Method and apparatus for sulfuric acid aerosol analysis

Claim 3

The method of claim 1 wherein said dry inert purge gas is heated to a temperature of between about 40*C and about 200*C prior to contact thereof with said porous filter medium.

Claim 4

The method of claim 1 wherein the gas stream formed in (B) is heated to and maintained at above the condensation temperature of the sulfuric acid vapors contained therein.

Claim 5

The method of claim 1 wherein the relative humidity of said sample gas stream is reduced to below 100 percent by heating to below about 110*C prior to contact thereof with said porous filter medium.

Claim 6

The method of claim 4 wherein said sample gas is heated by mixing thereof with heated dry inert purge gas.

Claim 7

The method of claim 1 wherein said sample gas is ambient air.

Claim 8

The method of claim 1 wherein said dry inert purge gas is air essentially free of sulfurous contaminants.

Claim 9

The method of claim 1 wherein said dry inert purge gas comprises a minor but effective amount of an inert wetting agent having a wetting affinity for the porous filter medium greater than that of sulfuric acid aerosol.

Claim 10

The method of claim 8 wherein said wetting agent is a C1 to C6 primary alcohol.

Claim 11

The method of claim 9 wherein said wetting agent is chosen from the group consisting of methanol, ethanol and mixtures thereof.

Claim 12

The method of claim 1 wherein said dry inert purge gas has a water content of less than about 10 parts per million.

Claim 13

Apparatus for determining the sulfuric acid aerosol content of a sample gas which comprises: A. a filter holder adapted (i) to hold a porous filter medium therein and (ii) to convey an exposed portion of filter medium held therein between a first sampling station and at least one other station defining a filter purging station; B. a porous filter medium held in said filter holder and adapted to collect sulfuric acid aerosol from a sample gas stream passing therethrough; C. means to convey a known quantity Of a sample gas to said sampling station and through said porous filter medium; D. means to convey a purge gas through said filter medium at said filter purging station; E. flame photometric detector means adapted to quantitatively analyze for sulfur; and F. means to convey filtered purge gas from said filter purging station into said flame photometric detector means.

Claim 14

Apparatus for determining the sulfuric acid aerosol content of a sample gas which comprises: A. a filter holder adapted (i) to hold a porous filter medium therein and (ii) to convey an exposed portion of filter medium held therein between a first sampling station and at least one other station defining a filter purging station; B. a porous filter medium held in said filter holder and adapted to collect sulfuric acid aerosol from a sample gas stream passing therethrough; C. means to convey a known quantity Of a sample gas to said sampling station and through said porous filter medium; D. means to convey a purge gas through said filter medium at said filter purging station; E. flame photometric detector means adapted to quantitatively analyze for sulfur; and F. means to convey filtered purge gas from said filter purging station into said flame photometric detector means.

Claim 15

Apparatus in accordance with claim 12 wherein (C) includes means to heat said sample gas prior to contact thereof with said filter medium.

Claim 16

Apparatus in accordance with claim 12 wherein (F) includes means to heat the purge gas stream flowing therethrough.

Claim 17

Apparatus in accordance with claim 12 wherein (D) includes means to heat said purge gas prior to contact thereof with said filter medium.

Claim 18

Apparatus in accordance with claim 12 wherein said flame photometric detector is fueled by hydrogen.

Claim 19

Apparatus in accordance with claim 12 wherein said flame photometric detector comprises signal processing circuitry adapted to amplify the output signal thereof.

Claim 20

Apparatus in accordance with claim 17 wherein said flame photometric detector comprises signal processing circuitry adapted to linearize the amplified signal thereof.

Claim 21

Apparatus in accordance with claim 12 comprising means to heat said purge gas of (D) and means to convey a portion of said purge gas into said means of (C), thereby to heat said sample gas.

Claim 22

Apparatus in accordance with claim 15 wherein said means to heat said purge gas is controlled by feedback circuitry associated with the output of said flame photometric detector, said circuitry being adapted to reduce heating of said purge gas as the flame photometric detector approaches an overloaded condition.

Claim 23

Apparatus in accordance with claim 12 wherein said filter holder of (A) comprises an inlet plate and an exhaust plate having interposed therebetween a two-position slidable shutter plate; said plates being urged together in gas tight relationship; said inlet and outlet plates being in fixed relationship to one another and having three coextensive apertures therethrough comprising a central aperture defining a sampling station and two lateral apertures positioned equidistantly to either side of said central aperture, each said lateral aperture defining a filter purging station; said slidable shutter plate having two apertures therethrough adapted to be coextensive with the central aperture and only one of the lateral apertures of the inlet and exhaust plates in a first position and being coextensive with the central aperture and the other of said lateral apertures of the inlet and exhaust plates in a second position; said slidable shutter plate including means to carry a porous filter medium exposed at each of the two apertures thereof and conduit means adapted to convey purge gas from each of said lateral filter purging stations of said exhaust plate to said flame photometric detector means.

Claim 24

The apparatus of claim 21 wherein said slidable shutter plate comprises: a slot therethrough located intermediate the opposed surfaces thereof, said slot traversing both apertures of said plate and defining a pathway for the carrying of a strip-form porous filter medium therein; a supply spool located at one end of said slot; a takeup spool located at the other end of said slot; said supply and takeup spools being adapted to receive and store said strip-form porous filter medium.