Hom-Ti Lee

Comparative study of lipid extraction from microalgae by organic solvent and supercritical CO2.

Pavlova sp. was employed to evaluate the efficiency of different lipid extraction methods. The microalgal crude lipids content determined using the mixed solvent with ultrasonic method was 44.7 wt.%. The triglyceride content obtained by the mixed solvent method was 15.6 wt.%. The extraction yield was the FAME yield divided by the maximum FAME (15.9 wt.%). The extraction yield was improved by cell disruption prior to extraction, and the highest triglyceride extraction yield of 98.7% was observed using the supercritical fluid extraction (SFE) method with bead-beating. The results indicate that the SFE method is effective and provides higher selectivity for triglyceride extraction though the total lipid extracted was less than that using solvent extraction.

Co-firing of paper mill sludge and coal in an industrial circulating fluidized bed boiler.

Co-firing of coal and paper mill sludge was conducted in a 103 MWth circulating fluidized bed boiler to investigate the effect of the sludge feeding rate on emissions of SOx, NOx, and CO. The preliminary results show that emissions of SOx and Nx decrease with increasing sludge feeding rate, but CO shows the reverse tendency due to the decrease in combustion temperature caused by a large amount of moisture in the sludge. All emissions met the local environmental requirements. The combustion ashes could be recycled as feed materials in the cement manufacturing process.

An investigation on pollutant emissions from co-firing of RDF and coal.

Pollutant emissions from co-firing of refuse derived fuel (RDF) and coal were investigated in a vortexing fluidized bed combustor (VFBC). RDF-5 was made of common municipal solid waste (MSW). CaCO(3) was injected in the combustor to absorb HCl at 850 degrees C. The results show that NO(x) and HCl emissions increase with RDF-5 co-firing ratio. The NO(x) concentration in flue gas at the bottom of the combustor is higher than that at the top. However, the trend of HCl released is reverse compared with NO(x) emissions. It was found that the HCl concentration decreases with increasing the molar ratio of Ca/Cl. However, the effect of CaCO(3) addition on HCl retention is not significant when the molar ratio of Ca/Cl is higher than 5. The chlorine content in fly ash increases obviously with the molar ratio of Ca/Cl. PCDD/Fs emissions decrease slightly with an addition of CaCO(3). In this study incomplete combustion is regarded as the main cause for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) formation.

Hot gas cleanup: pilot testing of moving bed filters

In recent issues of the magazine, J Smid, SS Hsiau, CY Peng and HT Lee have assessed granular moving bed hot gas particulate clean up systems for advanced IGCC and PFBC power stations; looked at the development of particulate collection devices; as well as highlighting new designs of moving bed filters. In the final part, they examine filter media and moving bed filter pilot plants.

Hot gas granular moving bed filters for advanced power systems

In advanced coal-fire cycles it is important to remove the fine particles from high temperature and high pressure gas streams, to satisfy gas turbine fuel quality requirements. J Smid, S S Hsiau, C Y Peng and H T Lee assess granular moving bed hot gas particulate clean-up systems for advanced IGCC and PFBC, under development in the USA.

Granular moving bed filters and adsorbers (GM-BF/A) — patent review: 1970-2000

Abstract Granular moving bed filters and adsorbers (GM-BF/A) for hot gas cleanup continue to be developed as a key component of current integrated gasification combined cycle and advanced pressurized fluidized bed combustion power generation systems. This paper contains a review of the patent literature on GM-BF/A equipment with sidewalls provided with a number of louvers or screenless granular moving bed systems. Patents granted to GM-BF/A equipment are categorized in groups according to thedesign characteristics. Non-uniform flow of a granular moving bed (filter medium, sorbent) is discussed in detail.

Moving bed filters for hot gas cleanup

In the December issue of Filtration+Separation, J Smid, S.S Hsiau, CY Peng and HT Lee assessed granular moving bed hot gas particulate clean up systems for advanced IGCC and PFBC advanced power stations, under development in the USA. They now turn their attention to the development of the particulate collection devices themselves…

Continuous lipid extraction of microalgae using high-pressure carbon dioxide.

Sequestering carbon, purifying water, and creating biofuel materials using microalgae are of global interest in the R&D field. However, extracting algal oil consumes a high amount of energy, which is an obstacle for the biofuel market. Nontoxic and recyclable high-pressure CO2 extraction processes are being developed by numerous researchers; however, most of these processes use batch operations mixed with a large amount of co-solvent and require improvement. We fabricated a continuous high-pressure CO2 extraction system, evaluating the optimal parameters for the extraction process. The various parameter tests included temperature, pressure, pretreatment methods, ratio, and the species of co-solvent. We integrated the optimal parameters from previous tests, using a 5-d continuous operation. Compared with traditional solvent extraction, a 90.56% extraction yield ratio was achieved using this continuous extraction method. This shows the stable, high extraction yields of this continuous high-pressure CO2 extraction system.

Emissions During Co-Firing of RDF-5 with Coal in a 22 t/h Steam Bubbling Fluidized Bed Boiler

The co-firing of biomass and fossil fuel in the same power plant is one of the most important issues when promoting the utilization of renewable energy in the world. Recently, the co-firing of coal together with biomass fuel, such as “densified refuse derived fuel” (d-RDF or RDF-5) or RPF (refuse paper & plastic fuel) from waste, has been considered as an environmentally sound and economical approach to both waste remediation and energy production in the world. Because of itscomplex characteristics when compared to fossil fuel, potential problems, such as combustion system stability, the corrosion of heat transfer tubes, the qualities of the ash, and the emissionof pollutants, are major concerns when co-firing the biomass fuel with fossil fuel in a traditional boiler. In this study, co-firing of coal with RDF-5 was conducted in a 22t/h bubbling fluidized bed (BFB) steam boiler to investigate the feasibility of utilizing RDF-5 as a sustainable fuels in a commercial coal-fired steam BFB boiler. The properties of the fly ash, bottom ash, and the emission of pollutants are analyzed and discussed in this study.

The Heat Release Ratio and Performance Test at a Small-Scale RDF-5 Bubbling Fluidized Bed Boiler

Design and operation of boilers using biomass or waste present a number of challenges. It is also well known that the flue gas emissions are strongly dependent on the fuel. Consequently, it is a major challenge to be able to control and maintain all emissions and combustion behavior under their designated limits for all fuel combinations required. Lately, the constant substantial rise in the price of fossil fuels has resulted with RDF (refuse derived fuel) technology becoming more valuable for generating heat in various types of boilers. A small-scale bubbling fluidized bed (BFB) RDF-fired boiler with a steam capacity of 4 ton/hr was developed by ITRI. In this paper, heat release in the fluidized bed region was calculated and the performance testing for this demonstration boiler including the items of bed temperature distribution, flue gas emissions, and the ash characteristics is analyzed and discussed. Finally, a series fuel flexibility tests were conducted in the RDF-5 BFBB.