A combustion system including a fuel storage stores solid fuel, a supply device connected to the fuel storage, a combustion device combusts supplied solid fuel, and a prediction device for predicting a switching time for types of solid fuel supplied from the fuel storage to the combustion device via the supply device. The prediction device comprises at least one processor configured to acquire a level of solid fuel stored in the fuel storage, predict, as the switching time, a future time when a level obtained by extrapolating time-dependent change in decrease in the level of the solid fuel reaches a threshold value, and display the switching time on a display device.

A process for combusting a high-moisture fuel to generate steam in which the high-moisture solid fuel is first dried by contacting with an oxygen-depleted gas stream while being heated by indirect heat exchange with a recirculating thermal fluid. The dried fuel is then combusted with a combustion air stream to produce a combustion products stream whose heat first is used to generate steam, and then to preheat the combustion air stream by indirect heat exchange in which a portion of the combustion air stream and/or a portion of the combustion products stream bypasses the heat exchanger. The combustion products stream also provides heat to dry the solid fuel via the recirculating thermal fluid.

A process for combusting a high-moisture fuel to generate steam in which the high-moisture solid fuel is first dried by contacting with an oxygen-depleted gas stream while being heated by indirect heat exchange with a recirculating thermal fluid. The dried fuel is then combusted with a combustion air stream to produce a combustion products stream whose heat first is used to generate steam, and then to preheat the combustion air stream by indirect heat exchange in which a portion of the combustion air stream and/or a portion of the combustion products stream bypasses the heat exchanger. The combustion products stream also provides heat to dry the solid fuel via the recirculating thermal fluid.

A boiler 7 includes: a combustion furnace 100 having a combustion chamber 100F therein; a heat exchanger 140 configured to transfer, to water, thermal energy obtained by burning a solid fuel in the combustion chamber 100F; a belt conveyor 120 including a movable loader 120a, disposed on a bottom of the combustion chamber 100F, and configured to move the solid fuel on the movable loader 120a in the combustion chamber 100F; and a fuel supplier 130 connected to a fuel supply port 111a that communicates an inside and an outside of the combustion furnace 100. The belt conveyor 120 has a starting point below the fuel supply port 111alb . The fuel supplier 130 includes a thickness adjuster 131 that adjusts a thickness of the solid fuel on the movable loader 120a of the belt conveyor 120.