Integrated process for fixed bed hydrocracking and ebullated bed hydroconversion with improved liquid/gas separation

The invention relates to an integrated process for ebullated bed hydroconversion (1000) of a first stream (100) of a heavy hydrocarbon fraction and "two-step" fixed bed hydrocracking (2000) (steps j and g) of a second stream (114) of a hydrocarbon feedstock, the "two-step" fixed bed hydrocracking (2000) comprises a desulfurization step (h) of the unconverted liquid fraction obtained from the second fixed bed hydrocracking step (g) in the form of a mixture with the gas stream (110) obtained from the specific separation step (e) of the ebullated bed hydroconversion process. The invention can incorporate the recycle of hydrogen and at least partially desulfurize the gas oil fraction obtained from the ebullated bed hydroconversion process. The specific separation step (e) is based on a gas/liquid separator comprising an internal cyclone and injection means for injecting at least the hydrocarbon liquid into the inlet of the cyclone, reducing entrainment of the fouling liquid in the separated gas stream and achievi