A process for feeding ethylene into a polymerization system includes providing a low-pressure ethylene stream, one or more low-pressure C3 to C20 monomer streams, an optional low-pressure inert solvent/diluent stream, and one or more reactors; metering the low-pressure ethylene stream, the one or more low-pressure C3 to C20 monomer streams, and the optional low-pressure inert solvent/diluent stream; blending the metered low-pressure ethylene stream, the metered one or more low-pressure C3 to C20 monomer streams, and the metered low-pressure optional inert solvent/diluent stream to form an ethylene-carrying low-pressure blended liquid feed stream; pressurizing the ethylene-carrying low-pressure blended liquid feed stream to the polymerization system pressure with one or more high-pressure pumps to thrm an ethylene-carrying high-pressure blended reactor feed stream; and feeding the ethylene-carrying high-pressure blended reactor feed stream to the one or more reactors.