Coal-fired electric power generating plants are under increasing pressure to reduce CO2 and other toxic emissions. However, using alternative fuels, such as solid biomass as a greenhouse gas neutral fuel, requires substantial plant modifications. In addition, burning biomass contributes to slagging and fouling of the plants' furnaces. Soil mixed in with the forest waste is the primary cause. HM3 Energy has developed an innovative process (trademarked "TorrB") to convert forest waste into fuel briquettes with low soil content. Unlike most pellets and briquettes produced from wood chips, these briquettes behave just like coal; i.e., they can be stored outdoors, are easily pulverized, and their heating value is similar to that of coal. The TorrB process uses torrefaction where the biomass is heated to a high temperature (200-300 degrees C) for a specified time duration in the absence of oxygen. The final product is a solid with a high energy value for use as combustion fuel in coal-fired power plants. This Phase II grant research will focus on developing commercial scale torrefaction equipment and process. HM3 Energy's TorrB torrefaction process and product have demonstrated clear viability as shown in the results of our NIFA-USDA-SBIR Phase I study using a small batch process. By taking the current proven torrefaction process and applying it to a scalable design which utilizes a continuously operating torrefaction system, we will be able to economically produce the large quantities of torrefied biomass required to operate coal-fired power plants. Our approach will be to develop, test and optimize the new torrefier equipment of our own design. When combined with the (waterless) contamination removal methodology developed in Phase I, we will then be ready to apply this knowledge to construction of a full commercial production facility. The potential impacts and benefits of large scale commercial use of torrefied biomass in place of coal are numerous. The forest waste feedstock is renewable and sustainable, and can be obtained from undesirable species (such as western Juniper) present in semiarid regions and through forest thinning and removal of accumulated forest debris - even bug-infested dying trees. By removing the undesired forest waste, the forest ecosystem will be less susceptible to insect and pathogens. There will also be a reduction in the potential for catastrophic forest fires. Overall, the nation's health and environment will be improved by a reduction in coal-fired power plant emissions of carbon dioxide, sulfur dioxide, nitrogen oxides, mercury and other toxic metals present in the coal and coal ash. In fact, America's supply of clean water is threatened by mercury pollution, much of which comes from coal-fired power plant emissions that get into water resources. Replacing coal, the greatest source of CO2, with carbon-neutral biomass fuel in the current installed base of coal-fired power plants could have the greatest impact on green house gases of any mitigation measure. Air quality, as well as the environmental health of water resources and ecosystems in forest, rangeland and farms, could be greatly enhanced. OBJECTIVES: The goal of this program is to demonstrate the practicality of a scalable process for converting woody biomass into a form which could replace coal in pulverized coal fired-plants. Our objective is to define operating conditions such that uniform and acceptable quality torrefied biomass is consistently produced. At the end of the program, sufficient data and operational experience will have been acquired to permit engineering design and operational protocol of a complete process unit which could produce multi-ton/hour quantities of densified solid fuel suitable as a replacement for coal in pulverized coal plants. This will be accomplished through the following activities: 1. Fabricate and operate a continuous prototype torrefier system, scalable to 10 to 20 times larger for commercial use. Operate the torrefier with all the necessary connecting equipment and lines, such as the feed hopper, cooler, thermal oxidizer and hot gas heating and re-circulating lines. 2. Test-torrefy three kinds of feedstock: woody biomass from a dry mountain region (Eastern Cascade Mountains), woody biomass from a wet mountain region (Western Cascade Mountains), and Arundo Donax, a giant reed that is a potential dedicated energy crop. 3. Determine optimum torrefaction conditions (operating temperature, residence time of biomass, and other aspects of the torrefier operation) using the prototype torrefier. Optimum torrefaction conditions will be determined from measurements of the heating value, ash content, grindability and uniformity of the torrefied product. 4. Determine the optimum briquetting conditions by monitoring and adjusting operating temperatures, pressures, and water content in the briquetting process. Briquette quality will be measured through analytical testing of grindability, hydrophobicity, and shape,structure and mechanical integrity of the briquettes. 5. Perform final testing of product by conducting test burns in a powdered coal-fired boiler that models operations of coal-fired boilers used at power plants. Burn 100% of our product in order to get data such as the degree of slagging and fouling in the boiler surfaces, ash analysis and amount of various gasses in the exhaust. APPROACH: PHASE 1 - Optimize methods of post-processing torrefied wood (operation of the pilot-scale briquetting equipment and development of analytical techniques for process control and quality analysis). 1) Determine ash content of torrefied product following ASTM D5630 or similar. Determine higher heating value of product using bomb calorimeter. Ash content and heating value are direct measures of the quality of the torrefied product. 2) Analyze grindability using Hardgrove Grindability Index (HGI), a measure utilized by the coal industry, as detailed in ASTM D409. (We'll use grindability of a torrefied sample as a measure of operational consistency by correlating the measure of grindability to the true measure of torrefaction quality.) 3) Determine quality of briquetting using grindability, hydrophobicity (studied following ASTM D570 or similar) and observing shape and structure of briquette. 4) Analyze Hazardous Air Pollutants (HAPs) using gas chromatograph (GC) and analyze volatile organic compounds (VOCs) using high performance liquid chromatography (HPLC). Test Drager Tubes as way to conveniently monitor HAPs. Phase II - Start up the continuous torrefier system. 1) Using at least three bed level detectors, high, desired level and low, carefully observe the functionality of the torrefier and associated auxiliaries. 2) Ensure hopper feed valve is air-tight while supplying feedstock to the torrefier, proper feedstock level is maintained. 3) Ensure torrefied biomass is withdrawn after a predetermined duration in the torrefier such that product is uniformly torrefied. 4) Ensure cooler is air tight and product is cooled below 150 degrees C so it doesn't combust when exiting torrefier. Vent stream is primarily steam, but some VOCs are mixed in and will be vented to thermal oxidizer. 5) Ensure thermal oxidizer has proper flow control so it thermally destructs VOCs discharged from plant's processing equipment, and provides energy to torrefier and dryer. 6) Collect data for heat and mass balance. 7) Identify any potential airborne pollutants. 8) Determine if measuring VOCs or HAPs can be used to indicate/control degree of torrefaction. Phase III 1) Process three types of feedstock - woody biomass from Western Cascade Mountains, woody biomass from Eastern Cascade Mountains, and Arundo Donax. 2) Have bulk solids engineering/design firm measure physical properties of Arundo Donax to make sure we can torrefy it in our torrefier. PROGRESS: 2011/09 TO 2012/08 OUTPUTS: During the first year of its SBIR Phase 2 grant, HM3 Energy has test-torrefied 4 kinds of woody biomass feedstock: (1) pine and juniper woody biomass from a dry mountain region (eastern Cascade Mountains); (2) Texas juniper/mesquite woody biomass; (3) Arundo Donax, a giant reed that is a potential dedicated energy crop; (4) palm kernel shells from Indonesia. We determined optimum torrefaction conditions (operating temperature, residence time of biomass, and other aspects of the torrefier operation) using our prototype torrefier. We test-densified each torrefied feedstock and were able to produce water resistant, sturdy briquettes for each on our lab-scale equipment. We determined the optimum briquetting conditions by monitoring and adjusting operating temperatures, pressures and water content in the briquetting process for our two primary feedstocks - juniper and pine. We also produced a torrefier design that is more economical to produce and fabricate than our original design. We provided samples of our lab-scale briquettes to numerous potential customers, advancing the awareness of torrefied biomass as a viable clean fuel to replace coal in coal-fired power plants. We presented information on torrefaction and our progress at the following events: BC-Korea Bioenergy Collaboratio (Vancouver, BC, Canada); Cleantech Open Presentation (Portland, OR); 2012 Oregon Future Energy Conference Presentation (Portland, OR); 5th International Bioenergy Conference Presentation (Prince George, BC, Canada); EUCI Webinar Presentation (nationwide webinar). In addition to the above, we met with stakeholders in several biomass rich communities to make them aware of the advantages of torrefied biomass energy. We filed three provisional patents, including several for our process, product and equipment design: (1) Method for making biofuel from biomass; (2) Method of refining torrefied biomass; and (3) Mass flow torrefier. PARTICIPANTS: Hiroshi Morihara, Principal Investigator, has given numerous presentations on torrefaction to a wide variety of audiences, including state, regional economic development, biomass energy conferences and the energy industry in general. He attended the USDA-SBIR Commercial Assistance (Larta Institute) Workshop and the Cleantech Competition to get greater knowledge on commercialization efforts. Assisted by David Carter, HM3 Energy Project Manager, Dr. Morihara devised and executed the research plan. They secured biomass for torrefaction and densification and determined optimum torrefaction and densification conditions. They worked with other HM3 Energy team members to design and build a mock-torrefier for gas flow testing. Mary McSwain and Eliot Shoemaker worked in the lab to dry, size and torrefy biomass for testing. McSwain also produced Power Point presentations for Dr. Morihara to use at conferences. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project. IMPACT: 2011/09 TO 2012/08 Initially, our intent for the SBIR Phase II effort was to develop, test and optimize a new torrefier equipment design. Soon after submission of the Phase II application, several key challenges that could prevent successful commercialization of our technology arose that forced us to change direction. The challenges and our response are as follows: Challenge 1: Realization that densification is the most important challenge to overcome for successful commercialization of torrefied biomass fuel. We realized that densification involved more challenges than the torrefaction alone. It is also hard to economically densify and produce water resistant material product continuously and reliably without the use of a binder. During the first half of the Phase II project, we completed a key step to overcome the challenges of densification by determining the process conditions required to successfully densify our two primary feed stocks (pine and juniper) economically and without a binder. Challenge 2: The functional design for the pilot scale torrefier developed for HM3 Energy by an engineering firm was found to be uneconomical in relation to both capital cost and operating cost. These issues were significant enough to make it impossible to pursue the original SBIR Phase 2 objectives 1, 2, 3, and 5. Specifically, the three problem areas were: (1) The engineering firm completed tests to determine the permeability of torrefied material. At the design superficial velocity, the differential pressure (dP) was too high. Special equipment is used to circulate the gases in the torrefier. At this dP, the static pressure requirement is very high, which limits the options for obtaining commercially available equipment. Inquiries with over 20 manufacturers of the special equipment resulted in only two models found to be available in the world. Capital cost of the blower equipment for a 90,000 T/yr plant and operating cost for electricity were estimated to be far too high to be economically viable. Verifying the engineering firm's data became imperative. The engineering firm originally developed a torrefier design that used a special device to maintain an even level of biomass in the torrefier. Several discussions with fabricators determined that this was not a viable option. The issues outlined above required a new gas distribution design. We developed a mock-torrefier for gas flow testing to overcome dP and gas distribution issues. Initial testing found that the differential pressures were actually much lower than those stated by the engineering. At the reduced differential pressures, our new torrefier design will be economical to fabricate and operate. Challenge 3: Successful commercialization of our torrefaction process in other markets would be seriously limited without testing feed stocks found in other parts of the U.S. and around the world. We increased our feedstock torrefaction research to include Arundo Donax, Palm Kernals and Texas juniper and mesquite. We have had successful torrefaction and densification to produce water resistant briquettes with all species tested.
