Developing New Alternative Energy in Virginia: Bio-Diesel from Algae

[摘要] The overall objective of this study was to select chemical processing equipment, install and operate that equipment to directly convert algae to biodiesel via a reaction patented by Old Dominion University (Pat. No. US 8,080,679B2). This reaction is a high temperature (250- 330{degrees}C) methylation reaction utilizing tetramethylammonium hydroxide (TMAH) to produce biodiesel. As originally envisioned, algal biomass could be treated with TMAH in methanol without the need to separately extract triacylglycerides (TAG). The reactor temperature allows volatilization and condensation of the methyl esters whereas the spent algae solids can be utilized as a high-value fertilizer because they are minimally charred. During the course of this work and immediately prior to commencing, we discovered that glycerol, a major by-product of the conventional transesterification reaction for biofuels, is not formed but rather three methoxylated glycerol derivatives are produced. These derivatives are high-value specialty green chemicals that strongly upgrade the economics of the process, rendering this approach as one that now values the biofuel only as a by-product, the main value products being the methoxylated glycerols. A horizontal agitated thin-film evaporator (one square foot heat transfer area) proved effective as the primary reactor facilitating the reaction and vaporization of the products, and subsequent discharge of the spent algae solids that are suitable for supplementing petrochemicalbased fertilizers for agriculture. Because of the size chosen for the reactor, we encountered problems with delivery of the algal feed to the reaction zone, but envision that this problem could easily disappear upon scale-up or can be replaced economically by incorporating an extraction process. The objective for production of biodiesel from algae in quantities that could be tested could not be met, but we implemented use of soybean oil as a surrogate TAG feed to overcome this limitation. The positive economics of this process are influenced by the following: 1. the weight percent of dry algae in suspension that can be fed into the evaporator, 2. the alga species??? ability to produce a higher yield of biodiesel, 3. the isolation of valuable methoxylated by-products, 4. recycling and regeneration of methanol and TMAH, and 5. the market value of biodiesel, commercial agricultural fertilizer, and the three methoxylated by-products. The negative economics of the process are the following: 1. the cost of producing dried, ground algae, 2. the capital cost of the equipment required for feedstock mixing, reaction, separation and recovery of products, and reactant recycling, and 3. the electrical cost and other utilities. In this report, the economic factors and results are assembled to predict the commercialization cost and its viability. This direct conversion process and equipment discussed herein can be adapted for various feedstocks including: other algal species, vegetable oil, jatropha oil, peanut oil, sunflower oil, and other TAG containing raw materials as a renewable energy resource.

[发布日期] 2012-03-29

[学科分类] 燃料技术

[关键词] algae;biofuels