Method for extracting herbal medicine

A method for extracting an herbal medicine comprising:

• step one, spray extraction:
• pulverizing herbs to 100 to 120 mesh fine powder, adding the fine powder and an extracting solvent, in a ratio of 6-7 L extracting solvent/1 kg fine powder, to an agitation tank (1), stirring a mixture of the fine powder and extracting solvent at 80-100 r/min for 1-1.5 hours, spraying the mixture to an extraction tank (3) at a spraying speed of 400 to 600 L/h, adding first additional extracting solvent to fill two-thirds to three-fourths of the extraction tank (3), the mixture being sprayed 2-3 cm below a surface of the extracting solvent in the extraction tank (3), spraying countercurrently second additional extracting solvent from a bottom of the extraction tank (3) at a speed of 1000-1600 L/h to form an extraction solution, the second additional extracting solvent being pumped from an extracting solvent tank (6) at a pump pressure of 3.0-5.0 MPa, the step one, spray extraction being conducted at room temperature;
• step two, pressure filtration and concentration:
• discharging the extraction solution from step one to a filter press (4) to remove insoluble waste at a speed of 400-600 L/h and a pressure of 0.4-0.7 MPa to store at an extraction storage tank (5), pumping the extraction solution from the extraction storage tank (5) to a vacuum concentration tank (10), concentrating the extraction solution in the vacuum concentration tank (10) under 0.08 MPa to 0.1 MPa and at 60-80° C. to form a concentrated extraction solution with a solution density of 1.0-1.3, the extracting solvent being recycled to the extracting solvent tank (6);
• step three, spray and countercurrent precipitation:
• spraying the concentrated extraction solution to a tube centrifuge (12) at a speed of 200-400 L/h, adding a precipitation solvent to fill two-thirds to three-fourths of the tube centrifuge (12), the concentrated extraction solution being sprayed 2-3 cm below a surface of the precipitation solvent in the tube centrifuge (12), spraying countercurrently additional precipitation solvent from a bottom of the tube centrifuge (12) at a speed of 1000-1400 L/h and a pressure of 2.0-4.0 MPa to form a precipitation solution, centrifuging the precipitation solution and discharging a supernatant through an overflow outlet (20) of the tube centrifuge (12) to a resting tank (17) at a speed of 600-900 L/h, the supernatant being stored in the resting tank (17) for 24 hours;
• and
• step four, concentrating reduced pressure and drying:
• concentrating the supernatant from the resting tank (17) under reduced pressure, drying by vacuum spray and freeze-dry to obtain the herbal medicine.