Renewable energy sources, such as biofuels, provide a substitute for fossil fuels and a means of reducing dependence on petroleum oil. In light of its low cost and wide availability, biomass is often used as a feedstock to produce bio-oil which, in turn, is used to produce biofuel.
Many different conversion processes have been developed for converting biomass to bio-oil. Existing biomass conversion processes include, for example, combustion, gasification, slow pyrolysis, fast pyrolysis, liquefaction and enzymatic conversion. Such conversion processes render liquid products that spontaneously separate into an aqueous phase and an organic phase. Bio-oil consists of the organic phase. Bio-oil may be processed into transportation fuels as well as into hydrocarbon chemicals and/or specialty chemicals.
While thermolysis processes and other conversion processes produce high yields of bio-oil, most, if not all, of the bio-oil produced is of low quality due to the presence of high levels of reactive organic molecules as well as solids including char, inorganics from biomass, scale from processing equipment and fines from heat transfer agents and catalysts. Also, the amount of dissolved metal in bio-oil greatly exceeds that of typical fossil fuels. This is likely attributable to the acidic nature of bio-oil which is capable of leaching and solubilizing cationic species.
Bio-oils thus require extensive secondary upgrading in order to be utilized as transportation fuels and/or as fuel additives. In one such method, bio-oils are subjected to a filtering process in order to remove undesirable solid particles. Since the residual solids often contain fine particles of less than 30 microns in size, fine-scale filters are required. Most filters capable of removing residual solids from bio-oil are rapidly clogged by gelatinous-type solids found in bio-oil. This rapid clogging can cause residual solids filtration methods to be expensive and challenging to scale up.
It should be understood that the above-described discussion is provided for illustrative purposes only and is not intended to limit the scope or subject matter of the appended claims or those of any related patent application or patent. Thus, none of the appended claims or claims of any related application or patent should be limited by the above discussion or construed to address, include or exclude each or any of the above-cited features or disadvantages merely because of the mention thereof herein.
Accordingly, there exists a need for improvements in methods and apparatus for the removal of residual solids from a fuel feedstream, such as bio-oil, having one or more of the attributes or capabilities described or shown in, or as may be apparent from, the other portions of this patent.