Catalytic coupling in-situ hydrogenation municipal sludge hydrothermal treatment method and system

The invention relates to the technical field of thermochemical treatment of municipal sludge, in particular to a catalytic coupling in-situ hydrogenation municipal sludge hydrothermal treatment method and system, which are suitable for hydrothermal liquefaction treatment of municipal sludge and are formed by continuously alternating catalytic hydrothermal desalination reaction, catalytic hydrothermal in-situ hydrogenation reaction and by-product recycling. The catalytic hydrothermal desalination reaction is used for removing nitrogen-containing compounds and inorganic salts in the sludge; the catalytic hydrothermal in-situ hydrogenation reaction is used for generating in-situ hydrogen so as to improve the grade of biological crude oil, and meanwhile, the hydrothermal oil yield is improved by utilizing Fe3O4 catalytic hydrothermal; and by-products, particularly recycled hot water phases, are recycled, so that the overall economic and environmental benefits of the system are improved. Harmless treatment of the