Natural gas hydrate underground in-situ desanding device and desanding method for double-layer pipe drilling

The invention relates to a natural gas hydrate underground in-situ desanding device and desanding method for double-layer pipe drilling, and belongs to the technical field of natural gas hydrate cementation breaking and desanding. An inner cylinder and an outer cylinder form a double-layer pipe structure; in the working process, axial flow of mixed slurry is converted into rotational flow through a swirler, so that the natural gas hydrate is stripped from silt by using centrifugal force and fluid shear force generated by autorotation of the cemented particles in a rotational flow field; and then under the condition that the natural gas hydrate returns to an offshore platform to be used by human beings, the silt is backfilled to the stratum in situ. The mining safety and reliability of the natural gas hydrate are guaranteed; and the device provides separation conditions for liquid and solid phases, has the advantages of particle sorting and rotational flow cementation breaking, solves the problem of cementatio