• Energy Research

A novel reaction mechanism of H 2 and CH 4 cogeneration from water hyacinth (Eichhornia crassipes) was originally proposed to increase the energy conversion efficiency. The glucose and xylose hydrolysates derived from cellulose and hemicellulose are fermented to cogenerate H 2 and CH 4 by two-step anaerobic fermentation. The total volatile solid of hyacinth leaves can theoretically cogenerate H 2 and CH 4 yields of 303 ml-H 2 /g-TVS and 211 ml-CH 4 / g-TVS, which dramatically increases the theoretical energy conversion efficiency from 19.1% in only H 2 production to 63.1%. When hyacinth leaves are pretreated with 3 wt% NaOH and cellulase in experiments, the cogeneration of H 2 (51.7 ml-H 2 /g-TVS) and CH 4 (143.4 ml-CH 4 / g-TVS) markedly increases the energy conversion efficiency from 3.3% in only H 2 production to 33.2%. Hyacinth leaves, which have the most cellulose and hemicellulose and the least lignin and ash, give the highest H 2 and CH 4 yields, while hyacinth roots, which have the most ash and the least cellulose and hemicellulose, give the lowest H 2 and CH 4 yields.

A chloroform-free novel process for the efficient production of biodiesel from wet microalgae is proposed. Crude biodiesel is produced through extraction with hexane after microwave-assisted transesterification (EHMT) of lipids in wet microalgae. Effects of different parameters, including reaction temperature, reaction time, methanol dosage, and catalyst dosage, on fatty acids methyl esters (FAMEs) yield are investigated. The yield of FAME extracted into the hexane from the wet microalgae is increased 6-fold after the transesterification of lipids. The yield of FAME obtained through EHMT of lipids in wet microalgae is comparable to that obtained through direct transesterification of dried microalgae biomass with chloroform; however, FAME content in crude biodiesel obtained through EHMT is 86.74%, while that in crude biodiesel obtained through the chloroform-based process is 75.93%. EHMT ensures that polar pigments present in microalgae are not extracted into crude biodiesel, which leads to a 50% reduction in nitrogen content in crude biodiesel.

Abstract Characteristics of sodium compounds additives on NO reduction at high temperature were investigated in a tube stove and a drop tube furnace. Sodium carbonate, sodium hydroxide and sodium acetate were chosen as Na additives to research the effect on NO reduction. It was found that sodium compounds could reduce NO emission and promoted NO reduction efficiency during pulverized coal combustion, coal reburning and urea-SNCR process. Adding sodium carbonate into crude coal gained 3.2%–34.8% of NO reduction efficiency on different combustion conditions during the coal combustion process. NO reduction efficiency was affected by sodium content and coal rank. Na additive performed NO reduction effect in whole Shenhua coal combustion process and in char rear combustion of Gelingping coal. Adding sodium hydroxide into the reburning coal increased NO reduction efficiency of the reburning technology. NO reduction efficiency was increased to 82.7% from 50.0% when the weight ratio sodium to the reburning coal was 3% and the ratio of the supplied air to the theoretical air of reburning fuel was 0.6. Sodium carbonate, sodium hydroxide and sodium acetate performed the promotion of NO reduction efficiency in urea-SNCR. Sodium acetate promoted NO reduction efficiency best while sodium hydroxide promoted worst at 800 °C. Sodium additives as SNCR promoter performed much better at lower temperature than at higher temperature, and they promoted NO reduction weakly in urea-SNCR when the temperature was greater than 900 °C.

Abstract This experiment investigates the performance of a micro combustor under different operation conditions, and its improvement with electrical heating inside. According to the results, extinction and blow out occurred at 0.08 and 0.4 L/min, respectively. Electrical heating enhanced the stability effectively. With electrical heating power of 1.05 and 4.70 W, the equivalence ratio ranges of stable combustion are extended from 0.362 – 6.52 to 0.178 – 7.66 and 0.126 – 9.43 on average, respectively, and it is more effective in the lean and low-flow-rate cases. The micro flame shows obvious shift downstream at high flow rates. The flames in the lean cases have higher robustness, their reaction region are closer to the nozzle outlet around 1.17 mm on average than in the rich cases. The heat loss and heat conduction of the micro combustor surface are found to be related to its performance. The rich cases at moderate flow rates have 0.086 W lower heat loss on average than the lean cases, which enhances the stability effectively. However, the rich cases have 0.013 W lower heat conduction on average at moderate flow rates, thus more severe shift downstream occurs.

Transcriptome sequencing and annotation was performed on Haematococcus pluvialis mutant red cells induced with high light under 15% CO2 to demonstrate why astaxanthin yield of the mutant was 1.7 times higher than that of a wild strain. It was found that 56% of 1947 differentially expressed genes were upregulated in mutant cells. Most significant differences were found in unigenes related to photosynthesis, carotenoid biosynthesis and fatty acid biosynthesis pathways. The pyruvate kinase increased by 3.5-fold in mutant cells. Thus, more pyruvate, which was beneficial to carotenoids and fatty acid biosynthesis, was generated. Phytoene synthase, zeta-carotene desaturase, lycopene beta-cyclase involved in β-carotene biosynthesis in mutant cells were upregulated by 10.4-, 4.4-, and 5.8-fold, respectively. Beta-carotene 3-hydroxylase catalyzing conversion of β-carotene into astaxanthin was upregulated by 18.4-fold. The fatty acid biosynthesis was promoted because of the upregulation of acetyl-CoA synthetase and acetyl-CoA carboxylase, thus increasing astaxanthin esterification and accumulation in mutant cells.

Abstract The catalytic effects of eight industrial wastes rich in Na, Fe, Ca and Al on Jincheng anthracite coal combustion were compared. The thermogravimetric experiments showed that Na-rich brine sludge (BS) and salt sludge (SS) exhibited better catalytic effects on coal combustion than Fe-rich iron mud (IM) and steel residue (SR). However, IM and SR exhibited better catalytic effects than Ca-rich white lime mud (WLM) and calcium carbide residue (CCR). Among the eight industrial wastes, Al-rich alumina residue (AR) and aluminium slag (AS) demonstrated the worst catalytic effects. BS, which contains more Na (mainly in the form of NaCl, which was equivalent to Na2O with a content of 13.14%) than SS (mainly in the form of NaCl and Na3Mg(CO3)2Cl, which were equivalent to Na2O with a content of 7.64%) does, reduced the ignition temperature of Jincheng coal from 582 °C to 561 °C because of the promoted transfer of oxygen to the carbon surface through the cyclic oxidation and reduction reactions between Na2O and Na2O2. IM, which contains more Fe (mainly in the form of γ-Fe2O3, which was equivalent to Fe2O3 with a content of 92.22%) than SR (mainly in the form of Fe2SiO4 and α-Fe, which were equivalent to Fe2O3 with a content of 8.29%) does, reduced the ignition temperature of Jincheng coal to 569 °C as a consequence of the enhanced transfer of oxygen to the carbon surface through the cyclic oxidation and reduction reactions between FeO and Fe2O3.

The biological hydrogen production from amino acids obtained by protein degradation was comprehensively investigated to increase heating value conversion efficiency. The five amino acids (i.e., alanine, serine, aspartic acid, arginine, and leucine) produced limited hydrogen (0.2-16.2 mL/g) but abundant soluble metabolic products (40.1-84.0 mM) during dark-fermentation. The carbon conversion efficiencies of alanine (85.3%) and serine (94.1%) during dark-fermentation were significantly higher than those of other amino acids. Residual dark-fermentation solutions treated with zeolite for NH4(+) removal were inoculated with photosynthetic bacteria to further produce hydrogen during photo-fermentation. The hydrogen yields of alanine and serine through combined dark- and photo-fermentation were 418.6 and 270.2 mL/g, respectively. The heating value conversion efficiency of alanine to hydrogen was 25.1%, which was higher than that of serine (21.2%).

Abstract The combination of dark and photo fermentation was studied with cassava starch as the substrate to increase the hydrogen yield and alleviate the environmental pollution. The different raw cassava starch concentrations of 10–25 g/l give different hydrogen yields in the dark fermentation inoculated with the mixed hydrogen-producing bacteria derived from the preheated activated sludge. The maximum hydrogen yield (HY) of 240.4 ml H2/g starch is obtained at the starch concentration of 10 g/l and the maximum hydrogen production rate (HPR) of 84.4 ml H2/l/h is obtained at the starch concentration of 25 g/l. When the cassava starch, which is gelatinized by heating or hydrolyzed with α-amylase and glucoamylase, is used as the substrate to produce hydrogen, the maximum HY respectively increases to 258.5 and 276.1 ml H2/g starch, and the maximum HPR respectively increases to 172 and 262.4 ml H2/l/h. Meanwhile, the lag time (λ) for hydrogen production decreases from 11 h to 8 h and 5 h respectively, and the fermentation duration decreases from 75–110 h to 44–68 h. The metabolite byproducts in the dark fermentation, which are mainly acetate and butyrate, are reused as the substrates in the photo fermentation inoculated with the Rhodopseudomonas palustris bacteria. The maximum HY and HPR are respectively 131.9 ml H2/g starch and 16.4 ml H2/l/h in the photo fermentation, and the highest utilization ratios of acetate and butyrate are respectively 89.3% and 98.5%. The maximum HY dramatically increases from 240.4 ml H2/g starch only in the dark fermentation to 402.3 ml H2/g starch in the combined dark and photo fermentation, while the energy conversion efficiency increases from 17.5–18.6% to 26.4–27.1% if only the heat value of cassava starch is considered as the input energy. When the input light energy in the photo fermentation is also taken into account, the whole energy conversion efficiency is 4.46–6.04%.

This study is aimed to examine the utilization of wastewater produced from the microwave irradiation upgrading process of Indonesian lignite. Physicochemical properties including total organic carbon (TOC), chemical oxygen demand (COD), organic functional groups, inorganic anions, inorganic cations, surface tension, pH, and electrical conductivity (EC) of the removed water were analysed. Results showed that TOC and COD increased with increased microwave time. Organic matters in removed water mainly consists of aromatic, aliphatic, and oxygen functional groups. During the microwave process, inorganic anions (SO42−, F− and Cl−) and cations (Na+, K+, Ca2+, etc.) gradually leached out from lignite. Concentrations of the dominant SO42− and Na+ ions initially increased and then decreased due to the competitive effect of leaching rate of ions and removal rate of water. Thus, EC initially increased and then decreased with total ion concentration, whereas surface tension and pH monotonously decreased. Moreover, pH must be improved and COD must be reduced before discharge or reuse of the removed water.