| 摘要 |
PROBLEM TO BE SOLVED: To separate/retrieve a C2+ fraction from a NOx-containing light gas such as FCC(fluid catalytic cracking) off-gas while suppressing NOx gum formation/deposition. SOLUTION: A method for separating the C2+ fraction comprises distilling a NOx-containing light gas and a liquid-phase component from a 1st-tier gas-liquid separatory tank 31 and the like in a NOx-containing light gas distillation column 62 and feeding a methane-removing column 61 with the resultant vapor-phase component. In the above process, a cryogenic system 1 is used, which includes multi-tier gas-liquid separatory tanks 31-34 where a feedstock is separated into a vapor-phase component and a liquid-phase component, a hydrogen/low-pressure methane separatory tank 51 where the vapor-phase component is separated into a hydrogen fraction and a low-pressure methane fraction, the methane-removing column 61 where the liquid-phase component is distilled and separated as the C2+ fraction, a refluxing tank 71 where the overhead component of the methane-removing column 61 is cooled, and the vapor-phase component and part of the liquid-phase component are separated as high-pressure methane fraction and medium-pressure methane fraction, respectively, and the rest is refluxed into the methane-removing column 61, and a cryogenic heat exchanger 41 where the vapor-phase component from the multi-tier gas-liquid separatory tanks 31-34 is subjected to heat exchange with the hydrogen fraction and the low-pressure/medium-pressure/high-pressure methane fractions and cooled. COPYRIGHT: (C)2007,JPO&INPIT
|
