Abstract: A process for the direct synthesis of urea from ammonia and carbon dioxide at high pressures and temperatures, with the formation of ammonium carbamate as intermediate, comprising a decomposition step of the ammonium carbamate and stripping of the gases formed, operating substantially at the same pressure as the synthesis step, wherein the recycled liquid streams are fed, at least partially, to the same decomposition and stripping step after being preheated by heat exchange with a stream included in the high-pressure synthesis cycle.

Abstract: A method of using a buoyancy fluid presenting density that is less than that of sea water, and that is confined in a rigid or flexible leaktight casing, so as to constitute an immersed buoyancy element, wherein the buoyancy fluid is a compound that is naturally in a gaseous state at ambient atmospheric temperature and pressure, and in a liquid state at the underwater depth to which the buoyancy element is immersed. A method is also disclosed for placing a buoyancy element in place between the surface and the bed of the sea, wherein fluid is stored in a tank on a surface ship as a liquid in the cooled or compressed liquid state, and is injected in the liquid state into a pipe from the surface where it is stored to an immersed casing at an underwater depth at which the underwater pressure is not greater than the vapor pressure of the gas corresponding to the compound at the temperature at the depth.

Abstract: A modular liquid/liquid gravity separation device for separating the aqueous phase and the oil phase of a crude oil at the sea bottom. The device has a plurality of separation modules coupled to a common manifold device. Each separation module has a fluid delivery pipe coupled to at least one gravity separation pipe by a tubular bend device. The common manifold device has a first tank fed with crude oil by a feed pipe resting on the sea bottom via a first inlet orifice, a plurality of first outlet orifices feeding crude oil to said delivery pipes. The aqueous and oil phases are separated within the separation pipes before being delivered into a second tank via second inlet orifices of the second tank to which the separation pipes are coupled. The oil phase is conveyed to the surface from the second tank via a first removal pipe. The aqueous phase is conveyed to the sea bottom.