METHOD OF NITROGEN GAS RECOVERY FROM GAS VENTS

A method of vapor recovery is provided. One embodiment of the method of vapor recovery includes providing a combined gas phase and liquid phase fluid, by way of a pipe, wherein the pipe comprises a gas vent. Then removing at least a portion of the gas phase fluid with the gas vent. Then compressing the removed portion of gas phase fluid, thereby forming compressed gas stream. And finally accumulating the compressed gas stream in a storage tank downstream of the compressor.

BACKGROUND

When a cryogenic liquid flows through pipes in an industrial complex, it is common for some of the liquid to vaporize, causing a, typically undesirable, two-phase flow. This flashing may occur due to heat transfer through the pipe, or simply due to the inevitable pressure drop as the liquid travels through the piping system. It is a common practice for there to be periodic vapor removal devices, referred to as cryovents, keep-full, keep-cold, gas vents, or vapor vents. In this document, these devices will be referred to as vapor vents.

These vapor vents are mechanical venting mechanisms that have a mechanical float that allows gas to exit when the liquid level drops. If these vapor vents are properly located, and properly functioning, they will maintain a liquid fluid flow through the pipeline.

Typically, the vapor that is released from these vapor vents is simply vented to the atmosphere. In some cases, it is desirable to capture and possibly recirculate this vapor. A need exists in the industry for a means of capturing, storing, and possibly reusing the vent vapor from a vapor vent.

SUMMARY

A method of vapor recovery is provided. One embodiment of the method of vapor recovery includes providing a combined gas phase and liquid phase fluid, by way of a pipe, wherein the pipe comprises a gas vent. Then removing at least a portion of the gas phase fluid with the gas vent. Then compressing the removed portion of gas phase fluid, thereby forming compressed gas stream. And finally accumulating the compressed gas stream in a storage tank downstream of the compressor.

DESCRIPTION OF PREFERRED EMBODIMENTS

The gas vent, also known as cryovents, keep-full, keep-cold, or vapor vents are well known to one of ordinary skill in the art. These gas vents, are typically designed with a small reservoir that is connected to the fluid handling pipeline. The gas vent may be situated at high points along the pipeline, or anywhere that the skilled artisan would know is an appropriate location. If only liquid is present in the pipeline at that location, the reservoir will thus contain only liquid. The gas vent will typically have a mechanical float that operates a vent valve. As vapor becomes present in the pipeline at this location, if properly designed and installed, this vapor will accumulate in the reservoir. This will cause the mechanical float to move and this will eventually open the vent valve, thereby allowing the vapor to leave the pipeline system.

Referring toFIG. 1, the sole FIGURE in this application, a method of vapor recovery100is described. One embodiment of the method of vapor recovery100includes providing a combined gas phase and liquid phase fluid103, by way of a pipe101, wherein the pipe101comprises a gas vent102. Then removing at least a portion of the gas phase fluid104with the gas vent102. Then compressing the removed portion of gas phase fluid104, thereby forming compressed gas stream106. And finally accumulating the compressed gas stream106in a storage tank107downstream of the compressor105.

The combined gas phase and liquid phase fluid103may be a cryogenic fluid. The combined gas phase and liquid phase fluid103may be selected from the group consisting of nitrogen, argon, oxygen, carbon dioxide, and combinations thereof. The combined gas phase and liquid phase fluid103may be at a pressure5psig or less. The compressor105may be configured to compress the removed portion of the gas phase fluid up to50psig. The compressor105may be configured to compress the removed portion of the gas phase from between25psig and45psig.

In another embodiment, the method of vapor recovery100includes providing at least a portion of the compressed gas stream109to an on-site user109downstream of the compressor105.

In another embodiment, the method of vapor recovery100includes providing at least a portion of the compressed gas stream109to an on-site user108downstream of the storage tank107.