Kinetic model for torrefaction of wood chips in a pilot-scale continuous reactor

Effects of temperature and residence time on continuous torrefaction of spruce wood

“…A few initiatives have demonstrated use of continuous reactors in pilot-or demonstration-scale [13][14][15], but published results so far are limited. Chang et al studied the possibility of using torrefaction as a pretreatment method prior to fast pyrolysis using a continuous auger reactor [13].…”

“…Evaluation of the proprietary REVE technology with measurement of heating values, elemental composition and sieve analysis of milled torrefied product, concluded that the pilot plant is suitable for continuous torrefaction at 300°C for 10 min at 40 kg/h [14]. Shang et al developed a kinetic model for torrefaction using a batch reactor and the model predicted mass yield and heating value for torrefied wood produced in a continuous auger reactor [15]. Residence times reported have generally been relatively long (30 min to 3 h), probably not feasible in a commercial scale as reactor size and thus investment costs increase with increased residence time.…”

Torrefaction of pine in a bench-scale screw conveyor reactor

“…This work documents the performance of a continuous, bench-scale torrefaction process based on screw conveyor reactor technology. While batch and moving bed reactor systems are more frequently described in academic literature, results from continuous, screw conveyor reactors are relatively scarce [2] with the exceptions of some recent publications (Shang et al [3]; Ohliger et al [4]). The experimental setup used in this work is unique in that temperature readings are taken from the surface of the rotating screw throughout the length of the reactor.…”

Char quality response surfaces from torrefaction of coppiced willow in a horizontal moving bed pilot plant

“…The Ghent University plant was reportedly tested from reactor wall temperatures between 275–375 °C and residence times from 5.75–16.7 min using commercial pine with maximum 6 mm dimension. Similar to other small scale screw conveyor torrefaction plants (Shang et al and Ohliger et al), that plant is indirectly heated, and as a result these plants utilize either high temperatures (300 °C and above), long residence times (> 30 min) or both, in order to achieve torrefaction severity in the typical range of 80–90 % mass yield. The CTU was designed and built to demonstrate more rapid, controllable, and flexible torrefaction by combining the precise feedstock flow control of a screw conveyor with the heating rate and temperature control of convective or direct heating that is typically employed in vertical moving beds, cyclonic systems, and tray contactors …”