Gasification of cyanobacterial in supercritical water

Abstract

Cyanobacterial collected from eutrophic freshwater lakes constituted intractable waste with a rich algae biomass content. Supercritical water gasification (SCWG) was proposed to treat the cyanobacterial and to produce hydrogen for energy. The H 2 yield reached 2.92 mol/kg at reaction conditions of 500 °C, 30 min and 22 MPa; this yield accounted for 26% of the total gaseous products. Abundant ammonia and dissolved reactive phosphorous were concentrated in the liquid product, which could be recovered and used as a liquid fertilizer. Solid residue, which accounted only for about 1% of the wet weight, was mainly composed of coke and ash. The efficiency of H 2 production was better than that from other biomass, because of the abundant organic matter in cyanobacterial. Thus, cyanobacterial are an ideal biomass feedstock for H 2 production from SCWG.

Characteristics of Cyanobacterial Biomass Gasification in Sub- and Supercritical Water

“…The SCWG experiments were performed according to previously reported methods using a 316 L stainless steel reaction kettle of 100 mL capacity, and the salt bath furnace was employed as its heating device. 3 In a typical experiment, cyanobacteria biomass with 96.15 wt % moisture content was loaded into the kettle and feedstock was added according to the temperature− pressure-loading curve. The temperature of the salt bath furnace was increased to the preset temperature and placed into a reaction kettle that was equipped with samples, such as SCWG experiments in the heating process, reaction conditions were controlled in 10 min retention time, 15 °C/min heating rate, and 32.57 g cyanobacteria biomass addition with 96.15 wt % moisture content, and SCW environment could be ensured when the reaction temperature increased to 400 °C.…”

“…In 2010, about 100 boats were used to collect 670 000 t of algae biomass that was mostly abandoned in low-lying places around the lakes. 3 Cyanobacteria biomass is characterized by numerous microcystis cells, as well as high moisture, organic matter, N, and P. 4 Eutrophication of freshwater lakes results in a massive and renewable output of cyanobacteria, and there is increased public concern about the disposal and resource utilization of cyanobacteria biomass.…”

“…Hydrothermal gasification in supercritical water appears to be a promising method for algal biomass conversion. 3,12,13 The energy recovery of microalgae biomass was originally applied in cultured microalgae feedstock through SCWG. We assessed the potential for using the process water from SCWG of different microalgae as a source of nutrients for cultivation.…”

“…A salvage operation was used as the daily management for cyanobacteria blooms removal in freshwater lakes to avoid degradation of water quality and ecology but resulted in unwieldy cyanobacteria biomass production. In 2010, about 100 boats were used to collect 670 000 t of algae biomass that was mostly abandoned in low-lying places around the lakes . Cyanobacteria biomass is characterized by numerous microcystis cells, as well as high moisture, organic matter, N, and P .…”

“…The high cost of the drying process poses many problems and prevents the use of most conversion technologies, which require a dry biomass. Hydrothermal gasification in supercritical water appears to be a promising method for algal biomass conversion. ,, …”