Light hydrocarbon recovery process in atmospheric and vacuum distillation units?

In brief: The gas at the top of the tower enters the compressor inlet; after pressure is increased, it is sent to the downstream side (such as the main oil-gas pipeline of the catalytic separation tower), while a circulation line exists between the outlet and the inlet to control the pressure； Meanwhile, the export is routed to the low-pressure flare system ； The catalyzer-free, low-pressure flare process is equipped with two-position cylinder valves that are interlocked with the compressor shutdown mechanism; this ensures that in the event of an unexpected shutdown of the unit, the gas phase can be directed to the low-pressure system, thereby ensuring smooth flow of the gas phase. The drawing is gone; I’m the one who handled the catalysis.

Gas recovery tower, Gas pressure stabilization tower, Gas pump, Bottom water seal tank

Two streams of low-pressure gas are combined in a liquid separation tank; the gas enters the compressor inlet from the top of the tank, and after being pressurized, it is sent to a gas holder or for catalytic desulfurization.

In simple terms, the naphtha, liquefied gas, etc. from various units pass through heat exchange before entering the debutanization tower, then the deethanization tower, followed by the liquefied gas absorption section, from which the various products are obtained. The principle is somewhat similar to the three-column cycle used in absorption stabilization in catalysis, but it is not exactly the same, as the target products and objectives differ.

If there is sufficient capacity in the load of the catalytic compressor, it can first be fed into the liquid separation tank and then directly connected to the compressor inlet for pressurization, before being sent to the catalytic absorption tower for recovery. However, a two-position cylinder valve must be installed for interlocking with the air compressor shutdown.

The simple process is described as follows: Low-pressure gas enters the separator tank at the compressor inlet where it is separated. After being compressed by the low-pressure compressor, it merges with the gas from the top of the desorption tower and enters the water-cooler at the compressor outlet for cooling. It then goes to the separator tank at the compressor outlet again for separation. The compressed gas proceeds to the bottom of the absorption tower, where it has some of its components absorbed by the lean absorption oil at the tower’s top. Subsequently, it moves under its own pressure to the bottom of the reabsorption tower, where it comes into contact in reverse flow with the lean reabsorption oil at the tower’s top; after absorption, the dry gas that meets the quality requirements is sent out of the unit to the dry gas desulfurization unit. The condensate from the compressor inlet separator tank is pumped back to the normal pressure reflux and product tanks. Part of the constant head oil is fed as a lean absorption oil from the constant head reflux and product pump to the top of the absorption tower, where it absorbs the compressed gas coming from the bottom of the tower in countercurrent flow. The absorbent oil and the compressor condensate pumped by the feed pump of the desorption tower are combined, then heat-exchanged with the naphtha at the bottom of the stabilizer before entering the desorption tower for desorption. The reboiler at the bottom of the desorption tower uses normal pressure steam as a heat source. The oil at the bottom of the desorption tower is pumped out, mixed with naphtha that has not been subjected to lean absorption, and after exchanging heat with the naphtha from the bottom of the stabilizer, it is sent to the stabilizer for further processing. The qualified LPG from the top of the tower is sent to the liquefied gas desulfurization unit via reflux from the top of the stabilizer and a product pump. After exchanging heat with the feed to the stabilizer and the feed to the desorption tower, the heated material is sent to the reforming unit. The light crude oil from Section 1 of the constant pressure column, after passing through the steam generator, is pumped by the lean-reinforced absorption oil pump into the lean-reinforced absorption oil heat exchanger, where it exchanges heat with the reinforced absorption oil. After being cooled to 40°C in the lean-reinforced absorption oil water cooler, it is sent to the absorption tower to absorb the gas from the top of the tower. The reinforced absorption oil at the bottom of the tower enters the lean-reinforced absorption oil heat exchanger under its own pressure; after heat exchange, it goes to the return line of Section 1 of the constant pressure column, where it merges with the oil from that section and enters the atmospheric pressure column. The absorption tower is equipped with two circulation returns.