Recent Measurements of ISP Concentration, Size, and Chemistry in a Recovery Boiler

Transcription

1 Recent Measurements of ISP Concentration, Size, and Chemistry in a Recovery Boiler Chris Shaddix Sandia National Labs Livermore, CA Don Holve Process Metrix San Ramon, CA and Rick Wessel Babcock & Wilcox Barberton, OH Colloquium on Black Liquor Combustion and Gasification Park City, UT May 15, 2003

2 Background and Motivation roles of carryover and fume to deposit formation and pluggage of superheater and convection pass fairly well established magnitude of problem of intermediate size particles (~ µm) unclear ISPs difficult to quantify (size and concentration) in fume-laden flow ISP formation routes and chemistry unclear microscopic examination of deposit cross-sections necessary to evaluate end effect previous sampling at Weyerhaeuser Longview boiler showed small concentrations of ISP in convection pass, but significant levels at superheater entrance desire data for comparison at superheater entrance, at more modern, less-burdened boiler (IP RB#3, Courtland, Alabama)

3 Courtland Measurement Campaign Aug 13 16, 2002 measurements performed: water-cooled pitot tube/thermocouple probe fume mass extractive probe virtual cyclone sampling probe (for ISP) PCSV laser scattering for in situ ISP measurement (PMC) impaction disk sampling of particulate (optical/sem microscopy) laser-induced breakdown spectroscopy (LIBS) for in situ measurement of particulate chemistry IR camera deposit imaging (Diamond Power) air duct profiling and liquor and fly ash chemistry (MTI) strain gauge measurements of deposit mass growth (IP) all sampling probes (other than fume probe) used at maintenance beam doors (front wall, 3 feet above nose arch)

4 IP Courtland Recovery #3 Operation Aug Firing Rate Virgin DS Flow Rate Heat Input per Plan Area 93% MCR (Manuf. Continuous Rating) lb/day (1,761 t/day) Btu/ft 2 -hr (2.65 MW t /m 2 ) Liquor Delivery Nozzle Arrangement BL Solids Content BL Temperature Nozzle Pressure Air Delivery Total Air Flow Air Flow Distribution Boiler Steam Steam Flow rate Steam Temperature Steam Pressure 4 B&W Splash Plate Nozzles One nozzle centered on each wall 70.6% 260ºF (127ºC) 17 psig (117 kpa) B&W 3-level Air system 740,000 lb/hr (335,600 kg/hr) Pri 38.3%, Sec 35.4%, Ter 26.3% Single-Drum Design 530,000 lb/hr (240,400 kg/hr) 900ºF (482ºC) 1270 psig (8.756 MPa)

5 Liquor and Fly Ash Analysis Virgin Liquor As-Fired Liquor Dry solids (%) HHV (Btu/lb d.s.) wt% d.s. wt% d.s. Total S Sulfate C H N Na K Cl ESP ash wt% in ash EF Na 27.8 K Cl Sulfate 58.8 Carbonate 2.9

6 Maintenance Beam Level modified doorway with open sampling port Overview of maintenance beam level on front wall (before removal of two of the beams) PCSV probe entering port LIBS probe inserted into port Sampling occurred through near-center and near-right doorways

7 Temperature and Velocity Measurements Temperature ( C) m depth 1-m depth Vertical Velocity (m/s) m depth 1-m depth Time (s) Time (s) Notes: mean temperature is ~ 960 deg C at maintenance beam level mean velocity is 9 m/s at 1-m depth and 11 m/s at 2-m depth standard deviation of velocity is m/s in vertical direction and m/s in horizontal plane (ignoring direct sootblower influence) Horizontal Velocity (m/s) sootblowers activated in 1st SH Time (s) 140

8 Fume Mass Concentration H 2O fume samples collected on 10th floor (upper furnace), through inspection ports N 2 -purged probe provided ~ 3:1 dilution limited cooling water flow restricted probe penetration and sample time probe operated non-isokinetically, to discriminate against ISP critical flow orifice sampling system recorded instantaneous gas sampling rate filter mass collection verified through both gravimetric and filter wash analysis inner probe deposition measured through probe wash analysis 3 m Schematic of sampling probe H 2O in Result: Fume concentration = g/nm 3 Photo of exposed and fresh filters

9 Virtual Impaction Sampling Probe new design for aerodynamically separating ISP from fume filter observed to rapidly plug operation of annular pump induces lower sample suction than purge most of purge pulled into annulus SEM on filter samples shows predominantly fume assumption of constant purge loss allows estimation of total particle concentration Result: Total collected particulate concentration ~ g/nm 3 fume-laden bulk flow N2 N2-diluted ISP design concept of sampling probe SEM of particles on collection filter

10 Light Scattering Measurement of ISP PCSV measures near-forward light scattering from low-power, 670 nm, cw laser interprets with Mie theory; measurement geometry minimizes sensitivity to particle shape or optical properties measures particle sizes, speed, and concentration for boiler sampling, implemented in 3 OD optical probe that fits within 3.75 OD water-jacket for recovery boiler application, est. ISP mass uncertainty ~ 30% Focusing lens Illumination laser Particle flow field Scattered light Receiver lens PCSV operating principle Transmitted beam photo of boiler optical probe Mask Fiber coupling to detector Beam stop Slit

11 ISP Size Distribution PCSV Data dn/dlnd (1/cm 3 ) dm/dlnd (g/m 3 ) PCSV 'data' points exponential fit median dataset from Longview boiler diameter (µm) diameter (µm) particle number density distribution particle mass distribution Notes: all data are 4 5 min. averages PCSV results similar for two sample ports and 1-m and 2-m insertion depths, and for various locations of active sootblowers dual-beam PCSV captures back-side of fume concentration peak ISP size distributions similar to Longview boiler perhaps more ISP here for large sizes

12 Mass Concentration of ISPs at Courtland (from PCSV) 4 Mass Concentration (g/nm 3 ) range of values at Longview thermoprobe port 0 12:00 PM 8/14/2002 1:00 PM 2:00 PM 3:00 PM 4:00 PM 5:00 PM Time Total mass concentration of ISPs ~ same at Courtland and Longview, though is quite variable over both short and intermediate time scales Fume mass from µm is steady at 0.8 ± 0.15 g/nm 3

13 ISP Mass and Superheater Deposit Buildup Mass Concentration (g/nm 3 ) SH#2 SH#1 SH# Strain (a.u.) 0 12:00 PM 8/14/2002 2:00 PM 4:00 PM Time 0.8 Only correlation appears to be for superheater #4 strain gauge may be fortuitous

14 Impaction Disk Measurements (30x Optical Microscopy) Courtland Longview

15 Analysis of Courtland Impaction Disks performed manual particle counting on optical microscopy images need to correct for size dependence of impaction efficiency calculate impaction efficiency from correlation for strips assume unity sticking efficiency on fumecoated surface corrected impaction counting ISP concentration lower than PCSV by factor of 2 3 (seems reasonable) dm/dlnd (g/nm 3 ) diameter (µm) PCSV data fit impaction plate (mean) impaction correction (11 m/s) impaction correction (6 m/s) impaction correction (4 m/s)

16 ISP Particle Chemistry Results from SEM-EDX EDX on Impaction Disks 1.0 Enrichment Factors (K and Cl) K Cl S Sulfidity, S/(Na 2 +K 2 ) Particle Size (µm) Similar depletions in K, Cl, and S with increasing size, up to ~ 100 µm

17 In Situ Particle Chemistry Sample Results from LIBS Measurements Emission Intensity (arb. units) C B Si Mn LIBS peak area (arb. units) Mn Si 200 B Wavelength (nm) time (minutes) shot (4-min.) average spectra in trace metal-rich 250 nm region single-shot time record of trace metal signals in 250 nm region difficulty of S detection with LIBS hinders differentiation between fume and ISP chemistry Investigated ISP detection via trace metals: single-shot trace metal detection possible with linear spectrometer/iccd system single-shot trace metal detection not possible with echelle cross-dispersion spectrometer system

18 Summary Extensive measurement campaign conducted at IP s Courtland recovery boiler #3 Fume mass loading in upper furnace found to be ~ 8 g/nm 3 ISP mass loading entering superheaters determined by PCSV to be g/nm 3, or ~ 4 45% of fume mass loading (similar to result at Weyerhaeuser Longview boiler) can confidently conclude that ISP contribute significantly to deposition in convection pass high variability in ISP concentrations suggests improved control is possible Correlation of ISP concentrations with strain gauge data evident for one of three SH sections SEM-EDX of impacted particles shows significant depletion of K, Cl, and S in larger ISP

19 Acknowledgments Mike Gregory and Andy Jones from International Paper Doug Scott, Dennis Morrison, Gil Hofacker, Sal Birtola, and Trey Cauley from Sandia Darren Garvis from Process Metrix Alarick Tavares from Diamond Power Ken Nichols and Bill Trout from Weyerheauser Co. Funding provided by DOE/OIT AF&PA Agenda2020 projects in Sensors & Control and Energy Performance