The present invention concerns a method of making a mineral melt by burning combustible material in the presence of inorganic particulate material and thereby forming a melt, comprising injecting fuel, particulate mineral material and combustion gas into a circulating combustion chamber (1) through an inlet conduit (4) and combusting the fuel in the circulating combustion chamber (1) thereby melting the mineral material to form a mineral melt and generating exhaust gases; separating the exhaust gases from the mineral melt, collecting the mineral melt (9) and passing the exhaust gases upwards through an exhaust pipe (10) to a conduit (11) of a heat exchange system; and supplying particulate mineral material and a first portion of waste mineral wool into the conduit (11) and pre-heating the supplied material in the heat exchange system, and supplying a second portion of waste mineral wool with a water content between 5 and 25% by weight directly to the inlet conduit (4).