P.C. Looy

Preliminary pilot plant tests of a corona discharge-electron beam hybrid combustion flue gas cleaning system

Pilot power plant tests of a corona discharge-electron beam hybrid combustion flow gas cleaning system have been conducted. Gas flow rate of the test loop is a heavy oil fired boiler flue gas with 1200 Nm/sup 3//h, and one electron beam generator (500 kV/spl times/30 mA) is used with a corona discharge ammonia radical injection system (60 kV/spl times/5 mA), SO/sub 2/, CO, CO/sub 2/, NH/sub 3/, NO, NO/sub x/ and O/sub 2/ gases are monitored. The results show that up to 85% of NO/sub x/ and 98% of SO/sub x/ in flue gases are removed under a corona discharge-electron beam hybrid operations with significant small amount of leaked ammonias from exhaust flue gases.

Collection efficiency of ultrafine particles by an electrostatic precipitator under DC and pulse operating modes

High particle collection efficiency in terms of particle weight volume mg/m/sup 3/ is well achieved by a conventional electrostatic precipitator (ESP). However, the collection efficiencies in terms of number density for the ultrafine (particle size between 0.01 to 0.1 /spl mu/m) or submicron particles by a conventional ESP are still relatively low. Therefore, it is necessary to improve the collection efficiency for ultrafine particles. In this work, attempts have been made to improve the ultrafine particle collection efficiency using the short pulse energizations. The present version of ESP consists of three sets of wire plate type electrodes. For ESP under DC operation modes, experimental results show that the collection efficiency for DC applied voltage decreases with increasing dust loading when particle density is larger than 2.5/spl times/10/sup 10/ part/m/sup 3/. For ESP under pulse operating modes, the particle collection efficiency increases with increasing pulse peak voltage until 25 kV then decreases with increasing pulse peak voltage. The ultrafine particle collection efficiency based on particle density by DC energizations is much higher compared with pulse energizations without DC bias may be due to the reentrainments of ultrafine particles.

Mercury and other trace elements removal characteristics of DC and pulse energized electrostatic precipitator

Removal of zinc rich ash and mercury from gas stream using electrostatic precipitators has been investigated. Dust particles collected from Mastsuyama municipal incineration plant thermal plasma ash volume reduction system were used to study the performance of ESP to collect zinc rich ash. The ash was analyzed by neutron activation analysis (NAA) using the McMaster Nuclear Reactor. Collection efficiency as high as 99.9% was obtained in the removal of Zn from the flue gas with DC energization of the ESP. The mercury concentration was measured using a cold vapor atomic absorption spectrometer (CV-AAS) after sampling (OSHA-140 method) from the flue gas stream. As a function of concentration, the mercury collection efficiency was higher at higher concentration of mercury. Higher collection efficiency was obtained under negative DC energization compared to other modes of energization of the ESP; however, power consumption under pulse application was much smaller compared to DC energization.

Semipilot plant pulse energized cold-precharger electrostatic precipitator tests for collection of moderately high resistivity flyash particles

The performance of an electrostatic precipitator (ESP) to collect moderately high resistivity flyash has been tested under pulse/precharger energization using the semipilot scale integrated electrostatics combustion flue gas (IECFG) cleaning system at Ontario Hydros 640 MJ/h Combustion Research Facility Center. The pulse energization enhanced the performance of the existing de-energized wire-plate electrostatic precipitator in collecting moderately high resistivity (/spl rho//spl sim/10/sup 10/ /spl Omega//spl middot/cm) flyash. A 26% improvement in particle collection efficiency and 30% energy saving were obtained with pulse energization, with moderately high resistivity flyash generated by burning high-sulfur (3.7%) Nova Scotia coal with limestone conditioning. The cold precharger specially designed to suit the three-stage wire-plate ESP has also been tested for its ability to improve the performance of ESP in reducing the back corona. With an additional 30% of energy supplied to the precharger it was possible to obtain up to 40% enhancement in collection efficiency. In general an enhancement factor of 1.8-2.8 was obtained with dust loading /spl sim/2 g/m/sup 3/. A thyratron switched pulse power supply was used for the ESP.

Reduction of NO/sub x/ from a combustion flue gas by a corona radical injection method

An experimental investigation has been conducted concerning the reduction of NO/sub x/ from combustion flue gases by means of corona radical injection methods. Corona discharge is generated by sharp hollow electrodes in the edge of the ceramic cylindrical tubes with grounded ring electrode on the surface. Ar-NH/sub 3/ mixture gas is passed through the hollow electrode and is disassociated to form NH/sub x/ radicals in the corona discharge zone located in the center of the flue gas flow ducts. It is shown that the reduction rate of NO/sub x/ increases with increasing corona current, and nonmonotonically depends on the ammonia flow rate.<<ETX>>

Pilot plant tests of a corona discharge-electron beam hybrid combustion flue gas cleaning system

Pilot plant tests of a corona discharge-electron beam hybrid combustion flow gas cleaning system have been conducted. Gas flow rate of the test loop is a heavy oil fired boiler flue gas with 1200 m/sup 3/N/h, and one electron beam generator (500 kV/spl times/30 mA) is used with a corona discharge ammonia radical injection system (60 kV/spl times/5 mA). SO/sub 2/, CO, CO/sub 2/, NH/sub 3/, NO, NO/sub x/ and O/sub 2/ gases are monitored. The results show that up to 85% of NO/sub x/ and 98% of SO/sub x/ in flue gases are removed under a corona discharge-electron beam hybrid operations with significant small amount of leaked ammonias.<<ETX>>

Modelling of quadrupole cold precharger dust particle charging characteristics

A model to predict dust particle charging characteristics in a quadrupole cold precharger is developed. The space-averaged ion density and electric field are shown to increase with increasing applied voltage or discharge current. The predicted dust particle charging characteristics agree well with simulated experiments within a factor of two for cold precharger operation after onset of corona discharges. The particle surface charge observed in the experiment increases with increasing applied voltage and agrees qualitatively well with the present model.<<ETX>>

Pulse power energization effects on ESP efficiency in collection of high resistivity flyash particles

A novel pulse module for enhancing electrostatic precipitator (ESP) performance has been developed and tested using Ontario Hydros 640 MJ/h Combustion Research Facility. The pulse energization enhanced the performance of the existing DC energized wire-plate ESP by suppressing back corona in collecting high-resistivity flyash (>or=10/sup 10/ Omega -cm). A 26% improvement in particle collection efficiency and a 30% energy saving were obtained with pulse energization in collecting high-resistivity, high-sulfur (3.7%) Nova Scotia coal flyash injected with limestone-water slurry as sorbent. The cold precharger specially designed for the three-stage wire-plate ESP has been tested for its ability to improve the ESPs performance in reducing the back corona. With an additional 30% energy supplied to the precharger it was possible to obtain up to a 40% enhancement in collection efficiency.<<ETX>>

Reduction of NOx and SOx from Combustion Flue Gases by a Corona Discharge-Electron Beam Hybrid System

The NOX and SOX emissions are the major cause of acid rain. The CO2 and CH4 emissions cause a greenhouse effect which leads to abnormal global heating of the atmosphere and can create a temperature inversion layer that traps pollutants. There is a vital interest in controlling these emissions — in the near term for acid rain and in the long term for the greenhouse effect.

Characterization of limestone-water slurry droplets generated by electrohydrodynamic atomization

High voltage DC electrohydrodynamic atomization characteristics of limestone-water slurries have been investigated experimentally using a hollow needle electrode nozzle. The results show that both the spray angle and the dispersion of the slurry droplets increases with increasing applied voltage. The mean diameter of the droplets decreases with increasing applied voltage. The results also seem to indicate that the applied voltage may also decrease the slurry flow rate from the nozzle in the present gravitationally fed system.<<ETX>>