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 | more efficient methods must be developed to transport biofuels, |
| energy system efficiencies must be improved, and |
| biomass energy must be more competitive with fossil fuels. |
The proposed biomass charcoal concept addresses the transportation issue by converting biomass to charcoal at dedicated facilities and transporting charcoal to the power plant site for use in generating electricity. Fuel supply reliability would also be improved by producing and stockpiling charcoal at dedicated facilities independent of the power plant. Energy system efficiencies could be improved by co-firing charcoal with coal in pulverized coal steam plants with thermal efficiencies around 35% compared to about 25% for stoker units. Biomass energy economics could be improved by more widespread adoption of co-firing by utilities because charcoal would not require costly modifications or additions to fuel handling, storage and feed systems.
A high yield technology for producing charcoal was developed at the University of Hawaii, Renewable Resource Research Laboratory. Biomass charcoal for power generation could be produced using the Antal high yield charcoal process. Depending on the biomass feedstock used, the fuel value of the product charcoal would be approximately 30,000 kJ/kg with a volatile content of about 25% and ash content in the 2 to 3% range.
The advantages of using charcoal for power generation are summarized in Table 1. Environmental factors could make co-firing charcoal with coal and other fossil fuels a practical strategic option for both existing and new advanced power generation systems. Environmental benefits include possible reduction in emissions of acid rain precursors such as sulfur dioxide and nitrogen oxides. Charcoal from dedicated energy crops could also reduce net emissions of carbon dioxide, a greenhouse gas that contributes to global warming, because carbon dioxide released by combustion would be offset by the carbon absorbed while growing the energy crop.
Successful demonstration of high yield charcoal technology and co-firing with coal would provide the stabilizing effect of a reliable bioenergy fuel supply and assist in the transition to dedicated biomass feedstock power systems. Investments in Clean Coal Technologies could be leveraged for biomass energy by using charcoal in advanced power systems currently in the commercialization phase.
| Co-firing Biomass Charcoal | Co-firing Biomass |
| Charcoal has an energy density similar to coal and could be economically transported from regional production sites to central power plants. | The low density and high moisture of biomass feedstocks increase costs for transportation and limit the capacity of biomass co-firing applications. |
| With properties similar to coal biomass charcoal could utilize the same equipment used for coal handling service at power plants. | Co-firing biomass requires a separate feed system operating in parallel with the coal feed systems. |
| Charcoal could be produced from a variety of agricultural and forestry residues and dedicated energy crops. Year round production would minimize charcoal storage requirements at the power plant. | Biomass feed systems may not accommodate co-firing of different feedstocks. Year-round operation would require storage of large quantities of biomass. |
Renewable Energy Technology Characterizations available on the DOE, Office of Utility Technologies web site included a draft report on biomass co-firing with coal in PC boilers. Data presented in the draft report for co-firing wood with coal to produce 15 MW were used in Table 2. The thermal and economic performance for co-firing charcoal and wood in a PC boiler were compared to illustrate the potential advantages of co-firing charcoal.
Operation and maintenance (O&M) costs for co-firing charcoal vs. wood in a PC boiler are presented on an incremental basis. The O&M incremental cost for wood and charcoal were compared based on use as a replacement for coal at $39.09/wet tonne. A wood price of $9.14/dry tonne was used in this example. The charcoal price was estimated at $75 per tonne. The higher annual fuel cost for charcoal vs. wood would be partially offset by lower transportation costs for charcoal. Co-firing of charcoal would also have economic advantage because a separate biomass feed system would not be required. The cost for biomass handling equipment used in Table 2 was $255.50/kW biomass capacity or approximately $3,800,000.
Table 2. Performance and Costs for
Co-firing 15% Wood
& Charcoal with Coal
| Indicator Name | 100 MW PC Boiler |
|
Wood (1) |
Charcoal |
|
| Biomass MW | 15 |
15 |
| Capacity Factor, % | 85% |
85% |
| Annual Energy From Biomass, GWh/yr. | 112 |
112 |
| Net Heat Rate, kJ/kWh | 11,066 |
10,929 |
| Biomass HHV, kJ/kg (dry) | 19,104 |
30,175 |
| Biomass Feed Rate, 1000 tonnes per year (dry) | 64.7 |
40.5 |
| O&M Cost Comparison, $/yr. (2) | base |
471,677 |
| Trucking Cost, $/yr. (3) | base |
(194,124) |
| Annual Cost of Capital, $/yr. (4) | base |
(945,064) |
| Annual Cost Comparison, $/yr. | base |
(667,511) |
| Notes: | ||
| (1) Performance and Cost Indicators from Biomass Co-Firing. | ||
| (2) Incremental O&M cost for wood excludes credit for consumables. | ||
| (3) Trucking cost for 40 km Haul @ $5/tonne | ||
| (4) P&I on 5 year loan at 10% interest rate. | ||
Phase I will evaluate, insofar as possible, the technical merit and feasibility of producing charcoal from biomass and co-firing charcoal with coal at existing pulverized coal and fluidized bed power plants.
Work Plan
Review methods for the collection, handling, storage, and transportation of biomass materials (crops or residues) to a charcoal plant and conversion of biomass to charcoal.
| Review alternative biomass feedstocks available in Hawaii: Construction and Demolition wood waste, green waste, agricultural residues and energy crops. Report on physical & chemical properties and biomass collection, handling, and storage and transportation methods. |
| Determine biomass feedstock preparation required for use as charcoal feedstock. |
| Produce charcoal from three sources of biomass from Hawaii, e.g., untreated wood waste, short rotation tropical trees, and energy cane (Bannagrass) using the HNEI laboratory charcoal reactor. |
| Determine composition and properties of the charcoals. Perform ultimate and proximate analyses and determine the charcoal heating value (HHV). Examine the charcoal suitability for co-firing with coal in PC and FBC boilers, e.g., measure the agglomerating value, grindability, ash softening and fusion temperatures. |
Review methods for handling and feeding of biomass charcoal into power boilers.
| Research methods for the transportation of charcoal and facilities for receiving & storing charcoal at the power plant site. |
| Evaluate impact of co-firing charcoal on power plant thermal performance and the influence on fly ash & bottom ash properties, air emissions, and overall economics of co-firing charcoal at various rates. |
Develop plan for the Phase II project
| Prepare conceptual design and cost estimates for a commercial scale charcoal reactor |
| Draft business plan for commercial production of charcoal and co-firing applications in Hawaii. |
| Identify major environmental and permitting considerations. |
Prepare and submit final report.
A 1990 paper by Antal and Mok (1) indicated that a significant increase in charcoal yield is achieved by operation at elevated pressure in a stagnant gaseous environment. In 1996, Antal, Croiset, Dai, DeAlmeida, Mok and Norberg (2) described a method for manufacturing charcoal from biomass that realized near-theoretical yields of 42 to 62% with a reaction time of about 15 minutes to 2 hours, depending on the moisture content of the feed. Eucalyptus, Kiawe, Leucaena wood and Kuki, Macadamia and Palm nutshells were tested in laboratory and pilot scale equipment. A copy of "High-Yield Biomass Charcoal" from Energy & Fuels, American Chemical Society, 1996 Vol.10, Number 3, is attached to this application.
Transnational Technology - Principal Investigator & Key Personnel
The Principal Investigator, James R. Arcate, has a strong interest in global sustainability and development issues, and energy-related R&D work experience. His background includes project engineering, cost and scheduling and project management during the planning and engineering, procurement, and construction phases. In addition to an academic background in chemical engineering, he recently earned a Certificate in International Business from the University of Hawaii at Manoa.
Mr. Arcate formed Transnational Technology in January 1997 and has been a private consultant in renewable energy research and development with emphasis on biomass energy conversion. From 1981-1990 with Hawaiian Dredging & Construction Co., he was construction QC manager on the H-Power Municipal Refuse Resource Recovery Project and senior project engineer on the 40 MW OTEC Pilot Plant Program and the OTEC Cold Water Pipe At-Sea Test.
With the Pacific International Center for High Technology Research (PICHTR), Mr. Arcate he was senior project engineer and construction manager on the Hawaii Biomass Gasification Facility for the U.S. DOE and the State of Hawaii. He was a senior project engineer and construction QC manager on the Open-Cycle Ocean Thermal Energy Conversion Plant for the U.S. DOE and the State of Hawaii. Initial operation of the Hawaii Biomass Gasification Facility made Mr. Arcate aware of the difficulties in handling bagasse and, in particular, the problems in the feeding bagasse into a high pressure fluidized bed gasifier. After leaving US Company A in 1997, Mr. Arcate formed Transnational Technology to research his ideas for biomass energy recovery using charcoal from biomass as a solid fuel for co-firing with coal.
Jeffrey N. Phillips, Mechanical Engineer specializing in Process Design, Optimization, and Plant Start-ups with expertise in filtration, solids handling, heat exchangers, and gas treating. Mr. Phillips holds a BA degree in Math from Austin College, a BSME from Washington University, and an MS & Ph.D. Mech. Eng. from Stanford. He worked for Shell Oil for 10 years helping to develop a coal gasification process, participated in the start-up of a $450 million coal gasification-based power plant in Holland, and was lead mechanical engineer on start-up of a $90 million elastomers plant in Ohio. Mr. Phillips also has had experience as a manufacturing engineer with Texas Instruments. He worked for Molten Metal Technology for 2 years as a research engineer where he investigated the feasibility of converting depleted uranium hexaflouride into uranium oxide pellets and HF gas, and helped start up a pilot plant that vitrified fly ash from municipal waste incinerators. He has been working closely with Mr. Arcate on developing the biomass charcoal co-firing concept.
Subcontractors
The Hawaii Natural Energy Institute (HNEI) was established in 1974 to seek new and renewable forms of energy that would supplant the nation's enormous dependence on petroleum. HNEI's earliest work focused on the search for alternative resources for the generation of electrical power. As a result of its pioneering research, HNEI has become one of the world's foremost sources of expertise on those electricity-producing technologies powered by renewable resources.
HNEI evaluated the best species of agricultural biomass crops, evaluated growing and harvesting techniques, and located and surveyed the best cultivation sites state-wide. The institute also was an early leader in conducting research on biomass-derived alcohol fuels for transportation use.
Michael J. Antal, Jr., Distinguished Professor of Renewable Energy Resources and Coral Industries Chair, invented at HNEI, an improved batch process for the conversion of wood and plant material to charcoal. The batch process can be completed in less than one hour with virtually instantaneous reloading without substantial cooling of the reactor. Yields of high quality charcoal range from 40% to 60%, depending upon the feedstock. Applications include wood, macadamia and kukui nut shells, coconut shells and husks, and other plant material.
Dr. Antal and his staff at HNEI will perform as subcontractor for research and laboratory testing related to biomass and charcoal. See attached letter to Transnational Technology from HNEI.
Other Participants
The AES Corporation, founded in 1981, is the world's largest global power company. AES owns or has an interest in eighty-two plants totaling almost 22,000 megawatts in 12 countries. In 1996, AES operated six U.S. plants totaling 1,069 MW. AES-Hawaii owns and operates a 180 MW coal fired circulating fluidized bed coal power plant on Oahu. AES has agreed to assist in evaluating the technical and economic feasibility of co-firing charcoal with coal in their plant. See attached letter to Transnational Technology from Keith Speak, AES-Hawaii.
