Description of the process flow

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Description of the process flow: The raw methanol coming from the methanol distillation section (or methanol storage area) is metered and then fed into the circulating methanol storage tank. The methanol exiting this tank is pressurized by a methanol feed pump and divided into two streams. It flows all the way to the top of the alcohol washing tower as the absorption liquid ； The other stream enters the shell side of the methanol preheater, where it exchanges heat with the syngas coming out of the reactor on the tube side of the methanol preheater; after this heat exchange, the methanol enters the methanol vaporization tower to be vaporized. The vaporized methanol coming out of the top of the methanol vaporization tower passes through the shell side and tube side of the gas heat exchanger, where it exchanges heat with the syngas leaving the tower, and then splits into two streams before entering the reactor. The first stream of methanol gas is superheated to the reaction temperature and enters from the top of the reactor ； The second stream of methanol vapor, after being slightly superheated, enters the reactor from the middle in measured amounts as a cold shock gas. A portion of the liquid at the bottom of the vaporization tower is discharged outside after heat is recovered in a wastewater cooler; heat is supplied into the tower by a vaporization tower reboiler heated by low-pressure steam. Methanol vapor entering the reactor undergoes a dehydration reaction in the presence of a catalyst to produce dimethyl ether. The crude dimethyl ether coming out of the bottom of the reactor first undergoes heat exchange with vaporized methanol in both the tube side and shell side of the gas heat exchanger; as a result, its temperature drops to 220°C. It then enters the tube side of the methanol preheater where it exchanges heat with the raw methanol, causing its temperature to drop to 130°C. After that, it goes into the crude dimethyl ether condenser where it is cooled to 40°C before being sent to the crude dimethyl ether storage tank for gas-liquid separation. After separation, the liquid phase consists of crude methanol, which enters the distillation section for further distillation ； The gas-phase stream (comprising components such as H2, CH4, CO2, and other non-condensable gases, along with saturated CH3OCH3 and CH3OH vapors) and the methoxide vapor coming from the methoxide metering tank merge and enter the alcohol scrubber tower, where the CH3OCH3 vapor is absorbed using methanol. The absorbent solution is returned to the crude methoxide storage tank, while the exhaust gas after absorption is sent for combustion in a flare after being depressurized. The crude dimethyl ether coming out of the crude dimethyl ether storage tank is pressurized by the feed pump of the distillation tower and then enters the middle part of the tower for distillation. The saturated dimethyl ether vapor exiting the top of the distillation tower is condensed in the distillation tower condenser and then sent back to the tower as reflux. The dimethyl ether product obtained from the upper part of the distillation tower flows automatically into the product dimethyl ether metering tank after being condensed in the product cooler. After the distillation column bottom liquid is discharged into the storage tank for such liquid, it is metered and sent back to the methanol vaporization tower for methanol recovery and reuse. The gaseous material exiting the top of the distillation column bottom liquid storage tank is fed into the distillation column bottom to recover the dimethyl ether and methanol vapors therein. After the dimethyl ether in the product dimethyl ether metering tank is analyzed and found to be of satisfactory quality, it is pumped into the dimethyl ether storage tank using a dimethyl ether feed pump. At startup, the raw material methanol vapor is heated using medium-pressure steam via a startup heater. The syngas at the reactor outlet is cooled in the start-up cooler before entering the methanol storage tank for reuse. Additionally, there is an underground tank that collects the methanol from the collection device; this methanol is then pressurized by a waste liquid pump and sent back to the methanol intermediate tank. The dimethyl ether tank farm is equipped with spherical tanks for storing dimethyl ether products, which are mainly transported to vehicle loading platforms and train loading platforms via dimethyl ether loading pumps. A small amount of dimethyl ether product is sent to the filling station via a dimethyl ether filling pump for bottling; after bottling, it is automatically measured using a dimethyl ether filling scale.