PNNL

Scientists and engineers at the Pacific Northwest National Laboratory have long performed research with HTL at a smaller scale—using high temperature and pressure to break down sludge into simpler compounds, turning them into biocrude oil. HTL is ideal for wet feedstock, as other processes used to treat solids require the material to be dried first, which is energy intensive.

Now, we are taking this research to the next level, innovating technology for larger-scale hydrothermal processing methods to convert wet waste feedstocks into biofuels. The following are three complementary systems that are helping to achieve this goal—all available to industry to use while accessing PNNL’s expertise.

MODULAR HYDROTHERMAL LIQUEFACTION SYSTEM

PNNL’s Modular Hydrothermal Liquefaction System—or MHTLS—has the following capabilities:

• Produces five times the biocrude of traditional “bench-scale” systems.
• A feed flow rate of slurry of 12 to 18 liters per hour.
• 24 hour per day attended operation with processing capability of about 2,000 liters of feed slurry in one week of operation.
• Routing mechanisms that separate biocrude and the liquids into storage tanks, where the research team can collect and study the end product

The MHTLS also has three operations sections, or skids:

• Skid 1 is where biomass feedstocks are prepared and staged. These feedstocks can include low-moisture solids like wood chips, corn stover, and wheat straw, and high-moisture solids like sludges and fruit pomace.
• Skid 2 is where the HTL processing occurs. Biomass is converted to liquid products and the byproducts—like ash—are removed via high pressure of 3,000 lbs per square inch and a high temperature of 660ºF.
• Skid 3 is where the products are separated—biocrude, aqueous byproduct, and gas—and stored via two separators. The first is a gas-liquid separator with a demister, which captures the gas and allows the liquid product to flow into a second separator, where biocrude/liquid separation takes place.

CATALYTIC HYDROTHERMAL GASIFICATION PDU SYSTEMS

The liquids captured in the collection tank during the HTL process contains a second potential fuel stream—methane. To obtain this fuel stream, PNNL’s Catalytic Hydrothermal Gasification PDU Systems consists of:

• An engineering-scale system comprising a mobile unit in a trailer and four fixed-bed reactors with heat integration. This mobile unit has been deployed for several pilot campaigns.
• Two fixed-bed bench-scale systems that allow for unattended operation.

The systems provide a Chemical Oxygen Demand (COD) reduction of greater than 95 percent.

UPGRADING PROCESS DEVELOPMENT UNIT SYSTEMS

When the biocrude enters the collection tank during the HTL process, it is not yet chemically ready for use. An upgrading step helps make it a compatible biofuel blendstock. PNNL possesses upgrading PDU systems to scale down biocrude pretreatment and upgrading methods:

• Biocrude pretreatment systems to remove trace metals.
• Several scales and modes of continuous flow hydrotreaters to remove heteroatoms such as nitrogen, oxygen, and sulfur.
• Four lab-scale down-flow trickle beds allow for unattended operation during long-duration tests and allow a biocrude feed rate of 3 to 25 milliliters
  per hour.
• Two bench-scale hydrotreaters, a fixed bed and a moving bed, allow a feed rate of 40 to 250 milliliters per hour.

If you are interested in working with PNNL bioenergy experts and capabilities, contact Corinne Drennan.