Energy-saving process and device for recovering C2 from refinery dry gas

An energy-saving process for recovering C2 from refinery dry gas, wherein the process flow is as follows:

• (1) sending refinery dry gas treated through deacidification, drying, compression and cooling by a dry gas pretreatment system to a multi-stage absorption tower, sending the gas phase at the top of the tower obtained from the multi-stage absorption tower to a fuel gas pipeline network or PSA unit, and sending the liquid phase at the bottom of the tower obtained from the multi-stage absorption tower to a high-pressure flash zone;
• (2) arranging multiple stages of high-pressure zone flash tanks in the high-pressure flash zone, and returning the gas phase obtained by flash to the compression section of the dry gas pretreatment system;
• and recycling one part of the obtained liquid phase back to the multi-stage absorption tower as a semi-lean solvent, and sending the other part to a low-pressure flash zone for treatment;
• and the multiple stages of high-pressure zone flash tanks are successively depressurized and connected in series, and the pressure of the last flash tank is 0.1˜0.3 MpaG;
• (3) arranging multiple stages of low-pressure zone flash tanks in the low-pressure flash zone, sending the gas phase, C2 concentrated gas to a C2 concentrated gas compressor system, recycling one part of the obtained liquid phase back to the multi-stage absorption tower as a secondary lean solvent, and sending the other part to a desorption tower;
• and the multiple stages of low-pressure zone flash tanks are successively depressurized and connected in series, and the pressure of the last flash tank is 0˜0.1 MpaG;
• (4) mixing the gas phase obtained from the desorption tower with the gas phase from the low-pressure flash zone and sending to an ethylene cracking furnace as C2 concentrated gas, returning part of the liquid phase obtained from the desorption tower to the multi-stage absorption tower as a lean solvent, sending the other part out of the battery limit as C4, and supplementing the C4 from the battery limit as fresh adsorbent.