Hybrid Air Separation Method with Noncryogenic Preliminary Enrichment and Cryogenic Purification Based on a Single Component Gas or Liquid Generator

Abstract

Large quantities of high purity and high pressure nitrogen or oxygen gas are produced using a portable system. A PSA, VSA, TSA, or permeable membrane system cleans the air of water and carbon dioxide, as normally required by the cryogenic distillation cycle, but additionally, a significant amount of the oxygen or nitrogen is also removed, depending on the desired produced gas. The removal of the oxygen or nitrogen before the cryogenic process permits the distillation column to be significantly shorter than would otherwise be required. This in turn reduces the size of the equipment such that it can easily be transported and setup. Additionally, a high pressure liquid pump is used to boost the pressure of the nitrogen or oxygen immediately before it goes through the last pass of the cryogenic heat exchanger where the liquid is vaporized and the incoming gas is cooled.

Description

[0001]The present application is related to U.S. Provisional Patent Application Ser. No. 61 / 074,118, filed on Jun. 19, 2008, which is incorporated herein by reference and to which priority is claimed pursuant to 35 USC 119.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The invention relates to the field of air separation plants, nitrogen or oxygen generators and high pressure nitrogen or oxygen delivery systems, including (but not limited to) those used for drilling and servicing oil and gas wells.[0004]2. Description of the Prior Art[0005]Many procedures and processes utilized by the oil and gas industry, as well as other industries, require the use of one of the components of air, most often nitrogen or oxygen. The use of one of the gases instead of air itself is dictated by the desired result: if oxidation (corrosion, burning, or explosions) is to be eliminated, then nitrogen is used; for many medical and industrial processes, high purity oxygen is required.[0006...

AI Technical Summary

Benefits of technology

[0013]Enriching of the feed flow to the distillation module with the desired component (oxygen for oxygen generators and nitrogen for nitrogen generators) requires fewer trays inside the distillation column than would be required if non-enriched air would have been supplied to the distillation column. Also the total amount of gas supplied to the distillation column is less than if regular air would have been supplied. The lower flow requires less column cross section resulting in smaller diameter trays. The smaller trays permit closer spacing of the trays. The use of fewer trays spaced closer to each other significantly shortens distillation column, and therefore the overall height of the distillation unit.

Problems solved by technology

Although this insures a supply of high purity gas (liquid nitrogen is typically 99.99% to 99.999% pure, liquid oxygen is typically 99.5% to 99.7% pure) at high flow rates and high pressures, there are often logistical issues in having sufficient supplies of liquid nitrogen available and delivered to the point of use.

Additionally the cost of the delivered liquid (product cost and delivery costs) and the losses incurred by cooling down the equipment and the boil-off of the storage tanks, make liquid use expensive.

This approach is widely used to address the logistical issues involved with using liquid, but the pressures achievable (less than 5000 psig) are limited by the existing gas compression equipment, and purities are limited to no more than 99% for nitrogen and 93% for oxygen.

In addition, these non-cryogenic systems can only deliver at best approximately 50% and typically 35% to 45% of the available desired component in the feed flow as a product; the remaining is eliminated as a waste gas.

The height of the distillation equipment required by this process is, by necessity, usually very tall (35 to 40 ft or taller) and difficult to transport and set up.

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