Abstract
First the theoretical basis for the demand of uniform gas distribution will be discussed.  Then the parameters influencing the precipitator efficiency are weighted with respect to the gas distribution, such as mean gas velocity, current density, current capsizing, sneakage, reentrainment, secondary flow and falling dust lumps.  The merits of the so-called skew distribution as claimed by various schools will be looked upon and examples from the field illustrating the possible advantages and disadvantage of a skew distribution will be revealed.  Furthermore, the different opinions on the "best" gas distribution will be critically commented upon and it will be claimed that too rigid attitudes to the quality of the cold air distribution quality are not justified.

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The paper presents the research upon the gas distribution in a physical model and the computer simulation of dust separation in a horizontal electrostatic precipitator with a flat inlet diffuser.  The research of a gas flow were carried out using the visualization method and the velocity measurement in cross sections of a chamber of the model.  By selecting suitable choking diffusion screens and deflecting vanes in a diffuser the oblique profiles of a gas velocity were obtained for different obliqueness degree.  One assumed that the velocity profiles obtained should guarantee higher performance of an ESP than those uniform profiles as used so far.  Those assumptions were proved by the results of computer simulation obtained using a program SYMULA-X.  The results of experiments and computer simulation are presented in a graphical form.

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Abstract
ATCO Power's Battle River Generating Station reduces unit output (derating) as a method of last resort to stay within the in-stack opacity limits required under its environmental approval.  Operating records indicate that the 375MW Unit 5 was derated by an average of 38 GWh per year due to high in-stack opacity.  These derated were caused by a combination of precipitator problems and coal quality.  Various precipitator upgrades were considered in order to decrease the amount of lost generation.  Options included replacing emitter wires, upgrading the controllers, and the installation of positive isolation to allow for "hot suit entry" repairs.  Skewed Gas Flow Technology (SGFT) was eventually selected and modifications were made to half of the twin-casing precipitators during the August 2000 shutdown.  As Unit 5 is equipped with two identical mirror image precipitator casings, this installation presented an ideal opportunity to evaluate the effectiveness of SGFT.  The evaluation consisted of three parts: before and after airflow measurements, duct and stack opacity monitoring, and simultaneous inlet and outlet dust loading tests.  The results of these tests show that the modified casing now produces opacity readings at the outlet that are 40% lower than those seen at the outlet of the unmodified casing.  The dust loading tests indicate an improvement of 27.5% in collection efficiency due to the installation of SGFT, based on the assumption of equality of the twin precipitator casings prior to the installation.  This paper includes a technical review and evaluation of the SGFT installation at Battle River Unit 5, as well as the rationale used to provide the initial economic justification.

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Abstract
Israel Electric Corp (IEC) owns and operates four 350 MW coal fired generating units at the MD-A station near Hadera, Israel.  IEC decided to implement Skewed Gas Flow Technology (DGFT) to improve precipitator performance and reduce the amount of conditioning agent require.
IEC chose to install SGFT in one chamber of a two-chambered precipitator and evaluate its performance before converting the other units.  The desired skewed gas flow profiles were achieved by modifying the inlet distribution screen and replacing the outlet screen.  Rigorous performance tests were conducted on both chambers on six days over a two week period and showed that SGFT had reduced particulate emissions by over 50%.
Based on these results, IEC proceeded to implement SGFT in their other units.  To date, SGFT has been installed in all four nits,  Performance tests made before and after the installation on the third unit again confirmed the SGFT reduced emissions by haft.
This paper examines the flow profiles before and after the modifications made to achieve SGFT and Presents the corresponding performance test resuts.

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