Electrostatic precipitator and gas sampling system

Claim 1

A gas sampling system for the removal of solid particles from a gas stream sampled from an ore reduction roaster for passage to a gas chromatography analysis unit, which system includes a sampling line adapted to be connected to such an ore reduction roaster for the passage through said sampling line of a gas stream laden with both coarse and finely divided solid particles a screen filter in said sampling line for the passage of said gas stream therethrough for the removal of coarse solid particles from said gas stream by said filter; an electrostatic precipitator for the removal of finely divided solid particles from said gas stream flowing from said screen filter; a transfer line interconnecting said screen filter and said electrostatic precipitator for the passage of a gas stream from said screen filter, after the removal of coarse solid particles therefrom by said screen filter, to said electrostatic precipitator; a gas chromatography unit; gas outlet means interconnecting said electrostatic precipitator and said gas chromatography unit for the flow of a gas stream from said electrostatic precipitator, after the removal of said finely divided solid particles from such a gas stream in said electrostatic precipitator; first valve means operatively associated with said transfer line for movement between open and closed positions for controlling the flow of a gas stream through said transfer line to said electrostatic precipitator; a gas supply line in gaseous communication with said transfer line upstream of said first valve means for the introduction into said transfer line of a blow-back gas; and second valve means operatively associated with said gas supply line for movement between open and closed positions for permitting the flow of blow-back gas when in said open position thereof through said gas supply line into said transfer line and, when in said closed position thereof, for preventing the flow of said gas stream froM said screen filter into said gas supply line, whereby said gas sampling system may be used with said first valve means in said open position thereof and with said second valve means in said closed position thereof to remove both coarse and finely divided solid particles from a gas stream sampled from an ore reduction roaster and to supply the resultingly cleaned gas stream through said gas outlet means to said gas chromatography unit, and whereby a blow-back gas may be introduced into said system through said gas supply line with said second valve means in said open position thereof and with said first valve means in said closed position to cause a reverse flow of gas through a part of said transfer line to said screen filter and then through said sampling line to dislodge solid particles from within said transfer and sampling lines and from said screen filter and to return resultingly dislodged solid particles to said reduction roaster; a sampling programmer for effecting intermittent analysis of gas samples supplied thereto and in which said first and second valve means are adapted to be operatively connected to such s sampling programmer for the control and automatic operation of said first and second valve means by such a sampling programmer for blow-back operation between successive analyses, said electrostatic precipitator comprising a closed housing with electrically conductive side walls and internally divided into an ionization chamber and a collector chamber by a partition extending downwardly into said housing but terminating upwardly of a floor of said housing to provide a dust collection chamber disposed downwardly of said ionization chamber and said collector chamber and through which said ionization chamber and said collector chamber are in gaseous communication with each other; an ionization electrode mounted in said ionization chamber on electrically insulating support means and comprising a wire formed into a plurality of interconnected stretches disposed transversely to the downward gas flow through said ionization chamber for gas flow around each said stretch of said wire; gas inlet means connected to said transfer line and communicating with said ionization chamber for the passage of a gas stream from said transfer line into said ionization chamber for downward flow therethrough into said dust collection chamber; high voltage electrical supply means electrically connected to said ionization electrode for the application thereto of a high electrical voltage relative to said electrically conductive side walls of said housing whereby electrical discharge from said ionization electrode causes dust particles in a gas stream flowing through said ionization chamber to become electrically charged; a collector electrode mounted in said collector chamber on electrically insulated support means and comprising a plate extending upwardly within said collector chamber for the passage of a gas stream along both faces thereof and having a lower edge disposed upwardly of said dust collection chamber and transversely to the gas flow from said dust collection chamber into said collector chamber and operative to cause additional electrical discharge into such a gas stream; high voltage electrical supply means electrically connected to said collector electrode for the application thereto of a high electrical voltage relative to said electrically conductive side walls of said housing; gas outlet means communicating with said collector chamber for the passage therefrom to a gas chromatography unit of a gas stream flowing from said dust collection chamber upwardly through said collector chamber, whereby electrically charged dust particles present in said gas stream flowing upwardly through said collector chamber are attracted to and collected on said collector electrode and a respective one of said electrically conductive side walls of said housing and whereby a gas stream flowing from a transfer line through said electrostatic precipitator must undergo a reversal of flow direction within Said electrostatic precipitator in passing out of said ionization chamber through said dust collection chamber and into said collector chamber thereof; said housing further including a cover plate detachably secured in a generally gas-tight manner to said side walls, in which said ionization electrode and said collector electrode of said electrostatic precipitator are mounted by respective ones of said electrically insulating support means which are in turn mounted on said partition and which is in turn secured to said cover plate whereby said partition and said electrodes of said electrostatic precipitator may readily be removed from within said housing thereof by detaching said cover plate from said side walls of said housing and withdrawing said partition and said electrodes from within said housing, in which each said high voltage electrical supply means of said electrostatic precipitator comprises an electrical terminal mounted on said cover plate and extending therethrough into a respective one of said ionization chamber and said collector chamber, which housing additionally includes a generally gastight casing detachably secured thereto about said electrical terminals outwardly of said cover plate, and in which electrostatic precipitator gas flow means are provided for the supply and discharge of an inert gas into and out of said gastight casing of said electrostatic precipitator, said gas inlet and gas outlet means commencing at said ionization chamber and said collector chamber respectively, extending through said casing and terminating at said side wall.