A combustion system using at least 90 wt % propylene glycol based liquid fuel includes a first fuel tank, a wick inserted in the first tank, a sensing unit configured to receive an activating signal and sense the liquid level of the propylene glycol based liquid fuel in the first fuel tank and send a fuel replenishment signal accordingly, a second fuel tank, a conduit system connected with the first and the second fuel tanks, and a drive unit connected with the conduit system and configured to receive the fuel replenishment signal so as to cause the propylene glycol based liquid fuel in the second fuel tank to replenish the first fuel tank through the conduit system as well as to cool the wick.

Disclosed is a method for calculating combustion in the bed of a waste incinerator. The method is based on a model of combustion in a waste incinerator bed and comprises a water evaporation model, a volatile matter analysis model, a volatile matter combustion model, and a fixed carbon combustion model. The volatile matter of the volatile matter combustion model comprises CO, H.sub.2, CH.sub.4, NH.sub.3, and H.sub.2S. The volatile matter combustion model comprises a combustion reaction equation for said volatile matter and O.sub.2, and respective equations for CO and CH.sub.4 reacting with water vapor. Equations governing the model of combustion in the bed of a waste incinerator comprise a continuity equation, an energy equation, a momentum equation, and a component equation. Boundary conditions of said governing equations comprise: equations of heat transfer and mass transfer from an upper boundary layer of the bed to the exterior; and equations of heat transfer and mass transfer from lower boundary layer of the bed to the exterior.

Disclosed is a method for calculating combustion in the bed of a waste incinerator. The method is based on a model of combustion in a waste incinerator bed and comprises a water evaporation model, a volatile matter analysis model, a volatile matter combustion model, and a fixed carbon combustion model. The volatile matter of the volatile matter combustion model comprises CO, H.sub.2, CH.sub.4, NH.sub.3, and H.sub.2S. The volatile matter combustion model comprises a combustion reaction equation for said volatile matter and O.sub.2, and respective equations for CO and CH.sub.4 reacting with water vapor. Equations governing the model of combustion in the bed of a waste incinerator comprise a continuity equation, an energy equation, a momentum equation, and a component equation. Boundary conditions of said governing equations comprise: equations of heat transfer and mass transfer from an upper boundary layer of the bed to the exterior; and equations of heat transfer and mass transfer from lower boundary layer of the bed to the exterior.

A bubbling fluidized bed combustion device (1) comprising a fluidization vessel (2), a fluidized sand bed (3) arranged in the fluidization vessel and an arrangement for monitoring the fluidized sand bed. The arrangement comprises at least one radar level gauge (4) arranged to repeatedly measure a distance (D) in the fluidization vessel from a reference point (5) to at least one portion (6) of the top surface of (7) the fluidized sand bed, and to provide a measurement signal (S) representative of the distance. The invention also relates to a method for monitoring a fluidized bed in a bubbling fluidized bed combustion device.

A bubbling fluidized bed combustion device (1) comprising a fluidization vessel (2), a fluidized sand bed (3) arranged in the fluidization vessel and an arrangement for monitoring the fluidized sand bed. The arrangement comprises at least one radar level gauge (4) arranged to repeatedly measure a distance (D) in the fluidization vessel from a reference point (5) to at least one portion (6) of the top surface of (7) the fluidized sand bed, and to provide a measurement signal (S) representative of the distance. The invention also relates to a method for monitoring a fluidized bed in a bubbling fluidized bed combustion device.

A wood pellet stove operable to mount to a wall includes a combustion chamber, a combustion chamber door, and a hopper. The combustion chamber has a front, back, and side. The combustion chamber door is in the front of the combustion chamber. The hopper is mounted at the side of the combustion chamber. The bottom of the hopper is below a top of the combustion chamber, and a top of the hopper is substantially coplanar with the top of the combustion chamber. The stove may also include a sight glass or fuel level monitoring system for determining a fuel level of the hopper without opening the hopper.