Enhanced extraction system and method based on ultrasonic excitation and acid fracturing integrated permeability enhancement for coal seam

An enhanced extraction system based on ultrasonic excitation and acid fracturing integrated permeability enhancement for a coal seam, comprising an ultrasonic excitation and acid fracturing integrated drilling device (a) located in an extraction borehole (2) and an ultrasonic control box (6) and a mixing tank (8) which are located outside the extraction borehole (2), wherein a liquid inlet end of the ultrasonic excitation and acid fracturing integrated drilling device (a) is connected to the mixing tank (8) by means of a fracturing pump (7);

• the ultrasonic excitation and acid fracturing integrated drilling device (a) comprises a liquid feed rod (a5), an ultrasonic transducer (a1), a fracturing cavity (a2) and a conical drill bit (a4) which are sequentially arranged from left to right and a plurality of openable tool assemblies (a3) located on left and right sides of the fracturing cavity (a2) in mirror symmetry;
• each said openable tool assembly (a3) comprises a slot (a31), a spool vertical moving rack (231) arranged beside the slot (a31) and capable of moving upwards and downwards, a tool gear (a33) fixed to a lower left corner of the slot (a31) and a tool (a34) fixed to a rotating shaft of the tool gear (a33), the tool gear (a33) is meshed with the spool vertical moving rack (a32), a side, away from the rotating shaft of the tool gear (a33), of the tool (a34) is provided with an arc-shaped edge, a spine of the tool (a34) is matched with an opening of the slot (a31) when the tool (a34) is retracted into the slot (a31), and a reset spring (a35) connected to the edge of the tool (a34) is arranged in a middle of a horizontal surface of an inner side of the slot (a31);
• when the fracturing cavity (a2) reaches a set pressure, the spool vertical moving rack (a32) moves upwards, and the tool gear (a33) rotates clockwise to drive the tool (a34) to be opened;
• and when the fracturing cavity (a2) does not reach the set pressure, the tool (a34) is retracted into the slot (a31) under the action of a resilience of the reset spring (a35).