Thermal coupling method for preparing ethylene by ethanol dehydration and device thereof

A thermal coupling method for preparing ethylene by ethanol dehydration, includes an ethanol dehydration reaction system, a quenching compression system, an alkaline washing system, a molecular sieve drying system and an ethylene purification and propylene refrigeration cycle system;

• preheating, vaporization and superheating a raw material of ethanol with ethanol dehydration reaction products in the ethanol dehydration reaction system serving as a heat source for;
• preheating a feed stream of the evaporation tower and heating of an overhead gas of a quenching tower with tower kettle fluid of an evaporation tower in the quenching compression system serving as a heat source;
• cooling a crude ethylene with products of ethylene in the alkaline washing system serving as a cold source;
• preheating circulating ethylene with tower kettle fluid of the evaporation tower in the molecular sieve drying system serving as a heat source;
• precooling a dried ethylene with the products of ethylene in the ethylene purification and propylene refrigeration cycle system serving as a cold source;
• cooling an overhead gas of a demethanizing tower and cooling of propylene with the circulating ethylene serving as a cold source;
• cooling an overhead gas of a purification tower and further cooling of the ethylene with low-temperature propylene serving as a cold source for;
• and
• heating the tower bottoms of the demethanizing tower, the tower bottoms of the purification tower and the products of ethylene with hot propylene serving as a heat source;
• the quenching compression system includes an evaporation tower, an evaporation tower feed preheater, an evaporation tower reboiler, a quenching tower, a quenching tower overhead gas heater, a second gas-liquid separation tank, an evaporation tower bottom cooler and a process water tank;
• the tower bottoms of the evaporation tower enter the quenching tower overhead gas heater to heat the overhead gas of the quenching tower, and then the tower bottoms of the evaporation tower are fed into the process water tank, the evaporation tower reboiler condensates are fed into the molecular sieve drying system;
• the alkaline washing system includes an alkaline washing tower, the crude ethylene cooler and a third gas-liquid separation tank;
• the products of ethylene from the ethylene purification and propylene refrigeration cycle system enter the crude ethylene cooler to cool crude ethylene produced in the alkaline washing tower, and then the products of ethylene are fed into a product ethylene heater;
• and
• the molecular sieve drying system includes drying towers, a circulating ethylene preheater and a steam condensate flash tank;
• the evaporation tower reboiler condensates from the quenching compression system enter the circulating ethylene preheater to preheat the circulating ethylene, and the cooled reboiler condensates are fed into the steam condensate flash tank;
• and
• dried crude ethylene from the molecular sieve drying system is fed into an ethylene chiller to be recooled by low-temperature propylene after being cooled to −32ºC by the liquid phase products of ethylene through an ethylene precooler, and then enters the demethanizing tower after being cooled to −40° C.;
• the overhead gas of the demethanizing tower is fed into a heating furnace as a fuel gas after being cooled to −68° C. by decompressed circulating ethylene in a demethanizing tower condenser and vaporized in a fuel gas tank;
• ethylene produced in the tower kettle is fed into the purification tower, and the products of ethylene produced from the top of the purification tower enter an ethylene reflux tank after being cooled to −36° C. by the low-temperature propylene through a purification tower condenser;
• a part of products of ethylene, serving as the circulating ethylene, are used as a cold source of a demethanizing tower condenser and a propylene cooler, and then are fed into the drying towers to serve as a desorbed gas;
• the rest products of ethylene are fed into an ethylene buffer tank;
• part of ethylene in the ethylene buffer tank is fed back to the top of the purification tower as reflux, and after cold energy is recycled from the rest of ethylene through the ethylene precooler and the crude ethylene cooler, the rest of ethylene is discharged out of the boundary region as the products of ethylene after being heated to 23° C. by hot propylene through a product ethylene heater;
• and a demethanizing tower reboiler and a purification tower reboiler are heated by hot propylene, and resulting propylene condensates are fed into a propylene collection tank;
• in the ethanol dehydration reaction system, a tube pass inlet of the ethanol preheater is connected with a raw material tank area;
• a shell pass inlet of the ethanol preheater is connected with a shell pass outlet of the ethanol evaporator;
• a tube pass outlet of the ethanol preheater is connected with an inlet of the ethanol evaporation tank;
• a shell pass outlet of the ethanol preheater is connected with an inlet of the first gas-liquid separation tank;
• a tube pass inlet of the ethanol evaporator is connected with an outlet in a bottom of the ethanol evaporation tank;
• a shell pass inlet of the ethanol evaporator is connected with a shell pass outlet of the ethanol superheater;
• a tube pass outlet of the ethanol evaporator is connected with an inlet in a right side of the ethanol evaporation tank;
• a tube pass inlet of the ethanol superheater is connected with an outlet ata top of the ethanol evaporation tank;
• a shell pass inlet of the ethanol superheater is connected with an outlet of the third reactor;
• a tube pass outlet of the ethanol superheater is connected with an inlet of the heating furnace;
• in the quenching compression system, an outlet of the tower kettle of the evaporation tower is connected with a shell pass inlet of the evaporation tower feed preheater;
• an outlet of the tower kettle of the quenching tower is connected with a tube pass inlet of the evaporation tower feed preheater;
• a tube pass outlet of the evaporation tower feed preheater is connected with an inlet at a top of the evaporation tower;
• a shell pass outlet of the evaporation tower feed preheater is connected with a shell pass inlet of the quenching tower overhead gas heater;
• an overhead steam outlet of the quenching tower is connected with a tube pass inlet of the quenching tower overhead gas heater;
• a tube pass outlet of the quenching tower overhead gas heater is connected with an inlet of the second gas-liquid separation tank;
• and
• a shell pass outlet of the quenching tower overhead gas heater is connected with an inlet of the evaporation tower bottom cooler.