Abstract: A gas supply system for dual-fuel or gas engines is adapted for integration with a boil-off gas reliquefaction plant. The system includes a cryogenic heat exchanger, a boil-off gas compressor having a boil-off gas preheater, and a nitrogen loop with a compander. The gas is in the form of liquefied natural gas from cargo tanks or condensate from the reliquefaction plant. The gas supply system also includes an evaporator (optimizer) that extracts cold duty from the gas, and/or an evaporator that is arranged in a closed loop, which includes at least one pump and a heating source for an intermediate medium used to optimize extraction of the cold duty.