A process for the direct thermal decomposition of hydrocarbons into solid carbon and hydrogen comprising: a. preheating a hydrocarbon gas stream conducting the hydrocarbon gas stream from at least one hydrocarbon gas stream inlet, located at the top part of a liquid metal reactor, to the bottom part of the liquid metal reactor, through a pre-heating conduct located surrounding the external perimeter of the liquid metal reactor, said pre-heating conduct being located inside a thermal insulation means, obtaining a pre-heated hydrocarbon gas stream at a temperature between 500 and 700°C; b. injecting the pre-heated hydrocarbon gas stream obtained in step (a) into the liquid metal reactor, in particular, into a reactor pool of the liquid metal reactor containing a liquid metal media, wherein said injection takes place at the bottom part of the liquid metal reactor through a porous section or a set of gas injection orifices; c. the hydrocarbon gas injected into the liquid metal reactor in step (b) moves upwards by buoyancy forming a multi-phase flow, a hydrocarbon gas comprising hydrogen and solid carbon, at the same time that the liquid metal media inside the reactor pool is maintained at a temperature comprised between 900 and 1200°C; d. the solid carbon obtained in step (c) is accumulated at the top of the reactor pool, on the free surface of the liquid metal media located inside the liquid metal reactor, forming a carbon layer made up of solid carbon particles; e. once the carbon layer reaches a determined thickness, the carbon particles constituting the carbon layer are displaced into at least one carbon extraction system consisting of a porous rigid section located at the top of the liquid metal reactor, above the free surface of the liquid metal media, from which the carbon particles are conducted into at least one recipient for collecting the carbon particles; f. at the same time, the gas comprising hydrogen obtained in step (c) leaves the reactor pool through the porous rigid section, being collected at a gas outlet collector from where the gas comprising hydrogen finally leaves the liquid metal reactor. a. preheating a hydrocarbon gas stream conducting the hydrocarbon gas stream from at least one hydrocarbon gas stream inlet, located at the top part of a liquid metal reactor, to the bottom part of the liquid metal reactor, through a pre-heating conduct located surrounding the external perimeter of the liquid metal reactor, said pre-heating conduct being located inside a thermal insulation means, obtaining a pre-heated hydrocarbon gas stream at a temperature between 500 and 700°C; b. injecting the pre-heated hydrocarbon gas stream obtained in step (a) into the liquid metal reactor, in particular, into a reactor pool of the liquid metal reactor containing a liquid metal media, wherein said injection takes place at the bottom part of the liquid metal reactor through a porous section or a set of gas injection orifices; c. the hydrocarbon gas injected into the liquid metal reactor in step (b) moves upwards by buoyancy forming a multi-phase flow, a hydrocarbon gas comprising hydrogen and solid carbon, at the same time that the liquid metal media inside the reactor pool is maintained at a temperature comprised between 900 and 1200°C; d. the solid carbon obtained in step (c) is accumulated at the top of the reactor pool, on the free surface of the liquid metal media located inside the liquid metal reactor, forming a carbon layer made up of solid carbon particles; e. once the carbon layer reaches a determined thickness, the carbon particles constituting the carbon layer are displaced into at least one carbon extraction system consisting of a porous rigid section located at the top of the liquid metal reactor, above the free surface of the liquid metal media, from which the carbon particles are conducted into at least one recipient for collecting the carbon particles; f. at the same time, the gas comprising hydrogen obtained in step (c) leaves the reactor pool through the porous rigid section, being collected at a gas outlet collector from where the gas comprising hydrogen finally leaves the liquid metal reactor.