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Various biooil conversion technologies are at different stages of development. The United States has developed experimental setups using various cracking methods, with a production capacity ranging from dozens to hundreds of kilograms per hour, and the highest oil yield reaching 70%. Italy has established a 500 kg/h facility, while Canada has set up a 200 t/d experimental facility. The main types include: entrained flow reactors, vacuum reactors, fixed-bed reactors (including sieve bed reactors), rotary kiln reactors (including rotating cone and rotating screw reactors), ablation plate reactors, ablation vortex reactors, fluidized bed reactors (including bubble beds and circulating beds), etc. The factors affecting the biooil yield include: pyrolysis temperature, the residence time of solids and gases in the reactor, heat transfer rate, and the rapid separation and cooling of steam generated during pyrolysis. Rapid heating of biomass plays an important role among these factors. 1. Fluidized bed pyrolyzer: Developed by the Georgia Institute of Technology in the United States; the reactor has a diameter of 15 cm, a height of 4.4 m, and a residence time of 1–2 seconds. In the system, the biomass particle size is 300–420 μm, the feeding rate is 15 kg/h, and the inlet temperature is maintained at 745°C. A higher flow rate of carrier gas is also used (at a ratio of 8:1 to the weight of the biomass). All inlet and outlet gases are controlled by a porous plate, and the reactor temperature is 400~550°C. The pyrolysis gas, water vapor, uncondensed steam, aerosols, and any fine dust present are fed into the demister, where most of the aerosols and fine dust are removed; the remaining mixture then enters the combustion furnace for burning. In the experiment, the yield of the organic condensed liquid was 58%, while the yield of coke was 12%. The calorific value of the resulting oil reached 24.57 MJ/kg; half of the total liquid products consisted of water. The maximum processing capacity of the existing setup is 50 kg/h. 2. Rapid fluidized bed pyrolyzer: The process developed by Waterloo University in Canada is a representative example. The raw material is air-dried wood chips with a particle size ranging from 30 to 170 mesh and a moisture content of around 7%, which are fed in using a screw feeder. Fine sand is used as the bed material, and the fluidized bed is equipped with electric heating to maintain a constant temperature. The heat required for pyrolysis is provided by the preheated fluidized gas, which, along with the carrier gas, are both gaseous products of the pyrolysis process. The solid biomass feed rate is 1.5~3 kg/h. The fine carbon powder generated by pyrolysis is carried out of the bed by the fluidizing gas; after separation in a cyclone separator, it enters the coke collection chamber. The gaseous products undergo two-stage condensation: the first stage of condensation collects asphalt-based products at 100°C, while the second stage collects light liquefied oils at room temperature. The uncondensed gas is filtered through a series of filters to remove impurities; part of it is compressed and returned to the reactor as fluidizing gas and carrier gas, while the rest is discharged from the system. The residence time of the reaction gas is about 0.5 s. When wood chips are used as the raw material, the liquid yield is as high as 65–70%, while it is 45–50% when straw is used. The liquid contains 15% to 30% water, depending mainly on the type of raw material and its moisture content. The bubbling fluidized bed reactor developed by Aston University in the UK has a processing capacity of 250 kg/h, and achieves a biooil yield of 75% when liquefying cork particles of 1–2 mm in size. 3. Vacuum pyrolyzer: Developed by Laval University in Canada, also known as a multi-bed pyrolyzer. The experimental equipment is 6 m tall and 0.7 m in diameter. The raw material (wood chips) enters from the sealed feed hopper at the top of the reactor; the wood chips have a size range of 1/4 to 1/2 sieve size (Taylor), with a feeding rate of 3.1 to 3.4 kg/h and a moisture content of 5.9%. The pyrolyzer is characterized by a low-pressure environment; the residence time of steam in the reactor is shorter than that in traditional cracking processes, which allows for an increased yield of liquids. The reactor needs to be preheated, with the temperature increasing continuously from top to bottom; a typical temperature range is from 200°C to 450°C. The system pressure is below 4000 Pa (30 mmHg). According to available information, units in Canada operating at a feed rate of 50 kg/h achieve a liquid yield of 65% and a coke yield of 20%. 4. Vortex ablation pyrolyzer: Developed by the U.S. Solar Energy Research Institute. The cylindrical wall of this reactor is heated to around 700°C; upon entering at high speed, the biomass particles slide along the circular wall in a spiral pattern. The sliding between the particles and the wall results in a very high heat transfer rate. Some of the partially pyrolyzed particles exit the reactor in a tangential direction, where they mix with newly added biomass particles before starting a new cycle at the inlet nozzle of the carrier gas. The carrier gases used were nitrogen and water vapor, at a mass ratio of 1:1.5 to the feed biomass. Particles of 2mm in size can remain in the pyrolyzer for 1 to 2 seconds, during which time 30 cycles are completed. This cycle makes the residence time of the particles independent of the steam residence time, thereby minimizing the impact of feed particle size on reactor operation. The yield of the liquid product was 67%, while the yields of coke and pyrolysis gas were 13% and 14%, respectively. Studies have shown that phenolic-containing extracts can be readily obtained from wood chip pyrolysis condensates, which is economically attractive. Currently, there are 1360 kg/h units in operation in the United States. 5. Rotating cone pyrolysis reactor: Developed jointly by the Department of Reaction Engineering at Twente University in the Netherlands and the BTG Institute. The pre-treated solid biomass, along with the preheated heat carrier (sand), enters the bottom of the rotating cone. The outer cone shell rotates at a speed of 1 r/s, and centrifugal force and friction cause the solid particles (hot sand and biomass particles) to rotate upward within the gap between the inner fixed cone shell and the outer rotating cone shell. During this process, biomass is rapidly decomposed into steam, which enters the cyclone separator through an outlet pipe; after passing through the carbonizer, the condensed vapor turns into oil. The bed temperature can be controlled by adjusting the fuel amount and air-fuel ratio ； The heat transfer rate can be adjusted by regulating the rotational speed of the conical rotor ； By adjusting the gap between the conical shells, the bed volume can be changed, thereby controlling the residence time of the pyrolysis steam. Solid residence time: 0.5 s, steam residence time: 0.3 s; bed temperature controlled at 500°C; heat transfer rate: 5000 K/s; product yield: 50%, gas: 20%, coke: 10%; feed rate: 10 kg/h. This reactor does not require a carrier gas to reduce the volume of the device, thereby minimizing the amount of gas that needs to be condensed and collected as well as the cost of the device; however, its operation and maintenance are more complex. 6. Spouted bed pyrolyzer: Developed by the University of the Basque Country in Spain. Its main feature is that the pyrolysis vapor can leave the reactor immediately, while the solid feedstock can circulate within the reactor until complete pyrolysis reduces its particle size, after which it is carried out by the gas flow; this approach allows for resolving the conflict between the residence time requirements of the feedstock particles and those of the product vapor. Another advantage of this device is the possibility of combining biomass pyrolysis with the refinement of the pyrolyzed oil. Considering that a certain amount of denser inert particles can often be added to a spouted reactor to enhance heat and mass transfer, using zeolite catalysts with catalytic cracking properties as such inert particles can improve the quality of the cracked oil. Experimental results prove this, but so far only those from small-scale devices are available. This post was last edited by ldhappyxun2006 on 2007-12-26 09:58.]