NOVELTY - The biomass torrefaction system comprises an inlet (22) to receive biomass particles, a reactor drum (12) configured to rotate about an axis of rotation, a heat source (30) upstream of the reactor drum to heat gas contained in the system to a temperature sufficient to torrefy the biomass particles during operation, a fan device coupled to the system to create, when the system is in operation, and a heated gas stream through the reactor drum sufficient to intermittently transport the biomass particles along the longitudinal length of the reactor drum.    USE - The system is useful for torrefying cellulosic biomass particles such as wood chips and giant cane chips.    ADVANTAGE - The system is capable of continuously and efficiently torrefying the cellulosic biomass particles of various sizes with high yield and reduced energy consumption in a consistent and controlled manner.    DETAILED DESCRIPTION - The biomass torrefaction system comprises an inlet (22) to receive biomass particles, a reactor drum (12) configured to rotate about an axis of rotation, a heat source (30) upstream of the reactor drum to heat gas contained in the system to a temperature sufficient to torrefy the biomass particles during operation, a fan device coupled to the system to create, when the system is present in operation, a heated gas stream through the reactor drum sufficient to intermittently transport the biomass particles along the longitudinal length of the reactor drum as the biomass particles are lifted by the flights and showered through the heated gas stream as the reactor drum rotates, gas ducts coupled to the reactor drum, heat source and fan device to recirculate a portion of gas exiting the reactor drum back to the heat source to reheat the gas for reintroduction into the reactor drum, a hopper located downstream of the reactor drum to collect torrefied biomass particles exiting the reactor drum and to discharge the torrefied biomass particles from the system, ducting to dispel exhaust gas from the system, control valves, dampers, ducting to route exhaust gas from the system to a remote device of the exhaust gas in an auxiliary or supplemental process, an airlock (26) coupled between the inlet and the reactor drum to limit the amount of oxygen entering the system when receiving the biomass particles, a seal mechanism between the reactor drum and adjacent structures, a steam plant coupled to the reactor drum to introduce steam into the reactor drum and assist in the torrefaction of the biomass particles, a control system configured to selectively adjust the speed of the fan device to regulate a speed of the flow of gas through the system, and a vent configured to subject the system to an external environment upon deflagration within the reactor drum. The reactor drum has flights of locations along a longitudinal length of the reactor drum, and is five feet in diameter. The heated gas stream directly heats the biomass particles as the gas stream intermittently transports the biomass particles through the reactor drum. The flights are configured to regulate movement of the biomass particles through the reactor drum for influencing a retention time of the biomass particles within the reactor drum and spaced around an inner circumference of the reactor drum in regular or irregular intervals and present in locations along the longitudinal length of the reactor drum, and interoperate with the heated gas stream to classify the biomass particles according to particle density by moving relatively denser particles with respect to similarly sized particles through the reactor drum more slowly. The control valves and dampers are positioned to regulate a pressure level within the system to inhibit the infiltration of oxygen into the system while enabling exhaust gas to exit the system. The remote device is a burner configured to utilize the exhaust gas to generate a heated medium for supplying heat via a heat exchanger to the gas, which passes through the reactor drum during operation. The seal mechanism includes a chamber between the reactor drum and an external environment, and is coupled to an inert or semi-inert gas source for selective purging of the chamber during operation. The heat source is an electrical immersion-type duct heater positioned upstream of the reactor drum, a heat exchanger positioned upstream of the reactor drum and a low oxygen burner positioned to directly heat the gas, which passes through the reactor drum during operation, and is configured to transfer heat from a heated gas isolated from the reactor drum to the gas, which passes through the reactor drum during operation. The control system is further: configured to selectively adjust the speed of the rotation of the reactor drum to regulate a time of residence of the biomass particles in the reactor drum; configured to selectively adjust the temperature of the flow of gas through the system; configured to selectively adjust parameters of the flow of gas through the system including volume, speed and/or pressure; configured to independently control operational parameters to regulate a torrefaction process of the biomass particles; configured to continuously or intermittingly adjust some of the operational parameters during operation to optimize the torrefaction process or tailor characteristics of the resultant torrefied biomass particles; and configured to torrefy biomass particles at a minimum rate of one ton of torrefied biomass particles per hour. The operational parameters includes a reactor inlet temperature, a reactor outlet temperature, an average residence time, oxygen content of the heated gas stream and/or gas flow characteristics. The control system includes sensors for monitoring some of the operational parameters. The torrefied biomass particles have an energy density of 20 GJ/ton. An INDEPENDENT CLAIM is included for a method of biomass torrefaction.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a biomass torrefaction system.    Reactor drum (12)    Longitudinal axis (16)    Inlet (22)    Airlock (26)    Heat source. (30)