for Mobile Facilities

Science (July 11, 2010) — Chemical engineers at Purdue University have developed a new method to process agricultural waste and other biomass into biofuels, and they are proposing the creation of mobile processing plants that would rove the Midwest to produce the fuels.

“What’s important is that you can process all kinds of available biomass– wood chips, switch grass, corn stover, rice husks, wheat straw …,” said Rakesh Agrawal, the Winthrop E. Stone Distinguished Professor of Chemical Engineering.

The approach sidesteps a fundamental economic hurdle in biofuels: Transporting biomass is expensive because of its bulk volume, whereas liquid fuel from biomass is far more economical to transport, he said.

“Material like corn stover and wood chips has low energy density,” Agrawal said. “It makes more sense to process biomass into liquid fuel with a mobile platform and then take this fuel to a central refinery for further processing before using it in internal combustion engines.”

The new method, called fast-hydropyrolysis-hydrodeoxygenation, works by adding hydrogen into the biomass-processing reactor. The hydrogen for the mobile plants would be derived from natural gas or the biomass itself. However, Agrawal envisions the future use of solar power to produce the hydrogen by splitting water, making the new technology entirely renewable.

The method, which has the shortened moniker of H₂Bioil — pronounced H Two Bio Oil — has been studied extensively through modeling, and experiments are under way at Purdue to validate the concept.

Findings are detailed in a research paper appearing online in June in the journal Environmental Science & Technology. The paper was written by former chemical engineering doctoral student Navneet R. Singh, Agrawal, chemical engineering professor Fabio H. Ribeiro and W. Nicholas Delgass, the Maxine Spencer Nichols Professor of Chemical Engineering.

Agrawal, Ribeiro and Delgass are developing reactors and catalysts to experimentally demonstrate the concept. Another paper by Agrawal and Singh addressing various biofuels processes, including fast-hydropyrolysis-hydrodeoxygenation, also appeared in June in the Annual Review of Chemical and Biomolecular Engineering.

The Environmental Science & Technology paper outlines the process, showing how a portion of the biomass is used as a source of hydrogen to convert the remaining biomass to liquid fuel.

“Another major thrust of this research is to provide guidelines on the potential liquid-fuel yield from various self-contained processes and augmented processes, where part of the energy comes from non-biomass sources such as solar energy and fossil fuel such as natural gas,” said Singh, who is now a researcher working at Bayer CropScience.

The new method would produce about twice as much biofuel as current technologies when hydrogen is derived from natural gas and 1.5 times the liquid fuel when hydrogen is derived from a portion of the biomass itself.

Biomass along with hydrogen will be fed into a high-pressure reactor and subjected to extremely fast heating, rising to as hot as 500 degrees Celsius, or more than 900 degrees Fahrenheit in less than a second. The hydrogen containing gas is to be produced by “reforming” natural gas, with the hot exhaust directly fed into the biomass reactor.

“The biomass will break down into smaller molecules in the presence of hot hydrogen and suitable catalysts,” Agrawal said.”The reaction products will then be subsequently condensed into liquid oil for eventual use as fuel. The uncondensed light gases such as methane, carbon monoxide, hydrogen and carbon dioxide, are separated and recycled back to the biomass reactor and the reformer.”

Purdue has filed a patent application on the method.

The general concept of combining biomass and carbon-free hydrogen to increase the liquid fuel yield has been pioneered at Purdue. The researchers previously invented an approach called a “hybrid hydrogen-carbon process,” or H₂CAR.

Both H₂CAR and H₂Bioil use additional hydrogen to boost the liquid-fuel yield. However, H₂Bioil is more economical and mobile than H₂CAR, Singh said.

“It requires less hydrogen, making it more economical,” he said. “It is also less capital intensive than conventional processes and can be built on a smaller scale, which is one of the prerequisites for the conversion of the low-energy density biomass to liquid fuel. So H₂Bioil offers a solution for the interim time period, when crude oil prices might be higher but natural gas and biomass to supply hydrogen to the H₂Bioil process might be economically competitive.”

The research was funded by the U.S. Department of Energy, the National Science Foundation and the U.S. Air Force Office of Scientific Research, and is affiliated with the Energy Center at Purdue’s Discovery Park.

Accessed & published by Henry Sapiecha

Main component and caloricity of biomass gas are different for difference of characteristic of biomass fuel and gasification method.

Through strict cleaning and thermal cracking, the dust & tar content of biomass gas are very tiny, which can meet the requirement for the internal-combustion engines normal operation.

Sourced and published by Henry Sapiecha 19th July 2009

Biomass Fuel Processing seems certain to play a role in our Sustainable Energy Future. Learn more about Biomass Fuel Processing here.

Direct Fired Wood Burners
The most common feedstock for direct fired wood burners is 3″ (76 mm) minus ground wood. Low moisture and dirt content are desirable however many burners can operate with high moisture wood (50%) at lower energy output. Minimum fines may also be desirable for maximum boiler efficiency depending on the boiler type. Urban Wood waste and forest residuals are common feedstock. Horizontal grinders are the most economical machine type to reduce wood for this application.

3-inch minus wood ground with a Peterson horizontal grinder

Short Fibre Applications
A growing number of specialized applications for biomass fuel require short fiber dry wood. These uses include the wood pellet industry, suspension burners (common in coal power plants) and certain gasification processes. The pellet industry needs a feedstock with a fiber length no longer than the pellet width. This is typically 0.25″ (6 mm) for household pellets and larger for industrial pellets. The feedstock needs to be dried to 5-8% moisture before the pellets are extruded.

Suspension burners also require short fiber wood, preferably less than 5 mm. The moisture level should be less than 20%. Some gasification processes also require low moisture feedstock although a short fiber length is not a requirement for many gasification processes.

There are a variety of processes that can result in a short fiber, dry finished product. The best process will depend on the type of feedstock and the initial moisture content. If the feedstock is primarily solid wood with high moisture content, a good process is to first chip and then dry the wood. The dry chips are then resized to the final fiber length specifi¬cation in a hammermill. The drying process works best with a consistent chip thickness. The fines may be screened out before drying since they can be entrained in the drying air stream. The fines can also be used for fuel in the dryer. The dry chips are more brittle so they are more readily reduced in the hammermill. Starting the process with short fiber chips (8-10 mm) will make the hammermill much more productive than longer fiber feedstock.

Short Fiber Chips produced by a Peterson 5900

Disc and Drum Chippers
Disc and drum chippers are the common machines used to reduce wood into short fiber chips. Disc chippers are the main type of chipper used to produce high quality wood chips for the pulp and paper industry. Disc chippers provide a more consistent chipping angle which results in more uniform chip thickness and length. The anvil gap, knife extension, counter knife angle, and attack angle can all be readily adjusted with a disc chipper to produce the highest quality chips. Drum chippers typically do not have the same number of parameters that can be fine turned to optimize the chip quality and minimize fines.

Peterson 5900 Chipper in Action
A typical chip length specification for the pulp industry is between 0.62″ (16 mm) and 1.12″ (28 mm). Modifications must be made to the disc, counter knife and chipping speed to produce the shorter chips (< 10 mm) that are preferred as feedstock for wood pellets and suspension burners. Peterson has developed and tested a sort chip configuration for the 5900 chipper and 5000H delimber, debarker chipper. Production with these machines will vary with wood species and tree size however 50-70 tons/hour will be typical in a wide range of feedstock. The fuel consumption will range from 0.2 – 0.5 gal./ton (0.76 – 1.9 liters/ton) depending on the wood moisture level. Fuel consumption of 0.2 gal/ton (0.76 liters/ton) will be typical for fresh wood.

Advantages of Debarking
Low bark content is required for household pellets in order to minimize ash. Removing the bark also cleans the wood, eliminating sand and dirt that can reduce the service life of chipper components and pelletizing dies. It may be advantageous to debark the wood to save on chipping and pelletizing costs even if a low ash final product is not needed. The bark that is removed can be used for fuel in the drying process or sold as high value landscape bark.

Peterson can pair the 4800 debarker with the 5900 chipper to achieve a low ash wood pellet. The 5000H delimber, debarker, chipper can provide even lower bark and ash content all within a single machine.
Peterson 4800 Flail paired with a Peterson 5900 Chipper

Dry Wood Processing
If the wood has dried from moisture loss after felling or from an infestation such as a pine beetle attack, chipping costs will be substantially higher than with fresh wood. With dry wood, a horizontal grinder may be the best choice for the primary reduction. Tests with Southern Pine show that the fuel consumption is twice as high chipping wood that has dried six months (low 40’s% moisture content.) compared to chipping fresh wood. Dry wood will fracture well in a horizontal grinder. Peterson is able to fine tune the rotor speed, bit type and grate openings to optimize the product size. If a short fiber product is required, the small grate openings can be used.

Sourced and published by Henry Sapiecha 19th JULY 2009

Mitsubishi Heavy to Test CO2

Recovery from Coal-fired Flue Gas

Mitsubishi Heavy Industries Ltd (MHI) and Southern Company, a major US power company, will jointly launch a field test in 2011 to recover high-purity carbon dioxide (CO₂) from coal-fired flue gas.

The two companies will set up a CO₂ recovery demonstration plant, which is designed to be built at a medium-scale thermal power station in Alabama, the US. Based on the results of this demonstration plant, they will aim to commercialize the recovery plant in the future.

The field test will be subsidized by the US government. The demonstration plant will be constructed in Plant Barry, a coal-fired power station owned by Southern’s subsidiary Alabama Power. Recovered CO₂ will be compressed and stored in an aquifer deep underground.

The demonstration plant is composed of various facilities such as those for pre-processing, CO₂ absorption/reclamation (absorption and reclamation towers) and CO₂ injection. The plant will recover 500t of CO₂ per day (equivalent to that produced when 25,000kW electricity is generated). The recovery rate is 90% or higher. The purity of recovered CO₂ is expected to be 99.9%.

The recovery process is as follows. Coal-fired flue gas contains not only CO₂ but also ‘impurities’ such as SOx, NOx, heavy metals and halogen compounds. These impurities are removed as much as possible in the pre-processing facilities, and the flue gas is cooled to near room temperature.

Flue gas with most impurities removed is taken into the absorption tower. Inside the tower, the gas is brought into contact with an absorbing solution so that only CO₂ is absorbed into the solution. The solvent, “KS-1,” is an amine-based material co-developed by MHI and Kansai Electric Power Co Inc.

Next, the solution containing CO₂ is sent to the reclamation tower, where CO₂ and the solution are separated from each other by heating. Then, CO₂ is recovered, and the solution is recycled.

MHI has already commercialized a system to recover CO₂ from natural gas-fired flue gas. But, in order to apply this system to coal-fired flue gas, an additional process is required to remove heavy metals and halogen compounds because the impurities contained in natural gas-fired flue gas are only SOx and NOx.

Electric Power Development Co Ltd is also testing a CO₂ recovery plant for coal-fired flue gas at its Matsushima Thermal Power Plant. However, the amount of CO₂ recovered at the plant is only 10t per day. Therefore, a field test needs to be carried out using a larger scale plant for commercialization.

In addition to the field test announced this time, MHI is planning to construct a demonstration plant with a recovery capacity of 3,000t per day in the UK and intends to start trial operations in 2015.

Sourced and published by Henry Sapiecha 1st July 2009