Method for recycling coal liquefaction residue

1. A method for recycling a coal liquefaction residue, comprising:

drying a coal liquefaction residue and pulverizing the dried coal liquefaction residue to obtain a pulverized coal liquefaction residue, the coal liquefaction residue comprising a waste product generated by a direct coal liquefaction process;

subjecting the pulverized coal liquefaction residue to a solvothermal extraction in an autoclave to obtain an extract liquid and a residue; and

distilling the extract liquid and recovering an organic solvent to obtain a solid extract.

2. The method as claimed in claim 1 , wherein a solvent for the solvothermal extraction is N-methylpyrrolidone, and the solvothermal extraction is conducted at a temperature of 300-400° C. for 0.5-1.5 h.

3. The method as claimed in claim 1 , wherein the coal liquefaction residue is dried at a temperature of 80-120° C. and pulverized to a particle size of less than or equal to 0.2 mm.

4. The method as claimed in claim 1 , wherein the distilling is conducted at a temperature of 80-110° C. and a vacuum degree of less than or equal to 0.05 Mpa.

5. The method as claimed in claim 1 , further comprising preparing a hot-pressed coal briquette using the solid extract as a binder, wherein the preparation of the hot-pressed coal briquette comprises:

mixing amounts of the solid extract and raw coal to obtain a first mixture; delivering the first mixture into a hot-pressing mold;

placing the hot-pressing mold in a high-temperature furnace;

heating the hot-pressing mold, and subjecting the first mixture to heat preservation and hot-pressing molding at a set pressure; and

cooling the hot-pressing mold to room temperature to obtain the hot-pressed coal briquette.

6. The method as claimed in claim 5 , wherein a weight ratio value of the solid extract to the raw coal is in the range of 5-25%, and the hot-pressing molding is conducted at a temperature of 250-500° C., and the heat preservation is conducted for 10-60 min.

7. The method as claimed in claim 5 , wherein the raw coal is selected from the group consisting of bituminous coal and anthracite.

8. The method as claimed in claim 1 , further comprising preparing a ceramsite using the residue obtained after subjecting the pulverized coal liquefaction residue to the solvothermal extraction in the autoclave as a raw material, wherein the preparation of the ceramsite comprises:

mixing alumina, bentonite and the residue obtained after subjecting the pulverized coal liquefaction residue to the solvothermal extraction in the autoclave to obtain a second mixture; and

subjecting the second mixture to granulation, pre-heating, and high-temperature sintering to obtain a finished ceramsite product.

9. The method as claimed in claim 8 , wherein the pre-heating is conducted at a temperature of 400-600° C. for 10-30 min, and the high-temperature sintering is conducted at a temperature of 900-1,200° C. for 10-60 min.