High flow rate sampler for measuring emissions at process components

Abstract

A new high flow rate sampling device and methods for measuring fugitive gas emissions are provided. The high flow rate sampler comprises an air mover connected to a flexible hose for drawing in air near a process component, such as a pump, compressor seal, flange, or pipe thread connection. A second sample hose draws air from the opposing side of the process component at a flow rate low enough not to affect capture of the leak by the first sample hose. Air measured from the first sample hose will contain fugitive emissions from the process component being measured, as well as from other process components. Air measured from the second sample hose will contain only fugitive emissions from surrounding process components and can then be subtracted from the measurement from the first sample hose to obtain the leak rate from the process component in question.

Description

FIELD OF THE INVENTIONThis invention relates generally to the measurement of fugitive air pollution emissions from a wide range of processes utilized in the natural gas, petroleum, petrochemical, and chemical industries.BACKGROUNDFugitive emissions are air pollution emissions that are not released from stacks designed as release points. Instead, fugitive emissions escape from industrial processes by means such as evaporation from wastewater treatment areas or leaks at process components. Leaks may occur at process components such as pumps, compressor seals, flanges, valves, pipe thread connections, and open ended lines on valves that are shut off. Rising concerns over hazardous air pollutants and greenhouse gases have led to the need for improved quantification of fugitive emissions to the environment.Fugitive emissions are very difficult to quantify without expensive and time consuming measurement programs. Consequently, the oil, gas, and chemical industries typically use technique...

AI Technical Summary

Benefits of technology

Alternatively, samples can be collected from the first and second sample hoses and analyzed at a later time. It is preferable that the flow rate in the first sample hose is adjustable, such as by attaching a gas regulator to the air mover, so that the vacuum created by the first sample hose can be adjusted for measuring leak rates under varying conditions. For example, breezy conditions at some sites may require a higher flow rate, ie. greater vacuum, to completely capture the leak, compared to a similar measurement indoors. Applying a high flow rate is an advantage of the present invention since the application of a high flow rate allows for a more complete capture of the gas emissions from leaking components.

since the application of a high flow rate allows for a more complete capture of the gas emissions from leaking components.

A three-way valve can be used to allow for sample collection or analysis of air from the first sample hose or the second sample hose. Most preferably, a solenoid can be used for rapid and automatic switching between measurement of contaminants in the first and second sample hoses. Continuous application of the vacuum created by the first sample hose while measuring contaminants in the second sample hose allows for background measurements to be made, which can be high if surrounding leaking components are present. The near-simultaneous measurement of background levels of contaminants is an advantage of the present invention so that measured leak rates can more accurately be attributed to the appropriate components.

Data acquisition can also be used with the present invention to allow for computer control, calculation and recording of leak rate data. Connections from a computer control system to the flow meter, solenoid and gas analyzer would allow for almost operator-free operation of the high flow rate sampling instrument with minor modifications to existing computer hardware and software.

Another aspect of the present invention is a method for more accurately measuring fugitive air emissions. The method of the present invention comprises the steps of drawing air from one side of a leaking component into a sample hose at a high flow rate to dominate air movement near the leaking component and allowing for complete capture of the leak. Simultaneously, drawing air from the other side of the component into a second sample hose, at a low enough flow rate not to effect capture of the leak, to measure background concentration of the gas in air not influenced by the leak. Measuring the air flow rate using a flow meter to allow for calculation of the leak rate, and measuring the exit concentration of air pollutants in the air stream of the high flow sample hose and low flow sample hose using a gas analyzer, such as a portable volatile organic compound (VOC) analyzer.

Problems solved by technology

Fugitive emissions are very difficult to quantify without expensive and time consuming measurement programs.

These techniques are easy to apply but have several large uncertainties inherent in there use, as described below.

The enclosure measurement technique is relatively accurate, but requires extensive time and effort to set up.

The time and expense associated with this technique makes it prohibitive for routine monitoring of gas leaks.

In practice, the actual ideal concentration is rarely achieved because the leak is not completely captured.

For leaks which escape from several points around a component, the area covered by the sampling probe flow rate may not be large enough to capture the plume.

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