Modular ammonia cracker

An ammonia cracker module 100 for converting ammonia into hydrogen, comprising a heat exchange reactor 130 and a heating system, the heat exchange reactor comprising: a first reaction zone 101 comprising a first working fluid flowpath 110, a first reactant flowpath 120, and one or more heat exchange interfaces positioned between the first flowpaths; a second reaction zone 102 comprising a second working fluid flowpath 113, a second reactant flowpath 122, and one or more heat exchange interfaces positioned between the second flowpaths; and a catalyst positioned to contact reactant fluid flowing through the first and second reactant flowpaths to convert ammonia flowing through the reactant flowpaths into hydrogen; and the heating system comprising a first heat source 104 configured to heat working fluid 108 to create a first heated working fluid, and a second heat source 105 configured to heat the first thermally depleted working fluid from the first working fluid flowpath and output a second heated working fluid, wherein the outlets of the first working fluid and first reactant flowpaths are in fluid communication with the inlets of the second working fluid and second reactant flowpaths respectively. A method of producing hydrogen from ammonia is specified.