THEORETICAL-ANALYSIS OF REMOVAL OF OXIDES OF SULFUR AND NITROGEN IN PULSED OPERATION OF ELECTROSTATIC PRECIPITATORS

An investigation has been made of the various plasma chemistry reactio ns that occur in the corona discharge of an electrostatic precipitator Operating in a typical flue gas. Calculations have been made of the r ate coefficients for electron dissociation of the principal gaseous co mponents, namely, nitrogen, oxygen and water vapor as functions of ele ctric field. In addition, calculations have been made of the rates of ionisation and attachment and also the rates of excitation of the prin cipal excited states, The calculations indicate that sulphur dioxide i s removed principally by reactions with OH radicals to produce sulphur ic acid, while nitrogen oxides are removed principally by reduction vi a the N radical to molecular nitrogen, However, for these reactions to occur, values of E/N Of 70 Td Or more are necessary, which is higher than the E/N of 30 Td at which electrical breakdown normally occurs; E is electric held strength and N is the gas number density, Approximat e calculations indicate that, for an E/N of 100 Td, voltage pulses of width less than 1 mu s need to be applied to avoid breakdown, It is al so shown that small quantities of nitrous oxide are produced and that the presence of water vapor has a significant effect on the plasma che mistry and increases the breakdown voltage.