The present invention comprises a waterless mixture which includes a biuret and/or urea, silica, and melamine particles coated with a layer of magnetite iron oxide for cleaning furnaces, heaters or boilers. A typical cleaning mixture comprises 30-50 percent silica, 20-50 percent biuret and/or urea, 20-40 percent melamine and 1-5 percent iron oxide. The cleaning can be performed at any time. This may lead to a reduction in fuel consumption, less air pollution, increased throughputs, and avoidance of equipment damage.