A clearance control apparatus providing compressed cooling air to a turbine casing in a gas turbine, the apparatus including: a cooling gas passage extending through an inner annular shell of the turbine casing; a cooling gas conduit connected to a compressor of the gas turbine and to the turbine casing, wherein the cooling gas conduit receives compressed air from the compressor and delivers the compressed air to the turbine casing, and wherein the cooling gas conduit is in fluid communication with the cooling gas passage, and a heat exchanger connected to the cooling gas conduit and to a fuel conduit delivering fuel to a combustor of the gas turbine, wherein the heat exchanger transfers heat from the cooling gas to the fuel.