Thermal Lance Operating Principle

The fundamental principle of a thermal lance is the rapid and highly exothermic oxidation of iron in a pure oxygen environment. The device is deceptively simple in its construction, comprising an outer steel pipe filled with smaller steel rods or a mix of steel and aluminum/magnesium wires. This packing increases the surface area of the fuel (the iron) exposed to the oxygen flow, promoting a more intense and sustained reaction. To initiate the process, the tip of the lance must be heated to iron’s ignition temperature, approximately 900 °C, typically using an oxy-acetylene torch. Once ignited, a self-sustaining reaction begins. The pressurized oxygen, usually at 4 to 10 bar (60 to 150 psi), flows through the pipe, reacting with the hot iron. This reaction, \(4Fe + 3O_2 \rightarrow 2Fe_2O_3\), releases a tremendous amount of energy, raising the temperature at the tip to between 3,500 °C and 4,500 °C. This temperature is well above the melting point of most materials, including steel, rock, and concrete. The kinetic energy of the high-pressure oxygen jet helps to physically blow away the molten material and slag, creating the cut or hole. The lance itself is consumed during this process, with burn rates varying depending on the lance diameter and oxygen pressure.