Oxygen-containing coal bed gas low-temperature rectification system and method capable of avoiding explosion limits

Abstract

The invention discloses oxygen-containing coal bed gas low-temperature rectification system and method capable of avoiding explosion limits. The system comprises a rectification tower, a reboiler, a coal bed gas input pipeline, a liquid nitrogen input pipeline, a circulation methane pipeline, a gas exhaust pipeline and a liquid methane output pipeline. The oxygen-containing coal bed gas enters from the middle part of the rectification tower, is partially and upwards used as steam stripping of a rectification section, and is in mass and heat transfer exchange with liquid on a tower plate; liquid nitrogen is injected from the top part of the rectification tower and is used as reflux liquid of the rectification tower; and through arranging an online methane content detector, the methane content of a gas-phase space between a first tower plate and the top part of a tower body and the methane content of a gas-phase space between a second tower plate and the first tower plate are monitored in real time, the methane content of the gas-phase space between the first tower plate and the top part of the tower body is ensured to be maintained to be less than 5 percent, and the methane contentof the gas-phase space between the second tower plate and the first tower plate is larger than 15 percent or smaller than 15 percent, so that the explosion limits are avoided.

Description

Technical field [0001] The present invention relates to coalbed methane treatment technology, in particular to a low-temperature rectification system and method for oxygen-containing coalbed methane that avoids the explosion limit. Background technique [0002] Low-concentration coal-bed methane not only contains 20%-50% of methane, but also contains a large amount of nitrogen and oxygen in the air, which is a harmful factor in coal mine production. It not only pollutes the air, but also when the air contains 5%-16 %, it will explode in case of fire and cause a safety accident. [0003] A cryogenic rectification tower is used to separate oxygen, nitrogen and other non-condensable gases from the oxygen-containing coalbed methane. High-purity methane is obtained at the bottom of the rectification tower to produce liquefied natural gas. The top of the tower discharges non-condensable gases such as oxygen and nitrogen. The volume fraction of methane in the stripping component from bot...

AI Technical Summary

Problems solved by technology

The volume fraction of methane in the stripping components from bottom to top inside the rectification tower is reduced from 98% to 2%, and there is a risk of crossing the explosion limit of 5% to 15%, which seriously reduces the safety of the rectification tower. Therefore, it is necessary to Design of a Cryogenic Rectification System for Oxygenated Coalbed Methane Avoiding the Explosive Limit

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