ESP Power and Its Relation to ESP Rebuilds
ESP Power and Its Relation to ESP Rebuilds Western Canada BLRBAC Meeting John A. Knapik – ESP Technical Consultant B&W Controls and Electrical Group Email: jaknapik@babcock. com Phone: 440 -666 -3876 October 25, 2017 © 2017 The Babcock & Wilcox Company. All rights reserved.
To Become an ESP Expert, You Simply have to Know Two Things 1. Precipitator efficiency is directly proportional to: • How quickly the dust in the ESP migrates toward the collecting plates to get captured. (Best monitored thru ESP total power [KW]) • The relative size of the ESP (SCA) © 2017 The Babcock & Wilcox Company. All rights reserved. 2
ESP power is a barometer for ESP performance The more ESP power, the higher the ESP collection efficiency © 2017 The Babcock & Wilcox Company. All rights reserved. THIS GRAPH IS FOR PRESENTATION OF THE CONCEPT, ONLY, AND SHOULD NOT BE ASSUMED TO REPRESENT ANY SPECIFIC APPLICATION. 3
Precipitator Relative Size (SCA) The relative size of an ESP is called its Specific Collecting Area (SCA) Example: Total ESP collecting surface area = 300, 000 ft 2 Total gas volume = 1, 000 ACFM 1) SCA of 300, 000/1, 000 (1000 s) = 300 © 2017 The Babcock & Wilcox Company. All rights reserved. 4 ESP
Increasing ESP Size 1. Doubling the precipitator physical size, doubles its SCA. New SCA = 600 2 X ESP 2. Or, reducing the flue gas volume in half, and keeping the ESP physical size the same, doubles its SCA. New SCA = 600 © 2017 The Babcock & Wilcox Company. All rights reserved. 5
To Become an ESP Expert, You Simply have to Know Two Things 1. Precipitator Efficiency is directly proportional to: • How quickly the dust in the ESP migrates toward the collecting plates to get captured. (Best monitored thru ESP Total Power [KW]) • The relative size of the ESP (SCA) 2. Therefore, whatever we can do to maximize the above two parameters will increase the ESP collection efficiency. © 2017 The Babcock & Wilcox Company. All rights reserved. 6
Rebuilding a Recovery Boiler ESP has an Impact on ESP Power and Outlet Emissions © 2017 The Babcock & Wilcox Company. All rights reserved. 7
Precipitator (ESP) Power is the summation of the secondary power (KW=KV*m. A) of all the power supplies on the ESP T-Rs and Bus Duct Rapping Systems © 2017 The Babcock & Wilcox Company. All rights reserved. 8
For every ESP, the power levels increase from inlet to outlet, but the easiest to understand barometer is total ESP power © 2017 The Babcock & Wilcox Company. All rights reserved. 9
If the Recovery ESP had Hoppers, the Catch in Each AVC Readings KV m. A SPM Voltage Control Readings Field 1 100 lb of Salt Cake in flue gas Field 2 Field 3 80% Efficiency 70% Efficiency 60% Efficiency 20 lb 6 lb 2. 4 lb 14 lb 3. 6 lb 80 lb THIS EXAMPLE IS FOR PRESENTATION OF THE CONCEPT, ONLY, AND SHOULD NOT BE ASSUMED TO REPRESENT ANY SPECIFIC APPLICATION. Total = 97. 6 lb removed out of 100 lb in = 97. 6% efficient © 2017 The Babcock & Wilcox Company. All rights reserved. 10 2. 4 lb of Salt Cake to stack
Recovery Boiler ESP Current Density by Field 90 ESP SECONDARY CURRENT u. A/ft 2 80 RECOVERY BOILER ESP CURRENT BY FIELD 70 LOW RANGE 60 HIGH RANGE 50 40 30 20 10 0 1 2 ESP FIELD NUMBER 3 BLR ESP Total KW Increases Roughly by a Factor of 3 from Inlet to Outlet © 2017 The Babcock & Wilcox Company. All rights reserved. 11 4
If your most recent ESP inspection showed cell charts similar to this (very poor), the power to those cells is compromised and their efficiency at collecting particulate matter (PM) has diminished. © 2017 The Babcock & Wilcox Company. All rights reserved. 12
Old Boiler ESP Rebuilds Utilized Wires and Weights – Today’s Rebuilds Use Rigid Discharge Electrodes (RDE) © 2017 The Babcock & Wilcox Company. All rights reserved. 13
Before ESP Rebuild 21, 600 ft 2 of CE Surface After ESP Rebuilding “in-kind” with weighted wires would improve power (efficiency) but is no longer done. Rigid electrodes are the superior technology. 21, 600 ft 2 of CE Surface © 2017 The Babcock & Wilcox Company. All rights reserved. 14
Before ESP Rebuild 21, 600 ft 2 of CE Surface After ESP Rebuilding with rigid electrodes at 12 in. spacing, as opposed to the weighted wire design at 9 in. – less gas passages, less collecting surfaces 16, 200 ft 2 of CE Surface © 2017 The Babcock & Wilcox Company. All rights reserved. 15
But how can rebuilding an ESP with rigid electrodes and progressively less collecting plate area have the same collection efficiency as a new weighted wire rebuild? © 2017 The Babcock & Wilcox Company. All rights reserved. 16
Before ESP Rebuild 21, 600 ft 2 of CE Surface After ESP Rebuild Or better yet, rebuilding with rigid electrodes at 15. 75 in. spacing, as opposed to the weighted wire design at 9 in. – even less collecting surface 11, 880 ft 2 of CE Surface © 2017 The Babcock & Wilcox Company. All rights reserved. 17
The Answer Rests in the Amount of Power Delivered to Each ft 2 of Collecting Plate in the Rebuild ORIGINAL IS AN OUTLET FIELD ON A 2 CHAMBER RECOVERY BOILER ESP WITH 40 GP ON 9" SPACING WITH WEIGHTED WIRE. GAS VOLUME IS 486, 000 ACFM. ESP CONFIGURATION CONDITION WW, 9", CONV. RDE, 12", CONV. RDE, 16", CONV. u. A/FT 2 69. 4 67. 9 71. 5 AREA 21600. 0 16200. 0 11880. 0 ESP POWER SUPPLY NO. OF GAS PASS VOLT 40 9 400 30 12 400 23 15. 75 400 AMP 240. 0 236. 0 243. 1 MA 1500 1100 850 KV 45 60 80 DENSITY KVA 96. 0 94. 4 97. 2 KW 67. 5 66 68 W/FT 2 3. 1 4. 1 5. 7 The above table shows theoretical size of the conventional power supply required for each rebuild scenario. Note that the input power remains relatively the same (approximately 96 KVA) but the amount of power in the ESP on each ft 2 of collecting plate increases proportionately. Conventional Transformer Rectifier Set © 2017 The Babcock & Wilcox Company. All rights reserved. 18
One Exception to Wide Plate Spacing 1. Unlike a coal-fired utility boiler ESP, a recovery boiler ESP sees a much higher dust loading at the inlet with a much finer size distribution 2. This characteristic produces a condition called “space charge” and renders 15. 75 in. gas passages in the inlet field prohibitive. If 15. 75 in. is used in the rest of the ESP (it is a very sound approach), then the first mechanical field will need to utilize 12 in. gas passages. 3. Last, because of the space charge, a very aggressive high voltage electrode must be used in the first mechanical field (see v-pin electrode at right). © 2017 The Babcock & Wilcox Company. All rights reserved. 19
How to Get Even Lower PM Emissions 1. Remember, collection efficiency is related to the size of the ESP and the total internal power (KW). 2. The new era of ESP power supplies utilizes a low ripple, almost DC waveform that increases ESP power by 25 to 35%. 3. More power in means less dust out. Often times 25 to 50% less outlet emissions High Frequency Power Supply (HFPS) Three-Phase Power Supply (TPPS) © 2017 The Babcock & Wilcox Company. All rights reserved. 20
Single Phase = Conventional TR Set Secondary Current 1. It produced an ESP DC waveform for current and voltage that looked like this. Peak 2. Because the wave does not cross zero (change polarity), it is DC and not AC. Min Secondary Voltage Peak 3. It is said to have a lot of “ripple” (35 to 45%) True DC: © 2017 The Babcock & Wilcox Company. All rights reserved. 21
High Frequency Power Supply (HFPS) Secondary Current 1. Over the last decade, a lot of conventional ESP TR sets have been replaced with power supplies that provide a more true DC (very little ripple [<1%] in the waveform). Peak 2. Their advantage is more output power. Secondary Voltage 3. More ESP power equates to higher collection efficiencies. True DC: © 2017 The Babcock & Wilcox Company. All rights reserved. 22
3 -Phase Power Supply (TPPS) 1. Since the 1960 s, the Europeans have been using 3 -phase power supplies on ESPs to reduce waveform ripple (0. 5 to 1. 5%) and increase total power. Secondary Current Peak 2. Their advantage is higher output power, almost as high as the HFPS, but with a higher reliability than a HFPS Secondary Voltage True DC: © 2017 The Babcock & Wilcox Company. All rights reserved. 23
Single Phase = Conventional TR Set Higher Power – How? Secondary Current Peak 1. Sparking in the ESP is relative to the peak value of the secondary voltage waveform. 2. The 3 -phase and the switch mode allow you to run at that peak voltage value. 3. That is why they produce more ESP current for the same peak voltage than a single-phase transformer can Min Secondary Voltage Peak True DC: © 2017 The Babcock & Wilcox Company. All rights reserved. 24
Although the Low Ripple Devices are More Efficient, They Still Will Require More Station Power ORIGINAL IS AN OUTLET FIELD ON A 2 CHAMBER RECOVERY BOILER ESP WITH 40 GP ON 9" SPACING WITH WEIGHTED WIRE. GAS VOLUME IS 486, 000 ACFM. ESP CONFIGURATION ESP POWER SUPPLY DENSITY CONDITION u. A/FT 2 AREA NO. OF GAS PASS VOLT AMP MA KV KVA KW W/FT 2 WW, 9", CONV. 69. 4 21600. 0 40 9 400 240. 0 1500 45 96. 0 67. 5 3. 1 RDE, 12", CONV. 67. 9 16200. 0 30 12 400 236. 0 1100 60 94. 4 66 4. 1 RDE, 16", CONV. 71. 5 11880. 0 23 15. 75 400 243. 1 850 80 97. 2 68 5. 7 WW, 9", LOW RIPPLE 69. 4 21600. 0 40 9 480 148. 2 1500 70 123. 2 105. 0 4. 9 RDE, 12", LOW RIPPLE 67. 9 16200. 0 30 12 480 139. 8 1100 90 116. 2 99. 0 6. 1 RDE, 16", LOW RIPPLE 71. 5 11880. 0 23 15. 75 480 120. 0 850 100 99. 8 85. 0 7. 2 NOTE: 100 KV IS THE LARGEST "STANDARD DESIGN" VOLTAGE RATING FOR A LOW RIPPLE POWER SUPPLY The above table shows theoretical size of the conventional and low ripple power supply required for each rebuild scenario. For roughly 25% more input power to the low ripple three-phase TR set, it will produce 50% more power out. © 2017 The Babcock & Wilcox Company. All rights reserved. 25
Advantages and Disadvantages of Low Ripple Power Supplies TPPS has lowest harmonic distortion, HFPS the highest HFPS is smaller and lighter than the TPPS HFPS controls are at the device, on the roof of the ESP and require their own cooling system. TPPS controls are separate, in the MCC room. TPPS is much more reliable HFPS is slightly more electrically efficient © 2017 The Babcock & Wilcox Company. All rights reserved. 26
Last Method to Increase ESP Collection Efficiency – Convert 1 Mechanical Field into 2 Electrical Fields © 2017 The Babcock & Wilcox Company. All rights reserved. 27
Re-Powering & Re-Sectionalizing to Increase ESP Efficiency Original = Poor Re-Powered = Very Good • 6 TR Sets • 6 Electrical Fields • 3 Mechanical Fields • 3 TR Sets • 3 Electrical Fields • 3 Mechanical Fields © 2017 The Babcock & Wilcox Company. All rights reserved. 28
Rebuild Utilizing 2 Electrical Fields Where Originally There Was Only 1 Gas Flow 2 Upper HV Frames © 2017 The Babcock & Wilcox Company. All rights reserved. 29
John A. Knapik Email: jaknapik@babcock. com Phone: 440 -666 -3876 DISCLAIMER The Babcock & Wilcox Company (B&W) assumes no liability or responsibility with respect to the use of, or for damages resulting from the use of, any information, methods, processes, or recommendations provided in this presentation. B&W expressly excludes and disclaims any and all warranties, whether expressed or implied, which might arise or apply under law or equity or custom or usage of trade, including, without limitation, any warranties of merchantability and/or fitness for a particular or intended purpose. © 2017 The Babcock & Wilcox Company. All rights reserved. 30
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