Fine Particle and Mist Removal by a wet ESP using 1.5 L/min/m 2 of water for Oxygen- Pulverized Coal Combustion

Transcription

1 Fine Particle and Mist Removal by a wet ESP using 1.5 L/min/m 2 of water for Oxygen- Pulverized Coal Combustion Bangwoo Han (bhan@kimm.re.kr) Hak-Joon Kim, Bangwoo Han, Yong-Jin Kim Korea Institute of Machinery and Materials (KIMM)

2 Contents I Introduction II Experiments III Results and Discussion IV Conclusion 2/19

3 Backgrounds - Global warming & Climate change Carbon dioxide (CO 2 ) emission Global temperature increase Most of the countries promised to reduce the greenhouse gas with the Kyoto Protocol. The Korea announced to reduce 30% of the greenhouse gas until 2020 at the 15 th United Nations Climate Change Conference. 3/19

4 Backgrounds - Oxygen-Pulverized coal combustion power plant desox depm deh 2 O & SOx - Concept of the Oxy-PC combustion and CCS (Carbon Capture and Storage) - For the successful development of the Oxy-PC combustion and CO 2 storage, highly efficient gas cleaning technology, specially for de-sox and de-pm, becomes also very important. 4/19

5 Backgrounds - Technical demands of gas cleaning for CCS Refer to Alstom development of oxyfuel PC and CFB power plants, 1 st Oxyfuel combustion conference (2009) 1-2 mg/nm 3 Target 5/19

6 Motivation - Technical limit of a current ESP for particle removal Current dry ESP Fine particles (Re-entrainment) Re-entrainment during rapping Flow direction Rapping periodically Current wet ESP Spraying a lot of water periodically Coarse particles Re-entrainment Efficiency decrease during rapping Efficiency decreases Conc. of10 mg/m 3 could not be guaranteed with current dry ESPs. A state of the art ESP technology for super low particle emission is necessary for CCS. 6/19

7 Purpose of this study 1 We investigated on changes of electrical and particle collection performance of ESPs in oxygen-co 2 combustion conditions and operation parameters of the ESPs, using a 0.7 MW oxy-pc combustion pilot plant. 2 We also developed a novel wet type ESP and combined with the conventional dry ESP to remove particles from Oxy-PC combustion near to 1-2 mg/m 3. To fully understand the performance of ESPs with real flue gas from Oxy-PC combustion. 7/19

8 0.7 MW pilot system for Oxy-PC Combustion Wet ESP Dry ESP Heat Exchanger Oxy-PC Boiler Flue Gas Condenser (FGC) Oxy-PC boiler Dry ESP Heat Exchanger Flue gas condenser Wet ESP CPU. Flue gas condenser comprised of water sprays and bath was used to partially remove water vapor in flue gas. 8/19

9 Diagram of our experiment * 질량측정방식의경우, 제 3 기관에의뢰하여광산란측정과동시에진행하였음. 3 Particle size distributions were measured with an on-site optical particle counter (1.109, Grimm) and off-site laser scattering particle size analyzer (Sympatec) Measurement of particle concentration based on total mass was also done using the EPA method 5. 9/19

10 Size distributions of dusts-air & Oxy with infurnace desox Off-Site method On- Site method The particle size distributions were similar regardless of the combustion mode of air or oxygen and the measurement method of on-site or off-site. both of the mode diameters were near to 2-3 mm. 10/19

11 Resistivity of dusts - Air & Oxy with infurnace desox Very similar Operation temperature 11/19

12 Dry ESP - Electrical characteristics with different combustion modes Corona current decreases with Oxy mode Corona current increased by temperature increase due to higher mobility of ions. Corona current decreased with oxy mode where CO 2 concentration was over 80% in the flue gas at the same applied voltage compared to air mode. Ionization energy of CO 2 is high and mobility of ions in CO 2 is low. 12/19

13 Dry ESP - Collection characteristics with different combustion modes EPA method 5 Optical particle counter The efficiencies were dependent on power consumption (=Voltage 2 ) regardless of the gas composition because the particles generated from the coal combustion are coarse which are not affected by gas composition. 13/19

14 Wet ESP - Basic concept - Concept of a wet ESP with water films on collection plates in this study - - Technical problem for making water film - High surface tension by hydrogen bonds Wet area - Uniform thin water film The wet ESP in this study has thin water films on collection plates, not spraying water onto the collection plates. To make a uniform film and minimize water consumption, we used surface treatments such as ball-blasting and coating with nano particles on the collection plates 14/19

15 Thin water film with water less than 1 L/min/m 2 - Thin water film on 3 m x 1 m plates - 15/19

16 Wet ESP - Electrical characteristic - Wet ESP in this study - - Electrical characteristics - Corona current of wet ESP decreased with oxy mode as similarly as dry ESP. Ionization energy of CO 2 is high and the mobility of ions in CO 2 is low. 16/19

17 Wet ESP - Collection characteristic - Size distributions before/after wet ESP - - Collection efficiency - Submicron particle size region The wet ESP was highly effective to remove particles for submicron particles size range (~95%). The particle collection efficiency was increased with power consumption. The ESP consumed water of only 1.5 lpm/m 2. 17/19

18 Final gas cleaning performance of ESPs Particle removal by dry and wet ESPs Gas removal By wet ESP Sampling location and number of measurements Dust concentration (mg/sm 3 ) #1 25,029.3 Before dry ESP #2 20,521.5 #3 10,903.0 #4 15,974.3 #1 3.7 After Wet ESP #2 2.5 #3 1.7 #4 1.4 With combination of dry and wet ESPs, we achieved particle concentrations near to 1-2 mg/nm 3. The wet ESP had gas removal performance because the ESP could remove partially sulfuric acid mists which were converted from SO 2 and SO 3 by a temperature drop at the flue gas condenser. 18/19

19 Conclusion We evaluated dry and wet ESPs for a 0.7 MW Oxy-PC combustion pilot plant at different air and oxygen modes and power consumption of the ESPs. Corona current with oxy mode decreased at the same applied voltage as air mode. The efficiency of the ESP was dependent on power consumption (=voltage 2 ) regardless of its mode of air or oxygen The ESP at oxy mode needs more higher applied voltage or larger ESP size (volume) compared to that at air mode to obtain similar particle collection efficiency. We developed a wet ESP with thin water films on the collection plates and with a water consumption of 1.5 L/min/m 2. With the wet ESP, the final concentration of 1-2 mg/nm 3 (Efficiency, 99.99%) was achieved in a 0.7 MW Oxy-PC combustion pilot plant. 19/19

20 Thanks for listening! 20/19