Overview of recent advances in thermo-chemical conversion of biomass.

a b s t r a c t This paper primarily presents an overall review of the use of microalgae as a biofuel feedstock. Among the microalgae that have potential as biofuel feedstock, Chlorella, specifically, was thoroughly discussed because of its ability to adapt both to heterotrophic and phototrophic culture conditions. The lipid content and biomass productivity of microalgae can be up to 80% and 7.3 g/l/d based on the dried weight of biomass, respectively, making microalgae an ideal candidate as a biofuel feedstock. The set-up of the system and the biomass productivity of microalgae cultivated in an open pond and a photobioreactor were also compared in this work. The effect of the culture condition is discussed based on the twostage culture period. The issues that were discussed include the light condition and the CO2, DO and N supply. The microalgal productivities under heterotrophic and phototrophic culture conditions were also compared and highlighted in this work. The harvesting process and type of flocculants used to aid the harvesting were highlighted by considering the final yield of biomass. A new idea regarding how to harvest microalgae based on positive and negative charges was also proposed in this work. The extraction methods and solvents discussed were primarily for the conventional and newly invented techniques. Conversion processes such as transesterification and thermochemical processes were discussed, sketched in figures and summarized in tables. The cost–benefit analysis of heterotrophic culture and the cultivation system was highlighted at the end of this work. Other benefits of microalgae are also mentioned in this work to give further support for the use of microalgae as a feedstock for biofuel production.

Conversion of microalgae to biofuel

Towards sustainable production of clean energy carriers from biomass resources

One of the main problems that happen during biomass gasification is tar formation, which could make this technology unsuccessfully from a commercial point of view. Tar content present in syngas defines its application, considering that limits - according to desired application - can be very demanding. There are two ways to overcome this problem: by optimizing gasification operation conditions and removal of tar from gas through in-situ (primary methods) or post-gasification (secondary methods) treatments. This way, multiple technologies have been developed considering the balance between efficiency and economy of the process, besides being (ecofriendly) environmentally acceptable. Some aspects related to tar formation, laboratory and industrial methods and technologies for its reduction-removal, as well as research and development in this area are reviewed and evaluated in this paper.

Reduction of tar generated during biomass gasification: A review

A literature review on gasification of lignocellulosic biomass in various types of fluidized bed gasifiers is presented. The effect of several process parameters such as catalytic bed material, bed temperature and gasifying agent on the performance of the gasifier and quality of the producer gas is discussed. Based on the priorities of researchers, the optimum values of various desired outputs in the gasification process including improved producer gas composition, enhanced LHV, less tar and char content, high gas yield and enhanced carbon conversion and cold gas efficiency have been reported. The characteristics and performance of different fluidized bed gasifiers were assessed and the obtained results from the literature have been extensively reviewed. Survey of literature revealed that several industrial biomass gasification plants using fluidized beds are currently conducting in various countries. However, more research and development of technology should be devoted to this field to enhance the economical feasibility of this process for future exploitations.

Gasification of lignocellulosic biomass in fluidized beds for renewable energy development: A review

A novel biomass air gasification process for producing tar-free higher heating value fuel gas

Experiment and Mathematical Modeling of a Bench-Scale Circulating Fluidized Bed Gasifier

There is a kind of gasifying method and device for new solid sediment-discharging dried powder flowing bed. The method is made up of six sections which are preparing coal, providing steam, gasifying,sediment-eliminating, cleaning dust and waste heat reclaiming. The cola is divided into two sections of coal flour small than 8mm and power coal small than 0.09mm. The device is made up of melted dust separating unit, gasifying unit. The invention realizes the combination of the high-temperature flow bed gasification, the semi carbon and coal gas the flowing bed cools the high-temperature sediment and gases which is generated by the flowing bed.

Solid slag-discharging dry-powder air-current bed gasification process and apparatus

A process for treating waste rubber and plastics includes breaking them into 10-100 mm blocks, feeding into lower part of gasifier, pyrolytic gasifying at 720-850 deg.C to generate tar-containing gas, cracking tar at 850-920 deg.C in upper part of gasifier to obtain clean gas. Its advantages are not containing high-molecular hydrocarbons, direct combustion after water washing, and simplified tailgas cleaning system.

Wang Yang

Papers

A novel biomass air gasification process for producing tar-free higher heating value fuel gas

Experiment and Mathematical Modeling of a Bench-Scale Circulating Fluidized Bed Gasifier

Solid slag-discharging dry-powder air-current bed gasification process and apparatus

Process for treating waste rubber or plastics and its gasifying equipment