Particulate separation system for mercury analysis

• US 20030110950A1
• Filed: 12/02/2002
• Published: 06/19/2003
• Est. Priority Date: 12/14/2001
• Status: Active Grant

• Current Assignee: Apogee Scientific Incorporated (Apogee Total Solutions Incorporated)
• Original Assignee: Apogee Scientific Incorporated (Apogee Total Solutions Incorporated)
• Inventors: Ebner, Timothy, Slye, Richard, Sjostrom, Sharon
• Granted Patent: US 6,736,883 B2
• Time in Patent Office: Days
• US Class Current: 96/413
• CPC Class Codes: B01D 2257/602 Mercury or mercury compounds
• CPC Class Codes: B01D 46/44 controlling filtration
• CPC Class Codes: B01D 53/30 Controlling by gas-analysis apparatus regulating non electrical variables in general G05D
• CPC Class Codes: G01N 33/0045 for Hg
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y10S 55/34 Indicator and controllers

Abstract

A particulate separation system for accurate measurement of vapor-phase mercury in a flue gas stream uses an inertial gas sampling filter in which the skin temperature of the filter element is controlled to allow vapor-phase mercury measurements while minimizing measurement artifacts caused by: (1) mercury thermally desorbing off particulates into the gas stream; and (2) mercury being removed from the vapor phase by collection on particulate matter at the gas/particle separation interface.

Claims

1. A gas sampling filter for use in a system for measurement of vapor-phase mercury in a flue gas stream, said filter comprising:

a filter element to separate particulates from the gas being sampled;

a heater heating the filter element;

a first temperature sensor measuring the temperature of the flue gas stream;

a second temperature sensor measuring the temperature of the filter element; and

a controller regulating the heater to minimize the difference between the temperature of the flue gas stream measured by the first temperature sensor and the temperature of the filter element measured by the second temperature sensor.

2. The gas sampling filter of claim 1 wherein the filter element comprises a sintered tube having a wall with sufficient porosity to allow a sample of the flue gas stream to be drawn through the wall of the sintered tube, and having an average pore size selected to separate particulates from the gas being sampled.

3. The gas sampling filter of claim 2 further comprising an outer tube surrounding the sintered tube, wherein flue gas passes through the sintered tube and a sample of flue gas is drawn through the wall of the sintered tube into the outer tube.

4. A gas sampling filter for use in a system for measurement of vapor-phase mercury in a flue gas stream, said filter comprising:

a sintered tube within the outer tube having an inlet and outlet for passing at least a portion of the flue gas stream, and having a wall with sufficient porosity to allow a sample of the flue gas stream to be drawn through the wall of the sintered tube, but having an average pore size selected to separate particulates from the flue gas being sampled;

a heater heating the sintered tube;

a first temperature sensor measuring the temperature of the flue gas stream;

a second temperature sensor measuring the temperature of the sintered tube; and

a controller regulating the heater to minimize the difference between the temperature of the flue gas stream measured by the first temperature sensor and the temperature of the sintered tube measured by the second temperature sensor.

5. The gas sampling filter of claim 4 further comprising an outer tube surrounding the sintered tube, wherein a sample of flue gas is drawn through the wall of the sintered tube into the outer tube.

6. The gas sampling filter of claim 5 wherein the heater surrounds the sintered tube and the outer tube.

7. A system for sampling vapor-phase mercury in a flue gas stream flowing through a duct, said system comprising:

an inlet probe to withdraw flue gas from the duct;

a gas sampling filter having a sintered tube receiving the flue gas withdrawn through the inlet probe, said sintered tube having a wall with sufficient porosity to allow a sample of the flue gas to be drawn through the wall of the sintered tube, but having an average pore size selected to separate particulates from the flue gas being sampled;

a heater heating the sintered tube;

a first temperature sensor measuring the temperature of the flue gas at the inlet probe;

a second temperature sensor measuring the temperature of the sintered tube; and

a controller regulating the heater to minimize the difference between the temperature of the flue gas measured by the first temperature sensor and the temperature of the sintered tube measured by the second temperature sensor; and

a blower drawing flue gas from the duct through the inlet probe and gas sampling filter.

8. The system of claim 7 further comprising a flow meter measuring the flow of flue gas through the gas sampling filter.

9. The system of claim 7 further comprising an outer tube surrounding the sintered tube, wherein a sample of flue gas is drawn through the wall of the sintered tube into the outer tube.

10. The system of claim 7 further comprising a flow control valve regulating the flow of flue gas through the gas sampling filter.

11. The system of claim 7 wherein the inlet probe further comprises a distal opening that can be adjustably positioned within the duct.

12. The system of claim 7 further comprising a support rod supporting the first temperature sensor within the duct adjacent to the inlet probe.