Flue Gas Particle Characterization at Different Parts of the Power Plant

Transcription

1 Flue Gas Particle Characterization at Different Parts of the Power Plant Ville Niemelä, Erkki Lamminen Dekati Ltd., Tampere, Finland A&WMA International Specialty Conference: Leapfrogging Opportunities for Air Quality Improvement May 10-14, 2010, Xi an, China

2 Introduction Power plants and coal combustion are major sources for fine particles This work focuses on particle measurements at power plant Particle characterization at plant allows Understanding particle formation and transformation Optimization of combustion process Optimization and control of cleaning systems

3 In this work we present: Sampling system for power plant flue gas PM measurements Sample dilution in different locations of the plant Controlled sample cooling and VOC control Measurement system for power plant PM measurements Particle concentration and size measurement at power plant environment Results for Particle concentration and size distribution in the flame, after heat exchangers and after baghouse filter Discussion Size distribution change Effect of baghouse filter cleaning system About PM transformation

4 Method 1: Sampling Temperature controlled probe Heated and cooled with pressurised air, 200 C Austenitic stainless steel for high temp measurement P and T measurement after probe Heated sampling line, 200 C DEED Two-stage dilution system ELPI Heated SS sampling line 200 c DEED PA T Dilution air heater and temperature controller, 200 C P STACK Control / removal of VOC and water

5 Method 2: Dilution with DEED Three-stage dilution: Heated dilution stage 1:10 reduces gaseous VOC concentration without condensation Evaporation tube at 350 C evaporates already condensed VOCs Cold dilution stage 1:10 cools down the sample without condensation (Extra 1:10 dilution stage on/off) Inlet (sample from CVS) 2.5 micron cyclone (optional) Pre-diluter with dilution ratio of 1 or 10 (OFF or ON) First dilution stage (PND 1) with dilution ratio of 10 Dilution at 150 C Evaporation tube (ET) 350 C Outlet (sample to ELPI) Second dilution stage (PND 2) with dilution ratio of 10 Dilution at ambient temperature

6 DEED Offers Two or three dilution stages plus evaporation tube High dilution ratios: 1:100 and 1:1000 Controlled sample cooling with low losses Heated 1st stage and evaporation tube prevent VOC and other volatile material condensation

7 Method 3: PM characterization with ELPI

8 ELPI offers Real-time particle size distribution 0.007/ µm Real-time number concentration, estimation for mass Wide dynamic range - from ambient concentrations up to power plant levels Particles are collected - option for size-selected chemical /physical analysis Option for particle charge level measurements (ESP studies)

9 Measurements: 4 MW pilot power plant in Finland Circulating Fluidised Bed combustion Wood pellets Baghouse filter Measurement locations: Right after the flame, T=800 C After heat exchangers, T=200 C After baghouse filter

10 Measurements

11 Results 1: PM concentration Number concentration Mass concentration Number concentration [1/cm3] 4.0E E E E E E E E E Hot Cool Mass concentration [mg/m3] Hot Cool Time [s] Time [s] Flame (hot location) has lower number concentration Mass concentration is the same Effect of soot blowing decrease number, increase in mass (fine particle washout)

12 Results 2: PM size distribution Number Mass Surface area dn/dlogdp [1/cm3] 4.0E E E E E E E E E+00 Hot Cool Soot blowing dm/dlogdp [mg/m3] Hot Cool Soot blowing da/dlogdp [µm²/cm³] 1.2E E E E E E E+00 Hot Cool Soot blowing dp [um] dp [um] dp [um] Increase in number-based size (and concentration) when T decreases dominated by small particles Mass distribution (coarse particles) remains the same except during soot blowing Bi-modal distribution (seen in surface area)

13 Results 3: Baghouse filter 4.0E+07 Baghouse filter 120 Filtration efficiency dn/dlogdp [1/cm3] 3.5E E E E E E E+06 Before filter After filter Filtration efficiency [%] Filtration efficiency 0.0E dp [um] dp [um] Efficiency 90% for number, 92% for mass Drop in efficiency at about 100 nm Concentration after the filter 10.8 mg/m 3

14 Discussion Reason for small particle size change Condensation? Agglomeration? Further chemical and SEM / TEM analysis possible

15 Conclusions A system capable of measuring PM size distribution and concentration in real time at different parts of the power plant anywhere from the flame to the flue gas exit Measurement shows clear change in particle size distribution when flue gas temperature decreases Size-resolved filtration efficiency for flue gas cleaning system

16 Thank you for your attention!