Todd R. Snyder

Laboratory analyses of corona discharges

Abstract An experimental research program was conducted to characterize corona generation from different electrode geometries in a range of conditions comparable to those found in electrostatic precipitators. A wire-parallel plate device and a wire-cylinder device were used to monitor the spatial distribution and temporal stability of corona discharges. Visual observations of corona phenomena were made with a sensitive video camera. Conditions that were varied in the experiments included temperature, corona electrode design, corona polarity, and method of energization. Measurements of the distributions of corona current and statistical analyses permit an assessment of the impact of corona electrode design on electrostatic precipitator performance. A description of the laboratory apparatus and a summary of experimental results is included.

Effects of Sorbent Injection on Particulate Properties: Part II. High-Temperature Sorbent Injection

Abstract This article is the first of a two-part series dealing with the effects of sorbent injection processes on particulate properties. Part I reviews the effects on particulate properties of low-temperature sorbent injection processes (those processes that treat flue gas at temperatures near 300 °F). Part II reviews the effects on particulate properties of high-temperature sorbent injection processes (those processes that involve sorbent injection into the combustion or economizer sections of a boiler). In this article, we review what is currently known about the effects of the low-temperature sorbent injection processes on electrical resistivity, particulate mass loading, particulate size distribution, particulate morphology and cohesivity. Mixtures of ash and sorbent produced by low-temperature sorbent injection processes are typically less cohesive than most types of fly ash. At temperatures within 30 °F of the water dew point, the combination of low cohesivity and low electrical resistivity of the...

Determination of Baghouse Performance from Coal and Ash Properties: Part I

Baghouse performance at utility coal-fired power plants is determined by baghouse design, operating procedures, and the characteristics of the ash that is collected as a dustcake on the fabric filter. The Electric Power Research Institute has conducted laboratory research to identify the fundamental properties of dustcake ash that influence baghouse performance. A database was assembled including measured characteristics of dustcake ash and data describing operating parameters and performance of full-scale and pilot-scale baghouses. Semi-empirical models were developed that describe the effects of particle morphology, particle size, ash cohesivity and ash chemistry on filtering pressure drop and particulate emissions. Cohesivity was identified as the primary ash characteristic affecting baghouse performance. Predictions of performance can be based on physical or chemical characterizations of the ash to be filtered. Part II of this article will discuss the effects of ash and coal chemistry, and baghouse de...

Laboratory analysis of back-corona discharge

Abstract An experimental research program was designed and performed to characterize back-corona generation and behaviour in a range of environments and geometries common to electrostatic precipitators (ESPs). A wire-parallel plate device was utilized to monitor the intensity and distribution of back-corona discharges. Back-corona was generated by subjecting a deposited layer of fly ash to corona current. Visual observations of back-corona emissions were made with a sensitive video camera. These observations provided new insight into the characteristics of back-corona phenomena. Conditions that were varied in the experiments included ash resistivity, corona electrode design, corona polarity, and ash-layer thickness and surface condition. The effect of pulsed energization on back-corona was also studied. Analyses of visual observations and measured distributions of corona- and back-corona current allowed an assessment of the effects of back-corona emissions on ESP-operating parameters.

Filtration Properties of Fly Ash from Fluidized Bed Combustion

Some of the features of the fluidized-bed combustion (FBC) process have a direct bearing on the particulate properties that most strongly influence filtering pressure drop. A laboratory program was conducted to experimentally determine the relative pressure drop characteristics of ashes from the TVA-EPRI 20-MW bubbling bed, atmospheric pressure FBC (AFBC) pilot plant and six pulverized-coal combustion (PC) units. The combined influences of measured particle and dust cake properties on filtering pressure drop were estimated with existing filtration theories. These theories predict a higher pressure drop for a dust cake produced with the AFBC ash than for one consisting of any of the PC ashes. Laboratory measurements were made of the flow resistance of idealized, simulated dust cakes to confirm these predictions. Field operating data from the fabric filters collecting some of the tested ashes were available to validate the laboratory results. The laboratory and field data show relatively good agreement. The...