含氧煤层气直接深冷分离甲烷的安全工艺方法

A safe process for purification of oxygen-bearing coal bed methane by direct cryogenic separation

提出了一种含氧煤层气直接深冷精馏分离甲烷的安全方法，其通过在精馏塔内通入氮气降低塔内氧含量到极限氧含量以下以确保精馏过程的安全，避免了预先对含氧煤层气进行脱氧处理的过程，同时利用制氮装置可回收氮气循环使用。该工艺方法使用混合制冷和氮制冷提供冷量，并将制氮装置用于工艺过程，所需的设备成熟，工艺过程安全性和适应性好，在正常和非正常工况下都能保证安全，适用于不同甲烷浓度的含氧煤层气，LNG产品能耗在0.7kWh/m3-1.7kWh/m3之间。

A safe direct cryogenic separation process for purification of methane from oxygen-bearing coal bed methane （CBM） was proposed, in which some nitrogen was injected to the cryogenic distillation column to ensure the safety by reducing the oxygen concentration to below the explosion limit. It didn＆#39;t require a pre-removal of oxygen from the raw gas and the nitrogen could be recycled by using a nitrogen generator. The needed cold energy was provided by a mixed-refrigerant cycle （MRC） and a nitrogen expansion refrigeration system, and a nitrogen generator was combined into the process. All the equipment needed were mature. The proposed process had good safety and flexibility, and could operate safely in various operating conditions and apply to the oxygen-bearing coal bed methane with various methane concentration. The energy consumption of LNG product was 0.8 to 2kWh per standard cubic meter of methane gas.