Continuous emission monitoring system

• US 5,861,316 A
• Filed: 08/20/1996
• Issued: 01/19/1999
• Est. Priority Date: 10/25/1994
• Status: Expired due to Fees

• Current Assignee: Evogen Incorporated
• Original Assignee: Midwest Research Institute
• Inventors: Cage, Brian R., Soderberg, Daniel R., Gorman, Paul G., Thornburg, Michael J., Going, John E.
• Primary Examiner(s): Pyon, Harold Y.
• Assistant Examiner(s): CARRILLO, BIBI SHARIDAN
• Application Number:
  US08/697,137
• Time in Patent Office: 882 Days
• Field of Search: 436/52, 436/83, 436/174, 436/177, 436/181, 427/80.01, 427/90, 427/82.03, 427/88, 55/235, 55/236, 55/237, 55/238, 55/270, 96/181, 96/209, 96/216, 96/197, 96/101, 95/82, 95/219, 73/863.12, 73/23.12
• US Class Current: 436/52
• CPC Class Codes: B01D 47/027 by directing the gas to be cleaned essentially tangential to the liquid surface
• CPC Class Codes: G01N 1/2211 with cyclones
• CPC Class Codes: Y10T 436/117497 with a continuously flowing sample or carrier stream
• CPC Class Codes: Y10T 436/25 including sample preparation
• CPC Class Codes: Y10T 436/25375 Liberation or purification of sample or separation of material from a sample [e.g., filtering, centrifuging, etc.]
• CPC Class Codes: Y10T 436/25875 Gaseous sample or with change of physical state

Abstract

A continuous emission monitoring system is disclosed for detecting toxic substances of various types in either stack gas or ambient air. Particular systems are illustrated for monitoring lewisite and chromium(VI). Each system employs a gas sampler that utilizes a high-volume, wet cyclone concentrator unit which scrubs the contaminants from the gas into water or another suitable scrubbing solution. In-line chemical processing of the contaminated sample thus obtained is accomplished either within the sampling unit or by an external chemistry processing module. After processing to provide an analyte in the sample indicative of the presence of a predetermined contaminant, the sample stream is delivered to an ion chromatograph or other analyzer to determine the presence and quantity of the analyte and indicate whether a danger level has been reached. This provides monitoring on an essentially real-time or near real-time basis.

Claims

1. A method of continuously monitoring a gas under observation for contaminants therein, said method comprising the steps of:

(a) providing a sampling device including an upright receptacle having a body presenting an upwardly extending, generally cylindrical wall presenting an inside surface,

(b) providing said wall with a generally vertically extending gas inlet slit therethrough tangential to the wall and substantially coextensive with said body,

(c) supplying a scrubbing liquid to said body and controlling the flow thereof to maintain the liquid at a predetermined volume within said body,

(d) continuously flowing the gas under observation into the body through said gas inlet slit tangentially of said wall to cause turbulent contact of the gas and scrubbing liquid and effect cyclonic spinning of the gas and scrubbing liquid within the body and the formation of a hollow, cylindrical column of spinning liquid that adheres to said inside surface, thereby scrubbing contaminants from the gas into the liquid to provide a contaminated liquid sample,

(e) flowing a sufficient amount of the gas through the body in said step (d) to provide a sampling rate enabling concentration of the contaminants in the scrubbing liquid to occur in real time,

(f) exhausting the gas from the body after contact with the scrubbing liquid,

(g) continuously subjecting the contaminated liquid sample to chemical processing on a real-time basis to provide a detectable substance indicative of the presence of a predetermined contaminant, including adding a modifier directly to the contaminated sample in said receptacle to effect, in real time, a conversion of the predetermined contaminant to said detectable substance inside the receptacle, and thereafter

(h) continuously analyzing the processed sample on a real-time basis, by a selected analytical method, to detect said substance and determine a quantity of the predetermined contaminant.

2. The method as claimed in claim 1, wherein said scrubbing liquid is supplied at a flow rate of up to approximately 10 milliliters per minute and the gas is supplied to said receptacle at a sampling rate of approximately 1,000 liters to 3,000 liters per minute.

3. The method as claimed in claim 1, wherein said predetermined contaminant is lewisite, and wherein said modifier for real-time conversion to said detectable substance is a predetermined concentration of hydrogen peroxide in water.

4. The method as claimed in claim 1, wherein said predetermined contaminant is chromium(VI), and wherein said modifier is 1N potassium hydroxide delivered to the receptacle at a rate of up to approximately 10 milliliters per minute.

5. The method as claimed in claim 1, wherein said predetermined contaminant is chromium(VI), and wherein said modifier provides a basic sample solution to maintain the chromium in a +6 oxidation state and thereby provide said detectable substance.

6. An apparatus for continuously monitoring a stack emission, air or other gas under observation for contaminants therein, said apparatus comprising:

a sampling device including an upright receptacle having a body presenting an upwardly extending, generally cylindrical wall presenting an inside surface,

said wall having a generally vertically extending gas inlet slit therein tangential to the wall and substantially coextensive with said body,

means communicating with said receptacle for supplying a scrubbing liquid thereto and controlling the flow thereof to maintain the liquid at a predetermined volume within said body,

vacuum supply means communicating with an upper end of said body for continuously flowing the stack emission, air or other gas under observation into the body through said gas inlet slit tangentially of said wall to cause turbulent contact of the gas and scrubbing liquid and effect cyclonic spinning of the gas and scrubbing liquid within the body and the formation of a hollow, cylindrical column of spinning liquid that adheres to said inside surface, thereby scrubbing contaminants from the gas into the liquid to provide a contaminated liquid sample and exhausting the gas from the upper end of the body,

said vacuum supply means flowing a sufficient amount of the gas through the body to provide a sampling rate enabling concentration of the contaminants in the scrubbing liquid to occur in real time,

means communicating with said receptacle for withdrawing the contaminated liquid sample therefrom and including a chemical processing module for subjecting the sample to preselected in-line chemical processing to provide, on a real-time basis, a detectable substance indicative of the presence of a predetermined contaminant in the contaminated liquid sample, and

detector means for receiving the processed sample and analyzing the same in real time to determine the presence and quantity of the predetermined contaminant.

7. The apparatus as claimed in claim 6, wherein said liquid-supplying means supplies the scrubbing liquid at a flow rate of up to approximately ten milliliters per minute, and said vacuum supply means flows the gas into said body at a sampling rate of approximately 1,000 liters to 3,000 liters per minute.

8. An apparatus for continuously monitoring a stack emission, air or other gas under observation for contaminants therein, said apparatus comprising:

a sampling device including an upright receptacle having a body presenting an upwardly extending, generally cylindrical wall presenting an inside surface,

said wall having a generally vertically extending gas inlet slit therein tangential to the wall and substantially coextensive with said body,

means communicating with said receptacle for supplying a scrubbing liquid and a modifier thereto, and for controlling the flow of the liquid to maintain the liquid at a predetermined volume within said body,

vacuum supply means communicating with an upper end of said body for continuously flowing the stack emission, air or other gas under observation into the body through said gas inlet slit tangentially of said wall to cause turbulent contact of the gas, scrubbing liquid and modifier and effect cyclonic spinning of the gas, scrubbing liquid and modifier within the body and the formation of a hollow, cylindrical column of spinning liquid that adheres to said inside surface, thereby scrubbing contaminants from the gas into the liquid to provide a contaminated liquid sample and exhausting the gas from the upper end of the body,

said vacuum supply means flowing a sufficient amount of the gas through the body to provide a sampling rate enabling concentration of the contaminants in the scrubbing liquid to occur in real time,

said modifier conditioning the contaminated liquid sample to provide, on a real-time basis, a detectable substance indicative of the presence of a predetermined contaminant in the contaminated liquid sample, and

detector means for receiving the conditioned sample and analyzing the same in real time to determine the presence and quantity of the predetermined contaminant.

9. The apparatus as claimed in claim 8, wherein said liquid-supplying means supplies the scrubbing liquid at a flow rate of up to approximately ten milliliters per minute, and said vacuum supply means flows the gas into said body at a sampling rate of approximately 1,000 liters to 3,000 liters per minute.

10. An apparatus for continuously monitoring a stack gas under observation for contaminants therein, said apparatus comprising:

a gas conditioner having an inlet line for receiving stack gas under observation, and means for mixing cooler air with the received gas to dilute the same and provide a conditioned gas of preselected temperature and moisture content at a rate of at least approximately 1,000 liters per minute,

a sampling device including an upright receptacle having a body presenting an upwardly extending, generally cylindrical wall presenting an inside surface,

said wall having a generally vertically extending gas inlet slit therein tangential to the wall, substantially coextensive with said body, and communicating with said conditioner,

means communicating with said receptacle for supplying a scrubbing liquid thereto at a flow rate of up to approximately ten milliliters per minute, and controlling the flow rate to maintain the liquid at a predetermined volume within said body,

vacuum supply means communicating with an upper end of said body for continuously flowing the conditioned gas into the body through said gas inlet slit tangentially of said wall to cause turbulent contact of the gas and scrubbing liquid and effect cyclonic spinning of the gas and scrubbing liquid within the body and the formation of a hollow, cylindrical column of spinning liquid that adheres to said inside surface, thereby scrubbing contaminants from the gas into the liquid to provide a contaminated liquid sample and exhausting the gas from the upper end of the body,

said vacuum supply means flowing the conditioned gas through the body at a sampling rate of at least approximately 1,000 liters per minute to cause concentration of the contaminants in the scrubbing liquid to occur in real time,

means connected to a liquid outlet on said receptacle for withdrawing a stream of the contaminated sample therefrom,

a chemical processing module having an inlet for receiving the sample stream from said withdrawing means, and including means for converting said sample, on a real-time basis, to an analyte in detectable form indicative of the presence of a predetermined contaminant, and means for delivering a processed sample stream containing said analyte at an output of said module, and

ion chromatograph means for analyzing the processed sample stream from the module output to detect said analyte and determining the quantity thereof in real time.

11. The apparatus as claimed in claim 10, wherein said converting means in the chemical processing module includes means for adding oxidizing and ionizing agents to the sample stream to convert a lewisite contaminant to an arsenate analyte for detection by said ion chromatograph means.

12. A method of continuously monitoring a gas under observation for contaminants therein, said method comprising the steps of:

(a) providing a sampling device including an upright receptacle having a body presenting an upwardly extending, generally cylindrical wall presenting an inside surface,

(b) providing said wall with a generally vertically extending gas inlet slit therethrough tangential to the wall and substantially coextensive with said body,

(c) supplying a scrubbing liquid to said body and controlling the flow thereof to maintain the liquid at a predetermined volume within said body,

(d) continuously flowing the gas under observation into the body through said gas inlet slit tangentially of said wall to cause turbulent contact of the gas and scrubbing liquid and effect cyclonic spinning of the gas and scrubbing liquid within the body and the formation of a hollow, cylindrical column of spinning liquid that adheres to said inside surface, thereby scrubbing contaminants from the gas into the liquid to provide a contaminated liquid sample,

(e) flowing a sufficient amount of the gas through the body in said step (d) to provide a sampling rate enabling concentration of the contaminants in the scrubbing liquid to occur in real time,

(f) exhausting the gas from the body after contact with the scrubbing liquid,

(g) continuously subjecting the contaminated liquid sample to chemical processing on a real-time basis to provide a detectable substance indicative of the presence of a predetermined contaminant, including withdrawing the contaminated sample from the receptacle and thereafter adding a modifier to the sample to effect, in real time, a conversion of the contaminant to said detectable substance, and

(h) continuously analyzing the processed sample on a real-time basis, by a selected analytical method, to detect said substance and determine a quantity of the predetermined contaminant.

13. The method as claimed in claim 12, wherein said predetermined contaminant is lewisite and said scrubbing liquid is water, and wherein said modifier is an oxidant.

14. The method as claimed in claim 12, wherein said predetermined contaminant is lewisite and said scrubbing liquid is water, and wherein said modifier includes potassium permanganate, acidified hydrogen peroxide and tris(hydroxymethyl)-aminomethane buffer.

15. The method as claimed in claim 12, wherein said scrubbing liquid is supplied at a flow rate of up to approximately 10 milliliters per minute and the gas is supplied to said receptacle at a sampling rate of approximately 1,000 liters to 3,000 liters per minute.