The overall goal of this process is to demonstrate the production of hydrocarbon fuels from lignocellulosic biomass in a two-step process consisting of fast pyrolysis and hydrotreating. This method can help answer key questions in the biofuels field, such as the impact of feedstock and operating conditions on the quality and yield of pyrolysis bio-oil, and the hydrocarbon product. The main advantage of this technique is that it allows for production of oil in industrially relevant reactors, and in sufficient quantities to evaluate the fully integrated process.
The general problems with pyrolysis operations are:feeding biomass reliably, keeping condensed vapors from plugging heated transfer lines in the condenser inlet, and achieving complete condensation. Catalyst plugging during hydrotreating due to instability of products is by oil, is just by using a two-stage process including a stabilization stage. Demonstrating the pyrolysis procedure will be Kellene Orton from the National Renewable Energy Laboratory.
The pyrolysis reactor used is a laboratory-built 5.0 centimeter inner diameter bubbling fluidized bed reactor equipped with a glass condensation system. Assemble the pyrolysis reactor, cyclone with tar receiver, and hot filter as described in the text protocol. For the first condenser, use a graphite ferrule in a compression union to couple the stainless steel tubing to a piece of borosilicate glass tubing fused to a standard taper joint.
Avoid overtightening. Apply silicone grease, or a Teflon sleeve, to the standard taper joint. Connect the first condenser to a two-necked flask placed in a container that will serve as an ice bath.
Make connections between vessels downstream of this point with 9-12 millimeter clear vinyl tubing. Secure the tubing with hose clamps on ground glass joints, spherical joints, and hose barbs on the glassware. Connect the outlet of the first condenser flask to the inlet of the electrostatic precipitator, or ESP.
Connect the outlet of the ESP to the upper connection of the cold finger condenser. Then, connect a U-tube pressure relief to the line between the ESP and cold finger condenser. Fill the U-tube half full with water.
Next, connect the receiver to a 500 milliliter two-necked flask placed in a container that will serve as a dry ice bath. Attach a knockout to the flask. Connect the outlet of the knockout to the inlet of the housing of the coalescing filter.
Place a container for holding dry ice around the bottom of the filter housing. Pour 200 milliliters of sand into the reactor. Then, pour two kilograms of ground biomass into the feed hopper.
Perform the leak check, heat the reactor, and prepare to operate it as described in the text protocol. Finally, add ice and dry ice to the condenser train. To begin the pyrolysis experiment, turn on the long copper valves and auger.
Turn on the feed system vibrators. Turn on ESP. Set the voltage to 5-10 kilovolts, as needed, to observe an arc at least once every two seconds.
Turn on the feeder at a low rate. And make sure that the biomass is feeding. Observe the bed temperature, and increase the set point as needed to compensate for increased heat load.
When the temperature has recovered to within two degrees Celsius of the set point, increase the feed rate by 100 grams per hour. Repeat the process until the desired feed rate is reached. Every 15 minutes, record the bed temperature, feed rate, dry test meter rate, and system pressures.
Verify that the ESP is still arcing correctly. Respond to changes as needed, refill the ice and dry ice, drain the ESP into a product collection jar as needed. Stop feeding after feeding enough biomass to obtain good mass balance closure.
Avoid overfilling the tar receiver or the condenser receivers. Weigh all parts of the condenser system to obtain total liquid yield. Pour the liquids from the condenser receivers into a common jar or bottle.
After cooling the system to below 50 degrees Celsius, collect tar from the receiver and the hot filter. Remove and weigh the bed material using a HEPA vacuum with a knockout vessel. Oxidize the system, and calculate yields as described in the text protocol.
Analyze the pyrolysis oil as described in the text protocol. The hydrotreating system used is a laboratory-built 1.3 centimeter inner diameter fixed-bed continuous flow reactor, with a gas and liquid feeding component, and a gas-liquid product separation component. Crush both catalysts, use ruthenium supported on carbon as the stage one catalyst for pyrolysis oil stabilization, and use cobalt molybdenum supported on alumina as the stage two catalyst for pyrolysis oil hydro-deoxygenation.
Sieve to retain 0.25 to 0.60 millimeter grains. Use stainless steel tubes and screens as the support media for the catalyst beds. Slowly and sequentially, pour the stage two catalyst grains, the stage one catalyst grains, and the original stage one catalyst extrudates into the reactor, while tapping on the outside of the reactor to form packed catalyst beds.
Load 32 milliliters of each catalyst to form a two-stage catalyst bed with 24 milliliters of each catalyst located in the isothermal zone. Place the reactor into the hydrotreater system by first installing the two heaters. Then, connect the reactor to the gas and liquid feed component and the gas-liquid product separation component.
After performing catalyst pre-treatment by sulfidation as described in the text protocol, adjust the hydrogen flow to 153 milliliters per minute, and maintain the system pressure at 10.3 megapascals. Set the temperature of the stage one catalyst bed to 220 degrees Celsius, and the temperature of the stage two catalyst bed to 400 degrees Celsius. Record the bed temperature and hydrogen flow baselines when the temperature, pressure, and hydrogen flow become stable.
Add di-tert-butyl disulfide to the pyrolysis oil feed at an amount equal to 150 ppms sulfur in pyrolysis oil. Fill one of the feeding pumps with the pyrolysis oil feed, and purge the feeding line until a liquid flow that is free of air bubbles is achieved. Pressurize the pump to 10.3 megapascals, and then connect to the reactor by opening the connecting valves.
Start feeding the pyrolysis oil at a flow rate of 4.8 milliliters per hour. This action starts the pyrolysis oil hydrotreating test. Check the status of the reactor, and record the parameters, such as temperature, pressure, flow rate, and volume, periodically.
Ensure that the catalyst bed temperatures are within plus or minus two degrees of the desired temperature, that the gas and liquid flow rates are exactly the same as the desired settings, and that the reactor pressure is within plus or minus 0.15 megapascals of the desired pressure. Also ensure the pressure drop across the catalyst bed is less than 0.35 megapascals. Collect the liquid samples every six hours by first switching the sampling trap to the bypass trap and reducing the pressure of the sampling trap.
Then, drain the liquid sample to collecting vials. Purge the sampling trap, and pressurize the sampling trap with nitrogen. Finally, redirect the product flow to the sampling trap.
Analyze the gas samples every two hours by using microgas chromatography. Conduct the test for 60 hours on stream, setting the reactor temperature to 100 degrees Celsius, and the hydrogen flow rate to 100 milliliters per minute. Terminate the test by stopping the pyrolysis oil feed.
Process and analyze the liquid products as described in the text protocol. This figure compares elemental analysis of the carbon, hydrogen, and oxygen content of the feedstock, the pyrolysis oil, and the upgraded fuel. It demonstrates successful conversion of biomass feedstocks to hydrocarbon liquid fuels in the two-step process.
The impact of hot gas filtration of pyrolysis vapors prior to condensation is demonstrated here. Hot gas filtration eliminates inorganic residues, but it also affects pyrolysis oil yield and oil properties, such as oil oxygen content. Detailed results demonstrate the yields and properties of upgraded fuels after hydrotreating.
Hot vapor filtered bio-oil leads to a slightly higher water-to-fuel ratio, and the properties of upgraded fuel for the two bio-oils are very similar. The major difference between hydrotreating of the two pyrolysis oils is that the catalyst bed of hot vapor filtered bio-oil showed much less deposition of minerals. This technique shows the conversion of lignocellulosic biomass, to hydrocarbon fuels via fast pyrolysis and hydrotreating, by using the needed conditions to produce a high-quality biofuel in good yield.
After this development, this technique paved the way for researchers to explore biomass feedstocks, policies and parameters, and hydrotreating catalysts and parameters with highest impact on overall carbon efficiency, for biofuel production. Don't forget that working with pyrolysis oil, and on hot-reactor systems, can be extremely hazardous. Precautions should always be taken while performing this technique.
Furthermore, safety rules and procedures should be strictly followed.
