is no risk of cracking the water wall at all

conclusion

from the above discussion, it can be seen that compared with the old furnace soot blower, the new long-range water soot blower has many advantages, such as good soot blowing effect, high efficiency, convenient layout, flexible adjustment and so on. Especially for today's large utility boilers, the area of water-cooled walls that need to be cleaned is large. The application of this kind of soot blower can give full play to the advantages of large purging area, simplify the system, and save investment

at present, German thermal power plants mostly use this kind of soot blower in the reconstruction of soot blowers for new and old units. Therefore, this soot blowing method can be called a safe, reliable, applicable and relatively mature furnace coking scheme on large utility boilers at present

III. configuration and

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