NOVELTY - Energy-saving device comprises feed pump (1), dimethyl ether removal tower (2), methanol washing tower (3), reflux tank (4), overhead reflux pump (5), reboiler (6), circulating water pump (7) and circulating water cooler (8). The methanol washing tower liquid outlet and inlet is connected to reflux tank. The reflux tank oil phase outlet is connected to overhead reflux pump inlet. The reflux pump outlet is connected with inlet of the top of dimethyl ether tower. The water phase outlet of reflux tank is connected with inlet of the circulating water pump.    USE - Energy-saving device used for C4 purification and removal of dimethyl ether (claimed).    ADVANTAGE - The method has reduced operation reflux ratio and heat consumption.    DETAILED DESCRIPTION - Energy-saving device comprises feed pump (1), dimethyl ether removal tower (2), methanol washing tower (3), reflux tank (4), overhead reflux pump (5), reboiler (6), circulating water pump (7) and circulating water cooler (8). The methanol washing tower liquid outlet and inlet is connected to reflux tank. The reflux tank oil phase outlet is connected to overhead reflux pump inlet. The reflux pump outlet is connected with inlet of the top of dimethyl ether tower. The water phase outlet of reflux tank is connected with inlet of the circulating water pump. The circulating water pump is connected with the shell of the circulating water cooler. The shell side of the circulating water cooler is connected with the liquid phase of methanol washing tower. The gas outlet of the methanol washing tower is connected with gas pipeline network. The circulating water cooler is connected with circulating cooling water pipe line where fresh water pipe line is connected to the entrance of return tank. The sewage pipe and circulating water pump outlet are connected. The bottom of the tower is connected with the inlet of the shell of the reboiler. The pipe path of the boiler is connected with the circulating water heating medium or with the condensate water of the device. An INDEPENDENT CLAIM is included for application of energy-saving device comprising carrying out desulfurization of C4 through the buffer tank, pumping into the dimethyl ether removal tower by feed pump, operating at 40-50 degrees C with pressure of 0.6-0.8 MPa, controlling dimethyl ether and methanol concentration to 10-50 ppm at 70-80 degrees C, heating at 90-110 degrees C using water or heating medium recovery apparatus as heat source, feeding dimethyl ether removal tower overhead vapor into the methanol washing tower, pumping washing liquid through the reflux tank, adjusting the washing cycle and water cycle cooling water overhead at 35-40 degrees C, pumping the oil phase into the overhead return to the top of rectification column, pumping aqueous phase into the circulating water by circulating water pump, pumping water back to methanol as washing cycle, pumping dimethyl ether into the gas pipeline network, feeding fresh water by reflux, controlling the methanol concentration to ensure absorption, heating dimethyl ether bottoms at 90-110 degrees C by heating medium, recovering condensate, returning gas phase back to rectifying tower bottom and taking liquid phase as follow-up decarburization tower feedstock.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic structure diagram of energy-saving device.    Feed pump (1)    Dimethyl ether removal tower (2)    Methanol washing tower (3)    Reflux tank (4)    Overhead reflux pump (5)    Reboiler (6)    Circulating water pump (7)    Circulating water cooler (8)