Title of Invention	SMART WALL BLOWING SYSTEM BASED ON LOCAL DEPOSITION PATTERN TO MAINTAIN FURNACE HEAT ABSORPTION OPOTIMALLY FOR COAL FIRED BOILERS
Abstract	An improved wall blowing system as claimed in Claim 1 comprising a logic panel and MMI panel is achieved by controlling the starting and stopping of wall blowers based on super heater steam spray flow high and low set points and maintenance of local heat absorption at an optimum level as well as avoidance of wall blowing when ash deposits are less as decided and based on heat flux signals from the Heat Flux Sensors (I-IFS) located in between the wall blowers, the system thus operated maintains furnace heat absorption optimally in any fuel fired boiler.

Title of Invention

SMART WALL BLOWING SYSTEM BASED ON LOCAL DEPOSITION PATTERN TO MAINTAIN FURNACE HEAT ABSORPTION OPOTIMALLY FOR COAL FIRED BOILERS

Abstract

An improved wall blowing system as claimed in Claim 1 comprising a logic panel and MMI panel is achieved by controlling the starting and stopping of wall blowers based on super heater steam spray flow high and low set points and maintenance of local heat absorption at an optimum level as well as avoidance of wall blowing when ash deposits are less as decided and based on heat flux signals from the Heat Flux Sensors (I-IFS) located in between the wall blowers, the system thus operated maintains furnace heat absorption optimally in any fuel fired boiler.

Full Text	FIELD AND BACKGROUND OF THE INVENTION The present invention relates to an improved wall blowing system for maintaining furnace heat absorption optimally in coal fired boilers and for resorting to wall blowing in areas where deiosition is high. The present invention particularly relates to wall blowing in pulverized coal fired boilers, which would operate automatically and only on need basis, ie. on the basis of the furnace requirement; ~primarily starting and stopping the wall blowing system to maintain the furnace water wall heat absorption within optimum range and secondly skipping wall blowing wherever the ash de.psit intensity is not high as indicated by heat flux sensors mounted between the wall blowers. The radiation (furnace and platent super heater) and convection zone heat transfer surfaces (other super heaters, economizer etc) of a boiler are designed according to the established practice, to absorb proportionately the heat released on combustion of fuel (Goal) such that various functions such as water preheating (economizer), steam generation (water wall), steam super heating (LTSH, Platent SH and Final SH), steam reheating and air heating are carried out optimally. The boiler furnace, where the fuel is burnt, absorbs the maximum amount of the heat released. Impurities, if present, in the fuels cause deposits on boiler water wall surfaces resulting in the reduction of furnace heat absorption. The pattern, nature and rate of such deposition vary along the various zones of the furnace. Due to the combined effects of differing heat release rates of fuels, and varying compositions, rate of depositions on water walls and further depending on boiler load, mill combinations, tilt etc, the net furnace heat absorption could vary from the design predetermined value dynamically from time to time. If the furnace heat absorption is lowered, the furnace outlet gas temperatures go up resulting in increased SH/RH sprays, increased metal temperatures as well as increased NOx levels due to higher furnace temperatures. The cycle efficiency of power plant depends on increases in sprays, viz, with increase in re— heater spray in 210 MW designs and with increase in both SH/RH sprays in 500 MW designs. On the other hand, if furnace heat absorption increases, the furnace outlet gas temperature and consequently SH/RH steam temperatures fall short of predetermined value resulting in lower efficiency. Due to fluctuating fuel characteristics, most of the boilers experience varying degrees of sprays or low steam temperature conditions. Hence, maintains of furnace heat absorption optimally is a key operational requirement to maintain efficient boiler performance. CONVENTIONAL WALL BLOWING SYSTEMS In known boilers, wall blowers are located at different elevations both above and below the burner zones on all the four walls for removing the deposits. As such all the wall blowers are normally operated once in a shift and sequentially one after the other; approximately 3 times a day all wall blowers are operated. The conventional wall blowing system has certain disadvantages viz, being routine and ritualistic in nature, it does not recognize and differentiate whether the furnace is absorbing the net heat optimally. In other words, whether it is absorbing heat which is less or more than the optimum value and once started, it resorts to wall blowing from the first to the last of wall blower. If the furnace deposition had been less, the excess furnace cleaning might result in higher furnace heat absorption and lesser super heated temperatures. Many a times the benefit of better heat absorption and super heater lesseer spray only for a shorter period of time with the rest of the period till the next wall blowing experiencing lesser heat absorption and higher spray. Yet another disadvantage of the conventional furnace wall blowing system is that the wall blowing is carried out ritually irrespective of whether there are deposits and thereby warranting cleaning in that zone or not, thus causing steam erosion of water wall tubes leading to tube thinning and necessitating replacement with new tubes. As such there is no measurement system or device to identify whether there exists deposits or not. It is an object of the present invention to mitigate the above drawbacks of the conventional devices for maintenance of net furnace heat absorption and provide an instrument to indicate the degree of deposition as well as measure the heat flux changes. A further object of the present invnetion is to maintain net furnace water wall heat absorption at an optimum range by activating the operation and stopping of the wall blowers by preselected signals such as super heater spray flow and heat flux as absorbed by the water walls. A further object of the present invention is to provide a mechanism based to eliminate/minimize unwarranted wall blowing wherever ash deposition is not high through measurement of heat flux by sensors mounted on water walls and thereby reduce steam erosion of water wall tubes also due to un—warranted wall blowing. THE Patent No.JP 62009113A2 describes controlling the - operation of the soot blowers by image data obtained by a pick up cameras provided to scan respective predetermined areas of the furnace. Plurality of images obtained from TV cameras pickup state of the dust accumulated on the water walls and optical images are converted into electrical signal which is further converted to digital signals and stored in image processing arithmetic unit. The image data, tube edge pattern and condition of the unit are processed by a dust thickness processing program. A temperature controlling device takes these data and decides the soot blower controlling signals based on programmed factors. This method has disadvantages namely when the ash content of the coal is high the visibility of the furnace is significantly affected. Japan Patent No.JP 62017512A2 teaches a method of group operation of soot blowers for effective removal of adhered substances based on a coat starting pattern derived from coal properties and the read operational pattern. This method has the disadvantage because of the fact that the coating pattern not only depends on the coal properties but also operational variables like excess air, tilt, load, the combination of which cannot be modeled, ie. monitored even for the same boiler. Japan Patent No.JP 11148633A2 illustrates a method by which the starting order of soot blowing is corrected automatically based on differential between calculated and reference furnace outlet temperature. Assuming the reference coal is an intermediate fuel coal, the method of approach is the gas temperature difference which would increases on the plus side for high fuel ratio (fixed carbon to volatile matter ratio in proximate analysis of coals) and on the minus side for low fuel ratio of coals. However, the furnace outlet temperature would vary dynamically due to various reasons other than or in addition to fuel ratio such as tilt, mill combination, Hence the prior art does not contain a teaching that the super heater spray level signals can be utilized for selecting high and low set points which in turn can atomatically start and stop the operation of soot/wall blowers for maintaining the net furnace heat absorption optimally and while doing so also can ensure that local wall blowing is resorted only where deposits have caused heat flux reduction above a certain percentage and wall blowing in that zone is skipped if heat flux reduction due to deposition is below a set percentage. SUMMARY OF THE INVENTION The new device developed by the applicant maintains the furnace water wall heat absorption at optimum levels by operating the predetermined set of wall blowers activated by the signals such as super heater spray exceeding "High" set points and permissive such as soot blowing header steam temperature, etc and by discontinuing operation of next wall blower when super heater spray level reduces below the low set point so that referred boiler parameter variations are minimized and the overall boiler performance is improved. During the above sequence only those blowers are activated if the heat flux below the set value, as sensed by the heat flux sensors located in between wall blowers. In this system wall blowers are operaed one wall after another wall, in staggered manner, but in sequence, as demanded by the sytem. The applicants have developed a new system or device for maintaining furnace heat absorption optimally in coal fired boilers having the following embodiments — 1. In addition to the generally existing burner tilting arrangement of tangential firing system, the new system would operate need based, to maintain the furnace heat absorption optimally so that neither super heater / re—heater steam temperatures falls short nor goes up resulting in higher super heater / re—heaer sprays which would take cognizance of the variations in net furnace heat absorption due to changes in coal quality, boiler load, mill combinations, burner tilt, etc. 2. The new system includes wall blowers only in those zones where ash deposits have built up causing significant reduction in heat transfer. 3. The developed system reduces the frequency of wall blowing to minimize the steam erosion of water wall tubes which happen due to wall blowing. 4. The invented system reduces the SH/RH sprays and thereby improve the cycle efficiency, or in other words, reduce the heat rate of the power plant to the extent possible by operational means as well as reduce the Demineralised (DM) water otherwise wasted as spray and also the associated energy needed to convert water to steam. 5. The new system prevents excursions of convection pass heat transfer surface metal temperatures above the permissible limit thereby reaming the respective designed creep life of metals. 6. This is a system which would cognize dynamically and operate automatically. 7. Thene.w system can find out the heat flux levels of each zone in each wall just before wall blowing / cleaning and decide whether that zone require wall blowing or not and skip if the reduction in heat flux is not significant and decide to blow if the reduction in heat flux is higher than the set percentage. For a better understanding of the invention, its operating advantages and specific results attained by its users, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. IN TUE ACCONPANYING DRAWINGS Figure 1 shows a block diagrame illustrating the various sub systems of the super heater spray flow (SHSF) of the present invention; Figure 2 shows pictorially the heat blocks sensor (HFS) assembly; Figure 3 shows a flow chart of the logics implemented in the logic panel; and Figure 4 shows pictorially the integration of the add—on system of the conventional / existing soot blowing system. Figure 1 which shows block diagram showing the various sub systems where in the Super Heater Spray Flow (SHSF) measured by a flow nozzle (1) and flow transmitter / current converer (2) and the milli ampere current signal is fed to a logic panel (3) for signal processing. Heat Flux Sensors (HFS) to measure the absorbed heat flux levels of the water wall zone located in between blowers whose output is fed to a signal conditioner/ transmitter for further processing and communicating to the logic panel. The logic panel is provided with input cards which converts the milli ampere current signal into compatible digital signals for processing. The electronic processor located in the logic panel processes the digital signal further and interacts with a personal computer based Man Machine Interface (MMI) system (4) and decides actuating the motorised wall blower (WB) through a Motor Control Center (MCC) (%) and wall blower local control (6). The wall blower moves forward into the furnace and rotates injecting steam on to the furnace walls on the fireside for cleaning the deposits. The wall blower retracts back after a predetermined time as commanded by the logic and the steam injection is also stopped actuated by the limit switches. With reference to Figure 2 HFS works on the well known princile of conductive heat transfer through metal wals. A sensing element of known size and thermal conductivity is embedded on the water wall. The absorbed heat flux by the water wall is quantified by the formula where Q is the heat flux, K is thermal conductivity of the sensor metal, A is the front area t is the temperature differential between the front and rear thermocouples and x is the distance between the front and rear thermocouples. The thermocouples are protected against flame radiation and other mechanical / electrical damages. The associated thermal guard around the sensor ensures proper heat transfer characteristics through the sensor. The entire HFS assembly is designed to fit in the existing water walls such that the sensing element facing the flame side. The signals from the thermocouples are suitably calibrated with associated signal conditioner / transmitter to directly give the absorbed heat flux by the water walls in that zone. With reference to Figure 3 the Super Heater Spray Flow (SHSF) goes up if the furnace heat absorption is reduced due to deposition, SHSF measurement is taken as monitoring signal for either starting the wall blowing or for stopping the wall blower. When the SHSF exceeds high set point, the logic decides to activate the wall blowing cycle in the sequence from where it was left. Actual wall blowing is started after ensuring permissives such as minimum steam temperature and steam pressure. The wall blowing is carried in increments of group of blowers and only those blowers are activated to blow when heat flux values as sensed by the associated heat flux sensor is below the set value or otherwise skipped to next blower. The SHSF is checked and reaches below low set point, the wall blowing sequence is halted and soot blowing steam header valve gets closed automatically and waits for the SHSF to exceed the set value for activating / starting the sequence aaain. In the improved system, the software has provisions facilitating switching over to operation of Long Retractable Soot Blowers (LRSBs) in the boiler furnace, as well as air preheater blowers whenever necessary and return back thereafter. Figure 4 illustrates flow char/logic system (as shown in Fig.3) is designed to respond appropriately to varying operational / performance conditions such as SHSF being continuously HIGH or LOW or when it is between the LOWER and HIGHER set points. Whenever SHSF measurement is continuously greater than the high set point, even after completing one cycle of wall blowing sequence, the logic changes over to operator interactive mode after giving an alarm, over which the operator can either decide to comtinue or change set point. Whenever SHSF measurement is continuously lower than the low set point for a preset period, the logic changes over to operator interactive mode after giving an alarm, over which the operator can either decide to continue or change set point. Whenever SHSF measurement is continuously lower than the high set point and greater than the low set point for a preset period, the logic activates a group of wall blowers and only those blowers are activated where heat flux level is below the set value, from where it was left previously. The logic has been built up so as to activate all blowers at least once over a specified period, if they have not been operated due heat flux reduction logics in the specified previous cycles, for the purpose of smooth functioning of the blowers over a prolonged period of operation. Whenever the fault occurs due to wall blowing steam parameters or the wall blower stuck up conditions, the system alarms and switches over to operator intervention mode to clear the faults. After the fault clearance, the operation can switch over to auto mode, where the system continues from where it was left. Similarly the auto operation of the system can be manually / automatically put on hold to facilitate operating blowers otehr than the boiler furnace such as Long Range Soot Blowers (LRSB) inthe convection pass of the boiler or Air preheaer blowers and resume back to furnace wall blowing from where it was left previously. The Man Machine Interface (MMI) deployed in this system is built with operator friendly displays through a personal computer. The system displays, the mimic of wall blower arrangement, soot blowing steam header valve open or close, drain temperature, steam temperature and pressure, super heater / re—heater spray flows, boiler main steam flow, blower status such as home position, forward, retract, alarm satus of wall blowing system, the status of timers built in the claimed logics and super heater high and low set points. The system installed can minimize the operator interventin, average super heater / re—heater sprays and the number of cycles of wall blowing significantly. The various features and the novelty which characterize the present invention are pointed out, with particularly, in the claims annexed to and forming the part of the disclosure. WE CLAIM: 1. An automated improved Wall Blowing System (WBS) comprising electrical/electronics hardwares such as water wall mounted heat flux sensor, and signal conditioner, flow transmitter/current converter, logic panel and MMI panel interfaced with the conventional soot blowing hardware and additional novel pre-programmed logics embedded as software as described herein by which the sequential starting and stopping of the wall blowers being activated by the high and low set points of super heater spray flow respectively and specific blowers are operable where the absorbed heat flux values falls below the predetermined value taking into cognizance of permissives such as soot blowing headedr steam pressure and temperature, response time and the exercise of the said logics through which the furnace heat absorption being maintained at optimum levels and consequently the excursions in furnace gas outlet temperatures and super heater/re-heater spray being controlled within a range and thus improving the overall boiler performance, the embedded software ensures that all blowers are operated once over a specified period the improved Wall Blowing System (WBS) being built with operator friendly displays and mimic said system maintains the furnace heat absorption optimally in any fuel fired boiler. 2. An improved wall blowing system as claimed in Claim 1 comprising a logic panel and MMI panel is achieved by controlling the starting and stopping of wall blowers based on super heater steam spray flow high and low set points and maintenance of local heat absorption at an optimum level as well as avoidance of wall blowing when ash deposits are less as decided and based on heat flux signals from the Heat Flux Sensors (I-IFS) located in between the wall blowers, the system thus operated maintains furnace heat absorption optimally in any fuel fired boiler. 3. An improved wall blowing system as claimed in Claims 1 and 2 comprising electricals and electronic hardwares and embedded softwares integrated with a data acquisition and display system. 4 An improved wall blowing system as claimed in any of claims 1 to 3 wherein Super Heater Spray Flow (SHSF) increases when the furnace heat absorptions reduced due to deposition, the SHSF measurement is taken as a monitoring signal for starting the wall blowing and when the SHSF decreases the respective measurement is used for stopping the wall blowing and heat flux signal is processed for activating said blowers in that zone when the heat flux signal has reduced below the set value and the logic decides to activate the wall blowing cycle in the sequence from where it was left and the actual wall blowing is started only after ensuring permissives such as minimum steam temperature and steam pressure, and the wall blowing is carried in increments of group of wall blowers, the SHSF is checked and compared with set point on completion of every group of wall blowing, and when SHSF' reaches below low set point, the wall blowing sequence is halted and soot blowing steam header valve gets closed automatically and waits for the SHSF to exceed the set value for activating/starting the sequence again. 5 An improved wall blowing system as claimed in any of the preceding claims wherein the preprogrammed logic through embedded software is built up so as to ensure that all blowers are operated at least once over a specified period, if not operated due to heat flux reduction logics in the specified previous cycles, it facilitates the smooth functioning of the blowers over a prolonged period of operation. 6 An improved wall blowing system as claimed in any of claims 1 to 5 wherein said Man Machine Interface (MMI) is built with operator friendly displays through a personal computer, the mimic of wall blower arrangement, soot blowing steam header valve, drain temperature, steam temperature and pressure, super heater/re-heater spray flows, boiler main steam flow, blower status such as home position, forward, retract, alarm status of wall blowing system, the status of timers and super heater spray flow ha4ng high and & low set points and, the current heat flux values of all Heat Flux Sensors (HFS). 7 An improved wall blowing system as claimed in any of claims 1 to 6 wherein said software has inbuilt provisions to alarm and call for operator intervention only under abnormal situations. 8 An improved wall blowing system as claimed in any of claims 1 to 7 wherein said software is provided with means for switching over or activating operation of other related systems like Long Retractable Soot Blowers (LRSBs) located at the convection pass and of below the nose of boiler furnace, activation of air preheater blowers as and when considered necessary and return back thereafter. 9 An improved wall blowing system as claimed in any of claims 1 to 8 wherein said software has provision for real time trending of data such as heat flux levels of all individual sensors over the entire furnace, super heater/re-heater spray levels and metal temperatures of selected super heater and reheater coils. 10 An improved smart wall blowing system as claimed in any of claims I to 9 wherein the data acquisition system facilitates survey and archiving of data such as cumulative super heater/re-heater spray levels, heat flux levels, as well as furnace outlet temperatures, metal temperatures of selected convection pass heat transfer coils etc. 11 An improved wall blowing system as claimed in any of the claims 1 to 10 wherein new soot blowing installation is incorporated in total and also as an add-on system to existing soot/wall blowing with much operational flexibility.

Full Text

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to an improved wall blowing system for maintaining furnace heat absorption optimally in coal fired boilers and for resorting to wall blowing in areas where deiosition is high.

The present invention particularly relates to wall blowing in pulverized coal fired boilers, which would operate automatically and only on need basis, ie. on the basis of the furnace requirement; ~primarily starting and stopping the wall blowing system to maintain the furnace water wall heat absorption within optimum range and secondly skipping wall blowing wherever the ash de.psit intensity is not high as indicated by heat flux sensors mounted between the wall blowers.
The radiation (furnace and platent super heater) and convection zone heat transfer surfaces (other super heaters, economizer etc) of a boiler are designed according to the established practice, to absorb proportionately the heat released on combustion of fuel (Goal) such that various functions such as water preheating (economizer), steam generation (water wall), steam super heating (LTSH, Platent SH and Final SH), steam reheating and air heating are carried out optimally.
The boiler furnace, where the fuel is burnt, absorbs the maximum amount of the heat released. Impurities, if present, in the fuels cause deposits on boiler water wall surfaces resulting in the reduction of furnace heat absorption. The pattern, nature and rate of such deposition vary along the various zones of the furnace. Due to the combined effects of differing heat release rates of fuels, and varying compositions, rate of depositions on water walls and further depending on boiler load, mill combinations, tilt etc, the net furnace heat absorption could vary from the design predetermined value dynamically from time to time.
If the furnace heat absorption is lowered, the furnace outlet gas temperatures go up resulting in increased SH/RH sprays, increased metal temperatures as well as increased NOx levels due to higher furnace temperatures. The cycle efficiency of power plant depends on increases in sprays, viz, with increase in re— heater spray in 210 MW designs and with increase in both SH/RH sprays in 500 MW designs. On the other hand, if furnace heat absorption increases, the furnace outlet gas temperature and consequently SH/RH steam temperatures fall short of predetermined value resulting in lower efficiency. Due to fluctuating fuel characteristics, most of the boilers experience varying degrees of sprays or low steam temperature conditions. Hence, maintains of furnace heat absorption optimally is a key operational requirement to maintain efficient boiler performance.

CONVENTIONAL WALL BLOWING SYSTEMS

In known boilers, wall blowers are located at different elevations both above and below the burner zones on all the four walls for removing the deposits. As such all the wall blowers are normally operated once in a shift and sequentially one after the other; approximately 3 times a day all wall blowers are operated.

The conventional wall blowing system has certain disadvantages viz, being routine and ritualistic in nature, it does not recognize and differentiate whether the furnace is absorbing the net heat optimally. In other words, whether it is absorbing heat which is less or more than the optimum value and once started, it resorts to wall blowing from the first to the last of wall blower. If the furnace deposition had been less, the excess furnace cleaning might result in higher furnace heat absorption and lesser super heated temperatures. Many a times the benefit of better heat absorption and super heater lesseer spray only for a shorter period of time with the rest of the period till the next wall blowing experiencing lesser heat absorption and higher spray.
Yet another disadvantage of the conventional furnace wall blowing system is that the wall blowing is carried out ritually irrespective of whether there are deposits and thereby warranting cleaning in that zone or not, thus causing steam erosion of water
wall tubes leading to tube thinning and necessitating replacement with new tubes. As such there is no measurement system or device to identify whether there exists deposits or not.

It is an object of the present invention to mitigate the above drawbacks of the conventional devices for maintenance of net furnace heat absorption and provide an instrument to indicate the degree of deposition as well as measure the heat flux changes.
A further object of the present invnetion is to maintain net furnace water wall heat absorption at an optimum range by activating the operation and stopping of the wall blowers by preselected signals such as super heater spray flow and heat flux as absorbed by the water walls.
A further object of the present invention is to provide a mechanism based to eliminate/minimize unwarranted wall blowing wherever ash deposition is not high through measurement of heat flux by sensors mounted on water walls and thereby reduce steam erosion of water wall tubes also due to un—warranted wall blowing.
THE
Patent No.JP 62009113A2 describes controlling the
-
operation of the soot blowers by image data obtained by a pick

up cameras provided to scan respective predetermined areas of

the furnace. Plurality of images obtained from TV cameras pickup state of the dust accumulated on the water walls and optical images are converted into electrical signal which is further converted to digital signals and stored in image processing arithmetic unit. The image data, tube edge pattern and condition of the unit are processed by a dust thickness processing program. A temperature controlling device takes these data and decides the soot blower controlling signals based on programmed factors. This method has disadvantages namely when the ash content of the coal is high the visibility of the furnace is significantly affected.
Japan Patent No.JP 62017512A2 teaches a method of group operation of soot blowers for effective removal of adhered substances based on a coat starting pattern derived from coal properties and the read operational pattern. This method has the disadvantage because of the fact that the coating pattern not only depends on the coal properties but also operational variables like excess air, tilt, load, the combination of which cannot be modeled, ie. monitored even for the same boiler.
Japan Patent No.JP 11148633A2 illustrates a method by which the starting order of soot blowing is corrected automatically based on differential between calculated and reference
furnace outlet temperature. Assuming the reference coal is an intermediate fuel coal, the method of approach is the gas temperature difference which would increases on the plus side for high fuel ratio (fixed carbon to volatile matter ratio in proximate analysis of coals) and on the minus side for low fuel ratio of coals. However, the furnace outlet temperature would vary dynamically due to various reasons other than or in addition to fuel ratio such as tilt, mill combination,
Hence the prior art does not contain a teaching that the super heater spray level signals can be utilized for selecting high and low set points which in turn can atomatically start and stop the operation of soot/wall blowers for maintaining the net furnace heat absorption optimally and while doing so also can ensure that local wall blowing is resorted only where deposits have caused heat flux reduction above a certain percentage and wall blowing in that zone is skipped if heat flux reduction due to deposition is below a set percentage.

SUMMARY OF THE INVENTION

The new device developed by the applicant maintains the furnace water wall heat absorption at optimum levels by operating the predetermined set of wall blowers activated by the signals such as super heater spray exceeding "High" set points and permissive
such as soot blowing header steam temperature, etc and by discontinuing operation of next wall blower when super heater spray level reduces below the low set point so that referred boiler parameter variations are minimized and the overall boiler performance is improved. During the above sequence only those blowers are activated if the heat flux below the set value, as sensed by the heat flux sensors located in between wall blowers. In this system wall blowers are operaed one wall after another wall, in staggered manner, but in sequence, as demanded by the sytem.
The applicants have developed a new system or device for maintaining furnace heat absorption optimally in coal fired boilers having the following embodiments —
1. In addition to the generally existing burner tilting arrangement of tangential firing system, the new system would operate need based, to maintain the furnace heat absorption optimally so that neither super heater / re—heater steam temperatures falls short nor goes up resulting in higher super heater / re—heaer sprays which would take cognizance of the variations in net furnace heat absorption due to changes in coal quality, boiler load, mill combinations, burner tilt, etc.

2. The new system includes wall blowers only in those zones where ash deposits have built up causing significant reduction in heat transfer.

3. The developed system reduces the frequency of wall blowing to minimize the steam erosion of water wall tubes which happen due to wall blowing.
4. The invented system reduces the SH/RH sprays and thereby improve the cycle efficiency, or in other words, reduce the heat rate of the power plant to the extent possible by operational means as well as reduce the Demineralised (DM) water otherwise wasted as spray and also the associated energy needed to convert water to steam.
5. The new system prevents excursions of convection pass heat transfer surface metal temperatures above the permissible limit thereby reaming the respective designed creep life of metals.
6. This is a system which would cognize dynamically and operate automatically.
7. Thene.w system can find out the heat flux levels of each zone in each wall just before wall blowing / cleaning and decide whether that zone require wall blowing or not and skip if the reduction in heat flux is not significant and decide to blow if the reduction in heat flux is higher than the set percentage.
For a better understanding of the invention, its operating advantages and specific results attained by its users, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.

IN TUE ACCONPANYING DRAWINGS

Figure 1 shows a block diagrame illustrating the various sub systems of the super heater spray flow (SHSF) of the present invention;
Figure 2 shows pictorially the heat blocks sensor (HFS) assembly;
Figure 3 shows a flow chart of the logics implemented in the logic panel; and
Figure 4 shows pictorially the integration of the add—on system of the conventional / existing soot blowing system.
Figure 1 which shows block diagram showing the various sub systems where in the Super Heater Spray Flow (SHSF) measured by a flow nozzle (1) and flow transmitter / current converer
(2) and the milli ampere current signal is fed to a logic panel (3) for signal processing. Heat Flux Sensors (HFS) to measure the absorbed heat flux levels of the water wall zone located in between blowers whose output is fed to a signal conditioner/
transmitter for further processing and communicating to the logic panel. The logic panel is provided with input cards which converts the milli ampere current signal into compatible digital signals for processing. The electronic processor located in the logic panel processes the digital signal further and interacts with a personal computer based Man Machine Interface (MMI) system (4) and decides actuating the motorised wall blower (WB) through a Motor Control Center (MCC) (%) and wall blower local control (6). The wall blower moves forward into the furnace and rotates injecting steam on to the furnace walls on the fireside for cleaning the deposits. The wall blower retracts back after a predetermined time as commanded by the logic and the steam injection is also stopped actuated by the limit switches.
With reference to Figure 2 HFS works on the well known princile of conductive heat transfer through metal wals. A sensing element of known size and thermal conductivity is embedded on the water wall. The absorbed heat flux by the water wall is quantified by the formula
where Q is the heat flux, K is thermal conductivity of the sensor metal, A is the front area t is the temperature differential between the front and rear thermocouples and x is the distance between the front and rear thermocouples. The thermocouples are protected against flame radiation and other mechanical / electrical damages. The associated thermal guard around the sensor ensures proper heat transfer characteristics through the sensor. The entire HFS assembly is designed to fit in the existing water walls such that the sensing element facing the flame side. The signals from the thermocouples are suitably calibrated with associated signal conditioner / transmitter to directly give the absorbed heat flux by the water walls in that zone.
With reference to Figure 3 the Super Heater Spray Flow (SHSF) goes up if the furnace heat absorption is reduced due to deposition, SHSF measurement is taken as monitoring signal for either starting the wall blowing or for stopping the wall blower. When the SHSF exceeds high set point, the logic decides to activate the wall blowing cycle in the sequence from where it was left. Actual wall blowing is started after ensuring permissives such as minimum steam temperature and steam pressure. The wall blowing is carried in increments of group of blowers and only those blowers are activated to blow when heat flux values
as sensed by the associated heat flux sensor is below the set value or otherwise skipped to next blower. The SHSF is checked and reaches below low set point, the wall blowing sequence is
halted and soot blowing steam header valve gets closed
automatically and waits for the SHSF to exceed the set value
for activating / starting the sequence aaain.
In the improved system, the software has provisions facilitating switching over to operation of Long Retractable Soot Blowers (LRSBs) in the boiler furnace, as well as air preheater blowers whenever necessary and return back thereafter.
Figure 4 illustrates flow char/logic system (as shown in Fig.3) is designed to respond appropriately to varying operational / performance conditions such as SHSF being continuously HIGH or LOW or when it is between the LOWER and HIGHER set points.
Whenever SHSF measurement is continuously greater than the high set point, even after completing one cycle of wall blowing sequence, the logic changes over to operator interactive mode after giving an alarm, over which the operator can either decide to comtinue or change set point.
Whenever SHSF measurement is continuously lower than the low set point for a preset period, the logic changes over to operator interactive mode after giving an alarm, over which the operator can either decide to continue or change set point.
Whenever SHSF measurement is continuously lower than the high set point and greater than the low set point for a preset period, the logic activates a group of wall blowers and only those blowers are activated where heat flux level is below the set value, from where it was left previously.

The logic has been built up so as to activate all blowers at least once over a specified period, if they have not been operated due heat flux reduction logics in the specified previous cycles, for the purpose of smooth functioning of the blowers over a prolonged period of operation.
Whenever the fault occurs due to wall blowing steam parameters or the wall blower stuck up conditions, the system alarms and switches over to operator intervention mode to clear the faults. After the fault clearance, the operation can switch over to auto mode, where the system continues from where it was left.
Similarly the auto operation of the system can be manually / automatically put on hold to facilitate operating blowers otehr than the boiler furnace such as Long Range Soot Blowers (LRSB) inthe convection pass of the boiler or Air preheaer blowers and resume back to furnace wall blowing from where it was left previously.
The Man Machine Interface (MMI) deployed in this system is built with operator friendly displays through a personal computer. The system displays, the mimic of wall blower arrangement, soot blowing steam header valve open or close, drain temperature, steam temperature and pressure, super heater / re—heater spray flows, boiler main steam flow, blower status such as home position, forward, retract, alarm satus of wall blowing system, the status of timers built in the claimed logics and super heater high and low set points.
The system installed can minimize the operator interventin, average super heater / re—heater sprays and the number of cycles of wall blowing significantly.
The various features and the novelty which characterize the present invention are pointed out, with particularly, in the claims annexed to and forming the part of the disclosure.

WE CLAIM:

1. An automated improved Wall Blowing System (WBS) comprising electrical/electronics hardwares such as water wall mounted heat flux sensor, and signal conditioner, flow transmitter/current converter, logic panel and MMI panel interfaced with the conventional soot blowing hardware and additional novel pre-programmed logics embedded as software as described herein by which the sequential starting and stopping of the wall blowers being activated by the high and low set points of super heater spray flow respectively and specific blowers are operable where the absorbed heat flux values falls below the predetermined value taking into cognizance of permissives such as soot blowing headedr steam pressure and temperature, response time and the exercise of the said logics through which the furnace heat absorption being maintained at optimum levels and consequently the excursions in furnace gas outlet temperatures and super heater/re-heater spray being controlled within a range and thus improving the overall boiler performance, the embedded software ensures that all blowers are operated once over a specified period the improved Wall Blowing System (WBS) being built with operator friendly displays and mimic said system maintains the furnace heat absorption optimally in any fuel fired boiler.

2. An improved wall blowing system as claimed in Claim 1 comprising a logic panel and MMI panel is achieved by controlling the starting and stopping of wall blowers based on super heater steam spray flow high and low set points and maintenance of local heat absorption at an optimum level as well as avoidance of wall blowing when ash deposits are less as decided and based on heat flux signals from the Heat Flux Sensors (I-IFS) located in between the wall blowers, the system thus operated maintains furnace heat absorption optimally in any fuel fired boiler.

3. An improved wall blowing system as claimed in Claims 1 and 2 comprising electricals and electronic hardwares and embedded softwares integrated with a data acquisition and display system.
4 An improved wall blowing system as claimed in any of claims 1 to 3 wherein Super Heater Spray Flow (SHSF)

increases when the furnace heat absorptions reduced due to deposition, the SHSF measurement is taken as a

monitoring signal for starting the wall blowing and when the SHSF decreases the respective measurement is used for
stopping the wall blowing and heat flux signal is processed for activating said blowers in that zone when the heat flux signal has reduced below the set value and the logic decides to
activate the wall blowing cycle in the sequence from where it was left and the actual wall blowing is started only after
ensuring permissives such as minimum steam temperature and steam pressure, and the wall blowing is carried in increments of group of wall blowers, the SHSF is checked and compared with set point on completion of every group of wall blowing, and
when SHSF' reaches below low set point, the wall blowing
sequence is halted and soot blowing steam header valve gets
closed automatically and waits for the SHSF to exceed the set
value for activating/starting the sequence again.
5 An improved wall blowing system as claimed in any of the preceding claims wherein the preprogrammed logic through embedded software is built up so as to ensure that all blowers are operated at least once over a specified period, if not

operated due to heat flux reduction logics in the specified previous cycles, it facilitates the smooth functioning of the blowers over a prolonged period of operation.

6 An improved wall blowing system as claimed in any of claims 1 to 5 wherein said Man Machine Interface (MMI) is built with operator friendly displays through a personal computer, the mimic of wall blower arrangement, soot blowing steam header valve, drain temperature, steam temperature and pressure, super heater/re-heater spray flows, boiler main steam flow, blower status such as home position, forward, retract, alarm status of wall blowing system, the status of timers and super heater spray flow ha4ng high and & low set points and, the current heat flux values of all Heat Flux Sensors (HFS).
7 An improved wall blowing system as claimed in any of claims 1 to 6 wherein said software has inbuilt provisions to alarm and call for operator intervention only under abnormal situations.
8 An improved wall blowing system as claimed in any of claims 1 to 7 wherein said software is provided with means for switching over or activating operation of other related systems like Long Retractable Soot Blowers (LRSBs) located at the convection pass and of below the nose of boiler furnace,
activation of air preheater blowers as and when considered necessary and return back thereafter.
9 An improved wall blowing system as claimed in any of claims 1 to 8 wherein said software has provision for real time trending of data such as heat flux levels of all individual sensors over the entire furnace, super heater/re-heater spray levels and metal temperatures of selected super heater and reheater coils.
10 An improved smart wall blowing system as claimed in any of claims I to 9 wherein the data acquisition system facilitates survey and archiving of data such as cumulative super heater/re-heater spray levels, heat flux levels, as well as furnace outlet temperatures, metal temperatures of selected convection pass heat transfer coils etc.
11 An improved wall blowing system as claimed in any of the claims 1 to 10 wherein new soot blowing installation is incorporated in total and also as an add-on system to existing soot/wall blowing with much operational flexibility.

Documents:

510-del-2001-claims.pdf

510-del-2001-correspondence-others.pdf

510-del-2001-correspondence-po.pdf

510-del-2001-description (complete).pdf

510-del-2001-drawings.pdf

510-del-2001-form-1.pdf

510-del-2001-form-19.pdf

510-del-2001-form-2.pdf

510-del-2001-form-3.pdf

510-del-2001-form-4.pdf

510-del-2001-form-5.pdf

510-del-2001-gpa.pdf

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Patent Number

219886

Indian Patent Application Number

510/DEL/2001

PG Journal Number

28/2008

Publication Date

11-Jul-2008

Grant Date

14-May-2008

Date of Filing

20-Apr-2001

Name of Patentee

BHARAT HEAVY ELECTRICALS LTD.

Applicant Address

Inventors:

#	Inventor's Name	Inventor's Address
1	S. KALYANASUNDARAM
2	K. NANDAKUMAR

PCT International Classification Number

C01B3/02; C01B3/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA