This invention discloses a fuel-fired
cascade heating device for the primary air duct of a boiler
coal mill, relating to the technical field of boiler auxiliary systems in thermal power plants. The device includes a large-capacity oil gun (1), a small-capacity oil gun (2), a primary air duct heating section (3), an oil gun
flame detection device (4), a
combustion air
system (5), and a local control cabinet (6). The large-capacity oil gun (1) and the small-capacity oil gun (2) have different rated fuel consumption. Both are installed on the primary air duct heating section (3), using
compressed air atomization to atomize the fuel and burn it within the duct. The
combustion air
system (5) draws
combustion air from the boiler's sealed air main
pipe and sends it into the primary air duct heating section (3). The local control cabinet (6) has a built-in PLC controller, which performs
cascade heating control on the large-capacity oil gun (1) and the small-capacity oil gun (2) according to a four-stage sequence: "simultaneous activation of both guns—stopping the small gun—switching between large and small guns—stopping all oil guns," gradually raising the primary
air temperature from ambient temperature to a target temperature range of 180–220°C. This invention solves the problem of
insufficient heating capacity of steam heat exchangers under
cold start conditions, which leads to insufficient
drying output of
coal mills. It achieves an
engineering-feasible trade-off between fuel consumption and heating rate, and can also serve as an auxiliary heat source for
plasma oil-free ignition systems.